Biomedical subjects

Johannes M Roob

Publications and source records attributed to Johannes M Roob.

7 recordsLinked to original sources

PubMed2005

[Comparison of clinical outcomes in peritoneal dialysis and hemodialysis].

In addition to kidney transplantation, peritoneal dialysis (PD) and hemodialysis represent two options for renal replacement therapy in patients with end-stage renal disease (ESRD). Given that most patients are suitable for both types of dialysis and that many of them require lifelong therapy, differences in clinical outcome between these treatments are of major interest. Differences between the two dialysis treatments have been described in single clinical aspects (e.g., hyperkalemia, volume status, blood pressure control, cardiac complications), the relevance of which are reflected by mortality rates. Data available so far indicate that overall outcome of patients with ESRD is comparable in the two types of dialysis. However, there are significant differences in subgroups of patients, such as those with diabetes or coronary heart disease. In order to achieve the best possible survival and quality of life in ESRD, the optimal sequence of dialysis treatments during the course of renal replacement therapy, rather than a single type of treatment, has to be considered. The "integrated care concept" takes into account this sequence of dialysis treatments, suggesting that patients should start on PD but be transferred to hemodialysis as soon as PD is no longer adequate. This concept allows longer preservation of residual renal function, better early survival on dialysis and better short-term results of graft survival after kidney transplantation. Thus, if medically suitable, PD should be the first treatment option in patients with ESRD who need renal replacement therapy.

Austria↗

PubMed2004

The effect of age on vitamin E status, metabolism, and function: metabolism as assessed by labeled tocopherols.

The effects of age on vitamin E metabolism were studied in 97 healthy 20-75-year-old male nonsmoking Austrian volunteers of the VITAGE project. After a single oral intake of 30 mg d(6)-RRR-alpha- and d(2)-RRR-gamma-tocopheryl acetate, blood and 24-hour urine was collected. Deuterated tocopherols in plasma and deuterated urinary metabolites were analyzed by GC-MS. A first evaluation revealed a similar uptake of d(6)-alpha- and d(2)-gamma-tocopherol during the first 6 hours, and then d(2)-gamma-tocopherol started to decrease. Urinary d(2)-gamma- carboxyethyl hydroxychroman metabolites (CEHCs) exceeded those of d(6)-alpha-CEHCs by about 10 times. There was no effect of age. Thus, there might be no need for a higher vitamin E intake for healthy elderly nonsmoking men.

Absorption↗

PubMed2004

Effects of vitamin E depletion/repletion on biomarkers of oxidative stress in healthy aging.

The effects on ex vivo LDL resistance to oxidation and biomarkers of in vivo oxidative stress in response to 3-month dietary vitamin E restriction to 25% of recommended intake and 2-month unrestricted dietary intake and supplementation with 800 IU/d were studied in 100 healthy, nonsmoking 20-75-year-old volunteers. Significant changes in vitamin E status were associated with decreases and increases, respectively, in LDL resistance to oxidation in the depletion and supplementation period and with decreases in lipid peroxidation and oxidative DNA modification in the supplementation period. Healthy aging was not associated with enhanced susceptibility to oxidation in the depletion period.

Adult↗

PubMed2004

The decrease in gamma-tocopherol in plasma and lipoprotein fractions levels off within two days of vitamin E supplementation.

The effects of vitamin E supplementation on alpha- and gamma-tocopherol concentrations were studied in plasma and lipoprotein fractions of five healthy volunteers taking 1000 IU/day of RRR alpha-tocopherol for 4 days. Although plasma alpha-tocopherol increased, gamma-tocopherol decreased. Compared with baseline, gamma-/alpha-tocopherol ratios decreased from 48 h onward (P < 0.001). They all leveled off within 48 h. From 12 h onward, gamma-/alpha-tocopherol ratios were higher in VLDL and IDL than in LDL and HDL, indicating that gamma-tocopherol is better maintained in triglyceride-rich lipoprotein fractions. These data suggest that vitamin E supplementation exceeding 2 days does not further decrease gamma-tocopherol concentrations.

Adult↗

PubMed2004

Does aging affect the response of vitamin E status to vitamin E depletion and supplementation?

