UCP2 mRNA Levels Research Articles

IGF2BP2/IMP2-Deficient Mice Resist Obesity through Enhanced Translation of Ucp1 mRNA and Other mRNAs Encoding Mitochondrial Proteins

Although variants in the IGF2BP2/IMP2 gene confer risk for type 2 diabetes, IMP2, an RNA binding protein, is not known to regulate metabolism. Imp2(-/-) mice gain less lean mass after weaning and have increased lifespan. Imp2(-/-) mice are highly resistant to diet-induced obesity and fatty liver and display superior glucose tolerance and insulin sensitivity, increased energy expenditure, and better defense of core temperature on cold exposure. Imp2(-/-) brown fat and Imp2(-/-) brown adipocytes differentiated in vitro contain more UCP1 polypeptide than Imp2(+/+) despite similar levels of Ucp1 mRNA; the Imp2(-/-)adipocytes also exhibit greater uncoupled oxygen consumption. IMP2 binds the mRNAs encoding Ucp1 and other mitochondrial components, and most exhibit increased translational efficiency in the absence of IMP2. In vitro IMP2 inhibits translation of mRNAs bearing the Ucp1 untranslated segments. Thus IMP2 limits longevity and regulates nutrient and energy metabolism in the mouse by controlling the translation of its client mRNAs.

Molecular cloning and tissue expression of uncoupling protein 1, 2 and 3 genes in Chinese perch (Siniperca chuatsi).

Uncoupling proteins (UCPs) are mitochondrial anion carrier proteins, which play important roles in several physiological processes, including thermogenesis, reactive oxygen species generation, growth, lipid metabolism and insulin secretion. Although the roles of UCPs are well understood in mammals, little is known in fish. To investigate the thermogenesis roles in Chinese perch (Siniperca chuatsi), we cloned the UCP1, 2 and 3. The UCP1 consisted of six exons and five introns, and the UCP2 consisted of eight exons and seven introns. The UCP1 was primarily expressed in liver, UCP2 was ubiquitously expressed, and UCP3 was primarily expressed in muscle. The mRNA levels of UCP1 and UCP2 in liver, and UCP3 in muscle were significantly increased after prolonged cold exposure, but did not change after prolonged heat exposure, suggesting that Chinese perch might have a mechanism of response to cold environment, but not to hot environment. The intestinal UCP1 mRNA level was significantly up-regulated after prolonged heat exposure, while the UCP2 mRNA level was significantly up-regulated after prolonged cold exposure, suggesting that the two paralogs might play different roles in intestine of Chinese perch. In addition, the phylogenetic analysis could shed new light on the evolutionary diversification of UCP gene family.

SET overexpression in HEK293 cells regulates mitochondrial uncoupling proteins levels within a mitochondrial fission/reduced autophagic flux scenario

We hypothesized that SET, a protein accumulated in some cancer types and Alzheimer disease, is involved in cell death through mitochondrial mechanisms. We addressed the mRNA and protein levels of the mitochondrial uncoupling proteins UCP1, UCP2 and UCP3 (S and L isoforms) by quantitative real-time PCR and immunofluorescence as well as other mitochondrial involvements, in HEK293 cells overexpressing the SET protein (HEK293/SET), either in the presence or absence of oxidative stress induced by the pro-oxidant t-butyl hydroperoxide (t-BHP). SET overexpression in HEK293 cells decreased UCP1 and increased UCP2 and UCP3 (S/L) mRNA and protein levels, whilst also preventing lipid peroxidation and decreasing the content of cellular ATP. SET overexpression also (i) decreased the area of mitochondria and increased the number of organelles and lysosomes, (ii) increased mitochondrial fission, as demonstrated by increased FIS1 mRNA and FIS-1 protein levels, an apparent accumulation of DRP-1 protein, and an increase in the VDAC protein level, and (iii) reduced autophagic flux, as demonstrated by a decrease in LC3B lipidation (LC3B-II) in the presence of chloroquine. Therefore, SET overexpression in HEK293 cells promotes mitochondrial fission and reduces autophagic flux in apparent association with up-regulation of UCP2 and UCP3; this implies a potential involvement in cellular processes that are deregulated such as in Alzheimer's disease and cancer.

