L-Carnitine suppresses oleic acid-induced membrane permeability transition of mitochondria

Addition of l-carnitine to the freezing extender improves post-thaw sperm quality of Okinawan native Agu pig

The objective of the present study was to establish whether the addition of l-carnitine (LC), which exhibits antioxidant activity, to the freezing extender improves the quality of cryopreserved Okinawan native Agu pig sperm. Ejaculated sperm frozen in an extender supplemented with 0, 1, 2.5, or 5 mM LC was thawed, and the integrities of mitochondria and the plasmalemma and other sperm characteristics were evaluated. The treatment with different concentrations of LC effectively improved sperm motility, mitochondrial and plasmalemmal integrities, and the proteolytic activity of acrosomal contents after freeze-thawing (P < 0.05). The proportion of post-thaw sperm possessing intact mitochondria and plasmalemma and higher proteolytic activity of acrosomal contents was markedly higher among sperm frozen in the presence of 2.5 mM LC than among sperm frozen in the extender without LC (P < 0.05). Furthermore, although the addition of LC to the freezing extender had no effect on disturbance of DNA damage and caspase activity, sperm treated with 2.5 mM LC during freezing exhibited significantly higher penetrability into matured oocytes in vitro than untreated sperm. Collectively, these results indicate that the addition of LC to the freezing extender effectively improved the post-thaw quality of Agu pig sperm by preventing mitochondrial dysfunction caused by oxidative stress during cryopreservation.

Placental mitochondrial function as a driver of angiogenesis and placental dysfunction

The placenta is a highly vascularized and complex foetal organ that performs various tasks, crucial to a healthy pregnancy. Its dysfunction leads to complications such as stillbirth, preeclampsia, and intrauterine growth restriction. The specific cause of placental dysfunction remains unknown. Recently, the role of mitochondrial function and mitochondrial adaptations in the context of angiogenesis and placental dysfunction is getting more attention. The required energy for placental remodelling, nutrient transport, hormone synthesis, and the reactive oxygen species leads to oxidative stress, stemming from mitochondria. Mitochondria adapt to environmental changes and have been shown to adjust their oxygen and nutrient use to best support placental angiogenesis and foetal development. Angiogenesis is the process by which blood vessels form and is essential for the delivery of nutrients to the body. This process is regulated by different factors, pro-angiogenic factors and anti-angiogenic factors, such as sFlt-1. Increased circulating sFlt-1 levels have been linked to different preeclamptic phenotypes. One of many effects of increased sFlt-1 levels, is the dysregulation of mitochondrial function. This review covers mitochondrial adaptations during placentation, the importance of the anti-angiogenic factor sFlt-1in placental dysfunction and its role in the dysregulation of mitochondrial function.

Protective effect of L-carnitine on platelet apoptosis during storage of platelet concentrate

BACKGROUND

Platelet apoptosis is considered as one of the important factors involved in platelet storage lesion (PSL) and affect the quality of platelets during storage. The beneficial effect of L-carnitine (LC) on platelet apoptosis during platelet concentrates (PCs) storage has not been fully investigated. The aim of this study was to evaluate the effects of LC on platelets of PC regarding their apoptosis markers during storage.

METHODS

Ten PCs from healthy donors were investigated in this study. PCs were prepared by platelet rich plasma (PRP) method and stored at 22±2°C with gentle agitation during storage. The effects of LC (15mM) on the platelet apoptosis were assessed by analyzing different indicative presence or absence of LC. Sampling was performed to evaluate apoptosis markers during platelet storage.

RESULTS

The results indicated significantly higher mitochondrial membrane potential for LC-treated platelets than the untreated on the days 2 and 5 of storage (P_day2=0.001, P_day5=0.001). Phosphatidylserine (PS) exposure significantly increased on the untreated compared with LC-treated platelets on the second and third days of storage (P_day2=0.014, P_day3=0.012). Also, active caspase 3 was lower in the LC- treated platelets than the control group on the day 5 of storage (P_day5=0.004). Cytosolic cytochrome C was so significantly lower in LC-treated compared to the untreated platelets during storage time (P_day2=0.002, P_day3=0.001, Pday5=0.001).

CONCLUSION

The results of this study indicate that the use of LC as an additive solution in platelets may be useful to reduce PSL by decreasing platelet apoptosis via mitochondrial pathway and increase platelet quality during storage.

