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Chronic Hyperinsulinemia Increases Myoblast Proliferation in Fetal Sheep Skeletal Muscle.

Endocrinology | 2016

Insulin is an important fetal growth factor. However, chronic experimental hyperinsulinemia in the fetus fails to accelerate linear and lean mass growth beyond normal rates. Mechanisms preventing accelerated lean mass accretion during hyperinsulinemia are unknown. To address potential mechanisms, late-gestation fetal sheep were infused with iv insulin and glucose to produce euglycemic hyperinsulinemia (INS) or saline for 7-9 days. Fetal substrate uptake and protein metabolic rates were measured. INS fetuses had 1.5-fold higher insulin concentrations (P < .0001) and equivalent glucose concentrations. INS fetuses had 20% more Pax7(+) nuclei in the biceps femoris, which indicates the potential for hyperinsulinemia to increase the number of myoblasts within late-gestation fetal skeletal muscle. Additionally, the percentage of Pax7(+) myoblasts that expressed Ki-67 was 1.3-fold higher and expression of myogenic regulatory factors was 50% lower in INS fetuses (MYF5 and MYOG [myogenin], P < .005), which indicates a shift toward myoblast proliferation over differentiation. There were no differences for fetal body, organ, or muscle weights, although INS placentas weighed 28% less (P < .05). Protein synthesis and accretion rates did not change in INS fetuses, nor did fiber muscle size. Essential amino acid concentrations were lower in the INS group (P < .05) except for tryptophan. Umbilical blood flow, net total amino acids, and O2 uptakes rates did not differ between groups. Arterial O2 content was 33% lower (P < .005) and norepinephrine was 100% higher in the INS fetuses (P < .01), all of which are factors that may counteract fetal protein accretion during hyperinsulinemia despite an increase in myoblast proliferation.

Pubmed ID: 27049667 RIS Download

Associated grants

  • Agency: NIDDK NIH HHS, United States
    Id: R01 DK088139
  • Agency: NIDDK NIH HHS, United States
    Id: R03 DK102972
  • Agency: NCATS NIH HHS, United States
    Id: KL2 TR001080
  • Agency: NCATS NIH HHS, United States
    Id: TL1 TR001081
  • Agency: NIDDK NIH HHS, United States
    Id: K01 DK090199
  • Agency: NICHD NIH HHS, United States
    Id: K12 HD057022
  • Agency: NICHD NIH HHS, United States
    Id: K12 HD068372
  • Agency: NCATS NIH HHS, United States
    Id: UL1 TR001082
  • Agency: NICHD NIH HHS, United States
    Id: K08 HD060688
  • Agency: NICHD NIH HHS, United States
    Id: R01 HD079404

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