TRPV4 is involved in irisin-induced endothelium-dependent vasodilation

The mechanisms of exercise improving cardiovascular function by stimulating Piezo1 and TRP ion channels: a systemic review

Mechanosensitive ion channels are widely distributed in the heart, lung, bladder and other tissues, and plays an important role in exercise-induced cardiovascular function promotion. By reviewing the PubMed databases, the results were summarized using the terms "Exercise/Sport", "Piezo1", "Transient receptor potential (TRP)" and "Cardiovascular" as the keywords, 124-related papers screened were sorted and reviewed. The results showed that: (1) Piezo1 and TRP channels play an important role in regulating blood pressure and the development of cardiovascular diseases such as atherosclerosis, myocardial infarction, and cardiac fibrosis; (2) Exercise promotes cardiac health, inhibits the development of pathological heart to heart failure, regulating the changes in the characterization of Piezo1 and TRP channels; (3) Piezo1 activates downstream signaling pathways with very broad pathways, such as AKT/eNOS, NF-κB, p38MAPK and HIPPO-YAP signaling pathways. Piezo1 and Irisin regulate nuclear localization of YAP and are hypothesized to act synergistically to regulate tissue mechanical properties of the cardiovascular system and (4) The cardioprotective effects of exercise through the TRP family are mostly accomplished through Ca2+ and involve many signaling pathways. TRP channels exert their important cardioprotective effects by reducing the TRPC3-Nox2 complex and mediating Irisin-induced Ca2+ influx through TRPV4. It is proposed that exercise stimulates the mechanosensitive cation channel Piezo1 and TRP channels, which exerts cardioprotective effects. The activation of Piezo1 and TRP channels and their downstream targets to exert cardioprotective function by exercise may provide a theoretical basis for the prevention of cardiovascular diseases and the rehabilitation of clinical patients.

The role and underlying mechanisms of irisin in exercise-mediated cardiovascular protection

Irisin, a product of the post-translational processing of fibronectin type III domain-containing protein 5 (FNDC5), is a novel myokine which is upregulated during exercise. This hormone not only promotes the transformation of white adipose tissue into a brown-fat-like phenotype but also enhances energy expenditure and mitigates fat accumulation. Its role is crucial in the management of certain metabolic disorders such as diabetes and heart disease. Of note, the type of exercise performed significantly affects blood irisin levels, indicating the critical role of physical activity in regulating this hormone. This article aims to summarize the current scientific understanding of the role of irisin and the mechanisms through which it mediates cardiovascular protection through exercise. Moreover, this article aims to establish irisin as a potential target for preventing and treating cardiovascular diseases.

The effect of irisin on the ultrastructure of the thoracic aorta in rat: A morphometric study

BACKGROUND

One of the most recent hormones to be identified and isolated is irisin, extracted from mouse skeletal muscle in 2012. Irisin has been proven to alter blood pressure, which has an impact on blood vessels, enhance endothelial functions, and prevent injury to endothelial cells. The current study aimed to study the effect of irisin on the ultrastructure of the rat thoracic aorta using the transmission electron microscope (TEM).

MATERIALS AND METHODS

Twenty female rats were recruited for this study and divided into a control group (non-injected), and four experimental groups (injected groups) each consisting of 4 rats. The experimental groups were injected intraperitoneally with different doses of irisin (250ng/mL, 500ng/mL, 1000ng/mL, and 2000ng/mL) twice a week for 4weeks. Then, the descending thoracic aorta of all experimental rats were resected and proceeded with imaging.

RESULTS

The results of this study showed a change in the thickness of the tunica intima, internal elastic lamina, elastic lamellae, and external elastic lamina concerning increasing injected irisin concentration. While there was a significant increase in the thickness of tunica media (P<0.0001) and smooth muscle cells (P<0.05). Also, the results showed a significant increase in the number of elastic lamellae in the tunica media (P<0.0001).

CONCLUSION

Irisin had a major impact on the elasticity of the rat thoracic aorta wall, suggesting that it influences the growth factors of the wall and activates smooth muscle cells in addition to endothelial cells.

