Lipolysis - a highly regulated multi-enzyme complex mediates the catabolism of cellular fat stores

Resistance to obesity prevents obesity development without increasing spontaneous physical activity and not directly related to greater metabolic and oxidative capacity

There are evidence that obese-resistant animals are more physically active, due to a higher rate of lipid oxidation. Efficiency in such pathways can favor greater spontaneous physical activity and, consequently, less body fat deposition. The aim of study was characterizing the nutritional profile and spontaneous physical activity in the condition of Resistance to Obesity (OR). Wistar rats were randomized into standard diet (SD; n = 50) and high-fat diet (HFD; n = 50) groups, after obesity induction, were redistributed into Control (C), False-control (FC), Propensity to obesity (OP) and OR, and then spontaneous physical activity was evaluated. Analyzed parameters: body mass (BM), epididymal (EF), retroperitoneal (RF), visceral (VF) and respective summations (∑), adiposity index (AI), nutritional, morphological, biochemical and metabolic parameters and protein quantification. The comparison of the groups was performed by ANOVA one or two factors, with 5% significance adopted. OP and FC presented high final MC values compared to C and OR. OR had lower EF, RF, VF, ∑ and IA compared to OP. OR had similar values to C and higher HDL than FC and OP. In GTT, OR and C presented similar values and both were lower than OP in the 30 minutes. OP promoted higher values than C for glycemic AUC. OR had higher PPARγ content than C and OP, as well as levels similar to C for leptin and insulin. Spontaneous physical activity did not differ between groups. The results were not enough to show that OR animals have greater lipid oxidative capacity, as well as greater spontaneous physical activity.

Insulin prevents fatty acid induced increase of adipocyte size

Metabolic disorders related to obesity are largely dependent on adipose tissue hypertrophy, which involves adipocyte hypertrophy and increased adipogenesis. Adiposize is regulated by lipid accumulation as a result of increased lipogenesis (mainly lipid uptake in mature adipocytes) and reduced lipolysis. Using realtime 2D cell culture analyses of lipid uptake, we show (1) that high glucose concentration (4.5 g/L) was required to accumulate oleic acid increasing lipid droplet size until unilocularization similar to mature adipocytes in few days, (2) oleic acid reduced Peroxisome-Proliferator Activated Receptor Gamma (PPARG) gene transcription and (3) insulin counteracted oleic acid-induced increase of lipid droplet size. Although the lipolytic activity observed in high versus low glucose (1 g/L) conditions was not altered, insulin was found to inhibit oleic acid induced gene transcription required for lipid storage such as Cell Death Inducing DFFA Like Effectors (CIDEC) and G0S2 (G0 switch gene S2), possibly through PPARA activity. Although this signalling pathway requires more detailed investigation, the results point out the differential mechanisms involved in the pro-adipogenic effect of insulin in absence versus its protective effect on adiposity in presence of oleic acid uptake.

Abbreviations: AICAR, 5-Aminoimidazole-4-carboxamide-1-D-ribofuranoside; AMPK, AMP-Activated protein kinase, ASCs, adipose stem cell; ATGL, adipose triglyceride lipase; BSA, Bovine serum albumin; CEBPA, CCAAT enhancer binding protein alpha; CIDEs, Cell Death Inducing DFFA Like Effectors; dA, differentiated adipocyte; DMEM, Dulbecco’s Modified Eagle’s Medium; FABPs, Fatty Acid Binding Proteins; FAT/CD36, Fatty acid translocase; FCS, Foetal calf serum; FN1, fibronectin 1; FFA, free fatty acid; G0S2, G0 switch gene S2; GLUTs, Glucose transporters; GPR120, G protein-coupled receptor 120; HG, high glucose; HSL, hormone sensitive lipase; INSR, insulin receptor; LG, low glucose; OA, oleic acid; PBS, Phosphate buffer saline; PPARs, Peroxisome-Proliferator Activated Receptors; PKA, Protein kinase cyclic AMP-dependent; PKG, Protein kinase cyclic GMP dependent; PTGS2, cytochrome oxidase 2; RTCA, realtime cell analysis; TG, triglyceride.

Recent Advances on the Role of ATGL in Cancer

The hypoxic state of the tumor microenvironment leads to reprogramming lipid metabolism in tumor cells. Adipose triglyceride lipase, also known as patatin-like phospholipase= domain-containing protein 2 and Adipose triglyceride lipase (ATGL), as an essential lipid metabolism-regulating enzyme in cells, is regulated accordingly under hypoxia induction. However, studies revealed that ATGL exhibits both tumor-promoting and tumor-suppressing effects, which depend on the cancer cell type and the site of tumorigenesis. For example, elevated ATGL expression in breast cancer is accompanied by enhanced fatty acid oxidation (FAO), enhancing cancer cells’ metastatic ability. In prostate cancer, on the other hand, tumor activity tends to be negatively correlated with ATGL expression. This review outlined the regulation of ATGL-mediated lipid metabolism pathways in tumor cells, emphasizing the Hypoxia-inducible factors 1 (HIF-1)/Hypoxia-inducible lipid droplet-associated (HIG-2)/ATGL axis, peroxisome proliferator-activated receptor (PPAR)/G0/G1 switch gene 2 (G0S2)/ATGL axis, and fat-specific protein 27 (FSP-27)/Early growth response protein 1 (EGR-1)/ATGL axis. In the light of recent research on different cancer types, the role of ATGL on tumorigenesis, tumor proliferation, and tumor metastasis was systemically reviewed.

Anti-adipogenic and Pro-lipolytic Effects on 3T3-L1 Preadipocytes by CX-4945, an Inhibitor of Casein Kinase 2

Casein kinase 2 (CK2) is a ubiquitously expressed serine/threonine kinase and is upregulated in human obesity. CX-4945 (Silmitasertib) is a CK2 inhibitor with anti-cancerous and anti-adipogenic activities. However, the anti-adipogenic and pro-lipolytic effects and the mode of action of CX-4945 in (pre)adipocytes remain elusive. Here, we explored the effects of CX-4945 on adipogenesis and lipolysis in differentiating and differentiated 3T3-L1 cells, a murine preadipocyte cell line. CX-4945 at 15 μM strongly reduced lipid droplet (LD) accumulation and triglyceride (TG) content in differentiating 3T3-L1 cells, indicating the drug’s anti-adipogenic effect. Mechanistically, CX-4945 reduced the expression levels of CCAAT/enhancer-binding protein-α (C/EBP-α), peroxisome proliferator-activated receptor-γ (PPAR-γ), fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and perilipin A in differentiating 3T3-L1 cells. Strikingly, CX-4945 further increased the phosphorylation levels of cAMP-activated protein kinase (AMPK) and liver kinase B-1 (LKB-1) while decreasing the intracellular ATP content in differentiating 3T3-L1 cells. In differentiated 3T3-L1 cells, CX-4945 had abilities to stimulate glycerol release and elevate the phosphorylation levels of hormone-sensitive lipase (HSL), pointing to the drug’s pro-lipolytic effect. In addition, CX-4945 induced the activation of extracellular signal-regulated kinase-1/2 (ERK-1/2), and PD98059, an inhibitor of ERK-1/2, attenuated the CX4945-induced glycerol release and HSL phosphorylation in differentiated 3T3-L1 cells, indicating the drug’s ERK-1/2-dependent lipolysis. In summary, this investigation shows that CX-4945 has strong anti-adipogenic and pro-lipolytic effects on differentiating and differentiated 3T3-L1 cells, mediated by control of the expression and phosphorylation levels of CK2, C/EBP-α, PPAR-γ, FAS, ACC, perilipin A, AMPK, LKB-1, ERK-1/2, and HSL.

Molecular Modeling of ABHD5 Structure and Ligand Recognition

Alpha/beta hydrolase domain-containing 5 (ABHD5), also termed CGI-58, is the key upstream activator of adipose triglyceride lipase (ATGL), which plays an essential role in lipid metabolism and energy storage. Mutations in ABHD5 disrupt lipolysis and are known to cause the Chanarin-Dorfman syndrome. Despite its importance, the structure of ABHD5 remains unknown. In this work, we combine computational and experimental methods to build a 3D structure of ABHD5. Multiple comparative and machine learning-based homology modeling methods are used to obtain possible models of ABHD5. The results from Gaussian accelerated molecular dynamics and experimental data of the apo models and their mutants are used to select the most likely model. Moreover, ensemble docking is performed on representative conformations of ABHD5 to reveal the binding mechanism of ABHD5 and a series of synthetic ligands. Our study suggests that the ABHD5 models created by deep learning-based methods are the best candidate structures for the ABHD5 protein. The mutations of E41, R116, and G328 disturb the hydrogen bonding network with nearby residues and suppress membrane targeting or ATGL activation. The simulations also reveal that the hydrophobic interactions are responsible for binding sulfonyl piperazine ligands to ABHD5. Our work provides fundamental insight into the structure of ABHD5 and its ligand-binding mode, which can be further applied to develop ABHD5 as a therapeutic target for metabolic disease and cancer.

