Association of SNPs in the UGT1A gene cluster with total bilirubin and mortality in the Diabetes Heart Study

OBJECTIVE

A negative relationship between total bilirubin concentration (TBili) and CVD risk has been documented in a series of epidemiological studies. In addition, TBili is thought to be under strong genetic regulation via the UGT1A gene family, suggesting it may be a heritable CVD risk factor. However, few studies directly relate TBili-associated UGT1A variants to CVD severity or outcome. This study replicated the genetic association for TBili in the Diabetes Heart Study (DHS), and examined the relationships of TBili-associated SNPs with measures of subclinical CVD and mortality.

METHODS

This investigation included 1220 self-described European American (EA) individuals from the DHS, a family-based study examining risk for macrovascular complications in type 2 diabetes (T2D). Genetic associations with TBili were examined using the Affymetrix Genome-wide Human SNP Array 5.0 and the Illumina Infinium Human Exome beadchip v1.0. Subsequent analyses assessed the relationships of the top TBili-associated SNPs with measures of vascular calcified plaque and mortality.

RESULTS

A genome-wide association study detected 18 SNPs within the UGT1A gene family associated with TBili at p < 5 × 10(-8). The top hit was rs887829 (p = 8.67 × 10(-20)). There was no compelling evidence of association between the top TBili-associated SNPs and vascular calcified plaque (p = 0.05-0.88). There was, however, evidence of association with all-cause mortality (p = 0.0004-0.06), the top hit being rs2741034.

CONCLUSION

These findings support a potential role for UGT1A genetic variants in risk for mortality in T2D. Further quantification of the extent of CVD risk conferred by UGT1A gene family variants in a high risk cohort with T2D is still required.

The Relationship among Homocysteine, Bilirubin, and Diabetic Retinopathy

BACKGROUND

Diabetic retinopathy is a common microvascular complication of diabetes mellitus (DM) and the leading cause of blindness in adults. Homocysteine, a risk factor with toxic effects on vascular endothelial cells, and bilirubin, a protectant with antioxidant and anti-inflammatory properties on the vasculature, have been reported to be linked to vaso-occlusive disorders. Therefore, the author of the present study investigated the association between the levels of plasma homocysteine and serum total bilirubin and the incidence of diabetic retinopathy as a chronic microvascular complication in patients with type 2 diabetes mellitus (T2DM).

METHODS

A total of 102 patients with T2DM who visited our hospital from January 2009 to January 2010 were assessed.

RESULTS

Of the 102 patients, the prevalence of diabetic retinopathy was 67 cases (65.7%) according to clinical ophthalmic examination. The duration of DM (P<0.001), age (P=0.003), fasting blood glucose (P=0.045) and urine albumin-creatinine ratio (P=0.015) in univariate analysis and plasma homocysteine level (P=0.038), duration of DM (P=0.001), and total bilirubin level (P=0.012) in multiple logistic regression analysis were statistically significantly associated with the incidence of diabetic retinopathy.

CONCLUSION

The present study indicates that homocysteine and bilirubin may be useful biomarkers for increased risk of diabetic retinopathy since retinopathy in patients with T2DM was linked to higher plasma homocysteine level and decreased serum total bilirubin level.

Association of Serum Total Bilirubin with Serum High Sensitivity C-reactive Protein in Middle-aged Men

Background

It has been suggested that bilirubin has an inverse association with cardiovascular disease (CVD) due to its antioxidant properties. However, there are few data regarding the relationship between serum total bilirubin (sTB) and risk factors for CVD in Koreans. This study aimed to evaluate the relationship between sTB and high sensitivity C-reactive protein (hsCRP), which is an independent risk factor for CVD.

Methods

We performed a cross sectional study in 6,800 men who were examined at a health promotion center at a university hospital in Korea between May 2005 and June 2006. We grouped the subjects according to values of serum hsCRP (above or below 1.0 mg/L) and compared the characteristics of the two groups. To evaluate the relationship between sTB and hsCRP, we classified the subjects according to quartile values of sTB. Multivariate logistic regression analyses were used to analyze the relationship of levels of sTB and hsCRP after adjusting for known risk factors for CVD.

Results

Serum hsCRP was significantly associated with body mass index (BMI), smoking, diabetes, hypertension, fasting plasma glucose, systolic blood pressure, alanine aminotransferase, and total cholesterol/high density lipoprotein (TC/HDL-C) ratio, but not with age or alcohol use. As levels of sTB increased, there was a decrease in age, numbers of smokers, BMI, and TC/HDL ratio. Compared to the lowest quartile of sTB, levels of hsCRP decreased with odds ratios of 0.82 (95% CI, 0.71 to 0.96), 0.75 (95% CI, 0.65 to 0.88), and 0.63 (95% CI, 0.54 to 0.74) in the 2nd, 3rd, and 4th quartiles of bilirubin, respectively.

Conclusion

Bilirubin may be inversely associated with hsCRP