Identification and Functional Analysis of APOB Variants in a Cohort of Hypercholesterolemic Patients.

Mutations in APOB are the second most frequent cause of familial hypercholesterolemia (FH). APOB is highly polymorphic, and many variants are benign or of uncertain significance, so functional analysis is necessary to ascertain their pathogenicity. Our aim was to identify and characterize APOB variants in patients with hypercholesterolemia. Index patients (n = 825) with clinically suspected FH were analyzed using next-generation sequencing. In total, 40% of the patients presented a variant in LDLR, APOB, PCSK9 or LDLRAP1, with 12% of the variants in APOB. These variants showed frequencies in the general population lower than 0.5% and were classified as damaging and/or probably damaging by 3 or more predictors of pathogenicity. The variants c.10030A>G;p.(Lys3344Glu) and c.11401T>A;p.(Ser3801Thr) were characterized. The p.(Lys3344Glu) variant co-segregated with high low-density lipoprotein (LDL)-cholesterol in 2 families studied. LDL isolated from apoB p.(Lys3344Glu) heterozygous patients showed reduced ability to compete with fluorescently-labelled LDL for cellular binding and uptake compared with control LDL and was markedly deficient in supporting U937 cell proliferation. LDL that was carrying apoB p.(Ser3801Thr) was not defective in competing with control LDL for cellular binding and uptake. We conclude that the apoB p.(Lys3344Glu) variant is defective in the interaction with the LDL receptor and is causative of FH, whereas the apoB p.(Ser3801Thr) variant is benign.

Prognostic Impact of Dihydropyrimidine Dehydrogenase Germline Variants in Unresectable Non-Small Cell Lung Cancer Patients Treated with Platin-Based Chemotherapy.

Platin-based chemotherapy is the standard treatment for patients with non-small cell lung cancer (NSCLC). However, resistance to this therapy is a major obstacle in successful treatment. In this study, we aimed to investigate the impact of several pharmacogenetic variants in patients with unresectable NSCLC treated with platin-based chemotherapy. Our results showed that DPYD variant carriers had significantly shorter progression-free survival and overall survival compared to DPYD wild-type patients, whereas DPD deficiency was not associated with a higher incidence of high-grade toxicity. For the first time, our study provides evidence that DPYD gene variants are associated with resistance to platin-based chemotherapy in NSCLC patients. Although further studies are needed to confirm these findings and explore the underlying mechanisms of this association, our results suggest that genetic testing of DPYD variants may be useful for identifying patients at a higher risk of platin-based chemotherapy resistance and might be helpful in guiding future personalized treatment strategies in NSCLC patients.

Analytical validation of a laboratory-development multigene pharmacogenetic assay.

OBJECTIVE: The implementation of pharmacogenetics (PGx) in clinical practice is an essential tool for personalized medicine. However, clinical laboratories must validate their procedures before being used to perform PGx studies in patients, in order to confirm that they are adequate for the intended purposes. METHODS: We designed a validation process for our in-house pharmacogenetic PCR-based method assay. RESULTS: The concordance to reference, repeatability and reproducibility was 100%. Sensitivity and specificity were 100% for the detection of variant diplotypes in CYP2C9, CYP3A5, TPMT, DPYD and UGT1A1 genes. The sensitivity was lower in the detection of CYP2C19 variants due to a limitation in the design that prevents the detection of CYP2C19 *2/*10 diplotype. CONCLUSIONS: The success of implementing clinical pharmacogenetic testing into routine clinical practice is dependent on the precision of genotyping. Limitations must be bearing in mind to guarantee the quality of PGx assays in clinical laboratory practice. We provided objective evidence that the necessary requirements in our laboratory-development assay were fulfilled.

Functional analysis of new variants at the low-density lipoprotein receptor associated with familial hypercholesterolemia.

