PP24 Adipose Tissue Anatomy and Development 2

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PP24Adipose Tissue Anatomy and Development 2

• Chapter 7 pg 119-135
• ANS 3043
• University of Florida
• Dr. Michael J. Fields

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Adipose Tissue Metabolism

• Lipogenesis processes involved in absorption of
  nutrients from blood and subsequent synthesis and
  esterificatin to form triglycerides in adipocyte
• Location is species dependent
• Cattle, Sheep, Pig occurs in adipose tissue
• Avian species occurs in liver
• (pate du fis gois fatty goose liver)
• Blood absorption of fatty acids (FA)
• Used for triglyceride (TAG) synthesis within
  adipose tissue

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Adipose Tissue Metabolism

• Diet source of FA
• Monogastrics FA used for adipocyte TAG
  synthesis
• Adipose tissues are similar to type of FA in diet
  ( you are what you eat)
• Ruminants rumen microbes modify FA before
  utilization
• Adipose tissue is not reflective of FA in diet
• De Novo synthesis of fatty acids and formation of
  TAG in adipocyte
• Principal substrate is species dependent
• Non-Ruminants glucose (Atkins diet)
• Ruminants acetate from rumen metabolism

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Adipose Tissue Metabolism

• Lipolysis release of FA from adipocyte
• Involves breakdown of TAG within adipocytes
• Results in diffusion of FA across cell membranes
• Controlled by enzymes called lipases
• Primarily stimulated by hormones with catabolic
  actions

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Adipose Tissue Metabolism

• Net Lipid Accretion rate of lipogenesis rate
  of lipolysis
• Role of FA in body metabolism
• FA are esterified to form TAG in adipose tissue
  and serve as energy storage
• Required for membrane synthesis
• Control of cellular metabolism and
  transcriptional control

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Composition of Lipid

• Lipid 76-94
• Protein 1-4
• Water 5-20

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Factors Influencing Lipid composition and
Metabolism

• Age and/or State of Maturity
• Younger Animals
• Smaller adipocytes with decreased of lipid but
  increased of water and protein
• Older Animals
• Larger adipocytes with increased of lipid but
  decreased of water and protein
• Anatomical Location of Adipose (Table 7.2,7.3)
• Composition differs within locations of body and
  rate at which fat is accumulated

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3 layers - pig
Deep in body, last fat metabolized
Heart
Muscle-less fat to avoid restriction
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Extract fat with lipid
Last fat in body
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Factors Influencing Lipid composition and
Metabolism

• Species
• Differences in adipose composition due to
  differences in lipid metabolism
• Ruminants vs. Monogastrics
• Growth rates differ between species, which
  influences adipocyte size and number along with
  adipocyte metabolism and composition

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Larger
Larger
Smaller
Smaller
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Nutrients Drive Fat Deposition
________
________
SQ subcutaneous PR perirenal IM -
intermuscular
Greater Fat
Less Fat





Less fat deposited
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Factors Influencing Lipid composition and
Metabolism

• Nutrition
• Increased and excess energy intake enhances lipid
  deposition
• Dependent on stage of animal development
• Reduced energy intake enhances lipolysis so FA
  are liberated for oxidation
• Dietary protein energy ratios are also
  important
• Diets with amino acid (AA) deficiencies will
  often result in increased lipogenesis
• Lean tissue cannot be maximized with AA imbalance

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Factors Influencing Lipid composition and
Metabolism

• Gender
• Increased fattening in females
• Females deposit fat in thighs
• Males deposit fat in stomach
• Associated with increased size of adipocytes but
  fewer number per unit of tissue than males and
  castrates
• Earlier closure of epiphyseal plate in females
  results in decreased growth and enhancement of
  fat deposition
• Estrogen promotes filling of fat depots
• Testosterone inhibits fat deposition
• Steroids affect lipid metabolism and distribution
  of fat among depots

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Female greater
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Factors Influencing Lipid composition and
Metabolism

• Breed and Genotype
• Differences in total amount of fat deposited and
  size of adipocytes
• Differences in fat deposition relative to
  location of fat in body
• Breeds with increased reproductive rates and milk
  production show increased KPH fat

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Factors Influencing Lipid composition and
Metabolism

• Environment
• Drastic changes in temperature can influence live
  weight gains and feed efficiencies
• Regulates adipocyte size and function via
  endocrine control
• Significant decreases in temperature and/or
  climatic changes enhances lipolysis

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Too hot energy required to keep cool
Too cold energy Required to keep warm
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Factors Influencing Lipid composition and
Metabolism

• Physical Activity
• Work and mating behaviors modify the amount of
  lipid contained in the body
• Increased lipolysis for energy production
• Hormones
• Insulin lipogenic, hypertrophic
• Transfers glucose into cells (converted to fat)
• High mating activity animals become thin
• 3 meals 3 insulin surges

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Factors Influencing Lipid composition and
Metabolism

• Glucocorticoids lipolytic
• IGF lipogenic
• Hyperplasia helps form new adipocytes, which
  divide and grow
• Glucagon lipolytic
• Low glucose causes glucagon to be secreted
• Breaks down fat for energy
• Growth Hormone lipolytic
• Epinephrine lipolytic
• Short term energy

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Factors Influencing Lipid composition and
Metabolism

• Thyroid Hormones lipolytic
• Cold more heat and energy needed
• Leptin
• Produced by adipocytes
• Circulating concentrations related to adipose
  tissue mass
• Leptin is elevated in obese animals and increases
  with overfeeding
• Leptin is lower in lean animals
• Appears to be involved in regulating feed intake
  and appetite

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