MicroRNAs involved in the browning process of adipocytes

The present review focuses on the role of miRNAs in the control of white adipose tissue browning, a process which describes the recruitment of adipocytes showing features of brown adipocytes in white adipose tissue. MicroRNAs (miRNAs) are a class of short non-coding RNAs (19-22 nucleotides) involved in gene regulation. Although the main effect of miRNAs is the inhibition of the translational machinery, thereby preventing the production of the protein product, the activation of protein translation has also been described in the literature. In addition to modifying translation, miRNAs binding to its target mRNAs also trigger the recruitment and association of mRNA decay factors, leading to mRNA destabilization, degradation, and thus to the decrease in expression levels. Although a great number of miRNAs have been reported to potentially regulate genes that play important roles in the browning process, only a reduced number of studies have demonstrated experimentally an effect on this process associated to changes in miRNA expressions, so far. These studies have shown, by using either primary adipocyte cultures or experimental models of mice (KO mice, mice overexpressing a specific miRNA) that miR-196a, miR-26 and miR-30 are needed for browning process development. By contrast, miR-155, miR-133, miR-27b and miR-34 act as negative regulators of this process. Further studies are needed to fully describe the miRNA network-involved white adipose tissue browning regulation (AU)

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Erratum to: MicroRNAs involved in the browning process of adipocytes

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Limited beneficial effects of piceatannol supplementation on obesity complications in the obese Zucker rat: gut microbiota, metabolic, endocrine, and cardiac aspects

Resveratrol is beneficial in obese and diabetic rodents. However, its low bioavailability raises questions about its therapeutic relevance for treating or preventing obesity complications. In this context, many related natural polyphenols are being tested for their putative antidiabetic and anti-obesity effects. This prompted us to study the influence of piceatannol, a polyhydroxylated stilbene, on the prevention of obesity complications in Zucker obese rats. A 6-week supplementation was followed by the determination of various markers in plasma, liver, adipose tissue and heart, together with a large-scale analysis of gut microbiota composition. When given in doses of 15 or 45 mg/kg body weight/day, piceatannol did not reduce either hyperphagia or fat accumulation. It did not modify the profusion of the most abundant phyla in gut, though slight changes were observed in the abundance of several Lactobacillus, Clostridium, and Bacteroides species belonging to Firmicutes and Bacteroidetes. This was accompanied by a tendency to reduce plasma lipopolysaccharides by 30 %, and by a decrease of circulating non-esterified fatty acids, LDL-cholesterol, and lactate. While piceatannol tended to improve lipid handling, it did not mitigate hyperinsulinemia and cardiac hypertrophy. However, it increased cardiac expression of ephrin-B1, a membrane protein that contributes to maintaining cardiomyocyte architecture. Lastly, ascorbyl radical plasma levels and hydrogen peroxide release by adipose tissue were similar in control and treated groups. Thus, piceatannol did not exhibit strong slimming capacities but did limit several obesity complications (AU)

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Impact of intermittent hypoxia and exercise on blood pressure and metabolic features from obese subjects suffering sleep apnea-hypopnea syndrome

Strategies designed to reduce adiposity and cardiovascular-accompanying manifestations have been based on nutritional interventions conjointly with physical activity programs. The aim of this 13-week study was to investigate the putative benefits associated to hypoxia plus exercise on weight loss and relevant metabolic and cardiorespiratory variables, when prescribed to obese subjects with sleep apnea syndrome following dietary advice. The participants were randomly distributed in the following three groups: control, normoxia, and hypoxia. All the subjects received dietary advice while, additionally, normoxia group was trained under normal oxygen concentration and Hypoxia group under hypoxic conditions. There was a statistically significant decrease in fat-free mass (Kg) and water (%) on the control compared to normoxia group (p < 0.05 and p < 0.01, respectively). Body weight, body mass index, and waist circumference decreased in all the groups after the study. Moreover, leukocyte count was increased after the intervention in hypoxia compared to control group (p < 0.05). There were no statistically significant variations within groups in other variables, although changes in appetite were found after the 13-week period. In addition, associations between the variations in the leukocyte count and fat mass have been found. The hypoxia group showed some specific benefits concerning appetite and cardiometabolic-related measurements as exertion time and diastolic blood pressure, with a therapeutical potential

