Richard T. Tulley

Dietary resistant starch upregulates total GLP-1 and PYY in a sustained day-long manner through fermentation in rodents.

Glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are anti-diabetes/obesity hormones secreted from the gut after meal ingestion. We have shown that dietary-resistant starch (RS) increased GLP-1 and PYY secretion, but the mechanism remains unknown. RS is a fermentable fiber that lowers the glycemic index of the diet and liberates short-chain fatty acids (SCFAs) through fermentation in the gut. This study investigates the two possible mechanisms by which RS stimulates GLP-1 and PYY secretion: the effect of a meal or glycemic index, and the effect of fermentation. Because GLP-1 and PYY secretions are stimulated by nutrient availability in the gut, the timing of blood sample collections could influence the outcome when two diets with different glycemic indexes are compared. Thus we examined GLP-1 and PYY plasma levels at various time points over a 24-h period in RS-fed rats. In addition, we tested proglucagon (a precursor to GLP-1) and PYY gene expression patterns in specific areas of the gut of RS-fed rats and in an enteroendocrine cell line following exposure to SCFAs in vitro. Our findings are as follows. 1) RS stimulates GLP-1 and PYY secretion in a substantial day-long manner, independent of meal effect or changes in dietary glycemia. 2) Fermentation and the liberation of SCFAs in the lower gut are associated with increased proglucagon and PYY gene expression. 3) Glucose tolerance, an indicator of increased active forms of GLP-1 and PYY, was improved in RS-fed diabetic mice. We conclude that fermentation of RS is most likely the primary mechanism for increased endogenous secretions of total GLP-1 and PYY in rodents. Thus any factor that affects fermentation should be considered when dietary fermentable fiber is used to stimulate GLP-1 and PYY secretion.

Effects of Resistant Starch, A Non-digestible Fermentable Fiber, on Reducing Body Fat

Objective: To assess the effects of energy dilution with non‐fermentable and fermentable fibers on abdominal fat and gut peptide YY (PYY) and glucagon‐like peptide (GLP)‐1 expressions, three rat studies were conducted to: determine the effects of energy dilution with a non‐fermentable fiber, compare similar fiber levels of fermentable and non‐fermentable fibers, and compare similar metabolizable energy dilutions with fermentable and non‐fermentable fibers.

Effects of caffeine ingestion on metabolism and performance during graded exercise

SummarySeven trained men were studied during graded cycle ergometer exercise to assess the effects of caffeine ingestion on metabolism and performance. A single blind experimental procedure was followed with one trial being performed 60 min after the subject ingested caffeine (5 mg·kg−1) while the second trial required the subject to ingest a placebo with the treatment order being counterbalanced. Subjects began exercising at a work load of 30 W while the load was increased by an additional 30 W every 3 min until the subject could not maintain the desired pedal frequency. Venous blood samples were obtained at each work load and assayed for free fatty acids (FFA), glycerol, lactic acid, and caffeine. There was no significant difference (p>0.05) in time to exhaustion between the two experimental treatments. Resting measurements of FFA and glycerol showed that ingestion of caffeine brought about significant (p<0.05) increases in plasma levels of both FFA and glycerol compared to values obtained during the placebo treatment. The rate of blood lactic acid accumulation was not significantly different (p>0.05) between the two exercise tests. These data suggest that a small dose of caffeine does not change the rate of blood lactate accumulation nor does it enhance performance during graded cycle ergometer exercise.

The effects of caffeine on graded exercise performance in caffeine naive versus habituated subjects.

SummaryThe physiological effects of caffeine on subjects habituated to caffeine is relatively unstudied compared to those of caffeine naive subjects during graded exercise. Thus, the purpose of this investigation was to determine the effects of caffeine on maximal oxygen consumption (VO2max) and the anaerobic threshold in these two populations. Seventeen moderately trained males were classified according to caffeine usage: (1) caffeine consumption 25 mg·day−1 or less (CN) (n=8) or (2) caffeine consumption above 300 mg·day−1 (CH) (n=9). The subjects were tested post-absorptive on the same cycle ergometer on three occasions with 7 days separating the tests. One hour before each test the subject ingested either a gelatin capsule (C); 3 mg·kg−1 body weight of caffeine (C3); or 5 mg·kg−1 body weight of caffeine (C5). The subject then performed an incrementalVO2max test beginning at 50 W and the work rate was increased 30 W every 2 min until the subject could not maintain the power output. Serial venous blood samples were drawn over 30 s at the end of each stage. The CN group significantly increased resting heart rate (fc) and expired ventilation volume (VE) after C3 and C5 andVO2 after C5. No significant differences were found for exerciseVE,VO2, respiratory excharge ratio,fc or time to exhaustion. There were no significant differences (P < 0.05) in the lactate threshold or the ventilatory threshold between treatment in either group. The CH subjects showed a significant increase (P<0.05) in resting plasma free fatty acid (FFA) concentration only during the C3 and C5 treatments. Plasma FFA levels were significantly increased (P < 0.05) at all times during C3 and C5 treatment in the CN subjects when compared to the control values. These data indicate that caffeine has no effect onVO2max or the anaerobic threshold seen during incremental, graded exercise. However, resting metabolism and ventilation, and both resting and exercise plasma FFA are increased in CN subjects.

