Atrial natriuretic peptide increases urinary albumin excretion in men with type 1 diabetes mellitus and established microalbuminuria

Progress and prospects of Sacubitril/Valsartan: Based on heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) is present in nearly half of patients with heart failure. The prevalence of heart failure with normal or near-normal ejection fractions increases more rapidly than in patients with reduced ejection fractions. Angiotensin-converting enzyme inhibitor (ACEI), angiotensin receptor blocker (ARB), aldosterone antagonist, β-blocker, and calcium channel blocker have not shown significant efficacy in HFpEF clinical trials. Sacubitril/Valsartan, combined angiotensin receptor blocker (Valsartan) with neprilysin inhibitor (Sacubitril), was the first-of-its-kind angiotensin receptor-neprilysin inhibitor (ARNI) to be developed. It has shown significant efficacy on HFpEF in recent studies. It is considered that most of the current Sacubitril/Valsartan studies are still concentrated in the field of heart failure, especially heart failure with reduced ejection fraction (HFrEF). This review discusses the latest advances in cardiovascular, renal, and metabolic aspects of Sacubitril/Valsartan, mainly in HFpEF, providing more evidence for further future research on Sacubitril/Valsartan and raising issues that should be paid attention. At the same time, this review will introduce the academic consensus on Sacubitril/Valsartan in treating HFpEF in China.

Effect of Sacubitril/Valsartan on renal function in patients with chronic kidney disease and heart failure with preserved ejection fraction: A real-world 12-week study

Patients with chronic kidney disease (CKD) are often complicated with heart failure with preserved ejection fraction (HFpEF). However, several drugs, including angiotensin-converting enzyme inhibitor (ACEI) and angiotensin receptor blocker (ARB), have not shown apparent benefits in terms of morbidity and mortality of HFpEF. PARAMOUNT and other studies have shown the potential benefits of Sacubitril/Valsartan on patients with HFpEF, but its effects on renal function and the effect of low-dose Sacubitril/Valsartan in actual clinical conditions have not been thoroughly evaluated. In our longitudinal and observational research, 353 patients were followed up for 12 weeks. We evaluated renal function [urinary protein, serum creatinine and estimated glomerular filtration rate (eGFR)] and cardiac function [NT-proBNP (brain natriuretic peptide), New York Heart Association (NYHA) classification, left ventricular ejection fraction (LVEF), left atrial width and left ventricular end-diastolic width] at baseline and during follow-up. Worsening renal function (WRF) was defined as an increased serum creatinine≥26.5umol/L or decreased eGFR≥20%. The decline of eGFR in the Sacubitril/Valsartan group was slower than that in the control group (p = 0.021). The outcome of proteinuria in the ACEI/ARB group was significantly better than that in the Sacubitril/Valsartan group (p = 0.001). In terms of echocardiogram, the average left atrial width in Sacubitril/Valsartan group decreased by 1.38 ± 3.02 mm, which was significantly lower than that in the ACEI/ARB group (p = 0.02). The increase of urine protein class in the ACEI/ARB group increased the risk of WRF with statistical significance (OR = 2.36, 95%CI 1.01-5.49, p = 0.047), but no statistical significance was found in all the patients or Sacubitril/Valsartan group. In conclusion, Sacubitril/Valsartan could more effectively slow down renal function decline and reverse myocardial remodeling in patients with CKD and HFpEF than ACEI/ARB, even at low doses, though its protective effect on urinary protein is not as good as that of ACEI/ARB.

A higher level of serum furin indicates a higher risk of microalbuminuria: results from a longitudinal study in Chinese adults

BACKGROUND

Furin, a key enzyme of natriuretic peptide system, has been suggested to play a role in microalbuminuria, but the association between furin and microalbuminuria has been scarcely studied.

METHODS

Leveraging a longitudinal cohort of Chinese adults who had urinary albumin measured twice 4 years apart, we examined the cross-sectional and prospective associations of baseline serum furin with microalbuminuria, adjusting for age, sex, education level, smoking, drinking, obesity, blood pressure, glucose, lipids, and antihypertensive medications.

RESULTS

The cross-sectional analysis in 2175 participants (53 ± 10 years, 38% men) found that a 10-time higher level of serum furin was significantly associated with a 64% higher risk of having microalbuminuria (OR = 1.64, P = 0.005). The longitudinal analysis found a positive association between baseline serum furin and dynamic elevation of albumin excretion during follow-up. The prospective analysis in 1357 participants free of microalbuminuria at baseline found that a 10-time higher level of serum furin at baseline was significantly associated with a 1.28-time higher risk of developing microalbuminuria 4 years later (OR = 2.28, P < 0.001).

