phytoestrogens and Muscular-Atrophy

Exercise has a beneficial effect on bone, possibly by stimulating estrogen receptor alpha. Because estrogen up-regulates this receptor, estrogen therapy combined with exercise training may be optimal for increasing bone mineral density. Studies combining estrogen therapy and exercise training in postmenopausal women show mixed results, but indicate that the combination of interventions may be more effective for increasing bone mass than either intervention alone. Plant-like estrogens (i.e phytoestrogens such as soy isoflavones) may act as weak estrogen agonists or antagonists, have small beneficial effects on bone, and may interact with exercise for increasing bone mineral density. Phytoestrogen derived from flaxseed (flax lignans) has not been evaluated as extensively as soy isoflavones and thus its effect on bone is difficult to determine. Estrogen or soy isoflavones given to postmenopausal women results in a small increase in lean tissue mass that may be mediated through estrogen receptor alpha on muscle or through decreased inflammation.

Topics: Aged; Aging; Bone and Bones; Estrogens; Exercise; Female; Humans; Muscle, Skeletal; Muscular Atrophy; Phytoestrogens

The aim of this study was to verify if six months of isoflavone supplementation could increase fat-free mass (FFM) and muscle mass index (MMI=appendicular FFM/height(2)) in obese-sarcopenic postmenopausal women.. Double-blind randomized study.. Eighteen sarcopenic-obese women completed the study (12 on isoflavones and six on placebo). Body composition was measured by dual-energy X-ray absorptiometry. Subjects ingested 70 mg of isoflavones per day (44 mg of diadzein, 16 mg glycitein and 10 mg genestein) or a placebo for 24 weeks.. The isoflavone group increased significantly appendicular (P=0.034), leg (P=0.016) FFM and MMI (P=0.037), but not the placebo group.. Six months of isoflavone supplementation increased FFM and MMI in obese-sarcopenic postmenopausal women.

Topics: Absorptiometry, Photon; Aged; Aging; Body Composition; Dietary Supplements; Double-Blind Method; Female; Humans; Isoflavones; Middle Aged; Muscle, Skeletal; Muscular Atrophy; Obesity; Phytoestrogens; Postmenopause; Treatment Outcome

8-Prenylnaringenin (8-PN) is a prenylflavonoid that originates from hop extracts and is thought to help prevent disuse muscle atrophy. We hypothesized that 8-PN affects muscle plasticity by promoting muscle recovery under disuse muscle atrophy. To test the promoting effect of 8-PN on muscle recovery, we administered an 8-PN mixed diet to mice that had been immobilized with a cast to one leg for 14 days. Intake of the 8-PN mixed diet accelerated recovery from muscle atrophy, and prevented reductions in Akt phosphorylation. Studies on cell cultures of mouse myotubes in vitro demonstrated that 8-PN activated the PI3K/Akt/P70S6K1 pathway at physiological concentrations. A cell-culture study using an inhibitor of estrogen receptors and an in vivo experiment with ovariectomized mice suggested that the estrogenic activity of 8-PN contributed to recovery from disuse muscle atrophy through activation of an Akt phosphorylation pathway. These data strongly suggest that 8-PN is a naturally occurring compound that could be used as a nutritional supplement to aid recovery from disuse muscle atrophy.

Topics: Animals; Cell Line; Enzyme Activation; Flavanones; Hindlimb Suspension; Male; Mice; Mice, Inbred C57BL; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Oncogene Protein v-akt; Phosphorylation; Phytoestrogens; Protein Biosynthesis; Recovery of Function; Signal Transduction; Treatment Outcome