Specificity of insulin or oxytocin stimulation of protein synthesis in adipose tissue

1964 ◽  
Vol 207 (5) ◽  
pp. 1169-1172 ◽  
Author(s):  
M. E. Krahl

Insulin stimulates glucose uptake, fat synthesis, and incorporation of amino acids into protein of rat adipose tissue. Other agents having insulinlike effects on glucose metabolism have now been tested for their ability to promote protein synthesis in this in vitro system. Rat epididymal fat pads were incubated in Krebs bicarbonate medium containing glucose or pyruvate, acetate-1-C14 as precursor for lipids, or (in separate experiments) histidine-2(ring)-C14 as precursor for protein. Glucose uptake was measured by the glucose oxidase method, and radioactivity of lipid and protein fractions was estimated. Synthetic oxytocin (Sandoz), 0.1–10 U/ml, stimulated glucose uptake, acetate incorporation into lipid, and histidine-C14 incorporation into protein when glucose was present; unlike insulin, oxytocin did not enhance protein synthesis when pyruvate replaced glucose in the medium. RNA (1 mg/ml), nicotinic acid (0.001 m), and protamine sulfate (1 mg/ml) each stimulated glucose uptake and acetate incorporation into lipid, but did not enhance histidine-C14 incorporation into protein. It is concluded that in adipose tissue insulin has a specific effect on protein synthesis which cannot be mimicked by other agents which stimulate glucose uptake or lipid synthesis.

1976 ◽  
Vol 158 (1) ◽  
pp. 9-16 ◽  
Author(s):  
O Meyuhas ◽  
L Reshef ◽  
F J Ballard ◽  
R W Hanson

1. Epididymal adipose tissue from the rat was maintained in culture for periods of up to 96h. 2. After an initial decrease in protein synthesis during the first 24h of culture, the adipose tissue recovered its capacity to synthesize and accumulate proteins of a relatively large size. 3. The activity of phosphoenolpyruvate carboxykinase decreased in a parallel manner, but increased again after 24h of incubation of the tissue in culture, to a value twice that noted in the tissue in vivo. This increase in enzyme activity was due to an increase in its rate of synthesis. 4. Both insulin and dexamethasone (9alpha-fluoro-16alpha-methyl-11beta,17,-21-trihydroxypregna-1,4-diene-3,20-dione) inhibited phosphoenolpyruvate carboxykinase synthesis, but dexamethasone also decreased total protein synthesis. 5. The half-life of phosphoenolpyruvate carboxykinase in adipose tissue cultured in vitro was 5-7h and was not altered by insulin or dexamethasone. 6. It is concluded that both insulin and glucocroticoids lower the activity of phosphoenolpyruvate carboxykinase in rat adipose tissue by decreasing its rate of synthesis.


1980 ◽  
Vol 188 (1) ◽  
pp. 185-192 ◽  
Author(s):  
P Ashby ◽  
D S Robinson

The lipoprotein lipase activity of epididymal fat-bodies from starved rats was measured during incubations at 37 degrees C in vitro. Protein synthesis independent activation of the enzyme, previously observed during incubations at 25 decrease C, also occurs at 37 degrees C. Protein-synthesis-dependent increases in the activity of the enzyme occur in the presence of insulin and are markedly potentiated by glucocorticoids. The effects on the activity of the enzyme of insulin alone, or in the presence of glucocorticoids, are correlated with its effects on total protein synthesis in the tissue. Adrenaline antagonizes the increase in activity of the enzyme brought about by insulin and abolishes the potentiation of insulin action by glucocorticoids. These changes may be due, at least in part, to its stimulation of inactivation of the enzyme in the tissue. It is suggested that changes in adipose-tissue lipoprotein lipase activity that occur with changes in nutritional status in vivo result from the combined effects of changes in plasma insulin and glucocorticoid concentrations.


