Associations of common variants at APLN and hypertension in Chinese subjects with and without diabetes

High-intensity interval training attenuates renal injury induced by myocardial ischemia-reperfusion in rats

BACKGROUND

High-intensity interval training (HIIT) has been recognized as an effective form of short-duration exercise. The purpose of this study was to assess whether HIIT could reduce renal injury induced by myocardial ischemia-reperfusion (MIR) in rats.

METHODS

Male Sprague-Dawley rats were randomly assigned to the Sham (SHAM), coronary artery occlusion (CAO), HIIT, and ischemic precondition (IPC) groups. Rats underwent 40 minutes of left anterior descending CAO under anesthesia, followed by 3 hours of reperfusion, to induce MIR. Postsurgery, rats were sacrificed, and their blood, heart, and kidney tissues were examined. The HIIT group underwent 4 weeks of HIIT training before surgery.

RESULTS

HIIT intervention significantly reduced renal injury after MIR and the concentrations of blood urea nitrogen (BUN) and creatinine (CRE) in the serum. Moreover, proinflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6, were significantly decreased, while the anti-inflammatory cytokine IL-10 was significantly increased in the serum. Additionally, HIIT intervention suppressed the expression of FoxO1, Bax/Bcl-2 ratio, TNF-α, and cleaved-caspase-3/caspase-3 ratio in kidney tissues, ultimately reducing renal cell apoptosis.

CONCLUSION

This study is the first to demonstrate that HIIT has effects similar to IPC, significantly reducing renal injury after MIR. HIIT regulates the production of proinflammatory and anti-inflammatory cytokines and inhibits renal cell apoptosis, thereby reducing the occurrence of cardiorenal syndrome.

Impact of the apelin/APJ axis in the pathogenesis of Parkinson's disease with therapeutic potential

The pathogenesis of Parkinson's disease (PD) remains elusive. There is still no available disease-modifying strategy against PD, whose management is mainly symptomatic. A growing amount of preclinical evidence shows that a complex interplay between autophagy dysregulation, mitochondrial impairment, endoplasmic reticulum stress, oxidative stress, and excessive neuroinflammation underlies PD pathogenesis. Identifying key molecules linking these pathological cellular processes may substantially aid in our deeper understanding of PD pathophysiology and the development of novel effective therapeutic approaches. Emerging preclinical evidence indicates that apelin, an endogenous neuropeptide acting as a ligand of the orphan G protein-coupled receptor APJ, may play a key neuroprotective role in PD pathogenesis, via inhibition of apoptosis and dopaminergic neuronal loss, autophagy enhancement, antioxidant effects, endoplasmic reticulum stress suppression, as well as prevention of synaptic dysregulation in the striatum, excessive neuroinflammation, and glutamate-induced excitotoxicity. Underlying signaling pathways involve phosphoinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin, extracellular signal-regulated kinase 1/2, and inositol requiring kinase 1α/XBP1/C/EBP homologous protein. Herein, we discuss the role of apelin/APJ axis and associated molecular mechanisms on the pathogenesis of PD in vitro and in vivo and provide evidence for its challenging therapeutic potential.

The traditional Chinese medicine formula Fufang-Zhenzhu-Tiaozhi protects myocardia from injury in diabetic minipigs with coronary heart disease

BACKGROUND AND PURPOSE

Diabetes mellitus (DM) is a major risk factor for coronary heart disease (CHD). Previous research has reported that the Fufang-Zhenzhu-Tiaozhi (FTZ) formula has obvious effects on the treatment of dyslipidemia and hyperglycemia. In the present study, we intended to establish a convenient DM-CHD model in minipigs and investigated the protective effect of FTZ against myocardial injury and its mechanism.

METHODS

The DM-CHD model was established by a high-fat/high-sucrose/high-cholesterol diet (HFSCD) combined with balloon injury in the coronary artery. Subsequently, sixteen Wuzhishan minipigs were assigned to three groups: control group, model group, and FTZ group. The model group and FTZ group were given a HFSCD, while the control group was given a normal diet (ND). FTZ was given with meals in the FTZ group. During this time, biochemical parameters, such as total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein (HDL-C), and fasting blood glucose (FBG), were measured by using testing kits. Insulin (INS) was determined by ELISA, and the homeostasis model assessment index of insulin resistance (HOMA-IR) was calculated to evaluate insulin resistance levels. After FTZ administration, the plasma levels of lactate dehydrogenase (LDH), creatine kinase isoenzyme MB (CK-MB), and cardiac troponin I (cTnI) were measured by using ELISA kits to evaluate myocardial injury. Coronary artery stenosis was analyzed by angiographic and HE staining. Myocardial ischemia was assayed with electrocardiogram (ECG). Moreover, cytokines, including interleukin-6 (IL-6), hypersensitive C-reactive protein (hs-CRP), and tumor necrosis factor-alpha (TNF-α), were measured by ELISA kits to assess inflammation. The myocardial tissue was collected, and the pathological morphology was observed by transmission electron microscopy (TEM), HE staining, and Masson staining. Western blots were used to detect the expression of PI3K, AKT, p-AKT, p-NF-κB, and NF-κB.

