The prevention of obesity, which leads to diabetes and other diseases, is a major concern for public health. There might be an optimal dietary fat to carbohydrate ratio for prevention and treatment of obesity. According to the Japanese Dietary Reference Intakes (RDA) for 2010, the optimal fat intake is 20-30% of energy for ages 1-29 y and 20-25% for ages 30 y and over. Upper boundary values of this recommendation were the median of the percentage of energy from dietary fat in Japanese. In a systematic review to estimate the optimal dietary fat to carbohydrate ratio, it was found that obese subjects with hyperinsulinemia (or insulin resistance) lost more weight on a mild low-carbohydrate (LC) (or low-glycemic load diet; 40% carbohydrate, 30-35% fat) than on a low-fat (LF) diet (55-60% carbohydrate, 20% fat), whereas those without hyperinsulinemia showed the opposite. In non-obese primarily insulin-sensitive subjects, decreasing fat rather than carbohydrate intake is generally more effective to prevent obesity. Physiological and molecular evidence supports this conclusion. Increased carbohydrate intake, especially in high-glycemic food, leads to postprandial hyperglycemia and hyperinsulinemia, which are exaggerated in obese insulin-resistant subjects. Even in an insulin-resistant state, insulin is able to stimulate fatty acid synthesis in liver, activate lipoprotein lipase, and prevent lipolysis in adipose tissues, which all facilitate adipose tissue enlargement. Optimal dietary fat to carbohydrate ratio may differ in populations depending on their prevalence for obesity. Because the prevalence of overweight/obesity in Japanese is low, a LF diet is recommended in the general population.
The fat-free mass (FFM) of athletes is typically large, and thus the FFM is often utilized to estimate their resting energy expenditure (REE). While the proportional contribution of organ-tissues to the total influence of FFM on REE is known for untrained individuals and female athletes, the extent to which this is valid for male athletes is unclear. The purpose of this study was to clarify the contribution of the components of FFM to REE in male athletes. Fifty-seven male athletes participated in this study. REE was assessed by indirect calorimetry and body composition by dual X-ray absorptiometry. The athletes were equally divided into three groups based on FFM: Small (S), Medium (M), and Large (L). When measured REE (REEm) was compared with REE estimated (REEe) based on the four organ-tissue compartments with set metabolic rates, REEm and REEe had a strong association (r=0.76, p<0.001). In addition, the absolute value of total REE became larger in accordance with body size (S: 1,643±144, M: 1,865±140, and L: 2,060±156 kcal/d) accompanied by increases in mass of all four organ-tissue compartments as body size increased. The consistency of REE/FFM in male athletes in spite of the difference in body size can be explained by the steadiness among the three groups of the relative contribution of each organ-tissue compartment to the FFM. Based on these results, the FFM is the major determinant of REE regardless of body size in male athletes.
Livestock and laboratory animals show compensatory growth when they are fed ad libitum following a period of restriction feeding. Lysine is a major limiting essential amino acid in the diets both for humans and animals. We hypothesized that changing dietary lysine levels from deficient to sufficient induced compensatory growth in young rats. We elucidated the effect of lysine sufficiency on the dynamics of hormones, relevant to muscle protein synthesis and degradation, insulin-like growth factor-I (IGF-I) and corticosterone, and on the expression of proteolytic-related genes in skeletal muscle during compensatory growth. Lysine sufficiency where the dietary lysine level was increased from 0.46% to 1.30% after 2 wk of subjecting the rats to the lower lysine level induced 80% enhancement of growth rate of rats. During compensatory growth with the lysine sufficiency, fractional muscle protein synthesis rates were higher whereas fractional muscle protein degradation rates were lower than those of the control group (p<0.05). After lysine sufficiency, the expression of atrogin-1/MAFbx mRNA was decreased in gastrocnemius muscle (p<0.05). With the lysine sufficiency, serum IGF-I concentration increased (p<0.05) whereas serum corticosterone decreased (p<0.05). These findings suggest that compensatory growth with lysine sufficiency is due to a change of hormone levels before and after changing diets, resulting in incrementation of protein synthesis and suppression of protein degradation of skeletal muscle.
Elevated circulating alanine aminotransferase (ALT) and γ-glutamyltranspeptidase (γ-GTP) activities in healthy and preclinical subjects are associated with increased risk for obesity, diabetes and related complications. In the present study, we examined the associations between these hepatic enzymes and circulating cytokines as markers for insulin sensitivity (adiponectin) and inflammation [interleukin-6 (IL-6)] in middle-aged Japanese men not being treated for metabolic diseases. We conducted a cross-sectional study of 310 Japanese men aged 40-69 y (mean±SD, 58.8±7.6 y) who were not being treated for metabolic diseases and who participated in health checkups in Japan. We analyzed their lifestyle factors, clinical factors, and plasma adiponectin and IL-6 concentrations. We determined associations between the concentrations of these cytokines and the clinical and lifestyle factors using Spearman's correlation analysis, Jonckheere-Terpstra's test and multiple linear regression. ALT activity was negatively associated with adiponectin (r=−0.302, p<0.001) but not with IL-6. γ-GTP activity was positively associated with IL-6 (r=0.335, p<0.001) and negatively associated with adiponectin (r=−0.129, p<0.05). Aspartate aminotransferase (AST) activity was positively associated with IL-6 (r=0.131, p<0.05) and negatively associated with adiponectin (r=−0.125, p<0.05). Multiple linear regression analyses showed that adiponectin was independently and negatively associated with ALT activity, while IL-6 was independently and positively associated with γ-GTP activity. Adiponectin and IL-6 were not independently associated with AST activity. The results of this study indicate that circulating ALT activity is negatively associated with adiponectin concentration, γ-GTP is positively associated with increased IL-6 concentration, and AST is not associated with these cytokines in middle-aged Japanese men not being treated for metabolic diseases.
