Comparative effects of temperature exposure on mass and oxidative enzyme activity of brown fat in insectivores, tupaiads and primates

Abstract

A study has been made to see if hyperplastic and biochemical responses similar to those which occur in temperature‐exposed rodents also occur in insectivores, protoprimates and primates. Representative insectivores included the shrewsSuncus murinus andCryptotis parva. The representative prottoprimate wasTupaia chinensis. The representative primate wasMacaca mulatta. Both shrews show a striking thermogenic response in the brown fat with respect to increased specific activity of α‐glycerophosphate oxidase and succinoxidase.Suncus also showed an increase in brown fat mass following cold exposure. In both shrews cold caused the brown fat to become darker in color.Cryptotis did not show a significant increase in brown fat mass, but this may be due to the fact that the cold exposure period was only four days. Thus the shrews appear to be rodent‐like with respect to effects of cold on brown fat. In the Tupaiads the ratio of brown fat to body weight is not nearly as high as in rodents nor is there a striking hyperplasia with cold exposure. Thus the brown fat would seem to be of less importance to the Tupaiads than to rodents and shrews and the Tupaiads appear to be intermediate in this respect between the insectivores and the true primates. AdultMacaca, in spite of eight months of cold exposure at about 4–6 C, showed no hyperplasia of the brown fat and no increase in oxidative enzyme levels. Thus in adult primates so far studied, the evidence indicates that brown fat does not play an important role in homeothermy as it does in rodents.

Selective Impairment of Glucose but Not Fatty Acid or Oxidative Metabolism in Brown Adipose Tissue of Subjects With Type 2 Diabetes

“…Previous investigations have concluded that a decrease in BAT glucose uptake in overweight or obese individuals (7) was suggestive of blunted BAT oxidative metabolism. Human autopsy studies and necropsy studies in various mammalian models, ranging from rodents to primates, have demonstrated age-dependent decreases in BAT capacity (volume) based on histopathological examination (36,37). However, the functionality of this tissue as a result of aging, obesity, or type 2 diabetes has been far less clear.…”

The “Skinny” on brown fat, obesity, and bone

“…Many nonhuman primate neonates have multilocular adipose cells consistent with BAT, including strepsirhines and both new and old world monkeys, although data from apes are lacking (Rowlatt et al, ). Multilocular adipocytes have also been reported in fetal and adult Macaca mulatta (Chaffee et al, ; Strieleman et al, ; Swick et al, ), adult M. fascicularis (Kates et al, ; Meyers et al, ), and adult Saimiri sciurea (Chaffee et al, ). In S. sciurea , tissue resembling BAT was described in the axilla, which appeared to have increased mitochondrial density following cold exposure (Chaffee et al, ).…”

The role of BAT in cardiometabolic disorders and aging

“…Age is one of the most significant determinants of BAT activity in all mammals, from rodents [74] to primates [75] and humans [76], independent of adiposity. BAT mass and activity is highest in infant humans and progressively decrease with age [76].…”