Mechanisms of lipoapoptosis: implications for human heart disease

A Barth Syndrome Patient-Derived D75H Point Mutation in TAFAZZIN Drives Progressive Cardiomyopathy in Mice

Cardiomyopathy is the predominant defect in Barth syndrome (BTHS) and is caused by a mutation of the X-linked Tafazzin (TAZ) gene, which encodes an enzyme responsible for remodeling mitochondrial cardiolipin. Despite the known importance of mitochondrial dysfunction in BTHS, how specific TAZ mutations cause diverse BTHS heart phenotypes remains poorly understood. We generated a patient-tailored CRISPR/Cas9 knock-in mouse allele (TazPM) that phenocopies BTHS clinical traits. As TazPM males express a stable mutant protein, we assessed cardiac metabolic dysfunction and mitochondrial changes and identified temporally altered cardioprotective signaling effectors. Specifically, juvenile TazPM males exhibit mild left ventricular dilation in systole but have unaltered fatty acid/amino acid metabolism and normal adenosine triphosphate (ATP). This occurs in concert with a hyperactive p53 pathway, elevation of cardioprotective antioxidant pathways, and induced autophagy-mediated early senescence in juvenile TazPM hearts. However, adult TazPM males exhibit chronic heart failure with reduced growth and ejection fraction, cardiac fibrosis, reduced ATP, and suppressed fatty acid/amino acid metabolism. This biphasic changeover from a mild-to-severe heart phenotype coincides with p53 suppression, downregulation of cardioprotective antioxidant pathways, and the onset of terminal senescence in adult TazPM hearts. Herein, we report a BTHS genotype/phenotype correlation and reveal that absent Taz acyltransferase function is sufficient to drive progressive cardiomyopathy.

IFITM3 mediates inflammation induced myocardial injury through JAK2/STAT3 signaling pathway

Myocarditis is an inflammation of the heart muscle often associated with viral infections and can lead to dilated cardiomyopathy. Interferon-induced transmembrane protein 3 (IFITM3) is a small endosomal membrane protein with anti-viral activity against multiple viruses and is also implicated in non-infectious diseases such as cancer and Alzheimer's Disease. Since the IFITM3 proteins are expressed both in T cells and in cardiomyocytes, it is reasonable to hypothesize that these molecules could affect myocarditis either through their effect on the autoimmune response or through direct modulation of cardiomyocyte damage. The aim of this study was to investigate the role of IFITM3 in experimental autoimmune myocarditis (EAM)-mediated myocardial injury. Immunization of rats with cardiac myosin results in substantial cardiac inflammation and is associated with increased expression of IFITM3 after 21 days. In vivo IFITM3 shRNA knockdown using the lentivirus transfection method reduced cardiac injury while restoring IFITM3 expression reversed the protective effect of IFITM3 RNA interference. To determine the direct impact of IFITM3, the rat ventricular cell line, H9c2, was treated with palmitic acid which causes apoptosis in these cells. Suppressing IFITM3 expression protects H9c2 cells while overexpressing IFITM3 enhances cell injury. JAK inhibitors reduced IFITM3-mediated myocardial cell injury. In conclusion, IFITM3 may mediate myocardial injury in EAM rats and palmitic acid-induced damage to H9c2 cells through the JAK2/STAT3 pathway.

Energy metabolism and redox balance: How phytochemicals influence heart failure treatment

Heart Failure (HF) epitomizes a formidable global health quandary characterized by marked morbidity and mortality. It has been established that severe derangements in energy metabolism are central to the pathogenesis of HF, culminating in an inadequate cardiac energy milieu, which, in turn, precipitates cardiac pump dysfunction and systemic energy metabolic failure, thereby steering the trajectory and potential recuperation of HF. The conventional therapeutic paradigms for HF predominantly target amelioration of heart rate, and cardiac preload and afterload, proffering symptomatic palliation or decelerating the disease progression. However, the realm of therapeutics targeting the cardiac energy metabolism remains largely uncharted. This review delineates the quintessential characteristics of cardiac energy metabolism in healthy hearts, and the metabolic aberrations observed during HF, alongside the associated metabolic pathways and targets. Furthermore, we delve into the potential of phytochemicals in rectifying the redox disequilibrium and the perturbations in energy metabolism observed in HF. Through an exhaustive analysis of recent advancements, we underscore the promise of phytochemicals in modulating these pathways, thereby unfurling a novel vista on HF therapeutics. Given their potential in orchestrating cardiac energy metabolism, phytochemicals are emerging as a burgeoning frontier for HF treatment. The review accentuates the imperative for deeper exploration into how these phytochemicals specifically intervene in cardiac energy metabolism, and the subsequent translation of these findings into clinical applications, thereby broadening the horizon for HF treatment modalities.

Mechanism of Obesity-Related Lipotoxicity and Clinical Perspective

The link between cellular exposure to fatty acid species and toxicity phenotypes remains poorly understood. However, structural characterization and functional profiling of human plasma free fatty acids (FFAs) analysis has revealed that FFAs are located either in the toxic cluster or in the cluster that is transcriptionally responsive to lipotoxic stress and creates genetic risk factors. Genome-wide short hairpin RNA screen has identified more than 350 genes modulating lipotoxicity. Hypertrophic adipocytes in obese adipose are both unable to expand further to store excess lipids in the diet and are resistant to the antilipolytic action of insulin. In addition to lipolysis, the inability of packaging the excess lipids into lipid droplets causes circulating fatty acids to reach toxic levels in non-adipose tissues. Deleterious effects of accumulated lipid in non-adipose tissues are known as lipotoxicity. Although triglycerides serve a storage function for long-chain non-esterified fatty acid and their products such as ceramide and diacylglycerols (DAGs), overloading of palmitic acid fraction of saturated fatty acids (SFAs) raises ceramide levels. The excess DAG and ceramide load create harmful effects on multiple organs and systems, inducing chronic inflammation in obesity. Thus, lipotoxic inflammation results in β cells death and pancreatic islets dysfunction. Endoplasmic reticulum stress stimuli induce lipolysis by activating cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) and extracellular signal-regulated kinase (Erk) 1/2 signaling in adipocytes. However, palmitic acid-induced endoplasmic reticulum stress-c-Jun N-terminal kinase (JNK)-autophagy axis in hypertrophic adipocytes is a pro-survival mechanism against endoplasmic reticulum stress and cell death induced by SFAs. Endoplasmic reticulum-localized acyl-coenzyme A (CoA): glycerol-3-phosphate acyltransferase (GPAT) enzymes are mediators of lipotoxicity, and inhibiting these enzymes has therapeutic potential for lipotoxicity. Lipotoxicity increases the number of autophagosomes, which engulf palmitic acid, and thus suppress the autophagic turnover. Fatty acid desaturation promotes palmitate detoxification and storages into triglycerides. As therapeutic targets of glucolipotoxicity, in addition to caloric restriction and exercise, there are four different pharmacological approaches, which consist of metformin, glucagon-like peptide 1 (GLP-1) receptor agonists, peroxisome proliferator-activated receptor-gamma (PPARγ) ligands thiazolidinediones, and chaperones are still used in clinical practice. Furthermore, induction of the brown fat-like phenotype with the mixture of eicosapentanoic acid and docosahexaenoic acid appears as a potential therapeutic application for treatment of lipotoxicity.

Incidence of atrial and ventricular arrhythmias in obese patients with heart failure with reduced ejection fraction treated with sacubitril/valsartan

AIM

To compare clinical outcomes among patients with heart failure and reduced ejection fraction (HFrEF) according to body mass index (BMI) after initiating treatment with an angiotensin-receptor neprilysin inhibitor (ARNI).

METHODS

We gathered data from 2016 to 2020 at the University Medical Center Mannheim; 208 consecutive patients were divided into two groups according to BMI (< 30 kg/m2 ; n = 116, ≥ 30 kg/m2 ; n = 92). Clinical outcomes, including mortality rate, all-cause hospitalizations and congestion, were systematically analysed.

RESULTS

At the 12-month follow-up, the mortality rate was similar in both groups (7.9% in BMI < 30 kg/m2 vs. 5.6% in BMI ≥ 30 kg/m2 ; P = .76). All-cause hospitalization before ARNI treatment was comparable in both groups (63.8% in BMI < 30 kg/m2 vs. 57.6% in BMI ≥ 30 kg/m2 ; P = .69). After ARNI treatment, the hospitalization rate was also comparable in both groups at the 12-month follow-up (52.2% in BMI < 30 kg/m2 vs. 53.7% in BMI ≥ 30 kg/m2 ; P = .73). Obese patients experienced more congestion compared with non-obese patients at follow-up, without statistical significance (6.8% in BMI < 30 kg/m2 vs. 15.5% in BMI ≥ 30 kg/m2 ; P = .11). Median left ventricular ejection fraction (LVEF) improved in both groups, but significantly more in non-obese compared with obese patients at the 12-month follow-up (from 26% [3%-45%] [min.-max.] vs. 29% [10%-45%] [min.-max.] [P = .56] to 35.5% [15%-59%] [min.-max.] vs. 30% [13%-50%] [min.-max.] [P = .03], respectively). The incidence of atrial fibrillation (AF), non-sustained (ns) and sustained ventricular tachycardia (VT) and ventricular fibrillation (VF) was less in non-obese than in obese patients after initiation of sacubitril/valsartan at the 12-month follow-up (AF: 43.5% vs. 53.7%; P = .20; nsVT: 9.8% vs. 28.4%; P = .01; VT: 14.1% vs. 17.9%; P = .52; VF: 7.6% vs. 13.4%; P = .23).

