Inducible hepatic expression of CREBH mitigates diet-induced obesity, insulin resistance, and hepatic steatosis in mice

CREBH promotes autophagy to ameliorate NASH by regulating Coro1a

Dysfunctional autophagy aggravates oxidative stress and inflammation in hepatocytes and accelerates the progression of nonalcoholic steatohepatitis (NASH). Here, we demonstrated that cAMP-responsive element-binding protein H (CREBH) is a transcriptional regulator of hepatic autophagy in response to diet-induced NASH. The results showed that the upregulation of CREBH in lipid-overloaded hepatocytes improves cell damage, dysfunction of autophagic flux and associated abnormal accumulation of the autophagosome marker LC3-II and autophagic substrate p62. CREBH deficiency aggravated the dysfunctional autophagy and liver injury and even caused NASH-associated liver fibrosis. In addition, the changing trend of autolysosomes and lysosome membrane-associated protein (LAMP1) was consistent with the expression level of CREBH. This result indicated that CREBH might promote autophagic degradation by restoring the formation of autolysosomes, thereby improving the blocked autophagic flux. Moreover, we observed that CREBH inhibited the expression of Coronin 1a (Coro1a), an autophagosome-lysosome fusion-related gene, through transcriptional regulation. The overexpression of Coro1a in LO2 liver cells inhibited autophagic flux and elevated inflammatory cytokine levels upon palmitic acid (PA) stimulation. Overall, our findings provide new insights into the regulatory role of CREBH in the progression of NASH and reveal that Coro1a is a novel target gene of CREBH based on the autophagy pathway.

Regulatory mechanisms of the cAMP-responsive element binding protein 3 (CREB3) family in cancers

The CREB3 family of proteins, encompassing CREB3 and its four homologs (CREB3L1, CREB3L2, CREB3L3, and CREB3L4), exerts pivotal control over cellular protein metabolism in response to unfolded protein reactions. Under conditions of endoplasmic reticulum stress, activation of the CREB3 family occurs through regulated intramembrane proteolysis within the endoplasmic reticulum membrane. Perturbations in the function and expression of the CREB3 family have been closely associated with the development of diverse diseases, with a particular emphasis on cancer. Recent investigations have shed light on the indispensable role played by CREB3 family members in modulating the onset and progression of various human cancers. This comprehensive review endeavors to provide an in-depth examination of the involvement of CREB3 family members in distinct human cancer types, accentuating their significance in the pathogenesis of cancer and the manifestation of malignant phenotypes.

Polysaccharide-rich fractions from Enteromorpha prolifera improve hepatic steatosis and gut barrier integrity in high-fat diet-induced obese mice linking to modulation of gut microbiota

Polysaccharides from Enteromorpha prolifera (EP) possess important benefits in the management of obesity and associated metabolic diseases, but to date, the underlying mechanism linking this alleviative effect of EP to gut microbiota remains obscure. This study aimed to investigate the effects of EP in improving lipid metabolism disorders and intestinal barrier disruption in mice with high-fat diet (HFD), and its association with modulation of gut microbiota. C57BL/6 mice were fed a control diet or a HFD with or without 5% EP for 12 weeks. Factors related to lipid metabolism, insulin signaling and intestinal barrier integrity, as well as the involvement of gut microbiota and metabolites, were measured. EP supplementation reduced HFD-induced adiposity and mitigated insulin resistance, hepatic steatosis and elevation of serum lipopolysaccharides (LPS). HFD impaired intestinal barrier integrity while improved due to EP. Moreover, EP administration ameliorated HFD-induced gut dysbiosis, as revealed by the increased short-chain fatty acid (SCFA)-producing bacteria (e.g., Bacteroides, Parabacteroides, Alloprevotella, and Ruminococcus) and gut barrier-protective Akkermansia muciniphila and decreased endotoxin-producing bacteria (e.g., Desulfovibrionaceae and Bilophila), accompanied by enrichment in intestinal SCFA content and reduction in circulating LPS level. The change of dominant bacterial genera is significantly correlated with improved metabolic profiles and intestinal permeability induced by EP. In conclusion, our results indicate that EP can attenuate HFD-induced metabolic disorders along with restoration of gut barrier integrity and lowering of circulating endotoxin, and these improvements are associated with modulation of gut microbiota composition and related metabolites. These data deepen mechanistic understanding of the anti-obesity and metabolic improving effects of EP.

In Vivo Two-Photon Imaging Analysis of Dynamic Degradation of Hepatic Lipid Droplets in MS-275-Treated Mouse Liver

The accumulation of hepatic lipid droplets (LDs) is a hallmark of non-alcoholic fatty liver disease (NAFLD). Appropriate degradation of hepatic LDs and oxidation of complete free fatty acids (FFAs) are important for preventing the development of NAFLD. Histone deacetylase (HDAC) is involved in the impaired lipid metabolism seen in high-fat diet (HFD)-induced obese mice. Here, we evaluated the effect of MS-275, an inhibitor of HDAC1/3, on the degradation of hepatic LDs and FFA oxidation in HFD-induced NAFLD mice. To assess the dynamic degradation of hepatic LDs and FFA oxidation in fatty livers of MS-275-treated HFD C57BL/6J mice, an intravital two-photon imaging system was used and biochemical analysis was performed. The MS-275 improved hepatic metabolic alterations in HFD-induced fatty liver by increasing the dynamic degradation of hepatic LDs and the interaction between LDs and lysozyme in the fatty liver. Numerous peri-droplet mitochondria, lipolysis, and lipophagy were observed in the MS-275-treated mouse fatty liver. Biochemical analysis revealed that the lipolysis and autophagy pathways were activated in MS-275 treated mouse liver. In addition, MS-275 reduced the de novo lipogenesis, but increased the mitochondrial oxidation and the expression levels of oxidation-related genes, such as PPARa, MCAD, CPT1b, and FGF21. Taken together, these results suggest that MS-275 stimulates the degradation of hepatic LDs and mitochondrial free fatty acid oxidation, thus protecting against HFD-induced NAFLD.

The Role and Mechanism of CREBH Regulating SIRT3 in Metabolic Associated Fatty Liver Disease

AIMS

To investigate the effect of cAMP response element-binding protein H (CREBH) on metabolic associated fatty liver disease by regulating sirtuin 3 (SIRT3).

MAIN METHODS

Two mouse models of fatty liver induced by a methionine-choline deficient (MCD) diet and a high-fat (HF) diet and an in vitro model of palmitic acid (PA) induced lipid-overloaded hepatocytes were constructed to detect the expression of CREBH, SIRT3, total acetylation, and downstream protein interactions and lipid metabolism phenotype, which were further validated in CREBH^-/- mice and lentivirus-overexpressing CREBH hepatocytes.

KEY FINDINGS

In fatty liver and lipid overload models, the expressions of CREBH and SIRT3 were down-regulated and their expression was positively correlated, accompanied by an increase in the level of total protein acetylation. Overexpression of CREBH alleviated excess lipid accumulation, impaired viability, and the ability to metabolize energy through the fatty acid oxidation pathway in hepatocytes in vitro. Furthermore, overexpression of CREBH restored the interaction of the deacetylase SIRT3 with the molecules carnitine palmitoyl-transferase 2 (CPT2) and long-chain acyl CoA dehydrogenase (ACADL) involved in the fatty acid oxidation pathway and their deacetylation status. However, CREBH^-/- aggravated the damage of lipid metabolism in the liver tissue of mice.

SIGNIFICANCE

CREBH increased the enzymatic activity of downstream factors by positively regulating the expression of SIRT3, which promoted the oxidative decomposition of fatty acids in hepatocytes and played an important role in fatty acid oxidation in MAFLD.