Anaplerotic input is sufficient to induce time-dependent potentiation of insulin release in rat pancreatic islets.
Nutrients that induce biphasic insulin release, such as glucose and leucine, provide acetyl-CoA and anaplerotic input in the beta-cell. The first phase of release requires increased ATP production leading to increased intracellular Ca(2+) concentration ([Ca(2+)](i)). The second phase requires increased [Ca(2+)](i) and anaplerosis. There is strong evidence to indicate that the second phase is due to augmentation of Ca(2+)-stimulated release via the K(ATP) channel-independent pathway. To test whether the phenomenon of time-dependent potentiation (TDP) has similar properties to the ATP-sensitive K(+) channel-independent pathway, we monitored the ability of different agents that provide acetyl-CoA and anaplerotic input or both of these inputs to induce TDP. The results show that anaplerotic input is sufficient to induce TDP. Interestingly, among the agents tested, the nonsecretagogue glutamine, the nonhydrolyzable analog of leucine aminobicyclo[2.2.1]heptane-2-carboxylic acid, and succinic acid methyl ester all induced TDP, and all significantly increased alpha-ketoglutarate levels in the islets. In conclusion, anaplerosis that enhances the supply and utilization of alpha-ketoglutarate in the tricarboxylic acid cycle appears to play an essential role in the generation of TDP.
Dept. of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Subhadra C
SC
Gunawardana
Yi-Jia
YJ
Liu
Michael J
MJ
Macdonald
Susanne G
SG
Straub
Geoffrey W G
GW
Sharp
D000105:Acetyl Coenzyme A / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000598:Amino Acids, Cyclic / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002952:Citric Acid Cycle / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D007656:Ketoglutaric Acids / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D013268:Stimulation, Chemical; D015854:Up-Regulation
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D007328:Insulin; D007656:Ketoglutaric Acids; C006504:2-aminobicyclo(2,2,1)heptane-2-carboxylic acid; D000105:Acetyl Coenzyme A; D005947:Glucose; D002118:Calcium