Carnitine and Peripheral Arterial Disease

Propionyl-L-carnitine for intermittent claudication

BACKGROUND

Peripheral arterial disease (PAD) is a manifestation of systemic atherosclerosis. Intermittent claudication is a symptomatic form of PAD that is characterized by pain in the lower limbs caused by chronic occlusive arterial disease. This pain develops in a limb during exercise and is relieved with rest. Propionyl-L-carnitine (PLC) is a drug that may alleviate the symptoms of PAD through a metabolic pathway, thereby improving exercise performance.

OBJECTIVES

The objective of this review is to determine whether propionyl-L-carnitine is efficacious compared with placebo, other drugs, or other interventions used for treatment of intermittent claudication (e.g. exercise, endovascular intervention, surgery) in increasing pain-free and maximum walking distance for people with stable intermittent claudication, Fontaine stage II.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL databases and the World Health Organization International Clinical Trials Registry Platform and the ClinicalTrials.gov trials register to July 7, 2021. We undertook reference checking and contact with study authors and pharmaceutical companies to identify additional unpublished and ongoing studies.

SELECTION CRITERIA

Double-blind randomized controlled trials (RCTs) in people with intermittent claudication (Fontaine stage II) receiving PLC compared with placebo or another intervention. Outcomes included pain-free walking performance (initial claudication distance - ICD) and maximal walking performance (absolute claudication distance - ACD), analyzed by standardized treadmill exercise test, as well as ankle brachial index (ABI), quality of life, progression of disease, and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, extracted data, and evaluated trials for risk of bias. We contacted study authors for additional information. We resolved any disagreements by consensus. We performed fixed-effect model meta-analyses with mean differences (MDs) and 95% confidence intervals (CIs). We graded the certainty of evidence according to GRADE.

MAIN RESULTS

We included 12 studies in this review with a total number of 1423 randomized participants. A majority of the included studies assessed PLC versus placebo (11 studies, 1395 participants), and one study assessed PLC versus L-carnitine (1 study, 26 participants). We identified no RCTs that assessed PLC versus any other medication, exercise, endovascular intervention, or surgery. Participants received PLC 1 grams to 2 grams orally (9 studies) or intravenously (3 studies) per day or placebo. For the comparison PLC versus placebo, there was a high level of both clinical and statistical heterogeneity due to study size, participants coming from different countries and centres, the combination of participants with and without diabetes, and use of different treadmill protocols. We found a high proportion of drug company-backed studies. The overall certainty of the evidence was moderate. For PLC compared with placebo, improvement in maximal walking performance (ACD) was greater for PLC than for placebo, with a mean difference in absolute improvement of 50.86 meters (95% CI 50.34 to 51.38; 9 studies, 1121 participants), or a 26% relative improvement (95% CI 23% to 28%). Improvement in pain-free walking distance (ICD) was also greater for PLC than for placebo, with a mean difference in absolute improvement of 32.98 meters (95% CI 32.60 to 33.37; 9 studies, 1151 participants), or a 31% relative improvement (95% CI 28% to 34%). Improvement in ABI was greater for PLC than for placebo, with a mean difference in improvement of 0.09 (95% CI 0.08 to 0.09; 4 studies, 369 participants). Quality of life improvement was greater with PLC (MD 0.06, 95% CI 0.05 to 0.07; 1 study, 126 participants). Progression of disease and adverse events including nausea, gastric intolerance, and flu-like symptoms did not differ greatly between PLC and placebo. For the comparison of PLC with L-carnitine, the certainty of evidence was low because this included a single, very small, cross-over study. Mean improvement in ACD was slightly greater for PLC compared to L-carnitine, with a mean difference in absolute improvement of 20.00 meters (95% CI 0.47 to 39.53; 1 study, 14 participants) or a 16% relative improvement (95% CI 0.4% to 31.6%). We found no evidence of a clear difference in the ICD (absolute improvement 4.00 meters, 95% CI -9.86 to 17.86; 1 study, 14 participants); or a 3% relative improvement (95% CI -7.4% to 13.4%). None of the other outcomes of this review were reported in this study.

AUTHORS' CONCLUSIONS

When PLC was compared with placebo, improvement in walking distance was mild to moderate and safety profiles were similar, with moderate overall certainty of evidence. Although In clinical practice, PLC might be considered as an alternative or an adjuvant to standard treatment when such therapies are found to be contraindicated or ineffective, we found no RCT evidence comparing PLC with standard treatment to directly support such use.