Optimization of staining with SYTO 9/propidium iodide: interplay, kinetics and impact on Brevibacillus brevis

Fluorophores SYTO 9 and propidium iodide (PI) are extensively applied in medicine, food industry and environmental monitoring to assess the viability of bacteria. However, the actual performance of these dyes remains largely unknown. In addition, their effects on the physiology of cells have not been elucidated. Here we characterized the effects of these two dyes on Brevibacillus brevis under optimized staining. We found that SYTO 9 entered cells continuously while PI tended to adhere to the cell wall before entering the cell. In addition, results showed that a high amount of the dyes altered the physicochemical properties of membranes, improving their breakthrough. These results provide new perspectives and ideas for improving the characterization of bacterial viability using flow cytometry.

Oleic Acid Alleviates Cadmium-Induced Oxidative Damage in Rat by Its Radicals Scavenging Activity

Toxic heavy metal cadmium wildly pollutes the environment and threats the human health. Effective treatment of cadmium-induced toxicity and organ damage is an important issue. Cadmium causes organ damage through inducing oxidative stress. Our previous study also found oleic acid (OA) synthesis-related gene can confer resistance to cadmium and alleviate cadmium-induced stress in yeast. However, its alleviation mechanism on cadmium stress especially in animals is still unclear. In this study, the alleviative effects of OA on cadmium and cadmium-induced oxidative stress in rats were investigated. Oral administration of 10, 20, and 30 mg/kg/day OA can significantly increase the survival rate of rats intraperitoneally injected with 30 mg/kg/day cadmium continuously for 7 days. Similar to ascorbic acid (AA), OA can significantly reduce the cadmium-induced lipid peroxidation in multiple organs of rats. The investigation of OA on superoxide dismutase (SOD) activity showed that OA increased the SOD activity of cadmium-treated rat organs. More important, OA reduced the level of superoxide radical O^2- of cadmium-treated rat organs. And OA exhibited a strong DPPH radicals scavenging activity at dose of 10, 20 and 30 mg/mL, which may contributed to alleviating cadmium-induced oxidative stress. This study revealed that OA could significantly alleviate cadmium stress via reducing cadmium-induced lipid peroxidation and SOD activity inhibition through its radicals scavenging activity.

Alzheimer's disease and metabolic syndrome: A link from oxidative stress and inflammation to neurodegeneration

Alzheimer's disease (AD) is the most common cause of dementia and one of the most important causes of morbidity and mortality among the aging population. AD diagnosis is made post-mortem, and the two pathologic hallmarks, particularly evident in the end stages of the illness, are amyloid plaques and neurofibrillary tangles. Currently, there is no curative treatment for AD. Additionally, there is a strong relation between oxidative stress, metabolic syndrome, and AD. The high levels of circulating lipids and glucose imbalances amplify lipid peroxidation that gradually diminishes the antioxidant systems, causing high levels of oxidative metabolism that affects cell structure, leading to neuronal damage. Accumulating evidence suggests that AD is closely related to a dysfunction of both insulin signaling and glucose metabolism in the brain, leading to an insulin-resistant brain state. Four drugs are currently used for this pathology: Three FDA-approved cholinesterase inhibitors and one NMDA receptor antagonist. However, wide varieties of antioxidants are promissory to delay or prevent the symptoms of AD and may help in treating the disease. Therefore, therapeutic efforts to achieve attenuation of oxidative stress could be beneficial in AD treatment, attenuating Aβ-induced neurotoxicity and improve neurological outcomes in AD. The term inflammaging characterizes a widely accepted paradigm that aging is accompanied by a low-grade chronic up-regulation of certain pro-inflammatory responses in the absence of overt infection, and is a highly significant risk factor for both morbidity and mortality in the elderly.

Evaluating effects of L-carnitine on human bone-marrow-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells showing potential for use in regenerative medicine. Culture techniques that are more stable and methods for the more efficient production of MSCs with therapeutic efficacy are needed. We evaluate the effects of growing bone marrow (Bm)-derived MSCs in the presence of L-carnitine, which is believed to promote lipid metabolism and to suppress apoptosis. The presence of L-carnitine decreased the degree of drug-induced apoptosis and suppressed adipogenic differentiation. Metabolomic analysis by means of the exhaustive investigation of metabolic products showed that, in addition to increased β-oxidation and the expression of all carnitine derivatives other than deoxycarnitine (an intermediate in carnitine synthesis), polysaturated and polyunsaturated acids were down-regulated. An integrated analysis incorporating both serial analysis of gene expression and metabolomics revealed increases in cell survival, suggesting the utility of carnitine. The addition of carnitine elevated the oxygen consumption rate by BmMSCs that had been cultured for only a few generations and those that had become senescent following repeated replication indicating that mitochondrial activation occurred. Our exhaustive analysis of the effects of various carnitine metabolites thus suggests that the addition of L-carnitine to BmMSCs during expansion enables efficient cell production.

