Nerve damage in patients with diabetes is known as diabetic neuropathy and is considered as the most prevalent microvascular complication—up to 60%—in Type 2 Diabetes Mellitus (T2DM) subjects [
The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are potent inhibitors of cholesterol biosynthesis. Various clinical trials have shown beneficial effects of statins in the prevention of cardiovascular diseases [
Simvastatin (SIMV), a lipophilic statin with intrinsic antioxidant activity, has been demonstrated to possess higher antihydroxyl radical activity than other statins [
Thus, based on the aforementioned evidence regarding the plausible relationship between OS and DPN, and the promising pleiotropic effects of statins on this scenario, this randomized clinical trial was performed to evaluate the value of SIMV and ROSUV concerning the reduction of OS in patients with T2DM and DPN.
A randomized, double-blind, placebo-controlled phase III clinical trial was performed at the Clinical and Experimental Therapeutics Institute, University of Guadalajara, Mexico. Subjects were assigned to three group treatments in blocks with a parallel sequence 1 : 1 : 1, through a randomized computer-based list generated by a different researcher unaware of the drugs given. Patients received once-a-day single-dose for 16 weeks of each treatment: controls received placebo, ezetimibe/SIMV (EZE/SIMV) 10/20 mg, and ROSUV 20 mg. We wanted to evaluate two high potency statins; in our Country, we lack rosuvastatin 5 mg dosage. Simvastatin monotherapy doses of 80 mg/day equal rosuvastatin 10 mg; however, high doses of statins increase the risk of adverse reactions; that is why we chose a combination therapy to reach similar effects and reduce adverse events. Patients were instructed to take their drugs in the evening at the same time every day. All drugs were similar in physical characteristics and presented in dark bottles, carefully filled by another group researcher who placed a respective tag with the patient code. Apart, patients were provided with a diary, whereby they wrote down the date and time of drug administration, as well as any drug adverse reactions experienced. Compliance was assessed by a coresearcher through pill counting and review of the diary provided. Such information was collected and registered every 4 weeks. The selection period was performed from February 2012 to January 2013. We did not influence or change their standard medications or lifestyle (dietary patterns and physical activity) during the study. Their family doctor was in charge of ensuring metabolic control, and we established frequent communication with them, to ensure none of the drugs implemented in our protocol suffered modifications. Also, patients were referred to their family physician or specialist if urgent treatment with statins or vitamin supplementation was required.
Inclusion criteria were as follows: ≥18 years old, T2DM defined by the American Diabetes Association criteria, DPN defined by Dyck [
When polyunsaturated fatty acids are oxidized by ROS, malondialdehyde (MDA) is produced upon fatty acid decomposition; thus, measurement of MDA has been used as an indicator of LPO. LPO plasma levels were measured by a commercial kit (Oxford Biomedical Research Inc., FR12) according to manufacturer’s instructions. This assay is based on the reaction of a chromogenic reagent, N-methyl-2-phenylindole, with MDA, which produces a chromophore with maximal absorbance at 586 nm. Results are expressed in
The plasma NO levels were indirectly estimated based on the determination of the NO metabolites, nitrate, and nitrite (
The NSS and NDS described by Dyck were obtained by physical examination and anamnesis [
The study was approved by the Research and Ethics Committee of the Health Science University Center, University of Guadalajara, Mexico, and by international instances (National Institutes of Health) with clinical trial identifier
The sample size was obtained by a clinical study design formula taking into account a difference change of 0.05
We assessed 131 patients, 57 were not eligible, and 74 were included and further divided into groups as follows: placebo, 24; EZE/SIMV, 25; and ROSUV, 25 (Figure
Clinical characteristics. Different population variables of each study group are enlisted; none of them were statistically different between groups.
