Metabolisms
Abstract
Genetic polymorphisms are associated with the development of nonalcoholic fatty liver disease (NAFLD). Semaphorin7a (Sema7a) deficiency in mouse peritoneal macrophages reduces fatty acid (FA) oxidation. Here, we identified 17 individuals with SEMA7A heterozygous mutations in 470 patients with biopsy-proven NAFLD. SEMA7A heterozygous mutations increased susceptibility to NAFLD, steatosis severity, and NAFLD activity scores in humans and mice. The Sema7aR145W mutation (equivalent to human SEMA7AR148W) significantly induced small lipid droplet accumulation in mouse livers compared with WT mouse livers. Mechanistically, the Sema7aR145W mutation increased N-glycosylated Sema7a and its receptor integrin β1 proteins in the cell membranes of hepatocytes. Furthermore, Sema7aR145W mutation enhanced its protein interaction with integrin β1 and PKC-α and increased PKC-α phosphorylation, which were both abrogated by integrin β1 silencing. Induction of PKCα_WT, but not PKCα_dominant negative, overexpression induced transcriptional factors Srebp1, Chrebp, and Lxr expression and their downstream Acc1, Fasn, and Cd36 expression in primary mouse hepatocytes. Collectively, our findings demonstrate that the SEMA7AR148W mutation is a potentially new strong genetic determinant of NAFLD and promotes intrahepatic lipid accumulation and NAFLD in mice by enhancing PKC-α–stimulated FA and triglyceride synthesis and FA uptake. The inhibition of hepatic PKC-α signaling may lead to novel NAFLD therapies.
Authors
Nan Zhao, Xiaoxun Zhang, Jingjing Ding, Qiong Pan, Ming-Hua Zheng, Wen-Yue Liu, Gang Luo, Jiaquan Qu, Mingqiao Li, Ling Li, Ying Cheng, Ying Peng, Qiaoling Xie, Qinglin Wei, Qiao Li, Lingyun Zou, Xinshou Ouyang, Shi-Ying Cai, James L. Boyer, Jin Chai
Abstract
Cardiovascular diseases, especially atherosclerosis and its complications, are a leading cause of death. Inhibition of the non-canonical IκB kinases TBK1 and IKKε with amlexanox restores insulin sensitivity and glucose homeostasis in diabetic mice and human subjects. Here we report that amlexanox improves diet-induced hypertriglyceridemia and hypercholesterolemia in Western diet (WD)-fed Ldlr-/- mice, and protects against atherogenesis. Amlexanox ameliorates dyslipidemia, inflammation and vascular dysfunction through synergistic actions that involve upregulation of bile acid synthesis to increase cholesterol excretion. Transcriptomic profiling demonstrates an elevated expression of key bile acid synthesis genes. Furthermore, we found that amlexanox attenuates monocytosis, eosinophilia and vascular dysfunction during WD-induced atherosclerosis. These findings demonstrate the potential of amlexanox as a new therapy for hypercholesterolemia and atherosclerosis.
Authors
Peng Zhao, Xiaoli Sun, Zhongji Liao, Hong Yu, Dan Li, Zeyang Shen, Christopher K. Glass, Joseph L. Witztum, Alan R. Saltiel
Abstract
Pathogenic variants in the human F Box and Leucine Rich Repeat Protein 4 (FBXL4) gene result in an autosomal recessive, multi-systemic, mitochondrial disorder involving variable mitochondrial depletion and respiratory chain (RC) complex deficiencies with lactic acidemia. As no FDA-approved effective therapies exist, we sought to characterize translational C. elegans and zebrafish animal models, as well as human fibroblasts, to study FBXL4-/- disease mechanisms and identify preclinical therapeutic leads. Developmental delay, impaired fecundity and neurologic and/or muscular activity, mitochondrial dysfunction, and altered lactate metabolism were identified in fbxl-1(ok3741) C. elegans. Detailed studies of a pyruvate dehydrogenase complex activator, dichloroacetate (DCA) in fbxl-1(ok3741) C. elegans demonstrated its beneficial effects on fecundity, neuromotor activity, and mitochondrial function. Validation studies were performed in fbxl4sa12470 zebrafish larvae and in FBXL4-/- human fibroblasts, which showed DCA efficacy in preventing brain damage, impairment of neurologic and/or muscular function, mitochondrial biochemical dysfunction, and stress-induced morphologic and ultrastructural mitochondrial defects. These data demonstrate that fbxl-1 (ok3741) C. elegans and fbxl4sa12470 zebrafish provide robust translational models to study mechanisms and identify preclinical therapeutic candidates for FBXL4-/- disease. Further, DCA is a lead therapeutic candidate with therapeutic benefit on diverse aspects of survival, neurologic and/or muscular function, and mitochondrial physiology that warrants rigorous clinical trial study in human subjects with FBXL4-/- disease.
