Objective: Examine the effects of metformin supplementation on lifespan and survival in B6C3F1 mice through long-term dietary intervention
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not applicable - statistical method • not mentioned
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Male B6C3F1 mice obtained from Harlan Breeders (Indianapolis) and maintained on ad libitum chow diet (Diet #5001, Purina Mills, Richmond, IN) prior to treatment assignment
Note: Mice were randomly assigned to treatment groups at 12 months of age
“male mice (Harlan Breeders; Indianapolis) were randomly assigned to treatment groups at 12 months of age”
Metformin from Caraco Pharmaceutical Laboratories mixed with powdered AIN-93M diet at 100 mg/kg diet (0.1% w/w) and cold-pressed into 1-gram pellets by BioServ. Chow produced every 3 months, never exceeding 50°C during processing
Note: Processing temperature controlled to ensure metformin stability. Light exposure minimized during production and storage
“Metformin was mixed with powdered diet and cold-pressed into 1-g pellets by BioServ. The chow was produced every 3 months during the length of the study, never was permitted to exceed 50 °C”
Stock metformin and all chow stored in darkness at 4°C to maintain metformin stability. Light/dark cycle in mouse facility not altered
Note: Storage conditions maintained to prevent metformin degradation
“Stock metformin and all chow were stored in the dark at 4 °C. The light/dark cycle in the mouse facility was not altered”
At 12 months of age, mice randomly assigned to control group (shifted to daily feeding with 13.3 kcal/day/mouse of AIN-93M control diet) or metformin group (shifted to identical quantity of AIN-93M diet supplemented with metformin at 100 mg/kg diet, approximately 10.6 mg/kg body weight per day)
Note: All mice fed daily. With rare exceptions, all food was consumed each day
“male mice (Harlan Breeders; Indianapolis) were randomly assigned to treatment groups at 12 months of age. In the control group, mice were shifted from ad lib chow feeding to daily feeding with 13.3 kcal/day/mouse of control diet”
Food intake and body weight measured on biweekly or bimonthly basis throughout the duration of the study
Note: Measurements continued until animal death or euthanasia
“Food intake and body weight were measured on a biweekly or bimonthly basis for the duration of the study”
Mice monitored for survival throughout study. Euthanasia criteria based on independent veterinary assessment according to AAALAC guidelines, only when animal condition incompatible with continued survival. Every animal found dead or euthanized was necropsied for pathology score
Note: Veterinary assessment required for euthanasia decisions. All animals underwent necropsy
“The criteria for euthanasia was based on an independent assessment by a veterinarian, according to AAALAC guidelines and only cases, where the condition of the animal was considered incompatible with continued survival, are represented in the curves. Every animal found dead or euthanized was necropsied for pathology score”
Survival curves plotted using Kaplan-Meier method, which includes all available animals at each time point
Note: Statistical analysis method for survival data
“Survival curves were plotted using the Kaplan-Meier method, which includes all available animals at each time point”
Male mice randomly assigned to treatment groups at 12 months of age. B6C3F1 0.1% metformin group: 36 mice; SD matched control group: 297 mice