Function and regulation of apelin/APJ system in digestive physiology and pathology

Expression and localization of apelin and apelin receptor protein in the oviduct of letrozole-induced hyperandrogenized mice

Apelin and its receptor (APJ) are expressed in the reproductive organs of some mammalian females. The function of oviduct has also been suggested to be compromised in the hyperandrogenism condition. However, expression of apelin and APJ has not been shown in the oviduct of hyperandrogenized mice. Thus, the present study has investigated the localization and expression of apelin and APJ in the letrozole-induced hyperandrogenized mice oviduct. Histomorphometric analysis showed decreased lumen of oviduct in the hyperandrogenized mice. Our results showed elevated expression of APJ and decreased abundance of apelin in the hyperandrogenized mice oviduct. This finding suggests impaired apelin signaling in the oviduct of hyperandrogenized mice. The expression of androgen receptor was upregulated while estrogen receptors were downregulated in the hyperandrogenized mice. The expression of HSP70 was also downregulated along with increased expression of active caspase 3 and BAX and decreased expression of BCL2 in hyperandrogenized mice. Furthermore, the phosphorylation of phospho-Ser473-Akt and phospho-Thr308-Akt also showed differential levels in the oviduct of hyperandrogenized mice. Whether this differential phosphorylation of Akt was solely due to impaired apelin signaling in the oviduct, remains unclear. Moreover, increased androgen signaling and suppressed estrogen signaling coincides with elevated apoptosis. In conclusion, hyperandrogenized conditions could also impair the gamete transport and fertilization process due to apoptosis in the oviduct. However, further study would be required to unravel the exact role of apelin signaling in the oviduct in relation to apoptosis.

The intestinal-level metabolic benefits of green tea catechins: Mechanistic insights from pre-clinical and clinical studies

BACKGROUND

The intestinal-level host-microbiota interaction has been implicated in the pathogenesis of chronic diseases. The current review is intended to provide a comprehensive insight into deciphering whether intestinal-level bioactivities mediate the overall metabolic health benefits of green tea catechins.

PURPOSE

We have comprehensively discussed pre-clinical and clinical evidences of intestinal-level changes in metabolism, microbiota, and metabolome due to catechin-rich green tea treatments, ultimately limiting metabolic diseases. Exclusive emphasis has been given to purified catechins and green tea, and discussions on extraintestinal mechanisms of metabolic health benefits were avoided.

METHODS

A literature search for relevant pre-clinical and clinical studies was performed in various online databases (e.g., PubMed) using specific keywords (e.g., catechin, intestine, microbiota). Out of all the referred literature, ∼15% belonged to 2021-2023, ∼51% were from 2011-2020, and ∼32% from 2000-2010.

RESULT

The metabolic health benefits of green tea catechins are indeed influenced by the intestinal-level bioactivities, including reduction of mucosal inflammation and oxidative stress, attenuation of gut barrier dysfunction, decrease in intestinal lipid absorption and metabolism, favorable modulation of mucosal nuclear receptor signaling, alterations of the luminal global metabolome, and mitigation of the gut dysbiosis. The results from the recent clinical studies support the pre-clinical evidences. The challenges and pitfalls of the currently available knowledge on catechin bioactivities have been discussed, and constructive directions to harness the translational benefits of green tea through future interventions have been provided.

CONCLUSION

The metabolism, metabolome, and microbiota at the intestinal epithelia play critical roles in catechin metabolism, pharmacokinetics, bioavailability, and bioactivities. Especially the reciprocal interaction between the catechins and the gut microbiota dictates the metabolic benefits of catechins.

Apelin C-Terminal Fragments: Biological Properties and Therapeutic Potential

Creation of bioactive molecules for treatment of cardiovascular diseases based on natural peptides is the focus of intensive experimental research. In the recent years, it has been established that C-terminal fragments of apelin, an endogenous ligand of the APJ receptor, reduce metabolic and functional disorders in experimental heart damage. The review presents literature data and generalized results of our own experiments on the effect of apelin-13, [Pyr]apelin-13, apelin-12, and their chemically modified analogues on the heart under normal and pathophysiological conditions in vitro and in vivo. It has been shown that the spectrum of action of apelin peptides on the damaged myocardium includes decrease in the death of cardiomyocytes from necrosis, reduction of damage to cardiomyocyte membranes, improvement in myocardial metabolic state, and decrease in formation of reactive oxygen species and lipid peroxidation products. The mechanisms of protective action of these peptides associated with activation of the APJ receptor and manifestation of antioxidant properties are discussed. The data presented in the review show promise of the molecular design of APJ receptor peptide agonists, which can serve as the basis for the development of cardioprotectors that affect the processes of free radical oxidation and metabolic adaptation.

