Screening and verifying the mutations in the LDLR and APOB genes in a Chinese family with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder. The primary objective of this study was to identify the major pathogenic mutations in a Chinese family with FH.

METHODS

Whole-genome sequencing (WGS) was used to identify variants of FH-related genes, including low-density lipoprotein receptor (LDLR), apolipoprotein B (APOB), and proprotein convertase subtilisin/kexin 9 (PCSK9). Bioinformatics software was used to predict signal peptides, transmembrane structures, and spatial construction information of the mutated sequences. Western blotting was performed on the mutant protein to determine the presence of the major structural domains of the LDLR. The PCSK9 and APOB genes were screened and analyzed. Moreover, the proband and his brother were treated with a PCSK9 inhibitor for 1 year, and the effect of the treatment on lipid levels was assessed.

RESULTS

WGS revealed two potentially pathogenic mutations in the LDLR gene. One was a novel mutation, c.497delinsGGATCCCCCAGCTGCATCCCCCAG (p. Ala166fs), and the other was a known pathogenic mutation, c.2054C>T (p. Pro685Leu). Bioinformatics prediction and in vitro experiments revealed that the novel mutation could not be expressed on the cell membrane. Numerous gene variants were identified in the APOB gene that may have a significant impact on the family members with FH. Thus, it is suggested that the severe manifestation of FH in the proband primarily resulted from the cumulative genetic effects of variants in both LDLR and APOB. However, a subsequent study indicated that treatment with a PCSK9 inhibitor (Evolocumab) did not significantly reduce the blood lipid levels in the proband or his brother.

CONCLUSIONS

The cumulative effect of LDLR and APOB variants was the primary cause of elevated blood lipid levels in this family. However, PCSK9 inhibitor therapy did not appear to be beneficial for the proband. This study emphasizes the importance of genetic testing in determining the most suitable treatment options for patients with FH.

Association between the triglyceride-glucose index and the presence and prognosis of coronary microvascular dysfunction in patients with chronic coronary syndrome

BACKGROUND

Coronary microvascular dysfunction (CMD) is a strong determinant of prognosis in patients with chronic coronary syndrome (CCS). The triglyceride-glucose index (TyG index), an alternative method to evaluate insulin resistance, is positively correlated with the incidence and adverse outcomes of cardiovascular diseases. However, the relationship between the TyG index and the presence and prognosis of CMD in CCS patients has not been investigated. Therefore, we aimed to evaluate the association between the TyG index and the presence and clinical outcomes of CMD among CCS patients.

METHODS

CCS patients who underwent coronary angiography between June 2015 to June 2019 were included. The TyG index was calculated as Ln[fasting triglycerides (mg/dL) × fasting blood glucose (mg/dL)/2]. Coronary angiography‑derived index of microvascular resistance (caIMR) was used to measure microvascular function, and CMD was defined as caIMR ≥ 25U. Patients with CMD were divided into three groups (T1, T2, and T3 groups) according to TyG tertiles. The primary endpoint was major adverse cardiac event (MACE).

RESULTS

Of 430 CCS patients, 221 patients had CMD. CMD patients had significantly higher TyG index than those without CMD. Sixty-three MACE was recorded during the follow-up duration among CMD patients, and the incidence rate of MACE was higher in the T3 group compared to T1/T2 groups (39.2% vs. 20.5% vs. 25.7%; P = 0.035). Multivariable logistic regression analysis showed that the TyG index was an independent predictor of CMD (OR, 1.436; 95% CI, 1.014-2.034; P = 0.042). Compared to the T1 group, the T3 group strongly correlated with the risk of MACE in CMD patients even after adjusting for additional confounding risk factors (HR, 2.132; 95%CI, 1.066-4.261; P = 0.032).

CONCLUSION

TyG index is significantly associated with the risk of CMD, and it is an independent predictor of MACE among CMD patients with CCS. This study suggests that the TyG index has important clinical significance for the early prevention and risk stratification of CMD.