Apolipoprotein B100 acts as a molecular link between lipid-induced endoplasmic reticulum stress and hepatic insulin resistance

Exploring the pathogenesis and immunological profiles of psoriasis complicated with MASLD

BACKGROUND

Both psoriasis and metabolic dysfunction-associated steatotic liver disease (MASLD) are immune-mediated chronic inflammatory diseases. Psoriasis manifests itself mainly as skin damage, while MASLD mainly involves the liver promoting liver fibrosis, which has a significant impact on patient health and quality of life. Some clinical studies have shown that there are mutually reinforcing mechanisms between these two diseases, but they are not clearly defined, and this paper aims to further explore their common pathogenesis.

METHODS

Gene expression profiling datasets (GSE30999, GSE48452) and single cell datasets (GSE151177, GSE186328) for psoriasis and MASLD were downloaded from the Gene Expression Omnibus (GEO) database. Common differential gene sets were obtained by gene differential analysis, and then functional enrichment of differential genes was performed to find associated transcription factors and PPI protein network analysis. Single-cell datasets were validated for gene expression and explored for cellular communication, gene set differential analysis and immune infiltration analysis.

RESULTS

We identified seven common differential genes, all of which were upregulated.The IL-17 pathway, tumor necrosis factor (TNF-α) pathway were shown in strong association with both diseases, and five transcription factors regulating the differential genes were predicted. Two key genes (MMP9, CXCL10) and three key transcription factors (TF) (IRF1, STAT1, NFKB1) were obtained by PPI protein network analysis. Single cell dataset verified the expression of key genes, and combined with gene set differential analysis, immune infiltration revealed that CD4+ T cells, NK cells and macrophages were heavily infiltrated in both diseases. IL-17, IL-1 and cGAS-STING pathways were highly expressed in both diseases, and both diseases share a similar immune microenvironment.

CONCLUSIONS

Our study reveals the common pathogenesis of psoriasis and MASLD from gene expression to immune cell similarities and differences, identifies key genes and regulatory pathways common to both, and elucidates the similarities in the immune microenvironment of both diseases, providing new ideas for subsequent studies on targeted therapy.

Fructose Induced KHK-C Increases ER Stress and Modulates Hepatic Transcriptome to Drive Liver Disease in Diet-Induced and Genetic Models of NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a liver manifestation of metabolic syndrome, and is estimated to affect one billion individuals worldwide. An increased intake of a high-fat diet (HFD) and sugar-sweetened beverages are risk-factors for NAFLD development, but how their combined intake promotes progression to a more severe form of liver injury is unknown. Here we show that fructose metabolism via ketohexokinase (KHK) C isoform increases endoplasmic reticulum (ER) stress in a dose dependent fashion, so when fructose is coupled with a HFD intake it leads to unresolved ER stress. Conversely, a liver-specific knockdown of KHK in C57BL/6J male mice consuming fructose on a HFD is adequate to improve the NAFLD activity score and exert a profound effect on the hepatic transcriptome. Overexpression of KHK-C in cultured hepatocytes is sufficient to induce ER stress in fructose free media. Upregulation of KHK-C is also observed in genetically obesity ob/ob, db/db and lipodystrophic FIRKO male mice, whereas KHK knockdown in these mice improves metabolic function. Additionally, in over 100 inbred strains of male or female mice hepatic KHK expression correlates positively with adiposity, insulin resistance, and liver triglycerides. Similarly, in 241 human subjects and their controls, hepatic Khk expression is upregulated in early, but not late stages of NAFLD. In summary, we describe a novel role of KHK-C in triggering ER stress, which offers a mechanistic understanding of how the combined intake of fructose and a HFD propagates the development of metabolic complications.

Development of a multiomics model for identification of predictive biomarkers for COVID-19 severity: a retrospective cohort study

BACKGROUND

COVID-19 is a multi-system disorder with high variability in clinical outcomes among patients who are admitted to hospital. Although some cytokines such as interleukin (IL)-6 are believed to be associated with severity, there are no early biomarkers that can reliably predict patients who are more likely to have adverse outcomes. Thus, it is crucial to discover predictive markers of serious complications.

METHODS

In this retrospective cohort study, we analysed samples from 455 participants with COVID-19 who had had a positive SARS-CoV-2 RT-PCR result between April 14, 2020, and Dec 1, 2020 and who had visited one of three Mayo Clinic sites in the USA (Minnesota, Arizona, or Florida) in the same period. These participants were assigned to three subgroups depending on disease severity as defined by the WHO ordinal scale of clinical improvement (outpatient, severe, or critical). Our control cohort comprised of 182 anonymised age-matched and sex-matched plasma samples that were available from the Mayo Clinic Biorepository and banked before the COVID-19 pandemic. We did a deep profiling of circulatory cytokines and other proteins, lipids, and metabolites from both cohorts. Most patient samples were collected before, or around the time of, hospital admission, representing ideal samples for predictive biomarker discovery. We used proximity extension assays to quantify cytokines and circulatory proteins and tandem mass spectrometry to measure lipids and metabolites. Biomarker discovery was done by applying an AutoGluon-tabular classifier to a multiomics dataset, producing a stacked ensemble of cutting-edge machine learning algorithms. Global proteomics and glycoproteomics on a subset of patient samples with matched pre-COVID-19 plasma samples was also done.

FINDINGS

We quantified 1463 cytokines and circulatory proteins, along with 902 lipids and 1018 metabolites. By developing a machine-learning-based prediction model, a set of 102 biomarkers, which predicted severe and clinical COVID-19 outcomes better than the traditional set of cytokines, were discovered. These predictive biomarkers included several novel cytokines and other proteins, lipids, and metabolites. For example, altered amounts of C-type lectin domain family 6 member A (CLEC6A), ether phosphatidylethanolamine (P-18:1/18:1), and 2-hydroxydecanoate, as reported here, have not previously been associated with severity in COVID-19. Patient samples with matched pre-COVID-19 plasma samples showed similar trends in muti-omics signatures along with differences in glycoproteomics profile.

INTERPRETATION

A multiomic molecular signature in the plasma of patients with COVID-19 before being admitted to hospital can be exploited to predict a more severe course of disease. Machine learning approaches can be applied to highly complex and multidimensional profiling data to reveal novel signatures of clinical use. The absence of validation in an independent cohort remains a major limitation of the study.

FUNDING

Eric and Wendy Schmidt.

Edible Bird’s Nest Regulates Hepatic Cholesterol Metabolism through Transcriptional Regulation of Cholesterol Related Genes

Objective. Hypercholesterolemia is a strong risk factor for cardiovascular diseases. Side effects associated with the use of pharmaceutical agents can cancel out their benefits. Dietary management of hypercholesterolemia is, therefore, receiving much attention due to fewer side effects. In this study, we explored the effectiveness of edible bird’s nest (EBN) in the prevention of hypercholesterolemia in rats. Methods. High-cholesterol diet (HCD) (4.5% cholesterol and 0.5% cholic acid) with or without EBN (low (2.5%) or high dose (20%)) was given to rats for 12 weeks, and their weights were observed. Simvastatin (10 mg/kg/day) was administered for the same period as a control drug. Serum and tissue samples were collected at the end of the study, from which biochemical parameters (lipid profiles, oxLDL, liver enzymes, urea, creatinine, uric acid, and lipase activity) and hepatic mRNA levels were measured. Results. The HCD group had higher levels of serum lipids, liver enzymes, uric acid, urea, and lipase activity compared with those of the other groups. The hepatic mRNA levels of cholesterol metabolism genes (APOB, PCSK9, HMGCR, LDLR, and CYP7A1) in the HCD group also tended toward increased cholesterol production and reduced cholesterol clearance. EBN, especially the highest dose, attenuated the HCD-induced changes, partly through improving the transcriptional regulation of hepatic cholesterol metabolism genes with fold changes of 0.7, 0.6, 0.5, 1.7, and 2.7, respectively, in comparison to the HCD group. In fact, EBN produced better results than simvastatin. Conclusion. Thus, the results suggest that EBN can regulate cholesterol metabolism and, therefore, be a source of functional ingredients for the management of hypercholesterolemia.