Authors
Manuela Lavorato, Eiko Nakamaru-Ogiso, Neal D. Mathew, Elizabeth Herman, Nina K. Shah, Suraiya Haroon, Rui Xiao, Christoph Seiler, Marni J. Falk
Abstract
Hepatic de novo lipogenesis is influenced by the branched-chain α-keto acid dehydrogenase (BCKDH) kinase (BCKDK). We aimed to determine whether circulating levels of the immediate substrates of BCKDH, the branched-chain α-ketoacids (BCKAs) and hepatic BCKDK expression are associated with the presence and severity of non-alcoholic fatty liver disease (NAFLD). Eighty metabolites (3 BCKA, 14 amino acids, 43 acylcarnitines, 20 ceramides) were quantified in plasma from 288 bariatric surgery patients with severe obesity (BMI > 35 kg/m2) with scored liver biopsy samples. Metabolite principal component analysis (PCA) factors, BCKA, branched-chain amino acids (BCAA), and the BCKA:BCAA ratio were tested for associations with steatosis grade and presence of non-alcoholic steatohepatitis (NASH). Of all analytes tested, only the valine-derived BCKA, α-ketoisovalerate, and the BCKA:BCAA ratio were associated with both steatosis grade and NASH. Gene expression analysis in liver samples from two independent bariatric surgery cohorts showed that hepatic BCKDK mRNA expression correlates with steatosis, ballooning, and levels of the lipogenic transcription factor SREBP1. Experiments in AML12 hepatocytes showed that SREBP1 inhibition lowers BCKDK mRNA expression. These findings demonstrate that higher plasma levels of BCKA and hepatic expression of BCKDK are features of human NAFLD/NASH and identify SREBP1 as a transcriptional regulator of BCKDK.
Authors
Thomas Grenier-Larouche, Lydia Coulter Kwee, Yann Deleye, Paola Leon-Mimila, Jacquelyn M. Walejko, Robert W. McGarrah, Simon Marceau, Sylvain Trahan, Christine Racine, André C. Carpentier, Aldons J. Lusis, Olga Ilkayeva, Marie-Claude Vohl, Adriana Huertas-Vazquez, Andre Tchernof, Svati H. Shah, Christopher B. Newgard, Phillip J. White
Abstract
Developmental cardiac tissue is regenerative while operating under low oxygen. After birth, ambient oxygen is associated with cardiomyocyte cell cycle exit and regeneration. Likewise, cardiac metabolism undergoes a shift with cardiac maturation. Whether there are common regulators of cardiomyocyte cell cycle linking metabolism to oxygen tension remains unknown. The objective of the study is to determine whether mitochondrial UCP2 is a metabolic oxygen sensor regulating cardiomyocyte cell cycle. Neonatal rat ventricular myocytes (NRVMs) under moderate hypoxia showed increased cell cycle activity and UCP2 expression. NRVMs exhibited a metabolic shift towards glycolysis, reduced citrate synthase, mtDNA, ΔΨm and DNA damage/oxidative stress while loss of UCP2 reversed this phenotype. Next, WT and UCP2KO mice kept under hypoxia for 4 weeks showed significant decline in cardiac function that was more pronounced in UCP2KO animals. Cardiomyocyte cell cycle activity was reduced while fibrosis and DNA damage was significantly increased in UCP2KO animals compared to WT under hypoxia. Mechanistically, UCP2 increased acetyl-CoA levels, histone acetylation and altered chromatin modifiers linking metabolism to cardiomyocyte cell cycle under hypoxia. Here, we show a novel role for mitochondrial UCP2 as an oxygen sensor regulating cardiomyocyte cell cycle activity, acetyl-CoA levels and histone acetylation in response to moderate hypoxia.
