Hormone-sensitive Lipase Research Articles

Design and Synthesis of Novel Indole Ethylamine Derivatives as a Lipid Metabolism Regulator Targeting PPARα/CPT1 in AML12 Cells.

Peroxisome proliferator-activated receptor alpha (PPARα) and carnitine palmitoyltransferase 1 (CPT1) are important targets of lipid metabolism regulation for nonalcoholic fatty liver disease (NAFLD) therapy. In the present study, a set of novel indole ethylamine derivatives (4, 5, 8, 9) were designed and synthesized. The target product (compound 9) can effectively activate PPARα and CPT1a. Consistently, in vitro assays demonstrated its impact on the lipid accumulation of oleic acid (OA)-induced AML12 cells. Compared with AML12 cells treated only with OA, supplementation with 5, 10, and 20 μM of compound 9 reduced the levels of intracellular triglyceride (by 28.07%, 37.55%, and 51.33%) with greater inhibitory activity relative to the commercial PPARα agonist fenofibrate. Moreover, the compound 9 supplementations upregulated the expression of hormone-sensitive triglyceride lipase (HSL) and adipose triglyceride lipase (ATGL) and upregulated the phosphorylation of acetyl-CoA carboxylase (ACC) related to fatty acid oxidation and lipogenesis. This dual-target compound with lipid metabolism regulatory efficacy may represent a promising type of drug lead for NAFLD therapy.

Dietary supplementation of cinnamaldehyde positively affects the physiology, feed utilization, growth, and body composition of striped catfish Pangasianodon hypophthalmus.

The study evaluated the effects of diverse cinnamaldehyde (CIN) supplementation doses on the physiological attributes, feed utilization, growth, and body composition of striped catfish Pangasianodon hypophthalmus. The study incorporated five doses of CIN supplementation, namely 0, 0.5, 1, 1.5, and 2gkg-1 feed, with four replicates per group. Commercial extruded isonitrogenous and isoenergetic feeds with crude protein and gross energy levels of 28.46% ± 0.23% and 3858.70 ± 18.06kcalkg-1, respectively, were used as test feeds. The initial weight of striped catfish was 5.57 ± 0.02g, and 30 fish were maintained in each cage (2 × 1 × 1 m3) for 60days. The results illustrated that the incorporation of CIN into the diet increases amylase and lipase levels and the ability of striped catfish to accumulate glucose, as the glucose tolerance test revealed that CIN 1.0 and 1.5gkg-1 reduced glucose content to its basal level at 3-4 h postinjection and upregulated the insulin receptor, hexokinase, and hormone-sensitive lipase genes. CIN 1.5gkg-1 also increased plasma total protein and high-density lipoprotein levels and reduced triglyceride and cholesterol levels. CIN 1.0-2.0 g kg-1 increased antioxidant capacity by increasing the levels of superoxide dismutase and glutathione and decreasing malondialdehyde levels. CIN 1.5gkg-1 was the best treatment for increasing final weight, the specific growth rate, protein retention, and the protein efficiency ratio and for decreasing the feed conversion ratio. CIN additionally increased meat protein and decreased meat and liver lipid content. This study concluded that 1.24gkg-1 is the optimal CIN dose calculated from the equation Y = - 0.1487x2 + 0.3702x + 5.0724 (R2 = 0.71) to increase growth and feed efficiency in striped catfish by increasing nonprotein catabolism and exerting antioxidant effects.

The preferential utilization of hepatic glycogen as energy substrates in largemouth bass (Micropterus salmoides) under short-term starvation.

