OBJECTIVEIngestion of probiotics can modify gut microbiota and alter insulin resistance and diabetes development in rodents. We hypothesized that daily intake of Lactobacillus reuteri increases insulin sensitivity by changing cytokine release and insulin secretion via modulation of the release of glucagon-like peptides (GLP)-1 and -2.
RESEARCH DESIGN AND METHODSA prospective, double-blind, randomized trial was performed in 21 glucose-tolerant humans (11 lean: age 49 6 7 years, BMI 23.6 6 1.7 kg/m 2 ; 10 obese: age 51 6 7 years, BMI 35.5 6 4.9 kg/m 2 ). Participants ingested 10 10 b.i.d. L. reuteri SD5865 or placebo over 4 weeks. Oral glucose tolerance and isoglycemic glucose infusion tests were used to assess incretin effect and GLP-1 and GLP-2 secretion, and euglycemichyperinsulinemic clamps with [6, H 2 ]glucose were used to measure peripheral insulin sensitivity and endogenous glucose production. Muscle and hepatic lipid contents were assessed by 1 H-magnetic resonance spectroscopy, and immune status, cytokines, and endotoxin were measured with specific assays.
RESULTSIn glucose-tolerant volunteers, daily administration of L. reuteri SD5865 increased glucose-stimulated GLP-1 and GLP-2 release by 76% (P < 0.01) and 43% (P < 0.01), respectively, compared with placebo, along with 49% higher insulin (P < 0.05) and 55% higher C-peptide secretion (P < 0.05). However, the intervention did not alter peripheral and hepatic insulin sensitivity, body mass, ectopic fat content, or circulating cytokines.
CONCLUSIONSEnrichment of gut microbiota with L. reuteri increases insulin secretion, possibly due to augmented incretin release, but does not directly affect insulin sensitivity or body fat distribution. This suggests that oral ingestion of one specific strain may serve as a novel therapeutic approach to improve glucose-dependent insulin release.Type 2 diabetes results from decreased insulin sensitivity and inadequate insulin secretion, which associate with diminished incretin response and subclinical chronic inflammation and subsequent impaired glucose tolerance (1-4). These pathogenic factors, frequently accompanied by hypercaloric high-fat low-fiber diets, may be associated with alterations in gut microbiota, which also occur in obesity (5) and type 2 diabetes (6).