Apelin andAPLNsingle nucleotide polymorphisms and combined hypertension and central retinal artery stenosis in a Chinese population

Association of genetic defects in the apelin-AGTRL1 system with myocardial infarction risk in Han Chinese

We aimed to test the hypothesis that apelin (APLN) and its receptor AGTRL1 (APLNR) genes may contribute to the pathogenesis of myocardial infarction in Han Chinese. This is a hospital-based, case-control association study, involving 1067 patients with myocardial infarction and 942 healthy controls. Myocardial infarction is diagnosed by electrocardiogram or anatomopathological examination. Eight polymorphisms in APLN gene and 5 in APLNR gene were genotyped using the TaqMan assay. Risk was summarized as odds ratio (OR) and 95% confidence interval (CI). In males, rs56204867-G allele (adjusted OR, 95% CI, p: 0.21, 0.08-0.55, 0.002) and rs2235309-T allele (0.60, 0.42-0.84, 0.004) was associated with a significantly reduced risk of myocardial infarction, and the mutations of rs2235310 was associated with an increased risk (1.41, 1.06-2.52, 0.021), as well as for rs948847-GG genotype (1.85, 1.23-2.91, 0.007). In females, the presence of rs56204867-AG and -GG genotypes was significantly associated with 44% and 50% reduced risk (0.56 and 0.50, 0.40-8.04 and 0.29-0.86, 0.007 and 0.036), respectively; for rs2235310, CC genotype was associated with 72% increased risk (1.72, 1.09-3.22, 0.016), and the odds of myocardial infarction was 3.47 for rs9943582-TT genotype (95% CI: 1.53-7.57, 0.009). The gender-specific association of APLN and APLNR genes with myocardial infarction was reinforced by further linkage and haplotype analyses. Finally, nomograms based on significant polymorphisms are satisfactory, with the C-indexes over 80% for both genders. Taken together, our findings indicate that APLN and APLNR genes are potential candidates in the pathogenesis of myocardial infarction in Han Chinese, and importantly their contribution is gender-dependent.

International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand

The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.

The association between apelin polymorphisms and hypertension in China: A meta-analysis

INTRODUCTION:

Apelin plays an important part in regulating blood pressure, metabolism, and the development of cancer. Recent studies have investigated the association of apelin polymorphisms and hypertension risk, but no meta-analysis has been conducted.

MATERIALS AND METHODS:

Five studies were included in this meta-analysis in total. The pooled odds ratio and its corresponding 95% confidence interval were calculated by the random-effect model.

RESULTS:

The overall pooled odds ratio of the distribution of rs3761581 G allelic frequency was 0.90 (95% confidence interval: 0.82-1.00). In female participants, the pooled odds ratio of the frequency of G allele was 1.01 (95% confidence interval: 0.89-1.14). For males, the pooled odds ratio of the frequency of G allele was 0.69 (95% confidence interval: 0.46-1.03). As for rs56204867, the overall pooled odds ratio of the frequency of G allele was 1.09 (95% confidence interval: 0.86-1.37). In females, the pooled odds ratio of the frequencies of the G allele was 1.05 (95% confidence interval: 0.86-1.29). In male participants, the frequency of G allele did not show significant correlation with hypertension (pooled odds ratio=1.21 95% confidence interval: 0.81-1.79).

CONCLUSION:

This meta-analysis revealed that there was no correlation between apelin polymorphisms, rs3761581 and rs56204867, and the prevalence of hypertension.

The impact of apelin and relaxin plasma levels in masked hypertension and white coat hypertension

Masked hypertension (HTN) and white coat hypertension represent two reverse forms of clinical HTN with questionable prognostic significance. Recent evidence supports that low apelin and relaxin plasma levels contribute to vascular damage accelerating atherogenesis and predisposing to HTN and cardiovascular (CV) events. The aim of this study was to compare apelin and relaxin plasma levels between patients with masked hypertension (MH) and those with white coat HTN (WCH). Overall, 130 patients not receiving antihypertensive therapy were studied. All patients underwent 24-hour ambulatory BP monitoring (ABPM) and office BP measurements. Plasma apelin and relaxin levels were measured by ELISA method. According to BP recordings, 24 subjects had MH (group A) and 32 had WCH (group B). Apelin (200 ± 111 pg/mL vs 305 ± 127 pg/mL, P < 0.01) and relaxin (35.2 ± 6.7 pg/mL vs 46.8 ± 23.6 pg/mL, P < 0.01) plasma levels were significantly lower in patients with MH compared to those with WCH, respectively. In conclusion, our findings showed that patients with MH had significantly lower apelin and relaxin levels compared to those with WCH. This observation implies an additional prognostic role for adipokines supporting the concept that MH is closer to essential HTN whereas WCH is a more benign condition.

