The Role of Oxytocin in Cardiovascular Protection

Oxytocin and cortisol concentrations in urine and saliva in response to physical exercise in humans

BACKGROUND

While peripheral markers of endogenous oxytocin and glucocorticoid release are widely employed in psychological and behavioural research, there remains uncertainty regarding the effectiveness of saliva and urine samples in accurately capturing fluctuating hormone levels in response to relevant stimuli. In addition, it is unclear whether and under which conditions, urinary concentrations correlate with salivary levels of oxytocin and cortisol.

METHODS

In the present study, two groups of healthy adult male and female participants (N=43) provided heart rate, saliva, and urine samples before and after exercising at different durations and intensities (3 ×10 min of running vs. 60 min of running). Effects of age, gender, cycle phase, and previous running experience were considered in the statistical analyses. Concentrations of oxytocin and cortisol were analysed in both saliva, and urine using validated assays.

RESULTS

Runners of both groups had significantly increased oxytocin concentrations in urine and saliva after running than before. Oxytocin in saliva was elevated after 10 min and peaked after 30 min of running. Only participants of the long-running group showed an increase in urinary cortisol concentrations following exercise (and only after 90 min of stimulus onset), and neither group had a significant increase in salivary cortisol levels. Oxytocin rise in urine and saliva from basal to post-run was strongly and significantly correlated, as was cortisol rise from basal to post-rest, but no correlations between absolute hormone concentrations were found for oxytocin.

CONCLUSIONS

Our results show that both urine and saliva are useful body fluids that can provide meaningful results when measuring oxytocin and cortisol concentrations after a physical stimulus. While temporal resolution may be better with salivary sampling as higher sampling frequency is possible, signal strength and robustness were better in urinary samples. Importantly, we report a strong correlation between the magnitude of change in oxytocin and cortisol concentrations in urine and saliva following physical exercise, but no correlations between absolute oxytocin concentrations in the two substrates.

Oxytocin does not acutely improve glucose tolerance in men with type 2 diabetes

AIM

To assess oxytocin's acute glucoregulatory impact in men with type 2 diabetes in the context of our previous findings that oxytocin improves β-cell responsivity in healthy men.

METHODS

In a double-blind, crossover comparison, intranasal oxytocin (24 IU) and placebo, respectively, were administered to 25 fasted men with non-insulin-treated type 2 diabetes (age ± standard error of the mean, 63.40 ± 1.36 years; body mass index, 27.77 ± 0.66 kg/m2; HbA1c, 6.86% ± 0.08%; Homeostatic Model Assessment of Insulin Resistance (HOMA-IR, 3.44 ± 0.39) 60 minutes before an oral glucose tolerance test (oGTT). Key outcomes were compared with previous results in men with normal weight or obesity.

RESULTS

Oxytocin compared with placebo increased plasma oxytocin concentrations and reduced the heart rate, but did not alter glucose metabolism in the 3 hours after oGTT onset (area under the curve, glucose, 2240 ± 80.5 vs. 2190 ± 69.5 mmol/L × min; insulin, 45 663 ± 4538 vs. 44 343 ± 4269 pmol/L × min; C-peptide, 235 ± 5.1 vs. 231 ± 15.9 nmol/L × min).

CONCLUSIONS

This outcome contrasts with the oxytocin-induced attenuation of early postprandial glucose excursions in normal-weight individuals, but is in line with the absence of respective effects in men with obesity. We conclude that insulin resistance in type 2 diabetes is associated with decreased sensitivity to the acute glucoregulatory effect of oxytocin in male individuals.

Role of oxytocin in bone

Oxytocin (OT) is a posterior pituitary hormone that, in addition to its role in regulating childbirth and lactation, also exerts direct regulatory effects on the skeleton through peripheral OT and oxytocin receptor (OTR). Bone marrow mesenchymal stem cells (BMSCs), osteoblasts (OB), osteoclasts (OC), chondrocytes, and adipocytes all express OT and OTR. OT upregulates RUNX2, BMP2, ALP, and OCN, thereby enhancing the activity of BMSCs and promoting their differentiation towards OB rather than adipocytes. OT also directly regulates OPG/RANKL to inhibit adipocyte generation, increase the expression of SOX9 and COMP, and enhance chondrocyte differentiation. OB can secrete OT, exerting influence on the surrounding environment through autocrine and paracrine mechanisms. OT directly increases OC formation through the NκB/MAP kinase signaling pathway, inhibits osteoclast proliferation by triggering cytoplasmic Ca2+ release and nitric oxide synthesis, and has a dual regulatory effect on OCs. Under the stimulation of estrogen, OB synthesizes OT, amplifying the biological effects of estrogen and OT. Mediated by estrogen, the OT/OTR forms a feedforward loop with OB. Apart from estrogen, OT also interacts with arginine vasopressin (AVP), prostaglandins (PGE2), leptin, and adiponectin to regulate bone metabolism. This review summarizes recent research on the regulation of bone metabolism by OT and OTR, aiming to provide insights into their clinical applications and further research.

Mini Review: the non-neuronal cardiac cholinergic system in type-2 diabetes mellitus

Diabetic heart disease remains the leading cause of death in individuals with type-2 diabetes mellitus (T2DM). Both insulin resistance and metabolic derangement, hallmark features of T2DM, develop early and progressively impair cardiovascular function. These factors result in altered cardiac metabolism and energetics, as well as coronary vascular dysfunction, among other consequences. Therefore, gaining a deeper understanding of the mechanisms underlying the pathophysiology of diabetic heart disease is crucial for developing novel therapies for T2DM-associated cardiovascular disease. Cardiomyocytes are equipped with the cholinergic machinery, known as the non-neuronal cardiac cholinergic system (NNCCS), for synthesizing and secreting acetylcholine (ACh) as well as possessing muscarinic ACh receptor for ACh binding and initiating signaling cascade. ACh from cardiomyocytes regulates glucose metabolism and energetics, endothelial function, and among others, in an auto/paracrine manner. Presently, there is only one preclinical animal model - diabetic db/db mice with cardiac-specific overexpression of choline transferase (Chat) gene - to study the effect of activated NNCCS in the diabetic heart. In this mini-review, we discuss the physiological role of NNCCS, the connection between NNCCS activation and cardiovascular function in T2DM and summarize the current knowledge of S-Nitroso-NPivaloyl-D-Penicillamine (SNPiP), a novel inducer of NNCCS, as a potential therapeutic strategy to modulate NNCCS activity for diabetic heart disease.

Control of Dopamine Signal in High-Order Receptor Complex on Striatal Astrocytes

The receptor-receptor interaction (RRI) of G protein-coupled receptors (GPCRs) leads to new functional entities that are conceptually distinct from the simple addition of signals mediated by the activation of the receptors that form the heteromers. Focusing on astrocytes, there is evidence for the existence of inhibitory and facilitatory RRIs, including the heteromers formed by the adenosine A2A and the dopamine D2 receptors, by A2A and the oxytocin receptor (OTR), and the D2-OTR heteromers. The possible involvement of these receptors in mosaicism has never been investigated in striatal astrocytes. By biophysical and functional approaches, we focused our attention on the existence of an A2A-D2-OTR high-order receptor complex and its role in modulating cytosolic calcium levels and endogenous glutamate release, when striatal astrocyte processes were stimulated with 4-aminopyridine. Functional data indicate a permissive role of OTR on dopamine signaling in the regulation of the glutamatergic transmission, and an inhibitory control mediated by A2A on both the D2-mediated signaling and on the OTR-facilitating effect on D2. Imaging biochemical and bioinformatic evidence confirmed the existence of the A2A-D2-OTR complex and its ternary structure in the membrane. In conclusion, the D2 receptor appears to be a hotspot in the control of the glutamate release from the astrocytic processes and may contribute to the regulation and integration of different neurotransmitter-mediated signaling in the striatum by the A2A-D2-OTR heterotrimers. Considering the possible selectivity of allosteric interventions on GPCRs organized as receptor mosaics, A2A-D2-OTR heterotrimers may offer selective pharmacological targets in neuropsychiatric disorders and neurodegenerative diseases.

