Note: Descriptions are shown in the official language in which they were submitted.
CA 02388287 2002-05-30
7126-1
THERAPIES FOR THE PREVENTION AND TREATMENT OF DIABETES
AND OBESITY
BY
TERRY E. GRAHAM
ERIK A. RICHTER
FARAH S. L. THONG
and
LINDSAY E. ROBINSON
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Therapies for the prevention and treatment of diabetes and obesity-
Field of the Invention
The field of the present invention is human physiology. The present invention
relates to
the prevention and treatment of diabetes and obesity by a system of health
management promoting
a reduced caffeine diet and the use of adenosine, adenosine analogues,
derivatives, conjugates
thereof and adenosine receptor agonists.
Background of the Invention
Diabetes is a condition characterized by the body's inability to transport
glucose from the
blood into adipose or skeletal muscle cells. This results in glucose build up
in the blood. Insulin
is the key hormone that regulates glucose uptake in the body. Type 2 diabetics
either do not make
enough insulin or their cells are insensitive to it. Type 1 diabetics do not
make insulin and have to
administer it to their bodies.
It is estimated that at least 120 million people worldwide are suffering from
Type 2
diabetes and this is predicted to almost double in our current decade (Shaw et
al., 2000). This is
attributed to aging populations, increases in obesity together with sedentary
lifestyles and poor
nutritional habits. As such it is clear that adopting a positive lifestyle
would both reduce the
probability of developing Type 2 diabetes and/or delay the onset and modify
the severity. In
Canada by 2000 there are expected to be 2.2 million diabetic patients and this
should increase to 3
million by 2010 (Meitzer et al, 1998; Tan and Maclxan 1995). About 90% of
these patients are
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expected to be Type 2 diabetics. Diabetes is a major concern not only because
of its well known
links with cardiovascular disease but also because of its increased risks of
blindness, kidney
disorders, peripheral neuropathies and vascular disorders. It is believed that
only about 50% of
Type 2 diabetics are diagnosed; this together with the wide ranging
complications make it difficult
to establish the total health costs and impact on the quality and quantity of
life. The underlying
etiology of Type 2 diabetes is not resolved, but it is clear that a negative
lifestyle in nutrition and
exercise are key factors.
Type 1 diabetics must administer insulin to themselves their entire life time.
Currently,
experimental studies are underway where beta islets cells are transplanted
into Type 1 diabetics.
Type 2 diabetics must control their diet, are encouraged to lose weight and to
exercise. Often they
ingest drugs that increase their cells' sensitivity to insulin (MetforminTM
and ThiazolidinedioneTM)
In addition, certain drugs stimulate the pancreas to release insulin
(sulfonylureas and benzoic acid
derivatives).
Skeletal muscle is a key target tissue for glucose metabolism and insulin
action. Skeletal
muscle is perhaps the most critical tissue in glucose management, it contains
approximately 80%
of the body's carbohydrate stores and is the largest tissue under insulin
regulation. Any changes
in the regulation of muscle glucose metabolism can have a profound influence
on the metabolism
and health of the body (Graham et al., 1999; Jequier and Tappy, 1999). For
example, muscle
glycogen accounts for 35% of the glucose storage following a mixed meal
(Taylor et al., 1993)
and 50-90% of the glucose disposal during an oral glucose tolerance test
(OGTT) (Brundin et al
1996; Cortright and Dohm, 199?). In contrast, chronic exposure to high levels
of exogenous
carbohydrate result in a decline in insulin sensitivity in muscle (Laybutt et
al., 1997). Muscle
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normally 'buffers' and stores ingested glucose, but habitual, excessive
carbohydrate intake can
impair this function, and for Type 2 diabetes, can impair glycemic control.
Glucose is taken into adipocytes and muscle cells via transporters. The main
transporter is
GLUT 4 and normally most of the cell's GLUT 4 is stored within the cell.
Insulin and other
metabolic signals can cause the GLUT 4 to translocate and become incorporated
into the
membrane. This results in greater glucose uptake by the cell. Obesity and/or a
sedentary lifestyle
are associated with a decreased ability of insulin to promote the
incorporation of GLUT 4
transporters into the muscle sarcolemma, but the mechanisms by which insulin
receptors,
signaling and/or GLUT 4 translocation are changed are far from established
(Cortight and Dohm,
1997).
Adenosine, a purine nucleoside, is a local metabolite produced in probably
every tissue. It
can be formed as a result of either ATP (adenosine triphosphate) or S-
adenosylhomocysteine
hydrolysis. This combined with a very short half life of approximately one
second has resulted in
it being designated as a 'retaliatory metabolite'. Adenosine can be produced
both infra- and
extracellularly and binds to cell surface insulin receptors (Shryock and
Belardinelli, 1997; Ralevic
and Burnstock, 1998). These consist of 4 subsets; A1, A2a, AZb, and A3. Al and
A2 receptors
are coupled to adenylate cyclase via Gi and Gs-proteins, respectively. While
these can alter
cAMP, A1 stimulation also activates phospholipase C, independent of cAMP and
leads to
formation of lipid by-products that activate protein kinases such as PKC
(Ralevec and Burnstock,
1998). The function of adenosine receptors in tissues such as the central
nervous system, heart
and cardiovascular system and adipocytes, have been studied extensively.
However, skeletal
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muscle has rarely been examined and there is no consensus regarding the roles
of adenosine in
skeletal muscle functions.
Adenosine is difficult to study in humans because it has a short half life.
There are many
adenosine receptor agonists and antagonists but most are not suitable for
human consumption.
However, trimethylxanthine (caffeine) and the dimethylxanthine, theophylline
(found in tea) are
nonselective adenosine receptor antagonists, are acceptable oral agents and,
in physiological
doses, most if not all of their actions on various tissues are due to this
property. Plasma
concentrations achieved by oral ingestion of 4-6 mg/kg of either these
methylxanthines or large
quantities of coffee or tea are 25-40 uM. Over 80% of North Americans consume
caffeine daily
and 20% consume greater than 5 mg/kg per day. Caffeine and theophylline are
safe and reliable
candidates to study the effects of adenosine receptor antagonism on glucose
metabolism.
In adipose tissue it is very clear that A1 receptor antagonism inhibits
insulin's ability to
either take up glucose or to promote lipogenesis (Xu et al., 1998; Mauriege et
al., 1995). It has
been repeatedly demonstrated that adipocyte A1 receptor is linked to insulin
signaling (Ralevic
and Burnstock, 1998; Green, 1987) and Tagasuga et al, (1999) showed that
adenosine augments
insulin-stimulated glucose uptake of adipocytes in vitro. For example, the A1
receptor
complement/function of adipocytes is adaptable by up- or down-regulation of
receptor number
and/or post-receptor signaling. Habitual exposure to antagonists caused an up
regulation of
receptors in some tissues but not in others (Green, 1987; Fredholm, 1995;
Zhang and Wells,
1990). Rodent adipocyte A1 receptors and the post receptor mechanisms were
unaffected by
chronic caffeine administration (Fredholm, 1995). However, Mauriege et al.,
(1995) presented
data suggesting that adipocytes from obese and lean women differed in their
adenosine sensitivity.
