Microsomal Triglyceride Transfer Protein Research Articles

Chemosensing of fat digestion by the expression pattern of GPR40, GPR120, CD36 and enteroendocrine profile in sheep

Gastrointestinal tract (GIT) epithelial cells detect nutrients in the lumen via G-protein coupled receptors (GPRs) located in the gut epithelial cells especially in enteroendocrine cells. Dietary free fatty acids (FFA) are the major energy source and also acts as signalling molecules for FFA receptors. Long chain fatty acids (LCFA) activate LCFA receptors, GPR40/FFAR1 and GPR120/FFAR4 which trigger intracellular signalling and release gut hormones or modifies gene expression that facilitate fat digestion and absorption. However, there is a paucity of information on chemosensing of nutrients and digestion in ruminants. Hence, present study was aimed to evaluate chemosensing of fat digestion and absorption by the expression pattern of GPR40, GPR120, chylomicron forming genes, fatty acid translocase (CD36/FAT), microsomal triglyceride transfer protein (MTTP) and apolipoprotein B (APOB) in the various segments of GIT in sheep supplemented with calcium salts of long chain fatty acids (CSLCFAs) along with the secretory patterns of gut peptides cholecystokinin (CCK) and peptide tyrosine tyrosine (PYY). The study was carried out for a period 60 days with eighteen adult ewes of 8–12 months of age and they were divided into three groups with six animals each as group-I, group-II and group-III. All the experimental animals were stall fed with a basal diet and maintained as per animal husbandry standards. Group-II and group-III were supplemented additionally with 3% and 5% CSLCFAs, respectively on dry matter intake. The results from the study indicated that the supplementation of CSLCFAs upregulated (P < 0.05) the relative mRNA expression of GPR40 and GPR120 in the various segments of GIT of sheep in correspondence to level of dietary fat. Abundance of mRNA expression of CD36, MTTP and APOB increased (P < 0.05) in the GIT of sheep in accordance to quantity of LCFAs in the diet where these genes facilitate fatty acid uptake. Feeding of CSLCFAs enhanced (P < 0.05) pre-feeding level of CCK from day 15 onwards, whereas, post-feeding CCK and PYY increased in all the experimental sheep. However, the increase was higher (P < 0.05) in sheep supplemented with CSLCFAs by 10.80 ± 1.45% and 14.25 ± 1.17%, respectively in comparison to group-I. The comprehensive results of the study concluded that feeding of additional CSLCFAs upregulated the expression of GPR40, GPR120, CD36, and chemosensing of LCFAs by these genes triggered the signalling transduction that enhanced CCK and PYY levels to facilitate fat digestion and absorption in accordance with quantity of dietary fat. This was further evident from the significant upregulation of MTTP and APOB in the various segments of GIT supported the high content of dietary fat at cellular fat metabolism in the gut that regulates the fatty acid uptake.

Effects of magnolol and honokiol blend on performance, egg quality, hepatic lipid metabolism, and intestinal morphology of hens at late laying cycle

Magnolol and its isomer honokiol are polyphenols with anti-oxidative and anti-inflammatory activities. We evaluated the effects of magnolol and honokiol supplementation alone or in combination with hen diets during the late laying cycle. A total of 540 Jingfen pink-shell laying hens (50 weeks old) were randomly assigned to six treatments: a control diet and diets supplemented with 300 mg/kg magnolol (M300), honokiol (H300), or 300 mg/kg total phenols with a magnolol/honokiol ratio of 2:1 (M200H100), 1:2 (M100H200), and 1:1 (M150H150). Compared with that of the control, all supplementation groups had higher laying rates and the M300, M100H200, and M150H150 groups showed comparatively lower feed conversion ratios. Magnolol and honokiol supplementation increased the Haugh units of fresh eggs at week 62 and alleviated the decline of the Haugh units of eggs stored for 14 days. Compared with that of the control group, the serum total antioxidant capacity of the M100H200 and M150H150 groups significantly increased, and all supplementation groups had higher total antioxidant capacity and lower malondialdehyde content in the liver. With respect to lipid metabolism, the M200H100 and M150H150 groups had lower total and relative liver weights compared with those of the control and H300 groups. The mRNA expression levels of CCAAT enhancer binding protein alpha, sterol regulatory element binding protein-1, fatty acid synthase and stearyl coenzyme A desaturase 1 involved in lipogenesis; microsomal triglyceride transfer protein and apolipoprotein B involved in fatty acid transport; and the proinflammatory cytokine interleukin-1 beta were lower in all supplementation groups compared with those in the control. With respect to gut health, the heights of the jejunum and ileum villi significantly increased in all supplementation groups compared with those of the control, and the jejunum villus heights of the M300 and M150H150 groups were higher than those of the H300 and M100H200 groups. The H300 and M150H150 groups had higher mRNA expression levels of zonula occludens-1 in the ileum compared with those in the control and M300 groups, whereas all supplementation groups had higher mRNA levels of claudin-1 than that of the control group. In conclusion, magnolol and honokiol improved hen performance and the albumen quality of fresh and stored eggs by improving the antioxidant capacity, liver lipid metabolism, and intestinal health of laying hens. The combination of magnolol and honokiol at a 1:1 ratio may be an optimal choice for hen diet supplementation.

