Complex effects of inhibiting hepatic apolipoprotein B100 synthesis in humans

Mipomersen (Kynamro®) is an antisense oligonucleotide (ASO) that inhibits apolipoprotein B (apoB) synthesis; its LDL lowering effects should, therefore, result from reduced secretion of VLDL. We enrolled 17 healthy volunteers who received placebo injections weekly for 3-wks followed by mipomersen weekly for 7-9 wks. Stable isotopes were used after each treatment to determine fractional catabolic rates (FCRs) and production rates (PRs) of apoB in VLDL, IDL, and LDL, and of TG in VLDL. Mipomersen significantly reduced apoB in VLDL, IDL, and LDL associated with increases in FCRs of VLDL and LDL apoB and reductions in PRs of IDL and LDL apoB. Unexpectedly, the PRs of VLDL apoB and VLDL TG were unaffected. siRNA knockdown of apoB expression in HepG2 cells demonstrated preservation of apoB secretion across a range of apoB synthesis. Titrated ASO knockdown of apoB mRNA in chow-fed mice showed preservation of both apoB and TG secretion. In contrast, titrated ASO knockdown of apoB mRNA in high fat fed mice resulted in stepwise reductions of both apoB and TG secretion. Mipomersen lowered all apoB-lipoproteins without reducing the PR of either VLDL apoB or TG. Our first-in-human data are consistent with longstanding models of post-transcriptional and post-translational regulation of apoB secretion, and are supported by experiments with siRNA in HepG2 cells and ASO in mice. These results indicate that targeting apoB synthesis can lower levels of apoB-lipoproteins without necessarily reducing VLDL secretion, thereby reducing the risk of steatosis associated with this therapeutic strategy

Lipoprotein lipase is frequently overexpressed or translocated in cervical squamous cell carcinoma and promotes invasiveness through the non-catalytic C terminus.

BACKGROUND: We studied the biological significance of genes involved in a novel t(8;12)(p21.3;p13.31) reciprocal translocation identified in cervical squamous cell carcinoma (SCC) cells. METHODS: The rearranged genes were identified by breakpoint mapping, long-range PCR and sequencing. We investigated gene expression in vivo using reverse-transcription PCR and tissue microarrays, and studied the phenotypic consequences of forced gene overexpression. RESULTS: The rearrangement involved lipoprotein lipase (LPL) and peroxisome biogenesis factor-5 (PEX5). Whereas LPL-PEX5 was expressed at low levels and contained a premature stop codon, PEX5-LPL was highly expressed and encoded a full-length chimeric protein (including the majority of the LPL coding region). Consistent with these findings, PEX5 was constitutively expressed in normal cervical squamous cells, whereas LPL expression was negligible. The LPL gene was rearranged in 1 out of 151 cervical SCCs, whereas wild-type LPL overexpression was common, being detected in 10 out of 28 tissue samples and 4 out of 10 cell lines. Forced overexpression of wild-type LPL and PEX5-LPL fusion transcripts resulted in increased invasiveness in cervical SCC cells, attributable to the C-terminal non-catalytic domain of LPL, which was retained in the fusion transcripts. CONCLUSION: This is the first demonstration of an expressed fusion gene in cervical SCC. Overexpressed wild-type or translocated LPL is a candidate for targeted therapy

The role of triacylglycerol in cardiac energy provision

Triacylglycerols (TAGs) constitute the main energy storage resource in mammals, by virtue of their high energy density. This in turn is a function of their highly reduced state and hydrophobicity. Limited water solubility, however, imposes specific requirements for delivery and uptake mechanisms on TAG-utilising tissues, including the heart, as well as intracellular disposition. TAGs constitute potentially the major energy supply for working myocardium, both through blood-borne provision and as intracellular TAG within lipid droplets, but also provide the heart with fatty acids (FAs) which the myocardium cannot itself synthesise but are required for glycerolipid derivatives with (non-energetic) functions, including membrane phospholipids and lipid signalling molecules. Furthermore they serve to buffer potentially toxic amphipathic fatty acid derivatives. Intracellular handling and disposition of TAGs and their FA and glycerolipid derivatives similarly requires dedicated mechanisms in view of their hydrophobic character. Dysregulation of utilisation can result in inadequate energy provision, accumulation of TAG and/or esterified species, and these may be responsible for significant cardiac dysfunction in a variety of disease states. This review will focus on the role of TAG in myocardial energy provision, by providing FAs from exogenous and endogenous TAG sources for mitochondrial oxidation and ATP production, and how this can change in disease and impact on cardiac function

