No description available.

No description available.

No description available.

The object of this study was to investigate the effects of an aldose reductase inhibitor, sorbinil (Pfizer inc), in relation to some of the biochemical, structural and functional changes associated with diabetic nerves. An animal model, the streptozotocin-induced diabetic rat was used and the following studies were performed: Motor nerve conduction velocity (MNCV) was measured in the tibial nerve over a 6 month period. A group of rats were examined at the onset of the experiment (OC) to provide a baseline for comparison to all other groups. Age matched control (AMC) animals showed a 13% increase in MNCV during the first 3 months of the experiment with little increase thereafter. The diabetic animals (DC) did not significantly differ over the experimental period from the OC animals and were thus slower conducting than the corresponding AMC group. Administration of sorbinil (25 mg/Kg) to rats from the onset of diabetes had no effect on MNCV by 3 months but had normalised values by 6 months. Nerve glucose, sorbitol, fructose and myo-inositol levels were examined by GLC. Sorbinil had no effect on nerve glucose values but prevented the 10-fold increase in nerve sorbitol values observed with the DC animals. Sorbinil partially normalised nerve fructose values after 3 months of treatment and fully normalised them after 6 months. Myo-inositol (MI) levels showed a 45% reduction by 3 months of diabetes but were normal after 6 months. Sorbinil showed a tendency to restore the reduced MI values by 3 months. Morphometric profiles were examined in the tibial nerve. Axon areas demonstrated a 14% reduction at both 3 and 6 months of diabetes while myelin areas were increased by 13 and 22% respectively. Sorbinil treatment allowed normal axon growth and normalised myelin areas. MNCV was examined in the tibial and gastrocnemius nerves. As above, diabetes prevented the normal MNCV maturation in the tibial nerve. Sorbinil administration (25 mg/Kg) to rats initially diabetic for 2 months, was ineffective in restoring MNCV in the tibial nerve though a partial recovery was observed after 4 months of treatment. MNCV in the gastrocnemius nerve of the DC animals continued to fall as the experiment progressed, reaching a 33% reduction below the OC animals by 3 months. A spontaneous recovery was observed thereafter. Sorbinil partially normalised MNCV in the gastrocnemius nerve after 1 month. These changes exactly paralleled the changes in nerve MI levels. Sorbinil reversed the already elevated nerve sorbitol levels after 1 month of treatment though nerve fructose levels were only partially normalised after 4 months. A morphometric evaluation of the triceps surae nerve (containing fibres to gastrocnemius and soleus muscles) after 4 months of the experiment demonstrated an 18% increase of myelin area in the DC animals. Axon areas were unaffected by diabetes. Sorbinil treatment for 2 months partially normalised myelin areas. Sorbinil administration at doses of 7.5, 12.5 and 25 mg/Kg to rats that had been diabetic for 2 months did not normalise MNCV in the tibial nerve. However, 12.5 and 25 mg/Kg produced a significant improvement in MNCV of the gastrocnemius nerve after 1 month of treatment. 7.5 mg/Kg had no effect in this nerve. All doses of sorbinil produced a trend towards reversing the already elevated nerve sorbitol levels, though 25 mg/Kg was effective after 1 month of treatment whereas 12.5 mg/Kg required 2 months. 7.5 mg/Kg did not fully normalise nerve sorbitol levels. Nerve fructose values remained elevated, though treatment with 25 mg/Kg of sorbinil produced a reduction towards normal values. All 3 doses partially normalised MI levels. For all DC groups, sciatic nerve water content was significantly elevated after a 1 month experimental period. Sorbinil treatment, either given from the induction of diabetes or given after rats were initially diabetic for 2 months, had only a small effect on water content and values remained elevated compared with the controls.

