The effect of changes in nutritional state on the lipolytic activity of rat adipose tissue

Changes in blood flow induced by the beta-adrenoceptor agonist isoproterenol (Iso) and a stable analogue of the major metabolite of arachidonic acid in adipose tissue, carbaprostacyclin (cPGI2), have been studied in rat periepididymal fat pad with in situ microdialysis measuring the distribution ratio of 0.2% ethanol in the dialysate (outflow) to that in the perfusate (inflow) (O/I ratio). Local perfusions of 1 microM cPGI2 or 1 microM Iso led to reversible decreases of the O/I ratio that were similar to the decrease induced by the vasodilating reference drug hydralazine (Hydra, 630 microM). Interestingly, a continuous perfusion of Hydra at a submaximal vasodilating concentration (63 microM) was sufficient to prevent further vasodilatation induced by Iso or cPGI2. To take advantage of this observation, experiments were designed to evaluate the influence of the vasodilating effect of Iso or cPGI2 on the ability of either to induce lipolysis in vivo. The results showed that the vasodilating effect of Iso could contribute to glycerol removal from the extracellular fluid and demonstrate that cPGI2 was devoid of lipolytic activity.

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Effect of nutrition on activity and release of lipase from rat adipose tissue

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1959.197.3.667 ◽

1959 ◽

Vol 197 (3) ◽

pp. 667-670 ◽

Cited By ~ 188

Author(s):

C. H. Hollenberg

Keyword(s):

Adipose Tissue ◽

Lipolytic Activity ◽

Fatty Acid Content ◽

Coconut Oil ◽

Nonesterified Fatty Acid ◽

Fat Tissue ◽

Fed State ◽

Oil Emulsion ◽

Rat Adipose Tissue ◽

Fasted Rats

Surviving rat adipose tissue induced lipolysis of a coconut oil emulsion as evidenced by a rise in the nonesterified fatty acid content of the medium following incubation. When tissue from fed rats was used addition of heparin to the medium accentuated this reaction, which, once initiated under these circumstances, continued unabated after the fat tissue was withdrawn. Heparin had no effect when fat from fasted rats was used, but the heparin response was restored by addition of glucose and insulin to the medium. Homogenates of fat from fed animals had significantly more lipolytic activity than those from fasted rats. It is concluded that lipolytic activity can be released from surviving adipose tissue of fed rats under the influence of heparin. The increase in activity in the fed state suggests that the lipase of adipose tissue may be concerned with the accumulation of fat in depots possibly by influencing the incorporation of chylomicrons into adipose tissue.

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THE EFFECT OF INCUBATION ON THE CHARACTERISTICS OF THE LIPOLYTIC ACTIVITY OF RAT ADIPOSE TISSUE

Canadian Journal of Biochemistry and Physiology ◽

10.1139/o62-082 ◽

1962 ◽

Vol 40 (6) ◽

pp. 703-707 ◽

Cited By ~ 76

Author(s):

C. H. Hollenberg

Keyword(s):

Adipose Tissue ◽

Lipoprotein Lipase ◽

Phosphate Buffer ◽

Lipolytic Activity ◽

Serum Triglyceride ◽

Fresh Tissue ◽

Intact Tissue ◽

Separate Type ◽

Tissue Homogenates ◽

Rat Adipose Tissue

A study has been made of the changes produced in the characteristics of the lipolytic activity of rat adipose tissue homogenates by prolonged preincubation of the intact tissue in phosphate buffer. Fresh tissue homogenates were markedly more active on a serum–triglyceride medium (activated substrate) than on triglyceride alone while little difference was noted with homogenates of preincubated tissue. The activity of fresh tissue homogenates was increased by addition of heparin; homogenates of incubated tissue were not affected. Fresh tissue homogenates were inhibited to a greater extent by protamine than were preparations of incubated material. Addition of glucose and insulin to the buffer partially maintained the activity of incubated tissue on activated substrate. These results indicate that while lipolytic activity of fresh rat adipose tissue has characteristics similar to lipoprotein lipase, the activity of incubated tissue differs from this enzyme in several respects. This study demonstrates the lability of lipoprotein lipase in rat adipose tissue and suggests the presence in this tissue of a separate type of lipolytic activity.

