Insulin resistance and the relationship between urinary Na(+)/K(+) and ambulatory blood pressure in a community of African ancestry

A Longitudinal Investigation on the Effects of Sodium and Potassium Intake on the Development of Hypertension and Abdominal Obesity from Childhood to Young Adulthood amongst Ellisras Rural Population, South Africa

BACKGROUND

Hypertension (HT) and obesity have both been on the rise in children. Each is associated with an increase in cardiovascular disease risk, and both track into adulthood.

OBJECTIVES

This study aimed to identify the association of sodium intake (Na), potassium (K) intake, and sodium-to-potassium (Na/K) ratio with the development of HT and abdominal obesity amongst the Ellisras rural population over time.

METHODS

In this longitudinal study, data on dietary intake of Na and K were collected using a 24 h recall questionnaire from a total of 325 participants tracked from 1999 (5-12 years), 2001 (7-14 years), and 2015 (18-30 years). The averages of Na and K intake were analysed using local food tables and the South African Food Composition Database System (SAFOODS). In addition, blood pressure (BP) and anthropometric measurements (waist circumference (WC) and height) were also examined. Parametric (independent t-test) and Chi-square/Fishers exact tests were conducted to determine the difference between the years for numerical data and categorical variables. A generalised estimating equation (GEE) was used to assess the association of Na intake, K intake and their ratio on BP, WC, and waist-to-height ratio (WHtR).

RESULTS

Our results indicate a significant positive association between K intake and WHtR, and even though the model was adjusted for age and sex, there was still an association with WHtR. The Na/K ratio was associated with both BP measurements and abdominal obesity, respectively. Furthermore, Na/K was shown to be associated with an increased risk of developing HT and abdominal obesity.

CONCLUSIONS

In our study, we observed that an increase in the Na/K ratio is a predictor of HT and abdominal obesity over time compared to Na and K alone. However, more studies are required to further prove this.

Dietary sodium:potassium ratio and CVD risk factors among Japanese adults: a retrospective cross-sectional study of pooled data from the National Health and Nutrition Survey, 2003-2017

Few studies have reported associations between the Na:K ratio and risk factors related to CVD among the general population in Asian countries. This study aimed to investigate the dietary Na:K ratio association with CVD risk factors among Japanese adults. This retrospective cross-sectional study included 48 800 Japanese participants (19 386 men and 29 414 women) aged ≥20 years, registered in the 2003-2017 National Health and Nutrition Survey. Multivariate OR and 95 % CI for risk of hypertension, high glycated HbA1c levels, hypercholesterolaemia, low serum levels of HDL-cholesterol and high non-HDL-cholesterol levels according to the Na:K ratio were estimated using logistic regression models. Dietary Na:K ratio decreased for both men and women from 2003 to 2017. Higher Na:K ratio and higher hypertension prevalence were observed (multivariate OR (fifth v. first quintiles) 1·27, 95 % CI 1·15, 1·40; Pfor trend < 0·001 for men and 1·12, 95 % CI 1·01, 1·23; Pfor trend = 0·007 for women). Higher Na:K ratio was associated with higher prevalence of high HbA1c levels in men (multivariate OR 1·56, 95 % CI 1·24, 1·96). Prevalence of low HDL-cholesterol levels was increased with higher Na:K ratio (Pfor trend =0·002 for men and <0·001 for women). No significant associations were found between Na:K ratio and hypercholesterolaemia in men or high non-HDL-cholesterol levels in both men and women. Our findings suggest that dietary Na:K ratio is associated with several CVD risk factors among Japanese adults.

Ambulatory Blood Pressure Profiles and Correlation with Cardiovascular Risk Factors in a Sample of 390 University Employees in Tanzania

Background

Hypertension is a major risk factor for cardiovascular morbidity and mortality. Increasingly, evidence suggests that 24-hour ambulatory blood pressure (BP) monitoring (ABPM) is more accurate than clinic BP in predicting cardiovascular risk. However, this association has not been widely studied in subSaharan Africa, especially in Tanzania.

