ABSTRACT
In the most-studied non-hibernator, the laboratory rat, cold-adaptation induces an enhancement of the capacity for nonshivering thermogenesis that is largely due to growth of brown adipose tissue (BAT). This growth involves hyperplasia of the BAT and proliferation of mitochondria in excess of cell proliferation so that individual cells contain more mitochondria. A marked enhancement in use of glucose is correlated with an adaptive increase in responsiveness to insulin, not only in BAT but also in white adipose tissue (WAT) and muscles. The presence of many TSH receptors in both BAT and WAT of guinea pigs suggests that this hormone may have a role in control of adipose tissues during adaptation to cold. The antilipolytic effect of insulin is normal, both against glucagon and against NA and dietary regulation of lipoprotein lipase activity in WAT occurs normally, presumably mediated by an action of insulin. A similar enhancement of glucose metabolism and insulin sensitivity occurs in the cold-adapted rat.
