Alternative therapies for type 2 diabetes - Review: type 2 diabetes

Alternative Medicine Review, Feb, 2002 by Lucy Dey, Anoja S. Attele, Chun-Su Yuan

Abstract

Type 2 diabetes is a chronic metabolic disease that has a significant impact on the health, quality of life, and life expectancy of patients, as well as on the health care system. Exercise, diet, and weight control continue to be essential and effective means of improving glucose homeostasis. However, lifestyle management measures may be insufficient or patient compliance difficult, rendering conventional drug therapies (i.e., oral glucose-lowering agents and insulin injection) necessary in many patients. In addition to adverse effects, drug treatments are not always satisfactory in maintaining euglycemia and avoiding late stage diabetic complications. As an alternative approach, medicinal herbs with antihyperglycemic activities are increasingly sought by diabetic patients and health care professionals. Commonly used herbs and other alternative therapies, less likely to have the side effects of conventional approaches for type 2 diabetes, are reviewed.

Introduction

Diabetes mellitus is a serious chronic metabolic disorder that has a significant impact on the health, quality of life, and life expectancy of patients, as well as on the health care system. In the United States, diabetes is the sixth leading cause of death. (1) Diabetes is divided into two major categories: type 1 diabetes (formerly known as insulin-dependent diabetes mellitus or IDDM) and type 2 diabetes (formerly known as non-insulin dependent diabetes mellitus or NIDDM). The overall prevalence of diabetes is approximately six percent of the population, of which 90 percent is type 2. (2) Treatment and care of diabetes represents a substantial portion of the national health care expenditure, over $105 billion annually. This represents a substantial portion of the health care expenditure -- more than one of every 10 U. S. health care dollars and one of four Medicare dollars. (3)

Type 2 diabetes represents a syndrome with disordered metabolism of carbohydrate and fat. The most prominent clinical feature is hyperglycemia (fasting plasma glucose level > 126 mg/ dL, or glycosylated hemoglobin [A.sub.1c] (Hb[A.sub.1c]) > 6.9%). (4) In most patients with type 2 diabetes, the onset is in adulthood, most commonly in obese people over 40 years of age. Hypertension, hyperlipidemia, hyperinsulinemia, and atherosclerosis are often associated with diabetes.

Pathophysiology and Complications

Type 2 diabetes is known to have a strong genetic component with contributing environmental determinants. Although the disease is genetically heterogeneous, there appears to be a fairly consistent phenotype once the disease is fully manifested. Whatever the pathogenic causes, the early stage of type 2 diabetes is characterized by insulin resistance in insulin-targeting tissues, mainly the liver, skeletal muscle, and adipocytes. Insulin resistance in these tissues is associated with excessive glucose production by the liver and impaired glucose utilization by peripheral tissues, especially muscle. These events undermine metabolic homeostasis, but may not directly lead to overt diabetes in the early stage. With increased insulin secretion to compensate for insulin resistance, baseline blood glucose levels can be maintained within normal ranges, but the patients may demonstrate impaired responses to prandial carbohydrate loading and to oral glucose tolerance tests. The chronic over-stimulation of insulin secretion gradually diminishes and eventually exhausts the islet beta-cell reserve. A state of absolute insulin deficiency ensues and overt clinical diabetes becomes fully blown. (5-7) The transition of impaired glucose tolerance to type 2 diabetes can also be influenced by ethnicity, degree of obesity, distribution of body fat, sedentary lifestyle, aging, and other concomitant medical conditions. (8)

The quality of life of type 2 diabetic patients with chronic and severe hypoglycemia is adversely affected. Characteristic symptoms of tiredness and lethargy can become severe and lead to a decrease in work performance in adults and an increase of falls in the elderly. (9) The most common acute complications are metabolic problems (hyperosmolar hyperglycemic nonketotic syndrome or HHNS) and infection. The long-term complications are macrovascular complications (hypertension, dyslipidemia, myocardial infarction, stroke), microvascular complications (retinopathy, nephropathy, diabetic neuropathy, diarrhea, neurogenic bladder, impaired cardiovascular reflexes, sexual dysfunction), and diabetic foot disorders. (9)

Conventional Therapies

The general consensus on treatment of type 2 diabetes is that lifestyle management is at the forefront of therapy options. In addition to exercise, weight control, and medical nutrition therapy, oral glucose-lowering drugs and injections of insulin are the conventional therapies. Since the most important pathological process during the development of diabetes involves three key organs, i.e., pancreatic islets, liver, and skeletal muscle, almost all anti-diabetic therapies are aimed at these organs. Pharmacological treatment is indicated when fasting glucose level exceeds 140 mg/dL, the postprandial glucose level exceeds 160 mg/ dL or Hb[A.sub.1c] exceeds 8.0 percen. (10)

Pharmacological Treatment and Limitations