Abstract
Previous studies showed that insulin-like growth factor-binding protein 5 (IGFBP5) plays a role in non-alcoholic fatty liver disease; however, its expression and function in goose fatty liver remain unknown. To address this, we obtained a full-length mRNA sequence of the goose IGFBP5 gene using a 5′-rapid amplification of cDNA ends assay and nested polymerase chain reaction (PCR). Additionally, using the newly acquired sequence of 5’-untraslated region, we determined the missing sequence of the first intron. Bioinformatics analysis revealed three exons and three introns in the goose IGFBP5 gene. Quantitative PCR analysis indicated that the mRNA abundance of IGFBP5 was significantly lower in goose fatty liver than in the normal liver. Comparison of transcriptomes of goose primary hepatocytes transfected with IGFBP5 overexpression vector versus those transfected with empty vector identified 777 differentially expressed genes (DEGs). The enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways indicated the focal adhesion, ECM-receptor interaction, regulation of the actin cytoskeleton, mitogen-activated protein kinase (MAPK) signaling, and GnRH signaling pathways. Immunoblotting revealed the induction of the p38 MAPK pathway by IGFBP5 overexpression, which is in line with the suppressed expression of IGFBP5 and p38 MAPK in goose fatty liver than in normal liver. These findings suggest that IGFBP5 is involved in the development of goose fatty liver via the p38 MAPK pathway.
Highlights
The liver plays an important role in insulin-mediated regulation of metabolism, especially through glucose and lipid homeostasis [1,2]
We synthesized complementary DNA and amplified it by 5 -rapid amplification of cDNA ends (5 -Rapid Amplification of cDNA Ends (RACE)) with Universal Primer Mix (UPM) and GSP1 (Table 1, Figure 1A) using total RNA samples isolated from the liver of Landes geese
As the RACE product showed a high level of background with no specific bands in the electrophoresis analysis (Figure 1B), nested polymerase chain reaction (PCR) was performed using Universal Primer Short (UPS) and GSP2/3/4 primers (Table 1, Figure 1A) with the RACE product as the template, and a strong band of approximately 400 bp was detected by electrophoresis (Figure 1B)
Summary
The liver plays an important role in insulin-mediated regulation of metabolism, especially through glucose and lipid homeostasis [1,2]. It is a major site for the synthesis of endocrine factors, such as insulin-like growth factors 1 and 2 (IGF1 and IGF2) and their binding proteins (IGF-binding proteins, IGFBPs) [3]. Several metabolic disorders, including non-alcoholic fatty liver disease (NAFLD), are associated with liver dysfunction. NAFLD is characterized by hepatic steatosis and is usually accompanied by insulin resistance (IR) [4–6]. NAFLD comprises multiple pathological syndromes, ranging from simple steatosis and steatohepatitis to fibrosis and even cirrhosis [6]. Goose fatty liver does not show any overt pathological syndromes [2,6]. The goose fatty liver is a unique model for NAFLD studies.
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