Blocking the urotensin II receptor pathway ameliorates the metabolic syndrome and improves cardiac function in obese mice

Mechanisms and risk factors of metabolic syndrome in children and adolescents

Metabolic syndrome (MetS) is a complex disorder characterized by abdominal obesity, elevated blood pressure, hyperlipidemia, and elevated fasting blood glucose levels. The diagnostic criteria for MetS in adults are well-established, but there is currently no consensus on the definition in children and adolescents. The etiology of MetS is believed to involve a complex interplay between genetic predisposition and environmental factors. While genetic predisposition explains only a small part of MetS pathogenesis, modifiable environmental risk factors play a significant role. Factors such as maternal weight during pregnancy, children's lifestyle, sedentariness, high-fat diet, fructose and branched-chain amino acid consumption, vitamin D deficiency, and sleep disturbances contribute to the development of MetS. Early identification and treatment of MetS in children and adolescents is crucial to prevent the development of chronic diseases later in life. In this review we discuss the latest research on factors contributing to the pathogenesis of MetS in children, focusing on non-modifiable and modifiable risk factors, including genetics, dysbiosis and chronic low-grade inflammation.

The Association of Passive Smoking and Serum Urotensin-II Levels in Children

Urotensin-II (UT-II) is the most powerful vasoconstrictor agent and is known to play a role in heart failure, diabetes, pulmonary hypertension and asthma. The effect of passive smoking on UT-II levels is unknown. The present study aims to evaluate serum UT-II levels in children exposed to passive smoke. The study included a total of 120 children; 47 children not exposed to passive smoke were included in Group 1 (control group), and 73 children exposed to passive smoke were included in Group 2. Serum samples of the participants were stored at -80 °C after centrifugation and were assessed at least two times with high-precision human ELISA kits. Serum UT-II levels were significantly higher in the children exposed to passive smoke than in the children not exposed. Furthermore, Group 2 was grouped according to the number of cigarettes smoked at home per day, type of passive smoking (second-hand smoke or third-hand smoke), and how many people in their family and/or living together smoked. There was a positive correlation between the number of cigarettes they were exposed to per day and serum UT-II levels. Passive smoking in childhood may be associated with high serum UT-II levels.

Inhibition of U-II/UT signaling ameliorates cystitis-associated bladder hyperactivity by targeting the RhoA/Rho-kinase pathway

Urotensin II (U-II) and its receptor (UT) are involved in the pathogenesis of various diseases; however, their association with the development of cystitis has not been elucidated. The present study was designed to investigate the functional role of U-II/UT signaling in cyclophosphamide (CYP)-induced cystitis. A total of 60 female rats were randomly divided into the control and CYP-treated groups. Intraperitoneal injection of CYP successfully induced cystitis in rats of the CYP-treated group. The protein and mRNA expression levels of U-II and UT were significantly enhanced in rat bladder tissues of the CYP-treated group. Furthermore, the results of the immunofluorescence staining analysis demonstrated that CYP treatment apparently increased the expression levels of UT in the urothelium layer, detrusor smooth muscle, and bladder interstitial Cajal-like cells. The selective antagonist of UT, SB657510 (10 μm), significantly suppressed the CYP-induced increase in the spontaneous contractions of muscle strips and ameliorated the bladder hyperactivity of CYP-treated rats. Moreover, CYP treatment significantly increased the protein expression levels of Ras homolog family member (Rho) A and Rho-associated protein kinase 2 in rat bladder tissues. Following pretreatment with the Rho-kinase inhibitor Y-27632 (10 μm), the inhibitory effects of SB657510 (10 μm) on the spontaneous contractions of muscle strips were eliminated. In conclusion, the results of the present study suggested that activation of U-II/UT signaling promoted the development of cystitis-associated-bladder hyperactivity by targeting the RhoA/Rho-kinase pathway, indicating that the U-II/UT signaling could serve as a novel target for the treatment of interstitial cystitis/bladder pain syndrome.

The Role of Urotensin-II in Obesity and Metabolic Syndrome in Pediatric Population

Background: Urotensin-II (U-II) is a short cyclic peptide that is widely recognized as one of the most potent vasoconstrictors. U-II plays a role in the pathophysiology of MS, participating in the development of essential hypertension, insulin resistance, hyperglycemia, and a proinflammatory state. Methods: This study comprised 52 obese children and adolescents with a body mass index (BMI) z score > 2, aged 10 to 18 years. Serum levels of U-II were assessed using an enzyme-linked immunosorbent assay along with other standard biochemical parameters. Results: Elevated serum levels of U-II were recorded in the group of obese subjects with MS when compared with the group of obese subjects without MS (4.99 (8.97–3.16) vs. 4.17 (5.17–2.03) ng/mL, median and IQR, p = 0.026). Furthermore, a subgroup of study subjects with high blood pressure had significantly higher U-II levels in comparison with the normotensive subgroup (4.98 (7.19–3.22) vs. 3.32 (5.06–1.97) ng/mL, p = 0.027), while the subgroup with a positive family history of high blood pressure had significantly higher U-II levels when compared with subjects who had a negative family history of elevated blood pressure (5.06 (6.83–4.45) vs. 3.32 (6.13–2.21) ng/mL, p = 0.039). Conclusions: To the best of the author’s knowledge, this is the first study on the levels of U-II in obese children and adolescents, including a possible link to MS.

