Low and high concentrations of butyrate regulate fat accumulation in chicken adipocytes via different mechanisms

Butyric acid reduced lipid deposition in immortalized chicken preadipocyte by inhibiting cell proliferation and differentiation

The hyperplasia and hypertrophy of preadipocytes were closely related to lipid deposition in animals. Butyric acid was reported to be involved in lipid metabolism. The aim of the current study was to investigate the effect of butyric acid on the proliferation and differentiation of the immortalized chicken preadipocyte 2 (ICP2). ICP2 were treated respectively with 12mM butyric acid for 48h in proliferation trial and 4mM butyric acid plus 200 μM oleic acid for 3 d in differentiation trial. For the proliferation trial, RNA-seq analysis revealed that 2039 genes were significantly up-regulated and 780 genes were significantly down-regulated with 12 mM butyric acid after 48 h treatment. Concurrently, Cell cycle, DNA replication and p53 signaling pathways were down-regulated in Butyric acid group. More importantly, 12 mM butyric acid restrained the expression of cell proliferation genes such as PCNA, CDK1 and CDK2 in Butyric acid group (P < 0.05), and the protein expression levels of PCNA and CDK1 were also significantly decreased (P < 0.05). The Oil red staining revealed a fewer presence of red fat droplets in ICP2 following treatment with 4 mM butyric acid, accompanied by decreased levels of total cholesterol (TC) and triglycerides (TG). RNA-seq analysis shown that the number of up and down-regulated genes were 2095 and 1042 respectively in OAB group (oleic acid+butyric acid) when compared with OA group (oleic acid). Meanwhile the AMPK signaling pathway, FOXO signaling pathway and focal adhesion were significantly enriched in OAB group. Additionally, 4 mM butyric acid inhibited the expression of lipid differentiation genes including FABP4, C/EBPα, PPARγ and LPL in OAB group (P < 0.05), as well as lipogenesis proteins such as FABP4, C/EBP-α and PPARγ (P < 0.05). In conclusion, 12 mM butyric acid effectively inhibited the proliferation of ICP2 by slowing down cell cycle progression, while 4 mM butyric acid alleviated lipid deposition by reducing the production of lipid droplets through inhibiting the expression of lipid differentiation marker genes and proteins.

Glucagon-like peptide-1 analog liraglutide reduces fat deposition in chicken adipocytes

Previously, we reported that glucagon-like peptide-1 (GLP-1) and its analog liraglutide could inhibit fat de novo synthesis in the liver and reduce abdominal fat accumulation in broiler chickens. Nevertheless, the impact of GLP-1 on adipocyte fat deposition remains enigmatic. This study aimed to investigate the effects of GLP-1, via its analog liraglutide, on chicken chicken adipocytes in vitro. Chemical assays, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were employed to assess the proliferation, differentiation, and fat deposition of chicken adipocytes. Our findings indicated that liraglutide significantly suppressed cell proliferation and promoted preadipocyte differentiation in comparison to the control group. This was evidenced by elevated triglyceride (TG) content and upregulated mRNA expression of lipogenesis-related enzymes, such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), as well as regulators including peroxisome proliferator-activated receptor γ (PPARγ), sterol regulatory element binding protein-1 (SREBP1) and CCAAT/enhancer binding protein α (CEBPα). In mature adipocytes, liraglutide attenuated fat deposition by inhibiting fat de novo synthesis, evidenced by decreased mRNA expression of ACC, FAS, PPARγ, C/EBPα, and SREBP1, and concurrent upregulation of phosphorylated AMP-activated protein kinase (p-AMPK) and phosphorylated ACC (p-ACC). This resulted in reduced accumulation of lipid droplets and TG content in mature adipocytes. Collectively, our findings indicate that liraglutide suppresses the proliferation of preadipocytes, enhances their differentiation, and concurrently inhibits de novo lipogenesis in mature adipocytes. This observation offers profound insights into the mechanisms that underlie liraglutide's anti-adipogenic effects, which could have significant implications for the treatment of obesity in broiler chickens.

