Characteristics of the study population
Among the DMR participants, a total of 718 participants with T2DM were enrolled, including 74 (10.31%) with CVDs and 644 (89.69%) without CVDs. The mean age of participants in DMR was 59.83±13.07 years, and 48.33% were female. Compared to participants without CVDs, those with CVDs were likely to be older. In addition, the differences in other characteristics were not statistically significant among those with or without CVDs (Table 1).
In the UKB, a total of 11002 participants with T2DM were enrolled, including 1607 (14.61%) with CVDs and 9395 (85.39%) without CVDs. The mean age of participants in UKB was 59.33±7.33 years, and 40.07% were female. Compared to participants without CVDs, those with CVDs were more likely to be old, male, current smoker, consume alcohol, have dyslipidemia, and were less likely to use insulin (Table 1).
Correlation between amino acid metabolisms
In both DMR and UKB, there was a significant correlation between any two amino acid metabolites. However, Gly was found not significantly correlated with His and Leu. In UKB, there is a negative correlation observed between Gly and Leu, Tyr, and Val, whereas in the DMR, Gly is positively correlated with Phe, Tyr, and Val (Table 2).
Associations between amino acids and CVDs in two studies
In DMR population, Ala and Tyr were retained in the stepwise multivariate linear regression model, with the β (95% confidence interval, CI) was 0.048 (0.022, 0.074) for Ala and -0.035 (-0.061, -0.008) for tyrosine. In the UKB, Ala (β=0.009, 95% CI: 0.000–0.018), Gln (β=0.010, 95% CI: 0.002–0.018), Gly (β=0.017, 95% CI: -0.026– -0.07), Leu (β=0.024, 95% CI: 0.007–0.041), and Val (β=0.031, 95% CI: -0.048– -0.013) were retained in the stepwise multivariate linear regression model (Table 3).
The association between amino acids and CVDs in the pooled population
The correlation between the eight amino acids in the two populations is shown in the supplementary material. Higher level of Ala (β=0.013, 95% CI: 0.005– 0.022), Gln (β=0.009, 95% CI: 0.001– 0.016), and Leu (β=0.018, 95% CI: 0.003– 0.033) were associated with increased risk of CVDs in the pooled population, while higher level of Gly (β=-0.017, 95% CI: -0.026– -0.008) and Val (β=-0.023, 95% CI: -0.038– -0.007) were associated with decreased risk of CVDs in the pooled population (Table S1).
After stratified by lifestyle, Ala (β=0.015, 95% CI: 0.001– 0.029), Gln (β=0.018, 95% CI:0.004– 0.032), and Gly (β=-0.029, 95% CI: -0.045– -0.013) were independently associated with CVDs among those with unfavorable lifestyle. Ala (β=0.016, 95% CI: 0.006– 0.026), Gly (β=-0.011, 95% CI: -0.021– -0.001), Leu (β=0.027, 95% CI: 0.010– 0.044), and Val (β=-0.033, 95% CI: -0.051– -0.015) were independently associated with CVDs among those with favorable lifestyle (Table 4).
After stratified by dyslipidemia, Ala (β=0.009, 95% CI: -0.000– 0.019), Gln (β=0.011, 95% CI:0.002– 0.021), and Gly (β=-0.020, 95% CI: -0.031– -0.009) were independently associated with CVDs in the non-dyslipidemia group. Ala (β=0.016, 95% CI: 0.003– 0.029), Leu (β=0.020, 95% CI: -0.003– 0.043), Phe (β=0.013, 95% CI: -0.002– 0.027), and Val (β=-0.034, 95% CI: -0.057– -0.010) were independently associated with CVDs in the dyslipidemia group (Table 4).
After stratified by Hb1ac, Ala (β=0.014, 95% CI:0.004– 0.024), Gln (β=0.015, 95% CI: 0.006– 0.024), Gly (β=-0.014, 95% CI: -0.025– -0.003), Leu (β=0.017, 95% CI: -0.002– 0.035), and Val (β=-0.025, 95% CI: -0.044– -0.006) were independently associated with CVDs among individuals with Hb1AC <7%. Gly (β=-0.020, 95% CI: -0.034– -0.005) was independently associated with CVDs among individuals with Hb1AC ≥7% (Table 4).