Role of peroxisome proliferator-activated receptor alpha in the expression of hepatic fatty acid oxidation-related genes in chickens

The mitochondrial TSPO ligand Atriol mitigates metabolic-associated steatohepatitis by downregulating CXCL1

BACKGROUND AND AIMS

The mitochondrial translocator protein (TSPO, 18 kDa) is pivotal in binding cholesterol and facilitating its transfer from the outer to the inner mitochondrial membrane. Atriol is a TSPO ligand disrupting cholesterol binding by targeting the cholesterol-recognition amino acid consensus domain. Prior research has shown that TSPO deficiency improved metabolic-associated steatohepatitis (MASH). We hypothesized that Atriol may have the potential to alleviate MASH.

METHODS AND RESULTS

In vitro cell culture studies revealed that Atriol treatment effectively mitigated MASH by restoring mitochondrial function, inhibiting the NF-κB signaling pathway, and reducing hepatic stellate cell (HSC) activation. SD male rats were fed a GAN diet for 10 months to induce MASH. During the final two weeks of feeding, rats received intraperitoneal Atriol administration daily. Atriol treatment significantly ameliorated MASH by reducing lipid accumulation, diminishing hepatic lobular inflammation and fibrosis, decreasing cell death, and inhibiting excessive bile acid synthesis. Moreover, Atriol restored mitochondrial function in primary hepatocytes isolated from MASH rats. In search of the mechanism(s) governing these effects, we found that Atriol downregulated the proinflammatory chemokine CXCL1 through the NF-κB signaling pathway or via myeloperoxidase (MPO) in HSCs and Kupffer cells. Additionally, in vitro, studies further suggested that CXCL1 treatment induced dysfunctional mitochondria, inflammation, HSCs activation, and macrophage migration, whereas Atriol countered these effects. Finally, the mitigating effects of Atriol on MASH were reproduced by pharmacological inhibition of NF-κB or MPO and neutralization of CXCL1.

CONCLUSION

Atriol ameliorates MASH both in vitro and in vivo, demonstrating its potential therapeutic benefits in managing MASH.

Enhancement of PPARα-Inhibited Leucine Metabolism-Stimulated β-Casein Synthesis and Fatty Acid Synthesis in Primary Bovine Mammary Epithelial Cells

Leucine, a kind of branched-chain amino acid, plays a regulatory role in the milk production of mammalian mammary glands, but its regulatory functions and underlying molecular mechanisms remain unknown. This work showed that a leucine-enriched mixture (LEUem) supplementation increased the levels of milk protein and milk fat synthesis in primary bovine mammary epithelial cells (BMECs). RNA-seq of leucine-treated BMECs indicated alterations in lipid metabolism, translation, ribosomal structure and biogenesis, and inflammatory response signaling pathways. Meanwhile, the supplementation of leucine resulted in mTOR activation and increased the expression of BCKDHA, FASN, ACC, and SCD1. Interestingly, the expression of PPARα was independently correlated with the leucine-supplemented dose. PPARα activated by WY-14643 caused significant suppression of lipogenic genes expression. Furthermore, WY-14643 attenuated leucine-induced β-casein synthesis and enhanced the level of BCKDHA expression. Moreover, promoter analysis revealed a peroxisome-proliferator-response element (PPRE) site in the bovine BCKDHA promoter, and WY-14643 promoted the recruitment of PPARα onto the BCKDHA promoter. Together, the present data indicate that leucine promotes the synthesis of β-casein and fatty acid and that PPARα-involved leucine catabolism is the key target.

Central administration of insulin-like growth factor-2 suppresses food intake in chicks

Insulin-like growth factor (IGF)-2 is a multifunctional hormone with structural and functional similarity to IGF-1 in mammals and chickens. We previously showed that intracerebroventricular administration of IGF-1 suppresses food intake in chicks. Also, central administration of IGF-2 suppresses food intake in rats. In the present study, we evaluated whether IGF-2 is involved in the regulation of food intake in chicks. We also examined the effects of fasting on the mRNA levels of IGF binding proteins (IGFBPs) in the liver and hypothalamus, because IGFBPs bind IGF-1 and -2 in plasma and block their binding to the receptors, and locally expressed IGFBPs also influence IGFs binding to the receptors in mammals. Intracerebroventricular administration of IGF-2 significantly suppressed food intake in chicks. The mRNA levels of IGFBPs in the hypothalamus were not affected by six hours of fasting. On the other hand, six hours of fasting markedly increased the mRNA levels of hepatic IGFBP-1 and -2 (5.47- and 6.95-fold, respectively). The mRNA levels of IGFBP-3 were also significantly increased (1.36-fold) by six hours of fasting, whereas the mRNA levels of IGF-2, IGFBP-4, and -5 were unchanged. These findings suggest that circulating IGF-2 may be involved in satiety signals, but its physiological role may be regulated by IGFBPs production in the liver in chicks.

