Ajuba functions as a co-activator of C/EBPβ to induce expression of PPARγ and C/EBPα during adipogenesis

METTL14 and WTAP play a crucial role in the regulation of bovine preadipocyte differentiation

m6A methylation is the most common mRNA modification in mammals and plays a significant role in regulating various biological functions. Some studies have demonstrated that the methyltransferase METTL3 can promote adipogenesis. However, the regulatory mechanisms of METTL14 and WTAP, both methyltransferases, in adipogenesis remain unclear. This study investigated their effects on bovine preadipocyte differentiation using siRNA-mediated knockdown combined with transcriptomic analysis. Silencing METTL14 and WTAP significantly impaired lipid droplet formation and revealed distinct regulatory pathways: METTL14 knockdown affected genes like JAK2 and STAT3, while WTAP suppression down-regulated PPARγ/FABP4 signalling pathway components. These findings demonstrate that WTAP specifically modulates bovine adipocyte differentiation through the PPARγ/FABP4 pathway.

Effect of gene CRTC2 on the differentiation of subcutaneous precursor adipocytes in goats

OBJECTIVE

The aim of this study was to obtain goat CRTC2 gene sequence and elucidate its biological properties, and further study the impact of overexpression and interference of CRTC2 on the cell differentiation of goat subcutaneous precursor adipocytes.

METHODS

The sequence of goat CRTC2 was cloned by reverse transcription (RT)-polymerase chain reaction (PCR) and its molecular characterization was analyzed. The expression of CRTC2 gene in goat tissues and subcutaneous precursor adipocytes differentiated from 0 to 120 h was examined by quantitative real-time PCR (qRT-PCR). The effects of CRTC2 on the subcutaneous precursor adipocyte differentiation were investigated by using liposome transfection, Bodipy, Oil Red O staining and qPCR.

RESULTS

The results showed that the cloned goat CRTC2 gene was 2363 bp long (coding sequence [CDS] 2082 bp), encoding 693 amino acids. The relative expression levels of CRTC2 gene were highest in liver and then in kidney (p<0.05). During differentiation, the highest expression of CRTC2 in subcutaneous precursor adipocytes was observed at 120 of differentiating (p<0.01). In addition, we found that overexpression of CRTC2 significantly increased the expression of lipid metabolism-related genes (C/EBPα, C/EBPβ, PPARγ, DGAT1, DGAT2, ACC, FASN, SREBP1, AP2, LPL, ATGL) and promoted lipid accumulation. We then chemically synthesized goat CRTC2 small interfering RNA and transfected it into goat subcutaneous precursor adipocytes. The results revealed that SiRNA-mediated interference with CRTC2 significantly inhibited its differentiation and suppressed lipid droplet aggregation.

CONCLUSION

So, this study indicates that CRTC2 is a positive regulator that promoting cell differentiation of subcutaneous adipocyte in goats, which lays the foundation for an in-depth study of the role of CRTC2 in lipid deposition in goats.

WWP1-SHARP1-C/EBPβ positive feedback loop modulates development of metabolic dysfunction-associated steatotic liver disease

BACKGROUND & AIMS

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant global health threat. The molecular mechanisms underlying regulation of MASLD remain largely unknown. This study aimed to investigate the role of the WW domain-containing ubiquitin E3 ligase 1 (WWP1)-enhancer-of-split and hairy-related protein 1 (SHARP1)-C/EBPβ signal loop in MASLD.

METHODS

In vivo and in vitro models of MASLD were established applying high-fat diet-fed (HFD) mice and free fatty acid (FFA)-treated hepatocytes. The relationships among SHARP1, WWP1, and C/EBPβ were examined using bioinformatics, immunoprecipitation, immunofluorescence, luciferase assays, chromatin immunoprecipitation. MASLD progression was evaluated based on food intake, energy expenditure, insulin resistance, hepatic steatosis, inflammation and white fat growth.

