Neurological complications associated with spontaneously occurring feline diabetes mellitus

The effects of voluntary exercise on histological and stereological changes of sciatic nerve, nitric oxide levels, and peripheral neuropathy caused by high-fat diet-induced type 2 diabetes in male rats

This research was conducted to investigate the possible beneficial impacts of voluntary exercise on sciatic tissue, nitric oxide levels, stereological changes, and peripheral neuropathy caused by "high-fat-diet (HFD)"-induced "type 2 diabetes mellitus (T2DM)" in male rats. Rats were put into four experimental groups at random: "healthy control (C), voluntary exercise (VE), diabetic (D), and diabetic rats treated by voluntary exercise (VED)"; each group contain eight animals. Animals in VE and VED groups performed "voluntary exercise (VE)" for ten weeks. Animals in D and VED groups became diabetic after receiving a HFD for four weeks and an intraperitoneal injection (IP) of "streptozotocin (STZ)" (35 mg/kg). In order to evaluate mechanical and thermal algesia, hot plate, tail withdrawal, and von Frey tests were carried out. At the end of this study, serum NOx levels were assessed, and histological and stereological analyses were conducted. Mechanical nociceptive thresholds indicated considerable reduction (p < 0.001) which was followed by a remarkable enhance (p < 0.001) in thermal nociceptive threshold of D group. Tissue changes were also seen in sciatic nerve of D group. Voluntary exercise modified thermal and mechanical sensitivity in diabetic rats. It also improved the damaged sciatic nerve in diabetic animals.

Neurogenic Bladder in Dogs, Cats and Humans: A Comparative Review of Neurological Diseases

Lower urinary tract disease (LUTD) includes abnormalities in the structure and function of the bladder and the urethra. LUTD caused by neurological disease is defined neurogenic bladder (NB). The integrity of the central nervous system (CNS) and peripheral nervous system (PNS) is required to explicate normal micturition, maintaining the proper function of bladder and urethra. The location and type of neurological lesions influence the pattern of clinical manifestations, potential treatment, and prognosis. Though, in dogs and cats, spinal cord injury is considered mainly responsible for bladder and/or urethra incompetence, other disorders, congenital or acquired, involving CNS or PNS, could play a role in NB. In veterinary medicine, the information about the epidemiology, prevalence, etiopathogenesis, diagnosis and treatment of NB are scattered. The aim of this study is to provide an overview of the epidemiology, prevalence, clinical findings, diagnosis and prognosis for NB in dogs and cats compared with humans.

Insulin expression in β cells is reduced within islets before islet loss in diabetic cats

OBJECTIVES

Diabetes mellitus is a common condition that requires intensive treatment and markedly impacts the welfare of affected cats. The aim of this study was to identify diabetes mellitus-associated perturbations in the feline pancreatic islet microenvironment. The utility of "clear, unobstructed brain/body imaging cocktails and computational analysis" (CUBIC) for three-dimensional pancreatic analysis was investigated.

METHODS

Formalin-fixed paraffin-embedded tissues from cats with diabetes mellitus, or control cats without pancreatic pathology, were retrospectively identified. Immunohistochemistry for synaptophysin and ionised calcium binding adaptor molecule 1, and immunofluorescence for insulin and synaptophysin, were used to assess changes in islets. An image analysis pipeline was developed to analyse images acquired from two-dimensional immunofluorescence. CUBIC was used to optically clear selected pancreas samples before immunofluorescence and deep three-dimensional confocal microscopy.

RESULTS

Diabetic cats have a significant reduction in synaptophysin-positive islet area. Whilst islets from diabetic patients have similar numbers of β cells to islets from control cats, significantly lower intensity of insulin expression can be observed in the former. CUBIC facilitates clear visualisation of pancreatic islets in three dimensions.

CLINICAL SIGNIFICANCE

The data presented support the theory that there is a decrease in function of β cells before their destruction, suggesting a potentially significant step in the pathogenesis of feline diabetes mellitus. In parallel, we demonstrate CUBIC as a valuable new tool to visualise the shape of feline pancreatic islets and to interrogate pathology occurring in the islets of diabetic pets.

Adipokines as potential biomarkers for type 2 diabetes mellitus in cats

Type 2 diabetes mellitus (T2DM) is no longer only a disease of humans, but also of domestic animals, and it particularly affects cats. It is increasingly thought that because of its unique characteristics, T2DM may belong not only to the group of metabolic diseases but also to the group of autoimmune diseases. This is due to the involvement of the immune system in the inflammation that occurs with T2DM. Various pro- and anti-inflammatory substances are secreted, especially cytokines in patients with T2DM. Cytokines secreted by adipose tissue are called adipokines, and leptin, adiponectin, resistin, omentin, TNF-α, and IL-6 have been implicated in T2DM. In cats, approximately 90% of diabetic cases are T2DM. Risk factors include older age, male sex, Burmese breed, presence of obesity, and insulin resistance. Diagnosis of a cat requires repeated testing and is complicated compared to human diagnosis. Based on similarities in the pathogenesis of T2DM between humans and cats, adipokines previously proposed as biomarkers for human T2DM may also serve in the diagnosis of this disease in cats.

