It is common knowledge that Glucose is one of the human body’s main fuels. At an energy-rich monosaccharide sugar level, glucose is broken down in human cells with the purpose of producing adenosine triphosphate. Adenosine triphosphate (ATP) empowers millions of biochemical reactions taking place in the human body.
It is a known fact that the body gets its glucose from the food we consume, especially food that is rich in starch, like bread, pasta, rice, potatoes, etc. Starch is a chain of glucose molecules called polysaccharides that gets broken down by the digestion enzymes in the independent glucose molecules.
Regulation Of Blood Glucose Level In Our Body!
Glucose gets absorbed into the bloodstream in the small intestine and moves to the liver through the hepatic portal vein. The liver cells in our body absorb most of this glucose and convert it to an insoluble polymer of glucose called glycogen.
Glycogen is stored by the liver and can be converted to glucose again when blood sugar levels fall. There are other types of simple sugars like sucrose, lactose, and fructose, which are fuels that aid the production of Adenosine triphosphate as well.
All cells in the human body need to produce energy and most of these can work with other fuels like lipids except nerve cells, which are known as neurons that are completely dependent on glucose for energy. This makes maintaining ideal blood-glucose levels important for the efficient functioning of the nervous system.
If blood sugar levels drop too low, which is called hypoglycemia, or spike too high, which is called hyperglycemia, it can lead to compromised neurological processes in the mind.
Sometimes, most human beings experience the effects of the drop in blood glucose level levels in the form of weakness, light-headedness, shakiness, and poor concentration.
However, chronic hyperglycemia, which is commonly referred to as diabetes causes neurological problems as well and can possibly lead to renal failure and atherosclerosis.
Glucose is one of the body’s principal fuels. It is a monosaccharide sugar that is rich in energy. It is broken down in the cells to produce ATP.
The human body obtains glucose from the food that is consumed, mainly starch-rich foods such as potatoes, rice, bread, and pasta. Starch is a polysaccharide, which is a chain of glucose molecules that is broken down by the digestive enzymes into independent glucose molecules.
Glucose is absorbed into the bloodstream in the small intestine, after which it travels to the liver via the hepatic portal vein. The liver cells, hepatocytes take in much of the glucose and change it into glycogen, glucose’s insoluble polymer.
This is deposited in the liver and can be reconverted into glucose when blood sugar levels fall. Some other simple sugars in daily diet such as fructose, sucrose, and lactose aid the production of Adenosine triphosphate as well.
All the human body’s cells need to make energy and while most can use other fuels such as lipids, Neurons, which are nerve cells depend almost exclusively on glucose for their energy, which is why the maintenance of blood sugar levels is essential for the proper functioning of the nervous system.
If sugar levels fall below the normal range (hypoglycemia) or rise beyond the normal range (hyperglycemia), it can lead to the neurological processes in the brain being compromised.
At times, most of us have experienced the side effects of low blood glucose levels like feeling light-headed, weak, and shaky, along with poor concentration.
Chronic hyperglycemia, which is a common feature of diabetes mellitus, also causes neurological problems and can be a potential contributory factor to both atherosclerosis and renal failure.
Regulation of Glucose
Over 24 hours a day, a person’s blood sugar levels fluctuate depending on the intake of food. Post meals, when the body is in an absorptive mode absorbing nutrients from the gut, glucose levels tend to rise, which is mitigated by the storage of glucose in the liver.
Post digestion and absorption of nutrients, when the body is in post-absorptive mode and the cells use glucose to produce energy, blood sugar levels level tend to drop.
In spite of these fluctuations, the body has to maintain blood sugar levels within a specific limit and the homeostatic mechanisms are responsible for maintaining normal blood glucose level levels.
Normal fasting blood sugar levels are usually in the 3.3 and 6.1mmol/L range and results exceeding this range could be an indication of diabetes.
The pancreas, a gland under the stomach, plays a vital role in blood glucose level regulation and exocrine as well as endocrine function.
The exocrine gland produces digestive enzymes which are secreted in the duodenum through the pancreatic duct. More than 90% of the pancreatic functions are dedicated to its exocrine functions.