E2F transcription factor 5, a new regulator in adipogenesis to mediate the role of Krüppel-like factor 7 in chicken preadipocyte differentiation and proliferation

E2F transcription factor 5 (E2F5) gene is a transcription factor, plays an important role in the development of a variety of cells. E2F5 is expressed in human and mouse adipocytes, but its specific function in adipogenesis is unclear. Krüppel-like factor 7 (KLF7) facilitates proliferation and inhibits differentiation in chicken preadipocytes. Our previous KLF7 chromatin immunoprecipitation-sequencing analysis revealed a KLF7-binding peak in the 3' flanking region of the E2F5, indicating a regulatory role of KLF7 in this region. In the present study, we investigated E2F5 potential role, the overexpression and knockdown analyses revealed that E2F5 inhibited the differentiation and promoted the proliferation of chicken preadipocytes. Moreover, we identified enhancer activity in the 3' flanking region (nucleotides +22661/+22900) of E2F5 and found that KLF7 overexpression increased E2F5 expression and luciferase activity in this region. Deleting the putative KLF7-binding site eliminated the promoting effect of KLF7 overexpression on E2F5 expression. Further, E2F5 reversed the KLF7-induced decrease in preadipocyte differentiation and increase in preadipocyte proliferation. Taken together, our findings demonstrate that KLF7 inhibits differentiation and promotes proliferation in preadipocytes by enhancing E2F5 transcription.

Sodium Butyrate Alleviates Free Fatty Acid-Induced Steatosis in Primary Chicken Hepatocytes via Regulating the ROS/GPX4/Ferroptosis Pathway

Fatty liver hemorrhagic syndrome (FLHS) in laying hens is a nutritional metabolic disease commonly observed in high-yielding laying hens. Sodium butyrate (NaB) and ferroptosis were reported to contribute to the pathogenesis of fatty liver-related diseases. However, the underlying mechanism of NaB in FLHS and whether it mediates ferroptosis remains unclear. A chicken primary hepatocyte induced by free fatty acids (FFAs, keeping the ratio of sodium oleate and sodium palmitate concentrations at 2:1) was established, which received treatments with NaB, the ferroptosis inducer RAS-selective lethal 3 (RSL3), and the inhibitor ferrostatin-1 (Fer-1). As a result, NaB increased biochemical and lipid metabolism indices, and the antioxidant level, while inhibiting intracellular ROS accumulation and the activation of the ferroptosis signaling pathway, as evidenced by a reduction in intracellular iron concentration, upregulated GPX4 and xCT expression, and inhibited NCOA4 and ACSL4 expression. Furthermore, treatment with Fer-1 reinforced the protective effects of NaB, while RSL3 reversed it by blocking the ROS/GPX4/ferroptosis pathway, leading to the accumulation of lipid droplets and oxidative stress. Collectively, our findings demonstrated that NaB protects hepatocytes by regulating the ROS/GPX4-mediated ferroptosis pathway, providing a new strategy and target for the treatment of FLHS.

Effects of Low or High Dosages of Dietary Sodium Butyrate on the Growth and Health of the Liver and Intestine of Largemouth Bass, Micropterus salmoides

