Association of chronic diabetes and hypertension in sural nerve morphometry: an experimental study

Anethole Prevents the Alterations Produced by Diabetes Mellitus in the Sciatic Nerve of Rats

Anethole is a terpenoid with antioxidant, anti-inflammatory, and neuronal blockade effects, and the present work was undertaken to study the neuroprotective activity of anethole against diabetes mellitus (DM)-induced neuropathy. Streptozotocin-induced DM rats were used to investigate the effects of anethole treatment on morphological, electrophysiological, and biochemical alterations of the sciatic nerve (SN). Anethole partially prevented the mechanical hyposensitivity caused by DM and fully prevented the DM-induced decrease in the cross-sectional area of the SN. In relation to electrophysiological properties of SN fibers, DM reduced the frequency of occurrence of the 3rd component of the compound action potential (CAP) by 15%. It also significantly reduced the conduction velocity of the 1st and 2nd CAP components from 104.6 ± 3.47 and 39.8 ± 1.02 to 89.9 ± 3.03 and 35.4 ± 1.56 m/s, respectively, and increased the duration of the 2nd CAP component from 0.66 ± 0.04 to 0.82 ± 0.09 ms. DM also increases oxidative stress in the SN, altering values related to thiol, TBARS, SOD, and CAT activities. Anethole was capable of fully preventing all these DM electrophysiological and biochemical alterations in the nerve. Thus, the magnitude of the DM-induced neural effects seen in this work, and the prevention afforded by anethole treatment, place this compound in a very favorable position as a potential therapeutic agent for treating diabetic peripheral neuropathy.

Sympathetic skin response for early detection of type 2 diabetic peripheral neuropathy and nephropathy

BACKGROUND

Diabetic peripheral neuropathy (DPN) and diabetic nephropathy (DN) are common complications of type 2 diabetes mellitus (T2DM). Although nerve conduction studies (NCS) and sympathetic skin response (SSR) can detect DPN, the more sensitive method for early diagnosis remains unclear. Furthermore, whether DPN can be used as a predictor for diabetic nephropathy needs clarification.

METHODS

We evaluated nerve conduction studies, sympathetic skin response, and the diabetic nephropathy indicator microalbuminuria (MAU) in 192 patients with type 2 diabetes mellitus and 50 healthy controls.

RESULTS

Patients with type 2 diabetes mellitus showed a lower sensory nerve conduction velocity (SCV), sensory active nerve potential (SNAP), motor nerve conduction velocity (MCV), and compound motor action potential (CMAP) than the controls on NCS. Abnormal rates for nerve conduction studies and sympathetic skin response were 75.0% and 83.3%, respectively, in patients with type 2 diabetes mellitus. Interestingly, 54.2% of patients with normal nerve conduction studies had an abnormal sympathetic skin response. Moreover, we found a positive correlation between sympathetic skin response and microalbuminuria for the first time. The abnormal rate of microalbuminuria was 53.8%, lower than that of abnormal nerve conduction studies or sympathetic skin response patients.

CONCLUSION

Sympathetic skin response is a more sensitive method than nerve conduction studies for the early diagnosis of diabetic peripheral neuropathy. Abnormal sympathetic skin response might serve as an indicator for early diabetic nephropathy. Additionally, diabetic peripheral neuropathy may occur earlier than diabetic nephropathy in the development of type 2 diabetes mellitus.

Diabetic neuropathy: Pathogenesis and evolving principles of management

The global rise of prediabetes and diabetes has spawned an epidemic of complications associated with these conditions. Neuropathy is the most common consequence, with distal symmetric polyneuropathy (DSP) being the most prevalent. Diabetic neuropathy (DN) is a debilitating consequence of diabetes mellitus resulting in the highest morbidity and death, besides imposing a substantial financial burden on the patient. Loss of sensory function commencing distally in the lower limbs, accompanied by discomfort and considerable morbidity, characterizes diabetic neuropathy. The clinical evaluation and therapeutic options for diabetic peripheral neuropathy are multifaceted. At least fifty percent of people with diabetes acquire diabetic neuropathy over time. Good glycemic control halts the evolution in individuals with Type 1 diabetes mellitus. These results have prompted fresh attempts to comprehend the origin and develop new guidelines for prevention and treatment. New recommendations have also been established for the treatment of painful DN using separate classes of medications, with an emphasis on avoiding the use of opioids. Although our comprehension of the intricacies of diabetic neuropathy has progressed significantly over the past decade, the unique processes driving the neuropathy in type 1 and type 2 diabetes remain unexplained. Currently, glycemic control and pain management are the only effective therapies. While glucose management significantly reduces neuropathy development in type 1 diabetics, the effect is considerably lower in type 2 diabetics. Evidence supports the use of anticonvulsants and antidepressants for diabetic peripheral neuropathy pain treatment. However, the absence of disease-modifying medications for diabetic DSP necessitates the identification of unrecognized modifiable risk factors. It is imperative to identify the 'missed' risk factors and targets, allowing comprehensive, individualized care for patients.

