Takayuki Nishimura

Seasonal variation of non-shivering thermogenesis (NST) during mild cold exposure

BackgroundThe physiological function of non-shivering thermogenesis (NST) has been investigated in recent years, and some studies have discussed the importance of NST with respect to human cold adaptation. The present study aimed to clarify individual and seasonal variations in NST that occurred as a result of mild cold exposure.MethodsSeventeen male university students participated in the present study during summer and winter. The climate chamber used was programmed so that ambient temperature dropped from 28°C to 16°C over an 80-min period. Physiological parameters of test subjects were recorded during the experiments.ResultsIncreases in oxygen intake (VO2) during cold exposure were significantly greater without shivering in winter than they were in summer. Respiratory exchange ratio (RER) was significantly lower during thermoneutral baseline and cold exposure in winter than it was during the same periods in summer. In addition, there was a significant negative correlation between ΔVO2 and ΔRER.ConclusionsIncrease of VO2 without shivering indicated increase of NST, and decrease of RER depends on the metabolization of fat in winter. These results suggested that NST activity was activated by seasonal acclimatization, and individual variation of NST depends on individual variation of fat metabolism.

Relationship between seasonal cold acclimatization and mtDNA haplogroup in Japanese

BackgroundThe purpose of this study was to elucidate the interaction between mtDNA haplogroup and seasonal variation that contributes to cold adaptation.MethodsThere were 15 subjects (seven haplotype D subjects and eight haplotype non-D subjects). In summer and winter, the subjects were placed in an environment where the ambient temperature dropped from 27 °C to 10 °C in 30 minutes. After that, they were exposed to cold for 60 minutes.ResultsIn summer, the decrease in rectal temperature and increase in oxygen consumption was smaller and cold tolerance was higher in the haplotype non-D group than in the haplotype D group. In winter, no significant differences were seen in rectal temperature or oxygen consumption, but the respiratory exchange ratio decreased in the haplotype D group.ConclusionsThe results of the present study suggest that haplogroup D subjects are a group that changes energy metabolism more, and there appears to be a relationship between differences in cold adaptability and mtDNA polymorphism within the population. Moreover, group differences in cold adaptability seen in summer may decrease in winter due to supplementation by seasonal cold acclimatization.

Effect of empathy trait on attention to various facial expressions: evidence from N170 and late positive potential (LPP)

BackgroundThe present study sought to clarify the relationship between empathy trait and attention responses to happy, angry, surprised, afraid, and sad facial expressions. As indices of attention, we recorded event-related potentials (ERP) and focused on N170 and late positive potential (LPP) components.MethodsTwenty-two participants (12 males, 10 females) discriminated facial expressions (happy, angry, surprised, afraid, and sad) from emotionally neutral faces under an oddball paradigm. The empathy trait of participants was measured using the Interpersonal Reactivity Index (IRI, J Pers Soc Psychol 44:113–126, 1983).ResultsParticipants with higher IRI scores showed: 1) more negative amplitude of N170 (140 to 200 ms) in the right posterior temporal area elicited by happy, angry, surprised, and afraid faces; 2) more positive amplitude of early LPP (300 to 600 ms) in the parietal area elicited in response to angry and afraid faces; and 3) more positive amplitude of late LPP (600 to 800 ms) in the frontal area elicited in response to happy, angry, surprised, afraid, and sad faces, compared to participants with lower IRI scores.ConclusionsThese results suggest that individuals with high empathy pay attention to various facial expressions more than those with low empathy, from very-early stage (reflected in N170) to late-stage (reflected in LPP) processing of faces.

Association of Physical Performance and Pain With Fear of Falling Among Community-Dwelling Japanese Women Aged 65 Years and Older.

AbstractOur aim was to explore the association of physical performance and pain with fear of falling among community-dwelling Japanese women.The subjects were 278 women aged 65 years and over. We collected information on fear of falling, painful joints, comorbidities, falls in the previous year, and cataracts. Walking time (distance of 6 m), chair stand time (5 times), grip strength, the timed up and go test (TUG), and functional reach were measured.The prevalence of fear of falling was 36.3%, and it increased with age, but it was not significant (P = 0.081). Multivariate logistic regression analysis showed that poor physical performance (longer walking time, longer chair stand time, weaker grip strength, and longer TUG) and pain (low back, and upper and lower extremity pain) were significantly associated with fear of falling after adjusting for age, body mass index, comorbidities, falls in the previous year, and cataracts.Maintaining physical functioning and managing pain may be important for elderly women with fear of falling.

