Lipotoxicity, an imbalance between lipogenesis de novo and fatty acid oxidation

Introduction: Our lab previously showed that cardiomyocyte Krüppel-like factor (KLF)-5 regulates cardiac fatty acid oxidation. Various studies have associated heart failure with altered cardiac fatty acid oxidation and lipotoxicity. Hypothesis: Aberrant regulation of KLF5 contributes to pathophysiology and metabolic perturbations in ischemic heart failure. Methods and Results: Analysis of KLF5 mRNA and protein levels in human ischemic heart failure samples and in rodent models 2- and 4-weeks post-myocardial infarction (MI) showed significantly increased KLF5 expression. To investigate the involvement of KLF5 in the pathophysiology of ischemic heart failure, we treated mice that were subjected to MI with a pharmacological KLF5 inhibitor (ML264). ML264 increased ejection fraction and reduced diastolic volume. Likewise, mice with cardiomyocyte-specific KLF5 deletion (αMHC-KLF5 -/- mice) were protected from ischemic heart failure. Lipidomic analysis by LC-MS/MS showed that αMHC-KLF5 -/- mice after MI had lower myocardial ceramide levels compared with control mice with MI. Accordingly, the expression of cardiac SPTLC1 and SPTLC2, which regulate de novo ceramide biosynthesis, was higher in control mice with MI and lower in αMHC-KLF5 -/- mice with MI. KLF5 overexpression in HL1 cardiomyocytes increased SPTLC1 and SPTLC2 mRNA and protein levels. ChIP-qPCR and luciferase promoter assays showed that KLF5 activates the promoters of these genes via direct binding. To assess the transcriptional effects of KLF5 independent from other changes that occur with MI, we generated a mouse model of inducible (Dox-ON), cardiomyocyte-specific expression of KLF5 (αMHC-rtTA-KLF5). Systolic dysfunction was evident 2-weeks following KLF5 induction. Heart tissue from these mice exhibited increased SPTLC1 and SPTLC2 mRNA and protein levels, and inhibition of SPT using myriocin suppressed myocardial ceramide levels and alleviated systolic dysfunction. Conclusions: KLF5 is induced during the development of ischemic heart failure in humans and mice, and stimulates expression of SPTLC1 and SPTLC2 that promote ceramide biosynthesis. KLF5 inhibition emerges as a novel therapeutic target to protect against ischemic heart failure.

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Vitamin B12 Induces Hepatic Fatty Infiltration through Altered Fatty Acid Metabolism

Cellular Physiology and Biochemistry ◽

10.33594/000000368 ◽

2021 ◽

Vol 55 (3) ◽

pp. 241-255

Keyword(s):

Fatty Acids ◽

Fatty Acid ◽

Vitamin B12 ◽

Fatty Acid Oxidation ◽

Lipid Droplets ◽

De Novo ◽

Quantitative Polymerase Chain Reaction ◽

Saturated Fatty Acids ◽

Fatty Infiltration ◽

Acid Oxidation

Background/Aims: Rise in global incidence of obesity impacts metabolic health. Evidence from human and animal models show association of vitamin B12 (B12) deficiency with elevated BMI and lipids. Human adipocytes demonstrated dysregulation of lipogenesis by low B12 via hypomethylation and altered microRNAs. It is known de novo hepatic lipogenesis plays a key role towards dyslipidaemia, however, whether low B12 affects hepatic metabolism of lipids is not explored. Methods: HepG2 was cultured in B12-deficient EMEM medium and seeded in different B12 media: 500nM(control), 1000pM(1nM), 100pM and 25pM(low) B12. Lipid droplets were examined by Oil Red O (ORO) staining using microscopy and then quantified by elution assay. Gene expression were assessed with real-time quantitative polymerase chain reaction (qRT-PCR) and intracellular triglycerides were quantified using commercial kit (Abcam, UK) and radiochemical assay. Fatty acid composition was measured by gas chromatography and mitochondrial function by seahorse XF24 flux assay. Results: HepG2 cells in low B12 had more lipid droplets that were intensely stained with ORO compared with control. The total intracellular triglyceride and incorporation of radio-labelled-fatty acid in triglyceride synthesis were increased. Expression of genes regulating fatty acid, triglyceride and cholesterol biosynthesis were upregulated. Absolute concentrations of total fatty acids, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), trans-fatty acids and individual even-chain and odd-chain fatty acids were significantly increased. Also, low B12 impaired fatty acid oxidation and mitochondrial functional integrity in HepG2 compared with control. Conclusion: Our data provide novel evidence that low B12 increases fatty acid synthesis and levels of individual fatty acids, and decreases fatty acid oxidation and mitochondrial respiration, thus resulting in dysregulation of lipid metabolism in HepG2. This highlights the potential significance of de novo lipogenesis and warrants possible epigenetic mechanisms of low B12.

