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Diabetes Mellitus, Type I

Image depicts tissue transglutaminase (tTg).
Image Depicts Tissue Transglutaminase (tTG).

What Are Anti-tissue Transglutaminase Antibodies?

[dropcap]A nti-tissue transglutaminase antibodies (anti-tTG) are connective tissue autoantibodies and can be detected in blood samples from affected persons who are reacting to gluten in the diet.

Autoantibodies are abnormal because they attack the body’s own tissue, which in the case of these antibodies is tissue transglutaminase 2 (TG2).

Q: What is tissue transglutaminase 2 (TG2)?

A: Tissue transglutaminase 2 (TG2) is an enzyme that appears in many cell locations and is particularly abundant in endothelial cells that line the small intestine. It has been implicated in a variety of cellular processes, such as differentiation, cell death, inflammation, cell migration and wound healing.

The cell appears to adapt the dynamics of this enzyme to meet specific sub-cellular needs or to respond to stress or other stimuli. Substantial evidence indicates that the location of TG2 within cells is critical for the regulation of its various biochemical activities, which subsequently trigger diverse downstream events,1

Although initially studied as an enzyme within cells, TG2 is now known to be secreted also into the extracellular space (between cells) or onto the cell surface.1

Abnormal activation of TG2 or deregulation of its function(s) is involved in a variety of human diseases, such as celiac disease, diabetes, neurodegenerative diseases, multiple sclerosis and rheumatoid arthritis. A role in inflammatory disorders and septic shock has also been shown. Moreover, multiple studies have revealed elevated TG2 expression in many types of cancer cells.1

What Are Anti-tissue Transglutaminase Antibodies In Celiac Disease and/or Gluten Sensitivity?

Sources:
  1. Piacentini M, D’Eletto M, Farrace MG, Rodolfo C, Del Nonno F, Ippolito G, Falasca L. Characterization of distinct sub-cellular location of transglutaminase type II: changes in intracellular distribution in physiological and pathological states. Cell Tissue Res. 2014 Dec;358(3):793-805. doi: 10.1007/s00441-014-1990-x. [↩] [↩] [↩]

Primary Sclerosing Cholangitis 

A 3D Image From Magnetic Resonace Cholangiography. NIHMS
A 3D Image From Magnetic Resonace Cholangiography showing biliary tree. NIHMS

What Is Primary Sclerosing Cholangitis?

[dropcap]P[/dropcap]rimary sclerosing cholangitis (PSC) is an uncommon, slowly progressive bile duct disease that results in stagnation or build-up of bile in the liver, called cholestasis.

Primary sclerosing cholangitis is characterized by sclerosis, or scarring inflammation in bile ducts both within the liver (intra-hepatic ducts), and outside the liver (extra-hepatic ducts), causing progressive narrowing and, eventually, obliteration of the bile ducts.

Primary sclerosing cholangitis comes under the umbrella term autoimune liver disease in which the end result is immune-mediated hepatocellular (liver cell) or hepatobiliary (bile duct) injury.1

Q: What happens when scarred bile ducts can no longer transport bile out of the liver?

A: Bile that cannot be removed from the liver by the biliary duct system backs up and damages the liver, causing cirrhosis.

Bile is continually made by the liver from phospholipids salt, cholesterol, and aging blood cells that it removes from circulation to be carried out of the liver. Bile also carries away waste products produced by normal metabolism and toxic substances that are removed by the liver for eventual elimination in stool. As such, bile must continually flow out of the liver to prevent build-up in the liver.

Bile is a greenish brown liquid made by the liver. Bile ducts carry it out of the liver to the gall bladder for storage until needed to aid in the digestion and absorption of fat from the small intestine. Bile emulsifies fat eaten in the diet so that the pancreatic enzyme called lypase can break it down into its fatty acid and glycerol components.

The liver is the largest organ within the body. It lies mostly in the upper part of the abdomen on the right side just under the diaphragm. About 70% of liver tissue is made up of cube shaped cells called hepatocytes that do the main work of the liver. Other cells (epithelial) form structure and are arranged in single layers around blood vessels, sinusoids, and bile ducts. 

Build-up of bile in the liver is the end result of the inflammatory process in primary sclerosing cholangitis, that by swelling and scarring of bile ducts impedes and eventually prevents bile flow out of the liver, leading to liver failure. There is no curative treatment available for primary sclerosing cholangitis, besides liver transplantation.2

The appearance of the intrahepatic and extrahepatic biliary ducts can be assessed by use of cholangiography, and magnetic resonance (MR) imaging is the best way to identify patients.  See image above.3

MR cholangiography offers a noninvasive method of obtaining images of the biliary system without the use of a contrast agent. There is no radiation exposure. Pulse sequences can be chosen to obtain bright bile or black bile cholangiograms. Image processing algorithms can be selected to obtain a three-dimensional representation of biliary anatomy and pathology, and those images can be rotated in any plane so that ductal anatomy and pathology can be seen to best advantage.4

There is no cure for primary sclerosing cholangitis but there are symptom treatments one of which is supplementation for low levels of vitamins A,D,E, and K. Liver transplant is the only effective option.

What Is Primary Sclerosing Cholangitis In Celiac Disease and/or Gluten Sensitivity?

Sources:
  1. Trivedi PJ, Adams DH. Mucosal immunity in liver autoimmunity: a comprehensive review. J Autoimmun. 2013 Oct;46:97-111. doi: 10.1016/j.jaut.2013.06.013. [↩]
  2. Kummen M, Schrumpf E, Boberg KM. Liver abnormalities in bowel diseases. Best Pract Res Clin Gastroenterol. 2013 Aug;27(4):531-42. doi: 10.1016/j.bpg.2013.06.013. [↩]
  3. Eaton JE, Talwalkar JA, Lazaridis KN, Gores GJ, Lindor KD. Pathogenesis of primary sclerosing cholangitis and advances in diagnosis and management. Gastroenterology. 2013 Sep;145(3):521-36. doi: 10.1053/j.gastro.2013.06.052. Epub 2013 Jul 1. [↩]
  4. Meakem TJ 3rd, Schnall MD. Magnetic resonance cholangiography. Gastroenterol Clin North Am. 1995 Jun;24(2):221-38. [↩]

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