Aim

To explore the relationship between 24-hour ABPM profiles and cardiovascular risk factors in comparison with clinic BP among Muhimbili University of Health and Allied Sciences (MUHAS) employees.

Methods

A descriptive cross-sectional study was conducted from October 2018 to February 2019. Socio-demographic and cardiovascular risk information was gathered. We used an automated ABPM device to record 24-hour ambulatory BP. Correlation between BP profiles and cardiovascular risk factors was done using Pearson’s correlation coefficient, and independent factors for hypertension were determined using logistic regression analysis. P-value of <0.05 was considered statistically significant.

Results

In total, 390 employees participated. Their mean age was 40.5 ± 8.9 years, and 53.6% were men. The mean office systolic and diastolic BP were 126±12 mmHg and 78±13 mmHg, respectively, while the corresponding values for mean 24-hour ABPM were 122±14 and 75±10 mmHg. The prevalence of hypertension was 23.1%. The prevalence of white coat hypertension was 16.2%, while masked hypertension and nocturnal non-dipping were present in 11.5 and 66.7%, respectively. Overall, the mean 24-hour systolic BP showed the strongest correlations with cardiovascular risk factors while mean office systolic BP showed least. Independent associated factors of hypertension were male gender, age ≥40 years, family history of hypertension, central obesity, raised cholesterol and uric acid levels, all p<0.01.

Conclusion

Compared to office BP, ABPM measurements had stronger correlations with cardiovascular risk factors in this population, and therefore likely to reflect true BP. ABPM has revealed high proportion of masked, white coat and nocturnal non-dipping, supporting use of ABPM to detect these clinically important BP profiles.

Hyperinsulinemia rather than insulin resistance itself induces blood pressure elevation in high fat diet-fed rats

OBJECTIVE

To investigate if insulin resistance per se or the accompanying hyperinsulinemia induced hypertension and its underlying mechanisms.

METHODS

Sprague-Dawley rats were randomized into normal diet-fed group (ND group) and high-fat diet-fed group (HFD group). Then, the HFD group was further randomly divided into the control group (HFD_C group), the PIO group (treated with pioglitazone), the STZ_DM group (to induce diabetes with streptozotocin) and the DM+Ins group (streptozotocin injection followed by insulin treatment). Insulin sensitivity, plasma insulin, endothelin-1, norepinephrine, aldosterone, angiotensinⅡ and 24-h urinary sodium excretion (USE) levels of the groups were measured and analyzed. A multiple stepwise regression analysis method was applied to exam our hypothesis.

RESULTS

Compared to HFD_C group, the groups with lower plasma insulin, the PIO group and STZ_DM group, showed higher USE and lower blood pressure. The groups with higher plasma insulin (but same level of insulin resistance), the HFD_C group and DM+Ins group, showed lower USE and higher blood pressure. The 24-h urinary sodium excretion was the most important contributor to the significant changes of blood pressure with an R² of 25.2% in this animal experiment.

CONCLUSIONS

It is the compensatory hyperinsulinemia rather than insulin resistance per se that causes blood pressure elevation. The urinary sodium excretion is the key mediator among the multiple mechanisms. Therapies targeting hyperinsulinemia and restricting salt intake may favor a better control of hypertension associated with insulin resistance.

