Short-term cold exposure induces persistent epigenomic memory in brown fat.

Deficiency of the epigenome modulator histone deacetylase 3 (HDAC3) in brown adipose tissue (BAT) impairs the ability of mice to survive in near-freezing temperatures. Here, we report that short-term exposure to mild cold temperature (STEMCT: 15°C for 24 h) averted lethal hypothermia of mice lacking HDAC3 in BAT (HDAC3 BAT KO) exposed to 4°C. STEMCT restored the induction of the thermogenic coactivator PGC-1α along with UCP1 at 22°C, which is greatly impaired in HDAC3-deficient BAT, and deletion of either UCP1 or PGC-1α prevented the protective effect of STEMCT. Remarkably, this protection lasted for up to 7 days. Transcriptional activator C/EBPß was induced by short-term cold exposure in mouse and human BAT and, uniquely, remained high for 7 days following STEMCT. Adeno-associated virus-mediated knockdown of BAT C/EBPß in HDAC3 BAT KO mice erased the persistent memory of STEMCT, revealing the existence of a C/EBPß-dependent and HDAC3-independent cold-adaptive epigenomic memory.

Successful Treatment with Dabrafenib/Trametinib of a Malignantly Transformed and Metastasized BRAF V600E Mutant Pleiomorphic Xanthoastrocytoma: A Case Report and Review of the Literature.

Introduction: Pleiomorphic xanthoastrocytoma (PXA) is considered a low-grade glioma with a favorable prognosis following surgical resection. We present a case report of a BRAFV600E mutant malignantly transformed and disseminated PXA that was successfully treated with BRAF-/MEK-targeted therapy (dabrafenib/trametinib). Case Presentation: At the age of 16 years, our patient underwent an initial subtotal resection of a right occipital PXA. Six months later, a reintervention for an asymptomatic tumor recurrence was performed and complete resection was achieved. The patient has been followed up by MRI for 14 years without arguments for recurrence but was lost to follow-up thereafter. At 38 years of age, he presented with a symptomatic local recurrence with extra-cerebral soft tissue extension, for which a third surgical resection was performed. Anatomopathological examination reported a grade 3 anaplastic PXA (aPXA); molecular analysis detected a BRAFV600E mutation. Three months later, before the initiation of radiotherapy, a local tumor recurrence was diagnosed, for which he underwent a fourth surgical resection. Radiotherapy was performed following the surgical debulking. One month after completion of radiotherapy, disease progression was documented including multiple sites of extracranial metastases (skeletal, lung, cervical lymph node, and subcutaneous metastases). Systemic treatment with a combination of BRAF-/MEK-inhibitors (dabrafenib/trametinib) was initiated and resulted in a rapid and deep tumor response (partial response according to RECISTv1.1) and absence of BRAFV600E mutant ctDNA in plasma at 6 weeks after treatment initiation. A near-complete metabolic remission was documented on [18F]FDG-PET/CT 3 months after starting systemic therapy. Conclusion: We present a rare case of malignant transformation and systemic dissemination of a BRAFV600E mutant PXA, occurring 20 years after the initial diagnosis. This case highlights the importance of long-term follow-up of patients diagnosed with these rare central nervous system tumors that initially are considered benign and also illustrates that BRAF/MEK inhibition can be an effective therapy for BRAFV600E mutated PXA, underscoring the importance of performing molecular genetic profiling of these tumors.

Very-low-density lipoprotein triglyceride and free fatty acid plasma kinetics in women with high or low brown adipose tissue volume and overweight/obesity.

Although a high amount of brown adipose tissue (BAT) is associated with low plasma triglyceride concentration, the mechanism responsible for this relationship in people is not clear. Here, we evaluate the interrelationships among BAT, very-low-density lipoprotein triglyceride (VLDL-TG), and free fatty acid (FFA) plasma kinetics during thermoneutrality in women with overweight/obesity who had a low (<20 mL) or high (≥20 mL) volume of cold-activated BAT (assessed by using positron emission tomography in conjunction with 2-deoxy-2-[18F]-fluoro-glucose). We find that plasma TG and FFA concentrations are lower and VLDL-TG and FFA plasma clearance rates are faster in women with high BAT than low BAT volume, whereas VLDL-TG and FFA appearance rates in plasma are not different between the two groups. These findings demonstrate that women with high BAT volume have lower plasma TG and FFA concentrations than women with low BAT volumes because of increased VLDL-TG and FFA clearance rates. This study was registered at ClinicalTrials.gov (NCT02786251).