CONCLUSIONS

A higher level of serum furin at baseline predicted an increased risk of developing microalbuminuria in Chinese adults. These findings indicate that furin might be a predictor or a risk factor for microalbuminuria but the causality still needs more investigations.

An observational study of the association between microalbuminuria and increased N-terminal pro-B-type natriuretic peptide in patients with subarachnoid hemorrhage

BACKGROUND

The urinary albumin/creatinine ratio (ACR) is a significant neurologic prognostic predictor in patients with aneurysmal subarachnoid hemorrhage (SAH). B-type natriuretic peptide (BNP) plays an important role in body fluid regulation in patients with SAH. The present study was performed to determine whether ACR was independent predictor for unfavorable neurological outcome and ACR was associated with increased N-terminal pro-BNP (NT-pro-BNP) after SAH.

METHODS

We studied 61 patients undergoing surgery who were admitted within 48 h after aneurysmal SAH onset between July 2008 and June 2010. Hunt and Hess grade and Fisher grade were recorded at admission. The Glasgow Coma Scale (GCS) score was calculated at admission and daily for seven postoperative days. Arterial blood was sampled at admission and for seven postoperative days to determine the PaO2/FIO2 ratio, C-reactive protein level, troponin I level, and NT-pro-BNP level. Urine was sampled at admission and daily for seven postoperative days to determine ACR and vanillylmandelic acid/creatinine ratio (VMACR). Neurological outcomes were assessed at hospital discharge by using the Glasgow Outcome Scale. Receiver operating characteristic curves were constructed for the predictive variables of unfavorable neurological outcomes, and the area under the curve (AUC) was determined. Multivariate logistic regression analyses were performed for the significant predictors of unfavorable neurological outcomes after SAH. Associations with NT-pro-BNP were evaluated by using the Spearman rank correlation test.

RESULTS

Of the 61 patients, 24 had unfavorable outcomes. The prevalence rate of microalbuminuria was 85 % (52/61). The highest NT-pro-BNP levels were above the normal range in 57 of 61 patients (93 %). According to the AUC, the Hunt and Hess grade, GCS score, the highest ACR, and highest VMACR were significant predictors of neurological outcome. Multivariate logistic regression analyses showed that the highest ACR and Hunt and Hess grade are independent prognostic predictors of unfavorable neurological outcomes. The highest NT-pro-BNP significantly correlated with the highest troponin I, highest ACR, and VMACR on admission.

CONCLUSIONS

The highest ACR is an independent prognostic predictor of unfavorable neurological outcomes after SAH. Moreover, plasma NT-pro-BNP elevation may be associated with the development of microalbuminuria.

Renal effects of the angiotensin receptor neprilysin inhibitor LCZ696 in patients with heart failure and preserved ejection fraction

BACKGROUND

Increases in serum creatinine with renin-angiotensin-aldosterone system (RAAS) inhibitors can lead to unnecessary discontinuation of these agents. The dual-acting angiotensin receptor neprilysin inhibitor LCZ696 improves clinical outcome patients with heart failure with reduced ejection fraction, and pilot data suggest potential benefit in heart failure with preserved ejection fraction (HFpEF). The effects of LCZ696 on renal function have not been assessed.

METHODS AND RESULTS

A total of 301 HFpEF patients were randomly assigned to LCZ696 or valsartan in the PARAMOUNT trial. We studied renal function [creatinine, estimated glomerular filtration rate (eGFR), cystatin C, and urinary albumin to creatinine ratio (UACR)] at baseline, 12 weeks, and after 36 weeks of treatment. Worsening renal function (WRF) was determined as an serum creatinine increase of >0.3 mg/dL and/or >25% between two time-points. Mean eGFR at baseline was 65.4 ± 20.4 mL/min per 1.73 m(2) . The eGFR declined less in the LCZ696 group than in the valsartan group (-1.5 vs. -5.2 mL/min per 1.73 m(2) ; P = 0.002). The incidence of WRF was lower in the LCZ696 group (12%) than in the valsartan group (18%) at any time-point, but this difference was not statistically significant (P = 0.18). Over 36 weeks, the geometric mean of UACR increased in the LCZ696 group (2.4-2.9 mg/mmol), whereas it remained stable in the valsartan group (2.1-2.0 mg/mmol; P for difference between groups = 0.016).

