Dietary α-Lactalbumin protects against thioacetamide-induced liver cirrhosis by maintaining gut-liver axis function in rats.

We tested the hypothesis that α-lactalbumin inhibits the disruption of intestinal barrier function and liver cirrhosis by restoring gut-liver axis function in thioacetamide (TAA) -treated rats. Rat diets were supplemented with α-lactalbumin replacing 50% of dietary protein. After consuming α-lactalbumin for one week, rats were intraperitoneally injected with TAA twice a week for 14 weeks. The α-lactalbumin-enriched diet significantly inhibited the elevation of plasma alanine aminotransferase, aspartate aminotransferase, and hyaluronic acids. The supplement significantly reduced plasma lipopolysaccharide levels and increased occludin mRNA level. Hepatic fibrosis and regenerative nodules was developed and intestinal villi were shortened by TAA; α-Lactalbumin attenuated these histopathological changes. These results indicated that α-lactalbumin improved intestinal barrier function, suppressing endotoxin levels. These data also suggested that α-lactalbumin ameliorated the impairment of the gut-liver axis by TAA, inhibiting the development of liver cirrhosis.

Low-protein diet decreased the adrenal function and spontaneous activity of mice during chronic heat stress.

Protein restriction is a well-known risk factor that induces the deterioration of various biological functions. However, little is known about the effects of protein restriction on behavioral markers and the adrenal function of mice exposed to chronic stress. Here we evaluated the effects of a low-protein diet on the spontaneous activity and adrenal function of chronic heat-stressed mice. ICR mice were fed a control diet (20% protein) or a low-protein diet (10% protein) for 14 consecutive days. From the 10th day of the diet period, the mice were repeatedly exposed to a temperature condition of 35 ± 1 °C for 2 hr/day for four consecutive days. The spontaneous activities of the mice were estimated for the behavioral analysis. On the last day, we performed a blood collection test and an ACTH stimulation test for adrenal function analysis. For the blood collection test, mice were exposed to heat stress again for 2 hr, and blood was collected immediately after this heat stress. We measured the plasma levels of corticotropin releasing hormone, adrenocorticotropin (ACTH), and corticosterone. For the ACTH stimulation test, cosyntropin was intraperitoneally administered, and the plasma corticosterone levels were measured. The spontaneous activity of the low-protein mice was significantly lower than that of the control mice during the dark period of heat stress. The plasma corticosterone levels were greatly increased by heat stress, with no significant difference between the control and low-protein groups. The ACTH stimulation test revealed that the plasma corticosterone concentration of the heat-stressed low-protein mice was significantly lower than that of the heat-stressed controls. In conclusion, the low-protein diet decreased the spontaneous activity and the adrenal function of mice during heat stress, which implies that protein restriction during chronic heat stress induces fatigue by reducing the adrenal function.

Acute supplementation of valine reduces fatigue during swimming exercise in rats.

We investigated the respective effects of the acute supplementation of valine, leucine, and isoleucine on metabolism-related markers by administering a swimming exercise test to rats. As a behavioral analysis, we evaluated the effect of valine and that of leucine on spontaneous activity after exercise. Acute supplementation of valine before exercise significantly suppressed the depression of the liver glycogen and the blood glucose after exercise, whereas leucine decreased the blood glucose and isoleucine had no effect. Valine or leucine supplementation significantly decreased the plasma corticosterone level after exercise, while isoleucine had no effect. In the behavioral analysis, valine significantly increased the spontaneous activity after exercise, whereas leucine had no effect. These results indicate that in rats, the acute supplementation of valine, not leucine or isoleucine, is effective for maintaining liver glycogen and blood glucose and increasing spontaneous activity after exercise, which could contribute to the reduction of fatigue during exercise.

Trypsin-Treated ß-Lactoglobulin Improves Glucose Tolerance in C57BL/6 Mice by Enhancing AMPK Activation and Glucose Uptake in Hepatocytes.

