An shRNA screen in primary human beta cells identifies the serotonin 1F receptor as a negative regulator of survival during transplant.

Unlabelled: Islet transplantation can cure type 1 diabetes, but peri-transplant beta cell death limits this procedure to those with low insulin requirements. Improving human beta cell survival or proliferation may make islet transplantation a possibility for more type 1 patients. To identify novel regulators of beta cell survival and proliferation, we conducted a pooled small hairpin RNA (shRNA) screen in primary human beta cells transplanted into immunocompromised mice.

Gut Microbiota-Derived Trimethylamine N-Oxide Contributes to Abdominal Aortic Aneurysm Through Inflammatory and Apoptotic Mechanisms.

Background: Large-scale human and mechanistic mouse studies indicate a strong relationship between the microbiome-dependent metabolite trimethylamine N-oxide (TMAO) and several cardiometabolic diseases. This study aims to investigate the role of TMAO in the pathogenesis of abdominal aortic aneurysm (AAA) and target its parent microbes as a potential pharmacological intervention.

Methods: TMAO and choline metabolites were examined in plasma samples, with associated clinical data, from 2 independent patient cohorts (N=2129 total).

Gut microbial trimethylamine is elevated in alcohol-associated hepatitis and contributes to ethanol-induced liver injury in mice.

There is mounting evidence that microbes residing in the human intestine contribute to diverse alcohol-associated liver diseases (ALD) including the most deadly form known as alcohol-associated hepatitis (AH). However, mechanisms by which gut microbes synergize with excessive alcohol intake to promote liver injury are poorly understood. Furthermore, whether drugs that selectively target gut microbial metabolism can improve ALD has never been tested.

Gut microbe-targeted choline trimethylamine lyase inhibition improves obesity via rewiring of host circadian rhythms.

Obesity has repeatedly been linked to reorganization of the gut microbiome, yet to this point obesity therapeutics have been targeted exclusively toward the human host. Here, we show that gut microbe-targeted inhibition of the trimethylamine N-oxide (TMAO) pathway protects mice against the metabolic disturbances associated with diet-induced obesity (DIO) or leptin deficiency (). Small molecule inhibition of the gut microbial enzyme choline TMA-lyase (CutC) does not reduce food intake but is instead associated with alterations in the gut microbiome, improvement in glucose tolerance, and enhanced energy expenditure.

Late-life intermittent fasting decreases aging-related frailty and increases renal hydrogen sulfide production in a sexually dimorphic manner.

Global average life expectancy continues to rise. As aging increases the likelihood of frailty, which encompasses metabolic, musculoskeletal, and cognitive deficits, there is a need for effective anti-aging treatments. It is well established in model organisms that dietary restriction (DR), such as caloric restriction or protein restriction, enhances health and lifespan.

IL-1 induces mitochondrial translocation of IRAK2 to suppress oxidative metabolism in adipocytes.

Chronic inflammation is a common feature of obesity, with elevated cytokines such as interleukin-1 (IL-1) in the circulation and tissues. Here, we report an unconventional IL-1R-MyD88-IRAK2-PHB/OPA1 signaling axis that reprograms mitochondrial metabolism in adipocytes to exacerbate obesity. IL-1 induced recruitment of IRAK2 Myddosome to mitochondria outer membranes via recognition by TOM20, followed by TIMM50-guided translocation of IRAK2 into mitochondria inner membranes, to suppress oxidative phosphorylation and fatty acid oxidation, thereby attenuating energy expenditure.

Genetic Deficiency of Flavin-Containing Monooxygenase 3 ( Fmo3) Protects Against Thrombosis but Has Only a Minor Effect on Plasma Lipid Levels-Brief Report.

Objective- FMO (flavin-containing monooxygenase) 3 converts bacterial-derived trimethylamine to trimethylamine N-oxide (TMAO), an independent risk factor for cardiovascular disease. We generated FMO3 knockout (FMO3KO) mouse to study its effects on plasma TMAO, lipids, glucose/insulin metabolism, thrombosis, and atherosclerosis. Approach and Results- Previous studies with an antisense oligonucleotide (ASO) knockdown strategy targeting FMO3 in LDLRKO (low-density lipoprotein receptor knockout) mice resulted in major reductions in TMAO levels and atherosclerosis, but also showed effects on plasma lipids, insulin, and glucose.

Loss of HDAC6 alters gut microbiota and worsens obesity.

