Leptin and Ghrelin Hormones and Body Weight (Research Paper Sample)

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Leptin and Ghrelin Hormones and Body Weight
Abstract
Background: Hormones play a significant role in regulating the amount of food taken by the body. These hormones are produced from various organs and each of them plays its significant role. Ghrelin and leptin are examples of hormones that play a role in food intake. In addition, the food eaten contributes to the weight together with other factors. The objective of the research is to analyze the effects of leptin and ghrelin on the body weight.
Materials and Methods: The study includes the analysis of various articles that have extensively covered the two hormones. In addition, it compares their study methods to enable the development of a valid conclusion. All the studies were conducted separately although they are related in that they talk about the same hormones.
Results: Leptin and ghrelin are like antagonist hormones. High levels of leptin in plasma and low levels of ghrelin can contribute to an increase in weight that had previously been lost. These hormones are produced under the influence of various factors although both of them are controlled by the hypothalamus.
Conclusions and Recommendations: Although there are various factors that can be used in the management of weight in patients who are classified to have excess weight or underweight based on their body mass index, the control of plasma ghrelin and leptin can be of great help. These hormones can be applied in controlling some of the growing concerns as increases in obese individuals worldwide.
Research Question
To what extent do Ghrelin and leptin hormones contribute to weight changes in human beings of various age-groups?
Introduction
A person’s stability in weight is determined by the quantity of food and other metabolites and the amount spent in metabolism (Klok, Jakobsdottir and Drent 22). In the case where the intake is more than the body’s metabolic rate, there is a tendency of an increase in weight. In addition, an increase in the body requirement and expenditure that is not proportional to the input results into a weight loss. However, there is an assumption that all the factors that affect metabolism are kept constant.
Weight is affected by various factors, some of which are modified knowingly by an individual whereas others are modified without knowing. However, these factors are related and cannot be dealt with independently. Some of the factors as the endocrine system modify certain behaviors that affect body weight. Leptin and Ghrelin are examples of hormones that affect body weight (Coll et al. 572).
Comparison and Analysis of the Articles
Ghrelin and leptin play a paramount role, not only in regulating the amount of food eaten, but also the weight of a person (Klok, Jakobsdottir and Drent 23). Therefore, these hormones have different quantities in different body states. The hormones are protein in nature. All of them are polypeptides, although leptin has a larger amino acid chain compared to ghrelin (Stylianou et al. 295). The main site of production of leptin is the adipose tissue. In addition, there are other body tissues that are capable of producing small quantities of leptin such as the stomach, placenta, lining of the mammary gland, and the heart (Klok, Jakobsdottir and Drent 23).
After production, leptin is released into the circulation, and it acts through its receptors that are located various body parts. The attachment to its specific receptors enables it to produce both local and systemic effects. Interestingly, circulating leptin is capable of crossing the blood-brain barrier and the cerebral spinal fluid (Stylianou et al. 295). The crossing into the blood-brain barrier enables it to bind to leptin receptors that are located in the hypothalamus. Its attachment to the hypothalamus has an impact on the manner in which certain genes are encoded and expressed, for example, the obesity gene (Klok, Jakobsdottir and Drent 22). Therefore, according to Stylianou et al. leptin has a higher concentration in obese people and a comparatively lower concentration in lean individuals (296).
Leptin can induce weight loss in an individual (Crujeiras et al. 5037). Weight loss comes as a result of decreasing the food intake as a result of suppressed appetite (Klok, Jakobsdottir and Drent 23). In addition, leptin increases the physical activity and the overall metabolic rate leading to increased energy consumption and a negative energy balance that predisposes one to weight loss (Crujeiras et al. 5038). According to Littman et al. (2), the regulation of energy balance by leptin is a long-term strategy that acts after a long duration of exposure.
Ghrelin is a twenty-eight amino acid polypeptide chain that is primarily produced in the stomach (Stylianou et al. 296). As opposed to leptin, is a fast-acting hormone and plays a paramount role in creating a positive energy balance. The action is as a result of increased intake of food and low expenditure in the form of metabolism. According to Littman et al. (8), a study that involve obese individuals, there was a decrease in ghrelin in most obese individuals, with the exception of those who had some genetic abnormalities as the Prader – Willi Syndrome.
