Fed (Absorptive) State Metabolism | Carbs, proteins, and fats
Apr 14, 2024
auto_awesome
Exploring the body's handling of carbohydrates, proteins, and fats after a meal. Discussion on glycolysis, Krebs cycle, and energy storage processes. Insight into liver metabolism post carb-heavy meal consumption and glycogen formation pathways. Understanding amino acids utilization in liver and muscles during fed state metabolism. Insights into insulin regulation, glucose transporters, and metabolic processes in various tissues.
Insulin plays a crucial role in glycogen synthesis and breakdown, energy utilization, and fatty acid regulation in the liver post-meal.
The liver's glycogen storage peaks 4-6 hours after eating, with later breakdown during fasting or exercise to maintain blood glucose levels.
Insulin modulation in liver metabolism involves controlling glycogen synthesis, inhibiting breakdown enzymes, and promoting proper energy production pathways.
The liver transforms excess glucose into fatty acids under insulin regulation, potentially leading to ketone formation in the absence of insulin presence.
Fructose metabolism differs from glucose, affecting energy regulation and potentially contributing to fat storage and liver diseases.
Deep dives
Glucose Metabolism in the Liver
After a carbohydrate-rich meal, glucose enters the bloodstream where the liver takes up a portion while the rest travels to other tissues. Insulin is essential for these tissues to uptake glucose. The liver processes glucose through the glycolytic pathway, storing most as glycogen. Additionally, the liver converts excess glucose into fatty acids through enzymes like citrate-lyase, primarily storing it as triglycerides in VLDLs for energy utilization elsewhere.
Glycogen Storage and Breakdown
The liver peeks its glycogen storage around 4-6 hours after a meal, then gradually breaks down stored glycogen during fasting or exercise to maintain blood glucose levels. Around 50% of glucose required after midnight comes from glycogenolysis in the liver, while the remaining glucose is synthesized from amino acids or fatty acids. The liver can convert glucose to fatty acids when overloaded, which may lead to ketone formation without insulin presence.
Insulin Regulation in Liver Metabolism
Insulin plays a crucial role in modulating liver metabolism. It stimulates glycogen synthesis enzymes and inhibits glycogen breakdown enzymes, aids in pyruvate production for energy utilization, and promotes Krebs cycle activity. Insulin inhibits fatty acid synthesis and ketone production is enhanced in its absence, leading to conditions like diabetic ketoacidosis.
Importance of Insulin in Liver Function
While the liver has some independence in glucose uptake, insulin regulates multiple metabolic processes within the liver. It stimulates glycogen synthesis, inhibits breakdown enzymes, and facilitates energy production. Insulin also inhibits fatty acid synthesis and controls ketone formation for proper metabolic balance.
Regulation of Liver Fatty Acid Synthesis
The process of converting glucose to fatty acids in the liver for storage is regulated by insulin. It stimulates enzymes like citrate-lyase for fatty acid generation and regulates the balance between glycolysis and fatty acid synthesis. Insulin influences metabolic pathways to ensure controlled energy utilization and storage within the liver.
Glucose Metabolism in the Liver
In the liver, glucose can be converted to glucose 6-phosphate, which can further store glycogen or undergo glycolysis. The liver can also reverse this process and release glucose into the blood for the body to use. Unlike muscle, the liver enzyme glucocyanose allows for this process, making the liver a crucial metabolic hub.
Fructose Metabolism and Lipogenesis
Fructose metabolism differs from glucose metabolism and leads to the production of fructose 1-6 bisphosphate through an important regulatory step in glycolysis. Factors like high ATP and citrate levels inhibit the enzyme phosphofructokinase 1, regulating energy production. High fructose intake can result in fat storage due to increased lipogenesis, potentially contributing to non-alcoholic fatty liver diseases and obesity.
Insulin's Role in Metabolism
Insulin plays a key role in metabolism by promoting the storage of nutrients. It induces lipoprotein lipase activity, stimulating the breakdown of triglycerides into fatty acids and glycerol in adipose tissue. Insulin also increases glucose uptake in adipocytes through Glut4 transporters, facilitating the conversion of glucose into glycerol 3-phosphate for fat storage. Additionally, insulin suppresses lipolysis, inhibiting the breakdown of stored fats into fatty acids.
Membership and Special Content
Listeners can access ad-free and early episodes by subscribing to the podcast membership. Subscribers receive exclusive content, such as in-depth episodes on medical, scientific, or biological topics. The membership helps support the podcast and enables the hosts to dedicate more time to creating valuable episodes for the audience.
