Pancreatic islet function in omega-3 fatty acid-depleted rats: alteration of calcium fluxes and calcium-dependent insulin release.
Considering the insufficient supply of long-chain polyunsaturated omega-3 fatty acids often prevailing in Western populations, this report deals mainly with alterations of Ca(2+) fluxes and Ca(2+)-dependent insulin secretory events in isolated pancreatic islets from omega-3-depleted rats. In terms of (45)Ca(2+) handling, the islets from omega-3-depleted rats, compared with those from normal animals, displayed an unaltered responsiveness to an increase in extracellular K(+) concentration, a lower inflow rate and lower fractional outflow rate of the divalent cation, and higher (45)Ca(2+)-labeled cellular pool(s) at isotopic equilibrium. The latter anomaly was corrected 120 min after intravenous injection of a novel medium-chain triglyceride-fish oil (MCT:FO) emulsion, distinct from a control omega-3-poor MCT-olive oil (MCT:OO) emulsion. At 8.3 mM D-glucose, insulin release was higher in islets from omega-3-depleted rats vs. control animals, coinciding with a higher cytosolic Ca(2+) concentration. The relative magnitude of the increase in insulin output attributable to a rise in D-glucose as well as extracellular Ca(2+) or K(+) concentration, to the absence vs. presence of verapamil and to the presence vs. absence of extracellular Ca(2+), theophylline, phorbol 12-myristate 13-acetate, or Ba(2+), was always more pronounced in islets from omega-3-depleted rats injected with the MCT:OO compared with the MCT:FO emulsion. A comparable situation prevailed when comparing islets from noninjected omega-3-depleted and normal rats. In light of these and previous findings, we propose that an impairment of Na(+),K(+)-ATPase activity plays a major, although not an exclusive, role in the perturbation of Ca(2+) fluxes and Ca(2+)-dependent secretory events in the islets from omega-3-depleted rats.
Zhang
Y
Y
Laboratory of Experimental Hormonology, Brussels Free University, 808 Route de Lennik, B-1070 Brussels, Belgium.
Oguzhan
B
B
Louchami
K
K
Chardigny
J-M
JM
Portois
L
L
Carpentier
Y A
YA
Malaisse
W J
WJ
Herchuelz
A
A
Sener
A
A
D000818:Animals; D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004032:Diet; D015525:Fatty Acids, Omega-3 / Q000378:metabolism* / Q000494:pharmacology; D005260:Female; D005395:Fish Oils / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D000069463:Olive Oil; D010938:Plant Oils / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013806:Theophylline / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D015525:Fatty Acids, Omega-3; D005395:Fish Oils; D007328:Insulin; D000069463:Olive Oil; D010938:Plant Oils; D001464:Barium; D013806:Theophylline; D014700:Verapamil; D005947:Glucose; D013755:Tetradecanoylphorbol Acetate; D011188:Potassium; D002118:Calcium