Sitagliptin, sitagliptin and metformin, or sitagliptin and amitriptyline attenuate streptozotocin-nicotinamide induced diabetic neuropathy in rats

Tanshinone IIA ameliorates experimental diabetic cardiomyopathy by inhibiting endoplasmic reticulum stress in cardiomyocytes via SIRT1

Diabetic cardiomyopathy (DCM) is a common complication in patients with diabetes, and ultimately leads to heart failure. Endoplasmic reticulum stress (ERS) induced by abnormal glycolipid metabolism is a critical factor that affects the occurrence and development of DCM. Additionally, the upregulation/activation of silent information regulation 2 homolog-1 (SIRT1) has been shown to protect against DCM. Tanshinone II A (Tan IIA), the main active component of Salviae miltiorrhizae radix et rhizome (a valuable Chinese medicine), has protective effects against cardiovascular disease and diabetes. However, its role and mechanisms in diabetes-induced cardiac dysfunction remain unclear. Therefore, we explored whether Tan IIA alleviates ERS-mediated DCM via SIRT1 and elucidated the underlying mechanism. The results suggested that Tan IIA alleviated the pathological changes in the hearts of diabetic mice, ameliorated the cytopathological morphology of cardiomyocytes, reduced the cell death rate, and inhibited the expression of ERS-related proteins and mRNA. The SIRT1 agonist inhibited the activities of glucose-regulated protein 78 (GRP78). Furthermore, the opposite results under the SIRT1 inhibitor. SIRT1 knockdown was induced by siRNA-SIRT1 transfection, and the degree of GRP78 acetylation was increased. Cumulatively, Tan IIA ameliorated DCM by inhibiting ERS and upregulating SIRT1 expression.

Empagliflozin mitigates type 2 diabetes-associated peripheral neuropathy: a glucose-independent effect through AMPK signaling

Diabetic peripheral neuropathy (DPN) represents a severe microvascular condition that dramatically affects diabetic patients despite adequate glycemic control, resulting in high morbidity. Thus, recently, anti-diabetic drugs that possess glucose-independent mechanisms attracted attention. This work aims to explore the potentiality of the selective sodium-glucose cotransporter-2 inhibitor, empagliflozin (EMPA), to ameliorate streptozotocin-induced DPN in rats with insight into its precise signaling mechanism. Rats were allocated into four groups, where control animals received vehicle daily for 2 weeks. In the remaining groups, DPN was elicited by single intraperitoneal injections of freshly prepared streptozotocin and nicotinamide (52.5 and 50 mg/kg, respectively). Then EMPA (3 mg/kg/p.o.) was given to two groups either alone or accompanied with the AMPK inhibitor dorsomorphin (0.2 mg/kg/i.p.). Despite the non-significant anti-hyperglycemic effect, EMPA improved sciatic nerve histopathological alterations, scoring, myelination, nerve fibers’ count, and nerve conduction velocity. Moreover, EMPA alleviated responses to different nociceptive stimuli along with improved motor coordination. EMPA modulated ATP/AMP ratio, upregulated p-AMPK while reducing p-p38 MAPK expression, p-ERK1/2 and consequently p-NF-κB p65 as well as its downstream mediators (TNF-α and IL-1β), besides enhancing SOD activity and lowering MDA content. Moreover, EMPA downregulated mTOR and stimulated ULK1 as well as beclin-1. Likewise, EMPA reduced miR-21 that enhanced RECK, reducing MMP-2 and -9 contents. EMPA’s beneficial effects were almost abolished by dorsomorphin administration. In conclusion, EMPA displayed a protective effect against DPN independently from its anti-hyperglycemic effect, probably via modulating the AMPK pathway to modulate oxidative and inflammatory burden, extracellular matrix remodeling, and autophagy.

