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| 2. |
- Archer, A, et al.
(author)
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Fasting-induced FGF21 is repressed by LXR activation via recruitment of an HDAC3 corepressor complex in mice
- 2012
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In: Molecular endocrinology (Baltimore, Md.). - : The Endocrine Society. - 1944-9917 .- 0888-8809. ; 26:12, s. 1980-1990
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Journal article (peer-reviewed)abstract
- The liver plays a pivotal role in the physiological adaptation to fasting and a better understanding of the metabolic adaptive responses may give hints on new therapeutic strategies to control the metabolic diseases. The liver X receptors (LXRs) are well-established regulators of lipid and glucose metabolism. More recently fibroblast growth factor 21 (FGF21) has emerged as an important regulator of energy homeostasis. We hypothesized that the LXR transcription factors could influence Fgf21 expression, which is induced in response to fasting. Wild-type, LXRα−/−, and LXRβ−/− mice were treated for 3 d with vehicle or the LXR agonist GW3965 and fasted for 12 h prior to the killing of the animals. Interestingly, serum FGF21 levels were induced after fasting, but this increase was blunted when the mice were treated with GW3965 independently of genotypes. Compared with wild-type mice, GW3965-treated LXRα−/− and LXRβ−/− mice showed improved insulin sensitivity and enhanced ketogenic response at fasting. Of note is that during fasting, GW3965 treatment tended to reduce liver triglycerides as opposed to the effect of the agonist in the fed state. The LXR-dependent repression of Fgf21 seems to be mainly mediated by the recruitment of LXRβ onto the Fgf21 promoter upon GW3965 treatment. This repression by LXRβ occurs through the recruitment and stabilization of the repressor complex composed of retinoid-related orphan receptor-α/Rev-Erbα/histone deacetylase 3 onto the Fgf21 promoter. Our data clearly demonstrate that there is a cross talk between the LXR and FGF21 signaling pathways in the adaptive response to fasting.
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| 5. |
- Korach-Andre, M, et al.
(author)
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Liver X receptors regulate de novo lipogenesis in a tissue-specific manner in C57BL/6 female mice
- 2011
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In: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 301:1, s. E210-E222
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Journal article (peer-reviewed)abstract
- The liver X receptors (LXRs) play a key role in cholesterol and bile acid metabolism but are also important regulators of glucose metabolism. Recently, LXRs have been proposed as a glucose sensor affecting LXR-dependent gene expression. We challenged wild-type (WT) and LXRαβ−/−mice with a normal diet (ND) or a high-carbohydrate diet (HCD). Magnetic resonance imaging showed different fat distribution between WT and LXRαβ−/−mice. Surprisingly, gonadal (GL) adipocyte volume decreased on HCD compared with ND in WT mice, whereas it slightly increased in LXRαβ−/−mice. Interestingly, insulin-stimulated lipogenesis of isolated GL fat cells was reduced on HCD compared with ND in LXRαβ−/−mice, whereas no changes were observed in WT mice. Net de novo lipogenesis (DNL) calculated from V̇o2and V̇co2was significantly higher in LXRαβ−/−than in WT mice on HCD. Histology of HCD-fed livers showed hepatic steatosis in WT mice but not in LXRαβ−/−mice. Glucose tolerance was not different between groups, but insulin sensitivity was decreased by the HCD in WT but not in LXRαβ−/−mice. Finally, gene expression analysis of adipose tissue showed induced expression of genes involved in DNL in LXRαβ−/−mice compared with WT animals as opposed to the liver, where expression of DNL genes was repressed in LXRαβ−/−mice. We thus conclude that absence of LXRs stimulates DNL in adipose tissue, but suppresses DNL in the liver, demonstrating opposite roles of LXR in DNL regulation in these two tissues. These results show tissue-specific regulation of LXR activity, a crucial finding for drug development.
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| 7. |
- Savva, C, et al.
(author)
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Obese mother offspring have hepatic lipidic modulation that contributes to sex-dependent metabolic adaptation later in life
- 2021
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In: Communications biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 4:1, s. 14-
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Journal article (peer-reviewed)abstract
- With the increasing prevalence of obesity in women of reproductive age, there is an urgent need to understand the metabolic impact on the fetus. Sex-related susceptibility to liver diseases has been demonstrated but the underlying mechanism remains unclear. Here we report that maternal obesity impacts lipid metabolism differently in female and male offspring. Males, but not females, gained more weight and had impaired insulin sensitivity when born from obese mothers compared to control. Although lipid mass was similar in the livers of female and male offspring, sex-specific modifications in the composition of fatty acids, triglycerides and phospholipids was observed. These overall changes could be linked to sex-specific regulation of genes controlling metabolic pathways. Our findings revised the current assumption that sex-dependent susceptibility to metabolic disorders is caused by sex-specific postnatal regulation and instead we provide molecular evidence supporting in utero metabolic adaptations in the offspring of obese mothers.