FGF21 Reduces Lipid Accumulation in Bovine Hepatocytes by Enhancing Lipid Oxidation and Reducing Lipogenesis via AMPK Signaling

During the periparturient period, dairy cows suffer drastic metabolic stress because of plasma increased non-esterified fatty acids (NEFAs) that stem from a negative energy balance. Fibroblast growth factor 21 (FGF21) is a hepatokine that activates the AMP-activated protein kinase (AMPK) signaling pathway to maintain intracellular energy balance and tissue integrity via the promotion of catabolism and the inhibition of anabolic regulation. FGF21 treatment caused a 50% reduction in triglyceride (TG) content in liver in dairy cows. However, it is not clear whether FGF21 regulates lipid metabolism in bovine liver. The purpose of this study was to evaluate the influence of FGF21 on lipid metabolism via AMPK signaling in bovine hepatocytes. The hepatocytes isolated from calves were treated with different concentrations of FGF21 or co-treated with AMPK inhibitor (BML-275). Herein, the study showed that FGF21 significantly reduced TG content in a dose–response manner and promoted very-low-density lipoprotein (VLDL) secretion via an up-regulation of the proteins (ApoB 100, ApoE and MTTP) involved in VLDL secretion. Otherwise, the genes associated with lipid transport (LDLR and CD36) and lipid oxidation (PPARGC1A, ACOX1 and CPT1A), were up-regulated following FGF21 treatment. Moreover, FGF21 treatment inhibited lipogenesis via SREBF1, ACACA, FASN and ACLY inhibition. After being co-treated with the AMPK inhibitor, FGF21-induced changes were reversed in some genes. In conclusion, these results indicate that FGF21 adaptively regulates energy metabolism for a negative impact on lipogenesis, strengthens lipid oxidation, and inhibited lipid transportation via AMPK signaling in bovine hepatocytes. The present data suggest the possibility that FGF21 has potential value in alleviating perinatal metabolic diseases in dairy cows, and specific research in vivo should be studied in more detail.

Iron Overload and the Risk of Diabetes in the General Population: Results of the Chinese Health and Nutrition Survey Cohort Study

BACKGROUND

Recent studies have found that there are significant associations between body iron status and the development of diabetes. In the present study, we aimed to analyze the association among iron overload (IO), insulin resistance (IR), and diabetes in Chinese adults, and to explore the sex difference.

METHODS

Men and women (age >19 years) who participated in the Chinese Health and Nutrition Survey and did not have diabetes at baseline were followed between 2009 and 2015 (n=5,779). Over a mean of 6 years, 75 participants were diagnosed with incident diabetes. Logistic regression was used to assess the risk factors associated with IO. Cox proportional hazard regression was used to estimate the risk of incident diabetes and to determine whether the risk differed among subgroups. Causal mediation analysis (CMA) was used to explore the mechanism linking IO and diabetes.

RESULTS

According to sex-stratified multivariable-adjusted Cox proportional hazards regression, IO increased the risk of incident diabetes. Women with IO had a higher risk of diabetes than men. Subgroup analysis with respect to age showed that the association between IO and diabetes was stronger in older women and younger men (P<0.001). CMA showed that liver injury (alanine transaminase) and lipid metabolism abnormalities (triglyceride, apolipoprotein B) contributed to the association between IO and diabetes.

CONCLUSION

IO is associated with diabetes and this association is sex-specific. IO may indirectly induce IR via liver injury and lipid metabolism abnormalities, resulting in diabetes.

Genetically Engineered Hamster Models of Dyslipidemia and Atherosclerosis

Animal models of human diseases play an extremely important role in biomedical research. Among them, mice are widely used animal models for translational research, especially because of ease of generation of genetically engineered mice. However, because of the great differences in biology between mice and humans, translation of findings to humans remains a major issue. Therefore, the exploration of models with biological and metabolic characteristics closer to those of humans has never stopped.Although pig and nonhuman primates are biologically similar to humans, their genetic engineering is technically difficult, the cost of breeding is high, and the experimental time is long. As a result, the application of these species as model animals, especially genetically engineered model animals, in biomedical research is greatly limited.In terms of lipid metabolism and cardiovascular diseases, hamsters have several characteristics different from rats and mice, but similar to those in humans. The hamster is therefore an ideal animal model for studying lipid metabolism and cardiovascular disease because of its small size and short reproduction period. However, the phenomenon of zygote division, which was unexpectedly blocked during the manipulation of hamster embryos for some unknown reasons, had plagued researchers for decades and no genetically engineered hamsters have therefore been generated as animal models of human diseases for a long time. After solving the problem of in vitro development of hamster zygotes, we successfully prepared enhanced green fluorescent protein (eGFP) transgenic hamsters by microinjection of lentiviral vectors into the zona pellucida space of zygotes. On this basis, we started the development of cardiovascular disease models using the hamster embryo culture system combined with the novel genome editing technique of clustered regularly interspaced short palindromic repeats (CRISPR )/CRISPR associated protein 9 (Cas9). In this chapter, we will introduce some of the genetically engineered hamster models with dyslipidemia and the corresponding characteristics of these models. We hope that the genetically engineered hamster models can be further recognized and complement other genetically engineered animal models such as mice, rats, and rabbits. This will lead to new avenues and pathways for the study of lipid metabolism and its related diseases.

Interaction between Sars-CoV-2 structural proteins and host cellular receptors: From basic mechanisms to clinical perspectives

Severe acute respiratory syndrome coronavirus 2 (Sars-CoV-2) has caused a global pandemic that has affected the lives of billions of individuals. Sars-CoV-2 primarily infects human cells by binding of the viral spike protein to angiotensin-converting enzyme 2 (ACE2). In addition, novel means of viral entry are currently being investigated, including Neuropillin 1, toll-like receptors (TLRs), cluster of differentiation 147 (CD147), and integrin α5β1. Enriched expression of these proteins across metabolic regulatory organs/tissues, including the circulatory system, liver, pancreas, and intestine contributes to major clinical complications among COVID-19 patients, particularly the development of hypertension, myocardial injury, arrhythmia, acute coronary syndrome and increased coagulation in the circulatory system during and post-infection. Pre-existing metabolic disease, such as cardiovascular disease, obesity, diabetes, and non-alcoholic fatty liver disease, is associated with increased risk of hospitalization, persistent post-infection complications and worse outcomes in patients with COVID-19. This review overviews the biological features of Sars-CoV-2, highlights recent findings that delineate the pathological mechanisms of COVID-19 and the consequent clinical diseases.

Genetically-engineered hamster models: applications and perspective in dyslipidemia and atherosclerosis-related cardiovascular disease

Cardiovascular disease is the leading cause of morbidity and mortality in both developed and developing countries, in which atherosclerosis triggered by dyslipidemia is the major pathological basis. Over the past 40 years, small rodent animals, such as mice, have been widely used for understanding of human atherosclerosis-related cardiovascular disease (ASCVD) with the advantages of low cost and ease of maintenance and manipulation. However, based on the concept of precision medicine and high demand of translational research, the applications of mouse models for human ASCVD study would be limited due to the natural differences in metabolic features between mice and humans even though they are still the most powerful tools in this research field, indicating that other species with biological similarity to humans need to be considered for studying ASCVD in future. With the development and breakthrough of novel gene editing technology, Syrian golden hamster, a small rodent animal replicating the metabolic characteristics of humans, has been genetically modified, suggesting that gene-targeted hamster models will provide new insights into the precision medicine and translational research of ASCVD. The purpose of this review was to summarize the genetically-modified hamster models with dyslipidemia to date, and their potential applications and perspective for ASCVD.

Pathophysiological communication between hepatocytes and non-parenchymal cells in liver injury from NAFLD to liver fibrosis

Non-alcoholic fatty liver disease (NAFLD) is a multifactorial disease that encompasses a spectrum of pathological conditions, ranging from simple steatosis (NAFL), nonalcoholic steatohepatitis (NASH), fibrosis/cirrhosis which can further progress to hepatocellular carcinoma and liver failure. The progression of NAFL to NASH and liver fibrosis is closely associated with a series of liver injury resulting from lipotoxicity, oxidative stress, redox imbalance (excessive nitric oxide), ER stress, inflammation and apoptosis that occur sequentially in different liver cells which ultimately leads to the activation of liver regeneration and fibrogenesis, augmenting collagen and extracellular matrix deposition and promoting liver fibrosis and cirrhosis. Type 2 diabetes is a significant risk factor in NAFLD development by accelerating liver damage. Here, we overview recent findings from human study and animal models on the pathophysiological communication among hepatocytes (HCs), Kupffer cells (KCs), hepatic stellate cells (HSCs) and liver sinusoidal endothelial cells (LSECs) during the disease development. The mechanisms of crucial signaling pathways, including Toll-like receptor, TGFβ and hedgehog mediated hepatic injury are also discussed. We further highlight the potentials of precisely targeting hepatic individual cell-type using nanotechnology as therapeutic strategy for the treatment of NASH and liver fibrosis.