Empagliflozin mitigates type 2 diabetes-associated peripheral neuropathy: a glucose-independent effect through AMPK signaling

Diabetic peripheral neuropathy (DPN) represents a severe microvascular condition that dramatically affects diabetic patients despite adequate glycemic control, resulting in high morbidity. Thus, recently, anti-diabetic drugs that possess glucose-independent mechanisms attracted attention. This work aims to explore the potentiality of the selective sodium-glucose cotransporter-2 inhibitor, empagliflozin (EMPA), to ameliorate streptozotocin-induced DPN in rats with insight into its precise signaling mechanism. Rats were allocated into four groups, where control animals received vehicle daily for 2 weeks. In the remaining groups, DPN was elicited by single intraperitoneal injections of freshly prepared streptozotocin and nicotinamide (52.5 and 50 mg/kg, respectively). Then EMPA (3 mg/kg/p.o.) was given to two groups either alone or accompanied with the AMPK inhibitor dorsomorphin (0.2 mg/kg/i.p.). Despite the non-significant anti-hyperglycemic effect, EMPA improved sciatic nerve histopathological alterations, scoring, myelination, nerve fibers' count, and nerve conduction velocity. Moreover, EMPA alleviated responses to different nociceptive stimuli along with improved motor coordination. EMPA modulated ATP/AMP ratio, upregulated p-AMPK while reducing p-p38 MAPK expression, p-ERK1/2 and consequently p-NF-κB p65 as well as its downstream mediators (TNF-α and IL-1β), besides enhancing SOD activity and lowering MDA content. Moreover, EMPA downregulated mTOR and stimulated ULK1 as well as beclin-1. Likewise, EMPA reduced miR-21 that enhanced RECK, reducing MMP-2 and -9 contents. EMPA's beneficial effects were almost abolished by dorsomorphin administration. In conclusion, EMPA displayed a protective effect against DPN independently from its anti-hyperglycemic effect, probably via modulating the AMPK pathway to modulate oxidative and inflammatory burden, extracellular matrix remodeling, and autophagy.

Peripheral Neuropathy Phenotyping in Rat Models of Type 2 Diabetes Mellitus: Evaluating Uptake of the Neurodiab Guidelines and Identifying Future Directions

Diabetic peripheral neuropathy (DPN) affects over half of type 2 diabetes mellitus (T2DM) patients, with an urgent need for effective pharmacotherapies. While many rat and mouse models of T2DM exist, the phenotyping of DPN has been challenging with inconsistencies across laboratories. To better characterize DPN in rodents, a consensus guideline was published in 2014 to accelerate the translation of preclinical findings. Here we review DPN phenotyping in rat models of T2DM against the 'Neurodiab' criteria to identify uptake of the guidelines and discuss how DPN phenotypes differ between models and according to diabetes duration and sex. A search of PubMed, Scopus and Web of Science databases identified 125 studies, categorised as either diet and/or chemically induced models or transgenic/spontaneous models of T2DM. The use of diet and chemically induced T2DM models has exceeded that of transgenic models in recent years, and the introduction of the Neurodiab guidelines has not appreciably increased the number of studies assessing all key DPN endpoints. Combined high-fat diet and low dose streptozotocin rat models are the most frequently used and well characterised. Overall, we recommend adherence to Neurodiab guidelines for creating better animal models of DPN to accelerate translation and drug development.

The microvascular hypothesis underlying neurologic manifestations of long COVID-19 and possible therapeutic strategies

With the ongoing distribution of the coronavirus disease (COVID) vaccines, the pandemic of our age is ending, leaving the world to deal with its well-documented aftereffects. Long COVID comprises a variety of symptoms, of which the neurological component prevails. The most permeating theory on the genesis of these symptoms builds upon the development of microvascular dysfunction similar to that seen in numerous vascular diseases such as diabetes. This can occur through the peripheral activation of angiotensin-converting enzyme 2 receptors, or through exacerbations of pro-inflammatory cytokines that can remain in circulation even after the infection diminishes. Several drugs have been identified to act on the neurovascular unit to promote repair, such as gliptins, and others. They also succeeded in improving neurologic outcome in diabetic patients. The repurposing of such drugs for treatment of long COVID-19 can possibly shorten the time to recovery of long COVID-19 syndrome.