Familial hypercholesterolemia is an autosomal dominant disease of lipid metabolism caused by defects in the genes LDLR, APOB, and PCSK9. The prevalence of heterozygous familial hypercholesterolemia (HeFH) is estimated between 1/200 and 1/250. Early detection of patients with FH allows initiation of treatment, thus reducing the risk of coronary heart disease. In this study, we performed in vitro characterization of new LDLR variants found in our patients. Genetic analysis was performed by Next Generation Sequencing using a customized panel of 198 genes in DNA samples of 516 subjects with a clinical diagnosis of probable or definitive FH. All new LDLR variants found in our patients were functionally validated in CHO-ldlA7 cells. The LDLR activity was measured by flow cytometry and LDLR expression was detected by immunofluorescence. Seven new variants at LDLR were tested: c.518 G>C;p.(Cys173Ser), c.[684 G>T;694 G>T];p.[Glu228Asp;Ala232Ser], c.926C>A;p.(Pro309His), c.1261A>G;p.(Ser421Gly), c.1594T>A;p.(Tyr532Asn), and c.2138delC;p.(Thr713Lysfs*17). We classified all variants as pathogenic except p.(Ser421Gly) and p.(Ala232Ser). The functional in vitro characterization of rare variants at the LDLR is a useful tool to classify the new variants. This approach allows us to confirm the genetic diagnosis of FH, avoiding the classification as "uncertain significant variants", and therefore, carry out cascade family screening.

Altered Underlying Renal Tubular Function in Patients With Chronic Hepatitis B Receiving Nucleos(t)ide Analogs in a Real-World Setting: The MENTE Study.

BACKGROUND: Cases of renal tubular dysfunction have been reported in patients with hepatitis B and in patients with human immunodeficiency virus who are undergoing tenofovir treatment. However, little is known about the impact on tubular function in patients with chronic hepatitis B (CHB) under long-term use of entecavir (ETV) and tenofovir disoproxil fumarate (TDF). We evaluated markers of renal tubular function and bone turnover in patients with CHB treated with ETV or TDF. PATIENTS AND METHODS: A multicenter, cross-sectional study was performed on markers of renal tubular function and bone turnover in hepatitis B virus-monoinfected patients on long-term treatment with Entecavir or Tenofovir (the MENTE study). The analyzed parameters were: retinol-binding protein/creatinine, neutrophil gelatinase-associated lipocalin/creatinine, excretion of phosphates, uric acid excretion, glomerular filtrate, protein/creatinine, albumin/creatinine, serum creatinine, phosphate, CTX, P1NP, vitamin D, and parathormone. RESULTS: A total of 280 patients (ETV: 89, TDF: 69, control: 122) were included in this study. The TDF group was associated with altered levels of retinol-binding protein (RBP)/creatinine (TDF 25% vs. 7% ETV and control; P<0.001). Protein/creatinine, uric acid excretion, P1NP1, and parathormone were higher in the TDF group. The proportion of patients with serum phosphate <2.5 mg/dL was higher in both the ETV and the TDF groups compared with the control. The multivariate analysis showed that the use of TDF was independently associated with a higher risk of altered excretion of RBP/creatinine (4.4; interquartile range: 1.4 to 14; P=0.013). CONCLUSIONS: We found an independent association between TDF use and altered RBP excretion. This finding indicates subclinical tubular damage. Because tubular dysfunction can precede the decline of renal function, close monitoring of RBP levels in patients with CHB on nucleos(t)ide analog treatment must be performed for early detection of TDF-related renal toxicity. In this study, these differences in tubular function were not associated with concomitant changes in markers of bone turnover.

Variants in the ITPA gene protect against ribavirin-induced hemolytic anemia in HIV/HCV-coinfected patients with all HCV genotypes.

BACKGROUND: A recent genome-wide association study reported a strong association with a single-nucleotide polymorphism (SNP) in the inosine triphosphate (ITPA) gene and hemolytic anemia in patients infected with hepatitis C virus (HCV) receiving pegylated interferon and ribavirin. We investigate these polymorphisms in a cohort of human immunodeficiency virus (HIV)/HCV-coinfected patients. METHODS: DNA was available for 161 patients with validated outcomes. We analyzed the association between the variants and week 4 hemoglobin reduction. Anemia over the course of therapy, ribavirin (RBV) dose reduction, serum RBV level, and rapid virological response (RVR) and sustained virological response (SVR) were also investigated. Using a candidate gene approach, ITPA variants rs1127354 and rs7270101 were tested using the ABI TaqMan kit. Multivariable models were used to identify predictors of anemia. RESULTS: A significant minority (33%) of patients were predicted to have reduced ITPase activity. The minor allele of each variant was associated with protection against week 4 anemia. In multivariable models only the genetic variants, creatinine, and zidovudine exposure remained significant. ITPase deficiency was not associated with RBV-dose reduction, RVR, or SVR. CONCLUSIONS: This study confirms that polymorphisms in the ITPA gene are associated with protection from RBV-induced anemia in HIV/HCV-coinfected patients but not improved clinical outcomes.

