Neopterin was not associated

with smoking in the multivariate model (Table 4). This community-based study among 7052 individuals investigated potential determinants of plasma neopterin, KTR and a large panel of kynurenines. Higher concentrations of neopterin, KTR and most kynurenines were observed in elderly compared to middle-aged subjects, and concentrations of Trp and most kynurenines were higher in men than in women. Furthermore, renal function was associated inversely with plasma levels of neopterin, KTR and most kynurenines. Lastly, higher concentrations of KTR, Trp and most kynurenines were found in overweight/obese compared to normal-weight participants, whereas Trp and most kynurenines were lower in heavy than in never smokers. The higher plasma levels of neopterin and KTR observed in the older group are in agreement LY294002 with previous studies [9-12, 33]. In the present study, elevated KTR in the elderly was driven mainly by markedly increased Kyn concentrations, indicating a more pronounced IDO activation in this age group. Elevated neopterin and KTR indicate increased IFN-γ activity in the older group, accompanying age-related inflammation [1]. Older click here age was also associated with higher concentrations of all kynurenines, except XA. Others have reported no association of age with serum

Kyn [13] or KA [34]. This discrepancy may be explained by a smaller sample size (n < 50) in previous studies. We

observed lower neopterin in men than in women in the middle-aged group, but not in the elderly. This observation is in accordance with published results [12]. There was no difference in KTR between genders in the present study in subjects aged 45–72 years, which is in agreement with a previous study on subjects older than 50 years of age [15], but in contrast to an observation of higher KTR in men in a younger population (21–64 years) [14]. This indicates no differences in activities of IDO or TDO between genders among middle-aged and elderly people, but possibly in younger subjects, including premenopausal women. The higher concentrations of Trp very and most kynurenines in men may be related to higher protein intake and/or turnover; the latter may be explained by higher muscle mass in men. The downstream effects on most kynurenines may simply reflect that Trp availability increases the flux through the kynurenine pathway, as more than 90% of Trp is metabolized through this pathway [3]. The higher concentrations of neopterin, KTR and kynurenines in individuals with moderately reduced renal function – indicated by lower eGFR (eGFR < 98 ml/min/1·73 m2 in the middle-aged and eGFR < 78·7 ml/min/1·73 m2 in the elderly) – are in line with studies in patients with severe renal disease reporting increased plasma concentrations of neopterin [18], Kyn [16, 17] and KA [17].