The psychophysiology of music-based interventions and the experience of pain

In modern times there is increasing acceptance that music-based interventions are useful aids in the clinical treatment of a range of neurological and psychiatric conditions, including helping to reduce the perception of pain. Indeed, the belief that music, whether listening or performing, can alter human pain experiences has a long history, dating back to the ancient Greeks, and its potential healing properties have long been appreciated by indigenous cultures around the world. The subjective experience of acute or chronic pain is complex, influenced by many intersecting physiological and psychological factors, and it is therefore to be expected that the impact of music therapy on the pain experience may vary from one situation to another, and from one person to another. Where pain persists and becomes chronic, aberrant central processing is a key feature associated with the ongoing pain experience. Nonetheless, beneficial effects of exposure to music on pain relief have been reported across a wide range of acute and chronic conditions, and it has been shown to be effective in neonates, children and adults. In this comprehensive review we examine the various neurochemical, physiological and psychological factors that underpin the impact of music on the pain experience, factors that potentially operate at many levels - the periphery, spinal cord, brainstem, limbic system and multiple areas of cerebral cortex. We discuss the extent to which these factors, individually or in combination, influence how music affects both the quality and intensity of pain, noting that there remains controversy about the respective roles that diverse central and peripheral processes play in this experience. Better understanding of the mechanisms that underlie music's impact on pain perception together with insights into central processing of pain should aid in developing more effective synergistic approaches when music therapy is combined with clinical treatments. The ubiquitous nature of music also facilitates application from the therapeutic environment into daily life, for ongoing individual and social benefit.

Stretch-induced compliance mechanism in pregnancy-induced cardiac hypertrophy and the impact of cardiovascular risk factors

Pressure overload-induced hypertrophy compromises cardiac stretch-induced compliance (SIC) after acute volume overload (AVO). We hypothesized that SIC could be enhanced by physiological hypertrophy induced by pregnancy's chronic volume overload. This study evaluated SIC-cardiac adaptation in pregnant women with or without cardiovascular risk (CVR) factors. Thirty-seven women (1st trimester, 1stT) and a separate group of 31 (3rd trimester, 3rdT) women [healthy or with CVR factors (obesity and/or hypertension and/or with gestational diabetes)] underwent echocardiography determination of left ventricular end-diastolic volume (LVEDV) and E/e' before (T0), immediately after (T1), and 15 min after (T2; SIC) AVO induced by passive leg elevation. Blood samples for NT-proBNP quantification were collected before and after the AVO. Acute leg elevation significantly increased inferior vena cava diameter and stroke volume from T0 to T1 in both 1stT and 3rdT, confirming AVO. LVEDV and E/e' also increased immediately after AVO (T1) in both 1stT and 3rdT. SIC adaptation (T2, 15 min after AVO) significantly decreased E/e' in both trimesters, with additional expansion of LVEDV only in the 1stT. NT-pro-BNP increased slightly after AVO but only in the 1stT. CVR factors, but not parity or age, significantly impacted SIC cardiac adaptation. A distinct functional response to SIC was observed between 1stT and 3rdT, which was influenced by CVR factors. The LV of 3rdT pregnant women was hypertrophied, showing a structural limitation to dilate with AVO, whereas the lower LV filling pressure values suggest increased diastolic compliance.NEW & NOTEWORTHY The sudden increase of volume overload triggers an acute myocardial stretch characterized by an immediate rise in contractility by the Frank-Starling mechanism, followed by a progressive increase known as the slow force response. The present study is the first to characterize echocardiographically the stretch-induced compliance (SIC) mechanism in the context of physiological hypertrophy induced by pregnancy. A distinct functional adaptation to SIC was observed between first and third trimesters, which was influenced by cardiovascular risk factors.

Lactobacillus reuteri inhibits Staphylococcus aureus-induced mastitis by regulating oxytocin releasing and gut microbiota in mice

Mastitis is the most frequent disease of cows and has well-recognized detrimental effects on animal wellbeing and dairy farm profitability. With the advent of the postantibiotic era, alternative antibiotic agents, especially probiotics, have received increasing attention in the treatment of mastitis. Based on research showing that Lactobacillus reuteri (L. reuteri) has anti-inflammatory effects, this study explored the protective effects and mechanisms of L. reuteri against mastitis induced by Staphylococcus aureus (S. aureus) in mice. First, mice with S. aureus-induced mastitis were orally administered L. reuteri, and the inflammatory response in the mammary gland was observed. The results showed that L. reuteri significantly inhibited S. aureus-induced mastitis. Moreover, the concentration of oxytocin (OT) and protein expression of oxytocin receptor (OTR) were measured, and inhibition of OTR or vagotomy reversed the protective effect of L. reuteri or its culture supernatant (LCS) on S. aureus-induced mastitis. In addition, in mouse mammary epithelial cells (MMECs), OT inhibited the inflammation induced by S. aureus by inhibiting the protein expression of OTR. It was suggested that L. reuteri protected against S. aureus-induced mastitis by releasing OT. Furthermore, microbiological analysis showed that the composition of the microbiota was altered, and the relative abundance of Lactobacillus was significantly increased in gut and mammary gland after treatment with L. reuteri or LCS. In conclusion, our study found the L. reuteri inhibited the mastitis-induced by S. aureus via promoting the release of OT, and treatment with L. reuteri increased the abundance of Lactobacillus in both gut and mammary gland.

Aging and age-related diseases with a focus on therapeutic potentials of young blood/plasma

Aging is accompanied by alterations in the body with time-related to decline of physiological integrity and functionality process, responsible for increasing diseases and vulnerability to death. Several ages associated with biomarkers were observed in red blood cells, and consequently plasma proteins have a critical rejuvenating role in the aging process and age-related disorders. Advanced age is a risk factor for a broad spectrum of diseases and disorders such as cardiovascular diseases, musculoskeletal disorders and liver, chronic kidney disease, neurodegenerative diseases, and cancer because of loss of regenerative capacity, correlated to reduced systemic factors and raise of pro-inflammatory cytokines. Most studies have shown that systemic factors in young blood/plasma can strongly protect against age-related diseases in various tissues by restoring autophagy, increasing neurogenesis, and reducing oxidative stress, inflammation, and apoptosis. Here, we focus on the current advances in using young plasma or blood to combat aging and age-related diseases and summarize the experimental and clinical evidence supporting this approach. Based on reports, young plasma or blood is new a therapeutic approach to aging and age-associated diseases.

The role of maternal hormones in regulating autonomic functions during pregnancy

Offspring development relies on numerous physiological changes that occur in a mother's body, with hormones driving many of these adaptations. Amongst these, the physiological functions controlled by the autonomic nervous system are required for the mother to survive and are adjusted to meet the demands of the growing foetus and to ensure a successful birth. The hormones oestrogen, progesterone, and lactogenic hormones rise significantly during pregnancy, suggesting they may also play a role in regulating the maternal adaptations linked to autonomic nervous system functions, including respiratory, cardiovascular, and thermoregulatory functions. Indeed, expression of pregnancy hormone receptors spans multiple brain regions known to regulate these physiological functions. This review examines how respiratory, cardiovascular, and thermoregulatory functions are controlled by these pregnancy hormones by focusing on their action on central nervous system circuits. Inadequate adaptations in these systems during pregnancy can give rise to several pregnancy complications, highlighting the importance in understanding the mechanistic underpinnings of these changes and potentially identifying ways to treat pregnancy-associated afflictions using hormones.

Impaired oxytocin signaling in the central amygdala in rats with chronic heart failure

Aims

Heart failure (HF) patients often suffer from cognitive decline, depression, and mood impairments, but the molecular signals and brain circuits underlying these effects remain elusive. The hypothalamic neuropeptide oxytocin (OT) is critically involved in the regulation of mood, and OTergic signaling in the central amygdala (CeA) is a key mechanism controlling emotional responses including anxiety-like behaviors. Based on this, we used in this study a well-established ischemic rat HF model and aimed to study alterations in the hypothalamus-to-CeA OTergic circuit.

Methods and Results

To study potential HF-induced changes in the hypothalamus-to-CeA OTertic circuit, we combined patch-clamp electrophysiology, immunohistochemical analysis, RNAScope assessment of OTR mRNA, brain region-specific stereotaxic injections of viral vectors and retrograde tracing, optogenetic stimulation and OT biosensors in the ischemic HF model. We found that most of OTergic innervation of the central amygdala (CeA) originated from the hypothalamic supraoptic nucleus (SON). While no differences in the numbers of SON→CeA OTertic neurons (or their OT content) was observed between sham and HF rats, we did observe a blunted content and release of OT from axonal terminals within the CeA. Moreover, we report downregulation of neuronal and astrocytic OT receptors, and impaired OTR-driven GABAergic synaptic activity within the CeA microcircuit of rats with HF.

