Tetrahydroindenoindole inhibits the progression of diabetes in mice

Diabetes is characterized by elevated fasting blood glucose (FBG) resulting from improper insulin regulation and/or insulin resistance. Herein we used female C57EIL/6J mouse models for type I diabetes (streptozotocin [STZ] treatment) and type 2 diabetes (high-fat diet) to examine the ability of 4b,5,9b,10-tetrahydroindeno[1,2-b]indole (THII) to intervene in the progression of diabetes. THII (100 mu M in drinking water) significantly diminished and partially reversed the increase in FBG levels produced by STZ. After 10 weeks on a high-fat diet, mice had normal FBG levels, but exhibited fasting hyperinsulemia and loss of glucose tolerance. THII significantly diminished these changes in glucose and insulin. In isolated liver mitochondria, THII inhibited succinate-dependent H2O2 production, while in white adipose tissue, THII inhibited NADPH oxidase-mediated H2O2 production and lipid peroxidation. Without intervention, such oxidative processes might otherwise promote diabetogenesis via inflammatory pathways. THII also increased O-2 consumption and lowered respiratory quotient (CO2 produced/O-2 consumed) in vivo, indicating a greater utilization of fat for metabolic fuel. Increased metabolic utilization of fat correlated with a decrease in the rate of body weight gain in THII-treated mice fed the high-fat diet. We conclude that THII may retard the progression of diabetes via multiple pathways, including the inhibition of oxidative and inflammatory pathways. (C) 2008 Elsevier Ireland Ltd. All rights reserved.