CONCLUSIONS

The incidence of congestion in obese patients was higher compared with non-obese patients. LVEF improved significantly more in non-obese compared with obese HFrEF patients. Furthermore, AF and the ventricular tachyarrhythmia rate were revealed more in obesity compared with those without obesity at the 12-month follow-up.

Cardiac lipid metabolism, mitochondrial function, and heart failure

A fine balance between uptake, storage, and the use of high energy fuels, like lipids, is crucial in the homeostasis of different metabolic tissues. Nowhere is this balance more important and more precarious than in the heart. This highly energy-demanding muscle normally oxidizes almost all the available substrates to generate energy, with fatty acids being the preferred source under physiological conditions. In patients with cardiomyopathies and heart failure, changes in the main energetic substrate are observed; these hearts often prefer to utilize glucose rather than oxidizing fatty acids. An imbalance between uptake and oxidation of fatty acid can result in cellular lipid accumulation and cytotoxicity. In this review, we will focus on the sources and uptake pathways used to direct fatty acids to cardiomyocytes. We will then discuss the intracellular machinery used to either store or oxidize these lipids and explain how disruptions in homeostasis can lead to mitochondrial dysfunction and heart failure. Moreover, we will also discuss the role of cholesterol accumulation in cardiomyocytes. Our discussion will attempt to weave in vitro experiments and in vivo data from mice and humans and use several human diseases to illustrate metabolism gone haywire as a cause of or accomplice to cardiac dysfunction.

Ginsenoside Rc from Panax Ginseng Ameliorates Palmitate-Induced UB/OC-2 Cochlear Cell Injury

By 2050, at least 700 million people will require hearing therapy while 2.5 billion are projected to suffer from hearing loss. Sensorineural hearing loss (SNHL) arises from the inability of the inner ear to convert fluid waves into neural electric signals because of injury to cochlear hair cells that has resulted in their death. In addition, systemic chronic inflammation implicated in other pathologies may exacerbate cell death leading to SNHL. Phytochemicals have emerged as a possible solution because of the growing evidence of their anti-inflammatory, antioxidant, and anti-apoptotic properties. Ginseng and its bioactive molecules, ginsenosides, exhibit effects that suppress pro-inflammatory signaling and protect against apoptosis. In the current study, we investigated the effects of ginsenoside Rc (G-Rc) on UB/OC-2 primary murine sensory hair cell survival in response to palmitate-induced injury. G-Rc promoted UB/OC-2 cell survival and cell cycle progression. Additionally, G-Rc enhanced the differentiation of UB/OC-2 cells into functional sensory hair cells and alleviated palmitate-induced inflammation, endoplasmic reticulum stress, and apoptosis. The current study offers novel insights into the effects of G-Rc as a potential adjuvant for SNHL and warrants further studies elucidating the molecular mechanisms.

Does the Mediterranean diet reduce the odds of diabetic nephropathy in women? A case–control study

Background

In recent decades, the prevalence of chronic diseases such as diabetes is increasing. One of the major complications of diabetes is diabetic nephropathy (DN), so it is important to find a way that can delay or control the onset of DN. Therefore, in this study, we investigated the relationship between the Mediterranean diet (MED) and the odds of DN.

Methods

This case–control study was performed among 210 women (30–65 years) who were referred to the Kowsar Diabetes Clinic in Semnan, Iran. Biochemical variables and anthropometric measurements were assessed. The food frequency questionnaire (FFQ) was used to calculate dietary intakes. Data from dietary intakes based on the FFQ were used to evaluate the MED score. Logistic regression was used to examine the associations.

Results

Our results showed that in the crude model with higher adherence to the MED (OR: 0.272; 95% CI: 0.154, 0.481; P = 0.001), the odds of DN has reduced by 73%, and in model 1, after controlling for potential confounders, with higher adherence to the MED (OR: 0.239; 95% CI: 0.128, 0.447; P = 0.001), the odds of DN has reduced by 76% compared to low adherence. Also, in model 1, significant associations were observed between high consumption of grains (OR: 0.360; 95% CI: 0.191, 0.676; P = 0.001), legumes (OR: 0.156; 95% CI: 0.083, 0.292; P = 0.001), vegetables (OR: 0.273; 95% CI: 0.149, 0.501; P = 0.001), fruits (OR: 0.179; 95% CI: 0.093, 0.347; P = 0.001), fish (OR: 0.459; 95% CI: 0.254, 0.827; P = 0.01), and reduced odds of DN (P &lt; 0.05).

Conclusion

We observed that with higher adherence to the MED, the odds of DN had reduced through mechanisms. However, additional studies are needed to confirm these findings.

Role of apolipoprotein O in autophagy via the p38 mitogen-activated protein kinase signaling pathway in myocardial infarction

OBJECTIVE

To explore the role and possible mechanisms of action of apolipoprotein O (APOO) in autophagy in Myocardial Infarction (MI) in vivo and in vitro.

METHODS

Differential gene expression and single Gene Set Enrichment Analysis (GSEA) were used to evaluate MI-related candidate genes. Animal and cell MI models were established. Sh-APOO, si-APOO, and SB203580 were used to inhibit the expression of APOO or p38MAPK. Western blot and qRT-PCR were used to analyze the expression levels of the target protein or mRNA. Apoptosis was observed using the TUNEL assay. The plasma concentrations of CK-MB and cTn-I in humans and mice were determined.

RESULTS

In the GSE23294 dataset, APOO mRNA was highly expressed in the left ventricle of mice with MI; GSEA revealed that APOO was positively correlated with p38MAPK, autophagy, and apoptosis. The plasma concentration of APOO in patients with MI was significantly higher than that in healthy subjects. The expression of APOO, Beclin-1, LC3, and Bax in mouse and AC16 cell MI models increased, while the level of Bcl-2 decreased. After silencing the APOO gene, the expression of APOO was downregulated; meanwhile, changes in autophagy, apoptosis and myocardial cell injury were reversed in vivo and in vitro. Furthermore, autophagy was alleviated after AC16 cells were treated with SB203580.

CONCLUSIONS

The increased APOO expression in mouse and cell MI models may activate autophagy and apoptosis by regulating the p38MAPK signaling pathway, thus aggravating the myocardial injury.

Plin5, a New Target in Diabetic Cardiomyopathy

Abnormal lipid accumulation is commonly observed in diabetic cardiomyopathy (DC), which can create a lipotoxic microenvironment and damage cardiomyocytes. Lipid toxicity is an important pathogenic factor due to abnormal lipid accumulation in DC. As a lipid droplet (LD) decomposition barrier, Plin5 can protect LDs from lipase decomposition and regulate lipid metabolism, which is involved in the occurrence and development of cardiovascular diseases. In recent years, studies have shown that Plin5 expression is involved in the pathogenesis of DC lipid toxicity, such as oxidative stress, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and insulin resistance (IR) and has become a key target of DC research. Therefore, understanding the relationship between Plin5 and DC progression as well as the mechanism of this process is crucial for developing new therapeutic approaches and exploring new therapeutic targets. This review is aimed at exploring the latest findings and roles of Plin5 in lipid metabolism and DC-related pathogenesis, to explore possible clinical intervention approaches.

Oocyte maturation under lipotoxic conditions induces carryover transcriptomic and functional alterations during post-hatching development of good-quality blastocysts: novel insights from a bovine embryo-transfer model

STUDY QUESTION

Does oocyte maturation under lipolytic conditions have detrimental carry-over effects on post-hatching embryo development of good-quality blastocysts after transfer?

SUMMARY ANSWER

Surviving, morphologically normal blastocysts derived from bovine oocytes that matured under lipotoxic conditions exhibit long-lasting cellular dysfunction at the transcriptomic and metabolic levels, which coincides with retarded post-hatching embryo development.

WHAT IS KNOWN ALREADY

There is increasing evidence showing that following maturation in pathophysiologically relevant lipotoxic conditions (as in obesity or metabolic syndrome), surviving blastocysts of good (transferable) morphological quality have persistent transcriptomic and epigenetic alteration even when in vitro embryo culture takes place under standard conditions. However, very little is known about subsequent development in the uterus after transfer.