Principal predictors of major adverse limb events in diabetic peripheral artery disease: A narrative review

Background and aims

The increasing prevalence of diabetes mellitus is causing a massive growth of peripheral artery disease incidences, a disabling complication of diabetic atherosclerosis, which leads often to the amputation of the affected limb. Critical limb ischemia is the terminal disease stage, which requires a prompt intervention to relieve pain and save limbs. However, patients undergoing revascularization often suffer from cardiovascular, cerebrovascular and major adverse limb events with poor outcomes. Furthermore, the same procedure performed in apparently similar patients has various outcomes and lack of an outcome predictive support causes a high lower limb arterial revascularization rate with disastrous effects for patients. We collected the main risk factors of major adverse limb events in a more readable and immediate format of the topic, to propose an overview of parameters to manage effectively peripheral artery disease patients and to propose basics of a new predictive tool to prevent from disabling vascular complications of the disease.

Methods

Most recent and updated literature about the prevalence of major adverse limb events in peripheral artery disease was reviewed to identify possible main predictors.

Results

In this article, we summarized major risk factors of limb revascularization failure and disabling vascular complications collecting those parameters principally responsible for major adverse limb events, which provides physio-pathological explanation of their role in peripheral artery disease.

Conclusion

We evaluated and listed a panel of possible predictors of MALE (Major Adverse Limb Event) in order to contribute to the development of a predictive score, based on a summary of the main risk factors reported in scientific articles, which could improve the management of peripheral artery disease by preventing vascular accidents.

Effectiveness of Propionyl-L-Carnitine Supplementation on Exercise Performance in Intermittent Claudication: A Systematic Review

Lower extremity peripheral artery disease (PAD) affects 8.5 million people in the United States and more than 200 million worldwide. The most significant risk factors for PAD are hyperlipidemia, hypertension, diabetes mellitus, chronic kidney disease, and smoking. Intermittent claudication (IC) is the predominant symptom of PAD, but only about 10% of patients with PAD experience IC and are associated with reduced exercise capacity. The pathophysiology of IC is characterized by different degrees of stenosis and obstruction, with a progressive reduction in distal perfusion pressure and blood flow. Supervised exercise therapy is recommended as the initial therapy for IC, but the recommendations for medical treatment of IC vary significantly. Propionyl L-carnitine is an acyl derivative of levocarnitine (L-carnitine) and is indicated for patients with the peripheral arterial occlusive disease. It corrects secondary muscle carnitine deficiency in patients with PAD, significantly improving the walking capacity; its levels increase in serum and muscle. Thus, it is suggested to enhance blood flow and oxygen supply to the muscle tissue via improved endothelial function, thereby reducing hypoxia-induced cellular and biochemical disruptions.

Pathophysiology of chronic peripheral ischemia: new perspectives

Peripheral arterial disease (PAD) affects individuals particularly over 65 years old in the more advanced countries. Hemodynamic, inflammatory, and oxidative mechanisms interact in the pathophysiological scenario of this chronic arterial disease. We discuss the hemodynamic, muscle tissue, and oxidative stress (OxS) conditions related to chronic ischemia of the peripheral arteries. This review summarizes the results of evaluating both metabolic and oxidative markers, and also therapy to counteract OxS. In conclusion, we believe different pathways should be highlighted to discover new drugs to treat patients suffering from PAD.

l-Carnitine Supplementation in Recovery after Exercise

Given its pivotal role in fatty acid oxidation and energy metabolism, l-carnitine has been investigated as ergogenic aid for enhancing exercise capacity in the healthy athletic population. Early research indicates its beneficial effects on acute physical performance, such as increased maximum oxygen consumption and higher power output. Later studies point to the positive impact of dietary supplementation with l-carnitine on the recovery process after exercise. It is demonstrated that l-carnitine alleviates muscle injury and reduces markers of cellular damage and free radical formation accompanied by attenuation of muscle soreness. The supplementation-based increase in serum and muscle l-carnitine contents is suggested to enhance blood flow and oxygen supply to the muscle tissue via improved endothelial function thereby reducing hypoxia-induced cellular and biochemical disruptions. Studies in older adults further showed that l-carnitine intake can lead to increased muscle mass accompanied by a decrease in body weight and reduced physical and mental fatigue. Based on current animal studies, a role of l-carnitine in the prevention of age-associated muscle protein degradation and regulation of mitochondrial homeostasis is suggested.