Conclusions

Our study provides first evidence that HF rats display various perturbations in the hypothalamus-to-amygdala OTergic circuit, and lays the foundation for future translational studies targeting either the OT system or GABAergic amygdala GABA microcircuit to ameliorate depression or mood impairments in rats or patients with chronic HF.

The effectiveness of a therapeutic robot, 'Paro', on behavioural and psychological symptoms, medication use, total sleep time and sociability in older adults with dementia: A systematic review and meta-analysis

OBJECTIVE

To evaluate the effectiveness of a therapeutic robot, 'Paro', on anxiety, agitation, depression, apathy, medication use, total sleep time, and sociability among older adults with dementia.

DESIGN

Systematic review and meta-analysis with narrative synthesis.

SETTING AND PARTICIPANTS

Older adults aged 60 years and above with any form of dementia in the community, nursing homes, or care facilities.

METHODS

A three-step search strategy was conducted by two independent reviewers. Nine databases were searched (January 2003 to November 2022). Randomised controlled, crossover, and cluster trials on Paro for older adults with dementia published in English were included. All relevant trials were screened and assessed for risk of bias. Data were extracted using the Cochrane data collection form. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to assess the quality of evidence.

RESULTS

In total, 12 articles involving 1461 participants were included. Results of the meta-analysis showed that Paro had a moderate effect on medication use (SMD: -0.63) and small effect on anxiety (SMD: -0.17), agitation (SMD: -0.27) and depression (SMD: -0.40). However, Paro exhibited negligible effect on total sleep time (SMD: -0.12). The overall quality of evidence for all outcomes were graded as low due to methodological limitations, small sample size, and wide confidence intervals. Narrative synthesis suggested that Paro reduced apathy and increase sociability.

CONCLUSION AND IMPLICATIONS

Paro could be a beneficial non-pharmacological approach to improve behavioural and psychological symptoms of dementia, reducing medication use, and increasing sociability for older adults with dementia. However, the results should be interpreted with caution as limited studies were available. Additionally, there were a variety of approaches across the studies (i.e. group and individual interventions, facilitated and non-facilitated) which made it difficult to determine which interventional approach is optimal to produce beneficial effects of Paro. Hence, more rigorous studies with a larger sample size are needed to fully understand the mechanism and effectiveness of Paro in older adults with dementia. The protocol was registered on PROSPERO (CRD42022296504).

Cardiac Effects of Phosphodiesterase-5 Inhibitors: Efficacy and Safety

The coexistence of cardiovascular disease and erectile dysfunction is widespread, possibly owing to underlying endothelial dysfunction in both diseases. Millions of patients with cardiovascular disease are prescribed phosphodiesterase-5 (PDE5) inhibitors for the management of erectile dysfunction. Although the role of PDE5 inhibitors in erectile dysfunction therapy is well established, their effects on the cardiovascular system are unclear. Preclinical studies investigating the effect of PDE5 inhibitors on ischemia-reperfusion injury, pressure overload-induced hypertrophy, and chemotoxicity suggested a possible clinical role for each of these medications; however, attempts to translate these findings to the bedside have resulted in mixed outcomes. In this review, we explore the biologic preclinical effects of PDE5 inhibitors in mediating cardioprotection. We then examine clinical trials investigating PDE5 inhibition in patients with heart failure, coronary artery disease, and ventricular arrhythmias and discuss why the studies likely have yet to show positive results and efficacy with PDE5 inhibition despite no safety concerns.

Circulating microRNA Profiles for Premature Cardiovascular Death in Patients with Kidney Failure with Replacement Therapy

INTRODUCTION

Patients with kidney failure with replacement therapy (KFRT) suffer from a disproportionately high cardiovascular disease burden. Circulating small non-coding RNAs (c-sncRNAs) have emerged as novel epigenetic regulators and are suggested as novel biomarkers and therapeutic targets for cardiovascular disease; however, little is known about the associations of c-sncRNAs with premature cardiovascular death in KFRT.

METHODS

In a pilot case-control study of 50 hemodialysis patients who died of cardiovascular events as cases, and 50 matched hemodialysis controls who remained alive during a median follow-up of 2.0 years, we performed c-sncRNAs profiles using next-generation sequencing to identify differentially expressed circulating microRNAs (c-miRNAs) between the plasma of cases and that of controls. mRNA target prediction and pathway enrichment analysis were performed to examine the functional relevance of differentially expressed c-miRNAs to cardiovascular pathophysiology. The association of differentially expressed c-miRNAs with cardiovascular mortality was examined using multivariable conditional logistic regression.

RESULTS

The patient characteristics were similar between cases and controls, with a mean age of 63 years, 48% male, and 54% African American in both groups. We detected a total of 613 miRNAs in the plasma, among which five miRNAs (i.e., miR-129-1-5p, miR-500b-3p, miR-125b-1-3p, miR-3648-2-5p, and miR-3150b-3p) were identified to be differentially expressed between cases and controls with cut-offs of p < 0.05 and log2 fold-change (log2FC) > 1. When using more stringent cut-offs of p-adjusted < 0.05 and log2FC > 1, only miR-129-1-5p remained significantly differentially expressed, with higher levels of miR-129-1-5p in the cases than in the controls. The pathway enrichment analysis using predicted miR-129-1-5p mRNA targets demonstrated enrichment in adrenergic signaling in cardiomyocytes, arrhythmogenic right ventricular cardiomyopathy, and oxytocin signaling pathways. In parallel, the circulating miR-129-1-5p levels were significantly associated with the risk of cardiovascular death (adjusted OR [95% CI], 1.68 [1.01-2.81] for one increase in log-transformed miR-129-1-5p counts), independent of potential confounders.

CONCLUSIONS

Circulating miR-129-1-5p may serve as a novel biomarker for premature cardiovascular death in KFRT.

Recent Developments in Protein Lactylation in PTSD and CVD: Novel Strategies and Targets

In 1938, Corneille Heymans received the Nobel Prize in physiology for discovering that oxygen sensing in the aortic arch and carotid sinus was mediated by the nervous system. The genetics of this process remained unclear until 1991 when Gregg Semenza while studying erythropoietin, came upon hypoxia-inducible factor 1, for which he obtained the Nobel Prize in 2019. The same year, Yingming Zhao found protein lactylation, a posttranslational modification that can alter the function of hypoxia-inducible factor 1, the master regulator of cellular senescence, a pathology implicated in both post-traumatic stress disorder (PTSD) and cardiovascular disease (CVD). The genetic correlation between PTSD and CVD has been demonstrated by many studies, of which the most recent one utilizes large-scale genetics to estimate the risk factors for these conditions. This study focuses on the role of hypertension and dysfunctional interleukin 7 in PTSD and CVD, the former caused by stress-induced sympathetic arousal and elevated angiotensin II, while the latter links stress to premature endothelial cell senescence and early vascular aging. This review summarizes the recent developments and highlights several novel PTSD and CVD pharmacological targets. They include lactylation of histone and non-histone proteins, along with the related biomolecular actors such as hypoxia-inducible factor 1α, erythropoietin, acid-sensing ion channels, basigin, and Interleukin 7, as well as strategies to delay premature cellular senescence by telomere lengthening and resetting the epigenetic clock.

Metabolic Acidosis Results in Sexually Dimorphic Response in the Heart Tissue

Metabolic acidosis (MA) is a highly prevalent disorder in a significant proportion of the population, resulting from imbalance in blood pH homeostasis. The heart, being an organ with very low regenerative capacity and high metabolic activity, is vulnerable to chronic, although low-grade, MA. To systematically characterize the effect of low-grade MA on the heart, we treated male and female mice with NH4Cl supplementation for 2 weeks and analyzed their blood chemistry and transcriptomic signature of the heart tissue. The reduction of pH and plasma bicarbonate levels without an associated change in anion gap indicated a physiological manifestation of low-grade MA with minimal respiratory compensation. On transcriptomic analysis, we observed changes in cardiac-specific genes with significant gender-based differences due to MA. We found many genes contributing to dilated cardiomyopathy to be altered in males, more than in females, while cardiac contractility and Na/K/ATPase-Src signaling were affected in the opposite way. Our model presents a systems-level understanding of how the cardiovascular tissue is affected by MA. As low-grade MA is a common ailment with many dietary and pharmaceutical interventions, our work presents avenues to limit chronic cardiac damage and disease manifestation, as well as highlighting the sex differences in MA-induced cardiovascular damage.

