Global risk management in type 2 diabetes: blood glucose, blood pressure, and lipids--update on the background of the current guidelines

Lumbar sympathetic pulsed radiofrequency combined with continuous epidural infusion for treatment of painful diabetic neuropathy: A report of two cases and a literature review

Diabetic neuropathy (DN), one of the most common late complications of diabetes mellitus, significantly affects distinct regions of the nervous system. Pain management is challenging in DN as no effective therapies exist that reverse the pathological course of DN. Several drugs are recommended as the first-line treatment for painful DN, but these are associated with various side-effects in the long term. This report presents two cases with painful DN who underwent lumbar sympathetic pulsed radiofrequency combined with continuous epidural infusion. The two cases were followed for 30 days. Lumbar sympathetic pulsed radiofrequency combined with continuous epidural infusion offered effective pain relief and improved the health-related quality of life in two patients with DN over this time period.

Statins and Neuropathic Pain: A Narrative Review

The frequently prescribed drug class of statins have pleiotropic effects and have been implicated in neuropathic pain syndromes. This narrative review examines studies of statin-induced neuropathic pain which to date have been conducted only in animal models. However, the pathophysiology of diabetic neuropathy in humans may shed some light on the etiology of neuropathic pain. Statins have exhibited a paradoxical effect in that statins appear to reduce neuropathic pain in animals but have been associated with neuropathic pain in humans. While there are certain postulated mechanisms offering elucidation as to how statins might be associated with neuropathic pain, there is, as the American Heart Association stated, to date no definitive association between statins and neuropathic pain. Statins are important drugs that reduce cardiovascular risk factors and should be prescribed to appropriate patients with these risk factors but some of this population is also at elevated risk for neuropathic pain from other causes.

High-glucose/high-cholesterol diet in zebrafish evokes diabetic and affective pathogenesis: The role of peripheral and central inflammation, microglia and apoptosis

Neuroinflammation and metabolic deficits contribute to the etiology of human affective disorders, such as anxiety and depression. The zebrafish (Danio rerio) has recently emerged as a powerful new model organism in CNS disease modeling. Here, we exposed zebrafish to 2% glucose and 10% cholesterol for 19 days to experimentally induce type 2 diabetes (DM) and to assess stress responses, microglia, inflammation and apoptosis. We analyzed zebrafish anxiety-like behavior in the novel tank and light-dark box (Days 15-16) tests, as well as examined their biochemical and genomic biomarkers (Day 19). Confirming DM-like state in zebrafish, we found higher whole-body glucose, triglyceride, total cholesterol, low-density lipoprotein levels and glucagon mRNA expression, and lower high-density lipoprotein levels. DM zebrafish also showed anxiety-like behavior, elevated whole-body cortisol and cytokines IFN-γ and IL-4, as well as higher brain mRNA expression of the glucocorticoid receptor, CD11b (a microglial biomarker), pro-inflammatory cytokines IL-6 and TNF-α (but not IL-1β or anti-inflammatory cytokines IL-4 and IL-10), GFAP (an astrocytal biomarker), neurotrophin BDNF, its receptors p75 and TrkB, as well as apoptotic Bax and Caspase-3 (but not BCl-2) genes. Collectively, this supports the overlapping nature of DM-related affective pathogenesis and emphasizes the role of peripheral and central inflammation and apoptosis in DM-related affective and neuroendocrine deficits in zebrafish.

N-ϒ-(l-Glutamyl)-l-Selenomethionine Inhibits Fat Storage via the Stearoyl-CoA Desaturases FAT-6 and FAT-7 and the Selenoprotein TRXR-1 in Caenorhabditis elegans

SCOPE

Selenium is an important nutrient for human health. The influence of dietary selenium on lipid metabolism remains largely unknown. N-γ-(l-glutamyl)-l-selenomethionine (Glu-SeMet) on inhibition of fat accumulation and its underlying mechanisms in the nematode Caenorhabditis elegans are investigated.