Analysis of Intestinal Microbiota and Metabolic Pathways before and after a 2-Month-Long Hydrolyzed Fish and Rice Starch Hypoallergenic Diet Trial in Pruritic Dogs

Intestinal microbiota alterations were described in allergic individuals and may improve with diets. Farmina Ultra Hypo (FUH), a hydrolyzed fish/rice starch hypoallergenic diet, is able to improve clinical signs in allergic dogs. Study objectives were to determine microbiota differences in allergic dogs before and after feeding with FUH for eight weeks. Forty skin allergic dogs were evaluated clinically before and after the diet. Unresponsive dogs were classified as canine atopic dermatitis (CAD); responsive dogs relapsing after challenge with previous foods were classified as being food reactive (AFR), and those not relapsing as doubtful (D). Sequencing of feces collected pre- and post-diet was performed, with comparisons between and within groups, pre- and post-diet, and correlations to possible altered metabolic pathways were sought. Microbiota in all dogs was dominated by Bacteroidota, Fusobacteriota, Firmicutes and Proteobacteria, albeit with large interindividual variations and with some prevalence changes after the diet. In general, bacteria producing short-chain fatty acids were increased in all samples. CAD dogs showed pre-and post-diet microbiota patterns different from the other two groups. Bacteria taxa were enriched post-diet only in the AFR group. Changes in metabolic pathways were observed mainly in the CAD group. FUH may be able to improve intestinal microbiota and thus clinical signs of skin allergy.

Exercise improves homeostasis of the intestinal epithelium by activation of apelin receptor-AMP-activated protein kinase signalling

Intestinal remodelling is dynamically regulated by energy metabolism. Exercise is beneficial for gut health, but the specific mechanisms remain poorly understood. Intestine-specific apelin receptor (APJ) knockdown (KD) and wild-type male mice were randomly divided into two subgroups, with/without exercise, to obtain four groups: WT, WT with exercise, APJ KD and APJ KD with exercise. Animals in the exercise groups were subjected to daily treadmill exercise for 3 weeks. Duodenum was collected at 48 h after the last bout of exercise. AMP-activated protein kinase (AMPK) α1 KD and wild-type mice were also utilized for investigating the mediatory role of AMPK on exercise-induced duodenal epithelial development. AMPK and peroxisome proliferator-activated receptor γ coactivator-1 α were upregulated by exercise via APJ activation in the intestinal duodenum. Correspondingly, exercise induced permissive histone modifications in the PR domain containing 16 (PRDM16) promoter to activate its expression, which was dependent on APJ activation. In agreement, exercise elevated the expression of mitochondrial oxidative markers. The expression of intestinal epithelial markers was downregulated due to AMPK deficiency, and AMPK signalling facilitated epithelial renewal. These data demonstrate that exercise-induced activation of the APJ-AMPK axis facilitates the homeostasis of the intestinal duodenal epithelium. KEY POINTS: Apelin receptor (APJ) signalling is required for improved epithelial homeostasis of the small intestine in response to exercise. Exercise intervention activates PRDM16 through inducing histone modifications, enhanced mitochondrial biogenesis and fatty acid metabolism in duodenum. The morphological development of duodenal villus and crypt is enhanced by the muscle-derived exerkine apelin through the APJ-AMP-activated protein kinase axis.

Inhibition of apelin/APJ axis enhances the potential of dendritic cell-based vaccination to modulate TH1 and TH2 cell-related immune responses in an animal model of metastatic breast cancer

PURPOSE

The immunosuppressive microenvironment of tumors reduces the effectiveness of immunotherapies. Apelin as an immunosuppressor peptide is expressed in the microenvironment of many tumors. Thus, inhibition of apelin-related protumor activities can promote the effectiveness of cancer immunotherapy. Here, we investigated the efficacy of a dendritic cell (DC) vaccine in combination with an apelin receptor antagonist, ML221, to modulate Th1 and Th2 cell-related responses in breast cancer-bearing mice.

MATERIALS AND METHODS

Tumor was induced in female BALB/c mice by injecting 7 ​× ​10⁵ 4T1 cells in the right flank. Tumor-bearing mice were then given PBS, ML221, DC vaccine and "ML221 + DC vaccine" for 21 days. On day 37, mice were sacrificed and the frequency of Th1/Th2 cells in spleen and serum levels of IFN-γ/IL-10 were determined using flow cytometry and ELISA, respectively. Lung metastasis was evaluated in lung tissues stained with hematoxylin and eosin. Finally, the obtained data were analyzed using appropriate statistical tests.

