Roubenoff R. Rall LC. Veldhuis JD. Kehayias JJ. Rosen C. Nicolson M. Lundgren N. Reichlin S.
Nutrition Exercise Physiology and Sarcopenia Laboratory, Jean Mayer U.S. Department of Agriculture, Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts 02111, USA. roubenoff:hnrc.tufts.edu
The relationship between growth hormone kinetics and sarcopenia in postmenopausal women: the role of fat mass and leptin.
Journal of Clinical Endocrinology & Metabolism. 83(5):1502-6, 1998 May. Abstract
Sarcopenia, the decline in body cell mass (BCM) and especially in muscle mass with age, is an important age-related cause of frailty and loss of independence in the elderly. Because the decline in BCM with age parallels a decline in GH secretion from young adulthood to old age, loss of GH secretion has been considered an important contributory cause of sarcopenia in the elderly. To test this hypothesis in a group of healthy postmenopausal women (n = 15; mean +/- SD age, 66.9 +/- 7.8 yr), 24-h GH concentrations and secretory kinetics were correlated with BCM (measured by whole body counting of 40K) and percent body fat (measured by dual energy x-ray absorptiometry or neutron inelastic scattering). Serum leptin levels were determined as a measure of adipocyte mass. Contrary to prediction, GH secretion was lower in women with higher BCM (r = 0.50; P < 0.05), whereas their mean fat mass was higher (r = 0.51, P < 0.05). These data indicate that sarcopenia in postmenopausal women is not associated with reduced GH secretion and is inversely correlated with fat mass. Serum leptin levels were inversely associated with GH secretion (r = -0.67; P < 0.006). Although a causal relationship has not been demonstrated, these data suggest that leptin could modulate GH secretion through its action on the aging hypothalamic-pituitary axis, or that GH regulates leptin secretion.
Proctor DN. Balagopal P. Nair KS.
Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN 55905, USA.
Age-related sarcopenia in humans is associated with reduced synthetic rates of specific muscle proteins. [Review] [33 refs] Source
Journal of Nutrition. 128(2 Suppl):351S-355S, 1998 Feb. Abstract
Sarcopenia of aging is not explained entirely on the basis of age-associated reduced physical activity. Progressive neuromuscular changes and diminishing anabolic hormone levels are thought to contribute to the pathogenesis of sarcopenia. Decline in muscle mass indicates a decline in muscle protein content. Recent studies demonstrated an age-related decline in synthesis rate of mixed muscle proteins, myosin heavy chain and mitochondrial protein. Reductions in myosin heavy chain and mitochondrial protein synthesis rates have been correlated with age-associated decrements in muscle strength and aerobic exercise tolerance, respectively. These changes have been reported as early as 50 y of age and are related to the decline in insulin-like growth factor (IGF)-I, testosterone and dehydroepiandrosterone (DHEA)-sulfate. The declining ability to remodel these important muscle proteins may therefore play a role in the development of muscle wasting, metabolic abnormalities and impaired physical functioning seen in old age. [References: 33]