Inflammatory markers, the tryptophan-kynurenine pathway, and vitamin B status after bariatric surgery

• Published in: PloS one Vol. 13; no. 2; p. e0192169
• Main Authors: Christensen, Monika H E, Fadnes, Dag J, Røst, Therese H, Pedersen, Eva R, Andersen, John R, Våge, Villy, Ulvik, Arve, Midttun, Øivind, Ueland, Per M, Nygård, Ottar K, Mellgren, Gunnar
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 05-02-2018; Public Library of Science (PLoS)
• Subjects: Acids; Angina pectoris; Anthranilic acid; Bariatric surgery; Biochemistry; Biology and Life Sciences; Biomarkers; Body weight loss; Cardiovascular disease; Cholesterol; Complications and side effects; Correlation analysis; Cytokines; Development and progression; Diabetes; Diabetic retinopathy; Enzymes; Gastrointestinal surgery; Glucose; Glucose tolerance; Hemoglobin; High density lipoprotein; Homeostasis; Hospitals; Hypertension; Immune response; Immunological tolerance; Inflammation; Insulin; Laboratories; Longitudinal studies; Medical research; Medicine and Health Sciences; Metabolic disorders; Metabolites; Metabolomics; Neopterin; Nutrition; Obesity; Patient outcomes; Patients; Physical Sciences; Physiological aspects; Plasma levels; Pyridoxine; Surgery; Triglycerides; Tryptophan; Vitamin B; Vitamin B6; Vitamins; Weight control; Norway
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0192169

Obesity is associated with increased inflammation and insulin resistance. In conditions with chronic immune activation, low plasma vitamin B6-levels are described, as well as an increased kynurenine:tryptophan-ratio (KTR). We investigated circulating tryptophan, kynurenine and its metabolites, neopterin, B-vitamins, CRP, and HbA1c in individuals with obesity before and after bariatric surgery.
This longitudinal study included 37 patients with severe obesity, scheduled for bariatric surgery. Blood samples were taken at inclusion and at three months and one year postoperatively.
We observed significant positive correlations between HbA1c and both 3-hydroxy-kynurenine and 3-hydroxyanthranilic acid at inclusion. After surgery, fasting glucose, HbA1C and triglycerides decreased, whereas HDL-cholesterol increased. Tryptophan, kynurenine and its metabolites, except for anthranilic acid, decreased during weight loss. The KTR and CRP decreased while vitamin B6 increased during the year following operation, indicating reduced inflammation (all p<0.05).
In patients with obesity subjected to bariatric surgery, levels of 3-hydroxykynurenine and 3-hydroxyanthranilic acid seemed to be positively correlated to impaired glucose tolerance. One year following surgery, plasma levels of the kynurenine metabolites were substantially decreased, along with a metabolic improvement. The relation of circulating kynurenine pathway metabolites with biomarkers of metabolic impairment in patients with obesity needs further evaluation.