The pathogenic mutations of APOA5 in Chinese patients with hyperlipidemic acute pancreatitis

BACKGROUND AND AIMS

To study the role of gene mutations in the development of severe hypertriglyceridemia (HTG) in patients with hyperlipidemic acute pancreatitis (HLAP), especially different apolipoprotein A5 (APOA5) mutations.

METHODS

Whole-exome sequencing was performed on 163 patients with HLAP and 30 patients with biliary acute pancreatitis (BAP). The pathogenicity of mutations was then assessed by combining clinical information, predictions of bioinformatics programs, information from multiple gene databases, and residue location and conservation. The pathogenic mutations of APOA5 were visualized using the software.

RESULTS

1. Compared with BAP patients, pathogenic mutations of APOA5 were frequent in HLAP patients; among them, the heterozygous mutation of p.G185C was the most common. 2. All six pathogenic mutations of APOA5 identified in this study (p.S35N, p.D167V, p.G185C, p.K188I, p.R223C, and p.H182fs) were positively correlated with severe HTG; they were all in the important domains of apolipoprotein A-V (apoA-V). Residue 223 is strictly conserved in multiple mammals and is located in the lipoprotein lipase (LPL)-binding domain (Pro215-Phe261). When Arg 223 is mutated to Cys 223, the positive charge of this residue is reduced, which is potentially destructive to the binding function of apoA-V to LPL. 3. Four new APOA5 mutations were identified, namely c.563A > T, c.667C > T, c.788G > A, and c.544_545 insGGTGC.

CONCLUSIONS

The pathogenic mutations of APOA5 were specific to the patients with HLAP and severe HTG in China, and identifying such mutations had clinical significance in elucidating the etiology and subsequent treatment.

Gene-environment interaction between APOA5 c.553G>T and pregnancy in hypertriglyceridemia-induced acute pancreatitis

BACKGROUND

The etiology of hypertriglyceridemia (HTG) and, consequently, HTG-induced acute pancreatitis (HTG-AP), is complex.

OBJECTIVE

Herein, we explore a possible gene-environment interaction between APOA5 c.553G>T (p.185Gly>Cys, rs2075291), a common variant associated with altered triglyceride levels, and pregnancy in HTG-AP.

METHODS

We enrolled 318 Chinese HTG-AP patients and divided them into 3 distinct groups: Group 1, male patients (n = 183); Group 2, female patients whose disease was unrelated to pregnancy (n = 105); and Group 3, female patients whose disease was related to pregnancy (n = 30). APOA5 rs2075291 genotype status was determined by Sanger sequencing. A total of 362 healthy Han Chinese subjects were used as controls. Data on body mass index, peak triglyceride level, age of disease onset, episode number, and clinical severity of HTG-AP were collected from each patient. Multiple comparisons, between patient groups, between patient groups and controls, or within each patient group, were performed.

RESULTS

A robust association of APOA5 rs2075291 with HTG-AP in general, and HTG-AP during pregnancy in particular, was demonstrated. The minor T allele showed a stronger association with Group 3 patients than with either Group 1 or Group 2 patients. This stronger association was due mainly to the much higher frequency of TT genotype in Group 3 patients (20%) than that (<6%) in Group 1 and Group 2 patients. Moreover, the TT genotype was associated with a significantly higher peak triglyceride level in Group 3 patients compared with the GG genotype.

CONCLUSION

Our findings provide evidence for an interaction between APOA5 rs2075291 and pregnancy in HTG-AP.