Breaking the vicious cycle: The interplay between loneliness, metabolic illness, and mental health

Loneliness, or perceived social isolation, is a leading predictor of all-cause mortality and is increasingly considered a public health epidemic afflicting significant portions of the general population. Chronic loneliness is itself associated with two of the most pressing public health epidemics currently facing the globe: the rise of mental illness and metabolic health disorders. Here, we highlight the epidemiological associations between loneliness and mental and metabolic health disorders and argue that loneliness contributes to the etiology of these conditions by acting as a chronic stressor that leads to neuroendocrine dysregulation and downstream immunometabolic consequences that manifest in disease. Specifically, we describe how loneliness can lead to overactivation of the hypothalamic-pituitary-adrenal axis and ultimately cause mitochondrial dysfunction, which is implicated in mental and metabolic disease. These conditions can, in turn, lead to further social isolation and propel a vicious cycle of chronic illness. Finally, we outline interventions and policy recommendations that can reduce loneliness at both the individual and community levels. Given its role in the etiology of the most prevalent chronic diseases of our time, focusing resources on alleviating loneliness is a vitally important and cost-effective public health strategy.

The Long Way of Oxytocin from the Uterus to the Heart in 70 Years from Its Discovery

The research program on oxytocin started in 1895, when Oliver and Schafer reported that a substance extracted from the pituitary gland elevates blood pressure when injected intravenously into dogs. Dale later reported that a neurohypophysial substance triggers uterine contraction, lactation, and antidiuresis. Purification of this pituitary gland extracts revealed that the vasopressor and antidiuretic activity could be attributed to vasopressin, while uterotonic and lactation activity could be attributed to oxytocin. In 1950, the amino-acid sequences of vasopressin and oxytocin were determined and chemically synthesized. Vasopressin (CYFQNCPRG-NH₂) and oxytocin (CYIQNCPLG-NH₂) differ by two amino acids and have a disulfide bridge between the cysteine residues at position one and six conserved in all vasopressin/oxytocin-type peptides. This characterization of oxytocin led to the Nobel Prize awarded in 1955 to Vincent du Vigneaud. Nevertheless, it was only 50 years later when the evidence that mice depleted of oxytocin or its receptor develop late-onset obesity and metabolic syndrome established that oxytocin regulates energy and metabolism. Oxytocin is anorexigenic and regulates the lean/fat mass composition in skeletal muscle. Oxytocin's effect on muscle is mediated by thermogenesis via a pathway initiated in the myocardium. Oxytocin involvement in thermogenesis and muscle contraction is linked to Prader-Willi syndrome in humans, opening exciting therapeutic avenues.

Study protocol for the sheMATTERS study (iMproving cArdiovascular healTh in new moThERS): a randomized behavioral trial assessing the effect of a self-efficacy enhancing breastfeeding intervention on postpartum blood pressure and breastfeeding continuation in women with hypertensive disorders of pregnancy

BACKGROUND

Individuals with hypertensive disorders of pregnancy (HDP) have an elevated lifetime risk of chronic hypertension, metabolic syndrome, and premature cardiovascular disease. Because breastfeeding duration and exclusivity have been associated in observational studies with improved cardiovascular health, optimizing breastfeeding in those with HDP might be an unrealized cardio-prevention approach, in particular because individuals with HDP have more breastfeeding challenges. Breastfeeding supportive interventions targeting one's breastfeeding self-efficacy have been shown to improve breastfeeding rates.

METHODS

We designed an open-label, multi-center 1:1 randomized behavioral trial to test whether a previously validated self-efficacy enhancing breastfeeding intervention can improve breastfeeding duration and/or exclusivity, and lower postpartum blood pressure at 12 months. Randomization is computer-generated and stratified by site (four hospitals in Montreal, Quebec and one hospital in Kingston, Ontario; all in Canada). Included are breastfeeding participants with HDP (chronic/gestational hypertension or preeclampsia) who delivered a live singleton infant at > 34 weeks, speak English or French, and have no contraindications to breastfeeding. Informed and written consent is obtained at hospitalization for delivery or a re-admission with hypertension within 1 week of discharge. Participants assigned to the intervention group receive a breastfeeding self-efficacy-based intervention delivered by a trained lactation consultant in hospital, with continued reactive/proactive support by phone or text message for up to 6 months postpartum. Regardless of group assignment, participants are followed for self-reported outcomes, automated office blood pressure, and home blood pressure at several time points with end of follow-up at 12 months.

DISCUSSION

This study will assess whether an intensive nurse-led behavioral intervention can improve breastfeeding rates and, in turn, postpartum blood pressure - an early marker for atherosclerotic cardiovascular disease. If effective, this form of enhanced breastfeeding support, along with closer BP and metabolic surveillance, can be implemented broadly in individuals lactating after HDP.

TRIAL REGISTRATION

ClinicalTrials.gov, # NCT04580927 , registered on Oct 9, 2020.

Oxytocin and Hypotension During Dilation and Evacuation Procedures at 18-24 Weeks Gestation

Oxytocin is a neurohormone that is routinely administered to patients during dilation and evacuation procedures (D&E) to control bleeding despite minimal evidence in support of this common practice. In this study, the authors sought to evaluate patients with hypotension after receiving oxytocin during D&E procedures. The secondary data from a double-blind, randomized, placebo-controlled trial involving 112 patients who underwent a D&E at 18-24 weeks gestation and prophylactically received an intravenous bolus of either 30 units of oxytocin in 500 mL of normal saline or 500 mL of saline alone at the start of the procedure were analyzed. Anesthesia providers measured blood pressure before, at the time of, and after study medication administration in 5-minute increments until the end of the procedure. No differences in demographic characteristics or mean blood pressure between the 2 groups were observed. The proportion of hypotensive patients was not statistically different at 5 minutes following fluid bolus (oxytocin 25% versus placebo 13%, P=.09). The proportion of hypotensive patients was similar by 10 minutes (oxytocin 20% versus placebo 16%, P=.62). A sample size of 112 provided the ability to detect a 23% difference in the proportion of patients who experienced hypotension (2-sided 95% CI, power of 80%). These findings suggest that oxytocin may have a transient hypotensive effect.

The Heart as a Target of Vasopressin and Other Cardiovascular Peptides in Health and Cardiovascular Diseases

The automatism of cardiac pacemaker cells, which is tuned, is regulated by the autonomic nervous system (ANS) and multiple endocrine and paracrine factors, including cardiovascular peptides. The cardiovascular peptides (CPs) form a group of essential paracrine factors affecting the function of the heart and vessels. They may also be produced in other organs and penetrate to the heart via systemic circulation. The present review draws attention to the role of vasopressin (AVP) and some other cardiovascular peptides (angiotensins, oxytocin, cytokines) in the regulation of the cardiovascular system in health and cardiovascular diseases, especially in post-infarct heart failure, hypertension and cerebrovascular strokes. Vasopressin is synthesized mostly by the neuroendocrine cells of the hypothalamus. There is also evidence that it may be produced in the heart and lungs. The secretion of AVP and other CPs is markedly influenced by changes in blood volume and pressure, as well as by other disturbances, frequently occurring in cardiovascular diseases (hypoxia, pain, stress, inflammation). Myocardial infarction, hypertension and cardiovascular shock are associated with an increased secretion of AVP and altered responsiveness of the cardiovascular system to its action. The majority of experimental studies show that the administration of vasopressin during ventricular fibrillation and cardiac arrest improves resuscitation, however, the clinical studies do not present consisting results. Vasopressin cooperates with the autonomic nervous system (ANS), angiotensins, oxytocin and cytokines in the regulation of the cardiovascular system and its interaction with these regulators is altered during heart failure and hypertension. It is likely that the differences in interactions of AVP with ANS and other CPs have a significant impact on the responsiveness of the cardiovascular system to vasopressin in specific cardiovascular disorders.

Oxytocin: A Multi-Functional Biomolecule with Potential Actions in Dysfunctional Conditions; From Animal Studies and Beyond

Oxytocin is a hormone secreted from definite neuroendocrine neurons located in specific nuclei in the hypothalamus (mainly from paraventricular and supraoptic nuclei), and its main known function is the contraction of uterine and/or mammary gland cells responsible for parturition and breastfeeding. Among the actions of the peripherally secreted oxytocin is the prevention of different degenerative disorders. These actions have been proven in cell culture and in animal models or have been tested in humans based on hypotheses from previous studies. This review presents the knowledge gained from the previous studies, displays the results from oxytocin intervention and/or treatment and proposes that the well described actions of oxytocin might be connected to other numerous, diverse actions of the biomolecule.

