The angiotensin II receptor type 2 polymorphism influences haemodynamic function and circulating RAS mediators in normotensive humans

Renin-angiotensin-aldosterone system activation in long-standing type 1 diabetes

BACKGROUND

In type 1 diabetes (T1D), adjuvant treatment with inhibitors of the renin-angiotensin-aldosterone system (RAAS), which dilate the efferent arteriole, is associated with prevention of progressive albuminuria and renal dysfunction. Uncertainty still exists as to why some individuals with long-standing T1D develop diabetic kidney disease (DKD) while others do not (DKD resistors). We hypothesized that those with DKD would be distinguished from DKD resistors by the presence of RAAS activation.

METHODS

Renal and systemic hemodynamic function was measured before and after exogenous RAAS stimulation by intravenous infusion of angiotensin II (ANGII) in 75 patients with prolonged T1D durations and in equal numbers of nondiabetic controls. The primary outcome was change in renal vascular resistance (RVR) in response to RAAS stimulation, a measure of endogenous RAAS activation.

RESULTS

Those with DKD had less change in RVR following exogenous RAAS stimulation compared with DKD resistors or controls (19%, 29%, 31%, P = 0.008, DKD vs. DKD resistors), reflecting exaggerated endogenous renal RAAS activation. All T1D participants had similar changes in renal efferent arteroilar resistance (9% vs. 13%, P = 0.37) irrespective of DKD status, which reflected less change versus controls (20%, P = 0.03). In contrast, those with DKD exhibited comparatively less change in afferent arteriolar vascular resistance compared with DKD resistors or controls (33%, 48%, 48%, P = 0.031, DKD vs. DKD resistors), indicating higher endogenous RAAS activity.

CONCLUSION

In long-standing T1D, the intrarenal RAAS is exaggerated in DKD, which unexpectedly predominates at the afferent rather than the efferent arteriole, stimulating vasoconstriction.

FUNDING

JDRF operating grant 17-2013-312.

Gender difference in the response to valsartan/amlodipine single-pill combination in essential hypertension (China Status II): An observational study

BACKGROUND

The China STATUS II is a prospective, multicentre, open-label, post-marketing, observational study including Chinese adults (aged ⩾ 18 years) with essential hypertension who were prescribed once-daily valsartan/amlodipine (Val/Aml 80/5 mg) single-pill combination. In order to examine gender differences in treatment response to Val/Aml, we further analysed data from the China STATUS II study.

METHODS

A total of 11,312 patients (6456 (57%) men and 4856 (43%) women) received the Val/Aml treatment for 8 weeks. After the treatment, we compared the proportion of patients not achieving the target systolic blood pressure (SBP: < 140 mm Hg) or diastolic blood pressure (DBP: < 90 mm Hg) in different age groups (by Fisher exact probability test) and estimated the changes in blood pressure (BP) according to age and gender, using a mixed model.

RESULTS

At enrolment, mean SBP was higher in the female versus the male patients (160.0 ± 12.71 versus 159.3 ± 12.31 mm Hg; p = 0.003), whereas the mean DBP was higher in the male versus the female patients (96.4 ± 10.65 versus 94.5 ± 10.72 mm Hg; p < 0.001). The overall proportion of women not achieving the target BP was less than that of men (57.41% versus 59.59%; p < 0.05) at 4 weeks and (22.22% versus 23.78%; p < 0.05) at 8 weeks after the Val/Aml treatment. Among both men and women, the proportion of patients not achieving the target SBP increased with age; however, the proportion not achieving the target DBP decreased with age. The mixed-model analysis showed that the changes in SBP were closely related to gender, indicating that the SBP-lowering effect after Val/Aml treatment might be better in women. In addition, the changes in DBP were closely related to age.

CONCLUSIONS

Gender might be a factor for consideration in the decision-making process of individualised antihypertensive therapy, in the future.

The effect of sex on humanin levels in healthy adults and patients with uncomplicated type 1 diabetes mellitus

Diabetes mellitus (DM) is associated with a loss of renal and vascular protection in women compared with men, but the responsible mechanisms are unclear. Recent experimental work implicated humanin (HN) as a novel cytoprotective hormone in DM. Our goal was to measure sex-related differences in HN levels in uncomplicated type 1 DM patients (T1D) and healthy controls (HC), as well as the interaction between HN, circulating neurohormones, and vascular function. Plasma HN, cGMP and aldosterone, blood pressure (BP), glomerular filtration rate, and effective renal plasma flow (inulin and para-aminohippurate) were measured in HC (11 men, 10 women) and T1D (23 men and 18 women) during clamped euglycemia (4-6 mmol·L(-1)). Plasma HN levels were generally lower in HC men by comparison with the women, but the differences were not statistically significant. In contrast, levels in the T1D men were higher compared with the T1D women (p = 0.026) and HC men (p < 0.0001). In the HC men, but not the women, HN correlated negatively with BP, but not with renal function, cGMP, or aldosterone. In the T1D men, HN negatively correlated with plasma cGMP. In the T1D women, HN did not correlate with neurohormones or vascular function. Future work should determine the role of HN in the pathogenesis of sex-related vascular function differences in DM.

