Albrecht Hoffmeister

Secretome protein enrichment identifies physiological BACE1 protease substrates in neurons.

Cell surface proteolysis is essential for communication between cells and results in the shedding of membrane‐protein ectodomains. However, physiological substrates of the contributing proteases are largely unknown. We developed the secretome protein enrichment with click sugars (SPECS) method, which allows proteome‐wide identification of shedding substrates and secreted proteins from primary cells, even in the presence of serum proteins. SPECS combines metabolic glycan labelling and click chemistry‐mediated biotinylation and distinguishes between cellular and serum proteins. SPECS identified 34, mostly novel substrates of the Alzheimer protease BACE1 in primary neurons, making BACE1 a major sheddase in the nervous system. Selected BACE1 substrates—seizure‐protein 6, L1, CHL1 and contactin‐2—were validated in brains of BACE1 inhibitor‐treated and BACE1 knock‐out mice. For some substrates, BACE1 was the major sheddase, whereas for other substrates additional proteases contributed to total substrate shedding. The new substrates point to a central function of BACE1 in neurite outgrowth and synapse formation. SPECS is also suitable for quantitative secretome analyses of primary cells and may be used for the discovery of biomarkers secreted from tumour or stem cells.

Secretome Protein Enrichment with Click Sugars Identifies Physiological Substrates of the Alzheimer Protease BACE1 in Primary Neurons

Cell surface proteolysis is essential for communication between cells and results in the shedding of membrane‐protein ectodomains. However, physiological substrates of the contributing proteases are largely unknown. We developed the secretome protein enrichment with click sugars (SPECS) method, which allows proteome‐wide identification of shedding substrates and secreted proteins from primary cells, even in the presence of serum proteins. SPECS combines metabolic glycan labelling and click chemistry‐mediated biotinylation and distinguishes between cellular and serum proteins. SPECS identified 34, mostly novel substrates of the Alzheimer protease BACE1 in primary neurons, making BACE1 a major sheddase in the nervous system. Selected BACE1 substrates—seizure‐protein 6, L1, CHL1 and contactin‐2—were validated in brains of BACE1 inhibitor‐treated and BACE1 knock‐out mice. For some substrates, BACE1 was the major sheddase, whereas for other substrates additional proteases contributed to total substrate shedding. The new substrates point to a central function of BACE1 in neurite outgrowth and synapse formation. SPECS is also suitable for quantitative secretome analyses of primary cells and may be used for the discovery of biomarkers secreted from tumour or stem cells.

Prevention of Rebleeding From Esophageal Varices in Patients With Cirrhosis Receiving Small-Diameter Stents Versus Hemodynamically Controlled Medical Therapy

BACKGROUND & AIMS Patients with cirrhosis and variceal hemorrhage have a high risk of rebleeding. We performed a prospective randomized trial to compare the prevention of rebleeding in patients given a small-diameter covered stent vs those given hepatic venous pressure gradient (HVPG)-based medical therapy prophylaxis. METHODS We performed an open-label study of patients with cirrhosis (92% Child class A or B, 70% alcoholic) treated at 10 medical centers in Germany. Patients were assigned randomly more than 5 days after variceal hemorrhage to groups given a small covered transjugular intrahepatic portosystemic stent-shunt (TIPS) (8 mm; n = 90), or medical reduction of portal pressure (propranolol and isosorbide-5-mononitrate; n = 95). HVPG was determined at the time patients were assigned to groups (baseline) and 2 weeks later. In the medical group, patients with an adequate reduction in HVPG (responders) remained on the drugs whereas nonresponders underwent only variceal band ligation. The study was closed 10 months after the last patient was assigned to a group. The primary end point was variceal rebleeding. Survival, safety (adverse events), and quality of life (based on the Short Form-36 health survey) were secondary outcome measures. RESULTS A significantly smaller proportion of patients in the TIPS group had rebleeding within 2 years (7%) than in the medical group (26%) (P = .002). A slightly higher proportion of patients in the TIPS group experienced adverse events, including encephalopathy (18% vs 8% for medical treatment; P = .05). Rebleeding occurred in 6 of 23 patients (26%) receiving medical treatment before hemodynamic control was possible. Per-protocol analysis showed that rebleeding occurred in a smaller proportion of the 32 responders (18%) than in nonresponders who received variceal band ligation (31%) (P = .06). Fifteen patients from the medical group (16%) underwent TIPS placement during follow-up evaluation, mainly for refractory ascites. Survival time and quality of life did not differ between both randomized groups. CONCLUSIONS Placement of a small-diameter, covered TIPS was straightforward and prevented variceal rebleeding in patients with Child A or B cirrhosis more effectively than drugs, which often required step-by-step therapy. However, TIPS did not increase survival time or quality of life and produced slightly more adverse events. Clinical Trial no: ISRCTN 16334693.

