Insulin is a vital organic compound and hormone that plays a crucial role in the chemistry of the human body. Produced in the pancreas, insulin helps regulate blood sugar levels by enabling cells to absorb glucose, which is then used for energy. It is essential for maintaining the body’s overall health, as it ensures that glucose circulates properly and doesn’t reach harmful levels in the blood. Understanding insulin’s function is important, especially for those managing conditions like diabetes, where insulin production or response is impaired.

What is Insulin?

Insulin is a vital hormone produced by the pancreas, primarily responsible for regulating blood sugar levels by facilitating the entry of glucose into cells. Chemically, insulin is a peptide hormone composed of 51 amino acids, arranged in two chains connected by disulfide bonds. Its chemical formula is represented as C₂₅₄H₃₇₇N₆₅O₇₅S₆. This structure enables insulin to effectively manage glucose metabolism, crucial for providing energy to the body’s cells.

Types of Insulin

Rapid-Acting Insulin

Rapid-acting insulin starts working within 15 minutes after injection and peaks in about 1 hour, providing an effective glucose management for approximately 2 to 4 hours. It is used primarily to control blood sugar levels during meals, commonly known as bolus insulin. Examples include insulin lispro (Humalog), insulin aspart (NovoLog), and insulin glulisine (Apidra).

Short-Acting Insulin

Short-acting insulin, or regular insulin, takes effect within 30 minutes and lasts 5 to 8 hours. Its peak action is around 2 to 3 hours after injection. This type of insulin is typically used before meals to manage rise in blood sugar that follows eating. It is often combined with longer-acting insulin for comprehensive blood sugar control.

Intermediate-Acting Insulin

Intermediate-acting insulin starts working about 1 to 2 hours after injection and remains effective for 12 to 18 hours. Its peak activity ranges from 4 to 12 hours. Often used twice daily, this type helps control blood sugar levels throughout the day and night. NPH insulin (Humulin N, Novolin N) is a common example of this category.

Long-Acting Insulin

Long-acting insulin shows a steady effect that starts within 1 to 2 hours and lasts up to 24 hours or more, with no pronounced peak. It mimics the insulin action seen in the body between meals and overnight. This type is crucial for maintaining baseline insulin levels and is usually administered once or twice a day. Examples include insulin glargine (Lantus) and insulin detemir (Levemir).

Ultra Long-Acting Insulin

Ultra long-acting insulin, with the longest duration of action, lasts over 24 hours, often up to 36 hours, with a very stable, peakless profile. Designed for once-daily dosing, it ensures all-day and all-night coverage with a very steady rate. Insulin degludec (Tresiba) and insulin glargine U-300 (Toujeo) are prominent forms of this insulin type.

Structure of Insulin

Insulin is a peptide hormone made up of two chains of amino acids, known as the A and B chains, linked together by disulfide bonds. The A chain consists of 21 amino acids, and the B chain is longer with 30 amino acids. These chains fold into a specific three-dimensional shape that is crucial for insulin’s function in regulating blood glucose levels. This structure allows insulin to bind to its receptor on the surfaces of cells, facilitating the uptake of glucose into the cells and helping to lower blood sugar levels in the body.

Role of Insulin

Insulin plays a crucial role in the body by regulating blood sugar levels. It acts as a key that allows glucose, the primary source of energy for cells, to enter various tissues in the body, including muscle and fat cells. When you eat, your blood sugar rises, prompting the pancreas to release insulin. This hormone helps cells absorb glucose, either to be used immediately for energy or to be stored for later use. By managing the level of glucose in the blood, insulin prevents it from becoming too high (hyperglycemia) or too low (hypoglycemia), maintaining overall balance and supporting metabolic functions.

Function of Insulin

Facilitates Glucose Uptake

Insulin enables cells in muscle, fat, and liver tissues to absorb glucose from the bloodstream, which they use for energy or store for future use.

Regulates Blood Sugar Levels

Insulin helps maintain optimal blood sugar levels by prompting cells to take in glucose, thereby preventing high blood sugar (hyperglycemia) after meals.