Hydrogen Sulfide and Irisin, Potential Allies in Ensuring Cardiovascular Health

Irisin is a myokine secreted under the influence of physical activity and exposure to low temperatures and through different exogenous stimuli by the cleavage of its precursor, fibronectin type III domain-containing protein 5 (FNDC5). It is mainly known for maintaining of metabolic homeostasis, promoting the browning of white adipose tissue, the thermogenesis process, and glucose homeostasis. Growing experimental evidence suggests the possible central role of irisin in the regulation of cardiometabolic pathophysiological processes. On the other side, hydrogen sulfide (H2S) is well recognized as a pleiotropic gasotransmitter that regulates several homeostatic balances and physiological functions and takes part in the pathogenesis of cardiometabolic diseases. Through the S-persulfidation of cysteine protein residues, H2S is capable of interacting with crucial signaling pathways, exerting beneficial effects in regulating glucose and lipid homeostasis as well. H2S and irisin seem to be intertwined; indeed, recently, H2S was found to regulate irisin secretion by activating the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α)/FNDC5/irisin signaling pathway, and they share several mechanisms of action. Their involvement in metabolic diseases is confirmed by the detection of their lower circulating levels in obese and diabetic subjects. Along with the importance of metabolic disorders, these modulators exert favorable effects against cardiovascular diseases, preventing incidents of hypertension, atherosclerosis, heart failure, myocardial infarction, and ischemia-reperfusion injury. This review, for the first time, aims to explore the role of H2S and irisin and their possible crosstalk in cardiovascular diseases, pointing out the main effects exerted through the common molecular pathways involved.

Irisin: A Potentially Fresh Insight into the Molecular Mechanisms Underlying Vascular Aging

Aging is a natural process that affects all living organisms, including humans. Aging is a complex process that involves the gradual deterioration of various biological processes and systems, including the cardiovascular system. Vascular aging refers to age-related changes in blood vessels. These changes can increase the risk of developing cardiovascular diseases, such as hypertension, atherosclerosis, and stroke. Recently, an exercise-induced muscle factor, irisin, was found to directly improve metabolism and regulate the balance of glucolipid metabolism, thereby counteracting obesity and insulin resistance. Based on a growing body of evidence, irisin modulates vascular aging. Adenosine monophosphate-activated protein kinase (AMPK) serves as a pivotal cellular energy sensor and metabolic modulator, acting as a central signaling cascade to coordinate various cellular processes necessary for maintaining vascular homeostasis. The vascular regulatory effects of irisin are closely intertwined with its interaction with the AMPK pathway. In conclusion, understanding the molecular processes used by irisin to regulate changes in vascular diseases caused by aging may inspire the development of techniques that promote healthy vascular aging. This review sought to describe the impact of irisin on the molecular mechanisms of vascular aging, including inflammation, oxidative stress, and epigenetics, from the perspective of endothelial cell function and vascular macroregulation, and summarize the multiple signaling pathways used by irisin to regulate vascular aging.

Role of TRPV4 on vascular tone regulation in pathophysiological states

Vascular tone regulation is a key event in controlling blood flow in the body. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) help regulate the vascular tone. Abnormal vascular responsiveness to various stimuli, including constrictors and dilators, has been observed in pathophysiological states although EC and VSMC coordinate to maintain the exquisite balance between contraction and relaxation in vasculatures. Thus, investigating the mechanisms underlying vascular tone abnormality is very important in maintaining vascular health and treating vasculopathy. Increased intracellular free Ca2+ concentration ([Ca2+]i) is one of the major triggers initiating each EC and VSMC response. Transient receptor potential vanilloid family member 4 (TRPV4) is a Ca2+-permeable non-selective ion channel, which is activated by several stimuli, and is presented in both ECs and VSMCs. Therefore, TRPV4 plays an important role in vascular responses. Emerging evidence indicates the role of TRPV4 on the functions of ECs and VSMCs in various pathophysiological states, including hypertension, diabetes, and obesity. This review focused on the link between TRPV4 and the functions of ECs/VSMCs, particularly its role in vascular tone and responsiveness to vasoactive substances.

New Insights into the Mutual Promotion of Rosacea, Anxiety, and Depression from Neuroendocrine Immune Aspects

Rosacea is a common chronic inflammatory skin disease with a complex etiology and undefined pathogenesis, and there is still a lack of targeted clinical treatment. Patients with rosacea are at a higher risk of anxiety and depression compared to the healthy population. Compared to skin conditions such as acne and psoriasis, rosacea has been much less studied in relation to multiple-etiology psychiatric disorders such as anxiety and depression. In contrast to the mainstream belief that the causal association between rosacea and psychiatric disorders is that rosacea increases the psychological burden of patients and thus triggers psychiatric disorders simply by altering their facial appearance, this review outlines the possible common mechanisms between rosacea and anxiety and depression disorders, starting from the pathophysiological mechanisms of transient receptor potential family cation channels, HPA axis, and Th1/Th17 cell polarization. It envisages the possibility of the neuroendocrine-immune interplay between rosacea and anxiety and depression, and new ideas on the complex causal relationship between rosacea and psychiatric disorders, offering more orientations to open up new therapeutic approaches for rosacea.

Perivascular Adipose Tissue and Vascular Smooth Muscle Tone: Friends or Foes?

