Vital staining and electron microscopy of the intramuscular nerve endings in the neuropathy of adult coeliac disease

Serum zonulin levels are increased in Alzheimer's disease but not in vascular dementia

BACKGROUND

Zonulin is involved in the integrity and functioning of both intestinal-epithelial barrier and blood-brain barrier (BBB) by regulating tight junction molecular assembly.

AIM

Since changes in microbiota and BBB may play a role in neurodegenerative disorders, we aimed to determine whether serum zonulin levels change in older patients affected by different types of dementia or mild cognitive impairment (MCI).

METHODS

We evaluated serum zonulin levels in patients with late-onset AD (LOAD), vascular dementia (VAD), MIXED (AD + VAD) dementia, amnestic MCI, and in healthy controls.

RESULTS

Compared with controls, serum zonulin increased in LOAD, MIXED dementia, and aMCI but not in VAD, independent of potential confounders (ANCOVA p = 0.01; LOAD vs controls, p = 0.01; MIXED vs. controls, p = 0.003; aMCI vs. controls, p = 0.04). Notably, aMCI converting to dementia showed significantly higher levels of zonulin compared with stable aMCI (p = 0.04). Serum zonulin inversely correlated with the standardized Mini-Mental State Examination (MMSE) score (p < 0.05), regardless of potential confounders.

DISCUSSION

We found increased serum zonulin levels in patients with aMCI, LOAD and MIXED dementia, but not in VAD; moreover, zonulin levels were higher in aMCI converting to AD compared with stable ones.

CONCLUSIONS

Our findings suggest that a dysregulation of intestinal-epithelial barrier and/or BBB may be an early specific event in AD-related neurodegeneration.

Cerebellar presence of immune cells in patients with neuro-coeliac disease

Although various neurodegenerative disorders have been associated with coeliac disease (CD), the underlying neuropathological link between these brain and gut diseases remains unclear. We postulated that the neuronal damage sporadically observed in CD patients is immune-mediated. Our aim was to determine if the loss of neurons, especially Purkinje cells, coincides with microglia activation and T- and B-cell infiltration in the cerebellum of patients with CD and a concomitant idiopathic neurological disease affecting the cerebellum (NeuroCD). Post-mortem cerebellar tissue was collected of validated NeuroCD cases. Gender- and age-matched genetic spinocerebellar ataxia (SCA) controls and non-neurological controls (NNC) were selected based on clinical reports and pathological findings. Cerebellar tissue of seventeen patients was included (6 NeuroCD, 5 SCA, 6 NNC). In SCA cases we found that the Purkinje cell layer was 58.6% reduced in comparison with NNC. In NeuroCD cases this reduction was even more prominent with a median reduction of 81.3% compared to NNC. Marked increased numbers of both CD3+ and CD8+ cells were observed in the NeuroCD but not in SCA patients. This coincided with significantly more microglial reactivity in NeuroCD patients. These findings demonstrate that the massive loss of Purkinje cells in the cerebellum of neuro CD patients is accompanied by local innate and T-cell mediated immune responses.

Corneal confocal microscopy demonstrates minimal evidence of distal neuropathy in children with celiac disease

OBJECTIVES

The aim of this study was to utilise corneal confocal microscopy to quantify corneal nerve morphology and establish the presence of sub-clinical small fibre damage and peripheral neuropathy in children with celiac disease.

METHODS

This is a cross-sectional cohort study of twenty children with celiac disease and 20 healthy controls who underwent clinical and laboratory assessments and corneal confocal microscopy. Corneal nerve fiber density (no.mm2), corneal nerve branch density (no.mm2), corneal nerve fiber length (mm.mm2), corneal nerve fiber tortuosity and inferior whorl length (mm.mm2) were quantified manually.

RESULTS

Corneal nerve fiber density (34.7±8.6 vs. 32.9±8.6; P = 0.5), corneal nerve branch density (47.2±24.5 vs. 47.3±20.0; P = 0.1) and corneal nerve fiber length (20.0±5.1 vs. 19.5±4.5; P = 0.8) did not differ between children with celiac disease and healthy controls. Corneal nerve fiber tortuosity (11.4±1.9 vs 13.5±3.0; P = 0.01) was significantly lower and inferior whorl length (20.0±5.5 vs 23.0±3.8; P = 0.06) showed a non-significant reduction in children with celiac disease compared to healthy controls. Inferior whorl length correlated significantly with corneal nerve fiber density (P = 0.005), corneal nerve branch density (P = 0.04), and corneal nerve fiber length (P = 0.002).