Advancing pharmacogenetic testing in a tertiary hospital: a retrospective analysis after 10 years of activity.

The field of pharmacogenetics (PGx) holds great promise in advancing personalized medicine by adapting treatments based on individual genetic profiles. Despite its benefits, there are still economic, ethical and institutional barriers that hinder its implementation in our healthcare environment. A retrospective analysis approach of anonymized data sourced from electronic health records was performed, encompassing a diverse patient population and evaluating key parameters such as prescribing patterns and test results, to assess the impact of pharmacogenetic testing. A head-to-head comparison with previously published activity results within the same pharmacogenetic laboratory was also conducted to contrast the progress made after 10 years. The analysis revealed significant utilization of pharmacogenetic testing in daily clinical practice, with 1,145 pharmacogenetic tests performed over a 1-year period and showing a 35% growth rate increase over time. Of the 17 different medical departments that sought PGx tests, the Oncology department accounted for the highest number, representing 58.47% of all genotyped patients. A total of 1,000 PGx tests were requested for individuals susceptible to receive a dose modification based on genotype, and 76 individuals received a genotype-guided dose adjustment. This study presents a comprehensive descriptive analysis of real-world data obtained from a public tertiary hospital laboratory specialized in pharmacogenetic testing, and presents data that strongly endorse the integration of pharmacogenetic testing into everyday clinical practice.

Intrapatient and interpatient pharmacokinetic variability of raltegravir in the clinical setting.

INTRODUCTION: Raltegravir (RAL) is the first in class integrase inhibitor and is licensed for administration at 400 mg twice daily. RAL pharmacokinetics are characterized by high interpatient variability and recently RAL plasma exposure has been correlated with efficacy. RAL is primarily metabolized by glucuronidation via uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) and UGT1A1*28 considered to be the main genetic variant associated with decreased UGT1A1 expression. This study investigated variability in RAL trough plasma concentrations (Ctrough) in the clinical setting, the effect of UGT1A1*28 and concomitant antiretrovirals. METHODS: A total of 86 patients, from Turin, Italy, and Madrid, Spain, were included in the analysis. Blood samples were obtained 10-14 hours postdose. Genotyping for UGT1A1*28 was conducted by sequencing. RESULTS: High interpatient and intrapatient variabilities were observed; 13 patients had ≥3 samples available, and the median coefficient of variation was 128 (64-265). Coadministration of RAL with atazanavir (ATV, n = 9) resulted in higher raltegravir Ctrough, 517 (307-2706) ng/mL when compared with patients not receiving ATV (n = 77) 223 (95-552; P = 0.02). UGT1A1*28 did not influence RAL plasma exposure. DISCUSSION: We have documented large intersubject and intrasubject variabilities in RAL plasma concentrations and confirmed the interaction with ATV. Further studies are required to better understand the mechanisms that influence the pharmacokinetics of RAL.

Genetic variants of ABCC10, a novel tenofovir transporter, are associated with kidney tubular dysfunction.

