"Effect of time-restricted feeding on high-fat diet-induced metabolic dysfunction in Drosophila melanogaster".

BACKGROUND: Metabolic alterations associated with obesity have been related to chronodisruption i.e., the desynchronization of molecular clocks that regulate circadian rhythms. The search for tools that improve the dietary treatment of obesity has recently focused on behaviors related to chronodisruption, and intermittent fasting is increasingly gaining interest. Studies in animal models have identified the benefits of time-restricted feeding (TRF) on metabolic alterations associated with changes in circadian rhythms induced by a high-fat diet. We aimed to evaluate the effect of TRF in flies with metabolic damage and chronodisruption. METHODS: Using high-fat diet fed Drosophila melanogaster as a model of metabolic damage and chronodisruption, we determined the impact of 12-h TRF on metabolic and molecular markers. Flies with metabolic dysfunction were switched to a control diet and randomly assigned to Ad libitum or a TRF regimen for seven days. We evaluated total triglyceride content, glycemia, weight, and 24 h mRNA expression rhythms of Nlaz (insulin resistance marker), clock genes (circadian rhythm molecular markers), and the neuropeptide Cch-amide2. RESULTS: Flies with metabolic damage that received TRF showed lower total triglyceride content, Nlaz expression, circulating glucose, and weight compared to Ad libitum. We observed the recovery of some of the high-fat diet-induced alterations in the amplitude of the circadian rhythm, particularly in the peripheral clock. CONCLUSIONS: TRF produced a partial reversal of metabolic dysfunction and chronodisruption of circadian cycles. GENERAL SIGNIFICANCE: TRF could be a useful tool to help to ameliorate metabolic and chronobiologic damage induced by a high-fat diet.

Secretory Factors from Calcium-Sensing Receptor-Activated SW872 Pre-Adipocytes Induce Cellular Senescence and A Mitochondrial Fragmentation-Mediated Inflammatory Response in HepG2 Cells.

Adipose tissue inflammation in obesity has a deleterious impact on organs such as the liver, ultimately leading to their dysfunction. We have previously shown that activation of the calcium-sensing receptor (CaSR) in pre-adipocytes induces TNF-α and IL-1ß expression and secretion; however, it is unknown whether these factors promote hepatocyte alterations, particularly promoting cell senescence and/or mitochondrial dysfunction. We generated conditioned medium (CM) from the pre-adipocyte cell line SW872 treated with either vehicle (CMveh) or the CaSR activator cinacalcet 2 µM (CMcin), in the absence or presence of the CaSR inhibitor calhex 231 10 µM (CMcin+cal). HepG2 cells were cultured with these CM for 120 h and then assessed for cell senescence and mitochondrial dysfunction. CMcin-treated cells showed increased SA-ß-GAL staining, which was absent in TNF-α- and IL-1ß-depleted CM. Compared to CMveh, CMcin arrested cell cycle, increased IL-1ß and CCL2 mRNA, and induced p16 and p53 senescence markers, which was prevented by CMcin+cal. Crucial proteins for mitochondrial function, PGC-1α and OPA1, were decreased with CMcin treatment, concomitant with fragmentation of the mitochondrial network and decreased mitochondrial transmembrane potential. We conclude that pro-inflammatory cytokines TNF-α and IL-1ß secreted by SW872 cells after CaSR activation promote cell senescence and mitochondrial dysfunction, which is mediated by mitochondrial fragmentation in HepG2 cells and whose effects were reversed with Mdivi-1. This investigation provides new evidence about the deleterious CaSR-induced communication between pre-adipocytes and liver cells, incorporating the mechanisms involved in cellular senescence.

Deleterious liver-adipose crosstalk in obesity: Hydroethanolic extract of Lampaya medicinalis Phil. (Verbenaceae) counteracts fatty acid-induced fibrotic marker expression in human hepatocytes.

