Improving Age-Related Cognitive Decline through Dietary Interventions Targeting Mitochondrial Dysfunction

Aging is inevitable and it is one of the major contributors to cognitive decline. However, the mechanisms underlying age-related cognitive decline are still the object of extensive research. At the biological level, it is unknown how the aging brain is subjected to progressive oxidative stress and neuroinflammation which determine, among others, mitochondrial dysfunction. The link between mitochondrial dysfunction and cognitive impairment is becoming ever more clear by the presence of significant neurological disturbances in human mitochondrial diseases. Possibly, the most important lifestyle factor determining mitochondrial functioning is nutrition. Therefore, with the present work, we review the latest findings disclosing a link between nutrition, mitochondrial functioning and cognition, and pave new ways to counteract cognitive decline in late adulthood through diet.

Cardiac tissue citric acid cycle intermediates in exercised very long-chain acyl-CoA dehydrogenase-deficient mice fed triheptanoin or medium-chain triglyceride

Anaplerotic odd-chain fatty acid supplementation has been suggested as an approach to replenish citric acid cycle intermediate (CACi) pools and facilitate adenosine triphosphate (ATP) production in subjects with long-chain fatty acid oxidation disorders, but the evidence that cellular CACi depletion exists and that repletion occurs following anaplerotic substrate supplementation is limited. We exercised very long-chain acyl-CoA dehydrogenase-deficient (VLCAD-/-) and wild-type (WT) mice to exhaustion and collected cardiac tissue for measurement of CACi by targeted metabolomics. In a second experimental group, VLCAD-/- and WT mice that had been fed chow prepared with either medium-chain triglyceride (MCT) oil or triheptanoin for 4 weeks were exercised for 60 minutes. VLCAD-/- mice exhibited lower succinate in cardiac muscle at exhaustion than WT mice suggesting lower CACi in VLCAD-/- with prolonged exercise. In mice fed either MCT or triheptanoin, succinate and malate were greater in VLCAD-/- mice fed triheptanoin compared to VLCAD-/- animals fed MCT but lower than WT mice fed triheptanoin. Long-chain odd acylcarnitines such as C19 were elevated in VLCAD-/- and WT mice fed triheptanoin suggesting some elongation of the heptanoate, but it is unknown what proportion of heptanoate was oxidized vs elongated. Prolonged exercise was associated with decreased cardiac muscle succinate in VLCAD-/- mice in comparison to WT mice. VLCAD-/- fed triheptanoin had increased succinate compared to VLCAD-/- mice fed MCT but lower than WT mice fed triheptanoin. Cardiac CACi were higher following dietary ingestion of an anaplerotic substrate, triheptanoin, in comparison to MCT.

Nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD): An evidence- and consensus-based approach

The nutrition management guideline for very-long chain acyl-CoA dehydrogenase deficiency (VLCAD) is the fourth in a series of web-based guidelines focusing on the diet treatment for inherited metabolic disorders and follows previous publication of guidelines for maple syrup urine disease (2014), phenylketonuria (2016) and propionic acidemia (2019). The purpose of this guideline is to establish harmonization in the treatment and monitoring of individuals with VLCAD of all ages in order to improve clinical outcomes. Six research questions were identified to support guideline development on: nutrition recommendations for the healthy individual, illness management, supplementation, monitoring, physical activity and management during pregnancy. This report describes the methodology used in its development including review, critical appraisal and abstraction of peer-reviewed studies and unpublished practice literature; expert input through two Delphi surveys and a nominal group process; and external review from metabolic physicians and dietitians. It includes the summary statements of the nutrition management recommendations for each research question, followed by a standardized rating based on the strength of the evidence. Online, open access of the full published guideline allows utilization by health care providers, researchers and collaborators who advise, advocate and care for individuals with VLCAD and their families and can be accessed from the Genetic Metabolic Dietitians International (https://GMDI.org) and Southeast Regional Genetics Network (https://southeastgenetics.org/ngp) websites.

Effects of fasting, feeding and exercise on plasma acylcarnitines among subjects with CPT2D, VLCADD and LCHADD/TFPD

BACKGROUND

The plasma acylcarnitine profile is frequently used as a biochemical assessment for follow-up in diagnosed patients with fatty acid oxidation disorders (FAODs). Disease specific acylcarnitine species are elevated during metabolic decompensation but there is clinical and biochemical heterogeneity among patients and limited data on the utility of an acylcarnitine profile for routine clinical monitoring.

METHODS

We evaluated plasma acylcarnitine profiles from 30 diagnosed patients with long-chain FAODs (carnitine palmitoyltransferase-2 (CPT2), very long-chain acyl-CoA dehydrogenase (VLCAD), and long-chain 3-hydroxy acyl-CoA dehydrogenase or mitochondrial trifunctional protein (LCHAD/TFP) deficiencies) collected after an overnight fast, after feeding a controlled low-fat diet, and before and after moderate exercise. Our purpose was to describe the variability in this biomarker and how various physiologic states effect the acylcarnitine concentrations in circulation.

