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Metabolism – Products and ExchangesFats/Lipids
Liver – Conversions via Krebs from AAs, Glucose, FAs to FAs
Liver – Formation of Lipoproteins
Blood – Movement as FAs, Glycerol
Adipose – Release as Glycerol and FAs
Adipose – Conversion to Mobile FA Form
TAG Lipase at Adipose
Metabolism – Products and ExchangesFats/Lipids
Some Considerations
• Triacylglycerol (TAG) Lipase and Insulin serve as key regulators for control, primarily anabolic pathway
• Fish (Carnivores for Sure) are Hyperinsulinemic (High Insulin)
Metabolism – Products and ExchangesFats/LipidsAnomalies
• Starvation– Insulin/Glucagon
Balance shifts triggering
– Hormones sensitive lipases and glucocorticosteriods
– Gluconeogenesis– Elevated
Proteolysis
Starvation Continued• Prolonged Starvation- Leads to Fatty Liver Syndrome and Ketosis Like Toxemia• Generalizations
– High carbohydrate intake elevates enzymes, insulin and TAG Lipase– Epidermal Growth Factor elevated, resulting in elevated brain storage of fats– Growth hormone responds to intake
Acute vs. ChronicChronic – Protein Usage – Carbohydrate SparingChronic – Decreased Lipogenesis, Increased LypolysisAcute – Above Reversed and Growth Hormone Acts Like Insulin
Metabolism – Products and ExchangesProteins
• 1 Protein Recycling a Normal Internal Cellular Process
• 2 Net Growth – Turnover and Degradation Balanced with or Less than Assimilation Providing Growth
• 3 Metabolic Maintenance – Synthesis and Degradation are Balanced, Synthesis via all Routes
• Protein Degradation and Synthesis 1 , 2, 3 are Energy Dependent Pathways
Metabolism – Products and ExchangesProtein Aging
• Primary – Dipeptide Bonds
• Secondary – Hydrogen Bonds
• Tertiary – Disulfide Bonds (β Pleated and Globular
• Quaternary – Disulfide Bonds (Usually Dimers and tetramers)
Metabolism – Products and ExchangesProtein Aging Continued
• Processes– Oxygen Radicals – Break Disulfide and Hydrogen
Bonds– Deamination – Break Amide Bonds– Proteases (Ca+ Dependent, Leak from Lysosomes)– Ubiquitin – Attaches Protein, Complex Fuses with
Lysosomes and Stored or Expelled, So Called Heat Shock Proteings
– High Glucose – Increased Oxygen Radical Formation
Metabolism – Products and ExchangesProtein Cycling
• Proteins Constantly Removed and Replaced– 23 to 42% elevation of 02 consumption in Atlantic Cod
a Carnivore
– 11 to 22% elevation of O2 consumption in Carp a Herbivore
– Tissue Demands (Table 2) • Cyclohexamide synthesis – 80% O2 consumption in
hepatocytes• Turnover rates vary – high in hepatocytes, low in muscle
• Go Back to Synthesis
Metabolism – Products and ExchangesProtein Synthesis
• The Process
– Transcription
– Translation
– Secondary Modification
Metabolism – Products and ExchangesProtein Dynamics
• Muscle – Primarily Post Mitotic, No Replacement with New Cells
• Serves as Primary Protein Storage Site
• While Protein Synthesis and Exchange are Low, Muscle Accounts for 50 to 80% of Body Mass
• Go to Table 2A (Atlantic Cod at 300g)
Tissue Growth 0% Growth 1% Efficiency 1%
Gill 4.4 10.1 10%
White Muscle .46% 1.94% 50%
Metabolism – Products and ExchangesProtein Dynamics (Figure 2)
% Consumption
Pro
tein
Syn
thes
is
Pro
tein
Gro
wth
Synthesis
Growth
Metabolism – Products and ExchangesProtein Dynamics Related to Bioenergetics
Basic Bioenergetics EquationConsumption = Growth – Respiration – Waste or C = G
– R – WExpanded EquationConsumption = Growth – Standard Metabolism –
Activity – Digestion – Feces – Urine
Or C = G – RS – RA – RD – F – UNote: RS, RA, RD are Specific Dynamic Action
Therefore the equation could be presented asC+ G – S – F – U S = Specific Dynamic Action
as Measured by O2 Uptake
Metabolism – Products and ExchangesProtein Dynamics – SDA Continued
Considerations• Specific Dynamic Action Function of
– Digestion– Gut Motility– Enzyme Synthesis– Absorption
• Clear Link to Essential Amino Acids (EAAs)– See Table 2B– Protein Synthesis Linked to Precursors– Gluconeogenesis and Lipogenesis Minor Processes– EAAs are Limiting
Metabolism – Products and ExchangesProtein Dynamics (Table 2B)
Fractional Rate of Protein Synthesis
Tissue Saline EAA Increase
Liver 39.50% 78.10% 2 - Fold
White Muscle 0.98% 2.29% 2 to 3 Fold
Metabolism – Products and ExchangesProtein Dynamics
Outcomes Due to Metabolic Shifts
• Energetics Related to Reproduction ie Vitellogen Production
• Response to Disease– Cellular Response ie Oxidative Burst– Antibody Production
• Contaminant Induction– P450 Production Competes with Other
Biosynthetic Pathways
Control of Feeding
• Genotypic Influences• Social Interactions – Pecking Order• Food Constituents – EFAs• Endogenous Factors – Such as:
– Cholecystokinin (CCK)– Bombesin – Gastrin releasing peptide– Neuropeptides (Brain and Pancreas)
• NPY for example• Not proven in fish, but known for mammals• Can regulate growth via
– Stimulant– Lignand of receptors for release of GH– Stimulator for GH release via GnRH which stimulates
somatotrophs
Growth Hormone (GH)
• Single-chain peptide
• Produced and stored in somatotroph cells of the pituitary
• Similar to those of prolactin and somatolactin thus included in the GH/prolactin family of hormones
• Assumes central role in the growth of fish
• Has osmoregulatory function as well
GH Continued
• Neuropeptide Y (NPY), Growth hormone releasing hormone (GHRH) and Gonadotropin releasing hormone (GnRH) major stimulating hormones
• Somatotropin release-inhibiting factor major inhibiting hormone
• Se figure 3 for other factors influencing the release of GH
Somatotroph Cell of Pituitary
NPY GHRH GnRH
+ +
SRIF
-
+
GHRelease
GH Continued
• Patterns of Release– Pulse as in Carp– Episodic as in Trout– Diurnal as in mammals?
• Degradation– Short lived 10 to 45 minutes depending of fish
species
• Responds to physiological state of the fish– Stress increases production
Physiological Response to GHStarvation
• Starved fish have higher GH levels than fed
• Both fed and starved will show a persistent decreased GH in response to cortisol levels in short term stress situations
• Chronic stress results in elevated GH levels
• Example – Yearling Coho salmon, held in fresh have depressed GH
GH in Mammals
• GH secretion amplitude (amount) and frequency dictate level of activity
• Number of receptors regulate level of action
• Number of receptors are under feed back to GH level
• GH binding protein serves a reservoir for GH
Tissue Action of GH
MissMe?
Liver – Increase Activity Related to Protein, Fat and Carbohydrate Utilization
Muscle – Increased Biosynthesis
Intestine – Increase in Amino Acid Mobilization and Protein Synthesis
Thyroid – Increased T4 Release
Cartilage – Increased Proteoglycan synthesis and Sulfate Uptake
Kidney – Increase GH Receptors, Cell Volume and Osmoregulation