Race, Natriuretic Peptides, and High-Carbohydrate Challenge: A Clinical Trial

Abstract

Rationale: Lower NP (natriuretic peptide) levels may contribute to the development of cardiometabolic diseases. Blacks have lower NP levels than middle-aged and older white adults. A high-carbohydrate challenge causes an upregulation of a negative ANP regulator microRNA-425 (miR-425), which reduces ANP (atrial-NP) levels in whites.

Objectives: We designed a prospective trial to study racial differences in (1) NP levels among young adults, (2) NP response to a high-carbohydrate challenge, and (3) explore underlying mechanisms for race-based differences.

Methods and results: Healthy self-identified blacks and whites received 3 days of study diet followed by a high-carbohydrate challenge. Gene expression from whole blood RNA was assessed in the trial participants. Additionally, atrial and ventricular tissue samples from the Myocardial Applied Genomics Network repository were examined for NP system gene expression. Among 72 healthy participants, we found that B-type-NP, NT-proBNP (N-terminal-pro-B-type NP), and MRproANP (midregional-pro-ANP) levels were 30%, 47%, and 18% lower in blacks compared with whites (P≤0.01), respectively. The decrease in MRproANP levels in response to a high-carbohydrate challenge differed by race (blacks 23% [95% CI, 19%-27%] versus whites 34% [95% CI, 31%-38]; P_interaction<0.001), with no change in NT-proBNP levels. We did not observe any racial differences in expression of genes encoding for NPs (NPPA/NPPB) or NP signaling (NPR1) in atrial and ventricular tissues. NP processing (corin), clearance (NPR3), and regulation (miR-425) genes were ≈3.5-, ≈2.5-, and ≈2-fold higher in blacks than whites in atrial tissues, respectively. We also found a 2-and 8-fold higher whole blood RNA expression of gene encoding for Neprilysin (MME) and miR-425 among blacks than whites.

Conclusions: Racial differences in NP levels are evident in young, healthy adults suggesting a state of NP deficiency exists in blacks. Impaired NP processing and clearance may contribute to race-based NP differences. Higher miR-425 levels in blacks motivate additional studies to understand differences in NP downregulation after physiological perturbations.

Clinical trial registration: URL: https://clinicaltrials.gov/ct2/show/NCT03072602. Unique identifier: NCT03072602.

Keywords: carbohydrate; gene expression; glucose; microRNA; natriuretic peptide.

Figure 1.

Study Cohorts and Laboratory Assessment

Figure 2.

Serum glucose (Panel A) and insulin (Panel B) levels at baseline and in response to a high-carbohydrate challenge in black and white Individuals. Data are presented as mean ± SEM. 2-way analysis of variance was used to generate p-values for serum glucose and serum insulin by race and time, and to assess for interaction with race and time.

Figure 3.

Differences in plasma MRproANP (Panel A) and NTproBNP (Panel B) in response to a high-carbohydrate challenge by race. Linear mixed models using natural log-transformed MRproANP and NTproBNP as the dependent variable and Time as the independent variable were used. Values are predicted log MRproANP (Panel A) and log NTproBNP (Panel B) with 95% confidence interval. Linear mixed models adjusted for age, sex, body mass index, and serum insulin levels were used to assess p-value by race.

Figure 4.

Differences in NPPA and NPPB expression levels between black and white individuals in left atrial tissue. The NPPA (Panel A) and NPPB (Panel B) expression levels were normalized to the housekeeping control gene 18s. The NPPA and NPPB expression levels in blacks (n=15) were relative to white (n=30) individuals from atrial tissues from organ donor hearts with normal ventricular function in the Myocardial Applied Genomics Network (MAGNet) repository. Data are presented as mean ± SEM. 2-sample t-test with Welch correction for unequal variance was used to assess the p-value by race.

Figure 5.

Differences corin, furin and NPR3 expression levels between black and white individuals in left atrial tissue. The corin (Panel A), furin (Panel B) and NPR3 (Panel C) expression levels were normalized to the housekeeping control gene 18s. The corin, furin and NPR3 expression levels in blacks (n=15) were relative to white (n=30) individuals from atrial tissues from organ donor hearts with normal ventricular function in the Myocardial Applied Genomics Network (MAGNet) repository. Data are presented as mean ± SEM. Data are presented as mean ± SEM. 2-sample t-test with Welch correction for unequal variance was used to assess the p-value by race.

Figure 6.

Differences in microRNA-425 and microRNA-155 expression levels between black and white individuals in left atrial tissue. The microRNA-425 (Panel A) and microRNA-155 (Panel B) expression levels were normalized to the housekeeping control gene U6. The microRNA-425 and microRNA-155 expression levels in blacks (n=15) were relative to white (n=30) individuals from atrial tissues from organ donor hearts with normal ventricular function in the Myocardial Applied Genomics Network (MAGNet) repository. Data are presented as mean ± SEM. Data are presented as mean ± SEM. 2-sample t-test with Welch correction for unequal variance was used to assess the p-value by race.

Figure 7.

Baseline differences in MME, microRNA-425, and microRNA-155 expression levels in whole blood by race. The MME (Panel A) expression levels was normalized to the housekeeping control gene 18s, while miR-425 (Panel B) and miR-155 (Panel C) expression levels were normalized to the single nucleotide U6. The MME, miR-425, and miR-155 expression levels in blacks (n=20) were relative to white (n=29) individuals. Data are presented as mean ± SEM. Data are presented as mean ± SEM. 2-sample t-test with Welch correction for unequal variance was used to assess the p-value by race.