RESULTS

SHARP1 were significantly reduced in the MASLD livers of mouse and human and in FA-treated hepatocytes. Hepatocyte-specific SHARP1 overexpression significantly inhibited MASLD development in HFD-fed mice. Wild-type SHARP1, but not deficient SHARP1 (SHARP1-K/R and SHARP1-P/A), was ubiquitinated and degraded by the E3 ligase WWP1. Wild-type SHARP1 was not ubiquitinated when WWP1 was deficient (WWP1-C886A, WWP1-C890A, WWP1-ΔWW3). Deficient SHARP1 exhibited better inhibitory activity against MASLD than the wild-type SHARP1. WWP1 overexpression reversed the suppression of MASLD induced by wild-type SHARP1 but did not affect that induced by deficient SHARP1. Deficient WWP1 did not inhibit the wild-type SHARP1-induced MASLD amelioration. Furthermore, in FA-treated hepatocytes, the interaction between SHARP1 and C/EBPβ weakened, resulting in more C/EBPβ binding to the Wwp1 promoter and subsequent WWP1 upregulation. SHARP1 overexpression or WWP1 interference partially blocked the effects of C/EBPβ on MASLD. Hesperidin was identified as a novel WWP1 inhibitor, and it significantly blocked WWP1 overexpression-induced MASLD progression.

CONCLUSION

The WWP1-SHARP1-C/EBPβ signal loop accelerates MASLD progression. This study provides novel insights into novel biomarkers and treatment approaches for MASLD.

Effect of DHCR7 on adipocyte differentiation in goats

Cholesterol is regarded as a signaling molecule in regulating the metabolism and function of fat cells, in which 7-Dehydrocholesterol reductase (DHCR7) is a key enzyme that catalyzes the conversion of 7-dehydrocholesterol to cholesterol, however, the exact function of DHCR7 in goat adipocytes remains unknown. Here, the effect of DHCR7 on the formation of subcutaneous and intramuscular fat in goats was investigated in vitro, and the result indicated that the mRNA level of DHCR7 showed a gradual downward trend in subcutaneous adipogenesis, but an opposite trend in intramuscular adipogenesis. In the process of subcutaneous preadipocytes differentiation, overexpression of DHCR7 inhibited the expression of adipocytes differentiation marker genes (CEBP/α, CEBP/β, SREBP1 and AP2), lipid metabolism-related genes (AGPAT6, FASN, SCD1 and LPL), and the lipid accumulation. However, in intramuscular preadipocyte differentiation, DHCR7 overexpression showed a promoting effect on adipocyte differentiation marker genes (CEBP/α, CEBP/β, PPARγ and SREBP1) and lipid metabolism-related genes (GPAM, AGPAT6, DGAT1 and SCD1) expression, and on lipid accumulation. In summary, our work demonstrated that DHCR7 played an important role in regulating adipogenic differentiation and lipid metabolism in preadipocytes in goats, which is of great significance for uncovering the underlying molecular mechanism of adipocyte differentiation and improving goat meat quality.

Effects of Opuntia stricta var. dillenii Extracts Obtained from Prickly Pear and an Industrial By-Product on Maturing Pre-Adipocytes

Opuntia stricta var. dillenii, a member of the Cactaceae family, produces a fruit known as prickly pear. This fruit is rich in bioactive compounds, including betalains and phenolic compounds, which play an important role in health promotion due to their antioxidant and anti-inflammatory properties. This study aims to investigate the impact of prickly pear extracts obtained from the whole fruit, peel, pulp, and an industrial by-product (bagasse) on the differentiation of 3T3-L1 pre-adipocytes. During the differentiation process, 3T3-L1 pre-adipocytes were treated with prickly pear extracts at concentrations ranging from 10 to 100 μg/mL from day 0 to day 8 post-induction. Moreover, the potential mechanisms justifying the observed effects were assessed by RT-PCR. All extracts led to an increase in both triacylglycerol accumulation and cell number. In conclusion, the analysed extracts demonstrated adipogenic effects in 3T3-L1 maturing pre-adipocytes by increasing the expression of the c/ebp-β, srebf-1, and c/ebp-α genes. Additionally, a potential anti-inflammatory effect was observed through the upregulation of adiponectin.

