I am looking to measure short chain fatty acids, carbohydrates, triglycerides, and cholesterol in the intestinal contents, intestinal tissue, portal vein, liver and cardiac serum. I will also be measuring RNA expression of certain markers.
I cannot fast the mice for too long because then there would be no intestinal content. Also, there have been reports of changes to hepatic metabolism with fairly short fasting periods (Article Fasting promotes functional changes in liver mitochondria
). The problem is, if I don't fast then there will likely be great variability in time elapsed since last meal which would obscure the results.Has anyone thought of a way to control for this? Could I fast for 5 hrs and then orally gavage liquid diet 2 hrs prior to sacrifice?
Thank you!
Dear Esther, Best wishes in your unusual research. Long-long time ago I performed studies on rats. We controlled feeding by giving food at fixed times 8 am and 8 pm for one hour. The results are described in my book "Practical mitochondriology" in the Chapter about liver energy metabolism (mitochondria). For the rats the periods after feeding were: absorbtion 1-2 hrs, satiety - the shortest lasted 2 hrs, and varied significantly between species, early fasting 8-12 hrs (after the last meal) and longer starvation 24 hrs. Mice are much smaller and thus you have establish first the metabolic periods. These will vary strongly between species. The best indicator are the liver's contents of: ATP, ADP and AMP, fatty acids, fatty-CoA. I do not know the essence of gut examination. Nobody did such experiments for mice.
Most importantly, you have to have exactly stated goals. The book is on my Research Gate page. The paper version you can buy very chepply at Kindle Amazon.com.
Treating the Intestine with Oral ApoA-I Mimetic Tg6F Reduces Tumor Burden in Mouse Models of Metastatic Lung Cancer. December 2018. Scientific Reports
Chattopadhyay et al. We measured the food in gms and therefore controlled the food uptake. We didn't need to fast the mice. Every Time the mice can be fed with a measured amount of food followed by fasting. A trial run for a few days may train the mice for the same.
Hi Esther Mezhibovsky,
In many metabolic studies, people follow the short term fasting before scarification. I would also recommend a short term fasting (4-6 h) and avoid long term (overnight) fasting if you have no plans for specific diet. Mice consume food to get most of the daily calories during the night (dark cycle). Yes, of course, Overnight fasting will cause metabolic stress. However, it is up to you what do you want to study.
In this study, mice have forced-fed with 0.5 ml of oil after fasting, and test lipid and triglyceride load from the intestine to the blood.
Article Deregulated Lipid Sensing by Intestinal CD36 in Diet-Induced...
So, If the liquid diet is necessary in your study, in case you want to check how much of short-chain fatty acids, carbohydrates, triglycerides, and cholesterol in your liquid diet will be absorbed through the intestine. Or you would like to compare liquid diet contents with blood and tissue metabolite contents to see the intestinal absorption rate. Then you may need to go for overnight fasting to remove completely normal diet contents from the stomach and organs. Then feed with a liquid/specific diet to do comparative metabolic study.
Most importantly, check with your ethical permit for this experimental design. or request for an upgrade in the permit.
Good luck with your experiments
BR
Jay
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