Experimental diabetes attenuates cerebral cortical-evoked forelimb motor responses

Motor skills training-induced activation of descending pathways mediating cortical command to hindlimb motoneurons in experimental diabetic rats

Diabetes disrupts the corticospinal tract (CST) system components that control hindlimb and trunk movement, resulting in weakness of the lower extremities. However, there is no information about a method to improve these disorders. This study aimed to investigate the rehabilitative effects of 2 weeks of aerobic training (AT) and complex motor skills training (ST) on motor disorders in streptozotocin-induced type 1 diabetic rats. In this study, electrophysiological mapping of the motor cortex showed that the diabetes mellitus (DM)-ST group had a larger motor cortical area compared to the DM-AT group and sedentary diabetic animals. Moreover, hand grip strength and rotarod latency increased in the DM-ST group; however, these two parameters did not change in the DM-AT group, as well as in control and sedentary diabetic rats. Furthermore, in the DM-ST group, cortical stimulation-induced and motor-evoked potentials were preserved after the interception of the CST; however, this potential disappeared after additional lesions were made on lateral funiculus, suggesting that their function extends to activating motor descending pathways other than the CST locating lateral funiculus. According to immunohistochemical analysis, the larger fibers present on the dorsal part of the lateral funiculus, which corresponds to the rubrospinal tract of the DM-ST group, expressed the phosphorylated growth-associated protein, 43 kD, which is a specific marker of axons with plastic changes. Additionally, electrical stimulation of the red nucleus revealed expansion of the hindlimb-responsible area and increased motor-evoked potentials of the hindlimb in the DM-ST group, suggesting a strengthening of synaptic connections between the red nucleus and spinal interneurons driving motoneurons. These results reveal that ST induces plastic changes in the rubrospinal tract in a diabetic model, which can compensate for diabetes by disrupting the CST system components that control the hindlimb. This finding suggests that ST can be a novel rehabilitation strategy to improve motor dysfunctions in diabetic patients.

The dual therapeutic effect of metformin nuclei‐based drugs modified with one of Tulbaghia violacea extract compounds

Novel Schiff base was synthesized from the condensation reaction of metformin with [4‐(Diethylamino) benzaldehyde (NBM). Different metal complexes were prepared using Pd (II), Pt (II), Cu (II), and V (IV) metal ions. All complexes showed the nonelectrolytic behavior. So, the expected molecular formulas for complexes were [Pd (NBM)Cl2], [Pt (NBM)Cl2], [Cu (NBM)2Cl2] and [VO (NBM)2]. The cytotoxicity of (NBM) Schiff base and its metal complexes on human cancer cell line, MCF‐7, was investigated. V (IV) and Cu (II) complexes showed potential blood glucose lowering effect higher than the commercial metformin drug. VO (II) complex has superior antioxidant activity more than the other synthesized compounds and the standard ascorbic acid. Molecular docking investigation proved the presence of interesting interactions between all synthesized compounds with the active site amino acids of EGFR tyrosine kinase (anticancer activity). The molecular docking of metal complexes has observed effective inhibition for the specific mTOR protein that is expected to aid the growth of the COVID‐19 virus.

Quality Control, Anti-Hyperglycemic, and Anti-Inflammatory Assessment of Colvillea racemosa Leaves Using In Vitro, In Vivo Investigations and Its Correlation with the Phytoconstituents Identified via LC-QTOF-MS and MS/MS

Colvillea racemosa is a cultivated ornamental plant that is a monotypic genus of Fabaceae. It is native to Madagascar, with limited studies. For the first time, the leaf quality control parameters, the anti-hyperglycemic and anti-inflammatory in vitro activity of Colvillea racemosa ethanol extract (CRE) and its fractions of petroleum ether (CRP), methylene chloride (CRMC), ethyl acetate (CREA), n-butanol (CRB), and methanol (CRME) were evaluated. It exhibited significant inhibition against α-amylase, α-glucosidase and membrane stabilization. CRB was the most active fraction, and in vivo studies revealed that oral treatment with CRB of STZ-induced diabetic rats efficiently lowered blood glucose by 67.78%, reduced serum nitric oxide and lipid peroxide levels by 41.23% and 38.45%, respectively, and increased the GSH level by 90.48%. In addition, compared with the diabetic group, there was a 52.2% decrease in serum VCAM, a 55.5% increase in paraoxonase, an improved lipid profile, and improved liver and kidney functions for a treated diabetic group with CRB. Metabolite profiling of CRB was determined by UPLC-ESI-QTOF-MS and tandem MS/MS. Twenty-three chromatographic peaks were identified, which were classified into phenolic compounds and amino acids. The characterized flavonoids were apigenin and luteolin derivatives.

