Targeted overexpression of inducible 6-phosphofructo-2-kinase in adipose tissue increases fat deposition but protects against diet-induced insulin resistance and inflammatory responses

HFD feeding for seven months abolishes STING disruption-driven but not female sex-based protection against hepatic steatosis and inflammation in mice

Stimulator of interferon genes (STING) is positively correlated with the degrees of liver inflammation in human metabolic dysfunction-associated steatotic liver disease (MASLD). In addition, STING disruption alleviates MASLD in mice fed a high-fat diet (HFD) for 3 months (3-m-HFD). Here we investigated the role of the duration of dietary feeding in regulating MASLD in mice and explored the involvement of STING in sex differences in MASLD. Both male and female STING-disrupted (STINGgt) and wild-type C57BL/6J mice were fed an HFD for 3 or 7 months (7-m-HFD). Additionally, female STINGgt mice upon ovariectomy (OVX) and 3-m-HFD were analyzed for MASLD. Upon 3-m-HFD, STINGgt mice exhibited decreased severity of MASLD compared to control. However, upon 7-m-HFD, STINGgt mice were comparable with wild-type mice in body weight, fat mass, and MASLD. Regarding regulating the liver RNA transcriptome, 7-m-HFD increased the expression of genes indicating proinflammatory activation of various liver cells. Interestingly, the severity of MASLD in female mice was much lighter than in male mice, regardless of STING disruption. Upon OVX, female STINGgt mice showed significantly increased severity of MASLD relative to sham control but were comparable with male STINGgt mice. Upon treatment with 17-beta estradiol (E2), hepatocytes revealed decreased fat deposition while macrophages displayed decreases in lipopolysaccharide-induced phosphorylation of Nfkb p65 and Jnk p46 independent of STING. These results suggest that 7-m-HFD, without altering female sex-based protection, abolishes STING disruption-driven protection of MASLD, likely through causing proinflammatory activation of multiple types of liver cells to offset the effect of STING disruption.

PFKFB3 protein in adipose tissue contributes to whole body glucose homeostasis

Age-dependent changes in adipose tissue are thought to play a role in development of insulin resistance. A major age-dependent change in adipose tissue is the downregulation of key proteins involved in carbohydrate metabolism. In the current study, we investigate the role of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) a key governor of the rate of glycolysis in adipocytes via the synthesis of fructose-2,6-bisphosphate that was significantly downregulated in aged mice. We employed an adipocyte-specific PFKFB3 mouse line to investigate the role of PFKFB3 on adipocyte function. In both aged mice and PFKFB3-knockout mice, we observed an increase in O-glcNAcylated proteins consistent with a shift in glucose metabolism toward the hexosamine biosynthetic pathway. Under chow-fed conditions, PFKFB3 knockout resulted in significantly smaller adipocyte area, but no difference in total fat mass. While glucose tolerance was unchanged under chow conditions, when mice were challenged with a 4 weeks high-fat feeding, PFKFB3 deletion led to a greater decrease in glucose tolerance as well as a significant increase in macrophage infiltration. These results indicate that perturbation of the glycolytic pathway in adipose tissue has multiple effects of adipocyte biology and may play a significant role in metabolic changes associated with aging. Results of this student support the notion that changes in glucose metabolism in adipose tissue impact whole-body metabolism.

The pathophysiology of visceral adipose tissues in cardiometabolic diseases

Central pattern of fat distribution, especially fat accumulation within the intraabdominal cavity increases risks for cardiometabolic diseases. Portal hypothesis combined with a pathological remodeling in visceral fat is considered the major etiological factor explaining the independent contribution of visceral obesity to cardiometabolic diseases. Excessive remodeling in visceral fat during development of obesity leads to dysfunctions in the depot, characterized by hypertrophy and death of adipocytes, hypoxia, inflammation, and fibrosis. Dysfunctional visceral fat secretes elevated levels of fatty acids, glycerol, and proinflammatory and profibrotic cytokines into the portal vein directly impacting the liver, the central regulator of systemic metabolism. These metabolic and endocrine products induce ectopic fat accumulation, insulin resistance, inflammation, and fibrosis in the liver, which in turn causes or exacerbates systemic metabolic derangements. Elucidation of underlying mechanisms that lead to the pathological remodeling and higher degree of dysfunctions in visceral adipose tissue is therefore, critical for the development of therapeutics to prevent deleterious sequelae in obesity. We review depot differences in metabolic and endocrine properties and expendabilities as well as underlying mechanisms that contribute to the pathophysiological aspects of visceral adiposity in cardiometabolic diseases. We also discuss impacts of different weight loss interventions on visceral adiposity and cardiometabolic diseases.

Novel targets of β-TrCP cooperatively accelerate carbohydrate and fatty acid consumption

Cellular energy is primarily produced from glucose and fat through glycolysis and fatty acid oxidation (FAO) followed by the tricarboxylic acid cycle in mitochondria; energy homeostasis is carefully maintained via numerous feedback pathways. In this report, we uncovered a new master regulator of carbohydrate and lipid metabolism. When ubiquitin E3 ligase β-TrCP2 was inducibly knocked out in β-TrCP1 knockout adult mice, the resulting double knockout mice (DKO) lost fat mass rapidly. Biochemical analyses of the tissues and cells from β-TrCP2 KO and DKO mice revealed that glycolysis, FAO, and lipolysis were dramatically upregulated. The absence of β-TrCP2 increased the protein stability of metabolic rate-limiting enzymes including 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), adipose triglyceride lipase (ATGL), carnitine palmitoyltransferase 1A (CPT1A), and carnitine/acylcarnitine translocase (CACT). Our data suggest that β-TrCP is a potential regulator for total energy homeostasis by simultaneously controlling glucose and fatty acid metabolism and that targeting β-TrCP could be an effective strategy to treat obesity and other metabolic disorders.

CDK6 inhibits de novo lipogenesis in white adipose tissues but not in the liver

Increased de novo lipogenesis (DNL) in white adipose tissue is associated with insulin sensitivity. Under both Normal-Chow-Diet and High-Fat-Diet, mice expressing a kinase inactive Cyclin-dependent kinase 6 (Cdk6) allele (K43M) display an increase in DNL in visceral white adipose tissues (VAT) as compared to wild type mice (WT), accompanied by markedly increased lipogenic transcriptional factor Carbohydrate-responsive element-binding proteins (CHREBP) and lipogenic enzymes in VAT but not in the liver. Treatment of WT mice under HFD with a CDK6 inhibitor recapitulates the phenotypes observed in K43M mice. Mechanistically, CDK6 phosphorylates AMP-activated protein kinase, leading to phosphorylation and inactivation of acetyl-CoA carboxylase, a key enzyme in DNL. CDK6 also phosphorylates CHREBP thus preventing its entry into the nucleus. Ablation of runt related transcription factor 1 in K43M mature adipocytes reverses most of the phenotypes observed in K43M mice. These results demonstrate a role of CDK6 in DNL and a strategy to alleviate metabolic syndromes.

Bariatric surgery-induced weight loss and associated genome-wide DNA-methylation alterations in obese individuals

BACKGROUND

Obesity is a multifactorial and chronic condition of growing universal concern. It has recently been reported that bariatric surgery is a more successful treatment for severe obesity than other noninvasive interventions, resulting in rapid significant weight loss and associated chronic disease remission. The identification of distinct epigenetic patterns in patients who are obese or have metabolic imbalances has suggested a potential role for epigenetic alterations in causal or mediating pathways in the development of obesity-related pathologies. Specific changes in the epigenome (DNA methylome), associated with metabolic disorders, can be detected in the blood. We investigated whether such epigenetic changes are reversible after weight loss using genome-wide DNA methylome analysis of blood samples from individuals with severe obesity (mean BMI ~ 45) undergoing bariatric surgery.

RESULTS

Our analysis revealed 41 significant (Bonferroni p < 0.05) and 1169 (false discovery rate p < 0.05) suggestive differentially methylated positions (DMPs) associated with weight loss due to bariatric surgery. Among the 41 significant DMPs, 5 CpGs were replicated in an independent cohort of BMI-discordant monozygotic twins (the heavier twin underwent diet-induced weight loss). The effect sizes of these 5 CpGs were consistent across discovery and replication sets (p < 0.05). We also identified 192 differentially methylated regions (DMRs) among which SMAD6 and PFKFB3 genes were the top hypermethylated and hypomethylated regions, respectively. Pathway enrichment analysis of the DMR-associated genes showed that functional pathways related to immune function and type 1 diabetes were significant. Weight loss due to bariatric surgery also significantly decelerated epigenetic age 12 months after the intervention (mean =  - 4.29; p = 0.02).

CONCLUSIONS

We identified weight loss-associated DNA-methylation alterations targeting immune and inflammatory gene pathways in blood samples from bariatric-surgery patients. The top hits were replicated in samples from an independent cohort of BMI-discordant monozygotic twins following a hypocaloric diet. Energy restriction and bariatric surgery thus share CpGs that may represent early indicators of response to the metabolic effects of weight loss. The analysis of bariatric surgery-associated DMRs suggests that epigenetic regulation of genes involved in endothelial and adipose tissue function is key in the pathophysiology of obesity.

