Post-heparin Lipoprotein Lipase Research Articles

Genetic and biochemical analysis of severe hypertriglyceridemia complicated with acute pancreatitis or with low post-heparin lipoprotein lipase mass.

Severe hypertriglyceridemia is a pathological condition caused by genetic factors alone or in combination with environmental factors, sometimes leading to acute pancreatitis (AP). In this study, exome sequencing and biochemical analyses were performed in 4 patients with hypertriglyceridemia complicated by obesity or diabetes with a history of AP or decreased post-heparin LPL mass. In a patient with a history of AP, SNP rs199953320 resulting in LMF1 nonsense mutation and APOE rs7412 causing apolipoprotein E2 were both found in heterozygous form. Three patients were homozygous for APOA5 rs2075291, and one was heterozygous. ELISA and Western blot analysis of the serum revealed the existence of apolipoprotein A-V in the lipoprotein-free fraction regardless of the presence or absence of rs2075291; furthermore, the molecular weight of apolipoprotein A-V was different depending on the class of lipoprotein or lipoprotein-free fraction. Lipidomics analysis showed increased serum levels of sphingomyelin and many classes of glycerophospholipid; however, when individual patients were compared, the degree of increase in each class of phospholipid among cases did not coincide with the increases seen in total cholesterol and triglycerides. Moreover, phosphatidylcholine, lysophosphatidylinositol, and sphingomyelin levels tended to be higher in patients who experienced AP than those who did not, suggesting that these phospholipids may contribute to the onset of AP. In summary, this study revealed a new disease-causing gene mutation in LMF1, confirmed an association between overlapping of multiple gene mutations and severe hypertriglyceridemia, and suggested that some classes of phospholipid may be involved in the pathogenesis of AP.

Effects of exercise training on ANGPTL3/8 and ANGPTL4/8 and their associations with cardiometabolic traits

Angiopoietin-like protein (ANGPTL) complexes 3/8 and 4/8 are established inhibitors of LPL and novel therapeutic targets for dyslipidemia. However, the effects of regular exercise on ANGPTL3/8 and ANGPTL4/8 are unknown. We characterized ANGPTL3/8 and ANGPTL4/8 and their relationship with in vivo measurements of lipase activities and cardiometabolic traits before and after a 5-month endurance exercise training intervention in 642 adults from the HERITAGE (HEalth, RIsk factors, exercise Training And GEnetics) Family Study. At baseline, higher levels of both ANGPTL3/8 and ANGPTL4/8 were associated with a worse lipid, lipoprotein, and cardiometabolic profile, with only ANGPTL3/8 associated with postheparin LPL and HL activities. ANGPTL3/8 significantly decreased with exercise training, which corresponded with increases in LPL activity and decreases in HL activity, plasma triglycerides, apoB, visceral fat, and fasting insulin (all P < 5.1 × 10−4). Exercise-induced changes in ANGPTL4/8 were directly correlated to concomitant changes in total cholesterol, LDL-C, apoB, and HDL-triglycerides and inversely related to change in insulin sensitivity index (all P < 7.0 × 10−4). In conclusion, exercise-induced decreases in ANGPTL3/8 and ANGPTL4/8 were related to concomitant improvements in lipase activity, lipid profile, and cardiometabolic risk factors. These findings reveal the ANGPTL3-4-8 model as a potential molecular mechanism contributing to adaptations in lipid metabolism in response to exercise training.

