Genetic variants in PCSK1 gene are associated with the risk of coronary artery disease in type 2 diabetes in a Chinese Han population: a case control study

Peak-agnostic high-resolution cis-regulatory circuitry mapping using single cell multiome data

Single same cell RNAseq/ATACseq multiome data provide unparalleled potential to develop high resolution maps of the cell-type specific transcriptional regulatory circuitry underlying gene expression. We present CREMA, a framework that recovers the full cis-regulatory circuitry by modeling gene expression and chromatin activity in individual cells without peak-calling or cell type labeling constraints. We demonstrate that CREMA overcomes the limitations of existing methods that fail to identify about half of functional regulatory elements which are outside the called chromatin 'peaks'. These circuit sites outside called peaks are shown to be important cell type specific functional regulatory loci, sufficient to distinguish individual cell types. Analysis of mouse pituitary data identifies a Gata2-circuit for the gonadotrope-enriched disease-associated Pcsk1 gene, which is experimentally validated by reduced gonadotrope expression in a gonadotrope conditional Gata2-knockout model. We present a web accessible human immune cell regulatory circuit resource, and provide CREMA as an R package.

Effects of the maternal and fetal proteome on birth weight: a Mendelian randomization analysis

Fetal growth is an indicator of fetal survival, regulated by maternal and fetal factors, but little is known about the underlying molecular mechanisms. We used Mendelian randomization to explore the effects of maternal and fetal genetically-instrumented plasma proteins on birth weight using genome-wide association summary data (n=406,063 with maternal and/or fetal genotype), with independent replication (n=74,932 mothers and n=62,108 offspring), and colocalisation. Higher genetically-predicted maternal levels of PCSK1 increased birthweight (mean-difference: 9g (95% CI: 5g, 13g) per 1 standard deviation protein level). Higher maternal levels of LGALS4 decreased birthweight (-54g (-29g, -80g)), as did VCAM1, RAD51D and GP1BA. In the offspring, higher genetically-predicted fetal levels of LGALS4 (46g (23g, 70g)) increased birthweight, alongside FCGR2B. Higher offspring levels of PCSK1 decreased birth weight (-9g (-16g, 4g), alongside LEPR. Results support maternal and fetal protein effects on birth weight, implicating roles for glucose metabolism, energy homeostasis, endothelial function and adipocyte differentiation.

Loss-of-function mutation in Pcsk1 increases serum APOA1 level and LCAT activity in mice

Background

The convertase subtilisin/kexin family 1 gene (PCSK1) has been associated in various human genetics studies with a wide spectrum of metabolic phenotypes, including early-onset obesity, hyperphagia, diabetes insipidus, and others. Despite the evident influence of PCSK1 on obesity and the known functions of other PCSKs in lipid metabolism, the role of PCSK1 specifically in lipid and cholesterol metabolism remains unclear. This study evaluated the effect of loss of PCSK1 function on high-density lipoprotein (HDL) metabolism in mice.

Results

HDL cholesterol, apolipoprotein A1 (APOA1) levels in serum and liver, and the activities of two enzymes (lecithin-cholesterol acyltransferase, LCAT and phospholipid transfer protein, PLTP) were evaluated in 8-week-old mice with a non-synonymous single nucleotide mutation leading to an amino acid substitution in PCSK1, which results in a loss of protein’s function. Mutant mice had similar serum HDL cholesterol concentration but increased levels of serum total and mature APOA1, and LCAT activity in comparison to controls.

Conclusions

This study presents the first evaluation of the role of PCSK1 in HDL metabolism using a loss-of-function mutant mouse model. Further investigations will be needed to determine the underlying molecular mechanism.

Coronary Heart Disease in Type 2 Diabetes Mellitus: Genetic Factors and Their Mechanisms, Gene-Gene, and Gene-Environment Interactions in the Asian Populations

