Diabetes Mellitus (PDF)

Description—A chronic disease of insulin deficiency or resistance, diabetes mellitus interferes with the metabolism of carbohydrates, proteins, and fats. Insulin in the blood facilitates the transfer of glucose into the cell to be used for energy or stored as glycogen. It also stimulates the formati...

Description—A chronic disease of insulin deficiency or resistance, diabetes mellitus interferes with the metabolism of carbohydrates, proteins, and fats. Insulin in the blood facilitates the transfer of glucose into the cell to be used for energy or stored as glycogen. It also stimulates the formation of proteins and free fatty acid storage. Without sufficient insulin being secreted by the pancreas, the body’s tissues do not have access to essential nutrients for fuel or storage. Diabetes mellitus affects an estimated 10.5 percent of the U.S. population or 34.2 million people. The prevalence of diabetes has increased greatly in the past decade, and more children and teenagers are being diagnosed with both type 1 (insulin requiring) and type 2 diabetes. The reasons are multifactorial but increasing numbers of obese individuals and inactivity are common risk factors. There are many long-term effects of diabetes. Diabetes is a leading cause of new cases of blindness, end-stage kidney disease, neuropathy, and lower limb amputation in the United States. It develops more often in people who are older than 40 and have a family history of diabetes, or are of African American, Hispanic, or Native American descent. It more than doubles the risk for stroke and heart disease. The disease also interferes with resistance to organisms, which may result in skin and bladder infections. Diabetic retinopathy results from microvascular changes in the retina of the eye, especially in poorly controlled diabetics. In patients who have had diabetes for 20 or more years, 80 percent develop retinopathy. How Insulin Works Insulin is the hormone made in the pancreas and released into the bloodstream as glucose rises. It helps sugar to enter the body’s cells, where it is used as fuel for the cell’s activities. When the sugar level rises, the pancreas secretes more insulin so that the larger amount of sugar can move out of the blood and into the cells. When the sugar level falls too low, insulin secretion is greatly reduced and the hormone glucagon is released. This causes the liver to release stored glycogen into the blood. Figure 17–10 How insulin works. Insulin is excreted by the pancreas into the blood. It circulates to an insulin receptor on the membrane of a cell. When it binds to the receptor, a signal is sent, and the gates in the cell wall open, allowing blood sugar to enter the cell to be converted to energy. To completely understand the role of insulin, we need to consider a basic fact of life. All living organisms are programmed to withstand cycles of feast and famine and have developed ways of storing energy for lean times. In humans and most animals, it is insulin that allows us to store glucose, protein, and fat in the liver, fat, and muscle cells until it is needed. Our bodies are programmed to store glucose and fat that produce excess weight and obesity when excessive calories are consumed, which leads to diabetes and numerous other illnesses. In the United States, obesity is at alarming incidence rates not only for adults but also for children. There is much concern about the future health of our population. There are two forms of diabetes: type 1 DM, or insulin-dependent diabetes mellitus, and type 2 DM, noninsulin-dependent diabetes mellitus, often called adult-onset form. Type 1 DM tends to afflict children and young people, and insulin replacement is necessary for survival. Refer to the information on Diabetes Mellitus (Type 1 DM), which summarizes the etiology, signs and symptoms, and treatment as they relate to children. Signs and Symptoms—Signs and symptoms of diabetes include fatigue and the three Ps; polyuria, polyphagia, and polydipsia. The elevated glucose level in the blood causes fluid to be withdrawn from the body’s tissues. The excess fluid in the blood causes polyuria and dehydration of the cells. The diabetic patient is frequently thirsty and has dry mucous membranes. The lens of the eye becomes affected by the hyperglycemia and edema, which results in visual difficulties. Characteristically, glycosuria is present when the threshold is exceeded to reabsorb glucose (about 180 mg per dL); the excess glucose spills over into urine. This wasting of sugar causes the weight loss and hunger of the type 1 DM patient. Diabetes Mellitus (Type 1 DM) Etiology—Type 1 diabetes can be considered a genetic disease. It is an autoimmune disorder that attacks the cells of the pancreas known as the islets of Langerhans. Signs and Symptoms—The diagnosis of diabetes in childhood is usually straightforward. The parents report an increased thirst, increased urination, and weight loss. The child will appear to be dehydrated and may have a sweet odor to the breath from the ketones (a by-product of fatty acids). A urinalysis will generally reveal a large amount of ketones and is positive for glucose. Treatment—A child with newly diagnosed type 1 DM will be admitted to the hospital for stabilization and treatment. Insulin injections or intravenous insulin are required for initial management. During hospitalization, the parents, caregivers, and the child (if of appropriate age) are taught to administer the insulin injections. Commonly, several types of insulin (short-acting, intermediate, and long-acting) will be used to control the elevated blood sugar and complications with childhood diabetes. Diabetes Mellitus (Type 2 DM) Etiology—Type 2 DM is the most common form, usually due to insulin resistance. This is a complex problem arising from the reduced effectiveness of insulin to facilitate glucose entering the cell. The blood sugar level rises, and the liver produces more sugar and often releases lipoproteins full of triglycerides that may decrease HDL cholesterol. Insulin resistance can also result from genetics, aging, and some medications, but being overweight and lack of exercise are the main nongenetic factors. About 90 percent of all newly diagnosed diabetics are overweight. Some of the hormones secreted by fat cells—for example, resistin—interfere with insulin action. The role of fat cells is being studied specifically because obesity is so often associated with the disease. In addition to resistance, other factors exist. The pancreas compensates by secreting more insulin. Eventually, the insulin-producing cells can no longer keep up, and glucose increases in the blood. Over time, this high level of sugar damages blood vessels, nerves, and other body tissues. It also causes a vicious cycle of increasing resistance and further exhausts the pancreas. Treatment—Treatment begins with a strict diet, planned to meet the nutritional needs of