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Metabolic Remodeling Induced by Adipocytes: A New Achilles' Heel in Invasive Breast Cancer?

Current Medicinal Chemistry ◽

10.2174/0929867325666180426165001 ◽

2020 ◽

Vol 27 (24) ◽

pp. 3984-4001 ◽

Cited By ~ 4

Author(s):

Camille Attané ◽

Delphine Milhas ◽

Andrew J. Hoy ◽

Catherine Muller

Keyword(s):

Breast Cancer ◽

Fatty Acid ◽

Cancer Cells ◽

Tumor Cells ◽

Fatty Acid Oxidation ◽

De Novo ◽

Metabolic Reprogramming ◽

Acid Oxidation ◽

Oxidation Inhibitors ◽

Metabolic Remodeling

Metabolic reprogramming represents an important hallmark of cancer cells. Besides de novo fatty acid synthesis, it is now clear that cancer cells can acquire Fatty Acids (FA) from tumor-surrounding adipocytes to increase their invasive capacities. Indeed, adipocytes release FA in response to tumor secreted factors that are transferred to tumor cells to be either stored as triglycerides and other complex lipids or oxidized in mitochondria. Like all cells, FA can be released over time from triglyceride stores through lipolysis and then oxidized in mitochondria in cancer cells. This metabolic interaction results in specific metabolic remodeling in cancer cells, and underpins adipocyte stimulated tumor progression. Lipolysis and fatty acid oxidation therefore represent novel targets of interest in the treatment of cancer. In this review, we summarize the recent advances in our understanding of the metabolic reprogramming induced by adipocytes, with a focus on breast cancer. Then, we recapitulate recent reports studying the effect of lipolysis and fatty acid oxidation inhibitors on tumor cells and discuss the interest to target these metabolic pathways as new therapeutic approaches for cancer.

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Human adenovirus 36 decreases fatty acid oxidation and increases de novo lipogenesis in primary cultured human skeletal muscle cells by promoting Cidec/FSP27 expression

International Journal of Obesity ◽

10.1038/ijo.2010.77 ◽

2010 ◽

Vol 34 (9) ◽

pp. 1355-1364 ◽

Cited By ~ 33

Author(s):

Z Q Wang ◽

Y Yu ◽

X H Zhang ◽

E Z Floyd ◽

W T Cefalu

Keyword(s):

Skeletal Muscle ◽

Fatty Acid ◽

Fatty Acid Oxidation ◽

Human Skeletal Muscle ◽

De Novo ◽

Human Adenovirus ◽

De Novo Lipogenesis ◽

Acid Oxidation ◽

Human Skeletal Muscle Cells ◽

Adenovirus 36

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Sex Differences in Hepatic De Novo Lipogenesis with Acute Fructose Feeding

Nutrients ◽

10.3390/nu10091263 ◽

2018 ◽

Vol 10 (9) ◽

pp. 1263 ◽

Cited By ~ 12

Author(s):

Wee Low ◽

Thomas Cornfield ◽

Catriona Charlton ◽

Jeremy Tomlinson ◽

Leanne Hodson

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

De Novo ◽

Dietary Fatty Acid ◽

De Novo Lipogenesis ◽

Liver Fat ◽

Acid Oxidation ◽

Free Sugars ◽

Isotope Tracer ◽

High Fructose

Dietary free sugars have received much attention over the past few years. Much of the focus has been on the effect of fructose on hepatic de novo lipogenesis (DNL). Therefore the aim of the present study was to investigate the effects of meals high and low in fructose on postprandial hepatic DNL and fatty acid partitioning and dietary fatty acid oxidation. Sixteen healthy adults (eight men, eight women) participated in this randomised cross-over study; study days were separated by a 4-week wash-out period. Hepatic DNL and dietary fatty acid oxidation were assessed using stable-isotope tracer methodology. Consumption of the high fructose meal significantly increased postprandial hepatic DNL to a greater extent than consumption of the low fructose meal and this effect was evident in women but not men. Despite an increase in hepatic DNL, there was no change in dietary fatty acid oxidation. Taken together, our data show that women are more responsive to ingestion of higher amounts of fructose than men and if continued over time this may lead to changes in hepatic fatty acid partitioning and eventually liver fat content.

