Modulation of transforming growth factor-β/follistatin signaling and white adipose browning: therapeutic implications for obesity related disorders

Crosstalk with lung fibroblasts shapes the growth and therapeutic response of mesothelioma cells

Mesothelioma is an aggressive cancer of the mesothelial layer associated with an extensive fibrotic response. The latter is in large part mediated by cancer-associated fibroblasts which mediate tumour progression and poor prognosis. However, understanding of the crosstalk between cancer cells and fibroblasts in this disease is mostly lacking. Here, using co-cultures of patient-derived mesothelioma cell lines and lung fibroblasts, we demonstrate that fibroblast activation is a self-propagated process producing a fibrotic extracellular matrix (ECM) and triggering drug resistance in mesothelioma cells. Following characterisation of mesothelioma cells/fibroblasts signalling crosstalk, we identify several FDA-approved targeted therapies as far more potent than standard-of-care Cisplatin/Pemetrexed in ECM-embedded co-culture spheroid models. In particular, the SRC family kinase inhibitor, Saracatinib, extends overall survival well beyond standard-of-care in a mesothelioma genetically-engineered mouse model. In short, we lay the foundation for the rational design of novel therapeutic strategies targeting mesothelioma/fibroblast communication for the treatment of mesothelioma patients.

Plasma Myostatin Increases with Age in Male Youth and Negatively Correlates with Vitamin D in Severe Pediatric Obesity

Obesity already causes non-communicable diseases during childhood, but the mechanisms of disease development are insufficiently understood. Myokines such as myostatin and irisin are muscle-derived factors possibly involved in obesity-associated diseases. This explorative study aims to investigate whether myostatin and irisin are associated with metabolic parameters, including the vitamin D status in pediatric patients with severe obesity. Clinical, anthropometric and laboratory data from 108 patients with severe obesity (>97th percentile) aged between 9 and 19 years were assessed. Myostatin, its antagonist follistatin, and irisin, were measured from plasma by ELISA. Myostatin concentrations, particularly in males, positively correlated with age and pubertal stage, as well as metabolic parameters such as insulin resistance. Irisin concentrations correlated positively with HDL and negatively with LDL cholesterol values. For follistatin, the associations with age and pubertal stage were inverse. Strikingly, a negative correlation of myostatin with serum vitamin D levels was observed that remained significant after adjusting for age and pubertal stage. In conclusion, there is an independent association of low vitamin D and elevated myostatin levels. Further research may focus on investigating means to prevent increased myostatin levels in interventional studies, which might open several venues to putative options to treat and prevent obesity-associated diseases.

The Gut Microbiota Metabolite Succinate Promotes Adipose Tissue Browning in Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease [CD] is associated with complex microbe-host interactions, involving changes in microbial communities, and gut barrier defects, leading to the translocation of microorganisms to surrounding adipose tissue [AT]. We evaluated the presence of beige AT depots in CD and questioned whether succinate and/or bacterial translocation promotes white-to-beige transition in adipocytes.

METHODS

Visceral [VAT] and subcutaneous [SAT] AT biopsies, serum and plasma were obtained from patients with active [n = 21] or inactive [n = 12] CD, and from healthy controls [n = 15]. Adipose-derived stem cells [ASCs] and AT macrophages [ATMs] were isolated from VAT biopsies.

RESULTS

Plasma succinate levels were significantly higher in patients with active CD than in controls and were intermediate in those with inactive disease. Plasma succinate correlated with the inflammatory marker high-sensitivity C-reactive protein. Expression of the succinate receptor SUCNR1 was higher in VAT, ASCs and ATMs from the active CD group than from the inactive or control groups. Succinate treatment of ASCs elevated the expression of several beige AT markers from controls and from patients with inactive disease, including uncoupling protein-1 [UCP1]. Notably, beige AT markers were prominent in ASCs from patients with active CD. Secretome profiling revealed that ASCs from patients with active disease secrete beige AT-related proteins, and co-culture assays showed that bacteria also trigger the white-to-beige switch of ASCs from patients with CD. Finally, AT depots from patients with CD exhibited a conversion from white to beige AT together with high UCP1 expression, which was corroborated by in situ thermal imaging analysis.

CONCLUSIONS

Succinate and bacteria trigger white-to-beige AT transition in CD. Understanding the role of beige AT in CD might aid in the development of therapeutic or diagnostic interventions.

