Thyroid peroxidase activity, hepatic glucose-6-phosphate dehydrogenase activity and corticosterone level in plasma and tissues of rats fed different dietary fats
D. Rosolowska-huszcz et al., Thyroid peroxidase activity, hepatic glucose-6-phosphate dehydrogenase activity and corticosterone level in plasma and tissues of rats fed different dietary fats, J ANIM FEED, 10(1), 2001, pp. 185-200
Thyroid and adrenal gland activity were evaluated together with liver lipog
enic activity in rats fed diets containing different fats. After one- week
of a fat- free regimen, male Wistar rats weighing 100-120 g (at the beginni
ng of the experiment) were divided into four groups fed diets with differen
t fats: L - lard, S - sunflower oil, P - palm oil, R - rape seed oil. The a
ctivity of thyroid peroxidase (TPO), the key enzyme in thyroid hormone bios
ynthesis, corticosterone (Cs) concentration in plasma, the adrenal glands,
aorta, and heart, plasma total cholesterol concentration and glucose-6-phos
phate dehydrogenase (G-6-PD) activity in the liver, as an index of lipogeni
c activity, were determined after fat-free feeding and after one and three
weeks of fat-supplying diets. TPO activity increased after one week on fat-
containing diets fed to groups S and P; after three weeks it was higher tha
n after the fat-free period in groups P, S and L and directly related to pa
lmitic acid intake and plasma total cholesterol concentration. Various patt
erns of changes in Cs concentration in plasma and tissues were observed sug
gesting an influence of dietary fat composition on hormone distribution. Af
ter three weeks of feeding fat, Cs concentration in plasma was lower than a
fter the fat-free regimen and did not differ among dietary groups, while in
tissues it was dependent on the type of dietary fat. Tissue Cs was higher
in the adrenals in groups P and R, in the aorta in group R, and in the hear
t in groups L and S, After three weeks of feeding fat the Cs concentration
in the aorta of groups S and L, and in the adrenals in group S was lower th
an after the fat- free regimen, whereas in the heart it was higher in all g
roups. The decrease in hepatic G-6-PD activity after introducing diets with
fats depended on the kind of dietary fat it decreased to lower levels in g
roups S and R than in groups L and P.
The results obtained indicate that dietary fat composition can affect thyro
id activity, hepatic lipogenesis and corticosterone secretion and/or distri
bution in different manners. This suggests that, among others, metabolic ef
fects of dietary fat can result from changes in relations between thyroid a
nd adrenal gland activities.