Plasma protein expression profiles, cardiovascular disease, and religious struggles among South Asians in the MASALA study

Abstract

Blood protein concentrations are clinically useful, predictive biomarkers of cardiovascular disease (CVD). Despite a higher burden of CVD among U.S. South Asians, no CVD-related proteomics study has been conducted in this sub-population. The aim of this study is to investigate the associations between plasma protein levels and CVD incidence, and to assess the potential influence of religiosity/spirituality (R/S) on significant protein-CVD associations, in South Asians from the MASALA Study. We used a nested case-control design of 50 participants with incident CVD and 50 sex- and age-matched controls. Plasma samples were analyzed by SOMAscan for expression of 1305 proteins. Multivariable logistic regression models and model selection using Akaike Information Criteria were performed on the proteins and clinical covariates, with further effect modification analyses conducted to assess the influence of R/S measures on significant associations between proteins and incident CVD events. We identified 36 proteins that were significantly expressed differentially among CVD cases compared to matched controls. These proteins are involved in immune cell recruitment, atherosclerosis, endothelial cell differentiation, and vascularization. A final multivariable model found three proteins (Contactin-5 [CNTN5], Low affinity immunoglobulin gamma Fc region receptor II-a [FCGR2A], and Complement factor B [CFB]) associated with incident CVD after adjustment for diabetes (AUC = 0.82). Religious struggles that exacerbate the adverse impact of stressful life events, significantly modified the effect of Contactin-5 and Complement factor B on risk of CVD. Our research is this first assessment of the relationship between protein concentrations and risk of CVD in a South Asian sample. Further research is needed to understand patterns of proteomic profiles across diverse ethnic communities, and the influence of resources for resiliency on proteomic signatures and ultimately, risk of CVD.

Figure 1

Analysis flow diagram.

Figure 2

Distribution of the log base 10 of 1305 median estimates from 1305 proteins. Distribution of the log base 10 of 1305 median estimates from 1,305 proteins.

Figure 3

Distribution of the log base 10 of 1305 standard deviation estimates from 1305 Proteins.

Figure 4

Distribution of the number of proteins that correlate with other proteins at the Spearman correlation coefficient of 0.5 or above. The purpose of this correlation analysis is to identify proteins that are least correlated to other proteins. For example, in the first bar of this graph, there are 459 proteins that are correlated at 0.5 or above with 0 to 20 other proteins. There are 23 proteins that are highly correlated (0.5 or above) with 660 to 700 other proteins.

Figure 5

Systems Biology Analysis of the 36 CVD Incidence Proteins. (A) Interactive network analysis. Ingenuity Pathways Analysis was applied to generate the interactive networks from the 36 proteins associated with CVD events. The interactive network with the highest statistical significance is shown here. Red indicates protein up-regulation and green denotes protein down-regulation in individuals with CVD event. The intensity of the node color indicates the degree of up-regulation (red) and down-regulation (green) in individuals with a CVD event as compared with the matched controls. Empty shapes reflect proteins/genes not differentially expressed or absent from the SOMAscan platform that were brought in as interactors. Proteins are coded by shape. Square: cytokine; vertical rhombus: enzyme; horizontal rhombus: peptidase; trapezoid: transporter; ellipse: transmembrane receptor; circle: other. Links reflect various potential interactions such as protein expression regulation, protein activity, or modification of the other protein–protein interactions. Red arrows indicate the 3 proteins significant in final multivariate CVD-protein signature models. (B) Upstream Regulator Analysis of CVD Incidence Proteins. Upstream regulators (i.e., a protein/gene that can affect the expression of another protein/gene) with highest statistical significance that best explain the observed expression changes in the input 36 protein list as their targets. The x-axis indicates the -log p-values. (C) Diseases and Bio Functions Analysis of CVD Incidence Proteins. Biological functions that are significantly enriched (i.e., statistically relative high number of proteins associated with CVD by the 36-input protein list. The x-axis indicates the -log p-values. (D) Upstream Regulator Analysis of CVD Incidence Proteins. Downstream targets of upstream regulators (i.e., proteins whose expression is affected by TGFB1, IL4, VEGFA, IFNG, IL1) of the 36 CVD-associated proteins. Red indicates up-regulation and green denotes down-regulation in individuals with a CVD event. Proteins are coded by shape. Square: cytokine; vertical rhombus: enzyme; horizontal rhombus: peptidase; trapezoid: transporter; ellipse: transmembrane receptor; circle: other. Links are color-coded. Red: leads to activation; blue: leads to inhibition; yellow: findings inconsistent with state of downstream protein; black: effect not predicted. The red arrows indicate the 3 proteins significant in final multivariate CVD-protein signature models. (E) Diseases and Bio Functions Analysis of CVD Proteins. Proteins among the input list that are linked to immune functions (Left) and vascular functions (Right). The color, shape, and link coding are the same as part (D).

Figure 5

Systems Biology Analysis of the 36 CVD Incidence Proteins. (A) Interactive network analysis. Ingenuity Pathways Analysis was applied to generate the interactive networks from the 36 proteins associated with CVD events. The interactive network with the highest statistical significance is shown here. Red indicates protein up-regulation and green denotes protein down-regulation in individuals with CVD event. The intensity of the node color indicates the degree of up-regulation (red) and down-regulation (green) in individuals with a CVD event as compared with the matched controls. Empty shapes reflect proteins/genes not differentially expressed or absent from the SOMAscan platform that were brought in as interactors. Proteins are coded by shape. Square: cytokine; vertical rhombus: enzyme; horizontal rhombus: peptidase; trapezoid: transporter; ellipse: transmembrane receptor; circle: other. Links reflect various potential interactions such as protein expression regulation, protein activity, or modification of the other protein–protein interactions. Red arrows indicate the 3 proteins significant in final multivariate CVD-protein signature models. (B) Upstream Regulator Analysis of CVD Incidence Proteins. Upstream regulators (i.e., a protein/gene that can affect the expression of another protein/gene) with highest statistical significance that best explain the observed expression changes in the input 36 protein list as their targets. The x-axis indicates the -log p-values. (C) Diseases and Bio Functions Analysis of CVD Incidence Proteins. Biological functions that are significantly enriched (i.e., statistically relative high number of proteins associated with CVD by the 36-input protein list. The x-axis indicates the -log p-values. (D) Upstream Regulator Analysis of CVD Incidence Proteins. Downstream targets of upstream regulators (i.e., proteins whose expression is affected by TGFB1, IL4, VEGFA, IFNG, IL1) of the 36 CVD-associated proteins. Red indicates up-regulation and green denotes down-regulation in individuals with a CVD event. Proteins are coded by shape. Square: cytokine; vertical rhombus: enzyme; horizontal rhombus: peptidase; trapezoid: transporter; ellipse: transmembrane receptor; circle: other. Links are color-coded. Red: leads to activation; blue: leads to inhibition; yellow: findings inconsistent with state of downstream protein; black: effect not predicted. The red arrows indicate the 3 proteins significant in final multivariate CVD-protein signature models. (E) Diseases and Bio Functions Analysis of CVD Proteins. Proteins among the input list that are linked to immune functions (Left) and vascular functions (Right). The color, shape, and link coding are the same as part (D).