RESULTS

Combination therapy with ML221 + DC vaccination was more effective in reducing tumor growth (P ​< ​0.0001), preventing lung metastasis (P ​< ​0.0001) and increasing survival rate (P ​< ​0.01) compared to the control group. Moreover, combination treatment substantially increased the frequency of Th1 cells while decreasing the frequency of Th2 cells in the spleen compared to the control group (P ​< ​0.01). It also reduced serum levels of IL-10 compared with the control group (P ​< ​0.05).

CONCLUSION

Our findings showed that combination therapy using ML221 + DC vaccine can be considered as an effective cancer therapeutic program to potentiate anti-tumor immune responses.

Andrographolide, a novel inducer of apelin gene expression

ETHNOPHARMACOLOGICAL RELEVANCE

Andrographis paniculata (A. paniculata) has been used as a traditional medicine in Asia and Scandinavia for centuries to remedy several illnesses. It has since been shown to possess antibacterial, antifungal, antiviral, anti-neoplasm, hepatoprotective, hypoglycemic, hypocholesterolemic, and energetic effects.

AIMS OF THE STUDY

This study sought to investigate the effect of Andrographolide on apelin gene expression and serum levels of glucose.

MATERIALS AND METHODS

In this study, 18 male rats were used. They were divided into three groups of six, including i) negative control group, ii) 3.5 mg/kg Andrographolide group, and iii) 7 mg/kg Andrographolide group. Apelin gene expression was investigated by real-time PCR method. Serum levels of glucose were measured by the photometric method.

RESULTS

The results of this study revealed that 3.5 and 7 mg doses per kg of body weight of andrographolide, for six days, significantly increased hepatic expression of apelin gene in male Wistar rats, as compared with the control group (p < 0.05). Serum levels of glucose at doses of 3.5 and 7 mg/kg of andrographolide, and in the control group, were 71.5 ± 8.96, 51.5 ± 2.64, and 93.87 ± 14.27 mg/dl, respectively. Andrographolide induced a decrease in serum levels of HDL-c and an increase in LDL-c/HDL-c ratio.

CONCLUSIONS

Our results suggest that Andrographolide can elicit an increase of hepatic apelin gene expression and a decrease in serum levels of blood glucose.

The Apelinergic System Immuno-Detection in the Abomasum and Duodenum of Sheep Grazing on Semi-Natural Pasture

Simple Summary

The semi-natural pastures in the Apennines represent the feed source for ovine, whose grazing activity helps to preserve the grassland’s biodiversity. Summer drought stress decreases the grassland pastoral value and affects the morpho-functional features of sheep’s digestive systems. A better knowledge of the gastrointestinal system of sheep may contribute to guaranteeing their welfare, a prerequisite for the sustainability of livestock production. This study aimed to immune-localize the apelinergic system in the abomasum and duodenum of sheep grazing on semi-natural pasture during the spring–summer season and to compare its behavior among animal groups fed with or without supplementation. The apelinergic system, composed of apelin and its receptor, is involved in foodintake and the secretion and absorption activities of the digestive apparatus. Apelinergic system molecules were localized at the abomasum lining epithelium and fundic glands level and at the duodenum lining and crypt epithelium, in addition to the neuroendocrine cells. Variations in reactivity were observed in the different feed groups; feed supplementation seemed to maintain the functionality of the apelinergic system in the organs near the status related to the better pasture phase, suggesting that it may be a suitable solution able to counteract the harmful effects of summer drought stress.

Abstract

Apelin (APLN) is an adipokine mainly produced by adipose tissue and related to an individual’s nutritional status as well as digestive apparatus functions. In this work, APLN and its receptor (APLNR) were investigated, by immunohistochemistry, in the abomasum and duodenum of 15 Comisana × Appenninica adult sheep reared in a semi-natural pasture. Organ samples were collected after maximum pasture flowering (M × F group) and after maximum pasture dryness (M × D group); the experimental group (E × p group) received a feed supplementation of 600 grams/day/head of barley and corn in addition to M × D group feeding. APLN and APLNR were identified in the lining epithelium and the fundic gland chief cells of the abomasum. APLNR was observed in the lining epithelium, in the crypts and the serotonin secreting cells of the duodenum. Similar reactivity was observed between the M × F and E × p groups, while the M × D group showed a lower intensity of immunostaining for both APLN and APLNR in all positive structures but the duodenal serotonin neuroendocrine cells. Hence, our findings show that the E × p group presents a picture quite overlapped with M × F and suggest that food supplementation has a maintaining effect on the apelinergic system expression in the investigated digestive tracts of the sheep.

