The Effects of Niacin and Aerobic Exercise in Postmenopausal Women Glucose, Insulin and C-Peptide Profiles

Downloa

Influence of Caloric Expenditure on Postprandial Triglyceride and Glucose Responses Following a High-Carbohydrate Meal

Purpose: To examine the effects of aerobic exercise expending 350 and 700 kcal of energy on postprandial triglyceride (Tg) and glucose responses following a high carbohydrate (CHO) meal. Methods: Non-active individuals (n=9 women/4 men; age=22.8±3.7 yrs; Ht=169±10.4 cm; Wt=75.7± 22.4 kg; BMI=26.1±5.8 kg/m2; VO2 max=34.1±6.9 ml/kg/min) completed three trials in a random order: 1) control trial, 2) single exercise session expending 350 kcal (EX350), and 3) single exercise session expending 700 kcal (EX700). Exercise consisted of treadmill walking at 60% VO2 max until 350 and 700 kcal of energy had been expended. The control session consisted of seated rest. The morning after each experimental session, a fasting (12hr) blood sample was collected followed by consumption of a high-CHO liquid meal (2.44 g/kg of fat free mass (CHO), 0.33 g/kg FFM fat, and 0.56 g/kg FFM protein. Blood was collected again at 1, 2, 3, 4, 5, and 6 hrs post-meal and analyzed for (Tg) and glucose concentrations. The areas under the curve (AUC) were calculated for both (Tg) and glucose concentrations. A repeated measures ANOVA was used to determine statistical significance (p\u3c0.05). Results: Baseline glucose concentrations were not different between trials (p=0.71). Postprandial AUC for glucose concentrations were not different between trials (p=0.38). Baseline Tg concentrations were not altered with exercise (p=.94) of 350 kcal (102.7±77.1 mg/dl) or 700 kcal (112.2±80.6 mg/dl) when compared with rest (115.3±113.9 mg/dl). Postprandial Tg concentrations following rest (937.3± 928.4 mg/dl) were not altered (p=0.37) following exercise of 350 kcal (807.1±605.1 mg/dl) or 700 kcal (867.3±672.6). Conclusion: The glucose and Tg responses following a high-CHO meal were unaffected by a prior exercise session. These results are in contrast to previous investigations that have used high-fat test meals demonstrating that a single bout of exercise reduces the postprandial Tg response. Substantial inter-subject variability was seen in the postprandial Tg responses following exercise ranging from reductions of 27.4% to increments of 17.4%. This study was supported by Texas Woman’s University’s Research Enhancement Program

Effect of Omega-3 Fatty Acids on Lipoprotein Profile and Particle Size in Hispanic Women

The effect of increased Ω3 fatty acids on lipoprotein sub-fractions has not been well studied in Hispanic women, a group with a high prevalence of dyslipidemia and metabolic syndrome. The purpose of this randomized, placebo-controlled trial was to examine the effect of a 90-day (90D) combined EPA+DHA supplementation on lipoprotein profiles of Hispanic women. Twenty-seven non-diabetic women were randomly assigned to the Ω3 group (n=17, 1.9 g/day EPA+DHA) or the placebo group (n=10, 2 g/day oleic acid). At baseline (0D) and 90D a fasting blood sample was drawn for determination of lipoprotein profile and lipoprotein particle sub-fractions. For the Ω3 group, total cholesterol increased 6.5%, triglycerides were reduced 14.8%, LDL concentration increased 5.6%, and total LDL particle size concentration increased 8.2% (P \u3c 0.05). Large LDL particle size concentration increased 16% from 0D to 90D, this change was not significant (P = 0.051). At 90D, total cholesterol, LDLs, and LDL particle concentration were higher in the Ω3 group compared to placebo (P \u3c 0.05). Omega-3 supplementation resulted in reduced plasma TGs and an increase in large LDL particle size concentration, yet had no effect on HDL particle size or concentration. Further research is necessary to examine the effects of increased Ω3 fatty acid intake in Hispanic women on dyslipidemia and related co-morbidities

The Influence of Dietary Sugars and Acute Exercise on Postprandial Triglyceride and Glucose Concentration