Apolipoprotein A4 Restricts Diet-induced Hepatic Steatosis via SREBF1-mediated Lipogenesis and Enhances IRS-PI3K-Akt Signaling

SCOPE

Hepatic steatosis and insulin resistance (IR) are risk factors for many metabolic syndromes such as NAFLD and T2DM. ApoA4 improves glucose hemostasis by increasing glucose-stimulated insulin secretion and glucose uptake via PI3K-Akt activation in adipocytes. However, whether ApoA4 has an effect on hepatic steatosis or IR remains unclear.

METHODS AND RESULTS

ApoA4-knockout (KO) aggravates diet-induced obesity, hepatic steatosis and IR in mice promoted by increased hepatic lipogenesis gene expression based on RNA-seq data. Conversely, liver-specific overexpression of ApoA4 via AAV-ApoA4 transduction reverses the effect in ApoA4-KO mice, accompanied by suppressed hepatic lipogenesis, increased lipolysis, and fatty acid oxidation. Short-term treatment with recombinant ApoA4 protein improves glucose clearance and liver insulin sensitivity, and reduces hepatic lipogenesis gene expression in the absence of insulin. Moreover, in primary hepatocytes and a hepatic cell line, ApoA4 improves hepatic glucose uptake via IRS-PI3K-Akt signaling and decreases fat deposition and hepatic lipogenesis gene expression by inhibiting SREBF1 activity.

CONCLUSION

ApoA4 restricts hepatic steatosis by inhibiting SREBF1-mediated lipogenesis and improves insulin sensitivity and glucose uptake via IRS-PI3K-Akt signaling in the liver. These findings indicate that ApoA4 may serve as a therapeutic target for obesity-associated NAFLD. This article is protected by copyright. All rights reserved.

Bioinformatics study of the potential therapeutic effects of ginsenoside Rf in reversing nonalcoholic fatty liver disease

OBJECTIVE

Ginsenoside Rf, a tetracyclic triterpenoid only present in Panax ginseng, has been proven to relieve lipid metabolism and inflammatory reactions, which can be a potential treatment for nonalcoholic fatty liver disease (NAFLD). Therefore, this study aimed to reveal the underlying mechanisms of ginsenoside Rf in the treatment of early-stage NAFLD (NAFL) by using a bioinformatics method and biological experiments.

METHODS

Target genes associated with NAFL were screened from the Gene Expression Omnibus (GEO) database, a database repository of high-throughput gene expression data and hybridization arrays, chips, and microarrays. Subsequently, gene set enrichment analysis was performed by using Gene Ontology enrichment analysis tool. Then, the binding capacity between ginsenoside Rf and NAFL-related targets was evaluated by molecular docking. Finally, the FFA-induced HepG2 cell model treated with ginsenoside Rf was adopted to verify the effect of ginsenoside Rf and the related mechanisms.

RESULTS

There were 41 common differentially expressed genes in the GEO dataset. Gene Ontology and Reactome pathway enrichment analysis of the differentially expressed genes showed that many pathways could be related to the pathogenesis of NAFL, including those participating in the cytokine-mediated signaling pathway, G protein-coupled receptor signaling pathway, and response to lipopolysaccharide. Finally, the qRT-PCR analysis results indicated that ginsenoside Rf therapy could ameliorate the transcription of ANXA2, BAZ1A, DNMT3L and MMP9.

CONCLUSION

Our research discovered the relevant mechanisms and basic pharmacological effects of ginsenoside Rf in the treatment of NAFL. These results might facilitate the development of ginsenoside Rf as an alternative medication for NAFL.

Differential expression of aerobic oxidative metabolism-related proteins in diabetic urinary exosomes

BACKGROUND

As a metabolic disease, any abnormality in the aerobic oxidation pathway of glucose may lead to the occurrence of diabetes. This study aimed to investigate the changes in proteins related to aerobic oxidative metabolism in urinary exosomes of diabetic patients and normal controls of different ages, and to further verify their correlation with the pathogenesis of diabetes.

METHODS

Samples were collected, and proteomic information of urinary exosomes was collected by LC-MS/MS. ELISA was used to further detect the expression of aerobic and oxidative metabolism-related proteins in urinary exosomes of diabetic patients and normal controls of different ages, and to draw receiver operating characteristic (ROC) curve to evaluate its value in diabetes monitoring.

RESULTS

A total of 17 proteins involved in aerobic oxidative metabolism of glucose were identified in urinary exosome proteins. Compared with normal control, the expressions of PFKM, GAPDH, ACO2 and MDH2 in diabetic patients were decreased, and the expression of IDH3G was increased. The concentrations of PFKM, GAPDH and ACO2 in urinary exosomes were linearly correlated with the expression of MDH2 (P<0.05). These four proteins vary with age, with the maximum concentration in the 45-59 age group. PFKM, GAPDH, ACO2, and MDH2 in urinary exosomes have certain monitoring value. When used in combination, the AUC was 0.840 (95% CI 0.764-0.915).

CONCLUSIONS

In diabetic patients, aerobic oxidative metabolism is reduced, and the expression of aerobic oxidative metabolism-related proteins PFKM, GAPDH, ACO2, and MDH2 in urinary exosomes is reduced, which may become potential biomarkers for monitoring changes in diabetes.

Latent autoimmune diabetes in adults: a focus on β-cell protection and therapy

Latent autoimmune diabetes in adults (LADA) is a heterogeneous disease sharing some phenotypic, genetic, and immunological features with both type 1 and 2 diabetes. Patients with LADA have a relatively slow autoimmune process and more residual islet β-cell function at onset, allowing a time window to protect residual islet β cells and delay or inhibit disease progression. It is crucial to discover various heterogeneous factors affecting islet β-cell function for precise LADA therapy. In this review, we first describe the natural history of LADA. Thereafter, we summarize β-cell function-related heterogeneous factors in LADA, including the age of onset, body mass index, genetic background, and immune, lifestyle, and environmental factors. In parallel, we evaluate the impact of current hypoglycemic agents and immune intervention therapies for islet β-cell protection. Finally, we discuss the opportunities and challenges of LADA treatment from the perspective of islet β-cell function protection.

Recent Advances in Adipose Tissue Dysfunction and Its Role in the Pathogenesis of Non-Alcoholic Fatty Liver Disease

Obesity is a serious ongoing health problem that significantly increases the incidence of nonalcoholic fatty liver disease (NAFLD). During obesity, adipose tissue dysfunction is obvious and characterized by increased fat deposition (adiposity) and chronic low-grade inflammation. The latter has been implicated to critically promote the development and progression of NAFLD, whose advanced form non-alcoholic steatohepatitis (NASH) is considered one of the most common causes of terminal liver diseases. This review summarizes the current knowledge on obesity-related adipose dysfunction and its roles in the pathogenesis of hepatic steatosis and inflammation, as well as liver fibrosis. A better understanding of the crosstalk between adipose tissue and liver under obesity is essential for the development of new and improved preventive and/or therapeutic approaches for managing NAFLD.

Advances in Unhealthy Nutrition and Circadian Dysregulation in Pathophysiology of NAFLD

Unhealthy diets and lifestyle result in various metabolic conditions including metabolic syndrome and non-alcoholic fatty liver disease (NAFLD). Much evidence indicates that disruption of circadian rhythms contributes to the development and progression of excessive hepatic fat deposition and inflammation, as well as liver fibrosis, a key characteristic of non-steatohepatitis (NASH) or the advanced form of NAFLD. In this review, we emphasize the importance of nutrition as a critical factor in the regulation of circadian clock in the liver. We also focus on the roles of the rhythms of nutrient intake and the composition of diets in the regulation of circadian clocks in the context of controlling hepatic glucose and fat metabolism. We then summarize the effects of unhealthy nutrition and circadian dysregulation on the development of hepatic steatosis and inflammation. A better understanding of how the interplay among nutrition, circadian rhythms, and dysregulated metabolism result in hepatic steatosis and inflammation can help develop improved preventive and/or therapeutic strategies for managing NAFLD.

PFKFB3-dependent glucose metabolism regulates 3T3-L1 adipocyte development

Proliferation and differentiation of preadipocytes, and other cell types, is accompanied by an increase in glucose uptake. Previous work showed that a pulse of high glucose was required during the first 3 days of differentiation in vitro, but was not required after that. The specific glucose metabolism pathways required for adipocyte differentiation are unknown. Herein, we used 3T3-L1 adipocytes as a model system to study glucose metabolism and expansion of the adipocyte metabolome during the first 3 days of differentiation. Our primary outcome measures were GLUT4 and adiponectin, key proteins associated with healthy adipocytes. Using complete media with 0 or 5 mM glucose, we distinguished between developmental features that were dependent on the differentiation cocktail of dexamethasone, insulin, and isobutylmethylxanthine alone or the cocktail plus glucose. Cocktail alone was sufficient to activate the capacity for 2-deoxglucose uptake and glycolysis, but was unable to support the expression of GLUT4 and adiponectin in mature adipocytes. In contrast, 5 mM glucose in the media promoted a transient increase in glucose uptake and glycolysis as well as a significant expansion of the adipocyte metabolome and proteome. Using genetic and pharmacologic approaches, we found that the positive effects of 5 mM glucose on adipocyte differentiation were specifically due to increased expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key regulator of glycolysis and the ancillary glucose metabolic pathways. Our data reveal a critical role for PFKFB3 activity in regulating the cellular metabolic remodeling required for adipocyte differentiation and maturation.