The Microsomal Triglyceride Transfer Protein Inhibitor, Lomitapide, Improves Vascular Function in Obesity

ObjectivesIn this study, we investigate the effect of lomitapide, a microsomal triglyceride transfer protein inhibitor, on cardiovascular function in obesity.HypothesisWe hypothesize that lipid level downregulation by lomitapide is a fundamental mechanism that improves cardiovascular function.MethodsEight‐week‐old C57/b6 mice were fed with a high fat diet (HFD) for 12 weeks in the presence and absence of lomitapide. Lomitapide was administered by gavage (1mg/Kg/Day) for the last 2 weeks of HFD feeding. Bodyweight, blood glucose, body composition, and lipid profile were determined. Vascular function and endothelial function markers were studied in aorta and mesenteric resistance arteries (MRA).ResultsLomitapide treatment reduced the body weight in obese mice. Blood glucose, % of fat mass, total cholesterol, and LDL levels were significantly reduced and the % of lean mass was significantly increased after lomitapide treatment. Aortic and mesenteric arteries vascular response to sodium nitroprusside (SNP) was similar among groups. However, the vascular response to acetylcholine (Ach) was improved in the treated group. This was associated with a decreased level of vascular endoplasmic (ER) reticulum stress, inflammation, and oxidative stress.ConclusionsTreatment with lomitapide attenuated the increase in body weight in obese mice and restored the lipid profile and vascular function. These effects were accompanied by a decrease in inflammation and oxidative stress.

Hibiscus sabdariffa extract improves hepatic steatosis, partially through IRS-1/Akt and Nrf2 signaling pathways in rats fed a high fat diet

Non-alcoholic fatty liver disease (NAFLD) has become a major world-wide health problem and is characterized by lipid accumulation in the liver induced by high fat diet (HFD) consumption. It is usually associated with inflammation, oxidative stress, and insulin resistance. Roselle extract (Hibiscus sabdariffa) is an herb which is used in traditional medicine. However, further study is necessary to represent the mechanism of NAFLD and find new preventive strategies. This study aims to investigate the protective effects of roselle extract on NAFLD rat models. Male Sprague–Dawley rats (n = 35) were divided into 5 groups, control, HFD, HFD + Simvastatin (HFD + SIM), HFD + 250 mg/kg BW, and HFD + 500 mg/kg BW of roselle extract (HFD + R250 and HFD + R500, respectively). The results showed that roselle extract reduced hepatic lipid contents, de novo lipogenesis enzymes, microsomal triglyceride transfer protein, inflammatory cytokines, malondialdehyde, and increased antioxidant properties, transporter related with lipoprotein uptake, and insulin signal proteins. Comparing to SIM, the HFD + R500 group exhibited the greater benefit in terms of anti-hepatic steatosis, antioxidant properties, and an ability to improve insulin resistance. This study demonstrates that roselle extract improved antioxidant properties and attenuated hepatic steatosis, liver inflammation, oxidative stress, and insulin resistance in HFD-induced NAFLD in rats, which could be used for NAFLD prevention.

MicroRNA-200c coordinates HNF1 homeobox B and apolipoprotein O functions to modulate lipid homeostasis in alcoholic fatty liver disease

Hepatic steatosis is an initial manifestation of alcoholic liver disease. An imbalance of hepatic lipid processes including fatty acid uptake, esterification, oxidation, and triglyceride secretion leads to alcoholic fatty liver (AFL). However, the precise molecular mechanisms underlying the pathogenesis of AFL remain elusive. Here, we show that mice deficient in microRNAs (miRs)-141 and -200c display resistance to the development of AFL. We found that miR-200c directly targets HNF1 homeobox B (Hnf1b), a transcriptional activator for microsomal triglyceride transfer protein (Mttp), as well as apolipoprotein O (ApoO), an integral component of the mitochondrial contact site and cristae organizing system complex. We show that expression of these miRs is significantly induced by chronic ethanol exposure, which is accompanied by reduced HNF1B and APOO levels. Furthermore, miR-141/200c deficiency normalizes ethanol-mediated impairment of triglyceride secretion, which can be attributed to the restored levels of HNF1B and MTTP, as well as phosphatidylcholine abundance. Moreover, we demonstrate that miR-141/200c deficiency restores ethanol-mediated inhibition of APOO expression and mitochondrial dysfunction, improving mitochondrial antioxidant defense capacity and fatty acid oxidation. Taken together, these results suggest that miR-200c contributes to the modulation of lipid homeostasis in AFL disease by cooperatively regulating Hnf1b and ApoO functions.