AAV-mediated hepatic LPL expression ameliorates severe hypertriglyceridemia and acute pancreatitis in Gpihbp1 deficient mice and rats

GPIHBP1 plays an important role in the hydrolysis of triglyceride (TG) lipoproteins by lipoprotein lipases (LPLs). However, Gpihbp1 knockout mice did not develop hypertriglyceridemia (HTG) during the suckling period but developed severe HTG after weaning on a chow diet. It has been postulated that LPL expression in the liver of suckling mice may be involved. To determine whether hepatic LPL expression could correct severe HTG in Gpihbp1 deficiency, liver-targeted LPL expression was achieved via intravenous administration of the adeno-associated virus (AAV)-human LPL gene, and the effects of AAV-LPL on HTG and HTG-related acute pancreatitis (HTG-AP) were observed. Suckling Gpihbp1-/- mice with high hepatic LPL expression did not develop HTG, whereas Gpihbp1-/- rat pups without hepatic LPL expression developed severe HTG. AAV-mediated liver-targeted LPL expression dose-dependently decreased plasma TG levels in Gpihbp1-/- mice and rats, increased post-heparin plasma LPL mass and activity, decreased mortality in Gpihbp1-/- rat pups, and reduced the susceptibility and severity of both Gpihbp1-/- animals to HTG-AP. However, the muscle expression of AAV-LPL had no significant effect on HTG. Targeted expression of LPL in the liver showed no obvious adverse reactions. Thus, liver-targeted LPL expression may be a new therapeutic approach for HTG-AP caused by GPIHBP1 deficiency.

Loss-of-Function Homozygous Variant in LPL Causes Type I Hyperlipoproteinemia and Renal Lipidosis

Lipoprotein lipase (LPL) is an important enzyme in lipid metabolism, individuals with LPL gene variants could present type I hyperlipoproteinemia, lipemia retinalis, hepatosplenomegaly, and pancreatitis. To date, there are no reports of renal lipidosis induced by type I hyperlipoproteinemia due to LPL mutation. Renal biopsy was conducted to confirm the etiological factor of nephrotic syndrome in a 44-year-old Chinese man. Lipoprotein electrophoresis, apoE genotype detection, and whole-exome sequencing were performed to confirm the dyslipidemia type and genetic factor. Analysis of the 3-dimensional protein structure and invitro functional study were conducted to verify variant pathogenicity. Renal biopsy revealed numerous CD68 positive foam cells infiltrated in the glomeruli; immunoglobulin and complement staining were negative; and electron microscopy revealed numerous lipid droplets and cholesterol clefts in the cytoplasm of foam cells. Lipoprotein electrophoresis revealed that the patient fulfilled the diagnostic criteria of type I hyperlipoproteinemia. The apoE genotype of the patient was the ε3/ε3 genotype. Whole-exome sequencing revealed an LPL (c.292G > A, p.A98T) homozygous variant with α-helix instability and reduced post-heparin LPL activity but normal lipid uptake capability compared to the wild-type variant. LPL (c.292G > A, p.A98T) is a pathogenic variant that causes renal lipidosis associated with type I hyperlipoproteinemia. This study provides adequate evidence of the causal relationship between dyslipidemia and renal lesions. However, further research is needed to better understand the pathogenetic mechanism of LPL variant-related renal lesions.

Correlation between chylomicronemia diagnosis scores and post-heparin lipoprotein lipase activity

IntroductionSustained chylomicronemia is a defect in post-prandial triglyceride management characterized by severe hypertriglyceridemia (triglyceride > 10 mmol/L) due to functional or genetic defects in lipoprotein lipase (LPL)-mediated triglyceride-rich lipoprotein lipolysis. Familial chylomicronemia syndrome (FCS) is a rare mendelian form of chylomicronemia caused by loss-of–function variants in LPL or LPL-related genes. Most individuals with chylomicronemia however present multifactorial chylomicronemia (MCS), in which LPL bio-availability and activity are variable. FCS and MCS differ in terms of clinical characteristics and risk of disease, and diagnosis scoring systems have been proposed to accurately distinguish FCS from MCS. ObjectiveThe aim of this study was to assess the strength of the relationship between plasma post-heparin LPL activity and two published chylomicronemia diagnosis scoring systems. Design and MethodsPost-heparin plasma LPL activity was measured using colorimetric assays in a sample of 29 subjects with sustained chylomicronemia (20 FCS and 9 MCS).Chylomicronemia diagnosis scores were obtained for all subjects using the scoring system A (model A), which integrates apolipoprotein B and free glycerol, a surrogate marker of triglyceride hydrolysis, and the scoring system B (model B). Correlation analyses were conducted to estimate the linear relationship between LPL activity and the two diagnosis scoring systems. ResultsThere was a significant (p < 0.001) difference in post-heparin LPL activity between FCS and MCS. Both scoring systems significantly correlated with post-heparin LPL activity (model A: rs = −0.64, p < 0.001; model B: rs = −0.54, p = 0.002). ConclusionsThese result suggest that chylomicronemia diagnosis scoring systems correlate with LPL activity and adequately contribute to distinguish FCS from MCS.

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

BackgroundType 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.ObjectiveThis study aims to explore the molecular mechanisms underlying lipoprotein lipase deficiency in two pedigrees with type 1 hyperlipoproteinemia.MethodsWe 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.ResultsProband 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.ConclusionsTwo 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.

Digenic Inheritance and Gene-Environment Interaction in a Patient With Hypertriglyceridemia and Acute Pancreatitis.

The etiology of hypertriglyceridemia (HTG) and acute pancreatitis (AP) is complex. Herein, we dissected the underlying etiology in a patient with HTG and AP. The patient had a 20-year history of heavy alcohol consumption and an 8-year history of mild HTG. He was hospitalized for alcohol-triggered AP, with a plasma triglyceride (TG) level up to 21.4 mmol/L. A temporary rise in post-heparin LPL concentration (1.5–2.5 times of controls) was noted during the early days of AP whilst LPL activity was consistently low (50∼70% of controls). His TG level rapidly decreased to normal in response to treatment, and remained normal to borderline high during a ∼3-year follow-up period during which he had abstained completely from alcohol. Sequencing of the five primary HTG genes (i.e., LPL, APOC2, APOA5, GPIHBP1 and LMF1) identified two heterozygous variants. One was the common APOA5 c.553G > T (p.Gly185Cys) variant, which has been previously associated with altered TG levels as well as HTG-induced acute pancreatitis (HTG-AP). The other was a rare variant in the LPL gene, c.756T > G (p.Ile252Met), which was predicted to be likely pathogenic and found experimentally to cause a 40% loss of LPL activity without affecting either protein synthesis or secretion. We provide evidence that both a gene-gene interaction (between the common APOA5 variant and the rare LPL variant) and a gene-environment interaction (between alcohol and digenic inheritance) might have contributed to the development of mild HTG and alcohol-triggered AP in the patient, thereby improving our understanding of the complex etiology of HTG and HTG-AP.

EPA and DHA Have Differential Effects on Cholesterol Ester Transfer Protein and Lipoprotein Lipase Activities Following Plasma Triglycerides Lowering

