Adipose Triglyceride Lipase Research Articles

Pharmacological Upregulation of Microglial Lipid Droplet Alleviates Neuroinflammation and Acute Ischemic Brain Injury

Lipid droplets (LDs) were reported to play an important role in the modulation of inflammation and various cellular processes among multiple cell types. However, LDs accumulation, its function and mechanisms of its formation during ischemic stroke remained poorly-identified. In this study, we observed increased LDs accumulation in microglia at the acute stage of ischemic stroke by immunofluorescence and flow cytometry. Transcriptomic analysis indicated that microglia accumulated with LDs were associated with inflammation and phagocytosis. Both inflammatory activation and phagocytosis of tissue debris in microglia could contribute to LDs formation. Moreover, through specific LDs depletion and overload experiments by pharmacological approaches, we proposed that LDs was critical for the maintenance of anti-inflammatory properties of microglia. Furthermore, Atglistatin, a specific adipose triglyceride lipase (ATGL) inhibitor, was shown to prevent proinflammatory cytokines production in primary microglia through decreased LDs lipolysis. After Atglistatin treatment, middle cerebral artery occlusion (MCAO) mice showed decreased infarct volume and improved neurobehavioral performance at the acute stage of stroke. Our findings provided a biological basis for microglial LDs regulation as a potential therapeutic strategy for acute ischemic stroke and uncovered the neuroprotective role of Atglistatin in the treatment of MCAO mice.

Acidosis-induced regulation of adipocyte G0S2 promotes crosstalk between adipocytes and breast cancer cells as well as tumor progression

Bidirectional interactions between cancer cells and their microenvironment govern tumor progression. Among the stromal cells in this microenvironment, adipocytes have been reported to upregulate cancer cell migration and invasion by producing fatty acids. Conversely, cancer cells alter adipocyte phenotype notably via increased lipolysis. We aimed to identify the mechanisms through which cancer cells trigger adipocyte lipolysis and evaluate the functional consequences on cancer progression. Here, we show that cancer cell-induced acidification of the extracellular medium strongly promotes preadipocyte lipolysis through a mechanism that does not involve lipophagy but requires adipose triglyceride lipase (ATGL) activity. This increased lipolysis is triggered mainly by attenuation of the G0/G1 switch gene 2 (G0S2)-induced inhibition of ATGL. G0S2-mediated regulation in preadipocytes affects their communication with breast cancer cells, modifying the phenotype of the cancer cells and increasing their resistance to chemotherapeutic agents in vitro. Furthermore, we demonstrate that the adipocyte-specific overexpression of G0S2 impairs mammary tumor growth and lung metastasis formation in vivo. Our results highlight the importance of acidosis in cancer cell-adipocyte crosstalk and identify G0S2 as the main regulator of cancer-induced lipolysis, regulating tumor establishment and spreading.

Exercise Equals the Mobilization of Visceral versus Subcutaneous Adipose Fatty Acid Molecules in Fasted Rats Associated with the Modulation of the AMPK/ATGL/HSL Axis.

Combining exercise with fasting is known to boost fat mass-loss, but detailed analysis on the consequential mobilization of visceral and subcutaneous WAT-derived fatty acids has not been performed. In this study, a subset of fasted male rats (66 h) was submitted to daily bouts of mild exercise. Subsequently, by using gas chromatography-flame ionization detection, the content of 22 fatty acids (FA) in visceral (v) versus subcutaneous (sc) white adipose tissue (WAT) depots was compared to those found in response to the separate events. Findings were related to those obtained in serum and liver samples, the latter taking up FA to increase gluconeogenesis and ketogenesis. Each separate intervention reduced scWAT FA content, associated with increased levels of adipose triglyceride lipase (ATGL) protein despite unaltered AMP-activated protein kinase (AMPK) Thr172 phosphorylation, known to induce ATGL expression. The mobility of FAs from vWAT during fasting was absent with the exception of the MUFA 16:1 n-7 and only induced by combining fasting with exercise which was accompanied with reduced hormone sensitive lipase (HSL) Ser563 and increased Ser565 phosphorylation, whereas ATGL protein levels were elevated during fasting in association with the persistently increased phosphorylation of AMPK at Thr172 both during fasting and in response to the combined intervention. As expected, liver FA content increased during fasting, and was not further affected by exercise, despite additional FA release from vWAT in this condition, underlining increased hepatic FA metabolism. Both fasting and its combination with exercise showed preferential hepatic metabolism of the prominent saturated FAs C:16 and C:18 compared to the unsaturated FAs 18:1 n-9 and 18:2 n-6:1. In conclusion, depot-specific differences in WAT fatty acid molecule release during fasting, irrelevant to their degree of saturation or chain length, are mitigated when combined with exercise, to provide fuel to surrounding organs such as the liver which is correlated with increased ATGL/ HSL ratios, involving AMPK only in vWAT.