BACKGROUND: Tenofovir (TFV) causes kidney tubular dysfunction (KTD) in some patients, but the mechanism is poorly understood. Genetic variants in TFV transporters are implicated; we explored whether ABCC10 transports TFV and whether ABCC10 single-nucleotide polymorphisms (SNPs) are associated with KTD. METHODS: TFV accumulation was assessed in parental and ABCC10-transfected HEK293 cells (HEK293-ABCC10), CD4(+) cells and monocyte-derived macrophages (MDMs). Substrate specificity was confirmed by cepharanthine (ABCC10 inhibitor) and small interfering RNA (siRNA) studies. Fourteen SNPs in ABCC10 were genotyped in human immunodeficiency virus-positive patients with KTD (n = 19) or without KTD (controls; n = 96). SNP and haplotype analysis was performed using Haploview. RESULTS: TFV accumulation was significantly lower in HEK293-ABCC10 cell lines than in parental HEK293 cells (35% lower; P = .02); this was reversed by cepharanthine. siRNA knockdown of ABCC10 resulted in increased accumulation of TFV in CD4(+) cells (18%; P = .04) and MDMs (25%; P = .04). Two ABCC10 SNPs (rs9349256: odds ratio [OR], 2.3; P = .02; rs2125739, OR, 2.0; P = .05) and their haplotype (OR, 2.1; P = .05) were significantly associated with KTD. rs9349256 was associated with urine phosphorus wasting (P = .02) and ß2 microglobulinuria (P = .04). CONCLUSIONS: TFV is a substrate for ABCC10, and genetic variability within the ABCC10 gene may influence TFV renal tubular transport and contribute to the development of KTD. These results need to be replicated in other cohorts.

Impact of inosine triphosphatase gene variants on the risk of anemia in HIV/hepatitis C virus-coinfected patients treated for chronic hepatitis C.

The role of rs1127354/rs7270101 alleles at the inosine triphosphatase (ITPA) gene on ribavirin-induced anemia was assessed in 74 patients with hepatitis C virus and human immunodeficiency virus coinfection. Anemia developed in 80% of patients with normal ITPA activity compared with 33% of those with reduced ITPA activity. In contrast, ITPA variants did not influence sustained virological response.

Noncirrhotic portal hypertension in HIV infection.

PURPOSE OF REVIEW: Liver disease in the HAART era is one of the leading causes of morbidity and mortality in HIV-infected individuals in Western countries. Even if the majority of cases rely on identifiable causes (viral hepatitis, steatohepatitis, alcohol abuse, drug toxicity, etc.), the cause of liver abnormalities remains unknown for a subset of patients, some of whom present with noncirrhotic portal hypertension (NCPH). RECENT FINDINGS: In 2006, the first reports of NCPH in HIV-infected patients attracted special attention. Typically, individuals unaware of any underlying liver illness presented with variceal bleeding, occasionally fatal. Interestingly, severe portal hypertension occurred in the absence of liver function impairment in most cases. Liver biopsy revealed a distinctive histological feature characterized by massive absence of portal veins along with focal obliteration of small portal veins. After extensive ruling out of other causes, the role of antiretroviral toxicity (particularly didanosine exposure) emerged as the major contributor to this condition. Other potential factors could be an enhanced microbial translocation from the gut and prothrombotic conditions. SUMMARY: NCPH is an uncommon condition, although increasingly being reported in HIV-infected individuals. It generally presents as a clinical episode of decompensated portal hypertension, generally with gastrointestinal bleeding. Long-lasting HIV infection and prolonged antiretroviral exposure are universally recognized in these patients. The involvement of didanosine has been highlighted in most series. Removal of this drug and prevention of variceal bleeding episodes are currently the most effective prophylactic and therapeutic interventions.

Influence of a single nucleotide polymorphism at the main ribavirin transporter gene on the rapid virological response to pegylated interferon-ribavirin therapy in patients with chronic hepatitis C virus infection.

The equilibrative nucleoside transporter 1 (ENT1) is the main protein involved in ribavirin cellular uptake. Polymorphisms at the ENT1 gene may influence ribavirin activity as part of hepatitis C virus (HCV) therapy. A retrospective study was conducted in 109 human immunodeficiency virus (HIV)-infected patients who were infected with HCV genotypes 1 or 4 who had received pegylated interferon (pegIFN)-ribavirin. Single nucleotide polymorphisms (SNPs) at the ENT1 gene were examined using TaqMan 5'-nuclease assays. In the study population, allelic frequencies at rs760370 were as follows: A3 (43 [39%] of 109 patients), AG (50 [46%] of 109 patients), and GG (16 [15%] of 109 patients). Achievement of rapid virological response was more frequent in GG carriers than in AA/AG carriers (50% vs 17%, respectively; P = .007). In multivariate analysis, the GG genotype (odds ratio [OR], 15.9; 95% confidence interval [CI], 2.8-92.2; P < .002), a baseline serum HCV-RNA level <600,000 IU/mL (OR, 45.7; 95% CI, 8.7-240.5; P <.001) and a serum ribavirin trough concentration >2.5 µg/mL (OR, 4.8; 95% CI, 1.3-17.1; P < .016) were associated with rapid virological response. When 2 or more of these factors were present, positive and negative predictive values of rapid virological response were 65% and 91%, respectively. In summary, a SNP rs760370A→G at the ENT1 gene influences the chance of rapid virological response to pegIFN-ribavirin therapy in HIV-infected patients with chronic HCV infection due to HCV genotypes 1 or 4, most likely modulating intracellular ribavirin exposure within hepatocytes.

