Week 14 Diabetes Flashcards
Early manifestations of hypoglycemia
- palpitations, tachycardia
- diaphoresis, anxiety
- weakness, hunger, nausea
diaphoresis
profuse perspiration
Manifestations of prolonged/severe hypoglycemia
- hypothermia
- confusion, hallucinations
- seizure, coma
hyperglycemia: early and later manifestations
Early:
- polydipsia, polyuria
- altered vision
- weight loss, mild dehydration
Late:
- cardiac arrhythmias
- coma
Location of the pancreas
behind the stomach between the spleen & the duodenum
Functions of the pancreas
Mostly exocrine: pancreatic juice contains enzymes for protein digestion 1-3% is islets - endocrine - insulin/glucagon secretion from islets of langerhans scattered throughout exocrine pancreas
Beta Cells
Secrete insulin. 65-80% of islet endocrine cells
Alpha cells
Secrete glucagon; 15-20% of the total islet;
Delta cells
Secrete somatostatin; 3-10% of islet endocrine ;
Role of somatostatin
inhibits both insulin & glucagon
pancreatic polypeptide cells
PP cells; secrete pancreatic polypeptide 3-5% of islet endocrine cells; Reduces appetite and food intake, thus regulating blood sugar.
Parasympathetic innervation of pancreatic islets
Parasympathetic innervation via Vagus nerve; Primary NT is ACh –> stimulates insulin release
Sympathetic innervation of pancreatic islets
Postganglionic fibres of the celiac ganglion; Primary NT is NE –> inhibits insulin secretion
Insulin synthesis and structure
Insulin is synthesized as proinsulin - mainly in the beta cells, but also in the brain. It is synthesized in RER, processed in golgi and then stored in secretory granules for hours or days before secretion. Proinsulin has A and B chain linked by disulphide bonds with a C peptide.
Regulation of insulin secretion
- Glucose is the major stimulator
- there are also neural, hormonal, and nutrient stimulants, but these are also considered glucose-dependent in order to protect agains inappropriate stimulation of insulin and hypoglycemia.
Key hormones that stimulate release of insulin
GIP GLP-1 Glucagon (sounds paradoxical, but it does)
glucotoxicity & lipotoxicity
prolonged glucose and free fatty acid exposure may cause apoptosis of B cells
Mechanism of insulin release from the B cell
- Glucose enters through a GLUT2 channel
- Glucokinase cleaves glucose to G6P
- G6P inhibits an ATP-dependent K+ channel, which stimulates influx of Ca2+ through a voltage-gated Ca2+ channel
- Influx of Ca2+ stimulates exocytosis of granules containing proinsulin.
Biological actions of insulin (conceptually)
- anabolic; promotes energy storage
- Targets muscle, fat, and liver
- critical role in growth and development
Action of insulin on muscle and adipocytes
- Insulin binds receptor on muscle cells and adipocytes
- Signalling pathway stimulates translocation of vesicles with GLUT 4 transporters to cell surface
- Glucose enters cells
Outcomes of insulin in adipose tissue
Lipogenesis (decreased lipolysis)
Outcomes of insulin in striated muscle
Glycogen and protein synthesis
Outcomes of insulin in the liver
Glycogen synthesis;
Lipogenesis (decreased gluconeogenesis)
The insulin receptor
A tyrosin kinase; 2 alpha subunits and 2 beta subunits.
Glucagon synthesis
- Synthesized as proglucagon in intestinal L cells and in pancreatic cells
- Proglucagon contains other glucagon-related peptides (GLPs)
Action of glucagon
- major site of action is in the liver (in contrast to insulin, which works on many tissues)
- Stimulates glycogenolysis and gluconeogenesis
- Aims to maintain blood glucose during fasting and exercise
where is glucagon cleared?
in the renal capillary bed
Stimulants of glucagon (hormonal, neural, nutrients)
- Hormonal: GIP and CCK
- Neural: ACh and NE
- Nutrients: low glucose and Ala or Arg
Action of cortisol in carbohydrate metabolism
- counterregulatory to insulin action (works like glucagon)
- Increases hepatic gluconeogenesis to maintain plasma glucose during fasting
Action of growth hormone in carbohydrate metabolism
Counterregulatory to insulin action and inhibits insulin.
