Endothelial nitric oxide synthase (eNOS) dysfunction induces insulin resistance and glucose
Endothelial nitric oxide synthase (eNOS) dysfunction induces insulin resistance and glucose intolerance. on gluconeogenesis was AMPK-dependent. Furthermore, the glucose-lowering effect and activation of AMPK by BH4 did not appear in mice with STZ-induced diabetes lacking eNOS. Consecutive administration of BH4 in mice ameliorated glucose intolerance and insulin resistance. Taken together, BH4 suppresses hepatic gluconeogenesis in an eNOS-dependent manner, and BH4 has a glucose-lowering effect as well as an insulin-sensitizing effect in diabetic mice. BH4 has potential in the treatment of type 2 diabetes. Nitric oxide (NO) is a biological messenger produced by NO synthase (NOS), which includes endothelial (eNOS), inducible (iNOS), and neuronal (nNOS) isoforms. eNOS-derived NO is well-known to have a pivotal role in physiological regulation of endothelial function (1,2). eNOS dysfunction occurs in conditions of diabetes and is known to induce insulin resistance and glucose intolerance (3C5). Insulin resistance caused by eNOS dysfunction is thought to be induced by endothelial dysfunction, leading to decreased skeletal muscle blood flow and glucose uptake (4). On the other hand, glucose transport in isolated skeletal muscle is lower in eNOS-deficient (eNOS?/?) mice, indicating that eNOS expressed in skeletal muscle also regulates its glucose uptake (4). Moreover, eNOS?/? mice are insulin resistant at the level of liver (5). These studies suggest that eNOS plays a central role in the regulation of glucose metabolism and insulin sensitivity and represents several IWP-2 price therapeutic focuses on for type 2 diabetes. The function of eNOS can be controlled by multiple elements such as for example mRNA manifestation of eNOS, l-arginine, influx of Ca2+, and tetrahydrobiopterin (BH4) (2,6,7). BH4 can be an important IWP-2 price cofactor for eNOS features and catalysis as an allosteric modulator of arginine binding (7,8). Binding of BH4 to eNOS elicits a conformational modification that escalates the affinity for binding of arginine-based ligands. BH4 binding also is important in dimer development of the energetic and stabilized type of eNOS (8). BH4 can be changed into 7,8-dihydrobiopterin (BH2) by contact with oxidative stress such as for example diabetes (8,9). Upsurge in BH2 induces dysfunction of eNOS, as BH2 can be inactive for NOS cofactor competes and function with BH4 for BH4 binding (8,9). Furthermore, in areas of diabetes and high blood sugar, de novo synthesis of BH4, which can be rate tied to GTP cyclohydrolase I (GTPCH I), can be impaired (10C13). Therefore, the option of BH4 can be reduced as well as the function of eNOS can be altered so the enzyme generates superoxide anion (O2?) than NO rather, a trend known as uncoupling (7 eNOS,8,14). Supplementation of BH4 can improve endothelial dysfunction by elevating the BH4-to-BH2 percentage, resulting in recoupling of eNOS, and continues to be used in medical trials with individuals with atherosclerotic illnesses for the anticipated vasodilatation ramifications of BH4 through NO creation (15). However, it really is unclear whether BH4 improves blood sugar insulin and rate of metabolism level of sensitivity in diabetic circumstances. In today’s study, we investigated the consequences of BH4 about blood sugar insulin and levels sensitivity in diabetic mice. Fasting blood sugar amounts are controlled from the known degree of hepatic gluconeogenesis, elevation which is the main reason behind fasting hyperglycemia in diabetes (16,17). We demonstrate right here that BH4 decreases fasting blood sugar levels and suppresses gluconeogenesis in liver in an eNOS-dependent manner. In addition, BH4 has an ameliorating effect on glucose intolerance as well as insulin resistance in diabetic mice. Using primary hepatocytes isolated from mouse liver, we have clarified the mechanism by which BH4 suppresses hepatic gluconeogenesis. These data suggest that BH4 has potential as a novel therapeutic approach to diabetes. RESEARCH DESIGN Klf1 AND METHODS Male C57/BL6 (wild-type) mice and male heterozygous Ins2Akita (diabetic Akita) mice, which exhibit hyperglycemia with reduced -cell mass caused by a point mutation in the insulin 2 gene that leads to misfolded insulin and severe endoplasmic reticulum stress, were obtained from Shimizu (Kyoto, Japan) (18). Male eNOS?/? mice in the C57/BL6 mice background were obtained from The Jackson Laboratory (Bar Harbor, ME). Male B6.V-Lepob/J (mice using Trizol (Invitrogen) as previously described (21). The mouse sequence of forward and reverse primers IWP-2 price to detect GTPCH I and DHFR, glucose 6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK), and glyceraldehyde-3-phosphate dehydrogenase as an inner control are shown in Supplementary Table 1. SYBR Green PCR Grasp Mix (Applied Biosystems, Foster, CA) was prepared for the quantitative RT-PCR run. The thermal cycling conditions were denaturation at 95C for 10 min followed by 50 cycles at 95C for 15 s and 60C for 1 min. mRNA levels were measured by real-time quantitative RT-PCR using ABI PRISM 7000 Sequence Detection System (Applied Biosystems). Biopterin analysis. Tissues or whole blood of wild-type mice and.