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When they removed endogenous adenosine (analogous to blocking the A1 receptor)
with
adenosine deaminase prior to exposing femoral adipocytes in vitro to insulin,
the adipocytes of
obese women responded (there was a decrease in lipolysis), but there was no
insulin response in
the adipocytes from the lean (but not exercise-trained) women. These data
suggest that adenosine
receptor number or function can be altered by obesity and by an exercise-
induced weight loss.
However, the putative roles of adenosine with skeletal muscle has not been
examined in such
studies despite it being far more critical than adipose tissue in insulin
resistance and glucose
management.
In contrast to adenosine receptor antagonism decreasing insulin's actions in
adipocytes,
Challiss and coworkers (Budohoski et al., 1984; Challiss et al., 1984; Challis
et al., 1992) have
repeatedly found that this results in increased insulin sensitivity in rodent
muscle in vitro. Only
Xu et al. (1998) have been able to confirm this finding; others have reported
that adenosine
receptor antagonism causes marked decreases in muscle glucose uptake (Webster
et al., 1996;
Vergauwen et al., 1994; Han et al., 1998). However, even among these
investigations there is
controversy as to whether adenosine is important in both fast and slow twitch
muscle, whether it
plays a role in resting muscle or only during exercise, and even whether human
tissue responds in
a similar fashion to rodent muscle. The results observed in skeletal muscle
are attributed to
antagonism of A1 receptors. There are reports that rodent muscle has A2a
receptors, but attempts
to demonstrate A1 receptor or its mRNA have been negative (Dixon et al.,
1996). There is no
published data for human muscle, but there are reports (Challis et al., 1992;
Webster et al., 1996)
refernng to unpublished findings that failed to show A1 receptors in human
muscle.
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Obese individuals have a decreased insulin sensitivity similar to diabetics,
and it is clear
that obesity is the dominant risk factor for developing Type 2 diabetes. There
is one report that
illustrated that adenosine-based responses of skeletal muscle were both
critical and altered with
obesity. Crist et al (1998) treated both normal and obese Zucker rats with an
A1 antagonist for one
week and then performed euglycemic-hyperinsulinemic clamps (there were no
clamps performed
on animals that were only acutely exposed to the antagonist). The lean animals
that were exposed
to the antagonist decreased whole body glucose disposal by 16%. Glucose uptake
by the heart and
liver were unaltered, while adipose tissue decreased its uptake by almost 50%
and muscle
decreased its uptake by 12-16%. However, absolute glucose uptake by muscle was
much greater
than that of adipose tissue as it represents a much larger mass. Assuming the
rats were 40%
muscle and 20% fat, 49% of the reduced glucose disposal could be attributed to
muscle and 9% to
adipose tissue. Mauriege et al (1995), Carey (2000) and Carey et al (1994)
demonstrated that
obesity and leanness are characterized by differences in adipocyte response to
adenosine and this
work by Crist et al (1998) showed that skeletal muscle of obese and lean
animals differs in either
the complement of adenosine A 1 and/or A2a receptors or their interaction with
insulin signaling
and GLUT 4 translocation. Although these studies indicate there is a role for
adenosine in glucose
uptake and obesity, no experiments have been conducted with obese humans.
In summary, there is evidence that adenosine is an important regulator of
insulin's actions
in animal adipose and skeletal muscle cells. Further there is evidence that
adenosine is an
important regulator of insulin action on adipose cells in humans. While human
muscle is a critical
tissue for glucose management, very little is known regarding adenosine's
actions on this tissue.
Preliminary experiments have shown that caffeine inhibits insulin's ability to
promote glucose
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uptake in skeletal muscles (Greer et al., 1998), and results in the body
having to secrete more
insulin in order to maintain glucose homeostasis in lean males (Battram et
al., 1999). However,
the sample numbers were low in these studies and these studies did not address
whether chronic
exposure to caffeine resulted in adaptations. Further, and more importantly,
it is unclear how
caffeine affects glucose uptake in muscle tissue of diabetics and the obese.
Given the high and growing frequency of obesity and Type 2 diabetes in our
society, as
well as the common ingestion of coffee, it is vital that these areas be
studied in detail. It is also
necessary to address the interaction between caffeine consumption and insulin
administration in
Type 1' diabetics.
As a result, there is a need for the development of superior therapies for the
prevention and
treatment of diabetes and obesity. To facilitate this need, there is a
requirement for greater
understanding of glucose uptake in skeletal muscles, specifically in muscles
of diabetic and obese
subjects. Further, there is a need for effective recommendations for diabetics
and the obese with
respect to nutrition and caffeine consumption. There is a further need to
develop drugs that aid
glucose uptake in cells, specifically for the prevention and treatment of
diabetes and obesity.
Summary of the Invention
The present invention relates to the discovery that adenosine receptor
antagonists inhibit
the uptake of glucose in cells.
According to one embodiment of the present invention, there is provided a a
diet plan
method for a disease selected from the group consisting of diabetes and
obesity wherein the diet
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plan method has a restricted amount of caffeine.
According to another embodiment of the present invention, there is provided a
preventative
diet plan method for a disease selected from the group consisting of Type 2
diabetes and obesity
wherein the diet plan method has a restricted amount of caffeine.
According to another embodiment of the present invention, there is provided a
diet plan
method for a disease selected from the group consisting of diabetes and
obesity wherein the diet
plan method promotes the use of decaffeinated coffee.
According to another embodiment of the present invention, there is provided a
preventative
diet plan method for a disease selected from the group consisting of Type 2
diabetes and obesity
wherein the diet plan method promotes the use of decaffeinated coffee.
According to another embodiment of the present invention, there is provided a
caffeine-
free appetite suppressants for diabetics which are caffeine free, low in
sugars and labelled as
"Diabetic Safe".
According to another embodiment of the present invention, there is provided a
caffeine-
free weight loss products for diabetics which are caffeine free, low in sugars
and labelled as
"Diabetic Safe".
According to another embodiment of the present invention, there is provided a
caffeine-
free energy drinks for diabetics which are caffeine free, low in sugars and
labelled as "Diabetic
Safe".
According to another embodiment of the present invention, there is provided
pharmaceutical compositions for diabetics which are caffeine free, low in
sugars, and labelled as
"Diabetic Safe"
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According to another embodiment of the present invention, there is provided
pharmaceutical compositions wherein the compositions are remedies for the
common cold.
