Standard rodent chow

Female Wistar Han (HsdBrlHan) rats used in these experiments were procured from the Herston Medical Research Centre (Brisbane, QLD, Australia) of The University of Queensland. On arrival at our facility, rats were approximately 3–4 weeks of age with a body weight in the range of ~50–70 g. Rats were caged in groups of two to three in a room with controlled temperature (23 ± 2°C) and a 12 h/12 h light–dark cycle. Standard rodent chow (Specialty Feeds, Glen Forrest, WA, Australia) and tap water were available to the rats ad libitum. Kimwipes (Kimberly-Clark Professional, Kirribilli, NSW, Australia) and Rat Chewsticks (Able Scientific, Canning Vale, WA, Australia) were provided as environmental enrichment. Rats were subject to acclimatization for at least 3 days prior to initiating experimentation. All the experiments herein were performed in the light phase. Approval of experimental procedures was obtained from the Animal Ethics Committee of The University of Queensland (Brisbane, QLD, Australia). The experiments were undertaken in accordance with the requirements of the Australian Code of Practice for the Care and Use of Animals for Scientific Purposes (8th edition, 2013).

After a one week acclimatization period, rats were randomly assigned into non-diabetic (Non-D) and streptozotocin diabetic (STZ-D) groups. Diabetes was induced by a single intraperitoneal injection of STZ (Streptozocin, S0130, Sigma-Aldrich, Macquarie Park, NSW, Australia, 60 mg/kg, dissolved in citrate buffer, pH 4.5) to overnight fasted animals under light isoflurane anaesthesia. Blood glucose (BG) was measured 48 h after STZ injection and all animals with BG ≥ 16 mmol/L were deemed diabetic (18.7–35.8 mmol/L range). Non-diabetic controls were injected with citrate buffer. One week later, rats were further divided into four experimental groups: chow fed (Standard rodent chow, 4.6% fat, 19% protein, 59.9% total carbohydrate, Specialty Feeds, Glen Forrest, WA, Australia)—non-diabetic (Non-D Chow) and STZ-diabetic (STZ-D Chow); ketogenic diet fed (SF10-053 Ketogenic Rodent Diet, 69% fat, 16% protein, 1.2% digestible carbohydrate, Specialty Feeds, Glen Forrest, WA, Australia)—non-diabetic (Non-D Keto) and STZ-diabetic (STZ-D Keto). STZ-D Chow animals were implanted subcutaneously with 1–2 sustained-release insulin pellets (RES-14PC Linplant, Linshin, Canada) according to manufacturer’s instructions. One week after the insertion of insulin implants and confirmation of BG reduction, the dietary interventions were initiated and maintained for 3 weeks.

Animals were purchased from the Herston Medical Research Centre (Brisbane, Australia) of The University of Queensland. A total of 45 female Wistar Han (HsdBrlHan) rats were used in this study. At the time of arrival in our research facility, the rats were ~3–4 weeks old and their body weights were in the range ~50–70 g. Rats were housed in small groups of two to three in individually ventilated cages in a room having a controlled temperature (23 ± 2°C) and a 12 h/12 h light–dark cycle. Standard rodent chow (Specialty Feeds, WA, Australia) and tap water were available to all rats ad libitum. Kimwipes (Kimberly-Clark Professional, NSW, Australia) and Rat Chewsticks (Able Scientific, WA, Australia) were provided in the individual cages as environmental enrichment. Rats were subject to acclimatization in the animal housing facility for at least 3 days prior to initiating experiments. The experiments on these rats were performed in the light phase. The procedures involving animal experimentation were approved by the Animal Ethics Committee of The University of Queensland (QLD, Australia). The experiments described herein were performed as per the requirements of the Australia Code of Practice for the Care and Use of Animals for Scientific Purposes (8th edition, 2013).