Carbonic anhydrase II/sodium-proton exchanger 1 metabolon complex in cardiomyopathy of ob-/- type 2 diabetic mice

Heart failure is the leading cause of death among diabetic people. Cellular and molecular entities leading to diabetic cardiomyopathy are, however, poorly understood. Coupling of cardiac carbonic anhydrase II (CAII) and Na⁺/H⁺ exchanger 1 (NHE1) to form a transport metabolon was analyzed in obese type 2 diabetic mice (ob^-/-) and control heterozygous littermates (ob^+/-). Echocardiography showed elevated systolic interventricular septum thickness and systolic posterior wall thickness in ob^-/- mice at 9 and 16 weeks. ob^-/- mice showed increased left ventricular (LV) weight/tibia length ratio and increased cardiomyocyte cross sectional area as compared to controls, indicating cardiac hypertrophy. Immunoblot analysis showed increased CAII expression in LV samples of ob^-/-vs. ob^+/- mice, and augmented Ser⁷⁰³ phosphorylation on NHE1 in ob^-/- hearts. Reciprocal co-immunoprecipitation analysis showed strong association of CAII and NHE1 in LV samples of ob^-/- mice. NHE1-dependent rate of intracellular pH (pH_i) normalization after transient acid loading of isolated cardiomyocytes was higher in ob^-/- mice vs. ob^+/-. NHE transport activity was also augmented in cultured H9C2 rat cardiomyoblasts treated with high glucose/high palmitate, and it was normalized after CA inhibition. We conclude that the NHE1/CAII metabolon complex is exacerbated in diabetic cardiomyopathy of ob^-/- mice, which may lead to perturbation of pH_i and [Na⁺] and [Ca²⁺] handling in these diseased hearts.

Urotensin II: an inflammatory cytokine

Urotensin II (UII) is a polypeptide molecule with neurohormone-like activity. It has been confirmed that UII is widely distributed in numerous organs of different animal species from fish to mammals, including humans. The UII receptor is orphan G-protein coupled receptor 14, also known as UT. The tissue distribution of UII and UT is highly consistent, and their expression may be regulated by autocrine and paracrine mechanisms. In the body, UII has many physiological and pathophysiological activities, such as vasoconstrictor and vasodilatory actions, cell proliferation, pro-fibrosis, neuroendocrine activity, insulin resistance, and carcinogenic and inflammatory effects, which have been recognized only in recent years. In fact, UII is involved in the process of inflammatory injury and plays a key role in the onset and development of inflammatory diseases. In this paper, we will review the roles UII plays in inflammatory diseases.

Chronic Urotensin-II Administration Improves Whole-Body Glucose Tolerance in High-Fat Diet-Fed Mice

Urotensin-II (U-II) is an endogenous peptide agonist of a G protein-coupled receptor-urotensin receptor. There are many conflicting findings about the effects of U-II on blood glucose. This study aims to explore the effects of U-II on glucose metabolism in high-fat diet-fed mice. Male C57BL/6J mice were fed a 45% high-fat diet or chow diet and were administered U-II intraperitoneally for in vivo study. Skeletal muscle C2C12 cells were used to determine the effects of U-II on glucose and fatty acid metabolism as well as mitochondrial respiratory function. In this study, we found that chronic U-II administration (more than 7 days) ameliorated glucose tolerance in high-fat diet-fed mice. In addition, chronic U-II administration reduced the weight gain and the adipose tissue weight, including visceral, subcutaneous, and brown adipose tissue, without a significant change in blood lipid levels. These were accompanied by the increased mRNA expression of the mitochondrial thermogenesis gene Ucp3 in skeletal muscle. Furthermore, in vitro treatment with U-II directly enhanced glucose and free fatty acid consumption in C2C12 cells with increased aerobic respiration. Taken together, chronic U-II stimulation leads to improvement on glucose tolerance in high-fat diet-fed mice and this effect maybe closely related to the reduction in adipose tissue weights and enhancement on energy substrate utilization in skeletal muscle.