The importance of soft tissue structures in the pathogenesis of diabetic complications in the hand and particularly the forefoot due to nerve damage or neuropathy has long been overlooked. This is partly due to the inability of most clinical techniques to examine tissue structures in vivo. Magnetic Resonance Imaging (MRI) provides a unique opportunity to study these tissues in detail. Through the use of a specially designed "targetted" radiofrequency coil, high-resolution imaging of the forefoot anatomy has been achieved. In addition to anatomical imaging, MRI has been used to give functional information about water dynamics in various tissue types, e. g. the fat pad and the muscles in the foot. The potential of this type of information to provide an insight into the severity and progression of diabetes has been investigated during this research work. In detail two patient groups with and without symptoms of neuropathy have been investigated. Deterioration of foot joints with a collapsed arch and intrinsic muscle wasting due to nerve damage were observed but more importantly several as yet unknown and unobserved phenomenon were also demonstrated. (i) At sites of maximum pressure resulting from neuropathic changes evidence of microhemorrhaging (or localised hemosiderin deposits) was observed through signal voids when using a gradient echo sequence. It is postulated that the occurrence of these voids is due to the paramagnetic iron core of the hemosiderin aggregate and therefore the signal from tissue in its proximity may be recovered with a spin echo sequence. (ii) The use of a Magnetisation Transfer (MT) sequence to provide functional information revealed a distinct change in MT activity deep within the fat pad of the foot at sites of maximum pressure. This is in contrast to the normal fat pad core which is MT inactive since its hydrophobic nature prevents the adsorption of free water. The fat pads of patients suffering from neuropathy showed various degrees of MT activity which hasbeen taken to indicate the presence of fibrotic material as a replacement for fat. This is consistent with current theories of the formation of neuropathic ulcers. The fibrotic tissue is likely to be the result of repetitive trauma to fat tissues leading to fibrosis where the condition of diabetes serves to catalyse its production via glycation and cross-linking of collagen. Histopathological examination of the fat pad tissues of similar patients, confirmed the presence of fibrosis. This is the first time that such a change in plantar fat pad tissue has been demonstrated in vivo. Further it was possible to correlate the extent of MT activity with disease severity. (iii) In an additional study of Limited Joint Mobility in the metacarpophalangeal (MCP) joints of the hand it was found that the cross-sectional area of the joint capsule reduced linearly with age for patients and controls and that there was no significant thickening relative to controls as postulated from work by others using plain radiographs

Neuropathy, a common complication of human diabetes, is not prevented by current antidiabetic therapy. Several mechanisms, some reversible, have been proposed. Clinical assessment of drug efficacy in this condition is difficult because of its slow and unpredictable development and its possible irreversibility, once established. A reliable animal model of diabetic neuropathy would be very useful. Changes such as reduced nerve conduction velocity are used as models but their relationship to neuropathy is uncertain. The main purpose of this study was to examine autonomic changes in the experimentally diabetic rat with the aim of identifying more appropriate models. The effects of three treatments which correct specific biochemical abnormalities which may underlie diabetic complications, were also studied.

The accurate assessment of human diabetic somatic polyneuropathy (DSPN) is important to define at risk patients, predict deterioration, and assess the efficacy of pathogenetic treatments. Corneal confocal microscopy (CCM) has been proposed as a surrogate endpoint for DSPN. Approximately 50% of patients with DSPN experience neuropathic pain or symptoms and the underlying reasons are not clearly elucidated. Vitamin D deficiency has been associated with diabetic complications including DSPN and diabetic retinopathy (DR). However there is a paucity of data regarding the interaction of vitamin D status with diabetic complications. This thesis shows that CCM can readily detect small fibre neuropathy prior to large fibre involvement and assess rapidly progressive nerve fibre loss prior to conventional thermal threshold testing. CCM has a superior diagnostic capabilities compared to intra-epidermal nerve fibres and correlates better with nerve conduction studies. Patients with LADA have a greater prevalence of small fibre neuropathy compared to matched patients with type 2 diabetes. Vitamin D deficiency is highly prevalent in patients with diabetes and despite relatively aggressive replacement regimens are inadequate in raising vitamin D levels in a significant proportion of patients. Vitamin D deficiency is not associated with DR but there is a strong association between painful DSPN and vitamin D insufficiency and more so with overt deficiency.

