L-Carnitine is an amino acid derivative widely known for its involvement in the transport of long-chain fatty acids into the mitochondrial matrix, where fatty acid oxidation occurs. Moreover, l-Carnitine protects the cell from acyl-CoA accretion through the generation of acylcarnitines. Circulating carnitine is mainly supplied by animal-based food products and to a lesser extent by endogenous biosynthesis in the liver and kidney. Human muscle contains high amounts of carnitine but it depends on the uptake of this compound from the bloodstream, due to muscle inability to synthesize carnitine. Mitochondrial fatty acid oxidation represents an important energy source for muscle metabolism particularly during physical exercise. However, especially during high-intensity exercise, this process seems to be limited by the mitochondrial availability of free l-carnitine. Hence, fatty acid oxidation rapidly declines, increasing exercise intensity from moderate to high. Considering the important role of fatty acids in muscle bioenergetics, and the limiting effect of free carnitine in fatty acid oxidation during endurance exercise, l-carnitine supplementation has been hypothesized to improve exercise performance. So far, the question of the role of l-carnitine supplementation on muscle performance has not definitively been clarified. Differences in exercise intensity, training or conditioning of the subjects, amount of l-carnitine administered, route and timing of administration relative to the exercise led to different experimental results. In this review, we will describe the role of l-carnitine in muscle energetics and the main causes that led to conflicting data on the use of l-carnitine as a supplement.

The application of non-targeted serum metabolomics profiling represents a noninvasive tool to identify new clinical biomarkers and to provide early diagnostic differentiation, and insight into the pathological mechanisms underlying hepatocellular carcinoma (HCC) progression. In this study, we used proton Nuclear Magnetic Resonance (¹H-NMR) Spectroscopy and multivariate data analysis to profile the serum metabolome of 64 HCC patients, in early (n = 28) and advanced (n = 36) disease stages. We found that ¹H-NMR metabolomics profiling could discriminate early from advanced HCC patients with a cross-validated accuracy close to 100%. Orthogonal partial least squares discriminant analysis (OPLS-DA) showed significant changes in serum glucose, lactate, lipids and some amino acids, such as alanine, glutamine, 1-methylhistidine, lysine and valine levels between advanced and early HCC patients. Moreover, in early HCC patients, Kaplan–Meier analysis highlighted the serum tyrosine level as a predictor for overall survival (OS). Overall, our analysis identified a set of metabolites with possible clinical and biological implication in HCC pathophysiology.

Small round cell osteosarcoma is a very rare type of osteosarcoma, histologically mimicking other small round cell malignancies of bone, most notably Ewing sarcoma. To distinguish small cell osteosarcoma from other primary small cell malignancies of bone, we evaluated the immunohistochemical (IHC) expression of CD99 and SATB2, a marker of osteoblastic differentiation. Second, we analyzed EWSR1 and FUS gene aberrations using fluorescence in situ hybridization and/or reverse transcription-polymerase chain reaction (RT-PCR) techniques to assess whether small cell osteosarcoma and Ewing sarcoma share the same genetic alteration analysis. Thirty-six cases of primitive small cell osteosarcoma of bone were included in this study. All the cases of small cell osteosarcoma showed strong nuclear expression of SATB2 associated with negativity for CD99 antibody or weak, cytoplasmic staining in few neoplastic cells. Reverse transcription-polymerase chain reaction was negative for EWS-FLI1 type 1-2, EWS-ERG type 1, and CIC-DUX4 in the 10 available cases of small cell osteosarcoma analyzed. Fluorescence in situ hybridization analysis was feasible with a readable signal in 13 cases of small cell osteosarcoma, and none of these cases showed any EWSR1 and FUS gene rearrangements. In conclusion, it appears extremely useful to combine IHC analysis of SATB2 and CD99 with molecular analysis of Ewing sarcoma-associated genetic aberrations, to differentiate small cell osteosarcoma from other small round cell malignancies of bone. The strong IHC expression of SATB2 associated with CD99 immunonegativity and the absence of EWSR1 and FUS gene rearrangements in small cell osteosarcoma argues against the existence of a morphologic/genetic continuum with Ewing sarcoma.