Palmitoleic acid induces the cardiac mitochondrial membrane permeability transition despite the presence of L-carnitine

Although palmitoleic acid (C16:1) is associated with arrhythmias, and increases in an age-dependent matter, the effects of L-carnitine, which is essential for the transport of long-chain fatty acids into the mitochondria, are unclear. It has been postulated that L-carnitine may attenuate palmitate (C16:0)-induced mitochondrial dysfunction and the apoptosis of cardiomyocytes. The aim of this study was to elucidate the activity of L-carnitine in the prevention of the palmitoleic acid-induced mitochondrial membrane permeability transition and cytochrome c release using isolated cardiac mitochondria from rats. Palmitoleoyl-CoA-induced mitochondrial respiration was not accelerated by L-carnitine treatment, and this respiration was slightly inhibited by oligomycin, which is an inhibitor of ATP synthase. Despite pretreatment with L-carnitine, the mitochondrial membrane potential decreased and mitochondrial swelling was induced by palmitoleoyl-CoA. In the presence of a combination of L-carnitine and tiron, a free radical scavenger, there was attenuated mitochondrial swelling and cytochrome c release following palmitoleoyl-CoA treatment. We concluded that palmitoleic acid, but not palmitate, induces the cardiac mitochondrial membrane permeability transition despite the presence of L-carnitine.

Micromolar changes in lysophosphatidylcholine concentration cause minor effects on mitochondrial permeability but major alterations in function

Mice deficient in group 1b phospholipase A2 have decreased plasma lysophosphatidylcholine and increased hepatic oxidation that is inhibited by intraperitoneal lysophosphatidylcholine injection. This study sought to identify a mechanism for lysophosphatidylcholine-mediated inhibition of hepatic oxidative function. Results showed that in vitro incubation of isolated mitochondria with 40-200μM lysophosphatidylcholine caused cyclosporine A-resistant swelling in a concentration-dependent manner. However, when mitochondria were challenged with 220μM CaCl2, cyclosporine A protected against permeability transition induced by 40μM, but not 80μM lysophosphatidylcholine. Incubation with 40-120μM lysophosphatidylcholine also increased mitochondrial permeability to 75μM CaCl2 in a concentration-dependent manner. Interestingly, despite incubation with 80μM lysophosphatidylcholine, the mitochondrial membrane potential was steady in the presence of succinate, and oxidation rates and respiratory control indices were similar to controls in the presence of succinate, glutamate/malate, and palmitoyl-carnitine. However, mitochondrial oxidation rates were inhibited by 30-50% at 100μM lysophosphatidylcholine. Finally, while 40μM lysophosphatidylcholine has no effect on fatty acid oxidation and mitochondria remained impermeable in intact hepatocytes, 100μM lysophosphatidylcholine inhibited fatty acid stimulated oxidation and caused intracellular mitochondrial permeability. Taken together, these present data demonstrated that LPC concentration dependently modulates mitochondrial microenvironment, with low micromolar concentrations of lysophosphatidylcholine sufficient to change hepatic oxidation rate whereas higher concentrations are required to disrupt mitochondrial integrity.

Why does brain metabolism not favor burning of fatty acids to provide energy? Reflections on disadvantages of the use of free fatty acids as fuel for brain

It is puzzling that hydrogen-rich fatty acids are used only poorly as fuel in the brain. The long-standing belief that a slow passage of fatty acids across the blood-brain barrier might be the reason. However, this has been corrected by experimental results. Otherwise, accumulated nonesterified fatty acids or their activated derivatives could exert detrimental activities on mitochondria, which might trigger the mitochondrial route of apoptosis. Here, we draw attention to three particular problems: (1) ATP generation linked to β-oxidation of fatty acids demands more oxygen than glucose, thereby enhancing the risk for neurons to become hypoxic; (2) β-oxidation of fatty acids generates superoxide, which, taken together with the poor anti-oxidative defense in neurons, causes severe oxidative stress; (3) the rate of ATP generation based on adipose tissue-derived fatty acids is slower than that using blood glucose as fuel. Thus, in periods of extended continuous and rapid neuronal firing, fatty acid oxidation cannot guarantee rapid ATP generation in neurons. We conjecture that the disadvantages connected with using fatty acids as fuel have created evolutionary pressure on lowering the expression of the β-oxidation enzyme equipment in brain mitochondria to avoid extensive fatty acid oxidation and to favor glucose oxidation in brain.