CONCLUSION

In patients with HFpEF, therapy with LCZ696 for 36 weeks was associated with preservation of eGFR compared with valsartan therapy, but an increase in UACR.

Atrial natriuretic peptide increases urinary albumin excretion in people with normoalbuminuric type-2 diabetes

BACKGROUND

Atrial natriuretic peptide (ANP) is elevated in patients with type-2 diabetes and microalbuminuria. The purpose of this study is to evaluate if ANP increases Urinary Albumin Eaxcretion Rate (UAER) in type-2 diabetes.

METHODS

Eight normoalbuminuric diabetic subjects underwent a randomised single blind study of 60 min intravenous infusion of ANP or vehicle. Eight non-diabetic controls underwent ANP infusion alone. Seven normoalbuminuric type-2 diabetes subjects received further ANP infusions during euglycaemia and during hyperglycaemia.

RESULTS

ANP increased urinary sodium (191.3 +/- 80.7 to 529.2 +/- 263.4 mumol/min, mean +/- SD, and P < 0.001) and UAER (72.2 +/- 73.4 to 224.9 +/- 182.9.5 mug/min, and P < 0.01) in diabetic subjects. In controls, UAER did not change significantly (P = 0.16); however, the natriuretic response to ANP was similar to diabetic subjects (P = 0.98). Hyperglycaemic did not enhance the albuminuric response to ANP (P = 0.88).

CONCLUSION

ANP increases UAER in normoalbuminuric type-2 diabetic subjects.

Elevated plasma concentrations of atrial and brain natriuretic peptide in type 1 diabetic subjects

BACKGROUND

The intravenous infusion of atrial (ANP) and brain (BNP) natriuretic peptides have been shown to increase urinary albumin excretion in type 1 diabetes.

AIMS

To measure plasma ANP and BNP concentrations in patients with type 1 diabetes and to examine the parameters associated with elevated plasma concentrations. Methods We measured plasma ANP and BNP concentrations, UAER, HbA1C systolic blood pressure, and left ventricular mass index. Plasma ANP and BNP were also measured in non-diabetic control subjects for comparison.

RESULTS

Using multivariate regression analysis plasma ANP correlated positively with HbA1C (1.9 + 0.47, p = 0.0002), UAER (0.37 + 0.05, p = 0.00001), SBP (1.26 + 0.5, p = 0.01) and LVMI (00.46 + 0.25, p = 0.07). BNP was positively related with LVMI (0.95 + 0.4, p = 0.02), and UAER (0.56 + 0.08, p = 0.001).

CONCLUSIONS

Plasma concentrations of ANP and BNP are elevated in some patients with type 1 diabetes. Plasma ANP concentrations are closely related to UAER and elevated plasma concentrations are associated with poor glycaemic control and systemic hypertension. Plasma BNP concentration is related to LVMI.

Glomerular abundance of nephrin and podocin in experimental nephrotic syndrome: different effects of antiproteinuric therapies

