Adult-onset hypothyroidism induces the amyloidogenic pathway of amyloid precursor protein processing in the rat hippocampus.

Thyroid dysfunction and dementia are conditions that become more prevalent with advancing age. Localised hypothyroidism of the central nervous system has been sugested in some patients with Alzheimer's disease. We investigated the consequence of adult-onset hypothyroidism on beta-amyloid precursor protein (APP) degrading pathways in rats treated with propylthiouracyl over a period of 5 weeks. We evaluated the amount of 3,5,3'-triiodothyronine nuclear receptors (TRalpha1 and TRbeta) and the expression of some APP processing indicators (i.e. APP, ADAM 10, BACE and PS1). The activity of secretases and Abeta peptides has been also quantified. The results obtained show that hypoactivity of the thyroid signalling pathway in the hippocampus induced an increase in the APP770-751/APP695 ratio accompanied by a modification in the amyloidogenic pathway for APP processing, leading to an increased amount of Abeta peptides. In this area of the brain, modification in the non-amyloidogenic pathway of APP processing characterised by alpha-secretase activity was only approximately 10% in hypothyroid rats compared to control rats. We suggest that hypothyroidism, which becomes more prevalent with advancing age, increased the vulnerability to the formation of amyloid deposits.

RARgamma and TRbeta expressions are decreased in PBMC and SWAT of obese subjects in weight gain.

In order to evaluate the expression of nuclear receptors at the peripheral level in obese subjects, messenger RNA (mRNA) levels of different isoforms of retinoic acid receptor (RAR), triiodothyronine (TR), and peroxisome proliferator-activated receptor (PPAR) were determined and compared in peripheral mononuclear blood cells (PBMC) and subcutaneous white adipose tissue (SWAT). Twelve lean subjects and 68 obese subjects divided into weight gain (WG), weight-stable (WS), and weight loss (WL) groups were studied. Nuclear receptor mRNA levels were assessed in PBMC and SWAT using a quantitative real-time reverse transcription polymerase chain reaction method. mRNA levels of RARgamma were significantly lower in PBMC of obese subjects (WG -19%, WS -30%, and WL -24.7%) as in SWAT of WG (-50%). Lower mRNA levels of TRbeta were observed in PBMC and SWAT of WG (-50.7% and -28%, respectively) just as for TRalpha in PBMC of WG (-19%). In contrast, retinoid X receptors alpha (RXRalpha) and RARalpha mRNA levels were higher in PBMC of obese subjects (+53% and +54.5% in WG, +56% and +67% in WS, and +68% and +49.7% in WL, respectively), while expression of RXRalpha was lower in SWAT of WG (-24.5%). As for PPARgamma, its mRNA level was significantly higher in PBMC of WG subjects (+34%) while its expression was not modified in SWAT, contrary to the PPARgamma2 isoform which was significantly higher. These data show that in both adipose tissue and blood compartment of obese subjects, expressions of RARgamma and TRbeta were downregulated. Thus, we suggest that the expression in PBMC of obese subjects may constitute new cellular indicators of nuclear receptor retinoid and thyroid status.

RARã and TRBeta expressions are decreased in PBMC and SWAT of obese subjects in weight gain

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In order to evaluate the expression of nuclear receptors at the peripheral level in obese subjects,messenger RNA (mRNA) levels of different isoforms of retinoic acid receptor (RAR), triiodothyronine(TR), and peroxisome proliferator-activated receptor (PPAR) were determined and compared in peripheral mononuclear blood cells (PBMC) and subcutaneous white adipose tissue (SWAT). Twelve lean subjects and 68 obese subjects divided into weight gain (WG), weight-stable (WS), and weight loss (WL) groups were studied. Nuclear receptor mRNA levels were assessed in PBMC and SWAT using a quantitative real-time reverse transcription polymerase chain (..) (AU)

Early decrease in resting energy expenditure with bedtime insulin therapy.

