title: Maternal food restriction enhances insulin-induced GLUT-4 translocation and insulin signaling pathway in skeletal muscle from suckling rats.
abstract: Restriction of protein calories during stages of immaturity has a major influence on glucose metabolism and increases the risk of type 2 diabetes in adulthood. However, it is known that reduction of food intake alleviates insulin resistance. We previously demonstrated an improved insulin-induced glucose uptake in skeletal muscle of chronically undernourished adult rats. The purpose of this work was to investigate whether this condition is present during suckling, a period characterized by physiological insulin resistance as well as elucidate some of the underlying mechanisms. With this aim, 10-d-old pups from food-restricted dams were studied. We showed that undernourished suckling rats are glucose normotolerants, despite their depressed insulin secretion capacity. The content of the main glucose transporters in muscle, GLUT-4 and GLUT-1, was not affected by undernutrition, but fractionation studies showed an improved insulin-stimulated GLUT-4 translocation. p38MAPK protein, implicated in up-regulation of intrinsic activity of translocated GLUT-4, was increased. These changes suggest an improved insulin-induced glucose uptake associated with undernutrition. Insulin receptor content as well as that of both regulatory and catalytic phosphoinositol 3-kinase subunits was increased by food restriction. Insulin receptor substrate-1-associated phosphoinositol 3-kinase activity after insulin was enhanced in undernourished rats, as was phospho-glycogen synthase kinase-3, in line with insulin hypersensitivity. Surprisingly, protein tyrosine phosphatase-1B association with insulin receptor was also increased by undernutrition. These adaptations to a condition of severely limited nutritional resources might result in changes in the development of key tissues and be detrimental later in life, when a correct amount of nutrients is available, as the thrifty phenotype hypothesis predicts.
authors.affiliation: Instituto de Bioquímica (Consejo Superior de Investigaciones Centíficas-Universidad Complutense de Madrid), Facultad de Farmacia, Universidad Complutense, Ciudad Universitaria, 28040 Madrid, Spain.
authors.forename: M L
authors.initials: ML
authors.lastname: Gavete
authors.forename: M A
authors.initials: MA
authors.lastname: Martín
authors.forename: C
authors.initials: C
authors.lastname: Alvarez
authors.forename: F
authors.initials: F
authors.lastname: Escrivá
mesh_terms: D000818:Animals; D000833:Animals, Suckling; D004038:Diet, Reducing; D002149:Energy Intake; D005260:Female; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000187:drug effects / Q000378:metabolism*; D009124:Muscle Proteins / Q000187:drug effects / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000502:physiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat