Glucagon-Like Peptide-2 Ameliorates Age-Associated Bone Loss and Gut Barrier Dysfunction in Senescence-Accelerated Mouse Prone 6 Mice.

INTRODUCTION: Senile osteoporosis is one of the most common age-related diseases worldwide. Glucagon like peptide-2 (GLP-2), a naturally occurring gastrointestinal peptide, possesses therapeutic effects on bone loss in postmenopausal women and ovariectomized rats. However, the role of GLP-2 in senile osteoporosis and underlying mechanisms has not been explored. METHODS: GLP-2 was subcutaneously injected into the 6-month-old male senile osteoporosis model of senescence-accelerated mouse prone 6 (SAMP6) mice for 6 weeks. SAMP6 subjected to normal saline and senescence-accelerated mouse resistant 1 served as control groups. Micro-computed tomography was performed to evaluate the bone mass and microarchitecture of the mice. Osteoblastic and osteoclastic activities were determined by biochemical, quantitative real-time PCR, histological, and histomorphometric analyses combined with hematoxylin-eosin, toluidine blue, and tartrate-resistant acid phosphatase staining. We also examined the proteins and structure of intestinal tight junction using immunohistochemical assay as well as a transmission electron microscope. Serum inflammation marker levels were measured using ELISA. Additionally, anti-oxidative enzymes GPX-4 and SOD-2 and receptors of GLP-2 and vitamin D expression in the ileum and colon were detected under immunofluorescence staining. RESULTS: Six-week GLP-2 treatment attenuated bone loss in SAMP6 mice, as evidenced by increased bone mineral density, improved microarchitecture in femora, and enhanced osteogenic activities. In contrast, the activity of osteoclastic activity was not obviously inhibited. Moreover, GLP-2 ameliorated tight junction structure and protein expression in the intestinal barrier, which was accompanied by the reduction of TNF-α level. The expression of receptors of intestinal GLP-2 and vitamin D in the ileum was elevated. Furthermore, the oxidative stress in the intestines was improved by increasing the GPX-4 and SOD-2 signaling. CONCLUSION: Our findings suggest that GLP-2 could ameliorate age-associated bone loss, tight junction structure, and improved antioxidant enzyme activity in the gut in SAMP6 mice. Amelioration of gut barrier dysfunction may potentially contribute to improving bone formation and provide evidence for targeting the entero-bone axis in the treatment of senile osteoporosis.

The relationship of sex hormone-binding globulin (SHBG) gene polymorphisms with serum SHBG level and metabolic syndrome in Chinese Han males.

OBJECTIVE: Epidemiological studies have shown that circulating sex hormone-binding globulin (SHBG) levels are lower in metabolic syndrome (MetS) patients than in non-MetS individuals. In this study, we investigated the relationship of polymorphisms in the SHBG gene with the serum SHBG levels and MetS in Han Chinese. METHODS: We performed a cross-sectional study of 316 subjects who were recruited from a health checkup population at Zhongshan Hospital, Fudan University. Anthropometric measurements, blood pressure, fasting plasma glucose, lipid levels, total testosterone, and SHBG levels were obtained in addition to the seven SHBG single-nucleotide polymorphisms (SNPs). RESULTS: The variant allele (AG or AA) carriers in rs6259, compared to the wild-type allele carriers (GG), have a lower risk for MetS [OR 0.56, 95% confidence interval (CI) 0.33-0.96] and higher serum SHBG and TT levels (P = 0.016, 0.004). CT or TT allele carriers in rs3760213, compared to CC allele carriers, also have a lower risk for MetS (OR 0.59, 95 % CI 0.34-1.00) and significantly higher SHBG and TT levels (P = 0.029, 0.009). Carriers having both of the variant alleles had the lowest risk of MetS (OR 0.51, 95 % CI 0.275-0.950) and the highest SHBG levels. The risk of MetS rose with the decrease in serum SHBG levels for rs6259 and rs376021 carriers. CONCLUSION: rs6259 and rs3760213 SNPs are associated with the risk of MetS and lower serum SHBG level in Chinese Han males.

GLP-2 ameliorates D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a signaling pathway in C2C12 cells and mice.

