生後早期のラットでは免疫ストレスによるLH分泌抑制反応が確立されていない

Some physiological functions display weak responses to stress in the early neonatal period; i.e., theyexhibit stress hyporesponse periods. In this study, we evaluated whether gonadotropin regulatory fac-tors exhibit stress hyporesponsive periods in male and female rats. Rats were intraperitoneally injectedwith lipopolysaccharide (100 μg/kg) (LPS group) or saline (control group) on postnatal day (PND) 5,10, 15, or 25. Then, their serum luteinizing hormone (LH) concentrations and hypothalamic mRNAlevels of gonadotropin regulatory factors; i.e., kisspeptin (Kiss1), the kisspeptin receptor (Kiss1r), andgonadotropin-releasing hormone (GnRH), were measured at 2 h after the injection. The hypothalamicmRNA levels of pro-inflammatory cytokines were also measured because they suppress gonadotropinsecretion. The serum LH concentration of the LPS group was lower than that of the control group atPND25 in both sexes, but no such difference was seen at PND5, 10, or 15 in either sex. In both sexes,the hypothalamic tumor necrosis factor (TNF)α and interleukin (IL)-6 mRNA expression levels of the LPSgroup were higher than those of the control group at PND25, but not at PND5 or 10. The hypothalamicIL-1β mRNA expression level of the LPS group was higher than that of the control group at all time points. The hypothalamic Kiss1, Kiss1r, and GnRH mRNA expression levels of the LPS and control groups did notdiffer at any time point in either sex. These findings suggest that gonadotropin regulatory factors exhibitstress hyporesponse periods. The hypothalamic–pituitary–gonadal axis (HPG) might become responsiveto immune stress between PND15 and 25, which could be related to enhanced hypothalamic cytokineexpression. The avoidance of infectious stress during the early neonatal period might be important fornormal development of the HPG axis

Developmental changes in the hypothalamic mRNA expression levels of PACAP and its receptor PAC1 and their sensitivity to fasting in male and female rats

The actions and responses of hypothalamic appetite regulatory and factors change markedly during the neonatal to pre-pubertal period. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been found to play pivotal roles in the regulation of metabolic and nutritional status through its specific receptor PAC1. PACAP/PAC1 have anorectic roles, and their functions are regulated by leptin in adulthood. In the present study, we showed that hypothalamic PACAP mRNA expression decreases during the neonatal to pre-pubertal period (from postnatal day 10 to 30) in both male and female rats. During this period, hypothalamic PACAP mRNA expression was not affected by 24 h fasting in either sex, while the serum leptin levels (leptin is a positive regulator of hypothalamic PACAP expression in adulthood) of both sexes were decreased by fasting. On the other hand, hypothalamic PAC1 mRNA expression did not change during the neonatal to pre-pubertal period in either sex; however, its levels were consistently higher in males than in females. Hypothalamic PAC1 mRNA expression was decreased by 24 h fasting in males, but no such changes were observed in females. These results indicate while hypothalamic PACAP expression is sensitive to a negative energy state and the serum leptin level in adulthood, no such relationships are seen in the pre-pubertal period. In addition, we speculate that differences in the gonadal steroidal milieu might induce sexual dimorphism in the basal hypothalamic PAC1 mRNA level and its response to fasting. The mechanisms responsible for and the physiological effects of such changes in hypothalamic PACAP and PAC1 expression during the developmental period remain to be clarified

The effects of chronic testosterone administration on body weight, food intake, and adipose tissue are changed by estrogen treatment in female rats

In females, estrogens play pivotal roles in preventing excess body weight (BW) gain. On the other hand, the roles of androgens in female BW, appetite, and energy metabolism have not been fully examined. We hypothesized that androgens’ effects on food intake (FI) and BW regulation change according to the estrogens’ levels. To evaluate this hypothesis, the effects of chronic testosterone administration in ovariectomized (OVX) female rats with or without estradiol supplementation were examined in this study. Chronic testosterone administration decreased BW, FI, white adipose tissue (WAT) weight, and adipocyte size in OVX rats, whereas it increased BW, WAT weight, and adipocyte size in OVX with estradiol-administered rats. In addition, chronic testosterone administration increased hypothalamic CYP19a1 mRNA levels in OVX rats, whereas it did not alter CYP19a1 mRNA levels in OVX with estradiol-administered rats, indicating that conversion of testosterone to estrogens in the hypothalamus may be activated in testosterone-administered OVX rats. Furthermore, chronic testosterone administration decreased hypothalamic TNF-α mRNA levels in OVX rats, whereas it increased hypothalamic IL-1β mRNA levels in OVX with estradiol-administered rats. On the other hand, IL-1β and TNF-α mRNA levels in visceral and subcutaneous WAT and liver were not changed by chronic testosterone administration in both groups. These data indicate that the effects of chronic testosterone administration on BW, FI, WAT weight, and adipocyte size were changed by estradiol treatment in female rats. Testosterone has facilitative effects on BW gain, FI, and adiposity under the estradiol-supplemented condition, whereas it has inhibitory effects in the non-supplemented condition. Differences in the responses of hypothalamic factors, such as aromatase and inflammatory cytokines, to testosterone might underlie these opposite effects

