Brief communication: Adrenal androgens and aging: Female chimpanzees (Pan troglodytes) compared with women

Ovarian cycling continues to similar ages in women and chimpanzees yet our nearest living cousins become decrepit during their fertile years and rarely outlive them. Given the importance of estrogen in maintaining physiological systems aside from fertility, similar ovarian aging in humans and chimpanzees combined with somatic aging differences indicates an important role for nonovarian estrogen. Consistent with this framework, researchers have nominated the adrenal androgen dehydroepiandrosterone (DHEA) and its sulfate (DHEAS), which can be peripherally converted to estrogen, as a biomarker of aging in humans and other primates. Faster decline in production of this steroid with age in chimpanzees could help explain somatic aging differences. Here, we report circulating levels of DHEAS in captive female chimpanzees and compare them with published levels in women. Instead of faster, the decline is slower in chimpanzees, but from a much lower peak. Levels reported for other great apes are lower still. These results point away from slowed decline but toward increased DHEAS production as one of the mechanisms underlying the evolution of human longevity. Am J Phys Anthropol 151:643–648, 2013. © 2013 Wiley Periodicals, Inc.     

An improved method of reconstitution of adipocyte glucose transport activity

The glucose transport activity of rat epididymal fat cells was reconstituted into egg lecithin liposomes with a high degree of reproducibility. The activity was solubilized with 20 mm sodium cholate in Buffer B (10 mm Tris-HCl, pH 7.5). After elimination of small molecules by gel filtration, the transport activity was incorporated into egg lecithin liposomes (Sigma, Type IX-E, homogeneously dispersed into Buffer B) by sonication (5 s), freezing (?70°C), thawing, and a second sonication (5 s). The sonication was done in a 16.8-mm polystyrene test tube (Sarstedt, 55-468) placed in a cup horn (from Heat Systems Ultrasonics) connected to a Branson's sonicator (W-185) at setting No. 3 (70 W of output). The optimum sample size was 80 μl, and the optimum clearance between the test tube and the sonicator horn was 2–3 mm. The concentration of egg lecithin at the reconstitution step was 25 mg/ml, and that of the microsomal protein was approximately 0.3–0.5 mg/ml. The glucose transport activity of reconstituted liposomes was assayed by incubating the latter with a mixture of d-[³H]glucose and l-[¹⁴C]glucose. The incubation was terminated by the addition of HgCl₂, and the reaction mixture was filtered with a Millipore filter (GSWP). The difference in the rates of uptake of d-glucose and l-glucose was regarded as representing the carrier-mediated glucose transport activity. The results of the assay indicated that the glucose transport activity could be reconstituted in a highly reproducible manner. The reconstituted activity was proportional, within a limit of experimental error, to the amount of protein used for reconstitution and was almost completely blocked by cytochalasin B, phloretin, or HgCl₂. However, a small amount of d-glucose was found to bind with the egg lecithin preparation.