Adipocyte inducible 6-phosphofructo-2-kinase suppresses adipose tissue inflammation and promotes macrophage anti-inflammatory activation

Obesity-associated inflammation in white adipose tissue (WAT) is a causal factor of systemic insulin resistance. To better understand how adipocytes regulate WAT inflammation, the present study generated chimeric mice in which inducible 6-phosphofructo-2-kinase was low, normal, or high in WAT while the expression of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (Pfkfb3) was normal in hematopoietic cells, and analyzed changes in high-fat diet (HFD)-induced WAT inflammation and systemic insulin resistance in the mice. Indicated by proinflammatory signaling and cytokine expression, the severity of HFD-induced WAT inflammation in WT → Pfkfb3^+/- mice, whose Pfkfb3 was disrupted in WAT adipocytes but not hematopoietic cells, was comparable with that in WT → WT mice, whose Pfkfb3 was normal in all cells. In contrast, the severity of HFD-induced WAT inflammation in WT → Adi-Tg mice, whose Pfkfb3 was over-expressed in WAT adipocytes but not hematopoietic cells, remained much lower than that in WT → WT mice. Additionally, HFD-induced insulin resistance was correlated with the status of WAT inflammation and comparable between WT → Pfkfb3^+/- mice and WT → WT mice, but was significantly lower in WT → Adi-Tg mice than in WT → WT mice. In vitro, palmitoleate decreased macrophage phosphorylation states of Jnk p46 and Nfkb p65 and potentiated the effect of interleukin 4 on suppressing macrophage proinflammatory activation. Taken together, these results suggest that the Pfkfb3 in adipocytes functions to suppress WAT inflammation. Moreover, the role played by adipocyte Pfkfb3 is attributable to, at least in part, palmitoleate promotion of macrophage anti-inflammatory activation.

Adipose tissue inflammation and systemic insulin resistance in mice with diet-induced obesity is possibly associated with disruption of PFKFB3 in hematopoietic cells

Obesity-associated inflammation in white adipose tissue (WAT) is a causal factor of systemic insulin resistance; however, precisely how immune cells regulate WAT inflammation in relation to systemic insulin resistance remains to be elucidated. The present study examined a role for 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in hematopoietic cells in regulating WAT inflammation and systemic insulin sensitivity. Male C57BL/6J mice were fed a high-fat diet (HFD) or low-fat diet (LFD) for 12 weeks and examined for WAT inducible 6-phosphofructo-2-kinase (iPFK2) content, while additional HFD-fed mice were treated with rosiglitazone and examined for PFKFB3 mRNAs in WAT stromal vascular cells (SVC). Also, chimeric mice in which PFKFB3 was disrupted only in hematopoietic cells and control chimeric mice were also fed an HFD and examined for HFD-induced WAT inflammation and systemic insulin resistance. In vitro, adipocytes were co-cultured with bone marrow-derived macrophages and examined for adipocyte proinflammatory responses and insulin signaling. Compared with their respective levels in controls, WAT iPFK2 amount in HFD-fed mice and WAT SVC PFKFB3 mRNAs in rosiglitazone-treated mice were significantly increased. When the inflammatory responses were analyzed, peritoneal macrophages from PFKFB3-disrputed mice revealed increased proinflammatory activation and decreased anti-inflammatory activation compared with control macrophages. At the whole animal level, hematopoietic cell-specific PFKFB3 disruption enhanced the effects of HFD feeding on promoting WAT inflammation, impairing WAT insulin signaling, and increasing systemic insulin resistance. In vitro, adipocytes co-cultured with PFKFB3-disrupted macrophages revealed increased proinflammatory responses and decreased insulin signaling compared with adipocytes co-cultured with control macrophages. These results suggest that PFKFB3 disruption in hematopoietic cells only exacerbates HFD-induced WAT inflammation and systemic insulin resistance.

The expression profile and role of non-coding RNAs in obesity

Latest years have experienced a dramatic upsurge in the knowledge about the function of non-coding transcripts in the determination of diverse human phenotypes including obesity. Several miRNAs and lncRNAs participate in the regulation of metabolic pathways leading to obesity. Several lncRNAs such as Mist, lincIRS2, lncRNA-p5549, H19, GAS5 and SNHG9 have been shown to be down-regulated in adipose tissues or other biological samples in the obese human or animal subjects. On the other hand, Meg3, Plnc1, Blnc1, AC092834.1, TINCR and PVT1 are among up-regulated lncRNAs in the obese subjects. Tens of miRNAs have differential expression between obese and non-obese subjects or between mature adipocytes and pre-adipocytes. Understanding the molecular mechanism of involvement of non-coding RNAs in the pathobiology of obesity would simplify design of therapeutic choices for protecting against obesity and its related comorbidities. We explain the available literature on the function of these transcripts in the pathobiology of obesity.

Adoptive transfer of Pfkfb3-disrupted hematopoietic cells to wild-type mice exacerbates diet-induced hepatic steatosis and inflammation

BACKGROUND AND OBJECTIVES

Hepatic steatosis and inflammation are key characteristics of non-alcoholic fatty liver disease (NAFLD). However, whether and how hepatic steatosis and liver inflammation are differentially regulated remains to be elucidated. Considering that disruption of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (Pfkfb3/iPfk2) dissociates fat deposition and inflammation, the present study examined a role for Pfkfb3/iPfk2 in hematopoietic cells in regulating hepatic steatosis and inflammation in mice.

METHODS

Pfkfb3-disrupted (Pfkfb3 ^+/-) mice and wild-type (WT) littermates were fed a high-fat diet (HFD) and examined for NAFLD phenotype. Also, bone marrow cells isolated from Pfkfb3 ^+/- mice and WT mice were differentiated into macrophages for analysis of macrophage activation status and for bone marrow transplantation (BMT) to generate chimeric (WT/BMT- Pfkfb3 ^+/-) mice in which Pfkfb3 was disrupted only in hematopoietic cells and control chimeric (WT/BMT-WT) mice. The latter were also fed an HFD and examined for NAFLD phenotype. In vitro, hepatocytes were co-cultured with bone marrow-derived macrophages and examined for hepatocyte fat deposition and proinflammatory responses.

RESULTS

After the feeding period, HFD-fed Pfkfb3 ^+/- mice displayed increased severity of liver inflammation in the absence of hepatic steatosis compared with HFD-fed WT mice. When inflammatory activation was analyzed, Pfkfb3 ^+/- macrophages revealed increased proinflammatory activation and decreased anti-proinflammatory activation. When NAFLD phenotype was analyzed in the chimeric mice, WT/BMT-Pfkfb3 ^+/- mice displayed increases in the severity of HFD-induced hepatic steatosis and inflammation compared with WT/BMT-WT mice. At the cellular level, hepatocytes co-cultured with Pfkfb3 ^+/- macrophages revealed increased fat deposition and proinflammatory responses compared with hepatocytes co-cultured with WT macrophages.

CONCLUSIONS

Pfkfb3 disruption only in hematopoietic cells exacerbates HFD-induced hepatic steatosis and inflammation whereas the Pfkfb3/iPfk2 in nonhematopoietic cells appeared to be needed for HFD feeding to induce hepatic steatosis. As such, the Pfkfb3/iPfk2 plays a unique role in regulating NAFLD pathophysiology.

New Insights into the Genetics of Latent Autoimmune Diabetes in Adults

PURPOSE OF REVIEW

Diabetes is a spectrum of clinical manifestations, including latent autoimmune diabetes in adults (LADA). However, it has been questioned whether LADA exists or simply is a group of misclassified type 1 diabetes (T1D) and type 2 diabetes (T2D) patients. This review will provide an updated overview of the genetics of LADA, highlight what genetics tell us about LADA as a diabetes subtype, and point to future directions in the study of LADA.

RECENT FINDINGS

Recent studies have verified the genetic overlap between LADA and both T1D and T2D and have contributed identification of a novel LADA-specific locus, namely, PFKFB3, and subtype-specific signatures in the HLA region. Genetic risk scores comprising T1D-risk variants have been shown to be a promising tool for discriminating diabetes subtypes and identifying patients rapidly progressing to insulin dependence. Genetic data support the existence of LADA, but further studies are needed to fully determine the place of LADA in the diabetes spectrum.

A Comprehensive Genome-Wide and Phenome-Wide Examination of BMI and Obesity in a Northern Nevadan Cohort

The aggregation of Electronic Health Records (EHR) and personalized genetics leads to powerful discoveries relevant to population health. Here we perform genome-wide association studies (GWAS) and accompanying phenome-wide association studies (PheWAS) to validate phenotype-genotype associations of BMI, and to a greater extent, severe Class 2 obesity, using comprehensive diagnostic and clinical data from the EHR database of our cohort. Three GWASs of 500,000 variants on the Illumina platform of 6,645 Healthy Nevada participants identified several published and novel variants that affect BMI and obesity. Each GWAS was followed with two independent PheWASs to examine associations between extensive phenotypes (incidence of diagnoses, condition, or disease), significant SNPs, BMI, and incidence of extreme obesity. The first GWAS examines associations with BMI in a cohort with no type 2 diabetics, focusing exclusively on BMI. The second GWAS examines associations with BMI in a cohort that includes type 2 diabetics. In the second GWAS, type 2 diabetes is a comorbidity, and thus becomes a covariate in the statistical model. The intersection of significant variants of these two studies is surprising. The third GWAS is a case vs. control study, with cases defined as extremely obese (Class 2 or 3 obesity), and controls defined as participants with BMI between 18.5 and 25. This last GWAS identifies strong associations with extreme obesity, including established variants in the FTO and NEGR1 genes, as well as loci not yet linked to obesity. The PheWASs validate published associations between BMI and extreme obesity and incidence of specific diagnoses and conditions, yet also highlight novel links. This study emphasizes the importance of our extensive longitudinal EHR database to validate known associations and identify putative novel links with BMI and obesity.