STUDY DESIGN, SIZE, DURATION

Bovine oocytes were matured in vitro in the presence of pathophysiologically relevant, high non-esterified fatty acid (NEFA) concentrations (HIGH PA), or in basal NEFA concentrations (BASAL) as a physiological control. Eight healthy multiparous non-lactating Holstein cows were used for embryo transfers. Good-quality blastocysts (pools of eight) were transferred per cow, and cows were crossed over for treatments in the next replicate. Embryos were recovered 7 days later and assessed for post-hatching development, phenotypic features and gene expression profile. Blastocysts from solvent-free and NEFA-free maturation (CONTROL) were also tested for comparison.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Recovered Day 14 embryos were morphologically assessed and dissected into embryonic disk (ED) and extraembryonic tissue (EXT). Samples of EXT were cultured for 24 h to assess cellular metabolic activity (glucose and pyruvate consumption and lactate production) and embryos' ability to signal for maternal recognition of pregnancy (interferon-τ secretion; IFN-τ). ED and EXT samples were subjected to RNA sequencing to evaluate the genome-wide transcriptome patterns.

MAIN RESULTS AND THE ROLE OF CHANCE

The embryo recovery rate at Day 14 p.i. was not significantly different among treatment groups (P > 0.1). However, higher proportions of HIGH PA embryos were retarded in growth (in spherical stage) compared to the more elongated tubular stage embryos in the BASAL group (P < 0.05). Focusing on the normally developed tubular embryos in both groups, HIGH PA exposure resulted in altered cellular metabolism and altered transcriptome profile particularly in pathways related to redox-regulating mechanisms, apoptosis, cellular growth, interaction and differentiation, energy metabolism and epigenetic mechanisms, compared to BASAL embryos. Maturation under BASAL conditions did not have any significant effects on post-hatching development and cellular functions compared to CONTROL.

LARGE-SCALE DATA

The datasets of RNA sequencing analysis are available in the NCBI's Gene Expression Omnibus (GEO) repository, series accession number GSE127889 (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE127889). Datasets of differentially expressed genes and their gene ontology functions are available in the Mendeley datasets at http://dx.doi.org/10.17632/my2z7dvk9j.2.

LIMITATIONS, REASONS FOR CAUTION

The bovine model was used here to allow non-invasive embryo transfer and post-hatching recovery on Day 14. There are physiological differences in some characteristics of post-hatching embryo development between human and cows, such as embryo elongation and trophoblastic invasion. However, the main carry-over effects of oocyte maturation under lipolytic conditions described here are evident at the cellular level and therefore may also occur during post-hatching development in other species including humans. In addition, post-hatching development was studied here under a healthy uterine environment to focus on carry-over effects originating from the oocyte, whereas additional detrimental effects may be induced by maternal metabolic disorders due to adverse changes in the uterine microenvironment. RNA sequencing results were not verified by qPCR, and no solvent control was included.

WIDER IMPLICATIONS OF THE FINDINGS

Our observations may increase the awareness of the importance of maternal metabolic stress at the level of the preovulatory oocyte in relation to carry-over effects that may persist in the transferrable embryos. It should further stimulate new research about preventive and protective strategies to optimize maternal metabolic health around conception to maximize embryo viability and thus fertility outcome.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Flemish Research Fund (FWO grant 11L8716N and FWO project 42/FAO10300/6541). The authors declare there are no conflicts of interest.

Fatty acids present in commercial albumin preparations differentially affect development of murine embryos before and during implantation

OBJECTIVE

To characterize fatty acid (FA) profile of commercially available albumin products and determine their effect on embryonic development.

DESIGN

Research study.

SETTING

Private research facility.

ANIMAL(S)

Outbred mice aged 4-8 weeks.

INTERVENTION(S)

Gas chromatography-mass spectrometry was used to quantify the FA content of 15 commercial albumins. Embryos were produced in media containing different albumin products, with or without carnitine or exogenous FA supplementation, to determine their effect on embryo development in vitro.

MAIN OUTCOME MEASURE(S)

Total micrograms of FA per milligram of albumin for the 15 albumin products, blastocyst development, cell number, allocation to the trophectoderm (TE) or inner cell mass (ICM), and evaluation of morphology during implantation.

RESULT(S)

The albumin products contained 0.07-16.77 μg total FA/mg albumin. Compared to media with with >1.4 μg FA/mg albumin, media with <0.5 μg FA/mg albumin supported improved blastocyst development, and addition of carnitine mitigated this difference. Addition of palmitoleic acid or oleic acid individually did not improve blastocyst development and decreased ICM:TE ratio. However, in the presence of carnitine, there was improved blastocyst development and maintenance of the ICM:TE ratio. Embryos cultured in Vitrolife human serum albumin with supplementation of carnitine, palmitoleic acid, and oleic acid were more likely to develop cells positive for POU5F1 in an extended embryo culture than embryos cultured in Origio serum protein substitute.

CONCLUSION(S)

Commercial albumin products contain FAs, which vary in abundance. These FAs have different effects on embryo development and quality before and during the implantation stage. Several of these albumin preparations are routinely used for human-assisted reproductive technologies; therefore, serious consideration is warranted when selecting a product for clinical use.

HSF1 functions as a key defender against palmitic acid-induced ferroptosis in cardiomyocytes

Palmitic acid (PA)-induced myocardial injury is considered a critical contributor to the development of obesity and type 2 diabetes mellitus (T2DM)-related cardiomyopathy. However, the underlying mechanism has not been fully understood. Here, we demonstrated that PA induced the cell death of H9c2 cardiomyoblasts in a dose- and time-dependent manner, while different ferroptosis inhibitors significantly abrogated the cell death of H9c2 cardiomyoblasts and primary neonatal rat cardiomyocytes exposed to PA. Mechanistically, PA decreased the protein expression levels of both heat shock factor 1 (HSF1) and glutathione peroxidase 4 (GPX4) in a dose- and time-dependent manner, which were restored by different ferroptosis inhibitors. Overexpression of HSF1 not only alleviated PA-induced cell death and lipid peroxidation but also improved disturbed iron homeostasis by regulating the transcription of iron metabolism-related genes (e.g., Fth1, Tfrc, Slc40a1). Additionally, PA-blocked GPX4 protein expression was evidently restored by HSF1 overexpression. Inhibition of endoplasmic reticulum (ER) stress rather than autophagy contributed to HSF1-mediated GPX4 expression. Moreover, GPX4 overexpression protected against PA-induced ferroptosis, whereas knockdown of GPX4 reversed the anti-ferroptotic effect of HSF1. Consistent with the in vitro findings, PA-challenged Hsf1-/- mice exhibited more serious ferroptosis, increased Slc40a1 and Fth1 mRNA expression, decreased GPX4 and TFRC expression and enhanced ER stress in the heart compared with Hsf1+/+ mice. Altogether, HSF1 may function as a key defender against PA-induced ferroptosis in cardiomyocytes by maintaining cellular iron homeostasis and GPX4 expression.

Docosahexaenoic acid protection against palmitic acid-induced lipotoxicity in NGF-differentiated PC12 cells involves enhancement of autophagy and inhibition of apoptosis and necroptosis

Lipotoxicity (LTx) leads to cellular dysfunction and cell death and has been proposed to be an underlying process during traumatic and hypoxic injuries and neurodegenerative conditions in the nervous system. This study examines cellular mechanisms responsible for docosahexaenoic acid (DHA 22:6 n‐3) protection in nerve growth factor‐differentiated pheochromocytoma (NGFDPC12) cells from palmitic acid (PAM)‐mediated lipotoxicity (PAM‐LTx). NGFDPC12 cells exposed to PAM show a significant lipotoxicity demonstrated by a robust loss of cell viability, apoptosis, and increased HIF‐1α and BCL2/adenovirus E1B 19 kDa protein‐interacting protein 3 gene expression. Treatment of NGFDPC12 cells undergoing PAM‐LTx with the pan‐caspase inhibitor ZVAD did not protect, but shifted the process from apoptosis to necroptosis. This shift in cell death mechanism was evident by the appearance of the signature necroptotic Topo I protein cleavage fragments, phosphorylation of mixed lineage kinase domain‐like, and inhibition with necrostatin‐1. Cultures exposed to PAM and co‐treated with necrostatin‐1 (necroptosis inhibitor) and rapamycin (autophagy promoter), showed a significant protection against PAM‐LTx compared to necrostatin‐1 alone. In addition, co‐treatment with DHA, as well as 20:5 n‐3, 20:4 n‐6, and 22:5 n‐3, in the presence of PAM protected NGFDPC12 cells against LTx. DHA‐induced neuroprotection includes restoring normal levels of HIF‐1α and BCL2/adenovirus E1B 19 kDa protein‐interacting protein 3 transcripts and caspase 8 and caspase 3 activity, phosphorylation of beclin‐1, de‐phosphorylation of mixed lineage kinase domain‐like, increase in LC3‐II, and up‐regulation of Atg7 and Atg12 genes, suggesting activation of autophagy and inhibition of necroptosis. Furthermore, DHA‐induced protection was suppressed by the lysosomotropic agent chloroquine, an inhibitor of autophagy. We conclude that DHA elicits neuroprotection by regulating multiple cell death pathways including enhancement of autophagy and inhibiting apoptosis and necroptosis.

