Lipoapoptosis: its mechanism and its diseases

Obese phenotype and natriuretic peptides in patients with heart failure with preserved ejection fraction

The results of several recent experimental studies using animal models and clinical trials suggested that obesity is not merely an epiphenomenon or a prominent comorbidity in patients with heart failure (HF). Indeed, recent studies suggest that obesity is intimately involved in the pathogenesis of HF with preserved ejection fraction (HFpEF). The most recent studies indicate that approximately 50% of HF patients have HFpEF. As standard pharmacological treatment usually shows only a weak or even neutral effect on primary outcomes in patients with HFpEF, treatment strategies targeted to specific groups of HFpEF patients, such as those with obesity, may increase the likelihood of reaching substantial clinical benefit. Considering the well-known inverse relationship between body mass index (BMI) values and B-type natriuretic peptide (BNP) levels, it is theoretically conceivable that the measurement of natriuretic peptides, using cutoff values adjusted for age and BMI, should increase diagnostic and prognostic accuracy in HFpEF patients. However, further experimental studies and clinical trials are needed to differentiate and better understand specific mechanisms of the various HFpEF phenotypes, including obese HFpEF.

Targeting chronic innate inflammatory pathways, the main road to prevention of osteoarthritis progression

Osteoarthritis (OA) is a chronic joint disease characterized by cartilage degradation, osteophyte formation, subchondral bone sclerosis, and synovitis. Systemic factors such as obesity and the components of the metabolic syndrome seem to contribute to its progression. Breakdown of cartilage ensues from an altered balance between mechanical overload and its absorption by this tissue. There is in this context a status of persistent local inflammation by means of the chronic activation of innate immunity. A broad variety of danger-associated molecular patterns inside OA joint are able to activate pattern recognition receptors, mainly TLR (toll-like receptor) 2 and 4, which are overexpressed in the OA cartilage. Chronic activation of innate immune responses in chondrocytes results in a robust production of pro-inflammatory cytokines and chemokines, as well as of tissue-destructive enzymes, downstream of NF-κB and MAPK (mitogen activated protein kinase) dependent pathways. Besides, the toxic effects of an excess of glucose and/or fatty acids, which share the same pro-inflammatory intracellular signalling pathways, may add fuel to the fire. Not only high concentrations of glucose can render cells prone to inflammation, but also AGEs (advanced glycation end products) are integrated into the TLR signalling network through their own innate immune receptors. Considering these mechanisms, we argue for the control of both primary inflammation and proteolytic catabolism as a preventive strategy in OA, instead of focusing treatment on the enhancement of anabolic responses. Even though this approach would not return to normal already degraded cartilage, it nonetheless might avoid damage extension to the surrounding tissue.

Glycerol-3-phosphate acyltransferases 3 and 4 direct glycerolipid synthesis and affect functionality in activated macrophages

Macrophage classical M1 activation via TLR4 triggers a variety of responses to achieve the elimination of foreign pathogens. During this process, there is also an increase in lipid droplets which contain large quantities of triacylglycerol (TAG) and phospholipid (PL). The functional consequences of this increment in lipid mass are poorly understood. Here, we studied the contribution of glycerolipid synthesis to lipid accumulation, focusing specifically on the first and rate-limiting enzyme of the pathway: glycerol-3-phosphate acyltransferase (GPAT). Using bone marrow-derived macrophages (BMDMs) treated with Kdo2-lipid A, we showed that glycerolipid synthesis is induced during macrophage activation. GPAT4 protein level and GPAT3/GPAT4 enzymatic activity increase during this process, and these two isoforms were required for the accumulation of cell TAG and PL. The phagocytic capacity of Gpat3−/− and Gpat4−/− BMDM was impaired. Additionally, inhibiting fatty acid β-oxidation reduced phagocytosis only partially, suggesting that lipid accumulation is not necessary for the energy requirements for phagocytosis. Finally, Gpat4−/− BMDM expressed and released more pro-inflammatory cytokines and chemokines after macrophage activation, suggesting a role for GPAT4 in suppressing inflammatory responses. Together, these results provide evidence that glycerolipid synthesis directed by GPAT4 is important for the attenuation of the inflammatory response in activated macrophages.

Association between insulin resistance and the development of cardiovascular disease

For many years, cardiovascular disease (CVD) has been the leading cause of death around the world. Often associated with CVD are comorbidities such as obesity, abnormal lipid profiles and insulin resistance. Insulin is a key hormone that functions as a regulator of cellular metabolism in many tissues in the human body. Insulin resistance is defined as a decrease in tissue response to insulin stimulation thus insulin resistance is characterized by defects in uptake and oxidation of glucose, a decrease in glycogen synthesis, and, to a lesser extent, the ability to suppress lipid oxidation. Literature widely suggests that free fatty acids are the predominant substrate used in the adult myocardium for ATP production, however, the cardiac metabolic network is highly flexible and can use other substrates, such as glucose, lactate or amino acids. During insulin resistance, several metabolic alterations induce the development of cardiovascular disease. For instance, insulin resistance can induce an imbalance in glucose metabolism that generates chronic hyperglycemia, which in turn triggers oxidative stress and causes an inflammatory response that leads to cell damage. Insulin resistance can also alter systemic lipid metabolism which then leads to the development of dyslipidemia and the well-known lipid triad: (1) high levels of plasma triglycerides, (2) low levels of high-density lipoprotein, and (3) the appearance of small dense low-density lipoproteins. This triad, along with endothelial dysfunction, which can also be induced by aberrant insulin signaling, contribute to atherosclerotic plaque formation. Regarding the systemic consequences associated with insulin resistance and the metabolic cardiac alterations, it can be concluded that insulin resistance in the myocardium generates damage by at least three different mechanisms: (1) signal transduction alteration, (2) impaired regulation of substrate metabolism, and (3) altered delivery of substrates to the myocardium. The aim of this review is to discuss the mechanisms associated with insulin resistance and the development of CVD. New therapies focused on decreasing insulin resistance may contribute to a decrease in both CVD and atherosclerotic plaque generation.

Reprogramming of basic metabolic pathways in microbial sepsis: therapeutic targets at last?

Sepsis is a highly lethal and urgent unmet medical need. It is the result of a complex interplay of several pathways, including inflammation, immune activation, hypoxia, and metabolic reprogramming. Specifically, the regulation and the impact of the latter have become better understood in which the highly catabolic status during sepsis and its similarity with starvation responses appear to be essential in the poor prognosis in sepsis. It seems logical that new interventions based on the recognition of new therapeutic targets in the key metabolic pathways should be developed and may have a good chance to penetrate to the bedside. In this review, we concentrate on the pathological changes in metabolism, observed during sepsis, and the presumed underlying mechanisms, with a focus on the level of the organism and the interplay between different organ systems.

Dietary grape seed proanthocyanidin extract regulates metabolic disturbance in rat liver exposed to lead associated with PPARα signaling pathway

Lead, a pervasive environmental hazard worldwide, causes a wide range of physiological and biochemical destruction, including metabolic dysfunction. Grape seed proanthocyanidin extract (GSPE) is a natural production with potential metabolic regulation in liver. This study was performed to investigate the protective role of GSPE against lead-induced metabolic dysfunction in liver and elucidate the potential molecular mechanism of this event. Wistar rats received GSPE (200 mg/kg) daily with or without lead acetate (PbA, 0.5 g/L) exposure for 56 d. According to biochemical and histopathologic analysis, GSPE attenuated lead-induced metabolic dysfunction, oxidative stress, and liver dysfunction. Liver gene expression profiling was assessed by RNA sequencing and validated by qRT-PCR. Expression of some genes in peroxisome proliferator-activated receptor alpha (PPARα) signaling pathway was significantly suppressed in PbA group and revived in PbA + GSPE group, which was manifested by Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes pathway analysis and validated by western blot analysis. This study supports that dietary GSPE ameliorates lead-induced fatty acids metabolic disturbance in rat liver associated with PPARα signaling pathway, and suggests that dietary GSPE may be a protector against lead-induced metabolic dysfunction and liver injury, providing a novel therapy to protect liver against lead exposure.