Nephrotic syndrome (NS) is a clinical state characterized by massive proteinuria, hypoalbuminemia, and eventual edema formation. Although the mechanisms underlying this phenomenon are not yet fully clarified, it is well accepted that nephrin and podocin are involved in the development of proteinuria. The effects of early treatment with various antiproteinuric therapies on proteinuria and glomerular staining of nephrin and podocin in rats with experimental NS have not been previously studied. Proteinuria and glomerular nephrin and podocin immunofluorescence were examined in rat kidneys with adriamycin-induced NS and the effects of antiproteinuric drug therapies during 5 wk with enalapril, losartan, alone or in combination, omapatrilat, and mycophenolate mofetil on these parameters were assessed. Injection of adriamycin caused a significant increase in daily (from 21.8 ± 1.4 to 983.1 ± 45.8 mg/day, P < 0.01) and cumulative protein excretion (from negligible values to 22,490 ± 931 mg, P < 0.001) during 5 wk. Early treatment with enalapril significantly decreased the daily (641.7 ± 82.4 mg/day, P < 0.0023) and cumulative proteinuria (15,727 ± 2,204 mg, P < 0.001). A similar effect, although to a lesser extent, was obtained after omapatrilat treatment: cumulative proteinuria was reduced to 18,706 ± 1,042 mg, P < 0.001. In contrast, losartan treatment did not significantly influence the cumulative proteinuria that remained comparable (20,351 ± 1,360 mg, P > 0.05) to that observed in untreated NS rats. Unexpectedly, when losartan was given in combination with enalapril, it abolished the beneficial effects of the latter. Pretreatment with mycophenolate mofetil exerted a moderate antiproteinuric effect, which appeared only during the last week of the experimental treatment. Nephrotic rats exhibited severe disruption of slit diaphragm structure as seen by rapid and profound loss of nephrin and podocin. Beneficial effects of enalapril, omapatrilat, and mycophenolate mofetil paralleled the preservation of nephrin, as determined immunohistochemically, and enabled prediction of significant antiproteinuric responses. Enalapril alone or in combination with losartan resulted in significant preservation of podocin. Pretreatment with enalapril, and to a lesser extent omapatrilat, is superior to losartan in reducing proteinuria in NS rats. A combination of ACE inhibitors with ANG II receptor blockers does not provide any advantageous antiproteinuric therapy in these animals. Nephrin loss is an indication of proteinuria in NS and the antiproteinuric effects of ACE inhibitors, vasopeptidase inhibitors, and mycophenolate mofetil attenuate this reduction. Not all the drugs which restore podocin reduce urinary protein in NS.

C-type natriuretic peptide as a podocyte hormone and modulation of its cGMP production by glucose and mechanical stress

BACKGROUND

High glucose and mechanical strain resulting from capillary hypertension are relevant risk factors affecting glomerular cells in diabetes. Altered activity of the natriuretic peptide (NP) system acting via vasorelaxing cyclic guanosine 5' monophosphate (cGMP) has been proposed to be one of the reasons for diabetes-dependent impairment of kidney function. Podocytes possess the NP receptors (NPRs) coupled to particular guanylyl cyclase. We investigated whether mechanical stress and high ambient glucose influence cGMP generation in podocytes stimulated with NPs. Additionally, the C-type natriuretic peptide (CNP) system has been characterized in these cells.

METHODS

Conditionally immortalized mouse podocytes were stimulated with NP for 15 minutes and cGMP was determined by enzymatic immunoassay. The mRNA expression for CNP and CNP-specific NPR-B was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, cGMP synthesis was measured in cells exposed to mechanical stress and to 30 mmol/L glucose for 3 days.

RESULTS

Production of cGMP upon stimulation of the NPR-B receptor with CNP and inhibition by an antagonist HS-142-1 was dose-dependent. RT-PCR showed that podocytes express mRNA not only for NPR-B but also for CNP. Mechanical stress reduced the cGMP response by 50%, both to atrial natriuretic peptide (ANP) and to CNP. Conversely, upon high glucose, the CNP-induced production of cGMP was elevated twofold in stretched and in control cells. Furthermore, as compared to ANP, stimulation with CNP caused a larger increase in cGMP levels in stretched as well as in nonstretched cells.

CONCLUSION

Expression of CNP together with potent NPR-B receptors suggests that in podocytes, CNP may act in an autocrine and/or paracrine manner. Furthermore, in a diabetic kidney, high glucose and mechanical stress may modulate the CNP-dependent cGMP production in podocytes in an opposite manner.

The albuminuric action of atrial natriuretic peptide is not modified by ACE-inhibition with perindopril in Type 2 diabetes

AIMS

Atrial natriuretic peptide (ANP) increases urine albumin excretion (UAER) in humans with Type 1 diabetes. The aim of this study was to establish if ANP increases UAER in microalbuminuric subjects with Type 2 diabetes and to examine whether the albuminuric action of ANP was inhibited by pre-treatment with the ACE-inhibitor perindopril.

METHODS

Seven microalbuminuric, normotensive males with Type 2 diabetes were entered into a randomised, double-blind, three-armed study of (i) intravenous infusion of ANP (0.25 microg/kg/min in 0.9% NaCl) after 3 weeks' pre-treatment with placebo, (ii) intravenous infusion of vehicle (0.9% NaCl only) after 3 weeks' pre-treatment with placebo, or (3) intravenous infusion of ANP (0.25 microg/kg/min in 0.9% NaCl) after 3 weeks' pre-treatment with perindopril, 4 mg daily.

