A 90-day Feeding Toxicity Study of l-Serine in Male and Female Fischer 344 Rats

A subchronic feeding study of l-serine (l-Ser) was conducted with groups of 10 male and 10 female Fischer 344 rats fed a powder diet containing 0, 0.06, 0.5, 1.5 or 5.0% concentrations of l-Ser for 90 days. There were no toxicologically significant, treatment-related changes with regards to body weight, food intake, water intake or urinalysis data. In several of the hematology, serum biochemistry and organ weight parameters, significant changes were observed between some of the treated groups and the controls. All these changes, however, were subtle and lacked any corresponding pathological findings. In addition, the increased or decreased values remained within the range of the historical control values. In fact, histopathological assessment revealed only sporadic and/or spontaneous lesions. In conclusion, the no-observed-adverse-effect-level (NOAEL) for l-Ser was, therefore, determined to be at least a dietary dose of 5.0% (2765.0 mg/kg body weight/day for males and 2905.1 mg/kg body weight/day for females) under the present experimental conditions

Novel, Objective, Multivariate Biomarkers Composed of Plasma Amino Acid Profiles for the Diagnosis and Assessment of Inflammatory Bowel Disease

BACKGROUND: Inflammatory bowel disease (IBD) is a chronic intestinal disorder that is associated with a limited number of clinical biomarkers. In order to facilitate the diagnosis of IBD and assess its disease activity, we investigated the potential of novel multivariate indexes using statistical modeling of plasma amino acid concentrations (aminogram). METHODOLOGY AND PRINCIPAL FINDINGS: We measured fasting plasma aminograms in 387 IBD patients (Crohn's disease (CD), n = 165; ulcerative colitis (UC), n = 222) and 210 healthy controls. Based on Fisher linear classifiers, multivariate indexes were developed from the aminogram in discovery samples (CD, n = 102; UC, n = 102; age and sex-matched healthy controls, n = 102) and internally validated. The indexes were used to discriminate between CD or UC patients and healthy controls, as well as between patients with active disease and those in remission. We assessed index performances using the area under the curve of the receiver operating characteristic (ROC AUC). We observed significant alterations to the plasma aminogram, including histidine and tryptophan. The multivariate indexes established from plasma aminograms were able to distinguish CD or UC patients from healthy controls with ROC AUCs of 0.940 (95% confidence interval (CI): 0.898-0.983) and 0.894 (95%CI: 0.853-0.935), respectively in validation samples (CD, n = 63; UC, n = 120; healthy controls, n = 108). In addition, other indexes appeared to be a measure of disease activity. These indexes distinguished active CD or UC patients from each remission patients with ROC AUCs of 0.894 (95%CI: 0.853-0.935) and 0.849 (95%CI: 0.770-0.928), and correlated with clinical disease activity indexes for CD (r(s) = 0.592, 95%CI: 0.385-0.742, p<0.001) or UC (r(s) = 0.598, 95%CI: 0.452-0.713, p<0.001), respectively. CONCLUSIONS AND SIGNIFICANCE: In this study, we demonstrated that established multivariate indexes composed of plasma amino acid profiles can serve as novel, non-invasive, objective biomarkers for the diagnosis and monitoring of IBD, providing us with new insights into the pathophysiology of the disease

Plasma and tissue BCAA and BCKA concentrations in lean and obese Zucker rats.

<p>Concentrations of BCAAs (Leu, Val and Ile: A, C, E) and BCKAs (KIC, KIV, and KMV: B, D, F) are shown for plasma (A, B), gastrocnemius muscle (C, D) and liver (E,F). Bars are mean ± SE; *P<0.05, n = 9 and 8 determinations for lean and obese rats, respectively.</p

Branched chain keto acid dehydrogenase activity in lean and obese Zucker rats^*.

*<p>Data from cohort C. Enzyme activities were measured at 30°C. Values are means ± SEM; n = 10 rats per group. NS indicates not significant, P>0.05.</p>a<p>Muscle and adipose tissue BCKDC activities were measured using the ¹³C method <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059443#pone.0059443-Matsumoto1" target="_blank">[57]</a>, which does not use U indicating µmol of NADH formed. BCKDC total activities were unavailable for muscle; neither total nor actual BCKDC activities were available for adipose tissue. Unfortunately, activation of BCKDH using lambda phosphatase did not work in these experiments. Additionally, the adipose tissue values were very low and too close to the level of detection and contamination from room air and are not reported.</p

Schematic of whole-body BCAA metabolism.

<p>Ketoacids are formed by reversible transamination catalyzed by the mitochondrial or cytosolic isoforms of branched chain amino acid transaminase (<i>BCAT</i>). The action of the branched chain keto acid dehydrogenase complex (<i>BCKDC</i>) in the mitochondrial matrix leads to the evolution of CO₂ from the 1-carbon of the keto acids including KIC, which was ¹⁴C labeled and measured from the expired air in these studies. Subsequent intramitochondrial metabolism leads to the formation of various acyl-coenzyme A (R-CoA) esters that can reversibly form acylcarnitines (not displayed). Neither FAD and NAD Cofactors nor CO₂ and H₂O substrates are displayed. Bold font indicates metabolites or corresponding acylcarnitines that were detected and measured quantitatively in the 24 h urines (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059443#pone-0059443-t004" target="_blank">Table 4</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059443#pone-0059443-t005" target="_blank">5</a>). AA, amino acids.</p