Is serotonin a valuable parameter in peripheral arterial disease?

Serum Irisin as a Predictor for Peripheral Arterial Disease: Insights from a Clinical Study

OBJECTIVE

The purpose of this study was to investigate the correlation between serum irisin concentration and peripheral arterial disease (PAD), and to establish clinical prediction nomograms for PAD occurrence by comparing and analyzing clinical data from patients with PAD and healthy controls.

METHODS

A total of 112 patients with PAD and 90 healthy individuals were recruited for the study. Clinical data from both groups were collected and serum irisin concentration was measured using enzyme-linked immunosorbent assay (ELISA). Correlation analysis was conducted. Risk factors for PAD were identified through univariate and multivariate logistic regression. The clinical prediction nomograms were established and validated.

RESULTS

A total of 202 patients were enrolled in this study, with an average age of 63.98 ± 10.40 years. Of these, 123 were male (60.9%) and 79 were female (39.1%). Hypertension was present in 104 patients (51.5%), diabetes in 59 patients (29.2%), dyslipidemia in 94 patients (46.5%), and 105 patients (52.0%) were smokers. Among them, 112 patients were assigned to the PAD group, which included 78 males (69.6%) and 34 females (30.4%), with an average age of 67.54 ± 10.31 years. In this group, 62 patients (55.4%) had hypertension, 53 (47.3%) had diabetes, 62 (55.4%) had dyslipidemia, and 78 (69.6%) were smokers. The Rutherford classification of these patients showed that 64 (57.1%) were at stage I, 25 (22.3%) at stage II, 16 (14.3%) at stage III, and 7 (6.3%) at stage IV. Serum irisin concentration in patients with PAD showed a significant positive correlation with serum high-density lipoprotein (HDL) (r = 0.255) and a significant negative correlation with Rutherford classification (r = -0.374) and smoking status (r = -0.263). Univariate and multivariate logistic regression analyses identified irisin, age, diabetes, dyslipidemia, smoking, creatinine (CR), and neutrophil/lymphocyte ratio (NLR) as independent risk factors for the development of PAD (P < 0.05). Based on these findings, a clinical prediction nomogram was established. Internal validation of the nomogram demonstrated strong discriminatory ability, with an area under the curve (AUC) of 0.942, indicating the model's excellent performance. Calibration curves and decision curve analyses further confirmed the model's robust calibration and clinical applicability.

CONCLUSIONS

This study concluded that serum irisin concentrations were significantly lower in the PAD group compared to the healthy control group, and that serum irisin concentrations in the PAD group were significantly correlated with serum HDL, Rutherford classification, and smoking status. Additionally, Irisin level, age, diabetes, dyslipidemia, smoking, CR, and NLR were identified as independent risk factors for PAD development. The clinical prediction nomogram based on these factors may aid in accurately predicting the risk of PAD development.

Tryptophan metabolites and incident cardiovascular disease: The EPIC-Norfolk prospective population study

BACKGROUND AND AIMS

Cardiovascular disease (CVD) remains the largest cause of death globally due to various risk factors. One novel potential contributor to CVD might be the metabolism of the essential amino acid tryptophan (Trp), which through many pathways can produce immunomodulatory metabolites such as kynurenine, indole-3-propionate and serotonin. We aim to identify the metabolites with the strongest association with cardiovascular disease, utilizing a substantial and diverse cohort of individuals. In our pursuit of this aim, our primary focus is to validate and reinforce the findings from previous cross-sectional studies.

METHODS

We used the community-based EPIC-Norfolk cohort (46.3 % men, age 59.8 ± 9.0) with a median follow-up of 22.1 (17.6-23.3) years to study associations between the relative levels of Trp metabolites measured with untargeted metabolomics and incident development of CVD. Serum from n = 11,972 apparently healthy subjects was analysed, of which 6982 individuals had developed CVD at the end of follow-up. Cox proportional hazard models were used to study associations, adjusted for sex, age, conventional cardiovascular risk factors and CRP. All metabolites were Ln-normalised prior to analysis.

