Abstract
Leptin resistance is either a condition induced by human obesity or a natural phenomenon associated with seasonality in ruminants. In the cardiovascular system, the leptin resistance state presence is a complex issue. Moreover, the perivascular adipose tissue (PVAT) appears to be crucial as a source of proinflammatory cytokines and as a site of interaction for leptin contributing to endothelium dysfunction and atherosclerosis progression. So the aim of this study was to examine the influence of the photoperiod on the action of exogenous leptin on gene expression of selected proinflammatory cytokines and their receptors in thoracic PVAT of ewe with or without prior lipopolysaccharide (LPS) stimulation. The experiment was conducted on 48 adult, female ewes divided into 4 group (n = 6 in each): control, with LPS intravenous (iv.) injection (400 ng/kg of BW), with leptin iv. injection (20 μg/kg BW), and with LPS and 30-minute-later leptin injection, during short-day (SD) and long-day (LD) seasons. Three hours after LPS/control treatment, animals were euthanized to collect the PVAT adherent to the aorta wall. The leptin injection enhanced IL1B gene expression only in the LD season; however, in both seasons leptin injection intensified LPS-induced increase in IL1B gene expression. IL1R2 gene expression was increased by leptin injection only in the SD season. Neither IL6 nor its receptor and signal transducer gene expressions were influenced by leptin administration. Leptin injection increased TNFA gene expression regardless of photoperiodic conditions. Only in the SD season did leptin treatment increase the gene expression of both TNFα receptors. To conclude, leptin may modulate the inflammatory reaction progress in PVAT. In ewe, the sensitivity of PVAT on leptin action is dependent upon the photoperiodic condition with stronger effects stated in the SD season.
Highlights
Perivascular adipose tissue (PVAT), the adipose tissue surrounding vessels, was primarily believed to play a structural role in protecting vessels during contraction
In the SD season, Tukey’s post hoc test showed that in comparison to the control group, the LEPR gene expression was increased after leptin injection (Tukey’s test, C vs. LEP, P ≤ 0:001)
[32] concluded that leptin can act on this tissue, especially on the expression of genes related to inflammation and immunity, but white adipose tissue (WAT) structure and functions are very different from PVAT, especially the thoracic one
Summary
Perivascular adipose tissue (PVAT), the adipose tissue surrounding vessels, was primarily believed to play a structural role in protecting vessels during contraction. It is well documented that PVAT is a crucial regulator of vascular function [1]. Being located in close contact with fibroblasts, vascular smooth muscle cells, or endothelial cells, PVAT can act in the endocrine or the paracrine way secreting adipokines (e.g., leptin, adiponectin, and resistin), cytokines, chemokines, etc. It is believed that anatomically, PVAT varies greatly depending on the location. The thoracic aorta is surrounded mostly by brown PVAT (thoracic PVAT); further on, the beige PVAT is present around the abdominal aorta (abdominal PVAT); and the white PVAT surrounds the small arteries (mesenteric PVAT) [1, 3].
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