Introduction: Diabetes is a leading cause of morbidity and mortality, worldwide, and is strongly associated with skeletal muscle mitochondrial dysfunction. Exercise has been recognized to improve diabetic outcomes by enhancing muscle mitochondrial turnover and insulin sensitivity. However, compliance to set exercise regimes is a major hurdle. Our laboratory has identified a novel protein, trim28 (T28), as a potential target for manipulating mitochondrial turnover and improving mitochondrial function.
Objectives: This research aimed to characterize the effect of muscle-specific trim28 knockout (T28KO) on mitochondrial function and glucose tolerance in a high fat fed, insulin resistant model.
Methods: T28KO mice were developed using the cre/lox system with developmentally expressed MCK-cre. Muscle-specific knockout of trim28 was confirmed via western blot. The effect of T28KO was characterized over a 16 week high fat diet regime by EchoMRI, oral glucose tolerance test (oGTT), intraperitoneal insulin tolerance test (ipITT), the comprehensive laboratory animal monitoring system (CLAMS) and Oroboros O2k analysis.
Results: At baseline, 4, 8 and 12 weeks post-diet, there were no significant differences between genotypes in total body, lean or fat mass. Neither glucose nor insulin tolerance was significantly different between the groups at these time points. T28 deletion did not affect whole-body oxygen consumption, energy expenditure or substrate preference at 3 and 7 weeks post-diet, though T28KO animals displayed a significant reduction in daytime activity 7 weeks post-diet (p=0.04). At 16 weeks post-diet, respiratory measurements in red gastrocnemius, as determined by a substrate-uncoupler-inhibitor titration protocol, did not differ between groups.
Conclusions: Whilst the current study failed to identify a metabolic consequence of T28 deletion, the possibility exists that this developmental knockout model underwent compensatory mechanisms during development. Hence, the potential for trim28 knockout to improve mitochondrial function and insulin sensitivity will be tested in an inducible cre mouse model, currently breeding in our laboratory.