Dipeptidyl peptidase-4 disturbs adipocyte differentiation via the negative regulation of the glucagon-like peptide-1/adiponectin-cathepsin K axis in mice under chronic stress conditions

Exposure to chronic psychosocial stress is a risk factor for metabolic disorders. Because dipeptidyl peptidase-4 (DPP4) and cysteinyl cathepsin K (CTSK) play important roles in human pathobiology, we investigated the role(s) of DPP4 in stress-related adipocyte differentiation, with a focus on the glucagon-like peptide-1 (GLP-1)/adiponectin-CTSK axis in vivo and in vitro. Plasma and inguinal adipose tissue from non-stress wild-type (DPP4+/+), DPP4-knockout (DPP4-/-) and CTSK-knockout (CTSK-/-) mice, and stressed DPP4+/+, DPP4-/-, CTSK-/-, and DPP4+/+ mice underwent stress exposure plus GLP-1 receptor agonist exenatide loading for 2 weeks and then were analyzed for stress-related biological and/or morphological alterations. On day 14 under chronic stress, stress decreased the weights of adipose tissue and resulted in harmful changes in the plasma levels of DPP4, GLP-1, CTSK, adiponectin, and tumor necrosis factor-α proteins and the adipose tissue levels of CTSK, preadipocyte factor-1, fatty acid binding protein-4, CCAAT/enhancer binding protein-α, GLP-1 receptor, peroxisome proliferator-activated receptor-γ, perilipin2, secreted frizzled-related protein-4, Wnt5α, Wnt11 and β-catenin proteins and/or mRNAs as well as macrophage infiltration in adipose tissue; these changes were rectified by DPP4 deletion. GLP-1 receptor activation and CTSK deletion mimic the adipose benefits of DPP4 deficiency. In vitro, CTSK silencing and overexpression respectively prevented and facilitated stress serum and oxidative stress-induced adipocyte differentiation accompanied with changes in the levels of pref-1, C/EBP-α, and PPAR-γ in 3T3-L1 cells. Thus, these findings indicated that increased DPP4 plays an essential role in stress-related adipocyte differentiation, possibly through a negative regulation of GLP-1/adiponectin-CTSK axis activation in mice under chronic stress conditions.

Gene co-expression patterns in Atlantic salmon adipose tissue provide a molecular link among seasonal changes, energy balance and age at maturity

Sexual maturation in many fishes requires a major physiological change that involves a rapid transition between energy storage and usage. In Atlantic salmon, this transition for the initiation of maturation is tightly controlled by seasonality and requires a high-energy status. Lipid metabolism is at the heart of this transition since lipids are the main energy storing molecules. The balance between lipogenesis (lipid accumulation) and lipolysis (lipid use) determines energy status transitions. A genomic region containing a transcription co-factor of the Hippo pathway, vgll3, is the main determinant of maturation timing in Atlantic salmon. Interestingly, vgll3 acts as an inhibitor of adipogenesis in mice and its genotypes are potentially associated with seasonal heterochrony in lipid storage and usage in juvenile Atlantic salmon. Here, we explored changes in expression of more than 300 genes directly involved in the processes of adipogenesis, lipogenesis and lipolysis, as well as the Hippo pathway in the adipose tissue of immature and mature Atlantic salmon with distinct vgll3 genotypes. We found molecular evidence consistent with a scenario in which immature males with different vgll3 genotypes exhibit contrasting seasonal dynamics in their lipid profiles. We also identified components of the Hippo signalling pathway as potential major drivers of vgll3 genotype-specific differences in adipose tissue gene expression. This study demonstrates the importance of adipose gene expression patterns for directly linking environmental changes with energy balance and age at maturity through genetic factors bridging lipid metabolism, seasonality and sexual maturation.

