Muscle and Liver Glycogen Levels in Lean and Obese Strains of Mice

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Abstract
Muscle and liver glycogen concentrations were determined in six strains of inbred mice (A/Fn, C3H/Fn, C57BL/Fn, I/Fn, BUB and Lt) of which only one could be considered to be truly non-obese. This lean strain, the I, showed higher muscle glycogen in both the fed (on either a 5 or 50% fat diet) and fasted states. In contrast to the other strains their muscle glycogen did not readily deplete following a fast. Two of the strains, the Lt and C57, were considered to be moderately obese and under some conditions they showed somewhat higher muscle glycogen levels than the severely obese strains, the A, C3H and BUB, but this pattern was not consistent. Our data suggest that an inverse correlation exists between muscle glycogen and body fat levels in these six mouse strains. Fed liver glycogen concentrations were usually greater in the five obese strains than in the I strain but no consistent pattern was found in the obese strains. These carbohydrate variations suggested endocrine differences among the strains. However, an explanation of these variations in terms of higher or lower titers of any hormone leads only to contradiction when the fat and protein differences of these strains are also considered.