Adipose Tissue Flashcards
Differentiate white and brown adipocytes based on shape, cytoplasm, # of lipid droplets, nuclei, size and function
- white: Scant ring of cytoplasm surrounding a single lipid droplet, nuclei are flat and eccentric, cells are large; role = glucose, fatty acid, lipoprotein & cholesterol metabolism
- Brown: Polygonal, lots of cytoplasm, contain multiple lipid droplets, round central nuclei, small, thermogenesis
In whom is brown adipose tissue most prominent
- in newborns, hibernating animals
What about BAT makes it thermogenic?
- Uncoupling protein-1 found within the mitochondria
When does UCP-1 appear
- third trimester
How many weeks into gestation do white adipose fat lobules appear
- 14th-16th week
What is the location gradient for the development of fat lobules
- head, trunk, limbs
What embryonic tissue are adipocytes dervived from; what other cell types are derived from this tissue
- mesenchyme
- chondrocytes, osteoblasts, myocytes
Describe the 5 stages of adipose tissue development with reference to the buccal fat pad specifically
1) Week 14 loose connective tissue composed of stellate cells and ground substance fill the cheeks
2) Week 14.5 - angiogenesis; blood vessels grow and signal areas where early fat cells organize into groups (aggregation of dense mass of mesenchymal cells)
3) Week 19 mesenchymal lobules develop and contain preadipocytes w/o lipid droplets
4) Week 22 primitive fat lobules appear; the vascular stalk of each lobule branch from one main vessel to enclose densely packed fat cells
5) 28 weeks fat lobules are well separated by interlobular septa
How do adipocyte diameter, weight & # vary between boys and girls?
They are the same until puberty and then girls have an increase in all measures due to increased estrogen
When can overfeeding result in an increased # of fat cells
- 1st year of life
- early childhood growth spurt
- prepubescent fattening
How does the ratio of limb to trunk skinfolds vary between males and females post puberty
- girls have a higher ration; ex. more fat stored in limbs than trunk
Where do females develop secondary sexual adipose tissue
- upper arms, shoulders, hips, thighs, medial calf
Why do skinfold measures decrease after puberty but adipose levels increase in females?
- Because an increase in muscle mass spreads the adipose tissue thin
- this pattern is similar in male trunk patterning but not limb due to large increase in muscle
Describe the steps of adipocyte metabolism
- Lipoprotein lipase acts on chylomicrons and VLD lipoproteins to form FFA which then pass into the cell or are converted into glycerol or bind to albumin in the blood
- once in the cell FFA are stored in the fat droplet as trigylcerides
What is the role of lipoprotein lipase; what controls its activity
- Regulation of fat cell triglyceride deposition around the body
- activity is promoted by insulin and cortisol, but inhibited by estrogen and growth hormone
Premenopausal women have _____ LPL activity in the ____ region than post menopausal women resulting in the ____ fat pattern
- greater
- gluteofemoral
- gynoid
Where is leptin secreted from
- adipose tissue
- stomach
- placenta
- muscle
Besides a potential role in satiety, what does leptin do
- interact with insulin
- involved in stress response
- reproductive function
- interacts with growth factor
How does leptin affect insulin; how does insulin affect leptin
- leptin inhibits insulin secretion directly
- insulin indirectly increases leptin by promoting fat deposition
what hormones does leptin stimulate the release of
- hypothalamic gonadotrophic releasing hormone and pituitary gonadotrophins
Is plasma leptin higher in men or women, how does this relate to % body fat?
- Higher in women
- Regardless of % fat, ie does not relate to body fat levels
How does leptin relate to estrogen and testosterone in females and males respectively
- positively associated to estrogen
- negatively associated to testosterone ( T inhibits or has no effect)
- after accounting for fat mass
how do leptin levels change from pre to post menopause
- it does not change
How do leptin levels change in puberty in boys vs girls
- Girls: Increases during puberty; at the end of puberty leptin is negatively associated with FSH and LH
- Boys: Increases prepuberty, but decreases at puberty
