The dual burden of metabolic abnormalities and tuberculosis among populations with low body mass index

Abstract

Background: Globally, metabolic abnormalities affect at least 20-25% of the adult population; active TB disease is the ninth leading cause of death. Our overall goal was to assess key human host factors, including vitamin D and the gut microbiome, which affect this dual burden and have bi-directional effects on inflammation. Specifically, our objectives were to: 1) assess the predictive performance of common anthropometric cut-offs utilized in diabetes population screening; 2) examine the association between vitamin D and metabolic indicators; 3) assess gut microbiota differences based on serum 25-hydroxyvitamin D (25[OH]D) status; among a population with a high prevalence of suspected or confirmed active TB disease and low or normal body mass index (BMI). Methods: At a rural hospital in South India, adult outpatients were enrolled after providing informed consent. Data collection included interviews, clinical examinations, anthropometry, and biological samples. Three study participant subsets were included in different analyses. Cornell University and the hospital institutional review boards approved study protocols. Results: Most study participants had BMI <25 kg/m2 (88.2%) or waist circumference (WC) < diabetes screening cut-offs among South Asian populations (79.3%), which would be considered low risk in diabetes screening. However, one-third of study participants either had glycated hemoglobin (HbA1c) ≥ 6.5% (12.3%) or between 5.7% and <6.5% (20.3%). BMI ≥25.0 kg/m2 demonstrated low sensitivity (0.21; 95% CI: 0.06, 0.35) as a screening indicator for HbA1c ≥ 6.5%. Median 25(OH)D was 51.8 nmol/L (IQR 36.0-70.0). Serum 25(OH)D was inversely associated with glycated hemoglobin and WC (both p<0.05), respectively, though not hypertension or gut microbiota diversity (all p>0.05). Most bacterial sequences in rectal swab samples were from the Firmicutes and Bacteroidetes phyla. Conclusions: Our findings indicate a high prevalence of elevated HbA1c (≥ 5.7%), and suggest the need for population-specific BMI and WC cut-offs in diabetes screening. Vitamin D status was associated with HbA1c, however not gut microbiome diversity. Further studies are needed to elucidate the potential roles of vitamin D and the gut microbiome in mitigating the dual burden of metabolic abnormalities and active TB disease among populations with low BMI in resource-limited settings.