Naturally occurring chromium compounds in Brewer's yeast and the saltbush plant

The activity of glucose tolerance factor (GTF), an active organic chromium (Cr) compound, was measured in extracts from Brewer's yeast and the saltbush plant (two natural sources known for their antidiabetic potential). GTF was found active both in vivo and in vitro. A dose-dependent increase in yeast fermentation was found. Maximal activity was reached with 10 ng Cr/ml in yeast extract and 150 ng Cr/ml in the saltbush preparation. In vivo studies were performed on streptozotcin-diabetic rats, a model for Type I diabetes, and on spiny mice and sand rats, models for type IT diabetes. A single dose of GTF orally administered to streptozotocin-diabetic rats immediately reduced blood glucose and lipids, reaching a maximum within 2-3 hours. The rate of decrease in blood glucose was dose dependent - 12% reduction after 3 hours for 70 ng Cr/animal and 22% reduction with 280 ng Cr/animal. The duration of the effect was also dose dependent: blood glucose levels of treated animals returned to initial values within 6 hours for 280 ng Cr/animal and 9 hours for 1120 ng Cr/animal. GTF was found to potentiate insulin action: 23.5% decrease in blood glucose values occurred within 120 min for GTF administered alone (P < .001); 12.5% decrease for marginal insulin: 0.005-0.025 mg/Kg (P < .001); and 42% decrease for simultaneous administration of both agents (P < .001). Oral glucose tolerance tests on Type II diabetic animals showed a remarkable improvement in glucose tolerance following an oral dose of GTF. GTF preparations from Brewer's yeast or saltbush have a remarkable effect on glucose metabolism both in vitro and in vivo.