R. M. Masanés

Oleoyl-estrone treatment affects the ponderostat setting differently in lean and obese Zucker rats

OBJECTIVE: To determine whether the slimming effects of treatment with oleoyl-estrone (OE) in liposomes of normal and obese rats are permanent, or disappear as soon as the treatment with the drug ceased. This study was devised to gain further knowledge on the postulated role of OE as a ponderostat signal, evaluating whether (in addition) it can lower the ponderostat setting of the rat.DESIGN: The rats were infused for 14 d (using osmotic minipumps) with oleoyl-estrone in liposomes at a dose of 3.5 μmol/kg· ·d, and were studied up to one month after the treatment ceased.SUBJECTS: Young adult lean controls (CL) or treated (TL) and obese controls (CO) or treated (TO) Zucker rats.MEASUREMENTS: Energy balance, blood glucose, liver glycogen, plasma insulin, leptin corticosterone, ACTH and estrone (free and total) concentrations, and expression of the OB gene in white adipose tissue (WAT).RESULTS: The loss of body weight caused by OE was recovered quickly in the TO, which gained weight at the same rate as the CO. TL rats, however remained at the low weight attained for one month after the treatment ceased. However, no differences were observed in calculated energy expenditure (EE) between the TL and TC rats once treatment had stopped. In TL and TO rats, liver glycogen concentrations decreased to normal shortly after treatment ceased, and leptin expression and concentrations remained normal and unchanged after the end of OE treatment. In TO rats, plasma glucose, insulin and leptin were lower than in the CO. Total estrone concentrations decreased rapidly in TL rats and more slowly in the TO, and free estrone followed a similar pattern.CONCLUSION: Continuous infusion of liposomes loaded with OE resulted in a decreased energy intake (EI), maintenance of EE and the utilization of body fat reserves in lean and obese rats alike. This process ended in obese rats as soon as the infusion ceased, so that even when the levels of free and total estrone in plasma remained high, there was a marked (and relatively fast) shift toward the basal situation, which translated into an increase in EI, maintenance of estimated EE and a marked buildup of energy stores. In lean rats, the effects of OE on leptin concentrations and OB gene expression persisted after infusion ended.

Oral gavage of oleoyl-oestrone has a stronger effect on body weight in male Zucker obese rats than in female.

This study was carried out to determine the effect of sex and oral administration of oleoyl‐oestrone on body weight of 12‐week‐old female and male Zucker obese (fa/fa) rats initially weighing 350–380 g and 405–420 g, respectively. The rats were maintained in standard conditions and given a daily oral gavage of 0.2 ml oleoyl‐oestrone dissolved in sunflower oil at a dose of 10 μmol/kg/day for 10 days, and their body weight and food intake was monitored. They were then killed, and their carcass composition (water, lipid, protein and total energy), liver lipids and glycogen and plasma chemistry, insulin, free and total oestrone were measured. Oral administration of oleoyl‐oestrone via gavage resulted in significant losses of fat, energy and–ultimately–weight. Treatment with oleoyl‐oestrone decreased food intake; the energy expenditure was kept close to that of controls at the expense of internal fat stores. Nevertheless, body protein and plasma metabolite homeostasis were preserved. The slimming effects were more marked in males than in females. Treatment increased circulating acyl‐oestrone and reduced to normal levels the high insulin observed in controls. Treatment of genetically obese rats with a daily oral gavage of oleoyl‐oestrone resulted in the loss of fat reserves with little modification of other metabolic parameters, except for lower plasma glucose and insulin levels. The results suggest that oleoyl‐oestrone, in addition to its slimming effects may be effective as an antidiabetic agent in type 2 diabetes.

EFFECT OF DIETARY PROTEIN CONTENT ON TISSUE PROTEIN SYNTHESIS RATES IN ZUCKER LEAN RATS

Abstract Protein synthesis rates were determined in representative tissues of lean Zucker rats fed diets containing varying amounts of protein for 30 days. The control group (RD) received a standard commercial diet (20% of protein-derived energy), the high protein group (HP) received a high protein diet (36% of protein-derived energy) and the hypoproteic group (LP) received a low protein diet (9.5% of protein-derived energy). The contribution of skin and skeletal muscle to the whole body weight is higher in Zucker lean rats than in other rat strains. In all dietary groups the tissues with the highest fractional protein synthesis rates were the small intestine, kidney and liver, followed by lungs, skin and finally muscle. The HP group showed significantly lower protein synthesis in the muscle and skin than the RD group; the LP group showed lower rates in skin, small intestine, kidneys and lungs. The data presented indicate that the adaptations to a diet rich in protein did not affect the rate of protein synthesis, and also that the limited availability of protein reduced the rate of protein synthesis in some visceral organs but not in the skeletal muscle nor the skin. This implies that nitrogen partitioning is adapted to protein availability in the diet.

Plasma acyl-estrone levels are altered in obese women.