RESULTS

Disease specific acylcarnitine species were higher after an overnight fast and decreased by approximately 60% two hours after a controlled breakfast meal. Moderate-intensity exercise increased the acylcarnitine species but it varied by diagnosis. When analyzed for a genotype/phenotype correlation, the presence of the common LCHADD mutation (c.1528G > C) was associated with higher levels of 3-hydroxyacylcarnitines than in patients with other mutations.

CONCLUSIONS

We found that feeding consistently suppressed and that moderate intensity exercise increased disease specific acylcarnitine species, but the response to exercise was highly variable across subjects and diagnoses. The clinical utility of routine plasma acylcarnitine analysis for outpatient treatment monitoring remains questionable; however, if acylcarnitine profiles are measured in the clinical setting, standardized procedures are required for sample collection to be of value.

Nutritional ketosis improves exercise metabolism in patients with very long-chain acyl-CoA dehydrogenase deficiency

A maladaptive shift from fat to carbohydrate (CHO) oxidation during exercise is thought to underlie myopathy and exercise-induced rhabdomyolysis in patients with fatty acid oxidation (FAO) disorders. We hypothesised that ingestion of a ketone ester (KE) drink prior to exercise could serve as an alternative oxidative substrate supply to boost muscular ATP homeostasis. To establish a rational basis for therapeutic use of KE supplementation in FAO, we tested this hypothesis in patients deficient in Very Long-Chain acyl-CoA Dehydrogenase (VLCAD). Five patients (range 17-45 y; 4 M/1F) patients were included in an investigator-initiated, randomised, blinded, placebo-controlled, 2-way cross-over study. Patients drank either a KE + CHO mix or an isocaloric CHO equivalent and performed 35 minutes upright cycling followed by 10 minutes supine cycling inside a Magnetic Resonance scanner at individual maximal FAO work rate (fatmax; approximately 40% VO₂ max). The protocol was repeated after a 1-week interval with the alternate drink. Primary outcome measures were quadriceps phosphocreatine (PCr), Pi and pH dynamics during exercise and recovery assayed by in vivo ³¹ P-MR spectroscopy. Secondary outcomes included plasma and muscle metabolites and respiratory gas exchange recordings. Ingestion of KE rapidly induced mild ketosis and increased muscle BHB content. During exercise at FATMAX, VLCADD-specific plasma acylcarnitine levels, quadriceps glycolytic intermediate levels and in vivo Pi/PCr ratio were all lower in KE + CHO than CHO. These results provide a rational basis for future clinical trials of synthetic ketone ester supplementation therapy in patients with FAO disorders. Trial registration: ClinicalTrials.gov. Protocol ID: NCT03531554; METC2014.492; ABR51222.042.14.

Nutritional Interventions for Mitochondrial OXPHOS Deficiencies: Mechanisms and Model Systems

Multisystem metabolic disorders caused by defects in oxidative phosphorylation (OXPHOS) are severe, often lethal, conditions. Inborn errors of OXPHOS function are termed primary mitochondrial disorders (PMDs), and the use of nutritional interventions is routine in their supportive management. However, detailed mechanistic understanding and evidence for efficacy and safety of these interventions are limited. Preclinical cellular and animal model systems are important tools to investigate PMD metabolic mechanisms and therapeutic strategies. This review assesses the mechanistic rationale and experimental evidence for nutritional interventions commonly used in PMDs, including micronutrients, metabolic agents, signaling modifiers, and dietary regulation, while highlighting important knowledge gaps and impediments for randomized controlled trials. Cellular and animal model systems that recapitulate mutations and clinical manifestations of specific PMDs are evaluated for their potential in determining pathological mechanisms, elucidating therapeutic health outcomes, and investigating the value of nutritional interventions for mitochondrial disease conditions.

Nutritional interventions in primary mitochondrial disorders: Developing an evidence base