Steatosis drives monocyte-derived macrophage accumulation in human metabolic dysfunction-associated fatty liver disease.

Background & Aims: Metabolic dysfunction-associated fatty liver disease (MAFLD) is a common complication of obesity with a hallmark feature of hepatic steatosis. Recent data from animal models of MAFLD have demonstrated substantial changes in macrophage composition in the fatty liver. In humans, the relationship between liver macrophage heterogeneity and liver steatosis is less clear. Methods: Liver tissue from 21 participants was collected at time of bariatric surgery and analysed using flow cytometry, immunofluorescence, and H&E microscopy. Single-cell RNA sequencing was also conducted on a subset of samples (n = 3). Intrahepatic triglyceride content was assessed via MRI and tissue histology. Mouse models of hepatic steatosis were used to investigate observations made from human liver tissue. Results: We observed variable degrees of liver steatosis with minimal fibrosis in our participants. Single-cell RNA sequencing revealed four macrophage clusters that exist in the human fatty liver encompassing Kupffer cells and monocyte-derived macrophages (MdMs). The genes expressed in these macrophage subsets were similar to those observed in mouse models of MAFLD. Hepatic CD14+ monocyte/macrophage number correlated with the degree of steatosis. Using mouse models of early liver steatosis, we demonstrate that recruitment of MdMs precedes Kupffer cell loss and liver damage. Electron microscopy of isolated macrophages revealed increased lipid accumulation in MdMs, and ex vivo lipid transfer experiments suggested that MdMs may serve a distinct role in lipid uptake during MAFLD. Conclusions: The human liver in MAFLD contains macrophage subsets that align well with those that appear in mouse models of fatty liver disease. Recruited myeloid cells correlate well with the degree of liver steatosis in humans. MdMs appear to participate in lipid uptake during early stages of MALFD. Impact and implications: Metabolic dysfunction associated fatty liver disease (MAFLD) is extremely common; however, the early inflammatory responses that occur in human disease are not well understood. In this study, we investigated macrophage heterogeneity in human livers during early MAFLD and demonstrated that similar shifts in macrophage subsets occur in human disease that are similar to those seen in preclinical models. These findings are important as they establish a translational link between mouse and human models of disease, which is important for the development and testing of new therapeutic approaches for MAFLD.

ß Cell function after Roux-en-Y gastric bypass surgery or reduced energy intake alone in people with obesity.

BackgroundThe effects of diet-induced weight loss (WL) and WL after Roux-en-Y gastric bypass (RYGB) surgery on ß cell function (BCF) are unclear because of conflicting results from different studies, presumably because of differences in the methods used to measure BCF, the amount of WL between treatment groups, and baseline BCF. We evaluated the effect of WL after RYGB surgery or reduced energy intake alone on BCF in people with obesity with and without type 2 diabetes.MethodsBCF (insulin secretion in relationship to plasma glucose) was assessed before and after glucose or mixed-meal ingestion before and after (a) progressive amounts (6%, 11%, 16%) of WL induced by a low-calorie diet (LCD) in people with obesity without diabetes, (b) ~20% WL after RYGB surgery or laparoscopic adjustable gastric banding (LAGB) in people with obesity without diabetes, and (c) ~20% WL after RYGB surgery or LCD alone in people with obesity and diabetes.ResultsDiet-induced progressive WL in people without diabetes progressively decreased BCF. Marked WL after LAGB or RYGB in people without diabetes did not alter BCF. Marked WL after LCD or RYGB in people with diabetes markedly increased BCF, without a difference between groups.ConclusionMarked WL increases BCF in people with obesity and diabetes but not in people with obesity without diabetes. The effect of RYGB-induced WL on BCF is not different from the effect of matched WL after LAGB or LCD alone.trial registrationNCT00981500, NCT02207777, NCT01299519.FundingNIH grants R01 DK037948, P30 DK056341, P30 DK020579, UL1 TR002345.

