Effect of apolipoprotein E (APOE) gene polymorphisms on the lipid profile of children being treated for acute lymphoblastic leukemia.

BACKGROUND: Medications used to treat acute lymphoblastic leukemia (ALL), such as L-asparaginase, can cause blood lipid disturbances. These can also be associated with polymorphisms of the lipoprotein lipase (LpL) and apolipoprotein E (APOE) genes. PROCEDURE: We aimed to investigate the association between lipid profile, certain LpL and APOE gene polymorphisms (rs268, rs328, rs1801177 and rs7412, rs429358 respectively) as well as the risk subgroup in 30 pediatric patients being treated for ALL, compared with 30 pediatric ALL survivors and 30 healthy controls. RESULTS: The only APOE gene polymorphism with significant allelic and genotypic heterogeneity was rs429358. Further analysis of this polymorphism showed that genotype (CC, CT, or TT) was significantly associated with (1) changes in the lipid profile at the end of consolidation (total cholesterol, LDL, apo-B100, and lipoprotein a) and during re-induction (total cholesterol and apo-B100), and (2) classification in the high risk-ALL subgroup (for CC genotype/C allele presence). CONCLUSIONS: Lipid abnormalities in children being treated for ALL may be associated with the APOE genotype, which is also possibly associated with risk stratification. Further research is needed to confirm the potential prognostic value of these findings.

Hypertriglyceridaemia Induced Pancreatitis Management: A Case Report.

Acute pancreatitis results in high morbidity and mortality. Gallstones and alcoholism are considered leading causes of acute pancreatitis. However, increasing prevalence of obesity, diabetes and lifestyle choices has resulted in Hypertriglyceridaemia induced pancreatitis (HTAP) becoming more common. HTAP is said to be more severe than other causes. The treatment options available vary including intravenous (IV) insulin, heparin, plasma exchange, fibrates, niacin, omega three fatty acids and dietary restrictions. This is a case report of a patient presenting with HTAP and the dilemma treating physicians faced in trying to balance the need for urgent treatment with invasiveness of procedure and paucity of evidence.

Decoding the role of angiopoietin-like protein 4/8 complex-mediated plasmin generation in the regulation of LPL activity.

After feeding, adipose tissue lipoprotein lipase (LPL) activity should be maximized, therefore the potent LPL-inhibitory activity of angiopoietin-like protein 4 (ANGPTL4) must be blocked by ANGPTL8 through formation of ANGPTL4/8 complexes. ANGPTL4/8 tightly binds and protects LPL but also partially inhibits its activity. Recently, we demonstrated ANGPTL4/8 also binds tissue plasminogen activator (tPA) and plasminogen to generate plasmin that cleaves ANGPTL4/8 to restore LPL activity. Although fully active LPL in the fat postprandially is desirable, ANGPTL4/8 removal could subject LPL to profound inhibition by ANGPTL3/8 (the most potent circulating LPL inhibitor), inhibition by other LPL inhibitors like ANGPTL4, ANGPTL3, and ApoC3 or interfere with ApoC2-mediated LPL activation. To understand better these potential paradoxes, we examined LPL inhibition by ANGPTL3/8, ANGPTL4, ANGPTL3, and ApoC3 and LPL stimulation by ApoC2 in the presence of ANGPTL4/8 + tPA + plasminogen. Remarkably, ANGPTL3/8-mediated LPL inhibition was almost completely blocked, with the mechanism being cleavage of fibrinogen-like domain-containing ANGPTL3 present in the ANGPTL3/8 complex. The LPL-inhibitory effects of ANGPTL4, ANGPTL3, and ApoC3 were also largely reduced in the presence of ANGPTL4/8 + tPA + plasminogen. In contrast, the ability of ApoC2 to stimulate LPL activity was unaffected by ANGPTL4/8-mediated plasmin generation. Together, these results explain how plasmin generated by increased postprandial ANGPTL4/8 levels in adipose tissue enables maximal LPL activity by preventing ANGPTL3/8, ANGPTL4, ANGPTL3, and ApoC3 from inhibiting LPL, while permitting ApoC2-mediated LPL activation to occur.

