Abstract
Exercise is effective for preventing the onset and development of type 2 diabetes mellitus (T2DM) in human cases; however, the effect of exercise on the pathophysiology using animal models of T2DM has not been fully evaluated. We applied voluntary exercise under pair-fed (P) conditions in db mice, an animal model of T2DM. Exercising (Ex) and sedentary (Se) mice were placed in a cage, equipped with a free or locked running wheel, for 4 weeks, respectively. The amount of food consumed by ad libitum-fed wild-type mice under the Se condition (ad-WT) was supplied to all mice, except ad libitum db mice (ad-db). Blood parameters and expression of the genes involved in nutrient metabolism were analyzed. PEx-db (pair-fed and exercising) mice showed significantly lower HbA1c, body weight and liver weight than PSe-db and ad-db mice. Decreased hepatic triglycerides in PEx-db mice corresponded to a lower expression of lipogenic enzyme genes in the liver. Moreover, PEx-db mice showed significantly lower plasma branched-chain amino acids (BCAA), arginine, proline, and tyrosine, in addition to increased skeletal muscle (SM) weight, than PSe-db and ad-db mice, in spite of little influence on the expression of the BCAA transaminase gene, in SM and WAT. We found that exercise under a food restriction condition decreases several amino acids, including BCAA, and may improve insulin sensitivity more than mere food restriction. We propose that the decreased concentration of blood amino acids may be a valuable marker evaluating the effects of exercise on diabetic conditions.
Highlights
The incidence of type 2 diabetes mellitus (T2DM) has recently grown worldwide [1, 2]
Objectives Exercise is effective for preventing the onset and development of type 2 diabetes mellitus (T2DM) in human cases; the effect of exercise on the pathophysiology using animal models of T2DM has not been fully evaluated
We found that exercise under a food restriction condition decreases several amino acids, including branched-chain amino acids (BCAA), and may improve insulin sensitivity more than mere food restriction
Summary
The incidence of type 2 diabetes mellitus (T2DM) has recently grown worldwide [1, 2]. T2DM has genetic predispositions, it is unlikely that the gene pool has changed appreciably over this short period of time [3, 4]. The growing incidence of T2DM may be related to lifestyle factors rather than genetic factors [1,2,3,4]. Exercise, one of these lifestyle factors, has markedly reduced in the past several decades, especially in developed countries [1, 5, 6]. We are obliged to perform experiments using experimental animals at present
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