Abstract Objectives Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are effective in reducing plasma triglyceride (TG) concentrations but have divergent effects on LDL cholesterol (LDL-C) concentrations. Differential regulations of cholesterol ester transfer protein (CETP) and lipoprotein lipase (LPL) activities are possible mechanisms of their differential effects. We assessed the effects of EPA and DHA supplementation on plasma lipid profiles and two enzyme activities involved in lipoprotein metabolism. Methods Nine men and twelve postmenopausal women (N = 21, 50–75y) with chronic inflammation (CRP &amp;gt; 2 mg/L) were enrolled in a randomized, double-blind, crossover trial consisting of a 4-wk lead-in phase with high oleic acid sunflower oil (3 g/d) followed by two 10-wk EPA and DHA supplementation phases (3 g/d each) separated by a 10-wk washout phase. Plasma was collected after the lead-in (baseline) and each n-3 fatty acid supplementation phase for analysis of TG, total cholesterol and HDL-C, and CETP and post-heparin LPL activities. LDL-C was estimated using the Friedewald formula. Results Subjects were recruited to have moderately elevated TG and LDL-C concentrations (mean ± SEM: 141 ± 11 and 130 ± 6 mg/dL, respectively). Compared to baseline, EPA supplementation lowered TG concentration (−28 ± 6 mg/dL, P &amp;lt; 0.001) and CETP activity (−1.6 ± 1.1 µg/mL/h, P &amp;lt; 0.05), whereas LDL-C concentration and LPL activity were unchanged. The changes in TG concentration and CETP activity were negatively correlated with baseline TG (r = −0.77 and −0.45, respectively, both P &amp;lt; 0.05). DHA supplementation lowered TG concentration (−31 ± 8 mg/dL, P &amp;lt; 0.001), and increased LDL-C concentration (+10 ± 4 mg/dL, P &amp;lt; 0.01) and LPL activity (+6.1 ± 4.0 mU/mL, P &amp;lt; 0.03), CETP activity was unchanged. The DHA-mediated increase in LPL activity was correlated with the baseline TG concentration and change in TG concentration (r = 0.64 and ρ = −0.45, respectively, both P &amp;lt; 0.05). Conclusions In the context of the established TG-lowering effects of EPA and DHA, these n-3 fatty acids affected CETP and LPL activities differently. DHA-induced change in LDL-C concentration may be related to increased LPL activity, and the conversion of very low-density lipoprotein to LDL. Funding Sources AFRI/NIFA; USDA.

Correlation between chylomicronemia diagnosis scores and post-heparin lipoprotein lipase activity

None.

Free glycerol correlate with post-heparin lipoprotein lipase activity and contribute to differentiate familial vs. multifactorial chylomicronemia

Free glycerol correlate with post-heparin lipoprotein lipase activity and contribute to differentiate familial vs. multifactorial chylomicronemia

Compound but non-linked heterozygous p.W14X and p.L279\xa0V LPL gene mutations in a Chinese patient with long-term severe hypertriglyceridemia and recurrent acute pancreatitis

BackgroundVariants in the lipoprotein lipase (LPL), apolipoprotein C-II (APOC2), apolipoprotein A-V (APOA5), GPIHBP1 and LMF1 genes may cause severe hypertriglyceridemia (HTG), which is now the second-leading aetiology of acute pancreatitis in China.MethodsThe patient and his family were assessed for gene variants by Sanger sequencing of exons and exon-intron junctions of the LPL, GPIHBP1, APOA5, APOC2, and LMF1 genes. Post-heparin blood was collected for LPL mass and activity detection.ResultsThe patient had suffered from long-term severe hypertriglyceridemia and recurrent abdominal pain for over 30 years, since age 26, and 3 bouts of acute pancreatitis. Two heterozygous LPL single-nucleotide polymorphisms (SNPs) were compound but dislinked: a single-nucleotide substitution (c.42G > A) resulting in the substitution of tryptophan with a stop codon (p.W14X) in one allele, and a single-nucleotide substitution (c.835C > G) resulting in a leucine-to-valine substitution (p.L279 V) in another allele. Only one SNP, p.L279 V, was detected in his son. Post-heparin LPL activity and mass were also lower in the patient.ConclusionTwo heterozygous LPL SNPs, W14X and L279 V, were newly found to be compound but dislinked, which may cause long-term severe hypertriglyceridemia and recurrent acute pancreatitis.

Clinical and biochemical features of different molecular etiologies of familial chylomicronemia