Long-Term Nutritional Counseling for a Patient with Lipoprotein Lipase Deficiency.

A one-year-and-nine-month-old Japanese boy was admitted with hypertriglyceridemia (fasting triglycerides 2548 mg/dL). After close examination, he was diagnosed with lipoprotein lipase (LPL) deficiency (compound heterozygous) and was immediately started on a fat-restricted dietary therapy. He responded well to the regimen (1200 kcal/day, 20 g fat/day) and his triglycerides decreased to 628 mg/dL within 7 days of starting the dietary therapy. It was decided to manage his illness without using any drugs because he was still an infant and responded well to a fat-restricted diet. During his hospital stay, dietitians provided him with nutritional counseling using a food exchange list, which was designed to easily calculate the fat content by including foods that are commonly served. His family quickly learned the skills to prepare a fat-restricted diet. Moreover, since dietary restrictions may have impaired the child's growth and development, the dietitians continued to intervene regularly after the child was discharged from the hospital. The dietitians confirmed that the patient was receiving nutritional intake appropriate for his growth and discussed the dietary concerns in his daily life and how to participate in school events that involved eating and drinking. Nutritional counseling was provided every 3-4 months from disease onset to age 23 years, except for a 14-month break at age 20 years. The patient grew up without developing acute pancreatitis, a serious complication of LPL deficiency. The long-term intervention of dieticians is necessary to achieve a balance between living on a strict diet for disease management and ensuring appropriate nutritional intakes for growth/development.

Lipoprotein lipase concentration in umbilical cord blood reflects neonatal birth weight.

BACKGROUND: Insulin resistance (IR) is exacerbated during pregnancy via increases in insulin counterregulatory hormones. Maternal lipids are strong determinants of neonatal growth, although triglyceride-rich lipoproteins (TGRLs) cannot be transferred directly to the fetus through the placenta. The catabolism of TGRLs under physiological IR and the reduced synthesis of lipoprotein lipase (LPL) are poorly understood. We examined the association of maternal and umbilical cord blood (UCB)-LPL concentrations with maternal metabolic parameters and fetal development. METHODS: Changes in anthropometric measures and lipid-, glucose-, and insulin-related parameters, including maternal and UCB-LPL concentrations, were examined in 69 women during pregnancy. The relationship between those parameters and neonatal birth weight was assessed. RESULTS: Parameters reflecting glucose metabolism did not change during pregnancy, whereas those associated with lipid metabolism and IR changed markedly, particularly in the second and third trimesters. In the third trimester, the maternal LPL concentration gradually decreased, by 54%, whereas the UCB-LPL concentration was âˆ¼2-fold higher than the maternal LPL concentration. Univariate and multivariate analyses showed that the UCB-LPL concentration was a significant determinant of neonatal birth weight, together with placental birth weight. CONCLUSION: The LPL concentration in UCB reflects neonatal development under a decreased LPL concentration in maternal serum.

[Seeking an Important Role on Metabolomics-Effects of ß-Estradiol on Lipoprotein Metabolism in Mammary Tumors].

The role of ß-estradiol (E2) in lipoprotein metabolism in mammary tumors remains unknown. Therefore the effect of E2 on secretion of lipoprotein lipase (LPL) from mouse mammary tumor FM3A cells was examined. The E2-treated FM3A cells increased active LPL secretion in a time- and dose-dependent manner. The activity of mitogen-activated protein kinase (MAPK) was elevated in the tumor cells treated with E2, and E2-stimulated secretion of LPL was suppressed by the MAPK kinase 1/2 inhibitor PD98059, extracellular signal-regulated kinase (ERK) 1/2 inhibitor FR180204, p38 MAPK inhibitor SB202190, and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. In addition, the effect of E2 on active LPL secretion was markedly suppressed by an inhibitor of mammalian target of rapamycin complex (mTORC) 1 and 2, KU0063794, but not by the mTORC1 inhibitor, rapamycin. Furthermore, a small interfering RNA (siRNA)-mediated decrease in the expression of rapamycin-insensitive companion of mTOR (Rictor), a pivotal component of mTORC2, suppressed the secretion of LPL by E2. Stimulatory secretion of LPL by E2 from the tumor cells is closely associated with activation of mTORC2 rather than mTORC1, possibly via the MAPK cascade.

