It is believed that CLA in monogastrics cause insulin resistance. In dairy cows, the milk fat depression effect is well-known and it is believed that there is very limited effect on metabolic and physiological parameters.
Hi behnam, i did an experiment on effect of n-3 and n-6 fatty acids on somatotropic axis and relation with insulin resistance on mRNA LEVEL in dairy cow (unpublish data)
omega-3 fatty acids increased insluin receptor and GH receptor but there we no effect on IGF-1 AND IGFBP and now am considering glucose transporter to know mechanism better.
We had administered a supplement of CLA (20 g/d) on the diet of periparturient dairy cows (from 4 wk before to 4 wk after calving) and we not observed adverse effects. On the contrary we have obtained a positive results at the blood level: lower adipose tissue mobilization (e.g. lower non esterified fatty acids), slightly increase of glucose and a lower inflammatory condition(e.g. higher levels of albumin and lipoproteins) after calving. Altogether these results exclude the appearance of a condition of insuline resistence status, at least during the periparturient period.
CLA is a Coniugated Linoleic Acid. Instead the CLA are several compounds, some of these are produced by the digestion of fat into the rumen. Among the several CLA molecules few have physiological positive effects, mainly those from ruminant animal. For Human effects of CLA you can see the recent review of Mc Crorie et al. Nutr Res Rev. 2011 Dec;24(2):206-27.
Dear Behnam,
Since you mention milk fat depression in your question, I assume that you mean the trans10, cis12 CLA isomer, since only this isomer has this effect. In humans both the cis9, trans 11 CLA isomer and the trans10, cis 12 CLA isomer have been reported to induce some form of insulin resistance in humans, although the (commercial) 50/50 mix of these isomers does not have this effect. Dairy cows produce the cis9, trans 11 CLA isomer in their nintestines. If we would dose trans-10, cis 12 CLA isomers to cows to suppress milk fat, they will get exposed to both isomers. It is difficult to predict what will happen with insulin resitance, but finding no effect would not be surprising. Please realize that insulin resistance as induced by CLA is not the same as inducing type 2 diabetes. CLA stimulates fat-metabolism, just as caffeine, and this may affect insulin sensitivity. Caffeine also induces insulin resitance, but no type 2 diabetes. ( caffeine even appears top protect against type 2 diabetes).
The explanation of Hiskias is correct about the effect of CLA in ruminant. For me is interesting to learn that it is possible to distinguish from different types of insulin resistence. Can you characterize better this aspect? How it is possible to identify insuline resistance from CLA/caffein from that induced by type 2 diabetes?
CLA shows antagonistic behavior with PPAR-gamma. Inhibition of PPAR-g activity either chemically or genetically causes insulin resistance.
Please go throught:-
1. http://www.ncbi.nlm.nih.gov/pubmed/18287349
2. http://www.ncbi.nlm.nih.gov/pubmed/23219922
To be more precise, the trans 10, cis12 CLA isomer is a partial agonist for PPAR gamma receptors. This means that it modulates PPAR gamma activation, and not just inhibits it. Cis9, trans 11 CLA also affects the PPAR gamma receptors. Its effect on the PPAR gamma receptor is more likely to be agonistic of nature. Exposure to a mixture of both isomers may balance out the effect on insulin resistance (as observed in humans). Please realize that partial (genetic) inhibition of PPAR gamma not necessarily increaes insulin resistance (http://www.jci.org/articles/view/8538 ). The regulation of metabolism by PPAR's is extremely complex. There are many PPAR isotypes with overlapping activities and there are many potential ligands for PPAR receptors circulating in our blood. Going for simple answers puts us at risk of giving incomplete answers.
Thus the CLA do not necessarily induces a state of insuline-resistance, but perhaps (and in a proper concentration) could optimize the use of "fuel" at cellular level. Do you think that this makes a sense?
I am quite convinced that trans 10, cis 12 CLA improves beta-oxidation of fats. Although quite some evidence exists for this, final proof for this has not been provided yet.
Fatty acids metabolism and nutrition is a growing field of research, and epigenetics has a lot to do with it.
Specifically, unsaturated fatty acids seem to be on the spotlight even more than saturated ones), among other reasons, due to the economic interest of enriching animal products.
In this sense, contradictory results can be found, as with Omega-3, so that it is timely to wait for more studies (in my opinion).
Regards,
Alfredo J. Escribano.
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