Secondary carnitine deficiency and impaired docosahexaenoic (22:6n-3) acid synthesis: a common denominator in the pathophysiology of diseases of oxidative phosphorylation and beta-oxidation

Dietary L-carnitine supplementation changes lipid metabolism and glucose utilization of Rhynchocypris lagowskii fed diets with different lipid sources

The widely available crop oil is an effective alternative to the increasingly scarce marine fish oil. However, simple alternative strategies have led to declining growth and the edible value of farmed fish. It is worthwhile to explore the effects of micro supplements in diets to improve the tolerance of fish to different dietary lipid sources, which finally optimizes the feeding strategies. This study aimed to investigate the regulation of L-carnitine and dietary oil conditions on nutrient composition, lipid metabolism, and glucose regulation of Rhynchocypris lagowskii. Four diets were prepared according to fish oil, fish oil supplemented with L-carnitine, corn oil, and corn oil supplemented with L-carnitine, and FO, LCFO, CO, and LCCO were labeled, respectively. R. lagowskii was fed experimental diets for 8 weeks, and the glucose tolerance test was performed. The CO diet significantly resulted in higher crude lipid content in muscle but a lower level of serum lipid parameters of R. lagowskii than the FO diet. However, dietary L-carnitine supplementation significantly reduced the crude lipid content in the hepatopancreas and muscle of the fish fed with the CO diet yet increased the serum lipid parameters. Additionally, the crude lipid content of muscle was reduced in the fish fed with an FO diet supplemented with L-carnitine. Compared with the FO diet, the CO diet significantly reduced the ratio of n3/n6 polyunsaturated fatty acid in the hepatopancreas and muscle of R.lagowskii. Dietary L-carnitine supplementation significantly reduced the contents of total saturated fatty acids and total monounsaturated fatty acids in hepatopancreas under both dietary lipid sources. The CO diet significantly up-regulated the expression of genes related to lipid uptake and adipogenesis in hepatopancreas, including lipoprotein lipase (lpl), acetyl-coenzyme A carboxylase alpha (accα), and sterol regulatory element binding protein-1 (srebp1), compared with the FO diet. While dietary L-carnitine supplementation significantly down-regulated the expressions of lpl, accα, srebp1, and fatty acid synthase in hepatopancreas and muscle of fish under both dietary lipid sources, along with up-regulated expression of carnitine palmitoyltransferase 1 in hepatopancreas. Moreover, the fish fed with a CO diet significantly increased the expression of glucose uptake and clearance and significantly down-regulated the expressions of glucose regulation-related genes, including glucose transporter 1, glycogen synthase 1, and phosphofructokinase in hepatopancreas and muscle, resulting in slower glucose uptake and clearance than fish fed with FO diet. Nevertheless, dietary L-carnitine supplementation up-regulated the expression of gluconeogenesis-related genes, including glucose-6-phosphatase and phosphoenolpyruvate carboxykinase in the hepatopancreas of R. lagowskii under both dietary lipid sources. In conclusion, a higher dietary n6 PUFA resulted in lipid deposition, decreased serum lipid parameters, and limited serum glucose utilization of R. lagowskii. While the regulatory effect of L-carnitine on lipid metabolism and glucose utilization of R. lagowskii varies with dietary lipid sources and tissues.

Differences in iron balance observed with dietary cholic acid supplementation and marginal iron deficiency in rats

We investigated whether a cholic acid (CA)-supplemented diet and marginal iron deficiency (MID) diet influence hepatic lipid accumulation and iron balance in rats for 2 weeks. The CA diet enhanced hepatic lipid accumulation and modulated iron metabolism such as enhancement of fecal iron excretion, reduction in iron absorption, and no alteration in plasma iron levels. The MID diet did not alter hepatic lipid concentrations with reduced iron concentration in the liver and plasma. In combination, influence of the CA supplementation on the hepatic iron concentration was opposite between iron-sufficient and MID conditions. In the liver, the CA diet enhanced lipocalin 2 expression, whereas the MID diet enhanced transferrin receptor 1 expression and reduced hepcidin expression. This study revealed an involvement of 12-hydroxylated bile acids in regulation of hepatic iron concentration under MID condition.

Patient-Derived Cellular Models for Polytarget Precision Medicine in Pantothenate Kinase-Associated Neurodegeneration

The term neurodegeneration with brain iron accumulation (NBIA) brings together a broad set of progressive and disabling neurological genetic disorders in which iron is deposited preferentially in certain areas of the brain. Among NBIA disorders, the most frequent subtype is pantothenate kinase-associated neurodegeneration (PKAN) caused by pathologic variants in the PANK2 gene codifying the enzyme pantothenate kinase 2 (PANK2). To date, there are no effective treatments to stop the progression of these diseases. This review discusses the utility of patient-derived cell models as a valuable tool for the identification of pharmacological or natural compounds for implementing polytarget precision medicine in PKAN. Recently, several studies have described that PKAN patient-derived fibroblasts present the main pathological features associated with the disease including intracellular iron overload. Interestingly, treatment of mutant cell cultures with various supplements such as pantothenate, pantethine, vitamin E, omega 3, α-lipoic acid L-carnitine or thiamine, improved all pathophysiological alterations in PKAN fibroblasts with residual expression of the PANK2 enzyme. The information provided by pharmacological screenings in patient-derived cellular models can help optimize therapeutic strategies in individual PKAN patients.

Exogenous tetracosahexaenoic acid modifies the fatty acid composition of human primary T lymphocytes and Jurkat T cell leukemia cells contingent on cell type

Tetracosahexaenoic acid (24:6ω-3) is an intermediate in the conversion of 18:3ω-3 to 22:6ω-3 in mammals. There is limited information about whether cells can assimilate and metabolize exogenous 24:6ω-3. This study compared the effect of incubation with 24:6ω-3 on the fatty acid composition of two related cell types, primary CD3+ T lymphocytes and Jurkat T cell leukemia, which differ in the integrity of the polyunsaturated fatty acid (PUFA) biosynthesis pathway. 24:6ω-3 was only detected in either cell type when cells were incubated with 24:6ω-3. Incubation with 24:6ω-3 induced similar increments in the amount of 22:6ω-3 in both cell types and modified the homeoviscous adaptations fatty acid composition induced by activation of T lymphocytes. The effect of incubation with 18:3ω-3 compared to 24:6ω-3 on the increment in 22:6ω-3 was tested in Jurkat cells because primary T cells cannot convert 18:3ω-3 to 22:6ω-3. The increment in the 22:6ω-3 content of Jurkat cells incubated with 24:6ω-3 was 19.5-fold greater than that of cells incubated with 18:3ω-3. Acyl-coA oxidase siRNA knockdown decreased the amount of 22:6ω-3 and increased the amount of 24:6ω-3 in Jurkat cells. These findings show exogenous 24:6ω-3 can be incorporated into primary human T lymphocytes and Jurkat cells and induces changes in fatty acid composition consistent with its conversion to 22:6ω-3 via a mechanism involving peroxisomal β-oxidation that is regulated independently from the integrity of the upstream PUFA synthesis pathway. One further implication is that consuming 24:6ω-3 may be an effective alternative means of achieving health benefits attributed to 20:5ω-3 and 22:6ω-3.

Aluminum as a Possible Cause Toward Dyslipidemia

Aluminum, the third most abundant metal present in the earth's crust, is present almost in all daily commodities we use, and exposure to it is unavoidable. The interference of aluminum with various biochemical reactions in the body leads to detrimental health effects, out of which aluminum-induced neurodegeneration is widely studied. However, the effect of aluminum in causing dyslipidemia cannot be neglected. Dyslipidemia is a global health problem, which commences to the cosmic of non-communicable diseases. The interference of aluminum with various iron-dependent enzymatic activities in the tri-carboxylic acid cycle and electron transport chain results in decreased production of mitochondrial adenosine tri-phosphate. This ultimately contributes to oxidative stress and iron-mediated lipid peroxidation. This mitochondrial dysfunction along with modulation of α-ketoglutarate and L-carnitine perturbs lipid metabolism, leading to the atypical accumulation of lipids and dyslipidemia. Respiratory chain disruption because of the accumulation of reduced nicotinamide adenine di-nucleotide as a consequence of oxidative stress and the stimulatory effect of aluminum exposure on glycolysis causes many health issues including fat accumulation, obesity, and other hepatic disorders. One major factor contributing to dyslipidemia and enhanced pro-inflammatory responses is estrogen. Aluminum, being a metalloestrogen, modulates estrogen receptors, and in this world of industrialization and urbanization, we could corner down to metals, particularly aluminum, in the development of dyslipidemia. As per PRISMA guidelines, we did a literature search in four medical databases to give a holistic view of the possible link between aluminum exposure and various biochemical events leading to dyslipidemia.