The concentration of butyric acid in the intestine increased with the increase in the content of fermentable dietary fibre; however, the potential physiological impact of a high dose of butyric acid on fish has not been sufficiently studied. The aim of this study was to investigate the effect of two dosages of butyric acid on the growth and health of the liver and intestine of the largemouth bass (Micropterus salmoides). Sodium butyrate (SB) was added to the diet at 0 g/kg (CON), 2 g/kg (SB2), and 20 g/kg (SB20), and the juvenile largemouth bass were fed to apparent satiation for 56 days. No significant difference was observed in the specific growth rate or hepatosomatic index among the groups (P > 0.05). The concentration of β-hydroxybutyric acid in the liver, the activities of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, and the concentrations of triglyceride and total cholesterol in serum increased significantly in the SB20 group compared to the CON group (P < 0.05). The relative expression of fas, acc, il1b, nfkb, and tnfa in the liver of the SB20 groups was also significantly higher than that of the CON group (P < 0.05). The above indicators in the group SB2 had similar change tendencies. The expression of nfkb and il1b in the intestine of both the SB2 and SB20 groups was significantly downregulated compared with that in the CON group (P < 0.05). The size of hepatocytes was enlarged, and the intracellular lipid droplets and the degree of hepatic fibrosis were increased in the SB20 group compared to the CON group. There was no significant difference in intestinal morphology among the groups. The above results indicated that neither 2 g/kg nor 20 g/kg SB had a positive effect on the growth of largemouth bass, while a high dosage of SB induced liver fat accumulation and fibrosis.

Adiponectin Reduces Lipid Content in Chicken Myoblasts by Activating AMPK Signaling Pathway

Studies in mammals have shown that adiponectin is secreted mainly by adipocytes, and it plays a crucial role in glucose and lipid metabolism in muscles. Clarifying the crosstalk role of adiponectin between adipose tissue and skeletal muscle tissue is very important for internal homeostasis. The glucose and lipid metabolism of chicken is different from that of mammals, and the role of adiponectin in chickens is unclear. Therefore, it is of great significance to study the effect and mechanism of adiponectin on lipid metabolism in chickens. In this study, the regulating effect of adiponectin on lipid metabolism in chicken myoblasts was explored by adding a certain concentration of exogenous recombinant adiponectin. Results showed that adiponectin reduced intracellular lipid content, increasing the mRNA expression of adiponectin receptor and cellular uptake of glucose and fatty acids. In addition, adiponectin activated the 5' adenosine monophosphate activated protein kinase (AMPK) signaling pathway. The above results suggested that adiponectin reduced intracellular lipid content, mainly by binding to adiponectin receptor, activating AMPK pathway, increasing cellular uptake of glucose and fatty acids, and promoting lipid oxidation.

Short-Chain Fatty Acids Modulate Healthy Gut Microbiota Composition and Functional Potential

Many studies have focused on the metabolic capacity of human gut microbiota to produce short-chain fatty acids and subsequent effects on host physiology. Given scarce data on how SCFAs produced by gut bacteria participate in cross-feeding to influence community structure and function, we evaluated the potential of SCFAs to modulate human gut microbiota in vitro. We employed anaerobic fecal cultivation in chemically defined medium supplemented with one of nine SCFAs to determine effects on both gut microbial community structure via 16S rRNA sequencing and function via genome reconstruction analysis. Each SCFA displayed significant and unique modulatory potential with respect to the relative abundance of bacterial taxa. Analysis of SCFA-supplemented communities revealed that alterations of individual closely related phylotypes displayed coherent changes, although exceptions were also observed which suggest strain-dependent differences in SCFA-induced changes. We used genome reconstruction to evaluate the functional implications of SCFA-mediated restructuring of fecal communities. We note that some SCFA-supplemented cultures displayed a reduction in the predicted abundance of SCFA producers, which suggests a possible undefined negative feedback mechanism. We conclude that SCFAs are not simply end-products of metabolism but also serve to modulate the gut microbiota through cross-feeding that alters the fitness of specified taxa. These results are important in the identification of prebiotics that elevate specific SCFAs for therapeutic benefit and highlight SCFA consumers as a salient part of the overall metabolic flux pertaining to bacterial fermentative processes.

