Clonal Hematopoiesis, Inflammation, Hemostasis, and Cardiometabolic Biomarkers: The Reasons for Geographic and Racial Differences in Stroke Study

BACKGROUND: Clonal hematopoiesis (CH) is implicated in the pathogenesis of multiple age-associated disorders including malignancy, cardiovascular disease (CVD), chronic kidney disease, and mortality. Some of these adverse outcomes may be mediated by CH-driven inflammatory dysregulation, but the association of CH with biomarkers in other pathways related to these outcomes has not been studied. We studied the association between CH and biomarkers of inflammation, hemostasis and cardiometabolic risk in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study.

METHODS: REGARDS is a prospective study that enrolled 30,239 Black and White individuals ≥45 years across United States between 2003 and 2007, and collected extensive health data by telephone and in-person exams. Biomarkers listed in Table 2, and CH were measured in baseline blood samples in an age-, sex-, and race-stratified cohort random sample (CRS). We excluded participants with prior history of CVD. Sequencing was performed at >500x depth to identify somatic mutations in 24 of the most common CH genes, capturing >95% of CH observed in the general population. CH was categorized based on variant allele frequency (VAF) of the dominant mutation as 0%, >0-<2%, 2-10% and >10%. Linear regression was used to calculate the age-, sex-, and race-adjusted difference in mean biomarker level for those with versus those without CH.

RESULTS: The study included 781 participants (mean age at enrollment: 66 years [SD 12.1], 46% male, 50% Black individuals). The prevalence of CH at varying VAF was: VAF 0% - 43.3%; VAF >0 to <2% - 32.5%; 2 to 10% - 18.4%; >10% - 5.8%. Mutations were most prevalent in DNMT3A (60.3%), then TET2 (13.8%) and ASXL1 (10.1%). The mean age was higher in participants with CH (73 years, SD 10) than in those without CH (61 years, SD 11). Distributions of the most common CH mutations at VAF ≥2% by age, sex and race are shown in Table 1. Mutations in DNMT3A were overrepresented in Black participants and women, whereas mutations in TET2 and ASXL1 were more common in White participants.

Associations of CH with inflammation, hemostasis and cardiometabolic biomarkers were presented in Table 2. Mean Log IL-8 was 0.23 (95% CI 0.05-0.41) units higher in those with high VAF CH (>10%) versus those without CH, with no association among other inflammation biomarkers. Among hemostasis biomarkers, mean log D-dimer was 0.26 (95% CI 0.01-0.52) units higher in those with high VAF CH versus those without CH. There was a non-significant trend towards an association between CH and lower Factor VIII and higher fibrinogen (Table 2). Among cardiometabolic biomarkers, mean log Adiponectin was 0.32 (95% CI 0.04-0.61) units higher in those with high VAF CH versus no CH. We did not identify a statistically significant association between CH and other cardiometabolic markers.

CONCLUSIONS: CH is prevalent in the general population, especially at low VAF. In addition to inflammatory dysregulation, findings here suggest possible other pathways for deleterious effects of CH on health via hemostasis and cardiometabolic pathways. Since our study was cross-sectional, we could not ascertain if CH leads to abnormal biomarker levels or if pathways represented by the above biomarkers predispose to CH. Studying associations of CH with serial biomarkers in a larger population, by specific mutations, and by sex and race will provide mechanistic insights on CH associated adverse outcomes.