Familial chylomicronemia syndrome (FCS) is an ultra-rare phenotype that is usually caused by biallelic mutations in the LPL gene encoding lipoprotein lipase, or less often in APOC2, APOA5, LMF1, or GPIHBP1 genes encoding cofactors or interacting proteins. We evaluated baseline phenotypes among FCS participants in a phase 3 randomized placebo-controlled trial of volanesorsen (NCT02211209). Baseline clinical, fasting, and postfat load metabolic markers were assessed. Targeted next-generation DNA sequencing plus custom bioinformatics was used to genotype subjects. Among 52 FCS individuals, 41 had biallelic LPL gene mutations (LPL-FCS patients): 82%, 7%, and 11% were missense, nonsense, and splicing variants, respectively. Eleven individuals had non-LPL-FCS; 2 had mutations in APOA5, 5 in GPIHBP1, and 1 each in LMF1 and APOC2 genes, respectively. Two other individuals were double heterozygotes, each with 1 normal LPL allele. All subjects had extremely high triglycerides (TGs) and chylomicrons, but very low levels of other lipoproteins. Compared with LPL-FCS individuals, non-LPL-FCS individuals were very similar for most traits, but had significantly higher postheparin LPL activity, higher 4-hour postprandial insulin and C-peptide levels; and higher low-density lipoprotein cholesterol levels. In non-LPL-FCS individuals compared to those with LPL-FCS, there were also nonsignificant trends toward lower levels of total and chylomicron TGs, lower 4-hour postprandial chylomicron TG levels, and higher very-low-density lipoprotein TG levels. Thus, LPL FCS and non-LPL FCS are largely phenotypically similar. However, LPL FCS patients have lower postheparin LPL activity and a trend toward higher TGs, whereas low-density lipoprotein cholesterol was higher in non-LPL-FCS patients.

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.

Alterations in plasma triglycerides lipolysis in patients with history of multifactorial chylomicronemia

Background and aimsThe heterogeneity and mechanisms of multifactorial chylomicronemia (MCM) remain poorly understood. To gain new insights, post heparin lipolysis measured at 60 min (PHLA60), in addition to the more commonly used 10 min (PHLA10), was assessed in patients with history of MCM. Methods62 consecutive MCM patients were studied. The evaluation included LPL, APOC2, APOA5, GPIHBP1, LMF1 and APOE gene sequencing, as well as pre- and post-heparin injection biochemical analysis, including lipid profiles, determination of apolipoprotein B, B-48, CII, CIII, lipoprotein lipase (LPL) concentrations (LPLC0, LPLC10 and LPLC60) and post-heparin LPL activity (PHLA10 and PHLA60). ResultsIn controls, PHLA60 did not differ from PHLA10, while in MCM patients, PHLA60 was significantly lower than PHLA10 (p<0.001). PHLA60 showed a bimodal distribution in MCM patients (p=0.03). One subgroup exhibited PHLA60 similar to controls, with persistent lipoprotein remodeling and, paradoxically, the highest basal plasma TG concentration. APOE ε4 was over-represented compared to the European population (p<0.05) and Apo CIII/Apo B ratio was increased (p<0.01). The other subgroup exhibited low PHLA60 (p<0.001) compared to both controls and the other MCM subgroup with a lipoprotein profile consistent with fast and transient remodeling. LMF1 p. Arg364Gln was over-represented compared to the European population (p<0.05). ConclusionsThe study showed that PHLA60 identifies a subgroup of MCM with a defect in lipolysability and/or hepatic clearance of triglycerides-rich lipoproteins, and a larger one with a defect in LPL availability. These findings provide new insights into the heterogeneity of MCM and might contribute to adjust treatment targeting.

Abstract 18157: Impact of Betatrophin (ANGPTL8) R59W Mutation for Future Diabetes, and Minimal Modification of Circulating Betatrophin With Strong Statins