According to another embodiment of the present invention, there is provided a
system for
health management of a disease selected from the group consisting of diabetes
and obesity
comprising counseling a patient regarding the consumption of non-caffeinated
products and
providing non-caffeinated products to the patient.
According to another embodiment of the present invention, there is provided a
method for
the prevention of a disease selected from the group consisting of Type 2
diabetes and obesity, in
patients with a susceptibility to one of diabetes and obesity, comprising the
steps of:
a. identifying patients with a susceptibility to one of diabetes and obesity,
b. counseling the patients regarding a restricted caffeinated diet, and
c. making available non-caffeinated products to the patients.
According to another embodiment of the present invention, there is provided a
method of
treatment for patients with a disease selected from the group consisting of
diabetes and obesity,
comprising
a counseling the patients regarding a restricted caffeinated diet, and
b making available non-caffeinated products to the patients.
According to another embodiment of the present invention, there is provided a
method of
treatment where the non-caffeinated products selected from the group
consisting of caffeine-free
coffee, colas, chocolate, energy drinks, pharmaceuticals and diet products.
According to another embodiment of the present invention, there is provided a
use of
decaffeinated coffee for the prevention of a disease selected from the group
consisting of Type 2
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diabetes and obesity.
According to another embodiment of the present invention, there is provided a
use of
decaffeinated coffee for the treatment of a disease selected from the group
consisting of diabetes
and obesity.
According to another embodiment of the present invention, there is provided a
use of
compounds selected from the group consisting of adenosine and adenosine
receptor agonists.
According to another embodiment of the present invention, there is provided a
adenosine
analogues, adenosine derivatives, adenosine conjugates and mixtures thereof as
a treatment for a
disease selected from the group consisting of diabetes and obesity.
According to another embodiment of the present invention, there is provided a
use of
compounds selected from the group consisting of adenosine, adenosine receptor
agonists,
adenosine analogues, adenosine derivatives, adenosine conjugates and mixtures
thereof as a
treatment for the prevention of a disease selected from the group consisting
of Type 2 diabetes and
obesity.
According to another embodiment of the present invention, there is provided a
use of
compounds selected from the group consisting of adenosine, adenosine receptor
agonists,
adenosine analogues, adenosine derivatives, adenosine conjugates and mixtures
thereof as a
method to offset the antagonistic effect of caffeine.
According to another embodiment of the present invention, there is provided a
labeling
system for diabetics and people susceptible to diabetes comprising labeling
food and
pharmaceutical products that are caffeine-free and low in simple sugars as
safe for diabetics.
According to another aspect of the present invention, there is provided a
sports drink
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comprising an adenosine receptor agonist.
Description of the Drawin;as
Figure 1 is a graph showing the blood glucose response before and during oral
glucose
tolerance tests.
Figure 2 is a graph showing the serum insulin response before and during oral
glucose
tolerance tests.
Figure 3 is a graph showing the serum C peptide response before and during
oral glucose
tolerance tests.
Figure 4 is a graph showing the effect of caffeine, coffee, decaffeinated
coffee and placebo
on glucose level during oral glucose tolerance tests.
Figure 5 is a graph showing the effect of caffeine, coffee, decaffeinated
coffee and placebo
on insulin level during oral glucose tolerance tests.
Figure 6 is a graph showing the effect of caffeine, coffee, decaffeinated
coffee and placebo
on C peptide level during oral glucose tolerance tests.
Definitions
Male Sprague-Dawley rats: a breed of rats commonly used in research.
soleus muscle strips: soleus muscle from rats that is gently torn into two or
three strips
for the purpose of studying metabolism.
3MGT: 3-methyl glucose is a labelled glucose and is used to study glucose
uptake or
transport.
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BMI: Body mass index
CPA: N6-cyclopentyladenosine (an adenosine A 1 agonist).
DPMA: N-[2-(3,5-dimethoxy-phenyl)-2-(2-methylphenyl)ethyl]-adenosine is a drug
that
is an adenosine receptor agonist.
GLUT-4: the main glucose transporter in the cell.
P13 kinase: phosphatidylinositol 3-kinase.
IRTK: insulin receptor tyrosine kinase is an insulin signalling factor that
promotes
movement and translocation of GLUT 4 into cell membranes
IRS-1: insulin receptor substrate -1 is an insulin signalling factor that
promotes movement
and translocation of GLUT 4 into cell membranes.
MAP kinase: mitogen-activated protein kinase is an insulin signalling factor
that
promotes movement and translocation of GLUT 4 into cell membranes.
Akt: serine/threonine kinase.
Detailed Description of the Invention
One aspect of the present invention is that caffeine is detrimental to glucose
uptake in
human skeletal muscle cells of healthy subjects (i.e. non-diabetic lean
males). Examples 1, 2, and
17 illustrate this aspect of the invention in more detail. This aspect of the
invention demonstrates
that caffeine ingestion affects glucose metabolism. Further, a caffeine-free
diet is beneficial to
insulin's action. Further still, compounds that act in the opposite manner to
caffeine (i.e.
adenosine receptor agonists) promote insulin's actions.
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Another aspect of the present invention is that caffeine is detrimental to
glucose uptake in
human skeletal muscle cells of obese and diabetic subjects. Examples 5, 6, 7,
8, 9, 11, 16, I8 and
19 describe this aspect of the invention in more detail. The result is that
diabetic and obese
patients will make effective nutritional choices for the treatment of diabetes
and obesity. Further,
people with a susceptibility to diabetes and obesity can make effective
nutritional choices for the
prevention of Type 2 diabetes and obesity. For example, it is beneficial for
diabetics to avoid
caffeine. Caffeine is present in many "everyday" products such as coffee, tea,
weight loss
products, energy drinks, soft drinks and pharmaceuticals, especially remedies
for the common
cold. Diabetics should avoid caffeine-containing products, and if possible
choose caffeine-
free/caffeine-reduced weight loss products, energy drinks, soft drinks and
pharmaceuticals.
Further, diabetics, obese patients and those susceptible to diabetes and
obesity should adopt a
system of health management to avoid/minimize caffeine consumption. Further,
another aspect of
the present invention relates to a labeling system for diabetics and people
susceptible to diabetes
comprising labeling food and pharmaceutical products that are caffeine-
free/caffeine-reduced and
low in simple sugars as safe for diabetics.
Another aspect of the present invention is that decaffeinated coffee increases
glucose
uptake. Example 3 describes this aspect of the invention in more detail.
