Treatment of Type 1 Diabetes

The goal of treatment for type 1 diabetes is to achieve tight metabolic control in order to reduce complications and mortality.[1,2] Treatment for type 1 diabetes consists of a series of interrelated components, including insulin therapy, medical nutrition therapy, physical activity, and self-monitoring of blood glucose (SMBG).[3]

Insulin

In healthy individuals, the pancreatic β cells produce a constant low level of insulin (basal insulin), as well as larger spikes in response to meal ingestion (prandial insulin). The goal of insulin replacement therapy in people with diabetes is to mimic normal pancreatic function as closely as possible.

Insulin pharmacology

Currently, most insulin used is human insulin produced by recombinant DNA technology, although pork and beef insulin preparations are still available in some places.[4] Insulins are categorized based on their onset of action: rapid-acting (onset of less than 15 minutes), short-acting (onset ½ hour to 2 hours), intermediate-acting/long-acting (onset 2-4 hours).[5] Common insulins and their action profiles appear in Table 1.

Table 1. Insulin action profiles[5]

Initiation of insulin therapy

Upon diagnosis, the first objective is to correct any existing metabolic abnormalities, such as moderate hyperglycemia or diabetic ketoacidosis (DKA).[6] If DKA is not present, then newly diagnosed type 1 patients may be managed on an outpatient basis, as this approach has been determined to be both safe and efficacious.[7]

After acute hyperglycemic crisis has been resolved, an insulin regimen must begin. Choice of insulin regimen should take into account patient metabolic needs, schedule and lifestyle, willingness to monitor and take injections, and ability to understand the complexities of an insulin regimen.[6] Choices for regimens include conventional therapy, intensified conventional therapy, and intensive therapy.[6] Conventional therapy regimens consist of 2 or 3 daily injections of a constant dose of insulin. Intensified conventional therapy regimens use 2 to 3 daily injections (not necessarily before each meal) with adjustments. Intensive therapy regimens use rapid-acting insulin before each of 3 daily meals in addition to a basal insulin, such as twice-daily NPH or once-daily ultralente or insulin glargine. Use of intensive therapy has been shown to be effective for reducing the risk of microvascular complications.[1]

Insulin adjustment

A variety of factors affect insulin requirements. Food consumption, glucose level, and activity level should be considered when making decisions about insulin dose.[8] There are also numerous factors that affect the rate at which insulin is absorbed, including factors related to insulin preparation, injection site, and other external factors.[4,6] A summary of factors affecting insulin absorption and insulin action appears in Table 2.

Table 2. Factors affecting insulin absorption and action[4,6]

Because there are numerous factors that affect insulin absorption and insulin action, insulin regimens require frequent adjustment in order to maintain optimal metabolic control. When metabolic goals are not being met, it is important to consider a variety of potential reasons for this outcome, including recent change in insulin type (eg, from short-acting to rapid-acting), changes in β-cell function (eg, beginning or end of Honeymoon phase), suboptimal injection technique, changes in lifestyle, life stressors, change of season (and concomitant changes in activity), menstrual periods, other hormonal changes such as onset of puberty or menopause, illness or injury, and gastroparesis.[6]

Medical nutrition therapy

Medical Nutrition therapy (MNT) is important not only in the management of diabetes and the prevention of complications, but also as an indispensable part of a healthy lifestyle.[3] The goals of medical nutrition therapy for all people with diabetes are: 1) to attain and maintain optimal metabolic control; 2) to prevent and treat all diabetes complications; 3) to improve health through healthy food choices; and 4) to address individual nutritional needs, taking into account personal preferences, cultural preferences, lifestyle, and willingness to change.[3]

In terms of carbohydrate content, premeal insulin dose should be adjusted to accommodate for carbohydrate content of a given meal. If insulin dose is fixed, then it is important that carbohydrate content be kept constant from day to day.[9] Carbohydrate should comprise 45% to 65% of caloric intake, and restricting carbohydrates to less than 130 g per day is not recommended.[3]

There are a number of different approaches to diabetes meal planning.[9] The exchange list is a system that categorizes foods based on their nutritional properties. Because the exchange list system is difficult to learn, many patients prefer the carbohydrate counting method. People who use this method can count carbohydrate grams, carbohydrate choices (where each choice is 15 g of carbohydrates), or can use a carbohydrate/insulin ratio (appropriate only for patients using a pump or for patients using a flexible regimen with a long-acting basal insulin combined with variable amounts of rapid-acting insulin at meals). In spite of the fact that many approaches to meal planning focus primarily on the amount of carbohydrate, approaches that also take into consideration glycemic index can have a benefit on glycemic control, over and above what can be achieved by using an approach that only considers carbohydrate amount.[3]

In spite of the increased popularity of the high-protein/low-carbohydrate diets, these are not recommended in diabetes management, and protein should be restricted to the RDA of 0.8 g/kg in patients with chronic kidney disease of any degree.[3] Intake of protein above 20% of caloric intake may be a risk factor for the development of renal disease; protein intake should be kept generally in the range of 10% of caloric intake. [3]

Physical activity

According to the American College of Sports Medicine, every adult should accumulate at least 30 minutes of moderate-intensity physical activity on most or all days of the week in order to promote good health and prevent chronic disease.[10] In addition to the health benefits of physical activity,[11,12] people with type 1 diabetes can also experience diabetes-specific benefits of physical activity, including lowered A1C and reduced insulin requirements.[13] People with type 1 diabetes can exercise safely if the proper self-management strategies are employed.