The Role of Deuterium 2H in the Pathogenesis of Heart Failure as Deduced by Food Studies from Six Individual Cases

Heart failure results from the loss of structural integrity of the heart and/or a decrease in the rate of maximal ATP production. In cases of relatively preserved structural integrity, a decrease in ATP production in the mitochondria leads to a decrease in the cardiac stroke volume, thereby increasing the heart rate required to maintain the cardiac output. For many years, the exact location of this defect in the metabolic energy cycle remained elusive. Evidence is presented here to show that it is not a single metabolic substrate involved but rather the heavy isotope of hydrogen 2H, deuterium, that is jamming the ATP nanomotors slowing the rate of ATP production. During the digestion of a meal, the cardiac heart rate is shown to be very sensitive to the level of deuterium contained in the fatty acids recently consumed. During strenuous exercise in the fasting state, the enzyme adipose triglyceride lipase (ATGL) is found to mobilize the highest deuterium triglycerides more rapidly than the healthier lower deuterium triglycerides, converting the adipose tissue into a deuterium-depleted energy pool. This is believed to contribute to the low resting heart rates frequently observed in athletes. In vulnerable individuals, i.e., those weakened by disease(s) or space explorers in a weightless environment, the decreased ability to perform strenuous exercise leads to higher deuterium levels in their adipose tissue compromising their ATP production. In these individuals, maintaining healthy deuterium levels is best achieved by an increased intake of lower deuterium-containing foods.

Cannabidiol treatment changes myocardial lipid profile in spontaneously hypertensive rats

Background and aimsHypertension is a potent risk factor for cardiovascular diseases, which are the leading worldwide cause of death. Within time increased blood pressure (BP) induces cardiac contractile dysfunction, metabolic alternations, and eventually, heart failure, which makes hypertension an area for seeking safe therapies such as phytocannabinoids. Methods and resultsIn the present study spontaneously hypertensive rats (SHRs) were used as an experimental model of genetically induced hypertension, where cannabidiol (CBD) was applied as a potential treatment (intraperitoneally administered for 2 weeks, 10 mg/kg) for elevated BP and related metabolic disturbances. Langendorff working heart system, Western blotting as well as gas-liquid chromatography were applied to determine radiolabeled 3H-palmitate uptake, incorporation, and oxidation, protein expression, as well as the content and fatty acid composition of different lipid fractions in the left ventricle and plasma, respectively. Most importantly, we noticed that 2-week CBD treatment was effective in upregulating ex vivo3H-palmitate uptake, oxidation, and its incorporation into triacylglycerol and cholesterol fractions with concomitant lowering free fatty acid, diacylglycerol, and phospholipid fractions, which was in agreement with in vivo studies and alternations in protein expressions of lipoprotein lipase, carnitine palmitoyltransferase I, 3-hydroxyacyl-CoA dehydrogenase, diacylglycerol acyltransferase 1, and adipose triglyceride lipase as well as proteins associated with eicosanoid signaling pathways and extracellular matrix remodeling in the heart of hypertensive rats. ConclusionOur study reveals that 2-week CBD administration substantially affects the energetic substrate milieu in cardiac muscle regarding fatty acids uptake and their further utilization without parallel significant alternations in cardiovascular parameters.

Discovery, characterization, and adipocyte differentiation regulation in perirenal adipose tissue of large yellow croaker (Larimichthys crocea).

