Gentiopicroside Ameliorates Diabetic Peripheral Neuropathy by Modulating PPAR- Γ/AMPK/ACC Signaling Pathway.

BACKGROUND/AIMS: Gentiopicroside is promising as an important secoiridoid compound against pain. The present study aimed to investigate the analgesic effect and the probable mechanism of Gentiopicroside on Diabetic Peripheral Neuropathy (DPN), and to figure out the association among Gentiopicroside, dyslipidemia and PPAR- γ/AMPK/ACC signaling pathway. METHODS: DPN rat models were established by streptozotocin and RSC96 cells were cultured. Hot, cold and mechanical tactile allodynia were conducted. Blood lipids, nerve blood flow, Motor Nerve Conduction Velocity (MNCV) and Sensory Nerve Conduction Velocity (SNCV) were detected. Gene and protein expression of PPAR- γ/AMPK/ACC pathway was analyzed by reverse transcription-quan titative polymerase chain reaction (RT-qPCR) and Westernblot. Besides, PPAR-γ antagonist GW9662 and agonist rosiglitazone, AMPK antagonist compound C and activator AICAR as well as ACC inhibitor TOFA were used to further confirm the relationship between PPAR-γ and AMPK. RESULTS: The results demonstrated that Gentiopicroside markedly ameliorated hyperalgesia with prolonged paw withdrawal latency to heat and cold stimuli and fewer responses to mechanical allodynia compared with DPN model group. Gentiopicroside regulated dyslipidemia, enhanced nerve blood flow and improved MNCV as well as SNCV. Gentiopicroside suppressed ACC expression through the activation of AMPK and PPAR-γ mediated the activation of AMPK and subsequent inhibition of ACC expression. CONCLUSION: In conclusion, the present study demon strated that Gentiopicroside exerted nerve-protective effect and attenuated experimental DPN by restoring dyslipidmia and improved nerve blood flow through regulating PPAR-γ/AMPK/ACC signal pathway. These results provided a promising potential treatment of DPN.

Heart rate variability and plasma norepinephrine concentration in diabetic dogs at rest.

Cardiac autonomic neuropathy in dogs with diabetic mellitus (DM) was evaluated using measurement of heart rate variability (HRV) and plasma norepinephrine (NE) concentration. Dogs were divided into 2 groups; the control non-DM group (n = 13) and the diabetic group (n = 22) which was further divided into the well-controlled DM (n = 11) and the poorly-controlled DM subgroups (n = 11) according to their fasting plasma fructosamine concentrations. The electrocardiogram (ECG) was recorded continuously for at least 30 min to yield HRV. The results showed that in the poorly-controlled DM subgroup, the average of normal R-R interval (mean N-N), SD of the mean of all 5-min segments of normal RR intervals (SDANN) were lower than the control group while heart rate was higher (P < 0.05). The NNA, SDNN, SDNN index and pNN50% were significantly lower when compared with the well-controlled DM subgroup (P < 0.05). The high frequency (HF) and total power were significantly lower while the ratio of low to high frequency (LF/HF) was higher (P < 0.05) when compared with the well-controlled DM subgroup. Moreover, in the poorly-controlled DM subgroup, plasma NE concentration was lower than the control group (210 ± 37 vs. 479 ± 74 pg/ml, P < 0.05). There was a significantly negative correlation between plasma NE and plasma fructosamine concentrations. It is concluded that cardiac autonomic neuropathy occurred in poorly-controlled DM dogs. The sympathetic activity was suppressed as shown by decrease in both plasma NE concentration and LF component.

Clinical peripheral neuropathy associated with diabetes mellitus in 3 dogs.

Clinical and electrodiagnostic findings in 3 spontaneously diabetic dogs with clinical peripheral neuropathy (PN) are reported. Clinical signs of a PN may develop in diabetic dogs with adequate glycemic control. In addition, laryngeal paralysis may develop in association with diabetes mellitus in dogs with clinical PN.

Diabetes mellitus-related morphoquantitative changes in the celiac ganglion neurons of the dog.

Diabetes mellitus is the most common endocrine disturbance of domestic carnivores and can cause autonomic neurological disorders, although these are still poorly understood in veterinary medicine. There is little information available on the quantitative adaptation mechanisms of the sympathetic ganglia during diabetes mellitus in domestic mammals. By combining morphometric methods and NADPH-diaphorase staining (as a possible marker for nitric oxide producing neurons), type I diabetes mellitus-related morphoquantitative changes were investigated in the celiac ganglion neurons in dogs. Twelve left celiac ganglia from adult female German shepherd dogs were examined: six ganglia were from non-diabetic and six from diabetic subjects. Consistent hypertrophy of the ganglia was noted in diabetic animals with increase of 55% in length, 53% in width, and 61.5% in thickness. The ordinary microstructure of the ganglia was modified leading to an uneven distribution of the ganglionic units and a more evident distribution of axon fascicles. In contrast to non-diabetic dogs, there was a lack of NADPH-diaphorase perikarial labelling in the celiac ganglion neurons of diabetic animals. The morphometric study showed that both the neuronal and nuclear sizes were significantly larger in diabetic dogs (1.3 and 1.39 times, respectively). The profile density and area fraction of NADPH-diaphorase-reactive celiac ganglion neurons were significantly larger (1.35 and 1.48 times, respectively) in non-diabetic dogs compared to NADPH-diaphorase-non-reactive celiac ganglion neurons in diabetic dogs. Although this study suggests that diabetic neuropathy is associated with neuronal hypertrophy, controversy remains over the possibility of ongoing neuronal loss and the functional interrelationship between them. It is unclear whether neuronal hypertrophy could be a compensation mechanism for a putative neuronal loss during the diabetes mellitus.