Comparing Pili Producing Gene (mtp-flp) in Susceptible and Resistant Dormant Mycobacterium Tuberculosis Strains with Active Clinical Isolates

Background: Pili producing genes in different life cycles of Mycobacterium tuberculosis (M. tuberculosis) were assessed. M. tuberculosis has two life cycles: dormant and active states. We aimed to assess the pili producing genes such as curli pili of M. tuberculosis (mtp) encoded by the mtp gene (Rv3312A) and fimbrial low-molecular-weight protein encoded by flp gene (Rv3656c) which were compared and analyzed. Methods: Two hundred M. tuberculosis isolates were investigated both at active and dormant states for production and expression of pili. The dormant M. tuberculosis was achieved by incubation in a sealed tube (modified Wayne method). The susceptibility of M. tuberculosis was evaluated on genes, rpob, inh, katg, and gyra by using multiplex polymerase chain reaction (PCR) and single-strand conformational polymorphism methods. The PCR–restriction fragment length polymorphism was used to express pili genes mtp and flp and then the PCR products was digested using restriction enzyme Fnu4HI, XmaI, and MspJI and AciI, TagII, and HaeII, respectively. The transmission electron microscopy was also used to detect pili in different isolates. The result was compared and analyzed using H37RV as a gold standard. Results: The mtp and flp PCR products were 263 and 122 bp in the studied strains irrespective of M. tuberculosis different life cycles, respectively. The PCR products were analyzed on 8% Polyacrylamide gel electrophoresis (PAGE), and in the 180/200 (20%), producing five fragments of 25,40,45,63,90 bp with the Fun4HI and two fragments of 126,138 bp with the XmaI and uncut with the MspJI for mtp gen were obtained at the dormant and active states of M. tuberculosis (P &lt; 0.05). Similarly in flp gene producing three fragments of 22,35,65 bp with AciI and two fragments of 35.87 bp with TagII and two fragments of 38.84 bp with HaeII were obtained (P &lt; 0.05). In contrast to genotyping analysis, the electron microscopy examination showed protruding of pili from M. tuberculosis, especially in dormant mycobacterium (15/100; 15%), that was multidrug resistance and extensive drug resistance isolates (P &gt; 0.05). Conclusion: Pili were shown by electron microscopy, although at the gene expression, the insignificant difference was observed at the dormant strains in comparison to active states. Therefore, we may conclude that other genes might be involved in pili production of M. tuberculosis that needs further investigation. Although, the resistance phenomena might influence the pili producing gene expression that showed in our results.

The microsomal triglyceride transfer protein inhibitor lomitapide improves vascular function in mice with obesity.

In this study, the effect of lomitapide, a microsomal triglyceride transfer protein inhibitor, on the cardiovascular function in obesity was investigated. Eight-week-old C57BL/6 mice were fed with high-fat diet for 12 weeks in the presence and absence of lomitapide. Lomitapide was administered by gavage (1 mg/kg/d) during the last 2 weeks of high-fat feeding. Body weight, blood glucose, body composition, and lipid profile were determined. Vascular function and endothelial function markers were studied in the aorta and mesenteric resistance arteries. Lomitapide treatment reduced body weight in mice with obesity. Blood glucose, percentage of fat mass, total cholesterol, and low-density lipoprotein levels were significantly reduced, and the percentage of lean mass was significantly increased after lomitapide treatment. The vascular response to sodium nitroprusside in the aorta and mesenteric arteries was similar among groups. However, the vascular response to acetylcholine was improved in the treated group. This was associated with decreased levels of vascular endoplasmic reticulum stress, inflammation, and oxidative stress. Treatment with lomitapide attenuated the increase in body weight in mice with obesity and restored the lipid profile and vascular function. These effects were accompanied by a decrease in inflammation and oxidative stress.

The exoWAT, endoWAT and ectoWAT Dictate Dysmetabolism, Dyslipidemia and Diabetes

Background & Objective: Three-tier model depicting physiology of metabolism and a timeline of dyslipidemia and diabetes is proposed. Methods & Results: OGTT glucose profiles of 1456 individuals, aged 15 to 80 years, who were not previously diagnosed as having T2D are analysed. A clinical model is conceptualized to explain the integrated physiology of pancreatic islet, hypothalamus, gut and peripheral tissues regulating the carbohydrate, fat, protein and energy metabolism. The beta cells regulate anabolism via insulin, somatostatin (delta) and amylin (gamma). The ‘Delta-Gamma system’ controls catabolism via glucagon and pancreatic polypeptide. Leptin regulates satiety and lipogenesis while ghrelin and fibroblast growth factor-21 regulate hunger and lipolysis by modulating insulin secretion. Dietary fat is deposited in the white adipose tissue (WAT) as exoWAT. Leptin induces ‘selective insulin resistance’ by simultaneously stimulating beta cells and microsomal triglyceride transfer protein (MTTP). Leptin regulates de-novo lipogenesis, endogenous fat deposition as endoWAT and promotes dyslipidemia and euglycemic hyperinsulinemia. WAT storage capacity (cWAT) is genetically determined. When cWAT is exceeded, fat deposition occurs ectopically in non-adipose tissues as ectoWAT and stimulates growth hormone, ghrelin and hyperglycemia. EctoWAT suppresses insulin, stimulates glucagon and ghrelin, leading to lipolysis, hyperglycemia, beta cell suppression-cum-failure. Calorie surplus, superimposed on genetic insulin resistance drives the timeline of dysmetabolism, which marches from healthy (exoWAT) and unhealthy (endoWAT) WAT stage, hepatic followed by peripheral ectoWAT stage, and finally the lipolytic stage. Conclusions: This model can explain the pathogenesis of T2D, its phenotypes and complications, GDM, PCOS as well as the mechanism of action of most antidiabetic drugs.

