Association of the inflammatory index of the diet with fibrinogen concentration and fibrin clot properties

Abstract

Introduction and aim: Cardiovascular disease (CVD), morbidity and mortality are increasing significantly in South Africa. Inflammation is known to play an integral part in CVD. Fibrinogen, an acute-phase protein, is a well-recognised risk marker for CVD and inflammation significantly up-regulates its expression. Fibrinogen concentration is also a main determinant of blood clot structure, which plays an important role in CVD event outcome. Increased fibrinogen concentration results in a denser clot with increased stability that is difficult to lyse. Several studies have shown that diet and inflammation are closely linked, and therefore, dietary inflammatory indices (DII) have been developed with the aim of determining the inflammatory potential of an individual's diet. These dietary inflammatory indices have been used successfully to determine the relationship between the diet and several health outcomes, including CVD. Less is known regarding the dietary inflammatory potential of African population groups whose dietary patterns and intakes differ from populations included in the development of these dietary inflammatory indices. African diets consist mainly of indigenous food, with rural populations having more traditional intakes and urban populations transitioning to more Westernised dietary intakes. Since diet influences inflammation and CVD is increasing exponentially in South Africa, we aim to describe the inflammatory potential of the diet of Black South Africans from both rural and urban settings and determine the relationship between the inflammatory potential of the diet (calculated using DII) and inflammatory markers, fibrinogen concentration and fibrin clot properties. Methods: This dissertation investigated 2010 apparently healthy Black South Africans who were recruited into the South African, North-West Province arm of the international Prospective Urban and Rural Epidemiology (PURE) study. The PURE study is a prospective study but only baseline data collected in 2005 were included in this dissertation in a cross-sectional analysis. Dietary intakes of the participants assessed by means of a quantitative food frequency questionnaire were used to calculate an energy-adjusted Dietary Inflammatory Index (E-DII) (a positive score indicates a more pro-inflammatory diet and negative score a more anti-inflammatory diet). Biochemical variables included blood lipids, glucose, liver enzymes and inflammatory markers - C-reactive protein (CRP), albumin, soluble urokinase-type plasminogen activator receptor (SuPAR) and interleukin-6 (IL-6) - as well as fibrinogen concentration and fibrin clot properties. Results: The PURE population consumed, on average, a pro-inflammatory diet with a mean E-DII of +0.37 ±1.25. Urban women consumed the most anti-inflammatory diet, although their mean E-DII was still reflective of a pro-inflammatory diet (0.25 ± 0.14), followed by urban men (0.31 ± 0.16). Rural iii men consumed the most pro-inflammatory diet (0.70 ± 0.66). In addition, the E-DII range of the PURE participants spanned only 61% of the theoretical E-DII range, reflecting a limited variety in the PURE diets. On average, urban women consumed higher amounts of 19 of the 28 antiinflammatory food components and urban men 5 of the 8 pro-inflammatory components. Age decreased across E-DII quartiles whereas the number of alcohol consumers (p<0.001) and tobacco users (p=0.001) increased. Most of the biochemical variables did not differ across E-DII quartiles, including the blood lipids (total cholesterol, high-density lipoprotein cholesterol, lowdensity lipoprotein cholesterol and triglyceride), the inflammatory markers (CRP, SuPAR, IL-6 and albumin), body mass index, fibrinogen and the clot properties. Only fasting glucose and the liver enzymes increased across the E-DII quartiles. Conclusion: This study described for the first time the inflammatory potential of a continental African study population. The inflammatory potential of the participants' diets differed significantly between men and women and those of rural/urban status, with urban women following the most antiinflammatory and rural men the most pro-inflammatory diet. The lack of variety within the PURE population's diet likely contributed to a lack of association between the E-DII and inflammatory markers, fibrinogen concentration and fibrin clot properties. This relationship should be investigated in study populations with a more varied diet with more overt anti- and proinflammatory properties. The results of this study highlight the need to better understand the role of the inflammatory potential of the diet in the context of food insecurity, unhealthy lifestyle practices and increased CVD incidence, which are highly prevalent in developing countries such