Adipose tissue is an essential tissue for lipid deposition in fish and is associated with excess lipid accumulation in aquaculture. However, the knowledge of the distribution and characterization of adipose tissue in fish still needs further investigation. This study for the first time discovered perirenal adipose tissue (PAT) in large yellow croaker by MRI and CT technologies. Then, the morphological and cytological characteristics of PAT were observed, showing a typical characteristic of white adipose tissue. Meanwhile, the mRNA expression of marker genes of white adipose tissue was highly expressed in PAT compared with the liver and muscle in large yellow croaker. Moreover, based on the discovery of PAT, preadipocytes from PAT were isolated, and the differentiation system of preadipocytes was established. The lipid droplet and TG content of cell were gradually increased during adipocyte differentiation. In addition, mRNA expressions of lipoprotein lipase, adipose triglyceride lipase, and transcription factors related to adipogenesis (cebpα, srebp1, pparα, and pparγ) were quantified to explain the regulation mechanism during the differentiation process. In summary, the present study first discovered perirenal adipose tissue in fish, then explored the characterization of PAT, and revealed the regulation of adipocyte differentiation. These results could advance the understanding of adipose tissue in fish and provide a novel idea for the study of the mechanism of lipid accumulation.

309-OR: Adipose RNA N6-Methyladenosine (m6A) Modification Promotes Obesity and Insulin Resistance through Suppressing Lipolysis

Excessive white adipose tissue (WAT) promotes insulin resistance and nonalcoholic fatty liver disease (NAFLD) in obesity; however, the WAT expansion mechanism remains poorly understood. We reported that WAT lipolysis is suppressed in obesity, likely contributing to WAT growth. Adipose triglyceride lipase (Atgl) catalyzes the lipolysis reaction, and its lipolytic activity is increased by phosphorylation and binding to cofactor Cgi58. The sympathetic nervous system activates adipocyte β adrenergic receptor (Adrb)/cAMP/PKA pathway to stimulate lipolysis via Atgl and Cgi58. In this study, we have identified a novel m6A modification of Adrb, Atgl, and Cgi58 transcripts that promotes obesity and metabolic disorders. We found that obesity was associated with increased expression of adipose Mettl3 and Mettl14 and elevated m6A levels in WAT. Mettl14 directly binds to Mettl3 to form a methyltransferase complex that catalyzes m6A on RNA. Insulin also increased Mettl14 expression and m6A levels in adipocytes. We generated adipocyte-specific Mettl14 knockout mice (Mettl14 Δfat) and placed mice on a high fat diet (HFD). Remarkably, Mettl14 Δfat mice, both males and females, were resistant to HFD-induced obesity, insulin resistance, and NAFLD. Adipose Adrb2/3, Atgl, and Cgi58 protein levels were significantly upregulated in Mettl14 Δfat mice and consequently, adipose β adrenergic signaling and lipolysis were significantly higher in Mettl14 Δfat than in Mettl14f/f mice. Mettl14 deficiency dramatically decreased the m6A content of Adrb2/3, Atgl, and Cgi58 transcripts in WAT; strikingly, m6A inhibition markedly increased translational rates of these transcripts in adipocytes. Collectively, these results unravel a previously unrecognized adipose Mettl14/m6A/translation axis that promotes obesity, insulin resistance, and NAFLD by suppressing adipose β adrenergic signaling, lipolysis, and fatty acid oxidation. Disclosure Q.Kang: None. L.Rui: None. D.Ren: None. Funding National Institutes of Health (R01DK130111)

Paeonia lactiflora root decreases lipid accumulation through the induction of lipolysis and thermogenesis via AMPK activation in 3T3‑L1 cells.

