Effect of dietary fat and aging on adipose tissue cellularity in mice differing in genetic predisposition to obesity

A line of mice had been developed which became obese when fed a commercial mouse breeder chow. This obese line was compared to a non-obese line at various ages to determine whether the type or amount of dietary fat would affect adipocyte size and number. Experimental diets containing beef tallow (38% of calories as beef fat and 2% as corn oil), corn oil (40% corn oil) or low fat (2% corn oil) were provided ad libitum at the time of weaning. Dorsoscapular subcutaneous fat pads were removed at 5, 6, 7, and 8 weeks and at 3, 6, 9, 12, 15, 18, and 21 months of age. Adipocyte size and number were determined histologically. Obese mice had enhanced adipocyte hyperplasia compared to the non-obese line. Only when eating the low fat diet did the obese mice have life-long elevated hypertrophy compared with their non-obese counterparts since non-obese mice responded to high fat feeding with a dramatic increase in adipocyte volume, regardless of type of fat. Body weight was greater in the obese line at all ages studied; however, some overlap in body weight was encountered between non-obese mice fed the high fat diets and genetically obese mice. Non-obese mice fed the low fat diet were smaller than mice in all other treatment groups throughout the study. Weight of the dorsoscapular subcutaneous adipose tissue was consistently greater in the obese line; however, high fat feeding greatly increased fat pad weight in non-obese mice.(ABSTRACT TRUNCATED AT 250 WORDS)