In December 2014, a workshop entitled "Nutritional Interventions in Primary Mitochondrial Disorders: Developing an Evidence Base" was convened at the NIH with the goals of exploring the use of nutritional interventions in primary mitochondrial disorders (PMD) and identifying knowledge gaps regarding their safety and efficacy; identifying research opportunities; and forging collaborations among researchers, clinicians, patient advocacy groups, and federal partners. Sponsors included the NIH, the Wellcome Trust, and the United Mitochondrial Diseases Foundation. Dietary supplements have historically been used in the management of PMD due to their potential benefits and perceived low risk, even though little evidence exists regarding their effectiveness. PMD are rare and clinically, phenotypically, and genetically heterogeneous. Thus patient recruitment for randomized controlled trials (RCTs) has proven to be challenging. Only a few RCTs examining dietary supplements, singly or in combination with other vitamins and cofactors, are reported in the literature. Regulatory issues pertaining to the use of dietary supplements as treatment modalities further complicate the research and patient access landscape. As a preface to exploring a research agenda, the workshop included presentations and discussions on what PMD are; how nutritional interventions are used in PMD; challenges and barriers to their use; new technologies and approaches to diagnosis and treatment; research opportunities and resources; and perspectives from patient advocacy, industry, and professional organizations. Seven key areas were identified during the workshop. These areas were: 1) defining the disease, 2) clinical trial design, 3) biomarker selection, 4) mechanistic approaches, 5) challenges in using dietary supplements, 6) standards of clinical care, and 7) collaboration issues. Short- and long-term goals within each of these areas were identified. An example of an overarching goal is the enrollment of all individuals with PMD in a natural history study and a patient registry to enhance research capability. The workshop demonstrates an effective model for fostering and enhancing collaborations among NIH and basic research, clinical, patient, pharmaceutical industry, and regulatory stakeholders in the mitochondrial disease community to address research challenges on the use of dietary supplements in PMD.

Mitochondrial disease patients' perception of dietary supplements' use

Surveys of mitochondrial disease physicians conducted through the Mitochondrial Medicine Society have shown that virtually all providers recommend a variety of dietary supplements as treatments to their patients in an effort to enhance energy production and reduce oxidative stress. In this survey, we asked patients and their parents about their experiences taking these dietary supplements for mitochondrial disease. The survey was disseminated through the North American Mitochondrial Disease Consortium (NAMDC) and the Rare Disease Clinical Research Network (RDCRN) registries and gathered 162 responses. The study ascertained each patient's mitochondrial disease diagnosis, dietary supplements used, adjunct therapy, and effects of the supplements on symptoms and health. Regardless of the specific underlying mitochondrial disease, the majority of the survey respondents stated they are or have been on dietary supplements. Most patients take more than four supplements primarily coenzyme Q10, l-carnitine, and riboflavin. The majority of patients taking supplements reported health benefits from the supplements. The onset of perceived benefits was between 2weeks to 3months of initiating intake. Supplements seem to be safe, with only 28% of patients experiencing mild side-effects and only 5.6% discontinuing their intake due to intolerance. Only 9% of patients had insurance coverage for their supplements and when paying out of pocket, 95% of them spend up to $500/month. Despite the use of concomitant therapies (prescribed medications, physical therapy, diet changes and other), 45.5% of patients think that dietary supplements are the only intervention improving their symptoms. Some limitations of this study include the retrospective collection of data probably associated with substantial recall bias, lack of longitudinal follow up to document pre- and post-supplement clinical status and second hand reports by parents for children which may reflect parents' subjective interpretation of symptoms severity and supplements effect rather than real patients' experience. More extensive prospective studies will help further elucidate this topic.

VLCAD deficiency: Follow-up and outcome of patients diagnosed through newborn screening in Victoria

Very long chain acyl-CoA dehydrogenase (VLCAD) deficiency is an inherited metabolic disorder of fatty acid oxidation. Treatment practices of the disorder have changed over the past 10-15years since this disorder was included in newborn screening programs and patients were diagnosed pre-symptomatically. A genotype-phenotype correlation has been suggested but the discovery of novel mutations make this knowledge limited. Herein, we describe our experience in treating patients (n=22) diagnosed through newborn screening and mutational confirmation and followed up over a median period of 104months. We report five novel mutations. In 2013 we formalised our treatment protocol, which essentially follows a European consensus paper from 2009 and our own experience. The prescribed low natural fat diet is relaxed for patients who are asymptomatic when reaching age 5years but medium-chain triglyceride oil is recommended before and after physical activity regardless of age. Metabolic stability, growth, development and cardiac function are satisfactory in all patients. There were no episodes of encephalopathy or hypoglycaemia but three patients had episodes of muscle pain with our without rhabdomyolysis. Body composition studies showed a negative association between dietary protein intake and percent body fat. Larger patient cohort and longer follow up time are required for further elucidation of genotype-phenotype correlations and for establishing the role of dietary protein in metabolic stability and long-term healthier body composition in patients with VLCAD deficiency.

Anaplerotic treatment of long-chain fat oxidation disorders with triheptanoin: Review of 15 years Experience

BACKGROUND

The treatment of long-chain mitochondrial β-oxidation disorders (LC-FOD) with a low fat-high carbohydrate diet, a diet rich in medium-even-chain triglycerides (MCT), or a combination of both has been associated with high morbidity and mortality for decades. The pathological tableau appears to be caused by energy deficiency resulting from reduced availability of citric acid cycle (CAC) intermediates required for optimal oxidation of acetyl-CoA. This hypothesis was investigated by diet therapy with carnitine and anaplerotic triheptanoin (TH).

