Lipoprotein Lipase Protein Expression Research Articles

Hypertriglyceridemia Results From an Impaired Catabolism of Triglyceride-Rich Lipoproteins in PLIN1-Related Lipodystrophy.

Pathogenic variants in PLIN1-encoding PLIN1 (perilipin-1) are responsible for an autosomal dominant form of familial partial lipodystrophy (FPL) associated with severe insulin resistance, hepatic steatosis, and important hypertriglyceridemia. This study aims to decipher the mechanisms of hypertriglyceridemia associated with PLIN1-related FPL. We performed an in vivo lipoprotein kinetic study in 6 affected patients compared with 13 healthy controls and 8 patients with type 2 diabetes. Glucose and lipid parameters, including plasma LPL (lipoprotein lipase) mass, were measured. LPL mRNA and protein expression were evaluated in abdominal subcutaneous adipose tissue from patients with 5 PLIN1-mutated FPL and 3 controls. Patients with PLIN1-mutated FPL presented with decreased fat mass, insulin resistance, and diabetes (glycated hemoglobin A1c, 6.68±0.70% versus 7.48±1.63% in patients with type 2 diabetes; mean±SD; P=0.27). Their plasma triglycerides were higher (5.96±3.08 mmol/L) than in controls (0.76±0.27 mmol/L; P<0.0001) and patients with type 2 diabetes (2.94±1.46 mmol/L, P=0.006). Compared with controls, patients with PLIN1-related FPL had a significant reduction of the indirect fractional catabolic rate of VLDL (very-low-density lipoprotein)-apoB100 toward IDL (intermediate-density lipoprotein)/LDL (low-density lipoprotein; 1.79±1.38 versus 5.34±2.45 pool/d; P=0.003) and the indirect fractional catabolic rate of IDL-apoB100 toward LDL (2.14±1.44 versus 7.51±4.07 pool/d; P=0.005). VLDL-apoB100 production was not different between patients with PLIN1-related FPL and controls. Compared with patients with type 2 diabetes, patients with PLIN1-related FPL also showed a significant reduction of the catabolism of both VLDL-apoB100 (P=0.031) and IDL-apoB100 (P=0.031). Plasma LPL mass was significantly lower in patients with PLIN1-related FPL than in controls (21.03±10.08 versus 55.76±13.10 ng/mL; P<0.0001), although the LPL protein expression in adipose tissue was similar. VLDL-apoB100 and IDL-apoB100 indirect fractional catabolic rates were negatively correlated with plasma triglycerides and positively correlated with LPL mass. We show that hypertriglyceridemia associated with PLIN1-related FPL results from a marked decrease in the catabolism of triglyceride-rich lipoproteins (VLDL and IDL). This could be due to a pronounced reduction in LPL availability, related to the decreased adipose tissue mass.

High producer variant of lipoprotein lipase may protect from hepatocellular carcinoma in alcohol-associated cirrhosis

Progression of alcohol-associated liver disease (ALD) is driven by genetic predisposition. The rs13702 variant in the lipoprotein lipase (LPL) gene is linked to non-alcoholic fatty liver disease. We aimed at clarifying its role in ALD. Patients with alcohol-associated cirrhosis, with (n= 385) and without hepatocellular carcinoma (HCC) (n= 656), with HCC attributable to viral hepatitis C (n= 280), controls with alcohol abuse without liver damage (n= 366), and healthy controls (n= 277) were genotyped regarding the LPL rs13702 polymorphism. Furthermore, the UK Biobank cohort was analysed. LPL expression was investigated in human liver specimens and in liver cell lines. Frequency of the LPL rs13702 CC genotype was lower in ALD with HCC in comparison to ALD without HCC both in the initial (3.9% vs. 9.3%) and the validation cohort (4.7% vs. 9.5%; p <0.05 each) and compared with patients with viral HCC (11.4%), alcohol misuse without cirrhosis (8.7%), or healthy controls (9.0%). This protective effect (odds ratio [OR]= 0.5) was confirmed in multivariate analysis including age (OR= 1.1/year), male sex (OR= 3.0), diabetes (OR= 1.8), and carriage of the PNPLA3 I148M risk variant (OR= 2.0). In the UK Biobank cohort, the LPL rs13702C allele was replicated as a risk factor for HCC. Liver expression of LPL mRNA was dependent on LPL rs13702 genotype and significantly higher in patients with ALD cirrhosis compared with controls and alcohol-associated HCC. Although hepatocyte cell lines showed negligible LPL protein expression, hepatic stellate cells and liver sinusoidal endothelial cells expressed LPL. LPL is upregulated in the liver of patients with alcohol-associated cirrhosis. The LPL rs13702 high producer variant confers protection against HCC in ALD, which might help to stratify people for HCC risk. Hepatocellular carcinoma is a severe complication of liver cirrhosis influenced by genetic predisposition. We found that a genetic variant in the gene encoding lipoprotein lipase reduces the risk for hepatocellular carcinoma in alcohol-associated cirrhosis. This genetic variation may directly affect the liver, because, unlike in healthy adult liver, lipoprotein lipase is produced from liver cells in alcohol-associated cirrhosis.