Elevated circulating fatty acids in obesity may induce hepatic steatosis, leading to liver inflammation, fibrosis and nonalcoholic fatty liver disease (NAFLD). On the other hand, impaired communication between hepatocytes and adipose tissue (AT) in obesity influences adipose lipolysis and fibrosis, negatively affecting metabolic function. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in Chilean folk medicine to treat inflammatory diseases. Hydroethanolic extract of lampaya (HEL) contains flavonoids that may explain its anti-inflammatory effect, but it is unknown whether HEL modulates fibrogenic processes in hepatocytes. We studied lipolysis and expression of fibrosis markers after exposure of visceral AT explants from subjects with obesity to HepG2-secreted factors. In addition, we evaluated the effect of HEL on palmitic acid (PA, C16:0) and oleic acid (OA; C18:1)-induced fibrotic marker expression in HepG2 hepatocytes. Results: Exposure to HepG2-secreted factors increased visceral AT lipolysis and expression of CTGF and collagen I. Exposure to OA/PA elevated collagen I, CTGF, fibronectin, α-smooth muscle actin, MMP-2 and MMP-9 expression in HepG2 cells, and these effects were prevented by HEL co-treatment. Conclusion: HEL effect counteracting OA/PA-induced fibrotic marker expression in HepG2 hepatocytes may represent a preventive approach against hepatic fibrosis and deleterious liver-adipose crosstalk in obesity.

The Adipocyte-Macrophage Relationship in Cancer: A Potential Target for Antioxidant Therapy.

Obesity has emerged as a major public health concern with a staggering 39% worldwide prevalence as of 2021. Given the magnitude of the problem and considering its association with chronic low-grade systemic inflammation, it does not come as a surprise that obesity is now considered one of the major risk factors for the development of several chronic diseases, such as diabetes, cardiovascular problems, and cancer. Adipose tissue dysfunction in obesity has taken center stage in understanding how changes in its components, particularly adipocytes and macrophages, participate in such processes. In this review, we will initially focus on how changes in adipose tissue upon excess fat accumulation generate endocrine signals that promote cancer development. Moreover, the tumor microenvironment or stroma, which is also critical in cancer development, contains macrophages and adipocytes, which, in reciprocal paracrine communication with cancer cells, generate relevant signals. We will discuss how paracrine signaling in the tumor microenvironment between cancer cells, macrophages, and adipocytes favors cancer development and progression. Finally, as reactive oxygen species participate in many of these signaling pathways, we will summarize the information available on how antioxidants can limit the effects of endocrine and paracrine signaling due to dysfunctional adipose tissue components in obesity.

Assessment of a consensus definition of obesity and metabolic health phenotypes in children at different pubertal stages.

Not all individuals with obesity develop metabolic complications, which has brought about the concepts of metabolically healthy and unhealthy obesity (MHO/MUO). However, inconsistent definitions of these conditions have limited their understanding. We assessed whether a recently-proposed consensus definition for MHO/MUO correlates with adiposity and reflects metabolic risk parameters during puberty. Low-middle income children from the Growth and Obesity Cohort Study (Santiago, Chile) were included (n = 949; 1692 visits at Tanner (T)2, T4 and/or one-year post menarche (1YPM)). Anthropometry, body composition and metabolic parameters were compared between MUO and MHO, and also in children without obesity. The risk for presenting MUO phenotype was significantly elevated with higher waist-height ratio (T2), zBMI (T2, T4), trunk fat, and C-reactive protein (T4). Elevated cardiometabolic indices were important predictors of the "unhealthy" phenotype allocation in children with or without obesity. Our observations suggest that the consensus definition in children at T2, T4 and 1YPM reflects metabolic risk and central obesity. Metabolic health phenotype allocation by this equation enables easy detection of risk factors that call for action to prevent long-term metabolic derangements in children with obesity and, importantly, also those without obesity.

