Diabetes Mellitus: Definition and Types

Diabetes Mellitus

• Diabetes mellitus is an endocrine disorder characterized by abnormal metabolism of carbohydrates, fats, and proteins.
• It is a group of metabolic diseases characterized by increased levels of glucose in the blood resulting from defects in insulin secretion, insulin action, or both.

Types of Diabetes

Type 1 Diabetes (Insulin Dependent Diabetes)

• Occurs mainly in children and young adults, but can also develop at any age.
• Characterized by autoimmune, cell-mediated, and selective destruction of the insulin-producing beta cells of the pancreatic islets in genetically predisposed persons.
• Results in low endogenous insulin secretion, impaired fat and protein metabolism, and inhibited lipolysis, leading to excessive production of fatty acids.
• Low plasma insulin levels decrease protein synthesis, leading to increased breakdown of structural proteins and weight loss.

Type 2 Diabetes (Non-Insulin Dependent Diabetes)

• Occurs in people 30 years and above, and obese individuals.
• Characterized by the pancreas producing insufficient endogenous insulin due to impaired insulin action, leading to increased hepatic glucose production and decreased insulin-mediated glucose uptake due to post-receptor defects.
• Affected by two factors: insulin resistance and a marked decrease in the ability of the pancreas to produce insulin.

Risk Factors for Diabetes Mellitus

• Family history of diabetes
• Age above 45 years
• Previously identified impaired fasting glucose or impaired glucose tolerance
• Hypertension (> 140/90 mmHg)
• History of gestational diabetes or delivery of babies over 5 kg
• Obesity

Causes of Diabetes Mellitus

Type 1 Diabetes

• Idiopathic and autoimmune processes

Type 2 Diabetes

• Pancreatic disorders (e.g., pancreatitis, pancreatectomy, cystic fibrosis)
• Glucocorticoids (e.g., Cushing's syndrome)
• Viral infections (e.g., mumps, Coxsackie virus B)
• Genetic defects of insulin action
• Drug-induced (e.g., corticosteroids, thiazide diuretics, and phenytoin)

General Pathophysiology

• Sugar and carbohydrate foods are broken down in the bowel and absorbed into blood as glucose.
• Glucose is stored as glycogen in the liver by the action of insulin.
• When sugar in blood rises above a certain level, the kidneys excrete excess sugar in urine, leading to large quantities of urine passed in an attempt to get rid of excess sugar.
• The excess urine leads to thirst, while the continuous drain of glucose from the body depletes tissues of vital energy supplies.
• In severe cases, since carbohydrates are no longer available, fat is mobilized from adipose tissues and broken down to produce energy.

Clinical Presentations

Type 1 Diabetes

• Rapid onset due to the inability of the pancreas to produce insulin
• Marked weight loss
• Increased blood sugar
• Polyuria and thirst
• High urine sugar and acetone
• Drowsiness
• Low plasma insulin
• Nocturia
• Muscular cramps
• Blurred vision

Type 2 Diabetes

• Gradual onset of symptoms
• Usually occurs in middle age or later
• Obesity is common
• Increased blood glucose levels
• Increased urine sugar
• Recurrent fungal infections
• Recurrent bacterial infections
• Polyuria and thirst
• Blurred vision

Cardinal Features

• Polyuria
• Polydipsia
• Polyphagia
• Paresthesia
• Glucosuria
• Weight loss/gain
• Weakness and fatigue

Investigations

• Urine: output is increased, pale in color, high specific gravity (1.030-1.040), and sugars present
• Blood: normal fasting sugars are about 4.5 mmol/l and rise to about 6.5 mmol/l (120 mg/100 ml) after a meal in diabetes; it may be over 11 mmol/l
• Oral glucose tolerance test: 75g of glucose is given orally to the fasting patient, and samples are taken every ½ hour for 2 hours; if the glucose levels in 2 hours are more than 10 mmol/l, it's diagnostic

Management

Aims

• To achieve and maintain satisfactory blood glucose levels
• Maintenance of desirable weight
• To prevent or delay the development of cardiovascular, renal, and neurological complications

Components

• Nutrition therapy
• Pharmacology therapy
• Monitoring
• Exercise
• Education

Nutrition Therapy

• It's a major factor in the control of diabetes mellitus
• The patient's energy requirements are calculated according to stature, age, sex, occupation, with the aim of attaining or maintaining a reasonable body weight, controlling blood glucose levels, and normalizing blood lipids and blood pressure
• The proportion of prescribed calories allocated to each food is approximately 50-60% carbohydrates, 20-30% fats, and 10-20% proteins
• Food intake is usually best divided into 3 meals a day

Drugs

• Type 2 diabetes: oral anti-diabetic agents (e.g., biguanides, sulphonylureas, thiazolidinediones, alpha-glucosidase inhibitors, and meglitinides)
• Type 1 diabetes: insulin injection (e.g., porcine insulin, human actrapid insulin, and humulin lente)

Monitoring

• Patients on multiple dose insulin or sulphonylureas should do self-monitoring of blood glucose
• At least prior to meal and snacks, at bedtime, prior to exercise, and after treating low blood glucose until they are normal

Physical Activity and Exercises

• Regular physical activity improves metabolic control, increases insulin sensitivity, improves cardiovascular health, and helps with weight loss and its maintenance
• There are two types of exercises: aerobic or endurance exercises (e.g., walking, running) and anaerobic or resistance exercises (e.g., lifting weights)

Diabetic Education

• Patients are provided with knowledge and skills on self-care management of their diabetes, including blood glucose monitoring, body weight monitoring, foot care, personal hygiene, healthy lifestyle/diet or physical activity, identifying targets for control, and stopping smoking.