The Construction and Analysis of the Aberrant lncRNA-miRNA-mRNA Network in Adipose Tissue from Type 2 Diabetes Individuals with Obesity

BACKGROUND

The prevalence of obesity and type 2 diabetes mellitus (T2DM) has become the most serious global public health issue. In recent years, there has been increasing attention to the role of long noncoding RNAs (lncRNAs) in the occurrence and development of obesity and T2DM. The aim of this work was to find new lncRNAs as potential predictive biomarkers or therapeutic targets for obesity and T2DM.

METHODS

In this study, we identified significant differentially expressed mRNAs (DEmRNAs) and differentially expressed lncRNAs (DElncRNAs) between adipose tissue of individuals with obesity and T2DM and normal adipose tissue (absolute log₂FC ≥ 1 and FDR < 0.05). Then, the lncRNA-miRNA interactions predicted by miRcode were further screened with a threshold of MIC > 0.2. Simultaneously, the mRNA-miRNA interactions were explored by miRWalk 2.0. Finally, a ceRNA network consisting of lncRNAs, miRNAs, and mRNAs was established by integrating lncRNA-miRNA interactions and mRNA-miRNA interactions.

RESULTS

Upon comparing adipose tissue from individuals with obesity and T2DM and normal adipose tissues, 364 significant DEmRNAs, including 140 upregulated and 224 downregulated mRNAs, were identified in GSE104674; in addition, 231 significant DEmRNAs, including 146 upregulated and 85 downregulated mRNAs, were identified in GSE133099. GO and KEGG analyses have shown that downregulated DEmRNAs in GSE104674 and GSE133099 were associated with obesity- and T2DM-related biological pathways, such as lipid metabolism, AMPK signaling, and insulin resistance. Furthermore, 28 significant DElncRNAs, including 14 upregulated and 14 downregulated lncRNAs, were found. Based on the predicted lncRNA-miRNA and mRNA-miRNA relationships, we constructed a competitive endogenous RNA (ceRNA) network, including five lncRNAs, ten miRNAs, and 15 mRNAs. KEGG-GSEA analysis revealed that four lncRNAs (FLG-AS1, SNAI3-AS1, AC008147.0, and LINC02015) in the ceRNA network were related to the biological pathways of metabolic diseases.

CONCLUSIONS

Through ceRNA network analysis, our study identified four new lncRNAs that may be used as potential biomarkers and therapeutic targets of obesity and T2DM, thus laying a foundation for future clinical studies.

Mice lacking adenosine 2A receptor reveal increased severity of MCD-induced NASH

Adenosine 2A receptor (A2AR) exerts a protective role in obesity-related non-alcoholic fatty liver disease. Here, we examined whether A2AR protects against non-alcoholic steatohepatitis (NASH). In C57BL/6J mice, feeding a methionine- and choline-deficient diet (MCD) resulted in significant weight loss, overt hepatic steatosis, and massive aggregation of macrophages in the liver compared with mice fed a chow diet. MCD feeding also significantly increased the numbers of A2AR-positive macrophages/Kupffer cells in liver sections although decreasing A2AR amount in liver lysates compared with chow diet feeding. Next, MCD-induced NASH phenotype was examined in A2AR-disrupted mice and control mice. Upon MCD feeding, A2AR-disruptd mice and control mice displayed comparable decreases in body weight and fat mass. However, MCD-fed A2AR-disrupted mice revealed greater liver weight and increased severity of hepatic steatosis compared with MCD-fed control mice. Moreover, A2AR-disupted mice displayed increased severity of MCD-induced liver inflammation, indicated by massive aggregation of macrophages and increased phosphorylation states of Jun-N terminal kinase (JNK) p46 and nuclear factor kappa B (NFκB) p65 and mRNA levels of tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6. In vitro, incubation with MCD-mimicking media increased lipopolysaccharide (LPS)-induced phosphorylation states of JNK p46 and/or NFκB p65 and cytokine mRNAs in control macrophages and RAW264.7 cells, but not primary hepatocytes. Additionally, MCD-mimicking media significantly increased lipopolysaccharide-induced phosphorylation states of p38 and NFκB p65 in A2AR-deficient macrophages, but insignificantly decreased lipopolysaccharide-induced phosphorylation states of JNK p46 and NFκB p65 in A2AR-deficient hepatocytes. Collectively, these results suggest that A2AR disruption exacerbates MCD-induced NASH, which is attributable to, in large part, increased inflammatory responses in macrophages.

RNA-Sequencing Analysis of Paternal Low-Protein Diet-Induced Gene Expression Change in Mouse Offspring Adipocytes

Increasing evidence indicates that parental diet affects the metabolism and health of offspring. It is reported that paternal low-protein diet (pLPD) induces glucose intolerance and the expression of genes involved in cholesterol biosynthesis in mouse offspring liver. The aim of the present study was to determine the effect of a pLPD on gene expression in offspring white adipose tissue (WAT), another important tissue for the regulation of metabolism. RNA-seq analysis indicated that pLPD up- and down-regulated 54 and 274 genes, respectively, in offspring WAT. The mRNA expression of many genes involved in lipogenesis was down-regulated by pLPD feeding, which may contribute to metabolic disorder. The expression of carbohydrate response element-binding protein β (ChREBP-β), an important lipogenic transcription factor, was also significantly lower in the WAT of pLPD offspring, which may have mediated the down-regulation of the lipogenic genes. By contrast, the LPD did not affect the expression of lipogenic genes in the WAT of the male progenitor, but increased the expression of lipid oxidation genes, suggesting that a LPD may reduce lipogenesis using different mechanisms in parents and offspring. These findings add to our understanding of how paternal diet can regulate metabolism in their offspring.

Exercise Rescues Gene Pathways Involved in Vascular Expansion and Promotes Functional Angiogenesis in Subcutaneous White Adipose Tissue

Exercise mitigates chronic diseases such as diabetes, cardiovascular diseases, and obesity; however, the molecular mechanisms governing protection from these diseases are not completely understood. Here we demonstrate that exercise rescues metabolically compromised high fat diet (HFD) fed mice, and reprograms subcutaneous white adipose tissue (scWAT). Using transcriptomic profiling, scWAT was analyzed for HFD gene expression changes that were rescued by exercise. Gene networks involved in vascularization were identified as prominent targets of exercise, which led us to investigate the vasculature architecture and endothelial phenotype. Vascular density in scWAT was found to be compromised in HFD, and exercise rescued this defect. Similarly, angiogenic capacity as measured by ex vivo capillary sprouting was significantly promoted with exercise. Together, these data demonstrate that exercise enhances scWAT vascularization and functional capacity for angiogenesis, and can prevent the detrimental effects of HFD. The improvement in these indices correlates with improvement of whole-body metabolism, suggesting that scWAT vascularization may be a potential therapeutic target for metabolic disease.

Disuse-induced insulin resistance susceptibility coincides with a dysregulated skeletal muscle metabolic transcriptome

Short-term muscle disuse is characterized by skeletal muscle insulin resistance, although this response is divergent across subjects. The mechanisms regulating inactivity-induced insulin resistance between populations that are more or less susceptible to disuse-induced insulin resistance are not known. RNA sequencing was conducted on vastus lateralis muscle biopsies from subjects before and after bed rest (n = 26) to describe the transcriptome of inactivity-induced insulin resistance. Subjects were separated into Low (n = 14) or High (n = 12) Susceptibility Groups based on the magnitude of change in insulin sensitivity after 5 days of bed rest. Both groups became insulin-resistant after bed rest, and there were no differences between groups in nonmetabolic characteristics (body mass, body mass index, fat mass, and lean mass). The High Susceptibility Group had more genes altered >1.5-fold (426 high versus 391 low) and more than twofold (73 high versus 55 low). Twenty-four genes were altered more than twofold in the High Susceptibility Group that did not change in the Low Susceptibility Group. 95 gene changes correlated with the changes in insulin sensitivity; 6 of these genes changed more than twofold in the High Susceptibility Group. Participants in the High Susceptibility Group were uniquely characterized with muscle gene responses described by a decrease in pathways responsible for lipid uptake and oxidation, decreased capacity for triglyceride export (APOB), increased lipogenesis (i.e., PFKFB3, FASN), and increased amino acid export (SLC43A1). These transcriptomic data provide a comprehensive examination of pathways and genes that may be useful biomarkers, or novel targets to offset muscle disuse-induced insulin resistance. NEW & NOTEWORTHY Short-term muscle disuse results in skeletal muscle insulin resistance through mechanisms that are not fully understood. Following a 5-day bed rest intervention, subjects were divided into High and Low Susceptibility Groups to inactivity-induced insulin resistance. This was followed by a genome-wide transcriptional analysis on muscle biopsy samples to gain insight on divergent insulin sensitivity responses. Our primary finding was that the skeletal muscle of subjects who experienced the most inactivity-induced insulin resistance (high susceptibility) was characterized by a decreased preference for lipid oxidation, increased lipogenesis, and increased amino acid export.

