Menopause status as the main factor explaining the gender differences of serum nitric oxide concentrations in middle-aged population

Dietary NO3- does not enhance endothelial dependent cutaneous vascular conductance in older women

Prior work has yet to determine whether the reduction of dietary nitrate (NO3-) to NO, via the enterosalivary pathway, may modify cutaneous vascular conductance (CVC) responses to local heating in older women. Changes occurring with the transition to menopause related to hormonal flux, increased adiposity, and/or decreased physical activity may further compound the negative influence of aging on nitric oxide (NO)-dependent CVC. Herein, we characterized changes in NO-dependent CVC following acute ingestion of 140 mL of NO3--rich beetroot juice in 24 older women (age: 65 ± 5 y, BMI: 31.2 ± 3.7 kg/m2). Red blood cell (RBC) flux was measured continuously via laser-Doppler flowmetry on the dorsal aspect of the forearm during local skin heating to 39 °C/44 °C before and 3 h after NO3- ingestion. NO-dependent changes in CVC were calculated as RBC flux/mean arterial blood pressure at 39 °C and normalized as a proportion of maximal CVC at 44 °C (%CVCmax). Changes (Δ) in fractional exhaled NO (FeNO) following NO3- ingestion were used an index of NO bioavailability. Despite increased FeNO (+81 ± 70 %, P < 0.001), %CVCmax at 39 °C was reduced (-16 ± 10 %, P < 0.001) following NO3- ingestion. A greater reduction in %CVCmax was weakly to moderately associated with higher body fat% (r = 0.45 [0.05-0.72], P = 0.029), central adiposity% (r = 0.50 [0.13-0.75], P = 0.012), neutrophil% (r = 0.42 [0.02-0.70], P = 0.041), and higher neutrophil to lymphocyte ratio (r = 0.49 [0.11-0.75], P = 0.016). These findings demonstrate a single dose of dietary NO3- does not promote CVC responses to local heating in sedentary older women with overweight and obesity. Correlation with multiple biomarkers suggest systemic inflammation may be involved.

Moving beyond inclusion: Methodological considerations for the menstrual cycle and menopause in research evaluating effects of dietary nitrate on vascular function

Recent reports have acknowledged the underrepresentation of women in the field of dietary nitrate (NO₃^-) research. Undoubtedly, greater participation from women is warranted to clarify potential sex differences in the responses to dietary NO₃^- interventions. However, careful consideration for the effects of sex hormones - principally 17β-estradiol - on endogenous nitric oxide (NO) synthesis and dietary NO₃^- reductase capacity is necessary for improved interpretation and reproducibility of such investigations. From available literature, we present a narrative review describing how hormonal variations across the menstrual cycle, as well as with menopause, may impact NO biosynthesis catalyzed by NO synthase enzymes and NO₃^- reduction via the enterosalivary pathway. In doing so, we address methodological considerations related to the menstrual cycle and hormonal contraceptive use relevant for the inclusion of premenopausal women along with factors to consider when testing postmenopausal women. Adherence to such methodological practices may explicate the utility of dietary NO₃^- supplementation as a means to improve vascular function among women across the lifespan.

Effect of dehydroepiandrosterone on atherosclerosis in postmenopausal women

In China, cardiovascular disease (CVD) has surpassed malignant tumours to become the disease with the highest mortality rate, and atherosclerosis (AS) is an important pathological cause of CVD. Dehydroepiandrosterone (DHEA) is the most abundant steroid hormone in circulating human blood and is a precursor of estrogen and androgen. DHEA is converted into a series of sex hormones in local peripheral tissues where its acts physiologically. DHEA also acts therapeutically, thereby avoiding the adverse systemic reactions to sex hormones. DHEA inhibits AS, thus inhibiting the development of CVD, and it improves the prognosis for CVD. The incidence of CVD in postmenopausal women is substantially higher than that in premenopausal women, and that incidence is believed to be related to a decrease in ovarian function. The current review analyzes the mechanisms of postmenopausal women's susceptibility to AS. They tend to have dyslipidemia, and their vascular smooth muscle cells (VSMCs) proliferate and migrate more. In addition, oxidative stress and the inflammatory response of endothelial cells (ECs) are more serious in postmenopausal women. This review also discusses how DHEA combats AS by countering these mechanisms, which include regulating the blood lipid status, protecting ECs (including coping with oxidative stress and inflammatory reactions of the vascular endothelium, inhibiting apoptosis of ECs, and inducing NO production) and inhibiting the proliferation and migration of VSMCs. As a result, DHEA has great value in preventing AS and inhibiting its progression in postmenopausal women.

