Adipose overexpression of phosphoenolpyruvate carboxykinase leads to high susceptibility to diet-induced insulin resistance and obesity

The neglected PCK1/glucagon (inter)action in nutrient homeostasis beyond gluconeogenesis: Disease pathogenesis and treatment

BACKGROUND

Glucagon plays a central role in hepatic adaptation during fasting, with the upregulation of hepatic phosphoenolpyruvate carboxykinase 1 (PCK1) traditionally associated with increased gluconeogenesis. However, recent experimental models and clinical studies have challenged this view, suggesting a more complex interplay between PCK1 and glucagon, which extends beyond gluconeogenesis and has broader implications for metabolic regulation in health and disease.

SCOPE OF REVIEW

This review provides a comprehensive overview of the current evidence on the multifaceted roles of PCK1 in glucagon-dependent hepatic adaptation during fasting, which is crucial for maintaining systemic homeostasis not only of glucose, but also of lipids and amino acids. We explore the relationship between PCK1 deficiency and glucagon resistance in metabolic disorders, including inherited PCK1 deficiency and metabolic dysfunction-associated steatotic liver disease (MASLD), and compare findings from experimental animal models with whole-body or tissue-specific ablation of PCK1 or the glucagon receptor. We propose new research platforms to advance the therapeutic potential of targeting PCK1 in metabolic diseases.

MAJOR CONCLUSIONS

We propose that hepatic PCK1 deficiency might be an acquired metabolic disorder linking alterations in lipid metabolism with impaired glucagon signaling. Our findings highlight interesting links between glycerol, PCK1 deficiency, elevated plasma alanine levels and glucagon resistance. We conclude that the roles of PCK1 and glucagon in metabolic regulation are more complex than previously assumed. In this (un)expected scenario, hepatic PCK1 deficiency and glucagon resistance appear to exert limited control over glycemia, but have broader metabolic effects related to lipid and amino acid dysregulation. Given the shift in glucagon research from receptor inhibition to activation, we propose that a similar paradigm shift is needed in the study of hepatic PCK1. Understanding PCK1 expression and activity in the glucagon-dependent hepatic adaptation to fasting might provide new perspectives and therapeutic opportunities for metabolic diseases.

Alx3 deficiency disrupts energy homeostasis, alters body composition, and impairs hypothalamic regulation of food intake

The coordination of food intake, energy storage, and expenditure involves complex interactions between hypothalamic neurons and peripheral tissues including pancreatic islets, adipocytes, muscle, and liver. Previous research shows that deficiency of the transcription factor Alx3 alters pancreatic islet-dependent glucose homeostasis. In this study we carried out a comprehensive assessment of metabolic alterations in Alx3 deficiency. We report that Alx3-deficient mice exhibit decreased food intake without changes in body weight, along with reduced energy expenditure and altered respiratory exchange ratio. Magnetic resonance imaging reveals increased adiposity and decreased muscle mass, which was associated with markers of motor and sympathetic denervation. By contrast, Alx3-deficient mice on a high-fat diet show attenuated weight gain and improved insulin sensitivity, compared to control mice. Gene expression analysis demonstrates altered lipogenic and lipolytic gene profiles. In wild type mice Alx3 is expressed in hypothalamic arcuate nucleus neurons, but not in major peripheral metabolic organs. Functional diffusion-weighted magnetic resonance imaging reveals selective hypothalamic responses to fasting in the arcuate nucleus of Alx3-deficient mice. Additionally, altered expression of proopiomelanocortin and melanocortin-3 receptor mRNA in the hypothalamus suggests impaired regulation of feeding behavior. This study highlights the crucial role for Alx3 in governing food intake, energy homeostasis, and metabolic nutrient partitioning, thereby influencing body mass composition.

Deciphering the role of classical oestrogen receptor in insulin resistance and type 2 diabetes mellitus: From molecular mechanism to clinical evidence

The biological actions of oestrogen are mediated by the oestrogen receptor α or β (ERα or ERβ), which are members of a broad nuclear receptor superfamily. Numerous in vivo and in vitro studies have demonstrated that loss of circulating oestrogen modulated by classical ERα and ERβ led to rapid changes in pancreatic β-cell and islet function, GLUT4 expression, insulin sensitivity and glucose tolerance, dysfunctional lipid homeostasis, oxidative stress, and inflammatory cascades. Remarkably, 17β-oestradiol (E2) can completely reverse these effects. This review evaluates the current understanding of the protective role of classical ER in critical pathways and molecular mechanisms associated with insulin resistance and type 2 diabetes mellitus (T2DM). It also examines the effectiveness of menopausal hormone therapy (MHT) in reducing the risk of developing T2DM in menopausal women. Clinical trials have shown the protective effects of MHT on glucose metabolism, which may be useful to treat T2DM in perimenopausal women. However, there are concerns about E2's potential side effects of obesity and hyperlipidaemia in menopausal women. Further studies are warranted to gain understanding and find other oestrogen alternatives for treatment of insulin resistance and T2DM in postmenopausal women.

The Role of Adipocytes Recruited as Part of Tumor Microenvironment in Promoting Colorectal Cancer Metastases

Adipose tissue dysfunction, which is associated with an increased risk of colorectal cancer (CRC), is a significant factor in the pathophysiology of obesity. Obesity-related inflammation and extracellular matrix (ECM) remodeling promote colorectal cancer metastasis (CRCM) by shaping the tumor microenvironment (TME). When CRC occurs, the metabolic symbiosis of tumor cells recruits adjacent adipocytes into the TME to supply energy. Meanwhile, abundant immune cells, from adipose tissue and blood, are recruited into the TME, which is stimulated by pro-inflammatory factors and triggers a chronic local pro-inflammatory TME. Dysregulated ECM proteins and cell surface adhesion molecules enhance ECM remodeling and further increase contractibility between tumor and stromal cells, which promotes epithelial-mesenchymal transition (EMT). EMT increases tumor migration and invasion into surrounding tissues or vessels and accelerates CRCM. Colorectal symbiotic microbiota also plays an important role in the promotion of CRCM. In this review, we provide adipose tissue and its contributions to CRC, with a special emphasis on the role of adipocytes, macrophages, neutrophils, T cells, ECM, and symbiotic gut microbiota in the progression of CRC and their contributions to the CRC microenvironment. We highlight the interactions between adipocytes and tumor cells, and potential therapeutic approaches to target these interactions.

The potential of therapeutic strategies targeting mitochondrial biogenesis for the treatment of insulin resistance and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a persistent metabolic disorder marked by deficiencies in insulin secretion and/or function, affecting various tissues and organs and leading to numerous complications. Mitochondrial biogenesis, the process by which cells generate new mitochondria utilizing existing ones plays a crucial role in energy homeostasis, glucose metabolism, and lipid handling. Recent evidence suggests that promoting mitochondrial biogenesis can alleviate insulin resistance in the liver, adipose tissue, and skeletal muscle while improving pancreatic β-cell function. Moreover, enhanced mitochondrial biogenesis has been shown to ameliorate T2DM symptoms and may contribute to therapeutic effects for the treatment of diabetic nephropathy, cardiomyopathy, retinopathy, and neuropathy. This review summarizes the intricate connection between mitochondrial biogenesis and T2DM, highlighting the potential of novel therapeutic strategies targeting mitochondrial biogenesis for T2DM treatment and its associated complications. It also discusses several natural products that exhibit beneficial effects on T2DM by promoting mitochondrial biogenesis.

Role of polyphenols in the management of diabetic complications

BACKGROUND

Diabetes Mellitus is an endocrine disorder that will affect, about 693 million adults by 2045 worldwide, (>50% increase from 2017). The conventional treatment of the disease, include the oral hypoglycemic drugs which are given in combination with other drugs and are known to possess various adverse effects like gastrointestinal disturbance, nausea, water retention etc. PURPOSE: Due to the urgent need of combating this disorder without side effects, the alternative and complementary therapies should be explored due to their natural origins and comparable safety. Herbal sources serve as new leads, due to the presence of phytoconstituents with potential therapeutic properties, efficacy and safety. In this review, we tried to summarise the polyphenolic phytoconstituents effective in the treatment of diabetic complications.

METHODS

A systematic literature search was conducted using 4 databases (Google scholar, Pubmed, Scopus, Embase) for the identification of relevant data. Search was performed using various key words such as "diabetes", "polyphenols", "marine sources","anti-diabetic polyphenols". The in vitro studies involving the cell lines used in diabetes and animal models were also considered for inclusion. Additional research papers were identified by reviewing abstracts, scrutinizing reference lists, and reviewing previously published review articles.