Missing pieces in decoding the brain oxytocin puzzle: Functional insights from mouse brain wiring diagrams

The hypothalamic neuropeptide, oxytocin (Oxt), has been the focus of research for decades due to its effects on body physiology, neural circuits, and various behaviors. Oxt elicits a multitude of actions mainly through its receptor, the Oxt receptor (OxtR). Despite past research to understand the central projections of Oxt neurons and OxtR- coupled signaling pathways in different brain areas, it remains unclear how this nonapeptide exhibits such pleiotropic effects while integrating external and internal information. Most reviews in the field either focus on neuroanatomy of the Oxt-OxtR system, or on the functional effects of Oxt in specific brain areas. Here, we provide a review by integrating brain wide connectivity of Oxt neurons and their downstream circuits with OxtR expression in mice. We categorize Oxt connected brain regions into three functional modules that regulate the internal state, somatic visceral, and cognitive response. Each module contains three neural circuits that process distinct behavioral effects. Broad innervations on functional circuits (e.g., basal ganglia for motor behavior) enable Oxt signaling to exert coordinated modulation in functionally inter-connected circuits. Moreover, Oxt acts as a neuromodulator of neuromodulations to broadly control the overall state of the brain. Lastly, we discuss the mismatch between Oxt projections and OxtR expression across various regions of the mouse brain. In summary, this review brings forth functional circuit-based analysis of Oxt connectivity across the whole brain in light of Oxt release and OxtR expression and provides a perspective guide to future studies.

Exploring cardiac effects after oxytocin 2.5 IU or carbetocin 100 μg: A randomised controlled trial in women undergoing planned caesarean delivery

BACKGROUND

Oxytocin can stimulate release of myocardial biomarkers troponin I and T, prolong QTc and induce ST-depression.

OBJECTIVE

To explore cardiac changes after either intravenous carbetocin or oxytocin.

STUDY DESIGN

Exploratory phase 4 randomised controlled trial.

SETTING

Obstetrics units of Oslo University Hospital, Norway between September 2015 and May 2018.

PARTICIPANTS

Forty healthy, singleton pregnant women aged 18 to 50 years at gestational age at least 36 weeks with a planned caesarean delivery.

INVENTIONS

Participants were randomised to receive either oxytocin 2.5 IU or carbetocin 100 μg immediately after delivery.

MAIN OUTCOME MEASURES

The primary endpoint was the assessment of troponin I within 48 h of study drug administration. Troponin I and T, and creatine kinase myocardial band assessments were measured before spinal anaesthesia (baseline), and again at 4, 10 and 24 h after delivery. QTc, ST-depression and relative increase in heart rate were recorded from start of study drug administration to 10 min after delivery. All adverse events were monitored.

RESULTS

Compared with the carbetocin group, higher troponin I levels were observed in the oxytocin group at 4 h and 10 h after delivery. For both treatment groups, an increase from baseline in troponin I and T was most pronounced at 10 h after delivery, and it had begun to decline by 24 h. QTc increased with time after administration of both study drugs, with a mean maximum increase of 10.4 ms observed at 9 min (P  < 0.001). No statistical differences were observed in QTc (P = 0.13) or ST-depression (P = 0.11) between the treatment groups.

CONCLUSIONS

Oxytocin 2.5 IU and carbetocin 100 μg caused a similar increase in QTc. The trial was underpowered with regards to ST-depression and the release of myocardial biomarkers and these warrant further investigation. Data from this trial will inform a larger phase 4 trial to determine potential drug differences in troponin release.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02528136.

Oxytocin and oxygen: the evolution of a solution to the ‘stress of life’

Oxytocin (OT) and the OT receptor occupy essential roles in our current understanding of mammalian evolution, survival, sociality and reproduction. This narrative review examines the hypothesis that many functions attributed to OT can be traced back to conditions on early Earth, including challenges associated with managing life in the presence of oxygen and other basic elements, including sulfur. OT regulates oxidative stress and inflammation especially through effects on the mitochondria. A related nonapeptide, vasopressin, as well as molecules in the hypothalamic–pituitary–adrenal axis, including the corticotropin-releasing hormone family of molecules, have a broad set of functions that interact with OT. Interactions among these molecules have roles in the causes and consequence of social behaviour and the management of threat, fear and stress. Here, we discuss emerging evidence suggesting that unique properties of the OT system allowed vertebrates, and especially mammals, to manage over-reactivity to the ‘side effects’ of oxygen, including inflammation, oxidation and free radicals, while also supporting high levels of sociality and a perception of safety.

This article is part of the theme issue ‘Interplays between oxytocin and other neuromodulators in shaping complex social behaviours’.

The Role of Blood-Derived Factors in Protection and Regeneration of Aged Tissues

Tissue regeneration substantially relies on the functionality of tissue-resident endogenous adult stem cell populations. However, during aging, a progressive decline in organ function and regenerative capacities impedes endogenous repair processes. Especially the adult human heart is considered as an organ with generally low regenerative capacities. Interestingly, beneficial effects of systemic factors carried by young blood have been described in diverse organs including the heart, brain and skeletal muscle of the murine system. Thus, the interest in young blood or blood components as potential therapeutic agents to target age-associated malignancies led to a wide range of preclinical and clinical research. However, the translation of promising results from the murine to the human system remains difficult. Likewise, the establishment of adequate cellular models could help to study the effects of human blood plasma on the regeneration of human tissues and particularly the heart. Facing this challenge, this review describes the current knowledge of blood plasma-mediated protection and regeneration of aging tissues. The current status of preclinical and clinical research examining blood borne factors that act in stem cell-based tissue maintenance and regeneration is summarized. Further, examples of cellular model systems for a more detailed examination of selected regulatory pathways are presented.

Oxytocin: An Old Hormone, A Novel Psychotropic Drug And Possible Use In Treating Psychiatric Disorders

BACKGROUND

Oxytocin is a nonapeptide synthesized in the paraventricular and supraoptic nuclei of the hypothalamus. Historically, this molecule has been involved as a key factor in the formation of infant attachment, maternal behavior and pair bonding and, more generally, in linking social signals with cognition, behaviors and reward. In the last decades, the whole oxytocin system has gained a growing interest as it was proposed to be implicated in etiopathogenesis of several neurodevelopmental and neuropsychiatric disorders.

METHODS

With the main goal of an in-depth understanding of the oxytocin role in the regulation of different functions and complex behaviors as well as its intriguing implications in different neuropsychiatric disorders, we performed a critical review of the current state of art. We carried out this work through PubMed database up to June 2021 with the search terms: 1) "oxytocin and neuropsychiatric disorders"; 2) "oxytocin and neurodevelopmental disorders"; 3) "oxytocin and anorexia"; 4) "oxytocin and eating disorders"; 5) "oxytocin and obsessive-compulsive disorder"; 6) "oxytocin and schizophrenia"; 7) "oxytocin and depression"; 8) "oxytocin and bipolar disorder"; 9) "oxytocin and psychosis"; 10) "oxytocin and anxiety"; 11) "oxytocin and personality disorder"; 12) "oxytocin and PTSD".

RESULTS

Biological, genetic, and epigenetic studies highlighted quality and quantity modifications in the expression of oxytocin peptide or in oxytocin receptor isoforms. These alterations would seem to be correlated with a higher risk of presenting several neuropsychiatric disorders belonging to different psychopathological spectra. Collaterally, the exogenous oxytocin administration has shown to ameliorate many neuropsychiatric clinical conditions.

CONCLUSION

Finally, we briefly analyzed the potential pharmacological use of oxytocin in patient with severe symptomatic SARS-CoV-2 infection due to its anti-inflammatory, anti-oxidative and immunoregulatory properties.