To elucidate the underlying mechanism of the energy metabolism in largemouth bass (Micropterus salmoides), cultured fish (initial body weight: 77.57 ± 0.75 g) in the present study were starved for 0 h, 12 h, 24 h, 48 h, 96 h and 192 h, respectively. The proximate composition analysis showed that short-term starvation induced a significant up-regulation in crude protein proportion in hepatic of cultured fish (P < 0.05). However, short-term starvation significantly decreased the hepatosomatic index and the viscerosomatic index of cultured fish (P < 0.05). The exact hepatic glycogen content in the group starved for 92 h presented remarkable decrease (P < 0.05). Meanwhile, compared with the weight change of lipid and protein (mg) in hepatic (y = 0.0007x2 - 0.2827x + 49.402; y = 0.0013x2 - 0.5666x + 165.31), the decreasing trend of weight in glycogen (mg) was more pronounced (y = 0.0032x2 - 1.817x + 326.52), which suggested the preferential utilization of hepatic glycogen as energy substrates under short-term starvation. Gene expression analysis revealed that the starvation down-regulated the expression of insulin-like growth factor 1 and genes of TOR pathway, such as target of rapamycin (tor) and ribosomal protein S6 (s6) (P < 0.05). In addition, the starvation significantly enhanced expression of lipolysis-related genes, including hormone-sensitive lipase (hsl) and carnitine palmitoyl transferase I (cpt1), but down-regulated lipogenesis as indicated by the inhibited expression of fatty acids synthase (fas), acetyl-CoA carboxylase 1 (acc1) and acetyl-CoA carboxylase 2 (acc2) (P < 0.05). Starvation of 24 h up-regulated the expression of glycolysis genes, glucokinase (gk), phosphofructokinase liver type (pfkl) and pyruvate kinase (pk), and then their expression returned to the normal level. Meanwhile, the expression of gluconeogenesis genes, such as glucose-6-phosphatase catalytic subunit (g6pc), fructose-1,6-bisphosphatase-1 (fbp1) and phosphoenolpyruvate carboxy kinase (pepck), was significantly inhibited with the short-term starvation (P < 0.05). In conclusion, short-term starvation induced an overall decline in growth performance, but it could deplete the hepatic glycogen accumulation and mobilize glycogen for energy effectively.

Functionally conserved PPARG exonic circRNAs enhance intramuscular fat deposition by regulating PPARG and HSL

Circular RNAs (circRNA) are a kind of endogenous biological macromolecules that play significant roles in many biological processes, including adipogenesis, a precisely orchestrated process that is mediated by a large number of factors. Among them, peroxisome proliferator-activated receptor gamma (PPARG), is undoubtedly the most important regulator of adipocyte development in all types of adipose tissue. The formation of intramuscular fat (IMF), is a key factor that influences the meat quality in livestock animals. PPARG has been demonstrated to show a positive correlation with IMF deposition although the regulatory mechanism involved is not known. This study demonstrates that PPARG mediates IMF deposition by producing multiple exonic circRNAs (circPPARGs). Three circPPARGs promote adipogenic differentiation and inhibit the proliferation of intramuscular preadipocytes and these effects are conserved across several species including buffaloes, cattle and mice. Notably, circPPARG1 interacts with PPARG protein to inhibit the transcription of hormone sensitive lipase (HSL) involved in lipolysis. In addition, the positive effects of circPPARG1 on IMF deposition were identified in mice in vivo. Thus, PPARG drives IMF deposition, not only through the common transcription factor pathway, but also by producing circRNAs. This study provides new insights into our understanding of the regulatory mechanisms of PPARG in IMF deposition.

Treatment with a new barbituric acid derivative suppresses diet-induced metabolic dysfunction and non-alcoholic fatty liver disease in mice

IntroductionNonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease, often accompanied by obesity, diabetes, and increased risks of depression and anxiety. Currently, there are no FDA-approved drugs to treat NAFLD and its related systemic symptoms. Previously, we identified a new barbituric acid derivative (BA-5) that expressed effectiveness against fibrosis and drug-resistant hepatocellular carcinoma. AimsThis study investigated the potential of BA-5 against high-fat diet (HFD)-induced NAFLD and mood disorders in mice. Main methodsSix-weeks-old male C57BL/6 mice were fed with a 45 % HFD for 8 weeks to induce NAFLD and associated metabolic disorders. Mice were treated with a BA-5 and the therapeutic effects and the underlying molecular mechanisms were investigated. Key findingsAdministration of BA-5 significantly reduced serum levels of alanine aminotransferase (ALT), low-density lipoprotein (LDL), fatty acids (FA), and triglycerides (TG) in HFD-fed mice. BA-5 treatment decreased expressions of hepatic lipogenesis-related markers (acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and ATP-citrate lyase (ACLY)), increased fatty acid oxidation markers (carnitine palmitoyltransferase 1A (CPT1A) and acyl-CoA oxidase 1 (ACOX1)), and attenuated hepatic fat accumulation in HFD-fed mice. Moreover, HFD-induced adipocyte size enlargement and activation of lipolysis markers such as phosphorylated (p)-hormone-sensitive lipase (HSL) 565, p-HSL 660, and perilipin were inhibited in BA-5-treated mice. Notably, HFD-induced anxiety- and depression-like behaviors significantly improved in the BA-5 treated group through enhanced anti-inflammatory responses in the hippocampus. SignificanceThis study provides new insights into clinical therapeutic strategies of barbituric acid derivatives for HFD-induced NAFLD and associated mood disturbances.