Myelin splitting, Schwann cell injury and demyelination in feline diabetic neuropathy.

Nerve biopsy samples from two cats with spontaneously occurring diabetes were examined. The predominant nerve fiber abnormalities observed were restricted to the myelin sheath and Schwann cell. Reactive, degenerative and proliferative Schwann cell changes were evident but the most striking abnormality encountered was splitting and ballooning of the myelin sheath. These observations highlight the significance of Schwann cell injury in the pathogenesis of diabetic neuropathy.

Long-term complications of diabetes mellitus, Part I: Retinopathy, nephropathy, neuropathy.

Diabetic retinopathy, nephropathy, and neuropathy occur infrequently in small animals, but are capable of causing significant disease. The clinical and histopathologic findings seen with these late complications of diabetes are discussed. The pathogenesis of these disorders is most likely multifactorial; metabolic alterations secondary to the hyperglycemic state, and microvascular changes seen with diabetes have both been implicated. Current treatment consists of aggressive control of the hyperglycemia, as research continues into the pathology of the late complications in attempts to find a definitive therapy.

Spontaneous diabetes mellitus in a rhesus monkey: neurophysiological studies.

Peripheral neuropathy is a common complication of human diabetes, but its occurrence in spontaneously diabetic monkeys is unknown. Four months after developing diabetes, a 22-year-old female rhesus monkey had nerve conduction studies which were compared with control data obtained from 9 nondiabetic rhesus monkeys. In the diabetic monkey, median and ulnar sensory action potential amplitudes and the median motor distal latency differed from controls by more than two standard deviations. Conduction velocities in the diabetic monkey were less than the mean values in controls, although none were beyond two standard deviations of control means. These electrophysiologic abnormalities are similar to those described in human diabetes and suggest that the spontaneously diabetic monkey peripheral nervous system may be a suitable model of experimental diabetic neuropathy.

[Diabetic neuropathy in dogs and cats--a bioptic electron microscopic study]. / Diabetische Neuropathie bei Hund und Katze--eine bioptisch-elektronenmikroskopische Studie.

Electron microscopic examination of peripheral nerves within dermal corium based upon skin biopsies (punch diameter = 6 mm) of chronic diabetic dogs and cats in comparison with normal controls revealed that more than 90% of the diabetic animals (31/34 dogs, 9/10 cats) had developed characteristic neuropathies. The main features were of axonal atrophy of myelinated and unmyelinated fibers, demyelination and - to a lesser degree - intraaxonal accumulation of glycogen (about 25%). In contrast with human diabetic polyneuropathy vascular basement membranes were throughout of normal appearance. Thickening of the perineural basement membranes were observed in a few canine cases only. Diagnostic procedures as well as questions on pathogenesis are discussed in detail.

Neuropathy associated with transient diabetes mellitus in 2 cats.

A 9-year-old spayed cat that flinched when touched responded poorly to methylprednisolone and phenobarbital. Hyperalbuminemia, hyperproteinemia, hyponatremia, hypochloremia, hyperglycemia and glycosuria resolved with insulin treatment. The flinching disappeared in 2 weeks and insulin use was unnecessary after 6 weeks. A 6-year-old castrated cat with diabetic ketoacidosis and azotemia responded to fluid and insulin therapy but developed a head tilt and insulin shock 2 weeks later. The cat recovered after 6 days of supportive treatment and no longer required insulin after 4 weeks.

Neuropathy associated with diabetes mellitus in the cat.

Distal polyneuropathy was associated with diabetes mellitus in 7 cats. Clinical signs relative to the neuropathy included a plantigrade stance, depressed patellar reflexes, hindlimb weakness, and poor postural reactions. Electromyography demonstrated reduced conduction velocity in the sciatic and ulnar nerves in 3 cats. A total of 5 cats had abatement of clinical signs following insulin therapy and blood glucose regulation or after resolution of the diabetes mellitus.

Peripheral neuropathy and hypotension in a diabetic dog.

Peripheral neuropathy and hypotension were found in a diabetic dog with profound weakness. Insulin therapy controlled the diabetes mellitus. As the blood glucose was normalized, the neurologic signs and hypotension resolved, suggesting a causal relationship.

Electrodiagnostic analysis of peripheral neuropathy in dogs with diabetes mellitus.

An elecrodiagnostic analysis was conducted on 5 dogs with spontaneously occurring diabetes mellitus that were maintained for a long-term study on canine diabetes. Abnormal electromyographic findings consisted of fibrillation potentials, positive sharp waves, and fasciculation potentials in the limb muscles of most dogs, The mean values (+/- SD) for motor nerve conduction velocities (NCV) of the ulnar and sciatic-tibial nerves were 57.6 +/- 11.2 and 52.1 +/- 7.4 m/s, respectively, for the 5 diabetic dogs. Values for motor NCV for clinically normal dogs in this laboratory were 56.0 +/- 7.6 and 66.6 +/- 7.1 m/s, respectively. The mean value (+/- SD) for the sensory NCV of the lateral superficial radial nerve in the diabetic dogs determined 4 months later was 45.2 +/- 7.9 m/s, compared with 53.1 +/- 6.0 m/s for normal dogs. Analysis of the evoked potentials recorded from the interosseous muscle after sciatic-tibial nerve stimulation revealed decreased amplitudes. Potentials evoked by stimulation at the hip, as compared with potentials evoked by stimulation at the hock, had temporal dispersion and diminished amplitude in the majority of the diabetic dogs.