Crossroads between peripheral atherosclerosis, western-type diet and skeletal muscle pathophysiology: emphasis on apolipoprotein E deficiency and peripheral arterial disease

Atherosclerosis is a chronic inflammatory process that, in the presence of hyperlipidaemia, promotes the formation of atheromatous plaques in large vessels of the cardiovascular system. It also affects peripheral arteries with major implications for a number of other non-vascular tissues such as the skeletal muscle, the liver and the kidney. The aim of this review is to critically discuss and assimilate current knowledge on the impact of peripheral atherosclerosis and its implications on skeletal muscle homeostasis. Accumulating data suggests that manifestations of peripheral atherosclerosis in skeletal muscle originates in a combination of increased i)-oxidative stress, ii)-inflammation, iii)-mitochondrial deficits, iv)-altered myofibre morphology and fibrosis, v)-chronic ischemia followed by impaired oxygen supply, vi)-reduced capillary density, vii)- proteolysis and viii)-apoptosis. These structural, biochemical and pathophysiological alterations impact on skeletal muscle metabolic and physiologic homeostasis and its capacity to generate force, which further affects the individual's quality of life. Particular emphasis is given on two major areas representing basic and applied science respectively: a)-the abundant evidence from a well-recognised atherogenic model; the Apolipoprotein E deficient mouse and the role of a western-type diet and b)-on skeletal myopathy and oxidative stress-induced myofibre damage from human studies on peripheral arterial disease. A significant source of reactive oxygen species production and oxidative stress in cardiovascular disease is the family of NADPH oxidases that contribute to several pathologies. Finally, strategies targeting NADPH oxidases in skeletal muscle in an attempt to attenuate cellular oxidative stress are highlighted, providing a better understanding of the crossroads between peripheral atherosclerosis and skeletal muscle pathophysiology.

Limb hemodynamics are not predictive of functional capacity in patients with PAD

To the practicing clinician, it seems obvious that limb hemodynamics would be the primary determinant of walking distance. However, other determinants, such as skeletal muscle metabolism, may play a role. Accordingly, in the current study, we examined the relationship between measures of limb hemodynamics and walking capacity in patients with peripheral arterial disease (PAD). We measured toe and ankle pressures for calculation of toe-(TBI) and ankle (ABI)-brachial indices; basal and hyperemic calf blood flow (CBF; by plethysmography); and initial (ICT) and absolute (ACT) claudication time using the Skinner-Gardner protocol. As expected, PAD patients had impaired limb hemodynamics with reduced TBI, ABI and a reduction in ABI post-exercise. However, there was no relationship between any of the hemodynamic variables (including ABI, ABI reduction post-exercise, TBI, baseline or maximal CBF) and walking distance as assessed by ICT or ACT. A subset of PAD patients with an ACT >750 s (n =16; ‘long claudicators’) were compared with a subset of PAD patients with an ACT <260 s (n = 16; ‘short claudicators’). The average ACT in the long claudicants was over fivefold greater than the short claudicators. Surprisingly, there were no differences between the two groups in any of the hemo-dynamic variables. There was also no relationship between the initial ABI, TBI, toe pressure, baseline or hyperemic CBF, and the improvement in ACT over the 3-month course of the study. This study found little relationship between hemodynamic variables and functional capacity in PAD. Accordingly, to assess the response to therapeutic interventions, exercise performance and functional status need to be directly measured, and cannot be predicted from hemodynamic measurements.

Association between physical activity and peripheral artery disease and carotid artery stenosis in a self-referred population of 3 million adults

OBJECTIVE

Although the relationship between physical activity and coronary heart disease is well characterized, a paucity of data exists on physical activity and vascular disease in other arterial territories. This study examined the prevalence of peripheral artery disease (PAD) and carotid artery stenosis (CAS) in association with physical activity.

