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Supplementation with the prebiotic pectin is associated with beneficial health effects. We aimed to characterize the cardioprotective actions of chronic high-esterified pectin (HEP) supplementation (10%) in a model of metabolic malprogramming in rats, prone to obesity and associated disorders: the progeny of mild calorie-restricted dams during the first half of pregnancy. Results show that pectin supplementation reverses metabolic malprogramming associated with gestational undernutrition. In this sense, HEP supplementation improved blood pressure, reduced heart lipid content, and regulated cardiac gene expression of atrial natriuretic peptide and lipid metabolism-related genes. Moreover, it caused an elevation in circulating levels of fibroblast growth factor 21 and a higher expression of its co-receptor β-klotho in the heart. Most effects are correlated with the gut levels of beneficial bacteria promoted by HEP. Therefore, chronic HEP supplementation shows cardioprotective actions, and hence, it is worth considering as a strategy to prevent programmed cardiometabolic alterations.

Evaluation of the performance of a new set of primers defined from the ORF1absequence, and its combination with a previously published set of primers from the Nsequence, to detect SARS-CoV-2 RNA by the loop-mediated isothermal amplification technique is presented. The ORF1abprimer set enables visual detection of SARS-CoV-2 RNA in 16 min. In addition, a simultaneous reaction with both ORF1aband Nprimers allows for higher sensitivity of detection, particularly when low numbers of copies are present (250 viral RNA copies). Further, the protocol is able to detect viral RNA in saliva samples. The procedure reported could be easily implemented in the generation of a new and sensitive rapid point-of care device for SARS-CoV-2 RNA visual detection.

Detrimental metabolic programming has become a determinant factor in obesity propensity and the development of metabolic disorders; therefore, the search of nutritional strategies to reverse it is very relevant. Pectin is a prebiotic with health-promoting effects, such as control of glucose homeostasis and lipid metabolism, although other possible health effects and the prevention of obesity have been poorly studied. We studied the effects of chronic physiological supplementation with high-esterified pectin (HEP) in the reversion of metabolic nutrition-sensitive malprogramming associated with gestational undernutrition. As a model of nutrition-sensitive malprogramming, we used the progeny of rats with mild calorie restriction (CR) during pregnancy and analyzed their performance under metabolic stress (high-sucrose diet). We focused on the study of the sensitivity to the main adipostatic/adipokine hormones, i.e., leptin, insulin, and adiponectin, at both peripheral (liver and circulating parameters) and central (hypothalamus) levels. Our main findings suggest that chronic HEP supplementation is able to prevent weight/fat gain, to substantially reverse the detrimental malprogramming caused by the CR condition, to improve general health circulating markers, to modulate oxidative/lipogenic balance in the liver and energy metabolism regulators in the hypothalamus, and to restore/improve adipostatic/adipokine sensitivity affected by maternal calorie restriction, both peripherally and centrally. HEP stands out as a food component potentially useful against the development of metabolic disorders and obesity.

We explored the potential of hesperidin and capsaicin, separately and in combination, to induce white adipose tissue (WAT) browning and to help body weight management in Western diet-fed rats. Adult male Wistar rats were fed for 8 weeks with Western diet and treated daily with hesperidin (100 mg/kg/day), capsaicin (4 mg/kg/day), hesperidin (100 mg/kg/day) + capsaicin (4 mg/kg/day), or the vehicle. Hesperidin and capsaicin separately, but not (or to a lesser extent) the combination, resulted in a decreased size of adipocytes and induced emergence of multilocular brown-like adipocytes positive for UCP1 and CIDEA in retroperitoneal WAT. Expression levels of browning markers, such as Prdm16, in inguinal WAT also increased with capsaicin treatment compared with the vehicle (145% ± 17% vs 92% ± 21%, P< 0.05), but no significant effects were found with the combination (106% ± 12%). Thus, the combination of both bioactives reduces the effectiveness of each compound to decrease the adipocyte size and induce WAT browning.

