10/30/2008 TTU AFS 4400/5500 1 Northern blot analysis C c-9 t-10 C c-9 t-10 PRE PI PDMI PRE PI PDMI An Wa A di t SCD RNA C c-9 t-10 C c-9 t-10 PRE PI PDMI PRE PI PDMI • Angus adipocytes expressed SCD higher than Wagyu adipocyte after short term (1 wk) of differentiation. • Both c9 t11 and t10 c12 RNA PRE PIM PDMI C 5 20 40 100 uM C 5 20 40 100 uM c-9, t-11 t-10, c-12 Both c9,t11 and t10,c12 CLA decreased SCD and FAS expression as the dose increased. RNA SCD FAS Northern blot analysis • SCD PPARγ and LPL were C Arg C Arg C Arg C Arg C Arg C Arg C Arg C Arg C Arg C Arg C Arg C Arg • SCD, PPARγ, and LPL were greater in preadipocytes incubated with arginine than in control. • t10,c12 CLA decreased SCD i d RNA SCD PPAR γ C/EBP β LPL TNF α Pref ‐1 RNA SCD PPAR γ C/EBP β LPL TNF α Pref ‐1 RNA Control Arg CLA Arg + CLA Control Arg CLA Arg + CLA SCD gene expression and not overcome by co- incubating with arginine. SCD RNA PPAR γ Control Arg CLA Arg + CLA γ Control Arg CLA Arg + CLA
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Northern blot analysis - TTUNorthern blot analysis C c-9 t-10 C c-9 t-10 PRE PI PDMI An Wa Adit SCD RNA • Angus adipocytes expressed SCD higher than Wagyu adipocyte after short term
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10/30/2008
TTU AFS 4400/5500 1
Northern blot analysis
C c-9 t-10 C c-9 t-10 PRE PI PDMI PRE PI PDMI
An Wa
A di t
SCD
RNA
C c-9 t-10 C c-9 t-10 PRE PI PDMI PRE PI PDMI • Angus adipocytes expressed SCD higher than Wagyu adipocyte after short term (1 wk) of differentiation.
• Both c9 t11 and t10 c12RNA
PREPIM
PDMIC 5 20 40 100 uM C 5 20 40 100 uM
c-9, t-11 t-10, c-12
Both c9,t11 and t10,c12 CLA decreased SCD and FAS expression as the dose increased.
RNA
SCD
FAS
Northern blot analysis
• SCD PPARγ and LPL wereC Arg C Arg C Arg C Arg C Arg C ArgC Arg C Arg C Arg C Arg C Arg C Arg • SCD, PPARγ, and LPL were
– When looking at these animals to study intramuscular fat
Postnatal Adipose Tissue
intramuscular fat• larger adipocytes
• more adipocytes
• these were the predominant theories• they found that adipocyte size is actually less in Wagyu than Angusgy g
– Numbers of adipocytes are differentrate of preadipoc te proliferation as t ice as high in
Postnatal Adipose Tissue
• rate of preadipocyte proliferation was twice as high in both subcutaneous and intramuscular adipose tissue from Wagyu vs. Angus cattle
– Japanese Black have the ability to accumulate IM lipid seemingly indefinitely Angus have genetic limitations in preadipocytep p ydifferentiation/proliferation
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TTU AFS 4400/5500 6
– Numbers of adipocytes are differentrate of preadipoc te proliferation as t ice as high in
Postnatal Adipose Tissue
• rate of preadipocyte proliferation was twice as high in both subcutaneous and intramuscular adipose tissue from Wagyu vs. Angus cattle
– Japanese Black have the ability to accumulate IM lipid seemingly indefinitely Angus have genetic limitations in preadipocytep p ydifferentiation/proliferation
• Adipose tissue as an endocrine tissue‐now more hormones produced in adipose tissue than the
Hormone Production
hormones produced in adipose tissue than the anterior pituitary– Leptin
• 16 kDa protein secreted from white adipocytes
• belongs to a class of helical cytokines
• similar to IL‐2 and GH
• four alpha‐helical bundle structures
• 1995 – ob protein leptin administration could eliminate obesity in the ob‐/ob‐mouse (ob protein = leptin)
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Hormone Production
Long-term signals regulating energy balance. Insulin and leptin are the two hormones that act as long-term regulators of food intake and energy balance. Both insulin and leptin act in the central nervous system to inhibit food intake and to increase energy expenditure Activation ofexpenditure. Activation ofthe sympathetic nervous system (SNS) is likely to contribute to the increase in energy expenditure.(Havel et al. 2000.)
• several splice variants of a single gene• “long form” contains 302 amino acids in intracellular domain
• expressed in various regions of the brain• categorized as a class I cytokine receptor (much like g y p (IL‐6, LIF)
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– Signal transduction pathways of class I cytokine receptors
Leptin Signaling
cytokine receptors• typically lack intrinsic tyrosine kinase activity• activation usually occurs following formation of homodimers
• leptin actually forms homodimers aggregation activates JAK/STAT pathway
– JAK = Janus Kinase
– STAT = signal transducers and activators of transcription
Leptin
• Leptin treatment (exogenous addition)– dose‐dependent decrease in food intake
– loss of body weight
– loss of fat depots
– increased metabolic rate
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Leptin
• Leptin is synthesized/secreted from white adipocytesadipocytes– example of adipose tissue acting as a an endocrine tissue acting on other tissues (brain e.g.)
– promoter of region of Leptin gene contains sites for C/EBP‐α and PPAR γ; therefore, adipose‐specific geneg
– increased leptin has a negative feedback loop on adipocytes to decrease the leptin production
Resistin
• discovered in 2001
• expression reduced by TZDs• expression reduced by TZDs
• C/EBP responsive gene
• Biological activities– impairment of glucose tolerance
antagonism of glucose uptake– antagonism of glucose uptake– inhibition of 3T3-L1 differentiation
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Adiponectin
• discovered in 1995
• secreted by differentiated adipocytes• secreted by differentiated adipocytes
• models of insulin resistance have reduced adiponectin levels
• exogenous adiponectin can stimulate fatty acid oxidation by skeletal muscleoxidation by skeletal muscle
• secretion is stimulated by TZDs
TNFα• TNFα (pro‐inflammatory cytokine)
– synthesized in neutrophils, activated T and Bsynthesized in neutrophils, activated T and B lymphocytes AND adipocytes
• neutrophils, T and B lymphocytes endocrine fashion• adipocytes paracrine/autocrine effect