Modulation of insulin secretion by leptin.
The present study examines the acute effect of leptin (50 nM) on insulin secretion and on the fractional outflow rates of 45Ca2+ and 86Rb+ from pancreatic islets isolated from male lean albino rats. Under a constant physiological glucose concentration (5.6 mM), the addition of leptin to the perifusion medium led to an increment in 45Ca2+ fractional outflow rate followed by a significant (p < 0.05) increase (26%) in the insulin release. At low glucose concentration (2.8 mM), leptin also elicited a significant (p < 0.05; 50-60%) increase in insulin secretion. However, under supraphysiological (16.7 mM) glucose concentration, the rapid first-phase insulin secretion response was abolished. At low glucose levels, islets perifused in the presence of leptin presented a lower 86Rb+ fractional outflow rate compared with perifused controls. In contrast, when glucose was switched to 16.7 mM, compared with controls, a slight increase in the 86Rb+ fractional outflow rate was observed instead. These in vitro data provide evidence that, by changing K+ fluxes, leptin might modulate insulin secretion from pancreatic islets.
Ceddia
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RB
Department of Physical Education, Fluminense Federal University, Rio de Janeiro, Brazil.
William
W N
WN
Carpinelli
A R
AR
Curi
R
R
D000818:Animals; D002118:Calcium / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D020738:Leptin; D008297:Male; D011506:Proteins / Q000494:pharmacology*; D051381:Rats; D012413:Rubidium / Q000378:metabolism
D007328:Insulin; D020738:Leptin; D011506:Proteins; D005947:Glucose; D012413:Rubidium; D002118:Calcium