RESULTS

Higher levels of Trp were inversely associated with mortality (HR 0.73; CI 0.64-0.83) and fatal CVD (HR 0.76; CI 0.59-0.99). Higher levels of kynurenine (HR 1.33; CI 1.19-1.49) and the [Kynurenine]/[Tryptophan]-ratio (HR 1.24; CI 1.14-1.35) were associated with a higher incident development of CVD. Serotonin was not associated with overall CVD, but we did find associations for myocardial infarction and stroke. Adjustment for CRP did not yield any discernible differences in effect size.

CONCLUSIONS

Tryptophan levels were inversely correlated with CVD, while several of its major metabolites (especially kynurenine and serotonin) were positively correlated. These findings indicate that mechanistic studies are required to understand the role of Trp metabolism in CVD with the goal to identify new therapeutic targets.

Serotonin-Mediated Activation of Serotonin Receptor Type 1 Oppositely Modulates Voltage-Gated Calcium Channel Currents in Rat Sensory Neurons Innervating Hindlimb Muscle

Serotonin (5-HT) is a multifaceted neurotransmitter that has been described to play a role as a peripheral inflammatory mediator when released in ischemic or injured muscle. Dorsal root ganglia (DRG) neurons are key sensors of noxious stimuli that are released under inflammatory conditions or mechanical stress. Little information is available on the specific 5-HT receptor subtypes expressed in primary afferents that help regulate reflex pressor responses. In the present study, the whole-cell patch-clamp technique was employed to examine the modulation of voltage-gated calcium channel (CaV) 2.2 currents by 5-HT and to identify the 5-HT receptor subtype(s) mediating this response in acutely dissociated rat DRG neurons innervating triceps surae muscle. Our results indicate that exposure of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled DRG neurons to 5-HT can exert three modulatory effects on CaV currents: high inhibition, low inhibition, and enhancement. Both 5-HT-mediated inhibition responses were blocked after pretreatment with pertussis toxin (PTX), indicating that 5-HT receptors are coupled to CaV2.2 via Gα i/o protein subunits. Application of selective serotonin receptor type 1 (5-HT1) agonists revealed that modulation of CaV2.2 currents occurs primarily after 5-HT1A receptor subtype stimulation and minimally from 5-HT1D activation. Finally, the intrathecal administration of the selective 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), significantly (P < 0.05) decreased the pressor response induced by intra-arterial administration of lactic acid. This suggests that 5-HT1A receptors are expressed presynaptically on primary afferent neurons innervating triceps surae muscle. Our findings indicate that preferential stimulation of 5-HT1 receptors, expressed on thin fiber muscle afferents, serves to regulate the reflex pressor response to metabolic stimuli. SIGNIFICANCE STATEMENT: The monoamine serotonin (5-HT), released under ischemic conditions, can contribute to the development of inflammation that negatively affects the exercise pressor reflex. The 5-HT receptor subtype and signaling pathway that underlies calcium channel modulation in dorsal root ganglia afferents, innervating hindlimb muscles, are unknown. We show that 5-HT can either block (primarily via serotonin receptor type 1 (5-HT1)A subtypes) or enhance voltage-gated calcium channel (CaV2.2) currents. Our findings suggest 5-HT exhibits receptor subtype selectivity, providing a complexity of cellular responses.

The relation between inter arm blood pressure difference and presence of cardiovascular disease: a review of current findings

Raised inter arm blood pressure difference (IABPD) is already well-known as a clinical sign of peripheral arterial diseases including aortic dissection and subclavian stenosis. However, there are several other diseases associated with high IABPD. Therefore, this study aimed to review the association between increased IABPD and the presence of lethal health conditions, the possible mechanisms behind this relationship, and its contributing risk factors. Significant IABPD has been observed in patients with atherosclerotic plaques, peripheral artery disease, coronary artery disease, and chronic kidney disease. Patients with high IABPD are also at more risk of left ventricular hypertrophy that may affect long-term cardiac function. Besides, brain injuries such as stroke, dementia, and Alzheimer's disease has been related to increased IABPD. Considering that raised IABPD is associated with multiple cardiovascular diseases and other organ damage, IABPD detection may be accurate for the early diagnosis and screening of these life-threatening diseases and help manage them better.

