Molecular screening of the human glutamine-fructose-6-phosphate amidotransferase 1 (GFPT1) gene and association studies with diabetes and diabetic nephropathy.
Increased glucose metabolism through the hexosamine pathway may result in insulin resistance, impaired insulin secretion, and diabetic nephropathy. We hypothesized that variants of GFPT1 encoding glutamine-fructose-6-phosphate amidotransferase, the rate limiting enzyme in this pathway, could increase GFPT1 gene expression and thus susceptibility to diabetes and diabetic nephropathy. To test this hypothesis, we screened for variation in the GFPT1 and flanking regions in Caucasian and African-American individuals. We tested each variant with over 5% allele frequency for an association with type 2 diabetes in Caucasian and African-American populations, and for an association with diabetic nephropathy in African-American subjects. We measured allele specific levels of GFPT1 mRNA and we compared mRNA levels across diagnostic categories for each ethnic group using RNA derived from transformed lymphocytes. None of the 8 variants detected altered the coding sequence or was present in a known regulatory region. We found a marginal association (p = 0.044) of 1/6 variants with diabetes in Caucasian subjects, and marginal associations of 2/7 variants with diabetic nephropathy among African-American subjects (p = 0.025, p = 0.041). Alleles marked by a variant in the 3' untranslated region were equally expressed, but in a small sample, GFPT1 mRNA levels were increased by 60% in Caucasians with diabetic nephropathy compared to diabetic individuals without nephropathy. Variants in the GFPT1 gene show suggestive evidence of an association with diabetic nephropathy among African-American individuals, and increased GFPT1 gene expression may characterize Caucasian subjects with diabetic nephropathy. Both findings need to be confirmed in other populations.
University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA. elbeinstevenc@uams.edu
Steven C
SC
Elbein
Hailing
H
Zheng
Yiwen
Y
Jia
Winston
W
Chu
Judith J
JJ
Cooper
Terri
T
Hale
Zhengxian
Z
Zhang
D001741:Black or African American / Q000235:genetics; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000208:ethnology / Q000235:genetics*; D003928:Diabetic Nephropathies / Q000175:diagnosis / Q000208:ethnology / Q000235:genetics*; D015870:Gene Expression / Q000235:genetics; D005787:Gene Frequency / Q000235:genetics; D005820:Genetic Testing; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000235:genetics* / Q000378:metabolism; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D020641:Polymorphism, Single Nucleotide; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D044465:White People / Q000235:genetics
D012333:RNA, Messenger; C497511:GFPT1 protein, human; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing)