Linking Enzyme Upregulation to Autophagic Failure: A Potential Biomarker for GM1 Gangliosidosis

With an increasing aging population, neurodegenerative diseases are having an increased impact on society. Typically, these diseases are diagnosed significantly past symptom onset, decreasing the possibility of effective treatment. A non-invasive biomarker and specific target are needed to diagnose and treat the disease before late-stage symptoms. GM1 Gangliosidosis is a lysosomal storage disease where lysosomal enzyme β-galactosidase is missing. As a result, GM1 ganglioside is not broken down and accumulates in the cell, ultimately leading to cell death. One of the main aspects of GM1 Gangliosidosis, and other neurodegenerative diseases, is impaired autophagy: reduced fusion of autophagosomes and lysosomes to degrade cellular waste.In this paper, we show that healthy cells (NSV3) have approximately 13 times more co-localization of lysosomes and autophagosomes than GM1 Gangliosidosis-diseased cells (GM1SV3), as demonstrated via immunofluorescence. GM1SV3 fold normal enzyme activity of β-galactosidase was downregulated while mannosidase, and hexosaminidase A were both upregulated. When inducing impaired autophagy in NSV3 via starvation, co-localization gradually decreases with increased starvation time. Most notably, after 48-hour starvation, healthy cells (NSV3) showed no significant difference in co-localization compared to GM1SV3. NSV3 under starvation conditions showed a significant increase between time starved and fold normal enzyme activity, with a positive correlation being observed. Activities of mannosidase, and hexosaminidase A of starved NSV3 closely resemble, and surpass, GM1SV3 after 12-hour starvation.These observations have the potential to expand the conversation regarding impaired autophagy as a potential biomarker for disease progression and diagnostics and as a treatment target.

An enzymatic method for erythrocyte acetylcholinesterase.

The acetylcholinesterase (EC 3.1.1.7) in 50 microL of a 61-fold dilution of erythrocytes in water hydrolyzes acetylcholine during a timed 20-min reaction at 37 degrees C. The resulting choline is measured by use of choline oxidase coupled to peroxidase, with phenol and aminoantipyrene to give a pink product that absorbs maximally at 500 nm. For calibration, a choline iodide standard is included in each batch of up to 19 samples. Accuracy was assessed by using specific inhibitors and measuring choline in the presence of excess erythrocyte solution. The standard curve for the assay is linear to threefold the normal enzyme activity. Between-batch precision was 0.40 kU/L at a mean of 11.5 kU/L (CV 3.5%), and comparison with an acetylthiocholine procedure (x) gave a good correlation: y = 1.02x - 0.27 kU/L (r = 0.991). Long-term precision (10 months), assessed from three sets of assays of samples from 17 individuals, was 0.71 kU/L at a mean of 11.7 kU/L (CV 6.1%).

CLINICAL EVALUATION OF ABNORMAL ENZYME CONTENT IN THE PANCREATIC JUICE OF CHILDREN

One hundred and sixty-five children were intubated and the enzyme activity of their duodenal juice studied. Seventy-six patients showed normal potency of all the pancreatic enzymes and had clinical conditions apparently unrelated to pancreatic secretions. The other 89 patients were included in this study and grouped as follows: Group I: Twenty-three children had minimal pancreatic enzyme activity and presumably were suffering from fibrocystic disease of the pancreas. Group II: Two children with minimal enzyme activity may have had a pancreatic deficiency of different etiology from that of Group I. Group III: Four children had transitory partial suppression of trypsin, lipase and amylase. In three, after recovery, repeated studies showed that their enzymes were normal. The fourth child died without the enzyme studies having been repeated. A fifth child had complete suppression of enzyme activity while ill with a respiratory infection. She is included in this group because, coincident with her clinical recovery, there was an appreciable return of enzyme activity. Clinically, these five children had nothing in common. Group IV (a): Twenty-five children had suppression of lipase activity in conjunction with a normal level for trypsin and amylase. Most of them had some type of gastrointestinal disturbance. Four had diseases of the respiratory system. Sixteen of these children were restudied. The return of lipase activity coincided roughly with a return to health: those who were studied at a time they were clinically well had normal enzyme activity, while those who were not well still had a reduced secretion of pancreatic lipase. None proved to be early cases of progressive pancreatic deficiency. Group IV (b): There were no children with deficient trypsin activity in the presence of normal lipase and amylase. Group IV (c): Sixteen children were deficient in amylolytic activity in conjunction with normal trypsin and lipase. Most of these children had gastrointestinal symptoms. Six of them had celiac disease. Group V: Eighteen children with extreme malnutrition had normal enzyme activity.