Difference in SBP between arms is a predictor of chronic kidney disease development in the general Korean population

OBJECTIVE

An increased inter-arm SBP difference (IASBPD) is associated with mortality and cardiovascular events, as well as peripheral vascular disease, which is attributed to subclavian stenosis. The aim of the present study was to investigate the association between the IASBPD and incident chronic kidney disease (CKD) in the Korean population.

METHODS

A retrospective cohort study was performed on 8780 Korean adults without baseline CKD. The bilateral blood pressure was measured sequentially and repeatedly at the first visit. IASBPD was defined as a BP at least 15 mmHg according to the National Institutes for Health and Clinical Excellence guidelines, and CKD was defined as an estimated glomerular filtration rate less than 60 ml/min per 1.73 m. We assessed the value of IASBPD to predict the incidence of CKD and investigated cardiovascular disease, including coronary heart disease and stroke.

RESULTS

Over a mean follow-up period of 8.5 years, 96 of 581 (16.5%) patients in the IASBPD group and 1037 of 8199 (12.6%) patients in the non-IASBPD group developed incident CKD. Compared with the non-IASBPD, an IASBPD was associated with incident CKD [hazard ratio (HR): 1.336, 95% confidence interval (CI): 1.08-1.65, P = 0.007]. After adjusting for potential confounders, including age, sex, hypertension, diabetes, and obesity, we found that the hazard ratio was also robust (hazard ratio 1.275, 95% CI 1.03-1.58, P = 0.024).

CONCLUSION

Increased IASBPD is an independent predictor of incident CKD in the general population.

The enhancement of serotonin-induced contraction of rat femoral artery is mediated by angiotensin II release from intact endothelium

We have performed an in vitro study on isolated intact or denuded femoral artery (FA) of healthy, diabetic, and/or rats submitted to the FA occlusion. The aim was to determine the contribution of endothelium and endothelial dysfunction (ED) on serotonin-induced action in FA. Further, the contribution of angiotensin II and cyclooxygenase products of arachidonic acid was investigated. A marker of ED, vWF was measured in animal serum. Serotonin induced contraction-dependent contraction of isolated FA, which was increased in preparations with endothelium. Pathological conditions such as endothelial denudation, nicotine-induced ED, diabetes or occlusion of FA reduced serotonin-induced contraction. Comparable reduction of serotonin-induced contraction was achieved after inhibition of AT1 receptors with losartan in isolated FA with intact endothelium. Our results demonstrate that angiotensin II contributes to the enhancement of serotonin-induced contraction of femoral arteries with intact endothelium. This increase is attenuated by endothelium removal, nicotine treatment, vascular occlusion, and/or hyperglycemia.

Clarification of serotonin-induced effects in peripheral artery disease observed through the femoral artery response in models of diabetes and vascular occlusion: The role of calcium ions

Recent findings have demonstrated that serotonin is an important participant in the development and progression of peripheral artery diseases. Taking this into consideration, the goals of this study were to investigate the effects of serotonin on isolated Wistar rat femoral arteries in both healthy and diabetic animals, with and without artery occlusion, with a particular focus on determining the role of calcium in this process. Contraction experiments with serotonin on intact and denuded femoral artery rings, in the presence or absence of nifedipine and ouabain (both separately, or in combination), as well as Ca²⁺ -free Krebs-Ringer bicarbonate solution were performed. The serotonin-induced results were concentration dependent, but only in healthy animals. The endothelium-dependent contraction of the femoral artery was assessed. In healthy animals, the endothelium-reliant part of contraction was dependent on the extracellular calcium, while the smooth muscle-related part was instead dependent on the intracellular calcium. In diabetic animals, both nifedipine and ouabain influenced serotonin-induced vascular effects by blocking intracellular calcium pathways. However, this was diminished after the simultaneous administration of both blockers.