Chylomicron Triglyceride Research Articles

The gut-facial aging axis: A two-sample Mendelian randomization and mediation analysis of gut microbiota, gut microbiota metabolic pathways, and blood metabolites.

Facial aging (FA) is a complex process influenced by both genetic and environmental factors. Gut microbiota (GM), gut microbiota metabolic pathways (GMMPs), and blood metabolites (BMs) have been implicated in the regulation of FA, but the causal and mediating effects of these factors remain unclear. We used summary-level data from genome-wide association studies (GWAS) of 16S rRNA gene sequencing data for GM (n=18 340), GWAS of GMMPs (n=7738), BMs (n=24 925), and GWAS of FA (n=423 999). We applied Mendelian randomization (MR) methods to estimate the causal effects of GM, GMMPs, and BMs on FA. We performed mediation analysis to quantify the proportion of the effects mediated by blood metabolites. We identified nine genus, two phylum, two families of GM, nine GM metabolic pathways, and 73 BMs that showed potential causal effects on FA. After Bonferroni correction, three BMs remained causally associated with FA, including average number of methylene groups per double bond (β, -0.023; 95% CI, -0.032∼-0.014; p=3.120×10-7) and average number of methylene groups in a fatty acid chain (β, -0.031; 95% CI, -0.045∼-0.016; p=2.062×10-5), which had strong negative causal effects on FA, and ratio of bisallylic groups to total fatty acids (β, 0.023; 95% CI, 0.017∼-0.029; p=8.441×10-15), which had a strong positive causal effect on FA. Mediation analysis revealed that histidine, average number of methylene groups in a fatty acid chain, and triglycerides in chylomicrons and largest VLDL particles mediated the effects of anaerofilum and/ or superpathway of Laspartate and Lasparagine biosynthesis on FA. Our study provides novel insights into the causal and mediating effects of GM, GMMPs, and BMs on FA. These findings may have implications for the development of new strategies for preventing or delaying FA.

Biological sex-related differences in the postprandial triglyceride response to intermittent hypoxaemia in young adults: a randomized crossover trial.

Obstructive sleep apnoea is characterized by chronic intermittent hypoxaemia and is independently associated with an increased risk of metabolic comorbidities (e.g. type II diabetes and ischaemic heart disease). These comorbidities could be attributable to hypoxaemia-induced alterations in blood lipid profiles. However, it remains unclear whether intermittent hypoxaemia alters triglyceridaemia differently between biological sexes. Therefore, we used a randomized crossover design to examine whether 6h of moderate intermittent hypoxaemia (15hypoxaemic cycles/h, 85% oxyhaemoglobin saturation) alters plasma triglyceride levels differently between men and women after a high-fat meal. Relative to men, women displayed lower levels of total triglycerides, in addition to denser triglyceride-rich lipoprotein triglycerides (TRL-TG; mainly very low-density lipoprotein triglycerides and chylomicron remnant triglycerides) and buoyant TRL-TG (mainly chylomicron triglycerides) during normoxia (ambient air) and intermittent hypoxaemia (sex × time: all P ≤ 0.008). Intermittent hypoxaemia led to higher triglyceride levels (condition: all P ≤ 0.016); however, this effect was observed only in men (sex × condition: all P ≤ 0.002). Compared with normoxia, glucose levels were higher in men and lower in women during intermittent hypoxaemia (sex × condition: P<0.001). The different postprandial responses between biological sexes occurred despite similar reductions in mean oxyhaemoglobin saturation and similar elevations in insulin levels, non-esterified fatty acid levels and mean heart rate (sex × condition: all P ≥ 0.185). These results support growing evidence showing that intermittent hypoxaemia impacts men and women differently, and they might help to explain biological sex-related discrepancies in the rate of certain comorbidities associated with intermittent hypoxaemia. KEY POINTS: Intermittent hypoxaemia is a key characteristic of obstructive sleep apnoea and alters lipid metabolism in multiple tissues, resulting in increased circulating triglyceride levels, an important risk factor for cardiometabolic diseases. Circulating triglyceride levels are regulated differently between biological sexes, with women typically displaying much lower fasting and postprandial triglyceride levels than men, partly explaining why women of all ages experience lower mortality rates from cardiometabolic diseases. In this study, healthy young men and women consumed a high-fat meal and were then exposed to 6h of intermittent hypoxaemia or ambient air. We show that postprandial triglyceride levels are significantly lower in women compared with men and that intermittent hypoxaemia leads to higher postprandial triglyceride levels in men only. These results might help us to understand better why women living with obstructive sleep apnoea experience lower rates of cardiometabolic diseases (e.g. type II diabetes and ischaemic heart disease) than men living with obstructive sleep apnoea.