The UCP2 -866G>A promoter region polymorphism is associated with nonalcoholic steatohepatitis.

Uncoupling protein 2 - UCP2 - regulates mitochondrial lipid fluxes and reactive oxygen species production by the respiratory chain. The -866 G>A UCP2 promoter region polymorphism has been linked to insulin resistance and lipid metabolism. The aim of this study was to assess whether the -866 G>A UCP2 polymorphism predisposes to nonalcoholic steatohepatitis in patients at risk, and the relationship with lipid metabolism and hepatic UCP2 expression. We considered 688 Italian patients who underwent liver biopsy for suspected NASH, and 232 healthy controls. The UCP2 -866 G>A polymorphism was determined by allele specific oligonucleotide probes, hepatic UCP2 mRNA levels by quantitative real-time PCR. UCP2 A/A genotype was associated with a reduced risk of nonalcoholic steatohepatitis (Odds Ratio 0.49, 95% C.I. 0.26-0.90; P = 0.02; adjusted for age, sex, BMI, impaired fasting glucose or diabetes, PNPLA3 I148M alleles and recruitment centre). The A/A genotype was associated with reduced risk of steatosis grade G2-G3 and nonalcoholic steatohepatitis in patients without (P = 0.003 and P = 0.01 respectively), but not in those with (P = NS) impaired fasting glucose/diabetes. The UCP2 A/A genotype was associated with higher hepatic UCP2 mRNA levels (adjusted P = 0.008). Concerning the metabolic traits, the UCP2 A/A genotype was associated with higher total serum cholesterol levels (adjusted P = 0.03), but not with serum HDL, triglycerides or impaired fasting glucose/diabetes. UCP2 -866 A/A genotype is associated with increased hepatic UCP2 expression and reduced risk of nonalcoholic steatohepatitis, particularly in subjects with normal fasting glucose.

N-3 polyunsaturated fatty acids decrease levels of doxorubicin-induced reactive oxygen species in cardiomyocytes -- involvement of uncoupling protein UCP2

BackgroundUse of the chemotherapeutic drug doxorubicin (DOX) is associated with serious cardiotoxicity, as it increases levels of reactive oxygen species (ROS). N-3 polyunsaturated fatty acid dietary supplements can be of benefit to patients undergoing cancer therapy. The aims of this study were to determine whether DOX-induced cardiotoxicity is related to mitochondrial uncoupling proteins and whether eicosapentaenoic acid (EPA, C20:5 n-3) or docosahexaenoic acid (DHA, C22:6 n-3) affects DOX-induced cardiomyocyte toxicity.ResultsTreatment of H9C2 cells with DOX resulted in decreased cell viability and UCP2 expression. Treatment with 100 μM EPA or 50 μM DHA for 24 h resulted in a maximal mitochondria concentration of these fatty acids and increased UCP2 expression. Pretreatment with 100 μM EPA or 50 μM DHA prevented the DOX-induced decrease in UCP2 mRNA and protein levels, but these effects were not seen with EPA or DHA and DOX cotreatment. In addition, the DOX-induced increase in ROS production and subsequent mitochondrial membrane potential change (∆ψ) were significantly attenuated by pretreatment with EPA or DHA.ConclusionEPA or DHA pre-treatment inhibits the DOX-induced decrease in UCP2 expression, increase in ROS production, and subsequent mitochondrial membrane potential change that contribute to the cardiotoxicity of DOX.Electronic supplementary materialThe online version of this article (doi:10.1186/s12929-014-0101-3) contains supplementary material, which is available to authorized users.