METHODS AND RESULTS

Triacylglyceride quantification and post-fixed Nile red staining methods are conducted to evaluate fat accumulation in wild-type N2 worms in normal or high-glucose diet. Glu-SeMet (0.01 µm) treatment effectively reduces fat storage in wild-type N2 C. elegans in both a normal and high-glucose diet. Further evidence shows that Glu-SeMet (0.01 µm) decreases the ratio of oleic acid/stearic acid (C18:1Δ9/C18:0) using gas chromatography-mass spectrometry analysis. The mRNA levels of fatty acid stearoyl-CoA desaturases, FAT-6 and FAT-7, and the mediator-15 (MDT-15) are downregulated while the wild-type N2 worms are co-treated with high glucose and Glu-SeMet (0.01 µm). The effect of reduced fat accumulation is absent in fat-6, fat-7, and trxr-1 mutant worms under high glucose and Glu-SeMet (0.01 µm) co-treatment.

CONCLUSIONS

This study demonstrates that Glu-SeMet inhibiting fat accumulation may be associated with FAT-6 and FAT-7 and the selenoprotein TRXR-1 in C. elegans. This study implies a potential for Glu-SeMet as a new treatment for obesity or its complications.

Neurological consequences of obesity

The high prevalence of obesity is associated with an enormous medical, social, and economic burden. The metabolic dysfunction, dyslipidaemia, and inflammation caused by obesity contribute to the development of a wide variety of disorders and effects on the nervous system. In the CNS, mild cognitive impairment can be attributed to obesity-induced alterations in hippocampal structure and function in some patients. Likewise, compromised hypothalamic function and subsequent defects in maintaining whole-body energy balance might be early events that contribute to weight gain and obesity development. In the peripheral nervous system, obesity-driven alterations in the autonomic nervous system prompt imbalances in sympathetic-parasympathetic activity, while alterations in the sensory-somatic nervous system underlie peripheral polyneuropathy, a common complication of diabetes. Pharmacotherapy and bariatric surgery are promising interventions for people with obesity that can improve neurological function. However, lifestyle interventions via dietary changes and exercise are the preferred approach to combat obesity and reduce its associated health risks.

Effects of Ezetimibe/Simvastatin and Rosuvastatin on Oxidative Stress in Diabetic Neuropathy: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Objective. To evaluate the effects of ezetimibe/simvastatin (EZE/SIMV) and rosuvastatin (ROSUV) on oxidative stress (OS) markers in patients with diabetic polyneuropathy (DPN). Methods. We performed a randomized, double-blind, placebo-controlled phase III clinical trial in adult patients with Type 2 Diabetes Mellitus (T2DM) and DPN, as evaluated by composite scores and nerve conduction studies (NCS). Seventy-four subjects with T2DM were allocated 1 : 1 : 1 to placebo, EZE/SIMV 10/20 mg, or ROSUV 20 mg for 16 weeks. All patients were assessed before and after treatment: primary outcomes were lipid peroxidation (LPO), and nitric oxide (NO) surrogate levels in plasma; secondary outcomes included NCS, neuropathic symptom scores, and metabolic parameters. Data were expressed as mean ± SD or SEM, frequencies, and percentages; we used nonparametric analysis. Results. LPO levels were reduced in both statin arms after 16 weeks of treatment (p < 0.05 versus baseline), without changes in the placebo group. NO levels were not significantly affected by statin treatment, although a trend towards significance concerning increased NO levels was noted in both statin arms. No significant changes were observed for the NCS or composite scores. Discussion. EZE/SIMV and ROSUV are superior to placebo in reducing LPO in subjects with T2DM suffering from polyneuropathy. This trial is registered with NCT02129231.

Severe hypertriglyceridemia and hypercholesterolemia accelerating renal injury: a novel model of type 1 diabetic hamsters induced by short-term high-fat / high-cholesterol diet and low-dose streptozotocin

Background

Hyperlipidemia is thought to be a major risk factor for the progression of renal diseases in diabetes. Recent studies have shown that lipid profiles are commonly abnormal early on type 2 diabetes mellitus (T2DM) with diabetic nephropathy. However, the early effects of triglyceride and cholesterol abnormalities on renal injury in type 1 diabetes mellitus (T1DM) are not fully understood and require reliable animal models for exploration of the underlying mechanisms. Hamster models are important tools for studying lipid metabolism because of their similarity to humans in terms of lipid utilization and high susceptibility to dietary cholesterol and fat.

