oxidation / thyroid

Discussion in 'Food and nutrition' started by Doe, Oct 2, 2003.

  1. Doe

    Doe Guest

    http://www.erc-iran.com/iced/6/abstract/SERUM%20PARAOXONASE%20ACTIVITY,%20
    LIPIDS,%20LIPOPROTEINS%20AND%20APOLIPOPROTEINS%20IN%20PATIENTS%20WITH%20TH YROID%20DYSFUNCTION.htm

    <<snip>> The presence of increased oxidation susceptibility in both hypo- and hyperthyroid subjects
    can be confirmed by decreased paraoxanase activity through two different mechanisms. <<snip>>

    Serum paraoxonase activity, lipids, lipoproteins and apolipoproteins in patients with thyroid
    dysfunction Raiszadeh F, Solati M, Arabi M, Azizi F. Endocrine Research Center, Shaheed Beheshti
    University of Medical Sciences, Tehran, Iran

    Paraoxonase is an HDL-linked enzyme, which can hydrolyze paraoxon in vitro. There have been some
    reports on its antioxidant effects in human serum, which inhibits LDL-c oxidation. Serum activity of
    this enzyme falls in patients with atherosclerotic coronary artery disease. Patients with thyroid
    dysfunction are more susceptible to oxidative stresses, and may show enhanced LDL-c oxidation. The
    purpose of this study was to evaluate serum paraxonase activity and lipid parameters in patients
    with hypo and hyperthyroidism.

    50 hypothyroid patients, 11 men and 39 women, aged 38.9±13.4 years, and 50 hyperthyroid patients, 20
    men and 30 women, aged 42.4±14.3 years, were studied.

    Serum paraoxonase activity was measured in fasting sera by spectrophotometer, measuring P-nitro
    phenol paraoxon after adding paraoxon to the sera. Apolipoproteins level was determined by
    immunoturbidometric assay.

    Hyper and hypothyroid patients did not show any significant differences in height, weight, and body
    mass index compared with the control group. Significant reduction in serum paraoxonase activity
    (44.8±22.6 vs. 67±36.8
    Iu/ml, P<0.001) and paraoxonase to HDL ratio (0.7±0.3 vs. 1.2±0.9, P<0.001) was present in
    hyperthyroid patients compared with the controls. In hypothyroid patients, lower serum
    paraoxonase activity (46.1±21 vs. 64.3±32.2 Iu/ml, P<0.05) was accompanied with lower paraoxonase
    to HDL ratio (0.8±0.4 vs.
    1.1±0.7, P<0.05).

    In hyperthyroid patients, significant reduction in serum triglyceride (112±53
    vs. 165±129 mg/dl, P<0.001), apolipoprotein A-I (136±20 vs. 153±26 mg/dl, P<0.001), apolipoprotein B
    (75±18 vs. 85±25 mg/dl, P<0.05), and cholesterol to HDL ratio (2.9±0.8 vs. 3.3±1.2, P<0.05) were
    shown to exist, as compared with the control group. While these patients showed no significant
    changes in serum total cholesterol, HDL-c, and LDL-c. Hypothyroid patients had significantly
    higher total cholesterol (224±69 vs. 184±41 mg/dl, P<0.001), LDL-c (133±59 vs. 93±36 mg/dl,
    P<0.001), apolipoprotein B (107±36 vs. 84±23 mg/dl, P<0.001), cholesterol to HDL ratio (4±1.4
    vs. 3.2±1.2 P<0.005), and LDL to HDL ratio
    (2.3±1.1 vs. 1.7±0.9, P<0.005), and lower apoA-I to apoB ratio (1.5±0.6 vs.
    3.9±0.5, P<0.001) compared with the control group. Serum levels of T4 in both groups were
    inversely correlated with total cholesterol, LDL, apo A-I, apo B, and cholesterol to HDL and LDL
    to HDL ratios.

    Hyperthyroidism accelerates mithochondrial oxidative metabolism, resulting in increased free radical
    production and lipid peroxidation. The increased oxidative stress causes higher consumption of
    antioxidant substances, including paraoxanase enzyme in hyperthyroid subjects. Decreased paraoxanase
    activity in hypothyroid subjects is attributable to the presence of high cholesterol and decreased
    LDL-receptor activity as strong pro-oxidant factors that favor increased antioxidant consumption.
    The presence of increased oxidation susceptibility in both hypo- and hyperthyroid subjects can be
    confirmed by decreased paraoxanase activity through two different mechanisms.

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