A genome-wide association study suggests an association of Chr8p21.3 (GFRA2) with diabetic neuropathic pain.

BACKGROUND: Neuropathic pain, caused by a lesion or a disease affecting the somatosensory system, is one of the most common complications in diabetic patients. The purpose of this study is to identify genetic factors contributing to this type of pain in a general diabetic population. METHOD: We accessed the Genetics of Diabetes Audit and Research Tayside (GoDARTS) datasets that contain prescription information and monofilament test results for 9439 diabetic patients, among which 6927 diabetic individuals were genotyped by Affymetrix SNP6.0 or Illumina OmniExpress chips. Cases of neuropathic pain were defined as diabetic patients with a prescription history of at least one of five drugs specifically indicated for the treatment of neuropathic pain and in whom monofilament test result was positive for sensory neuropathy in at least one foot. Controls were individuals who did not have a record of receiving any opioid analgesics. Imputation of non-genotyped SNPs was performed by IMPUTE2, with reference files from 1000 Genomes Phase I datasets. RESULTS: After data cleaning and relevant exclusions, imputed genotypes of 572 diabetic neuropathic pain cases and 2491 diabetic controls were used in the Fisher's exact test. We identified a cluster in the Chr8p21.3, next to GFRA2 with a lowest p-value of 1.77 × 10(-7) at rs17428041. The narrow-sense heritability of this phenotype was 11.00%. CONCLUSION: This genome-wide association study on diabetic neuropathic pain suggests new evidence for the involvement of variants near GFRA2 with the disorder, which needs to be verified in an independent cohort and at the molecular level.

Investigation of known estimated glomerular filtration rate loci in patients with type 2 diabetes.

AIMS: To replicate the association of genetic variants with estimated glomerular filtration rate (GFR) and albuminuria, which has been found in recent genome-wide studies in patients with Type 2 diabetes. METHODS: We evaluated 16 candidate single nucleotide polymorphisms for estimated GFR in 3028 patients with Type 2 diabetes sampled from clinics across Tayside, Scotland, UK, who were included in the Genetics of Diabetes Audit and Research Tayside (GoDARTs) study. These single nucleotide polymorphisms were tested for their association with estimated GFR at entry to the study, with albuminuria, and with time to stage 3B chronic kidney disease (estimated GFR<45 ml/min/1.73 m(2)). We also stratified the effects on estimated GFR in patients with (n = 2096) and without albuminuria (n = 613). RESULTS: rs1260326 in GCKR (ß=1.30, P = 3.23E-03), rs17319721 in SHROOM3 (ß = -1.28, P-value = 3.18E-03) and rs12917707 in UMOD (ß = 2.0, P-value = 8.84E-04) were significantly associated with baseline estimated GFR. Analysis of effects on estimated GFR, stratified by albuminuria status, showed that in those without albuminuria (normoalbuminura; n = 613), UMOD had a significantly stronger effect on estimated GFR (ß(normo) = 4.03 ± 1.23 vs ß(albuminuria) = 1.72 ± 0.76, P = 0.002) compared with those with albuminuria, while GCKR (ß(normo) = 0.45 ± 0.89 vs ß(albuminuria) = 1.12 ± 0.55, P = 0.08) and SHROOM3 (ß(normo) = -0.07 ± 0.89 vs ß(albuminuria) = -1.43 ± 0.53, P = 0.003) had a stronger effect on estimated GFR in those with albuminuria. UMOD was also associated with a lower rate of transition to stage 3B chronic kidney disease (hazard ratio = 0.83[0.70, 0.99], P = 0.03). CONCLUSION: The genetic variants that regulate estimated GFR in the general population tend to have similar effects in patients with Type 2 diabetes and in this latter population, it is important to adjust for albuminuria status while investigating the genetic determinants of renal function.