Variation in the HSL Gene and Its Association with Carcass and Meat Quality Traits in Yak

Hormone-sensitive lipase (HSL) is involved in the breakdown of triacylglycerols in adipose tissue, which influences muscle tenderness and juiciness by affecting the intramuscular fat content (IMF). This study analyzed the association between different genotypes and haplotypes of the yak HSL gene and carcass and meat quality traits. We used hybridization pool sequencing to detect exon 2, exon 8, and intron 3 variants of the yak HSL gene and genotyped 525 Gannan yaks via KASP to analyze the effects of the HSL gene variants on the carcass and meat quality traits in yaks. According to the results, the HSL gene is highly expressed in yak adipose tissue. Three single nucleotide polymorphisms (SNPs) were identified, with 2 of them located in the coding region and one in the intron region. Variants in the 2 coding regions resulted in amino acid changes. The population had 3 genotypes of GG, AG, and AA, and individuals with the AA genotype had lower WBSF values (p &lt; 0.05). The H3H3 haplotype combinations could improve meat tenderness by reducing the WBSF values and the cooking loss rate (CLR) (p &lt; 0.05). H1H1 haplotype combinations were associated with the increased drip loss rate (DLR) (p &lt; 0.05). The presence of the H1 haplotype was associated the increased CLR in yaks, while that of the H2 haplotype was associated with the decreased DLR in yaks (p &lt; 0.05). These results demonstrated that the HSL gene may influence the meat quality traits in yaks by affecting the IMF content in muscle tissues. Consequently, the HSL gene can possibly be used as a biomarker for improving the meat quality traits in yaks in the future.

Follistatin-like 1 is a myokine regulating lipid mobilization during endurance exercise and recovery.

The aim of this study was to investigate the role of the follistatin-like 1 (Fstl1) and disco-interacting protein 2 homolog A (DIP2a) axis in relation to lipid metabolism during and after endurance exercise and to elucidate the mechanisms underlying the metabolic effects of Fstl1 on adipocytes, considering its regulation by exercise and muscle mass and its link to obesity. Twenty-nine sedentary males participated in endurance exercise, and blood samples were collected during and after the exercise. Body composition, Fstl1, glycerol, epinephrine, growth hormone, and atrial natriuretic peptide were measured. 3T3-L1 adipocytes, with or without DIP2a knockdown, were treated with Fstl1 to assess glycerol release, cyclic AMP/cyclic GMP production, and hormone sensitive lipase phosphorylation. The association between DIP2a gene expression levels in human adipose tissues and exercise-induced lipolysis was examined. Fstl1 levels significantly increased during endurance exercise and following recovery, correlating with lean body mass and lipolysis. In 3T3-L1 adipocytes, Fstl1 increased glycerol release, cyclic GMP production, and hormone sensitive lipase activation, but these effects were attenuated by DIP2a knockdown. DIP2a gene expression in human adipose tissues correlated with serum glycerol concentrations during endurance exercise. Fstl1 is a myokine facilitating lipid mobilization during and after endurance exercise through DIP2a-mediated lipolytic effects in adipocytes.

Hydrolases &amp; Lipases in GtoPdb v.2023.3

Listed in this section are hydrolases not accumulated in other parts of the Concise Guide, such as monoacylglycerol lipase and acetylcholinesterase. Pancreatic lipase is the predominant mechanism of fat digestion in the alimentary system; its inhibition is associated with decreased fat absorption. CES1 is present at lower levels in the gut than CES2 (P23141), but predominates in the liver, where it is responsible for the hydrolysis of many aliphatic, aromatic and steroid esters. Hormone-sensitive lipase is also a relatively non-selective esterase associated with steroid ester hydrolysis and triglyceride metabolism, particularly in adipose tissue. Endothelial lipase is secreted from endothelial cells and regulates circulating cholesterol in high density lipoproteins.

