Flashcards in Molecular Basis of T2D Deck (25)
Which type of diabetes has a greater genetic contribution?
What are the 2 stages of T2D?
1. Insulin resistance
-serum glucose may be normal, but insulin levels are elevated and sensitivity is beginning to decrease
-Increased risk for CVD
-Early stages of disease, beta cells break down
Explain counter regulation
After insulin does its job, and serum glucose levels decrease, glucagon is released to promote glucose production
What do insulin levels do to galactose?
Insulin increases the volume of distribution of galactose
What is the rate limiting step in glucose metab?
Insulin-regulated transport across the plasma membrane
Describe the process of inc transporters on membrane
1. Insulin binds its receptor and promotes translocation of GLUT4 (fat and muscle cells) onto the cell surface
2. Contraction of skeletal muscle (ie exercise) promotes increased numbers of GLUT4 receptors on the cell surface and also increases cell's sensitivity to insulin
Chronic exercisers have inc total amt of available GLUT4
1 &2 are regulated by two dif pathways
Define insulin insensitivity
Inability to stim glucose uptake by body tissues AND inability of insulin to suppress hepatic output of glucose
What tissue is responsible for most of the insulin dependent glucose disposal?
What is the cause of elevated fasting glucose levels in T2D?
Increased hepatic output
What 2 things can cause hyperglycemia following a meal in T2D?
1. Inability of insulin to stimulate glucose uptake
2. Inability of insulin to shut down hepatic glucose production
What is the euglycemic insulin/glucose clamp?
Gold standard for measuring insulin resistance: Infuse insulin at a constant rate and infuse glucose at a rate that will achieve a stable serum glucose level. The rate of glucose utilization is then equal to the rate of glucose infusion. If you are insulin resistant, less glucose is needed to maintain a predetermined serum glucose level
Describe the time frame for sources of glucose after a fast
After about 4 hours, glucose levels dec
Glycogen is responsible for the rise in glucose levels until about hour 10. After that, they begin to decline. Gluconeogenesis takes over and peaks at 2 days and continues to maintain a constant level
What is the major determinant of fasting blood glucose?
Glucose output from the liver
What level should glucose uptake be by the muscle during fasting?
What does insulin stimulate in fat cells?
Uptake of fatty acids and their storage
What happens in insulin resistant fat cells?
Fat cells can't take up glucose, can't maintain TGs and the rate of FA release into the blood increases.
What happens to glucagon levels after a normal meal in normal people and in T2D?
-T2D: do not decrease/go up after a meal
What is responsible for the greatest morbidity and mortality in diabetics?
What determines the rate of TG synthesis in the liver?
#FAs in the blood. So since fat is insulin insensitive and they thus release more FAs, then more TGs are made by the liver. In addition, after a meal, there are FAs from that meal, which the liver also makes into TGs. This leads to increased CV risk and for a fatty liver
What is insulin's role in stimulating the production of new FAs/TGs?
Insulin actually stimulates the synthesis of new FAs/TGs by the liver...
There is a disconnect here...if insulin stimulates the synthesis of new FAs by the liver...but the liver is resistant to the actions of insulin (in terms of glucose), then why is there increased FA synthesis in insulin resistant people?
Insulin resistance is SELECTIVE
-The liver is resistant to the inhibitory effects of insulin on glucose output, but maintains sensitivity to the actions of insulin on lipids (ie it produces more lipids for the reasons stated in other answers)
Explain how selective insulin resistance fits in to pre-diabetes
-Explains why people with hyperinsulinemia (pre diabetes) are at inc risk for CV events, even in absence of hyperglycemia
-In pre-diabetes, insulin remains selectively able to regulate blood glucose (to an extent), but perhaps it is not able to control the liver's production of fatty acids
Predisposition to T2 diabetes is related to...
Amt of fat you have and the distribution of body fat [apple (upperbody/truncal obesity) vs pear(gynoid obesity)]
Is BMI a good indicator of adiposity?
NO! Doesn't take muscle into account, and diabetes is a disease of the fat cell