Effects of different doses of resveratrol on body fat and serum parameters in rats fed a hypercaloric diet

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Recently resveratrol, a compound naturally occurring in various plants, has been proposed as a potential anti-obesity compound. The aim of the present work was to analyse the effects of different doses of resveratrol on body fat and serum parameters in rats. Thirty-two male Sprague-Dawley rats were randomly divided into four groups and fed on a hypercaloric diet for 6 weeks. The doses oftrans-resveratrol used were 6, 30 and 60 mg/kg body weight/d in RSV1, RSV2 and RSV3 groups respectively. The stability of resveratrol when added to the diet was evaluated. Blood samples were collected, and white adipose tissue from different anatomical locations, interscapular brown adipose tissue, gastrocnemious muscles and liver were weighed. Commercial kits were used to measure serum cholesterol, glucose, triacylglycerols and non-esterified fatty acids. While the lowest dose did not have a body fat reducing effect, the intermediate dose reduced all the white adipose depots. The highest dose significantly reduced mesenteric and subcutaneous depots but not epididymal and perirenal tissues. Although the reduction in all the anatomical locations analysed was 19% in the RSV3 group, in the RSV2 group it was 24%. No significant differences among the experimental groups were found in brown adipose tissue, gastrocnemious muscle or liver weights. Serum parameters were not affected by resveratrol intake because no differences among the experimental groups were observed. These results suggest that resveratrol is a molecule with potential anti-obesity effect. The most effective of the three experimental doses was 30 mg/kg body weight/d (AU)

Influence of dietary macronutrient composition on adiposity and cellularity of different fat depots in Wistar rats

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The aim of this study was to investigate the role of dietary macronutrient content on adiposity parameters and adipocyte hypertrophy/hyperplasia in subcutaneous and visceral fat depots from Wistar rats using combined histological and computational approaches. For this purpose, male Wistar rats were distributed into 4 groups and were assigned to different nutritional interventions: Control group (chow diet); high-fat group, HF (60% E from fat); high-fat-sucrose group, HFS (45% E from fat and 17% from sucrose); and high-sucrose group, HS (42% E from sucrose). At day 35, rats were sacrificed, blood was collected, tissues were weighed and fragments of different fat depots were kept for histological analyses with the new softwareAdiposoft. Rats fed with HF, HFS and HS diets increased significantly body weight and total body fat against Control rats, being metabolic impairments more pronounced on HS rats than in the other groups. Cellularity analyses usingAdiposoft revealed that retroperitoneal adipose tissue is histologically different than mesenteric and subcutaneous ones, in relation to bigger adipocytes. The subcutaneous fat pad was the most sensitive to the diet, presenting adipocyte hypertrophy induced by HF diet and adipocyte hyperplasia induced by HS diet. The mesenteric fat pad had a similar but attenuated response in comparison to the subcutaneous adipose tissue, while retroperitoneal fat pad only presented adipocyte hyperplasia induced by the HS diet intake after 35 days of intervention. These findings provide new insights into the role of macronutrients in the development of hyperplastic obesity, which is characterized by the severity of the clinical features. Finally, a new tool for analyzing histological adipose samples is presented (AU)

Comparación entre los efectos de CLA y CLNA sobre la grasa corporal, parámetros séricos y composición del hígado / A comparison between CLNA and CLA effects on body fat, serum parameters and liver composition

