MUDr. Dana Maňasková


Vyhledávání na medicinman.cz
 

Exkrece metabolitů vit. E a Reabsorbce

Eliminace celková

  • A kinetic study in 10 adult non-smokers (Bruno et al., 2005)
  • Consumed D3-RRR-alpha-tocopheryl acetate and D6-all-rac-alpha-tocopheryl acetate
  • One dose of 75 mg each, for six days
    • Tissue alpha-tocopherol efflux rate was 0.191 pools/day [2]

Denní exkrece močí a stolicí

  • 5.1 ± 0.9 mg alpha-tocopherol [2]
  • 4 mg
    • Including 0.8 mg/day of non-absorbed fraction (Novotny et al., 2012)[2]

Urinary alpha-CEHC excretion

  • 76 free-living healthy Japanese women (18–33 years) consuming their usual diet without dietary supplements (Imai et al., 2011)
    • Mean: 5.9 ± 1.6 mg/day intake
    • Alpha-CEHC excretion was measured in a single 24-hour urine sample collected on day 4
    • Intake of alpha-tocopherol was significantly related to urinary alpha-CEHC excretion [2]
  • Seven healthy men received a controlled diet providing 2.1 ± 1.9 mg/day of alpha-tocopherol
  • Then supplemented with 50 (week 2), 150 (week 3), 350 (week 4) and 800 (week 5) mg/day of RRR-alpha-tocopherol (Schultz et al., 1995)
    • Alpha-CEHC in 24-hour urine was not detectable in case of no supplementation or supplementation with 50 mg/day [2]
    • Increased with higher supplementation doses (150–800 mg/day) [2]
  • Urinary alpha-CEHC appeared in detectable concentrations above a plasma alpha-tocopherol concentration of 30–50 micromol/L
  • Healthy men and women (18–35 years, non-smokers and smokers)
    • Baseline alpha-tocopherol intake (food record) of 5.3–5.5 mg/day
      • Received D3-RRR-alpha-tocopheryl acetate and D6-all-rac-alpha-tocopheryl acetate
        • One dose of 75 mg each, for six days (Bruno et al., 2005) [2]
    • Alpha-CEHC concentrations in 24-hour urine were
      • Variable between subjects
      • Not different between groups before supplementation
      • Increased 4–5.5-fold after six days of supplementation
      • Then decreased to pre-study concentrations, or even below, after 17 days [2]
  • A study in 233 adults (median age ± SD: 33.3 ± 12.5 years) (Lebold et al., 2012)
    • Urinary excretion of alpha-tocopherol metabolites
      • Alpha-CEHC
      • Alpha-carboxymethylbutyl hydrochroman [2]
    • Plasma alpha-tocopherol concentrations nad 33 micromol/L
      • Significantly higher urinary alpha-CEHC concentration
      • Median alpha-tocopherol intake 17.8 mg/day
      • Median urinary alpha-CEHC concentration 4.1 micromol/g creatinine [2]
    • Plasma alpha-tocopherol concentrations pod 33 micromol/L
      • Median alpha-tocopherol intake 8.6 mg/day
    • Median urinary alpha-CEHC concentration 1.6 micromol/g creatinine [2]
    • Urinary alpha-CEHC excretion significantly correlated with
      • Significantly correlated with plasma alpha-tocopherol (mmol/mol cholesterol)
      • Significantly correlated with usual alpha-tocopherol intake in the whole population
      • Increased by 0.086 micromol/g creatinine for every 1 mg increase in dietary alpha-tocopherol [2]
    • Median excretion
      • Remained at a plateau of about 1.39 micromol/g creatinine
        • Until an intake of about 9 mg alpha-tocopherol/day, then the slope of the curve increased [2]
  • Comparison of urinary alpha-CEHC concentration of
    • 6 healthy unsupplemented controls
    • 3 patients with ‘ataxia with vitamin E deficiency’ (AVED)
      • Lacking alpha-TTP (two adults, one child, with or without supplementation with all-rac-alpha-tocopheryl acetate or RRR-alpha-tocopherol) [2]
    • Alpha-CEHC excretion in urine = amount of liver alpha-tocopherol which has exceeded the capacity of binding to alpha-TTP (Schuelke et al., 2000) [2]
    • Two of the controls were supplemented with 400 mg RRR or all-rac-alpha-tocopherol for five days
      • Curve of urinary alpha-CEHC according to plasma alpha-tocopherol concentration
        • Urinary alpha-CEHC was close to 0 mg/day for plasma concentrations below about 30–40 micromol/L
          • Above plasmtaic 30–40 micromol/L - urinary alpha-CEHC excretion increased [2]
  • Urinary alpha-CEHC excretion responds to alpha-tocopherol supplementation
    • Is a marker of saturation of the liver alpha-TPP binding capacity [2]