Obesity is associated with high risk of mortality globally because obesity is associated with development of diseases such as diabetes, dyslipidemia, fatty liver disease, hypertension, and cancer. The present study aimed to identify the mechanism of action related to the anti‑obesity activity of Paeonia lactiflora root (PLR) based on its effects on lipid droplet accumulation. The inhibitory activity on lipid accumulation was analyzed through Oil‑Red O staining, and the changes in levels of lipid accumulation‑related proteins were analyzed using Western blot analysis. And the contents of triacylglycerol and free glycerol were analyzed using an ELISA Kit. PLR significantly inhibited the accumulation of lipid droplets and triacylglycerol in differentiating 3T3‑L1 cells. PLR increased phosphorylated‑hormone sensitive lipase (HSL), HSL and adipose triglyceride lipase (ATGL) and decreases perilipin‑1 in differentiating and fully differentiated 3T3‑L1 cells. Furthermore, treatment of fully differentiated 3T3‑L1 cells with PLR resulted in increased free glycerol levels. PLR treatment increased levels of peroxisome proliferator‑activated receptor‑gamma coactivator‑1 alpha (PGC‑1α), PR domain containing16 (PRDM16) and uncoupling protein 1 (UCP‑1) in both differentiating and fully differentiated 3T3‑L1 cells. However, the PLR‑mediated increase in lipolytic, such as ATGL and HSL, and thermogenic factors, such as PGC‑1a and UCP‑1, were decreased by inhibition of AMP‑activated protein kinase (AMPK) with Compound C. Taken together, these results suggest that PLR exerted anti‑obesity effects by regulating lipolytic and thermogenic factors via AMPK activation. Therefore, the present study provided evidence that PLR is a potential natural agent for the development of drugs to control obesity.

Antiobesity Effects of Lactobacillus paracasei Subsp. paracasei, L. casei 431 on High-Fat Diet-Induced Obese Rats.

Obesity is currently regarded as a global concern, and the key objectives of the global health strategy include its prevention and control. Probiotic supplementation can help achieve these objectives. This study aimed to assess whether a probiotic strain Lactobacillus paracasei ssp. paracasei, Lactobacillus casei 431 (henceforth, L. casei 431) possesses antiobesogenic properties. High-fat diet-induced obese Sprague-Dawley rats were treated with L. casei 431 for 10 weeks, and the outcomes were compared with those of rats treated with the antiobesity medication orlistat. Body weights, epididymal fat, and tissues from mice were assessed. Furthermore, serological and histological analyses were performed. Epididymal fat accumulation was significantly reduced in groups administered L. casei 431 and orlistat. Furthermore, L. casei 431 and orlistat treatments lowered serum alanine transaminase, aspartate aminotransferase, and triglyceride (TG) levels. Hematoxylin and eosin staining of the liver and epididymal adipose tissues showed that the L. casei 431-treated groups exhibited reduced lipid buildup and adipocyte size. Furthermore, sterol regulatory element-binding protein 1c, adipose TG lipase, and lipoprotein lipase messenger RNA (mRNA) levels were upregulated, leading to lipid oxidation and degradation, in L. casei 431-supplemented groups. Furthermore, carnitine palmitoyltransferase 1, a major factor in lipolysis, was consistently upregulated at the protein level after L. casei 431 administration. Collectively, these results demonstrate the potential of L. casei 431 in alleviating obesity in rats through optimizing lipid metabolism and some related biomarkers.

Adipose triglyceride lipase promotes prostaglandin-dependent actin remodeling by regulating substrate release from lipid droplets.

Lipid droplets (LDs), crucial regulators of lipid metabolism, accumulate during oocyte development. However, their roles in fertility remain largely unknown. During Drosophila oogenesis, LD accumulation coincides with the actin remodeling necessary for follicle development. Loss of the LD-associated Adipose Triglyceride Lipase (ATGL) disrupts both actin bundle formation and cortical actin integrity, an unusual phenotype also seen when the prostaglandin (PG) synthase Pxt is missing. Dominant genetic interactions and PG treatment of follicles indicate that ATGL acts upstream of Pxt to regulate actin remodeling. Our data suggest that ATGL releases arachidonic acid (AA) from LDs to serve as the substrate for PG synthesis. Lipidomic analysis detects AA-containing triglycerides in ovaries, and these are increased when ATGL is lost. High levels of exogenous AA block follicle development; this is enhanced by impairing LD formation and suppressed by reducing ATGL. Together, these data support the model that AA stored in LD triglycerides is released by ATGL to drive the production of PGs, which promote the actin remodeling necessary for follicle development. We speculate that this pathway is conserved across organisms to regulate oocyte development and promote fertility.