RESULTS

Polyphenols, a group of phytoconstituents are known worldwide for their tremendous antioxidant potential. So, various research groups have explored their mechanism and therapeutic value in diabetic complications, to improve the insulin sensitivity and glucose metabolism, in controlling the glycemic conditions.

CONCLUSION

Polyphenols exhibit effective therapeutic potential in managing diabetic complications through their multifaceted mechanism of action. They exhibit antioxidative, anti-inflammatory, and anti-glycemic properties, which collectively contribute to their beneficial effects in mitigating diabetic complications. Thus, the inclusion of polyphenols into the diet, may be cosidered as an approach of managing diabetes on long term basis. In this review, we have tried to identify polyphenols effective in diabetes and summarize their mechanism of action along with their potential, for the treatment of diabetic complications.

Serum anti-PCK1 antibody levels are a prognostic factor for patients with diabetes mellitus

BACKGROUND

Autoantibodies develop in autoimmune diseases, cancer, diabetes mellitus (DM), and atherosclerosis-related diseases. However, autoantibody biomarkers have not been successfully examined for diagnosis and therapy.

METHODS

Serological identification of antigens through recombinant cDNA expression cloning (SEREX) was used for primary screening of antigens. The cDNA product was expressed in bacteria and purified. Amplified luminescent proximity homogeneous assay-linked immunosorbent assay (AlphaLISA) was used to evaluate antibody levels in serum samples.

RESULTS

Phosphoenolpyruvate carboxykinase 1 (PCK1) was recognized as an antigen by serum IgG antibodies in the sera of patients with atherosclerosis. AlphaLISA showed significantly higher serum antibody levels against recombinant PCK1 protein in patients with DM and cardiovascular disease than in healthy donors, but not in those with acute ischemic stroke, transient ischemic attack, or obstructive sleep apnea syndrome. The area under the receiver operating characteristic curve for anti-PCK1 antibodies was 0.7024 for DM. The serum anti-PCK1 antibody levels were associated with age, platelet count, and blood pressure. Anti-PCK1-antibody-positive patients showed significantly lower overall survival than the negative patients.

CONCLUSIONS

Serum anti-PCK1 antibody levels were found to be associated with DM. The anti-PCK1 antibody marker is useful for predicting the overall survival of patients with DM.

Astaxanthin and DHA supplementation ameliorates the proteomic profile of perinatal undernutrition-induced adipose tissue dysfunction in adult life

Maternal diet is an essential factor that directly and indirectly regulates fetal growth. Exposure to certain environmental conditions substantially impacts an individual's short- and long-term health. Adipose tissue dysfunction is a worldwide chronic disease caused by improper lipid build-up in adipose tissue leading to obesity. Therefore, it is the need of the hour to invent anti-obesity agents. As a keto-carotenoid, Astaxanthin (AsX) has been shown to have preventive effects against problems associated with obesity. A crucial role in the pathogenesis of obesity has been attributed to dietary polyunsaturated fatty acids. Adipose tissue plays a vital role in maintaining overall body homeostasis. Metabolic dysfunction of white adipocytes forms a critical step in the emergence of insulin resistance and related diseases. Here we aim to investigate the effect of AsX and Docosahexaenoic acid (DHA) supplementation on the proteomic profile of perinatal undernutrition-induced adipose tissue dysfunction in adult life using a rat model. The LC-MS/MS quantitative proteomics enabled us to identify differentially expressed proteins in perinatal undernourished but AsX and DHA-supplemented animal models. Data are available via ProteomeXchange with identifier PXD041772.This study explored biological roles, molecular functions of differentially expressed proteins, and pathways related to adipose tissue dysfunction induced by undernutrition and its effective modulation by AsX and DHA.

Modulation of insulin signaling pathway genes by ozone inhalation and the role of glucocorticoids: A multi-tissue analysis

Air pollution is associated with increased risk of metabolic diseases including type 2 diabetes, of which dysregulation of the insulin-signaling pathway is a feature. While studies suggest pollutant exposure alters insulin signaling in certain tissues, there is a lack of comparison across multiple tissues needed for a holistic assessment of metabolic effects, and underlying mechanisms remain unclear. Air pollution increases plasma levels of glucocorticoids, systemic regulators of metabolic function. The objectives of this study were to 1) determine effects of ozone on insulin-signaling genes in major metabolic tissues, and 2) elucidate the role of glucocorticoids. Male Fischer-344 rats were treated with metyrapone, a glucocorticoid synthesis inhibitor, and exposed to 0.8 ppm ozone or clean air for 4 h, with tissue collected immediately or 24 h post exposure. Ozone inhalation resulted in distinct mRNA profiles in the liver, brown adipose, white adipose and skeletal muscle tissues, including effects on insulin-signaling cascade genes (Pik3r1, Irs1, Irs2) and targets involved in glucose metabolism (Hk2, Pgk1, Slc2a1), cell survival (Bcl2l1), and genes associated with diabetes and obesity (Serpine1, Retn, Lep). lucocorticoid-dependent regulation was observed in the liver and brown and white adipose tissues, while effects in skeletal muscle were largely unaffected by metyrapone treatment. Gene expression changes were accompanied by altered phosphorylation states of insulin-signaling proteins (BAD, GSK, IR-β, IRS-1) in the liver. The results show that systemic effects of ozone inhalation include tissue-specific regulation of insulin-signaling pathway genes via both glucocorticoid-dependent and independent mechanisms, providing insight into mechanisms underlying adverse effects of pollutants.

Extracellular Vesicles as Carriers of Adipokines and Their Role in Obesity

Extracellular vesicles (EVs) have lately arisen as new metabolic players in energy homeostasis participating in intercellular communication at the local and distant levels. These nanosized lipid bilayer spheres, carrying bioactive molecular cargo, have somehow changed the paradigm of biomedical research not only as a non-classic cell secretion mechanism, but as a rich source of biomarkers and as useful drug-delivery vehicles. Although the research about the role of EVs on metabolism and its deregulation on obesity and associated pathologies lagged slightly behind other diseases, the knowledge about their function under normal and pathological homeostasis is rapidly increasing. In this review, we are focusing on the current research regarding adipose tissue shed extracellular vesicles including their characterization, size profile, and molecular cargo content comprising miRNAs and membrane and intra-vesicular proteins. Finally, we will focus on the functional aspects attributed to vesicles secreted not only by adipocytes, but also by other cells comprising adipose tissue, describing the evidence to date on the deleterious effects of extracellular vesicles released by obese adipose tissue both locally and at the distant level by interacting with other peripheral organs and even at the central level.

Is insulin resistance tissue-dependent and substrate-specific? The role of white adipose tissue and skeletal muscle

Insulin resistance (IR) refers to a reduction in the ability of insulin to exert its metabolic effects in organs such as adipose tissue (AT) and skeletal muscle (SM), leading to chronic diseases such as type 2 diabetes, hepatic steatosis, and cardiovascular diseases. Obesity is the main cause of IR, however not all subjects with obesity develop clinical insulin resistance, and not all clinically insulin-resistant people have obesity. Recent evidence implies that IR onset is tissue-dependent (AT or SM) and/or substrate-specific (glucometabolic or lipometabolic). Therefore, the aims of the present review are 1) to describe the glucometabolic and lipometabolic activities of insulin in AT and SM in the maintenance of whole-body metabolic homeostasis, 2) to discuss the pathophysiology of substrate-specific IR in AT and SM, and 3) to highlight novel validated tests to assess tissue and substrate-specific IR that are easy to perform in clinical practice. In AT, glucometabolic IR reduces glucose availability for glycerol and fatty acid synthesis, thus decreasing the esterification and synthesis of signaling bioactive lipids. Lipometabolic IR in AT impairs the antilipolytic effect of insulin and lipogenesis, leading to an increase in circulating FFAs and generating lipotoxicity in peripheral tissues. In SM, glucometabolic IR reduces glucose uptake, whereas lipometabolic IR impairs mitochondrial lipid oxidation, increasing oxidative stress and inflammation, all of which lead to metabolic inflexibility. Understanding tissue-dependent and substrate-specific IR is of paramount importance for early detection before clinical manifestations and for the development of more specific treatments or direct interventions to prevent chronic life-threatening diseases.

