stålballe
2009-05-12, 17:38
Hittade en studie som visar att C- och E-vitamin motverkar förbättrad insulinkänslighet vid träning.
Antioxidants prevent health-promoting effects
of physical exercise in humans
Exercise promotes longevity and ameliorates type 2 diabetes
mellitus and insulin resistance. However, exercise also increases
mitochondrial formation of presumably harmful reactive oxygen
species (ROS). Antioxidants are widely used as supplements but
whether they affect the health-promoting effects of exercise is
unknown. We evaluated the effects of a combination of vitamin C
(1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as
measured by glucose infusion rates (GIR) during a hyperinsulinemic,
euglycemic clamp in previously untrained (n 19) and pretrained
(n 20) healthy young men. Before and after a 4 week
intervention of physical exercise, GIR was determined, and muscle
biopsies for gene expression analyses as well as plasma samples
were obtained to compare changes over baseline and potential
influences of vitamins on exercise effects. Exercise increased parameters
of insulin sensitivity (GIR and plasma adiponectin) only in
the absence of antioxidants in both previously untrained (P <
0.001) and pretrained (P < 0.001) individuals. This was paralleled
by increased expression of ROS-sensitive transcriptional regulators
of insulin sensitivity and ROS defense capacity, peroxisomeproliferator-
activated receptor gamma (PPAR), and PPAR coactivators
PGC1 and PGC1 only in the absence of antioxidants (P <
0.001 for all). Molecular mediators of endogenous ROS defense
(superoxide dismutases 1 and 2; glutathione peroxidase) were also
induced by exercise, and this effect too was blocked by antioxidant
supplementation. Consistent with the concept of mitohormesis,
exercise-induced oxidative stress ameliorates insulin resistance
and causes an adaptive response promoting endogenous antioxidant
defense capacity. Supplementation with antioxidants may
preclude these health-promoting effects of exercise in humans.
http://www.pnas.org/content/early/2009/05/11/0903485106.full.pdf+html
Antioxidants prevent health-promoting effects
of physical exercise in humans
Exercise promotes longevity and ameliorates type 2 diabetes
mellitus and insulin resistance. However, exercise also increases
mitochondrial formation of presumably harmful reactive oxygen
species (ROS). Antioxidants are widely used as supplements but
whether they affect the health-promoting effects of exercise is
unknown. We evaluated the effects of a combination of vitamin C
(1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as
measured by glucose infusion rates (GIR) during a hyperinsulinemic,
euglycemic clamp in previously untrained (n 19) and pretrained
(n 20) healthy young men. Before and after a 4 week
intervention of physical exercise, GIR was determined, and muscle
biopsies for gene expression analyses as well as plasma samples
were obtained to compare changes over baseline and potential
influences of vitamins on exercise effects. Exercise increased parameters
of insulin sensitivity (GIR and plasma adiponectin) only in
the absence of antioxidants in both previously untrained (P <
0.001) and pretrained (P < 0.001) individuals. This was paralleled
by increased expression of ROS-sensitive transcriptional regulators
of insulin sensitivity and ROS defense capacity, peroxisomeproliferator-
activated receptor gamma (PPAR), and PPAR coactivators
PGC1 and PGC1 only in the absence of antioxidants (P <
0.001 for all). Molecular mediators of endogenous ROS defense
(superoxide dismutases 1 and 2; glutathione peroxidase) were also
induced by exercise, and this effect too was blocked by antioxidant
supplementation. Consistent with the concept of mitohormesis,
exercise-induced oxidative stress ameliorates insulin resistance
and causes an adaptive response promoting endogenous antioxidant
defense capacity. Supplementation with antioxidants may
preclude these health-promoting effects of exercise in humans.
http://www.pnas.org/content/early/2009/05/11/0903485106.full.pdf+html