K K-CEHC (2,5,7,8-tetramethyl-2(2P-carboxyethyl)-6-hydroxychroman) is a urinary vitamin E metabolite with a truncated phytyl tail.

The maximum dietary protein intake that does not cause adverse effects in a healthy population is uncertain. We tested whether a high protein intake enhances oxidative stress. Adult rats were adapted to different casein-based diets containing either an adequate (13.8%; AP), medium (25.7%; MP), or high (51.3%; HP) level of crude protein; a fourth group received a HP diet but no RRR-alpha-tocopherol acetate (HP-toc). After 15 wk of feeding, plasma protein carbonyl concentration, liver lipid peroxide levels [thiobarbituric acid-reacting substances (TBARS)], reduced glutathione (GSH) status and leucine kinetics ([1-(13)C]leucine) were measured. Higher concentrations of protein carbonyls and TBARS were found in rats fed the AP and the HP-toc diets compared with those fed the MP and HP diets (P: < 0.05). GSH concentrations in plasma did not differ but total blood GSH concentrations were significantly (P: < 0.05) lower in rats fed the HP-toc diet compared with those fed the AP, MP and HP diets. Liver GSH concentrations were significantly (P: < 0.01) lower in rats fed the AP diet compared with the other groups. Rates of postabsorptive leucine oxidation (LeuOX) and flux (Q(Leu)) were positively correlated with the dietary protein level (for AP, MP, and HP, respectively: LeuOX, 74.9 +/- 28.5, 109 +/- 35.2, 142.3 +/- 38.4 micromol/(kg. h); Q(Leu), 425 +/- 102, 483 +/- 82, 505 +/- 80 micromol/(kg. h). Only HP-toc resulted in a significantly greater protein breakdown (PB(Leu)) and Q(Leu). No difference was seen in nonoxidative leucine disposal. Long-term intake of high protein diets did not increase variables of oxidative stress, in contrast to our initial hypothesis. An unexpected finding was that adequate protein feeding (AP) may in fact induce oxidative stress.

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A method for the direct extraction and routine analysis of the vitamin E metabolites ␥ -and ␣ -carboxyethyl hydroxychroman ( ␥ -and ␣ -CEHC) from human urine has been developed. A relatively small sample volume (5 ml) can be used and, after enzymatic hydrolysis of the conjugated forms and acidification, the metabolites are extracted with diethyl ether. Recovery of ␣ -and ␥ -CEHC was compared to that of trolox, used as an internal standard, added to 24-h urine collections from vitamin E-unsupplemented volunteers. Various solvent conditions were initially tested; acidification and ether extraction gave the highest recovery. It was found that after addition and extraction from urine, trolox, ␣ -and ␥ -CEHC are recovered to a similar extent, hence trolox is viable as an internal standard. The samples were analyzed by both GC and HPLC with electrochemical detection (ECD). HPLC-ECD was found to give higher selectivity and higher sensitivity compared to GC or HPLC with UV detection at 290 nm. The HPLC-ECD detection limit was 10 fmol, linearity (r 2 Ͼ 0.98) was achieved in the range of 40 to 200 fmol, which was found to be optimal for 24-h urines from unsupplemented subjects. Inter-sample variability was typically 2-5%. This greater sensitivity and selectivity means that vitamin E metabolites can be analyzed even in unsupplemented subjects. It is also possible to measure unconjugated forms of the metabolites. Typically these were found to represent ϳ 10% of the total ␣ -and ␥ -CEHC. This method can be used routinely for the determination of vitamin E metabolites in urine. The new extraction and detection methods described are relatively quick, less laborious, and more cost-effective than previously available methods. -Lodge, J. K., M. G. Traber, A. Elsner, and R. Brigelius-Flohé. A rapid method for the extraction and determination of vitamin E metabolites in human urine. J.

Patients with ␣ -tocopherol transfer protein ( ␣ -TTP) defects experience neurological symptoms characteristic of vitamin E deficiency and depend on continuous high ␣ -tocopherol supplements. We investigated the excretion of 2,5,7,8-tetramethyl-2(2 -carboxyethyl)-6-hydroxychroman ( ␣ -CEHC), a urinary metabolite of ␣ -tocopherol, as a putative marker for the ␣ -tocopherol status of ␣ -TTP-deficient patients and control subjects. In three patients vitamin E supplementation was stopped for short periods of time, during which plasma ␣ -tocopherol concentrations and urinary ␣ -CEHC excretion were measured. In the patients, plasma ␣ -tocopherol decreased below normal ( Ͻ 5 mol/l) but ␣ -CEHC excretion remained above the range of unsupplemented control subjects (0.118-0.306 mg/day, n ‫؍‬ 6). In healthy subjects, however, ␣ -CEHC excretion was increased only after surpassing a plasma ␣ -tocopherol threshold of 30-40 mol/l. Such a threshold did not exist in patients. The general mechanism of ␣ -tocopherol degradation did not appear to differ between patients and control subjects.The presumed mechanism of -and subsequent ␤ -oxidation was supported by the detection of ␣ -CPHC, an ␣ -CEHC homolog with a side chain longer by 3 carbon atoms, both in supplemented patients and in control subjects. -Schuelke, M., A. Elsner, B. Finckh, A. Kohlschütter, C. Hübner, and R. Brigelius-Flohé. Urinary ␣ -tocopherol metabolites in ␣ -tocopherol transfer protein-deficient patients .