Lipid Metabolism and Cancer

Lipid metabolism is involved in the regulation of numerous cellular processes, such as cell growth, proliferation, differentiation, survival, apoptosis, inflammation, movement, membrane homeostasis, chemotherapy response, and drug resistance. Reprogramming of lipid metabolism is a typical feature of malignant tumors. In a variety of cancers, fat uptake, storage and fat production are up-regulated, which in turn promotes the rapid growth, invasion, and migration of tumors. This paper systematically summarizes the key signal transduction pathways and molecules of lipid metabolism regulating tumors, and the role of lipid metabolism in programmed cell death. In conclusion, understanding the potential molecular mechanism of lipid metabolism and the functions of different lipid molecules may facilitate elucidating the mechanisms underlying the occurrence of cancer in order to discover new potential targets for the development of effective antitumor drugs.

Adiponectin Reduces Lipid Content in Chicken Myoblasts by Activating AMPK Signaling Pathway

Studies in mammals have shown that adiponectin is secreted mainly by adipocytes, and it plays a crucial role in glucose and lipid metabolism in muscles. Clarifying the crosstalk role of adiponectin between adipose tissue and skeletal muscle tissue is very important for internal homeostasis. The glucose and lipid metabolism of chicken is different from that of mammals, and the role of adiponectin in chickens is unclear. Therefore, it is of great significance to study the effect and mechanism of adiponectin on lipid metabolism in chickens. In this study, the regulating effect of adiponectin on lipid metabolism in chicken myoblasts was explored by adding a certain concentration of exogenous recombinant adiponectin. Results showed that adiponectin reduced intracellular lipid content, increasing the mRNA expression of adiponectin receptor and cellular uptake of glucose and fatty acids. In addition, adiponectin activated the 5' adenosine monophosphate activated protein kinase (AMPK) signaling pathway. The above results suggested that adiponectin reduced intracellular lipid content, mainly by binding to adiponectin receptor, activating AMPK pathway, increasing cellular uptake of glucose and fatty acids, and promoting lipid oxidation.

PEX19 Coordinates Neutral Lipid Storage in Cells in a Peroxisome-Independent Fashion

Cellular lipid metabolism is tightly regulated and requires a sophisticated interplay of multiple subcellular organelles to adapt to changing nutrient supply. PEX19 was originally described as an essential peroxisome biogenesis factor that selectively targets membrane proteins to peroxisomes. Metabolic aberrations that were associated with compromised PEX19 functions, were solely attributed to the absence of peroxisomes, which is also considered the underlying cause for Zellweger Spectrum Disorders. More recently, however, it was shown that PEX19 also mediates the targeting of the VCP/P97-recuitment factor UBXD8 to the ER from where it partitions to lipid droplets (LDs) but the physiological consequences remained elusive. Here, we addressed the intriguing possibility that PEX19 coordinates the functions of the major cellular sites of lipid metabolism. We exploited the farnesylation of PEX19 and deciphered the organelle-specific functions of PEX19 using systems level approaches. Non-farnesylated PEX19 is sufficient to fully restore the metabolic activity of peroxisomes, while farnesylated PEX19 controls lipid metabolism by a peroxisome-independent mechanism that can be attributed to sorting a specific protein subset to LDs. In the absence of this PEX19-dependent LD proteome, cells accumulate excess triacylglycerols and fail to fully deplete their neutral lipid stores under catabolic conditions, highlighting a hitherto unrecognized function of PEX19 in controlling neutral lipid storage and LD dynamics.

Transcriptomic profile of longissimus thoracis associated with fatty acid content in Nellore beef cattle

The beef fatty acid (FA) profile has the potential to impact human health, and displays polygenic and complex features. This study aimed to identify the transcriptomic FA profile in the longissimus thoracis muscle in Nellore beef cattle finished in feedlot. Forty-four young bulls were sampled to assess the beef FA profile by considering 14 phenotypes and including differentially expressed genes (DEG), co-expressed (COE), and differentially co-expressed genes (DCO) analyses. All samples (n = 44) were used for COE analysis, whereas 30 samples with extreme phenotypes for the beef FA profile were used for DEG and DCO. A total of 912 DEG were identified, and the polyunsaturated (n = 563) and unsaturated ω-3 (n = 346) FA sums groups were the most frequently observed. The COE analyses identified three modules, of which the blue module (n = 1776) was correlated with eight of 14 FA phenotypes. Also, 759 DCO genes were listed, and the oleic acid (n = 358) and monounsaturated fatty acids sum (n = 120) were the most frequent. Furthermore, 243 and 13, 319 and seven, and 173 and 12 gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways were enriched respectively for the DEG, COE, and DCO analyses. Combining the results, we highlight the unexplored GIPC2, ASB5, and PPP5C genes in cattle. Besides LIPE and INSIG2 genes in COE modules, the ACSL3, ECI1, DECR2, FITM1, and SDHB genes were signaled in at least two analyses. These findings contribute to understand the genetic mechanisms underlying the beef FA profile in Nellore beef cattle finished in feedlot.

Recruitment of Peroxin14 to lipid droplets affects lipid storage in Drosophila

Both peroxisomes and lipid droplets regulate cellular lipid homeostasis. Direct inter-organellar contacts as well as novel roles for proteins associated with peroxisome or lipid droplets occur when cells are induced to liberate fatty acids from lipid droplets. We have shown a non-canonical role for as subset of peroxisome-assembly (Peroxin) proteins in this process. Transmembrane proteins Peroxin3, Peroxin13 and Peroxin14 surround newly formed lipid droplets. Trafficking of Peroxin14 to lipid droplets was enhanced by loss of Peroxin19, which directs insertion of transmembrane proteins like Peroxin14 into the peroxisome bilayer membrane. Accumulation of Peroxin14 around lipid droplets did not induce changes to peroxisome size or number, nor was co-recruitment of the remaining Peroxins needed to assemble peroxisomes observed. Increasing the relative level of Peroxin14 surrounding lipid droplets affected recruitment of Hsl lipase. Fat-body specific reduction of these lipid droplet-associated Peroxins causes a unique effect on larval fat body development and affected their survival on lipid-enriched or minimal diets.

DECR1 directly activates HSL to promote lipolysis in cervical cancer cells

Fatty acids have a high turnover rate in cancer cells to supply energy for tumor growth and proliferation. Lipolysis is particularly important for the regulation of fatty acid homeostasis and in the maintenance of cancer cells. In the current study, we explored how 2,4-Dienoyl-CoA reductase (DECR1), a short-chain dehydrogenase/reductase associated with mitochondrial and cytoplasmic compartments, promotes cancer cell growth. We report that DECR1 overexpression significantly reduced the triglyceride (TAG) content in HeLa cells; conversely, DECR1 silencing increased intracellular TAG content. Subsequently, our experiments demonstrate that DECR1 promotes lipolysis via effects on hormone sensitive lipase (HSL). The direct interaction of DECR1 with HSL increases HSL phosphorylation and activity, facilitating the translocation of HSL to lipid droplets. The ensuing enhancement of lipolysis thus increases the release of free fatty acids. Downstream effects include the promotion of cervical cancer cell migration and growth, associated with the enhanced levels of p62 protein. In summary, high levels of DECR1 serves to enhance lipolysis and the release of fatty acid energy stores to support cervical cancer cell growth.

Residues of the minimal sequence of G0S2 collectively contribute to ATGL inhibition while C-and N-terminal extensions promote binding to ATGL

The protein encoded by the G0/G1 switch gene 2 (G0S2) is a potent inhibitor of adipose triglyceride lipase (ATGL) and thus an important regulator of intracellular lipolysis. Since dysfunction of lipolysis is associated with metabolic diseases including diabetes and obesity, inhibition of ATGL is considered a therapeutic strategy. G0S2 interacts with ATGL's patatin-domain to mediate non-competitive inhibition, however atomic details of the inhibition mechanism are incompletely understood. Sequences of G0S2 from higher organisms show a highly conserved N-terminal part, including a hydrophobic region covering amino acids 27 to 42. We show that predicted G0S2 orthologs from platypus, chicken and Japanese rice-fish are able to inhibit human and mouse ATGL, emphasizing the contribution of conserved amino acid to ATGL inhibition. Our site directed mutagenesis and truncation studies give insights in the protein-protein interaction on a per-residue level. We determine that the minimal sequence required for ATGL inhibition ranges from amino acids 20 to 44. Residues Y27, V28, G30, A34 G37, V39 or L42 within this sequence play a substantial role in ATGL inhibition. Furthermore, we show that unspecific interactions of the N-terminal part (amino acids 20-27) of the minimal sequence facilitate the interaction to ATGL. Our studies also demonstrate that full-length G0S2 shows higher tolerance to specific single amino acid exchanges in the hydrophobic region due to the stronger contributions of unspecific interactions. However, exchanges of more than one amino-acid in the hydrophobic region also result in the loss of function as ATGL inhibitor even in the full-length protein.

A potential role of nettle (Urtica dioica) extract on growth, biochemical changes and reproductive performance of convict cichlid (Amatitlania nigrofasciata)

This study was carried out to investigate the effects of methanolic extract of nettle (Urtica dioica) on growth, reproduction, biochemical and immunological parameters of female convict cichlid (Amatitlania nigrofasciata). For this purpose, 54 fish were distributed in 3 treatments included: without supplementation (control), 0.1 g (NE0.1), and 0.5 g (NE0.5) nettle extract per kilogram feed over 56 days. The highest final weight (4.2 ± 0.1 g), weight gain (2.8 ± 0.1 g), and specific growth rate (2.0 ± 0.0% day^-1) were recorded in NE0.1 group. Higher and lower feed conversion ratio were obtained in control and NE0.1 treatments, respectively. Hepatosomatic and viscerosomatic indices in NE0.1 treatment were significantly lower compared with control treatment. Fish fed NE0.1 showed significantly lower glucose (55.2 ± 6.5 mg g^-1), cholesterol (28.4 ± 3.3 mg g^-1), and triglyceride (211.5 ± 39.0 mg g^-1) levels. Total protein (36.3 ± 3.4 mg g^-1) and albumin (2.7 ± 0.1 mg g^-1) showed a marked increase in NE0.1 treatment. Same trend was observed in C3, C4, and IgM concentrations. NE0.1 showed the highest number of eggs per female (183.7 ± 10.2), hatching rate (97 ± 0.7%), and larval survival rate at 3 days post hatch (86.3 ± 0.6%) compared with the other treatments. These findings indicated that 0.1 g methanolic extract of nettle kg feed^-1 could enhance growth, improve metabolic, and immune function of convict cichlid. Moreover, this study confirmed that appropriate dose of nettle can positively promote reproductive performance which makes it as a valuable and cost-effective herb in aquaculture industry.

Lipid Droplets, Phospholipase A2, Arachidonic Acid, and Atherosclerosis

Lipid droplets, classically regarded as static storage organelles, are currently considered as dynamic structures involved in key processes of lipid metabolism, cellular homeostasis and signaling. Studies on the inflammatory state of atherosclerotic plaques suggest that circulating monocytes interact with products released by endothelial cells and may acquire a foamy phenotype before crossing the endothelial barrier and differentiating into macrophages. One such compound released in significant amounts into the bloodstream is arachidonic acid, the common precursor of eicosanoids, and a potent inducer of neutral lipid synthesis and lipid droplet formation in circulating monocytes. Members of the family of phospholipase A₂, which hydrolyze the fatty acid present at the sn-2 position of phospholipids, have recently emerged as key controllers of lipid droplet homeostasis, regulating their formation and the availability of fatty acids for lipid mediator production. In this paper we discuss recent findings related to lipid droplet dynamics in immune cells and the ways these organelles are involved in regulating arachidonic acid availability and metabolism in the context of atherosclerosis.

Lipid Droplet-Associated Proteins in Cardiomyopathy

BACKGROUND

The heart requires a high rate of fatty-acid oxidation (FAO) to meet its energy needs. Neutral lipids are the main source of energy for the heart and are stored in lipid droplets (LDs), which are cytosolic organelles that primarily serve to store neutral lipids and regulate cellular lipid metabolism. LD-associated proteins (LDAPs) are proteins either located on the surface of the LDs or reside in the cytosol and contribute to lipid metabolism. Therefore, abnormal cardiac lipid accumulation or FAO can alter the redox state of the heart, resulting in cardiomyopathy, a group of diseases that negatively affect the myocardial function, thereby leading to heart failure and even cardiac death.

SUMMARY

LDs, along with LDAPs, are pivotal for modulating heart lipid homeostasis. The proper cardiac development and the maintenance of its normal function depend largely on lipid homeostasis regulated by LDs and LDAPs. Overexpression or deletion of specific LDAPs can trigger myocardial dysfunction and may contribute to the development of cardiomyopathy. Extensive connections and interactions may also exist between LDAPs. Key Message: In this review, the various mechanisms involved in LDAP-mediated regulation of lipid metabolism, the association between cardiac development and lipid metabolism, as well as the role of LDAPs in cardiomyopathy progression are discussed.

Brown and beige adipose tissue: a novel therapeutic strategy for obesity and type 2 diabetes mellitus

Mammalian adipose tissue can be divided into two major types, namely, white adipose tissue (WAT) and brown adipose tissue (BAT). According to classical view, the main function of WAT is to store excess energy in the form of triglycerides, while BAT is a thermogenic tissue that acts a pivotal part in maintaining the core body temperature. White adipocytes display high plasticity and can transdifferentiate into beige adipocytes which have many similar morphological and functional properties with brown adipocytes under the stimulations of exercise, cold exposure and other factors. This phenomenon is also known as 'browning of WAT'. In addition to transdifferentiation, beige adipocytes can also come from de novo differentiation from tissue-resident progenitors. Activating BAT and inducing browning of WAT can accelerate the intake of glycolipids and reduce the insulin secretion requirement, which may be a new strategy to improve glycolipids metabolism and insulin resistance of obese and type 2 diabetes mellitus (T2DM) patients. This review mainly discusses the significance of brown and beige adipose tissues in the treatment of obesity and T2DM, and focuses on the effect of the browning agent on obesity and T2DM, which provides a brand-new theoretical reference for the prevention and treatment of obesity and T2DM.

Metabolomics of Lung Microdissections Reveals Region- and Sex-Specific Metabolic Effects of Acute Naphthalene Exposure in Mice

Naphthalene is a ubiquitous environmental contaminant produced by combustion of fossil fuels and is a primary constituent of both mainstream and side stream tobacco smoke. Naphthalene elicits region-specific toxicity in airway club cells through cytochrome P450 (P450)-mediated bioactivation, resulting in depletion of glutathione and subsequent cytotoxicity. Although effects of naphthalene in mice have been extensively studied, few experiments have characterized global metabolomic changes in the lung. In individual lung regions, we found metabolomic changes in microdissected mouse lung conducting airways and parenchyma obtained from animals sacrificed at 3 timepoints following naphthalene treatment. Data on 577 unique identified metabolites were acquired by accurate mass spectrometry-based assays focusing on lipidomics and nontargeted metabolomics of hydrophilic compounds. Statistical analyses revealed distinct metabolite profiles between the 2 lung regions. Additionally, the number and magnitude of statistically significant exposure-induced changes in metabolite abundance were different between airways and parenchyma for unsaturated lysophosphatidylcholines, dipeptides, purines, pyrimidines, and amino acids. Importantly, temporal changes were found to be highly distinct for male and female mice with males exhibiting predominant treatment-specific changes only at 2 h postexposure. In females, metabolomic changes persisted until 6 h postnaphthalene treatment, which may explain the previously characterized higher susceptibility of female mice to naphthalene toxicity. In both males and females, treatment-specific changes corresponding to lung remodeling, oxidative stress response, and DNA damage were observed. Overall, this study provides insights into potential mechanisms contributing to naphthalene toxicity and presents a novel approach for lung metabolomic analysis that distinguishes responses of major lung regions.

Cardioprotective Effects of Palmitoleic Acid (C16:1n7) in a Mouse Model of Catecholamine-Induced Cardiac Damage Are Mediated by PPAR Activation

Palmitoleic acid (C16:1n7) has been identified as a regulator of physiological cardiac hypertrophy. In the present study, we aimed to investigate the molecular pathways involved in C16:1n7 responses in primary murine cardiomyocytes (PCM) and a mouse model of isoproterenol (ISO)-induced cardiac damage. PCMs were stimulated with C16:1n7 or a vehicle. Afterwards, RNA sequencing was performed using an Illumina HiSeq sequencer. Confirmatory analysis was performed in PCMs and HL-1 cardiomyocytes. For an in vivo study, 129 sv mice were orally treated with a vehicle or C16:1n7 for 22 days. After 5 days of pre-treatment, the mice were injected with ISO (25 mg/kg/d s. c.) for 4 consecutive days. Cardiac phenotyping was performed using echocardiography. In total, 129 genes were differentially expressed in PCMs stimulated with C16:1n7, including Angiopoietin-like factor 4 (Angptl4) and Pyruvate Dehydrogenase Kinase 4 (Pdk4). Both Angptl4 and Pdk4 are proxisome proliferator-activated receptor α/δ (PPARα/δ) target genes. Our in vivo results indicated cardioprotective and anti-fibrotic effects of C16:1n7 application in mice. This was associated with the C16:1n7-dependent regulation of the cardiac PPAR-specific signaling pathways. In conclusion, our experiments demonstrated that C16:1n7 might have protective effects on cardiac fibrosis and inflammation. Our study may help to develop future lipid-based therapies for catecholamine-induced cardiac damage.

Anti-Obesity Effect of α-Cubebenol Isolated from Schisandra chinensis in 3T3-L1 Adipocytes

The efficacy of α-cubebenol isolated from Schisandra chinensis has been studied in several diseases, including cecal ligation, puncture challenge-induced sepsis, and degranulation of neutrophils. To identify the novel functions of α-cubebenol on lipid metabolism, alterations on the regulation of lipogenesis, lipolysis, and inflammatory response were observed in 3T3-L1 adipocytes treated with α-cubebenol. Most lipogenic targets, including lipid accumulation, level of lipogenic transcription factors, and expression of lipogenic regulators, were suppressed in MDI (3-isobutyl-1-methylxanthine, dexamethasone, and insulin)-stimulated 3T3-L1 adipocytes treated with α-cubebenol without significant cytotoxicity. In addition, similar inhibition effects were observed in the iNOS-induced COX-2 mediated pathway and NLRP3 inflammasome pathway of MDI-stimulated 3T3-L1 cells treated with α-cubebenol. Lipolytic targets, such as cAMP concentration, expression of adenylyl cyclase and PDE4, and their downstream signaling pathway, in MDI-stimulated 3T3-L1 cells were stimulated by the α-cubebenol treatment. The levels of transcription factors and related proteins for β-oxidation were significantly higher in the MDI + α-cubebenol treated group than in the MDI + Vehicle treated group. These results show that α-cubebenol has a novel role as a lipogenesis inhibitor, lipolysis and β-oxidation stimulator, and inflammasome suppressor in MDI-stimulated 3T3-L1 adipocytes.

Contradictory roles of lipid metabolism in immune response within the tumor microenvironment

Complex interactions between the immune system and tumor cells exist throughout the initiation and development of cancer. Although the immune system eliminates malignantly transformed cells in the early stage, surviving tumor cells evade host immune defense through various methods and even reprogram the anti-tumor immune response to a pro-tumor phenotype to obtain unlimited growth and metastasis. The high proliferation rate of tumor cells increases the demand for local nutrients and oxygen. Poorly organized vessels can barely satisfy this requirement, which results in an acidic, hypoxic, and glucose-deficient tumor microenvironment. As a result, lipids in the tumor microenvironment are activated and utilized as a primary source of energy and critical regulators in both tumor cells and related immune cells. However, the exact role of lipid metabolism reprogramming in tumor immune response remains unclear. A comprehensive understanding of lipid metabolism dysfunction in the tumor microenvironment and its dual effects on the immune response is critical for mapping the detailed landscape of tumor immunology and developing specific treatments for cancer patients. In this review, we have focused on the dysregulation of lipid metabolism in the tumor microenvironment and have discussed its contradictory roles in the tumor immune response. In addition, we have summarized the current therapeutic strategies targeting lipid metabolism in tumor immunotherapy. This review provides a comprehensive summary of lipid metabolism in the tumor immune response.

In-depth triacylglycerol profiling using MS3 Q-Trap mass spectrometry

Total triacylglycerol (TAG) level is a key clinical marker of metabolic and cardiovascular diseases. However, the roles of individual TAGs have not been thoroughly explored in part due to their extreme structural complexity. We present a targeted mass spectrometry-based method combining multiple reaction monitoring (MRM) and multiple stage mass spectrometry (MS³) for the comprehensive qualitative and semiquantitative profiling of TAGs. This method referred as TriP-MS3 - triacylglycerol profiling using MS³ - screens for more than 6,700 TAG species in a fully automated fashion. TriP-MS3 demonstrated excellent reproducibility (median interday CV ∼ 0.15) and linearity (median R² = 0.978) and detected 285 individual TAG species in human plasma. The semiquantitative accuracy of the method was validated by comparison with a state-of-the-art reverse phase liquid chromatography (RPLC)-MS (R² = 0.83), which is the most commonly used approach for TAGs profiling. Finally, we demonstrate the utility and the versatility of the method by characterizing the effects of a fatty acid desaturase inhibitor on TAG profiles in vitro and by profiling TAGs in Caenorhabditis elegans.

Cytochrome P450 2F2 (CYP2F2) negatively regulates browning in 3T3-L1 white adipocytes

Cytochromes P450 (CYPs) are a multigene superfamily of constitutively expressed and inducible enzymes responsible for the detoxification of many endogenous and exogenous compounds and for the metabolism of numerous medications. The cytochrome P450 2F2 (CYP2F2) subfamily is preferentially expressed in the respiratory tract, but its functional role in adipocytes has never been explored. We found that CYP2F2 was highly expressed during the differentiation of the C3H10T1/2 murine mesenchymal stem cells to adipocytes and here we have explored its functional role in adipocytes. The expression of thermogenic marker proteins such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), PR domain containing 16 (PRDM16), and uncoupling protein 1 (UCP1) and beige-fat specific genes were significantly increased in Cyp2f2-deficient 3T3-L1 adipocytes. Moreover, Cyp2f2 silencing led to reduced adipogenesis and lipogenesis, and enhanced lipid catabolism through the increased expression of lipolytic and fatty acid oxidative enzymes. A mechanistic study to identify molecular signals for CYP2F2-mediated negative regulation in the browning of white adipocytes revealed that CYP2F2 impairs the beta-3 adrenergic receptor (β3-AR) activation as well as its downstream regulators including protein kinase A (PKA), p38 mitogen-activated protein kinase (p38 MAPK), and activating transcription factor 2 (ATF2). This data provides evidence that CYP2F2 is a negative regulator of lipid catabolism and browning in white adipocytes, suggesting that inhibitors of CYP2F2 could be potential drugs for the treatment of obesity with a focus on enhancing energy expenditure.

Ameliorative Effect of Annona muricata (Graviola) Extract on Hyperglycemia Induced Hepatic Damage in Type 2 Diabetic Mice

Annona muricata (AM) is evergreen plant of the Annonaceae family and known to have anticancer and antidiabetic effects. However, anti-diabetic mechanisms of AM extracts (AME) associated with hepatic glucose regulation and lipid metabolism remain unclear. In this study, we investigated the protective effect of AME extracted on hepatic damage in diabetic mice. Diabetes was induced by a high-fat diet with two-times streptozotocin (STZ) injection (60 mg/kg BW) in C57BL/6 male mice. The diabetic mice were daily administered with AME (50 or 100 mg/kg BW) by gavage for 9 weeks. Biomarkers related to energy metabolism and insulin signaling were examined to identify the effect of AME on hyperglycemia induced hepatic damage. AME supplementation reduced levels of FBG, HbA1c, HOMA-IR and hepatic lipid profiles as well as enhanced insulin signaling by increased the protein levels of IRS-1 accompanied GLUT2 in diabetic mice. Especially low dose of AME showed the beneficial effect of reducing oxidative stress (4-HNE, protein carbonyls, Nrf2, NQO1) and improved hepatic morphology demonstrated by lipid droplets along with upregulation of lipophagy (pAMPK, p-mTOR/mTOR, LC3-2/LC3-1) in diabetic mice. Moreover, AME supplementation ameliorated hepatic lipid metabolism (FAS, SREBP1c, C/EBPα, PPARγ, CPT1A, PPARα) and energy metabolism (pAMPK, PGC1α) in diabetic mice. Taken together, this study suggested that AME could be helpful to prevent hepatic abnormality by regulation of insulin signaling associated with energy metabolism and autophagy in diabetes.

Polysaccharides from Volvariella volvacea inhibit fat accumulation in C. elegans dependent on the aak-2/nhr-49-mediated pathway

Volvariella volvacea has bioactivities in improving immunity, anti-oxidation, and alleviating obesity, which is an excellent functional food. Polysaccharide from Volvariella volvacea (VPS), one of the main bioactive components, exerts a potential fat-lowering effect, but its exact mechanism remains unclear. In this study, the effects and molecular pathways of VPS regulate the fat deposition of Caenorhabditis elegans. Results showed that VPS at low (250 μg/ml), medium (500 μg/ml) and high (750 μg/ml) concentrations all reduced the overall fat, without inhibitory effects on the growth and movement abilities of nematode. VPS at 500 μg/ml could dramatically decrease the triglyceride (TG) level of wild-type nematode, while no significant changes in TG content were observed in mutants deficient in aak-2 (energy receptor), nhr-49 (nuclear transcription factor), fat-5, and fat-7 genes. VPS declines fat storage of C. elegans, largely through the aak-2/nhr-49-mediated fatty acid synthesis pathway, and partially the acs-2-mediated fatty acid oxidation pathway. PRACTICAL APPLICATIONS: A model illustrates the mechanism of polysaccharide from Volvariella volvacea (VPS) inhibiting fat accumulation in Caenorhabditis elegans. VPS may directly or indirectly activate the energy sensor aak-2, which governs lipid metabolism. Results demonstrate that VPS regulates fat metabolism including fatty acid oxidation (FAO) and fatty acid synthesis (FAS), rather than lipolysis. In the FAO, VPS promotes FAO by up-regulating the mRNA and protein levels of acs-2. In FAS, VPS significantly down-regulated the transcriptional regulator nhr-49 and the downstream targets fat-5, fat-6, and fat-7, thereby declining the overall fat deposition. In conclusion, VPS inhibits the fat accumulation of C. elegans largely dependent on an aak-2/nhr-49-mediated FAS pathway.

Understanding Metabolic Remodeling in Mycobacterium smegmatis to Overcome Energy Exigency and Reductive Stress Under Energy-Compromised State

Mycobacteria such as Mycobacterium tuberculosis, the causative agent of tuberculosis that annually kills several million people worldwide, and Mycobacterium smegmatis, the non-pathogenic fast-growing mycobacteria, require oxidative phosphorylation to meet their energy requirements. We have previously shown that deletion of one of the two copies of atpD gene that codes for the ATP synthase β-subunit establishes an energy-compromised state in M. smegmatis. Here we report that upon such deletion, a major routing of electron flux occurs through the less energy-efficient complexes of its respiratory chain. ΔatpD bacterium also shows an increased reduced state which is further confirmed by the overexpression of WhiB3, a major redox sensor. We show a substantial modulation of the biosynthesis of cell wall associated lipids and triacylglycerol (TAG). An accumulation of TAG-containing lipid bodies is further confirmed by using ¹⁴C oleate incorporation. Interestingly, the mutant also shows an overexpression of TAG-degrading lipase genes, and the intracellular lipolytic enzymes mediate TAG hydrolysis for their utilization as energy source. We believe that our in vitro energy-depleted model will allow us to explore the critical link between energy metabolism, redox homeostasis, and lipid biosynthesis during ATP-depleted state, which will enhance our understanding of the bacterial adaptation, and will allow us to identify novel drug targets to counter mycobacterial infections.

The Influence of Epigenetic Modifications on Metabolic Changes in White Adipose Tissue and Liver and Their Potential Impact in Exercise

Background: Epigenetic marks are responsive to a wide variety of environmental stimuli and serve as important mediators for gene transcription. A number of chromatin modifying enzymes orchestrate epigenetic responses to environmental stimuli, with a growing body of research examining how changes in metabolic substrates or co-factors alter epigenetic modifications.

Scope of Review: Here, we provide a systematic review of existing evidence of metabolism-related epigenetic changes in white adipose tissue (WAT) and the liver and generate secondary hypotheses on how exercise may impact metabolism-related epigenetic marks in these tissues.

Major Conclusions: Epigenetic changes contribute to the complex transcriptional responses associated with WAT lipolysis, hepatic de novo lipogenesis, and hepatic gluconeogenesis. While these metabolic responses may hypothetically be altered with acute and chronic exercise, direct testing is needed.

A simple, rapid, and sensitive fluorescence-based method to assess triacylglycerol hydrolase activity

Lipases constitute an important class of water-soluble enzymes that catalyze the hydrolysis of hydrophobic triacylglycerol (TAG). Their enzymatic activity is typically measured using multistep procedures involving isolation and quantification of the hydrolyzed products. We report here a new fluorescence method to measure lipase activity in real time that does not require the separation of substrates from products. We developed this method using adipose triglyceride lipase (ATGL) and lipoprotein lipase (LpL) as model lipases. We first incubated a source of ATGL or LpL with substrate vesicles containing nitrobenzoxadiazole (NBD)-labeled TAG, then measured increases in NBD fluorescence, and calculated enzyme activities. Incorporation of NBD-TAG into phosphatidylcholine (PC) vesicles resulted in some hydrolysis; however, incorporation of phosphatidylinositol into these NBD-TAG/PC vesicles and increasing the ratio of NBD-TAG to PC greatly enhanced substrate hydrolysis. This assay was also useful in measuring the activity of pancreatic lipase and hormone-sensitive lipase. Next, we tested several small-molecule lipase inhibitors and found that orlistat inhibits all lipases, indicating that it is a pan-lipase inhibitor. In short, we describe a simple, rapid, fluorescence-based triacylglycerol hydrolysis assay to assess four major TAG hydrolases: intracellular ATGL and hormone-sensitive lipase, LpL localized at the extracellular endothelium, and pancreatic lipase present in the intestinal lumen. The major advantages of this method are its speed, simplicity, and elimination of product isolation. This assay is potentially applicable to a wide range of lipases, is amenable to high-throughput screening to discover novel modulators of triacylglycerol hydrolases, and can be used for diagnostic purposes.

Lipolysis and lipophagy play individual and interactive roles in regulating triacylglycerol and cholesterol homeostasis and mitochondrial form in zebrafish

Neutral lipases-mediated lipolysis and acid lipases-moderated lipophagy are two main processes for degradation of lipid droplets (LDs). However, the individual and interactive roles of these metabolic pathways are not well known across vertebrates. This study explored the roles of lipolysis and lipophagy from the aspect of neutral and acid lipases in zebrafish. We established zebrafish strains deficient in either adipose triglyceride lipase (atgl-/-; AKO fish) or lysosomal acid lipase (lal-/-; LKO fish) respectively, and then inhibited lipolysis in the LKO fish and lipophagy in the AKO fish by feeding diets supplemented with the corresponding inhibitors Atglistatin and 3-Methyladenine, respectively. Both the AKO and LKO fish showed reduced growth, swimming activity, and oxygen consumption. The AKO fish did not show phenotypes in adipose tissue, but mainly accumulated triacylglycerol (TAG) in liver, also, they had large LDs in the hepatocytes, and did not stimulate lipophagy as a compensation response but maintained basal lipophagy. The LKO fish reduced total lipid accumulation in the body but had high cholesterol content in liver; also, they accumulated small LDs in the hepatocytes, and showed increased lipolysis, especially Atgl expression, as a compensatory mechanism. Simultaneous inhibition of lipolysis and lipophagy in zebrafish resulted in severe liver damage, with the potential to trigger mitophagy. Overall, our study illustrates that lipolysis and lipophagy perform individual and interactive roles in maintaining homeostasis of TAG and cholesterol metabolism. Furthermore, the interactive roles of lipolysis and lipophagy may be essential in regulating the functions and form of mitochondria.

Simultaneous Application of High-Intensity Focused Electromagnetic and Synchronized Radiofrequency for Fat Disruption: Histological and Electron Microscopy Porcine Model Study

BACKGROUND

Radiofrequency (RF) and high-intensity focused electromagnetic (HIFEM) technologies are used for noninvasive body shaping as standalone modalities.

OBJECTIVE

To examine the effects of novel synchronized RF and HIFEM on subcutaneous adipose tissue in a porcine animal model.

MATERIALS AND METHODS

Seven large white pigs aged 6 months received 3 abdominal treatments of simultaneous application of synchronized RF and HIFEM (30 minutes, once per week). Punch biopsies of treated and control subcutaneous tissue were collected at the baseline, 4 days, 2 weeks, 1 month, and 2 months. Specimens were examined by light and scanning electron microscopy. Adipocyte volume was analyzed. Fat tissue temperature was measured in situ (fiber optic probes) and superficially (thermal imager).

RESULTS

Fat layer was heated to temperatures of 42 to 45°C. Signs of fat apoptosis (shape alternations and pyknotic nuclei) appeared at day 4 and peaked between 2 weeks and 1 month. Adipocyte volume decreased significantly (p < .001) by 31.1% at 2 weeks, 1 month (-23.6%), and 2 months (-22.0%). Control samples showed healthy adipocytes. Scanning electron microscopy micrographs corroborated histology findings, showing flattened, volume-depleted and disrupted adipocytes.

CONCLUSION

Synchronized RF with HIFEM procedure resulted in a significant and sustained fat reduction with no adverse events.

Elevated S-adenosylhomocysteine induces adipocyte dysfunction to promote alcohol-associated liver steatosis

It has been previously shown that chronic ethanol administration-induced increase in adipose tissue lipolysis and reduction in the secretion of protective adipokines collectively contribute to alcohol-associated liver disease (ALD) pathogenesis. Further studies have revealed that increased adipose S-adenosylhomocysteine (SAH) levels generate methylation defects that promote lipolysis. Here, we hypothesized that increased intracellular SAH alone causes additional related pathological changes in adipose tissue as seen with alcohol administration. To test this, we used 3-deazaadenosine (DZA), which selectively elevates intracellular SAH levels by blocking its hydrolysis. Fully differentiated 3T3-L1 adipocytes were treated in vitro for 48 h with DZA and analysed for lipolysis, adipokine release and differentiation status. DZA treatment enhanced adipocyte lipolysis, as judged by lower levels of intracellular triglycerides, reduced lipid droplet sizes and higher levels of glycerol and free fatty acids released into the culture medium. These findings coincided with activation of both adipose triglyceride lipase and hormone sensitive lipase. DZA treatment also significantly reduced adipocyte differentiation factors, impaired adiponectin and leptin secretion but increased release of pro-inflammatory cytokines, IL-6, TNF and MCP-1. Together, our results demonstrate that elevation of intracellular SAH alone by DZA treatment of 3T3-L1 adipocytes induces lipolysis and dysregulates adipokine secretion. Selective elevation of intracellular SAH by DZA treatment mimics ethanol's effects and induces adipose dysfunction. We conclude that alcohol-induced elevations in adipose SAH levels contribute to the pathogenesis and progression of ALD.