RESULTS

A DM-CHD model in minipigs with glucose-lipid metabolism disorder, coronary artery incrassation and myocardial damage was successfully established through balloon injury in the coronary artery combined with HFSCD. FTZ effectively inhibited coronary artery incrassation and protected the myocardium against injury in DM-CHD minipigs. FTZ decreased proinflammatory cytokine levels and upregulated the protein expression of the PI3K/Akt pathway in the myocardium.

CONCLUSIONS

A novel DM-CHD model in minipigs was successfully established through balloon injury in the coronary artery combined with HFSCD. FTZ has a protective effect against myocardial injury in DM-CHD by inhibiting inflammation and activating the PI3K/AKT signaling pathway.

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.

A promoter polymorphism in APJ gene is significantly associated with blood pressure changes and hypertension risk in Chinese women

The aim of this study was to interrogate the gender-specific association of 5 well-defined polymorphisms in apelin/APJ system with both blood pressure changes and hypertension risk in a northeastern Chinese population. This is a population-based case-control study, including 650 hypertensive patients and 645 normotensive controls. Data were analyzed by STATA and Haplo.Stats. The genotype distributions of 5 study polymorphisms were in Hardy-Weinberg equilibrium in both genders. The rs7119375 and rs10501367 were completely linked. The genotypes (P = 0.001) and alleles (P < 0.001) of rs7119375 differed significantly between patients and controls in women. Carriers of rs7119375-AA genotype had significant higher systolic blood pressure (SBP) than carriers of rs7119375-GG genotype in both patients and controls of female gender (P < 0.01). Moreover, carriers of rs7119375-A allele were 1.80 times more likely to develop hypertension relative to carriers of rs7119375-GG genotype after adjusting for age, body mass index and glucose (odds ratio: 1.80; 95% confidence interval: 1.03–3.16; P = 0.040). Further allele combination analysis supported the leading contribution of rs7119375 to hypertension risk. Our findings demonstrated that the mutation of promoter polymorphism rs7119375 in APJ gene was significantly associated with elevated SBP and increased hypertension risk in Chinese women.

Apelinergic System Structure and Function

Apelin and apela (ELABELA/ELA/Toddler) are two peptide ligands for a class A G-protein-coupled receptor named the apelin receptor (AR/APJ/APLNR). Ligand-AR interactions have been implicated in regulation of the adipoinsular axis, cardiovascular system, and central nervous system alongside pathological processes. Each ligand may be processed into a variety of bioactive isoforms endogenously, with apelin ranging from 13 to 55 amino acids and apela from 11 to 32, typically being cleaved C-terminal to dibasic proprotein convertase cleavage sites. The C-terminal region of the respective precursor protein is retained and is responsible for receptor binding and subsequent activation. Interestingly, both apelin and apela exhibit isoform-dependent variability in potency and efficacy under various physiological and pathological conditions, but most studies focus on a single isoform. Biophysical behavior and structural properties of apelin and apela isoforms show strong correlations with functional studies, with key motifs now well determined for apelin. Unlike its ligands, the AR has been relatively difficult to characterize by biophysical techniques, with most characterization to date being focused on effects of mutagenesis. This situation may improve following a recently reported AR crystal structure, but there are still barriers to overcome in terms of comprehensive biophysical study. In this review, we summarize the three components of the apelinergic system in terms of structure-function correlation, with a particular focus on isoform-dependent properties, underlining the potential for regulation of the system through multiple endogenous ligands and isoforms, isoform-dependent pharmacological properties, and biological membrane-mediated receptor interaction. © 2018 American Physiological Society. Compr Physiol 8:407-450, 2018.

Genotype screening of APLN rs3115757 variant in Egyptian women population reveals an association with obesity and insulin resistance

AIMS

Apelin is one of adipokines that plays a pivotal role in energy metabolism, insulin sensitivity and vascular integrity. A definite genetic variant of apelin gene (APLN), rs3115757, was recently introduced to potentially influence apelin expression in adipocytes. The aim of our study was to explore the sights of a potential association of this functional variant with obesity traits, insulin resistance indices as well as type 2 diabetes mellitus (T2DM) prevalence.

METHODS

Genotype screening for rs3115757 variant in 151 Egyptian female samples was conducted. Fasting levels of serum insulin and lipid profile, in addition to plasma glucose were measured. Cochran-Armitage trend test was used to decide the risk allele and evaluate the association between the candidate variant and obesity using a case-control design.