Expression of STING Is Increased in Liver Tissues From Patients With NAFLD and Promotes Macrophage-Mediated Hepatic Inflammation and Fibrosis in Mice

BACKGROUND & AIMS

Transmembrane protein 173 (TMEM173 or STING) signaling by macrophage activates the type I interferon-mediated innate immune response. The innate immune response contributes to hepatic steatosis and non-alcoholic fatty liver disease (NAFLD). We investigated whether STING regulates diet-induced in hepatic steatosis, inflammation, and liver fibrosis in mice.

METHODS

Mice with disruption of Tmem173 (STING^gt) on a C57BL/6J background, mice without disruption of this gene (controls), and mice with disruption of Tmem173 only in myeloid cells were fed a standard chow diet, a high-fat diet (HFD; 60% fat calories), or a methionine- and choline-deficient diet (MCD). Liver tissues were collected and analyzed by histology and immunohistochemistry. Bone marrow cells were isolated from mice, differentiated into macrophages, and incubated with 5,6-dimethylxanthenone-4-acetic acid (DMXAA; an activator of STING) or cyclic guanosine monophosphate-adenosine monophosphate (cGAMP). Macrophages or their media were applied to mouse hepatocytes or human hepatic stellate cells (LX2) cells, which were analyzed for cytokine expression, protein phosphorylation, and fat deposition (by oil red O staining after incubation with palmitate). We obtained liver tissues from patients with and without NAFLD and analyzed these by immunohistochemistry.

RESULTS

Non-parenchymal cells of liver tissues from patients with NAFLD had higher levels of STING than cells of liver tissues from patients without NAFLD. STING^gt mice and mice with disruption only in myeloid cells developed less severe hepatic steatosis, inflammation, and/or fibrosis after the HFD or MCD than control mice. Levels of phosphorylated c-Jun N-terminal kinase and p65 and mRNAs encoding tumor necrosis factor and interleukins 1B and 6 (markers of inflammation) were significantly lower in liver tissues from STING^gt mice vs control mice after the HFD or MCD. Transplantation of bone marrow cells from control mice to STING^gt mice restored the severity of steatosis and inflammation after the HFD. Macrophages from control, but not STING^gt, mice increased markers of inflammation in response to lipopolysaccharide and cGAMP. Hepatocytes and stellate cells cocultured with STING^gt macrophages in the presence of DMXAA or incubated with the medium collected from these macrophages had decreased fat deposition and markers of inflammation compared with hepatocytes or stellate cells incubated with control macrophages.

CONCLUSIONS

Levels of STING were increased in liver tissues from patients with NAFLD and mice with HFD-induced steatosis. In mice, loss of STING from macrophages decreased the severity of liver fibrosis and the inflammatory response. STING might be a therapeutic target for NAFLD.

Regulation of adipose tissue inflammation by adenosine 2A receptor in obese mice

Adenosine 2A receptor (A2AR) exerts anti-inflammatory effects. However, the role of A2AR in obesity-associated adipose tissue inflammation remains to be elucidated. The present study examined the expression of A2AR in adipose tissue of mice with diet-induced obesity and determined the effect of A2AR disruption on the status of obesity-associated adipose tissue inflammation. WT C57BL/6J mice and A2AR-disrupted mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity and adipose tissue inflammation. In vitro, bone marrow-derived macrophages from A2AR-disrupted mice and WT control mice were treated with palmitate and examined for macrophage proinflammatory activation. Compared with that of low-fat diet (LFD)-fed WT mice, A2AR expression in adipose tissue of HFD-fed WT mice was increased significantly and was present predominantly in adipose tissue macrophages. The increase in adipose tissue A2AR expression in HFD-fed mice was accompanied with increased phosphorylation states of c-Jun N-terminal kinase 1 p46 and nuclear factor kappa B p65 and mRNA levels of interleukin (Il)-1beta, Il6 and tumor necrosis factor alpha. In A2AR-disrupted mice, HFD feeding induced significant increases in adipose tissue inflammation, indicated by enhanced proinflammatory signaling and increased proinflammatory cytokine expression, and adipose tissue insulin resistance, indicated by a decrease in insulin-stimulated Akt phosphorylation relative to those in WT mice. Lastly, A2AR disruption enhanced palmitate-induced macrophage proinflammatory activation. Taken together, these results suggest that A2AR plays a protective role in obesity-associated adipose tissue inflammation, which is attributable to, in large part, A2AR suppression of macrophage proinflammatory activation.

First Genome-Wide Association Study of Latent Autoimmune Diabetes in Adults Reveals Novel Insights Linking Immune and Metabolic Diabetes

OBJECTIVE

Latent autoimmune diabetes in adults (LADA) shares clinical features with both type 1 and type 2 diabetes; however, there is ongoing debate regarding the precise definition of LADA. Understanding its genetic basis is one potential strategy to gain insight into appropriate classification of this diabetes subtype.

RESEARCH DESIGN AND METHODS

We performed the first genome-wide association study of LADA in case subjects of European ancestry versus population control subjects (n = 2,634 vs. 5,947) and compared against both case subjects with type 1 diabetes (n = 2,454 vs. 968) and type 2 diabetes (n = 2,779 vs. 10,396).

RESULTS

The leading genetic signals were principally shared with type 1 diabetes, although we observed positive genetic correlations genome-wide with both type 1 and type 2 diabetes. Additionally, we observed a novel independent signal at the known type 1 diabetes locus harboring PFKFB3, encoding a regulator of glycolysis and insulin signaling in type 2 diabetes and inflammation and autophagy in autoimmune disease, as well as an attenuation of key type 1-associated HLA haplotype frequencies in LADA, suggesting that these are factors that distinguish childhood-onset type 1 diabetes from adult autoimmune diabetes.

CONCLUSIONS

Our results support the need for further investigations of the genetic factors that distinguish forms of autoimmune diabetes as well as more precise classification strategies.

The potential utility of PFKFB3 as a therapeutic target

INTRODUCTION

It has been known for over half a century that tumors exhibit an increased demand for nutrients to fuel their rapid proliferation. Interest in targeting cancer metabolism to treat the disease has been renewed in recent years with the discovery that many cancer-related pathways have a profound effect on metabolism. Considering the recent increase in our understanding of cancer metabolism and the enzymes and pathways involved, the question arises as to whether metabolism is cancer's Achilles heel. Areas covered: This review summarizes the role of 6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) in glycolysis, cell proliferation, and tumor growth, discussing PFKFB3 gene and isoenzyme regulation and the changes that occur in cancer and inflammatory diseases. Pharmacological options currently available for selective PFKFB3 inhibition are also reviewed. Expert opinion: PFKFB3 plays an important role in sustaining the development and progression of cancer and might represent an attractive target for therapeutic strategies. Nevertheless, clinical trials are needed to follow up on the promising results from preclinical studies with PFKFB3 inhibitors. Combination therapies with PFKFB3 inhibitors, chemotherapeutic drugs, or radiotherapy might improve the efficacy of cancer treatments targeting PFKFB3.

Glucose tolerance in obese men is associated with dysregulation of some angiogenesis-related gene expressions in subcutaneous adipose tissue

Obesity and its metabolic complications are one of the most profound public health problems and result from interactions between genes and environmental. The development of obesity is tightly connected with dysregulation of intrinsic gene expression mechanisms controlling majority of metabolic processes, which are essential for regulation many physiological functions, including insulin sensitivity, cellular proliferation and angiogenesis. Our objective was to evaluate if expression of angiogenesis related genes VEGF-A, CYR61, PDGFC, FGF1, FGF2, FGFR2, FGFRL1, E2F8, BAI2, HIF1A, and EPAS1 at mRNA level in adipose tissue could participate in the development of obesity and metabolic complications. We have shown that expression level of VEGF-A, PDGFC, FGF2, and FGFRL1 genes is decreased in adipose tissue of obese men with normal glucose tolerance (NGT) versus a group of control subjects. At the same time, in this group of obese individuals a significant up-regulation of CYR61, FGF1, FGFR2, E2F8, BAI2, and HIF1A gene expressions was observed. Impaired glucose tolerance (IGT) in obese patients associates with down-regulation of CYR61 and FGFR2 mRNA and up-regulations of E2F8, FGF1, FGF2, VEGF-A and its splice variant 189 mRNA expressions in adipose tissue versus obese (NGT) individuals. Thus, our data demonstrate that the expression of almost all studied genes is affected in subcutaneous adipose tissue of obese individuals with NGT and that glucose intolerance is associated with gene-specific changes in the expression of E2F8, FGF1, FGF2, VEGF-A, CYR61 and FGFR2 mRNAs. The data presented here provides evidence that VEGF-A, CYR61, PDGFC, FGF1, FGF2, FGFR2, FGFRL1, E2F8, BAI2, and HIF1A genes are possibly involved in the development of obesity and its complications.