APPROACH AND RESULTS

The association between physical activity and vascular disease was examined in >3 million self-referred US participants in the United States from 2003 to 2008 who completed a medical and lifestyle questionnaire in the Life Line screening program. All subjects were evaluated by screening ankle brachial indices <0.90 for PAD and ultrasound imaging for CAS >50%. Multivariable logistic regression modeling was used to estimate odds of disease. Among 3 250 350 subjects, 63% of the population engaged in some leisure time vigorous physical activity. After adjustment for age, sex, race/ethnicity, hypertension, hypercholesterolemia, smoking status, diabetes mellitus, body mass index, and family history of cardiovascular disease, subjects who reported any physical activity had a significantly lower odds of PAD (odds ratio, 0.64; 95% confidence interval, 0.63-0.65) and CAS (odds ratio, 0.80; 95% confidence interval, 0.79-0.81). The association between physical activity with PAD and CAS was robust when stratified by sex, race, and age categories. Physical activity intensity frequency was associated with lower PAD and CAS in a graded manner (P trend <0.0001 for both). Findings seemed unaffected by confounding by comorbidity or indication.

CONCLUSIONS

In a large population-based study, higher levels of physical activity were independently associated with lower odds of vascular disease in the lower extremities and carotid arteries.

Nitric oxide and reactive oxygen species in limb vascular function: what is the effect of physical activity?

Nitric oxide (NO) is known to be one of the most important regulatory compounds within the cardiovascular system where it is central for functions such as regulation of blood pressure, blood flow, and vascular growth. The bioavailability of NO is determined by a balance between, on one hand, the extent of enzymatic and non-enzymatic formation of NO and on the other hand, removal of NO, which in part is dependent on the reaction of NO with reactive oxygen species (ROS). The presence of ROS is dependent on the extent of ROS formation via mitochondria and/or enzymes such as NAD(P)H oxidase (NOX) and xanthine oxidase (XO) and the degree of ROS removal through the antioxidant defense system or other reactions. The development of cardiovascular disease has been proposed to be closely related to a reduced bioavailability of NO in parallel with an increased presence of ROS. Excessive levels of ROS not only lower the bioavailability of NO but may also cause cellular damage in the cardiovascular system. Physical activity has been shown to greatly improve cardiovascular function, in part through improved bioavailability of NO, enhanced endogenous antioxidant defense and a lowering of the expression of ROS-forming enzymes. Regular physical activity is therefore likely to be a highly useful tool in the treatment of cardiovascular disease. Future studies should focus on which form of exercise may be most optimal for enhancing NO bioavailability and improving cardiovascular health.

Oxidative damage and myofiber degeneration in the gastrocnemius of patients with peripheral arterial disease

Peripheral arterial disease (PAD), a manifestation of systemic atherosclerosis that produces blockages in arteries supplying the legs, affects an estimated 27 million people in Europe and North America. Increased production of reactive oxygen species by dysfunctional mitochondria in leg muscles of PAD patients is viewed as a key mechanism of initiation and progression of the disease. Previous studies demonstrated increased oxidative damage in homogenates of biopsy specimens from PAD gastrocnemius compared to controls, but did not address myofiber-specific damage. In this study, we investigated oxidative damage to myofibers as a possible cause of the myopathy of PAD. To achieve this, we developed and validated fluorescence microscopy procedures for quantitative analysis of carbonyl groups and 4-hydroxy-2-nonenal (HNE) adducts in myofibers of biopsy specimens from human gastrocnemius. PAD and control specimens were evaluated for differences in 1) myofiber content of these two forms of oxidative damage and 2) myofiber cross-sectional area. Furthermore, oxidative damage to PAD myofibers was tested for associations with clinical stage of disease, degree of ischemia in the affected leg, and myofiber cross-sectional area. Carbonyl groups and HNE adducts were increased 30% (p < 0.0001) and 40% (p < 0.0001), respectively, in the myofibers of PAD (N = 34) compared to control (N = 21) patients. Mean cross-sectional area of PAD myofibers was reduced 29.3% compared to controls (p < 0.0003). Both forms of oxidative damage increased with clinical stage of disease, blood flow limitation in the ischemic leg, and reduced myofiber cross-sectional area. The data establish oxidative damage to myofibers as a possible cause of PAD myopathy.

l-Carnitine plus cilostazol versus cilostazol alone for the treatment of claudication in patients with peripheral artery disease: A multicenter, randomized, double-blind, placebo-controlled trial

