Although the functions of metabolic enzymes and nuclear receptors in controlling physiological homeostasis have been established, their crosstalk in modulating metabolic disease has not been explored. Genetic ablation of the xenobiotic-metabolizing cytochrome P450 enzyme CYP2E1 in mice markedly induced adipose browning and increased energy expenditure to improve obesity. CYP2E1 deficiency activated the expression of hepatic peroxisome proliferator-activated receptor alpha (PPARα) target genes, including fibroblast growth factor (FGF) 21, that upon release from the liver, enhanced adipose browning and energy expenditure to decrease obesity. Nineteen metabolites were increased in Cyp2e1-null mice as revealed by global untargeted metabolomics, among which four compounds, lysophosphatidylcholine and three polyunsaturated fatty acids were found to be directly metabolized by CYP2E1 and to serve as PPARα agonists, thus explaining how CYP2E1 deficiency causes hepatic PPARα activation through increasing cellular levels of endogenous PPARα agonists. Translationally, a CYP2E1 inhibitor was found to activate the PPARα–FGF21–beige adipose axis and decrease obesity in wild-type mice, but not in liver-specific Ppara-null mice. The present results establish a metabolic crosstalk between PPARα and CYP2E1 that supports the potential for a novel anti-obesity strategy of activating adipose tissue browning by targeting the CYP2E1 to modulate endogenous metabolites beyond its canonical role in xenobiotic-metabolism.

The RGD motif is a cell adhesion sequence that binds to integrins, a receptor family for extracellular matrix proteins. We previously reported that the RGDX₁X₂ sequence, where X₁X₂ is VF or NY, is required for integrin αvβ5-mediated cell adhesion. However, the importance and applications of the X₁X₂ combinations and their surrounding sequences of integrin αvβ5-binding RGDX₁X₂-containing peptides have not been comprehensively elucidated. Therefore, we aimed to identify an RGD-containing peptide with enhanced integrin αvβ5 binding activity. We synthesized various peptides based on the RGDVF and RGDNY peptides to optimize the N-terminal, C-terminal, and X₁X₂ combinations of the RGDX₁X₂ sequence. These peptides were immobilized on maleimide-functionalized bovine serum albumin-coated plates via a thiol-maleimide reaction, and cell adhesion was evaluated using HeLa cells and human dermal fibroblasts. Consequently, CPPP-RGDTF and CPPP-RGDTFI were identified as highly active peptides for integrin αvβ5-mediated cell adhesion. CPPP-RGDTF and CPPP-RGDTFI are expected to serve as cell adhesion molecules for developing culture substrates and biomaterials. Furthermore, these findings provide important novel insights into the interaction between the RGD motifs and integrins.

Metabolic dysfunction–associated steatohepatitis (MASH) — previously described as nonalcoholic steatohepatitis (NASH) — is a major driver of liver fibrosis in humans, while liver fibrosis is a key determinant of all-cause mortality in liver disease independent of MASH occurrence. CCAAT/enhancer binding protein α (CEBPA), as a versatile ligand-independent transcriptional factor, has an important function in myeloid cells, and is under clinical evaluation for cancer therapy. CEBPA is also expressed in hepatocytes and regulates glucolipid homeostasis; however, the role of hepatocyte-specific CEBPA in modulating liver fibrosis progression is largely unknown. Here, hepatic CEBPA expression was found to be decreased during MASH progression both in humans and mice, and hepatic CEBPA mRNA was negatively correlated with MASH fibrosis in the human liver. Cebpa ^ΔHep mice had markedly enhanced liver fibrosis induced by a high-fat, high-cholesterol, high-fructose diet or carbon tetrachloride. Temporal and spatial hepatocyte-specific CEBPA loss at the progressive stage of MASH in Cebpa ^ΔHep,ERT2 mice functionally promoted liver fibrosis. Mechanistically, hepatocyte CEBPA directly repressed Spp1 transactivation to reduce the secretion of osteopontin, a fibrogenesis inducer of hepatic stellate cells. Forced hepatocyte-specific CEBPA expression reduced MASH-associated liver fibrosis. These results demonstrate an important role for hepatocyte-specific CEBPA in liver fibrosis progression, and may help guide the therapeutic discoveries targeting hepatocyte CEBPA for the treatment of liver fibrosis.

ATP1A3 , a mutated gene for AHC, RDP, and CAPOS, is also associated with polymicrogyria by different functional variants.

Mutations in LAMB2 , encoding laminin β ₂ , cause Pierson syndrome and occasionally milder nephropathy without extrarenal abnormalities. The most deleterious missense mutations that have been identified affect primarily the N-terminus of laminin β ₂ . On the other hand, those associated with isolated nephropathy are distributed across the entire molecule, and variants in the β ₂ LEa-LF-LEb domains are exclusively found in cases with isolated nephropathy. Here we report the clinical features of mild isolated nephropathy associated with 3 LAMB2 variants in the LEa-LF-LEb domains (p.R469Q, p.G699R, and p.R1078C) and their biochemical characterization. Although Pierson syndrome missense mutations often inhibit laminin β ₂ secretion, the 3 recombinant variants were secreted as efficiently as WT. However, the β ₂ variants lost pH dependency for heparin binding, resulting in aberrant binding under physiologic conditions. This suggests that the binding of laminin β ₂ to negatively charged molecules is involved in glomerular basement membrane (GBM) permselectivity. Moreover, the excessive binding of the β ₂ variants to other laminins appears to lead to their increased deposition in the GBM. Laminin β ₂ also serves as a potentially novel cell-adhesive ligand for integrin α ₄ β ₁ . Our findings define biochemical functions of laminin β ₂ variants influencing glomerular filtration that may underlie the pathogenesis of isolated nephropathy caused by LAMB2 abnormalities.