Feline Adipose Derived Multipotent Stromal Cell Transdifferentiation Into Functional Insulin Producing Cell Clusters

Diabetes mellitus (DM) is one of the most prevalent feline endocrinopathies, affecting up to 1% of pet cats. De novo generation of functional insulin producing cell (IPC) clusters via transdifferentiation of feline adipose-derived multipotent stromal cells (ASCs) may not only provide a viable, functional cell therapy for feline DM, but may also serve as a platform for developing a comparable human treatment given feline and human DM similarities. Cells were induced to form IPCs with a novel, three-stage culture process with stromal or differentiation medium under static and dynamic conditions. Clusters were evaluated for intracellular zinc, viability, intracellular insulin, glucagon, and somatostatin, ultrastructure, glucose stimulated insulin secretion in the presence or absence of theophylline, and protein and gene expression. Isolated cells were multipotent, and cell clusters cultured in both media had robust cell viability. Those cultured in differentiation medium contained zinc and mono- or polyhormonal α-, β-, and δ-like cells based on immunohistochemical labeling and Mallory-Heidenhan Azan-Gomori’s staining. Ultrastructurally, cell clusters cultured in differentiation medium contained insulin granules within vesicles, and clusters had a concentration-dependent insulin response to glucose in the presence and absence of theophylline which increased both insulin secretion and intracellular content. Expression of NK6.1, Pax6, Isl1, Glut2, RAB3A, glucagon, insulin, and somatostatin increased with differentiation stage for both sexes, and expression of nestin at stages 1 and 2 and Neurod1 at stage 2 was higher in cells from female donors. The cluster insulin secretion responses and endocrine and oncogene gene expression profiles were inconsistent with insulinoma characteristics. A total of 180 proteins were upregulated in differentiated clusters, and the majority were associated with biological regulation, metabolic processes, or stimulus response. Dynamic culture of IPC clusters resulted in clusters composed of cells primarily expressing insulin that released higher insulin with glucose stimulation than those in static culture. Collectively, the results of this study support generation of functional IPC clusters using feline ASCs isolated from tissues removed during routine sterilization. Further, cluster functionality is enhanced with dynamic, motion-driven shear stress. This work establishes a foundation for development of strategies for IPC therapy for short or long-term diabetes treatment and may represent an option to study prevention and treatment of diabetes across species.

Clinical Course and Diagnostic Findings of Biopsy Controlled Presumed Immune-Mediated Polyneuropathy in 70 European Cats

There is a paucity of information on the clinical course and outcome of young cats with polyneuropathy. The aim of the study was to describe the clinical features, diagnostic investigations, and outcome of a large cohort of cats with inflammatory polyneuropathy from several European countries. Seventy cats with inflammatory infiltrates in intramuscular nerves and/or peripheral nerve biopsies were retrospectively included. Information from medical records and follow up were acquired via questionnaires filled by veterinary neurologists who had submitted muscle and nerve biopsies (2011–2019). Median age at onset was 10 months (range: 4–120 months). The most common breed was British short hair (25.7%), followed by Domestic short hair (24.3%), Bengal cat (11.4%), Maine Coon (8.6%) and Persian cat (5.7%), and 14 other breeds. Male cats were predominantly affected (64.3%). Clinical signs were weakness (98.6%) and tetraparesis (75.7%) in association with decreased withdrawal reflexes (83.6%) and, less commonly, cranial nerve signs (17.1%), spinal pain/hyperesthesia (12.9%), and micturition/defecation problems (14.3%). Onset was sudden (30.1%) or insidious (69.1%), and an initial progressive phase was reported in 74.3%. Characteristic findings on electrodiagnostic examination were presence of generalized spontaneous electric muscle activity (89.6%), decreased motor nerve conduction velocity (52.3%), abnormal F-wave studies (72.4%), pattern of temporal dispersion (26.1%) and unremarkable sensory tests. The clinical course was mainly described as remittent (49.2%) or remittent-relapsing (34.9%), while stagnation, progressive course or waxing and waning were less frequently reported. Relapses were common and occurred in 35.7% of the cats' population. An overall favorable outcome was reported in 79.4% of patients. In conclusion, young age at the time of diagnosis and sudden onset of clinical signs were significantly associated with recovery (p &lt; 0.05). Clinical and electrodiagnostic features and the remittent-relapsing clinical course resembles juvenile chronic inflammatory demyelinating polyneuropathy (CIDP), as seen in human (children/adolescents), in many aspects.

Comparative Pathology of the Peripheral Nervous System

The peripheral nervous system (PNS) relays messages between the central nervous system (brain and spinal cord) and the body. Despite this critical role and widespread distribution, the PNS is often overlooked when investigating disease in diagnostic and experimental pathology. This review highlights key features of neuroanatomy and physiology of the somatic and autonomic PNS, and appropriate PNS sampling and processing techniques. The review considers major classes of PNS lesions including neuronopathy, axonopathy, and myelinopathy, and major categories of PNS disease including toxic, metabolic, and paraneoplastic neuropathies; infectious and inflammatory diseases; and neoplasms. This review describes a broad range of common PNS lesions and their diagnostic criteria and provides many useful references for pathologists who perform PNS evaluations as a regular or occasional task in their comparative pathology practice.