Metformin can mitigate skeletal dysplasia caused by Pck2 deficiency

As an important enzyme for gluconeogenesis, mitochondrial phosphoenolpyruvate carboxykinase (PCK2) has further complex functions beyond regulation of glucose metabolism. Here, we report that conditional knockout of Pck2 in osteoblasts results in a pathological phenotype manifested as craniofacial malformation, long bone loss, and marrow adipocyte accumulation. Ablation of Pck2 alters the metabolic pathways of developing bone, particularly fatty acid metabolism. However, metformin treatment can mitigate skeletal dysplasia of embryonic and postnatal heterozygous knockout mice, at least partly via the AMPK signaling pathway. Collectively, these data illustrate that PCK2 is pivotal for bone development and metabolic homeostasis, and suggest that regulation of metformin-mediated signaling could provide a novel and practical strategy for treating metabolic skeletal dysfunction.

Brown Adipose Tissue Sheds Extracellular Vesicles That Carry Potential Biomarkers of Metabolic and Thermogenesis Activity Which Are Affected by High Fat Diet Intervention

Brown adipose tissue (BAT) is a key target for the development of new therapies against obesity due to its role in promoting energy expenditure; BAT secretory capacity is emerging as an important contributor to systemic effects, in which BAT extracellular vesicles (EVs) (i.e., batosomes) might be protagonists. EVs have emerged as a relevant cellular communication system and carriers of disease biomarkers. Therefore, characterization of the protein cargo of batosomes might reveal their potential as biomarkers of the metabolic activity of BAT. In this study, we are the first to isolate batosomes from lean and obese Sprague–Dawley rats, and to establish reference proteome maps. An LC-SWATH/MS analysis was also performed for comparisons with EVs secreted by white adipose tissue (subcutaneous and visceral WAT), and it showed that 60% of proteins were exclusive to BAT EVs. Precisely, batosomes of lean animals contain proteins associated with mitochondria, lipid metabolism, the electron transport chain, and the beta-oxidation pathway, and their protein cargo profile is dramatically affected by high fat diet (HFD) intervention. Thus, in obesity, batosomes are enriched with proteins involved in signal transduction, cell communication, the immune response, inflammation, thermogenesis, and potential obesity biomarkers including UCP1, Glut1, MIF, and ceruloplasmin. In conclusion, the protein cargo of BAT EVs is affected by the metabolic status and contains potential biomarkers of thermogenesis activity.

Bisphenol A (BPA) Leading to Obesity and Cardiovascular Complications: A Compilation of Current In Vivo Study

BPA is one of the most common endocrine disruptors that is widely being manufactured daily nationwide. Although scientific evidence supports claims of negative effects of BPA on humans, there is also evidence suggesting that a low level of BPA is safe. However, numerous in vivo trials contraindicate with this claim and there is a high possibility of BPA exposure could lead to obesity. It has been speculated that this does not stop with the exposed subjects only, but may also cause transgenerational effects. Direct disruption of endocrine regulation, neuroimmune and signaling pathways, as well as gut microbiata, has been identified to be interrupted by BPA exposure, leading to overweight or obesity. In these instances, cardiovascular complications are one of the primary notable clinical signs. In regard to this claim, this review paper discusses the role of BPA on obesity in the perspective of endocrine disruptions and possible cardiovascular complications that may arise due to BPA. Thus, the aim of this review is to outline the changes in gut microbiota and neuroimmune or signaling mechanisms involved in obesity in relation to BPA. To identify potentially relevant articles, a depth search was done on the databases Nature, PubMed, Wiley Online Library, and Medline & Ovid from the past 5 years. According to Boolean operator guideline, selected keywords such as (1) BPA OR environmental chemical AND fat OR LDL OR obese AND transgenerational effects or phenocopy (2) Endocrine disruptors OR chemical AND lipodystrophy AND phenocopy (3) Lipid profile OR weight changes AND cardiovascular effect (4) BPA AND neuroimmune OR gene signaling, were used as search terms. Upon screening, 11 articles were finalized to be further reviewed and data extraction tables containing information on (1) the type of animal model (2) duration and dosage of BPA exposure (3) changes in the lipid profile or weight (4) genes, signaling mechanism, or any neuroimmune signal involved, and (5) transgenerational effects were created. In toto, the study indicates there are high chances of BPA exposure affecting lipid profile and gene associated with lipolysis, leading to obesity. Therefore, this scoping review recapitulates the possible effects of BPA that may lead to obesity with the evidence of current in vivo trials. The biomarkers, safety concerns, recommended dosage, and the impact of COVID-19 on BPA are also briefly described.

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.

Phosphoenolpyruvate carboxykinase in cell metabolism: Roles and mechanisms beyond gluconeogenesis

BACKGROUND

Phosphoenolpyruvate carboxykinase (PCK) has been almost exclusively recognized as a critical enzyme in gluconeogenesis, especially in the liver and kidney. Accumulating evidence has shown that the enhanced activity of PCK leads to increased glucose output and exacerbation of diabetes, whereas the defects of PCK result in lethal hypoglycemia. Genetic mutations or polymorphisms are reported to be related to the onset and progression of diabetes in humans.

SCOPE OF REVIEW

Recent studies revealed that the PCK pathway is more complex than just gluconeogenesis, depending on the health or disease condition. Dysregulation of PCK may contribute to the development of obesity, cardiac hypertrophy, stroke, and cancer. Moreover, a regulatory network with multiple layers, from epigenetic regulation, transcription regulation, to posttranscription regulation, precisely tunes the expression of PCK. Deciphering the molecular basis that regulates PCK may pave the way for developing practical strategies to treat metabolic dysfunction.

MAJOR CONCLUSIONS

In this review, we summarize the metabolic and non-metabolic roles of the PCK enzyme in cells, especially beyond gluconeogenesis. We highlight the distinct functions of PCK isoforms (PCK1 and PCK2), depict a detailed network regulating PCK's expression, and discuss its clinical relevance. We also discuss the therapeutic potential targeting PCK and the future direction that is highly in need to better understand PCK-mediated signaling under diverse conditions.

Salvia hispanica L. (chia) seed promotes body fat depletion and modulates adipocyte lipid handling in sucrose-rich diet-fed rats

The aim of this study was to analyze the effects of Salvia hispanica L. (chia) seed upon metabolic pathways that play a key role in adipose tissue lipid handling which could be involved in visceral adiposity reduction developed in rats fed a sucrose-rich diet (SRD). Male Wistar rats were fed with a reference diet (RD) -6 months- or SRD-3 months. Then, the last group was randomly divided into two subgroups. One subgroup continued receiving the SRD up to 6 months and the other was fed with a SRD where whole chia seed was incorporated as the source of dietary fat for the next 3 months (SRD + CHIA). Results showed that chia seed in the SRD-fed rat reduced the abdominal and thoracic circumferences, carcass fat content, adipose tissue weights, and visceral adiposity index. This was accompanied by an improvement in insulin sensitivity and plasma lipid profile. In epididymal adipose tissue, the decreased fat cell triglyceride content was associated with a reduction in both, FAT/CD 36 plasma membrane levels and the fat synthesis enzyme activities. There were not changes in oxidative CPT enzyme activities. PKCβ and the precursor and mature forms of SREBP-1 protein levels were decreased, while pAMPK was increased. Our findings suggest that chia seed supplementation can modulate essential pathways of lipid metabolism in adipose tissue, contributing to reduced visceral fat accumulation in SRD-fed rats.

Effects of high-fat diet and Apoe deficiency on retinal structure and function in mice

To investigate the effects of a high-fat diet (HFD) and apolipoprotein E (Apoe) deficiency on retinal structure and function in mice. Apoe KO mice and wild-type C57BL/6J mice were given a low-fat diet (LFD) or a HFD for 32 weeks. Blood glucose, serum lipids, body weight and visceral fat weight were evaluated. Retinal sterol quantification was carried out by isotope dilution gas chromatography-mass spectrometry. The cholesterol metabolism related genes SCAP-SREBP expressions were detected by qRT-PCR. Retinal function was recorded using an electroretinogram. The thickness of each layer of the retina was measured by optical coherence tomography. Fundus fluorescein angiography was performed to detect retinal vasculature changes. Immunohistochemical staining was used to determine the expression of NF-κB, TNF-α and VEGFR2 in the retina among HFD, HFD Apoe^-/-, LFD Apoe^-/- and WT mice retinas. HFD feeding caused the mice to gain weight and develop hypercholesterinemia, while Apoe^-/- abnormalities also affected blood lipid metabolism. Both HFD and Apoe deficiency elevated retinal cholesterol, especially in the HFD Apoe^-/- mice. No up-regulated expression of SCAP-SREBP was observed as a negative regulator. Impaired retinal functions, thinning retinas and abnormal retinal vasculature were observed in the peripheral retinas of the HFD and Apoe^-/- mice compared with those in the normal chow group, particularly in the HFD Apoe^-/- mice. Moreover, the expression of NF-κB in the retinas of the HFD and Apoe^-/- mice was increased, together with upregulated TNF-α mRNA levels and TNF-α expression in the layer of retinal ganglion cells of the peripheral retina. At the same time, the expression level of VEGFR2 was elevated in the intervention groups, most notably in HFD Apoe^-/- mice. HFD or Apoe gene deletion had certain adverse effects on retinal function and structure, which were far below the combined factors and induced harm to the retina. Furthermore, HFD caused retinal ischemia and hypoxia. Additionally, Apoe abnormality increased susceptibility to ischemia. These changes upregulated NF-κB expression in ganglion cells and activated downstream TNF-α. Simultaneously, they activated VEGFR2, accelerating angiogenesis and vascular permeability. All of the aforementioned outcomes initiated inflammatory responses to trigger ganglion cell apoptosis and aggravate retinal neovascularization.

