The Gut Microbiome and Diabetes Status in the Multiethnic Cohort

Abstract

Abstract Objectives As features of the gut microbiome may promote the development of type 2 diabetes (T2D), we examined the hypothesis that gut microbiome composition differs by glycemic/diabetes status within a subset of the Multiethnic Cohort. We also estimated the association of lipopolysaccharide-binding protein (LBP) as a measure of circulating bacterial endotoxin with T2D. This outer membrane component of gram-negative bacteria may affect glucose metabolism. Methods In 2013–16, cohort members from 5 ethnic groups completed clinic visits, questionnaires, and stool collections. Participants with self-reported T2D and/or taking medication were considered T2D cases. Those with fasting glucose >125 and 100–125 mg/dL were classified as undiagnosed (UT2D) and prediabetes (PT2D). We characterized the gut microbiome through 16S rRNA gene sequencing (V1-V3). Plasma LBP was measured by ELISA. Linear regression was applied to estimate associations of gut microbiome community structure and LBP with T2D status adjusting for relevant confounders. Results Among 1756 participants (59.9–77.4 years), 315 (18%) were T2D, 158 (9%) UT2D, 518 (29%) PT2D, and 765 (44%) normoglycemic (NG). The Shannon diversity index was lower (6.30, 6.25, 6.28, 6.18; P = 0.02) and LBP was higher (26.0, 26.6, 28.6, 28.2 µg/mL; P = 0.0009) in T2D than NG participants. Of 10 phyla, Actinobacteria and Firmicutes were inversely associated with T2D status (P = 0.004). Six of 161 genera were significantly related to T2D status after Bonferroni adjustment: the abundance of Clostridium sensu stricto 1, Lachnospira, Lachnospiraceae NC2004, and Peptostreptococcaceae was lower, while Lachnospiraceae uncultured and Escherichia-Shigella were more abundant among T2D than NG participants. In general, those with PT2D and UT2D had values closer to NG than T2D individuals. Conclusions Participants with T2D showed a lower abundance of bacteria capable of fermenting plant polysaccharides and higher levels of gram-negative endotoxin-producing bacteria indicating that a less favorable pattern of gut microbiome community structure may contribute to T2D through endotoxin binding to toll-like receptors via LBP and activation of the NFkB pathway associated with chronic systemic inflammation. Funding Sources NIH grants P01CA169530, U01CA164973, P30CA071789, #UL1TR000130, R01HL140335.