Michiyo Kimura

Influence of one bout of vigorous exercise on ascorbic acid in plasma and oxidative damage to DNA in blood cells and muscle in untrained rats

We investigated the influence of a single exhaustive bout of downhill running on oxidative damage to DNA and changes of antioxidant vitamin concentrations in rats. Plasma vitamin E levels were unchanged up to 48 hr postexercise. However, plasma ascorbic acid (AA) levels increased after the exercise, then decreased thereafter. This increase corresponded to a marked decrease in AA concentration in the adrenal glands. The activity of hepatic l-gulono-gamma-lactone oxidase, which catalyzes AA synthesis, was unaltered after the exercise. The weight of the adrenal glands was significantly increased 24 hr postexercise. These results indicate that the change in the plasma AA concentration after vigorous exercise was due mainly to the release of AA from the adrenal glands. The plasma creatine phosphokinase (CPK) activity and white blood cell (WBC) count increased 3 to 6 hr postexercise. Over this same period, a marker of oxidative DNA damage, 8-hydroxydeoxyguanosine in DNA, increased in the WBC, but not in the foreleg muscle. Lipid peroxide and vitamin E levels were also unchanged in the foreleg muscle. There was a positive correlation between CPK activity in the plasma and DNA damage in the WBC, suggesting that the DNA damage in the WBC was closely related with muscle damage due to exercise.

Application and adaptation of the in vitro micronucleus assay for the assessment of nutritional requirements of cells for DNA damage prevention

DNA damage is a fundamental cause of developmental and degenerative diseases. The in vitro cytokinesis-block micronucleus cytome (CBMN-Cyt) assay is an established comprehensive method for assessing cytostasis and chromosome stability in cells. Originally developed to study the acute effects of single environmental genotoxicants, creative applications and adaptations to the basic protocol have allowed its use in evaluating the impacts of dietary micronutrients and micronutrient combinations (nutriomes) on DNA damage. In this review, we examine some of these studies and the important findings they have generated with respect to nutrient/nutrient, nutrient/genotype and nutrient/genotoxicant interactions, as well as assessment of the carcinogenic (or protective) potential of whole dietary patterns. In addition, we outline current knowledge gaps and technical limitations and propose future adaptations to enhance the applicability of the CBMN-Cyt method for in vivo predictions.

Effect of different types of carbohydrate supplementation on glycogen supercompensation in rat skeletal muscle

The purpose of this study was to examine the effects of glucose and sucrose supplement on glycogen accumulation in rat skeletal muscle and liver after exhaustive endurance exercise. Four- to five-week-old male Sprague-Dawley rats with an initial body weight ranging from 90 to 110 g were used for this study. All rats were trained by using a 7-day-long swimming exercise program, during which rats swam 6 h/day in two 3-h bouts separated by 45 min of rest. On the next day of the last training, all trained animals performed 240 min of swimming exercise with a weight equivalent to 3 % of their body weight to deplete muscle and liver glycogen. After glycogen-depleting exercise, rats were given a rodent chow diet plus either 5 % sucrose (SUC), 5 % glucose (GLU) or water (CON) for 6 h or 24 h. Despite equal amount of carbohydrate intake, glycogen concentration in rat epitrochlearis muscle of the GLU group rats was significantly higher compared with those observed in the CON (p<0.001) and the SUC groups (p<0.01). No significant difference in liver glycogen was observed among three groups. These results indicate that glucose supplementation rather than sucrose supplementation efficiently promotes glycogen supercompensation in rat skeletal muscle.