Good, Bad, or Ugly: the Biological Roles of Bone Marrow Fat

PURPOSE OF REVIEW

Bone marrow fat expresses mixed characteristics, which could correspond to white, brown, and beige types of fat. Marrow fat could act as either energy storing and adipokine secreting white fat or as a source of energy for hematopoiesis and bone metabolism, thus acting as brown fat. However, there is also a negative interaction between marrow fat and other elements of the bone marrow milieu, which is known as lipotoxicity. In this review, we will describe the good and bad roles of marrow fat in the bone, while focusing on the specific components of the negative effect of marrow fat on bone metabolism.

RECENT FINDINGS

Lipotoxicity in the bone is exerted by bone marrow fat through the secretion of adipokines and free fatty acids (FFA) (predominantly palmitate). High levels of FFA found in the bone marrow of aged and osteoporotic bone are associated with decreased osteoblastogenesis and bone formation, decreased hematopoiesis, and increased osteoclastogenesis. In addition, FFA such as palmitate and stearate induce apoptosis and dysfunctional autophagy in the osteoblasts, thus affecting their differentiation and function. Regulation of marrow fat could become a therapeutic target for osteoporosis. Inhibition of the synthesis of FFA by marrow fat could facilitate osteoblastogenesis and bone formation while affecting osteoclastogenesis. However, further studies testing this hypothesis are still required.

PPARGC1A rs3736265 G>A polymorphism is associated with decreased risk of type 2 diabetes mellitus and fasting plasma glucose level

It has been reported that peroxisome proliferator-activated receptor gamma (PPARG) and peroxisome proliferator-activated receptor gamma co-activator 1 (PPARGC1) family (e.g. PPARGC1A and PPARGC1B) are key agents in the development and pathophysiology of type 2 diabetes mellitus (T2DM). In this study, we designed a case-control study and selected PPARG rs1801282 C>G, PPARG rs3856806 C>T, PPARGC1A rs8192678 C>T, PPARGC1A rs2970847 C>T, PPARGC1A rs3736265 G>A, PPARGC1B rs7732671 G>C and PPARGC1B rs17572019 G>A polymorphisms to assess the relationship between these polymorphisms and T2DM using the SNPscan method. A total of 502 T2DM patients and 784 non-diabetic controls were enrolled. We found that PPARGC1A rs3736265 G>A polymorphism was correlated with a borderline decreased susceptibility of T2DM. In a subgroup analysis by age, sex, alcohol use, smoking status and body mass index, a significantly decreased risk of T2DM in <65 years and female groups was found. Haplotype comparison analysis indicated that CTTCGGG and CTCTGGG haplotypes with the order of PPARG rs1801282 C>G, PPARG rs3856806 C>T, PPARGC1A rs8192678 C>T, PPARGC1A rs2970847 C>T, PPARGC1A rs3736265 G>A, PPARGC1B rs7732671 G>C and PPARGC1B rs17572019 G>A polymorphisms in gene position significantly increased the risk of T2DM. However, CCCCACA haplotype conferred a decreased risk to T2DM. We also found that PPARGC1A rs3736265 A allele decreased the level of fasting plasma glucose (FPG), while increased the level of Triglyceride. In conclusion, Our findings suggest that variants of PPARGC1A rs3736265 G>A polymorphism decrease the level of FPG, improving the expectation of study in individual's prevention strategies to T2DM.

Muscle Atrophy Measurement as Assessment Method for Low Back Pain Patients

Low back pain is one of the most common pain disorders defined as pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, sometimes with accompanying leg pain. The meaning of the symptomatic atrophy of paraspinal muscles and some pelvic muscles has been proved. Nowadays, a need for new diagnostic tools for specific examination of low back pain patients is posited, and it has been proposed that magnetic resonance imaging assessment toward muscle atrophy may provide some additional information enabling the subclassification of that group of patients.

Diabetic ketoacidosis in acromegaly; a rare complication precipitated by corticosteroid use

Diabetic ketoacidosis has been described in the literature as a rare possible initial presentation of acromegaly before a diagnosis of acromegaly is eventually made. Indeed, diabetic ketoacidosis is a recognised complication of acromegaly. There are a number of factors that can predispose patients with acromegaly to diabetes as well as to diabetic ketoacidosis. These include high levels of growth hormone and insulin-like growth factor 1 in acromegaly and the effect on glycaemia by medications used in the management of acromegaly. Ketoacidosis has been described in patients with acromegaly even without the presence of an underlying autoimmune diabetes. Patients with acromegaly and ketoacidosis often respond to treatment and may not require long-term insulin.

Translational Aspects of Sphingolipid Metabolism in Renal Disorders

Sphingolipids, long thought to be passive components of biological membranes with merely a structural role, have proved throughout the past decade to be major players in the pathogenesis of many human diseases. The study and characterization of several genetic disorders like Fabry’s and Tay Sachs, where sphingolipid metabolism is disrupted, leading to a systemic array of clinical symptoms, have indeed helped elucidate and appreciate the importance of sphingolipids and their metabolites as active signaling molecules. In addition to being involved in dynamic cellular processes like apoptosis, senescence and differentiation, sphingolipids are implicated in critical physiological functions such as immune responses and pathophysiological conditions like inflammation and insulin resistance. Interestingly, the kidneys are among the most sensitive organ systems to sphingolipid alterations, rendering these molecules and the enzymes involved in their metabolism, promising therapeutic targets for numerous nephropathic complications that stand behind podocyte injury and renal failure.

Enoyl-CoA hydratase-1 regulates mTOR signaling and apoptosis by sensing nutrients

The oncogenic mechanisms of overnutrition, a confirmed independent cancer risk factor, remain poorly understood. Herein, we report that enoyl-CoA hydratase-1 (ECHS1), the enzyme involved in the oxidation of fatty acids (FAs) and branched-chain amino acids (BCAAs), senses nutrients and promotes mTOR activation and apoptotic resistance. Nutrients-promoted acetylation of lys101 of ECHS1 impedes ECHS1 activity by impairing enoyl-CoA binding, promoting ECHS1 degradation and blocking its mitochondrial translocation through inducing ubiquitination. As a result, nutrients induce the accumulation of BCAAs and FAs that activate mTOR signaling and stimulate apoptosis, respectively. The latter was overcome by selection of BCL-2 overexpressing cells under overnutrition conditions. The oncogenic effects of nutrients were reversed by SIRT3, which deacetylates lys101 acetylation. Severely decreased ECHS1, accumulation of BCAAs and FAs, activation of mTOR and overexpression of BCL-2 were observed in cancer tissues from metabolic organs. Our results identified ECHS1, a nutrients-sensing protein that transforms nutrient signals into oncogenic signals.Overnutrition has been linked to increased risk of cancer. Here, the authors show that exceeding nutrients suppress Enoyl-CoA hydratase-1 (ECHS1) activity by inducing its acetylation resulting in accumulation of fatty acids and branched-chain amino acids and oncogenic mTOR activation.

Serum lipid profile as a marker of liver impairment in hepatitis B Cirrhosis patients

BACKGROUND

Chronic HBV infection is a major cause of Cirrhosis and an important risk factor to develop hepatocellular carcinoma. The study is conducted to find out the changes in the lipid metabolism of HBV-cirrhosis patients.

METHODS

In the present study, serum lipid profiles of patients with HBV-cirrhosis were assessed by utilizing micro-lab and gas chromatography, while risk factors for transmission of HBV-cirrhosis studied through the standard questionnaire.