AIMS: In type 2 diabetes (T2D), insulin-induced weight gain may stem from a reduction in resting energy expenditure (REE). We sought to determine the early effects of insulin introduction on REE in 20 poorly controlled T2D patients. METHODS: After improving the glycaemia, REE was measured on Day 0 and Day 4 during two treatment regimens: bedtime insulin (n=10, group 1); and one off (3-day) intravenous insulin infusion (n=10, group 2). RESULTS: Both groups were similar in age, gender, BMI, C-peptide, HbA(1c) and initial REE. By Day 4, fasting glycaemia had similarly improved in both groups: group 1: -5.3+/-2.7mmol/L vs group 2: -5.8+/-4.2 mmol/L. In group 2, the second REE was measured 12h after stopping the intravenous insulin infusion, whereas subcutaneous insulin was maintained in group 1. REE did not change in group 2 (-1.3+/-6.5%), whereas it decreased significantly in group 1 (-8.0+/-7.0%; P<0.05). CONCLUSION: Bedtime insulin led to an early and specific reduction in REE.

Thyroid hormone receptor alpha plays an essential role in the normalisation of adult-onset hypothyroidism-related hypoexpression of synaptic plasticity target genes in striatum.

Thyroid hormone (TH) deficiency leads to molecular changes resulting in behavioural deficits. TH action is mediated by two types of nuclear receptors (TRs), TRalpha and TRbeta, which control target gene transcription. The relative contributions of the two TR products in mediating adult TH responses are poorly understood. As TRalpha1 transcripts are widely distributed in the brain, they presumably mediate most of the TH effects. This report examines the role and specific functions of T3 receptor isoforms on regulation of striatal synaptic plasticity indicators using adult hypothyroid mutant mice that fail to express single or multiple TR gene products. We then evaluated the effect of this hypothyroidism, with or without subsequent administration of T3, on T3 nuclear receptor (TRalpha1, TRbeta) and synaptic plasticity gene expression in TRalpha(0/0), TRbeta(-/-) and wild-type 129/SV mice. Hypothyroid wild-type mice exhibited reduced TRbeta, RC3, CaMKII and Rhes expression. The mRNA levels of Rhes and CaMKII were the same in all three hypothyroid substrains. By contrast, hypothyroid TRbeta(-/-) mice had higher RC3 mRNA levels than wild-type. T3 administration restored TRbeta, RC3 and CaMKII levels in hypothyroid wild-type mice, without significant Rhes upregulation. T3 administration normalised expression of all genes studied in hypothyroid TRbeta(-/-) but not TRalpha(0/0) mice. Thus, TRalpha apparently plays an essential role in restoring the expression of the TH-regulated genes potentially involved in striatal synaptic plasticity.

Role of adipogenic and thermogenic genesin susceptibility or resistance to developdiet-induced obesity in rats

The aim of the present work was to assess whether changes in adipose tissue geneexpression related with adipogenesis and/or thermogenesis could be involved in themechanism conferring susceptibility or resistance to develop obesity in high-fat fedoutbreed rats. For this purpose, male Wistar rats were fed with standard laboratorydiet (control group) or high fat diet. After 15 days, two groups of rats with significantdifferences on body weight gain in response to the high fat diet were characterizedand identified as diet-induced obesity (DIO) and diet resistant (DR) rats. A significantincrease in visceral white adipose tissue (WAT) PPARã and aP2 (p<0.05)mRNA levels associated to a decrease in RARã expression (p<0.05) was observed inDIO rats, suggesting an increase of adipogenesis. Furthermore, our data showed amarked increase in brown adipose tissue (BAT) of UCP1 mRNA in DIO animals(p<0.01) (without affecting PGC-1á gene expression), whereas no changes werefound in WAT UCP2 gene expression. All these data suggest that the variationsfound in the expression pattern of PPARã, aP2 and RARã by high-fat diet could beinvolved, at least in part, in the differences in body weight gain and adiposityobserved between DR and DIO animals. The compensatory adaptations through theincrease in energy expenditure by changes on the expression levels of UCP1 seem notto be enough to avoid the obesity onset in the DIO group (AU)

