Efficacy of Oral Mixed Tocotrienols in Diabetic Peripheral Neuropathy: A Randomized Clinical Trial

Pharmacological and non-pharmacological treatments for neuropathic pain: Systematic review and French recommendations

Neuropathic pain remains a significant unmet medical need. Several recommendations have recently been proposed concerning pharmacotherapy, neurostimulation techniques and interventional management, but no comprehensive guideline encompassing all these treatments has yet been issued. We performed a systematic review of pharmacotherapy, neurostimulation, surgery, psychotherapies and other types of therapy for peripheral or central neuropathic pain, based on studies published in peer-reviewed journals before January 2018. The main inclusion criteria were chronic neuropathic pain for at least three months, a randomized controlled methodology, at least three weeks of follow-up, at least 10 patients per group, and a double-blind design for drug therapy. Based on the GRADE system, we provide weak-to-strong recommendations for use and proposal as a first-line treatment for SNRIs (duloxetine and venlafaxine), gabapentin and tricyclic antidepressants and, for topical lidocaine and transcutaneous electrical nerve stimulation specifically for peripheral neuropathic pain; a weak recommendation for use and proposal as a second-line treatment for pregabalin, tramadol, combination therapy (antidepressant combined with gabapentinoids), and for high-concentration capsaicin patches and botulinum toxin A specifically for peripheral neuropathic pain; a weak recommendation for use and proposal as a third-line treatment for high-frequency rTMS of the motor cortex, spinal cord stimulation (failed back surgery syndrome and painful diabetic polyneuropathy) and strong opioids (in the absence of an alternative). Psychotherapy (cognitive behavioral therapy and mindfulness) is recommended as a second-line therapy, as an add-on to other therapies. An algorithm encompassing all the recommended treatments is proposed.

The emerging role of dyslipidemia in diabetic microvascular complications

PURPOSE OF REVIEW

To summarize recent advancements in our understanding of the impact of dyslipidemia on microvascular complications in type 2 diabetes (T2D), with an emphasis on peripheral neuropathy and nephropathy.

RECENT FINDINGS

Mounting evidence suggests that rigorous glycemic control only mitigates certain microvascular complications in T2D patients. Particularly, well regulated blood glucose levels only marginally improve peripheral neuropathy in the T2D setting. Dyslipidemia, an abnormal lipid profile, is emerging as a key factor in peripheral neuropathy. Furthermore, although glycemic control may prevent or slow nephropathy, recent developments demonstrate that dyslipidemia can also affect kidney outcomes in normoglycemic patients. Transcriptomic, epigenomic, and lipidomic investigations, as well as integrative approaches, are shedding light on potential pathomechanisms. These molecular studies are identifying possible targets for therapeutic intervention. Complementing molecular research, lifestyle interventions are on-going to assess whether dietary choices and/or exercise, weight-loss, or surgical interventions, such as bariatric surgery, can ameliorate peripheral neuropathy and nephropathy in T2D patients.

SUMMARY

Dyslipidemia is an emerging mechanism in microvascular complications in T2D. Elucidating the molecular pathomechanisms may pinpoint potential lipid-centric treatments. Interventional studies of dietary changes, exercise, or weight-loss surgery may also positively impact these highly prevalent and morbid complications.

[Diabetic polyneuropathy]

Approximately one of three people with diabetes is affected by distal symmetric sensorimotor polyneuropathy (DSPN) which is associated with marked impairment in quality of life due to partly excruciating neuropathic pain on the one hand and painless foot ulcers on the other hand. The prevalence of painful DSPN may reach up to one quarter of patients with diabetes, while DSPN may be asymptomatic in up to half of the patients affected. Regrettably, DSPN still remains underdiagnosed. Typical neuropathic symptoms include pain, paresthesias and numbness particularly in the feet and calves. The management of DSPN includes three cornerstones: (1) lifestyle modification, causal treatment aimed at near-normoglycemia and multifactorial cardiovascular risk intervention, (2) pathogenesis-derived treatment and (3) symptomatic treatment of neuropathic pain. Multimodal pain treatment should not only aim at pain relief, but also allow for improvement in quality of sleep, mobility, and general quality of life.