F-wave parameters for the tibial nerve in Miniature Dachshunds with and without naturally acquired thoracolumbar intervertebral disk herniation

OBJECTIVE

To determine values of F-wave parameters for the tibial nerve in clinically normal Miniature Dachshunds and those with thoracolumbar intervertebral disk herniation (IVDH).

ANIMALS

53 Miniature Dachshunds (10 clinically normal and 43 with various clinical grades of thoracolumbar IVDH).

PROCEDURES

F-waves were elicited in the interosseous muscles of 1 hind limb in each dog by stimulation of the tibial nerve. F-wave parameters were measured for 32 stimuli/dog, and mean values were calculated. Linear regression was performed to assess correlations between F-wave parameters and clinical severity of IVDH.

RESULTS

For clinically normal dogs, mean ± SD values of shortest F-wave latency, mean F-wave conduction velocity, mean F-wave duration, and ratio of the mean F-wave amplitude to M response amplitude were 8.6 ± 0.6 milliseconds, 83.7 ± 6.1 m/s, 6.6 ± 1.5 milliseconds, and 9.8 ± 8.5%, respectively. F-wave persistence was 100%. Mean F-wave duration was positively correlated with clinical grade of IVDH. Linear regression yielded the following regression equation: F-wave duration (milliseconds) = 6.0 + 2.7 × IVDH grade. One dog with grade 2 IVDH had a mean F-wave duration shorter than that of all 5 dogs with grade 1 IVDH; 1 dog with grade 3 IVDH had a longer duration than that of all 10 dogs with grade 4 IVDH.

CONCLUSIONS AND CLINICAL RELEVANCE

Mean F-wave duration was correlated with the severity of inhibitory motor tract dysfunction in the spinal cord of dogs. F-wave examination may be useful for objective functional evaluation of upper motor neurons in the spinal cord.

Chronic pain in cats: Recent advances in clinical assessment

PRACTICAL RELEVANCE

Chronic pain is a feline health and welfare issue. It has a negative impact on quality of life and impairs the owner-cat bond. Chronic pain can exist by itself or may be associated with disease and/or injury, including osteoarthritis (OA), cancer, and oral and periodontal disease, among others.

CLINICAL CHALLENGES

Chronic pain assessment is a fundamental part of feline practice, but can be challenging due to differences in pain mechanisms underlying different conditions, and the cat's natural behavior. It relies mostly on owner-assessed behavioral changes and time-consuming veterinary consultations. Beyond OA - for which disease-specific clinical signs have been described - little is known regarding other feline conditions that produce chronic pain.

RECENT ADVANCES

Knowledge of the subject has, however, greatly improved in the past few years, informed by study of the mechanisms of pain in cats with OA and the development of pain scales that can be used by owners or veterinarians. Pain scales may facilitate the diagnosis and follow-up evaluation of chronic painful conditions, providing a basis for therapeutic decision-making. Assessment of quality of life is also recommended in cats with chronic pain, and its improvement can be used as a positive outcome in response to therapy.

AIMS

This article reviews recent advances and presents the challenges and some future perspectives on clinical chronic pain assessment. The most common feline chronic conditions associated with pain are also described.

Translational pain assessment: could natural animal models be the missing link?

Failure of analgesic drugs in clinical development is common. Along with the current "reproducibility crisis" in pain research, this has led some to question the use of animal models. Experimental models tend to comprise genetically homogeneous groups of young, male rodents in restricted and unvarying environments, and pain-producing assays that may not closely mimic the natural condition of interest. In addition, typical experimental outcome measures using thresholds or latencies for withdrawal may not adequately reflect clinical pain phenomena pertinent to human patients. It has been suggested that naturally occurring disease in veterinary patients may provide more valid models for the study of painful disease. Many painful conditions in animals resemble those in people. Like humans, veterinary patients are genetically diverse, often live to old age, and enjoy a complex environment, often the same as their owners. There is increasing interest in the development and validation of outcome measures for detecting pain in veterinary patients; these include objective (eg, locomotor activity monitoring, kinetic evaluation, quantitative sensory testing, and bioimaging) and subjective (eg, pain scales and quality of life scales) measures. Veterinary subject diversity, pathophysiological similarities to humans, and diverse outcome measures could yield better generalizability of findings and improved translation potential, potentially benefiting both humans and animals. The Comparative Oncology Trial Consortium in dogs has pawed the way for translational research, surmounting the challenges inherent in veterinary clinical trials. This review describes numerous conditions similarly applicable to pain research, with potential mutual benefits for human and veterinary clinicians, and their respective patients.

AAVrh10 Gene Therapy Ameliorates Central and Peripheral Nervous System Disease in Canine Globoid Cell Leukodystrophy (Krabbe Disease)

Globoid cell leukodystrophy (GLD), or Krabbe disease, is an inherited, neurologic disorder that results from deficiency of a lysosomal enzyme, galactosylceramidase. Most commonly, deficits of galactosylceramidase result in widespread central and peripheral nervous system demyelination and death in affected infants typically by 2 years of age. Hematopoietic stem-cell transplantation is the current standard of care in children diagnosed prior to symptom onset. However, disease correction is incomplete. Herein, the first adeno-associated virus (AAV) gene therapy experiments are presented in a naturally occurring canine model of GLD that closely recapitulates the clinical disease progression, neuropathological alterations, and biochemical abnormalities observed in human patients. Adapted from studies in twitcher mice, GLD dogs were treated by combination intravenous and intracerebroventricular injections of AAVrh10 to target both the peripheral and central nervous systems. Combination of intravenous and intracerebroventricular AAV gene therapy had a clear dose response and resulted in delayed onset of clinical signs, extended life-span, correction of biochemical defects, and attenuation of neuropathology. For the first time, therapeutic effect has been established in the canine model of GLD by targeting both peripheral and central nervous system impairments with potential clinical implications for GLD patients.

Electrophysiologic confirmation of heterogenous motor polyneuropathy in young cats

Background

Reports of motor polyneuropathies in young cats are scarce. Further, in‐depth electrophysiologic evaluation to confirm a motor polyneuropathy in young cats of various breeds other than 2 Bengal cats is lacking.

Hypothesis/Objectives

To confirm a motor polyneuropathy in young cats of various breeds.

Animals

Five young cats with heterogenous chronic or relapsing episodes of weakness.

Methods

Retrospective case series. Cats were presented for evaluation of generalized neuromuscular disease and underwent electrophysiologic examination including electromyography, nerve conduction, and repetitive nerve stimulation. Minimum database and muscle and nerve biopsy analyses were carried out. Descriptive statistics were performed.

Results

Disease onset was at 3 months to 1 year of age and in 5 breeds. The most common clinical sign (5 of 5 cats) was weakness. Additional neurologic deficits consisted of palmigrade and plantigrade posture (4/4), low carriage of the head and tail (4/4), and variable segmental reflex deficits (5/5). Motor nerve conduction studies were abnormal for the ulnar (4/4), peroneal (5/5), and tibial (2/2) nerves (increased latencies, reduced amplitudes, slow velocities). A marked decrement was observed on repetitive nerve stimulation of the peroneal nerve in 3 cats for which autoimmune myasthenia gravis was ruled out. All sensory nerve conduction studies were normal. Histologic evaluation of muscle and nerve biopsies supported heterogenous alterations consistent with motor polyneuropathy with distal nerve fiber loss.

Conclusions and Clinical Importance

Heterogenous motor polyneuropathies should be considered in young cats of any breed and sex that are presented with relapsing or progressive generalized neuromuscular disease.

Improving the translation of analgesic drugs to the clinic: animal models of neuropathic pain

Neuropathic pain remains an area of considerable unmet clinical need. Research based on preclinical animal models has failed to deliver truly novel treatment options, questioning the predictive value of these models. This review addresses the shortcomings of rodent in vivo models commonly used in the field and highlights approaches which could increase their predictivity, including more clinically relevant assays, outcome measures and animal characteristics. The methodological quality of animal studies also needs to be improved. Low internal validity and incomplete reporting lead to a waste of valuable research resources and animal lives, and ultimately prevent an objective assessment of the true predictivity of in vivo models.

Mechanisms of diabetic neuropathy: Schwann cells

As ensheathing and secretory cells, Schwann cells are a ubiquitous and vital component of the endoneurial microenvironment of peripheral nerves. The interdependence of axons and their ensheathing Schwann cells predisposes each to the impact of injury in the other. Further, the dependence of the blood-nerve interface on trophic support from Schwann cells during development, adulthood, and after injury suggests these glial cells promote the structural and functional integrity of nerve trunks. Here, the developmental origin, injury-induced changes, and mature myelinating and nonmyelinating phenotypes of Schwann cells are reviewed prior to a description of nerve fiber pathology and consideration of pathogenic mechanisms in human and experimental diabetic neuropathy. A fundamental role for aldose-reductase-containing Schwann cells in the pathogenesis of diabetic neuropathy, as well as the interrelationship of pathogenic mechanisms, is indicated by the sensitivity of hyperglycemia-induced biochemical alterations, such as polyol pathway flux, formation of reactive oxygen species, generation of advanced glycosylation end products (AGEs) and deficient neurotrophic support, to blocking polyol pathway flux.