Pharmacopuncture of Taraxacum platycarpum extract reduces localized fat by regulating the lipolytic pathway

Localized fat deposits are associated with health and aesthetic problems that mainly affect a large proportion of individuals. Recently, bioactive constituents of TP have been reported to affect lipid metabolism. In this study, we performed a network pharmacological analysis to assume potential lipolytic effects of TP and investigated the actual lipolytic effects of TP extract injection on local body fat and its underlying mechanism. Using the genes related to active compounds of TP, the network was constructed. Through the Functional Enrichment Analysis, Lipid Metabolism and Fatty Acid Metabolism were expected to be affiliated with the network, which implied possible lipolytic effects of TP. On the comparison between TP network and Obesity-related Gene Sets, about three-fourths of elements were in common with the gene sets, which indicated a high relevance between TP and obesity. Based on the genes in lipolysis-related pathways, Perilipin, CGI-58, ATGL, HSL and MGL were selected to identify the actual lipolytic effects of TP. TP injection reduced the inguinal fat weight. Also, the diameter of the adipocytes was decreased by the TP treatment in HFD-induced obese mice. In addition, TP suppressed lipid accumulation in differentiated 3T3-L1 adipocytes. Moreover, because the expression of Perilipin was increased, CGI-58, ATGL, HSL and MGL were markedly decreased. Furthermore, glycerol release was down-regulated by the TP treatment. TP exerted its lipolytic effects by regulating the lipolysis machinery through stimulation of lipases. Based on the present findings, TP is expected to be a potent component of injection lipolysis for removing localized body fat.

Roles of Phase Separation for Cellular Redox Maintenance

The oxidation reaction greatly alters characteristics of various cellular components. In exchange for efficient energy production, mitochondrial aerobic respiration substantially increases the risk of excess oxidation of cellular biomolecules such as lipids, proteins, nucleic acids, and numerous small molecules. To maintain a physiologically balanced cellular reduction-oxidation (redox) state, cells utilize a variety of molecular machineries including cellular antioxidants and protein degradation complexes such as the ubiquitin-proteasome system or autophagy. In the past decade, biomolecular liquid-liquid phase separation (LLPS) has emerged as a subject of great interest in the biomedical field, as it plays versatile roles in the maintenance of cellular homeostasis. With regard to redox homeostasis, LLPS arose as a major player in both well-characterized and newly emerging redox pathways. LLPS is involved in direct redox imbalance sensing, signal transduction, and transcriptional regulation. Also, LLPS is at play when cells resist redox imbalance through metabolic switching, translational remodeling, activating the DNA damage response, and segregation of vulnerable lipids and proteins. On the other hand, chronic accumulation of phase-separated molecular condensates such as lipid droplets and amyloid causes neurotoxic outcomes. In this review we enumerate recent progress on understanding how cells utilize LLPS to deal with oxidative stress, especially related to cell survival or pathogenesis, and we discuss future research directions for understanding biological phase separation in cellular redox regulation.

Identification of prognostic lipid droplet-associated genes in pancreatic cancer patients via bioinformatics analysis

BACKGROUND

Pancreatic cancer is the fourth leading cause of cancer deaths in the United States both in females and in males, and is projected to become the second deadliest cancer by 2030. The overall 5-year survival rate remains at around 10%. Cancer metabolism and specifically lipid metabolism plays an important role in pancreatic cancer progression and metastasis. Lipid droplets can not only store and transfer lipids, but also act as molecular messengers, and signaling factors. As lipid droplets are implicated in reprogramming tumor cell metabolism and in invasion and migration of pancreatic cancer cells, we aimed to identify lipid droplet-associated genes as prognostic markers in pancreatic cancer.

METHODS

We performed a literature search on review articles related to lipid droplet-associated proteins. To select relevant lipid droplet-associated factors, bioinformatics analysis on the GEPIA platform (data are publicly available) was carried out for selected genes to identify differential expression in pancreatic cancer versus healthy pancreatic tissues. Differentially expressed genes were further analyzed regarding overall survival of pancreatic cancer patients.

RESULTS

65 factors were identified as lipid droplet-associated factors. Bioinformatics analysis of 179 pancreatic cancer samples and 171 normal pancreatic tissue samples on the GEPIA platform identified 39 deferentially expressed genes in pancreatic cancer with 36 up-regulated genes (ACSL3, ACSL4, AGPAT2, BSCL2, CAV1, CAV2, CAVIN1, CES1, CIDEC, DGAT1, DGAT2, FAF2, G0S2, HILPDA, HSD17B11, ICE2, LDAH, LIPE, LPCAT1, LPCAT2, LPIN1, MGLL, NAPA, NCEH1, PCYT1A, PLIN2, PLIN3, RAB5A, RAB7A, RAB8A, RAB18, SNAP23, SQLE, VAPA, VCP, VMP1) and 3 down-regulated genes (FITM1, PLIN4, PLIN5). Among 39 differentially expressed factors, seven up-regulated genes (CAV2, CIDEC, HILPDA, HSD17B11, NCEH1, RAB5A, and SQLE) and two down-regulation genes (BSCL2 and FITM1) were significantly associated with overall survival of pancreatic cancer patients. Multivariate Cox regression analysis identified CAV2 as the only independent prognostic factor.

CONCLUSIONS

Through bioinformatics analysis, we identified nine prognostic relevant differentially expressed genes highlighting the role of lipid droplet-associated factors in pancreatic cancer.

The Drosophila model to interrogate triacylglycerol biology

The deposition of storage fat in the form of triacylglycerol (TAG) is an evolutionarily conserved strategy to cope with fluctuations in energy availability and metabolic stress. Organismal TAG storage in specialized adipose tissues provides animals a metabolic reserve that sustains survival during development and starvation. On the other hand, excessive accumulation of adipose TAG, defined as obesity, is associated with an increasing prevalence of human metabolic diseases. During the past decade, the fruit fly Drosophila melanogaster, traditionally used in genetics and developmental biology, has been established as a versatile model system to study TAG metabolism and the etiology of lipid-associated metabolic diseases. Similar to humans, Drosophila TAG homeostasis relies on the interplay of organ systems specialized in lipid uptake, synthesis, and processing, which are integrated by an endocrine network of hormones and messenger molecules. Enzymatic formation of TAG from sugar or dietary lipid, its storage in lipid droplets, and its mobilization by lipolysis occur via mechanisms largely conserved between Drosophila and humans. Notably, dysfunctional Drosophila TAG homeostasis occurs in the context of aging, overnutrition, or defective gene function, and entails tissue-specific and organismal pathologies that resemble human disease. In this review, we summarize the physiology and biochemistry of TAG in Drosophila and outline the potential of this organism as a model system to understand the genetic and dietary basis of TAG storage and TAG-related metabolic disorders.

Multiple strategies with the synergistic approach for addressing colorectal cancer

Cancer treatment is improving widely over time, but finding a proper defender to beat them seems like a distant dream. The quest for identification and discovery of drugs with an effective action is still a vital work. The role of a membrane protein called P-glycoprotein, which functions as garbage chute that efflux the waste, xenobiotics, and toxins out of the cancer cells acts as a major reason behind the therapeutic failure of most chemotherapeutic drugs. In this review, we mainly focused on a multiple strategies by employing 5-Fluorouracil, curcumin, and lipids in Nano formulation for the possible treatment of colorectal cancer and its metastasis. Eventually, multidrug resistance and angiogenesis can be altered and it would be helpful in colorectal cancer targeting.We have depicted the possible way for the depletion of colorectal cancer cells without disturbing the normal cells. The concept of focusing on multiple pathways for marking the colorectal cancer cells could help in activating one among the pathways if the other one fails. The activity of the 5-Fluorouracil can be enhanced with the help of curcumin which acts as a chemosensitizer, chemotherapeutic agent, and even for altering the resistance. As we eat to survive, so do the cancer cells. The cancer cells utilize the energy source to stay alive and survive. Fatty acids can be used as the energy source and this concept can be employed for targeting the colorectal cancer cells and also for altering the resistant part.

Dissecting lipid droplet biology with coherent Raman scattering microscopy

Lipid droplets (LDs) are lipid-rich organelles universally found in most cells. They serve as a key energy reservoir, actively participate in signal transduction and dynamically communicate with other organelles. LD dysfunction has been associated with a variety of diseases. The content level, composition and mobility of LDs are crucial for their physiological and pathological functions, and these different parameters of LDs are subject to regulation by genetic factors and environmental inputs. Coherent Raman scattering (CRS) microscopy utilizes optical nonlinear processes to probe the intrinsic chemical bond vibration, offering label-free, quantitative imaging of lipids in vivo with high chemical specificity and spatiotemporal resolution. In this Review, we provide an overview over the principle of CRS microscopy and its application in tracking different parameters of LDs in live cells and organisms. We also discuss the use of CRS microscopy in genetic screens to discover lipid regulatory mechanisms and in understanding disease-related lipid pathology.