Identification and Characterization of Two Novel Compounds: Heterozygous Variants of Lipoprotein Lipase in Two Pedigrees With Type I Hyperlipoproteinemia.

Background: Type I hyperlipoproteinemia, characterized by severe hypertriglyceridemia, is caused mainly by loss-of-function mutation of the lipoprotein lipase (LPL) gene. To date, more than 200 mutations in the LPL gene have been reported, while only a limited number of mutations have been evaluated for pathogenesis. Objective: This study aims to explore the molecular mechanisms underlying lipoprotein lipase deficiency in two pedigrees with type 1 hyperlipoproteinemia. Methods: We conducted a systematic clinical and genetic analysis of two pedigrees with type 1 hyperlipoproteinemia. Postheparin plasma of all the members was used for the LPL activity analysis. In vitro studies were performed in HEK-293T cells that were transiently transfected with wild-type or variant LPL plasmids. Furthermore, the production and activity of LPL were analyzed in cell lysates or culture medium. Results: Proband 1 developed acute pancreatitis in youth, and her serum triglycerides (TGs) continued to be at an ultrahigh level, despite the application of various lipid-lowering drugs. Proband 2 was diagnosed with type 1 hyperlipoproteinemia at 9 months of age, and his serum TG levels were mildly elevated with treatment. Two novel compound heterozygous variants of LPL (c.3G>C, p. M1? and c.835_836delCT, p. L279Vfs*3, c.188C>T, p. Ser63Phe and c.662T>C, p. Ile221Thr) were identified in the two probands. The postheparin LPL activity of probands 1 and 2 showed decreases of 72.22 ± 9.46% (p<0.01) and 54.60 ± 9.03% (p<0.01), respectively, compared with the control. In vitro studies showed a substantial reduction in the expression or enzyme activity of LPL in the LPL variants. Conclusions: Two novel compound heterozygous variants of LPL induced defects in the expression and function of LPL and caused type I hyperlipoproteinemia. The functional characterization of these variants was in keeping with the postulated LPL mutant activity.

An anti-ANGPTL3/8 antibody decreases circulating triglycerides by binding to a LPL-inhibitory leucine zipper-like motif.

Triglycerides (TG) are required for fatty acid transport and storage and are essential for human health. Angiopoietin-like-protein 8 (ANGPTL8) has previously been shown to form a complex with ANGPTL3 that increases circulating TG by potently inhibiting LPL. We also recently showed that the TG-lowering apolipoprotein A5 (ApoA5) decreases TG levels by suppressing ANGPTL3/8-mediated LPL inhibition. To understand how LPL binds ANGPTL3/8 and ApoA5 blocks this interaction, we used hydrogen-deuterium exchange mass-spectrometry and molecular modeling to map binding sites of LPL and ApoA5 on ANGPTL3/8. Remarkably, we found that LPL and ApoA5 both bound a unique ANGPTL3/8 epitope consisting of N-terminal regions of ANGPTL3 and ANGPTL8 that are unmasked upon formation of the ANGPTL3/8 complex. We further used ANGPTL3/8 as an immunogen to develop an antibody targeting this same epitope. After refocusing on antibodies that bound ANGPTL3/8, as opposed to ANGPTL3 or ANGPTL8 alone, we utilized bio-layer interferometry to select an antibody exhibiting high-affinity binding to the desired epitope. We revealed an ANGPTL3/8 leucine zipper-like motif within the anti-ANGPTL3/8 epitope, the LPL-inhibitory region, and the ApoA5-interacting region, suggesting the mechanism by which ApoA5 lowers TG is via competition with LPL for the same ANGPTL3/8-binding site. Supporting this hypothesis, we demonstrate that the anti-ANGPTL3/8 antibody potently blocked ANGPTL3/8-mediated LPL inhibition in vitro and dramatically lowered TG levels in vivo. Together, these data show that an anti-ANGPTL3/8 antibody targeting the same leucine zipper-containing epitope recognized by LPL and ApoA5 markedly decreases TG by suppressing ANGPTL3/8-mediated LPL inhibition.