Clinical characteristics | Placebo |
EZE/SIMV |
ROSUV |
---|---|---|---|
Gender (M/F)†, |
7/17 (29/71) | 10/15 (40/60) | 12/13 (48/52) |
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Age (years) |
54.7 ± 9.6 | 55.0 ± 12.0 | 54.0 ± 10.5 |
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Weight (kg) |
73.7 ± 11.4 | 75.4 ± 13.9 | 76.9 ± 18.7 |
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Height (mt) |
1.59 ± 0.09 | 1.60 ± 0.10 | 1.62 ± 0.13 |
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Body mass index (kg/m2) |
29.3 ± 4.3 | 29.4 ± 4.1 | 29.0 ± 4.7 |
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DM type 2 duration (years)† | 10.5 ± 8.3 | 10.2 ± 6.6 | 12.1 ± 8.3 |
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Systolic blood pressure (mmHg) |
142 ± 25 | 144 ± 25 | 135 ± 17 |
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Diastolic blood pressure (mmHg) |
84 ± 11 | 81 ± 10 | 81 ± 7 |
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Smoking (Y/N)†, |
9/15 (38/62) | 8/17 (32/68) | 12/13 (48/52) |
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Concomitant drugs, |
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NSAID | 1 (4) | 2 (8) | 2 (8) |
Angiotensin Converter Enzyme Inhibitor | 3 (13) | 3 (13) | 2 (8) |
Angiotensin Receptor Blocker | 2 (8) | 1 (4) | |
Calcium antagonist | 2 (8) | ||
Aspirin | 1 (4) | 1 (4) | |
Proton Pump Inhibitors | 2 (8) | 2 (8) | |
Benzodiazepine | 1 (4) | ||
Diuretics | 1 (4) | 3 (13) | |
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DM type 2 treatment, |
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Insulin | 1 (4.2) | 2 (8.0) | 4 (16.0) |
Metformin | 5 (20.8) | 5 (20.0) | 3 (12.0) |
Glyburide | 15 (62.5) | 1 (4.0) | 11 (44.0) |
Metformin/glyburide | 1 (4.2) | 13 (52.0) | 2 (8.0) |
Metformin/insulin | 2 (8.3) | 2 (8.0) | 3 (12.0) |
Metformin/glyburide/insulin | 2 (8.0) | 2 (8.0) | |
Other combinations |
Mean ± SD unless specified different.
Flow diagram of study selection.
Basal LPO levels in the placebo, EZE/SIMV, and ROSUV groups were
Oxidative stress (OS) and vascular function markers. (a) Lipid Peroxidation (LPO) levels in plasma, as assessed by malondialdehyde concentration. (b) Nitric oxide levels in plasma, as assessed by nitrate/nitrite (
Basal NO levels in the placebo, EZE/SIMV, and ROSUV groups were
Baseline NSS values in the placebo, EZE/SIMV, and ROSUV groups were
Screening levels and changes from screening in (a) neuropathic symptoms score (NSC), (b) neuropathic disability score (NDS), and (c) analog pains scale (APS) score after 16 weeks of treatment. Data is expressed as mean ± SEM,
The electrophysiological data are shown in Table
Nerve conduction studies. Values of different nerve parameters are reported before and after treatment in all groups.
