Citations: 1-2
<1>
Authors
Roubenoff R. Rall LC. Veldhuis JD. Kehayias JJ. Rosen C. Nicolson M.
Lundgren N. Reichlin S.
Institution
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
Title
The relationship between growth hormone kinetics and
sarcopenia in postmenopausal women: the role of fat mass and
leptin.
Source
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.
<2>
Authors
Proctor DN. Balagopal P. Nair KS.
Institution
Endocrine Research Unit, Mayo Clinic and Foundation, Rochester, MN 55905,
USA.
Title
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]