Conjugated Linoleic Acid Inhibits Differentiation of Pre- and Post- Confluent 3T3-L1 Preadipocytes But Inhibits Cell Proliferation Only in Preconfluent Cells

Abstract

Conjugated linoleic acid (CLA; 18:2) is a group of isomers (mainly 9-cis, 11-trans and 10-trans, 12-cis) of linoleic acid. CLA is the product of rumen fermentation and can be found in the milk and muscle of ruminants. Animals fed CLA have a lower body fat content. The objective of this study was to establish the possible mechanisms by which CLA affects adipogenesis. 3T3-L1 is a well-established cell line that is used extensively in studying adipocyte biology. These cells typically grow in a culture medium until they reach confluence, at which time they are induced to differentiate by hormonal treatment (d 0). Treatment of 3T3-L1 cells with 25 to 100 micromol/L CLA inhibited differentiation in a dose-dependent manner, while linoleic acid treatment did not differ from DMSO-treated controls. Continuous treatment from d -2, -1, 0 or 2 to d 8 and treatment from d -2 to d 0 and from d 0 to d 2 inhibited differentiation. Differentiation was monitored morphologically (oil Red-O staining), enzymatically (reduction of activity of glycerol-3-phosphate dehydrogenase), and by northern analysis of peroxisome proliferator-activated receptor gamma2, CCAAT/enhancer binding protein alpha and adipocyte specific protein 2 mRNA. CLA inhibited cell proliferation of nonconfluent cells but did not affect cell division of confluent cells, as indicated by 5-bromo-2'-deoxyuridine incorporation and mitochondria metabolism. Therefore, CLA inhibited differentiation before confluence and during induction. However, cellular proliferation was only inhibited prior to induction. These results imply that fat reduction caused by CLA treatment may be attributed to its inhibition of both proliferation and differentiation of preadipocytes in animals.

Regulation of lipid accumulation in 3T3-L1 cells: insulin-independent and combined effects of fatty acids and insulin

“…A novel finding of the present study is that treatment with oleic or linoleic acid, independent of insulin, was sufficient to induce lipid accumulation in 3T3-L1 cells. Many studies of adipocyte lineage cells report the addition of various hormone cocktails either with FCS (Brodie et al, 1999;Guo et al, 2000;Kang et al, 2003; or without FCS (Ding and Mersmann, 2001;Ding et al, 2002;Hsu and Ding, 2003;Hutley et al, 2003) in addition to FA to promote differentiation. These studies report that oleic and linoleic acids promote lipid accumulation in adipocytes.…”

“…However, octanoate appeared to attenuate differentiation in 3T3-L1 cells (Han et al, 2002). Conjugated linoleic acids have also been reported to inhibit differentiation in 3T3-L1 cells (Brodie et al, 1999;Kang et al, 2003).…”

“…However, octanoate appeared to attenuate differentiation in 3T3-L1 cells (Han et al, 2002). Conjugated linoleic acids have also been reported to inhibit differentiation in 3T3-L1 cells (Brodie et al, 1999;Kang et al, 2003).One potential mechanism of enhanced adipogenesis from fatty acids (FA) may potentially be via peroxisome proliferator-activated receptors (PPARs) (Tontonoz et al, 1994a and1994b;Grimaldi, 2001;Bishop-Bailey and Wray, 2003). During differentiation of preadipocytes to adipocytes, PPAR-g, PPAR-a and CCAAT/enhancer-binding protein factors (C/EBP) a, b, d and z are important transcription factors involved in the regulation of this mechanism (Lee et al, 1999;Kersten et al, 2000;Lacasa et al, 2001); PPAR-g being activated prior to the activation of C/EBP-a.…”

Conjugated linoleic acid and obesity control: efficacy and mechanisms

“…20,37,57 Consequently, several studies have demonstrated that CLA inhibits differentiation and represses adipocyte gene expression during the in vitro differentiation of mouse 3T3-L1 preadipocytes into adipocytes. 47,60,61 Owing to the differentiation of preadipocytes into adipocytes is an essential step to get mature adipocytes, which possess capability to take up, synthesize and store lipids, the inhibition on the differentiation of preadipocytes by CLA attributes to the observed lower triglyceride content and small adipocyte size.…”

Os efeitos do ácido linoléico conjugado no metabolismo animal: avanço das pesquisas e perspectivas para o futuro

“…Em outras palavras, a inibição da expressão desses genes resultaria na redução da lipogênese. Tal hipótese foi reforçada por Brodie et al 117 , Choi et al 118 , Takahashi et al 104 e Kang et al 109 , cujos trabalhos com culturas de pré-adipócitos 3T3-L1 e adipócitos humanos demonstram que o CLA inibe a ativação de fatores de transcrição que controlam a expressão de genes codificantes das proteínas C/EBPα, SCD e GLUT4, todas envolvidas no processo de diferenciação de celulas adiposas. Na verdade, os estudos apontam que a redução da gordura corporal induzida pelo CLA ocorre não somente pela diminuição do número de adipócitos, mas também, ou até mesmo somente, pela redução do seu tamanho.…”