Perivascular adipose tissue (PVAT) is a specialized type of adipose tissue that surrounds most mammalian blood vessels. PVAT is a metabolically active, endocrine organ capable of regulating blood vessel tone, endothelium function, vascular smooth muscle cell growth and proliferation, and contributing critically to cardiovascular disease onset and progression. In the context of vascular tone regulation, under physiological conditions, PVAT exerts a potent anticontractile effect by releasing a plethora of vasoactive substances, including NO, H₂S, H₂O₂, prostacyclin, palmitic acid methyl ester, angiotensin 1-7, adiponectin, leptin, and omentin. However, under certain pathophysiological conditions, PVAT exerts pro-contractile effects by decreasing the production of anticontractile and increasing that of pro-contractile factors, including superoxide anion, angiotensin II, catecholamines, prostaglandins, chemerin, resistin, and visfatin. The present review discusses the regulatory effect of PVAT on vascular tone and the factors involved. In this scenario, dissecting the precise role of PVAT is a prerequisite to the development of PVAT-targeted therapies.

Activation of TRPV4 by lactate as a critical mediator of renal fibrosis in spontaneously hypertensive rats after moderate- and high-intensity exercise

Moderate-intensity exercise training has been regarded a healthy way to alleviate kidney fibrosis by the transforming growth factor-beta (TGFβ) signaling pathway. However, the impact of different intensity exercise training on renal function is unknown, and the underlying mechanism is also unclear. The purpose of this study is to explore the effect of lactic acid in different intensity exercise training on renal fibrosis in spontaneous hypertension. Masson’s trichrome staining, immunohistochemistry, lactic acid kit, and Western blotting were applied on the excised renal tissue from six male Wistar–Kyoto rats (WKY) and 18 male spontaneously hypertensive rats (SHR), which were randomly divided into a sedentary hypertensive group (SHR), moderate-intensity exercise hypertensive group (SHR-M), and high-intensity exercise hypertensive group (SHR-H). The results revealed that renal and blood lactic acid, as well as the key fibrotic protein levels of transient receptor potential vanilloid 4 (TRPV4), TGFβ-1, phospho-Smad2/3 (p-Smad2/3), and connective tissue growth factor (CTGF), were significantly decreased in the SHR-M group when compared with the SHR and SHR-H groups. In further in vitro experiments, we selected normal rat kidney interstitial fibroblast (NRK-49F) cells. By immunofluorescence and Western blotting techniques, we found that TRPV4 antagonists (RN-1734) markedly inhibited lactate-induced fibrosis. In conclusion, compared with previous studies, high-intensity exercise training (HIET) can cause adverse effects (renal damage and fibrosis). High concentrations of lactic acid can aggravate renal fibrosis conditions via activating TRPV4-TGFβ1-SMAD2/3-CTGF-mediated renal fibrotic pathways in spontaneous hypertension. This finding might provide new ideas for treating hypertensive nephropathy with different intensity exercise in the future.

Irisin, a fascinating field in our times

Irisin is a muscle-secreted hormone that is generated by cleavage of membrane protein FNDC-5 (fibronectin type III domain-containing protein 5). Irisin is considered to be a mediator of exercise-induced metabolic improvements, such as browning of white adipose tissue, and is known to alleviate several chronic non-metabolic diseases. Thus, irisin may be an ideal therapeutic target for metabolic and non-metabolic diseases. However, several controversies regarding irisin have hindered its clinical translation. We review the generation, regulation (especially in exercise), and metabolic as well as therapeutic effects of irisin on metabolic and non-metabolic diseases. Furthermore, we discuss controversies regarding irisin and highlight potential future research directions.

Irisin Regulates Cardiac Responses to Exercise in Health and Diseases: a Narrative Review

Exercise has been recognized as an important non-pharmacological approach for the prevention, treatment, and rehabilitation of cardiovascular diseases, but the mechanisms of exercise in promoting cardiovascular health remain unclear. Exercise generates cardiac benefits via stimulating muscle to secret hundreds of myokines that directly enter circulation and target heart tissue. Therefore, inter-organ communication between skeletal muscle and heart may be one important regulating pattern, and such communication can occur through secretion of molecules, frequently known as myokines. Irisin, a newly identified myokine, is cleaved from fibronectin type III domain-containing protein 5 (FNDC5) and secreted by the stimulation of exercise. Recently, accumulating evidence focusing on the interaction between irisin and cardiac function has been reported. This review highlights the molecular signaling by which irisin regulates the benefits of exercise on cardiac function both in physiological and pathological process, and discusses the clinical potential of irisin in treating heart diseases. Exercise generates various cardiovascular benefits through stimulating skeletal muscle to secrete irisin. The exercise "hormone" irisin, both produced by exercise or recombinant form, exerts therapeutic effects in a group of cardiovascular disorders including heart failure, myocardial infarction, atherosclerosis and hypertension. However, the molecular mechanisms involved remain ambiguous.This review highlights the most up-to-date findings to bridge the gap between exercise, irisin and cardiovascular diseases, and discusses the potential clinical prospect of irisin.