A positive effect of all-transretinoic acid (ATRA) on white adipose tissue (WAT) oxidative and thermogenic capacity has been described and linked to an in vivo fat-lowering effect of ATRA in mice. However, little is known about the effects of ATRA on mitochondria in white fat. Our objective has been to characterize the effect of ATRA on mitochondria biogenesis and oxidative phosphorylation (OXPHOS) capacity in mature white adipocytes. Transcriptome analysis, oxygraphy, analysis of mitochondrial DNA (mtDNA), and flow cytometry-based analysis of mitochondria density were performed in mature 3T3-L1 adipocytes after 24 h incubation with ATRA (2 µM) or vehicle. Selected genes linked to mitochondria biogenesis and function and mitochondria immunostaining were analyzed in WAT tissues of ATRA-treated as compared with vehicle-treated mice. ATRA upregulated the expression of a large set of genes linked to mtDNA replication and transcription, mitochondrial biogenesis, and OXPHOS in adipocytes, as indicated by transcriptome analysis. Oxygen consumption rate, mtDNA content, and staining of mitochondria were increased in the ATRA-treated adipocytes. Similar results were obtained in WAT depots of ATRA-treated mice. We conclude that ATRA impacts mitochondria in adipocytes, leading to increased OXPHOS capacity and mitochondrial content in these cells.

Recent findings in animals suggest that diet-related factors can programme adipose tissue features in early life and remodel white adipose tissue (WAT) towards a brown adipose tissue (BAT)-like phenotype in adulthood, while impacting on body fat content and susceptibility to obesity. The purpose of this review is to address the significance of these results and their applicability in humans.

Obesity and degenerative joint disease (osteoarthritis, OA) are two multifactorial pathologies that are becoming major medical issues with the aging of the world population. The relationship of OA with obesity is complex, involving both biomechanical and metabolic links. Dysregulated production of adipose tissue-derived inflammatory mediators, hyperlipidemia, and increased systemic oxidative stress are conditions frequently associated with obesity that may favor joint degeneration. In addition, it is remarkable that many regulatory factors have been implicated in the development, maintenance and function of both adipose tissues and cartilage and other articular joint tissues. Disturbances in these factors may underlie additional links between obesity and OA. In this review, molecular players at the intersection of adipose tissue and joint cell biology - including differentiation signals and transcription factors, extracellular matrix components and remodelers, joint cell- and adipose tissue cell-derived mediators (cytokines, adipokines), hypoxia inducible transcription factors, lipids, advanced glycation end products and miRNAs - are reviewed, with emphasis on their dysregulation in obesity and OA. Knowledge of these factors may illuminate a novel, adipocentric avenue for the pathogenesis and therapy of OA and other joint diseases.

El presente artículo es la adaptación a las normas de publicación de la revista A ctividadD ietéticadel Documento de Postura del Comité Científico “5 al día” respecto del consumo de zumos de frutas en el marco de una alimentación saludable. La postura fue aprobada en la V Reunión del Comité Científico, celebrada en Madrid el 4 de abril de 2009. La controversia suscitada en torno a los criterios y parámetros para evaluar los zumos de frutas y/o de hortalizas, dentro del propio Comité Científico “5 al día”, ha promovido la creación de este documento de postura para evaluar, justificar y consensuar la incorporación de los zumos a las recomendaciones de consumo de frutas u hortalizas promovidas desde la Asociación “5 al día”, así como las declaraciones de consumo permitidas.

Establecer un consenso para las recomendaciones de raciones de consumo de frutas y hortalizas frescas, desecadas o deshidratadas, así como de productos elaborados a partir de dichos alimentos es un objetivo y una prioridad de la Asociación para la Promoción del Consumo de Frutas y Hortalizas “5 al día”. El Comité Científico de “5 al día”, creado en octubre de 2005 como órgano asesor en materias de alimentación, nutrición y dietética, ha elaborado el Documento Director en el que se han revisado y consensuado los criterios y parámetros básicos que deben tenerse en cuenta para evaluar y valorar todos los alimentos candidatos a ser incluidos en las recomendaciones de consumo de frutas y hortalizas “5 al día” en España. Sin menoscabo de realizar una evaluación caso a caso, la aplicación del Documento Director por parte de la asociación facilita la selección de alimentos enmarcados en el mensaje “5 al día”, según criterios legales, tecnológicos, nutricionales, alimentarios y de promoción de la salud. El presente artículo es una adaptación del Documento Director para ser publicado en la revista Actividad Dietética.

