Table 1. Characteristics of the study cohort by sex and ethnicity.
| Variable | All (N=552) |
Male (N=282) |
Female (N=270) |
P | Chinese (N=305) |
Malay (N=148) |
Indian (N=99) | P |
|---|---|---|---|---|---|---|---|---|
| Metabolic risk factors | ||||||||
| BMI (kg/m2) | 16.5 (3.1) | 16.7 (3.1) | 16.4 (3.1) | 0.209 | 16.3 (2.7) | 16.8 (3.5) | 17.0 (3.5) | 0.056 |
| Abdominal circumference (cm) | 58.6 (8.8) | 59.1 (8.9) | 58.1 (8.6) | 0.216 | 57.8 (7.9) | 58.4 (9.4) | 61.5 (10.0) | 0.002 |
| Body fat percentage (%) | 21.4 (8.1) | 19.4 (76) | 23.5 (8.1) | <0.001 | 20.8 (7.3) | 20.5 (8.4) | 24.8 (8.9) | 0.001 |
| Systolic blood pressure (mmHg) | 102.5 (8.7) | 103.6 (9.1) | 101.3 (8.1) | 0.002 | 102.4 (8.9) | 102.5 (8.6) | 102.7 (8.3) | 0.942 |
| Diastolic blood pressure (mmHg) | 60.4 (6.6) | 61.0 (6.7) | 59.9 (6.3) | 0.054 | 60.5 (6.8) | 60.1 (6.2) | 60.8 (6.4) | 0.596 |
| Fasting plasma glucose (mmol/L) | 4.6 (0.4) | 4.7 (0.4) | 4.6 (0.4) | <0.001 | 4.7 (0.4) | 4.5 (0.3) | 4.6 (0.3) | <0.001 |
| Fasting plasma insulin (mIU/L) | 5.3 (4.3) | 5.2 (4.2) | 5.5 (5.2) | 0.088 | 5.1 (3.6) | 5.1 (4.7) | 6.4 (5.8) | <0.001 |
| Homeostasis model assessment for insulin resistance (HOMA-IR) | 1.4 (1.6) | 1.3 (1.2) | 1.5 (1.9) | 0.299 | 1.4 (2.0) | 1.3 (0.9) | 1.7 (1.1) | 0.005 |
| High sensitivity C-reactive protein (hsCRP) (mg/L) | 0.4 (0.7) | 0.3 (0.7) | 0.4 (0.8) | 0.058 | 0.3 (0.5) | 0.5 (0.9) | 0.5 (1.0) | 0.004 |
| Triglyceride (mmol/L) | 0.8 (0.4) | 0.8 (0.4) | 0.9 (0.4) | 0.035 | 0.8 (0.4) | 0.8 (0.5) | 0.8 (0.3) | 0.591 |
| Total cholesterol (mmol/L) | 4.6 (0.8) | 4.5 (0.8) | 4.7 (0.8) | 0.004 | 4.7 (0.9) | 4.6 (0.7) | 4.5 (0.8) | 0.073 |
| HDL-cholesterol (mmol/L) | 1.5 (0.3) | 1.5 (0.3) | 1.5 (0.3) | 0.132 | 1.5 (0.3) | 1.5 (0.3) | 1.4 (0.3) | <0.001 |
| LDL-cholesterol (mmol/L) | 2.8 (0.7) | 2.7 (0.7) | 2.9 (0.7) | 0.001 | 2.8 (0.8 | 2.7 (0.6) | 2.7 (0.7) | 0.679 |
| Metabolic risk scores | ||||||||
| Metabolic syndrome score (MetS) | -0.3 (2.5) | -0.3 (2.7) | -0.2 (2.3) | 0.741 | -0.3 (2.5) | -0.6 (2.3) | 0.1 (2.5) | 0.08 |
| Fatty liver index (FLI) | 0.9 (1.6) | 0.9 (1.7) | 0.9 (1.6) | 0.728 | 0.8 (1.2) | 0.9 (1.6) | 1.3 (2.2) | 0.003 |
| Tryptophan-kynurenine pathway metabolite concentrations and ratios | ||||||||
| Tryptophan (TRP) (μmol/L) | 59.4 (9.9) | 59.2 (10.3) | 59.6 (9.5) | 0.576 | 60.7 (10.1) | 55.9 (8.5) | 60.7 (10.2) | <0.001 |
| Kynurenine (KYN) (μmol/L) | 1.5 (0.3) | 1.5 (0.3) | 1.5 (0.3) | 0.394 | 1.5 (0.3) | 1.5 (0.3) | 1.6 (0.3) | 0.017 |
| Kynurenic acid (KA) (nmol/L) | 47.6 (15.6) | 47.9 (16.9) | 47.3 (14.1) | 0.657 | 48.2 (16.2) | 46.1 (14.0) | 48.3 (15.9) | 0.381 |
| 3-hydroxykynurenine (HK) (nmol/L) | 50.0 (15.9) | 50.5 (14.4) | 49.5 (17.3) | 0.474 | 48.6 (14.3) | 51.1 (17.8) | 52.9 (17.2) | 0.042 |
| Xanthurenic acid (XA) (nmol/L) | 11.6 (5.7) | 11.8 (6.0) | 11.3 (5.3) | 0.251 | 12.5 (5.5) | 9.9 (5.8) | 11.0 (5.6) | <0.001 |
| Hydroxyanthranilic acid (HAA) (nmol/L) | 40.1 (12.2) | 41.4 (12.1) | 38.8 (12.2) | 0.011 | 42.2 (12.7) | 38.0 (10.1) | 36.9 (12.7) | <0.001 |
| Quinolinic acid (QA) (nmol/L) | 451.7 (111.2) | 461.8 (116.9) | 441.1 (104.1) | 0.028 | 452.0 (114.5) | 458.6 (102.0) | 440.6 (114.5) | 0.458 |
| KYN/TRP ratio *100 (indoleamine-2,3-dioxygenase-1 (IDO1) activity) | 2.6 (0.5) | 2.7 (0.6) | 2.6 (5.3) | 0.194 | 2.5 (0.5) | 2.8 (0.5) | 2.7 (0.6) | <0.001 |
| HK/KYN ratio (kynurenine monooxygenase (KMO) activity) | 32.8 (8.8) | 33.0 (8.1) | 32.7 (9.6) | 0.737 | 32.6 (8.5) | 33.0 (9.5) | 33.3 (8.9) | 0.763 |
| XA/HK ratio *100 (kynurenine aminotransferase (KAT) activity) | 24.0 (10.5) | 24.2 (10.7) | 23.8 (10.3) | 0.638 | 26.7 (10.5) | 19.7 (8.5) | 22.1 (11.1) | <0.001 |
| HAA/HK ratio *100 (kynureninase (KYNU) activity) | 84.9 (28.7) | 86.1 (28.0) | 83.6 (29.5) | 0.310 | 91.4 (30.0) | 78.9 (24.4) | 73.8 (25.6) | <0.001 |
Abbreviations: N: number of participants· Data shown are N (%) for categorical variables and mean (SD) for continuous variables except for insulin, homeostasis model assessment for insulin resistance (HOMA-IR), high sensitivity C-reactive protein (hsCRP), metabolic risk score (MRS) and fatty liver index (FLI) which are represented as median (interquartile range) as they are not normally distributed. Two sided P-values less than 0.05 considered significant·