Differential responses of white adipose tissue and brown adipose tissue to calorie restriction during aging.

Age-related adipose tissue dysfunction is potentially important in the development of insulin resistance and metabolic disorder. Caloric restriction (CR) is a robust intervention to reduce adiposity, improve metabolic health, and extend healthy lifespan. Both white adipose tissue (WAT) and brown adipose tissue (BAT) are involved in energy homeostasis. CR triggers the beiging of WAT in young mice, however, the effects of CR on beiging of WAT and function of BAT during aging are unclear. This study aimed to investigate how age and CR impact the beiging of WAT, the function of BAT, and metabolic health in mice. C57BL/6 mice were fed CR diet (40% less than the ad libitum diet) for 3 months initiated in young (3 months), middle-aged (12 months), and old (19 months) stage. We found age-related changes in different types of adipose tissue including adipocyte enlargement, declined beiging of WAT, and declined thermogenic and beta-oxidational function of BAT. Moreover, CR attenuated age-associated adipocyte enlargement and prevented the age-related decline in beiging potential of WAT. These protective effects on the beiging potential were significant in iWAT at all three ages, which were significant in eWAT at young and old age. In contrast, thermogenic and beta-oxidational function of BAT further declined after CR in the young age group. In conclusion, our findings reveal the contribution of WAT beiging decline to age-related metabolic disorder, and suggest nutritional intervention, specifically targeting WAT beiging, as an effective approach to metabolic healthy during aging.