Insights into therapeutic targets and biomarkers using integrated multi-'omics' approaches for dilated and ischemic cardiomyopathies

At present, heart failure (HF) treatment only targets the symptoms based on the left ventricle dysfunction severity; however, the lack of systemic 'omics' studies and available biological data to uncover the heterogeneous underlying mechanisms signifies the need to shift the analytical paradigm towards network-centric and data mining approaches. This study, for the first time, aimed to investigate how bulk and single cell RNA-sequencing as well as the proteomics analysis of the human heart tissue can be integrated to uncover HF-specific networks and potential therapeutic targets or biomarkers. We also aimed to address the issue of dealing with a limited number of samples and to show how appropriate statistical models, enrichment with other datasets as well as machine learning-guided analysis can aid in such cases. Furthermore, we elucidated specific gene expression profiles using transcriptomic and mined data from public databases. This was achieved using the two-step machine learning algorithm to predict the likelihood of the therapeutic target or biomarker tractability based on a novel scoring system, which has also been introduced in this study. The described methodology could be very useful for the target or biomarker selection and evaluation during the pre-clinical therapeutics development stage as well as disease progression monitoring. In addition, the present study sheds new light into the complex aetiology of HF, differentiating between subtle changes in dilated cardiomyopathies (DCs) and ischemic cardiomyopathies (ICs) on the single cell, proteome and whole transcriptome level, demonstrating that HF might be dependent on the involvement of not only the cardiomyocytes but also on other cell populations. Identified tissue remodelling and inflammatory processes can be beneficial when selecting targeted pharmacological management for DCs or ICs, respectively.

Male and Female Animals Respond Differently to High-Fat Diet and Regular Exercise Training in a Mouse Model of Hyperlipidemia

Inappropriate nutrition and a sedentary lifestyle can lead to obesity, one of the most common risk factors for several chronic diseases. Although regular physical exercise is an efficient approach to improve cardiometabolic health, the exact cellular processes are still not fully understood. We aimed to analyze the morphological, gene expression, and lipidomic patterns in the liver and adipose tissues in response to regular exercise. Healthy (wild type on a normal diet) and hyperlipidemic, high-fat diet-fed (HFD-fed) apolipoprotein B-100 (APOB-100)-overexpressing mice were trained by treadmill running for 7 months. The serum concentrations of triglyceride and tumor necrosis factor α (TNFα), as well as the level of lipid accumulation in the liver, were significantly higher in HFD-fed APOB-100 males compared to females. However, regular exercise almost completely abolished lipid accumulation in the liver of hyperlipidemic animals. The expression level of the thermogenesis marker, uncoupling protein-1 (Ucp1), was significantly higher in the subcutaneous white adipose tissue of healthy females, as well as in the brown adipose tissue of HFD-fed APOB-100 females, compared to males. Lipidomic analyses revealed that hyperlipidemia essentially remodeled the lipidome of brown adipose tissue, affecting both the membrane and storage lipid fractions, which was partially restored by exercise in both sexes. Our results revealed more severe metabolic disturbances in HFD-fed APOB-100 males compared to females. However, exercise efficiently reduced the body weight, serum triglyceride levels, expression of pro-inflammatory factors, and hepatic lipid accumulation in our model.

Activation of dsRNA-Dependent Protein Kinase R by miR-378 Sustains Metabolic Inflammation in Hepatic Insulin Resistance

MicroRNAs (miRNAs) are noncoding small RNAs that regulate various pathophysiological cellular processes. Here, we report that expression of the miR-378 family was significantly induced by metabolic inflammatory inducers, a high-fructose diet, and inflammatory cytokine tumor necrosis factor-α. Hepatic miRNA profiling revealed that expression of miR-378a was highly upregulated, which, in turn, targeted the 3'-untranslated region of PPARα mRNA, impaired mitochondrial fatty acid β-oxidation, and induced mitochondrial and endoplasmic reticulum stress. More importantly, the upregulated miR-378a can directly bind to and activate the double-strand RNA (dsRNA)-dependent protein kinase R (PKR) to sustain the metabolic stress. In vivo, genetic depletion of miR-378a prevented PKR activation and ameliorated inflammatory stress and insulin resistance. Counterbalancing the upregulated miR-378a using nanoparticles encapsulated with an anti-miR-378a oligonucleotide restored PPARα activity, inhibited PKR activation and ER stress, and improved insulin sensitivity in fructose-fed mice. Our study delineated a novel mechanism of miR-378a in the pathogenesis of metabolic inflammation and insulin resistance through targeting metabolic signaling at both mRNA (e.g., PPARα) and protein (e.g., PKR) molecules. This novel finding of functional interaction between miRNAs (e.g., miR-378a) and cellular RNA binding proteins (e.g., PKR) is biologically significant because it greatly broadens the potential targets of miRNAs in cellular pathophysiological processes.

Sexual Dimorphism of NAFLD in Adults. Focus on Clinical Aspects and Implications for Practice and Translational Research

Nonalcoholic fatty liver disease (NAFLD) embraces the clinico-pathological consequences of hepatic lipotoxicity and is a major public health problem globally. Sexual dimorphism is a definite feature of most human diseases but, under this aspect, NAFLD lags behind other medical fields. Here, we aim at summarizing and critically discussing the most prominent sex differences and gaps in NAFLD in humans, with emphasis on those aspects which are relevant for clinical practice and translational research. Sexual dimorphism of NAFLD is covered with references to the following areas: disease prevalence and risk factors, pathophysiology, comorbidities, natural course and complications. Finally, we also discuss selected gender differences and whether sex-specific lifestyle changes should be adopted to contrast NAFLD in men and women.

Sex-dependent effects of ambient PM2.5 pollution on insulin sensitivity and hepatic lipid metabolism in mice

Background & aims

Emerging evidence supports ambient fine particulate matter (PM_2.5) exposure is associated with insulin resistance (IR) and hepatic lipid accumulation. In this study, we aimed to evaluate the sex-dependent vulnerability in response to PM_2.5 exposure and investigate the underlying mechanism by which PM_2.5 modulates hepatic lipid metabolism.

Methods

Both male and female C57BL/6 mice were randomly assigned to ambient PM_2.5 or filtered air for 24 weeks via a whole body exposure system. High-coverage quantitative lipidomics approaches and liquid chromatography-mass spectrometry techniques were performed to measure hepatic metabolites and hormones in plasma. Metabolic studies, histological analyses, as well as gene expression levels and molecular signal transduction analysis were applied to examine the effects and mechanisms by which PM_2.5 exposure-induced metabolic disorder.

Results

Female mice were more susceptible than their male counterparts to ambient PM_2.5 exposure-induced IR and hepatic lipid accumulation. The hepatic lipid profile was changed in response to ambient PM_2.5 exposure. Levels of hepatic triacylglycerols (TAGs), free fatty acids (FFAs) and cholesterol were only increased in female mice from PM group compared to control group. Plasmalogens were dysregulated in the liver from PM_2.5-exposed mice as well. In addition, exposure to PM_2.5 led to enhanced hepatic ApoB and microsomal triglyceride transport protein expression in female mice. Finally, PM_2.5 exposure inhibited hypothalamus-pituitary-adrenal (HPA) axis and decreased glucocorticoids levels, which may contribute to the vulnerability in PM_2.5-induced metabolic dysfunction.

Conclusions

Ambient PM_2.5 exposure inhibited HPA axis and demonstrated sex-associated differences in its effects on IR and disorder of hepatic lipid metabolism. These findings provide new mechanistic evidence of hormone regulation in air pollution-mediated metabolic abnormalities of lipids and more personalized care should be considered in terms of sex-specific risk factors.

Physical inactivity and excessive sucrose consumption are associated with higher serum lipids in subjects with Taq1B CETP polymorphism

BACKGROUND

Dyslipidaemias result from the interaction between genetic and environmental factors, including diet disequilibrium and physical inactivity. Among the genetic factors associated with serum lipids, the Taq1B CETP polymorphism has been investigated. The B1 allele has been considered as a risk factor for dyslipidaemia because of its association with greater CETP levels and higher serum triglycerides. The present study aimed to determine the role of the Taq1B polymorphism with lipid and anthropometric variables and its interaction with diet and physical activity.

METHODS

In total, 215 subjects were enrolled in this cross-sectional study. Diet intake was evaluated using a 3-day food consumption record and physical activity was determined in accordance with World Health Organization recommendations. The Taq1B CETP polymorphism was determined by allelic discrimination.

RESULTS

Subjects with the B1B2/B2B2 genotype, who had a sucrose consumption ≥5% of the total kcal day^-1 , had higher levels of total cholesterol (TC) [165.55 (142.21-188.89) mg dL^-1 versus 200.19 (184.79-215.60) mg dL^-1 ; P for interaction = 0.034] and low-density lipoprotein [99.29 (75.52-123.05) mg dL^-1 versus 128.64 (113.59-143.69) mg dL^-1 ; P for interaction = 0.037] than subjects with the B1B1 genotype. Subjects who did not perform physical activity and had the B1B2/B2B2 genotype showed significantly higher levels of TC [177.48 (161.36-193.60) mg dL^-1 versus 194.49 (185.43-203.56) mg mL^-1 ; P for interaction = 0.033] than subjects with the B1B1 genotype.

