Exercise, Nutrition, and Supplements in the Muscle Carnitine Palmitoyl-Transferase II Deficiency: New Theoretical Bases for Potential Applications

EPA and DHA acylcarnitines are less cardiotoxic than are saturated and monounsaturated long-chain acylcarnitines

Elevated levels of fatty acid-derived long-chain acylcarnitines are detrimental to cardiac health, primarily because of their adverse effects on mitochondrial function and key metabolic pathways in the heart. While trans-fatty acids are considered harmful and omega-3 polyunsaturated fatty acids (PUFAs) are considered beneficial, the specific properties of acylcarnitines derived from these types of fatty acids are not characterized. This study aimed to compare the effects of saturated palmitoylcarnitine (PC), monounsaturated cis-oleoylcarnitine (cis-OC), trans-elaidoylcarnitine (trans-EC), and polyunsaturated eicosapentaenoylcarnitine (EPAC) and docosahexaenoylcarnitine (DHAC) on heart function, cardiac cell viability, mitochondrial functionality, and insulin signaling pathways. Saturated and monounsaturated acylcarnitines, particularly trans-EC, significantly reduced cardiac contractility at concentrations of 8-12 μM, and trans-EC was identified as the most cardiotoxic acylcarnitine. Conversely, the presence of EPAC and DHAC in the perfusion buffer did not impair heart functionality. Saturated and monounsaturated acylcarnitines also drastically reduced H9C2 cell viability and suppressed mitochondrial OXPHOS by up to 70% at 25 μM, whereas PUFA-derived acylcarnitines caused only a 20%-25% reduction in OXPHOS and did not decrease cell viability. Furthermore, PC, cis-OC, and trans-EC significantly inhibited Akt phosphorylation, whereas EPAC and DHAC had a much weaker effect on insulin signaling. In conclusion, saturated and monounsaturated acylcarnitines, particularly trans-EC, exert significant cardiotoxic effects, primarily through the impairment of cardiac mitochondrial function. The omega-3 PUFA-derived acylcarnitines EPAC and DHAC are safe and less likely to damage cardiac mitochondria, cardiac cells, and the heart than other acylcarnitines. PUFA intake might be safer than other long-chain fatty acid-containing lipid sources in patients with FAODs and cardiometabolic diseases.

Circulatory response to exercise relative to oxygen uptake assessed in the follow-up of patients with fatty acid beta-oxidation disorders

Patients with fatty acid oxidation disorders (FAODs) experience muscle symptoms due to impaired ATP metabolism and the toxicity of accumulated mitochondrial FAO substrates or intermediates, especially during catabolic states. A major issue is the absence of specific and sensible biomarkers to evaluate metabolic equilibrium. The relationship between cardiac output (Q) and oxygen consumption (VO2) during incremental exercise (dQ/dVO2) provides an indirect surrogate of mitochondrial function. A high dQ/dVO2 slope indicates impaired oxidative phosphorylation in skeletal muscle during exercise. Our study aimed to evaluate dQ/dVO2 as a potential marker of the severity of FAODs. We retrospectively collected clinical, laboratory parameters and treatment data for FAOD patients over 6 years old, including a disease severity score, plasma acylcarnitines and cardiopulmonary exercise tests with Q measurement via thoracic bioelectrical impedance. FAO flux was measured in whole blood and in myoblasts when available. We included 27 FAOD patients followed from 2015 to 2022, with deficiencies in LCHAD (n = 10), CPT2 (n = 6), VLCAD (n = 7), or MADD (n = 4). CPT2 deficient patients with severe scores had the highest C18:1-, C16-, C18-acylcarnitines, and dQ/dVO2. In these patients, dQ/dVO2 was positively correlated with C18:1, C16, and C18 acylcarnitines. In a linear multivariate regression model, dQ/dVO2 was significantly associated with the severity score (B = 0.831, p = 0.008) and triheptanoin treatment (B = -0.547, p = 0.025). dQ/dVO2 and plasma long-chain acylcarnitines might be useful to monitor CPT2D, as these parameters associate with our clinical severity score and could reflect altered mitochondrial functions.

Investigating the Link between Ketogenic Diet, NAFLD, Mitochondria, and Oxidative Stress: A Narrative Review

Together with the global rise in obesity and metabolic syndrome, the prevalence of individuals who suffer from nonalcoholic fatty liver disease (NAFLD) has risen dramatically. NAFLD is currently the most common chronic liver disease and includes a continuum of liver disorders from initial fat accumulation to nonalcoholic steatohepatitis (NASH), considered the more severe forms, which can evolve in, cirrhosis, and hepatocellular carcinoma. Common features of NAFLD includes altered lipid metabolism mainly linked to mitochondrial dysfunction, which, as a vicious cycle, aggravates oxidative stress and promotes inflammation and, as a consequence, the progressive death of hepatocytes and the severe form of NAFLD. A ketogenic diet (KD), i.e., a diet very low in carbohydrates (<30 g/die) that induces "physiological ketosis", has been demonstrated to alleviate oxidative stress and restore mitochondrial function. Based on this, the aim of the present review is to analyze the body of evidence regarding the potential therapeutic role of KD in NAFLD, focusing on the interplay between mitochondria and the liver, the effects of ketosis on oxidative stress pathways, and the impact of KD on liver and mitochondrial function.

Biomarkers of Redox Balance Adjusted to Exercise Intensity as a Useful Tool to Identify Patients at Risk of Muscle Disease through Exercise Test

The screening of skeletal muscle diseases constitutes an unresolved challenge. Currently, exercise tests or plasmatic tests alone have shown limited performance in the screening of subjects with an increased risk of muscle oxidative metabolism impairment. Intensity-adjusted energy substrate levels of lactate (La), pyruvate (Pyr), β-hydroxybutyrate (BOH) and acetoacetate (AA) during a cardiopulmonary exercise test (CPET) could constitute alternative valid biomarkers to select "at-risk" patients, requiring the gold-standard diagnosis procedure through muscle biopsy. Thus, we aimed to test: (1) the validity of the V'O2-adjusted La, Pyr, BOH and AA during a CPET for the assessment of the muscle oxidative metabolism (exercise and mitochondrial respiration parameters); and (2) the discriminative value of the V'O2-adjusted energy and redox markers, as well as five other V'O2-adjusted TCA cycle-related metabolites, between healthy subjects, subjects with muscle complaints and muscle disease patients. Two hundred and thirty subjects with muscle complaints without diagnosis, nine patients with a diagnosed muscle disease and ten healthy subjects performed a CPET with blood assessments at rest, at the estimated 1st ventilatory threshold and at the maximal intensity. Twelve subjects with muscle complaints presenting a severe alteration of their profile underwent a muscle biopsy. The V'O2-adjusted plasma levels of La, Pyr, BOH and AA, and their respective ratios showed significant correlations with functional and muscle fiber mitochondrial respiration parameters. Differences in exercise V'O2-adjusted La/Pyr, BOH, AA and BOH/AA were observed between healthy subjects, subjects with muscle complaints without diagnosis and muscle disease patients. The energy substrate and redox blood profile of complaining subjects with severe exercise intolerance matched the blood profile of muscle disease patients. Adding five tricarboxylic acid cycle intermediates did not improve the discriminative value of the intensity-adjusted energy and redox markers. The V'O2-adjusted La, Pyr, BOH, AA and their respective ratios constitute valid muscle biomarkers that reveal similar blunted adaptations in muscle disease patients and in subjects with muscle complaints and severe exercise intolerance. A targeted metabolomic approach to improve the screening of "at-risk" patients is discussed.