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Role of adipogenic and thermogenic genes in susceptibility or resistance to develop diet-induced obesity in rats

The aim of the present work was to assess whether changes in adipose tissue geneexpression related with adipogenesis and/or thermogenesis could be involved in themechanism conferring susceptibility or resistance to develop obesity in high-fat fedoutbreed rats. For this purpose, male Wistar rats were fed with standard laboratorydiet (control group) or high fat diet. After 15 days, two groups of rats with significantdifferences on body weight gain in response to the high fat diet were characterizedand identified as diet-induced obesity (DIO) and diet resistant (DR) rats. A significantincrease in visceral white adipose tissue (WAT) PPARã and aP2 (p<0.05)mRNA levels associated to a decrease in RARã expression (p<0.05) was observed inDIO rats, suggesting an increase of adipogenesis. Furthermore, our data showed amarked increase in brown adipose tissue (BAT) of UCP1 mRNA in DIO animals(p<0.01) (without affecting PGC-1á gene expression), whereas no changes werefound in WAT UCP2 gene expression. All these data suggest that the variationsfound in the expression pattern of PPARã, aP2 and RARã by high-fat diet could beinvolved, at least in part, in the differences in body weight gain and adiposityobserved between DR and DIO animals. The compensatory adaptations through theincrease in energy expenditure by changes on the expression levels of UCP1 seem notto be enough to avoid the obesity onset in the DIO group (AU)

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Role of adipogenic and thermogenic genes in susceptibility or resistance to develop diet-induced obesity in rats.

The aim of the present work was to assess whether changes in adipose tissue gene expression related with adipogenesis and/or thermogenesis could be involved in the mechanism conferring susceptibility or resistance to develop obesity in high-fat fed outbreed rats. For this purpose, male Wistar rats were fed with standard laboratory diet (control group) or high fat diet. After 15 days, two groups of rats with significant differences on body weight gain in response to the high fat diet were characterized and identified as diet-induced obesity (DIO) and diet resistant (DR) rats. A significant increase in visceral white adipose tissue (WAT) PPARgamma and aP2 (p < 0.05) mRNA levels associated to a decrease in RARgamma expression (p < 0.05) was observed in DIO rats, suggesting an increase of adipogenesis. Furthermore, our data showed a marked increase in brown adipose tissue (BAT) of UCP1 mRNA in DIO animals (p < 0.01) (without affecting PGC-1alpha gene expression), whereas no changes were found in WAT UCP2 gene expression. All these data suggest that the variations found in the expression pattern of PPARgamma, aP2 and RARgamma by high-fat diet could be involved, at least in part, in the differences in body weight gain and adiposity observed between DR and DIO animals. The compensatory adaptations through the increase in energy expenditure by changes on the expression levels of UCP1 seem not to be enough to avoid the obesity onset in the DIO group.

Effect of vitamin A content in cafeteria diet on the expression of nuclear receptors in rat subcutaneous adipose tissue.

The aim of this study was to determine the effects of cafeteria diet containing control or elevated level of vitamin A on the expression of nuclear receptors in adipose tissue. Male Wistar rats were submitted to 3 experimental diets during 8 weeks, a standard diet and two hyper-energetic, hyperlipidic "cafeteria" diets containing normal (Caf) or higher (Caf+) vitamin A level. During the experiment, body weights and energy intakes were measured. At the end of the experimental period, subcutaneous adipose tissue (Swat) and all the fat mass were removed and weighted. Nuclear receptors mRNA levels of RARalpha, RARgamma, RXRalpha, PPARgamma were measured in the Swat by a real-time semi-quantitative RT-PCR method. We observed that energy intake of Caf+ and Caf groups was significantly higher than that of the control group. Despite a higher increase of the energy intake in the Caf group compared to the Caf+ group, no significant difference was observed in the body weight gain of the Caf+ compared to the Caf group. The Caf+ and Caf diets led to a significant increase of adipose tissue in cafeteria groups as observed in the Swat depot. The mRNA levels of PPARgamma and RXRalpha were significantly increased in the Caf+ group as compared to control group, with a significant positive correlation between these two parameters. Expressions of RARalpha and RARgamma were not modified in experimental groups compared to controls. In conclusion, 8-week exposure to cafeteria diets with normal and higher levels of vitamin A led to an increase of adiposity in rats, associated, only in the group fed with the higher vitamin A level cafeteria diet, with an increase of PPARgamma and RXRalpha expressions in subcutaneous adipose tissue.