Alterations in gut microbiota are known to affect intestinal inflammation and obesity. Antibiotic treatment can affect weight gain by elimination of histone deacetylase (HDAC) inhibitor-producing microbes, which are anti-inflammatory by augmenting regulatory T (T) cells. We asked whether mice that lack HDAC6 and have potent suppressive T cells are protected from microbiota-induced accelerated weight gain.

Akt3 inhibits adipogenesis and protects from diet-induced obesity via WNK1/SGK1 signaling.

Three Akt isoforms, encoded by 3 separate genes, are expressed in mammals. While the roles of Akt1 and Akt2 in metabolism are well established, it is not yet known whether Akt3 plays a role in metabolic diseases. We now report that Akt3 protects mice from high-fat diet-induced obesity by suppressing an alternative pathway of adipogenesis via with no lysine protein kinase-1 (WNK1) and serum/glucocorticoid-inducible kinase 1 (SGK1).

Postprandial gut microbiota-driven choline metabolism links dietary cues to adipose tissue dysfunction.

The human body is an integrated circuit between microbial symbionts and our Homo sapien genome, which communicate bi-directionally to maintain homeostasis within the human meta-organism. There is now strong evidence that microbes resident in the human intestine can directly contribute to the pathogenesis of obesity and associated cardiometabolic disorders. In fact, gut microbes represent a filter of our greatest environmental exposure - the foods we consume.

Δ-5 Fatty Acid Desaturase Impacts Metabolic Disease by Balancing Proinflammatory and Proresolving Lipid Mediators.

Objective: Human genetic variants near the FADS (fatty acid desaturase) gene cluster (-) are strongly associated with cardiometabolic traits including dyslipidemia, fatty liver, type 2 diabetes mellitus, and coronary artery disease. However, mechanisms underlying these genetic associations are unclear.

Approach And Results: Here, we specifically investigated the physiological role of the Δ-5 desaturase FADS1 in regulating diet-induced cardiometabolic phenotypes by treating hyperlipidemic LDLR (low-density lipoprotein receptor)-null mice with antisense oligonucleotides targeting the selective knockdown of .

The TMAO-Producing Enzyme Flavin-Containing Monooxygenase 3 Regulates Obesity and the Beiging of White Adipose Tissue.

Emerging evidence suggests that microbes resident in the human intestine represent a key environmental factor contributing to obesity-associated disorders. Here, we demonstrate that the gut microbiota-initiated trimethylamine N-oxide (TMAO)-generating pathway is linked to obesity and energy metabolism. In multiple clinical cohorts, systemic levels of TMAO were observed to strongly associate with type 2 diabetes.

Regulation of Hepatic Triacylglycerol Metabolism by CGI-58 Does Not Require ATGL Co-activation.

Adipose triglyceride lipase (ATGL) and comparative gene identification 58 (CGI-58) are critical regulators of triacylglycerol (TAG) turnover. CGI-58 is thought to regulate TAG mobilization by stimulating the enzymatic activity of ATGL. However, it is not known whether this coactivation function of CGI-58 occurs in vivo.

Emerging roles of flavin monooxygenase 3 in cholesterol metabolism and atherosclerosis.

Purpose Of Review: Atherosclerosis and associated cardiovascular disease still remain the largest cause of mortality worldwide. Several recent studies have discovered that metabolism of common nutrients by gut microbes can produce a proatherogenic metabolite called trimethylamine-N-oxide (TMAO). The goal of this review is to discuss emerging evidence that the hepatic enzyme that generates TMAO, flavin monooxygenase 3 (FMO3), plays a regulatory role in maintaining whole body cholesterol balance and atherosclerosis development.

The TMAO-Generating Enzyme Flavin Monooxygenase 3 Is a Central Regulator of Cholesterol Balance.

Circulating levels of the gut microbe-derived metabolite trimethylamine-N-oxide (TMAO) have recently been linked to cardiovascular disease (CVD) risk. Here, we performed transcriptional profiling in mouse models of altered reverse cholesterol transport (RCT) and serendipitously identified the TMAO-generating enzyme flavin monooxygenase 3 (FMO3) as a powerful modifier of cholesterol metabolism and RCT. Knockdown of FMO3 in cholesterol-fed mice alters biliary lipid secretion, blunts intestinal cholesterol absorption, and limits the production of hepatic oxysterols and cholesteryl esters.

Cardiomyocyte-specific deficiency of ketone body metabolism promotes accelerated pathological remodeling.

