Blood biomarkers for estimating energy intake in Japanese male collegiate athletes: a pilot study.

BACKGROUND: Athletes should be informed of their required energy intake in preparation for sports competitions. However, the environment in which dietary surveys can be conducted to determine the required energy intake for sports competitions is limited, and such survey will require a substantial amount of time and effort from athletes and dietitians. If certain biomarkers for estimating the energy intake can be identified, they may compensate for the shortcomings of these dietary surveys. We aimed to identify the blood biomarkers to estimate the energy intake/basal metabolic rate ratio of male athletes. METHODS: Twenty-six male athletes from a university physical education department were included and underwent measurements of height, weight, and body composition, as well as blood sampling. The dietary assessment included a 3-day dietary recall and collection of meal photographs. The basal metabolic rate was estimated using the lean body mass, while the daily energy intake/basal metabolic rate ratio was used as an index to determine the energy intake. From the 36 selected blood biomarkers, we identified the independent biomarkers for inclusion in the multiple regression analysis by assessing for pairwise correlations and multicollinearity. A formula for estimating the energy intake/basal metabolic rate was then developed using the stepwise method. A p-value of < 0.05 was considered significant. RESULTS: Overall, 18 of the 36 blood biomarkers were selected, and multiple regression analysis revealed that triiodothyronine, white blood cell count, and triglyceride level were significant factors that can be used to estimate the energy intake/basal metabolic rate, accounting for 60.4% of the variance. No systematic errors were observed in the estimated values, calculated using the estimation formula and dietary assessment results. CONCLUSIONS: A combination of free triiodothyronine level, white blood cell count, and triglyceride level can be used for estimating the energy intake/basal metabolic rate of male athletes, thus compensating for the shortcomings of dietary surveys.

Protective Effects of Voluntary Exercise on Hepatic Fat Accumulation Induced by Dietary Restriction in Zucker Fatty Rats.

Weight control based on dietary restriction (DR) alone can cause lipid metabolic failure and progression to fatty liver. This study aimed to investigate the effect of exercise on preventing DR-induced hepatic fat accumulation in Zucker fatty (ZF) rats by focusing on the relationship between adipose tissue lipolysis and hepatic fat uptake. Six-week-old male ZF rats were randomly assigned to obese, DR, or DR with exercise (DR + Ex) groups. The DR and DR + Ex groups were fed a restricted diet, with the latter also undergoing voluntary exercise. After 6 weeks, hepatic fat accumulation was observed in the DR group, whereas intrahepatic fat was markedly reduced in the DR + Ex group. Compared with the obese (Ob) group, the DR group exhibited 2.09-fold expression of hepatic fatty acid translocase (FAT)/CD36 proteins (p < 0.01) and 0.14-fold expression of hepatic fatty acid-binding protein (FABP)1 (p < 0.01). There were no significant differences between the DR + Ex group and the Ob group. FAT/CD36 and hepatic triglyceride (TG) expression levels were strongly positively correlated (r = 0.81, p < 0.001), whereas there was a strong negative correlation between FABP1 and hepatic TG expression levels (r = -0.65, p < 0.001). Our results suggest that hepatic fat accumulation induced by DR in ZF rats might be prevented through exercise-induced modifications in FAT/CD36 and FABP1 expression.

Characterization of fat metabolism in the fatty liver caused by a high-fat, low-carbohydrate diet: A study under equal energy conditions.

The pathology of fatty liver due to increased percentage of calories derived from fat without increased overall caloric intake is largely unclear. In this study, we aimed to characterize fat metabolism in rats with fatty liver resulting from consumption of a high-fat, low-carbohydrate (HFLC) diet without increased caloric intake. Four-week-old male Sprague-Dawley rats were randomly assigned to the control (Con) and HFLC groups, and rats were fed the corresponding diets ad libitum. Significant decreases in food intake per gram body weight were observed in the HFLC group compared with that in the Con group. Thus, there were no significant differences in body weights or caloric intake per gram body weight between the two groups. Marked progressive fat accumulation was observed in the livers of rats in the HFLC group, accompanied by suppression of de novo lipogenesis (DNL)-related proteins in the liver and increased leptin concentrations in the blood. In addition, electron microscopic observations revealed that many lipid droplets had accumulated within the hepatocytes, and mitochondrial numbers were reduced in the hepatocytes of rats in the HFLC group. Our findings confirmed that consumption of the HFLC diet induced fatty liver, even without increased caloric intake. Furthermore, DNL was not likely to be a crucial factor inducing fatty liver with standard energy intake. Instead, ultrastructural abnormalities found in mitochondria, which may cause a decline in ß-oxidation, could contribute to the development of fatty liver.

Immobilization induces nuclear accumulation of HDAC4 in rat skeletal muscle.

The study described herein aimed to examine changes in HDAC4 and its downstream targets in immobilization-induced rat skeletal muscle atrophy. Eleven male Wistar rats were used, and one hindlimb was immobilized in the plantar flexion position using a plaster cast. The contralateral, non-immobilized leg served as an internal control. After 10 days, the gastrocnemius muscles were removed from both hindlimbs. Ten days of immobilization resulted in a significant reduction (-27.3 %) in gastrocnemius muscle weight. A significant decrease in AMPK phosphorylation was also observed in nuclear fractions from immobilized legs relative to the controls. HDAC4 expression was significantly increased in immobilized legs in both the cytoplasmic and nuclear fractions. Moreover, Myogenin and MyoD mRNA levels were upregulated in immobilized legs, resulting in increased Atrogin-1 mRNA expression. Our data suggest that nuclear HDAC4 accumulation is partly related to immobilization-induced muscle atrophy.

Effects of habitual exercise and dietary restriction on intrahepatic and periepididymal fat accumulation in Zucker fatty rats.

BACKGROUND: Habitual exercise and dietary restriction are commonly recommended to prevent or ameliorate obesity and lifestyle-related diseases, including fatty liver. This study investigated the effects of habitual exercise and dietary restriction on hepatic triglyceride (TG) levels, serum leptin levels, and histological adipocyte size in periepididymal adipose tissue from Zucker fatty (ZF) rats. METHODS: Six-week-old male ZF rats were randomly assigned to one of three groups: sedentary (Sed), sedentary and dietary restriction (Sed + DR), and training and dietary restriction (Tr + DR). Male Zucker lean (L) rats were used as control animals. All rats had access to water and the allowed quantity of food ad libitum. The rats in the Sed + DR and Tr + DR groups were fed a 30% restricted diet, while those in the Tr + DR group exercised voluntarily on a wheel ergometer. After 12 weeks, the rats were sacrificed for a histological examination of their liver and periepididymal adipose tissue. Hepatic and serum TG, serum total cholesterol, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, free fatty acid, and leptin levels were also measured. RESULTS: The hepatic TG levels were significantly higher in the Sed + DR group than in the L (P < 0.001) and Sed (P < 0.05) groups. By contrast, the hepatic TG levels in the Tr + DR group were significantly lower than those in the Sed (P < 0.05) and Sed + DR (P < 0.001) groups, but not significantly different from the L group values. The periepididymal adipocytes were significantly larger in the Sed, Sed + DR, and Tr + DR groups than in the L group (P < 0.001) and were significantly smaller in the Tr + DR group compared to the Sed and Sed + DR groups (P < 0.001). CONCLUSIONS: Our results suggest a relationship between lipid metabolism and the size of adipose cells in ZF rats. Exercising plays an important role in decreasing hepatic TG levels, serum leptin levels, and the size of adipose cells.