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The NuGOwiki Metabolite Database is a joint initiative of NuGO and HMDB
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| Trans-10 Cis-12 Conjugated Linoleic Acid | |
|---|---|
| [[Image:{{{Image}}}|thumb|220px|2D structure for Trans-10 Cis-12 Conjugated Linoleic Acid]] | |
| Chemical Name | trans-10,cis-12-conjugated linoleic acid |
| Chemical Formula | C18H32O2 |
| CAS Number | 2420-56-6 |
| Chemical Information | no HMDB metabocard available |
| Biochemical Taxonomy | Non-Saturated Fatty Acid |
| Functional Taxonomy | carcinogen |
| Nutritional Taxonomy | non-essential n-6 polyunsaturated fatty acid |
| Metabolic Pathways | lipid metabolism, glucose metabolism |
| Biofluid Location | serum/plasma |
| Tissue Location | membrane lipid fractions |
| Normal Biofluid Concentrations | ~1.2 ug total CLA / mg lipid |
| Normal Tissue Concentrations | ~3.8 ug total CLA / mg adipose tissue lipid |
| Diseases / Conditions Related to Nutrition | atherosclerosis, insulin resistance |
| Other (Monogenic Disorders) | not available |
| Abnormal Biofluid Concentrations | not available |
| Abnormal Tissue Concentrations | not available |
| Physiological Processes | |
| Authors: | |
| Affiliations: |
Contents |
Introduction
guidelines
Conjugated linoleic acids are a family of positional and geometric isomers of linoleic acid (C18:2n-6) where one or both of the double bonds are either in the cis or in the trans configuration (see also Cis-trans isomerism). Double bonds are said to be "conjugated" when they are seperated from each other by one single bond, e.g -CH=CH-CH=CH-. CLA are found naturally in products derived from ruminant animals like beef, lamb and other diary products as these fatty acids are formed by bacterial biohydrogenation of linoleic acid in the rumen. {reader-comment; suspect the label cis-9, trans-10 linoleic acid (below)should read cis-9, trans-11}
Biological Function
guidelines
trans10,cis12 CLA is a non essential fatty acid and has therefore not a biological function. However, consumption of this fatty acid may affect pathways involved in atherogenesis, carcinogenesis, obesity and insulin resistance (see below)[1]. In addition, trans10, cis CLA is a potent inhibitor of milk fat synthesis in cows, and the magnitude of milk fat depression is often correlated with the fat content of this isomer [2].
Catabolism
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guidelines
Both trans10,cis12 CLA and cis9,trans11 CLA isomers have been shown to undergo elongation and desaturation processes similar to those that occur with linoleic acid, maintaining the conjugated diene structure. CLA metabolism may interfere with eicosanoid formation. Other metabolites with 16 carbon atoms (conjugated 16:2 and 16:3, which are probably derived from peroxisomal beta-oxidation of CLA and its metabolites, respectively) have been detected [3]. Both CLA isomers are oxidised significantly more than linoleic acid. This suggests an efficient metabolism of CLA and its metabolites in peroxisomes.
Diseases / Conditions Related to Nutrition
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Body composition
Several studies in animal models have shown that trans10,cis12 CLA reduces body fat mass. Human studies are however less conclusive, which may be attributed to the use of CLA mixtures rather then the single trans10,cis12 CLA isomer in most studies, as well as study length [4].
Atherosclerosis
Studies in rabbits, hamsters and transgenic mice have indicated that intake of CLA either prevents or reduces the growth of atherosclerotic lesions [5]. However, the anti-atherogenic properties of CLA may be mainly attributable to the cis9,trans11 CLA isomer, as in apolipoprotein E knockout mice, cis9, trans11 CLA decreased whereas trans10,cis12 CLA increased lesion size [6]. Data from human studies on atherosclerosis are not available, and effects of trans10,cis12 CLA on cardiovascular risk factors like plasma lipids and lipoproteins are inconsistent [7].
Cancer
In vitro studies tend to support the anti-cancer effects of CLA and show that they can inhibit cell proliferation, inhibit eicosanoid production and induce apoptosis. However, recent reports indicate that trans10,cis12 CLA can elicit pro-carcinogenic effects in animal models of colon and prostate cancer and can increase prostaglandin production in cells [8].
Insulin resistance
The commercially available CLA mixture seems to have little, if any, effect on lipid and glucose metabolism in humans. However, the trans10,cis12 CLA isomer caused a clear impairment of the metabolic profile (lowered HDL cholesterol, increased VLDL triglycerides, increased blood glucose levels and a significant reduction in insulin sensitivity) when given to abdominally obese men [9]. Supplementation of trans10,cis12-CLA, as compared to cis9,trans11-CLA, in healthy subjects did not reveal any changes in insulin concentrations, insulin resistance (HOMA-IR) or insulin sensitivity (revised QUICKI), although blood glucose levels were marginally increased [10]. The trans10,cis12 CLA isomer also caused insulin resistance in various (transgenic) mouse models [11].
Associated decreased protein/metabolite profile
Associated increased protein/metabolite profile
Other (Monogenic) Disorders
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No genetic diseases have been described associated with trans10,cis12 CLA
Nutritional Information
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Food sources
Although there are 28 different CLA isomers, the major isomer in natural food is the cis9,trans11 isomer accounting for about 80% of CLA intake in the diet, whereas the trans10,cis12 isomer is accounting for less than 1% of the total CLA intake. However, CLA can also be prepared commercially by heating linoleic acid under alkaline conditions or by partial hydrogenation of linoleic acid. The resulting CLA mixture often consists of equal amounts of cis9,trans11 CLA and trans10,cis12 CLA isomers, although the chemical method for synthesis will allow a variety of ratios for the two isomers in the final mixture.
Dietary intake
The average daily intake of total CLA ranges from neglible to about 1500 mg in Australian population. The average intake in the UK is between 400 and 600 mg per day. Dietary intake of trans10,cis12 CLA is negligable unless CLA supplements are taken.
Toxicity
Human data from 14 clinical trials have shown that a CLA supplementation dose of around 3 grams per day is safe.
Drivers for biological variation
Vulnerable groups
Other resources
guidelines
- British Nutrition Foundation about conjugated linoleic acid [12]
- Current listing of scientific literature on CLA since 1987 [13]
Links
guidelines
- Wikipedia conjugated linoleic acid [14]