Konjac Glucomannan Attenuated Triglyceride Metabolism during Rice Gruel Tolerance Test.

In a recent study, we showed that konjac glucomannan (KGM) inhibits rice gruel-induced postprandial increases in plasma glucose and insulin levels. To extend this research, we investigated the effects of KGM addition to rice gruel on pre- and postprandial concentrations of circulating lipoprotein lipase (LPL), glycosylphosphatidylinositol-anchored high-density lipoprotein-binding protein 1 (GPIHBP1), hepatic triglyceride lipase (HTGL), free fatty acids (FFA), and triglycerides (TG). A total of 13 Japanese men, without diabetes, dyslipidemia, or gastrointestinal diseases, interchangeably ingested rice gruel containing no KGM (0%G), rice gruel supplemented with 0.4% KGM (0.4%G), and rice gruel supplemented with 0.8% KGM (0.8%G), every Sunday for 3 weeks. Blood samples were obtained at baseline and at 30, 60, and 120 min after ingestion to measure the abovementioned lipid parameters. Lipid parameters showed small, but significant, changes. Significant reductions were found in circulating FFA levels among all participants. Circulating TG levels significantly declined at 30 min and then remained nearly constant in the 0.8%G group but exhibited no significant difference in the 0%G and 0.4%G groups. Although circulating levels of LPL and GPIHBP1 significantly decreased in the 0%G and 0.4%G groups, they increased at 120 min in the 0.8%G group. Participants in the 0%G and 0.4%G groups showed significant decreases in circulating HTGL levels, which was not observed in the 0.8%G group. Our results demonstrate the novel pleiotropic effects of KGM. Supplementation of rice gruel with KGM powder led to TG reduction accompanied by LPL and GPIHBP1 elevation and HTGL stabilization, thereby attenuating TG metabolism.

Comparison of angiopoietin-like protein 3 and 4 reveals structural and mechanistic similarities.

Elevated plasma triglycerides are a risk factor for coronary artery disease, which is the leading cause of death worldwide. Lipoprotein lipase (LPL) reduces triglycerides in the blood by hydrolyzing them from triglyceride-rich lipoproteins to release free fatty acids. LPL activity is regulated in a nutritionally responsive manner by macromolecular inhibitors including angiopoietin-like proteins 3 and 4 (ANGPTL3 and ANGPTL4). However, the mechanism by which ANGPTL3 inhibits LPL is unclear, in part due to challenges in obtaining pure protein for study. We used a new purification protocol for the N-terminal domain of ANGPTL3, removing a DNA contaminant, and found DNA-free ANGPTL3 showed enhanced inhibition of LPL. Structural analysis showed that ANGPTL3 formed elongated, flexible trimers and hexamers that did not interconvert. ANGPTL4 formed only elongated flexible trimers. We compared the inhibition of ANGPTL3 and ANGPTL4 using human very-low-density lipoproteins as a substrate and found both were noncompetitive inhibitors. The inhibition constants for the trimeric ANGPTL3 (7.5 ± 0.7 nM) and ANGPTL4 (3.6 ± 1.0 nM) were only 2-fold different. Heparin has previously been reported to interfere with ANGPTL3 binding to LPL, so we questioned if the negatively charged heparin was acting in a similar fashion to the DNA contaminant. We found that ANGPTL3 inhibition is abolished by binding to low-molecular-weight heparin, whereas ANGPTL4 inhibition is not. Our data show new similarities and differences in how ANGPTL3 and ANGPTL4 regulate LPL and opens new avenues of investigating the effect of heparin on LPL inhibition by ANGPTL3.