Therapeutic approach with commercial supplements for pantothenate kinase-associated neurodegeneration with residual PANK2 expression levels

Background

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare neurogenetic disorders frequently associated with iron accumulation in the basal nuclei of the brain characterized by progressive spasticity, dystonia, muscle rigidity, neuropsychiatric symptoms, and retinal degeneration or optic nerve atrophy. Pantothenate kinase-associated neurodegeneration (PKAN) is one of the most widespread NBIA subtypes. It is caused by mutations in the gene of pantothenate kinase 2 (PANK2) that result in dysfunction in PANK2 enzyme activity, with consequent deficiency of coenzyme A (CoA) biosynthesis, as well as low levels of essential metabolic intermediates such as 4′-phosphopantetheine, a necessary cofactor for essential cytosolic and mitochondrial proteins.

Methods

In this manuscript, we examined the therapeutic effectiveness of pantothenate, panthetine, antioxidants (vitamin E and omega 3) and mitochondrial function boosting supplements (L-carnitine and thiamine) in mutant PANK2 cells with residual expression levels.

Results

Commercial supplements, pantothenate, pantethine, vitamin E, omega 3, carnitine and thiamine were able to eliminate iron accumulation, increase PANK2, mtACP, and NFS1 expression levels and improve pathological alterations in mutant cells with residual PANK2 expression levels.

Conclusion

Our results suggest that several commercial compounds are indeed able to significantly correct the mutant phenotype in cellular models of PKAN. These compounds alone or in combinations are of common use in clinical practice and may be useful for the treatment of PKAN patients with residual enzyme expression levels.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02465-9.

Fatty Acids: A Safe Tool for Improving Neurodevelopmental Alterations in Down Syndrome?

The triplication of chromosome 21 causes Down syndrome (DS), a genetic disorder that is characterized by intellectual disability (ID). The causes of ID start in utero, leading to impairments in neurogenesis, and continue into infancy, leading to impairments in dendritogenesis, spinogenesis, and connectivity. These defects are associated with alterations in mitochondrial and metabolic functions and precocious aging, leading to the early development of Alzheimer’s disease. Intense efforts are currently underway, taking advantage of DS mouse models to discover pharmacotherapies for the neurodevelopmental and cognitive deficits of DS. Many treatments that proved effective in mouse models may raise safety concerns over human use, especially at early life stages. Accumulating evidence shows that fatty acids, which are nutrients present in normal diets, exert numerous positive effects on the brain. Here, we review (i) the knowledge obtained from animal models regarding the effects of fatty acids on the brain, by focusing on alterations that are particularly prominent in DS, and (ii) the progress recently made in a DS mouse model, suggesting that fatty acids may indeed represent a useful treatment for DS. This scenario should prompt the scientific community to further explore the potential benefit of fatty acids for people with DS.

The Effects of a Meldonium Pre-Treatment on the Course of the LPS-Induced Sepsis in Rats

A dysregulated and overwhelming response to an infection accompanied by the exaggerated pro-inflammatory state and metabolism disturbance leads to the fatal outcome in sepsis. Previously we showed that meldonium, an anti-ischemic drug clinically used to treat myocardial and cerebral ischemia, strongly increases mortality in faecal-induced peritonitis (FIP) in rats. We postulated that the same mechanism that is responsible for the otherwise strong anti-inflammatory effects of meldonium could be the culprit of the increased mortality. In the present study, we applied the LPS-induced model of sepsis to explore the presence of any differences from and/or similarities to the FIP model. When it comes to energy production, despite some shared similarities, it is evident that LPS and FIP models of sepsis differ greatly. A different profile of sympathoadrenal activation may account for this observation, as it was lacking in the FIP model, whereas in the LPS model it was strong enough to overcome the effects of meldonium. Therefore, choosing the appropriate model of sepsis induction is of great importance, especially if energy homeostasis is the main focus of the study. Even when differences in the experimental design of the two models are acknowledged, the role of different patterns of energy production cannot be excluded. On that account, our results draw attention to the importance of uninterrupted energy production in sepsis but also call for much-needed revisions of the current recommendations for its treatment.

Dietary L-carnitine affects the expression of genes involved in apoptosis and fatty acid metabolism in rooster testes

Thirty-six 12-week-old breeder roosters (Ross 308) were randomly allocated into three groups to receive L-carnitine (LC): LC-0, LC-250 or LC-500 mg/kg of diet to evaluate the effects of dietary LC on the expression of apoptotic-related genes and desaturases and elongase mRNA transcript levels, in the cockerel testicles. Alteration of Bak (Bcl2 antagonist/killer), Bcl2, Cas3, Cas8, Cas9, Elovl2, Elovl4, Elovl5, Fads1, Fads2 and Scd expression at 24 and 34 weeks of age was compared by real-time quantitative PCR. The expression of Bcl2 and Elovl5 was significantly up-regulated (p < .05), while Cas8 expression (p < .05) and Bak/Bcl2 ratio were reduced (p < .02) in the cockerel testicles at 24 weeks of age. Although Bak mRNA abundance decreased by dietary LC, Bak/Bcl2 ratio was not affected by the treatments at 34 weeks of age. The expression of Cas3 was down-regulated, while Fads2 was up-regulated in the cockerel testicles by dietary LC at 34 weeks of age (p < .05). The results demonstrate the beneficial effects of LC supplementation in suppression of the Bak/Bcl2 ratio by altering Bak and Bcl2 mRNA abundance and, ultimately, prevention of apoptosis. Furthermore, LC increased the expression of Elovl5 and Fads2 genes which are involved in the metabolism of long chain fatty acids.

Manipulation of fatty acid profiles in roosters' testes, alteration in sexual hormones, improvements in testicular histology characteristics and elevation sperm quality factor by L-carnitine

The present study was designed to investigate the effects of different levels of l-carnitine (LC) on sperm quality factor (SQF), alterations in testis fatty acid profiles, testicular histology and reproductive hormones in young roosters. Eighteen broiler breeders (Ross 308) weighed at 3 months of age. They were randomly classified while each group had six birds. There were three experimental groups based on the LC concentrations (i.e. LC-0, LC-250, LC-500 mg per kg of diet). After two weeks of adaptation, semen samples were collected and evaluated for seminal attributes every two weeks (from week 24 to week 34). At the end of the experiments, four roosters from each treatment group were sacrificed in order to analyze testicular histology, testis fatty acid profiles and reproductive hormones. Supplementing the diet with two of the LC levels for 22 weeks caused significant rise in sperm concentration, viability and SQF compared to that of the control group (P < 0.05). Quadratic analysis in terms of number of seminiferous tubules and spermatogenesis index were significant (P<0.05). Tubular differentiation index improved linearly by the increasing levels of LC supplementation (P<0.01). The analysis of fatty acid profiles showed that LC significantly (P < 0.05) reduced the percentages of C14:0, C21:0, total saturated fatty acids, total odd-chain fatty acids and n-6/n-3 ratio. Moreover, LC significantly increased the percentage of C20:5n-3 (Eicosapentaenoic acid; EPA) (P < 0.05). Analysis of the correlation coefficient revealed that the SQF is in consistency with EPA (r = 0.98; P < 0.04). In contrast, SQF negatively and significantly correlates with odd-chain fatty acids (r = - 0.99; P < 0.001). The desaturation index for C16 fatty acids (16:1cis/C16:0) negligibly increased linearly as LC was added to the diet (P < 0.05). Furthermore, LC caused the roosters to have significant (P < 0.05) high levels of total testosterone and FSH concentrations. The concentration of LH in different treatment groups, however, turned out to be similar in response to the different levels of LC. In conclusion, long-term supplementation of rooster diet with LC can have beneficial effects on SQF and testis histology. The benefits include alterations in testicular histology, reproductive hormones and testicular fatty acid profiles.

