Supplementary Material for: Influence of the IDOL Gene Variants on LDL-C Levels in Turkısh Patients with Familial Hypercholesterolemia

INTRODUCTION
The inducible degrader of low-density lipoprotein receptor (IDOL), an E3 ubiquitin ligase, was recently identified as a regulator of the LDL receptor (LDLR) pathway. Shortly, IDOL stimulates LDLR degradation through ubiquitination. However, the association of IDOL gene variants with plasma lipid levels is controversial. No previous study in the Turkish population has reported the relationship between variants of the IDOL gene and LDL-C levels. Our study aims to investigate the effects of genetic variants in the human IDOL gene, which may be a therapeutic target in human cholesterol metabolism, on LDL-C levels.
METHODS
We sequenced all coding, critical intronic, and untranslated regions of the IDOL gene in 125 controls (77 women, 48 men) and 125 patients (64 women, 61 men) with definite or probable Familial Hypercholesterolemia (FH) according to the criteria of the Dutch Lipid Clinic Network (DLCN), in whom no pathogenic/likely pathogenic LDLR variants are present.
RESULTS
We identified 12 different IDOL gene variants, including the p.(N342S) and p.(G51S), whose association with LDL-C levels has been investigated, and classified them into common and rare variants. A rare variant p.(G51S) was only detected in patients the patient group. We compared the Minor Allele Frequency (MAF) distribution of common variants between patient and control groups and examined the association of their genotypic distribution with plasma LDL-C levels using genetic models (dominant, recessive, overdominant, codominant). There was no statistically significant difference in the parameters of the patient and control groups (p>0.05).
CONCLUSION
Our findings suggest that the common IDOL variants we identified do not associate with the LDL-C level in the Turkish population. Rare variants, that were not found to be statistically significant in our study, should be emphasized and supported with further research.

引言
诱导型低密度脂蛋白受体降解蛋白（inducible degrader of low-density lipoprotein receptor，IDOL）是一种E3泛素连接酶（E3 ubiquitin ligase），近期被鉴定为低密度脂蛋白受体（low-density lipoprotein receptor，LDLR）通路的调控因子。简而言之，IDOL可通过泛素化作用促进LDLR的降解。然而，IDOL基因变异与血浆脂质水平之间的关联尚存争议。此前尚无针对土耳其人群的研究报道IDOL基因变异与低密度脂蛋白胆固醇（low-density lipoprotein cholesterol，LDL-C）水平之间的关联。本研究旨在探究可作为人类胆固醇代谢治疗靶点的人IDOL基因的遗传变异对LDL-C水平的影响。

研究方法
我们对125名对照个体（女性77名，男性48名）以及125名符合荷兰脂质诊所网络（Dutch Lipid Clinic Network，DLCN）标准的确诊或疑似家族性高胆固醇血症（Familial Hypercholesterolemia，FH）患者的IDOL基因全部编码区、关键内含子区及非翻译区进行了测序，所有受试者均未携带致病性/疑似致病性LDLR变异。

研究结果
我们共鉴定出12种不同的IDOL基因变异，其中包括p.(N342S)与p.(G51S)（其与LDL-C水平的关联已有相关研究），并将这些变异分为常见变异与罕见变异两类。罕见变异p.(G51S)仅在患者组中被检出。我们比较了患者组与对照组间常见变异的次要等位基因频率（Minor Allele Frequency，MAF）分布情况，并采用显性、隐性、超显性及共显性四种遗传模型分析了其基因型分布与血浆LDL-C水平之间的关联。患者组与对照组的各项参数均无统计学显著性差异（p>0.05）。

结论
本研究结果表明，在土耳其人群中，我们鉴定出的常见IDOL基因变异与LDL-C水平无显著关联。本研究未发现具有统计学显著性的罕见变异，此类变异仍需进一步研究加以验证与补充。