Enhanced insulin secretion and sensitization in diabetic mice on chronic treatment with a transient receptor potential vanilloid 1 antagonist.

Inhibition of transient receptor potential vanilloid 1 (TRPV1) suppresses calcitonin gene-related peptide (CGRP) secretion in pancreatic nerve fiber cells, thereby stimulating insulin secretion. We examined the effects of repeat administration of the TRPV1 antagonist N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)tetrahydropyrazine-1(2H)-carboxamidte monohydrochloride (BCTC) to ob/ob mice, a model of type 2 diabetes with insulin resistance, on whole body glucose and lipid metabolism.We measured blood parameters, including levels of glucose, insulin, and triglycerides, and performed the oral glucose tolerance test (OGTT) after repeat administration of BCTC to ob/ob mice twice a day for four weeks.We found that BCTC treatment reduced fasting glucose, triglyceride, and insulin levels in the whole body. The effects were comparable to that of pioglitazone, a major insulin-sensitizing agent. Further, we found that administration of BCTC significantly increased plasma insulin secretion in the OGTT, which differed from the effect of pioglitazone treatment.Our study is the first to show the anti-diabetic pharmacological effects of the TRPV1 signal inhibitor BCTC. These findings suggest that TRPV1 antagonists may represent a new class of drugs effective in treating type 2 diabetes mellitus because of their dual effects as insulin sensitizers and secretagogues.