CONCLUSIONS

We provide evidence that subjects with inadequate environmental factors carriers of the polymorphic genotype had higher serum lipid levels than subjects with the B1B1 genotype.

Deiminated proteins and extracellular vesicles as novel biomarkers in pinnipeds: Grey seal (Halichoerus gryptus) and harbour seal (Phoca vitulina)

Peptidylarginine deiminases (PADs) are phylogenetically conserved calcium-dependent enzymes which post-translationally convert arginine into citrulline in target proteins in an irreversible manner, leading to functional and structural changes in target proteins. Protein deimination can cause the generation of neo-epitopes, affect gene regulation and also allow for protein moonlighting and therefore facilitate multifaceted functions of the same protein. PADs are furthermore a key regulator of cellular release of extracellular vesicle (EVs), which are found in most body fluids and participate in cellular communication via transfer of cargo proteins and genetic material. In this study, post-translationally deiminated proteins and EVs were assessed in sera of two seal species, grey seal and harbour seal. We report a poly-dispersed population of serum-EVs, which were positive for phylogenetically conserved EV-specific markers and characterised by transmission electron microscopy. A number of deiminated proteins critical for immune and metabolic functions were identified in the seal sera and varied somewhat between the two species under study, while some targets were in common. EV profiles of the seal sera further revealed that key microRNAs for inflammation, immunity and hypoxia also vary between the two species. Protein deimination and EVs profiles may be useful biomarkers for assessing health status of sea mammals, which face environmental challenges, including opportunistic infection, pollution and shifting habitat due to global warming.

Deiminated proteins and extracellular vesicles - Novel serum biomarkers in whales and orca

Peptidylarginine deiminases (PADs) are a family of phylogenetically conserved calcium-dependent enzymes which cause post-translational protein deimination. This can result in neoepitope generation, affect gene regulation and allow for protein moonlighting via functional and structural changes in target proteins. Extracellular vesicles (EVs) carry cargo proteins and genetic material and are released from cells as part of cellular communication. EVs are found in most body fluids where they can be useful biomarkers for assessment of health status. Here, serum-derived EVs were profiled, and post-translationally deiminated proteins and EV-related microRNAs are described in 5 ceataceans: minke whale, fin whale, humpback whale, Cuvier's beaked whale and orca. EV-serum profiles were assessed by transmission electron microscopy and nanoparticle tracking analysis. EV profiles varied between the 5 species and were identified to contain deiminated proteins and selected key inflammatory and metabolic microRNAs. A range of proteins, critical for immune responses and metabolism were identified to be deiminated in cetacean sera, with some shared KEGG pathways of deiminated proteins relating to immunity and physiology, while some KEGG pathways were species-specific. This is the first study to characterise and profile EVs and to report deiminated proteins and putative effects of protein-protein interaction networks via such post-translationald deimination in cetaceans, revealing key immune and metabolic factors to undergo this post-translational modification. Deiminated proteins and EVs profiles may possibly be developed as new biomarkers for assessing health status of sea mammals.

Protein Deimination and Extracellular Vesicle Profiles in Antarctic Seabirds

Pelagic seabirds are amongst the most threatened of all avian groups. They face a range of immunological challenges which seem destined to increase due to environmental changes in their breeding and foraging habitats, affecting prey resources and exposure to pollution and pathogens. Therefore, the identification of biomarkers for the assessment of their health status is of considerable importance. Peptidylarginine deiminases (PADs) post-translationally convert arginine into citrulline in target proteins in an irreversible manner. PAD-mediated deimination can cause structural and functional changes in target proteins, allowing for protein moonlighting in physiological and pathophysiological processes. PADs furthermore contribute to the release of extracellular vesicles (EVs), which play important roles in cellular communication. In the present study, post-translationally deiminated protein and EV profiles of plasma were assessed in eight seabird species from the Antarctic, representing two avian orders: Procellariiformes (albatrosses and petrels) and Charadriiformes (waders, auks, gulls and skuas). We report some differences between the species assessed, with the narrowest EV profiles of 50-200 nm in the northern giant petrel Macronectes halli, and the highest abundance of larger 250-500 nm EVs in the brown skua Stercorarius antarcticus. The seabird EVs were positive for phylogenetically conserved EV markers and showed characteristic EV morphology. Post-translational deimination was identified in a range of key plasma proteins critical for immune response and metabolic pathways in three of the bird species under study; the wandering albatross Diomedea exulans, south polar skua Stercorarius maccormicki and northern giant petrel. Some differences in Gene Ontology (GO) biological and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways for deiminated proteins were observed between these three species. This indicates that target proteins for deimination may differ, potentially contributing to a range of physiological functions relating to metabolism and immune response, as well as to key defence mechanisms. PAD protein homologues were identified in the seabird plasma by Western blotting via cross-reaction with human PAD antibodies, at an expected 75 kDa size. This is the first study to profile EVs and to identify deiminated proteins as putative novel plasma biomarkers in Antarctic seabirds. These biomarkers may be further refined to become useful indicators of physiological and immunological status in seabirds-many of which are globally threatened.

Pyk2-dependent phosphorylation of LSR enhances localization of LSR and tricellulin at tricellular tight junctions

Tight junctions (TJs) are cellular junctions within the mammalian epithelial cell sheet that function as a physical barrier to molecular transport within the intercellular space. Dysregulation of TJs leads to various diseases. Tricellular TJs (tTJs), specialized structural variants of TJs, are formed by multiple transmembrane proteins (e.g., lipolysis-stimulated lipoprotein receptor [LSR] and tricellulin) within tricellular contacts in the mammalian epithelial cell sheet. However, the mechanism for recruiting LSR and tricellulin to tTJs is largely unknown. Previous studies have identified that tyrphostin 9, the dual inhibitor of Pyk2 (a nonreceptor tyrosine kinase) and receptor tyrosine kinase platelet-derived growth factor receptor (PDGFR), suppresses LSR and tricellulin recruitment to tTJs in EpH4 (a mouse mammary epithelial cell line) cells. In this study, we investigated the effect of Pyk2 inhibition on LSR and tricellulin localization to tTJs. Pyk2 inactivation by its specific inhibitor or repression by RNAi inhibited the localization of LSR and downstream tricellulin to tTJs without changing their expression level in EpH4 cells. Pyk2-dependent changes in subcellular LSR and tricellulin localization were independent of c-Jun N-terminal kinase (JNK) activation and expression. Additionally, Pyk2-dependent LSR phosphorylation at Tyr-237 was required for LSR and tricellulin localization to tTJs and decreased epithelial barrier function. Our findings indicated a novel mechanism by which Pyk2 regulates tTJ assembly and epithelial barrier function in the mammalian epithelial cell sheet.

Nuclear lipid droplets derive from a lipoprotein precursor and regulate phosphatidylcholine synthesis

The origin and physiological significance of lipid droplets (LDs) in the nucleus is not clear. Here we show that nuclear LDs in hepatocytes are derived from apolipoprotein B (ApoB)-free lumenal LDs, a precursor to very low-density lipoproprotein (VLDL) generated in the ER lumen by microsomal triglyceride transfer protein. ApoB-free lumenal LDs accumulate under ER stress, grow within the lumen of the type I nucleoplasmic reticulum, and turn into nucleoplasmic LDs by disintegration of the surrounding inner nuclear membrane. Oleic acid with or without tunicamycin significantly increases the formation of nucleoplasmic LDs, to which CTP:phosphocholine cytidylyltransferase α (CCTα) is recruited, resulting in activation of phosphatidylcholine (PC) synthesis. Perilipin-3 competes with CCTα in binding to nucleoplasmic LDs, and thus, knockdown and overexpression of perilipin-3 increases and decreases PC synthesis, respectively. The results indicate that nucleoplasmic LDs in hepatocytes constitute a feedback mechanism to regulate PC synthesis in accordance with ER stress.

The origin and physiological significance of lipid droplets (LDs) in the nucleus is not clear. Here authors show that nucleoplasmic LDs in hepatocytes are derived from apolipoprotein B (ApoB)-free lumenal LDs and constitute a feedback mechanism to regulate PC synthesis in accordance with ER stress.