Fasting induces ANGPTL4 and reduces LPL activity in human adipose tissue

ObjectiveStudies in mice have shown that the decrease in lipoprotein lipase (LPL) activity in adipose tissue upon fasting is mediated by induction of the inhibitor ANGPTL4. Here, we aimed to validate this concept in humans by determining the effect of a prolonged fast on ANGPTL4 and LPL gene and protein expression in human subcutaneous adipose tissue. MethodsTwenty-three volunteers ate a standardized meal at 18.00 h and fasted until 20.00 h the next day. Blood was drawn and periumbilical adipose tissue biopsies were collected 2 h and 26 h after the meal. ResultsConsistent with previous mouse data, LPL activity in human adipose tissue was significantly decreased by fasting (−60%), concurrent with increased ANGPTL4 mRNA (+90%) and decreased ANGPTL8 mRNA (−94%). ANGPTL4 protein levels in adipose tissue were also significantly increased by fasting (+46%), whereas LPL mRNA and protein levels remained unchanged. In agreement with the adipose tissue data, plasma ANGPTL4 levels increased upon fasting (+100%), whereas plasma ANGPTL8 decreased (−79%). Insulin, levels of which significantly decreased upon fasting, downregulated ANGPTL4 mRNA and protein in primary human adipocytes. By contrast, cortisol, levels of which significantly increased upon fasting, upregulated ANGPTL4 mRNA and protein in primary human adipocytes as did fatty acids. ConclusionANGPTL4 levels in human adipose tissue are increased by fasting, likely via increased plasma cortisol and free fatty acids and decreased plasma insulin, resulting in decreased LPL activity.This clinical trial was registered with identifier NCT03757767.

Glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 and angiopoietin-like protein 4 are associated with the increase of lipoprotein lipase activity in epicardial adipose tissue from diabetic patients

Background and aimsEpicardial adipose tissue (EAT) is a visceral AT, surrounding myocardium and coronary arteries. Its volume is higher in Type 2 diabetic (DM2) patients, associated with cardiovascular disease risk. Lipoprotein lipase (LPL) hydrolyses triglycerides (TG) from circulating lipoproteins, supplying fatty acids to AT, contributing to its expansion. We aimed to evaluate LPL expression and activity in EAT from DM2 and no DM2 patients, and its regulators ANGPTL4, GPIHBP1 and PPARγ levels, together with VLDLR expression and EAT LPL association with VLDL characteristics. MethodsWe studied patients undergoing coronary by-pass graft (CABG) divided into CABG-DM2 (n = 21) and CABG-noDM2 (n = 29), and patients without CABG (No CABG, n = 30). During surgery, EAT and subcutaneous AT (SAT) were obtained, in which LPL activity, gene and protein expression, its regulators and VLDLR protein levels were determined. Isolated circulating VLDLs were characterized. ResultsEAT LPL activity was higher in CABG-DM2 compared to CABG-noDM2 and No CABG (p=0.002 and p<0.001) and in CABG-noDM2 compared to No CABG (p=0.02), without differences in its expression. ANGPTL4 levels were higher in EAT from No CABG compared to CABG-DM2 and CABG-noDM2 (p<0.001). GPIHBP1 levels were higher in EAT from CABG-DM2 and CABG-noDM2 compared to No CABG (p= 0.04). EAT from CABG-DM2 presented higher PPARγ levels than CABG-noDM2 and No CABG (p=0.02 and p=0.03). No differences were observed in VLDL composition between groups, although EAT LPL activity was inversely associated with VLDL-TG and TG/protein index (p<0.05). ConclusionsEAT LPL regulation would be mainly post-translational. The higher LPL activity in DM2 could be partly responsible for the increase in EAT volume.

The response of gene expression associated with intramuscular fat deposition in the longissimus dorsi muscle of Simmental×Yellow breed cattle to different energy levels of diets.