The significant role of carnitine and fatty acids during pregnancy, lactation and perinatal period. Nutritional support in specific groups of pregnant women

BACKGROUND & AIMS

Pregnancy is characterized by a complexity of metabolic processes that may impact fetal health and development. Women's nutrition during pregnancy and lactation is considered important for both mother and infant. This review aims to investigate the significant role of fatty acids and carnitine during pregnancy and lactation in specific groups of pregnant and lactating women.

METHODS

The literature was reviewed using relevant data bases (e.g. Pubmed, Scopus, Science Direct) and relevant articles were selected to provide information and data for the text and associated Tables.

RESULTS

Dynamic features especially of plasma carnitine profile during pregnancy and lactation, indicate an extraordinarily active participation of carnitine in the intermediary metabolism both in pregnant woman and in neonate and may also have implications for health and disease later in life. Maternal diets rich in trans and saturated fatty acids can lead to impairments in the metabolism and development of the offspring, whereas the consumption of long chain-polyunsaturated fatty acids during pregnancy plays a beneficial physiologic and metabolic role in the health of offspring.

CONCLUSIONS

Pregnant women who are underweight, overweight or obese, with gestational diabetes mellitus or diabetes mellitus and those who choose vegan/vegetarian diets or are coming from socially disadvantaged areas, should be nutritionally supported to achieve a higher quality diet during pregnancy and/or lactation.

Antioxidant dietary approach in treatment of fatty liver: New insights and updates

Non-alcoholic fatty liver disease (NAFLD) is a common clinicopathological condition, encompassing a range of conditions caused by lipid deposition within liver cells. To date, no approved drugs are available for the treatment of NAFLD, despite the fact that it represents a serious and growing clinical problem in the Western world. Identification of the molecular mechanisms leading to NAFLD-related fat accumulation, mitochondrial dysfunction and oxidative balance impairment facilitates the development of specific interventions aimed at preventing the progression of hepatic steatosis. In this review, we focus our attention on the role of dysfunctions in mitochondrial bioenergetics in the pathogenesis of fatty liver. Major data from the literature about the mitochondrial targeting of some antioxidant molecules as a potential treatment for hepatic steatosis are described and critically analysed. There is ample evidence of the positive effects of several classes of antioxidants, such as polyphenols (i.e., resveratrol, quercetin, coumestrol, anthocyanins, epigallocatechin gallate and curcumin), carotenoids (i.e., lycopene, astaxanthin and fucoxanthin) and glucosinolates (i.e., glucoraphanin, sulforaphane, sinigrin and allyl-isothiocyanate), on the reversion of fatty liver. Although the mechanism of action is not yet fully elucidated, in some cases an indirect interaction with mitochondrial metabolism is expected. We believe that such knowledge will eventually translate into the development of novel therapeutic approaches for fatty liver.

Dried blood spot omega-3 and omega-6 long chain polyunsaturated fatty acid levels in 7-9 year old Zimbabwean children: a cross sectional study

BACKGROUND

Omega-3 long chain-polyunsaturated fatty acids (LC-PUFAs)-docosahexaenoic acid (DHA), docosapentaenoic acid (DPA) and eicosapentaenoic acid (EPA)- and omega-6 LC-PUFA arachidonic acid (ARA), are essential for optimum physical and mental development in children. Prior to this study, the blood omega-3 LC-PUFA levels were unknown in Zimbabwean children, particularly in those aged 7-9 years, despite the documented benefits of LC-PUFAs. Documentation of the LC-PUFA levels in this age group would help determine whether interventions, such as fortification, are necessary. This study aimed to determine dried whole blood spot omega-3 and omega-6 LC-PUFA levels and LC-PUFA reference intervals among a selected group of Zimbabwean children aged 7-9 years old.

METHODS

We conducted a cross sectional study from September 2011 to August 2012 on a cohort of peri-urban, Zimbabwean children aged 7-9 years. The children were born to mothers enrolled at late pregnancy into an HIV prevention program between 2002 and 2004. Dried whole blood spots were sampled on butylated hydroxytoluene antioxidant impregnated filter papers and dried. LC-PUFAs were quantified using gas liquid chromatography. Differences in LC-PUFAs between groups were compared using the Kruskal Wallis test and reference intervals determined using non-parametric statistical methods.

RESULTS

LC-PUFAs levels were determined in 297 Zimbabwean children of whom 170 (57.2 %) were girls. The study determined that LC-PUFAs (wt/wt) ranges were EPA 0.06-0.55 %, DPA 0.38-1.98 %, DHA 1.13-3.52 %, ARA 5.58-14.64 % and ARA: EPA ratio 15.47-1633.33. Sixteen participants had omega-3 LC-PUFAs levels below the determined reference intervals, while 18 had higher omega-6 LC-PUFAs. The study did not show gender differences in omega-3 and omega-6 LC-PUFAs levels (all p > 0.05). EPA was significantly higher in the 8 year age group compared to those aged 7 and 9 years (median; 0.20 vs 0.17 vs 0.18, respectively, p = 0.049). ARA: EPA ratio was significantly higher in the 7 year age group compared to those aged 8 and 9 years (median; 64.38 vs 56.43 vs 55.87 respectively, p = 0.014).

CONCLUSIONS

In this cohort of children, lower EPA levels and higher ARA: EPA ratios were observed compared to those reported in apparently healthy children elsewhere. The high ARA: EPA ratios might increase the vulnerability of these children to inflammatory pathologies. Identification and incorporation into diet of locally produced foodstuffs rich in omega-3 LC-PUFAs is recommended as well as advocating for dietary supplementation with omega-3 fish oils and algae based oils.

Interplay between TDP-43 and docosahexaenoic acid-related processes in amyotrophic lateral sclerosis

BACKGROUND

Docosahexaenoic acid (DHA), a key lipid in nervous system homeostasis, is depleted in the spinal cord of sporadic amyotrophic lateral sclerosis (sALS) patients. However, the basis for such loss was unknown.

METHODS

DHA synthetic machinery was evaluated in spinal cord samples from ALS patients and controls by immunohistochemistry and western blot. Further, lipid composition was measured in organotypic spinal cord cultures by gas chromatography and liquid chromatography coupled to mass spectrometry. In these samples, mitochondrial respiratory functions were measured by high resolution respirometry. Finally, Neuro2-A and stem cell-derived human neurons were used for evaluating mechanistic relationships between TDP-43 aggregation, oxidative stress and cellular changes in DHA-related proteins.

RESULTS

ALS is associated to changes in the spinal cord distribution of DHA synthesis enzymatic machinery comparing ten ALS cases and eight controls. We found increased levels of desaturases (ca 95% increase, p<0.001), but decreased amounts of DHA-related β-oxidation enzymes in ALS samples (40% decrease, p<0.05). Further, drebrin, a DHA-dependent synaptic protein, is depleted in spinal cord samples from ALS patients (around 40% loss, p<0.05). In contrast, chronic excitotoxicity in spinal cord increases DHA acid amount, with both enhanced concentrations of neuroprotective docosahexaenoic acid-derived resolvin D, and higher lipid peroxidation-derived molecules such as 8-iso-prostaglandin-F2-α (8-iso-PGF2α) levels. Since α-tocopherol improved mitochondrial respiratory function and motor neuron survival in these conditions, it is suggested that oxidative stress could boost motor neuron loss. Cell culture and metabolic flux experiments, showing enhanced expression of desaturases (FADS2) and β-oxidation enzymes after H2O2 challenge suggest that DHA production can be an initial response to oxidative stress, driven by TDP-43 aggregation and drebrin loss. Interestingly, these changes were dependent on cell type used, since human neurons exhibited losses of FADS2 and drebrin after oxidative stress. These features (drebrin loss and FADS2 alterations) were also produced by transfection by aggregation prone C-terminal fragments of TDP-43.