RESULTS

Baseline parameters were similar on all three study days. During the placebo/vehicle arm there was no change in urine flow rate (UFR, P=0.61), urine cyclic guanosine monophosphate (UcGMP P=0.48) or UAER (P=0.99). During the placebo/ANP arm there was a rise in UFR [13.7+/-2.8 (mean+/-sd) to 25.7+/-7.7 mL/min, P<0.001], UcGMP (60.0+/-36.6 to 160.8+/-118.5 micromol/mmolCr, P=0.045) and UAER [5.13 [2.4-11.6][median (range)] to 71.6 [21.6-175.1] mg/mmolCr, P<0.001]. Pre-treatment with perindopril did not alter the changes in UFR (P=0.63), UcGMP (P=0.46) or UAER (P=0.99) to infusion of ANP, compared with the placebo/ANP arm.

CONCLUSION

ANP increases UAER in microalbuminuric patients with Type 2 diabetes and the albuminuric action of ANP is not inhibited by pre-treatment with the ACE inhibitor perindopril.

Renoprotective effects of VPI versus ACEI in normotensive nephrotic rats on different sodium intakes

BACKGROUND

Control of blood pressure (BP) and optimal reduction of proteinuria (Uprot) are necessary for long-term renoprotection. Unfortunately, angiotensin-converting enzyme inhibitors (ACEI) and angiotensin II (Ang II) antagonists are not effective during sodium repletion. Vasopeptidase inhibitors (VPI) cause dual inhibition of ACE and neutral endopeptidase, the latter resulting in decreased atrial natriuretic peptide (ANP) breakdown and thus enhanced natriuresis. Therefore, in contrast with ACEI, VPI may be effective during high sodium intake.

METHODS

To test this hypothesis, the renoprotective actions of the new VPI gemopatrilat (GEM) were studied during low (0.05% NaCl) and high (3.0% NaCl) sodium diets in normotensive Wistar rats with established adriamycin nephrosis. The ACEI lisinopril (LIS) was used as control. Rats received either GEM (0.3 mg/g chow), an equihypotensive dose of LIS (75 mg/L drinking water), or vehicle (VEH) from week 6 (that is, established Uprot) until sacrifice. The effect of therapy was monitored by measuring systolic BP and Uprot (weekly) and structural renal damage at the end of study (week 16).

RESULTS

During low sodium, GEM effectively reduced Uprot (-48 +/- 4%), but LIS was more effective (-80 +/- 2%), while Uprot slightly increased in VEH (+23 +/- 2%). The focal glomerulosclerosis (FGS) score after GEM (38 +/- 14) was lower than in the VEH group (79 +/- 27), although this was not significant. LIS (18 +/- 6) reduced FGS significantly. Remarkably, on high sodium, GEM was completely ineffective in reducing BP, Uprot and structural renal injury, just like LIS.

CONCLUSIONS

The renoprotective actions of VPI depend on dietary sodium intake in normotensive nephrotic rats: therapeutic efficacy is fully blunted by a high sodium diet. During a low sodium diet, gemopatrilat was renoprotective, but less effective than lisinopril. Whether higher doses of the VPI could improve its renoprotective efficacy remains to be elucidated.

Atrial natriuretic peptide-induced microalbuminuria is associated with endothelial dysfunction in noncomplicated type 1 diabetes patients

BACKGROUND

Microalbuminuria reflects widespread vascular dysfunction in type 1 diabetes mellitus and results from increased glomerular sieving caused by changes in transglomerular pressure and/or permselectivity characteristics of the glomerular basement membrane. Increased tubular reabsorption or degradation of albumin will offset an early increase in albuminuria. We hypothesized that the infusion of atrial natriuretic peptide (ANP) as a tool to increase glomerular permeability might uncover changes in permselectivity in patients with uncomplicated type 1 diabetes.

METHODS

We investigated whether these patients were characterized by endothelial and/or vascular dysfunction. We therefore studied 46 normoalbuminuric patients (urinary albumin excretion [UAE] < 10 microg/min) with type 1 diabetes and 44 healthy controls. Measurements of renal hemodynamics and albuminuria were performed before (baseline) and during the infusion of ANP (0.01 microg/kg/min). On a separate occasion, endothelial function was assessed by the intra-arterial infusion of acetylcholine (ACh), an endothelial-dependent vasodilator.