Diabetes Mellitus-Related Dysfunction of the Motor System

Although motor deficits in humans with diabetic neuropathy have been extensively researched, its effect on the motor system is thought to be lesser than that on the sensory system. Therefore, motor deficits are considered to be only due to sensory and muscle impairment. However, recent clinical and experimental studies have revealed that the brain and spinal cord, which are involved in the motor control of voluntary movement, are also affected by diabetes. This review focuses on the most important systems for voluntary motor control, mainly the cortico-muscular pathways, such as corticospinal tract and spinal motor neuron abnormalities. Specifically, axonal damage characterized by the proximodistal phenotype occurs in the corticospinal tract and motor neurons with long axons, and the transmission of motor commands from the brain to the muscles is impaired. These findings provide a new perspective to explain motor deficits in humans with diabetes. Finally, pharmacological and non-pharmacological treatment strategies for these disorders are presented.

Visual evoked potentials in offspring born to mothers with overweight, obesity and gestational diabetes

Background

Overweight, obesity, and gestational diabetes (GD) during pregnancy may negatively affect neurodevelopment in the offspring. However, the mechanisms are unclear and objective measures of neurodevelopment in infancy are scarce. We hypothesized that these maternal metabolic pathologies impair cortical visual evoked potentials (cVEPs), a proxy for visual and neuronal maturity.

Design

The PREOBE study included 331 pregnant women stratified into four groups; normal weight (controls), overweight, obesity, and GD (the latter including mothers with normal weight, overweight and obesity). In a subsample of the offspring at 3 months (n = 157) and at 18 months (n = 136), we assessed the latencies and amplitudes of the P100 wave from cVEPs and calculated visual acuity.

Results

At 3 months of age, visual acuity was significantly poorer in offspring born to GD mothers. At 18 months of age, there were no differences in visual acuity but infants born to GD mothers had significantly longer latencies of cVEPs when measured at 15’, and 30’ of arc. The group differences at 30’ remained significant after confounder adjustment (mean [SD] 121.0 [16.0] vs. 112.6 [7.6] ms in controls, p = 0.007) and the most prolonged latencies were observed in offspring to GD mothers with concurrent overweight (128.9 [26.9] ms, p = 0.002) and obesity (118.5 [5.1] ms, p = 0.020).

Conclusions

Infants born to mothers with GD, particularly those with concurrent overweight or obesity, have prolonged latencies of visual evoked potentials at 18 months of age, suggesting that this maternal metabolic profile have a long lasting, non-optimal, effect on infants´ brain development.

Effect of streptozotocin-induced diabetes on motor representations in the motor cortex and corticospinal tract in rats

Motor disorders in patients with diabetes are associated with diabetic peripheral neuropathy, which can lead to symptoms such as lower extremity weakness. However, it is unclear whether central motor system disorders can disrupt motor function in patients with diabetes. In a streptozotocin-induced rat model of type 1 diabetes, we used intracortical microstimulation to evaluate motor representations in the motor cortex, recorded antidromic motor cortex responses to spinal cord stimulation to evaluate the function of corticospinal tract (CST) axons, and used retrograde labeling to evaluate morphological alterations of CST neurons. The diabetic rats exhibited size reductions in the hindlimb area at 4 weeks and in trunk and forelimb areas after 13 weeks, with the hindlimb and trunk area reductions being the most severe. Other areas were unaffected. Additionally, we observed reduced antidromic responses in CST neurons with axons projecting to lumbar spinal segments (CST-L) but not in those with axons projecting to cervical segments (CST-C). This was consistent with the observation that retrograde-labeled CST-L neurons were decreased in number following tracer injection into the spinal cord in diabetic animals but that CST-C neurons were preserved. These results show that diabetes disrupts the CST system components controlling hindlimb and trunk movement. This disruption may contribute to lower extremity weakness in patients.

