KLKB1 and CLSTN2 are associated with HDL-mediated cholesterol efflux capacity in a genome-wide association study

Sexually Dimorphic Effects of CYP2B6 in the Development of Fasting-Mediated Steatosis in Mice: Role of the Oxylipin Products 9-HODE and 9-HOTrE

Background: Cytochrome P450 2B6 (CYP2B6) is a sexually dimorphic, anti-obesity CYP enzyme responsible for the metabolism of xeno- and endobiotics, including the metabolism of polyunsaturated fatty acids (PUFAs) into 9-hydroxyoctadecadienoic acid (9-HODE) and 9-hydroxyoctadecatrienoic acid (9-HOTrE). However, humanized CYP2B6 transgenic (hCYP2B6-Tg) mice are sensitive to diet-induced hepatic steatosis despite their resistance to obesity. The purpose of this study was to determine if 9-HODE, 9-HOTrE, or other factors contribute to the sexually dimorphic steatosis observed in hCYP2B6-Tg mice. Results: Cyp2b9/10/13-null (Cyp2b-null) mice were injected with either 9-HODE or 9-HOTrE for 2 days and were then subjected to a fasting period of 20 h to induce steatosis. Serum lipids were moderately increased, especially in females, after 9-HODE (triglycerides (TGs), very low-density lipoproteins (VLDLs)) and 9-HOTrE (high-density lipoproteins (HDLs), low-density lipoproteins (LDLs), cholesterol) treatment. No change in hepatic lipids and few changes in hepatic gene expression were observed in mice treated with either oxylipin, suggesting that these oxylipins had minimal to moderate effects. Therefore, to further investigate CYP2B6's role in steatosis, hCYP2B6-Tg and Cyp2b-null mice were subjected to a 20 h fast and compared. Both male and female hCYP2B6-Tg mice exhibited increased steatosis compared to Cyp2b-null mice. Serum cholesterol, triglycerides, HDLs, and VLDLs were increased in hCYP2B6-Tg males. Serum triglycerides and VLDLs were decreased in hCYP2B6-Tg females, suggesting the greater hepatic retention of lipids in females. Hepatic oxylipin profiles revealed eight perturbed oxylipins in female hCYP2B6-Tg mice and only one in males when compared to Cyp2b-null mice. RNA-seq also demonstrated greater effects in females in terms of the number of genes and gene ontology (GO) terms perturbed. There were only a few overlapping GO terms between sexes, and lipid metabolic processes were enriched in hCYP2B6-Tg male mice but were repressed in hCYP2B6-Tg females compared to Cyp2b-nulls. Conclusions: hCYP2B6-Tg mice are sensitive to fasting-mediated steatosis in males and females, although the responses are different. In addition, the oxylipins 9-HODE and 9-HOTrE are unlikely to be the primary cause of CYP2B6's pro-steatotic effects.

Lipoprotein(a) concentrations and cardiovascular disease in patients with chronic kidney disease: Results from the German Chronic Kidney Disease study

BACKGROUND

Lipoprotein(a) (Lp(a)) is a causal, genetically determined risk factor for cardiovascular disease (CVD) in the general population. Patients with chronic kidney disease (CKD) have an increased CVD risk and elevated Lp(a) concentrations. Only a few studies on Lp(a) were performed in persons with mild-to-moderate CKD; none of them used genetic variants to explore potential causal associations.

OBJECTIVES

This study aims to investigate the association of measured and genetically predicted Lp(a) concentrations on prevalent and incident CVD events in the German Chronic Kidney Disease (GCKD) study.

METHODS

The study included 5043 participants of European ancestry with an estimated glomerular filtration rate (eGFR) between 30 and 60 mL/min/1.73 m2 or an eGFR >60 mL/min/1.73 m2 in the presence of overt albuminuria with a follow-up of 6.5 years.

RESULTS

With each 10 mg/dL higher Lp(a) concentration, odds for prevalent CVD (1290 events) increased 1.065-fold (95%CI: 1.042-1.088, p < 0.001). The risk was significantly higher in patients with Lp(a) ≥50 mg/dL but most pronounced in Lp(a) ≥70 mg/dL (odds ratio = 1.775 [1.409-2.231], p < 0.001) compared to Lp(a) <30 mg/dL. Each 10 mg/dL higher Lp(a) concentration and Lp(a) ≥70 mg/dL increased the risk for incident 3-point major adverse cardiovascular events (MACEs) (474 events): hazard ratio [HR] = 1.037 [1.009-1.067], p = 0.009 and HR = 1.335 [1.001-1.781], p = 0.050), respectively. Similar results were obtained for 4-point MACE (653 events). Analyses based on apo(a) isoforms and genetically predicted Lp(a) concentrations led to even stronger associations.

CONCLUSIONS

In patients with mild-to-severe CKD, elevated Lp(a) concentrations and genetic determinants of Lp(a) concentrations are significantly associated with CVD at baseline and during follow-up, independent of traditional risk factors.

Performing highly parallelized and reproducible GWAS analysis on biobank-scale data

Genome-wide association studies (GWAS) are transforming genetic research and enable the detection of novel genotype-phenotype relationships. In the last two decades, over 60 000 genetic associations across thousands of traits have been discovered using a GWAS approach. Due to increasing sample sizes, researchers are increasingly faced with computational challenges. A reproducible, modular and extensible pipeline with a focus on parallelization is essential to simplify data analysis and to allow researchers to devote their time to other essential tasks. Here we present nf-gwas, a Nextflow pipeline to run biobank-scale GWAS analysis. The pipeline automatically performs numerous pre- and post-processing steps, integrates regression modeling from the REGENIE package and supports single-variant, gene-based and interaction testing. It includes an extensive reporting functionality that allows to inspect thousands of phenotypes and navigate interactive Manhattan plots directly in the web browser. The pipeline is tested using the unit-style testing framework nf-test, a crucial requirement in clinical and pharmaceutical settings. Furthermore, we validated the pipeline against published GWAS datasets and benchmarked the pipeline on high-performance computing and cloud infrastructures to provide cost estimations to end users. nf-gwas is a highly parallelized, scalable and well-tested Nextflow pipeline to perform GWAS analysis in a reproducible manner.