Diabetes Flashcards
What is glucose?
monosaccharide used for ATP cycle for energy
What is glycogen?
a polysaccharide of glucose that serves as a form of energy storage
What is glucagon?
a peptide hormone produced by alpha cells of pancreas that raises the concentration of glucose and fatty acids in the bloodstream; is the main catabolic hormone of the body.
What is somatostatin?
a hormone that many different tissues produce, but it is found primarily in the nervous and digestive systems. The primary function of somatostatin is to prevent the production of other hormones and also stop the unnatural rapid reproduction of cells — such as those that may occur in tumours. The hormone also acts as a neurotransmitter and has a role in the GI tract.
What 2 features characterise diabetes?
- Hyperglycaemia = high blood glucose
- Caused by lack of insulin or reduced action of insulin
The pancreas has both endocrine and exocrine functions. Briefly describe the function of each
- Exocrine; related to digestion
- Endocrine; related to insulin
What is the pancreas composed of?
Islets of Langerhans –> endocrine cells that secrete hormones
What 4 groups of cells make up the Islets of Langerhans? What does each group secrete?
- Alpha cells –> glucagon (25% of total hormone produce)
- Beta cells –> insulin (75%)
- Delta cells –> somatostatin (5%)
- F cells –> pancreatic polypeptide (involved in satiety)
How is insulin formed?
- Production of pro insulin (insulin in yellow and c peptide in red) –> Proinsulin is the prohormone precursor to insulin made in the beta cells of the islets of Langerhans
- Cleavage at two sites: The cleavage sites are each located after a pair of basic residues (lysine-64 and arginine-65, and arginine-31 and −32).
- Equal amounts of insulin and c peptide produced
Why would a c peptide test be carried out?
A c peptide test can be carried out to determine how much insulin the body is producing.
What are the effects of insulin on the liver?
- Stimulates liver to store glucose in from of glycogen inhibits glycogenolysis (inhibits glycogen metabolism)
- Inhibits gluconeogenesis (inhibits generation of glucose)
Effects of insulin on muscle and adipose tissue regarding carbohydrates?
- Increases rate of glucose transport across cell membrane
- Increases rate of glycolysis
- Stimulates glycogenesis (glycogen synthesis)
Effects of insulin on muscle and adipose tissue regarding lipids?
- Decreases rate of lipolysis (lowers fatty acids)
- Stimulates fatty acid and triacyglycerol synthesis in tissues
- It increases the uptake of triglycerides from the blood into adipose tissue and muscle
Effects of insulin on muscle and adipose tissue regarding proteins??
- It increases the rate of transport of some amino acids into tissues
- It increases the rate of protein synthesis in muscle, adipose tissue, liver, and other tissues
- It decreases the rate of protein degradation in muscle (and perhaps other tissues).
Effects of insulin on the pancreas?
High insulin levels reduce the glucagon secretion from alpha cells of pancreas (to decrease levels of blood glucose)
How can diabetes be a risk factor for atherosclerosis?
High glucose levels leads to formation of pro-inflammatory molecules
Insulin effects on cancer growth?
- Insulin is a growth factor and effectively stimulates cancer cell growth
- Insulin excess is assumed to be a cancer-promoting factor
What are the 4 ways to diagnose diabetes?
- Fasting glucose
- Random glucose
- Two hours reading post OGTT
- HbA1c
What fasting glucose result is said to be diabetes?
≥ 7mmol/litre
What is important to note about random glucose tests in asymptomatic patients?
Must be repeated twice
What is an OGTT?
Oral glucose tolerance test; patient asked to take a glucose drink and their blood glucose level is measured before and at intervals
What is an HbA1c test?
Average blood glucose levels for last 2/3 months
Both fasting glucose and two hours glucose reading results can be used to diagnose diabetes
What can an impaired gasting glucose and impaired glucose tolerance indicate?
Prediabetes
What is prediabetes?
Characterised by the presence of blood glucose levels that are higher than normal but not yet high enough to be classed as diabetes. Depends on HbA1c criteria:
- Reflects average plasma glucose over the previous 8 to 12 weeks
- ≥ 48 mmol/mol = diabetes
- ≥41 and <48 mmol/mol = pre-diabetes
LIFESTYLE CHANGES
Classification of diabetes
Type 1 vs type 2 diabetes cause?
Type 1: Autoimmune destruction of insulin producing beta cells in the Islet of Langerhan
Type 2: Body is unable to metabolise glucose which leads to high blood levels; body does not produce enough insulin OR the body’s cells do not react to insulin
When does T1D typically occur? Who does it typically affect?
- Occur any age (BUT peaks around puberty)
- Equal sex incidence but after 15 years if age two-fold increase risk in male
There is a strong genetic component behind T1D. Certain genotypes of which system are considered as the strongest genetic risk factors for T1D? What are these genotypes?
- HLA Class II genotypes
- DR4-DQ8
- DR3-DQ2
These genotypes can cause autoimmunity, often triggered by environmental factors (e.g. infections such as flu).
What is HLA?
The human leukocyte antigen (HLA) system or complex is a group of related proteins that are encoded by the major histocompatibility complex (MHC) gene complex in humans. These cell-surface proteins are responsible for the regulation of the immune system.
What 4 autoantibodies are markers of beta cell autoimmunity in T1D?
- Insulin autoantibodies
- Glutamic acid decarboxylase autoantibodies (GAD)
- Islet antigen-2 autoantibodies (IA-2)
- ZnT8 transporter autoantibodies
These autoantibodies can be measured to diagnose T1D
Risk factors for T1D?
- Family History (genetic susceptibility)
- Perinatal factors - Low birth weight
- Viral infections
- Diet – cow’s milk
How does T1D present?
- Rapid onset (often few weeks)
- Weight loss + osmotic symptoms (polydipsia, polyuria, nocturia) + low energy
- Abdominal pain
- Often slim (but N.B. overweight people can also develop T1D)
- Can present as diabetes ketoacidosis (DKA)