Severe hypertriglyceridemia and its correlation with clinical atherosclerosis and pancreatitis investigated in beta-quantification

Abstract Background Severe hypertriglyceridemia is commonly associated with pancreatitis and questionably atherosclerotic cardiovascular disease (ASCVD). However, while some patients develop those sequelae at relatively low levels, others with extreme levels remain spared from it. Purpose This study serves to validate, whether the distribution of triglycerides (TG), either in very-low-density lipoprotein (VLDL) particles or chylomicrons (CM) can be decisive for the development of clinical disease. Methods Patients with TG levels above 500 mg/dL, who routinely visited our lipid outpatient clinic between 2016 and 2021 with their lipid panel done via beta-quantification were retrospectively investigated for the presence of clinical pancreatitis and ASCVD via electronic chart-review. Results In total, 221 patients met eligibility criteria, with a mean age of 48 years, BMI of 29.7, with 72.4% males. Median TG and low-density lipoprotein cholesterol levels were 827 mg/dL and 62 mg/dL, respectively. A history of pancreatitis was present in 13.7% of patients, while ASCVD was present in 20.7%. TG distribution, described as the ratio of TG in VLDL per TG in CM showed no significant differences with regards to pancreatitis incidence (p=0.393). For ASCVD, the ratio was significantly higher in those with ASCVD vs those without (3.54 vs 2.25) (p=0.008). CM-dominant TG distribution was present in 19.5% of patients and was associated with higher total TG levels (2122 mg/dL vs 825 mg/dL), compared to VLDL-dominant TG distribution. Conclusion A higher relative amount of TGs in VLDL compared to CM, as most prevalent pattern, was associated with ASCVD, while very high levels of TG frequently relate to hyperchylomicronemia.

FRI105 Getting Fam-iliar With Familial Chylomicronemia Syndrome: A Case Report

Abstract Background: Familial chylomicronemia syndrome (FCS) is a rare autosomal recessive lipid disorder of chylomicron metabolism causing severe hypertriglyceridemia that affects ∼1/1,000,000 individuals. Case Presentation: A 36-year-old male with a history of severely elevated triglyceride levels, recurrent pancreatitis, and biopsy-proven focal segmental glomerulosclerosis presented with severely elevated triglycerides. His initial acute pancreatitis episode was at 30 years old and attributed to alcohol intake. Triglyceride levels were not obtained at the time. He abstained from alcohol; however, his follow up triglyceride level was elevated (5,005 mg/dL, n=35-160 mg/dL) which normalized on an insulin infusion. He started fenofibrate and fish oil. After several additional hospital admissions for either pancreatitis or asymptomatic hypertriglyceridemia with a peak triglyceride level of 14,385 mg/dL, he committed to a low fat and vegan diet. Generic fish oil was transitioned to icosapent ethyl, and he was additionally started on niacin and atorvastatin. Even after following a strict diet and medication adherence, he continued having multiple admissions for acute pancreatitis, most recently complicated by dialysis dependent acute kidney injury in the setting of necrotizing pancreatitis. He has no known history of hypertriglyceridemia in his family. Due to persistent and severe hypertriglyceridemia despite conventional treatment, we suspected an underlying genetic cause, such as FCS. FCS should be suspected in those with recurrent pancreatitis, lipemia retinalis, and/or milky colored blood specimens. Eruptive xanthomas may also be present. Our patient did not have evidence of eruptive xanthomas on physical examination, but ophthalmology evaluation did show lipemia retinalis. The most common genetic pathologic variant in FCS is in the lipoprotein lipase-1 gene (LPL) that codes for an enzyme which assists in the lipolysis of plasma triglycerides (TG) in chylomicrons. Other common genes associated with severe hypertriglyceridemia are APOC2, APOAV, LMF-1, and GPIHBP-1. The mainstay of treatment for FCS are medications to reduce triglyceride levels and a significantly low-fat diet below 25 grams daily. Medium chain triglycerides can be utilized as they do not require enzymes to break down. Otherwise, there are currently no FDA-available therapies specifically targeted for use in those with FCS. Conclusions: This case demonstrates the unfortunate outcome of familial chylomicronemia syndrome despite concerted efforts to reduce triglyceride levels and eliminate additional risk factors. Presentation: Friday, June 16, 2023

Contribution of intestinal triglyceride-rich lipoproteins to residual atherosclerotic cardiovascular disease risk in individuals with type 2 diabetes on statin therapy