A group of obese women (BMI>27 kg/m2; N=73) was studied together with lean controls (BMI <27 kg/m2; N=25). Three groups were defined by the compliance with: BMI lower than 27 kg/m2, glycaemia lower than 5.5 mM and insulinaemia lower than 0.2 nM (controls, group 1, N=19). The subjects with BMI>27 kg/m2, glucose >5.5 mM and insulin >0.2 nM constituted group 3 (N=41), and those with BMI>27 with glycaemia and/or insulinaemia lower than the limits set constituted group 2 (N=32). The women in group 3 had higher fat content, BMI and fat-free mass than those in group 2 and the controls. There were no changes in most plasma parameters, such as free estrone and β-estradiol. Leptin levels were higher in groups 2 and 3 than in controls. In controls, leptin and acyl-estrone levels were well correlated with BMI and fat content; this correlation was not found in groups 2 and 3 for acyl-estrone, although it was found for leptin. Acyl-estrone levels were lower than expected in most obese women when compared to those of controls, suggesting an altered availability or function of this hormone. In obese women, acyl-estrone levels –and probably function– are lower than expected, contrasting with maintained leptin-BMI correlations. The role of insulin in the control of body weight, perhaps through acyl estrone-mediated effects, should be re-evaluated.

Short-term treatment with estrone oleate in liposomes (Merlin-2) does not affect the expression of the ob gene in Zucker obese rats

Young female Zucker fa/fa rats of 370-430 g were implanted with osmotic minipumps releasing 3.5 μmol/dayúkg of estrone oleate in liposomes (Merlin-2) into the bloodstream for up to 14 days. Merlin-2 induced a sustained loss of appetite, and a decrease in body weight of 3.5%, which contrasts with the 8.2% increase in controls during the period studied. Plasma insulin, glucose and urea decreased, and liver glycogen increased with Merlin-2 treatment. Plasma ACTH and corticosterone increased to a maximum at the end of the experiment. The expression of the ob gene in adipose tissue was unchanged, and plasma leptin levels were also unchanged by treatment. Estrone levels increased more than 1500-fold, and estrone oleate rose 100-fold during treatment. The fact that estrone oleate had no effect on the leptin levels or expression in obese rats, in contrast with the marked inhibition observed in the lean suggests that the functionality of the leptin receptor is essential for estrone oleate inhibition of the ob gene. This also suggests that leptin may control ob gene expression in white adipose tissue and that estrone oleate may activate this process. The slimming effect of estrone oleate is, thus, not directly dependent on leptin, since both normoleptinemic and hyperleptinemic animals lose fat following treatment nor are the effects on appetite and energy expenditure mediated by leptin. However, leptin levels and the expression of the ob gene are directly linked with estrone oleate function. A possible involvement of leptin in estrone oleate action is postulated. The results support the participation of estrone oleate in the control of body weight and hint at the complexity of its regulation by leptin and glucocorticoids.

Effect of food deprivation on rat plasma estrone fatty acid esters

The present study was devised to determine whether the circulating levels of estrone fatty esters are modified by 6–48 h starvation in the rat, in parallel to changes in fat reserves, as a test to check the plausibility of its function as a ponderostat signal in the mammal. Food deprivation resulted in a decrease in glucose and triacylglycerols, rapid disappearance of liver glycogen and increases in fatty acids and, especially, 3‐hydroxybutyrate. Insulin and leptin decreased, corticosterone and free estrone increased from 6 h onwards and total estrone levels were maintained. Starvation reduced the lipid content of the rat by 25.6%. Plasma esterified estrone levels decreased more slowly, by 13% in 48 h, but its circulating mass decreased in the same proportion as the total lipid content of the rat. The small change in circulating estrone fatty esters is consistent with the postulated role of oleoyl‐estrone as a medium‐term ponderostat signal.

Changes in UCP expression in tissues of Zucker rats fed diets with different protein content.

The effect of dietary protein content on the uncoupling proteins (UCP) 1, 2 and 3 expression in a number of tissues of Zucker lean and obese rats was studied. Thirty-day-old male Zucker lean (Fa/?) and obese (fa/fa) rats were fed on hyperproteic (HP, 30% protein), standard (RD, 17% protein) or hypoproteic (LP, 9% protein) dietsad libitum for 30 days. Although dietary protein intake affected the weights of individual muscles in lean and obese animals, these weights were similar. In contrast, huge differences were observed in brown adipose tissue (BAT) and liver weights. Lean rats fed on the LP diet generally increased UCP expression, whereas the HP group had lower values. Obese animals, HP and LP groups showed higher UCP expression in muscles, with slight differences in BAT and lower values for UCP3 in subcutaneous adipose tissue. The mean values of UCP expression in BAT of obese rats were lower than in their lean counterpart, whereas the expression in skeletal muscle was increased. Thus, expression of UCPs can be modified by dietary protein content, in lean and obese rats. A possible thermogenic function of UCP3 in muscle and WAT in obese rats must be taken into account.ResumenSe determina el efecto de cambios moderados en el contenido proteico de la dieta sobre la expresión de las proteínas desacoplantes 1, 2 y 3 en distintos tejidos de la rata Zucker. A ratas Zucker macho de 30 días de edad, tanto delgadas (Fa/?) como obesas (fa/fa), se les administraad libitum una dieta hiperproteica (HP, 30% de contenido proteico), estándar (RD, 17% de contenido proteico) o hipoproteica (LP, 9% de contenido proteico) durante 30 días. Los pesos de los músculos individuales son similares en los animales delgados y en los obesos, aunque ligeramente influenciados por el tipo de dieta; este hecho contrasta con las grandes diferencias detectadas en el hígado y en el tejido adiposo marrón. Los animales delgados alimentados con dieta LP incrementan la expresión de las UCP, mientras que los alimentados como dieta HP muestran valores más bajos. Los animales obesos, tanto los alimentados con dieta LP como con dieta HP, muestran una mayor expresión de UCP en músculo, con pequeñas diferencias en el tejido adiposo marrón y valores muy bajos para la UCP3 en el tejido adiposo subcutáneo. Los valores promedio de la expresión de UCP en el tejido adiposo marrón de las ratas obesas son menores de los de las ratas delgadas, mientras que la expresión en los músculos es superior. Así, la expresión de las UCP puede ser modificada por la ingesta crónica de dietas con dstinto contenido proteico, tanto en ratas delgadas como obesas. Se debe considerar el posible papel termogénico de la UCP3 en el músculo y en el tejido adiposo blanco de las ratas obesas.

