Diabetes: Physiology and Types

• Physical activity has a number of benefits to selected chronic diseases.
• Discussed chronic diseases include diabetes, osteoporosis, and obesity.

Diabetes Physiology

• For a normal person, carbohydrate digestion and absorption in the intestine releases glucose in the blood.
• The pancreas releases insulin.
• Glucose uptake occurs in the liver, muscle, and adipose tissue.

What is Diabetes?

• Diabetes is a metabolic disease characterized by hyperglycemia.
• Hyperglycemia is a high glucose concentration in the blood.
• Fasting blood sugar more than 100 mg/dl indicates hyperglycemia.
• More than 126 mg/dl blood indicates diabetes.
• Insulin assists in glucose uptake.
• Insulin is a naturally occurring hormone produced by the pancreas.
• Diabetes is due to defects of insulin.
• Defects can be from insulin deficiency, resistance to insulin, or both.

Types of Diabetes

• Type I diabetes is rare and present from birth.
• Type II diabetes accounts for 90 to 95% of diabetic cases.
• Type II typically presents as an adult onset, but can be found in children.
• Type II is commonly present due to obesity.

Diabetes Symptoms

• Common symptoms of diabetes include excessive thirst (polydipsia).
• Another symptom is increased hunger (polyphagia).
• Other symptoms include lethargy and stupor, blurred vision, and acetone breath.
• Additional symptoms are weight loss and Kussmaul breathing (hyperventilation).
• Some experience nausea, vomiting, and abdominal pain.
• Frequent urination (polyuria) and glucose in the urine (glycosuria) are other symptoms.

Diabetic Trend

• Diabetes cases are trending upwards.

Glucose Uptake via Insulin Action

• Insulin is a protein.
• Glucose must have insulin to move from blood into a cell.
• Increased blood glucose causes the pancreas to secrete insulin.
• Insulin binds to a signaling receptor on a cell membrane and activates a pathway.
• This stimulates 'Glut transporters' inside the cell, which bind to the cell surface.
• Vesicles open for glucose entry into the cell.
• Glucose is then stored as glycogen

Insulin Resistance

• Insulin resistance means less glucose uptake for a given insulin concentration.
• A long-term effect of insulin resistance is increased insulin secretion.
• Another effect of insulin resistance is β-cell death.
• Obesity is a major contributor to insulin resistance, specifically intra-abdominal fat.

Physical Activity/Exercise and Glucose Uptake

• There is limited knowledge on this subject.
• Exercise provides an insulin-independent uptake mechanism.
• Exercise stimulates ‘Glut transporters’ for glucose uptake.
• A hypothesized mechanism is calcium-mediated uptake.
• Dynamic exercise can increase glucose uptake 50-fold.

Exercise and Diabetics

• Leg glucose uptake increases over time during exercise as measured in mmol/min.
• 200 Watts shows the greatest increase, followed by 130 Watts, and then 65 Watts.

Treating Diabetes

• One critical objective is to reduce overweight/obesity.
• Ideal treatment options include diet, medications, and lifestyle modifications.

Interventions

• A UK diabetes study focused on diet only vs. diet and medication.
• A Finland study focused on the effect of lifestyle modification.
• A DPP study focused on lifestyle modifications vs. medication.

UK Diabetes Study: Diet vs Medication

• The UK diabetes study examined the effect of weight loss through diet on diabetes.
• It also studied the effect of diabetes medications (Metformin, Exogenous Insulin).
• 5012 diabetics were put on a diet in the first 3 months resulting in a 5 kg weight loss.
• After 3 months, half continued diet therapy only.
• The other half continued diet and medication therapy.
• Adding medications was found to control blood glucose better.
• Incorporating an active lifestyle with diet can prevent weight gain.

Finnish Diabetes Prevention Study

• The Finnish Diabetes Prevention Study focused on combining diet and exercise.
• It included 522 pre-diabetics.
• The participants had fasting glucose between 100 and 125 mg/dl, and were insulin resistant.
• Participants were 40-65 years old and overweight (BMI>25 kg/m²).
• The study included a 3-year follow-up.
• There was a control group that received oral explanations once a year.
• Benefits were explained such as good diet, weight reduction, and regular physical activity.
• The intervention group followed the ‘whole nine yards’ approach.
• The intervention group had 5 major goals.
• These included 5% body weight loss.
• Other included less than 30% of total caloric intake from fat, less than 10% from saturated fat.
• Further goals included increased fiber intake.
• Finally, moderate exercise for at least 30 mins/day and more than 4 hrs/week.
• The primary outcome measure was the incidence of diabetes.
• The intervention group had a big decrease in diabetes incidence.
• Exercising had an independent effect in decreasing diabetes, even in the absence of weight loss.
• Lifestyle modification was found to be ‘super effective'.
• Medication works better than just dietary modification.
• Lifestyle modification works wonders.

USA Diabetes Prevention Program

• A USA diabetes prevention program was conducted
• It measured the incidence of diabetes using three groups of 3200 prediabetics.
• The three groups included control, medication, and lifestyle modification.
• The control group received a placebo and standard recommendations.
• They received written information and one meeting explaining benefits of a healthy lifestyle.
• The medication group received Metformin and standard recommendations.
• Metformin works to increase uptake of glucose into the liver from blood.
• The lifestyle modification group followed the "whole nine yards".
• The lifestyle modification group had a goal to maintain a 7% weight loss from baseline weight.
• They followed a low-calorie and low-fat diet.
• The exercise followed was moderate intensity activity for at least 150 min/week.
• There was a 4-year follow up.
• Independent lifestyle modification effects include weight loss and preventing weight gain.
• Medication effects include minimal weight loss even with an exercise effect, though it does have side effects.
• Diet only resulted in regaining weight rapidly, exercise effects were absent, and there was an earlier need for medications.
• Different modes can be adopted to increase physical activity.