Month: January 2019

The APOB48 protein thus produced exclusively by the intestine is processed to synthesize chylomicrons that are responsible for the lipid uptake from the diet. In the liver, the APOB mRNA is translated in the APOB100 protein that is involved in the synthesis of VLDL and LDL. In transgenic rabbits expressing the rbapobec1-shRNA, the level of APOBEC1 gene expression and the level of editing are significantly reduced in the intestine. The ability to synthesize chylomicrons in response to a diet challenge is reduced. The productions of LDL and VLDL are not significantly modified;Shanzhiside-methylester but the production of HDL is modified since HDL is processed from chylomicrons and remnants that are reduced. The lean phenotype is thus consecutive to the reduced lipids uptake by the enterocytes through the low synthesis of chylomicrons after each food challenge. The absence of obese phenotype in transgenic rabbits expressing the human APOBEC1 enzyme in the intestine is amazing. Indeed, we were expecting for a long-term gain of weight in these animals since the human APOBEC1 transgene should have enhanced the level of editing of the APOB mRNA. It has been already published that in the rabbit species, around 90% of the APOB mRNA was edited in the intestine. Accordingly, our results have shown that more than 95% of APOB mRNA were edited. However,Sesamoside in the present study, the expression of the human APOBEC1 transgene was not able to enhance the level of editing, and consequently, animals did not elicit any obese phenotype. One explanation is that the editing was already at its maximum in wild type animals, and that the over-expression of APOBEC1 was inefficient. It has been reported that the editing results from the activity of the APOB mRNA editing complex, a multicomponent protein complex with enzymatic and regulatory activities. Thus, we suggest that the editing was limited by the availability or activity of other components of the editing complex. More surprisingly, in transgenic rabbits expressing the human APOBEC1 gene, the plasma level of triglycerides in the chylomicrons + VLDL fraction was not enhanced after a fat-rich diet for 8 days as it was in wild type rabbits.

In double transgenic animals, the level of editing was similar to that of wild type animals, despite the reduced expression of the rabbit APOBEC1 gene in the intestine. This proves that the human APOBEC1 enzyme expressed in the intestine by the transgene was able to counterbalance the default of rabbit APOBEC1 enzyme due to the shRNA targeting the rabbit APOBEC1 mRNA. Interestingly,Myrislignan the plasma level of APOB48 was highly enhanced in the human APOBEC1 transgenic rabbits L02 by the high fat/high cholesterol diet challenge. Since editing was not modified in the intestine of these animals, it is likely that the high plasma concentration of APOB48 originated from the liver, where a significant editing of the APOB mRNA was measured consecutively to the leaking expression of the human APOBEC1 transgene. The plasma lipid levels and lipoprotein distributions were assayed in human APOBEC1 transgenic rabbits submitted to the high fat/high cholesterol diet and starvation/ feeding challenge. Surprisingly,Dehydrodiisoeugenol the concentrations of triglycerides in the plasma and also in the chylomicrons + VLDL fraction were not enhanced by the diet, by opposition to what we were expecting for in these rabbits characterized by a high level of circulating APOB48. Clearly, in these animals, the high circulating APOB48 did not contribute to a high synthesis of chylomicrons. Other differences were further detected throughout the starvation/ feeding challenge. These could be consecutive to the leaking expression of the human APOBEC1 gene in the liver, which induced the liver editing of the APOB mRNA and thus the reduction of the hepatic synthesis of APOB100 protein. The total mass of body lipids and growth curves were determined from a series of litters including newborns of each genotype. The transgenic animals expressing the human APOBEC1 gene gained weight and possessed a total lipid mass as the wild type animals. This was not surprising since in these transgenic animals, the APOB mRNA editing and the production of chylomicrons were similar to those determined in wild type rabbits. A small number of animals of rIFABP-hapobec1 transgenic lines L01 and L02 were weighed for a longer time, in order to detect possible long-term modifications consecutive to limited but sustained modifications of the level of editing that we might have not been able to detect earlier.