A Case Series Assessing the Effects of Lomitapide on Carotid Intima-Media Thickness in Adult Patients with Homozygous Familial Hypercholesterolaemia in a Real-World Setting.

IntroductionHomozygous familial hypercholesterolaemia (HoFH) is characterised by extremely elevated levels of low-density lipoprotein cholesterol (LDL-C) and results from multiple mutations in genes affecting the LDL receptor pathway. Patients are at risk of premature atherosclerotic cardiovascular disease (ASCVD) and premature death. Lomitapide is a microsomal triglyceride transfer protein inhibitor developed to treat HoFH, but cardiovascular outcome data are lacking.MethodsWe evaluated detailed data from five HoFH patients and one patient with heterozygous FH (HeFH) and a very severe phenotype. We also analysed confirmatory data from a further 8 HoFH cases. In total, we analysed data from patients in seven global centres in six countries who were all treated with lomitapide with long-term follow-up. Carotid intima-media thickness (CIMT) imaging was recorded on an ad hoc basis to monitor ASCVD in HoFH.ResultsLomitapide resulted in marked decreases in LDL-C of 56.8–93.9% [77.7–93.9% in the 6 initial cases (mean nadir 64.8 ± 30.1 mg/dL); 56.8–86.0% in the 8 confirmatory cases (mean nadir 131.4 ± 38.2 mg/dL)]. CIMT regressed in 50% of cases (mean follow-up 5.0 ± 3.1 years in initial six cases, and 4.4 ± 1.4 years in confirmatory cases). In the remaining patients, CIMT showed little further change. In patients where assessments of plaque area were available, regression or stabilisation in CIMT was accompanied by clinically significant regression of plaque area.ConclusionsLomitapide reduces LDL-C levels in patients with HoFH and severe LDL-C phenotypes, and results in stabilisation and/or regression of CIMT, which is an established marker of ASCVD risk. Additional data are needed to determine if this confers a survival benefit in these very high-risk patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12325-021-02031-y.

Methionine-Mediated Regulation of Intestinal Structure and Lipid Transport in the Rice Field Eel (Monopterus albus)

An eight-week feeding trial discusses how methionine affects intestinal barrier and lipid transport on rice field eel (Monopterus albus). Six isoenergetic and isonitrogenous feeds contained different levels of methionine (0, 2 g/kg, 4 g/kg, 6 g/kg, 8 g/kg, or 10 g/kg). Compared with M0 (0 g/kg), gastric amylase, lipase, and trypsin were remarkably increased as dietary methionine ( P &lt; 0.05 ); intestinal amylase, lipase, and trypsin were remarkably increased in M8 (8 g/kg) ( P &lt; 0.05 ). Compared with M0, gastric fovea was remarkably increased ( P &lt; 0.001 ), gastric epithelium is neater in M8 than that in M0, intestinal villus height and muscular thickness are remarkably increased in M8 ( P &lt; 0.001 ), and amounts of goblet cells per root in M8 were increased ( P &gt; 0.05 ), while intestinal crypt depth was markedly decreased ( P &lt; 0.001 ). Lipid droplets in the intestinal villus and mucosal layer in the M8 (8 g/kg) group were more than that in M0 (0 g/kg). Compared with M0 (0 g/kg), the intestinal gcn2 and eif2α were downregulated in M8 (8 g/kg) ( P &lt; 0.01 and P &lt; 0.05 , respectively), while occ, cl12, cl15, zo-1, zo-2, hdlbp, ldlrap, npc1l1, cd36, fatp1, fatp2, fatp6, apo, apoa, apob, apoc, apoe, mct1, mct2, mct8, lpl, mttp, moat2, and dgat2 were upregulated markedly in M8 (8 g/kg). Intestinal eif2α expression was positively correlated with gcn2, and intestinal zo-1, cl15, fatp6, ldlrap, mct2, mct8, apo, apob, mct1, apoc, fatp1, mttp, cd36, occ, npc1l1, hdlbp, fatp2, apoe, lpl, and moat2 gene expression was negatively correlated with gcn2. In conclusion, methionine deficiency affected the gastric and intestinal structures, damaged the intestinal barrier, and decreased lipid and fatty acid transport. Besides, gcn2 could be activated when M. albus was fed methionine-deficient feed.

