Does sex influence near-infrared spectroscopy-derived indicators of microvascular reactivity and the response to acute dietary capsaicin

Effects of selective serotonin reuptake inhibitor (SSRI) use on cardiometabolic health and risk in young healthy individuals: A preliminary matched pairs study

Selective serotonin reuptake inhibitors (SSRIs) are a class of drugs that are frequently used to treat psychological disorders, but the comprehensive effects on cardiometabolic health in young healthy populations are not well described. Healthy men and women using SSRIs and sex-, age-, height-, and weight-matched controls were assessed. Anthropometrics, blood pressure (BP), arterial stiffness (AS), heart rate variability (HRV), near-infrared vascular occlusion test (NIRS-VOT), and blood lipid profile were assessed, with subsequent Framingham CVD risk score calculation. There were no significant differences in central or peripheral BP or AS due to SSRI use (all, p > 0.39, Cohen's d < 0.48). HRV was not different between groups (all, p > 0.43, Cohen's d < 0.44), except for HFpeak, which was lower in SSRI users (0.20 ± 0.05 vs. 0.28 ± 0.06 Hz, p = 0.04, Cohen's d = 1.26). There were no significant differences in blood lipids (all, p > 0.22, Cohen's d < 0.09) or Framingham risk scores (both, p > 0.68, Cohen's d < 0.14) between groups. There were no significant differences in microvascular reactivity between groups, however, reperfusion slope was lower in SSRI users (1.2 ± 0.9 vs. 2.0 ± 1.1%/s, p = 0.10, Cohen's d = 0.93). SSRIs do not appear to have any significant effects on blood pressure, heart rate variability, arterial stiffness, or lipid profile in young healthy individuals but may influence microvascular function.

Dyslipidemia Impacts Cardiometabolic Health and CVD Risk in a Relatively Young Otherwise Healthy Population

Dyslipidemia, abnormal levels of lipids in the bloodstream, is associated with cardiovascular disease risk (CVD). The purpose of this study was to evaluate the effects of dyslipidemia on cardiometabolic health in relatively young, healthy adults. Participants were 54 healthy males and females aged 18-60 years. Participants were assessed for anthropometrics, body composition, blood pressure and vascular stiffness indicators, microvascular health, and glucose and lipid levels. Using a cross-sectional approach, participants were characterized and grouped as having dyslipidemia or not, and then statistically assessed to determine whether differences in other cardiometabolic health measures existed between the groups. There were significant differences between groups for body weight and composition (total mass, muscle mass, visceral fat, bone mass, and body mass index, all, p < 0.027, Cohen's d > 0.605) with the dyslipidemia group being higher. There were significant differences between groups for peripheral and central blood pressures (all, p < 0.003, Cohen's d > 0.899), as well as for vascular stiffness indicators (pulse pressure, augmentation pressure, augmentation index, augmentation index 75) (all, p < 0.022, Cohen's d > 0.672) with elevations noted in the dyslipidemia group. Ten-year CVD risk was significantly different between groups, with an average risk of 0.8% in the normal lipids group and a risk of 5.4% in the dyslipidemia group (p < 0.001, Cohen's d = 1.260). However, there were no significant differences in macro- or micronutrient intake between groups (all, p > 0.166, Cohen's d < 0.412). There is a significant impact on cardiometabolic health in individuals with dyslipidemia who are otherwise healthy, which may increase individual risk for CVD. Trial Registration: ClinicalTrials.gov identifier: NCT06544915.

Comparison of analysis strategies to assess sex differences in microvascular reperfusion using near-infrared spectroscopy

