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Mast cells' involvement in inflammation pathways linked to depression: evidence in mastocytosis
Editor’s Note: Mast Cell Activation Disorder (or mastocytosis) has, of late, become increasingly implicated in chronic degenerative diseases of all kinds. Therefore, this study’s assertion that mastocytosis is rare is most likely inaccurate, as researchers have been finding it to play a major role in the symptoms of many illnesses, including Lyme disease, chronic fatigue syndrome and fibromyalgia. For more information, see Lawrence B. Afrin’s book, Never Bet Against Occam (2016). 
Converging sources of evidence point to a role for inflammation in the development of depression, fatigue and cognitive dysfunction. More precisely, the tryptophan (TRP) catabolism is thought to play a major role in inflammation-induced depression. Mastocytosis is a rare disease in which chronic symptoms, including depression, are related to mast cell accumulation and activation.
Our objectives were to study the correlations between neuropsychiatric features and the TRP catabolism pathway in mastocytosis in order to demonstrate mast cells' potential involvement in inflammation-induced depression.
Fifty-four patients with mastocytosis and a mean age of 50.1 years were enrolled in the study and compared healthy age-matched controls. Depression and stress were evaluated with the Beck Depression Inventory revised and the Perceived Stress Scale. All patients had measurements of TRP, serotonin (5-HT), kynurenine (KYN), indoleamine 2,3-dioxygenase 1 (IDO1) activity (ratio KYN/TRP), kynurenic acid (KA) and quinolinic acid (QA).
Patients displayed significantly lower levels of TRP and 5-HT without hypoalbuminemia or malabsorption, higher IDO1 activity, and higher levels of KA and QA, with an imbalance towards the latter. High perceived stress and high depression scores were associated with low TRP and high IDO1 activity.
In conclusion, TRP metabolism is altered in mastocytosis and correlates with perceived stress and depression, demonstrating mast cells' involvement in inflammation pathways linked to depression.
Source: By Georgin-Lavialle S1,2,3 Moura DS1,2,4, Salvador A5,6, Chauvet-Gelinier JC7,8, Launay JM9, Damaj G10, Côté F2, Soucié E11, Chandesris MO1, Barète S1,2, Grandpeix-Guyodo C1, Bachmeyer C3, Alyanakian MA12, Aouba A13, Lortholary O1,14, Dubreuil P1,11, Teyssier JR15, Trojak B6,7, Haffen E15,16,17, Vandel P17,18, Bonin B7,8; French Mast Cell Study Group, Hermine O1,2,13, Gaillard R1,5,6,19. Collaborators. Mast cells' involvement in inflammation pathways linked to depression: evidence in mastocytosis. Mol Psychiatry.  2016 Nov;21(11):1511-1516. doi: 10.1038/mp.2015.216. Epub 2016 Jan 26.