Association of HMGCR rs17671591 and rs3761740 with lipidemia and statin response in Uyghurs and Han Chinese

Introduction

Cardiovascular disease (CVD) is the primary cause of human death, and constitutes significant health and economic burdens worldwide (Tsao et al., 2023; Ralapanawa & Sivakanesan, 2021; Erbel et al., 2014). Coronary heart disease kills more than 7.96 million people worldwide in 2006 and 9.48 million in 2016 (GBD 2016 Causes of Death Collaborators, 2016). CVD is a complex disease that involves multiple mechanisms and cell types, and is affected by many risk factors such as diabetes, hyperlipidemia, smoking, hypertension, lack of exercise, obesity, and heredity (Visseren et al., 2021). Dyslipidemia plays a very important role in the occurrence and development of CVD (Arvanitis & Lowenstein, 2023; O’Malley et al., 2020).

Dyslipidemia is a disease characterized by a series of lipid metabolic disorders, such as those involving abnormally elevated plasma levels of lipid and lipoprotein dysfunction (Wang et al., 2018; Ahmad & Leake, 2019). Dyslipidemia is mainly characterized by an increase in plasma total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), triglyceride (TG), and a decrease in high density lipoprotein cholesterol (HDL-C) (Smith, 2019; Xiao et al., 2019). Dyslipidemia is a major risk factor for CVD according to data from 2009 to 2012, with more than 100 million American adults age 20 and older having total cholesterol levels of 200 mg/dL (5.17 mol /L) or higher, and nearly 31 million having total cholesterol levels of 240 mg/dL (6.20 mol /L) or higher (Mozaffarian et al., 2016). Genetic factors, including single nucleotide polymorphisms (SNPs), are a major risk factor for dyslipidemia (Liu et al., 2017; Lu et al., 2017).

Mammalian 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is an endoplasmic reticulum-localized glycoprotein consisting of a hydrophobic n-terminal domain that spans the cell membrane eight times and a large soluble C-terminal domain that projects into the cytoplasm (Liscum et al., 1985). HMGCR is a rate-limiting enzyme for cholesterol synthesis and is closely related to plasma cholesterol content (Luo, Yang & Song, 2020).

Statins are currently recognized as the primary treatment for lowering blood lipids (Grundy et al., 2019). HMGCR is both a rate-limiting enzymatic step for endogenous cholesterol production and a therapeutic target for statins, which reduce cholesterol production in the liver (Istvan & Deisenhofer, 2001). The reduction of cholesterol in the liver further leads to the upregulation of low-density lipoprotein receptors, which enhances the clearance of TC and LDL-C from the circulation, thereby reducing lipid levels (Brown & Goldstein, 1997). However, despite the effectiveness of statins, there is significant variation in how individual patients respond to them (Simon et al., 2006). Pharmacogenetic studies have demonstrated the effect of genetic polymorphism on the wide variability of responses to statins observed in patients (Reiner, 2014; Schmitz & Drobnik, 2003). In addition, genome-wide association studies have identified several genetic variants associated with higher or lower responses to statin therapy, primarily in genes associated with cholesterol homeostasis (Barber et al., 2010). It has also been reported that HMGCR SNPS are associated with lipid levels after statin treatment (Cuevas et al., 2016).

HMGCR is the rate-limiting enzyme for cholesterol synthesis and the main target of statin therapy. In this study, HMGCR rs17671591 and rs3761740 were selected to evaluate their effects on blood lipid levels and the lipid-lowering effect of statin in Han Chinese and Uyghur populations.