A Sedentary and Unhealthy Lifestyle Fuels Chronic Disease Progression by Changing Interstitial Cell Behaviour: A Network Analysis

Managing chronic diseases, such as heart disease, stroke, diabetes, chronic lung disease and Alzheimer’s disease, account for a large proportion of health care spending, yet they remain in the top causes of premature mortality and are preventable. It is currently accepted that an unhealthy lifestyle fosters a state of chronic low-grade inflammation that is linked to chronic disease progression. Although this is known to be related to inflammatory cytokines, how an unhealthy lifestyle causes cytokine release and how that in turn leads to chronic disease progression are not well known. This article presents a theory that an unhealthy lifestyle fosters chronic disease by changing interstitial cell behavior and is supported by a six-level hierarchical network analysis. The top three networks include the macroenvironment, social and cultural factors, and lifestyle itself. The fourth network includes the immune, autonomic and neuroendocrine systems and how they interact with lifestyle factors and with each other. The fifth network identifies the effects these systems have on the microenvironment and two types of interstitial cells: macrophages and fibroblasts. Depending on their behaviour, these cells can either help maintain and restore normal function or foster chronic disease progression. When macrophages and fibroblasts dysregulate, it leads to chronic low-grade inflammation, fibrosis, and eventually damage to parenchymal (organ-specific) cells. The sixth network considers how macrophages change phenotype. Thus, a pathway is identified through this hierarchical network to reveal how external factors and lifestyle affect interstitial cell behaviour. This theory can be tested and it needs to be tested because, if correct, it has profound implications. Not only does this theory explain how chronic low-grade inflammation causes chronic disease progression, it also provides insight into salutogenesis, or the process by which health is maintained and restored. Understanding low-grade inflammation as a stalled healing process offers a new strategy for chronic disease management. Rather than treating each chronic disease separately by a focus on parenchymal pathology, a salutogenic strategy of optimizing interstitial health could prevent and mitigate multiple chronic diseases simultaneously.

Oxytocin-induced endothelial nitric oxide dependent vasorelaxation and ERK1/2-mediated vasoconstriction in the rat aorta

Oxytocin is a neuropeptide produced primarily in the hypothalamus and plays an important role in the regulation of mammalian birth and lactation. It has been shown that oxytocin has important cardiovascular protective effects. Here we investigated the effects of oxytocin on vascular reactivity and underlying the mechanisms in human umbilical vein endothelial cells (HUVECs) in vitro and in rat aorta ex vivo. Oxytocin increased phospho-eNOS (Ser 1177) and phospho-Akt (Ser 473) expression in HUVECs in vitro and the aorta of rat ex vivo. Wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), inhibited oxytocin-induced Akt and eNOS phosphorylation. In the rat aortic rings, oxytocin induced a biphasic vascular reactivity: oxytocin at low dose (10^-9–10^-8 M) initiated a vasorelaxation followed by a vasoconstriction at high dose (10^-7 M). L-NAME (a nitric oxide synthase inhibitor), endothelium removal or wortmannin abolished oxytocin-induced vasorelaxation, and slightly enhanced oxytocin-induced vasoconstriction. Atosiban, an oxytocin/vasopressin 1a receptor inhibitor, totally blocked oxytocin-induced relaxation and vasoconstriction. PD98059 (ERK1/2 inhibitor) partially inhibited oxytocin-induced vasoconstriction. Oxytocin also increased aortic phospho-ERK1/2 expression, which was reduced by either atosiban or PD98059, suggesting that oxytocin-induced vasoconstriction was partially mediated by oxytocin/V1aR activation of ERK1/2. The present study demonstrates that oxytocin can activate different signaling pathways to cause vasorelaxation or vasoconstriction. Oxytocin stimulation of PI3K/eNOS-derived nitric oxide may participate in maintenance of cardiovascular homeostasis, and different vascular reactivities to low or high dose of oxytocin suggest that oxytocin may have different regulatory effects on vascular tone under physiological or pathophysiological conditions.

Sports activities at a young age decrease hypertension risk-The J-Fit+ study

This study aimed to assess (1) blood pressure between young, current athletes, and non-athletes early in life; (2) hypertension prevalence between former athletes and the general population later in life; and (3) understand the mechanisms between exercise training and hypertension risks in the form of DNA methylation. Study 1: A total of 354 young male participants, including current athletes, underwent blood pressure assessment. Study 2: The prevalence of hypertension in 1269 male former athletes was compared with that in the Japanese general population. Current and former athletes were divided into three groups: endurance-, mixed-, and sprint/power-group. Study 3: We analyzed the effect of aerobic- or resistance-training on DNA methylation patterns using publicly available datasets to explore the possible underlying mechanisms. In young, current athletes, the mixed- and sprint/power-group exhibited higher systolic blood pressure, and all groups exhibited higher pulse pressure than non-athletes. In contrast, the prevalence of hypertension in former athletes was significantly lower in all groups than in the general population. Compared to endurance-group (reference), adjusted-hazard ratios for the incidence of hypertension among mixed- and sprint/power-group were 1.24 (0.87-1.84) and 1.50 (1.04-2.23), respectively. Moreover, aerobic- and resistance-training commonly modified over 3000 DNA methylation sites in skeletal muscle, and these were suggested to be associated with cardiovascular function-related pathways. These findings suggest that the high blood pressure induced by exercise training at a young age does not influence the development of future hypertension. Furthermore, previous exercise training experiences at a young age could decrease the risk of future hypertension.

Nanogenerator-Based Sensors for Energy Harvesting From Cardiac Contraction

Biomedical electric devices provide great assistance for health and life quality. However, their maintainable need remains a serious issue for the restricted duration of energy storage. Therefore, scientists are investigating alternative technologies such as nanogenerators that could harvest the mechanical energy of the human heart to act as the main source of energy for the pacemaker. Cardiac contraction is not a source for circulation; it utilizes body energy as an alternative energy source to recharge pacemaker devices. This is a key biomedical innovation to protect patients’ lives from possible risks resulting from repeated surgery. A batteryless pacemaker is possible via an implantable energy collecting tool, exchanging the restriction of the current batteries for a sustainable self-energy resource technique. In this context, the physiology of heart energy in the preservation of blood distribution pulse generation and the effects of cardiac hormones on the heart’s pacemaker shall be outlined. In this review, we summarized different technologies for the implantable energy harvesters and self-powered implantable medical devices with emphasis on nanogenerator-based sensors for energy harvesting from cardiac contraction. It could conclude that recent hybrid bio-nanogenerator systems of both piezoelectric and triboelectric devices based on biocompatible biomaterials and clean energy are promising biomedical devices for harvesting energy from cardiac and body movement. These implantable and wearable nanogenerators become self-powered biomedical tools with high efficacy, durability, thinness, flexibility, and low cost. Although many studies have proven their safety, there is a need for their long-term biosafety and biocompatibility. A further note on the biocompatibility of bio-generator sensors shall be addressed.

Oxytocin ameliorates KCC2 decrease induced by oral bacteria-derived LPS that affect rat primary cultured cells and PC-12 cells

Inflammation, especially neuroinflammation, which is caused by stress, leads to central nervous system (CNS) dysfunction. Because lipopolysaccharides (LPSs) cause neuroinflammation, we investigated the effect of LPSs to CNS. In PC-12 cells, LPSs derived from oral bacteria reduced the expression of KCC2, a Cl^- transporter. LPS derived from P. gingivalis (P. g) administered to rat primary cultured cells also reduced the KCC2 expression. However, LPSs derived from E. coli did not reduce the KCC2 expression. LPS treatment activated TLR4, IL-1β, and REST gene expressions, which led to KCC2 inactivation in PC-12 cells. The mechanism of KCC2 has been shown to play an important role in brain maturation, function (such as the GABA switch), and behavioral problems, we investigated the GABA function. We found that the GABA function was changed from inhibitory to excitatory by the LPS derived from P. g treatment. We demonstrated that the GSK3β also involved in the KCC2 reduction by LPS treatment. We show that oxytocin rescued the reduction in KCC2 expression caused by LPSs by inhibiting GSK3β signaling but vasopressin could not. Considered together, our results indicate that the LPSs from oral bacteria but not the LPS from E. coli increase the risk for brain disorders and oxytocin might be a candidate to overcome the abnormal behavior caused by brain disorders such as psychiatric disorders.

Oxytocin and Related Peptide Hormones: Candidate Anti-Inflammatory Therapy in Early Stages of Sepsis

Sepsis is a potentially life-threatening systemic inflammatory syndrome characterized by dysregulated host immunological responses to infection. Uncontrolled immune cell activation and exponential elevation in circulating cytokines can lead to sepsis, septic shock, multiple organ dysfunction syndrome, and death. Sepsis is associated with high re-hospitalization and recovery may be incomplete, with long term sequelae including post-sepsis syndrome. Consequently, sepsis continues to be a leading cause of morbidity and mortality across the world. In our recent review of human chorionic gonadotropin (hCG), we noted that its major properties including promotion of fertility, parturition, and lactation were described over a century ago. By contrast, the anti-inflammatory properties of this hormone have been recognized only more recently. Vasopressin, a hormone best known for its anti-diuretic effect, also has anti-inflammatory actions. Surprisingly, vasopressin's close cousin, oxytocin, has broader and more potent anti-inflammatory effects than vasopressin and a larger number of pre-clinical studies supporting its potential role in limiting sepsis-associated organ damage. This review explores possible links between oxytocin and related octapeptide hormones and sepsis-related modulation of pro-inflammatory and anti-inflammatory activities.

