Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models.

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

Fatty acids homeostasis during fasting predicts protection from chemotherapy toxicity.

Fasting exerts beneficial effects in mice and humans, including protection from chemotherapy toxicity. To explore the involved mechanisms, we collect blood from humans and mice before and after 36 or 24 hours of fasting, respectively, and measure lipid composition of erythrocyte membranes, circulating micro RNAs (miRNAs), and RNA expression at peripheral blood mononuclear cells (PBMCs). Fasting coordinately affects the proportion of polyunsaturated versus saturated and monounsaturated fatty acids at the erythrocyte membrane; and reduces the expression of insulin signaling-related genes in PBMCs. When fasted for 24 hours before and 24 hours after administration of oxaliplatin or doxorubicin, mice show a strong protection from toxicity in several tissues. Erythrocyte membrane lipids and PBMC gene expression define two separate groups of individuals that accurately predict a differential protection from chemotherapy toxicity, with important clinical implications. Our results reveal a mechanism of fasting associated with lipid homeostasis, and provide biomarkers of fasting to predict fasting-mediated protection from chemotherapy toxicity.

Effect of Lauric vs. Oleic Acid-Enriched Diets on Leptin Autoparacrine Signalling in Male Mice.

High-fat diets enriched with lauric acid (SOLF) do not enhance leptin production despite expanding white adipose tissue (WAT). Our study aimed at identifying the influence of SOLF vs. oleic acid-enriched diets (UOLF) on the autoparacrine effect of leptin and was carried out on eight-week-old mice consuming control chow, UOLF or SOLF. Phosphorylation of kinases integral to leptin receptor (LepR) signalling pathways (705Tyr-STAT3, 473Ser-Akt, 172Thr-AMPK), adipocyte-size distribution, fatty acid content, and gene expression were analyzed in WAT. SOLF enhanced basal levels of phosphorylated proteins but reduced the ability of leptin to enhance kinase phosphorylation. In contrast, UOLF failed to increase basal levels of phosphorylated proteins and did not modify the effect of leptin. Both SOLF and UOLF similarly affected adipocyte-size distribution, and the expression of genes related with adipogenesis and inflammation. WAT composition was different between groups, with SOLF samples mostly containing palmitic, myristic and lauric acids (>48% w/w) and UOLF WAT containing more than 80% (w/w) of oleic acid. In conclusion, SOLF appears to be more detrimental than UOLF to the autoparacrine leptin actions, which may have an impact on WAT inflammation. The effect of SOLF and UOLF on WAT composition may affect WAT biophysical properties, which are able to condition LepR signaling.

Cholecystokinin promotes functional expression of the aquaglycerol channel aquaporin 7 in adipocytes.

BACKGROUND AND PURPOSE: Cholecystokinin (CCK) promotes triglyceride storage and adiponectin production in white adipose tissue (WAT), suggesting that CCK modulates WAT homeostasis. Our goal was to investigate the role of CCK in regulating the expression and function of the aquaglycerol channel aquaporin 7 (AQP7), a protein that is pivotal for maintaining adipocyte homeostasis and preserving insulin responsiveness. EXPERIMENTAL APPROACH: The effect of the bioactive fragment of CCK, CCK-8, in regulating adipose AQP7 expression and glycerol efflux was assessed in rats as well as in preadipocytes. Moreover, the involvement of insulin receptors in the effects of CCK-8 was characterized in preadipocytes lacking insulin receptors. KEY RESULTS: CCK-8 induced AQP7 gene expression in rat WAT, concomitantly increasing plasma glycerol concentration. In isolated preadipocytes, CCK-8 also enhanced both AQP7 expression and glycerol leakage. The effects of CCK-8 were independent of the lipolysis rate, as CCK-8 failed to promote fatty acid release by adipocytes. In addition, CCK-8 did not enhance hormone sensitive lipase phosphorylation, which is the rate-limiting step of lipolysis. Moreover, the effects of CCK-8 were dependent on the activation of protein kinase B and PPARγ. Silencing insulin receptor expression inhibited CCK-8-induced Aqp7 expression in preadipocytes. Furthermore, insulin enhanced the effect of CCK-8. CONCLUSIONS AND IMPLICATIONS: CCK regulates AQP7 expression and function, and this effect is dependent on insulin. Accordingly, CCK receptor agonists could be suitable for preserving and improving insulin responsiveness in WAT.

