The use of mice in diabetes research: The impact of experimental protocols

Abstract

Mice are used extensively in preclinical diabetes research to model various aspects of blood glucose homeostasis. Careful experimental design is vital for maximising welfare and improving reproducibility of data. Alongside decisions regarding physiological characteristics of the animal cohort (e.g., sex, strain and age), experimental protocols must also be carefully considered. This includes choosing relevant end points of interest and understanding what information they can provide and what their limitations are. Details of experimental protocols must, therefore, be carefully planned during the experimental design stage, especially considering the impact of researcher interventions on preclinical end points. Indeed, in line with the 3Rs of animal research, experiments should be refined where possible to maximise welfare. The role of welfare may be particularly pertinent in preclinical diabetes research as blood glucose concentrations are directly altered by physiological stress responses. Despite the potential impact of variations in experimental protocols, there is distinct lack of standardisation and consistency throughout the literature with regards to several experimental procedures including fasting, cage changing and glucose tolerance test protocol. This review firstly highlights practical considerations with regard to the choice of end points in preclinical diabetes research and the potential for novel technologies such as continuous glucose monitoring and glucose clamping techniques to improve data resolution. The potential influence of differing experimental protocols and in vivo procedures on both welfare and experimental outcomes is then discussed with focus on standardisation, consistency and full disclosure of methods.

The glucose tolerance test in mice: Sex, drugs and protocol

“…It is worth noting that male mice were more sensitive to these interventions than females, with a higher magnitude and duration of blood glucose increases regardless of cage change method, fast length or oestrous stage, as previously seen with regards to other researcher interventions. 33 Overall, these results challenge the concept that the use of female mice should be avoided due to increased variability due to the oestrous cycle. 5,6 Another reason researchers may predominately study male mice in GTTs is that females are more glucose-tolerant than males in both the basal and glucose-intolerant state.…”

“…Data are mean ± SEM (n = 5 for males, females in P-E and females in M-D) 4 | DISCUSSION Despite being one of the most commonly used tools in metabolic research, GTTs are poorly standardized. Researcher intervention cannot be completely avoided in a GTT and it is clear that even minor interventions contribute to increases in blood glucose concentrations 33. However, some interventions undertaken as part of the GTT protocol (eg, different fasting protocols) may be particularly stressful to mice13,14,20 which we hypothesized could further increase blood glucose concentrations and potentiate glucose intolerance [37][38][39][40][41][42].…”

The use of mice in diabetes research: The impact of physiological characteristics, choice of model and husbandry practices

“…We have also detailed how animal welfare can be enhanced through husbandry refinements, but refinements can also be made to common experimental procedures used in preclinical diabetes research. 1 The replacement of animals is harder to achieve.…”

“…When planning an in vivo experiment, many factors inherent to the mouse model exist. These must be considered alongside experimental planning 1 for the hypothesis to be appropriately tested and to ensure robustness and reproducibility of results. This review discusses commonly used mouse models, when they are appropriate to use and considerations for their use.…”

Diabetes basic science research takes centre stage

“…Two of the current RD Lawrence Fellows (Anna Long 3 and Elisa de Franco 4 ) brought their specialist areas alive with up to date, focused reviews. Four established diabetes researchers (Susan Ozanne, 5 Aileen King, 6,7 Alison McNeilly 8 and Kathleen Gillespie 9 ) also accepted the challenge of writing stimulating review articles on a range of topics, and they were assisted in this by junior researchers in their groups. And finally, this year's recipient of the Diabetes UK Dorothy Hodgkin Lecture, Ewan Pearson, has contributed a thought-provoking review of his lecture entitled 'Drugs, genes and diabetes' , 10 which makes a strong case for identifying the effects of genetic variation on therapeutic responses to allow targeted clinical treatment for diabetes.…”