Plasma ribavirin trough concentrations at week 4 predict hepatitis C virus (HCV) relapse in HIV-HCV-coinfected patients treated for chronic hepatitis C.

The influence of ribavirin trough concentrations (RBV C(trough)) on the risk of hepatitis C virus (HCV) relapse was retrospectively analyzed in 99 HIV-HCV-coinfected patients who achieved end-of-treatment response with pegylated alpha interferon plus weight-based RBV. The independent predictors (odds ratio [OR] [95% confidence interval (CI)]) of HCV relapse were RBV plasma C(trough) of <2.5 microg/ml (4.5 [1.3 to 15.5]), baseline serum HCV RNA (2.5 [1.2 to 5.1]), and HCV genotype 1 or 4 (13.3 [2.6 to 66.7]). Monitoring of RBV C(trough) may permit early adjustment of RBV dosage to avoid HCV relapse.

Population pharmacokinetic modeling of the association between 63396C->T pregnane X receptor polymorphism and unboosted atazanavir clearance.

Atazanavir (ATV) plasma concentrations are influenced by CYP3A4 and ABCB1, which are regulated by the pregnane X receptor (PXR; NR1I2). PXR expression is correlated with CYP3A4 in liver in the absence of enzyme inducers. The PXR single nucleotide polymorphism (SNP) 63396C→T (rs2472677) alters PXR expression and CYP3A4 activity in vitro, and we previously showed an association of this polymorphism with unboosted ATV plasma concentrations. The aim of this study was to develop a population pharmacokinetic analysis to quantify the impact of 63396C→T and diurnal variation on ATV clearance. A population analysis was performed with 323 plasma samples from 182 randomly selected patients receiving unboosted ATV. Two hundred fifty-nine of the blood samples were collected at random time points, and 11 patients had a full concentration-time profile at steady state. Nonlinear mixed effects modeling was applied to explore the effects of PXR 63396C→T, patient demographics, and diurnal variation. A one-compartment model with first-order absorption and lag time best described the data. Population clearance was 19.7 liters/h with interpatient variability or coefficient of variation (CV) of 21.5%. Homozygosity for the T allele for PXR 63396 was associated with a 17.0% higher clearance that was statistically significant. Evening dosing was associated with 34% higher bioavailability than morning dosing. Patient demographic factors had no effect on ATV clearance. These data show an association of PXR 63396C→T and diurnal variation on unboosted ATV clearance. The association is likely to be mediated through an effect on hepatic PXR expression and therefore expression of its target genes (e.g., CYP3A4, SLCO1B1, and ABCB1), which are known to be involved in ATV clearance.

Use of the HCP5 single nucleotide polymorphism to predict hypersensitivity reactions to abacavir: correlation with HLA-B*5701.

OBJECTIVES: To study the correlation between the HLA-B*5701 allele and the single nucleotide polymorphism in HCP5 (rs2395029). PATIENTS AND METHODS: All HIV patients naive for abacavir seen at our institution between September 2007 and December 2008 were prospectively screened for HLA-B*5701. HCP5 rs2395029 genotyping was carried out by allelic discrimination using the TaqMan 5'-nuclease assay. High-resolution HLA class I typing was undertaken using sequence-specific primers. RESULTS: A total of 245 HIV patients were included in the study. A good correlation between HLA-B*5701 and HCP5 was observed (negative and positive predictive values of 100% and 93%, respectively). CONCLUSIONS: The use of HCP5 rs2395029 testing could be as useful as HLA-B*5701 typing to prevent the abacavir hypersensitivity reaction. Given that HCP5 testing is cheaper, less time-consuming and easier to perform than HLA typing, it may confidently replace the latter in clinical settings.