Hypertension the 'Missed Modifiable Risk Factor' for Diabetic Neuropathy: a Systematic Review

Diabetes and hypertension stand as the major non-infectious diseases affecting 34.2 million and 1.28 billion people respectively. The literature on the impact of diabetes on hypertension and vice versa is evolving. The major objectives of this review were to compile the evolving literature establishing the role of hypertension in diabetic neuropathy, derive the exact mechanisms for its pathogenesis, and describe evidence-based precise individualized management of diabetic neuropathy in patients having diabetes complicated by hypertension. A systematic review was conducted by searching databases of PubMed, Embase, and Scopus covering the literature from inception to 2022. We included all observational and experimental studies, including both human and animal studies looking into the correlation between diabetic neuropathy and hypertension. Hypertension poses to be the leading modifiable risk factor for the development of diabetic neuropathy, especially distal symmetrical polyneuropathy, producing abnormal nerve conduction parameters and increased vibration perception threshold in patients with diabetes mellitus. Thus, we advocate that good glycemic control in patients with diabetes needs to be supported with strict blood pressure control for preventing and delaying the onset of diabetic neuropathy.

Determinants of Diabetic Peripheral Neuropathy and Their Clinical Significance: A Retrospective Cohort Study

BACKGROUND

In this study, we investigated the epidemiological characteristics and predictors of diabetic peripheral neuropathy (DPN) in adult patients with type 2 diabetes mellitus (DM).

METHODS

The study was designed as a retrospective cohort trial at the First Affiliated Hospital of Wenzhou Medical University. From January 2017 to December 2020, a total of 1,262 patients with DM were enrolled to assess the risk factors for DPN. The patients were divided into two groups (DPN group and non-DPN group). The Mann-Whitney U test or t-test, receiver operating characteristic (ROC) analyses, univariate chi-square analyses, and multiple logistic regression analyses were used to analyze the adjusted predictors of DPN.

RESULTS

The overall prevalence of DPN in DM patients was 72.7% (n = 793/1,091). Multivariate analysis revealed that age > 66 years (odds ratio [OR], 2.647; 95% confidence interval [CI] 1.469-4.770; p = 0.002), history of hypertension (OR, 1.829; 95% CI 1.146-2.920; p = 0.011), neutrophil (NE) levels exceeding 4.0 × 10⁹/L (OR 0.256; 95% CI 0.162-0.405; p = 0.001), lymphocyte (LY) levels over 3.0 × 10⁹/L (OR 7.173; 95% CI 4.258-12.086; p = 0.000), HbA1c > 7.7% (OR 3.151; 95% CI 1.959-5.068; p = 0.000), and FT3 > 4.4 pmol/L (OR 0.417; 95% CI 0.263-0.662; p = 0.000) were six significant predictive factors for the prevalence of DPN.

CONCLUSIONS

High levels of LY, HbA1c, history of hypertension, and > 66 years of age increase the risk of DPN in adult patients with DM, while high levels of NE and FT3 were protective factors of DPN. Thus, the prediction of DPN can significantly be improved by identifying older patients over the age of 66 and history of hypertension, as well as establishing the biochemical cutoff values of NE, LY, HbA1c, and FT3.

Autophagy and mTOR Pathways Mediate the Potential Renoprotective Effects of Vitamin D on Diabetic Nephropathy

Introduction

Not only is diabetic nephropathy (DN) the most common cause of end-stage renal disease worldwide, but it also increases the risk of mortality up to fourteen times compared to normoalbuminuric diabetic patients.

Aim

The aim of the current study was the evaluation of the renoprotective effects of vitamin D in DN and the possible interplay between autophagy and mTOR pathways.