Exploring the role of body mass index in relationship of serum nitric oxide and advanced glycation end products in apparently healthy subjects

This study aimed to identify any association of serum nitric oxide (NO) and advanced glycation end products (AGEs) with body mass index (BMI) in apparently healthy subjects. In this cross-sectional study, participants were 90 apparently healthy subjects, categorized into three BMI groups as follows: BMI≤19.5 (n = 21), 19.6≤BMI≤24.9 (n = 35), and BMI≥25 (n = 34). Serum levels of NO were measured by griess reaction method. Determination of serum pentosidine and carboxymethyllysine (CML) was done using ELISA. Median (95% confidence interval [CI]: lower- upper) of serum NO in subjects with BMI≥25 were 68.94 (CI: 55.01–70.56) μmol/L, which was higher compared with 19.6≤BMI≤24.9 and BMI≤19.5 groups (22.65 (CI: 19.29–28.17) μmol/L and 8.00 (CI: 9.12–29.58) μmol/L, respectively). Serum NO positively correlated with BMI in total subjects (r = 0.585, p<0.001), which this correlation was significant in both male and female groups (r = 0.735, p<0.001 and r = 0.476, p = 0.001, respectively). Serum pentosidine and CML were significantly lower in subjects with higher BMI. Further, BMI showed negative correlations with pentosidine and CML (r = -0.363, p<0.001 and r = -0.484, p<0.001, respectively). There were not any significant differences in serum NO, pentosidine, and CML levels between sex groups. After adjusting the effects of confounders (BMI, sex, age, and waist to hip ratio), serum NO significantly correlated with serum pentosidine and CML (r = -0.319, p = 0.003 and r = -0.433, p<0.001, respectively). It is concluded that higher BMI is accompanied by increased serum NO and suppressed pentosidine and CML.

Circulating markers of nitric oxide homeostasis and cardiometabolic diseases: insights from population-based studies

Emerging data suggest that impaired nitric oxide (NO) homeostasis has a key role in development of cardiometabolic disorders. The association between circulating levels of NO metabolites, i.e. nitrate and nitrite (NOx), and risk of chronic diseases has not yet been fully clarified. This work aims to address epidemiologic aspects of NO metabolism and discusses different physiologic and pathophysiologic conditions influencing circulating NOx. Further, cross-sectional associations of serum NOx with metabolic disorders are described and along the way, potential short-term and long-term power of serum NOx for predicting cardiometabolic outcomes are reviewed. Results from population-based studies show that circulating NOx is affected by aging, smoking habits, pregnancy, menopause status, thyroid hormones, and various pathologic conditions including type 2 diabetes, insulin resistance, hypertension, and renal dysfunction. Lifestyle factors, especially dietary habits, but also smoking habits and the degree of physical activity influence NO homeostasis and the circulating levels of NOx. Elevated serum NOx, due to increased iNOS activity, is associated with increased incidence of metabolic syndrome, different obesity phenotypes, and cardiovascular events.

The Nitrate-Nitrite-Nitric Oxide Pathway: Findings from 20 Years of the Tehran Lipid and Glucose Study

CONTEXT

We describe here the contributions of the Tehran lipid and glucose study (TLGS) to understanding different aspects of the nitrate (NO3)-nitrite (NO2)-nitric oxide (NO) pathway in health and disease.

EVIDENCE ACQUISITION

All English-language documents from the TLGS, focused on NO pathway were searched using the PubMed, Scopus, and Embase databases.

RESULTS

Reference values of serum concentrations of NO metabolites (nitrate+nitrite or NOx) were 11.5 - 76.4, 10.1 - 65.6, and 10.3 - 66.8 μmol/L in men, women, and the total population, respectively. Circulating NOx was affected by age, smoking habits, menopause status, thyroid hormones, and various pathologic conditions. Elevated serum NOx was related to increased incidence of metabolic syndrome (odds ratio (OR) = 1.75, 95% confidence interval (CI) = 1.19 - 2.59), hypertriglyceridemic-waist phenotype (OR = 1.39, 95% CI = 1.05 - 1.93), chronic kidney disease (OR = 1.86, 95% CI = 1.10 - 3.14) in women, and cardiovascular disease (hazard ratio (HR) = 1.35, 95% CI = 1.01 - 1.80] in the total population. In participants with low vitamin C intake, higher intakes of NO2 (≥ 8.77 mg/d) were accompanied with increased risk of diabetes (HR = 2.43, 95% CI = 1.45 - 4.05). A decreased risk of hypertension (OR = 0.58, 95% CI = 0.33 - 0.98) and chronic kidney disease (OR = 0.50, 95% CI = 0.24 - 0.89) was observed in response to higher intakes of NO2.

CONCLUSIONS

Circulating NOx is associated with and could predict the risk of metabolic disorders in a general population. Moreover, dietary NO3/NO2 exposure from usual diets seems to contribute to development of noncommunicable diseases.

Reproductive Assessment: Findings from 20 Years of the Tehran Lipid and Glucose Study

CONTEXT

Reproductive domains of the Tehran lipid and glucose study (TLGS) are unique in that they provide reliable information on reproduction of an urban population of West Asia. The aim of this review is to present the most important reproductive findings of TLGS.

EVIDENCE ACQUISITION

This review is summarizing all articles published in the context of reproductive aspects of TLGS results over the 20-year follow-up. A comprehensive databases search was conducted in PubMed (including Medline), Web of Science and Scopus for retrieving articles on the reproductive histories in context of the TLGS.

