By Dr Ananya Mandal, MD
Origins of the word metabolism
The word metabolism is derived from the Greek word “Metabolismos” or from the French word métabolisme. In Greek metabole means a “change” and metaballein means to change. The combination of the words is derived from meta meaning “over” and ballein meaning “to throw”. (From ballistics).
Overview of the history of metabolism
Metabolism and metabolic pathways have been studied over several centuries and has moved from examining whole animals in early studies, to examining individual metabolic reactions in modern biochemistry and molecular biology.
Early metabolic studies
Metabolic studies have been conducted as early as thirteenth century by Ibn al-Nafis (1213-1288), who stated that "the body and its parts are in a continuous state of dissolution and nourishment, so they are inevitably undergoing permanent change."
The original recorded and more sophisticated studies of metabolism began in the closing decades of the sixteenth century. It was during this time that direct observation was augmented by instrumentation that allowed for quantification and, therefore, verification in sciences especially of biological systems. In medicine, progress depended on the application of the exact sciences of chemistry, mathematics and physics to the study of function.
Santorio Sanctorius and ‘insensible perspiration’
Santorio Sanctorius (1561- 1636) contributed by exploring insensible perspiration. His efforts over years of experimentation gave rise to the metabolic balance studies. The first controlled experiments in human metabolism were published by Santorio Santorio in 1614 in his book ''Ars de statica medecina''. In his experiments he weighed himself before and after eating, sleep, working, sex, fasting, drinking, and excreting. He found that most of the food he took in was lost through what he called "insensible perspiration".
What were initial studies of metabolism conducted on?
Initial studies of metabolism were conducted on living animals or human volunteers. The mechanisms of these metabolic processes had not yet been identified and a vital force was thought to animate living tissue.
19th century metabolic studies
It was in the 19th century when Louis Pasteur was experimenting with fermentation of sugar to alcohol by yeast, he noted that fermentation was catalyzed by substances within the yeast cells he called "ferments".
This discovery, along with the publication by Friedrich Wöhler in 1828 of the chemical synthesis of urea laid the basis for organic compounds and chemical reactions found in cells that form the basis of metabolic pathways.
20th century metabolic studies
Eduard Buchner in the beginning of the 20th century advanced the knowledge further by discovering enzymes. He found that the study of the chemical reactions of metabolism was a different branch from the biological study of cells and began to understand the basics of biochemistry. Early 20th century saw rapid development in biochemical studies.
The most notable findings was the discovery of the citric acid cycle or Kreb’s cycle by Hans Krebs who made huge contributions to the study of metabolism. He discovered the urea cycle and later, working with Hans Kornberg, the citric acid cycle and the glyoxylate cycle.
Current metabolic studies
Metabolism is now studied with the help of molecular biotechnology techniques and genomics. Instruments such as chromatography, X-ray diffraction, NMR spectroscopy, radioisotopic labelling, electron microscopy and molecular dynamics simulations are commonly used. These techniques have allowed the discovery and detailed analysis of the metabolic pathways and the genetic basis of metabolic disorders.
Studies over the last two centuries have also made advances in the understanding of drug metabolism and metabolism of xenobiotics.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)