Aims/hypothesisThis study explored the hypothesis that significant abnormalities in the metabolism of intestinally derived lipoproteins are present in individuals with type 2 diabetes on statin therapy. These abnormalities may contribute to residual CVD risk.MethodsTo investigate the kinetics of ApoB-48- and ApoB-100-containing lipoproteins, we performed a secondary analysis of 11 overweight/obese individuals with type 2 diabetes who were treated with lifestyle counselling and on a stable dose of metformin who were from an earlier clinical study, and compared these with 11 control participants frequency-matched for age, BMI and sex. Participants in both groups were on a similar statin regimen during the study. Stable isotope tracers were used to determine the kinetics of the following in response to a standard fat-rich meal: (1) apolipoprotein (Apo)B-48 in chylomicrons and VLDL; (2) ApoB-100 in VLDL, intermediate-density lipoprotein (IDL) and LDL; and (3) triglyceride (TG) in VLDL.ResultsThe fasting lipid profile did not differ significantly between the two groups. Compared with control participants, in individuals with type 2 diabetes, chylomicron TG and ApoB-48 levels exhibited an approximately twofold higher response to the fat-rich meal, and a twofold higher increment was observed in ApoB-48 particles in the VLDL1 and VLDL2 density ranges (all p < 0.05). Again comparing control participants with individuals with type 2 diabetes, in the latter, total ApoB-48 production was 25% higher (556 ± 57 vs 446 ± 57 mg/day; p < 0.001), conversion (fractional transfer rate) of chylomicrons to VLDL was around 40% lower (35 ± 25 vs 82 ± 58 pools/day; p=0.034) and direct clearance of chylomicrons was 5.6-fold higher (5.6 ± 2.2 vs 1.0 ± 1.8 pools/day; p < 0.001). During the postprandial period, ApoB-48 particles accounted for a higher proportion of total VLDL in individuals with type 2 diabetes (44%) compared with control participants (25%), and these ApoB-48 VLDL particles exhibited a fivefold longer residence time in the circulation (p < 0.01). No between-group differences were seen in the kinetics of ApoB-100 and TG in VLDL, or in LDL ApoB-100 production, pool size and clearance rate. As compared with control participants, the IDL ApoB-100 pool in individuals with type 2 diabetes was higher due to increased conversion from VLDL2.Conclusions/interpretationAbnormalities in the metabolism of intestinally derived ApoB-48-containing lipoproteins in individuals with type 2 diabetes on statins may help to explain the residual risk of CVD and may be suitable targets for interventions.Trial registrationClinicalTrials.gov NCT02948777.Graphical

The early effects of sleeve gastrectomy on postprandial chylomicron triglycerides during the progression of type 2 diabetes

BackgroundIt remains unclear whether early sleeve gastrectomy (SG) improves postprandial very-low-density lipoprotein (VLDL) as well as chylomicron triglycerides (TGs) in a weight-independent manner in patients with or without type 2 diabetes (DM). Herein we investigated the early effects of SG on postprandial VLDL and chylomicron kinetics. MethodsA liquid meal test was performed before and after 1 week of SG. The plasma was collected for postprandial triglyceride-rich lipoprotein kinetics analyses, including VLDLs and chylomicrons, isolated by high-speed ultracentrifugation. Lipidomics and metabolomics were used to profile lipid and metabolite compositions of plasma and postprandial chylomicrons. De novo fatty acid synthesis in intestinal epithelial cells treated with chylomicron metabolites was examined using RT-PCR, immunoblotting, and free fatty acid measurement. ResultsWe found that patients with DM had markedly higher VLDL TGs than patients without DM, and such an increase was still retained after SG. In contrast, SG significantly decreased postprandial chylomicron TGs, but surprisingly, the degree of the reduction in patients with DM was less prominent than in patients without DM, confirmed by untargeted lipidomics analysis. Moreover, 5 unique metabolites potentially linked to de novo fatty acid synthesis from the pathway analysis were discovered by further metabolomic analysis of postprandial chylomicrons from patients with DM who underwent SG and verified by In vitro intestinal epithelial cell culture experiments. ConclusionsSG in 1 week did not impact postprandial VLDL but decreased chylomicron TGs. Patients with DM keep higher postprandial chylomicron TG concentrations than patients without it after SG, potentially through some unique metabolites that increase intestinal fatty acid synthesis. These results implicate the timing for SG to reach lower intestinal fatty acid synthesis and postprandial chylomicron TG production is prior to the diagnosis of DM to potentially reduce cardiovascular risks.

Pea Fiber Lowers Fasting and Postprandial Blood Triglyceride Concentrations in Humans ,

The effect of a pea cell wall fiber preparation with a high content of soluble fiber on fasting and postprandial blood lipids was investigated in young healthy subjects. Inclusion of 33 g pea fiber product/10 MJ (20 g dietary fiber) in a low fiber diet was tested in five men and six women (mean age 23 y) in a strictly controlled randomized cross-over intervention study over 2 wk separated by a 2-wk period of habitual diet consumption. No significant differences in fasting concentrations of total cholesterol, LDL cholesterol or HDL cholesterol were observed, whereas total and VLDL triglyceride concentrations were lower when subjects consumed the pea fiber diet compared with the low fiber diet (P < 0.05). Postprandial response to pea fiber was studied in eight men. Addition of 12 g pea fiber product/ 10 MJ to a breakfast meal and 15 g/10 MJ to the following lunch meal resulted in significantly lower total triglyceride (P = 0.01), chylomicron triglyceride (P = 0.03) and insulin (P = 0.003) concentrations after the lunch meal compared with results following the same meal without pea fiber. No differences were observed in glycemic response. In conclusion, this source of dietary fiber lowered fasting and postprandial triglyceride concentrations but did not change fasting cholesterol concentrations.