The potential of conjugated linoleic acid (CLA) as an anti-obesity molecule forhumans is still a matter for debate. Thus, a great deal of scientific work is focussed onthe research of new effective molecules without deleterious effects on health. The aimof the present work was to analyse the effects of jacaranda seed oil, rich in a conjugatedlinolenic acid (CLNA), jacaric acid (cis-8,trans-10,cis-12), on body fat, serumparameters and liver composition in rats, and to compare these effects with those oftrans-10,cis-12 CLA. Twenty-six male Wistar rats were divided into three groups fedwith high-fat diets, supplemented or not (control group) with 0.5% trans-10,cis-12CLA (CLA group) or 0.5% jacaric acid (CLNA group) for 7 weeks. No statisticaldifferences in food intake or in final body weight were found. Whereas CLA reducedadipose tissue size, CLNA did not. Both CLA and CLNA significantly reduced non-HDL-cholesterol. In spite of a lack of significant changes in glucose and insulin levels,HOMA-IR index was significantly increased, as well as did non-esterified fattyacid levels in CLNA-fed rats. No changes in liver composition were observed. Inconclusion, under our experimental conditions, jacaric acid, unlike CLA, does notshow a body-fat lowering effect. Even though it leads to a healthy lipoprotein profile,it impairs insulin function. Consequently, it cannot be proposed as an anti-obesitymolecule(AU)

El potencial del ácido linoleico conjugado(CLA) como molécula anti-obesidad para sereshumanos sigue siendo una cuestión en debate.Por ello, gran cantidad de trabajos científicosse centra en la investigación de nuevas moléculaseficaces y sin efectos nocivos sobre la salud.El objetivo del presente trabajo fue estudiar, enrata, los efectos del aceite de semillas de jacaranda,rico en un ácido linolénico conjugado(CLNA), el ácido jacárico (cis-8,trans-10,cis-12), sobre la grasa corporal, parámetros séricosy la composición del hígado, y comparar estosefectos con los del trans-10,cis-12 CLA. Se utilizaron26 ratas Wistar macho divididas en tresgrupos que fueron alimentados durante 7semanas con dietas hipergrasas, suplementadaso no (grupo control) al 0,5% con el trans-10,cis-12 CLA (grupo CLA) o al 0,5% con elácido jacárico (grupo CLNA). No se encontrarondiferencias significativas en la ingesta dedieta, ni en el peso corporal final, ni en la composicióndel hígado. El CLA redujo la masaadiposa, pero no lo hizo el CLNA. Ambos disminuyeronsignificativamente el colesterol no-HDL. A pesar de la ausencia de cambios significativosen la glucemia e insulinemia, el índiceHOMA-IR y los niveles séricos de AGLaumentaron significativamente en las ratas alimentadascon CLNA. En conclusión, en nuestrascondiciones experimentales, el ácido jacárico,a diferencia del CLA, no muestra un efectoreductor de la grasa corporal. A pesar de quemejora el perfil de lipoproteínas, altera la funcióninsulínica. Por lo tanto, este CLNA nopuede ser propuesto como una molécula antiobesidad(AU)

Adiposity and serum parameters in hamsters fed energy restricted diets supplemented or not with trans-10, cis-12 conjugated linoleic acid

Numerous studies have demonstrated that conjugated linoleic acid (CLA) modulatesbody composition, reducing body fat accumulation in various mammalianspecies. However, very few studies have been carried out to assess the effect of CLAon previously stored body fat. The aim of the present work was to analyse the effectivenessof trans-10,cis-12 CLA in improving alterations produced by high-fat feedingin body fat and serum parameters when it was included in an energy-restricteddiet. For this purpose male Syrian Golden hamsters were fed on high-fat diet for 7weeks in order to increase their body fat content, and a further 25% energy-restricteddiet supplemented or not with 0.5% trans-10,cis-12 CLA for 3 weeks. Adipose tissues,liver and gastrocnemious muscles were dissected and weighed. Adipocyte diameterand number were assessed in epididymal adipose tissue. Total cholesterol, triacylglycerols,non-esterified fatty acids and glucose were measured in serum. Threeweeks of energy restriction resulted in a reduction in body weight and white adiposetissue size in all anatomical locations, without changes in liver and gastrocnemiousmuscle weights. Epididymal adipocyte size was reduced, but total adipocyte numberremained unchanged. Serum cholesterol, triacylglycerols and glucose were significantlyreduced. No differences were observed between the restricted groups (controland CLA supplemented). In conclusion, under our experimental conditions, theaddition of trans-10,cis-12 CLA to the diet does not increase the benefits producedby energy restriction (AU)