FTO and PLAG1 Genes Expression and FTO Methylation Predict Changes in Circulating Levels of Adipokines and Gastrointestinal Peptides in Children

Adipokines and gastrointestinal tract hormones are important metabolic parameters, and both epigenetic factors and differential gene expression patterns may be associated with the alterations in their concentrations in children. The function of the FTO gene (FTO alpha-ketoglutarate dependent dioxygenase) in the regulation of the global metabolic rate is well described, whereas the influence of protooncogene PLAG1 (PLAG1 zinc finger) is still not fully understood. A cross-sectional study on a group of 26 children with various BMI values (15.3–41.7; median 28) was carried out. The aim was to evaluate the dependencies between the level of methylation and expression of aforementioned genes with the concentration of selected gastrointestinal tract hormones and adipokines in children. Expression and methylation were measured in peripheral blood mononuclear DNA by a microarray technique and a restriction enzyme method, respectively. All peptide concentrations were determined using the enzyme immunoassay method. The expression level of both FTO and PLAG1 genes was statistically significantly related to the concentration of adipokines: negatively for apelin and leptin receptor, and positively for leptin. Furthermore, both FTO methylation and expression negatively correlated with the concentration of resistin and visfatin. Cholecystokinin was negatively correlated, whereas fibroblast growth factor 21 positively correlated with methylation and expression of the FTO gene, while FTO and PLAG1 expression was negatively associated with the level of cholecystokinin and glucagon-like peptide-1. The PLAG1 gene expression predicts an increase in leptin and decrease in ghrelin levels. Our results indicate that the FTO gene correlates with the concentration of hormones produced by the adipose tissue and gastrointestinal tract, and PLAG1 gene may be involved in adiposity pathogenesis. However, the exact molecular mechanisms still need to be clarified.

ACE2 in the Gut: The Center of the 2019-nCoV Infected Pathology

The 2019-nCoV is a rapidly contagious pneumonia caused by the recently discovered coronavirus. Although generally the most noticeable symptoms are concentrated in the lungs, the disorders in the gastrointestinal tract are of great importance in the diagnosis of 2019-nCoV. The angiotensin-converting enzyme 2 (ACE2), an important regulator of many physiological functions, including blood pressure and nutrients absorption, is recently identified as a vital entry for 2019-nCoV to enter host cells. In this review, we summarize its functions both physiologically and pathologically. We also elaborate its conflicting roles from the clews of contemporary researches, which may provide significant indications for pharmacological investigations and clinical uses.

Lung-brain axis

The appreciation of human microbiome is gaining strong grounds in biomedical research. In addition to gut-brain axis, is the lung-brain axis, which is hypothesised to link pulmonary microbes to neurodegenerative disorders and behavioural changes. There is a need for analysis based on emerging studies to map out the prospects for lung-brain axis. In this review, relevant English literature and researches in the field of 'lung-brain axis' is reported. We recommend all the highlighted prospective studies to be integrated with an interdisciplinary approach. This might require conceptual research approaches based on physiology and pathophysiology. Multimodal aspects should include experimental animal units, while exploring the research gaps and making reference to the already existing human data. The overall microbiome medicine is gaining more ground. Aetiological paths and experimental recommendations as per prospective studies in this review will be an important guideline to develop effective treatments for any lung induced neurodegenerative diseases. An in-depth knowledge of the bi-directional communication between host and microbiome in the lung could help treatment to respiratory infections, alleviate stress, anxiety and enhanced neurological effects. The timely prevention and treatment of neurodegenerative diseases requires paradigm shift of the aetiology and more innovative experimentation.Impact statementThe overall microbiome medicine is gaining more ground. An in-depth knowledge of the bi-directional communication between host and microbiome in the lung could confer treatment to respiratory infections, alleviate stress, anxiety and enhanced neurological effects. Based on this review, we recommend all the highlighted prospective studies to be integrated and be given an interdisciplinary approach. This might require conceptual research approaches based on physiology and pathophysiology. Multimodal aspects should include experimental animal units; while exploring the research gaps and making reference to the already existing human data.

Elabela Protects Spontaneously Hypertensive Rats From Hypertension and Cardiorenal Dysfunctions Exacerbated by Dietary High-Salt Intake

Objectives: Arterial hypertension, when exacerbated by excessive dietary salt intake, worsens the morbidity and mortality rates associated with cardiovascular and renal diseases. Stimulation of the apelinergic system appears to protect against several circulatory system diseases, but it remains unknown if such beneficial effects are conserved in severe hypertension. Therefore, we aimed at determining whether continuous infusion of apelinergic ligands (i.e., Apelin-13 and Elabela) exerted cardiorenal protective effects in spontaneously hypertensive (SHR) rats receiving high-salt diet.

Methods: A combination of echocardiography, binding assay, histology, and biochemical approaches were used to investigate the cardiovascular and renal effects of Apelin-13 or Elabela infusion over 6 weeks in SHR fed with normal-salt or high-salt chow.