Electrodiagnostic testing and histopathologic changes confirm peripheral nervous system myelin abnormalities in the feline model of niemann-pick disease type C

Niemann-Pick disease type C (NPC disease) is an incurable, neurodegenerative, autosomal recessive disease caused by mutations in either the NPC1 or the NPC2 gene. These mutations affect the intracellular trafficking of lipids and cholesterol, resulting in the intralysosomal accumulation of unesterified cholesterol and glycosphingolipids. These abnormalities are associated with clinical ataxia and impaired motor and intellectual development, and death frequently occurs in adolescence. The incidence of peripheral neuropathy in NPC patients is not known. We investigated peripheral nerves in the naturally occurring feline model of NPC disease, which has proven to be critical for understanding both disease pathogenesis and for evaluating experimental therapies. Electrodiagnostic studies revealed significantly slowed motor and sensory nerve conduction velocities in affected cats in the absence of altered M-wave amplitude. Histologic and ultrastructural analyses showed thin myelin sheaths, membranous debris, myelin figures, lipid vacuolization of Schwann cell cytoplasm, and expanded paranodal areas. Axonal degeneration was not identified. There was a shift to small myelinated fibers in affected cats, and there were significant decreases in fiber diameter, axon diameter, and myelin thickness. These changes were similar to those described in the murine NPC disease model and in rare patients in whom nerve biopsy has been performed. Characterization of the demyelinating neuropathy is necessary for evaluating clinical trials that target only the CNS aspects of NPC.

High energy diets-induced metabolic and prediabetic painful polyneuropathy in rats

To establish the role of the metabolic state in the pathogenesis of polyneuropathy, an age- and sex-matched, longitudinal study in rats fed high-fat and high-sucrose diets (HFSD) or high-fat, high-sucrose and high-salt diets (HFSSD) relative to controls was performed. Time courses of body weight, systolic blood pressure, fasting plasma glucose (FPG), insulin, free fatty acids (FFA), homeostasis model assessment-insulin resistance index (HOMA-IR), thermal and mechanical sensitivity and motor coordination were measured in parallel. Finally, large and small myelinated fibers (LMF, SMF) as well as unmyelinated fibers (UMF) in the sciatic nerves and ascending fibers in the spinal dorsal column were quantitatively assessed under electron microscopy. The results showed that early metabolic syndrome (hyperinsulinemia, dyslipidemia, and hypertension) and prediabetic conditions (impaired fasting glucose) could be induced by high energy diet, and these animals later developed painful polyneuropathy characterized by myelin breakdown and LMF loss in both peripheral and central nervous system. In contrast SMF and UMF in the sciatic nerves were changed little, in the same animals. Therefore the phenomenon that high energy diets induce bilateral mechanical, but not thermal, pain hypersensitivity is reflected by severe damage to LMF, but mild damage to SMF and UMF. Moreover, dietary sodium (high-salt) deteriorates the neuropathic pathological process induced by high energy diets, but paradoxically high salt consumption, may reduce, at least temporarily, chronic pain perception in these animals.

Effect of trans-fat, fructose and monosodium glutamate feeding on feline weight gain, adiposity, insulin sensitivity, adipokine and lipid profile

The incidence of obesity and type 2 diabetes mellitus (T2DM) is increasing, and new experimental models are required to investigate the diverse aspects of these polygenic diseases, which are intimately linked in terms of aetiology. Feline T2DM has been shown to closely resemble human T2DM in terms of its clinical, pathological and physiological features. Our aim was to develop a feline model of diet-induced weight gain, adiposity and metabolic deregulation, and to examine correlates of weight and body fat change, insulin homeostasis, lipid profile, adipokines and clinical chemistry, in order to study associations which may shed light on the mechanism of diet-induced metabolic dysregulation. We used a combination of partially hydrogenated vegetable shortening and high-fructose corn syrup to generate a high-fat-high-fructose diet. The effects of this diet were compared with an isoenergetic standard chow, either in the presence or absence of 1.125 % dietary monosodium glutamate (MSG). Dual-energy X-ray absorptiometry body imaging and a glucose tolerance test were performed. The present results indicate that dietary MSG increased weight gain and adiposity, and reduced insulin sensitivity (P < 0.05), whereas high-fat-high-fructose feeding resulted in elevated cortisol and markers of liver dysfunction (P < 0.01). The combination of all three dietary constituents resulted in lower insulin levels and elevated serum β-hydroxybutyrate and cortisol (P < 0.05). This combination also resulted in a lower first-phase insulin release during glucose tolerance testing (P < 0.001). In conclusion, markers of insulin deregulation and metabolic dysfunction associated with adiposity and T2DM can be induced by dietary factors in a feline model.

Orthopedic examination in the cat: clinical tips for ruling in/out common musculoskeletal disease

PATIENT GROUP

The majority of cats will develop radiographic evidence of degenerative joint disease by the time they are 12 years of age, and many will suffer from a decline in quality of life associated with undiagnosed and untreated orthopedic disease.

PRACTICAL RELEVANCE

A focused, efficient orthopedic examination, including gait observation and palpation (awake and under sedation), supplemented with appropriate history, is key in ruling in, or out, clinically important musculoskeletal disease. Identifying problems assists in both developing a diagnostic plan and monitoring response to treatment.

CLINICAL CHALLENGES

Many clinicians feel uncomfortable in their ability to reliably perform an orthopedic examination in the cat, and diagnosis and evaluation of response to treatment in cats with orthopedic disease can be challenging. Hands-on training in feline orthopedic examination is limited in many veterinary curricula. Additional constraints may include failure to obtain important information in the history that indicates feline orthopedic disease, lack of appropriate facilities in which to conduct a complete orthopedic examination, and inability to obtain the most important information during the time available to conduct the examination. These problems can create gaps in the practitioner's ability to provide excellent care for a large proportion of the feline population.