Efecto del extracto hidroalcohólico de la planta Lampaya medicinalis Phil . sobre marcadores inflamación inducidos por ácidos grasos en hepatocitos humanos HepG2

RESUMEN Introducción: la enfermedad de hígado graso no alcohólico (EHGNA) se caracteriza por la acumulación de gotas lipídicas (GL) y sobre expresión de la proteína de GL Perilipina 1 (PLIN1) en los hepatocitos. En su patogénesis y progresión participan NF-ĸB, caspasa-1 y citoquinas proinflamatorias como IL-1β. La medicina popular del norte de Chile utiliza la planta Lampaya medicinalis Phil. (Verbenaceae) contra enfermedades. Objetivo: evaluar el efecto de un extracto hidroalcohólico de lampaya (EHL) sobre la expresión de marcadores inflamatorios y proteínas asociadas a las GL en hepatocitos tratados con ácidos grasos. Métodos: se incubó hepatocitos HepG2 con 0,66 mM de ácido oleico (AO) y 0,33 mM de ácido palmítico (AP) por 24 o 48 horas en presencia o no de EHL. Se evaluó la expresión proteica de NF-ĸB, PLIN1 y caspasa-1 por Western blot y la expresión de ARNm de IL-1β por qPCR. Resultados: los hepatocitos tratados por 48 h con AO/AP mostraron un aumento en la expresión de IL-1β que fue revertido por la co-incubación con EHL. Conclusión: estos antecedentes aportan nueva evidencia respecto a la actividad biológica del EHL en un modelo de alteraciones metabólicas e inflamatorias, asociadas a la EHGNA, inducidas por AO/AP en hepatocitos humanos.

ABSTRACT Introduction: Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of lipid droplets (LD) and overexpression of the LD-associated protein Perilipin 1 (PLIN1). NF-ĸB, caspase-1 and proinflammatory cytokine such as IL-1β participate in the pathogenesis and progression of NAFLD. Traditional medicine in northern Chile uses the plant Lampaya medicinalis Phil. (Verbenaceae) against diseases. Objective: To evaluate the effect of a hydroalcoholic extract of lampaya (HEL) on the expression of inflammatory markers and LD-associated proteins in hepatocytes treated with fatty acids. Methods: HepG2 hepatocytes were incubated with 0.66 mM oleic acid (OA) and 0.33 mM palmitic acid (PA) for 24 or 48 h in the presence or not of HEL. The protein expression of NF-ĸB, PLIN1 and caspase-1 was evaluated by Western blot while the mRNA expression of IL-1β was assessed by qPCR. Results: hepatocytes treated for 48 h with OA/AP showed an increase in IL-1β expression that was reversed by co-incubation with HEL. Conclusion: These antecedents provide new evidence regarding the biological activity of HEL in a model of metabolic and inflammatory alterations, associated with NAFLD, induced by OA/PA in human hepatocytes.

Lampaya Medicinalis Phil. decreases lipid-induced triglyceride accumulation and proinflammatory markers in human hepatocytes and fat body of Drosophila melanogaster.

BACKGROUND: Excess hepatic triglyceride (TG) accumulation (steatosis) commonly observed in obesity, may lead to non-alcoholic fatty liver disease (NAFLD). Altered regulation of intracellular lipid droplets (LD) and TG metabolism, as well as activation of JNK-mediated proinflammatory pathways may trigger liver steatosis-related disorders. Drosophila melanogaster is an animal model used for studying obesity and its associated disorders. In Drosophila, lipids and glycogen are stored in the fat body (FB), which resembles mammalian adipose tissue and liver. Dietary oversupply leads to obesity-related disorders, which are characterized by FB dysfunction. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in folk medicine of Chile to counteract inflammatory diseases. Hydroethanolic extract of lampaya (HEL) contains considerable amounts of flavonoids that may explain its anti-inflammatory effect. METHODS: We studied whether HEL affects palmitic acid (PA, C16:0) and oleic acid (OA; C18:1)-induced TG accumulation and proinflammatory marker content in HepG2 hepatocytes as well as impaired lipid storage and proinflammatory molecule expression in Drosophila melanogaster fed a high-fat diet (HFD). RESULTS: In HepG2 hepatocytes, exposure to OA/PA elevated TG content, FABP4, ATGL and DGAT2 expression, and the JNK proinflammatory pathway, as well as TNF-α and IL-6 production, while diminished FAS expression. These effects were prevented by HEL co-treatment. In Drosophila larvae fed a HFD, HEL prevented TG accumulation and downregulated proinflammatory JNK pathway activation. CONCLUSION: HEL effect counteracting OA/PA- and HFD-induced lipid accumulation and proinflammatory marker expression in HepG2 hepatocytes and Drosophila larvae may represent a preventive approach against hepatic steatosis and inflammation, associated to obesity and NAFLD.