RESULTS

The epidemiological and etiological risk factors strongly associated with HBV-cirrhosis patients compared to controls, included as family history, shave from the barber, blood transfusion (without proper screening), mutual sharing of household contents, positive surgery history, and dental treatment. The HBV-cirrhosis patients have significantly lower level (p < 0.001) of lipid profile including total cholesterol (96.65 mg/dl), TAG (82.85 mg/dl), VLDL-C (16.57 mg/dl), LDL-C (68.27 mg/dl), HDL-C (27 mg/dl) and total lipid (424.76 mg/dl) in comparison to controls, indicating hypolipidemia in patients. The MELD score indicated mild prognostic values of the hepatic function for the study group. The result of total fatty acid composition of HBV-cirrhotic patients with comparison of control subjects reveals that palmitic (24.54 g/100 g) and palmitoleic acid (4.65 g/100 g) were significantly (p < 0.05) higher whereas eicosatrienoic (0.09 g/100 g), arachidonic (3.57 g/100 g), linoleic (22.75 g/100 g) and α-linolenic acid (0.12 g/100 g) were significantly lower. Marker for stearoyl-CoA desaturase (SCD = ∆9-desaturase) activity i.e. palmitoleic: palmitic (0.2) and oleic: stearic acid (1.5) ratios, originated higher in HBV-cirrhotic patients, while PUFA: SFA (0.6) was lower in HBV-cirrhosis patients as compared with control subjects. The serum SFA and MUFA were increased while PUFA were reduced in both total and free form.

CONCLUSION

Present study concluded that hypolipidemia observed in HBV-cirrhosis patients, MELD were found to be independent predictors of survival and alteration in fatty acid composition, possibly due to impairment in fatty acid metabolism by enzymatic elongation and desaturation.

Ginkgolide A ameliorates non-alcoholic fatty liver diseases on high fat diet mice

Non-alcoholic fatty liver disease (NAFLD) is one of the most common diseases worldwide and has continuously increased. NAFLD refers to a spectrum of diseases ranging from fatty liver to steatohepatitis, cirrhosis, and even to hepatocyte carcinoma. Excessive fatty acid enters the cell and the mitochondria undergo stress and unremoved ROS can trigger a form of cell apoptosis known as 'lipoapoptosis'. NASH arises from damaged liver hepatocytes due to lipotoxicity. NASH not only involves lipid accumulation and apoptosis but also inflammation. Ginkgo biloba has been tested clinical trials as a traditional medicine for asthma, bronchitis and cardiovascular disease. The effects of Ginkgolide A (GA), derived from the ginkgo biloba leaf, are still unknown in NAFLD. To determine the protective effects of GA in NAFLD, we examined the fatty liver disease condition in the non-esterified fatty acid (NEFA)-induced HepG2 cell line and in a high fat diet mouse model. The findings of this study suggest that GA is non-toxic at high concentrations in hepatocytes. Moreover, GA was found to inhibit cellular lipogenesis and lipid accumulation by causing mitochondrial oxidative stress. GA showed hepatoprotective efficacy by inducing cellular lipoapoptosis and by inhibiting cellular inflammation. The results demonstrated that GA may be feasible as a therapeutic agent for NAFLD patients.

Obesity-induced cardiac lipid accumulation in adult mice is modulated by G protein-coupled receptor kinase 2 levels

Background

The leading cause of death among the obese population is heart failure and stroke prompted by structural and functional changes in the heart. The molecular mechanisms that underlie obesity-related cardiac remodeling are complex, and include hemodynamic and metabolic alterations that ultimately affect the functionality of the myocardium. G protein-coupled receptor kinase 2 (GRK2) is an ubiquitous kinase able to desensitize the active form of several G protein-coupled receptors (GPCR) and is known to play an important role in cardiac GPCR modulation. GRK2 has also been recently identified as a negative modulator of insulin signaling and systemic insulin resistance.

Methods

We investigated the effects elicited by GRK2 downregulation in obesity-related cardiac remodeling. For this aim, we used  9 month-old wild type (WT) and GRK2+/− mice, which display circa 50% lower levels of this kinase, fed with either a standard or a high fat diet (HFD) for 30 weeks. In these mice we studied different parameters related to cardiac growth and lipid accumulation.

Results

We find that GRK2+/− mice are protected from obesity-promoted cardiac and cardiomyocyte hypertrophy and fibrosis. Moreover, the marked intracellular lipid accumulation caused by a HFD in the heart is not observed in these mice. Interestingly, HFD significantly increases cardiac GRK2 levels in WT but not in GRK2+/− mice, suggesting that the beneficial phenotype observed in hemizygous animals correlates with the maintenance of GRK2 levels below a pathological threshold. Low GRK2 protein levels are able to keep the PKA/CREB pathway active and to prevent HFD-induced downregulation of key fatty acid metabolism modulators such as Peroxisome proliferator-activated receptor gamma co-activators (PGC1), thus preserving the expression of cardioprotective proteins such as mitochondrial fusion markers mitofusin MFN1 and OPA1.

Conclusions

Our data further define the cellular processes and molecular mechanisms by which GRK2 down-regulation is cardioprotective during diet-induced obesity, reinforcing the protective effect of maintaining low levels of GRK2 under nutritional stress, and showing a role for this kinase in obesity-induced cardiac remodeling and steatosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0474-6) contains supplementary material, which is available to authorized users.

From Molecules to the Clinic: Linking Schizophrenia and Metabolic Syndrome through Sphingolipids Metabolism

Metabolic syndrome (MS) is a prevalent and severe comorbidity observed in schizophrenia (SZ). The exact nature of this association is controversial and very often accredited to the effects of psychotropic medications and disease-induced life-style modifications, such as inactive lifestyle, poor dietary choices, and smoking. However, drug therapy and disease-induced lifestyle factors are likely not the only factors contributing to the observed converging nature of these conditions, since an increased prevalence of MS is also observed in first episode and drug-naïve psychosis populations. MS and SZ share common intrinsic susceptibility factors and etiopathogenic mechanisms, which may change the way we approach clinical management of SZ patients. Among the most relevant common pathogenic pathways of SZ and MS are alterations in the sphingolipids (SLs) metabolism and SLs homeostasis. SLs have important structural functions as they participate in the formation of membrane “lipid rafts.” SLs also play physiological roles in cell differentiation, proliferation, and inflammatory processes, which might be part of MS/SZ common pathophysiological processes. In this article we review a plausible mechanism to explain the link between MS and SZ through a disruption in SL homeostasis. Additionally, we provide insights on how this hypothesis can lead to the developing of new diagnostic/therapeutic technologies for SZ patients.

Characterization of transcription factor response kinetics in parallel

BACKGROUND

Transcription factors (TFs) are effectors of cell signaling pathways that regulate gene expression. TF networks are highly interconnected; one signal can lead to changes in many TF levels, and one TF level can be changed by many different signals. TF regulation is central to normal cell function, with altered TF function being implicated in many disease conditions. Thus, measuring TF levels in parallel, and over time, is crucial for understanding the impact of stimuli on regulatory networks and on diseases.

RESULTS

Here, we report the parallel analysis of temporal TF level changes due to multiple stimuli in distinct cell types. We have analyzed short-term dynamic changes in the levels of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), signal transducer and activator of transcription 3 (Stat3), cAMP response element-binding protein (CREB), glucocorticoid receptor (GR), and TATA binding protein (TBP), in breast and liver cancer cells after tumor necrosis factor-alpha (TNF-α) and palmitic acid (PA) exposure. In response to both stimuli, NF-kB and CREB levels were increased, Stat3 decreased, and TBP was constant. GR levels were unchanged in response to TNF-α stimulation and increased in response to PA treatment.

CONCLUSIONS

Our results show significant overlap in signaling initiated by TNF-α and by PA, with the exception that the events leading to PA-mediated cytotoxicity likely also include induction of GR signaling. These results further illuminate the dynamics of TF responses to cytokine and fatty acid exposure, while concomitantly demonstrating the utility of parallel TF measurement approaches in the analysis of biological phenomena.

