To develop a nutritional formula on enhancing the endurance of heavy load exercise, and evaluate its efficacy comprehensively.

Sixty C57BL/6J male mice were randomly divided into control group (CON group) and low-, medium- and high-dose nutritional formula groups (LDF, MDF and HDF groups), with 15 mice in each group. Each group received intervention with nutritional formula at corresponding dose for 2 weeks, and underwent adaptive training and heavy load exercise in the 1st and 2nd weeks, respectively. Exhaustion exercise time, skeletal muscle antioxidant indicators (SOD, MDA, PC and GSH), fatigue related indicators (serum URA, LDH and LA), muscle glycogen, and serum exercise injury related indicators (ALT, AST, CK and CK-MB) were measured and detected in the mice, and comprehensive evaluation was conducted according to relevant evaluation standards.

The LDF group, MDF group and HDF group had significantly prolonged running exhaustion time than the CON group (P<0.05), with the HDF group showing the greatest improvement (P<0.05). Compared with the CON group, the activities of SOD and GSH in the skeletal muscles were significantly increased (P<0.05), while the levels of MDA and PC in skeletal muscles were obviously decreased in the 3 doses of nutritional formula groups (P<0.05). PAS staining of the skeletal muscles displayed that the glycogen content was significantly increased in the MDF group and the HDF group than the CON group (P<0.05), and the highest increase was observed in the HDF group (P<0.05). Biochemical test revealed that the levels of LDH, LA, ALT, AST, CK, and CK-MB were remarkably lower in the 3 doses of nutritional formula groups than the CON group (P<0.05).

The nutritional formula can significantly improve the endurance and skeletal muscle antioxidant capacity in mice under heavy load exercise, and has anti-fatigue and -injury protection effects. This nutritional formula can be used to support physical fitness during heavy load endurance exercise.

To explore the effect of chenodeoxycholic acid (CDCA) on the expression of glucagon-like peptide-1 (GLP-1) in the intestine of mice induced by high-fat diet (HFD) through farnesoid X receptor (FXR), and investigate the related mechanism.

Forty C57BL/6 mice were divided into control group, HFD group, HFD+CDCA group, HFD+Z-Gug (FXR antagonist) group, and HFD+CDCA+Z-Gug group, with 8 animals in each group. During intervention for 8 weeks, body weight and 24-hour food intake were measured every week. At the 8th week, oral glucose tolerance test (OGTT) and intraperitoneal glucose tolerance test (IPGTT) were conducted. After the mice were sacrificed, the serum levels of GLu, TG, CHO, LDL-C and HDL-C were detected; the expression levels of GLP-1 and FXR in intestinal tissues were detected by immunofluorescence assay; and the mRNA levels of TNF-α, IL-6, IL-1β, Gcg and FXR were detected by RT-qPCR; the serum level of GLP-1 was detected by ELISA, and the proportion of intraepithelial lymphocytes (IELs) subsets and the expression of CD26/DPP4 were detected by flow cytometry.

Compared with the control group, the HFD group had increased body weight, abnormal serum glucose and lipid metabolism, impaired oral glucose tolerance, and weakened secretion of gastrointestinal hormones (P<0.05), enhanced FXR expression at mRNA and protein levels, declined Gcg mRNA level and GLP-1 secretion level (P<0.05), increased mRNA levels of intestinal inflammatory factors TNF-α, IL-6 and IL-1β (P<0.05), raised proportions of TCRαβ⁺ IELs, TCRαβ⁺CD8αα⁺ IELs, and TCRαβ⁺CD8αβ⁺ IELs but reduced proportion of TCRγδ⁺IELs, and increased total CD26/DPP4 expression in IELs (P<0.05). Compared with the HFD group, HFD+CDCA treatment resulted in significantly increased body weight, impaired oral glucose tolerance, decreased secretion of gastrointestinal hormones, increased FXR mRNA and protein expression, and decreased Gcg mRNA expression and GLP-1 secretion (P<0.05); decreased proportions of TCRαβ⁺ IELs, TCRαβ⁺CD8αα⁺ IELs and TCRααβ⁺CD8αβ⁺ IELs but increased proportion of TCRγδ⁺ cells in IELs, and increased expression of total CD26/DPP4 in IELs (P<0.05), which were significantly improved after Z-Gug intervention (P<0.05).

CDCA may inhibit the expression and secretion of GLP-1 in intestinal tissue by activating FXR, and reduce the secretion of GLP-1. At the same time, CDCA may inhibit the expression of related inflammatory factors, regulate the proportions of IELs subsets, up-regulate the expression level of CD26/DPP4, promote the degradation of GLP-1 and aggravate insulin resistance.

To identify the effect of acute stress induced by composite factors on intestinal barrier dysfunction and explore the relevant mechanism.

Twenty male C57BL/6 mice (7-8 weeks old, body mass 20-22 g) were randomly divided into control group (CON group, n=10) and model group (MOD group, n=10). To establish an acute stress model of complex factors, the mice of the MOD group were given rest of 4 h, sleep deprivation of 15 h, and then followed by 3 h of noise (120 dB)/flash (2 000±500 lx) and 2 h of forced swimming (water temperature 26±1 ℃, water depth 45 cm) within 24 h. While the mice in the CON group were placed in a noiseless environment with constant temperature and humidity and normal circadian rhythm but been given no any treatment. At the end of forced swimming, the mice from the MOD group were anesthetized for blood samples and then euthanized. Serum markers of intestinal injury were detected by immunoenzyme-linked adsorption assay kit, morphological changes in colonic tissues were observed by HE staining, protein and mRNA levels of colonic tissue barrier function related molecules and inflammatory factors were detected by immunofluorescence, immunohistochemistry and RT-qPCR, and intestinal flora changes were analyzed by 16S rRNA technique.

Compared with the CON group, the serum markers of intestinal damage, lipopolysaccharide (LPS), intestinal fatty acid binding protein (I-FABP) and Zonulin were significantly increased in the MOD group (P < 0.05). HE staining showed that intestinal tissue damage was obvious in the MOD group. The results of immunofluorescence staining and RT-qPCR showed that the levels of mechanical barrier related molecules Zona occludens 1 (ZO-1) and Occludin were obviously decreased (P < 0.05). Immunohistochemistry and PAS staining indicated the number of chemical barriers associated goblet cells, and expression of mucin2 (Muc-2), antimicrobial peptide regenerating islet derived-3γ (Reg3γ) and regenerating islet derived-3β (Reg3β) were notably reduced (P < 0.05). Intestinal flora β diversity significantly changed, with harmful bacteria Bacteroidetes and Desulfovibrio significantly increased, while beneficial bacteria Rumenococcus family, norank_f_Erysipelotrichaceae, Gemella genus and Erysipelotrichaceae genus declined (P < 0.05). The levels of TNF-α, IL-6 and ROS were significantly enhanced (P < 0.05).

Acute stress of complex factors significantly induces intestinal injury and barrier dysfunction.