Specific Jak3 Downregulation in Lymphocytes Impairs γc Cytokine Signal Transduction and Alleviates Antigen-driven Inflammation In Vivo

Jak3, one of the four members comprising the Jak family of cytosolic tyrosine kinases, has emerged as a promising target for nontoxic immunotherapies. Although a number of Jak inhibitors has already demonstrated efficacy, they suffer from secondary effects apparently associated to their pan-Jak activity. However, whether selective Jak3 inhibition would afford therapeutic efficacy remains unclear. To address this question we have investigated the immunosuppressive potential of selective Jak3 intervention in lymphocytes using RNA interference (RNAi) technology in vitro and in vivo. Using synthetic small interference RNA (siRNA) sequences we achieved successful transfections into human and mouse primary T lymphocytes. We found that Jak3 knockdown was sufficient to impair not only interleukin-2 (IL-2) and T cell receptor (TCR)-mediated cell activation in vitro, but also antigen-triggereds welling, inflammatory cell infiltration, and proinflammatory cytokine raise in vivo. Furthermore, Jak1 (which mediates gamma c cytokine signaling in conjunction with Jak3) cosilencing did not provide higher potency to the aforementioned immunosuppressant effects. Our data provides direct evidences indicating that Jak3 protein plays an important role in gamma c cytokine and antigen-mediated T cell activation and modulates Th1-mediated inflammatory disorders, all in all highlighting its potential as a target in immunosuppressive therapies

Hypothalamic miRNAs: emerging roles in energy balance control

The hypothalamus is a crucial central nervous system area controlling appetite, body weight and metabolism. It consists in multiple neuronal types that sense, integrate and generate appropriate responses to hormonal and nutritional signals partly by fine-tuning the expression of specific batteries of genes. However, the mechanisms regulating these neuronal gene programmes in physiology and pathophysiology are not completely understood. MicroRNAs (miRNAs) are key regulators of gene expression that recently emerged as pivotal modulators of systemic metabolism. In this article we will review current evidence indicating that miRNAs in hypothalamic neurons are also implicated in appetite and whole-body energy balance control

Akkermansia muciniphila inversely correlates with the onset of inflammation, altered adipose tissue metabolism and metabolic disorders during obesity in mice

Recent evidence indicates that the gut microbiota plays a key role in the pathophysiology of obesity. Indeed, diet-induced obesity (DIO) has been associated to substantial changes in gut microbiota composition in rodent models. In the context of obesity, enhanced adiposity is accompanied by low-grade inflammation of this tissue but the exact link with gut microbial community remains unknown. In this report, we studied the consequences of high-fat diet (HFD) administration on metabolic parameters and gut microbiota composition over different periods of time. We found that Akkermansia muciniphila abundance was strongly and negatively affected by age and HFD feeding and to a lower extend Bilophila wadsworthia was the only taxa following an opposite trend. Different approaches, including multifactorial analysis, showed that these changes in Akkermansia muciniphila were robustly correlated with the expression of lipid metabolism and inflammation markers in adipose tissue, as well as several circulating parameters (i.e., glucose, insulin, triglycerides, leptin) from DIO mice. Thus, our data shows the existence of a link between gut Akkermansia muciniphila abundance and adipose tissue homeostasis on the onset of obesity, thus reinforcing the beneficial role of this bacterium on metabolism

Hypothalamic pregnenolone mediates recognition memory in the context of metabolic disorders

