Professor University of Manitoba, University of Manitoba Winnipeg, Manitoba, Canada
Grant Hatch (University of Manitoba, University of Manitoba)| Laura Cole (University of Manitoba, University of Manitoba)| Marilyne Vandel (University of Manitoba, University of Manitoba)| Vernon Dolinsky (University of Manitoba, University of Manitoba)
Introduction: Tafazzin is a transacylase enzyme that remodels the phospholipid cardiolipin with fatty acids. Mutations in tafazzin result in the X-linked genetic disease Barth Syndrome. Some Barth syndrome patients exhibit a lean phenotype and tafazzin knockdown mice, an animal model of Barth Syndrome, are protected from diet-induced obesity. We hypothesized that tafazzin deficiency in both the liver and beta cells of the pancreas contribute to this lean phenotype.
Methods: Embyros from mice containing loxP-flanked Taz (flox) were previously generated by using sperm from a Taz flox male (Taz-fl/Y) for in vitro fertilization of wild type C57BL/6J oocytes (Dr. Douglas Strathdee, Beaton Institute, Glasgow, UK). The resulting heterozygous female (Taz-fl/+) and hemizygous males (Taz-fl/Y) were bred >9 times to a C57BL/6 background. To specifically delete Taz in the liver, mice homozygous/hemizygous for the floxed Taz allele are mated with B6.Cg-Speer6-ps1Tg(Alb-cre)21Mgn/J strain of mice transgenic for cre recombinase under the albumin (Albumin) promoter (AlbuminCre). The B6.Cg-Speer6-ps1Tg(Alb-cre)21Mgn/J strain of mice are obtained from Jackson Laboratories. Subsequent breeding took place between female mice heterozygous for the floxed Taz allele (Taz-fl/+, without AlbuminCre) with male mice which are wildtype (+/+) as well as male mice which are hemizygous for the floxed Taz allele (Taz-fl/Y) and heterozygous for the AlbuminCre transgene. This generated male and female mice which are hemizygous for the floxed Taz allele (Taz-fl/Y) and homozygous for the floxed allele (Taz-fl/Taz-fl) with AlbuminCre expression (liver specific knockout of Taz). Littermate controls included both male and female floxed Taz (Taz-fl/Y, Taz-fl/Taz-fl) without AlbuminCre expression (flox controls) and wildtype Taz with AlbuminCre (cre recombinase controls). The same protocol was used to generate pancreatic beta cell-specific TazKO mice driven under the Ins1 promoter using B6.Cg-Tg(Ins1-cre/ERT)1Lphi/J strain of mice. In addition, liver- and pancreatic beta cell-specific double knockout mice were generated. 4 Month old male mice were fed a high-fat (23%, w/w) (Envigo Teklad, Rodent diet cat# TD.130261) for up to 8 weeks. Body weights were measured weekly and fat accumulating tissues weighed after 8 weeks.
Results: Liver-specific or pancreatic beta cell-specific male tafazzin knockout mice accumulated weight gain (≈40% increase in body weight) at the same rate as control animals (Figure 1). However, the liver- and beta cell-specific double tafazzin knockout mice exhibited a reduced rate of weight gain by 8 weeks (≈26% increase in body weight) compared to control or the single tafazzin knockout animals. In addition, at 8 weeks the double tafazzin knockout mice exhibited reduced weight gain in tissues known to accumulate fat including the liver, the gonadal, inguinal and perirenal white adipose tissues and the brown adipose tissue.
Conclusion: The data suggest that liver- and pancreatic beta cell-specific double tafazzin knockout male mice are protected from high fat diet induced weight gain and fat accumulation.
Figure 1. Body weight, % increase in body weight, liver and fat pad weights in control (Black), liver TazKO (Liver KO) (Red), pancreatic beta cell TazKO (B Cell KO) (Green) and liver- and pancreatic beta cell-specific double TazKO (Liver & Beta KO) (Yellow) male mice fed a high fat diet for up to 8 weeks, n=2-4.