The Five Insulin Types

December 5th, 2010

Insulin is divided into 5 types: rapid-acting, short-acting (or fast acting), intermediate-acting, long-acting and pre-mixed insulin. The different types of insulin vary in the amount of time until they begin to work (onset), how long they take to achieve the greatest blood concentration and effectiveness (peak) and how long they continue to control blood sugar (duration). The effects of insulin, including onset, peak and duration times, vary from individual to individual and from day to day.

Depending on the brand, rapid-acting insulin has an average onset of from 5 to 15 minutes, peak of 30 minutes to 3 hours, and duration of 3 to 5 hours. It's normally injected with meals, and used in combination with a longer acting insulin.

Short-acting insulin (also called regular insulin) has an average onset of 30 minutes to an hour, peak of 2 to 4 hours, and duration of 4 to 8 hours, depending on if it's injected or used in an insulin pump. It's taken 30 minutes to an hour before a meal, and may be combined with long-acting insulin.

Intermediate-acting insulin (also called NPH insulin or lente insulin) has an average onset of 2 to 4 hours, a peak of 4 to 10 hours, and duration of 10 to 18 hours. It's often used in combination with rapid or short-acting insulin.

The effects of long-acting insulin (sometimes called background insulin or basal insulin) typically cover a full day. There are two types of long-acting insulin: insulin glargine (Lantus) and insulin detemir (Levemir). Typical onset for Lantus is within 4 to 6 hours. Lantus is delivered steadily and so does not peak, and has an average duration of 24 hours.

Typical onset for Levemir insulin is between 2 to 3 hours. Levemir peaks slightly between 8 to 10 hours, and the duration is dose-dependent, between 6 to 23 hours. Long-acting insulin is often used in combination with rapid or short-acting insulin, or an oral diabetes medication in the case of type 2 diabetics.

Premixed insulin is a combination of short and intermediate-acting insulin in the same vial or insulin pen. It's normally taken twice a day before meals.

Warning Signs for Insulin Dependent Diabetics

December 10th, 2010

Most type 1 diabetics get very good at managing their disease. They can identify when their blood glucose is too high or too low, and skillfully balance a mixture of short, intermediate and long-lasting insulin. They stay up to date on the latest innovations in diabetes control - from the insulin pen through the insulin pump to the implantable glucose monitor. They know the importance of the glycemic index and staying physically active. They deftly adjust their diabetes medication to counteract changes in diet, activity level, stress, illness, and even their menstrual cycle.

Another often overlooked aspect of successful diabetes control is educating family, friends and co-workers about diabetes danger signs that may require medical attention. An unexpected insulin spike or rise or drop in blood sugar can cause a medical emergency for an insulin dependent diabetic, and those close to them should know what to watch for and how to respond. According to WebMD, the following are diabetes symptoms that should never be ignored:

1) Extreme thirst or hunger, blurry vision or frequent urination. These are all warning signs of uncontrolled blood sugar which, if left unchecked, could lead to serious, even life-threatening, conditions.

2) Appearing "drunk". Appearing intoxicated can be a sign of low blood sugar. Low blood sugar can result from a medication such as long-acting insulin working too well. A diabetic in this condition may not realize the seriousness of the situation, and lose consciousness.

3) Infections, gum problems and foot wounds. Diabetics are prone to infection, including fungal infections and foot ulcers, and even a small cut or sore can be risky. It's important for diabetics to watch for skin rashes, practice proper foot care, and to see a doctor if a wound gets infected or is slow to heal.

4) Eye problems and changes in vision. Diabetics are also prone to retinopathy (damage to the retina of the eye), which can cause vision loss. Talk to your doctor about any changes in vision, eye pain, or visual disturbances like seeing spots or lights, and see an ophthalmologist yearly.

5) Symptoms of heart disease. Diabetics are at increased risk of heart disease, heart attack and stroke, and they and those close to them should be aware of and alert for symptoms such as chest pain, shortness of breath, nausea, anxiety, dizziness, sweating, and a rapid or irregular pulse. It's also possible to have heart disease and not have obvious symptoms, so your doctor should evaluate your risk factors regularly.

