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- Niemi, MEK, et al.
(author)
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- 2021
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swepub:Mat__t
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- Baldassarri, M, et al.
(author)
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Gain- and Loss-of-Function CFTR Alleles Are Associated with COVID-19 Clinical Outcomes
- 2022
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In: Cells. - : MDPI AG. - 2073-4409. ; 11:24
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Journal article (peer-reviewed)abstract
- Carriers of single pathogenic variants of the CFTR (cystic fibrosis transmembrane conductance regulator) gene have a higher risk of severe COVID-19 and 14-day death. The machine learning post-Mendelian model pinpointed CFTR as a bidirectional modulator of COVID-19 outcomes. Here, we demonstrate that the rare complex allele [G576V;R668C] is associated with a milder disease via a gain-of-function mechanism. Conversely, CFTR ultra-rare alleles with reduced function are associated with disease severity either alone (dominant disorder) or with another hypomorphic allele in the second chromosome (recessive disorder) with a global residual CFTR activity between 50 to 91%. Furthermore, we characterized novel CFTR complex alleles, including [A238V;F508del], [R74W;D1270N;V201M], [I1027T;F508del], [I506V;D1168G], and simple alleles, including R347C, F1052V, Y625N, I328V, K68E, A309D, A252T, G542*, V562I, R1066H, I506V, I807M, which lead to a reduced CFTR function and thus, to more severe COVID-19. In conclusion, CFTR genetic analysis is an important tool in identifying patients at risk of severe COVID-19.
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- 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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- Barros, RPA, et al.
(author)
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Participation of ERalpha and ERbeta in glucose homeostasis in skeletal muscle and white adipose tissue
- 2009
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In: American journal of physiology. Endocrinology and metabolism. - : American Physiological Society. - 1522-1555 .- 0193-1849. ; 297:1, s. E124-E133
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Journal article (peer-reviewed)abstract
- Glucose uptake and homeostasis are regulated mainly by skeletal muscle (SM), white adipose tissue (WAT), pancreas, and the liver. Participation of estradiol in this regulation is still under intense investigation. We have demonstrated that, in SM of male mice, expression of the insulin-regulated glucose transporter (GLUT)4 is reduced by estrogen receptor (ER)β agonists. In the present study, to investigate the relative contributions of ERα and ERβ in glucose homeostasis, we examined the effects of tamoxifen (Tam) on GLUT4 expression in SM and WAT in wild-type (WT) and ER−/− mice. ERβ−/− mice were characterized by fasting hypoglycemia, increased levels of SM GLUT4, pancreatic islet hypertrophy, and a belated rise in plasma insulin in response to a glucose challenge. ERα−/− mice, on the contrary, were hyperglycemic and glucose intolerant, and expression of SM GLUT4 was markedly lower than in WT mice. Tam had no effect on glucose tolerance or insulin sensitivity in WT mice. In ERα−/− mice, Tam increased GLUT4 and improved insulin sensitivity. i.e., it behaved as an ERβ antagonist in SM but had no effect on WAT. In ERβ−/− mice, Tam did not affect GLUT4 in SM but acted as an ERα antagonist in WAT, decreasing GLUT4. Thus, in the interplay between ERα and ERβ, ERβ-mediated repression of GLUT4 predominates in SM but ERα-mediated induction of GLUT4 predominates in WAT. This tissue-specific difference in dominance of one ER over the other is reflected in the ratio of the expression of the two receptors. ERα predominates in WAT and ERβ in SM.
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- Fallerini, Chiara, et al.
(author)
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Common, low-frequency, rare, and ultra-rare coding variants contribute to COVID-19 severity
- 2022
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In: Human Genetics. - : Springer Nature. - 0340-6717 .- 1432-1203. ; 141:1, s. 147-173
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Journal article (peer-reviewed)abstract
- The combined impact of common and rare exonic variants in COVID-19 host genetics is currently insufficiently understood. Here, common and rare variants from whole-exome sequencing data of about 4000 SARS-CoV-2-positive individuals were used to define an interpretable machine-learning model for predicting COVID-19 severity. First, variants were converted into separate sets of Boolean features, depending on the absence or the presence of variants in each gene. An ensemble of LASSO logistic regression models was used to identify the most informative Boolean features with respect to the genetic bases of severity. The Boolean features selected by these logistic models were combined into an Integrated PolyGenic Score that offers a synthetic and interpretable index for describing the contribution of host genetics in COVID-19 severity, as demonstrated through testing in several independent cohorts. Selected features belong to ultra-rare, rare, low-frequency, and common variants, including those in linkage disequilibrium with known GWAS loci. Noteworthily, around one quarter of the selected genes are sex-specific. Pathway analysis of the selected genes associated with COVID-19 severity reflected the multi-organ nature of the disease. The proposed model might provide useful information for developing diagnostics and therapeutics, while also being able to guide bedside disease management.
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- Gabbi, C, et al.
(author)
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Action mechanisms of Liver X Receptors
- 2014
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In: Biochemical and biophysical research communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 446:3, s. 647-650
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Journal article (peer-reviewed)
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- Gabbi, C, et al.
(author)
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Minireview: liver X receptor beta: emerging roles in physiology and diseases
- 2009
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In: Molecular endocrinology (Baltimore, Md.). - : The Endocrine Society. - 0888-8809 .- 1944-9917. ; 23:2, s. 129-136
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Journal article (peer-reviewed)abstract
- Liver X receptors, LXRα and LXRβ, are nuclear receptors belonging to the large family of transcription factors. After activation by oxysterols, LXRs play a central role in the control of lipid and carbohydrate metabolism as well as inflammation. The role of LXRα has been extensively studied, particularly in the liver and macrophages. In the liver it prevents cholesterol accumulation by increasing bile acid synthesis and secretion into the bile through ATP-binding cassette G5/G8 transporters, whereas in macrophages it increases cholesterol reverse transport. The function of LXRβ is still under investigation with most of the current knowledge coming from the study of phenotypes of LXRβ−/− mice. With these mice new emerging roles for LXRβ have been demonstrated in the pathogenesis of diseases such as amyotrophic lateral sclerosis and chronic pancreatitis. The present review will focus on the abnormalities described so far in LXRβ−/− mice and the insight gained into the possible roles of LXRβ in human diseases.
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- 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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24. |
- Sweed, N, et al.
(author)
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Liver X receptor β regulates bile volume and the expression of aquaporins and cystic fibrosis transmembrane conductance regulator in the gallbladder
- 2021
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In: American journal of physiology. Gastrointestinal and liver physiology. - : American Physiological Society. - 1522-1547 .- 0193-1857. ; 321:34, s. G243-G251
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Journal article (peer-reviewed)abstract
- This report reveals a novel and specific role of the nuclear receptor liver X receptor β (LXRβ) in controlling biliary tree pathophysiology. LXRβ−/− mice have high gallbladder bile volume and are affected by a cholangiopathy that resembles cystic fibrosis. We found LXRβ to regulate the expression of both aquaporins water channels and the cystic fibrosis transmembrane conductance regulator. This opens a new field in biliary tree pathophysiology, enlightening a possible transcription factor controlling CFTR expression.
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