The Role of RNA Editing in Cancer Development and Metabolic Disorders

Numerous human diseases arise from alterations of genetic information, most notably DNA mutations. Thought to be merely the intermediate between DNA and protein, changes in RNA sequence were an afterthought until the discovery of RNA editing 30 years ago. RNA editing alters RNA sequence without altering the sequence or integrity of genomic DNA. The most common RNA editing events are A-to-I changes mediated by adenosine deaminase acting on RNA (ADAR), and C-to-U editing mediated by apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (APOBEC1). Both A-to-I and C-to-U editing were first identified in the context of embryonic development and physiological homeostasis. The role of RNA editing in human disease has only recently started to be understood. In this review, the impact of RNA editing on the development of cancer and metabolic disorders will be examined. Distinctive functions of each RNA editase that regulate either A-to-I or C-to-U editing will be highlighted in addition to pointing out important regulatory mechanisms governing these processes. The potential of developing novel therapeutic approaches through intervention of RNA editing will be explored. As the role of RNA editing in human disease is elucidated, the clinical utility of RNA editing targeted therapies will be needed. This review aims to serve as a bridge of information between past findings and future directions of RNA editing in the context of cancer and metabolic disease.

Nicotine enhances alcoholic fatty liver in mice: Role of CYP2A5

Tobacco and alcohol are often co-abused. Nicotine can enhance alcoholic fatty liver, and CYP2A6 (CYP2A5 in mice), a major metabolism enzyme for nicotine, can be induced by alcohol. CYP2A5 knockout (cyp2a5^-/-) mice and their littermates (cyp2a5^+/+) were used to test whether CYP2A5 has an effect on nicotine-enhanced alcoholic fatty liver. The results showed that alcoholic fatty liver was enhanced by nicotine in cyp2a5^+/+ mice but not in the cyp2a5^-/- mice. Combination of ethanol and nicotine increased serum triglyceride in cyp2a5^+/+ mice but not in the cyp2a5^-/- mice. Cotinine, a major metabolite of nicotine, also enhanced alcoholic fatty liver, which was also observed in cyp2a5^+/+ mice but not in the cyp2a5^-/- mice. Nitrotyrosine and malondialdehyde (MDA), markers of oxidative/nitrosative stress, were induced by alcohol and were further increased by nicotine and cotinine in cyp2a5^+/+ mice but not in the cyp2a5^-/- mice. Reactive oxygen species (ROS) production during microsomal metabolism of nicotine and cotinine was increased in microsomes from cyp2a5^+/+ mice but not in microsomes from cyp2a5^-/- mice. These results suggest that nicotine enhances alcoholic fatty liver in a CYP2A5-dependent manner, which is related to ROS produced during the process of CYP2A5-dependent nicotine metabolism.

Liver function and dysfunction - a unique window into the physiological reach of ER stress and the unfolded protein response

The unfolded protein response (UPR) improves endoplasmic reticulum (ER) protein folding in order to alleviate stress. Yet it is becoming increasingly clear that the UPR regulates processes well beyond those directly involved in protein folding, in some cases by mechanisms that fall outside the realm of canonical UPR signaling. These pathways are highly specific from one cell type to another, implying that ER stress signaling affects each tissue in a unique way. Perhaps nowhere is this more evident than in the liver, which-beyond being a highly secretory tissue-is a key regulator of peripheral metabolism and a uniquely proliferative organ upon damage. The liver provides a powerful model system for exploring how and why the UPR extends its reach into physiological processes that occur outside the ER, and how ER stress contributes to the many systemic diseases that involve liver dysfunction. This review will highlight the ways in which the study of ER stress in the liver has expanded the view of the UPR to a response that is a key guardian of cellular homeostasis outside of just the narrow realm of ER protein folding.

Heat Shock Proteins and Autophagy Pathways in Neuroprotection: from Molecular Bases to Pharmacological Interventions

Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease and Huntington's disease (HD), amyotrophic lateral sclerosis, and prion diseases are all characterized by the accumulation of protein aggregates (amyloids) into inclusions and/or plaques. The ubiquitous presence of amyloids in NDDs suggests the involvement of disturbed protein homeostasis (proteostasis) in the underlying pathomechanisms. This review summarizes specific mechanisms that maintain proteostasis, including molecular chaperons, the ubiquitin-proteasome system (UPS), endoplasmic reticulum associated degradation (ERAD), and different autophagic pathways (chaperon mediated-, micro-, and macro-autophagy). The role of heat shock proteins (Hsps) in cellular quality control and degradation of pathogenic proteins is reviewed. Finally, putative therapeutic strategies for efficient removal of cytotoxic proteins from neurons and design of new therapeutic targets against the progression of NDDs are discussed.

Lipocalin-2 in Fructose-Induced Fatty Liver Disease

The intake of excess dietary fructose most often leads to non-alcoholic fatty liver disease (NAFLD). Fructose is metabolized mainly in the liver and its chronic consumption results in lipogenic gene expression in this organ. However, precisely how fructose is involved in NAFLD progression is still not fully understood, limiting therapy. Lipocalin-2 (LCN2) is a small secreted transport protein that binds to fatty acids, phospholipids, steroids, retinol, and pheromones. LCN2 regulates lipid and energy metabolism in obesity and is upregulated in response to insulin. We previously discovered that LCN2 has a hepatoprotective effect during hepatic insult, and that its upregulation is a marker of liver damage and inflammation. To investigate if LCN2 has impact on the metabolism of fructose and thereby arising liver damage, we fed wild type and Lcn2^−/− mice for 4 or 8 weeks on diets that were enriched in fructose either by adding this sugar to the drinking water (30% w/v), or by feeding a chow containing 60% (w/w) fructose. Body weight and daily intake of food and water of these mice was then measured. Fat content in liver sections was visualized using Oil Red O stain, and expression levels of genes involved in fat and sugar metabolism were measured by qRT-PCR and Western blot analysis. We found that fructose-induced steatosis and liver damage was more prominent in female than in male mice, but that the most severe hepatic damage occurred in female mice lacking LCN2. Unexpectedly, consumption of elevated fructose did not induce de novo lipogenesis or fat accumulation. We conclude that LCN2 acts in a lipid-independent manner to protect the liver against fructose-induced damage.

Added fructose as a principal driver of non-alcoholic fatty liver disease: a public health crisis

Fatty liver disease affects up to one out of every two adults in the western world. Data from animal and human studies implicate added sugars (eg, sucrose and high-fructose corn syrup) in the development of fatty liver disease and its consequences. Added fructose in particular, as a component of added sugars, may pose the greatest risk for fatty liver disease. Considering that there is no requirement for added sugars in the diet, dietary guidelines should recommend reducing the intake of added sugars to just 5% of total calories in order to decrease the prevalence of fatty liver disease and its related consequences.

Naltrexone changes the expression of lipid metabolism-related proteins in the endoplasmic reticulum stress induced hepatic steatosis in mice

Endoplasmic reticulum (ER) stress is closely associated with several chronic diseases such as obesity, atherosclerosis, type 2 diabetes, and hepatic steatosis. Steatosis in hepatocytes may also lead to disorders such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), fibrosis, and possibly cirrhosis. Opioid peptides are involved in triglyceride and cholesterol dysregulation. Naltrexone also attenuates ER stress induced hepatic steatosis in mice. In this study, we evaluated the effects of naltrexone on the expression of lipid metabolism-related nuclear factors and enzymes in the ER stress induced hepatic steatosis. C57/BL6 mice received saline, DMSO and naltrexone as control groups. In a fourth group, ER stress was induced by tunicamycin (TM) injection and in the last group, naltrexone was given before TM administration. Histopathological evaluations, real-time RT-PCR and western blot were performed. We found that GRP78, IRE1α, PERK and ATF6 gene expression and steatosis significantly reduced in naltrexone treated animals. Naltrexone alleviated the gene and protein expression of SREBP1c. Expression of ACAT1, apolipoprotein B (ApoB) and PPARα also increased after naltrexone treatment. In conclusion, this study, for the first time, shows that naltrexone has a considerable role in attenuation of ER stress-induced liver injury.

