Dr. Ir. Happy Nursyam, MS

Week: 5

Metabolism – Products and ExchangesFats/Lipids

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