RESULTS

At baseline, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were greater in patients with diabetes (GFR, 121 +/- 3 versus 106 +/- 2 mL/min/1.73 m(2); ERPF, 558 +/- 16 versus 527 +/- 13 mL/min/1.73 m(2); P < 0.001). The infusion of ANP increased filtration fraction. There were no differences in these responses between groups. UAE was significantly greater in patients with diabetes after the ANP infusion (15.8 +/- 1.4 [+183%] versus 9.5 +/- 1.3 microg/min [+96%]; P < 0.01). A subgroup of patients with diabetes with an enhanced albuminuric response (change in UAE > 2 SD of controls) to ANP infusion (mean UAE, 30.3 +/- 1.0 microg/min; 425% +/- 61%) was characterized by a diminished vasodilatory response to ACh (maximal forearm blood flow, 17.2 +/- 2.9 [+563%] versus 26.3 +/- 2.3 mL/min/dL [+800%] in patients with diabetes with a normal albuminuric response; P < 0.05).

CONCLUSIONS

In a subgroup of patients with uncomplicated type 1 diabetes, an increase in glomerular permselectivity can be unmasked by the infusion of ANP. These patients are characterized by a diminished vascular response to ACh.

Brain natriuretic peptide increases urinary albumin and alpha-1 microglobulin excretion in Type 1 diabetes mellitus

Atrial natriuretic peptide (ANP) increases urinary albumin excretion in Type 1 diabetes mellitus (DM). Brain natriuretic peptide (BNP) is structurally and functionally related to ANP, but its effect on urine albumin excretion rate (UAER) is unknown.

AIMS

To compare the albuminuric effects of intravenous infusion of ANP and BNP, and to assess the effect of both peptides on tubular protein excretion.

METHODS

Eight subjects with Type 1 DM were randomised to a three leg, double blind, and placebo controlled study. On each study day, subjects were euglycaemic clamped and subsequently water loaded (20 mL/kg orally, plus urine losses) to steady state diuresis. When in steady state, creatinine clearance was estimated in three separate 1 hour periods. At the end of the first period, a 1 hour intravenous infusion of either placebo, ANP 0.025 microg/kg/min, or BNP 0.025 microg/kg/min was administered. There followed a 1 hour recovery period. Urine was collected at 15 min intervals for estimation of urine albumin (ACR) and alpha1 microglobulin creatinine ratio (MCR). Results were analysed by anova.

RESULTS

Creatinine clearance was similar on the three study days, and was unaltered by any infusion. ACR was unaltered by placebo (1.3 +/- 0.5-1.2 +/- 0.4 mg/mmol, mean +/- SD, p = 0.81), but increased compared to placebo with infusion of both ANP (1.2 +/- 0.4-9.8 +/- 8.4 mg/mmol, P = 0.0004), and BNP (1.1 +/- 0.4-13.4 +/- 8.6 mg/mmol, P = 0.0001). The MCR was unaltered by placebo infusion (P = 0.89), but increased compared with placebo after infusion of ANP (5.4 +/- 0.9-12.3 +/- 4.2 mg/mmol, P < 0.0001), and BNP (5.4 +/- 0.8-12.1 +/- 2.5 mg/mmol, P < 0.0001).

CONCLUSIONS

Intravenous infusion of BNP and ANP both increase the urine excretion of albumin and the tubular protein alpha1 microglobulin, independent of creatinine clearance.

Acute hyperglycaemia causes elevation in plasma atrial natriuretic peptide concentrations in Type 1 diabetes mellitus

AIMS

To examine the effect of acute hyperglycaemia on atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) concentrations in Type 1 diabetes.

METHODS

The study was two limb, randomized, and single-blind. Eight Type 1 diabetes subjects were clamped at euglycaemia by intravenous infusion of insulin. When euglycaemia was established, the insulin infusion rate was left unaltered for the remainder of the protocol, and an intravenous infusion of either 500 ml 0.9% saline or 500 ml 10% dextrose was administered over 1 h. Blood was collected for estimation of plasma glucose, ANP and BNP concentrations at 30 min intervals for 2 h from the start of the infusion period. One week later, each subject received the alternate infusion. Results are expressed as mean +/- standard deviation, and were analysed by ANOVA.