A Combination of Single-Nucleotide Polymorphisms Is Associated with Interindividual Variability in Cholecalciferol Bioavailability in Healthy Men

Background: Most people require dietary vitamin D to achieve the recommended concentration of 25-hydroxyvitamin D [25(OH)D] in the blood. However, the response to vitamin D supplementation is highly variable among individuals.Objective: We assessed whether the variability in cholecalciferol bioavailability was associated with single-nucleotide polymorphisms (SNPs) in candidate genes.Methods: In a single-group design, 39 healthy adult men with a mean ± SD age of 33 ± 2 y and mean ± SD body mass index (in kg/m2) of 22.9 ± 0.3 were genotyped with the use of whole-genome microarrays. After an overnight fast, plasma 25(OH)D status was measured, and the subjects then consumed a meal that provided 5 mg cholecalciferol as a supplement. Plasma chylomicron cholecalciferol concentration was measured over 8 h, and cholecalciferol response was assessed by calculating the postprandial area under the curve. Partial least squares regression was used to test the association of SNPs in or near candidate genes (61 genes representing 3791 SNPs) with the postprandial cholecalciferol response.Results: The postprandial chylomicron cholecalciferol concentration peaked at 5.4 h. The cholecalciferol response was extremely variable among individuals (CV: 47%). It correlated with the chylomicron triglyceride (TG) response (r = 0.60; P < 0.001) but not with the fasting plasma 25(OH)D concentration (r = 0.04; P = 0.83). A significant (P = 1.32 × 10−4) partial least squares regression model that included 17 SNPs in 13 genes (including 5 that have been associated with chylomicron TG response) was associated with the variance in the cholecalciferol response.Conclusion: In healthy men, there is a high interindividual variability in cholecalciferol bioavailability that is associated with a combination of SNPs located in or near genes involved in both vitamin D and lipid metabolism. This trial was registered at clinicaltrials.gov as NCT02100774.

The Isolation of Flowing Mesenteric Lymph in Mice to Quantify In Vivo Kinetics of Dietary Lipid Absorption and Chylomicron Secretion.

Intestinal lipoproteins, especially triglyceride-rich chylomicrons, are a major driver of metabolism, inflammation, and cardiovascular diseases. However, isolating intestinal lipoproteins is very difficult in vivo because they are first secreted from the small intestine into the mesenteric lymphatics. Chylomicron-containing lymph then empties into the subclavian vein from the thoracic duct to deliver components of the meal to the heart, lungs, and, ultimately, whole-body circulation. Isolating naïve chylomicrons is impossible from blood since chylomicron triglyceride undergoes hydrolysis immediately upon interaction with lipoprotein lipase and other lipoprotein receptors in circulation. Therefore, the original 2-day lymph fistula procedure, described by Bollman et al. in rats, has historically been used to isolate fresh mesenteric lymph before its entry into the thoracic vein. That protocol has been improved upon and professionalized by the laboratory of Patrick Tso for the last 45 years, allowing for the analysis of these critical lipoproteins and secretions from the gut. The Tso lymph fistula procedure has now been updated and is presented here visually for the first time. This revised procedure is a single-day surgical technique for installing a duodenal feeding tube, cannulating the mesenteric lymph duct, and collecting lymph after a meal in conscious mice. The major benefits of these new techniques include the ability to reproducibly collect lymph from mice (which harnesses the power of genetic mouse models); the reduced anesthesia time for mice during the implantation of the duodenal infusion tube and the lymph cannula; the ability to continuously sample lymph throughout the feeding and post-prandial period; the ability to quantitatively measure hormones and cytokines before their dilution and enzymatic hydrolysis in blood; and the ability to collect large quantities of lymph for isolating intestinal lipoproteins. This technique is a powerful tool for directly and quantitatively measuring dietary nutrient absorption, intestinal lipoprotein synthesis, and chylomicron secretion.

Liver-specific overexpression of lipoprotein lipase improves glucose metabolism in high-fat diet-fed mice.

The liver is the main organ that regulates lipid and glucose metabolism. Ectopic lipid accumulation in the liver impairs insulin sensitivity and glucose metabolism. Lipoprotein lipase (LPL), mainly expressed in the adipose tissue and muscle, is a key enzyme that regulates lipid metabolism via the hydrolysis of triglyceride in chylomicrons and very-low-density lipoproteins. Here, we aimed to investigate whether the suppression level of hepatic lipid accumulation via overexpression of LPL in mouse liver leads to improved metabolism. To overexpress LPL in the liver, we generated an LPL-expressing adenovirus (Ad) vector using an improved Ad vector that exhibited considerably lower hepatotoxicity (Ad-LPL). C57BL/6 mice were treated with Ad vectors and simultaneously fed a high-fat diet (HFD). Lipid droplet formation in the liver decreased in Ad-LPL-treated mice relative to that in control Ad vector-treated mice. Glucose tolerance and insulin resistance were remarkably improved in Ad-LPL-treated mice compared to those in control Ad vector-treated mice. The expression levels of fatty acid oxidation-related genes, such as peroxisome proliferator-activated receptor α, carnitine palmitoyltransferase 1, and acyl-CoA oxidase 1, were 1.7–2.0-fold higher in Ad-LPL-treated mouse livers than that in control Ad-vector-treated mouse livers. Furthermore, hepatic LPL overexpression partly maintained mitochondrial content in HFD-fed mice. These results indicate that LPL overexpression in the livers of HFD-fed mice attenuates the accumulation of lipid droplets in the liver and improves glucose metabolism. These findings may enable the development of new drugs to treat metabolic syndromes such as type 2 diabetes mellitus and non-alcoholic fatty liver disease.