The effects of ghrelin on energy balance are regulated by the hypothalamus (Coll et al. 572). Once ghrelin is produced by the stomach, it goes into the bloodstream and reaches the brain where it can cross the blood-brain barrier and bind to the receptors in the hypothalamus (Klok, Jakobsdottir and Drent 24). Ghrelin reduces leptin-induced reduction in food intake by affecting the expression of certain peptides (Klok, Jakobsdottir and Drent 24). In addition, ghrelin has also been shown to induce food intake among healthy and obese human beings by inducing hunger. A study with mice as subjects showed that an increase in food intake after giving ghrelin is attributed to the stimulation of gastric emptying (Lindqvist et al. 123)
The levels of ghrelin and leptin in plasma are affected by various factors. An example is the presence or absence insulin resistance. Obesity is presumed to be a predisposing factor to insulin resistance. It is expected that with obesity, there is a decrease in leptin levels and an increase in ghrelin levels (Klok, Jakobsdottir and Drent 25). However, in a study by Stylianou et al. (296), it was found that the plasma levels of ghrelin were found to be lower in obese adolescents who had insulin resistance compared to obese adolescents who did not have insulin resistance, or those who were not obese.
In addition, according to Hassanain et al. (121), the levels of ghrelin in serum are significantly lower in obese people compared to those who are not obese. Although the study involved children, the results are similar to the findings by Stylianou et al. Low levels in ghrelin is attributed to a down- regulatory mechanism by an increased amount of insulin or leptin (Hassanain et al. 119). The down-regulation is thought to be a physiological adaptation to the high positive energy balance that is associated with obesity (Hassanain et al. 119).
Insulin resistance is associated with an increase in insulin in circulation. According to a study by Stylianou et al. (297), an increase in circulating insulin did not have a significant effect on the ghrelin levels in plasma. However, therapeutic doses of insulin could decrease the circulating plasma ghrelin depending on the dose (Stylianou et al. 299). Therefore, in obese individuals who have an increased level of insulin in the blood, the low levels of ghrelin can be attributed to insulin (Stylianou et al. 299).
Ghrelin is thought to play a pivotal role in meal initiation (Klok, Jakobsdottir and Drent 24). However, according to a study by Andreas et al. (125), there are certain factors that can increase the serum concentration of leptin and lower the level of ghrelin even with overeating and obesity. An example is the palatable diet. The study that involved the use of rats and mice found out that despite an increase in leptin and a decrease in ghrelin, the rats still had a tendency of overeating (Lindqvist et al. 123). Therefore, neither leptin nor ghrelin can control the food intake and energy expenditure in rats that are exposed to palatable food (Lindqvist et al. 131).
In addition, the expression of ghrelin and leptin could be affected by the type of nutrients ingested (Lindqvist et al. 131). Another study also revealed that in humans, certain conditions as obesity and anorexia nervosa could also contribute to a loss in the plasma ghrelin levels that is related to the intake from meals (Stylianou et al. 299).
In a study involving the mice where increased leptin concentration did not induce a reduced food intake indicates the suppression in action of leptin (Lindqvist et al. 131). The effectiveness of leptin to reduce the food intake could be attributed to the development of resistance to leptin. Leptin resistance has also been demonstrated in obese human beings who have high levels of leptin in serum and adipose tissue, yet they have very little response to the treatment with leptin (Klok, Jakobsdottir and Drent 25). The trend could be attributed to long periods of overeating. This affects the functioning of the leptin system so that the hypothalamus that is responsible for its regulation becomes less sensitive to the increasing heparin level (Klok, Jakobsdottir and Drent 25).
The resistance of obese patients to leptin has posed a challenge to the medical team in their efforts to manage obesity. They have been put to task in developing drugs that can overcome the loss of sensitivity to leptin by the hypothalamus (Stylianou et al. 297). Alternatively, the remedy can involve an alteration in the normal pathways in leptin functioning through the development o...