Effects of soy protein isolate and soy peptide preload on gastric emptying rate and postprandial glycemic control in healthy humans.

BACKGROUND: This study aims to compare the effects of soy protein isolate (SPI) and soy peptide (PEP) preload 30 min before a 75-g oral glucose tolerance test (OGTT) on the gastric emptying rate, plasma insulin, and blood glucose responses. METHODS: Nine healthy young subjects were evaluated on four occasions. The participants consumed a 200-ml solution containing either 20 g of SPI or PEP in experiment 1. In experiment 2, 30 min after consuming either 20 g of SPI or PEP solutions, an OGTT was performed to evaluate the individual glycemic response. The gastric emptying rate was measured by the 13C-sodium acetate breath test. Blood glucose and plasma insulin were measured before and after consuming either the SPI or PEP solutions and during the OGTT. RESULTS: In experiment 1, plasma insulin levels were higher 30 min after consuming the PEP solution than after the SPI solution. PEP resulted in a faster gastric emptying rate than SPI. In experiment 2, just before performing the OGTT, the plasma insulin response was higher for PEP than for SPI. Fifteen minutes after starting the OGTT, the blood glucose response was lower after consuming PEP than after SPI. The gastric emptying rate tended to be faster after consuming PEP than after SPI (p = 0.08). CONCLUSION: A PEP preload might be slightly more effective for the suppression of postprandial blood glucose excursion compared with SPI; thus, a PEP preload potentially induces an enhanced insulin response just before the OGTT.

Effects of Unilateral Arm Warming or Cooling on the Modulation of Brachial Artery Shear Stress and Endothelial Function during Leg Exercise in Humans.

AIM: We examined the effect of modulating the shear stress (SS) profile using forearm warming and cooling on subsequent endothelial function in the brachial artery (BA) during exercise. METHODS: Twelve healthy young subjects immersed their right forearm in water (15 ℃ or 42 ℃) during a leg cycling exercise at 120-130 bpm for 60 min. The same exercise without water immersion served as a control. The BA diameter and blood velocity were simultaneously recorded using Doppler ultrasonography to evaluate the antegrade, retrograde, and mean shear rates (SRs, an estimate of SS) before, during, and after exercise. The endothelial function in the right BA was evaluated using flow-mediated dilation (FMD) (%) using two-dimensional high-resolution ultrasonography before (baseline) and 15 and 60 min after exercise. RESULTS: During exercise, compared with the control trial, higher antegrade and mean SRs and lower retrograde SRs were observed in the warm trial; conversely, lower antegrade and mean SRs and higher retrograde SRs were observed in the cool trial. At 15 min postexercise, no significant change was observed in the FMD from baseline in the warm (Δ%FMD: +1.6%, tendency to increase; p = 0.08) and control trials (Δ%FMD: +1.1%). However, in the cool trial, the postexercise FMD at 60 min decreased from baseline (Δ%FMD: -2.7%) and was lower than that of the warm (Δ%FMD: +1.5%) and control (Δ%FMD: +1.2%) trials. Accumulated changes in each SR during and after exercise were significantly correlated with postexercise FMD changes. CONCLUSION: Modulation of shear profiles in the BA during exercise appears to be associated with subsequent endothelial function.

Suppression of Oral Sweet Sensations during Consumption of Sweet Food in Humans: Effects on Gastric Emptying Rate, Glycemic Response, Appetite, Food Satisfaction and Desire for Basic Tastes.

Suppression of oral sweet sensation (OSS) acutely reduces intake of sweet-tasting food due to lower liking. However, little is known about other physiological responses during both the prandial and postprandial phase. Here, we explored the effects of Gymnema sylvestre (GS)-based suppression of OSS of several types of sweet-tasting food (muffin, sweet yogurt, banana) on gastric emptying, blood glucose (BG), plasma insulin (PI), appetite indices (hunger, fullness and prospective consumption), satisfaction and desire for tastes. Fifteen healthy subjects (22 ± 3 years, 9 women) took part in the study. Subjects rinsed their mouth with either GS solution or distilled water before eating the sweet-tasting food. Subjects felt decreased sweet taste intensity and reduced taste liking associated with GS rinsing after consuming each food, compared with rinsing with distilled water (p < 0.05). Gastric emptying, BG, PI and appetite indices during and after the prandial phase did not significantly change with GS rinsing compared to rinsing with distilled water (p > 0.05). Higher desire for sweet taste as well as lower satisfaction (p < 0.05) in the postprandial phase were observed with GS rinsing. These results suggest that the suppression of OSS does not affect gastric emptying, glycemic response and appetite during and after consumption of sweet-tasting food.