METHODS

Fifty-two documented LC-FOD patients were studied in this investigation (age range: birth to 51 years). Safety monitoring included serial quantitative measurements of routine blood chemistries, blood levels of carnitine and acylcarnitines, and urinary organic acids.

RESULTS

The average frequency of serious clinical complications were reduced from ~60% with conventional diet therapy to 10% with TH and carnitine treatment and mortality decreased from ~65% with conventional diet therapy to 3.8%. Carnitine supplementation was uncomplicated.

CONCLUSION

The energy deficiency in LC-FOD patients was corrected safely and more effectively with the triheptanoin diet and carnitine supplement than with conventional diet therapy. Safe intervention in neonates and infants will permit earlier intervention following pre-natal diagnosis or diagnosis by expanded newborn screening.

Carnitine supplementation in high-fat diet-fed rats does not ameliorate lipid-induced skeletal muscle mitochondrial dysfunction in vivo

Muscle lipid overload and the associated accumulation of lipid intermediates play an important role in the development of insulin resistance. Carnitine insufficiency is a common feature of insulin-resistant states and might lead to incomplete fatty acid oxidation and impaired export of lipid intermediates out of the mitochondria. The aim of the present study was to test the hypothesis that carnitine supplementation reduces high-fat diet-induced lipotoxicity, improves muscle mitochondrial function, and ameliorates insulin resistance. Wistar rats were fed either normal chow or a high-fat diet for 15 wk. One group of high-fat diet-fed rats was supplemented with 300 mg·kg(-1)·day(-1) L-carnitine during the last 8 wk. Muscle mitochondrial function was measured in vivo by (31)P magnetic resonance spectroscopy (MRS) and ex vivo by high-resolution respirometry. Muscle lipid status was determined by (1)H MRS (intramyocellular lipids) and tandem mass spectrometry (acylcarnitines). High-fat diet feeding induced insulin resistance and was associated with decreases in muscle and blood free carnitine, elevated levels of muscle lipids and acylcarnitines, and an increased number of muscle mitochondria that showed an improved capacity to oxidize fat-derived substrates when tested ex vivo. This was, however, not accompanied by an increase in muscle oxidative capacity in vivo, indicating that in vivo mitochondrial function was compromised. Despite partial normalization of muscle and blood free carnitine content, carnitine supplementation did not induce improvements in muscle lipid status, in vivo mitochondrial function, or insulin sensitivity. Carnitine insufficiency, therefore, does not play a major role in high-fat diet-induced muscle mitochondrial dysfunction in vivo.

[MITOCHONDRIAL DYSFUNCTION: MODERN ASPECTS OF THERAPY (REVIEW)]

Mitochondrial diseases are considered as one of the major problems of modern interdisciplinary neonatology and pediatrics. Mitochondrial pathology can be revealed as refractory myoclonic or multifocal seizures, craniofacial dysostosis, dysmetabolic manifestations and respiratory disorders. Central nervous system (CNS), muscles, heart, liver and kidneys is involved in this pathological process. An important criterion for diagnosis of mitochondrial dysfunction is increases in blood lactate and pyruvate levels; the absolute criterion - molecular genetic diagnostic studies of mitochondrial DNA. Polymorphism of clinical symptoms complicates the process of early diagnostics, the lack clear recommendations complicates therapy. Modern aspects of treatment of mitochondrial dysfunction in various neurological syndromes are based primarily in improving the efficiency of the processes of oxidative phosphorylation at the system level. Dietary carbohydrate restriction, and medication (Coenzyme Q10, Idebenonum, Cofactors, drugs which reduce lactic acidosis- Dimephosphon, Dichloroacetate, Antioxidants, Anticonvulsants and Antidiabetic agents, vitamins C, E, K, hemotransfusions) is prescribed. Such complex approach allows us to achieve a reduction in lactate-acidosis, and improve the condition of patients in 70% of cases.

Ketogenic diet in neuromuscular and neurodegenerative diseases

An increasing number of data demonstrate the utility of ketogenic diets in a variety of metabolic diseases as obesity, metabolic syndrome, and diabetes. In regard to neurological disorders, ketogenic diet is recognized as an effective treatment for pharmacoresistant epilepsy but emerging data suggests that ketogenic diet could be also useful in amyotrophic lateral sclerosis, Alzheimer, Parkinson's disease, and some mitochondriopathies. Although these diseases have different pathogenesis and features, there are some common mechanisms that could explain the effects of ketogenic diets. These mechanisms are to provide an efficient source of energy for the treatment of certain types of neurodegenerative diseases characterized by focal brain hypometabolism; to decrease the oxidative damage associated with various kinds of metabolic stress; to increase the mitochondrial biogenesis pathways; and to take advantage of the capacity of ketones to bypass the defect in complex I activity implicated in some neurological diseases. These mechanisms will be discussed in this review.