Inhibition of ghrelin activity by the receptor antagonist [D-Lys3]-GHRP-6 enhances hepatic fatty acid oxidation and gluconeogenesis in a growing pig model

Despite its central role in regulating energy intake and metabolism, ghrelin is little understood when it comes to its effects on hepatic lipid and glucose metabolism. Growing pigs were intravenously injected with ghrelin receptor antagonist [D-Lys3]-GHRP-6 (DLys; 6 mg/kg body weight) for seven days to determine whether ghrelin plays a role in glucose and lipid metabolism. DLys treatment significantly reduced body weight gain and adipose histopathology found that DLys treatment dramatically reduced adipocyte size. DLys treatment significantly increased serum NEFA and insulin levels, hepatic glucose level and HOMA-IR, and significantly decreased serum TBA level of growing pigs after fasting. Moreover, DLys treatment changed the dynamics of serum metabolic parameters, including glucose, NEFA, TBA, insulin, GH, leptin, and cortisol. Liver transcriptome showed that DLys treatment affected the metabolism-related pathways. Compared with the control group, adipose tissue lipolysis (the adipose triglyceride lipase level was significantly increased), hepatic gluconeogenesis (the G6PC protein level was significantly increased) and fatty acid oxidation (the CPT1A protein level was significantly increased) were promoted in the DLys group. DLys treatment expanded degrees of oxidative phosphorylation in the liver, coming about in a higher NAD+ /NADH proportion and enactment of the SIRT1 signaling pathway. Additionally, the liver protein levels of the DLys group were significantly higher than those of the control group for GHSR, PPAR alpha, and PGC-1. To summarize, inhibition of ghrelin activity can significantly affect metabolism and alter energy levels by enhancing fat mobilization, hepatic fatty acid oxidation and gluconeogenesis without affecting fatty acid uptake and synthesis in the liver.

Pharmacological inhibition of lipolysis prevents adverse metabolic outcomes during glucocorticoid administration

ObjectiveGlucocorticoids are one of the most commonly prescribed classes of anti-inflammatory drugs; however, chronic treatment promotes iatrogenic (drug-induced) diabetes. As part of their physiological role, glucocorticoids stimulate lipolysis to spare glucose. We hypothesized that persistent stimulation of lipolysis during glucocorticoid therapy plays a causative role in the development of iatrogenic diabetes. MethodsMale C57BL/6J mice were given 100 μg/mL corticosterone (Cort) in the drinking water for two weeks and were fed either normal chow (TekLad 8640) or the same diet supplemented with an adipose triglyceride lipase inhibitor (Atglistatin - 2 g/kg diet) to inhibit the first step of lipolysis. ResultsHerein, we report for the first time that glucocorticoid administration promotes a unique state of substrate excess and energetic overload in skeletal muscle that primarily results from the rampant mobilization of endogenous fuels. Inhibiting lipolysis protected mice from Cort-induced gains in fat mass, excess ectopic lipid accrual, hyperinsulinemia, and hyperglycemia. The role lipolysis plays in Cort-mediated pathology appears to differ between tissues. Within skeletal muscle, Cort-induced lipolysis facilitated diversion of glucose-derived carbons toward the pentose phosphate and hexosamine biosynthesis pathways but contributed to <3% of the Cort-induced genomic adaptations. In contrast, Cort stimulation of lipolysis accounted for ∼35% of the genomic changes in the liver but had minimal impact on hepatic metabolites reported. ConclusionsThese data support the idea that activation of lipolysis plays a causal role in the progression toward iatrogenic diabetes during glucocorticoid therapy with differential impact on skeletal muscle and liver.

Effects of Starvation and Refeeding on Glucose Metabolism and Immune Responses in Macrobrachium rosenbergii.