CREBH mediates metabolic inflammation to hepatic VLDL overproduction and hyperlipoproteinemia

Metabolic inflammation is closely associated with hyperlipidemia and cardiovascular disease. However, the underlying mechanisms are not fully understood. The current study established that cAMP-responsive-element-binding protein H (CREBH), an acute-phase transcription factor, enhances very-low-density lipoprotein (VLDL) assembly and secretion by upregulating apolipoprotein B (apoB) expression and contributes to metabolic inflammation-associated hyperlipoproteinemia induced by TNFα, lipopolysaccharides (LPS), and high-fat diet (HFD) in mice. Specifically, overexpression of CREBH significantly induced mRNA and protein expression of apoB in McA-7777 cells. Luciferase assay further revealed that the presence of CREBH could significantly increase the activity of the apoB gene promoter. In contrast, genetic depletion of CREBH in mice resulted in significant reduction in expression of hepatic apoB mRNA. Challenging mice with an acute fat load led to upregulation of triglyceride (TG)-rich lipoprotein secretion in wild type mice, but not in CREBH-null mice. TNFα treatment activated hepatic CREBH expression, which in turn enhanced hepatic apoB biosynthesis and VLDL secretion. Metabolic inflammation induced by LPS or HFD also resulted in overproduction of apoB and hyperlipoproteinemia in wild type mice, but not in CREBH-null mice. This study demonstrates that CREBH could be a mediator between metabolic inflammation and hepatic VLDL overproduction in chronic metabolic disorders. This novel finding establishes CREBH as the first transcription factor that regulates apoB expression on the transcriptional level and the subsequent VLDL biosynthesis in response to metabolic inflammation. The study also provides novel insight into the pathogenesis of hyperlipidemia in metabolic syndrome.

KEY MESSAGES

CREBH mediates inflammatory signaling to VLDL overproduction in metabolic stress. Activation of CREBH in inflammation enhances mRNA and protein expression of apoB. CREBH presents a potential novel therapeutic target for hyperlipoproteinemia.

Prevention of hepatic fibrosis with liver microsomal triglyceride transfer protein deletion in liver fatty acid binding protein null mice

Blocking hepatic very low-density lipoprotein secretion through genetic or pharmacologic inhibition of microsomal triglyceride transfer protein (Mttp) causes hepatic steatosis, yet the risks for developing hepatic fibrosis are poorly understood. We report that liver-specific Mttp knockout mice (Mttp-LKO) exhibit both steatosis and fibrosis, which is exacerbated by a high-transfat/fructose diet. When crossed into germline liver fatty acid (FA) binding protein null mice (Mttp-LKO, i.e., double knockout mice) hepatic steatosis was greatly diminished and fibrosis prevented, on both low-fat and high-fat diets. The mechanisms underlying protection include reduced long chain FA uptake, shifts in FA distribution (lipidomic profiling), and metabolic turnover, specifically decreased hepatic 18:2 FA and triglyceride species and a shift in 18:2 FA use for oxidation versus incorporation into newly synthesized triglyceride. Double knockout mice were protected against fasting-induced hepatic steatosis (a model of enhanced exogenous FA delivery) yet developed steatosis upon induction of hepatic de novo lipogenesis with fructose feeding. Mttp-LKO mice, on either the liver FA binding protein null or Apobec-1 null background (i.e., apolipoprotein B100 only) exhibited only subtle increases in endoplasmic reticulum stress, suggesting that an altered unfolded protein response is unlikely to account for the attenuated phenotype in double knockout mice. Acute, antisense-mediated liver FA binding protein knockdown in Mttp-LKO mice also reduced FA uptake, increased oxidation versus incorporation of 18:2 species with complete reversal of hepatic steatosis, increased hepatic injury, and worsened fibrosis.

CONCLUSION

Perturbing exogenous hepatic FA use modulates both hepatic steatosis and fibrosis in the setting of hepatic Mttp deletion, adding new insight into the pathophysiological mechanisms and consequences of defective very low-density lipoprotein secretion. (Hepatology 2017;65:836-852).

Glucagon regulates hepatic lipid metabolism via cAMP and Insig-2 signaling: implication for the pathogenesis of hypertriglyceridemia and hepatic steatosis

Insulin induced gene-2 (Insig-2) is an ER-resident protein that inhibits the activation of sterol regulatory element-binding proteins (SREBPs). However, cellular factors that regulate Insig-2 expression have not yet been identified. Here we reported that cyclic AMP-responsive element-binding protein H (CREBH) positively regulates mRNA and protein expression of a liver specific isoform of Insig-2, Insig-2a, which in turn hinders SREBP-1c activation and inhibits hepatic de novo lipogenesis. CREBH binds to the evolutionally conserved CRE-BP binding elements located in the enhancer region of Insig-2a and upregulates its mRNA and protein expression. Metabolic hormone glucagon and nutritional fasting activated CREBH, which upregulated expression of Insig-2a in hepatocytes and inhibited SREBP-1c activation. In contrast, genetic depletion of CREBH decreased Insig-2a expression, leading to the activation of SREBP-1c and its downstream lipogenic target enzymes. Compromising CREBH-Insig-2 signaling by siRNA interference against Insig-2 also disrupted the inhibitory effect of this signaling pathway on hepatic de novo triglyceride synthesis. These actions resulted in the accumulation of lipid droplets in hepatocytes and systemic hyperlipidemia. Our study identified CREBH as the first cellular protein that regulates Insig-2a expression. Glucagon activated the CREBH-Insig-2a signaling pathway to inhibit hepatic de novo lipogenesis and prevent the onset of hepatic steatosis and hypertriglyceridemia.

Bax Inhibitor-1 regulates hepatic lipid accumulation via ApoB secretion

In this study, we explored the effects of Bax Inhibitor-1 (BI-1) on ApoB aggregation in high-fat diet (HFD)-induced hepatic lipid accumulation. After 1 week on a HFD, triglycerides and cholesterol accumulated more in the liver and were not effectively secreted into the plasma, whereas after 8 weeks, lipids were highly accumulated in both the liver and plasma, with a greater effect in BI-1 KO mice compared with BI-1 WT mice. ApoB, a lipid transfer protein, was accumulated to a greater extent in the livers of HFD-BI-1 KO mice compared with HFD-BI-1 WT mice. Excessive post-translational oxidation of protein disulfide isomerase (PDI), intra-ER ROS accumulation and folding capacitance alteration were also observed in HFD-BI-1 KO mice. Higher levels of endoplasmic reticulum (ER) stress were consistently observed in KO mice compared with the WT mice. Adenovirus-mediated hepatic expression of BI-1 in the BI-1 KO mice rescued the above phenotypes. Our results suggest that BI-1-mediated enhancement of ApoB secretion regulates hepatic lipid accumulation, likely through regulation of ER stress and ROS accumulation.

The role of ER stress in lipid metabolism and lipotoxicity

The endoplasmic reticulum (ER) is a cellular organelle important for regulating calcium homeostasis, lipid metabolism, protein synthesis, and posttranslational modification and trafficking. Numerous environmental, physiological, and pathological insults disturb ER homeostasis, referred to as ER stress, in which a collection of conserved intracellular signaling pathways, termed the unfolded protein response (UPR), are activated to maintain ER function for cell survival. However, excessive and/or prolonged UPR activation leads to initiation of self-destruction through apoptosis. Excessive accumulation of lipids and their intermediate products causes metabolic abnormalities and cell death, called lipotoxicity, in peripheral organs, including the pancreatic islets, liver, muscle, and heart. Because accumulating evidence links chronic ER stress and defects in UPR signaling to lipotoxicity in peripheral tissues, understanding the role of ER stress in cell physiology is a topic under intense investigation. In this review, we highlight recent findings that link ER stress and UPR signaling to the pathogenesis of peripheral organs due to lipotoxicity.

Herbal Acupuncture for the Treatment of Obesity

Obesity is the state of excessive body fat accumulation and is mainly caused by consuming more calories than are burned through physical activity. Herbal acupuncture (HA), also known as pharmacopuncture, has been increasingly used in clinics of Korean medical to alleviate obesity. This review analyzed four clinical studies and 16 animal studies on the effectiveness of HA as a treatment for obesity. Clinical evidence suggests that various kinds of HA might be beneficial for treating obesity; however, further investigations with well-designed, evidence-based, randomized clinical trials are needed. Animal studies support the idea that HA might be beneficial for the treatment of obesity and provide possible mechanisms, such as anti-inflammation, antioxidation, modulating lipid metabolism and so on, to explain the effect of HA on obesity. This review, based on the evidence collected, suggests that HA could have a beneficial effect for alleviating obesity by modulating inflammation, oxidative stress, lipid metabolism, leptin, and the insulin signal.

MicroRNAs and Noncoding RNAs in Hepatic Lipid and Lipoprotein Metabolism: Potential Therapeutic Targets of Metabolic Disorders

Noncoding RNAs and microRNAs (miRNAs) represent an important class of regulatory molecules that modulate gene expression. The role of miRNAs in diverse cellular processes such as cancer, apoptosis, cell differentiation, cardiac remodeling, and inflammation has been intensively explored. Recent studies further demonstrated the important roles of miRNAs and noncoding RNAs in modulating a broad spectrum of genes involved in lipid synthesis and metabolic pathways. This overview focuses on the role of miRNAs in hepatic lipid and lipoprotein metabolism and their potential as therapeutic targets for metabolic syndrome. This includes recent advances made in the understanding of their target pathways and the clinical development of miRNAs in lipid metabolic disorders.