the individual patient and to control the blood sugar level. Diet can have a significant impact on controlling blood sugar and diabetes. Losing as little as 10 pounds will reduce blood sugar levels. A recent study determined that a high-fiber diet lowered blood sugar levels by 10 percent, a reduction similar to the effect of some medications. Exercise may be the most important intervention. It not only increases glucose metabolism, but it also increases insulin sensitivity, which causes fat and muscle cells to better respond to insulin. Diet and exercise can have a significant effect in preventing diabetes, but as a treatment, they can only go so far. In most people, the problem of insulin production and insulin resistance tend to worsen in time despite weight loss, diet, and exercise. When diet alone is inadequate, insulin injections or the use of oral hypoglycemic drugs are indicated. Injections may be necessary initially once a day, using long-acting insulin; when control is more difficult, short-acting insulin, injected before meals, may be needed. Diabetic patients are taught to evaluate their glucose level by performing a finger stick for blood analysis. The amount of insulin injected is based on the findings. Hypoglycemic drugs are taken orally to aid in the metabolism of sugar. Oral therapy is adequate only for type 2 DM patients. The drugs used today address insulin resistance and secretion to reduce blood sugar levels. Providers are using more drugs and using them more aggressively. Drugs can be categorized according to their actions (see the following). Increasing Insulin Supplies 1.​ Sulfonylureas stimulate beta cells to release more insulin. This works for a while but then may become ineffective. These drugs can work too well, causing hypoglycemia that can be dangerous for older patients because it causes fainting, falls, and fractures. 2.​ Rapid-acting insulin stimulators are similar to sulfonylureas but faster. They are of short duration and are less apt to cause hypoglycemia. Two drugs in this class are Prandin and Starlix. 3.​ Antidiabetic drugs, relatively recently approved, are available. The dipeptidyl peptidase-4 inhibitors, Onglyza (saxagliptin) and Januvia (sitagliptin), increase the presence of gut hormones, which are advantageous for insulin secretion and decrease glucagon levels. In 2008, colesevelam was approved as a glucose-lowering agent. It is an old drug used for a number of years to lower cholesterol. 4.​ Injection of insulin subcutaneously is the ultimate method of overriding pancreatic dysfunction. Type 1 diabetics who lack insulin are dependent on injections. Patients with type 2 diabetes often can control their disease with diet, exercise, and medications, but if that fails, insulin is the most potent and effective therapy. They usually require higher doses because of the need to overcome resistance. A form of insulin that can be inhaled is being developed. Initial trials have yielded promising results. Lowering Blood Sugar by Other Means 1.​ Alpha-glucosidase inhibitors block the action of a digestive enzyme that breaks down carbohydrates into smaller sugars. The effect is to moderate blood sugar surges after a meal. These drugs are weaker than some others but very safe. 2.​ Biguanides work to lower sugar levels by blocking the release of glucose by the liver. The only drug currently approved is Glucophage, and it works well in overweight people because it does not cause weight gain or risk of hypoglycemia. 3.​ Thiazolidinediones (TZD) reduces insulin resistance by modulating activity of nuclear transcription factors. They show promise in improving the lipid profiles and other metabolic factors. Multi-Drug Approach More providers are using a multi-drug approach to management. Previously, they would do one thing at a time: diet and exercise, then drug after drug until ineffective, and then insulin. By using drug combinations, lower doses of each are effective, and therefore fewer side effects occur. This approach better addresses the new view of diabetes as a syndrome instead of a simple disease of high blood sugar. A common drug combination is metformin and sulfonylurea. Clinical trial with metformin-TZD combination showed improved effectiveness in control of blood sugar, insulin sensitivity, and islet cell function. When insulin becomes necessary, combining it with oral medications may mean a lower dose of insulin is needed. Future Treatments It is hoped that continual genetic work will reveal new information on diabetes and its treatment, but researchers realize this will take some time to determine. Some researchers are focusing on preventing the complications associated with diabetes, such as atherosclerosis; others focus on therapies directed at fat cells. Pancreatic and islet transplantations show encouraging promise. A study also revealed that the simple action of taking an aspirin a day is a very effective health strategy for diabetics and would help those with cardiovascular disease. Controlling blood pressure and lowering LDL are crucial even if there is no evidence of coronary disease. Maintaining Health The glucose level of the blood can be affected by circumstances other than food or insulin. For example, the diabetic requires either less insulin or more food when engaging in a high level of physical activity. Adjustments are also required with illness. A patient who has diarrhea or vomiting may require less insulin. Pregnancy, the use of contraceptives, a fever, and periods of stress all influence the diabetic’s need for supplemental insulin or oral hypoglycemic therapy. Specific symptoms indicate whether the blood sugar is too high or too low. A diabetic must always be aware of their physical condition. Should the blood sugar level become significantly low, they may enter into insulin shock; if it goes very high, there is a possibility of a diabetic coma. Both situations require urgent attention. When patients sense impending shock, they will drink orange juice or eat a piece of candy immediately. A patient going into a coma needs an urgent blood sugar measurement and injections of insulin. Diabetic patients must be encouraged to maintain their optimal level of health. They must guard against injury, especially to the lower extremities, because of difficulty healing. They must use extreme caution when cutting toenails and must not try to remove corns or calluses themselves. Diabetics frequently suffer amputations as a result of infection from an injury that would not heal or from the loss of peripheral circulation, which causes tissue ischemia. Patients should be encouraged to visit an ophthalmologist at least yearly to detect the possibility of retinal changes. The provider must be alert to signs of cardiovascular complications and urinary tract involvement. Cerebral vascular disease, coronary artery disease, and renal failure resulting from vascular deterioration in the kidney are common.