Starvation is a common challenge for aquatic animals in both natural and cultured environments. To investigate the effects of starvation and refeeding on glucose metabolism and immunity in Macrobrachium rosenbergii, prawns were starved for 14days and then refed for 7days. Results showed that both glucose and trehalose levels decreased significantly at the beginning of starvation, followed by a significant decrease in glycogen content in the hepatopancreas and muscle. Triglyceride and total protein reserves were also mobilized under starvation, with a slightly quicker response from triglycerides. The mRNA levels of glycolysis (glucokinase) and anabolism-related enzymes (glycogen branching enzyme, diacylglycerol acyltransferase, and transpeptidase) decreased during starvation, while gluconeogenic potential was induced, as indicated by up-regulated transcriptional levels of gluconeogenic enzymes (phosphoenolpyruvate carboxykinase) and catabolism-related enzymes (glycogen debranching enzyme, adipose triglyceride lipase, and cathepsin B). Starvation also stimulated the expression of the crustacean hyperglycemic hormone and inhibited insulin-like peptide expression, indicating their potential role in glucose metabolism regulation. In addition, starvation increased the mRNA levels of superoxide dismutase and prophenoloxidase, indicating an influence on the immune system. After bacterial infection, starved prawns showed enhanced activity of non-specific immunological parameters and reduced mortality. Refeeding for 7days led to a recovery of physiological and biochemical indices and transcriptional levels of metabolism/immune-related genes. Our findings provide a better understanding of the mechanisms underlying energy utilization, metabolic adaptation, and immune response to starvation in M. rosenbergii.

Inhibition of lipid droplet accumulation by Solanumnigrum by suppressing adipogenesis and inducing lipolysis, thermogenesis and autophagy in 3T3‑L1 cells.

It has been reported that Solanum nigrum exhibits anti-obesity effects in animal models induced by a high-fat diet. However, research on how Solanum nigrum exerts its anti-obesity effects is currently limited. Thus, the present study focused on identifying the mechanism of action associated with the anti-obesity activity of Solanum nigrum aerial part (SNAP), which significantly inhibited the accumulation of lipid droplets in differentiating 3T3-L1 cells. Intracellular lipid accumulation in 3T3-L1 cells was analyzed by Oil-Red O staining and glycerol content was analyzed using an ELISA kit. In addition, changes in protein expression within 3T3-L1 cells were analyzed using western blot analysis. It decreased the expression level of adipogenic proteins such as CCAAT/enhancer-binding protein α, Peroxisome proliferator-activated receptor γ, fatty acid binding protein 4, and adiponectin. In addition, SNAP increased the expression levels of lipolytic proteins, such as adipose triglyceride lipase and hormone-sensitive lipase, while decreasing perilipin-1. The treatment of fully differentiated 3T3-L1 cells increased the free glycerol levels. SNAP treatment resulted in increased AMP-activated protein kinase phosphorylation and the expression levels of thermogenic proteins (peroxisome proliferator-activated receptor-γ coactivator 1-α, PR domain containing 16 and uncoupling protein 1) and an autophagic protein (LC3-II). Overall, these results suggested that SNAP inhibited lipid droplet accumulation by suppressing adipogenesis and promoting lipolysis, thermogenesis and autophagy.

P204 CARDIAC INVOLVEMENT IN NEUTRAL LIPID STORAGE DISEASE (NLSD): A CASE REPORT

Abstract Introduction Neutral Lipid Storage Diseases (NLSDs) are rare diseases with autosomal recessive transmission characterized by a defect in the metabolism of triglycerides that accumulate in many tissues. Vacuoles containing lipids in white blood cells (Jordans anomaly) are considered a diagnostic marker. In particular, NLSD–M (NLSD–myopathy) is caused by mutations in the PNPLA2 gene (Patatin Like Phospholipase Domain Containing 2, chromosome 11p15.5) that codes for an enzyme involved in the first phase of triglyceride hydrolysis in adipose tissue. In this patient the mutation of the PNPLA2 gene is c.542delCA, truncating the protein with loss of the hydrophobic domain. This mutation is associated with more severe infiltrative and arrhythmic cardiac involvement than those known in the literature. Case Report 52–year–old man with NLSD–M. The first symptoms of the disease appeared when he turned 35: weakness and atrophy of axial and proximal muscles, increased CK, scoliosis, fatty liver, electromyographic changes, arterial hypertension, dyslipidemia, renal failure and hypertransaminasemia. At 49, ECG revealed sinus rhythm, absence of ventricular repolarization abnormalities and echocardiogram revealed wall hypertrophy with a trabecular appearance of the left ventricle, sigmoid interventricular septum, preserved EF (58%), moderate diastolic dysfunction, left atrial enlargement, absence of significant valvulopathies. Cardiac MRI revealed lipid infiltration. An ICD was implanted for sustained ventricular tachycardia. At 50, atrial fibrillation was detected. EF was 53% and there was a small partially organized circumferential pericardial effusion. The last medical check, performed at 52 during hospitalization for atrial fibrillation with high ventricular response associated with hypokalemia and hypomagnesaemia, revealed ST–T alterations on ECG and a further reduction of EF to 46% on echocardiogram. Conclusions There is currently no medical treatment. A dietary supplement with medium–chain fatty acids (CNT–02) can be used to slow down the accumulation of lipids. The search for specific mutation is important to stratify cardiac risk.

