ansci 519
Download
Skip this Video
Download Presentation
AnSci 519

Loading in 2 Seconds...

play fullscreen
1 / 35

AnSci 519 - PowerPoint PPT Presentation


  • 70 Views
  • Uploaded on

AnSci 519. Post-Absorptive CHO Metabolism Lance Baumgard. CHO digestion and absorption: monogastric vs ruminants. Post-Absorptive Terminology. Catabolism Breaking down of a nutrient or tissue Anabolic Creating/synthesizing a tissue Oxidation

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' AnSci 519' - joshua-cruz


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
ansci 519

AnSci 519

Post-Absorptive CHO Metabolism

Lance Baumgard

post absorptive terminology
Post-Absorptive Terminology
  • Catabolism
    • Breaking down of a nutrient or tissue
  • Anabolic
    • Creating/synthesizing a tissue
  • Oxidation
    • Utilizing a nutrient to generate ATP, CO2 and H20
  • Glycolysis
    • Breaking down of glucose…into pyruvate
  • Gluconeogenesis
    • Making of glucose…from non carbohydrate precursors
  • Glycogen
    • Storage form of glucose (Liver and muscle)
      • Glycogen synthesis (glycogenesis)
      • Glycogenolysis
  • TCA Cycle
    • Products of glycolysis enter TCA cycle and generate ATP
primary potential fuel sources
Primary Potential Fuel Sources
  • Volatile Fatty Acids (VFA)
    • Primarily in ruminants
    • Controversy on how much large intestine VFA in monogastrics contribute to energy
  • Non-Esterified Fatty Acids (NEFA): a.k.a Free Fatty acids
    • From adipose tissue break down
  • Amino Acids
    • Efficiency of capturing ATP from AA oxidation is very poor……large amount of heat released
  • Glucose
    • Absorbed from GIT
    • Released from liver (and kidney during starvation)
      • Gluconeogenesis and glycogen breakdown
    • Stored in muscle
post absorptive glucose metabolism
Post-absorptive glucose metabolism
  • Options for absorbed glucose
    • 1) Oxidation: produces CO2 and H20
    • 2) Glycolysis:
      • Production of pyruvate
        • TCA cycle (with O2)
        • Lactate (with no O2)
    • 3) Stored as glycogen
    • 4) Stored as fat
    • 5) Carbons utilized for amino acid synthesis

Catabolic

Anabolic

types of metabolic pathways
Types of Metabolic Pathways

Catabolic Pathways: produce free energy compounds

Anabolic Pathways:utilize these compounds

slide8

Overview

of Dietary

Catabolism

glucose
Glucose
  • The most important metabolic fuel in monogastrics are glucose and fatty acids.
  • The most important metabolic fuel in ruminants is acetate
  • In normal circumstances, glucose is the only fuel the brain uses
    • Can use ketones during starvation
  • Adult human brain requires ~120 g glucose/day
    • Whole body only requires ~160 g/glucose/day
    • ~20 g of glucose in circulation
    • Liver glycogen stores about ~150-180 g of glucose
    • Muscle glycogen stores about ~300-350 g of glucose
  • Only the liver can secrete/release glucose
  • Muscle can not
glucose1
Glucose
  • To ensure the continuous provision of glucose to the brain and other tissues, metabolic fuels are stored when food is plenty
  • To provide glucose over longer periods, the body transforms non-carbohydrate compounds into glucose through gluconeogenesis.
    • Amino acids, lactate and glycerol
slide11

Glucose

Oxidation

Glycolysis (10 successive reactions)

2 Pyruvate

Cytosol

Mitochondria

2 Acetyl CoA

O2

TCA

Cycle

CO2

NADH

ATP

Electron Transport Chain

glycogen
Glycogen
  • Glycogen synthesis
    • Occurs in the liver and muscle
    • The synthesis of a branched polysaccharide form glucose….resembles amylopectin
    • Liver stores are especially important as an emergency source of blood glucose
  • Glycogenolysis
    • Breakdown of glycogen into glucose
    • Liver secretes the glucose, muscle only oxidizes glycogen released glucose
slide13

Gluconeogenesis

Propionate

(gut)

Amino Acids

(gut, muscle)

Glycerol

(fat mobilization)

Glucose

Lactic Acid

(Gut & Cori Cycle)

slide14
Gluconeogenesis
    • Glucose requirements
      • Central nervous system
        • 15 – 20% of glucose utilization
      • Pregnancy
        • For fetus
      • Lactation
        • Lactose synthesis
      • Lipid synthesis
        • NADPH for fatty acid synthesis
        • Glycerol
slide15
Precursors for gluconeogenesis

% of Glucose from:

PrecursorFedFasted

Propionate 40 – 60 0

Amino acids 15 – 30 35

(Primarily Alanine,

Glutamine, Glutamate)