Transient metabolic improvement in obese mice treated with navitoclax or dasatinib/quercetin.

Senescent cells accumulate with obesity in the white adipose tissue of mice and humans. These senescent cells enhance the pro-inflammatory environment that, with time, contributes to the onset of glucose intolerance and type 2 diabetes. Glucose intolerance in mouse models of obesity has been successfully reversed by the elimination of senescent cells with the senolytic compounds navitoclax or the combination of dasatinib and quercetin (D/Q). In this work, we generated obese mice by high-fat diet feeding, and treated them with five consecutive cycles of navitoclax or D/Q during 16 weeks. We observed an efficient reduction in the white adipose tissue of the senescence markers senescence-associated ß-galactosidase activity, Cdkn2a-p16 and Cdkn2a-p19 at the end of the 5 cycles. Mice treated with both navitoclax and D/Q showed an improvement of their insulin sensitivity and glucose tolerance during a short period of time (cycles 3 and 4), that disappeared at the fifth cycle. Also, these mice tended to increase the expression at their adipose tissue of the adipogenic genes Pparg and, Cebpa, as well as their plasma adiponectin levels. Together, our work shows that two different senolytic treatments, acting through independent pathways, are transiently effective in the treatment of obesity-induced metabolic disorders.

Energy Restriction and Colorectal Cancer: A Call for Additional Research.

: Colorectal cancer has the second highest cancer-related mortality rate, with an estimated 881,000 deaths worldwide in 2018. The urgent need to reduce the incidence and mortality rate requires innovative strategies to improve prevention, early diagnosis, prognostic biomarkers, and treatment effectiveness. Caloric restriction (CR) is known as the most robust nutritional intervention that extends lifespan and delays the progression of age-related diseases, with remarkable results for cancer protection. Other forms of energy restriction, such as periodic fasting, intermittent fasting, or fasting-mimicking diets, with or without reduction of total calorie intake, recapitulate the effects of chronic CR and confer a wide range of beneficial effects towards health and survival, including anti-cancer properties. In this review, the known molecular, cellular, and organismal effects of energy restriction in oncology will be discussed. Energy-restriction-based strategies implemented in colorectal models and clinical trials will be also revised. While energy restriction constitutes a promising intervention for the prevention and treatment of several malignant neoplasms, further investigations are essential to dissect the interplay between fundamental aspects of energy intake, such as feeding patterns, fasting length, or diet composition, with all of them influencing health and disease or cancer effects. Currently, effectiveness, safety, and practicability of different forms of fasting to fight cancer, particularly colorectal cancer, should still be contemplated with caution.

Specific Deletion of the Astrocyte Leptin Receptor Induces Changes in Hippocampus Glutamate Metabolism, Synaptic Transmission and Plasticity.

The aim of this study was to indentify the involvement of leptin receptors (LepR) in astrocytes in hippocampal synaptic transmission and plasticity and metabolism. To this end we used a genetic mouse model (GFAP-LepR-/-) of specific LepR ablation in GFAP positive cells and recorded excitatory postsynaptic potentials (fEPSPs) within the CA1 area. Glutamate (Glu) uptake and the expression of Glu transporters (EEAT3, GLT-1 and GLAST) and enzymes involved in Glu metabolism (glutamine synthase, GABA decarboxylase 65 and 67) were quantified. Modifications in the expression of GFAP, the glucose transporter (GLUT)-1, and the monocarboxylate transporters MCT-2 and MCT-4, were also analyzed. The results show that depletion of LepR in GFAP positive cells reduced basal synaptic transmission within the CA1 area and impaired N-methyl-d-aspartate (NMDA)-evoked long-term depression (NMDA-LTD). Hippocampal slices from GFAP-LepR-/- mice displayed lower Glu uptake efficacy together with up-regulation of GLT-1, glutamine synthase, GFAP and GLUT-1. In conclusion, astrocyte LepRs are involved in the maintenance of Glu homeostasis and Glu neurotransmission within the hippocampus. Our findings support a role of hippocampal LepRs in synaptic plasticity, which could have an impact on memory and learning processes.

