Metabolic States

Front 1

Identify the basic tissue compartments that play key roles in metabolic interconversions in the body.

Back 1

- brain/neural tissue
- skeletal muscle
- heart/cardiac muscle
- adipose tissue
- liver
- other peripheral tissues

Front 2

Briefly describe the unique characteristics of each compartment that plays a key role in metabolic interconversions, in terms of those metabolic interconversions.

Back 2

- brain/neural tissue - high/constant e demand; fuel stores:none; preferred fuel: glucose(ketone bodies during starvation); no fuel sources exported
- skeletal muscle
-- (resting): fuel stores:takes up glucose using GLUT4 as a transporter that is upregulated by insulin to make and store glycogen; preferred fuel; FAs; no fuel sources exported
-- (excercise): no fuel stores; preferred fuel: glucose; fuel sources exported: lactate (used in liver or cardiac muscle)
- heart/cardiac muscle - no fuel stores so O2 deficit causes eschimia and infarct; preferred fuel: FAs, but can use lactate; no fuel exported
- adipose tissue - fuel stores:triglycerides; preferred fuel: FAs Fuel exports: FAs and glycerol (breaks TGs down to FAs and glycerol, which goes to liver for gluconeogenesis)
- liver - fuel stores: glycogen, triglycerides; focal point; Preferred fuel: anything - AAs, glucose, FAs; can store a lot of glycogen; Fuel exports: FAs, glucose, ketone bodies
- other peripheral tissues - what they use depends on insulin/glucagon ratio (either rely on glucose in blood or oxidative metabolism of FA for e)

Front 3

Identify the two distinct metabolic states of the body and tell when each would normally occur.

Back 3

- absorptive (fed) state - when ingested nutrients are entering the blood stream (4hrs)
- postabsorptive state - afterwards, till you eat again; fasting state

Front 4

Describe how CHO, fats and proteins are utilized during the absorptive and the postabsorptive states.

Back 4

- Absorptive
-- CHO - major fuel for all body cells; liver and skeletal musc. store it as glycogen; liver and adipose tissue package excess as TG/fat
-- AAs - protein synthesis; excess is deaminated in liver, forms keto acid, which enters Kreb's cycle or is used for FA synthesis
-- FAs - can take FAs out of micells and make TG
- Postabsorptive state:
-- glucose and FA are meeting the e needs
-- glycogenolysis in liver: break down glycogen to form glucose
-- gluconeogenesis in liver: after 4-6 hours, uses pyruvic and lactic acid to make glucose; after long fast main export is ketones
-- glycolysis in skeletal muscle
-- ketogenesis in liver: FAs turned into keto acids - generates ATP

Front 5

Identify the normonal and neural regulation during the absorptive and the postabsorptive states.

Back 5

Absorptive:
- Insulin:primary regulator; triggered by rising blood glucose levels(above 100 mg/dl), elevate plasma AAs, GI tract hormones (GIP, gastrin, CCK), parasympathetic activity (activates the pancreas)
- thyroxine - stimulates gluc. uptake and protein synthesis; stimulates BMR
- testosterone/androgens
- growth hormone
Postabsorptive state:
- insulin secretion dec.
- glucagon secretion inc. - main effect in liver; stimulates glycogenolysis, ketogenesis, gluconeogenesis; effect in adipose tissue: lypolysis
- SNS - releases epinephrine; intensifies glucagon's influence; stimulates lypolysis
- cortisol - intensifies glucagon's effect
- growth hormone - anti-insulin effects

Front 6

What is the primary regulator of metabolic events during the absorptive state?

Back 6

- Insulin

Front 7

List insulin's metabolic effects

Back 7

- enhances glucose uptake
- inc. AA uptake and protein synthesis
- inc. glycogenesis
- inc lipogenesis/dec lypolysis (in adipose tissue)
- inc TG synthesis/dec. ketogenesis (in liver)

Front 8

Why is it important to maintain a homeostatic plasma glucose level?

Back 8

- the brain constantly needs e but has no stores of it
- it only uses glucose, or ketones if need be
- because of the blood/brain barrier can't use FAs etc

Front 9

Describe the regulation of metabolism during the postabsorptive state.

Back 9

- the metabolism is geared toward either making glucose available in the brain, or sparing glucose for use by organs that need it most (esp. the brain)
- insulin secretion dec.
- glucagon secretion inc. - main effect in liver; stimulates glycogenolysis, ketogenesis, gluconeogenesis; effect in adipose tissue: lypolysis
- SNS - releases epinephrine; intensifies glucagon's influence; stimulates lypolysis
- cortisol - intensifies glucagon's effect
- growth hormone - anti-insulin effects

Front 10

In what ways does liver metabolism help in maintaining normal blood glucose levels.

Back 10

- when glucose is low, glycogenolysis happens in the liver; gluconeogenesis in the liver using pyruvic and lactic acid to make glucose; after 6 hrs, makes mostly ketones
- when glucose is high; stimulated by insulin to take up glucose, and make glycogen; can store a lot

Front 11

Compare/contrast the metabolic profile of skeletal muscle under the following conditions:during rest vs. esertion; absorptive state vs. postabsorptive state.

Back 11

R vs E - R: takes up glucose, builds glycogen; uses GLUT-4 to take it up, e needs met by FAs; E - e need met by glucose; glycogenolysis; slow twitch uses FA more than fast twitch can; generates pyruvic acid/lactate (which can be used in liver/cardiac muscle)
A vs. P-A: A - similar to the resting state; P-A - glycolysis used, so that glucose can be spared

Front 12

GLUT-4

Back 12

the glucose transporter in skeletal muscle
- upregulated by insulin - insulin binds to receptor, causes it to be translocated to the cell membrane and to start taking up glucose out of the blood