Clearing-factor lipase in adipose tissue. A medium in which the enzyme activity of tissue from starved rats increases in vitro.
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ABSTRACT:
SUBMITTER: Salaman MR
PROVIDER: S-EPMC1265053 | biostudies-other | 1966 Jun
REPOSITORIES: biostudies-other
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Project description:1. Evidence is presented that the increase in clearing-factor lipase activity that occurs when adipose tissue from starved rats is incubated in a defined medium in vitro is due to an increase in the total enzyme content of the system. It is shown that the clearing-factor lipase activity rises to reach a plateau level where, it is suggested, rates of enzyme synthesis and of enzyme destruction become balanced. 2. The presence of heparin in the incubation medium results in the extraction of part of the clearing-factor lipase originally present in the adipose tissue and this could provide the stimulus for the increase in total enzyme content. 3. Glucose is required in the incubation medium at a very low concentration. It can be replaced by fructose, but not by pyruvic acid, lactic acid, glyceric acid or dihydroxyacetone. 4. Adrenaline and corticotrophin inhibit the increase in enzyme activity when they are present in the incubation medium. 5. The high clearing-factor lipase activity associated with adipose tissue of fed rats is decreased by 50% within 3hr. of the injection of puromycin.
| S-EPMC1265054 | biostudies-other
Project description:The stability at 42 degrees C of clearing-factor lipase in adipose tissue, and in intact fat-cells isolated from it, was investigated. That portion of the total activity of the tissue which is associated with the fat-cell is stable under such conditions. This stability is markedly diminished when the fat-cell is disrupted.
| S-EPMC1165972 | biostudies-other
Project description:1. Clearing-factor lipase was assayed in acetone-ether-dried powders of heart and adipose tissue of pigs. The enzyme activity in heart was higher than that in adipose tissue. The activity in the outer layer of subcutaneous fat was greater than that in the inner subcutaneous fat and the perirenal fat, which had similar activities. 2. Starvation for 48h, but not for 24h, decreased the activity of the heart enzyme. 3. Starvation for 24h caused a rapid decrease in the activity in all three adipose tissues, but even after 72h of starvation the activity was still highest in the outer subcutaneous fat. 4. Plasma fatty acid, glucose and insulin concentrations were determined in fed and starved pigs. Starvation decreased the plasma insulin concentration and increased the non-esterified fatty acid concentration.
| S-EPMC1165964 | biostudies-other
Project description:The progressive increase in clearing-factor lipase activity that occurs during the incubation of adipose tissue from starved rats in an appropriate medium at 25 degrees C is shown to occur in two stages. The first of these is not inhibited by cycloheximide, whereas the second is.
| S-EPMC1177659 | biostudies-other
Project description:1. When adipose tissue from starved rats is incubated in a medium containing glucose, insulin, heparin and actinomycin (5mug./ml.) the total clearing-factor lipase activity of the system increases at least tenfold over a period of 9hr. In the absence of actinomycin, enzyme activity also increases, but to a lesser extent and for only about 3hr. Some enzyme activity appears in the incubation medium in both the presence and the absence of actinomycin. 2. When the glucose and insulin of the incubation medium are replaced by pyruvate and heparin is omitted, an increase in the total clearing-factor lipase activity in the presence of actinomycin still occurs, but only after a lag of several hours. When only heparin is omitted from the medium, the rise in enzyme activity begins immediately, but there is a shoulder in the time-course curve after a few hours. In the absence of heparin, little enzyme activity appears in the incubation medium. 3. The increases in enzyme activity in the presence of actinomycin are prevented if puromycin (0.5mg./ml.) is present in the incubation medium. 4. Catecholamines and corticotrophin inhibit the increase in enzyme activity caused by actinomycin. 5. The clearing-factor lipase activity of adipose tissue from fed animals declines with a half-life of between 1 and 1.5hr. when the tissue is incubated in the presence of puromycin. The clearing-factor lipase activity of adipose tissue from starved animals is stable under similar circumstances, as is the raised activity found after such tissue has been incubated in the presence of actinomycin. 6. Clearing-factor lipase extracted from adipose tissue of fed animals is less stable in solution than that extracted from the tissue of starved animals after this has been incubated in the presence of actinomycin.
| S-EPMC1198557 | biostudies-other
Project description:The lipoprotein lipase (clearing-factor lipase) activity of the white adipose tissue from rats aged between 1 and 145 days was determined. Five adipose-tissue sites (epididymal, uterine, subcutaneous, perirenal and intramuscular) together with serum concentrations of triacylglycerol, cholesterol and glucose were studied. The pattern of enzyme-activity change was remarkably similar in all the sites studied, although the growth of the tissues proceeded non-uniformly. After a peak of activity early in suckling, lipoprotein lipase activity fell to low values by 20 days of age. At weaning (21 days) the activity increased sharply and within 5 days high values were regained. The serum triacylglycerol and cholesterol concentrations were low at birth and reached peaks of concentration coincidentally with the minima of white-adipose-tissue lipoprotein lipase activities, seen late in suckling. The changes in enzyme activity were related to other metabolic changes in adipose tissue and with the known changes in plasma insulin concentrations occurring during development.