Promotes Glycogen Synthesis

Insulin stimulates the liver and muscle cells to convert glucose into glycogen, a stored form of glucose, which the body can use during periods of fasting or increased energy demand.

Inhibits Glucose Production

Insulin signals the liver to stop producing glucose through a process called gluconeogenesis, helping to keep blood sugar levels stable between meals and overnight.

Enhances Fat Storage

Insulin facilitates the uptake of fatty acids and glycerol into fat cells, converting them into triglycerides that store as fat tissue, thus promoting fat storage.

Supports Amino Acid Absorption

Insulin aids in the absorption of amino acids, the building blocks of proteins, into muscle cells, promoting protein synthesis and preventing protein breakdown.

Triggers of Insulin

The primary trigger for insulin release is the rise in blood glucose levels that occurs after eating. When you consume carbohydrates, they break down into glucose, which enters the bloodstream and signals the pancreas to secrete insulin. Additionally, the consumption of certain amino acids from proteins and hormones like incretins, released by the gut during food intake, can also stimulate insulin production. Other factors, such as the autonomic nervous system and some medications, can influence insulin release, ensuring the body maintains balanced blood sugar levels.

Examples of Insulin

Insulin Lispro (Humalog)

Rapid-acting insulin taken before meals, starts working in 15 minutes, peaks in about an hour, and lasts 2 to 4 hours.

Insulin Aspart (NovoLog)

Insulin aspart, another rapid-acting insulin similar to insulin lispro, takes effect within 15 minutes of injection, peaks around 1 to 3 hours, and lasts for 3 to 5 hours. It’s typically used to manage blood sugar spikes during meals.

Insulin Glargine (Lantus)

It is a long-acting insulin that provides a steady level of insulin in the body for a full 24 hours. It begins working a few hours after injection and helps maintain a stable blood glucose level throughout the day and night without a peak.

Insulin Detemir (Levemir)

Insulin detemir, a long-acting insulin, varies in duration from 18 to 23 hours depending on the dosage. It slowly releases insulin, lowering blood sugar levels and is typically administered once or twice daily.

Insulin Degludec (Tresiba)

Insulin degludec, an ultra long-acting insulin, offers over 42 hours of consistent insulin levels, maintaining stable, predictable blood sugar control, typically with once-daily administration.

Side Effects of Insulin

• Hypoglycemia (Low Blood Sugar): The most common side effect, characterized by dizziness, sweating, confusion, and palpitations.
• Weight Gain: Insulin promotes fat storage by facilitating the uptake of fatty acids and glycerol into fat cells, converting them into stored triglycerides.
• Injection Site Reactions: Injection of insulin can cause redness, swelling, and irritation at the injection site.
• Lipodystrophy: Repeated insulin injections at the same site can cause fatty tissue to either thicken or shrink, affecting insulin absorption.
• Allergic Reactions: Rarely, individuals may experience systemic allergic reactions to insulin, including rash, itching, or severe symptoms like anaphylaxis.
• Edema: Fluid retention and swelling, particularly in the ankles and feet, may occur when starting insulin therapy or changing doses.
• Hypokalemia (Low Potassium Levels): Insulin can cause potassium to move into cells, potentially leading to dangerously low serum potassium levels.

FAQs

Is Insulin Good or Bad for You?

Insulin is essential for glucose regulation and energy management, making it crucial for overall health, especially in diabetics.

How Long Can a Diabetic Go Without Insulin?

Diabetics without insulin can experience life-threatening complications within hours or days, depending on their condition’s severity.

What Happens if a Non-Diabetic Takes Insulin?

If a non-diabetic takes insulin, it can cause dangerously low blood sugar levels (hypoglycemia), which can be fatal without intervention.

Is Insulin a Chemical Drug?

Medical professionals use insulin, a peptide hormone naturally synthesized by the pancreas, to manage diabetes. It is not a chemical drug.