Triazolo[4,5-d]pyrimidin-5-amines based ERK3 inhibitors fail to demonstrate selective effects on adipocyte function

Extracellular signal-regulated kinase 3 (ERK3 also designated MAPK6 — mitogen-activated protein kinase 6) is a ubiquitously expressed kinase participating in the regulation of a broad spectrum of physiological and pathological processes. Targeted inhibition of the kinase may allow the development of novel treatment strategies for a variety of types of cancer and somatic pathologies, as well as preserving metabolic health, combat obesity and diabetes. We chose and synthesized three triazolo [4,5-d]pyrimidin-5-amines proposed previously as putative ERK3 inhibitors to assess their selectivity and biological effects in terms of metabolic state impact in living cells. As it was previously shown that ERK3 is a major regulator of lipolysis in adipocytes, we focused on this process. Our new results indicate that in addition to the previously identified lipolytic enzyme ATGL, ERK3 also regulates hormone-sensitive lipase (HSL) and monoglyceride lipase (MGL). Moreover, this kinase also promotes the abundance of fatty acid synthase (FASN) as well as protein kinase cAMP-activated catalytic subunit alpha (PKACα). To investigate various effects of putative ERK3 inhibitors on lipolysis, we utilized different adipocyte models. We demonstrated that molecules exhibit lipolysis-modulating effects; however, the effects of triazolo [4,5-d]pyrimidin-5-amines based inhibitors on lipolysis are not dependent on ERK3. Subsequently, we revealed a wide range of the compounds’ possible targets using a machine learning-based prediction.Therefore, the tested compounds inhibit ERK3 in vitro, but the biological effect of this inhibition is significantly overlapped and modified by some other molecular events related to the non-selective binding to other targets.

Cortisol and epinephrine alter the adipose functions and the mobilization of PCBs in adipose tissue slices from elephant seal

Marine mammals are exposed to increasing intensities of anthropogenic stressors such as acoustic disturbance and contaminants. Correlative studies have suggested concerning shifts in behavioral and physiological status of stress-exposed individuals, which could alter the health and survival of marine mammal populations. However, functional studies of the effects of multiple stressors on marine mammals are lacking. To fill in this gap, we recently developed an ex vivo approach of precision-cut adipose tissue slices (PCATS) to study the impact of stressors on the function of an essential endocrine organ: the adipose tissue. In the present study, we investigated the impact of hormones associated with the stress response on adipose tissue from northern elephant seals (Mirounga angustirostris). Blubber biopsies were collected from 17 weaned northern elephant seal pups, separated into inner and outer layers, dissected into PCATS, and cultured for 48 hours. To mimic prolonged and short-term exposure to physiological stress, PCATS were treated with 2 µM cortisol (CORT) for the entire 48 hours or 100 nM epinephrine (EPI) for the last 12 hours of culture, respectively. Hormones were applied individually or in combination. CORT and EPI exhibited an interacting, blubber layer-dependent, effect on adipose tissue biology, as quantified by gene expression in PCATS, and release of glycerol, free fatty acids, leptin and polychlorinated biphenyls into culture media. EPI stimulated a higher rate of lipolysis than CORT in PCATS from both blubber layers. The combination of CORT and EPI upregulated the expression of adipose triglyceride lipase in inner blubber PCATS and downregulated hormone-sensitive lipase in outer blubber-derived PCATS. Expression of the leptin gene and secretion of the leptin adipokine were both decreased by EPI, while addition of CORT attenuated this effect in inner blubber PCATS only. CORT also increased the expression of the antioxidant enzyme glutathione peroxidase 3 in PCATS from both blubber layers. Polychlorinated biphenyls exhibited selective and limited mobilization from PCATS treated with stress hormones, highlighting the lipophilic properties of these toxic compounds. This study showed that physiological stress can impact several essential functions of marine mammal blubber, such as lipolysis and adipokine production.

Benzyl isothiocyanate inhibits TNFα-driven lipolysis via suppression of the ERK/PKA/HSL signaling pathway in 3T3-L1 adipocytes

Tumor necrosis factor α (TNFα), an inflammatory cytokine, induces lipolysis and increases circulating concentrations of free fatty acids. In addition, TNFα is the first adipokine produced by adipose tissue in obesity, contributing to obesity-associated metabolic disease. Given that benzyl isothiocyanate (BITC) is a well-known anti-inflammatory agent, we hypothesized that BITC can ameliorate TNFα-induced lipolysis and investigated the working mechanisms involved. We first challenged 3T3-L1 adipocytes with TNFα to induce lipolysis, which was confirmed by increased glycerol release, decreased protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and perilipin 1 (PLIN1), and increased phosphorylation of ERK, protein kinase A (PKA), and hormone-sensitive lipase (HSL). However, inhibition of ERK or PKA significantly attenuated the lipolytic activity of TNFα. Meanwhile, pretreatment with BITC significantly ameliorated the lipolytic activity of TNFα; the TNFα-induced phosphorylation of ERK, PKA, and HSL; the TNFα-induced ubiquitination of PPARγ; the TNFα-induced decrease in PPARγ nuclear protein binding to PPAR response element; and the TNFα-induced decrease in PLIN1 protein expression. Our results indicate that BITC ameliorates TNFα-induced lipolysis by inhibiting the ERK/PKA/HSL signaling pathway, preventing PPARγ proteasomal degradation, and maintaining PLIN1 protein expression.

