Failure of glucose tolerance factor-containing brewer's yeast to ameliorate spontaneous diabetes in C57BL/KsJ db/db mice

Glucose tolerance factor (GTF), the biologically active form of Cr³⁺, has been ascribed a role in the potentiation of insulin action and glucose homeostasis. The present study investigated the effects of dietary supplementation with GTF-rich brewer's yeast (Saccharomyces cerevisiae) or GTF-deprived Torula yeast (Torulaspora delbrueckii) in genetically diabetic C57BL/KsJ db/db mice. At 15 weeks of age, db/db mice exhibited increased body weight, hyperphagia, hyperglycaemia, hyperinsulinemia and increased glycosylated haemoglobins compared with control (+/+) mice. During 56 days consumption of diets supplemented with 50 g brewer's yeast or Torula yeast per kg, body weights of both groups of db/db mice decreased by 35%, in association with 1.2-1.7 fold increases of food intake, plasma glucose, glycosylated haemoglobins and an 83% decrease of plasma insulin. With the exception of slightly decreased weight loss, addition of brewer's yeast as opposed to Torula yeast did not affect tissue or plasma chromium nor ameliorate any of the parameters monitored including glucose tolerance and insulin sensitivity at 52-54 days. These findings do not support the contention that the glucose intolerance of genetically diabetic C57BL/KsJ db/db mice partly reflects GTF deficiency.