Evaluation of UGT1A1 and SULT1A1 polymorphisms with lipid levels in women with different hormonal status

Evaluation of UGT1A1 and CYP3A Genotyping and Single-Point Irinotecan and Metabolite Concentrations as Predictors of the Occurrence of Adverse Events in Cancer Treatment

PURPOSE

The variability on irinotecan (IRI) pharmacokinetics and toxicity has been attributed mostly to genetic variations in the UGT1A1 gene, responsible for conjugation of the active metabolite SN-38. Also, CYP3A mediates the formation of inactive oxidative metabolites of IRI. The association between the occurrence of severe adverse events, pharmacokinetics parameters, and UGT1A1 and CYP3A4 predicted phenotypes was evaluated, as the evaluation of [SN-38]/IRI dose ratio as predictor of severe adverse events.

METHODS

Forty-one patients undergoing IRI therapy were enrolled in the study. Blood samples were collected 15 min after the end of drug the infusion, for IRI, SN-38, SN-38G, bilirubin concentrations measurements, and UGT1A1 and CYP3A genotype estimation. Data on adverse event was reported.

RESULTS

Fifteen patients (36.5%) developed grade 3/4 adverse events. A total of 9.8% (n = 4) of the patients had UGT1A1 reduced activity phenotype, and 48.7% (n = 20) had UGT1A1 and 63.4% (n = 26) CYP3A intermediary phenotypes. Severe neutropenia and diarrhea were more prevalent in patients with reduced UGT1A1 in comparison with functional metabolism (50% and 75% versus 0% and 13%, respectively). SN-38 levels and its concentrations adjusted by IRI dose were significantly correlated to toxicity (rs = 0.31 (p = 0.05) and rs = 0.425 (p < 0.01)). The [SN-38]/IRI dose ratio had a ROC curve of 0.823 (95% CI 0.69-0.956) to detect any severe adverse event and 0.833 (95% CI 0.694-0.973) to detect severe diarrhea. The cut-off of 0.075 ng mL-1 mg-1 had 100% sensitivity and 65.7% specificity to predict severe diarrhea.

CONCLUSION

Our data confirmed the relevance of the pre-emptive genotypic information of UGT1A1. The [SN-38]/IRI ratio, measured 15 min after the end of the IRI infusion, was a strong predictor of severe toxicity and could be applied to minimize the burden of patients after IRI administration.

Decreased Serum Bilirubin Is Associated With Silent Cerebral Infarction

Objective—

The presence of silent cerebral infarction (SCI) increases the risk of transient ischemia attack, symptomatic stroke, cardiovascular disease, and dementia. Total bilirubin (TB) levels were demonstrated to be decreased in carotid intima–media thickness, cardiovascular disease, stroke, and peripheral arterial disease. However, little information is available concerning the correlation between TB and SCI.

Approach and Results—

A cross-sectional study was conducted to evaluate the association between TB and SCI in 2865 subjects (1831 men and 1034 women) undergoing medical checkup. The participants with SCI had lower TB levels than those without SCI. The subjects with a low TB had a higher prevalence of SCI. Moreover, partial correlation showed that TB levels were tightly correlated with brachial-ankle pulse wave velocity after adjusting for confounding covariates ( r =−0.149; P <0.001). Multivariate logistic regression analysis revealed that higher TB was associated with a lower risk of SCI (odds ratio, 0.925; 95% confidence interval, 0.897–0.954; P <0.001).

Conclusions—

TB is a novel biochemical indicator for SCI regardless of classical cardiovascular risk factors. Early measurement of TB may be useful to assess the risk of SCI.

Mixed modeling of meta-analysis P-values (MixMAP) suggests multiple novel gene loci for low density lipoprotein cholesterol

Informing missing heritability for complex disease will likely require leveraging information across multiple SNPs within a gene region simultaneously to characterize gene and locus-level contributions to disease phenotypes. To this aim, we introduce a novel strategy, termed Mixed modeling of Meta-Analysis P-values (MixMAP), that draws on a principled statistical modeling framework and the vast array of summary data now available from genetic association studies, to test formally for locus level association. The primary inputs to this approach are: (a) single SNP level p-values for tests of association; and (b) the mapping of SNPs to genomic regions. The output of MixMAP is comprised of locus level estimates and tests of association. In application of MixMAP to summary data from the Global Lipids Gene Consortium, we suggest twelve new loci (PKN, FN1, UGT1A1, PPARG, DMDGH, PPARD, CDK6, VPS13B, GAD2, GAB2, APOH and NPC1) for low-density lipoprotein cholesterol (LDL-C), a causal risk factor for cardiovascular disease and we also demonstrate the potential utility of MixMAP in small data settings. Overall, MixMAP offers novel and complementary information as compared to SNP-based analysis approaches and is straightforward to implement with existing open-source statistical software tools.