Intermittent claudication (IC) is the predominant symptom of peripheral artery disease (PAD), and is associated with reduced exercise capacity. The pathophysiology of IC is related to reduced blood flow and impaired skeletal muscle oxidative metabolism; however, the efficacy of metabolic therapies is not well established. We evaluated the effect of cilostazol plus l-carnitine versus cilostazol alone on exercise performance, quality of life (QOL), and safety. In a double-blind, placebo-controlled trial, PAD patients with stable IC were randomized to either l-carnitine 1 g or matching placebo twice-daily, on a background of cilostazol. Treadmill and QOL assessments were performed at baseline, 90, and 180 days. The primary endpoint was the difference between groups in the natural-log-transformed ( ln) ratio in peak walking time (PWT) between baseline and 180 days. The combination of cilostazol and l-carnitine was well tolerated. In the modified intent-to-treat population ( n = 145), the mean ln ratio in PWT was 0.241 for cilostazol/l-carnitine versus 0.134 for cilostazol/placebo ( p = 0.076), corresponding to mean increases of 1.99 and 1.36 minutes, respectively. In the per-protocol population ( n = 120), the mean ln ratio in PWT was 0.267 for cilostazol/l-carnitine versus 0.145 for cilostazol/placebo ( p = 0.048). QOL measures were also improved in the cilostazol/l-carnitine group. These findings support larger trials of l-carnitine in combination with cilostazol in the treatment of IC. ClinicalTrials.gov Identifier: NCT00822172

Development of an in vitro model of myotube ischemia

Critical limb ischemia causes severe damage to the skeletal muscle. This study develops a reproducible model of myotube ischemia by simulating, in vitro, the critical parameters that occur in skeletal muscle ischemia. Monolayers of C2C12 myoblasts were differentiated into mature myotubes and exposed to nutrition depletion, hypoxia and hypercapnia for variable time periods. A range of culture media and gas mixture combinations were used to obtain an optimum ischemic environment. Nuclear staining, cleaved caspase-3 and lactate dehydrogenase (LDH) release assay were used to assess apoptosis and myotube survival. HIF-1α concentration of cell lysates, pH of conditioned media as well as partial pressures of oxygen (PO₂) and carbon dioxide (PCO₂) in the media were used to confirm ischemic simulation. Culturing myotubes in depleted media, in a gas mixture containing 20% CO+80% N₂ for 6-12 h increased the PCO₂ and decreased the pH and PO₂ of culture media. This attempts to mimic the in vivo ischemic state of skeletal muscle. These conditions were used to study the potential tissue-protective effects of erythropoietin (EPO) in C2C12 myotubes exposed to ischemia. EPO (60 ng/ml) suppressed LDH release, decreased cleaved caspase-3 and reduced the number of apoptotic nuclei, suggesting significantly decreased ischemia-induced apoptosis in myotubes (P<0.01) and a potential role in tissue protection. Additional therapeutic agents designed for tissue protection can also be evaluated using this model.

Critical update for the clinical use of L-carnitine analogs in cardiometabolic disorders

Acetyl-L-carnitine (ALC) and propionyl-L-carnitine (PLC) are two naturally occurring carnitine derivates formed by carnitine acetyltransferase. The beneficial cardiovascular effects of ALC and PLC have been extensively evaluated in animals and humans during the last 20 years. For instance, many clinical trials have suggested ALC and PLC as potential strategies in the management of peripheral arterial disease, heart and cerebral ischemia, and congestive heart failure. As a result, several experts have already aimed to revise the clinical evidence supporting the therapeutic use of ALC and PLC. On the basis of their conclusions, our aim was a critical review of the effectiveness of ALC and PLC in the treatment of cardiovascular diseases. Type 2 diabetes mellitus is an independent risk factor for the development of cardiovascular disease. Therefore we also describe recent studies that have addressed the emerging use of ALC and PLC amelioration of the insulin resistant state and its related morbidities.

L-Carnitine and intestinal inflammation

The intestinal barrier is one of the most dynamic surfaces of the body. It is here where a single layer of epithelial cells mediates the intricate encounters that occur between the host's immune system and a multitude of potential threats present in the intestinal lumen. Several key factors play an important role in the final outcome of this interaction, including the state of oxidative stress, the level of activation of the immune cells, and the integrity of the epithelial barrier. This chapter describes the main evidence demonstrating the impact that l-carnitine has on each of these factors. These findings, combined with the demonstrated safety profile of l-carnitine, underscore the potential therapeutic value of l-carnitine supplementation in humans suffering from intestinal inflammation and highlight the functional data supporting an association between Crohn's disease and mutations in the l-carnitine transporter genes.

