Biomarkers of Inflammation, Oxidative Stress, and Endothelial Dysfunction in Early Detection of Diabetic Foot Ulcers

Abstract

Background Diabetic foot ulcers (DFUs) represent a severe complication of diabetes, contributing to increased morbidity, escalating healthcare expenses, and a heightened risk of limb amputation. Early detection is crucial for preventing ulcer progression. Biomarkers offer a non-invasive approach to identifying at-risk individuals. This study evaluates emerging serum biomarkers for early DFU detection in the South Indian population, focusing on inflammation, oxidative stress, and endothelial dysfunction markers. Materials and methods A cross-sectional study was carried out at our tertiary care hospital, which is affiliated with Kakatiya Medical College, Telangana, India. The study included 189 diabetic patients, who were classified into three groups: Control (n=63) - individuals with diabetes but no ulcers, Pre-ulcer (n=63) - patients exhibiting pre-ulcerative foot conditions, and ulcer (n=63) - patients with active foot ulcers. Serum biomarkers analyzed included interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), C-reactive protein (CRP) (inflammatory markers), malondialdehyde (MDA) (oxidative stress marker), matrix metalloproteinase (MMP-9) (extracellular matrix degradation), and vascular endothelial growth factor (VEGF), intercellular adhesion molecule (ICAM-1) (endothelial dysfunction markers). Peripheral neuropathy evaluation was conducted using the Semmes-Weinstein monofilament test (10 g) and vibration perception threshold (VPT) measurement with a biothesiometer. Peripheral arterial disease (PAD) was assessed using the ankle-brachial index (ABI) with a Doppler ultrasound device and classified using Wagner's grading system. All the analyses were performed using established statistical methods. Results The serum concentrations of IL-6, TNF-α, CRP, MDA, and MMP-9 were notably higher in DFU patients (p < 0.05). Among the inflammatory markers, IL-6 (F = 319.75, p < 0.001), TNF-α (F = 186.03, p < 0.001), and CRP (F = 326.12, p < 0.001) showed a progressive increase across groups. MDA (F = 290.95, p < 0.001) reflected elevated oxidative stress, while MMP-9 (F = 356.21, p < 0.001) exhibited the strongest association with DFU severity. In addition, fasting plasma glucose and HbA1c levels were significantly higher in pre-ulcer and ulcer groups compared to controls (p < 0.001), with HbA1c showing strong positive correlations with MMP-9, CRP, and other biomarkers. VEGF and ICAM-1 were markedly elevated in pre-ulcer patients, indicating early vascular impairment. Among all parameters, MMP-9 and CRP demonstrated the highest diagnostic potential for DFU detection. Conclusion Findings suggest that systemic inflammation, oxidative stress, and vascular dysfunction play key roles in the pathogenesis of DFUs. Elevated VEGF and ICAM-1 levels in pre-ulcer patients point to early vascular impairment, supporting their potential as early biomarkers. MMP-9 and CRP showed strong correlations with ulcer severity, highlighting their diagnostic utility for early screening. Additionally, HbA1c levels were significantly associated with biomarker elevations, reinforcing the impact of poor glycemic control on DFU progression. However, given the known limitations of HbA1c in anemic individuals, combining it with objective serum biomarkers may enhance diagnostic accuracy and risk stratification. Integrating such a biomarker-based approach into routine diabetes care could enable earlier intervention and reduce DFU-related complications.

Keywords: biomarkers; crp; diabetic foot ulcer; early detection; endothelial dysfunction; inflammation; mmp-9; oxidative stress; south indian population.

Figure 1. Correlations between biomarkers and clinical parameters (HbA1c, ABI, and Ulcer Severity)

IL-6: Interleukin-6; TNF-α: Tumor Necrosis Factor-Alpha; hs-CRP: High-sensitive C-Reactive Protein; MDA: Malondialdehyde; MMP-9: Matrix Metalloproteinase-9; VEGF: Vascular Endothelial Growth Factor; ICAM-1: Intercellular Adhesion Molecule 1