The ontogeny of insulin signaling in the preterm baboon model.
Hyperglycemia, a prevalent condition in premature infants, is thought to be a consequence of incomplete suppression of endogenous glucose production and reduced insulin-stimulated glucose disposal in peripheral tissues. However, the molecular basis for these conditions remains unclear. To test the hypothesis that the insulin transduction pathway is underdeveloped with prematurity, fetal baboons were delivered, anesthetized, and euthanized at 125 d gestational age (GA), 140 d GA, or near term at 175 d GA. Vastus lateralis muscle and liver tissues were obtained, and protein content of insulin signaling molecules [insulin receptor (IR)-beta, IR substate-1, p85 subunit of phosphatidylinositol 3-kinase, Akt, and AS160] and glucose transporters (GLUT)-1 and GLUT4 was measured by Western blotting. Muscle from 125 d GA baboons had markedly reduced GLUT1 protein content (16% of 140 d GA and 9% of 175 d GA fetuses). GLUT4 and AS160 also were severely reduced in 125 d GA fetal muscle (43% of 175 d GA and 35% of 175 d GA, respectively). In contrast, the protein content of IR-beta, IR substate-1, and Akt was elevated by 1.7-, 5.2-, and 1.9-fold, respectively, in muscle from 125 d GA baboons when compared with 175 d GA fetuses. No differences were found in the content of insulin signaling proteins in liver. In conclusion, significant gestational differences exist in the protein content of several insulin signaling proteins in the muscle of fetal baboons. Reduced muscle content of key glucose transport-regulating proteins (GLUT1, GLUT4, AS160) could play a role in the pathogenesis of neonatal hyperglycemia and reduced insulin-stimulated glucose disposal.
Department of Pediatrics, Diabetes Division, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229, USA. blanco@uthscsa.edu
Cynthia L
CL
Blanco
Hanyu
H
Liang
Joaquin
J
Joya-Galeana
Ralph A
RA
DeFronzo
Donald
D
McCurnin
Nicolas
N
Musi
D000818:Animals; D000831:Animals, Newborn; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D004195:Disease Models, Animal; D005260:Female; D005865:Gestational Age; D051272:Glucose Transporter Type 1 / Q000378:metabolism; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D007328:Insulin / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D008099:Liver / Q000196:embryology / Q000378:metabolism; D008297:Male; D008992:Monkey Diseases / Q000097:blood / Q000378:metabolism / Q000503:physiopathology*; D018482:Muscle, Skeletal / Q000196:embryology / Q000378:metabolism; D010215:Papio; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011972:Receptor, Insulin / Q000378:metabolism; D015398:Signal Transduction
D001786:Blood Glucose; D051272:Glucose Transporter Type 1; D051275:Glucose Transporter Type 4; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt