The role of plasma lipoprotein lipase, hepatic lipase and GPIHBP1 in the metabolism of remnant lipoproteins and small dense LDL in patients with coronary artery disease

Conventional HDL Subclass Measurements Mask Thyroid Hormone-dependent Remodeling Activity Sites in Hypothyroid Individuals

Context

Earlier nuclear magnetic resonance spectroscopy (NMR) studies of plasma lipoproteins estimated by size as small, medium, and large particles, demonstrated hypothyroidism was associated with increases in very low-density lipoprotein (VLDL), low-density lipoprotein (LDL), and intermediate-density lipoprotein (IDL) subclass particle number but variable changes in the high-density lipoprotein (HDL) subclasses. These disparate changes in HDL might be explained by reduced activity of the thyroid hormone-dependent remodeling proteins whose subclass specificity may be obscured when the 5 HDL subclasses identified by NMR are combined by size.

Objective

This work aimed to determine whether directional changes in particle number of individually measured HDL subclasses correlate with reduced activity of their thyroid hormone-dependent remodeling proteins in hypothyroid individuals.

Methods

VLDL, LDL, IDL, and HDL subclasses were measured by NMR in 13 thyroidectomized individuals 1 month following thyroid hormone withdrawal and 3 months after replacement. Changes in particle numbers in each subclass were compared when expressed individually and by size.

Results

Following thyroid hormone withdrawal, plasma lipids and VLDL, LDL, and IDL subclass particle number increased. HDL particle number nearly doubled in very small HDL-1 (P = .04), declined in small HDL-2 (P = .02), and increased 2-fold in HDL-5 (P = .0009).

Conclusion

The increment in HDL-1 and decline in HDL-2 subclasses is consistent with their precursor-product relationship and reduced lecithin cholesterol acyltransferase activity while the almost 2-fold increase in large HDL-5 is indicative of diminished action of hepatic lipase, phospholipid transfer protein, and endothelial lipase. These findings are inapparent when the 5 subclasses are expressed conventionally by size. This linking of specific HDL subclasses with HDL remodeling protein function provides new details about the specificity of their interactions.

Relationship Between Serum Betatrophin, GPIHBP1, and LDL Subfractions in Patients With Gestational Diabetes Mellitus

OBJECTIVES

Gestational diabetes mellitus (GDM) leads to changes in the lipid metabolism. In this study, we aimed to compare serum levels of LDL subfractions, betatrophin, and glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 (GPIHBP1) between patients with GDM and healthy pregnant women.

DESIGN AND METHODS

We designed a prospective case-control study with 41 pregnant women. Subjects were divided into two groups: GDM and control. Betatrophin and GPIHBP1 levels were measured by ELISA method. Lipoprint LDL subfraction kit was used to perform LDL subfraction analysis electrophoretically.

RESULTS

Serum levels of LDL6 subfraction, betatrophin, and GPIHBP1 were found to be higher in GDM group compared to the controls (p<0.001). The mean LDL size were also found larger in GDM group. A positive correlation was found between betatrophin and GPIHBP1 levels (rho=0.96, p<0.001).

CONCLUSIONS

Our findings suggest that betatrophin, and GPIHBP1 levels were found to be increased in GDM. This maybe the result of adaptive mechanisms in response to insulin resistance, but also this relationship should be evaluated for their effects on impaired lipid metabolism and lipoprotein lipase metabolism. There is a need for further prospective studies with larger samples to fully elucidate the mechanisms of this relationship both in pregnant patients and the other patient groups.

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.

Changes in the profile of circulating HDL subfractions in severe obese adolescents following a weight reduction program

BACKGROUND AND AIMS

Epidemiological studies show that obese adolescents are candidates to suffer cardiovascular pathologies in adulthood. In order to detect subfractions with a diagnostic value for future cardiovascular disorders, we analyzed the complete lipoprotein profile of severely obese adolescents.

METHODS AND RESULTS

Twenty-eight obese adolescents free from comorbidities were admitted into a weight reduction program. Anthropometric parameters were monitored. The circulating lipoproteins and glycemia were measured at the beginning and at the end of the study by conventional blood analysis as well as by using lipoprotein electrophoresis. Twenty-one puberty-matched normal-weight adolescents were recruited as controls. After 4 months, participants improved anthropometric parameters. Blood analysis indicated that circulating lipoproteins were in the healthy range during intervention. Nevertheless, results obtained from lipoprotein electrophoresis showed a significant increase in the large high-density lipoprotein subfraction in the obese population at the end of intervention, but significantly lower than normal-weight counterparts. In addition, intermediate- and low-density lipoprotein subfractions were in the healthy range in controls and in obese adolescents during intervention.

CONCLUSIONS

Altogether, it seems that the obese adolescents with no comorbidities do not develop a clear dyslipidemia. However, low values of large high-density lipoprotein subfractions could be considered as candidate predictors to develop cardiovascular disease in the future. For this reason, diet and exercise are key tools to fight against this pathology.

REGISTRATION NUMBER FOR CLINICAL TRIALS

ISRCTN99414527.

Small Dense Low-Density Lipoprotein Cholesterol Is the Most Atherogenic Lipoprotein Parameter in the Prospective Framingham Offspring Study

Background

Elevated plasma levels of direct low‐density lipoprotein cholesterol (LDL‐C), small dense LDL‐C (sdLDL‐C), low‐density lipoprotein (LDL) triglycerides, triglycerides, triglyceride‐rich lipoprotein cholesterol, remnant lipoprotein particle cholesterol, and lipoprotein(a) have all been associated with incident atherosclerotic cardiovascular disease (ASCVD). Our goal was to assess which parameters were most strongly associated with ASCVD risk.

Methods and Results

Plasma total cholesterol, triglycerides, high‐density lipoprotein cholesterol, direct LDL‐C, sdLDL‐C, LDL triglycerides, remnant lipoprotein particle cholesterol, triglyceride‐rich lipoprotein cholesterol, and lipoprotein(a) were measured using standardized automated analysis (coefficients of variation, <5.0%) in samples from 3094 fasting subjects free of ASCVD. Of these subjects, 20.2% developed ASCVD over 16 years. On univariate analysis, all ASCVD risk factors were significantly associated with incident ASCVD, as well as the following specialized lipoprotein parameters: sdLDL‐C, LDL triglycerides, triglycerides, triglyceride‐rich lipoprotein cholesterol, remnant lipoprotein particle cholesterol, and direct LDL‐C. Only sdLDL‐C, direct LDL‐C, and lipoprotein(a) were significant on multivariate analysis and net reclassification after adjustment for standard risk factors (age, sex, hypertension, diabetes mellitus, smoking, total cholesterol, and high‐density lipoprotein cholesterol). Using the pooled cohort equation, many specialized lipoprotein parameters individually added significant information, but no parameter added significant information once sdLDL‐C (hazard ratio, 1.42; P<0.0001) was in the model. These results for sdLDL‐C were confirmed by adjusted discordance analysis versus calculated non–high‐density lipoprotein cholesterol, in contrast to LDL triglycerides.

Conclusions

sdLDL‐C, direct LDL‐C, and lipoprotein(a) all contributed significantly to ASCVD risk on multivariate analysis, but no parameter added significant risk information to the pooled cohort equation once sdLDL‐C was in the model. Our data indicate that small dense LDL is the most atherogenic lipoprotein parameter.

Changes in serum levels of angiopoietin-like protein-8 and glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 after ezetimibe therapy in patients with dyslipidemia

Changes in serum levels of angiopoietin-like protein-8 (ANGPTL8) and glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 (GPIHBP1) in patients with dyslipidemia after ezetimibe therapy remain to be elucidated. Thirty-eight patients who initially received ezetimibe and were followed for 16 weeks were enrolled. Various parameters were investigated before and after 16 weeks of ezetimibe treatment in all patients. In addition, the patients were also divided into metabolic syndrome (MetS) (n = 22) and Non-MetS (n = 16) groups, and various parameters were compared between these groups. ANGPTL8 was significantly positively correlated with triglyceride (TG) and negatively correlated with high-density lipoprotein cholesterol (HDL-C) before treatment in all patients and in the MetS group. After treatment, TC and LDL-C were significantly decreased in all patients, and in both the MetS and Non-MetS groups, whereas there were no changes in TG or HDL-C. Serum levels of remnant-like particle cholesterol (RLP-C) significantly decreased in all patients and in the MetS group. The ANGPTL8 level before treatment was significantly positively associated with TG and negatively correlated with HDL-C in all patients and in the MetS group. ANGPTL8 and GPIHBP1were significantly decreased after treatment in all patients. GPIHBP1 was also significantly decreased after treatment in both groups. In conclusion, this is the first report to support the possibility of a new effect of ezetimibe therapy. Ezetimibe significantly decreased the serum level of LDL-C, but not TG or HDL-C, while reducing ANGPTL8 and GPIHBP1 in all patients with dyslipidemia. In addition, ezetimibe significantly decreased RLP-C levels in the MetS group.

High-throughput transcriptome sequencing reveals the developmental toxicity mechanisms of niclosamide in zebrafish embryo

Niclosamide (NIC) is the most widely used molluscicides for preventing the occurrence of schistosomiasis disease, and its residues can be found in various environmental samples. However, the toxicity mechanism of NIC during early developmental stage remains largely unknown. In the present study, zebrafish embryos were acutely exposed to NIC at an environmentally realistic concentration (0 and 40 μg/L) until 120 h post-fertilization. Transcriptomic sequencing was performed to provide mechanistic insight into developmental impairment. Pathway enrichment analyses found that biological processes related to lipid metabolism were significantly affected in exposed zebrafish larvae. Consistently, biochemical measurements showed that NIC developmental exposure depleted lipid storage, elevated lipid utilization, but inhibited lipid synthesis. Furthermore, as characterized by pathway enrichment and hormonal levels, steroid hormone biosynthesis was also significantly disrupted by NIC exposure in zebrafish larvae, indicating the endocrine disrupting potential of NIC. Detoxifying phase I and II processes (e.g., metabolism, conjugation and elimination) were significantly activated by NIC exposure. Overall, our findings suggest that NIC developmental exposure at an environmentally realistic concentration disturbs the lipid metabolism, induces endocrine disruption and initiates detoxifying capacity in zebrafish larvae, which will provide preliminary clues for developmental toxicity mechanisms of NIC.

