The effects of chronic testosterone administration on body weight, food intake, and fat weight were age-dependent

Previously, we showed that chronic testosterone administration increased body weight (BW) and food intake (FI), but did not alter fat weight, in young female rats. To examine our hypothesis that the effects of androgens on BW, FI and body composition might be age-dependent, the effects of chronic testosterone administration were evaluated in rats of different ages; i.e., young and middle-aged rats. Although chronic testosterone administration increased BW gain, FI, and feed efficiency in both young and middle-aged rats, it increased visceral fat weight in middle-aged rats, but not in young rats. Therefore, it is possible that testosterone promotes the conversion of energy to adipose tissue and exacerbates fat accumulation in older individuals. In addition, although the administration of testosterone increased the serum leptin level, it did not alter hypothalamic neuropeptide Y mRNA expression in middle-aged rats. On the contrary, the administration of testosterone did not affect the serum leptin levels of young rats. Thus, testosterone might induce hypothalamic leptin resistance, which could lead to fat accumulation in older individuals. Testosterone might disrupt the mechanisms that protect against adiposity and hyperphagia and represent a risk factor for excessive body weight and obesity, especially in older females

Effects of chronic testosterone administration on the degree of preference for a high-fat diet and body weight in gonadal-intact and ovariectomized female rats

Energy balance and reproductive functions are closely linked in some species. The sex hormones (estrogens and androgens) are involved in the regulation of appetite, metabolism, body weight (BW), and body composition in mammals. Previously, we showed that the effects of testosterone on BW, appetite, and fat weight were markedly affected by alterations to the gonadal hormonal milieu. In this study, we examined whether testosterone administration changes food preferences and whether these effects of testosterone depend on gonadal status in female rats. We also evaluated the underlying mechanisms responsible for these effects, focusing on hypothalamic inflammation and endoplasmic reticulum (ER) stress. In gonadal-intact (sham) female rats, chronic testosterone administration promoted a preference for a high-fat diet (HFD) and increased BW gain, fat weight, and adipocyte size, whereas no such effects were observed in ovariectomized (OVX) rats. Testosterone administration increased hypothalamic interleukin-1 mRNA expression in the sham rats, but not the OVX rats. On the contrary, testosterone administration decreased the hypothalamic mRNA levels of ER stress-response genes in the OVX rats, but not the sham rats. These testosterone-induced alterations in OVX rats might represent a regulatory mechanism for preventing hypothalamic inflammation and the overconsumption of a HFD. In conclusion, testosterone’s effects on food preferences and the subsequent changes were affected by gonadal status. Testosterone-induced changes in hypothalamic inflammatory cytokine production and ER stress might be related to these findings

Effects of DHT injection

To clarify the direct effects of androgens, the changes in the hypothalamic levels of reproductive and appetite regulatory factors induced by chronic dihydrotestosterone (DHT) administration were evaluated in female rats. DHT treatment increased the BW and food intake of the ovariectomized rats, but not the estradiol (E2)-treated rats. DHT administration suppressed the expression of a hypothalamic anorexigenic factor. Although the kisspeptin (Kiss1) mRNA levels of the anterior hypothalamic block (the anteroventral periventricular nucleus, AVPV) were increased in the E2-treated rats, DHT administration did not affect the Kiss1 mRNA levels of the AVPV in the ovariectomized or E2-treated rats. Conversely, DHT administration reduced the Kiss1 mRNA levels of the posterior hypothalamic block (the arcuate nucleus, ARC) in the ovariectomized rats. Although the Kiss1 mRNA levels of the posterior hypothalamic block (ARC) were decreased in the E2-treated rats, DHT administration did not affect the Kiss1 mRNA levels of the ARC in these rats. Serum luteinizing hormone levels of these groups exhibited similar patterns to the Kiss1 mRNA levels of the ARC. These results showed that DHT affects the production of hypothalamic reproductive and appetite regulatory factors, and that these effects of DHT differ according to the estrogen milieu

Effects of Low Energy Availability on Reproductive Functions and Their Underlying Neuroendocrine Mechanisms