Inflammatory stress and altered angiogenesis evoked by very high-fat diets in mouse liver / Las dietas ricas en grasa estimulan procesos inflamatorios y angiogénicos en hígado de ratón

Background: Non-alcoholic fatty liver disease (NAFLD), a condition that leads to fibrosis, is caused by intake of very high-fat diets (HFDs). However, while the negative impact on the liver of these diets has been an issue of interest, systematic research on the effect of HFDs are lacking. Objective: To characterize the overall impact of HFDs on both molecular and morphological signs of liver remodeling. Methods: A study was conducted on male C57BL/6J mice to assess the effect of 4- and 8-week HFDs (60% kcal from fat) on (I) liver steatosis and fibrosis, and (II) expression of factors involved in inflammation and angiogenesis. Results: After an 8-week HFD, vascular endothelial growth factor type-2 receptor (VEGF-R2) and fatty acid translocase/trombospondin-1 receptor (CD36) were overexpressed in liver tissue of mice given HFDs. These changes suggest impaired liver angiogenesis and occurred together with (I) increased GPR78-BiP and EIF2alpha phosphorylation, suggesting endoplasmic reticulum stress, (II) induction of Col1a1 gene expression, a marker of fibrosis, and (III) increased CD31 immunolabeling, consistent with active angiogenesis and fibrosis. Conclusion: Our data show that very HFDs promote a rapid inflammatory response, as well as deregulation of angiogenesis, both consistent with development of liver fibrosis

Antecedentes: El hígado graso no alcohólico (HGNA) es una enfermedad hepática que ocasiona fibrosis y se genera por la ingesta de dietas ricas en grasa. Aunque los efectos nocivos de este tipo de dietas son de gran interés, no son muy abundantes los estudios sistemáticos sobre las consecuencias que su consumo puede tener en el hígado. Objetivo: Evaluar los efectos de una dieta rica en grasa sobre el remodelado hepático, tanto a nivel morfológico como molecular. Métodos: Se utilizaron ratones macho C57BL/6J tratados durante 4/8 semanas con una dieta que contenía un 60% de las kilocalorías procedentes de grasa sobre: 1) la aparición de esteatosis y/o fibrosis hepática y 2) la expresión de factores implicados en procesos de inflamación y angiogénesis. Resultados: Tras 8 semanas de dieta se observó un incremento en el receptor del factor de crecimiento vascular endotelial tipo 2 (R2-FCVE) y en la translocasa de ácidos grasos (CD36). Estos cambios, que sugieren que los procesos angiogénicos del hígado están alterados, fueron simultáneos a: 1) un aumento del GPR78-BiP y de la fosforilación de EIF2alpha, marcadores de estrés del retículo endoplásmico, 2) la inducción en la expresión del gen de colágeno Col1a1, indicador de fibrosis y 3) un incremento de células inmunofluorescentes para CD31 compatible con procesos de angiogénesis y de fibrosis. Conclusiones: Nuestros resultados muestran que las dietas con alto contenido en grasa inducen la rápida activación de respuestas inflamatorias, así como alteraciones en la angiogénesis, siendo ambos procesos compatibles con el desarrollo de fibrosis hepática

Potential Role of Leptin in Cardiac Steatosis Induced by Highly Saturated Fat Intake during Adolescence.

SCOPE: To identify the age-dependent effect of diets containing elevated amounts of either saturated or unsaturated fatty acids on cardiac steatosis in mice. METHODS AND RESULTS: Five- and eight-week-old C57BL/6J mice cohorts are given free access to either a saturated or an unsaturated fatty-acid-enriched diet during 8 weeks. Body weight (BW) and food intake are monitored during this period. Cardiac lipid content, carnitine palmitoyltransferase-I (CPT-I) activity, and the amount of uncoupling proteins 2 and 3 (UCP2 and UCP3) are analyzed and correlated with blood leptin concentration. Leptin and PPARγ gene expression is quantified in white adipose tissue (WAT). Both diets have a similar effect on food intake, BW, and adiposity, independently of the age. Nevertheless, cardiac steatosis is specifically identified in adolescent mice consuming the saturated diet. These animals also display lower activity of cardiac CPT-I, a down-regulation of cardiac UCP2, together with lower concentration of plasma leptin. Accordingly, leptin gene expression is reduced in the visceral WAT. CONCLUSION: Consumption of diets containing elevated amounts of saturated fat during adolescence and early adult life promotes cardiac steatosis in mice. An insufficient endocrine activity of WAT, in terms of leptin production, may account for such an effect.