Role of endogenous incretins in the regulation of postprandial lipoprotein metabolism.

Incretins are known to influence lipid metabolism in the intestine when administered as pharmacologic agents. The aggregate influence of endogenous incretins on chylomicron production and clearance is less clear, particularly in light of opposing effects of co-secreted hormones. Here, we tested the hypothesis that physiological levels of incretins may impact on production or clearances rates of chylomicrons and VLDL. A group of 22 overweight/obese men was studied to determine associations between plasma levels of glucagon-like peptides 1 and 2 (GLP-1 and GLP-2) and glucose-dependent insulinotropic polypeptide (GIP) after a fat-rich meal and the production and clearance rates of apoB48- and apoB100-containing triglyceride-rich lipoproteins. Subjects were stratified by above- and below-median incretin response (area under the curve). Stratification yielded subgroups that differed about two-fold in incretin response. There were neither differences in apoB48 production rates in chylomicrons or VLDL fractions nor in apoB100 or triglyceride kinetics in VLDL between men with above- vs below-median incretin responses. The men with above-median GLP-1 and GLP-2 responses exhibited higher postprandial plasma and chylomicron triglyceride levels, but this could not be related to altered kinetic parameters. No differences were found between incretin response subgroups and particle clearance rates. We found no evidence for a regulatory effect of endogenous incretins on contemporaneous chylomicron or VLDL metabolism following a standardised fat-rich meal. The actions of incretins at pharmacological doses may not be reflected at physiological levels of these hormones.

Enterocyte-specific ATGL overexpression affects intestinal and systemic cholesterol homeostasis

Enterocytes of the small intestine (SI) play an important role in maintaining systemic lipid levels by regulating dietary lipid absorption and postprandial lipoprotein secretion. An excessive amount of dietary-derived triglycerides (TGs) taken up by the apical side of enterocytes or basolaterally internalized lipoprotein remnants can be transiently stored in cytosolic lipid droplets (cLDs). As mice lacking adipose TG lipase (ATGL) in the SI display massive accumulation of cLDs but also delayed cholesterol absorption, we hypothesized that SI-specific overexpression of ATGL (Atgl iTg) might have beneficial effects on lipid homeostasis in the gut and possibly throughout the body. Here, we demonstrate that Atgl iTg mice had only modestly increased enzymatic activity despite drastically elevated Atgl mRNA levels (up to 120-fold) on chow diet, and was highly induced upon high-fat/high-cholesterol diet (HF/HCD) feeding. Atgl iTg mice showed markedly reduced intestinal TG concentrations after acute and chronic lipid challenge without affecting chylomicron TG secretion. Circulating plasma cholesterol levels were significantly lower in Atgl iTg mice under different feeding conditions, contrasting the accelerated uptake of dietary cholesterol into the circulation after HF/HCD feeding. In the fasted state, gene expression analysis revealed modulation of PPARα and liver X receptor (LXR) target genes by an increased fatty acid release, whereas the decreased plasma cholesterol concentrations in refed mice were more likely due to changes in HDL synthesis and secretion. We conclude that ATGL, in addition to its role in TG catabolism, plays a critical role in whole-body cholesterol homeostasis by modulating PPARα and LXR signaling in intestinal enterocytes.

Identification of Key Excipients for the Solubilization and Structural Characterization of Lipoprotein Lipase, An Enzyme for Hydrolysis of Triglyceride.

Lipoprotein lipase (LPL) is an essential enzyme that hydrolyzes triglycerides in chylomicrons and very low-density lipoprotein into glycerol and fatty acids. One major hurdle in using LPL as a therapeutic has been its poor solubility/stability after purification. Solutions used to preserve purified LPL commonly contain either heparin, or concentrated glycerol and sodium chloride, resulting in hypertonic solutions. These solutions are not acceptable as pharmaceutical formulations. This paper describes the identification of a key excipient, sodium laurate, which can solubilize LPL in an isotonic environment without heparin or concentrated glycerol. A follow-up multi-variant study was performed to identify the effect of sodium laurate and its interaction with sodium chloride on the solubility and processing conditions of LPL. The LPL concentration (up to 14mg/mL) achievable in pharmaceutically relevant and salt-free conditions was identified to be closely correlated to the concentration of sodium laurate, which was co-concentrated with LPL. The result that sodium laurate increases stability of LPL characterized by differential scanning calorimetry and UV absorbance spectra suggests that the mechanism of solubilization of LPL by sodium laurate is related to LPL structural stabilization. The findings indicate that substrates and their enzymatic products can be strong stabilizers for other protein molecules.

