Higher Human Biology Unit 2 – Physiology and Health Section 16 – Blood Glucose Levels and Obesity

What Can You Remember? What are the two types of lipoprotein? Which lipoprotein is considered the “good” transporter? Where does the “good” lipoprotein take the cholesterol? What is an atheroma? Describe the process of atherosclerosis What is the blood clot called when it is mobile? What are the diseases caused by a blood clot in the heart? What are the diseases caused y a blood clot outside the heart.

a – Atherosclerosis and Blood Vessel Damage We will be learning… To describe the relationship between elevated blood glucose levels and atherosclerosis

b – Hormonal Control We will be learning… To describe the role of pancreatic receptors and the role of hormones in negative feedback control of blood glucose through insulin, glucagon and adrenaline

c - Diabetes We will be learning… To state that there are two forms of diabetes; type 1 and 2. To describe the properties, symptoms and conditions that increase the likelihood of developing type 2 diabetes To describe the chemical test that allows blood sugar levels to be monitored To state and describe the glucose tolerance test for diabetes

d -Obesity We will be learning… To be able to describe obesity as a major risk factor in cardiovascular disease To be able to calculate BMI To understand the role of diet and exercise in reducing obesity and cardiovascular disease

Blood Glucose Levels and Vascular Disease Normal blood glucose levels are 5 mmol/l If a person has untreated diabetes blood glucose levels become elevated Chronic elevation of blood glucose levels (30mmol/l) leads to damage to blood vessels because the endothelial cells take up more glucose than normal.

Microvascular (small vessel) Disease When lining cells of a small blood vessel such as an arteriole take in more glucose than normal they become weaker as their basement membrane becomes thicker. They lose strength and may burst and bleed (haemorrhage) into surrounding tissues A tissue may be affected by being flooded with leaked blood of by not receiving enough oxygen Microvascular disease can - Damage the retina, affecting vision Damage the kidneys, causing renal failure Affect the nerves in the extremities

haemorrhage of blood vessels in the retina The damage may develop into atherosclerosis and lead to cardiovascular disease, stroke or peripheral vascular disease. Damaged smaller blood vessels may result in haemorrhage of blood vessels in the retina, renal failure or peripheral nerve dysfunction. haemorrhage of blood vessels in the retina

Regulation of Blood Glucose The body obtains glucose when food is eaten The process of negative feedback is responsible for regulating blood glucose concentration. The pancreas has receptors (islets of Langerhans) which respond to high glucose levels by producing the hormone insulin. Insulin activates the conversion of glucose to glycogen in the liver, decreasing blood glucose concentration. The pancreas also has receptors that respond to low glucose levels by producing glucagon. Glucagon activates the conversion of glycogen to glucose in the liver increasing blood glucose levels.

Increase in Blood Glucose When glucose levels in the blood increase Pancreas secretes more This insulin increases permeability of cells to glucose They take in more glucose for fuel The insulin also travels to the liver where high insulin levels also make the liver cells more permeable to glucose so they absorb more In the liver cells the glucose molecules are joined to form glycogen which is stored in the liver. Glucose levels in the blood return to normal

Decrease in Blood Glucose Glucagon released by the pancreas stimulates the conversion of glycogen to glucose Glucose levels in the blood return to normal

Control of blood sugar: Insulin and glucagon Insulin and glucagon are two hormones that control how much glucose (sugar) is in the blood These hormones are made in the pancreas. Your pancreas contains small groups of cells called the islets (or islands) of Langerhans.

Pancreas When you eat a meal, the amount of sugar in your blood rises. The cells in your pancreas react by making more insulin. When your blood sugar levels are low, the cells in your pancreas react by making more glucagon.

Adrenaline (Epinephrine) During exercise or fight or flight responses, glucose levels are raised by adrenaline. Adrenaline is released from the adrenal glands stimulating glucagon secretion and inhibiting insulin secretion. Epinephrine overrides the homeostatic control and promotes the breakdown of glycogen by glucagon to glucose. Epinephrine inhibits insulin secretion

Adrenaline – Stress Response The adrenal glands produce the hormone adrenaline in an emergency when the body needs a quick supply of glucose (for ‘fight or flight’) Adrenaline is secreted by the adrenal gland and inhibits the secretion of insulin and promotes the breakdown of glycogen to glucose, overriding the normal homeostatic control. When the crisis is over the normal homeostatic control then returns the blood sugar level to its norm.

