IDOL regulates systemic energy balance through control of neuronal VLDLR expression.

Liver X receptors limit cellular lipid uptake by stimulating the transcription of Inducible Degrader of the LDL Receptor (IDOL), an E3 ubiquitin ligase that targets lipoprotein receptors for degradation. The function of IDOL in systemic metabolism is incompletely understood. Here we show that loss of IDOL in mice protects against the development of diet-induced obesity and metabolic dysfunction by altering food intake and thermogenesis. Unexpectedly, analysis of tissue-specific knockout mice revealed that IDOL affects energy balance, not through its actions in peripheral metabolic tissues (liver, adipose, endothelium, intestine, skeletal muscle), but by controlling lipoprotein receptor abundance in neurons. Single-cell RNA sequencing of the hypothalamus demonstrated that IDOL deletion altered gene expression linked to control of metabolism. Finally, we identify VLDLR rather than LDLR as the primary mediator of IDOL effects on energy balance. These studies identify a role for the neuronal IDOL-VLDLR pathway in metabolic homeostasis and diet-induced obesity

Gene regulation by Early B-cell Factor (EBF)

In this study we aimed at defining genes that are controlled by Early B-cell Factor (EBF), that could explain the severe block in B-cell development observed in EBF-/- mice. The fact that EBF appears to be important for the transcriptional control of genes encoding proteins in the pre-B and B-cell receptor complex implied to us that EBF could be a common regulator of other components in the pre-B and B-cell receptor. In addition to the immunoglobulin (Ig) heavy chain, the surrogate light chains and the Ig associated alfa protein the pre-B cell receptor also consists of the second Ig associated beta protein as well as B-cell specific kinase (Blk). The hypothesis that EBF is involved in regulating other components in the B-cell receptor was further strengthened by information from the EBF-/- mouse indicating that its pro-B cells completely lacked B29 transcripts. This was an intriguing finding, since B29 is expressed in normal pro-B cells as well as in pro-B cells from E2A-/- mice displaying a similar B-cell differentiation block as the EBF-/- mouse. We examined the promoter DNA sequence of murine B29 (Ig-beta) and Blk and found potential EBF DNA binding sites. In electrophoretic mobility shift assay (EMSA) EBF interacted with three independent sites in the B29 promoter and with a single site in the Blk promoter. EBF could also activate both the B29 and the Blk promoters in transfected epitheloid HeLa cells, indicating that EBF functionally interacted with these promoters. The importance of the EBF binding sites for the function of the Blk and B29 promoters appeared to be stage dependent, since mutation of the EBF sites had an impact on promoter function in pre-B cell lines, but not in a B-cell line. However, B29 and Blk as well as EBF are expressed in mature B-cells and B29 even in plasma cells. Thus, there seems to be a shift in transcription factor usage, from EBF to other factors, at the transition from pre-B to B-cells. We also show data suggesting that EBF may also have additional roles as a negative regulator of the Ig gene expression in late B cell development. This may signify that transcription factors considered to be of importance mainly in the early differentiation stages can have important, unrevealed roles during late development

Inhibition of p300/CBP by Early B-Cell Factor

Early B-cell factor (EBF) is a DNA binding protein required for early B-cell development. It activates transcription of several B-cell-specific genes, including the λ5 gene, which encodes a protein necessary for signaling by the pre-B-cell receptor. In an effort to understand the mechanism by which EBF activates transcription, we examined its interaction with the coactivator protein p300/CBP. We found that two domains of EBF each bind the histone acetyltransferase (HAT)/CH3 domain of p300/CBP both in vitro and in vivo. Surprisingly, transcriptional activation by EBF was not sensitive to E1A, a potent p300/CBP inhibitor. In fact, overexpressed EBF mimicked E1A by severely repressing the activity of several other transcription factors, including E47, a protein that acts cooperatively with EBF to promote transcription of the λ5 gene. This broad inhibitory profile correlated with EBF's ability to repress the HAT activity of p300/CBP in vivo and in vitro. However, such a repressed complex is not likely to form at the λ5 promoter in vivo since (i) EBF could not bind p300/CBP and DNA simultaneously and (ii) the cooperativity imparted by E47 was sensitive to E1A. Our data reveal an intriguing inhibitory property of EBF—a property shared only by E1A, Twist, Pu.1, and the Hox family of homeodomain proteins—and suggest that E47 and EBF play distinct roles during λ5 promoter activation

