Sulphonylureas lower
blood glucose but other metabolic effects have been little studied. In an assessment of
carbohydrate and
amino acid metabolism in 9 patients with
non-insulin-dependent diabetes mellitus (
NIDDM) before and after 3 months'
therapy with
gliclazide, glycaemic control was improved (mean +/- S.D. glycosylated haemoglobin 13.8 +/- 1.9% before
therapy, 10.2 +/- 2.1% after
therapy (p less than 0.01], but fasting
amino acid levels were not altered. In contrast, postprandial levels of
branched chain amino acids (BCAA) were significantly reduced: total BCAA (
valine,
leucine, and
isoleucine) 120 mins following a standard test meal fell from 717 +/- 71 mumol/l before
therapy to 600 +/- 90 mumol/l after 3 months'
therapy (p less than 0.01). This finding implies an increased action of endogenous
insulin on skeletal muscle to promote uptake of BCAA postprandially and, in accord with this, peripheral
insulin levels were significantly increased following
drug treatment (peak
insulin level 55.6 +/- 20.2 mU/l before
therapy, 91.3 +/- 17.9 mU/l after
therapy (p less than 0.01]. Sulphonylurea drugs therefore do not simply have a hypoglycaemic action but also affect
amino acid metabolism in
NIDDM patients.