Hemodialysis acutely improves hepatic CYP3A4 metabolic activity

The uremic syndrome remains poorly understood despite the widespread availability of dialysis for almost four decades. To date, assessment of the biologic activity of uremic toxins has focused primarily on in vitro effects, rather than on specific biochemical pathways or enzymatic activity in vivo. The activity of cytochrome P450 (CYP) 3A4, the most important enzyme in human drug metabolism, is decreased in uremia. The purpose of this study was to assess the effect of hemodialysis and hence varying concentrations of uremic toxins on CYP3A4 activity using the 14 C-erythromycin breath test and the traditional phenotypic trait measure, 20-min 14 CO 2 flux. CYP3A4 activity increased by 27% postdialysis (P ‫؍‬ 0.002 compared with predialysis) and was significantly inversely related to plasma blood urea nitrogen concentration (r s ‫؍‬ ؊0.50, P ‫؍‬ 0.012), but not to several middle molecules. This is the first study in humans characterizing uremia as a state in which hepatic CYP3A4 activity is acutely improved by hemodialysis. J Am Soc Nephrol 17: 2363 -2367 The regulation of CYP3A4 in ESRD patients undergoing hemodialysis has not been well studied. Alterations in CYP3A4 expression and/or activity have been observed in experimental models of uremia (2,3,8 to 13) and a recent report using the 14 C-erythromycin breath test demonstrates that CYP3A4 activity is reduced in ESRD patients compared to healthy subjects (14). Although restoration of kidney function after transplantation leads to a sustained improvement in the uremic state and in hepatic drug metabolism (2,15), hemodialysis therapy only temporarily improves uremia and does not appear to generate long-term improvements in CYP3A function (2). However, the acute effect of hemodialysis on CYP3A4 activity in vivo has not been studied to date. We hypothesized that hepatic CYP3A4 activity would be inversely related to the level of uremic toxins, and that removal of uremic toxins via hemodialysis would lead to acute changes in CYP3A4 activity. Thus, the purpose of this study was to assess the effect of conventional hemodialysis on hepatic CYP3A4 metabolic activity in ESRD patients using the erythromycin breath test and the phenotypic trait measure 20-min 14 CO 2 flux, and to evaluate the relationship between CYP3A4 activity and the concentrations of several uremic toxins. Materials and Methods Study Subjects Twelve patients with ESRD and undergoing chronic hemodialysis participated in this study after providing written informed consent. All subjects underwent a screening evaluation that was based on a complete medical history, physical examination, medication history, and conventional biochemical tests. Eligibility criteria included normal hepatic function, body weight within 40% of ideal weight for height, body frame size, and sex according to the 1983 Metropolitan Life Insurance Company weight tables (16), documented compliance with dialysis prescriptions as determined by a Kt/V Ն1.20 within the 28-d period before the study day, and a negative pregnancy test for women of child-bearing potential. Subjects taking drugs known to inhibit or induce CYP3A4 or with a known sensitivity or previous adverse reaction to erythromycin were excluded. All participants were instructed to abstain from grapefruit products and herbal supplements/teas for at least 72 h before and during the study day

NOS3 gene polymorphisms are associated with risk markers of cardiovascular disease, and interact with omega-3 polyunsaturated fatty acids

Objective Omega-3 polyunsaturated fatty acids (n-3 PUFA) may protect against the development of cardiovascular disease (CVD). Genotype at key genes such as nitric oxide synthase (NOS3) may determine responsiveness to fatty acids. Gene–nutrient interactions may be important in modulating the development of CVD, particularly in high-risk individuals with the metabolic syndrome (MetS). Methods Biomarkers of CVD risk, plasma fatty acid composition, and NOS3 single nucleotide polymorphism (SNP) genotype (rs11771443, rs1800783, rs1800779, rs1799983, rs3918227, and rs743507) were determined in 450 individuals with the MetS from the LIPGENE dietary intervention cohort. The effect of dietary fat modification for 12 weeks on metabolic indices of the MetS was determined to understand potential NOS3 gene–nutrient interactions. Results Several markers of inflammation and dyslipidaemia were significantly different between the genotype groups. A significant gene–nutrient interaction was observed between the NOS3 rs1799983 SNP and plasma n-3 PUFA status on plasma triacylglycerol (TAG) concentrations. Minor allele carriers (AC + AA) showed an inverse association with significantly higher plasma TAG concentrations in those with low plasma n-3 PUFA status and vice versa but the major allele homozygotes (CC) did not. Following n-3 PUFA supplementation, plasma TAG concentrations of minor allele carriers of rs1799983 were considerably more responsive to changes in plasma n-3 PUFA, than major allele homozygotes. Conclusions Carriers of the minor allele at rs1799983 in NOS3 have plasma TAG concentrations which are more responsive to n-3 PUFA. This suggests that these individuals might show greater beneficial effects of n-3 PUFA consumption to reduce plasma TAG concentrations

Effects of dietary fat modification on oxidative stress and inflammatory markers in the LIPGENE study.

