Abstract
Cold exposure promotes fat oxidation and modulates the energy metabolism in adipose tissue through multiple mechanisms. However, it is still unclear about heat-generating capacity and lipid mobilization of different fat depots without functional mitochondrial uncoupling protein 1 (UCP1). In this study, we kept finishing pigs (lack a functional UCP1 gene) under cold (5-7°C) or room temperature (22-25°C) and determined the effects of overnight cold exposure on fatty acid composition and transcriptional profiles of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). And the plasma metabolomes of porcine was also studied by LC-MS-based untargeted metabolomics. We found that the saturated fatty acids (SFAs) content was decreased in SAT upon cold exposure. While in VAT, the relative content of lauric acid (C12:0), myristic acid (C14:0) and lignoceric acid (C24:0) were decreased without affecting total SFA content. RNA-seq results showed SAT possess active organic acid metabolism and energy mobilization upon cold exposure. Compared with SAT, cold-induced transcriptional changes were far less broad in VAT, and the differentially expressed genes (DEGs) were mainly enriched in fat cell differentiation and cell proliferation. Moreover, we found that the contents of organic acids like creatine, acamprosate, DL-3-phenyllactic acid and taurine were increased in plasma upon overnight cold treatment, suggesting that cold exposure induced lipid and fatty acid metabolism in white adipose tissue (WAT) might be regulated by functions of organic acids. These results provide new insights into the effects of short-term cold exposure on lipid metabolism in adipose tissues without functional UCP1.
Highlights
The global epidemic of metabolic syndrome has become the major health hazard of the modern world [1]
There were no significant differences in backfat thickness between COLD and RT pigs (Figure 1C)
We found that TG content was not affected after overnight cold exposure in subcutaneous adipose tissue (SAT) while TG level was significantly decreased after cold-treated in visceral adipose tissue (VAT) (Figure 1F)
Summary
The global epidemic of metabolic syndrome has become the major health hazard of the modern world [1]. The syndrome is mostly driven by excess energy intake and concomitant obesity [2]. To control the ongoing obesity epidemic, both active lifestyle and new treatment approaches to induce weight loss are required. Cold Exposure Affects Porcine Fat adaptive thermogenesis, including shivering and facultative thermogenesis, to increase mobilization of energy to maintain body temperature. The most important heat source from cold exposure is facultative thermogenesis, which increases metabolic reactions by activating BAT function and browning of WAT through the activation of b adrenergic signaling in both humans and mice [3, 4]. In the past decades, targeting the activity of BAT and browning of WAT to increase energy expenditure is a promising strategy to combat obesity
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