Sympathetic activity in brown adipose tissue from rats adapted to a high protein, carbohydrate-free diet.
Previous studies have shown that adaptation of rats to a high protein, carbohydrate-free (HP) diet results in a marked reduction in brown adipose tissue (BAT) thermogenic capacity. The present experiments were carried out to assess BAT sympathetic activity in HP diet-adapted rats. It was found that interscapular brown adipose tissue (IBAT) norepinephrine (NE) content, fractional turnover rate and calculated rate of turnover were markedly reduced in HP-fed rats. Replacement of the HP diet by a control, balanced diet for 24 h did not affect BAT NE content significantly, but restored fractional turnover rate and turnover rate values to those of control animals. Exposure to cold (4 degrees) for a short period (8 h) induced a marked increase in IBAT NE fractional turnover rate and calculated turnover rate in both HP and control rats. The cold-induced rise of turnover rate over values at ambient temperature (25 degrees C) was higher in HP rats than in controls. Rectal temperature after 8 h of cold exposure did not differ in HP and control rats. The data suggest that the decreased thermogenic capacity of rats adapted to a high protein, carbohydrate-free diet is due to a reduced sympathetic outflow to BAT, which can be rapidly reactivated by cold stimulation.
Department of Biochemistry, School of Medicine, USP, Ribeirão Preto, SP, Brazil.
M N
MN
Brito
N A
NA
Brito
M A
MA
Garófalo
I C
IC
Kettelhut
R H
RH
Migliorini
D000222:Adaptation, Physiological / Q000502:physiology; D002001:Adipose Tissue, Brown / Q000294:innervation* / Q000378:metabolism; D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology; D003080:Cold Temperature; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000502:physiology*
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009638:Norepinephrine