25-hydroxycholecalciferol stimulation of muscle metabolism.

Abstract

A B S T R A C T Intact diaphragms from vitamin D-deficient rats were incubated in vitro with ['H]leucine. Oral administration of 10 ug (400 U) of cholecalciferol 7 h before incubation increased leucine incorporation into diaphragm muscle protein by 136% (P <0.001) of the preparation from untreated animals. Nephrectomy did not obliterate this response. ATP content of the diaphragm muscle was also enhanced 7 h after administration of the vitamin. At 4 h after administration of cholecalciferol, serum phosphorus concentration was reduced by 0.7 mg/100 ml (P <0.025) and the rate of inorganic 'PO. accumulation by diaphragm muscle was increased by 18% (P < 0.025) over the untreated animals. Increasing serum phosphate concentration of the vitamin D-deficient animals by dietary supplementation with phosphate for 3 days failed to significantly enhance leucine incorporation into protein. However, supplementation of the rachitogenic, vitamin D-deficient diet with phosphorus for 3 wk stimulated the growth of the animal and muscle ATP levels. This increase in growth and muscle ATP content attributed to the addition of phosphorus to the diet was less than the increase in growth and muscle ATP levels achieved by the addition of both phosphorus and vitamin D to the diet.To eliminate systemic effects of the vitamin, the epitrochlear muscle of the rat foreleg of vitamin D-depleted rats was maintained in tissue culture. Addition of 20 ng/ml of Dr. Birge is a recipient of an American Heart Association Investigatorship. Dr. Haddad is a recipient of a National Institutes of Health Career Development Award.Received for publication 24 February 1975 and in revised form 9 July 1975. pg/ml were without effect. Analysis of muscle cytosol in sucrose density gradients revealed a protein fraction which specifically bound 25-OHD3 and which demonstrated a lesser affinity for 1,25-(OH)2D3. These studies suggest that 25-OHD3 may influence directly the intracellular accumulation of phosphate by muscle and thereby play an important role in the maintenance of muscle metabolism and function.

Les effets musculaires de la vitamine D : application à la perte musculaire liée à l’âge

“…Chez les sujets adultes, ce syndrome est représenté essentiellement par une faiblesse musculaire proximale avec, par exemple, des difficultés à monter les escaliers, à se lever d'une position assise ou accroupie et à soulever des objets lourds. Ajouté à ces observations cliniques, Birge et Haddad (1975), au milieu des années 1970, ont montré que la vitamine D influence directement le méta-bolisme phospho-calcique au sein du diaphragme de rats défi-cients. Depuis, plusieurs études ont montré que le métabolite actif de la vitamine D (1,25(OH) 2 vitamine D) affecte le mé-tabolisme des cellules musculaires en régulant l'expression de nombreux gènes et diverses voies intracellulaires.…”

Papel da vitamina D na função neuro-muscular

“…A partir da exposição aos raios ultravioleta B (UVB), o 7-dehidrocolesterol presente na derme e epiderme é transformado em vitamina D 3 . Esta forma não metabolicamente ativa é transportada pela corrente sanguínea até o fígado, onde sofre uma hidroxilação no carbono 25 …”

“…Os primeiros trabalhos sobre as ações da vitamina D no músculo esquelético tratavam do mecanismo intracelular de contração muscular e foram realizados em animais (1,3,4,13). Mais tarde surgiram estudos clínicos demonstrando a presença de uma miopatia em pacientes com osteomalácia por deficiência grave de vitamina D (14).…”

“…Vários investigadores pesquisaram a participação da deficiência de vitamina D no aumento da oscilação postural e da incidência de quedas entre idosos (3,(9)(10)(11)35). Em um estudo realizado com 83 idosos institucionalizados australianos, observou-se que aqueles que já haviam sofrido alguma queda apresentavam níveis plasmáticos mais baixos de 25(OH)D e mais elevados de PTH do que os que nunca haviam caído (9).…”

“…Entretanto, receptores deste hormônio podem ser encontrados em quase todos tecidos do nosso organismo e outras ações não relacionadas ao metabolismo mineral têm sido imputadas a ele. Dentre estes efeitos estão as ações sobre o músculo esquelético envolvendo o transporte de cálcio e a síntese protéica (1)(2)(3)(4). Além disto, a deficiência de vitamina D tem sido relacionada à diminuição da força e da massa muscular (5)(6)(7)(8), com prejuízo do equilíbrio e aumento da incidência de quedas (9)(10)(11).…”