Effects of straight alkyl chain, extra hydroxylated alkyl chain and branched chain amino acids on gastric emptying evaluated using a non-invasive breath test in conscious rats

A High Amylose Wheat Diet Improves Gastrointestinal Health Parameters and Gut Microbiota in Male and Female Mice

High amylose wheat (HAW) contains more resistant starch than standard amylose wheat (SAW) and may have beneficial effects on gastrointestinal health. However, it is currently unclear whether these effects differ according to the level of HAW included in the diet or between males and females. Male and female C57BL/6 mice (n = 8/group/sex) were fed SAW65 (65% SAW; control), HAW35 (35% HAW), HAW50 (50% HAW) or HAW65 (65% HAW) diet for eight weeks. Female but not male, mice consuming any amount of HAW exhibited accelerated gastric emptying compared to SAW65 group. In both sexes, relative colon weights were higher in the HAW65 group compared to SAW65 group and in females, relative weights of the small intestine and cecum were also higher in the HAW65 group. In females only, colonic expression of Pyy and Ocln mRNAs were higher in the HAW65 group compared to HAW35 and HAW50 groups. In both sexes, mice consuming higher amounts of HAW (HAW50 or HAW65) had increased fecal bacterial load and relative abundance of Bacteroidetes phylum and reduced relative abundance of Firmicutes compared to SAW65 group. These data are consistent with a beneficial impact of HAW on gastrointestinal health and indicate dose-dependent and sex-specific effects of HAW consumption.

The Effect of Isoleucine Supplementation on Body Weight Gain and Blood Glucose Response in Lean and Obese Mice

Chronic isoleucine supplementation prevents diet-induced weight gain in rodents. Acute-isoleucine administration improves glucose tolerance in rodents and reduces postprandial glucose levels in humans. However, the effect of chronic-isoleucine supplementation on body weight and glucose tolerance in obesity is unknown. This study aimed to investigate the impact of chronic isoleucine on body weight gain and glucose tolerance in lean and high-fat-diet (HFD) induced-obese mice. Male C57BL/6-mice, fed a standard-laboratory-diet (SLD) or HFD for 12 weeks, were randomly allocated to: (1) Control: Drinking water; (2) Acute: Drinking water with a gavage of isoleucine (300 mg/kg) prior to the oral-glucose-tolerance-test (OGTT) or gastric-emptying-breath-test (GEBT); (3) Chronic: Drinking water with 1.5% isoleucine, for a further six weeks. At 16 weeks, an OGTT and GEBT was performed and at 17 weeks metabolic monitoring. In SLD- and HFD-mice, there was no difference in body weight, fat mass, and plasma lipid profiles between isoleucine treatment groups. Acute-isoleucine did not improve glucose tolerance in SLD- or HFD-mice. Chronic-isoleucine impaired glucose tolerance in SLD-mice. There was no difference in gastric emptying between any groups. Chronic-isoleucine did not alter energy intake, energy expenditure, or respiratory quotient in SLD- or HFD-mice. In conclusion, chronic isoleucine supplementation may not be an effective treatment for obesity or glucose intolerance.

Influence of amino acids on gastric adaptive relaxation (accommodation) in rats as evaluated with a barostat

Aim: The present study aimed to evaluate the effects of selected straight alkyl chain, hydroxylated chain and branched chain amino acids on gastric adaptive relaxation, as these have previously been shown to have differing effects on gastric emptying. Materials and Methods: Gastric adaptive relaxation was evaluated using a barostat in rats under urethane anesthesia. The pressure within the balloon, introduced from the mouth to the stomach, was changed stepwise from 1 to 8 mmHg. The increased volume just after the increase of balloon pressure was defined as distension-induced gastric adaptive relaxation (accommodation). Amino acids were administered orally or intravenously. Results: As compared with control rats administered with distilled water, those rats that were orally administered amino acids having straight alkyl chain and extra hydroxylated alkyl chain, such as glycine and l-serine, had significantly enhanced gastric adaptive relaxation, but administration of l-alanine and l-threonine did not. Branched chain amino acids, such as l-isoleucine, l-leucine and l-valine, also did not significantly influence gastric adaptive relaxation. Glycine and l-serine showed the same efficacy when administered intravenously. Conclusion: Among the amino acids evaluated in the present study, glycine and l-serine significantly enhanced gastric adaptive relaxation, suggesting that short alkyl chain amino acids may enhance gastric adaptive relaxation as compared with the other amino acids. These findings may suggest that glycine and l-serine would be useful in the therapy of functional dyspepsia, especially for early satiety, because the dysfunction of adaptive relaxation is one of the causes of early satiety.

Correlation Between Gastric Emptying and Gastric Adaptive Relaxation Influenced by Amino Acids

Background/Aims

Amino acids have many physiological activities. We report the correlation between gastric emptying and gastric adaptive relaxation using tryptophan and amino acids with a straight alkyl chain, hydroxylated chain, and branched chain. Here we sought to further clarify the correlation between gastric emptying and gastric adaptive relaxation by using other amino acids.

Methods

In Sprague-Dawley rats, gastric emptying was evaluated by a breath test using [1-¹³C] acetic acid. The expired ¹³CO₂ pattern, T_max, C_max, and AUC_120min values were used as evaluation items. Gastric adaptive relaxation was evaluated in a barostat experiment. Individual amino acids (1 g/kg) were administered orally 30 minutes before each breath test or barostat test.

Results

L-phenylalanine and L-tyrosine did not influence gastric emptying. All other amino acids, ie, L-proline, L-histidine, L-cysteine, L-methionine, L-aspartic acid, L-glutamic acid, L-asparagine, L-arginine, L-glutamine, and L-lysine significantly delayed and inhibited gastric emptying. L-Cysteine and L-aspartic acid significantly enhanced and L-methionine and L-glutamine significantly inhibited gastric adaptive relaxation. L-Phenylalanine moved the balloon toward the antrum, suggesting strong contraction of the fundus. T_max showed a significant positive correlation (r = 0.709), and C_max and AUC_120min each showed negative correlations (r = 0.613 and 0.667, respectively) with gastric adaptive relaxation.

Conclusion

From the above findings, it was found that a close correlation exists between gastric emptying and adaptive relaxation, suggesting that enhanced gastric adaptive relaxation inhibits gastric emptying.