RESULTS

The homozygous G risk allele carriers showed higher values of body mass index (BMI) and waist circumference (P=0.001,0.02, respectively) as compared to CC or CG genotypes. As for GG genotype carriers, the risk of developing morbid obesity in lean subjects, (BMI<25), is twelve times the risk in subjects carrying other genotypes (OR=12.09, 95% CI: 1.4, 104.8, P=0.024). On the other hand, GG carriers are shown to be more resistant to insulin. Significantly after correction for BMI and age effects, GG genotype carriers showed 14% and 41% increment in insulin level and resistance (OR=1.14, 95% CI: 1.06, 1.23, P=0.001), (OR=1.42, 95% CI: 1.19, 1.70, P<0.001), respectively.

CONCLUSION

These results suggest a prospective role mediated by this variant in mounting obesity disorders and as significant as insulin resistance complications.

Genetic differences and aberrant methylation in the apelin system predict the risk of high-altitude pulmonary edema

Hypoxia-inducible factor stimulates the expression of apelin, a potent vasodilator, in response to reduced blood arterial oxygen saturation. However, aberrations in the apelin system impair pulmonary vascular function, potentially resulting in the development of high-altitude (HA)-related disorders. This study aimed to elucidate the genetic and epigenetic regulation of apelin, apelin receptor (APLNR), and endothelial nitric oxide synthase (NOS3) in HA adaptation and HA pulmonary edema (HAPE). A genome-wide association study and sequencing identified variants of apelin, APLNR, and NOS3 that were validated in a larger sample size of HAPE-patients (HAPE-p), HAPE-free controls (HAPE-f), and healthy highland natives (HLs). Apelin-13 and nitrite levels and apelin and NOS3 expression were down-regulated in HAPE-p (P < 0.001). Among the several studied polymorphisms, apelin rs3761581, rs2235312, and rs3115757; APLNR rs11544374 and rs2282623; and NOS3 4b/4a, rs1799983, and rs7830 were associated with HAPE (P < 0.03). The risk allele rs3761581G was associated with a 58.6% reduction in gene expression (P = 0.017), and the risk alleles rs3761581G and rs2235312T were associated with low levels of apelin-13 and nitrite (P < 0.05). The latter two levels decreased further when both of these risk alleles were present in the patients (P < 0.05). Methylation of the apelin CpG island was significantly higher in HAPE-p at 11.92% than in HAPE-f and HLs at ≤ 7.1% (P < 0.05). Moreover, the methylation effect was 9% stronger in the 5' UTR and was associated with decreased apelin expression and apelin-13 levels. The rs3761581 and rs2235312 polymorphisms and methylation of the CpG island influence the expression of apelin in HAPE.

The contributory role of angiotensin receptor-like 1 gene multiple polymorphisms in hypertension among northeastern Han Chinese

Background and Objective

Via direct sequencing, we have recently identified six common polymorphisms in angiotensin receptor-like 1 (AGTRL1) gene, and found only two polymorphisms were significantly associated with hypertension in a family-based analysis on 1,015 southern Han Chinese. Extending our previous work and considering the ubiquity of epistasis in determining disease susceptibility, we, in this study, sought to explore the potential interaction of AGTRL1 gene six polymorphisms with hypertension in a large northeastern Han Chinese population.

Methods and Results

This was a case-control study involving 1,009 sporadic hypertensive patients and 756 normotensive controls. Data were analyzed by Haplo.Stats and multifactor dimensionality reduction (MDR) softwares. There were no deviations from Hardy-Weinberg equilibrium for all polymorphisms. The genotypes and alleles of rs7119675 and rs11544374 differed significantly between the two groups (P<0.0005), even after the Bonferroni correction. Under three genetic models, significant association was consistently observed for rs7119675 and rs11544374, and this association was independent of confounding factors. Taking rs7119375 as an example, the odds of having hypertension was 2.46 (95% confidence interval (95% CI): 2.06–2.94), 2.82 (95% CI: 2.29–3.46) and 3.97 (95% CI: 2.37–6.64) under additive, dominant and recessive models (P<0.001), respectively, whereas the adjusted risk estimates were slightly attenuated but still significant. The frequencies of most derived haplotypes differed significantly between patients and controls. Haplotype-phenotype analyses indicated marginal association for triglyceride (P_Sim = 0.011) and total cholesterol (P_Sim = 0.025) in patients and for triglyceride in controls (P_Sim = 0.023). The overall best MDR model included rs11544374, rs7119375 and rs948847 with the maximal testing accuracy of 0.737 and cross-validation consistency of 10 out of 10 (P<0.0001). Further interaction entropy graph suggested that the interaction of rs7119375 with rs11544374 and rs948847 was strongly antagonized.

Conclusions

Our findings demonstrate that AGTRL1 genetic polymorphisms might contribute to the development of hypertension independently and/or through complex interaction.