Efecto del extracto hidroalcohólico de la planta Lampaya medicinalis Phil. (Verbenaceae) sobre la esteatosis inducida in vitro en hepatocitos humanos / Effect of the hydroalcoholic extract of the plant Lampaya medicinalis Phil. (Verbenaceae) on in vitro-induced steatosis in human hepatocytes

INTRODUCCIÓN: La enfermedad del hígado graso no alcohólico (EHGNA) es la forma más común de enfermedad hepática. A nivel celular se caracteriza por la acumulación de triglicéridos (TG) en forma de gotas lipídicas (GL) dando lugar a esteatosis e inflamación. Entre los factores relevantes para la síntesis de TG se encuentran las enzimas DGAT1/2 que catalizan la etapa final de la síntesis de TG, y la proteína FABP4 que transporta lípidos intracelulares y se expresa en modelos de enfermedad hepática dependiente de obesidad. Por otra parte, TNF-α es una reconocida citoquina involucrada en el proceso inflamatorio en la EHGNA. La medicina popular del norte de Chile ha utilizado la planta Lampaya medicinalis Phil. (Verbenaceae) para el tratamiento de algunas enfermedades inflamatorias. OBJETIVO: Evaluar el efecto de un extracto hidroalcóholico de lampaya (EHL) sobre la esteatosis y expresión de marcadores de inflamación en hepatocitos tratados con ácidos grasos. Diseño experimental: Estudio in vitro en cultivos de la línea celular humana HepG2 tratadas con ácido oleico (AO) y ácido palmítico (AP). MÉTODOS: Se incubó hepatocitos HepG2 con AO/AP por 24 horas en presencia o no de EHL. Se evaluó la presencia de GL y el contenido de TG intracelulares por Oil Red O y Nile Red, respectivamente. La expresión de DGAT1/2, FABP4 y TNF-α fue evaluada por qPCR. RESULTADOS: Los hepatocitos tratados con AO/AP mostraron un aumento en las GL y TG, así como una mayor expresión de DGAT2 en comparación al control. El cotratamiento con EHL revirtió los efectos inducidos por AO/AP. CONCLUSIONES: EHL revierte el incremento en las GL, TG y en la expresión de DGAT2 inducido por AO/AP en células HepG2. Estos hallazgos sugieren un efecto hepatoprotector de la Lampaya contra la esteatosis, y apoyarían su uso complementario en el tratamiento de patologías con componente inflamatorio como la EHGNA.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease. At the cellular level, it is characterized by the accumulation of triglycerides (TG) in the form of lipid droplets (LD), which leads to steatosis and inflammation. Among relevant factors for TG synthesis are the enzymes DGAT1/2 catalyzing the final stage of TG synthesis, and the protein FABP4 which transports intracellular lipids and is expressed in cell models of obesity-dependent liver disease. Additionally, TNF-α is a cytokine involved in the inflammatory process associated to NAFDL. Lampaya medicinalis Phil. (Verbenaceae) is a plant used in folk medicine in northern Chile to treat some inflammatory diseases. OBJECTIVE: To evaluate the effect of the hydroalcoholic extract of lampaya (HEL) on steatosis and the expression of inflammatory markers in hepatocytes treated with fatty acids. Study design: In vitro study in cultures of the human HepG2 cell line treated with oleic acid (OA) and palmitic acid (PA). METHODS: HepG2 hepatocytes were incubated with OA/PA for 24 hours in the presence and absence of HEL. The formation of LD and the accumulation of intracellular TG were assessed by Oil Red O and Nile Red, respectively. The expression of DGAT1/2, FABP4 and TNF-α was assessed by qPCR. RESULTS: The treatment with OA/PA increased the levels of LD and TG as well as the expression of DGAT2 in HepG2 hepatocytes compared to control cells. HEL cotreatment counteracted OA/PA-induced effects. CONCLUSIONS: HEL prevents the increase in LD and TG levels and DGAT2 expression induced by OA/PA in HepG2 cells. These findings suggest that lampaya may have a protective effect against hepatic steatosis, which would support its complementary use in the treatment of pathologies associated with inflammation, such as NAFLD.

