Obesity-related structural and functional changes in the kidney develop early in the course of obesity and occur independently of hypertension, diabetes, and dyslipidemia. Activating the renal ...cannabinoid-1 receptor (CB
R) induces nephropathy, whereas CB
R blockade improves kidney function. Whether these effects are mediated
a specific cell type within the kidney remains unknown. Here, we show that specific deletion of CB
R in the renal proximal tubule cells did not protect the mice from obesity, but markedly attenuated the obesity-induced lipid accumulation in the kidney and renal dysfunction, injury, inflammation, and fibrosis. These effects associated with increased activation of liver kinase B1 and the energy sensor AMP-activated protein kinase, as well as enhanced fatty acid
-oxidation. Collectively, these findings indicate that renal proximal tubule cell CB
R contributes to the pathogenesis of obesity-induced renal lipotoxicity and nephropathy by regulating the liver kinase B1/AMP-activated protein kinase signaling pathway.
Background and Purpose
Obesity, an important risk factor for developing chronic kidney disease (CKD), affects the kidneys by two main molecular signalling pathways: the endocannabinoid/CB1 receptor ...system, whose activation in obesity promotes renal inflammation, fibrosis, and injury, and the inducible NOS (iNOS), which generates ROS resulting in oxidative stress. Hence, a compound that inhibits both peripheral CB1 receptors and iNOS may serve as an effective therapeutic agent against obesity‐induced CKD.
Experimental Approach
Here, we describe the effect of a novel peripherally restricted, orally bioavailable dual CB1 receptor/iNOS antagonist, MRI‐1867 (3 mg·kg−1), in ameliorating obesity‐induced CKD, and compared its metabolic and renal efficacies to a stand‐alone peripheral CB1 receptor antagonist (JD5037; 3 mg·kg−1), iNOS antagonist (1400W; 10 mg·kg−1), and pair feeding. Mice with high‐fat diet‐induced obesity were treated orally with these compounds or vehicle (Veh) for 28 days. Standard diet‐fed mice treated with Veh served as controls.
Key Results
Enhanced expression of CB1 receptors and iNOS in renal tubules was found in human kidney patients with obesity and other CKDs. The hybrid inhibitor ameliorated obesity‐induced kidney morphological and functional changes via decreasing kidney inflammation, fibrosis, oxidative stress, and renal injury. Some of these features were independent of the improved metabolic profile mediated via inhibition of CB1 receptors. An additional interesting finding is that these beneficial effects on the kidney were partially associated with modulating renal adiponectin signalling.
Conclusions and Implications
Collectively, our results highlight the therapeutic relevance of blocking CB1 receptors and iNOS in ameliorating obesity‐induced CKD.
Both non-alcoholic fatty liver disease (NAFLD) and the multitarget complexity of microRNA (miR) suppression have recently raised much interest, but the in vivo impact and context-dependence of ...hepatic miR-target interactions are incompletely understood. Assessing the relative in vivo contributions of specific targets to miR-mediated phenotypes is pivotal for investigating metabolic processes.
We quantified fatty liver parameters and the levels of miR-132 and its targets in novel transgenic mice overexpressing miR-132, in liver tissues from patients with NAFLD, and in diverse mouse models of hepatic steatosis. We tested the causal nature of miR-132 excess in these phenotypes by injecting diet-induced obese mice with antisense oligonucleotide suppressors of miR-132 or its target genes, and measured changes in metabolic parameters and transcripts.
Transgenic mice overexpressing miR-132 showed a severe fatty liver phenotype and increased body weight, serum low-density lipoprotein/very low-density lipoprotein (LDL/VLDL) and liver triglycerides, accompanied by decreases in validated miR-132 targets and increases in
. Likewise, liver samples from both patients with NAFLD and mouse models of hepatic steatosis or non-alcoholic steatohepatitis (NASH) displayed dramatic increases in miR-132 and varying decreases in miR-132 targets compared with controls. Furthermore, injecting diet-induced obese mice with anti-miR-132 oligonucleotides, but not suppressing its individual targets, reversed the hepatic miR-132 excess and hyperlipidemic phenotype.