Reversal of intramyocellular lipid accumulation by lipophagy and a p62-mediated pathway

We have previously observed the reversal of lipid droplet deposition in skeletal muscle of morbidly obese patients following bariatric surgery. We now investigated whether activation of autophagy is the mechanism underlying this observation. For this purpose, we incubated rat L6 myocytes over a period of 6 days with long-chain fatty acids (an equimolar, 1.0 mM, mixture of oleate and palmitate in the incubation medium). At day 6, the autophagic inhibitor (bafilomycin A1, 200 nM) and the autophagic activator (rapamycin, 1 μM) were added separately or in combination for 48 h. Intracellular triglyceride (TG) accumulation was visualized and quantified colorimetrically. Protein markers of autophagic flux (LC3 and p62) and cell death (caspase-3 cleavage) were measured by immunoblotting. Inhibition of autophagy by bafilomycin increased TG accumulation and also increased lipid-mediated cell death. Conversely, activation of autophagy by rapamycin reduced both intracellular lipid accumulation and cell death. Unexpectedly, treatment with both drugs added simultaneously resulted in decreased lipid accumulation. In this treatment group, immunoblotting revealed p62 degradation (autophagic flux), immunofluorescence revealed the colocalization of p62 with lipid droplets, and co-immunoprecipitation confirmed the interaction of p62 with ADRP (adipose differentiation-related protein), a lipid droplet membrane protein. Thus the association of p62 with lipid droplet turnover suggests a novel pathway for the breakdown of lipid droplets in muscle cells. In addition, treatment with rapamycin and bafilomycin together also suggested the export of TG into the extracellular space. We conclude that lipophagy promotes the clearance of lipids from myocytes and switches to an alternative, p62-mediated, lysosomal-independent pathway in the context of chronic lipid overload (*P<0.05, **P<0.01, ***P<0.001, ****P<0.0001).

Insulin Signaling and Heart Failure

Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed.

c-Jun N-terminal kinase-mediated Rubicon expression enhances hepatocyte lipoapoptosis and promotes hepatocyte ballooning

AIM: To clarify the relationship between autophagy and lipotoxicity-induced apoptosis, which is termed “lipoapoptosis,” in non-alcoholic steatohepatitis.

METHODS: Male C57BL/6J mice were fed a high-fat diet (HFD) for 12 wk, after which the liver histology and expression of proteins such as p62 or LC3 were evaluated. Alpha mouse liver 12 (AML12) cells treated with palmitate (PA) were used as an in vitro model.

RESULTS: LC3-II, p62, and Run domain Beclin-1 interacting and cysteine-rich containing (Rubicon) proteins increased in both the HFD mice and in AML12 cells in response to PA treatment. Rubicon expression was decreased upon c-Jun N-terminal kinase (JNK) inhibition at both the mRNA and the protein level in AML12 cells. Rubicon knockdown in AML12 cells with PA decreased the protein levels of both LC3-II and p62. Rubicon expression peaked at 4 h of PA treatment in AML12, and then decreased. Treatment with caspase-9 inhibitor ameliorated the decrease in Rubicon protein expression at 10 h of PA and resulted in enlarged AML12 cells under PA treatment. The enlargement of AML12 cells by PA with caspase-9 inhibition was canceled by Rubicon knockdown.

CONCLUSION: The JNK-Rubicon axis enhanced lipoapoptosis, and caspase-9 inhibition and Rubicon had effects that were cytologically similar to hepatocyte ballooning. As ballooned hepatocytes secrete fibrogenic signals and thus might promote fibrosis in the liver, the inhibition of hepatocyte ballooning might provide anti-fibrosis in the NASH liver.

Cardiac Myocyte-specific Knock-out of Calcium-independent Phospholipase A2γ (iPLA2γ) Decreases Oxidized Fatty Acids during Ischemia/Reperfusion and Reduces Infarct Size

Calcium-independent phospholipase A2γ (iPLA2γ) is a mitochondrial enzyme that produces lipid second messengers that facilitate opening of the mitochondrial permeability transition pore (mPTP) and contribute to the production of oxidized fatty acids in myocardium. To specifically identify the roles of iPLA2γ in cardiac myocytes, we generated cardiac myocyte-specific iPLA2γ knock-out (CMiPLA2γKO) mice by removing the exon encoding the active site serine (Ser-477). Hearts of CMiPLA2γKO mice exhibited normal hemodynamic function, glycerophospholipid molecular species composition, and normal rates of mitochondrial respiration and ATP production. In contrast, CMiPLA2γKO mice demonstrated attenuated Ca(2+)-induced mPTP opening that could be rapidly restored by the addition of palmitate and substantially reduced production of oxidized polyunsaturated fatty acids (PUFAs). Furthermore, myocardial ischemia/reperfusion (I/R) in CMiPLA2γKO mice (30 min of ischemia followed by 30 min of reperfusion in vivo) dramatically decreased oxidized fatty acid production in the ischemic border zones. Moreover, CMiPLA2γKO mice subjected to 30 min of ischemia followed by 24 h of reperfusion in vivo developed substantially less cardiac necrosis in the area-at-risk in comparison with their WT littermates. Furthermore, we found that membrane depolarization in murine heart mitochondria was sensitized to Ca(2+) by the presence of oxidized PUFAs. Because mitochondrial membrane depolarization and calcium are known to activate iPLA2γ, these results are consistent with salvage of myocardium after I/R by iPLA2γ loss of function through decreasing mPTP opening, diminishing production of proinflammatory oxidized fatty acids, and attenuating the deleterious effects of abrupt increases in calcium ion on membrane potential during reperfusion.

Knockdown of triglyceride synthesis does not enhance palmitate lipotoxicity or prevent oleate-mediated rescue in rat hepatocytes

Experiments in a variety of cell types, including hepatocytes, consistently demonstrate the acutely lipotoxic effects of saturated fatty acids, such as palmitate (PA), but not unsaturated fatty acids, such as oleate (OA). PA+OA co-treatment fully prevents PA lipotoxicity through mechanisms that are not well defined but which have been previously attributed to more efficient esterification and sequestration of PA into triglycerides (TGs) when OA is abundant. However, this hypothesis has never been directly tested by experimentally modulating the relative partitioning of PA/OA between TGs and other lipid fates in hepatocytes. In this study, we found that addition of OA to PA-treated hepatocytes enhanced TG synthesis, reduced total PA uptake and PA lipid incorporation, decreased phospholipid saturation and rescued PA-induced ER stress and lipoapoptosis. Knockdown of diacylglycerol acyltransferase (DGAT), the rate-limiting step in TG synthesis, significantly reduced TG accumulation without impairing OA-mediated rescue of PA lipotoxicity. In both wild-type and DGAT-knockdown hepatocytes, OA co-treatment significantly reduced PA lipid incorporation and overall phospholipid saturation compared to PA-treated hepatocytes. These data indicate that OA's protective effects do not require increased conversion of PA into inert TGs, but instead may be due to OA's ability to compete against PA for cellular uptake and/or esterification and, thereby, normalize the composition of cellular lipids in the presence of a toxic PA load.

Nuclear receptor FXR: A potential therapeutic target for non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) has become a very common chronic liver disease all over the world. The high incidence of NAFLD is closely related to obesity, diabetes and metabolic disorders. Insulin resistance and dyslipidemia following the hepatic proinflammatory response and fibrosis are the primary features of NAFLD deterioration. Nuclear receptor farnesoid X receptor (FXR) regulates lipid metabolism and homeostasis. Clarification of FXR function and features can provide a better understanding of the pathophysiological characteristics of non-alcoholic steatohepatitis (NASH) and illuminate the mechanism of NAFLD/NASH potential therapeutic targets. FXR activation can inhibit the de novo hepatic lipogenesis, improve insulin sensitivity and protect against bile acid-induced cytotoxicity. Clinical studies indicated that FXR agonists or modulators are very promising for the clinical treatment of NAFLD and NASH. This review focuses on the important regulatory role of FXR in NASH.

Lipotoxic brain microvascular injury is mediated by activating transcription factor 3-dependent inflammatory and oxidative stress pathways

Dysfunction of the cerebrovasculature plays an important role in vascular cognitive impairment (VCI). Lipotoxic injury of the systemic endothelium in response to hydrolyzed triglyceride-rich lipoproteins (TGRLs; TGRL lipolysis products) or a high-fat Western diet (WD) suggests similar mechanisms may be present in brain microvascular endothelium. We investigated the hypothesis that TGRL lipolysis products cause lipotoxic injury to brain microvascular endothelium by generating increased mitochondrial superoxide radical generation, upregulation of activating transcription factor 3 (ATF3)-dependent inflammatory pathways, and activation of cellular oxidative stress and apoptotic pathways. Human brain microvascular endothelial cells were treated with human TGRL lipolysis products that induced intracellular lipid droplet formation, mitochondrial superoxide generation, ATF3-dependent transcription of proinflammatory, stress response, and oxidative stress genes, as well as activation of proapoptotic cascades. Male apoE knockout mice were fed a high-fat/high-cholesterol WD for 2 months, and brain microvessels were isolated by laser capture microdissection. ATF3 gene transcription was elevated 8-fold in the hippocampus and cerebellar brain region of the WD-fed animals compared with chow-fed control animals. The microvascular injury phenotypes observed in vitro and in vivo were similar. ATF3 plays an important role in mediating brain microvascular responses to acute and chronic lipotoxic injury and may be an important preventative and therapeutic target for endothelial dysfunction in VCI.