Protective effect of the hydroalcoholic extract from Lampaya medicinalis Phil. (Verbenaceae) on palmitic acid- impaired insulin signaling in 3T3-L1 adipocytes.

BACKGROUND: Obesity is strongly associated with insulin resistance (IR). IR at the molecular level may be defined as a diminished activation of insulin signaling-related molecules (IRS-1/Akt/AS160) as well as reduced glucose uptake. Subject with obesity have elevated plasma levels of saturated fatty acids, such as palmitic acid (PA), which triggers insulin signaling disruption in vivo and in vitro. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in folk medicine of Northern Chile to counteract inflammatory diseases. Hydroethanolic extracts of lampaya (HEL) contain considerable amounts of flavonoids that may explain the biological activity of the plant. The aim of this study was to assess whether HEL exposure protects against PA-disrupted insulin signaling and glucose uptake in adipocytes. METHODS: Cytotoxicity of a range of HEL concentrations (0.01-10 µg/mL) was evaluated in 3T3-L1 adipocytes. Cells were exposed or not to 0.1 µg/mL of HEL before adding 0.65 mM PA or vehicle and incubated with 100 nM insulin (or vehicle) for 15 min. Phosphorylation of Tyr-IRS-1, Ser-Akt, Thr-AS160 was evaluated by Western blot. Glucose uptake was assessed using the 2-NBDG analogue. RESULTS: HEL was not cytotoxic at any concentration assessed. PA-induced reduction in insulin-stimulated phosphorylation of IRS-1, Akt and AS160 and glucose uptake were abolished by co-treatment with HEL. CONCLUSION: These findings give new insights about the effect of HEL ameliorating PA- impaired IRS-1/Akt/AS160 pathway and glucose uptake in adipocytes. More studies should focus on lampaya, since might represent a preventive approach in individuals whose circulating PA levels contribute to IR.

Calcium-Sensing Receptor in Adipose Tissue: Possible Association with Obesity-Related Elevated Autophagy.

Autophagy is upregulated in adipose tissue (AT) from people with obesity. We showed that activation of the calcium-sensing receptor (CaSR) elevates proinflammatory cytokines through autophagy in preadipocytes. Our aim is to understand the role of CaSR on autophagy in AT from humans with obesity. We determined mRNA and protein levels of CaSR and markers of autophagy by qPCR and western blot in human visceral AT explants or isolated primary preadipocytes (60 donors: 72% female, 23-56% body fat). We also investigated their association with donors' anthropometric variables. Donors' % body fat and CaSR mRNA expression in AT were correlated (r = 0.44, p < 0.01). CaSR expression was associated with mRNA levels of the autophagy markers atg5 (r = 0.37, p < 0.01), atg7 (r = 0.29, p < 0.05) and lc3b (r = 0.40, p < 0.01). CaSR activation increased becn and atg7 mRNA expression in AT. CaSR activation also upregulated LC3II by ~50%, an effect abolished by the CaSR inhibitor. Spermine (CaSR agonist) regulates LC3II through the ERK1/2 pathway. Structural equation model analysis suggests a link between donors' AT CaSR expression, AT autophagy and expression of Tumor Necrosis Factor alpha TNF-α. CaSR expression in visceral AT is directly associated with % body fat, and CaSR activation may contribute to obesity-related disruption in AT autophagy.

Hydroethanolic Extract of Lampaya Medicinalis Phil. (Verbenaceae) Decreases Proinflammatory Marker Expression in Palmitic Acid-exposed Macrophages.