Obesity and type 2 diabetes are associated with cognitive dysfunction. Because the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggest that pregnenolone’s effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically unhealthy patients with obesity. Our data reveal an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders.This work was supported by the Swiss National Science Foundation (no.176206; NCCR Synapsy grant no.185897) to C.S.; the European Research Council (ERC) advanced grant SYNEME to J.C.B.; Instituto de Salud Carlos III (ISCIII)—Fondo Europeo de Desarrollo Regional (FEDER) (PI17/00296), RETICs Oftared (RD16/0008/0014), and Generalitat de Catalunya (2017SGR737) to X.G.; Ministerio de Ciencia e Innovación (BFU2017-83317-P) to D.S.; Ministerio de Economia, Industria y Competitividad, Maria de Maeztu (MDM-2017-0729) to Institut de Neurociencies, Universitat de Barcelona; ISCIII-FEDER (PI14/01126, PI17/01019), the National Institutes of Health (NIA grants 1R01AG056850-01A1, R21AG056974, and R01AG061566), Fundació La Marató de TV3 (20141210), and Generalitat de Catalunya (SLT006/17/00119) to J.F.; ISCIII-FEDER (PI17/00279 and PI20/0042), Fundació La Marató de TV3 (201614.31), and Generalitat de Catalunya (SLT008/18/00127) to A.J.; Plan Nacional de I+D funded by the Agencia Estatal de Investigación (AEI) and FEDER (PID2019-111669RB-I00 and PID2020-115055RB-I00), CIBEREHD, the center grant P50AA011999 Southern California Research Center for ALPD and Cirrhosis funded by NIAAA/NIH, Generalitat de Catalunya (SGR-2017-1112), the European Cooperation in Science & Technology (COST) ACTION CA17112, FUNDACIÓN BBVA (“ER stress-mitochondrial cholesterol axis in obesity-associated insulin resistance and comorbidities”), and Red Nacional 2018-102799-T de Enfermedades Metabólicas y Cáncer and Fundació La Marató de TV3 (201916/31) to J.C.F.-C.; and ERC consolidator grant MITOSENSING (725004), ISCIII-FEDER (PI16/00963), “la Caixa” Foundation (ID100010434) under agreement LCF/PR/HR19/52160016, and CERCA Programme/Generalitat de Catalunya to M.C. D.A. is supported by ISCIII (INT19/00016) and Generalitat de Catalunya PERIS program (SLT006/17/125), A.P. is supported by Hospital Clínic de Barcelona (“Ajut Josep Font”), A.O. is supported by a Miguel Servet contract (CP19/00083) from ISCIII-FEDER, and R.H.-T. is supported by a Marie Skłodowska-Curie Action fellowship (H2020-MSCA-IF) and NEUROPREG (891247). S.R. is a recipient of Juan de la Cierva Formación (FJCI-2016-28911) and Incorporación (IJC2018-037341-I) programs from the Spanish Ministry of Science and Innovation. This work was carried out in part at Esther Koplowitz Centre.Peer reviewe

Reduced alfa-MSH underlies hypothalamic ER-stress-induced hepatic gluconeogenesis

Alterations in ER homeostasis have been implicated in the pathophysiology of obesity and type-2 diabetes (T2D). Acute ER stress induction in the hypothalamus produces glucose metabolism perturbations. However, the neurobiological basis linking hypothalamic ER stress with abnormal glucose metabolism remains unknown. Here, we report that genetic and induced models of hypothalamic ER stress are associated with alterations in systemic glucose homeostasis due to increased gluconeogenesis (GNG) independent of body weight changes. Defective alpha melanocyte-stimulating hormone (α-MSH) production underlies this metabolic phenotype, as pharmacological strategies aimed at rescuing hypothalamic α-MSH content reversed this phenotype at metabolic and molecular level. Collectively, our results posit defective α-MSH processing as a fundamental mediator of enhanced GNG in the context of hypothalamic ER stress and establish α-MSH deficiency in proopiomelanocortin (POMC) neurons as a potential contributor to the pathophysiology of T2D

Mitochondrial cristae-remodeling protein OPA1 in POMC neurons couples Ca2+ homeostasis with adipose tissue lipolysis

© 2021 The Authors.Appropriate cristae remodeling is a determinant of mitochondrial function and bioenergetics and thus represents a crucial process for cellular metabolic adaptations. Here, we show that mitochondrial cristae architecture and expression of the master cristae-remodeling protein OPA1 in proopiomelanocortin (POMC) neurons, which are key metabolic sensors implicated in energy balance control, is affected by fluctuations in nutrient availability. Genetic inactivation of OPA1 in POMC neurons causes dramatic alterations in cristae topology, mitochondrial Ca2+ handling, reduction in alpha-melanocyte stimulating hormone (α-MSH) in target areas, hyperphagia, and attenuated white adipose tissue (WAT) lipolysis resulting in obesity. Pharmacological blockade of mitochondrial Ca2+ influx restores α-MSH and the lipolytic program, while improving the metabolic defects of mutant mice. Chemogenetic manipulation of POMC neurons confirms a role in lipolysis control. Our results unveil a novel axis that connects OPA1 in POMC neurons with mitochondrial cristae, Ca2+ homeostasis, and WAT lipolysis in the regulation of energy balance.This work was supported by Agencia Estatal de Investigación y Fondo Social Europeo, Proyecto BFU2016-76973-R FEDER (C.V.A.); AG052005, AG052986, AG051459, DK111178 from NIH and NKFI-KKP-126998 from Hungarian National Research, Development and Innovation Office (T.L.H.); MR/P009824/2 from Medical Research Council UK (G.D.); and Ayudas Fundación BBVA a Investigadores y Creadores Culturales (2015), European Research Council (ERC) under the European Union’s Horizon 2020 Research And Innovation Program (grant agreement 725004) and CERCA Programme/Generalitat de Catalunya (M.C.). A.O. is supported by a Miguel Servet contract (CP19/00083) from Instituto de Salud Carlos III and co-financed by FEDER

