Interactions between the Metabolism of L-Leucine and D-Glucose in the Pancreatic β-Cells

Abstract

β-Cell-rich pancreatic islets micro dissected from obese-hyperglycemic mice were used to study interactions between the metabolism of L-leucinc and D-glucose. L-leucine reduced the islet content of aspartic acid whereas D-glucose, when added to L-leucine-incubatcd islets, increased the contents of aspartic acid and γ-aminobutyric acid (GABA). D-glucose also increased the incorporation of L-leucine carbon into aspartic acid, GABA and glutamic acid suggesting stimulation of a malate shuttle mechanism. When expressed per mole of the individual amino acids, the incorporation of Lleucine carbon into GABA was 2.5-4 times higher than into glutamic acid indicating intracellular compartmentation of the latter amino acid. Both L-leucine and D-leucine stimulated ¹⁴CO₂ production from ¹⁴C-labelled D-glucose. L-leucine did not affect ³H₂O production from tritiated D-glucose. The present data do not indicate a role of other amino acids or D-glucose in L-leucine-stimulated insulin release.

Key words

Pancreatic β-Cells - Amino Acid Contents - Leucine Carbon Incorporation - Glucose Oxidation - Glucose Utilization