| S-EPMC1185698 | biostudies-other
Project description:Metabolic syndrome is characterized by visceral adiposity, insulin resistance, high triglyceride (TG)- and low high-density lipoprotein cholesterol-levels, hypertension, and diabetes-all of which often cause cardiovascular and cerebrovascular diseases. It remains unclear, however, why visceral adiposity but not subcutaneous adiposity causes insulin resistance and other pathological situations. Lipoprotein lipase (LPL) catalyzes hydrolysis of TG in plasma lipoproteins. In the present study, we investigated whether the effects of angiotensin II (AngII) on TG metabolism are mediated through an effect on LPL expression. Adipose tissues were divided into visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) for comparison. AngII accelerated LPL expression in SAT but, on the contrary, suppressed its expression in VAT. In both SAT and VAT, AngII signaled through the same type 1 receptor. In SAT, AngII increased LPL expression via c-Src and p38 MAPK signaling. In VAT, however, AngII reduced LPL expression via the Gq class of G proteins and the subsequent phospholipase C β4 (PLCβ4), protein kinase C β1, nuclear factor κB, and inducible nitric oxide synthase signaling pathways. PLCβ4 small interfering RNA experiments showed that PLCβ4 expression is important for the AngII-induced LPL reduction in VAT, in which PLCβ4 expression increases in the evening and falls at night. Interestingly, PLCβ4 expression in VAT decreased with fasting, while AngII did not decrease LPL expression in VAT in a fasting state. In conclusion, AngII reduces LPL expression through PLCβ4, the expression of which is regulated by feeding in VAT, whereas AngII increases LPL expression in SAT. The different effects of AngII on LPL expression and, hence, TG metabolism in VAT and SAT may partly explain their different contributions to the development of metabolic syndrome.
| S-EPMC4598143 | biostudies-literature
Project description:1. Incubation of intact epididymal adipose tissue from fed rats at 37 degrees in an albumin solution at pH7.4 in vitro results in rapid loss of clearing-factor lipase activity until a low activity, stable to prolonged incubation, is attained. The clearing-factor lipase activity of intact tissue from starved rats, which is initially much less than that of tissue from fed rats, is mainly stable to incubation at 37 degrees . 2. Much of the clearing-factor lipase activity of intact epididymal adipose tissue from fed rats is inactivated by collagenase. The enzyme activity of intact tissue from starved rats is not inactivated by collagenase. 3. The clearing-factor lipase activity of fat cells isolated from the epididymal adipose tissue of fed rats is stable to prolonged incubation at 37 degrees . It represents only a small proportion of the total activity of the intact tissue. In starved rats, the isolated fat cells contain a much higher proportion of the activity of the intact tissue. Their activity is also stable at 37 degrees . 4. Incubation of isolated fat cells in a serum-based medium leads to a progressive rise in clearing-factor lipase activity. Actinomycin increases the extent of this rise in activity. No rise in clearing-factor lipase activity occurs when stromal-vascular cells isolated from epididymal adipose tissue are incubated in the medium. 5. The findings indicate that less than 20% of the activity of intact adipose tissue from fed rats is retained when fat cells are isolated from the tissue by collagenase treatment. The activity that is lost could be that which normally functions in the uptake of triglyceride fatty acids by the tissue.
| S-EPMC1187693 | biostudies-other
Project description:The lipoprotein lipase activity of the lung, skeletal muscle, heart muscle and brown adipose tissue of the rat was studied during the period from late foetal to adult life. The enzyme activity in all four tissues emerged substantially during the first 24th after birth. Subsequently, heart and lung enzyme activity remained relatively constant per unit wet weight of tissue. The enzyme activity present in brown adipose tissue and skeletal muscle was elevated per unit weight of tissue during suckling compared with other periods of life. Delivery of near-term foetuses stimulated the emergence of enzyme activity in all four tissues with the same time course as that evoked by normal delivery. The significance of the presence of the enzyme in the tissues and the activity changes which occurred during development are discussed in relation to possible mechanisms of control.
| S-EPMC1185933 | biostudies-other
Project description:Previous studies have shown that the ratio of lipoprotein lipase (LPL) catalytic activity to LPL mass in tissues differs in different conditions, but it is not clear whether this occurs by a change in the catalytic efficiency of the LPL molecules, or because of a shift in the relation between active and inactive forms of the enzyme. To explore this, we have measured LPL activity and mass in detergent extracts of rat tissues. LPL specific activity was high and similar in heart, skeletal muscle, lung and brain. The liver had significantly lower specific activity, which is in accord with previous findings that the liver takes up and catabolizes LPL. The specific activity was also low in adipose tissue from fasted rats. When tissue extracts were applied to columns of heparin-agarose and eluted by a gradient of NaCl, a peak of active LPL was eluted at 1.0 M NaCl, but there was also a peak of inactive LPL protein, which was eluted at 0.6 M NaCl. In adipose tissue, LPL activity decreased by 70-80% during an overnight fast, whereas LPL mass decreased by only 20-40%. The mass ratio between inactive and active LPL, as separated by heparin-agarose chromatography, increased from 0.5 to over 2 during the fast. In hearts there was no significant difference between fed and fasted rats in total LPL activity, LPL mass or in the distribution between inactive and active forms. The results indicate that the relation between inactive (probably monomeric) and active (dimeric) forms of LPL is a target for post-translational regulation in adipose tissue.
| S-EPMC1216995 | biostudies-other