Metabolism and Regulation of Body Temperature

Dr Than Kyaw

23 October 2011

Physiology I

• Nutritional Food and Energy MetabolismWhat are nutritional food?Types of foodHow they are used in the body?

• Body Temperature and ThermoregulationHeat productionHeat exchange form and to the bodyThermal controlHypothermia and hyperthermia

Nutritional feeds

• Food or Feed?• Feed: edible things containing nutrients

essential for animal’s growth and production• Basic feeds

Protein sourcesCarbohydrate and lipid sourcesVitamins and mineral sourcesWater

• Concentrates (mainly mono-gastric animals)What are they?

• Roughages (mainly – ruminant animals) What are they?• Digestion and fate of the digested material

Nutritional feeds

Intake of feed Digestion

productsAbsorption

Use store

GUT INSTESTINE BODY TISSUES

BLOOD

- Bacteria: digestion of sugars, starch, fiber, and protein for the cow.

- Protozoa: swallow and digest bacteria, starch granules, and some fiber.

- Fungi: a small fraction of the rumen microflora

but important in splitting plant fibers open to

make them more easily digested by the bacteria.

Rumen microbes (micro flora)

Protozoan covered with chains of bacteria

Bacteria attacking a strand of Fiber taken from a cow’s rumen.

- Bacteria – account for about 80% of rumen metabolism - 1011 bacteria/ml of rumen fluid

- Protozoa – 20% (106 protozoa/ml of rumen content)

- Fungus - very small number

Metabolism

Metabolism

AnabolismConstructive processe.g. Synthesis of proteins from a/a

CatabolismDestructive processe.g. Break down of protein into individual a/a

Both processes take place in the body at the same time

- chemical processes that occur in living organisms, resulting in growth, production of energy, elimination of waste material

Basal metabolism (BM)

- minimum amount of energy required to maintain vital

functions in an animal at complete rest

- BM - measured in a fasting individual who is awake and

resting in a comfortably warm environment

- Many hormones contributes to the regulation of metabolism

Metabolism

- Two periods of metabolism 1. Absorptive state - the period shortly following a meal during which

nutrients are being absorbed from GI tract2. Post-absorptive state

- the period during which there is no net absorption

Metabolism

Many hormones contributes to the regulation of metabolism

- During absorptive state blood level of glucose, amino/a, triglycrides

increase (product of starch, glycogen, protein and cellulose)

- Overall goals of metabolic processes during this period is to

increase the use of these nutrients by cells of the body OR store

them for later use

Metabolism

Glucose

- predominant product of C/H digestion following a typical meal

- blood glucose level – about 150% of fasting level

- Insulin (produced by pancreas) – primary stimulant

endocrine regulator

- It affects – C/H, Protein (amino/a), lipid metabolism

MetabolismAbsorptive state

Portein

Glycogen, lipid

Chylomicron = tryglyceride+ cholesterol+ Intracellular protein

Absorptive periodMetabolic fate of glucose, amino/a, and tryglycrides absorbed form GI tract

Blood Glucose

MetabolismAbsorptive state

uptake of glucose by Muscle, Liver

(Stored as glycogen)Insulin

Amino acids

uptake of amino/a Used for protein

synthesis by all cellsInsulin

- All essential amino/a are needed (balanced ration)

- Protein synthesis is slow; not all amino/a used up

- Excess amino/a - cannot be stored as in glucose

MetabolismAbsorptive state

Enters

Triglyceride synthesis path way mainly in hepatocytes and secreted into the blood stream as lipoproteins (VLDLs, very low density lipoproteins)

Gluconeogenesis (liver, kidney)

Chylomicrons – produced in Intestinal cellsLipoproteins – produced in liver

Chylomicrons ,Lipoproteins in blood

LDLs (low density lipoproteins)

Higher cholestrol

Lipoprotein lipase

MetabolismAbsorptive state

Formation of chylomicrons in an intestinal cell

MetabolismPost-absorptive state

After digestion & absorption - blood glucose level

Insulin ( cell) secretion

Glucagon (α cell) secretion

- Glucose storage- Synthesis of glycogen, protein, lipids

stop

- Release of stored glucose- Glucogenolysis

stimulate

What happened after stored glucose and glycogens are used up?

MetabolismPost-absorptive state

FastingMaintenance

Lipolysis - Adipose tissueGluconeogenesis - proteins

Growth hormoneGlucocorticoids

ExerciseWork

Rapid depletion of stored glycogen in muscle ( within 2-3 min)

Other energy supplies1. Glycogenolysis in liver &

non-working muscles2. Lypolysis in adipose t/s

- Catecholamines- Glucagon - Insulin

Rapid mobilization

MetabolismPost-absorptive state

Ruminants 45 – 80 mg/dL

Dog 70 - 110 mg/dL

Horse 60 – 110 mg/dL

-lower than other animals (Why?)

-Relatively small amount of glucose-yielding C/H digestion in S/I-Most C/H consumed – fermentative digestion in rumen – products – VFAs (not glucose)

- acetic, propionic, butyric/a

Blood glucose in Ruminants

Maintenance of blood glucose level

Continuous, high rate of gluconeogenesis (liver)VFA (propionic/a)

Glucagon

Blood glucose is maintained by

MetabolismPost-absorptive state

PropionateCO2

(Phosphoenolpyruvate)

Simplified gluconeogenesis in ruminants

2 ATP lost

4 ATP gained

SIMPLIFIED GLYCOLYSIS

8 ATP from glycolysis 6 ATP from oxidation of pyruvate24 ATP from Kreb cycle

Total: 38 ATP for each molecule of glucose

• One mole of glucose, this reaction releases 2.80 MJ of energy • That translates to 15.6 kJ, or 3.75 kcal, per gram.

• generally rounded to 4 kcal/g of sugar

• On a per-gram basis, all carbohydrates yield essentially the same amount of energy as glucose

C6H12O6 + 6O2 −→ 6CO2 + 6H2O.

Combustion of glucose molecule

Summary of metabolic organs and mechanisms

Ketosis

Ketone Body FormationAcetoneAcetoacetateβ-hydroxybutyrate

High in blood, urine, and milk

• High milk production• Starvation – Negative Energy Balance (BCS 4 or 5)• Massive Fat Mobilization

• More common in dairy cows (peak milk production)• Rapid need of glucose for milk sugar synthesis• Increased mobilization of fat depot leads to ketone body

production

Ketosis

• Treatment – glucose infusion• Glucocorticoides injections

- enhance gluconeogenesis• Feeding sodium propionate (unpalatable)

PropionateCO2

(Phosphoenolpyruvate)

Simplified gluconeogenesis in ruminants

Body Temperature and Heat regulation