Modulation of muscle UCP expression by oleoyl-estrone in the rat

The aim of this study was to determine wether the maintenance of thermogenesis induced by oleoyl-estrone was mediated by modulation of the expression of UCPs. Female adult Zucker lean rats(220-230 g) were used. Osmotic minipumps were inserted under the skin on the rats and connected to the left jugular vein. They delivered a lipid dropled suspension containing oleoyl-estrone (3.5 mmol/kg day, treated) or only the vehicle (control animals). Two weeks after the implantation of the pumps, samples of interscapular brown adipose tissue (BAT) and muscles extensor digitorum longus, tibialis anterior and soleus were obtained and UCP1, UCP2 and UCP3 mRNAs determined by Northern blot. Oleoyl-estrone treatment does not modify UCP1 or UCP2 expression and provokes significant changes in UCP3 expression: increases in BAT and the red-fibre soleus muscle, decreases in the white and red-fibre tibialis anterior muscle and remains unchanged in the white- fibre extensor digitorum longus muscle.

Alteraciones hormonales en mujeres jóvenes con obesidad mórbida

Fundamento La obesidad humana es una enfermedad de amplia distribucion que presenta una considerable variabilidad en su gravedad, manifestaciones metabolicas y endocrinas y etiologia. En el presente estudio hemos determinado si en mujeres adultas jovenes la obesidad morbida sin complicaciones afecta con diferente intensidad los valores circulantes de hormonas que se ha postulado que intervienen en el desarrollo y mantenimiento de la obesidad. Sujetos y metodo Se estudiaron y determinaron los valores circulantes medios (desviacion estandar [DE]) de las hormonas y proteinas relacionadas con el control del peso corporal en 20 mujeres obesas morbidas (indice de masa corporal, 52,6 [8,3] kg/m2) y 10 controles de peso normal (indice de masa corporal 19,9 [2,1] kg/m2) de edades similares. Resultados En las mujeres obesas se evidenciaron concentraciones mas altas de insulina y leptina, y mas bajas de cortisol y de la globulina que se une al cortisol (CBG). No se apreciaron diferencias para la tiroxina libre, hormona estimuladora del tiroides, estrona libre, acilestrona y sulfato de deshidroepiandrosterona. Conclusiones Los resultados indican que la obesidad morbida implica la alteracion de los principales sistemas hormonales que controlan la disponibilidad de energia y la respuesta a los retos externos, con la notable excepcion del tiroides. Hay claras alteraciones en la insulina y leptina mientras que los cambios en el cortisol pueden estar correlacionados con factores distintos a la obesidad. Los valores de acilestrona menores de lo esperado apuntan a un posible deficit de esta senal de ponderostato en las mujeres obesas. La edad relativamente joven de las mujeres del estudio puede ayudar a explicar la relativa suavidad de los cambios hormonales observados.

Absorption of a protein gavage in Zucker lean rats. Influence of protein content in the diet.

The rate of protein absorption was measured in Zucker lean rats. Rats were fed with a bolus that contained ca. 300 mg of 14 C-labelled protein at the beginning of the light cycle. Blood was extracted from the portal vein at intervals up to 9 hours after gavage. Label incorporation into tissue protein was monitored. The digestion and absorption of protein was slow, and 9 hours after the gavage, 20% of the bolus remained in the stomach. Forty percent of the protein was absorbed in the first hour. This was followed first by a linear absorption process, then by the amino acid incorporation into tissue proteins. The appearance of label in the portal vein increased progressively for up to four hours, shifting to a progressive decrease that coincides with the maintenance of this label in the tissues. The skin, the striated muscle and the liver showed the highest amounts of labelled proteins. The application of this model to animals fed low-(LP) or high-protein (HP) content diets showed that the HP group digested the protein faster than the LP group, and that catabolism of the amino acids was higher in the HP group. The LP group digested protein much more slowly than the RD (control) group, but protein accretion was more efficient.