No description available.

Rationale and hypothesis: Diabetic sensory neuropathy involves a distal dying-back of nerve fibers. Neuronal mitochondrial function is impaired in diabetes and Sirtuin 2 (SIRT2) is a sensor of redox state that regulates cellular bioenergetics. The role of SIRT2 in regulating the phenotype of adult sensory neurons derived from both control and diabetic rats or wild type and SIRT2 knockout (KO) mice was studied. It was hypothesized that sensory neurons under a hyperglycemic state would have a lowered NAD+/NADH ratio thus deactivating the SIRT2 pathway. It was further hypothesized that the down regulation of SIRT2 would diminish the activity of the AMP-activated protein kinase (AMPK) pathway resulting in mitochondrial dysfunction. This defect would contribute to distal dying-back of axons observed in diabetes. Methodology: Type 1 diabetes was induced in rodents by streptozotocin (STZ). Adult sensory neurons derived from control or STZ-diabetic rats or control and SIRT2 knockout (KO) mice were cultured in defined media with varying doses of neurotrophic factors and D-glucose. Protein levels were determined by quantitative Western blotting and neurite outgrowth quantified by immunocytochemistry. Plasmid transfection was initiated for overexpression of SIRT2 constructs and Seahorse XF24 analyzer was utilized to measure mitochondrial function of cultured neurons. Results: Overexpression of SIRT2 elevated total neurite outgrowth in cultures derived from control and STZ-diabetic rats. Cultures derived from SIRT2 KO mice exhibited diminished neurite outgrowth. The AMPK pathway was inhibited under high glucose treatment through activation of the polyol pathway. Pharmacological inhibition of the polyol pathway improved mitochondrial bioenergetics and neurite outgrowth in sensory neurons. Augmented expression of electron transport proteins and increased mitochondrial mass was associated with enhanced bioenergetic function. Conclusion: SIRT2 is a key component driving mitochondrial function and axon regeneration through the activation of AMPK pathway. In diabetes this pathway is suppressed via elevated polyol pathway activity. / October 2016

Damage to peripheral nerves following trauma or disease has a number of consequences including burning pain, muscle wasting, paralysis, or organ dysfunction. The most common form of neuropathy is that associated with metabolic abnormality, notably diabetes. Many diabetics, especially those with poor blood sugar control, ultimately develop a distal symmetrical and painful neuropathy that initially affects the longest peripheral axons, but with time spreads proximally. Deficiency in neurotrophic support has been proposed to contribute to the development of diabetic neuropathy. Recently, peripheral gene delivery of vascular endothelial growth factor (VEGF), neurotrophin-3 (NT-3), NGF, BDNF or hepatocyte growth factor (HGF) has been shown to facilitate the continuous production of neurotrophic factors and alleviate the diabetic neuropathy. The role of glial cell-derived neurotrophic factor (GDNF) in the pathogenesis and therapeutics of diabetic neuropathy is not well defined. The main objectives of this research sought to inspect the protective effect of GDNF peripheral gene delivery during hyperglycemia- or constriction- induced sciatic nerve injury in rats. In present proposal, we propose to investigate the change in organization and expressions of GDNF signaling complex in the sciatic nerve following injury in the initial stage. Subsequently, the recombinant adenovirus was used gene delivery system for GDNF to evaluate the potential of intramuscular administration of gene delivery for prevent nerve degeneration, and the molecular mechanism of GDNF to ameliorate neuropathy will be clarified. The above study would enable us to test the hypothesis that the topical gene delivery might be a suitable strategy for the treatment of diabetic neuropathy and other disorders in peripheral nerve. Furthermore, the results of animal studies might be extrapolated for future clinical application.