Nonalcoholic Fatty Liver Disease Pandemic Fuels the Upsurge in Cardiovascular Diseases

Cardiovascular diseases (CVDs) remain a leading cause of death worldwide. Among the major risk factors for CVD, obesity and diabetes mellitus have received considerable attention in terms of public policy and awareness. However, the emerging prevalence of nonalcoholic fatty liver disease (NAFLD), as the most common liver and metabolic disease and a cause of CVD, has been largely overlooked. Currently, the number of individuals with NAFLD is greater than the total number of individuals with diabetes mellitus and obesity. Epidemiological studies have established a strong correlation between NAFLD and an increased risk of CVD and CVD-associated events. Although debate continues over the causal relationship between NAFLD and CVD, many mechanistic and longitudinal studies have indicated that NAFLD is one of the major driving forces for CVD and should be recognized as an independent risk factor for CVD apart from other metabolic disorders. In this review, we summarize the clinical evidence that supports NAFLD as a risk factor for CVD epidemics and discuss major mechanistic insights regarding the acceleration of CVD in the setting of NAFLD. Finally, we address the potential treatments for NAFLD and their potential impact on CVD.

Diabetes Mellitus Severity and a Switch From Using Lipoprotein Lipase to Adipose-Derived Fatty Acid Results in a Cardiac Metabolic Signature That Embraces Cell Death

Background

Fatty acid (FA) provision to the heart is from cardiomyocyte and adipose depots, plus lipoprotein lipase action. We tested how a graded reduction in insulin impacts the source of FA used by cardiomyocytes and the cardiac adaptations required to process these FA.

Methods and Results

Rats injected with 55 (D55) or 100 (D100) mg/kg streptozotocin were terminated after 4 days. Although D55 and D100 were equally hyperglycemic, D100 showed markedly lower pancreatic and plasma insulin and loss of lipoprotein lipase, which in D55 hearts had expanded. There was minimal change in plasma FA in D55. However, D100 exhibited a 2‐ to 3‐fold increase in various saturated, monounsaturated, and polyunsaturated FA in the plasma. D100 demonstrated dramatic cardiac transcriptomic changes with 1574 genes differentially expressed compared with only 49 in D55. Augmented mitochondrial and peroxisomal β‐oxidation in D100 was not matched by elevated tricarboxylic acid or oxidative phosphorylation. With increasing FA, although control myocytes responded by augmenting basal respiration, this was minimized in D55 and reversed in D100. Metabolomic profiling identified significant lipid accumulation in D100 hearts, which also exhibited sizeable change in genes related to apoptosis and terminal deoxynucleotidyl transferase dUTP nick‐end labeling–positive cells.

Conclusions

With increasing severity of diabetes mellitus, when the diabetic heart is unable to control its own FA supply using lipoprotein lipase, it undergoes dramatic reprogramming that is linked to handling of excess FA that arise from adipose tissue. This transition results in a cardiac metabolic signature that embraces mitochondrial FA overload, oxidative stress, triglyceride storage, and cell death.

MicroRNA-21 abrogates palmitate-induced cardiomyocyte apoptosis through caspase-3/NF-κB signal pathways

Objective:

The aim of the study was to investigate the role of microRNA-21 (miR-21) in cardiomyocyte apoptosis and to determine a possible mechanism.

Methods:

H9c2 embryonic rat heart-derived cells were used in the study. Cell viability was determined using the 3-(4.5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay, and flow cytometry was used to evaluate cell apoptosis. Reverse transcription-polymerase chain reaction and western blot assays were used to detect mRNA and protein expression of the apoptosis-related proteins and miR-21. ELISA was used to detect reactive oxygen species (ROS).

Results:

Palmitate exposure greatly reduced miR-21 expression in cardiomyocytes. Apoptosis increased when miR-21 was inhibited with or without palmitate exposure. Consistently, reduced apoptosis was observed when miR-21 was overexpressed in cardiomyocytes. Caspase-3 activity was reduced after palmitate exposure. Bcl-2 protein expression was increased in H9c2 cells when transfected with the miR-21 mimic. MiR-21 overexpression alone did not induce ROS or DNA fragmentation; however, in conjunction with palmitate exposure, miR-21 mimic reduced ROS and DNA fragmentation. Moreover, palmitate administration overcame the antioxidant effect of 3 mM N-acetylcysteine to significantly inhibit apoptosis, DNA fragmentation, and caspase-3 activity. The exposure to palmitate greatly reduced p65 and p-p38 expression in the nucleus. A p38 inhibitor had no effect on the expression of Bcl-2 and cleaved caspase-3 in H9c2 cells alone; however, when combined with exposure to palmitate the p38 inhibitor induced Bcl-2 expression and inhibited caspase-3 activity. The p38 inhibitor by itself did not induce apoptosis, ROS production, or DNA fragmentation in H9c2 cells, but when palmitate was included with the p38 inhibitor, apoptosis, ROS production, and DNA fragmentation were reduced.

Conclusion:

miR-21 protects cardiomyocytes from apoptosis that is induced by palmitate through the caspase-3/NF-κB signal pathways.

High-density lipoprotein ameliorates palmitic acid-induced lipotoxicity and oxidative dysfunction in H9c2 cardiomyoblast cells via ROS suppression

Background

High levels circulating saturated fatty acids are associated with diabetes, obesity and hyperlipidemia. In heart, the accumulation of saturated fatty acids has been determined to play a role in the development of heart failure and diabetic cardiomyopathy. High-density lipoprotein (HDL) has been reported to possess key atheroprotective biological properties, including cellular cholesterol efflux capacity, anti-oxidative and anti-inflammatory activities. However, the underlying mechanisms are still largely unknown. Therefore, the aim of the present study is to test whether HDL could protect palmitic acid (PA)-induced cardiomyocyte injury and explore the possible mechanisms.

Results

H9c2 cells were pretreated with HDL (50–100 μg/ml) for 2 h followed by PA (0.5 mM) for indicated time period. Our results showed that HDL inhibited PA-induced cell death in a dose-dependent manner. Moreover, HDL rescued PA-induced ROS generation and the phosphorylation of JNK which in turn activated NF-κB-mediated inflammatory proteins expressions. We also found that PA impaired the balance of BCL₂ family proteins, destabilized mitochondrial membrane potential, and triggered subsequent cytochrome c release into the cytosol and activation of caspase 3. These detrimental effects were ameliorated by HDL treatment.

Conclusion

PA-induced ROS accumulation and results in cardiomyocyte apoptosis and inflammation. However, HDL attenuated PA-induced lipotoxicity and oxidative dysfunction via ROS suppression. These results may provide insight into a possible molecular mechanism underlying HDL suppression of the free fatty acid-induced cardiomyocyte apoptosis.

Impact of Blood or Erythrocyte Membrane Fatty Acids for Disease Risk Prediction: Focusing on Cardiovascular Disease and Chronic Kidney Disease

Fatty acids (FAs) are essential nutrients and main constituents of cell membranes that are involved in the signaling pathway and associated with health conditions. We investigated if blood or erythrocyte membrane FAs can predict the risk of cardiovascular disease (CVD), chronic kidney disease (CKD), and related complications. Omega-3 (n-3) FAs are important predictors for metabolic syndrome, diabetes, CVD, and CKD risks, and the n-3 index is also a good biomarker for sudden cardiac death in coronary artery disease. Linoleic acid, which is one of the major n-6 FAs reflecting recent dietary FA intake, may predict CVD risk and mortality in the general population and patients with CKD. Monounsaturated FAs (MUFAs) are also related to diabetes or diabetic nephropathy. Oleic acid, a major MUFA, is an emerging marker that is related to acute coronary syndrome, low glomerular filtration rate, and vascular calcification in patients with CKD, and can be modified by n-3 FA supplementation. Saturated FAs, trans-FAs, and FA desaturation/elongation are associated with CVD risk; however, few studies have been conducted on patients with CKD. In summary, blood or erythrocyte membrane FA measurements are important for CVD and CKD risk prediction and management. Further studies are needed to elucidate the FAs for their risk predictions.

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.

