Timing in Glucose Metabolism

By Ifeyinwa Ugo-Amadi

Located in the abdominal cavity, just behind the stomach is an organ that functions as both as an 
endocrine and exocrine gland. It produces hormones such as insulin, glucagon, somatostatin and pancreatic polypeptide which are important for body metabolism. It also secretes digestive enzymes that assist in digestion and absorption of nutrients. This organ is the pancreas.
Very crucial in the functions carried out by the pancreas is the maintenance of glucose homeostasis in the body. The endocrine cells which are the alpha, beta, delta and gamma cells secrete different hormones for this purpose.  The alpha cells secrete glucagon which increases the level of glucose in the blood by breaking down glycogen stored in the liver cells. The beta cells secrete insulin which reduces the amount of glucose in the body by signalling body cells to take up the glucose for energy and also signals the liver to store up the excess glucose as glycogen. The delta cells secrete somatostatin which regulates the activities of the alpha and beta cells while the gamma cells secrete pancreatic polypeptide which stimulates gastric juice secretion.
It is necessary to regulate the blood glucose level as overtime, high blood glucose levels could result in complications such as cardiovascular disease, nerve damage, kidney damage, blindness and gangrene. Low blood glucose is not better off as it could lead to seizures, loss of consciousness and death. This explains the regulatory relationship between glucagon and insulin – glucagon is secreted in response to need for glucose while insulin is secreted when glucose level is high.
Type 2 diabetes has been described as a complex metabolic disease that arises due to interactions between genetic disposition and environmental factors. One of such environmental factors has to do with disturbance of the circadian rhythms due to loss of sleep or nocturnal lifestyle.  Circadian rhythm is an endogenously generated 24 hour cycle in the physiological processes of living beings which responds primarily to light and darkness in an organism's environment. Cell regeneration, hormone production and other biological activities are linked to this cycle. These rhythms are driven by biological clocks coordinated by a master clock in the brain. Scientists observed that knocking out the clock genes of the pancreas in mice led to obesity and type 2 diabetes due to malfunctioning of the pancreas.
Since organs of the body including the pancreas gets to shut down for each day, it implies that at a certain time of the day (late hours), no gastric juice, insulin or glucagon is secreted by the pancreas. Foods taken at a time when organs involved in glucose metabolism aren’t anticipating glucose can’t be metabolized effectively. This can lead to extra fat in the liver and contribute to diabetes. This is because metabolic disorders can develop when environment, genetics or behaviour disrupts the synchrony of these clocks.

Reference
 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4078443/
http://millar.bio.ed.ac.uk/circad.html
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