This study was designed to estimate dietary energy level on intramuscular fat (IMF) deposition in Simmental×Yellow breed cattle. Results showed that ultimate weight and average daily gain in high and medium energy groups were significantly higher than low-energy group, yet feed conversion ratio was significantly lower. IMF content was significantly increased by dietary energy increasing, whereas longissimus muscle shear force significantly decreased. Serum-free fatty acids, triglycerides and glucose significantly increased by dietary energy increasing, whereas growth hormone (GH) significantly decreased. Enzyme activities of lipoprotein lipase (LPL), fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) significantly increased by dietary energy increasing, whereas hormone-sensitive lipase (HSL) and carnitine palmitoyltransferase-1 (CPT-1) significantly diminished. Peroxisome proliferator-activated receptor γ, sterol regulatory element-binding protein 1, stearoyl-CoA desaturase, adipocyte-fatty acid-binding proteins, ACC, LPL, and FAS gene or protein expression significantly increased by dietary energy increasing, whereas HSL, CPT-1, and GH gene or protein expression significantly decreased. These results indicated that high dietary energy promoting IMF deposition is mainly by downregulating pituitary GH gene expression, decreasing serum GH concentration, increasing lipogenic genes levels of mRNA, enzyme activities and protein expression, and decreasing lipolytic genes levels of mRNA, enzyme activities, and protein expression.

Intermittent Fasting Alleviates the Increase of Lipoprotein Lipase Expression in Brain of a Mouse Model of Alzheimer's Disease: Possibly Mediated by β-hydroxybutyrate.

Intermittent fasting has been demonstrated to protect against Alzheimer's disease (AD), however, the mechanism is unclear. Histone acetylation and lipoprotein lipase (LPL) are involved in AD progression. Importantly, LPL has been documented to be regulated by histone deacetylases (HDACs) inhibitors (increase histone acetylation level) in adipocyte and mesenchymal stem cells, or by fasting in adipose and muscle tissues. In brain, however, whether histone acetylation or fasting regulates LPL expression is unknown. This study was designed to demonstrate intermittent fasting may protect against AD through increasing β-hydroxybutyrate, a HDACs inhibitor, to regulate LPL. We also investigated microRNA-29a expression associating with regulation of LPL and histone acetylation. The results showed LPL mRNA expression was increased and microRNA-29a expression was decreased in the cerebral cortex of AD model mice (APP/PS1), which were alleviated by intermittent fasting. No significant differences were found in the total expression of LPL protein (brain-derived and located in capillary endothelial cells from peripheral tissues) in the cerebral cortex of APP/PS1 mice. Further study indicated that LPL located in capillary endothelial cells was decreased in the cerebral cortex of APP/PS1 mice, which was alleviated by intermittent fasting. LPL and microRNA-29a expression were separately increased and down-regulated in 2 μM Aβ25−35-exposed SH-SY5Y cells, but respectively decreased and up-regulated in 10 μM Aβ25−35-exposed cells, which were all reversed by β-hydroxybutyrate. The increase of HDAC2/3 expression and the decrease of acetylated H3K9 and H4K12 levels were alleviated in APP/PS1 mice by intermittent fasting treatment, as well in 2 or 10 μM Aβ25−35-exposed cells by β-hydroxybutyrate treatment. These findings above suggested the results from APP/PS1 mice were consistent with those from cells treated with 2 μM Aβ25−35. Interestingly, LPL expression was reduced (0.2-folds) and microRNA-29a expression was up-regulated (1.7-folds) in HDAC2-silenced cells, but respectively increased (1.3-folds) and down-regulated (0.8-folds) in HDAC3-silenced cells. Furthermore, LPL expression was decreased in cells treated with microRNA-29a mimic and increased with inhibitor treatment. In conclusion, intermittent fasting inhibits the increase of brain-derived LPL expression in APP/PS1 mice partly through β-hydroxybutyrate-mediated down-regulation of microRNA-29a expression. HDAC2/3 may be implicated in the effect of β-hydroxybutyrate on microRNA-29a expression.

ANGPTL3 is part of the machinery causing dyslipidemia majorily via LPL inhibition in mastitis mice

Previous investigations have shown that inflammation induces changes in lipid and lipoprotein metabolism, and increased expression of angiopoietin-like protein 3 (ANGPTL3) contributes to the development of dyslipidemia. Here we investigated whether there is a correlation between increased ANGPTL3 expression and dyslipidemia in mastitis mice. Thirty mice were divided into two groups: control group and Staphylococcus aureus (S. aureus)–induced mastitis mice group. Changes in the levels of blood lipids [total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C)]; activity of myeloperoxidase (MPO); concentrations of plasma inflammation biomarkers [interferon-γ (IFNγ), tumor necrosis factor α (TNFα), and interleukin-1α (IL-1α)]; concentration of plasma ANGPTL3 protein; lipoprotein lipase (LPL) activities in postheparin plasma; expressions of hepatic N-acetylgalactosaminyltransferase 2 (GALNT2), hepatic ANGPTL3 and adipose LPL were determined. The major results indicated specific pathological mammary tissue changes, elevated MPO activity, reduced GALNT2 mRNA expression, elevated ANGPTL3 mRNA and protein expression and reduced LPL mRNA and protein expression. In plasma samples the S.aureus infused mice displayed elevated ANGPTL3 protein concentration, TG, TC and LDL-C levels, and reduced postheparin LPL activities and HDL-C level. The data suggests that ANGPTL3 is part of the machinery causing dyslipidemia majorily via LPL inhibition in mastitis mice.

