Kazuhisa Shimodaira

Osteoblast cells (MG‐63 and HOS) have aromatase and 5α‐reductase activities

Both aromatase and 5α‐reductase activities were found by whole‐cell assay in osteoblast‐like cells, MG‐63 and HOS. Aromatase activity was measured by the [3H] water release method, and the formation of 5α‐androstanedione from androstenedione was expressed as 5α‐reductase activity. When CGS16949A, an inhibitor of aromatase, was added to the incubation medium at a concentration of 2 × 10‐9 M, sufficient to completely inhibit placental aromatase activity, only 63% to 68% inhibitions were observed. When progesterone, a competitive inhibitor of 5α‐reductase, was added at a concentration of 10‐5 M, 28% to 40% inhibitions were recorded. Because the release of [3H] from [1β‐3H] androstenedione into water by 5α‐reductase is reported, results from the present study suggest that the measurement of aromatase activity in osteoblasts by the [3H] water release method may overestimate aromatase activity owing to the inclusion of 5α‐reductase activity. The results also suggest that osteoblast cells may play an important role in bone metabolism by transforming androgens into estrogens and more biologically active androgen derivatives.

Associations between levels of hydroxylated PCBs and PCBs in serum of pregnant women and blood thyroid hormone levels and body size of neonates

The purpose of this study was to investigate possible associations between concentrations of hydroxylated PCBs (OH-PCBs) and PCBs in the serum of women in the first trimester of pregnancy and thyroid hormone levels and body size of newborn infants in 79 mother-neonate pairs. We measured 16 OH-PCB isomers and 29 PCB isomers in the serum of Japanese women sampled at 11.1±1.9 weeks of gestation. The concentrations of free thyroxine (fT4) and thyroid stimulating hormone (TSH) were measured in whole blood spots on filter papers sampled from the neonates. Dietary and lifestyle information of the mothers were obtained by self-administered questionnaires. Geometric mean (GM) concentrations of the sum of 16 OH-PCB isomers and of 29 PCB isomers were 1.2×10(2)pg/g wet wt. and 69ng/g lipid wt., respectively, in maternal serum. The GM concentrations of neonatal fT4 and TSH were 2.21ng/dL and 1.37μIU/mL, respectively. Multiple regression analysis was performed using measures of neonatal thyroid hormones as dependent variable and serum levels of OH-PCBs/PCBs and other potential covariates (age, pre-pregnancy weight, smoking status, etc.) as independent variables. The results demonstrated a significant positive association between the concentrations of some OH-PCB isomers and that of neonatal TSH. There were no significant associations between levels of PCBs and neonatal fT4, or between OH-PCBs/PCBs and body size of neonates. We conclude that exposure to/body burden of OH-PCBs, but not PCBs, at environmental levels during the first trimester of pregnancy can affect neonatal thyroid hormone status.

Exposure to pyrethroids insecticides and serum levels of thyroid-related measures in pregnant women

Possible association between environmental exposure to pyrethroid insecticides and serum thyroid-related measures was explored in 231 pregnant women of 10-12 gestational weeks recruited at a university hospital in Tokyo during 2009-2011. Serum levels of free thyroxine (fT4), thyroid stimulating hormone (TSH) and thyroid biding globulin (TBG) and urinary pyrethroid insecticide metabolite (3-phenoxybenzoic acid, 3-PBA) were measured. Obstetrical information was obtained from medical records and dietary and lifestyle information was collected by self-administered questionnaire. Geometric mean concentration of creatinine-adjusted urinary 3-PBA was 0.363 (geometric standard deviation: 3.06) μg/g cre, which was consistent with the previously reported levels for non-exposed Japanese adult females. The range of serum fT4, TSH and TBG level was 0.83-3.41 ng/dL, 0.01-27.4 μIU/mL and 16.4-54.4 μg/mL, respectively. Multiple regression analysis was carried out by using either one of serum levels of thyroid-related measures as a dependent variable and urinary 3-PBA as well as other potential covariates (age, pre-pregnancy BMI, parity, urinary iodine, smoking and drinking status) as independent variables: 3-PBA was not found as a significant predictor of serum level of thyroid-related measures. Lack of association may be due to lower pyrethroid insecticide exposure level of the present subjects. Taking the ability of pyrethroid insecticides and their metabolite to bind to nuclear thyroid hormone (TH) receptor, as well as their ability of placental transfer, into consideration, it is warranted to investigate if pyrethroid pesticides do not have any effect on TH actions in fetus brain even though maternal circulating TH level is not affected.

Prenatal pyrethroid insecticide exposure and thyroid hormone levels and birth sizes of neonates.

