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Table 2 Characteristics of four clusters generated by k-means clustering based on relative abundances of amino acids in sweat for both healthy and CFS participants

From: Sex differences in amino acids lost via sweating could lead to differential susceptibilities to disturbances in nitrogen balance and collagen turnover

  Cluster 1 (n = 7) Cluster 2 (n = 14) Cluster 3 (n = 23) Cluster 4 (n = 10) Cluster differences (p < 0.05)
Number      
 Females 2 3 12 0  
 Males 1 11 8 10  
 CF females 2 0 2 0  
 CF males 2 0 1 0  
Most abundant sweat amino acids expressed as percentage (%) of all amino acids
  Serine 23.5 Serine 29.1 Serine 24.5 Histidine 19.7  
  Glycine 14.1 Glycine 14.2 Glycine 17.4 Serine 13.8  
  Alanine 13.1 Alanine 9.7 Alanine 12.7 Ornithine 12.0  
  Aspartate 7.6 Histidine 7.1 Aspartate 6.1 Glycine 11.5  
  Total 58.3 Total 60.1 Total 60.7 Total 57.1  
BCAA in sweat, µmol/L, (SE)
 Leucine 489 (61) 122 (24) 227 (23) 341 (54) C1 > C2 = C3; C4 > C2
 Isoleucine 350 (37) 83 (18) 167 (17) 184 (34) C1 > C2 = C3; C1 > C4 = C3; C4 > C2
 Valine 690 (69) 173 (36) 348 (37) 274 (47) C1 > C3 > C2; C1 > C4 = C3; C4 = C2
 Total 1529 378 742 799 C1 > C2 = C3; C4 > C2
Essential amino acids (non-BCAA), µmol/L, (SE)
 Cystathionine 5.1 (1.2) 0 1.7 (0.8) 0 C1 = C3 > C2 = C4
 Cystine 6.7 (0.6) 0 2.4 (0.4) 0 C1 > C3 > C2 = C4
 Histidine 886 (88) 344 (74) 525 (60) 2024 (527) C4 > C1 = C2 = C3
 Lysine 404 (46) 112 (27) 183 (19) 877 (202) C4 > C1 = C2 = C3
 Methionine 45 (7) 2 (1) 19 (2) 1 (1) C1 > C3 > C2 = C4
 Phenylalanine 297 (35) 65 (13) 129 (13) 197 (32) C1 > C3 = C2; C4 > C2
 Threonine 263 (132) 369 (120) 443 (33) 139 (28) ns
 Tryptophan 128 (18) 20 (7) 70 (8) 137 (33) C1 > C2; C4 > C3 = C2
 Tyrosine 397 (50) 114 (36) 199 (18) 77 (38) C1 > C2 = C3 = C4
Non-essential amino acids, µmol/L, (SE)
 Alanine 2002 (203) 528 (152) 1208 (129) 724 (134) C1 > C2 = C4; C3 > C2
 Asparagine 357 (54) 53 (13) 163 (20) 66 (10) C1 > C3 > C2; C1 > C4
 Aspartic acid 1218 (236) 270 (55) 560 (66) 192 (38) C1 > C2 = C3 = C4
 Glutamic acid 537 (68) 250 (88) 384 (55) 222 932) ns
 Glutamine 78 (12) 83 (18) 106 (26) 73 (34) ns
 Glycine 2298 (469) 765 (226) 1616 (159) 999 (177) C1 > C2 = C4; C3 > C2
 Hydroxylysine 67 (8) 10 (8) 50 (7) 82 (28) C4 > C2
 Hydroxyproline 45 (4) 0 23 (3) 0 C1 > C3 > C2 = C4
 Ornithine 909 (202) 212 (56) 325 (38) 1255 (329) C4 > C2 = C3; C4 > C3
 Proline 375 (86) 119 (28) 242 (24) 89 (11) C1 > C2 = C4; C3 > C4
 Serine 3647 (442) 1700 (504) 2189 (185) 1219 (226) C1 > C2 = C4; C1 > C4
Total amino acids in sweat, µmol/L, (SE)
  15,573 (3235) 5414 (1434) 9188 (862) 9258 (1761) C1 > C2