Genetic cause of hyperglycaemia and response to treatment in diabetes.
BACKGROUND
Type 2 diabetes shows evidence of underlying heterogeneity. No studies have assessed whether different causes for diabetes change the response to oral hypoglycaemic therapy. In a few cases, patients with diabetes caused by mutations in the hepatocyte nuclear factor 1alpha (HNF-1alpha) gene have been described as sensitive to the hypoglycaemic effects of sulphonylureas. We aimed to see whether the glycaemic response to the sulphonylurea gliclazide and the biguanide metformin differed in HNF-1alpha diabetes and type 2 diabetes, and to investigate the mechanism for differences in sulphonylurea sensitivity.


METHODS
We did a randomised crossover trial of glicazide and metformin in 36 patients, either with diabetes caused by HNF-1alpha mutations or type 2 diabetes, who were matched for body-mass index and fasting plasma glucose. The primary outcome was reduction in fasting plasma glucose. Analysis was by intention to treat. We assessed possible mechanisms for sulphonylurea sensitivity through insulin sensitivity, insulin secretory response to glucose and tolbutamide, and tolbutamide clearance.


RESULTS
Patients with HNF-1alpha diabetes had a 5.2-fold greater response to gliclazide than to metformin (fasting plasma glucose reduction 4.7 vs 0.9 mmol/L, p=0.0007) and 3.9-fold greater response to gliclazide than those with type 2 diabetes (p=0.002). Patients with HNF-1alpha diabetes had a strong insulin secretory response to intravenous tolbutamide despite a small response to intravenous glucose, and were more insulin sensitive than those with type 2 diabetes. Sulphonylurea metabolism was similar in both patient groups.


CONCLUSIONS
The cause of hyperglycaemia changes the response to hypoglycaemic drugs; HNF-1alpha diabetes has marked sulphonylurea sensitivity. This pharmacogenetic effect is consistent with models of HNF-1alpha deficiency, which show that the beta-cell defect is upstream of the sulphonylurea receptor. Definition of the genetic basis of hyperglycaemia has implications for patient management.
Diabetes and Vascular Medicine, Peninsula Medical School, Exeter, UK.
Ewan R
ER
Pearson
Bryan J
BJ
Starkey
Roy J
RJ
Powell
Fiona M
FM
Gribble
Penny M
PM
Clark
Andrew T
AT
Hattersley
D018528:ATP-Binding Cassette Transporters / Q000187:drug effects / Q000502:physiology; D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000032:analysis; D004268:DNA-Binding Proteins; D003920:Diabetes Mellitus / Q000097:blood / Q000188:drug therapy* / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000188:drug therapy / Q000235:genetics; D005215:Fasting / Q000097:blood; D005260:Female; D005907:Gliclazide / Q000494:pharmacology / Q000627:therapeutic use*; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000235:genetics*; D007004:Hypoglycemic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008687:Metformin / Q000494:pharmacology / Q000627:therapeutic use*; D008875:Middle Aged; D009687:Nuclear Proteins; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug / Q000187:drug effects / Q000502:physiology; D064233:Sulfonylurea Receptors; D014157:Transcription Factors / Q000235:genetics*
D018528:ATP-Binding Cassette Transporters; D001786:Blood Glucose; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D007004:Hypoglycemic Agents; D009687:Nuclear Proteins; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D008687:Metformin; D005907:Gliclazide