Insulin secretion regulation in pancreatic islets from taurine-supplemented mice

Author(s)

Rosane Aparecida Ribeiro

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2009-03-16

Examining board members

Everardo Magalhães Carneiro; Licio Augusto Velloso; Claudio Chrysostomo Werneck; Silvana Bordin; Carla Roberta de Oliveira Carvalho

• Advisor: Everardo Magalhães Carneiro

Abstract

In this study, we investigated the effects of taurine (TAU)-supplementation (2% in the drinking water) on glucose tolerance and insulin secretion stimulated by different secretagogues in adult mice. TAU-supplemented mice showed enhanced glucose tolerance and insulin sensitivity when compared to controls (CTL). In addition, their islets secreted more insulin in response to high concentrations of glucose and L-leucine. L-[U-14C]leucine oxidation was higher in TAU islets compared with CTL islets, whereas D-[U-14C]glucose oxidation, ATP levels, and the protein expression of the glucose transporter (GLUT) 2 and of glucokinase (GCK) were similar. 45Ca uptake induced by high glucose concentrations was increased in TAU islets as well as the expression of the ß2 subunit of the L-type Ca2+ channel. In addition, the insulin secretion induced by carbachol (Cch) and IBMX, but not, by forskolin and PMA was higher in TAU-supplemented compared with CTL islets. The higher insulin secretion in the presence of Cch is accompanied by an increase in the expression of PL (phospholipase) C ß 2 protein and a higher intracellular Ca2+ mobilization. Besides, TAU-supplemented islets showed increased PK (protein kinase) Aa expression. Since the increase in Ca2+ uptake induced by glucose in TAU islets was minimized by the presence of the PKA inhibitor, H89, this kinase seems to be important for the better Ca2+ handling in these islets. TAUsupplementation also turns the a-cells more sensitivity since these cells secreted more glucagons compared with CTL islets. In conclusion, TAU supplementation enhances glucose tolerance and insulin sensitivity in mice and turns the islets more sensitive to nutrients and to potentiators of secretion. The effect on insulin secretion seems to be linked to a better Ca2+ handling by ß-cells. (AU)