New concepts for treatment of non-insulin-dependent diabetes mellitus

A network pharmacology approach to determine active compounds and action mechanisms of ge-gen-qin-lian decoction for treatment of type 2 diabetes

Traditional Chinese medicine (TCM) herbal formulae can be valuable therapeutic strategies and drug discovery resources. However, the active ingredients and action mechanisms of most TCM formulae remain unclear. Therefore, the identification of potent ingredients and their actions is a major challenge in TCM research. In this study, we used a network pharmacology approach we previously developed to help determine the potential antidiabetic ingredients from the traditional Ge-Gen-Qin-Lian decoction (GGQLD) formula. We predicted the target profiles of all available GGQLD ingredients to infer the active ingredients by clustering the target profile of ingredients with FDA-approved antidiabetic drugs. We also applied network target analysis to evaluate the links between herbal ingredients and pharmacological actions to help explain the action mechanisms of GGQLD. According to the predicted results, we confirmed that a novel antidiabetic ingredient from Puerariae Lobatae radix (Ge-Gen), 4-Hydroxymephenytoin, increased the insulin secretion in RIN-5F cells and improved insulin resistance in 3T3-L1 adipocytes. The network pharmacology strategy used here provided a powerful means for identifying bioactive ingredients and mechanisms of action for TCM herbal formulae, including Ge-Gen-Qin-Lian decoction.

Insulin resistance and the modulation of rat cardiac K(+) currents

K(+) currents were measured using a whole cell voltage-clamp method in enzymatically isolated rat ventricular myocytes obtained from two hyperinsulinemic, insulin-resistant models. Fructose-fed rats as well as genetically obese rats, both of which are resistant to the metabolic effects of insulin, were used. The normal augmentation of a calcium-independent sustained K(+) current was reduced or abolished in insulin-resistant states. This resistance can be reversed by the insulin-sensitizing drug metformin. Vanadyl sulfate (3-4 wk treatment or after 5-6 h in vitro) enhanced the sustained K(+) current. The in vitro effect of vanadyl was blocked by cycloheximide. Insulin resistance of the K(+) current was not reversed by vanadyl sulfate. The results show that insulin resistance is expressed in terms of insulin actions on ion channels, in addition to its actions on metabolism. This resistance can be reversed by the insulin-sensitizing drug metformin. Vanadate compounds, which mimic the effects of insulin on metabolism, also mimic the augmenting effects of insulin on a cardiac K(+) current in a manner suggesting synthesis of new channels.

Mechanisms by which Thiazolidinediones Enhance Insulin Action

Thiazolidinediones (TZDs) are an exciting new class of insulin-sensitizing drugs being used currently for the treatment of non-insulin-dependent diabetes mellitus. The molecular target of these compounds is thought to be the nuclear hormone receptor, peroxisome proliferator-activated receptor gamma (PPARgamma). PPARgamma is expressed predominantly in adipose tissue, yet a major site of TZD-responsive glucose disposal is skeletal muscle. Potential explanations for this paradox are discussed in this review.