Decreased expression of retinoid nuclear receptor (RAR alpha and RAR gamma) mRNA determined by real-time quantitative RT-PCR in peripheral blood mononuclear cells of hypothyroid patients.

In vivo assessment of the cellular impact of thyroid hormones on target tissues might be of help for physiological studies and to evaluate the consequences of various diseases of the thyroid gland in humans. Given the tenuous relationship between retinoid and tri-iodothyronine (T3) status and that retinoids have also intracellular roles, the aim of this study was to determine the effect of hypothyroidism on the expression of T3 nuclear receptors (TR) and retinoic acid nuclear receptors (RAR, RXR) in human peripheral blood mononuclear cells (PBMC). Using real time RT-PCR, we quantified the relative amount of mRNA of the thyroid (TR alpha and TR beta) and retinoid (RAR alpha, RAR gamma, and RXR alpha) nuclear receptors in PBMC of euthyroid (n = 22) compared with hypothyroid (n = 22) subjects. Classical plasma parameters (free T3 (FT3), free thyroxine (T4) (FT4), thyroid-stimulating hormone (TSH), retinol (ROH), retinol-binding protein (RBP) and transthyretin (TTR)) were also measured. In hypothyroid subjects, the concentration of TSH was elevated, and dramatically low T3 and T4 concentrations were associated with a decrease in the expression of TR beta. Expression of RAR alpha and RAR gamma significantly decreased in hypothyroid versus control subjects, while an increased concentration of ROH was emphasised by hypothyroidism. These results first indicated that primary hypothyroidism induces hypoactivation of the retinoid nuclear pathway in PBMC, which was not predicted by the plasma ROH level. Further investigations will be necessary to evaluate these parameters in very small changes in thyroid hormone production such as mild (subclinical) hypothyroidism.

Effect of vitamin A content in cafeteria diet on the expression of nuclear receptors in rat subcutaneous adipose tissue

The aim of this study was to determine the effects of cafeteria diet containing control or elevated level of vitamin A on the expression of nuclear receptors in adipose tissue. Male Wistar rats were submitted to 3 experimental diets during 8 weeks, a standard diet and two hyper-energetic, hyperlipidic "cafeteria" diets containing normal (Caf) or higher (Caf+) vitamin A level. During the experiment, body weights and energy intakes were measured. At the end of the experimental period, subcutaneous adipose tissue (Swat) and all the fat mass were removed and weighted. Nuclear receptors mRNA levels of RARa, RARg, RXRa, PPARg were measured in the Swat by a real-time semi-quantitative RT-PCR method. We observed that energy intake of Caf+ and Caf groups was significantly higher than that of the control group. Despite a higher increase of the energy intake in the Caf group compared to the Caf+ group, no significant difference was observed in the body weight gain of the Caf+ compared to the Caf group. The Caf+ and Caf diets led to a significant increase of adipose tissue in cafeteria groups as observed in the Swat depot. The mRNA levels of PPARg and RXRa were significantly increased in the Caf+ group as compared to control group, with a significant positive correlation between these two parameters. Expressions of RARa and RARg were not modified in experimental groups compared to controls. In conclusion, 8-week exposure to cafeteria diets with normal and higher levels of vitamin A led to an increase of adiposity in rats, associated, only in the group fed with the higher vitamin A level cafeteria diet, with an increase of PPARg and RXRa expressions in subcutaneous adipose tissue