Anti‑adipogenic effect and underlying mechanism of lignan‑enriched nutmeg extract on 3T3‑L1 preadipocytes.

Nutmeg is the seed derived from Myristica fragrans. Nutmeg seeds contain alkylbenzene derivatives such as myristicin, which are toxic to the human organism, and lignan compounds such as nectandrin B, which possess anti-aging and anti-diabetic properties. However, the anti-adipogenic, prolipolytic and anti-inflammatory effects of lignan-enriched nutmeg extract (LNX) on preadipocytes remain unclear. In the present study, the effects of LNX on lipid accumulation, glycerol release and inflammatory cyclooxygenase-2 (COX-2) expression in differentiated 3T3-L1 preadipocytes were investigated. Oil red O staining demonstrated that treatment with LNX resulted in a concentration-dependent reduction in lipid accumulation in differentiating 3T3-L1 preadipocytes without affecting cell growth. Mechanistically, LNX treatment at 6 µg/ml led to a reduction in phosphorylation levels of signal transducer and activator of transcription 3 (STAT3), whereas it did not influence the peroxisome proliferator-activated receptor gamma (PPAR-γ) and CCAAT enhancer binding protein alpha (C/EBP-α) expression levels during 3T3-L1 preadipocyte differentiation. In addition, LNX treatment at 6 µg/ml led to a decrease in fatty acid synthase (FAS) expression levels on day (D) 2, but not D5 and D8, during preadipocyte differentiation. Treatment with LNX at 6 µg/ml did not affect the expression levels of perilipin A during preadipocyte differentiation. In differentiated 3T3-L1 adipocytes, LNX treatment at 6 µg/ml did not stimulate glycerol release and hormone-sensitive lipase phosphorylation, which are known lipolysis hallmarks. Furthermore, LNX treatment at the doses tested had no effect on tumor necrosis factor alpha-induced COX-2 expression in 3T3-L1 preadipocytes. Collectively, these results demonstrated that LNX has an anti-adipogenic effect on differentiating 3T3-L1 preadipocytes, which is mediated by the downregulation of STAT3 phosphorylation and FAS expression.

IL-27 increases energy storage in white adipocytes by enhancing glucose uptake and fatty acid esterification

ABSTRACT The cytokine interleukin (IL)-27 has been reported to induce thermogenesis in white adipocytes. However, it remains unknown whether IL-27-mediated adipocyte energy dissipation is paralleled by an elevated energy supply from lipids and/or carbohydrates. We hypothesized that IL-27 increases lipolysis and glucose uptake in white adipocytes, thereby providing substrates for thermogenesis. Unexpectedly, we found that treatment of 3T3-L1 adipocytes with IL-27 reduced intra- and extracellular free fatty acid (FFA) concentrations and that phosphorylation of hormone-sensitive lipase (HSL) was not affected by IL-27. These results were confirmed in subcutaneous white adipocytes. Further, application of IL-27 to 3T3-L1 adipocytes increased intracellular triglyceride (TG) content but not mitochondrial ATP production nor expression of enzymes involved in beta-oxidation indicating that elevated esterification rather than oxidation causes FFA disappearance. In addition, IL-27 significantly increased GLUT1 protein levels, basal glucose uptake as well as glycolytic ATP production, suggesting that increased glycolytic flux due to IL-27 provides the glycerol backbone for TG synthesis. In conclusion, our findings suggest IL-27 increases glucose uptake and TG deposition in white adipocytes.