Punicalagin attenuates palmitate-induced lipotoxicity in HepG2 cells by activating the Keap1-Nrf2 antioxidant defense system

SCOPE

Free fatty acids (FFA) could induce hepatocyte lipotoxicity, which plays an important role in the initiation of nonalcoholic fatty liver disease (NAFLD). Inhibition of FFA-induced lipotoxicity is suggested as a potential treatment for nonalcoholic fatty liver disease. The aim of the current study is to explore the effect of punicalagin, a polyphenol abundant in pomegranate, on FFA-induced hepatic lipotoxicity and its potential mechanisms.

METHODS AND RESULTS

HepG2 cells were exposed to 250 μM palmitate for 24 h with or without punicalagin pretreatment. Punicalagin pretreatment attenuated palmitate-induced mitochondrial membrane potential lost, ATP depletion, and reactive oxygen species production. Punicalagin also increased hepatocyte viability by blocking mitochondria-mediated caspase-dependent apoptosis. The hepatoprotective effect was associated with an exaggerated phosphorylation of extracellular signal regulated kinase as well as significant nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and target genes induction. Blockage of extracellular signal regulated kinase by a pharmacological inhibitor abrogated the cytoprotective effect of punicalagin and its induction of Nrf2 pathway. Knockdown of Nrf2 by specific small interfering RNA also diminished the protective effects of punicalagin, while knockdown of Kelch-like ECH-associated protein 1 (Keap1) with small interfering RNA could promote Nrf2 nuclear translocation and exert similar protection as punicalagin treatment.

CONCLUSIONS

These findings suggest that punicalagin could effectively attenuate FFA-induced lipotoxicity by activating Keap1-Nrf2 cytoprotective signaling pathway.

Lipid metabolism and signaling in cardiac lipotoxicity

The heart balances uptake, metabolism and oxidation of fatty acids (FAs) to maintain ATP production, membrane biosynthesis and lipid signaling. Under conditions where FA uptake outpaces FA oxidation and FA sequestration as triacylglycerols in lipid droplets, toxic FA metabolites such as ceramides, diacylglycerols, long-chain acyl-CoAs, and acylcarnitines can accumulate in cardiomyocytes and cause cardiomyopathy. Moreover, studies using mutant mice have shown that dysregulation of enzymes involved in triacylglycerol, phospholipid, and sphingolipid metabolism in the heart can lead to the excess deposition of toxic lipid species that adversely affect cardiomyocyte function. This review summarizes our current understanding of lipid uptake, metabolism and signaling pathways that have been implicated in the development of lipotoxic cardiomyopathy under conditions including obesity, diabetes, aging, and myocardial ischemia-reperfusion. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.

Insufficiency of phosphatidylethanolamine N-methyltransferase is risk for lean non-alcoholic steatohepatitis

Although obesity is undoubtedly major risk for non-alcoholic steatohepatitis (NASH), the presence of lean NASH patients with normal body mass index has been recognized. Here, we report that the insufficiency of phosphatidylethanolamine N-methyltransferase (PEMT) is a risk for the lean NASH. The Pemt−/− mice fed high fat-high sucrose (HFHS) diet were protected from diet-induced obesity and diabetes, while they demonstrated prominent steatohepatitis and developed multiple liver tumors. Pemt exerted inhibitory effects on p53-driven transcription by forming the complex with clathrin heavy chain and p53, and Pemt−/− mice fed HFHS diet demonstrated prominent apoptosis of hepatocytes. Furthermore, hypermethylation and suppressed mRNA expression of F-box protein 31 and hepatocyte nuclear factor 4α resulted in the prominent activation of cyclin D1. PEMT mRNA expression in liver tissues of NASH patients was significantly lower than those with simple steatosis and we postulated the distinct clinical entity of lean NASH with insufficiency of PEMT activities.

Myocardial Structural and Biological Anomalies Induced by High Fat Diet in Psammomys obesus Gerbils

BACKGROUND

Psammomys obesus gerbils are particularly prone to develop diabetes and obesity after brief period of abundant food intake. A hypercaloric high fat diet has been shown to affect cardiac function. Here, we sought to determine whether a short period of high fat feeding might alter myocardial structure and expression of calcium handling proteins in this particular strain of gerbils.

METHODS

Twenty Psammomys obesus gerbils were randomly assigned to receive a normal plant diet (controls) or a high fat diet. At baseline and 16-week later, body weight, plasma biochemical parameters (including lipid and carbohydrate levels) were evaluated. Myocardial samples were collected for pathobiological evaluation.

RESULTS

Sixteen-week high fat dieting resulted in body weight gain and hyperlipidemia, while levels of carbohydrates remained unchanged. At myocardial level, high fat diet induced structural disorganization, including cardiomyocyte hypertrophy, lipid accumulation, interstitial and perivascular fibrosis and increased number of infiltrating neutrophils. Myocardial expressions of pro-apoptotic Bax-to-Bcl-2 ratio, pro-inflammatory cytokines [interleukin (IL)-1β and tumor necrosis factor (TNF)-α], intercellular (ICAM1) and vascular adhesion molecules (VCAM1) increased, while gene encoding cardiac muscle protein, the alpha myosin heavy polypeptide (MYH6), was downregulated. Myocardial expressions of sarco(endo)plasmic calcium-ATPase (SERCA2) and voltage-dependent calcium channel (Cacna1c) decreased, while protein kinase A (PKA) and calcium-calmodulin-dependent protein kinase (CaMK2D) expressions increased. Myocardial expressions of ryanodine receptor, phospholamban and sodium/calcium exchanger (Slc8a1) did not change.

CONCLUSIONS

We conclude that a relative short period of high fat diet in Psammomys obesus results in severe alterations of cardiac structure, activation of inflammatory and apoptotic processes, and altered expression of calcium-cycling determinants.

Squalene is lipotoxic to yeast cells defective in lipid droplet biogenesis

The toxic effect of overloaded lipids on cell physiology and viability was described in various organisms. In this study we focused on the potential lipotoxicity of squalene, a linear triterpene synthesized in eukaryotic cells as an intermediate in sterol biosynthesis. Squalene toxicity was studied in the yeast Saccharomyces cerevisiae, a model unicellular eukaryote established in lipotoxicity studies. Squalene levels in yeast are typically low but its accumulation can be induced under specific conditions, e.g. by inhibition of squalene monooxygenase with the antimycotic terbinafine. At higher levels squalene is stored in lipid droplets. We demonstrated that low doses of terbinafine caused severe impairment of growth and loss of viability of the yeast mutant dga1Δ lro1Δ are1Δ are2Δ unable to form lipid droplets and that these defects were linked to squalene accumulation. The hypersensitivity of the lipid droplet-less mutant to terbinafine was alleviated by decreasing squalene accumulation with low doses of squalene synthase inhibitor zaragozic acid. Our results proved that accumulated squalene is lipotoxic to yeast cells if it cannot be efficiently sequestered in lipid droplets. This supports the hypothesis about the role of squalene in the fungicidal activity of terbinafine. Squalene toxicity may represent also a limiting factor for production of this high-value lipid in yeast.