Coffee is comprised of
many compounds, caffeine constituting a mere 1-3% of the content. The benefits
of this aspect of
the invention are that (1) decaffeinated coffee contains a compound or
compounds that aids
glucose uptake, (2) consumption of decaffeinated coffee helps to treat or
prevent diabetes and
obesity, and (3) coffee is a biological source of an adenosine receptor
agonist useful for increased
uptake of glucose.
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Another aspect of the present invention is that adenosine, adenosine
analogues, derivatives
and conjugates thereof promote glucose uptake in skeletal muscle in healthy,
diabetic and obese
subjects. Examples 3 and 16 describe this aspect of the invention in more
detail. As a result,
adenosine, adenosine analogues, derivatives and conjugates thereof can be used
to prevent and
treat diabetes and obesity.
Another aspect of the invention relates to the role of adenosine receptor
antagonists during
exercise. Examples 10 and 11 describe this aspect of the invention. As a
result, the use of
adenosine receptor agonists in sports drinks, is beneficial for getting
glucose into the muscle in
recovery from exercise.
Another aspect of the invention relates to the role of adenosine receptor
antagonists on
blood response to high and low index glycemic foods in non-diabetic and
diabetic volunteers.
Examples 17 and 18 describe this aspect of the invention. The result is that
diabetic patients will
make effective nutritional choices for the treatment of diabetes. Further,
people with a
susceptibility to diabetes can make effective nutritional choices for the
prevention of Type 2
diabetes.
Methods and Materials
The methods and materials employed in this invention are common to those
skilled in the
art. The methods and materials for the hyperinsulinemic euglycemic glucose
clamp test are found
in Greer et al., 2001. The methods and materials for the oral glucose
tolerance test (OGTT) are
described in Graham et al., 2001.
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Examples
Example 1. Caffeine ingestion decreases glucose disposal during
hyperinsulinemic euglycemic
clamp in humans.
Nine, lean sedentary males underwent two hyperinsulinemic euglycemic clamp
sessions,
one following caffeine ingestion (Smg/kg) and one following placebo
(dextrose). Trials were
separated by one week. Prior to each clamp session, subjects withdrew from
methylxanthine
containing products for 48 hours. Following caffeine ingestion, glucose
disposal was 6.38 +/-0.76
mg/kg/min compared with 8.42 +/- 0.63 mg/kg/min in the placebo. This
represents a 24%
decrease in glucose disposal following adenosine receptor antagonism by
caffeine. Furthermore
caffeine ingestion resulted in a 35°lo decrease in carbohydrate storage
compared to placebo and is
consistent with the decreased glucose uptake observed with caffeine
administration. Since skeletal
muscle is the most likely site for insulin-mediated glucose disposal, these
data suggest that
adenosine plays a role in regulating glucose uptake in human skeletal muscle.
Example 2. Caffeine ingestion increases circulating insulin in humans during
an oral glucose
tolerance test.
Young, fit, adult males (n=18) underwent two oral glucose tolerance tests
(OGTT). The
subjects ingested caffeine (5 mg/kg) or placebo (double blind) and one hour
later, ingested 75 g of
dextrose. Prior to the OGTT there were no differences between or within trials
in circulating
serum insulin, or C peptide, or blood glucose or lactate. Following the OGTT
all of these
parameters increased (p < 0.05) for the duration of the OGTT. Caffeine
ingestion resulted in an
increase (p < 0.05) in serum fatty acids, glycerol and plasma epinephrine.
During the OGTT these
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decreased to match those of the placebo trial. In the caffeine trial the serum
insulin and C peptide
concentrations were significantly greater (p < 0.05) than for placebo for the
last 90 minutes of the
OGTT (see Figures 2 and 3) and the area under the curve for both measures were
60 and 37%
greater (p < 0.05) respectively. This prolonged, greater elevation in insulin
did not result in a
lower blood glucose level (see Figure 1); there were no differences between
trials. The data
support the hypothesis that caffeine ingestion impairs glucose disposal.
Further, the data suggests
this is due to adenosine receptor antagonism in skeletal muscle.
Example 3. Impaired response to an oral glucose tolerance test following
ingestion of caffeine
in alkaloid form or as a component of coffee.
Ten healthy male subjects, who were not regular caffeine users, underwent an
oral glucose
tolerance test on four occasions following the ingestion of either pure
alkaloid caffeine capsules
(Smg/kg) (AC), caffeinated coffee (CC), decaffeinated coffee, or placebo
capsules (PL). Venous
blood samples were taken at -30, 0 (treatment given), 60 (OGTT administered),
75, 90, 120, 150
and 180 minutes and were analyzed for glucose, insulin, C peptide, glycerol,
free fatty acids and
lactate. Area under the curve (AUC) were calculated for the two hours of the
OGTT. As
previously seen, AC demonstrated a higher AUC for insulin (see Figure 5) than
both PL (p<0.002)
and DC (p<0.001) respectively. As well, insulin AUC for CC showed a similar
trend to AC,
approaching a significantly higher insulin AUC than DC (p<0.08). AUC for
peptide C (See
Figure 6) demonstrated similar results to insulin, again with AC showing
higher values than both
PL (p<0.02) and DC (p<0.001) and CC approaching significantly higher values
that DC (p<0.08).
AUC for glucose with AC was higher than both CC (p<0.04) and DC (p<0.01)
respectively and
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CC was higher that DC (p=0.05). As well, PL demonstrated higher AUC for
glucose than DC
(p<0.02) See Figure 4. In conclusion, it appears than CC can elicit a similar
insulin insensitivity
as observed with AC, but to a lesser extent. These results also suggest that
some component of
coffee may enhance insulin-mediated glucose uptake in resting humans. This
component acts as
an adenosine receptor agonist.
Example 4. The determination of adenosine receptors in skeletal muscle.
The purpose of this study was to investigate the presence of A1 and A2
adenosine
receptors (AR) in rat and human skeletal muscle. Adenosine receptor-stimulated
adenylate
cyclase activity studies were conducted to determine cAMP responses in the
presence of AR
agonists using rat skeletal muscle homogenates. Subsequently, Western blotting
experiments were
conducted to identify the A1 and A2 receptor proteins in rodent and human
skeletal muscle
samples. In the initial experiments, NECA (an A2 AR agonist) produced a
significant 7.5-fold
increase in cAMP production in rat oxidative muscle homogenates with no effect
on glycolytic
samples. There was little effect of R-PIA (an A1 AR agonist) on cAMP levels in
any fiber type.
Western blotting revealed A I and A2 AR protein bands in rat and human
skeletal muscle samples.
A1 and A2a expression was observed in similar amounts in both oxidative and
glycolytic rodent
fibers. A2a expression was highest in the liver compared to muscle and heart
homogenates. Both
rodent oxidative and glycolytic skeletal muscle homogenates had a
significantly greater A1 and A
2 expression compared to heart. In conclusion, both receptor subtypes appear
to be present in
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oxidative and glycolytic muscle fibers in rodents and both receptor subtypes
appear to be present
in human skeletal muscle.