Integration of flux measurements to resolve changes in anabolic and catabolic metabolism in cardiac myocytes

Although ancillary pathways of glucose metabolism are critical for synthesizing cellular building blocks and modulating stress responses, how they are regulated remains unclear. In the present study, we used radiometric glycolysis assays, [¹³C₆]-glucose isotope tracing, and extracellular flux analysis to understand how phosphofructokinase (PFK)-mediated changes in glycolysis regulate glucose carbon partitioning into catabolic and anabolic pathways. Expression of kinase-deficient or phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in rat neonatal cardiomyocytes co-ordinately regulated glycolytic rate and lactate production. Nevertheless, in all groups, >40% of glucose consumed by the cells was unaccounted for via catabolism to pyruvate, which suggests entry of glucose carbons into ancillary pathways branching from metabolites formed in the preparatory phase of glycolysis. Analysis of ¹³C fractional enrichment patterns suggests that PFK activity regulates glucose carbon incorporation directly into the ribose and the glycerol moieties of purines and phospholipids, respectively. Pyrimidines, UDP-N-acetylhexosamine, and the fatty acyl chains of phosphatidylinositol and triglycerides showed lower ¹³C incorporation under conditions of high PFK activity; the isotopologue ¹³C enrichment pattern of each metabolite indicated limitations in mitochondria-engendered aspartate, acetyl CoA and fatty acids. Consistent with this notion, high glycolytic rate diminished mitochondrial activity and the coupling of glycolysis to glucose oxidation. These findings suggest that a major portion of intracellular glucose in cardiac myocytes is apportioned for ancillary biosynthetic reactions and that PFK co-ordinates the activities of the pentose phosphate, hexosamine biosynthetic, and glycerolipid synthesis pathways by directly modulating glycolytic intermediate entry into auxiliary glucose metabolism pathways and by indirectly regulating mitochondrial cataplerosis.

Cyclic GMP-AMP Ameliorates Diet-induced Metabolic Dysregulation and Regulates Proinflammatory Responses Distinctly from STING Activation

Endogenous cyclic GMP-AMP (cGAMP) binds and activates STING to induce type I interferons. However, whether cGAMP plays any roles in regulating metabolic homeostasis remains unknown. Here we show that exogenous cGAMP ameliorates obesity-associated metabolic dysregulation and uniquely alters proinflammatory responses. In obese mice, treatment with cGAMP significantly decreases diet-induced proinflammatory responses in liver and adipose tissues and ameliorates metabolic dysregulation. Strikingly, cGAMP exerts cell-type-specific anti-inflammatory effects on macrophages, hepatocytes, and adipocytes, which is distinct from the effect of STING activation by DMXAA on enhancing proinflammatory responses. While enhancing insulin-stimulated Akt phosphorylation in hepatocytes and adipocytes, cGAMP weakens the effects of glucagon on stimulating hepatocyte gluconeogenic enzyme expression and glucose output and blunts palmitate-induced hepatocyte fat deposition in an Akt-dependent manner. Taken together, these results suggest an essential role for cGAMP in linking innate immunity and metabolic homeostasis, indicating potential applications of cGAMP in treating obesity-associated inflammatory and metabolic diseases.

A role for PFKFB3/iPFK2 in metformin suppression of adipocyte inflammatory responses

Metformin improves obesity-associated metabolic dysregulation, but has controversial effects on adipose tissue inflammation. The objective of the study is to examine the direct effect of metformin on adipocyte inflammatory responses and elucidate the underlying mechanisms. Adipocytes were differentiated from 3T3-L1 cells and treated with metformin at various doses and for different time periods. The treated cells were examined for the proinflammatory responses, as well as the phosphorylation states of AMPK and the expression of PFKFB3/iPFK2. In addition, PFKFB3/iPFK2-knockdown adipocytes were treated with metformin and examined for changes in the proinflammatory responses. The following results were obtained from the study. Treatment of adipocytes with metformin decreased the effects of lipopolysaccharide on inducing the phosphorylation states of JNK p46 and on increasing the mRNA levels of IL-1β and TNFα. In addition, treatment with metformin increased the expression of PFKFB3/iPFK2, but failed to significantly alter the phosphorylation states of AMPK. In PFKFB3/iPFK2-knockdown adipocytes, treatment with metformin did not suppress the proinflammatory responses as did it in control adipocytes. In conclusion, metformin has a direct effect on suppressing adipocyte proinflammatory responses in an AMPK-independent manner. Also, metformin increases adipocyte expression of PFKFB3/iPFK2, which is involved in the anti-inflammatory effect of metformin.

Of mice and humans through the looking glass: "reflections" on epigenetics of lipid metabolism

Over the past decade, epigenetics has emerged as a new layer of regulation of gene expression. Several investigations demonstrated that nutrition and lifestyle regulate lipid metabolism by influencing epigenomic remodeling. Studies on animal models highlighted the role of epigenome modifiers in specific metabolic contexts and established clear links between dysregulation of epigenetic mechanisms and metabolic dysfunction. The relevance of findings in animal models has been translated to humans, as epigenome-wide association studies (EWAS) deeply investigated the relationship between lifestyle and epigenetics in human populations. In this review, we will provide an outlook of recent studies addressing the link between epigenetics and lipid metabolism, by comparing results obtained in animal models and in human subjects.

The epigenetic signature of systemic insulin resistance in obese women

AIMS/HYPOTHESIS

Insulin resistance (IR) links obesity to type 2 diabetes. The aim of this study was to explore whether white adipose tissue (WAT) epigenetic dysregulation is associated with systemic IR by genome-wide CG dinucleotide (CpG) methylation and gene expression profiling in WAT from insulin-resistant and insulin-sensitive women. A secondary aim was to determine whether the DNA methylation signature in peripheral blood mononuclear cells (PBMCs) reflects WAT methylation and, if so, can be used as a marker for systemic IR.

METHODS

From 220 obese women, we selected a total of 80 individuals from either of the extreme ends of the distribution curve of HOMA-IR, an indirect measure of systemic insulin sensitivity. Genome-wide transcriptome and DNA CpG methylation profiling by array was performed on subcutaneous (SAT) and visceral (omental) adipose tissue (VAT). CpG methylation in PBMCs was assayed in the same cohort.

RESULTS

There were 647 differentially expressed genes (false discovery rate [FDR] 10%) in SAT, all of which displayed directionally consistent associations in VAT. This suggests that IR is associated with dysregulated expression of a common set of genes in SAT and VAT. The average degree of DNA methylation did not differ between the insulin-resistant and insulin-sensitive group in any of the analysed tissues/cells. There were 223 IR-associated genes in SAT containing a total of 336 nominally significant differentially methylated sites (DMS). The 223 IR-associated genes were over-represented in pathways related to integrin cell surface interactions and insulin signalling and included COL5A1, GAB1, IRS2, PFKFB3 and PTPRJ. In VAT there were a total of 51 differentially expressed genes (FDR 10%); 18 IR-associated genes contained a total of 29 DMS.

CONCLUSIONS/INTERPRETATION

In individuals discordant for insulin sensitivity, the average DNA CpG methylation in SAT and VAT is similar, although specific genes, particularly in SAT, display significantly altered expression and DMS in IR, possibly indicating that epigenetic regulation of these genes influences metabolism.

Glucose and Palmitate Differentially Regulate PFKFB3/iPFK2 and Inflammatory Responses in Mouse Intestinal Epithelial Cells

The gene PFKFB3 encodes for inducible 6-phosphofructo-2-kinase, a glycolysis-regulatory enzyme that protects against diet-induced intestine inflammation. However, it is unclear how nutrient overload regulates PFKFB3 expression and inflammatory responses in intestinal epithelial cells (IECs). In the present study, primary IECs were isolated from small intestine of C57BL/6J mice fed a low-fat diet (LFD) or high-fat diet (HFD) for 12 weeks. Additionally, CMT-93 cells, a cell line for IECs, were cultured in low glucose (LG, 5.5 mmol/L) or high glucose (HG, 27.5 mmol/L) medium and treated with palmitate (50 μmol/L) or bovine serum albumin (BSA) for 24 hr. These cells were analyzed for PFKFB3 and inflammatory markers. Compared with LFD, HFD feeding decreased IEC PFKFB3 expression and increased IEC proinflammatory responses. In CMT-93 cells, HG significantly increased PFKFB3 expression and proinflammatory responses compared with LG. Interestingly, palmitate decreased PFKFB3 expression and increased proinflammatory responses compared with BSA, regardless of glucose concentrations. Furthermore, HG significantly increased PFKFB3 promoter transcription activity compared with LG. Upon PFKFB3 overexpression, proinflammatory responses in CMT-93 cells were decreased. Taken together, these results indicate that in IECs glucose stimulates PFKFB3 expression and palmitate contributes to increased proinflammatory responses. Therefore, PFKFB3 regulates IEC inflammatory status in response to macronutrients.

Role of Inflammatory Signaling in the Differential Effects of Saturated and Poly-unsaturated Fatty Acids on Peripheral Circadian Clocks

Inflammatory signaling may play a role in high-fat diet (HFD)-related circadian clock disturbances that contribute to systemic metabolic dysregulation. Therefore, palmitate, the prevalent proinflammatory saturated fatty acid (SFA) in HFD and the anti-inflammatory, poly-unsaturated fatty acid (PUFA), docosahexaenoic acid (DHA), were analyzed for effects on circadian timekeeping and inflammatory responses in peripheral clocks. Prolonged palmitate, but not DHA, exposure increased the period of fibroblast Bmal1-dLuc rhythms. Acute palmitate treatment produced phase shifts of the Bmal1-dLuc rhythm that were larger in amplitude as compared to DHA. These phase-shifting effects were time-dependent and contemporaneous with rhythmic changes in palmitate-induced inflammatory responses. Fibroblast and differentiated adipocyte clocks exhibited cell-specific differences in the time-dependent nature of palmitate-induced shifts and inflammation. DHA and other inhibitors of inflammatory signaling (AICAR, cardamonin) repressed palmitate-induced proinflammatory responses and phase shifts of the fibroblast clock, suggesting that SFA-mediated inflammatory signaling may feed back to modulate circadian timekeeping in peripheral clocks.