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.

Impact of serum levels of lipoprotein lipase, hepatic lipase, and endothelial lipase on the progression of coronary artery disease

Purpose

The purpose of this study was to investigate the relationship between serum levels of lipoprotein lipase (LPL), hepatic lipase (HL), and endothelial lipase (EL) and the progression of coronary artery disease (CAD).

Materials and methods

According to the inclusion criteria, exclusion criteria, diagnostic criteria, angiography results, and the random matching scheme, the enrolled patients were divided into the following two groups: the progression-free group (n = 47) and the progression group (n = 15). The baseline characteristics and various biochemical parameters were obtained from the medical records and medical history. Serum LPL, HL, and EL levels were detected by ELISA. The correlation between serum LPL, HL, and EL levels and coronary lesions was statistically analyzed with SPSS software.

Results

Significant differences were observed in serum levels of HL and EL between the progression-free group and the progression group (HL, 75.5 ± 39.2 ng/mL vs. 125.1 ± 42.1 ng/mL, P < 0.05; EL, 139.2 ± 59.6 pg/mL vs. 175.1 ± 40.1 pg/mL, P < 0.05), while the difference in the LPL level was not significant (P > 0.05). Receiver operating characteristic curve (ROC) analysis showed that the area under the curve (AUC) values of LPL, HL, and EL were 0.506 (95% CI: 0.369–0.642, P = 0.9470), 0.792 (95% CI: 0.664–0.888, P < 0.0001), and 0.693 (95% CI: 0.553–0.811, P = 0.0095), respectively. Additionally, logistic regression analysis showed that the serum level of HL was an independent risk factor for coronary artery lesion progression.

Conclusion

Serum levels of EL and HL, but not the serum level of LPL, were positively correlated with the progression of CAD. The serum level of HL was an independent risk factor for the progression of CAD, while the serum level of EL or LPL was not an independent risk factor for the progression of CAD. For the diagnosis of CAD progression, the serum level of HL was better than the serum level of EL or LPL.

An automated method for measuring lipoprotein lipase and hepatic triglyceride lipase activities in post-heparin plasma

BACKGROUND

Lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) play a central role in triglyceride-rich lipoprotein metabolism by catalyzing the hydrolysis of triglycerides. Quantification of LPL and HTGL activity is useful for diagnosing lipid disorders, but there has been no automated method for measuring these lipase activities.

METHODS

The automated kinetic colorimetric method was used for assaying LPL and HTGL activity in the post-heparin plasma using the natural long-chain fatty acid 2-diglyceride as a substrate. LPL activity was determined with apoCII and HTGL activity was determined without apoCII with 2 channel of auto-analyzer.

RESULTS

The calibration curve for dilution tests of the LPL and HTGL activity assay ranged from 0.0 to 500 U/L. Within-run CV was obtained within a range of 5%. No interference was observed in the testing of specimens containing potentially interfering substances. The measurement range of LPL activity in the post-heparin plasma was 30-153 U/L, while HTGL activity was 135-431 U/L in normal controls.

CONCLUSIONS

The L PL and HTGL activity assays are applicable to quantitating the LPL and HTGL activity in the post-heparin plasma. This assay is more convenient and faster than radiochemical assay and highly suitable for the detection of lipid disorders.

Atherogenic postprandial remnant lipoproteins; VLDL remnants as a causal factor in atherosclerosis

Oxidized LDL (Ox-LDL) and chylomicron (CM) remnants have been suggested to be the most atherogenic lipoproteins that initiate and exacerbate coronary atherosclerosis. In this review, we propose a hypothesis of the causal lipoproteins in atherosclerosis based on our recent findings on postprandial remnant lipoproteins (RLP). Plasma RLP-C and RLP-TG increased significantly after food intake, especially a fat load. More than 80% of the TG increase after the fat load consisted of the TG in RLP, which contained significantly greater apoB100 than apoB48 particles as VLDL remnants. The majority of the LPL in non-heparin plasma was found in RLP as an RLP-LPL complex and released into the circulation after hydrolysis. Plasma LPL did not increase after food intake, which may have caused the partial hydrolysis of CM and VLDL as well as the significant increase of RLP-TG in the postprandial plasma. LPL was inversely correlated with the RLP particle size after food intake. We showed that VLDL remnants are the major atherogenic lipoproteins in the postprandial plasma associated with insufficient LPL activity and a causal factor in the initiation and progression of atherosclerosis. We also propose "LPL bound TG-rich lipoproteins" as a new definition of remnant lipoproteins based on the findings of the RLP-LPL complex in the non-heparin plasma.