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

Review A State of Natriuretic Peptide Deficiency

Measurement of natriuretic peptides (NPs) has proven its clinical value as biomarker, especially in the context of heart failure (HF). In contrast, a state partial NP deficiency appears integral to several conditions in which lower NP concentrations in plasma presage overt cardiometabolic disease. Here, obesity and type 2 diabetes have attracted considerable attention. Other factors - including age, sex, race, genetics, and diurnal regulation - affect the NP "armory" and may leave some individuals more prone to development of cardiovascular disease. The molecular maturation of NPs has also proven complex with highly variable O-glycosylation within the biosynthetic precursors. The relevance of this regulatory step in post-translational propeptide maturation has recently become recognized in biomarker measurement/interpretation and cardiovascular pathophysiology. An important proportion of people appear to have reduced effective net NP bioactivity in terms of receptor activation and physiological effects. The state of NP deficiency, then, both entails a potential for further biomarker development and could also offer novel pharmacological possibilities. Alleviating the state of NP deficiency before development of overt cardiometabolic disease in selected patients could be a future path for improving precision medicine.

Cardiovascular biomarkers in pregnancy with diabetes and associations to glucose control

AIM

Cardiovascular disease (CVD) is a leading cause of death in both men and women. Type 1 and 2 diabetes mellitus (DM1 and DM2) are well-known risk factors for CVD. In addition, gestational diabetes mellitus (GDM) is a female sex-specific risk factor for CVD. Here, we measure circulating concentrations of cardiac troponin T (cTNT), N-terminal pro-B-type natriuretic peptide (NT-proBNP) and growth differentiation factor 15 (GDF-15) during pregnancy-a window of time often referred to as a cardiovascular stress test for women.

METHODS

This study utilized data from 384 pregnant women: 64 with DM1, 16 with DM2, 35 with GDM and 269 euglycemic controls. Blood was predominantly sampled within a week before delivery. Cardiovascular biomarker concentrations were measured in serum using electrochemiluminescence immunoassay.

RESULT

Circulating cTnT levels were higher in women with DM1, DM2 and GDM as compared to controls, whereas NT-proBNP and GDF-15 levels were only increased in women with DM1. Glucose dysregulation, assessed by third trimester HbA1c levels, positively correlated with all three CVD biomarker levels, whereas pregestational body mass index correlated negatively with GDF-15.

CONCLUSIONS

Our results support the presence of myocardial affection in women with diabetic disorders during pregnancy. Although pregestational DM1 in this study was associated with the most adverse CVD biomarker profile, women with GDM displayed an adverse cTnT profile similar to what we found in women with pregestational DM2. This supports that women with GDM should be offered long-term intensified cardiovascular follow-up and lifestyle advice following delivery, similarly to the well-established CV follow-up of women with pregestational DM.

Comparative study of cardio-protective effects of zinc oxide nanoparticles and zinc sulfate in streptozotocin-induced diabetic rats

The cardio-protective effects of zinc oxide nanoparticles (Zn NPs) against diabetes-induced cardiopathy were evaluated and compared with zinc sulfate (ZnSO₄). A total of 120 Wistar rats were randomly categorized as healthy and diabetic groups. Then, the 2 groups were classified in 5 subgroups. The animals received oral supplementations containing different Zn NP (ie, doses of 1, 3, and 10mg/kg) and ZnSO₄ (30mg/kg) concentrations over 8 weeks. Blood and cardiac tissue samples were collected in the different time intervals and subjected to biochemical and histopathological analysis. Zn NPs showed dual effects, as its middle dose played protective role and recovered cardiac damages evidenced by significant reduction of serum cholesterol, HDL-cholesterol, lipoprotein (a), atherogenic index, TNF-α, cardiac MDA, B-type natriuretic peptide and caspase-3 activity. Apoptosis indices and histopathological features also were improved. However, the highest dose was found to be toxic and resulted in aggravation of the injuries. Another interesting finding is the ability of the higher doses of Zn-NPs (3 and 10mg/kg) to elevate cardiac zinc levels above the normal range in healthy animal. ZnSO₄ also helped to recuperation of the damages, but the middle dose of Zn NPs was more efficient as compared to ZnSO₄. Conclusively, Zn NPs have the potential for Zn delivery in diabetic patients.

Increased plasma concentrations of midregional proatrial natriuretic Peptide is associated with risk of cardiorenal dysfunction in type 1 diabetes

BACKGROUND

To examine possible associations between midregional proatrial natriuretic peptide (MR-proANP) and diabetic complications at baseline and risk of mortality and end-stage renal disease (ESRD) during follow-up in type 1 diabetes.