Lpl-C310R mutation is associated with impaired glucose tolerance and endoplasmic reticulum stress in skeletal muscle

Primary Hypertriglyceridemia refers to a loss-of-function genetic defect which prevents the triglyceride (TG) in chylomicrons (CM) from lipolysis, leading to the accumulation of TG. The mutation of lipoprotein lipase (LPL) gene has been recognized as the main cause of primary hypertriglyceridemia. Recently, a new LPL gene mutation p.C310R(c. T928C) was identified in a family with hypertriglyceridemia. The proband was manifested by severe hypertriglyceridemia and diabetes. Skeletal muscle is the major LPL-synthesizing tissue and insulin response target tissue. However, little is known about the effects of LPL gene mutation on skeletal muscle. This study is intended to observe the effects of LPL-C310R mutation on glycolipid metabolism and skeletal muscle. We found that a significantly decreased LPL plasma concentration, activity and the expression levels in skeletal muscle were observed in LplC310R/+ mice comparing to wild type mice. Those mutant mice also exhibited increased fasting plasma TG, free fat acids (FFA) and insulin, as well as FFA in muscle, and decreased glucose tolerance. Enhanced expression of BIP and elevated phosphorylation of IRE1α were observed in skeletal muscle, suggesting increased endoplasmic reticulum stress (ERS). Consistent with this, increased phosphorylation of JNK was also observed. Meanwhile, remarkably enhanced phosphorylation of IRS-1 (Ser307) and decreased phosphorylation of AKT were observed in skeletal muscle of mutant mice, suggesting impaired insulin signaling. Significant lipid deposition and morphological changes in endoplasmic reticulum and mitochondria were observed in the skeletal muscle of mutant mice but not in wild type control. Results demonstrate Lpl C310R mutation caused impaired glucose tolerance, ER stress and impaired insulin signaling in skeletal muscle.

1051-P: Selective Targeting of Angiopoietin-Like 3 (ANGPTL3) via the Second-Generation Antisense Oligonucleotide (ASO) ISIS-703802 (AKCEA-ANGPTL3-LRx) in Subjects with Familial Partial Lipodystrophy (FPLD)

FPLD is an extreme form of metabolic dyslipidemia and diabetes caused by selective loss of peripheral subcutaneous fat. Currently, there are no approved therapies for this rare cause of diabetes in the U.S. Reductions in circulating levels of the hepatokine ANGPTL3 either by mutations in humans or by targeted drugs in rodents are associated with reductions in triglyceride levels and provide protection from atherosclerosis, making it an attractive target for patients with FPLD and metabolic dyslipidemia. The objective of this proof-of concept, Phase 2, open-label study was to assess the early efficacy and safety of a strategy that targets ANGPTL3 via ISIS-703802 (AKCEA-ANGPTL3-LRx) in patients with FPLD. Four patients with FPLD (3F/1M; age range: 38-47; 1 with LMNA R482Q, 1 with LMNA R584H, and 2 with no causative genetic variant) with diabetes (HbA1c&amp;gt;6.5%) and hypertriglyceridemia (≥ 500 mg/dL or ≥ 200 mg/dL for patients meeting genetic or family history criteria) were included. Patients received the study drug at a subcutaneous dose of 20 mg weekly for 26 weeks. Primary endpoint was the percent change in serum triglycerides from baseline to week 27. All other endpoints were also analyzed at week 27. Treatment resulted in a 60±26 (mean±SD) % reduction in triglycerides from a baseline of 818±432 mg/dL. Consistent with antisense reduction of ANGPTL3 mRNA, circulating ANGPTL3 levels were lowered by 55±10%. Treatment was also associated with 51±27% reduction in circulating apoC3 levels, 64±24% reduction in total VLDL and chylomicron triglycerides, and 18±15% reduction in total cholesterol. In addition, HbA1c showed a modest mean absolute reduction of 0.2±1.0 % The drug was well tolerated and there were no new safety signals observed. Although a small study, these results suggest that targeting ANGPTL3 in patients with FPLD could successfully address metabolic dyslipidemia. Disclosure M. Foss-Freitas: None. B. Akinci: Advisory Panel; Self; Aegerion Pharmaceuticals, Regeneron Pharmaceuticals. Research Support; Self; Gemphire Therapeutics Inc. Speaker’s Bureau; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Novartis AG, Novo Nordisk A/S, Sanofi-Aventis, Servier. A.H. Neidert: None. R.P. Hench: None. M. Swaidan: None. E.A. Oral: Consultant; Self; Aegerion Pharmaceuticals, Akcea Therapeutics, Regeneron Pharmaceuticals. Research Support; Self; Aegerion Pharmaceuticals, Akcea Therapeutics, Gemphire Therapeutics Inc., GI Dynamics Inc., Regeneron Pharmaceuticals. Funding Ionis Pharmaceuticals, Inc.; Akcea Therapeutics

Impact of proprotein convertase subtilisin/kexin type 9 inhibition with evolocumab on the postprandial responses of triglyceride-rich lipoproteins in type II diabetic subjects