Subjects with the metabolic syndrome (MetS) have enhanced oxidative stress and inflammation. Dietary fat quality has been proposed to be implicated in these conditions. We investigated the impact of four diets distinct in fat quantity and quality on 8-iso-PGF2α (a major F2-isoprostane and oxidative stress indicator), 15-keto-13,14-dihydro-PGF2α (15-keto-dihydro-PGF2α, a major PGF2α metabolite and marker of cyclooxygenase-mediated inflammation) and C-reactive protein (CRP). In a 12-week parallel multicentre dietary intervention study (LIPGENE), 417 volunteers with the MetS were randomly assigned to one of the four diets: two high-fat diets (38 % energy (%E)) rich in SFA or MUFA and two low-fat high-complex carbohydrate diets (28 %E) with (LFHCC n-3) or without (LFHCC) 1·24 g/d of very long chain n-3 fatty acid supplementation. Urinary levels of 8-iso-PGF2α and 15-keto-dihydro-PGF2α were determined by RIA and adjusted for urinary creatinine levels. Serum concentration of CRP was measured by ELISA. Neither concentrations of 8-iso-PGF2α and 15-keto-dihydro-PGF2α nor those of CRP differed between diet groups at baseline (P>0·07) or at the end of the study (P>0·44). Also, no differences in changes of the markers were observed between the diet groups (8-iso-PGF2α, P = 0·83; 15-keto-dihydro-PGF2α, P = 0·45; and CRP, P = 0·97). In conclusion, a 12-week dietary fat modification did not affect the investigated markers of oxidative stress and inflammation among subjects with the MetS in the LIPGENE study

ACC2 gene polymorphisms, metabolic syndrome, and gene-nutrient interactions with dietary fat.

Acetyl-CoA carboxylase β (ACC2) plays a key role in fatty acid synthesis and oxidation pathways. Disturbance of these pathways is associated with impaired insulin responsiveness and metabolic syndrome (MetS). Gene-nutrient interactions may affect MetS risk. This study determined the relationship between ACC2 polymorphisms (rs2075263, rs2268387, rs2284685, rs2284689, rs2300453, rs3742023, rs3742026, rs4766587, and rs6606697) and MetS risk, and whether dietary fatty acids modulate this in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). Minor A allele carriers of rs4766587 had increased MetS risk (OR 1.29 [CI 1.08, 1.58], P = 0.0064) compared with the GG homozygotes, which may in part be explained by their increased body mass index (BMI), abdominal obesity, and impaired insulin sensitivity (P 35% energy) (OR 1.62 [CI 1.05, 2.50], P = 0.027), particularly a high intake (>5.5% energy) of n-6 polyunsaturated fat (PUFA) (OR 1.82 [CI 1.14, 2.94], P = 0.01; P = 0.05 for gene-nutrient interaction). Saturated and monounsaturated fat intake did not modulate MetS risk. Importantly, we replicated some of these findings in an independent cohort. In conclusion, the ACC2 rs4766587 polymorphism influences MetS risk, which was modulated by dietary fat, suggesting novel gene-nutrient interactions

Discovery of Ruzasvir (MK-8408): A Potent, Pan-Genotype HCV NS5A Inhibitor with Optimized Activity against Common Resistance-Associated Polymorphisms

We describe the research that led to the discovery of compound <b>40</b> (ruzasvir, MK-8408), a pan-genotypic HCV nonstructural protein 5A (NS5A) inhibitor with a “flat” GT1 mutant profile. This NS5A inhibitor contains a unique tetracyclic indole core while maintaining the imidazole–proline–valine Moc motifs of our previous NS5A inhibitors. Compound <b>40</b> is currently in early clinical trials and is under evaluation as part of an all-oral DAA regimen for the treatment of chronic HCV infection