Satomi Oshima

Associations between the Serum 25(OH)D Concentration and Lipid Profiles in Japanese Men

AIM Low circulating 25-hydroxyvitamin D [25(OH)D] concentration has been linked to a high prevalence of cardiovascular disease. One explanation for this phenomenon is that there is an association between the serum 25(OH)D level and lipid profiles. However, studies examining this relationship are limited and have yielded inconsistent results. We thus aimed to evaluate the association between the serum 25(OH)D concentration and lipid profiles in Japanese men taking into consideration confounding factors, including the visceral fat area (VFA) and cardiorespiratory fitness. METHODS A total of 136 men (age range: 20-79 years) participated in our study. Fasting blood samples were analyzed to determine the 25(OH)D, oxidized low-density lipoprotein (oxLDL), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), apolipoprotein (Apo)A-1 and ApoB levels. The VFA was evaluated on magnetic resonance imaging (MRI), and cardiorespiratory fitness was assessed by measuring the peak oxygen uptake (VO2 peak). RESULTS The median 25(OH)D concentration was 35.6 nmol/L, and the prevalence of 25(OH)D deficiency was 78.7%. A multiple linear regression analysis revealed that the serum 25(OH)D concentration was inversely related to the LDL-C/HDL-C, TG, ApoB and ApoB/ApoA-1 values, even after adjusting for age, season, smoking status, alcohol consumption, medication use, vitamin D intake, calcium intake, VFA and cardiorespiratory fitness. CONCLUSIONS Serum 25(OH)D level is inversely correlated with the LDL-C/HDL-C, TG, ApoB and ApoB/ApoA-1 values in Japanese men, independent of the VFA and cardiorespiratory fitness.

Vitamin D supplementation reduces insulin resistance in Japanese adults: a secondary analysis of a double-blind, randomized, placebo-controlled trial

Higher circulating 25-hydroxyvitamin D (25[OH]D) concentration has been linked to a lower prevalence of insulin resistance and type 2 diabetes mellitus. However, randomized controlled trials have not clarified the effect of vitamin D supplementation on insulin resistance in healthy adults. The objective of this study was to assess the effect of vitamin D supplementation for 1 year on insulin resistance; the study was a secondary analysis of a clinical trial. We hypothesized that increased 25(OH)D concentration after vitamin D supplementation for 1 year would significantly improve insulin resistance. Ninety-six healthy adults participated in this study, of whom 81 completed the study. The participants randomly received daily either 420 IU vitamin D3 or placebo in a double-blind manner for 1 year. The levels of fasting insulin, glucose, and other parameters were assessed at baseline and after 1 year of intervention. Homeostasis model assessment of insulin resistance index was calculated from insulin and glucose levels. Visceral fat area and physical activity were also investigated. Serum 25(OH)D and 1,25-dihydroxyvitamin D concentrations were significantly increased by approximately 29.5 nmol/L and 7.0 pg/mL, respectively, after 1-year vitamin D supplementation. After vitamin D supplementation, fasting glucose levels and values of homeostasis model assessment of insulin resistance index significantly decreased from 88.3 to 85.3 mg/dL (P < .01) and 1.17 to 0.84 (P < .01), respectively, and the results were independent of physical activity and visceral fat accumulation. In conclusion, the present study showed that vitamin D supplementation for 1 year effectively improves fasting glucose level and insulin resistance in healthy Japanese adults.

Cardiorespiratory Fitness and Visceral Fat Are Key Determinants of Serum Fibroblast Growth Factor 21 Concentration in Japanese Men

CONTEXT Fibroblast growth factor-21 (FGF21) is an important metabolic regulator suggested to improve glucose metabolism and prevent dyslipidemia. An FGF21-resistant state that increases circulating FGF21 has been reported in obese patients. Although regular exercise prevents metabolic disease, the relationship of the fitness level to serum FGF21 level and body fat distribution in humans remains poorly understood. OBJECTIVE The objective of the study was to determine the relationship among the serum FGF21 concentration, cardiorespiratory fitness (CRF) level, and visceral fat area (VFA). DESIGN Serum FGF21 was measured by an ELISA in 166 middle-aged and elderly Japanese men (aged 30-79 y) and 25 untrained and 21 endurance-trained young men (aged 19-29 y). CRF was assessed by measuring the peak oxygen uptake (VO2peak) and VFA by magnetic resonance imaging. RESULTS In the middle-aged and elderly subjects, the serum FGF21 level correlated with the VO2peak (r = -0.355, P < .001) and VFA (r = 0.487, P < .001). Stepwise multiple regression analysis showed VFA to be most strongly associated with the serum FGF21 level (β = .360, P < .001), and VO2peak was also an independent predictor of the serum FGF21 level (β = -.174, P = .019). Furthermore, the proportion of subjects with an FGF21 level below the limit of detection was significantly higher among the endurance-trained than among the untrained young men (71.4% vs 24.0%, P = .001), and the VO2peak and VFA were independently associated with an undetectable FGF21 level (P < .05). CONCLUSIONS CRF and VFA are key determinants of the circulating FGF21 concentration.