Monoclonal antibodies to proprotein convertase subtilisin/kexin type 9 (PCSK9) significantly lower the levels of low-density lipoprotein and very-low-density lipoproteins (VLDL), but their effect on postprandial lipoprotein metabolism in dyslipidemic subjects is unclear. This study aimed to investigate the effects of evolocumab on postprandial lipid responses, ectopic fat depots, whole-body cholesterol synthesis, hepatic lipogenesis, and fat oxidation in patients with type II diabetes. The trial was a single-phase, nonrandomized study of 12-week treatment with evolocumab 140mgsubcutaneously every 2weeks in 15 patients with type II diabetes on background statin therapy. Cardiometabolic responses to a high-fat mixed meal were assessed before and at the end of the intervention period. Evolocumab treatment reduced significantly postprandial rises in plasma total triglyceride (by 21%; P<.0001) and VLDL1 triglyceride (by 15%; P=.018), but the increase in chylomicron triglyceride after the meal was not significantly perturbed (P=.053). There were reduced postprandial responses in plasma total apolipoprotein C-III (by 14%; P<.0001) and apolipoprotein B-48 concentration (by 17%; P=.0046) and in "remnant-like particles" cholesterol (by 29%; P<.0001) on the PCSK9 inhibitor. Treatment reduced the steady-state (ie, fasting and postprandial) concentrations of VLDL2 cholesterol by 50% (P<.0001) and VLDL2 triglyceride by 29% (P<.0001), in addition to the 78% reduction of low-density lipoprotein cholesterol (P<.001). The changes in apolipoprotein C-III associated significantly with reduction in postprandial responses of remnant-like particles cholesterol and triglyceride-rich lipoprotein cholesterol. Evolocumab therapy did not influence liver fat accumulation, hepatic de novo lipogenesis, or fasting β-hydroxybutyrate but did increase total body cholesterol synthesis (P<.01). Evolocumab treatment improved postprandial responses of triglyceride-rich lipoproteins and measures of cholesterol-enriched remnant particles in type II diabetic subjects. These results indicate that postprandial phenomena need to be taken into account in assessing the full range of actions of PCSK9 inhibitors in dyslipidemic individuals.

Why Do Men Accumulate Abdominal Visceral Fat?

Men have a higher tendency to accumulate abdominal visceral fat compared to pre-menopausal women. The accumulation of abdominal visceral fat in men, which is a strong independent predictor of mortality, is mainly due to the higher dietary fat uptake by their abdominal visceral fat. Since dietary fat is absorbed by the enterocytes and transported to the circulation in the forms of chylomicrons and very low density lipoproteins (VLDLs), it is crucial to understand how these lipoproteins are different between men and women. The chylomicrons in men are generally bigger in size and more in quantity than those in women. During the postprandial state, these chylomicrons congest the lamina propria and the low-pressure lymphatics. In this paper, we propose that this congestion predisposes the chylomicron triglycerides to hydrolysis by lipoprotein lipase (LPL). The liberated fatty acids are then stored by the nearby abdominal visceral adipocytes, leading to the accumulation of abdominal visceral fat. These mechanisms perhaps explain why men, through their bigger and higher production of chylomicrons, are more likely to accumulate abdominal visceral fat than pre-menopausal women. This accumulation eventually leads to belly enlargement, which confers men their apple-shaped body.

1338-P: Lipoprotein Insulin Resistance Scores Decrease after a Lifestyle Intervention among Obese Adolescents with Prediabetes

Introduction: Insulin resistance (IR) is associated with impaired lipid metabolism. The Lipoprotein Insulin Resistance Index (LP-IR) is a novel composite biomarker that estimates IR from lipoprotein particle size and concentration, and prospectively predicts type 2 diabetes (T2D) in adults. Less is known about LP-IR and T2D risk in youth. This study evaluated the effect of a lifestyle intervention on LP-IR scores in obese Latino youths with prediabetes. Methods: Obese Latino adolescents (n=27, 15.5±1.1 years, 13 male/14 female) with prediabetes (defined as a 2-hour, post-challenge glucose ≥120 mg/dL) completed a 12-week intervention including nutrition education (one hour/week) and moderate-to-vigorous physical activity (three hours/week). Measurements at baseline and 12 weeks included anthropometrics, total, large, medium, and small lipoprotein particle concentrations (VLDL and chylomicron, LDL, and HDL), mean lipoprotein particle sizes (VLDL, LDL, HDL), lipid concentrations (total triglyceride, VLDL and chylomicron triglyceride, and HDL cholesterol), and LP-IR scores using nuclear magnetic resonance spectroscopy. Results: After adjusting for body fat and sex, significant reductions in LP-IR scores (63.2±14.4 vs. 59.0±15.5 units, p=0.013), large VLDL and chylomicron particle concentration (9.1±7.8 vs. 7.3±6.2 nmol/L, p=0.004), total HDL particle concentration (30.2±4.3 vs. 28.3±3.9 μmol/L, p=0.013), total triglyceride concentration (144.5±91.9 vs. 122.9±77.9 mg/dL, p=0.002), as well as VLDL and chylomicron triglyceride concentration (117.5±66.7 vs. 102.0±55.7 mg/dL, p=0.020) were observed following lifestyle intervention. Conclusion: Lifestyle intervention significantly reduces LP-IR scores and lipoprotein particle parameters in obese adolescents with prediabetes and may decrease future risk of cardiometabolic disorders through improvements in insulin resistance and lipoprotein metabolism. Disclosure A.M. Renteria-Mexia: None. M. Olson: None. M.A. Connelly: Employee; Self; LabCorp. S. Vega-López: None. A. Williams: None. G.Q. Shaibi: None. Funding National Institute on Minority Health and Health Disparities (P20MD002316, U54MD002316); Programa para el Desarrollo Profesional Docente, para el Tipo Superior, México (to A.M.R-M.)

