Dickkopf (Dkk)-2 is a beige fat-enriched adipokine to regulate adipogenesis

Fusobacterium mortiferum and its metabolite 5-aminovaleric acid promote the development of colorectal cancer in obese individuals through Wnt/β-catenin pathway by DKK2

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide, with high incidence and mortality rates. An increasing body of research suggests that obesity is a significant risk factor for the development of CRC. Moreover, recent findings have highlighted the close association between the gut microbiota and both obesity and CRC. Despite this, the specific mechanisms by which the gut microbiota influences obesity and CRC remain unclear. This study aims to explore the role of the gut bacterium Fusobacterium mortiferum and its metabolite 5-aminovaleric acid (5-AVA) in the development of obesity and CRC. Our study found that the metabolite 5-aminovaleric acid produced by Fusobacterium mortiferum significantly inhibits the expression of the tumor suppressor DKK2. This inhibition leads to enhanced proliferation of CRC cells. Furthermore, we discovered that Fusobacterium mortiferum and 5-AVA can activate the Wnt/β-catenin signaling pathway by inhibiting DKK2, thereby promoting tumor growth. This finding was validated in CRC mouse models and in vitro experiments. Additional mechanistic studies revealed that 5-AVA interacts with the demethylase KDM6B, affecting the demethylation process of DKK2 and subsequently activating the Wnt/β-catenin signaling pathway. Our study retrospectively collected fecal samples from patients who underwent gastrointestinal endoscopy at the Sixth Affiliated Hospital of Sun Yat-sen University over the past five years. Participants were stratified into a healthy control group and an adenoma group based on the outcomes of their colonoscopies. Following this, we conducted metagenomic analysis to identify differential bacteria, and based on the results, we performed bacterial cultivation and metabolomic profiling. The roles of the targeted bacteria and their metabolites were further validated through animal models and cellular assays, employing techniques such as Western Blot, qPCR, immunohistochemistry, molecular docking simulations, and gene overexpression studies. This study uncovers the potential carcinogenic effects of Fusobacterium mortiferum and 5-AVA in the development of obesity and CRC. Our research emphasizes the complex interplay between the gut microbiota and host metabolism and suggests new directions for future research to explore how modulation of the gut microbiota could prevent and treat CRC.

Downregulated DKK2 may serve as a molecular mechanism of high-fat diet-induced myocardial injury via Wnt/β-catenin pathway

OBJECTIVE

High-fat diet could induce structural and functional disorders of the heart, but the underlying mechanism remains elusive. This study aimed to explore related mechanism of obesity cardiomyopathy.

METHODS

Obesity model was established by feeding rats with a high-fat diet, and H9c2 cells were stimulated with palmitic acid to mimic high-fat stimulation. Whole transcriptome analysis results showed that the expression of Dickkopf-2 (DKK2) in obesity cardiomyopathy group was significantly lower than that in control group and simple obesity group. Overexpression and knockdown of DKK2 was achieved by infection with lentivirus. Weight, blood glucose, lipids, blood pressure, and insulin, HE staining, Sirius red staining and echocardiography results were analyzed in rats at 8 and 16 weeks after various interventions. qRT-PCR and western blots were used to detect the expression of RNAs and proteins.

RESULTS

High-fat diet-induced obese rats presented with changes in serum lipid, insulin, and increases in myocardial inflammation and fibrosis. Protein and mRNA expression levels of DKK2 were significantly decreased in the obesity cardiomyopathy group compared with the obesity and control group. In vitro, knockdown of DKK2 activated β-catenin/Wnt3a pathway, while overexpress of DKK2 inhibited β-catenin/Wnt3a expression.

CONCLUSION

Activating DKK2 may serve as a novel therapeutic intervention option for obesity cardiomyopathy and obesity-related metabolic disorders, and future studies are needed to validate this hypothesis.

Integrated analysis strategy of genome-wide functional gene mining reveals DKK2 gene underlying meat quality in Shaziling synthesized pigs

BACKGROUND

Shaziling pig is a well-known indigenous breed in China who has superior meat quality traits. However, the genetic mechanism and genomic evidence underlying meat quality characteristics of Shaziling pigs are still unclear. To explore and investigate the germplasm characteristics of Shaziling pigs, we totally analyzed 67 individual's whole genome sequencing data for the first time (20 Shaziling pigs [S], 20 Dabasha pigs [DBS], 11 Yorkshire pigs [Y], 10 Berkshire pigs [BKX], 5 Basha pigs [BS] and 1 Warthog).

RESULTS

A total of 2,538,577 SNPs with high quality were detected and 9 candidate genes which was specifically selected in S and shared in S to DBS were precisely mined and screened using an integrated analysis strategy of identity-by-descent (IBD) and selective sweep. Of them, dickkopf WNT signaling pathway inhibitor 2 (DKK2), the antagonist of Wnt signaling pathway, was the most promising candidate gene which was not only identified an association of palmitic acid and palmitoleic acid quantitative trait locus in PigQTLdb, but also specifically selected in S compared to other 48 Chinese local pigs of 12 populations and 39 foreign pigs of 4 populations. Subsequently, a mutation at 12,726-bp of DKK2 intron 1 (g.114874954 A > C) was identified associated with intramuscular fat content using method of PCR-RFLP in 21 different pig populations. We observed DKK2 specifically expressed in adipose tissues. Overexpression of DKK2 decreased the content of triglyceride, fatty acid synthase and expression of relevant genes of adipogenic and Wnt signaling pathway, while interference of DKK2 got contrary effect during adipogenesis differentiation of porcine preadipocytes and 3T3-L1 cells.