CONCLUSION

Corneal confocal microscopy demonstrates minimal evidence of neuropathy in children with celiac disease.

Dietary Gluten and Neurodegeneration: A Case for Preclinical Studies

Although celiac disease (CD) is an autoimmune disease that primarily involves the intestinal tract, mounting evidence suggests that a sizeable number of patients exhibit neurological deficits. About 40% of the celiac patients with neurological manifestations have circulating antibodies against neural tissue transglutaminase-6 (tTG6). While early diagnosis and strict adherence to a gluten-free diet (GFD) have been recommended to prevent neurological dysfunction, better therapeutic strategies are needed to improve the overall quality of life. Dysregulation of the microbiota-gut-brain axis, presence of anti-tTG6 antibodies, and epigenetic mechanisms have been implicated in the pathogenesis. It is also possible that circulating or gut-derived extracellular structures and including biomolecular condensates and extracellular vesicles contribute to disease pathogenesis. There are several avenues for shaping the dysregulated gut homeostasis in individuals with CD, non-celiac gluten sensitivity (NCGS) and/or neurodegeneration. In addition to GFD and probiotics, nutraceuticals, such as phyto and synthetic cannabinoids, represent a new approach that could shape the host microbiome towards better prognostic outcomes. Finally, we provide a data-driven rationale for potential future pre-clinical research involving non-human primates (NHPs) to investigate the effect of nutraceuticals, such as phyto and synthetic cannabinoids, either alone or in combination with GFD to prevent/mitigate dietary gluten-induced neurodegeneration.

The Neuropathology of Gluten-Related Neurological Disorders: A Systematic Review

Gluten-related neurological disorders (GRND) represent a spectrum of neurological manifestations that are triggered by gluten. In coeliac disease, a T-cell mediated enteropathy is triggered by gluten in genetically predisposed individuals. The underlying pathological mechanism of the neurological dysfunction is not yet clear. The aim of this review is to collate existing neuropathological findings in GRND as a means of aiding the understanding of the pathophysiology. A systematic search of the Pubmed Database yielded 188 articles, of which 32 were included, containing 98 eligible cases with a description of pathological findings in GRND. In gluten ataxia, loss of Purkinje cells, atrophy, gliosis and astrocytosis were apparent, as well as diffuse lymphocytic infiltration and perivascular cuffing with lymphocytes. In patients with large-fiber neuropathy, nerve biopsies revealed axonopathy, loss of myelinated fibers and focal and perivascular infiltration by inflammatory cells. Inflammatory infiltrate was also observed in muscle in myopathy and in cerebrum of patients with encephalopathy and patients with epilepsy. Such changes were not seen in skin biopsies from patients with small fiber neuropathies. The findings from this systematic review suggest an immune mediated pathogenesis for GRND. Future research should focus on the characterization of the inflammatory cell infiltrates and identifying target epitopes.

Myopathy associated with gluten sensitivity

Ataxia and peripheral neuropathy are the most common neurological manifestations of gluten sensitivity. Myopathy is a less common and poorly characterized additional neurological manifestation of gluten sensitivity. We present our experience with 13 patients who presented with symptoms and signs suggestive of a myopathy and in whom investigation led to the diagnosis of gluten sensitivity. Three of these patients had a neuropathy with or without ataxia in addition to the myopathy. The mean age at onset of the myopathic symptoms was 54 years. Ten patients had neurophysiological evidence of myopathy. Inflammatory myopathy was the most common finding on neuropathological examination. One patient had basophilic rimmed vacuoles suggestive of inclusion-body myositis. Six patients received immunosuppressive treatment in addition to starting on a gluten-free diet; five improved and one remained unchanged. Among seven patients not on immunosuppressive treatment, four showed clinical improvement of the myopathy with a gluten-free diet. The improvement was also associated with reduction or normalization of serum creatine kinase level. The myopathy progressed in one patient who refused the gluten-free diet. Myopathy may be another manifestation of gluten sensitivity and is likely to have an immune-mediated pathogenesis. A gluten-free diet may be a useful therapeutic intervention.

Neurologic manifestations of gastrointestinal disease

Although previously considered rare, neurologic manifestations of gastrointestinal diseases are increasingly recognized. Understanding of Whipple disease and gluten sensitivity is in transition and these conditions are becoming the province of neurologists. Recent improvements in diagnostic testing have improved our understanding and case finding for vitamin B12 deficiency. Many patients with these conditions present with neurologic manifestations alone. Therefore, these conditions are becoming the province of neurologists, and neurologic manifestations of gastrointestinal disease are becoming a more common part of neurologic practice.

