Abnormal regulation of intermediary metabolism after oral glucose ingestion in myotonic dystrophy.

The responses of plasma insulin and blood intermediary metabolites to oral glucose (75 g) were determined in 10 subjects with myotonic dystrophy. Results were compared with responses in 10 normal control subjects matched for age, sex, and body mass index. Fasting hyperinsulinemia was observed in the myotonic subjects (7.5 +/- 1.6 v 2.4 +/- 0.4 mU/L; P less than .005) and plasma insulin concentration remained significantly higher following oral glucose (F = 38.09; P less than .001). Total cumulative insulin release was markedly higher in the myotonic subjects (4,984.3 v 1,286.6 mU/L; P less than .0001). Basal blood glucose concentration was normal (4.8 +/- 0.2 v 4.7 +/- 0.1 mmol/L), although overall blood glucose was elevated in the myotonic subjects following oral glucose ingestion (F = 5.37; P less than .05). Glucose tolerance was normal in all subjects. Fasting blood lactate was higher in the myotonic subjects (1.31 +/- 0.13 v 0.94 +/- 0.08 mmol/L; P less than .05) and remained significantly elevated following the ingestion of glucose (F = 7.22; P less than .02). Blood pyruvate response was also higher in the myotonic subjects (F = 5.88; P less than .05). Basal blood glycerol was elevated in the myotonic subjects (0.12 +/- 0.02 v 0.05 +/- 0.01 mmol/L; P less than .005) and remained elevated following oral glucose (F = 11.31; P less than .005). No significant overall differences were observed in ketone bodies, alanine, or fatty acids between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)