Beyond Genetic Factors in Familial Amyloidotic Polyneuropathy: Protein Glycation and the Loss of Fibrinogen's Chaperone Activity

Familial amyloidotic polyneuropathy (FAP) is a systemic conformational disease characterized by extracellular amyloid fibril formation from plasma transthyretin (TTR). This is a crippling, fatal disease for which liver transplantation is the only effective therapy. More than 80 TTR point mutations are associated with amyloidotic diseases and the most widely accepted disease model relates TTR tetramer instability with TTR point mutations. However, this model fails to explain two observations. First, native TTR also forms amyloid in systemic senile amyloidosis, a geriatric disease. Second, age at disease onset varies by decades for patients bearing the same mutation and some mutation carrier individuals are asymptomatic throughout their lives. Hence, mutations only accelerate the process and non-genetic factors must play a key role in the molecular mechanisms of disease. One of these factors is protein glycation, previously associated with conformational diseases like Alzheimer's and Parkinson's. The glycation hypothesis in FAP is supported by our previous discovery of methylglyoxal-derived glycation of amyloid fibrils in FAP patients. Here we show that plasma proteins are differentially glycated by methylglyoxal in FAP patients and that fibrinogen is the main glycation target. Moreover, we also found that fibrinogen interacts with TTR in plasma. Fibrinogen has chaperone activity which is compromised upon glycation by methylglyoxal. Hence, we propose that methylglyoxal glycation hampers the chaperone activity of fibrinogen, rendering TTR more prone to aggregation, amyloid formation and ultimately, disease

Abdominal pain is associated with anxiety and depression scores in a sample of the general adult population with no signs of organic gastrointestinal disease

Background: Abdominal pain is common in the community, but only a subset meet diagnostic criteria for irritable bowel syndrome (IBS). Although anxiety and depression have been linked to IBS, the role of mood disturbances in the remainder with symptoms remains unclear. We aimed to study the associations between abdominal pain, anxiety, depression, and quality of life in the general population who were free of organic colonic disease by colonoscopy. Methods: Two hundred and seventy-two randomly selected subjects from the general population, mean age 54 years (27–71), were clinically evaluated, had a colonoscopy and laboratory investigations to exclude organic gastrointestinal (GI) disease. All subjects completed GI symptom diaries for 1 week, the Rome II modular questionnaire, the Hospital Anxiety and Depression Scale, and Short Form 36. Key Results: Twenty-two subjects were excluded due to organic disease; 1532 daily symptom records were available for analysis in the remainder. Thirty-four percent (n = 83) recorded at least one episode of abdominal pain on the diary. Twelve percent fulfilled Rome II criteria for IBS. Both anxiety and depression scores were higher in subjects who reported abdominal pain vs those who did not (P < 0.0005 and P < 0.0005). Anxiety and depression scores independently from IBS diagnosis (Rome II) predicted pain reporting and also correlated positively with pain burden. Quality of life scores were generally lower in subjects with abdominal pain. Conclusions & Inferences: Anxiety and depression are linked to functional abdominal pain, not only in subjects with IBS but also in otherwise healthy people with milder, subtle GI symptoms