Purpose: Examine the effects of prior aerobic exercise on postprandial triglyceride (PPTG) and glucose concentration following a mixed liquid meal (LM) made with either glucose or fructose sugars. Methods: Sedentary pre-menopausal women (n=16; age=28.2±6.1yrs; Wt. = 61.2±10.5kg; BMI= 23.2±2.9 kg/m2; VO2 max =30.8±4.2 ml/kg/min) completed four trials in random order: 1) Control-Fructose, 2) Control-Glucose, 3) Exercise-Fructose, 4) Exercise-Glucose. Exercise consisted of treadmill walking at 65% VO2 max expending 500 calories. Control consisted of resting in the laboratory for approximately 1 hour. Trials were completed 15 hours prior to the LM. The morning after each trial, a fasting (12hr) blood sample was collected followed by the consumption of the LM providing approximately 20 kcal/kg fat-free mass with a macronutrient composition of 55% carbohydrate, 15% protein, and 30% fat. The LM was blended with whole milk and ice cream plus a glucose or fructose powder. The glucose and fructose powder accounted for half of the total carbohydrate content within the LM. Blood was collected again at 0.5, 1, 1.5, 2, 3, 4, 5, and 6 hours post-LM and analyzed for TG and glucose concentration. The areas under the curve (AUC) were calculated for both TG and glucose concentration using the trapezoidal method. A repeated measures ANOVA was used to determine statistical significance (p-1•6hr-1) when compared to the three other trials (Rest-Fructose: 856.5±309.9 mg•dl-1•6hr-1, Exercise-Fructose: 838.0±324.5 mg•dl-1•6hr-1, and Rest-Glucose: 862.1±339.4 mg•dl-1•6hr-1), respectively. No differences in the TG AUC were reported between the other three trials. Glucose AUC was unchanged between the trials (p = .19; Control-Fructose = 660.4 ± 67.2 mg•dl-1•6hr-1; Exercise-Fructose = 636.3 ± 74.8 mg•dl-1•6hr-1; Control-Glucose = 633.3 ± 91.4 mg•dl-1•6hr-1; Exercise-Glucose = 633.3 ± 72.6 mg•dl-1•6hr-1). Discussion: The PPTG AUC was smaller following the Exercise-Glucose trial only. Investigations have reported that glucose supplemented into a meal lowers PPTG AUC when compared to fructose. Acute exercise has been reported to lower PPTG AUC following the ingestion of an extremely high-fat or high-carbohydrate meal. Most postprandial investigations using mixed meals have reported no change in glucose AUC following acute exercise. This study was funded by Texas Woman’s University and the Texas Chapter of the American College of Sports Medicine

Effects of Competition on Performance and Physiological Responses in Female Athletes

Competition can increase an athlete’s performance. The competitive drive frequently displayed by athletes may not exist if athletes are unaware of the competition. The purpose of this study is to determine if performance is improved when the athlete is not informed of the competitive setting. Eighteen college-aged females were recruited. All participants were current or former college or high school athletes (age: 20.9 ± 1.8 yrs., HT: 172 ± 6.7 cm, WT: 68.1 ± 9.9 kg). Athletes were blinded to the purpose of the study. Prior to participation in experimental trials, athletes’ maximal oxygen consumption (VO2max: 41.0 ± 5.4 mL/kg/min; HRmax: 189 ± 9 b/p) was measured on a treadmill and they also performed a 20 min time trial for familiarization. In a balanced cross-over design, the athletes performed two 20 min time trials on separate days. The control trial (CT) was performed with only one athlete running. The competition trial (COMP) consisted of two athletes matched for VO2max (≤ 5 mL·minˉ¹·kgˉ¹), running on treadmills that were side by side. The athletes were not informed that they were competing with the other athlete during COMP. Overall distance, peak HR, and peak RPE were compared between CT and COMP using a paired samples t-test (

Dose Effect of Whey Protein on Gut Hormone Responses in Pre-Diabetics and Type 2 Diabetics