Painful neuropathy: Mechanisms

Painful neuropathy, like the other complications of diabetes, is a growing healthcare concern. Unfortunately, current treatments are of variable efficacy and do not target underlying pathogenic mechanisms, in part because these mechanisms are not well defined. Rat and mouse models of type 1 diabetes are frequently used to study diabetic neuropathy, with rats in particular being consistently reported to show allodynia and hyperalgesia. Models of type 2 diabetes are being used with increasing frequency, but the current literature on the progression of indices of neuropathic pain is variable and relatively few therapeutics have yet been developed in these models. While evidence for spontaneous pain in rodent models is sparse, measures of evoked mechanical, thermal and chemical pain can provide insight into the pathogenesis of the condition. The stocking and glove distribution of pain tantalizingly suggests that the generator site of neuropathic pain is found within the peripheral nervous system. However, emerging evidence demonstrates that amplification in the spinal cord, via spinal disinhibition and neuroinflammation, and also in the brain, via enhanced thalamic activity or decreased cortical inhibition, likely contribute to the pathogenesis of painful diabetic neuropathy. Several potential therapeutic strategies have emerged from preclinical studies, including prophylactic treatments that intervene against underlying mechanisms of disease, treatments that prevent gains of nociceptive function, treatments that suppress enhancements of nociceptive function, and treatments that impede normal nociceptive mechanisms. Ongoing challenges include unraveling the complexity of underlying pathogenic mechanisms, addressing the potential disconnect between the perceived location of pain and the actual pain generator and amplifier sites, and finding ways to identify which mechanisms operate in specific patients to allow rational and individualized choice of targeted therapies.

Cortical evoked potentials in children of diabetic mothers

Type 1 diabetic mothers' infants show a delay of visual evoked potential (VEP) significantly related to some parameters of poor metabolic control during pregnancy. In the present paper we analyzed the characteristics of VEPs and somatosensory evoked potentials (SEPs) recorded in 16 three-year-old type 1 diabetic mothers' children (DMC). Compared with controls (23 nondiabetic mothers' healthy matched children), DMC showed significantly delayed mean latency of VEP (P2) and SEP (P22). In 3 cases (19%), we found pathological responses (+3 SD from the mean value of controls) of VEPs and SEPs. At the age of 3 years, the offspring of type 1 diabetic mothers showed delay of cortical evoked responses in both visual and somatosensory systems.

Forced-exercise delays neuropathic pain in experimental diabetes: effects on voltage-activated calcium channels

Physical exercise produces a variety of psychophysical effects, including altered pain perception. Elevated levels of centrally produced endorphins or endocannabinoids are implicated as mediators of exercise-induced analgesia. The effect of exercise on the development and persistence of disease-associated acute/chronic pain remains unclear. In this study, we quantified the physiological consequence of forced-exercise on the development of diabetes-associated neuropathic pain. Euglycemic control or streptozotocin (STZ)-induced diabetic adult male rats were subdivided into sedentary or forced-exercised (2-10 weeks, treadmill) subgroups and assessed for changes in tactile responsiveness. Two weeks following STZ-treatment, sedentary rats developed a marked and sustained hypersensitivity to von Frey tactile stimulation. By comparison, STZ-treated diabetic rats undergoing forced-exercise exhibited a 4-week delay in the onset of tactile hypersensitivity that was independent of glucose control. Exercise-facilitated analgesia in diabetic rats was reversed, in a dose-dependent manner, by naloxone. Small-diameter (< 30 μm) DRG neurons harvested from STZ-treated tactile hypersensitive diabetic rats exhibited an enhanced (2.5-fold) rightward (depolarizing) shift in peak high-voltage activated (HVA) Ca(2+) current density with a concomitant appearance of a low-voltage activated (LVA) Ca(2+) current component. LVA Ca(2+) currents present in DRG neurons from hypersensitive diabetic rats exhibited a marked depolarizing shift in steady-state inactivation. Forced-exercise attenuated diabetes-associated changes in HVA Ca(2+) current density while preventing the depolarizing shift in steady-state inactivation of LVA Ca(2+) currents. Forced-exercise markedly delays the onset of diabetes-associated neuropathic pain, in part, by attenuating associated changes in HVA and LVA Ca(2+) channel function within small-diameter DRG neurons possibly by altering opioidergic tone.

