Summary
The insulinotropic effects of L-leucine and α-ketoisocaproic acid have been compared in perifused isolated pancreatic islets. In contrast to α-ketoisocaproic acid (10 mM), L-leucine (10 mM) released less insulin in the presence than in the absence of glucose (5 mM). Changes of islet cell metabolism accompanying insulin release were studied by recording the fluorescence of reduced pyridine nucleotides. The traces of L-leucine-or α-ketoisocaproic acid-induced fluorescence increase differed both in the absence and in the presence of glucose (5 mM). When the medium perif using the islets contained 30 mM L-leucine, α-ketoisocaproic acid (10 mM) still triggered a significant insulin release. These results argue against an indirect action of α-ketoisocaproic acid via transformation to L-leucine. Isocaproic acid (10 mM), L-α-hydroxyisocaproic acid (10 mM) or α-ketoisovaleric acid stimulated no remarkable insulin release, demonstrating that the strong insulinotropic effect of α-ketoisocaproic acid is coupled both to its α-ketogroup and to the length of its carbon chain.
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Panten, U., Christians, J., Kriegstein, E.V. et al. Studies on the mechanism of L-leucine- and α-ketoisocaproic acid — Induced insulin release from perifused isolated pancreatic islets. Diabetologia 10, 149–154 (1974). https://doi.org/10.1007/BF01219672
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DOI: https://doi.org/10.1007/BF01219672