Berberine as a Potential Multi-Target Agent for Metabolic Diseases: A Review of Investigations for Berberine

Berberine (BBR) is a botanic alkaloid extracted from Coptis chinensis (Huanglian), which has various properties, compassing anti-hyperglycemia, anti-obesity, anti-inflammation, and improves insulin resistance, etc. Several researches have confirmed that BBR has effective actions in treating glycolipid metabolic abnormalities. BBR is also beneficial in regulating intestinal flora. Metabolic diseases are strongly associated with metabolic disorders, which are growing in the population and dramatically impacting human health, which also have been considered as a leading cause of diseases and death globally. This review is to evaluate the metabolic properties of BBR, and its potential application to the treatment of metabolic diseases by its effective actions on metabolic disorders.

Obesity and COVID-19: Molecular Mechanisms Linking Both Pandemics

The coronavirus disease 2019 COVID-19 pandemic is rapidly spreading worldwide and is becoming a major public health crisis. Increasing evidence demonstrates a strong correlation between obesity and the COVID-19 disease. We have summarized recent studies and addressed the impact of obesity on COVID-19 in terms of hospitalization, severity, mortality, and patient outcome. We discuss the potential molecular mechanisms whereby obesity contributes to the pathogenesis of COVID-19. In addition to obesity-related deregulated immune response, chronic inflammation, endothelium imbalance, metabolic dysfunction, and its associated comorbidities, dysfunctional mesenchymal stem cells/adipose-derived mesenchymal stem cells may also play crucial roles in fueling systemic inflammation contributing to the cytokine storm and promoting pulmonary fibrosis causing lung functional failure, characteristic of severe COVID-19. Moreover, obesity may also compromise motile cilia on airway epithelial cells and impair functioning of the mucociliary escalators, reducing the clearance of severe acute respiratory syndrome coronavirus (SARS-CoV-2). Obese diseased adipose tissues overexpress the receptors and proteases for the SARS-CoV-2 entry, implicating its possible roles as virus reservoir and accelerator reinforcing violent systemic inflammation and immune response. Finally, anti-inflammatory cytokines like anti-interleukin 6 and administration of mesenchymal stromal/stem cells may serve as potential immune modulatory therapies for supportively combating COVID-19. Obesity is conversely related to the development of COVID-19 through numerous molecular mechanisms and individuals with obesity belong to the COVID-19-susceptible population requiring more protective measures.

Lean maternal hyperglycemia alters offspring lipid metabolism and susceptibility to diet-induced obesity in mice†

We previously developed a model of gestational diabetes mellitus (GDM) in which dams exhibit glucose intolerance, insulin resistance, and reduced insulin response to glucose challenge only during pregnancy, without accompanying obesity. Here, we aimed to determine how lean gestational glucose intolerance affects offspring risk of metabolic dysfunction. One cohort of offspring was sacrificed at 19 weeks, and one at 31 weeks, with half of the second cohort placed on a high-fat, high-sucrose diet (HFHS) at 23 weeks. Exposure to maternal glucose intolerance increased weights of HFHS-fed offspring. Chow-fed offspring of GDM dams exhibited higher body fat percentages at 4, 12, and 20 weeks of age. At 28 weeks, offspring of GDM dams fed the HFHS but not the chow diet (CD) also had higher body fat percentages than offspring of controls (CON). Exposure to GDM increased the respiratory quotient (Vol CO2/Vol O2) in offspring. Maternal GDM increased adipose mRNA levels of peroxisome proliferator-activated receptor gamma (Pparg) and adiponectin (Adipoq) in 31-week-old CD-fed male offspring, and increased mRNA levels of insulin receptor (Insr) and lipoprotein lipase (Lpl) in 31-week-old male offspring on both diets. In liver at 31 weeks, mRNA levels of peroxisome proliferator-activated receptor alpha (Ppara) were elevated in CD-fed male offspring of GDM dams, and male offspring of GDM dams exhibited higher mRNA levels of Insr on both diets. Neither fasting insulin nor glucose tolerance was affected by exposure to GDM. Our findings show that GDM comprising glucose intolerance only during pregnancy programs increased adiposity in offspring, and suggests increased insulin sensitivity of subcutaneous adipose tissue.

Lingguizhugan decoction attenuates diet-induced obesity and hepatosteatosis via gut microbiota

BACKGROUND

Obesity is a major risk factor for a variety of diseases such as diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. Restricting energy intake, or caloric restriction (CR), can reduce body weight and improve metabolic parameters in overweight or obese patients. We previously found that Lingguizhugan decoction (LZD) in combination with CR can effectively lower plasma lipid levels in patients with metabolic syndrome. However, the mechanism underlying CR and LZD treatment is still unclear.

AIM

To investigate whether CR and LZD improve metabolic parameters by modulating gut microbiota.

METHODS

We extracted the water-soluble components out of raw materials and dried as LZD extracts. Eight-week old male C57BL/6 mice were treated with a 3-d treatment regime that included 24 h-fasting followed by gavage of LZD extracts for 2 consecutive days, followed by a normal diet (ND) ad libitum for 16 wk. To test the effects of gut microbiota on diet-induced obesity, 8-wk old male C57BL/6 mice received fecal microbiota transplantation (FMT) from CR and LZD-treated mice every 3 d and were fed with high-fat diet (HFD) ad libitum for 16 wk. Control mice received either saline gavage or FMT from ND-fed mice receiving saline gavage as mentioned above. Body weight was monitored bi-weekly. Food consumption of each cage hosting five mice was recorded weekly. To monitor blood glucose, total cholesterol, and total triglycerides, blood samples were collected via submandibular bleeding after 6 h fasting. Oxygen consumption rate was monitored with metabolic cages. Feces were collected, and fecal DNA was extracted. Profiles of gut microbiota were mapped by metagenomic sequencing.

RESULTS

We found that CR and LZD treatment significantly reduced the body weight of mice fed with ND (28.71 ± 0.29 vs 28.05 ± 0.15, P < 0.05), but did not affect plasma total cholesterol or total triglyceride levels. We then transplanted the fecal microbiota collected from CR and LZD-treated mice under ND feeding to HFD-fed mice. Intriguingly, transplanting the mice with fecal microbiota from CR and LZD-treated mice potently reduced body weight (44.95 ± 1.02 vs 40.53 ± 0.97, P < 0.001). FMT also reduced HFD-induced hepatosteatosis, in addition to improved glycemic control. Mechanistic studies found that FMT increased OCR of the mice and suppressed the expression and protein abundance of lipogenic genes in the liver. Metagenomic analysis revealed that HFD drastically altered the profile of gut microbiota, and FMT modified the profile of the gut microbiota.

CONCLUSION

Our study suggests that CR and LZD improve metabolic parameters by modulating gut microbiota.