Dietary resistant starch increases hypothalamic POMC expression in rats.

Resistant starch (RS) is fermentable dietary fiber. Inclusion of RS in the diet causes decreased body fat accumulation and altered gut hormone profile. This study investigates the effect of feeding RS on the neuropeptide messenger RNA (mRNA) expressions in the arcuate nucleus (ARC) of the hypothalamus and whether vagal afferent nerves are involved. The rats were injected intraperitoneally with capsaicin to destroy unmyelinated small vagal afferent nerve fibers. The cholecystokinin (CCK) food suppression test was performed to validate the effectiveness of the capsaicin treatment. Then, capsaicin‐treated rats and vehicle‐treated rats were subdivided into a control diet or a RS diet group, and fed the corresponding diet for 65 days. At the end of study, body fat, food intake, plasma peptide YY (PYY) and glucagon‐like peptide 1 (GLP‐1), and hypothalamic pro‐opiomelanocortin (POMC), neuropeptide Y (NPY), agouti‐related peptide (AgRP) gene expressions were measured. RS‐fed rats had decreased body fat, increased POMC expression in the hypothalamic ARC, and elevated plasma PYY and GLP‐1 in both the capsaicin and vehicle‐treated rats. Hypothalamic NPY and AgRP gene expressions were not changed by RS or capsaicin. Therefore, destruction of the capsaicin‐sensitive afferent nerves did not alter the response to RS in rats. These findings suggest that dietary RS might reduce body fat through increasing the hypothalamic POMC expression and vagal afferent nerves are not involved in this process. This is the first study to show that dietary RS can alter hypothalamic POMC expression.

Fluid replacement drinks during high intensity exercise effects on minimizing exercise-induced disturbances in homeostasis

SummaryThe purpose of these experiments was to examine the influence of various fluid replacement drinks on exercise-induced disturbances in homeostasis during heavy exercise. Nine trained cyclists performed constant load exercise on a cycle ergometer to fatigue on three occasions with 1-week separating experiments. The work rate was set initially at ∼ 85% of

Normolipidemic Subjects With Low HDL Cholesterol Levels Have Altered HDL Subpopulations

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High-amylose resistant starch increases hormones and improves structure and function of the gastrointestinal tract: a microarray study.

(range 82–88%) with fatigue being defined as a 10% decline in power output below the initial value. During each experiment subjects consumed one of the following three beverages prior to and every 15 min during exercise: (1) non-electrolyte placebo (NEP; 31 mosmol · kg−1); (2) glucose polymer drink containing electrolytes (GP; 7% CHO, 231 mosmol · kg−1), and (3) electrolyte placebo drink without carbohydrate (EP; 48 mosmol · kg−1). Both the GP and EP beverage contained sodium citrate/citric acid (C) as a flavoring agent while C was not contained in the NEP drink. Although seven of nine subjects worked longer during the GP and EP treatment when compared with the NEP trial, the difference was not significant (P>0.05). No differences (P>0.05) existed between the GP and EP treatments in performance time. Exercise changes in rectal temperature, heart rate, Δ % plasma volume and plasma concentrations of total protein, free fatty acids, glucose, lactate, potassium, chloride, calcium, and sodium did not differ (P>0.05) between trials. In contrast, blood hydrogen ion concentration [H+] was significantly lower (P<0.05) at 30 min of exercise during the GP and EP treatment when compared with the NEP run. These data provide evidence that electrolyte drinks do not minimize exercise-induced disturbances in blood-electrolyte concentrations during heavy execrcise when compared with nonelectrolyte drinks; however, these results suggest that fluid replacement beverages containing buffers (i.e. C) and/or electrolytes may minimize blood alterations in [H+] during intense exercise. Additional research is required to determine if the buffering influence of these beverages has an ergogenic benefit during heavy exercise.