Tumor-secreted GRP78 induces M2 polarization of macrophages by promoting lipid catabolism

Macrophages in hypoxic regions of advanced colorectal tumors often exhibit M2-type features, but prefer oxygen-consuming lipid catabolism, which is contradictory in oxygen demand and supply. In this study, the results from bioinformatics analysis and intestinal lesions immunohistochemistry of 40 colorectal cancer patients illustrated that glucose-regulatory protein 78 (GRP78) was positively correlated with M2 macrophages. Furthermore, tumor-secreted GRP78 could enter macrophages and polarize them to M2-type. Mechanistically, entered GRP78 located in lipid droplets of macrophages, and elevated protein stabilization of adipose triglyceride lipase ATGL by interacting with it to inhibit its ubiquitination. Increased ATGL promoted the hydrolysis of triglycerides and the production of arachidonic acid (ARA) and docosahexaenoic acid (DHA). Excessive ARA and DHA interacted with PPARγ to encourage its activation, which mediated the M2 polarization of macrophages. In summary, our study showed that secreted GRP78 in the tumor hypoxic microenvironment mediated the domestication of tumor cells to macrophages and maintained tumor immunosuppressive microenvironment by promoting lipolysis, and the lipid catabolism not only provides energy for macrophages but also plays an important role in maintenance of immunosuppressive properties.

Apocynin alleviates weight gain and obesity-induced adipose tissue inflammation in high-fat diet-fed C57BL/6 mice.

Obesity involves chronic low-grade inflammation within adipose tissue. Apocynin (APO) is a therapeutic agent for the treatment of inflammatory diseases. Therefore, the present study aimed to investigate whether APO can reduce weight gain and obesity-induced adipose tissue inflammation. C57BL/6 mice were administered APO or orlistat (Orli) as a positive control with a high-fat diet (HFD) for 12 weeks. Lipopolysaccharide-stimulated 3T3-L1 adipocytes were used for the in vitro study. Our results showed a significantly lower white adipose tissue (WAT) mass index in 10 mg/kg APO-treated mice than in 20 mg/kg Orli-treated mice. Moreover, the protein expression of adipose triglyceride lipase, fatty acid synthase, sterol regulatory element-binding transcription factor 1, and peroxisome proliferator-activated receptor γ was reversed in the WAT of 10 mg/kg APO-treated mice. Furthermore, APO reduced the expression of the macrophage marker F4/80, decreased the mRNA levels of tumor necrosis factor-α and monocyte chemoattractant protein-1, and increased the mRNA levels of interleukin-10 in WAT. APO decreased the phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase, and p65 in vivo and in vitro. Notably, APO had a stronger effect on the amelioration of adipose tissue inflammation than Orli did. Our findings lay the foundation for research on the use of APO as an agent to ameliorate weight gain and obesity-induced inflammatory diseases.

Sympathetic tone dictates the impact of lipolysis on FABP4 secretion

Levels of circulating fatty acid binding protein 4 (FABP4) protein are strongly associated with obesity and metabolic disease in both mice and humans, and secretion is stimulated by β-adrenergic stimulation both in vivo and in vitro. Previously, lipolysis-induced FABP4 secretion was found to be significantly reduced upon pharmacological inhibition of adipose triglyceride lipase (ATGL) and was absent from adipose tissue explants from mice specifically lacking ATGL in their adipocytes (ATGLAdpKO). Here, we find that upon activation of β-adrenergic receptors in vivo, ATGLAdpKO mice unexpectedly exhibited significantly higher levels of circulating FABP4 as compared with ATGLfl/fl controls, despite no corresponding induction of lipolysis. We generated an additional model with adipocyte-specific deletion of both FABP4 and ATGL (ATGL/FABP4AdpKO) to evaluate the cellular source of this circulating FABP4. In these animals, there was no evidence of lipolysis-induced FABP4 secretion, indicating that the source of elevated FABP4 levels in ATGLAdpKO mice was indeed from the adipocytes. ATGLAdpKO mice exhibited significantly elevated corticosterone levels, which positively correlated with plasma FABP4 levels. Pharmacological inhibition of sympathetic signaling during lipolysis using hexamethonium or housing mice at thermoneutrality to chronically reduce sympathetic tone significantly reduced FABP4 secretion in ATGLAdpKO mice compared with controls. Therefore, activity of a key enzymatic step of lipolysis mediated by ATGL, per se, is not required for in vivo stimulation of FABP4 secretion from adipocytes, which can be induced through sympathetic signaling.