Lipoprotein lipase and lipid profiles in plasma and placenta from normal pregnancies compared with patients with intrahepatic cholestasis of pregnancy

ObjectiveTo analyse lipoprotein lipase (LPL) expression and lipid levels in placenta and plasma of patients with intrahepatic cholestasis of pregnancy (ICP) and normal pregnancies. MethodsThis prospective study included 30 patients with ICP and 30 gestational-age-matched pregnancies without any complications. Enzyme-linked immunosorbent assays were used to investigate plasma LPL levels from 28 weeks of gestation, at 4-weekly intervals, to 38 weeks of gestation, and data were assessed longitudinally. Immunohistochemistry, Western blotting and real-time polymerase chain reaction were used to detect placental LPL expression and activity. Placental triglyceride and total cholesterol levels were also analysed. The clinical data related to ICP and lipid profiles were collected retrospectively. ResultsPlasma LPL concentration increased with gestational age in both groups, but the increase was limited in the ICP group. Immunohistochemistry revealed LPL staining mainly in syncytiotrophoblasts, and 3,3′-diamino-benzidine tetrahydrochloride wt% was lower in ICP placenta compared with normal placenta (p<0.01). LPL protein and mRNA expression in ICP placenta were significantly lower than in normal placenta (p<0.01). LPL activity was not significantly different in both groups. Correlation analysis indicated that the plasma LPL level was negatively associated with the corresponding concentration of total bile acid (r=−0.57) in the ICP group. ConclusionReduced LPL expression in placenta, limited increase in LPL level in maternal plasma, and abnormal lipid profiles were found in patients with ICP. LPL was possibly related to ICP by participating abnormal lipid metabolism.

MicroRNA-590 Inhibits Lipoprotein Lipase Expression and Prevents Atherosclerosis in apoE Knockout Mice.

Recent studies have suggested that miR-590 may play critical roles in cardiovascular disease. This study was designed to determine the effects of miR-590 on lipoprotein lipase (LPL) expression and development of atherosclerosis in apolipoprotein E knockout (apoE−/−) mice and explore the potential mechanisms. En face analysis of the whole aorta revealed that miR-590 significantly decreased aortic atherosclerotic plaque size and lipid content in apoE−/− mice. Double immunofluorescence staining in cross-sections of the proximal aorta showed that miR-590 agomir reduced CD68 and LPL expression in macrophages in atherosclerotic lesions. MiR-590 agomir down-regulated LPL mRNA and protein expression as analyzed by RT-qPCR and western blotting analyses, respectively. Consistently, miR-590 decreased the expression of CD36 and scavenger receptor A1 (SRA1) mRNA and protein. High-performance liquid chromatography (HPLC)analysis confirmed that treatment with miR-590 agomir reduced lipid levels either in plasma orinabdominal cavity macrophages of apoE−/− mice. ELISA analysis showed that miR-590 agomir decreased plasma levels of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), monocyte chemotactic protein-1 (MCP-1), interleukin-1β (IL-1β)and interleukin-6 (IL-6). In contrast, treatment with miR-590 antagomir prevented or reversed these effects. Taken together, these results reveal a novel mechanism of miR-590 effects, and may provide new insights into the development of strategies for attenuating lipid accumulation and pro-inflammatory cytokine secretion.

MicroRNA-590 attenuates lipid accumulation and pro-inflammatory cytokine secretion by targeting lipoprotein lipase gene in human THP-1 macrophages.

Accumulating evidence suggests that microRNA-590 (miR-590) has protective effects on cardiovascular diseases, but the mechanism is unknown. Interestingly, previous studies from our laboratory and others have shown that macrophage-derived lipoprotein lipase (LPL) might accelerate atherosclerosis by promoting lipid accumulation and inflammatory response. However, the regulation of LPL at the post-transcriptional level by microRNAs has not been fully understood. In this study, we explored whether miR-590 affects the expression of LPL and its potential subsequent effects on lipid accumulation and pro-inflammatory cytokine secretion in human THP-1 macrophages. Using bioinformatics analyses and dual-luciferase reporter assays, we found that miR-590 directly inhibited LPL protein and mRNA expression by targeting LPL 3'UTR. LPL Activity Assays showed that miR-590 reduced LPL activity in the culture media. Oil Red O staining and high-performance liquid chromatography assays showed that miR-590 had inhibitory effects on the lipid accumulation in human THP-1 macrophages. We also illustrated that miR-590 alleviated pro-inflammatory cytokine secretion in human THP-1 macrophages as measured by ELISA. With the method of small interfering RNA, we found that LPL siRNA can inhibit the miR-590 inhibitor-induced increase in lipid accumulation and secretion of pro-inflammatory cytokines in oxLDL-treated human THP-1 macrophages. MiR-590 attenuates lipid accumulation and pro-inflammatory cytokine secretion by targeting LPL gene in human THP-1 macrophages. Therefore, targeting miR-590 may offer a promising strategy to treat atherosclerotic cardiovascular diseases.

