Related Experiment Video
Updated: Aug 1, 2026
07:07
Determining Glucose Metabolism Kinetics Using 18F-FDG Micro-PET/CT
Published on: May 2, 2017
Summary
During starvation, plasma carnitine levels rise before muscle carnitine increases. This shift in carnitine metabolism and decreased carnitine palmityl transferase activity may explain reduced metabolic rate during prolonged fasting.
Area of Science:
- Metabolic Regulation
- Nutritional Biochemistry
- Physiology
Background:
- Starvation triggers significant whole-body fuel utilization shifts, prioritizing fat oxidation and ketone production for energy conservation.
- The precise mechanisms governing these metabolic adaptations, particularly the role of carnitine in fat metabolism during fasting, remain incompletely understood.
- Carnitine is crucial for transporting long-chain fatty acids into mitochondria for oxidation, making it a key regulator of fat utilization.
Purpose of the Study:
- To investigate the dynamic interplay between plasma and muscle carnitine levels, their esters, and energy substrates during prolonged starvation in a canine model.
- To elucidate the relationship between carnitine metabolism, carnitine palmityl transferase activity, and metabolic rate changes during fasting.
Main Methods:
- Eight beagle dogs underwent an 8-day starvation period, with measurements taken on days 3, 5, and 8.
- Analysis included plasma and muscle free carnitine (FC), long-chain esters (LCE), total carnitine (TC), and substrate-hormone profiles.
- Muscle carnitine palmityl transferase (CPT) activity was assessed, alongside body weight changes.
Main Results:
- A significant decrease in body weight was observed throughout the starvation period.
- Plasma TC, FC, and LCE levels increased significantly by day 3, preceding significant increases in muscle TC and FC observed by day 8.
- A significant decrease in muscle CPT activity occurred by day 8, coinciding with the rise in muscle carnitine.
Conclusions:
- Plasma carnitine levels rise before muscle carnitine during prolonged starvation in dogs.
- The observed decrease in carnitine palmityl transferase activity may be linked to, or a consequence of, the changes in muscle carnitine levels.
- These carnitine-related adaptations might contribute to the reduced metabolic rate characteristic of prolonged starvation.
More Related Videos
08:30Intraperitoneal Glucose Tolerance Test, Measurement of Lung Function, and Fixation of the Lung to Study the Impact of Obesity and Impaired Metabolism on Pulmonary Outcomes
Published on: March 15, 2018
11:03Measurement of Fatty Acid β-Oxidation in a Suspension of Freshly Isolated Mouse Hepatocytes
Published on: September 9, 2021
Related Concept Videos
01:20Fates of Pyruvate
Pyruvate is the end product of glycolysis, where glucose is oxidized to pyruvate, simultaneously reducing NAD+ to NADH. Two molecules of ATP are also produced by substrate-level phosphorylation.
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
In aerobic organisms, pyruvate is metabolized via the citric acid cycle to produce reduced coenzymes NADH and FADH2. These coenzymes are then oxidized in the electron transport chain to produce ATP and, in the process, regenerate the NAD+ and FAD. As seen in some cell types and organisms, fermentation...
01:28Overview of Fatty Acid Metabolism
Lipids also are sources of energy that power cellular processes. Like carbohydrates, lipids are composed of carbon, hydrogen, and oxygen, but these atoms are arranged differently. Most lipids are nonpolar and hydrophobic. Major types include fats and oils, waxes, phospholipids, and steroids.
Fatty acids are catabolized in a process called beta-oxidation, which takes place in the matrix of the mitochondria and converts their fatty acid chains into two-carbon units of acetyl groups. The acetyl...
Fatty acids are catabolized in a process called beta-oxidation, which takes place in the matrix of the mitochondria and converts their fatty acid chains into two-carbon units of acetyl groups. The acetyl...
01:24Overview of Lipid Metabolism
Lipid metabolism is a crucial process in the human body that involves the synthesis and degradation of lipids. This process is essential for energy production, cell membrane formation, and hormone production, among other functions.
Lipolysis: The Breakdown of Lipids:
Lipolysis is the process of breaking down lipids, particularly triglycerides, into glycerol and fatty acids. This process typically occurs in the adipose tissue and is triggered by various hormones, including glucagon and...
Lipolysis: The Breakdown of Lipids:
Lipolysis is the process of breaking down lipids, particularly triglycerides, into glycerol and fatty acids. This process typically occurs in the adipose tissue and is triggered by various hormones, including glucagon and...
01:25Metabolic States of the Body: The Absorptive State
During the absorptive state, which lasts approximately four hours after a meal, the body absorbs nutrients from the gastrointestinal tract. The carbohydrates, proteins, and lipids we consume are broken down into monosaccharides, amino acids, and free fatty acids for absorption. While carbohydrates and proteins are absorbed as-is, lipids are absorbed in their broken-down forms and then re-esterified into triglycerides within enterocytes before being packaged into chylomicrons. These absorbed...
01:18Metabolic States of the Body: The Postabsorptive State
The postabsorptive state usually starts about four hours after a meal and lasts until the next meal is eaten. During this time, the digestive system stops absorbing nutrients, and the body uses stored energy reserves to maintain stable blood glucose levels.
Initially, glycogen stored in the liver is broken down to release glucose into the bloodstream, while glycogen in the muscles is broken down to supply glucose for energy directly within the muscle cells. As glycogen stores diminish,...
Initially, glycogen stored in the liver is broken down to release glucose into the bloodstream, while glycogen in the muscles is broken down to supply glucose for energy directly within the muscle cells. As glycogen stores diminish,...
01:24Metabolic States of the Body: Fasting and Starvation
During the initial hours of fasting, the body uses up its glycogen stores as an energy source. Once these glycogen reserves are depleted, the body begins breaking down stored triglycerides and structural proteins. During this stage, glycerol becomes a key substrate for gluconeogenesis, while free fatty acids undergo beta-oxidation to provide energy for tissues, such as skeletal muscle. In the fasting state, the body spares protein breakdown as much as possible to conserve muscle and structural...