Induction of a glucose-dependent insulin secretory response by the nonmetabolizable amino acid alpha-aminoisobutyric acid.

The effects of the nonmetabolizable amino acid alpha-aminoisobutyric acid (AIB) on insulin release were evaluated using beta cell-rich pancreatic islets from ob/ob mice. Both AIB and L-alanine promptly induced transient insulin release during column perifusion of islet cells. The secretory response was dependent on an elevated level of glucose and effectively suppressed by removal of Na+. The insulin release elicited by AIB fulfilled the criteria of a physiological event in being suppressed by clonidine or lowering of the temperature to 22 degrees C. AIB effectively promoted the increase in sodium (total as well as ionized cytoplasmic) obtained with ouabain blockage of the Na/K pump. When added to a medium containing 11 mM glucose, AIB altered cytoplasmic Ca2+ in terms of both an initial transitory rise and transformation of existing oscillations into a sustained elevation. It is concluded that amino acids can stimulate insulin release from mature beta cells by virtue of being cotransported with Na+.