Association of Adiponectin and Leptin Levels with Endothelial Dysfunction in Patients with Metabolic Syndrome: A Cross-Sectional Clinical Study

Background: Metabolic syndrome (MetS) is defined by a group of cardiometabolic disorders such as central obesity, insulin resistance, dyslipidemia, and hypertension, all of which lead to an increased cardiovascular risk. One early indicator of vascular injury in MetS is endothelial dysfunction. Two important adipokines released by adipose tissue, adiponectin and leptin, may affect endothelial function via pro- and anti-inflammatory pathways, respectively. Objective: To assess the association between circulating adiponectin and leptin levels and endothelial dysfunction in adult patients diagnosed with metabolic syndrome. Methods: This cross-sectional research was carried out between January 2024 and April 2025 at two tertiary care institutions in Pakistan. There were one hundred individuals with metabolic syndrome in all. Adiponectin and leptin levels in blood were measured using ELISA, and endothelial function was evaluated using flow-mediated dilatation (FMD) of the brachial artery. Endothelial dysfunction was indicated by a flow-mediated dilatation (FMD) of less than 6%. Associations were found using statistical techniques such as t-tests, Pearson's correlation, and multivariate regression. Results: Patients exhibiting endothelial dysfunction (64%) had markedly reduced adiponectin levels (3.8 ± 1.1 μg/mL) and elevated leptin levels (24.7 ± 5.1 ng/mL) in comparison to those with normal endothelial function. Adiponectin had a favorable association with FMD (r = 0.54, p < 0.001), but leptin showed a significant negative correlation (r = -0.48, p < 0.001). Both adipokines continued to serve as independent predictors of endothelial function after adjustments for metabolic variables. Conclusion: Adiponectin insufficiency and hyperleptinemia are significantly correlated with compromised endothelial function in metabolic syndrome. These adipokines may function as early indicators and therapeutic targets for the mitigation of cardiovascular risk.