Abstract
Functional perivascular adipose tissue (PVAT) is necessary to maintain vascular physiology through both mechanical support and endocrine or paracrine ways. PVAT shows a brown adipose tissue (BAT)-like feature and the browning level of PVAT is dependent on the anatomic location and species. However, it is not clear whether PVAT browning is involved in the vascular tone regulation in spontaneously hypertensive rats (SHRs). In the present study, we aimed to illustrate the effect of aging on PVAT browning and subsequent vasomotor reaction in SHRs. Herein we utilized histological staining and western blot to detect the characteristics of thoracic PVAT (tPVAT) in 8-week-old and 16-week-old SHR and Wistar-Kyoto (WKY) rats. We also detected vascular reactivity analysis to determine the effect of tPVAT on vasomotor reaction during aging. The results showed that tPVAT had a similar phenotype to BAT, including smaller adipocyte size and positive uncoupling protein-1 (UCP1) staining. Interestingly, the tPVAT of 8-week-old SHR showed increased BAT phenotypic marker expression compared to WKY, whereas the browning level of tPVAT had a more dramatic decrease from 8 to 16 weeks of age in SHR than age-matched WKY rats. The vasodilation effect of tPVAT on aortas had no significant difference in 8-week-old WKY and SHR, whereas this effect is obviously decreased in 16-week-old SHR compared to WKY. In contrast, tPVAT showed a similar vasoconstriction effect in 8- or 16-week-old WKY and SHR rats. Moreover, we identified an important vasodilator adenosine, which regulates adipocyte browning and may be a potential PVAT-derived relaxing factor. Adenosine is dramatically decreased from 8 to 16 weeks of age in the tPVAT of SHR. In summary, aging is associated with a decrease of tPVAT browning and adenosine production in SHR rats. These may result in attenuated vasodilation effect of the tPVAT in SHR during aging.
Highlights
MATERIALS AND METHODSPerivascular adipose tissue (PVAT) is a structure surrounding most of the blood vessels, which plays vital roles in vascular physiopathology (Brown et al, 2014)
HE staining revealed that Thoracic PVAT (tPVAT) showed a similar phenotype to interscapular BAT (iBAT), including smaller adipocyte size and increased uncoupling protein-1 (UCP1) staining compared to subcutaneous WAT (sWAT) (Figures 1A,B)
TPVAT and iBAT shared a similar thermogenic marker protein expression pattern including UCP1, PPARγ, and PGC1α (Figure 1C). These demonstrate that tPVAT has similar features to iBAT, whereas it is clearly different from sWAT
Summary
Perivascular adipose tissue (PVAT) is a structure surrounding most of the blood vessels, which plays vital roles in vascular physiopathology (Brown et al, 2014). Thoracic PVAT (tPVAT) shares structural, genetic, and proteomics features with BAT (Chang et al, 2012), including several small multilocular lipid droplets and abundant mitochondria. Previous studies showed that the tPVAT of spontaneously hypertensive rats (SHRs) has structural and functional changes compared with Wistar-Kyoto (WKY) rats (Galvez et al, 2006). Aging is associated with whole-body adipose tissue redistribution, with a relative loss of BAT in interscapular area and an accumulation of WAT in the trunk and visceral areas (Schosserer et al, 2017). Little is known about the changes in browning level in the tPVAT of SHR rats during aging
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