Research Progress on the Involvement of ANGPTL4 and Loss-of-Function Variants in Lipid Metabolism and Coronary Heart Disease: Is the "Prime Time" of ANGPTL4-Targeted Therapy for Coronary Heart Disease Approaching?

BACKGROUND: Multiple genetic studies have confirmed the definitive link among the loss-of-function variants of angiogenin-like protein 4 (ANGPTL4), significantly decreased plasma triglyceride (TG) levels, and reduced risk of coronary heart disease (CHD). The potential therapeutic effect of ANGPTL4 on dyslipidemia and CHD has been widely studied. OBJECTIVE: This review provides a detailed introduction to the research progress on the involvement of ANGPTL4 in lipid metabolism and atherosclerosis and evaluates the efficacy and safety of ANGPTL4 as a therapeutic target for CHD. RELEVANT FINDINGS: By inhibiting lipoprotein lipase (LPL) activity, ANGPTL4 plays a vital role in the regulation of lipid metabolism and energy balance. However, the role of ANGPTL4 in regulating lipid metabolism is tissue-specific. ANGPTL4 acts as a locally released LPL inhibitor in the heart, skeletal muscle and small intestine, while ANGPTL4 derived from liver and adipose tissue mainly acts as an endocrine factor that regulates systemic lipid metabolism. As a multifunctional protein, ANGPTL4 also inhibits the formation of foam cells in macrophages, exerting an anti-atherogenic role. The function of ANGPTL4 in endothelial cells is still uncertain. The safety of ANGPTL4 monoclonal antibodies requires further evaluation due to their potential adverse effects. CONCLUSION: The biological characteristics of ANGPTL4 are much more complex than those demonstrated by genetic studies. Future studies must elucidate how to effectively reduce the risk of CHD while avoiding potential atherogenic effects and other complications before the "prime time" of ANGPTL4-targeted therapy arrives.

LPL deletion is associated with poorer response to ibrutinib-based treatments and overall survival in TP53-deleted chronic lymphocytic leukemia.

Ibrutinib-based therapy represents a recent success in managing high-risk CLL patients with 17p/TP53 deletion. However, a subset of CLL patients are resistant to therapy. Deletion of lipoprotein lipase (LPL) has been postulated as a potential evasion mechanism to ibrutinib-based therapy. In this study, we assessed for LPL deletion by fluorescence in situ hybridization in 176 consecutive CLL patients with 17p/TP53 deletion. LPL deletion was detected in 35 (20%) of CLL patients. Patients with LPL deletion (del) showed a higher frequency of CD38 expression but have comparable frequencies of somatic hypermutation and ZAP-70 expression compared with patients with normal (nml) LPL. Gene mutation analysis showed that TP53 was mutated in 68% of LPL-del versus 91% of LPL-nml patients. The overall response to ibrutinib-based therapy was 57%, including 37% complete remission (CR) and 20% partial remission (PR) in patients with LPL-del versus 90% (56% CR and 34% PR) in patients with LPL-nml (p < 0.001). LPL-del patients also showed a poorer overall survival (OS) compared with patients with LPL-nml (median OS, 236 months versus undefined, p < 0.001). In summary, the data presented establish an association between LPL deletion, resistance to ibrutinib-based therapy, and poorer overall survival in TP53-deleted CLL patients. We suggest that LPL deletion might be utilized as a biomarker for risk stratification and to predict therapeutic response in this high-risk group of CLL patients.

Simple and rapid real-time monitoring of LPL activity in vitro.