In recent years, lipid metabolism has gained greater attention in several diseases including cancer. Dysregulation of fatty acid metabolism is a key component in breast cancer malignant transformation. In particular, de novo lipogenesis provides the substrate required by the proliferating tumor cells to maintain their membrane composition and energetic functions during enhanced growth. However, it appears that not all breast cancer subtypes depend on de novo lipogenesis for fatty acid replenishment. Indeed, while breast cancer luminal subtypes rely on de novo lipogenesis, the basal-like receptor-negative subtype overexpresses genes involved in the utilization of exogenous-derived fatty acids, in the synthesis of triacylglycerols and lipid droplets, and fatty acid oxidation. These metabolic differences are specifically associated with genomic and proteomic changes that can perturb lipogenic enzymes and related pathways. This behavior is further supported by the observation that breast cancer patients can be stratified according to their molecular profiles. Moreover, the discovery that extracellular vesicles act as a vehicle of metabolic enzymes and oncometabolites may provide the opportunity to noninvasively define tumor metabolic signature. Here, we focus on de novo lipogenesis and the specific differences exhibited by breast cancer subtypes and examine the functional contribution of lipogenic enzymes and associated transcription factors in the regulation of tumorigenic processes.

Long-term high-fat diet (HFD) consumption can cause weight gain and obesity, two conditions often associated with hepatic non-alcoholic fatty liver and oxidative stress. Oleoylethanolamide (OEA), a lipid compound produced by the intestine from oleic acid, has been associated with different beneficial effects in diet-induced obesity and hepatic steatosis. However, the role of OEA on hepatic oxidative stress has not been fully elucidated. In this study, we used a model of diet-induced obesity to study the possible antioxidant effect of OEA in the liver. In this model rats with free access to an HFD for 77 days developed obesity, steatosis, and hepatic oxidative stress, as compared to rats consuming a low-fat diet for the same period. Several parameters associated with oxidative stress were then measured after two weeks of OEA administration to diet-induced obese rats. We showed that OEA reduced, compared to HFD-fed rats, obesity, steatosis, and the plasma level of triacylglycerols and transaminases. Moreover, OEA decreased the amount of malondialdehyde and carbonylated proteins and restored the activity of antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase, which decreased in the liver of HFD-fed rats. OEA had also an improving effect on parameters linked to endoplasmic reticulum stress, thus demonstrating a role in the homeostatic control of protein folding. Finally, we reported that OEA differently regulated the expression of two transcription factors involved in the control of lipid metabolism and antioxidant genes, namely nuclear factor erythroid-derived 2-related factor 1 (Nrf1) and Nrf2, thus suggesting, for the first time, new targets of the protective effect of OEA in the liver.

Medium-chain fatty acids (MCFA) are dietary components with a chain length ranging from 6 to 12 carbon atoms. MCFA can cross the blood-brain barrier and in the brain can be oxidized through mitochondrial β-oxidation. As components of ketogenic diets, MCFA have demonstrated beneficial effects on different brain diseases, such as traumatic brain injury, Alzheimer’s disease, drug-resistant epilepsy, diabetes, and cancer. Despite the interest in MCFA effects, not much information is available about MCFA metabolism in the brain. In this study, with a gas chromatography-mass spectrometry (GC-MS)-based metabolomics approach, coupled with multivariate data analyses, we followed the metabolic changes of U87MG glioblastoma cells after the addition of octanoic (C8), or decanoic (C10) acids for 24 h. Our analysis highlighted significant differences in the metabolism of U87MG cells after the addition of C8 or C10 and identified several metabolites whose amount changed between the two groups of treated cells. Overall, metabolic pathway analyses suggested the citric acid cycle, Warburg effect, glutamine/glutamate metabolism, and ketone body metabolism as pathways influenced by C8 or C10 addition to U87MG cells. Our data demonstrated that, while C8 affected mitochondrial metabolism resulting in increased ketone body production, C10 mainly influenced cytosolic pathways by stimulating fatty acid synthesis. Moreover, glutamine might be the main substrate to support fatty acids synthesis in C10-treated cells. In conclusion, we identified a metabolic signature associated with C8 or C10 addition to U87MG cells that can be used to decipher metabolic responses of glioblastoma cells to MCFA treatment.