Increased uptake of dietary retinoids at the maternal-fetal barrier in the nitrofen model of congenital diaphragmatic hernia

Background/PurposeThe retinol signaling pathway is disrupted in congenital diaphragmatic hernia (CDH). Since there is no fetal retinol synthesis, maternal retinol has to cross the placenta. Nitrofen interferes with the retinol-binding protein (RBP) transfer pathway in CDH. However, in RBP knockout mice, retinol has been shown to be present. In this model, increased uptake of maternal dietary retinyl ester (RE) bounded in low-dense-lipoprotein (LDL) through low-density-lipoprotein-receptor 1 (LRP1) and increased activity of RE hydrolysis by lipoprotein-lipase (LPL) have been found. The aim of this study was to investigate the RE transfer pathway in the nitrofen CDH model. MethodsPregnant rats were treated with nitrofen or vehicle on gestational day (D9) and sacrificed on D21. Immunohistochemistry was performed to evaluate LRP1 and LPL protein expression. Serum LDL levels were measured by ELISA. Pulmonary and serum retinoid levels were measured using HPLC. ResultsMarkedly increased trophoblastic and pulmonary LRP1 and LPL immunoreactivity were observed in CDH compared to controls. Significantly increased serum LDL and RE levels were observed in CDH compared to controls. ConclusionsThe increased uptake of dietary retinoids at the maternal-fetal barrier in the nitrofen CDH model suggests that the RE transfer pathway may be the main source of retinol in this model.

Telmisartan increases lipoprotein lipase expression via peroxisome proliferator-activated receptor-alpha in HepG2 cells

In addition to their hypotensive properties, angiotensin receptor blockers (ARBs) have been shown to exert clinical antidyslipidemic effects. The mechanism underlying these ARB lipid metabolic effects remains unclear. Some ARBs, for example, telmisartan, activate peroxisome proliferator-activated activated receptor-gamma (PPAR-gamma). We hypothesized that PPAR-gamma–activating ARBs might exert antidyslipidemic effects via PPAR-alpha. In this study, we assessed the effect of telmisartan on the expression of PPAR-alpha and lipoprotein lipase (LPL). PPAR-alpha expression was detected by reverse-transcription polymerase chain reaction and Western blot in HepG2 hepatocytes as well as differentiated C2C12 myocytes treated with increasing concentrations of telmisartan (0.1–10 μmol/L) for 48 h. Results showed that 1 μmol/L and 10 μmol/L telmisartan significantly increased the expression of PPAR-alpha mRNA and protein in HepG2 cells (p < 0.01). No effect was shown in differentiated C2C12 cells. Similarly, 1 µmol/L and 10 μmol/L telmisartan significantly increased the expression of LPL mRNA and protein in HepG2 cells (p < 0.01), and this increase was significantly (p < 0.01) inhibited by the PPAR-alpha–specific antagonist MK886. These results indicate that certain of the antidyslipidemic effects of telmisartan might be mediated via increased PPAR-alpha–dependent induction of LPL expression.

Placental expression of lipoprotein lipase and endothelial lipase in women with severe preeclampsia

