Skeletal muscle-specific Cre recombinase expression, controlled by the human α-skeletal actin promoter, improves glucose tolerance in mice fed a high-fat diet
Cre-loxP systems are frequently used in mouse genetics as research tools for studying tissue-specific functions of numerous genes/proteins. However, the expression of Cre recombinase in a tissue-specific manner often produces undesirable changes in mouse biology that can confound data interpretation when using these tools to generate tissue-specific gene knockout mice. Our objective was to characterise the actions of Cre recombinase in skeletal muscle, and we anticipated that skeletal muscle-specific Cre recombinase expression driven by the human α-skeletal actin (HSA) promoter would influence glucose homeostasis.
Eight-week-old HSA-Cre expressing mice and their wild-type littermates were fed a low- or high-fat diet for 12 weeks. Glucose homeostasis (glucose/insulin tolerance testing) and whole-body energy metabolism (indirect calorimetry) were assessed. We also measured circulating insulin levels and the muscle expression of key regulators of energy metabolism.
Whereas tamoxifen-treated HSA-Cre mice fed a low-fat diet exhibited no alterations in glucose homeostasis, we observed marked improvements in glucose tolerance in tamoxifen-treated, but not corn-oil-treated, HSA-Cre mice fed a high-fat diet vs their wild-type littermates. Moreover, Cre dissociation from heat shock protein 90 and translocation to the nucleus was only seen following tamoxifen treatment. These improvements in glucose tolerance were not due to improvements in insulin sensitivity/signalling or enhanced energy metabolism, but appeared to stem from increases in circulating insulin.
The intrinsic glycaemia phenotype in the HSA-Cre mouse necessitates the use of HSA-Cre controls, treated with tamoxifen, when using Cre-loxP models to investigate skeletal muscle-specific gene/protein function and glucose homeostasis.
KeywordsCre recombinase Glucose tolerance Insulin Skeletal muscle
Bovine serum albumin
- D-Ala2 GIP
D-Ala2 glucose-dependent insulinotropic polypeptide
Glucose-stimulated insulin secretion
Glycogen synthase kinase
Human α-skeletal actin
Heat shock protein
Muscle creatine kinase
Mammalian target of rapamycin
Peroxisome proliferator-activated receptor
Voltage-dependent anion-selective channel
We thank J. Kruger (Health Sciences Laboratory Animal Services, University of Alberta) for husbandry and maintenance of our HSA-Cre mouse colony.
RAB, JEC and JRU were involved with conception and design of the study. RAB, KG, MDM, KLH, MA, HA and FE were involved with data acquisition. RAB, KG and MDM were involved with data analysis and interpretation. RAB and JRU drafted the manuscript. All authors contributed to critically revising the article for important intellectual content and gave their final approval of the version to be published. JRU is the guarantor of this work.
These studies were supported in part by a discovery grant (RGPIN 04946) from the Natural Sciences and Engineering Research Council of Canada to JRU. JRU is a Scholar of the Canadian Diabetes Association and a New Investigator of the Heart and Stroke Foundation of Alberta, NWT & Nunavut. RAB is a postdoctoral fellow of the Canadian Institutes of Health Research and the Canadian Diabetes Association.
Duality of interest
The authors declare that there is no duality of interest associated with this manuscript.