Blood Sugar Regulation in Mammals

The concentration of glucose in human blood typically ranges between 80–110 mg per 100 cm³ of blood.

This level is maintained to:

1. Supply energy to cells, particularly brain cells, which cannot utilize other energy sources.
2. Maintain osmotic pressure in the blood, which governs the balance of water between blood and surrounding tissues.

1. Eating too many sugary foods: When a person consumes too many sugary or carbohydrate-rich foods, the body cannot produce enough insulin to regulate the sugar, leading to high blood sugar.
2. Lack of exercise: When someone does not exercise, their body does not use glucose for energy. This causes the sugar to remain in the blood instead of entering the cells.
3. Stress: Stress causes the body to release hormones like cortisol, which increases sugar levels in the blood as the body prepares for "fight or flight."
4. Illness: When the body is fighting an illness, hormones are released to help deal with it. These hormones can increase blood sugar levels.
5. Low insulin production: If the pancreas does not produce enough insulin, glucose cannot enter the cells and stays in the blood, leading to high sugar levels.

Consequences of high blood sugar levels

High blood sugar levels (hyperglycemia):

1. Leads to increased osmotic pressure in the blood.
2. Cells lose water to the blood, causing cellular dehydration.
3. Persistent hyperglycemia can damage blood vessels, nerves, and organs.

Low blood sugar levels (hypoglycemia):

1. Leads to reduced osmotic pressure, causing water to move from the blood into tissues.
2. Cells are deprived of glucose, leading to energy shortages, which can result in:

• Fainting.
• Convulsions.
• Coma in severe cases.

The pancreas plays a central role in blood sugar regulation by secreting two hormones: insulin and glucagon. These hormones are produced by specialized cells in the Islets of Langerhans.

When blood sugar rises (after eating)

1. The rise in glucose levels triggers the secretion of insulin by the beta cells of the pancreas.
2. Insulin facilitates:

• Conversion of glucose to glycogen: Excess glucose is converted into glycogen and stored in the liver and muscles.
• Conversion of glucose to fats: The liver converts glucose into fat, which is stored under the skin and around organs such as the heart, blood vessels, and kidneys.
• Glucose uptake by cells: Insulin promotes the uptake of glucose by body cells, especially muscle and adipose tissues, reducing blood glucose levels to the normal range.

When blood sugar falls (during fasting or exercise)

1. Low glucose levels trigger the secretion of glucagon by the alpha cells of the pancreas.
2. Glucagon stimulates:

• Breakdown of glycogen: Glycogen stored in the liver is broken down into glucose, which is released into the bloodstream.
• Gluconeogenesis: The liver produces glucose from non-carbohydrate sources (e.g., amino acids and fats).

Diabetes mellitus is a chronic condition caused by the body's inability to regulate blood glucose levels effectively.

Causes of diabetes

• Type 1 diabetes: The body's immune system destroys the insulin-producing beta cells in the pancreas, resulting in little or no insulin production.
• Type 2 diabetes: Cells become resistant to insulin, or the pancreas does not produce enough insulin to meet the body's needs.

1. Genetic factors: A family history of diabetes increases the likelihood of developing the condition. Certain genetic mutations can impair insulin production or function.
2. Obesity: Excess body fat, particularly around the abdomen, leads to insulin resistance. Insulin resistance makes it harder for cells to absorb glucose from the blood.
3. Sedentary lifestyle: Lack of physical activity reduces the body's ability to use insulin effectively. This contributes to insulin resistance and high blood sugar levels.
4. Unhealthy diet: Consuming excessive sugar, refined carbohydrates, and processed foods can strain the pancreas and lead to insulin resistance over time.
5. Autoimmune disorders (Type 1 diabetes): The immune system attacks insulin-producing cells in the pancreas, leading to insufficient insulin production.

Effects of diabetes

1. Persistent hyperglycemia: Excess glucose in the blood cannot be converted into glycogen or fat. This increases the osmotic pressure of the blood, leading to dehydration as water is drawn out of cells.
2. Kidney effects: Excess glucose is excreted in urine, reducing water reabsorption in the kidney tubules. Results in large volumes of dilute urine and severe dehydration.
3. Alternative energy sources: The body uses fats and proteins as energy sources since glucose is unavailable to cells. This leads to rapid weight loss and, in severe cases, muscle wasting.

Treatment

Insulin therapy: Insulin injections help regulate blood glucose levels, allowing cells to utilize glucose efficiently.

Proper regulation of blood sugar is crucial for:

1. Providing energy: Ensures a steady supply of glucose to cells, especially the brain.
2. Maintaining osmotic balance: Prevents dehydration of cells or excessive water influx into tissues.
3. Avoiding long-term complications: Prevents damage to blood vessels, kidneys, and nerves caused by chronic hyperglycemia or hypoglycemia.