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Adipose Tissue (Fat /ssue)
Ayhan BİLİR
Agnes ARCHIBONG
• Adipose /ssue is a specialize connec/ve /ssue
that plays an important role in energy
homeostasis
...
• Groups of adipose /ssue are found through
our loose connec/ve /ssue
...
• The human body has limited capacity to store
carbohydrate and protein, therefore energy
reserves are stored within lipid droplets of
adipocytes in the form of Triglycerides
...
• They are the most concentrated form of
metabolic energy storage available to humans
...
• Adipocytes are also major endocrine organ
...
• RESIM KOY
• There are two types of adipose /ssue:
– White adipocytes (Uniloclar)
...
• White adipocytes
– White adipose /ssue is the predominant type of
adipose /ssue in adult humans
...
– White adipose /ssue func/ons as :
• Energy storage
• Cushioning of vital organs
• Secre/on of hormones
• In lacta/ng females, mammary fat pad plays an
important role in suppor/ng breast func/ons
...
• White adipose /ssue produces a variety of
hormones, growth factors and cytokines
...
– It regulates energy homeostasis in the body
– Lep/n inhibits food intake and loss of body weight
and s/mulate metabolic rate
...
– Lep/n aso par/cipates in an endocrine signaling
pathway
...
• Enzymes in adipose /ssue include TNF-‐α, TGF,
IGF-‐1, Interleukin -‐6 and Prostaglandins
Differen/a/on of Adipocytes
• Like all connec/ve /ssue cells, adipocytes are derived
from undifferen/ated mesenchymal stem cells
...
• White fat adipocytes can transdifferen/ate into
brown fatlike adipocytes following cold exposure
and β-‐adrenegic signling
...
Structure of Adipocytes and Adipose Tissue
• Uniocular adipocytes are large cells, nearly 100µm
or more in diameter
...
• The nucleus in adipocytes is flajened and
displaced to one side of the lipid mass
...
• In rou/ne histologic sec/on, the lipid is lost
through extrac/on by organic solvents such as
xylene
...
• Silver stains shows each adipocyte surrounded by
re/cular fibers (Type III collagen)
...
• The lipid mass in the adipocyte is not membrane
bound
...
Regula/on of adipose /ssue
• Adipose /ssue regula/on is controlled by the
Brain-‐gut-‐adipose axis
...
• The amount of an individual’s adipose /ssue is
determined two physiologic systems
...
• Ghrelin
• Pep/d YY (PYY)
• Long term weight regula/on
– This system controls appe/te and metabolism on a
con/nual basis (over months and years)
...
Ques/on: Which hormones are secreted during
hunger?
• Deposi/on and mobiliza/on of lipid are
influenced by neural and hormonal factors
...
Triglycerides are then
stored within the cell as a lipid droplet
...
• Fajy acids pass through the adipocyte cell
membrane to enter a capillary
...
• Brown Adipose Tissue
• Mul/locular brown adipose /ssue conatain
numerous fat droplets
...
• The UCP-‐1 gene encodes a specific
mitochondrial protein called uncoupling protein
(uco-‐1) or thermogenin (a 33kD interr
mitochondrial membrane) is essen/al for brown
adipocytes metabolism
...
• UCP-‐1 gene is ac/vated by norepinephrine
s/mula/on, which also protects brown
adipocytes by inhibi/ng apoptosis
...
• UCP-‐2 is linked to hyperinsulinemia and obesity
...
• UCP-‐4 is a brain specific molecule
...
Ross
histology page 263
...
• Conven/onal lipoma consists of mature white
adipocytes
...
• Angiolipoma contains adipocytes separated by
unusually large number of vascular channels
...
• Brown adipose /ssue tumors are called
Hibernoma
...
• Pure hibernomas are very rare
...
• It is based on detec/on of high-‐energy gamma
rays
...
• This is because malignant cells metabolise
glucose at a greater rate than normal cells