Deciphering the Neuroprotective Role of Glucagon-like Peptide-1 Agonists in Diabetic Neuropathy: Current Perspective and Future Directions

Diabetic neuropathy is referred to as a subsequential and debilitating complication belonging to type 1 and type 2 diabetes mellitus. It is a heterogeneous group of disorders with a particularly complex pathophysiology and also includes multiple forms, ranging from normal discomfort to death. The evaluation of diabetic neuropathy is associated with hyperglycemic responses, resulting in an alteration in various metabolic pathways, including protein kinase C pathway, polyol pathway and hexosamine pathway in Schwann and glial cells of neurons. The essential source of neuronal destruction is analogous to these respective metabolic pathways, thus identified as potential therapeutic targets. These pathways regulating therapeutic medications may be used for diabetic neuropathy, however, only target specific drugs could have partial therapeutic activity. Various antidiabetic medications have been approved and marketed, which possess the therapeutic ability to control hyperglycemia and ameliorate the prevalence of diabetic neuropathy. Among all antidiabetic medications, incretin therapy, including Glucagon-like peptide-1 receptor agonists and dipeptidyl peptidase-4 inhibitors, are the most favorable medications for the management of diabetes mellitus and associated peripheral neuropathic complications. Besides enhancing glucose-evoked insulin release from pancreatic β-cells, these therapeutic agents also play a vital role to facilitate neurite outgrowth and nerve conduction velocity in dorsal root ganglion. Furthermore, incretin therapy also activates cAMP and ERK signalling pathways, resulting in nerve regeneration and repairing. These effects are evidently supported by a series of preclinical data and investigations associated with these medications. However, the literature lacks adequate clinical trial outcomes related to these novel antidiabetic medications. The manuscript emphasizes the pathogenesis, current pharmacological approaches and vivid description of preclinical and clinical data for the effective management of diabetic neuropathy.

Food restriction promotes damage reduction in rat models of type 2 diabetes mellitus

There are several animal models of type 2 diabetes mellitus induction but the comparison between models is scarce. Food restriction generates benefits, such as reducing oxidative stress, but there are few studies on its effects on diabetes. The objective of this study is to evaluate the differences in physiological and biochemical parameters between diabetes models and their responses to food restriction. For this, 30 male Wistar rats were distributed in 3 groups (n = 10/group): control (C); diabetes with streptozotocin and cafeteria-style diet (DE); and diabetes with streptozotocin and nicotinamide (DN), all treated for two months (pre-food restriction period). Then, the 3 groups were subdivided into 6, generating the groups CC (control), CCR (control+food restriction), DEC (diabetic+standard diet), DER (diabetic+food restriction), DNC (diabetic+standard diet) and DNR (diabetic+food restriction), treated for an additional two months (food restriction period). The food restriction (FR) used was 50% of the average daily dietary intake of group C. Throughout the treatment, physiological and biochemical parameters were evaluated. At the end of the treatment, serum biochemical parameters, oxidative stress and insulin were evaluated. Both diabetic models produced hyperglycemia, polyphagia, polydipsia, insulin resistance, high fructosamine, hepatic damage and reduced insulin, although only DE presented human diabetes-like alterations, such as dyslipidemia and neuropathy symptoms. Both DEC and DNC diabetic groups presented higher levels of protein carbonyl groups associated to lower antioxidant capacity in the plasma. FR promoted improvement of glycemia in DNR, lipid profile in DER, and insulin resistance and hepatic damage in both diabetes models. FR also reduced the protein carbonyl groups of both DER and DNR diabetic groups, but the antioxidant capacity was improved only in the plasma of DER group. It is concluded that FR is beneficial for diabetes but should be used in conjunction with other therapies.

Cathepsin D plays a role in endothelial-pericyte interactions during alteration of the blood-retinal barrier in diabetic retinopathy

Inflammation plays an important role in the pathogenesis of diabetic retinopathy. We have previously demonstrated the effect of cathepsin D (CD) on the mechanical disruption of retinal endothelial cell junctions and increased vasopermeability, as well as increased levels of CD in retinas of diabetic mice. Here, we have also examined the effect of CD on endothelial-pericyte interactions, as well as the effect of dipeptidyl peptidase-4 (DPP4) inhibitor on CD in endothelial-pericyte interactions in vitro and in vivo. Cocultured cells that were treated with pro-CD demonstrated a significant decrease in the expression of platelet-derived growth factor receptor-β, a tyrosine kinase receptor that is required for pericyte cell survival; N-cadherin, the key adherens junction protein between endothelium and pericytes; and increases in the vessel destabilizing agent, angiopoietin-2. The effect was reversed in cells that were treated with DPP4 inhibitor along with pro-CD. With pro-CD treatment, there was a significant increase in the phosphorylation of the downstream signaling protein, PKC-α, and Ca²⁺/calmodulin-dependent protein kinase II in endothelial cells and pericytes, which disrupts adherens junction structure and function, and this was significantly reduced with DPP4 inhibitor treatment. Increased CD levels, vasopermeability, and alteration in junctional-related proteins were observed in the retinas of diabetic rats, which were significantly changed with DPP4 inhibitor treatment. Thus, DPP4 inhibitors may be used as potential adjuvant therapeutic agents to treat increased vascular leakage observed in patients with diabetic macular edema.-Monickaraj, F., McGuire, P., Das, A. Cathepsin D plays a role in endothelial-pericyte interactions during alteration of the blood-retinal barrier in diabetic retinopathy.