Since elevated plasma triglycerides are an independent risk factor for cardiovascular diseases, lipoprotein lipase (LPL) is an interesting target for drug development. However, investigation of LPL remains challenging, as most of the commercially available assays are limited to the determination of LPL activity. Thus, we focused on the evaluation of a simple in vitro real-time fluorescence assay for the measurement of LPL activity that can be combined with additional cell or molecular biological assays in the same cell sample. Our procedure allows for a more comprehensive characterization of potential regulatory compounds targeting the LPL system. The presented assay procedure provides several advantages over currently available commercial in vitro LPL activity assays:1.12-well cell culture plate design for the simultaneous investigation of up to three different compounds of interest (including all assay controls).2.24 h real-time acquisition of LPL activity for the identification of the optimal time point for further measurements.3.Measurement of LPL activity can be supplemented by additional cell or molecular biological assays in the same cell sample.

The Importance of Fatty Acids as Nutrients during Post-Exercise Recovery.

It is well recognized that whole-body fatty acid (FA) oxidation remains increased for several hours following aerobic endurance exercise, even despite carbohydrate intake. However, the mechanisms involved herein have hitherto not been subject to a thorough evaluation. In immediate and early recovery (0-4 h), plasma FA availability is high, which seems mainly to be a result of hormonal factors and increased adipose tissue blood flow. The increased circulating availability of adipose-derived FA, coupled with FA from lipoprotein lipase (LPL)-derived very-low density lipoprotein (VLDL)-triacylglycerol (TG) hydrolysis in skeletal muscle capillaries and hydrolysis of TG within the muscle together act as substrates for the increased mitochondrial FA oxidation post-exercise. Within the skeletal muscle cells, increased reliance on FA oxidation likely results from enhanced FA uptake into the mitochondria through the carnitine palmitoyltransferase (CPT) 1 reaction, and concomitant AMP-activated protein kinase (AMPK)-mediated pyruvate dehydrogenase (PDH) inhibition of glucose oxidation. Together this allows glucose taken up by the skeletal muscles to be directed towards the resynthesis of glycogen. Besides being oxidized, FAs also seem to be crucial signaling molecules for peroxisome proliferator-activated receptor (PPAR) signaling post-exercise, and thus for induction of the exercise-induced FA oxidative gene adaptation program in skeletal muscle following exercise. Collectively, a high FA turnover in recovery seems essential to regain whole-body substrate homeostasis.

Identification and functional characterization of a novel heterozygous missense variant in the LPL associated with recurrent hypertriglyceridemia-induced acute pancreatitis in pregnancy.

BACKGROUND: Acute pancreatitis in pregnancy (APIP) is a life-threatening disease for both mother and fetus. To date, only three patients with recurrent hypertriglyceridemia-induced APIP (HTG-APIP) have been reported to carry rare variants in the lipoprotein lipase (LPL) gene, which encodes the key enzyme responsible for triglyceride (TG) metabolism. Coincidently, all three patients harbored LPL variants on both alleles and presented with complete or severe LPL deficiency. METHODS: The entire coding regions and splice junctions of LPL and four other TG metabolism genes (APOC2, APOA5, GPIHBP1, and LMF1) were analyzed by Sanger sequencing in a Han Chinese patient who had experienced two episodes of HTG-APIP. The impact of a novel LPL missense variant on LPL protein expression and activity was analyzed by transient expression in HEK293T cells. RESULTS: A novel heterozygous LPL missense variant, p.His210Leu (c.629A > T), was identified in our patient. This variant did not affect protein synthesis but significantly impaired LPL secretion and completely abolished the enzymatic activity of the mutant protein. CONCLUSION: This report describes the first identification and functional characterization of a heterozygous variant in the LPL that predisposed to recurrent HTG-APIP. Our findings confirm a major genetic contribution to the etiology of individual predisposition to HTG-APIP.