AbstractObjective: Leptin, a hormone that regulates food intake and energy metabolism, is present in breast milk. The aim of this study was to determine whether milk leptin concentration is correlated with maternal circulating leptin and BMI and with body weight gain of infants.Research Methods and Procedures: A group of 28 non-obese women (BMI between 16.3 and 27.3 kg/m2) who breast-fed their infants for at least 6 months and their infants were studied. Venous blood and milk samples were obtained from mothers at 1, 3, 6, and 9 months of lactation, and leptin concentration was determined. Infant body weight and height were followed until 2 years of age.Results: During the whole lactation period, milk leptin concentration correlated positively with maternal plasma leptin concentration and with maternal BMI. In addition, milk leptin concentration at 1 month of lactation was negatively correlated with infant BMI at 18 and 24 months of age. A better negative correlation was also found between log milk leptin concentration at 1 and at 3 months of lactation and infant BMI from 12 to 24 months of age.Discussion: We concluded that, in a group of non-obese mothers, infant body weight during the first 2 years may be influenced by milk leptin concentration during the first stages of lactation. Thus, moderate milk-borne maternal leptin appears to provide moderate protection to infants from an excess of weight gain. These results seem to point out that milk leptin is an important factor that could explain, at least partially, the major risk of obesity of formula-fed infants with respect to breast-fed infants.

Background/Aims:Retinoic acid (RA), the carboxylic acid form of vitamin A, through the activation of cognate receptors, stimulates the transcription of the gene encoding uncoupling protein 1 (UCP1), which is critical to brown adipose tissue (BAT) thermogenesis. RA was previously shown to down-regulate the steady state levels of retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) in primary brown adipocytes differentiated in culture. Our aim was to study the impact of RA-treatment and vitamin A status on the expression levels of these receptors in vivo. Methods:Three-week-old mice were fed standard chow or a vitamin A deficient diet for 10 weeks, after which animals on both diets were treated with all-transRA (ATRA, 100 mg·Kg−1·day−1) or vehicle during 4 days. Levels of UCP1, RARα and RXRα in BAT were determined by immunoblotting. Results:ATRA-treatment resulted in a reduction of the specific RARα and especially RXRα content in BAT that paralleled the induction of UCP1 appearance in the tissue. RARα and RXRα levels per gram of BAT were reduced in mice chronically fed the vitamin A-deficient diet. Conclusion:RA modulates the expression of cognate receptors in BAT, suggesting auto regulation of the retinoid effect on the thermogenic system (Mol Cell Biochem 266:25–30, 2004)

To determine whether there are variations in leptin levels according to the β3-adrenoceptor (β3-AR) Trp64Arg and uncoupling protein 1 (UCP1) −3826A→G polymorphisms, given the regulatory role of catecholamines through the β3-AR in leptin production and the previously reported association of the UCP1 −3826A→G variant with obesity. A total of 160 men and 172 women randomly chosen from a nationwide population-based obesity cross-sectional survey in Spain were studied. Body mass index (BMI), waist-to-hip ratio (WHR), leptin, insulin, fasting and 2-hour post-glucose load glycemia, high-density lipoprotein (HDL)-, low-density lipoprotein (LDL)-, and total cholesterol, and triglyceride plasma levels were measured. β3-AR Trp64Arg and UCP1 −3826A→G genotypes were determined by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). UCP1 −3826G allele frequency was higher in men than in women (0.31 v0.22, P= .015) and in obese women than in non-obese women (0.31 v0.17, P= .008). Women carriers of the Arg64 or the alleles also showed higher leptin levels than noncarriers. Multiple linear regression analysis showed that the Arg64 allele is associated with higher leptin levels after the adjustment for gender, age, WHR, and the degree of glucose tolerance. In conclusion, the β3-AR Trp64Arg polymorphism might have an impact on the mechanisms involved in leptin release from adipose tissue. Furthermore, our results agree with the previously reported association between UCP1 −3826G allele and obesity and point to a gender-related effect.