Chronic Pancreatitis—Definition, Etiology, Investigation and Treatment

BACKGROUND Chronic pancreatitis has an annual incidence of 23 per 100 000 population in Germany, where it accounts for about 10 000 hospital admissions per year. The disease shortens the life expectancy of its sufferers by an average of 23%. It most commonly affects men aged 20 to 40. METHODS A systematic search for pertinent literature retrieved 19 569 publications, 485 of which were considered in the creation of this guideline, including 67 randomized controlled trials (RCTs). A consensus conference reached agreement on a total of 156 definitions and recommendations. RESULTS The identification of genetic risk factors for pancreatitis is now well established. The diagnosis is made mainly with ultrasonography of the pancreas; if the findings are uncertain, further studies can be performed, including endosonography and endosonographically assisted fine-needle puncture for the examination of small foci of disease. Computed tomography and MRI/magnetic resonance cholangiopancreatography are supplementary diagnostic methods. Endoscopic retrograde cholangiopancreatography is now used almost exclusively for treatment, rather than for diagnosis. 30% to 60% of patients develop complications of chronic pancreatitis, including pseudocysts, bile-duct stenosis, or medically intractable pain, which can be treated with an endoscopic or surgical intervention. Patients with steatorrhea, a pathological pancreatic function test, or clinical evidence of malabsorption should be given pancreatin supplementation. The head of the pancreas should be resected if it contains an inflammatory pseudotumor. CONCLUSION The management of patients with chronic pancreatitis requires close interdisciplinary collaboration, as it can be treated medically and endoscopically as well as surgically.

Autoimmunity, Intestinal Lymphoid Hyperplasia, and Defects in Mucosal B-Cell Homeostasis in Patients With PTEN Hamartoma Tumor Syndrome

The Phosphatase And Tensin Homolog Deleted On Chromosome 10 (PTEN) regulates the phosphoinositol-3-kinase (PI3K)-AKT signaling pathway. In a series of 34 patients with PTEN mutations, we described gastrointestinal lymphoid hyperplasia, extensive hyperplastic tonsils, thymus hyperplasia, autoimmune lymphocytic thyroiditis, autoimmune hemolytic anemia, and colitis. Functional analysis of the gastrointestinal mucosa-associated lymphoid tissue revealed increased signaling via the PI3K-AKT pathway, including phosphorylation of S6 and increased cell proliferation, but also reduced apoptosis of CD20(+)CD10(+) B cells. Reduced activity of PTEN therefore affects homeostasis of human germinal center B cells by increasing PI3K-AKT signaling via mammalian target of rapamycin as well as antiapoptotic signals.

Differences in bleeding behavior after endoscopic band ligation: a retrospective analysis

BackgroundEndoscopic band ligation (EBL) is generally accepted as the treatment of choice for bleeding from esophageal varices. It is also used for secondary prophylaxis of esophageal variceal hemorrhage. However, there is no data or guidelines concerning endoscopic control of ligation ulcers. We conducted a retrospective study of EBL procedures analyzing bleeding complications after EBL.MethodsWe retrospectively analyzed data from patients who underwent EBL. We analyzed several data points, including indication for the procedure, bleeding events and the time interval between EBL and bleeding.Results255 patients and 387 ligation sessions were included in the analysis. We observed an overall bleeding rate after EBL of 7.8%. Bleeding events after elective treatment (3.9%) were significantly lower than those after treatment for acute variceal hemorrhage (12.1%). The number of bleeding events from ligation ulcers and variceal rebleeding was 14 and 15, respectively. The bleeding rate from the ligation site in the group who underwent emergency ligation was 7.1% and 0.5% in the group who underwent elective ligation. Incidence of variceal rebleeding did not vary significantly. Seventy-five percent of all bleeding episodes after elective treatment occurred within four days after EBL. 20/22 of bleeding events after emergency ligation occured within 11 days after treatment. Elective EBL has a lower risk of bleeding from treatment-induced ulceration than emergency ligation.ConclusionsPatients who underwent EBL for treatment of acute variceal bleeding should be kept under medical surveillance for 11 days. After elective EBL, it may be reasonable to restrict the period of surveillance to four days or even perform the procedure in an out-patient setting.