El objetivo del presente trabajo consiste en determinar las consecuencias de un alto contenido en vitamina A en dieta de cafetería sobre la expresión de receptores nucleares en el tejido adiposo. Así, ratas macho Wistar se dividieron en tres grupos : Durante 8 semanas, el grupo control se alimentó con pienso estándar, mientras que los grupos tratados recibieron una dieta rica en grasa (dieta de cafetería) enriquecida (Caf+) o no (Caf) con vitamina A. El peso corporal y la ingesta se determinaron durante todo el experimento. Al final del tratamiento, se pesó el tejido adiposo subcutáneo (Swat) y las otras reservas de grasa. Los niveles de ARNm de los receptores nucleares RARa, RARg, RXRa, PPARg se determinaron en el Swat con un método semi-cuantitativo de RT-PCR en tiempo real. Las ingestas energéticas de los grupos Caf+ y Caf fueron significativamente mayores que las del grupo control. A pesar del aumento en la ingesta del grupo Caf respecto del Caf+, no se observaron diferencias significativas en el aumento de peso corporal entre ambos grupos. Además, las dietas de los grupos Caf+ y Caf provocaron un claro aumento del tamaño de las reservas de grasa, incluido el peso del Swat. Los niveles de ARNm de PPARg yRXRa se incrementaron significativamente en el grupo Caf+ respecto del control, con correlación positiva entre ambos. En cambio, no se modificó la expresión de RARa y RARg. En suma, 8 semanas de alimentación con dieta de cafetería con niveles normales o elevados de vitamina A dan lugar a aumento de la adiposidad en la rata, asociado con aumento de la expresión de PPARg y RXRa en el tejido adiposo subcutáneo solo en el grupo que recibió suplemento de vitamina A

Aging affects the retinoic acid and the triiodothyronine nuclear receptor mRNA expression in human peripheral blood mononuclear cells.

BACKGROUND: Inadequate retinoid status has often been described as occurring with aging. Moreover, subclinical hypothyroid status has also been evoked in the elderly. Several studies performed in animals have described the crucial incidence of age-related hypo-functioning of retinoid and thyroid signalling pathways, particularly in the brain. OBJECTIVE: The aim of the present study was to clarify whether aging modifies retinoid and thyroid signalling in humans. METHODS: Using real-time RT-PCR the relative amount of mRNA of the retinoid (RARalpha, RARgamma and RXRalpha) and thyroid (TRalpha and TRbeta) nuclear receptors in peripheral blood mononuclear cells (PBMC) of young (24-57 years old, n = 22) compared with elderly (69-90 years old, n = 24) healthy subjects was quantitated. Classical plasma parameters used to characterize the retinoid and thyroid status - retinol (ROH), retinol-binding protein (RBP), free triiodothyronine (FT3) and thyroxine (FT4), thyroid-stimulating hormone (TSH) and transthyretin (TTR) - were also assessed. RESULTS: RARgamma expression was significantly decreased in elderly versus young subjects while no modification of the retinoid-related plasma parameters ROH and RBP were emphasized by aging. Concerning thyroid criteria, the elderly exhibited an increase in TSH concentration (+39%) without significant modifications of FT3 and FT4, which indicated an age-related sub-clinical hypothyroidism. Concurrently, the amount of TR mRNA (alpha as well as beta subtypes) was significantly decreased in the elderly. CONCLUSION: These data constitute the first evidence of an age-related hypo-activation of the retinoid and thyroid nuclear pathways in PBMC. Further study of the possible association between the expression of the retinoid and thyroid nuclear receptors and age-related cognitive alterations in humans would be interesting.

Differential effect of retinoic acid and triiodothyronine on the age-related hypo-expression of neurogranin in rat.