BACKGROUND: The study aimed to investigate the effect of Glucagon-like peptide-2 (GLP-2) on muscle aging in vivo and in vitro. METHODS: Six-week-old C57BL/6J mice were administered with D-galactose (200 mg/kg/day, intraperitoneally) for 8weeks, followed by daily subcutaneous injections of GLP-2 (300 or 600 µg/kg/day) for 4weeks. Skeletal muscle function and mass were evaluated using relative grip strength and muscle weight. The sizes and types of muscle fibers and apoptosis were assessed through histological analysis, immunofluorescence staining, and TUNEL staining, respectively. C2C12 myotubes were treated with D-galactose (40 mg/mL) and GLP-2. Protein expression of differentiation-related myogenic differentiation factor D (MyoD), myogenin (MyoG), and myosin heavy chain (Myhc), degradation-related Muscle RING finger 1 (MuRF-1), and muscle atrophy F-box (MAFbx)/Atrogin-1, and apoptosis-related B-cell leukemia/lymphoma 2 (Bcl-2) and Bax, were assessed using western blots. The Pi3k inhibitor LY294002 was applied to investigate whether GLP-2 regulated myogenesis and myotube aging via IGF-1/Pi3k/Akt/FoxO3a signaling pathway. RESULTS: The results demonstrated that GLP-2 significantly reversed the decline in muscles weight, relative grip strength, diameter, and cross-sectional area of muscle fibers induced by D-galactose in mice. Apart from suppressing the expressions of MuRF-1 and Atrogin-1 in the muscles and C2C12 myotubes, GLP-2 significantly increased the expressions of MyoD, MyoG, and Myhc compared to the D-galactose. GLP-2 significantly suppressed cell apoptosis. Western blot analysis indicated that the regulation of GLP-2 may be attributed to the activation of theIGF-1/Pi3k/Akt/FoxO3a phosphorylation pathway. CONCLUSIONS: This study suggested that GLP-2 ameliorated D-galactose induced muscle aging by IGF-1/Pi3k/Akt/FoxO3a pathway.

Calorie restriction from a young age preserves the functions of pancreatic ß cells in aging rats.

Calorie restriction (CR) is a simple method for delaying aging process, extending lifespan, and preventing the onset of aging-related diseases, such as diabetes. However, the mechanism, by which CR influences ß-cell functions during the aging process, still remains unclear. In this study, sixteen 8-week-old male Sprague-Dawley rats were randomized to control group with food intake ad libitum and CR group fed with 70% of food intake of the control group. Twenty-four weeks later, the body weights of the rats with CR were significantly lower with the smaller amounts of perirenal and epididymal fats, compared to those of control rats. The ß-cell activity, as judged by the early insulin secretion in the intraperitoneal glucose tolerance test, was significantly higher in the CR group than that in control animals. Moreover, CR animals showed the increased ß-cell mass and proliferation of ß-cells in pancreas. The plasma level of malondialdehyde was lower in CR rats than that in control rats, while the activities of superoxide dismutase, catalase and glutathione peroxidase in plasma were higher in CR rats than control rats. These results indicate that aging is associated with the increases in oxidative stress, which was, however, alleviated by CR. In conclusion, CR from a young age preserves the principal ß-cell function of early insulin secretion in rats probably by stimulating the ß-cell proliferation. Our observations provide the evidence for clinical significance of CR in preventing ß-cell dysfunction during the aging process, which may delay the onset of aging-related disease, including diabetes in humans.

Lower levels sex hormone-binding globulin independently associated with metabolic syndrome in pre-elderly and elderly men in China.

OBJECTIVE: To examine the relationship between sex hormone-binding globulin (SHBG) and the metabolic syndrome (MetS) in pre-elderly and elderly men in China. METHODS: A cross-sectional study was done among 437 men, aged 45 to 94 years old. Early morning fasting sera were assayed for total testosterone (TT), SHBG and other biochemical markers. Free testosterone (FT) was calculated. RESULTS: The SHBG level of the MetS group was significantly lower than those without MetS 35.70 (25.18, 47.10) nmol/L vs. 41.90 (31.80, 55.20) nmol/L; P < 0.001). As the number of MetS components increases, SHBG and TT levels became lower. SHBG correlated with age, as did TT and most of metabolic components. Body mass index (BMI), high density lipoprotein-cholesterol (HDL-C), triglyceride (TG), and TT remained independently associated with SHBG by multivariate regression analysis. In a logistic regression taking MetS as the dependent variable, SHBG (95% confidence interval (95% CI): 0.975-0.994, P = 0.018) and homeostasis model assessment for insulin resistance (HOMA-IR) (95%CI: 1.535-2.647, P < 0.001) were included in the final model. CONCLUSIONS: Lower SHBG is independently associated with MetS among pre-elderly and elderly men. SHBG may be an independent predictor of MetS, but the mechanism of how SHBG is involved in MetS requires further studied.