Effect of divergence in residual feed intake on expression of lipid metabolism-related genes in the liver of meat-type ducks1

Lipid metabolism is considered one of the important factors affecting residual feed intake (RFI). However, the relationship between RFI and expression of lipid metabolism-related genes is unknown in meat-type ducks. To address this issue, a total of 1,000 male meat-type ducks with similar body weight were randomly selected to measure body weight gain and feed intake from 21 to 42 d of age to estimate RFI. The 8 greatest- (high RFI [HRFI]) and lowest- (low RFI [LRFI]) ranking birds were then selected for the present study. Relative expressions of key genes, namely sirtuin 1 (Sirt1), forkhead box O1 (Foxo1), peroxisome proliferator-activated receptor gamma (PPARγ), sterol regulatory element-binding transcription factor 1c (SREBP-1c), fas cell surface death receptor (FAS), acetyl-CoA carboxylase alpha (ACC), carnitine palmitoyltransferase 1A (CPT1A), and acyl-CoA oxidase 1 (ACOX1), were then determined in the HRFI and LRFI ducks by quantitative PCR. The results showed that RFI, feed conversion ratio (FCR), and average daily feed intake (ADFI) were significantly lower (P < 0.05) in LRFI ducks than in HRFI ducks. In addition, expression of Sirt1, Foxo1, CPT1A, and ACOX1 were significantly higher in LRFI ducks than in HRFI ducks (P < 0.05), whereas PPARγ and FAS expression levels were significantly lower in LRFI ducks than in HRFI ducks (P < 0.01). Correlation analysis showed that Sirt1, CPT1A, and ACOX1 expressions were significantly negatively correlated with FCR (r = -0.81 to -0.93; P < 0.01), whereas PPARγ and FAS expressions were significantly positively correlated with FCR (r = 0.74 to 0.87; P < 0.01). PPARγ expression was significantly positively correlated with RFI (r = 0.83; P < 0.01), whereas CPT1A and ACOX1 expressions were significantly negatively correlated with RFI (r = -0.84 to -0.89; P < 0.01). Sirt1 mRNA expression was positively correlated with Foxo1, CPT1A, and ACOX1 mRNA expression (r = 0.78 to 0.92; P < 0.01). Association of Foxo1 with CPT1A and ACOX1 was positive (r = 0.88 to 0.96; P < 0.01). These results suggest that genes related to fatty acid oxidation are upregulated in the liver of ducks with high feed efficiency, while genes associated with lipid synthesis are downregulated. Furthermore, the inclusion of lipid metabolism-related genes in future breeding programs might be beneficial for selecting ducks with greater feed efficiency phenotype.

A novel duplicated insertion/deletion (InDel) of the CPT1a gene and its effects on growth traits in goat

Carnitine palmitoyltransferase 1a (CPT1a) is a rate-limited enzyme in the mitochondrial fatty acid β-oxidation pathway. It acts as a bridge between PPARα and the fatty acid oxidation pathways and is closely related to ruminant growth and development. In this study, one 12 bp InDel polymorphism of the CPT1a gene was identified in 700 goats, and we designated these three genotypes II, ID, and DD. Association analysis showed that the InDel polymorphism was closely associated with trunk index (p = 0.008) and body length index (p = 0.034) in Hainan black goats, and body length (p = 0.010), chest circumference (p = 0.004), chest depth (p = 0.029), and huckle bone width (p = 0.002) in Nubian goats, as well as the chest circumference (p = 0.016) in the Fuqing goat breed. In both kids and adult goats, qRT-PCR results showed that the CPT1a gene was expressed in all tissues, showing the highest mRNA levels in the liver, lung, spleen, and kidney, followed by the adipose tissue and brain. This indicates an association between the InDel of the CPT1a gene and growth traits in selected goat breeds, which may facilitate marker-assisted selection in goat genetics and breeding.