Given the important role of retinoids and thyroid hormone for optimal brain functioning and the tenuous relationship between retinoic acid (RA) and triiodothyronine (T3) signalings, we compared the effects of RA or T3 administrations on RA and T3 nuclear receptors (RAR, RXR and TR) and on their target genes, neuromodulin (GAP43) and neurogranin (RC3) in 24-month-old rats. Quantitative real time PCR and western blot analysis allowed us to verify that retinoid and thyroid signalings and GAP43 and RC3 expression are affected by age. By in situ hybridization we observed a decreased expression of RC3 in hippocampus, striatum and cerebral cortex. RARbeta, RXRbeta/gamma and GAP43 were up-regulated by RA as well as T3 treatment. The abundance of TRalpha/beta mRNA and RC3 expression were only increased by T3 administration in the whole brain. This up-regulator effect of T3 on RC3 was only observed in the striatum. During aging, T3 become a limiting factor alone able to correct the age-related concomitant hypo-activation of retinoid and thyroid signalings and alterations of synaptic plasticity.

Expression of neurogranin and neuromodulin is affected in the striatum of vitamin A-deprived rats.

Our previous data showed that vitamin A deficiency (VAD) induces, in whole brain, a reduced amount of mRNA for brain retinoic acid (RA) and triiodothyronine (T3) nuclear receptors (i.e., RAR, RXR, and TR, respectively), which is accompanied by reduced amounts of mRNA and protein of neurogranin (RC3, a neuronal protein involved in synaptic plasticity) as well as selective behavioral impairment. Given the important role of retinoids for optimal brain functioning, the effects of vitamin A depletion and subsequent administration of RA or T3 on the mRNA levels of RA and T3 nuclear receptors and on two target genes' (RC3 and neuromodulin or GAP43) mRNA and protein levels were examined in the hippocampus, striatum, and cerebral cortex. A quantitative real-time polymerase chain reaction (PCR), in situ hybridization, and Western blot analysis demonstrated that the striatal region is the brain site where both RA and T3 signaling pathways are most affected by VAD. Indeed, rats fed a vitamin A-free diet for 10 weeks exhibited decreased expression of RAR, RXR, TR, RC3, and GAP43 in the striatum. The administration of T3 to these vitamin A-deprived rats reversed the reduction in mRNA levels of RA and T3 nuclear receptors and in mRNA and protein levels of target genes in this region. These data suggest that modifications that appear preferentially in the striatum, a region highly sensitive to vitamin A bioavailability, may contribute to neurobiological alterations and the spatial learning impairment that occurs in vitamin A-deprived animals.

Retinoic acid reverses the PTU related decrease in neurogranin level in mice brain.

Recent data have shown that fine regulation of retinoid mediated gene expression is fundamentally important for optimal brain functioning in aged mice. Nevertheless, alteration of the thyroid hormone signalling pathway may be a limiting factor, which impedes retinoic acid (RA) from exerting its modulating effect. Mild hypothyroidism is often described in the elderly. Thus, in the present study, it was of interest to determine if RA exerts its neurological modulating effect in mild hypothyroidism. To obtain further insight into this question, mice were submitted to a low propylthiouracyl (PTU) drink (0.05%) in order to slightly reduce the serum level of triiodothyronine (T3). A quantitative evaluation of RA nuclear receptors (RAR, RXR), T3 nuclear receptor (TR) and of neurogranin (RC3, a RA target gene which codes for a protein considered as a good marker of synaptic plasticity) in PTU treated mice injected with vehicle or RA or T3 was carried out. The PTU-related decrease in expression of RAR, RXR and RC3 was restored following RA or T3 administration, as observed in aged mice. The amount of TR mRNA, which was not affected in PTU treated mice, was increased only after T3 treatment as observed in overt hypothyroidism. These results suggest that neurobiological alterations observed in aged mice are probably related to RA and T3 signalling pathway modifications associated, in part, with mild changes in thyroid function.

Hyperlipidic diets induce early alterations of the vitamin A signalling pathway in rat colonic mucosa.