Phosphodiesterases as targets for intermittent claudication

Intermittent claudication (IC) is one of the most frequent forms of lower extremity peripheral arterial disease (PAD) and is most commonly caused by arterial atherosclerosis. Its clinical manifestation includes fatigue, discomfort, or pain occurring in limb muscles due to exercise-induced ischemia, thus limiting the ability of IC patients to walk and exercise. In addition to lifestyle changes (diet, exercise, and smoking cessation), pharmacological treatments are needed. Pathologically, atherosclerotic lesions cause a mismatch in oxygen supply and metabolic demand in the leg muscles during walking/exercise. This subjects the muscles to repeated ischemia and reperfusion injury that can alter structure and oxidative metabolism, resulting in insufficient utilization of oxygen supply. Despite extensive research efforts, cilostazol and pentoxifylline are the only drugs indicated for relieving the symptoms of IC, with cilostazol demonstrating significant improvement in walking distance and quality of life in these patients. Originally developed as a PDE3 inhibitor, cilostazol was later found to have several other pharmacological actions, and its success has been attributed to its multifactorial actions on platelets, endothelium, smooth muscle, and lipid profiles. Using cilostazol as an example, we discuss the rationales and pitfalls of targeting PDEs in IC, and potential strategies for the development of new and more effective pharmacological treatments.

Alternative prevention and treatment of cardiovascular disease, part 2

This article discusses alternative therapies for secondary prevention and treatment of major cardiac disorders: congestive heart failure, hypertension, dyslipidemias, and peripheral vascular disease. The role of various therapies (eg, herbal and botanic preparations, supplements, mind/body interventions, other alternative modalities of care) are addressed relative to each disease state and will hopefully give the practitioner or student a readily accessible suite of integrative therapies for common cardiac illnesses.

Propionyl l-carnitine: intermittent claudication and peripheral arterial disease

Peripheral arterial disease (PAD) is a clinical manifestation of underlying aorto-iliac and leg atherosclerosis that is characterized by different stages of stenosis and obstruction. It affects approximately 12% of the adult population and about 20% of people over the age of 70 years, and is associated with increased cardiovascular (CV) and cerebrovascular morbidity. Intermittent claudication (IC) is the major symptom of PAD; it is defined as cramping leg pain (in the buttock, thigh, or calf) while/after clim bing one or two flights of stairs, or during walking. The goals of IC management are to: slow the progression of local and systemic atherosclerosis, prevent major fatal and nonfatal CV events (myocardial infarction and stroke), improve walking capacity, prevent and reduce resting pain and cutaneous lesions. Propionyl L-carnitine is an acyl derivative of levocarnitine (L-carnitine) and is indicated for patients with peripheral arterial occlusive disease. It corrects secondary muscle carnitine deficiency in patients with PAD, significantly improving the walking capacity; it is a free radical that produces positive effects on endothelial function; it protects from oxidative stress; and it enhances most measures of quality of life. The recent Trans-Atlantic Inter-Society Consensus II update recommends the use of propionyl L-carnitine in combination with physical training to improve the symptoms associated with PAD.

Pharmacological treatment of patients with chronic critical limb ischemia: L-propionyl-carnitine enhances the short-term effects of PGE-1

PURPOSE

To evaluate the therapeutic effects of L-propionyl-carnitine (LPC) in patients with critical limb ischemia (CLI), as defined by the TASC guidelines.

METHODS

The study, double-blinded, randomised, assessed intravenous infusion of LPC 1.2 g/day in combination with PGE-1, 60 mg/day (LPC group: 37 patients), or PGE-1 only (control group: 38 patients) in a total of 75 patients suffering from CLI. Treatment duration was 20 days. We evaluated rest pain, maximum walking distance (MWD) and skin ulcer size.

RESULTS

In both groups we observed a significant reduction in pain score and ulcer size and an increase in MWD. In the patients treated with the combination, the improvement was greater: median value for pain score decreased from 2.75 to 0.85 in the LPC group and from 2.51 to 1.71 in the control group; MWD increased from 55 M to 130 M in the LPC group, and from 55 M to 102 M in the control group; median decrease of ulcer size was significantly greater in patients treated with LPC + PGE1.

CONCLUSIONS

Our study shows that LPC, whose effectiveness on claudication is already known, has favourable effects in patients with CLI, since it reinforces the effects produced by PGE-1.

