Atrial natriuretic factor in hypertensive and normotensive diabetic patients

Nuclear factor (erythroid-derived 2)-like 2 (NFE2L2) is a novel therapeutic target for diabetic complications

Diabetes is a leading cause of death and disability. In 2004, 3.4 million people worldwide died of symptoms relating to high blood sugar. Diabetic complications are caused by organ damage resulting from long-term exposure to high blood sugar, and include diseases such as heart failure, kidney failure, vision loss and neuropathy. The transcription factor nuclear factor (erythroid-derived 2)-like 2 (NFE2L2, also known as NRF2) is an important component of the intracellular antioxidant machinery and a target for treatment of diabetic complications. This article reviews the role of NFE2L2 in diabetic complications with a focus on diabetic nephropathy, cardiomyopathy, neuropathy and retinopathy. Activation of NFE2L2 protects against oxidative stress in vitro and in vivo, and represents an important target for prophylaxis and treatment of diabetic complications. NFE2L2 has potential clinical applications for diabetic patients in the near future.

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.

Plasma brain natriuretic peptide levels in normotensive Type 2 diabetic patients without cardiac disease and macroalbuminuria

To clarify the relationship of the plasma brain natriuretic peptide (BNP) levels to diabetic complications, we studied plasma BNP levels in 100 normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. The values of plasma BNP levels were not significantly different between patients with microalbuminuria and those with normoalbuminuria (12.2 +/- 2.0 vs. 12.3 +/- 1.3 pg/ml, means +/- S.E.M.), and neither were the BNP levels of patients with and without retinopathy significantly different (15.7 +/- 3.4 vs. 11.4 +/- 1.0 pg/ml). BNP levels of the subjects with cerebral vascular disease (CVD) were not statistically different from those of subjects without CVD (17.5 +/- 5.5 vs. 11.7 +/- 1.0 pg/ml), although mean BNP value of subjects with CVD was higher than that of subjects without it. With regard to peripheral vascular disease (PVD), BNP levels of the subjects with PVD were not statistically different from those of subjects without PVD (13.5 +/- 2.3 vs. 12.1 +/- 1.2 pg/ml). We also studied radial arterial oxygen tension of 45 patients and compared these levels between those with and without diabetic complications. However, we could not find statistical differences between them. In conclusion, our study suggests that BNP and arterial oxygen tension levels will not be affected by retinopathy, microalbuminuria, CVD, and PVD in normotensive diabetic patients without clinical cardiac disease and macroalbuminuria. Therefore, when normotensive diabetic patients without macroalbuminuria show increased plasma level of BNP, we should examine their cardiac function in detail, considering subclinical cardiac disease.

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.

The kidney: an unwilling accomplice in syndrome X

The ability of insulin to stimulate glucose disposal by muscle varies widely within the population at large. Individuals with muscle insulin resistance develop type 2 diabetes if they cannot compensate for this defect by secreting large amounts of insulin. Although this philanthropic effort on the part of the pancreatic B-cell may prevent gross decompensation of glucose homeostasis, it renders such individuals at increased risk to develop a cluster of abnormalities (syndrome X) associated with coronary heart disease. Although the kidney is not considered to be an insulin sensitive tissue, two features of syndrome X, hyperuricemia and hypertension, are likely to be dependent on the retention of normal insulin action on the kidney. More specifically, there is evidence to support the hypothesis that elevated plasma insulin concentrations may enhance renal sodium retention and decrease urinary uric acid clearance. As such, it is possible that a normal kidney response to the compensatory hyperinsulinemia associated with insulin resistance in nondiabetic subjects contributes to the development of hyperuricemia and hypertension in such individuals.

Factors influencing LVM in hypertensive type-1 diabetic patients

Diabetes mellitus is associated with a high prevalence of hypertension and left ventricular hypertrophy (LVH), and a causative relationship with abnormal sodium metabolism in diabetic patients has been suggested. Factors influencing left ventricular mass (LVM) were assessed in 30 hypertensive type-1 diabetic patients, mean age 46 +/- 9 (range 24-67) years, with a mean duration of diabetes and hypertension of 19 +/- 10 and 6 +/- 5 years, respectively. In the total study population, casual blood pressure was 163/94 +/- 24/10 mmHg and 24 h blood pressure was 155/87 +/- 17/8 mmHg. Twenty-four-hour urine samples were obtained to measure daily albumin excretion (0.77 +/- 1.06 g) and dietary sodium intake was assessed as 24 h sodium excretion (173 +/- 77 mmol). Creatinine clearance averaged 1.41 +/- 0.53 ml/s. LVM determined by echocardiography was 221 +/- 74 g (range 104-408 g) and 33% of the patients had LVH. Multiple regression analysis identified dietary sodium intake and plasma atrial natriuretic peptide as independent predictors of LVM (R2 = 0.52, p < 0.001). No significant association was found between LVM and blood pressure or albuminuria. The results propose dietary sodium intake as an important factor in the development of LVH in hypertensive type-1 diabetic patients.