Comparison of lipoprotein lipase glycosylation from adipocytes in lean and obese Zucker rats

C‐mannosylation is a type of protein glycosylation involving a covalently attached mannose sugar to the C2 carbon of an indole ring on tryptophan. Lipoprotein lipase (LPL), is an enzyme involved in lipid metabolism, hydrolysis of triglycerides in chylomicrons and very low‐density lipoproteins. LPL is mainly expressed in adipose tissue, muscle tissue, and macrophages, and it has been shown to contain a C‐mannosylated tryptophan in LPL‐overexpressing cell lines. Metabolic disorders, such as diabetes and obesity, leads to a deficiency of LPL function. LPL can be regulated at post‐transcriptional levels in a tissue specific manner that also depends on the nutritional state and hormonal level of the tissue. The goal of this project is to determine whether LPL is C‐mannosylated in adipose tissue from obese and lean Zucker rats. The Zucker fatty rat is a well‐established model of obesity and insulin resistance. Obese Zucker rats have high levels of lipids and cholesterol in their bloodstream, and their adipocytes are increased in size and number. LPL was isolated by immunoprecipitation (IP) using a monoclonal antibody specific for the LPL protein and by using heparin‐sepharose affinity chromatography. The isolated protein was analyzed by mass spectrometry utilizing the peptide mass fingerprint technique and low‐energy CID tandem MS/MS to identify C‐mannosylated tryptophan residues. The results of this experiment further the knowledge of the role that obesity plays in the post‐translational modification of LPL in adipose tissue.Support or Funding InformationNSF‐OIA‐1738707This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

MENOPAUSAL STAGE INFLUENCES LIPOPROTEIN SUBCLASS PROFILE IN HABITUALLY ACTIVE WOMEN

Menopause is associated with increased cardiovascular disease risk, in part due to worsening cholesterol profile with advancing menopausal stage. The effect of menopausal stage on lipoprotein cholesterol, lipoprotein particle size and number in active midlife women has not been evaluated.PURPOSETo evaluate differences in lipoprotein subclass concentrations between highly‐fit, habitually active women at distinct menopausal stages.METHODSWomen (40–65 yr) were healthy habitually active highly‐fit pre‐, peri‐, and postmenopausal women (PRE, n = 10, VO2peak = 47.0 ± 2.4 ml/kg/min, PERI, n = 12, VO2peak = 49.1 ± 2.4 ml/kg/min, and POST, n = 13, VO2peak = 43.8 ± 1.8 ml/kg/min). Menopausal stage was defined using the STRAW+10 criteria. Particle subclass concentrations and mean particle sizes (were measured using nuclear magnetic resonance spectroscopy (LabCorp). Calculated lipids (total triglyceride, total VLDL and chylomicron triglyceride, and total HDL cholesterol) were also analyzed. Blood samples for lipoprotein particle analysis were collected during days 1–6 of the menstrual cycle for PRE. ANOVAs with Holm‐Sidak post hoc testing were used to determine differences between groups for each lipid outcome. Nonparametric tests were employed if assumptions were not met. Data are presented as mean ± SEM.RESULTSThere was a significant effect of menopause stage on total HDL cholesterol (p = 0.010) with greater HDL cholesterol in POST (88.5 ± 2.2 mg/dl) vs. PRE (72.2 ± 5.7 mg/dl, p = 0.032) and total HDL particle concentration (p = 0.010) with significantly greater total HDL particle concentration in POST (40.2 ± 1.1 μmol/L) compared with PRE (34.9 ± 1.5 μmol/L, p = 0.023) and POST compared with PERI (PERI, 35.5 ± 1.3 μmol/L, p = 0.033). There was a trend for an effect of menopausal status on large HDL particle concentration (p = 0.072) with progressively greater large HDL particle concentration with each advancing stage (PRE 12.1 ± 1.1 μmol/L, PERI, 14.0 ± 1.2 μmol/L, POST, 15.5 ± 0.6 μmol/L). There was no significant effect of menopausal stage on medium or small HDL particle concentration or HDL size (all p&gt;0.05). There was an effect of menopausal stage on large LDL particle concentration (p = 0.039) with greater concentration of large LDL particles in PRE (479 ± 52.6 nmol/L) vs. POST (663 ± 47.5 nmol/L, p = 0.034) but no effect of menopausal stage on small LDL, IDL, or total LDL particle concentration, or LDL size (all p&gt;0.05). There was no effect of menopausal status on any VLDL &amp; chylomicron particle concentration or VLDL size (all p&gt;0.05).CONCLUSIONThese data indicate that in healthy, highly fit women, advancing menopausal stage does not have a negative effect on many lipoprotein particle concentrations. Habitual physical activity may eliminate or potentially reverse some of the negative consequences of menopause on lipids.Support or Funding InformationFunding Sources: American College of Sports Medicine Foundation Doctoral Student Research Grant (Serviente), National Institute on Aging Grant T32‐AG049676 (Pennsylvania State University), University of Massachusetts Amherst Provost's Undergraduate Research Fellowship (Chalvin).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.