Table 2. Characteristics of the study cohort by BMI categories.
| All | Underweight | Normal weight | Overweight | Obese | P | |
|---|---|---|---|---|---|---|
| N (%) | 552 | 37 (6.7%) | 422 (76.4%) | 65 (11.8%) | 28 (5.1%) | |
| Sex | ||||||
| Male | 282 (51.1%) | 18 (7.0%) | 219 (77.6%) | 30 (10.6%) | 15 (5.3%) | reference |
| Female | 270 (48.9%) | 19 (4.7%) | 203 (75.2%) | 35 (13.0%) | 13 (4.8%) | 0.825 |
| Ethnicity | ||||||
| Chinese | 305 (55.3%) | 21 (6.9%) | 246 (80.7%) | 28 (9.2%) | 10 (3.3%) | reference |
| Malay | 148 (26.8%) | 6 (4.1%) | 112 (75.7%) | 18 (12.2%) | 12 (8.1%) | 0.01 |
| Indian | 99 (17.9%) | 10 (10.1%) | 64 (64.6%) | 19 (19.2%) | 6 (6.1%) | 0.075 |
| Metabolic risk factors | ||||||
| BMI (kg/m2) | 16.5 (3.1) | 12.7 (0.6) | 15.7 (1.5) | 20.7 (1.1) | 25.3 (2.6) | <0.001 |
| Abdominal circumference (cm) | 58.6 (8.8) | 49.3 (2.1) | 56.1 (5.0) | 70.8 (4.5) | 80.5 (7.5) | <0.001 |
| Body fat percentage (%) | 21.4 (8.1) | 12.9 (2.7) | 19.2 (5.6) | 32.4 (4.5) | 36.7 (5.8) | <0.001 |
| Systolic blood pressure (mmHg) | 102.5 (8.7) | 99.6 (9.0) | 101.4 (8.2) | 114.1 (7.6) | 102.5 (8.7) | <0.001 |
| Diastolic blood pressure (mmHg) | 60.4 (6.6) | 58.6 (6.0) | 60.3 (6.7) | 60.6 (5.9) | 63.6 (6.1) | 0.026 |
| Fasting plasma glucose (mmol/L) | 4.6 (0.4) | 4.5 (0.5) | 4.6 (0.4) | 4.7 (0.3) | 4.7 (0.4) | <0.001 |
| Fasting plasma nsulin (mIU/L) | 6.7 (6.6) | 4.2 (2.9) | 5.4 (2.8) | 10.9 (7.7) | 18.4 (19.2) | <0.001 |
| Homeostasis model assessment for insulin resistance (HOMA-IR) | 1.4 (1.6) | 0.9 (0.6) | 1.1 (0.6) | 2.3 (1.8) | 4.0 (5.0) | <0.001 |
| High sensitivity C-reactive protein (hsCRP) (mg/L) | 1.2 (2.5) | 0.6 (1.0) | 0.8 (2.2) | 2.2 (3.1) | 3.6 (3.3) | <0.001 |
| Triglyceride (mmol/L) | 0.8 (0.4) | 0.8 (0.3) | 0.8 (0.4) | 1.0 (0.4) | 1.2 (0.7) | <0.001 |
| Total cholesterol (mmol/L) | 4.6 (0.8) | 4.7 (0.9) | 4.6 (0.8) | 4.6 (0.7) | 4.6 (0.8) | 0.994 |
| HDL-cholesterol (mmol/L) | 1.5 (0.3) | 1.6 (0.3) | 1.5 (0.3) | 1.3 (0.2) | 1.2 (0.2) | <0.001 |
| LDL-cholesterol (mmol/L) | 2.8 (0.7) | 2.8 (0.8) | 2.7 (0.7) | 2.9 (0.7) | 2.9 (0.8) | 0.128 |
| Metabolic risk scores | ||||||
| Metabolic syndrome score (MetS) | 0.0 (2.3) | -1.7 (1.3) | -0.6 (1.5) | 2.2 (1.8) | 5.2 (3.9) | <0.001 |
| Fatty liver index (FLI) | 2.7 (6.7) | 0.4 (0.2) | 1.0 (0.8) | 5.5 (2.9) | 22.1 (19.5) | <0.001 |
| Tryptophan-kynurenine pathway metabolite concentrations and ratios | ||||||
| Tryptophan (TRP) (µmol/L) | 59.4 (9.9) | 57.1 (11.4) | 59.3 (7.2) | 59.7 (9.9) | 64.4 (9.6) | 0.006 |
| Kynurenine (KYN) (µmol/L) | 1.5 (0.3) | 1.4 (0.3) | 1.5 (0.3) | 1.6 (0.3) | 1.8 (0.3) | <0.001 |
| Kynurenic acid (KA) (nmol/L) | 47.6 (15.6) | 45.5 (12.6) | 46.3 (14.4) | 53.3 (22.5) | 56.3 (15.6) | <0.001 |
| 3-hydroxykynurenine (HK) (nmol/L) | 50.0 (15.9) | 48.0 (15.4) | 49.0 (14.3) | 52.1 (15.2) | 62.3 (28.2) | <0.001 |
| Xanthurenic acid (XA) (nmol/L) | 11.6 (5.7) | 11.5 (7.0) | 11.1 (5.2) | 12.7 (6.4) | 15.4 (7.0) | <0.001 |
| Hydroxyanthranilic acid (HAA) (nmol/L) | 40.1 (12.2) | 34.6 (10.7) | 38.9 (11.1) | 45.2 (13.8) | 53.8 (14.1) | <0.001 |
| Quinolinic acid (QA) (nmol/L) | 451.6 (111.3) | 412.6 (133.3) | 439.7 (101.5) | 498.8 (119.4) | 571.3 (100.2) | <0.001 |
| KYN/TRP ratio *100 (indoleamine-2,3-dioxygenase-1 (IDO1) activity) | 2.6 (0.5) | 2.5 (0.6) | 2.6 (0.5) | 2.8 (0.5) | 2.8 (0.4) | 0.006 |
| HK/KYN ratio (kynurenine monooxygenase (KMO) activity) | 32.8 (8.8) | 34.6 (11.6) | 32.6 (8.1) | 32.1 (7.4) | 35.6 (15.4) | 0.750 |
| XA/HK ratio *100 (kynurenine aminotransferase (KAT) activity) | 24.0 (10.5) | 25.9 (15.1) | 23.5 (9.8) | 25.2 (11.5) | 26.3 (11.2) | 0.372 |
| HAA/HK ratio *100 (kynureninase (KYNU) activity) | 84.9 (28.7) | 78.5 (32.3) | 83.7 (27.5) | 90.9 (28.8) | 97.3 (37.9) | 0.001 |
Abbreviations: N: number of participants· Data shown are N (%) for categorical variables and mean (SD) for continuous variables. Two sided P-values less than 0.05 considered significant·