Oxytocin promotes epicardial cell activation and heart regeneration after cardiac injury

Cardiovascular disease (CVD) is one of the leading causes of mortality worldwide, and frequently leads to massive heart injury and the loss of billions of cardiac muscle cells and associated vasculature. Critical work in the last 2 decades demonstrated that these lost cells can be partially regenerated by the epicardium, the outermost mesothelial layer of the heart, in a process that highly recapitulates its role in heart development. Upon cardiac injury, mature epicardial cells activate and undergo an epithelial-mesenchymal transition (EMT) to form epicardium-derived progenitor cells (EpiPCs), multipotent progenitors that can differentiate into several important cardiac lineages, including cardiomyocytes and vascular cells. In mammals, this process alone is insufficient for significant regeneration, but it might be possible to prime it by administering specific reprogramming factors, leading to enhanced EpiPC function. Here, we show that oxytocin (OXT), a hypothalamic neuroendocrine peptide, induces epicardial cell proliferation, EMT, and transcriptional activity in a model of human induced pluripotent stem cell (hiPSC)-derived epicardial cells. In addition, we demonstrate that OXT is produced after cardiac cryoinjury in zebrafish, and that it elicits significant epicardial activation promoting heart regeneration. Oxytocin signaling is also critical for proper epicardium development in zebrafish embryos. The above processes are significantly impaired when OXT signaling is inhibited chemically or genetically through RNA interference. RNA sequencing data suggests that the transforming growth factor beta (TGF-β) pathway is the primary mediator of OXT-induced epicardial activation. Our research reveals for the first time an evolutionary conserved brain-controlled mechanism inducing cellular reprogramming and regeneration of the injured mammalian and zebrafish heart, a finding that could contribute to translational advances for the treatment of cardiac injuries.

Oxytocin Protects Against Isoproterenol-Induced Cardiac Hypertrophy by Inhibiting PI3K/AKT Pathway via a lncRNA GAS5/miR-375-3p/KLF4-Dependent Mechanism

Cardiac hypertrophy is caused by cardiac volume or pressure overload conditions and ultimately leads to contractile dysfunction and heart failure. Oxytocin (OT), an endocrine nonapeptide, has been identified as a cardiovascular homeostatic hormone with anti-hypertrophic effects. However, the underlying mechanism remains elusive. In this study, we aimed to investigate the role and mechanism of OT in cardiac hypertrophy. The rats with cardiac hypertrophy induced by isoproterenol (ISO) were treated with or without oxytocin. Cardiac functional parameters were analyzed by echocardiography. The changes in cell surface area were observed using wheat germ agglutinin (WGA) or immunofluorescence staining. The expressions of cardiac hypertrophy markers (B-Natriuretic Peptide, BNP and β-myosin heavy chain, β-MHC), long non-coding RNA Growth (LcRNA) Arrest-Specific transcript 5 (lncRNA GAS5), miR-375-3p, and Kruppel-like factor 4 (Klf4) were detected by qRT-PCR. KLF4 protein and PI3K/AKT pathway related proteins were detected by Western blot. The interactions among lncRNA GAS5, miR-375-3p, and Klf4 were verified by dual-luciferase reporter assays. The findings showed that OT significantly attenuated cardiac hypertrophy, increased expressions of lncRNA GAS5 and KLF4, and decreased miR-375-3p expression. In vitro studies demonstrated that either knock-down of lncRNA GAS5 or Klf4, or over-expression of miR-375-3p blunted the anti-hypertrophic effects of OT. Moreover, down-regulation of lncRNA GAS5 promoted the expression of miR-375-3p and inhibited KLF4 expression. Similarly, over-expression of miR-375-3p decreased the expression of KLF4. Dual-luciferase reporter assays validated that lncRNA GAS5 could sponge miR-375-3p and Klf4 was a direct target gene of miR-375-3p. In addition, OT could inactivate PI3K/AKT pathway. The functional rescue experiments further identified OT regulated PI3K/AKT pathway through lncRNA GAS5/miR-375-3p/KLF4 axis. In summary, our study demonstrates that OT ameliorates cardiac hypertrophy by inhibiting PI3K/AKT pathway via lncRNA GAS5/miR-375-3p/KLF4 axis.

The Gasotransmitter Hydrogen Sulfide and the Neuropeptide Oxytocin as Potential Mediators of Beneficial Cardiovascular Effects through Meditation after Traumatic Events

Trauma and its related psychological and somatic consequences are associated with higher cardiovascular morbidity. The regulation of both the gasotransmitter hydrogen sulfide (H2S) and the neuropeptide oxytocin (OT) have been reported to be affected during physical and psychological trauma. Both mediators are likely molecular correlates of trauma-induced cardiovascular complications, because they share parallel roles and signaling pathways in the cardiovascular system, both locally as well as on the level of central regulation and the vagus nerve. Meditation can alter the structure of specific brain regions and can have beneficial effects on cardiovascular health. This perspective article summarizes the evidence pointing toward the significance of H2S and OT signaling in meditation-mediated cardio-protection.

Weighted gene co-expression network-based approach to identify key genes associated with anthracycline-induced cardiotoxicity and construction of miRNA-transcription factor-gene regulatory network

BACKGROUND

Cardiotoxicity is a common complication following anthracycline chemotherapy and represents one of the serious adverse reactions affecting life, which severely limits the effective use of anthracyclines in cancer therapy. Although some genes have been investigated by individual studies, the comprehensive analysis of key genes and molecular regulatory network in anthracyclines-induced cardiotoxicity (AIC) is lacking but urgently needed.

METHODS

The present study integrating several transcription profiling datasets aimed to identify key genes associated with AIC by weighted correlation network analysis (WGCNA) and differentially expressed analysis (DEA) and also constructed miRNA-transcription factor-gene regulatory network. A total of three transcription profiling datasets involving 47 samples comprising 41 rat heart tissues and 6 human induced pluripotent stem cell-derived cardiomyocytes (hiPSCMs) samples were enrolled.

RESULTS

The WGCNA and DEA with E-MTAB-1168 identified 14 common genes affected by doxorubicin administrated by 4 weeks or 6 weeks. Functional and signal enrichment analyses revealed that these genes were mainly enriched in the regulation of heart contraction, muscle contraction, heart process, and oxytocin signaling pathway. Ten (Ryr2, Casq1, Fcgr2b, Postn, Tceal5, Ccn2, Tnfrsf12a, Mybpc2, Ankrd23, Scn3b) of the 14 genes were verified by another gene expression profile GSE154603. Importantly, three key genes (Ryr2, Tnfrsf12a, Scn3b) were further validated in a hiPSCMs-based in-vitro model. Additionally, the miRNA-transcription factor-gene regulatory revealed several top-ranked transcription factors including Tcf12, Ctcf, Spdef, Ebf1, Sp1, Rcor1 and miRNAs including miR-124-3p, miR-195-5p, miR-146a-5p, miR-17-5p, miR-15b-5p, miR-424-5p which may be involved in the regulation of genes associated with AIC.

CONCLUSIONS

Collectively, the current study suggested the important role of the key genes, oxytocin signaling pathway, and the miRNA-transcription factor-gene regulatory network in elucidating the molecular mechanism of AIC.

Love and longevity: A Social Dependency Hypothesis

Mammals, including humans, are reliant for survival and reproduction on adaptations associated with sociality and physiological investment, which can be linked to interactions with their parents or other bonded adult conspecifics. A wide range of evidence in human and non-human mammal species links social behaviors and relationships - including those characterized by what humans call "love" - to positive health and longevity. In light of this evidence, we propose a Social Dependency Hypothesis of Longevity, suggesting that natural selection has favored longer and healthier adult lives in species or in individuals exhibiting enhanced caregiver responsibilities contributing to the success of the next generation. In highlighting cellular, physiological, and behavioral effects of mammalian reproductive hormones, we examine the specific hypothesis that the neuropeptide oxytocin links longevity to the benefits of parental investment and associated relationships. Oxytocin is a pleiotropic molecule with anti-oxidant and anti-inflammatory properties, capable of regulating the hypothalamic-pituitary-adrenal axis, the parasympathetic nervous system and other systems associated with the management of various challenges, including chronic diseases and therefore may be crucial to establishing the maximum longevity potential of a species or an individual.