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A transcription-dependent mechanism, akin to that in adipose tissue, modulates lipoprotein lipase activity in rat heart

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00634.2006 ◽

2007 ◽

Vol 293 (4) ◽

pp. E908-E915 ◽

Cited By ~ 14

Author(s):

Gengshu Wu ◽

Liyan Zhang ◽

Jitendra Gupta ◽

Gunilla Olivecrona ◽

Thomas Olivecrona

Keyword(s):

Adipose Tissue ◽

Lipoprotein Lipase ◽

Actinomycin D ◽

Cell Metabolism ◽

Active Form ◽

Protein S ◽

Nutritional State ◽

Inactive Form ◽

Rat Adipose Tissue ◽

Fasted Rats

The enzyme lipoprotein lipase (LPL) releases fatty acids from lipoprotein triglycerides for use in cell metabolism. LPL activity is rapidly modulated in a tissue-specific manner. Recent studies have shown that in rat adipose tissue this occurs by a shift of extracellular LPL toward an inactive form catalyzed by an LPL-controlling protein whose expression changes in response to the nutritional state. To explore whether a similar mechanism operates in other tissues we injected actinomycin D to block transcription of the putative LPL controlling protein(s). When actinomycin was given to fed rats, heparin-releasable LPL activity increased by 160% in heart and by 150% in a skeletal muscle (soleus) in 6 h. Postheparin LPL activity in blood increased by about 200%. To assess the state of extracellular LPL we subjected the spontaneously released LPL in heart perfusates to chromatography on heparin-agarose, which separates the active and inactive forms of the lipase. The amount of lipase protein released remained relatively constant on changes in the nutritional state and/or blockade of transcription, but the distribution between the active and inactive forms changed. Less of the LPL protein was in the active form in perfusates from hearts from fed compared with fasted rats. When glucose was given to fasted rats the proportion of LPL protein in the active form decreased. Actinomycin D increased the proportion that was active, in accord with the hypothesis that the message for a rapidly turning over LPL-controlling protein was being removed.

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THE EFFECT OF INCUBATION ON THE CHARACTERISTICS OF THE LIPOLYTIC ACTIVITY OF RAT ADIPOSE TISSUE

Canadian Journal of Biochemistry and Physiology ◽

10.1139/y62-082 ◽

1962 ◽

Vol 40 (1) ◽

pp. 703-707

Author(s):

C. H. Hollenberg

Keyword(s):

Adipose Tissue ◽

Lipoprotein Lipase ◽

Phosphate Buffer ◽

Lipolytic Activity ◽

Serum Triglyceride ◽

Fresh Tissue ◽

Intact Tissue ◽

Separate Type ◽

Tissue Homogenates ◽

Rat Adipose Tissue

A study has been made of the changes produced in the characteristics of the lipolytic activity of rat adipose tissue homogenates by prolonged preincubation of the intact tissue in phosphate buffer. Fresh tissue homogenates were markedly more active on a serum–triglyceride medium (activated substrate) than on triglyceride alone while little difference was noted with homogenates of preincubated tissue. The activity of fresh tissue homogenates was increased by addition of heparin; homogenates of incubated tissue were not affected. Fresh tissue homogenates were inhibited to a greater extent by protamine than were preparations of incubated material. Addition of glucose and insulin to the buffer partially maintained the activity of incubated tissue on activated substrate. These results indicate that while lipolytic activity of fresh rat adipose tissue has characteristics similar to lipoprotein lipase, the activity of incubated tissue differs from this enzyme in several respects. This study demonstrates the lability of lipoprotein lipase in rat adipose tissue and suggests the presence in this tissue of a separate type of lipolytic activity.

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