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| 10. |
- Al-Qahtani, SM, et al.
(author)
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17β-Estradiol suppresses visceral adipogenesis and activates brown adipose tissue-specific gene expression
- 2017
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In: Hormone molecular biology and clinical investigation. - : Walter de Gruyter GmbH. - 1868-1891 .- 1868-1883. ; 29:1, s. 13-26
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Journal article (peer-reviewed)abstract
- Both functional ovaries and estrogen replacement therapy (ERT) reduce the risk of type 2 diabetes (T2D). Understanding the mechanisms underlying the antidiabetic effects of 17β-estradiol (E2) may permit the development of a molecular targeting strategy for the treatment of metabolic disease. This study examines how the promotion of insulin sensitivity and weight loss by E2 treatment in high-fat-diet (HFD)-fed mice involve several anti-adipogenic processes in the visceral adipose tissue. Magnetic resonance imaging (MRI) revealed specific reductions in visceral adipose tissue volume in HFD+E2 mice, compared with HFD mice. This loss of adiposity was associated with diminished visceral adipocyte size and reductions in expression of lipogenic genes, adipokines and of the nuclear receptor
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| 11. |
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| 12. |
- Archer, A, et al.
(author)
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Skeletal muscle as a target of LXR agonist after long-term treatment: focus on lipid homeostasis
- 2014
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In: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 306:5, s. E494-E502
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Journal article (peer-reviewed)abstract
- The liver X receptors (LXR)α and LXRβ are transcription factors belonging to the nuclear receptor family, which play a central role in metabolic homeostasis, being master regulators of key target genes in the glucose and lipid pathways. Wild-type (WT), LXRα−/−, and LXRβ−/−mice were fed a chow diet with (treated) or without (control) the synthetic dual LXR agonist GW3965 for 5 wk. GW3965 raised intrahepatic triglyceride (TG) level but, surprisingly, reduced serum TG level through the activation of serum lipase activity. The serum TG reduction was associated with a repression of both catecholamine-stimulated lipolysis and relative glucose incorporation into lipid in isolated adipocytes through activation of LXRβ. We also demonstrated that LXRα is required for basal (nonstimulated) adipocyte metabolism, whereas LXRβ acts as a repressor of lipolysis. On the contrary, in skeletal muscle (SM), the lipogenic and cholesterol transporter LXR target genes were markedly induced in WT and LXRα−/−mice and to a lesser extent in LXRβ−/−mice following treatment with GW3965. Moreover, TG content was reduced in SM of LXRβ−/−mice, associated with increased expression of the main TG-lipase genes Hsl and Atgl. Energy expenditure was increased, and a switch from glucose to lipid oxidation was observed. In conclusion, we provide evidence that LXR might be an essential regulator of the lipid balance between tissues to ensure appropriate control of the flux of fuel. Importantly, we show that, after chronic treatment with GW3965, SM becomes the target tissue for LXR activation, as opposed to liver, in acute treatment.
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| 13. |
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| 14. |
- Gounarides, JS, et al.
(author)
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Effect of dexamethasone on glucose tolerance and fat metabolism in a diet-induced obesity mouse model
- 2008
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In: Endocrinology. - : The Endocrine Society. - 0013-7227 .- 1945-7170. ; 149:2, s. 758-766
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Journal article (peer-reviewed)abstract
- Prolonged exposure to elevated glucocorticoid levels is known to produce insulin resistance (IR), a hallmark of diabetes mellitus. Although not fully elucidated, the underlying molecular mechanisms by which glucocorticoids induce IR may provide potential targets for pharmacological interventions. Here we characterized muscle lipid metabolism in a dexamethasone-aggravated diet-induced obesity murine model of IR. Male C57BL/6 mice on a high-fat diet for 2 months when challenged with dexamethasone showed elevated food consumption and weight gain relative to age and diet-matched animals dosed with saline only. Dexamethasone treatment impaired glucose tolerance and significantly increased the intramyocellular lipid content in the tibialis anterior muscle (TA). A good correlation (r = 0.76, P < 0.01) was found between accumulation in intramyocellular lipid content in the TA and visceral adiposity. The linoleic acid (18:2) to polyunsaturated acid ratio was increased in the dexamethasone-treated animals (+29%; P < 0.01), suggesting a possible increase in stearoyl-CoA desaturase 2 activity, as reported in Sertoli cells. The treatment was also accompanied by a reduction in the percent fraction of ω-3 and long-chain polyunsaturated fatty acids in the TA. Analysis of the low-molecular-weight metabolites from muscle extracts showed that there was no dysregulation of muscle amino acids, as has been associated with dexamethasone-induced muscle proteolysis. In conclusion, dexamethasone-induced insulin resistance in diet-induced obese mice is associated with a profound perturbation of lipid metabolism. This is particularly true in the muscle, in which an increased uptake of circulating lipids along with a conversion into diabetogenic lipids can be observed.