Complementary Role of Oxytocin and Vasopressin in Cardiovascular Regulation

The neurons secreting oxytocin (OXY) and vasopressin (AVP) are located mainly in the supraoptic, paraventricular, and suprachiasmatic nucleus of the brain. Oxytocinergic and vasopressinergic projections reach several regions of the brain and the spinal cord. Both peptides are released from axons, soma, and dendrites and modulate the excitability of other neuroregulatory pathways. The synthesis and action of OXY and AVP in the peripheral organs (eye, heart, gastrointestinal system) is being investigated. The secretion of OXY and AVP is influenced by changes in body fluid osmolality, blood volume, blood pressure, hypoxia, and stress. Vasopressin interacts with three subtypes of receptors: V1aR, V1bR, and V2R whereas oxytocin activates its own OXTR and V1aR receptors. AVP and OXY receptors are present in several regions of the brain (cortex, hypothalamus, pons, medulla, and cerebellum) and in the peripheral organs (heart, lungs, carotid bodies, kidneys, adrenal glands, pancreas, gastrointestinal tract, ovaries, uterus, thymus). Hypertension, myocardial infarction, and coexisting factors, such as pain and stress, have a significant impact on the secretion of oxytocin and vasopressin and on the expression of their receptors. The inappropriate regulation of oxytocin and vasopressin secretion during ischemia, hypoxia/hypercapnia, inflammation, pain, and stress may play a significant role in the pathogenesis of cardiovascular diseases.

The wonder exerkines-novel insights: a critical state-of-the-art review

Several benefits can be acquired through physical exercise. Different classes of biomolecules are responsible for the cross-talk between distant organs. The secretome of skeletal muscles, and more widely the field of organokines, is ever-expanding. “Exerkine” has emerged as the umbrella term covering any humoral factors secreted into circulation by tissues in response to exercise. This review aims at describing the most interesting exerkines discovered in the last 3 years, which are paving the way for both physiological novel insights and potential medical strategies. The five exerkines identified all play a significant role in the healthy effect of exercise. Specifically: miR-1192, released by muscles and myocardium into circulation, by modulating cardioprotective effect in trained mice; miR-342-5p, located into exosomes from vascular endothelial cells, also a cardioprotective miRNA in trained young humans; apelin, released by muscles into circulation, involved in anti-inflammatory pathways and muscle regenerative capacity in rats; GDF-15, released into circulation from yet unknown source, whose effects can be observed on multiple organs in young men after a single bout of exercise; oxytocin, released by myoblasts and myotubes, with autocrine and paracrine functions in myotubes. The systemic transport by vesicles and the crosstalk between distant organs deserve a deep investigation. Sources, targets, transport mechanisms, biological roles, population samples, frequency, intensity, time and type of exercise should be considered for the characterization of existing and novel exerkines. The “exercise is medicine” framework should include exerkines in favor of novel insights for public health.

Oxytocin and Bone: Review and Perspectives

Recent data demonstrate the anabolic effect of oxytocin on bone. Bone cells express oxytocin receptors. Oxytocin promotes osteoblasts differentiation and function, leading to an increased bone formation with no effect on bone resorption and an improvement of bone microarchitecture. Oxytocin is synthetized by osteoblasts, and this synthesis is stimulated by estrogen. Animal studies demonstrate a direct action of oxytocin on bone, as the systemic administration of oxytocin prevents and reverses the bone loss induced by estrogen deficiency. Although oxytocin is involved in bone formation in both sexes during development, oxytocin treatment has no effect on male osteoporosis, underlining the importance of estrogen that amplifies its local autocrine and paracrine secretion. There are few human data showing a decrease in the oxytocin serum level in anorexia nervosa independently of estrogen and in amenorrheic women associated with impaired bone microarchitecture; in post-menopausal women a higher oxytocin serum level is associated with higher bone density, but not in osteoporotic men. Oxytocin displays many effects that may be beneficial in the management of osteoporosis, cardiovascular diseases, cognitive disorders, breast cancer, diabetes and body fat gain, all age-related diseases affecting elderly women, opening exciting therapeutic perspectives, although the issue is to find a single route, dosage and schedule able to reach all these targets.

H2S and Oxytocin Systems in Early Life Stress and Cardiovascular Disease

Today it is well established that early life stress leads to cardiovascular programming that manifests in cardiovascular disease, but the mechanisms by which this occurs, are not fully understood. This perspective review examines the relevant literature that implicates the dysregulation of the gasomediator hydrogen sulfide and the neuroendocrine oxytocin systems in heart disease and their putative mechanistic role in the early life stress developmental origins of cardiovascular disease. Furthermore, interesting hints towards the mutual interaction of the hydrogen sulfide and OT systems are identified, especially with regards to the connection between the central nervous and the cardiovascular system, which support the role of the vagus nerve as a communication link between the brain and the heart in stress-mediated cardiovascular disease.

The Effects of Oxytocin on Appetite Regulation, Food Intake and Metabolism in Humans

The hypothalamic peptide oxytocin and its receptor are involved in a range of physiological processes, including parturition, lactation, cell growth, wound healing, and social behavior. More recently, increasing evidence has established the effects of oxytocin on food intake, energy expenditure, and peripheral metabolism. In this review, we provide a comprehensive description of the central oxytocinergic system in which oxytocin acts to shape eating behavior and metabolism. Next, we discuss the peripheral beneficial effects oxytocin exerts on key metabolic organs, including suppression of visceral adipose tissue inflammation, skeletal muscle regeneration, and bone tissue mineralization. A brief summary of oxytocin actions learned from animal models is presented, showing that weight loss induced by chronic oxytocin treatment is related not only to its anorexigenic effects, but also to the resulting increase in energy expenditure and lipolysis. Following an in-depth discussion on the technical challenges related to endogenous oxytocin measurements in humans, we synthesize data related to the association between endogenous oxytocin levels, weight status, metabolic syndrome, and bone health. We then review clinical trials showing that in humans, acute oxytocin administration reduces food intake, attenuates fMRI activation of food motivation brain areas, and increases activation of self-control brain regions. Further strengthening the role of oxytocin in appetite regulation, we review conditions of hypothalamic insult and certain genetic pathologies associated with oxytocin depletion that present with hyperphagia, extreme weight gain, and poor metabolic profile. Intranasal oxytocin is currently being evaluated in human clinical trials to learn whether oxytocin-based therapeutics can be used to treat obesity and its associated sequela. At the end of this review, we address the fundamental challenges that remain in translating this line of research to clinical care.

Oxytocin Downregulates the CaV1.2 L-Type Ca2+ Channel via Gi/cAMP/PKA/CREB Signaling Pathway in Cardiomyocytes

Oxytocin (OT) and its receptor (OTR) are expressed in the heart and are involved in the physiological cardiovascular functional system. Although it is known that OT/OTR signaling is cardioprotective by reducing the inflammatory response and improving cardiovascular function, the role of OT in the cardiac electrical excitation modulation has not been clarified. This study investigates the molecular mechanism of the action of OT on cardiomyocyte membrane excitation focusing on the L-type Ca²⁺ channel. Our methodology uses molecular biological methods and a patch-clamp technique on rat cardiomyocytes with OT, combined with several signal inhibitors and/or activators. Our results show that long-term treatment of OT significantly decreases the expression of Cav1.2 mRNA, and reduces the L-type Ca²⁺ channel current (I_Ca.L) in cardiomyocytes. OT downregulates the phosphorylated component of a transcription factor adenosine-3′,5′-cyclic monophosphate (cAMP) response element binding protein (CREB), whose action is blocked by OTR antagonist and pertussis toxin, a specific inhibitor of the inhibitory GTP-binding regulators of adenylate cyclase, Gi. On the other hand, the upregulation of Cav1.2 mRNA expression by isoproterenol is halted by OT. Furthermore, inhibition of phospholipase C (PLC) was without effect on the OT action to downregulate Cav1.2 mRNA—which suggests a signal pathway of Gi/protein kinase A (PKA)/CREB mediated by OT/OTR. These findings indicate novel signaling pathways of OT contributing to a downregulation of the Cav1.2-L-type Ca²⁺ channel in cardiomyocytes.