Negative Feedback Control When a factor deviates from the norm and is returned to normal it often overshoots the mark, which triggers the reverse set of corrective mechanisms. Receptors Receptors Messages Messages Decrease in a factor Increase in a factor Normal Conditions Effectors Effectors Corrective Response Corrective Response

Diabetes Diabetics suffering from Diabetes mellitus can not produce enough (if any) insulin which causes their blood sugar level to get too high. Because of this the kidneys can not reabsorb all of the glucose from the glomerular filtrate and so glucose is excreted in the urine. Diabetes used to be fatal but can now be treated with a carefully controlled diet or insulin injections.

What is Diabetes Mellitus? A failure to control blood glucose levels and an impaired ability to store glucose in the form of liver and muscle glycogen Vascular disease can be a chronic complication of diabetes There are two types of diabetes: Type 1 Type 2 or adult onset diabetes

Type 1 Diabetes Type 1 diabetes usually occurs in childhood or early teens The person is unable to produce insulin Cells in the liver have the normal number of insulin receptors on their surface. They can therefore respond to insulin if given as a treatment (insulin injections) Treatment would involve regular doses of insulin

Type 2 Diabetes Type 2 diabetes or adult onset diabetes typically develops later in life and occurs mainly in overweight individuals. The person is able to produce insulin but their cells are less sensitive to it. Decreased number of insulin receptors, normal conversion of glucose to glycogen is prevented Treatment includes weight loss, diet control and in some cases insulin The insulin resistance is linked to a decrease in the number of insulin receptors in the liver leading to a failure in converting glucose into glycogen.

Both types of diabetes, if left untreated, results in a rapid increase in blood glucose levels following a meal The kidney filtrate is so rich in glucose that much is not reabsorbed Glucose is excreted in the urine Glucose in the urine is an indicator of diabetes Glucose tolerance tests are used to diagnose diabetes After fasting, a person has their blood glucose level measured They then consume a known mass of glucose, glucose load Blood glucose level is monitored (2hours) and glucose tolerance curve produced A ‘normal’ person’s glucose level rises to a maximum then drops quickly well within the time period Insulin production is normal

Symptoms of Diabetes Mellitus Classic symptoms of diabetes are – Frequent urination, with large volumes of urine (especially at night) Excessive thirst Hunger Weight loss Other symptoms – Fatigue Blurry vision Gum and urinary tract infections Slow healing of skin

Complications Associated with Diabetes Nerve damage Vascular disease can be caused by chronic diabetes Hypertension Stroke Kidney disease Increased risk of atherosclerosis Impaired vision due to cataracts or damaged retinas.

Diabetic ulceration

Testing for Diabetes In both types of diabetes, individuals blood glucose will rise rapidly after a meal and the kidneys are unable to cope resulting in glucose being lost in the urine. Testing urine for the presence of glucose is often used as an indicator of diabetes. Glucose tolerance test can be used to diagnose diabetes. The blood glucose levels of the individual are measured after fasting and two hours after drinking 250-330ml glucose solution.

Glucose Tolerance Test If your urine tests positive for glucose then a glucose tolerance test is used to diagnose diabetes Prior to having the test, you will be asked not to eat or drink certain fluids for 8-12 hours. Before the test, a blood sample is taken so your blood glucose can be measured. You will then be given a sweet glucose drink. After drinking the glucose drink, your blood glucose will be measured again after two hours.

Glucose Tolerance Curves Severe diabetic – insulin injections and carefully controlled diet needed Glucose level remains high Mild diabetic – condition controlled by diet Delayed response Glucose level returns to normal quickly Not diabetic - Insulin production normal 16/02/2019

Obesity Obesity is a major risk factor for cardiovascular disease and type 2 diabetes. Obesity is characterised by excess body fat in relation to lean body tissue (muscle). A body mass index (BMI) greater than 30 is used to indicate obesity. BMI = weight height2

Causes of Obesity High fat diet Energy intake should limit fats and free sugars Fats have a high calorific value Free sugars need no metabolic energy to be expended to digest them. Free sugars include monosaccharides and disaccharides that are added to foods by manufacturers, cooks or consumers, and sugars naturally present in honey, syrups, fruit juices and fruit concentrates Decrease in physical activity

Measurement of Body Fat To achieve accurate measurements of body fat other tests can be carried out. It is important to measure body density to allow the degree of accuracy to be increased. Other tests that can be carried out to measure body fat are: Densitometry Skin fold thickness Bioelectrical impedance Waist-hip ratio BMI

Body Mass Index (BMI) Classification BMI (kg/m2) Associated health risks Underweight Less than 18.5 Low Normal 18.5 - 24.9 Average Overweight Moderate Obese class 1 Obese class 2 Obese class 3 Greater than 25.0 25.0 – 29.9 30.0 – 34.9 35.0 – 39.9 Greater than 40.0 Increased Moderate increase. Severe increase. Very severe increase.