Advances in diabetes treatment and diabetes medication continue to increase both the quality of life and the life expectancy of both insulin dependent and non insulin dependent diabetics. And promising treatments such as an artificial pancreas, islet cell transplants, glucose monitoring "tattoos", novel ways of delivering insulin without insulin injections and even a diabetes vaccine are in the early stages or on the horizon. While it will never be a good thing to be diabetic, it's no longer the tribulation it used to be.

Researchers Bioengineer Cells from Testicles to Produce Insulin

December 15th, 2010

Researchers have briefly "cured" Type 1 diabetes in lab mice using cells extracted from the testicles of deceased human donors. The spermatogonial cells used in the experiment normally produce sperm in men. Scientists extracted them from the donors, bioengineered them to act like the beta cells in the pancreas that produce human insulin, and transplanted them into mice. The transplanted cells successfully secreted insulin, reducing blood sugar levels in the mice for about a week.

While exciting, the breakthrough doesn't yet amount to a cure for insulin dependent diabetes in humans. "These cells don't secrete enough insulin to cure diabetes in humans yet," cautions the study's senior researcher G. Ian Gallicano, an associate professor at Georgetown University Medical Center. However, Gallicano is hopeful that transplanting the spermatogonial cells into different parts of the body may lead to longer blood sugar control. "We know spermatogonial stem cells have the potential to do what we want them to do," says Gallicano, and we know how to improve their yield."

The researchers chose to work with spermatogonial cells because they behave a lot like human eggs, and can be chemically instructed to behave like embryonic stem cells. Stem cells are unspecialized or "undifferentiated" cells that have the potential to develop or differentiate into many different types of cells.

Earlier attempts to transplant insulin-producing beta cells (also called islet cells) found in the pancreas achieved some success, but islet cells transplants are handicapped by the body's autoimmune system's attempts to destroy the new tissue, which it sees as an invader. While they no longer require diabetes medication, islet cell transplant recipients must take powerful immunosuppressive drugs with undesirable side effects, including an increased risk of infection and cancer. A major benefit of spermatogonial cell transplants is that they avoid arousing an auto-immune response.

One obvious disadvantage is that the procedure can only be performed in males, although the fundamental approach might be applicable to the female counterpart of sperm-producing cells, oocytes. Another concern is the potential for spermatogonial cell transplant recipients to develop a type of tumor called a teratoma, associated with the abnormal development of germ (reproductive) cells. But Gallicano is convinced that it would take many more spermatogonial cells than would be required to produce insulin to cause such a tumor.

Gallicano and his fellow researchers are hopeful that they've taken the first step towards reducing diabetic hyperglycemia in humans and eliminating the need for diabetes drugs. This gives hope to the almost 24 million Americans with diabetes, one of the leading causes of death in the US. There are two main types of diabetes: type 1, which requires lifelong insulin injections; and the much more common type 2, which can be controlled by diet, exercise, and, if needed, oral diabetes medication. Both types must be managed carefully to avoid serious complications.

Islet Transplantation Eliminates the Need for Insulin Injections

December 15th, 2010

laboartory equipment

Islet cells are sugar-sensing cells in the pancreas that release insulin in order to maintain normal blood sugar levels in the body. In type 1 diabetes, the cells can no longer make insulin because the body's immune system has destroyed them. Type 1 diabetics must take daily insulin injections, usually a complex combination of short and long acting insulin.

Islet cell transplantation involves removing insulin-producing cells from a donor pancreas and transferring them into a person with diabetes. It's a non-surgical procedure in which the donated cells are inserted through a needle directly into the liver. Scientists developed the procedure in the 1960s, but the first islet transplantation attempts didn't take place until the 1990's. To everyone's disappointment, only 8% of the first transplants were successful. The problem was the same faced in other organ or tissue transplants - the recipient's immune system recognized the islets as foreign invaders, and attacked them. Adding to the problem, the anti-rejection drugs in use at the time interfered with insulin's effectiveness.

Canadian researchers at the University of Alberta (U of A) made a major breakthrough in 1999. Using sophisticated islet collection and preparation techniques and improved anti-rejection drugs, they achieved an impressive initial 100% success rate for the first month. But most of their patients eventually had to return to insulin injections as the transplanted islets lost their ability to function, although taking lower doses.