Cardiorespiratory Fitness is a Strong Predictor of the Cardio-ankle Vascular Index in Hypertensive Middle-aged and Elderly Japanese Men

AIM This study aimed to examine whether cardiorespiratory fitness (CRF) is associated with arterial stiffening, evaluated using the cardio-ankle vascular index (CAVI), independent of visceral fat (VF) in middle-aged and elderly Japanese men. We also examined whether the relationship between CRF and the CAVI is modified by age and/or hypertension. METHODS The CAVI was determined in 157 Japanese men (age range, 30-79 years), including 96 hypertensive subjects (61.1%). CRF was assessed by measuring the peak oxygen uptake (VO2peak). The subjects were divided into low- and high-CRF groups, and the VF area was assessed using magnetic resonance imaging. RESULTS The VO2peak correlated with the CAVI following adjustment for age and body mass index in the middle-aged and elderly groups (all the subjects: r=-0.285, p＜0.001; middle-aged: r=-0.240, p=0.040; elderly: r=-0.225, p=0.049). VF also correlated with the CAVI (r=0.230, p=0.004). A multiple linear regression analysis revealed that age (β=0.406, p<0.001) and the VO2peak (β=-0.186, p=0.015) were associated with the CAVI independently of VF and the mean blood pressure. Two way ANCOVA adjusted for age demonstrated that the hypertensive individuals had higher CAVI values than the normotensive individuals in the low-CRF group, whereas no significant differences in the CAVI were observed in the high-CRF group (p for interaction <0.05). CONCLUSIONS In the present study, CRF was found to be associated with the CAVI, independent of age and VF, in hypertensive middle-aged and elderly Japanese men.

High cardiorespiratory fitness can reduce glycated hemoglobin levels regardless of polygenic risk for Type 2 diabetes mellitus in nondiabetic Japanese men.

High cardiorespiratory fitness (CRF) is associated with a reduced risk of Type 2 diabetes mellitus (T2DM) and improved β-cell function; genetic factors also determine these risks. This cross-sectional study investigated whether CRF modifies the association of polygenic risk of T2DM with glucose metabolism in nondiabetic Japanese men. Fasting plasma glucose, insulin, and glycated hemoglobin (HbA1c) levels were measured in 174 Japanese men (age: 20-79 yr). β-Cell function and insulin resistance were evaluated by calculating HOMA-β and HOMA-IR, respectively. CRF was assessed by measuring maximal oxygen uptake (V̇o2max). Subjects were divided into the low and high CRF groups within each age group according to the median V̇o2max. Eleven single nucleotide polymorphisms (SNPs) associated with T2DM were analyzed and used to calculate genetic risk score (GRS); subjects were divided into the low, middle, and high GRS groups. The high GRS group had higher HbA1c levels than the low GRS group in both the low and high CRF groups (P < 0.05). Furthermore, the individuals with a high GRS had a lower HOMA-β than those with a low GRS regardless of CRF (P < 0.05). In multiple linear regression analysis, although GRS was a significant predictor of HbA1c (β = 0.153, P = 0.025), V̇o2max was also associated with HbA1c (β = -0.240, P = 0.041) independent of GRS. These results suggest that CRF is associated with HbA1c levels independent of GRS derived from T2DM-related SNPs; however, it does not modify the association of GRS with increased HbA1c or impaired β-cell function.

Changes in Stress and Appetite Responses in Male Power-Trained Athletes during Intensive Training Camp

An intensive consecutive high-volume training camp may induce appetite loss in athletes. Therefore, this study aimed to investigate the changes in stress and appetite responses in male power-trained athletes during an intensive training camp. The measurements at Day 2 and at the end of a 9-day intensive training camp (Camp1 and Camp2, respectively) were compared with those of the resting period (Rest) and the regular training period (Regular; n = 13). The stress state was assessed based on plasma cortisol level, salivary immunoglobulin A level, and a profile of mood states score. The sensation of appetite was assessed using visual analog scale scores, and fasting plasma acylated ghrelin, insulin, and glucose were measured. The cortisol concentrations were significantly higher at Camp2 (466.7 ± 60.7 nmol∙L−1) than at Rest (356.3 ± 100.9 nmol∙L−1; p = 0.002) or Regular (361.7 ± 111.4 nmol∙L−1; p = 0.003). Both prospective and actual food consumption significantly decreased at Camp2, and acylated ghrelin concentration was significantly lower at Camp1 (34.2 ± 8.0 pg∙mL−1) and Camp2 (32.0 ± 8.7 pg∙mL−1) than at Rest (47.2 ± 11.2 pg∙mL−1) or Regular (53.4 ± 12.6 pg∙mL−1). Furthermore, the change in acylated ghrelin level was negatively correlated with the change in cortisol concentration. This study’s findings suggest that an early-phase physiological stress response may decrease the acylated ghrelin level in male power-trained athletes during an intensive training camp.