Moderate-Intensity Exercise Improves Endothelial Function by Altering Gut Microbiome Composition in Rats Fed a High-Fat Diet

BACKGROUND

Obesity changes gut microbial ecology and is related to endothelial dysfunction. Although the correlation between gut microbial ecology and endothelial dysfunction has been studied in obese persons, the underlying mechanisms by which exercise enhances endothelial function in this group remain unclear. This study investigated whether exercise improves endothelial function and alters gut microbiome composition in rats fed a high-fat diet (HFD).

METHODS

Obesity was induced by an HFD for 11 weeks. Whole-body composition and endothelium-dependent relaxation of mesenteric arteries were measured. Blood biochemical tests were performed, and gut microbiomes were characterized by 16S rRNA gene sequencing on an Illumina HiSeq platform.

RESULTS

Exercise training for 8 weeks improved body composition in HFD-fed rats. Furthermore, compared with the untrained/HFD group, aerobic exercise significantly increased acetylcholine-induced, endothelium-dependent relaxation in mesenteric arteries (P < 0.05) and circulating vascular endothelial growth factor levels (P < 0.01) and decreased circulating C-reactive protein levels (P < 0.05). In addition, exercise and HFD resulted in alterations in the composition of the gut microbiome; exercise reduced the relative abundance of Clostridiales and Romboutsia. Moreover, 12 species of bacteria, including Romboutsia, were significantly associated with parameters of endothelial function in the overall sample.

CONCLUSIONS

These results suggest that aerobic exercise enhances endothelial function in HFD-fed rats by altering the composition of the gut microbiota. These findings provide new insights on the application of physical exercise for improving endothelial function in obese persons.

Irisin is an Effector Molecule in Exercise Rehabilitation Following Myocardial Infarction (Review)

Background: Regular exercise is an effective non-pharmacological therapy for treatment and prevention of cardiovascular disease (CVD). The therapeutic benefits of exercise are mediated partly through improved vascular and increase in metabolic health. Release of exercise-responsive myokines, including irisin, is associated with beneficial effects of exercise in CVD patients.

Observations: The present review provides an overview of the role of exercise in cardiac rehabilitation of patients with myocardial infarction (MI). Further, the role of irisin as a motion-responsive molecule in improving vascular and metabolic health is explored. Possible mechanism of cardioprotective effect of irisin-mediated exercise on myocardial infarction are also summarized in this review.

Conclusion and significance of the review: Irisin is associated with reduced inflammation, antioxidant properties, and anti-apoptotic effect, implying that it is a potential key mediator of the beneficial effects of exercise on vascular and metabolic health. The findings show that irisin is a promising therapeutic target for treatment of patients with cardiovascular disease, particularly post-MI. Further research should be conducted to elucidate the potential mechanisms of cardioprotective effects of irisin and explored whether irisin induced by exercise exerts rehabilitation effects post-MI.

Irisin relaxes rat thoracic aorta: MEK1/2 signaling pathway, KV channels, SKCa channels, and BKCa channels are involved in irisin-induced vasodilation

This study investigated the effects of irisin on vascular smooth muscle contractility in rat thoracic aorta, and the hypothesis that mitogen-activated protein kinase kinase (MEK1/2) signaling pathway, voltage-gated potassium (KV) channels, small-conductance calcium-activated potassium (SKCa) channels, and large-conductance calcium-activated potassium (BKCa) channels may have roles in these effects. Isometric contraction-relaxation responses of isolated thoracic aorta rings were measured with an organ bath model. The steady contraction was induced with 10-5 M phenylephrine (PHE), and then the concentration-dependent responses of irisin (10-9-10-6 M) were examined in endothelium-intact and -denuded rat thoracic aortas. Also, the effects of irisin incubations on PHE-mediated contraction and acetylcholine (ACh) - mediated relaxation were studied. Irisin exerted the vasorelaxant effects in both endothelium-intact and -denuded aortic rings at concentrations of 10-8, 10-7, and 10-6 M compared with the control groups (p < 0.001). Besides, pre-incubation of aortic rings with irisin (10 nM, 100 nM, or 1 µM for 30 min) augmented ACh-mediated (10-9-10-5) vasodilation in PHE-precontracted thoracic aorta segments but did not modulate PHE-mediated (10-9-10-5) contraction. In addition, MEK1/2 inhibitor U0126, KV channel blocker XE-991, SKCa channel blocker apamin, and BKCa channel blocker tetraethylammonium (TEA) incubations significantly inhibited the irisin-induced relaxation responses. In conclusion, the first physiological findings were obtained regarding the functional relaxing effects of irisin in rat thoracic aorta. The findings demonstrated that irisin induces relaxation responses in endothelium-intact and (or) endothelium-denuded aortic rings in a concentration-dependent manner. Furthermore, this study is the first to report that irisin-induced relaxation responses are related to the activity of the MEK1/2 pathway, KV channels, and calcium-activated K+ (SKCa and BKCa) channels.