Architecture of the outbred brown fat proteome defines regulators of metabolic physiology.

Brown adipose tissue (BAT) regulates metabolic physiology. However, nearly all mechanistic studies of BAT protein function occur in a single inbred mouse strain, which has limited the understanding of generalizable mechanisms of BAT regulation over physiology. Here, we perform deep quantitative proteomics of BAT across a cohort of 163 genetically defined diversity outbred mice, a model that parallels the genetic and phenotypic variation found in humans. We leverage this diversity to define the functional architecture of the outbred BAT proteome, comprising 10,479 proteins. We assign co-operative functions to 2,578 proteins, enabling systematic discovery of regulators of BAT. We also identify 638 proteins that correlate with protection from, or sensitivity to, at least one parameter of metabolic disease. We use these findings to uncover SFXN5, LETMD1, and ATP1A2 as modulators of BAT thermogenesis or adiposity, and provide OPABAT as a resource for understanding the conserved mechanisms of BAT regulation over metabolic physiology.

Insufficient sleep and obesity: cause or consequence.

Sleep is an ancient and evolutionarily conserved biological process that, when disturbed, increases the risk for a variety of diseases in people, including diabetes, cardiovascular disease, kidney disease, and cancer. Although results from epidemiological studies support the link between insufficient sleep and an increased risk of obesity, the directionality of this link is unknown. Results from short-term controlled clinical studies, conducted almost exclusively in people who are normal weight, demonstrate that sleep restriction increases hunger, appetite, energy intake, and body weight. However, the authors are not aware of any studies that have evaluated the effect of more than 3 weeks of experimental sleep restriction on obesity risk factors, and few studies have been conducted in people with preexisting obesity. This Perspective reviews the link between insufficient sleep and obesity risk and the potential therapeutic effects of sleep extension in people with chronic sleep insufficiency.

Glucagon-like peptide-1, glucose-dependent insulinotropic polypeptide, and glucagon receptor poly-agonists: a new era in obesity pharmacotherapy.

Achieving successful long-term weight loss with lifestyle modification in people with obesity is difficult and underscores the need for effective pharmacotherapy. Since 1947, a total of 18 medications have been approved by the US Food and Drug Administration for treating obesity; however, only 5 remain available for long-term use in the US. Semaglutide, a glucagon-like peptide-1 (GLP-1) receptor agonist approved in 2021, demonstrated much greater weight loss than previous medications, which stimulated the development of poly-agonists that combine GLP-1 receptor agonism with glucose-dependent insulinotropic polypeptide (GIP) and glucagon receptor agonism. The potential of this approach was recently demonstrated by the extraordinary weight loss achieved by tirzepatide, a GLP-1/GIP receptor dual agonist. The therapeutic efficacy of poly-agonists is likely to change the treatment paradigm for obesity. However, the use of medications for obesity, as for other chronic diseases, will likely require lifelong treatment, which makes it important to analyze the long-term efficacy, safety, and economic implications of chronic pharmacotherapy.

Physiological interindividual variability in endogenous estradiol concentration does not influence adipose tissue and hepatic lipid kinetics in women.

Objective: Increased triglyceride (TG) and apolipoprotein B-100 (apoB-100) concentrations in plasma are important risk factors for cardiovascular disease in women. Administration of some estrogen preparations raises plasma TG and apoB-100 concentrations by increasing hepatic very low-density lipoprotein (VLDL) TG and apoB-100 secretion rates. However, the influence of physiological variation in endogenous estradiol on VLDL-TG and VLDL-apoB-100 metabolism and on free fatty acid (FFA) release into plasma (the major source of fatty acids for VLDL-TG production) is not known. Design and methods: We measured basal VLDL-TG, VLDL-apoB-100, and plasma FFA kinetics by using stable isotopically labeled tracers in 36 eumenorrheic, premenopausal women (age: 33 ± 2 years, BMI: 31 ± 1 kg/m2; mean ± s.e.m.) during the follicular phase of the menstrual cycle; participants were divided into two groups based on low (n = 18) or high (n = 18) plasma estradiol concentrations (defined as below or above the median value of 140 pmol/L in the whole group). Results: Mean plasma estradiol concentration was >3-fold higher in the high-estradiol than in the low-estradiol group (299 ± 37 and 96 ± 7 pmol/L, P < 0.001); there was no difference in plasma progesterone concentrations between the two groups (P = 0.976). There were no significant differences in plasma FFA concentration, FFA rate of appearance in plasma, VLDL-TG and VLDL-apoB-100 concentrations, hepatic VLDL-TG and VLDL-apoB-100 secretion rates, VLDL-TG and VLDL-apoB-100 plasma clearance rates, and mean residence times (all P ≥ 0.45). No significant associations were found between plasma estradiol concentration and FFA, VLDL-TG, and VLDL-apoB-100 concentrations and kinetics (all P > 0.19). Conclusions: Plasma estradiol concentration is not an important correlate of basal plasma FFA, VLDL-TG, and VLDL-apoB-100 kinetics in premenopausal women.

