Search PubMed⌕ Search

Biomedical subjects

Toshiyuki Yasui

Publications and source records attributed to Toshiyuki Yasui.

23 records · Page 2Linked to original sources
PubMed2002

The obesity in bilateral ovariectomized rats is related to a decrease in the expression of leptin receptors in the brain.

We investigated the expression levels of leptin receptors in the brain of ovariectomized (OVX) rats. The mean expression level of ob mRNA in adipose tissues of OVX rats was significantly (P < 0.01) lower than that in the SHAM operation group rats, and the mean body weight of OVX rats was significantly (P < 0.01) greater than that in the SHAM group rats. However, there were no differences between serum leptin concentrations in these two groups. The mean level of leptin receptor (OB-R) mRNA expression in the brain tissue and the mean level of long form type OB-R (OB-RL) mRNA expression in the hypothalamus of the OVX rats were significantly (P < 0.05) lower than those in the SHAM group rats. These changes were cancelled by supplementation with 17 beta-estradiol in OVX rats. These results suggested that not only changes in the expression level of ob mRNA in adipose tissue and the serum leptin concentration but also changes in the OB-R mRNA in the brain are involved in the body weight increase in OVX rats and that a decrease in OB-R makes transmission of signals to suppress the amount of food intake difficult, thus leading to an increase in body weight.

Animals↗
PubMed2002

Effects of leptin on gonadotropin secretion in juvenile female rat pituitary cells.

OBJECTIVE: Leptin is an adipocyte-derived hormone, which is the product of the obese gene and it is thought to play important roles in pubertal development and maintenance of reproductive function in the female. In a study using adult male or female rats, it was found that leptin stimulated the secretion of gonadotropin directly from the pituitary in a dose-related manner. However, there is no study in juvenile female rats before puberty. METHODS: In this study, we cultured pituitary cells from 4-, 6- and 8-week-old female Wistar rats with leptin (0-10(-7)mol/l) and gonadotropin-releasing hormone (GnRH) (0 or 10(-8) mol/l). Basal or GnRH-stimulated secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and their synthesis within cells were determined by radioimmunoassay (RIA). RESULTS: Leptin induced bell-shaped dose--response curves of basal LH and FSH secretion from cultured cells of every age-group of rats studied. The most effective concentration of leptin on the basal secretion of LH and FSH from 6- and 8-week-old cultured pituitary cells was 10(-10) mol/l. This leptin concentration was consistent with circulating physiological serum leptin levels at each age. As for juvenile 4-week-old pituitary cells, the most effective concentration was 10(-11) mol/l which was lower than that of 6- and 8-week-old rats. It was consistent with the circulating serum leptin levels of 4-week-old rats. Also, the synthesis and the GnRH-stimulated secretion of LH and FSH were effectively controlled by leptin at concentrations similar to the serum leptin levels of given ages. CONCLUSIONS: Leptin induced pituitary cells to synthesize and secrete both LH and FSH regardless of the presence or absence of GnRH. The concentration of leptin that induced the greatest synthesis and secretion of gonadotropins from pituitary cells changed around the pubertal period. The most effective leptin concentrations in each experiment were similar to the physiological serum leptin level at each animal age. These results indicate that leptin stimulates gonadotrophs not only in the pubertal and the mature period but also in the juvenile period before puberty. It is also conceivable that leptin may modulate the sensitivity of gonadotrophs until the appearance of GnRH stimulation, and may be the factor that brings about puberty onset.

Animals↗
PubMedDate not supplied

Undercarboxylated osteocalcin concentration in postmenopausal women receiving hormone therapy daily and on alternate days.

OBJECTIVE: Undercarboxylated osteocalcin (ucOC) is a sensitive marker of vitamin K status. The authors examined the difference in serum ucOC concentrations in postmenopausal women receiving hormone therapy (HT) daily and on alternate days, and assessed the association between ucOC and triglyceride concentrations, which are related to the transport of vitamin K. DESIGN: Seventy-three postmenopausal women were recruited for this study. Thirty-seven women received 0.625 mg of conjugated equine estrogens (CEE) and 2.5 mg of medroxyprogesterone acetate (MPA) daily, and 36 women received 0.625 mg of CEE and 2.5 mg of MPA on alternate days. The concentrations of serum ucOC, bone turnover markers, lipid profiles, and hormones were measured before and after 12 months of HT. RESULTS: The ucOC concentration in women taking HT daily was significantly (P < 0.01) lower than that in women taking HT on alternate days. Serum ucOC concentrations during HT showed a significant (P < 0.01) inverse correlation with estradiol concentrations during HT. Serum estradiol concentrations during HT showed a significant (P < 0.01) positive correlation with triglyceride concentrations during HT. Furthermore, ucOC concentrations during HT showed a significant (P < 0.05) inverse correlation with triglyceride concentrations in women receiving HT. CONCLUSIONS: The effect of HT on alternate days on ucOC concentration was weaker than the effect of HT daily. In addition, ucOC concentration after 12 months of HT daily might be decreased due to the conversion of ucOC to carboxylated OC by the effect of vitamin K through increased triglyceride levels induced by oral CEE.

Biomarkers↗
PubMedDate not supplied

Different effects of oral conjugated equine estrogens and transdermal estrogen on undercarboxylated osteocalcin concentration in postmenopausal women.

OBJECTIVE: Undercarboxylated osteocalcin (ucOC) is a sensitive marker of vitamin K status, and triglyceride (TG) has been shown to be the main transporter of vitamin K. In the present study, we examined the difference between ucOC concentrations in postmenopausal women receiving hormone therapy (HT) with oral conjugated equine estrogens (CEE) and transdermal estradiol (TE2). We also examined the associations of ucOC concentration with estradiol concentration and TG. DESIGN: Ninety-two postmenopausal women were recruited for this study. Serum concentrations of ucOC, intact osteocalcin, estradiol, and TG were measured before and after 12 months of HT. Forty-six women received oral administration of 0.625 mg of CEE and 2.5 mg of medroxyprogesterone acetate daily, and 46 women received transdermal administration of 50 mug of 17beta-estradiol twice weekly and 2.5 mg of medroxyprogesterone acetate daily. RESULTS: The ucOC concentration in women during HT with oral CEE was significantly (P < 0.01) lower than that in women during HT with TE2. Serum estradiol concentrations during HT with CEE showed a significant inverse correlation with ucOC concentrations and the ratio of ucOC/OC during HT (P < 0.05 and P < 0.01, respectively). In addition, the serum ucOC concentration in women with an increased percentage of change in TG was significantly (P < 0.01) lower than that in women with a decreased percentage of change in TG during HT with oral CEE. CONCLUSION: The effect of HT with TE2 on ucOC concentration in women is weaker than the effect of HT with oral CEE. Suppression of ucOC concentration in postmenopausal women during HT with oral CEE might be associated with the effect of vitamin K through increased TG induced by oral CEE.

Administration, Cutaneous↗