Betatrophin (ANGPTL8), also known as “Lipasin” (lipoprotein lipase inhibitor), has been reported as a dual-regulator of glucose and lipid metabolism. Functional variant R59W in betatrophin gene is common in Japanese (minor allele 25%) compared with Caucasian (5%). Little is known about long-term impact of this gene variant, and also about the effect of lipid-lowering drugs on this hormone. Methods: A total of 205 cases with dyslipidemia evaluated with baseline 75gOGTT, and post-heparin lipoprotein lipase activities were registered as a long-term cohort. As lipid-lowering trial, a total of 44 patients (Male 21, Age 65±11 ys) with primary dyslipidemia, and 18 genetically confirmed heterozygous familial hypercholesterolemia (FH) (Male 12, Age 65±10 ys,) were analyzed. Non-FH dyslipidemia was treated with 10mg Atorvastatin, and FH was treated with 20mg Rosuvastatin for 8 weeks. Plasma TG and betatrophin levels were log-transformed for statistical analysis. Results: In long-term cohort, 57 cases already showed diabetic pattern at baseline, 148 cases (Male 82, age 56±15 ys, hetero-FH 48 cases, mean follow-up period 10±3 ys) without diabetes at baseline were finally analyzed. Sixty-two cases (42%) developed newly diabetes mellitus during the follow-up, significantly fewer in FH than non-FH (25% vs. 50%, p &lt;0.005). No differences in BMI, fasting glucose, HbA1c in baseline with R59W genotype. In low LPL activity group (n=31), W carriers showed significant increase in HbA1c compared with RR (2.1±0.5 vs. 0.9±0.4 %, p &lt;0.05), but no differences in normal LPL group. In lipid lowering trial, baseline betatrophin levels were lower in FH group (19±13 vs. 13±6 ng/mL, p &lt;0.05), but no difference with/without R59W variant. Statin treatment slightly decreased betatrophin in dyslipidemia group (-4%, p &lt;0.01) and in FH group (-5%, p &lt;0.01). Changes in betatrophin were positively correlated with changes in LDL-C with statins in both groups. Conclusion: Betatrophin R59W variant was a susceptibility factor of future diabetes mellitus with low LPL activity. Baseline betatrophin levels were lower in FH group than other primary dyslipidemia in lipid-lowering trial. Strong statin treatments slightly decreased betatrophin levels, but effect sizes were minimal.

Antidyslipidemic and Antioxidant Activities of Tinospora cordifolia Stem Extract in Alloxan Induced Diabetic Rats

The antidyslipidemic activities of Tinospora cordifolia (T. cordifolia): family Menispermaceae, Hindi name: Giloya; Gurch or Tinospora in english, extract have been studied in alloxan induced diabetic rats. In this model, oral administration of stem extract (500 mg/kg bw. p.o.) for 30 days resulted significant decreased in the levels of blood glucose, plasma lipids and reactivated post heparin lipoprotein lipase activity in alloxan induced diabetic rats. Furthermore, the stem extract (50–500 μg) when tested for its antioxidant activity, shown to inhibit the generation of super oxide anions and hydroxyl radicals, in both enzymic and non-enzymic systems in vitro. The results of the present study demonstrated antidyslipidemic and antioxidant activities of T. cordifolia which could help in prevention of diabetic-dyslipidemia and related complications.

Does liver-derived ANGPTL3 play a role in cardiometabolic risk? Current evidence and future perspectives