Dietary Supplementation of Calcium Propionate and Calcium Butyrate Improves Eggshell Quality of Laying Hens in the Late Phase of Production

The aim of this study was to evaluate the effects of dietary supplementation of calcium propionate and calcium butyrate on the laying performance, eggshell quality, and expression of genes related to calcium and phosphorus metabolism in the tibia. One hundred and twenty 70-week-old Isa Brown hens were randomly assigned to three treatments, and each treatment had four replicates of 10 birds fed a basal diet (control) or a basal diet supplemented with 0.5% calcium propionate (CP) or 0.5% calcium butyrate (CB) for 8 weeks. The CB and CP treatments had no significant effect (P>0.05) on the laying rate, egg production, egg weight, and feed efficiency. The eggshell percentage was increased from week 2 (P<0.05) and eggshell thickness was elevated at week 8 (P<0.01) by both CP and CB treatments. Compared to the control treatment, the CB treatment increased serum calcium and phosphorus levels at week 4 (P<0.05), whereas the CP and CB treatments decreased serum phosphorus at weeks 6 and 8, respectively (P<0.05). Dietary supplementation had no effect on the bone index and bending strength of the tibia (P>0.05). The calcium and phosphorus content of the tibia was decreased by the CB treatment (P<0.05). In the spleen, NF-κB and IL-6 transcript levels were not influenced (P>0.05) but TNF-α transcript levels were decreased by the CP treatment (P<0.05). In the tibia, the expression levels of NF-κB, TNF-α, and IL-17 were not affected by the CP or CB treatment (P>0.05). The CP and CB treatments had no significant effect on the transcript levels of RANKL, OPG, RNUX2, OPN, α-Clotho, and VDR (P>0.05). In contrast, PHEX transcript levels were increased by the CP treatment (P<0.05). The expression levels of osteocalcin (P=0.094) and FGF23 (P=0.087) tended to decrease under the CB treatment. In conclusion, dietary supplementation of 0.5% calcium butyrate or 0.5% calcium propionate improved the eggshell quality of aged laying hens, possibly as a result of decreased deposition or enhanced mobilization of bone calcium and phosphorus.

Short-chain fatty acids activate acetyltransferase p300

Short-chain fatty acids (SCFAs) acetate, propionate, and butyrate are produced in large quantities by the gut microbiome and contribute to a wide array of physiological processes. While the underlying mechanisms are largely unknown, many effects of SCFAs have been traced to changes in the cell's epigenetic state. Here, we systematically investigate how SCFAs alter the epigenome. Using quantitative proteomics of histone modification states, we identified rapid and sustained increases in histone acetylation after the addition of butyrate or propionate, but not acetate. While decades of prior observations would suggest that hyperacetylation induced by SCFAs are due to inhibition of histone deacetylases (HDACs), we found that propionate and butyrate instead activate the acetyltransferase p300. Propionate and butyrate are rapidly converted to the corresponding acyl-CoAs which are then used by p300 to catalyze auto-acylation of the autoinhibitory loop, activating the enzyme for histone/protein acetylation. This data challenges the long-held belief that SCFAs mainly regulate chromatin by inhibiting HDACs, and instead reveals a previously unknown mechanism of HAT activation that can explain how an influx of low levels of SCFAs alters global chromatin states.

Butyrate Alters Pyruvate Flux and Induces Lipid Accumulation in Cultured Colonocytes

Butyrate is considered the primary energy source of colonocytes and has received wide attention due to its unique health benefits. Insight into the mechanistic effects of butyrate on cellular and metabolic function relies mainly on research in in-vitro-cultured cells. However, cells in culture differ from those in vivo in terms of metabolic phenotype and nutrient availability. For translation, it is therefore important to understand the impact of different nutrients on the effects of butyrate. We investigated the metabolic consequences of butyrate exposure under various culturing conditions, with a focus on the interaction between butyrate and glucose. To investigate whether the effects of butyrate were different between cells with high and low mitochondrial capacity, we cultured HT29 cells under either low- (0.5 mM) or high- (25 mM) glucose conditions. Low-glucose culturing increased the mitochondrial capacity of HT29 cells compared to high-glucose (25 mM) cultured HT29 cells. Long-term exposure to butyrate did not alter mitochondrial bioenergetics, but it decreased glycolytic function, regardless of glucose availability. In addition, both high- and low-glucose-grown HT29 cells showed increased lipid droplet accumulation following long-term butyrate exposure. Acute exposure of cultured cells (HT29 and Caco-2) to butyrate increased their oxygen consumption rate (OCR). A simultaneous decrease in extracellular acidification rate (ECAR) was observed. Furthermore, in the absence of glucose, OCR did not increase in response to butyrate. These results lead us to believe that butyrate itself was not responsible for the observed increase in OCR, but, instead, butyrate stimulated pyruvate flux into mitochondria. Indeed, blocking of the mitochondrial pyruvate carrier prevented a butyrate-induced increase in oxygen consumption. Taken together, our results indicate that butyrate itself is not oxidized in cultured cells but instead alters pyruvate flux and induces lipid accumulation.

