The gluconeogenic glucose-6-phosphatase gene is expressed during oxygen-limited conditions in the white shrimp Penaeus (Litopenaeus) vannamei: Molecular cloning, membrane protein modeling and transcript modulation in gills and hepatopancreas.

The white shrimp Penaeus (Litopenaeus) vannamei is the most economically important crustacean species cultivated in the Western Hemisphere. This crustacean shifts its metabolism to survive under extreme environmental conditions such as hypoxia, although for a limited time. Glucose-6-phosphatase (G6Pase) is a key enzyme contributing to maintain blood glucose homeostasis through gluconeogenesis and glycogenolysis. To our knowledge, there are no current detailed studies about cDNA or gene sequences of G6Pase from any crustacean reported. Herein we report the shrimp P. (L.) vannamei cDNA and gene sequences. The gene contains seven exons interrupted by six introns. The deduced amino acid sequence has 35% identity to other homolog proteins, with the catalytic amino acids conserved and phylogenetically close to the corresponding invertebrate homologs. Protein molecular modeling predicted eight transmembrane helices with the catalytic site oriented towards the lumen of the endoplasmic reticulum. G6Pase expression under normoxic conditions was evaluated in hepatopancreas, gills, and muscle and the highest transcript abundance was detected in hepatopancreas. In response to different times of hypoxia, G6Pase mRNA expression did not change in hepatopancreas and became undetectable in muscle; however, in gills, its expression increased after 3 h and 24 h of oxygen limitation, indicating its essential role to maintain glycemic control in these conditions.

The potential role of sesquiterpene lactones isolated from medicinal plants in the treatment of the metabolic syndrome - A review.

Metabolic syndrome comprises a cluster of metabolic disorders related to the development of cardiovascular disease and type 2 diabetes mellitus. In latter years, plant secondary metabolites have become of special interest because of their potential role in preventing and managing metabolic syndrome. Sesquiterpene lactones constitute a large and diverse group of biologically active compounds widely distributed in several medicinal plants used for the treatment of metabolic disorders. The structural diversity and the broad spectrum of biological activities of these compounds drew significant interests in the pharmacological applications. This review describes selected sesquiterpene lactones that have been experimentally validated for their biological activities related to risk factors of metabolic syndrome, together with their mechanisms of action. The potential beneficial effects of sesquiterpene lactones discussed in this review demonstrate that these substances represent remarkable compounds with a diversity of molecular structure and high biological activity, providing new insights into the possible role in metabolic syndrome management.

Dual SGLT1/SGLT2 Inhibitor Phlorizin Ameliorates Non-Alcoholic Fatty Liver Disease and Hepatic Glucose Production in Type 2 Diabetic Mice.

PURPOSE: NAFLD is a hepatic component of type 2 diabetes mellitus (T2D), in which impaired hepatic glucose production plays an important role. Inhibitors of sodium glucose transporter 2 (SGLT2) reduce glycemia and exert beneficial effects on diabetic complications. Recently, dual SGLT1/2 inhibition has been proposed to be more effective in reducing glycemia. We hypothesized that improving hepatic glucose metabolism induced by SGLT1/2 inhibition could be accompanied by beneficial effects on NAFLD progression. METHODS: Glycemic homeostasis, hepatic glucose production and NAFLD features were investigated in obese T2D mice, treated with SGLT1/2 inhibitor phlorizin for 1 week. RESULTS: T2D increased glycemia; insulinemia; hepatic expression of phosphoenolpyruvate carboxykinase (PEPCK), glucose-6-phosphatase (G6Pase) and glucose transporter 2 (Slc2a2 gene); hepatocyte nuclear factors 1A/4A/3B-binding activity in Slc2a2; endogenous glucose production; liver weight, plasma transaminase concentration as well as hepatic inflammation markers, and induced histological signals of non-alcoholic steatohepatitis (NASH, according to NASH-CRN Pathology Committee System). Phlorizin treatment restored all these parameters (mean NASH score reduced from 5.25 to 2.75 P<0.001); however, plasma transaminase concentration was partially reverted and some hepatic inflammation markers remained unaltered. CONCLUSION: NAFLD accompanies altered hepatic glucose metabolism in T2D mice and that greatly ameliorated through short-term treatment with the dual SGLT1/2 inhibitor. This suggests that altered hepatic glucose metabolism participates in T2D-related NAFLD and highlights the pharmacological inhibition of SGLTs as a useful approach not only for controlling glycemia but also for mitigating development and/or progression of NAFLD.

Supplementation with beta-hydroxy-beta-methylbutyrate impacts glucose homeostasis and increases liver size in trained mice.

ß-hydroxy-ß-methyl butyrate (HMB) is a bioactive metabolite derived from the amino acid leucine, usually applied for muscle mass increase during physical training, as well as for muscle mass maintenance in debilitating chronic diseases. The hypothesis of the present study is that HMB is a safe supplement for muscle mass gain by strength training. Based on this, the objective was to measure changes in body composition, glucose homeostasis and hepatic metabolism of HMB supplemented mice during strength training. Two of four groups of male mice (n = 6/group) underwent an 8-week training period session (climbing stairs) with or without HMB supplementation (190 mg/kgBW per day). We observed lower body mass gain (4.9 ± 0.43% versus 1.2 ± 0.43, p < 0.001) and increased liver mass (40.9 ± 0.9 mg/gBW versus 44.8 ± 1.3, p < 0.001) in the supplemented trained group compared with the non-supplemented groups. The supplemented trained group had an increase in relative adipose tissue mass (12.4 ± 0.63 mg/gBW versus 16.1 ± 0.88, P < 0.01) compared to the non-supplemented untrained group, and an increase in fasting blood glucose (111 ± 4.58 mg/dL versus 122 ± 3.70, P < 0.05) and insulin resistance (3.79 ± 0.19 % glucose decay/min versus 2.45 ± 0.28, P < 0.05) comparing with non-supplemented trained group. Adaptive heart hypertrophy was observed only in the non-supplemented trained group (4.82 ± 0.05 mg/gBW versus 5.12 ± 0.13, P < 0.05). There was a higher hepatic insulin-like growth factor-1 expression (P = 0.002) in supplemented untrained comparing with non-supplemented untrained group. Gene expression of gluconeogenesis regulatory factors was increased by training and reduced by HMB supplementation. These results confirm that HMB supplementation associated with intensive training protocol drives changes in glucose homeostasis and liver metabolism in mice.