Action of the sympathetic nervous system in carbohydrate metabolism
can directly stimulate hepatic glucose output
action of the parasympathetic nervous system in carbohydrate metabolism
can directly stimulate hepatic glucose uptake via the vagus nerve.
Macrovascular outcomes of diabetes
- Cardiovascular: MI, angina, heart failure
- Cerebrovascular: Stroke
- Peripheral vascular: foot ulceration, ischemia/gangrene, amputation, Charcot foot
Microvascular outcomes of diabetes
- Retinopathy: proliferative, hemorrhage, retinal detachment, blindness
- Nephropathy: Microabuminuria, GFR decline, end-stage renal disease
- Neuropathy: peripheral numbness or pain, cranial
How does insulin act on cells to help them take up glucose?
Insulin binds receptor (a tyrosine kinase), stimulating a cascade involving PI-3, which causes vesicles containing GLUT4 transporters to be translocated to the cell surface so that glucose may enter the cell.
Triggers for GLUT4 translocation
Insulin and exercise
2 modes of insulin secretion
the ‘basal-bolus’ concept
Basal - consistent release of insulin to suppress glucose between meals and overnight.
Prandial - spikes of insulin to facilitate glucose uptake after meals
Compare human basal, analogue basal, human bolus, and analogue bolus insulin (2)
Human basal insulin has a peak midway, whereas analog basal is much more steady throughout the day. With this in mind, human basal is not ideal for T1D because hypoglycemia may occur and they may not sense the warning signs. Analogue bolus acts much faster than human bolus, so it is preferred.
Random blood glucose result for diagnosing diabetes
> 11.1 mmol/L
Screening for diabetes (2)
Anyone who is high risk
- Age > 40 years or high risk screen every 3 years
- first degree relative or very high risk for another reason, screen every 6-12 months.
What kinds of exercise have been shown to improve glycemic control and lower morbidity in people with diabetes? How much and what type of exercise is recommended for people with diabetes?
- 150 minutes of moderate-to-vigorous aerobic exercise per week
- include resistance exercises 2 or more times a week
- set physical activity goals and involve a multidisciplinary team if available
- minimize uninterupted sedentary time
Should we aim for weight loss in diabetes?
- the goal is to prevent weight gain, promote weight loss, and prevent weight re-gain
- Weight loss of 5-10% (in CDM slides for the rest)
Serum osmolality equation
2[Na] + [HCO3] + [urea]
Actions of Incretin Agents
Differences in effects of GLP-1 agonists and DPP-4 Inhibitors
Compare and Contrast GLP-1 R Agonists and DPP-4 Inhibitors
- administration
- GLP-1 concentrations made available
- targets of action
- activating portal glucose sensor
- increasing insulin and/or glucagon secretion
- Effects on gastric emptying, weight loss, GIT symptoms
TZD Actions
- reduces insulin resistance by sensitizing insulin receptors
- modify adipocyte differentieation –> reduced Leptin levels –> increased appetite –> increased wt
- Inhibits VEGF-induced angiogenesis
AIC Targets for people who have diabetes in different contexts (4)
- < 6.5 for adults with type II diabetes to reduce risk of chronic kidney disease and retinopathy if at low risk of hypotension
- <7 for most adults with Type I or Type II diabetes
- 7-8.5 if recurrent hypoglycemia and/or unaware of hypoglycemia warning signs, limited life expectancy, frail/elderly
- No A1C measurement recommended at end of life
tight glycemic control minimizes risk of microvascular complications, though this is not the case for macrovascular risk.
Which two families of diabetes drugs pose CV benefits?
GLP-1 agonists and SGLT2 inhibitors