Caloric restriction induces H2O2 formation as a trigger of AMPK-eNOS-NO pathway in obese rats: Role for CAMKII.

Caloric restriction (CR) improves endothelial function through the upregulation of adenosine monophosphate-activated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS). Moreover, hydrogen peroxide (H2O2) is upregulated in yeast subjected to CR. Our aim was to assess if mild short-term CR increases vascular H2O2 formation as a link with AMPK and eNOS activation. Twelve-week old Zucker obese (fa/fa) and control Zucker lean male rats were fed a standard chow either ad libitum (AL, n=10) or with a 20% CR (CR, n=10) for two weeks. CR significantly improved relaxation to ACh in fa/fa rats because of an enhanced endogenous production of H2O2 in aortic rings (H2O2 levels fa/faAL=0.5 ±â€¯0.05 nmol/mg vs. H2O2 levels fa/faCR=0.76 ±â€¯0.07 nmol/mg protein; p<0.05). Expression of mitochondrial superoxide dismutase (Mn-SOD) and total SOD activity were increased in aorta from fa/fa animals after CR. In cultured aortic endothelial cells, serum deprivation or 2-deoxy-d-glucose induced a significant increase in: i) superoxide anion and H2O2 levels, ii) p-AMPK/AMPK and p-eNOS/eNOS expression and iii) nitric oxide levels. This effect was reduced by catalase and strongly inhibited by Ca2+/calmodulin-dependent kinase II (CamkII) silencing. In conclusion, we propose that mild short-term CR might be a trigger of mechanisms aimed at protecting the vascular wall by the increase of H2O2, which then activates AMPK and nitric oxide release, thus improving endothelium-dependent relaxation. In addition, we demonstrate that CAMKII plays a key role in mediating CR-induced AMPK activation through H2O2 increase.

The cholecystokinin receptor agonist, CCK-8, induces adiponectin production in rat white adipose tissue.

BACKGROUND AND PURPOSE: A cholecystokinin (CCK) system has been identified in white adipose tissue (WAT). Nevertheless, the endocrine actions of CCK on WAT remain unknown. Our goal was to investigate the role of CCK in regulating the production of adiponectin, an adipokine expressed in WAT, which is pivotal in preserving energy homeostasis. EXPERIMENTAL APPROACH: The effect of the bioactive CCK fragment CCK-8 on adiponectin production was studied both in vivo and in vitro. CCK-8 effects were characterized in rats treated with selective CCK1 and CCK2 receptor antagonists as well as in pre-adipocytes carrying the selective silencing of either CCK1 or CCK2 receptors. The influence of insulin on CCK-8 responses was also analysed. KEY RESULTS: In WAT, CCK-8 increased plasma adiponectin levels and the expression of the adiponectin gene (Adipoq). In pre-adipocytes, CCK-8 up-regulated adiponectin production. CCK-8 effects were abolished by L-365,260, a selective CCK2 receptor antagonist. CCK2 receptor knockdown also abolished the effects of CCK-8 in pre-adipocytes. Moreover, in vitro CCK-8 effects were blocked by triciribine, a specific inhibitor of protein kinase B (Akt) and by the PPARγ antagonist T0070907. Silencing the expression of the insulin receptor inhibited CCK-8-induced Adipoq expression in pre-adipocytes. Furthermore, insulin potentiated the effect of CCK-8. CONCLUSION AND IMPLICATIONS: CCK-8 stimulates adiponectin production in WAT by acting on CCK2 receptors, through a mechanism involving both Akt and PPARγ. Moreover, CCK-8 actions are only observed in the presence of insulin. Our results could have translational value in the design of new insulin-sensitizing therapies.

