Diabetes Flashcards
Cardinal Signs of Diabetes
Polydipsia (extreme thirst)
Polyuria (high volumes of urine production)
Polyphagia ( Lack of weight- gain)
Diagnosis of Diabetes
Fasting blood glucose >= 126 mg/dl
A1C >= 6.5%
Random glucose >= 200mg/dl
2 hr postprandial glucose >= 200mg/dl during an OGTT
Type 1 Diabetes
Glucose intolerance
- No functional insulin-secretion: near to complete loss of pancreatic cells
- These patients cannot secrete insulin during high levels of blood glucose so they have to take exogenous insulin (medications)
- Early onset (mean = 12)
- Patients at risk of metabolic acidosis
Auto-antigens associated with Type 1 diabetes
Insulin, islet antigen 2, Phogin, Zinc transporter, Glutamic acid decarboxylase, Voltage gated Ca, Vesicle associated membrane protein-2
Consequences of lack of insulin
Hyperglycemia -
1. Decreased glucose uptake in cells where glucose uptake in insulin dependent patients
2. decreases glycogen synthesis
3. Increased conversion of amino acids to glucose (gluconeogenesis)
Glucosuria -
1. due to high blood pressure
Hyperlipidemia -
1. Increased fatty acid mobilization from fat cells
2. increased fatty acid oxidation - Ketoacidosis
Unhibited glucagon -
1.Increased glucagon levels in the presence of increased blood glucose levels
Complications due to hyperglycemia
- Cardiovascular- Hyperglycemia can cause damage to small and large blood vessels which lead to compromised blood flow
- Neuropathy - accumulation of glucose in nerves that then gets reduced to aldose reductase through the poyol pathway so the ability of the nerves to prevent oxidative damage is compromized
- Nephropathy - Can compromise kidney functions due to renal vascular changes and changes in the glomerular basement membrane
- Ocular - Cataracts, retinal microaneurysms and hemorrhage
- Increased susceptibility to infections
Goal of insulin therapy and monitoring
Goal : Keeping average blood glucose levels below 150 mg/dL
Goal therapy levels
- Fasting : 70-110 mg/dL
- Pre meal : 80-130 mg/dL
- Post meal : <180 mg/dL
HbA1C: <7%
IDEAL goals of therapy
- Fasting : 70-90 mg/dL
- Pre meal : 70 - 105 mg/dL
- Post meal : <120-160
HbA1C : <6%
Is tight glycemic control worth the risk of hypoglycemia
Yes,
running the risk of hyperglycemia is worth it due to the life threatining factors associated with diabetes and high levels of A1C
Non-obese type 2 diabetes (non-insulin dependent)
Incidence in diabetic population: 10%
Age of Onset: Often under 25 ( also known as MODY)
Family history: Yes
Insulin secretion in response to glucose challenge: Low
- Mutations in specific beta cell proteins
Obese Type 2 diabetes (non-insulin dependent)
Incidence in diabetic population: 80%
Age of Onset: Usually over 35
Family history: yes
Insulin secretion in response to glucose challenge: Due to the high body mass although their body produces regular levels of insulin its not enough for their body mass
how does hypergylcemia lead to covalent modification of proteins?
Oxidation products of glucose react irreversibly with proteins which form advanced glycation end products which leads to loss of normal protein functions and can cause acceleration of aging (leads to many long term complications of diabetes
Receptor of advanced glycation endproducts (RAGE)
peptides bind to CML and CEL to bind to RAGE and cause inflammation
Complications due to hyperglycemia
Neuropathy Mechanism
The Polyol Pathway is how nerves process glucose for storage. When high levels of glucose are present this pathway depletes NADPH. With low levels of NADPH the nerves cannot protect neurons from oxidative damage leading to neuropathic problems
Complications due to hyperglycemia
Protein Modification
- Hexosamine pathway - due to high levels of glucose we also see a high level of Fructose-6-P which is taken into the hexosamine pathway and made into glucosamine-6-P which can become UDP-GlcNAc and can become a side chain to proteins and alter their function
- Protein Kinase C pathway - Glyceraldehyde-3-P enters this pathway to bind to DAG which activates protein kinase C
The insulin receptor
Role of alpha subunit
to repress the catalytic activity of the beta subunit (cross-linked). This repression is relieved when insulin binds
The insulin receptor
Role of beta subunit
Autophosphorylation
Contains the tyrosine kinase catalytic domains
Insulin effects on various tissues
1.Liver
Inhibits : glycogenolysis, Ketogenesis, gluconeogenesis
Stimulates: glycogen synthesis, triglyceride synthesis
2. Skeletal Muscle
Stimulates: glucose transport, amino acid transport
3. Adipose Tissue
Stimulates: triglyceride storage, glucose transports
Glucose disposal during fasting state
75% is non-insulin dependent: Liver GI, Brain
25% is insulin dependent in skeletal muscle
- glucagon is secreted to prevent hypoglycemia
Glucose Disposal during fed state
80-85% is insulin dependent in skeletal muscle
4-5% is insulin dependent in adipose tissue
Glucagon secretion is inhibited
Insulin inhibits release of fatty acids from adipose tissue
Glucose transporters
GLUT 1 (Km 1-2mM)
- constitutive and widely expressed throughout the tissue (also in Beta cells in the liver but small amount)
GLUT 2 (Km 15-20mM)
- constitutive and expressed in beta cells in the liver
GLUT 3 (Km <1mM)
- constitutive and expressed in neurons
GLUT 4 (Km 5mM)
- insulin- induced and found in the skeletal muscle adipocytes
Site of insulin production and secretion
Islets of Langerhans
Actions of pancreatic polypeptide hormones
- Glucagon
- this is secreted when blood glucose levels are low and it will stimulate glycogen breakdown to increase the blood glucose - Insulin
- which is released when glucose levels are hight and it stimulates the uptake and utilization of glucose - Amylin
- this is co secreted with insulin and it will slow gastric emptying, decrease food intake (make you feel full) and inhibit glucagon secretion - Somatostatin
- this is a general inhibitor of secretion
What are the 4 pancreatic polypeptide hormones
Glucagon, insulin, somatostatin, and amylin