Limited contribution of insulin resistance and metabolic parameters to obesity-associated increases in ambulatory blood pressure in a black African community

Although accounting for a striking proportion of obesity effects on blood pressure (BP) in other populations, the extent to which obesity-associated increases in BP are explained by insulin resistance and metabolic changes in populations of African ancestry is uncertain. We determined the contribution of insulin resistance and associated metabolic abnormalities to variations in office or ambulatory BP in a black African community with prevalent obesity and hypertension. In 1225 randomly selected participants of black South African ancestry (age>16years, 43.1% obese, 47.4% abdominal obesity), we assessed adiposity indexes, the homeostasis model of insulin resistance (HOMA-IR) and associated metabolic abnormalities and office or ambulatory (n ​= ​798) BP. In separate models, waist circumference (p ​< ​0.0005-<0.0001) and HOMA-IR (p ​< ​0.51–0.005), were independently associated with office, 24 ​h, day or night systolic (SBP) or diastolic (DBP) BP. However, whilst a one standard deviation increase in waist circumference translated into a 1.47–3.08 ​mm Hg increased in office, 24-h SBP or DBP, in mediation analysis HOMA-IR accounted for only 0.12–0.30 ​mm Hg of the impact of a one standard deviation effect of waist circumference on office, and 24-h SBP and 0.003–0.17 ​mm Hg of the impact of a one standard deviation effect of waist circumference on office and 24-h DBP. In conclusion, in a black African community, insulin resistance accounts for a negligible proportion of the impact of obesity on office or ambulatory BP.

Involvement of NLRP3 inflammasome in the impacts of sodium and potassium on insulin resistance in normotensive Asians

Salt, promoting oxidative stress, contributes to insulin resistance, whereas K, inhibiting oxidative stress, improves insulin sensitivity. Oxidative stress activation of NLRP3 inflammasome is a central player in the induction of insulin resistance. Therefore, we hypothesised that NLRP3 inflammasome may mediate the effects of salt and K on insulin resistance. In all, fifty normotensive subjects were recruited from a rural community of Northern China. The protocol included a low-salt diet for 7 d, then a high-salt diet for 7 d and a high-salt diet with K supplementation for another 7 d. In addition, THP-1 cells were cultured in different levels of Na with and without K. The results showed that salt loading elevated fasting blood glucose, insulin and C-peptide levels, as well as insulin resistance, whereas K supplementation reversed them. Meanwhile, additional K reversed the active effects of high salt on NLRP3 inflammasome in both the subjects and THP-1 cells, and the change of insulin resistance index notably related with the alteration of plasma IL-1β, the index of NLRP3 inflammasome activation, during intervention in the subjects. Additional K ameliorated oxidative stress induced by high salt in both the subjects and cultured THP-1 cells, and the change of oxidative stress related with the alteration of plasma IL-1β during intervention in the subjects. In vitro, antioxidant N-acetyl-l-cysteine significantly prevented the active effects of high Na or oxidant Rosup on NLRP3 inflammasome, so did K. Our study indicates that oxidative stress modulation of NLRP3 inflammasome may be involved in the impacts of Na and K on insulin resistance.

Salt intakes in sub-Saharan Africa: a systematic review and meta-regression

Background

High sodium intake increases the risk of hypertension and cardiovascular diseases. For this reason the World Health Organization recommends a maximum intake of 2 g per day and a 30 % reduction in population sodium intake by 2025. However, in global reviews, data on sodium intake in sub-Saharan Africa have been limited.

Methods

A systematic review was conducted to identify studies reporting sodium intake in sub-Saharan African populations. Meta-regression analyses were used to test the effect of year of data collection and method of data collection (urinary/dietary), as well as any association between sex, urban/rural status or a country’s economic development, and population sodium intake.

Results

We identified 42 papers reporting 67 estimates of adult population sodium intakes and 12 estimates of child population sodium intakes since 1967. Of the 67 adult populations, 54 (81 %) consumed more than 2 g sodium/day, as did four of the 12 (33 %) child populations. Sixty-five adult estimates were included in the meta-regression, which found that urban populations consumed higher amounts of salt than rural populations and that urine collection gave lower estimates of sodium intake than dietary data.

Conclusions

Sodium intake in much of sub-Saharan Africa is above the World Health Organization’s recommended maximum intake and may be set to increase as the continent undergoes considerable urbanization. Few identified studies used stringent measurement criteria or representative population samples. High quality studies will be required to identify where and with whom to intervene, in order to meet the World Health Organization’s target of a 30 % reduction in population sodium intake and to demonstrate progress towards this target.