Forty year follow-up of three patients with complete absence of apolipoprotein B-containing lipoproteins

Complete deficiency of apolipoprotein (apo) B-containing lipoproteins can result from both abetalipoproteinemia (ABL) and homozygous hypobetalipoproteinemia (HoHBL), caused by bi-allelic loss-of-function variants in the MTTP and APOB genes encoding microsomal triglyceride transfer protein and apolipoprotein (apo) B, respectively. Both conditions are associated with failure to assemble and secrete apo B-containing lipoproteins from intestine and liver, resulting in absence of chylomicrons, very low-density lipoproteins and remnants, and low-density lipoproteins. Because absorption and transport of fat soluble vitamins requires intact production of apo B-containing lipoproteins, untreated patients develop fat soluble vitamin deficiencies, with associated clinical features including atypical retinitis pigmentosa, osteopenia, neuromyopathy and coagulopathy. Other features include acanthocytosis on the peripheral blood film, fat malabsorption and hepatosteatosis. We describe two patients with ABL and one with HoHBL who have each been on high dose oral fat soluble vitamin replacement under the care of the same physician for more than four decades. Each patient has remained clinically stable. A recent liver biopsy from an ABL patient showed mild macrovesicular steatosis, patchy microvesicular steatosis and mild fibrosis. These observations add to our understanding of the long term trajectory of ABL and HoHBL, and emphasize the importance of compliance to treatment and follow up.

Attenuation of obesity-induced hyperlipidemia reduces tumor growth

Accumulating evidence suggests that hyperlipidemia is associated with obesity and cancer mortality in humans. We tested the hypotheses that inhibition of microsomal triglyceride transfer protein (MTP) would attenuate obesity-induced hyperlipidemia and reduce tumor growth by treating BCR-ABL B cell tumor-bearing hyperlipidemic obese ob/ob obese mice with a MTP inhibitor. MTP inhibition in tumor-bearing mice reduced concentrations of plasma apoB100 5-fold together with a corresponding decrease in VLDL triacylglycerol (TG) and cholesterol. Inhibition of MTP decreased tumor volume by 50%. MTP inhibitor did not alter tumor cell viability in vitro, suggesting that the in vivo tumor shrinkage effect was related to altered circulating lipids. Tumor volume reduction occurred without change in the protein expression of LDLR, FASN and HMGCR in the tumor, suggesting a lack of compensatory mechanisms in response to decreased hyperlipidemia. Expression of genes encoding GLUT4 and PEPCK was increased 6- and 10-fold, respectively, but no change in the expression of genes encoding regulatory enzymes of glycolysis was observed, suggesting that the tumors were not dependent on or switching to carbohydrates for energy requirement to support their growth. No change of proliferative signaling PI3K/AKT and ERK pathways after MTP inhibition was observed in the tumors. In conclusion, MTP inhibition decreased dyslipidemia and tumor growth in obese, insulin resistant mice. Therefore, decreasing VLDL secretion could be further explored as an adjuvant therapeutic intervention together with standard care to reduce tumor growth in obese patients.

Oxidant resistant human apolipoprotein A-I functions similarly to the unmodified human isoform in delaying atherosclerosis progression and promoting atherosclerosis regression in hyperlipidemic mice.

BackgroundTransgenic overexpression of apolipoprotein A-I (apoA1) has been shown to delay atherosclerosis lesion progression and promote lesion regression in mouse models; however, apoA1 is subject to oxidation by myeloperoxidase (MPO) and loss of function. The activity of oxidant resistant human apoA1 was compared to unmodified human apoA1 in mouse models of atherosclerosis progression and regression.Methods and resultsHuman apoA1 and the MPO oxidant resistant 4WF isoform transgenic mice were bred to LDL receptor deficient (LDLr KO) mice and fed a western-type diet. High level expression of these human apoA1 isoforms did not lead to increased HDL-cholesterol levels on the LDLr KO background. In males and females, lesion progression was studied over time, and both apoA1 and 4WF transgenic mice vs. LDLr KO mice had significant and similar delayed lesion progression and reduced non-HDL cholesterol. Using time points with equivalent lesion areas, lesion regression was initiated by feeding the mice a low-fat control diet containing a microsomal triglyceride transfer protein inhibitor for 7 weeks. Lesions regressed more in the male apoA1 and 4WF transgenics vs. the LDLr KO, but the 4WF isoform was not superior to the unmodified isoform in promoting lesion regression.ConclusionsBoth human apoA1 and the 4WF MPO oxidant resistant apoA1 isoform delayed lesion progression and promoted lesion regression in LDLr KO mice, with more pronounced effects in males than females; moreover, the 4WF isoform functioned similarly to the unmodified human apoA1 isoform.

