Short-term handling of the slimming agent oleoyl-estrone in liposomes (Merlin-2) by the rat

Estrogens and the regulation of glucose metabolism

The main estrogens: estradiol, estrone, and their acyl-esters have been studied essentially related to their classical estrogenic and pharmacologic functions. However, their main effect in the body is probably the sustained control of core energy metabolism. Estrogen nuclear and membrane receptors show an extraordinary flexibility in the modulation of metabolic responses, and largely explain gender and age differences in energy metabolism: part of these mechanisms is already sufficiently known to justify both. With regard to energy, the estrogen molecular species act essentially through four key functions: (1) Facilitation of insulin secretion and control of glucose availability; (2) Modulation of energy partition, favoring the use of lipid as the main energy substrate when more available than carbohydrates; (3) Functional protection through antioxidant mechanisms; and (4) Central effects (largely through neural modulation) on whole body energy management. Analyzing the different actions of estrone, estradiol and their acyl esters, a tentative classification based on structure/effects has been postulated. Either separately or as a group, estrogens provide a comprehensive explanation that not all their quite diverse actions are related solely to specific molecules. As a group, they constitute a powerful synergic action complex. In consequence, estrogens may be considered wardens of energy homeostasis.

Oleoyl-estrone is a precursor of an estrone-derived ponderostat signal

Oleoyl-estrone (OE) is a powerful anti-obesity compound that decreases food intake, decreases insulin resistance and circulating cholesterol. OE stimulates a severe loss of body fat by decreasing adipose tissue lipid synthesis and maintaining lipolysis. Therefore, the body economy loses lipid energy because energy expenditure is maintained. This study analyses the discrepancy between OE effects and the distribution of labelled OE in plasma. Estrone radioimmunoassay of organic solvent plasma extracts of rats treated with OE showed the massive presence of acyl-estrone, but saponification did not release estrone, but containing similar unknown compound. Analysis of label distribution in plasma after oral gavages of (3)H-OE showed the presence of a more hydrophilic compound than OE or any estrogen as well as (3)H(2)O, formed from (3)H-OE in the acidic stomach medium. OE was not attached to a specific transporter in plasma. Through serum HPLC analysis we found W, a labelled derivative more hydrophilic than OE or estrone. The results were confirmed using (14)C-OE. HPLC-MS/MS studies showed that plasma OE levels were one order of magnitude lower than those of W. When liver cell cytosols from rats laden with (3)H-OE were incubated with nuclei from untreated rats, the OE-derived label (i.e., Ws) was found attached to nuclear DNA. Neither estradiol nor estrone interfered with its binding. W is a fairly hydrophilic compound of low molecular weight containing the estrone nucleus, but it is not an ester because saponification or esterases do not yield estrone as OE does. It is concluded that OE acts through its conversion to W, its active form; which binds to a nuclear receptor different from that of estrogen. The estimated W serum levels are proportional to the pharmacological OE effects in vivo. We postulate W as a new type of hormone that exerts the full range of in vivo effects thus far attributed to OE. The full identification of W is anticipated to open the way for the development of new OE-like anti-obesity drugs.

Oleoyl-estrone

Oleoyl-estrone (OE) is a powerful slimming agent that is also present in plasma and adipose tissue, where it is synthesized. It acts through the formation of a derivative W. OE effects (and W levels) are proportional to the dose. OE reduces food intake but maintains energy expenditure (thermogenesis). The energy gap is fulfilled with adipose tissue fat, sparing body protein and maintaining glycemia (and glycogen) with lower insulin and leptin levels. OE (in fact W) acts through specific receptors, different from those of estrogen. OE increases cholesterol catabolism, reducing hypercholesterolemia in obese rats. The main metabolic effect on adipose tissue is lowering of lipid synthesis, maintaining unchanged the intracellular lipolytic processes; the imbalance favors the progressive loss of fat, which is largely used by the muscle. OE administration induces additive effects with other antiobesity agents, such as β(3)-adrenergic agonists, forcing a massive loss of lipid. Corticosteroids markedly limit OE action by altering the liver control of lipogenesis. OE also inhibits the action of 17β-hydroxysteroid dehydrogenase, decreasing the synthesis of β-estradiol and testosterone. Discontinuous treatment allows for maximal efficacy both in rats and humans. OE has the advantage that the loss of fat is maintained and does not require additional dietary limitations.

Action profile of the antiobesity drug candidate oleoyl-estrone in rats

Oleoyl-estrone (OE) has been presented as a potential antiobesity therapeutic, but the published series of studies from one laboratory has not yet been independently confirmed, and the exact mechanism of action is unknown. Based on the hypothesis that OE has potential for the treatment of obesity, male and female rats were chronically treated with several doses of OE to evaluate the impact of this compound on energy metabolism. Body weight, body composition, energy balance parameters and the expression of hypothalamic neuropeptides regulating food intake as well as key markers of the reproductive system were examined. OE impressively reduced food consumption and body weight gain in both sexes. Although a major part of the loss in body weight could be explained by decreased fat mass, a substantial loss of lean mass also occurred after OE administration. The loss of weight can be sufficiently explained by the suppression of food consumption, as there were no major changes in energy expenditure, locomotor activity or respiratory quotient. In situ hybridization data showed no significant change in the expression of key neuropeptides and hormone receptors regulating feeding behavior after OE treatment. Cocaine-amphetamine-regulated transcript (CART) mRNA levels were decreased in the arcuate nucleus of OE-treated rats. Hypogonadism and low plasma testosterone levels were found in OE-treated males, whereas females showed substantially increased liver size. The present data suggest that OE decreases food intake and body weight but also appears to cause a significant impact on the hypothalamus-pituitary-reproductive axis.