Changes in pain-free walking based on time in accommodating pain-free exercise therapy for peripheral arterial disease

Symptoms of intermittent claudication (IC) can be relieved by lifestyle modification, medications, and walking exercises. The intensity of the walking exercise is still debatable. The goal of this study was to determine the effects of accommodating pain-free walking exercise therapy program length on pain-free walking. A descriptive, longitudinal study with repeated measures of exercise capacity was conducted. An IC questionnaire was administered to assess IC signs, symptoms, and lifestyle. Walking was performed on a treadmill for 30 to 50 minutes below the participant's individualized walking pain threshold. The study included patients diagnosed with IC due to peripheral arterial disease. All participants were randomly assigned to three groups. Group A (n = 28) participated in the walking program for 2-9 weeks, group B (n = 30) for 10-14 weeks, and group C (n = 26) for 15-94 weeks. The main outcome measure of the study was to determine changes in exercise capacity: walking distance (miles), walking duration (minutes), and walking speed (mph). Group A increased the amount of distance, duration, and speed walked from pretest to posttest by 80% (P < .001), 27% (P < .001), and 37% (P < .001), respectively. Group B increased the amount of distance, duration, and speed walked from pretest to posttest by 122% (P < .001), 56% (P < .001), and 43% (P < .001), respectively. Group C increased the amount of distance, duration, and speed walked from pretest to posttest by 26% (P = .002), 22% (P = .002), and 5% (P = .541) respectively. We reached the conclusion that a walking program of 10-14 weeks is optimal for achieving the best improvements in walking distance, duration, and speed.

Pharmacologic therapy for intermittent claudication

Peripheral artery disease, defined as atherosclerosis in the lower extremities, affects nearly 8.5 million people in the United States. Due to the frequent asymptomatic manifestation of peripheral artery disease, diagnosis may be delayed and its true incidence underestimated. However, some patients may experience aching pain, numbness, weakness, or fatigue, a condition termed intermittent claudication. Peripheral atherosclerosis is associated with cardiovascular risk and physical impairment; therefore, treatment goals are aimed at decreasing cardiovascular risk, as well as improving quality of life. Little debate exists regarding the management of cardiovascular risk reduction, which consists of both antiplatelet therapy and risk factor modification. Despite recently published guidelines, the treatment of intermittent claudication is less well established and the management remains controversial and uncertain. Exercise remains the first-line therapy for intermittent claudication; however, pharmacologic treatment is often necessary. Although only two prescription drugs have been approved by the U.S. Food and Drug Administration for the treatment of intermittent claudication, several supplements and investigational agents have been evaluated. Therapeutic optimization should balance the anticipated improvements in quality of life with the potential safety risks.

Supervised Exercise in Intermittent Claudication: A Sedentary Notion?

The benefit of exercise in the management of intermittent claudication has been explored through extensive research in the preceding decades. Within the clinical setting, there is often little differentiation between home-based and supervised exercise regimens. We examined the history and qualification of supervised exercise as a distinct treatment modality from nonsupervised exercise in intermittent claudication. A Medline, Embase, Ovid, Cochrane Database, and Google Scholar search was performed on all studies published until December 31, 2007, investigating the use of supervised exercise in peripheral arterial disease. Supervised exercise is well grounded in evidence to support its superiority over nonsupervised exercise in the management of intermittent claudication, conveying marked improvement in symptomatology, function, and quality of life. Further research is required to determine the nature of the advantage that supervision affords.

Propionyl-L-carnitine in Leriche-Fontaine stage II peripheral arterial obstructive disease

Peripheral arterial obstructive disease (PAOD) of the lower limbs affects 5% of the adult population. Uncontrolled arteriopathy is established due to a microcirculatory deficit, which may be present despite a good Winsor index and which leads to exhaustion of the functional microcirculatory reserve. The target of this study was to examine possible improvements in microvascular and tissue homeostasis by the administration of propionyl-L-carnitine (PLC). A total of 26 patients were enrolled in this study, aged 65 +/- 15 years; two males were diagnosed at stage IIA and 17 males and seven females at stage IIB PAOD. The main criterion of inclusion was the worsening of walking distance during the last month. In this study the duration of therapy was 33 days. PLC was administered in three flasks, each containing 300 mg in 250 cc saline by continuous infusion. The following parameters were measured before and after treatment: pain-free and maximum walking distance (measured on a treadmill at 3.2 km/hr with a gradient of 12%), recovery time from pain after maximum walking distance, ankle-brachial index by means of the Doppler apparatus, and evaluation of the microcirculation using capillaroscopy. The results showed that therapy with PLC was effective at restoring activity of skeletal muscle in ischemic conditions. In particular, capillaroscopy showed improvement in the angioarchitecture in the microcirculation fields, expressed as increased numbers of visible capillaries and diminution in the time of loss of sodium fluorescein marker. The clinical data showed increased walking distance and diminished time to recover from pain, and the clinical improvement correlated with improved microcirculatory function. From these preliminary data has emerged an indication of therapy with PLC for chronic obstructive arteriopathy of the lower limbs at stage II. Further studies with higher numbers of patients and more controlled variables are planned.