A New lncRNA, lnc-LLMA, Regulates Lipid Metabolism in Pig Hepatocytes.

A large variety of long noncoding RNAs (lncRNAs) have been discovered through high-throughput sequencing technology and some have been demonstrated to play important roles in lipid metabolism regulation. In our study, we found a highly expressed lncRNA (lnc-LLMA, liver lipid metabolism-associated lncRNA) in the liver of Duroc pigs, which was enriched in the nucleus. It displays potent tissue specificity among different pig breeds. Overexpression of lnc-LLMA can cause a decline in intracellular triglyceride (TG) levels and increases in ATP and mitochondrial DNA levels in pig primary hepatocytes and HepG2 cells. In addition, the expression levels of MTTP, APOB, CPT1α, and other genes were increased by overexpression of lnc-LLMA. It downregulated expression of G6Pase and SREBP1 genes. Chromatin isolation by RNA purification (ChRIP) experiments demonstrated that microsomal triglyceride transfer protein (MTTP) and glycogen synthase 2 (GYS2) were the potential interacting proteins of lnc-LLMA. The overexpression of the GYS2 gene rescued the decreasing intracellular TG levels caused by the increase of lnc-LLMA. Similarly, overexpression of MTTP was also able to save the lnc-LLMA-induced decrease in intracellular TG. Our study demonstrated that this novel lncRNA was closely related to lipid metabolism and affected lipid transport and mitochondrial function through MTTP and GYS2. Our results provided a new direction for further studying the effect of lncRNA on lipid metabolism regulation.

Quantification of Microsomal Triglyceride Transfer Protein in Non Alcoholic Fatty Liver Disease Patients: A Cross-sectional Study

Introduction: Non Alcoholic Fatty Liver Disease (NAFLD) is one of the common liver disease characterised by fat accumulation in hepatocytes. NAFLD is a broad spectrum of simple steatosis, Non Alcoholic Steatohepatitis (NASH), cirrhosis and hepatocellular carcinoma. Triglycerides (TG) are exported in the form of Very Low Density Lipoprotein (VLDL). VLDL are formed by incorporation of TG into apo-B by Microsomal Triglyceride transfer Protein (MTP). Therefore, MTP is a key protein for lipid transport. Estimation of MTP protein levels and its correlation with simple steatosis and steatohepatitis can be helpful in understanding its role in NAFLD progression. Aim: To estimate the serum levels of MTP in simple steatosis and steatohepatitis and also to check its correlation with TG and VLDL in NAFLD patients with and without co-morbidities. Materials and Methods: The present cross-sectional study was carried out in Department of Cell Biology and Molecular Genetics, Sri Devaraj Urs Academy of Higher Education and Research, Kolar, Karnataka, India, between November 2019 to January 2021. Study participants included 60 NAFLD subjects which were divided into simple steatosis (group 1, n=10) and steatohepatitis (group 2, n=50). These subjects were further subdivided into cases with co-morbidities and cases without co-morbidities. Serum levels of MTP, high sensitivity C Reactive Protein (hsCRP), Fasting Blood Sugar (FBS), liver enzymes, lipid profile were assessed. Statistical analysis was done by using unpaired Student’s t-test and Pearson’s correlation. Results: The mean age was 46.5 years in steatosis group and 48.85 years in steatohepatitis group. In steatosis group, there were 5 (50%) males and 5 (50%) females, whereas in steatohepatitis group 32 (64%) were females and 18 (36%) were males. The serum levels of MTP were significantly decreased in simple steatosis cases with co-morbidities as compared to cases without co-morbidities (p=0.006). A significant negative correlation was observed between MTP v/s TG and MTP v/s VLDL (r=-0.665, p=0.036) in simple steatosis cases with and without co-morbidities. Same trend was observed in steatohepatitis cases but the correlation was insignificant (r=-0.08, p=0.563). Conclusion: The serum levels of MTP decreases as the NAFLD progresses. A significant decrease in serum levels of MTP was also observed in cases with co-morbidities as compared to cases without co-morbidities. Serum levels of MTP showed negative correlation with TG and VLDL in simple steatosis cases.

Microsomal triglyceride transfer protein-mediated transfer of β-carotene from donor to acceptor vesicles in vitro.