Before beginning any exercise program, a thorough screening for cardiovascular disease, peripheral arterial disease, retinopathy, nephropathy, and neuropathy should be undertaken.[3] Adequate warm-up, stretching, and proper footwear are essential. In terms of metabolic control, activity should not be initiated if blood glucose levels are lower than 100 mg/dL or greater than 250 mg/dL with concomitant ketosis.[14] A full list of physical activity guidelines appears in Table 3. It is important to note that physical activity may have a delayed effect on blood glucose levels, so increased monitoring may be required following vigorous exercise in order to prevent delayed hypoglycemia.

Table 3. Physical activity and glycemic control[14]

Self-monitoring of blood glucose (SMBG)

Although SMBG is not a treatment per se, it is a critical part of diabetes self-management, and it is an important predictor of glycemic control.[15] Based on the results of the Diabetes Control and Complications Trial (DCCT),[1] which showed that near-normal glucose levels greatly reduced the risk of diabetic complications, the American Diabetes Association (ADA) recommends that glycemic levels should be as close to normal as possible, with preprandial glucose levels between 90 and 130 mg/dL and postprandial glucose levels less than 180 mg/dL for adults.[3] Younger children or people with hypoglycemia unawareness may require modified glycemic targets in order to prevent severe hypoglycemia. In order to achieve glycemic targets and prevent aymptomatic hypoglycemia, monitoring at least 3 times per day is recommended.[3]

References

1. Diabetes Control and Complications Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med. 1993;329:977-986.
2. Hellman R, Regan J, Rosen H. Effect of intensive treatment of diabetes on the risk of death or renal failure in NIDDM or IDDM. Diabetes Care. 1997;20:258-264.
3. American Diabetes Association. Standards of medical care in diabetes-2006. Diabetes Care. 2006;29(suppl 1):S4-S42.
4. Heinemann L. Insulin pharmacology. In: Pickup JC and Williams G, eds. Textbook of Diabetes 2. Malden, MA: Blackwell Science Ltd.;2003:42.1-42.15.
5. http://www.diabetes.org/uedocuments/Insulin-tables.pdf Accessed on 5/10/04.
6. Beaser RS. Designing a conventional insulin treatment program. In: Beaser RS and the staff of the Joslin Diabetes Center, eds. Joslin’s Diabetes Deskbook: A Guide for Primary Care Providers. Boston, MA: Joslin Diabetes Center; 2001:233-271.
7. Siminerio LM, Charron-Prochownik D, Banion C, Schreiner B. Comparing outpatient and inpatient diabetes education for newly diagnosed pediatric patients. Diabetes Educator. 1999;25:895-906.
8. American Diabetes Association. Insulin administration. Diabetes Care. 2004;27(suppl 1):S106-S110.
9. Hill JBC, Beaser RS. Medical nutrition therapy. In: Beaser RS and the staff of the Joslin Diabetes Center, eds. Joslin’s Diabetes Deskbook: A Guide for Primary Care Providers. Boston, MA: Joslin Diabetes Center; 2001:63-99.
10. Pate RR, Pratt M, Blair SN, Haskell WL, Macera CA, Bouchard C. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA. 1995;273:402-407.
11. Laaksonen DE, Atalay M, Niskanen LK, et al. Aerobic exercise and the lipid profile in type 1 diabetic men: a randomized controlled trial. Med Sci Sports Exer. 2000;1541-1548.
12. Lehmann R, Kaplan V, Bingisser R, Bloch K, Spinas GA. Impact of physical activity on cardiovascular risk factors in IDDM. Diabetes Care. 1997;20:1603-1611.
13. Beaser RS. Exercise. In: Beaser RS and the staff of the Joslin Diabetes Center, eds. Joslin’s Diabetes Deskbook: A Guide for Primary Care Providers. Boston, MA: Joslin Diabetes Center; 2001:101-124.
14. American Diabetes Association. Physical activity/exercise and diabetes. Diabetes Care. 2004; 27(suppl 1):S58-S62.
15. Levine BS, Anderson BJ, Butler DZ, Antisdel JE, Brackett J, Laffell LMB. Predictors of glycemic control and short-term adverse outcomes in youth with type 1 diabetes. J Pediatr. 2001;August:197-203.