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Effect of moderate fat/high sucrose diet on glycogen synthesis rates in rat skeletal muscle upon the cessation of voluntary wheel running
Author(s) -
Borengasser Sarah Jean,
Laye Matthew,
Morris Tyler,
Booth Frank,
Thyfault John
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a691-a
Subject(s) - medicine , endocrinology , basal (medicine) , glycogen , insulin , skeletal muscle , sucrose , glycogen synthase , sed , chemistry , biology , biochemistry
Voluntary wheel running (VWR) (21 days; 6 km/night) rats display enhanced skeletal muscle insulin sensitivity in vitro which quickly decreases to sedentary levels after the cessation of running for 53 h. We sought to explore the impact of ceasing physical activity on the insulin sensitivity of muscle if rats consumed a diet higher in fat and sugar. At 21 days of age, rats began VWR; 2 weeks later rats were switched from a normal rat chow to a moderate fat (34%), high sucrose (25%) diet. After 42–43 days of VWR, rats were sacrificed at 5 h (WL5), 53 h (WL53), and 173 h (WL173) after wheel lock. We measured glycogen synthesis (GS) under basal and insulin‐stimulated (100 nM) conditions in extensor digitorum longus (EDL) muscle strips. We found basal and insulin‐stimulated GS was elevated in the WL5 rats. At WL53, basal GS returned to sedentary levels, while insulin‐stimulated GS was maintained. However, at WL53 and WL173, there was a trend for basal GS to be less when compared to WL5. The delta increase in GS (delta = insulin – basal) tended to be greater at WL53 than at WL5 and SED. GS represents the non‐oxidative disposal of glucose and considered the most important mechanism for controlling euglycemia. These results demonstrate the cessation of physical activity combined with a moderate fat/high sucrose diet leads to a reduction in the ability to synthesize glycogen in EDL muscle under both basal and insulin‐stimulated conditions.