Obesity is the major cause of alterations in insulin secretion and calcium fluxes by isolated islets from aged rats.
To investigate the alterations in insulin secretion induced by aging, 2-month-old, 12-month-old, and 12-month old lean rats (submitted to a caloric restriction during the last month that causes a weight loss of approximately 20%) were studied. As expected, glucose intolerance and increased insulin response were observed during IV-GTT in 12-month-old rats. These effects were, however, reversed by weight loss. Insulin secretion was investigated in isolated islets both during static incubation and perifusion. In 12-month-old rats insulin secretion and 45Ca2+ efflux were lower only in the second phase of the hormonal secretion, suggesting an involvement of voltage-sensitive calcium channels in these phenomena. Considering that in vivo and in vitro alterations were reversed after weight loss, it is possible to conclude that obesity is probably a major cause of impaired insulin secretion in 12-month-old albino rats. Since 14C-glucose metabolism was not changed in islets from aged rats, the effect of obesity on insulin secretion is not due to altered glucose metabolism in pancreatic B-cells.
Machado
U F
UF
Department of Physiology and Biophysics, University of São Paulo, Brazil.
Nogueira
C R
CR
Carpinelli
A R
AR
D000375:Aging / Q000502:physiology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology; D046508:Culture Techniques; D007328:Insulin / Q000502:physiology*; D007515:Islets of Langerhans / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D009765:Obesity / Q000503:physiopathology*; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar
D001786:Blood Glucose; D015220:Calcium Channels; D007328:Insulin; D002118:Calcium