GLP-1 and GIP have been shown to increase following a 50 g dose of whey protein prior to a high glycemic load in type 2 diabetics. However, this increase is reduced in diabetics compared to healthy individuals. Pancreatic polypeptide (PP) and peptide tyrosine tyrosine (PYY) also increase, while ghrelin decreases after the consumption of whey protein; however, it is not known if a similar hormone response occurs with a lower dose of whey protein prior to a glycemic load or if there is a dose effect. Our hypothesis was that 20 g and 30 g of whey protein would increase GLP-1, GIP, PP, and PYY and decrease ghrelin in a dose dependent manner. PURPOSE: The purpose of this study was to examine the effect of two different doses of whey protein ingested 30 min prior to a 50 g OGTT on gut hormone and incretin response. METHODS: Nine diabetic and pre-diabetic participants (n=9, mean ± SD; age: 64.3 + 8.1 yrs.; BMI: 29.4 + 6.0 kg/m2; HbA1c: 6.4 + 0.6%) completed three trials. The randomly assigned trials consisted of: ingestion of 250ml of water (CON); 250 ml of water + 20 g whey (20g); 250ml of water + 30 g whey (30g), prior to completing a 50 g OGTT. Blood was collected at -30, 0, 15, 30, 60, 90, 120, and 150 min for the measurement of GIP, GLP-1, ghrelin, PP, and PYY. The whey protein was administered immediately following the -30 min and the 50 g OGTT began immediately after the 0 min blood draw. Metabolites were measured using multiplex fluorescent detection. One-way repeated measure ANOVA was used for statistical analysis for each dependent variable (P \u3c 0.05). RESULTS: 20g and 30g of whey protein significantly increased incremental area under the curve (AUC) of GIP 32% and 38% compared to CON. 30g significantly decreased ghrelin AUC -13.9% and -20% compared to 20g and CON. 30g significantly increased PP AUC 28% compared to CON only. There were no differences in ghrelin and PP AUC between 20g and CON. There were no significant differences for GLP-1 and PYY between all trials. CONCLUSION: 30 g of whey protein prior to a glucose challenge increased secretion of GIP and PP and decreased ghrelin in type 2 and pre-diabetics. There seems to be a dose effect relationship between whey, ghrelin, and PP. 30 g of whey preload may induce insulinotropic and satiety effects from GIP, PP, and ghrelin responses in type 2 and pre-diabetics

The Dose Effect of Whey Protein on Insulin Responses in Pre-Diabetics and Type 2 Diabetics

People with pre-diabetes and type 2 diabetes have shown an increase in insulin secretion after ingesting 55 g of whey protein coupled with a glycemic challenge. However, the effect of lower amounts of whey protein on insulin responses remains unclear. Our hypothesis was that both 20 g and 30 g of whey consumption prior to an oral glucose tolerance test (OGTT) would produce an increase in insulin secretion, with 30 g producing the greatest increase compared to a control. PURPOSE: The purpose of this study was to examine the effect of two different doses of whey protein ingested 30 min prior to a 50 g OGTT on glucose, insulin, C-peptide, and glucagon responses. METHODS: Diabetic or pre-diabetic participants (n=9, mean ± SD; age: 64.3 + 8.1 yrs; BMI: 29.4 + 6.0 kg/m2; body fat percentage: 42.5 + 7.8 %; fasting plasma glucose: 6.9 + 1.2 mmol/l; HbA1c: 6.4 + 0.6 %) completed three trials. The randomly assigned trials consisted of: 250 ml of water (CON), 250 ml of water + 20 g whey (20g), and 250 ml of water + 30 g whey (30g), followed by an OGTT. Blood was collected at -30, 0, 15, 30, 60, 90, 120, and 150 min for the measurement of glucose, insulin, C-peptide, and glucagon. The whey protein mixture was administered immediately following the -30 min blood draw, and the 50 g OGTT began immediately following the 0 min blood draw. Glucose was analyzed using a YSI 2900D glucose analyzer and insulin, C-peptide, and glucagon were measured via multiplex fluorescent detection (MagPix). A one-way repeated measures ANOVA (pRESULTS: Incremental area under the curve (AUC) for glucose presented no difference between the 3 trials. Insulin AUC was significantly increased from CON to 20g (p=0.004, 36.3%), CON to 30g (p=0.002, 61.7%), and 20g to 30g (p=0.030, 18.6%). C-peptide and glucagon AUC significantly increased from CON to 20g (p=0.018, 20.6%; p=0.046, 33.1%) and CON to 30g (p=0.001, 30.1%; p=0.017, 33.7%). CONCLUSION: Whey protein elicited a dose response on plasma insulin, increasing concentrations from CON to 20g, and 20g to 30g, however plasma glucose was unaffected. 20g and 30g displayed similar responses for glucagon. Neither 20 g nor 30 g of whey protein may be adequate to provide glycemic improvement in the disease management of type 2 or pre-diabetes