Intestinal oleoyl-estrone esterase activity in the Wistar rat

Low-dose oral oleoyl-estrone (OE) (i.e. in dairy products) is hydrolysed to estrone, which promotes growth and fat deposition. However, pharmacological doses of OE are absorbed largely intact and elicit fat losses. Thus, in order to find out how the intestine handles OE, esterase activity (at pH 5, 7 or 8) was measured in rat stomach, duodenum, jejunum, ileum, cecum, large intestine, and liver using OE as substrate. There were no sex-related differences. Pure pancreatic cholesterol-ester esterase hydrolysed OE even in the absence of taurocholate. The differences in the pH-related activity distribution pattern and selective inhibition and taurocholate dependence show that, in addition to the luminal (i.e. pancreatic) cholesterol-ester esterase, other esterases hydrolyse OE; these combined activities may be sufficient to rapidly dispose of pharmacological doses of OE. Female rats received a tritium-labeled OE gavage; the luminal and tissue label content were measured up to 24 h. The high retention of label in the stomach suggest that this may be a significant site of absorption. The rapid decrease of label in intestinal lumen (and rat tissues) shortly after the administration, hint at rapid absorption and disposal. In conclusion, the high OE-esterase activity and early absorption of OE are indicative of upper gastro-intestinal tract absorption skipping most of the medium-tract esterases.

Tamoxifen does not prevent the mobilization of body lipids elicited by oleoyl-estrone

Oleoyl-estrone is a powerful, slimming adipose tissue-derived signal that has biological effects widely opposed to those of its estrone moiety. The present experiment was designed to determine whether oleoyl-estrone effects on body energy are mediated by the estrogen receptor, blocked with the antagonist tamoxifen. Male Wistar rats were given daily oral doses of 10 micromol/kg d of oleoyl-estrone in oil containing 0 or 0.40 mg/kg d of tamoxifen. The data were compared with controls receiving only oil or 50 nmol/kg d of free estrone. After 10 days, the rats were killed, and their body composition and plasma metabolites and hormones were analyzed. Rats receiving estrone increased their body energy and lipid content compared with controls. Both groups of oleoyl-estrone-treated rats lost body weight, energy, and lipid; the losses in the rats receiving tamoxifen alone were less marked than in those receiving oleoyl-estrone. No significant changes in plasma glucose or triacylglycerols were observed. The patterns of change of estrone sulphate, estradiol, and oleoyl-estrone were consistent with a noticeable hydrolysis of oleoyl-estrone. The lack of differences in the fat mass in oleoyl-estrone-treated rats irrespective of the presence of tamoxifen suggested that the estrogenic pathway was not responsible for the slimming effects observed. Thus, it can be concluded that oleoyl-estrone effects are not mediated through its conversion to estrone or estradiol acting through the estrogen receptor. Tamoxifen partly mimicked the slimming effects of oleoyl-estrone; this could be speculatively explained by tamoxifen acting through the oleoyl-estrone signalling pathway.

Anomalous lipoproteins in obese Zucker rats

AIMS

Obesity is characterized by dislipoproteinaemia with increased cholesterol and triacylglycerol levels and lower chylomicra disposal rates. We studied here whether these alterations were related to lipoprotein number and/or size and composition.

METHODS

Plasma from lean and obese Zucker rats was fractionated into lipoprotein classes (chylomicra, very low density lipoprotein (VLDL), low density lipoprotein (LDL) and high density lipoprotein (HDL)) by differential centrifugation. The apoprotein and lipid composition of each fraction were measured. Lipoprotein particle size was estimated by dynamic light scattering and used to tabulate the mean diameter and volume of lipoprotein micelles. Particle mass was calculated from the density and volume. The mass of lipids and protein in each fraction/ml of plasma allowed the estimation of mean particle concentration and then the number of molecules of lipid and protein/unit of lipoprotein micelle.

RESULTS

A large part of hyperlipidaemia of obese rats is due to the accumulation of chylomicra: 1.3 +/- 0.2 mg/ml in lean rats [LR] (34% of all lipoproteins) and 8.2 +/- 0.9 mg/ml in the obese rats [OR] (66% of all lipoproteins). Lipid percentage composition of lipoproteins was similar in both groups. The particle size of LDL and HDL was much higher in OR than in LR: LDLs weighed 31.1 +/- 7.5 ag (LR) vs. 273 +/- 81 ag (OR), and HDLs weighed 31.7 +/- 12.6 ag (LR) and 375 +/- 103 ag (OR). In chylomicra and VLDL there was a relative scarcity of apoproteins in OR compared with LR. The whole architecture of LDLs is altered in OR, with a predominance of surface lipids: phospholipid and free cholesterol, and lower amounts of core lipids: triacylglycerols and cholesterol esters, with surface/core lipids ratios of 0.74 (LR) and 1.89 (OR). The consequences of anomalous LDL and HDL composition, size and overall structure may result in magnified lipoprotein metabolism alterations that hamper their ability to transfer apolipoproteins to larger chylomicra and VLDL, and to alter cholesterol transfer and binding of their apoproteins to cell surface receptors. The smaller number of LDL and HDL particles may further compound these difficulties and thus change the free to esterified cholesterol ratios observed in OR.

