Mild-cold water swimming does not exacerbate white adipose tissue browning and brown adipose tissue activation in mice.

The present study investigated the effects of swimming physical training either thermoneutral or below thermoneutral water temperature on white (WAT) and brown (BAT) adipose tissue metabolism, morphology, and function. C57BL/6J male mice (n = 40; weight 25.3 ± 0.1 g) were divided into control (CT30), cold control (CT20), trained (TR30), and cold trained (TR20) groups. Swimming training consisted of 30-min exercise at 30°C (control) or 20°C (cold) water temperature. After 8-week training, adipose tissues were excised and inguinal (ingWAT) and BAT were processed for histology, lipolysis, and protein contents of total OXPHOS, PGC1α, and UCP1 by western blotting analysis. Swimming training reduced body weight gain independently of water temperature (P < 0.05). ingWAT mass was decreased for TR30 in comparison to other groups (P < 0.05), while for BAT, there was a significant increase in CT20 in relation to CT30, and both trained groups were significantly increased in relation to control groups (P < 0.05). ingWAT mean adipocyte area was smaller for trained groups, and seemed to present multilocular adipocytes. Lipolytic activity and protein content of UCP1, PGC1α, and mitochondrial markers were increased in trained groups for ingWAT (P < 0.05), independent of water temperature (P > 0.05), and these patterns were not observed for BAT (P > 0.05). Our findings suggest that mild-cold water exposure and swimming physical exercise seem to, independently, promote browning in ingWAT with no effects on BAT; however, the association of exercise and mild-cold water did not exacerbate these effects.