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  • Key words Insulin secretion impairment, secondary sulphonylurea failure, mitochondria, maternal inheritance.  (1)
  • glucose transport  (1)
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  • 1
    ISSN: 1432-0428
    Keywords: Key words Insulin secretion impairment, secondary sulphonylurea failure, mitochondria, maternal inheritance.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Mutations in the mitochondrial gene were recently identified in a large pedigree of diabetes mellitus and deafness. As the mitochondrial gene is maternally inherited, Japanese diabetic patients whose mothers were also diabetic were screened, using peripheral leucocytes, for an A to G transition at nucleotide pair 3243 of the mitochondrial gene, a tRNALeu(UUR) mutation. This mutation was identified in four pedigrees from among 300 unrelated patients who were screened. Diabetes co-segregated with the mutation, except in one young subject, and was maternally inherited. The apparent onset of disease occurred between 11 and 68 years of age. Some of the affected members developed hearing impairment and congestive heart failure due to cardiomyopathy, though generally long after the onset of diabetes, and these patients had therefore not been diagnosed as having a specific form of diabetes. The duration of sulphonylurea treatment was not more than 8 years in these pedigrees and affected members were prone to progression to insulin-requiring diabetes. Thus, these patients were secondary sulphonylurea failures. Long-term follow-up revealed that the underlying disorder in affected members is a progressive impairment of insulin secretion. Some were initially diagnosed as having IDDM based on an apparent acute onset in youth and the clinical severity of their diabetes. Others were regarded as having MODY with an aggressive course. The mitochondrial gene mutation or diabetes is not transmitted to all offspring of the affected mothers. In conclusion, a mitochondrial tRNALeu(UUR) gene mutation accounts for slightly more than 1 % of diabetic patients with maternally inherited disease and manifests a wide range of diabetic phenotypes, from the NIDDM phenotype to IDDM, in Japanese. [Diabetologia (1994) 37: 504–510]
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Clonal beta-cell line ; insulin secretion ; glucose transport ; glucose phosphorylation ; glucose utilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Glucose-stimulated insulin secretion, glucose transport, glucose phosphorylation and glucose utilization have been characterized in the insulinoma cell line MIN6, which is derived from a transgenic mouse expressing the large T-antigen of SV40 in pancreatic beta cells. Glucose-stimulated insulin secretion occurred progressively from 5 mmol/l glucose, reached the maximal level approximately seven-fold above the basal level at 25 mmol/l, and remained at this level up to 50 mmol/l. Glucose transport was very rapid with the half-maximal uptake of 3-O-methyl-d-glucose being reached within 15 s at 22 °C. Glucose phosphorylating activity in the cell homogenate was due mainly to glucokinase; the Vmax value of glucokinase activity was estimated to be 255±37 nmol·h−1·mg protein−1, constituting approximately 80% of total phosphorylating activity, whereas hexokinase activity constituted less than 20%. MIN6 cells exhibited mainly the high Km component of glucose utilization with a Vmax of 289±18 nmol·h−1·mg protein−1. Thus, glucose utilization quantitatively and qualitatively reflected glucose phosphorylation in MIN6 cells. In contrast, MIN7 cells, which exhibited only a small increase in insulin secretion in response to glucose, had 4.7-fold greater hexokinase activity than MIN6 cells with a comparable activity of glucokinase. These characteristics in MIN6 cells are very similar to those of isolated islets, indicating that this cell line is an appropriate model for studying the mechanism of glucose-stimulated insulin secretion in pancreatic beta cells.
    Type of Medium: Electronic Resource
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