The E23K variant of KCNJ11 encoding the pancreatic beta-cell adenosine 5'-triphosphate-sensitive potassium channel subunit Kir6.2 is associated with an increased risk of secondary failure to sulfonylurea in patients with type 2 diabetes.
BACKGROUND
Several studies suggest that genetic factors may play a role in the different responses to antidiabetic therapy; however, conclusive evidence is still lacking.


OBJECTIVE
The objective of the study was to investigate whether diabetic patients carrying the E23K variant in KCNJ11 are at increased risk for secondary sulfonylurea failure.


METHODS
Secondary sulfonylurea failure was defined as fasting plasma glucose greater than 300 mg/dl despite sulfonylurea-metformin combined therapy and appropriate diet, in the absence of other conditions causing hyperglycemia.


METHODS
The study was conducted in an ambulatory care facility.


METHODS
A total of 525 Caucasian type 2 diabetic patients were enrolled in the study.


METHODS
Sulfonylurea treatment was followed by sulfonylurea-metformin combined therapy and then insulin treatment.


METHODS
Secondary failure was the main outcome measure.


RESULTS
Of the diabetic patients enrolled in the study, 38.5% were E23E homozygous, 51.4% were E23K heterozygous, and 10.1% were K23K homozygous. The frequency of carriers of the K allele was 58 and 66.8% among patients treated with oral therapy or secondary sulfonylurea failure, respectively (odds ratio, 1.45; 95% confidence interval, 1.01-2.09; P = 0.04). Adjustment for age, gender, fasting glycemia, glycosylated hemoglobin, age at diagnosis, and duration of diabetes in a logistic regression analysis did not change this association (odds ratio, 1.69; 95% confidence interval, 1.02-2.78; P = 0.04). Islets isolated from carriers of the K allele showed no differences in glucose-stimulated insulin secretion and a tendency toward reduced response upon glibenclamide stimulation (P = 0.09). After 24-h exposure to high (16.7 mmol/liter) glucose concentration, impairment of glibenclamide-induced insulin release was significantly (P = 0.01) worse with the E23K variant.


CONCLUSIONS
These data suggest that the E23K variant in KCNJ11 may influence the variability in the response of patients to sulfonylureas, thus representing an example of pharmacogenetics in type 2 diabetes.
Sesti
Giorgio
G
Dipartimento di Medicina Sperimentale e Clinica, Università Magna Graecia, Viale Europa, Località Germaneto, 88100 Catanzaro, Italy. sesti@unicz.it
Laratta
Emanuela
E
Cardellini
Marina
M
Andreozzi
Francesco
F
Del Guerra
Silvia
S
Irace
Concetta
C
Gnasso
Agostino
A
Grupillo
Maria
M
Lauro
Renato
R
Hribal
Marta Letizia
ML
Perticone
Francesco
F
Marchetti
Piero
P
D000328:Adult; D000368:Aged; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000235:genetics*; D005260:Female; D014644:Genetic Variation; D006801:Humans; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics*; D013453:Sulfonylurea Compounds / Q000627:therapeutic use*; D017211:Treatment Failure; D000099161:Kcnj11 Channel
D007004:Hypoglycemic Agents; D024661:Potassium Channels, Inwardly Rectifying; D013453:Sulfonylurea Compounds; D000099161:Kcnj11 Channel