METHODS

Observational study including 667 patients, with plasma MR-proANP measured at baseline. Complications were defined as micro- (n = 168) or macroalbuminuria (n = 190) (urinary albumin excretion rate (UAER) 30-299 or ≥ 300 mg/24h), previous cardiovascular disease (CVD) (n = 143), cardiac autonomic dysfunction (heart rate variability < 11 beats/min) (n = 369), and retinopathy (n = 523). Adjustments included gender, age, systolic blood pressure, estimated glomerular filtration rate (eGFR), UAER, HbA1c, total cholesterol, 24-hour urinary sodium excretion (24h-U(Na)), body mass index, daily insulin dose, antihypertensive treatment, and smoking in linear regression analyses and analysis of covariance models. Development of ESRD (dialysis, renal transplantation, or GFR/eGFR < 15 ml/min/1.73 m(2)) and mortality was recorded through national registers.

RESULTS

The cohort included 293 (44%) females, aged 55 ± 13 years. Plasma MR-proANP (median (interquartile)) was 74.7 (49.2-116.8) pmol/L. Adjusted, MR-proANP correlated positively with age and UAER and negatively with eGFR, 24h-U(Na), total cholesterol, and HbA1c (P < 0.05). Moreover, MR-proANP levels increased with albuminuria degree and were higher in patients with previous CVD (P ≤ 0.001), but similar in patients with or without autonomic dysfunction or retinopathy (P ≥ 0.076). During follow-up (3.5 (3.1-4.0) years), higher MR-proANP concentrations predicted ESRD and mortality combined (n = 35) adjusted for gender, age, systolic blood pressure, eGFR, and previous CVD (hazard ratio per 1SD increase in logANP: 2.8 (1.6-4.7; P < 0.001)).

CONCLUSIONS

Increased plasma MR-proANP was associated with impaired renal function, increased albuminuria, and previous CVD. Moreover, MR-proANP concentrations were associated with increased risk of development of ESRD and mortality combined during follow-up.

Impaired diastolic function and elevated Nt-proBNP levels in type 1 diabetic patients without overt cardiovascular disease

Diabetic cardiomyopathy is an important complication of type 1 diabetes mellitus. Diastolic heart failure is an early manifestation of diabetic cardiac disease. Nt-proBNP is a valuable marker of ventricular dysfunction. The aim of this study was to determine Nt-proBNP concentrations in type 1 diabetic patients and determine their relationship with ventricular diastolic dysfunction (DD) and carotid artery intima media thickness (CIMT) measurements. Sixty-seven type 1 diabetic patients (30.2 ± 8.0 years; W/M: 24/43) without known cardiovascular disease and 48 healthy controls (30.5 ± 6.4 years; W/M: 19/29) were recruited. Nt-proBNP levels were measured. Conventional and tissue Doppler echocardiography were used to evaluate left ventricular diastolic function and CIMT. Nt-proBNP in diabetic patients was significantly higher than in controls (38 ± 34.8 vs. 15.1 ± 12.7 pg/ml) (P = 0.004). Ea level was higher (12.3 ± 3 vs. 10.3 ± 4 cm/s, P = 0.003) and E/Ea ratio was lower in patients (6.6 ± 2.5 vs. 9.7 ± 5.9, P = 0.001) compared with controls. Ratio of DD was higher in patients than controls (11.1 vs. 2.1%, P = 0.01). CIMT measurements in diabetic patients were higher than controls (0.54 ± 0.11 vs. 0.48 ± 0.05 mm, P = 0.02). Logistic regression revealed age and HbA1c to be independently associated with the presence of DD. Nt-proBNP levels are elevated in type 1 diabetic patients without overt cardiovascular disease and the presence of DD is increased in diabetic patients in comparison with controls. Nt-proBNP levels do not seem to be related to the presence of DD and subclinical atherosclerosis in this group of patients.

Eye complications and markers of morbidity and mortality in long-term type 1 diabetes