Results: High-salt intake upregulated the cardiac and renal expression of APJ receptor in SHR. Importantly, Elabela was more effective than Apelin-13 in reducing high blood pressure, cardiovascular and renal dysfunctions, fibrosis and hypertrophy in high-salt fed SHR. Unlike Apelin-13, the beneficial effects of Elabela were associated with a counter-regulatory role of the ACE/ACE2/neprilysin axis of the renin-angiotensin-aldosterone system (RAAS) in heart and kidneys of salt-loaded SHR. Interestingly, Elabela also displayed higher affinity for APJ in the presence of high salt concentration and better resistance to RAAS enzymes known to cleave Apelin-13.

Conclusion: These findings highlight the protective action of the apelinergic system against salt-induced severe hypertension and cardiorenal failure. As compared with Apelin-13, Elabela displays superior pharmacodynamic and pharmacokinetic properties that warrant further investigation of its therapeutic use in cardiovascular and kidney diseases.

Apelin‑13 alleviates diabetic nephropathy by enhancing nitric oxide production and suppressing kidney tissue fibrosis

Diabetes is a serious metabolic disease, and the kidney damage induced by diabetes also seriously affects the survival of patients. Apelin is a molecule that plays a crucial role in lipid metabolism, and recent studies have revealed that apelin-13, a subtype of apelin, plays an important role in regulating blood glucose levels. However, the role of apelin-13 in diabetic nephropathy remains unclear. In the present study, a rat model of diabetic nephropathy was constructed by the injection of streptozocin (STZ). During this process, these rats were injected with apelin-13. The blood glucose, urine protein and insulin levels were determined weekly. Next, the expression of angiotensin domain type 1 receptor-associated protein (APJ), endothelial nitric oxide synthase (eNOS), E-cadherin and α-smooth muscle actin (α-SMA) in the kidney tissues was determined with western blotting. Then, the endothelial cells of glomerular vessels were cultured with high glucose medium. These cells were treated with apelin-13 for 24 h. Finally, cell viability of these cells and the expression of APJ, eNOS, E-cadherin and α-SMA in these cells were determined with western blotting. As a result, treatment of apelin-13 induced the lower levels of blood glucose and urine protein. In addition, application of apelin-13 promoted the production of insulin and alleviated the insulin resistance. Treatment with apelin-13 promoted the expression of APJ, eNOS and E-cadherin while it suppressed the expression of α-SMA in kidney tissues of rats and endothelial cells of glomerular vessels. Furthermore, application of apelin-13 also promoted the cell viability of these cells. In conclusion, apelin-13 relieved diabetic nephropathy by promoting the production of nitric oxide (NO) and alleviating the fibrosis of kidney tissues.

Neuroprotective gain of Apelin/APJ system

Apelin is an endogenous ligand of G protein-coupled receptor APJ. In recent years, many studies have shown that the apelin/APJ system has neuroprotective properties, such as anti-inflammatory, anti-oxidative stress, anti-apoptosis, and regulating autophagy, blocking excitatory toxicity. Apelin/APJ system has been proven to play a role in various neurological diseases and may be a promising therapeutic target for nervous system diseases. In this paper, the neuroprotective properties of the apelin/APJ system and its role in neurologic disorders are reviewed. Further understanding of the pathophysiological effect and mechanism of the apelin/APJ system in the nervous system will help develop new therapeutic interventions for various neurological diseases.

Breast milk apelin level increases with maternal obesity and high-fat feeding during lactation

OBJECTIVE

Recent evidence indicates that levels of breast milk (BM) hormones such as leptin can fluctuate with maternal adiposity, suggesting that BM hormones may signal maternal metabolic and nutritional environments to offspring during postnatal development. The hormone apelin is highly abundant in BM but its regulation during lactation is completely unknown. Here, we evaluated whether maternal obesity and overnutrition impacted BM apelin and leptin levels in clinical cohorts and lactating rats.

METHODS

BM and plasma samples were collected from normal-weight and obese breastfeeding women, and from lactating rats fed a control or a high fat (HF) diet during lactation. Apelin and leptin levels were assayed by ELISA. Mammary gland (MG) apelin expression and its cellular localization in lactating rats was measured by quantitative RT-PCR and immunofluorescence, respectively.

RESULTS

BM apelin levels increased with maternal BMI, whereas plasma apelin levels decreased. BM apelin was also positively correlated with maternal insulin and C-peptide levels. In rats, maternal HF feeding exclusively during lactation was sufficient to increase BM apelin levels and decrease its plasma concentration without changing body weight. In contrast, BM leptin levels increased with maternal BMI in humans, but did not change with maternal HF feeding during lactation in rats. Apelin is highly expressed in the rat MG during lactation and was mainly localized to mammary myoepithelial cells. We found that MG apelin gene expression was up-regulated by maternal HF diet and positively correlated with BM apelin content and maternal insulinemia.