It was reported that trypsin-treated ß-lactoglobulin (ß-LG) had a glucose-lowering effect in the oral glucose tolerance test (OGTT) in mice and a dipeptidyl peptidase-4 (DPP-4) inhibition activity in vitro. However, whether trypsin-treated ß-LG improves glucose tolerance by inhibiting DPP-4 in vivo has not yet been examined, and the mechanism of the glucose-lowering effect of trypsin-treated ß-LG is thus unclear. Here we investigated the detailed mechanism underlying the glucose tolerance effect of trypsin-treated ß-LG. The oral administration of trypsin-treated ß-LG significantly decreased the blood glucose concentrations in both the OGTT and an intraperitoneal glucose tolerance test (IPGTT). However, trypsin-treated ß-LG did not increase the insulin secretion after glucose loading. Trypsin-treated ß-LG potently increased the level of phosphorylated AMP-activated protein kinase (AMPK) in human hepatocellular carcinoma (HepG2) cells and in mice hepatocytes. Moreover, trypsin-treated ß-LG significantly enhanced glucose uptake into the HepG2 cells. These results indicate that trypsin-treated ß-LG decreases blood glucose levels after glucose loading by upregulating AMPK activation and glucose uptake in the liver, which could contribute to the reduction of postprandial hyperglycemia.

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.

AIM: Some amino acids been known to influence gastric emptying. Thus we have evaluated the effects of straight alkyl chain, extra hydroxylated alkyl chain and branched chain amino acids on gastric emptying. MATERIALS AND METHODS: Gastric emptying was evaluated in rats after feeding with Racol (nutrient formulae) containing [1-(13)C] acetic acid. Using a breath test, the content of (13)CO2 in their expired air was measured by infrared analyzers. Rats were orally administered with test amino acids, while control rats were administered orally with distilled water. RESULTS: The expired (13)CO2 content in the expired air increased with time, peaked after about 30 min and decreased thereafter. Among the amino acids having an alkyl chain, L-serine, L-alanine and L-glycine, significantly decreased the (13)CO2 content and Cmax, and delayed Tmax, suggesting inhibition and delay of gastric emptying. AUC(120min) values of L-alanine and L-glycine also decreased significantly. L-Threonine significantly decreased (13)CO2 content and delayed Tmax, but had no influence on Cmax and AUC(120min) values, suggesting a delay of gastric emptying. L-Isoleucine and L-leucine and L-valine significantly decreased (13)CO2 content, suggesting inhibition of the gastric emptying, but Cmax, Tmax and AUC(120min) values were not significantly affected. CONCLUSION: The results show that the amino acids used in the present study had different effects on gastric emptying. Moreover, it was found that inhibition and delay of gastric emptying were clearly classifiable by analyzing the change in (13)CO2 content of the expired air and the Cmax, Tmax and AUC(120min) values.

Simultaneous measurement of gastric emptying and gastrocecal transit times in conscious rats using a breath test after ingestion of [1-13C] acetic acid and lactose-[13C] ureide.

This study reports a method for the evaluation of both gastric emptying and gastrocecal transit times in rats simultaneously by using the same breath testing system measuring equipment. Male rats were used after fasting. Gastric emptying and gastrocecal transit time were evaluated by using [1-13C] acetic acid (8 mg/kg) and lactose-[13C] ureide (60 mg/kg), respectively. A mixture of both 13C-labelled compounds dissolved in Racol (liquid nutrient formula) was administered orally. The level of 13CO2 in the expired air was measured using an infrared spectrometer at appropriate intervals for a period of 420 min. The level of 13CO2 in the expired air from [1-13C] acetic acid increased with time and peaked at about 30 min before decreasing, while that from lactose-[13C] ureide increased after about 180 min. The time taken to reach the maximum value of gastric emptying (Tmax) was 27.5±0.9 min. Gastrocecal transit time was 180±11.5 min, which was calculated as the time before the 13CO2 value increased again. These results accorded with the results of gastric emptying and gastrocecal transit time evaluated by using each 13C-labelled compound separately. These results demonstrate that this method is useful for the simultaneous evaluation of gastric emptying and gastrocecal transit times in rats.