Objective To investigate the effect of abnormal lipid metabolism in the pathogenesis of preeclampsia.Methods Thirty women with severe preeclampsia who delivered by cesarean section in the International Peace Maternity & Child Health Hospital from November 1,2011 to June 30,2012,were included as the study group.Thirty normal pregnant women delivered during the same period by cesarean section were included as the control group.The mRNA levels of lipoprotein lipase (LPL) and endothelial lipase (EL) in the placentas were quantified by real-time polymerase chain reaction.The expression of LPL/EL protein was detected by Western-blot assay and the distribution on the placenta was determined by immunohistochemical staining.The maternal serum level of lipid markers was detected by automatic biochemical analyzer.Difference between the two groups was compared with t-test or rank-sum test.Results (1) The triglyceride (TG) concentration [(3.35±0.80) mmol/L vs (2.75± 0.92) mmol/L,t =3.082,P=0.003] and atherosclerosis index (AI) (2.76±0.46 vs 2.47±0.34,t=3.066,P=0.003) increased in the study group compared with the control group,while the concentration of high-density lipoprotein-cholestrol (HDL-c) decreased[(1.64 ± 0.34) mmol/L vs (1.85 ± 0.22) mmol/L,t=-3.157,P =0.003].(2) The median level of LPL mRNA expression in placenta of the study group was higher than that of the control [1.26 (0.46-1.58) vs 0.52 (0.34-0.84),Z=-2.587,P=0.010],whereas the expression of EL mRNA was lower [0.65 (0.48-0.76) vs 1.32 (0.94-1.62),Z=-4.154,P=0.000].(3) Immunohistochemical analysis showed that the placenta EL and LPL located in cytoplasm of syncytiotrophoblast cells at the materno-placental interface and of endothelial cells at the feto-placental interface.(4) Compared with the control group,the median level of LPL protein expression in placenta inthe study group increased [0.68(0.46-0.83) vs 0.31(0.15-0.55),Z=3.335,P=0.001],and the expression of EL protein decreased [0.13 (0.11 0.16) vs 0.70(0.56 0.81),Z=-5.711,P=0.000].The expression of LPL protein was negatively correlated with that of EL protein (r=-0.501,P=0.000).Conclusions Abnormal lipid metabolism contributes to the pathogenesis of severe preeclampsia. Key words: Pre-eclampsia; Lipoprotein lipase; Endothelial lipase; Placenta

Kaempferol improves carcase characteristics in broiler chickens by regulating ANGPTL3 gene expression

1. The objective of this study was to examine the beneficial effects of kaempferol, a naturally occurring polyphenol, on carcase characteristics in broiler chickens and the mechanisms involved in this regulation. 2. Broiler chickens were randomly divided into 7 groups: control, carrier control, kaempferol (0·3%), kaempferol (0·6%), hypercholesterolemic (HLD), HLD and kaempferol (0·3%), HLD and kaempferol (0·6%). 3. Seven weeks after treatment, carcase characteristics, lipid levels in the blood and liver, expression of hepatic Angiopoietin-like protein 3 (ANGPTL3) mRNA, and expression of adipose lipoprotein lipase (LPL) protein were determined. 4. Treatment with kaempferol (0·3 or 0·6%) significantly increased plasma high-density lipoprotein cholesterol levels, decreased percentage of abdominal fat, thickness of subcutaneous fat, plasma and hepatic total cholesterol and triglyceride concentrations, muscle malondialdehyde level and down-regulated expression of ANGPTL3 mRNA concomitantly with up-regulated expression of LPL protein in normal and hypercholesterolemic broiler chickens. 5. Kaempferol (0·3 or 0·6%) treatment had no significant effect on the values of percentage of breast muscle, percentage of leg muscle, carcase weight and eviscerated percentage. 6. The results suggest that kaempferol improves carcase characteristics by decreasing expression of ANGPTL3 in broiler chickens.

Diffuse Large B-Cell Lymphomas Utilize Endogenous and Exogenous Fatty Acids for Cell Growth and Survival