Gallic acid and p-coumaric acid attenuate type 2 diabetes-induced neurodegeneration in rats

The brain of diabetics revealed deterioration in many regions, especially the hippocampus. Hence, the present study aimed to evaluate the effects of gallic acid and p-coumaric acid against the hippocampal neurodegeneration in type 2 diabetic rats. Adult male albino rats were randomly allocated into four groups: Group 1 served as control ones and others were induced with diabetes. Group 2 considered as diabetic, and groups 3 and 4 were further orally treated with gallic acid (20 mg/kg b.wt./day) and p-coumaric acid (40 mg/kg b.wt./day) for six weeks. Diabetic rats revealed significant elevation in the levels of serum glucose, blood glycosylated hemoglobin and serum tumor necrosis factor-α, while the level of serum insulin was significantly declined. Furthermore, the brain of diabetic rats showed a marked increase in oxidative stress and a decrease of antioxidant parameters as well as upregulation the protein expression of Bax and downregulation the protein expression of Bcl-2 in the hippocampus. Treatment of diabetic rats with gallic acid and p-coumaric acid significantly ameliorated glucose tolerance, diminished the brain oxidative stress and improved antioxidant status, declined inflammation and inhibited apoptosis in the hippocampus. The overall results suggested that gallic acid and p-coumaric acid may inhibit hippocampal neurodegeneration via their potent antioxidant, anti-inflammatory and anti-apoptotic properties. Therefore, both compounds can be recommended as hopeful adjuvant agents against brain neurodegeneration in diabetics.

Protective effects of triptolide on TLR4 mediated autoimmune and inflammatory response induced myocardial fibrosis in diabetic cardiomyopathy

ETHNOPHARMACOLOGICAL RELEVANCE

Triptolide is a most important active ingredient extracted from traditional Chinese medicine Tripterygium, which has been widely used to treat glomerulonephritis as well as immune-mediated disorders, likely for its immunosuppressive, anti-proliferative and anti-inflammatory effects.

AIM OF THE STUDY

In this study, we have investigated the potential protective effects of triptolide against diabetic cardiomyopathy (DCM) by regulating immune system, attenuating inflammatory response, thus resulting in decreased cardiac fibrosis and improved left ventricle function.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into 5 groups: normal group, diabetic group and diabetic rats treated with triptolide (50, 100, or 200μg/kg/day resp) for 8 weeks. Cardiac function was performed by echocardiography and histopathology of the hearts was examined with HE, Masson staining and scanning electron microscopy. Immune regulation mediator, macrophage infiltration, inflammatory response and cardiac fibrosis related cytokines were measured by RT-PCR, Western blot and Immunohistochemistry staining.

RESULTS

In the diabetic group, the expressions of TLR4 and NF-κB p65 were both up-regulated, which was associated with increased pro-inflammatory cytokines, coupled with cardiac fibrosis and impaired left ventricular function. Interestingly, pathological structure and function of left ventricle were both significantly improved in the triptolide treated groups. Furthermore, the immune mediator TLR4, downstream activator NF-κB p65, macrophage infiltration (CD68+), pro-inflammatory cytokines (TNF-α, IL-1β), cell adhesion molecule (VCAM-1) and chemokine (MCP-1) were significantly suppressed when treated with medium and high dosage triptolide compared with the diabetic group. Moreover, cardiac fibrosis pathway including α-SMA, TGF-β1, vimentin and collagen accumulations were observed significantly decreased in the triptolide treated groups.

CONCLUSIONS

Our data demonstrated that the protective effects of triptolide against DCM might attribute to inhibition of TLR4-induced NF-κB/IL-1β immune pathway, suppression of NF-κB/TNF-α/VCAM-1 inflammatory pathway and down-regulation of TGF-β1/α-SMA/Vimentin fibrosis pathway.