Dexmedetomidine Alleviates Intracerebral Hemorrhage-Induced Anxiety-Like Behaviors in Mice Through the Inhibition of TRPV4 Opening

Post-stroke anxiety severely affects recovery in patients with intracerebral hemorrhage (ICH). Dexmedetomidine (Dex), a highly selective alpha 2 adrenal receptor (α2-AR) agonist, was recently found to exert an excellent protective effect against mental disorders including anxiety. The transient receptor potential vanilloid 4 (TRPV4) channel is involved in a series of diseases such as asthma, cancer, anxiety, and cardiac hypertrophy. This study examines whether Dex improved ICH-induced anxiety via the inhibition of TRPV4 channel opening. A rodent model of moderate ICH in the basal ganglia was established using autologous blood injection (20 μl). Mice were treated with Dex (25 μg/kg, intraperitoneal injection) every day for 3 days post-ICH. GSK1016790A (1 μmol/2 μl), an agonist of TRPV4, was administered via the left lateral ventricle. Thirty days post-ICH, post-stroke anxiety was evaluated by elevated plus-maze and open-field tests. Following behavioral tests, superoxide dismutase (SOD), malondialdehyde (MDA), astrocytic activation, and A1-and A2-type astrocytes were determined. Primary astrocytes were exposed to hemin to simulate ICH in vitro. Compared with sham-treated mice, Dex administration ameliorates ICH-induced decreases of distance and time in the open-arm, reduces distance and time in the central zone, increases astrocytic activation and A1-type astrocytes, elevates MDA content, downregulates total SOD contents, and decreases A2-type astrocytes. However, GSK1016790A partially reversed the neuroprotective effects of Dex. In addition, Dex significantly inhibited hemin-induced astrocytic activation in vitro. Dex improves ICH-induced anxiety-like behaviors in mice, and the mechanism might be associated with the inhibition of TRPV4-channel opening.

Physiological role of K+ channels in irisin-induced vasodilation in rat thoracic aorta

Irisin, an exercise-induced myokine, has been shown to have a peripheral vasodilator effect. However, little is known about the mechanisms underlying its effects. In this study, it was aimed to investigate the vasoactive effects of irisin on rat thoracic aorta, and the hypothesis that voltage-gated potassium (KV) channels, ATP-sensitive potassium (KATP) channels, small-conductance calcium-activated potassium (SKCa) channels, large-conductance calcium-activated potassium (BKCa) channels, intermediate-conductance calcium-activated potassium (IKCa) channels, inward rectifier potassium (Kir) channels, and two-pore domain potassium (K2P) channels may have roles in these effects. Isometric contraction-relaxation responses of isolated thoracic aorta rings were measured with an organ bath model. The steady contraction was induced with both 10-5 M phenylephrine and 45 mM KCl, and then the concentration-dependent responses of irisin (10-9-10-6 M) were examined. Irisin exerted the vasorelaxant effects in both endothelium-intact and -denuded aortic rings at concentrations of 10-8, 10-7, and 10-6 M (p < 0.001). Besides, KV channel blocker 4-aminopyridine, KATP channel blocker glibenclamide, SKCa channel blocker apamin, BKCa channel blockers tetraethylammonium and iberiotoxin, IKCa channel blocker TRAM-34, and Kir channel blocker barium chloride incubations significantly inhibited the irisin-induced relaxation responses. However, incubation of K2P TASK-1 channel blocker anandamide did not cause a significant decrease in the relaxation responses of irisin. In conclusion, the first physiological findings were obtained regarding the functional relaxing effects of irisin in rat thoracic aorta. Furthermore, this study is the first to report that irisin-induced relaxation responses are associated with the activity of KV, KATP, SKCa, BKCa, IKCa, and Kir channels.

The Emerging Role of Irisin in Cardiovascular Diseases

Irisin, a novel hormone like polypeptide, is cleaved and secreted by an unknown protease from a membrane‐spanning protein, FNDC5 (fibronectin type III domain‐containing protein 5). The current knowledge on the biological functions of irisin includes browning white adipose tissue, regulating insulin use, and anti‐inflammatory and antioxidative properties. Dysfunction of irisin has shown to be involved in cardiovascular diseases such as hypertension, coronary artery disease, myocardial infarction, and myocardial ischemia–reperfusion injury. Moreover, irisin gene variants are also associated with cardiovascular diseases. In this review, we discuss the current knowledge on irisin‐mediated regulatory mechanisms and their roles in the pathogenesis of cardiovascular diseases.