Asians are more susceptible to type 2 diabetes mellitus (T2D) and its coronary heart disease (CHD) complications than the Western populations, possibly due to genetic factors, higher degrees of obesity, insulin resistance, and endothelial dysfunction that could occur even in healthy individuals. The genetic factors and their mechanisms, along with gene-gene and gene-environment interactions associated with CHD in T2D Asians, are yet to be explored. Therefore, the objectives of this paper were to review the current evidence of genetic factors for CHD, summarize the proposed mechanisms of these genes and how they may associate with CHD risk, and review the gene-gene and gene-environment interactions in T2D Asians with CHD. The genetic factors can be grouped according to their involvement in the energy and lipoprotein metabolism, vascular and endothelial pathology, antioxidation, cell cycle regulation, DNA damage repair, hormonal regulation of glucose metabolism, as well as cytoskeletal function and intracellular transport. Meanwhile, interactions between single nucleotide polymorphisms (SNPs) from different genes, SNPs within a single gene, and genetic interaction with environmental factors including obesity, smoking habit, and hyperlipidemia could modify the gene's effect on the disease risk. Collectively, these factors illustrate the complexities of CHD in T2D, specifically among Asians.

Mouse Models of Human Proprotein Convertase Insufficiency

The kexin-like proprotein convertases perform the initial proteolytic cleavages that ultimately generate a variety of different mature peptide and proteins, ranging from brain neuropeptides to endocrine peptide hormones, to structural proteins, among others. In this review, we present a general introduction to proprotein convertase structure and biochemistry, followed by a comprehensive discussion of each member of the kexin-like subfamily of proprotein convertases. We summarize current knowledge of human proprotein convertase insufficiency syndromes, including genome-wide analyses of convertase polymorphisms, and compare these to convertase null and mutant mouse models. These mouse models have illuminated our understanding of the roles specific convertases play in human disease and have led to the identification of convertase-specific substrates; for example, the identification of procorin as a specific PACE4 substrate in the heart. We also discuss the limitations of mouse null models in interpreting human disease, such as differential precursor cleavage due to species-specific sequence differences, and the challenges presented by functional redundancy among convertases in attempting to assign specific cleavages and/or physiological roles. However, in most cases, knockout mouse models have added substantively both to our knowledge of diseases caused by human proprotein convertase insufficiency and to our appreciation of their normal physiological roles, as clearly seen in the case of the furin, proprotein convertase 1/3, and proprotein convertase 5/6 mouse models. The creation of more sophisticated mouse models with tissue- or temporally-restricted expression of specific convertases will improve our understanding of human proprotein convertase insufficiency and potentially provide support for the emerging concept of therapeutic inhibition of convertases.

Genetic Variability of the Glucose-Dependent Insulinotropic Peptide Gene Is Involved in the Premature Coronary Artery Disease in a Chinese Population with Type 2 Diabetes

BACKGROUND

Glucose-dependent insulinotropic polypeptide (GIP) is closely related to diabetes and obesity, both of which are confirmed to increase the risk of coronary artery disease (CAD). Our study aimed to investigate whether the polymorphisms in GIP genes could affect the risk of cardiovascular disease in type 2 diabetic patients in the Chinese Han population.

METHODS

We selected and genotyped two haplotype-tagging single nucleotide polymorphisms (tag-SNPs) (rs2291725 C>T, rs8078510 G>A) of GIP gene based on CHB data in HapMap Phase II database (r² < 0.8). The case-control study of Chinese Han population involved 390 diabetic patients with CAD as positive group and 276 diabetic patients without CAD as control group. Allele and genotype frequencies were compared between the two groups.

RESULTS

In dominant inheritance model, the carriers of T/T or T/C had a lower risk of CAD (OR = 0.635, 95% CI = 0.463-0.872, p = 0.005), even after adjustment other CAD risk factors (gender, age, BMI, smoking status, dyslipidemia, hypertension history, and diabetic duration) (OR' = 0.769, 95% CI' = 0.626-0.945, p' = 0.013). The allele A at rs8078510 was associated with decreased risk of CAD (OR = 0.732, p = 0.039). p = 0.018 in subgroup analysis, individuals with higher BMI (≥24 kg/m²) had increased risk for CAD when carrying C/C at rs2291725 (OR' = 1.291, 95% CI' = 1.017-1.639, p' = 0.036). In age < 55 men and age < 65 women, the carriers of allele C at rs2291725 had a higher risk of CAD than noncarriers (OR = 1.627, p = 0.015). Carriers of allele G in rs8078510 had higher susceptibility to CAD (OR = 2.049, 95% = CI 1.213-3.463, p = 0.007). p = 0.004; in addition, allele G in rs8078510 would bring higher CAD risk to the carriers who ever smoked (OR = 1.695, 95% CI = 1.080-2.660, p = 0.021).