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Microcytophotometric analysis of human osteoclast metabolism: lack of activity in certain oxidative pathways indicates inability to sustain biosynthesis during resorption.

Journal of Histochemistry & Cytochemistry ◽

10.1177/42.5.8157931 ◽

1994 ◽

Vol 42 (5) ◽

pp. 599-606 ◽

Cited By ~ 31

Author(s):

R A Dodds ◽

M Gowen ◽

J N Bradbeer

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

De Novo ◽

Krebs Cycle ◽

Maximal Activity ◽

Good Evidence ◽

Acid Oxidation ◽

Atp Production ◽

Metabolic Characteristics

It has been proposed that highly biosynthetic cells oxidize fatty acids to generate ATP while maintaining high levels of glucose metabolism through the glycolytic and pentose shunt systems to supply biosynthetic intermediates. We investigated the metabolic strategies and substrate for ATP production in the osteoclast. We used in situ quantitative microcytophotometric techniques to determine the maximal activity of the pentose shunt (glucose-6-phosphate dehydrogenase; G6PD), the glycolytic pathway (glyceraldehyde-3-phosphate dehydrogenase and lactate dehydrogenase; G3PD and LDH), fatty acid oxidation (beta-hydroxyacyl dehydrogenase; HOAD), and the Krebs cycle (succinate dehydrogenase; SDH) in human osteoclasts in situ, and related these enzyme activities to the degree of involvement of the cells in resorption. Unlike other highly biosynthetic cells, such as chondrocytes and macrophage polykaryons, osteoclasts associated with bone resorption were deficient in G3PD, LDH, and G6PD activity. However, osteoclasts did demonstrate a capacity for fatty acid oxidation which increased in cells apposed to the bone surface. The lack of significant glycolytic and pentose shunt activity in the osteoclast provides good evidence that resorbing osteoclasts, unlike phagocytosing macrophage polykaryons, have the metabolic characteristics of cells with greatly reduced capabilities of de novo mRNA synthesis but which do maintain high rates of ATP production. The possibility that the loss of glycolytic activity is a prelude to cell death is discussed.

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Treatment with a polyherbal extract improves fat metabolism, attenuates hepatic stellate cell activation and fibrogenesis.

10.1101/2021.08.06.455195 ◽

2021 ◽

Author(s):

Pavan Kumar Bellamakondi ◽

Rizwan Baig Mirza ◽

Onkar Murthy Mallappa ◽

Azeemuddin Mohammed ◽

Hariprasad VR ◽

...

Keyword(s):

Fatty Acid ◽

Fatty Acid Oxidation ◽

Cell Activation ◽

De Novo ◽

Stellate Cell ◽

Stellate Cells ◽

De Novo Lipogenesis ◽

Acid Oxidation ◽

Polyherbal Formulation

Non-alcoholic steatohepatitis (NASH) involves dysregulations in denovo lipogenesis, fatty acid oxidation, and fibrogenesis. Targeting these pathways holds promise for the treatment of liver disorders. Here we test the extract of a polyherbal formulation (namely Liv.52), which is approved by the Government of India's Drug Regulatory Authority - AYUSH. The current study evaluates the effect of Liv.52 on denovo lipogenesis, fatty acid oxidation, and fibrogenesis. Both in vivo and in vitro model systems were employed to evaluate the efficacy of this polyherbal formulation. Male Wistar rats were dosed with Liv.52 for 2 weeks (250mg/k.g) and expression levels of the genes involved in de novo lipogenesis and fatty acid oxidation pathways were analysed by quantitative real time PCR. Liv.52 treatment resulted in increased hepatic fatty acid oxidation and decreased de novo lipogenesis in these rats. It also reduced hepatic stellate cell activation in CCL4 treated Wistar rats as evidenced by histological evaluation. For in vitro experiments, HepG2 cells were cultured under lipotoxic conditions (using 200 micro molar palmitic acid) and the conditioned media from these cells were used for inducing activation and fibrogenesis in human hepatic stellate cells (HHSteC). Treatment with lipotoxic conditioned media resulted in activation of hepatic stellate cells and fibrogenesis, as evidenced by increased expression of alpha-smooth muscle actin (alpha-SMA), and desmin (markers of stellate cell activation) and increased levels of collagen and lumican (markers of fibrogenesis). Treatment with Liv.52 reversed the up-regulation of alpha-SMA, collagen and lumican levels in HHSteC cells. These results indicate that Liv.52 exerts its hepatoprotective effect by improving fatty acid metabolism and fibrogenesis.

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