CONCLUSIONS

Our findings provide an analysis strategy for mining functional genes of important economic traits and provide fundamental data and molecular evidence for improving pig meat quality traits and molecular breeding.

Comprehensive molecular and morphological resolution of blubber stratification in a deep-diving, fasting-adapted seal

Blubber is a modified subcutaneous adipose tissue in marine mammals that provides energy storage, thermoregulation, hydrodynamic locomotion, and buoyancy. Blubber displays vertical stratification by lipid content, fatty acid composition, and vascularization, leading to the assumption that deeper blubber layers are metabolically active, while superficial layers are mainly structural and thermoregulatory. However, few studies have examined functional stratification of marine mammal blubber directly, especially in pinnipeds. We characterized morphological and transcriptional differences across blubber layers in the northern elephant seal, a deep-diving and fasting-adapted phocid. We collected blubber from seals early in their fasting period and divided blubber cores into three similarly sized portions. We hypothesized that the innermost blubber portion would have higher 1) heterogeneity in adipocyte size, 2) microvascular density, and 3) expression of genes associated with metabolism and hormone signaling than outer blubber. We found that adipocyte area and variance increased from outermost (skin-adjacent) to innermost (muscle-adjacent) blubber layers, suggesting that inner blubber has a higher capacity for lipid storage and turnover than outer blubber. Inner blubber had a higher proportion of CD144+ endothelial cells, suggesting higher microvascular density. In contrast, outer blubber had a higher proportion of CD4+ immune cells than inner blubber, suggesting higher capacity for response to tissue injury. Transcriptome analysis identified 61 genes that were differentially expressed between inner and outer blubber layers, many of which have not been studied previously in marine mammals. Based on known functions of these genes in other mammals, we suggest that inner blubber has potentially higher 1) adipogenic capacity, 2) cellular diversity, and 3) metabolic and neuroendocrine signaling activity, while outer blubber may have higher 1) extracellular matrix synthesis activity and 2) responsiveness to pathogens and cell stressors. We further characterized expression of nine genes of interest identified by transcriptomics and two adipokines with higher precision across blubber layers using targeted assays. Our study provides functional insights into stratification of blubber in marine mammals and a molecular key, including CD144, CD4, HMGCS2, GABRG2, HCAR2, and COL1A2, for distinguishing blubber layers for physiological and functional studies in seals.

Modeling microRNA-driven post-transcriptional regulation using exon-intron split analysis in pigs

The contribution of microRNAs (miRNAs) to mRNA post-transcriptional regulation has often been explored by the post hoc selection of downregulated genes and determining whether they harbor binding sites for miRNAs of interest. This approach, however, does not discriminate whether these mRNAs are also downregulated at the transcriptional level. Here, we have characterized the transcriptional and post-transcriptional changes in mRNA expression in two porcine tissues: gluteus medius muscle of fasted and fed Duroc gilts and adipose tissue of lean and obese Duroc-Göttingen minipigs. Exon-intron split analysis of RNA-seq data allowed us to identify downregulated mRNAs with high post-transcriptional signals in fed or obese states, and we assessed whether they harbor binding sites for upregulated miRNAs in any of these two physiological states. We found 26 downregulated mRNAs with high post-transcriptional signals in the muscle of fed gilts and 21 of these were predicted targets of miRNAs upregulated in fed pigs. For adipose tissue, 44 downregulated mRNAs in obese minipigs displayed high post-transcriptional signals, and 25 of these were predicted targets of miRNAs upregulated in the obese state. These results suggest that the contribution of miRNAs to mRNA repression is more prominent in the skeletal muscle system. Finally, we identified several genes that may play relevant roles in the energy homeostasis of the pig skeletal muscle (DKK2 and PDK4) and adipose (SESN3 and ESRRG) tissues. By differentiating transcriptional from post-transcriptional changes in mRNA expression, exon-intron split analysis provides a valuable view of the regulation of gene expression, complementary to canonical differential expression analyses.

Salidroside promoted osteogenic differentiation of adipose-derived stromal cells through Wnt/β-catenin signaling pathway

BACKGROUND

Bone disease causes short-term or long-term physical pain and disability. It is necessary to explore new drug for bone-related disease. This study aimed to explore the role and mechanism of Salidroside in promoting osteogenic differentiation of adipose-derived stromal cells (ADSCs).

METHODS

ADSCs were isolated and treated with different dose of Salidroside. Cell count kit-8 (CCK-8) assay was performed to assess the cell viability of ADSCs. Then, ALP and ARS staining were conducted to assess the early and late osteogenic capacity of ADSCs, respectively. Then, differentially expressed genes were obtained by R software. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of the differentially expressed genes were further analyzed. The expression of OCN, COL1A1, RUNX2, WNT3A, and β-catenin were measured by real-time PCR and Western blot analysis. Last, β-catenin was silenced by small interfering RNA.

RESULTS

Salidroside significantly increased the ADSCs viability at a dose-response manner. Moreover, Salidroside enhanced osteogenic capacity of ADSCs, which are identified by enhanced ALP activity and calcium deposition. A total of 543 differentially expressed genes were identified between normal and Salidroside-treated ADSCs. Among these differentially expressed genes, 345 genes were upregulated and 198 genes were downregulated. Differentially expressed genes enriched in the Wnt/β-catenin signaling pathway. Western blot assay indicated that Salidroside enhanced the WNT3A and β-catenin expression. Silencing β-catenin partially reversed the promotion effects of Salidroside. PCR and Western blot results further confirmed these results.

CONCLUSION

Salidroside promoted osteogenic differentiation of ADSCs through Wnt/β-catenin signaling pathway.