Dietary β-carotene is the most abundant vitamin A precursor. Once absorbed by the enterocytes, the provitamin A carotenoid can either be cleaved into retinoids (vitamin A and its derivatives) or incorporated in its intact form within chylomicrons to be distributed throughout the body for utilization and/or storage by other tissues. From the liver, together with endogenous lipids, intact β-carotene can also be incorporated within very low-density lipoprotein/low-density lipoprotein (VLDL/LDL) for transport to other tissues and organs. Microsomal triglyceride transfer protein (MTP) is a key regulator of lipoprotein biosynthesis in intestine and liver as it facilitates the incorporation of dietary and endogenous lipids into nascent lipoproteins. MTP is also critical for transferring β-carotene into lipoprotein particles for secretion. Here, we present an in vitro method to assess the transfer of β-carotene by MTP from donor to acceptor vesicles. This transfer can be assessed by precipitating donor vesicles and measuring amounts of β-carotene transferred to acceptor vesicles. The levels of transferred β-carotene are quantified by HPLC analysis and intrinsic fluorescence of β-carotene. This chapter demonstrates the feasibility of this method which is also useful to study the role of MTP for incorporation of other carotenoids that are known to be carried within VLDL/LDL and chylomicrons for organ distribution.

Effect of MTTP -493G/T, I128T, Q95H and Q244E polymorphisms on hepatic steatosis in patients with chronic hepatitis

BackgroundChronic hepatitis C is characterized by a progressive deterioration of liver function and is involved in metabolic complications, such as hepatic steatosis. ObjectiveThe aim of this study was to investigate the role of host and viral characteristics associated with -493G/T (rs1800591), I128T (rs3816873), Q95H (rs61733139), and Q244E (rs17599091) Single Nucleotide Polymorphisms (SNPs) in the Microsomal Triglyceride Transfer Protein (MTTP) gene on hepatic steatosis in chronic hepatitis C. MethodsSNPs were genotyped by PCR-RFLP and analyzed in combination with host and viral characteristics by multiple logistic regression in different genetic models of inheritance. ResultsThe authors analyzed 236 patients with chronic hepatitis C, and 53% had hepatic steatosis. The mutated allele frequencies were > 5%, and the genotypes were in Hardy-Weinberg equilibrium (p ≥ 0.05). It was observed that patients with HCV genotype 3 infection (OR = 2.74, 95% CI 1.24‒6.06, p = 0.013), female sex (OR = 2.28, 95% CI 1.21‒4.28, p = 0.011) and moderate- and high-intensity liver inflammatory activity (A2-A3) (OR = 3.61, 95% CI 1.86‒7.01, p < 0.001) alone exhibited a higher risk of steatosis. The results of multiple logistic regression analysis for interaction showed that for the -493G/T SNP, when the GT/TT genotype (dominant model) and the GT genotype (codominant model) were each combined with HCV genotype 3 infection, an 11.51-fold (95% CI 2.08‒63.59, p = 0.005) and a 15.69-fold (95% CI 2.46‒99.85, p = 0.004) increased risk of steatosis, respectively, was observed. For the I128T SNP, when both the IT/TT genotype (dominant model) and the IT genotype (codominant model) were combined with HCV genotype 3 infection, an 8.51-fold (95% CI 1.59‒45.54, p = 0.012) and an 8.40 fold (95% CI 1.51‒46.91, p = 0.015) increased risk of steatosis, respectively, was observed. ConclusionThe present study showed that the viral genotype combined with the -493G/T and I128T SNPs in the MTTP gene influences hepatic steatosis.

Lomitapide Reduces LDL-C and Favourably Affects Carotid Intima Media Thickness in Adult Patients with Homozygous Familial Hypercholesterolaemia in a Real-World Setting

<h3>Lead Author's Financial Disclosures</h3> D.B. has received consulting fees from Amryt. <h3>Study Funding</h3> Amryt Pharma. <h3>Background/Synopsis</h3> Homozygous familial hypercholesterolaemia (HoFH) is a rare genetic condition characterized by markedly elevated levels of low-density lipoprotein cholesterol (LDL-C) secondary to bi-allelic pathogenic mutations affecting key proteins in the LDL receptor pathway. Lomitapide is a microsomal triglyceride transfer protein (MTP) inhibitor that acts independently of the LDL receptor and is licenced for the treatment of adult patients with HoFH. To date, there are few prospective cardiovascular outcomes data for HoFH patients receiving lomitapide. <h3>Objective/Purpose</h3> To evaluate the effect of lomitapide use on carotid intima-media thickness (CIMT) in patients with HoFH. <h3>Methods</h3> Thirteen HoFH patients (mean+/-SD age 29.3+/-12.5 years) in seven global centers were treated in accordance with the lomitapide product label and local clinical practice. Patients underwent routine laboratory testing, including lipid and liver panels. CIMT imaging was recorded to monitor atherosclerotic cardiovascular disease (ASCVD) according to local protocols. <h3>Results</h3> Lomitapide resulted in marked decreases in LDL-C (mean+/-SD: 76.5+/-11.7%; range 56.8-93.9% at the lowest point). Notably, eight patients achieved LDL-C levels below the European Atherosclerosis Society target of <100mg/dL, and three patients achieved LDL-C <70mg/dL at least once. Over a mean follow-up of 3.9+/-2.3 years between measurements, CIMT regressed in 7 cases. The remaining patients demonstrated no progression (Supplementary Table). In two patients where assessments of plaque area were available, modest regression or stabilisation in CIMT (0.82mm to 0.65mm over 24 months [20.7% reduction]; 0.56mm to 0.57mm over 26 months [1.8% increase]) was accompanied by clinically significant regression of plaque area (147.1mm2 to 120.5mm2 [18.1% reduction]; 64.0 mm2to 42.1 mm2 [34.7% reduction]. Calculation of vascular age in n=9 patients indicated mean improvement of -18.8+/-32.6 years (range -60 to +30 years). Elevations in ALT/AST enzyme levels >3x upper limit of normal were evident in 6/13 patients. In all cases, these elevations either resolved without intervention or were managed with brief, transient reductions in lomitapide dose. <h3>Conclusions</h3> Lomitapide dramatically reduces LDL-C levels in patients with HoFH, and results in stabilisation and/or regression of CIMT, which is an established marker of ASCVD risk.

