Induction of Body Weight Loss through RNAi-Knockdown of APOBEC1 Gene Expression in Transgenic Rabbits

Abstract

In the search of new strategies to fight against obesity, we targeted a gene pathway involved in energy uptake. We have thus investigated the APOB mRNA editing protein (APOBEC1) gene pathway that is involved in fat absorption in the intestine. The APOB gene encodes two proteins, APOB100 and APOB48, via the editing of a single nucleotide in the APOB mRNA by the APOBEC1 enzyme. The APOB48 protein is mandatory for the synthesis of chylomicrons by intestinal cells to transport dietary lipids and cholesterol. We produced transgenic rabbits expressing permanently and ubiquitously a small hairpin RNA targeting the rabbit APOBEC1 mRNA. These rabbits exhibited a moderately but significantly reduced level of APOBEC1 gene expression in the intestine, a reduced level of editing of the APOB mRNA, a reduced level of synthesis of chylomicrons after a food challenge, a reduced total mass of body lipids and finally presented a sustained lean phenotype without any obvious physiological disorder. Interestingly, no compensatory mechanism opposed to the phenotype. These lean transgenic rabbits were crossed with transgenic rabbits expressing in the intestine the human APOBEC1 gene. Double transgenic animals did not present any lean phenotype, thus proving that the intestinal expression of the human APOBEC1 transgene was able to counterbalance the reduction of the rabbit APOBEC1 gene expression. Thus, a moderate reduction of the APOBEC1 dependent editing induces a lean phenotype at least in the rabbit species. This suggests that the APOBEC1 gene might be a novel target for obesity treatment.

An apolipoprotein B100 mimotope prevents obesity in mice

“…In contrast, the BVFs should not be of direct relevance to gut-derived lipoproteins, which are dominated by ApoB48 in both humans and mice [ 2 ]. It should be interesting to see how our immunization approach performs in rabbit, which exhibits a more human-like lipoprotein profile than mouse [ 4 ].…”

“…Given that VLDL and chylomicrons play central roles in the peripheral deposition of liver- or gut-derived fatty acids [ 3 ], the ApoBs could be considered as potential therapeutic targets in obesity. Indeed, it was recently shown that a partial reduction in ApoB48 levels in chow-fed rabbits (by RNA interference directed against Apobec1, ApoB mRNA-editing enzyme, catalytic polypeptide 1) led to a leaner and apparently healthier phenotype [ 4 ]. It remains to be seen whether such an approach can truly avoid the adverse effects associated with inborn deficiency of intestinal ApoB [ 5 ].…”

The Role of RNA Editing in Cancer Development and Metabolic Disorders

“…A transgenic rabbit model with reduced expression of APOBEC1 presented a lean phenotype compared to wild type when challenged with a high-fat diet (122). This phenotype is consistent with (i) apoB48's role in promoting chylomicron formation and lipid absorption, and (ii) observations in earlier studies that apoB48/apoB100 ratio and APOBEC1 expression were higher in obese and diabetic rats (123, 124).…”

“…In cancer cells with elevated ADAR-mediated RNA editing, such as breast and lung cancers, downregulation of ADAR expression reduces their tumorigenic capacity (17, 39, 185). To counteract apoB48-mediated chylomicron formation and lipid absorption, expression of APOBEC1 was reduced to create transgenic rabbits that are resistant to diet-induced obesity (122). Beyond altering the expression of RNA editases, molecular tools are also being developed to perform selective inhibition of RNA editing.…”

Comparative transcriptomics reveals specific responding genes associated with atherosclerosis in rabbit and mouse models

“…Another Interesting gene is APOBEC1, which is apolipoprotein B (apoB) mRNA-editing enzyme and has been linked with cholesterol control ( Fig 4A ). Previous research showed that APOBEC1 is expressed in mouse liver[ 34 ], but extremely lowly expressed in human and rabbit liver[ 35 , 36 ]. Here our data showed that APOBEC1 was lowly expressed in the liver of NZW LF, JW LF and WHHL LF rabbits (FPKM<2), but upregulated in the liver of NZW HF rabbit (FPKM = 8, S4 Fig ).…”