Effects of Fat and Fatty Acids on the Formation of Autolysosomes in the Livers from Yellow Catfish Pelteobagrus Fulvidraco

Abstract

The autophagy-lysosome pathway, which involves many crucial genes and proteins, plays crucial roles in the maintenance of intracellular homeostasis by the degradation of damaged components. At present, some of these genes and proteins have been identified but their specific functions are largely unknown. This study was performed to clone and characterize the full-length cDNA sequences of nine key autolysosome-related genes (vps11, vps16, vps18, vps33b, vps41, lamp1, mcoln1, ctsd1 and tfeb) from yellow catfish Pelteobagrus fulvidraco. The expression of these genes and the transcriptional responses to a high-fat diet and fatty acids (FAs) (palmitic acid (PA) and oleic acid (OA)) were investigated. The mRNAs of these genes could be detected in heart, liver, muscle, spleen, brain, mesenteric adipose tissue, intestine, kidney and ovary, but varied with the tissues. In the liver, the mRNA levels of the nine autolysosome-related genes were lower in fish fed a high-fat diet than those fed the control, indicating that a high-fat diet inhibited formation of autolysosomes. Palmitic acid (a saturated FA) significantly inhibited the formation of autolysosomes at 12 h, 24 h and 48 h incubation. In contrast, oleic acid (an unsaturated FA) significantly induced the formation of autolysosomes at 12 h, but inhibited them at 24 h. At 48 h, the effects of OA incubation on autolysosomes were OA concentration-dependent in primary hepatocytes of P. fulvidraco. The results of flow cytometry and laser confocal observations confirmed these results. PA and OA incubation also increased intracellular non-esterified fatty acid (NEFA) concentration at 12 h, 24 h and 48 h, and influenced mRNA levels of fatty acid binding protein (fabp) and fatty acid transport protein 4 (fatp4) which facilitate FA transport in primary hepatocytes of P. fulvidraco. The present study demonstrated the molecular characterization of the nine autolysosome-related genes and their transcriptional responses to fat and FAs in fish, which provides the basis for further exploring their regulatory mechanism in vertebrates.

Novel insights for PI3KC3 in mediating lipid accumulation in yellow catfish Pelteobagrus fulvidraco

“…Fatty acid is the directly factor that regulated intracellular lipid level. In the present study, we found that FA incubation markedly increased lipid and NEFA level in hepatocytes from yellow cat sh, in agreement with other studies (Wu et al 2019;Wu et al 2020;Song et al 2020). In addition, FA incubation signi cantly reduced the mRNA and the protein level of PI3KC3, but increased the mRNA and the protein level of PPARα and PPARγ.…”

“…FA was added as a mixture of palmitic acid and oleic acid at a ratio of 1:1. The form and the concentration of FA were selected according to our pilot trial and the publications of the in vitro studies (Wu et al 2019;Wu et al 2020; Chen et al 2020a; Song et al 2020). Then, after 24 h incubation, cells were collected to determine the promoter activity, based on the manufacturer's instruction of the Dual-luciferase Reporter Assay System (Promega).…”

Growth performance, nucleic acids, leptin and adiponectin and their receptor gene expression were significantly affected by feeding different lipid supplementation in GIFT tilapia juveniles

“…When lower than the optimal lipid level, feed nutrients were insufficient or unbalanced to meet the lipid and energy requirements of fish body growth (Rahimnejad et al., 2015). When higher than the optimal lipid level, the higher lipid could result in excessive deposition of fish body fat, stressing response, damaging liver function and reducing growth (Tian et al., 2015; Wu et al., 2019). High dietary lipid levels could lead to a decline in growth and feed utilization for tilapia and cause a substantial increase in intraperitoneal fat deposition (Chang et al., 2018).…”

miR-101b Regulates Lipid Deposition and Metabolism of Primary Hepatocytes in Teleost Yellow Catfish Pelteobagrus fulvidraco

“…In the present study, PA increased TG content, but reduced ME and FAS activities, and mRNA concentrations of 6pgd , fas , acca and cd36 . Studies in our laboratory pointed out that PA elevated NEFA content and regulated gene expression of lipid absorption in hepatocytes of yellow catfish [ 33 ]. The decreased gene expression and enzymatic activities related to lipid absorption as well as lipogenesis contributed to suppress lipid accumulation [ 3 ].…”