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Clinical‐scale investigation of stable isotopes in human blood: δ 13 C and δ 15 N from 406 patients at the Johns Hopkins Medical Institutions
Author(s) -
Kraft Rebecca A.,
Jahren A. Hope,
Saudek Christopher D.
Publication year - 2008
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.3780
Subject(s) - chemistry , human blood , whole blood , venous blood , medicine , zoology , physiology , biology
Objective chemical biomarkers are needed in clinical studies of diet‐related diseases to supplement subjective self‐reporting methods. We report on several critical experiments for the development of clinically legitimate dietary stable isotope biomarkers within human blood. Our examination of human blood revealed the following: (1) Within blood clot and serum from anonymous individuals (201 males, 205 females) we observed: mean serum δ 13 C = −19.1 ± 0.8‰ (standard deviation, SD); clot, −19.3 ± 0.8‰ (SD); range = −15.8‰ to −23.4‰. Highly statistically significant differences are observed between clot and serum, males and females for both clot and serum. For 15 N (n = 206), mean serum = +8.8 ± 0.5‰ (SD); clot +7.4 ± 0.4‰ (SD); range = +6.3‰ to +10.5‰. Blood serum is enriched in 15 N relative to blood clot by +1.4‰ on average, which may reflect differing protein amino acid content. Serum nitrogen is statistically significantly different for males and females, however, clot shows no statistical difference. (2) Relative to clot, capillary blood is marginally different for 13 C, but not 15 N. Clot 13 C is not significantly different from serum; however, it is depleted in 15 N by 1.5‰ relative to serum. (3) We assessed the effect of blood additives (sodium fluoride and polymerized acrylamide resin) and laboratory process (autoclaving, freeze drying) commonly used to preserve or prepare venous blood. On average, no alteration in δ 13 C or δ 15 N is detected compared with unadulterated blood from the same individual. (4) Storage of blood with and without the additives described above for a period of up to 115 days exhibits statistically significant differences for 13 C and 15 N for sodium fluoride. However, storage for unadulterated blood and blood preserved with polymerized acrylamide resin does not change the δ 13 C or δ 15 N isotopic composition of the blood in a significant way. With these experiments, we gain a clinical context for future development of a stable isotope based dietary biomarker. Copyright © 2008 John Wiley & Sons, Ltd.