Mechanisms of amino acid-induced insulin secretion from the glucose-responsive BRIN-BD11 pancreatic B-cell line

The effects of different classes of amino acids known to be transported and utilized by pancreatic B-cells were examined using the novel glucose-responsive pancreatic B-cell line, BRIN-BD11. Amino acids tested included α-aminoisobutyric acid, L-alanine, L-arginine, L-glutamine, glycine, L-leucine, L-lysine, L-proline and L-serine. At non-stimulatory (1.1 mmol/l) glucose, acute incubations with either 1 or 10 mmol/l amino acid evoked 1.3- to 4.7-fold increases of insulin release. Raising glucose to 16.7 mmol/l enhanced the effects of all amino acids except L-glutamine, and increased insulin output at 10 mmol/l compared with 1 mmol/l amino acid. Glyceraldehyde (10 mmol/l) also served to promote 10 mmol/l amino acid-induced insulin secretion with the exceptions of L-arginine, glycine, L-lysine and L-proline. At 16.7 mmol/l glucose, diazoxide (300 μmol/l) significantly decreased the secretory response to all amino acids except L-glutamine. Likewise, verapamil (20 μmol/l) or depletion of extracellular Ca²⁺ reduced insulin output indicating the importance of Ca²⁺ influx in the actions of amino acids. These data indicate that BRIN-BD11 cells transport and utilize amino acids, acting in association with glycolysis, K⁺-ATP channels and/or voltage-dependent Ca²⁺ channels to promote Ca²⁺ influx and insulin secretion. The response of BRIN-BD11 cells to glucose and amino acids indicates that this is a useful cell line for future research on the mechanisms of nutrient regulation of insulin secretion.