Microarray analysis of multiple candidate genes and associated plasma proteins for nephropathy secondary to type 2 diabetes among Chinese individuals.
OBJECTIVE
Evolving research suggests that common and rare alleles jointly constitute the genetic landscape of complex disease. We studied the association between 43 pathway-related candidate genes with 'intermediate phenotype' (i.e. corresponding plasma protein) and diabetic nephropathy in a customised microarray of 1,536 SNPs.


METHODS
In this case-control study of type 2 diabetic Chinese individuals with and without diabetic nephropathy, cases (n = 545) were defined on the basis of a spot urinary albumin/creatinine ratio (ACR) > 113 mg/mmol; the value for controls (n = 503) was ACR < 3.3 mg/mmol. Genotyping was performed using Illumina GoldenGate assay.


RESULTS
No single nucleotide polymorphism (SNP) remained significant in single locus analysis after correction for multiple testing. Therefore, we explored the best approximately 1% SNPs. Of these 13 SNPs, four clustered to a 5' end NADPH oxidase homologue 4 (NOX4) haplotype (GGCC frequency = 0.776) with estimated OR for diabetic nephropathy of 2.05 (95% CI 1.04-4.06) (heterozygous) and 2.48 (1.27-4.83) (homozygous) (p = 0.0055). The haplotype was correlated with plasma Cu/Zn superoxide dismutase (SOD) concentration, suggesting increased oxidative burden. Endothelin-1 SNP (rs1476046G>A, frequency = 0.252) was correlated with plasma C-terminal pro-endothelin-1 concentrations with an estimated OR for diabetic nephropathy of (heterozygous) 1.26 (0.96-1.66) and (homozygous) 1.87 (1.13-3.12) (p = 0.0072). Nitric oxide synthase 1 (NOS1) 5' haplotype (TGTC frequency = 0.38) also revealed a suggestive association with diabetic nephropathy: heterozygous 1.26 (0.95-1.67), homozygous 1.57 (1.04-2.35) (p = 0.0073). A rare NADPH oxidase homologue 1 (NOX1)-coding non-synonymous SNP (Arg315His, frequency = 0.006) was found exclusively among cases.


CONCLUSIONS
Our preliminary observations suggest that common haplotypes from NOX4 and endothelin-1 SNP correlated with plasma Cu/Zn SOD and C-terminal pro-endothelin-1 concentrations, respectively, and might have conferred diabetic nephropathy susceptibility. Common NOS1 and rare NOX1 variants also revealed a suggestive association with diabetic nephropathy. Future studies to validate our observation are needed.
Department of Medicine, Alexandra Hospital, 378 Alexandra Road, Singapore, Republic of Singapore. Su_chi_lim@alexhosp.com.sg
S C
SC
Lim
J J
JJ
Liu
H Q
HQ
Low
N G
NG
Morgenthaler
Y
Y
Li
L Y
LY
Yeoh
Y S
YS
Wu
S K
SK
Goh
C Y
CY
Chionh
S H
SH
Tan
Y C
YC
Kon
P C
PC
Soon
Y M
YM
Bee
T
T
Subramaniam
C F
CF
Sum
K S
KS
Chia
D000368:Aged; D044466:Asian People / Q000235:genetics*; D001798:Blood Proteins / Q000235:genetics; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000208:ethnology / Q000235:genetics*; D003928:Diabetic Nephropathies / Q000208:ethnology / Q000235:genetics*; D019332:Endothelin-1 / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000208:ethnology; D006239:Haplotypes; D006801:Humans; D008297:Male; D008875:Middle Aged; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics*; D052248:Nitric Oxide Synthase Type I / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D020641:Polymorphism, Single Nucleotide; D012846:Singapore / Q000453:epidemiology
D001798:Blood Proteins; D019332:Endothelin-1; C496320:NOS1 protein, human; D052248:Nitric Oxide Synthase Type I; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human