Reproducible and persistent weakness in adult rats after surgical resection of motor cortex: evaluation with limb placement test

OBJECT

The purpose of this study was to develop a new rat model for surgical brain injury with motor weakness and to find an adequate behavior test for the application of the model.

METHODS

Thirty rats were divided into three groups: craniectomy (n = 10), durotomy (n = 10), and corticectomy (n = 10) groups. The coordinates of the three points from the bregma (coordinate A = +4,+1, B = -2,+1, and C = +4,+6). We evaluated right limb motor performance by the modified limb placement test and the cylinder test.

CONCLUSION

Persistent motor weakness was observed for 2 months in the corticectomy group by the limb placement test, whereas the cylinder test could not detect the weakness. We established a reproducible and persistent rat brain injury model and found that the modified limb placement test is sensitive enough to evaluate residual subtle weakness in this model.

1-methylnicotinamide (MNA) in prevention of diabetes-associated brain disorders

The present study has been designed to establish the potential benefits from 1-methylnicotinamide (MNA) treatment on brain disorders associated with type 1 diabetes. All experiments were carried out after 6 weeks of streptozotocin-induced diabetes (60 mg/kg of body weight, i.p.) in male Wistar rats treated for 5 weeks with or without MNA (100 mg/kg of body weight, per os in drinking water) after 1 week of diabetes induction. Diabetes was shown to reduce monoamine neurotransmitter serotonin transporters activity, as assessed by significant inhibition of [2-(14)C]serotonin uptake, that was accompanied by elevation of spontaneous mediator release in rat brain synaptosomes. Treatment with MNA slightly attenuated diabetes-induced changes in brain serotoninergic system. The precise mechanism underlying MNA action on central serotonin neurotransmission is not known, but appears to be linked to metabolic and signalling pathways involved in controlling synaptic function rather than being associated with direct modulation of serotonin transporters. In particular, MNA action was associated with its partial normalizing effects on such biochemical indices of neuropathy development as decrease in synaptosomal Na(+),K(+)-ATPase activity and plasma membrane depolarization of synaptic endings. Elevated sorbitol formation in brain and NAD(+) deficits resulted from diabetes as major metabolic imbalances were remarkably countered by MNA treatment. However, diabetes-induced decrease in cytosolic NAD(+) to NADH ratio in brain remained unchanged. Notably, MNA supplementation to diabetic rats caused a slight lowering effect on blood glucose level. Accordingly, our findings indicate that neuroprotective properties of MNA are linked to modulation of synaptic activity through multiple mechanisms. In conclusion, we suggest that 1-methylnicotinamide might be a useful agent for treating brain failures related to diabetes.

Insulin and IGF-I prevent brain atrophy and DNA loss in diabetes

The aim of this study was to identify factors that regulate the bulk of adult brain mass, and test the hypothesis that concomitantly reduced insulin and insulin-like growth factor (IGF) levels are pathogenic for brain atrophy associated with impaired learning and memory in diabetes. Doses of insulin, or insulin plus IGF-I that were too small to prevent hyperglycemia were infused for 12 weeks into the brain lateral ventricles of streptozotocin-diabetic adult rats. Brain wet, water and dry weights were significantly decreased in diabetic rats; insulin prevented these decreases. The decrease in brain DNA and protein contents in diabetic rats was prevented by the combination treatment, but not by insulin alone. Levels of several glia- and neuron-associated proteins were reduced in diabetes; these reductions were also prevented by the combination treatment. Although hyperglycemia was not prevented in plasma or cerebrospinal fluid, insulin prevented brain atrophy but not bulk DNA loss in diabetes, whereas the combination prevented both. Insulin actively prevented the loss of brain water content as well. Brain atrophy is associated with concomitantly reduced levels of insulin and IGF in other disorders such as Alzheimer's disease.