CONCLUSION

The genetic variability of GIP gene is associated with CAD and it may play a role in the premature CAD in the Chinese Han population with type 2 diabetes.

The Effects of Sleeve Gastrectomy on Glucose Metabolism and Glucagon-Like Peptide 1 in Goto-Kakizaki Rats

PURPOSE

To investigate the effects of sleeve gastrectomy (SG) on glucose metabolism and changes in glucagon-like peptide 1 (GLP-1) in Goto-Kakizaki (GK) rats.

METHODS

GK rats were randomly assigned to one of three groups: SG, SG pair-fed plus sham surgery (PF-sham), and ad libitum-fed no surgery (control). Food intake, body weight, blood glucose, GLP-1 and insulin levels, and GLP-1 expression in the jejunum and ileum were compared.

RESULTS

The SG rats exhibited lower postoperative food intake, body weight, and fasting glucose than did the control rats (P < 0.05). SG significantly improved glucose and insulin tolerance (P < 0.05). Plasma GLP-1 levels were higher in SG rats than in control or PF-sham rats in the oral glucose tolerance test (OGTT) (P < 0.05). Blood glucose levels expressed as a percentage of baseline were higher in SG rats than in control rats after exendin (9-39) administration (P < 0.05). The levels of GLP-1 expression in the jejunum and ileum were higher in SG rats than in PF-sham and control rats (P < 0.05).

CONCLUSIONS

Improvement of glucose metabolism by SG was associated with increased GLP-1 secretion. SG contributes to an increase in plasma GLP-1 levels via increased GLP-1 expression in the mucosa of the jejunum and/or ileum.

The Associations between Apolipoprotein E Gene Epsilon2/Epsilon3/Epsilon4 Polymorphisms and the Risk of Coronary Artery Disease in Patients with Type 2 Diabetes Mellitus

Background and Objective: Apolipoprotein E (APOE) plays important roles in lipoprotein metabolism and cardiovascular disease. Evidence suggests the APOE gene epsilon2/epsilon3/epsilon4 (ε2/ε3/ε4) polymorphisms might be associated with the susceptibility of coronary artery disease (CAD) in patients with type 2 diabetes mellitus (T2DM). However, no clear consensus has yet been established. Therefore, the aim of this meta-analysis is to provide a precise conclusion on the potential association between APOE ε2/ε3/ε4 polymorphisms and the risk of CAD in patients with T2DM based on case-control studies.

Methods: Pubmed, Embase, Chinese National Knowledge Infrastructure (CNKI), and Wanfang databases were searched for all relevant studies prior to August 2017 in English and Chinese language. The pooled odds ratios (ORs) and their corresponding 95% confidence intervals (CIs) were used to assess the strength of the relationships. The between-study heterogeneity was evaluated by Cochran's Q-test and the I² index to adopt fixed- or random- effect models.

Results: A total of 13 studies were eligible for inclusion. There was evidence for significant associations between APOE ε4 mutation and the risk of CAD in patients with T2DM (for ε3/ε4 vs. ε3/ε3: OR = 1.69, 95% CI = 1.38–2.08, P < 0.001; for ε4/ε4 vs. ε3/ε3: OR = 2.72, 95% CI = 1.61–4.60, P < 0.001; for ε4/ε4+ε3/ε4 vs. ε3/ε3: OR = 1.83, 95% CI = 1.52–2.22, P < 0.001; for ε4 allele vs. ε3 allele: OR = 1.64, 95% CI = 1.40–1.94, P < 0.001). In contrast, no significant associations were found in genetic model of APOE ε2 mutation (for ε2/ε2 vs. ε3/ε3: OR = 1.67, 95% CI = 0.90–3.09, P = 0.104; for ε2/ε3 vs. ε3/ε3: OR = 1.18, 95% CI = 0.93–1.51, P = 0.175; for ε2/ε2+ε2/ε3 vs. ε3/ε3: OR = 1.26, 95% CI = 0.88–1.82, P = 0.212; for ε2 allele vs. ε3 allele: OR = 1.34, 95% CI = 0.98–1.84, P = 0.07).

Conclusions: The APOE gene ε4 mutation is associated with an increased risk of CAD in patients with T2DM, while the ε2 variation has null association with this disease.