Drug combinations in diabetic neuropathic pain: an experimental validation

BACKGROUND

Diabetic neuropathy is the most common complication of diabetes mellitus, and the different drug combinations available do not provide effective pain relief. The present study was performed to observe the effect of amitripyline, duloxetine, sitagliptin, and pregabalin, and their combinations on streptozotocin (STZ)-induced diabetic neuropathy.

METHODS

Diabetic neuropathy was induced by STZ, and the tail-flick test was used to assess thermal hyperalgesia before and after (at 30, 60, and 120 min) drug administration. One week after STZ administration, the blood glucose level was observed to be in the diabetic range.

RESULTS

Administration of all the drugs except sitagliptin increased the tail-flick latency significantly as compared to control. Further, the drugs amitriptyline, duloxetine, and pregabalin showed significant pain-relieving effect, when either two of them were administered in combination, although the different combinations had varied degree of pain relief. However, sitagliptin was observed to have no effect when administered alone or in combination with the other three drugs.

CONCLUSIONS

Therefore, the study provides new insights concerning combined therapy of pain, which further needs clinical exploration.

Effect of polysaccharide from Bacillus subtilis sp. on cardiovascular diseases and atherogenic indices in diabetic rats

BACKGROUND

Diabetes mellitus induces chronic complications such as cardiovascular damage, cataracts and retinopathy, nephropathy, and polyneuropathy. The main aim of the study was to isolate and identify both of bacterial strain and exopolysaccharide to assess the possible efficiency of exopolysaccharide (BSEPS) from Bacillus subtilus sp .suppress on cardiovascular diseases, atherogenic and coronary risk indices in diabetic rats.

METHODS

The bacterial strain used was isolated from mangrove tree sediment by serial dilution and the spread-plate technique and identified by morphological, physiological, and biochemical characteristics, and by 16S rRNA analysis. The BSEPS was extracted from the bacterial supernatant by four volumes child ethanol then the functional groups, MW and chemical analysis were detected by Fourier-transform infrared (FTIR), gel permeation chromatograph (GPC) and High-performance liquid chromatography (HPLC). Also an antioxidant activity was measured by using 2,2-diphenyl-1-picrylhydrazyl (DPPH). Thirty-two male Sprague-Dawley rats were equally randomized into four groups: control group supplemented with normal saline (Group I); the second group supplemented with BSEPS (Group II); diabetic group supplemented with normal saline (Group III) and the diabetic group supplemented with BSEPS (Group IV). Diabetes was induced by Streptozotocin (STZ) (65 mg/kg BW) intraperitoneally. BSEPS (100 mg/kg BW) was administered orally for four weeks, following STZ induction.

RESULTS

The isolated strain was identified based on 16S rRNA sequence as Bacillus subtilis sp. suppress. A preliminary chemical analysis of BSEPS indicated that the monosaccharides were mannuronic acid, glucuronic acid, glucose, galactose, and mannose in a molar ratio of 1.6:1.5:1.0:2.3:1.4, respectively, with a molecular weight of 1.66 × 10(4) g mol(-1) and a molecular number of 7.64 × 10(3) g mol(-1). BSEPS inhibited 2,2-diphenyl-1-picrylhydrazyl radical activity, and BSEPS supplement reduced glucose (p < 0.05) and troponin levels while insulin levels increased (p < 0.05). BSEPS also reduced total serum cholesterol, low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglycerides, and elevated high-density lipoprotein-cholesterol (HDL). In parallel, intercellular adhesion molecule (ICAM), and vascular cell adhesion molecule (VCAM) levels in STZ-induced diabetic rats were reduced. Moreover, polysaccharides reduced atherogenic and coronary risk indices, which were confirmed by histopathological examination of the heart and aorta.

CONCLUSIONS

Our study suggests that BSEPS improves hyperglycemia, dyslipidemia, and cardiovascular disease risk in STZ-induced diabetic rats.