Effect of estradiol on hepatopancreatic lipid metabolism in the swimming crab, Portunus trituberculatus

Estradiol is an important sex steroid hormone that involved in regulation of animal lipid metabolism. However, the effect of estradiol on lipid metabolism in swimming crab (Portunus trituberculatus) is unclear. The present study investigated the effect of four concentrations of exogenous estradiol (0, 0.01, 0.1 and 1 μg g^-1 crab weight) on the expression levels of lipid metabolism-related genes, lipid composition and histology of hepatopancreas in the P. trituberculatus. The results showed that the mRNA levels of carnitine palmitoyltransferase I and II (CPT-I and CPT-II) increased significantly at the low concentrations (0.01 μg g^-1 and 0.1 μg g^-1), while decreased significantly in the highest concentration (1 μg g^-1). The mRNA levels of acyl-CoA oxidase (ACOX), fatty acid transport protein (FATP), fatty acid-binding protein (FABP), diacylglycerol acyltransferase 1 (DGAT1) and acetyl-CoA carboxylase (ACC) were significantly down-regulated. The transcripts of fatty acid synthase (FAS) and fatty acyl desaturase (FAD) decreased significantly only in 1 μg g^-1 treatment. All estradiol treatments (0.01, 0.1 and 1 μg g^-1) had significantly higher percentages of 20:4n6, 20:5n3 and 22:6n3, but lower percentages of total monounsaturated fatty acids and polar lipids than the control treatment (0 μg g^-1). Histological observations indicated the size of B cell became larger under estradiol treatment. The results indicated that estradiol promoted lipid catabolism in the hepatopancreas of P. trituberculatus.

Effects of perfluorooctane sulfonate on genes controlling hepatic fatty acid metabolism in livers of chicken embryos

Per- and polyfluoroalkyl substances (PFAS) are synthetic surfactants with a wide variety of applications; however, due to their stability, they are particularly resistant to degradation and, as such, are classed as persistent organic pollutants. Perfluorooctane sulfonate (PFOS) is one such PFAS that is still detectable in a range of different environmental settings, despite its use now being regulated in numerous countries. Elevated levels of PFOS have been detected in various avian species, and the impact of this on avian health is of interest when determining acceptable levels of PFOS in the environment. Due to its similarities to naturally occurring fatty acids, PFOS has potential to disrupt a range of biological pathways, particularly those associated with lipid metabolism, and this has been shown in various species. In this study, we have investigated how in ovo exposure to environmentally relevant levels of PFOS affects expression of genes involved in lipid metabolism of developing chicken embryos. We have found a broad suppression of transcription of genes involved in fatty acid oxidation and PPAR-mediated transcription with more significant effects apparent at lower doses of PFOS. These results highlight the need for more research investigating the biological impacts of low levels of PFAS to properly inform environmental policy governing their regulation.

Improved systemic metabolism and adipocyte biology in miR-150 knockout mice

INTRODUCTION

Short non-coding micro-RNAs (miRNAs) are post-transcriptional factors that directly regulate protein expression by degrading or inhibiting target mRNAs; however, the role of miRNAs in obesity and cardiometabolic disease remains unclarified. Based on our earlier study demonstrating that miR-150 influences lipid metabolism, we have studied effects of miR-150 on systemic metabolism and adipocyte biology.

MATERIALS AND METHODS

Metabolic phenotypes including body weight, food intake, body composition, glucose tolerance and insulin sensitivity were assessed in WT and global miR-150 KO male mice fed a high-fat diet. Molecular changes in epididymal adipose tissue were evaluated through qRT-PCR and Western blotting.

RESULTS

miR-150 KO mice displayed lower body weight characterized by a reduction in % fat mass while % lean mass was increased. Lower body weight was associated with reduced food consumption and an increase in circulating leptin concentrations, as well as enhanced insulin sensitivity and glucose tolerance compared with WT mice. Absence of miR-150 resulted in increased mTOR expression known to participate in increased leptin production leading to reduction of food intake. Expression of PGC-1α, another target gene of miR-150, was also increased together with upregulation of PPARα and glycerol kinase in adipose tissue as well as other genes participating in triglyceride degradation and lipid oxidation.

CONCLUSION

miR-150 KO mice showed metabolic benefits accompanied by reduced body weight, decreased energy intake, and enhanced lipid metabolism. miR-150 may represent both a biomarker and novel therapeutic target regarding obesity and insulin resistance.