Related Experiment Video
Updated: Aug 7, 2026
09:41
Measuring the Rate of Lipolysis in Ex Vivo Murine Adipose Tissue and Primary Preadipocytes Differentiated In Vitro
Published on: March 17, 2023
Proteolytic and lipolytic responses to starvation
1Department of Molecular and Cellular Physiology, Tufts University School of Medicine, Boston, Massachusetts, USA.
Nutrition (Burbank, Los Angeles County, Calif.)
|July 4, 2006
Summary
Mammals adapt to starvation by breaking down proteins and fats for energy. Different tissues use varied pathways, including the ubiquitin-proteasome system and autophagy, to manage these essential metabolic shifts.
Area of Science:
- Metabolic Regulation
- Cellular Physiology
- Biochemistry
Background:
- Mammals employ complex physiological adaptations to survive periods of starvation.
- These adaptations involve hormonal and neural signals that trigger catabolic processes.
- Understanding these responses is crucial for metabolic and physiological research.
Purpose of the Study:
- To elucidate the diverse proteolysis and lipolysis pathways activated during mammalian starvation.
- To investigate the tissue-specific and duration-dependent mechanisms of nutrient mobilization.
- To explore the interplay between proteolytic and lipolytic responses.
Main Methods:
- Analysis of proteolysis pathways (ubiquitin-proteasome system, lysosomal pathways, macroautophagy, chaperone-mediated autophagy).
- Examination of lipolysis and triacylglycerol breakdown.
- Investigation of metabolic fuel utilization (fatty acids, glycerol, ketone bodies).
Main Results:
- Skeletal muscle protein breakdown is mainly mediated by the ubiquitin-proteasome system.
- Lysosomal proteolysis is stimulated in most other tissues during fasting.
- Short-term starvation activates macroautophagy, while long-term starvation activates chaperone-mediated autophagy.
- Lipolysis increases, providing fatty acids for energy and glycerol for gluconeogenesis.
- Hepatic fatty acid oxidation produces ketone bodies for energy, particularly for the brain.
Conclusions:
- Mammalian starvation survival involves a coordinated activation of proteolysis and lipolysis across various tissues.
- The specific pathways utilized are dependent on tissue type and starvation duration.
- Interactions between proteolysis and lipolysis, such as chaperone-mediated autophagy in response to ketone bodies, highlight integrated survival strategies.
Related Concept Videos
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...
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,...
01:23Stringent Response in E. coli
Bacterial growth is closely tied to nutrient availability, with cells proliferating exponentially under favorable conditions and entering a stationary phase when resources become scarce. This transition is mediated by a regulatory mechanism known as the stringent response, which allows bacteria to adapt to nutrient deprivation by modulating gene expression and metabolic activity.During nutrient scarcity, intracellular amino acid levels decline. It results in the accumulation of uncharged tRNAs...
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...
01:27Autophagy
Autophagy is a self-digesting process by which a cell protects itself from threats both within and outside the cell, ranging from abnormal proteins to invading bacteria. In this process, obsolete components of the cell and invading microbes are degraded by hydrolytic enzymes active in an acidic environment of the lysosomal lumen.
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...
An autophagic pathway consists of a series of signaling events activated in response to diverse stress and physiological conditions such as food deprivation,...