GOALS

The above challenges can mostly be overcome with advanced planning and with consideration of the unique behavioral aspects related to feline handling. As discussed in this review, the aim of the initial orthopedic examination is to localize the problem to a specific limb, ideally to a region or joint of the limb, which can further direct diagnostics such as radiography or arthrocentesis. This should provide a basis for follow-up and assessment of whether treatment strategies are effective.

Neuromuscular Disorders in the Cat: Clinical Approach to Weakness

Practical relevance Weakness is a relatively common clinical presentation in feline medicine and can be caused by primary neuromuscular disease or by diseases of other body systems affecting the neuromuscular system secondarily. Successful work-up relies on a thorough clinical and neurological examination, and logical problem solving, based on an understanding of the underlying neuroanatomical and pathophysiological mechanisms.

Clinical challenges Feline neuromuscular diseases can be a diagnostic challenge. On initial inspection, the presenting signs can mimic disorders of other body systems, particularly cardiovascular, pulmonary and orthopaedic disease, or may be confused with systemic illnesses. Additionally, because many different pathologies of the feline neuromuscular system converge to a similar clinical phenotype, further diagnostic steps such as electrodiagnostics, cerebrospinal fluid analysis, and muscle and nerve biopsies must be considered even after neuromuscular dysfunction has been identified.

Audience This review provides a framework for the clinical approach to the weak cat and gives a practical summary of neuromuscular diseases for the general practitioner and specialist alike.

Evidence base Many diseases affecting the feline neuromuscular system have been well described in the veterinary literature, mostly based on retrospective case reports and series. The evidence base for the treatment of feline neuromuscular diseases remains very limited.

Nutrient excess and altered mitochondrial proteome and function contribute to neurodegeneration in diabetes

Diabetic neuropathy is a major complication of diabetes that results in the progressive deterioration of the sensory nervous system. Mitochondrial dysfunction has been proposed to play an important role in the pathogenesis of the neurodegeneration observed in diabetic neuropathy. Our recent work has shown that mitochondrial dysfunction occurs in dorsal root ganglia (DRG) sensory neurons in streptozotocin (STZ) induced diabetic rodents. In neurons, the nutrient excess associated with prolonged diabetes may trigger a switching off of AMP kinase (AMPK) and/or silent information regulator T1 (SIRT1) signaling leading to impaired peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1α) expression/activity and diminished mitochondrial activity. This review briefly summarizes the alterations of mitochondrial function and proteome in sensory neurons of STZ-diabetic rodents. We also discuss the possible involvement of AMPK/SIRT/PGC-1α pathway in other diabetic models and different tissues affected by diabetes.

Long-term pain in cats: how much do we know about this important welfare issue?

PRACTICAL RELEVANCE

Long-term pain in cats is an important welfare issue but is often overlooked and undertreated.

AUDIENCE

All practitioners are faced with cats that require analgesic intervention to improve their quality of life.

PATIENT GROUP

Any cat may potentially experience long-term pain and discomfort. Degenerative joint disease and diabetic-related pain is more common in middle-aged or older individuals, whereas persistent postsurgical pain can occur at any age and is seen in young cats following onychectomy.

EVIDENCE BASE

Robust evidence on long-term pain issues in cats - specifically, relating to prevalence, etiology, and treatment protocols and outcomes - is missing from the veterinary literature. The aim of this review is to summarise the current state of knowledge. In doing so, it takes a practical approach, highlighting the obvious, and some not so obvious, causes of long-term pain in cats; some aspects that warrant closer attention; our ability to recognize pain and monitor how this impacts on quality of life; and today's treatment options.

Acquired motor neuron loss causing severe pelvic limb contractures in a young cat

PRESENTATION

This report describes a kitten with paraplegia and extensor rigidity of the pelvic limbs associated with motor neuron loss and chronic denervation of skeletal muscle. Persistent skeletal muscle atrophy and degeneration had resulted in immobile stifle and hock joints and severe pelvic limb rigidity consistent with a neurogenic form of arthrogryposis. Both pelvic limbs were equally affected and the kitten showed no signs of pain.

INVESTIGATIONS

Electromyography identified spontaneous activity in the pelvic limbs. Muscle and peripheral nerve biopsies showed pathology consistent with denervation. On necropsy, 3 weeks after admittance, severe degenerative changes including axonal necrosis and myelin degeneration were confirmed in the lumbar spinal cord.

CLINICAL RELEVANCE

There are very few descriptions of feline motor neuron degeneration in the literature and obtaining an ante-mortem diagnosis is difficult. Although an inherited disorder cannot be ruled out, a condition acquired congenitally in utero or postnatally was suspected in this case.

Animal models of pain: progress and challenges

Many are frustrated with the lack of translational progress in the pain field, in which huge gains in basic science knowledge obtained using animal models have not led to the development of many new clinically effective compounds. A careful re-examination of animal models of pain is therefore warranted. Pain researchers now have at their disposal a much wider range of mutant animals to study, assays that more closely resemble clinical pain states, and dependent measures beyond simple reflexive withdrawal. However, the complexity of the phenomenon of pain has made it difficult to assess the true value of these advances. In addition, pain studies are importantly affected by a wide range of modulatory factors, including sex, genotype and social communication, all of which must be taken into account when using an animal model.