Plasma adrenomedullin level in children with obesity: relationship to left ventricular function

BACKGROUND

Obese children are at increased risk for abnormal cardiac structure and function. Little is known about adrenomedullin (AM), a cytokine produced in various organs and tissues, as a biomarker of cardiac hypertrophy in obese children. This study aimed to assess the plasma AM levels in a cohort of obese children and its relationship to left ventricular (LV) functions.

METHODS

The study included 60 obese children and 60 non-obese children matched for age and gender as control group. Blood pressure, serum lipid profile, fasting glucose, insulin and plasma AM and the homeostatic model assessment of insulin resistance (HOMA-IR) were measured. Cardiac dimensions and LV functions were assessed using conventional echocardiography.

RESULTS

Compared to control subjects, obese children had higher blood pressure (P = 0.01), insulin (P = 0.001), HOMA-IR (P = 0.001), and AM (P = 0.001). Moreover, obese children had higher LV mass index (LVMI) (P = 0.001), indicating LV hypertrophy; prolonged isovolumic relaxation times (P = 0.01), prolonged mitral deceleration time (DcT) (P = 0.01) and reduced ratio of mitral E-to-mitral A-wave peak velocity (P = 0.01), indicating LV diastolic dysfunction. Laboratory abnormalities were only present in children with LV hypertrophy. In multivariate analysis in obese children with LV hypertrophy, AM levels were positively correlated with LVMI [odds ratio (OR) 1.14, 95% confidence interval (Cl) 1.08-1.13, P = 0.0001] and mitral DcT (OR 2.25, 95% CI 1.15-2.05, P = 0.01) in the presence of higher blood pressure and HOMA-IR. A cut-off value of AM at 52 pg/mL could differentiate obese children with and without left ventricular hypertrophy at a sensitivity of 94.32% and specificity of 92.45%.

CONCLUSIONS

Plasma AM levels may be elevated in obese children particularly those with LV hypertrophy and is correlated with higher blood pressure and insulin resistance. Measurement of plasma AM levels in obese children may help to identify those at high risk of developing LV hypertrophy and dysfunction.

Apelin and Visfatin Plasma Levels in Healthy Individuals With High Normal Blood Pressure

BACKGROUND

High normal blood pressure (BP; 130-139/85-89 mm Hg) is related with increased cardiovascular (CV) risk compared to normal BP (120-129/80-84 mm Hg) or/and optimal BP (<120/80 mm Hg). Low apelin plasma levels have been associated with arterial hypertension and atherosclerosis, while high visfatin plasma levels may promote vascular inflammation and atherosclerotic plaque destabilization and have been evaluated as a marker for identifying stages of essential hypertension. We sought to compare the apelin and visfatin plasma levels between subjects with high normal BP and subjects with normal or optimal BP matched for age, gender, smoking, and body mass index (BMI).

METHODS

Twenty-five subjects with high normal BP (office BP 136±3/88±2 mm Hg, age 57±4 years, 76% males, 32% smokers, BMI 24.0±1.7 kg/m2) and 35 subjects with normal or optimal BP (office BP 118±2/78±2 mm Hg, age 55±7 years, 63% males, 29% smokers, BMI 23.2±1.4 kg/m2) were studied. The apelin and visfatin plasma levels were determined with the enzyme-linked immunosorbent assay.

RESULTS

Compared to normal or optimal BP subjects, apelin levels were significantly lower (205±108 vs. 325±152 pg/ml, P < 0.001) and visfatin levels significantly higher (11.0±2.0 vs. 7.2±0.9 ng/ml, P = 0.002) in high normal BP subjects. No significant differences were found between the 2 groups (P = NS) regarding the basic clinical characteristics, the glycemic/lipid profile, and the renal function parameters.

CONCLUSIONS

The emerging, from the present study, data raise the hypothesis that lower apelin and higher visfatin plasma levels in high normal BP subjects compared to normal or optimal BP individuals could partially explain the higher CV risk of the high normal BP group.

Genetic Determination of Serum Levels of Diabetes-Associated Adipokines

Adipose tissue secretes an abundance of proteins. Some of these proteins are known as adipokines and adipose-derived hormones which have been linked with metabolic disorders, including type 2 diabetes, and even with cancer. Variance in serum adipokine concentration is often closely associated with an increase (obesity) or decrease (lipodystrophy) in fat tissue mass, and it is affected by age, gender, and localization of the adipose tissue. However, there may be genetic variants which, in consequence, influence the serum concentration of a certain adipokine, and thereby promote metabolic disturbances or, with regard to the "protective" allele, exert beneficial effects. This review focuses on the genetic determination of serum levels of the following adipokines: adiponectin, chemerin, leptin, progranulin, resistin, retinol binding protein 4, vaspin, adipsin, apelin, and omentin. The article reports on the latest findings from genome-wide association studies (GWAS) and candidate gene studies, showing variants located in/nearby the adipokine genes and other (non-receptor) genes. An extra chapter highlights adipokine-receptor variants. Epigenetic studies on adipokines are also addressed.