Methods

Twenty-four male Golden Syrian hamsters (100–110 g) were rendered diabetes by intraperitoneal injections of streptozotocin (STZ) on consecutive 3 days at dose of 30 mg/kg, Ten days after STZ injections, hamsters with a plasma Glu concentration more than 12 mmol/L were selected as insulin deficient ones and divided into four groups (D-C, D-HF, D-HC, and D-HFHC), and fed with commercially available standard rodent chow, high-fat diet, high-cholesterol diet, high-fat and cholesterol diet respectively, for a period of four weeks.

Results

After an induction phase, a stable model of renal injury was established with the aspects of early T1DM kidney disease, These aspects were severe hypertriglyceridemia, hypercholesterolemia, proteinuria with mesangial matrix accumulation, upgraded creatinine clearance, significant cholesterol and triglyceride deposition, and increasing glomerular surface area, thickness of basement membrane and mesangial expansion. The mRNA levels of sterol regulatory element binding protein-1c, transforming growth factors-β, plasminogen activator inhibitor-1, tumor necrosis factor-α and interleukin-6 in the D-HFHC group were significantly up-regulated compared with control groups.

Conclusions

This study presents a novel, non-transgenic, non-surgical method for induction of renal injury in hamsters, which is an important complement to existing diabetic models for pathophysiological studies in early acute and chronic kidney disease, especially hyperlipidemia. These data suggest that both severe hypertriglyceridemia and hypercholesterolemia can accelerate renal injury in the early development of T1DM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0041-5) contains supplementary material, which is available to authorized users.

Long-chain acyl coenzyme A synthetase 1 overexpression in primary cultured Schwann cells prevents long chain fatty acid-induced oxidative stress and mitochondrial dysfunction

AIMS

High circulating long chain fatty acids (LCFAs) are implicated in diabetic neuropathy (DN) development. Expression of the long-chain acyl-CoA synthetase 1 (Acsl1) gene, a gene required for LCFA metabolic activation, is altered in human and mouse diabetic peripheral nerve. We assessed the significance of Acsl1 upregulation in primary cultured Schwann cells.

RESULTS

Acsl1 overexpression prevented oxidative stress (nitrotyrosine; hydroxyoctadecadienoic acids [HODEs]) and attenuated cellular injury (TUNEL) in Schwann cells following 12 h exposure to LCFAs (palmitate, linoleate, and oleate, 100 μM). Acsl1 overexpression potentiated the observed increase in medium to long-chain acyl-carnitines following 12 h LCFA exposure. Data are consistent with increased mitochondrial LCFA uptake, largely directed to incomplete beta-oxidation. LCFAs uncoupled mitochondrial oxygen consumption from ATP production. Acsl1 overexpression corrected mitochondrial dysfunction, increasing coupling efficiency and decreasing proton leak.

INNOVATION

Schwann cell mitochondrial function is critical for peripheral nerve function, but research on Schwann cell mitochondrial dysfunction in response to hyperlipidemia is minimal. We demonstrate that high levels of a physiologically relevant mixture of LCFAs induce Schwann cell injury, but that improved mitochondrial uptake and metabolism attenuate this lipotoxicity.

CONCLUSION

Acsl1 overexpression improves Schwann cell function and survival following high LCFA exposure in vitro; however, the observed endogenous Acsl1 upregulation in peripheral nerve in response to diabetes is not sufficient to prevent the development of DN in murine models of DN. Therefore, targeted improvement in Schwann cell metabolic disposal of LCFAs may improve DN phenotypes.

Role of insulin signaling impairment, adiponectin and dyslipidemia in peripheral and central neuropathy in mice