Irisin has no effect on lipolysis in 3T3-L1 adipocytes or fatty acid metabolism in HepG2 hepatocytes

Irisin, a newly identified myokine responsible for browning of white or beige adipocytes, has been reported to be present at reduced levels in diabetic patients and associated with obesity, serum triglyceride (TG) levels, and intrahepatic TG levels. We wondered whether irisin could directly affect fatty acid and TG metabolism in adipocytes and hepatocytes. We examined the effects of various concentrations of irisin on lipolysis (according to Oil Red O staining, free fatty acid release, and glycerol release), protein expression of HSL and ATGL, and mRNA expression of other lipid-related genes (UCP-1, PPARγ, FABP-4, HSL, ATGL, PPARα, and CPT-1) in mature 3T3-L1 adipocytes, as well as mRNA levels of genes involved in the synthesis (SREBP-1C and FAS) and β-oxidation (PPARα and CPT-1) of fatty acids in HepG2 hepatocytes under physiological or hyperglycemic conditions. Our results revealed that although irisin significantly increased the mRNA levels of UCP-1 and PPARα, it failed to show detectable effects on lipolysis, HSL or ATGL protein levels, or the mRNA expression of other lipid-related genes in mature 3T3-L1 adipocytes. In HepG2 hepatocytes, high glucose induced the upregulation of SREBP-1C and FAS and the downregulation of PPARα; however, no significant effect of irisin on gene expression was observed under either physiological or hyperglycemic conditions. We therefore conclude that irisin has no significant direct effect on lipolysis in 3T3-L1 adipocytes or on fatty acid metabolism in HepG2 hepatocytes.

Functional modification of adipocytes by grape seed extract impairs their pro-tumorigenic signaling on colon cancer stem cells and the daughter cancer cells.

With global rise in obesity, it is imperative that we identify obesity-driven factors that increase growth and progression of colorectal cancer (CRC), and also discover and develop agents with anti-CRC efficacy under obese conditions. Here in, we investigated grape seed extract (GSE), a well-defined agent with both preventive and anti-CRC efficacy, for its potential to impair pro-tumorigenic signaling of adipocytes on CRC/colon cancer stem cells (CSCs) and associated molecular mechanisms, to control CRC under obese conditions. GSE treatment significantly decreased the growth and invasion promoting effects of both mouse and human adipocytes on CRC cells. Moreover, GSE exerted a direct inhibitory effect, as well as it strongly reduced the growth promoting signals of adipocytes, on colon CSCs. These GSE effects were associated with a decrease in both mRNA and protein levels of various CSC-associated molecules. Notably, GSE effects on adipocytes were not due to changes in lipid content, but by inducing the 'browning' of adipocytes as evidenced by an increase in UCP-1 mRNA level and mitochondriogenesis. Together, these findings, for the first time, suggest the ability of GSE to induce 'brown remodeling' of white adipocytes, which causes functional modification of adipocytes thus impairing their pro-tumorigenic signals on colon CSCs/CRC cells.

Triiodothyronine regulates distribution of thyroid hormone receptors by activating AMP-activated protein kinase in 3T3-L1 adipocytes and induces uncoupling protein-1 expression.

The purposes of this study were to examine whether thermogenesis in 3T3-L1 adipocytes is related to variations in thyroid hormone receptors (TRs) that are differently regulated by triiodothyronine (T3), and the possible role of AMP-activated protein (AMPK) in thermogenesis after cell differentiation. Differentiated 3T3-L1 adipocytes were maintained under four conditions: normal control group, T3 treatment group, AMPK agonist (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside) treatment group, and T3 and AMPK inhibitor (Compound C) treatment group. Real-time polymerase chain reaction was then performed to evaluate the changes in TRα and TRβ mRNA levels in the cells, as well as marker genes for brown adipose tissue including uncoupling protein (UCP)-1 and Cidea. Western blotting was carried out for the cells to detect the expressions of TRα, TRβ, and AMPK protein levels. After T3 treatment, the mRNA and protein levels of TRα decreased compared with the control group, while TRβ mRNA and protein levels increased markedly at the same time. We also found elevated mRNA levels of UCP-1 and Cidea after exposure to T3. However, the distribution of TRs was reversed by Compound C. AMPK protein levels were clearly activated by T3. Our results suggest that the distribution of TRs is related to thermogenesis, and AMPK may participate in the alterations.

