The isolation of glucose tolerance factors from brewer's yeast and their relationship to chromium

Growth of brewer's yeast in the presence of Cr³⁻ led to increased yields of substances with GTF activity in assays performed with isolated adipocytes. The formation of these substances may be a means of diminishing the toxic effects of Cr on yeast. During fractionation of extracts of brewer's yeast the Cr was easily dissociated from any complexes that may have been present. The GTF activity for both yeast and adipocytes was isolated in cationic and anionic small amino-acid or peptide-like molecules. These substances caused increased glycolysis in yeast and increased glycolysis and fatty acid synthesis in adipocytes. No evidence was found that GTF aided the binding of insulin to its receptor. The GTF activity could only be demonstrated with adipocytes from rats fed a torula yeast—high sucrose diet, which may have caused the rats to have a decreased sensitivity to insulin.