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Familial hypercholesterolemia (FH, OMIM number #143890), a life-threatening monogenic disorder characterized by high levels of low-density lipoprotein cholesterol (LDL-C), is classified into dominant and recessive types (1). The dominant form of FH may result from mutations in the LDLR, APOB, and PCSK9 genes (2). However, mutations in the low-density lipoprotein receptor (LDLR) adaptor protein-1 (LDLRAP1) gene cause an autosomal recessive inheritance pattern of FH called autosomal recessive hypercholesterolemia (ARH, OMIM number #603813). The LDLRAP1 protein, encoded by the LDLRAP1 gene, is required for receptor-mediated endocytosis of LDL-C (2). ARH is a rare disorder with an estimated prevalence of less than 1 in a population of one million. This disease is considered a phenocopy of the most severe form of FH, homozygous familial hypercholesterolemia (HoFH; OMIM number 143890). Hence, most ARH patients are clinically indiscernible from HoFH, which is caused by two defective LDLR genes with an approximate prevalence of one individual per million (8). Considering that ARH patients may develop aggressive and premature atherosclerotic cardiovascular disease (ASCVD) due to hypercholesterolemia during early adulthood, lipid-lowering therapy must be initiated during childhood (3). Early identification of ARH patients through genetic analysis of the proband and their relatives can provide prognosis and subsequently appropriate, timely treatment. In this report, we describe a novel variant, c.649G>T, p.Glu217Ter, in the homozygous state in exon 7 of the LDLRAP1 gene, causing severe ARH.

Background: Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder resulting from mutations of the LDLRAP1 gene, which leads to elevated LDL-C levels. Here, using whole exome sequencing (WES), we describe a 22-year-old Iranian female who carries a novel nonsense mutation in LDLRAP1. Methods: Genetic investigations were performed for the patient and her family. She showed LDL-C level of 720 mg/dL since the age of 11 years. At the age of 13 years old, aortic valve repair surgery was performed due to severe aortic valve stenosis (AVS). At the age of 17, along with prescription of rosuvastatin plus ezetimibe, coronary angiography displayed the presence of serious stenotic lesions of the coronary arteries and also aortic valve, making the patient eligible for coronary artery bypass grafting (CABG) and aortic valve replacement (AVR). Results: Genetic analysis showed the presence of a previously unreported homozygous LDLRAP1 gene variant, c.649G>T, generating a nonsense mutation at amino acid 217, shortening the ARH protein from 308 to 217 amino acid, which removes AP-2 binding domain of ARH, as an important part in LDL uptake.Conclusion: During a 10-year treatment, we observed a 74% reduction in LDL-C level. Despite the treatment with maximal dose of rosuvastatin plus ezetimibe, the results of coronary angiography demonstrated severe supravalvular aortic stenosis (SVAS) resulted in significant stenotic lesions of the coronary arteries and aortic valve. This highlights the importance of WES in early diagnosis of ARH, and it is proposed to prevent or at least delay the onset of the cardiovascular events.

Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder caused by pathogenic variants in the low-density lipoprotein receptor (LDLR) adaptor protein 1 (LDLRAP1) gene, encoding for the LDLRAP1 protein, which impairs internalization of hepatic LDLR. There are variable responses of ARH patients to treatment and the pathophysiological mechanism(s) for this variability remains unclear. This is in part caused by absence of reliable cellular models to evaluate the effect of LDLRAP1 mutations on the LDLRAP1 protein function and its role in LDLR internalization. Here, we aimed to validate patient-specific induced pluripotent stem cell (iPSC)-derived hepatocyte-like cells (HLCs) as an appropriate tool to model ARH disease. Fibroblasts from an ARH patient carrying the recently reported nonsense mutation, c.649G>T, were reprogrammed into hiPSCs using Sendai viral vectors. In addition, we used clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) to create an LDLRAP1 gene (also known as ARH) knockout in two different human iPSC lines. ARH patient-derived iPSCs, ARH-knockout iPSC lines, and control iPSCs were efficiently differentiated into HLCs. Western blot analysis demonstrated the absence of LDLRAP1 in HLCs derived from patient and knockout iPSCs, and this was associated with a decreased low-density lipoprotein cholesterol (LDL-C) uptake in ARH-mutant/knockout HLCs compared to control HLCs. In conclusion, we determined that the recently described c.649G>T point mutation in LDLRAP1 induces absence of the LDLRAP1 protein, similar to what is seen following LDLRAP1 knockout. This causes a decreased, although not fully absent, LDL-uptake in ARH-mutant/knockout HLCs. As knockout of LDLRAP1 or presence of the c.649G>T point mutation results in absence of LDLRAP1 protein, residual LDL uptake might be regulated by LDLRAP1-independent internalization mechanisms. Patient-specific iPSC-derived HLCs can therefore be a powerful tool to further decipher LDLRAP1 mutations and function of the protein.