Adverse cardiac remodeling augments adipose tissue ß-adrenergic signaling and lipolysis counteracting diet-induced obesity

Cardiac triacylglycerol accumulation is a common characteristic of obesity and type 2 diabetes and strongly correlates with heart morbidity and mortality. We have previously shown that cardiomyocyte-specific perilipin 5 overexpression (Plin5-Tg) provokes significant cardiac steatosis via lowering cardiac lipolysis and fatty acid (FA) oxidation. In strong contrast to cardiac steatosis and lethal heart dysfunction in adipose triglyceride lipase deficiency, Plin5-Tg mice do not develop heart dysfunction and show a normal life span on chow diet. This finding prompted us to study heart function and energy metabolism in Plin5-Tg mice fed high-fat diet (HFD). Plin5-Tg mice showed adverse cardiac remodeling on HFD with heart function only being compromised in one-year-old mice, likely due to reduced cardiac FA uptake, thereby delaying deleterious cardiac lipotoxicity. Notably, Plin5-Tg mice were less obese and protected from glucose intolerance on HFD. Changes in cardiac energy catabolism in Plin5-Tg mice increased ß-adrenergic signaling, lipolytic, and thermogenic protein expression in adipose tissue ultimately counteracting HFD-induced obesity. Acute cold exposure further augmented ß-adrenergic signaling in Plin5-Tg mice, whereas housing at thermoneutrality did not protect Plin5-Tg mice from HFD-induced obesity albeit blood glucose and insulin levels remained low in transgenic mice. Overall, our data suggest that the limited capacity for myocardial FA oxidation on HFD increases cardiac stress in Plin5-Tg mice, thereby stimulating adipose tissue ß-adrenergic signaling, triacylglycerol catabolism, and thermogenesis. However, long-term HFD-mediated metabolic stress causes contractile dysfunction in Plin5-Tg mice, which emphasizes the importance of a carefully controlled dietary regime in patients with cardiac steatosis and hypertrophy.

Impact of B cell specific neutral lipid accumulation on B cell activation and function

Abstract Obesity and its resultant inflammation have been shown to lead to a multitude of disease states, including Type II diabetes and cancer. Immune cells play a role in perpetuating obesity related diseases. B cells have been shown to infiltrate the visceral adipose tissue of obese individuals, where they activate other immune cells and produce autoantibodies. This study examined the impact of B cell neutral lipid accumulation on B cell function and activation, using B cell specific comparative gene identification-58 (CGI-58) knockout mice (bCKO). CGI-58 is the co-activator of adipose triglyceride lipase, a key enzyme initiating lipid droplet lipolysis. CGI-58 knockout and flox control mice were fed a low-fat diet for 16 or 32 weeks. B cells from bCKO mice exhibited a higher level of neutral lipid accumulation than other cell types and flox control B cells. Unimmunized bCKO mice showed increased percentages of spontaneous germinal center B cells compared to flox controls. Isolated bCKO B cells survived in culture significantly better than flox control B cells, which was concurrent with decreased levels of cellular and mitochondrial ROS and mitochondrial membrane potential in bCKO B cells compared to flox B cells. Furthermore, bCKO mice had increased numbers of crown-like structures in their visceral adipose tissues and elevated protein levels in their urine, predictors of metabolic disorder. Together, our results suggest that neutral lipid accumulation in B cells alone leads to non-specific survival and activation of B cells by downregulating ROS production and modulating mitochondrial functions. Supported by a grant from NIH (RO1 GM064625)