AbstractAbstract 1581 BackgroundIt is well-recognized that de novo long chain fatty acid (FA) synthesis, driven by the key enzyme fatty acid synthase (FASN), is crucial for the growth and survival of many types of cancer cells. We and others have observed FASN protein expression in diffuse large B-cell lymphoma (DLBCL) tumors. Furthermore, we have shown that higher levels of FASN in DLBCL tumors strongly predicted inferior survival, which was independent from the international prognostic index. We also recently demonstrated that, in addition to FA synthesis, various cancer cells can acquire FA from circulating lipoproteins, using the secreted enzyme lipoprotein lipase (LPL), and that this promotes cell growth. DLBCL, however, has never been examined in this regard. In this study, we investigated the functional significance of both de novo FA synthesis via FASN and exogenous FA uptake via LPL in DLBCL. MethodsLevels of FASN and LPL mRNAs in DLBCL cell lines (SUDHL4, SUDHL10, OCI-LY3, OCI-LY19) were studied using reverse transcriptase polymerase chain reaction. We determined FASN and LPL protein expression by flow cytometry using a novel anti-LPL antibody that we developed. DLBCL cell lines were cultured +/− Cerulenin (an inhibitor of FASN), Orlistat (an inhibitor of FASN and LPL), or in lipoprotein-depleted serum +/− supplementation with very low density lipoprotein (VLDL) particles. The MTT assay was used to assess cell proliferation. ResultsDLBCL cell lines exhibited >10-fold variation in levels of FASN mRNA. Cerulenin and Orlistat each caused dose-dependent inhibition of proliferation of each cell line. The cells were partially rescued by the addition of palmitic acid, the FA product of FASN. Surprisingly, flow cytometry revealed that SUDHL4 and OCI-LY3 cells, which did not secrete LPL or show detectable LPL activity, displayed the enzyme on the cell surface. Moreover, in stark contrast to several other cancer cell lines, DLBCL cells were exquisitely sensitive to withdrawal of lipoproteins from the culture media. Indeed, 75–95% of the cells underwent apoptosis after only 24 hours in lipoprotein-depleted serum. In complete serum, the provision of VLDL particles did not rescue DLBCL cells from FA synthesis inhibition using Cerulenin, suggesting that the serum contains sufficient lipoproteins to saturate the FA uptake system. This prediction was validated in experiments utilizing lipoprotein-depleted serum, in which add-back of VLDL particles completely rescued the cells from Cerulenin-induced demise in a dose-related manner, with full restoration at approximately 100–200mcg/ml of VLDL. ConclusionsOur data demonstrate that DLBCL cells employ both de novo FA synthesis via FASN and exogenous FA uptake using LPL to satisfy their strict requirement for FA. Interference with either pathway, using FASN inhibitors or lipoprotein-depleted serum, is cytotoxic indicating that neither alone is sufficient to support proliferation. Further, DLBCL cells show a striking dependency on exogenous FA of dietary origin compared with all other cancer cells we have examined. The observation that the cell lines can be rescued by provision of VLDL particles strongly supports the functional significance of the exogenous FA uptake pathway for DLBCL. Our data thus demonstrate that the extracellular lipase LPL is critical for the growth and survival of DLBCL cells. Surprisingly, the cells deploy LPL to their surface, and we speculate that this promotes efficient FA acquisition from circulating lipoproteins. Recognition that DLBCL relies on both synthesis and uptake of FA will provide guidance for drug development and dietary modifications to effectively target the metabolic requirements of this tumor. Disclosures:No relevant conflicts of interest to declare.

Lipoprotein lipase is differentially expressed in prognostic subsets of chronic lymphocytic leukemia but displays invariably low catalytical activity

Lipoprotein lipase (LPL) expression has been shown to correlate with IGHV mutational status and to predict outcome in chronic lymphocytic leukemia (CLL). We here investigated the prognostic impact of LPL expression in relation to other prognostic markers including IGHV3-21 usage in 140 CLL patients. Additionally, we studied the catalytic activity of LPL in CLL cells. A significant difference in LPL mRNA expression was detected in IGHV unmutated compared to mutated CLL patients ( p < 0.001). However, the poor-prognostic mutated/stereotyped IGHV3-21 patients did not differ from other mutated CLL cases. Clinical outcome was significantly different in CLL cases with high versus low LPL expression ( p < 0.001), and LPL expression exceeded mutation status/IGHV3-21 usage as an independent prognostic marker. Finally, LPL protein expression correlated significantly with mRNA expression and was higher in IGHV unmutated versus mutated CLL ( p = 0.018), although the majority of synthesized protein was catalytically inactive indicating a non-catalytical function in CLL.

Metformin promotes induction of lipoprotein lipase in skeletal muscle through activation of adenosine monophosphate–activated protein kinase

Metformin is known to increase lipoprotein lipase (LPL) mass level in serum. Lipoprotein lipase is produced by adipose tissue and skeletal muscles. This study aimed to examine the effect of metformin on LPL production in adipocytes and skeletal muscle cells and to investigate the mechanism by which metformin enhances LPL production. 3T3-L1 preadipocytes and L6 skeletal muscle cells were incubated with metformin or 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR). Lipoprotein lipase activity, LPL protein expression, and LPL messenger RNA (mRNA) expression were measured. Metformin increased LPL activity only in skeletal muscle cells. To clarify the mechanism of this phenomenon, AICAR, which is well known as an activator of adenosine monophosphate–activated protein kinase (AMPK), was used. Metformin and AICAR enhanced phosphorylated AMPK in skeletal muscle cells by Western blot analysis. Like metformin, AICAR increased LPL activity only in skeletal muscle cells. Both metformin and AICAR also enhanced LPL protein and LPL mRNA expressions in skeletal muscle cells but not in adipocytes. Phosphorylated AMPK protein expression was decreased when AMPK signaling was interfered by AMPK α small interfering RNA. Lipoprotein lipase activity and LPL expression, which were enhanced by 1 μmol/L metformin, were reduced by AMPK α small interfering RNA. These results suggest that metformin increases LPL activity, LPL protein expression, and LPL mRNA expression through activation of AMPK in skeletal muscle cells but not in adipocytes.