Fibronectin type III domain-containing 5 in cardiovascular and metabolic diseases: a promising biomarker and therapeutic target

Cardiovascular and metabolic diseases are the leading causes of death and disability worldwide and impose a tremendous socioeconomic burden on individuals as well as the healthcare system. Fibronectin type III domain-containing 5 (FNDC5) is a widely distributed transmembrane glycoprotein that can be proteolytically cleaved and secreted as irisin to regulate glycolipid metabolism and cardiovascular homeostasis. In this review, we present the current knowledge on the predictive and therapeutic role of FNDC5 in a variety of cardiovascular and metabolic diseases, such as hypertension, atherosclerosis, ischemic heart disease, arrhythmia, metabolic cardiomyopathy, cardiac remodeling, heart failure, diabetes mellitus, and obesity.

Irisin in atherosclerosis

Irisin, a novel exercise-induced myokine, has been shown to play important roles in increasing white adipose tissue browning, regulating energy metabolism and improving insulin resistance. Growing evidence suggests a direct role for irisin in preventing atherosclerosis (AS) by inhibiting oxidative stress, improving dyslipidemia, facilitating anti-inflammation, reducing cellular damage and recovering endothelial function. In addition, some studies have noted that serum irisin levels play an essential role in cardiovascular diseases (CVDs) risk prediction, highlighting that irisin has the potential to be a useful predictive marker and therapeutic target of AS, especially in monitoring therapeutic efficacy. This review summarizes the understanding of irisin-mediated regulation in essential biological pathways and functions in atherosclerosis and prompts further exploitation of the biological properties of irisin in the pathogenesis of atherosclerosis.

Serum Irisin May Predict Cardiovascular Events in Elderly Patients With Chronic Kidney Disease Stage 3-5

OBJECTIVE

Irisin is a circulating myokine released from skeletal muscles after physical exercise. Irisin production decreases during the course of chronic kidney disease (CKD) as a potential consequence of sarcopenia and physical inactivity.

METHODS

This observational study explored the relationship of serum irisin with cardiovascular outcome in 79 patients with stage 3-5 CKD.

RESULTS

Serum irisin was significantly higher in healthy subjects (n = 20) than that in CKD patients (7 ± 2 vs. 3.1 ± 0.9 μg/mL; P = .0001) and was higher in patients with CKD stage 3 (3.2 ± 1 μg/mL) than in patients at stage 4 and 5 taken together (n = 36, 2.8 ± 0.7 μg/mL, P = .05). Patients in the lowest serum irisin tertile had lower serum 1,25(OH)₂D levels (21 ± 11 pg/mL) than patients in the middle (30 ± 13 pg/mL; P = .005) and the highest tertile (27 ± 14 pg/mL; P = .047). Patients in the highest tertile had lower Kauppila score (10.6 ± 6.9) than patients in the middle (11.8 ± 5.5; P = .007) and the lowest tertile (6.9 ± 6.8; P = .043). Twenty patients suffered from cardiovascular events during a 3-year follow-up. A Cox regression model using age, body weight, presence of diabetes mellitus, gender, Kauppila calcification score, serum values of FGF23 (as logarithm), phosphate, sclerostin, albumin and cholesterol, estimated glomerular filtration rate, and serum irisin tertiles as covariates showed that patients in the highest tertile of serum irisin had a lower cardiovascular risk than patients in the middle tertile (B, 2.38; odds ratio, 10.8; 95% confidence interval, 1.65-58.13; P = .013) or in the lowest tertile (B, 1.61; odds ratio, 5; 95% confidence interval, 1.09-22.83; P = .038).

CONCLUSIONS

These findings suggest that serum irisin may be a marker of cardiovascular outcome in patients with CKD.