Rs46522 in the Ubiquitin-Conjugating Enzyme E2Z Gene Is Associated with the Risk of Coronary Artery Disease in Individuals of Chinese Han Population with Type 2 Diabetes

AIMS

We investigated the association between ubiquitin-conjugating enzyme E2Z (UBE2Z) gene SNP rs46522 and the risk of CAD in a Chinese Han population with type 2 diabetes and explored a possible interactive effect with environmental risk factors of CAD.

METHODS

665 patients with T2D were enrolled; 390 were CAD patients and 275 were non-CAD patients. Genotype analysis of rs46522 (T>C) was performed using PCR-RFLP.

RESULTS

The SNP rs47522 was associated with the risk of CAD supposing recessive inheritance model (TT versus CC+CT, OR' = 1.277, 95%CI' 1.039-1.570, p' = 0.020) and codominant model (TT versus CT, OR' = 1.673, 95%CI' 1.088-2.570, p' = 0.019) after adjustment for confounders of CAD. A synergistic effect of rs46522 and BMI was discovered (β = 0.012, p for interreaction = 0.028). In subgroup analysis, minor allele T was significantly associated with CAD in overweight and obesity subgroup (p = 0.034), and the association was also proved in recessive model (OR = 1.537, 95%CI 1.075-2.196, p = 0.018). Smokers with genotype TT had threefold risk of CAD in comparison to nonsmokers with genotype TC or CC (p < 0.001).

CONCLUSIONS

The SNP rs46522 in UBE2Z gene is associated with the risk of CAD in the individuals of Chinese Han descent with type 2 diabetes and is of synergistic effect with BMI.

Proprotein convertases in atherogenesis

PURPOSE OF REVIEW

The proprotein convertases subtilisin/kexin (PCSKs) are endoproteases identified as activators of precursors from hormones and peptides. On the basis of the variety of substrates and regulation in disease, they have been recognized as mediators in atherogenesis. The discovery of PCSK9, which regulates low-density lipoprotein receptor cell membrane availability, has led to a resurgence of interest in these enzymes and their function in cardiovascular diseases.

RECENT FINDINGS

Recent data demonstrate that PCSKs are expressed in human atheroma and are regulated in animal models of atherosclerosis. In animal models, inhibition of PCSKs, such as PCSK3, affects cell proliferation and migration as well as inflammation, reducing atherosclerosis. In addition, targeting PCSK9 lowers cholesterol levels and has now been demonstrated to lessen vascular lesion formation in mice. Experimentally investigated novel anti-PCSK9 strategies include genome editing and vaccination. Furthermore, studies show that PCSKs contribute to the initiation and progression of cardiometabolic risk factors, such as insulin resistance and obesity.

SUMMARY

PCSKs affect cardiovascular diseases on multiple levels, including atherosclerotic lesion formation as well as their contribution to cardiometabolic risk factors. PCSK9 is a key regulator of plasma cholesterol levels, thereby potentially affecting atherosclerosis and has rapidly emerged as a pharmacological target.

Defective transport of the obesity mutant PC1/3 N222D contributes to loss of function

Mutations in the PCSK1 gene encoding prohormone convertase 1/3 (PC1/3) are strongly associated with obesity in humans. The PC1/3(N222D) mutant mouse thus far represents the only mouse model that mimics the PC1/3 obesity phenotype in humans. The present investigation addresses the cell biology of the N222D mutation. Metabolic labeling experiments reveal a clear defect in the kinetics of insulin biosynthesis in islets from PC1/3(N222D) mutant mice, resulting in an increase in both proinsulin and its processing intermediates, predominantly lacking cleavage at the Arg-Arg site. Although the mutant PC1/3 zymogen is correctly processed to the 87-kDa form, pulse-chase immunoprecipitation experiments, labeling, and immunohistochemical experiments using uncleavable variants all demonstrate that the PC1/3-N222D protein is largely mislocalized compared with similar wild-type (WT) constructs, being predominantly retained in the endoplasmic reticulum. The PC1/3-N222D mutant also undergoes more efficient degradation via the ubiquitin-proteasome system than the WT enzyme. Lastly, the mutant PC1/3-N222D protein coimmunoprecipitates with WT PC1/3 and exerts a modest effect on intracellular retention of the WT enzyme. These profound alterations in the cell biology of PC1/3-N222D are likely to contribute to the defective insulin biosynthetic events observed in the mutant mice and may be relevant to the dramatic contributions of polymorphisms in this gene to human obesity.