Genetic predisposition in patients with hypertension and normal ejection fraction to oxidative stress.

The role of oxidative stress (OXS) due to myocardial nitric oxide synthase (NOS) uncoupling related to oxidative depletion of its cofactor tetrahydrobiopterin (BH4) emerged in the pathogenesis of heart failure with preserved ejection fraction. We determined the prevalence of six single nucleotide polymorphisms (SNPs) of genes encoding enzymes related to OXS, BH4 metabolism, and NOS function in ≥60-year-old 94 patients with hypertension and 18 age-matched controls with normal ejection fraction. Using echocardiography, 56/94 (60%) patients with hypertension had left ventricular (LV) diastolic dysfunction (HTDD+ group) and 38/94 (40%) patients had normal LV diastolic function (HTDD- group). Four SNPs (rs841, rs3783641, rs10483639, and rs807267) of guanosine triphosphate cyclohydrolase-1, the rate-limiting enzyme in BH4 synthesis, one (rs4880) of manganese superoxide dismutase, and one (rs1799983) of endothelial NOS genes were genotyped using real-time polymerase chain reaction method and Taqman probes. Protein carbonylation, BH4, and total biopterin levels were measured from plasma samples. No between-groups difference in minor allele frequency of SNPs was found. We calculated a genetic score indicating risk for OXS based on the minor allele frequencies of the SNPs. A high genetic risk for OXS was significantly associated with HTDD+ even after adjustment for confounding variables (odds ratio [95% confidence interval]:4.79 [1.12-20.54]; P = .035). In both patient groups protein carbonylation (P < .05 for both), plasma BH4 (P < .01 for both) and in the HTDD+ group total biopterin (P < .05) increased versus controls. In conclusion, in patients with hypertension and normal ejection fraction, a potential precursor of heart failure with preserved ejection fraction, a partly genetically determined increased OXS, seems to be associated with the presence of LV diastolic dysfunction.

Demonstration of an intramitochondrial invertase activity and the corresponding sugar transporters of the inner mitochondrial membrane in Jerusalem artichoke (Helianthus tuberosus L.) tubers.

Genetic evidences indicate that alkaline/neutral invertases are present in plant cell organelles, and they might have a novel physiological function in mitochondria. The present study demonstrates an invertase activity in the mitochondrial matrix of Helianthus tuberosus tubers. The pH optimum, the kinetic parameters and the inhibitor profile of the invertase activity indicated that it belongs to the neutral invertases. In accordance with this topology, transport activities responsible for the mediation of influx/efflux of substrate/products were studied in the inner mitochondrial membrane. The transport of sucrose, glucose and fructose was shown to be bidirectional, saturable and independent of the mitochondrial respiration and membrane potential. Sucrose transport was insensitive to the inhibitors of the proton-sucrose symporters. The different kinetic parameters and inhibitors as well as the absence of cross-inhibition suggest that sucrose, glucose and fructose transport are mediated by separate transporters in the inner mitochondrial membrane. The mitochondrial invertase system composed by an enzyme activity in the matrix and the corresponding sugar transporters might have a role in both osmoregulation and intermediary metabolism.

Silymarin and vitamin E reduce amiodarone-induced lysosomal phospholipidosis in rats.

Several antioxidants have been shown to reduce lysosomal phospholipidosis, which is a potential mechanism of amiodarone toxicity, and prevent amiodarone toxicity by antioxidant and/or non-antioxidant mechanisms. The aim of this study was to test whether the co-administration of two structurally different antioxidants vitamin E and silymarin with amiodarone can reduce amiodarone-induced lysosomal phospholipidosis, and if yes, by reducing the tissue concentration of amiodarone and desethylamiodarone or by their antioxidant action. To this end, male Fischer 344 rats were treated by gavage once a day for 3 weeks and randomly assigned to the following four experimental groups: 1, control; 2, amiodarone (150 mg/(kg per day)); 3, amiodarone (150 mg/(kg per day)) plus vitamin E (100 mg/(kg per day)); 4, amiodarone (150 mg/(kg per day)) plus silymarin (60 mg/(kg per day)) treated groups. Total plasma phospholipid (PL), liver-conjugated diene, thiobarbituric acid reactive substances (TBARSs), amiodarone and desethylamiodarone concentrations were determined and the extent of lysosomal phospholipidosis in the liver was estimated by a semi-quantitative electron microscopic method. Amiodarone treatment increased significantly the liver-conjugated diene (P<0.001), TBARS (P=0.012), plasma total PL (P<0.001) concentrations compared with control. Antioxidants combined with amiodarone significantly decreased the liver-conjugated diene (P<0.001 for both), TBARS (P=0.016 for vitamin E, P=0.053 borderline for silymarin) and plasma total PL (P=0.058 borderline for vitamin E, P<0.01 for silymarin) concentrations compared with amiodarone treatment alone. Silymarin significantly (P=0.021) reduced liver amiodarone, but only tended to decrease desethylamiodarone concentration; however, vitamin E failed to do so. Amiodarone treatment increased lysosomal phospholipidosis (P<0.001) estimated by semi-quantitative electron microscopic method and both antioxidants combined with amiodarone reduced significantly (P<0.001 for both) the amiodarone-induced lysosomal phospholipidosis. In conclusion, silymarin presumably reduced lysosomal phospholipidosis by both antioxidant action and its liver amiodarone concentration decreasing effect, while vitamin E exerted similar effect by antioxidant action alone. Thus, both antioxidant action and inhibition of tissue uptake of amiodarone might have an important role in the preventative effect of antioxidants against amiodarone toxicity.