One of the tissues or organs affected by diabetes is the nervous system, predominantly the peripheral system (peripheral polyneuropathy and/or painful peripheral neuropathy) but also the central system with impaired learning, memory and mental flexibility. The aim of this study was to test the hypothesis that the pre-diabetic or diabetic condition caused by a high-fat diet (HFD) can damage both the peripheral and central nervous systems. Groups of C57BL6 and Swiss Webster mice were fed a diet containing 60% fat for 8 months and compared to control and streptozotocin (STZ)-induced diabetic groups that were fed a standard diet containing 10% fat. Aspects of peripheral nerve function (conduction velocity, thermal sensitivity) and central nervous system function (learning ability, memory) were measured at assorted times during the study. Both strains of mice on HFD developed impaired glucose tolerance, indicative of insulin resistance, but only the C57BL6 mice showed statistically significant hyperglycemia. STZ-diabetic C57BL6 mice developed learning deficits in the Barnes maze after 8 weeks of diabetes, whereas neither C57BL6 nor Swiss Webster mice fed a HFD showed signs of defects at that time point. By 6 months on HFD, Swiss Webster mice developed learning and memory deficits in the Barnes maze test, whereas their peripheral nervous system remained normal. In contrast, C57BL6 mice fed the HFD developed peripheral nerve dysfunction, as indicated by nerve conduction slowing and thermal hyperalgesia, but showed normal learning and memory functions. Our data indicate that STZ-induced diabetes or a HFD can damage both peripheral and central nervous systems, but learning deficits develop more rapidly in insulin-deficient than in insulin-resistant conditions and only in Swiss Webster mice. In addition to insulin impairment, dyslipidemia or adiponectinemia might determine the neuropathy phenotype.

Chewing the fat: genetic approaches to model dyslipidemia-induced diabetic neuropathy in mice

Emerging clinical evidence now suggests that dyslipidemia may be strongly linked with the development and progression of neuropathy in diabetic patients, and dyslipidemia is considered an important risk factor for the development of diabetic neuropathy. However, because of important species differences, current animal models fall short of accurately replicating human diabetic dyslipidemia. Rodents resist expansion in low-density lipoprotein cholesterol (LDL-C) and typically maintain or increase high-density lipoprotein cholesterol (HDL-C), despite prolonged high-fat feeding. Here, we discuss the findings of Hinder et al., in which they utilized novel genetic experimental approaches to develop a diabetic mouse model with human-like dyslipidemia. The authors created a mouse with an apolipoprotein E (ApoE) knockout in conjunction with a leptin receptor mutation. A triple mutant mouse with both ApoE and apolipoprotein B48 knockout and leptin deficiency was also created in an effort to generate a model of diabetic dyslipidemia that better mimics the human condition. The long-term goal of these studies is to develop more faithful models to address how hyperglycemia and hyperlipidemia may drive the development and progression of neuropathy. Hinder and colleagues were successful at creating a diabetic mouse model with severe hypertriglyceridemia, hypercholesterolemia, and a significant increase in the total cholesterol to HDL-C ratio. This work was successful in establishing a model of diabetic dyslipidemia that more closely emulates the poor lipid profile observed in human diabetic patients with neuropathy. This commentary will also review current models used to study the effects of dyslipidemia on diabetic neuropathy and highlight a proposed mechanism for the role of dyslipidemia in the pathogenesis of diabetic neuropathy.

Apolipoprotein E knockout as the basis for mouse models of dyslipidemia-induced neuropathy

Dyslipidemia has been identified as an important pathogenic risk factor for diabetic neuropathy, but current animal models do not adequately reproduce the lipid profile observed in human diabetics (increased triglycerides with an elevated LDL-cholesterol and reduced HDL-cholesterol). High fat feeding of mice produces hyperlipidemia, but mice are resistant to increases in the LDL to HDL ratio, reducing the potential for peripheral lipid deposits to impact neuropathy, as is postulated to occur in human subjects. Genetic manipulations provide an alternative approach to reproducing a neuropathic plasma lipid profile. Based on findings from the atherosclerosis literature, we began with knockout of ApoE. Since knockout of ApoE alone only partially mimics the human diabetic lipid profile, we examined the impact of its combination with a well-characterized model of type 2 diabetes exhibiting neuropathy, the db/db mouse. We added further gene manipulations to increase hyperlipidemia by using mice with both ApoE and ApoB48 knockout on the ob/+ (leptin mutation) mice. In all of these models, we found that either the db/db or ob/ob genotypes had increased body weight, hyperlipidemia, hyperglycemia, and evidence of neuropathy compared with the control groups (db/+ or ob/+, respectively). We found that ApoE knockout combined with leptin receptor knockout produced a lipid profile most closely modeling human dyslipidemia that promotes neuropathy. ApoE knockout combined with additional ApoB48 and leptin knockout produced similar changes of smaller magnitude, but, notably, an increase in HDL-cholesterol. Our data suggest that the overall effects of ApoE knockout, either directly upon nerve structure and function or indirectly on lipid metabolism, are insufficient to significantly alter the course of diabetic neuropathy. Although these models ultimately do not deliver optimal lipid profiles for translational diabetic neuropathy research, they do present glycemic and lipid profile properties of value for future therapeutic investigations.