MicroRNA-351 eases insulin resistance and liver gluconeogenesis via the PI3K/AKT pathway by inhibiting FLOT2 in mice of gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is known as different degree glucose intolerance that is initially identified during pregnancy. MicroRNAs (miRs) may be a potential candidate for treatment of GDM. Herein, we suggested that miR‐351 could be an inhibitor in the progression of GDM via the phosphoinositide 3‐kinase/protein kinase B (PI3K/AKT) pathway. Microarray analysis was used to identify differentially expressed genes and predict miRs regulating flotillin 2 (FLOT2). Target relationship between miR‐351 and FLOT2 was verified. Gestational diabetes mellitus mice were treated with a series of mimic, inhibitor and small interfering RNA to explore the effect of miR‐351 on insulin resistance (IR), cell apoptosis in pancreatic tissues and liver gluconeogenesis through evaluating GDM‐related biochemical indexes, as well as expression of miR‐351, FLOT2, PI3K/AKT pathway‐, IR‐ and liver gluconeogenesis‐related genes. MiR‐351 and FLOT2 were reported to be involved in GDM. FLOT2 was the target gene of miR‐351. Gestational diabetes mellitus mice exhibited IR and liver gluconeogenesis, up‐regulated FLOT2, activated PI3K/AKT pathway and down‐regulated miR‐351 in liver tissues. Additionally, miR‐351 overexpression and FLOT2 silencing decreased the levels of FLOT2, phosphoenolpyruvate carboxykinase, glucose‐6‐phosphatase, fasting blood glucose, fasting insulin, total cholesterol, triglyceride, glyeosylated haemoglobin and homeostasis model of assessment for IR index (HOMA‐IR), extent of PI3K and AKT phosphorylation, yet increased the levels of HOMA for islet β‐cell function, HOMA for insulin sensitivity index and glucose transporter 2 expression, indicating reduced cell apoptosis in pancreatic tissues and alleviated IR and liver gluconeogenesis. Our results reveal that up‐regulation of miR‐351 protects against IR and liver gluconeogenesis by repressing the PI3K/AKT pathway through regulating FLOT2 in GDM mice, which identifies miR‐351 as a potential therapeutic target for the clinical management of GDM.

Glyoxalase 1 Modulation in Obesity and Diabetes

Significance: Obesity and type 2 diabetes mellitus are increasing globally. There is also increasing associated complications, such as non-alcoholic fatty liver disease (NAFLD) and vascular complications of diabetes. There is currently no licensed treatment for NAFLD and no recent treatments for diabetic complications. New approaches are required, particularly those addressing mechanism-based risk factors for health decline and disease progression. Recent Advances: Dicarbonyl stress is the abnormal accumulation of reactive dicarbonyl metabolites such as methylglyoxal (MG) leading to cell and tissue dysfunction. It is a potential driver of obesity, diabetes, and related complications that are unaddressed by current treatments. Increased formation of MG is linked to increased glyceroneogenesis and hyperglycemia in obesity and diabetes and also down-regulation of glyoxalase 1 (Glo1)-which provides the main enzymatic detoxification of MG. Glo1 functional genomics studies suggest that increasing Glo1 expression and activity alleviates dicarbonyl stress; slows development of obesity, related insulin resistance; and prevents development of diabetic nephropathy and other microvascular complications of diabetes. A new therapeutic approach constitutes small-molecule inducers of Glo1 expression-Glo1 inducers-exploiting a regulatory antioxidant response element in the GLO1 gene. A prototype Glo1 inducer, trans-resveratrol (tRES)-hesperetin (HESP) combination, in corrected insulin resistance, improved glycemic control and vascular inflammation in healthy overweight and obese subjects in clinical trial. Critical Issues: tRES and HESP synergize pharmacologically, and HESP likely overcomes the low bioavailability of tRES by inhibition of intestinal glucuronosyltransferases. Future Directions: Glo1 inducers may now be evaluated in Phase 2 clinical trials for treatment of NAFLD and vascular complications of diabetes.

Calpain Inhibition Attenuates Adipose Tissue Inflammation and Fibrosis in Diet-induced Obese Mice

Adipose tissue macrophages have been proposed as a link between obesity and insulin resistance. However, the mechanisms underlying these processes are not completely defined. Calpains are calcium-dependent neutral cysteine proteases that modulate cellular function and have been implicated in various inflammatory diseases. To define whether activated calpains influence diet-induced obesity and adipose tissue macrophage accumulation, mice that were either wild type (WT) or overexpressing calpastatin (CAST Tg), the endogenous inhibitor of calpains were fed with high (60% kcal) fat diet for 16 weeks. CAST overexpression did not influence high fat diet-induced body weight and fat mass gain throughout the study. Calpain inhibition showed a transient improvement in glucose tolerance at 5 weeks of HFD whereas it lost this effect on glucose and insulin tolerance at 16 weeks HFD in obese mice. However, CAST overexpression significantly reduced adipocyte apoptosis, adipose tissue collagen and macrophage accumulation as detected by TUNEL, Picro Sirius and F4/80 immunostaining, respectively. CAST overexpression significantly attenuated obesity-induced inflammatory responses in adipose tissue. Furthermore, calpain inhibition suppressed macrophage migration to adipose tissue in vitro. The present study demonstrates a pivotal role for calpains in mediating HFD-induced adipose tissue remodeling by influencing multiple functions including apoptosis, fibrosis and inflammation.

Bromodomain-containing protein 2 induces insulin resistance via the mTOR/Akt signaling pathway and an inflammatory response in adipose tissue

Insulin resistance is a major metabolic abnormality in a large majority of patients with type II diabetes. Bromodomain-containing protein 2 (Brd2), a transcriptional co-activator/co-repressor with switch mating type/sucrose non-fermenting (SWI/SNF)-like functions that regulates chromatin, suppresses adipocyte differentiation and regulates pancreatic β-cell biology. However, the effects of Brd2 on insulin resistance remain unknown. Here, overexpression of Brd2 in white adipose tissue of wild-type (WT) mice led to insulin resistance. Brd2 overexpression induced the expression of nuclear Factor-κΒ (NF-κΒ) target genes, mainly involving proinflammatory and chemotactic factors, in adipocytes. Furthermore, it decreased the expression of DEP domain containing mTOR-interacting protein (Deptor) to enhance mechanistic target of rapamycin (mTOR) signaling, thus blocking insulin signaling. Collectively, these results provided evidence for a novel role of Brd2 in chronic inflammation and insulin resistance, suggesting its potential in improving insulin resistance and treating metabolic disorders.

Gender Differences in Adipocyte Metabolism and Liver Cancer Progression

Liver cancer is the third most common cancer type and the second leading cause of deaths in men. Large population studies have demonstrated remarkable gender disparities in the incidence and the cumulative risk of liver cancer. A number of emerging risk factors regarding metabolic alterations associated with obesity, diabetes and dyslipidemia have been ascribed to the progression of non-alcoholic fatty liver diseases (NAFLD) and ultimately liver cancer. The deregulation of fat metabolism derived from excessive insulin, glucose, and lipid promotes cancer-causing inflammatory signaling and oxidative stress, which eventually triggers the uncontrolled hepatocellular proliferation. This review presents the current standing on the gender differences in body fat compositions and their mechanistic linkage with the development of NAFLD-related liver cancer, with an emphasis on genetic, epigenetic and microRNA control. The potential roles of sex hormones in instructing adipocyte metabolic programs may help unravel the mechanisms underlying gender dimorphism in liver cancer and identify the metabolic targets for disease management.

ALOX5AP Overexpression in Adipose Tissue Leads to LXA4 Production and Protection Against Diet-Induced Obesity and Insulin Resistance

Eicosanoids, such as leukotriene B4 (LTB4) and lipoxin A4 (LXA4), may play a key role during obesity. While LTB4 is involved in adipose tissue inflammation and insulin resistance, LXA4 may exert anti-inflammatory effects and alleviate hepatic steatosis. Both lipid mediators derive from the same pathway, in which arachidonate 5-lipoxygenase (ALOX5) and its partner, arachidonate 5-lipoxygenase-activating protein (ALOX5AP), are involved. ALOX5 and ALOX5AP expression is increased in humans and rodents with obesity and insulin resistance. We found that transgenic mice overexpressing ALOX5AP in adipose tissue had higher LXA4 rather than higher LTB4 levels, were leaner, and showed increased energy expenditure, partly due to browning of white adipose tissue (WAT). Upregulation of hepatic LXR and Cyp7a1 led to higher bile acid synthesis, which may have contributed to increased thermogenesis. In addition, transgenic mice were protected against diet-induced obesity, insulin resistance, and inflammation. Finally, treatment of C57BL/6J mice with LXA4, which showed browning of WAT, strongly suggests that LXA4 is responsible for the transgenic mice phenotype. Thus, our data support that LXA4 may hold great potential for the future development of therapeutic strategies for obesity and related diseases.