Acute hypoxic preconditioning prevents palmitic acid-induced cardiomyocyte apoptosis via switching metabolic GLUT4-glucose pathway back to CD36-fatty acid dependent

Metabolic syndrome is a risk factor for the development of cardiovascular diseases. Myocardial cell damage leads to an imbalance of energy metabolism, and many studies have indicated that short-term hypoxia during myocardial cell injury has a protective effect. In our previous animal studies, we found that short-term hypoxia in the heart has a protective effect, but long-term hypoxia increases myocardial cell injury. Palmitic acid (PA)-treated H9c2 cardiomyoblasts and neonatal rat ventricle cardiomyocytes were used to simulate hyperlipidemia model, which suppress cluster of differentiation 36 (CD36) and activate glucose transporter type 4 (GLUT4). We exposed the cells to short- and long-term hypoxia and investigated the protective effects of hypoxic preconditioning on PA-induced lipotoxicity in H9c2 cardiomyoblasts and neonatal rat cardiomyocytes. Preconditioning with short-term hypoxia enhanced both CD36 and GLUT4 metabolism pathway protein levels. Expression levels of phospho-PI3K, phospho-Akt, phospho-AMPK, SIRT1, PGC1α, PPARα, CD36, and CPT1β induced by PA was reversed by short-term hypoxia in a time-dependent manner. PA-induced increased GLUT4 membrane protein level was reduced in the cells exposed to short-term hypoxia and si-PKCζ. Short-term hypoxia, resveratrol and si-PKCζ rescue H9c2 cells from apoptosis induced by PA and switch the metabolic pathway from GLUT4 dependent to CD36 dependent. We demonstrate short-term hypoxic preconditioning as a more efficient way as resveratrol in maintaining the energy metabolism of hearts during hyperlipidemia and can be used as a therapeutic strategy.

What Is Lipotoxicity?

Enlarged fat cells in obese adipose tissue diminish capacity to store fat and are resistant to the anti-lipolytic effect of insulin. Insulin resistance (IR)-associated S-nitrosylation of insulin-signaling proteins increases in obesity. In accordance with the inhibition of insulin-mediated anti-lipolytic action, plasma free fatty acid (FFA) levels increase. Additionally, endoplasmic reticulum stress stimuli induce lipolysis by activating cyclic adenosine monophosphate/Protein kinase A (cAMP/PKA) and extracellular signal-regulated kinase ½ (ERK1/2) signaling in adipocytes. Failure of packaging of excess lipid into lipid droplets causes chronic elevation of circulating fatty acids, which can reach to toxic levels within non-adipose tissues. Deleterious effects of lipid accumulation in non-adipose tissues are known as lipotoxicity. In fact, triglycerides may also serve a storage function for long-chain non-esterified fatty acids and their products such as ceramides and diacylglycerols (DAGs). Thus, excess DAG, ceramide and saturated fatty acids in obesity can induce chronic inflammation and have harmful effect on multiple organs and systems. In this context, chronic adipose tissue inflammation, mitochondrial dysfunction and IR have been discussed within the scope of lipotoxicity.

The Effect of Glycation on Epidermal Lipid Content, Its Metabolism and Change in Barrier Function

BACKGROUND/AIMS

Advanced glycation end products, which are linked to both aging and hyperglycemia, cause marked functional and structural alterations in human skin. Though it is well known that the metabolism of glucose is closely associated with that of fatty acid (FA), sharing the same energy-yielding reaction pathways as glucose, its effect on the epidermis has been unclear so far.

METHODS

Content of ceramides, cholesterol and FA in a reconstructed epidermal model glycated by glyoxal was analyzed by high-performance thin-layer chromatography. FA species extracted from HaCaT keratinocytes was determined by gas chromatography/mass spectrometry. Regulation of FA synthesis was analyzed by real-time PCR. For physiological analysis, excised mouse skin was glycated using a vertical diffusion cell and used for the evaluation of barrier function by transepidermal water loss measurement and observation of penetration of sodium fluorescein.

RESULTS

Saturated FA content was significantly increased in glycated epidermis, and glycation upregulated mRNA expression of FA elongases 2 and 3 and FA synthase in HaCaT cells. Further, both inside-out and outside-in barriers were disrupted in glycated excised skin.

CONCLUSION

Biological and physical change in the epidermis, especially upregulation of FA synthesis by glycation, contributed to barrier disruption, and inhibiting glycation may offer an effective treatment option for aged or glycated skin.

Dopamine induces lipid accumulation, NADPH oxidase-related oxidative stress, and a proinflammatory status of the plasma membrane in H9c2 cells

Excess catecholamine levels are suggested to be cardiotoxic and to underlie stress-induced heart failure. The cardiotoxic effects of norepinephrine and epinephrine are well recognized. However, although cardiac and circulating dopamine levels are also increased in stress cardiomyopathy patients, knowledge regarding putative toxic effects of excess dopamine levels on cardiomyocytes is scarce. We now studied the effects of elevated dopamine levels in H9c2 cardiomyoblasts. H9c2 cells were cultured and treated with dopamine (200 μM) for 6, 24, and 48 h. Subsequently, the effects on lipid accumulation, cell viability, flippase activity, reactive oxygen species (ROS) production, subcellular NADPH oxidase (NOX) protein expression, and ATP/ADP and GTP/GDP levels were analyzed. Dopamine did not result in cytotoxic effects after 6 h. However, after 24 and 48 h dopamine treatment induced a significant increase in lipid accumulation, nitrotyrosine levels, indicative of ROS production, and cell death. In addition, dopamine significantly reduced flippase activity and ATP/GTP levels, coinciding with phosphatidylserine exposure on the outer plasma membrane. Furthermore, dopamine induced a transient increase in cytoplasmic and (peri)nucleus NOX1 and NOX4 expression after 24 h that subsided after 48 h. Moreover, while dopamine induced a similar transient increase in cytoplasmic NOX2 and p47^phox expression, in the (peri)nucleus this increased expression persisted for 48 h where it colocalized with ROS. Exposure of H9c2 cells to elevated dopamine levels induced lipid accumulation, oxidative stress, and a proinflammatory status of the plasma membrane. This can, in part, explain the inflammatory response in patients with stress-induced heart failure.

Hepatosteatosis and estrogen increase apolipoprotein O production in the chicken

Apolipoprotein O (ApoO) is a recently discovered plasma apolipoprotein that may also play a role in the mitochondrial inner membrane. Possibly due to this complexity, its physiological functions have not been elucidated yet. To gain insight from a non-mammalian experimental system, we have investigated the regulation of ApoO levels in an alternative, well-suited model for studies on lipid metabolism, the chicken. qPCR using specific primer pairs and Western blot analysis with our rabbit anti-chicken ApoO antiserum demonstrated ApoO in the liver of chickens fed a control or a fat-enriched diet, as well as in 2 chicken hepatoma cell lines, LMH cells and the estrogen-responsive LMH-2A cells, under conditions of lipid loading by incubation with BSA-complexed oleic acid. Induced triglyceride accumulation in both the liver and the hepatic cells was associated with significantly increased levels of ApoO mRNA and protein. Furthermore, upon treatment for 24 h with estrogen of the estrogen receptor-expressing LMH-2A cells, quantitative analysis of ApoO transcripts and Western blotting revealed increases of ApoO expression. Finally, upon a single administration of estrogen to roosters that leads to hyperlipidemia, higher hepatic levels of both ApoO transcript and protein were observed within 24 h. Based on these data, we propose that hepatic expression of ApoO is tightly linked not only to diet-induced hepatosteatosis, but also to increased lipoprotein-production induced by, e.g., hormones. The findings support a role of ApoO as an effector of compromised mitochondrial function that likely accompanies the onset of non-alcoholic fatty liver disease.

Chronic cocaine use and its association with myocardial steatosis evaluated by 1H magnetic resonance spectroscopy in African Americans

OBJECTIVES

Cardiac steatosis is a manifestation of ectopic fat deposition and is associated with obesity. The impact of chronic cocaine use on obesity measures and on the relationship between obesity measures and cardiac steatosis is not well-characterized. The objectives of this study were to compare obesity measures in chronic cocaine users and nonusers, and to explore which factors, in addition to obesity measures, are associated with myocardial triglyceride in African Americans, using noninvasive magnetic resonance spectroscopy.

METHODS

Between June 2004 and January 2014, 180 healthy African American adults without HIV infection, hypertension, and diabetes were enrolled in an observational proton magnetic resonance spectroscopy and imaging study investigating factors associated with cardiac steatosis.

RESULTS

Among these 180 participants, 80 were chronic cocaine users and 100 were nonusers. The median age was 42 (interquartile range, 34-47) years. Obesity measures trended higher in cocaine users than in nonusers. The median myocardial triglyceride was 0.6% (interquartile range, 0.4%-1.1%). Among the factors investigated, years of cocaine use, leptin, and visceral fat were independently associated with myocardial triglyceride. Body mass index and visceral fat, which were significantly associated with myocardial triglyceride in noncocaine users, were not associated with myocardial triglyceride content in cocaine users.

CONCLUSIONS

This study shows (1) cocaine users may have more fat than nonusers and (2) myocardial triglyceride is independently associated with duration of cocaine use, leptin, and visceral fat in all subjects, whereas leptin and high-density lipoprotein cholesterol, but not visceral fat or body mass index, in cocaine users, suggesting that chronic cocaine use may modify the relationships between obesity measures and myocardial triglyceride.