Diabetic neuropathy: clinical manifestations and current treatments

Diabetic peripheral neuropathy is a prevalent, disabling disorder. The most common manifestation is distal symmetrical polyneuropathy (DSP), but many patterns of nerve injury can occur. Currently, the only effective treatments are glucose control and pain management. While glucose control substantially decreases the development of neuropathy in those with type 1 diabetes, the effect is probably much smaller in those with type 2 diabetes. Evidence supports the use of specific anticonvulsants and antidepressants for pain management in patients with diabetic peripheral neuropathy. However, the lack of disease-modifying therapies for diabetic DSP makes the identification of new modifiable risk factors essential. Growing evidence supports an association between components of the metabolic syndrome, including prediabetes, and neuropathy. Studies are needed to further explore this association, which has implications for the development of new treatments for this common disorder.

Hyperlipidemia: a new therapeutic target for diabetic neuropathy

Emerging data establish dyslipidemia as a significant contributor to the development of diabetic neuropathy. In this review, we discuss how separate metabolic imbalances, including hyperglycemia and hyperlipidemia, converge on mechanisms leading to oxidative stress in dorsal root ganglia (DRG) sensory neurons. We conclude with suggestions for novel therapeutic strategies to prevent or reverse diabetes-induced nerve degeneration.

Effects of blood pressure lowering and intensive glucose control on the incidence and progression of retinopathy in patients with type 2 diabetes mellitus: a randomised controlled trial

AIMS/HYPOTHESIS

The aim of the present study was to investigate the effect of blood pressure lowering and intensive glucose control on the incidence and progression of retinopathy in type 2 diabetic patients.

METHODS

The Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation (ADVANCE) Retinal Measurements study, a substudy of ADVANCE, is a randomised (using a central, computer-based procedure) controlled 2 x 2 factorial trial comprising a double-blind comparison of blood pressure lowering with perindopril-indapamide vs placebo, and an open comparison of standard vs intensive glucose control targeting a HbA(1c) of < or = 6.5% in 1,602 diabetic patients from ADVANCE centres with access to retinal cameras conducted from 2001 to 2008. At baseline and the final visit, seven-field stereoscopic retinal photographs were taken and graded by blinded readers (gradeable baseline and final photographs from 1,241 patients). Progression of > or =2 steps in the Early Treatment of Diabetic Retinopathy Study classification (using the eye with worst grading) was the primary outcome.

RESULTS

Retinopathy progressed in 59 (4.8%) patients and developed in 128 (10.3%) patients over 4.1 years. Fewer patients on blood pressure-lowering treatment (n = 623) experienced incidence or progression of retinopathy compared with patients on placebo (n = 618), but the difference was not significant (OR 0.78; 95% CI 0.57-1.06; p = 0.12). Blood pressure-lowering treatment reduced the occurrence of macular oedema (OR 0.50; 95% CI 0.29-0.88; p = 0.016) and arteriovenous nicking compared with placebo (OR 0.60; 95% CI 0.38-0.94; p = 0.025). Compared with standard glucose control (n = 611), intensive glucose control (n = 630) did not reduce (p = 0.27) the incidence and progression of retinopathy (OR 0.84; 95% CI 0.61-1.15). Lower, borderline significant risks of microaneurysms, hard exudates and macular oedema were observed with intensive glucose control, adjusted for baseline retinal haemorrhages. These effects of the two treatments were independent and additive. Adverse events in the ADVANCE study are reported elsewhere.

CONCLUSIONS/INTERPRETATION

Blood pressure lowering or intensive glucose control did not significantly reduce the incidence and progression of retinopathy, although consistent trends towards a benefit were observed, with significant reductions in some lesions observed with both interventions.

TRIAL REGISTRATION

ClinicalTrials.gov ID no. NCT00145925.

FUNDING

Grants from Servier and the National Health and Medical Research Council of Australia.