Mitochondrial cristae-remodeling protein OPA1 in POMC neurons couples Ca2+ homeostasis with adipose tissue lipolysis

Appropriate cristae remodeling is a determinant of mitochondrial function and bioenergetics and thus represents a crucial process for cellular metabolic adaptations. Here, we show that mitochondrial cristae architecture and expression of the master cristae-remodeling protein OPA1 in proopiomelanocortin (POMC) neurons, which are key metabolic sensors implicated in energy balance control, is affected by fluctuations in nutrient availability. Genetic inactivation of OPA1 in POMC neurons causes dramatic alterations in cristae topology, mitochondrial Ca2+ handling, reduction in alpha-melanocyte stimulating hormone (α-MSH) in target areas, hyperphagia, and attenuated white adipose tissue (WAT) lipolysis resulting in obesity. Pharmacological blockade of mitochondrial Ca2+ influx restores α-MSH and the lipolytic program, while improving the metabolic defects of mutant mice. Chemogenetic manipulation of POMC neurons confirms a role in lipolysis control. Our results unveil a novel axis that connects OPA1 in POMC neurons with mitochondrial cristae, Ca2+ homeostasis, and WAT lipolysis in the regulation of energy balance

Hypothalamic pregnenolone mediates recognition memory in the context of metabolic disorders

Obesity and type-2 diabetes are associated with cognitive dysfunction. Since the hypothalamus is implicated in energy balance control and memory disorders, we hypothesized that specific neurons in this brain region are at the interface of metabolism and cognition. Acute obesogenic diet administration in mice impaired recognition memory due to defective production of the neurosteroid-precursor pregnenolone in the hypothalamus. Genetic interference with pregnenolone synthesis by Star deletion in hypothalamic POMC, but not AgRP neurons, deteriorated recognition memory independently of metabolic disturbances. Our data suggested that pregnenolone's effects on cognitive function were mediated via an autocrine mechanism on POMC neurons, influencing hippocampal long-term potentiation. The relevance of central pregnenolone on cognition was also confirmed in metabolically-unhealthy obese patients. Our data reveals an unsuspected role for POMC neuron-derived neurosteroids in cognition. These results provide the basis for a framework to investigate new facets of POMC neuron biology with implications for cognitive disorders

Specific Jak3 Downregulation in Lymphocytes Impairs γc Cytokine Signal Transduction and Alleviates Antigen-driven Inflammation In Vivo

Jak3, one of the four members comprising the Jak family of cytosolic tyrosine kinases, has emerged as a promising target for nontoxic immunotherapies. Although a number of Jak inhibitors has already demonstrated efficacy, they suffer from secondary effects apparently associated to their pan-Jak activity. However, whether selective Jak3 inhibition would afford therapeutic efficacy remains unclear. To address this question we have investigated the immunosuppressive potential of selective Jak3 intervention in lymphocytes using RNA interference (RNAi) technology in vitro and in vivo. Using synthetic small interference RNA (siRNA) sequences we achieved successful transfections into human and mouse primary T lymphocytes. We found that Jak3 knockdown was sufficient to impair not only interleukin-2 (IL-2) and T cell receptor (TCR)-mediated cell activation in vitro, but also antigen-triggereds welling, inflammatory cell infiltration, and proinflammatory cytokine raise in vivo. Furthermore, Jak1 (which mediates γc cytokine signaling in conjunction with Jak3) cosilencing did not provide higher potency to the aforementioned immunosuppressant effects. Our data provides direct evidences indicating that Jak3 protein plays an important role in γc cytokine and antigen-mediated T cell activation and modulates Th1-mediated inflammatory disorders, all in all highlighting its potential as a target in immunosuppressive therapies