Lecture Notes: Metabolic Integration

Introduction

• Today's lecture focuses on how metabolic cycles and pathways are interconnected.
• Various organs play roles in these processes, with a special emphasis on the liver as the metabolic hub.

Key Organs in Metabolism

Brain

• Control center of the body.
• Consumes 60% of body's glucose.
• Important for maintaining glucose levels—too little can cause lethargy and cognitive issues.

Pancreas

• Regulates blood glucose by secreting insulin when blood sugar is high.
• Secretes digestive enzymes like trypsin and chymotrypsin.

Intestines

• Small Intestines: Absorb nutrients.
• Large Intestines: Absorb water and electrolytes.

Stomach

• Main role in digestion by producing chyme.
• Secretes peptide hormones that control eating behaviors.

Liver

• Metabolic hub of the body.
• Connects various metabolic pathways and cycles.
• Key player in glucose regulation and toxin inactivation via the portal vein.

Metabolic Intermediates

Glucose 6 Phosphate

• Facilitates pathways like pentose phosphate pathway, glycogen synthesis, glycolysis, and glucose release into blood.

Muscle Types

Skeletal Muscle

• Activated in rapid bursts and endurance activities.
• Can serve as an energy source during starvation.

Cardiac Muscle

• Functions consistently over a lifetime and should not be broken down.

Creatine Kinase

• Catalyzes reversible phosphorylation reactions to generate ATP in muscle cells.
• Used to analyze muscle damage.

Adipose Tissue

Subcutaneous Fat

• Located under the skin (e.g., thighs, buttocks).

Visceral Fat

• Surrounds vital organs, associated with higher cardiovascular disease risks.

Kidneys

• Essential for filtering blood and waste elimination.
• Kidney failure often leads to critical conditions.

Metabolic Cycles

Triacylglycerol Cycle

• Maintains energy-rich fatty acids in circulation.
• Involves glycerol 3 phosphate and connects liver and adipose tissue.

Important Hormones

Insulin

• Secreted when blood sugar is high.
• Stimulates glucose uptake, glycogen, and fatty acid synthesis.

Glucagon

• Secreted when blood sugar is low.
• Stimulates glucose production and glycogen breakdown.

Ghrelin and Leptin

• Ghrelin: Hunger hormone.
• Leptin: Appetite suppressant.
• Leptin resistance can lead to overeating and weight gain.

Factors Influencing Metabolic Homeostasis

• Genetic inheritance, nutrition, and exercise.
• Maintain healthy weight to reduce disease risk.

Weight Loss Drugs and Substitutes

• Drugs like ephedrine and lorcaserin affect metabolism and appetite.
• Olestra, a fat substitute, can cause nutrient malabsorption and side effects.

Glycemic Index (GI)

• Measures how quickly a carbohydrate-containing food raises blood sugar levels.
• Foods with low GI (<55) are healthier, minimizing blood sugar spikes.
• Combining high GI foods with low GI foods can balance blood sugar levels.

Conclusion

• Importance of making healthy scientific choices daily.
• Encourage questions and further discussions via email or the Remind app.

Review Question: Remember to send the answer through the Remind app.