CONCLUSIONS

sALS is associated with tissue-specific DHA-dependent synthetic machinery alteration. Furthermore, excitotoxicity sinergizes with oxidative stress to increase DHA levels, which could act as a response over stress, involving the expression of DHA synthetic enzymes. Later on, this allostatic overload could exacerbate cell stress by contributing to TDP-43 aggregation. This, at its turn, could blunt this protective response, overall leading to DHA depletion and neuronal dysfunction.

Quercetin Attenuates Chronic Ethanol-Induced Hepatic Mitochondrial Damage through Enhanced Mitophagy

Emerging evidence suggested mitophagy activation mitigates ethanol-induced liver injury. However, the effect of ethanol on mitophagy is inconsistent. Importantly, the understanding of mitophagy status after chronic ethanol consumption is limited. This study evaluated the effect of quercetin, a naturally-occurring flavonoid, on chronic ethanol-induced mitochondrial damage focused on mitophagy. An ethanol regime to mice for 15 weeks (accounting for 30% of total calories) led to significant mitochondrial damage as evidenced by changes of the mitochondrial ultrastructure, loss of mitochondrial membrane potential and remodeling of membrane lipid composition, which was greatly attenuated by quercetin (100 mg/kg.bw). Moreover, quercetin blocked chronic ethanol-induced mitophagy suppression as denoted by mitophagosomes-lysosome fusion and mitophagy-related regulator elements, including LC3II, Parkin, p62 and voltage-dependent anion channel 1 (VDAC1), paralleling with increased FoxO3a nuclear translocation. AMP-activated protein kinase (AMPK) and extracellular signal regulated kinase 2 (ERK2), instead of AKT and Sirtuin 1, were involved in quercetin-mediated mitophagy activation. Quercetin alleviated ethanol-elicited mitochondrial damage through enhancing mitophagy, highlighting a promising preventive strategy for alcoholic liver disease.

Metabolomic analysis of exercise effects in the POLG mitochondrial DNA mutator mouse brain

Mitochondrial DNA (mtDNA) mutator mice express a mutated form of mtDNA polymerase gamma that results an accelerated accumulation of somatic mtDNA mutations in association with a premature aging phenotype. An exploratory metabolomic analysis of cortical metabolites in sedentary and exercised mtDNA mutator mice and wild-type littermate controls at 9-10 months of age was performed. Pathway analysis revealed deficits in the neurotransmitters acetylcholine, glutamate, and aspartate that were ameliorated by exercise. Nicotinamide adenine dinucleotide (NAD) depletion and evidence of increased poly(adenosine diphosphate-ribose) polymerase 1 (PARP1)activity were apparent in sedentary mtDNA mutator mouse cortex, along with deficits in carnitine metabolites and an upregulated antioxidant response that largely normalized with exercise. These data highlight specific pathways that are altered in the brain in association with an accelerated age-related accumulation of somatic mtDNA mutations. These results may have relevance to age-related neurodegenerative diseases associated with mitochondrial dysfunction, such as Alzheimer's disease and Parkinson's disease and provide insights into potential mechanisms of beneficial effects of exercise on brain function.

Treatment options for lactic acidosis and metabolic crisis in children with mitochondrial disease

The mitochondrial pyruvate oxidation route is a tightly regulated process, which is essential for aerobic cellular energy production. Disruption of this pathway may lead to severe neurometabolic disorders with onset in early childhood. A frequent finding in these patients is acute and chronic lactic acidemia, which is caused by increased conversion of pyruvate via the enzyme lactate dehydrogenase. Under stable clinical conditions, this process may remain well compensated and does not require specific therapy. However, especially in situations with altered energy demands, such as febrile infections or longer periods of fasting, children with mitochondrial disorders have a high risk of metabolic decompensation with exacerbation of hyperlactatemia and severe metabolic acidosis. Unfortunately, no controlled studies regarding therapy of this critical condition are available and clinical outcome is often unfavorable. Therefore, the aim of this review was to formulate expert-based suggestions for treatment of these patients, including dietary recommendations, buffering strategies and specific drug therapy. However, it is important to keep in mind that a specific therapy for the underlying metabolic cause in children with mitochondrial diseases is usually not available and symptomatic therapy especially of severe lactic acidosis has its ethical limitations.

Nonalcoholic Fatty liver disease: pathogenesis and therapeutics from a mitochondria-centric perspective

Nonalcoholic fatty liver disease (NAFLD) describes a spectrum of disorders characterized by the accumulation of triglycerides within the liver. The global prevalence of NAFLD has been increasing as the obesity epidemic shows no sign of relenting. Mitochondria play a central role in hepatic lipid metabolism and also are affected by upstream signaling pathways involved in hepatic metabolism. This review will focus on the role of mitochondria in the pathophysiology of NAFLD and touch on some of the therapeutic approaches targeting mitochondria as well as metabolically important signaling pathways. Mitochondria are able to adapt to lipid accumulation in hepatocytes by increasing rates of beta-oxidation; however increased substrate delivery to the mitochondrial electron transport chain (ETC) leads to increased reactive oxygen species (ROS) production and eventually ETC dysfunction. Decreased ETC function combined with increased rates of fatty acid beta-oxidation leads to the accumulation of incomplete products of beta-oxidation, which combined with increased levels of ROS contribute to insulin resistance. Several related signaling pathways, nuclear receptors, and transcription factors also regulate hepatic lipid metabolism, many of which are redox sensitive and regulated by ROS.

From genome to phenome-Simple inborn errors of metabolism as complex traits

Sporadically, patients with a proven defect in either mFAO or OXPHOS are described presenting with a metabolic profile and clinical phenotype expressing concurrent defects in both pathways. Biochemical linkages between both processes are tight. Therefore, it is striking that concurrent dysfunction of both systems occurs so infrequent. In this review, the linkages between OXPHOS and mFAO and the hypothesized processes responsible for concurrent problems in both systems are reviewed, both from the point of view of primary biochemical connections and secondary cellular responses, i.e. signaling pathways constituting nutrient-sensing networks. We propose that affected signaling pathways may play an important role in the phenomenon of concurrent defects. Recent data indicate that interference in the affected signaling pathways may resolve the pathological phenotype even though the primary enzyme deficiency persists. This offers new (unexpected) prospects for treatment of these inborn errors of metabolism. This article is part of a Special Issue entitled: From Genome to Function.

Omega-3 supplementation alters mitochondrial membrane composition and respiration kinetics in human skeletal muscle

Studies have shown increased incorporation of omega-3 fatty acids into whole skeletal muscle following supplementation, although little has been done to investigate the potential impact on the fatty acid composition of mitochondrial membranes and the functional consequences on mitochondrial bioenergetics. Therefore, we supplemented young healthy male subjects (n = 18) with fish oils [2 g eicosapentaenoic acid (EPA) and 1 g docosahexanoic acid (DHA) per day] for 12 weeks and skeletal muscle biopsies were taken prior to (Pre) and following (Post) supplementation for the analysis of mitochondrial membrane phospholipid composition and various assessments of mitochondrial bioenergetics. Total EPA and DHA content in mitochondrial membranes increased (P < 0.05) ∼450 and ∼320%, respectively, and displaced some omega-6 species in several phospholipid populations. Mitochondrial respiration, determined in permeabilized muscle fibres, demonstrated no change in maximal substrate-supported respiration, or in the sensitivity (apparent Km) and maximal capacity for pyruvate-supported respiration. In contrast, mitochondrial responses during ADP titrations demonstrated an enhanced ADP sensitivity (decreased apparent Km) that was independent of the creatine kinase shuttle. As the content of ANT1, ANT2, and subunits of the electron transport chain were unaltered by supplementation, these data suggest that prolonged omega-3 intake improves ADP kinetics in human skeletal muscle mitochondria through alterations in membrane structure and/or post-translational modification of ATP synthase and ANT isoforms. Omega-3 supplementation also increased the capacity for mitochondrial reactive oxygen species emission without altering the content of oxidative products, suggesting the absence of oxidative damage. The current data strongly emphasize a role for omega-3s in reorganizing the composition of mitochondrial membranes while promoting improvements in ADP sensitivity.