The endocrine gland secretes different hormones that regulate blood sugar levels, which include glucagon, somatostatin, and insulin.
Response to Increased blood glucose level levels
When the body is in the absorptive state, a spike in blood sugar levels is identified by the beta cells of the islets of the pancreas, thus leading them to spike the release of insulin in the bloodstream. Insulin causes stimulation of muscle and adipose cells to absorb glucose from the blood.
- The transport of glucose into cells and Insulin
In order to penetrate cells, glucose needs a family of transmembrane transporters, which are known as GLUT (Glucose Transporter), of which the most diverse is GLUT4, which is found on fat cells and muscle.
Upon binding of insulin to the insulin receptors, cells are triggered to elevate the number of glucose transporters, which leads to more glucose being transported into cells, which in turn will cause a corresponding fall in blood sugar levels.
The hormone insulin’s effects on the body’s cells include:
- The promotion of glycolysis, which breaks down blood glucose level for cellular energy
- The promotion of glycogenesis, which helps in conversion of glucose to glycogen for storage
- The inhibition of lipolysis, which breaks down lipids for the release of energy.
So, insulin’s main function is to help the body use carbohydrates as an energy source and spare its reserves of fat.
Response to decreased blood glucose level levels
When the body is in the post-absorptive state, insulin, and blood sugar levels drop, which causes Pancreas’s alpha cells to release the hormone glucagon.
Unlike insulin, glucagon increases blood sugar levels and encourages the body to spare glucose utilization.
Glucagon mainly works on the hepatocytes in the liver:
- For the conversion of glycogen into glucose and release it into the bloodstream.
- Encourage gluconeogenesis, which manufactures glucose from lactic acid and other metabolites.
The binding of glucagon to glucagon receptors triggers a sequence of linked enzyme reactions that result in the activation of glycogen phosphorylase, which is an enzyme that is responsible for the mobilization of reserves of glycogen into free glucose. The release of Glucagon is hindered by somatostatin as well as insulin.
The control of blood sugar levels is a good example of homeostatic control through negative feedback, where the corrective response, stimulated by deviation from normal blood glucose level, is deactivated by a return to normal levels.
For instance, a drop in blood glucose level causes the production of glucagon, which raises blood sugar levels. Therefore, as blood glucose level rises, the signal to produce glucagon is deactivated.
Other hormones that regulate blood sugar levels levels
Besides glucagon and insulin, there are a host of other hormones like somatostatin that play a vital role in the regulation of blood sugar levels.
Somatostatin reduces the motility of the gut, furthers nutrient absorption, and inhibits pancreatic exocrine secretions.
- Gastrin and Cholecystokinin
The GI tract releases hormones like gastrin and cholecystokinin, which trigger the pancreas to release insulin by predicting the absorption of nutrients.
- Stress hormones
When the body is under stress, the neuro-endocrine functions cause the release of stress hormones like adrenaline (epinephrine), which spikes blood glucose level levels by mobilization of glycogen and suppression of the release of insulin.
Other hormones like pancreatic polypeptide (PP) and amylin also play a part in the regulation of blood sugar levels, but their roles are still not understood very clearly.
Neuroregulation of blood glucose level levels
The nervous system’s autonomic division is responsible for modulating the release of glucagon and insulin. The supportive stimulation occurring with exercise triggers glucagon production, which in turn maintains blood glucose level levels which would otherwise drop as muscles utilize glucose for energy.
During the resting phase, parasympathetic activity triggers the digestion as well as the release of insulin in order to deal with the expected spike in blood glucose level levels.
So, while there are still many aspects of the complex function of blood glucose level regulation that are yet to be understood, Diabetes is essentially a dysfunction of the metabolism of glucose in the human body.
Amanda Wingfield is a certified Diabetes Management Specialist who also holds an MD in Endocrinology, with certifications from ABIM and AACE. She has a decade of experience serving thousands of patients through her independent practice and has been working in the capacity of an expert diabetes consultant for the past 4 years. Ms. Wingfield is revered by her regular readers for her in-depth research and evidence-based analysis of diabetes medications, supplements, and treatments, and her highly critical style of writing.