RESULTS

Baseline plasma glucose (P = 0.8), ANP (P = 0.8) and BNP (P = 0.8) concentrations were similar on the study days. Plasma glucose rose with dextrose (6.1 + 0.5-15.1 + 2.8 mmol/l, P = 0.9). Plasma ANP concentrations were unaltered by saline infusion (76.5 +/- 14.7-77.7 +/- 15.2 pg/ml, P = 0.9), but increased with dextrose infusion (79 +/- 14-134 +/- 17.1 pg/ml, P < 0.0001), and were higher with dextrose than saline infusion (P < 0.0001). Plasma concentrations of BNP were not significantly altered by infusion of either dextrose (5.1 +/- 3.9-9.3 +/- 5.4 pg/ml, P = 0.63) or saline (4.3 +/- 3.5-6 +/- 5.2 pg/ml, P = 0.84).

CONCLUSIONS

Plasma concentrations of ANP, but not BNP, rise in response to acute hyperglycaemia in Type 1 diabetes.

Enhanced albuminuric response to atrial natriuretic peptide in normoalbuminuric patients with Type 1 diabetes mellitus--a pilot study

AIMS

To ascertain whether intravenous infusion of atrial natriuretic peptide (ANP) can induce microalbuminuria in patients with Type 1 diabetes mellitus (DM), as already demonstrated in patients with microalbuminuria, and to compare the albuminuric response to ANP infusion in Type 1 DM and a matched group of healthy non-diabetic controls.

METHODS

Eight normoalbuminuric DM patients participated in a three limb, randomized, double-blind, placebo-controlled study. Subjects were kept euglycaemic by insulin infusion, and subsequently water-loaded (20 ml/kg orally plus urinary losses). When in steady state, a 30-min infusion of either placebo, ANP 0.025 mg x kg(-1).min(-1) or ANP 0.05 mg x kg(-1) x min(-1) was administered intravenously. Urine was collected every 15 min for 90 min for the estimation of albumin-creatinine ratio (ACR). In addition, eight nondiabetic volunteers received a single infusion of ANP 0.025 mg x kg(-1) x min(-1).

RESULTS

ACR was unaltered by placebo in DM subjects (1.4 +/- 0.7-1.7 +/- 1.1 mg/mmol, mean +/- SD, ANOVA, P > 0.9), and by low dose ANP in controls (1.4 +/- 0.9-2.6 +/- 1.9 mg/mmol, P = 0.4). ACR increased with low dose ANP (1.3 +/- 0.5-14.6 +/- 13.6 mg/mmol, P = 0.02), and high dose ANP (1.3 +/- 0.7-26.4 +/- 31 mg/mmol, P = 0.01) in DM subjects. The ACR response to low dose ANP was greater in the DM than control subjects (P = 0.02).

CONCLUSIONS

ANP increases urine albumin excretion rate in normoalbuminuric Type 1 DM patients, and this effect is more pronounced than in healthy volunteers.

Angiotensin-converting enzyme inhibition by quinapril blocks the albuminuric effect of atrial natriuretic peptide in Type 1 diabetes and microalbuminuria

AIMS

This study examined the effect of angiotensin-converting enzyme inhibition, administered at doses with no effect on systemic blood pressure, on the albuminuric action of atrial natriuretic peptide (ANP).

METHODS

Seven Type 1 diabetic patients with established microalbuminuria participated in a two limb, single-blind, placebo controlled study. Subjects were administered quinapril 10 mg daily or placebo for 7 days prior to study. On the study day, subjects were euglycaemic clamped and subsequently fluid loaded (20 ml/kg tap water orally plus urinary losses). At steady state diuresis, a 1 h intravenous infusion of ANP 0.05 mg.kg(-1) x min(-1) was administered. Urine was collected at 15-min intervals for estimation of albumin-creatinine ratio (ACR). Results were analysed by ANOVA.

RESULTS

Baseline mean arterial pressure was similar after pre-treatment with quinapril and placebo (98.7 +/- 3.8 vs. 100 +/- 4.5 mmHg, mean +/- SD, P > 0.5), and was unaltered by ANP infusion on either study day. Baseline ACR was similar on quinapril and placebo (P = 0.13). ANP infusion induced a rise in urine ACR with placebo (58.4 +/- 40.2 to 393.6 +/- 262.9 mg/mmol, P = 0.006), but not with quinapril (29.3 +/- 10.7 to 81.5 +/- 43 mg/mmol, P = 0.15). The urine ACR response to ANP infusion was higher with placebo than with quinapril (P = 0.02).

CONCLUSIONS

Quinapril blocks the albuminuric effect of intravenous infusion of ANP in subjects with Type 1 diabetes mellitus and established microalbuminuria. This action is independent of changes in mean arterial pressure and creatinine clearance.