CONCLUSIONS

Our study indicates that BM apelin levels increase with long- and short-term overnutrition, possibly via maternal hyperinsulinemia and transcriptional upregulation of MG apelin expression in myoepithelial cells. Apelin regulates many physiological processes, including energy metabolism, digestive function, and development. Further studies are needed to unravel the consequences of such changes in offspring development.

Pretreatment with Lactobacillus fermentum XY18 Relieves Gastric Injury Induced by HCl/Ethanol in Mice via Antioxidant and Anti-Inflammatory Mechanisms

Aim

Lactobacillus fermentum XY18 (LF-XY18) is a bacterial strain with satisfactory antioxidant properties in vitro that we previously isolated from Xinjiang yogurt. This article will explore the preventive effect of LF-XY18 on acute gastric injury and provide the basis for the innovative development and application of lactic acid bacteria (LAB).

Methods

Kunming mice underwent gastric injury induced by hydrochloric acid and ethanol. LF-XY18 isolated from yogurt in Xinyuan County in the Yili region of Xinjiang was subsequently administered intragastrically to mice for 2 weeks to explore the mechanism of LF-XY18 in preventing gastric injury via its antioxidant effects.

Results

There was decreased gastric juice volume, gastric injury area, and formation of gastric mucosal lesions in the LF-XY18 mice as compared to those in the control mice, while LF-XY18 prevented the decrease in the gastric juice pH value in mice. Compared with the gastric injury model group mice, LF-XY18 reduced the serum levels of motilin, substance P, interleukin-6, interleukin-12, tumor necrosis factor-α, and interferon-γ but increased the serum levels of somatostatin and vasoactive intestinal peptide. The activities of superoxide dismutase, glutathione peroxidase, glutathione, and nitric oxide were increased in the gastric tissue of the LF-XY18 mice compared with the control mice, but malondialdehyde activity was decreased in the LF-XY18 mice. Quantitative polymerase chain reaction analysis illustrated that in the gastric tissue of LF-XY18 mice, the messenger RNA (mRNA) expression of occludin, epidermal growth factor (EGF), EGF receptor, vascular EGF, inhibitor kappa-B-α, neuronal nitric oxide synthase, endothelial nitric oxide synthase, cuprozinc superoxide dismutase, manganese superoxide dismutase, and catalase was stronger than that in the control mice, but the mRNA expression of activated B cells (NF-κB), inducible nitric oxide synthase, and cyclooxygenase-2 was weaker than in the control mice.

Conclusion

These results indicate that LF-XY18 has a potential role in the prevention of gastric injury through antioxidant effects, and a high concentration (1.0 × 10⁹ CFU/kg b.w.) of LF-XY18 has a stronger anti-gastric injury effect than a low concentration (1.0 × 10⁸ CFU/kg b.w.).

Apelin-13 inhibits apoptosis and excessive autophagy in cerebral ischemia/reperfusion injury

Apelin-13 is a novel endogenous ligand for an angiotensin-like orphan G-protein coupled receptor, and it may be neuroprotective against cerebral ischemia injury. However, the precise mechanisms of the effects of apelin-13 remain to be elucidated. To investigate the effects of apelin-13 on apoptosis and autophagy in models of cerebral ischemia/reperfusion injury, a rat model was established by middle cerebral artery occlusion. Apelin-13 (50 μg/kg) was injected into the right ventricle as a treatment. In addition, an SH-SY5Y cell model was established by oxygen-glucose deprivation/reperfusion, with cells first cultured in sugar-free medium with 95% N₂ and 5% CO₂ for 4 hours and then cultured in a normal environment with sugar-containing medium for 5 hours. This SH-SY5Y cell model was treated with 10^–7 M apelin-13 for 5 hours. Results showed that apelin-13 protected against cerebral ischemia/reperfusion injury. Apelin-13 treatment alleviated neuronal apoptosis by increasing the ratio of Bcl-2/Bax and significantly decreasing cleaved caspase-3 expression. In addition, apelin-13 significantly inhibited excessive autophagy by regulating the expression of LC3B, p62, and Beclin1. Furthermore, the expression of Bcl-2 and the phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway was markedly increased. Both LY294002 (20 μM) and rapamycin (500 nM), which are inhibitors of the PI3K/Akt/mTOR pathway, significantly attenuated the inhibition of autophagy and apoptosis caused by apelin-13. In conclusion, the findings of the present study suggest that Bcl-2 upregulation and mTOR signaling pathway activation lead to the inhibition of apoptosis and excessive autophagy. These effects are involved in apelin-13-induced neuroprotection against cerebral ischemia/reperfusion injury, both in vivo and in vitro. The study was approved by the Animal Ethical and Welfare Committee of Jining Medical University, China (approval No. 2018-JS-001) in February 2018.

