Probiotic supplementation prevents high-fat, overfeeding-induced insulin resistance in human subjects

The purpose of the present study was to determine whether probiotic supplementation (Lactobacillus casei Shirota (LcS)) prevents diet-induced insulin resistance in human subjects. A total of seventeen healthy subjects were randomised to either a probiotic (n 8) or a control (n 9) group. The probiotic group consumed a LcS-fermented milk drink twice daily for 4 weeks, whereas the control group received no supplementation. Subjects maintained their normal diet for the first 3 weeks of the study, after which they consumed a high-fat (65% of energy), high-energy (50% increase in energy intake) diet for 7 d. Whole-body insulin sensitivity was assessed by an oral glucose tolerance test conducted before and after overfeeding. Body mass increased by 0.6 (SE 0.2) kg in the control group (P<0.05) and by 0.3 (SE 0.2) kg in the probiotic group (P>0.05). Fasting plasma glucose concentrations increased following 7 d of overeating (control group: 5.3 (SE 0.1) v. 5.6 (SE 0.2) mmol/l before and after overfeeding, respectively, P<0.05), whereas fasting serum insulin concentrations were maintained in both groups. Glucose AUC values increased by 10% (from 817 (SE 45) to 899 (SE 39) mmol/l per 120 min, P<0.05) and whole-body insulin sensitivity decreased by 27% (from 5.3 (SE 1.4) to 3.9 (SE 0.9), P<0.05) in the control group, whereas normal insulin sensitivity was maintained in the probiotic group (4.4 (SE 0.8) and 4.5 (SE 0.9) before and after overeating, respectively (P>0.05). These results suggest that probiotic supplementation may be useful in the prevention of diet-induced metabolic diseases such as type 2 diabetes.