Insulin gene VNTR genotype is associated with insulin sensitivity and secretion in infancy.
OBJECTIVE
We have previously demonstrated that insulin sensitivity and secretion at age 1 year was in part related to variation in weight and height gain during infancy. In order to determine whether genetic variation at the insulin gene could also influence these associations, we have studied the relationship between insulin gene variable number of tandem repeat (INS VNTR) genotypes, insulin secretion and early postnatal growth.


METHODS
We assessed fasting and dynamic insulin secretion in 99 healthy infants at age 1 year, using a short intravenous glucose tolerance test (sIVGTT). Infants were genotyped at the -23 HphI locus, as a surrogate marker for INS VNTR allele classes I and III. Anthropometric data were recorded at birth and at 1 year. Data are shown as median (interquartile range).


RESULTS
Fasting insulin levels were higher in III/III infants (n = 9) than in I/I infants [n = 55; 27.4 (17.6-75.6) pmol/l vs. 18.1 (10.3-25.2) pmol/l; P < 0.05]. Insulin secretion during the sIVGTT, as estimated by the serum insulin area under the curve, was also higher in III/III infants [2417 (891-4041) pmol min/l vs. 1208 (592-2284) pmol min/l; P < 0.05]. Fasting and postload plasma glucose levels were similar in both groups. Analysis of covariance showed that genotype differences in fasting insulin sensitivity and insulin secretion were independent of size at birth, postnatal growth velocity and current body mass index.


CONCLUSIONS
Significant associations between INS VNTR genotype and both insulin sensitivity and secretion were apparent in infancy; these might interact with childhood appetite and nutrition to impact the development of childhood obesity and insulin resistance.
Bazaes
R A
RA
Institute of Maternal and Child Research, School of Medicine, University of Chile, Santiago, Chile.
Petry
C J
CJ
Ong
K K
KK
Avila
A
A
Dunger
D B
DB
Mericq
M V
MV
D000704:Analysis of Variance; D019540:Area Under Curve; D001786:Blood Glucose / Q000032:analysis; D016009:Chi-Square Distribution; D005260:Female; D005819:Genetic Markers; D005838:Genotype; D005951:Glucose Tolerance Test; D006801:Humans; D007223:Infant; D007328:Insulin / Q000235:genetics* / Q000378:metabolism; D007333:Insulin Resistance / Q000235:genetics*; D000078790:Insulin Secretion; D008297:Male; D018598:Minisatellite Repeats; D011446:Prospective Studies
D001786:Blood Glucose; D005819:Genetic Markers; D007328:Insulin