Acta Diabetol DOI 10.1007/s00592-008-0082-3
ORIGINAL ARTICLE
Pulsed infrared light therapy does not increase nitric oxide concentration in the blood of patients with type 1 and type 2 diabetes mellitus David Alan Arnall Æ Arnold G. Nelson Æ Laura Stambaugh Æ ` ngels Cebria` i Iranzo Æ Nu´ria Sanz Sevilla Æ M. A Laura Lo´pez Bueno Æ Isabel Sanz Æ Sheridan B. Arnall
Received: 14 August 2008 / Accepted: 19 November 2008 Ó Springer-Verlag 2008
Abstract The purpose of this study was to determine if NO blood concentrations increased acutely following an 8-week course of pulsed infrared light therapy (PILT) which could be linked to an improvement in peripheral protective sensation (PPS) in patients who have profound chronic diabetic peripheral neuropathy. A total of 22 subjects with the diagnosis of type 1 (N = 2) or type 2 (N = 20) diabetes participated in the study. PILT was administered to one foot chosen at random with the other foot serving as a within-subject control (no treatment). Patients underwent 24 treatments (3 times/week, for 8 weeks) for 30 min per treatment. Venous blood samples
D. A. Arnall (&) Physical Therapy Department, East Tennessee State University, Box 70624, Johnson City, TN 37614, USA e-mail:
[email protected];
[email protected] A. G. Nelson Department of Kinesiology, Louisiana State University, 112 Long Field House, Baton Rouge, LA 70803, USA L. Stambaugh GE Analytical Instruments, 6060 Spine Road, Boulder, Colorado 80301, USA ` . Cebria` i Iranzo L. Lo´pez Bueno N. Sanz Sevilla M. A Departamento de Fisioterapia, Universitat de Vale`ncia, C/ Gasco´ Oliag, 3, 46010 Valencia, Spain I. Sanz Hospital Clı´nico Universitario de Valencia, 46020 Valencia, Spain S. B. Arnall 130 Laurel View Drive, Jonesborough, TN 37659, USA
were taken during the last 5 min of treatment from veins in the dorsum of the control and experimental feet and were later analyzed for NO concentration. Contrary to the popular supposition, PILT treatments actually resulted in a significantly (P \ 0.05) decreased concentration of NO. Additionally, there were no significant differences between the treated and untreated feet. Since in individuals where PILT has significantly improved PPS, PILT did not stimulate an increased NO content in the blood, it appears that infrared light improves peripheral protective sensation in patients by a mechanism other than an increased NO production. Keywords Peripheral neuropathy Peripheral protective sensation Type 1 diabetes mellitus Type 2 diabetes mellitus Infrared light modality Physical therapy PILT Infrared light
Introduction Patients with diabetes have pathological complications that accompany the physiological impairment of either making no insulin (type 1), or developing peripheral resistance to insulin (type 2). In either form of diabetes, the derangement of the normal insulin-to-glucose relationship makes the maintenance of euglycemia challenging. Chronic recurring hyperglycemia brings with it a plethora of chronic, debilitating conditions such as peripheral vascular disease, atherosclerosis, hypertension, neuropathies, and compromised wound healing. Recently a new treatment, pulsed infrared light therapy (PILT), has become available and represents a new modality for the treatment of diabetic neuropathies and the loss of peripheral protective sensation (LOPS). PILT gives
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patients with diabetes hope that LOPS may be prevented or reversed as long as afferent nerves in the feet and legs have not permanently stopped functioning. The exact mechanism of action of PILT in the treatment of LOPS is not understood although several authors [1–4] have suggested that it is likely due to an increased blood concentration of nitric oxide (NO). NO has been shown to stimulate the growth of capillaries in, in vivo animal models [5] as well as causing vasodilation in the vascular bed thus creating a cellular environment in which the tissues can have improved perfusion [6]. Farinfrared (wavelength = 5.6–1,000 lm) has been shown to improve skin blood flow, and the effect of far-infrared on increasing skin blood flow was suppressed by pretreatment with NG-nitro-L-arginine methyl ester, an endothelial nitric oxide synthase inhibitor [7]. There is, however, no published evidence to date that links increased blood NO concentration secondary to a regular therapeutic program of applied PILT to the improvement of LOPS in patients with diabetes mellitus. Moreover, there is a paucity in the literature of papers that explain the mechanism of action for the restoration of peripheral protective sensation. In fact, a recent study by Lavery et al. [8] suggests that any gains in LOPS can be attributed to a ‘‘placebo effect’’. The purpose of this research was to determine if NO production increased during the application of PILT to the feet of patients with either type 1 or type 2 diabetes who were experiencing LOPS. Additionally, this research was limited to those individuals that had demonstrated a significant improvement in peripheral sensation subsequent to PILT.