Pyrethroid insecticides have been shown to possess thyroid hormone disrupting properties in previous animal studies. In this study, the relationship between maternal exposure to pyrethroid insecticides during pregnancy and neonatal thyroid hormone status (free thyroxine (fT4) and thyroid stimulating hormone (TSH) in whole blood) and birth sizes were explored in 147 mother-neonate pairs in Tokyo. The concentration of 3-phenoxybenzoic acid (3-PBA) in maternal urine, sampled in the first trimester of gestation, was used for pyrethroid exposure assessment. Neonatal fT4 and TSH were within the normal range except for one elevated TSH (but normal fT4) in a neonate. Multiple regression analyses with stepwise variable selection did not extract maternal 3-PBA as significant for neonatal fT4 and TSH, indicating that maternal pyrethroid exposure had no apparent effect on the neonatal thyroid hormone status of the neonate subjects. For birth weight and head circumference, maternal 3-PBA was selected as significant with a positive partial regression coefficient along with other factors known to increase birth sizes of neonates (gestational weeks or maternal BMI). It was not clear if this was causal because no biological mechanism was apparent.

Maternal Exposure to Pyrethroid Insecticides during Pregnancy and Infant Development at 18 Months of Age

The possible association between maternal exposure to pyrethroid insecticides (PYRs) during pregnancy and infant development was explored. Levels of exposure to PYRs was assessed by metabolite (3-phenoybenzoic acid, 3-PBA) concentration in maternal spot urine sampled in the first trimester of index pregnancy, and infant development was assessed at 18 months of age using the Kinder Infants Development Scale (KIDS), which is based on a questionnaire to the caretaker. The relationship between KIDS score and maternal urinary 3-PBA levels was examined by a stepwise multiple regression analysis using biological attributes of the mother and infant, breast feeding, and nursing environment as covariates. The analysis extracted 3-PBA and the nursing environment as significant to explain the KIDS score at 18 months of age with positive partial regression coefficients. Inclusion of fish consumption frequency of the mother during pregnancy as an independent variable resulted in the selection of fish consumption as significant, while the two variables were marginally insignificant but still with a positive coefficient with the KIDS score. The result suggested a positive effect of maternal PYR exposure on infant development, the reason for which is not clear, but an unknown confounding factor is suspected.

A Cohort Study of the Level of Plasma Oxytocin associated with AutismSpectrum Disorder in Japanese Males, Females and Pregnant Females

Oxytocin (OXT), which is a nonapeptide hormone with amidation of the C-terminal carboxyl and an internal disulfide bridge between two cysteines, is secreted mainly from the posterior pituitary gland. Recently, OXT was shown to play important key roles in social interactions and social behavior. Specifically, a series of studies investigated the relationship between autism spectrum disorder (ASD) and OXT. Few large-scale research reports have been published on plasma OXT levels in Japanese individuals. Investigation of a possible association between ASD and plasma OXT levels will be valuable for OXT research. Here, we measured plasma OXT levels in about 200 pregnant Japanese females during early gestation, the second trimester of pregnancy, the last trimester of pregnancy, and in the funiculus umbilical is shortly after delivery utilizing an OXT enzyme immunoassay kit. As a results, the average plasma OXT levels of 11 Japanese males 22-65 years old and 11 non-pregnant females 23-59 years old were 31.7 ± 10.2 and 25.3 ± 6.1 pg/mL, respectively. Moreover, OXT levels in plasma in early gestation, the second trimester of pregnancy, the last trimester of pregnancy, and the funiculus umbilicalis were 27.88 ± 10.88 (n=43), 33.06 ± 16.06 (n=111), 42.97 ± 35.96 (n=91) and 34.66 ± 22.42 pg/mL (n=130), respectively. Little information regarding plasma OXT levels among the Japanese population is available. We suggest that these results may be valuable on a broad scale in prospective cohorts when examining an association between the mother and the formative influence on her child with ASD, after conducting a follow-up determination of OXT levels in Japanese individuals.

骨芽細胞UMR106-01の5α-reductase活性に対するestradiolの影響

Bone is known to be a target organ of not only estrogens, but also androgens. The mechanism by which these steroids exert their action on bone cells is still poorly understood. In the present study, the effect of 17 beta-estradiol (E2) on 5 alpha-reductase activity, converting testosterone (T) to a more potent biological androgen, dihydrotestosterone (DHT), was assessed in an osteoblast-like cell line of rat origin (UMR106-01). Cells were incubated under standardized conditions with varying concentrations of E2 (10(-12)-10(-6) M) for 48 hours. Incubation medium was replaced when the cells were preconfluent and thereafter at 24 hour intervals. Then the cells were harvested. Each cell homogenate was incubated with [4-14C]-T. DHT was detected as a single metabolite on silicagel thin layer chromatography. 5 alpha-reductase activity was determined by measuring the amount of labeled DHT from T. The radiochemical purity of DHT recovered after incubation was confirmed by recrystallization to constant specific activity. Under the conditions used, no estrogen was detected. Production of insulin-like growth factor-I and alkaline phosphatase in UMR106-01 was increased when E2 was added into the culture medium, however, 5 alpha-reductase activity was significantly decreased by the addition of 10(-12) M to 10(-6) M of E2. Maximum inhibition was noticed at 10(-10) M. Our results demonstrate that UMR106-01 cells have a capacity to transform T into the biologically more potent androgen, DHT. The result, that the enzyme activity was influenced by E2, suggests the regulatory mechanism of both sex steroids on the steroid metabolism in osteoblasts.