Swimming in cold water upregulates genes involved in thermogenesis and the browning of white adipose tissues.

The purpose of this study was to investigate whether there is an interacting effect of six weeks of swimming in cold water on the gene expression of browning markers in adipose tissue in rodents. Twenty male Wistar rats were randomly divided into four groups: Control (C, 25 °C), Cold Exposure (CE, 4 °C), Swimming in tepid Water (STW, 30 °C), and Swimming in Cold Water (SCW, 15 °C). The swimming included 2-3 min intervals, 1 min rest, until exhaustion, three days a week for six weeks, with 3 to 6% of bodyweight overload. Rats from CE were exposed to cold for 2 h per day, five days per week. After the experimental protocol, interscapular brown (BAT) and inguinal subcutaneous white (WAT) fat tissues were excised, weighed, and processed for beiging and mitochondrial biogenesis markers gene expression. The experimental protocols resulted in an apparent increase in the number of brown adipocytes (per mm2) in the adipose deposits compared to the C group; substantial changes were observed in the SCW group. Compared to other groups, cold exposure alone increased significantly serum norepinephrine, and also β2-adrenergic receptor expression was upregulated in the adipocytes compared to the C group. The STW group increased the expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) coactivator-1 alpha (PGC-1α), β2-adrenergic receptor, and CCAAT/enhancer-binding proteins-α(c/EBP-α) in WAT in comparison with the C group(p < 0.05). In both adipocytes, the SCW intervention significantly upregulated the expression of PGC-1α, PPAR-γ, and c/EBP-α genes in comparison with the C and CE groups. In addition, the expression of TFAM and UCP1 was upregulated substantially in the SCW group compared to other groups. Our data demonstrate that swim training and cold exposure present additive effects in the expression of genes involved in the beiging process and mitochondrial biogenesis markers in BAT and WAT. In addition, it seems that the upregulation of these genes is related to the activation of β2-adrenergic receptors.