Silencing alanine transaminase 2 in diabetic liver attenuates hyperglycemia by reducing gluconeogenesis from amino acids.

Hepatic gluconeogenesis from amino acids contributes significantly to diabetic hyperglycemia, but the molecular mechanisms involved are incompletely understood. Alanine transaminases (ALT1 and ALT2) catalyze the interconversion of alanine and pyruvate, which is required for gluconeogenesis from alanine. We find that ALT2 is overexpressed in the liver of diet-induced obese and db/db mice and that the expression of the gene encoding ALT2 (GPT2) is downregulated following bariatric surgery in people with obesity. The increased hepatic expression of Gpt2 in db/db liver is mediated by activating transcription factor 4, an endoplasmic reticulum stress-activated transcription factor. Hepatocyte-specific knockout of Gpt2 attenuates incorporation of 13C-alanine into newly synthesized glucose by hepatocytes. In vivo Gpt2 knockdown or knockout in liver has no effect on glucose concentrations in lean mice, but Gpt2 suppression alleviates hyperglycemia in db/db mice. These data suggest that ALT2 plays a significant role in hepatic gluconeogenesis from amino acids in diabetes.

Metabolic subtypes of patients with NAFLD exhibit distinctive cardiovascular risk profiles.

BACKGROUND AND AIMS: We previously identified subsets of patients with NAFLD with different metabolic phenotypes. Here we align metabolomic signatures with cardiovascular disease (CVD) and genetic risk factors. APPROACH AND RESULTS: We analyzed serum metabolome from 1154 individuals with biopsy-proven NAFLD, and from four mouse models of NAFLD with impaired VLDL-triglyceride (TG) secretion, and one with normal VLDL-TG secretion. We identified three metabolic subtypes: A (47%), B (27%), and C (26%). Subtype A phenocopied the metabolome of mice with impaired VLDL-TG secretion; subtype C phenocopied the metabolome of mice with normal VLDL-TG; and subtype B showed an intermediate signature. The percent of patients with NASH and fibrosis was comparable among subtypes, although subtypes B and C exhibited higher liver enzymes. Serum VLDL-TG levels and secretion rate were lower among subtype A compared with subtypes B and C. Subtype A VLDL-TG and VLDL-apolipoprotein B concentrations were independent of steatosis, whereas subtypes B and C showed an association with these parameters. Serum TG, cholesterol, VLDL, small dense LDL5,6 , and remnant lipoprotein cholesterol were lower among subtype A compared with subtypes B and C. The 10-year high risk of CVD, measured with the Framingham risk score, and the frequency of patatin-like phospholipase domain-containing protein 3 NAFLD risk allele were lower in subtype A. CONCLUSIONS: Metabolomic signatures identify three NAFLD subgroups, independent of histological disease severity. These signatures align with known CVD and genetic risk factors, with subtype A exhibiting a lower CVD risk profile. This may account for the variation in hepatic versus cardiovascular outcomes, offering clinically relevant risk stratification.

Revising mental representations of faces based on new diagnostic information.