Our findings identify miR-132 as a key regulator of hepatic lipid homeostasis, functioning in a context-dependent fashion via suppression of multiple targets and with cumulative synergistic effects. This indicates reduction of miR-132 levels as a possible treatment of hepatic steatosis.
Aims
To evaluate the specific role of the endocannabinoid/cannabinoid type‐1 (CB1R) system in modulating mitochondrial dynamics in the metabolically active renal proximal tubular cells (RPTCs).
...Materials and methods
We utilized mitochondrially‐targeted GFP in live cells (wild‐type and null for the CB1R) and electron microscopy in kidney sections of RPTC‐CB1R‐/‐ mice and their littermate controls. In both in vitro and in vivo conditions, we assessed the ability of CB1R agonism or fatty acid flux to modulate mitochondrial architecture and function.
Results
Direct stimulation of CB1R resulted in mitochondrial fragmentation in RPTCs. This process was mediated, at least in part, by modulating the phosphorylation levels of the canonical fission protein dynamin‐related protein 1 on both S637 and S616 residues. CB1R‐induced mitochondrial fission was associated with mitochondrial dysfunction, as documented by reduced oxygen consumption and ATP production, increased reactive oxygen species and cellular lactate levels, as well as a decline in mitochondrial biogenesis. Likewise, we documented that exposure of RPTCs to a fatty acid flux induced CB1R‐dependent mitochondrial fission, lipotoxicity and cellular dysfunction.
Conclusions
CB1R plays a key role in inducing mitochondrial fragmentation in RPTCs, leading to a decline in the organelle's function and contributing to the renal tubular injury associated with lipotoxicity and other metabolic diseases.
Altered glucose reabsorption
the facilitative glucose transporter 2 (GLUT2) during diabetes may lead to renal proximal tubule cell (RPTC) injury, inflammation, and interstitial fibrosis. These ...pathologies are also triggered by activating the cannabinoid-1 receptor (CB
R), which contributes to the development of diabetic nephropathy (DN). However, the link between CB
R and GLUT2 remains to be determined. Here, we show that chronic peripheral CB
R blockade or genetically inactivating CB
Rs in the RPTCs ameliorated diabetes-induced renal structural and functional changes, kidney inflammation, and tubulointerstitial fibrosis in mice. Inhibition of CB
R also downregulated GLUT2 expression, affected the dynamic translocation of GLUT2 to the brush border membrane of RPTCs, and reduced glucose reabsorption. Thus, targeting peripheral CB
R or inhibiting GLUT2 dynamics in RPTCs has the potential to treat and ameliorate DN. These findings may support the rationale for the clinical testing of peripherally restricted CB
R antagonists or the development of novel renal-specific GLUT2 inhibitors against DN.
Adipose tissue (AT) plays a major role in metabolic adaptations in postpartum (PP) dairy cows. The endocannabinoid (eCB) system is a key regulator of metabolism and energy homeostasis; however, ...information about this system in ruminants is scarce. Therefore, this work aimed to assess the eCB system in subcutaneous AT, and to determine its relation to the metabolic profile in peripartum cows. Biopsies of AT were performed at 14 d prepartum, and 4 and 30 d PP from 18 multiparous peripartum cows. Cows were categorized retrospectively according to those with high body weight (BW) loss (HWL, 8.5 ± 1.7% BW loss) or low body weight loss (LWL, 2.9 ± 2.5% BW loss) during the first month PP. The HWL had higher plasma non-esterified fatty acids and a lower insulin/glucagon ratio PP than did LWL. Two-fold elevated AT levels of the main eCBs, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), were found 4 d PP compared with prepartum in HWL, but not in LWL cows. AT levels of the eCB-like molecules oleoylethanolamide, palmitoylethanolamide, and of arachidonic acid were elevated PP compared with prepartum in all cows. The abundance of monoglyceride lipase (MGLL), the 2-AG degrading enzyme, was lower in HWL vs. LWL AT PP. The relative gene expression of the cannabinoid receptors CNR1 and CNR2 in AT tended to be higher in HWL vs. LWL PP. Proteomic analysis of AT showed an enrichment of the inflammatory pathways' acute phase signaling and complement system in HWL vs. LWL cows PP. In summary, eCB levels in AT were elevated at the onset of lactation as part of the metabolic adaptations in PP dairy cows. Furthermore, activating the eCB system in AT is most likely associated with a metabolic response of greater BW loss, lipolysis, and AT inflammation in PP dairy cows.