Dicarbonyl stress in clinical obesity

The glyoxalase system in the cytoplasm of cells provides the primary defence against glycation by methylglyoxal catalysing its metabolism to D-lactate. Methylglyoxal is the precursor of the major quantitative advanced glycation endproducts in physiological systems - arginine-derived hydroimidazolones and deoxyguanosine-derived imidazopurinones. Glyoxalase 1 of the glyoxalase system was linked to anthropometric measurements of obesity in human subjects and to body weight in strains of mice. Recent conference reports described increased weight gain on high fat diet-fed mouse with lifelong deficiency of glyoxalase 1 deficiency, compared to wild-type controls, and decreased weight gain in glyoxalase 1-overexpressing transgenic mice, suggesting a functional role of glyoxalase 1 and dicarbonyl stress in obesity. Increased methylglyoxal, dicarbonyl stress, in white adipose tissue and liver may be a mediator of obesity and insulin resistance and thereby a risk factor for development of type 2 diabetes and non-alcoholic fatty liver disease. Increased methylglyoxal formation from glyceroneogenesis on adipose tissue and liver and decreased glyoxalase 1 activity in obesity likely drives dicarbonyl stress in white adipose tissue increasing the dicarbonyl proteome and related dysfunction. The clinical significance will likely emerge from on-going clinical evaluation of inducers of glyoxalase 1 expression in overweight and obese subjects. Increased transcapillary escape rate of albumin and increased total body interstitial fluid volume in obesity likely makes levels of glycation of plasma protein unreliable indicators of glycation status in obesity as there is a shift of albumin dwell time from plasma to interstitial fluid, which decreases overall glycation for a given glycemic exposure.

A low-cost system to easily measure spontaneous physical activity in rodents

Spontaneous physical activity (SPA) can be responsible for variations of a lot of physiological parameters at the molecular, cellular, tissue, and systemic levels. It is increasingly recognized that good understanding of a large part of experimental results requires weighting them by SPA in order to reduce variability and thus to decrease the number of animals necessary to conduct a study. However, because of the high cost of this equipment, only a few laboratories are equipped with such equipment to measure the SPA of their animals. Here we present an effective, adaptable, and affordable system to measure SPA in rodents based on video acquisition of the animal in its own environment. We compared results obtained with our system to those collected at the same time with a commercial system of actimetry recording, and we found a high degree of correlation between these two approaches ( r = 0.93; P < 0.001). We also were able to detect small variations of SPA induced by a special environment like chronic hypoxia exposure (25% less spontaneous activity compared with animals in normoxia, P < 0.05) or during the circadian cycle (107% more activity during the nocturnal phase compared with the diurnal phase, P < 0.05).

Association of PCK1 with Body Mass Index and Other Metabolic Features in Patients With Psychotropic Treatments

Weight gain is a major health problem among psychiatric populations. It implicates several receptors and hormones involved in energy balance and metabolism. Phosphoenolpyruvate carboxykinase 1 is a rate-controlling enzyme involved in gluconeogenesis, glyceroneogenesis and cataplerosis and has been related to obesity and diabetes phenotypes in animals and humans. The aim of this study was to investigate the association of phosphoenolpyruvate carboxykinase 1 polymorphisms with metabolic traits in psychiatric patients treated with psychotropic drugs inducing weight gain and in general population samples. One polymorphism (rs11552145G > A) significantly associated with body mass index in the psychiatric discovery sample (n = 478) was replicated in 2 other psychiatric samples (n1 = 168, n2 = 188), with AA-genotype carriers having lower body mass index as compared to G-allele carriers. Stronger associations were found among women younger than 45 years carrying AA-genotype as compared to G-allele carriers (-2.25 kg/m, n = 151, P = 0.009) and in the discovery sample (-2.20 kg/m, n = 423, P = 0.0004). In the discovery sample for which metabolic parameters were available, AA-genotype showed lower waist circumference (-6.86 cm, P = 0.008) and triglycerides levels (-5.58 mg/100 mL, P < 0.002) when compared to G-allele carriers. Finally, waist-to-hip ratio was associated with rs6070157 (proxy of rs11552145, r = 0.99) in a population-based sample (N = 123,865, P = 0.022). Our results suggest an association of rs11552145G > A polymorphism with metabolic-related traits, especially in psychiatric populations and in women younger than 45 years.

Effect of dietary fat modification on subcutaneous white adipose tissue insulin sensitivity in patients with metabolic syndrome

SCOPE

To determine whether the insulin resistance that exists in metabolic syndrome (MetS) patients is modulated by dietary fat composition.

METHODS AND RESULTS

Seventy-five patients were randomly assigned to one of four diets for 12 wk: high-saturated fatty acids (HSFAs), high-MUFA (HMUFA), and two low-fat, high-complex carbohydrate (LFHCC) diets supplemented with long-chain n-3 (LFHCC n-3) PUFA or placebo. At the end of intervention, the LFHCC n-3 diet reduced plasma insulin, homeostasis model assessment of insulin resistance, and nonsterified fatty acid concentration (p < 0.05) as compared to baseline Spanish habitual (BSH) diet. Subcutaneous white adipose tissue (WAT) analysis revealed decreased EH-domain containing-2 mRNA levels and increased cbl-associated protein gene expression with the LFHCC n-3 compared to HSFA and HMUFA diets, respectively (p < 0.05). Moreover, the LFHCC n-3 decreased gene expression of glyceraldehyde-3-phosphate dehydrogenase with respect to HMUFA and BSH diets (p < 0.05). Finally, proteomic characterization of subcutaneous WAT identified three proteins of glucose metabolism downregulated by the LFHCC n-3 diet, including annexin A2. RT-PCR analysis confirmed the decrease of annexin A2 (p = 0.027) after this diet.

CONCLUSION

Our data suggest that the LFHCC n-3 diet reduces systemic insulin resistance and improves insulin signaling in subcutaneous WAT of MetS patients compared to HSFA and BSH diets consumption.

Bone-marrow mesenchymal stem cell transplantation to treat diabetic nephropathy in tree shrews

Diabetic nephropathy (DN) is a common microvascular complication of diabetes. We used a new DN model in tree shrews to validate the use of bone-marrow mesenchymal stem cell (BM-MSC) transplantation to treat DN. The DN tree shrew model was established by a high-sugar and high-fat diet and four injections of streptozotocin. 4',6-Diamidino-2-phenylindole labelled BM-MSCs were injected into tree shrews. The DN tree shrew model was successfully established. Blood glucose was significantly increased ( p < 0.01) during the entire experiment. DN tree shrews showed dyslipidemia, insulin resistance and increased 24-h proteinuria. At 21 days after BM-MSC transplantation, glucose and levels of triglycerides, total cholesterol and 24-h urine volume were lower than in tree shrews with DN alone ( p < 0.01) but were still higher than control values ( p < 0.01). Levels of creatinine and urea nitrogen as well as 24-h proteinuria were lower for DN tree shrews with BM-MSCs transplantation than DN alone ( p < 0.05). High-sugar and high-fat diet combined with STZ injection can induce a tree shrew model of DN. BM-MSCs injection can home to damaged kidneys and pancreas, for reduced 24-h proteinuria and improved insulin resistance.

Curcumin and diabetes: a systematic review

Turmeric (Curcuma longa), a rhizomatous herbaceous perennial plant of the ginger family, has been used for the treatment of diabetes in Ayurvedic and traditional Chinese medicine. The active component of turmeric, curcumin, has caught attention as a potential treatment for diabetes and its complications primarily because it is a relatively safe and inexpensive drug that reduces glycemia and hyperlipidemia in rodent models of diabetes. Here, we review the recent literature on the applications of curcumin for glycemia and diabetes-related liver disorders, adipocyte dysfunction, neuropathy, nephropathy, vascular diseases, pancreatic disorders, and other complications, and we also discuss its antioxidant and anti-inflammatory properties. The applications of additional curcuminoid compounds for diabetes prevention and treatment are also included in this paper. Finally, we mention the approaches that are currently being sought to generate a "super curcumin" through improvement of the bioavailability to bring this promising natural product to the forefront of diabetes therapeutics.

