Lack of plasma albumin impairs intravascular lipolysis and explains the associated free fatty acids deficiency and hypertriglyceridemia

<p>Abstract</p> <p>Background</p> <p>Abnormalities in lipid metabolism and transport are hallmarks in analbuminemic Nagase rats (NAR) and humans. Triglyceridemia is nearly 3- to 5-fold higher in female NAR than in control Sprague-Dawley rats (SDR). Also, NAR present with a severe plasma free fatty acid (FFA) deficit. There are conflicting results regarding the mechanisms underlying NAR hypertriglyceridemia.</p> <p>Objective</p> <p>We aimed at investigating whether liver lipogenesis and triglyceride secretion rates into the plasma contribute to the hypertriglyceridemia in NAR. We also studied whether heparin or albumin administration would release the hypothesized lipolysis inhibition in NAR.</p> <p>Methods</p> <p>The incorporation of tritiated water into lipids and the linear accumulation rate of plasma triglycerides after Triton WR1339 injection were the measures of liver lipogenesis and triglyceride secretion rates.</p> <p>Results</p> <p>Lipogenesis (596 ± 40 vs. 929 ± 124 μmol ³H₂O/g/h) and triglyceride (4.25 ± 1.00 vs. 7.04 ± 1.68 mg/dL/min) secretion rates were slower (<it>P </it>≤ 0.05) in fasted NAR than in control SDR. The injection of either heparin or albumin elicited an increase in NAR plasma FFA levels over time. FFA levels reached control levels 90 min after the albumin administration, increasing from 0.36 ± 0.05 to 1.34 ± 0.16 mEq/L (<it>P </it>≤ 0.05). These results indicate that the lack of plasma albumin inhibits intravascular lipolysis and causes the FFA deficit observed in NAR.</p> <p>Conclusion</p> <p>NAR hepatic triglyceride synthesis and output do not contribute to NAR hypertriglyceridemia. We propose that the lack of albumin diminishes intravascular lipolysis which reduces the plasma triglyceride removal rate and explain both NAR hypertriglyceridemia and FFA deficiency.</p

The C242T polymorphism of the p22-phox gene (CYBA) is associated with higher left ventricular mass in Brazilian hypertensive patients

<p>Abstract</p> <p>Background</p> <p>Reactive oxygen species have been implicated in the physiopathogenesis of hypertensive end-organ damage. This study investigated the impact of the C242T polymorphism of the p22-phox gene (CYBA) on left ventricular structure in Brazilian hypertensive subjects.</p> <p>Methods</p> <p>We cross-sectionally evaluated 561 patients from 2 independent centers [Campinas (n = 441) and Vitória (n = 120)] by clinical history, physical examination, anthropometry, analysis of metabolic and echocardiography parameters as well as p22-phox C242T polymorphism genotyping. In addition, NADPH-oxidase activity was quantified in peripheral mononuclear cells from a subgroup of Campinas sample.</p> <p>Results</p> <p>Genotype frequencies in both samples were consistent with the Hardy- Weinberg equilibrium. Subjects with the T allele presented higher left ventricular mass/height^2.7than those carrying the CC genotype in Campinas (76.8 ± 1.6 vs 70.9 ± 1.4 g/m^2.7; p = 0.009), and in Vitória (45.6 ± 1.9 vs 39.9 ± 1.4 g/m^2.7; p = 0.023) samples. These results were confirmed by stepwise regression analyses adjusted for age, gender, blood pressure, metabolic variables and use of anti-hypertensive medications. In addition, increased NADPH-oxidase activity was detected in peripheral mononuclear cells from T allele carriers compared with CC genotype carriers (p = 0.03).</p> <p>Conclusions</p> <p>The T allele of the p22-phox C242T polymorphism is associated with higher left ventricular mass/height^2.7and increased NADPH-oxidase activity in Brazilian hypertensive patients. These data suggest that genetic variation within NADPH-oxidase components may modulate left ventricular remodeling in subjects with systemic hypertension.</p

Plant Uncoupling Mitochondrial Protein And Alternative Oxidase: Energy Metabolism And Stress.