•

The saturated fatty acid (SFA) palmitate differentially modulates the circadian timekeeping mechanism in peripheral clocks;

•

Palmitate induces time-dependent phase shifts that coincide with its rhythmic induction of inflammatory signaling;

•

Time-dependent nature of the palmitate-induced phase shifts and inflammatory signaling is cell specific;

•

Inhibitors of inflammatory signaling repress the proinflammatory and phase shifting effects of palmitate;

•

Inflammatory signaling plays a role in the mechanism by which palmitate alters circadian timekeeping in peripheral clocks.

Circadian or 24-hour clocks throughout the body mediate the local temporal coordination of tissue- or cell-specific processes necessary for normal inflammatory responses and metabolic homeostasis. Dysregulation of peripheral clocks and their timekeeping function contribute to obesity-related metabolic disorders (e.g., type 2 diabetes). Our data unveil a novel mechanism by which mutual interactions between peripheral clocks and inflammatory signaling pathways dysregulate circadian timekeeping, and exacerbate proinflammatory responses to saturated fatty acids. These studies will guide the development of chronotherapeutic drug and/or dietary omega-3 fatty acid treatments for managing and preventing metabolic disorders and other inflammation-related pathologies (e.g., cardiovascular disease, stroke, arthritis).

Oestrogen exerts anti-inflammation via p38 MAPK/NF-κB cascade in adipocytes

BACKGROUND

Oestrogen has anti-inflammatory property in obesity. However, the mechanism is still not defined.

OBJECTIVE

To investigate the effect of oestrogen on LPS-induced monocyte chemoattractant protein-1 (MCP-1) production in adipocytes.

METHODS

Lipopolysaccharides (LPS) was used to imitate inflammatory responses and monocyte chemotactic protein-1 (MCP-1) was selected as an inflammatory marker to observe. 17β-Estradiol (E₂), SB203580 (SB), pyrrolidine dithiocarbamate (PDTC), pertussis toxin (PTX), wortmannin (WM), p65 siRNA and p38 MAPK siRNA were pre-treated respectively or together in LPS-induced MCP-1. Then p38 MAPK and NF-κB cascade were silenced successively to observe the change of each other. Lastly, oestrogen receptor (ER) α agonist, ERβ agonist and ER antagonist were utilised.

RESULTS

LPS-induced MCP-1 largely impaired by pre-treatment with E₂, SB, PDTC or silencing NF-κB subunit. E₂ inhibited LPS-induced MCP-1 in a time- and dose-dependent manner, which was related to the suppression of p65 translocation to nucleus. Furthermore, LPS rapidly activated p38 MAPK, while E₂ markedly inhibited this activation. It markedly attenuated LPS-stimulated p65 translocation to nucleus and MCP-1 production by transfecting with p38 MAPK siRNA or using p38 MAPK inhibitor. The oestrogen's inhibitory effect was mimicked by the ERα agonist, but not by the ERβ agonist. The inhibition of E₂ on p38 MAPK phosphorylation was prevented by ER antagonist.

CONCLUSIONS

E₂ inhibits LPS-stimulated MCP-1 in adipocytes. This effect is related to the inhibition of p38 MAPK/NF-κB cascade, and ERα appears to be the dominant ER subtype in these events.

Berberine Ameliorates Hepatic Steatosis and Suppresses Liver and Adipose Tissue Inflammation in Mice with Diet-induced Obesity

Increasing evidence demonstrates that berberine (BBR) is beneficial for obesity-associated non-alcoholic fatty liver disease (NAFLD). However, it remains to be elucidated how BBR improves aspects of NAFLD. Here we revealed an AMP-activated protein kinase (AMPK)-independent mechanism for BBR to suppress obesity-associated inflammation and improve hepatic steatosis. In C57BL/6J mice fed a high-fat diet (HFD), treatment with BBR decreased inflammation in both the liver and adipose tissue as indicated by reduction of the phosphorylation state of JNK1 and the mRNA levels of proinflammatory cytokines. BBR treatment also decreased hepatic steatosis, as well as the expression of acetyl-CoA carboxylase and fatty acid synthase. Interestingly, treatment with BBR did not significantly alter the phosphorylation state of AMPK in both the liver and adipose tissue of HFD-fed mice. Consistently, BBR treatment significantly decreased the phosphorylation state of JNK1 in both hepatoma H4IIE cells and mouse primary hepatocytes in both dose-dependent and time-dependent manners, which was independent of AMPK phosphorylation. BBR treatment also caused a decrease in palmitate-induced fat deposition in primary mouse hepatocytes. Taken together, these results suggest that BBR actions on improving aspects of NAFLD are largely attributable to BBR suppression of inflammation, which is independent of AMPK.

Bovine (Bos taurus) Bone Marrow Mesenchymal Cell Differentiation to Adipogenic and Myogenic Lineages

PURPOSE

We evaluated the effect of peroxisome proliferator-activated receptor (PPAR) agonists on the differentiation and metabolic features of bovine bone marrow-derived mesenchymal cells induced to adipogenic or myogenic lineages.

METHODS

Cells isolated from 7-day-old calves were cultured in basal medium (BM). For adipogenic differentiation, cells were cultured for one passage in BM and then transferred to a medium supplemented with either rosiglitazone, telmisartan, sirtinol or conjugated c-9, t-11 linoleic acid; for myogenic differentiation, third-passage cells were added with either bezafibrate, telmisartan or sirtinol. The expression of PPARx03B3; (an adipogenic differentiation marker), myosin heavy chain (MyHC; a myogenic differentiation marker) and genes related to energy metabolism were measured by quantitative real-time PCR in a completely randomized design.

RESULTS

For adipogenic differentiation, 20 µM telmisartan showed the highest PPARx03B3; expression (15.58 ± 0.62-fold, p < 0.0001), and differences in the expression of energy metabolism-related genes were found for hexokinase II, phosphofructokinase, adipose triglyceride lipase, acetyl-CoA carboxylase α(ACACα) and fatty acid synthase (p < 0.001), but not for ACACβ (p = 0.4275). For myogenic differentiation, 200 µM bezafibrate showed the highest MyHC expression (73.98 ± 11.79-fold), and differences in the expression of all energy metabolism-related genes were found (p < 0.05).

CONCLUSIONS

Adipocyte and myocyte differentiation are enhanced with telmisartan and bezafibrate, respectively, and energy uptake, storage and mobilization are improved with both.

Kinome Screen Identifies PFKFB3 and Glucose Metabolism as Important Regulators of the Insulin/Insulin-like Growth Factor (IGF)-1 Signaling Pathway

The insulin/insulin-like growth factor (IGF)-1 signaling pathway (ISP) plays a fundamental role in long term health in a range of organisms. Protein kinases including Akt and ERK are intimately involved in the ISP. To identify other kinases that may participate in this pathway or intersect with it in a regulatory manner, we performed a whole kinome (779 kinases) siRNA screen for positive or negative regulators of the ISP, using GLUT4 translocation to the cell surface as an output for pathway activity. We identified PFKFB3, a positive regulator of glycolysis that is highly expressed in cancer cells and adipocytes, as a positive ISP regulator. Pharmacological inhibition of PFKFB3 suppressed insulin-stimulated glucose uptake, GLUT4 translocation, and Akt signaling in 3T3-L1 adipocytes. In contrast, overexpression of PFKFB3 in HEK293 cells potentiated insulin-dependent phosphorylation of Akt and Akt substrates. Furthermore, pharmacological modulation of glycolysis in 3T3-L1 adipocytes affected Akt phosphorylation. These data add to an emerging body of evidence that metabolism plays a central role in regulating numerous biological processes including the ISP. Our findings have important implications for diseases such as type 2 diabetes and cancer that are characterized by marked disruption of both metabolism and growth factor signaling.

Type 2 diabetes alters metabolic and transcriptional signatures of glucose and amino acid metabolism during exercise and recovery

AIMS/HYPOTHESIS

The therapeutic benefit of physical activity to prevent and treat type 2 diabetes is commonly accepted. However, the impact of the disease on the acute metabolic response is less clear. To this end, we investigated the effect of type 2 diabetes on exercise-induced plasma metabolite changes and the muscular transcriptional response using a complementary metabolomics/transcriptomics approach.

METHODS

We analysed 139 plasma metabolites and hormones at nine time points, and whole genome expression in skeletal muscle at three time points, during a 60 min bicycle ergometer exercise and a 180 min recovery phase in type 2 diabetic patients and healthy controls matched for age, percentage body fat and maximal oxygen consumption (VO2).

RESULTS

Pathway analysis of differentially regulated genes upon exercise revealed upregulation of regulators of GLUT4 (SLC2A4RG, FLOT1, EXOC7, RAB13, RABGAP1 and CBLB), glycolysis (HK2, PFKFB1, PFKFB3, PFKM, FBP2 and LDHA) and insulin signal mediators in diabetic participants compared with controls. Notably, diabetic participants had normalised rates of lactate and insulin levels, and of glucose appearance and disappearance, after exercise. They also showed an exercise-induced compensatory regulation of genes involved in biosynthesis and metabolism of amino acids (PSPH, GATM, NOS1 and GLDC), which responded to differences in the amino acid profile (consistently lower plasma levels of glycine, cysteine and arginine). Markers of fat oxidation (acylcarnitines) and lipolysis (glycerol) did not indicate impaired metabolic flexibility during exercise in diabetic participants.

