Inflammatory Load Across Diabetes Duration: CRP and ESR Patterns and Their Metabolic Correlates

Abstract

Highlights: What are the main findings? Inflammatory burden in type 2 diabetes follows a nonlinear cross-sectional pattern across disease duration, with elevated CRP in early metabolic stages and in long-standing disease. CRP correlates significantly with adiposity (BMI) and atherogenic dyslipidemia (triglyceride-to-HDL ratio), but not with HbA1c, suggesting that inflammation reflects metabolic phenotype rather than short-term glycemic control. What are the implications of the main findings? Systemic inflammation in T2DM appears to be driven by adipose–lipid metabolic dysfunction in early disease and by organ damage (particularly renal impairment) in advanced stages. Targeting adiposity and dyslipidemia may represent a key strategy for modulating inflammatory load beyond glucose-centered management. Background: Type 2 diabetes mellitus (T2DM) is characterized by chronic low-grade inflammation that contributes to cardiometabolic complications. While diabetes duration reflects cumulative metabolic exposure, its relationship with systemic inflammatory burden remains insufficiently defined. We aimed to investigate inflammatory patterns across diabetes duration and to explore their metabolic and cardio–renal correlates. Methods: This real-world cross-sectional study included 250 adults with T2DM. Diabetes duration was analyzed both continuously and across four predefined strata (0–4, 5–9, 10–14, and ≥15 years). Inflammatory burden was assessed using C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Given the skewed distribution of CRP, log-transformed CRP was used in regression analyses. Nonlinear associations were evaluated using quadratic regression models. This approach was selected because preliminary descriptive analyses suggested a non-monotonic relationship between diabetes duration and CRP levels. Inclusion of a quadratic term allowed formal testing of a potential curvilinear association between diabetes duration and inflammatory burden. Spearman correlations were performed to assess associations with metabolic, renal, and cardiovascular variables. Results: CRP showed a nonlinear cross-sectional association across diabetes duration strata. Median CRP values were higher in early (0–4 years: 0.62 mg/L) and long-standing diabetes (≥15 years: 0.77 mg/L) compared with intermediate-duration groups (p = 0.063). Quadratic regression confirmed a U-shaped relationship (adjusted β_duration = −0.079, p < 0.001; β_duration2 = 0.0027, p < 0.001; R2 = 0.326). ESR differed significantly across duration strata (p = 0.002), with the highest levels observed in long-standing diabetes. CRP correlated positively with BMI (ρ = 0.151; p = 0.017) and triglyceride-to-HDL ratio (ρ = 0.215; p < 0.001), but not with HbA1c. Both CRP and ESR were more strongly associated with functional CKD (ρ = 0.350 and 0.429, respectively; p < 0.001) than with ASCVD. Conclusions: Inflammatory burden in T2DM shows a nonlinear cross-sectional pattern across diabetes duration, characterized by elevated levels in early and long-standing disease. Systemic inflammation appears more closely linked to renal dysfunction than to established cardiovascular disease. These findings support a cardio–renal–inflammatory axis in which prolonged diabetes exposure contributes to renal decline, which in turn amplifies systemic inflammatory activation.