Drosophila Lipophorin Receptors Mediate the Uptake of Neutral Lipids in Oocytes and Imaginal Disc Cells by an Endocytosis-Independent Mechanism

Lipids are constantly shuttled through the body to redistribute energy and metabolites between sites of absorption, storage, and catabolism in a complex homeostatic equilibrium. In Drosophila, lipids are transported through the hemolymph in the form of lipoprotein particles, known as lipophorins. The mechanisms by which cells interact with circulating lipophorins and acquire their lipidic cargo are poorly understood. We have found that lipophorin receptor 1 and 2 (lpr1 and lpr2), two partially redundant genes belonging to the Low Density Lipoprotein Receptor (LDLR) family, are essential for the efficient uptake and accumulation of neutral lipids by oocytes and cells of the imaginal discs. Females lacking the lpr2 gene lay eggs with low lipid content and have reduced fertility, revealing a central role for lpr2 in mediating Drosophila vitellogenesis. lpr1 and lpr2 are transcribed into multiple isoforms. Interestingly, only a subset of these isoforms containing a particular LDLR type A module mediate neutral lipid uptake. Expression of these isoforms induces the extracellular stabilization of lipophorins. Furthermore, our data indicate that endocytosis of the lipophorin receptors is not required to mediate the uptake of neutral lipids. These findings suggest a model where lipophorin receptors promote the extracellular lipolysis of lipophorins. This model is reminiscent of the lipolytic processing of triglyceride-rich lipoproteins that occurs at the mammalian capillary endothelium, suggesting an ancient role for LDLR–like proteins in this process

Effects of CETP inhibition with anacetrapib on metabolism of VLDL-TG and plasma apolipoproteins C-II, C-III, and E

Cholesteryl ester transfer protein (CETP) mediates the transfer of HDL cholesteryl esters for triglyceride (TG) in VLDL/LDL. CETP inhibition, with anacetrapib, increases HDL-cholesterol, reduces LDL-cholesterol, and lowers TG levels. This study describes the mechanisms responsible for TG lowering by examining the kinetics of VLDL-TG, apoC-II, apoC-III, and apoE. Mildly hypercholesterolemic subjects were randomized to either placebo (N = 10) or atorvastatin 20 mg/qd (N = 29) for 4 weeks (period 1) followed by 8 weeks of anacetrapib, 100 mg/qd (period 2). Following each period, subjects underwent stable isotope metabolic studies to determine the fractional catabolic rates (FCRs) and production rates (PRs) of VLDL-TG and plasma apoC-II, apoC-III, and apoE. Anacetrapib reduced the VLDL-TG pool on a statin background due to an increased VLDL-TG FCR (29%; P = 0.002). Despite an increased VLDL-TG FCR following anacetrapib monotherapy (41%; P = 0.11), the VLDL-TG pool was unchanged due to an increase in the VLDL-TG PR (39%; P = 0.014). apoC-II, apoC-III, and apoE pool sizes increased following anacetrapib; however, the mechanisms responsible for these changes differed by treatment group. Anacetrapib increased the VLDL-TG FCR by enhancing the lipolytic potential of VLDL, which lowered the VLDL-TG pool on atorvastatin background. There was no change in the VLDL-TG pool in subjects treated with anacetrapib monotherapy due to an accompanying increase in the VLDL-TG PR

Effects of PCSK9 Inhibition With Alirocumab on Lipoprotein Metabolism in Healthy Humans