Lactate 15 40

Glycerol 5 25

slide16

Gluconeogenesis

Glucose

Pyruvate

Lactate and Amino acids

Acetyl CoA

OAA

Amino Acids

TCA

Cycle

Propionate

(from rumen fermentation)

slide17
Mechanism of gluconeogenesis
  • Controlling enzymes
    • Pyruvate carboxylase

(Pyr > OAA)

    • NAD-malate

dehydrogenase

(Mal > OAA)

    • PEP carboxykinase

(OAA > PEP)

    • Fructose-1,6-

diphosphatase

(Fru-1,6-P > Fru-6-P)

    • Glucose-6-phosphatase

(Glu-6-P > Glu)

  • Hormones
    • Glucagon and

Glucorticoids

    • Insulin

From Van Soest, 1994

hormonal control of glucose homeostasis
Hormonal Control of Glucose Homeostasis
  • Insulin
    • Synthesized by the pancreas
    • Stimulated by increased glucose concentrations
    • Causes glucose storage (glycogen and fat)
    • Shuts down gluconeogenesis
    • Shuts down glycogenolysis
  • Glucagon
    • Synthesized by the pancreas
    • Stimulated by a reduction in glucose concentrations
    • Stimulates glycogenolysis AND gluconeogenesis
  • Epinephrine
    • Synthesized by the adrenal gland
    • Causes immediate glycogenolysis
    • Increase glucose during “flight or fight”
slide19

Glucose Coordinators

Glucagon

Epinephrine

Cortisol

Insulin

Lipogenesis/Lipolysis

Gluconeogenesis/Glycolysis

Glycogenolysis/Glycogen Synthesis

Anabolic

Catabolic

slide21

Insulin Release

Insulin secretion in beta cells is triggered by rising blood glucose levels. Starting with the uptake of glucose by the GLUT2 transporter, the glycolytic phosphorylation of glucose causes a rise in the ATP:ADP ratio. This rise inactivates the potassium channel that depolarizes the membrane, causing the calcium channel to open up allowing calcium ions to flow inward. The ensuing rise in levels of calcium leads to the exocytotic release of insulin from their storage granule.

slide22

Insulin Action

Insulin binding to the insulin receptor induces a signal transduction cascade which allows the glucose transporter (GLUT4) to transport glucose into the cell.

slide25

pancreatic islet

b cells

glucose

insulin

glucose

glucose

glucose

fat cells

GI tract

slide26

fat

muscle

pancreas

Insulin

Amino acids

Glucagon

liver

Nutrient Director

Glucose

Circulating Nutrients

Fatty acids

Amino acids

Glucose

Fatty acids

WELL FED ANIMAL

High insulin levels

Low glucagon and epinephrine

GIT

slide27

fat

muscle

pancreas

Amino acids

Glucagon

Insulin

liver

Nutrient Director

Glucose

gluconeogenesis & glycogenolysis

Circulating Nutrients

Fatty acids

Amino acids

Glucose

Fatty acids

HUNGRY ANIMAL

Low insulin levels

High glucagon and epinephrine

GIT

history of insulin
History of Insulin
  • 1869 Paul Langerhans (German) was studying the structure of the pancreas when he noticed exocrine tissue. The function of the "little heaps of cells", later known as the Islets of Langerhans
  • 1889 German physician Oscar Minkowski removed the pancreas from a healthy dog to demonstrate the pancreas’s assumed role in digestion.
    • Several days after the dog\'s pancreas was removed, he noticed a swarm of flies feeding on the dog\'s urine
  • 1921: first patient injected with canine insulin
  • 1922: Eli Lilly purchases the patent for making insulin from the University of Toronto for $1
  • 1980: Eli Lilly marketed the first synthetic insulin, Humulin (genetic engineered)
slide32

meal

100

Blood glucose, mg/dl

90

80

absorption

gluconeogenesis

Reciprocity in patterns

glycogenolysis

Time after feeding (h)…

slide33

temporal pattern relative to CHO meal

Glucagon

Glucose

Insulin

Meal

slide34

Boo!

Glucose

Epinephrine

post absorptive cho metabolism ruminants vs monogastrics
Post absorptive CHO metabolism: ruminants vs. monogastrics
  • Monogastrics:
    • Oxidize glucose for energy and energy storage
    • Blood glucose averages 80-100 mg/dl
    • Gluconeogenesis occurs many hours after a meal
    • Much of circulating glucose is diet derived
  • Ruminants:
    • Oxidizes acetate for energy and energy storage
    • Gluconeogenesis immediately after meal
      • ~100% of circulating glucose is derived from gluconeogenesis
    • Blood glucose averages 40-60 mg/dl
    • Circulating glucose is NOT derived from diet
ad