Low-fasting triglyceride levels are associated with non-invasive markers of advanced liver fibrosis among adults in the United States

BACKGROUND

Elevated fasting triglyceride is often associated with metabolic syndrome and non-alcoholic fatty liver disease (NAFLD), the most common form of chronic liver disease. On the other hand, as liver disease progresses, patients may develop hepatocellular dysfunction that impairs triglyceride production.

AIM

To test the hypothesis that lower fasting triglyceride levels may paradoxically indicate more advanced liver disease.

METHODS

A cross-sectional analysis of 11 947 adults aged 20 years or older without chronic viral hepatitis from the National Health and Nutrition Examination Survey 1999-2010 was performed to analyze the relationships between fasting triglyceride levels and five validated non-invasive indices of liver fibrosis, including Fibrosis 4 Score (FIB4), NAFLD Fibrosis Score (NFS), Ast-Platelet Ration Index, AST/ALT ratio and BARD.

RESULTS

Low-fasting triglyceride levels were consistently associated with elevated liver fibrosis indices. Individuals in the lowest quintile of triglycerides (TG) had an adjusted odds ratio (OR) of 3.0 (95% CI, 1.7-5.2; P < 0.001) for advanced fibrosis estimated by FIB4 score and OR of 1.8 (95% Cl, 1.2-2.7; P = 0.009) estimated by NFS, compared to individuals in the highest quintile. This association remained highly significant when restricted to individuals with abnormal LFTs from suspected NAFLD. This inverse relationship was continuous, and more pronounced among men and whites (P interaction <0.001 and 0.008 respectively), but not modified by age or body mass index. In addition, fasting TG had a stronger, more direct association with liver fibrosis indices than did albumin or total bilirubin.

CONCLUSIONS

Fasting triglyceride levels were inversely associated with liver fibrosis indicators in American adults, especially among white men. Our findings suggest that sequential lipid measurements may serve as a useful disease marker in the management of chronic liver disease patients.

Activation of hepatic CREBH and Insig signaling in the anti-hypertriglyceridemic mechanism of R-α-lipoic acid

The activation of sterol regulatory element binding proteins (SREBPs) is regulated by insulin-induced genes 1 and 2 (Insig-1 and Insig-2) and SCAP. We previously reported that feeding R-α-lipoic acid (LA) to Zucker diabetic fatty (ZDF) rats improves severe hypertriglyceridemia. In this study, we investigated the role of cyclic AMP-responsive element binding protein H (CREBH) in the lipid-lowering mechanism of LA and its involvement in the SREBP-1c and Insig pathway. Incubation of McA cells with LA (0.2 mM) or glucose (6 mM) stimulated activation of CREBH. LA treatment further induced mRNA expression of Insig-1 and Insig-2a, but not Insig-2b, in glucose-treated cells. In vivo, feeding LA to obesity-induced hyperlipidemic ZDF rats activated hepatic CREBH and stimulated transcription and translation of Insig-1 and Insig-2a. Activation of CREBH and Insigs induced by LA suppressed processing of SREBP-1c precursor into nuclear SREBP-1c, which subsequently inhibited expression of genes involved in fatty acid synthesis, including FASN, ACC and SCD-1, and reduced triglyceride (TG) contents in both glucose-treated cells and ZDF rat livers. Additionally, LA treatment also decreased abundances of very low density lipoprotein (VLDL)-associated apolipoproteins, apoB100 and apoE, in glucose-treated cells and livers of ZDF rats, leading to decreased secretion of VLDL and improvement of hypertriglyceridemia. This study unveils a novel molecular mechanism whereby LA lowers TG via activation of hepatic CREBH and increased expression of Insig-1 and Insig-2a to inhibit de novo lipogenesis and VLDL secretion. These findings provide novel insight into the therapeutic potential of LA as an anti-hypertriglyceridemia dietary molecule.

Consumption of sucrose, but not high fructose corn syrup, leads to increased adiposity and dyslipidaemia in the pregnant and lactating rat

Excess consumption of added sugars, including sucrose and high fructose corn syrup (HFCS-55), have been implicated in the global epidemics of obesity and type 2 diabetes. This study aimed to investigate and compare the impact of maternal consumption of sucrose or HFCS-55 during pregnancy and lactation on the metabolic health of the dam and her offspring at birth. Female Albino Wistar rats were given access to chow and water, in addition to a sucrose or HFCS-55 beverage (10% w/v) before, and during pregnancy and lactation. Maternal glucose tolerance was determined throughout the study, and a postmortem was conducted on dams following lactation, and on offspring within 24 h of birth. Sucrose and HFCS-55 consumption resulted in increased total energy intake compared with controls, however the increase from sucrose consumption was accompanied by a compensatory decrease in chow consumption. There was no effect of sucrose or HFCS-55 consumption on body weight, however sucrose consumption resulted in increased adiposity and elevated total plasma cholesterol in the dam, while HFCS-55 consumption resulted in increased plasma insulin and decreased plasma non-esterified fatty acids (NEFA). Maternal HFCS-55 consumption was associated with decreased relative liver weight and plasma NEFA in the offspring at birth. There was no effect of either treatment on pup weight at birth. These findings suggest that both sucrose and HFCS-55 consumption during pregnancy and lactation have the potential to impact negatively on maternal metabolic health, which may have adverse consequences for the long-term health of the offspring.

MicroRNA regulation of mitochondrial and ER stress signaling pathways: implications for lipoprotein metabolism in metabolic syndrome

The development of metabolic syndrome is closely associated with the deregulation of lipid metabolism. Emerging evidence has demonstrated that microRNAs (miRNAs) are intensively engaged in lipid and lipoprotein metabolism by regulating genes involved in control of intracellular lipid synthesis, mitochondrial fatty acid oxidation, and lipoprotein assembly. Mitochondrial dysfunction induced by altered miRNA expression has been proposed to be a contributing factor in the onset of metabolic diseases, while at the same time, aberrant expression of certain miRNAs is associated with the induction of endoplasmic reticulum (ER) stress induced by nutrient-surplus. These studies position miRNAs as a link between oxidative stress and ER stress, two cellular stress pathways that are deregulated in metabolic disease and are associated with very-low-density lipoprotein (VLDL) overproduction. Dyslipoproteinemia frequently accompanied with metabolic syndrome is initiated largely by the overproduction of VLDL and altered biogenesis of high-density lipoprotein (HDL). In this review, we highlight recent findings on the regulatory impact of miRNAs on the metabolic homeostasis of mitochondria and ER as well as their contribution to the aberrant biogenesis of both VLDL and HDL in the context of metabolic disorders, in an attempt to gain further insights into the molecular mechanisms of dyslipidemia in the metabolic syndrome.

Hepatic mitochondrial and ER stress induced by defective PPARα signaling in the pathogenesis of hepatic steatosis

Emerging evidence demonstrates a close interplay between disturbances in mitochondrial function and ER homeostasis in the development of the metabolic syndrome. The present investigation sought to advance our understanding of the communication between mitochondrial dysfunction and ER stress in the onset of hepatic steatosis in male rodents with defective peroxisome proliferator-activated receptor-α (PPARα) signaling. Genetic depletion of PPARα or perturbation of PPARα signaling by high-fructose diet compromised the functional activity of metabolic enzymes involved in mitochondrial fatty acid β-oxidation and induced hepatic mitochondrial stress in rats and mice. Inhibition of PPARα activity further enhanced the expression of apolipoprotein B (apoB) mRNA and protein, which was associated with reduced mRNA expression of the sarco/endoplasmic reticulum calcium ATPase (SERCA), the induction of hepatic ER stress, and hepatic steatosis. Restoration of PPARα activity recovered the metabolic function of the mitochondria and ER, alleviated systemic hypertriglyceridemia, and improved hepatic steatosis. These findings unveil novel roles for PPARα in mediating stress signals between hepatic subcellular stress-responding machinery and in the onset of hepatic steatosis under conditions of metabolic stress.

Evolving concepts in the pathogenesis of NASH: beyond steatosis and inflammation

Non-alcoholic steatohepatitis (NASH) is characterised by hepatic steatosis and inflammation and, in some patients, progressive fibrosis leading to cirrhosis. An understanding of the pathogenesis of NASH is still evolving but current evidence suggests multiple metabolic factors critically disrupt homeostasis and induce an inflammatory cascade and ensuing fibrosis. The mechanisms underlying these changes and the complex inter-cellular interactions that mediate fibrogenesis are yet to be fully elucidated. Lipotoxicity, in the setting of excess free fatty acids, obesity, and insulin resistance, appears to be the central driver of cellular injury via oxidative stress. Hepatocyte apoptosis and/or senescence contribute to activation of the inflammasome via a variety of intra- and inter-cellular signalling mechanisms leading to fibrosis. Current evidence suggests that periportal components, including the ductular reaction and expansion of the hepatic progenitor cell compartment, may be involved and that the Th17 response may mediate disease progression. This review aims to provide an overview of the pathogenesis of NASH and summarises the evidence pertaining to key mechanisms implicated in the transition from steatosis and inflammation to fibrosis. Currently there are limited treatments for NASH although an increasing understanding of its pathogenesis will likely improve the development and use of interventions in the future.

