Procedures

Procedure 1: Diet adminstration

Reagents and solutions

• Standard low-fat chow diet (CD), 17% calories from fat (fatty acids comprise 0.8% saturated, 1.3% monounsaturated and 2.9% polyunsaturated fats), 25% from protein, 58% from carbohydrates, caloric content of 3.1 kcal g−1 (Envigo Teklad, LM-485, 7912, Indianapolis, IN, USA)
• High fat diet (HFD), 60.3% calories from fat (fatty acid profile comprises 37% saturated, 47% monounsaturated, 16% polyunsaturated fats), 18.4% from protein, 21.3% from carbohydrates caloric content of 5.1 kcal g/L (Envigo Teklad, TD06414, Indianapolis, IN, USA)

Steps

1. Controls are provisioned with a single standard low-fat CD, and treatment animals with HFD.
2. A total of 1348 female individuals (n = 663 on CD and n = 685 on HFD) from 76 strains are studied, labelled using ear tags, and randomly assigned to a diet.
3. 77 % of animals (n = 527) started on HFD at ages between 50–185 d, but some started on the diet as early as 26 d or as late as 358 d. Only 12 cases were placed on HFD at an age greater than 365 d, and these are excluded from the results.

Procedure 2: Body weight

Equipment, software, and supplies

• Balance scale

Steps

Introductory Comments: From Oct 2011 to Dec 2018, both parental strains (C57BL/6J and DBA/2J) , their F1 progeny D2B6F1 and 73 BXD strains, are followed from the breeding program into their entry into the aging colony; typically approximately 120 +/- 66d of age but with a wide range, from 26 to 358d, until their death.

1. All mice are inspected daily, and deaths recorded with a precision of 1 d. Moribund animals (approximately 10%) are euthanized, and those above the average of 200 d are included in lifespan calculations. For the analysis, only those individuals with deaths between April 2012 and November 2018 are considered.
2. Individuals are weighed, to the nearest 0.1g, every other month until their death.