Effects of vitamin A deficiency and repletion on rat insulin secretion in vivo and in vitro from isolated islets.
We studied the effects of vitamin A deficiency and repletion on rat insulin release and islet cellular retinol binding protein (CRBP) and cellular retinoic acid binding protein (CRABP). Biphasic insulin release from vitamin A-deficient perifused islets was markedly impaired. Release remained impaired with retinoic acid (RA) repletion, 2 micrograms/g diet compared to release from islets of rats repleted with retinol in the form of retinyl palmitate, 4 micrograms/g diet. Release normalized with RA, 8 micrograms/g diet. Vitamin A deficiency did not affect islet insulin content, cell size, number or structure. In vivo, vitamin A-deficient rats had impaired glucose-induced acute insulin release and glucose intolerance, which improved with repletion. Normal islets had greater concentrations of CRBP than CRABP; vitamin A deficiency reduced CRBP but not CRABP levels. We conclude retinol is required for normal insulin secretion. Retinoic acid may substitute for retinol in this function.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D002352:Carrier Proteins / Q000378:metabolism; D002149:Energy Intake; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism* / Q000473:pathology; D011506:Proteins / Q000378:metabolism; D051381:Rats; D018168:Receptors, Retinoic Acid; D012177:Retinol-Binding Proteins / Q000378:metabolism; D054840:Retinol-Binding Proteins, Cellular; D014212:Tretinoin / Q000172:deficiency / Q000494:pharmacology; D014801:Vitamin A / Q000494:pharmacology; D014802:Vitamin A Deficiency / Q000378:metabolism*
D001786:Blood Glucose; D002352:Carrier Proteins; D007328:Insulin; D011506:Proteins; D018168:Receptors, Retinoic Acid; D012177:Retinol-Binding Proteins; D054840:Retinol-Binding Proteins, Cellular; D014801:Vitamin A; D014212:Tretinoin