Acute effect of oral sensation of sweetness on celiac artery blood flow and gastric myoelectrical activity in humans.

Little is known about the effect of sweet taste stimulus on gastrointestinal motility and splanchnic blood flow. We examined whether gastric myoelectrical activity and/or celiac artery blood flow (CABF), which perfuses the stomach, are increased following an oral sensation of sweetness. After overnight fasting, 11 subjects rested for 5min and sipped, but not swallowed, one of four solutions for 1min. The fluid was then spat out, and subjects remained at rest for a further 10min. Fluids were approximately 15ml of three glucose solutions (4, 16, or 48%) or distilled water. Subjects completed trials with all four solutions in a randomized order. During each trial, gastric myoelectrical activity and CABF were continuously measured using electrogastrography and pulsed Doppler ultrasonography, respectively. None of the four solutions affected gastric myoelectrical activity. CABF was significantly increased after oral stimuli by all three glucose solutions, but not by water. There were no significant differences in the increments in CABF among the three glucose solutions. These results suggest that a sweet taste stimulus above a certain level of intensity acutely increases CABF during cephalic phase, without augmentation of gastric myoelectrical activity.

Effect of aerobic leg exercise training on subcutaneous adipose tissue of thigh in young Japanese women.

A one-legged training model was adopted to assess the influence of moderate-intensity exercise training on subcutaneous adipose tissue, especially focusing on the trained limb. Eight young sedentary Japanese women (ages 21-23 yr) participated in a 12-week training program. The leg was assigned randomly to trained or untrained limb. Each subject performed a supervised 60-min one-legged cycle ergometer training session three times a week. The exercise intensity was set at approximately 40% of peak VO(2) ("moderate" intensity, i.e., below the estimated lactate threshold), which was determined before training. Each subject performed a one-legged incremental cycle exercise test until exhaustion to determine the peak VO(2) of each leg (the trained and untrained legs being investigated separately). The areas of subcutaneous fat and the remaining nonfat tissues of the thigh were evaluated by our novel visualized measuring system based on ultrasonography. The fat cross-sectional areas of the trained and untrained thigh were not different after training (trained: 68.6+/-17.8 vs. untrained: 68.3+/-18.5 cm(2)). The non-fat (muscle and bone) area was also similar between the trained and untrained limb. In addition, there was no systematic influence of the training on the total and lean body mass. After training, the duration time of the one-legged cycle incremental exercise test by the trained leg was significantly improved unilaterally (trained: 1049+/-122 vs. untrained: 930+/-109 s, p<0.05) without any difference of peak VO(2). The results indicate that moderate one-legged aerobic training did not induce any compositional change in the trained thigh; rather, what did improve were certain peripheral factor alone relating to endurance.

Autonomic nervous activities assessed by heart rate variability in pre- and post-adolescent Japanese.

There are many studies with respect to the age-related change of the characteristics of beat-to-beat heart rate variability (HRV), reflected by cardiac autonomic control, especially focusing on adulthood (i.e., aging related to the incidence of metabolic syndrome) in Japanese individuals. However, it is not still clear how basic control matures during childhood. This study was, therefore, designed to explore the HRV characteristics of pre- and post-adolescent Japanese, in a cross-sectional manner. Resting HRV data was recorded in a relaxing supine position from 136 healthy individuals between 8 and 20 years (48 boys between 8 and 14 years; 88 girls between 8 and 20 years) who were instructed to breathe periodically (0.25 Hz). Frequency-domain analysis (i.e., the spectral analysis based on an autoregressive model) of short-term, stationary R-R intervals was performed to evaluate the low- (LF; below 0.15 Hz) and high- (HF; 0.15-0.40 Hz) frequency powers. The HF to total power represents the vagal control of heart rate (PNS indicator), and the ratio of LF to HF (LF/HF) is considered to relate to the sympathetic modulations (SNS indicator). Both PNS and SNS indices had substantially no effect from age and/or gender in the range between 8 and 20 years. In conclusion, the control of the cardiac autonomic nervous system in Japanese seems already to be compatible with that in adulthood before approximately 10 years. In other word, the cardiac autonomic modulation would presumably be maturated before the age of approximately 7-8 years, though further research is awaited.