Glucose fluctuation increased hepatocyte apoptosis under lipotoxicity and the involvement of mitochondrial permeability transition opening

Oxidative stress is considered to be an important factor in producing lethal hepatocyte injury associated with nonalcoholic fatty liver disease (NAFLD). Glucose fluctuation, more pronounced in patients with diabetes, has been recognized as an even stronger oxidative stress inducer than the sustained hyperglycemia. Here, we investigated the role of glucose variability in the development of the NAFLD based on hepatocyte apoptosis and possible mechanisms. To achieve this goal we studied C57BL/6J mice that were maintained on a high fat diet (HFD) and injected with glucose (3 g/kg) twice daily to induce intermittent high glucose (IHG). We also studied hepatic L02 cells incubated with palmitic acid (PA) to induce steatosis. The following experimental groups were compared: normal glucose (NG), sustained high glucose (SHG) and IHG with or without PA. We found that, although hepatic enzyme levels and liver lipid deposition were comparable between HFD mice injected with glucose or saline, the glucose injected mice displayed marked hepatocyte apoptosis and inflammation, accompanied by increased lipid peroxide in liver. In vitro, in the presence of PA, IHG increased L02 cell apoptosis and oxidative stress and produced pronounced mitochondrial dysfunction relative to the NG and SHG groups. Furthermore, treatment with the mitochondrial permeability transition (MPT) inhibitor, cyclosporin A (1.5 μmol/l), prevented mitochondrial dysfunction, oxidative stress and hepatocyte apoptosis. Our data suggests that IHG under lipotoxicity might contribute to the development of NAFLD by increasing oxidative stress and hepatocyte apoptosis via MPT and its related mitochondrial dysfunction.

Saturated phosphatidic acids mediate saturated fatty acid-induced vascular calcification and lipotoxicity

Recent evidence indicates that saturated fatty acid-induced (SFA-induced) lipotoxicity contributes to the pathogenesis of cardiovascular and metabolic diseases; however, the molecular mechanisms that underlie SFA-induced lipotoxicity remain unclear. Here, we have shown that repression of stearoyl-CoA desaturase (SCD) enzymes, which regulate the intracellular balance of SFAs and unsaturated FAs, and the subsequent accumulation of SFAs in vascular smooth muscle cells (VSMCs), are characteristic events in the development of vascular calcification. We evaluated whether SMC-specific inhibition of SCD and the resulting SFA accumulation plays a causative role in the pathogenesis of vascular calcification and generated mice with SMC-specific deletion of both Scd1 and Scd2. Mice lacking both SCD1 and SCD2 in SMCs displayed severe vascular calcification with increased ER stress. Moreover, we employed shRNA library screening and radiolabeling approaches, as well as in vitro and in vivo lipidomic analysis, and determined that fully saturated phosphatidic acids such as 1,2-distearoyl-PA (18:0/18:0-PA) mediate SFA-induced lipotoxicity and vascular calcification. Together, these results identify a key lipogenic pathway in SMCs that mediates vascular calcification.

Lean heart: Role of leptin in cardiac hypertrophy and metabolism

Leptin is an adipokine that has been linked with the cardiovascular complications resulting from obesity such as hypertension and heart disease. Obese patients have high levels of circulating leptin due to increased fat mass. Clinical and population studies have correlated high levels of circulating leptin with the development of cardiac hypertrophy in obesity. Leptin has also been demonstrated to increase the growth of cultured cardiomyocytes. However, several animal studies of obese leptin deficient mice have not supported a role for leptin in promoting cardiac hypertrophy so the role of leptin in this pathological process remains unclear. Leptin is also an important hormone in the regulation of cardiac metabolism where it supports oxidation of glucose and fatty acids. In addition, leptin plays a critical role in protecting the heart from excess lipid accumulation and the formation of toxic lipids in obesity a condition known as cardiac lipotoxicity. This paper focuses on the data supporting and refuting leptin’s role in promoting cardiac hypertrophy as well as its important role in the regulation of cardiac metabolism and protection against cardiac lipotoxicity.

Essential role of Nrf2 in the protective effect of lipoic acid against lipoapoptosis in hepatocytes

Excess of saturated free fatty acids, such as palmitic acid (PA), in hepatocytes has been implicated in nonalcoholic fatty liver disease. α-Lipoic acid (LA) is an antioxidant that protects against oxidative stress conditions. We have investigated the effects of LA in the early activation of oxidative and endoplasmic reticulum stress, lipid accumulation, and Nrf2-mediated antioxidant defenses in hepatocytes treated with PA or in rats fed a high-fat diet. In primary human hepatocytes, a lipotoxic concentration of PA triggered endoplasmic reticulum stress, induced the apoptotic transcription factor CHOP, and increased the percentage of apoptotic cells. Cotreatment with LA prevented these effects. Similar results were found in mouse hepatocytes in which LA attenuated PA-mediated activation of caspase 3 and reduced lipid accumulation by decreasing PA uptake and increasing fatty acid oxidation and lipophagy, thereby preventing lipoapoptosis. Moreover, LA augmented the proliferation capacity of hepatocytes after PA challenge. Antioxidant effects of LA ameliorated reactive oxygen species production and endoplasmic reticulum stress and protected against mitochondrial apoptosis in hepatocytes treated with PA. Cotreatment with PA and LA induced an early nuclear translocation of Nrf2 and activated antioxidant enzymes, whereas reduction of Nrf2 by siRNA abolished the benefit of LA on PA-induced lipoapoptosis. Importantly, posttreatment with LA reversed the established damage induced by PA in hepatocytes, as well as preventing obesity-induced oxidative stress and lipoapoptosis in rat liver. In conclusion, our work has revealed that in hepatocytes, Nrf2 is an essential early player in the rescue of oxidative stress by LA leading to protection against PA-mediated lipoapoptosis.

Body mass index (BMI) is associated with microalbuminuria in Chinese hypertensive patients

There is no general consensus on possible factors associated with microalbuminuria in hypertensive patients nor any reported study about this issue in Chinese patients. To examine this issues, 944 hypertensive patients were enrolled in a study based on a cross-sectional survey conducted in Southern China. Multivariate regression analyses were performed to identify the factors related with the presence of microalbuminuria and urinary excretion of albumin. The prevalence of microalbuminuria in hypertensive and non-diabetic hypertensive patients were 17.16% and 15.25%, respectively. Body mass index (BMI), but not waist circumference (WC), were independently associated with microalbuminuria and the values of urinary albumin to creatinine ratio (ACR) based on multiple regression analyses, even after excluding diabetic patients and patients taking inhibitors of the renin-angiotensin system from the analyses. Furthermore, patients with obesity (BMI ≥28) had higher levels of ACR, compared with those with normal weight (BMI <24 kg/m²) and overweight (24 kg/m²≤ BMI < 28). In conclusion, BMI, as a modifiable factor, is closely associated with microalbuminuria among Chinese hypertensive patients, which may provide a basis for future development of intervention approaches for these patients.

Mmu-miR-615-3p regulates lipoapoptosis by inhibiting C/EBP homologous protein

Lipoapoptosis occurring due to an excess of saturated free fatty acids such as palmitate is a key pathogenic event in the initiation of nonalcoholic fatty liver disease. Palmitate loading of cells activates the endoplasmic reticulum stress response, including induction of the proapoptotic transcription factor C/EBP homologous protein (CHOP). Furthermore, the loss of microRNAs is implicated in regulating apoptosis under conditions of endoplasmic reticulum (ER) stress. The aim of this study was to identify specific microRNAs regulating CHOP expression during palmitate-induced ER stress. Five microRNAs were repressed under palmitate-induced endoplasmic reticulum stress conditions in hepatocyte cell lines (miR-92b-3p, miR-328-3p, miR-484, miR-574-5p, and miR-615-3p). We identified miR-615-3p as a candidate microRNA which was repressed by palmitate treatment and regulated CHOP protein expression, by RNA sequencing and in silico analyses, respectively. There is a single miR-615-3p binding site in the 3′untranslated region (UTR) of the Chop transcript. We characterized this as a functional binding site using a reporter gene-based assay. Augmentation of miR-615-3p levels, using a precursor molecule, repressed CHOP expression; and under these conditions palmitate- or tunicamycin-induced cell death were significantly reduced. Our results suggest that palmitate-induced apoptosis requires maximal expression of CHOP which is achieved via the downregulation of its repressive microRNA, miR-615-3p. We speculate that enhancement of miR-615-3p levels may be of therapeutic benefit by inhibiting palmitate-induced hepatocyte lipoapoptosis.