Method

Subjects

This is a single-center prospective cohort study of the effects of HMGCR rs17671591 and rs3761740 on blood lipid levels before lipid-lowering therapy and statin responsiveness. In this study, patients who were hospitalized in the Heart Center of the First Affiliated Hospital of Xinjiang Medical University from 2008 to 2022 with long-term oral statins were selected, and patients’ informed consent and signatures were required. Inclusion criteria: a) Uyghur or Han population aged 30–75; b) first diagnosed with coronary heart disease after admission; c) never took lipid-lowering medication before admission; d) started oral statin (atorvastatin 10 mg/day, rosuvastatin 5 mg/day) lipid-lowering treatment after admission; and e) follow up time ≥1 month. Exclusion criteria: a) patients with lost follow-up data; b) patients who adjusted their medication dosage or changed to different types of statins during the follow-up period; c) chronic renal insufficiency; d) fatty liver; e) cirrhosis; f) thyroid disease; or g) patients with genetic sequencing errors. The specific process is shown in Fig. 1. The hospital information platform was used to collect information of patients. Clinical data, blood lipid levels, and biochemical indexes of each patient were collected before oral statin and after oral statin administration for >1 month. The following information was collected: ethnicity, sex, age, blood glucose, alanine aminotransferase (ALT), TC, TG, HDL-C, LDL-C, apolipoprotein A1 (APOA1), apolipoprotein (APOB), lipoprotein a (Lpa), and non-HDL-C, where non-HDL-C = TC-HDL-C. All specimens collected were transported to the Xinjiang CHD VIP Laboratory on dry ice at predetermined intervals. Blood glucose, ALT, TC, TG, HDL-C, LDL-C, APOA1, APOB, and Lpa were all tested by the clinical laboratory of the First Affiliated Hospital of Xinjiang Medical University using a biochemical analyzer (Dimension AR/AVL Clinical Chemistry System, Newark, NJ, USA).

Results

Discussion

In this project, we mainly studied the effects of rs17671591 and rs3761740 of HMGCR on plasma lipid levels before and after oral statin in Han Chinese and Uyghur populations, as well as the effects on lipid lowering response after oral statin in two populations.

Mammalian HMGCR is an ER-localized glycoprotein consisting of a hydrophobic N-terminal domain that spans the membrane eight times, large hydrophilic C-terminal domain located on the cytoplasmic side, transmembrane domains 2–6 that function as a sterol-sensing domain (SSD) that sensitizes HMGCR to sterol levels in the endoplasmic reticulum, and a cytoplasmic C-terminal domain that is responsible for converting HMG-CoA to valerate using two NADPH molecules as reducing agents (Liscum et al., 1985). HMGCR plays one of the most important roles in cholesterol biosynthesis and is one of the two rate-limiting enzymes in cholesterol biosynthesis. It is also regulated by many factors and is crucial for maintaining lipid homeostasis in the body (Luo, Yang & Song, 2020). HMGCR is the main target of statins for lipid reduction (Istvan & Deisenhofer, 2001).

Some studies have proved that effective lipid changes can be seen in the 4th week of atorvastatin dose range of 10–80 mg (Jones et al., 2005), and this result has also been proved in other studies (Szapary et al., 2004) where the lipid level remained basically stable after 4 weeks (Cannon et al., 2004; Niemi et al., 2004), and so this study selected patients who took oral statin for more than 1 month as the study object. In the Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines, the dosing recommendations were provided according to SLCO1B1, ABCG2, and CYP2C9 genotypes. A dose of atorvastatin at 10 mg once daily and a dose of rosuvastatin at 5 mg once daily is associated with the lowest risk for statin-associated musculoskeletal symptoms (Cooper-DeHoff et al., 2022), so we chose patients who took 10 mg of atorvastatin daily or 5 mg of rosuvastatin daily as subjects. In this study, we confirmed that oral statin can effectively reduce TC, TG, LDL-C, and APOB, which is consistent with the results of Jones et al. (2005). However, the effect of statins on HDL-C is controversial. Jones et al.’s (2005) study proved that statins can increase HDL-C, while Szapary et al.’s (2004) study proved that statin treatment does not affect the plasma concentration of HDL-C. This difference may be related to the dose of statin or the different ethnic genetic background of the study subjects. In this study, it was proved that the plasma HDL-C concentration of the Han population was significantly reduced after statin treatment, while the plasma HDL-C concentration of the Uyghur population was not significantly changed after statin treatment. Our study also proved that statins can effectively reduce plasma levels of TG, TC, LDL-C, APOA1, APOB, and non-HDL-C in both Han and Uyghur subjects.

The rs17671591 polymorphism is an intergenic variation located near the HMGCR gene promoter region (chr5:74,615,021); however, it is not directly located in the gene expression regulatory element or the region affecting the enzyme structure or conformation. The dominant model of rs17671591 polymorphism is associated with HDL-C plasma levels and affects the change of LDL-C and HDL-C plasma concentrations after statin treatment (Cuevas et al., 2016). The Treating to New Targets (TNT) study also showed an association between HMGCR rs17671591 and statin response (Thompson et al., 2009), but a genome-wide association (GWAS) study also proved that rs17671591 polymorphism was not associated with low density lipoprotein level after taking atorvastatin (Deshmukh et al., 2012). In this study, we found that the HMGCR rs17671591 genotype was associated with the rate of high TC before oral statin, APOA1 and the rate of high APOA1 after oral statin, and the change of APOA1 after oral statin in Han subjects. In the Uyghur population, we found that the HMGCR rs17671591 genotype was associated with LDL-C, low HDL-C, high LDL-C, high TC, and high non-HDL-C before oral statin; LDL-C, and high LDL-C after oral statin; and the change of LDL-C after oral statin. The difference of rs17671591 effects between the two ethnic groups may be due to their different genetic backgrounds.

