🍎Medical Nutrition Therapy I Unit 8 – Diabetes: Pathophysiology and Types

What is Diabetes?

• Diabetes is a chronic metabolic disorder characterized by high blood glucose levels (hyperglycemia)
• Occurs when the body cannot produce enough insulin or effectively use the insulin it produces
  • Insulin is a hormone produced by the pancreas that regulates blood glucose levels
• Leads to impaired glucose metabolism and utilization by the body's cells
• Can cause damage to various organs and tissues over time if left uncontrolled
• Affects millions of people worldwide and is a major public health concern
• Classified into different types based on the underlying pathophysiology and etiology

Types of Diabetes

• Type 1 diabetes (T1D)
  • Autoimmune disorder where the body's immune system attacks and destroys insulin-producing beta cells in the pancreas
  • Usually diagnosed in children and young adults but can occur at any age
  • Requires lifelong insulin therapy to manage blood glucose levels
• Type 2 diabetes (T2D)
  • Most common form of diabetes, accounting for 90-95% of all cases
  • Characterized by insulin resistance and/or decreased insulin production
  • Often associated with obesity, physical inactivity, and genetic factors
  • Can be managed through lifestyle modifications, medication, and sometimes insulin therapy
• Gestational diabetes
  • Develops during pregnancy due to hormonal changes that affect insulin sensitivity
  • Usually resolves after delivery but increases the risk of developing T2D later in life
• Other types of diabetes
  • Latent Autoimmune Diabetes in Adults (LADA)
  • Maturity-Onset Diabetes of the Young (MODY)
  • Secondary diabetes caused by other conditions (pancreatic disease, endocrine disorders, medications)

Pathophysiology of Diabetes

• Type 1 diabetes
  • Autoimmune destruction of insulin-producing beta cells in the pancreas
  • Leads to absolute insulin deficiency and inability to regulate blood glucose levels
  • Genetic and environmental factors play a role in the development of T1D
• Type 2 diabetes
  • Combination of insulin resistance and impaired insulin secretion
  • Insulin resistance occurs when cells become less responsive to insulin, leading to decreased glucose uptake and utilization
  • Impaired insulin secretion results from beta cell dysfunction and reduced insulin production
  • Progression from normal glucose tolerance to prediabetes and eventually T2D
• Gestational diabetes
  • Hormonal changes during pregnancy (increased levels of cortisol, prolactin, and human placental lactogen) can lead to insulin resistance
  • Increased insulin resistance puts additional stress on the pancreas to produce more insulin
  • If the pancreas cannot compensate for the increased insulin demand, hyperglycemia develops

Risk Factors and Causes

• Type 1 diabetes
  • Genetic predisposition (certain HLA gene variants)
  • Environmental triggers (viral infections, early exposure to cow's milk or cereals)
  • Autoimmune factors (presence of autoantibodies against beta cells)
• Type 2 diabetes
  • Obesity and excess body fat, especially abdominal obesity
  • Physical inactivity and sedentary lifestyle
  • Family history and genetic susceptibility
  • Age (risk increases with advancing age)
  • Race/ethnicity (higher risk in African Americans, Hispanics, Native Americans, and Asian Americans)
  • Prediabetes (impaired fasting glucose or impaired glucose tolerance)
  • Metabolic syndrome (cluster of conditions including hypertension, dyslipidemia, and abdominal obesity)
• Gestational diabetes
  • Overweight or obesity before pregnancy
  • Family history of diabetes
  • Advanced maternal age (>25 years)
  • Previous history of gestational diabetes or delivering a baby weighing >9 pounds
  • Polycystic ovary syndrome (PCOS)

Symptoms and Diagnosis

• Common symptoms of diabetes
  • Polyuria (increased urination)
  • Polydipsia (increased thirst)
  • Polyphagia (increased hunger)
  • Unexplained weight loss
  • Fatigue and weakness
  • Blurred vision
  • Slow-healing wounds or frequent infections
• Diagnosis of diabetes
  • Fasting plasma glucose (FPG) test: $\geq 126$ mg/dL on two separate occasions
  • Oral glucose tolerance test (OGTT): 2-hour plasma glucose $\geq 200$ mg/dL after a 75-gram glucose load
  • Glycated hemoglobin (A1C) test: $\geq 6.5\%$
  • Random plasma glucose test: $\geq 200$ mg/dL with classic symptoms of hyperglycemia
• Screening for diabetes
  • Recommended for adults aged 45 years and older or those with risk factors
  • Repeated every 3 years if results are normal, more frequently if prediabetes is detected