Exenatide

Exenatide (Byetta) is a novel, synthetic, incretin mimetic, glucoregulatory peptide approved in the US and Europe for the treatment of patients with type 2 diabetes mellitus who have inadequate glycaemic control despite receiving treatment with maximum tolerated doses of metformin and/or a sulfonylurea. In randomised, controlled, phase III trials and post hoc completer analyses in this patient population, the addition of subcutaneous exenatide twice daily significantly improved glycaemic control and was associated with progressive and significant bodyweight reduction from baseline for up to 2 years. The overall intensity of glycaemic control with exenatide was similar to that achieved with once-daily insulin glargine or twice-daily biphasic insulin aspart. Exenatide was generally well tolerated. Most adverse events were mild to moderate in severity and gastrointestinal in nature. The overall rate of hypoglycaemia was similar to rates observed with placebo (when administered with metformin) and insulin comparators (when administered with metformin and a sulfonylurea). The addition of exenatide to therapy with metformin and a sulfonylurea provided significant improvements in treatment satisfaction and patients' health-related quality of life (HR-QOL). The drug was also cost effective compared with pioglitazone, glibenclamide (glyburide), insulin glargine (all in combination with metformin and/or a sulfonylurea) and metformin alone. Overall, adjunctive therapy with exenatide is a valuable therapeutic option in patients with type 2 diabetes requiring moderate improvements in glycaemic control despite treatment with metformin and/or a sulfonylurea.

Rationale and design of the AdRem study: Evaluating the effects of blood pressure lowering and intensive glucose control on vascular retinal disorders in patients with type 2 diabetes mellitus

The ADVANCE Retinal Measurements (AdRem) Study is a large intervention study evaluating the effects of target driven intensive glucose control and placebo controlled blood pressure lowering on retinal vascular changes. AdRem is a sub-study of the ADVANCE Study (Action in Diabetes and Vascular disease), a 2x2 factorial randomized controlled trial with an ACE inhibitor-diuretic combination (perindopril-indapamide) and a gliclazide MR-based regimen in patients with type 2 diabetes mellitus. The AdRem study is based on seven-field stereoscopic retinal photographs of both eyes. These are taken within 3 months after randomization in ADVANCE (baseline), at the biennial and at the final visit. The primary outcome is progression of two or more steps in ETDRS classification. Secondary outcomes include progression of retinal vascular lesions and distortion of retinal vascular geometry. Retinal photographs are made on film and digitized at a central laboratory. The AdRem study uses fully digitized quality control and grading. Between August 2002 and January 2004 1978 patients were included in the AdRem study, from 39 centers in 14 countries. Approximately 85% comply with the strict AdRem quality requirements. Publication of the results is expected in early 2008. The AdRem study is designed to provide reliable evidence on the effects of intensive glucose control and blood pressure lowering on both diabetic retinopathy and abnormalities of retinal vasculature in patients with type 2 diabetes mellitus.

Exenatide

Exenatide is an incretin mimetic. It improves glycaemic control via various glucoregulatory mechanisms, including glucose-dependent insulinotropism, suppression of inappropriately high glucagon levels, delayed gastric emptying and reduction of food intake. In three large, well designed, phase III trials in adults with type 2 diabetes mellitus and suboptimal glycaemic control despite treatment with metformin and/or a sulfonylurea, mean changes from baseline in glycosylated haemoglobin (HbA(1c)) significantly favoured subcutaneous exenatide 5 or 10microg twice daily over placebo after 30 weeks' treatment (primary endpoint). Relative to placebo, reductions from baseline in bodyweight were significantly greater with twice-daily exenatide 5microg (in two studies) or 10microg (in all three studies). Post hoc completer analyses revealed that the beneficial effects of exenatide on HbA(1c) and bodyweight were maintained for up to 82 weeks. Adjunctive therapy with subcutaneous exenatide 10microg twice daily improved glycaemic control to a similar extent as insulin glargine in patients with type 2 diabetes suboptimally controlled with metformin plus a sulfonylurea in a large, well designed, 26-week, phase III trial. Subcutaneous exenatide was generally well tolerated in patients with type 2 diabetes. The incidence of hypoglycaemia in patients receiving exenatide plus metformin was similar to that seen in placebo plus metformin recipients; however, in patients receiving a sulfonylurea (with or without metformin), the incidence of hypoglycaemia was numerically higher with exenatide than with placebo.