Extending evidence for the rapid revision of mental representations of what other people are like, we explored whether people also rapidly revise their representations of what others look like. After learning to ascribe positive or negative behavioral information to a target person and generating a visualization of their face in a reverse-correlation task, participants learned new information that was (a) counter-attitudinal and diagnostic about the person's character or (b) neutral and non-diagnostic, and then they generated a second visualization. Ratings of these visualizations in separate samples of participants consistently revealed revision effects: Time 2 visualizations assimilated to the counter-attitudinal information. Weaker revision effects also emerged after learning neutral information, suggesting that the evaluative extremity of visualizations may dilute when encountering any additional information. These findings indicate that representations of others' appearance may change upon learning more about them, particularly when this new information is counter-attitudinal and diagnostic.

Intracerebral administration of CTLA-4 and PD-1 immune checkpoint blocking monoclonal antibodies in patients with recurrent glioblastoma: a phase I clinical trial.

BACKGROUND: Patients with recurrent glioblastoma (rGB) have a poor prognosis with a median overall survival (OS) of 30-39 weeks in prospective clinical trials. Intravenous administration of programmed cell death protein 1 and cytotoxic T-lymphocyte-associated antigen 4 inhibitors has low activity in patients with rGB. In this phase I clinical trial, intracerebral (IC) administration of ipilimumab (IPI) and nivolumab (NIVO) in combination with intravenous administration of NIVO was investigated. METHODS: Within 24 hours following the intravenous administration of a fixed dose (10 mg) of NIVO, patients underwent a maximal safe resection, followed by injection of IPI (10 mg; cohort-1), or IPI (5 mg) plus NIVO (10 mg; cohort-2) in the brain tissue lining the resection cavity. Intravenous administration of NIVO (10 mg) was repeated every 2 weeks (max. five administrations). Next generation sequencing and RNA gene expression profiling was performed on resected tumor tissue. RESULTS: Twenty-seven patients were enrolled (cohort-1: n=3; cohort-2: n=24). All patients underwent maximal safe resection and planned IC administrations and preoperative NIVO. Thirteen patients (cohort-1: n=3; cohort-2: n=10) received all five postoperative intravenous doses of NIVO. In cohort-2, 14 patients received a median of 3 (range 1-4) intravenous doses. Subacute postoperative neurological deterioration (n=2) was reversible on steroid treatment; no other central nervous system toxicity was observed. Immune-related adverse events were infrequent and mild. GB recurrence was diagnosed in 26 patients (median progression-free survival (PFS) is 11.7 weeks (range 2-152)); 21 patients have died due to progression. Median OS is 38 weeks (95% CI: 27 to 49) with a 6-month, 1-year, and 2-year OS-rate of, respectively, 74.1% (95% CI: 57 to 90), 40.7% (95% CI: 22 to 59), and 27% (95% CI: 9 to 44). OS compares favorable against a historical cohort (descriptive Log-Rank p>0.003). No significant difference was found with respect to PFS (descriptive Log-Rank test p>0.05). A higher tumor mRNA expression level of B7-H3 was associated with a significantly worse survival (multivariate Cox logistic regression, p>0.029). CONCLUSION: IC administration of NIVO and IPI following maximal safe resection of rGB was feasible, safe, and associated with encouraging OS. TRIAL REGISTRATION: NCT03233152.

Patient Determinants for Histologic Diagnosis of NAFLD in the Real World: A TARGET-NASH Study.

Much of the current data on nonalcoholic fatty liver disease (NAFLD) are derived from biopsy-based studies that may introduce ascertainment and selection bias. Selection of patients for liver biopsy has implications for clinical practice and the reported epidemiology of NAFLD. The aim of this study was to determine patient factors predictive of histologic versus empiric clinical diagnosis of NAFLD in real-world practice. Adults from TARGET-NASH were included in this study. Descriptive statistics are provided for the cohort and compare the characteristics of histologic NAFLD versus patients with clinically diagnosed NAFLD, followed by logistic regression and machine-learning models to describe predictors of liver biopsy. The records of 3,474 subjects were analyzed; median age was 59 years, 59% were female, 75% were White, and median body mass index was 32 kg/m2. Using histologic and/or clinical criteria, a diagnosis of nonalcoholic steatohepatitis was made in 37%, and cirrhosis in 33%. Comorbid conditions included cardiovascular disease (19%), mental health diagnoses (49%), and osteoarthritis (10%). Predictors of a biopsy diagnosis included White race, female sex, diabetes, and elevated alanine aminotransferase (ALT). ALT increased the odds of liver biopsy by 14% per 10-point rise. Machine-learning analyses showed non-White patients with ALT <69 had only a 0.06 probability of undergoing liver biopsy. ALT was the dominant variable that determined liver biopsy. Conclusions: In this real-world cohort of patients with NAFLD, two-thirds of patients did not have a liver biopsy. These patients were more likely to be non-White, older, with a normal ALT, showing potential gaps in or knowledge about this population.