A vitamin E depletion/supplementation study was conducted in 100 healthy 20-75-year-old volunteers. The responses of vitamin E status to 3-week dietary vitamin E restriction to approximately 25% of recommended intake and 2-month unrestricted dietary intake plus 800 IU/d of RRR-alpha-tocopherol were studied as a function of age. Plasma alpha-tocopherol concentrations were closely related to cholesterol concentrations, which increased with age (P < 0.001). Upon dietary restriction, plasma alpha-tocopherol concentrations decreased significantly (P < 0.001) but independently of age. Plasma alpha-tocopherol responses to supplementation increased significantly with age, but this effect disappeared after standardization for cholesterol. gamma-Tocopherol concentrations decreased to less than 30% of baseline.

Adult↗

PubMed2003

Effects of vitamin E and carotenoid status on oxidative stress in health and disease. Evidence obtained from human intervention studies.

Vitamin E and carotenoids are known to act as antioxidants both in vitro and in vivo. In this review we present a series of studies in healthy subjects and in patients who exhibit either acute or chronic oxidative stress. In the EU-Commission funded VITAGE project we investigated the status and effects of vitamin E and carotenoids on oxidative stress in 300 healthy volunteers. Depletion studies limiting dietary vitamin E or carotenoid intake to approximately 25% of the dietary reference intakes and subsequent repletion by supplementation with either large doses of vitamin E or intermediate doses of carotenoids showed significant changes in ex vivo LDL oxidizability, total plasma peroxide concentrations and urinary 8-oxo-7,8-dihydro-2(')-deoxyguanosine excretion. Patients on chronic hemodialysis present with oxidative stress in the presence of normal vitamin E but impaired vitamin C status and, due to anemia, need to be treated with parenteral iron. We studied the effects of a single oral dose of vitamin E taken 6 h prior to intravenous infusion of 100 mg iron, which exceeded the iron-binding capacity of transferrin. Vitamin E significantly reduced and in combination with a single dose of vitamin C completely abrogated acute oxidative stress induced by the iron load. Patients with cystic fibrosis are exposed to chronic oxidative stress due to an overproduction of reactive oxygen species as a result of neutrophil-dominated lung inflammation and impaired antioxidant status. Biochemical vitamin E and carotenoid deficiencies could be fully corrected even in the presence of fat malabsorption using intermediate doses of either RRR alpha-tocopherol or all-rac alpha-tocopheryl acetate and water-miscible all-trans beta-carotene. Long-term supplementation reduced ex vivo LDL oxidizability, in vivo lipid peroxidation and lung inflammation.

Aging↗

PubMed2000

Vitamin E attenuates oxidative stress induced by intravenous iron in patients on hemodialysis.

Intravenous iron application to anemic patients on hemodialysis leads to an "oversaturation" of transferrin. As a result, non-transferrin-bound, redox-active iron might induce lipid peroxidation. To test the hypothesis that vitamin E attenuates lipid peroxidation in patients receiving 100 mg of iron(III) hydroxide sucrose complex intravenously during a hemodialysis session, 22 patients were investigated in a randomized cross-over design, either with or without a single oral dose of 1200 IU of all-rac-alpha-tocopheryl acetate taken 6 h before the hemodialysis session. Blood was drawn before and 30, 60, 90, 135, and 180 min after the start of the iron infusion, and areas under the curve (AUC0-180 min) of ratios of plasma malondialdehyde (MDA) to cholesterol and plasma total peroxides to cholesterol (two markers of lipid peroxidation) were determined as the outcome variables. At baseline of the session without vitamin E supplementation, plasma alpha-tocopherol concentrations (27.6 +/- 1.8 micromol/L) and ratios of alpha-tocopherol to cholesterol (5.88 +/- 1.09 mmol/mol) were normal, plasma MDA concentrations were above normal (1.20 +/- 0.28 micromol/ L), and bleomycin-detectable iron (BDI), indicating the presence of redox-active iron, was not detectable. Upon iron infusion, BDI and MDA concentrations increased significantly (P < 0.001). BDI concentrations explained the increase over baseline in MDA concentrations (MDA = 1.29 +/- 0.075 x BDI). Vitamin E supplementation, leading to a 68% increase in plasma alpha-tocopherol concentrations, significantly reduced the AUC0-180 min of MDA to cholesterol (P = 0.004) and peroxides to cholesterol (P = 0.002). These data demonstrate that a single oral dose of vitamin E attenuates lipid peroxidation in patients on hemodialysis receiving intravenous iron. Given that intravenous iron is applied repeatedly to patients on hemodialysis, this therapeutic approach may protect against oxidative stress-related degenerative disease in the long term.

Adult↗