High Intensity Interval Exercise Does Not Influence Overnight GH Secretion in Overweight Sedentary Young Women

Exercise and sleep are the two major factors that influence growth hormone (GH) secretion and it has been well established that there is a strong positive relationship between exercise intensity and GH release. This dose-dependent response may also be correlated with the lactate response to exercise, with steady-state exercise intensities above the lactate threshold eliciting a greater GH pulse. It has yet to be determined, however, if high-intensity interval exercise (HIE) can influence overnight pulsatile GH secretion, which accounts for the majority of daily GH release. PURPOSE: To determine if HIE significantly increased overnight GH secretion compared to continuous moderate-intensity exercise (MOD), or no exercise (CON) in young women. METHODS: Five young, sedentary women (mean ± SD age: 22.6 ± 1.3 y; BMI: 27.4 ± 3.1 kg/m2; body fat: 39.2 ± 1.7 %; VO2max: 29.4 ± 5.7 mL/kg/min) were studied on three different occasions during the follicular phase of their menstrual cycle (CON: no exercise; MOD: 30-min of continuous cycling at 50% of peak power determined from the VO2max test; and HIE: 4 30-s “all-out” sprints at a resistance equal to 6.5% body mass with 4.5-min recovery. Each trial was randomly assigned and separated by a minimum of one month. For each visit, participants reported to the lab at 1700h, exercised from 1730h – 1800h, and remained in the lab until 0700h the following morning. The overnight GH secretory profile of each trial was determined from 10-min sampling of venous blood from 1730h – 0600h (12.5 h) using deconvolution analysis. RESULTS: Mean power output during MOD was 80.6 ± 6.3 W (68.2 ± 9.7 %VO2max). Estimated exercising energy expenditure for MOD (145.1 ± 11.2 kcal) was significantly lower than HIE (204.5 ± 15.5 kcal, P = 0.002). Peak lactate was significantly higher during MOD (4.7 ± 0.9 mmol/L) compared to CON (0.9 ± 0.2 mmol/L, P = 0.002) and was highest during HIE (11.2 ± 2.1 mmol/L) compared to MOD (P \u3c 0.001) and CON (P \u3c 0.001). Calculated GH AUC (0 – 120 min) was significantly greater in HIE (1018.2 ± 576.1 ng· min/mL) than CON (181.7 ± 138.9 ng· min/mL, P = 0.009), but not MOD (544.7 ± 160.7 ng· min/mL). Overnight GH production rate (ng/mL/min) determined by deconvolution analysis was not significantly different between CON (1040.3 ± 242.0), MOD (1429.2 ± 206.0), and HIE (1831.2 ± 873.8, P = 0.107). Other GH secretory variables: basal GH concentration (ng/mL), number of GH peaks, GH pulse amplitude and mass, and interpulse interval were not different between the three trials. CONCLUSION: For these untrained, overweight sedentary young women, a single bout of exercise was insufficient to significantly affect overnight pulsatile GH secretion. Adiposity is a negative determinant of GH secretion, and the GH response to exercise in these women was extremely variable. Aerobic fitness, prior training, as well as several metabolic factors associated with obesity (e.g., increased insulin and circulating free fatty acids) can also influence GH secretion and should be taken into account as potential mediators of the GH response to exercise