CONCLUSIONS/INTERPRETATION

Type 2 diabetic individuals showed specific exercise-regulated gene expression. These data provide novel insight into potential mechanisms to ameliorate the disturbed glucose and amino acid metabolism associated with type 2 diabetes.

Metformin and metabolic diseases: a focus on hepatic aspects

Metformin has been widely used as a first-line anti-diabetic medicine for the treatment of type 2 diabetes (T2D). As a drug that primarily targets the liver, metformin suppresses hepatic glucose production (HGP), serving as the main mechanism by which metformin improves hyperglycemia of T2D. Biochemically, metformin suppresses gluconeogenesis and stimulates glycolysis. Metformin also inhibits glycogenolysis, which is a pathway that critically contributes to elevated HGP. While generating beneficial effects on hyperglycemia, metformin also improves insulin resistance and corrects dyslipidemia in patients with T2D. These beneficial effects of metformin implicate a role for metformin in managing non-alcoholic fatty liver disease. As supported by the results from both human and animal studies, metformin improves hepatic steatosis and suppresses liver inflammation. Mechanistically, the beneficial effects of metformin on hepatic aspects are mediated through both adenosine monophosphate-activated protein kinase (AMPK)-dependent and AMPK-independent pathways. In addition, metformin is generally safe and may also benefit patients with other chronic liver diseases.

Myeloid cell-specific disruption of Period1 and Period2 exacerbates diet-induced inflammation and insulin resistance

The circadian clockworks gate macrophage inflammatory responses. Given the association between clock dysregulation and metabolic disorders, we conducted experiments to determine the extent to which over-nutrition modulates macrophage clock function and whether macrophage circadian dysregulation is a key factor linking over-nutrition to macrophage proinflammatory activation, adipose tissue inflammation, and systemic insulin resistance. Our results demonstrate that 1) macrophages from high fat diet-fed mice are marked by dysregulation of the molecular clockworks in conjunction with increased proinflammatory activation, 2) global disruption of the clock genes Period1 (Per1) and Per2 recapitulates this amplified macrophage proinflammatory activation, 3) adoptive transfer of Per1/2-disrupted bone marrow cells into wild-type mice potentiates high fat diet-induced adipose and liver tissue inflammation and systemic insulin resistance, and 4) Per1/2-disrupted macrophages similarly exacerbate inflammatory responses and decrease insulin sensitivity in co-cultured adipocytes in vitro. Furthermore, PPARγ levels are decreased in Per1/2-disrupted macrophages and PPARγ2 overexpression ameliorates Per1/2 disruption-associated macrophage proinflammatory activation, suggesting that this transcription factor may link the molecular clockworks to signaling pathways regulating macrophage polarization. Thus, macrophage circadian clock dysregulation is a key process in the physiological cascade by which diet-induced obesity triggers macrophage proinflammatory activation, adipose tissue inflammation, and insulin resistance.

Metformin ameliorates hepatic steatosis and inflammation without altering adipose phenotype in diet-induced obesity

Non-alcoholic fatty liver disease (NAFLD) is closely associated with obesity and insulin resistance. To better understand the pathophysiology of obesity-associated NAFLD, the present study examined the involvement of liver and adipose tissues in metformin actions on reducing hepatic steatosis and inflammation during obesity. C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity-associated NAFLD and treated with metformin (150 mg/kg/d) orally for the last four weeks of HFD feeding. Compared with HFD-fed control mice, metformin-treated mice showed improvement in both glucose tolerance and insulin sensitivity. Also, metformin treatment caused a significant decrease in liver weight, but not adiposity. As indicated by histological changes, metformin treatment decreased hepatic steatosis, but not the size of adipocytes. In addition, metformin treatment caused an increase in the phosphorylation of liver AMP-activated protein kinase (AMPK), which was accompanied by an increase in the phosphorylation of liver acetyl-CoA carboxylase and decreases in the phosphorylation of liver c-Jun N-terminal kinase 1 (JNK1) and in the mRNA levels of lipogenic enzymes and proinflammatory cytokines. However, metformin treatment did not significantly alter adipose tissue AMPK phosphorylation and inflammatory responses. In cultured hepatocytes, metformin treatment increased AMPK phosphorylation and decreased fat deposition and inflammatory responses. Additionally, in bone marrow-derived macrophages, metformin treatment partially blunted the effects of lipopolysaccharide on inducing the phosphorylation of JNK1 and nuclear factor kappa B (NF-κB) p65 and on increasing the mRNA levels of proinflammatory cytokines. Taken together, these results suggest that metformin protects against obesity-associated NAFLD largely through direct effects on decreasing hepatocyte fat deposition and on inhibiting inflammatory responses in both hepatocytes and macrophages.

De novo lipogenesis in human fat and liver is linked to ChREBP-β and metabolic health

Clinical interest in de novo lipogenesis has been sparked by recent studies in rodents demonstrating that de novo lipogenesis specifically in white adipose tissue produces the insulin-sensitizing fatty acid palmitoleate. By contrast, hepatic lipogenesis is thought to contribute to metabolic disease. How de novo lipogenesis in white adipose tissue versus liver is altered in human obesity and insulin resistance is poorly understood. Here we show that lipogenic enzymes and the glucose transporter-4 are markedly decreased in white adipose tissue of insulin-resistant obese individuals compared with non-obese controls. By contrast, lipogenic enzymes are substantially upregulated in the liver of obese subjects. Bariatric weight loss restored de novo lipogenesis and glucose transporter-4 gene expression in white adipose tissue. Notably, lipogenic gene expression in both white adipose tissue and liver was strongly linked to the expression of carbohydrate-responsive element-binding protein-β and to metabolic risk markers. Thus, de novo lipogenesis predicts metabolic health in humans in a tissue-specific manner and is likely regulated by glucose-dependent carbohydrate-responsive element-binding protein activation.

Gly482Ser mutation impairs the effects of peroxisome proliferator-activated receptor γ coactivator-1α on decreasing fat deposition and stimulating phosphoenolpyruvate carboxykinase expression in hepatocytes

Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) is a transcriptional coactivator of nuclear receptor peroxisome proliferator-activated receptor γ that critically regulates glucose and fat metabolism. Although clinical evidence suggests that Gly482Ser polymorphism of PGC-1α is associated with an increased incidence of nonalcoholic fatty liver disease, a direct role for Gly482Ser mutation in altering PGC-1α actions on hepatocyte fat deposition remains to be explored. We hypothesized that Gly482Ser mutation impairs the abilities of PGC-1α in ameliorating overnutrition-induced hepatocyte fat deposition and in stimulating hepatocyte expression of cytosolic phosphoenolpyruvate carboxykinase (PEPCK-C; encoded by a key PGC-1α target gene). In the present study, treatment of cultured hepatocytes with palmitate induced fat deposition, serving as a cell model of hepatic steatosis. Upon overexpression of wild-type PGC-1α, H4IIE cells exhibited a significant decrease in palmitate-induced hepatocyte fat deposition compared with control cells and/or cells upon overexpression of mutant PGC-1α (Gly482Ser). Overexpression of wild-type PGC-1α, but not mutant PGC-1α, also caused a significant increase in hepatocyte expression of carnitine palmitoyl transferase 1a, a rate-determining enzyme that transfers long-chain fatty acids into mitochondria for oxidation. In addition, overexpression of mutant PGC-1α did not stimulate PEPCK-C expression as overexpression of wild-type PGC-1α did, likely due to a decrease in the ability of mutant PGC-1α in increasing PEPCK promoter transcription activity. Together, these results suggest that Gly482Ser mutation impairs the abilities of PGC-1α in decreasing fat deposition and in stimulating PEPCK-C expression in cultured hepatocytes.

A role for inducible 6-phosphofructo-2-kinase in the control of neuronal glycolysis

Increased glycolysis is the result of the sensing of glucose by hypothalamic neurons. The biochemical mechanisms underlying the control of hypothalamic glycolysis, however, remain to be elucidated. Here we showed that PFKFB3, the gene that encodes for inducible 6-phosphofructo-2-kinase (iPFK2), was expressed at high abundance in both mouse hypothalami and clonal hypothalamic neurons. In response to re-feeding, PFKFB3 mRNA levels were increased by 10-fold in mouse hypothalami. In the hypothalamus, re-feeding also decreased the phosphorylation of AMP-activated protein kinase (AMPK) (Thr172) and the mRNA levels of agouti-related protein (AgRP), and increased the mRNA levels of cocaine-amphetamine-related transcript (CART). Similar results were observed in N-43/5 clonal hypothalamic neurons upon treatment with glucose and/or insulin. In addition, knockdown of PFKFB3/iPFK2 in N-43/5 neurons caused a decrease in rates of glycolysis, which was accompanied by increased AMPK phosphorylation, increased AgRP mRNA levels and decreased CART mRNA levels. In contrast, overexpression of PFKFB3/iPFK2 in N-43/5 neurons caused an increase in glycolysis, which was accompanied by decreased AMPK phosphorylation and decreased AgRP mRNA levels and increased CART mRNA levels. Together, these results suggest that PFKFB3/iPFK2 responds to re-feeding, which in turn stimulates hypothalamic glycolysis and decreases hypothalamic AMPK phosphorylation and alters neuropeptide expression in a pattern that is associated with suppression of food intake.