Exercise benefits a variety of organ systems in mammals, and some of the best-recognized effects of exercise on muscle are mediated by the transcriptional co-activator PPAR-γ co-activator-1 α (PGC1-α). Here we show in mouse that PGC1-α expression in muscle stimulates an increase in expression of FNDC5, a membrane protein that is cleaved and secreted as a newly identified hormone, irisin. Irisin acts on white adipose cells in culture and in vivo to stimulate UCP1 expression and a broad program of brown-fat-like development. Irisin is induced with exercise in mice and humans, and mildly increased irisin levels in the blood cause an increase in energy expenditure in mice with no changes in movement or food intake. This results in improvements in obesity and glucose homeostasis. Irisin could be therapeutic for human metabolic disease and other disorders that are improved with exercise.

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A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis

The nuclear receptor PPARgamma is a ligand-activated transcription factor that plays an important role in the control of gene expression linked to a variety of physiological processes. PPARgamma was initially characterized as the master regulator for the development of adipose cells. Ligands for PPARgamma include naturally occurring fatty acids and the thiazolidinedione (TZD) class of antidiabetic drugs. Activation of PPARgamma improves insulin sensitivity in rodents and humans through a combination of metabolic actions, including partitioning of lipid stores and the regulation of metabolic and inflammatory mediators termed adipokines. PPARgamma signaling has also been implicated in the control of cell proliferation, atherosclerosis, macrophage function, and immunity. Here, we review recent advances in our understanding of the diverse biological actions of PPARgamma with an eye toward the expanding therapeutic potential of PPARgamma agonist drugs.

Fat and beyond: the diverse biology of PPARgamma.

https://www.kidney-international.org/article/S0085-2538(15)53124-4/pdf

Cisplatin nephrotoxicity: Mechanisms and renoprotective strategies

https://dash.harvard.edu/bitstream/handle/1/33766533/nihms372870.pdf?sequence=4

SIRT1 Is Required for AMPK Activation and the Beneficial Effects of Resveratrol on Mitochondrial Function

The increasing incidence of obesity and its co-morbid conditions poses a great challenge to global health. In addition to cardiovascular disease and diabetes, epidemiological data demonstrate a link between obesity and multiple types of cancer. The molecular mechanisms underlying how obesity causes an increased risk of cancer are poorly understood. Obesity disrupts the dynamic role of the adipocyte in energy homeostasis, resulting in inflammation and alteration of adipokine (for example, leptin and adiponectin) signalling. Additionally, obesity causes secondary changes that are related to insulin signalling and lipid deregulation that may also foster cancer development. Understanding these molecular links may provide an avenue for preventive and therapeutic strategies to reduce cancer risk and mortality in an increasingly obese population.

Molecular mechanisms of cancer development in obesity

The coactivator peroxisome proliferator-activated receptor-gamma coactivator 1 α (PGC-1α) coordinates a broad set of transcriptional programs that regulate the response of skeletal muscle to exercise. However, the complete transcriptional network controlled by PGC-1α has not been described. In this study, we used a qPCR-based screen of all known transcriptional components (Quanttrx) to identify transcription factors that are quantitatively regulated by PGC-1α in cultured skeletal muscle cells. This analysis identified hypoxia-inducible factor 2 α (HIF2α) as a major PGC-1α target in skeletal muscle that is positively regulated by both exercise and β-adrenergic signaling. This transcriptional regulation of HIF2α is completely dependent on the PGC-1α/ERRα complex and is further modulated by the action of SIRT1. Transcriptional profiling of HIF2α target genes in primary myotubes suggested an unexpected role for HIF2α in the regulation of muscle fiber types, specifically enhancing the expression of a slow twitch gene program. The PGC-1α–mediated switch to slow, oxidative fibers in vitro is dependent on HIF2α, and mice with a muscle-specific knockout of HIF2α increase the expression of genes and proteins characteristic of a fast-twitch fiber-type switch. These data indicate that HIF2α acts downstream of PGC-1α as a key regulator of a muscle fiber-type program and the adaptive response to exercise.

https://www.pnas.org/content/pnas/107/50/21866.full.pdf

PGC-1α regulates a HIF2α-dependent switch in skeletal muscle fiber types

Synergy between PPARγ Ligands and Platinum-Based Drugs in Cancer

Purpose: Current therapy for lung cancer involves multimodality therapies. However, many patients are either refractory to therapy or develop drug resistance. KRAS and epidermal growth factor receptor ( EGFR ) mutations represent some of the most common mutations in lung cancer, and many studies have shown the importance of these mutations in both carcinogenesis and chemoresistance. Genetically engineered murine models of mutant EGFR and KRAS have been developed that more accurately recapitulate human lung cancer. Recently, using cell-based experiments, we showed that platinum-based drugs and the antidiabetic drug rosiglitazone (PPARγ ligand) interact synergistically to reduce cancer cell and tumor growth. Here, we directly determined the efficacy of the PPARγ/carboplatin combination in these more relevant models of drug resistant non–small cell lung cancer.

Experimental Design: Tumorigenesis was induced by activation of either mutant KRAS or EGFR . Mice then received either rosiglitazone or carboplatin monotherapy, or a combination of both drugs. Change in tumor burden, pathology, and evidence of apoptosis and cell growth were assessed.

Results: Tumor burden remained unchanged or increased in the mice after monotherapy with either rosiglitazone or carboplatin. In striking contrast, we observed significant tumor shrinkage in mice treated with these drugs in combination. Immunohistochemical analyses showed that this synergy was mediated via both increased apoptosis and decreased proliferation. Importantly, this synergy between carboplatin and rosiglitazone did not increase systemic toxicity.

Conclusions: These data show that the PPARγ ligand/carboplatin combination is a new therapy worthy of clinical investigation in lung cancers, including those cancers that show primary resistance to platinum therapy or acquired resistance to targeted therapy.

https://clincancerres.aacrjournals.org/content/clincanres/14/20/6478.full.pdf

Elnaz Naseri

Papers

PGC-1α regulates a HIF2α-dependent switch in skeletal muscle fiber types

Synergy between PPARγ Ligands and Platinum-Based Drugs in Cancer

Regression of drug-resistant lung cancer by the combination of rosiglitazone and carboplatin.