The Role of Lipids, Lipid Metabolism and Ectopic Lipid Accumulation in Axon Growth, Regeneration and Repair after CNS Injury and Disease

Axons in the adult mammalian nervous system can extend over formidable distances, up to one meter or more in humans. During development, axonal and dendritic growth requires continuous addition of new membrane. Of the three major kinds of membrane lipids, phospholipids are the most abundant in all cell membranes, including neurons. Not only immature axons, but also severed axons in the adult require large amounts of lipids for axon regeneration to occur. Lipids also serve as energy storage, signaling molecules and they contribute to tissue physiology, as demonstrated by a variety of metabolic disorders in which harmful amounts of lipids accumulate in various tissues through the body. Detrimental changes in lipid metabolism and excess accumulation of lipids contribute to a lack of axon regeneration, poor neurological outcome and complications after a variety of central nervous system (CNS) trauma including brain and spinal cord injury. Recent evidence indicates that rewiring lipid metabolism can be manipulated for therapeutic gain, as it favors conditions for axon regeneration and CNS repair. Here, we review the role of lipids, lipid metabolism and ectopic lipid accumulation in axon growth, regeneration and CNS repair. In addition, we outline molecular and pharmacological strategies to fine-tune lipid composition and energy metabolism in neurons and non-neuronal cells that can be exploited to improve neurological recovery after CNS trauma and disease.

Molecular Mechanisms of the Anti-obesity Properties of Agardhiella subulata in Mice Fed a High-Fat Diet

The overweight and obese population has skyrocketed, resulting in a high incidence of metabolic disorders. Agardhiella subulata (AS) contains a variety of beneficial components, such as sulfur-containing polysaccharides (dietary fiber) and astaxanthin, which is considered to have anti-obesity potential. In this study, we investigated the effects and possible mechanisms of dietary AS on high-fat diet (HFD)-induced obesity in mice. AS supplementation significantly reduced HFD-induced weight gain (19%) and the visceral adiposity index (4.1%). In addition, the level of total cholesterol, triglyceride, and low-density lipoprotein was significantly decreased; adiponectin was significantly increased in serum and fecal triglyceride excretion was significantly higher in mice fed AS compared with mice on an HFD. Preadipocyte factor 1 and Sry-box transcription factor 9 that were significantly higher than the levels found for the HFD group lead to reduced adipogenesis. Moreover, accompanying the lipolysis and fatty acid β-oxidation that occur in the AS group, the concentration of non-esterified fatty acids was lowered to 0.4 ± 0.1 mEq/L. In addition, peroxisome proliferator-activated receptor γ and phosphorylation acetyl-CoA carboxylase increased 1.5- and 1-fold, thus increasing the expression of adiponectin and the activation of AMPK and ultimately resulting in lower blood glucose levels. The results of this study suggest that AS supplementation increases lipid excretion and improves energy metabolism to prevent obesity in mice fed a HFD.

Analgesic and Anticancer Activity of Benzoxazole Clubbed 2-Pyrrolidinones as Novel Inhibitors of Monoacylglycerol Lipase

Ten benzoxazole clubbed 2-pyrrolidinones (11–20) as human monoacylglycerol lipase inhibitors were designed on the criteria fulfilling the structural requirements and on the basis of previously reported inhibitors. The designed, synthesized, and characterized compounds (11–20) were screened against monoacylglycerol lipase (MAGL) in order to find potential inhibitors. Compounds 19 (4-NO₂ derivative) and 20 (4-SO₂NH₂ derivative), with an IC₅₀ value of 8.4 and 7.6 nM, were found most active, respectively. Both of them showed micromolar potency (IC₅₀ value above 50 µM) against a close analogue, fatty acid amide hydrolase (FAAH), therefore considered as selective inhibitors of MAGL. Molecular docking studies of compounds 19 and 20 revealed that carbonyl of 2-pyrrolidinone moiety sited at the oxyanion hole of catalytic site of the enzyme stabilized with three hydrogen bonds (~2 Å) with Ala51, Met123, and Ser122, the amino acid residues responsible for the catalytic function of the enzyme. Remarkably, the physiochemical and pharmacokinetic properties of compounds 19 and 20, computed by QikProp, were found to be in the qualifying range as per the proposed guideline for good orally bioactive CNS drugs. In formalin-induced nociception test, compound 20 reduced the pain response in acute and late stages in a dose-dependent manner. They significantly demonstrated the reduction in pain response, having better potency than the positive control gabapentin (GBP), at 30 mg/kg dose. Compounds 19 and 20 were submitted to NCI, USA, for anticancer activity screening. Compounds 19 (NSC: 778839) and 20 (NSC: 778842) were found to have good anticancer activity on SNB-75 cell line of CNS cancer, exhibiting 35.49 and 31.88% growth inhibition (% GI), respectively.

Hydro alcoholic green tea extract effect on high fat diet treated NMRI mice and 3T3L1 cells

Purpose

In order to counteract the obesity has epidemics, since current anti-obesity drugs effects remain limited, there is a need to provide new options. As a project aiming to assess potential anti obesity natural compounds, the effects of consumption of a minimal dose of green tea hydro alcoholic extract (GT) on adipocyte differentiation of 3T3L1 cell line were investigated.

Methods

Obesity was induced in female NMRI mice (which are less used overall) by the use of a high fat diet. Mice were divided into four groups of control (C), treated control (TC), obese (O) and treated obese (TO). TC and TO groups received 8 mg/Kg/day of GT for 8 weeks, and weighted weekly, after what biochemical and histological parameters were measured. GT was used at doses of 100,150 and 200 µg/ml on 3T3L1, and staining with Oil-red-O was done for estimation of fat droplet accumulation.

Results

Body weight was found to be affected significantly by GT. Blood glucose levels did not show significant changes between groups, while triglycerides levels of the O group was significantly higher than the C group, but the TO group showed no significant difference with the C group upon GT treatment. Liver and visceral fat tissues showed more normalized tissue and less fat accumulation in the TO group. TO and TC groups showed an ameliorated morphologic state of liver tissues. GT was also able to decrease fat droplet formation in a dose-dependent manner.

Conclusions

Adding a minimal amount of GT to the daily consumption may have preventive effects on fat accumulation in healthy subjects, while in obese cases, GT shows significant therapeutic effect.

Reduced Liver Autophagy in High-Fat Diet Induced Liver Steatosis in New Zealand Obese Mice

Non-alcoholic fatty liver disease (NAFLD), as a consequence of overnutrition caused by high-calorie diets, results in obesity and disturbed lipid homeostasis leading to hepatic lipid droplet formation. Lipid droplets can impair hepatocellular function; therefore, it is of utmost importance to degrade these cellular structures. This requires the normal function of the autophagic-lysosomal system and the ubiquitin-proteasomal system. We demonstrated in NZO mice, a polygenic model of obesity, which were compared to C57BL/6J (B6) mice, that a high-fat diet leads to obesity and accumulation of lipid droplets in the liver. This was accompanied by a loss of autophagy efficiency whereas the activity of lysosomal proteases and the 20S proteasome remained unaffected. The disturbance of cellular protein homeostasis was further demonstrated by the accumulation of 3-nitrotyrosine and 4-hydroxynonenal modified proteins, which are normally prone to degradation. Therefore, we conclude that fat accumulation in the liver due to a high-fat diet is associated with a failure of autophagy and leads to the disturbance of proteostasis. This might further contribute to lipid droplet stabilization and accumulation.

Shared genetic etiology between Parkinson's disease and blood levels of specific lipids

Parkinson’s disease (PD) is characterized by the degeneration of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies. The mechanisms underlying these molecular and cellular effects are largely unknown. Previously, based on genetic and other data, we built a molecular landscape of PD that highlighted a central role for lipids. To explore which lipid species may be involved in PD pathology, we used published genome-wide association study (GWAS) data to conduct polygenic risk score-based analyses to examine putative genetic sharing between PD and blood levels of 370 lipid species and lipid-related molecules. We found a shared genetic etiology between PD and blood levels of 25 lipids. We then used data from a much-extended GWAS of PD to try and corroborate our findings. Across both analyses, we found genetic overlap between PD and blood levels of eight lipid species, namely two polyunsaturated fatty acids (PUFA 20:3n3-n6 and 20:4n6), four triacylglycerols (TAG 44:1, 46:1, 46:2, and 48:0), phosphatidylcholine aa 32:3 (PC aa 32:3) and sphingomyelin 26:0 (SM 26:0). Analysis of the concordance—the agreement in genetic variant effect directions across two traits—revealed a significant negative concordance between PD and blood levels of the four triacylglycerols and PC aa 32:3 and a positive concordance between PD and blood levels of both PUFA and SM 26:0. Taken together, our analyses imply that genetic variants associated with PD modulate blood levels of a specific set of lipid species supporting a key role of these lipids in PD etiology.

