IGF alters jejunal glucose transporter expression and serum glucose levels in immature rats.
Milk-borne insulin-like growth factors (IGFs) enhance nutrient absorption in the immature intestine, which is characterized by low levels of glucose oxidation. We therefore hypothesized that feeding a rat milk substitute (RMS) devoid of growth factors to rat pups would lower serum glucose levels relative to dam-fed control rats and that supplementation of RMS with physiological doses of either IGF-I or IGF-II would normalize serum glucose levels via increased jejunal glucose transporter 2 (GLUT2) and high-affinity Na(+)-glucose cotransporter (SGLT1) expression. We found lower serum glucose concentrations in RMS-fed pups; in contrast, serum glucose levels in the IGF-supplemented pups were similar to those of dam-fed controls. RT-PCR and laser scanning confocal microscopy similarly demonstrated that IGF supplementation increased expression of jejunal glucose transporters. Further experiments demonstrated that IGF supplementation altered mRNA levels of key mitochondrial enzymes without altering jejunal lactase activity. We conclude that IGF-I and IGF-II supplementation increases serum glucose levels in the immature rat pup fed artificial formula and alters gene expression of the jejunal glucose transporters.
Lane
Robert H
RH
Department of Pediatrics, David Geffen School of Medicine at University of California Los Angeles, Mattel Children's Hospital, Los Angeles, California 90095-1752, USA. rlane@mednet.ucla.edu
Dvorak
Bohuslav
B
MacLennan
Nicole K
NK
Dvorakova
Katerina
K
Halpern
Melissa D
MD
Pham
Tho D
TD
Philipps
Anthony F
AF
D000821:Animal Feed; D000818:Animals; D000833:Animals, Suckling; D001786:Blood Glucose / Q000378:metabolism*; D001835:Body Weight / Q000187:drug effects; D004032:Diet; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D007583:Jejunum / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D043322:Lactase; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008892:Milk / Q000737:chemistry; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051269:Sodium-Glucose Transporter 1; D013002:Somatomedins / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000378:metabolism
D001786:Blood Glucose; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495676:Slc5a1 protein, rat; D051269:Sodium-Glucose Transporter 1; D013002:Somatomedins; D043322:Lactase; D001616:beta-Galactosidase