Objective: To investigate the effects of short‐term cafeteria (CAF) diet feeding on the expression of adipogenic transcription factors and their association with adiposity. Research Methods and Procedures: Four‐week‐old male and female Wistar rats were fed CAF diet or standard chow for 2 weeks. Body weight, energy intake, tissue weights, and serum parameters were determined. Peroxisome proliferator‐activated receptor (PPAR)‐γ2, PPARα, CCAAT enhancer‐binding protein‐α, and adipocyte differentiation and determination factor 1 mRNAs in gonadal white adipose tissue (gWAT) (visceral depot) and inguinal white adipose tissue (iWAT) (subcutaneous depot) and in interscapular brown adipose tissue were measured by reverse transcription‐polymerase chain reaction. Results: Short‐term CAF diet feeding resulted in increases in body weight, adipose tissue weights, and lipid serum levels. Increased adiposity was more related to an increase in visceral fat than an increase in subcutaneous fat. This difference was associated with a higher expression of key adipogenic transcription factors (mainly PPARγ2 and CCAAT enhancer‐binding protein‐α) in gWAT when compared with iWAT. Higher hypertrophy of gWAT was found in females, whereas males showed a higher hypertrophy of iWAT. Differential gender and depot response to CAF diet could be explained by depot and gender differential expression of key adipogenic transcription factors, especially PPARγ2. Hence, reduced hypertrophy of female iWAT and defective thermogenesis in interscapular brown adipose tissue in response to CAF diet were related to decreased PPARγ2 mRNA levels, whereas increased hypertrophy in male iWAT and gWAT and in female gWAT was related to a tendency toward increased PPARγ2 mRNA levels in response to overfeeding. Discussion: Our results suggest the involvement of PPARγ2 in gender‐ and depot‐specific effects of CAF diet on development and function in adipose tissues.

Resistin is a hormonal factor synthesised by adipocytes that was first thought to be related with the resistance to insulin in obesity, but whose function is not yet completely established. Here we have studied the ontogenic pattern of resistin mRNA expression in different white adipose tissue depots (WAT) – epididymal, inguinal, mesenteric and retroperitoneal – and in brown adipose tissue (BAT), as well as the circulating resistin levels, in rats of different ages (from the suckling period to one year of age). Resistin mRNA was determined by Northern blotting, and serum levels by enzyme immunoassay. In WAT, resistin expression remains almost constant with age, except in early development, where there is a peak of expression in the epididymal and retroperitoneal depots, and a decrease in the inguinal one, while the expression remains constant for the mesenteric depot. Moreover, there is a site-specific difference regarding resistin expression: all the depots express characteristic levels of mRNA, especially at the age of 2 months, the moment when resistin mRNA levels are significantly higher in the epididymal and the retroperitoneal than in the inguinal and mesenteric WAT and than in the BAT. The transient increased resistin expression in the epididymal and the retroperitoneal WAT at a period of time in which there is a change in diet (from milk to chow) suggests a common nutritional regulation of the resistin gene. Circulating resistin levels increase with age probably reflecting the increase in the body fat content.

Previous studies have shown that chronic hypoxia leads to changes in skeletal muscle structure (fibre size and type) and activities of several bioenergetic enzymes. Whether this occurs also in conditions characterised by intermittent hypoxia, such as the obstructive sleep apnoea syndrome (OSAS), is unknown. To explore this possibility, we obtained a needle biopsy of the quadriceps femorisin 12 consecutive stable outpatients with severe OSAS (52±9 year, apnoea–hypopnoea index 70±14h−1) (x±SD) and in six healthy volunteers (49±8 year), where we quantified fibre type, size and protein content, as well as phosphofructo-kinase (PFK) and cytochrome oxidase (CytOx) activities. We found that fibre-type distribution was similar in patients and controls. In contrast, the diameter of type II fibres (74±10μm vs. 56±11μm, P<0.05) and protein content (100±14 vs. 88±8μg/mg) was higher in patients with OSAS. Likewise, we observed upregulation of CytOx (0.93±0.38 vs. 0.40±0.22μkat/mg protein, P<0.01) and PFK activities (5.35±4.8 vs. 1.3±1.3μkat/mg protein, P<0.05) in patients with OSAS. These results show that, paralleling which occurs in conditions characterised by continuous hypoxia, patients with OSAS (and intermittent hypoxia) also show structural and bioenergetic changes in their skeletal muscle.

