Bilirubin, Blood Surface Tension and Ibn Sina.

It is said that nothing in this world was created without a purpose. Everything we see around us is in one way or another useful. What have we, as medical students and professionals, always been told about bilirubin? That is a byproduct in the degradation of heme and helps in iron cycle in the body. That if its serum level is more than 1.0 to 1.2 mg/dL, it is called jaundice. Then we talk about Kernicterus, Dubin Johnson's, Rotor's, Crigler najjar Syndromes etc etc, disorders of bilirubin. On the whole, bilirubin is considered as a marker of hepatic disease. But what we are not taught is the purpose of bilirubin. In our medical curriculum, we immerse ourselves in blood levels of substances, lab tests, drug treatment and we tend to overlook simple basics of Medicine.

In spring 2016, I had got my hands on a commentary of Ibn Sina's (Avicenna) 'Canon of Medicine' (Al Qanun Fil Tibb). Considered as one of the most authentic and all time greats in the history of Medical literature. It had large portions of the original book translated into English, along with commentary by contemporary Doctors. This encyclopedia of Medical literature was written in, as early as, year 1025 and it had been one of the foundations of modern Medicine as we know it today. This book deals with a wide range of topics related to health and medicine. It talks about temperaments of bodies, body types, effect of seasons on health, effect of sun, moon and stars on health, Health injury and skull fractures etc. While going through the pages with pure amazement, I stumbled upon a phrase "Bilirubin is essential to maintain optimal surface tension of blood'. I was thinking, the author knew about surface tension of liquids in the year 1025? Surface tension was supposed to be modern physics?  Furthermore, it said that Bilirubin reduces blood surface tension so that the blood could travel through small capillaries without any difficulty. If bilirubin levels were low, blood surface tension would go up and blood would not pass through small capillaries. I felt like I am reading a modern book on Physics rather than a doctor's observations 1000 years ago. Skeptical about the observations made in this book, I searched for clinical research on this topic, published in various peer reviewed Journals. To my astonishment, it was right, recent research did show that Bilirubin decreases blood surface tension.

When added to water, bilirubin decreases the surface tension of the solution and favoring the emulsification of fats and oils. Click Here.

In a study involving 150 patients, the researches concluded that there is a correlation between blood surface tension and activity of plasma gamma-glutamyltransferase (a liver enzyme) and this correlation was based on changes of bile acids in the blood. Inference? There is correlation between blood surface tension and bile acids. Click Here.

According to a study conducted at University or Berne, Switzerland, Bilirubin impairs the surface tension activity of porcine lipid extract. Click Here.

Hay's test:

The test is based on the principle that Bile salts reduce the surface tension of a liquid. Sulfur power is sprinkled over surface of urine sinks to the bottom when bile salts are present in it. While sulfur particles remain on the surface when bile salts are absent in urine. Click Here.
It was concluded in a clinical study that Bile salts were the main determinants of urine surface tension. Click Here.
Thus Bilirubin is not only important for liver function but also for kidney function. It helps the blood to flow through the renal capillaries and the urine to flow out, thus maintaining harmony in the filtering process.
Apart from surface tension reducing properties,

• Bilirubin increases blood viscosity, acts as an anti oxidant, helps in emulsification of fats, plays an important role in heme and iron cycle in the body.
• Decreases the risk of Hypertension by inactivating and inhibiting the synthesis of reactive oxygen species in vascular cells. Click Here. 
• Bilirubin acts as a Cardio-metabolic signaling molecule. Click Here. 
• Bilirubin as Cardioprotective: Recent literature reports an inverse relationship between bilirubin levels and CAD (Heart disease.). It may be in part attributed to bilirubin's anti inflammatory, anti oxidant, vasodilatory, anti-apoptotic, anti-proliferative properties. Click Here. 
• Chronic Hyperbilirubinemia (example- Gilbert's syndrome) prevent the development of IHD (ischemic heart disease) by increasing the serum antioxidant capacity. Click Here. 
• Bilirubin has Renal protective actions and reduces Cardiovascular and overall mortality in Dialysis patients. Click Here. 

Coming back to our original discussion, how did a physician in 1025 know about this? And nothing in this universe was created without purpose.