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Articles by F. M Matschinsky
Total Records ( 2 ) for F. M Matschinsky
  S Sayed , D. R Langdon , S Odili , P Chen , C Buettger , A. B Schiffman , M Suchi , R Taub , J Grimsby , F. M Matschinsky and C. A. Stanley
  OBJECTIVE

Heterozygous activating mutations of glucokinase have been reported to cause hypoglycemia attributable to hyperinsulinism in a limited number of families. We report three children with de novo glucokinase hyperinsulinism mutations who displayed a spectrum of clinical phenotypes corresponding to marked differences in enzyme kinetics.

RESEARCH DESIGN AND METHODS

Mutations were directly sequenced, and mutants were expressed as glutathionyl S-transferase–glucokinase fusion proteins. Kinetic analysis of the enzymes included determinations of stability, activity index, the response to glucokinase activator drug, and the effect of glucokinase regulatory protein.

RESULTS

Child 1 had an ins454A mutation, child 2 a W99L mutation, and child 3 an M197I mutation. Diazoxide treatment was effective in child 3 but ineffective in child 1 and only partially effective in child 2. Expression of the mutant glucokinase ins454A, W99L, and M197I enzymes revealed a continuum of high relative activity indexes in the three children (26, 8.9, and 3.1, respectively; wild type = 1.0). Allosteric responses to inhibition by glucokinase regulatory protein and activation by the drug RO0281675 were impaired by the ins454A but unaffected by the M197I mutation. Estimated thresholds for glucose-stimulated insulin release were more severely reduced by the ins454A than the M197I mutation and intermediate in the W99L mutation (1.1, 3.5, and 2.2 mmol/l, respectively; wild type = 5.0 mmol/l).

CONCLUSIONS

These results confirm the potency of glucokinase as the pancreatic β-cell glucose sensor, and they demonstrate that responsiveness to diazoxide varies with genotype in glucokinase hyperinsulinism resulting in hypoglycemia, which can be more difficult to control than previously believed.

  N Gao , J Le Lay , W Qin , N Doliba , J Schug , A. J Fox , O Smirnova , F. M Matschinsky and K. H. Kaestner
 

Foxa1 and Foxa2 play both redundant and distinct roles in early pancreas development. We demonstrate here that inducible ablation of both transcription factors in mature mouse β-cells leads to impaired glucose homeostasis and insulin secretion. The defects in both glucose-stimulated insulin secretion and intracellular calcium oscillation are more pronounced than those in β-cells lacking only Foxa2. Unexpectedly, in contrast to the severe reduction of β-cell-enriched factors contributing to metabolic and secretory pathways, expression of a large number of genes that are involved in neural differentiation and function is significantly elevated. We further demonstrate that expression of carbohydrate response element-binding protein (ChREBP or Mlxipl), an important transcriptional regulator of carbohydrate metabolism, is significantly affected in compound Foxa1/a2 mutant β-cells. ChREBP expression is directly controlled by Foxa1 and Foxa2 in both the fetal endocrine pancreas as well as mature islets. These data demonstrate that Foxa1 and Foxa2 play crucial roles in the development and maintenance of β-cell-specific secretory and metabolic pathways.

 
 
 
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