OBJECTIVE: Dietary factors can be associated with colorectal cancer. Fatty acids modulate gene expression in various tissues, mediated by activation of the peroxisome proliferator activated receptor: PPAR. Vitamin A signalling is mediated by retinoic acid (RA) receptors (RAR) and retinoid X receptors (RXR). The steroid nuclear receptors PPAR, RAR, RXR, are DNA-binding proteins and they induce gene transcription upon activation by specific ligands and interacting with distinct promoter sequences in the target genes. The aim of this study was to investigate the impact of hyperlipidic diets on the expression of PPARg, RXRa and RARb mRNA in rat colon. METHODS: Rats were fed during 4 weeks with the following diets: a cafeteria diet where 60% of the energy was supplied as lipids and a high fat diet (HFD) represented by 25% of a safflower oil (w/w) rich in polyunsaturated fatty acids, mainly n-6. Nuclear receptors mRNA were quantified by realtime RT-PCR with TaqMan probe process or SYBRGreen I chemical. RESULTS: The cafeteria diet and the HFD induced a significant decrease in RARb mRNA: -36% (p<0.02) and -64% (P<0.001) respectively. Simultaneously, an increased expression of PPARg mRNA was observed for cafeteria diet +35% (P<0.05) and for HFD +45% (P<0.05). The level of RXRa mRNA was significantly increased for cafeteria diet: +53% (P<0.0002), while no significant difference in RXRa mRNA was observed in colonic mucosa rats whose fed with the 25% HFD. CONCLUSIONS: These results showed that an hyperlipidic diet could induce early modifications in the pattern of expression of nuclear receptors in rat colon. Many mechanisms could be probably involved but one hypothesis is that a modification of the balance between the nuclear receptors, resulting from an increased expression of PPARg, could induce a decreased expression of RARb in rat colon.

Relationship between peroxisome proliferator-activated receptor gamma and retinoic acid receptor alpha gene expression in obese human adipose tissue.

OBJECTIVE: To investigate in human adipose tissue a possible relationship between per oxisome proliferator-activated receptor gamma (PPARgamma) and retinoic acid receptor alpha (RARalpha) gene expression, two genes involved in the control of adipocyte differentiation. SUBJECTS: Ten lean control women (age 31-60 y, body mass index (BMI) 18-24.7 kg/m(2)) and an obese group of 15 women (age 27-62 y, BMI 30-57.5 kg/m(2)), of whom 10 subjects were in weight-gain phase and five were in weight-loss phase. MEASUREMENTS: We assessed the relative PPARgamma and RARalpha mRNA levels in subcutaneous abdominal adipose tissue using a real-time PCR method. RESULTS: PPARgamma mRNA level were significantly increased (+91%; P<0.01) in obese women compared to lean control women. In the obese group, we observed a PPARgamma mRNA level 42% lower in weight-loss obese than in weight-gain obese subjects. We obtained a positive correlation (r=0.56; P<0.01) between PPARgamma mRNA level and the BMI of all subjects. Relative mRNA abundance level of RARalpha in subcutaneous adipose tissue of obese subjects is significantly lower than in control subjects (-56%, P<0.01), and a negative correlation was found between PPARgamma and RARalpha mRNA levels in subcutaneous adipose tissue of subjects study (r=-0.75; P<0.01). CONCLUSION: Our findings suggest that obesity is associated with an inverse relationship between PPARgamma and RARalpha expressions in human subcutaneous adipose tissue. Modulations of nuclear receptor profile could be an important event in the body's early adaptive mechanisms promoting adipose tissue plasticity and leading to the onset of obesity.

Transglutamines and endocrine system (minireview).