Alternatives to the Streptozotocin-Diabetic Rodent

The study of diabetic neuropathy has relied primarily on the use of streptozotocin-treated rat and mouse models of type 1 diabetes. This chapter will review the creation and use of other rodent models that have been developed in order to investigate the contribution of factors besides insulin deficiency to the development and progression of diabetic neuropathy as it occurs in obesity, type 1 or type 2 diabetes. Diabetic peripheral neuropathy is a complex disorder with multiple mechanisms contributing to its development and progression. Even though many animal models have been developed and investigated, no single model can mimic diabetic peripheral neuropathy as it occurs in humans. Nonetheless, animal models can play an important role in improving our understanding of the etiology of diabetic peripheral neuropathy and in performing preclinical screening of potential new treatments. To date treatments found to be effective for diabetic peripheral neuropathy in rodent models have failed in clinical trials. However, with the identification of new endpoints for the early detection of diabetic peripheral neuropathy and the understanding that a successful treatment may require a combination therapeutic approach there is hope that an effective treatment will be found.

Comparative anti-inflammatory and lipid-normalizing effects of metformin and omega-3 fatty acids through modulation of transcription factors in diabetic rats

BACKGROUND

Emerging evidence suggests beneficial effects of omega-3 fatty acids on diabetic complications. The present study compared the progressive effects of metformin and flax/fish oil on lipid metabolism, inflammatory markers, and liver and renal function test markers in streptozotocin-nicotinamide-induced diabetic rats.

METHODS

Streptozotocin-induced diabetic rats were randomized into control and four diabetic groups: streptozotocin (STZ), metformin (200 mg/kg body weight (b.w)/day (D)), flax and fish oil (500 mg/kg b.w/D).

RESULTS

Metformin and flax and fish oil exhibited increased expression of transcription factor peroxisome proliferator-activated receptor γ while the treatment downregulated sterol regulatory element-binding protein 1 and nuclear factor kβ as compared to those of the STZ group. Apart from modulation of transcription factor expression, the expression of fatty acid synthase, long chain acyl CoA synthase, and malonyl-CoA-acyl carrier protein transacylase was lowered by flax/fish oil treatment. Serum cholesterol, triglycerides, and VLDL were also significantly reduced in the treatment groups as compared to those in the STZ group. Although pathological abnormalities were seen in the liver and kidneys of rats on metformin, no significant changes in liver/renal function markers were observed at day 15 and day 30 of the treatment groups. Flax/fish oil had protective effects toward pathological abnormalities in the liver and kidney. Flax/fish oil improved lipid profile and alkaline phosphatase at day 30 as compared to that at day 15.

CONCLUSIONS

The present study demonstrates potential beneficial effects of metformin and flax/fish oil intervention in improving serum lipid profile by regulating the expression of transcription factors and genes involved in lipid metabolism in diabetic rats. In addition, these interventions also lowered the expression of atherogenic cytokines. The protective effects of flax/fish oil are worth investigating in human subjects on metformin monotherapy.

Retrospective Study on the Analgesic Activity of a Topical (TT-CTAC) Cream in Patients With Diabetic Neuropathy and Other Chronic Pain Conditions

Treatment of chronic pain in diabetic neuropathy or neuropathic pain of other origins is challenging. Compounded topical formulations have evolved as potential treatment options. The objective of this retrospective study was to evaluate the efficacy of a compounded topical cream (Transdermal Therapeutics). Two versions of TT-CTAC cream were evaluated: cream 6B and cream 7B. Both creams contain ketamine (10%), baclofen (2%), gabapentin (6%), amitriptyline (4%), bupivacaine (2%), and clonidine (0.2%). Additionally, one cream (7B) contains nifedipine (2%). The primary efficacy outcome was the change in numeric pain intensity score from pretreatment to posttreatment. Secondary outcomes were qualitative grading (excellent, good, poor, or no effect), reduction in oral medication, and avoiding referral to a pain specialist. Information on 283 patients was evaluated, 205 received the 7B and 78 received 6B creams. The pain score decreased by 2.4 ± 2.4 (35%) with the 6B cream (from 7.8 ± 1.6 to 5.4 ± 2.0, P < 0.001) and by 3.0 ± 2.4 (40%) with the 7B cream (from 7.5 ± 1.7 to 4.5 ± 2.2, P < 0.001). Excellent or good effects were reported in 82% of the patients in the 6B and in 70% in the 7B groups. Reduction in oral pain medication was seen in 35% of the patients in the 7B and in 20% in the 6B groups. In the opinion of the treating physicians, the cream therapy caused the avoidance of a pain specialist referral in 53% of the patients in the 6B and in 39% in the 7B groups. The creams were equally effective in diabetic neuropathy, neuropathic pain, or other chronic pain states. We conclude that both creams provided excellent pain relief in the majority of the patients studied and may be a useful modality for pain therapy.