Magnetic Resonance Imaging Bone Edema at Enrollment Predicts Rapid Radiographic Progression in Patients with Early RA: Results from the Nagasaki University Early Arthritis Cohort.

Objective. To clarify whether magnetic resonance imaging (MRI) bone edema predicts the development of rapid radiographic progression (RRP) in the Nagasaki University Early Arthritis Cohort of patients with early-stage rheumatoid arthritis (RA). Methods. Patients with early-stage RA (n = 76) were enrolled and underwent 1.5-T MRI of both wrists and finger joints. Synovitis, bone edema, and bone erosion were evaluated using the Rheumatoid Arthritis Magnetic Resonance Imaging Scoring (RAMRIS). RRP was defined as an annual increment > 3 at 1 year by the Genant-modified Sharp score of plain radiographs. A multivariate logistic regression analysis was performed to establish the risk factors for RRP. Results. Median disease duration at enrollment was 3 months. RRP was found in 12 of the 76 patients at 1 year. A univariate analysis revealed that matrix metalloprotease-3, RAMRIS bone edema score, and RAMRIS bone erosion score were associated with RRP. Multivariate logistic regression analyses demonstrated that the RAMRIS bone edema score at enrollment (5-point increase, OR 2.18, 95% CI 1.32–3.59, p = 0.002) was the only independent predictor of the development of RRP at 1 year. A receiver-operating characteristic analysis identified the best cutoff value for RAMRIS bone edema score as 5. RRP was significantly rare among the patients with a RAMRIS bone edema score < 5 at enrollment (2 from 50 patients). Conclusion. Our findings suggest that MRI bone edema is closely associated with the development of RRP in patients with early-stage RA. Physicians should carefully control the disease activity when MRI bone edema is observed in patients with early RA.

Relationship between mitochondrial haplogroup and seasonal changes of physiological responses to cold

BackgroundPhysiological responses to cold exhibit individual variation that can be affected by various factors, such as morphological characteristics, seasonal changes, and lifestyle; however, the genetic factors associated with this variation remain unclear. Recent studies have identified mtDNA as a potential genetic factor affecting cold adaptation. In addition, non-shivering thermogenesis (NST), a process closely related to mitochondrial dynamics, has also been suggested as an important factor affecting human response to cold. The present study aimed to clarify the relationship between mitochondrial haplogroup and NST during periods of mild cold exposure.MethodsSeventeen healthy university students (D: n = 8, non-D: n = 9) participated in the present study during summer and winter. A climate chamber was programmed so that ambient temperature inside dropped from 28°C to 16°C over the course of an 80-minute period. Physiological parameters were recorded throughout the course of the experiments.ResultsIncreases in VO2 were significantly greater during periods of cold exposure in winter than they were during periods of cold exposure in summer, and individuals from the D group exhibited greater winter values of ΔVO2 than individuals from the non-D group.Tre was significantly lower during periods of rest and cold exposure in winter; however, no significant difference was observed between Tre values of individuals in the D and non-D groups. In addition, althoughT¯dist was significantly lower during periods of rest in winter than it was during those same periods in summer, no significant seasonal differences in values ofT¯dist were observed during periods of cold exposure.ConclusionsResults of the present study indicated that NST was greater in winter, and that the D group exhibited greater NST than the non-D group during winter. Despite the differences between groups in NST, no significant differences in rectal and skin temperatures were found between groups in either season. Therefore, it was supposed that mitochondrial DNA haplogroups had a greater effect on variation in energy expenditure involving NST than they had on insulative responses. Future studies are necessary in order to investigate more multiple candidate genes related to human cold adaptation and to elucidate the relationship between gene polymorphism and physiological polytypism.

Association of maternal pre-pregnancy weight, weight gain during pregnancy, and smoking with small-for-gestational-age infants in Japan.

