Project description:The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1Î±) is a chief activator of the mitochondrial and metatolic program in skeletal muscle (skm) and prevents atrophy. Here we tested whether PGC-1Î± overexpression could restructure the transcriptome and metabolism of cultured human skeletal myotubes, which display an athropic phenotype. An oligonucleotide microarray analysis was used to reveal PGC-1Î± effects on the whole transcriptome, and the possible impact on fuel metabolism reprogramming was examined. Fifty-three different genes displayed changed expression levels in response to PGC-1Î±: 42 upregulated and 11 downregulated. Main associations of gene ontologies (GO) for the upregulated genes were mitochondrial components and processes and this correlated with an increase in COX activity, an indicator of mitochondrial content. Palmitate and lactate oxidation to CO2 was enhanced, but not glucose oxidation. The other most significant GO associations of upregulated genes were chemotaxis and cytokine activity, and accordingly, several cytokines, including IL8, CXCL6, CCL5 and CCL8, were within top induced genes. Among the most regulated genes were also potential metabolic regulators of fatty acid and glucose storage. FITM1/FIT1 induction was associated with an increased number of lipid droplets with smaller area, while triglyceride levels were modestly increased in oleate-incubated cells. Downregulation of CALM1, the calcium-modulated Î´ subunit of phosphorylase kinase, was linked to inactivation of glycogen phosphorylase and greater accumulation of glycogen. The most upregulated gene was PVALB, which is also related to calcium signaling. In conclusion, only the deficient mitochondrial transcriptional program of cultured myotubes is rescued by PGC-1Î±. New PGC-1Î± gene targets and pathways arise, some of which may mediate its activating effects in processes such as lipid and carbohydrate storage and angiogenesis. 6 samples from 3 different skeletal muscle cell cultures were used: 3 were transfected with adenovirus containing PGC-1aplha and 3 with adenovirus containing GFP (control). The 3 PGC-1alpha samples were compared against the control samples.

Project description:T helper 17 (Th17) cells are a distinct subset of CD4+ T cells necessary for maintaining gut homeostasis and have prominent roles in autoimmunity and inflammation1. Th17 cells have unique metabolic features, including a stem cell-like signature2,3 and reliance on mitochondrial respiratory chain function and tricarboxylic acid (TCA) cycle to coordinate metabolic and epigenetic remodeling4,5. Dynamic changes in mitochondrial membrane morphology are key to sustain organelle function6. However, it remains unclear whether mitochondrial membrane remodeling orchestrates metabolic and differentiation events in Th17 cells. Here we demonstrate that mitochondrial membrane fusion and tight cristae organization are required for Th17 cell function (i.e. cytokine expression) but dispensable in other T cell subsets. We find that Th17 cells rely on mitochondrial fusion as a result of their low metabolic activity. Thus, lowering metabolic activity in other T cell subsets by nutrient restriction was sufficient to increase reliance on mitochondrial fusion for effector function. Transcriptional, proteomic, and metabolomic profiling identified the serine/threonine kinase liver associated kinase B1 (LKB1) as an essential node coupling mitochondrial function to cytokine expression in T cells. By genetic and metabolomic approaches, we demonstrate that LKB1 regulates IL-17A expression by controlling TCA cycle metabolites and transcriptional remodeling. Th-17 cell-specific deletion of optic atrophy 1 (OPA1), a protein involved in mitochondrial inner membrane fusion and cristae organization, reduced autoimmune pathogenesis in a mouse model of multiple sclerosis, while additional deletion of LKB1 restored disease. Our findings highlight distinct mitochondrial requirements in CD4+ T cells, identify mitochondrial membrane fusion as a major determinant of Th17 responses, and reveal LKB1 as a sensor of mitochondrial integrity that links mitochondrial cues to effector programs in Th17 cells.

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Metabolic dysregulation contributes to the development of dysferlinopathy

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