The Linkage Between Inflammation and the Progression of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2D) is a chronic metabolic disorder in which inflammation plays a central role in its onset, progression, and complications. Identifying reliable biomarkers is essential to improve risk prediction, disease monitoring, and early intervention. Methods: A total of 169 Ecuadorian participants were stratified into four clinical groups: non-diabetic controls (NDC), controlled T2D (C-T2D), uncontrolled T2D (NC-T2D), and diabetic kidney disease (DKD). Circulating levels of cytokines (IL-6, IL-8, TNF-α), adipokines (leptin, adiponectin), and PBMC-derived microRNAs (miR-146a, miR-155) were quantified. Associations with disease stage were evaluated using ROC curve analysis and logistic regression. Results: Leptin showed the strongest association with T2D (OR = 13.76, 95% CI: 6.47–29.26), followed by IL-8 (OR = 6.73, 95% CI: 3.30–13.70) and IL-6 (OR = 4.43, 95% CI: 2.26–8.97). Adiponectin distinguished NC-T2D from DKD (OR = 4.15, 95% CI: 1.77–9.71), underscoring its potential as an indicator of renal complications. Interestingly, TNF-α levels declined across disease stages, possibly reflecting subclinical inflammation in Ecuadorian NDC with high rates of obesity and dyslipidemia. PBMC-derived miR-146a was upregulated in T2D patients, contrasting with prior serum-based studies and emphasizing the importance of compartment-specific analysis. miR-155 was elevated in C-T2D, suggesting a compensatory immune-regulatory mechanism that diminishes with poor glycemic control and advanced disease. Conclusions: Inflammatory cytokines, adipokines, and microRNAs act in distinct yet complementary ways in T2D. Leptin, IL-6, and IL-8 emerge as strong predictors of disease, while miR-146a and miR-155 provide additional insight into immune-inflammatory regulation. Integrated biomarker panels may enhance patient stratification and support personalized monitoring of T2D progression.