PLACEBO | EZE/SIMV | ROSUV | |||||||
---|---|---|---|---|---|---|---|---|---|
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|
|
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Baseline | Final |
|
Baseline | Final |
|
Baseline | Final |
| |
Lower limbs | |||||||||
Sural nerve | |||||||||
Lat (ms) | 4.0 ± 0.5 | 3.6 ± 0.2 |
|
4.1 ± 0.4 | 3.7 ± 0.1 |
|
4.1 ± 0.6 | 3.8 ± 0.2 | 0.070 |
Amp ( |
10.9 ± 12.0 | 15.9 ± 2.8 | 0.084 | 9.5 ± 3.2 | 14.8 ± 2.9 | 0.477 | 12.6 ± 6.6 | 15.2 ± 2.3 | 0.538 |
Peroneal nerve | |||||||||
Lat (ms) | 3.8 ± 0.8 | 3.7 ± 0.2 | 0.207 | 3.7 ± 0.5 | 3.6 ± 0.2 | 0.210 | 3.6 ± 0.9 | 3.5 ± 0.1 | 0.810 |
Amp (mV) | 4.7 ± 3.1 | 5.0 ± 0.5 | 0.191 | 4.5 ± 1.7 | 4.4 ± 0.4 | 0.835 | 4.7 ± 2.6 | 4.5 ± 0.5 | 0.296 |
Vel (m/s) | 39.3 ± 4.4 | 40.6 ± 1.1 |
|
40.6 ± 3.8 | 41.5 ± 0.9 | 0.111 | 39.9 ± 4.1 | 40.0 ± 0.8 | 0.944 |
Tibiae nerve | |||||||||
Lat (ms) | 4.2 ± 1.3 | 4.1 ± 0.2 | 0.395 | 4.4 ± 0.9 | 4.5 ± 0.3 | 0.562 | 4.3 ± 1.1 | 4.3 ± 0.2 | 0.776 |
Amp (mV) | 8.4 ± 4.3 | 9.1 ± 1.2 | 0.070 | 8.3 ± 3.3 | 7.9 ± 0.7 | 0.390 | 8.2 ± 3.2 | 8.3 ± 0.9 | 0.972 |
Vel (m/s) | 42.1 ± 5.4 | 43.1 ± 1.3 |
|
44.2 ± 5.2 | 45.0 ± 0.9 | 0.057 | 45.2 ± 6.3 | 44.4 ± 1.3 | 0.136 |
Upper limbs | |||||||||
Median motor nerve | |||||||||
Lat (ms) | 4.6 ± 1.4 | 5.5 ± 0.5 | 0.655 | 6.5 ± 1.8 | 5.6 ± 1.0 | 0.655 | 4.4 ± 0.8 | 5.0 ± 0.1 | 0.317 |
Amp (mV) | 6.0 ± 1.3 | 4.5 ± 0.9 | 0.180 | 6.5 ± 1.0 | 8.0 ± 0.8 | 0.655 | 9.2 ± 3.9 | 7.3 ± 1.4 | 0.180 |
Vel (m/s) | 47.4 ± 5.9 | 45.7 ± 3.8 | 0.180 | 49.7 ± 3.8 | 51.2 ± 2.3 | 1.000 | 41.7 ± 3.5 | 51.3 ± 4.9 | 0.317 |
Median sensitive nerve | |||||||||
Lat (ms) | 3.8 ± 0.6 | 3.7 ± 0.1 | 0.141 | 3.9 ± 0.6 |
|
0.076 | 4.3 ± 0.7 |
|
0.539 |
Amp ( |
26.0 ± 14.5 | 26.4 ± 4.0 | 0.553 | 22.2 ± 14.0 | 18.3 ± 2.4 | 0.476 | 15.8 ± 6.4 | 21.6 ± 2.5 | 0.266 |
Vel (m/s) | 52.2 ± 6.0 | 53.1 ± 1.3 | 0.195 | 51.1 ± 5.2 | 52.8 ± 1.3 | 0.083 | 52.8 ± 5.2 | 52.8 ± 1.5 | 0.778 |
Ulnar motor nerve | |||||||||
Lat (ms) | 3.5 ± 0.6 | 3.2 ± 0.1 | 0.031 | 3.3 ± 0.3 | 3.4 ± 0.1 | 0.479 | 3.4 ± 0.4 | 3.3 ± 0.1 | 0.468 |
Amp (mV) | 8.3 ± 2.7 | 8.2 ± 0.7 | 0.888 | 8.9 ± 2.7 | 8.0 ± 0.3 | 0.338 | 8.3 ± 1.6 | 8.1 ± 0.4 | 0.394 |
Vel (m/s) | 51.2 ± 8.5 | 51.6 ± 2.0 | 0.776 | 55.0 ± 4.8 | 53.7 ± 1.3 | 0.198 | 54.0 ± 4.4 | 53.9 ± 1.1 | 0.649 |
Ulnar sensitive nerve | |||||||||
Lat (ms) | 3.8 ± 0.8 | 3.6 ± 0.1 | 0.629 | 3.7 ± 0.4 | 3.8 ± 0.1 | 0.673 | 3.7 ± 0.7 | 3.7 ± 0.1 | 0.175 |
Amp ( |
21.2 ± 23.9 | 21.5 ± 2.9 | 0.127 | 19.8 ± 12.6 | 19.5 ± 3.1 | 0.936 | 16.9 ± 7.7 | 17.8 ± 2.2 | 0.913 |
Vel (m/s) | 53.7 ± 4.5 | 53.5 ± 1.5 | 0.463 | 55.5 ± 5.7 | 55.1 ± 1.2 | 0.380 | 54.3 ± 5.7 | 54.3 ± 1.1 | 0.448 |
Mean ± SEM,
Metabolic characteristics are shown in Table
Metabolic characteristics. Biochemical parameters are reported for each treatment group before and after intervention.