The incidence of type 1 diabetes is rising all over the world. Furthermore, the increased life-expectancy of type 1 diabetic patients is likely to cause a higher number of diabetes-related micro- and macrovascular complications in the years to come. In order to examine the level of long-term complications in type 1 diabetes as well as potential markers of micro- and macroangiopathy, a population-based cohort of Danish type 1 diabetic patients was examined in order to achieve the following aims: 1. To evaluate diabetic retinopathy as a long-term marker of all-cause mortality in type 1 diabetes (Paper I). 2. To estimate the long-term incidence and associated risk factors of blindness (Paper II) and cataract surgery (Paper III) in type 1 diabetes. 3 To use retinal vascular analyses in order to investigate the associations of long-term micro- and macrovascular complications and retinal vascular diameters (Paper IV) and retinal fractals (Paper V) in type 1 diabetes. 4. To examine N-terminal pro brain natriuretic peptide (Paper VI) and osteoprotegerin (Paper VII) as non-invasive markers of micro- and macrovascular complications in type 1 diabetes. In Paper I it was a major finding that, despite a mean age of only 38.3 years at baseline, 44.7% of the patients died during the 25-year follow-up. Patients who had proliferative retinopathy as well as proteinuria at the baseline examination had a significantly higher mortality. For these, the 10-year survival was only 22.2%. As demonstrated in Paper II, blindness is an important issue in type 1 diabetes. The 25-year cumulative incidence of blindness was 7.5%. Glycaemic regulation and maculopathy at baseline were both identified as risk factors of blindness. Finally, mortality was higher in patients who went blind during the follow-up. Cataract surgery is quite common in type 1 diabetes. In Paper III a 25-year cumulative incidence of 20.8% was found. Adjusted for mortality, this was even higher (29.4%). As compared to patients without diabetes, cataract surgery takes place approximately 20 years earlier in type 1 diabetic patients. Age and maculopathy at baseline were both identified as predictors of cataract surgery. In Paper IV it was demonstrated that patients with retinal arteriolar narrowing were 2.17 and 3.17 times more likely to have nephropathy and macrovascular disease, respectively. This was an important finding that suggests that retinal fundus photos may be used in order to predict the risk of non-ophthalmological complications in type 1 diabetes. Retinal fractal analysis is another way to evaluate the vascular system of the retina. In Paper V we found associations between retinal fractal and microvascular - but not macrovascular--disease. For instance, patients with lower fractal dimensions were more likely to have proliferative retinopathy (OR 1.45, 95% CI 1.04-2.03) and neuropathy (OR 1.42, 95% CI 1.01-2.01). NT-proBNP is likely to be a future predictor of diabetes-related complications. In Paper VI higher levels of NT-proBNP were related to nephropathy (OR 5.03, 95% CI 1.77-14.25), neuropathy (OR 4.08, 95% CI 1.52-10.97) and macrovascular disease (OR 5.84, 95% CI 1.65-20.74). These associations should be confirmed in future prospective studies. As opposed to NT-proBNP, osteoprotegerin is less likely to be a predictor of either micro- or macrovascular disease in type 1 diabetes. As demonstrated in Paper VII, even though association between higher levels of OPG and nephropathy were found in an age- and sex-adjusted model (OR 2.54, 95% CI 1.09-5.90), this was no longer statistically significant when other factors were taken into account. Overall, it was demonstrated that various complications such as mortality, blindness and cataract surgery were high in type 1 diabetes. Furthermore, retinal arteriolar narrowing, decreased retinal fractals and plasma NT-proBNP were associated with various micro- and macrovascular complications. If confirmed by prospective studies, these modalities may be used in order to identify patients at risk of diabetes-related complications. This could, ultimately, lead to decreased mortality and morbidity in type 1 diabetic patients.

Blood pressure lowering for the prevention and treatment of diabetic kidney disease

The current pandemic of diabetes mellitus will inevitably be followed by an epidemic of chronic kidney disease. It is anticipated that 25-40% of patients with type 1 diabetes and 5-40% of patients with type 2 diabetes will ultimately develop diabetic kidney disease. The control of blood pressure represents a key component for the prevention and management of diabetic nephropathy. There is a strong epidemiological connection between hypertension in diabetes and adverse outcomes in diabetes. Hypertension is closely linked to insulin resistance as part of the 'metabolic syndrome'. Diabetic nephropathy may lead to hypertension through direct actions on renal sodium handling, vascular compliance and vasomotor function. Recent clinical trials also support the utility of blood pressure reduction in the prevention of diabetic kidney disease. In patients with normoalbuminuria, transition to microalbuminuria can be prevented by blood pressure reduction. This action appears to be significant regardless of whether patients have elevated blood pressure or not. The efficacy of ACE inhibition appears to be greater than that achieved by other agents with a similar degree of blood pressure reduction; although large observational studies suggest the risk of microalbuminuria may be reduced by blood pressure reduction, regardless of modality. In patients with established microalbuminuria, ACE inhibitors and angiotensin receptor antagonists (angiotensin receptor blockers [ARBs]) consistently reduce the risk of progression from microalbuminuria to macroalbuminuria, over and above their antihypertensive actions. The clinical utility of combining these strategies remains to be established. In patients with overt nephropathy, blood pressure reduction is associated with reduced urinary albumin excretion and, subsequently, a reduced risk of renal impairment or end stage renal disease. In addition to actions on systemic blood pressure, it is now clear that ACE inhibitors and ARBs also reduce proteinuria in patients with diabetes. This anti-proteinuric activity is distinct from other antihypertensive agents and diuretics. Although there is a clear physiological rationale for blockade of the renin angiotensin system, which is strongly supported by clinical studies, to achieve the optimal lowering of blood pressure, particularly in the setting of established diabetic renal disease, a number of different antihypertensive agents will always be needed. In the end, the choice of agents should be individualised to achieve the maximal tolerated reduction in blood pressure and albuminuria. Ultimately, no matter how it is achieved, so long as it is achieved, renal risk can be reduced by agents that lower blood pressure and albuminuria.