Example 5. Caffeine ingestion increases circulating insulin in obese males
during an oral glucose
tolerance test.
Four young, obese (BMI > 30) nondiabetic males, underwent an OGTT similar to
Example
2. When lean males (n=18) underwent OGTT with and without caffeine ingestion
the AUCs for
GLU were 168 and 208 mM/2 h, respectively. The comparable data for the obese
males were very
similar (167 and 229 mM/2 h). However, there were marked differences for
insulin: the lean
males had AUCs of 3274 and 5242 uU/ml/2h for placebo and caffeine
respectively, while
comparable data for the obese males were 6938 and 10,968 uU/ml/2 h. The obese
subjects had an
insulin response to an OGTT that was over 100% greater than that of the lean
subjects, and the
insulin resistance induced by caffeine ingestion was twice as large.
Example 6. Effects of caffeine ingestion on the insulin response in humans
during an oral
glucose tolerance test before and after a weight loss program.
Six, obese (BMI = 30-38 kg/m2) men performed an OGTT one hour after ingesting
caffeine (Smg/kg) or placebo (P). The two OGTT's were repeated after a twelve
week nutrition-
exercise intervention during which time subjects abstained from caffeine and
lost 3-12 kg. There
were no differences among the four trials in insulin, C-peptide or glucose
prior to the OGTT.
Prior to the twelve week intervention, caffeine ingestion resulted in a
greater (p=0.043) insulin
response during the OGTT, although there were no differences in blood glucose.
Following the
intervention there was no detectable change in the OGTT response for either
placebo or caffeine.
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Similarly, caffeine still resulted in a greater (p=0.056) increase in insulin
during the OGTT
compared to placebo. The intervention successfully lowered body weight, but
failed to improve
the insulin response to glucose ingestion, and the caffeine ingestion
continued to exaggerate this
response.
Example 7. Effect of caffeine on the insulin/glucose response to an OGTT in
obese, resting
males.
Young, sedentary, obese males (n=28) underwent two OGTT's ingesting caffeine
(5
mg/kg) or placebo followed by 75g of dextrose one hour later. Prior to the
OGTT there were no
differences between or within trials in insulin or glucose levels. Caffeine
resulted in significantly
greater (p< 0.05) glucose and insulin for the last 90 minutes and 105 minutes
respectively of the
OGTT. The area under the curve during the OGTT was greater following caffeine
for both insulin
(9455.8 uIU/ml/2h +/- 640.7) and glucose (260.1 mM/2h +/- 22.4) in comparison
to placebo
(7037.9 uIU/ml/2h +/- 631.5 and 188.5 mM/2h +/- 25.3) respectively (p < 0.05).
The results
indicate that caffeine ingestion may exaggerate insulin resistance associated
with obesity.
Example 8. Characterization of the impact of Adenosine receptor antagonism on
obese and
Type 2 diabetics, with emphasis on the ability of caffeine to generate insulin
resistance.
Groups of obese (BMI > 30) (n=18), and Type 2 diabetic (n=18) males, age 18-30
years
old are undergoing two OGTTs, with and without caffeine ingestion one hour
prior to the OGTT.
The results will be compared to the current data base; containing data (28,40)
collected in an
identical fashion for 30 lean (BMI of less than 25) males age 18-30 years.
Lean subjects have BMI
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of less than 25, the obese are class I (BMI 30-34), abdominal obese (waist
circumference > 100
cm) and the diabetics have the same anthropometry. The diabetics are
volunteers who have been
well controlled for a year, with glycosylated hemoglobin levels between 6.5-
9.5% for at least three
months. They have similar levels of obesity, are not insulin-dependent, and
are not on oral
hypoglycemic agents, but rather diet-controlled. Their participation is
medically approved and
they are screened for hypertension and angina. The area under the curve for
insulin and C-peptide
is greater for the obese and even greater for the diabetic subjects. Following
caffeine ingestion the
area under the curves for insulin and C-peptide are increased in the lean
subjects. Caffeine causes
an even greater response in these parameters for the obese and diabetic
subjects. Data also
includes plasma catecholamines, methylxanthines, FFA, and glycerol.
Example 9. Effect of habitual caffeine ingestion on glucose uptake
The subjects of this trial are lean, obese and obese males with Type 2
diabetes (n=8 each,
age 18-30 years) which have had their exercise habits, diet and caffeine
consumption regulated.
All subjects are sedentary (weekly activity of less than one hour). For one
month prior to the
study, subjects are monitored to establish that their exercise habits are
regular, they are weight
stable and their diet is energy, macronutrient and caffeine stable. They are
monitored to ensure
that they maintain these patterns for the following three months. In a double-
blind, crossover
design they consume either caffeinated or decaffeinated coffee for one month
with the two trials
separated by a one month 'washout' period. Subjects are provided with packets
of ground coffee
and brewing instructions. For the caffeinated treatment, the coffee packets
deliver 4.5 mg/kg of
caffeine in their coffee (2 mugs of coffee) twice a day. At 0, 1 and 4 weeks
of each trial the
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subjects undergo an OGTT lhour following ingestion of 2 mugs of their
prescribed coffee. No
exercise is performed within two days of the OGTT and carbohydrate ingestion
is regulated.
Muscle biopsies are taken before and after each OGTT. Blood samples are
analyzed and biopsies
are analyzed for A1 and A2a receptor protein and mRNA, cAMP, glycogen and IRTK
activity,
IRS-1 associated PI3K, Akt and GSK-3. Prior to treatments, the obese and
diabetic subjects are
insulin resistive and have a greater insulin response to caffeine. Habitual
ingestion of coffee
upregulates A1 receptors progressively over the month. During the transition
(i.e., at one week), a
decrease in the insulin response is observed. Upon habituation (one month),
the response returns
to normal.
Example 10. Caffeine impairs glucose uptake but not insulin signaling in
rested and exercised
human skeletal muscle.
The role of adenosine in regulating insulin-stimulated glucose uptake in human
skeletal
muscle is not known. We investigate the effects of caffeine, a non-selective
adenosine receptor
antagonist, on skeletal muscle glucose uptake during a 100 minute euglycemic-
hyperinsulinemic
(100~uU/ml) clamp. On two occasions, seven males performed one hour one-legged
knee extensor
exercise three hours before the clamp. Caffeine (Smg/kg) or placebo was
administered in a
randomized, double blind fashion one hour before the clamp. Whole body glucose
disposal was
reduced (p<0.05) in caffeine (37.5 +/- 3.1 ~mol/min/kg) vs. placebo (54.1 +/-
2.9pmo1/min/kg).
