A Genome-Wide Association Study Identifies Blood Disorder-Related Variants Influencing Hemoglobin A With Implications for Glycemic Status in U.S. Hispanics/Latinos.

OBJECTIVE: We aimed to identify hemoglobin A (HbA)-associated genetic variants and examine their implications for glycemic status evaluated by HbA in U.S. Hispanics/Latinos with diverse genetic ancestries.

RESEARCH DESIGN AND METHODS: We conducted a genome-wide association study (GWAS) of HbA in 9,636 U.S. Hispanics/Latinos without diabetes from the Hispanic Community Health Study/Study of Latinos, followed by a replication among 4,729 U.S. Hispanics/Latinos from three independent studies.

RESULTS: Our GWAS and replication analyses showed 10 previously known and novel loci associated with HbA at genome-wide significance levels ( < 5.0 × 10). In particular, two African ancestry-specific variants, rs334 and -rs1050828, which are causal mutations for sickle cell disease and deficiency, respectively, had ∼10 times larger effect sizes on HbA levels (β = -0.31% [-3.4 mmol/mol]) and -0.35% [-3.8 mmol/mol] per minor allele, respectively) compared with other HbA-associated variants (0.03-0.04% [0.3-0.4 mmol/mol] per allele). A novel Amerindian ancestry-specific variant, -rs145546625, was associated with HbA and hematologic traits but not with fasting glucose. The prevalence of hyperglycemia (prediabetes and diabetes) defined using fasting glucose or oral glucose tolerance test 2-h glucose was similar between carriers of rs334 or -rs1050828 HbA-lowering alleles and noncarriers, whereas the prevalence of hyperglycemia defined using HbA was significantly lower in carriers than in noncarriers (12.2% vs. 28.4%, < 0.001). After recalibration of the HbA level taking -rs334 and -rs1050828 into account, the prevalence of hyperglycemia in carriers was similar to noncarriers (31.3% vs. 28.4%, = 0.28).

CONCLUSIONS: This study in U.S. Hispanics/Latinos found several ancestry-specific alleles associated with HbA through erythrocyte-related rather than glycemic-related pathways. The potential influences of these nonglycemic-related variants need to be considered when the HbA test is performed.