TY - JOUR
T1 - Adenylyl cyclase inhibitory pathway is differentially modified in rat white and brown fat by high-energy diets
AU - Kenan, Yael
AU - Levinson, Martha
AU - Pines, Mark
AU - Naim, Michael
PY - 1997/6
Y1 - 1997/6
N2 - Incubation of white adipose tissue (WAT) adipocytes from rats fed a high-energy diet (Exp group) with antilipolytic G(i)-coupled adenylyl cyclase inhibitory agonists, nicotinic acid (Nic) and N6-(L-2- phenylisopropyl)adenosine (PIA), resulted in lower cellular adenosine 3',5'- cyclic monophosphate (cAMP) levels than in stimulated adipocytes from rats fed a nutritionally balanced diet (Con group). In contrast to WAT, incubation of brown adipose tissue (BAT) adipocytes with Nic yielded higher cAMP levels in the Exp vs. Con rats. In both WAT and BAT adipocytes, pertussis toxin treatment abolished the differences in Nic- and PIA-inhibited cAMP formation between Exp and Con animals. Immunoblotting of adipocyte membranes indicated a lower content of G(i)α but not G8α in BAT membranes of Exp vs. Con animals after 6 and 10 wk of feeding. No such differences were found in the G8α or G(i)α contents of WAT membranes. Thus the inhibitory pathway of adenylyl cyclase is proposed to be sensitized in WAT and desensitized in BAT of rats fed high-energy diets. These modifications in sensitivity are in line with reduced cAMP and lipolysis in WAT and increased cAMP and thermogenesis in BAT during obesity.
AB - Incubation of white adipose tissue (WAT) adipocytes from rats fed a high-energy diet (Exp group) with antilipolytic G(i)-coupled adenylyl cyclase inhibitory agonists, nicotinic acid (Nic) and N6-(L-2- phenylisopropyl)adenosine (PIA), resulted in lower cellular adenosine 3',5'- cyclic monophosphate (cAMP) levels than in stimulated adipocytes from rats fed a nutritionally balanced diet (Con group). In contrast to WAT, incubation of brown adipose tissue (BAT) adipocytes with Nic yielded higher cAMP levels in the Exp vs. Con rats. In both WAT and BAT adipocytes, pertussis toxin treatment abolished the differences in Nic- and PIA-inhibited cAMP formation between Exp and Con animals. Immunoblotting of adipocyte membranes indicated a lower content of G(i)α but not G8α in BAT membranes of Exp vs. Con animals after 6 and 10 wk of feeding. No such differences were found in the G8α or G(i)α contents of WAT membranes. Thus the inhibitory pathway of adenylyl cyclase is proposed to be sensitized in WAT and desensitized in BAT of rats fed high-energy diets. These modifications in sensitivity are in line with reduced cAMP and lipolysis in WAT and increased cAMP and thermogenesis in BAT during obesity.
KW - Adenosine 3',5'-cyclic monophosphate
KW - Brown adipose tissue
KW - Dietary obesity
KW - G proteins
KW - G(i) function
KW - Rats
KW - White adipose tissue
UR - http://www.scopus.com/inward/record.url?scp=0030739471&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.1997.272.6.e1043
DO - 10.1152/ajpendo.1997.272.6.e1043
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C2 - 9227450
AN - SCOPUS:0030739471
SN - 0193-1849
VL - 272
SP - E1043-E1049
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 6 35-6
ER -