Total (area under the curve) insulin-stimulated glucose uptake (arterio-venous
concentration
difference x blood flow) was higher (p<0.05) in the exercised (63.3 +/- 13.1
mmol/100min) than
rested (37.0 +/- 6.7 mmol/100min) leg. However caffeine reduced (p<0.05) total
insulin-
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stimulated glucose uptake equally in exercised (32.9 +/- 3.7 mmol/100min) and
rested (17.9 +/-
6.2 mmol/100min) legs. Insulin increased insulin receptor tyrosine kinase
(IRTK), insulin
receptor substrate 1-associated phospatidylinositol 3-kinase (P13K) activities
and serine
phosphorylation of Akt significantly, but similarly in rested and exercised
legs. Furthermore,
insulin decreased glycogen synthase kinase-3 (GSK-3) activity equally in
rested and exercised
legs. However, caffeine had no effect on insulin-stimulated IRTK, P13K, AKT,
or GSK-3 in
relaxed or exercised legs. We conclude in humans 1) caffeine impairs insulin
stimulated glucose
uptake in rested and exercised skeletal muscles, and 2) caffeine-induced
impairment of insulin-
stimulated muscle glucose uptake is not accompanied by alterations in IRTK,
P13K, Akt or GSK-
3.
Example 11. Effect of exercise training on the response to Adenosine receptor
antagonism and
its association with alterations in glucose management.
Lean, sedentary males, and obese males with and without Type 2 diabetes (n=8
each) are
performing a 12-week, exercise training program. Subjects are selected to have
similar initial
fitness levels (V02 max) and diet and caffeine habits are controlled
throughout the study. During
the pretreatment period, subjects consume a weight maintenance diet (55%
carbohydrate, 20%
protein, 25% fat). Their body composition is assessed for total adiposity as
well as visceral and
subcutaneous fat before and after the treatment by Magnetic Resonance Imaging
(MRI). The
exercise program is supervised and consists of walking or running on a
treadmill at 40 - 60% of
HR reserve for 60 minutes five times per week. Subjects increase their energy
intake to keep their
weight stable to minimize changes in adipose tissue. Thus, major alterations
in metabolic
responses are more likely attributed to training adaptations in muscle.
Euglycemic
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hyperinsulinemic clamp tests with and without caffeine are performed before
and after the training
program (those after the training are performed at least 48 hours after the
last exercise). Muscle
biopsies are taken before and after each clamp and analyzed. Insulin
sensitivity increases as does
A1 receptors. The relative improvement is greatest in the Type 2 diabetics and
least in the lean
subjects.
Example 12. Effect of adenosine on skeletal muscle glucose transport.
Male Sprague-Dawley rats are used in all the following examples. Soleus muscle
strips are
incubated as described by Bonen et al (1992), Wilkes and Bonen (2000) and
Bonen et al (1994) to
determine glucose transport. Basal and insulin-stimulated 3-O-methyl glucose
transport (3MGT) is
examined in a dose dependent (0-10 nM) manner during a 10 minute incubation
period in
appropriate buffer (Bonen et al., 1994). Comparison of this dose-response
relationship of insulin,
and the A1 agonist CPA, and A2 agonist DPMA on 3MGT is conducted. 3MGT rates
are linear
for up to 20 minutes. The 10 minute period is therefore a convenient time
point to acquire
sufficient counts in the muscle at a reasonable cost of using radiolabelled
3MGT.
Optimal stimulating concentrations of insulin, CPA, and DPMA are established
for 3MGT.
Insulin stimulated 3MGT is inhibited by LY29004, an inhibitor of PI3-kinase,
2) CPA- and
DPMA-induced increases in 3MGT are also inhibited by LY29004, and 3) exposure
to these
stimulators alone or in combination have additive effect on 3MGT.
Example 13. Effect of adenosine on membrane-bound GLUT 4 translocation and
intrinsic
activity.
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The optimal glucose transport stimulating concentrations of insulin, CPA and
DPMA, are
used to determine the increase, or lack thereof, in surface GLUT 4 using the
method of
radiolabelling the surface GLUT 4 with bis-mannose photolabel which has been
used successfully
by Bonen et al (1992), Han et al. (1998) and Wilkes and Bonen (2000) and
others (Etgen et al.,
1996; Lund et al., 1995). With this procedure 3H-bis-mannose (2-N-4(1-azi-
2,2,2-trifluoroethyl)-
benzoyl-1,3-bis-(D-mannose-4-yloxy)-2-propylamine) (ATB-[2-3H]BMPA) is
provided to
isolated muscles exposed to one of the treatments. The muscle is frozen (-
80°C), solubilized crude
membranes are prepared (Han and Bonen, 1998) and GLUT 4 is then
immunoprecipitated with
affinity purified anti-GLUT 4 to separate it from surface GLUT 1 that is also
labeled. SDS/PAGE
is used to separate GLUT 4 and remaining proteins. Then the gel is cut into 4
mm slices which are
solubilized and counted for 3H.
These experiments are designed to determine whether insulin and the A1 and A2
agonists
translocate and/or activate GLUT 4. In many experiments, the fold increases in
surface GLUT 4
and 3MGT by insulin and by contracting muscle are nearly identical (Etgen et
al., 1996, Lund et
al., 1995, Reynolds et al., 1997). Thus, by combining the observations on
glucose transport and
surface GLUT 4 one can ascertain whether 3MGT increments in muscle are due to
increases in
surface GLUT 4 (i.e. same fold increase in 3MGT and surface detectable GLUT
4). A mismatch
in the fold increases in these responses, indicates that the activity of
surface detectable GLUT 4
has been altered. This basic approach is commonly used to ascertain if there
is a change in
intrinsic activity of surface GLUT 4 (Bonen et al., 1992; Han and Bonen, 1998;
Wilkes and
Bonen, 2000; Hansen et al., 1998).
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The demonstration of a 1:1 relationship between glucose transport and surface
GLUT 4
accumulation by insulin, CPA and DPMA, leads to additional experiments to
identify insulin-
sensitive and CPA and DPMA-sensitive intracellular GLUT4 pools. Han and Bonen
(1998) and
Lemieux et a1.(2000) have experience with various muscle fractionation
procedures and
identification of intracellular GLUT 4 pools using a variety of marker
proteins. These
experiments potentially reveal novel means of stimulating GLUT 4 translocation
from insulin-
insensitive pools.
Example 14. Determination of the signaling proteins associated with GLUT 4
translocation
which are activated by adenosine.