Authors
Vagner O.C. Rigaud, Clare Zarka, Justin Kurian, Daria Harlamova, Andrea Elia, Nicole Kasatkin, Jaslyn Johnson, Michael Behanan, Lindsay Kraus, Hannah Pepper, Nathaniel W. Snyder, Sadia Mohsin, Steven Houser, Mohsin Khan
Abstract
The ribosomal protein S6 kinase 1 (S6K1) is a relevant effector downstream the mammalian target of rapamycin complex 1 (mTORC1), best known for its role in the control of lipid homeostasis. Consistent with this, mice lacking the S6k1 gene have a defect in their ability to induce the commitment of fat precursor cells to the adipogenic lineage, which contributes to a significant reduction of fat mass. Here, we assess the therapeutic blockage of S6K1 in diet-induced obese mice challenged with LY2584702 tosylate, a specific oral S6K1 inhibitor initially developed for the treatment of solid tumours. We show that diminished S6K1 activity hampers fat mass expansion and ameliorates dyslipidaemia and hepatic steatosis, while modifying transcriptome-wide gene expression programs relevant for adipose and liver function. Accordingly, impaired mTORC1 signalling in fat (decreased) and liver (increased) co-segregated with defective epithelial-mesenchymal transition, being prominent the decreased expression of Cd36 (coding for a fatty acid translocase) and Lgals1 (Galectin 1) in both tissues. All these factors combined align with reduced adipocyte size and improved lipidomic signatures in the liver, while hepatic steatosis and hypertriglyceridemia were improved in treatments lasting either 3 months or 6 weeks.
Authors
Aina Lluch, Sonia R. Veiga, Jèssica Latorre, José M. Moreno-Navarrete, Núria Bonifaci, Van Dien Nguyen, You Zhou, Marcus Horing, Gerhard Liebisch, Vesa M. Olkkonen, David Llobet-Navas, George Thomas, Ruth Rodriguez-Barrueco, José M. Fernández-Real, Sara C. Kozma, Francisco J. Ortega
Abstract
Infantile spasms syndrome (IS) is a devastating early-onset epileptic encephalopathy associated with poor neurodevelopmental outcomes. When first-line treatment options, including adrenocorticotropic hormone and vigabatrin, are ineffective, the ketogenic diet (KD) is often employed to control seizures. Since the therapeutic impact of the KD is influenced by the gut microbiota, we examined whether targeted microbiota manipulation, mimicking changes induced by the KD, would be valuable in mitigating seizures. Employing a rodent model of symptomatic IS, we show that both the KD and antibiotic administration reduce spasm frequency and are associated with improved developmental outcomes. Spasm reductions were accompanied by specific gut microbial alterations, including increases in Streptococcus thermophilus and Lactococcus lactis. Mimicking the fecal microbial alterations in a targeted probiotic, we administered these species in a 5:1 ratio. Targeted probiotic administration reduced seizures and improved locomotor activities in control diet–fed animals, similar to KD-fed animals, while a negative control (Ligilactobacillus salivarius) had no impact. Probiotic administration also increased antioxidant status and decreased proinflammatory cytokines. Results suggest that a targeted probiotic reduces seizure frequency, improves locomotor activity in a rodent model of IS, and provides insights into microbiota manipulation as a potential therapeutic avenue for pediatric epileptic encephalopathies.
Authors
Chunlong Mu, Naghmeh Nikpoor, Thomas A. Tompkins, Anamika Choudhary, Melinda Wang, Wendie N. Marks, Jong M. Rho, Morris H. Scantlebury, Jane Shearer
Abstract
Apolipoprotein C-III (apoC-III) is a critical regulator of triglyceride metabolism and correlates positively with hypertriglyceridemia and cardiovascular disease (CVD). ApoC-III also induces sterile inflammation via inflammasome activation, another CVD risk factor. It remains unclear if therapeutic apoC-III lowering reduces CVD risk, nor is it understood if the CVD correlation depends on the lipid-lowering or anti-inflammatory properties. Therefore, we determined the impact of interventional apoC-III lowering on atherogenesis via apoC-III antisense oligonucleotide (ASO) administration in two hypertriglyceridemic mouse models where the intervention lowers plasma triglycerides (Apoe-/-Ndst1f/fAlb-Cre+, Ldlr-/-Ndst1f/fAlb-Cre+) and in a third lipid-refractory model where the ASO cannot lower plasma triglycerides (Ldlr-/-Lrp1f/fAlb-Cre+). A high-cholesterol Western diet ApoC-III ASO treatment did not alter atherosclerotic lesion size but did significantly attenuate advanced and unstable plaque development in the two triglyceride responsive mouse models. In contrast, no lesion size or composition improvement was observed with apoC-III ASO in the lipid-refractory Ldlr-/-Lrp1f/fAlb-Cre+ mice. To circumvent confounding effects of continuous high cholesterol feeding, we tested the impact of interventional apoC-III lowering when switching to a cholesterol-poor diet after 12-weeks of Western diet. In this diet-switch regimen, ApoC-III ASO treatment significantly reduced plasma triglycerides, atherosclerotic lesion progression, and necrotic core area and increased fibrous cap thickness in Ldlr-/-Ndst1f/fAlb-Cre+ mice. Again, ApoC-III ASO treatment did not alter triglyceride levels, lesion development and lesion composition in Ldlr-/-Lrp1f/fAlb-Cre+ mice after the diet-switch. Thus, therapeutic apoC-III targeting increased fibrous cap thickness, and reduced necrotic core area and lesion size after diet intervention when triglyceride-lowering is achieved in murine models. Our findings suggest that interventional apoC-III lowering might be an effective strategy to reduce atherosclerosis lesion size and improve plaque stability.