It is known that metabolic disturbances suppress reproductive functions in females. The mechanisms underlying metabolic and nutritional effects on reproductive functions have been established based on a large body of clinical and experimental data. From the 1980s to 1990s, it was revealed that disrupted gonadotropin-releasing hormone (GnRH) secretion is the main cause of reproductive impairments in metabolic and nutritional disorders. From the late 1990s to early 2000s, it was demonstrated that, in addition to their primary functions, some appetite- or metabolism-regulating factors affect GnRH secretion. Furthermore, in the early 2000s, kisspeptin, which is a potent positive regulator of GnRH secretion, was newly discovered, and it has been revealed that kisspeptin integrates the effects of metabolic status on GnRH neurons. Recent studies have shown that kisspeptin mediates at least some of the effects of appetite- and metabolism-regulating factors on GnRH neurons. Thus, kisspeptin might be a useful clinical target for treatments aimed at restoring reproductive functions in individuals with metabolic or nutritional disturbances, such as those who exercise excessively, experience marked weight loss, or suffer from eating disorders. This paper presents a review of what is currently known about the effects of metabolic status on reproductive functions and their underlying mechanisms by summarizing the available evidence

Effects of testosterone injection

The effects of androgens on gonadotropin-releasing hormone (GnRH) secretion in females have not been fully established. To clarify the direct effects of androgens on hypothalamic reproductive factors, we evaluated the effects of chronic testosterone administration on hypothalamic GnRH regulatory factors in ovariectomized (OVX) female rats. Both testosterone and estradiol reduced the serum luteinizing hormone levels of OVX female rats, indicating that, as has been found for estrogen, testosterone suppresses GnRH secretion via negative feedback. Similarly, the administration of testosterone or estradiol suppressed the hypothalamic mRNA levels of kisspeptin and neurokinin B, both of which are positive regulators of GnRH, whereas it did not affect the hypothalamic mRNA levels of the kisspeptin receptor or neurokinin 3 receptor. On the contrary, the administration of testosterone, but not estradiol, suppressed the hypothalamic mRNA expression of prodynorphin, which is a negative regulator of GnRH. The administration of testosterone did not alter the rats’ serum estradiol levels, indicating that testosterone’s effects on hypothalamic factors might be induced by its androgenic activity. These findings suggest that as well as estrogen, androgens have negative feedback effects on GnRH in females and that the underlying mechanisms responsible for these effects are similar, but do not completely correspond, to the mechanisms underlying the effects of estrogen on GnRH

Pilot study of the optimal protocol of low dose step‐up follicle stimulating hormone therapy for infertile women

Purpose: To evaluate the optimized protocol of low dose follicle‐stimulating hormone (FSH) therapy that has a starting dose of 50 IU/62.5 IU with a small increment dose (12.5 IU) for women with World Health Organization (WHO) II ovulatory disorder and unexplained infertility. Methods: Anovulatory women with WHO group II ovulatory disorder (ovulation induction [OI] patients, n = 29), and with an unexplained infertility (ovarian stimulation [OS] patients, n = 21) were enrolled. The protocol of low dose step‐up FSH therapy was optimized for the starting dose as 50 IU (body mass index [BMI] < 20 group) and 62.5 IU (BMI ≥ 20 group) with the increment dose of 12.5 IU. Study outcomes were ovulation, monofollicular development and other variables. Results: In the OIpatients, the ovulation rate was 100% (BMI < 20 group) and 90.9% (BMI ≥ 20 group). Monofollicular development was 80.0% (BMI < 20) and 77.3% (BMI ≥ 20). The pregnancy rate was 60% (3/5 BMI < 20) and 18.2% (4/22 BMI ≥ 20). There was no multiple pregnancy. In the OSpatients, the ovulation rate was 100%. Monofollicular development was 85.7% (BMI < 20) and 76.6% (BMI ≥ 20). No pregnancy was achieved in the OSpatients. Conclusion: Optimized protocol of low dose FSH therapy setting a starting dose 50 IU/62.5 IU by BMI with an increment dose of 12.5 IU was safe and highly effective in WHO group II anovulatory patients. However, this protocol seemed uneffective for patients with unexplained infertility

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

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

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