The Anatomy of Adipose Tissue in Captive Macaca Monkeys and Its Implications for Human Biology

Abstract

In a sample of 31 sedentary, ad libitum-fed monkeys, most specimens had less than 5 % adipose tissue by weight. Total fatness correlated closely with the number of adipocytes per kilogram lean body mass, but not at all with mean adipocyte volume, except in specimens below 5 % fat. The total number of adipocytes per kilogram of lean body mass increased more than tenfold in the most obese specimens. These data suggest that, like humans but in contrast to laboratory rodents, adipocyte proliferation, not adipocyte enlargement, is the chief mechanism of adipose tissue expansion except in very lean monkeys. Adipose tissue was found in all the typical mammalian depots and in the superficial abdominal paunch, which enlarged disproportionately in obese specimens, forming an almost continuous layer over most of the body. Site-specific differences in the activities of some glycolytic enzymes were similar to those of other mammals. Adipocytes in the paunch depot showed biochemical properties in common with those in the groin depots. The distribution and cellularity of adipose tissue in normal humans were similar to those of exceptionally obese monkeys. Many of the interspecific and sex differences can be attributed to the much greater abundance of adipose tissue in humans, and may not be associated with hair reduction or aquatic habits. Some minor changes in the size or shape of certain adipose depots may have arisen recently under sexual selection. The relevance of laboratory rodents as animal models of human obesity is assessed from comparison of the cellular structure, anatomical distribution and enzyme profiles of adipose tissue in monkeys with those of human and other mammals.

Transdifferentiation properties of adipocytes in the adipose organ

“…It should be noted that although epididymal fat is considered as a visceral depot by many authors, it is not in fact found in humans. The human adipose organ in lean adults accounts for ϳ8 -18% of body weight in males and for 14 -28% in females (ϳ5% in monkeys) (84). The morphology of human adipose tissues is identical to that of murine tissues.…”

MECHANISMS IN ENDOCRINOLOGY: White, brown and pink adipocytes: the extraordinary plasticity of the adipose organ

“…The distribution of the visceral depots is very similar to that described in rodents, but the omental depot is particularly well developed in humans. In lean adults, the human adipose organ accounts for 8-18% of body weight in males and for 14-28% in females (w5% in monkeys) (88,89).…”

Seasonal variation in the body fat of Japanese macaques Macaca fuscata.

“…They also showed that females tend to carry more fat than males. Pond and Mattacks (1987) reported a low fat percentage in captive-reared pigtailed (Macaca nemestrina) and long-tailed macaques (M. fascicularis). Tanaka et al (1995) regarded 35% as a criterion for obesity among captive-bred long-tailed macaques, based on division using the fat-free soft tissue mass as the denominator, its value being equivalent to about 25% using body mass as the denominator.…”

“…Fat accumulation has been studied in various primates, including humans and other anthropoids (McFarland 1997), human infants (Kuzawa 1998;Pawlowski 1998), captive macaques (Pond and Mattacks 1987;Tanaka et al 1995), captive African hominoids (McFarland and Zihlman 1997), and wild orangutans (Knott 1997). Cheirogaleid lemurs, such as Cheirogaleus medius (Fietz and Ganzhorn 1999) and Microcebus murinus (Schmid 1999) are exceptional primates because they hibernate, relying on fat deposited in the tail.…”