BACKGROUND: Alirocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9 (PCSK9), lowers plasma low-density lipoprotein (LDL) cholesterol and apolipoprotein B100 (apoB). Although studies in mice and cells have identified increased hepatic LDL receptors as the basis for LDL lowering by PCSK9 inhibitors, there have been no human studies characterizing the effects of PCSK9 inhibitors on lipoprotein metabolism. In particular, it is not known whether inhibition of PCSK9 has any effects on very low-density lipoprotein or intermediate-density lipoprotein (IDL) metabolism. Inhibition of PCSK9 also results in reductions of plasma lipoprotein (a) levels. The regulation of plasma Lp(a) levels, including the role of LDL receptors in the clearance of Lp(a), is poorly defined, and no mechanistic studies of the Lp(a) lowering by alirocumab in humans have been published to date. METHODS: Eighteen (10 F, 8 mol/L) participants completed a placebo-controlled, 2-period study. They received 2 doses of placebo, 2 weeks apart, followed by 5 doses of 150 mg of alirocumab, 2 weeks apart. At the end of each period, fractional clearance rates (FCRs) and production rates (PRs) of apoB and apo(a) were determined. In 10 participants, postprandial triglycerides and apoB48 levels were measured. RESULTS: Alirocumab reduced ultracentrifugally isolated LDL-C by 55.1%, LDL-apoB by 56.3%, and plasma Lp(a) by 18.7%. The fall in LDL-apoB was caused by an 80.4% increase in LDL-apoB FCR and a 23.9% reduction in LDL-apoB PR. The latter was due to a 46.1% increase in IDL-apoB FCR coupled with a 27.2% decrease in conversion of IDL to LDL. The FCR of apo(a) tended to increase (24.6%) without any change in apo(a) PR. Alirocumab had no effects on FCRs or PRs of very low-density lipoproteins-apoB and very low-density lipoproteins triglycerides or on postprandial plasma triglycerides or apoB48 concentrations. CONCLUSIONS: Alirocumab decreased LDL-C and LDL-apoB by increasing IDL- and LDL-apoB FCRs and decreasing LDL-apoB PR. These results are consistent with increases in LDL receptors available to clear IDL and LDL from blood during PCSK9 inhibition. The increase in apo(a) FCR during alirocumab treatment suggests that increased LDL receptors may also play a role in the reduction of plasma Lp(a). CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01959971

Employees’ Career Transition and Growth: A Study of Women-Owned Micro Businesses in Balogun Market, Lagos, Nigeria

The study aims at investigating the effect of voluntary career transition on women-owned micro business growth. The independent variable ‘voluntary career transition’ is used as a single construct while the dependent variable ‘business growth’ is decomposed as a multi-construct of sales, employees and assets growth. The population of the study comprises 384 persons, while the sample size used is 250 micro businesses owned by women, who are formal employees of organisations. Average distribution is used to select the number of questionnaires that were distributed by the ten lines of business selected for the study. The study employs self-constructed questionnaire items to measure the independent, while an adopted questionnaire is used for firm growth. Frequencies and descriptive statistics are used to analyse the data collected from 104 questionnaire respondents, while the regression analysis is used to test the hypotheses. The findings indicate that voluntary career transition has a very high positive effect on the employment creation, a high positive effect on the sales growth and a very low positive effect on the asset growth of the business under study. The study, therefore, concludes that although carrier transition from paid employment to micro-businesses might be a difficult carrier choice and unattractive decision, for most women, it has been proven to be a contributing factor that affects the growth of women micro business. The study, therefore, suggests that organisational management and policymakers should encourage intrapreneurs and micro businesses

Moderating effects of cross-border entrepreneurship on innovation and growth: a study of medium enterprises in south-west, Nigeria

The study focused on moderating effect of cross-border entrepreneurship on the relationship between innovation and firm growth using medium scale techno-based manufacturing firms in South-West geo-political zone of Nigeria. Beyond determining this general objective, the study also sought to establish relationship between innovation (exploration and exploitation) and firm growth. Mail questionnaire was administered on 400 sample size. Correlation, Multiple-regression analysis and Ordinal Linear-by-Linear Association Model was conducted using SPSS 25 to strengthen the findings. The findings show high moderating effect of internationalization on the high positive relationship between innovation and firm growth. The findings are inconsistent with previous findings. The study suggests that techno-based manufacturing firms can embark and successfully compete internationally through innovative activities in order to achieve high growth of their firms

Technological innovativeness and growth: a study of small scale manufacturing firms in Lagos State

The study has the general objective to determine the extent of the relationship between technological innovativeness and firm growth using small scale manufacturing firms in Lagos State. The independent variable of technological innovativeness was operationalized into product-oriented innovativeness and process-oriented innovativeness, while the dependent variables of firm growth were operationalized into sales growth, employment growth, growth in firm size and market shares growth. This study employs exploration correlational research design. The sample population of a small scale enterprise in Lagos State accounts for eleven thousand and forty-four (11,044). Yamane’s formula was used to get the sample size of three hundred and eighty-six (386), this was approximated to the nearest hundred to have 400 for equal distribution. Data gathered for this study was analyzed using the Pearson’s Product Moment Correlation analysis in order to determine the relationship between them and a simple linear regression analysis to establish the extent of relationship between them using statistical Package for Social Science (SPSS) version 2.3. The correlation statistic shows that the linkage between the independent and dependent variables was low to moderate that product-oriented innovativeness shows a moderate positive relationship with sales and employment growth, while the process-oriented innovativeness shows low positive relationship with firm size thus allowing for regression analysi