Epigallocatechin gallate counteracts oxidative stress in docosahexaenoxic acid-treated myocytes

Skeletal muscle is a key organ of mammalian energy metabolism, and its mitochondria are multifunction organelles that are targets of dietary bioactive compounds. The goal of this work was to examine the regulation of mitochondrial dynamics, functionality and cell energy parameters using docosahexaenoic acid (DHA), epigallocatechin gallate (EGCG) and a combination of both in L6 myocytes. Compounds (at 25μM) were incubated for 4h. Cells cultured with DHA displayed less oxygen consumption with higher ADP/ATP ratio levels concomitant with downregulation of Cox and Ant1 gene expression. The disruption of energetic homeostasis by DHA, increases intracellular reactive oxygen species (ROS) levels and decreases mitochondrial membrane potential. The defence mechanism to counteract the excess of ROS production was by the upregulation of Ucp2, Ucp3 and MnSod gene expression. Moreover myocytes cultured with DHA had a higher mitochondrial mass with a higher proportion of large and elongated mitochondria, whereas the fission genes Drp1 and Fiss1 and the fusion gene Mfn2 were downregulated. In myocytes co-incubated with DHA and EGCG, ROS levels and the adenosine diphosphate (ADP)/adenosine triphosphate (ATP) ratio were similar to untreated myocytes and the decrease of oxygen consumption, higher mitochondrial mass and the overexpression of Ucp2 and Ucp3 genes were similar to the DHA-treated cells with also a higher amount of mitochondrial deoxyribonucleic acid (DNA), and reduced Drp1 and Fiss1 gene expression levels. In conclusion the addition of EGCG to DHA returned the cells to the control conditions in terms of mitochondrial morphology, energy and redox status, which were unbalanced in the DHA-treated myocytes.

Cyclodextrin-Clathrated Limonin Suppresses Diet-Induced Obesity in Mice

Limonin (Lim) is a white crystalline substance usually found in orange and lemon seeds. In this paper, we report the antiobesity effects of cyclodextrin (CD)-treated Lim along with naringenin (Ng) and hesperetin (Hes). We demonstrated that Lim, Ng and Hes decreased cell viability in 3T3-L1 preadipocyte cells. Lim, Ng and Hes inhibited the adipocyte differentiation in response to adipogenic inducers. The evidence for this inhibition included fewer Oil Red O positive droplets and a decreased expression of the adipocyte-specific gene PPARγ2. In animal studies, Lim-, Hes- and combination-treated mice gained less body weight than control mice did. The plasma triglyceride and cholesterol levels were significantly reduced by Lim and the other substances. Furthermore, Lim increased the mRNA levels of lipid metabolism-related genes, including Acox1, UCP2 and CPT1 in the liver. This study suggests that CD-treated Lim prevents diet-induced obesity in mice by inducing lipid metabolism-related genes in the liver. Practical Applications Limonin (Lim) is a limonoid that has a bitter taste and is a water-insoluble substance found in citrus fruits. It has several important biological properties. Citrus Lim does not dissolve in water, which makes it unsuitable for use in oral preparations. In the present study, we used a cyclodextrin-treated Lim that is very easily dissolved in water. In this report, we demonstrated the anti-adipogenic effects of citrus Lim in 3T3-L1 preadipocyte cells. We also used cyclodextrin-clathrated Lim, naringenin and hesperetin to examine the hypocholesterolemic activities in mice. The results from our study showed that Lim and these two flavonoid-related compounds can be used to develop oral preparations that may have possible lipid-lowering properties and may be able to reduce diet-induced obesity.