Energy-dissipation in plant mitochondria can be mediated by inner membrane proteins via two processes: redox potential-dissipation or proton electrochemical potential-dissipation. Alternative oxidases (AOx) and the plant uncoupling mitochondrial proteins (PUMP) perform a type of intrinsic and extrinsic regulation of the coupling between respiration and phosphorylation, respectively. Expression analyses and functional studies on AOx and PUMP under normal and stress conditions suggest that the physiological role of both systems lies most likely in tuning up the mitochondrial energy metabolism in response of cells to stress situations. Indeed, the expression and function of these proteins in non-thermogenic tissues suggest that their primary functions are not related to heat production.25271-8

Safranine As A Fluorescent Probe For The Evaluation Of Mitochondrial Membrane Potential In Isolated Organelles And Permeabilized Cells.

The mitochondrial electrical membrane potential (Δψ) is the main component of the proton motive force (Δp) generated across the inner mitochondrial membrane during electron flow through the respiratory chain. Among the techniques available to assess Δψ, methods that rely on the spectrophotofluorometric responses of dyes are widely employed for whole suspensions of isolated mitochondria or permeabilized cells. Safranine is one of the dyes currently used most often for this purpose. Safranine is a lipophilic cationic dye that undergoes optical shifts upon its potential-dependent distribution between the external medium and the intramitochondrial compartment and on its stacking to inner mitochondrial membrane anionic sites. The association between the optical changes of safranine and the membrane potential allows unknown Δψ values to be estimated from an equation describing their relationship. Here, we describe the use of safranine as a fluorescent indicator of Δψ in isolated mitochondria and digitonin-permeabilized cells. We present suitable conditions to employ safranine as a Δψ indicator.810103-1

Overexpression Of Plant Uncoupling Mitochondrial Protein In Transgenic Tobacco Increases Tolerance To Oxidative Stress.

An Arabidopsis thaliana cDNA clone encoding a plant uncoupling mitochondrial protein (AtPUMP1) was overexpressed in transgenic tobacco plants. Analysis of the AtPUMP1 mRNA content in the transgenic lines, determined by Northern blot, revealed variable levels of transgene expression. Antibody probing of Western blots of mitochondrial proteins from three independent transgenic lines showed significant accumulation of AtPUMP1 in this organelle. Overproduction of AtPUMP1 in transgenic tobacco plants led to a significant increase in tolerance to oxidative stress promoted by exogenous hydrogen peroxide as compared to wild-type control plants. These results provide the first biological evidence for a role of PUMP in protection of plant cells against oxidative stress damage.35203-

Oxidative Stress In Hypercholesterolemic Ldl (low-density Lipoprotein) Receptor Knockout Mice Is Associated With Low Content Of Mitochondrial Nadp-linked Substrates And Is Partially Reversed By Citrate Replacement.

We have previously proposed that hypercholesterolemic LDL receptor knockout (k/o) mice mitochondria possess a lower antioxidant capacity due to a large consumption of reducing equivalents from NADPH to sustain high rates of lipogenesis. In this work, we tested the hypothesis that this k/o mice mitochondrial oxidative stress results from the depletion of NADPH-linked substrates. In addition, the oxidative stress was further characterized by showing a lower mitochondrial GSH/GSSG ratio and a higher liver content of protein carbonyls as compared to controls. The activity of the antioxidant enzyme system glutathione reductase/peroxidase did not differ in k/o and control mitochondria. The faster spontaneous oxidation of endogenous NADPH in the k/o mitochondria was prevented by the addition of exogenous catalase, indicating that this oxidation is mediated by mitochondrially generated H(2)O(2). The higher rate of H(2)O(2) production was also prevented by the addition of exogenous isocitrate that maintains NADP fully reduced. The hypothesis that high rates of lipogenesis in the k/o cells decrease mitochondrial NADPH/NADP(+) ratio due to consumption of NADPH-linked substrates was supported by two findings: (i) oxygen consumption supported by endogenous NAD(P)H-linked substrates was slower in k/o than in control mitochondria, but was similar in the presence of exogenous isocitrate; (ii) in vivo treatment of k/o mice with sodium citrate/citric acid drinking solution for 2 weeks partially restored both the rate of oxygen consumption supported by NAD(P)H-linked substrates and the mitochondrial capacity to sustain reduced NADPH. In conclusion, the data demonstrate that the mitochondrial oxidative stress in hypercholesterolemic LDL receptor knockout mice is the result of a low content of mitochondrial NADPH-linked substrates in the intact animal that can be, at least in part, replenished by oral administration of citrate.44444-5

Mitochondrial Dna Damage Associated With Lipid Peroxidation Of The Mitochondrial Membrane Induced By Fe2+-citrate.

