Reduced Reverse Cholesterol Transport Efficacy in Healthy Men with Undesirable Postprandial Triglyceride Response.

Elevation of nonfasting triglyceride (TG) levels above 1.8 g/L (2 mmol/L) is associated with increased risk of cardiovascular diseases. Exacerbated postprandial hypertriglyceridemia (PP-HTG) and metabolic context both modulate the overall efficacy of the reverse cholesterol transport (RCT) pathway, but the specific contribution of exaggerated PP-HTG on RCT efficacy remains indeterminate. Healthy male volunteers (n = 78) exhibiting no clinical features of metabolic disorders underwent a postprandial exploration following consumption of a typical Western meal providing 1200 kcal. Subjects were stratified according to maximal nonfasting TG levels reached after ingestion of the test meal into subjects with a desirable PP-TG response (GLow, TG < 1.8 g/L, n = 47) and subjects with an undesirable PP-TG response (GHigh, TG > 1.8 g/L, n = 31). The impact of the degree of PP-TG response on major steps of RCT pathway, including cholesterol efflux from human macrophages, cholesteryl ester transfer protein (CETP) activity, and hepatic high-density lipoprotein (HDL)-cholesteryl ester (CE) selective uptake, was evaluated. Cholesterol efflux from human macrophages was not significantly affected by the degree of the PP-TG response. Postprandial increase in CETP-mediated CE transfer from HDL to triglyceride-rich lipoprotein particles, and more specifically to chylomicrons, was enhanced in GHigh vs GLow. The hepatic HDL-CE delivery was reduced in subjects from GHigh in comparison with those from GLow. Undesirable PP-TG response induces an overall reduction in RCT efficacy that contributes to the onset elevation of both fasting and nonfasting TG levels and to the development of cardiometabolic diseases.

Complex Influence of Gonadotropins and Sex Steroid Hormones on QT Interval Duration.

CONTEXT: QT interval duration is longer in women than in men. Sex steroid hormones have inconsistently been suggested to explain this difference. The implication of gonadotropins has never been studied. OBJECTIVE: We report here the combined influence of sex steroid hormones and gonadotropins on QT interval duration in healthy subjects and patients with congenital adrenal hyperplasia (CAH) as a model of T and progesterone overexpression. DESIGN AND PATIENTS: Eighty-four CAH patients (58 women) and 84 healthy subjects matched and paired for sex and age were prospectively included. Circulating concentrations of 17-OH-progesterone, progesterone, T, estradiol, FSH, and LH were measured concomitantly to the recording of a digitized electrocardiogram. RESULTS: QTcFridericia (QTcF) was shorter in women with CAH than in control women (404 ± 2 vs 413 ± 2.1 milliseconds; P ≤ .001). 17-OH-progesterone, progesterone, the progesterone/estradiol ratio, and total T were higher in women with CAH than in female controls (P < .05), whereas FSH was lower (P ≤ .05). According to multivariable analysis in all women, the progesterone/estradiol ratio (ß = -0.33) and FSH levels (ß = 0.34) were related to QTcF (r = 0.5; P < .0001), with no influence of CAH or healthy status. QTcF was not different between CAH (404.7 ± 3.7 milliseconds) or healthy men (396 ± 2.8 milliseconds). For men, QTcF (r = 0.48; P < .01) was negatively related to free T (ß = -0.29) and positively to FSH levels (ß = 0.34). CONCLUSION: Cardiac repolarization is influenced by complex interactions between sex steroid hormones and gonadotropins, depending on gender. Our results indicate that the progesterone/estradiol ratio in women, T in men, and FSH in both genders are major determinants of ventricular repolarization with opposite effects on QTc interval.

A pharmacokinetic-pharmacodynamic model for predicting the impact of CYP2C9 and VKORC1 polymorphisms on fluindione and acenocoumarol during induction therapy.