Physiological Responses to a 60-Minute Zumba® Class in College Age Females

Zumba® is a group exercise format that incorporates aerobic dance components and claims to be an appropriate physical activity to be included in an exercise prescription for improving cardiorespiratory fitness. The purpose of this study was to determine the energy expenditure and physiological effects of a 58.6 min Zumba® class and compare the average METs of the Zumba® class to the ACSM’s definition of vigorous activity of 6 METs. All participants (n=30) were volunteers from Zumba® classes at Texas Woman’s University. Participants attended three Zumba® classes to become familiar with the choreography. The Zumba® session where data was collected was performed in a standard class setting identical to the three familiarization classes. The Zumba® class was composed of 16 songs corresponding to a specific set of choreography. The Zumba® class was divided into a warm up phase, aerobic phase, and cool down phase. Oxygen consumption (VO2) was measured using a K4b2 Cosmed unit that the participant wore during the Zumba® class. A one sample t test was used to determine if there was a significant difference between the METs of the Zumba® class and 6 METs. A repeated measures ANOVA, with a Bonferroni post-hoc test, was used to determine if there was a significant difference between variables in the three phases of the Zumba® class. Significance level was set at p ≤ .05. Mean METs for the full Zumba® class (5.7 ± 1.8 METs) was not significantly different (p \u3c 0.05) from 6 METs. The HR during the aerobic phase (164 ± 12 bpm) was significantly higher (p \u3c 0.05) than the warm up (148 ± 25 bpm) and cool down phase (139 ± 20 bpm). Similarly, %HRmax was highest in the aerobic phase relative to warm up and cool down (83.7 ± 6.1% vs 75.2 ± 12.6% and 71.0 ± 10.4%, p \u3c 0.05, respectively). The cool down phase had a significantly lower (p \u3c 0.05) VO2 and energy expenditure (14.7 ± 4.9 ml/kg/min and 5.0 ± 1.3 kcal/min, respectively) than the warm up (20.2 ± 7.0 ml/kg/min and 6.8 ± 2.1 kcal/min) and aerobic phases (21.0 ± 6.8 ml/kg/min and 7.2 ± 1.9 kcal/min). Based on these results, Zumba® meets the ACSM Guidelines for the minimum recommendation for aerobic exercise intensity as a moderate intensity (3-6 METs) exercise

The Effect of Repeated 40 Meter Sprint Trials on Salivary Cortisol in Elite Youth Female Soccer Players

The outcome of an intense exercise session is a stress response, potentially resulting in an increase in circulating cortisol. The acute cortisol response due to intense exercise may vary when comparing elite youth athletes and may not be noticeable in athletic performance. PURPOSE: The purpose of this study was to compare salivary cortisol responses between older (17-19 yo) and younger (11-13 yo) elite female soccer players after repeated 40m sprint trials. METHODS: All participants (n=8) were current United States Soccer Federation Development Academy players. Participants were placed into young (n=4, mean ± SD; age 12 ± 0 yrs; weight 48.3 ± 10.0 kg) and older (n=4, mean ± SD; 17 ± 1 yrs; weight; 60.2 ± 7.1 kg), and completed 3 trials. The control day (CON) consisted of collection of 2ml saliva samples at 0, 30 and 60 min, while participants sat quietly. Sprint Day 1 (SD1) and Sprint Day 2 (SD2) consisted of collection of a baseline saliva sample prior to sprinting, followed by ten 40m sprints with 30 seconds rest between sprints. On SD1 and SD2, additional saliva samples were then collected, immediately, 15, 30, 45, and 60 min following the last sprint. Sprint time (ST) was also recorded for each 40m sprint. Salivary cortisol (SC) levels were determined through enzyme-linked immunosorbent assay (ELISA) with sensitivity range RESULTS: There was a significant overall interaction between age and treatment days (F(2,12) = 4.586, p=0.033). An increase from CON to SD1 in the young group SC AUC (65.69%) was followed by an increase from SD1 to SD2 (46.66%). The older group increased SC AUC from CON to SD1 (157.52%) but decreased from SD1 to SD2 (-25.28%). There was a significant interaction between age and SC AUC (F(1,6) = 11.521, p=0.015) from SD1 and SD2. Additionally, ST did not significantly change, on either day, from sprint 1 to 10 in either group (F(1,6) = 1.075, p=0.34). CONCLUSION: The salivary cortisol response appears to differ in these elite athletes. Based on SC, the stress response in the mature youth athletes appears to decline, where the younger youth athlete appears to have an increase in the stress response to repetitive intense exercise. The physiological responses may not be outwardly observable as athletic performance, as sprint time values did not differ between the groups