Iron imbalance/accumulation has been implicated in oxidative injury associated with many degenerative diseases such as hereditary hemochromatosis, beta-thalassemia, and Friedreich's ataxia. Mitochondria are particularly sensitive to iron-induced oxidative stress - high loads of iron cause extensive lipid peroxidation and membrane permeabilization in isolated mitochondria. Here we detected and characterized mitochondrial DNA damage in isolated rat liver mitochondria exposed to a Fe2+-citrate complex, a small molecular weight complex. Intense DNA fragmentation was induced after the incubation of mitochondria with the iron complex. The detection of 3' phosphoglycolate ends at the mtDNA strand breaks by a 32P-postlabeling assay, suggested the involvement of hydroxyl radical in the DNA fragmentation induced by Fe2+-citrate. Increased levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine also suggested that Fe2+-citrate-induced oxidative stress causes mitochondrial DNA damage. In conclusion, our results show that iron-mediated lipid peroxidation was associated with intense mtDNA damage derived from the direct attack of reactive oxygen species.78505-1

Simvastatin Inducing Pc3 Prostate Cancer Cell Necrosis Mediated By Calcineurin And Mitochondrial Dysfunction.

In the present study we analyzed the mechanisms of simvastatin toxicity for the PC3 human prostate cancer cell line. At 10 microM, simvastatin induced principally apoptosis, which was prevented by mevalonic acid but not by cyclosporin A, the inhibitor of calcineurin and mitochondrial permeability transition (MPT). At 60 microM, simvastatin induced the necrosis of PC3 cells insensitive to mevalonic acid. Cell necrosis was preceded by a threefold increase in cytosolic free Ca(2+) concentration and a significant decrease in both respiration rate and mitochondrial membrane potential. Both mitochondrial dysfunction and necrosis were sensitive to the compounds cyclosporin A and bongkrekic acid, as well as the calcineurin inhibitor FK506. We have concluded that simvastatin-induced PC3 cells apoptosis is dependent on 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibition and independent of MPT, whereas necrosis is dependent on mitochondrial dysfunction caused, at least in part, by calcineurin.40307-1

Embryo mitochondrial DNA depletion is reversed during early embryogenesis in cattle

The extensive replication of mitochondria during oogenesis and the wide variability in mitochondrial DNA (mtDNA) copy numbers present in fully grown oocytes indicate that mtDNA amount may play an important role during early embryogenesis. Using bovine oocytes derived from follicles of different sizes to study the influence of mtDNA content on development, we showed that oocytes obtained from small follicles, known to be less competent in developing into blastocysts, contain less mtDNA than those originating from larger follicles. However, because of the high variability in copy number, a more accurate approach was examined in which parthenogenetic one-cell embryos were biopsied to measure their mtDNA content and then cultured to assess development capacity. Contrasting with previous findings, mtDNA copy number in biopsies was not different between competent and incompetent embryos, indicating that mtDNA content is not related to early developmental competence. To further examine the importance of mtDNA on development, one-cell embryos were partially depleted of their mtDNA (64% ± 4.1% less) by centrifugation followed by the removal of the mitochondrial-enriched cytoplasmic fraction. Surprisingly, depleted embryos developed normally into blastocysts, which contained mtDNA copy numbers similar to nonmanipulated controls. Development in depleted embryos was accompanied by an increase in the expression of genes (TFAM and NRF1) controlling mtDNA replication and transcription, indicating an intrinsic ability to restore the content of mtDNA at the blastocyst stage. Therefore, we concluded that competent bovine embryos are able to regulate their mtDNA content at the blastocyst stage regardless of the copy numbers accumulated during oogenesis82 issue 1 on pages1768