生後早期の心理的ストレスが雌雄ラットの性成熟、性行動に与える影響

Purpose: We studied the influence of psychological stress during the early neonatal period on sexual maturation and sexual behavior in rats. Methods: Neonatal male and female rats were divided into control (C) and maternal separation (MS) groups (n = 20‐24 per group). The pups in the MS groups were placed in isolation cages for 240 minutes/d from postnatal days 2‐11. Vaginal opening (VO) in females and preputial separation (PS) in males (indicators of sexual maturation) were monitored, as was the estrous cycle in females. Thereafter, sexual behavior was monitored twice at 13 and 15 weeks of age. Results: As for sexual maturation, the onset of PS occurred significantly earlier in the MS group than in the C group, whereas the onset of VO did not differ between the groups. The length of the estrous cycle did not differ between the groups. The frequencies of sexual behaviors did not differ between the groups in either sex. Conclusions: In conclusion, early‐life psychological stress induced by MS advanced sexual maturation in male rats, whereas it did not affect sexual maturation in female rats. On the other hand, early‐life psychological stress might not affect sexual behavior in adulthood in either sex

胎生期に低栄養を経験した雌ラットにおける加齢時の食欲促進因子および抑制因子の発現に関する研究

Fetal growth retardation, which affects short- and long-term fetal brain development, is associated with metabolic, hematological, and thermal disturbances, which can increase the risk of metabolic syndrome later in life. Orexigenic and anorexigenic factors regulate food intake and energy expenditure. We studied how the expression of these factors was affected by food deprivation (FD) in middle-aged female rats that had been subjected to prenatal undernutrition. Eight pregnant rats were divided into two groups,the normal nutrition (NN) (n = 4) group and the undernutrition (UN) (n = 4) group, which received 50%(approximately 11 g) of the daily food intake of the normal nutrition rats from day 13 of pregnancy to delivery. The pups from these dams were defined as the maternal NN (mNN) and maternal UN (mUN) groups, respectively. After weaning, all of the pups were housed and allowed ad libitum access to food and water. At the age of 6 months, both groups of pups were sub-divided into three groups. One group was allowed to consume normal amounts of food (Fed), and the other two groups were subjected to 24 h or 48 h FD (n = 7–8 per group). The rats’ serum leptin levels and hypothalamic mRNA expression levels of various orexigenic or anorexigenic factors were measured. In both the mNN and mUN rats, the serum leptin levels of the 24 h and 48 h FD groups tended to be lower than those of the Fed group, and the serum leptin levels of the 24 h FD mUN rats and the Fed mUN rats differed significantly. The hypothalamic neuropeptide Y (NPY) mRNA expression levels of the 24 h and 48 h FD groups were significantly higher in the mUN rats than in the mNN rats. In addition, among the mUN rats the hypothalamic NPY mRNA expression levels of the 48 h FD group were significantly higher than those of the Fed group. In both the mNN and mUN rats, prepro-orexin mRNA expression was lower in the 48 h FD group than in the corresponding Fed group. Among the mUN rats, the 48 h FD group exhibited significantly lower hypothalamic proopiomelanocortin (POMC) mRNA expression than the Fed group, and a similar tendency was seen among the mNN rats. Among the mNN rats, the 24 h FD group displayed significantly higher hypothalamic leptin receptor (OBRb) mRNA levels than the Fed group. However, no such differences were seen among the mUN rats. As a result, the hypothalamic OBRb mRNA expression levels of the mUN rats in the 24 h and 48 h FD groups were lower than those of the corresponding mNN rat groups. These findings indicate that rats that are subjected to prenatal undernutrition exhibit upregulated expression of orexigenic factors and are more sensitive to FD in middle age, which might increase their risk of developing metabolic disorders in later life

Clinical outcome of various metformin treatments for women with polycystic ovary syndrome

