Enhanced Proteolytic and Glycooxidative Activity in Visceral Adipose Tissue in Obesity: A Tissue-Level Comparative Study

Adipose tissue expansion in obesity is accompanied by extracellular matrix (ECM) remodeling, regulated by matrix metalloproteinases (MMPs). Visceral adipose tissue (VAT) is metabolically more active than subcutaneous adipose tissue (SAT). However, depot-specific differences in proteolytic activity and protein glycooxidation remain incompletely characterized. In this case–control study, we assessed the activity of six matrix metalloproteinases (MMP-1, -2, -7, -9, -11, and -13) using a fluorescence resonance energy transfer (FRET) assay and quantified advanced glycation- and glycooxidation-related markers in paired VAT, SAT, and plasma samples obtained from 40 patients with obesity and 21 non-obese controls. The activities of all assessed MMPs were greater in patients with obesity than in the control group (p < 0.01 for all MMPs). Direct tissue-compartment comparisons showed that MMP activity and glycooxidation-related markers were most pronounced in VAT, with markedly higher values in obese individuals compared with controls. In VAT of obese individuals, median MMP activity was approximately 50–60% higher compared with controls. Amyloid cross-β-structure, vesperlysine, and pentosidine were significantly elevated in VAT in obesity, whereas plasma levels were markedly lower and showed limited group differences. No significant differences were observed between obese participants with and without metabolic syndrome. Obesity is associated with a depot-specific molecular profile characterized by enhanced proteolytic and glycooxidative activity predominantly within visceral adipose tissue. These findings highlight the importance of tissue-compartment-specific assessment in obesity.