Experiments with insulin, CPA and DPMA are performed in isolated muscles using
optimal stimulating concentrations to determine which signaling proteins are
activated. For this
purpose, isolated rodent muscles are incubated with either basal or maximal
insulin concentrations
with and without either CPA or DPMA. Glucose transport is determined by 3MGT,
measured over
minutes. The muscle samples are analyzed for IRTK, IRS-1 associated PI3
kinase, p38 MAP
kinase and Akt activities. The critical exposure time to activate signaling
proteins is established in
pilot work. Wilkes et al. (2000a) and Wilkes et al. (2000b) have found that 5
minute exposure
provides the optimal period for detecting signaling protein activation for
insulin in incubated
muscles. Lemieux et al (2000) have recently found that there are several
intracellular GLUT 4
pools that are independently activated, thus it is conceivable that CPA and
DPMA may recruit
GLUT 4 from one of these 'non-insulin sensitive' pools. Optimal exposure times
required for
signaling protein activation by CPA and DPMA are established.. We do not
assume that these are
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the same as for insulin. We establish that blocking P13-kinase with LY29004
blocks downstream
activation of Akt by insulin, and by CPA and DPMA.
Example 15. The impact of overexpressing A:l or A2a receptors on muscle
glucose uptake.
Electroporation, a method of non-viral gene transfer uses electric pulses
(electroporation)
to transfect prokaryotic and eukaryotic cells in vitro. Mir et al. (1999)
demonstrated conclusively
that it is possible to transfer plasmid DNA into skeletal muscle in vivo by
using electroporation.
The extent of the transfection is dependent on the voltage selected, pulse
duration, number of
pulses and their frequency. Thus, it appears that electroporation increases
gene transfer into
muscle not only by muscle-fiber permeabilization but also by the direct effect
on the DNA
molecule (Mir et al., 1999). They have demonstrated i) the very large increase
in gene expression
that could be attained, ii) the long-term stability of the effect (i.e. up to
nine months), iii) the
reduction in variability, iv) its application to a variety of species (mouse,
rat, rabbit, monkey), and
v) being able to regulate the degree of expression (Mir et al., 1999).
We are using the electroporation and cDNA injection procedures of Mir et al.
(1999) to
overexpress either the A1 or the A2a receptor alone or in combination in
soleus muscle. The
contralateral leg (sham electroporation) serves as control. We examine
insulin, CPA and DPMA-
stimulated 3MGT, insulin signaling and the GLUT 4 responses in the isolated
soleus muscles that
contain the upregulated proteins. These experiments establish whether the
increased availability
of either A 1 or A2a receptors, alone or in combination, further increase
insulin, CPA and DPMA-
stimulated 3MGT, and GLUT-4 translocation or activation, by means of
procedures described in
experiments outlined above.
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Example 16. Characterization of the impact of an adenosine receptor agonist in
obese and Type
2 diabetics, with emphasis on the ability of adenosine receptor agonist to
increase glucose uptake.
Groups of obese (BMI>30) (n=18), and Type 2 diabetic (n=18) males, age 18-30
years
undergo two OGTT's, with and without adenosine receptor agonist ingestion one
hour prior to
OGTT. Venous blood samples are taken at -30, 0 (treatment given), 60 (OGTT
administered), 75,
90, 120, I50 and 180 minutes and are analyzed for glucose, insulin, C peptide,
glycerol, free fatty
acids and lactate. Area under the curve are calculated for the 2 hours of the
OGTT. The obese
subjects are class 1 (BMI 30-34), abdominal obese (waist circumference > 100
cm) and the
diabetics have the same anthropometry. The diabetics are volunteers who have
been well
controlled for a year, with glycosylated hemoglobin levels between 5.4-
9.9°Io for at least three
months. They have similar levels of obesity, are not insulin-dependent, and
are not on oral
hypoglycaemic agents, but rather diet-controlled. Their participation is
medically approved and
they are screened for hypertension and angina.
Example 17. Effect of caffeinated coffee on the insulin and glucose responses
to either a high or
low glycemic index breakfast cereal in lean, resting males.
To date the majority of studies investigating caffeine and insulin resistance
have compared
pure caffeine with a standard 75 g oral dextrose load (OGTT) against a placebo
treatment. The
current study investigated whether impaired glucose management occurs with
normal foods,
namely following ingestion of coffee and either a high or low glycemic index
(GI) breakfast
cereal. Young (age = 24 ~ 2 year), non-obese (BMI = 25 ~ 1 kg/mz), non-
diabetic males (n = 6)
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underwent four separate trials approximately one week apart, in a randomized
order. The four
treatments were: (1) caffeinated (5 mg/kg) coffee with either a high glycemic
index or (2) low
glycemic index cereal or (3) decaffeinated coffee with either a high glycemic
index or (4) low
glycemic index cereal. Cereal with 150 ml skim milk resulted in 75g total
carbohydrate for both
the high (GI = 81) and low (GI = 41) glycemic index meals. This amount of
carbohydrate was
chosen to provide the same amount of carbohydrate (75g) as that used in our
previous caffeine and
OGTT studies in lean and obese males. Venous blood samples were taken prior to
ingestion of
coffee (t= -60 minutes) and cereal (t=0 minutes) and at t =15, 30, 4S, 60, 90
and 120 minutes after
cereal ingestion.
There were no differences among the four trials in insulin, C-peptide or
glucose prior
cereal ingestion. Insulin and C-peptide area under the curves were
significantly increased with
caffeinated coffee (p<0.05). Specifically, after the high glycemic index meal,
insulin area under
the curve increased 93% with caffeinated (3039 ~ 413 uIU/ml/2h) vs
decaffeinated (1574 ~ 257
uIU/ml/2h) coffee, while after the low glycemic index meal, it was 69% higher
with caffeinated
(1449 ~ 194 uIU/ml/2h) vs decaffeinated (85b ~ 148 uIIJ/ml/2h) coffee.
Similarly, C-peptide area
under the curve increased 54% with caffeinated (567 ~ 79 ng/ml/2h) vs
decaffeinated (369 ~ 48
ng/ml/2h) coffee after the high glycemic index meal and was 39% higher with
caffeinated (258 ~
42 ng/ml/2h) vs decaffeinated (185 ~ 12 ng/ml/2h) coffee after the low
glycemic index meal. The
increased insulin and C-peptide responses with caffeinated coffee occurred
with significantly
elevated blood glucose (p<0.05). Specifically, after the high glycemic index
meal, glucose area
under the curves were 186 ~ 46 and 14 ~ 20 mM/2h with caffeinated and
decaffeinated coffee,
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respectively, while after the low glycemic index meal, glucose results were 88
~ 23 and 5.3 ~ 14
mM/2h with caffeinated and decaffeinated coffee, respectively.