The effect of empagliflozin on arterial stiffness and heart rate variability in subjects with uncomplicated type 1 diabetes mellitus

Background

Individuals with type 1 diabetes mellitus are at high risk for the development of hypertension, contributing to cardiovascular complications. Hyperglycaemia-mediated neurohormonal activation increases arterial stiffness, and is an important contributing factor for hypertension. Since the sodium glucose cotransport-2 (SGLT2) inhibitor empagliflozin lowers blood pressure and HbA1c in type 1 diabetes mellitus, we hypothesized that this agent would also reduce arterial stiffness and markers of sympathetic nervous system activity.

Methods

Blood pressure, arterial stiffness, heart rate variability (HRV) and circulating adrenergic mediators were measured during clamped euglycaemia (blood glucose 4–6 mmol/L) and hyperglycaemia (blood glucose 9–11 mmol/L) in 40 normotensive type 1 diabetes mellitus patients. Studies were repeated after 8 weeks of empagliflozin (25 mg once daily).

Results

In response to empagliflozin during clamped euglycaemia, systolic blood pressure (111 ± 9 to 109 ± 9 mmHg, p = 0.02) and augmentation indices at the radial (-52% ± 16 to -57% ± 17, p = 0.0001), carotid (+1.3 ± 1 7.0 to -5.7 ± 17.0%, p < 0.0001) and aortic positions (+0.1 ± 13.4 to -6.2 ± 14.3%, p < 0.0001) declined. Similar effects on arterial stiffness were observed during clamped hyperglycaemia without changing blood pressure under this condition. Carotid-radial pulse wave velocity decreased significantly under both glycemic conditions (p ≤ 0.0001), while declines in carotid-femoral pulse wave velocity were only significant during clamped hyperglycaemia (5.7 ± 1.1 to 5.2 ± 0.9 m/s, p = 0.0017). HRV, plasma noradrenalin and adrenaline remained unchanged under both clamped euglycemic and hyperglycemic conditions.

Conclusions

Empagliflozin is associated with a decline in arterial stiffness in young type 1 diabetes mellitus subjects. The underlying mechanisms may relate to pleiotropic actions of SGLT2 inhibition, including glucose lowering, antihypertensive and weight reduction effects.

Trial registration

Clinical trial registration: NCT01392560

Renal hyperfiltration and systemic blood pressure in patients with uncomplicated type 1 diabetes mellitus

BACKGROUND

Patients with type 1 diabetes mellitus (DM) and renal hyperfiltration also exhibit systemic microvascular abnormalities, including endothelial dysfunction. The effect of renal hyperfiltration on systemic blood pressure (BP) is less clear. We therefore measured BP, renal hemodynamic function and circulating renin angiotensin aldosterone system (RAAS) mediators in type 1 DM patients with hyperfiltration (n = 36, DM-H, GFR≥135 ml/min/1.73 m(2)) or normofiltration (n = 40, DM-N), and 56 healthy controls (HC). Since renal hyperfiltration represents a state of intrarenal RAAS activation, we hypothesized that hyperfiltration would be associated with higher BP and elevated levels of circulating RAAS mediators.

METHODS

BP, glomerular filtration rate (GFR - inulin), effective renal plasma flow (paraaminohippurate) and circulating RAAS components were measured in DM-H, DM-N and HC during clamped euglycemia (4-6 mmol/L). Studies were repeated in DM-H and DM-N during clamped hyperglycemia (9-11 mmol/L).

RESULTS

Baseline GFR was elevated in DM-H vs. DM-N and HC (167±6 vs. 115±2 and 115±2 ml/min/1.73 m(2), p<0.0001). Baseline systolic BP (SBP, 117±2 vs. 111±2 vs. 109±1, p = 0.004) and heart rate (76±1 vs. 67±1 vs. 61±1, p<0.0001) were higher in DM-H vs. DM-N and HC. Despite higher SBP in DM-H, plasma aldosterone was lower in DM-H vs. DM-N and HC (42±5 vs. 86±14 vs. 276±41 ng/dl, p = 0.01). GFR (p<0.0001) and SBP (p<0.0001) increased during hyperglycemia in DM-N but not in DM-H.

CONCLUSIONS

DM-H was associated with higher heart rate and SBP values and an exaggerated suppression of systemic aldosterone. Future work should focus on the mechanisms that explain this paradox in diabetes of renal hyperfiltration coupled with systemic RAAS suppression.

