Skin Capillary Density and Microvascular Reactivity in Obese Subjects with and without Metabolic Syndrome

Obesity is associated with increased cardiovascular morbidity and mortality. We hypothesized that microvascular function may be impaired in obese subjects with metabolic syndrome (OB-MetSnd) compared to obese subjects without MetSnd (OB) and healthy subjects (HS). In this cross-sectional study, we evaluated skin capillary density (SCD) in OB-MetSnd (n=20, 12 women, BMI=36.5±1.1kg/m2), OB (n=25, 16 women, BMI=34.5±0.7kg/m2), and HS (n=30, 22 women, BMI=22.8±0.3kg/m2) groups. SCD was evaluated by intravital video-microscopy at rest and after post-occlusive reactive hyperemia (PORH) and venous congestion (VC). OB-MetSnd subjects exhibited significant differences in the values of MetSnd components and in leptin and HOMA-IR levels compared to OB and HS individuals. There were no differences in SCD among groups in resting conditions. The OB-MetSnd group failed to show a significant increase in the number of recruited capillaries during PORH and VC compared to the SCD evaluated at rest. A negative correlation of SCD with waist circumference, BMI, blood pressure, and HOMA-IR was observed after PORH and VC. When obese subjects were analyzed according to their HOMA-IR quartiles, a significant decrease in SCD was observed during POHR (P=0.02). Our findings showed that obese subjects have structural and functional alterations in skin microcirculation that are proportional to the increase in the degree of global and central obesity. In addition, in OB-MetSnd subjects, the cutaneous capillaries at rest are already maximally recruited, indicating an absence of functional capillary reserve. This may be related to the insulin resistance observed in OB-MetSnd individuals.