Abstract
This study aimed to investigate the direct influence of a decrease in the cellular thiamin level, before the onset of anorexia (one of the symptoms of thiamin deficiency) on glycogen metabolism and the AMP-activated protein kinase (AMPK) activation levels in skeletal muscle at rest and in response to exercise. Male Wistar rats were classified as the control diet (CON) group or the thiamin-deficient diet (TD) group and consumed the assigned diets for 1 week. Skeletal muscles were taken from the rats at rest, those that underwent low-intensity swimming (LIS), or high-intensity intermittent swimming (HIS) conducted immediately before dissection. There were no significant differences in food intake, locomotive activity, or body weight between groups, but thiamin pyrophosphate in the skeletal muscles of the TD group was significantly lower than that of the CON group. Muscle glycogen and lactate levels in the blood and muscle were equivalent between groups at rest and in response to exercise. The mitochondrial content was equal between groups, and AMPK in the skeletal muscles of TD rats was normally activated by LIS and HIS. In conclusion, with a lowered cellular thiamin level, the exercise-associated glycogen metabolism and AMPK activation level in skeletal muscle were normally regulated.
Highlights
Thiamin is a water-soluble vitamin that functions as a cofactor for pyruvate dehydrogenase (PDH), one of three enzymes the composing pyruvate dehydrogenase complex (PDC)which is a rate-limiting enzyme in carbohydrate metabolism by catalyzing acetyl-CoA production from pyruvate acid
These results confirmed that thiamin-deficient diet (TD) rats did not present thiamin deficiency-associated symptoms, such as anorexia, abnormal behavior, and weight loss
The results of this study revealed that even if cellular thiamin levels in skeletal muscles were clearly decreased by a thiamin-deficient diet, regulations of glycogen metabolism and AMPK activation in the skeletal muscle were maintained in response to exercise
Summary
Which is a rate-limiting enzyme in carbohydrate metabolism by catalyzing acetyl-CoA production from pyruvate acid It is well-known that prolonged lower thiamin intake causes symptoms such as anorexia; weight loss; abnormal behavior; and serious diseases, including beriberi and Wernicke-Korsakoff syndrome. Given the thiamin imbalance between supply and demand theoretically precedes the incidence of a serious disorder, and the metabolic disturbance associated with thiamin imbalance possibly appears without noticeable symptoms. This “creeping change” would affect the carbohydrate metabolism especially in athletes and physically active subjects, who are engaging in vigorous training programs and in specific nutritional strategies. These circumstances may lead to a negative thiamin imbalance in the cell, absolutely and relatively, and could affect the exercise performance
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