Aim: Polycystic ovary syndrome (PCOS) is an ovulatory disorder and insulin resistance and diabetes are involved in its pathophysiology. Metformin, an anti‐diabetic agent, has been reported to be useful to induce ovulation. Methods: Metformin treatment was classified into four types: (1) clomiphene–metformin combination treatment for clomiphene‐resistant patients; (2) clomiphene–metformin combination for clomiphene‐sensitive patients; (3) clomiphene–metformin combination for naïve patients; and (4) metformin monotherapy. The patients underwent physical, endocrinological, and clinical examinations for their ovulation rates, pregnancy rates, and follicular development. Results: The ovulation rates, pregnancy rates, and single follicular development were not significantly different among the clomiphene–metformin combination treatment groups. In the Body Mass Index (BMI) subanalysis, the pregnancy rate was higher in the BMI≥30 kg/m2 group than in the other three groups with a BMI of ≤30 kg/m2 in both cycles and cases. The ovulation rates and pregnancy rates were significantly higher in the group with a fasting insulin of ≥15 μU/mL than in the groups with a fasting insulin of <15 μU/mL in both cycles and cases. Conclusion: Clomiphene–metformin combination treatment appears to be useful, at least for clomiphene‐resistant patients, and a BMI of >30 kg/m2 and a fasting insulin of ≥15 μU/mL appear to be predictors of a good result with this treatment

生後早期の免疫ストレスによる成長後の性行動の低下は、血中アンドロゲン濃度の低下と無関係に起きる

Purpose: It is known that various types of stress in early life increase the incidence of diabetes, myocardial infarctions, and psychiatric disorders in adulthood. We examined the mechanism by which neonatal immune stress reduces sexual behavior in adult male rats. Methods: Male rats were randomly divided into 3 groups: the control (n=17), postnatal day 10 lipopolysaccharide (PND10LPS) (n=31), and PND25LPS (n=16) groups, which received intraperitoneal injections of LPS (100 μg/kg) or saline (injection volume: ≤0.1 ml/g) on postnatal days 10 and 25. In experiment 1, male rats (age: 11 to 12 weeks) were put together with female rats in a one-to-one setting for mating, and sexual behavior (mounting, intromission, and ejaculation) was monitored for 30 minutes. The serum levels of luteinizing hormone (LH) and testosterone (T) and the hypothalamic mRNA expression levels of factors related to sexual behavior were examined. After experiment 1 finished, the remaining 37 male rats were used for experiment 2: the control group (n=8), PND10 LPS group (n=21) and PND25LPS group (n=8) these rats had been given an i.p. injection of the saline during the expriment1. All of the rats were orchidectomized at 14 weeks of age. After a 3 week recovery period, a silastic tube containing crystalline T was subcutaneously implanted into the back of each rat. The rats’ sexual behavior, serum hormone concentrations, and hypothalamic mRNA expression levels were assessed. Results: In experiment 1, preputial separation occurred significantly later in the PND10LPS group than in the control group. The frequency of sexual behavior was significantly lower in the PND10LPS group than in the control group. The serum T concentrations of the PND10LPS and PND25LPS groups were significantly lower than that of the control group, but the serum LH concentrations of the 3 groups did not differ significantly. The hypothalamic mRNA expression levels of progesterone receptor B (PRB) and gonadotropin-releasing hormone (GnRH) were significantly lower in the PND10LPS and PND25LPS groups than in the control group, whereas the hypothalamic PRA+B mRNA expression levels of the 3 groups did not differ significantly. In experiment 2, after T supplementation the frequency of sexual behavior was significantly lower in the PND10LPS and PND25LPS groups than in the control group, although there were no significant differences in the serum T or LH concentrations or the hypothalamic PRB, PRA+B, or GnRH mRNA expression levels of the 3 groups. Conclusion: In male rats, immune stress in the early neonatal period delayed sexual maturation, reduced sexual behavior, suppressed the serum T concentration, and downregulated the hypothalamic mRNA expression levels of GnRH and the PR in adulthood. The delayed sexual maturation was presumed to have been caused by the reduction in the serum T concentration. However, the rats that experienced neonatal stress exhibited reduced sexual behavior irrespective of their serum T concentrations

Prenatal undernutrition disrupted the sexual maturation, but not the sexual behavior, in male rats

Purpose: Exposure to various stressors, including psychological, metabolic, and immune, in the perinatal period induces long‐lasting effects in physiological function and increase the risk of metabolic disorders in later life. In the present study, sexual maturation and sexual behavior were assessed in prenatally undernourished mature male rats. Methods: All the pregnant rats were divided into the maternal normal nutrition (mNN) group and the maternal undernutrition (mUN) group. The mUN mothers received 50% of the amount of the daily food intake of the mNN mothers. Preputial separation and sexual behavior were observed in randomly selected pups of the mNN and mUN groups. Results: The body weight of the mothers was significantly lighter in the mUN group than in the mNN group. Similarly, the pups in the mUN group showed a significantly lower body weight than those in the mNN group from postnatal day (PND) 1 to PND 15. The preputial separation day was significantly delayed in the mUN group, compared to the mNN group. Sexual behavior did not show any significant difference between the two groups. Conclusion: These findings indicated that prenatal undernutrition delayed sexual maturation, but did not suppress sexual behavior, in mature male rats