İrisin ve Vasküler Kontraktilite Üzerine Etkileri

Bu derleme, irisin hakkındaki mevcut bilgileri ve irisinin vasküler tonusa aracılık etmedeki etkin rolünü özetleme çabasıdır. Egzersiz kronik, bulaşıcı olmayan hastalıkların, tip 2 diyabetin ve özellikle kardiyovasküler hastalıkların önlenmesinde bir dayanak noktasıdır. Egzersiz/fiziksel aktiviteye yanıt olarak üretilen yeni bir miyokin olan irisin, beyaz yağ dokusunun ‘esmerleşmesini’ teşvik ederek enerji harcamalarında artışa neden olur. Bu hormonun ilk tanımında, öncül fibronektin tip III alan içeren protein 5’ten ayrılan irisinin dolaşımdaki yüksek seviyeleri, insülin direncinin azalmasıyla düzelmiş glikoz homeostazı ile ilişkilendirilmiştir. İrisinin insanda farklı hedef doku veya organlar üzerindeki etkileri, sağlığın desteklenmesi veya çeşitli metabolik hastalıkların düzenlenmesinde fizyolojik işlevlerini ortaya çıkarmıştır. İrisinin işlevinin anlaşılmasının birçok hastalık ve gelişiminin anlaşılmasında anahtar olabileceğine inanılmaktadır. İrisinin metabolik düzenleme, enerji harcaması ve glikoz homeostazında kilit bir rol oynadığı gösterilmiştir. Hem hayvanlarda hem de insanlarda yapılan çeşitli çalışmalardan elde edilen yeni bulgular, irisinin vasküler aktiviteyi modüle etmek gibi başka olumlu etkilere de sahip olabileceğini ve böylece egzersiz kaynaklı birçok sağlık yararına aracılık ettiğini göstermektedir. Deneysel bulgular, irisinin hipertansiyon gibi anormal vazokonstriksiyona bağlı hastalıkların tedavisinde yararlı bir ajan olabileceğini düşündürmektedir. Bununla birlikte, irisinin rolü ve işlevi hakkındaki veriler tartışmaya yol açmıştır. Hipertansiyon tedavisinde irisinin etkinliğini belirlemek için daha ayrıntılı mekanizma çalışmaları ve in vivo çalışmalar gereklidir. İrisinin etki mekanizmalarının anlaşılmasındaki bir başka güçlü sınırlama ise, insanlarda ve hayvanlarda bugüne kadar halen tanımlanamayan irisin reseptörü hakkındaki bilgi eksikliğidir.

Irisin: A New Code Uncover the Relationship of Skeletal Muscle and Cardiovascular Health During Exercise

Exercise not only produces beneficial effects on muscle itself via various molecular pathways, but also mediates the interaction between muscles and other organs in an autocrine/paracrine manner through myokines, which plays a positive role in maintaining overall health. Irisin, an exercise-derived myokine, has been found involved in the regulation of some cardiovascular diseases. However, the relationship between irisin and cardiovascular health is not fully elucidated and there are some divergences on the regulation of irisin by exercise. In this review, we present the current knowledge on the origin and physiology of irisin, describe the regulation of irisin by acute and chronic exercises, and discuss the divergences of the related research results. Importantly, we discuss the role of irisin as a biomarker in the diagnosis of cardiovascular diseases and describe its treatment and molecular mechanism in some cardiovascular diseases. It is expected that irisin will be used as a therapeutic agent to combat cardiovascular diseases or other disorders caused by inactivity in the near future.

The Potential Role of Irisin in Vascular Function and Atherosclerosis: A Review

Exercise is an effective intervention for both the prevention and the treatment of obesity and insulin resistance because skeletal muscle secretes many bioactive proteins that contribute to the beneficial effect of exercise. It has been revealed that irisin plays an important role in metabolic homeostasis and both acute and chronic exercises increase circulating irisin in experimental animal models and in humans. Although previous studies have reported that the irisin-related signaling mechanism may play a beneficial role in the treatment of metabolic diseases including obesity, metabolic syndrome, insulin resistance, and diabetes mellitus, studies on whether irisin plays a key role in vascular function and vascular complications are still insufficient. Therefore, the current review aims to summarize the accumulating evidence showing the potential role of irisin, especially in vascular reactivity and vascular abnormalities such as atherosclerosis.

Transient receptor potential vanilloid 4 channels as therapeutic targets in diabetes and diabetes-related complications

With an estimated 425 million diabetes patients worldwide in 2019, type 2 diabetes has reached a pandemic proportion and represents a major unmet medical need. A key determinant of the development and progression of type 2 diabetes is pancreatic -cell dysfunction, including the loss of cell mass, the impairment of insulin biosynthesis and inadequate exocytosis. Recent studies have shown that transient receptor potential vanilloid 4 (TRPV4), a Ca2+ -permeable non-selective cation channel, is involved in -cell replication, insulin production and secretion. TRPV4 agonists have insulinotropic activity in pancreatic -cell lines, but the prolonged activation of TRPV4 leads to -cell dysfunction and death. In addition, TRPV4 is involved in a wide variety of pathophysiological activities, and has been reported to play an important role in diabetes-related complications, such as obesity, cardiovascular diseases, diabetic retinopathy, nephropathy and neuropathy. In a rodent type 2 diabetes model, Trpv4 agonists promote vasodilation and improve cardiovascular function, whereas Trpv4 antagonists reduce high-fat diet-induced obesity, insulin resistance, diabetic nephropathy, retinopathy and neuropathy. These findings raise interest in using TRPV4 as a therapeutic target for type 2 diabetes. In this review, we intend to summarize the latest findings regarding the role of TRPV4 in diabetes as well as diabetes-related conditions, and to evaluate its potential as a therapeutic target for diabetes and diabetes-related diseases.