The "his and hers" of the renin-angiotensin system

Sex differences exist in the regulation of arterial pressure and renal function by the renin-angiotensin system (RAS). This may in part stem from a differential balance in the pressor and depressor arms of the RAS. In males, the ACE/AngII/AT(1)R pathways are enhanced, whereas, in females, the balance is shifted towards the ACE2/Ang(1-7)/MasR and AT(2)R pathways. Evidence clearly demonstrates that premenopausal women, as compared to aged-matched men, are protected from renal and cardiovascular disease, and this differential balance of the RAS between the sexes likely contributes. With aging, this cardiovascular protection in women is lost and this may be related to loss of estrogen postmenopause but the possible contribution of other sex hormones needs to be further examined. Restoration of these RAS depressor pathways in older women, or up-regulation of these in males, represents a therapeutic target that is worth pursuing.

The effect of direct renin inhibition alone and in combination with ACE inhibition on endothelial function, arterial stiffness, and renal function in type 1 diabetes

OBJECTIVE

Diabetes is associated with renin-angiotensin system (RAS) activation, leading to renal and systemic vascular dysfunction that contribute to end-organ injury and significant morbidity. RAS blockade with ACE inhibitors reduces, but does not abolish, RAS effects. Accordingly, our aim was to determine if direct renin inhibition alone, and in combination with an ACE inhibitor, corrects early hemodynamic abnormalities associated with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Arterial stiffness (augmentation index), flow-mediated vasodilatation (FMD), and renal hemodynamic function (inulin and paraaminohippurate clearance) were measured at baseline under clamped euglycemic and hyperglycemic conditions (n = 21). Measures were repeated after 4 weeks of aliskiren therapy and again after aliskiren plus ramipril.

RESULTS

Blood pressure-lowering effects of aliskiren were similar during clamped euglycemia and hyperglycemia. Combination therapy augmented this effect under both glycemic conditions (P = 0.0005). Aliskiren reduced arterial stiffness under clamped euglycemic and hyperglycemic conditions, and the effects were augmented by dual RAS blockade (-3.4 ± 11.2 to -8.0 ± 11.5 to -14.3 ± 8.4%, respectively, during euglycemia, P = 0.0001). During clamped euglycemia, aliskiren increased FMD; dual therapy exaggerated this effect (5.1 ± 3.3 to 7.5 ± 3.0 to 10.8 ± 3.5%, repeated-measures ANOVA, P = 0.0001). Aliskiren monotherapy caused renal vasodilatation during clamped hyperglycemia only. In contrast, dual therapy augmented renal vasodilatory effects during clamped euglycemia and hyperglycemia.

CONCLUSIONS

In patients with uncomplicated type 1 diabetes, aliskiren-based dual RAS blockade is associated with greater arterial compliance, FMD, and renal vasodilatation.

Hyperfiltration and effect of nitric oxide inhibition on renal and endothelial function in humans with uncomplicated type 1 diabetes mellitus

Studies of experimental diabetes mellitus (DM) suggest that increased nitric oxide (NO) bioactivity contributes to renal hyperfiltration. However, the role of NO in mediating hyperfiltration has not been fully elucidated in humans. Our aim was to examine the effect of NO synthase inhibition on renal and peripheral vascular function in normotensive subjects with uncomplicated type 1 DM. Renal function and brachial artery flow-mediated vasodilatation (FMD) were measured before and after an intravenous infusion of the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (l-NMMA) in 21 healthy control and 37 type 1 DM patients. Measurements in DM participants were made under clamped euglycemic conditions. The effect of l-NMMA on circulating and urinary NO metabolites (NO(x)) and cGMP and on urinary prostanoids was also determined. Baseline characteristics were similar in the two groups. For analysis, the DM patients were divided into those with hyperfiltration (DM-H, n = 18) and normal glomerular filtration rate (GFR) levels (DM-N, n = 19). Baseline urine NO(x) and cGMP were highest in DM-H. l-NMMA led to a decline in GFR in DM-H (152 ± 16 to 140 ± 11 ml·min(-1)·1.73 m(-2)) but not DM-N or healthy control participants. The decline in effective renal plasma flow in response to l-NMMA (806 ± 112 to 539 ± 80 ml·min(-1)·1.73 m(-2)) in DM-H was also exaggerated compared with the other groups (repeated measures ANOVA, P < 0.05), along with declines in urinary NO(x) metabolites and cGMP. Baseline FMD was lowest in DM-H compared with the other groups and did not change in response to l-NMMA. l-NMMA reduced FMD and plasma markers of NO bioactivity in the healthy control and DM-N groups. In patients with uncomplicated type 1 DM, renal hyperfiltration is associated with increased NO bioactivity in the kidney and reduced NO bioactivity in the systemic circulation, suggesting a paradoxical state of high renal and low systemic vascular NO bioactivity.