Fructose-induced salt-sensitive blood pressure differentially affects sympathetically mediated aortic stiffness in male and female Sprague-Dawley rats

Knocking Out Sodium Glucose-Linked Transporter 5 Prevents Fructose-Induced Renal Oxidative Stress and Salt-Sensitive Hypertension

BACKGROUND

A fructose high-salt (FHS) diet increases systolic blood pressure and Ang II (angiotensin II)-stimulated proximal tubule (PT) superoxide (O2-) production. These increases are prevented by scavenging O2- or an Ang II type 1 receptor antagonist. SGLT4 (sodium glucose-linked cotransporters 4) and SGLT5 are implicated in PT fructose reabsorption, but their roles in fructose-induced hypertension are unclear. We hypothesized that PT fructose reabsorption by SGLT5 initiates a genetic program enhancing Ang II-stimulated oxidative stress in males and females, thereby causing fructose-induced salt-sensitive hypertension.

METHODS

We measured systolic blood pressure in male and female Sprague-Dawley (wild type [WT]), SGLT4 knockout (-/-), and SGLT5-/- rats. Then, we measured basal and Ang II-stimulated (37 nmol/L) O2- production by PTs and conducted gene coexpression network analysis.

RESULTS

In male WT and female WT rats, FHS increased systolic blood pressure by 15±3 (n=7; P<0.0027) and 17±4 mm Hg (n=9; P<0.0037), respectively. Male and female SGLT4-/- had similar increases. Systolic blood pressure was unchanged by FHS in male and female SGLT5-/-. In male WT and female WT fed FHS, Ang II stimulated O2- production by 14±5 (n=6; P<0.0493) and 8±3 relative light units/µg protein/s (n=7; P<0.0218), respectively. The responses of SGTL4-/- were similar. Ang II did not stimulate O2- production in tubules from SGLT5-/-. Five gene coexpression modules were correlated with FHS. These correlations were completely blunted in SGLT5-/- and partially blunted by chronically scavenging O2- with tempol.

CONCLUSIONS

SGLT5-mediated PT fructose reabsorption is required for FHS to augment Ang II-stimulated proximal nephron O2- production, and increases in PT oxidative stress likely contribute to FHS-induced hypertension.

Angiotensin II-stimulated proximal nephron superoxide production and fructose-induced salt-sensitive hypertension

Angiotensin II (ANG II) increases proximal tubule superoxide (O2-) production more in rats fed a 20% fructose normal-salt diet compared with rats fed a 20% glucose normal-salt diet. A 20% fructose high-salt diet (FHS) increases systolic blood pressure (SBP), whereas a 20% glucose high-salt diet (GHS) does not. However, it is unclear whether FHS enhances ANG II-induced oxidative stress in proximal tubules and whether this contributes to increases in blood pressure in this model. We hypothesized that FHS augments the ability of ANG II to stimulate O2- production by proximal tubules, and this contributes to fructose-induced salt-sensitive hypertension. We measured SBP in male Sprague-Dawley rats fed FHS and GHS and determined the effects of 3 mM tempol and 50 mg/kg losartan for 7 days. We then measured basal and ANG II-stimulated (3.7 × 10-8 M) O2- production by proximal tubule suspensions and the role of protein kinase C. FHS increased SBP by 27 ± 5 mmHg (n = 6, P < 0.006) but GHS did not. Rats fed FHS + tempol and GHS + tempol showed no significant increases in SBP. ANG II increased O2- production by 11 ± 1 relative light units/µg protein/s in proximal tubules from FHS-fed rats (n = 6, P < 0.05) but not in tubules from rats fed GHS. ANG II did not significantly stimulate O2- production by proximal tubules from rats fed FHS + tempol or FHS + losartan. The protein kinase C inhibitor Gö6976 blunted ANG II-stimulated O2- production. In conclusion, FHS enhances the sensitivity of proximal tubule O2- production to ANG II, and this contributes to fructose-induced salt-sensitive hypertension.NEW & NOTEWORTHY A diet containing amounts of fructose consumed by 17 million Americans causes salt-sensitive hypertension. Oxidative stress is an initiating cause of this model of fructose-induced salt-sensitive hypertension increasing blood pressure. This salt-sensitive hypertension is prevented by losartan and thus is angiotensin II (ANG II) dependent. Fructose-induced salt-sensitive hypertension depends on ANG II stimulating oxidative stress in the proximal tubule. A fructose/high-salt diet augments the ability of ANG II to stimulate proximal tubule O2- via protein kinase C.

Acute Intake of Fructose Increases Arterial Pressure in Humans: A Meta-Analysis and Systematic Review

Hypertension is a major cardiac risk factor. Higher blood pressures are becoming more prevalent due to changing dietary habits. Here, we evaluated the impact on blood pressure in human subjects after acutely ingesting fructose using meta-analysis. A total of 89 studies were collected from four different electronic databases from 1 January 2008 to 1 August 2023. Of these studies, 10 were selected that fulfilled all the criteria for this meta-analysis. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), and blood glucose level were analyzed using the Cohen's d analysis or standardized mean difference at a confidence interval (CI) of 95%. The SBP, DBP, and MAP showed medium effect size; HR and glucose level displayed small effect size. The standardized mean difference of normal diet groups and fructose diet groups showed a significant increase in SBP (p = 0.04, REM = 2.30), and DBP (p = 0.03, REM = 1.48) with heterogeneity of 57% and 62%, respectively. Acute fructose ingestion contributes to an increase in arterial pressure in humans. The different parameters of arterial pressure in humans correlated with each other. These findings support further rigorous investigation, retrospective of necessity, into the effect of chronic dietary of fructose in humans in order to better understand the impact on long term arterial pressure.

Longitudinal Associations of Dietary Fructose, Sodium, and Potassium and Psychological Stress with Vascular Aging Index and Incident Cardiovascular Disease in the CARDIA Cohort

We explored how dietary behaviors (sucrose, fructose, sodium, and potassium consumption) and endured psychological stress in young adult males and females impact the vascular aging index (VAI) and CVD risk by mid-life. Data were obtained from the Coronary Artery Risk Development in Young Adults Study, an ongoing longitudinal study. The included participants (n = 2656) had undergone carotid artery ultrasound at year 20 allowing VAIs to be calculated. Demographics, dietary data, and depression scores were obtained at baseline and year 20 of follow-up. Regression analyses were used to assess the predictors of VAI. Cox regression analyses were conducted to assess the risk of CVD, stroke, and all-cause mortality. Predictors of vascular aging were found to be sex-specific. In females, depression scores at baseline were positively associated with VAI (B-weight = 0.063, p = 0.015). In males, sodium intake at year 20 positively predicted VAI (B-weight = 0.145, p = 0.003) and potassium intake inversely predicted VAI (B-weight = -0.160, p < 0.001). BMI significantly predicted CVD, stroke, and death. Fructose consumption at year 20 was a significant predictor of CVD risk while having high blood pressure at baseline was significantly associated with stroke risk. Our findings support the promotion of nutrient-specific behavior changes to prevent vascular aging in early adulthood and CVD risk in mid-life.