Omega-3 fatty acids in neurodegenerative diseases: focus on mitochondria

Mitochondrial dysfunction represents a common early pathological event in brain aging and in neurodegenerative diseases, e.g., in Alzheimer's (AD), Parkinson's (PD), and Huntington's disease (HD), as well as in ischemic stroke. In vivo and ex vivo experiments using animal models of aging and AD, PD, and HD mainly showed improvement of mitochondrial function after treatment with polyunsaturated fatty acids (PUFA) such as docosahexaenoic acid (DHA). Thereby, PUFA are particular beneficial in animals treated with mitochondria targeting toxins. However, DHA showed adverse effects in a transgenic PD mouse model and it is not clear if a diet high or low in PUFA might provide neuroprotective effects in PD. Post-treatment with PUFA revealed conflicting results in ischemic animal models, but intravenous administered DHA provided neuroprotective efficacy after acute occlusion of the middle cerebral artery. In summary, the majority of preclinical data indicate beneficial effects of n-3 PUFA in neurodegenerative diseases, whereas most controlled clinical trials did not meet the expectations. Because of the high half-life of DHA in the human brain clinical studies may have to be initiated much earlier and have to last much longer to be more efficacious.

Role of oxidative stress in the pathogenesis of nonalcoholic steatohepatitis

The worldwide rising prevalence of obesity and insulin resistance is associated with a parallel increase in nonalcoholic fatty liver disease (NAFLD). NAFLD is characterized by excess accumulation of triglyceride in the hepatocyte due to increased inflow of free fatty acids and/or de novo lipogenesis caused by various drugs and multiple defects in energy metabolism. Accumulation of lipids in the hepatocyte impairs the oxidative capacity of the mitochondria, increasing the reduced state of the electron transport chain (ETC) complexes and stimulating peroxisomal and microsomal pathways of fat oxidation. The consequent increased generation of reactive oxygen species (ROS) and reactive aldehydic derivatives causes oxidative stress and cell death, via ATP, NAD, and glutathione depletion and DNA, lipid, and protein damage. Oxidative stress also triggers production of inflammatory cytokines, causing inflammation and a fibrogenic response. This ultimately results in the development of nonalcoholic steatohepatitis (NASH), which can result in end-stage liver disease. The current therapeutic strategies for NASH treatment are mostly directed toward correction of the risk factors. Stimulation of mitochondrial function may also prevent NASH development, protecting the cell against the increased flux of reduced substrates to the ETC and ROS generation.

Hepatic response to aluminum toxicity: dyslipidemia and liver diseases

Aluminum (Al) is a metal toxin that has been implicated in the etiology of a number of diseases including Alzheimer's, Parkinson's, dialysis encephalopathy, and osteomalacia. Al has been shown to exert its effects by disrupting lipid membrane fluidity, perturbing iron (Fe), magnesium, and calcium homeostasis, and causing oxidative stress. However, the exact molecular targets of aluminum's toxicity have remained elusive. In the present review, we describe how the use of a systems biology approach in cultured hepatoblastoma cells (HepG2) allowed the identification of the molecular targets of Al toxicity. Mitochondrial metabolism is the main site of the toxicological action of Al. Fe-dependent and redox sensitive enzymes in the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) are dramatically decreased by Al exposure. In an effort to compensate for diminished mitochondrial function, Al-treated cells stabilize hypoxia inducible factor-1α (HIF-1α) to increase ATP production by glycolysis. Additionally, Al toxicity leads to an increase in intracellular lipid accumulation due to enhanced lipogenesis and a decrease in the β-oxidation of fatty acids. Central to these effects is the alteration of α-ketoglutarate (KG) homeostasis. In Al-exposed cells, KG is preferentially used to quench ROS leading to succinate accumulation and HIF-1α stabilization. Moreover, the channeling of KG to combat oxidative stress leads to a reduction of l-carnitine biosynthesis and a concomitant decrease in fatty acid oxidation. The fluidity and interaction of these metabolic modules and the implications of these findings in liver-related disorders are discussed herein.

Plasma fatty acids as diagnostic markers in autistic patients from Saudi Arabia

Backgrounds

Autism is a family of developmental disorders of unknown origin. The disorder is characterized by behavioral, developmental, neuropathological and sensory abnormalities, and is usually diagnosed between the ages of 2 and 10 with peak prevalence rates observed in children aged 5-8 years. Recently, there has been heightened interest in the role of plasma free fatty acids (FA) in the pathology of neurological disorders. The aim of this study is to compare plasma fatty acid profiles of Saudi autistic patients with those of age-matching control subjects in an attempt to clarify the role of FA in the etiology of autism.

Methods

26 autistic patients together with 26-age-matching controls were enrolled in the present study. Methyl esters of FA were extracted with hexane, and the fatty acid composition of the extract was analyzed on a gas chromatography.

Results

The obtained data proved that fatty acids are altered in the plasma of autistic patients, specifically showing an increase in most of the saturated fatty acids except for propionic acid, and a decrease in most of polyunsaturated fatty acids. The altered fatty acid profile was discussed in relation to oxidative stress, mitochondrial dysfunction and the high lead (Pb) concentration previously reported in Saudi autistic patients. Statistical analysis of the obtained data shows that most of the measured fatty acids were significantly different in autistic patients compared to age -matching controls.

Conclusions

Receiver Operating Characteristic (ROC) curve analysis shows satisfactory values of area under the curve (AUC) which could reflect the high degree of specificity and sensitivity of the altered fatty acids as biomarkers in autistic patients from Saudi Arabia.

Mitochondrial response to controlled nutrition in health and disease

Mitochondria exert crucial physiological functions that create complex links among nutrition, health, and disease. While mitochondrial dysfunction with subsequent impairment of oxidative phosphorylation (OXPHOS) is the hallmark of the rare inherited OXPHOS diseases, OXPHOS dysfunction also plays a central role in the pathophysiology of common conditions such as type 2 diabetes and various neurodegenerative disorders. Dietary interventions, especially calorie restriction, have been shown to improve the course of these diseases and to extend the lifespan. Few data are available on the impact of nutraceuticals (macronutrients, vitamins, and cofactors) on primary inherited OXPHOS diseases. This review presents recent knowledge about the impact of nutritional modulation on mitochondria and lifespan regulation and about the development of potential treatments for mitochondrial dysfunction diseases.

Hepatic steatosis in n-3 fatty acid depleted mice: focus on metabolic alterations related to tissue fatty acid composition

Background

There are only few data relating the metabolic consequences of feeding diets very low in n-3 fatty acids. This experiment carried out in mice aims at studying the impact of dietary n-3 polyunsaturated fatty acids (PUFA) depletion on hepatic metabolism.

Results

n-3 PUFA depletion leads to a significant decrease in body weight despite a similar caloric intake or adipose tissue weight. n-3 PUFA depleted mice exhibit hypercholesterolemia (total, HDL, and LDL cholesterol) as well as an increase in hepatic cholesteryl ester and triglycerides content. Fatty acid pattern is profoundly modified in hepatic phospholipids and triglycerides. The decrease in tissue n-3/n-6 PUFA ratio correlates with steatosis. Hepatic mRNA content of key factors involved in lipid metabolism suggest a decreased lipogenesis (SREBP-1c, FAS, PPARγ), and an increased β-oxidation (CPT1, PPARα and PGC1α) without modification of fatty acid esterification (DGAT2, GPAT1), secretion (MTTP) or intracellular transport (L-FABP). Histological analysis reveals alterations of liver morphology, which can not be explained by inflammatory or oxidative stress. However, several proteins involved in the unfolded protein response are decreased in depleted mice.

Conclusion

n-3 PUFA depletion leads to important metabolic alterations in murine liver. Steatosis occurs through a mechanism independent of the shift between β-oxidation and lipogenesis. Moreover, long term n-3 PUFA depletion decreases the expression of factors involved in the unfolded protein response, suggesting a lower protection against endoplasmic reticulum stress in hepatocytes upon n-3 PUFA deficiency.