Characterization and Duodenal Transcriptome Analysis of Chinese Beef Cattle With Divergent Feed Efficiency Using RNA-Seq

Residual feed intake (RFI) is an important measure of feed efficiency for agricultural animals. Factors associated with cattle RFI include physiology, dietary factors, and the environment. However, a precise genetic mechanism underlying cattle RFI variations in duodenal tissue is currently unavailable. The present study aimed to identify the key genes and functional pathways contributing to variance in cattle RFI phenotypes using RNA sequencing (RNA-seq). Six bulls with extremely high or low RFIs were selected for detecting differentially expressed genes (DEGs) by RNA-seq, followed by conducting GO, KEGG enrichment, protein-protein interaction (PPI), and co-expression network (WGCNA, n = 10) analysis. A total of 380 differentially expressed genes was obtained from high and low RFI groups, including genes related to energy metabolism (ALDOA, HADHB, INPPL1), mitochondrial function (NDUFS1, RFN4, CUL1), and feed intake behavior (CCK). Two key sub-networks and 26 key genes were detected using GO analysis of DEGs and PPI analysis, such as TPM1 and TPM2, which are involved in mitochondrial pathways and protein synthesis. Through WGCNA, a gene network was built, and genes were sorted into 27 modules, among which the blue (r = 0.72, p = 0.03) and salmon modules (r = -0.87, p = 0.002) were most closely related with RFI. DEGs and genes from the main sub-networks and closely related modules were largely involved in metabolism; oxidative phosphorylation; glucagon, ribosome, and N-glycan biosynthesis, and the MAPK and PI3K-Akt signaling pathways. Through WGCNA, five key genes, including FN1 and TPM2, associated with the biological regulation of oxidative processes and skeletal muscle development were identified. Taken together, our data suggest that the duodenum has specific biological functions in regulating feed intake. Our findings provide broad-scale perspectives for identifying potential pathways and key genes involved in the regulation of feed efficiency in beef cattle.

The Athlete and Gut Microbiome: Short-chain Fatty Acids as Potential Ergogenic Aids for Exercise and Training

Short-chain fatty acids (SCFAs) are metabolites produced in the gut via microbial fermentation of dietary fibers referred to as microbiota-accessible carbohydrates (MACs). Acetate, propionate, and butyrate have been observed to regulate host dietary nutrient metabolism, energy balance, and local and systemic immune functions. In vitro and in vivo experiments have shown links between the presence of bacteria-derived SCFAs and host health through the blunting of inflammatory processes, as well as purported protection from the development of illness associated with respiratory infections. This bank of evidence suggests that SCFAs could be beneficial to enhance the athlete's immunity, as well as act to improve exercise recovery via anti-inflammatory activity and to provide additional energy substrates for exercise performance. However, the mechanistic basis and applied evidence for these relationships in humans have yet to be fully established. In this narrative review, we explore the existing knowledge of SCFA synthesis and the functional importance of the gut microbiome composition to induce SCFA production. Further, changes in gut microbiota associated with exercise and various dietary MACs are described. Finally, we provide suggestions for future research and practical applications, including how these metabolites could be manipulated through dietary fiber intake to optimize immunity and energy metabolism.