The Urotensin II System and Carotid Atherosclerosis: A Role in Vascular Calcification

BACKGROUND AND AIMS

The aims of the present study were to determine the expression of urotensin II (UII), urotensin-II related peptide (URP), and their receptor (UT) in stable and unstable carotid atherosclerosis, and determine the effects of UII on human aortic smooth muscle cell (SMCs) calcification.

METHODS AND RESULTS

We examined UII, URP, and UT protein expression in 88 carotid endarterectomy specimens using immunohistochemistry. Expression of UII, URP, and UT was more evident in unstable compared to stable plaques (P < 0.05). Multivariate Spearman correlation analyses revealed significant positive correlations between UII, URP and UT overall staining and presence of calcification, severity of stenosis and inflammation (P < 0.05). Subjects undergoing carotid endarterectomy had significantly higher plasma UII levels, as assessed by ELISA, when compared with normolipidemic healthy control subjects (P < 0.05). Incubation of human aortic SMCs cultured in phosphate media with varying concentrations of UII resulted in a significant increase in calcium deposition and alkaline phosphatase activity. UII also significantly increased β-catenin translocation and expression of ALPL, BMP2, ON, and SOX9 (P < 0.05). Incubation of cells with phosphate medium alone increased the expression of the pre-UT and mature UT (P < 0.01), and addition of UII had a synergistic effect on pre-UT protein expression (P < 0.001) compared to phosphate medium alone.

CONCLUSIONS

Upregulation of UII, URP, and UT in unstable carotid endarterectomy plaques and plasma, and the stimulatory effect of UII on vascular smooth muscle cell calcification suggest that the UII system may play a role in the pathogenesis of vascular calcification and stability of atherosclerosis.

Effects of urotensin II on intracellular pH regulation in cultured human internal mammary artery smooth muscle cells

The Na(+)-H(+) exchanger (NHE) and the Na(+)-HCO3(-) co-transporter (NBC) have been confirmed as two major active acid extruders in many mammalian cells. Whether the NHE and NBC functional co-exist in human internal mammary artery smooth muscle cells (HIMASMCs) remains unclear. The aims of the present study were to investigate the acid-extruding mechanisms and to explore the effects of urotensin-II (U-II), a powerful vasoconstrictor, on pHi regulators in HIMASMCs. We investigated the changes of pHi by BCECF-fluorescence in HIMASMCs. We found that (a) two Na(+)-dependent acid extruders, i.e. NHE and NBC, functionally co-exist; (b) U-II (3-100 nM) induced a concentration-dependent intracellular acidosis; and (c) U-II (3-100 nM) caused a concentration-dependent increase on NHE activity, while decrease on NBC activity. In summary, we demonstrate for the first time that two acid-extruders, NHE and NBC, functionally co-exist in HIMASMCs. Moreover, U-II induces a concentration-dependent intracellular acidosis through the balanced effect of its effect on increasing NHE activity and decreasing NBC activity.

Selective inhibition of PI3K/Akt/mTOR signaling pathway regulates autophagy of macrophage and vulnerability of atherosclerotic plaque

Macrophage infiltration contributes to the instability of atherosclerotic plaques. In the present study, we investigated whether selective inhibition of PI3K/Akt/mTOR signaling pathway can enhance the stability of atherosclerotic plaques by activation of macrophage autophagy. In vitro study, selective inhibitors or siRNA of PI3K/Akt/mTOR pathways were used to treat the rabbit's peritoneal primary macrophage cells. Inflammation related cytokines secreted by macrophages were measured. Ultrastructure changes of macrophages were examined by transmission electron microscope. mRNA or protein expression levels of autophagy related gene Beclin 1, protein 1 light chain 3 II dots (LC3-II) or Atg5-Atg12 conjugation were assayed by quantitative RT-PCR or Western blot. In vivo study, vulnerable plaque models were established in 40 New Zealand White rabbits and then drugs or siRNA were given for 8 weeks to inhibit the PI3K/Akt/mTOR signaling pathway. Intravascular ultrasound (IVUS) was performed to observe the plaque imaging. The ultrastructure of the abdominal aortic atherosclerosis lesions were analyzed with histopathology. RT-PCR or Western blot methods were used to measure the expression levels of corresponding autophagy related molecules. We found that macrophage autophagy was induced in the presence of Akt inhibitor, mTOR inhibitor and mTOR-siRNA in vitro study, while PI3K inhibitor had the opposite role. In vivo study, we found that macrophage autophagy increased significantly and the rabbits had lower plaque rupture incidence, lower plaque burden and decreased vulnerability index in the inhibitors or siRNA treated groups. We made a conclusion that selective inhibition of the Akt/mTOR signal pathway can reduce macrophages and stabilize the vulnerable atherosclerotic plaques by promoting macrophage autophagy.