Chemical inhibition of fatty acid absorption and cellular uptake limits lipotoxic cell death

Chronic elevation of plasma free fatty acid (FFA) levels is commonly associated with obesity, type 2 diabetes, cardiovascular disease and some cancers. Experimental evidence indicates FFA and their metabolites contribute to disease development through lipotoxicity. Previously, we identified a specific fatty acid transport inhibitor CB16.2, a.k.a. Lipofermata, using high throughput screening methods. In this study, efficacy of transport inhibition was measured in four cell lines that are models for myocytes (mmC2C12), pancreatic β-cells (rnINS-1E), intestinal epithelial cells (hsCaco-2), and hepatocytes (hsHepG2), as well as primary human adipocytes. The compound was effective in inhibiting uptake with IC50s between 3 and 6μM for all cell lines except human adipocytes (39μM). Inhibition was specific for long and very long chain fatty acids but had no effect on medium chain fatty acids (C6-C10), which are transported by passive diffusion. Derivatives of Lipofermata were evaluated to understand structural contributions to activity. Lipofermata prevented palmitate-mediated oxidative stress, induction of BiP and CHOP, and cell death in a dose-dependent manner in hsHepG2 and rnINS-1E cells, suggesting it will prevent induction of fatty acid-mediated cell death pathways and lipotoxic disease by channeling excess fatty acids to adipose tissue and away from liver and pancreas. Importantly, mice dosed orally with Lipofermata were not able to absorb (13)C-oleate demonstrating utility as an inhibitor of fatty acid absorption from the gut.

Reference values of myocardial structure, function, and tissue composition by cardiac magnetic resonance in healthy African-Americans at 3T and their relations to serologic and cardiovascular risk factors

Cardiac magnetic resonance (CMR) is a standard of reference for cardiac structure and function. Recent advances in T1 mapping and spectroscopy also provide assessment of myocardial tissue composition. However, the reference ranges of left ventricular parameters have rarely been assessed in an African-American (AA) population without known cardiac disease. To estimate the reference values of myocardial structure, function, and tissue composition by CMR and to explore their relationships to serologic factors and cardiovascular risk factors in asymptomatic AAs with low Framingham risk, between November 2010 and June 2012, 92 healthy AAs aged ≥21 years, from Baltimore, MD, were enrolled in an observational study. CMR examination was performed on a 3T scanner. Proton magnetic resonance spectroscopy was performed to noninvasively quantify myocardial triglyceride content. Native T1 values were obtained from modified Look-Locker inversion recovery sequence. The median age was 37 (interquartile range IQR 27 to 44) years (41% men). The median native T1 time of the myocardium was 1,228 ms (IQR 1,200 to 1,263) with no gender difference. The median myocardial fat content was 0.6% (IQR 0.7% to 4.6%). Native T1 time was not influenced by age, sex, and body mass index. Among the factors investigated, myocardial fat and elevated C-reactive protein (>2.0 mg/dL) were independently associated with T1 relaxation time. Native T1 time was also independently associated with left ventricular end-diastolic volume indexed to body surface area. In conclusion, this study of asymptomatic AAs provides reference ranges for cardiovascular structure, function, and tissue composition. Alterations in myocardial fat are associated with native T1 time, a CMR measure of interstitial fibrosis.

Serum phospholipid monounsaturated fatty acid composition and Δ-9-desaturase activity are associated with early alteration of fasting glycemic status

Because alterations in blood fatty acid (FA) composition by dietary lipids are associated with insulin resistance and related metabolic disorders, we hypothesized that serum phospholipid FA composition would reflect the early alteration of fasting glycemic status, even in people without metabolic syndrome (MetS). To examine this hypothesis, serum phospholipid FA, desaturase activities, fasting glycemic status, and cardiometabolic parameters were measured in study participants (n = 1022; 30-69 years; male, n = 527; female, n = 495; nondiabetics without disease) who were stratified into normal fasting glucose (NFG) and impaired fasting glucose (IFG) groups. Total monounsaturated FA (MUFA), oleic acid (OA; 18:1n-9), dihomo-γ-linolenic acid (DGLA; 20:3n-6), Δ-9-desaturase activity (D9D; 18:1n-9/18:0), and DGLA/linoleic acid (20:3n-6/18:2n-6) in serum phospholipids were significantly higher in IFG subjects than NFG controls. Study subjects were subdivided into 4 groups, based on fasting glucose levels and MetS status. Palmitoleic acid (16:1n-7) was highest in IFG-MetS and lowest in NFG-non-MetS subjects. Oleic acid and D9D were higher in IFG-MetS than in the other 3 groups. Dihomo-γ-linolenic acid and DGLA/linoleic acid were higher in MetS than in non-MetS, regardless of fasting glucose levels. The high-sensitivity C-reactive proteins (hs-CRPs) and 8-epi-prostaglandin-F2α were higher in IFG than in NFG, regardless of MetS status. Oxidized low-density lipoproteins were higher in IFG-MetS than in the other 3 groups. Total MUFAs, OA, and D9D were positively correlated with homeostasis model assessment of insulin resistance, fasting glucose, triglyceride, hs-CRP, and 8-epi-prostaglandin-F2α. Palmitoleic acid was positively correlated with triglyceride and hs-CRP. Lastly, total MUFA, OA, palmitoleic acid, and D9D were associated with early alteration of fasting glycemic status, therefore suggesting that these may be useful markers for predicting the risk of type 2 diabetes and cardiometabolic diseases.

Myocardial Steatosis and Necrosis in Atria and Ventricles of Rats Given Pyruvate Dehydrogenase Kinase Inhibitors

Pharmaceutical therapies for non-insulin-dependent diabetes mellitus (NIDDM) include plasma glucose lowering by enhancing glucose utilization. The mitochondrial pyruvate dehydrogenase (PDH) complex is important in controlling the balance between glucose and fatty acid substrate oxidation. Administration of pyruvate dehydrogenase kinase inhibitors (PDHKIs) to rats effectively lowers plasma glucose but results in myocardial steatosis that in some instances is associated primarily with atrial and to a lesser degree with ventricular pathology. Induction of myocardial steatosis is not dose-dependent, varies from minimal to moderate severity, and is either of multifocal or diffuse distribution. Ventricular histopathology was restricted to few myocardial degenerative fibers, while that in the atrium/atria was of either acute or chronic appearance with the former showing myocardial degeneration/necrosis, acute myocarditis, edema, endothelial activation (rounding up), endocarditis, and thrombosis associated with moderate myocardial steatosis and the latter with myocardial loss, replacement fibrosis, and no apparent or minimal association with steatosis. The evidence from these evaluations indicate that excessive intramyocardial accumulation of lipid may be either primarily adverse or represents an indicator of other adversely affected cellular processes.

Apolipoprotein O is mitochondrial and promotes lipotoxicity in heart

Diabetic cardiomyopathy is a secondary complication of diabetes with an unclear etiology. Based on a functional genomic evaluation of obesity-associated cardiac gene expression, we previously identified and cloned the gene encoding apolipoprotein O (APOO), which is overexpressed in hearts from diabetic patients. Here, we generated APOO-Tg mice, transgenic mouse lines that expresses physiological levels of human APOO in heart tissue. APOO-Tg mice fed a high-fat diet exhibited depressed ventricular function with reduced fractional shortening and ejection fraction, and myocardial sections from APOO-Tg mice revealed mitochondrial degenerative changes. In vivo fluorescent labeling and subcellular fractionation revealed that APOO localizes with mitochondria. Furthermore, APOO enhanced mitochondrial uncoupling and respiration, both of which were reduced by deletion of the N-terminus and by targeted knockdown of APOO. Consequently, fatty acid metabolism and ROS production were enhanced, leading to increased AMPK phosphorylation and Ppara and Pgc1a expression. Finally, we demonstrated that the APOO-induced cascade of events generates a mitochondrial metabolic sink whereby accumulation of lipotoxic byproducts leads to lipoapoptosis, loss of cardiac cells, and cardiomyopathy, mimicking the diabetic heart-associated metabolic phenotypes. Our data suggest that APOO represents a link between impaired mitochondrial function and cardiomyopathy onset, and targeting APOO-dependent metabolic remodeling has potential as a strategy to adjust heart metabolism and protect the myocardium from impaired contractility.

