Morphological characterization of the melanin-concentrating hormone in the brain of humans, rodents, and birds
The regulation of food intake and energy balance is an extremely complex process involving numerous physiological and neurobiological mechanisms. The central nervous system, particularly the hypothalamus, plays a key role in integrating these mechanisms. Signals from various areas of the brain, which originate from peripheral systems such as the digestive system and adipose tissue, arrive in the form of humoral and neural impulses. In response to these factors, the hypothalamus decides whether an increase or decrease in food intake is necessary.
Factors Influencing Food Intake
One of the factors influencing food intake is our mood, which is also affected by the limbic system and other higher brain structures. This complex system explains why some individuals feel hunger in stressful or anxious situations. Understanding these processes is essential for addressing dietary habits and obesity.
Melanin Concentrating Hormone (MCH) and Its Receptors
Melanin concentrating hormone, or MCH, is a peptide consisting of 19 amino acids, first identified in salmon. In the salmon brain, the hormone plays a role in regulating skin color; however, no proven effect on skin pigmentation has been found in mammals. MCH has been detected in the brains of various mammalian species in numerous studies, where it plays a key role in the regulation of food intake and energy homeostasis. The highest concentration of MCH neurons is found in the lateral hypothalamus and the zona incerta, which are responsible for stimulating appetite.
The MCH receptors, MCHR1 and MCHR2, mediate the effects of the hormone. The MCHR1 receptor is widely distributed among mammals, while the functional form of MCHR2 is not found in all species. Interactions between MCH and its receptors fundamentally influence food intake. For example, in cases of starvation, the level of MCH mRNA increases, leading to an increase in food intake. Additionally, studies of transgenic mice have shown that increased expression of MCH can lead to obesity, while the absence of MCHR1 results in reduced food intake without an increase in metabolism leading to obesity.
Neuropathological Studies and the Role of MCH in Mood Disorders
Melanin concentrating hormone not only plays a role in regulating food intake but also projects into the limbic system, influencing the treatment of mood disorders such as anxiety and depression. Molecules capable of inhibiting the MCHR1 receptor, as potential therapeutic agents, may provide promising solutions for mental health issues that pose global challenges in modern society. At the same time, enhancing the activity of the MCH system may also be a target in research aimed at increasing the body weight of livestock.
Research goals include identifying substances that can increase endogenous MCH hormone levels in animals, thereby improving nutritional efficiency and production metrics. To safely investigate the effects on the MCH system, morphological analyses are necessary to aid in understanding the localization of the hormone and its receptors. Research projects will employ various pathological techniques to ensure reliable and comprehensive results.
Immunohistochemical Studies on the MCH System
To morphologically identify melanin concentrating hormone and its receptors, researchers employ various immunohistochemical techniques. Immunohistochemistry allows for the detection of antigens in samples, where primary antibodies and biotinylated secondary antibodies can label the antigens. During this process, color precipitation occurs through enzymatic cleavage of a colorless substrate, enabling visualization of tissues.
Our research group has standardized various methods for identifying MCH and MCHR1, including chromogenic immunohistochemistry, receptor autoradiography, and immunofluorescent immunohistochemistry. During sample preparation, we used formalin fixation and paraffin embedding, as well as freezing in liquid nitrogen. These procedures contribute to the accurate localization of the hormone and its receptors across different species, including mammals and birds.
In our studies, labeling with MCH and MCHR1 antibodies confirmed strong immunopositivity observed in the rat hypothalamus, while dual labeling successfully demonstrated overlap between the hormone and receptor. Our results align with previous research data and contribute to a deeper understanding of the hormone and receptor system, which is crucial for nutritional and neurological research.
