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In balance-the relationship between the glucagon-producing alpha cells and the insulin-producing beta cells of the normal endocrine pancreas.

Pancreas

Illustration of a normal pancreas


The pancreas [1] is the organ that produces the insulin hormone. The pancreas also produces glucagon, [2] a hormone in opposition to insulin, which forces the release of glucose [3] into the bloodstream.

Although we focus mainly on its insulin-secreting capabilities, the pancreas is actually comprised of two sections. The endocrine area is connected with natural insulin production. The exocrine [4] area is connected with production of needed digestive enzymes, and is actually the larger of the two, by far. [5] Problems with the exocrine section of the pancreas can produce disorders such as pancreatic insufficiency.

The pancreas produces hormones in the islets of Langerhans. Among them, glucagon is produced by the alpha cells, while insulin and amylin are produced in the beta cells. Somatostatin inhibits the release of all three, and is secreted by the delta cells.

Beta cells and insulin productionEdit

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The pancreas has 2 separate sections, the exocrine, which deals with the digestive process, and the endocrine, which deals with the production of insulin (Beta cells) and glucagon (Alpha cells).

Healthy beta cells are constantly making insulin and storing it, as seen in this photo link below. [6] Those same beta cells release small amounts of insulin day & night, whether the person's eaten or not. This is how the body distributes its natural basal insulin. This is important to the body because it is the basal insulin which allows cells to use blood sugar.

When the insulin level drops, this signals the liver to release glucose by converting stored carbohydrates (glycogen) into glucose for fuel. This release and conversion raises blood glucose levels. It's the body's built in "fail-safe" mechanism to prevent hypoglycemia.

When this occurs, if there are not enough stored carbohydrates in the form of glycogen, the liver will convert protein into glucose in an attempt to keep the body going. If there's not enough carbohydrates or enough protein in the diet, the liver will begin turning body muscle into glucose to keep itself alive.

Glucose [7] is important enough to the bodies of all mammals that there are 5 different glucose transporters [8] which carry it to the various body cells. Each of them distribute glucose to a specific area of the body.

Normal insulin secretionEdit

Insulin glucose

Illustration of how glucose rises after meals and how the normal working pancreas responds by secreting insulin above the basal (body's needs without food) level to manage the rise in glucose. Glucose levels are at top-insulin levels at bottom. The large rises seen in both are due to meals.

White2

Another view of endogenous (produced by the body) insulin production of a non-diabetic human. The basal, or body's needs minus the processing of food, insulin levels are the lower, often wavy lines shown. The sharp peaks represent how the body responds automatically with secretion of additional insulin to handle the extra glucose creating by eating meals, which are referred to as post-prandial (after-meals) on this graph. People using insulin try to re-create this pattern as much as possible by using fast or short-acting insulin at meal times.

In those without diabetes, the healthy pancreas secretes insulin in pulses or spurts. Basal insulin secretion is a series of small pulses or spurts at a given rate day and night; these insulin pulses or spurts are to take care of the body's basic needs. When someone without diabetes eats a meal, the pancreas goes into higher gear, turning out larger quantities of post-prandial insulin to handle the additional glucose created by the food. This phase of insulin secretion is often referred to as the first phase, while the steady, slow basal rate is termed the second phase. [9]

Dogs who don't have diabetes have a similar insulin secreting pattern to people who don't have diabetes, with the same two phases intended for the same purposes as in humans. [10]

It is this pattern that diabetics try to mimic as closely as possible; with basal insulin injections for the body's needs without considering food and bolus insulin injections to cover meals replacing the Basal and Postprandial insulin their bodies no longer produce or do not produce in sufficient quantity. [11]

When there's not enough beta cell insulin production to meet the body's basal needs, it can happen very quickly. The problem is when the beta cells aren't able to produce the needed insulin, the body interprets the low fasting insulin level as a sign the blood glucose levels need to be raised. The liver then dumps a large amount of glucose into the bloodstream, regardless if those levels are high or not. (Human diabetics refer to this as a liver dump.)

The failure of the first phase of insulin discussed above above is what brings about the vicious circle of glucose toxicity, which, in turn, damages even more of the insulin-producing beta cells.

For further information relevant to canine diabetes, see insulin and pancreatitis. I16

ReferencesEdit

  1. Pancreas. Wikipedia.
  2. Glucagon. Colorado State University School of Veterinary Medicine.
  3. Illustration-How Glucose is Released Into the Body. National Institutes of Health.
  4. The Exocrine Pancreas.
  5. Human Pancreatic Acinar Cell Carcinoma Case. Harvard University.
  6. Healthy Beta Cell--Insulin Granules Shown In Red.
  7. Nussey, SS., Whitehead, SA. (2001). Endocrinology-an Integrated Approach-Glucose Turnover. National Institutes of Health (NIH).
  8. Nussey, SS., Whitehead, SA. (2001). Endocrinology-an Integrated Approach-Glucose Transporters. National Institutes of Health (NIH).
  9. Insulin Release. Wikipedia.
  10. Hess, Rebecka S. (May 2008). Managing Diabetes Mellitus in Dogs. DVM 360.
  11. White, John R., et. al. (June 2003). Novel insulins and strict glycemic control. Postgraduate Medicine.

More InformationEdit

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