Magnolia extract (BL153) protection of heart from lipid accumulation caused cardiac oxidative damage, inflammation, and cell death in high-fat diet fed mice

Magnolia as an herbal material obtained from Magnolia officinalis has been found to play an important role in anti-inflammation, antioxidative stress, and antiapoptosis. This study was designed to investigate the effect of Magnolia extract (BL153) on obesity-associated lipid accumulation, inflammation, oxidative stress, and apoptosis in the heart. C57BL/6 mice were fed a low- (10 kcal% fat) or high-fat (60 kcal% fat) diet for 24 weeks to induce obesity. These mice fed with high-fat diet (HFD) were given a gavage of vehicle, 2.5, 5, or 10 mg/kg body weight BL153 daily. The three doses of BL153 treatment slightly ameliorated insulin resistance without decrease of body weight gain induced by HFD feeding. BL153 at 10 mg/kg slightly attenuated a mild cardiac hypertrophy and dysfunction induced by HFD feeding. Both 5 mg/kg and 10 mg/kg of BL153 treatment significantly inhibited cardiac lipid accumulation measured by Oil Red O staining and improved cardiac inflammation and oxidative stress by downregulating ICAM-1, TNF-α, PAI-1, 3-NT, and 4-HNE. TUNEL staining showed that BL153 treatment also ameliorated apoptosis induced by mitochondrial caspase-3 independent cell death pathway. This study demonstrates that BL153 attenuates HFD-associated cardiac damage through prevention of HFD-induced cardiac lipid accumulation, inflammation, oxidative stress, and apoptosis.

Myocardial steatosis and its association with obesity and regional ventricular dysfunction: evaluated by magnetic resonance tagging and 1H spectroscopy in healthy African Americans

BACKGROUND

Cardiac steatosis is common in patients with diabetes or obesity, and cardiac steatosis may result in cardiomyopathy. However, factors associated with cardiac steatosis have not been reported in healthy individuals without diabetes and hypertension. The objectives of this study were to explore factors associated with myocardial triglyceride levels, and to examine the association between myocardial triglyceride and regional left ventricular (LV) function in healthy African Americans (AAs).

METHODS

Between November 2010 and June 2012, 92 healthy AAs aged 21 years or older, without clinical evidence of cardiac dysfunction, coronary artery disease, diabetes, or hypertension from Baltimore, Maryland, were enrolled in an observational proton magnetic resonance spectroscopy and imaging study investigating factors associated with cardiac steatosis, and the relationships between cardiac steatosis and LV volumes and LV function.

RESULTS

Among the participants, all had a low Framingham risk; 31 had a normal BMI, 23 were overweight and 38 were obese. The median myocardial triglyceride content was 0.5% (IQR: 0.3-1.0%). Among the factors investigated, BMI (R2=0.43, p=<0.0001) was independently associated with myocardial triglyceride. Overall, myocardial triglyceride was not associated with LV EF/structure, but may be associated with regional LV function.

CONCLUSIONS

In healthy AA adults, obesity is associated with cardiac steatosis. In contrast to studies in patients with diabetes suggesting a link between cardiac steatosis and LV dysfunction, this study found no relationship between cardiac steatosis and left ventricular volumes or EF, though there is some evidence suggesting that cardiac steatosis may be associated with LV regional function in healthy AA women.

Palmitic acid affects proliferation and differentiation of neural stem cells in vitro

High-lipid diet composed of saturated fatty acids (SFAs) has significant detrimental effects on brain homeostasis, and deleterious effects of SFAs on various cells have been well documented. However, the effects of SFAs on neural stem Cells (NSCs) function have not been fully explored. The aim of this study was to determine whether palmitic acid (PA) affected the proliferation and differentiation of murine-derived NSCs. The results showed that PA dose dependently suppressed viability of NSCs and was cytotoxic at high concentrations. The toxic levels of PA inhibited the proliferation of NSCs as shown by reduced bromodeoxyuridine labeling of NSCs, which is correlated with reactive oxygen species generation. Pretreatment of the cells with the antioxidant N-acetyl-L-cysteine inhibitor significantly attenuated the effects of PA on the proliferation of NSCs. Furthermore, nontoxic levels of PA promoted astrocytogenesis in the differentiated NSCs, associated with Stat3 activation and altered expression of serial of basic helix-loop-helix transcription factor genes. Altogether, our data have demonstrated that PA has a significant impact on proliferation and differentiation of NSCs in vitro and may be useful for elucidating the role of SFAs in regulating NSCs fate in physiological and pathological settings.

Alteration of energy substrates and ROS production in diabetic cardiomyopathy

Diabetic cardiomyopathy is initiated by alterations in energy substrates. Despite excess of plasma glucose and lipids, the diabetic heart almost exclusively depends on fatty acid degradation. Glycolytic enzymes and transporters are impaired by fatty acid metabolism, leading to accumulation of glucose derivatives. However, fatty acid oxidation yields lower ATP production per mole of oxygen than glucose, causing mitochondrial uncoupling and decreased energy efficiency. In addition, the oxidation of fatty acids can saturate and cause their deposition in the cytosol, where they deviate to induce toxic metabolites or gene expression by nuclear-receptor interaction. Hyperglycemia, the fatty acid oxidation pathway, and the cytosolic storage of fatty acid and glucose/fatty acid derivatives are major inducers of reactive oxygen species. However, the presence of these species can be essential for physiological responses in the diabetic myocardium.

Long-term effects of early overnutrition in the heart of male adult rats: role of the renin-angiotensin system

To analyze the long-term effects of early overfeeding on the heart and coronary circulation, the effect of ischemia-reperfusion (I/R) and the role of the renin-angiotensin system (RAS) was studied in isolated hearts from control and overfed rats during lactation. On the day of birth litters were adjusted to twelve pups per mother (controls) or to three pups per mother (overfed). At 5 months of age, the rats from reduced litters showed higher body weight and body fat than the controls. The hearts from these rats were perfused in a Langendorff system and subjected to 30 min of ischemia followed by 15 min of reperfusion (I/R). The myocardial contractility (dP/dt) and the coronary vasoconstriction to angiotensin II were lower, and the expression of the apoptotic marker was higher, in the hearts from overfed rats compared to controls. I/R reduced the myocardial contractily, the coronary vasoconstriction to angiotensin II and the vasodilatation to bradykinin, and increased the expression of (pro)renin receptor and of apoptotic and antiapoptotic markers, in both experimental groups. I/R also increased the expression of angiotensinogen in control but not in overfed rats. In summary, the results of this study suggest that early overnutrition induces reduced activity of the RAS and impairment of myocardial and coronary function in adult life, due to increased apoptosis. Ischemia-reperfusion produced myocardial and coronary impairment and apoptosis, which may be related to activation of RAS in control but not in overfed rats, and there may be protective mechanisms in both experimental groups.

Metabolomic profiling reveals a role for caspase-2 in lipoapoptosis

The accumulation of long-chain fatty acids (LCFAs) in non-adipose tissues results in lipid-induced cytotoxicity (or lipoapoptosis). Lipoapoptosis has been proposed to play an important role in the pathogenesis of several metabolic diseases, including non-alcoholic fatty liver disease, diabetes mellitus, and cardiovascular disease. In this report, we demonstrate a novel role for caspase-2 as an initiator of lipoapoptosis. Using a metabolomics approach, we discovered that the activation of caspase-2, the initiator of apoptosis in Xenopus egg extracts, is associated with an accumulation of LCFA metabolites. Metabolic treatments that blocked the buildup of LCFAs potently inhibited caspase-2 activation, whereas adding back an LCFA in this scenario restored caspase activation. Extending these findings to mammalian cells, we show that caspase-2 was engaged and activated in response to treatment with the saturated LCFA palmitate. Down-regulation of caspase-2 significantly impaired cell death induced by saturated LCFAs, suggesting that caspase-2 plays a pivotal role in lipid-induced cytotoxicity. Together, these findings reveal a previously unknown role for caspase-2 as an initiator caspase in lipoapoptosis and suggest that caspase-2 may be an attractive therapeutic target for inhibiting pathological lipid-induced apoptosis.

TLR4 activation under lipotoxic conditions leads to synergistic macrophage cell death through a TRIF-dependent pathway

Macrophage dysfunction in obesity and diabetes may predispose to the development of diabetic complications, such as infection and impaired healing after tissue damage. Saturated fatty acids, such as palmitate, are present at elevated concentrations in the plasma of patients with metabolic disease and may contribute to the pathogenesis of diabetes and its sequelae. To examine the effect of lipid excess on macrophage inflammatory function, we determined the influence of palmitate on LPS-mediated responses in peritoneal macrophages. Palmitate and LPS led to a profound synergistic cell death response in both primary and RAW 264.7 macrophages. The cell death had features of apoptosis and necrosis and was not dependent on endoplasmic reticulum stress, ceramide generation, or reactive oxygen species production. Instead, we uncovered a macrophage death pathway that required TLR4 signaling via TRIF but was independent of NF-κB, MAPKs, and IRF3. A significant decrease in macrophage lysosomal content was observed early in the death pathway, with evidence of lysosomal membrane damage occurring later in the death response. Overexpression of the transcription factor TFEB, which induces a lysosomal biogenic program, rescued the lysosomal phenotype and improved viability in palmitate- and LPS-treated cells. Our findings provide new evidence for cross-talk between lipid metabolism and the innate immune response that converges on the lysosome.