AIM The aim of this study was to evaluate the associations of maternal pre-pregnancy body mass index (BMI), weight gain during pregnancy, and smoking, with small-for-gestational-age (SGA) births among Japanese women. MATERIALS AND METHODS Subjects were pregnant women who gave birth to single, term infants (37-42 weeks) at a clinic and hospital in the Nagasaki area between 2012 and 2013. To examine associations with SGA, 49 underweight (BMI<18.5 kg/m(2)) and 579 normal-weight (18.5 ≤ BMI<25.0 kg/m(2)) Japanese women with either appropriate-for-gestational-age or SGA infants were selected and analyzed. RESULTS The prevalence of SGA infants was 6.8%. Seven percent of women were current smokers. Prevalence of pre-pregnancy underweight and gestational weight gain less than recommendation were 20.8% and 16.7%, respectively. Multivariate logistic regression was performed to assess factors affecting SGA infants in the pregnant women. After adjusting for covariates, the amount of maternal weight gain below recommendation (odds ratio (OR), 2.72; 95% confidence interval (CI), 1.37-5.39) and maternal smoking status (OR, 2.80; 95% CI, 1.14-6.91) were significantly and independently associated with SGA births. Pre-pregnancy maternal weight status showed a borderline association (OR, 1.91; 95% CI, 0.96-3.83, p=0.067). CONCLUSION To prevent SGA births, education regarding the adequate nutrition and the adverse effect of maternal smoking is important for the women of reproductive age.

Gender difference in N170 elicited under oddball task.

BackgroundSome studies have reported gender differences in N170, a face-selective event-related potential (ERP) component. This study investigated gender differences in N170 elicited under oddball paradigm in order to clarify the effect of task demand on gender differences in early facial processing.FindingsTwelve males and 10 females discriminated targets (emotional faces) from non-targets (emotionally neutral faces) under an oddball paradigm, pressing a button as quickly as possible in response to the target. Clear N170 was elicited in response to target and non-target stimuli in both males and females. However, females showed more negative amplitude of N170 in response to target compared with non-target, while males did not show different N170 responses between target and non-target.ConclusionsThe present results suggest that females have a characteristic of allocating attention at an early stage when responding to faces actively (target) compared to viewing faces passively (non-target). This supports previous findings suggesting that task demand is an important factor in gender differences in N170.

Illusory self-motion (Vection) may be inhibited by hypobaric hypoxia

INTRODUCTION Previous reports have shown that higher altitudes can alter human perception. We add further evidence to this claim, describing a new finding in which higher altitudes inhibit the perception of illusory self-motion, i.e., vection. METHOD We compared vection strength under both normal and high altitude (hypobaric hypoxia) conditions. In the high altitude condition, atmospheric pressure in the climatic chamber was decreased to 13,123 ft (4000 m; 492 ft/150 m x min(-1)) for 28 min and then maintained at the 13,123-ft (4000-m) level for 30 min by a preprogrammed operation. Vection was induced by an optic flow stimulus. RESULTS Significant differences were observed between the normal and high altitude conditions for all three of the vection strength measurements (latency, duration, and magnitude). Vection was decreased by 14.6%, and Spo2 was decreased by 16.7% in the hypoxia condition. CONCLUSION Vection was inhibited in the high altitude condition. Applications of this finding include informing aircraft pilots of this effect of self-motion perception inhibition at higher altitudes to promote safer flying.

Experimental evidence reveals the UCP1 genotype changes the oxygen consumption attributed to non-shivering thermogenesis in humans

Humans have spread out all over the world adapting to many different cold environments. Recent worldwide genome analyses and animal experiments have reported dozens of genes associated with cold adaptation. The uncoupling protein 1 (UCP1) gene enhances thermogenesis reaction in a physiological process by blocking ATP (adenosine triphosphate) synthesis on a mitochondrial membrane in brown adipose tissues. To our knowledge, no previous studies have shown an association between variants of the UCP1 gene and physiological phenotypes concerning non-shivering thermogenesis (NST) under the condition of low temperature in humans. We showed that the degree of NST for healthy subjects in an artificial climate chamber is significantly different among UCP1 genotypes. Defining the haplotypes covering the UCP1 region (39.4 kb), we found that the frequency of the haplotype with the highest NST was significantly correlated with latitudes and ambient temperature. Thus, the data in this study provide the first evidence that the UCP1 genotype alters the efficiency of NST in humans, and likely supports the hypothesis that the UCP1 gene has been related to cold adaptation in human evolutionary history.