Insulin promotes the expression of the gluconeogenic rate-limiting enzymes phosphoenolpyruvate carboxykinase (Pepck) and glucose 6-phosphatase (G6pase) through PI3k/Akt/mTOR signaling pathway in goose hepatocytes

To identify what makes insulin have an activating or inhibiting role in gluconeogenesis in goose hepatocytes and whether insulin regulates PEPCK and G6Pase through the PI3k/Akt/mTOR pathway or not, goose primary hepatocytes were isolated and cultured in vitro. After 12h cultured in serum-free medium, hepatocytes were incubated for 24 h in the medium with no addition (control) or with the addition of 50, 100, and 150 nM of insulin, 1000 nM NVP-BEZ235, or co-addition of 150nM insulin and 1000nM NVP-BEZ235. Glucose concentration and PEPCK and G6Pase expression were determined. The results showed that PEPCK and G6Pase mRNA levels and activities were up regulated in the 50, 100, and 150nM insulin treatments, while glucose concentration was not significantly altered (p > 0.05). Compared with the activation role of 150nM insulin alone, the co-treatment with1000nM NVP-BEZ235 and 150nM insulin significantly down regulated PEPCK mRNA level and G6Pase protein activity (p < 0.05). However, there is a different result on mRNA level of G6Pase. In conclusion, G6Pase and PEPCK are up regulated by insulin through PI3k/Akt/mTOR pathway in goose hepatocytes. However, G6Pase mRNA and protein levels may be regulated by insulin through different signaling pathways.(AU)

Insulin promotes the expression of the gluconeogenic rate-limiting enzymes phosphoenolpyruvate carboxykinase (Pepck) and glucose 6-phosphatase (G6pase) through PI3k/Akt/mTOR signaling pathway in goose hepatocytes

To identify what makes insulin have an activating or inhibiting role in gluconeogenesis in goose hepatocytes and whether insulin regulates PEPCK and G6Pase through the PI3k/Akt/mTOR pathway or not, goose primary hepatocytes were isolated and cultured in vitro. After 12h cultured in serum-free medium, hepatocytes were incubated for 24 h in the medium with no addition (control) or with the addition of 50, 100, and 150 nM of insulin, 1000 nM NVP-BEZ235, or co-addition of 150nM insulin and 1000nM NVP-BEZ235. Glucose concentration and PEPCK and G6Pase expression were determined. The results showed that PEPCK and G6Pase mRNA levels and activities were up regulated in the 50, 100, and 150nM insulin treatments, while glucose concentration was not significantly altered (p > 0.05). Compared with the activation role of 150nM insulin alone, the co-treatment with1000nM NVP-BEZ235 and 150nM insulin significantly down regulated PEPCK mRNA level and G6Pase protein activity (p < 0.05). However, there is a different result on mRNA level of G6Pase. In conclusion, G6Pase and PEPCK are up regulated by insulin through PI3k/Akt/mTOR pathway in goose hepatocytes. However, G6Pase mRNA and protein levels may be regulated by insulin through different signaling pathways.

Elevated tissue omega-3 fatty acid status prevents age-related glucose intolerance in fat-1 transgenic mice.

The objective of this study was to investigate the impact of elevated tissue omega-3 (n-3) polyunsaturated fatty acids (PUFA) status on age-related glucose intolerance utilizing the fat-1 transgenic mouse model, which can endogenously synthesize n-3 PUFA from omega-6 (n-6) PUFA. Fat-1 and wild-type mice, maintained on the same dietary regime of a 10% corn oil diet, were tested at two different ages (2 months old and 8 months old) for various glucose homeostasis parameters and related gene expression. The older wild-type mice exhibited significantly increased levels of blood insulin, fasting blood glucose, liver triglycerides, and glucose intolerance, compared to the younger mice, indicating an age-related impairment of glucose homeostasis. In contrast, these age-related changes in glucose metabolism were largely prevented in the older fat-1 mice. Compared to the older wild-type mice, the older fat-1 mice also displayed a lower capacity for gluconeogenesis, as measured by pyruvate tolerance testing (PTT) and hepatic gene expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase). Furthermore, the older fat-1 mice showed a significant decrease in body weight, epididymal fat mass, inflammatory activity (NFκ-B and p-IκB expression), and hepatic lipogenesis (acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) expression), as well as increased peroxisomal activity (70-kDa peroxisomal membrane protein (PMP70) and acyl-CoA oxidase1 (ACOX1) expression). Altogether, the older fat-1 mice exhibit improved glucose homeostasis in comparison to the older wild-type mice. These findings support the beneficial effects of elevated tissue n-3 fatty acid status in the prevention and treatment of age-related chronic metabolic diseases.