The Insulin-Like Effects of Low Molecular Weight Thiols: Role of Trace Metal Contamination of Commercial Thiols

Summary

During the investigation of insulin-like effects of low molecular weight thiols in rat adipocytes it was found that thiol autoxidation to H₂O₂ occurred even in the absence of albumin and cells. Since chromatography of the thiols on a chelating ion exchange resin prevented H₂O₂ formation, it is likely that trace metal contaminations of the thiol preparations catalyzed thiol autoxidation in oxygenated solutions. Incubation of rat adipocytes with 1 mM dithioerythritol and low concentrations of dialyzed albumin stimulated 2-deoxy-glucose transport, glucose metabolism to CO₂ and lipids, and formate oxidation. Thiol pretreatment with a chelating ion exchange resin or in most instances incubation with EDTA or catalase prevented these effects. The antilipolytic effect of dithioerythritol was also abolished by catalase. The insulin-like effects of thiols therefore appear to be solely mediated by H₂O₂ generated during thiol autoxidation catalyzed by trace metal contaminants either of albumin or of the commercial thiol preparation itself.

Key-Words

Thiols - H₂O₂ - Adipocytes - Insulin Action - Glucose Transport - Glucose Oxidation - Lipolysis