Bilirubin and beyond: a review of lipid status in Gilbert's syndrome and its relevance to cardiovascular disease protection

Gilbert's syndrome (GS) is characterized by a benign, mildly elevated bilirubin concentration in the blood. Recent reports show clear protection from cardiovascular disease in this population. Protection of lipids, proteins and other macromolecules from oxidation by bilirubin represents the most commonly accepted mechanism contributing to protection in this group. However, a recent meta-analysis estimated that bilirubin only accounts for ~34% of the cardioprotective effects within analysed studies. To reveal the additional contributing variables we have explored circulating cholesterol and triacylglycerol concentrations, which appear to be decreased in hyperbilirubinemic individuals/animals, and are accompanied by lower body mass index in highly powered studies. These results suggest that bilirubin could be responsible for the development of a lean and hypolipidemic state in GS. Here we also discuss the possible contributing mechanisms that might reduce circulating cholesterol and triacylglycerol concentrations in individuals with syndromes affecting bilirubin metabolism/excretion, which we hope will stimulate future research in the area. In summary, this article is the first review of lipid status in animal and human studies of hyperbilirubinemia and explores possible mechanisms that could contribute to lowering circulating lipid parameters and further explain cardiovascular protection in Gilbert's syndrome.

Short communication: UGT1A1*28 variant allele is a predictor of severe hyperbilirubinemia in HIV-infected patients on HAART in southern Brazil

Highly active antiretroviral therapy (HAART) has increased the survival of HIV-infected patients. However, adverse effects play a major role in adherence to HAART. Some protease inhibitors (mainly atazanavir and indinavir) act as inhibitors of uridine diphosphate-glucuronosyltransferase (UGT1A1), the enzyme responsible for hepatic conjugation of bilirubin. Variations in the promoter region of the UGT1A1 gene (UGT1A1*28, rs8175347) can influence bilirubin plasma levels, modulating the susceptibility to hyperbilirubinemia. Aiming to analyze the association between UGT1A1*28 allele and hyperbilirubinemia in individuals exposed to HAART, we evaluated 375 HIV-positive individuals on antiretroviral therapy. Individuals carrying the UGT1A1*28 allele had a higher risk of developing severe hyperbilirubinemia [prevalence ratio (PR)=2.43, 95% confidence interval (CI) 1.08-5.45, p=0.032] as well as atazanavir users (PR=7.72, 95% CI=3.14-18.98, p<0.001). This is the first description of such an association in Brazilian HIV patients, which shows that in African-American and Euroamerican HAART users, the UGT1A1*28 allele also predisposes to severe hyperbilirubinemia, especially in those exposed to atazanavir.

Are polymorphisms in oestrogen receptors genes associated with lipid levels in response to hormone therapy?

BACKGROUND

Polymorphisms in the oestrogen receptor 1 (ESR1) and oestrogen receptor 2 (ESR2) genes are associated with intermediate or endpoint markers of cardiovascular disease and with the efficacy of postmenopausal hormone therapy (HT). Contradictory findings have been described in the past and the role of these genetics variants remains unclear.

METHODS

A cross-sectional study was carried out with 266 postmenopausal women, of whom 115 received oral HT (HT+) and 151 did not receive any HT (HT-). We analysed three single-nucleotide polymorphisms (SNPs) in ESR1 (rs1801132, rs7757956 and rs2813544) and two in ESR2 (rs3020450 and rs7154455) and derived haplotypes with three additional polymorphisms that had been previously investigated by our group (ESR1 rs2234693 and ESR2 rs1256049 and rs4986938).

RESULTS

The ESR1 rs2813544 polymorphism was associated with low-density lipoprotein cholesterol (LDL-C) in HT+ postmenopausal women (p = 0.044; pC = 0.388), while one ESR2 gene haplotype was associated with total cholesterol (T-chol) (p = 0.015; pC = 0.090) and LDL-C in HT+ postmenopausal women (p = 0.021; pC = 0.126).

CONCLUSION

Our findings suggest that, in HT+ postmenopausal women, the rs2813544 polymorphism may influence LDL-C levels and, as previously described, ESR2 rs1256049 is associated with T-chol and LDL-C. No previous study has investigated the association of this SNP set with lipoprotein levels in women while taking into account the hormonal status of the patients.