1. Metabolism is...
    • the sum of the physical and chemical procceses involved in:
    • Producing and expending energy from endogenous and exogenous sources
    • synthesising and degrading structural and functional tissue components
    • Disposal of resultant waste products
  2. idea of metabolism is..
    to match energy imput to output
  3. examples of energy output
    • mechanical work (muscle contraction)
    • synthetic reaction (fuel storage tissue building)
    • membrane transport (minerals, organic anions/cations, amino acids)
    • signal generation conduction (electrical, chemical, mechanical)
    • heat production (temperature regulation, inefficient chemical rxns)
    • detoxification degradation (urea formation, conjugation, oxidation, reduction)
  4. Energy (metabolism) is...
    • energy metabolism is measured in "units of heat"
    • the traditional unit for heat is the Calorie (cal)
    • 1 cal is the amount of energy required to heat 1g of water by 1 C
    • The international system unit for energy is the Joule (J). 1 cal = 4.184 J
    • Metabolic rate (energy/unit time) is expressed as watts (i.e J/sec, or more commonly kilogoules/hour)
  5. Gross energy
    fecal energy (most significalt loss for most foodstuffs)
  6. Apparent digestible energy
    Urinary energy and digestive gases (methane in ruminants, urea from proteins)
  7. metabolizable energy
    specific dynamic actions (energy loss as food is being digested (transfer and storage) processing energy (can see a rise in body temp)
  8. Basal metabolic rate
    • the metabolic rate of a fasted individual that is conducting no work and is maintained at a thermally neutral environment
    • common measurement in humans
  9. Resting metabolic rate
    • the metabolic rate after 12 hours of fasting, at an ambient temp. under relaxed conditions
    • differs from BMR as it includes: variable amounts od SDA and energy used in productive processes
  10. measurement of metabolic rate
    • direct calorimetery (liberate heat)
    • indirect calorimetery (measuring O2 utilisation or CO2 production)
  11. types of ways to measure metabolism
    • Lavoisier's calorimeter (direct)
    • Indirect- open circuit or closed circuit indirect calorimeter
  12. Stable isotopes
    • carbon dioxide entry method (14 CO2 infused. specific activity of CO2 in body fluids provides an index of CO2 production
    • Double labelled water method
  13. factors influencing metabolic rate
    • Body size
    • sex
    • nutritional status (unfed have decreased MR)
    • age (metabolic rate decreases w/ age)
    • Temperature (extremes increase MR)
    • Disease conditions
    • excercise
    • hormal balance
    • productive processes (pregnancy, lactation, egg production)
  14. Obesity problems
    • in humans: 1.6 billion adults (15+) were overweight, 400mil were obese
    • in pets: 24-44% of dogs and 25% of cats are obese (and seen in rabbits, budgies, parakeets
  15. health effects of obese animals
    • 61% show signs of a pre-diabetic state
    • 24% have locomotion problems
    • the risk for circulatory disease doubles
    • decreased immune resistance to infectious dz
    • increased anaesthetic risk
    • increased risk for wound breakdowns post sx
  16. regulation of energy stores
    • Sight, smell of food--> hypothalamus
    • glucose in duodenum/portal vein--> hypothalamus
    • hypotalamus signals either appetite/hunger centre or satiety centre
    • other influences: serotonin, neuropepide Y, insulin, enterostatin, corticotrophin releasing factor, cortisol
  17. Regulation of appetite/satiety
    • Fat to brain hormonal communication system
    • gut to brain hormonal communication system
  18. Fat to brain hormonal communication system
  19. Gut to brain hormonal communication systems
    • Cholecystokinin (CCK)
    • ghrelin
    • Peptide YY (PYY)
    • glucagon like peptide (GLP-1)
    • oxyntomodulin
  20. Cholecytokinin (CCK)
    • Gut to brain
    • released in Small intestine
    • decreases food intake
  21. Glucagon like peptide (GLP-1 and 2)
    • Gut to brain
    • released in distal gut in reponse to food
    • decreases food intake
    • acts in arcuate nucleus of hypothalimus
  22. oxyntomodulin
    • gut to brain
    • released by distal gut in response to food
    • (proportional to caloric intake)
    • decreased food in take, increased energy expendeture
    • structurally related to GLP
    • promote loss of weight
    • elevated in some forms of anorexia in humans
  23. Leptin
    • fat to brain
    • produced by adipose tissue and acts w/in the hypothalamus to regulate energy
  24. Animals unable to produce leptin...
    • become obese w/in weeks of birth
    • overeat
    • have a low BMR (affects metabolism)
    • low body temp
    • physically inactive
    • Tx w/ exogenous leptin corrects all of these abnormalities
    • (thus leptin affects metabolism)
    • works in some species but not all (humans), no drugs developed yet... too many problems
  25. Neg. feedback system of Leptin
    increase adipose tissues, increase leptin production, increase leptin in plasma, decrease neuropeptide Y, decrease food intake, increase activity level/metabolic rate/temp, modulate hormones decrease adipose tissue
  26. Ghrelin
    • (Gut to brain)
    • proposed as a peripheral signal for food intake and nutritional status
    • 28 aa protein hormone (various locations)
    • produced from various tissues pituitary, hypothalamus, bowel, placenta, kidney, and stomach (80%)
    • 2 major biologic activites:
    • 1) regulation of energy balance (stimulates hunger, suppress fat utilization in adipose tissue, stimulates gastric emptying, positive effects on CV function (possibly via GH)
    • 2) stimulation of growth hormone secretion: (ligand for growth hormone secretagogue receptors, potently stimulates secretion of growth hormone (GHRH and GHRH independed)
  27. PYY- 3-36 peptide
    • Acts as an agonist for NPY specifically at Y2 receptor. found in neurones endocrine cells of the upper and lower GI tract, the pituitary and adrenal glands and in the repiratory tract
    • released from GU tract post prandially
    • in proportion to caloric content and energy source
    • fats>carbohydrates>proteins
    • in addition gastrin and CCK affects secretion
    • Local actions: it inhibits gastric acid production, exocrine secretions from the pancreas GI secretions and GI mobility.
    • central actions: it inhibits food intake and ultimately weight gain via the hypothalamus
    • increases w/in 15min, peaks at 60 min, remains elevated for 6 hours
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