The near-infrared spectroscopy (NIRS) vascular occlusion test (VOT) assesses microvascular reperfusion. Two strategies have been used to quantify reperfusion following reactive hyperemia, but it is unclear whether both yield similar results when comparing biological sex. This study aimed to determine whether sex differences in NIRS-based microvascular reperfusion are similarly apparent using the 10-s reactive hyperemia slope of the tissue saturation index (StO2) signal (slope 2) and the halftime to maximal reperfusion (T ½). Healthy, recreationally active males (n = 31) and females (n = 31) between 18 and 82 years took part in this study. A NIRS VOT was performed on the tibialis anterior muscle, and reperfusion was quantified using slope 2 (% s-1) and T ½ (s). Adipose tissue thickness (ATT) was higher in females (P = 0.009), which was associated with a lower StO2 (P = 0.001) and oxygenated hemoglobin (O2Hb) (P = 0.05) signal range. The StO2 slope 2 was significantly steeper in males versus females (P = 0.001) but not after correcting for ATT (P = 0.295). There were no sex differences in StO2 T ½ (P = 0.067) or O2Hb T ½ (P = 0.197). In a subset of males (n = 26) and females (n = 21) with similar ATT, there were no sex differences in StO2 slope 2 (P = 0.068), StO2 T ½ (P = 0.491), or O2Hb T ½ (P = 0.899). An ATT-corrected StO2 slope 2 or the T ½ approach is recommended for analysis of NIRS-based microvascular reperfusion when differences in ATT are present between sexes.NEW & NOTEWORTHY Sex differences in near-infrared spectroscopy (NIRS)-based microvascular reperfusion have been previously reported. We found that greater adipose tissue thickness in females reduces kinetic measures of NIRS-based microvascular reperfusion. Sex differences are eliminated when performing an adipose tissue thickness correction, when the NIRS signal range is accounted for, or when adipose tissue thickness is similar between sexes. This highlights the importance of considering factors that affect NIRS signals, such as adipose tissue thickness, when drawing comparisons between groups.

Environmental exposure to wildfire smoke may reduce microvascular oxygenation during graded handgrip exercise: A case series

Wildfire smoke (WFS) is an urgent and rapidly growing threat to global health. Aside from obvious threats to pulmonary function, increases in cardiac abnormalities or myocardial infarction have been documented during WF season, but little is known about the effects of WFS on cardiovascular health. We investigated the effect of nonoccupational WFS exposure on cardiovascular and pulmonary function at rest and during graded handgrip exercise through a case series of young, healthy adults (n = 4, 25 ± 6 years) assessed after ≥3 days of bad or good air quality. Peripheral and estimated central blood pressures, vascular stiffness, and microvascular function (Near infrared spectroscopy, NIRS) were assessed at rest, and during rhythmic handgrip exercise. WFS did not appear to alter resting peripheral, central BP, or vascular stiffness (all, p > 0.05). Slope 1 and slope 2 from the NIRS-vascular occlusion test (NIRS-VOT) were not different between conditions (p > 0.05). The change in SmO2 during exercise was lower (p = 0.02,η p 2 $$ {\eta}_{\mathrm{p}}^2 $$  = 0.62) with bad air quality. These preliminary findings suggest modest effects of environmental WFS exposure on muscle microvascular function during exercise in healthy adults. Future work is needed to elucidate the physiological changes with WFS exposure and the increased risk of cardiovascular events, perhaps exacerbated through physical activity.

Capsaicin pretreatment attenuates salt-sensitive hypertension by alleviating AMPK/Akt/Nrf2 pathway in hypothalamic paraventricular nucleus

Background

Long term hypertension seriously promotes target organ damage in the brain and heart, and has increasingly become serious public health problem worldwide. The anti-hypertensive effects of capsaicin has been reported, however, the role and mechanism of capsaicin within the brain on salt-induced hypertension have yet to be elucidated. This study aimed to verify the hypothesis that capsaicin attenuates salt-induced hypertension via the AMPK/Akt/Nrf2 pathway in hypothalamic paraventricular nucleus (PVN).

Methods

Dahl salt-sensitive (Dahl S) rats were used as animal model for the present study. Rats were randomly divided into four groups based on their dietary regimen (0.3% normal salt diet and 8% high salt diet) and treatment methods (infusion of vehicle or capsaicin in the PVN). Capsaicin was chronically administered in the PVN throughout the animal experiment phase of the study that lasted 6 weeks.