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Expanding role for the apelin/APJ system in physiopathology

Apelin is a bioactive peptide known as the ligand of the G protein-coupled receptorAPJ. Diverse active apelin peptides exist under the form of 13, 17 or 36 aminoacids, originated from a common 77-amino-acid precursor. Both apelin and APJmRNA are widely expressed in several rodent and human tissues and have functionaleffects in both the central nervous system and peripheral tissues. Apelin has beenshown to be involved in the regulation of cardiovascular functions, fluid homeostasis,vessel formation and cell proliferation. More recently, apelin has been describedas an adipocyte-secreted factor (adipokine), up-regulated in obesity. By acting as circulatinghormone or paracrine factor, adipokines are involved in physiological regulations(fat depot development, energy storage, metabolism or eating behavior) or inthe promotion of obesity-associated disorders (type 2 diabetes and cardiovasculardysfunctions). In this regard, expression of apelin gene in adipose tissue is increasedby insulin and TNFalpha. This review will consider the main roles of apelin in physiopathologywith particular attention on its role in energy balance regulation and inobesity-associated disorders (AU)

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Adiposity and serum parameters in hamsters fedenergy restricted diets supplemented or not withtrans-10, cis-12 conjugated linoleic acid

Numerous studies have demonstrated that conjugated linoleic acid (CLA) modulatesbody composition, reducing body fat accumulation in various mammalianspecies. However, very few studies have been carried out to assess the effect of CLAon previously stored body fat. The aim of the present work was to analyse the effectivenessof trans-10,cis-12 CLA in improving alterations produced by high-fat feedingin body fat and serum parameters when it was included in an energy-restricteddiet. For this purpose male Syrian Golden hamsters were fed on high-fat diet for 7weeks in order to increase their body fat content, and a further 25% energy-restricteddiet supplemented or not with 0.5% trans-10,cis-12 CLA for 3 weeks. Adipose tissues,liver and gastrocnemious muscles were dissected and weighed. Adipocyte diameterand number were assessed in epididymal adipose tissue. Total cholesterol, triacylglycerols,non-esterified fatty acids and glucose were measured in serum. Threeweeks of energy restriction resulted in a reduction in body weight and white adiposetissue size in all anatomical locations, without changes in liver and gastrocnemiousmuscle weights. Epididymal adipocyte size was reduced, but total adipocyte numberremained unchanged. Serum cholesterol, triacylglycerols and glucose were significantlyreduced. No differences were observed between the restricted groups (controland CLA supplemented). In conclusion, under our experimental conditions, theaddition of trans-10,cis-12 CLA to the diet does not increase the benefits producedby energy restriction (AU)

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Expanding role for the apelin/APJ systemin physiopathology

Apelin is a bioactive peptide known as the ligand of the G protein-coupled receptorAPJ. Diverse active apelin peptides exist under the form of 13, 17 or 36 aminoacids, originated from a common 77-amino-acid precursor. Both apelin and APJmRNA are widely expressed in several rodent and human tissues and have functionaleffects in both the central nervous system and peripheral tissues. Apelin has beenshown to be involved in the regulation of cardiovascular functions, fluid homeostasis,vessel formation and cell proliferation. More recently, apelin has been describedas an adipocyte-secreted factor (adipokine), up-regulated in obesity. By acting as circulatinghormone or paracrine factor, adipokines are involved in physiological regulations(fat depot development, energy storage, metabolism or eating behavior) or inthe promotion of obesity-associated disorders (type 2 diabetes and cardiovasculardysfunctions). In this regard, expression of apelin gene in adipose tissue is increasedby insulin and TNFá. This review will consider the main roles of apelin in physiopathologywith particular attention on its role in energy balance regulation and inobesity-associated disorders (AU)

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Effects of trans-10, cis-12 conjugated linoleic acid on body fat and serum lipids in young and adult hamsters