BACKGROUND: Obesity is a major health problem associated with increased comorbidities, which are partially triggered by inflammation. Proinflammatory macrophage infiltration in adipose tissue of individuals with obesity increases chronic inflammation. Obesity is associated with elevated plasma levels of saturated fatty acids, such as palmitic acid (PA), which promotes inflammation in vivo and in vitro. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in the folk medicine of Northern Chile to counteract inflammation of rheumatic diseases. Hydroethanolic extract of lampaya (HEL) contains spectrophotometrically defined compounds that may contribute to the observed effect on inflammation. METHODS: We evaluated the phytochemical composition of HEL by high-performance liquid chromatography coupled to diode array detection (HPLC-DAD) and liquid chromatography-electrospray ionization- tandem mass spectrometry (LC-ESI-MS/MS). We assessed whether the exposure to HEL affects PA-induced expression of proinflammatory factors in THP-1 macrophages. RESULTS: HPLC-DAD and LC-ESI-MS/MS analyses showed the presence of considerable amounts of flavonoids in HEL. The PA-induced phosphorylation of the inflammatory pathway mediators IKK and NF-κB, as well as the elevated expression and secretion of proinflammatory cytokines (IL-6, TNF-α), were reduced in cells pre-exposed to HEL. CONCLUSION: These findings give new insights about the effect of HEL reducing IKK/NF-κB proinflammatory pathway, likely explained by the number of flavonoids contained in the extract. More studies would be needed to define the possible role of Lampaya as a preventive approach in subjects with obesity whose circulating PA might contribute to chronic inflammation.

Is Mitochondrial Dysfunction a Common Root of Noncommunicable Chronic Diseases?

Mitochondrial damage is implicated as a major contributing factor for a number of noncommunicable chronic diseases such as cardiovascular diseases, cancer, obesity, and insulin resistance/type 2 diabetes. Here, we discuss the role of mitochondria in maintaining cellular and whole-organism homeostasis, the mechanisms that promote mitochondrial dysfunction, and the role of this phenomenon in noncommunicable chronic diseases. We also review the state of the art regarding the preclinical evidence associated with the regulation of mitochondrial function and the development of current mitochondria-targeted therapeutics to treat noncommunicable chronic diseases. Finally, we give an integrated vision of how mitochondrial damage is implicated in these metabolic diseases.

Calcium sensing receptor activation in THP-1 macrophages triggers NLRP3 inflammasome and human preadipose cell inflammation.

Excess adipose tissue (AT) associates with inflammation and obesity-related diseases. We studied whether calcium-sensing receptor (CaSR)-mediated NLRP3 inflammasome activation in THP-1 macrophages elevates inflammation in LS14 preadipocytes, modeling deleterious AT cell crosstalk. THP-1 macrophages exposed to cinacalcet (CaSR activator, 2 µM, 4 h) showed elevated proinflammatory marker and NLRP3 inflammasome mRNA, pro-IL-1ß protein and caspase-1 activity, whereas preincubation with CaSR negative modulators prevented these effects. The key NLRP3 inflammasome component ASC was silenced (siRNA) in THP-1 cells, and inflammasome activation was evaluated (qPCR, Western blot, caspase-1 activity) or they were further cultured to obtain conditioned medium (CoM). Exposure of LS14 preadipocytes to CoM from cinacalcet-treated THP-1 elevated LS14 proinflammatory cytokine expression, which was abrogated by THP-1 inflammasome silencing. Thus, CaSR activation elevates THP-1-induced inflammation in LS14 preadipocytes, via macrophage NLRP3 inflammasome activation. Modulating CaSR activation may prevent deleterious proinflammatory cell crosstalk in AT, a promising approach in obesity-related metabolic disorders.

GDF-11 prevents cardiomyocyte hypertrophy by maintaining the sarcoplasmic reticulum-mitochondria communication.