While the existence of an indigenous placental microbiota remains controversial, several pathogens are known to be involved in adverse pregnancy outcomes. Fusobacterium nucleatum is an oral bacterium ...that is one of several bacteria associated with preterm birth. Oral fusobacteria translocate to the placenta hematogenously; however, the mechanisms localizing them to the placenta remain unclear. Here, using peanut agglutinin, we demonstrate that the level of Gal-GalNAc (Galβ1−3GalNAc; Thomsen Friedenreich antigen) found on trophoblasts facing entering maternal blood rises during gestation and is recognized by the fusobacterial Fap2 Gal-GalNAc lectin. F. nucleatum binding to human and mouse placenta correlates with Gal-GalNAc levels and is reduced upon O-glycanase treatment or with soluble Gal-GalNAc. Fap2-inactivated F. nucleatum shows reduced binding to Gal-GalNAc-displaying placental sections. In a mouse model, intravenously injected Fap2-expressing F. nucleatum, but not a Fap2 mutant, reduces mouse fetal survival by 70%.
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•Gal-GalNAc level rises throughout gestation in human and mouse placenta•Placental Gal-GalNAc is displayed in direct contact with maternal blood•Fap2 mediates binding of F. nucleatum to Gal-GalNAc displayed in the placenta
Parhi et al. find that the oncofetal antigen Gal-GalNAc is displayed on trophoblast cells facing maternal blood and that its level rises during gestation. Gal-GalNAc is recognized by the Fusobacterium nucleatum lectin Fap2, facilitating fusobacterial colonization of the placenta.
Summary
Our aim was to evaluate the effects of valproic acid (VPA) on the function of the placental barrier in vivo, in pregnant mice. Studies were conducted on gestational days 12.5 (mid‐gestation) ...or 17.5 (late gestation), following intraperitoneal treatment with 200 mg/kg VPA or the vehicle. Indocyanine green (ICG; 0.167 mg, i.v.) was used as a marker for the placental barrier permeability. Transporter expression was evaluated by quantitative ‐PCR. VPA treatment was associated with a 40% increase (p < 0.05) in accumulation of ICG in maternal liver in mid‐pregnancy and a decrease by one fifth (p < 0.05) in late pregnancy. Ex vivo, VPA treatment led to a 20% increase (p < 0.05) in fetal ICG emission in mid‐pregnancy. Also in mid‐pregnancy, the placental expression of the L‐type amino acid transporter, the organic anion–transporting polypeptide (Oatp)4a1 (thyroid hormone transporter), and the reduced folate carrier was lower in VPA‐treated mice (p < 0.05). In late pregnancy, hepatic Oatp4a1 levels were 40% less than in controls (p > 0.05). The observed changes in placental transporter expression and function support further research into the potential role of the placenta in the adverse pregnancy outcomes of VPA. Near‐infrared imaging provides a noninvasive, nonradioactive tool for future studies on the effects of epilepsy and antiepileptic drugs on tissue transport functions.
The endocannabinoid (eCB) system is increasingly recognized as being crucially important in obesity-related hepatic steatosis. By activating the hepatic cannabinoid-1 receptor (CB1R), eCBs modulate ...lipogenesis and fatty acid oxidation. However, the underlying molecular mechanisms are largely unknown.
We combined unbiased bioinformatics techniques, mouse genetic manipulations, multiple pharmacological, molecular, and cellular biology approaches, and genomic sequencing to systematically decipher the role of the hepatic CB1R in modulating fat utilization in the liver and explored the downstream molecular mechanisms.