The aim of the present work was to determine whether t-10, c-12 conjugated linoleic acid (CLA) feeding was able to reduce body fat accumulation and improve the serum lipid profile in adult hamsters fed an atherogenic diet, in order to compare these effects with those observed in young growing hamsters. Young and adult hamsters were fed semi-purified atherogenic diets supplemented with 0.5% linoleic acid or 0.5% t-10, c-12 CLA for 6 weeks. Body weight and food intake were measured every two days. Adipose tissue from different anatomical locations, liver and gastrocnemious muscle were dissected and weighed. Cholesterol, triacylglycerols, non-esterified fatty acids and proteins were determined spectrophotometrically and water content by gravimetry. In young hamsters, no significant differences were found in food intake, final body weight and gastrocnemious muscle weight. White adipose tissue weights were reduced, liver weight was increased and cholesterol and triacylglycerols in both serum and liver were reduced. In adult hamsters, CLA feeding decreased food intake and adipose tissue weights. No changes were observed in other parameters. The present study demonstrates that age has an influence in hamster responsiveness to t-10, c-12 CLA because, although when this isomer is added to an atherogenic diet it reduces body fat accumulation in both young and adults hamsters, the lessening of the effects on serum lipids brought about by atherogenic feeding is only observed in young animals. Moreover, it is clear that liver is a target for CLA in young but not in adult hamsters (AU)

El objetivo del presente estudio fue determinar si el isómero t-10, c-12 del ácido linoleico conjugado (ALC) era capaz de reducir la acumulación de grasa corporal y de mejorar el perfil lipídico en hámsteres adultos alimentados con una dieta aterogénica, con el fin de compararlos con los observados en hámsteres jóvenes en crecimiento. Los animales se alimentaron con dietas aterogénicas suplementadas con 0,5% de ácido linoleico ó 0,5% de ALC t-10, c-12 durante 6 semanas. Se midió cada dos días la ingesta de alimento y el peso corporal. Se diseccionaron y pesaron tejidos adiposos de diferentes localizaciones anatómicas, el hígado y los dos músculos gastrocnemios. El colesterol, los triglicéridos, los ácidos grasos libres y las proteínas se valoraron espectrofotométricamente ricamente y el agua por gravimetría. En los animales jóvenes no se observaron diferencias significativas en la ingesta, el peso corporal final y el peso de los músculos gastrocnemios. Los pesos de los tejidos adiposos blancos se redujeron, el peso de hígado aumentó y el colesterol y los triglicéridos disminuyeron, tanto en suero como en higado. En hámsteres adultos, el ALC disminuyó la ingesta y los pesos de los tejidos adiposos, pero no se observaron cambios en los demás parámetros. El presente estudio demuestra que la edad influye en la respuesta del hámster al ALC t-10, c-12 porque, aunque al ser anadido a una dieta aterogénica reduce la grasa corporal tanto en animales jóvenes como adultos, la atenuación de los efectos de esta dieta sobre los lípidos séricos sólo se pone de manifiesto en los jóvenes. Además, sólo en estos últimos, el hígado es claramente una diana para el ALC (AU)

The body fat-lowering effect of conjugated linoleic acid: a comparison between animal and human studies

Different reasons which justify differences between rodents and humans in body fat reduction produced by conjugated linoleic acid (CLA) could be proposed. The doses used in humans are lower then those used in rodents. Human experiments have been performed with CLA isomer mixtures instead of isolated isomers. The variable dilution of t-10, c-12, the active isomer, among different preparations might explain the reduced responsiveness in humans. Diet composition may modulate CLA effects on body fat accumulation. As far as human studies are concerned, a specific dietary pattern has not been established. As a result differences among studies and also among subjects in the same study are likely. In rodents, the effects of CLA vary with genotype, suggesting that genetic predisposition to fat accumulation can play an important role in the effectiveness of CLA. Human volunteers with different body mass index have participated in the published studies and even in the same experiment. So, differences in lipid metabolism among subjects could help to explain the discrepancies observed in the literature. Age and maturity may also be crucial. Experiments using rodents have been conducted with growing animals and there is little evidence of CLA effectiveness in adult animals. By contrast, human studies have been performed with adults. Inhibition of lipogenesis in white adipose tissue is one of the mechanisms which have been proposed to explain the body-fat lowering effect of CLA, but lipogenesis in this tissue is very low in humans. Another mechanism suggested is increased fatty acid oxidation in the liver associated with peroxisome proliferation, but humans are relatively insensitive to this effect (AU)