Objective:Genetically obese (fa/fa) Zucker rats display markedly elevated circulating leptin levels compared with their lean counterparts; this is expected because of the lack of a LepR‐mediated feedback inhibition. The aim of this study was to determine the effect of the leptin receptor mutation in the Zucker rat on gastric leptin production and on the response to 14 hours of starvation. The response to a short‐term period of food intake (20 minutes) on gastric leptin release was also analyzed. Research Methods and Procedures:Leptin mRNA expression in the gastric mucosa and in adipose tissue depots (epididymal, retroperitoneal, mesenteric, and inguinal) was assessed by reverse transcriptase‐polymerase chain reaction and serum and stomach leptin content by enzyme‐linked immunosorbent assay. Results:Obese Zucker rats overexpressed leptin in the stomach. They overexpress leptin in the inguinal adipose tissue but not in visceral adipose tissue depots, indicating tissue‐specific obesity‐dependent differences. Gastric leptin expression is regulated by feeding conditions in lean but not in obese (fa/fa) rats. In lean animals, leptin mRNA levels decrease in fasting conditions and increase rapidly with a short period of food intake. Obese Zucker rats also overdisplay stomach leptin levels. Feeding acutely stimulates leptin secretion by the stomach in lean, and to a lesser extent, in obese rats. Discussion:These results indicate impaired regulation of leptin expression in the stomach of obese (fa/fa) Zucker rats. However, there is still an effect of the nutritional status on gastric leptin levels despite the lack of a functional leptin receptor.

Objective:To investigate the effects of short‐term (15 days) cafeteria‐diet feeding on the expression of α‐ and β‐adrenergic receptors (AR) and its association with lipolytic stimulation in isolated retroperitoneal white adipocytes. Research Methods and Procedures:Six female and 6 male Wistar rats (4 weeks old) were fed a cafeteria diet plus standard diet for 15 days. The remaining 12 age‐ and sex‐matched rats received a standard diet only. White retroperitoneal adipose tissue was isolated and used for the determination of both α2and β‐AR expression and for in vitro studies of lipolytic activity. Results:In female control rats, we found higher lipolytic capacities located at the postreceptor level and a lower α2/β3‐AR ratio than male rats. Cafeteria‐diet feeding for 15 days decreased lipolytic activity in both male and female rats and altered the α2A‐ and β3‐AR protein levels with an increase of α2A‐AR in males and a β3‐AR decrease in females. Discussion:Our results indicate that a 15‐day cafeteria‐diet feeding induced an increase in the α2/β3‐AR balance and impaired adipose tissue lipolytic activity, which was higher in males and may contribute to the development of increased fat mass. The higher functionality of α2‐AR, together with the minor role developed by β3‐AR and lower lipolytic capacities located at the postreceptor level in cafeteria‐diet‐fed male rats compared with female rats, may be responsible for the gender‐dependent differences observed in this study.

It has been reported recently that the stomach can produce and store leptin and release it, both into the blood and into the gastrointestinal lumen, in response to food intake. Here, we have followed the ontogenic pattern of leptin mRNA expression and leptin levels in stomach during the perinatal period, which were compared with adults. Leptin mRNA expression was assessed by reverse transcriptase-polymerase chain reaction, and tissue leptin content by enzyme-linked immunosorbent assay and localised by immunohistochemistry. Leptin mRNA is expressed at low levels in rat stomach in prenatal stages. It increased from 4 to 8 hr of life in suckling rats, an increase not observed in the fasted pups, which were separated from their mothers immediately after birth. Leptin expression rose steadily after birth during the first month of life, with a marked increase from 15-day-old rats, followed by a parallel increase in leptin levels from day 21 of life, which was coincident with the change from suckling to a solid diet. The immunohistochemical analysis showed leptin immunoreactivity at different levels of the stomach mucosa, suggesting that during early development leptin could derive from different sources. During the pre- and neonatal periods, leptin is mainly located at the superficial epithelium (suggesting maternal origin from amniotic cells and mammary glandular cells, respectively). At the beginning of the chow diet, the stomach produces leptin in the glands (main source from 15 days of life), suggesting an endogenous production of the protein after that period. The present work demonstrates the expression of leptin mRNA and leptin protein in the stomach of neonate rats, and shows that the ontogenic profile of leptin appearance in the stomach during the perinatal period is probably related to the onset of suckling and to the change of diet from milk to solid chow. © 2001 Wiley-Liss, Inc.