particles, as well as a decreased VLDL production rate and lower TC and TG levels in the absence of the protein [3]. Furthermore, in vitro studies demonstrated that the protein is able to directly stimulate FFA release from adipose cells into the media [3,8]. Similarly, in humans, evidence for a role of ANGPTL3 in modulating lipid, lipoprotein and FFA metabolism came from identifying and characterizing individuals carrying inactivating mutations in the ANGPTL3 gene and presenting familial combined hypolipidemia (FHBL2, OMIM #605019) [3,9–12]. In fact, by sequencing or resequencing the ANGPTL3 gene in families with combined hypolipidemia or hypocholesterol emia not linked to the APOB gene, many study groups have contributed to the identif ication of different ANGPTL3 loss-of-function (LOF) mutations in previous years [9–12] . The largest cohort of subjects carrying inactivating ANGPTL3 LOF mutations was described in people living in the little town of Campodimele (Latina, Italy) [10]. By studying these subjects and collecting data from other study groups, we had the unique opportunity to better characterize the effect of the complete deficiency of the protein on lipids, and in a subgroup, of lipoprotein composition and lipoprotein-related protein as well as the effect on levels of FFAs, glucose and insulin [3,10,13]. FHBL2, due to ANGPTL3 LOF mutations, affects proand anti-atherogenic lipoprotein metabolism, and appears to be transmitted as a recessive trait [3]. In particular, homozygous subjects for ANGPTL3 LOF mutations show low levels of all lipid components (TC, HDL and TGs), while heterozygotes show inter mediate levels of lipids as compared with noncarriers ANGPTL3 deficiency: evidence on pro& anti-atherogenic lipoprotein & free fatty acid metabolism Elevated cholesterol and triglyceride (TG) levels, low HDL cholesterol and sustained elevation of free fatty acid (FFA) levels are major modifiable risk factors for cardiovascular disease and insulin resistance [1,2]. Recently, the liverderived ANGPTL3 component of the family of angiopoietin-like proteins has attracted interest for its role in the regulation of all these risk factors, becoming a possible new target for cardiometabolic risk modulation [3]. ANGPTL3 contains an N-terminal coiledcoil domain, responsible for the inhibition of lipoprotein lipase (LPL) activity, and a C-terminal fibrinogen-like domain, connected by a linker region [3–5]. ANGPTL3 is cleaved into two fragments and activated by the action of proprotein convertases [6,7]. Most of the actual knowledge on ANGPTL3 metabolic functions derives from in vitro and in vivo studies in which the protein is deficient or absent. Indeed, the first discovery of ANGPTL3 as a potential modulator of lipid, lipoprotein and FFA metabolism came from studies in ANGPTL3-null (ANGPTL3) or -deficient mice (KK/San), which presented very low levels of total cholesterol (TC) and TGs, and in which treatment with recombinant or adenoviral Angptl3 resulted in elevation of TC, TG and FFAs [3]. Subsequently, experimental data shed light onto the mechanism by which ANPGTL3 regulates lipids and lipoprotein metabolism: in the null animal model, increased postheparin LPL and hepatic lipase (HL) activities, and a lower hepatic TG secretion rate were demonstrated, which translates into an increased catabolic rate of VLDL “ ...as ANGPTL3 seems to be involved in the partitioning of fatty acids and regulation of free fatty acid-induced insulin sensitivity, it appears to be an ideal target to modulate cardiovascular risk in the context of atherogenic dyslipidemia and insulin resistance... ”

Metabolism of plasma cholesterol and lipoprotein parameters are related to a higher degree of insulin sensitivity in high HDL-C healthy normal weight subjects

BackgroundWe have searched if plasma high density lipoprotein-cholesterol (HDL-C) concentration interferes simultaneously with whole-body cholesterol metabolism and insulin sensitivity in normal weight healthy adult subjects.MethodsWe have measured the activities of several plasma components that are critically influenced by insulin and that control lipoprotein metabolism in subjects with low and high HDL-C concentrations. These parameters included cholesteryl ester transfer protein (CETP), phospholipid transfer protein (PLTP), lecithin cholesterol acyl transferase (LCAT), post-heparin lipoprotein lipase (LPL), hepatic lipase (HL), pre-beta-1HDL, and plasma sterol markers of cholesterol synthesis and intestinal absorption.ResultsIn the high-HDL-C group, we found lower plasma concentrations of triglycerides, alanine aminotransferase, insulin, HOMA-IR index, activities of LCAT and HL compared with the low HDL-C group; additionally, we found higher activity of LPL and pre-beta-1HDL concentration in the high-HDL-C group. There were no differences in the plasma CETP and PLTP activities.ConclusionsThese findings indicate that in healthy hyperalphalipoproteinemia subjects, several parameters that control the metabolism of plasma cholesterol and lipoproteins are related to a higher degree of insulin sensitivity.

