LBODP109 Astrocytes Affect The Metabolism Of Proopiomelanocortin (pomc) Neurons Through The Release Of Exosomes That Are Modified In A Fatty Acid Specific Manner

Astrocytes influence neighboring neurons through the release of a variety of signals, including exosomes, micro-vesicles that contain a vast heterogeneity of molecules such as cytokines, growth factors, RNAs and micro-RNAs (mi-RNAs) that modify target cells. We hypothesized that hypothalamic astrocytes communicate the metabolic status via exosomes to neighboring POMC neurons to modify their functions in the promotion of satiety and energy expenditure. To this end, primary hypothalamic astrocyte cultures were treated with palmitic acid (PA; 0.5 mM), oleic acid (OA; 0.5 mM) or vehicle for 24 hours and exosomes were isolated from the media and applied (1.25 or 2.50 µg/mL) to a POMC neuronal cell line for 24 hours. Exosomes released in response to PA (E-PA) or OA (E-OA) increased POMC expression (p < 0. 05) with no effect on the expression of markers of ER stress (CHOP) and inflammation [interleukin (IL)-6] compared to exosomes released from vehicle treated astrocytes (E-V) or with no exosomes (control). Seahorse Cell Mito Stress test was performed to determinate modifications in metabolism in the POMC neurons in response to these treatments. The mitochondrial spare respiratory capacity of neurons was increased (p < 0. 0001) in response to both doses of E-PA and E-OA, with the maximal respiration (p < 0. 0001) increasing with E-PA (both doses) or 2.50 µg/mL of E-OA compared to E-V or control. Next-generation miRNA sequencing analysis established the modifications of miRNAs contained in exosomes released by hypothalamic astrocytes in response to PA, with miR-199a-3p and miR-145-5p content being higher in E-PA compared to E-V. Transfection of POMC neurons with a mimetic of miR-199a-3p (1.5 pmol) increased POMC expression and insulin-like growth factor 1 receptor (IGF1r) protein levels (p<0. 05). Moreover, levels of mTOR as well as p70S6k, reported targets of miR-199a-3p, were decreased (both p<0. 05). Mimetic overexpression of miR-145-5p reduced POMC expression (p < 0. 001) and protein levels of insulin receptor substrate 1 (IRS1; p < 0. 001), which is a known target of this miRNA. These results suggest that astrocytes communicate with neurons via exosomes, with the exosomes content being modulated in response to the nutritional environment. The messages contained in astrocytic exosomes can directly alter the neuropeptide expression in targeted neurons as well as of the levels of receptors and factors involved in cell protection, metabolism, and nutrient sensing, with specific miRNAs participating in this process. Furthermore, cellular respiration of POMC neurons treated with fatty acid-modified astrocytic exosomes is modified in a manner that suggests they are preparing for a possible respiratory stress by increasing their spare respiratory capacity and maximal respiration.

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Folliculin-interacting protein FNIP2 impacts on overweight and obesity through a polymorphism in a conserved 3' untranslated region

BACKGROUND

Overweight and obesity are defined by an anomalous or excessive fat accumulation that may compromise health. To find single-nucleotide polymorphisms (SNPs) influencing metabolic phenotypes associated with the obesity state, we analyze multiple anthropometric and clinical parameters in a cohort of 790 healthy volunteers and study potential associations with 48 manually curated SNPs, in metabolic genes functionally associated with the mechanistic target of rapamycin (mTOR) pathway.

RESULTS

We identify and validate rs2291007 within a conserved region in the 3'UTR of folliculin-interacting protein FNIP2 that correlates with multiple leanness parameters. The T-to-C variant represents the major allele in Europeans and disrupts an ancestral target sequence of the miRNA miR-181b-5p, thus resulting in increased FNIP2 mRNA levels in cancer cell lines and in peripheral blood from carriers of the C allele. Because the miRNA binding site is conserved across vertebrates, we engineered the T-to-C substitution in the endogenous Fnip2 allele in mice. Primary cells derived from Fnip2 C/C mice show increased mRNA stability, and more importantly, Fnip2 C/C mice replicate the decreased adiposity and increased leanness observed in human volunteers. Finally, expression levels of FNIP2 in both human samples and mice negatively associate with leanness parameters, and moreover, are the most important contributor in a multifactorial model of body mass index prediction.

