Rare LPL gene missense mutation in an infant with hypertriglyceridemia

Characterization of sexual dimorphism in ANGPTL4 levels and function

ANGPTL4 is an attractive pharmacological target for lowering plasma triglycerides and cardiovascular risk. Since most preclinical studies on ANGPTL4 were performed in male mice, little is known about sexual dimorphism in ANGPTL4 regulation and function. Here, we aimed to study potential sexual dimorphism in ANGPTL4 mRNA and protein levels and ANGPTL4 function. Additionally, we performed exploratory studies on the function of ANGPTL4 in the liver during fasting using Angptl4-transgenic and Angptl4-/- mice. Compared to female mice, male mice showed higher hepatic and adipose ANGPTL4 mRNA and protein levels, as well as a more pronounced effect of genetic ANGPTL4 modulation on plasma lipids. By contrast, very limited sexual dimorphism in ANGPTL4 levels was observed in human liver and adipose tissue. In human and mouse adipose tissue, ANGPTL8 mRNA and/or protein levels were significantly higher in females than males. Adipose LPL protein levels were higher in female than male Angptl4-/- mice, which was abolished by ANGPTL4 (over) expression. At the human genetic level, the ANGPTL4 E40K loss-of-function variant was associated with similar plasma triglyceride reductions in women and men. Finally, ANGPTL4 ablation in fasted mice was associated with changes in hepatic gene expression consistent with PPARα activation. In conclusion, the levels of ANGPTL4 and the magnitude of the effect of ANGPTL4 on plasma lipids exhibit sexual dimorphism. Nonetheless, inactivation of ANGPTL4 should confer a similar metabolic benefit in women and men. Expression levels of ANGPTL8 in human and mouse adipose tissue are highly sexually dimorphic, showing higher levels in females than males.

Rare novel LPL mutations are associated with neonatal onset lipoprotein lipase (LPL) deficiency in two cases

Background

Lipoprotein lipase (LPL) deficiency is a monogenic lipid metabolism disorder biochemically characterized by hypertriglyceridemia (HTG) inherited in an autosomal recessive manner. Neonatal onset LPL deficiency is rare. The purpose of this study was to clarify the clinical features of neonatal LPL deficiency and to analyze the genetic characteristics of LPL gene.

Methods

In order to reach a definite molecular diagnose, metabolic diseases-related genes were sequenced through gene capture and next generation sequencing. Meanwhile, the clinical characteristics and follow-up results of the two newborns were collected and analyzed.

Results

Three different mutations in the LPL gene were identified in the two newborns including a novel compound heterozygous mutation (c.347G > C and c.472 T > G) and a reported homozygous mutation (c.836 T > G) was identified. Interestingly, both the two neonatal onset LPL deficiency patients presented with suffered recurrent infection in the hyperlipidemia stage, which was not usually found in childhood or adulthood onset LPL deficiency patients.

Conclusion

The two novel mutaitons, c.347G > C and c.472 T > G, identified in this study were novel, which expanded the LPL gene mutation spectrum. In addition, suffered recurrent infection in the hyperlipidemia stage implied a certain correlation between immune deficiency and lipid metabolism abnormality. This observation further supplemented and expanded the clinical manifestations of LPL deficiency.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12887-021-02875-x.

A Novel Lipoprotein Lipase Mutation in an Infant With Glycogen Storage Disease Type-Ib and Severe Hypertriglyceridemia

Glycogen storage disease (GSD) Ib is a rare genetic metabolic disorder caused by gene mutation in the glucose 6-phosphate transport gene SLC37A4 (OMIM# 602671). This study aimed to explore the association between a novel lipoprotein lipase (LPL) mutation and severe hypertriglyceridemia in a GSD Ib infant with severe hypertriglyceridemia. A 5-month-old girl was admitted to our hospital because of repeated episodes of low-grade fever over the past month and because of neutropenia. The patient was diagnosed with GSD Ib and severe hypertriglyceridemia based on clinical manifestations and laboratory test results. Next-generation sequencing and Sanger sequencing were then applied to DNA from the peripheral blood of the patient and her parents to analyze gene mutations. Pathogenicity prediction analysis was performed using Sorting Intolerant From Tolerant (SIFT) and PolyPhen-2 platforms. The results revealed that this infant carried a compound heterozygous variation in the SLC37A4 gene, a c.1043T > C (p.L348P) mutation derived from her mother and a c.572C > T (p.P191L) mutation derived from her father. In addition, a novel c.483delA (p. A162Pfs^*10) frameshift mutation was found in the patient's LPL gene exon 4, which was derived from the heterozygous carrier of her father. The SIFT and PolyPhen-2 prediction programs indicated that these mutations were likely harmful. Medium-chain triglyceride milk and granulocyte colony-stimulating factor subcutaneous injection alleviated the symptoms. Our findings identified a novel LPL gene frameshift mutation combined with SLC37A4 gene compound heterozygous mutations in a GSD Ib infant with severe hypertriglyceridemia.