Circulating Irisin and esRAGE as Early Biomarkers of Decline of Metabolic Health

A decline in metabolic health may take place before observing any alteration in the levels of the traditional metabolic markers. New indicators of metabolic derangement are therefore compelling. Irisin is a myokine with important metabolic functions. The role of irisin as a metabolic biomarker in humans has not been fully established yet. We quantified plasma irisin and esRAGE in 106 apparently healthy individuals and we performed a cluster analysis to evaluate their associations with metabolic profile. Plasma levels of various traditional markers of metabolic risk (i.e., glucose and lipid levels) were all within the ranges of normality. We identified two clusters of individuals. Compared to cluster 2, individuals in cluster 1 had higher irisin levels, a metabolic profile shifted toward the limits of the reference ranges and lower esRAGE levels. The traditional metabolic blood tests seem not to be enough to identify a metabolic decline early. Irisin increase and esRAGE decrease may reflect a metabolic derangement at the beginning of its development. The role of these molecules as early biomarkers of decline of metabolic health seems an interesting topic to be further explored.

Exercise restores impaired endothelium-derived hyperpolarizing factor-mediated vasodilation in aged rat aortic arteries via the TRPV4-KCa2.3 signaling complex

Background

Aging leads to structural and functional changes in the vasculature characterized by arterial endothelial dysfunction and stiffening of large elastic arteries and is a predominant risk factor for cardiovascular disease, the leading cause of morbidity and mortality in modern societies. Although exercise reduces the risk of many age-related diseases, including cardiovascular disease, the mechanisms underlying the beneficial effects of exercise on age-related endothelial function fully elucidated.

Purpose

The present study explored the effects of exercise on the impaired endothelium-derived hyperpolarizing factor (EDHF)–mediated vasodilation in aged arteries and on the involvement of the transient receptor potential vanilloid 4 (TRPV4) channel and the small-conductance calcium-activated potassium (K_Ca2.3) channel signaling in this process.

Methods

Male Sprague-Dawley rats aged 19–21 months were randomly assigned to a sedentary group or to an exercise group. Two-month-old rats were used as young controls.

Results

We found that TRPV4 and K_Ca2.3 isolated from primary cultured rat aortic endothelial cells pulled each other down in co-immunoprecipitation assays, indicating that the two channels could physically interact. Using ex vivo functional arterial tension assays, we found that EDHF-mediated relaxation induced by acetylcholine or by the TRPV4 activator GSK1016790A was markedly decreased in aged rats compared with that in young rats and was significantly inhibited by TRPV4 or K_Ca2.3 blockers in both young and aged rats. However, exercise restored both the age-related and the TRPV4-mediated and K_Ca2.3-mediated EDHF responses.

Conclusion

These results suggest an important role for the TRPV4-K_Ca2.3 signaling undergirding the beneficial effect of exercise to ameliorate age-related arterial dysfunction.

TRP Channels in Angiogenesis and Other Endothelial Functions

Angiogenesis is the growth of blood vessels mediated by proliferation, migration, and spatial organization of endothelial cells. This mechanism is regulated by a balance between stimulatory and inhibitory factors. Proangiogenic factors include a variety of VEGF family members, while thrombospondin and endostatin, among others, have been reported as suppressors of angiogenesis. Transient receptor potential (TRP) channels belong to a superfamily of cation-permeable channels that play a relevant role in a number of cellular functions mostly derived from their influence in intracellular Ca²⁺ homeostasis. Endothelial cells express a variety of TRP channels, including members of the TRPC, TRPV, TRPP, TRPA, and TRPM families, which play a relevant role in a number of functions, including endothelium-induced vasodilation, vascular permeability as well as sensing hemodynamic and chemical changes. Furthermore, TRP channels have been reported to play an important role in angiogenesis. This review summarizes the current knowledge and limitations concerning the involvement of particular TRP channels in growth factor-induced angiogenesis.

Transient receptor potential (TRP) channels: a metabolic TR(i)P to obesity prevention and therapy

Cellular transport of ions, especially by ion channels, regulates physiological function. The transient receptor potential (TRP) channels, with 30 identified so far, are cation channels with high calcium permeability. These ion channels are present in metabolically active tissues including adipose tissue, liver, gastrointestinal tract, brain (hypothalamus), pancreas and skeletal muscle, which suggests a potential role in metabolic disorders including obesity. TRP channels have potentially important roles in adipogenesis, obesity development and its prevention and therapy because of their physiological properties including calcium permeability, thermosensation and taste perception, involvement in cell metabolic signalling and hormone release. This wide range of actions means that organ-specific actions are unlikely, thus increasing the possibility of adverse effects. Delineation of responses to TRP channels has been limited by the poor selectivity of available agonists and antagonists. Food constituents that can modulate TRP channels are of interest in controlling metabolic status. TRP vanilloid 1 channels modulated by capsaicin have been the most studied, suggesting that this may be the first target for effective pharmacological modulation in obesity. This review shows that most of the TRP channels are potential targets to reduce metabolic disorders through a range of mechanisms.