CONCLUSIONS

The main conclusions of this study are the key importance of chylomicron analysis for a better understanding of the transfer of lipids, and the altered lipoprotein size and apoprotein distribution in obese rats, which seriously hamper cholesterol interchange, resulting in hypercholesterolaemia, and thus triggering even more far-reaching consequences for the well-being of the obese.

Daily oral oleoyl-estrone gavage induces a dose-dependent loss of fat in Wistar rats

OBJECTIVE

To establish whether single daily oral doses of oleoyl-estrone result in dose-dependent slimming effects on normal weight rats, and to determine the changes in energy parameters induced by this treatment.

RESEARCH METHODS AND PROCEDURES

The effects of a daily oral gavage of oleoyl-estrone (0, 0.2, 0.5, 1, 2, 5, 10, and 20 micromol/kg per day) in 0.2 ml of sunflower oil given over a 10-day period were studied in groups, each of which contained six adult female Wistar rats initially weighing 190 to 230 g. A group of intact control rats receiving no gavage was included for comparison. Body weight and food intake were measured daily. Rats were killed on day 10 of treatment, and body composition (protein nitrogen, lipids, and water), liver lipids, and plasma parameters (glucose, triacylglycerols, total cholesterol, free fatty acids, 3-hydroxybutyrate, urea, aspartate, alanine transaminases, insulin, leptin, and free and acyl-estrone) were measured.

RESULTS

The administration of oleoyl-estrone resulted in a dose-dependent loss of body fat, because of a partly maintained energy expenditure combined with decreased food intake. The differences in the energy budget were met by internal fat pools. The changes recorded did not affect the levels of the main plasma energy homeostasis indicators: unaltered glucose, triacylglycerols, free fatty acids, 3hydroxybutyrate, and urea. Protein was accrued even under conditions of severe lipid store drainage. There were no changes in transaminases. No lipid accumulation was recorded in the liver. Plasma insulin and leptin levels decreased with increased oleoyl-estrone doses, whereas the levels of free and esterified estrone increased with treatment, although not in proportion to the dose received.

DISCUSSION

Oral treatment with oleoyl-estrone resulted in the specific dose-related loss of fat reserves with little change to other metabolic parameters. These results agree with the postulated role of oleoyl-estrone as a ponderostat signal.

Oral oleoyl-estrone induces the rapid loss of body fat in Zucker lean rats fed a hyperlipidic diet

OBJECTIVE

To test whether oleoyl-estrone affects body weight when given orally, which may help curtail the secondary growth-boosting effects of derived estrone.

DESIGN

The rats were fed for 15 days with a powdered hyperlipidic diet (16.97 MJ/kg metabolizable energy) in which 46.6% was lipid-derived and 16.1% protein-derived energy (HL group), containing 1.23+/-0.39micromol/kg of fatty-acyl esters of estrone. This diet was supplemented with additional oleoyl-estrone to produce diets with 2.5 micromol/kg (diet OE2.5), 4.4 micromol/kg (diet OE4.4), and 33.3 micromol/kg content in fatty-acyl estrone (diet OE33).

SUBJECTS

Twelve-week old female Zucker lean (Fa/?) rats initially weighing 200-235g.

MEASUREMENTS

Food intake and body weight changes; urine and droppings production and nitrogen content. Body composition (water, lipid, protein) and total energy. Energy and nitrogen balances. Plasma chemistry including free amino acids.

RESULTS

Oral administration of oleoyl-estrone in a hyperlipidic diet resulted in significant losses of fat, energy and, ultimately, weight, which were dependent on the dose of oleoyl-estrone ingested. Treatment induced the maintenance of energy expenditure combined with lower food intake, creating an energy gap that was filled with internal fat stores whilst preserving body protein. The decrease in food intake was not a consequence of food aversion but of diminished appetite. Energy expenditure was practically constant for all groups except for the OE33, which showed values about 25% lower than the controls. In most of the groups studied, there was a net protein deposition in spite of severe lipid and energy drainage. Amino acid levels agreed with this N-sparing shift. In spite of lowered energy intake, the N balance was positive or near zero in all groups, with a sizeable N-gap in controls and in lower-dose groups that disappeared in the OE33 group.

CONCLUSION

Treatment of rats with a hyperlipidic diet containing added oleoyl-estrone resulted in the dose-related loss of fat reserves with scant modification of other metabolic parameters and preservation of body protein. The results agree with the postulated role of oleoyl-estrone as a ponderostat signal and open the way for its development as anti-obesity drug.