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Along with the increase in life expectancy over the last century, the prevalence of age-related disorders, such as neurodegenerative diseases continues to rise. This is the case of Alzheimer's, Parkinson's, Huntington's diseases and Multiple sclerosis, which are chronic disorders characterized by neuronal loss in motor, sensory or cognitive systems. Accumulating evidence has suggested the presence of a strong correlation between metabolic changes and neurodegeneration. Indeed epidemiologic studies have shown strong associations between obesity, metabolic dysfunction, and neurodegeneration, while animal models have provided insights into the complex relationships between these conditions. In this context, hormones such as leptin, ghrelin, insulin and IGF-1 seem to play a key role in the regulation of neuronal damage, toxic insults and several other neurodegenerative processes. This review aims to presenting the most recent evidence supporting the crosstalk linking energy metabolism and neurodegeneration, and will focus on metabolic manipulation as a possible therapeutic tool in the prevention and treatment of neurodegenerative diseases.

Mitochondrial dysfunction plays a primary role in neurodevelopmental anomalies and neurodegeneration of Down syndrome (DS) subjects. For this reason, targeting mitochondrial key genes, such as PGC-1α/PPARGC1A, is emerging as a good therapeutic approach to attenuate cognitive disability in DS. After demonstrating the efficacy of the biguanide metformin (a PGC-1α activator) in a cell model of DS, we extended the study to other molecules that regulate the PGC-1α pathway acting on PPAR genes. We, therefore, treated trisomic fetal fibroblasts with different doses of pioglitazone (PGZ) and evaluated the effects on mitochondrial dynamics and function. Treatment with PGZ significantly increased mRNA and protein levels of PGC-1α. Mitochondrial network was fully restored by PGZ administration affecting the fission-fusion mitochondrial machinery. Specifically, optic atrophy 1 (OPA1) and mitofusin 1 (MFN1) were upregulated while dynamin-related protein 1 (DRP1) was downregulated. These effects, together with a significant increase of basal ATP content and oxygen consumption rate, and a significant decrease of reactive oxygen species (ROS) production, provide strong evidence of an overall improvement of mitochondria bioenergetics in trisomic cells. In conclusion, we demonstrate that PGZ is able to improve mitochondrial phenotype even at low concentrations (0.5 μM). We also speculate that a combination of drugs that target mitochondrial function might be advantageous, offering potentially higher efficacy and lower individual drug dosage.

Tumour cells have long been considered defective in mitochondrial respiration and mostly dependent on glycolytic metabolism. However, this assumption is currently challenged by several lines of evidence in a growing number of tumours. Ovarian cancer (OC) is one of the most lethal cancers worldwide, but it continues to be a poorly understood disease and its metabolic features are far to be elucidated. In this context, we investigated the role of tumour necrosis factor receptor-associated protein 1 (TRAP1), which is found upregulated in several cancer types and is a key modulator of tumour cell metabolism. Surprisingly, we found that TRAP1 expression inversely correlated with grade, stage and lower survival in a large cohort of OC patients. Accordingly, TRAP1 silencing induced resistance to cisplatin, resistant cells showed increased oxidative metabolism compared with their sensitive counterpart, and the bioenergetics cellular index of higher grade tumours indicated increased mitochondrial respiration. Strikingly, cisplatin resistance was reversible upon pharmacological inhibition of mitochondrial oxidative phosphorylation by metformin/oligomycin. At molecular level, increased oxidative metabolism in low TRAP1-expressing OC cells and tissues enhanced production of inflammatory mediators such as interleukin (IL)-6 and IL-8. Mechanistically, we identified members of the multidrug resistance complex (MDR) as key mediators of such metabolism-driven, inflammation-induced process. Indeed, treatment of OC cell lines with TNFα and IL6 induced a selective increase in the expression of TAP1 and multidrug resistance protein 1, whereas TAP1 silencing sensitized cells to cisplatin-induced apoptosis. Our results unveil a novel role for TRAP1 and oxidative metabolism in cancer progression and suggest the targeting of mitochondrial bioenergetics to increase cisplatin efficacy in human OC.Cell Death and Differentiation advance online publication, 20 May 2016; doi:10.1038/cdd.2016.39.