Plasma concentration of tryptophan and pregnancy-induced hypertension

Abstract

Introduction. Pregnancy-induced hypertension (PIH) is one of the main clinical problems of unexplained etiopathogenesis. New factors involved in the pathogenesis of this disease are still being searched. The available literature lacks data regarding the differences in tryptophan concentrations in physiological and PIH-complicated pregnancy. Previous studies have shown that L-tryptophan treatment reduces blood pressure in hypertensive rats. The direct vascular effects of tryptophan have not been fully explored. In this study, the stimulating effect of tryptophan on the development of PIH was revealed. The aim of the present study was to assess the differences in plasma tryptophan concentrations in physiological pregnancies and pregnancies complicated with hypertension in the third trimester. Material and methods. The study was carried on 105 complicated by PIH and 105 pregnant women with blood pressure within normal limits between 25 and 41 weeks of gestation. Tryptophan concentration was determined by the automated ion-exchange chromatography using an Amino Acid Analyser (AAA 400) by Ingos, Czech Republic. Tryptophan concentration was expressed in μmol/cm 3 plasma. Results. The mean concentration of tryptophan in the third trimester of physiological pregnancy was found to be 0.035 ± 0.009 μmol/cm

Differential Distribution of Tryptophan-Metabolites in Fetal and Maternal Circulations During Normotensive and Preeclamptic Pregnancies

“…Though elevated Kyn, KA, and 5-HT as well as decreased MLT in PE-maternal serum have been reported [20,26,33,38], we do not detect significant differences in Kyn, KA, 5-HT, or MLT in either maternal or umbilical serum between NT and PE. However, we found that ILA was elevated in PEmaternal and umbilical vein sera.…”

“…Our observation that PE does not elevate Trp and Kyn in either maternal or fetal serum is consistent with the previous reports [25,33], in which PE did not change Trp and Kyn levels in maternal serum from the 2nd trimester of pregnancy [33], nor did PE alter Trp levels in umbilical serum from the 3rd trimester [25]. However, our observation contradicts the study by Grafka et al who demonstrated a 2.8-fold increase of Trp in PE-maternal serum from the 3rd trimester [20]. In addition, we do not find increases in KA and 5-HT, nor do we see a decrease in MLT in PE-maternal serum and increases in 5-HT and 5-HIAA in PE-umbilical vein serum [25].…”

“…The ratio of Kyn/Trp increases during pregnancy, suggesting enhanced Kyn metabolism [18]. A potential role of excess Trp and its metabolites in PE has been proposed, as placental [19] and maternal plasma Trp concentrations are elevated in PE [18,20]. These elevated Trp levels could be associated with decreases in expression of indoleamine 2,3-dioxygenase (IDO, a rate-limiting enzyme for the Kyn pathway) and Trp-metabolic activity in PE placentas [17,21,22].…”

The Role of the Kynurenine Pathway in the (Patho) physiology of Maternal Pregnancy and Fetal Outcomes: A Systematic Review

“…Given the lower kynurenine concentration in women with PIH versus PE as identified through metabolomics, 48 and the similar concentration of kynurenine in PE and healthy women, it seems that women with PIH have both an increased tryptophan and a decreased kynurenine concentration. 49,50 These data thus suggest a decreased flux of tryptophan through the KP in maternal blood in PIH which differs from PE, and potentially represents an altered activity of other KP degrading enzymes, such as hepatic TDO2.…”

“…Abbreviations: GC, gas chromatography; HPLC, high-performance liquid chromatography; IEx, Ion-exchange chromatography; KP, kynurenine pathway; LC, liquid chromatography; MS, mass spectrometry; MS/MS, tandem mass spectrometry; NM, not mentioned; UHPLC, ultra-high-performance liquid chromatography; UV, ultraviolet.van Zundert et al 11 studies, tryptophan was significantly higher in women with PIH compared to controls (QS = 5, mean (SD): 99 (7) vs 35 (9) µmol/L, N = 210, P < .00005) 49. However, in a smaller cohort study, this difference was not observed (QS = 4, mean (SD): 38.1 (10.3) vs 35.6 (9.5) µmol/L, N = 22).…”