Hunan insect tea polyphenols provide protection against gastric injury induced by HCl/ethanol through an antioxidant mechanism in mice

The purposes of this study were to explore the preventive and treatment effects of Hunan insect tea polyphenols (HITPs) on gastric injury in mice induced by HCl/ethanol and to investigate their molecular mechanisms of action. Both HITPs and ranitidine inhibited the formation and further deterioration of gastric mucosal lesions, reduced the secretion of gastric juice, and raised gastric juice pH compared to the control. The HITPs-H treated group had lower serum levels of motilin, substance P, and endothelin than the control group, but they had higher serum levels of vasoactive intestinal peptide and somatostatin. Mice treated with HITPs had lower serum levels of cytokines interleukin (IL)-6, IL-12, tumor necrosis factor-α (TNF-α), and interferon-γ than the control group. The activities of superoxide dismutase (SOD), nitric oxide, and glutathione peroxidase (GSH-Px) were higher in the gastric tissues of HITP-treated mice, but the malondialdehyde content was lower. Quantitative PCR analysis indicated that the mRNA expression of occludin, epidermal growth factor (EGF), EGF receptor (EGFR), vascular EGF (VEGF), inhibitor kappaB-α, cuprozinc-superoxide dismutase, manganese-superoxide dismutase, GSH-Px, neuronal nitric oxide synthase, and endothelial NOS increased significantly in the gastric tissues of HITP-treated mice. However, the activated B cell, inducible NOS, cyclooxygenase-2, TNF-α, IL-1 beta, and IL-6 mRNA expression levels in the HITPs group were lower than those in the control group. The protective effect of a high concentration (200 mg per kg bw) of HITPs on gastric injury induced by HCl/ethanol was stronger than that of a low concentration (100 mg per kg bw) of HITPs. High-performance liquid chromatography (HPLC) revealed that the HITPs contained cryptochlorogenic acid, (-)-epicatechin gallate, and isochlorogenic acid C. Taken together, our findings indicate that the HITPs played a role in the prevention of gastric damage. The antioxidant effect of the HITPs contributed to their potential value in the prevention and treatment of gastric injury. HITPs have broad prospects as biologically active substances for food development.

Unraveling the Role of ACE2, the Binding Receptor for SARS-CoV-2, in Inflammatory Bowel Disease

Angiotensin-converting enzyme 2 (ACE2) has been highlighted for its role as a receptor for SARS-CoV-2, responsible for the current COVID-19 pandemic. This review summarizes current knowledge about ACE2 as a multifunctional protein, focusing on its relevance in inflammatory bowel disease (IBD). As an enzyme, ACE2 may be protective in IBD because it favors the counter-regulatory arm of the renin-angiotensin system or deleterious because it metabolizes other anti-inflammatory/repairing elements. Meanwhile, as a receptor for SARS-CoV-2, the impact of ACE2 expression/activity on infection is still under debate because no direct evidence has been reported and, again, both protective and deleterious pathways are possible. Research has shown that ACE2 regulates the expression of the neutral amino acid transporter B0AT1, controlling tryptophan-associated intestinal inflammation and nutritional status. Finally, intact membrane-bound or shed soluble ACE2 can also trigger integrin signaling, modulating the response to anti-integrin biologic drugs used to treat IBD (such as vedolizumab) and fibrosis, a long-term complication of IBD. As such, future studies on ACE2 expression/activity in IBD can improve monitoring of the disease and explore an alternative pharmacological target.

Next Generation Sequencing Identify Rare Copy Number Variants in Non-syndromic Patent Ductus Arteriosus

Patent ductus arteriosus (PDA) is a common congenital cardiovascular malformation with both inherited and acquired causes. Several genes have been reported to be related to PDA, but the molecular pathogenesis is still unclear. Here, we screened a population matched cohort of 39 patients with PDA and 100 healthy children using whole exome sequencing (WES). And identified 10 copy number variants (CNVs) and 20 candidate genes using Gene ontology (GO) functional enrichment analysis. In gene network analysis, we screened 7 pathogenic CNVs of 10 candidate genes (MAP3K1, MYC, VAV2, WDR5, RXRA, APLNR, TJP1, ERCC2, FOSB, CHRNA4). Further analysis of transcriptome array showed that 7 candidate genes (MAP3K1, MYC, VAV2, APLNR, TJP1, FOSB, CHRNA4) were indeed significantly expressed in human embryonic heart. Moreover, CHRNA4 was observed the most important genes. Our data provided rare CNVs as potential genetic cause of PDA in humans and also advance understanding of the genetic components of PDA.