Žlučí

  • Excess alpha-tocopherol - i.e. not incorporated into nascent VLDL or entering the liver by reverse lipoprotein uptake
  • Other tocopherols and tocotrienols are secreted in the bile
  • Considering a mean alpha-tocopherol concentration in human bile
    • 8.4 ± 0.9 µmol/L (Leo et al., 1995)
      • Bile production in humans of about 750 mL/day (Boyer and Bloomer, 1974; Boyer, 2013)
        • About 2.7 mg (6.3 µmol) of alpha-tocopherol is secreted in the bile per day [2]
  • Oxidative metabolites of alpha-tocopherol are also secreted in the bile (Schultz et al., 1995; Wu and Croft, 2007) [2]

SRB1

  • Excretion of alpha-tocopherol with biliary secretion [8]

Faeces

  • Kinetic study in adults who ingested 0.78 µg 14C-labelled-RRR-alpha-tocopherol and provided faecal samples over 21 days (Chuang et al., 2011) --23.2 ± 5.8 % of the labelled dose was eliminated via the faeces
  • Novotny et al. (2012)
    • Mean faecal losses of alpha-tocopherol cca 3.15 mg/day [2]

Reabsorbce

  • The end products of VE catabolism traditionally considered excretion products are a group of
      • Metabolites—short-chain
    • Long-chain derivatives
      • Some of those long-forms have recently been found in plasma
        • Biological activity assayed in in vitro systems
        • Now considered a new class of regulatory metabolites (Galli et al. 2017; Schmölz et al., 2016; Takada et. al., 2010; Reboul et al., 2011; Kaempf-Rotzoll, 2003; Brigelius-Flohe, 1999) [8]
  • Role of metabolic products derived from the catabolism of alpha-tocopherol is still uncertain
  • Some studies point toward these products being the ones that would really be behind many of the beneficial effects attributed to VE
    • Alpha-carboxyethyl-6-hydroxychromans (CEHC)
      • Related to anti-proliferative [8]
      • Anti-atherosclerotic potential [8]
      • Could offer specific protection against inflammation and oxidation [8] (Wallert et al., 2014; Schubert et al., 2018) [8]


Skin

  • Alpha-Tocopherol is secreted by sebaceous glands
  • Dermal losses have not been quantified (Wu and Croft, 2007).

Breast milk

  • Secrete alpha-tocopherol via their breast milk
  • Alpha-Tocopherol content in human milk of about 3.5 mg/L (EFSA NDA Panel, 2013)(Antonakou et al. ;2011)
  • Five studies (Schweigert et al., 2004; Quiles et al., 2006; Romeu-Nadal et al., 2006; Sziklai-Laszlo et al., 2009; Antonakou et al., 2011)
    • Mothers of full-term infants in the EU
    • Mean alpha-tocopherol concentration in human milk, measured by high-performance liquid chromatography (HPLC)
      • Ranged 3 mg/L - 25 mg/L (including all stages of lactation)
      • Highest value (25 mg/L) was observed in colostrum samples (three days post partum) (Quiles et al., 2006) [2]
  • Mean maternal ‘vitamin E’ intake (Quiles et al., 2006; Antonakou et al., 2011) [2]
    • 6 to 11 mg/day
  • Unsupplemented women
    • The mean alpha-tocopherol concentration in mature milk ranged between 3.5 - 5.7 mg/L (mid-point of 4.6 mg/L) [2]
      • Mean milk transfer of 0.8 L/day during the first six months of lactation in exclusively breastfeeding women (Butte et al., 2002; FAO/WHO/UNU, 2004; EFSA NDA Panel, 2009) [2]
      • Concentration of alpha-tocopherol in mature human milk of 4.6 mg/L [2]
      • Secretion of alpha-tocopherol into milk during lactation is estimated to be 3.7 mg/day [2]
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Poslední aktualizace: 21. 2. 2020 0:41:02