Evidence that the anti-obesity effect of conjugated linoleic acid is independent of effects on stearoyl-CoA desaturase1 expression and enzyme activity

doi:10.1016/j.bbrc.2004.01.087

Biochemical and Biophysical Research Communications

Volume 315, Issue 3, 12 March 2004, Pages 532-537

https://doi.org/10.1016/j.bbrc.2004.01.087 Get rights and content

Abstract

The trans-10,cis-12 isomer of conjugated linoleic acid (CLA) reduces body fat gain in animals and inhibits stearoyl-CoA desaturase (SCD) activity in 3T3-L1 adipocytes. To test whether CLA’s body fat reduction is mediated by SCD1, wild-type and SCD1-null mice were fed diet supplemented with 0.2% trans-10,cis-12 (t10c12) CLA for 4 weeks. The t10c12 CLA-supplemented diet significantly reduced body fat mass in both wild type and SCD1-null mice. Similarly, t10c12 CLA diet decreased blood triglyceride and free fatty acid levels regardless of SCD1 genotypes. Mice fed t10c12 CLA exhibited increased mRNA expression of fatty acid synthase and uncoupling protein 2 in both genotypes. Taken together, the effects of t10c12 CLA on reduction of body fat gain, blood parameters, and mRNA expression in both SCD1-null mice and wild-type mice were similar, indicating that the anti-obesity effect of t10c12 CLA may be independent of the effects of this CLA isomer on SCD1 gene expression and enzyme activity.

Section snippets

Materials and methods

Animals and diets. The generation of targeted SCD1-null mice has been previously described [29]. Mice (7-weeks-old) were maintained on a 12 h dark/light cycle and were fed a semipurified diet (TD00107, 99% basal mix, Harlan Sprague–Dawley, Madison, WI). Corn oil was used as a fat source because it contains high level of linoleic acid, the parent fatty acid of CLA. The diet was composed as follows (ingredient, g/kg): sucrose, 101; casein, “vitamin-free” test, 255; corn starch, 169; maltodextrin,

Results and discussion

There are similarities in the physiological states of SCD1-null mice and normal mice fed diets containing CLA, including reduction of body fat mass [1], serum leptin levels [31], and significant decrease of palmitoleate and oleate accompanied by enhanced levels of palmitate and stearate [20], [25]. However, there are also differences between SCD1-null mice and CLA-treated normal mice in that SCD1-null mice exhibit enhanced insulin sensitivity and reduce liver lipids [25], whereas normal mice

Acknowledgements

We thank Jayne M. Storkson and Karen J. Albright for excellent technical support and Agnieszka Dobrzyn for GC analysis. This research was supported in part by gift funds administered through the University of Wisconsin-Madison Food Research Institute. M.W.P. is an inventor of CLA use patents that are assigned to the Wisconsin Alumni Research Foundation.