This study was the first to examine the effects of caffeine on blood glucose
management
using coffee and a more typical breakfast meal as opposed to pure caffeine and
an OGTT. The
results of the current study support our previous findings in that the
ingestion of caffeinated coffee
(equivalent to 5 mg caffeine per kg body weight) prior to a 75g carbohydrate
load (breakfast
cereal) resulted in impaired glucose management in lean, healthy males.
Overall, insulin, C-
peptide, and glucose responses were elevated and prolonged with caffeinated
coffee and either a
high or low glycemic index cereal. Furthermore, the results suggest that the
caffeine-induced
impairment in blood glucose management was more pronounced after ingestion of
the high
glycemic index cereal, which represents a very common type of breakfast cereal
consumed in the
general population.
Example 18: Effect of caffeine on blood glucose response to a high glycemic
index cereal in
young type 1 diabetics.
Young type 1 diabetics (5 females and 1 male) who had been diagnosed for an
average of
8.3 ~ 5.4 years volunteered to perform two trials in a randomized, double
blind study design.
Subjects were given either placebo or caffeine-containing (5 mg/kg) capsules
and 30 minutes later
they self-administered the appropriate amount of insulin for the ingestion of
60 g of carbohydrates
in the form of a high glycemic cereal with 125 ml of 1% milk. The amount of
self-administered
insulin and injection site were the same for both trials. Venous blood glucose
was measured prior
to capsule ingestion, prior to insulin injection, and immediately following
ingestion of the cereal
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meal (t = 0 minutes). Blood glucose was then measured every 15 minutes for the
next 2.5 hours.
The 72 % difference in the glucose area under the curve for the caffeine and
placebo trials (598 +
7.4 and 347 ~ 7.4 mM/2.5 h, respectively) were significantly different (p <
0.01). The results from
this study strongly suggest that caffeine ingestion caused a substantial
impairment in glucose
management which resulted in type 1 diabetics experiencing a high and
prolonged elevation in
blood glucose. These findings have important implications for type 1 diabetics
who consume
caffeine since individuals with type 1 diabetes lack the ability to produce
endogenous insulin and
thus must self-monitor their blood glucose levels and insulin requirements
throughout the day.
Example 19: The effect of caffeine on glucose and insulin responses in obese
individuals with
type 2 diabetes.
Obese (BMI = 32 ~ 1 kg/m2) type 2 diabetic males (n = 8, age = 46 ~ 2 year)
underwent
two OGTTs, with and without caffeine (5 mg/kg) one hour prior to ingestion of
75g of dextrose.
Subjects had an average glycosylated hemoglobin level of 7.8 ~ 0.1°Io,
had no diabetes-related
visual or renal complications, and were not taking insulin to control their
diabetes. Subjects were
required to abstain from caffeine-containing food and beverages, alcohol,
exercise and oral
hypoglycemic medication for 48 hours prior to each trial. Venous blood samples
were taken prior
to ingestion of caffeine or placebo (time = -60 minutes) and the 75 g glucose
load (t = 0 minutes)
with subsequent samples taken at t =15, 30, 60, 90, 120, 150 and 180 minutes
after glucose
ingestion. Based on our previous findings in obese males, the current protocol
with obese type 2
diabetic subjects was designed to monitor blood glucose levels (as well as
other blood
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metabolites) for an additional hour beyond the standard OGTT protocol we had
previously used
(i.e. 3 hour instead of 2 hour post glucose ingestion).
Average fasting blood glucose was 6.7 ~ 0.3 mM and there were no differences
between or
within trials in blood glucose levels prior to ingestion of the oral glucose
load. Ingestion of
caffeine resulted in significantly elevated (p< 0.05) blood glucose for the
last hour of the OGTT
(from 120 to 180 minutes following glucose ingestion) when compared with
placebo.
Furthermore, when subjects ingested caffeine, blood glucose remained
significantly elevated (p <
0.05) at 180 minutes following ingestion of the OGTT (8.4 ~ 0.8 vs 7.4 ~ 1.0
mM for caffeine and
placebo, respectively) compared with baseline values.
Thus, our study investigating the influence of caffeine followed by an OGTT in
obese type 2
diabetics suggests that caffeine ingestion leads to elevated and prolonged
blood glucose levels in
these individuals. This caffeine-induced effect on blood glucose levels is
comparable to our
previous findings in both lean and obese non-diabetic subjects and provides
further support for a
negative impact of caffeine on blood glucose management. Furthermore, we have
now
demonstrated that caffeine ingestion creates a situation (i.e hyperglycemia)
in which there are
greater demands on insulin secretion in those already experiencing insulin
resistance, such as
obese type 2 diabetics. Overall, our results suggest that an individual with
type 2 diabetes will
spend a prolonged period of time in a hyperglycemic state following ingestion
of caffeine and an
oral glucose load. This negative impact of caffeine may have important
implications since
prolonged hyperglycemia is associated with a variety of long-term
complications, such as
microvascular, renal and visual complications.
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Pharmaceutical compositions
Pharmaceutical compositions of the above compounds are used to treat patients
that are
obese and or have diabetes. Vehicles for delivering the compounds of the
present invention to
target tissues throughout the human body include saline and DSW (S%dextrose
and water).
Excipients used for the preparation or oral dosage forms of the compounds of
the present
invention include additives such as a buffer, solubilizer, suspending agent,
emulsifying agent
viscosity controlling agent, flavour, lactose filler, antioxidant,
preservative or dye. There are
preferred excipients for parenteral and other administration. These excipients
include serum
albumin, glutamic or aspartic acid, phospholipids and fatty acids.
The preferred formulation is in liquid form stored in a vial or an intravenous
bag. The
compounds of the present invention may also be formulated in solid or
semisolid form, for
example pills, tablets, creams, ointments, powders, emulsions, gelatin
capsules, capsules,
suppositories, gels or membranes.
Acceptable routes of administration include intravenous, oral, topical,
rectal, parenteral
(injectable), local, inhalant and epidural administration. The compositions of
the invention may
also be conjugated to transport molecules or included in transport modalities
such as vesicles and
micelles to facilitate transport of the molecules. Methods for the preparation
of pharmaceutically
acceptable compositions that can be administered to patients are known in the
art.
The compositions of the invention may also be conjugated to transport
molecules,
monoclonal antibodies or transport modalities such as vesicles and micelles
that preferentially
target recipient cells.
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Pharmaceutical compositions including the compounds of the present invention
can be
administered to humans and animals. Dosages to be administered depend on
individual patient
condition, indication of the drug, physical and chemical stability of the
drug, toxicity, the desired
effect and on the chosen route of administration. These pharmaceutical
compositions are used to
treat obesity and diabetes.
Although the invention has been described with preferred embodiments, it is to
be
understood that modifications may be resorted to as will be apparent to those
skilled in the art.
Such modifications and variations are to be considered within the purview and
scope of the
present invention.
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