Odette Champigny

Distribution of the uncoupling protein 2 mRNA in the mouse brain

The present study was conducted to investigate the brain distribution of the recently cloned uncoupling protein 2 (UCP2). Northern blot analyses were first carried out to confirm the presence of UCP2 in the brain. These analyses revealed the brain presence of UCP2 mRNA and the absence of the mRNAs encoding uncoupling protein 1 and uncoupling protein 3. They also demonstrate that UCP2 mRNA expression was abundant in the hypothalamus and not affected by cold acclimation. In situ hybridization histochemistry was used to determine the brain distribution of the mRNA encoding UCP2. A markedly intense hybridization signal was found in the hypothalamus, the ventral septal region, the caudal hindbrain (medulla), the ventricular region, and the cerebellum. A very highly intense hybridization signal was apparent in the suprachiasmatic nucleus, the medial parvicellular part of the paraventricular hypothalamic nucleus, the arcuate nucleus, the dorsal motor nucleus of the vagus nerve, and the choroid plexus. The specifically localized expression of UCP2 mRNA suggests that this mRNA has a neuronal localization. Neuronal expression was particularly manifest in the nucleus of the horizontal limb of the diagonal band, the submedius thalamic nucleus and the dorsal motor nucleus of the vagus nerve, where agglomerations of the silver grains delineated individual cells. The role played by UCP2 in the brain has yet to be fully described, but the pattern of distribution of the transcript suggests that this mitochondrial protein is part of neuronal circuitries controlling neuroendocrine functions, autonomic responses, and the general arousal of the brain. Given the involvement of the proteins from the uncoupling proteins family in the uncoupling of cellular respiration, it can be argued that UCP2 contributes to the metabolic rate and thermoregulation of these circuitries. In addition, by promoting oxygen consumption in the brain, UCP2 could control the production of reactive oxygen species and thereby influence the process of neural degeneration. J. Comp. Neurol. 397:549–560, 1998.

Essential cis-Acting Elements in Rat Uncoupling Protein Gene Are in an Enhancer Containing a Complex Retinoic Acid Response Domain

Transgenic mice were generated with a transgene containing the 211-base pair (bp) enhancer and 0.4 kilobase pairs of 5′-flanking DNA of the uncoupling protein (ucp) gene. Expression of this transgene was restricted to brown adipose tissue and was inducible by cold exposure or treatment of transgenic mice by norepinephrine, retinoic acid (RA), or CL-316,243 β3-adrenoreceptor agonist. A search for retinoic acid response elements in the ucp gene enhancer was undertaken using mutagenesis and transfection of cultured cells with chloramphenicol acetyltransferase constructs. Deletion or mutations of several putative retinoic acid response elements were ineffective. Mutations of a TGAATCA region dramatically decreased the transcriptional activity in the presence of RA. In vitro this region was able to bind a complex containing proteins recognized by antibodies against Jun or Fos. Mutations of an adjacent region related to an inverted repeat of type 2 also markedly decreased RA effect. This region was able to bind in vitro retinoid X receptor α and retinoic acid receptor β. The two regions form an activating region between bp −2421 and −2402 (referred to as the ucp gene-activating region), which has an enhancer activity but cannot confer RA response to a promoter. This response was obtained with a larger DNA fragment (bp −2489 to −2398) constituting a complex RA response domain.

Leptin and Corticosterone Have Opposite Effects on Food Intake and the Expression of UCP1 mRNA in Brown Adipose Tissue of lepob/lepob Mice

The present study was conducted to assess the interaction effect of leptin and corticosterone on food intake and the expression of uncoupling protein 1 (UCP1) mRNA in interscapular brown adipose tissue (IBAT). To this end, a 3 × 3 factorial experiment was designed in which adrenalectomized (ADX) lepob/lepob mice were subjected to three doses of corticosterone and three doses of leptin. The results confirm the anorectic and orexigenic effects of leptin and corticosterone, respectively. The results also emphasize the abilities of leptin and corticosterone to respectively increase and reduce the expression of UCP1 mRNA in IBAT. The effects of leptin and corticosterone on food intake and the expression of UCP1 mRNA translated into effects on body weight and body composition; leptin reduced body weight and corticosterone increased the weight of IBAT. The present results do not provide evidence for leptin-corticosterone interactions in the control of food intake and thermogenesis. Corticosterone increased food ...

Comment to Shinohara et al. (1991) FEBS Letters 293, 1731̄74 The uncoupling protein is not expressed in rat liver

Using Northern blot analysis, immunoblotting with purified antibodies and Polymerase Chain Reaction analysis, we were unable to detect the Uncoupling Protein‐UCP or its mRNA in liver of control, cold‐exposed or newborn rats. The unique expression of this protein in brown adipocytes was confirmed. These data refute the surprising recent report on UCP expression in rat liver (Shinohara (1991) FEBS Lett. 293, 173–174). Moreover we report that the hybridization signal obtained by these authors is probably non‐specific and due to the 3′ non‐coding domain of the UCP cDNA probe.

Contributions of studies on uncoupling proteins to research on metabolic diseases.

Abstract. Ricquier D, Fleury C, Larose M, Sanchis D, Pecqueur C, Raimbault S, Gelly C, Vacher D, Cassard‐Doulcier A‐M, Lévi‐Meyrueis C, Champigny O, Miroux B, Bouillaud F (Centre National de la Recherche Scientifique, Centre de Recherche sur l’Endocrinologie Moléculaire et le Développement, Meudon, France). Contributions of studies on uncoupling proteins to research on metabolic diseases. (Minisymposium: Genes & Obesity). J Intern Med 1999; 245: 637–642.

Alanine Turnover Rate and Its Hepatic Metabolism Are Increased in Midpregnant Rat

At mid pregnancy (12th day) fed rats exhibit a drop of blood alanine level when the weight of the fetoplacental unit is still negligible. A primed infusion A-V method was used to measure alanine kinetics in fed midpregnant rats and virgin controls, using L-[2,3-3H]alanine as a tracer. Alanine turnover and metabolic clearance rates were higher on day 12 than in virgin controls. The increase in alanine turnover rate was accounted for by an increase in alanine degradation. Since the liver is the main site of alanine degradation, alanine uptake was studied in isolated hepatocytes. Hepatocytes isolated from midpregnant rats utilized 50% more alanine than those from virgin controls. This increase was mainly due to metabolism rather than incorporation into proteins. In conclusion, the alanine turnover rate and its hepatic metabolism are increased in fed midpregnant rats, resulting in the decrease in blood alanine.