title: Taurine supplementation restores glucose and carbachol-induced insulin secretion in islets from low-protein diet rats: involvement of Ach-M3R, Synt 1 and SNAP-25 proteins.
abstract: Isolated islets from low-protein (LP) diet rats showed decreased insulin secretion in response to glucose and carbachol (Cch). Taurine (TAU) increases insulin secretion in rodent islets with a positive effect upon the cholinergic pathway. Here, we investigated the effect of TAU administration upon glucose tolerance and insulin release in rats fed on a normal protein diet (17%) without (NP) or with 2.5% of TAU in their drinking water (NPT), and LP diet fed rats (6%) without (LP) or with TAU (LPT). Glucose tolerance was found to be higher in LP, compared to NP rats. However, plasma glucose levels, during ipGTT, in LPT rats were similar to those of controls. Isolated islets from LP rats secreted less insulin in response to increasing glucose concentrations (2.8-22.2 mmol/L) and to 100 μmol/L Cch. This lower secretion was accompanied by a reduction in Cch-induced internal Ca(2+) mobilization. TAU supplementation prevents these alterations, as judged by the higher secretion induced by glucose or Cch in LPT islets. In addition, Ach-M3R, syntaxin 1 and synaptosomal associated protein of 25 kDa protein expressions in LP were lower than in NP islets. The expressions of these proteins in LPT were normalized. Finally, the sarcoendoplasmatic reticulum Ca(2+)-ATPase 3 protein expression was higher in LPT and NPT, compared with controls. In conclusion, TAU supplementation to LP rats prevented alterations in glucose tolerance as well as in insulin secretion from isolated islets. The latter effect involves the normalization of the cholinergic pathway, associated with the preservation of exocytotic proteins.
authors.affiliation: Departamento de Anatomia, Biologia Celular e Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil 13083-865.
authors.forename: Thiago M
authors.initials: TM
authors.lastname: Batista
authors.forename: Rosane A
authors.initials: RA
authors.lastname: Ribeiro
authors.forename: Andressa G
authors.initials: AG
authors.lastname: Amaral
authors.forename: Camila A M
authors.initials: CA
authors.lastname: de Oliveira
authors.forename: Antonio C
authors.initials: AC
authors.lastname: Boschero
authors.forename: Everardo M
authors.initials: EM
authors.lastname: Carneiro
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002217:Carbachol / Q000008:administration & dosage; D018753:Diet, Protein-Restricted; D019587:Dietary Supplements; D005786:Gene Expression Regulation; D005947:Glucose / Q000008:administration & dosage; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D043587:Receptor, Muscarinic M3 / Q000235:genetics / Q000378:metabolism; D050825:Synaptosomal-Associated Protein 25 / Q000235:genetics / Q000378:metabolism; D050827:Syntaxin 1 / Q000235:genetics / Q000378:metabolism; D013654:Taurine / Q000097:blood / Q000494:pharmacology*
chemical_list: D007328:Insulin; D043587:Receptor, Muscarinic M3; C494210:Snap25 protein, rat; C494213:Stx1a protein, rat; D050825:Synaptosomal-Associated Protein 25; D050827:Syntaxin 1; D013654:Taurine; D002217:Carbachol; D005947:Glucose