Using an unbiased normalized phylogenetic profiling analysis, we found that the CB1R evolutionarily coevolves with peroxisome proliferator-activated receptor-alpha (PPARα), a key regulator of hepatic lipid metabolism. In diet-induced obese (DIO) mice, peripheral CB1R blockade (using AM6545) induced the reversal of hepatic steatosis and improved liver injury in WT, but not in PPARα−/− mice. The antisteatotic effect mediated by AM6545 in WT DIO mice was accompanied by increased hepatic expression and activity of PPARα as well as elevated hepatic levels of the PPARα-activating eCB-like molecules oleoylethanolamide and palmitoylethanolamide. Moreover, AM6545 was unable to rescue hepatic steatosis in DIO mice lacking liver sirtuin 1 (SIRT1), an upstream regulator of PPARα. Both of these signaling molecules were modulated by the CB1R as measured in hepatocytes exposed to lipotoxic conditions or treated with CB1R agonists in the absence/presence of AM6545. Furthermore, using microRNA transcriptomic profiling, we found that the CB1R regulated the hepatic expression, acetylation, and transcriptional activity of p53, resulting in the enhanced expression of miR-22, which was found to specifically target SIRT1 and PPARα.
We provide strong evidence for a functional role of the p53/miR-22/SIRT1/PPARα signaling pathway in potentially mediating the antisteatotic effect of peripherally restricted CB1R blockade.
The elucidated molecular signaling pathway by which hepatic CB1R regulates hepatic lipid homeostasis. Activation of hepatic CB1R increases p53 expression, acetylation, nuclear localization,and transcriptional activity that together promote the expression of miR-22, which in turn reduces the expression and activity of PPARα and SIRT1. These events lead to reduced fatty acid oxidation and fat accumulation in the liver (left). Treatment with AM6545, a peripherally restricted CB1R antagonist, disrupts this signaling pathway and ameliorates hepatic steatosis by also increasing hepatic OEA and PEA, which may activate PPARα directly, resulting in the enhanced efficacy of AM6545 in ameliorating hepatic steatosis (right). Display omitted
•PPARα is the top-ranked NAFLD-related gene that is coevolved with the CB1R.•Hepatic PPARα and SIRT1 expression and activity are regulated by the CB1R.•Reversal of hepatic steatosis by peripheral CB1R blockade requires intact SIRT1 and PPARα signaling.•Hepatic PPARα and SIRT1 are direct targets of miR-22, whose expression is regulated via CB1R-induced modulation of p53 expression, acetylation, and transcriptional activity.
WWOX, a well-established tumor suppressor, is frequently lost in cancer and plays important roles in DNA damage response and cellular metabolism.
We re-analyzed several genome-wide association ...studies (GWAS) using the Type 2 Diabetes Knowledge Portal website to uncover WWOX's association with metabolic syndrome (MetS). Using several engineered mouse models, we studied the effect of somatic WWOX loss on glucose homeostasis.
Several WWOX variants were found to be strongly associated with MetS disorders. In mouse models, somatic ablation of Wwox in skeletal muscle (WwoxΔSKM) results in weight gain, glucose intolerance, and insulin resistance. Furthermore, WwoxΔSKM mice display reduced amounts of slow-twitch fibers, decreased mitochondrial quantity and activity, and lower glucose oxidation levels. Mechanistically, we found that WWOX physically interacts with the cellular energy sensor AMP-activated protein kinase (AMPK) and that its loss is associated with impaired activation of AMPK, and with significant accumulation of the hypoxia inducible factor 1 alpha (HIF1α) in SKM.
Our studies uncover an unforeseen role of the tumor suppressor WWOX in whole-body glucose homeostasis and highlight the intimate relationship between cancer progression and metabolic disorders, particularly obesity and type-2 diabetes.
Genetics, Metabolic Syndrome, Diabetes.
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•Several WWOX variants and single nucleotide polymorphisms are associated with a number of metabolic syndrome disorders.•Somatic ablation of Wwox in skeletal muscle (WwoxΔSKM) results in metabolic syndrome disorder.•WwoxΔSKM mice display reduced amount of slow-twitch fibers and decreased mitochondrial quantity and activity.•WWOX loss is associated with impaired activation of AMPK and with significant accumulation of HIF1α in SKM.
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