The Pancreatitis-Associated Protein in Hereditary and Chronic Alcoholic Pancreatitis

The pancreatitis-associated protein (PAP) was investigated in patients with hereditary and chronic alcoholic pancreatitis. Blood levels of pancreatic enzymes and PAP were measured in nine families with hereditary pancreatitis; in three of them, the mutation N21I, and in six, the R117H variant of the cationic trypsinogen were present. In all family members, similar to controls, only normal values of the PAP were found. There was no evidence for polymorphism of the PAP gene in patients with hereditary or alcoholic pancreatitis. Immunohistochemically PAP was detected in the apical parts of the acinar cells but not in ducts, interstitial tissue, islets, or blood vessels. Intensity of PAP labeling was directly related to the deterioration of the acinar units, and its concentration was inversely related to chymotrypsinogen immunoreactivity in the same tissue. Similar immunohistochemical findings were present in chronic alcoholic and hereditary pancreatitis. We conclude that there is a lack of PAP polymorphism in hereditary and alcoholic pancreatitis and that expression of the PAP in both groups of patients is related to the degree of cellular damage of the pancreas.

Genetic and biochemical evidence for a functional role of BACE1 in the regulation of insulin mRNA expression

Beta‐site amyloid precursor protein cleaving enzyme (BACE1) is highly expressed in pancreatic β‐cells. The BACE1 gene is located in a region associated with a high diabetes risk in PIMA Indians.

Sonographic diagnosis and Endo-SPONGE assisted vacuum therapy of anastomotic leakage following posterior pelvic exenteration for ovarian cancer without using a protective stoma

Anastomotic leakage is a very significant complication after posterior pelvic exenteration and a major cause of postoperative morbidity and mortality. We present a patient who underwent an optimal debulking surgery for an advanced stage ovarian cancer (FIGO IIIC). On postoperative day 12, transvaginal ultrasound revealed an anastomotic dehiscence following an unsuspicious computer tomography scan the day before. The patient was successfully managed by transanal vacuum therapy without re-laparotomy within a period of 4 weeks after diagnosis. We conclude that high-resolution transvaginal ultrasound is a crucial method in the management of complications after surgery and even allow diagnosing leakages of colorectal anastomosis. In selected cases characterized by a small leak size and a local peritonitis confined to the pelvis a transanal vacuum therapy may avoid both surgical re-intervention and creating a secondary diverting stoma.

Complete Analysis of the Human Mesotrypsinogen Gene (PRSS3) in Patients with Chronic Pancreatitis

Background/Aims: A sustained imbalance of pancreatic proteases and their inhibitors seems to be important for the development of chronic pancreatitis (CP). Mesotrypsin (PRSS3) can degrade intrapancreatic trypsin inhibitors that protect against CP. Genetic variants that cause higher mesotrypsin activity might increase the risk for CP. Methods: We analyzed all 5 exons and the adjacent non-coding sequences of PRSS3 by direct sequencing of 313 CP patients and 327 controls. Additionally, exon 4 was investigated in 855 patients and 1,294 controls and a c.454+191G>A variant in 855 patients and 1,467 controls. The c.499A>G (p.T167A) variant was analyzed functionally using transiently transfected HEK 293T cells. Results: In the exonic regions, the previously described common c.94_96delGAG (p.E32del) variant and a novel p.T167A non-synonymous alteration were identified. Extended analysis of the p.T167A variant revealed no association to CP and in functional assays p.T167A showed normal secretion and activity. Variants of the intronic regions, including the extensively analyzed c.454+191G>A alteration, were not associated with the disease. Haplotype reconstruction using variants with a minor allele frequency of >1% revealed no CP-associated haplotype. Conclusions: Although the trypsin inhibitor-degrading activity qualified PRSS3 as a candidate for a novel CP susceptibility gene, we found no association between a specific variant or haplotype and CP in our cohort with a high suspicion of genetically determined disease.