Transglutaminases catalyze the posttranslation modification of proteins by catalyzing Ca2+ dependent acyl-transfer reaction resulting in the formation of new g-amide bonds between g-carboxamide groups of peptide-bound glutamine residues and various primary amines. Such glutamine residue serves as acyl-donor and the most common acyl-acceptors are e-amino groups of peptide-bound lysine residues or primary amino groups of some naturally occurring polyamines, like putrescine or spermidine. The active site of cysteine reacts first with the g-carboxamide group of glutamine residue to form the acyl-enzyme intermediate under the release of ammonia. In the second step, the complex reacts with a primary amine to form an isopeptide bond and liberate the reactivated enzyme. The presence of transglutaminases has been observed in various endocrine glands such as human pituitary, which was investigated by immunohistochemical methods using specific antibodies. A significant increase in the expression and activity of tissue transglutaminase was observed during involution of thymus. In the genital tract of the male rat two different forms of the enzyme transglutaminase could be identified and characterized. the presence of p53 and tissues transglutaminase gene expressions in human normal and pathologic adrenal tissues. The Ca2+-responsive enzyme transglutaminase, which catalyzes the cross-bridging of proteins, was found in pancreatic islet cells.

A retinoic acid receptor antagonist suppresses brain retinoic acid receptor overexpression and reverses a working memory deficit induced by chronic ethanol consumption in mice.

BACKGROUND: Chronic ethanol consumption induces disorders in the biosynthesis of retinoic acid, an active derivative of vitamin A. Recent evidence suggests that an alteration in the retinoic acid signaling pathway leads to impairments in learning and memory in adult mice. We have previously shown that chronic ethanol consumption in mice produces an increased expression of the brain retinoic acid receptor beta (RARbeta) mRNA. These results prompted us to examine whether suppressing the overexpression of retinoid receptors in alcohol-treated mice by RAR antagonist administration would reverse their cognitive impairment. METHODS: After 10 months of ethanol consumption (12% v/v in drinking water), C57BL/6 mice were submitted to a working memory task in a T-maze. Then, mice of the control and the ethanol-treated groups received an RARbeta antagonist (CD2665 0.6 mg/kg) for 22 days. The behavioral effect of CD2665 administration was evaluated on a spontaneous alternation task and the neurochemical effect was measured by quantifying the mRNA expression of RARalpha, RARbeta, retinoid X receptor (RXRbeta/gamma) and tissue transglutaminase (tTG; a retinoic acid-target gene). RESULTS: Mice submitted to ethanol treatment exhibited a progressive decrease in spontaneous alternation rates over successive trials. Moreover, these mice displayed an increased expression of brain RARbeta and RXRbeta/gamma mRNA, together with an increased level of tTG mRNA and enzymatic activity. The administration of CD2665 to alcohol-treated mice totally reversed the working memory deficit and suppressed the overexpression of brain RARbeta, RXRbeta/gamma and tTG mRNA, whereas the same treatment in control mice decreased only the RARbeta mRNA level without affecting memory performance. CONCLUSION: These data point to the potential role of the retinoid signaling pathway in memory processes and suggest that the overexpression of brain RARbeta and RXRbeta/gamma could be responsible, at least in part, for some memory impairments observed during chronic ethanol consumption.

Selective age-related changes in the PKC-sensitive, calmodulin-binding protein, neurogranin, in the mouse brain.

Brain ageing is associated with a dysregulation of intracellular calcium (Ca(2+)) homeostasis which leads to deficits in Ca(2+)-dependent signalling pathways and altered neuronal functions. Given the crucial role of neurogranin/RC3 (Ng) in the post-synaptic regulation of Ca(2+) and calmodulin levels, age-dependent changes in the levels of Ng mRNA and protein expression were analysed in 3, 12, 24 and 31-month-old mouse brains. Ageing produced significant decreases in Ng mRNA expression in the dorsal hippocampal subfields, retrosplenial and primary motor cortices, whereas no reliable changes were seen in any other cortical regions examined. Western blot indicated that Ng protein expression was also down-regulated in the ageing mouse brain. Analysis of Ng immunoreactivity in both hippocampal CA1 and retrosplenial areas indicated that Ng protein in aged mice decreased predominantly in the dendritic segments of pyramidal neurones. These data suggest that age-related changes of post-synaptic Ng in selected brain areas, and particularly in hippocampus, may contribute to altered Ca(2+)/calmodulin-signalling pathways and to region-specific impairments of synaptic plasticity and cognitive decline.