Sustained PGC-1α2 or PGC-1α3 expression induces astrocyte dysfunction and degeneration.

Peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) transcriptional coactivators are key regulators of energy metabolism-related genes and are expressed in energy-demanding tissues. There are several PGC-1α variants with different biological functions in different tissues. The brain is one of the tissues where the role of PGC-1α isoforms remains less explored. Here, we used a toxin-based mouse model of Parkinson's disease (PD) and observed that the expression levels of variants PGC-1α2 and PGC-1α3 in the nigrostriatal pathway increases at the onset of dopaminergic cell degeneration. This increase occurs concomitant with an increase in glial fibrillary acidic protein levels. Since PGC-1α coactivators regulate cellular adaptive responses, we hypothesized that they could be involved in the modulation of astrogliosis induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Therefore, we analysed the transcriptome of astrocytes transduced with expression vectors encoding PGC-1α1 to 1α4 by massively parallel sequencing (RNA-seq) and identified the main cellular pathways controlled by these isoforms. Interestingly, in reactive astrocytes the inflammatory and antioxidant responses, adhesion, migration, and viability were altered by PGC-1α2 and PGC-1α3, showing that sustained expression of these isoforms induces astrocyte dysfunction and degeneration. This work highlights PGC-1α isoforms as modulators of astrocyte reactivity and as potential therapeutic targets for the treatment of PD and other neurodegenerative disorders.

Postmenopausal hormone use and cutaneous melanoma risk: A French prospective cohort study.

Cutaneous melanoma has been suspected to be influenced by female hormones. Several studies reported a positive association between menopausal hormone therapy (MHT) use and melanoma risk; however, previous findings were conflicting. We sought to explore the associations between MHT use and melanoma risk in a prospective cohort of women in France, where a particularly wide variety of MHT formulations are available. E3N is a prospective cohort of 98,995 French women aged 40-65 years in 1990. MHT use was assessed through biennial self-administered questionnaires. We used Cox proportional hazards regression models adjusted for age and skin cancer risk factors. Over 1990-2008, 444 melanoma cases were ascertained among 75,523 postmenopausal women. Ever use of MHT was associated with a higher melanoma risk (hazard ratio (HR) = 1.35, 95% confidence intervals (CI) = 1.07-1.71). The association was strongest among past users (HR = 1.55, CI = 1.17-2.07, homogeneity for past vs. recent use: p = 0.11), and users of MHT containing norpregnane derivatives (HR = 1.59, CI = 1.11-2.27), although with no heterogeneity across types of MHT (p = 0.13). Among MHT users, the association was similar across durations of use. However, a higher risk was observed when treatment onset occurred shortly after menopause (<6 months: HR = 1.55, CI = 1.16-2.07 vs. ≥2 years). Associations between MHT use and melanoma risk were similar after adjustment for UV exposure, although MHT users were more likely to report sunscreen use than nonusers. Our data do not support a strong association between MHT use and melanoma risk. Further investigation is needed to explore potential effect modification by UV exposure on this relationship.

The weight of nutrients: kynurenine metabolites in obesity and exercise.

Obesity ultimately results from an imbalance between energy intake and expenditure. However, in addition to their bioenergetic value, nutrients and their metabolites can function as important signalling molecules in energy homeostasis. Indeed, macronutrients and their metabolites can be direct regulators of metabolism through their actions on different organs. In turn, target organs can decide to use, store or transform the incoming nutrients depending on their physiological context and in coordination with other cell types. Tryptophan-kynurenine metabolites are an example of a family of compounds that can serve as systemic integrators of energy metabolism by signalling to different cell types. These include adipocytes, immune cells and muscle fibres, in addition to the well-known effects of kynurenine metabolites on the central nervous system. In the context of energy metabolism, several of the effects elicited by kynurenic acid are mediated by the G-protein-coupled receptor, GPR35. As GPR35 is expressed in tissues such as the adipose tissue, immune cells and the gastrointestinal tract, this receptor could be a potential therapeutic target for the treatment of obesity, diabetes and other metabolic diseases. In addition, metabolic disorders often coincide with states of chronic inflammation, which further highlights GPR35 as an integration node in conditions where inflammation skews metabolism. Defining the molecular interplay between different tissues in the regulation of energy homeostasis can help us understand interindividual variability in the response to nutrient intake and develop safe and efficient therapies to fight obesity and metabolic disease.

Oral contraceptive use and cutaneous melanoma risk: a French prospective cohort study.

Cutaneous melanoma has been suspected to be influenced by female hormones. Several studies reported a positive association between oral contraceptive (OC) use and melanoma risk. However, findings were conflicting and data from large prospective studies are lacking. E3N is a prospective cohort of 98,995 French women aged 40-65 years at inclusion in 1990. Exposure to lifetime OC use was assessed in 1992 and through biennial questionnaire updates. To assess the association between OC use and melanoma risk, we used Cox models adjusted for age, pigmentary traits, residential ultraviolet (UV) exposure in county of birth and at inclusion and family history of skin cancer. Over 1992-2008, 539 melanoma cases were ascertained among 79,365 women. In age-adjusted models, we found a modest positive association between ever use of OCs and melanoma risk (hazard ratio (HR) = 1.18, 95% confidence intervals (CIs) = 0.98-1.42), which was reduced after adjustment (HR = 1.14, 95% CI = 0.95-1.38). The association was stronger in long-term users (duration ≥10 years: HR = 1.33, 95% CI = 1.00-1.75) and in women who used high-estrogen OCs (HR = 1.27, 95% CI = 1.04-1.56). Among users, there was an inverse association with age at first use (ptrend < 0.01), but no evidence of an association with age at last use or time since last use. OC use was positively associated with tanning bed use (OR = 1.14, CI = 1.01-1.29), sunburns (ptrend = 0.5) and sunscreen use (OR = 1.13, CI = 1.00-1.28) since age 25. Overall, our findings do not support a strong association between OC use and melanoma risk and suggest intentional UV exposure in OC users, which supports a potential confusion by UV exposure in this relationship.

Small molecule PGC-1α1 protein stabilizers induce adipocyte Ucp1 expression and uncoupled mitochondrial respiration.

OBJECTIVE: The peroxisome proliferator-activated receptor-γ coactivator-1α1 (PGC-1α1) regulates genes involved in energy metabolism. Increasing adipose tissue energy expenditure through PGC-1α1 activation is potentially beneficial for systemic metabolism. Pharmacological PGC-1α1 activators could be valuable tools in the fight against obesity and metabolic disease. Finding such compounds has been challenging partly because PGC-1α1 is a transcriptional coactivator with no known ligand-binding properties. While, PGC-1α1 activation is regulated by several mechanisms, protein stabilization is a crucial limiting step due to its short half-life under unstimulated conditions. METHODS: We designed a cell-based high-throughput screening system to identify PGC-1α1 protein stabilizers. Positive hits were tested for their ability to induce endogenous PGC-1α1 protein accumulation and activate target gene expression in brown adipocytes. Select compounds were analyzed for their effects on global gene expression and cellular respiration in adipocytes. RESULTS: Among 7,040 compounds screened, we highlight four small molecules with high activity as measured by: PGC-1α1 protein accumulation, target gene expression, and uncoupled mitochondrial respiration in brown adipocytes. CONCLUSIONS: We identify compounds that induce PGC-1α1 protein accumulation and show that this increases uncoupled respiration in brown adipocytes. This screening platform establishes the foundation for a new class of therapeutics with potential use in obesity and associated disorders.