[Dietary therapy of epilepsy]

Reappraisal of ketogenic diets (KD) were delayed in Japan compared to USA and Korea. The reasons are unknown, but possible explanations are (1) Japanese food culture prefers rice and less fat and (2) ACTH therapy is preferred for West syndrome in Japan. Since Japanese child neurologists were surprised at dramatic effects on glucose transporter 1 deficiency syndrome (Glut-1DS) in 2003, KD have been slowly accepted for treatment of epilepsy in Japan. New generation KD including modified Atkins diet (mAD) are preferred to classical KD. KD can be causal therapy in Glut-1DS and some of mitochondrial disorders, though anti-epileptic drugs are symptomatic therapy. KD can alleviate intractable seizures in epilepsies with brain malformation in addition to West syndrome and Dravet syndrome, etc. KD may work for brain tumor, cancer, neurodegenerative disorders including Alzheimer's disease. C7-8 triglycerides or fatty acid esters are under development as medicines replacing KD.

The elusive magic pill: finding effective therapies for mitochondrial disorders

The incidence of mitochondrial diseases has been estimated at 11.5/100,000 (1:8500) worldwide. In the USA up to 4000 newborns annually are expected to develop a mitochondrial disease. More than 50 million adults in the USA also suffer from diseases in which primary or secondary mitochondrial dysfunction is involved. Mitochondrial dysfunction has been identified in cancer, infertility, diabetes, heart diseases, blindness, deafness, kidney disease, liver disease, stroke, migraine, dwarfism, and resulting from numerous medication toxicities. Mitochondrial dysfunction is also involved in normal aging and age-related neurodegenerative diseases, such as Parkinson and Alzheimer diseases. Yet most treatments available are based on empiric data and clinician experience because of the lack of randomized controlled clinical trials to provide evidence-based treatments for these disorders. Here we explore the current state of research for the treatment of mitochondrial disorders.

Very long-chain acyl-CoA dehydrogenase deficiency: the effects of accidental fat loading in a patient detected through newborn screening

Very long-chain acyl-CoA dehydrogenase deficiency (VLCADD) is an autosomal recessive disorder of fatty acid oxidation. The majority of patients with VLCADD can be detected through newborn screening (NBS) with elevated levels of the tetradecanoyl carnitine species. An 11-month-old infant, diagnosed with late-onset VLCADD (genotype: T848C/G1322A) through newborn screening at birth, was admitted with emesis, severe lethargy, limpness in extremities, loss of muscle tone and an elevated CK level. He was mistakenly given Ketocal formula (about 8 g/kg per day long-chain fat-over six times his usual intake) instead of his usual Monogen formula for 2.5 days before being admitted. Once admitted, he was started on Monogen and IV (10% dextrose) fluids. He was discharged home after four days in the hospital without any sequelae of this accidental fat loading event. The report highlights several important points about this particular case and more generally about patients with VLCADD detected through NBS: (1) the amount of time in which patients might become severely symptomatic and the nature of these symptoms after fat loading; (2) the time frame for complete recovery after beginning of treatment; (3) the importance of alerting home-care companies and families about formula delivery errors and their repercussions.

Prevention of alcoholic fatty liver and mitochondrial dysfunction in the rat by long-chain polyunsaturated fatty acids

BACKGROUND/AIMS

We reported that reduced dietary intake of polyunsaturated fatty acids (PUFA) such as arachidonic (AA,20:4n6,omega-6) and docosahexaenoic (DHA,22:6n3,omega-3) acids led to alcohol-induced fatty liver and fibrosis. This study was aimed at studying the mechanisms by which a DHA/AA-supplemented diet prevents alcohol-induced fatty liver.

METHODS

Male Long-Evans rats were fed an ethanol or control liquid-diet with or without DHA/AA for 9 weeks. Plasma transaminase levels, liver histology, oxidative/nitrosative stress markers, and activities of oxidatively-modified mitochondrial proteins were evaluated.

RESULTS

Chronic alcohol administration increased the degree of fatty liver but fatty liver decreased significantly in rats fed the alcohol-DHA/AA-supplemented diet. Alcohol exposure increased oxidative/nitrosative stress with elevated levels of ethanol-inducible CYP2E1, nitric oxide synthase, nitrite and mitochondrial hydrogen peroxide. However, these increments were normalized in rats fed the alcohol-DHA/AA-supplemented diet. The number of oxidatively-modified mitochondrial proteins was markedly increased following alcohol exposure but significantly reduced in rats fed the alcohol-DHA/AA-supplemented diet. The suppressed activities of mitochondrial aldehyde dehydrogenase, ATP synthase, and 3-ketoacyl-CoA thiolase in ethanol-exposed rats were also recovered in animals fed the ethanol-DHA/AA-supplemented diet.