Potential Role of Tocotrienols on Non-Communicable Diseases: A Review of Current Evidence

Tocotrienol (T3) is a subfamily of vitamin E known for its wide array of medicinal properties. This review aimed to summarize the health benefits of T3, particularly in prevention or treatment of non-communicable diseases (NCDs), including cardiovascular, musculoskeletal, metabolic, gastric, and skin disorders, as well as cancers. Studies showed that T3 could prevent various NCDs, by suppressing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the mevalonate pathway, inflammatory response, oxidative stress, and alternating hormones. The efficacy of T3 in preventing/treating these NCDs is similar or greater compared to tocopherol (TF). TF may lower the efficacy of T3 because the efficacy of the combination of TF and T3 was lower than T3 alone in some studies. Data investigating the effects of T3 on osteoporosis, arthritis, and peptic ulcers in human are limited. The positive outcomes of T3 treatment obtained from the preclinical studies warrant further validation from clinical trials.

Reactive Oxygen Comes of Age: Mechanism-Based Therapy of Diabetic End-Organ Damage

Reactive oxygen species (ROS) have been mainly viewed as unwanted by-products of cellular metabolism, oxidative stress, a sign of a cellular redox imbalance, and potential disease mechanisms, such as in diabetes mellitus (DM). Antioxidant therapies, however, have failed to provide clinical benefit. This paradox can be explained by recent discoveries that ROS have mainly essential signaling and metabolic functions and evolutionally conserved physiological enzymatic sources. Disease can occur when ROS accumulate in nonphysiological concentrations, locations, or forms. By focusing on disease-relevant sources and targets of ROS, and leaving ROS physiology intact, precise therapeutic interventions are now possible and are entering clinical trials. Their outcomes are likely to profoundly change our concepts of ROS in DM and in medicine in general.

Novel Insights into Sensorimotor and Cardiovascular Autonomic Neuropathy from Recent-Onset Diabetes and Population-Based Cohorts

The most prevalent chronic complications of diabetes are diabetic neuropathies, among which distal sensorimotor polyneuropathy (DSPN) and cardiovascular autonomic neuropathy (CAN) are the best studied. Their major clinical sequelae such as foot ulcers, neuropathic pain, and orthostatic hypotension are associated with lower quality of life and increased risk of mortality. Here we discuss the recent insights into DSPN and CAN focusing on two prospective cohorts; that is, the German Diabetes Study (GDS) including recent-onset diabetes patients and the population-based Cooperative Health Research in the Region of Augsburg, Germany (KORA) surveys. The insights from these studies investigating novel tools for early detection and prediction of (pre)diabetic neuropathy as well as biomarkers of oxidative stress and inflammation should ultimately culminate in improving the health care of patients affected by this serious condition.

The Role of Tocotrienol in Protecting Against Metabolic Diseases

Obesity is a major risk factor for diabetes, and these two metabolic conditions cause significant healthcare burden worldwide. Chronic inflammation and increased oxidative stress due to exposure of cells to excess nutrients in obesity may trigger insulin resistance and pancreatic β-cell dysfunction. Tocotrienol, as a functional food component with anti-inflammatory, antioxidant, and cell signaling-mediating effects, may be a potential agent to complement the current management of obesity and diabetes. The review aimed to summarize the current evidence on the anti-obesity and antidiabetic effects of tocotrienol. Previous studies showed that tocotrienol could suppress adipogenesis and, subsequently, reduce body weight and fat mass in animals. This was achieved by regulating pathways of lipid metabolism and fatty acid biosynthesis. It could also reduce the expression of transcription factors regulating adipogenesis and increase apoptosis of adipocytes. In diabetic models, tocotrienol was shown to improve glucose homeostasis. Activation of peroxisome proliferator-activated receptors was suggested to be responsible for these effects. Tocotrienol also prevented multiple systemic complications due to obesity and diabetes in animal models through suppression of inflammation and oxidative stress. Several clinical trials have been conducted to validate the antidiabetic of tocotrienol, but the results were heterogeneous. There is no evidence showing the anti-obesity effects of tocotrienol in humans. Considering the limitations of the current studies, tocotrienol has the potential to be a functional food component to aid in the management of patients with obesity and diabetes.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.