Trans‐10,Cis‐12 conjugated linoleic acid reduces triglyceride content while differentially affecting peroxisome proliferator activated receptor γ2 and aP2 expression in 3T3‐L1 preadipocytes

Abstract

A series of experiments was conducted using 3T3-L1 preadipocytes as the cell model to determine: (i) whether the triglyceride (TG)-lowering effects of a crude mixture of conjugated linoleic acid (CLA) isomers were due to a specific isomer of CLA and the timing of treatment, (ii) if CLA reduced TG content by inhibiting a key regulator of adipogenesis, (iii) if CLA incorporated into either neutral lipid or phospholipid cell fractions, and (iv) whether the effects of CLA treatment were reversible. Trans-10,cis-12 CLA reduced TG content, whereas the cis-9,trans-11 isomer increased TG content compared to vehicle [bovine serum albumin (BSA)] controls. Treatment with 50 microM trans-10,cis-12 CLA during the entire 6 d of differentiation reduced TG content to a greater extent than treatment during either the first 3 d or last 3 d of differentiation. Trans-10,cis-12 CLA treatment of preadipocyte cultures for 48 h increased peroxisome proliferator activated receptor gamma2 (PPARgamma2) protein expression compared to cultures treated with linoleic acid (LA) or the BSA controls. CLA had no effect on adipose P2 (aP2), a fatty acid-binding protein regulated by PPARgamma2. Both the cis-9,trans-11 and the trans-10,cis-12 isomers of CLA were incorporated into neutral lipids and phospholipids. However, cis-9,trans-11 CLA levels were one- to twofold higher than trans-10,cis-12 CLA levels. Moreover, trans-10,cis-12 CLA treatment reduced cis-11 18:1 concentrations in both neutral lipids and phospholipids while increasing cis-9 18:1 and 18:2 concentrations. Palmitoleic acid (16:1) levels were also lower in the neutral lipid fraction of cultures treated with trans-10,cis-12 CLA. Supplementing trans-10,cis-12 CLA-treated cultures (50 microM) with increasing levels of LA resulted in a dose-dependent increase in TG content compared to cultures treated with 50 microM CLA alone. LA supplementation also prevented some of the morphological changes associated with trans-10,cis-12 CLA treatment as seen with scanning electron microscopy. Treatment with 50 microM trans-10,cis-12 CLA for 6 d decreased PPARgamma2 levels, and supplementation of CLA-treated cultures with LA increased PPARgamma2 levels compared with cultures treated with CLA alone. Taken together, these data indicate that in cultures of 3T3-L1 preadipocytes: (i) trans-10,cis-12 CLA is the TG-lowering isomer of CLA, and its effects are dependent on dose, duration of treatment, and the amount of LA in the cultures; (ii) trans-10,cis-12 CLA treatment alters the monounsaturated fatty acid profile of neutral- and phospholipids of the cultures; and (iii) although acute (2-d) trans-10,cis-12 CLA treatment increased PPARgamma2 protein levels, chronic (6-d) treatment decreased PPARgamma2 levels.

Conjugated linoleic acid and obesity control: efficacy and mechanisms

“…75,76 A similar study in cows has shown that supplementation with 100 g/day of CLA for 1 day decreased fatty acid synthesis and desaturation. 77 Supporting data have been reported by other studies using the cultures of human preadipocytes 48,78,79 and stromal vascular cells from human adipose tissue. 80 Data from the above studies collectively suggest that CLA decreases triglyceride content, in part, by decreasing fatty acid synthesis, uptake and esterification into triglyceride by adipocytes, at least in certain species and model systems.…”

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

“…A ativação de PPAR γ 2 pelo CLA, particularmente pelo isômero trans-10, cis-12, tem sido demonstrada em cultura de adipócitos 3T3-L1 de roedores, como mecanismo responsável pela redução da composição corporal 118,136 . É importante ressaltar que, segundo Evans et al 137 , a ativação de PPAR γ 2 pelo trans-10, cis-12 CLA modularia o efeito redutor da gordura corporal em curto prazo (48h), visto que os autores observaram inibição de PPAR γ 2 quando o tempo de contato com o CLA aumentou (6 dias).…”

“…É importante ressaltar que, segundo Evans et al 137 , a ativação de PPAR γ 2 pelo trans-10, cis-12 CLA modularia o efeito redutor da gordura corporal em curto prazo (48h), visto que os autores observaram inibição de PPAR γ 2 quando o tempo de contato com o CLA aumentou (6 dias). A maioria dos estudos objetivando buscar os alvos moleculares da ação redutora da gordura corporal pelo CLA em adipócitos, reúne dados que permitem concluir que a inibição de PPAR γ, particularmente pelo trans-10, cis-12 CLA, levaria à redução da gordura corporal pela modulação da expressão gênica no sentido de inibir a diferenciação celular e alterar a atividade de proteínas envolvidas na lipogênese e na lipólise 109,136 . É importante a ressalva de que, nos estudos citados anteriormente, o tempo de exposição dos adipó-citos aos isômeros de CLA até os efeitos serem observados foi superior a 5 dias, confirmando que, em longo prazo, segundo Evans et al 136 , o efeito do trans-10, cis-12 CLA é de fato inibir PPAR γ. Um dado interessante é o do trabalho de Brown et al 138 , segundo o qual quando as células foram expostas ao isômero cis-9, trans-11, houve aumento de PPAR γ e, conseqüentemente, das proteínas codificadas pelos genes que estão sob seu controle transcricional, promovendo a adipogê-nese.…”

Cyclic phosphatidic acid influences the expression and regulation of cyclic nucleotide phosphodiesterase 3B and lipolysis in 3T3-L1 cells

“…Adipose differentiation is a complex process by which fibroblast-like undifferentiated cells are converted into cells that accumulate lipid droplets [2]. It has been reported that PPARγ plays a critical role in adipogenesis [2] [3]. PPARγ is a nuclear hormone receptor that plays an essential role in lipid and glucose homeostasis and predominantly expressed in the adipose tissue [2].…”

“…PPARγ is a nuclear hormone receptor that plays an essential role in lipid and glucose homeostasis and predominantly expressed in the adipose tissue [2]. Upon agonist binding, PPARγ drives the expression of several adipocyte-specific genes [3] such as FABP4 (fatty acid binding protein 4) and CD36 (scavenger receptor).…”