Structure and Function of Angiopoietin-like Protein 3 (ANGPTL3) in Atherosclerosis

BACKGROUND

Angiopoietin-Like Proteins (ANGPTLs) are structurally related to the angiopoietins. A total of eight ANGPTLs (from ANGPTL1 to ANGPTL8) have been identified so far. Most ANGPTLs possess multibiological functions on lipid metabolism, atherosclerosis, and cancer. Among them, ANGPTL3 has been shown to regulate the levels of Very Low-Density Lipoprotein (VLDL) made by the liver and play a crucial role in human lipoprotein metabolism.

METHOD

A systematic appraisal of ANGPTLs was conducted, focusing on the main features of ANGPTL3 that has a significant role in atherosclerosis.

RESULTS

Angiopoietins including ANGPTL3 are vascular growth factors that are highly specific for endothelial cells, perform a variety of other regulatory activities to influence inflammation, and have been shown to possess both pro-atherosclerotic and atheroprotective effects.

CONCLUSION

ANGPTL3 has been demonstrated as a promising target in the pharmacological management of atherosclerosis. However, many questions remain about its biological functions.

Blood miR-1275 is associated with risk of ischemic stroke and inhibits macrophage foam cell formation by targeting ApoC2 gene

Apolipoprotein C2 (ApoC2) is an important member of the apolipoprotein C family and functions as a major activator of lipoprotein lipase (LPL). In cardiovascular and cerebrovascular systems, the lipolytic activity of the LPL-ApoC2 complex is critical for the metabolism of triglyceride-rich lipoproteins and contributes to the pathogenesis of ischemic stroke (IS). However, the regulation of ApoC2 in IS development remains unclear. In this study, we first explored potential ApoC2-targeting microRNAs (miRNAs) by bioinformatics tool and compared the miRNA expression profiles in the blood cells of 25 IS patients and 25 control subjects by miRNA microarray. miR-1275 was predicted to bind with the 3' untranslated region of ApoC2, and a significant reduction of blood miR-1275 levels was observed in IS patients. Dual-luciferase reporter assay and quantitative RT-PCR confirmed the regulation of ApoC2 by miR-1275 in THP-1 derived macrophages. miR-1275 also inhibited cellular uptake of ox-LDL and suppressed formation of macrophage foam cell. Furthermore, the whole blood miR-1275 levels were validated in 279 IS patients and 279 control subjects by TaqMan assay. miR-1275 levels were significantly lower in IS cases and logistic regression analysis showed that miR-1275 level was negatively associated with the occurrence of IS (adjusted OR, 0.76; 95% CI, 0.69-0.85; p < 0.001). Addition of miR-1275 to traditional risk factors showed an additive prediction value for IS. Our study shows that blood miR-1275 levels were negatively associated with the occurrence of IS, and miR-1275 might exert an athero-protective role against the development of IS by targeting ApoC2 and blocking the formation of macrophage foam cells.

Rare LPL gene missense mutation in an infant with hypertriglyceridemia

BACKGROUND

Severe hypertriglyceridemia usually results from a combination of genetic and environmental factors and is most often attributable to mutations in the lipoprotein lipase (LPL) gene.

OBJECTIVES

The aim of this study was to identify rare mutations in the LPL gene causing severe hypertriglyceridemia.

METHODS

A Chinese infant who presented classical features of severe hypertriglyceridemia recruited for DNA sequencing of the LPL gene. The pathogenicity grade of the variants was defined based on the prediction of pathogenicity using in silico prediction tools. Review some studies to understand the molecular mechanisms underlying the severe hypertriglyceridemia.

RESULTS

We identified a rare mutation in the LPL gene causing severe hypertriglyceridemia: a nucleotide substitution (c.836T>G) resulting in a leucine to arginine substitution at position 279 of the protein (p.Leu279Arg).The pathogenicity of the variant was predicted by in silico analysis using PolyPhen2 and SIFT prediction programs, which indicated that mutation p.Leu279Arg is probably harmful. We have also reviewed published studies concerning the molecular mechanisms underlying severe hypertriglyceridemia. A missense mutation in the 6 exon of the LPL gene is reportedly associated with LPL deficiency.

CONCLUSIONS

We have here identified a rare pathogenic mutation in the LPL gene in a Chinese infant with severe hypertriglyceridemia.