Abstract 11802: IRF2BP2 Regulates Hormone Sensitive Lipase and Lipolysis in Human Adipocytes and in Mice

Background: IRF2BP2, a transcriptional co-factor, has emerged as a potential regulator of circulating lipid levels based on several coronary artery disease (CAD) genome-wide association studies (GWAS) studies. However, the role of IRF2BP2 in adipocytes, which regulate fat storage, energy expenditure, and fatty acid release, remains unexplored. Our aim is to investigate the role of IRF2BP2 in adipocyte function regulation. Methods: Human adipocyte stem cells (hASC) were differentiated into adipocytes for in vitro studies. We used the CRISPR system and lentiviral expression constructs to knockout (KO) and overexpress (OE) IRF2BP2. Control, IRF2BP2 KO and IRF2BP2 OE adipocytes were assessed by several methods, including RNA-seq, western blot analysis, and functional assessment of lipolysis and glucose uptake. IRF2BP2 chromatin immunoprecipitation (ChIP)-seq was performed in vitro . Adiponectin-Cre mice were crossed with Irf2bp2 flox/flox mice to generate adipocyte-specific KO (AKO) animals. We evaluated the effect of IRF2BP2 KO on adipose morphology and gene profiles. Circulating fatty acids were assessed in control and AKO mice. Results: IRF2BP2 deletion or OE in hASC-differentiated adipocytes did not affect adipocyte differentiation or glucose uptake. However, triglyceride lipolysis was markedly increased in KO cells. Conversely, IRF2BP2 OE suppressed lipolysis. RNA-seq analysis of control vs. IRF2BP2 KO or OE cells identified the enrichment of lipid catabolic pathways. Notably, IRF2BP2 KO upregulated, whereas IRF2BP2 OE downregulated the mRNA and protein levels of LIPE (i.e. hormone sensitive lipase, or HSL). Further, ChIP-seq analysis demonstrates strong binding of IRF2BP2 to a LIPE enhancer, suggesting direct regulation. In mice, Irf2bp2 AKO increased circulating fatty acids, accompanied by a reduction of adipocyte size. LIPE mRNA and protein expression in adipose tissue was also elevated. Finally, Irf2bp2 AKO induces massive adipose tissue inflammation, evidenced by F4/80 staining and chemotaxis gene markers expression. Conclusions: We established IRF2BP2, as a novel transcriptional regulator of adipocyte lipolysis, through the key lipolytic gene LIPE, which may shed light on deciphering the role of IRF2BP2 in CAD.

Food deprivation reduces sensitivity of liver Igf1 synthesis pathways to growth hormone in juvenile gopher rockfish (Sebastes carnatus)

Growth hormone (Gh) regulates growth in part by stimulating the liver to synthesize and release insulin-like growth factor-1 (Igf1), which then promotes somatic growth. However, for fish experiencing food limitation, elevated blood Gh can occur even with low circulating Igf1 and slow growth, suggesting that nutritional stress can alter the sensitivity of liver Igf1 synthesis pathways to Gh. Here, we examined how recent feeding experience affected Gh regulation of liver Igf1 synthesis pathways in juvenile gopher rockfish (Sebastes carnatus) to illuminate mechanisms underlying the nutritional modulation of Igf1 production. Juvenile gopher rockfish were maintained under conditions of feeding or complete food deprivation (fasting) for 14 d and then treated with recombinant sea bream (Sparus aurata) Gh or saline control. Gh upregulated hepatic igf1 mRNA levels in fed fish but not in fasted fish. The liver of fasted rockfish also showed a lower relative abundance of gene transcripts encoding teleost Gh receptors 1 (ghr1) and 2 (ghr2), as well as reduced protein levels of phosphorylated janus tyrosine kinase 2 (pJak2) and signal transducer and activator of transcription 5 (pStat5), which function to induce igf1 gene transcription following Gh binding to Gh receptors. Relative hepatic mRNA levels for suppressors of cytokine signaling (Socs) genes socs2, socs3a, and socs3b were also lower in fasted rockfish. Socs2 can suppress Gh activation of Jak2/Stat5, and fasting-related variation in socs expression may reflect modulated inhibitory control of igf1 gene transcription. Fasted rockfish also had elevated liver mRNA abundances for lipolytic hormone-sensitive lipase 1 (hsl1) and Igf binding proteins igfbp1a, -1b and –3a, reduced liver mRNAs encoding igfbp2b and an Igfbp acid labile subunit-like (igfals) gene, and higher transcript abundances for Igf1 receptors igf1ra and igf1rb in skeletal muscle. Together, these findings suggest that food deprivation impacts liver Igf1 responsiveness to Gh via multiple mechanisms that include a downregulation of hepatic Gh receptors, modulation of the intracellular Jak2/Stat5 transduction pathway, and possible shifts in Socs-inhibitory control of igf1 gene transcription, while also demonstrating that these changes occur in concert with shifts in liver Igfbp expression and muscle Gh/Igf1 signaling pathway components.

