Phenotypic Heterogeneity and Associations of Two Aldose Reductase Gene Polymorphisms With Nephropathy and Retinopathy in Type 2 Diabetes

  1. Ying Wang, MD, CHB,
  2. Maggie C.Y. Ng, BSC, PHD,
  3. Shao-Chin Lee, PHD,
  4. Wing-Yee So, MBCHB, MRCP,
  5. Peter C.Y. Tong, MBCHB, MRCP,
  6. Clive S. Cockram, MD, FRCP,
  7. Julian A.J.H. Critchley, PHD, FRCP and
  8. Juliana C.N. Chan, MD, FRCP
  1. Divisions of Clinical Pharmacology and Endocrinology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, Hong Kong SAR
  1. Address correspondence and reprint requests to Professor Juliana C.N. Chan, Divisions of Clinical Pharmacology and Endocrinology, Department of Medicine and Therapeutics, Prince of Wales Hospital, Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR. E-mail: jchan{at}cuhk.edu.hk

Abstract

OBJECTIVE—We investigated the phenotypic features of diabetic microvascular complications and their association with a (CA)n microsatellite and a C/T polymorphism at the 5′ region of the aldose reductase gene (ALR2) in a consecutive cohort of 738 Chinese type 2 diabetic patients.

RESEARCH DESIGN AND METHODS—Of the entire patient cohort, 392 were free of diabetes complications, or uncomplicated, 159 had diabetic nephropathy, 66 had diabetic retinopathy, and 121 had both diabetic nephropathy and retinopathy. Nephropathy was defined as urinary albumin excretion rate (AER) ≥20 μg/min and albumin-to-creatinine ratio ≥3.5 mg/mmol in two urine collections. Retinopathy was defined by the presence of hemorrhages, exudates, laser marks, and fibrous proliferation or by a history of vitrectomy. (CA)n and C/T polymorphisms were examined by PCR followed by capillary electrophoresis and digestion with BfaI, respectively.

RESULTS—In the whole cohort, patients with diabetic retinopathy (n = 187) had higher blood pressure and lower BMI, while those with diabetic nephropathy (n = 280) had higher blood pressure, waist-to-hip ratio, and lipid profile than those without the respective complications. The z+6 carriers of the (CA)n polymorphism were less common in patients with diabetic retinopathy than those without diabetic retinopathy (n = 551) (4.3 vs. 9.3%, P = 0.04). The CT/TT carriers had a higher AER than the CC carriers (30.2 ×/÷ 7.2 vs. 21.9 ×/÷ 6.9 μg/min, P = 0.03). Further subgroup analysis was performed after excluding uncomplicated patients with <5 years disease duration. The group with both diabetic nephropathy and retinopathy had higher frequencies of the z-2 allele (25.7 vs. 16.9%, P = 0.03) and T allele (26.4 vs. 18.5%, P = 0.04) and a lower frequency of the z+6 allele (1.7 vs. 5.5%, P = 0.054) than the uncomplicated group. Multiple logistic regression analysis confirmed that z-2 carrying (odds ratio 2.6, 95% CI 1.20–5.83, P = 0.02) and CT/TT genotypes (OR 2.5, 95% CI 1.19–5.19, P = 0.02) were independent predictors for both diabetic nephropathy and retinopathy.

CONCLUSIONS—Chinese type 2 diabetic patients exhibited phenotypic differences in terms of risk factors for both diabetic nephropathy and diabetic retinopathy. Both the z-2 allele of (CA)n polymorphism and T allele of ALR2 were independently associated with severe diabetic microvascular complications.

Footnotes

  • A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

    • Accepted April 16, 2003.
    • Received July 22, 2002.
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