Objective: Exploitation of protective metabolic pathways within injured myocardium still remains an unclarified therapeutic target in heart disease. Moreover, while the roles of altered fatty acid and glucose metabolism in the failing heart have been explored, the influence of highly dynamic and nutritionally modifiable ketone body metabolism in the regulation of myocardial substrate utilization, mitochondrial bioenergetics, reactive oxygen species (ROS) generation, and hemodynamic response to injury remains undefined.

Methods: Here we use mice that lack the enzyme required for terminal oxidation of ketone bodies, succinyl-CoA:3-oxoacid CoA transferase (SCOT) to determine the role of ketone body oxidation in the myocardial injury response.

Role of choline deficiency in the Fatty liver phenotype of mice fed a low protein, very low carbohydrate ketogenic diet.

Though widely employed for clinical intervention in obesity, metabolic syndrome, seizure disorders and other neurodegenerative diseases, the mechanisms through which low carbohydrate ketogenic diets exert their ameliorative effects still remain to be elucidated. Rodent models have been used to identify the metabolic and physiologic alterations provoked by ketogenic diets. A commonly used rodent ketogenic diet (Bio-Serv F3666) that is very high in fat (~94% kcal), very low in carbohydrate (~1% kcal), low in protein (~5% kcal), and choline restricted (~300 mg/kg) provokes robust ketosis and weight loss in mice, but through unknown mechanisms, also causes significant hepatic steatosis, inflammation, and cellular injury.

Ketone body metabolism and cardiovascular disease.

Ketone bodies are metabolized through evolutionarily conserved pathways that support bioenergetic homeostasis, particularly in brain, heart, and skeletal muscle when carbohydrates are in short supply. The metabolism of ketone bodies interfaces with the tricarboxylic acid cycle, β-oxidation of fatty acids, de novo lipogenesis, sterol biosynthesis, glucose metabolism, the mitochondrial electron transport chain, hormonal signaling, intracellular signal transduction pathways, and the microbiome. Here we review the mechanisms through which ketone bodies are metabolized and how their signals are transmitted.

Successful adaptation to ketosis by mice with tissue-specific deficiency of ketone body oxidation.

During states of low carbohydrate intake, mammalian ketone body metabolism transfers energy substrates originally derived from fatty acyl chains within the liver to extrahepatic organs. We previously demonstrated that the mitochondrial enzyme coenzyme A (CoA) transferase [succinyl-CoA:3-oxoacid CoA transferase (SCOT), encoded by nuclear Oxct1] is required for oxidation of ketone bodies and that germline SCOT-knockout (KO) mice die within 48 h of birth because of hyperketonemic hypoglycemia. Here, we use novel transgenic and tissue-specific SCOT-KO mice to demonstrate that ketone bodies do not serve an obligate energetic role within highly ketolytic tissues during the ketogenic neonatal period or during starvation in the adult.

Low-carbohydrate ketogenic diets, glucose homeostasis, and nonalcoholic fatty liver disease.

Purpose Of Review: Obesity-associated nonalcoholic fatty liver disease (NAFLD) is highly prevalent, for which weight loss is the generally recommended clinical management. Low-carbohydrate ketogenic diets have been successful in promoting weight loss, but variations in the range of metabolic responses to these diets indicate that the effects of altering macronutrient content are not completely understood. This review focuses on the most recent findings that reveal the relationship between low-carbohydrate diets and NAFLD in rodent models and humans.

Human muscle-derived cell populations isolated by differential adhesion rates: phenotype and contribution to skeletal muscle regeneration in Mdx/SCID mice.

Muscle-derived stem cells (MDSCs) isolated from murine skeletal tissue by the preplate method have displayed the capability to commit to the myogenic lineage and regenerate more efficiently than myoblasts in skeletal and cardiac muscle in murine Duchenne Muscular Dystrophy mice (mdx). However, until now, these studies have not been translated to human muscle cells. Here, we describe the isolation, by a preplate technique, of candidate human MDSCs, which exhibit myogenic and regenerative characteristics similar to their murine counterparts.

Hepatic steatosis, inflammation, and ER stress in mice maintained long term on a very low-carbohydrate ketogenic diet.

Low-carbohydrate diets are used to manage obesity, seizure disorders, and malignancies of the central nervous system. These diets create a distinctive, but incompletely defined, cellular, molecular, and integrated metabolic state. Here, we determine the systemic and hepatic effects of long-term administration of a very low-carbohydrate, low-protein, and high-fat ketogenic diet, serially comparing these effects to a high-simple-carbohydrate, high-fat Western diet and a low-fat, polysaccharide-rich control chow diet in C57BL/6J mice.