Lipid Metabolism in Rats is Modified by Nitric Oxide Availability Through a Ca++-Dependent Mechanism

We studied lipid metabolism and the antioxidant defense system in plasma and liver of rats fed diets supplemented with L(omega)-nitro-L-arginine methyl ester (L-NAME), isosorbide dinitrate (DIS), L-arginine (Arg), or the associations of these drugs. Liver hydroperoxide and thiobarbituric-acid-reactive substance (TBARS) levels were decreased by Arg and increased by L-NAME or DIS treatments. Oxidized glutathione and conjugated dienes were increased by DIS. Nitrate + nitrite levels and serum calcium ([Ca(++)]) were incremented by Arg or DIS and reduced by L-NAME. Superoxide dismutase and catalase activities decreased under Arg treatment, while L-NAME or DIS caused stimulation. Liver high-density lipoprotein (HDL) cholesterol was increased by DIS or NAME (alone or associated with Arg). Free fatty acids and neutral and polar lipids were increased by Arg, L: -NAME, and DIS. However, predominating phospholipid synthesis increased the neutral/polar ratio. Decreased levels of nitric oxide (NO) (low [Ca(++)]) was directly associated with increased fatty acid synthetase, decreased phospholipase A(2), carnitine-palmitoyl transferase, and fatty acid desaturase activities. Raised NO (high [Ca(++)]) inversely correlated with increased phospholipase-A(2) and acyl-coenzyme A (CoA) synthetase and decreased fatty acid synthetase and beta-oxidation rate. Arg or DIS produced changes that were partially reverted by association with L-NAME. Based on these observations, prolonged therapeutical approaches using drugs that modify NO availability should be carefully considered.

Essential polyunsaturated fatty acids in plasma and erythrocytes of children with inborn errors of amino acid metabolism

Essential fatty acids (EFAs), and their longer-chain more-unsaturated derivatives (LCPUFAs) in particular, are essential for normal growth and cognitive development during childhood. Children with inborn errors of amino acid metabolism represent a risk population for a reduced LCPUFA status because their diet is low in EFAs and LCPUFAs. We have investigated the EFA and LCPUFA status of children with various amino acid metabolism disorders (not PKU) under treatment. Fatty acid profiles of plasma and erythrocyte phospholipids of 33 patients (aged 0-18 years) and 38 matched controls were determined by gas-liquid chromatography. Food-frequency questionnaires were used to assess the mean fatty acid intake. The dietary intake of the EFAs linoleic acid (LA) and alpha-linolenic acid (ALA) was comparable in both groups, while the LCPUFA intake was much lower in patients. This was associated with lower relative concentrations (% of total fatty acids) of n-3 docosahexaenoic acid (DHA) in plasma and erythrocyte phospholipids. Concentrations of arachidonic acid (AA) did not differ. The same was observed for the two EFAs LA and ALA. Thus, as compared to healthy controls, children with amino acid metabolism disorders have a lower intake of LCPUFAs and have lower concentrations of DHA but not of AA in plasma and erythrocyte phospholipids. This suggests that endogenous AA synthesis might guarantee an adequate AA status. The lower DHA status, however, warrants further investigations regarding the impact of DHA supplementation on growth and development of these children.

Clinical perspectives of statin-induced rhabdomyolysis

Fear of muscle toxicity remains a major reason that patients with hyperlipidemia are undertreated. Recent evaluations of statin-induced rhabdomyolysis offer new insights on the clinical management of both muscle symptoms and hyperlipidemia after rhabdomyolysis. The incidence of statin-induced rhabdomyolysis is higher in practice than in controlled trials in which high-risk subjects are excluded. Accepted risks include age; renal, hepatic, and thyroid dysfunction; and hypertriglyceridemia. New findings suggest that exercise, Asian race, and perioperative status also may increase the risk of statin muscle toxicity. The proposed causes and the relationship of drug levels to statin rhabdomyolysis are briefly reviewed along with the problems with the pharmacokinetic theory. Data suggesting that patients with certain metabolic abnormalities are predisposed to statin rhabdomyolysis are presented. The evaluation and treatment of patients' muscle symptoms and hyperlipidemia after statin rhabdomyolysis are presented. Patients whose symptoms are related to other disorders need to be identified. Lipid management of those whose symptoms are statin-related is reviewed including treatment suggestions.

Mutations in mtDNA-encoded cytochrome c oxidase subunit genes causing isolated myopathy or severe encephalomyopathy

We report on clinical, histological and genetic findings in two patients carrying novel heteroplasmic mutations in the mitochondrial cytochrome c oxidase subunit genes COII and COIII. The first patient, a 35 year-old man had a multisystemic disease, with clinical symptoms of bilateral cataract, sensori-neural hearing loss, myopathy, ataxia, cardiac arrhythmia, depression and short stature and carried a 7970 G>T (E129X) nonsense mutation in COII. A sudden episode of metabolic encephalopathy caused by extremely high blood lactate lead to coma. The second patient developed exercise intolerance and rhabdomyolysis at age 22 years. A heteroplasmic missense mutation 9789 T>C (S195P) was found in skeletal muscle, but not in blood and myoblasts pointing to a sporadic mutation. Our report of two patients with isolated COX deficiency and new mutations in COX subunit genes may help to draw more attention to this type of mtDNA defects and provide new aspects for counselling affected families.

Relative carnitine deficiency in autism

A random retrospective chart review was conducted to document serum carnitine levels on 100 children with autism. Concurrently drawn serum pyruvate, lactate, ammonia, and alanine levels were also available in many of these children. Values of free and total carnitine (p < 0.001), and pyruvate (p = 0.006) were significantly reduced while ammonia and alanine levels were considerably elevated (p < 0.001) in our autistic subjects. The relative carnitine deficiency in these patients, accompanied by slight elevations in lactate and significant elevations in alanine and ammonia levels, is suggestive of mild mitochondrial dysfunction. It is hypothesized that a mitochondrial defect may be the origin of the carnitine deficiency in these autistic children.

Is autism a disorder of fatty acid metabolism? Possible dysfunction of mitochondrial beta-oxidation by long chain acyl-CoA dehydrogenase

Long chain acyl-CoA dehydrogenase (LCAD) has recently been shown to be the mitochondrial enzyme responsible for the beta-oxidation of branched chain and unsaturated fatty acids [Biochim. Biophys. Acta 1393 (1998) 35; Biochim. Biophys. Acta 1485 (2000) 121]. Whilst disorders of short, medium and very long chain acyl dehydrogenases are known, there is no known disorder of LCAD deficiency in humans. Experimental LCAD deficiency in mice shows an acyl-carnitine profile with prominent elevations of unsaturated fatty acid metabolites C14:1 and C14:2 [Hum. Mol. Genet. 10 (2001) 2069]. A child with autism whose acyl-carnitine profile also shows these abnormalities is presented, and it is hypothesized that the child may have LCAD deficiency. Additional metabolic abnormalities seen in this patient include alterations of TCA energy production, ammonia detoxification, reduced synthesis of omega-3 DHA, and abnormal cholesterol metabolism. These metabolic changes are also seen as secondary abnormalities in dysfunction of fatty acid beta-oxidation, and have also been reported in autism. It is hypothesized that LCAD deficiency may be a cause of autism. Similarities between metabolic disturbances in autism, and those of disorders of fatty acid beta-oxidation are discussed.

The possible role of essential fatty acids in the pathophysiology of malnutrition: a review

Biochemical evidence of essential fatty acid deficiency (EFAD) may exist in protein-energy malnutrition (PEM). EFAD is characterised by low 18:2omega6, often in combination with low 20:4omega6 and 22:6omega3, and high 18:1omega9 and 20:3omega9. Some PEM symptoms, notably skin changes, impaired resistance to infections, impaired growth rate and disturbed development may at least partly be explained by EFAD. One or more of the following factors could induce EFAD in PEM: low EFA intake, poor lipid digestion, absorption, transport, desaturation and increased EFA beta-oxidation and peroxidation. EFAD may perpetuate itself by decreasing lipid absorption and transport, and aggravate PEM by impairing nutrient absorption and dietary calorie utilisation. Micronutrient deficiencies may contribute to the impaired EFA bioavailability and metabolism. Nutritional rehabilitation strategies in PEM may consider adequate intakes of EFA and micronutrients, e.g. by promoting breastfeeding. More research is required to gain detailed insight into the role of EFAD in PEM.