to change physician-directed pharmacological interventions that patients were receiving when they entered the study. The research staff provided the patients with information concerning the benefits and risks associated with their participation in the study after which the prospective subjects signed a consent form and entered the study. All subjects were interviewed concerning their medical history. Pertinent patient information consisted of: (1) years living with diabetes; (2) height, weight, and body mass index (BMI); (3) current medication inventory; (4) most recent available glycosylated hemoglobin (HbA1C); (5) history of a nephropathy or a retinopathy since the diagnosis of diabetes; (6) a standard cardiovascular risk profile evaluating hypercholesterolemia, hypertriglyceridemia, hypertension, smoking history, and physical activity level. A summary of the anthropomorphic characteristics and other pertinent subject information are contained in Table 1. Tests and measurements Body mass index, physical activity, ankle/brachial index, foot temperature (both feet), vibratory sensation assessed by biothesiometry, and peripheral protective sensation assessed by monofilaments were measured and are reported elsewhere [1]. Treatment application
Methods
Once all medical histories and preliminary measurements were completed, one foot was randomly designated as the experimental foot (received PILT), while the contralateral foot acted as the within-subject control (received no treatment).
Subjects
Pulsed infrared light therapy
This study was reviewed and approved by the Comite´ E´tico of the Hospital Clı´nico de Valencia, Valencia, Spain prior to recruiting subjects and the gathering of data. A total of 22 patients with the clinical diagnosis of type 1 (N = 2) or type 2 (N = 20) diabetes mellitus participated in this study. All subjects that started in the study remained until the study ended. The subjects were recruited from the Asociacı´on de Diabetes of Valencia, Spain who lived in Valencia or in the semiautonomous region of the Province of Valencia. Subject exclusion criteria for this study included: (1) open wounds in either lower extremity; (2) an abnormal hematocrit which was \30% or [50%; (3) an abnormal hemoglobin which was \9 g dl-1 or[18 g dl-1; (4) and if the patient was in acute renal failure. No attempt was made
The unit delivering the PILT to the experimental foot was a RevitaMedÒ infrared light therapy RL-1001SP device (Sports Medicine Technologies/RevitaMed Therapeutic Systems, 19401 N. Cave Creek Road, Suite #28, Phoenix, Arizona 85024 USA). Gallium-arsenide light emitting diodes (LEDs) delivered near-infrared light at a wavelength of 880 nm and visible red light at a wave length of 650 nm. The PILT control unit was connected to a neoprene pad (19.5 cm 9 12.0 cm 9 0.5 cm) into which was embedded an array of LEDs. The LED array was arranged in six rows of five LEDs emitting infrared light at 880 nm alternating with five rows of four LEDs emitting visible red light at a wavelength of 650 nm (near-infrared light). This pattern permitted a total of 50 LEDs to be evenly dispersed throughout the treatment neoprene pad area.
