Fat
Fat is made from fats, also known as lipids.
Intra-Abdominal Obesity
IAA can be measured using waist circumference, which is strongly correlated with CT/MRI (the gold standard)
adipo
Fat Growth
Adipocyte energy intake comes primarily from two sources - glucose and lipids.
Effects of insulin on fat are:
Carbohydrate Metabolism
- Increased glucose uptake, through GLUT-4 transporters,
- Increased glycolysis and production of DHAP and glycerol 3-phosphate
- Increased activity of the pentose phosphate pathway and subsequent NADPH production
Lipid Metabolism
- Increased FFA absorption from chylomicrons and VLDL through action of lipoprotein lipase
- Increased TAG synthesis from a high insulin/glycogen ratio
- Decreased TAG degradation
Excess caloric intake over time can lead to changes in adipocyte enzymes and obesity.
Shrinking Fat
As blood sugar (and insulin) levels fall, the liver begins breaking down glycogen in a process called glycogenolysis to liberate glucose. As these stores run out within a day or two, and blood sugar begins to depend on fat release.
Fat responds to a high epinephrine/insulin ratio by activating hormone-sensitive lipase (via cAMP and PKA) to chop triacylglycerols (TAGs) in glycerol and FFAs, which are released into the blood.
FFAs are transported on albumin and taken up by various tissues, while glycerol is returned to the liver for TAG synthesis or gluconeogenesis.
Decreased lipoprotein lipase activity leads to decreased FFA uptake.
Mitochondrial Uncoupling
Chemical uncouplers, including dinitrophenol and salicylate (aspirin), are lipid-soluble compounds with a pKa near 7.2.
Uncoupling proteins include UCP1-5, and are found in various tissues.
Uncouplers enter the inner mitochondria and induce proton leak into the mitochondrial matrix without generating ATP. This energy is instead released as heat.
Uncoupling occurs in brown adipose tissue in response to norepiniephrine stimulation, triggering heat generation.
The endocrine system is composed of several glands that secrete hormones. It has diverse and critical roles in regulating aspects of body function, including cardiovascular, metabolic, and immunologic functions.