Identification of differentially expressed genes and pathways in lipoprotein lipase gene heterozygous knockout mice through gene microarray analysis / 上海交通大学学报（医学版）

Objective • To screen the differentially expressed genes (DEGs) and pathways in the islet tissues of lipoprotein lipase (Lpl) gene heterozygous knockout (Lpl+/-) mice and wild type (WT) mice, and explore the molecular mechanism of pathogenesis of type 2 diabetes mellitus (T2DM) mediated by lipotoxicity. Methods • The islets of Lpl+/- mice and WT mice were isolated and purified. DEGs were screened by gene microarray analysis. Gene Ontology (GO) function analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of DEGs were performed. The expressions of key genes were verified by quantitative real-time PCR (qPCR). Results • A total of 187 DEGs were identified. GO functional analysis and KEGG pathway analysis showed that DEGs were mainly involved in the biological processes such as immune cell proliferation and differentiation, inflammatory signaling pathways and cell adhesion. Among the top 10 DEGs screened from Lpl+- mice and WT mice, gremlin 1 (Grem1) gene was closely related to the function of islet β cells, while the result of qPCR was consistent with that of gene microarray analysis. Conclusion • Multiple signaling pathways are involved in the process of T2DM mediated by lipotoxicity, which may lead to the dysfunction of islet β cells by inhibiting Grem1 expression.

MicroRNA-138 Suppresses Adipogenic Differentiation in Human Adipose Tissue-Derived Mesenchymal Stem Cells by Targeting Lipoprotein Lipase.

PURPOSE: Adipogenic differentiation of adipose tissue-derived mesenchymal stem cells (AMSCs) is critical to many disease-related disorders, such as obesity and diabetes. Studies have demonstrated that miRNA-138 (miR-138) is closely involved in adipogenesis. However, the mechanisms affected by miR-138 remain unclear. This work aimed to investigate interactions between miR-138 and lipoprotein lipase (LPL), a key lipogenic enzyme, in AMSCs. MATERIALS AND METHODS: Human AMSCs (hAMSCs) isolated from human abdomen tissue were subjected to adipogenic differentiation medium. Quantitative real-time polymerase chain reaction and Western blot assay were applied to measure the expressions of miR-138, LPL, and the two adipogenic transcription factors cytidine-cytidine-adenosine-adenosine-thymidine enhancer binding protein alpha (C/EBPα) and peroxisome proliferator-activated receptor gamma (PPARγ). The relationship between miR-138 and LPL was predicted utilizing the miRTarBase database and validated by dual luciferase reporter assay. RESULTS: Showing increases in C/EBPα and PPARγ expression levels, hAMSCs were induced into adipogenic differentiation. During adipogenesis of hAMSCs, miR-138 expression was significantly downregulated. Overexpression of miR-138 by transfection inhibited hAMSCs adipogenic differentiation in vitro. Mechanically, LPL was a target of miR-138. LPL expression was upregulated during adipogenesis of hAMSCs, and this upregulation was reversed by miR-138 overexpression. Functionally, silencing of LPL by transfection exerted similar inhibition of the expressions of C/EBPα and PPARγ. Meanwhile, LPL ectopic expression was able to partly abolish the suppressive effect of miR-138 overexpression on adipogenic differentiation of hAMSCs. CONCLUSION: Upregulation of miR-138 inhibits adipogenic differentiation of hAMSCs by directly downregulating LPL.

The VLDL receptor plays a key role in the metabolism of postprandial remnant lipoproteins.

A new concept to account for the process of postprandial remnant lipoprotein metabolism is proposed based on the characteristics of lipoprotein particles and their receptors. The characteristics of remnant lipoprotein (RLP) were investigated using an immuno-separation method. The majority of the postprandial lipoproteins increased after fat intake was shown to be VLDL remnants, not chylomicron (CM) remnants, based on the significantly high ratio of apoB100/apoB48 in the RLP and the high degree of similarity in the particle size of the apoB48 and apoB100 carrying lipoproteins, which fluctuate in parallel during a 6 h period after fat intake. The VLDL receptor was discovered as a receptor for TG-rich lipoprotein metabolism and is located in peripheral tissues such as skeletal muscle, adipose tissue, etc., but not in the liver. Postprandial VLDL particles are strongly bound and internalized into cells expressing the VLDL receptor. Ligands that bind to VLDL receptor, such as LPL and Lp(a), present in RLP. The presence of various specific ligands in VLDL remnants may enhance the capacity for binding to the VLDL receptor, which play the role primarily for energy delivery to the peripheral tissues, but is also a causal factor in atherogenic diseases when excessively and/or continuously remained in plasma.