Objective:The aim of this study was to determine the sex‐dependent differences in the response of key parameters involved in thermogenesis and control of body weight in brown adipose tissue (BAT) and white adipose tissue (WAT) in postcafeteria‐fed rats, a model of dietary obesity. Research Methods and Procedures:BAT and WAT were obtained from male and female control and postcafeteria‐fed Wistar rats. Postcafeteria‐fed rats were initially fed with cafeteria diet from day 10 of life until day 110 (cafeteria period) and with standard chow diet from then until day 180 of life (postcafeteria period). Body mass and energy intake were evaluated. Biometric parameters were analyzed in interscapular BAT (IBAT). Levels of uncoupling protein 1 (UCP1), α2‐adrenergic receptor (AR), and β3‐AR proteins and UCP1, UCP2, UCP3, β3‐AR, and leptin mRNAs, in IBAT or WAT, were studied by Western blot and Northern blot analyses, respectively. Results:Rats attained 59% (females) and 39% (males) increase in body weight at the end of the cafeteria period. During the postcafeteria period, the rats showed a loss of body weight, which was higher in females. Postcafeteria‐fed female rats also presented higher activation of thermogenic parameters in IBAT, including UCP1, UCP2, and UCP3 mRNAs. Female control rats showed lower levels of both α2 and β3‐ARs in BAT compared with male rats, but these levels in postcafeteria‐fed female and male rats were the same, because males tended to down‐regulate them. Levels of leptin mRNA in response to the postcafeteria state depended on gender and the specific WAT depot studied. Discussion:It is suggested that in postcafeteria‐fed female rats, BAT thermogenic capacity becomes more efficiently activated than in males. Female rats also showed a bigger weight loss. The parallel regulation of the levels of UCP2 and UCP3 mRNAs, with respect to UCP1 mRNA, with higher activation in female postcafeteria‐fed rats, suggests a possible role of both UCP2 and UCP3 in the regulation of energy expenditure and in the control of body weight. The distinct responses to overweight of α2 and β3‐ARs—which were sex dependent—and leptin mRNA—which depended on both sex and WAT depot—also support the different response of thermogenesis‐related parameters between overweight males and females.

Objective:To gain insight into the in vivo modulation of the expression of the adipogenic transcription factors PPARγ2, C/EBPα, and ADD1/SREBP1c by retinoids and its relationship with whole‐body adiposity. Research Methods and Procedures:Three‐week‐old mice were fed with standard chow or a vitamin A‐deficient diet for 10 weeks. During the 4 days immediately before they were killed, the animals were treated either with all‐transretinoic acid (tRA; 100 mg/kg per day, subcutaneously) or vehicle. The specific levels of the mRNAs for the three transcription factors were analyzed in epididymal white adipose tissue (eWAT) and inguinal white adipose tissue and in brown adipose tissue (BAT). Other parameters determined were leptin and UCP2 levels in white adipose tissue depots, total cholesterol and triglyceride serum levels, energy intake, body weight, and adiposity. Results:Vitamin A‐deficient diet feeding led to a marked increase of adiposity and to a small increase of body weight. Hypertrophy of white adipose tissue depots correlated with enhanced PPARγ2 expression. Hypertrophy of BAT, in contrast, correlated with a decrease of PPARγ2 expression that may contribute to the known reduced thermogenic potential of BAT under conditions of vitamin A restriction. Treatment with tRA triggered a reduction of adiposity and body weight that correlated with a down‐regulation of PPARγ2 expression in all adipose tissues. The effects of tRA were more pronounced in eWAT, where C/EBPα and ADD1/SREBP1c levels were also reduced. The response to tRA was impaired in the eWAT and BAT of animals fed the vitamin A‐deficient diet. Discussion:The results emphasize the importance of retinoids as physiological regulators of adipose tissue development and function in intact animals.