Discovery and characterization of the first genuine avian leptin gene in the rock dove (Columba livia)

Leptin, the key regulator of mammalian energy balance, has been at the center of a great controversy in avian biology for the last 15 years since initial reports of a putative leptin gene (LEP) in chickens. Here, we characterize a novel LEP in rock dove (Columba livia) with low similarity of the predicted protein sequence (30% identity, 47% similarity) to the human ortholog. Searching the Sequence-Read-Archive database revealed leptin transcripts, in the dove's liver, with 2 noncoding exons preceding 2 coding exons. This unusual 4-exon structure was validated by sequencing of a GC-rich product (76% GC, 721 bp) amplified from liver RNA by RT-PCR. Sequence alignment of the dove leptin with orthologous leptins indicated that it consists of a leader peptide (21 amino acids; aa) followed by the mature protein (160 aa), which has a putative structure typical of 4-helical-bundle cytokines except that it is 12 aa longer than human leptin. Extra residues (10 aa) were located within the loop between 2 5'-helices, interrupting the amino acid motif that is conserved in tetrapods and considered essential for activation of leptin receptor (LEPR) but not for receptor binding per se. Quantitative RT-PCR of 11 tissues showed highest (P < .05) expression of LEP in the dove's liver, whereas the dove LEPR peaked (P < .01) in the pituitary. Both genes were prominently expressed in the gonads and at lower levels in tissues involved in mammalian leptin signaling (adipose; hypothalamus). A bioassay based on activation of the chicken LEPR in vitro showed leptin activity in the dove's circulation, suggesting that dove LEP encodes an active protein, despite the interrupted loop motif. Providing tools to study energy-balance control at an evolutionary perspective, our original demonstration of leptin signaling in dove predicts a more ancient role of leptin in growth and reproduction in birds, rather than appetite control.

Anti-lipoapoptotic effect of Artemisia capillaris extract on free fatty acids-induced HepG2 cells

Background

Artemisia capillaris (AC) has been recognized as one of the promising candidates for hepatoprotective, hypoglycemic, hypolipidemic, antiobesitic and anti-inflammatory therapeutic effectiveness. This study evaluated the inherent mechanism and anti-apoptotic activity of 30% ethanol extract of AC (AC extract) 100 μg/ml on free fatty acids (FFAs)-induced HepG2 cellular steatosis and lipoapoptosis.

Methods

Hepatic steatosis was induced by culturing HepG2 cells with a FFAs mixture (oleic and palmitic acid at the proportion of 2:1) for 24 h, thus ultimately giving rise to lipoapoptosis. Cell viability and lipid accumulation were detected by MTT assay and Oil Red O staining method respectively and Caspase-3, −9, Bax, Bcl-2, p-JNK and PUMA were measured for lipoapoptosis after 24 hours.

Results

AC extract significantly improved the FFAs-induced steatosis without cytotoxicity and Caspase-3, −9, Bax and Bcl-2 were modulated profitably to HepG2 cells after AC treatment. In addition, AC extract inhibited the activation of c-Jun NH₂ terminal kinase (JNK) and PUMA, which mechanism is related to non-alcoholic steatohepatitis (NASH).

Conclusions

Combined together, AC extract exerted an obvious hypolipidemic and anti-apoptotic effect, indicating that AC extract might have potential therapeutic herb against NASH.

Proteases in cardiometabolic diseases: Pathophysiology, molecular mechanisms and clinical applications

Cardiovascular disease is the leading cause of death in the U.S. and other developed countries. Metabolic syndrome, including obesity, diabetes/insulin resistance, hypertension and dyslipidemia is a major threat for public health in the modern society. It is well established that metabolic syndrome contributes to the development of cardiovascular disease collective called as cardiometabolic disease. Despite documented studies in the research field of cardiometabolic disease, the underlying mechanisms are far from clear. Proteases are enzymes that break down proteins, many of which have been implicated in various diseases including cardiac disease. Matrix metalloproteinase (MMP), calpain, cathepsin and caspase are among the major proteases involved in cardiac remodeling. Recent studies have also implicated proteases in the pathogenesis of cardiometabolic disease. Elevated expression and activities of proteases in atherosclerosis, coronary heart disease, obesity/insulin-associated heart disease as well as hypertensive heart disease have been documented. Furthermore, transgenic animals that are deficient in or over-express proteases allow scientists to understand the causal relationship between proteases and cardiometabolic disease. Mechanistically, MMPs and cathepsins exert their effect on cardiometabolic diseases mainly through modifying the extracellular matrix. However, MMP and cathepsin are also reported to affect intracellular proteins, by which they contribute to the development of cardiometabolic diseases. On the other hand, activation of calpain and caspases has been shown to influence intracellular signaling cascade including the NF-κB and apoptosis pathways. Clinically, proteases are reported to function as biomarkers of cardiometabolic diseases. More importantly, the inhibitors of proteases are credited with beneficial cardiometabolic profile, although the exact molecular mechanisms underlying these salutary effects are still under investigation. A better understanding of the role of MMPs, cathepsins, calpains and caspases in cardiometabolic diseases process may yield novel therapeutic targets for treating or controlling these diseases. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Mixed lineage kinase 3 deficient mice are protected against the high fat high carbohydrate diet-induced steatohepatitis

BACKGROUND & AIMS

C-Jun N-terminal kinase (JNK) activation is pivotal in the development of nonalcoholic steatohepatitis (NASH). Mixed lineage kinase 3 (MLK) 3 is one of the mitogen activated protein kinase kinase kinase (MAP3K) that mediates JNK activation in the liver. Despite this concept, the role of MLK3 in modulating liver injury during nutrient excess has not been explored. Our aim was to determine if MLK3 deficient mice were protected against high fat high carbohydrate (HFHC) diet-induced NASH.

METHODS

We employed eight-week-old Mlk3(-/-) male C57BL/6J mice, and wild type (WT) mice C57BL/6J as controls. Mice were fed a HFHC or a chow diet adlib for 16 weeks.

RESULTS

Hepatic JNK activating phosphorylation was readily absent in the Mlk3(-/-) mice fed the HFHC diet, but not in WT mice. This inhibition of JNK activation was hepatoprotective. Despite a comparable increase in weight gain, hepatic steatosis by histological examination and hepatic triglyceride quantification was reduced in HFHC diet-fed Mlk3(-/-) mice compared with WT mice. In addition, compared with the WT mice, HFHC diet-fed Mlk3(-/-) mice had significantly attenuated liver injury as manifested by reduced ALT levels, hepatocyte apoptosis, markers of hepatic inflammation and indices of hepatic fibrogenesis.

CONCLUSION

Our results suggest that loss of MLK3 in mice is protective against HFHC diet-induced NASH, in a weight-independent fashion, through attenuation of JNK activation. MLK3 is a potential therapeutic target for the treatment of human NASH.

Saturated free fatty acid sodium palmitate-induced lipoapoptosis by targeting glycogen synthase kinase-3β activation in human liver cells

BACKGROUND

Elevated serum saturated fatty acid levels and hepatocyte lipoapoptosis are features of nonalcoholic fatty liver disease (NAFLD).

AIM

The purpose of this study was to investigate saturated fatty acid induction of lipoapoptosis in human liver cells and the underlying mechanisms.

METHODS

Human liver L02 and HepG2 cells were treated with sodium palmitate, a saturated fatty acid, for up to 48 h with or without lithium chloride, a glycogen synthase kinase-3β (GSK-3β) inhibitor, or GSK-3β shRNA transfection. Transmission electron microscopy was used to detect morphological changes, flow cytometry was used to detect apoptosis, a colorimetric assay was used to detect caspase-3 activity, and western blot analysis was used to detect protein expression.