CONCLUSIONS

We propose that rs2291007 influences human leanness through an evolutionarily conserved modulation of FNIP2 mRNA levels.

Author Correction: Identification and characterization of Cardiac Glycosides as senolytic compounds

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

SIRT1 enhances glucose tolerance by potentiating brown adipose tissue function

OBJECTIVE

SIRT1 has been proposed to be a key signaling node linking changes in energy metabolism to transcriptional adaptations. Although SIRT1 overexpression is protective against diverse metabolic complications, especially in response to high-fat diets, studies aiming to understand the etiology of such benefits are scarce. Here, we aimed to identify the key tissues and mechanisms implicated in the beneficial effects of SIRT1 on glucose homeostasis.

METHODS

We have used a mouse model of moderate SIRT1 overexpression, under the control of its natural promoter, to evaluate glucose homeostasis and thoroughly characterize how different tissues could influence insulin sensitivity.

RESULTS

Mice with moderate overexpression of SIRT1 exhibit better glucose tolerance and insulin sensitivity even on a low fat diet. Euglycemic-hyperinsulinemic clamps and in-depth tissue analyses revealed that enhanced insulin sensitivity was achieved through a higher brown adipose tissue activity and was fully reversed by housing the mice at thermoneutrality. SIRT1 did not influence brown adipocyte differentiation, but dramatically enhanced the metabolic transcriptional responses to β3-adrenergic stimuli in differentiated adipocytes.

CONCLUSIONS

Our work demonstrates that SIRT1 improves glucose homeostasis by enhancing BAT function. This is not consequent to an alteration in the brown adipocyte differentiation process, but as a result of potentiating the response to β3-adrenergic stimuli.

Therapeutic effect of γ-secretase inhibition in KrasG12V-driven non-small cell lung carcinoma by derepression of DUSP1 and inhibition of ERK

Here, we have investigated the role of the Notch pathway in the generation and maintenance of Kras(G12V)-driven non-small cell lung carcinomas (NSCLCs). We demonstrate by genetic means that γ-secretase and RBPJ are essential for the formation of NSCLCs. Of importance, pharmacologic treatment of mice carrying autochthonous NSCLCs with a γ-secretase inhibitor (GSI) blocks cancer growth. Treated carcinomas present reduced HES1 levels and reduced phosphorylated ERK without changes in phosphorylated MEK. Mechanistically, we show that HES1 directly binds to and represses the promoter of DUSP1, encoding a dual phosphatase that is active against phospho-ERK. Accordingly, GSI treatment upregulates DUSP1 and decreases phospho-ERK. These data provide proof of the in vivo therapeutic potential of GSIs in primary NSCLCs.

Telomerase reverse transcriptase delays aging in cancer-resistant mice

Telomerase confers limitless proliferative potential to most human cells through its ability to elongate telomeres, the natural ends of chromosomes, which otherwise would undergo progressive attrition and eventually compromise cell viability. However, the role of telomerase in organismal aging has remained unaddressed, in part because of the cancer-promoting activity of telomerase. To circumvent this problem, we have constitutively expressed telomerase reverse transcriptase (TERT), one of the components of telomerase, in mice engineered to be cancer resistant by means of enhanced expression of the tumor suppressors p53, p16, and p19ARF. In this context, TERT overexpression improves the fitness of epithelial barriers, particularly the skin and the intestine, and produces a systemic delay in aging accompanied by extension of the median life span. These results demonstrate that constitutive expression of Tert provides antiaging activity in the context of a mammalian organism.