Early B-Cell Factor (O/E-1) Is a Promoter of Adipogenesis and Involved in Control of Genes Important for Terminal Adipocyte Differentiation

Olf-1/early B-cell factor (O/E-1) is a transcription factor important for B-lymphocyte and neuronal gene regulation. Here we report that all three known O/E genes (O/E-1, -2, and -3) are expressed in mouse adipose tissue and are upregulated during adipocyte differentiation. Forced expression of O/E-1 in either the preadipocyte cell line 3T3-L1 or mouse embryonic fibroblasts augmented adipogenesis, and constitutive expression of O/E-1 in uncommitted NIH 3T3 fibroblasts led to initiation of adipocyte differentiation. Furthermore, a dominant negative form of O/E-1 partially suppressed 3T3-L1 adipogenesis, indicating that expression from endogenous O/E target genes is required for 3T3-L1 terminal differentiation. Thus, our data point to the importance of O/E target genes for adipocyte differentiation and suggest a novel role for O/E-1 as an initiator and stimulator of adipogenesis

Early B-Cell Factor, E2A, and Pax-5 Cooperate To Activate the Early B Cell-Specific mb-1 Promoter

Previous studies have suggested that the early-B-cell-specific mb-1(Igα) promoter is regulated by EBF and Pax-5. Here, we used in vivo footprinting assays to detect occupation of binding sites in endogenous mb-1 promoters at various stages of B-cell differentiation. In addition to EBF and Pax-5 binding sites, we detected occupancy of a consensus binding site for E2A proteins (E box) in pre-B cells. EBF and E box sites are crucial for promoter function in transfected pre-B cells, and EBF and E2A proteins synergistically activated the promoter in transfected HeLa cells. Other data suggest that EBF and E box sites are less important for promoter function at later stages of differentiation, whereas binding sites for Pax-5 (and its Ets ternary complex partners) are required for promoter function in all mb-1-expressing cells. Using DNA microarrays, we found that expression of endogenous mb-1 transcripts correlates most closely with EBF expression and negatively with Id1, an inhibitor of E2A protein function, further linking regulation of the mb-1 gene with EBF and E2A. Together, our studies demonstrate the complexity of factors regulating tissue-specific transcription and support the concept that EBF, E2A, and Pax-5 cooperate to activate target genes in early B-cell development

Gene expression analysis suggests that EBF-1 and PPARγ2 induce adipogenesis of NIH-3T3 cells with similar efficiency and kinetics

Differentiation of multipotent mesenchymal stem cells into lipid-accumulating adipocytes is a physiological process induced by transcription factors in combination with hormonal stimulation. We have used Affymetrix microarrays to compare the adipogenic differentiation pathways of NIH-3T3 fibroblasts induced to undergo in vitro differentiation by ectopic expression of early B cell factor (EBF)-1 or peroxisome proliferator-activated receptor (PPAR)gamma 2. These experiments revealed that commitment to the adipogenic pathway in the NIH-3T3 cells was not reflected in gene expression until 4 days after induction of differentiation. Furthermore, gene expression patterns at the earlier time points after stimulation indicated that EBF-1 and PPAR gamma 2 induced different sets of genes, while the similarities increased upon differentiation, and that several genes linked to adipocyte differentiation were also transiently induced in the vector-transduced cells. These data suggest that the initial activation of genes associated with adipocyte development is independent of commitment to the adipogenic pathway and that EBF-1 and PPAR gamma 2 induce adipocyte differentiation with comparable kinetics and efficiency

Pnpla3 silencing with antisense oligonucleotides ameliorates nonalcoholic steatohepatitis and fibrosis in Pnpla3 I148M knock-in mice

