Exploring the link between left ventricular remodelling and the leukocyte profile of a young black and white population: the African-PREDICT study

Abstract

Background and motivation: Early vascular deterioration is associated with additional strain on the heart which is linked to cardiac remodelling and increased left ventricular mass (LVM). Increased LVM contributes to cardiovascular morbidity and mortality in a general population. Unhealthy lifestyle risk factors such as smoking, alcohol abuse and physical inactivity, all contribute to low-grade inflammation and in turn lead to increased levels of leukocytes. In result to the low-grade inflammation and a higher leukocyte count, early vascular changes may occur. Leukocytes are involved in the process of cardiac remodelling and for instance associated with left ventricular mass index (LVMi) in elderly populations with known hypertensive heart disease. Limited literature is available in young South African populations regarding the links of leukocytes and LVMi. Aim: The aim of this study was to investigate the link between LVMi and leukocyte count in a young South African population, free from overt cardiovascular diseases. Methodology: Cross-sectional data of 800 participants from the African Prospective study on the Early Detection and Identification of Cardiovascular disease and Hypertension (African-PREDICT) was used. Healthy black and white men and women between the ages of 20-30 years, with normal brachial blood pressures were included. Participants with left and right bundle branch blocks were identified with electrocardiogram data and excluded from this study. All participants completed a general health questionnaire from which their socio-economic status scores were determined. Anthropometric measurements were performed to determine body height, body weight and waist circumference, as well as body mass index and body surface area. Physical activity was measured and active energy expenditure (AEE) was calculated and normalised for weight. Twenty-four-hour ambulatory blood pressure measurements were performed. LVM was measured by echocardiography and calculated with a standard formula, normalised for body surface area and defined as LVMi. EDTA whole blood samples were analysed for leukocyte counts and neutrophil to lymphocyte ratio (NLR) was calculated additionally. Statistical analyses were performed with the IBM® SPSS® Statistics, Version 24. Results: Socio-economic score, body surface area, systolic blood pressure (SBP), mean arterial pressure, monocyte count and NLR were higher in the white group (all p≤0.017) compared to the black group. The white group had lower interleukin-6 and AEE (both p<0.001), as well as higher anti-inflammatory medication use (p=0.036) than their black counterparts. In single regression analyses, a negative correlation was found between LVMi and leukocyte count (r=–0.16; p=0.003), monocytes (r=–0.13; p=0.015) and NLR (r=–0.13 p=0.014) in the white population only. These results were confirmed with partial correlation analyses after adjusting for age and sex. In multiple regression analysis, an inverse association of LVMi with leukocyte count (Model 1: Adjusted R2=0.201; β=–0.08; p=0.017) and monocytes (Model 2: Adjusted R2=0.205; β=–0.11; p=0.002) was found in the total group. After stratification by sex and ethnicity, the inverse association between LVMi and leukocyte count (Model 1: Adjusted R2=0.094; =–0.30; p=0.001) as well as NLR (Model 3: Adjusted R2=0.053; –0.19; p=0.025) existed in white men only, whereas an inverse association between LVMi and monocytes was seen in white men (Model 2: Adjusted R2=0.075; =–0.25; p=0.004) and white women (Model 2: Adjusted R2=0.060; =–0.21; p=0.005). After additionally adjusting for interleukin-6, the inverse association between LVMi with leukocyte count and monocytes remained in all cases, but disappeared between LVMi and NLR. General conclusion: In this study, LVMi and leukocytes, specifically monocytes and NLR, were inversely associated in the white population. The inverse association between LVMi and monocytes may indicate potential premature onset of monocyte depletion and reduced capacity of cardiac repair in this young white South African population.