Acetyl-L-carnitine suppresses thyroid hormone-induced and spontaneous anuran tadpole tail shortening

Mitochondrial membrane permeability transition (MPT) plays a crucial role in apoptotic tail shortening during anuran metamorphosis. L-carnitine is known to shuttle free fatty acids (FFAs) from the cytosol into mitochondria matrix for β-oxidation and energy production, and in a previous study we found that treatment with L-carnitine suppresses 3, 3', 5-triiodothyronine (T3 ) and FFA-induced MPT by reducing the level of FFAs. In the present study we focus on acetyl-L-carnitine, which is also involved in fatty acid oxidation, to determine its effect on T3 -induced tail regression in Rana rugosa tadpoles and spontaneous tail regression in Xenopus laevis tadpoles. The ladder-like DNA profile and increases in caspase-3 and caspase-9 indicative of apoptosis in the tails of T3 -treated tadpoles were found to be suppressed by the addition of acetyl-L-carnitine. Likewise, acetyl-L-carnitine was found to inhibit thyroid hormone regulated spontaneous metamorphosis in X. laevis tadpoles, accompanied by decreases in caspase and phospholipase A2 activity, as well as non-ladder-like DNA profiles. These findings support our previous conclusion that elevated levels of FFAs initiate MPT and activate the signaling pathway controlling apoptotic cell death in tadpole tails during anuran metamorphosis.

Protective effects of L-carnitine on intestinal ischemia/reperfusion injury in a rat model

BACKGROUND

Ischemia/reperfusion (IR) injury of the intestine is a major problem in abdominal pathological condition and is associated with a high morbidity and mortality. The purpose of the study is to determine whether the L-carnitine can prevent the harmful effects of small intestinal IR injury in rats.

METHODS

Thirty Sprague-Dawley rats were randomly divided into three groups. Sham operated group (S), for shamoperated, the IR group for rats submitted to 45-minute of intestinal ischemia and 2-hour reperfusion, and IR+L group for those IR group treated with L-carnitine before reperfusion. All the rats were given EmGFP labelled E. coli DH5α through gavage 2-hour before the operative procedure. Afterwards the bacterial translocation (BT) from mesenteric lymph nodes (MLN), liver, spleen, lung and portal vein blood were detected. And the colony forming units/g (CFU/g) were counted. The TNF-α, IL-1β, IL-6, and IL-10 in serum were measured by ELISA. The morphometric study was measured by Chius classification.

RESULTS

The levels of BT were higher in the IR group than IR+L group (P < 0.05). The E. coli DH5α was hardly detected in the S group. The IR+L rats had enhancement of IL-10 and suppressed production of serum TNF-α, IL-1β and IL-6, compared to IR group rats (P < 0.05). The degree of pathological impairment in small intestine was lighter in IR+L than IR group (P < 0.05).

CONCLUSIONS

The L-carnitine pretreatment has a positive effect on reducing levels of BT, on inhibiting secretion of proinflammatory cytokines, and on lessening intestinal mucosa injury during small intestinal IR injury.

KEYWORDS

L-carnitine; Ischemia/reperfusion injury; Intestine.

Protective action of L-carnitine on cardiac mitochondrial function and structure against fatty acid stress

Cardiovascular risks are frequently accompanied by high serum fatty acid levels. Although recent studies have shown that fatty acids affect mitochondrial function and induce cell apoptosis, L-carnitine is essential for the uptake of fatty acids by mitochondria, and may attenuate the mitochondrial dysfunction and apoptosis of cardiocytes. This study aimed to elucidate the activity of L-carnitine in the prevention on fatty acid-induced mitochondrial membrane permeability transition and cytochrome c release using isolated cardiac mitochondria from rats. Palmitoyl-CoA-induced mitochondrial respiration that was observed with L-carnitine was inhibited with oligomycin. The palmitoyl-CoA-induced mitochondrial membrane depolarization and swelling were greatly inhibited by the presence of L-carnitine. In ultrastructural observations, terminally swollen and ruptured mitochondria with little or no distinguishable cristae structures were induced by treatment with palmitoyl-CoA. However, the severe morphological damage in cardiac mitochondria was dramatically inhibited by pretreatment with L-carnitine. Treatment with L-carnitine also attenuated 4-hydroxy-L-phenylglycine- and rotenone-induced mitochondrial swelling even when the L-carnitine could not protect against the decrease in oxygen consumption associated with these inhibitors. Furthermore, L-carnitine completely inhibited palmitoyl-CoA-induced cytochrome c release. We concluded that L-carnitine is essential for cardiac mitochondria to attenuate the membrane permeability transition, and to maintain the ultrastructure and membrane stabilization, in the presence of high fatty acid β-oxidation. Consequently, the cells may be protected against apoptosis by L-carnitine through inhibition of the fatty acid-induced cytochrome c release.