A critical role of hepatic GABA in the metabolic dysfunction and hyperphagia of obesity.

Hepatic lipid accumulation is a hallmark of type II diabetes (T2D) associated with hyperinsulinemia, insulin resistance, and hyperphagia. Hepatic synthesis of GABA, catalyzed by GABA-transaminase (GABA-T), is upregulated in obese mice. To assess the role of hepatic GABA production in obesity-induced metabolic and energy dysregulation, we treated mice with two pharmacologic GABA-T inhibitors and knocked down hepatic GABA-T expression using an antisense oligonucleotide. Hepatic GABA-T inhibition and knockdown decreased basal hyperinsulinemia and hyperglycemia and improved glucose intolerance. GABA-T knockdown improved insulin sensitivity assessed by hyperinsulinemic-euglycemic clamps in obese mice. Hepatic GABA-T knockdown also decreased food intake and induced weight loss without altering energy expenditure in obese mice. Data from people with obesity support the notion that hepatic GABA production and transport are associated with serum insulin, homeostatic model assessment for insulin resistance (HOMA-IR), T2D, and BMI. These results support a key role for hepatocyte GABA production in the dysfunctional glucoregulation and feeding behavior associated with obesity.

Associations Among Adipose Tissue Immunology, Inflammation, Exosomes and Insulin Sensitivity in People With Obesity and Nonalcoholic Fatty Liver Disease.

BACKGROUND AND AIMS: Insulin resistance is a key factor in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). We evaluated the importance of subcutaneous abdominal adipose tissue (SAAT) inflammation and both plasma and SAAT-derived exosomes in regulating insulin sensitivity in people with obesity and NAFLD. METHODS: Adipose tissue inflammation (macrophage and T-cell content and expression of proinflammatory cytokines), liver and whole-body insulin sensitivity (assessed using a hyperinsulinemic-euglycemic clamp and glucose tracer infusion), and 24-hour serial plasma cytokine concentrations were evaluated in 3 groups stratified by adiposity and intrahepatic triglyceride (IHTG) content: (1) lean with normal IHTG content (LEAN; N = 14); (2) obese with normal IHTG content (OB-NL; N = 28); and (3) obese with NAFLD (OB-NAFLD; N = 28). The effect of plasma and SAAT-derived exosomes on insulin-stimulated Akt phosphorylation in human skeletal muscle myotubes and mouse primary hepatocytes was assessed in a subset of participants. RESULTS: Proinflammatory macrophages, proinflammatory CD4 and CD8 T-cell populations, and gene expression of several cytokines in SAAT were greater in the OB-NAFLD than the OB-NL and LEAN groups. However, with the exception of PAI-1, which was greater in the OB-NAFLD than the LEAN and OB-NL groups, 24-hour plasma cytokine concentration areas-under-the-curve were not different between groups. The percentage of proinflammatory macrophages and plasma PAI-1 concentration areas-under-the-curve were inversely correlated with both hepatic and whole-body insulin sensitivity. Compared with exosomes from OB-NL participants, plasma and SAAT-derived exosomes from the OB-NAFLD group decreased insulin signaling in myotubes and hepatocytes. CONCLUSIONS: Systemic insulin resistance in people with obesity and NAFLD is associated with increased plasma PAI-1 concentrations and both plasma and SAAT-derived exosomes. ClinicalTrials.gov number: NCT02706262 (https://clinicaltrials.gov/ct2/show/NCT02706262).

A CSF pseudocyst.

A 51-year-old female with prior history of ventriculoperitoneal shunt presented with worsening abdominal distension. Her abdomen was diffusely tender and firm with a slight fluid wave. CT imaging with IV contrast was notable for a large cystic lesion in the abdominal cavity with the differential of CSF pseudocyst versus ovarian mass. She underwent paracentesis of the cyst with interventional radiology and required a revision of her ventriculoperitoneal shunt. CSF pseudocysts are a rare complication of ventriculoperitoneal shunts, however, are an important consideration in patients presenting with abdominal complaints and require specialized intervention and assessment.

