role of hormones in the control of body fuel/energy mechanism has been appreciated for close to a century (Dzamko & Steinberg,2009). This concept was identified by the groundbreaking findings by the scientists, Banting et al. (1922) that the hormone, insulin could effectively restore euglycaemia. This paper seeks to give an in depth understanding of metabolism by definition and gives the various component of metabolism and finally the hormonal influence of metabolism. This paper looks into the various substrates that are influence the hormonal actions in fuel metabolism, circumstances under which they occur and the various pathways followed during these metabolisms (Becker, 2001). The intermediary compounds are also considered to the effect. In conclusion, the paper discuses the medical conditions that would arise once these hormones fail to act.
Metabolism is a biological process that takes place in living organisms throughout their lives, once metabolism stops the individuals automatically dies. A complex process involves high-level cell cooperation with virtually all body cells working in tandem. Metabolism constitutes two words; catabolism and anabolism (Storey, 2004). Catabolism in other words can be referred to as destructive metabolism as it degrades the complex molecules to simple molecules that can be consumed by the cells. During this breakdown, there is energy production which is used in another process that is the opposite of catabolism i.e. anabolism (Storey, 2004). Anabolism involves the building of the complex molecules like carbohydrates, fats, and lipids from the basic molecules like amino acids. In anabolism, there is energy consumption unlike catabolism where energy is produced (Storey, 2004).
Before the metabolism process, the energy sources (food substance that are taken in) are first degraded into simpler substances that can be transported into the cells for metabolism. This process is catalyzed be protein-based substances called enzymes (Storey, 2004). Enzymes shows specificity in their actions and only acts on substrates that are compatible with them. Thus for metabolism to take place, enzymes are required as precursors (Becker, 2001). The breakdown of the complex molecules is necessary as the large particles of the raw food materials cannot pass the semi-permeable walls of the cell membrane of a cell.
Roles of hormones in the control of body fuel/energy mechanism in humans
In the body, metabolism is influenced by several factors amongst them including hormones. The hormones are produced in the endocrine system of the body and are involved in controlling many activities of the body. Besides metabolism, hormones produced by the endocrine system are also involved in mood control, tissue development, growth, and development (Storey, 2004). The deficiency or surpluses of the substrates in the body influence which hormone to be produced and eventually which substrate to be oxidized. In this paper, a number of hormones have been considered in relation to their influence on metabolism.
Insulin is one of the hormones of that influences the metabolism processes, after every meals that is reach in carbohydrates, there is subsequent increase in the sugar level in blood. This contradicts the homeostasis standard of the body in relation to sugar level in the blood. The body the responds by producing insulin hormone that will act on the excess sugar by converting them to glycogen thus reducing the sugar level in blood (Storey, 2004). Subsequently, in the event of starvation, there will be low sugar level experience in blood, because the balance has to be obtained, the body will respond by producing another hormone called glucagon that stimulates the release of glucose into the blood to control the level of sugar.
Apart from glucagon and insulin that are produced by the liver in response to varied sugar levels in the body, ephinephrine and norephiephrine are also hormones produced in the body and unlike insulin and glucagon that has effect in the liver, they have effect in the muscles tissues. In the muscle tissues, they respond to low sugar level in the muscles (Storey, 2004). With regard to this, they will cause more sugar to be transported in the muscles where they can be utilized for the production of energy needed by the muscles.
Thyroid hormone is also responsible for various metabolic influences in human body. It absence necessitates various abnormalities in the body including growth, development and metabolism. The interest in this paper is its metabolic effect. Thyroid hormone influences several metabolic pathways in the cell and this culminates into overall increase in the body Basic Metabolic Rate (BMR). The increase in body BMR has a resultant effect in Adenosine Try-Phosphate (ATP) hydrolysis and increase in the body temperature (Storey, 2004). The metabolic effect of thyroid hormone includes the following; in lipid metabolism, increase of thyroid hormone subsequently leads to increase of fatty acids in the cell plasma and facilitates there oxidation. In carbohydrates metabolism, it influences entry of insulin into the cells and at the same time promotes glycogenolysis and gluconeogenesis (Storey, 2004).
In an event that the hormones are not produced in the dynamic concentration of the substrates, there will be major physiological challenges in the body that can lead to various medical conditions. Failure to metabolize these substrates always leads to a condition. These conditions either can be genetically passed to the succeeding generation or be acquired through lifestyle (Becker, 2001). For instance, failure of the body to respond by producing insulin hormones in the situation where blood sugar level is high normally leads to a medical condition, diabetes type I. On the other hand, failure to secrete glucagon hormone in low sugar level in blood can lead to diabetes type II (Becker, 2001).
Hyperthyroidism is another condition that comes into play due to high concentration of thyroid hormone in blood. The contrary is the hypothyroidism that indicates abnormally low thyroid hormone in the blood. Both situations lead to medical conditions in which the affected shows retarded growth and slow puberty development.
Role of hormones in the control of body fuel/energy mechanism in rats
Close to over seventy years ago, the gene which is responsible for the extreme cases of diabetic and obese phenotype in ob/ob (obese) mouse were positively identified by another scientist, Zhang et al. (1994). Several seminal studies were then published in confirmation of the fact that an expression of a protein product contained in the ob gene called leptin was primarily present in the mammalian adipose tissue. Leptin is a secreted protein which is found in a serum form and its administration leads to a dramatic gain in weight, glucose homeostasis as well as feeding behavior as pointed out by Becker et al. (1995), Campfield et al. (1995), Frederich et al. (1995a) and Cusin et al.(1995). After leptin was discovered, another protein which is secreted by the adipocytes was identified by the screening of CDNA library derived from the adipose as well as by the experiment involving transcript profiling in the differentiation of adipocytes (Maeda et al.
1996).This protein was called adiponectin.
As opposed to the circulating levels of leptin which are usually elevated in obese animals with a reflection of an increase in the size of adipocyte cell in rodents and humans (Frederich et al.,1995b, Frederich et al., 1995),the levels of serum adiponectin as well as the expression of mRNA in the adipose tissue are reduced in obese as well as type 2 diabetic humans. Just like leptin, the administration of the hormone adiponectin was discovered to have certain beneficial effects on insulin sensitivity and glucose homeostasis on obese rodents as indicated in the work of Yamauchi et al., (2001).
The role of glucagon and insulin control of fuel metabolism in humans
The endocrine pancreas is pointed out by Wasserman, O'Doherty and Zinker (1995) to be very important in the control of fuel metabolism by the human liver during intense physical activities such as exercising. The secretions from the pancreases are drained into the portal vein just net to the liver. This anatomical order of things is crucial for the proper hepatic function because pancreatic hormones are known to be the key regulators of the liver's intermediary metabolism. In response to a moderate level of exercise intensity, insulin and glucagon gets secreted from the pancreases in order to decrease or increase the level of metabolism. The roles of insulin and glucagon are opposite to each other. This endocrine response is noted to be crucial for the maintenance of the degree of glucose homeostasis during the exercise period. The rises in the level of glucagon as well as the fall in the level of insulin are noted to be crucial for the simulation of the process of hepatic glycogenolysis. The response of glucagon is important for the gluconeogenesis increase as a result of exercise. Additionally, insulin and glucagon are essential for the process of increasing the rate of hepatic fat oxidation at the time of exercise. The fall in the level of insulin is noted by Wasserman, O'Doherty and Zinker (1995) to enhance the level of NEFA mobilization from the adipose tissue as a consequence of NEFA's availability to the liver. The glucagon increase is noted to enhance the…