Effects of risperidone on energy balance in female C57BL/6J mice

ObjectiveTo investigate the effect of risperidone on energy expenditure and weight gain in female C57BL/6J mice.Design and MethodsBody weight and composition, food intake, energy expenditure, and activity were determined weekly. mRNA expression of uncoupling protein 1 in brown adipose tissue, orexin and brain-derived neurotrophic factor in the hypothalamus were quantified by Real-Time PCR.ResultsRisperidone tended to induce a greater body weight gain (P=0.052) and significantly higher food intake (P=0.038) relative to the placebo-treated group. Risperidone-treated mice had a higher resting energy expenditure (P=0.001), and total energy expenditure (P=0.005) than the placebo group. There were no effects of treatment, time, and treatment by time on NREE between groups. Risperidone-treated mice showed a significantly lesser locomotor activity than placebo-treated mice over 3 weeks (P<0.001). Risperidone induced a higher UCP1 mRNA (P=0.003) and a lower orexin mRNA (P=0.001) than placebo.DiscussionRisperidone-induced weight gain is associated with hyperphagia and a reduction in locomotor activity in C57BL/6J mice. Additionally, higher total and resting energy expenditure were accompanied by higher levels of UCP1 mRNA in BAT. The increased total energy expenditure could not offset the total intake of energy through risperidone-induced hyperphagia, therefore resulting in weight gain in female C57BL/6J mice.

In uncontrolled diabetes, thyroid hormone and sympathetic activators induce thermogenesis without increasing glucose uptake in brown adipose tissue

Recent advances in human brown adipose tissue (BAT) imaging technology have renewed interest in the identification of BAT activators for the treatment of obesity and diabetes. In uncontrolled diabetes (uDM), activation of BAT is implicated in glucose lowering mediated by intracerebroventricular (icv) administration of leptin, which normalizes blood glucose levels in streptozotocin (STZ)-induced diabetic rats. The potent effect of icv leptin to increase BAT glucose uptake in STZ-diabetes is accompanied by the return of reduced plasma thyroxine (T4) levels and BAT uncoupling protein-1 (Ucp1) mRNA levels to nondiabetic controls. We therefore sought to determine whether activation of thyroid hormone receptors is sufficient in and of itself to lower blood glucose levels in STZ-diabetes and whether this effect involves activation of BAT. We found that, although systemic administration of the thyroid hormone (TR)β-selective agonist GC-1 increases energy expenditure and induces further weight loss in STZ-diabetic rats, it neither increased BAT glucose uptake nor attenuated diabetic hyperglycemia. Even when GC-1 was administered in combination with a β(3)-adrenergic receptor agonist to mimic sympathetic nervous system activation, glucose uptake was not increased in STZ-diabetic rats, nor was blood glucose lowered, yet this intervention potently activated BAT. Similar results were observed in animals treated with active thyroid hormone (T3) instead of GC-1. Taken together, our data suggest that neither returning normal plasma thyroid hormone levels nor BAT activation has any impact on diabetic hyperglycemia, and that in BAT, increases of Ucp1 gene expression and glucose uptake are readily dissociated from one another in this setting.

UCP1 mRNA does not produce heat

Because of the possible role of brown adipose tissue and UCP1 in metabolic regulation, even in adult humans, there is presently considerable interest in quantifying, from in-vitro data, the thermogenic capacities of brown and brite/beige adipose tissues. An important issue is therefore to establish which parameters are the most adequate for this. A particularly important issue is the relevance of UCP1 mRNA levels as estimates of the degree of recruitment and of the thermogenic capacity resulting from differences in physiological conditions and from experimental manipulations. By solely following UCP1 mRNA levels in brown adipose tissue, the conclusion would be made that the tissue's highest activation occurs after only 6h in the cold and then successively decreases to being only some 50% elevated after 1month in the cold. However, measurement of total UCP1 protein levels per depot ("mouse") reveals that the maximal thermogenic capacity estimated in this way is reached first after 1month but represents an approx. 10-fold increase in thermogenic capacity. Since this in-vitro measure correlates quantitatively and temporally with the acquisition of nonshivering thermogenesis, this must be considered the most physiologically relevant parameter. Similarly, observations that cold acclimation barely increases UCP1 mRNA levels in classical brown adipose tissue but leads to a 200-fold increase in UCP1 mRNA levels in brite/beige adipose tissue depots may overemphasise the physiological significance of these depots, as the high fold-increases are due to very low initial levels, and the UCP1 mRNA levels reached are at least an order of magnitude lower than in brown adipose tissue; furthermore, based on total UCP1 protein amounts, the brite/beige depots attain only about 10% of the thermogenic capacity of the classical brown adipose tissue depots. Consequently, inadequate conclusions may be reached if UCP1 mRNA levels are used as a proxy for the metabolic significance of recruited versus non-recruited brown adipose tissue and for estimating the metabolic significance of brown versus brite/beige adipose tissues. This article is part of a Special Issue entitled Brown and White Fat: From Signaling to Disease.