The effect of apelin-13 on gastric ischemia/reperfusion injury: the roles of sensory nerves and vagus nerve

Apelin is a peptide that plays a role in physiological processes such as angiogenesis, apoptosis, and proliferation. The aim of this study was to investigate the role of capsaicin-sensitive afferent neurons and vagus in the effect of apelin against ischemia/reperfusion (I/R) injury. The experimental groups were (1) control, (2) I/R, (3) apelin + I/R, (4) vagotomy + I/R, (5) vagotomy + apelin + I/R, (6) capsaicin + I/R, (7) capsaicin + apelin + I/R, (8) lorglumide + I/R, and (9) lorglumide + apelin + I/R. To test the potential gastroprotective effect of apelin-13, apelin-13 (2 mg/kg i.v.) was administered just before both ischemia and reperfusion. A vagotomy was performed 1 week before I/R in the vagotomized groups; capsaicin (125 mg/kg s.c.) was administrated 2 weeks before I/R in the capsaicin-treated groups and lorglumide (5 mg/kg i.p.) was administered 30 min before I/R in the lorglumide-treated groups. After I/R, a variety parameters in gastric tissue were analyzed. cfos expression was determined in brainstem samples. In the I/R group, the lesion index, myeloperoxidase activity, lipid peroxidation, nitric oxide, and tumor necrosis factor-α increased, and mucosal blood flow, prostaglandin-E₂, and calcitonin gene related peptide decreased. Apelin prevented the damaging effects of I/R and increased cfos expression in brainstem areas. Vagotomy, capsaicin, and lorglumide largely eliminated the gastroprotective effects of apelin-13. This study showed that sensory nerves and the vagus play regulatory roles in apelin-induced gastroprotection. Cholecystokinin may play a role in the effect of apelin through sensory neurons.

Roles of the Hepatic Endocannabinoid and Apelin Systems in the Pathogenesis of Liver Fibrosis

Hepatic fibrosis is the consequence of an unresolved wound healing process in response to chronic liver injury and involves multiple cell types and molecular mechanisms. The hepatic endocannabinoid and apelin systems are two signalling pathways with a substantial role in the liver fibrosis pathophysiology-both are upregulated in patients with advanced liver disease. Endogenous cannabinoids are lipid-signalling molecules derived from arachidonic acid involved in the pathogenesis of cardiovascular dysfunction, portal hypertension, liver fibrosis, and other processes associated with hepatic disease through their interactions with the CB₁ and CB₂ receptors. Apelin is a peptide that participates in cardiovascular and renal functions, inflammation, angiogenesis, and hepatic fibrosis through its interaction with the APJ receptor. The endocannabinoid and apelin systems are two of the multiple cell-signalling pathways involved in the transformation of quiescent hepatic stellate cells into myofibroblast like cells, the main matrix-producing cells in liver fibrosis. The mechanisms underlying the control of hepatic stellate cell activity are coincident despite the marked dissimilarities between the endocannabinoid and apelin signalling pathways. This review discusses the current understanding of the molecular and cellular mechanisms by which the hepatic endocannabinoid and apelin systems play a significant role in the pathophysiology of liver fibrosis.

Involvement of Novel Adipokines, Chemerin, Visfatin, Resistin and Apelin in Reproductive Functions in Normal and Pathological Conditions in Humans and Animal Models

It is well known that adipokines are endocrine factors that are mainly secreted by white adipose tissue. Their central role in energy metabolism is currently accepted. More recently, their involvement in fertility regulation and the development of some reproductive disorders has been suggested. Data concerning the role of leptin and adiponectin, the two most studied adipokines, in the control of the reproductive axis are consistent. In recent years, interest has grown about some novel adipokines, chemerin, visfatin, resistin and apelin, which have been found to be strongly associated with obesity and insulin-resistance. Here, we will review their expression and role in male and female reproduction in humans and animal models. According to accumulating evidence, they could regulate the secretion of GnRH (Gonadotropin-Releasing Hormone), gonadotropins and steroids. Furthermore, their expression and that of their receptors (if known), has been demonstrated in the human and animal hypothalamo-pituitary-gonadal axis. Like leptin and adiponectin, these novel adipokines could thus represent metabolic sensors that are able to regulate reproductive functions according to energy balance changes. Therefore, after investigating their role in normal fertility, we will also discuss their possible involvement in some reproductive troubles known to be associated with features of metabolic syndrome, such as polycystic ovary syndrome, gestational diabetes mellitus, preeclampsia and intra-uterine growth retardation in women, and sperm abnormalities and testicular pathologies in men.