Association between skeletal muscle mass and serum concentrations of lipoprotein lipase, GPIHBP1, and hepatic triglyceride lipase in young Japanese men.

BACKGROUND: Two important regulators for circulating lipid metabolisms are lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL). In relation to this, glycosylphosphatidylinositol anchored high-density lipoprotein binding protein 1 (GPIHBP1) has been shown to have a vital role in LPL lipolytic processing. However, the relationships between skeletal muscle mass and lipid metabolism, including LPL, GPIHBP1, and HTGL, remain to be elucidated. Demonstration of these relationships may lead to clarification of the metabolic dysfunctions caused by sarcopenia. In this study, these relationships were investigated in young Japanese men who had no age-related factors; participants included wrestling athletes with abundant skeletal muscle. METHODS: A total of 111 young Japanese men who were not taking medications were enrolled; 70 wrestling athletes and 41 control students were included. The participants' body compositions, serum concentrations of lipoprotein, LPL, GPIHBP1 and HTGL and thyroid function test results were determined under conditions of no extreme dietary restrictions and exercises. RESULTS: Compared with the control participants, wrestling athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), higher serum concentrations of LPL (p < 0.001) and GPIHBP1 (p < 0.001), and lower fat mass index (p = 0.024). Kruskal-Wallis tests with Bonferroni multiple comparison tests showed that serum LPL and GPIHBP1 concentrations were significantly higher in the participants with higher SMI. Spearman's correlation analyses showed that SMI was positively correlated with LPL (ρ = 0.341, p < 0.001) and GPIHBP1 (ρ = 0.309, p = 0.001) concentration. The serum concentrations of LPL and GPIHBP1 were also inversely correlated with serum concentrations of triglyceride (LPL, ρ = - 0.198, p = 0.037; GPIHBP1, ρ = - 0.249, p = 0.008). Serum HTGL concentration was positively correlated with serum concentrations of total cholesterol (ρ = 0.308, p = 0.001), low-density lipoprotein-cholesterol (ρ = 0.336, p < 0.001), and free 3,5,3'-triiodothyronine (ρ = 0.260, p = 0.006), but not with SMI. CONCLUSIONS: The results suggest that increased skeletal muscle mass leads to improvements in energy metabolism by promoting triglyceride-rich lipoprotein hydrolysis through the increase in circulating LPL and GPIHBP1.

Gender-related relation between metabolic syndrome and S447X and HindIII polymorphisms of lipoprotein lipase gene in northern Iran.

BACKGROUND: Metabolic syndrome is a cluster of conditions that increase risk of cardiovascular morbidity and mortality. Among genetic factors that contributed to incidence of metabolic syndrome, Polymorphisms of Lipoprotein lipase (LPL) are major candidates especially because of their effect on obesity and dyslipidemia. S447X (rs328) and Hind III (rs320) Polymorphisms of LPL gene have been reported to change LPL activity, resulting in altered triglyceride (TG) and high density lipoprotein Cholesterol (HDL-C) levels. This study investigates the effects of these gene polymorphisms on factors affecting metabolic syndrome in northern population of Iran. METHODS: Studied population included 223 adults consisting 90 women and 133 men with body mass index (BMI) ≥ 30 kg/m2 as obese subjects, and 156 healthy participants as a control group with BMI <25 that included 68 women and 88 men. All factors causing metabolic syndrome were evaluated. Also DNA was extracted from blood samples and HindIII and S447X LPL gene polymorphisms were screened by polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). CONCLUSIONS: The present study proves that some genotypes of S447X were associated with a reduced risk of developing low HDL-C only in men, while the protective effects of HindIII on hypertriglyceridemia were only seen in women [corrected]. The point is that this relation is affected by the weight profile of the participants. It can be concluded that there is a gender-related relation between the polymorphisms of LPL gene and the risk factors for incidence of metabolic syndrome in the northern population of Iran.