Evaluation of the effects of pioglitazone on perivascular adipose tissue function, properties, and structure in a rat model of type-2 diabetes

Perivascular adipose tissue (PVAT) plays an important role in many physiological and pathological processes, such as regulation of vascular tone. The aim of this study is to evaluate the effects of pioglitazone on functional, structural, and biochemical properties of PVAT in an experimental model of type-2 diabetes (T2DM). T2DM was induced by high-fat-diet/low-dose-streptozotocin in rats, and pioglitazone (20 mg/kg/p.o.) was administered for 6 weeks. Changes in biochemical parameters, PVAT-mass, vascular-reactivity in thoracic-aorta, as well as PVAT adipocytokine and PPARG-expression levels, and histopathology were evaluated. Pioglitazone administration improved blood glucose and lipid profiles in T2DM. Pioglitazone did not change the anticontractile effect of PVAT on aortic contractile reactivity and besides, had no influence on endothelium-dependent and -independent relaxation responses. Pioglitazone administration increased PVAT-mass and tumor necrotizing factor-α levels, while adiponectin, leptin, and interleukin-6 levels were unchanged. Also, a prominent increase was observed in PPARG-expression in T2DM-Pio group. Moreover, pioglitazone decreased liver steatosis, aortic wall thickening, and myocardial damage, whereas increased adipocyte size and adiposity in PVAT. Overall, pioglitazone treatment changed the mass and in part the inflammatory profile of PVAT but did not modify vasoreactivity in T2DM. This study provides novel findings in relationship with the adipogenic effect of pioglitazone and PVAT function.