Growth differentiation factor 11 (GDF11) is a novel factor with controversial effects on cardiac hypertrophy both in vivo and in vitro. Although recent evidence has corroborated that GDF11 prevents the development of cardiac hypertrophy, its molecular mechanism remains unclear. In our previous work, we showed that norepinephrine (NE), a physiological pro-hypertrophic agent, increases cytoplasmic Ca2+ levels accompanied by a loss of physical and functional communication between sarcoplasmic reticulum (SR) and mitochondria, with a subsequent reduction in the mitochondrial Ca2+ uptake and mitochondrial metabolism. In order to study the anti-hypertrophic mechanism of GDF11, our aim was to investigate whether GDF11 prevents the loss of SR-mitochondria communication triggered by NE. Our results show that: a) GDF11 prevents hypertrophy in cultured neonatal rat ventricular myocytes treated with NE. b) GDF11 attenuates the NE-induced loss of contact sites between both organelles. c) GDF11 increases oxidative mitochondrial metabolism by stimulating mitochondrial Ca2+ uptake. In conclusion, the GDF11-dependent maintenance of physical and functional communication between SR and mitochondria is critical to allow Ca2+ transfer between both organelles and energy metabolism in the cardiomyocyte and to avoid the activation of Ca2+-dependent pro-hypertrophic signaling pathways.

Author Correction: Caveolin-1 impairs PKA-DRP1-mediated remodelling of ER-mitochondria communication during the early phase of ER stress.

Following publication of the article, the authors wrote to point out the following mistake.

Caveolin-1 impairs PKA-DRP1-mediated remodelling of ER-mitochondria communication during the early phase of ER stress.

Close contacts between endoplasmic reticulum and mitochondria enable reciprocal Ca2+ exchange, a key mechanism in the regulation of mitochondrial bioenergetics. During the early phase of endoplasmic reticulum stress, this inter-organellar communication increases as an adaptive mechanism to ensure cell survival. The signalling pathways governing this response, however, have not been characterized. Here we show that caveolin-1 localizes to the endoplasmic reticulum-mitochondria interface, where it impairs the remodelling of endoplasmic reticulum-mitochondria contacts, quenching Ca2+ transfer and rendering mitochondrial bioenergetics unresponsive to endoplasmic reticulum stress. Protein kinase A, in contrast, promotes endoplasmic reticulum and mitochondria remodelling and communication during endoplasmic reticulum stress to promote organelle dynamics and Ca2+ transfer as well as enhance mitochondrial bioenergetics during the adaptive response. Importantly, caveolin-1 expression reduces protein kinase A signalling, as evidenced by impaired phosphorylation and alterations in organelle distribution of the GTPase dynamin-related protein 1, thereby enhancing cell death in response to endoplasmic reticulum stress. In conclusion, caveolin-1 precludes stress-induced protein kinase A-dependent remodelling of endoplasmic reticulum-mitochondria communication.

Autophagy mediates calcium-sensing receptor-induced TNFα production in human preadipocytes.

Obesity is a major current public health problem worldwide due to the severe co-morbid conditions that this disease entails. The development of obesity-related cardiometabolic disorders is in direct association with adipose tissue inflammation that leads to its functional impairment. Activation of the Calcium-Sensing Receptor (CaSR) in adipose tissue contributes to inflammation and adipose dysfunction. Autophagy, a process of cell component degradation, is closely related to inflammation in many diseases, however, whether autophagy is associated with CaSR-induced inflammation remains unknown. Using LS14 and SW872 preadipose cell lines as well as primary human preadipocytes, we show that CaSR activation with the allosteric activator cinacalcet induces autophagosome formation. Cinacalcet-induced LC3II content elevation was precluded by knockdown of the CaSR and enhanced by CaSR overexpression, indicating a specific effect. Autophagy inhibition using 3-methyladenine prevented CaSR-induced TNFα production, indicating that autophagy contributes to CaSR-induced inflammation in human preadipocytes. Our results suggest that modulation of CaSR-induced autophagy is an attractive target in obese inflamed adipose tissue, to prevent the development of diseases triggered by adipose dysfunction. We describe a novel mechanism and possible new target to modulate and prevent adipose inflammation and hence the resulting disease-generating adipose tissue dysfunction.

Autophagy and oxidative stress in non-communicable diseases: A matter of the inflammatory state?