Over ten years later, islet transplantation is still an experimental procedure. Rejection issues remain, and it's difficult to obtain the typically 1 million islet cells needed for one procedure - the equivalent of two pancreases. Islet transplants are currently being performed at 17 research centers across the US, but are not widely available. The procedure is normally restricted to type 1 diabetics between the ages of 18 and 65 who have had diabetes for more than 5 years and have trouble with blood glucose control, resulting in serious complications.

In a successful islet cell transplant, the donor islets make insulin and release it into the patient's bloodstream. They also monitor and stabilize blood sugar levels, eliminating the need for daily insulin injections and frequent blood sugar monitoring. But islet transplant patients must take strong anti-rejection drugs for the rest of their lives, many of which have serious side effects. Unfortunately, most patients need more than one transplant to produce enough insulin that they can stop taking insulin injections. Although islet transplants still fall short of a cure, a successful procedure improves the quality of life of the patient, and lowers the risk of serious long-term diabetes complications such as stroke, heart disease, kidney disease, and eye and nerve damage.

Progress continues to be made towards better anti-rejection drugs, and improved methods to transplant the cells. Researchers are also attempting to obtain donor islets from other sources such as animals, and even trying to grow islet cells in the laboratory. The University of Wisconsin Health Centre claims about 80% of patients receiving an islet transplant have been able to stop taking insulin completely, and that those that still need insulin injections achieved better glucose control. As the procedure is still so new, the longest known period of insulin independence following a US transplant is 4 years. The pioneering U of A program reports that 15-20% of their patients remain insulin independent for 5 years after treatment, and these results are improving.

In the meantime, most Type 1 diabetics will continue to control their condition with diet, exercise, lifestyle changes and a combination of short and long acting insulin, and to follow the developments in islet transplants with great interest.

Blood Glucose and the Glycemic Index

December 16th, 2010

Proper diet is crucial for diabetics, as food can have both short and long term effects on blood glucose control. For reasons researchers have yet to uncover, blood sugar levels soar after eating, and many diabetics need to time their insulin injections around meal times to aid in controlling blood sugar. One thing researchers do know - the higher the glycemic index of a food, the more impact it has on blood glucose.

The glycemic index (GI) is a measure of the influence that a particular food has on blood sugar levels. It takes into account the fact that different types of carbohydrates perform differently in our bodies. The GI ranks carbohydrates on a scale of 1 to 100 based on how quickly they raise blood sugar.

Low GI foods are in the range of 0 to 55, medium are ranked 56 to 69, and high are scored 70 and above. Foods with a high GI are rapidly digested and absorbed, resulting in a rapid spike in blood sugar and insulin demand. Foods with a low GI are digested and absorbed more slowly, resulting in a more gradual increase in blood sugar and insulin. Because they're digested more gradually, low GI foods reduce hunger and keep you feeling full longer.

In general, the more fiber a food has, the lower its GI. Whole grains like oats, barley and bran, nuts, eggs, milk, meat, legumes, fructose, most fruits and vegetables, and low carbohydrate foods are low on the GI. Whole wheat products, basmati rice sweet potatoes and sucrose rank medium on the GI. Most high carbohydrate foods like potatoes, watermelon, white bread, white rice, candy, pastries, most baked goods, low fiber breakfast cereals and glucose are all high on the glycemic index. The resourceful Australians have developed a low GI potato called "Carisma", but sadly, it's not yet available in North America.

A low GI diet reduces the body's insulin levels and insulin resistance, and improves overall blood glucose control in both type 1 and type 1 diabetics. As a rule, diabetics are advised to eat foods that are low to medium on the GI, but a diabetic who is experiencing a period of low blood sugar may want to eat a high GI food to quickly raise their blood sugar. You can use a glycemic index chart to search for low glycemic food choices, and to check the glycemic index of your favorite foods. Bear in mind that other factors will affect the impact a food has on blood sugar, such as fat and protein content, ripeness, cooking method, the combination of foods eaten, the time of day, and your insulin and activity levels.

Recent studies indicate that the risk of diabetes and other diseases is closely related to the overall GI of our diets. A US study of national data spanning almost 90 years found that the rising consumption of high GI corn syrup (widely used to sweeten soft drinks and processed foods) and decreasing intake of dietary fiber parallels the explosion of type 2 diabetes in America. The World Health Organization recommends a low GI diet to prevent and combat the "diseases of affluence" that are rampant in North America - diabetes, obesity and heart disease.