Hepatic safety profile of raltegravir in HIV-infected patients with chronic hepatitis C.

BACKGROUND: Patients with chronic hepatitis C virus (HCV) infection experience antiretroviral-associated liver toxicity more frequently than HIV mono-infected persons. Herein, we report the hepatic safety profile of raltegravir in a relatively large group of HIV/HCV co-infected patients, a population that was poorly represented in the registrational studies. METHODS: Prospective, observational study of all antiretroviral-experienced HIV-infected patients who initiated raltegravir from January 2006 to January 2009 at a reference HIV clinic. Clinical data, laboratory parameters and liver stiffness measured at baseline, week 4 and every 3 months thereafter were collected. Chronic hepatitis C was defined as positive serum HCV-RNA. Grade 1-4 hepatotoxicity was defined following the AIDS Clinical Trials Group definition for liver enzyme elevations (LEEs). A control group of patients who initiated protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) was examined similarly. RESULTS: Data from 218 HIV-infected patients on raltegravir were analysed, 126 HIV mono-infected and 92 HIV/HCV co-infected patients. Any degree of LEEs occurred in 10 (7.9%) HIV mono-infected and 23 (25%) co-infected patients (relative risk 3.1; 95% confidence interval 2.9-3.4; P = 0.002). Severe hepatotoxicity (grade 3-4), however, was only seen in 3 (1.4%) patients, all co-infected with HCV. It occurred at months 1, 15 and 15, respectively. In all three subjects other reasons than raltegravir exposure most likely explained LEEs. Multivariate analysis revealed HCV co-infection as the only independent variable associated with any degree of hepatotoxicity on raltegravir (P = 0.03). Finally, the rate of LEEs in patients on raltegravir was lower than in those who were treated with PIs or NNRTIs. CONCLUSIONS: LEEs are less frequent in patients treated with raltegravir than with other antiretroviral drug classes. However, HIV/HCV co-infected patients treated with raltegravir experienced LEEs more frequently than HIV mono-infected persons. In this series, LEEs in patients treated with raltegravir were uniformly mild and no cases of grade 3-4 hepatotoxicity could be directly attributed to the drug. These results reinforce the overall hepatic safety profile of raltegravir.

Simplification from protease inhibitors to once- or twice-daily raltegravir: the ODIS trial.

BACKGROUND: Raltegravir has demonstrated good antiviral activity and safety profile in twice-daily (bid) dosing. However, its long terminal elimination half-life might allow once-daily (qd) administration. METHODS: Consecutive HIV-infected individuals at our clinic under protease inhibitor (PI)-based regimens with plasma HIV-RNA <50 copies/mL for > 24 weeks were invited to replace PIs with raltegravir. Patients were randomly assigned to raltegravir 800 mg qd, 400 mg bid, or twice daily for the first 3 months and then once daily. RESULTS: A total of 222 patients completed 24 weeks of follow-up on raltegravir (149 once-daily arm, 35 twice-daily arm, and 38 twice-daily to once-daily arm). At inclusion, mean CD4+ count was 574±308 cells/µL. Within 24 weeks, 13 (5.9%) patients experienced virological failure: 12 (6.4%) in the once-daily arms, and 1 (2.9%) in the twice-daily arm (P = .18). The rate of virological failure was 16.2% (12/74) in patients with prior nucleoside reverse transcriptase inhibitor (NRTI) resistance but only 0.7% (1/148) in the rest (P < .001). CONCLUSION: A switch from PIs to raltegravir in HIV-infected patients with undetectable plasma HIV-RNA effectively sustains viral suppression, as long as prior NRTI resistance had not been selected. No significant differences were seen when comparing raltegravir twice daily or once daily in this context, although once-daily dosing tended to perform less well.

The benefit of simplification from tipranavir/ritonavir 500/200 bid to 500/100 bid guided by therapeutic drug monitoring.