Effect of metformin on Schwann cells under hypoxia condition

Metformin, which is the first-line drug for the treatment of diabetes mellitus type 2, has been proved to possess beneficial effects on nerve regeneration in many studies. However, the underlying mechanism is currently unclear. The present study was designed to investigate the potential beneficial effect of metformin on SCs under hypoxia condition, which is a biological process at the injury site. The cell number and cell viability of SCs were examined using fluorescence observation and MTT assay. The migration of SCs was evaluated using a Transwell chamber. The expression and secretion of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell derived neurotrophic factor (GDNF) and neural cell adhesion molecule (N-CAM) in SCs were assayed by RT-PCR and ELISA method. The results showed that metformin could help SCs recover from hypoxia injury and inhibit hypoxia-induced apoptosis. In addition, metformin could partially reverse the detrimental effect of hypoxia on cell number, viability, migration and adhesion. Metformin is also capable of maintaining the biological activities of SCs after hypoxia injury, such as increasing the expression and secretion of BDNF, NGF, GDNF, and N-CAM. Further studies showed that pre-incubation with AMPK (5'-AMP-activated protein kinase) inhibitor Compound C might partially inhibit the effect of metformin mentioned above, indicating the possible involvement of AMPK pathway in the beneficial effects of metformin on peripheral nervous system. In conclusion, metformin is capable of alleviating hypoxia-induced injury to SCs and AMPK pathway might be involved in this process.

Immunohistochemical, apoptotic and biochemical changes by dipeptidyl peptidase-4 inhibitor-sitagliptin in type-2 diabetic rats

BACKGROUND

Diabetes is a major public health problem that is rapidly increasing in prevalence. In this study, the effects of sitagliptin, a dipeptidyl peptidase-4 inhibitor, were examined on newborn diabetic rat model.

METHODS

Wistar albino newborn rats were divided into control (Ctrl), sitagliptin (Sit), diabetic and diabetic+Sit groups. On the second day after the birth, 100mg/kg streptozotocin (STZ) was administered intraperitoneally in a single dose to induce type-2 diabetes in rats. The Sit and diabetic+Sit groups were administered sitagliptin (1.5mg/kg subcutaneous) as of the day 5 for 15 days. The pancreas sections were stained with insulin (INS), glucagon (GLU), somatostatin (SS), glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-1 receptor (GLP-1R) antibodies by the streptavidin-biotin peroxidase technique. The TUNEL method for apoptosis and biochemical analysis were performed in the pancreas and serum, respectively.

RESULTS

Body weight and blood glucose levels showed significant differences among all groups on days 11 and 20. In diabetic rats following treatment with sitagliptin, the area percentage of INS immunopositive cells increased while the area percentage of SS immunopositive cells decreased, insignificantly. A significant increase was observed on the area percentage of GLU, GLP-1 and GLP-1R immunopositive cells in the diabetic+Sit group when compared to the diabetic group. The area percentage of apoptotic cells was the same among all groups. While serum glutathione and malondialdehyde levels demonstrated insignificant alterations, the catalase and superoxide dismutase activity significantly changed among four groups.

CONCLUSION

According to our findings, sitagliptin may be a useful therapeutic agent to a certain extent of type-2 diabetic condition.

Clinical utility and patient considerations in the use of the sitagliptin-metformin combination in Chinese patients

The prevalence of diabetes mellitus (DM) continues to increase each year. However, the efficacy of glucose-lowering therapies remains unsatisfactory. Moreover, the clinical characteristics and manifestations of DM in Chinese patients are different from those in Western patients. Thus, it is imperative to develop an optimal treatment protocol for lowering blood glucose levels in Chinese patients with DM. Sitagliptin has been used in People's Republic of China, and sitagliptin and metformin combination therapy may not alter their individual pharmacokinetics. To date, several clinical trials undertaken to investigate the efficacy of sitagliptin and metformin combination therapy have revealed that it effectively controlled glycated hemoglobin, fasting plasma glucose, and postprandial plasma glucose levels to a greater extent than sitagliptin or metformin alone. In addition, the combined therapy was well tolerated and induced few side effects, which were largely mild. Furthermore, the combined therapy was easy to administer, and the patients receiving this therapy showed good compliance. Therefore, for Chinese patients with type 2 DM, sitagliptin and metformin combination therapy is preferred.