Describing the Weight-Reduced State: Physiology, Behavior, and Interventions.

Although many persons with obesity can lose weight by lifestyle (diet and physical activity) therapy, successful long-term weight loss is difficult to achieve, and most people who lose weight regain their lost weight over time. The neurohormonal, physiological, and behavioral factors that promote weight recidivism are unclear and complex. The National Institute of Diabetes and Digestive and Kidney Diseases convened a workshop in June 2019, titled "The Physiology of the Weight-Reduced State," to explore the mechanisms and integrative physiology of adaptations in appetite, energy expenditure, and thermogenesis that occur in the weight-reduced state and that may oppose weight-loss maintenance. The proceedings from the first session of this workshop are presented here. Drs. Michael Rosenbaum, Kevin Hall, and Rudolph Leibel discussed the physiological factors that contribute to weight regain; Dr. Michael Lowe discussed the biobehavioral issues involved in weight-loss maintenance; Dr. John Jakicic discussed the influence of physical activity on long-term weight-loss maintenance; and Dr. Louis Aronne discussed the ability of drug therapy to maintain weight loss.

Importance of Adipose Tissue NAD+ Biology in Regulating Metabolic Flexibility.

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme that regulates cellular energy metabolism in many cell types. The major purpose of the present study was to test the hypothesis that NAD+ in white adipose tissue (WAT) is a regulator of whole-body metabolic flexibility in response to changes in insulin sensitivity and with respect to substrate availability and use during feeding and fasting conditions. To this end, we first evaluated the relationship between WAT NAD+ concentration and metabolic flexibility in mice and humans. We found that WAT NAD+ concentration was increased in mice after calorie restriction and exercise, 2 enhancers of metabolic flexibility. Bariatric surgery-induced 20% weight loss increased plasma adiponectin concentration, skeletal muscle insulin sensitivity, and WAT NAD+ concentration in people with obesity. We next analyzed adipocyte-specific nicotinamide phosphoribosyltransferase (Nampt) knockout (ANKO) mice, which have markedly decreased NAD+ concentrations in WAT. ANKO mice oxidized more glucose during the light period and after fasting than control mice. In contrast, the normal postprandial stimulation of glucose oxidation and suppression of fat oxidation were impaired in ANKO mice. Data obtained from RNA-sequencing of WAT suggest that loss of NAMPT increases inflammation, and impairs insulin sensitivity, glucose oxidation, lipolysis, branched-chain amino acid catabolism, and mitochondrial function in WAT, which are features of metabolic inflexibility. These results demonstrate a novel function of WAT NAMPT-mediated NAD+ biosynthesis in regulating whole-body metabolic flexibility, and provide new insights into the role of adipose tissue NAD+ biology in metabolic health.

Dynamic Shifts in the Composition of Resident and Recruited Macrophages Influence Tissue Remodeling in NASH.

Macrophage-mediated inflammation is critical in the pathogenesis of non-alcoholic steatohepatitis (NASH). Here, we describe that, with high-fat, high-sucrose-diet feeding, mature TIM4pos Kupffer cells (KCs) decrease in number, while monocyte-derived Tim4neg macrophages accumulate. In concert, monocyte-derived infiltrating macrophages enter the liver and consist of a transitional subset that expresses Cx3cr1/Ccr2 and a second subset characterized by expression of Trem2, Cd63, Cd9, and Gpmnb; markers ascribed to lipid-associated macrophages (LAMs). The Cx3cr1/Ccr2-expressing macrophages, referred to as C-LAMs, localize to macrophage aggregates and hepatic crown-like structures (hCLSs) in the steatotic liver. In C-motif chemokine receptor 2 (Ccr2)-deficient mice, C-LAMs fail to appear in the liver, and this prevents hCLS formation, reduces LAM numbers, and increases liver fibrosis. Taken together, our data reveal dynamic changes in liver macrophage subsets during the pathogenesis of NASH and link these shifts to pathologic tissue remodeling.