Neuropathic pain in dogs and cats: if only they could tell us if they hurt

Neuropathic pain is difficult to diagnose in veterinary patients because they are unable to verbalize their pain. By assuming that neuropathic pain may exist based on the history of events that each patient has experienced, a focused client history and neurologic examination may identify a lesion resulting in persistent or spontaneous pain. Once neuropathic pain is diagnosed, a trial analgesic or acupuncture session(s) should be prescribed with instructions for owners to observe behavior. Dosing of the analgesic can be titrated to the patient's needs while avoiding adverse effects. When a particular analgesic may be ineffectual, an alternate class should be tried. As research into the neurobiologic mechanisms of neuropathic pain continues, specific therapies for its management should eventually appear in the human clinical setting and subsequently be investigated for veterinary clinical use.

Reduced NGF secretion by Schwann cells under the high glucose condition decreases neurite outgrowth of DRG neurons

BACKGROUND

Schwann cells (SCs) have been supposed to play prominent roles in axonal regeneration under various diseases. Here, to evaluate the direct interaction between SCs and dorsal root ganglion (DRG) neurons under a diabetic condition, the effects of Schwann cell-conditioned media on neurite outgrowth of DRG neurons were investigated.

METHODS

Immortalized mouse Schwann cells (IMS) were cultured under 5.5 mM glucose (NG) or 30 mM glucose (HG) conditions for 4 days. IMS-conditioned media (IMS-media) were added to the culture media of neurons isolated from 8-week-old DDY mice. Neurons were cultured for 48 h with or without mouse recombinant NGF (mrNGF) or nerve growth factor (NGF) neutralizing antibody. The concentrations of NGF in IMS-media by ELISA and neurite outgrowth by a computed image analysis system were evaluated.

RESULTS

Neurite outgrowth was significantly enhanced by IMS-media (IMS-media (-): 177+/-177 microm, IMS-media (+): 1648+/-726). The neurite outgrowth cultured with IMS-media obtained under the HG condition was significantly reduced compared with that under the NG condition (NG: 1474+/-652, HG: 734+/-331). The NGF concentrations were significantly lower in IMS-media under the HG condition than in those under the NG condition. The accelerated neurite outgrowth by IMS-media was inhibited by NGF neutralizing antibody.

CONCLUSIONS

These results suggest that SCs play important roles in neurite outgrowth of DRG neurons, and that the decreased NGF secretion by SCs under the diabetic condition would cause a defect of axonal regeneration, resulting in the development of diabetic neuropathy.

F-wave conduction velocity, persistence, and amplitude for the tibial nerve in clinically normal cats

OBJECTIVE

To establish a method of F-wave evaluation and to determine normative values of F-wave parameters, including F-wave conduction velocity, persistence, and amplitude for the tibial nerve in cats.

ANIMALS

30 clinically normal cats.

PROCEDURES

F-waves elicited in the interosseous muscles by stimulation of the tibial nerve were recorded, and linear regression analyses of the shortest latency versus the length of the tibial nerve and the limb length were performed. F-wave persistence was calculated by dividing the number of recorded F-waves by the number of stimuli.

RESULTS

The correlation coefficient between F-wave latency and nerve length was 0.92, and that between F-wave latency and limb length was 0.58. Mean +/- SD F-wave conduction velocity of the tibial nerve was calculated to be 97.1 +/- 5.0 m/s. Linear regression analysis yielded the regression equation as follows: F-wave latency (milliseconds) = 2.60 + (0.02 x nerve length [mm]). Mean F-wave persistence and amplitude were 98.7 +/- 2.3% and 1.01 +/- 0.62 mV, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that nerve length should be used for nerve conduction studies of F-waves in felids. The regression equation for F-wave latency, conduction velocity, persistence, and amplitude may contribute to the diagnosis of nervous system diseases or injury in cats, such as trauma to the spinal cord or diabetic neuropathy.

Endoneurial microvascular pathology in feline diabetic neuropathy

Endoneurial capillaries in nerve biopsies from 12 adult diabetic cats with varying degrees of neurological dysfunction were examined for evidence of microvascular pathology and compared to nerves obtained at necropsy from 7 adult non-diabetic cats without clinical evidence of neurological dysfunction. As reported previously [Mizisin, A.P., Nelson, R.W., Sturges, B.K., Vernau, K.M., LeCouteur, R.A., Williams, D.C., Burgers, M.L., Shelton, G.D., 2007. Comparable myelinated nerve pathology in feline and human diabetes mellitus. Acta Neuropathol. 113, 431-442.], the diabetic cats had elevated glycosylated hemoglobin and serum fructosamine levels, decreased motor nerve conduction velocity and compound muscle action potential (CMAP) amplitude, and markedly decreased myelinated nerve fiber densities. Compared to non-diabetic cats, there was a non-significant 26% increase in capillary density and a significant (P<0.009) 45% increase in capillary size in diabetic cats. Capillary luminal size was also significantly (P<0.001) increased, while an index of vasoconstriction was significantly decreased (P<0.001) in diabetic cats compared to non-diabetic controls. No differences in endothelial cell size, endothelial cell number or pericyte size were detected between non-diabetic and diabetic cats. In diabetic cats, basement membrane thickening, seen as a reduplication of the basal lamina, was significantly (P<0.0002) increased by 73% compared to non-diabetic controls. Regression analysis of either myelinated nerve fiber density or CMAP amplitude against basement membrane size demonstrated a negative correlation with significant slopes (P<0.03 and P<0.04, respectively). These data demonstrate that myelinated nerve fiber injury in feline diabetic neuropathy is associated with microvascular pathology and that some of these changes parallel those documented in experimental rodent and human diabetic neuropathy.