Molecular mediators of hepatic steatosis and liver injury

Obesity and its associated comorbidities are among the most prevalent and challenging conditions confronting the medical profession in the 21st century. A major metabolic consequence of obesity is insulin resistance, which is strongly associated with the deposition of triglycerides in the liver. Hepatic steatosis can either be a benign, noninflammatory condition that appears to have no adverse sequelae or can be associated with steatohepatitis: a condition that can result in end-stage liver disease, accounting for up to 14% of liver transplants in the US. Here we highlight recent advances in our understanding of the molecular events contributing to hepatic steatosis and nonalcoholic steatohepatitis.

Molecular mediators of hepatic steatosis and liver injury

Obesity and its associated comorbidities are among the most prevalent and challenging conditions confronting the medical profession in the 21st century. A major metabolic consequence of obesity is insulin resistance, which is strongly associated with the deposition of triglycerides in the liver. Hepatic steatosis can either be a benign, noninflammatory condition that appears to have no adverse sequelae or can be associated with steatohepatitis: a condition that can result in end-stage liver disease, accounting for up to 14% of liver transplants in the US. Here we highlight recent advances in our understanding of the molecular events contributing to hepatic steatosis and nonalcoholic steatohepatitis.

Therapeutic strategies in Friedreich’s ataxia

Friedreich's ataxia is caused by a pronounced lack of frataxin, a mitochondrial protein of not fully understood function. Lack of frataxin homologues in yeast and mice leads to increased sensitivity to oxidative stress, depletion of proteins with iron-sulfur clusters like respiratory chain complexes I-III and aconitase, and to iron accumulation in mitochondria. Similar effects have been demonstrated in human disease with increased markers of oxidative DNA damage in urine and impaired oxidative phosphorylation in in vivo exercise studies using 31 Phosphorus magnetic resonance spectroscopy (31P-MRS). Therapeutical trials mainly focus on antioxidative treatment with coenzyme Q10 or its short-chain variant idebenone. Promising effects on cardiac hypertrophy in uncontrolled preliminary studies contrast with minor effects in controlled trials and no effect of antioxidants on neurological deficits has been established. Preliminary encouraging 31P-MRS data exist for the treatment with L-carnitine but not with creatine. However, all these interventions may take effect too late in the pathogenic process. Alternative strategies aiming at an enhancement of frataxin by stem cell transplantation, gene transfer or frataxin supplementation are desirable. Additionally, more efficient biomarkers are needed to monitor treatment effects.

Effects of carnitine and taurine on fatty acid metabolism and lipid accumulation in the liver of cats during weight gain and weight loss

OBJECTIVE

To determine the effects of carnitine (Ca) or taurine (Ta) supplementation on prevention of lipid accumulation in the liver of cats.

ANIMALS

24 adult cats.

PROCEDURE

Cats were fed a weight-gaining diet sufficient in n-6 polyunsaturated fatty acids (PUFAs), low in long-chain n-3 PUFAs (n-3 LPUFA), and containing corn gluten for 20 weeks. Cats gained at least 30% in body weight and were assigned to 4 weight-reduction diets (6 cats/diet) for 7 to 10 weeks (control diet, control plus Ca, control plus Ta, and control plus Ca and Ta).

RESULTS

Hepatic lipids accumulated significantly during weight gain and weight loss but were not altered by Ca orTa after weight loss. Carnitine significantly increased n-3 and n-6 LPUFAs in hepatic triglycerides, decreased incorporation of 13C palmitate into very-low-density lipoprotein and hepatic triglycerides, and increased plasma ketone bodies. Carnitine also significantly increased weight loss but without altering the fat to lean body mass ratio. Taurine did not significantly affect any variables. Diets low in n-3 LPUFAs predisposed cats to hepatic lipidosis during weight gain, which was further exacerbated during weight loss. Mitochondrial numbers decreased during weight gain and weight loss but were not affected by treatment. Carnitine improved fatty acid oxidation and glucose utilization during weight loss without correcting hepatic lipidosis.

CONCLUSIONS AND CLINICAL RELEVANCE

The primary mechanism leading to hepatic lipidosis in cats appears to be decreased fatty acid oxidation. Carnitine may improve fatty acid oxidation but will not ameliorate hepatic lipidosis in cats fed a diet low in n-3 fatty acids.

Possible mechanism for the neuroprotective effects of L-carnitine on methamphetamine-evoked neurotoxicity

Some of the damage to the CNS that is observed following amphetamine and methamphetamine (METH) administration is known to be linked to increased formation of free radicals. This increase could be, in part, related to mitochondrial dysfunction and/or cause damage to the mitochondria, thereby leading to a failure of cellular energy metabolism and an increase in secondary excitotoxicity. The actual neuronal damage that occurs with METH-induced toxicity seems to affect dopaminergic cells in particular. METH-induced toxicity is related to an increase in the generation of both reactive oxygen (hydroxyl, superoxide, peroxide) and nitrogen (nitric oxide) species. Peroxynitrite (ONOO(-)), which is a reaction product of either superoxide or nitric oxide, is the most damaging radical. It can be reduced by antioxidants such as selenium, melatonin, and the selective nNOS inhibitor, 7-nitroindazole. METH-induced toxicity has been previously shown to increase production of the peroxynitrite stress marker, 3-nitrotyrosine (3-NT), in vitro, in cultured PC12 cells, and also in vivo, in the striatum of adult male mice. Pre- and post-treatment of mice with l-carnitine (LC) significantly attenuated the production of 3-NT in the striatum after METH exposure. LC is a mitochondriotropic compound in that it carries long-chain fatty acyl groups into mitochondria for beta-oxidation. It was shown also to play a protective role against various mitochondrial toxins, such as 3-nitropropionic acid. The protective effects of LC against METH-induced toxicity could be related to its prevention of possible metabolic compromise produced by METH and the resulting energy deficits. In particular, LC may be maintaining the mitochondrial permeability transition (MPT) and modulating the activation of the mitochondrial permeability transition pores (mPTP), especially the cyclosporin-dependent mPTP. The possible neuroprotective mechanism of LC against METH-toxicity and the role of the mitochondrial respiratory chain and the generation of free radicals and their subsequent action on the MPT and mPTP are also being examined using an in vitro model of NGF-differentiated pheochromocytoma cells (PC12). In preliminary experiments, the pretreatment of PC12 cells with LC (5 mM), added 10 min before METH (500 micro M), indicated that LC enhances METH-induced DA depletion. The role of LC in attenuating METH-evoked toxicity is still under investigation and promises to reveal information regarding the underlying mechanisms and role of mitochondria in the triggering of cell death.

Hormonal modulation of delta6 and delta5 desaturases: case of diabetes

Animal biosynthesis of high polyunsaturated fatty acids from linoleic, alpha-linolenic and oleic acids is mainly modulated by the delta6 and delta5 desaturases through dietary and hormonal stimulated mechanisms. From hormones, only insulin activates both enzymes. In experimental diabetes mellitus type-1, the depressed delta6 desaturase is restored by insulin stimulation of the gene expression of its mRNA. However, cAMP or cycloheximide injection prevents this effect. The depression of delta6 and delta5 desaturases in diabetes is rapidly correlated by lower contents of arachidonic acid and higher contents of linoleic in almost all the tissues except brain. However, docosahexaenoic n-3 acid enhancement, mainly in liver phospholipids, is not explained yet. In experimental non-insulin dependent diabetes, the effect upon the delta6 and delta5 desaturases is not clear. From all other hormones glucagon, adrenaline, glucocorticoids, mineralocorticoids, oestriol, oestradiol, testosterone and ACTH depress both desaturases, and a few hormones: progesterone, cortexolone and pregnanediol are inactive.