Objective: Nonalcoholic fatty liver disease (NAFLD) is becoming a leading cause of advanced chronic liver disease. The progression of NAFLD, including nonalcoholic steatohepatitis (NASH), has a strong genetic component, and the most robust contributor is the patatin-like phospholipase domain-containing 3 (PNPLA3) rs738409 encoding the 148M protein sequence variant. We hypothesized that suppressing the expression of the PNPLA3 148M mutant protein would exert a beneficial effect on the entire spectrum of NAFLD. Methods: We examined the effects of liver-targeted GalNAc3-conjugated antisense oligonucleotide (ASO)-mediated silencing of Pnpla3 in a knock-in mouse model in which we introduced the human PNPLA3 I148M mutation. Results: ASO-mediated silencing of Pnpla3 reduced liver steatosis (p = 0.038) in homozygous Pnpla3 148M/M knock-in mutant mice but not in wild-type littermates fed a steatogenic high-sucrose diet. In mice fed a NASH-inducing diet, ASO-mediated silencing of Pnpla3 reduced liver steatosis score and NAFLD activity score independent of the Pnpla3 genotype, while reductions in liver inflammation score (p = 0.018) and fibrosis stage (p = 0.031) were observed only in the Pnpla3 knock-in 148M/M mutant mice. These responses were accompanied by reduced liver levels of Mcp1 (p = 0.026) and Timp2 (p = 0.007) specifically in the mutant knock-in mice. This may reduce levels of chemokine attracting inflammatory cells and increase the collagenolytic activity during tissue regeneration. Conclusion: This study provides the first evidence that a Pnpla3 ASO therapy can improve all features of NAFLD, including liver fibrosis, and suppress the expression of a strong innate genetic risk factor, Pnpla3 148M, which may open up a precision medicine approach in NASH. Keywords: PNPLA3, NAFLD, NASH, Fibrosis, Live

Inhibition of the Renal Apical Sodium Dependent Bile Acid Transporter Prevents Cholemic Nephropathy in Mice with Obstructive Cholestasis.

BACKGROUND & AIMS Cholemic nephropathy (CN) is a severe complication of cholestasis-associated liver diseases, with no specific treatment. We revisited the pathophysiology to identify therapeutic strategies. METHODS Cholestasis was induced by bile duct ligation (BDL) in mice. Bile flux in kidneys and livers was visualized by intravital imaging, supported by MALDI-MSI and LC-MS/MS. The effect of AS0369, a systemically bioavailable apical sodium-dependent bile acid transporter (ASBT) inhibitor, was evaluated by intravital imaging, RNA-sequencing, histological, blood, and urine analyses. Translational relevance was assessed by ASBT immunostaining in kidney biopsies of CN patients, analysis of mice with humanized BA spectrum, and by analysis of serum bile acids (BA) and kidney injury molecule (KIM-1) in liver disease and hyperbilirubinemia patients. RESULTS Proximal tubular epithelial cells (TEC) reabsorbed and enriched BA, leading to oxidative stress and death of proximal TEC, casts in distal tubules and collecting ducts, peritubular capillaries leakiness, and glomerular cysts. Renal ASBT inhibition by AS0369 blocked BA uptake into TEC and prevented kidney injury up to 6 weeks after BDL. Similar results were obtained in mice with humanized BA composition. In advanced liver disease patients, serum BA were the main determinant of KIM-1 levels. ASBT expression in TEC was preserved in biopsies from CN patients, further highlighting the translational potential of targeting ASBT for treatment of CN. CONCLUSIONS BA enrichment in proximal TEC followed by oxidative stress and cell death is an early key event in CN. Inhibiting renal ASBT and consequently BA enrichment in TEC prevents CN and systemically decreases BA concentrations. IMPACT AND IMPLICATIONS Cholemic nephropathy (CN) is a severe complication of cholestasis with an unmet clinical need for therapy. We demonstrate that CN is triggered by the renal accumulation of bile acids (BA)- that are considerably increased in the systemic blood. Specifically, the proximal tubular epithelial cells (TEC) of the kidney take up BA via the apical sodium-dependent bile acid transporter (ASBT). We developed a therapeutic compound that blocks ASBT in the kidneys, prevents BA overload in TEC, and almost completely abolished all disease hallmarks in a CN mouse model. Renal ASBT inhibition represents a potential therapeutic strategy for CN patients