The Effect of Insulin, TNFα and DHA on the Proliferation, Differentiation and Lipolysis of Preadipocytes Isolated from Large Yellow Croaker (Pseudosciaena Crocea R.)

Xinxia Wang,Yizhen Wang,Ming Huang,Shuhong Zhao

doi:10.1371/journal.pone.0048069

Abstract

Fish final product can be affected by excessive lipid accumulation. Therefore, it is important to develop strategies to control obesity in cultivated fish to strengthen the sustainability of the aquaculture industry. As in mammals, the development of adiposity in fish depends on hormonal, cytokine and dietary factors. In this study, we investigated the proliferation and differentiation of preadipocytes isolated from the large yellow croaker and examined the effects of critical factors such as insulin, TNFα and DHA on the proliferation, differentiation and lipolysis of adipocytes. Preadipocytes were isolated by collagenase digestion, after which their proliferation was evaluated. The differentiation process was optimized by assaying glycerol-3-phosphate dehydrogenase (GPDH) activity. Oil red O staining and electron microscopy were performed to visualize the accumulated triacylglycerol. Gene transcript levels were measured using SYBR green quantitative real-time PCR. Insulin promoted preadipocytes proliferation, stimulated cell differentiation and decreased lipolysis of mature adipocytes. TNFα and DHA inhibited cell proliferation and differentiation. While TNFα stimulated mature adipocyte lipolysis, DHA showed no lipolytic effect on adipocytes. The expressions of adipose triglyceride lipase (ATGL), fatty acid synthase (FAS), lipoprotein lipase (LPL) and peroxisome proliferator-activated receptor α, γ (PPARα, PPARγ) were quantified during preadipocytes differentiation and adipocytes lipolysis to partly explain the regulation mechanisms. In summary, the results of this study indicated that although preadipocytes proliferation and the differentiation process in large yellow croaker are similar to these processes in mammals, the effects of critical factors such as insulin, TNFα and DHA on fish adipocytes development are not exactly the same. Our findings fill in the gaps in the basic data regarding the effects of critical factors on adiposity development in fish and will facilitate the further study of molecular mechanism by which these factors act in fish and the application of this knowledge to eventually control obesity in cultured species.

Highlights

The use of high-lipid diets in aquaculture has proven to be protein saving and growth-promoting effect in some species [1], but leads to excessive fat deposition that may affect animal health and reduce harvest yields [2]
Preadipocytes Morphology and Proliferation In the present study, we first established a preadipocytes culture system using the adipose tissue of the large yellow croaker
Lipids do not seem to be a requisite for the differentiation of preadipocyte cell lines or primary preadipocytes [20,21,22], as hormones such as insulin, dexamethasone, and 3-isobuty-1-methylxanthine (IBMX) play a more significant role in adipocyte differentiation

Summary

Introduction

The use of high-lipid diets in aquaculture has proven to be protein saving and growth-promoting effect in some species [1], but leads to excessive fat deposition that may affect animal health and reduce harvest yields [2]. Insulin is required for adipocyte differentiation in mammals and birds [5,6], and exerts an inhibitory effect on adipocyte lipolysis [7]. TNFa has been proven to affect many aspects of adipocyte function in mammals, ranging from adipocyte development to lipid metabolism [10]. Considering all of these diverse actions, TNFa appears to play a negative role in the development of adipose tissue. Data measuring the ability of insulin, TNFa and DHA to manipulate adiposity development in non-mammal species, such as fish, are still scarce

Methods

Results

Conclusion