Abstract 18569: Impact of ER-Stress Affecting Variant of XBP-1 Gene on Lipids, Diabetes, Chronic Kidney Disease, and Coronary Artery Disease

Objective: ER function is fundamentally important in all cell types, and the key transcription factor X-box binding protein 1 (XBP-1) regulates many genes of ER-stress and also hepatic lipogenesis. A functional polymorphism (-116G&gt;C) in the promoter region of XBP1 has been identified, and -116C allele was associated with higher ER-stress in vitro . CC homozygotes are quite common in Japanese (41%) compared with European (7% in NCBI database). Even though higher ER-stress would be associated with coronary risk factors, few data exist regarding clinical importance of this polymorphism as a cardiovascular risk factor. Methods: A total of 272 patients (137 males, mean age of 57 ± 14) suspected coronary artery disease were enrolled. Genotypes were determined by PCR-RFLP, and lipid profiles with ultracentrifugation, 75gOGTT, post-heparin lipoprotein lipase activities (PHLA), and eGFR were analyzed. Coronary stenosis index (CSI) was estimated with angiography in 125 patients (69 males, mean age of 63 ± 11, Diabetes 45%). Results: No difference was observed in age and sex with genotypes. CC homozygotes showed higher BMI (CC vs. GC+GG = 24.8 ± 3.3 vs. 23.4 ± 3.2, p &lt;0.05). CC homozygotes showed higher apoB/LDL-C ratio (0.94 ± 0.1 vs. 0.87 ± 0.1, p &lt;0.05), and higher LDL-TG (46 ± 94 vs. 28 ± 21, p &lt;0.05) suggesting presence of small dense-LDL. CC homozygotes showed higher hepatic transaminases, suggesting hepatic inflammation such as NAFLD. Hypertension was more frequent in CC homozygotes (79 vs. 54%, P&lt;0.05). Also C carriers showed lower eGFR (CC+GC vs. GG = 77.3±21 vs. 83.0±24, p &lt;0.05). Unexpectedly, CC homozygotes showed higher HOMA-beta (141 ± 178 vs. 91 ± 56, p &lt;0.05), and lower HbA1c (5.9 ± 1.0 vs. 6.3 ± 1.3 %, p &lt;0.05). In coronary angiography, CC homozygotes showed higher CSI in non-diabetes group (21 ± 9 vs. 11 ± 11, p &lt;0.005), but not significant in diabetes group. Conclusion: Functional XBP1 variant showed significant impacts on advanced coronary artery disease with deteriorating lipid profile, hypertension, and chronic kidney disease.

Effects of conjugated linoleic acid supplementation and exercise on post-heparin lipoprotein lipase, butyrylcholinesterase, blood lipid profile and glucose metabolism in young men

This study was designed to investigate the effects of conjugated linoleic acid (CLA) supplementation and endurance exercise training-induced changes on post-heparin lipoprotein lipase (PH-LPL) and butyrylcholinesterase (BChE) activities along with leptin, insulin and lipid levels in plasma by a randomized double blind experiment. Eighteen sedentary male volunteers were randomly divided into CLA and Placebo (PLC) supplementation groups. Both groups underwent daily supplementation of either 3g CLA or 3g placebo for 30days, respectively, and performed exercise on a bicycle ergometer 3 times per week for 30–40min at 50% VO2 peak workload. For plasma glucose, insulin and leptin levels and BChE activity fasting blood was used. For PH-LPL measurements, blood was collected 15min after 50IU/kg iv heparin injection. In all groups, there is a statistically significant decrease in BChE (p=0.03, p=0.02) and leptin (p=0.002), insulin and HOMA-IR levels (p=0.02). Exercise with or without CLA supplementation decreased insulin levels and increased insulin sensitivity. PH-LPL activity was increased significantly in both groups, displaying increased fatty acid mobilization. We conclude that though CLA supplementation and exercise can affect these parameters, CLA is not more effective than exercise alone. Hence, a prolonged supplementation regime may be more effective. Taken together in our small study group, our findings display that BChE is a potential marker for synthetic function of liver, fat metabolism, an obesity marker, a function long overlooked.