RESULTS

The data showed that sodium palmitate was able to induce lipoapoptosis in L02 and HepG2 cells. Western blot analysis showed that sodium palmitate activated GSK-3β protein, which was indicated by dephosphorylation of GSK-3β at Ser-9. However, inhibition of GSK-3β activity with lithium chloride treatment or knockdown of GSK-3β expression with shRNA suppressed sodium palmitate-induced lipoapoptosis in L02 and HepG2 cells. On a molecular level, inhibition of GSK-3β expression or activity suppressed sodium palmitate-induced c-Jun-N-terminal kinase (JNK) phosphorylation and Bax upregulation, whereas GSK-3β inhibition did not affect endoplasmic reticulum stress-induced activation of unfolded protein response.

CONCLUSIONS

The present data demonstrated that saturated fatty acid sodium palmitate-induced lipoapoptosis in human liver L02 and HepG2 cells was regulated by GSK-3β activation, which led to JNK activation and Bax upregulation. This finding indicates that GSK-3β inhibition may be a potential therapeutic target to control NAFLD.

Mechanisms of palmitate-induced cell death in human osteoblasts

Lipotoxicity is an overload of lipids in non-adipose tissues that affects function and induces cell death. Lipotoxicity has been demonstrated in bone cells in vitro using osteoblasts and adipocytes in coculture. In this condition, lipotoxicity was induced by high levels of saturated fatty acids (mostly palmitate) secreted by cultured adipocytes acting in a paracrine manner. In the present study, we aimed to identify the underlying mechanisms of lipotoxicity in human osteoblasts. Palmitate induced autophagy in cultured osteoblasts, which was preceded by the activation of autophagosomes that surround palmitate droplets. Palmitate also induced apoptosis though the activation of the Fas/Jun kinase (JNK) apoptotic pathway. In addition, osteoblasts could be protected from lipotoxicity by inhibiting autophagy with the phosphoinositide kinase inhibitor 3-methyladenine or by inhibiting apoptosis with the JNK inhibitor SP600125. In summary, we have identified two major molecular mechanisms of lipotoxicity in osteoblasts and in doing so we have identified a new potential therapeutic approach to prevent osteoblast dysfunction and death, which are common features of age-related bone loss and osteoporosis.

Obesity and risk of sepsis: a population-based cohort study

OBJECTIVE

Sepsis, the syndrome of microbial infection complicated by systemic inflammation, is associated with significant morbidity and mortality. To determine if obesity increases risk of sepsis events.

DESIGN AND METHODS

Data from the 30,239 subject population-based longitudinal cohort study REasons for Geographic and Racial Differences in Stroke (REGARDS) were used. Using measurements at the start of the study, we defined obesity using body mass index (BMI; <18.5 kg/m(2) = underweight, 18.5-24.9 = normal, 25.0-29.9 = overweight, 30.0-39.9 = obese, ≥40 = morbidly obese) and waist circumference (WC; [male ≤102 cm or female ≤88 cm] = normal, [male >102 cm or female >88 cm] = obese). Over an 8-year observation period, we evaluated the association between obesity and subsequent sepsis events, adjusting for sociodemographic factors, health behaviors, chronic medical conditions, statin use, and high-sensitivity C-reactive protein.

RESULTS

There were 975 incident sepsis events. Compared to those with a BMI of 18.5-24.9, sepsis risk was higher only for BMI ≥ 40 (hazard ratio [HR] 1.57, [1.16-2.14]). Risk of sepsis was associated with increased WC (HR 1.34 [1.14-1.56]). In a model with both BMI and WC, sepsis risk was associated with increased WC (HR 1.47 [1.20-1.79]) but not BMI.

CONCLUSIONS

Obesity is independently associated with future sepsis events. WC is a better predictor of future sepsis risk than BMI.

Abdominal obesity is associated with albuminuria in women: the 2011 Korea National Health and Nutrition Examination Survey

BACKGROUND

The effects of obesity on the kidney, apart from diabetes or hypertension, have not drawn much attention. Moreover, only a few studies have reported the relationship between obesity status and albuminuria in Asian countries, including South Korea. Therefore, this study aimed to investigate the association between obesity status and albuminuria in Korean adults.

METHODS

We analyzed data from the 2011 Korea National Health and Nutrition Examination Survey. Of the 4,979 subjects included in the general-population group, 3,274 were sorted into a nondiabetic and nonhypertensive population group. Obesity status was measured by body mass index and waist circumference. Albuminuria was defined as a urine albumin-to-creatinine ratio ≥30 mg/g.

RESULTS

Abdominally obese women were at higher risk for albuminuria than were women without abdominal obesity both in the general population (odds ratio [OR], 95% confidence interval [CI]: 2.08 [1.04-4.16]) and in the nondiabetic and nonhypertensive population (OR [95% CI]: 6.96 [2.34-20.64]) after further adjustment for confounders. Among generally nonobese women, abdominally obese women were at higher risk for albuminuria than were women without abdominal obesity both in the general population (OR [95% CI]: 2.82 [1.51-5.29]) and in the nondiabetic and nonhypertensive population (OR [95% CI]: 5.32 [1.47-19.22]).

CONCLUSION

Abdominal obesity is associated with an increased risk for albuminuria in Korean women, independently of diabetes or hypertension. Screening for abdominal obesity, especially in women, may therefore provide earlier identification of individuals at risk for developing renal disease and cardiovascular disease, even those who are nondiabetic and nonhypertensive.

Enhanced endoplasmic reticulum SERCA activity by overexpression of hepatic stimulator substance gene prevents hepatic cells from ER stress-induced apoptosis

Although the potential pathogenesis of nonalcoholic fatty liver disease (NAFLD) is unclear, increasing evidence indicates that endoplasmic reticulum (ER) stress may link free fatty acids to NAFLD. Since we previously reported that hepatic stimulator substance (HSS) could protect the liver from steatosis, this study is aimed to investigate whether HSS protection could be related with its inhibition on ER stress. The HSS gene was stably transfected into BEL-7402 hepatoma cells and effectively expressed in ER. The palmitic acid (PA)-induced heptocyte lipotoxicity was reproduced in the HSS-transfected cells, and HSS alleviation of the ER stress and apoptosis were subsequently examined. The results showed that PA treatment led to a heavy accumulation of fatty acids within the cells and a remarkable increase in reactive oxygen species (ROS). However, in the HSS-expressing cells, production of ROS was inhibited and ER stress-related marker glucose-regulated protein 78 (GRP-78), sterol regulatory element-binding protein (SREBP), anti-phospho-PRK-1ike ER kinase (p-PERK), anti-phospho-eukaryotic initiation factor 2α (p-eIF2α), and anti-C/EBP homologous protein (CHOP) were downregulated compared with the wild-type or mutant HSS-transfected cells. Furthermore, PA treatment severely impaired the activity of sarco-endoplasmic reticulum Ca(2+)-ATPase (SERCA), leading to imbalanced calcium homeostasis during ER stress, which could be rescued in the HSS-trasfected cells. The protection provided by HSS to the SERCA is identical to that observed with N-acetyl-l-cysteine (NAC) and sodium dimercaptopropane sulfonate (Na-DMPS), which are two typical free radical scavengers. As a consequence, the rate of ER stress-mediated apoptosis in the HSS-expressing cells was significantly reduced. In conclusion, the protective effect of HSS against ER stress may be associated with the removal of ROS to restore the activity of the SERCA.

Lipids and cell death in yeast

Understanding lipid-induced malfunction represents a major challenge of today's biomedical research. The connection of lipids to cellular and organ dysfunction, cell death, and disease (often referred to as lipotoxicity) is more complex than the sole lipotoxic effects of excess free fatty acids and requires genetically tractable model systems for mechanistic investigation. We herein summarize recent advances in the field of lipid-induced toxicity that employ the established model system for cell death and aging research of budding yeast Saccharomyces cerevisiae. Studies in yeast have shed light on various aspects of lipotoxicity, including free fatty acid toxicity, sphingolipid-modulated cell death as well as the involvement of cardiolipin and lipid peroxidation in the mitochondrial pathways of apoptosis. Regimens used range from exogenously applied lipids, genetic modulation of lipolysis and triacylglyceride synthesis, variations in sphingolipid/ceramide metabolism as well as changes in peroxisome function by either genetic or pharmacological means. In future, the yeast model of programmed cell death will further contribute to the clarification of crucial questions of lipid-associated malfunction.