Evidence for altered expression of the GTP-dependent regulatory proteins, Gs and Gi, in adipocytes from aged rats

Green, A; Johnson, Jackie

doi:10.1042/bj2580607

Cited by 19 publications

(8 citation statements)

References 28 publications

(28 reference statements)

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“…Cholera-toxin-catalysed ADP-ribosylation has been used on several occasions to establish the relative amounts of a-Gs in plasma membranes [11,20,27]. In agreement with the reports quoted above, cholera toxin catalysed the ADP-ribosylation of two major peptides of 42 kDa and 46-48 kDa in plasma membranes isolated from rat adipocytes (Fig.…”

Section: Resultssupporting

confidence: 80%

“…Diabetes has been reported to alter the expression and phosphorylation state of a-G1 [29]. On the other hand, aging and obesity have also been associated with alterations in G-protein subunit expression [27,30]. These modifications at the level of signal transduction may well reflect mechanisms by which the lipolytic response of adipose tissue, among others, is regulated in different physiological circumstances.…”

Section: Resultsmentioning

confidence: 99%

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Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats

Ros

Alonso

Moreno

1992

Biochemical Journal

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The effects of litter removal on the status of different components of the hormone-sensitive adenylate cyclase system were analysed in plasma membranes of rat adipocytes. These effects were correlated with the decreased lipolytic response of adipose tissue. No changes in total number of A1 adenosine receptors or their affinity were detected in response to litter removal. In contrast, beta-adrenergic receptors showed a decrease (35%) in total number of receptors, without any significant change in their affinity. The status of alpha-GS and alpha-Gi, the alpha-subunits of G proteins which mediate stimulation and inhibition respectively of adenylate cyclase, were probed by cholera- and pertussis-toxin-catalysed ADP-ribosylation respectively and by immunoblot. Associated with litter removal, decreases of 63% and 62% in the incorporation of [alpha 32P]ADP-ribose catalysed by cholera toxin and pertussis toxin into alpha-Gs and alpha-Gi respectively were detected. Immunoblotting using RM/1 (anti-alpha-Gs) and AS/7 (anti-alpha-Gi) antisera also showed decreases in the levels of alpha-Gs (52%) and alpha-Gi (55%) in adipocyte membranes from litter-removed rats compared with lactating rats. Alterations in the status of hormone-sensitive adenylate cyclase components, such as those described herein, may be biochemical mechanism(s) by which adipose tissue shows a decreased lipolytic response during recovery from lactation.

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Section: Resultssupporting

confidence: 80%

Section: Resultsmentioning

confidence: 99%

Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats

Ros

Alonso

Moreno

1992

Biochemical Journal

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“…A similar result was obtained for genetically obese (ob/ob) mice compared with lean littermates (Begin-Heick 1990). Preferential change of the short isoform was found in white adipocytes of aged rats, which exhibited a marked increase in G s S detected by both immunoblotting and cholera toxin-induced ADP ribosylation (Green & Johnson 1989). Interestingly, an identical reduction in both G s subforms was also reported in the adipocytes of obese (fa/fa) Zucker rats (Strassheim et al 1991).…”

Section: The (Non)identity Of the Short And Long Variants Of G Ssupporting

confidence: 66%

The decrease in the short variant of gsalpha protein is associated with an increase in [3H]CGP12177 binding, [3H]ouabain binding and Na, K-ATPase activity in brown adipose tissue plasma membranes of cold-acclimated hamsters

Bouřová

Novotn²,

Svoboda³

1999

Journal of Molecular Endocrinology

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Sucrose density gradient purified plasma membranes isolated from brown adipose tissue of cold-acclimated hamsters (4-10 weeks at 0-4 C) were analysed for the content of the short (G s S) and long (G s L) variants of G s protein (the subunit of the stimulatory G protein) and compared with the membranes isolated from control animals. The relative ratio between the two variants (G s S/G s L) decreased from 0·48 to 0·24 (P<0·01). This result, obtained by electrophoretic resolution of membrane proteins by standard SDS-PAGE and an immunoblot analysis with an antiserum oriented against an internal sequence of G s , was verified by resolution on urea-containing gels and an antiserum oriented against the C-terminus decapeptide of G s .Under these conditions, the G s S/G s L ratio was decreased from 0·41 to 0·31 (P<0·05). The total amount of both isoforms (G s S plus G s L) decreased to 83% (P<0·05) or 68% (P<0·01) by standard or urea SDS-PAGE respectively. These data demonstrate that cold-acclimation of hamster brown adipose tissue is associated with preferential decrease in the plasma membrane density of the short variant of the G s protein.This decrease was paralleled by an increase in the other plasma membrane constituents, [ 3 H]CGP12177 binding sites, [3 H]ouabain binding sites and Na,K-ATPase activity to 147%, 212% and 191% respectively.

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“…A diminished response of the receptoraG proteinaadenylyl cyclase membrane complex or alterations in the cyclic AMP signaling pathway have been shown to occur with age in rats (Gregerman, 1994). Other studies have shown increased sensitivity to antilipolytic agents, such as adenosine, in older rats (Green & Johnson, 1989;Hoffman et al, 1984). A recent study comparing young lean versus old obese Sprague Dawley rats was performed to examine age effects on stimulatory (G S ) and inhibitory (G i GTP-binding proteins.…”

Section: Effects Of Age On the Recruitment Of Fat Substrates: In Vitrmentioning

confidence: 99%

Lipid metabolism in the elderly

2000

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Adiposity increases with age. The size of the adipose tissue mass is determined by the balance between the recruitment of lipid substrates (ie free fatty acids) from adipose tissue and their subsequent oxidation by respiring tissues. Thus, change in the liberation of free fatty acids from adipocytes, the capacity of respiring tissue to oxidize free fatty acids or a combination of both may contribute to the age-related increase in body fat. This review focuses on studies that have examined the effect of age on free fatty acid release and the capacity of respiring tissues to oxidize fat. In vitro studies have shown that hormonal and pharmacological stimulation of lipolysis diminished with age. Despite this cellular defect, however, in vivo studies suggest that fatty acids are recruited from adipose tissue in excess of the energy demands of the body in older individuals. The capacity of respiring tissues, in particular skeletal muscle, to oxidize fat declines with age. The age-related decrease in fat oxidation is related to a reduction in both the quantity and oxidative capacity of respiring tissue. Taken together, these results suggest that an age-related decrease in the capacity of respiring tissues to oxidize fat, rather than decreased free fatty acid release, is a more likely determinant of lipid imbalance and the age-related increase in adiposity. Interventions designed to increase the mass or oxidative capacity of respiring tissue, therefore, may be effective in counteracting the age-related reduction in fat oxidation. Descriptors: aging; lipid metabolism; free fatty acids; adipose tissue; fat-free mass

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Evidence for altered expression of the GTP-dependent regulatory proteins, Gs and Gi, in adipocytes from aged rats

Cited by 19 publications

References 28 publications

Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats

Effects of litter removal on the lipolytic response and the regulatory components of the adenylate cyclase in adipocytes isolated from lactating rats

The decrease in the short variant of gsalpha protein is associated with an increase in [3H]CGP12177 binding, [3H]ouabain binding and Na, K-ATPase activity in brown adipose tissue plasma membranes of cold-acclimated hamsters

Lipid metabolism in the elderly

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