The rs3761740 polymorphism is a variant located in the upstream region of the HMGCR gene chr5:75336308 (GRCh38.p14), but it not directly located in gene expression regulatory elements or regions affecting enzyme structure or conformation. Previous studies have not found a correlation between rs3761740with LDL-C and statins response to LDL-C effect (Angelini et al., 2017). However, the results of this study are not completely consistent with this. In the Han population, there was no significant correlation between rs3761740 with blood lipids and lipid-lowering effect of statins. In the Uyghur population, we found that the HMGCR rs3761740 genotype was associated with TC, LDL-C, non-HDL-C, the rate of high TC, the rate of high LDL-C, the rate of high non-HDL-C before oral statin; and TC, TG, LDL-C, APOB, highTC, high LDL-C, low HDL-C, high APOB, and high non-HDL-C after oral statin.

The lipid-lowering effect of statins is different for each person. Many genetic mutations are related to the effectiveness of statins. These genes can be divided into two groups. First are those that are directly related to lipoprotein metabolism and affect either LDL production or its catabolism. The second group are drug metabolism–related genes that affect statin pharmacokinetics. Some studies have proved that the genetic variation of HMGCR is related to the resistance of statins, but it is not certain if it is due to the ability of statins to inhibit the enzyme or from the greater compensatory upregulation of the HMGCR gene (Sun et al., 2023). High-dose statin therapy is associated with lower blood lipids (Li et al., 2021), but the risk of intolerance with high-dose statins is also increased (Cooper-DeHoff et al., 2022). It is very important to predict the lipid-lowering effect of statins and choose low-dose statins that can effectively reduce blood lipids according to the predicted results. In our study, we found that the HMGCR rs17671591 additive model (CT and CC+TT) was associated with the change of LDL-C after oral statin in the Uyghur population. This SNP can be used to predict the efficacy of statins in the Chinese Uyghur population and provide strategies for precision therapy.

Different genetic models are supported by their assumed inheritance pattern, although no optimal models have been established (Horita & Kaneko, 2015). The levels of significance obtained from different models may be similar, but not exactly the same (Horita & Kaneko, 2015; Clarke et al., 2011). Although the analysis of multiple models may lead to concerns about multiple comparisons, the unified direction and association obtained may further support the association between SNP and disease status (Horita & Kaneko, 2015; Wu et al., 2015). In this study, different gene models were established to verify the relationship between each gene model, blood lipids, and statin response, and the consistent influence on the direction and association of each model can better support the conclusions.

The differences between this study and previous studies and between Han and Uyghur populations in this study are not surprising, as lipid concentrations are a complex feature of environmental and genetic factors and their interactions. Because genetic studies rely primarily on genetic diversity, other unexplained interactions are often excluded, including traits such as age, sex, ethnic origin, sample size, heterogeneity among patients, study design, use of different endpoints, evaluation time, drug dosage, strict inclusion/exclusion criteria, and underlying disease. As a result, it becomes very difficult to draw the same conclusions after comparing different studies, so the results tend to apply only to specific populations.

This study also has some limitations. First of all, the multivariate adjustment factors included in this study only included age, sex, and liver function as possible risk factors, but did not include other potential risk factors affecting blood lipids including diet, exercise, smoking, drinking, and BMI. Second, the follow-up time of this study was ≥1 month and was not fixed, but we ensured that each subject did not change the lipid-lowering drugs and dosage during the study period. Some studies have proved that blood lipids tend to be stable after oral statin for 4 weeks (Cannon et al., 2004; Niemi et al., 2004), so the unfixed time had little effect on blood lipids after taking drugs.

Conclusion

In this article, we mainly studied the effects of HMGCR rs17671591 and rs3761740 on plasma lipid levels before and after oral statin in Han Chinese and Uyghur populations, as well as the effects on lipid lowering response after oral statin in two populations. We found that the SNP of HMGCR was associated with the lipid-lowering effect of statins and provides the possibility to predict the reactivity of statins in different individuals.

Supplemental Information