Brown Fat Expresses Adiponectin in Humans

The presence of brown adipose tissue (BAT) in humans is unclear. Pheochromocytomas (PHEO) are rare tumors of neuroectodermal origin which occur in 0.1-0.2% of patients with hypertension. We sought to evaluate the presence and activity of BAT surrounding adrenal PHEO in a well-studied sample of 11 patients who were diagnosed with PHEO and then underwent adrenalectomy. Areas of white fat (WAT) and BAT surrounding PHEO were obtained by Laser Capture Microdissection for analysis of uncoupling protein (UCP)-1 and adiponectin mRNA expression. Adiponectin and UCP-1 mRNA levels were significantly higher in BAT than in WAT (0.62 versus 0.15 and 362.4 versus 22.1, resp., P < 0.01 for both). Adiponectin mRNA levels significantly correlated with urinary metanephrines (r = 0.76, P < 0.01), vanilly mandelic acid (VMA) (r = 0.95, P < 0.01), and serum adiponectin levels (r = 0.95, P < 0.01). Serum adiponectin levels significantly decreased (24.2 ± 2 μg/mL versus 18 ± 11 μg/mL, P < 0.01) after adrenalectomy in PHEO subjects. This study provides the following findings: (1) BAT surrounding PHEO expresses adiponectin and UCP-1 mRNA, (2) expression of adiponectin mRNA is significantly higher in BAT than in WAT surrounding PHEO, and (3) catecholamines and serum adiponectin levels significantly correlate with BAT UCP-1 and adiponectin mRNA.

Lipoic Acid Improves Mitochondrial Function in Nonalcoholic Steatosis Through the Stimulation of Sirtuin 1 and Sirtuin 3

Nonalcoholic steatosis is an important hepatic complication of obesity linked to mitochondrial dysfunction and oxidative stress. Lipoic acid (LA) has been reported to have beneficial effects on mitochondrial function and to attenuate oxidative stress. The sirtuin (SIRT) family has been demonstrated to play an important role in the regulation of mitochondrial function and in the activation of antioxidant defenses. In this study, we analyzed the potential protective effect of LA supplementation, via the modulation of mitochondrial defenses through the SIRT pathway, against oxidative stress associated with high-fat feeding. Wistar rats were fed a standard diet (control group (C), n = 10), a high-fat diet (obese group (OB), n = 10) and a high-fat diet supplemented with LA (OLIP, n = 10). A group pair-fed to the latter group (pair-fed OLIP group (PFO), n = 6) was also included. LA prevented hepatic triglyceride (TG) accumulation (-68.2%) and liver oxidative damage (P < 0.01) through the inhibition of hydroperoxide (H(2)O(2)) production (P < 0.001) and the stimulation of mitochondrial antioxidant defenses. LA treatment upregulated manganese superoxide dismutase (SOD2) (60.6%) and glutathione peroxidase (GPx) (100.2%) activities, and increased the reduced glutathione (GSH): oxidized glutathione (GSSG) ratio and UCP2 mRNA levels (P < 0.001-P < 0.01). Moreover, this molecule reduced oxidative damage in mitochondrial DNA (mtDNA) and increased mitochondrial copy number (P < 0.001- P < 0.01). LA treatment decreased the acetylation levels of Forkhead transcription factor 3a (Foxo3a) and PGC1β (P < 0.001- P < 0.01) through the stimulation of SIRT3 and SIRT1 (P < 0.001). In summary, our results demonstrate that the beneficial effects of LA supplementation on hepatic steatosis could be mediated by its ability to restore the oxidative balance by increasing antioxidant defenses through the deacetylation of Foxo3a and PGC1β by SIRT1 and SIRT3.

