Two problems with analyzing natriuretic Peptide levels: obesity and acute myocardial infarction

The optimal time of B-type natriuretic peptide sampling associated with post-myocardial infarction remodelling after primary percutaneous coronary intervention

Aims

To find the optimal time to evaluate plasma B-type natriuretic peptide (BNP), which is related to post-myocardial infarction remodelling (PMIR), we measured serial plasma BNP levels according to time protocols after primary percutaneous coronary intervention (PCI).

Background

It has been established that plasma BNP levels can predict the development of PMIR in patients with ST-elevation myocardial infarction (STEMI). However, the time of plasma BNP sampling associated with PMIR is still controversial.

Methods

We analysed 42 patients who were diagnosed as PMIR on six-month follow-up echocardiography among 131 patients with STEMI. We then compared clinical variables including plasma BNP between the remodelling group and the non-remodelling group. The plasma BNP level was obtained on hospital admission (acute phase), at two to five days (early phase), three to four weeks (late phase) and at the six-month follow up (long term).

Results

Early-phase and long-term BNP levels were higher in the remodelling group. The serial plasma BNP levels, according to study protocols, showed a biphasic pattern of elevation. In multiple logistic regression analyses, early-phase BNP [odds ratio (OR): 1.013, p < 0.01] and acute-phase BNP levels (OR: 1.007, p = 0.02) were independent predictors of PMIR. However, early-phase BNP level was statistically a more powerful predictor of PMIR during follow up.

Conclusion

Consecutive BNP levels after primary PCI showed a biphasic peak elevation during follow up. Earlyphase plasma BNP level was an independent predictor of PMIR in patients with STEMI.

C-type natriuretic peptide plasma levels are reduced in obese adolescents

The high prevalence of obesity in children may increase the magnitude of lifetime risk of cardiovascular disease (CD). At present, explicit data for recommending biomarkers as routine pre-clinical markers of CD in children are lacking. C-type natriuretic peptide (CNP) is assuming increasing importance in CD; in adults with heart failure, its plasma levels are related to clinical and functional disease severity. We have previously reported five different reference intervals for blood CNP as a function of age in healthy children; however, data on plasma CNP levels in obese children are still lacking. Aim of this study was to assess CNP levels in obese adolescents and verify whether they differ from healthy subjects. Plasma CNP was measured in 29 obese adolescents (age: 11.8 ± 0.4 years; BMI: 29.8 ± 0.82) by radioimmunoassay and compared with the reference values of healthy subjects. BNP was also measured. Both plasma CNP and BNP levels were significantly lower in the obese adolescents compared to the appropriate reference values (CNP: 3.4 ± 0.2 vs 13.6 ± 2.3 pg/ml, p<0.0001; BNP: 18.8 ± 2.6 vs 36.9 ± 5.5 pg/ml, p=0.003). There was no significant difference between CNP values in males and females. As reported in adults, we observed lower plasma CNP and BNP levels in obese children, suggesting a defective natriuretic peptide system in these patients. An altered regulation of production, clearance and function of natriuretic peptides, already operating in obese adolescents, may possibly contribute to the future development of CD. Thus, the availability of drugs promoting the action of natriuretic peptides may represent an attractive therapeutic option to prevent CD.

Impact of obesity on the expression profile of natriuretic peptide system in a rat experimental model

Natriuretic peptides (NPs) play an important role in obesity and aim of this study was to evaluate, in cardiac tissue of obese Zucker rats (O, n = 29) their transcriptomic profile compared to controls (CO, n = 24) by Real-Time PCR study; CNP protein expression was evaluated by immunostaining and immunometric tests. Myocardial histology was performed, confirming no alteration of organ structure. While ANP and BNP are cardiac peptides, CNP is mainly an endothelial hormone; thus its expression, as well as that of NPR-B and NPR-C, was also evaluated in kidney and lung of an animal subgroup (n = 20). In heart, lower BNP mRNA levels in O vs CO (p = 0.02) as well as ANP and CNP (p = ns), were detected. NPR-B/NPR-A mRNA was similar in O and CO, while NPR-C was numerically lower (p = ns) in O than in CO. In kidney, CNP/NPR-B/NPR-C mRNA was similar in O and CO, while in lung CNP/NPR-C expression decreased and NPR-B increased (p = ns) in O vs CO. Subdividing into fasting and hyperglycemic rats, the pattern of mRNA expression for each gene analyzed remained unchanged. The trend observed in heart, kidney and lung for CNP protein concentrations and immunohistochemistry reflected the mRNA expression. TNF-α and IL-6 mRNA were measured in each tissue and no significant genotype effect was detected in any tissue. The main NP variations were observed at the cardiac level, suggesting a reduced release by cardiac cells. The understanding of mechanisms involved in the modulation of the NP system in obesity could be a useful starting point for future clinical study devoted to identifying new obesity treatment strategies.