# Onion Peel Powder's Impact on the Leptin Receptors in the Hippocamp of Obese Rats
## 4 Discussion
The increase in the number of astrocytes in the hippocampus in obesity is linked to similar mechanisms of inflammation and cellular stress seen in other brain regions, such as the hypothalamus, but with unique implications for cognitive functions like learning, memory, and mood regulation. The increase in astrocytes in the hippocampus in obesity is a response to metabolic, inflammatory, and oxidative stress. While initially protective, this response becomes maladaptive when inflammation is persistent. As a result, the overactivity and proliferation of astrocytes can impair hippocampal function, potentially contributing to the cognitive and emotional challenges often seen in individuals with obesity. Understanding these mechanisms highlights the potential for therapeutic strategies targeting inflammation and astrocyte reactivity to protect hippocampal function and improve cognitive outcomes in individuals with obesity [49; 50; 51]. Obesity is a social, health, and therapeutic problem. The World Health Organization (WHO) classified obesity as an epidemic of our time, with over 50% of adults struggling with overweight and/or obesity. Flavonoids, present in onions, among other substances, are increasingly used in the prevention and treatment of obesity. One of the most active is quercetin, which controls the adipose tissue mass by inducing adipocyte apoptosis or inhibiting their formation [52]. The reduction in body weight observed after taking onion peel powder may be related to its bioactive compounds (quercetin), which affect metabolic and hormonal pathways. Quercetin can activate AMP-activated protein kinase (AMPK), promoting fatty acid oxidation and glucose uptake while inhibiting fat storage, which additionally helps in weight reduction [53]. Furthermore, onion peel might influence gut microbiota, which can improve metabolism and leptin signaling [54]. Quercetin has also been demonstrated to exert neuroprotective effects due to its anti-inflammatory properties, and furthermore, it improves cognitive functions [55; 56]. In addition, quercetin reducesthe production of pro-inflammatory cytokines, suppresses pro-inflammatory pathways such as NF-kB, and enhances anti-inflammatory mediators like IL-10, potentially restoring the balance of adipose tissue. This may indicate significant benefits in limiting cellular changes associated with inflammation [10; 57]. However, there is a lack of information on how bioactive compounds affect the structure and functioning of the brain after exposure to a high-energy diet. It is known that obesity is associated with an increase in the presence of inflammatory cytokines in the hippocampus, which in turn impairs its neuroplasticity, resulting in damaged hippocampus-dependent memory [58; 59]. The presented study revealed that bioactive components in onion peel powder resulted in a significant increase in the mean number of LepR-IR neurons in obese animals. Conversely, no significant changes were noted in the average number of LepR-IR neurons in the groups of \"non-obese\" rats. Furthermore, our findings reveal that the mean size of LepR-IR neurons was markedly larger in the group of obese rats that were administered onion peel powder with food in comparison to the obese group. It can be reasonably inferred that the bioactive compounds in onion peel powder probably exert an anti-inflammatory effect by reducing the cellular changes that manifest in the hippocampus as a consequence of obesity. The present study is limited because it does not include additional analyses, which some may consider a key element in the scientific process. The study aimed to determine the immunoexpression of leptin receptors in the rat hippocampus using the IHC method based on data from the existing global literature, indicating that the leptin receptor is widely distributed in the hippocampus, particularly in rodents [14; 19].