Comparable myelinated nerve pathology in feline and human diabetes mellitus

The occurrence of diabetic neuropathy in cats provides an opportunity to study the development and treatment of neurological complications not present in diabetic rodent models, where few pathological alterations are evident. The present study further defines pathological alterations in nerve biopsies from 12 cats with spontaneously occurring diabetes mellitus. Peroneal nerve biopsies displayed concurrent injury to both Schwann cells and axons of myelinated fibers that was remarkably similar to that present in human diabetic neuropathy. In addition to demyelination, remyelination (constituting 20-84% of the total myelinated fiber population) was indicated by fibers with inappropriately thin myelin sheaths. Unlike our previous investigations, striking axonal injury was apparent, and consisted of dystrophic accumulations of membranous debris or neurofilaments, as well as degenerative fiber loss resulting in a 50% decrease in myelinated fiber density. In spite of extensive fiber loss, regenerative clusters were apparent, suggesting that axonal regeneration was not completely frustrated. These data highlight the potential utility of feline diabetic neuropathy as a model that faithfully replicates the nerve injury in human diabetes mellitus.

Usefulness of combined electrophysiological examinations for detection of neural dysfunction in cats with lumbar hematomyelia

We conducted combined electrophysiological examinations including F-wave, motor nerve conduction velocity (MNCV), spinal cord-evoked potential (SCEP), and needle electromyography (EMG) in two cats involved in traffic accidents that consequently developed hind limb paralysis caused by lumbar hematomyelia. F-wave could no longer be elicited within 3 days after the accident, and the MNCV and compound muscle action potential (CMAP) amplitude decreased in a time-dependent manner, with CMAP no longer being evoked after 7 or 8 days. EMG showed abnormalities such as fibrillation and positive sharp waves after 6 to 8 days. These results suggest that such combined electrophysiological examinations may provide objective, quantitative data for motor nerve dysfunction in cats with lumbar hematomyelia.

Feline Models of Type 2 Diabetes Mellitus

Feline diabetes mellitus (FDM) closely resembles human type 2 diabetes mellitus (T2DM) in many respects including clinical, physiological, and pathological features of the disease. These features include age of onset of FDM in middle age, association with obesity, residual but declining insulin secretion, development of islet amyloid deposits, loss of approximately 50% of beta-cell mass, and development of complications in several organ systems including peripheral polyneuropathy and retinopathy. Many of the pathological aspects of the disease are also experimentally inducible, facilitating study of the pathogenesis of these lesions. Physiological aspects of FDM and obesity are also well studied in the cat and provide an excellent basis for comparative studies of human T2DM. The relatively short generation time of cats along with breed predispositions to development of FDM may allow for more rapid screening and identification of genetic markers for diabetes susceptibility. FDM, in both spontaneous and inducible forms, therefore provides a good animal model of human T2DM and may provide additional insights into the pathogenesis of this important condition.

Sural nerve pathology in diabetic patients with minimal but progressive neuropathy

AIMS/HYPOTHESIS

The early pathological features of human diabetic neuropathy are not clearly defined. Therefore we quantified nerve fibre and microvascular pathology in sural nerve biopsies from diabetic patients with minimal neuropathy.

METHODS

Twelve diabetic patients underwent detailed assessment of neuropathy and fascicular sural nerve biopsy at baseline, with repeat assessment of neuropathy 8.7+/-0.6 years later.

RESULTS

At baseline, neuropathic symptoms, neurological deficits, quantitative sensory testing, cardiac autonomic function and peripheral nerve electrophysiology showed minimal abnormality, which deteriorated at follow-up. Myelinated fibre density, fibre and axonal area, and g-ratio were normal but teased fibre studies showed paranodal abnormalities (p<0.001), segmental demyelination (p<0.01) and remyelination (p<0.01) without axonal degeneration. Unassociated Schwann cell profile density (p<0.04) and unmyelinated axon density (p<0.001) were increased and axon diameter was decreased (p<0.007). Endoneurial capillaries demonstrated basement membrane thickening (p<0.006), endothelial cell hyperplasia (p<0.004) and a reduction in luminal area (p<0.007).

CONCLUSIONS/INTERPRETATION

The early pathological features of human diabetic neuropathy include an abnormality of the myelinated fibre Schwann cell and unmyelinated fibre degeneration with regeneration. These changes are accompanied by a significant endoneurial microangiopathy.