CONCLUSIONS

Addition of DHA/AA prevents alcohol-induced fatty liver and mitochondrial dysfunction in an animal model by protecting various mitochondrial enzymes most likely through reducing oxidative/nitrosative stress.

[Neuroradiologic findings of glutaric aciduria type I]

Glutaric aciduria type I is a rare disorder of organic acid metabolism caused by deficiency of glutaryl-CoA dehydrogenase, a mitochondrial enzyme. Improper degeneration of amino acids: tryptophan, lysine, and hydroxylysine, results in increased levels of glutaric acid, which typically becomes clinically manifest as an acute dystonic crisis in young children. Accumulation of glutaric acid causes neurotoxicity in the basal ganglia and fronto-temporal cortex which can lead to progressive dystonia, hypotonia, permanently impaired speech and seizures. Because dietary and drug therapy may alter the natural history of the disease, early diagnosis of such patients is critical. We report the magnetic resonance (MR) imaging findings in a 16 year-old girl with this disorder who presented with a chronic dystonic syndrome and previously diagnosed of brain paralysis. MR imaging demonstrated bilateral involvement of the putamina and periventricular white matter, and bilateral temporal atrophy and widened Silvian fissures.

Safe and Effective Use of the Ketogenic Diet in Children with Epilepsy and Mitochondrial Respiratory Chain Complex Defects

PURPOSE

To evaluate the clinical efficacy and safety of the ketogenic diet (KD) for patients with intractable childhood epilepsy and mitochondrial respiratory chain (RC) complex defects.

METHODS

A retrospective analysis evaluated outcomes in 14 children with intractable epilepsy and RC complex defects who were treated with the classic KD involving a 4:1 lipid to nonlipid ratio (% by weight), but without an initial fast and fluid restriction. Outcome measures included seizure frequency, electroencephalography (EEG) findings, the number of antiepileptic drugs, and adverse reactions.

RESULTS

Of the 14 patients, 9 had Complex I defects, 1 had a Complex II defect, 3 had Complex IV defects, and 1 had combined Complex I and IV defects. Two patients with Complex IV defects showed clinical progress compatible with the Leigh disease. The epileptic diagnoses were as follows: 5 patients were diagnosed with infantile spasms, 4 with the Lennox-Gastaut syndrome, 1 with the Landau-Kleffner syndrome, 1 with nonspecific generalized seizure disorder, and 3 with partial seizure disorder. The study found that 7 patients became seizure-free after commencing the KD, three of whom successfully completed the diet without relapse. One patient with a greater than 90% seizure reduction, and 2 patients with seizure reductions between 50% and 90%, remained on the diet. Four patients, including two diagnosed with the Leigh disease, did not show any favorable responses to the diet or ceased the diet due to complications.

CONCLUSIONS

The KD was a safe and effective therapy for seizures in children with intractable epilepsy and RC complex defects.

Dietary intervention and oxidative phosphorylation capacity

Secondary deterioration of mitochondrial function has been reported in patients with anorexia and cancer-related malnutrition. Inadequate nutrition, failure to thrive and feeding problems are also common symptoms in children with primary oxidative phosphorylation defects. As a standard intervention protocol we advise an age-appropriate diet and energy intake in our patients diagnosed with a mitochondrial dysfunction. By comparing the results of the first and the second samples from a group of children who underwent repeated muscle biopsies, we observed biochemical improvement in the mitochondrial function in 7 out of 10 patients following dietary advice and intervention. We suggest evaluating the nutritional state by interpretation of the skeletal muscle biochemistry in patients with a suspected oxidative phosphorylation defect. Since an insufficient dietary intake could play a role in secondary mitochondrial dysfunction, nutritional intervention should be performed prior to the biopsy. On the other hand, our data suggest that optimizing the nutritional and energy intake might also improve the utilization of the residual mitochondrial energy-generating capacity in patients with primary oxidative phosphorylation defects.

Effects of odd-numbered medium-chain fatty acids on the accumulation of long-chain 3-hydroxy-fatty acids in long-chain L-3-hydroxyacyl CoA dehydrogenase and mitochondrial trifunctional protein deficient skin fibroblasts

The treatment for patients with genetic disorders of mitochondrial long-chain fatty acid beta-oxidation is directed toward providing sufficient sources of energy for normal growth and development, and at the same time preventing the adverse effects that precipitate or result from metabolic decompensation. Standard of care treatment has focused on preventing the mobilization of lipids that result from fasting and providing medium-chain triglycerides (MCT) in the diet in order to bypass the long-chain metabolic block. MCTs that are currently available as commercial preparations are in the form of even-chain fatty acids that are predominately a mixture of octanoate and decanoate. Recently, the use of odd-chain fatty acids has been proposed as an alternative treatment. We have shown previously that the even-numbered medium-chain fatty acids (MCFAs) that are found in MCT preparations can reduce the accumulation of potentially toxic long-chain metabolites of fatty acid oxidation (FAO). In the current study, we undertook to determine if the same is true of odd-numbered MCFAs. We found that provision of odd-chain species does decrease the build-up of long-chain FAO intermediates in our in vitro skin fibroblast model, but to a lesser extent than even-numbered MCFAs.