Endurance training blocks uncoupling protein 1 up-regulation in brown adipose tissue while increasing uncoupling protein 3 in the muscle tissue of rats fed with a high-sugar diet

The mitochondrial uncoupling proteins (UCPs) of interscapular brown adipose tissue (iBAT) and of muscles play important roles in energy balance. For instance, the expression of UCP1 and UCP3 are modulated by free fatty acid gradients induced by high-sugar diets and acute exercise that is dependent on sympathetic stimulation. However, the effects of endurance training in animals fed with high-sugar diets are unknown. This study aims to evaluate the long-term effects of diet and exercise on UCP1 and UCP3 levels and energy balance efficiency. Rats fed with standard or high-sugar (HSD) diets were simultaneously subjected to running training over an 8-week period. After the training period, the rats were decapitated, and the iBAT and gastrocnemius muscle tissues were removed for evaluation of the β₃-receptor, Ucp1, and Ucp3 mRNA and protein expression, which were analyzed by quantitative reverse transcriptase polymerase chain reaction and Western blot, respectively. Groups fed with an HSD displayed a higher adiposity index and iBAT weight (P < .05), whereas exhibited an up-regulation of Ucp1 mRNA and protein levels (P < .05). Training increased β₃-receptor mRNA in iBAT and reduced the Ucp3 mRNA in muscle tissues. In association with an HSD, training restored the increasing β₃-receptor mRNA and greatly up-regulated the levels of Ucp3 mRNA. Therefore, training blocked the HSD-induced up-regulation of UCP1 expression in iBAT, whereas it up-regulated the expression of Ucp3 mRNA in muscle. These results suggest that training enhances the relationship between Ucp1/Ucp3 mRNA levels, which could result in higher energy efficiency, but not when HSD-induced elevated sympathetic activity is maintained.

Administration of a murine diet supplemented with conjugated linoleic acid increases the expression and activity of hepatic uncoupling proteins

Daily intake of conjugated linoleic acid (CLA) has been shown to reduce body fat accumulation and to increase body metabolism; this latter effect has been often associated with the up-regulation of uncoupling proteins (UCPs). Here we addressed the effects of a CLA-supplemented murine diet (~2% CLA mixture, cis-9, trans-10 and trans-10, cis-12 isomers; 45% of each isomer on alternating days) on mitochondrial energetics, UCP2 expression/activity in the liver and other associated morphological and functional parameters, in C57BL/6 mice. Diet supplementation with CLA reduced both lipid accumulation in adipose tissues and triacylglycerol plasma levels, but did not augment hepatic lipid storage. Livers of mice fed a diet supplemented with CLA showed high UCP2 mRNA levels and the isolated hepatic mitochondria showed indications of UCP activity: in the presence of guanosine diphosphate, the higher stimulation of respiration promoted by linoleic acid in mitochondria from the CLA mice was almost completely reduced to the level of the stimulation from the control mice. Despite the increased generation of reactive oxygen species through oxi-reduction reactions involving NAD(+)/NADH in the Krebs cycle, no oxidative stress was observed in the liver. In addition, in the absence of free fatty acids, basal respiration rates and the phosphorylating efficiency of mitochondria were preserved. These results indicate a beneficial and secure dose of CLA for diet supplementation in mice, which induces UCP2 overexpression and UCP activity in mitochondria while preserving the lipid composition and redox state of the liver.