Placebo | Ezetimibe/simvastatin | Rosuvastatin | |||||||
---|---|---|---|---|---|---|---|---|---|
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|
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Baseline | Final |
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Baseline | Final |
|
Baseline | Final |
| |
Fasting plasma glucose (mg/dL) | 186.4 ± 14.48 | 150.2 ± 11.20 |
|
146.64 ± 9.92 | 152.6 ± 14.00 | 0.620 | 192.04 ± 12.73 | 179.2 ± 15.20 | 0.520 |
Urea (mg/dL) | 29.5 ± 2.1 | 28.9 ± 2.2 | 0.520 | 30.03 ± 1.51 | 32.5 ± 1.9 | 0.280 | 31.22 ± 2.27 | 28.6 ± 2.2 | 0.300 |
Creatinine (mg/dL) | 0.79 ± 0.04 | 0.84 ± 0.05 | 0.180 | 0.82 ± 0.04 | 0.85 ± 0.05 | 0.570 | 0.84 ± 0.04 | 0.80 ± 0.04 | 0.320 |
AST (U/L) | 21.9 ± 1.89 | 21.8 ± 1.4 | 0.820 | 24.63 ± 0.99 | 27.1 ± 2.5 |
0.270 | 27.8 ± 1.91 | 26.7 ± 1.2 |
0.700 |
ALT (U/L) | 20.2 ± 1.43 | 20.5 ± 1.9 | 0.990 | 28.57 ± 3.26 | 28.4 ± 3.1 |
0.570 | 31.22 ± 2.47 | 30.3 ± 2.4 |
0.870 |
GGT (U/L) | 34.73 ± 6.49 | 39.4 ± 8.6 | 0.270 | 39.83 ± 9.04 | 33.7 ± 3.7 | 0.780 | 44.33 ± 6.93 | 43.9 ± 7.7 | 0.260 |
Bilirubin (mg/dL) | 0.70 ± 0.06 | 0.56 ± 0.05 | 0.052 | 0.61 ± 0.04 | 0.64 ± 0.06 | 0.800 | 0.83 ± 0.05 | 0.65 ± 0.07 |
|
Cholesterol (mg/dL) | 211.43 ± 11.73 | 202.3 ± 8 | 0.610 | 210.56 ± 9.94 | 129.3 ± 9.7 |
|
217.2 ± 8.04 | 142.7 ± 8.8 |
|
LDL (mg/dL) | 126.68 ± 8.76 | 109.6 ± 7.8 |
|
117.45 ± 7.16 | 61.7 ± 6.1 |
|
133.56 ± 7.96 | 75 ± 8.1 |
|
HDL (mg/dL) | 36.95 ± 2.61 | 39.7 ± 2.5 | 0.470 | 36.23 ± 2.06 | 32.7 ± 2.1 | 0.090 | 36.79 ± 1.91 | 36.5 ± 2.3 | 0.360 |
Triglycerides (mg/dL) | 240.13 ± 27.41 | 242.4 | 0.590 | 234.63 ± 49.96 | 161.9 ± 21.2 |
0.055 | 220.6 ± 24.49 | 168.4 ± 24.4 |
|
CK (U/L) | 82.21 ± 13.78 | 82.8 ± 10.3 | 0.930 | 95.92 ± 14.4 | 86.4 ± 8.3 | 0.460 | 114.93 ± 18.44 | 157.3 ± 35.1 | 0.190 |
HBA1C % (mmol/mol) | 8.8 (73) ± 0.36 | 9.2 (77) ± 0.5 | 0.260 | 7.8 (62) ± 0.32 | 8.1 (65) ± 0.4 | 0.250 | 9.0 (75) ± 0.40 | 9.4 (79) ± 0.4 |
0.090 |
Mean ± SEM
Diabetes can damage the peripheral nervous system in various ways, DPN being the most common presentation [
There are several underlying mechanisms suggested to be linked to the development and progression of DPN caused by dyslipidemias [
Furthermore, as patients with diabetes exhibit impaired NO availability, thereby contributing to endothelial dysfunction [
Although OS has been implicated in the development and progression of diabetic neuropathies, we did not observe a superior effect of statins over placebo on the clinical outcomes after 16 weeks of intervention. However, we observed a trend towards significance on the NSS values in the EZE/SIMV group when compared to placebo (
Limitations include the lack of homogenization of lifestyle changes previous to randomization and throughout the study. Some of the patients could change their antidiabetic medications during the protocol, because their family physician was in charge of their glucose control; however, we ensured no statins and/or antioxidants were taken during the duration of the study. Most of the clinical trials that evaluate DPN are performed for a minimum of 12 months to ensure modifications in clinical outcomes; probably the duration of our trial was too short to demonstrate changes in clinical and nerve conduction parameters; however, the main objective was to evaluate the statins effect on oxidative stress.
In summary, this trial demonstrated that EZE/SIMV and ROSUV are superior to placebo in reducing LPO levels in T2DM after 16 weeks of treatment. Future larger randomized clinical trials and for longer period of time are needed, in order to confirm the favorable effects that statins may have on OS in T2DM subjects suffering from DPN.
The authors have no conflict of interests to report.
The authors acknowledge Hospital Civil de Guadalajara “Dr. Juan I. Menchaca” for their support by processing biochemical outcomes and grants by COECYTJAL PS-2008-717.