Increased carnitine palmitoyl transferase 1 expression and decreased sterol regulatory element–binding protein 1c expression are associated with reduced intramuscular triglyceride accumulation after insulin therapy in high-fat–diet and streptozotocin-induced diabetic rats

We previously reported that early insulin treatment reduced intramuscular triglyceride content in type 2 diabetes mellitus Sprague-Dawley rats; the underlying mechanisms are, however, not completely understood. Here we investigated the regulation of insulin on molecular expressions involved in lipid metabolism pathways in skeletal muscle of high-fat–diet and streptozotocin-induced diabetic Sprague-Dawley rats. Neutral protamine Hagedorn insulin and gliclazide were initiated at the third day after streptozotocin injection and lasted for 3 weeks. Compared with normal rats, untreated diabetic rats had a 30% and 61% increase in lipoprotein lipase protein expression and activity, which were decreased by insulin and gliclazide ( P < .05). Fatty acid translocase protein was down-regulated by 45% in untreated diabetic rats, which was up-regulated by 31% and 26% with insulin and gliclazide, respectively ( P < .05). Insulin failed to affect fatty acid transport protein 1 and fatty acid binding protein expressions. Carnitine palmitoyl transferase 1 had a 47% decrease in untreated diabetic rats, which was normalized by insulin ( P < .05). Moreover, compared with normal rats, untreated diabetic rats had higher expressions of sterol regulatory element–binding protein 1c, tumor necrosis factor α, and Tyr 705 phosphorylation of signal transducer and activator of transcription 3 levels, which all were down-regulated after insulin treatment. These results suggested that early insulin reduced intramuscular triglyceride levels in diabetic rats potentially through amelioration of lipid dysfunction and inhibition of lipid synthesis.

Increased effect of fucoidan on lipoprotein lipase secretion in adipocytes

Aims Fucoidan, a sulfated polysaccharide extracted from brown seaweed ( F. vesiculosus) is recognized as an effective anticoagulant but its anti-lipidemic potency has not been well defined. We investigated the effect of fucoidan on lipoprotein lipase (LPL) secretion by human adipocytes. Main methods LPL mRNA and protein expressions were measured using semi-quantitative RT-PCR, ELISA and immunohistochemistry in cultured adipocytes with or without fucoidan treatment. LPL enzyme activity was determined by a fluorometric assay. Key findings In cultured adipocytes, fucoidan induced LPL secretion in a dose- and time-dependent manner. An initial increase in LPL was maintained at a significant level but much slower than that in heparin-treated cells. Fucoidan also dose-dependently induced a cofactor of LPL, the apolipoprotein C-II (ApoC-II) secretion. In fucoidan-treated cells, LPL mRNA was time-dependently increased and LPL protein expression was also inceased. Treatment with both heparin and fucoidan showed no further increase in media LPL activity compared to heparin alone. In the conditioned medium from fucoidan-treated cells followed for 4 h, LPL activity decayed exponentially with half-life of about 180 min. In addition, the extracellular LPL mass in cycloheximide (a protein synthesis inhibitor) and fucoidan-treated cells did not change markedly, but LPL shifted significantly from active to inactive form. Significance These results suggest that fucoidan acts like heparin by releasing LPL in addition to increasing the intracellular transport and decreasing the degradation of LPL in the medium. Furthermore, LPL and ApoC-II secretion induced by fucoidan may be involved in regulating plasma triglyceride lowering clearance.

C-reactive protein enhances macrophage lipoprotein lipase expression

High serum levels of C-reactive protein (CRP), a strong predictor of cardiovascular events, are documented in patients with type 2 diabetes. Accumulating evidence suggests that CRP could directly promote arterial damage. To determine the role of CRP in diabetic atherosclerosis, we examined the effect of CRP on the expression of macrophage lipoprotein lipase (LPL), a proatherogenic molecule upregulated in type 2 diabetes. Treatment of human macrophages with native CRP increased, in a dose- and time-dependent manner, LPL protein expression and secretion. Modified CRP reproduced these effects. Preincubation of human macrophages with antioxidants, protein kinase C (PKC), and mitogen-activated protein kinase (MAPK) inhibitors prevented CRP-induced LPL expression. Exposure of human macrophages to CRP further increased intracellular reactive oxygen species generation, classic PKC isozymes expression, and extracellular signal-regulated protein kinase 1/2 phosphorylation. In CRP-treated J774 macrophages, increased macrophage LPL mRNA levels and enhanced binding of nuclear proteins to the activated protein-1 (AP-1)-enhancing element were observed. These effects were prevented by antioxidants, as well as by PKC, MAPK, and AP-1 inhibitors. These data show for the first time that CRP directly increases macrophage LPL expression and secretion. Given the predominant role of macrophage LPL in atherogenesis, LPL might represent a novel factor underlying the adverse effect of CRP on the diabetic vasculature.