The influence of age and gender on uncoupling protein 2 (UCP2) expression and its relationship with leptin expression in subcutaneous adipose tissue has been studied in humans. Samples of subcutaneous adipose tissue were obtained from 41 adult subjects (20 women and 21 men), with an age range of 28 to 84 years, and body mass index (BMI) of 19 to 36 Kgm−2. UCP2 and leptin mRNA expression was determined by northern blot. In women, both leptin and UCP2 expression in the subcutaneous adipose tissue increased significantly with age (r= 0.490 p< 0.05 and r= 0.475 p< 0.05, respectively). In men, in contrast, a negative correlation was found between leptin expression and age (r= −0.678 p< 0.001), while no significant correlation was apparent between UCP2 expression and age (r= −0.077). In addition, there was a positive correlation between UCP2 and leptin expression in women (r= 0.656 p< 0.01). These data show important gender dependent differences in the age-related changes in leptin and UCP2 expression in subcutaneous adipose tissue in humans.

A novel potential regulatory pathway of brown adipose tissue (BAT) thermogenesis was recently recognized after identifying retinoic acid (RA) as a transcriptional activator of the uncoupling protein (UCP) gene. Here we provide evidence that the UCP responsiveness to RA in primary cultures of brown adipocytes involves RA receptor α (RARα), and show, in the same system and also in CHO cells, that RA down‐regulates the steady‐state levels of RARα and especially of retinoid X receptor α, suggesting autoregulation of the retinoid pathway and therefore supporting the idea of a physiological role for it in controlling the thermogenic capacity of BAT.

The effects of starvation on the thermogenic parameters of three different mitochondrial subpopulations in brown adipose tissue (BAT) of both post-cafeteria obese and lean rats were investigated. Tissue from different BAT depots from fed and 24 h starved rats were collected, pooled and three mitochondrial subpopulations were isolated by differential centrifugation; the M1 fraction (1000 g), the M3 fraction (3000 g) and the M15 fraction (15000 g). Thermogenic parameters were measured in the three mitochondrial subtypes, and uncoupling protein (UCP) mRNA was determined in BAT. The results showed that starvation induced a decrease in mitochondrial turnover in BAT from both lean and obese rats. Moreover, a selective net loss of UCP from the lightest mitochondrial fraction (M15) in lean rats, with a concomitant reduction of UCP mRNA was observed. The reductions did not occur in obese rats and, as a result, a change in UCP distribution between the mitochondrial subpopulations was produced, with an increase in the M1 mitochondrial subtype. The lack of response of UCP to starvation observed in BAT of obese rats compared with the decrease seen in lean animals, is a consequence of a different mitochondrial subpopulation composition and/or a different response of a particular subpopulation to starvation.

The effects of retinoic acid (RA) isomers (all-trans-RA and 9-cis-RA) on the appearance of uncoupling protein (UCP; thermogenin), the only unequivocal molecular marker of the brown adipocyte differentiated phenotype, have been investigated in primary cultures of brown adipocytes, in the brown adipocyte cell line HIB 1B and directly in intact mice. The results obtained with cultured cells indicate that retinoids function as inducers of the appearance of UCP and, at the same time, partially inhibit brown adipocyte cell proliferation. The two RA isomers displayed similar effectiveness as UCP inducers, their effect being comparable with that triggered by noradrenaline, so far considered to be the main modulator of UCP gene expression. The effectiveness of retinoids as UCP inducers was dependent on the stage of brown adipocyte differentiation, being maximal in confluent primary cells and in the medium–late differentiation stage of HIB 1B cells. Corroborating the results obtained in vitro, we show that administration of all-trans-RA or 9-cis-RA to mice leads to an increase in their brown adipose tissue specific UCP content. 9-cis-RA treatment also prevented the loss of UCP on cold deacclimation. To our knowledge, this is the first report of a stimulatory effect of retinoid compounds on UCP induction in vivo.

The effects of both dietary obesity and a food deprivation period of 24 hours on fatty acid composition of brown adipose tissue have been investigated. Long time exposure to a hypercaloric high‐fat diet such as the cafeteria diet induced an important tissue fatty acid accumulation, mainly for the major saturated and monounsaturated fatty acids. Notable metabolic differences have been observed in the behaviour of control and obese rats facing a food deprivation period: a preferential utilization of the most abundant saturated fatty acids in control rats and a minor response in obese rats, with a greater fat accumulation in the interscapular brown adipose tissue.