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2013, Obesity Research and Clinical Practice
Citation Excerpt :
Furthermore, since t10, c12-CLA inhibits SCD-1 and de novo fatty acid synthesis, there is a possibility that inhibition of SCD-1 does not influence fatty acid composition. In vivo experiments using SCD-1 null mice revealed that the body fat-reducing effect of CLA is SCD-1 independent [67]. Interestingly, replenishment of oleic acid in t10, c12-CLA-treated human adipocyte attenuated the t10, c12-CLA-induced inflammatory response [68].
Conjugated linoleic acid (CLA), which is a generic term to describe isomers of octadecadienoic acid, has been reported to exert various beneficial physiological effects. Accumulating data show that CLA, especially trans10, cis12 (t10, c12)-CLA, has a potent body fat-reducing effect, which is prominent in mice and to a lesser extent rats. In addition, several clinical studies have demonstrated the body fat- and weight-reducing effect of CLA in humans. However, t10, c12-CLA evokes severe lipodystrophy in mice that results in impaired glucose metabolism. Therefore, while CLA is a promising agent for the amelioration of obesity and obesity-related diseases, it is important to establish its safety prior to common use in humans. In addition, it is important to elucidate the details of the molecular mechanisms of CLA. Here, we focus on the response of adipocyte to CLA.
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This close association between SCD-1 and DGAT2 enhances the efficiency of TG synthesis [35]. However, 10,12 CLA's reduction in body fat mass was similar in SCD-1 knockout and wild-type mice, suggesting that CLA's antiobesity properties are independent of SCD-1 in mice [36]. We previously demonstrated that long-term treatment (i.e., 12 days) of differentiating primary human preadipocytes with 10,12 CLA decreased the MUFA/SFA ratio and the mRNA levels of SCD-1 [22].
Conjugated linoleic acid (CLA) reduces adiposity in vivo. However, mechanisms mediating these changes are unclear. Therefore, we treated cultures of human adipocytes with trans-10, cis-12 (10,12) CLA, cis-9, trans-11 (9,11) CLA or other trans fatty acids (FA), and measured indices of lipid metabolism. The lipid-lowering effects of 10,12 CLA were unique, as other trans FA did not reduce TG content to the same extent. Using low levels of [¹⁴C]-CLA isomers, it was shown that both isomers were readily incorporated into acylglycerols and phospholipids, albeit at lower levels than [¹⁴C]-oleic or [¹⁴C]-linoleic acids. When using [¹⁴C]-acetic acid and [¹⁴C]-pyruvic acid as substrates, 30 μM 10,12 CLA, but not 9,11 CLA, decreased de novo synthesis of triglyceride, free FA, diacylglycerol, cholesterol esters, cardiolipin, phospholipids and ceramides within 3–24 h. Treatment with 30 μM 10,12 CLA, but not 9,11 CLA, decreased total cellular lipids within 3 days and the ratio of monounsaturated FA (MUFA) to saturated FA, and increased C18:0 acyl-CoA levels within 24 h. Consistent with these data, stearoyl-CoA desaturase (SCD)-1 mRNA and protein levels were down-regulated by 10,12 CLA within 7–12 h, respectively. The mRNA levels of liver X receptor (LXR)α and sterol regulatory element binding protein (SREBP)-1c, transcription factors that regulate SCD-1, were decreased by 10,12 CLA within 5 h. These data suggest that the isomer-specific decrease in de novo lipid synthesis by 10,12 CLA is due, in part, to the rapid repression of lipogenic transcription factors that regulate MUFA synthesis, suggesting an anti-obesity mechanism unique to this trans FA.
Characterization of the acute lactational response to trans-10, cis-12 conjugated linoleic acid
2011, Journal of Dairy Science
Citation Excerpt :
Briefly, some isomers of CLA that decreased the desaturase index did not cause MFD, and inhibition of the SCD enzyme by sterculic acid or CoEDTA dramatically reduced FA desaturation without any effect on milk fat synthesis. Last, CLA reduction of adiposity in mice was independent of the SCD enzyme as CLA reduced body fatness in the SCD1 null mouse (Kang et al., 2004). Abomasally infused trans-10, cis-12 CLA was incorporated into milk fat within 6 h, and steady-state concentrations were quickly established by use of a priming dose.
Trans-10, cis-12 conjugated linoleic acid (CLA) is a potent inhibitor of milk fat synthesis in the dairy cow. The decrease in milk fat yield during abomasal infusion of CLA reaches a nadir after 3 to 5 d. The acute responses to CLA were evaluated using 4 cows in a crossover design. Cows were milked with the aid of oxytocin every 4 h from −28 to 80 h and every 6 h from 86 to 116 h relative to the initiation of abomasal CLA infusion. An initial priming dose of 7.5 g of CLA was given at time zero followed by infusion of 2.5 g every 4 h for 72 h. Plasma CLA reached a near-steady-state concentration by 4 h, and initial plasma enrichments were greatest in the triglyceride and nonesterified fatty acid fractions. Milk CLA concentration peaked at 6 h and reached steady state by 22 h. At termination of the infusion, decreases in milk CLA concentration and yield and plasma CLA concentration were best fit by a reciprocal-linear function. Milk fat percentage decreased progressively after 2 h and was significant by 14 h. Milk fatty acid profile was initially unchanged, but between 18 and 36 h after initiation of the CLA dose the proportions of fatty acids progressively shifted, resulting in an increase in fatty acids >C16 and a decrease in fatty acids <C16 by 38 to 46 h. In contrast, changes in the desaturase index were immediate, with a significant decrease by 6 h and a near-maximal decrease by 10 h. Thus, stearoyl desaturase enzyme was more acutely responsive to CLA than other enzymes in milk fat synthesis. The initial decrease in milk fat synthesis involved an equal depression of short- and long-chain fatty acid pathways and was followed thereafter by a more pronounced decrease in the synthesis of de novo fatty acids.
Overexpression of stearoyl-CoA desaturase-1 results in an increase of conjugated linoleic acid (CLA) and n-7 fatty acids in 293 cells