Inflammatory stress and altered angiogenesis evoked by very high-fat diets in mouse liver.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD), a condition that leads to fibrosis, is caused by intake of very high-fat diets (HFDs). However, while the negative impact on the liver of these diets has been an issue of interest, systematic research on the effect of HFDs are lacking. OBJECTIVE: To characterize the overall impact of HFDs on both molecular and morphological signs of liver remodeling. METHODS: A study was conducted on male C57BL/6J mice to assess the effect of 4- and 8-week HFDs (60% kcal from fat) on (i) liver steatosis and fibrosis, and (ii) expression of factors involved in inflammation and angiogenesis. RESULTS: After an 8-week HFD, vascular endothelial growth factor type-2 receptor (VEGF-R2) and fatty acid translocase/trombospondin-1 receptor (CD36) were overexpressed in liver tissue of mice given HFDs. These changes suggest impaired liver angiogenesis and occurred together with (i) increased GPR78-BiP and EIF2α phosphorylation, suggesting endoplasmic reticulum stress, (ii) induction of Col1a1 gene expression, a marker of fibrosis, and (iii) increased CD31 immunolabeling, consistent with active angiogenesis and fibrosis. CONCLUSION: Our data show that very HFDs promote a rapid inflammatory response, as well as deregulation of angiogenesis, both consistent with development of liver fibrosis.

Expression analysis of a cholecystokinin system in human and rat white adipose tissue.

AIM: Cholecystokinin (CCK) participates in the storage of dietary triglycerides in white adipose tissue (WAT). Our goal was to characterize, both in subcutaneous (Sc-WAT) and visceral WAT (Vis-WAT), the functional expression of the two known CCK receptors, CCK-1 (CCK-1R) and CCK-2 (CCK-2R), as well as of CCK. MAIN METHODS: Gene and protein expression was assessed in different cell types of rat and human WAT by means of RT-PCR and western-blot, respectively. The functionality of CCK-Rs was tested by quantifying protein kinase B (Akt) phosphorylation after treatment of pre-adipocytes with the bioactive fragment of CCK, CCK-8. The CCK receptor subtype involved in Akt phosphorylation was investigated by using selective CCK-1R (SR-27,897) and CCK-2R antagonists (L-365,260). KEY FINDINGS: In rats, CCK-1R (Cckar) and CCK-2R (Cckbr) gene expression was detected in the two types of WAT analyzed as well as in isolated adipocytes, mesenchymal stem cells and pre-adipocytes. CCK-1R and CCK-2R proteins were identified in adipocytes and, to a minor extent, in pre-adipocytes. In addition, CCK-2R were detected in subcutaneous mesenchymal stem cells. Gene expression of the CCK precursor preproCCK as well as CCK immunoreactivity were also found in Sc-WAT and Vis-WAT. In human WAT, CCK gene expression as well as CCK-2Rs and CCK were also identified. CCK-8 evoked Akt phosphorylation in rat pre-adipocytes, and this effect was antagonized by SR-27,897 and L-365,260. SIGNIFICANCE: Our data show that both human and rat WAT express a complete CCK system, and suggest that CCK may have an autocrine/paracrine role in regulating adipose tissue biology.

Cholecystokinin is involved in triglyceride fatty acid uptake by rat adipose tissue.

The incorporation of plasma triglyceride (TG) fatty acids to white adipose tissue (WAT) depends on lipoprotein lipase (LPL), which is regulated by angiopoietin-like protein-4 (ANGPTL-4), an unfolding molecular chaperone that converts active LPL dimers into inactive monomers. The production of ANGPTL-4 is promoted by fasting and repressed by feeding. We hypothesized that the postprandial hormone cholecystokinin (CCK) facilitates the storage of dietary TG fatty acids in WAT by regulating the activity of the LPL/ANGPTL-4 axis and that it does so by acting directly on CCK receptors in adipocytes. We report that administration of CCK-8 (a bioactive fragment of CCK) to rats: (i) reduces plasma ANGTPL-4 levels; (ii) represses Angptl-4 expression in WAT and (iii) simultaneously enhances LPL activity in this tissue without inducing Lpl expression. In vivo CCK-8 effects are specifically antagonized by the CCK-2 receptor (CCK-2R) antagonist, L-365,260. Moreover, CCK-8 downregulates Angptl-4 expression in wild-type pre-adipocytes, an effect that is not observed in engineered pre-adipocytes lacking CCK-2R. These effects have functional consequences as CCK-8 was found to promote the uptake of dietary fatty acids by WAT, as demonstrated by means of proton nuclear magnetic resonance (1H-NMR). The efficacy of acute CCK-8 administration was not reduced after chronic CCK-8 treatment. Moreover, the effects of CCK-8 on WAT were not associated to the increase of circulating insulin. Our results show that cholecystokinin promotes lipid storage in WAT by acting on adipocyte CCK-2R, suggesting a pivotal role for CCK in TG homeostasis.