The Relationship between Serum 25-Hydroxyvitamin D Concentration, Cardiorespiratory Fitness, and Insulin Resistance in Japanese Men

Here, we aim to investigate the independent and combined associations of serum 25-hydroxyvitamin D (25(OH)D) and cardiorespiratory fitness (CRF) with glucose metabolism. Fasting blood samples of 107 men aged 40–79 years were analyzed for 25(OH)D, glucose, insulin, glycated hemoglobin, and lipid profile. Homeostasis model assessment of insulin resistance index (HOMA-IR) was calculated from the fasting concentrations of glucose and insulin. Visceral fat area (VFA) was determined by magnetic resonance imaging and CRF by measuring maximal oxygen uptake. Median 25(OH)D concentration was 36.3 nmol/L, while the prevalence of 25(OH)D deficiency was 74.8%. Participants with high CRF had significantly lower HOMA-IR, glycated hemoglobin, and insulin values than participants with low CRF (p < 0.05). Higher 25(OH)D concentration was strongly correlated with lower HOMA-IR and insulin values independent of VFA (p < 0.01) but significantly affected by CRF. In the high CRF group, participants with higher 25(OH)D concentration had lower HOMA-IR values than participants with low 25(OH)D concentration (p < 0.05). Higher 25(OH)D and CRF are crucial for reducing insulin resistance regardless of abdominal fat. In addition, higher 25(OH)D concentration may strengthen the effect of CRF on reducing insulin resistance in middle-aged and elderly Japanese men with high CRF.

Serum 25-Hydroxyvitamin D Concentrations Are Inversely Correlated with Hepatic Lipid Content in Male Collegiate Football Athletes

Lower serum 25-hydroxyvitamin D (25(OH)D) concentrations are associated with more weight and fat mass gain in adults in the general population, but it is unknown whether this is the case in collegiate football athletes with greater body weight. This study aimed to investigate associations of serum 25(OH)D concentrations with body fat and ectopic fat accumulation, and to determine which fat indicators are closely related to serum 25(OH)D in male collegiate football athletes. Thirty-four collegiate athletes aged 21 years were recruited. Serum 25(OH)D concentrations and the levels of visceral fat area (VFA), vastus lateralis intramyocellular lipid (IMCL), extramyocellular lipid (EMCL), and intrahepatic lipid (IHCL) were measured. Serum 25(OH)D concentrations were negatively associated with the IHCL values (r = −0.372, p = 0.030), and the relationship remained after adjustment for several factors (r = −0.378, p = 0.047). Additionally, multiple stepwise regression analysis of IHCL content as the dependent variable indicated that 25(OH)D concentrations were a stronger predictor of IHCL content (β = −0.363, p = 0.030) than % body fat and VO2peakFFM. Higher serum 25(OH)D concentrations are more closely related to lower IHCL content rather than any other fat indicators, suggesting that increasing serum 25(OH)D concentrations may have some effect that inhibits lipid accumulation in hepatic tissue, especially in heavy athletes.

Health Issues and Preventive Strategies for Heavy Athletes

Some athletes are required to increase their body weight, since it directly influences their performance. Rugby, Judo, American football, Weight lifting, Field throwing, Bodybuilding, and Sumo are sports where heavy athletes are particularly successful. In fact, for the majority of athletes in these sports, their body mass index (BMI) exceeds 25 kg/m2. Unfortunately, since it is difficult to increase body weight as fat-free mass (FFM), accumulation of unintentional body fat is often observed in heavy athletes, especially among non-elite players. In fact, linemen in American football have a high prevalence of metabolic syndrome and/or insulin resistance (Borchers et al. 2009). Overfeeding and the ensuing creation of a positive energy balance are essential for increasing body weight. However, overeating increases the risk for developing visceral fat accumulation and becoming insulin resistant if done without an adequate dietary plan. While developing health issues from overfeeding is dependent upon one’s genetic complement to some degree, dietary composition and food choices for overfeeding significantly influence the magnitude of visceral fat accumulation as well as the extent of plasma insulin response. Screening and monitoring which involve the periodic measure of body composition as well as biochemical assessments may help to prevent cardiometabolic risks for heavy athletes. These precautions will help ensure a sound physical condition for their playing days and also for their health during the remainder of their lives (Haskins et al. 2011).

Resting Energy Expenditure in Japanese Athletes-as Applied to Dietary Management for Athletes-

Resting energy expenditure (REE) is known to be influenced by different factors, such as body size, body composition (including mass of internal organs and tissues), thyroid hormones, and menstrual cycle. However, the relationship between these factors and REE has not been fully investigated nor reviewed in a way that is optimally useful for the athletic population. Thus the purpose of the chapter is to introduce and summarize studies which have investigated these relationships in Japanese athletes. Fat-free mass (FFM) constitutes not just skeletal muscle, but also internal organs with high metabolic rates. As FFM becomes larger, these tissues and organs also become larger. Since athletes typically have a large FFM, FFM is the major determinant of REE in athletes and consequently it is strongly recommended that FFM be used to estimate REE for Japanese athletes. The daily energy requirement can be estimated based on the REE, and therefore REE is an important part of a sound dietary management program for maximizing athletic performance. Nevertheless, further studies are necessary to investigate such poorly understood factors as genetic background and brown adipose tissue, as well as how these and other elements influence the REE of Japanese athletes.