Despite being among the most potent protease inhibitors, the use of tipranavir (TPV) is hampered by a high pill burden and frequent side effects compared with other boosted protease inhibitors. A total of 10 patients receiving TPV/ritonavir (TPV/RTV) 500/200 for longer than 6 months were randomized to stay on the same dosing schedule or switch to TPV/RTV 500/100. Although all patients on TVP/RTV 500/200 remained stable for the next 12 weeks, 3 out of 5 patients who switched doses experienced benefits in terms of reducing aminotransferases and total cholesterol. Fasting triglycerides were also reduced in 2 of them. Plasma HIV-RNA remained undetectable in all patients, despite the observed decline in TPV trough concentrations.

Loss-of-function mutation of PCSK9 as a protective factor in the clinical expression of familial hypercholesterolemia: A case report.

RATIONALE: Proprotein convertase subtilisin/kexin 9 or PCSK9 is a protein whose main function is to regulate the number of low-density lipoprotein receptors (LDLR) present on the cell surface. Loss-of-function mutations in PCSK9 have been related to low LDL-cholesterol levels and a decrease in the risk of cardiovascular events. PATIENT CONCERNS: We present the case of a 27-year-old woman, offspring of a patient with familial homozygous hypercholesterolemia, who presented with mild-moderate hypercholesterolemia. DIAGNOSIS: Genetic analysis was performed by next generation sequencing using a customized panel of 198 genes. Sanger sequencing was used to confirm the presence of the variants of interest. The genetic analysis showed a pathogenic heterozygous mutation in LDLR [exon 6:c.902A>G:p(Asp301Gly)], as well as a loss-of-function heterozygous variant in PCSK9 [exon1:c.137 G>T:p.(Arg46Leu)]. The genetic analysis of the index case's mother revealed compound heterozygosity for 2 different mutations in LDLR [c.902A>G:p.(Asp301Gly); c.1646G>T:p.(Gly549Val)] in exon 6 and in exon 11, respectively, and the same loss-of-function variant in PCSK9 that had been found in her daughter [(PCSK9:exon1:c.137G>T:p.(Arg46Leu)]. The maternal grandfather of the index case presented the same genetic variants as his granddaughter. INTERVENTIONS: The index case did not receive any specific treatment for hypercholesterolemia. The loss-of-function variant in PCSK9 protected her from higher LDL-cholesterol levels, provided she kept partial activity of the LDLR. In her mother, instead, a PCSK9 inhibitor was tried but failed to achieve lipid control. The reason for this may be the complete absence in LDL receptor activity. LDL apheresis was started afterwards, resulting in adequate lipid level control. OUTCOMES: To the date, the index case has achieved to maintain adequate total and LDL-cholesterol levels without any other intervention. She has had no known cardiovascular complication. LESSONS: Loss-of-function mutations in PCSK9 could protect from developing more severe forms of hypercholesterolemia. The finding of these mutations (LDLR-PCSK9) in three consecutive generations could imply an adaptive mechanism against the development of hypercholesterolemia.

Familial hypercholesterolemia: A single-nucleotide variant (SNV) in mosaic at the low density lipoprotein receptor (LDLR).

BACKGROUND AND AIMS: Familial hypercholesterolemia is most frequently caused by genetic variants in the LDLR gene. Most of LDLR pathogenic variants are missense, followed by splicing and deletion/insertions variants. Mosaicism is a genetic condition in which an individual shows more than one clone of cells with different genotypes. The objective of this article was the molecular characterization of a patient with hypercholesterolemia. METHODS AND RESULTS: Genetic analysis of DNA from peripheral blood and saliva was performed by NGS, Sanger sequencing and pyrosequencing technologies. NGS analysis detected the pathogenic variant LDLR:c.1951G > T:p.(Asp651Tyr) in 9%-12% of reads. The presence of the variant was confirmed by pyrosequencing analysis. The variant found was functional characterized using an in vitro model (CHO-ldlA7 cells). Activity and expression of cell surface LDLR were measured by flow cytometry. Colocalization LDLR-Dil-LDL was detected by immunofluorescence. The LDLR activity showed 80% uptake, 50% binding and 53% expression of cell surface LDLR regarding wild type. CONCLUSIONS: Herein, we report the first case of a mosaic single nucleotide variant affecting the LDLR gene in a patient with familial hypercholesterolemia. As it has been described for other pathologies, mosaicism could be underestimated in FH and its detection will improve with the introduction of NGS technologies in the diagnostic routine.