The aim of the present work is to investigate the effect of starvation on brown adipose tissue thermogenic activity with aging. Interscapular brown adipose tissue from female Wistar rats of different ages was used; half of them were fed and the other half were starved for 24 hours. Mitochondria were isolated and mitochondrial protein content, GDP‐binding, Cytochrome‐c Oxidase activity and uncoupling protein levels were measured. Results show a decrease of all studied parameters, indicating a diminished thermogenic activity with age. The response to starvation is almost the same in all the parameters studied: a general reduction with starvation and a progressive disappearance of this response to starvation with aging. On the whole, these results would indicate a deficient regulation of brown adipose tissue thermogenic activity in old animals, as it happens in other animal models with an alterated thermogenesis.

The effects of 2-methoxyestradiol (2ME), a naturally occurring mammalian metabolite of 17 β-estradiol, on adipocyte growth has been investigated in mouse brown adipose tissue precursor cells developed in primary culture. 2ME inhibits brown adipocyte proliferation in a dose-response manner (IC50 = 1.7 × 10-6 M for DNA synthesis), with much higher potency than its hormone precursor 17β-estradiol, and cells acquire the typical differentiated morphology - more round with a higher content of triglycerides. 2ME causes similar effects in the immortal brown adipocyte tumor-derived hibernoma cell line HIB 1B and the immortal 3T3-F442A white adipocyte line. These findings suggest a possible role for 2ME in adipocyte proliferation, and probably in the differentiation process, entering the cells in the adipogenic program.

The effects of olive tree (poly)phenols (OPs) are largely dependent upon their bioavailability and metabolization by humans. Absorption, distribution, metabolism, and excretion (ADME) are fundamental for the nutritional efficacy and toxicological impact of foods containing OPs. This review includes studies on the administration of hydroxytyrosol (HT), oleuropein (Ole), or other OPs and foods, products, or mixtures that contain them. Briefly, data from in vivostudies indicate that OPs are absorbable by intestinal cells. Both absorption and bioavailability depend upon each compound and/or the matrix in which it is contained. OPs metabolism begins in enterocytes and can also continue in the liver. Metabolic phase I mainly consists of the hydrolysis of Ole, which results in an increase in the HT content. Phase II metabolic reactions involve the conjugation of (poly)phenols mainly with glucuronide and sulfate groups. This review offers a complete perspective of the ADME processes of OPs, which could support the future nutritional and/or toxicological studies in this area.

BackgroundResearch on biomarkers that provide early information about the development of future metabolic alterations is an emerging discipline. Gene expression analysis in peripheral blood mononuclear cells (PBMC) is a promising tool to identify subjects at risk of developing diet-related diseases.ObjectiveWe analysed PBMC expression of key energy homeostasis-related genes in a time-course analysis in order to find out early markers of metabolic alterations due to sustained intake of high-fat (HF) and high-protein (HP) diets.DesignWe administered HF and HP diets (4 months) to adult Wistar rats in isocaloric conditions to a control diet, mainly to avoid overweight associated with the intake of hyperlipidic diets and, thus, to be able to characterise markers of metabolically obese normal-weight (MONW) syndrome. PBMC samples were collected at different time points of dietary treatment and expression of relevant energy homeostatic genes analysed by real-time reverse transcription-polymerase chain reaction. Serum parameters related with metabolic syndrome, as well as fat deposition in liver, were also analysed.ResultsThe most outstanding results were those obtained for the expression of the lipolytic gene carnitine palmitoyltransferase 1a (Cpt1a). Cpt1aexpression in PBMC increased after only 1 month of exposure to both unbalanced diets, and this increased expression was maintained thereafter. Interestingly, in the case of the HF diet, Cpt1aexpression was altered even in the absence of increased body weight but correlated with alterations such as higher insulin resistance, alteration of serum lipid profile and, particularly, increased fat deposition in liver, a feature characteristic of metabolic syndrome, which was even observed in animals fed with HP diet.ConclusionsWe propose Cpt1agene expression analysis in PBMC as an early biomarker of metabolic alterations associated with MONW phenotype due to the intake of isocaloric HF diets, as well as a marker of increased risk of metabolic diseases associated with the intake of HF or HP diets.