Effect of high-dose vitamins, coenzyme Q and high-fat diet in paediatric patients with mitochondrial diseases

We reviewed the medical records of all patients with confirmed mitochondrial diseases treated with any or all of thiamin, riboflavin, coenzyme Q, vitamin C (approximately 10 mg/kg per day) and a high-fat diet (50-60% of caloric intake) between 1997 and 2003. There were 15 patients (9 male): 10 had enzymatic deficiency and 10 had a molecular diagnosis. Age at diagnosis was 11 months to 17 years 10 months. Treatment was commenced at time of clinical diagnosis in 12 patients. Follow-up period was 3 days to 7 years (median 22 months). Improvement was reported in 9 patients, of whom 4 attained further developmental skills, but this was only temporary in 6 patients. Five patients died during the follow-up period (3 days to 7 years). Patients with the 3243A > G mutation showed no significant change in the course of their disease, except for fewer migraine attacks. Of the six patients who had seizures, one has had a significant reduction in the severity of the seizures and one has had no further seizures. Plasma lactate levels were noncontributory. We conclude that high-dose vitamin and cofactor treatment and, where applicable, high-fat diet, are well tolerated and possibly effective in the short term, but ineffective in the longer term.

Nutritional cofactor treatment in mitochondrial disorders

Mitochondrial disorders are degenerative diseases characterized by a decrease in the ability of mitochondria to supply cellular energy requirements. Substantial progress has been made in defining the specific biochemical defects and underlying molecular mechanisms, but limited information is available about the development and evaluation of effective treatment approaches. The goal of nutritional cofactor therapy is to increase mitochondrial adenosine 5'-triphosphate production and slow or arrest the progression of clinical symptoms. Accumulation of toxic metabolites and reduction of electron transfer activity have prompted the use of antioxidants, electron transfer mediators (which bypass the defective site), and enzyme cofactors. Metabolic therapies that have been reported to produce a positive effect include Coenzyme Q(10) (ubiquinone); other antioxidants such as ascorbic acid, vitamin E, and lipoic acid; riboflavin; thiamin; niacin; vitamin K (phylloquinone and menadione); creatine; and carnitine. A literature review of the use of these supplements in mitochondrial disorders is presented.

Respiratory complex II defect in siblings associated with a symptomatic secondary block in fatty acid oxidation

The mitochondrial oxidative phosphorylation and fatty acid oxidation pathways have traditionally been considered independent major sources of cellular energy production; however, case reports of patients with specific enzymatic defects in either pathway have suggested the potential for a complex interference between the two. This study documents a new site of interference between the two pathways, a site in respiratory complex II capable of producing clinical signs of a block in fatty acid oxidation and reduced in vitro activity of acyl-CoA dehydrogenases. The initial patient, and later her newborn sibling, had mildly dysmorphic features, lactic acidosis and a defect in mitochondrial respiratory complex II associated with many biochemical features of a block in fatty acid oxidation. Results of in vitro probing of intact fibroblasts from both patients with methyl[2H3]palmitate and L-carnitine revealed greatly increased [2H3]butyrylcarnitine; however, the ratio of dehydrogenase activity with butyryl-CoA with anti-MCAD inactivating antibody (used to reveal SCAD-specific activity) to that with octanoyl-CoA was normal, excluding a selective SCAD or MCAD deficiency. Respiratory complex II was defective in both patients, with an absent thenoyltrifluoroacetone-sensitive succinate Q reductase activity that was partially restored by supplementation with duroquinone. Although secondary, the block in fatty acid oxidation was a major management problem since attempts to provide essential fatty acids precipitated acidotic decompensations. This study reinforces the need to pursue broadly the primary genetic defect within these two pathways, making full use of increasingly available functional and molecular diagnostic tools.