Variants of Lipolysis-Related Genes in Korean Patients with Very High Triglycerides

We investigated the prevalence and characteristics of variants of five lipolysis-related genes in Korean patients with very high triglycerides (TGs). Twenty-six patients with TG levels >885 mg/dL were selected from 13545 Korean subjects. Five candidate genes, LPL, APOC2, GPIHBP1, APOA5, and LMF1, were sequenced by targeted next-generation sequencing. Predictions of functional effects were performed and matched against public databases of variants. Ten rare variants of three genes were found in nine (34.6%) patients (three in LPL, four in APOA5, and three in LMF1). Five were novel and all variants were suspected of being disease-causing. Nine were heterozygous, and one (3.8%) had a homozygous rare variant of LPL. Six common variants of four genes were observed in 25 (96.2%) patients (one in LPL, one in GPIHBP1, two in APOA5, and two in LMF1). The c.G41T variant of GPIHBP1 and c.G533T variant of APOA5 were most frequent and found in 15 (57.7%) and 14 (53.8%) patients, respectively. Rare homozygous variants of the genes were very uncommon, while diverse rare heterozygous variants were commonly identified. Taken together, most study subjects may be manifesting the combined effects of rare heterozygous variants and common variants.

Hypertriglyceridemic acute pancreatitis in emergency department: Typical clinical features and genetic variants

OBJECTIVE

To investigate the clinical characteristics of patients with hypertriglyceridemic acute pancreatitis (HTGAP), and the molecular foundation contributing to hypertriglyceridemia in such patients.

METHODS

Clinical data from 329 patients with acute pancreatitis (AP) were analyzed. The patients were divided into the HTGAP group, with fasting serum triglyceride (TG) levels ≥500 mg/dL (5.65 mmol/L), and the non-HTGAP (NHTGAP) group. Targeted next-generation sequencing was applied to 11 HTGAP patients to identify the genetic mutations associated with hypertriglyceridemia, including apolipoprotein A-V (APOA5), APOC2, APOC3 and APOE, BLK, LPL, GPIHBP1 and LMF1.

RESULTS

Patients in the HTGAP group, compared with those in the NHTGAP group, had a higher mortality rate (7.5% vs 0.7%, P = 0.001), more commonly seen severe AP (17.5% vs 5.2%, P = 0.004) as well as a higher recurrence rate (32.4% vs 19.9%, P = 0.070). DNA sequencing showed that two patients carried the same compound of p.G185C and p.V153M heterozygous mutations located in the APOA5 gene. Two patients carried a homozygous variation of p.C14F, in the GPIHBP1 gene. One patient had a homozygous variation of p.R176C in the APOE gene. And a rare heterozygous LMF1 gene mutation of p.P562R was detected in two patients.

CONCLUSIONS

HTGAP was significantly severe than NHTGAP, with a high recurrence rate. Genetic information may be useful in the clinical setting for the investigation of the pathogenesis of HTGAP and its interventions.

The c.553G>T Genetic Variant of the APOA5 Gene and Altered Triglyceride Levels in the Asian Population: A Meta-Analysis of Case-Control Studies

AIM

To explore the association of the APOA5 gene c.553G>T polymorphism with hypertriglyceridemia (HTG) susceptibility and altered triglyceride levels.

METHODS

We searched the PubMed, Google Scholar, and CNKI databases for published studies relating to analyses of these associations. Case-control and comparative studies of the association between the APOA5 c.553G>T variant and altered triglyceride levels were included. In total, the meta-analysis involved 10 studies on HTG, which provided 2219 cases and 3401 controls. To measure the correlation between the c.553G>T polymorphism and HTG susceptibility, odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. The overall OR was calculated using a random-effects model.

RESULTS

Compared with APOA5 c.553 GG carriers, c.553T carriers displayed an increased risk of HTG in the Asian population, with an overall random effects OR of 3.55 (95% CI: 2.46-5.13) in the dominant model. There was significant heterogeneity among the studies (P_{heterogeneity}: Chi² = 45.80, I² = 75.98%), which may be largely explained by certain patient types. Both the sensitivity analysis and publication bias suggested that the overall result was acceptable. Subgroup analysis showed a large difference in serum triglyceride levels based on the c.553 G > T polymorphism in healthy individuals and HTG patients. APOA5 c.553T carriers exhibit higher triglyceride levels than GG carriers.

CONCLUSION

Our results suggest that APOA5 c. 553T is an independent risk factor for HTG and increased triglyceride levels in the Asian population. APOA5 c. 553T could be employed as a genetic risk marker for HTG and increased triglyceride levels.