Non-communicable diseases (NCDs), also known as chronic diseases, are long-lasting conditions that affect millions of people around the world. Different factors contribute to their genesis and progression; however they share common features, which are critical for the development of novel therapeutic strategies. A persistently altered inflammatory response is typically observed in many NCDs together with redox imbalance. Additionally, dysregulated proteostasis, mainly derived as a consequence of compromised autophagy, is a common feature of several chronic diseases. In this review, we discuss the crosstalk among inflammation, autophagy and oxidative stress, and how they participate in the progression of chronic diseases such as cancer, cardiovascular diseases, obesity and type II diabetes mellitus.

Efecto de la activación del receptor sensor de calcio sobre la expresión de genes lipogénicos en células HepG2 / Effect of calcium sensing receptor activation on lipogenic gene expression in HepG2 cells

Introduction: The Calcium Sensing Receptor (CaSR) is expressed in human fat cells, and its stimulation may be associated with adipose tissue dysfunction. The multisystemic character of obesity and the search of deepening the scope of the activation of CaSR in this disorder allows us to study the response of this protein in tissues that differ from adipose. Objective: To evaluate the effect of CaSR activation on the expression of lipogenic genes in a model of excess glucose and fatty acids in HepG2 human liver cells. Materials and methods: The effect of the calcimimetic cinacalcet (allosteric agonist of CaSR) on the content of triglycerides (fluorimetry) in a model of glucose supply and on the expression of lipogenic genes (qPCR) in hyperglycemia and hyperlipidemia conditions in the Liver cell line HepG2. Results: Cinacalcet, glucose (25 mM) and oleic acid (0.6 mM) did not affect cell viability. Activation of CaSR in the presence of glucose failed to increase the intracellular triglyceride content at 72 hours. Under these conditions, no response was observed for the factors coding for lipogenic genes (SREBP1c and FAS) at 24 hours of stimulation with cinacalcet in the liver cells. In the case of the over supply of fatty acids, the HepG2 cells did not show a variation in the gene expression of the DGAT enzymes after exposure to cinacalcet. Conclusion:Under conditions of glucose exposure, cinacalcet did not show a response in the triglyceride content, nor in the expression of genes related to hepatic lipogenesis. Therefore, stimulation of CaSR would not be associated with hepatic steatosis in HepG2 cells exposed to glucose.

Calcium-sensing receptor activates the NLRP3 inflammasome in LS14 preadipocytes mediated by ERK1/2 signaling.

The study of the mechanisms that trigger inflammation in adipose tissue is key to understanding and preventing the cardiometabolic consequences of obesity. We have proposed a model where activation of the G protein-coupled calcium sensing receptor (CaSR) leads to inflammation and dysfunction in adipose cells. Upon activation, CaSR can mediate the expression and secretion of proinflammatory factors in human preadipocytes, adipocytes, and adipose tissue explants. One possible pathway involved in CaSR-induced inflammation is the activation of the NLR family, pyrin domain-containing 3 (NLRP3) inflammasome, that promotes maturation and secretion of interleukin (IL)-1ß. The present work aimed to study whether CaSR mediates the activation of NLRP3 inflammasome in the human adipose cell model LS14. We assessed NLRP3 inflammasome priming and assembly after cinacalcet-induced CaSR activation and evaluated if this activation is mediated by downstream ERK1/2 signaling in LS14 preadipocytes. Exposure to 2 µM cinacalcet elevated mRNA expression of NLRP3, CASP-1, and IL-1ß, as well as an increase in pro-IL-1ß protein. In addition, CaSR activation triggered NLRP3 inflammasome assembly, as evidenced by a 25% increase in caspase-1 activity and 63% IL-1ß secretion. CaSR silencing (siRNA) abolished the effect. Upstream ERK pathway inhibition decreased cinacalcet-dependent activation of NLRP3 inflammasome. We propose CaSR-dependent NLRP3 inflammasome activation in preadipocytes through ERK signaling as a novel mechanism for the development of adipose dysfunction, that may favor the cardiovascular and metabolic consequences of obesity. To the best of our knowledge, this is the first report linking the inflammatory effect of CaSR to NLRP3 inflammasome induction in adipose cells.