Fatty heart, cardiac damage, and inflammation

Type 2 diabetes and obesity are associated with systemic inflammation, generalized enlargement of fat depots, and uncontrolled release of fatty acids (FA) into the circulation. These features support the occurrence of cardiac adiposity, which is characterized by an increase in intramyocardial triglyceride content and an enlargement of the volume of fat surrounding the heart and vessels. Both events may initially serve as protective mechanisms to portion energy, but their excessive expansion can lead to myocardial damage and heart disease. FA overload promotes FA oxidation and the accumulation of triglycerides and metabolic intermediates, which can impair calcium signaling, β-oxidation, and glucose utilization. This leads to damaged mitochondrial function and increased production of reactive oxygen species, pro-apoptotic, and inflammatory molecules, and finally to myocardial inflammation and dysfunction. Triglyceride accumulation is associated with left ventricular hypertrophy and dysfunction. The enlargement of epicardial fat in patients with metabolic disorders, and coronary artery disease, is associated with the release of proinflammatory and proatherogenic cytokines to the subtending tissues. In this review, we examine the evidence supporting a causal relationship linking FA overload and cardiac dysfunction. Also, we disentangle the separate roles of FA oxidation and triglyceride accumulation in causing cardiac damage. Finally, we focus on the mechanisms of inflammation development in the fatty heart, before summarizing the available evidence in humans. Current literature confirms the dual (protective and detrimental) role of cardiac fat, and suggests prospective studies to establish the pathogenetic (when and how) and possible prognostic value of this potential biomarker in humans.

Changes in myofilament proteins, but not Ca²⁺ regulation, are associated with a high-fat diet-induced improvement in contractile function in heart failure

Pathological conditions such as diabetes, insulin resistance, and obesity are characterized by elevated plasma and myocardial lipid levels and have been reported to exacerbate the progression of heart failure (HF). Alterations in cardiomyocyte Ca(2+) regulatory properties and myofilament proteins have also been implicated in contractile dysfunction in HF. However, our prior studies reported that high saturated fat (SAT) feeding improves in vivo myocardial contractile function, thereby exerting a cardioprotective effect in HF. Therefore, we hypothesized that SAT feeding improves contractile function by altering Ca(2+) regulatory properties and myofilament protein expression in HF. Male Wistar rats underwent coronary artery ligation (HF) or sham surgery (SH) and were fed normal chow (SHNC and HFNC groups) or a SAT diet (SHSAT and HFSAT groups) for 8 wk. Contractile properties were measured in vivo [echocardiography and left ventricular (LV) cannulation] and in isolated LV cardiomyocytes. In vivo measures of contractility (peak LV +dP/dt and -dP/dt) were depressed in the HFNC versus SHNC group but improved in the HFSAT group. Isolated cardiomyocytes from both HF groups were hypertrophied and had decreased percent cell shortening and a prolonged time to half-decay of the Ca(2+) transient versus the SH group; however, SAT feeding reduced in vivo myocyte hypertrophy in the HFSAT group only. The peak velocity of cell shortening was reduced in the HFNC group but not the HFSAT group and was positively correlated with in vivo contractile function (peak LV +dP/dt). The HFNC group demonstrated a myosin heavy chain (MHC) isoform switch from fast MHC-α to slow MHC-β, which was prevented in the HFSAT group. Alterations in Ca(2+) transients, L-type Ca(2+) currents, and protein expression of sarco(endo)plasmic reticulum Ca(2+)-ATPase and phosphorylated phospholamban could not account for the changes in the in vivo contractile properties. In conclusion, the cardioprotective effects associated with SAT feeding in HF may occur at the level of the isolated cardiomyocyte, specifically involving changes in myofilament function but not sarcoplasmic reticulum Ca(2+) regulatory properties.

Preimplantation exposure of mouse embryos to palmitic acid results in fetal growth restriction followed by catch-up growth in the offspring

Free fatty acids (FFAs) are energy substrates for many cell types, but in excess, some FFAs can accumulate in nonadipose cells, inducing apoptosis. Also known as lipotoxicity, this phenomenon may play a role in the development of obesity-related disease. Obesity is common among reproductive age women and is associated with adverse pregnancy and fetal outcomes; however, little is known about the effects of excess FFAs on embryos and subsequent fetal development. To address this knowledge gap, murine blastocysts were cultured in excess palmitic acid (PA), the most abundant saturated FFA in human serum, and ovarian follicular fluid. Targets susceptible to aberrations in maternal physiology, including embryonic IGF1 receptor (IGF1R) expression, glutamic pyruvate transaminase (GPT2) activity, and nuclei count, were measured. PA-exposed blastocysts demonstrated altered IGF1R expression, increased GPT2 activity, and decreased nuclei count. Trophoblast stem cells derived from preimplantation embryos were also cultured in PA. Cells exposed to increasing doses of PA demonstrated increased apoptosis and decreased proliferation. To demonstrate long-term effects of brief PA exposure, blastocysts cultured for 30 h in PA were transferred into foster mice, and pregnancies followed through Embryonic Day (ED)14.5 or delivery. Fetuses resulting from PA-exposed blastocysts were smaller than controls at ED14.5. Delivered pups were also smaller but demonstrated catch-up growth and ultimately surpassed control pups in weight. Altogether, our data suggest brief PA exposure results in altered embryonic metabolism and growth, with lasting adverse effects on offspring, providing further insight into the pathophysiology of maternal obesity.

Metabolic characterization of volume overload heart failure due to aorto-caval fistula in rats

Metabolic interactions between adipose tissue and the heart may play an active role in progression of heart failure (HF). The aim of the study was to examine changes in myocardial and adipose tissue metabolism and gene expression in a rat HF model induced by chronic volume overload. HF was induced by volume overload from aorto-caval fistula (ACF) in 3-month-old male Wistar rats and animals were studied in the phase of decompensated HF (22nd week). HF rats showed marked eccentric cardiac hypertrophy, pulmonary congestion, increased LV end-diastolic pressure, and intraabdominal fat depletion. HF rats had preserved glucose tolerance, but increased circulating free fatty acids (FFA) and attenuated insulin response during oral glucose challenge. Isolated organ studies showed preserved responsiveness of adipose tissue lipolysis and lipogenesis to epinephrine and insulin in ACF. The heart of HF animals had markedly reduced triglyceride content (almost to half of controls), attenuated anti-oxidative reserve (GSH/GSSG), upregulated HF markers (ANP, periostin, thrombospondin-4), specific signaling pathways (Wnt, TGF-β), and downregulated enzymes of mitochondrial fatty acid oxidation, citric acid cycle, and respiratory chain. Adipose tissue transcription profiling showed upregulated receptor for gastric inhibitory polypeptide. In conclusion, ACF-induced HF model displays several deregulations of systemic metabolism. Despite elevation of systemic FFAs, myocardial triglycerides are low and insulin levels are attenuated, arguing against a role of lipotoxicity or insulin resistance in this model. Attenuated postprandial insulin response and relative lack of its antilipolytic effects may facilitate intraabdominal fat depletion observed in ACF-HF animals.

Defining the molecular nexus of cancer, type 2 diabetes and cardiovascular disease

The metabolic syndrome is characterized by a state of metabolic dysfunction resulting in the development of several chronic diseases that are potentially deadly. These metabolic deregulations are complex and intertwined and it has been observed that many of the mechanisms and pathways responsible for diseases characterizing the metabolic syndrome such as type 2 diabetes and cardiovascular disease are linked with cancer development as well. Identification of molecular pathways common to these diverse diseases may prove to be a critical factor in disease prevention and development of potential targets for therapeutic treatments. This review focuses on several molecular pathways, including AMPK, PPARs and FASN that interconnect cancer development, type 2 diabetes and cardiovascular disease. AMPK, PPARs and FASN are crucial regulators involved in the maintenance of key metabolic processes necessary for proper homeostasis. It is critical to recognize and identify common pathways deregulated in interrelated diseases as it may provide further information and a much more global picture in regards to disease development and prevention. Thus, this review focuses on three key metabolic regulators, AMPK, PPARs and FASN, that may potentially serve as therapeutic targets.

Plasma esterified and non-esterified fatty acids metabolic profiling using gas chromatography-mass spectrometry and its application in the study of diabetic mellitus and diabetic nephropathy

Using gas chromatography-mass spectrometry (GC-MS), a new metabolic profiling method was established to assess the levels of non-esterified fatty acids (NEFAs) and esterified fatty acids (EFAs) in plasma. The extraction method was simple and robust without removing protein process. With this method 25 fatty acids (FAs), both EFAs and NEFAs, can be recognized simultaneously with only 10 μL plasma. 15 of the 25 can be precisely quantified. The method was validated and then applied into clinical metabonomics research. Five clinical groups including 150 cases were involved. The relationship between FA levels and diabetic mellitus (DM) as well as diabetic nephropathy (DN) pathology was speculated. Furthermore, the possible pathological causes and effects were discussed in detail. Potential biomarkers (p value <0.01) were screened with Student's t-test. With the application of partial least squares-discriminant analysis (PLS-DA), different stages were distinguished. The result may be useful for the pathology study of metabolic syndromes, and may also be helpful for monitoring the progression of DM and DN.