Se pueden proponer diferentes razones para justificar las diferencias en el efecto reductor de la grasa corporal inducido por ácido linoleico conjugado (ALC) entre roedores y humanos. Las dosis utilizadas en humanos son menores que las empleadas en roedores. Además, en humanos se suelen utilizar mezclas de isómeros de ALC en lugar de isómeros aislados. La dilución variable del isómero activo, t-10, c-12, en las distintas mezclas podría explicar la baja respuesta observada en los humanos. La composición de la dieta puede modular los efectos del ALC. En los estudios con humanos no se establece un patrón de alimentación concreto y específico, lo que hace probables las diferencias entre estudios, e incluso entre los individuos de un mismo estudio. Los estudios en roedores han puesto de manifiesto que los efectos del ALC varían con el genotipo del animal, lo que sugiere que la eficacia del ALC puede depender de la predisposición del individuo a la acumulación de grasa corporal. En los estudios con humanos han participado individuos con distintos valores de índice de masa corporal, incluso en un mismo estudio. Por tanto, las diferencias en el metabolismo lipídico entre los distintos individuos pueden ayudar a explicar las discrepancias encontradas en la bibliografía. La edad y el estado de maduración pueden (..) (AU)

Body fat-lowering effect of conjugated linoleic acid is not due to increased lipolysis

The ability of conjugated linoleic acid (CLA) to reduce adiposity may be due to changes in energy expenditure and/or direct effects on adipocyte lipid metabolism. The aim of the present work was to analyse if CLA supplementation modifies lipolytic activity in adipose tissue from hamsters fed on high-fat diet. Hamsters were divided into two groups and fed on diets supplemented with either 0.5% linoleic acid (control) or 0.5% trans-10,cis-12 CLA. After 6 weeks, animals were fasted overnight and adipose tissues were dissected and weighed. Adipocytes were isolated by collagenase digestion and incubated in Krebs-Ringer bicarbonate buffer with or without several agents acting at different levels of the lipolytic cascade. Adipocyte diameters were measured by microscopy. Adipose tissue DNA content was assessed by spectrophotometry. Animals fed on CLA diet showed significantly reduced adipose tissue mass. No differences between both groups was found for basal lipolysis, lipolytic effects of isoproterenol, forskolin, dibutyryl-cAMP and isobutylmethylxanthine, and pD2 for isoproterenol. A similar total DNA amount was found in adipose tissue of both groups, showing that CLA diet had no effect on total cell number per fat pad. Although DNA content per gram tissue, an indirect reverse index of cell size, was significantly increased in CLA fed hamsters, microscopy did not reveal differences in medium mature adipocyte diameter, nor in cell size distribution between both groups. These results suggest that adipose tissue size reduction induced by trans-10,cis-12 CLA intake is not due to changes in lipolysis. Reduced preadipocyte differentiation into mature adipocytes may account for this fat-lowering effect