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Acta Diabetol Table 1 Subjects anthropomorphic data BMI (kg/m2)
Experimental foot
HbA1c
Pedometer average (miles/d)
80
33
Right
6
None
2.3104
72
31
Left
–
None
2.3409
60
26
Right
6.6
1.9
12
2.7889
74
27
Right
7.2
3.9
2
13
2.7258
108
40
Left
6.5
3.2
64/M
2
13
2.6244
77
29
Right
7.4
5.4
66/F 69/F
2 2
14 15
2.4964 2.5281
105 68
42 27
Left Right
5.5 –
3.9 None
76/F
2
17
2.5921
62
24
Left
8.8
3.8
58/F
2
17
2.4649
105
43
Left
11
2.1
55/M
2
18
3.2523
127
39
Left
8
5.5
56/F
2
18
2.5921
104
40
Right
–
1.0
73/F
2
18
2.4336
62
26
Right
8.2
1.3
70/F
2
19
2.4964
60
24
Left
6.3
2.2
65/F
2
20
2.1025
93
44
Left
–
1.7
65/F
2
20
2.4649
75
30
Right
6.7
4.3
63/F
2
20
2.4649
77
31
Right
7.7
3.5
70/F
2
21
2.1904
85
39
Left
7.8
1.5
63/M
2
24
2.6244
75
29
Right
–
3.4
68/M
2
30
2.6896
75
28
Right
6.6
1.3
38/M
1
24
3.3124
72
22
Left
7.8
4.4
35/F
1
24
2.4649
75
30
Left
6.7
3.0
Age/Gender
DM type
W/DM (Years)
Height (m)
69/F
2
11
2.4336
61/F
2
12
58/M
2
12
40/M
2
50/F
Weight (kg)
The RevitaMedÒ Unit provides seven different frequency settings dispersing light from the lowest setting of 1 at 73 Hz up to a setting of 7 at 4,672 Hz. Each increase in the setting is a doubling of the frequency, i.e. a setting of 2 is equal to a frequency of 146 Hz and a setting of 3 is equal to a frequency of 292 Hz. In this study, each subject received on the experimental foot PILT at a setting of 4, which was equal to a frequency of 584 Hz, for 30 min, 3 times per week, for 8 weeks. PILT was delivered by placing one neoprene pad on the volar surface of the foot and one neoprene pad on the dorsum of the foot effectively encompassing the entire foot from the toes to the heel. These pads were held in place by two Velcro straps (See Fig. 1). Collection of serum samples
Fig. 1 RevitaMed units and pad placement on a patient
Six to ten milliliters of blood were taken from veins in the dorsum of the control and the experimental foot at time zero (baseline) and at 4 weeks and at the end of the study at 8 weeks. The blood samples were drawn at the end of a treatment session before the PILT was removed, i.e. blood was drawn from the foot veins while the patient was still exposed to the infrared light. The dorsal pad was moved to
expose the veins while it was still lit up and giving the treatment. Blood samples were drawn up into non-heparinized tubes and allowed to clot at room temperature, and then spun down in a table top centrifuge separating the cells from the serum. After centrifugation, aliquots of serum were stored at -60°C until baseline, 4 and 8 week samples could be analyzed together.
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Nitric oxide determination
350.0 Control
Statistical Analysis A two-way ANOVA (treatment 9 week) with repeated measures was used to compare the NO values. Significance was set at P \ 0.05. Post hoc ANOVA analysis involved, where appropriate, the use of a Bonferroni t test.
300.0
[NO] picomoles
Frozen samples of serum were thawed and prepared for analysis. Determination of NO followed the technique of Braman and Hendrix [9]. Aliquots of duplicate serum samples were prepared by chemically converting serum nitrates, nitrites and nitrosothiols back to nitric oxide in the presence of vanadium (III) chloride in a 1 M hydrochloric acid mixture at a pressure of 4–7 Torr and at a temperature of -12°C. A chemiluminescent assay using ozone as a reactant with NO was employed. A nitrate calibration curve was prepared from a stock solution of sodium nitrate. The linear correlation values for the calibration curve were C.99. Sample concentrations of NO were determined by comparing the serum concentration against the calibration curve.
PILT
250.0 200.0
* *
150.0 100.0 50.0 0.0
0
4
8
Week of Treatment
Fig. 2 Concentration of NO at week-0, -4, and -8. asterick indicates a week-8 value significantly different (P \ 0.05) than a week-0 or week-4 value
significant, The main effect for week [F(2, 42) = 6.37, P \ 0.004], however, was significant. Post hoc analysis showed that this significance was due to both the treated and control feet having a significant average 23–25% decline in NO concentration between week-4 and -8.
Discussion Results Descriptive information Descriptive information (e.g. BMI and physical activity) is presented in Table 1. Of the 22 patients in this study, 45% (n = 10) had BMI’s over 30 ranging from 31 to 44. The remaining 55% (n = 12) had BMI’s B30 ranging from 30 to 22. Only 7 subjects walked more than 10,000 steps per day indicating that for these seven subjects, their physical activity was adequate for reducing body weight and improving insulin sensitivity [10]. The remaining 15 were only mildly engaged in physical activity and never met the goal of 10,000 steps per day.
