Development and evaluation of novel rodent model of PCOS mimicking clinical phenotype in human disease – Middle East Fertility Society Journal

Change in body weight

Obesity, which is more prevalent there than in the general population but not in lean-PCOS, is one of the etiological factors for PCOS. DHT specifically activated the androgen receptor, which led to an increase in body fat, intra-abdominal adipose tissue, and subcutaneous adipose tissue depots, which significantly increased the rats’ body weight. Insulin resistance is not brought on by obesity [31]. There is a significant rise in central adiposity and hyperinsulinemia associated with insulin resistance and type 2 diabetes along with fructose. The increased body weight in DHEA rats was significant when compared to the control groups, in contrast to PCOS women, but was unrelated to changes in relative body fat mass. This might be due to less prolonged fructose consumption.

Estrous cyclicity impairment

While the estrus cycle of the DHEA-exposed rats was arrested in the estrus stage and showed longer cycle duration when compared with control group, the androgen DHT induced rat PCOS model exhibits irregular cycles and a predominance of the “pseudo-diestrus” phase. According to our research, fructose causes hyperinsulinemia, increased fat deposition, and disruption of the estrus cycle which is consistent with other study [32]. Rats that were given both androgen and fructose showed impaired cyclicity and diestrus phase arrest.

Oral glucose tolerance test and insulin resistance

Type 2 diabetes, insulin resistance, hyperinsulinemia, and glucose intolerance are more prevalent in women with PCOS. The results of the OGTT demonstrate that type 2 diabetes is present in both androgens and that chronic fructose consumption causes fasting blood glucose levels to be elevated. The level of serum insulin is crucial for regulating blood sugar. When compared to the DHT group, the DHT+ f group’s insulin level was significantly higher. Additionally, the DHEA+F group demonstrated an increase in insulin level, though it was not statistically different from DHEA. In contrast to the DHT+f and DHEA+f animals, which displayed impaired glucose intolerance when compared to the androgen groups, the fructose-treated group demonstrated a normal profile towards glucose tolerance, according to the AUC of various day points. Blood sugar levels were higher in DHT+f and DHEA+f at the 30-, 60-, and 120-min time points, demonstrating each compound’s unique contribution to decreased insulin sensitivity. Metformin, as anticipated, caused a statistically significant decrease in the fasting serum insulin levels in the rats given DHT+f. Concurrent fructose consumption may have led to structural changes in pancreatic cells, resulting in hyperinsulinemia and an inability to control serum blood glucose, which would have indicated insulin resistance [33, 34].

Ultrasonography

Control rat USG ovarian scans reveal the presence of follicles with typical shapes. The USG scan of rats exposed to DHT and DHT+f, on the other hand, shows the formation of multiple follicles. It is interesting to note that fewer follicles are present in the metformin and clomiphene-treated animals than in the DHT+f animals. But compared to control animals, there were more follicles visible. The findings mentioned above indicate that androgen exposure causes cystic induction of PCOS in these animals, but fructose administration concurrently may have exacerbated the absence of cystic follicles. Although less than the DHT+f group, the DHEA+f group has displayed small, oblong, distorted follicles. More than measuring the effects of the treatment groups, the USG scan was intended to confirm the induction of PCOS.

Reproductive hormones

Hyperandrogenism is an important feature for diagnosing of PCOS. Lower FSH levels and increase in LH, testosterone, and E2 in DHT+f group is significant compared with control and DHT group, whereas fructose alone did not much alter hormonal profile. However, FSH decreased, and LH and testosterone significantly increased in the DHEA+ f group compared to the control group. Besides, fructose-consumption significantly profound LH and testosterone levels in animals compared without fructose. Hypersecretion of luteinizing hormone and testosterone levels demonstrates the development of the PCOS hallmark feature that prevents fertilization. The increased production of testosterone precursors or dysregulation of the androgen synthesis process due to a rate-limited enzyme could both contribute to high levels of excess testosterone. In the present study, estradiol levels are significantly higher in DHT +f on compared with DHT and control group showing responsible cause lower FSH level causing anovulation in ovary.

Reproductive organ and body fat weights

Due to excessive cyst formation brought on by abnormal folliculogenesis and steroidogenesis, the ovarian weight of the DHT+f and DHEA + f groups was significantly higher than that of the control DHT and DHEA groups. The development of the reproductive organs is, however, said to be stunted in female rats exposed to DHT due to altered hormonal balance. In the current study, we discovered that, when compared to the control group, the rats exposed to DHT for 90 days produced a significant decrease in ovarian weight. In contrast to the control group, the fructose group did not significantly reduce the weight of the ovaries. By likely normalizing folliculogenesis and steroidogenesis, metformin, and clomiphene significantly reduced ovary weight, indicating a promising role for treatment in PCOS women. In line with earlier studies on the DHT model, DHT increased the depots of abdominal fat. The assessment of abdominal and subcutaneous fats revealed profound obesity, a prominent phenotype seen in PCOS women, in the DHT+f group when compared to the control and DHT groups. Such reduced fats may be the result of hyperinsulinemia, steroidogenesis, and insulin resistance. On the other hand, DHEA +f was not found to be significant when compared to the DHEA group, failing to establish an obese state. This may be because fructose was administered to patients with DHEA for a shorter period of time.

Histopathology

The control group’s representation of the graafian follicle in Fig. 10a is very clear, showing an ovum that is immediately encircled by corona radiata. The zona granulosa layer, which has nucleated granulosa cells, and the antrum (a fluid-filled space) are also parts of the graafian follicle. Figure 10b and c of the DHT and DHT+F groups show large antral follicles and a thickened theca interna cell layer, but no ovum or granulosa cells are present. These show that polycystic ovary is present. Additionally, atresia-prone follicles are seen. The animals that received DHT showed disruptive characteristics, such as the presence of numerous large follicles with large fluid-filled antral spaces, atretic and cystic follicles, a distinctive hyperthecosis of the internal layers, and thinning of the zona granulosa, but in DHEA+F, zona granulosa were thick, the presence of cystic follicles is due to the abnormal androgen levels like risen luteinizing hormone, testosterone levels, and decreased follicle-stimulating hormone levels. Metformin did not seem to have a major impact, though there were some follicles with a healthy granulosa layer and lesser number of cystic follicles as compared to animals exposed to DHT+F alone.

In the group that has been treated with clomiphene, there is evidence of a developing follicle with an antrum and an ovum that is encircled by granulosa cells. The presence of the corpus luteum signals ovulation. In the group that only received fructose alone, no noteworthy results were found.