BACKGROUND AND OBJECTIVE: Vitamin K epoxide reductase complex, subunit 1 (VKORC1) and cytochrome P450 2C9 (CYP2C9) polymorphisms are taken into account when predicting a safe oral dose of coumarin anticoagulant therapy, but little is known about the effects of genetic predictors on the response to fluindione and acenocoumarol. The aims of this study were to characterize the relationship between fluindione and acenocoumarol concentrations and the international normalized ratio (INR) response, and to identify genetic predictors that are important for dose individualization. METHODS: Fluindione concentrations, S- and R-acenocoumarol concentrations, the INR and genotype data from healthy subjects were used to develop a population pharmacokinetic-pharmacodynamic model in Monolix software. Twenty-four White healthy subjects were enrolled in the pharmacogenetic study. The study was an open-label, randomized, two-period cross-over study. The subjects received two doses of an oral anticoagulant: 20 mg of fluindione (period A) or 4 mg of acenocoumarol (period B). The pharmacokinetics and pharmacodynamics were studied from day 2 to day 3. RESULTS: A two-compartment model with a first-order input model was selected as the base model for the two drugs. The pharmacodynamic response was best described by an indirect action model with S-acenocoumarol concentrations and fluindione concentrations as the only exposure predictors of the INR response. Three covariates (CYP2C9 genotype, VKORC1 genotype and body weight) were identified as important predictors for the pharmacokinetic-pharmacodynamic model of S-acenocoumarol, and four covariates (CYP2C9 genotype, VKORC1 genotype, CYP1A2 phenotype and body weight) were identified as predictors for the pharmacokinetic-pharmacodynamic model of fluindione. Because some previous studies have shown a dose-response relationship between smoking exposure and the CYP1A2 phenotype, it was also noted that smokers have greater CYP1A2 activity. CONCLUSION: During initiation of therapy, CYP2C9 and VKORC1 genetic polymorphisms are important predictors of fluindione and acenocoumarol pharmacokinetic-pharmacodynamic responses. Our result suggests that it is important to take the CYP1A2 phenotype into account to improve individualization of fluindione therapy, in addition to genetic factors.

Effects of type of smoking (pipe, cigars or cigarettes) on biological indices of tobacco exposure and toxicity.

Although all forms of smoking are harmful, smoking pipes or cigars is associated with lower exposure to the lethal products of tobacco products and lower levels of morbidity and mortality than smoking cigarettes. Cytochrome P-450-1A (CYP1A) is a major pathway activating carcinogens from tobacco smoke. Our primary aim was to compare CYP1A2 activity in individuals smoking pipes or cigars only, cigarettes only and in non-smokers. We studied 30 smokers of pipes or cigars only, 28 smokers of cigarettes only, and 30 non-smokers male subjects matched for age. CYP1A2 activity was assessed as the caffeine metabolic ratio in plasma. One-day urine collection was used for determining exposure to products of tobacco metabolism. Nitrosamine and benzo[a]pyrene DNA adducts were measured in lymphocytes. CYP1A2 activity was greater (p<0.0001) in cigarette smokers (median: 0.61; interquartile range: 0.52-0.76) than in pipe or cigar smokers (0.27; 0.21-0.37) and non-smokers (0.34; 0.25-0.42) who did not differ significantly. Urinary cotinine and 1-hydroxypyrene levels were higher in cigarette smokers than in pipe or cigar smokers and higher in the later than in non-smokers. DNA adducts levels were significantly lower in pipe or cigar smokers than in cigarette smokers. In multivariate analysis, cigarette smoking was the only independent predictor of CYP1A2 activity (p<0.0001) and of 1-hydroxypyrene excretion in urine (p=0.0012). In this study, pipe or cigar smoking was associated with lower exposure to products of tobacco metabolism than cigarette smoking and to an absence of CYP1A2 induction. Cigarette smoking was the only independent predictor of CYP1A2 activity in smokers. However, inhalation behaviour, rather than the type of tobacco smoked, may be the key factor linked to the extent of tobacco exposure and CYP1A2 induction. Our results provide a reasonable explanation for the results of epidemiological studies showing pipe or cigar smoking to present fewer health hazards than cigarette smoking.