Mutations in the promoter of adenylyl cyclase (AC)-III gene, overexpression of AC-III mRNA, and enhanced cAMP generation in islets from the spontaneously diabetic GK rat model of type 2 diabetes

• Published in: Diabetes (New York, N.Y.) Vol. 47; no. 3; pp. 498 - 504
• Main Authors: ABDEL-HALIM, S. M, GUENIFI, A, BING HE, BEI YANG, MUSTAFA, M, HÖJEBERG, B, HILLERT, J, BAKHIET, M, EFENDIC, S
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.03.1998
• Subjects: Adenylyl Cyclases - genetics; Animals; Base Sequence; Biological and medical sciences; Cohort Studies; Cyclic AMP - biosynthesis; Diabetes Mellitus, Type 2 - enzymology; Diabetes Mellitus, Type 2 - genetics; Diabetes Mellitus, Type 2 - pathology; Diabetes. Impaired glucose tolerance; Disease Models, Animal; DNA Primers - chemistry; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Gene Expression Regulation, Enzymologic - genetics; In Situ Hybridization; In Vitro Techniques; Insulin - metabolism; Insulin Secretion; Islets of Langerhans - chemistry; Islets of Langerhans - metabolism; Islets of Langerhans - pathology; Male; Medical sciences; Medicin och hälsovetenskap; Mutation - genetics; Polymerase Chain Reaction; Promoter Regions, Genetic - genetics; Rats; Rats, Inbred Strains; Rats, Wistar; RNA, Messenger - analysis; RNA, Messenger - genetics; Endocrinopathy; Animal model; Rat; Enzyme; Isozyme; Transcription promoter; Rodentia; Langerhans islet; Phosphorus-oxygen lyases; Cyclic AMP; Lyases; Gene expression; Non insulin dependent diabetes; Adenylate cyclase; Vertebrata; Mammalia; Mutation; Endocrine pancreas
• ISSN: 0012-1797; 1939-327X
• DOI: 10.2337/diabetes.47.3.498

Mutations in the promoter of adenylyl cyclase (AC)-III gene, overexpression of AC-III mRNA, and enhanced cAMP generation in islets from the spontaneously diabetic GK rat model of type 2 diabetes. S M Abdel-Halim , A Guenifi , B He , B Yang , M Mustafa , B Höjeberg , J Hillert , M Bakhiet and S Efendić Department of Molecular Medicine, Karolinska Hospital, Stockholm, Sweden. samy.abdel-halim@molmed.ki.se Abstract Glucose-induced insulin release is decreased in the spontaneously diabetic GK rat, a nonobese rodent model of type 2 diabetes. Forskolin restores the impaired insulin release in both the isolated perfused pancreas and isolated islets from these rats (Abdel-Halim et al., Diabetes 45:934-940, 1996). We demonstrate here that the insulinotropic effect of forskolin in the GK rat is due to increased generation of cAMP and that it is associated with overexpression of adenylyl cyclase (AC)-III mRNA and gene mutations. The AC-III mRNA overexpression was demonstrated by in situ hybridization using oligonucleotide probes binding to different regions of the rat AC-III mRNA. It was associated with the presence of two point mutations identified at positions -28 bp (A --> G) and -358 bp (A --> C) of the promoter region of the AC-III gene and was demonstrable in both GK rat islets and peripheral blood cells. Transfection of COS cells with a luciferase reporter gene system revealed up to 25-fold increased promoter activity of GK AC-III promoter when compared with normal rat promoter (P < 0.0001). In conclusion, forskolin restores the impaired insulin release in islets of the GK rat through enhanced cAMP generation. This is linked to overexpression of AC-III mRNA in GK islets due to two functional point mutations in the promoter region of the AC-III gene.