Role of MiR-325-3p in the Regulation of CFL2 and Myogenic Differentiation of C2C12 Myoblasts

Skeletal myogenesis is required to maintain muscle mass and integrity, and impaired myogenesis is causally linked to the etiology of muscle wasting. Recently, it was shown that excessive uptake of saturated fatty acids (SFA) plays a significant role in the pathogenesis of muscle wasting. Although microRNA (miRNA) is implicated in the regulation of myogenesis, the molecular mechanism whereby SFA-induced miRNAs impair myogenic differentiation remains largely unknown. Here, we investigated the regulatory roles of miR-325-3p on CFL2 expression and myogenic differentiation in C2C12 myoblasts. PA impeded myogenic differentiation, concomitantly suppressed CFL2 and induced miR-325-3p. Dual-luciferase analysis revealed that miR-325-3p directly targets the 3'UTR of CFL2, thereby suppressing the expression of CFL2, a crucial factor for actin dynamics. Transfection with miR-325-3p mimic resulted in the accumulation of actin filaments (F-actin) and nuclear Yes-associated protein (YAP) in myoblasts and promoted myoblast proliferation and cell cycle progression. Consequently, miR-325-3p mimic significantly attenuated the expressions of myogenic factors and thereby impaired the myogenic differentiation of myoblasts. The roles of miR-325-3p on CFL2 expression, F-actin modulation, and myogenic differentiation suggest a novel miRNA-mediated regulatory mechanism of myogenesis and PA-inducible miR-325-3p may be a critical mediator between obesity and muscle wasting.

Inflammatory Signaling and Brown Fat Activity

Obesity is characterized by a state of chronic inflammation in adipose tissue mediated by the secretion of a range of inflammatory cytokines. In comparison to WAT, relatively little is known about the inflammatory status of brown adipose tissue (BAT) in physiology and pathophysiology. Because BAT and brown/beige adipocytes are specialized in energy expenditure they have protective roles against obesity and associated metabolic diseases. BAT appears to be is less susceptible to developing inflammation than WAT. However, there is increasing evidence that inflammation directly alters the thermogenic activity of brown fat by impairing its capacity for energy expenditure and glucose uptake. The inflammatory microenvironment can be affected by cytokines secreted by immune cells as well as by the brown adipocytes themselves. Therefore, pro-inflammatory signals represent an important component of the thermogenic potential of brown and beige adipocytes and may contribute their dysfunction in obesity.

In utero Androgen Excess: A Developmental Commonality Preceding Polycystic Ovary Syndrome?

In utero androgen excess reliably induces polycystic ovary syndrome (PCOS)-like reproductive and metabolic traits in female monkeys, sheep, rats, and mice. In humans, however, substantial technical and ethical constraints on fetal sampling have curtailed safe, pathogenic exploration during gestation. Evidence consistent with in utero origins for PCOS in humans has thus been slow to amass, but the balance now leans toward developmental fetal origins. Given that PCOS is familial and highly heritable, difficulties encountered in discerning genetic contributions to PCOS pathogenesis are puzzling and, to date, accounts for <10% of PCOS presentations. Unaccounted heritability notwithstanding, molecular commonality in pathogenic mechanisms is emerging, suggested by co-occurrence at the same gene loci of (1) PCOS genetic variants (PCOS women), (2) epigenetic alterations in DNA methylation (PCOS women), and (3) bioinformatics, gene networks-identified, epigenetic alterations in DNA methylation (female rhesus monkeys exposed to testosterone (T) in utero). In addition, naturally occurring hyperandrogenism in female monkeys singles out individuals with PCOS-like reproductive and metabolic traits accompanied by somatic biomarkers of in utero T exposure. Such phenotypic and molecular convergence between highly related species suggests not only dual genetic and epigenetic contributions to a developmental origin of PCOS but also common molecular pathogenesis extending beyond humans.

Hyperandrogenic origins of polycystic ovary syndrome - implications for pathophysiology and therapy

INTRODUCTION

Polycystic ovary syndrome (PCOS) diagnosis comprises combinations of female hyperandrogenism, menstrual irregularity and polycystic ovaries. While it is a familial and highly prevalent endocrine disorder, progress towards a cure is hindered by absence of a definitive pathogenic mechanism and lack of an animal model of naturally occurring PCOS.

AREAS COVERED

These include an overview of PCOS and its potential etiology, and an examination of insights gained into its pathogenic origins. Animal models derived from experimentally-induced hyperandrogenism during gestation, or from naturally-occurring PCOS-like traits, most reliably demonstrate reproductive, neuroendocrine and metabolic pathogenesis.

EXPERT OPINION

Genetic studies, while identifying at least 17 PCOS risk genes, account for <10% of women with PCOS. A number of PCOS risk genes involve regulation of gonadotropin secretion or action, suggesting a reproductive neuroendocrine basis for PCOS pathogenesis. Consistent with this notion, a number of animal models employing fetal androgen excess demonstrate epigenetic induction of PCOS-like traits, including reproductive neuroendocrine and metabolic dysfunction. Monkey models are most comprehensive, while mouse models provide molecular insight, including identifying the androgen receptor, particularly in neurons, as mediating androgen-induced PCOS-like programming. Naturally-occurring female hyperandrogenism is also demonstrated in monkeys. Animal models are poised to delineate molecular gateways to PCOS pathogenesis.