Extracellular macrophage migration inhibitory factor (MIF) downregulates adipose hormone-sensitive lipase (HSL) and contributes to obesity

Attenuation of adipose hormone sensitive lipase (HSL) may impair lipolysis and exacerbate obesity. We investigate the role of cytokine, macrophage migration inhibitory factor (MIF) in regulating adipose HSL and adipocyte hypertrophy. Extracellular MIF downregulates HSL in an autocrine fashion, by activating the AMPK/JNK signaling pathway upon binding to its membrane receptor, CD74. WT mice fed high fat diet (HFD), as well as mice overexpressing MIF, both had high circulating MIF levels and showed suppression of HSL during the development of obesity. Blocking the extracellular action of MIF by a neutralizing MIF antibody significantly reduced obesity in HFD mice. Interestingly, intracellular MIF binds with COP9 signalosome subunit 5 (Csn5) and JNK, which leads to an opposing effect to inhibit JNK phosphorylation. With global MIF deletion, adipocyte JNK phosphorylation increased, resulting in decreased HSL expression, suggesting that the loss of MIF's intracellular inhibitory action on JNK was dominant in Mif−/− mice. Adipose tissue from Mif−/− mice also exhibited higher Akt and lower PKA phosphorylation following HFD feeding compared with WT, which may contribute to the downregulation of HSL activation during more severe obesity. Both intracellular and extracellular MIF have opposing effects to regulate HSL, but extracellular actions predominate to downregulate HSL and exacerbate the development of obesity during HFD.

FATP4 deletion in liver cells induces elevation of extracellular lipids via metabolic channeling towards triglycerides and lipolysis

Evidence from mice with global deletion of fatty-acid transport protein4 (FATP4) indicates its role on β-oxidation and triglycerides (TG) metabolism. We reported that plasma glycerol and free fatty acids (FA) were increased in liver-specific Fatp4 deficient (L-FATP4−/−) mice under dietary stress. We hypothesized that FATP4 may mediate hepatocellular TG lipolysis. Here, we demonstrated that L-FATP4−/− mice showed an increase in these blood lipids, liver TG, and subcutaneous fat weights. We therefore studied TG metabolism in response to oleate treatment in two experimental models using FATP4-knockout HepG2 (HepKO) cells and L-FATP4−/− hepatocytes. Both FATP4-deificient liver cells showed a significant decrease in β-oxidation products by ∼30–35% concomitant with marked upregulation of CD36, FATP2, and FATP5 as well as lipoprotein microsomal-triglyceride-transfer protein genes. By using 13C3D5-glycerol, HepKO cells displayed an increase in metabolically labelled TG species which were further increased with oleate treatment. This increase was concomitant with a step-wise elevation of TG in cells and supernatants as well as the secretion of cholesterol very low-density and high-density lipoproteins. Upon analyzing TG lipolytic enzymes, both mutant liver cells showed marked upregulated expression of hepatic lipase, while that of hormone-sensitive lipase and adipose-triglyceride lipase was downregulated. Lipolysis measured by extracellular glycerol and free FA was indeed increased in mutant cells, and this event was exacerbated by oleate treatment. Taken together, FATP4 deficiency in liver cells led to a metabolic shift from β-oxidation towards lipolysis-directed TG and lipoprotein secretion, which is in line with an association of FATP4 polymorphisms with blood lipids.

Vitisin A-13-O-β-D-glucoside and Vitisin A from Iris lactea inhibit lipogenesis and promote lipolysis via the PKA/HSL pathway during adipogenic transdifferentiation of C2C12 cells