Effect of TEA domain transcription factor 1 (TEAD1) on the differentiation of intramuscular preadipocytes in goats

TEA domain transcription factor 1 (TEAD1), also called TEF-1, acts as a transcriptional enhancer to regulate muscle-specific gene expression. However, the role of TEAD1 in regulating intramuscular preadipocyte differentiation in goats is unclear. The aim of this study was to obtain the sequence of TEAD1 gene and elucidate the effect of TEAD1 on goat intramuscular preadipocyte differentiation in vitro and its possible mechanism. The results showed that the goat TEAD1 gene CDS region sequence was 1311 bp. TEAD1 gene was widely expressed in goat tissues, with the highest expression in brachial triceps (p < 0.01). The expression of TEAD1 gene in goat intramuscular adipocytes at 72 h was extremely significantly higher than that at 0 h (p < 0.01). Overexpression of goat TEAD1 inhibited the accumulation of lipid droplets in goat intramuscular adipocyte. The relative expression of differentiation marker genes SREBP1, PPARγ, C/EBPβ were significantly down-regulated (all p < 0.01), but PREF-1 was significantly up-regulated (p < 0.01). Binding analysis showed that there were multiple binding sites between the DNA binding domain of goat TEAD1 and the promoter binding region of SREBP1, PPARγ, C/EBPβ and PREF-1. In conclusion, TEAD1 negatively regulates the differentiation of goat intramuscular preadipocytes.

Acteoside improves adipocyte browning by CDK6-mediated mTORC1-TFEB pathway

Adipocyte browning increases energy expenditure by thermogenesis, which has been considered a potential strategy against obesity and its related metabolic diseases. Phytochemicals derived from natural products with the ability to improve adipocyte thermogenesis have aroused extensive attention. Acteoside (Act), a phenylethanoid glycoside, exists in various medicinal or edible plants and has been shown to regulate metabolic disorders. Here, the browning effect of Act was evaluated by stimulating beige cell differentiation from the stromal vascular fraction (SVF) in the inguinal white adipose tissue (iWAT) and 3 T3-L1 preadipocytes, and by converting the iWAT-SVF derived mature white adipocytes. Act improves adipocyte browning by differentiation of the stem/progenitors into beige cells and by direct conversion of mature white adipocytes into beige cells. Mechanistically, Act inhibited CDK6 and mTOR, and consequently relieved phosphorylation of the transcription factor EB (TFEB) and increased its nuclear retention, leading to induction of PGC-1α, a driver of mitochondrial biogenesis, and UCP1-dependent browning. These data thus unveil a CDK6-mTORC1-TFEB pathway that regulates Act-induced adipocyte browning.

Ablation of Tas1r1 Reduces Lipid Accumulation Through Reducing the de Novo Lipid Synthesis and Improving Lipid Catabolism in Mice

Amino acid sensing plays an important role in regulating lipid metabolism by sensing amino acid nutrient disturbance. T1R1 (umami taste receptor, type 1, member 1) is a membrane G protein-coupled receptor that senses amino acids. Tas1r1-knockout (KO) mice were used to explore the function of umami receptors in lipid metabolism. Compared with wild-type (WT) mice, Tas1r1-KO mice showed decreased fat mass (P < 0.05) and adipocyte size, lower liver triglyceride (7.835 ± 0.809 vs 12.463 ± 0.916 mg/g WT, P = 0.013) and total cholesterol levels (0.542 ± 0.109 vs 1.472 ± 0.044 mmol/g WT, P < 0.001), and reduced lipogenesis gene expressions in adipose and liver tissues. Targeted liver amino acid metabolomics showed that the amino acid content of Tas1r1-KO mice was significantly decreased, which was consistent with the branched-chain ketoacid dehydrogenase protein levels. Proteomics analysis showed that the upregulated proteins were enriched in lipid and steroid metabolism pathways, and parallel reaction monitoring results illustrated that Tas1r1 ablation promoted lipid catabolism through oxysterol 7 α-hydroxylase and insulin-like growth factor binding protein 2. In summary, Tas1r1 disruption in mice could reduce lipid accumulation by reducing de novo lipid synthesis and improving lipid catabolism.