Currently, protein requirements are generally determined based on nitrogen balance studies, but there are a variety of limitations associated with this method. The indicator amino acid oxidation (IAAO) method, with a theoretical base that differs widely from the nitrogen balance method, was developed as an alternative method for humans. The objective of the present study was to evaluate protein intakes for metabolic demands and protein quality, using protein itself, in rats employing the IAAO technique with L-[1-13C]phenylalanine. Male Wistar/ST rats (5-6 wk old) received a graded casein (4.3, 8.6, 12.9, 17.2, 21.5, 25.8%), or a wheat gluten (7.2, 10.8, 14.4, 18.0, 21.6, 25.2%) diet, along with L-[1-13C]phenylalanine. An isotopic plateau in breath was achieved 210 min after the start of the 13C ingestion. The protein intakes for metabolic demands were calculated by applying a mixed-effect change-point regression model to breath 13CO2 data, which identified a breakpoint at minimal breath 13CO2 in response to graded protein intake. The protein intakes for metabolic demands determined by the IAAO method were 13.1 g/kg BW/d for casein and 18.1 g/kg BW/d for wheat gluten, showing a tendency similar to that determined by the nitrogen balance method. These results demonstrated that the IAAO method could be employed to evaluate not only the protein intakes for metabolic demands, but the dietary protein quality in freely living rats, suggesting that this method might be viable in a clinical setting.
We recently reported that the oral intake of β-cryptoxanthin exerted anti-obesity effects by lowering visceral fat levels. In the present study, we characterized the molecular mechanisms underlying the lipid-lowering effects of β-cryptoxanthin on 3T3-L1 cells. Consistent with our previous findings, β-cryptoxanthin rapidly reduced the level of intracellular lipids in 3T3-L1 cells as assessed by Oil red O staining. Using an in vitro nuclear receptor binding assay, we demonstrated the ability of β-cryptoxanthin to bind to and activate members of the retinoic acid receptor (RAR) family. Accordingly, treatment of cells with LE540, an RAR antagonist, abolished the β-cryptoxanthin-dependent suppression of 3T3-L1 adipogenesis, suggesting that β-cryptoxanthin mediates its effects on 3T3-L1 cells via RAR activation. In addition, real-time RT-PCR analysis revealed that β-cryptoxanthin down-regulates mRNA expression of PPARγ, a key regulator of adipocyte differentiation, and that this inhibition was blocked by LE540 treatment. Taken together, these data indicate that RAR activation contributes to the molecular mechanism by which β-cryptoxanthin prevents obesity.
The loss of vitamin B12 in round herring meats during various cooking treatments was evaluated. Although amounts of vitamin B12 were three times greater in the viscera (37.5±10.6 μg/100 g fresh weight) than in the meats, about 73% of total vitamin B12 found in the whole fish body (except for head and bones) were recovered in the meats (5.1±1.0 μg of vitamin B12). The vitamin B12 contents of the round herring's meats were significantly decreased up to ~62% during cooking by grilling, boiling, frying, steaming, and microwaving. There was, however, no loss of vitamin B12 during vacuum-packed pouch cooking. Model experiment using hydroxocobalamin suggest that loss of vitamin B12 is dependent on the degree of temperature and time used in conventional cooking, and is further affected by the concomitant ingredients of food. Retention of vitamin B12 was not dependent on vacuum or temperature (or both) used in the vacuum-packed pouch cooking.
The purpose of this study was to improve the efficiency of the microbiological assays for biotin, niacin, and pantothenic acid by using lyophilized cells from Lactobacillus plantarum ATCC 8014. The use of lyophilized cells as an inoculum was assessed to avoid time-consuming processes like cell precultivation and washing. The authors also examined the effects of various protectants such as skim milk, sucrose, sorbitol, and trehalose on the assay. The viable cell counts of the lyophilized cells were found to be approximately equal for different protectants. The standard curves for biotin, niacin, and pantothenic acid concentrations obtained using lyophilized cells with sucrose and intact cells gave similar linear ranges. Furthermore, the measured vitamin concentrations of the standard reference material 3280 were in the range of the established values. Therefore, lyophilized cells with sucrose are potential alternative inocula for the turbidimetric method. This will increase the overall convenience associated with microbiological assays.
Buckwheat has been shown to have various health benefits such as reduction of hypertension and improvement of hypercholesterolemia; however, its effect on diabetes has not been fully elucidated. In this study, buckwheat bran extracts (BBE) inhibited sucrase activity in vitro more effectively than buckwheat. Balb/c mice pretreated with BBE showed dose-dependent reductions of blood glucose, greater than those observed with control mice, within 60 min following oral sucrose administration. Blood glucose levels in mice pretreated with buckwheat extracts were also significantly lower compared to those in control mice within 30 min following oral administration of sucrose. However, rutin, one of the abundant polyphenols of BBE, did not lower blood glucose level. Our data indicate that components of BBE other than rutin have inhibitory activity against sucrase in vivo. These results suggest that BBE could have beneficial effects on diabetes.