Abstract
Background: The Kynurenine pathway (KP) is involved in various disorders, but little is known about the KP and psychosomatic complaints. The aim was to study the peripheral KP and psychosomatic comorbidity in subjects with morbid obesity. Methods: Psychosomatic comorbidity (perceived general health, muscle-skeletal pain, well-being, mood disorders, fatigue, self-esteem, sleepiness, and sense of humour) was registered, and serum samples were collected six months before and after bariatric surgery. Results: A total of 141 subjects (men/women, 116/25) with a mean age of 43.0 (SD 8.7) years and BMI of 42.1 (SD 3.8) kg/m2 were included. No significant associations were seen between the psychosomatic disorders and the KP. There was a significant downregulation of all KP metabolites after surgery, a reduction in CRP, and strong associations between CRP and the KP, particularly with the ratios of Kynurenine/Tryptophan and Quinolinic acid (QA)/Xanthurenic acid (XA). The QA/XA ratio was negatively associated with diabetes. Conclusions: The peripheral KP seemed to be of minor importance for the psychosomatic comorbidity in subjects with morbid obesity. The downregulation of all KP metabolites after bariatric surgery indicated reduced inflammation. The QA/XA ratio seemed to be a marker of insulin sensitivity and favourable glucose control.
Highlights
Accepted: 2 March 2022The metabolism of Tryptophan (Trypt) through the Kynurenine pathway (KP) is complex and is involved in immunological and inflammatory disorders, psychiatric illness, cognition, pain, metabolic and endocrine diseases, exercise, and others [1–4]
Out of 159 subjects included in the study, 7 were excluded because of comorbidity not related to obesity, 8 for missing or inadequately filled-in questionnaires, and 3 for lack of serum for the KP analyses
The results reveal the uncertain relations between clinical disorders and the KP metabolites
Summary
The metabolism of Tryptophan (Trypt) through the Kynurenine pathway (KP) is complex and is involved in immunological and inflammatory disorders, psychiatric illness, cognition, pain, metabolic and endocrine diseases, exercise, and others [1–4]. These disorders often occur together and have shared biological characteristics, such as low-grade chronic inflammation and dysregulation of the KP [4–11]. Monitoring the KP has not been standardised Both concentrations of the metabolites and ratios between the concentrations have been reported [12]. There was a significant downregulation of all KP metabolites after surgery, a reduction in CRP, and strong associations between CRP and the KP, with the ratios of Kynurenine/Tryptophan and Quinolinic acid (QA)/Xanthurenic acid (XA). Conclusions: The peripheral KP seemed to be of minor importance for the psychosomatic comorbidity in subjects with morbid obesity
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