Complications of Diabetes

• Acute complications
  • Diabetic ketoacidosis (DKA): life-threatening condition caused by insulin deficiency and high levels of ketones in the blood
  • Hyperosmolar hyperglycemic state (HHS): severe hyperglycemia leading to dehydration and electrolyte imbalances
  • Hypoglycemia: low blood glucose levels caused by excessive insulin, skipped meals, or increased physical activity
• Chronic complications
  • Microvascular complications
    • Retinopathy: damage to the blood vessels in the retina, potentially leading to vision loss or blindness
    • Nephropathy: damage to the kidneys, leading to impaired kidney function and end-stage renal disease
    • Neuropathy: damage to the nerves, causing numbness, tingling, pain, and loss of sensation in the extremities
  • Macrovascular complications
    • Cardiovascular disease: increased risk of heart attack, stroke, and peripheral artery disease
    • Cerebrovascular disease: increased risk of stroke and cognitive impairment
  • Other complications
    • Foot problems (ulcers, infections, and amputations) due to neuropathy and poor circulation
    • Skin conditions (bacterial and fungal infections)
    • Dental problems (gingivitis and periodontitis)
    • Increased risk of certain cancers (liver, pancreas, endometrium, colon, and breast)

Treatment and Management

• Goals of diabetes management
  • Achieve and maintain near-normal blood glucose levels
  • Prevent or delay the development of complications
  • Improve overall quality of life
• Insulin therapy for type 1 diabetes
  • Multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII) using an insulin pump
  • Basal-bolus regimen: long-acting insulin for basal needs and rapid-acting insulin for meals and corrections
• Pharmacological treatment for type 2 diabetes
  • Metformin: first-line medication that reduces hepatic glucose production and improves insulin sensitivity
  • Sulfonylureas: stimulate insulin secretion from the pancreas
  • Thiazolidinediones: improve insulin sensitivity in peripheral tissues
  • DPP-4 inhibitors: enhance the action of incretin hormones, which stimulate insulin secretion and suppress glucagon release
  • GLP-1 receptor agonists: slow gastric emptying, increase insulin secretion, and reduce glucagon secretion
  • SGLT2 inhibitors: promote glucose excretion in the urine and reduce renal glucose reabsorption
• Lifestyle modifications
  • Healthy eating habits: balanced diet, portion control, and carbohydrate counting
  • Regular physical activity: at least 150 minutes of moderate-intensity aerobic exercise per week
  • Weight management: achieving and maintaining a healthy body weight
  • Stress management and adequate sleep
• Self-monitoring of blood glucose (SMBG)
  • Regularly checking blood glucose levels using a glucometer
  • Helps guide treatment decisions and identify patterns of hyperglycemia or hypoglycemia
• Education and support
  • Diabetes self-management education (DSME) programs
  • Medical nutrition therapy (MNT) provided by registered dietitians
  • Psychosocial support to address emotional and mental health needs

Nutritional Considerations

• Carbohydrate management
  • Monitoring carbohydrate intake is crucial for blood glucose control
  • Carbohydrate counting: estimating the amount of carbohydrates in meals and snacks to guide insulin dosing or medication adjustments
  • Choosing complex carbohydrates (whole grains, legumes, fruits, and vegetables) over simple sugars and refined carbohydrates
• Glycemic index (GI) and glycemic load (GL)
  • GI measures how quickly a food raises blood glucose levels compared to pure glucose
  • GL takes into account both the GI and the amount of carbohydrates in a serving of food
  • Low GI and GL foods are preferred for better glycemic control
• Fiber intake
  • Adequate fiber intake (25-30 grams per day) helps improve glycemic control, promotes satiety, and supports digestive health
  • Sources of fiber include whole grains, fruits, vegetables, legumes, and nuts
• Protein and fat intake
  • Protein intake should be individualized based on kidney function and overall health status
  • Choosing lean protein sources (poultry, fish, lean meats, and plant-based proteins) over high-fat meats
  • Limiting saturated and trans fats, which can increase the risk of cardiovascular disease
  • Incorporating healthy fats (monounsaturated and polyunsaturated fats) from sources like olive oil, avocados, nuts, and fatty fish
• Meal planning and timing
  • Distributing carbohydrate intake evenly throughout the day to prevent large fluctuations in blood glucose levels
  • Eating regular meals and snacks to match insulin or medication regimens
  • Adjusting meal times and insulin doses for physical activity and special occasions
• Hydration and alcohol consumption
  • Maintaining adequate hydration by drinking water and unsweetened beverages
  • Limiting alcohol intake, as it can interfere with blood glucose control and contribute to hypoglycemia
  • If consuming alcohol, doing so in moderation and with food to minimize the risk of hypoglycemia