Context: A study by researchers from the Tata Institute of Fundamental Research, Mumbai (TIFR) shows that glucose controls the function of SIRT1 directly. 

About SIRT1

  • SIRT1 is an enzyme that deacetylates proteins that contribute to cellular regulation (reaction to stressors, longevity). Sirtuin 1 is a protein that in humans is encoded by the SIRT1 gene. SIRT1 stands for sirtuin. 


This study paves the way to regulating this function, which might be beneficial in tackling lifestyle disorders and ageing-related diseases.

  • An enzyme called SIRT1 is associated with regulation of metabolic activities and also ageing.
  • The study next seeks to investigate if glucose-dependent control can dictate gene expression during feed-fast cycles. 

The relation between metabolic diseases and wrong feeding regimen:

  • Feed-fast cycle: Every organism has evolved so as to feed and then alternately fast.  This cycle and the metabolism-related to this is largely taken care of by the liver.
  • There are several enzymes in the liver, including alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and gamma-glutamyl transpeptidase (GGT).
  • Role of glucose: Glucose controls the functions of a protein SIRT1 which in turn maintains everyday feed-fast cycles and is also associated with longevity.
  • In normal healthy individuals, SIRT1 protein levels are known to increase during fasting and decrease during feed, which is essential to maintain a balance between glucose and fat metabolism.
  • Diseases: Glucose puts a check on the activity of SIRT1 in the fed state. 
    • In the absence of this check, SIRT1 activity increases and results in hyperglycemia in a fasted state, mimicking diabetic state. 
    • Constant feeding or high calorie intake that leads to sustained reduction in the levels of SIRT1 (by glucose) is associated with ageing and obesity.


About Fat metabolism

Digestion and absorption

Fats or lipids eaten by the body are 

  1. Cleaved by enzymes, 
  2. Absorbed in the small intestine, and 
  3. Then transported in chylomicrons via the lymphatic system into the bloodstream, where they reach the liver, peripheral tissues (with LDL receptors) and adipose tissue (storage).

Enzymes in fat metabolism

An enzyme is a chemical that accelerates (speeds up) chemical reactions within the body. 

  • The main lipases of the human digestive system are pancreatic lipase (PL) and pancreatic lipase related protein 2 (PLRP2), which are secreted by the pancreas. 
  • Lipase is the major enzyme that breaks down dietary fats into smaller molecules called fatty acids and glycerol. 
  • This is done when lipase hydrolyzes lipids, the ester bonds in triglycerides
  • Hydrolysis is the breakdown of fat by the addition of water.

Lipid transport

Circulating lipids are transported in lipoproteins because the hydrophobic lipids are insoluble in plasma.

Fat malabsorption

It can be caused if the liver is not producing enough bile or there is a lack of pancreatic enzymes like lipase.