Molecular Mechanisms of Sphingolipid Transport on Plasma Lipoproteins.

Sphingolipids are biomolecules with diverse physiological functions in signaling as well as plasma membrane structure. They are associated with either cellular membranes or plasma lipoproteins and any changes in their levels may contribute to certain metabolic diseases. Sphingolipids are evenly distributed in lipoproteins and may be used as prognostic and diagnostic markers. Mechanisms involved in the transport of sphingolipids have been recently explored and here we discuss the most recent advances in the molecular mechanisms of sphingolipids transport by lipoproteins. It has been shown that microsomal triglyceride transfer protein (MTP) and ATP-binding cassette transporter family A protein 1 (ABCA1) play an important role in plasma sphingolipid homeostasis. However, the exact mechanisms are not well known. Though much research has already been done to emphasize the impact of sphingolipids changes in many pathological disorders, understanding mechanisms by which circulating lipoproteins assist in transporting sphingolipids may provide novel information that may help in devising strategies to therapeutically target these pathways to treat various metabolic disorders.

Lomitapide Effectively Reduces Triglyceride (TG) Levels in Familial Chylomicronemia Syndrome (FCS)

Lead Author's Financial Disclosures A.C. has received consulting fees from Amryt. Study Funding Amryt Pharma. Background/Synopsis FCS is a rare autosomal recessive disorder caused by impaired lipoprotein lipase (LPL) function, resulting in elevated TG levels, intense abdominal pain, hepatosplenomegaly, and recurrent episodes of acute pancreatitis. Treatment requires a strict, extremely low-fat diet (<10% fat/day) to control TG levels <750-1000mg/dL, which does not fully control the disease. Lomitapide is a microsomal triglyceride transfer protein (MTP) inhibitor that prevents assembly of triglycerides (TGs) into chylomicrons, in addition to very low-density lipoproteins and thereby reduces circulating levels of TGs. Objective/Purpose The LOCHNES study was designed to evaluate the efficacy and safety of lomitapide in FCS. Methods This open-label, single arm LOCHNES study of lomitapide in FCS, enrolled adult patients ≥18 years with genetically confirmed FCS, elevated fasting TG≥750mg/dL and a history of pancreatitis, across 3 Italian centres. Patients were administered escalating-doses of lomitapide to maximum tolerated dose (MTD) for 26 weeks. The primary endpoint was the percent change in TGs from baseline to week 26, with lomitapide in combination with other lipid lowering therapy. Results Eighteen patients were enrolled in the study (mean+/-SD: age 46.6+/-16.7y; body mass index 23.7+/-4.1kg/m2). Median baseline TG levels were 1804mg/dL (range 810-4151mg/dL). Lomitapide increased from standard starting dose 5mg/day at baseline to mean 32.8+/-17.8mg/day at week 26. Median TGs reduced to 305mg/dL (range 70-1818mg/dL) at week 26. This equates to a 70.5% reduction in median fasting triglyceride levels. At week 26, 13 patients achieved TGs ≤750mg/dL. Treatment with lomitapide was generally well tolerated with no patient discontinuations. Adverse events were mild to moderate and were mainly related to gastrointestinal tolerability (n=9) and ALT/AST enzyme elevations ≥3x upper limit of normal (n=4). Where available (n=13), liver MRI imaging revealed increases in hepatic fat in some patients (n=5/13), and three patients with a baseline hepatic fat >20% (range 22-30%), experienced increases to 30-50% hepatic fat at 26 weeks. No patient experienced an episode of acute pancreatitis or severe abdominal pain during lomitapide treatment. One patient who temporarily interrupted lomitapide treatment due to an episode of diarrhoea, experienced acute pancreatitis during the treatment interruption period. Conclusions Lomitapide is effective in reducing triglycerides in FCS and preventing the recurrence of acute pancreatitis in this pilot study. The extent of the benefit of lomitapide to patients with FCS should be further evaluated in a larger prospective clinical trial. A.C. has received consulting fees from Amryt.