Mitochondrial dysfunction in nonalcoholic steatohepatitis

The pathogenesis of nonalcoholic steatohepatitis (NASH) is poorly understood and the mechanisms are still being elucidated. Mitochondrial dysfunction participates at different levels in NASH pathogenesis since it impairs fatty liver homeostasis and induces overproduction of free radicals that in turn trigger lipid peroxidation and cell death. In this article, we review the role of mitochondria in fat metabolism, energy homeostasis and reactive oxygen species production, with a focus on the role of mitochondrial impairment and uncoupling proteins in the pathophysiology of NASH progression. The potential effects of some molecules targeted to mitochondria are also discussed.

Beta-oxidation is essential for mouse oocyte developmental competence and early embryo development

Oocyte and embryo metabolism are closely linked with their subsequent developmental capacity. Lipids are a potent source of cellular energy, yet little is known about lipid metabolism during oocyte maturation and early embryo development. Generation of ATP from lipids occurs within mitochondria via beta-oxidation of fatty acids, with the rate-limiting step catalyzed by carnitine palmitoyl transferase I (CPT1B), a process also requiring carnitine. We sought to investigate the regulation and role of beta-oxidation during oocyte maturation and preimplantation development. Expression of Cpt1b mRNA, assessed by real-time RT-PCR in murine cumulus-oocyte complexes (COCs), increased following hormonal induction of oocyte maturation and ovulation in vivo with human chorionic gonadotropin (5 IU) and in embryos reaching the blastocyst stage. Beta-oxidation, measured by the production of (3)H(2)O from [(3)H]palmitic acid, was significantly increased over that in immature COCs following induction of maturation in vitro with epidermal growth factor (3 ng/ml) and follicle-stimulating hormone (50 mIU/ml). The importance of lipid metabolism for oocyte developmental competence and early embryo development was demonstrated by assessing the rate of embryo development following inhibition or upregulation of beta-oxidation with etomoxir (an inhibitor of CPT1B) or L-carnitine, respectively. Inhibition of beta-oxidation during oocyte maturation or zygote cleavage impaired subsequent blastocyst development. In contrast, L-carnitine supplementation during oocyte maturation significantly increased beta-oxidation, improved developmental competence, and in the absence of a carbohydrate energy supply, significantly increased 2-cell cleavage. Thus, carnitine is an important cofactor for developing oocytes, and fatty acids are an important energy source for oocyte and embryo development.

L-carnitine is essential to beta-oxidation of quarried fatty acid from mitochondrial membrane by PLA(2)

Mitochondrial beta-oxidation is an important system involved in the energy production of various cells. In this system, the function of L-carnitine is essential for the uptake of fatty acids to mitochondria. However, it is unclear whether or not endogenous respiration, ADP-induced O(2) consumption without substrates, is caused by L-carnitine treatment. In this study, we investigated whether L-carnitine is essential to the beta-oxidation of quarried fatty acids from the mitochondrial membrane by phospholipase A(2) (PLA(2)) using isolated mitochondria from the liver of rats. Intact mitochondria were incubated in a medium containing Pi, CoA and L-carnitine. The effect of L-carnitine treatment on ADP-induced mitochondrial respiration was observed without exogenous respiratory substrate. Increase in mitochondrial respiration was induced by treatment with L-carnitine in a concentration-dependent manner. Treatment with rotenone, a complex I blocker, completely inhibited ADP-induced oxygen consumption even in the presence of L-carnitine. Moreover, the L-carnitine dependent ADP-induced mitochondrial oxygen consumption did not increase when PLA(2) inhibitors were treated before ADP treatment. The L-carnitine-dependent ADP-induced oxygen consumption did contribute to ATP productions but not heat generation via an uncoupling system. These results suggest that L-carnitine might be essential to the beta-oxidation of quarried fatty acids from the mitochondrial membrane by PLA(2).

CARNITINE HOMEOSTASIS, MITOCHONDRIAL FUNCTION, AND CARDIOVASCULAR DISEASE

Carnitines are involved in mitochondrial transport of fatty acids and are of critical importance for maintaining normal mitochondrial function. This review summarizes recent experimental and clinical studies showing that mitochondrial dysfunction secondary to a disruption of carnitine homeostasis may play a role in decreased NO signaling and the development of endothelial dysfunction. Future challenges include development of agents that can positively modulate L-carnitine homeostasis which may have high therapeutic potential.