The effects of dipeptidyl peptidase-4 inhibition on microvascular diabetes complications

We performed a review of the literature to determine whether the dipeptidyl peptidase-4 inhibitors (DPP4-I) may have the capability to directly and positively influence diabetic microvascular complications. The literature was scanned to identify experimental and clinical evidence that DPP4-I can ameliorate diabetic microangiopathy. We retrieved articles published between 1 January 1980 and 1 March 2014 in English-language peer-reviewed journals using the following terms: ("diabetes" OR "diabetic") AND ("retinopathy" OR "retinal" OR "nephropathy" OR "renal" OR "albuminuria" OR "microalbuminuria" OR "neuropathy" OR "ulcer" OR "wound" OR "bone marrow"); ("dipeptidyl peptidase-4" OR "dipeptidyl peptidase-IV" OR "DPP-4" OR "DPP-IV"); and ("inhibition" OR "inhibitor"). Experimentally, DPP4-I appears to improve inflammation, endothelial function, blood pressure, lipid metabolism, and bone marrow function. Several experimental studies report direct potential beneficial effects of DPP4-I on all microvascular diabetes-related complications. These drugs have the ability to act either directly or indirectly via improved glucose control, GLP-1 bioavailability, and modifying nonincretin substrates. Although preliminary clinical data support that DPP4-I therapy can protect from microangiopathy, insufficient evidence is available to conclude that this class of drugs directly prevents or decreases microangiopathy in humans independently from improved glucose control. Experimental findings and preliminary clinical data suggest that DPP4-I, in addition to improving metabolic control, have the potential to interfere with the onset and progression of diabetic microangiopathy. Further evidence is needed to confirm these effects in patients with diabetes.

Zinc supplementation alleviates diabetic peripheral neuropathy by inhibiting oxidative stress and upregulating metallothionein in peripheral nerves of diabetic rats

We investigated the effect of zinc supplementation on the expression of metallothionein, lipid peroxidation (malondialdehyde, MDA), and poly(ADP-ribose) polymerase-1 (PARP-1) in the sciatic nerve, motor nerve conduction velocity of the left sciatic posterior tibial nerve in streptozotocin (STZ)-induced diabetic rats. Twenty-four male rats were equally divided into four groups. The first group served as untreated controls although the second group received 5 mg/kg/day zinc chloride. The third group was treated with STZ to induce diabetes, and the fourth group was treated with STZ and supplemented with zinc. A gradual but insignificant decline in motor nerve conduction velocity was observed at 2 weeks of induction of diabetes. Zinc supplementation markedly attenuated the decrease in motor nerve conduction velocity at week 8 post-induction of diabetes. Furthermore, the tactile response threshold of diabetic rats receiving normal saline was lower than that of diabetic rats receiving zinc supplementation. Additionally, zinc supplementation accentuated the increase in the mRNA transcript levels of metallothionein but attenuated the increase in the mRNA transcript levels of PARP-1. At week 8 post-induction of diabetes, diabetic rats receiving normal saline had markedly higher MDA contents than diabetic rats receiving zinc supplementation. In conclusion, the present study shows that zinc has a protective effect against diabetes-induced peripheral nerve damage by stimulating metallothionein synthesis and downregulating oxidative stress.

Diabetes mellitus may induce cardiovascular disease by decreasing neuroplasticity

Neuroplasticity has been defined "the ability of the nervous system to respond to intrinsic or extrinsic stimuli by reorganizing its structure, function and connections". The nervous system monitors and coordinates internal organ function. Thus neuroplasticity may be associated with the pathogenesis of other diseases besides neuropsychiatric diseases. Decreased neuroplasticity is associated with cardiovascular disease (CVD) and a disease related to decreased neuroplasticity may confer a greater CVD risk. Diabetes mellitus (DM) is related to CVD and DM induces decreased neuroplasticity, which is manifested as depression, Alzheimer's disease and diabetic neuropathy. Therefore we conclude that DM may induce CVD by decreasing neuroplasticity.