Authors
Bastian Ramms, Sohan Patel, Xiaoli Sun, Ariane R. Pessentheiner, G. Michelle Ducasa, Adam E. Mullick, Richard G. Lee, Rosanne M. Crooke, Sotirios Tsimikas, Joseph L. Witztum, Philip L.S.M. Gordts
Abstract
Insulin secretion from pancreatic β cells is essential for glucose homeostasis. An insufficient response to the demand for insulin results in diabetes. We previously showed that β cell–specific deletion of Zfp148 (β-Zfp148KO) improves glucose tolerance and insulin secretion in mice. Here, we performed Ca2+ imaging of islets from β‑Zfp148KO and control mice fed both a chow and a Western-style diet. β-Zfp148KO islets demonstrated improved sensitivity and sustained Ca2+ oscillations in response to elevated glucose levels. β-Zfp148KO islets also exhibited elevated sensitivity to amino acid–induced Ca2+ influx under low glucose conditions, suggesting enhanced mitochondrial phosphoenolpyruvate-dependent (PEP-dependent), ATP-sensitive K+ channel closure, independent of glycolysis. RNA-Seq and proteomics of β-Zfp148KO islets revealed altered levels of enzymes involved in amino acid metabolism (specifically, SLC3A2, SLC7A8, GLS, GLS2, PSPH, PHGDH, and PSAT1) and intermediary metabolism (namely, GOT1 and PCK2), consistent with altered PEP cycling. In agreement with this, β-Zfp148KO islets displayed enhanced insulin secretion in response to l-glutamine and activation of glutamate dehydrogenase. Understanding pathways controlled by ZFP148 may provide promising strategies for improving β cell function that are robust to the metabolic challenge imposed by a Western diet.
Authors
Christopher H. Emfinger, Eleonora de Klerk, Kathryn L. Schueler, Mary E. Rabaglia, Donnie S. Stapleton, Shane P. Simonett, Kelly A. Mitok, Ziyue Wang, Xinyue Liu, Joao A. Paulo, Qinq Yu, Rebecca L. Cardone, Hannah R. Foster, Sophie L. Lewandowski, José C. Perales, Christina M. Kendziorski, Steven P. Gygi, Richard G. Kibbey, Mark P. Keller, Matthias Hebrok, Matthew J. Merrins, Alan D. Attie
Abstract
Vertical sleeve gastrectomy (VSG) results in an increase in the number of hormone-secreting enteroendocrine cells (EECs) in the intestinal epithelium, however the mechanism remains unclear. Notably, the beneficial effects of VSG are lost in a mouse model lacking the nuclear bile acid receptor, farnesoid X receptor (FXR). FXR is a nuclear transcription factor that has been shown to regulate intestinal stem cell (ISC) function in cancer models. Therefore, we hypothesized that the VSG-induced increase in EECs is due to changes in intestinal differentiation driven by an increase in bile acid signaling through FXR. To test this, we performed VSG in mice that express eGFP in ISC/progenitor cells and performed RNA-seq on GFP-positive cells sorted from the intestinal epithelia. We also assessed changes in EEC number (marked by GLP-1) in mouse intestinal organoids following treatment with bile acids, an FXR agonist, and a FXR antagonist. RNA-seq of ISCs revealed that bile acids receptors are expressed in ISCs and that VSG explicitly alters expression of several genes that regulate EEC differentiation. Mouse intestinal organoids treated with bile acids and two different FXR agonists increased GLP-1-positive cell numbers, and administration of an FXR antagonist blocked these effects. Taken together, these data indicate that VSG drives ISC fate towards EEC differentiation through bile acid signaling.
Authors
Ki-Suk Kim, Bailey C.E. Peck, Yu-Han Hung, Kieran Koch-Laskowski, Landon Wood, Priya H. Dedhia, Jason R. Spence, Randy J. Seeley, Praveen Sethupathy, Darleen A. Sandoval
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