Effect of Hovenia Dulcis Thunb liquid on the expression of UCP2 gene in ethanol-induced superfatted L-02 cells in vitro

Objective To establish the model of alcohol-induced hepatocyte steatosis in L-02 liver cells in vitro,investigate the relationship between cell damage,UCP2 gene expression and ethanol concentrations in L-02 cells of steatosis,and explore the protective effect of Hovenia Dulcis Thunb extracted liquid.Method Hovenia Dulcis Thunb extracted liquid at the most compatible dosage was applied to the L-02 cells of steatosis.Then UCP2 mRNA was detected by the semi-quantitative RT-PCR method.Results In steatosis model groups,UCP2 mRNA expression was downregulated ( P ＜0.05).In the steatosis groups treated with Hovenia Dulcis Thunb extracted liquid,UCP2 mRNA level was significantly increased compared to steatosis group ( its expression level increased from 0.4859 to 0.7442 after treatment of 0.6％ ethanol,P＜ 0.05).Conclusions Ethanol can down-regulate the UCP2 mRNA expression of L-02 cells in a certain period.The low expression of UCP2 mRNA is probably relevant to the occurrence of alcoholic fatty liver disease.Hovenia Dulcis Thunb can prevent from the cell toxicity of ethanol and decrease the degree of steatosis.Hovenia Dulcis Thunb extracted liquid can increase the expression level of UCP2 mRNA in the L-02 cells. Key words: Rhamnaceae; Plant extracts/pharmacology; Ethanol/pharmacology; Hepatocytes/drug effects/metabolism; Fatty liver, alcoholic/metabolism/genetics; Uncoupling protein 2/metabolism/genetics

Retinaldehyde dehydrogenase 1 regulates a thermogenic program in white adipose tissue.

Promoting brown adipose tissue (BAT) formation and function may reduce obesity. Recent data link retinoids to energy balance, but a specific role for retinoid metabolism in white versus brown fat is unknown. Retinaldehyde dehydrogenases (Aldhs), also known as aldehyde dehydrogenases, are rate-limiting enzymes that convert retinaldehyde (Rald) to retinoic acid. Here we show that Aldh1a1 is expressed predominately in white adipose tissue (WAT), including visceral depots in mice and humans. Deficiency of the Aldh1a1 gene induced a BAT-like transcriptional program in WAT that drove uncoupled respiration and adaptive thermogenesis. WAT-selective Aldh1a1 knockdown conferred this BAT program in obese mice, limiting weight gain and improving glucose homeostasis. Rald induced uncoupling protein-1 (Ucp1) mRNA and protein levels in white adipocytes by selectively activating the retinoic acid receptor (RAR), recruiting the coactivator PGC-1α and inducing Ucp1 promoter activity. These data establish Aldh1a1 and its substrate Rald as previously unrecognized determinants of adipocyte plasticity and adaptive thermogenesis, which may have potential therapeutic implications.

Uncoupling protein 2 negatively regulates glucose-induced glucagon-like peptide 1 secretion

It is known that endogenous levels of the incretin hormone glucagon-like peptide 1 (GLP1) can be enhanced by various secretagogues, but the mechanism underlying GLP1 secretion is still not fully understood. We assessed the possible effect of uncoupling protein 2 (UCP2) on GLP1 secretion in mouse intestinal tract and NCI-H716 cells, a well-characterized human enteroendocrine L cell model. Localization of UCP2 and GLP1 in the gastrointestinal tract was assessed by immunofluorescence staining. Ucp2 mRNA levels in gut were analyzed by quantitative RT-PCR. Human NCI-H716 cells were transiently transfected with siRNAs targeting UCP2. The plasma and ileum tissue levels of GLP1 (7-36) amide were measured using an ELISA kit. UCP2 was primarily expressed in the mucosal layer and colocalized with GLP1 in gastrointestinal mucosa. L cells secreting GLP1 also expressed UCP2. After glucose administration, UCP2-deficient mice showed increased glucose-induced GLP1 secretion compared with wild-type littermates. GLP1 secretion increased after NCI-H716 cells were transfected with siRNAs targeting UCP2. UCP2 was markedly upregulated in ileum tissue from ob/ob mice, and GLP1 secretion decreased compared with normal mice. Furthermore, GLP1 secretion increased after administration of genipin by oral gavage. Taken together, these results reveal an inhibitory role of UCP2 in glucose-induced GLP1 secretion.