Oligostilbenes are a group of natural products derived from the polymerization of stilbene monomers. Despite the demonstration of their activities in regulating lipid metabolism, the function of oligostilbenes in the adipogenic transdifferentiation of multipotent myoblast cells remains unknown. Hence, the five oligostilbenes from Iris lactea were tested for their regulatory effects on adipogenic transdifferentiation of C2C12 myoblast cells. As a result, it was shown that Vitisin A-13-O-β-D-glucoside (VitAOG), Vitisin A (VitA) and Hopeaphenol (Hop) can greatly inhibit the adipogenic transdifferentiation of C2C12 cells by reducing lipid accumulation and downregulating the expression of peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer binding protein beta (C/EBPβ) and fatty acid binding proteins 4 (FABP4). In contrast, Vitisin D (VitD) and Isohopeaphenol (Isohop) promote adipogenic transdifferentiation of C2C12 cells by increasing lipid accumulation and upregulating the expression of adipogenesis and lipogenesis markers. Further research found that the lipolytic protein levels of adipocyte triglyceride lipase (ATGL) and phosphorylation of hormone-sensitive lipase (HSL) were elevated by VitAOG and VitA. Additionally, VitAOG and VitA maintain lipid homeostasis by improving mitochondrial function. Taken together, our study reveals an effect of oligostilbenes on lipid metabolism in C2C12 cells, and VitAOG and VitA can be regarded as potential candidates for the treatment of obesity and other disorders of lipid metabolism.

SCD1-related epigenetic modifications affect hormone-sensitive lipase (Lipe) gene expression in cardiomyocytes

Stearoyl-CoA desaturase 1 (SCD1) is an enzyme that is involved in the regulation of lipolysis in the heart. SCD1 also affects epigenetic mechanisms, such as DNA and histone modifications, in various tissues. Both epigenetic modifications and changes in lipid metabolism are involved in the heart's response to hypoxia. The present study tested the hypothesis that SCD1 and epigenetic modifications interact to control lipolysis in cardiomyocytes under normoxic and hypoxic conditions. We found that the inhibition of SCD1 activity and loss of SCD1 expression reduced global DNA methylation levels, DNA methyltransferase (DNMT) activity, and DNMT1 expression in HL-1 cardiomyocytes and the mouse heart. We also found that the inhibition of adipose triglyceride lipase is involved in the control of global DNA methylation levels in cardiomyocytes in an SCD1-independent manner. Additionally, SCD1 inhibition reduced expression of the hormone-sensitive lipase (Lipe) gene through an increase in methylation of the Lipe gene promoter. Under hypoxic conditions, SCD1 inhibition abolished hypoxia-inducible transcription factor 1α, likely through decreases in histone deacetylase, protein kinase A, and abhydrolase domain containing 5 protein levels, leading to the attenuation of DNA hypomethylation by DNMT1. Hypoxia led to demethylation of the Lipe promoter in cardiomyocytes with SCD1 inhibition, which increased Lipe expression. These results indicate that SCD1 is involved in the control of epigenetic mechanisms in the heart and may affect Lipe expression through changes in methylation in its promoter region. Therefore, SCD1 may be considered a key player in the epigenetic response to normoxia and hypoxia in cardiomyocytes.

Changes in brown adipose tissue induced by resveratrol and its analogue pterostilbene in rats fed with a high-fat high-fructose diet

Natural bioactive compounds have attracted a great deal of attention since some of them can act as thermogenesis activators. In recent years, special interest has been placed on resveratrol and its analogue pterostilbene, a dimethylether derivative that shows higher bioavailability. The aim of the present study is to compare the effects of resveratrol and its derivative pterostilbene on the thermogenic capacity of interscapular brown adipose tissue (iBAT) in rats under a high-fat high-fructose diet. Rats were divided into four experimental groups: control, high-fat high-fructose diet (HFHF) and HFHF diet supplemented with 30 mg/kg body weight/day of pterostilbene (PT30) or resveratrol (RSV30), for eight weeks. Weights of adipose tissues, iBAT triglycerides, carnitine palmitoyltransferase 1A (CPT1A) and citrate synthase (CS) activities, protein levels of uncoupling protein 1 (UCP1), sirtuins (SIRT1 and 3), AMP-activated protein kinase (AMPK), glucose transporter (GLUT4), fatty acid synthase (FAS), nuclear respiratory factor (NRF1), hormone-sensitive lipase (HSL), adipose triglyceride lipase (ATGL), CD36 and FATP1 fatty acid transporters, peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1) activation and the batokines EPDR1 and NRG4 were assessed in iBAT. The results show that some key proteins related to thermogenesis were modified by either pterostilbene or resveratrol, although the lack of effects on other crucial proteins of the thermogenic machinery suggest that these compounds were not able to stimulate this process in iBAT. Overall, these data suggest that the effects of stilbenes on brown adipose tissue thermogenic capacity depend on the metabolic status, and more precisely on the presence or absence of obesity, although further studies are needed to confirm this hypothesis.