Central and peripheral nervous system pathology of homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency

An autopsy case of homocystinuria due to 5,10-methylenetetrahydrofolate reductase deficiency is presented. A 15-year-old boy had mental retardation, epilepsy, and peripheral neuropathy. A sural nerve biopsy revealed a decreased number of myelinated fibers, abnormally thick myelinated fiber groups, and numerous thinner unmyelinated fibers. The autopsy study revealed unusual findings of peripheral neuropathy and spheroid formation in addition to arterial structural abnormalities and perivascular demyelination which are common in cases of homocystinuria. The peripheral neuropathy and spheroid formation may be related to the low level of serum folic acid. The presence of peripheral neuropathy should be ascertained in cases of 5,10-methylenetetrahydrofolate reductase deficiency.

The motor end-plate fine structure and ultrastructural localization of acetylcholine receptors in amyotrophic lateral sclerosis

The motor end-plate fine structure and distribution of junctional acetylcholine receptors (AChRs) in patients with amyotrophic lateral sclerosis (ALS) were studied. Morphometric analysis was carried out in 74 end-plates (92 innervated and 47 denuded postsynaptic regions) from 10 patients with ALS. AChR was studied by means of peroxidase-labeled alpha-bungarotoxin binding in 45 end-plates (86 innervated and 36 denuded postsynaptic regions) from 6 patients with ALS. The postsynaptic regions were denuded of their nerve terminals in 33.8% (9.8% in controls). However, the postsynaptic folds in denuded regions were fairly well preserved, as were junctional AChRs. No highly simplified postsynaptic regions were observed. These results suggest that reinnervation of the skeletal muscle by nerve sprouting in ALS may occur in the previously denuded postsynaptic regions and the preserved postsynaptic regions including AChRs, the basement membrane, and Schwann cells may play an important role in this process.

Localization of methylene blue paramolybdate in vitally stained nerves

Methylene blue taken up by living neurons can be preserved for electron microscopy in a fixative containing osmium tetroxide and ammonium paramolybdate at pH 5.2. Paramolybdate is the buffer, precipitating agent and main osmotic ingredient; it does not function as an electron stain unless methylene blue is present. The low pH keeps the dye/paramolybdate complex from dissolving. Neither the low pH nor drastic dehydration from water to absolute ethanol harm the tissue. The staining mechanism involves cationic methylene blue associating with anionic structures such as microtubules and neurofilaments in the living cell; during fixation paramolybdate forms a precipitate with the dye at the staining sites. This fixative does not preserve microtubules unless they are first vitally stained.

The neurological manifestations of malabsorption

The clinical and pathological findings in patients with neurological disorders in association with disordered function of the small intestine, in particular coeliac disease, are outlined. The possible significance of the abnormalities of pyridoxine, tyrosine and tryptophan metabolism are considered in relation to biopterin derivatives and their relevance to neurological dysfunction.

Chronic mild diarrhoea, stunted growth and neuromuscular abnormalities

This report describes a 3 year-old girl with signs of ventricular hypertrophy, short stature, and persistent diarrhoea (without steatorrhoea or creatorrhoea) which was resistant to therapy. There was no clinical evidence of myopathy but a myopathic pattern was found on electromyography. Biochemical studies revealed no abnormalities. Routine histological studies of biopsied muscle showed no obvious structural abnormalities. Examination of 1 micrometer tissue sections revealed groups of atrophic fibers. Electronmicroscopy revealed widened spaces between the myofibrils with disruption of filament arrangement. The mitochondria in the motor end-plates were very distended and almost devoid of cristae.

Neurological disorders and adult coeliac disease

An investigation into the incidence of neurological disorder in 30 patients with adult coeliac disease has shown that three patients had severe depression, two had epileptiform convulsions, and one patient only had signs of involvement of the peripheral nervous system. Motor nerve conduction velocity was low in only one patient. When the nerve conduction velocities of the group on a gluten-free diet were compared with the group who were not on a gluten-free diet, there was no statistically significant difference. Similarly, nerve conduction velocities in patients with a low serum pyridoxal level were not significantly different from those with normal serum pyridoxal levels. Measurements of the serum level of pyridoxal in 30 patients confirmed that pyridoxine deficiency occurs in adult coeliac disease and that the restriction of gluten from the diet appeared to affect pyridoxal levels favourably.

Neurological disease after partial gastrectomy

Clinical and laboratory signs of neurological disease were found in 14 patients many years after partial gastrectomy. Vitamin B(12) deficiency occurred in most patients, but only those three who had signs of subacute combined degeneration of the cord and no osteomalacia responded well to treatment.