Mechanisms mediating renal sympathetic nerve activation in obesity-related hypertension

Excessive renal sympathetic nerve activation may be one of the mechanisms underlying obesity-related hypertension. Impaired baroreflex sensitivity, adipokine disorders-such as leptin, adiponectin, and resistin-activation of the renin-angiotensin system, hyperinsulinemia, insulin resistance, and renal sodium retention present in obesity increase renal sympathetic nerve activity, thus contributing to the development of hypertension. Renal sympathetic denervation reduces both renal sympathetic activity and blood pressure in patients with obesity-related hypertension.

Racial differences in abnormal ambulatory blood pressure monitoring measures: Results from the Coronary Artery Risk Development in Young Adults (CARDIA) study

BACKGROUND

Several ambulatory blood pressure monitoring (ABPM) measures have been associated with increased cardiovascular disease risk independent of clinic blood pressure (BP). African Americans have higher clinic BP compared with Whites but few data are available on racial differences in ABPM measures.

METHODS

We compared ABPM measures between African American (n = 178) and White (n = 103) participants at the Year 5 Coronary Artery Risk Development in Young Adults study visit. BP was measured during a study visit and the second and third measurements were averaged. ABPM was conducted over the following 24 hours.

RESULTS

Mean ± SD age of participants was 29.8 ± 3.8 years and 30.8 ± 3.5 years for African Americans and Whites, respectively. Mean daytime systolic BP (SBP) was 3.90 (SD 1.18) mm Hg higher among African Americans compared with Whites (P < 0.001) after age-gender adjustment and 1.71 (SD 1.03) mm Hg higher after multivariable adjustment including mean clinic SBP (P = 0.10). After multivariable adjustment including mean clinic SBP, nighttime SBP was 4.83 (SD 1.11) mm Hg higher among African Americans compared with Whites (P < 0.001). After multivariable adjustment, the African Americans were more likely than Whites to have nocturnal hypertension (prevalence ratio: 2.44, 95% CI: 0.99-6.05) and nondipping (prevalence ratio: 2.50, 95% CI: 1.39-4.48). The prevalence of masked hypertension among African Americans and Whites was 4.4% and 2.1%, respectively, (P = 0.49) and white coat hypertension was 3.3% and 3.9%, respectively (P = 0.99). Twenty-four hour BP variability on ABPM was higher among African Americans compared with Whites.

CONCLUSIONS

These data suggest racial differences in several ABPM measures exist.

Sodium-to-potassium ratio and blood pressure, hypertension, and related factors

The potential cost-effectiveness and feasibility of dietary interventions aimed at reducing hypertension risk are of considerable interest and significance in public health. In particular, the effectiveness of restricted sodium or increased potassium intake on mitigating hypertension risk has been demonstrated in clinical and observational research. The role that modified sodium or potassium intake plays in influencing the renin-angiotensin system, arterial stiffness, and endothelial dysfunction remains of interest in current research. Up to the present date, no known systematic review has examined whether the sodium-to-potassium ratio or either sodium or potassium alone is more strongly associated with blood pressure and related factors, including the renin-angiotensin system, arterial stiffness, the augmentation index, and endothelial dysfunction, in humans. This article presents a systematic review and synthesis of the randomized controlled trials and observational research related to this issue. The main findings show that, among the randomized controlled trials reviewed, the sodium-to-potassium ratio appears to be more strongly associated with blood pressure outcomes than either sodium or potassium alone in hypertensive adult populations. Recent data from the observational studies reviewed provide additional support for the sodium-to-potassium ratio as a superior metric to either sodium or potassium alone in the evaluation of blood pressure outcomes and incident hypertension. It remains unclear whether this is true in normotensive populations and in children and for related outcomes including the renin-angiotensin system, arterial stiffness, the augmentation index, and endothelial dysfunction. Future study in these populations is warranted.