La capacidad del ácido linoleico conjugado (ALC) para reducir la adiposidad puede deberse a cambios en el gasto energético y/o a efectos directos sobre el metabolismo lipídico de los adipocitos. En el presente trabajo se estudia si la ingestión de ALC modifica la actividad lipolítica del tejido adiposo en hámsters alimentados con una dieta hipergrasa. Los animales se divididieron en dos grupos y alimentaron durante 6 semanas con dietas suplementadas al 0,5% con ácido linoleico (control) o con el isómero trans-10,cis-12 del ALC, respectivamente. Los animales se sacrificaron tras una noche de ayuno y, previa disección se pesaron sus depósitos adiposos. Los adipocitos se aislaron mediante digestión con colagenasa y se incubaron en tampón Krebs-Ringer bicarbonato sin y con varias sustancias que actúan a diferentes niveles de la cascada lipolítica. Se midieron sus diámetros medios mediante microscopía y se determinó el contenido en DNA del tejido adiposo por espectrofotometría. Los animales que ingirieron ALC presentaron una reducción del tamaño de los depósitos adiposos. No se encontraron diferencias significativas entre ambos grupos en la lipolisis basal, en los efectos lipolíticos del isoproterenol, forscolina, dibutiril-cAMP e isobutilmetilxantina, ni en la pD2 del isoproterenol. El contenido total de DNA del tejido adiposo fue similar en ambos grupos, lo que indica que el ALC no afectó al número total de adipocitos por depósito adiposo. Aunque el contenido de DNA por gramo de tejido, un índice inverso del tamaño celular, aumentó significativamente, el análisis microscópico no mostró diferencias en el diámetro medio de los adipocitos maduros ni en su distribución por tamaño celular. Estos resultados sugieren que la reducción del tamaño del tejido adiposo inducida por la ingestión de ALC no se debe a cambios en la lipolisis, sino posiblemente a una menor diferenciación de los preadipocitos a adipocitos maduros

Papel de las proteínas desacoplantes en la obesidad / Role of uncoupling proteins in obesity

El descubrimiento de una proteína de la membrana mitocondrial interna de adipocitos marrones, la UCP1, supuso un importante avance en el conocimiento del proceso termogénico, así como del funcionamiento del tejido adiposo marrón. Esta proteína es sólo importante en neonatos y animales pequeños, no obstante el posterior hallazgo de proteínas análogas a la UCP1 (UCP2, ampliamente distribuida, y UCP3, presente principalmente en músculo) con un funcionamiento similar y presentes también en tejido humano, creó nuevas perspectivas y objetivos científicos. Estas proteínas desacoplan la cadena respiratoria de la fosforilación oxidativa, disipando así energía en forma de calor sin que se produzca ATP, mediante un mecanismo aún debatido. De los estudios de regulación realizados trasciende que su actividad se ve modificada ante distintos estímulos fisiológicos y nutricionales, observándose una mayor actividad de las mismas en situaciones en las que se requiere un aumento del gasto energético. Los estudios realizados en humanos parecen corroborar los resultados obtenidos en la experimentación con animales, por lo que podría plantearse la actuación sobre la actividad o la cantidad de estas proteínas en humanos como medio para combatir el sobrepeso y la obesidad. Sin embargo, existe aún una evidente necesidad de completar y mejorar la información existente acerca de la importancia de estas proteínas transportadoras de protones en humanos. (AU)

Efectos de la administración de fluoxetina en el peso corporal y el gasto energético en ratas obesas / Effects of fluotexine administration on body weight and energy expenditure in obese rats

La fluoxetina es un inhibidor selectivo de la recaptación de serotonina, que ha demostrado producir una reducción de peso en ratas magras. El objetivo del presente trabajo fue estudiar la eficacia de un tratamiento crónico con este fármaco en ratas Zucker obesas y analizar la posible implicación de un efecto termogénico en su mecanismo de acción. Los animales, ratas Zucker fa/fa, fueron tratados durante 14 días con fluoxetina (10 mglkgld) administrada por vía intraperitoneal. Cada día se midió el consumo de oxígeno en los animales durante la hora anterior a la administración del fármaco y durante los 90 minutos posteriores. Tras el sacrificio de los animales, se pesaron los depósitos adiposos de diferentes localizaciones anatómicas (interescapular, subcutánea, perirrenal, epididimal) y el músculo gastrocnemio y se midió el consumo de oxígeno en tejido adiposo marrón interescapular y en músculo soleus. El tratamiento redujo de forma significativa la ingesta de alimento y el peso corporal de los animales. El efecto se hizo patente no sólo en los depósitos adiposos, sino también en el músculo gastrocnemio. Dado que el fármaco no modificó el consumo de oxígeno, ni en animal entero ni en los dos tejidos estudiados, se puede concluir que la reducción de peso que produjo se debió exclusivamente a su efecto anorexígeno (AU)