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Background: Serum lipids, including total cholesterol (TC), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-c), increase during pregnancy. Serum Proprotein Convertase Subtilisin Kexin 9 (PCSK9) is a vital regulator in lipoprotein metabolism. Circulating PCSK9 downregulates the LDL receptor on the surface of liver cells inhibiting clearance of LDL-c., Objective: To determine the influence of weeks of pregnancy and obesity on circulating levels of essential lipid lipoproteins and PCSK9 in women with normal, uncomplicated pregnancies and deliveries., Methods: We performed a comprehensive lipid and lipoprotein profile during each trimester of pregnancy in 70 mostly Caucasian women with uncomplicated normal pregnancies and deliveries. Based on their first trimester BMI, we placed them into one of three categories: (<25 kg/m 2 n=23, 25-30 kg/m 2 n=25, or >30 n=22) kg/m 2 . Cholesterol, triglycerides, LDL cholesterol (LDL-c), non-HDL particles, and lipoprotein(a) were measured by spectrophotometry, ion mobility, and immunoturbidimetric assays. Elisa assay determined PCSK9 (active and total). Homeostatic Model Assessment (HOMA-IR) assessed insulin resistance in the second and third trimesters of pregnancy., Results: Total and active PCSK9, LDL-c, and nonHDL particle concentrations were higher than reported for non-pregnant normal values, increased after the first trimester of pregnancy, and were highest from mid-gestation to the last trimester of pregnancy in the overweight and the obese., Conclusion: PCSK9 levels rise as normal pregnancy progresses. Levels are higher in persons who are obese, even after adjustment for insulin resistance. Defining normal PCSK9 levels during pregnancy must adjust for gestational age and BMI., Competing Interests: Declaration of Competing Interest We confirm no known conflicts of interest associated with this publication, and there has been no financial support for this work that could have influenced the outcome. Dr Wren is Medical Director at Quest and Dr Lopez has a registered patent for the PCSK9 assay. Analysis and reporting was blind to the clinical data. We also confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that all have approved the order of our authors., (Copyright © 2022. Published by Elsevier Inc.)

High levels of cholesterol, especially as low-density lipoprotein (LDL), are a well-known risk factor for atherosclerotic-related diseases. The key atherogenic property of LDL is its ability to form atherosclerotic plaque. Proprotein convertase subtilisin/kexin-9 (PCSK9) is an indirect regulator of plasma LDL levels by controlling the number of LDL receptor molecules expressed at the plasma membrane, especially in the liver. Herein, we performed a combination of affinity chromatography, mass spectrometry analysis and identification, and gene expression studies to identify proteins that interact with PCSK9. Through these studies, we identified three proteins, alpha-1-antitrypsin (A1AT), alpha-1-microglobulin/bikunin precursor (AMBP), and apolipoprotein H (APOH) expressed by C3A cells that interact with PCSK9. The expression levels of A1AT and APOH increased in cells treated with MITO+ medium, a condition previously shown to affect the function of PCSK9, as compared to treating with Regular (control) medium. However, AMBP expression did not change in response to the treatments. Additional studies are required to determine which of these proteins can modulate the expression/function of PCSK9. The identification of endogenous modulators of PCSK9's function could lead to the development of novel diagnostic tests or treatment options for patients suffering hypercholesterolemia in combination with other chronic metabolic diseases., Competing Interests: Conflicts of Interest None declared.

Proprotein convertase subtilisin-kexin 9 (PCSK9) appears to be involved in multiple processes. A ProtoArray Human Protein Microarray was used to identify proteins interacting with biotinylated PCSK9. Fifteen novel proteins interacting with PCSK9 were identified using this technique. Only two of these proteins, sterol carrier protein 2 and hepatoma-derived growth factor, related protein 3, have known functions. The identification of proteins that could affect the expression/function of PCSK9 is of great interest due to potential implications in personalized medicine for hypercholesterolemic patients.

Statins are the first-line treatment for hypercholesterolemic patients. Herein, the effects of three statins on complex formation between proprotein convertase subtilisin-kexin 9 (PCSK9) and the low density lipoprotein receptor (LDLR), a critical step for the PCSK9-dependent degradation of LDLR in the lysosome, were examined. Human hepatocyte-like C3A cells grown in control (containing 10% fetal bovine serum) or MITO+ (supplemented with BD™ MITO + serum extender) medium were also treated with atorvastatin (Atorv), lovastatin (Lov), or pravastatin (Prav) for 24 h. RNA and protein expression studies and determinations of PCSK9/LDLR complex formation were performed. As expected, the statins increased the expression of PCSK9 and LDLR independently of the medium employed. Interestingly, Atov and Lov caused increases in PCSK9/LDLR complex formation, whereas Prav decreased complex formation when compared to cells treated without drugs. These results may explain why Prav works better for statin intolerant patients than other statins such as Atorv and Lov., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Heart disease ends the life of more people than any other disease in the United States. High levels of low density lipoprotein (LDL)-cholesterol cause heart diseases by increasing the formation of atherosclerotic plaques. Proprotein convertase subtilisin/kexin-9 (PCSK9) indirectly regulates plasma LDL levels by controlling the LDL receptor expression at the plasma membrane. PCSK9 also appears to modulate glucose intolerance, insulin resistance, abdominal obesity, inflammation, and hypertension. The magnitude of PCSK9's involvement in the onset of these metabolic abnormalities appears to be associated with age, sex, and ethnic background. Another regulator, the inducible degrader of the LDL receptor (IDOL), works by enhancing the ubiquitination of the LDL receptor. Herein, we will review the functions and regulatory mechanisms of PCSK9. The effects of PCSK9 on the LDL receptor, the relationship of this convertase with IDOL, and treatments currently available against hypercholesterolemia are also discussed., (Copyright © 2017 Elsevier Inc. All rights reserved.)