Blood mononuclear cell coenzyme Q10 concentration and mitochondrial respiratory chain succinate cytochrome-c reductase activity in phenylketonuric patients

Coenzyme Q10 (CoQ10) serves as an electron carrier within the mitochondrial respiratory chain (MRC), where it is integrally involved in oxidative phosphorylation and consequently ATP production. It has recently been suggested that phenylketonuria (PKU) patients may be susceptible to a CoQ10 deficiency as a consequence of their phenylalanine-restricted diet, which avoids foods rich in CoQ10 and its precursors. Furthermore, the high phenylalanine level in PKU patients not on dietary restriction may also result in impaired endogenous CoQ10 production, as previous studies have suggested an inhibitory effect of phenylalanine on HMG-CoA reductase, the rate-controlling enzyme in CoQ10 biosynthesis. We investigated the effect of both dietary restriction and elevated plasma phenylalanine concentration on blood mononuclear cell CoQ10 concentration and the activity of MRC complex II + III (succinate:cytochrome-c reductase; an enzyme that relies on endogenous CoQ10) in a PKU patient population. The concentrations of CoQ10 and MRC complex II + III activity were not found to be significantly different between the PKU patients on dietary restriction, PKU patients off dietary restriction and the control group, although plasma phenylalanine levels were markedly different. The results from this investigation suggest that dietary restriction and the elevated plasma phenylalanine levels of PKU patients do not effect mononuclear cell CoQ10 concentration and consequently the activity of complex II + III of the MRC.

Nutritional and exercise-based therapies in the treatment of mitochondrial disease

PURPOSE OF REVIEW

This review will critically summarize the nutritional and exercise-based interventions that have been used to treat mitochondrial disease, with a focus on the biochemical or molecular rationale for their use as well as recent advances in the field.

RECENT FINDINGS

Many nutritional-based treatment strategies have been used in an attempt to target energy impairment and its sequelae. Recently, coenzyme Q10, idebenone and triacylglycerol have been shown to bypass defective respiratory enzymes or scavenge free radicals, whereas creatine monohydrate has provided an alternative energy source. Thiamine has been used to decrease lactate levels and increase flux through aerobic metabolism, and riboflavin has been used as a precursor to complexes I and II. Several therapies employing various antioxidants in combination with other supplements have been effective at targeting several of the final common pathways of mitochondrial disease. Miscellaneous supplements, such as L-arginine and uridine, have also had recent success. However, although positive responses have been reported with these agents, many reports have shown no benefit, and there is widespread disparity in the literature. An alternative approach to treatment is exercise training. Both resistance and endurance exercise training have had positive outcomes in patients with mitochondrial disease, although several questions remain to be answered.

SUMMARY

There is no currently recognized treatment for mitochondrial disease. Future clinical trials are needed, as well as research into the potential for in-vitro screening of various compounds within affected cells from patients. Until this time, an accurate diagnosis will facilitate treatment on a case-by-case basis.

Treatment of cardiomyopathy and rhabdomyolysis in long-chain fat oxidation disorders using an anaplerotic odd-chain triglyceride

The current dietary treatment of long-chain fatty acid oxidation defects (high carbohydrate with medium-even-chain triglycerides and reduced amounts of long-chain fats) fails, in many cases, to prevent cardiomyopathy, rhabdomyolysis, and muscle weakness. We hypothesized that the apparent defect in energy production results from a depletion of the catalytic intermediates of the citric acid cycle via leakage through cell membranes (cataplerosis). We further hypothesized that replacing dietary medium-even-chain fatty acids (precursors of acetyl-CoA) by medium-odd-chain fatty acids (precursors of acetyl-CoA and anaplerotic propionyl-CoA) would restore energy production and improve cardiac and skeletal muscle function. We fed subjects with long-chain defects a controlled diet in which the fat component was switched from medium-even-chain triglycerides to triheptanoin. In three patients with very-long-chain acyl-CoA dehydrogenase deficiency, this treatment led rapidly to clinical improvement that included the permanent disappearance of chronic cardiomyopathy, rhabdomyolysis, and muscle weakness (for more than 2 years in one child), and of rhabdomyolysis and weakness in the others. There was no evidence of propionyl overload in these patients. The treatment has been well tolerated for up to 26 months and opens new avenues for the management of patients with mitochondrial fat oxidation disorders.

Diagnosis and treatment of childhood mitochondrial diseases

Mitochondrial cytopathies are caused by genetic alterations of nuclear- or mitochondrial-encoded genes involved in the synthesis of subunits of the electron transport chain. Mutations of mitochondrial DNA are associated with a wide range of clinical presentations [1-4]. The ubiquitous nature of mitochondria and the role of the mitochondria in cellular metabolism result in the potential for any tissue in the body to be affected [5-7,8..,9]. Although some children with mitochondrial disease present with life-threatening lactic acidosis in the newborn period, the majority of children come to clinical attention for nonspecific problems, including failure to thrive, developmental delay, seizures, hypotonia, and loss of developmental milestones. The diagnosis of these disorders is made through careful clinical evaluation, coupled with biochemical, morphologic, and molecular biologic techniques. Genetic counseling is difficult due to unique aspects of mitochondrial genetics. Despite advances in our understanding of mitochondrial biochemistry and genetics, treatment options remain limited.