Skin fold thickness Densitometry Bioelectrical Impedence

Role of Exercise and Diet in Reducing Obesity Obesity is linked to high fat diets and decrease in physical activity. In the diet fats and free sugars should be limited due to the high calorific value of fats and free sugars don’t require the expenditure of metabolic energy to digest them. Exercise increases the energy expenditure and preserves lean tissue.

Role of Exercise in Reducing Risk Factors for CVD Exercise can help to reduce the risk factors for CVD by: Keeping weight under control Minimising stress Reducing hypertension Improving HDL blood lipid profiles

Now try these questions. 1. What is microvascular disease. 2 Now try these questions . . . . 1. What is microvascular disease? 2. What problems are associated with ‘Microvascular disease’? 3. Describe ‘Type 1’ diabetes 4. Discuss ‘Type 2’ diabetes

1. What is microvascular disease 1. What is microvascular disease? When lining cells of a small blood vessel such as an arteriole take in more glucose than normal they become weaker They lose strength and may burst and bleed (haemorrhage) into surrounding tissues A tissue may be affected by being flooded with leaked blood of by not receiving enough oxygen 2. What problems are associated with ‘Microvascular disease’? Damage the retina, affecting vision Damage the kidneys, causing renal failure Affect the nerves in the extremities

3. Describe ‘Type 1’ diabetes First occurs in childhood or early teens Ability of pancreatic cells to produce insulin is absent Cells in the liver have the normal number of insulin receptors on their surface They can therefore respond to insulin if given as a treatment (insulin injections) 4. Discuss ‘Type 2’ diabetes Adult onset, sufferer overweight or obese Pancreatic cells able to produce insulin Decreased number of insulin receptors, normal conversion of glucose to glycogen is prevented Treatment includes weight loss, diet control and in some cases insulin

a – Atherosclerosis and Blood Vessel Damage Now I can….. Describe the relationship between elevated blood glucose levels and atherosclerosis b – Hormonal Control Describe the role of pancreatic receptors and the role of hormones in negative feedback control of blood glucose through insulin, glucagon and adrenaline

c - Diabetes Now I can….. State that there are two forms of diabetes; type 1 and 2. Describe the properties, symptoms and conditions that increase the likelihood of developing type 2 diabetes Describe the chemical test that allows blood sugar levels to be monitored State and describe the glucose tolerance test for diabetes

d -Obesity Now I can….. Describe obesity as a major risk factor in cardiovascular disease Calculate BMI Understand the role of diet and exercise in reducing obesity and cardiovascular disease

Adrenaline (epinephrine) Section 16 Word Meaning Adrenaline (epinephrine) hormone that stimulates the release of glucose from glycogen during stress or exercise Body mass index relative measurement based on height and weight Glucagon hormone produced by the pancreas that stimulates the conversion of glycogen into glucose in the liver Glycogen storage carbohydrate located in the liver and muscle tissues Homeostasis maintenance of a steady state in the cells of a living organism Insulin hormone produced by the pancreas that stimulates the conversion of glucose into glycogen in the liver

Give an account of Type 2 diabetes under the headings: causes; (2 marks) effects. (6 marks) diagnosis and treatment (2 marks)

Causes (maximum of 2 marks): Type 2 diabetes results from reduced cellular sensitivity to insulin…… …caused by a reduction in the number of insulin-receptors on liver cells. It is associated mainly with increasing obesity in adulthood. Effects (maximum of 6 marks): Diabetes of all forms means that the body is unable to control the rise in blood glucose levels after meals. Diabetics have chronically high blood glucose levels… …which damage blood vessels walls. This leads to the development of vascular diseases in large blood vessels… …e.g. atherosclerosis / stroke / myocardial infarction. In small blood vessels of vulnerable tissues it can cause haemorrhaging in the retina, resulting in reduced vision / damage to the glomeruli, resulting in renal failure / slowing down of impulses in the peripheral nervous system, resulting in loss of control and sensation. (1 mark for naming a cause and 1 additional mark for naming the resultant effect) Diagnosis and treatment (maximum of 2 marks) Diabetes is diagnosed by a glucose tolerance test… …which involves blood tests taken before, and 2 hours after taking a drink containing 75g of glucose. The patient should have fasted for 8 hours before the test. Treatment is usually administered by adjusting diet… …reducing energy intake and increasing exercise levels.