Light/dark cycle-dependent metabolic changes in adipose tissue of pinealectomized rats.
We investigated the effects of pinealectomy on adipose tissue metabolism at different times of day. Adult male Wistar rats were divided into two groups: pinealectomized and control (sham-operated). Eight weeks after surgery, the animals were killed at three different times (at 8.00 a.m., at 4.00 p.m. and 11.00 p.m.). We collected blood samples for glucose, insulin, corticosterone, and leptin determinations, and periepididymal adipocytes for in vitro insulin-stimulated glucose uptake, oxidation, and incorporation into lipids. Pinealectomy caused insulin resistance as measured by 2-deoxyglucose uptake (a fall of approximately 40 % in the maximally insulin-stimulated rates) accompanied by hypercorticosteronemia at the three time points investigated without changes in plasma insulin an or leptin levels. Furthermore, pinealectomy increased the insulin-induced glucose incorporation into lipids (77 %) at 4.00 p.m. and insulin-induced glucose oxidation in the morning and in the afternoon, while higher rates were observed in the evening and in the morning in control rats. In conclusion, cell responsiveness to insulin was differentially affected by pineal ablation and time of day, and persistent insulin resistance was obtained in pinealectomized rats. We hypothesize that pinealectomy exposes the animal to an inadequate match between energy requirements and fuel mobilization.
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, 1524 Prof. Lineu Prestes Ave., 05508-900 São Paulo, Brazil.
M I
MI
Alonso-Vale
C N
CN
Borges-Silva
G F
GF
Anhê
S
S
Andreotti
M A
MA
Machado
J
J
Cipolla-Neto
F B
FB
Lima
D017667:Adipocytes / Q000378:metabolism* / Q000528:radiation effects; D000273:Adipose Tissue / Q000378:metabolism / Q000528:radiation effects; D000704:Analysis of Variance; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight / Q000502:physiology / Q000528:radiation effects; D002940:Circadian Rhythm / Q000502:physiology*; D003345:Corticosterone / Q000097:blood*; D004734:Energy Metabolism / Q000502:physiology / Q000528:radiation effects; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance / Q000502:physiology* / Q000528:radiation effects; D020738:Leptin / Q000097:blood; D008027:Light; D050356:Lipid Metabolism; D008297:Male; D008550:Melatonin / Q000502:physiology; D017440:Photoperiod; D010870:Pineal Gland / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011972:Receptor, Insulin / Q000378:metabolism / Q000528:radiation effects
D001786:Blood Glucose; D007328:Insulin; D020738:Leptin; D011972:Receptor, Insulin; D008550:Melatonin; D003345:Corticosterone