RESULTS

The mean (SD) age at menarche and menopause was 13 (1.2) and 49.6 (4.5) years respectively. While pills were the most commonly used modern methods at the initiation of TLGS, the prevalence of condoms rose sharply and significantly over the follow up duration. Among women with history of gestational diabetes, the risk of diabetes and dyslipidemia progression were 2.44 and 1.2 fold higher than others. Prevalences of PCOS and idiopathic hirsutism among reproductive age participants of TLGS were 8.5% (95% CI: 6.8% - 10.2%) and 13.0% (95% CI: 10.9% - 15.1%), respectively. Trend of cardio-metabolic risk factors among women with PCOS showed that there were no statistically significant differences between mean changes of each cardio metabolic variables between PCOS and healthy women; PCOS status also significantly associated with increased hazard of diabetes and prediabetes among women aged younger than 40 years (HR: 4.9; 95% CI: 2.5 - 9.3, P value < 0.001)) and (HR: 1.7; 95% CI: 1.1 - 2.6), P value < 0.005), respectively.

CONCLUSIONS

The population based nature of TLGS provides a unique opportunity for valid assessment of reproductive issues, the results of which could provide new information for modification of existing guidelines.

The Effect of Being Aerobically Active vs. Inactive on Cutaneous Vascular Conductance during Local Heat Stress in an Older Population

Objective: To test the hypothesis that long- term aerobically trained elderly individuals have a greater amount of bioavailable nitric oxide (NO) and have a larger cutaneous vasodilation during local heat stress compared to their inactive elderly counterparts.

Methods: Eight aerobically trained and 8 inactive older men (>60 years old) participated in this study. NO bioavailability in blood and intradermal dialysate were measured with an ozone based chemiluminescence NO analyzer. Cutaneous vasodilator response to local heating was obtained using laser Doppler velocimetry.

Results: Whole blood NO were similar in older- trained and inactive subjects (0.75 ± 0.56 and 0.38 ± 0.32 μM, respectively; Mann–Whitney, p = 0.153), as was intradermal dialysate NO before (7.82 ± 6.32 and 4.18 ± 1.89 μM, respectively) and after local heating (7.16 ± 6.27 and 5.88 ± 3.97 μM, respectively, p = 0.354). The cutaneous vasodilator response of the older- inactive group was smaller than the older- trained group [Group-Time interaction, F_{(24, 264)} = 12.0, p < 0.0001]. When compared to a young group the peak vasodilator response of the older- trained subjects was similar. However, the time to initial dilation was 3.1 and 2.2 times longer (p < 0.05) in older- inactive and older- trained subjects, respectively, compared to young subjects.

Conclusions: Our data support the hypothesis that the age-related reductions in cutaneous vasodilation can possibly be restored by maintaining an aerobic training regimen (at least 3 years). However, some residual effects of aging remain, specifically a delayed cutaneous vasodilator response to local heating is still present in active older adults. We found no evidence for an increase in systemic or local NO-bioavailability with an extended commitment to aerobic fitness.

Predictors of coronary artery disease in middle-aged Taiwanese women at premenopause, postmenopause and after undergoing hysterectomy

AIMS AND OBJECTIVES

To examine the predictors of coronary artery disease among middle-aged women at various menopausal statuses.

BACKGROUND

Few studies have explored coronary artery disease predictors among middle-aged women at various menopausal statuses, particularly with the inclusion of women who underwent a hysterectomy.

DESIGN

A cross-sectional design was adopted.

METHODS

Two hundred and twenty-five middle-aged women who were waiting for catheterisation examinations because of possible coronary artery disease were selected. These patients were divided into premenopausal (n = 41), postmenopausal (n = 143) and women who had undergone a hysterectomy groups (n = 41). The differences in the risk factors for coronary artery disease between patients with coronary artery disease (catheterisation results showing stenosis of >50% in at least one major coronary artery) and those without coronary artery disease in the three groups were compared.

RESULTS

The participants were aged 56·8 ± 5·9 years. In the premenopausal group, the odds of coronary artery disease among ever or current smokers was 8·46 times the odds of coronary artery disease for the never smokers. In the postmenopausal group, the odds of coronary artery disease among diabetes patients was 2·89 times the odds of coronary artery disease for those without diabetes. Each additional point on the Chinese Beck Depression Inventory-II increased the risk of coronary artery disease by 5%. In the hysterectomy group, each additional increase in 1 mmHg in systolic blood pressure increased the risk of coronary artery disease by 4%.

CONCLUSIONS

Smoking, diabetes, depression and systolic blood pressure are predictors of coronary artery disease in middle-aged women at premenopause, postmenopause and after undergoing hysterectomy respectively.

RELEVANCE TO CLINICAL PRACTICE

These results are beneficial for middle-aged women at various menopausal stages to effectively implement prevention of coronary artery disease. These findings were among women being evaluated for possible coronary artery disease, we suggest the need for further study in lager, longitudinal studies.