Stop feeding cancer: pro-inflammatory role of visceral adiposity in liver cancer

Liver cancer is the fifth most common cancer in the world with an estimated over half a million new cases diagnosed every year. Due to the difficulty in early diagnosis and lack of treatment options, the prevalence of liver cancer continues to climb with a 5-year survival rate of between 6% and 11%. Coinciding with the rise of liver cancer, the prevalence of obesity has rapidly increased over the past two decades. Evidence from epidemiological studies demonstrates a higher risk of hepatocellular carcinoma (HCC) in obese individuals. Obesity is recognised as a low-grade inflammatory disease, this is of particular relevance as inflammation has been proposed as the seventh hallmark of cancer development with abdominal visceral adiposity considered as an important source of pro-inflammatory stimuli. Emerging evidence points towards the direct role of visceral adipose tissue rather than generalised body fat in carcinogenesis. Cytokines such as IL-6 and TNF-α secreted from visceral adipose tissue have been demonstrated to induce a chronic inflammatory condition predisposing the liver to a protumourigenic milieu. This review focuses on excess visceral adiposity rather than simple obesity; particularly adipokines and their implications for chronic inflammation, lipid accumulation, insulin resistance, Endoplasmic Reticulum (ER) stress and angiogenesis. Evidence of molecular signalling pathways that may give rise to the onset and progression of HCC in this context are depicted. Delineation of the pro-inflammatory role of visceral adiposity in liver cancer and its targeting will provide better rational and therapeutic approaches for HCC prevention and elimination. The concept of a central role for metabolism in cancer is the culmination of an effort that began with one of the 20th century's leading biochemists and Nobel laureate of 1931, Otto Warburg.

5-hydroxytryptamine actions in adipocytes: involvement of monoamine oxidase-dependent oxidation and subsequent PPARγ activation

Serotonin (5-HT) is a brain neurotransmitter instrumental for the antidepressant action of selective inhibitors of serotonin reuptake (SSRIs) while it also plays important roles in peripheral organs. Recently, the 5-HT oxidation products, 5-hydroxyindoleacetate and 5-methoxy-indoleacetate, have been shown to bind to peroxisome proliferator-activated receptor γ (PPARγ) and to enhance lipid accumulation in preadipocytes. Since we already reported that adipocytes exhibit elevated monoamine oxidase (MAO) and primary amine oxidase activities, we verified how adipocytes readily oxidize 5-HT, with the objective to determine whether such oxidation promotes PPARγ activation and lipid storage. To this aim, serotonin was tested on cultured 3T3 F442A preadipocytes and on human adipocytes. Results showed that 5-HT was oxidized by MAO in both models. Daily treatment of 3T3 F442A preadipocytes for 8 days with 100-500 μM 5-HT promoted triglyceride accumulation and emergence of adipogenesis markers. At 250 μM, 5-HT alone reproduced half of 50 nM insulin-induced adipogenesis, and exhibited an additive differentiating effect when combined with insulin. Moreover, the 5-HT-induced expression of PPARγ-responsive genes (PEPCK, aP2/FABP4) was blocked by GW 9662, a PPARγ-inhibitor, or by pargyline, a MAO-inhibitor. In human fat cells, 6-h exposure to 100 μM 5-HT increased PEPCK expression as did the PPARγ-agonist rosiglitazone. Since hydrogen peroxide, another amine oxidation product, did not reproduce such enhancement, we propose that serotonin can promote PPARγ activation in fat cells, via the indoleacetate produced during MAO-dependent oxidation. Such pathway could be involved in the adverse effects of several antidepressant SSRIs on body weight gain.

Transgenic mouse models resistant to diet-induced metabolic disease: is energy balance the key?

The prevalence and economic burden of obesity and type 2 diabetes is a driving force for the discovery of molecular targets to improve insulin sensitivity and glycemic control. Here, we review several transgenic mouse models that identify promising targets, ranging from proteins involved in the insulin signaling pathway, alterations of genes affecting energy metabolism, and transcriptional metabolic regulators. Despite the diverse endpoints in each model, a common thread that emerges is the necessity for maintenance of energy balance, suggesting pharmacotherapy must target the development of drugs that decrease energy intake, accelerate energy expenditure in a well controlled manner, or augment natural compensatory responses to positive energy balance.

Adipose tissue overexpression of vascular endothelial growth factor protects against diet-induced obesity and insulin resistance

During the expansion of fat mass in obesity, vascularization of adipose tissue is insufficient to maintain tissue normoxia. Local hypoxia develops and may result in altered adipokine expression, proinflammatory macrophage recruitment, and insulin resistance. We investigated whether an increase in adipose tissue angiogenesis could protect against obesity-induced hypoxia and, consequently, insulin resistance. Transgenic mice overexpressing vascular endothelial growth factor (VEGF) in brown adipose tissue (BAT) and white adipose tissue (WAT) were generated. Vessel formation, metabolism, and inflammation were studied in VEGF transgenic mice and wild-type littermates fed chow or a high-fat diet. Overexpression of VEGF resulted in increased blood vessel number and size in both WAT and BAT and protection against high-fat diet-induced hypoxia and obesity, with no differences in food intake. This was associated with increased thermogenesis and energy expenditure. Moreover, whole-body insulin sensitivity and glucose tolerance were improved. Transgenic mice presented increased macrophage infiltration, with a higher number of M2 anti-inflammatory and fewer M1 proinflammatory macrophages than wild-type littermates, thus maintaining an anti-inflammatory milieu that could avoid insulin resistance. These studies suggest that overexpression of VEGF in adipose tissue is a potential therapeutic strategy for the prevention of obesity and insulin resistance.

Alterations of protein complexes and pathways in genetic information flow and response to stimulus contribute to Escherichia coli resistance to balofloxacin

Protein-protein interactions are important biological processes and essential for a global understanding of cell functions. To date, little is known about the protein interactions and roles of the protein interacting networks and protein complexes in bacterial resistance to antibiotics. In the present study, we investigated protein complexes in Escherichia coli exposed to an antibiotic balofloxacin (BLFX). One homomeric and eight heteromeric protein complexes involved in BLFX resistance were detected. Potential roles of these complexes that are played in BLFX resistance were characterized and categorized into four functional areas: information streams, monosaccharide metabolism, response to stimulus and amino acid metabolic processes. Protein complexes involved in information streams and response to stimulus played more significant roles in the resistance. These results are consistent with previously published mechanisms on the acquired quinolone-resistance through the GyrA-GyrB complex, and two novel antibiotic-resistant pathways were identified: upregulation of genetic information flow and alteration of the response to a stimulus. The balance of the two pathways will be a viable means of reducing BLFX-resistance.

Long-term voluntary running improves diet-induced adiposity in young adult mice

The hypothesis of the present study was that physical activity improves diet-induced obesity in young adult mice. Four-week-old male C57BL/6 mice (n=15/group) were fed the AIN93G diet or a 45% high-fat diet (% kJ) with or without access to in-cage activity wheels for 14 weeks. The high-fat diet increased percentage fat body mass compared to the AIN93G diet (P=.042); running reduced percentage fat body mass (P<.0001) and increased percentage lean body mass (P<.0001) in mice fed either diet. Compared with the AIN93G diet, the high-fat diet increased plasma concentrations of insulin (P<.05) and leptin (P<.05) in sedentary mice and inflammatory cytokines monocyte chemotactic protein-1 (MCP-1) (P<.05) and plasminogen activator inhibitor-1 (P<.05) in both sedentary and running mice. The high-fat diet did not affect angiogenic factors vascular endothelial growth factor and platelet-derived growth factor-BB. Running reduced plasma insulin (P<.05) and MCP-1 (P<.05) and increased platelet-derived growth factor-BB (P<.05) in mice fed the high-fat diet. Running reduced leptin (P<.05) and increased plasma vascular endothelial growth factor (P<.0001) regardless of diet fed. In summary, consumption of the high-fat diet increased adiposity in young adult mice; running reduced adiposity, normalized plasma insulin and leptin, and reduced MCP-1 despite continued consumption of the high-fat diet. These results suggest that voluntary running may reduce diet-induced obesity and proinflammation and that young mice may be a useful model of their human age equivalents in studying moderate physical exercise and obesity and obesity-related diseases.

De novo lipogenesis in adipose tissue is associated with course of morbid obesity after bariatric surgery

Objective

De novo lipogenesis is involved in fatty acid biosynthesis and could be involved in the regulation of the triglyceride storage capacity of adipose tissue. However, the association between lipogenic and lipolytic genes and the evolution of morbidly obese subjects after bariatric surgery remains unknown. In this prospective study we analyze the association between the improvement in the morbidly obese patients as a result of bariatric surgery and the basal expression of lipogenic and lipolytic genes.

Methods

We study 23 non diabetic morbidly obese patients who were studied before and 7 months after bariatric surgery. Also, we analyze the relative basal mRNA expression levels of lipogenic and lipolytic genes in epiploic visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT).

