Associations of hs-CRP, TNF-α, and IL-6 with obesity in Nigerian adults with type 2 diabetes: a cross-sectional study

Abstract

Inflammation contributes to obesity-related metabolic dysfunction in type 2 diabetes (T2DM), yet evidence from sub-Saharan Africa remains limited, particularly from studies adjusting for medication use and endemic infections. This study investigated associations between high-sensitivity C-reactive protein (hs-CRP), tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and obesity in Nigerian adults with T2DM, adjusting for medication use and asymptomatic malaria. This cross-sectional study included 151 adults with T2DM and 100 age- and sex-frequency-matched healthy controls from Southwest Nigeria. Plasma inflammatory markers were measured by enzyme-linked immunosorbent assay. Multivariable logistic regression examined associations with obesity (body mass index ≥ 30 kg/m²), adjusting for age, sex, metformin use, statin use, and asymptomatic malaria rapid diagnostic test status. All models were restricted to participants with T2DM; near-universal metformin use (98%) limited the ability to estimate its independent effect. Sensitivity analyses included log-transformed biomarker concentrations. Participants with T2DM had significantly higher hs-CRP, TNF-α, and IL-6 concentrations than controls (all p < 0.001). hs-CRP showed the strongest correlation with body mass index (ρ = 0.42, p < 0.001) and waist circumference (ρ = 0.38, p < 0.001). In fully adjusted models, hs-CRP (aOR = 1.35, 95% CI: 1.10–1.66, p = 0.004) and TNF-α (aOR = 1.06, 95% CI: 1.01–1.12, p = 0.018) were associated with obesity, whereas IL-6 was not (aOR = 1.04, 95% CI: 0.99–1.09, p = 0.118). When all three biomarkers were included simultaneously, hs-CRP remained associated with obesity (aOR = 1.32, 95% CI: 1.08–1.62, p = 0.007), whereas TNF-α and IL-6 did not. Sensitivity analyses yielded materially similar findings. Inflammatory biomarkers, particularly hs-CRP, were associated with obesity in Nigerian adults with T2DM. The consistent association of hs-CRP with obesity suggests this readily measurable biomarker may help identify individuals with obesity-related inflammation, though prospective studies are needed to establish clinical utility. The near-universal metformin use limits interpretation, and the cross-sectional design precludes causal inference. Not applicable (observational study).