CL316243 treatment mitigates the inflammation in white adipose tissues of juvenile adipocyte-specific Nfe2l1 knockout mice

Nuclear factor-erythroid 2-related factor 1 (NFE2L1) is a key transcription factor that regulates cellular adaptive responses to various stresses. Our previous studies revealed that adult adipocyte-specific Nfe2l1-knockout [Nfe2l1(f)-KO] mice show adipocyte hypertrophy and severe adipose inflammation, which can be worsened by rosiglitazone, a peroxisome proliferator-activated receptor γ agonist. To further assess the crucial roles of NFE2L1 in adipocytes, we investigated the effect of CL316243, a β3 adrenergic agonist that promotes lipolysis via a post-translational mechanism, on adipose inflammation in juvenile Nfe2l1(f)-KO mice. In contrast to adult mice, 4-week-old juvenile Nfe2l1(f)-KO mice displayed a normal fat distribution but reduced fasting plasma glycerol levels and elevated adipocyte hypertrophy and macrophage infiltration in inguinal and gonadal WAT. In addition, Nfe2l1(f)-KO mice had decreased expression of multiple lipolytic genes and reduced lipolytic activity in WAT. While 7 days of CL316243 treatment showed no significant effect on adipose inflammation in Nfe2l1-Floxed control mice, the same treatment dramatically alleviated macrophage infiltration and mRNA expression of inflammation and pyroptosis-related genes in WAT of Nfe2l1(f)-KO mice. Together with previous findings in adult mice, the current study highlights that NFE2L1 plays a fundamental regulatory role in lipolytic gene expression and thus might be an important target to improve adipose plasticity and lipid homeostasis.

RORα regulates hepatic lipolysis by inducing transcriptional expression of PNPLA3 in mice

Nonalcoholic fatty liver diseases (NAFLDs) are characterized by excessive triacylglycerol (TAG) accumulation in the liver which contributes to hepatocyte dysfunction, inflammation, and fibrosis. Patatin-like phospholipase domain-containing 3 (PNPLA3; also known as adiponutrin) has emerged as an important enzyme leading to hepatic TAG hydrolysis. Because the I148M substitution in the PNPLA3 gene markedly reduces hepatic TAG hydrolase activity, this genetic variation is strongly associated with increased hepatic TAG in the full spectrum of NAFLDs. The Retinoic acid-related orphan receptor α (RORα) regulates various target genes related to lipid metabolism. Here, we investigated the role of RORα on PNPLA3-mediated hepatic lipid hydrolysis. With blockade of lipid esterification and β-oxidation, RORα enhanced TAG hydrolysis, resulting in increased free glycerol levels. We found a putative RORα response element on the upstream of PNPLA3 gene that was activated by RORα. Furthermore, the inhibitory action of cJUN on the RORα/PNPLA3 axis was enhanced under lipid stress and contributed to hepatic lipid accumulation. In summary, we showed for the first time that RORα activates the transcription of PNPLA3, which suggests that RORα and its ligands represent potential precision therapeutic approaches for NAFLDs.

Hormone-sensitive lipase couples intergenerational sterol metabolism to reproductive success

Triacylglycerol (TG) and steryl ester (SE) lipid storage is a universal strategy to maintain organismal energy and membrane homeostasis. Cycles of building and mobilizing storage fat are fundamental in (re)distributing lipid substrates between tissues or to progress ontogenetic transitions. In this study, we show that Hormone-sensitive lipase (Hsl) specifically controls SE mobilization to initiate intergenerational sterol transfer in Drosophila melanogaster. Tissue-autonomous Hsl functions in the maternal fat body and germline coordinately prevent adult SE overstorage and maximize sterol allocation to embryos. While Hsl-deficiency is largely dispensable for normal development on sterol-rich diets, animals depend on adipocyte Hsl for optimal fecundity when dietary sterol becomes limiting. Notably, accumulation of SE but not of TG is a characteristic of Hsl-deficient cells across phyla including murine white adipocytes. In summary, we identified Hsl as an ancestral regulator of SE degradation, which improves intergenerational sterol transfer and reproductive success in flies.

Prolyl isomerase Pin1 interacts with adipose triglyceride lipase and negatively controls both its expression and lipolysis

BACKGROUND

Lipolysis is essential for the supply of nutrients during fasting, the control of body weight, and remodeling of white adipose tissues and thermogenesis. In the obese state, lipolysis activity and the expression of adipose triglyceride lipase (ATGL), a rate-limiting enzyme, is suppressed. However, the mechanism underlying the regulation of ATGL remains largely unknown. We previously reported that a high-fat diet obviously increases protein levels of the prolyl isomerase, Pin1, in epididymal white adipose tissue (epiWAT) of mice and that Pin1 KO mice are resistant to developing obesity.

RESULTS

The present study found that deletion of the Pin1 gene in epiWAT upregulated lipolysis and increased ATGL protein expression by ~2-fold. In addition, it was demonstrated that Pin1 directly associated with ATGL and enhanced its degradation through the ubiquitin proteasome system. Indeed, Pin1 overexpression decreased ATGL expression levels, whereas Pin1 knockdown by siRNA treatment upregulated ATGL protein levels without altering mRNA levels. Moreover, under a high fat diet (HFD)-fed condition, adipocyte-specific Pin1 KO (adipoPin1 KO) mice had 2-fold increase lipolytic activity and upregulated β-oxidation-related gene expressions. These mice also gained less body weight, and had better glucose metabolism according to the results of glucose and insulin tolerance tests.

CONCLUSION

Taken together, these results showed that Pin1 directly interacted with and degraded ATGL via a ubiquitin-proteasome system, consequently causing the downregulation of lipolysis. Therefore, Pin1 could be considered a target for the treatment of dyslipidemia and related disorders.

Effects of different oxygen tensions on differentiated human preadipocytes lipid storage and mobilisation

Adipose tissue expansion has been suggested to impair oxygen (O₂) diffusion in the adipose tissue and cause hypoxia. This study aimed at characterising the effects of hypoxia on adipocyte lipid storage and mobilisation functions. Human preadipocytes were exposed to different O₂ tensions (3, 10 and 21%) either acutely for 24 h after differentiation (acute exposure) or during differentiation (14d, chronic hypoxia). Lipoprotein lipase (LPL) activity was decreased dose-dependently by both acute and chronic hypoxia (p < .05). Acute exposure to 3, and 10% O₂ stimulated the expression of lipid storage gene, while chronic exposure to 3% O₂ inhibited the expression of genes involved in lipid storage and mobilisation (p < .05). Acute hypoxia dose-dependently stimulated basal lipolysis. Conversely, chronic hypoxia did not affect basal lipolysis but significantly decreased isoproterenol-stimulated lipolysis (p < .05). In conclusion, the effects of hypoxia on human adipocyte lipid storage and mobilisation functions are complex but could favour ectopic fat deposition.

Dietary fat content and adipose triglyceride lipase and hormone-sensitive lipase gene expressions in adults' subcutaneous and visceral fat tissues

INTRODUCTION

We examined the association of adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) gene expressions, as the key regulators of lipolysis, with dietary fat quantity and composition in subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT).

METHODS

In this observational study, samples were collected from patients undergoing elective abdominal surgery. Participants were categorized into two groups based on their body mass index (BMI) status. Dietary, anthropometric, and biochemical data were collected before surgery. Linear regression was performed to determine the association of dietary fat content with ATGL and HSL gene expressions in SAT and VAT.

RESULTS

152 individuals with a mean ± SD age of 40.7 ± 13.2 years and a median (inter-quartile range) BMI of 39.4 (26.5-45.3 kg/m²) participated in this study, of whom 54 were non-obese (BMI<30 kg/m²), and 98 were obese (BMI≥30 kg/m²). Among non-obese participants, positive associations were observed between ATGL mRNA expression and reported intakes of total fatty acids (TFA) (β=0.306, P = 0.025), myristic (β=0.285, P = 0.038), palmitic (β=0.417, P = 0.002), oleic (β=0.333, P = 0.017), dairy trans (β=0.374, P = 0.006), and other trans FAs (β=0.369, P = 0.006) in SAT. In contrast, inverse associations between HSL mRNA expression and reported intakes of TFAs (β=-0.377, P = 0.005), myristic (β=-0.282, P = 0.039), palmitic (β=-0.372, P = 0.006), stearic (β=-0.314, P = 0.020), and oleic acid (β=-0.372, P = 0.007) were observed in SAT. No associations were observed among obese participants, nor in VAT among non-obese individuals.

CONCLUSION

ATGL and HSL mRNA expressions in SAT were associated with dietary fat quantity and composition among non-obese adults.