Recent advances in the study of fatty acid desaturases from animals and lower eukaryotes

The biosynthesis of polyunsaturated fatty acids (PUFAs) in different organisms can involve a variety of pathways, catalyzed by a complex series of desaturation and elongation steps. A range of different desaturases have been identified to date, capable of introducing double bonds at various locations on the fatty acyl chain. Some recently identified novel desaturases include a delta4 desaturase from marine fungi, and a bi-functional delta5/delta6 desaturase from zebrafish. Using molecular genetics approaches, these desaturase genes have been isolated, identified, and expressed in variety of heterologous hosts. Results from these studies will help increase our understanding of the biochemistry of desaturases and the regulation of PUFA biosynthesis. This is of significance because PUFAs play critical roles in multiple aspects of membrane physiology and signaling mechanisms which impact human health and development.

A secondary respiratory chain defect in a patient with Fanconi-Bickel syndrome

A North African boy, the son of consanguineous parents, presented at 8 years of age with hypophosphataemic rickets due to De Toni-Debré-Fanconi syndrome. Hepatomegaly and abnormalities of carbohydrate metabolism were suggestive of Fanconi-Bickel syndrome. This was confirmed by the detection of a mutation within GLUT2, the gene encoding the liver-type facilitative glucose transporter. The study of the respiratory chain revealed a deficiency of complexes I, III and IV in muscle. Mechanisms responsible for an impairment ofmitochondrial function, which we interpret as a secondary phenomenon, are discussed.

Efficacy of carnitine in the treatment of children with attention-deficit hyperactivity disorder

To determine safety and the efficacy of carnitine treatment in children with attention-deficit hyperactivity disorder (ADHD). The ADHD behavior was observed by parents completing the Child Behavior Checklist (CBCL) and by teachers completing the Conners teacher-rating score, in a randomized, double-blind, placebo-controlled double-crossover trial. In 13/24 boys receiving carnitine, home behavior improved as assessed with the CBCL total score (P < 0.02). In 13/24 boys, school behavior improved as assessed with the Conners teacher-rating score (P < 0.05). Before treatment, the CBCL total and sub-scores were significantly different from those of normal Dutch boys (P < 0.0001). Responders showed a significant improvement of the CBCL total scores compared to baseline (P < 0.0001). In the majority of boys no side effects were seen. At baseline and after carnitine treatment, responders showed higher levels of plasma-free carnitine (P < 0.03) and acetylcarnitine (P < 0.05). Compared to baseline, the carnitine treatment caused in the responsive patients a decrease of 20-65% (8-48 points) as assessed by the CBCL total problem rating scale. Treatment with carnitine significantly decreased the attention problems and aggressive behavior in boys with ADHD.

Long-term n-3 FA deficiency modifies peroxisome proliferator-activated receptor beta mRNA abundance in rat ocular tissues

Peroxisomal proliferator-activated receptors (PPAR) are a FA-response system involved in diverse cellular responses. FA regulate PPAR activity and modulate PPAR mRNA abundance. Increasing evidence indicates that PUFA are required for optimal neuronal development and function. To gain insight into the mechanism for nutrition-induced impairment of neuronal development and function we investigated the effect of chronic n-3 FA deficiency on PPAR mRNA levels in rat brain and ocular tissues. Rats were fed for three generations a diet designed to reduce DHA levels in tissues, and the abundance of PPARalpha and PPARbeta transcripts was measured by hybridization with specific probes. Chronic consumption of the a-linolenic acid (LNA)-insufficient diet caused a remarkable modification in DHA content in membrane phospholipids. The results reported here indicate that PPARa mRNA levels did not exhibit significant variation in ocular, hepatic, or nervous tissues from rats fed the experimental diet. In contrast, PPARalpha mRNA normalized to beta-actin mRNA was 21% higher in ocular tissue from F3 generation rats consuming the LNA-deficient diet but was independent of diet in hepatic and nervous tissues. The absolute abundance of PPARbeta transcripts showed a 17% increase in ocular tissue from rats consuming the LNA-deficient diet (F3 generation). The biological significance of the reported changes in PPARbeta mRNA in ocular tissue remains to be determined.

Straight-chain acyl-CoA oxidase knockout mouse accumulates extremely long chain fatty acids from alpha-linolenic acid: evidence for runaway carousel-type enzyme kinetics in peroxisomal beta-oxidation diseases

Extremely long chain polyunsaturated fatty acids (ELCPs) with >24 carbons and four or more double bonds are normally found in excitatory tissues but have no known function, and are greatly increased in brain and other tissues of humans with peroxisomal disorders. Straight-chain acyl-CoA oxidase (AOX) catalyzes the first, rate-limiting step of peroxisomal beta-oxidation of very-long-chain saturated and unsaturated fatty acids. We have studied the polyunsaturated fatty acid metabolism of AOX knockout mice (AOX-/- as a model of human AOX deficiency (pseudo-neonatal adrenoleukodystrophy), and as a genetic tool to test the putative peroxisomal beta-oxidation involvement in polyunsaturated fatty acid synthesis. Liver lipids of 26-day-old weanling AOX-/- mice livers accumulate n-3 and n-6 ELCPs from C24 to C30 with 5 and 6 double bonds, have 356 +/- 66 microg/g docosahexaenoic acid (22:6n-3), similar to congenic (AOX -/* = AOX+/+ and AOX+/-) controls (401 +/- 96 microg/g), but increased 22:5n-6 (22.4 +/- 3.7 vs 6.4 +/- 1.5 microg/g). AOX+/* mice injected intraperitoneally at 23 days with [U-(13)C]-18:3n-3 show strong labeling of 22:6n-3 after 72 h, whereas AOX -/- mice display less labeling of 22:6n-3 but strong tracer incorporation into 24:6n-3, 26:6n-3, and 28:6n-3, after the same period. These data suggest that ELCPs are natural runaway elongation by-products of 22:6n-3 and 22:5n-6 synthesis, which are normally disposed of by peroxisomal beta-oxidation. Under conditions with impaired peroxisomal beta-oxidation, such as Zellweger syndrome and adrenoleukodystrophies, ELCPs accumulate due to increased synthesis and impaired disposal. Two mechanisms for the formation of these runaway elongation by-products and the involvement of secondary carnitine deficiency in this process are proposed: n-3 ELCPs are synthesized by a carnitine-dependent multifunctional mitochondrial docosahexaenoic acid synthase (mtDHAS) which normally synthesizes primarily 22:6n-3, while n-6 ELCPs are synthesized by independent elongation enzymes in the endoplasmic reticulum.

Changes in fatty acid concentrations in tissues of African catfish, Clarias gariepinus Burchell, as a consequence of dietary carnitine, fat and lysine supplementation

A study was undertaken to examine the effect of different dietary carnitine (200 and 1000 mg/kg diet) and fat (90 and 190 g/kg diet) supplementation on growth and fatty acid concentrations of fish fed either with a low- (13 g/kg) or a high-lysine (21 g/kg) diet. African catfish (22.7 g/fish), Clarias gariepinus Burchell, juveniles were stocked (sixteen aquaria, twenty-five fish per aquarium) and fed for a maximum of 74 d. Dietary lysine had a clear effect on growth performance and feed conversion ratios, but dietary carnitine supplements had no effect. High-carnitine supplements increased total carnitine content (P<0.0004) and reduced tissue free carnitine: acyl-carnitine ratio (P<0.05) compared with low-carnitine supplements. High-fat supplements decreased liver carnitine concentrations. Clear effects on liver fatty acid concentrations were observed in high-carnitine-fed fish compared with low-carnitine-fed fish. The primary liver fatty acids affected were n-6 (linoleic acid), n-3 (eicosapentanoic acid) and n-3 (docosahexanoic acid). The whole-body fatty acid balance suggested that n-3 disappeared (apparently by beta-oxidation) more readily than n-6 and/or n-3. From 774 mg n-3 eaten by high-lysine-high-fat-low-carnitine fish, 58 % was not assimilated into body tissues. High-carnitine-fed fish showed an increase in n-3 oxidation by 7 % compared with low-carnitine fish. Although dietary carnitine did not improve body growth, these results support the hypothesis that carnitine can enhance the mobilisation of long-chain fatty acids towards oxidation.