vitamin-k-semiquinone-radical and Hyperglycemia

Recent studies have indicated that osteocalcin, a peptide secreted by osteoblasts, functions as an anti-diabetogenic hormone in mice. Osteocalcin knock out mice exhibit obesity, hyperglycemia, and decreased insulin secretion relative to wild-type mice. Treatment with non-carboxylated osteocalcin upregulates energy expenditure, and ameliorates obesity and diabetes in mouse models of obesity-related diabetes. Of interest, the beneficial effects of osteocalcin were shown to be specific to non-carboxylated osteocalcin. This appears, however, inconsistent with recent clinical studies showing insulin-sensitizing effects of vitamin K, which promotes gamma-carboxylation of osteocalcin. These findings shed new light on the crosstalk between bone and energy expenditure, and lead to new questions. These questions include: (1) Does non-carboxylated osteocalcin exert the beneficial effects in humans?; (2) Does warfarin, a vitamin K antagonist, improve insulin, sensitivity and lower blood glucose levels?; (3) and Do estrogen and bisphosphonate, which reduce circulating osteocalcin, contribute to insulin resistance and obesity? These issues await further investigations.

Topics: Animals; Bone Density Conservation Agents; Diabetes Mellitus; Diphosphonates; Estrogens; Humans; Hyperglycemia; Hypoglycemic Agents; Insulin Resistance; Mice; Obesity; Osteoblasts; Osteocalcin; Vitamin K; Warfarin

The role of gamma-glutamyl-carboxylated growth arrest-specific 6 (cGas6) in mediating the beneficial effect of vitamin K (VK) on regulating glucose metabolism remains elusive. We took a three-pronged approach-evaluating human type 2 diabetes (T2D), high-fat diet (HFD)-fed mice, and in vitro cultured myotubes-to address this. Blood samples were collected from both T2D patients and control subjects; skeletal muscle and blood samples were collected from HFD-fed mice with or without VK supplementation (1, 3, and 5 µg/kg BW, 8 weeks); and the molecular mechanism of cGas6 was dissected using GGCX, Gas6, AXL, or IR siRNA-transfected cultured myotubes. Plasma cGas6 and VK were significantly lower in T2D patients compared with control; and cGas6 and the cGas6/Gas6 ratio were positively correlated with VK and inversely correlated with fasting glucose in T2D patients, suggesting an important role for plasma VK and cGas6 in maintaining glucose homeostasis in T2D. Animal studies revealed that VK supplementation dose-dependently upregulated plasma cGas6; stimulated the protein expression of cGas6, PI3K, pAKT, and GLUT4 in skeletal muscle; and reduced hyperglycemia in HFD-fed T2D mice. And in vitro mRNA knockdown studies demonstrated the requirement of cGas6 in mediating the positive effect of VK on glucose metabolism via stimulating the PI3K/pAKT/GLUT4 signaling pathway in high glucose-treated myotubes. These results demonstrate a significant involvement of cGas6 in mediating the beneficial effect of VK on regulating glucose homeostasis in T2D.

Topics: Adult; Animals; Biomarkers; Blood Glucose; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Female; Humans; Hyperglycemia; Intercellular Signaling Peptides and Proteins; Male; Mice; Middle Aged; Vitamin K

Topics: Albumins; Base Sequence; Cells, Cultured; DNA Damage; DNA, Mitochondrial; Endothelium, Vascular; Glucose; Glycation End Products, Advanced; Humans; Hyperglycemia; Models, Biological; Molecular Sequence Data; Reperfusion Injury; Sequence Deletion; Vitamin K

Topics: Humans; Hyperglycemia; Thioctic Acid; Vitamin A; Vitamin K; Vitamins