Mastering Nutrition

Carbs Spare Protein In a Way Fat Can't | MWM Energy Metabolism Cliff Notes #16

Sep 18, 2017

This podcast explores the concept of anaplerosis and its importance in the citric acid cycle. It discusses how carbs and protein are the primary sources of anaplerosis, and how carbs can spare the need for protein. The podcast also delves into the limited contribution of fatty acids in anaplerosis compared to carbs and protein. Furthermore, it explores the role of carbohydrates, fat, and anaplerosis in energy metabolism, including the importance of protein goals in a ketogenic diet.

10:20

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Quick takeaways

Carbohydrates are the main substrates for anaplerosis in the citric acid cycle, filling up the cycle and ensuring its continuous functioning.

Protein becomes the dominant anaplerotic substrate when carbohydrates are restricted, highlighting the importance of meeting protein goals on a ketogenic diet.

Deep dives

Anaplarosis: Filling up the Citric Acid Cycle

In this podcast episode, the concept of anaplarosis is explored, which refers to the ability of carbohydrates to fill up the citric acid cycle. The citric acid cycle, or Krebs cycle, is not only essential for energy metabolism but also involves intermediates that can leave the cycle for other processes. To keep the cycle running, these intermediates need to be replaced, which is where anaplarosis comes in. It allows the lost intermediates to be replenished and ensures the continuous functioning of the citric acid cycle. Carbohydrates, particularly pyruvate from glucose, are the primary substrates for anaplarosis, but other amino acids, such as alanine, aspartate, and glutamate, can also play a role.

Accumulation of Acetyl CoA in Biosynthetic Reaction: Implications for Citric Acid Cycle

00:31

Introduction

1min

Pyruvate Metabolism and Anaplerosis

4min

The Role of Carbohydrates and Protein in Anaplyrosis and Fat Metabolism

2min

The Role of Carbohydrates and Fat in Energy Metabolism

3min

“Anaplerosis” means “to fill up” and refers to substrates and reactions that fill up a metabolic pathway as its own substrates leak out for other purposes. The citric acid cycle is a central example of this because its intermediates are often used to synthesize other components the cell needs. On a mixed diet where carbohydrate provides much of the energy, pyruvate serves as the main anaplerotic substrate. During carbohydrate restriction, protein takes over. Fat is the least anaplerotic of the macronutrients because the main product of fatty acid metabolism, acetyl CoA, is not directly anaplerotic. There are several very minor pathways that allow some anaplerosis from fat, but they are unlikely to eclipse the need for protein to support this purpose during carbohydrate restriction. Thus, carbs and protein are the two primary sources of anaplerosis. This means carbs can spare the need for protein, and that protein requirements rise on a carb-restricted diet.

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Mastering Nutrition

Carbs Spare Protein In a Way Fat Can't | MWM Energy Metabolism Cliff Notes #16

Podcast summary created with Snipd AI

Quick takeaways

Deep dives

Anaplarosis: Filling up the Citric Acid Cycle

Carbohydrates and Protein in Anaplarosis

Accumulation of Acetyl CoA in Biosynthetic Reaction: Implications for Citric Acid Cycle

Remember Everything You Learn from Podcasts