2010, Biochemical and Biophysical Research Communications
Citation Excerpt :
In addition, the c9t11 and t10c12 isomers appeared to have divergent effects on body fat [27] and milk fat [3,19] and regulated different gene expression [13,36]. It was demonstrated that the t10c12 isomer inhibited SCD activity in mouse [28] and 3T3-L1 adipocytes [6,15] by a posttranslational mechanism [7,8], not regulation at the level of mRNA expression or RNA stability [24]. Although feedback regulation appeared to regulate the expression of the desaturase gene in animal cells, it is not clear if the increase of t10c12-CLA in SCD1 cells inhibits SCD activity conversely in the present study.
The effect of human SCD1 heterologous expression on cellular fatty acid synthesis was investigated in the current study. The SCD1 gene expression cassette and PGK-neomycin-selectable marker cassette were co-introduced into HEK 293 cells by electroporation, and subsequently, SCD1 expression was evaluated by fatty acid analysis. RT-PCR analysis indicated that the foreign SCD1 gene could be expressed in transformed cell lines. Total lipid analysis of the transformed cells fed with vaccenic acid (t11-18:1) as a substrate showed that SCD1 expression resulted in an increase in c9t11-CLA from 0.73–1.03% to 2.69–2.86% (p < 0.05) and that the conversion efficiency was elevated from 5.11–6.88% to 16.49–20.06% (p < 0.05). Surprisingly, the concentration of t10c12-CLA was also increased, from 0.10–0.41% to 1.35–1.69% in SCD1 cells (p < 0.05). SCD1 expression also resulted in a significant (p < 0.05) increase in palmitoleic acid (16:1 n-7) from 1.56–2.26% to 3.47–4.04% and cis-vaccenic acid (18:1 n-7) from 2.42–3.97% to 6.20–7.22%, and the corresponding conversion ratio of n-7 fatty acid was elevated from 12.01–16.70% to 22.62–24.13% (p < 0.05). This study demonstrates that the foreign SCD1 gene was expressed with high efficiency and induced elevated c9t11-CLA, t10c12-CLA, and n-7 fatty acid levels in mammalian cells.
Trans-10,cis-12-conjugated linoleic acid instigates inflammation in human adipocytes compared with preadipocytes
2010, Journal of Biological Chemistry
Citation Excerpt :
It appears that 10,12-CLA, rather than 9,11-CLA, is the anti-obesity isomer in this supplement (reviewed in Ref. 11). Potential mechanisms responsible for these anti-obesity properties of 10,12-CLA include: 1) decreasing energy intake or increasing energy expenditure (12–16), 2) decreasing lipogenesis or increasing lipolysis (17–20), 3) decreasing adipogenesis or increasing delipidation (21–25), and 4) increasing adipocyte apoptosis (26–28). There is, however, concern about potential adverse side effects of CLA supplementation, including lipodystrophy (28), steatosis (29), macrophage infiltration to white adipose tissue (WAT (5)), and insulin resistance (9, 30–32).
We showed previously in cultures of primary human adipocytes and preadipocytes that lipopolysaccharide and trans-10,cis-12-conjugated linoleic acid (10,12-CLA) activate the inflammatory signaling that promotes insulin resistance. Because our published data demonstrated that preadipocytes are the primary instigators of inflammatory signaling in lipopolysaccharide-treated cultures, we hypothesized that they played the same role in 10,12-CLA-mediated inflammation. To test this hypothesis, we employed four distinct models. In model 1, a differentiation model, CLA activation of MAPK and induction of interleukin-8 (IL-8), IL-6, IL-1β, and cyclo-oxygenase-2 (COX-2) were greatest in differentiated compared with undifferentiated cultures. In model 2, a cell separation model, the mRNA levels of these inflammatory proteins were increased by 10,12-CLA compared with bovine serum albumin vehicle in the adipocyte fraction and the preadipocyte fraction. In model 3, a co-culture insert model, inserts containing ∼50% adipocytes (AD50) or ∼100% preadipocytes (AD0) were suspended over wells containing AD50 or AD0 cultures. 10,12-CLA-induced IL-8, IL-6, IL-1β, and COX-2 mRNA levels were highest in AD50 cultures when co-cultured with AD0 inserts. In model 4, a conditioned medium (CM) model, CM collected from CLA-treated AD50 but not AD0 cultures induced IL-8 and IL-6 mRNA levels and activated phosphorylation of MAPK in naive AD0 and AD50 cultures. Consistent with these data, 10,12-CLA-mediated secretions of IL-8 and IL-6 from AD50 cultures were higher than from AD0 cultures. Notably, blocking adipocytokine secretion prevented the inflammatory capacity of CM from 10,12-CLA-treated cultures. These data suggest that CLA instigates the release of inflammatory signals from adipocytes that subsequently activate adjacent preadipocytes.
Antiobesity mechanisms of action of conjugated linoleic acid
2010, Journal of Nutritional Biochemistry
Conjugated linoleic acid (CLA), a family of fatty acids found in beef, dairy foods and dietary supplements, reduces adiposity in several animal models of obesity and some human studies. However, the isomer-specific antiobesity mechanisms of action of CLA are unclear, and its use in humans is controversial. This review will summarize in vivo and in vitro findings from the literature regarding potential mechanisms by which CLA reduces adiposity, including its impact on (a) energy metabolism, (b) adipogenesis, (c) inflammation, (d) lipid metabolism and (e) apoptosis.

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Evidence that the anti-obesity effect of conjugated linoleic acid is independent of effects on stearoyl-CoA desaturase1 expression and enzyme activity

Abstract

Section snippets

Materials and methods

Results and discussion

Acknowledgements

Atherosclerosis

Poult. Sci.

Biochem. Biophys. Res. Commun.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Lipid Res.

J. Biol. Chem.

J. Nutr.

J. Biol. Chem.

J. Lipid Res.

Prostaglandins Leukot. Essent. Fatty Acids

Biochem. Biophys. Res. Commun.

J. Nutr.

J. Nutr.

J. Nutr.

J. Nutr.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

J. Nutr.

Biochem. Biophys. Res. Commun.