Materials and Methods

Fifty male Wistar albino rats were divided (10/group) into control, DN group, insulin-treated DN group, vitamin D-treated DN group, and combined insulin and vitamin D-treated DN group. Assessments of systolic blood pressure, albuminuria, creatinine clearance, serum glucose, insulin, urea, creatinine, inflammatory cytokines, oxidative stress markers, and rat kidney gene expression of mTOR were performed. Histopathological and immunohistochemical assessments of autophagy marker LC3 in rat kidneys were also performed.

Results

DN was associated with significant increases in SBP, urinary albumin, serum glucose, urea, creatinine, inflammatory cytokines, MDA, and mTOR gene expression (P < 0.05). However, there was significant decrease in creatinine clearance, serum insulin, GSH, and H score value of LC3 when compared with control group (P < 0.05). The combination of insulin and vitamin D treatment significantly restored DN changes when compared with the other treated groups, except in oxidative stress markers where there was an insignificant difference between the combination-treated and insulin-treated groups (P > 0.05).

Conclusion

It has been concluded that vitamin D is a potent adjuvant therapy in treatment of DN via downregulation of mTOR gene expression, stimulation of autophagy, and antioxidant, anti-inflammatory, and hypotensive effects.

Superimposition of hypertension on diabetic peripheral neuropathy affects small unmyelinated sensory nerves in the skin and myelinated tibial and sural nerves in rats with alloxan-induced type 1 diabetes

Diabetic peripheral neuropathy (DPN) is a major complication of diabetes mellitus, and hypertension is considered to be a risk factor for DPN in patients with type 1 diabetes (T1DM). However, the morphological effects of hypertension on DPN are unclear. In this study, we investigated the effect of hypertension on DPN by investigating the changes in unmyelinated and myelinated nerve fibers in hypertensive rats with alloxan (AL)-induced T1DM. Thirteen-week-old WBN/Kob rats with AL-induced diabetes were allocated to receive tap water only (AL group), tap water containing 0.5% saline (0.5AN group), or tap water containing 0.75% saline (0.75AN group) for 15 weeks. Hyperglycemia was maintained for 15 weeks, and the animals were euthanized at 28 weeks. By 23 weeks of age, the systolic blood pressure was significantly higher in the 0.75AN and 0.5AN groups than in the AL group and was unchanged in all groups at 28 weeks. The number of intraepidermal sensory unmyelinated nerve fibers was significantly smaller in the 0.75AN and 0.5AN groups than in the AL group. The axonal size in the myelinated tibial and sural nerve fibers was significantly smaller in the 0.75AN group than in the AL group. Furthermore, luminal narrowing and endothelial hypertrophy were observed in the endoneurial tibial nerve vessels in the 0.75AN group. These findings suggest that superimposing hypertension on hyperglycemia may accelerate a reduction in the number of small unmyelinated sensory nerve fibers in the skin and induce mild axonal atrophy in myelinated tibial and sural nerve fibers in rats with AL-induced T1DM.

Hypertension Contributes to Neuropathy in Patients With Type 1 Diabetes

BACKGROUND

Diabetic peripheral neuropathy (DPN) can lead to foot ulceration and amputation. There are currently no disease-modifying therapies for DPN. The aim of this study was to determine if hypertension contributes to DPN in patients with type 1 diabetes mellitus (T1DM).

METHODS

Subjects with T1DM (n = 70) and controls (n = 78) underwent a comprehensive assessment of DPN.

RESULTS

Hypertension was present in 40 of 70 T1DM subjects and 20 of 78 controls. Hypertension was associated with abnormal nerve conduction parameters (P = 0.03 to <0.001), increased vibration perception threshold (P = 0.01) and reduced corneal nerve fiber density and length (P = 0.02) in subjects with T1DM. However, after adjusting for confounding factors only tibial compound motor action potential and nerve conduction velocity were associated with hypertension (P = 0.03) and systolic blood pressure (P < 0.01 to <0.0001). Hypertension had no effect on neuropathy in subjects without diabetes.

CONCLUSIONS

This study shows that hypertension is associated with impaired nerve conduction in T1DM. It supports previous small trials showing that angiotensin-converting enzyme inhibitors improve nerve conduction and advocates the need for larger clinical trials with blood pressure lowering agents in DPN.

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.