Results

Our results demonstrated that PVN pretreatment with capsaicin can slow down raise of the blood pressure elevation and heart rate (HR) of Dahl S hypertensive rats given high salt diet. Interestingly, the cardiac hypertrophy was significantly improved. Furthermore, PVN pretreatment with capsaicin induced decrease in the expression of mRNA expression of NADPH oxidase-2 (NOX2), inducible nitric oxide synthase (iNOS), NOX4, p-IKKβ and proinflammatory cytokines and increase in number of positive cell level for Nrf2 and HO-1 in the PVN of Dahl S hypertensive rats. Additionally, the protein expressions of phosphatidylinositol 3-kinase (p-PI3K) and phosphorylated protein kinase-B (p-AKT) were decreased, phosphorylated adenosine monophosphate-activated protein kinase (p-AMPK) were increased after the PVN pretreatment with capsaicin.

Conclusion

Capsaicin pretreatment attenuates salt-sensitive hypertension by alleviating AMPK/Akt/iNOS pathway in the PVN.

Sex-specific microvascular and hemodynamic responses to passive limb heating in young adults

OBJECTIVE

We examined sex-specific microvascular reactivity and hemodynamic responses under conditions of augmented resting blood flow induced by passive heating compared to normal blood flow.

METHODS

Thirty-eight adults (19 females) completed a vascular occlusion test (VOT) on two occasions preceded by rest with or without passive heating in a randomized, counterbalanced order. Skeletal muscle tissue oxygenation (StO2, %) was assessed with near-infrared spectroscopy (NIRS), and the rate of desaturation and resaturation as well as maximal StO2 (StO2max) and prolonged hypersaturation (area under the curve, StO2AUC) were quantified. Before the VOT, brachial artery blood flow (BABF), vascular conductance, and relative BABF (BABF normalized to forearm lean mass) were determined. Sex × condition ANOVAs were used. A p-value ≤.05 was considered statistically significant.

RESULTS

Twenty minutes of heating increased BABF compared to the control (102.9 ± 28.3 vs. 36.0 ± 20.9 mL min-1; p < .01). Males demonstrated greater BABF than females (91.9 ± 34.0 vs. 47.0 ± 19.1 mL min-1; p < .01). There was no sex difference in normalized BABF. There were no significant interactions for NIRS-VOT outcomes, but heat did increase the rate of desaturation (-0.140 ± 0.02 vs. -0.119 ± 0.03% s-1; p < .01), whereas regardless of condition, males exhibited greater rates of resaturation and StO2max than females.

CONCLUSIONS

These results suggest that blood flow is not the primary factor causing sex differences in NIRS-VOT outcomes.

Limb, sex, but not acute dietary capsaicin, modulate the near-infrared spectroscopy-vascular occlusion test estimate of muscle metabolism

The downward slope during the near-infrared spectroscopy (NIRS)-vascular occlusion test (NIRS-VOT) is purported as a simplified estimate of metabolism. Whether or not the NIRS-VOT exhibits sex- or limb-specificity or may be acutely altered remains to be elucidated. Thus, we investigated if there is limb- or sex specificity in tissue desaturation rates (DeO2) during a NIRS-VOT, and if acute dietary capsaicin may alter this estimate of muscle metabolism. Young healthy men (n = 25, 21 ± 4 years) and women (n = 20, 20 ± 1 years) ingested either placebo or capsaicin, in a counterbalanced, single-blind, crossover design after which a simplified NIRS-VOT was conducted to determine the DeO2 (%/s), as an estimate of oxidative muscle metabolism, in both the forearm (flexors) and thigh (vastus lateralis). There was a significant limb effect with the quadriceps having a greater DeO2 than the forearm (-2.31 ± 1.34 vs. -1.78 ± 1.22%/s, p = 0.007, ηp 2 = 0.19). There was a significant effect of sex on DeO2 (p = 0.005, ηp 2 = 0.203) with men exhibiting a lesser DeO2 than women (-1.73 ± 1.03 vs. -2.36 ± 1.32%/s, respectively). This manifested in significant interactions of limb*capsaicin (p = 0.001, ηp 2 = 0.26) as well as limb*capsaicin*sex on DeO2 (p = 0.013, ηp 2 = 0.16) being observed. Capsaicin does not clearly alter O2-dependent muscle metabolism, but there was apparent limb and sex specificity, interacting with capsaicin in this NIRS-derived assessment.