Results

When the basal acetyl-CoA carboxylase 1 (ACC1), acetyl-CoA synthetase 2 (ACSS2) and ATP citrate lyase (ACL) expression in SAT was below percentile-50, there was a greater decrease in weight (P = 0.006, P = 0.034, P = 0.026), body mass index (P = 0.008, P = 0.033, P = 0.034) and hip circumference (P = 0.033, P = 0.021, P = 0.083) after bariatric surgery. In VAT, when the basal ACSS2 expression was below percentile-50, there was a greater decrease in hip circumference (P = 0.006). After adjusting for confounding variables in logistic regression models, only the morbidly obese patients with SAT or VAT ACSS2 expression≥P50 before bariatric surgery had a lower percentage hip circumference loss (<P50) after bariatric surgery (SAT: P = 0.039; VAT: P = 0.033).

Conclusions

A lower basal ACSS2, ACC1 and ACL expression, genes involved in de novo lipogenesis, is associated with a better evolution of anthropometric variables after bariatric surgery. Thus, the previous state of the pathways involved in fatty acid metabolism may have repercussions on the improvement of these patients.

Combined transcriptomic-(1)H NMR metabonomic study reveals that monoethylhexyl phthalate stimulates adipogenesis and glyceroneogenesis in human adipocytes

Adipose tissue is a major storage site for lipophilic environmental contaminants. The environmental metabolic disruptor hypothesis postulates that some pollutants can promote obesity or metabolic disorders by activating nuclear receptors involved in the control of energetic homeostasis. In this context, monoethylhexyl phthalate (MEHP) is of particular concern since it was shown to activate the peroxisome proliferator-activated receptor γ (PPARγ) in 3T3-L1 murine preadipocytes. In the present work, we used an untargeted, combined transcriptomic-¹H NMR-based metabonomic approach to describe the overall effect of MEHP on primary cultures of human subcutaneous adipocytes differentiated in vitro. MEHP stimulated rapidly and selectively the expression of genes involved in glyceroneogenesis, enhanced the expression of the cytosolic phosphoenolpyruvate carboxykinase, and reduced fatty acid release. These results demonstrate that MEHP increased glyceroneogenesis and fatty acid reesterification in human adipocytes. A longer treatment with MEHP induced the expression of genes involved in triglycerides uptake, synthesis, and storage; decreased intracellular lactate, glutamine, and other amino acids; increased aspartate and NAD, and resulted in a global increase in triglycerides. Altogether, these results indicate that MEHP promoted the differentiation of human preadipocytes to adipocytes. These mechanisms might contribute to the suspected obesogenic effect of MEHP.

Using an untargeted combined transcriptomic-¹H NMR-based metabonomic approach, we describe the overall effect of monoethyl-hexyl phthalate (MEHP) on primary cultures of human subcutaneous adipocytes differentiated in vitro. MEHP rapidly and selectively stimulated glyceroneogenesis, a metabolic pathway involved in the control of fatty acid release from adipose tissue. A longer treatment with MEHP promoted the differentiation of human preadipocytes to adipocytes. These mechanisms might contribute to an obesogenic effect of MEHP.

Berberine-improved visceral white adipose tissue insulin resistance associated with altered sterol regulatory element-binding proteins, liver x receptors, and peroxisome proliferator-activated receptors transcriptional programs in diabetic hamsters

The diabetic "lipotoxicity" hypothesis presents that fat-induced visceral white adipose tissue insulin resistance plays a central role in the pathogenesis of type 2 diabetes. Berberine, a hypolipidemic agent, has been reported to have antidiabetic activities. The molecular mechanisms for this property are, however, not well clarified. Therefore in this study type 2 diabetic hamsters were induced by high-fat diet with low-dose streptozotocin. Then, we investigated the gene expression alterations and explored the molecular mechanisms underlying the therapeutic effect of berberine on fat-induced visceral white adipose tissue insulin resistance in diabetic hamsters by microarray analysis followed by real-time reverse transcription-polymerase chain reaction (RT-PCR) confirmation. Type 2 diabetic hamsters exhibited hyperglycemia and relative hyperinsulinemia, glucose intolerance, insulin resistance, intra-adipocyte lipid accumulation, significant increase in body weight and visceral white adipose tissue weight, abnormal serum adipokines levels, and deleterious dyslipidemia. Furthermore, they had increased sterol regulatory element-binding proteins (SREBPs) expression and decreased liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs) expression in visceral white adipose tissue. After 9-week berberine treatment, fat-induced insulin resistance and diabetic phenotype in type 2 diabetic hamsters were significantly improved. Compared with diabetic hamsters, expression of LXRs and PPARs significantly increased and SREBPs significantly decreased in visceral white adipose tissue from berberine-treated diabetic hamsters. These results suggest that altered visceral white adipose tissue LXRs, PPARs, and SREBPs transcriptional programs are involved in the therapeutic mechanisms of berberine on fat-induced visceral white adipose tissue insulin resistance in type 2 diabetic hamsters.

Inhibition of glyceroneogenesis by histone deacetylase 3 contributes to lipodystrophy in mice with adipose tissue inflammation

We have reported that the nuclear factor-κB (NF-κB) induces chronic inflammation in the adipose tissue of p65 transgenic (Tg) mice, in which the NF-κB subunit p65 (RelA) is overexpressed from the adipocyte protein 2 (aP2) gene promoter. Tg mice suffer a mild lipodystrophy and exhibit deficiency in adipocyte differentiation. To understand molecular mechanism of the defect in adipocytes, we investigated glyceroneogenesis by examining the activity of cytosolic phosphoenolpyruvate carboxykinase (PEPCK) in adipocytes. In aP2-p65 Tg mice, Pepck expression is inhibited at both the mRNA and protein levels in adipose tissue. The mRNA reduction is a consequence of transcriptional inhibition but not alteration in mRNA stability. The Pepck gene promoter is inhibited by NF-κB, which enhances the corepressor activity through activation of histone deacetylase 3 (HDAC3) in the nucleus. HDAC3 suppresses Pepck transcription by inhibiting the transcriptional activators, peroxisome proliferator-activated receptor-γ, and cAMP response element binding protein. The NF-κB activity is abolished by Hdac3 knockdown or inhibition of HDAC3 catalytic activity. In a chromatin immunoprecipitation assay, HDAC3 interacts with peroxisome proliferator-activated receptor-γ and cAMP response element binding protein in the Pepck promoter when NF-κB is activated by TNF-α. These results suggest that HDAC3 mediates NF-κB activity to repress Pepck transcription. This mechanism is responsible for inhibition of glyceroneogenesis in adipocytes, which contributes to lipodystrophy in the aP2-p65 Tg mice.

Nr4a1 siRNA expression attenuates α-MSH regulated gene expression in 3T3-L1 adipocytes

Several recent investigations have underscored the growing role of melanocortin signaling in the peripheral regulation of lipid, glucose, and energy homeostasis. In addition, the melanocortins play a critical role in the central control of satiety. These observations, and the latest reports highlighting the emerging role of the nuclear hormone receptor (NR) 4A subgroup in metabolism, have prompted us to investigate the cross talk between [Nle(4), d-Phe(7)] (NDP)-α-MSH and Nr4a signaling in adipose. We have shown that NDP-MSH strikingly and preferentially induces the expression of the NR4A subgroup (but not any other members of the NR superfamily) in differentiated 3T3-L1 adipocytes. Utilization of quantitative PCR on custom-designed metabolic TaqMan low-density arrays identified the concomitant and marked induction of the mRNAs encoding Il-6, Cox2, Pdk4, and Pck-1 after NDP-MSH treatment. Similar experiments demonstrated that the mRNA expression profile induced by cAMP and NDP-MSH treatment displayed unique but also overlapping properties and suggested that melanocortin-mediated induction of gene expression involves cAMP-dependent and -independent signaling. Nr4a1/Nur77 small interfering RNA (siRNA) expression suppressed NDP-MSH-mediated induction of Nr4a1/Nur77 and Nr4a3/Nor-1 (but not Nr4a2/Nurr1). Moreover, expression of the siRNA-attenuated NDP-MSH mediated induction of the mRNAs encoding Il-6, Cox2/Ptgs2, and Pck-1 expression. In addition, Nur77 siRNA expression attenuated NDP-MSH-mediated glucose uptake. In vivo, ip administration of NDP-MSH to C57 BL/6J (male) mice significantly induced the expression of the mRNA encoding Nur77 and increased IL-6, Cox2, Pck1, and Pdk4 mRNA expression in (inguinal) adipose tissue. We conclude that Nur77 expression is necessary for MSH-mediated induction of gene expression in differentiated adipocytes. Furthermore, this study demonstrates cross talk between MSH and Nr4a signaling in adipocytes.