1959 ◽  
Vol 234 (12) ◽  
pp. 3111-3114 ◽  
Author(s):  
Albert I. Winegrad ◽  
Walter N. Shaw ◽  
Francis D.W. Lukens ◽  
William C. Stadie

1990 ◽  
Vol 70 (1) ◽  
pp. 199-206 ◽  
Author(s):  
O. ADEOLA ◽  
B. W. McBRIDE ◽  
R. O. BALL ◽  
L. G. YOUNG

Subcutaneous adipose tissue and intercostal and sartorius muscles from five barrows and five gilts at 20 kg liveweight were used to study lipogenesis, lipolysis, Na+, K+-ATPase-dependent respiration and protein synthesis. Lipogenesis rate measured by 14C-acetate incorporation into lipid was similar between barrows and gilts; and 100 μg insulin per mL enhanced (P < 0.1) subcutaneous adipose tissue lipogenesis by 74%. Lipolysis rate quantitated by glycerol release was similar between barrows and gilts (3546 and 4160 nmol g−1 2 h−1). Adenosine deaminase and norepinephrine together enhanced adipose tissue lipolytic response by 102%. Fractional and absolute rates of protein synthesis were similar between barrows and gilts (3.24 and 3.69% d−1; 6.01 and 6.06 mg g−1 d−1); and between intercostal and sartorius muscles. Barrows had lower Na+, K+-ATPase-dependent respiration than gilts and the maintenance of Na+ and K+ transmembrane ionic gradient in the muscle preparations accounted for 23–26% of total respiration. Key words: Pigs, adipose tissue, skeletal muscle, metabolism


2004 ◽  
Vol 33 (1) ◽  
pp. 11-19 ◽  
Author(s):  
RY Li ◽  
HD Song ◽  
WJ Shi ◽  
SM Hu ◽  
YS Yang ◽  
...  

In addition to serving as a fat depot, adipose tissue is also considered as an important endocrine organ that synthesizes and secretes a number of factors. Leptin is an adipocyte-derived hormone that plays a vital role in energy balance. Expression of leptin is regulated by dietary status and hormones. In the present study, we report that galanin, an orexigenic peptide, inhibits leptin expression and secretion in rat adipose tissue and in 3T3-L1 adipocytes. Treatment with galanin (25 micro g/animal) induced approximately 46% down-regulation of leptin secretion at 15 min, followed by 40, 37 and 47% decreases in leptin secretion at 1, 2 and 4 h respectively. Although Northern blot analysis of adipose tissue from the same animals showed that leptin mRNA expression in adipose tissue was unaffected by galanin treatment for 2 h, galanin treatment for 4 h led to decline of leptin mRNA expression in a dose-dependent manner. Meanwhile, treating the rats with galanin had no effect on leptin mRNA expression in the hypothalamus. The inhibitory action of the galanin on leptin mRNA and protein levels was also observed in vitro. When incubated with 10 nM galanin for 48 h, leptin mRNA expression and protein secretion also decreased in 3T3-L1 adipocytes. On the other hand, galanin was found not only to express in rat adipose tissue, but also to increase about 8-fold after fasting. Based on these data, we speculate that increased galanin expression in rat adipose tissue after fasting may be involved in reducing leptin expression and secretion in fasting rats.


FEBS Letters ◽  
1974 ◽  
Vol 49 (1) ◽  
pp. 65-69 ◽  
Author(s):  
P. Zumstein ◽  
J. Zapf ◽  
E.R. Froesch

1964 ◽  
Vol 207 (6) ◽  
pp. 1215-1220 ◽  
Author(s):  
Alisa Gutman ◽  
Eleazar Shafrir

Rat adipose tissue from different body sites was shown to contain uridine diphosphoglucose (UDPG)-transglucosylase activity, which on the basis of protein content was comparable to or higher than that reported for muscle or liver. In epididymal adipose tissue, the activity of UDPG-glycogen transglucosylase and phosphorylase, as well as the content of glycogen per wet weight, decreased with increasing age of the animals in parallel with the decrease of tissue protein content. On prolonged fast the activity of UDPG-glycogen transglucosylase and phosphorylase per milligram protein dropped by 25–50% of the control value. On refeeding, the extent of changes was variable but, in general, at 24 hr control or higher levels of activity were reached and at 48 hr the activities were elevated. The ratio of glucose 6-phosphate independent activity of UDPG-glycogen transglucosylase to total activity was not affected by fasting and refeeding or by the administration of glucose with insulin. In adrenalectomized rats, with high adipose tissue glycogen, no change in UDPG-glycogen transglucosylase was found, whereas the levels of phosphorylase were elevated. Epinephrine in vivo and in vitro did not affect the activity of UDPG-glycogen transglucosylase of adipose tissue.


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