ADIPOCYTE HYPERPLASIA AND HYPERTROPHY

Adipoblasts

___ (precursors to adipocytes) are small, typically less than 20 μm in diameter, and start to form small lipid droplets near the center of the cell.

Mature

As adipocytes mature, they increase in size. ___ adipocytes can have diameters ranging from 120 μm and can grow up to 300 μm in diameter, especially in obese animals

nucleus

• In immature adipocytes, cytoplasm takes up a large portion of the cell, but as the cell matures, the lipid droplet expands to take up more than 95% of the cytoplasmic volume. This forces the ___ to the periphery of the cell.

Cattle

___: At birth, most of the adipocytes in cattle have unilocular lipid (one large lipid droplet in each cell).

unilocular

Sheep: Like cattle, most adipocytes in sheep have ____ lipid at birth. However, those with multilocular lipid (many small lipid droplets) transition to unilocular lipid by 2 to 3 weeks of age.

multilocular

Pigs: Pigs are born with ___ lipid in their adipocytes, and the transition to unilocular lipid occurs after birth.

maturity

These species differences may be linked to the stage of ____ at birth, which can influence the development of adipose tissue.

hyperplasia

Fat cell ____ (the formation of new fat cells) primarily occurs prenatally, but there is some adipoblast proliferation during the perinatal period (around birth). However, once the adipoblast differentiates into an adipocyte, it stops proliferating.

hypertrophy

Early growth biologists believed that fat cells were fully developed prenatally and that increases in adiposity were solely due to ____ (increase in cell size) of existing adipocytes. This belief has been shown to be inaccurate.

excess

Recruitment of new adipocytes (fat cells) occurs throughout life, especially when ___ energy is available for fat deposition. This leads to the formation of a new population of smaller adipocytes, as they are newly recruited.

bimodal

• These newly recruited adipocytes contribute to a ___ distribution of adipocyte sizes, with older, larger cells and newly recruited, smaller cells existing within the tissue.

existing

As animals age and accumulate more fat, ___ adipocytes undergo hypertrophic growth, meaning they increase in diameter and volume.

diameter

The increase in ___ can lead to a much more significant increase in volume, which results in a larger fat mass

recruited

As adipocyte size increases with age, new adipocytes are ____, evidenced by their small size compared to the older, larger adipocytes

obesity

• In cases of ___, repeated phases of hyperplasia (formation of new adipocytes) are especially common, contributing to the excessive fat accumulation.