PPS As reported previously [1], individuals on average saw a significant (P \ 0.05) increase in PPS.
Although recent pharmacological advances have made the management of diabetes easier, the loss of PPS has been more difficult to treat. A new therapy, PILT, has recently been shown to effectively reduce pain [4] and improve neuropathies by partially restoring PPS [1–4]. The subjects in this study were volunteers with chronic diabetes mellitus (11? years since diagnosis). The average age was 63 years for the patients with type-2 diabetes, and 37 years for the patients with type-1 diabetes. The HbA1C data on these subjects indicated that only 8 out of the 22 were in good control. The rest were clearly not managing their blood sugars closely. None of these patients had nephropathies, and only one of the patients reported sustaining a retinopathy. None of them reported having had neuropathic ulcers since the time of their diagnosis with diabetes mellitus. The single most important piece of information to come out of this controlled and blinded study is the fact that NO values fell over the 8 weeks of treatment both in the control and the experimental feet.
NO concentration Conclusions The influence of the PILT treatment upon NO concentration is shown in Fig. 2. Both the main effect for treatment [F(1, 21) = 2.44, P = 0.13] and the interaction between treatment and week [F(2, 42) = 0.65, P = 0.52] were not
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PILT, when administered for 30 min/day for three days per week for 8 weeks, is a viable non-invasive treatment for chronic, and profound losses in PPS in patients with long
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standing diabetes mellitus. Improvements in the peripheral sensation were stunning. Nearly all subjects (n = 20 out of 22) were able to return to a completely normal sensory condition in which the Semmes-Weinstein monofilaments below the 5.07 monofilament were detected. While the mechanism of action for this sensory improvement is thought to be the increased production of NO, none of the currently published studies to date have actually measured NO. This study stands alone in the literature as the only human trial study that has measured NO concentrations in serum samples in patients undergoing infrared light therapy for the improvement of their LOPS. The findings of this study contradict the long-held belief that NO is the blood factor that is responsible for the improvement in LOPS. In fact this study showed that blood NO concentration significantly drops between week-4 and -8 of PILT. This suggests that the improvement in LOPS and the restoration of normal sensation is probably not due to an increased cellular production of nitric oxide. Hence, any improvement in LOPS must be due to some other mechanism. Alternative to the Lavery et al. [8] proposed placebo effect, a possible mechanism could be related to an increase in skin (and/or other tissues) temperatures. Patients in this study described a warm and pleasant sensation of heat even though PILT is a ‘‘cold’’ therapy meaning that it does not intentionally produce significant heat. It is quite possible that the combination of nearinfrared and visible light warmed the superficial tissues. This increased tissue temperature could then cause an increase in blood flow. Additionally, the increased tissue temperature could induce the expression of heat shock proteins. McCarty [11] suggests that the induction of heat shock proteins may improve the microvascular complications of diabetes as well as have a potential for preventing or treating neurodegenerative disorders. It is interesting to note that Lavery et al. [8] warmed the control foot to 37°C. Since diabetic mean foot temperatures can range between 27 and 30°C [12], Lavery et al. [8] could have increased tissue temperature by as much as 7°C, and thus induced a heat effect as well. Acknowledgments We would like to thank Tom Neuman (ReviteMed Corporation) for supplying the equipment for this study. Jose´ Tomas Real, MD (Endocrinology Section––Proves Funcionales––of the Hospital Clı´nico Universitario de Valencia, Valencia, Spain), Dr. Teresa Pedro, Drs. Luis Such, Luis M. Such and Antonio Alberola (Physiology Department in the Medical School of the Universidad de Valencia, Valencia, Spain), Dr. Vicente Andreu (International Office of the Universidad de Valencia, Valencia, Spain), Drs. Celedonia Igual Camacho and Dr. Nı´colas Este´vez (Escuela de Fisioterapia of the Universidad de Valencia, Valencia, Spain) for all of their logistic,
material, intellectual, and moral support. We would like to thank Libia Sanz (Institute of Medicine in Valencia, Spain) for all of her help in preparing the blood samples to be shipped back to the United States. Special thanks are extended to Marı´a Deltoro Garcı´a, the director of the Diabetes Association of Valencia, Spain for her tireless efforts in recruiting patients for this study. None of the authors has a conflict of interest (financial or otherwise) in the subject matter of this manuscript.
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