Background: Autosomal recessive hypercholesterolemia (ARH) is a rare monogenic disorder resulting from mutations of the LDLRAP1 gene, which leads to elevated LDL-C levels. Here, using whole exome sequencing (WES), we describe a 22-year-old Iranian female who carries a novel nonsense mutation in LDLRAP1. Methods: Genetic investigations were performed for the patient and her family. She showed LDL-C level of 720 mg/dL since the age of 11 years. At the age of 13 years old, aortic valve repair surgery was performed due to severe aortic valve stenosis (AVS). At the age of 17, along with prescription of rosuvastatin plus ezetimibe, coronary angiography displayed the presence of serious stenotic lesions of the coronary arteries and also aortic valve, making the patient eligible for coronary artery bypass grafting (CABG) and aortic valve replacement (AVR).Results: Genetic analysis showed the presence of a previously unreported homozygous LDLRAP1 gene variant, c.649G>T, generating a nonsense mutation at amino acid 217, shortening the ARH protein from 308 to 217 amino acid, which removes AP-2 binding domain of ARH, as an important part in LDL uptake.Conclusion: During a 10-year treatment, we observed a 74% reduction in LDL-C level. Despite the treatment with maximal dose of rosuvastatin plus ezetimibe, the results of coronary angiography demonstrated severe supravalvular aortic stenosis (SVAS) resulted in significant stenotic lesions of the coronary arteries and aortic valve. This highlights the importance of WES in early diagnosis of ARH, and it is proposed to prevent or at least delay the onset of the cardiovascular events.

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Klotho is a newly discovered protein with pleotropic effects and have affected different fields of renal medicine from translational research to clinical nephrology. Here we want to summarize some new scopes in the field of renal fibrosis and Klotho with this hope that in future it could be implemented as a new therapeutic strategy to combat the renal fibrosis.Copyright © 2013, Nephrology and Urology Research Center; Published by Kowsar Corp. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background: Multidrug-resistant (MDR) strains of Acinetobacter baumannii have been increasingly reported as a major cause of nosocomial infections, and have created major therapeutic problems worldwide. Objectives: The aim of the present study was to evaluate the role of proton motive force (PMF)-dependent efflux mechanism in the multiple resistance phenotype of A. baumannii clinical strains. Materials and Methods: A total of 65 A. baumannii clinical strains were collected from hospitals in Tehran. These were tested for antimicrobial susceptibility using disc agar diffusion and broth microdilution methods. Active efflux was assessed by ethidium bromide accumulation assays. Further evaluations were performed by the determination of the minimum inhibitory concentrations and the accumulation of ciprofloxacin against selected MDR A. baumannii in the presence and absence of carbonyl cyanide m-chlorophenylhydrazone (CCCP), an inhibitor of PMF. Results: Ninety five percent of strains were MDR, with high rate of resistance to ciprofloxacin (92.3%), gentamicin (89.2%), and ceftazidime (93.8%). Colistin and imipenem were the most effective antibiotics with resistance rates of 1.5% and 44.6%, respectively. MDR strains showed a four-fold reduction in the MIC of ciprofloxacin when tested in the presence of the efflux pump inhibitor. The addition of CCCP led to a significant increase in the accumulation of ethidium bromide and ciprofloxacin. Conclusions: PMF-dependent efflux mechanism appears to play an important role in the MDR phenotype of A. baumannii clinical strains.