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| 15. |
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| 16. |
- Korach-André, M, et al.
(author)
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Liver X receptors as regulators of metabolism
- 2015
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In: Biomolecular concepts. - : Walter de Gruyter GmbH. - 1868-503X .- 1868-5021. ; 6:3, s. 177-90
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Journal article (peer-reviewed)abstract
- The liver X receptors (LXR) are crucial regulators of metabolism. After ligand binding, they regulate gene transcription and thereby mediate changes in metabolic pathways. Modulation of LXR and their downstream targets has appeared to be a promising treatment for metabolic diseases especially atherosclerosis and cholesterol metabolism. However, the complexity of LXR action in various metabolic tissues and the liver side effect of LXR activation have slowed down the interest for LXR drugs. In this review, we summarized the role of LXR in the main metabolically active tissues with a special focus on obesity and associated diseases in mammals. We will also discuss the dual interplay between the two LXR isoforms suggesting that they may collaborate to establish a fine and efficient system for the maintenance of metabolism homeostasis.
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| 17. |
- Korach-Andre, M, et al.
(author)
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Separate and overlapping metabolic functions of LXRalpha and LXRbeta in C57Bl/6 female mice
- 2010
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In: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 298:2, s. E167-E178
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Journal article (peer-reviewed)abstract
- The two liver X receptors (LXRs), LXRα and LXRβ, are transcriptional regulators of cholesterol, lipid, and glucose metabolism and are both activated by oxysterols. Impaired metabolism is linked with obesity, insulin resistance, and type 2-diabetes (T2D). In the present study, we aimed to delineate the specific roles of LXRα and -β in metabolic processes. C57Bl/6 female mice were fed a normal or a high-fat diet (HFD) and metabolic responses in wild-type, LXRα−/−, LXRβ−/−, and LXRαβ−/−mice were analyzed. Whole body fat and intramyocellular lipid contents were measured by nuclear magnetic resonance. Energy expenditure was measured in individual metabolic cages. Glucose, insulin, and pyruvate tolerance tests were performed and gene expression profiles analyzed by qPCR. We found that both LXRβ−/−and LXRαβ−/−mice are resistant to HFD-induced obesity independently of the presence of high cholesterol. Using tolerance tests, we found that, on an HFD, LXRβ−/−mice enhanced their endogenous glucose production and became highly insulin resistant, whereas LXRα−/−and LXRαβ−/−mice remained glucose tolerant and insulin sensitive. Gene expression profiling confirmed that LXRβ is the regulator of lipogenic genes in visceral white adipose tissue (WAT) and muscle tissue and, surprisingly, that Ucp1 and Dio2 are not responsible for the protection against diet-induced obesity observed in LXRβ−/−and LXRαβ−/−mice. LXRα is required for the control of cholesterol metabolism in the liver, while LXRβ appears to be a major regulator of glucose homeostasis and energy utilization and of fat storage in muscle and WAT. We conclude that selective LXRβ agonists would be novel pharmaceuticals in the treatment of T2D.
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| 18. |
- Savva, C, et al.
(author)
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Estrogen Receptor beta (ERβ) Regulation of Lipid Homeostasis-Does Sex Matter?
- 2020
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In: Metabolites. - : MDPI AG. - 2218-1989. ; 10:3
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Journal article (peer-reviewed)abstract
- In this communication, we aim to summarize the role of estrogen receptor beta (ERβ) in lipid metabolism in the main metabolic organs with a special focus on sex differences. The action of ERβ is tissue-specific and acts in a sex-dependent manner, emphasizing the necessity of developing sex- and tissue-selective targeting drugs in the future.
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