Lecture 53: Muscle and Adipose Metabolism Flashcards
Adipose tissue is sometimes considered the largest endocrine gland due to its?
-Hormone production
Describe the process of Lipolysis:
During fasting state (low insulin levels) –> Epinephrine (not glucagon) –> activates PKA –> phosphorylates Hormone sensitive lipase –> provides energy for the body.
Describe the process of lipogenesis:
Fed state –> activates insulin –> dephosphorylates Lipoprotein Lipase (LPL) –> breaks down fatty acids for storage of TAGs in adipocytes.
Why can’t the adipocyte make glycerol 3 phosphate?
It doesn’t have Glycerol Kinase. Glycerol 3 phosphate in the adipocyte comes from DHAP.
In what state are TAGs made?
- High insulin/glucagon ratio (FED STATE)
- Increase in GLUT-4 adipocyte transporters
Insulin stimulates synthesis and secretion of ______ by adipocytes?
LPL
-Apo C-II in the CM and VLDL
What happens during Type I diabetes in relation to TAG lipolysis?
-Your body thinks your are starving due to low insulin levels and activates HSL, which degrades TAGs and makes Ketone Bodies for the brain to use.
Whats happens to glycerol once the TAGs are degraded in the adipocyte?
Goes to the liver –> Glycerol –> Glycerol 3 P –> DHAP –> Gluconeogenesis
What is unique about white adipose tissue?
This tissue reclaims some of the FA that it mobilizes
-it releases energy in a regulated fashion
Abdominal (white) adipose tissue
- Highly responsive to Epinephrine (activated)
- Antilypolytic effect of insulin is low
Brown adipose tissue
- Abundant mitochondria
- Babies have this (heat production) due to uncouplers (UCP-1/Thermogenin)
- H+ channel proteins
2 causes of Insulin Resistance:
- Obesity predisposes a person to Insulin Resistance
- However, insulin resistance can also be a result of absence of adipose tissue
Leptin
- mediates appetite suppression
- Induces UCP-1 (generates heat)
Obese and their leptin levels:
Obese people have normal/high leptin levels
-
AMPK
-activated during low energy state levels
Metabolic syndome
- causes Obesity due to insulin resistance
- hyperglycemia, hyperinsulinemia, and hypertriacylglerolemia (due to elevated fatty acids)
Type I (slow twitch) mucle
- Slow ATP hydrolysis
- appears Red
- high oxidative capacity
- Good capillary supply
Type IIB (sast glycolytic) muscle
- Fast ATP hydrolysis
- Lots of glycogen storage
- low oxidative capacity
- appears White
- Poor capillary supply
Skeletal muscle requires…
-An ability for aerobic respiration bc it take some time for your blood supply to kick in. You will need ATP before that, and so you need Type IIB muscles
Reservoir of high energy phosphate bonds…
Creatine phosphate
How is Hormone sensitive lipase activated in adipocytes?
Via Epinephrine and low insulin levels. Adipocytes don’t really have Glucagon receptors