Hepatocyte-specific Ptpn6 deletion promotes hepatic lipid accretion, but reduces NAFLD in diet-induced obesity: potential role of PPARγ

Hepatocyte-specific Shp1 knockout mice (Ptpn6(H-KO)) are protected from hepatic insulin resistance evoked by high-fat diet (HFD) feeding for 8 weeks. Unexpectedly, we report herein that Ptpn6(H-KO) mice fed an HFD for up to 16 weeks are still protected from insulin resistance, but are more prone to hepatic steatosis, as compared with their HFD-fed Ptpn6(f/f) counterparts. The livers from HFD-fed Ptpn6(H-KO) mice displayed 1) augmented lipogenesis, marked by increased expression of several hepatic genes involved in fatty acid biosynthesis, 2) elevated postprandial fatty acid uptake, and 3) significantly reduced lipid export with enhanced degradation of apolipoprotein B (ApoB). Despite more extensive hepatic steatosis, the inflammatory profile of the HFD-fed Ptpn6(H-KO) liver was similar (8 weeks) or even improved (16 weeks) as compared to their HFD-fed Ptpn6(f/f) littermates, along with reduced hepatocellular damage as revealed by serum levels of hepatic enzymes. Interestingly, comparative microarray analysis revealed a significant up-regulation of peroxisome proliferator-activated receptor gamma (PPARγ) gene expression, confirmed by quantitative polymerase chain reaction. Elevated PPARγ nuclear activity also was observed and found to be directly regulated by Shp1 in a cell-autonomous manner.

CONCLUSION

These findings highlight a novel role for hepatocyte Shp1 in the regulation of PPARγ and hepatic lipid metabolism. Shp1 deficiency prevents the development of severe hepatic inflammation and hepatocellular damage in steatotic livers, presenting hepatocyte Shp1 as a potential novel mediator of nonalcoholic fatty liver diseases in obesity.

High-refined-carbohydrate and high-fat diets induce comparable hepatic tumorigenesis in male mice

Previous studies demonstrated that diet-induced obese mice fed a semi-purified high-fat diet (HFD) had greater liver tumorigenesis than mice fed a non-semi-purified diet. Because ingredients present in standard unpurified diets may elicit potential chemopreventive properties that are not present in semi-purified diets, the present study evaluated hepatic tumorigenic effects of dietary fat by replacing it with refined carbohydrates [digestible saccharides; high-carbohydrate diet (HCD)] in a semi-purified diet without altering other components. Two-wk-old C57Bl/6J male mice were randomly injected i.p. with either the liver-specific carcinogen diethylnitrosamine (25 mg/kg body weight) to induce liver cancer or saline as the nontumor control. At age 6 wk, mice with or without cancer initiation were further randomly assigned to an HFD (26% and 60% energy from carbohydrates and fat, respectively) or an HCD (66% and 12% energy from carbohydrates and fat, respectively) and consumed food ad libitum for 24 wk. Results showed that HCD-fed mice had a comparable degree of hepatic tumorigenesis (tumor number and volume) as HFD-fed mice, despite having significantly reduced body weights. HCD feeding induced greater hepatic endoplasmic reticulum (ER) stress-mediated protein kinase RNA-activated-like kinase (PERK) activation and oncogenic interleukin-6/signal transducer and activator of transcription 3 signaling than HFD feeding. HCD-stimulated PERK signaling was associated with elevated expression of prosurvival markers in tumors, including induced protein kinase B activation, increased extracellular signal-regulated kinases 1/2 phosphorylation, and elevated cyclin D1 protein expression. However, HCD-mediated PERK activation in tumors was also positively associated with markers of proapoptosis, which included elevated CCAAT/enhancer-binding protein homology protein expression and increased cleaved caspase-3. HCD-fed mice had greater severity in hepatic steatosis than HFD-fed mice. HCD-induced steatosis exacerbation was associated with increased expression in hepatic de novo lipogenic markers that can promote ER stress. Together, these data indicated that chronic HCD consumption by mice can produce comparable severity of hepatic tumorigenesis as HFD consumption, potentially through upregulating PERK-mediated ER stress.

Proanthocyanidins protect against early diabetic peripheral neuropathy by modulating endoplasmic reticulum stress

Diabetic peripheral neuropathy (DPN) is the most common and troublesome complication of type 2 diabetes mellitus (T2DM). Recent findings reveal an important role of endoplasmic reticulum (ER) stress in the development of DPN and identify a potential new therapeutic target. Schwann cells (SC), the myelinating cells in peripheral nervous system, are highly susceptible to ER homeostasis. Grape seed proanthocyanidins (GSPs) have been reported to improve DPN of type 1 diabetic rats and relieve ER stress in skeletal muscles and pancreas of T2DM. We investigated the potential role of ER stress in SC in regulating DPN of T2DM and assessed whether early intervention of GSPs would prevent DPN by modulating ER stress. The present study was performed in Sprague-Dawley rats made T2DM with low-dose streptozotocin and a high-carbohydrate/high-fat diet and in rat SC cultured in serum from type 2 diabetic rats. Diabetic rats showed a typical characteristic of T2DM and slowing of nerve conduction velocity (NCV) in sciatic/tibial nerves. The lesions of SC, Ca(2+) overload and ER stress were present in sciatic nerves of diabetic rats, as well as in cell culture models. GSPs administration significantly decreased the low-density lipoprotein level and increased NCV in diabetic rats. GSPs or their metabolites also partially prevented cell injury, Ca(2+) overload and ER stress in animal and cell culture models. Therefore, ER stress is implicated in peripheral neuropathy in animal and cell culture models of T2DM. Prophylactic GSPs treatment might have auxiliary preventive potential for DPN partially by alleviating ER stress.

Apolipoprotein B100 quality control and the regulation of hepatic very low density lipoprotein secretion

Apolipoprotein B (apoB) is the main protein component of very low density lipoprotein (VLDL) and is necessary for the assembly and secretion of these triglyceride (TG)-rich particles. Following release from the liver, VLDL is converted to low density lipoprotein (LDL) in the plasma and increased production of VLDL can therefore play a detrimental role in cardiovascular disease. Increasing evidence has helped to establish VLDL assembly as a target for the treatment of dyslipidemias. Multiple factors are involved in the folding of the apoB protein and the formation of a secretion-competent VLDL particle. Failed VLDL assembly can initiate quality control mechanisms in the hepatocyte that target apoB for degradation. ApoB is a substrate for endoplasmic reticulum associated degradation (ERAD) by the ubiquitin proteasome system and for autophagy. Efficient targeting and disposal of apoB is a regulated process that modulates VLDL secretion and partitioning of TG. Emerging evidence suggests that significant overlap exists between these degradative pathways. For example, the insulin-mediated targeting of apoB to autophagy and postprandial activation of the unfolded protein response (UPR) may employ the same cellular machinery and regulatory cues. Changes in the quality control mechanisms for apoB impact hepatic physiology and pathology states, including insulin resistance and fatty liver. Insulin signaling, lipid metabolism and the hepatic UPR may impact VLDL production, particularly during the postprandial state. In this review we summarize our current understanding of VLDL assembly, apoB degradation, quality control mechanisms and the role of these processes in liver physiology and in pathologic states.

Mechanisms of Liver Injury in Non-Alcoholic Steatohepatitis

Non-alcoholic steatohepatitis (NASH) is a disorder marked by alterations in hepatic lipid homeostasis as well as liver injury in the form of cell death, inflammation and fibrosis. Research into the pathophysiology of NASH is dynamic. New concepts from the fields of cell biology, microbiology, immunology and genetics are being tested for their applicability to NASH; discoveries in each of these areas are enriching our understanding of this complex disease. This review summarizes how recent developments from the bench and bedside are merging with more traditional concepts to reshape our view of NASH pathogenesis. Highlights include human studies that emphasize the role of de novo lipogenesis in NASH and experimental work uncovering a role for the inflammasome in NASH. Genetic predispositions to NASH are being clarified, and intestinal microbiome is emerging as a determinant of fatty liver. These unique ideas are now taking their place within an integrated picture of NASH pathogenesis.