Levo-Propionyl-Carnitine Improves the Effectiveness of Supervised Physical Training on the Absolute Claudication Distance in Patients With Intermittent Claudication

The mechanisms by which supervised physical training improves walking ability in patients with intermittent claudication (IC) are microcirculatory, rheological, and metabolic. The main mechanism of levo-propionylcarnitine (LPC) is metabolic; it increases the walking ability in claudicants, providing an additional energy to the ischemic muscle by an anaplerotic activity. Therefore, the current study was carried out to ascertain whether the combined treatment has a synergistic effect. The results confirm the effectiveness of supervised physical training in patients with IC, and we recommend the use of LPC during the exercise training program, at least in patients with severe claudication. Finally, underlining the similar mechanisms of physical training and LPC treatment, the study suggests that a cycle of LPC infusions could be advised in patients with severe claudication who cannot be included, for various reasons, in an exercise rehabilitation program.

Propionyl-L-Carnitine Prevents Age-Related Myocardial Remodeling in the Rabbit

Age-related cardiac remodeling is characterized by changes in myocardial structure, which include fibrosis (ie, increased collagen concentration). The pathogenetic mechanisms of age-related cardiac changes and possible pharmacologic interventions are still a matter of investigation. A morphometric analysis of collagen accumulation was performed in Sirius Red-stained left ventricular sections of 3-month-old and 5-6-year-old animals after a 9-month period of propionyl-L-carnitine treatment (PLC; 120 mg Kg(-1) day(-1) per os); aged rabbits showed decreased interstitial collagen accumulation and no changes in cellularity and apoptotic rate compared to controls. Age-related expression of vascular cell adhesion molecule-1 (VCAM-1)-positive microvessels was also reduced in PLC-treated rabbits. In vitro, the 16-hour, 10-microM PLC treatment reduced collagen type 1 and VCAM-1 transcripts, which were investigated by reverse transcription-polymerase chain reaction, more markedly in cardiac fibroblasts from aged donors. In the latter, the anti-VCAM-1 antibody treatment was found to be associated with a reduction in collagen type I transcripts. Our results demonstrated that long-term PLC treatment partially prevents age-related interstitial remodeling and suggests that a more complex interstitial cell-to-cell signaling regulates senescent myocardium properties.

Intermittent claudication: an overview

Intermittent claudication (IC) is defined by leg muscle pain, cramping and fatigue brought on by ambulation/exercise; relieved on rest; and caused by inadequate blood supply and is the primary symptom of peripheral arterial disease (PAD). PAD has a detrimental effect on the quality of life. PAD is a debilitating atherosclerotic disease of the lower limbs and is associated with an increased risk of cardiovascular morbidity and mortality. IC is an extremely important marker of atheroma. Up to 60% patients with IC have significant underlying coronary and/or carotid disease and 40% of all patients suffering from IC die or suffer a stroke within 5 years of presentation. The therapeutic intervention of IC essentially aims at providing symptomatic relief and reducing the systemic cardiovascular complications. Although exercise therapy is one of the most efficacious conservative treatments for claudication, the pharmacotherapeutic goals can be best achieved through an increase in the walking capacity to improve quality of life and a decrease in rates of amputation. In the development of treatment for IC, an aggressive non-pharmacological intervention and pharmacological treatment of the risk factors associated with IC are considered. In the next 2 years, the results of major trials of drugs that stabilize and regress atherosclerosis such as statins and angiotensin converting enzyme inhibitors, and anti-platelet agents, recombinant growth factors and immune modulators will be available for IC. Levocarnitine (l-carnitine) and a derivative, propionyl levocarnitine, are emerging agents that increase the pain-free walking and improve the quality of life in IC patients by working at the metabolism and exercise performance of ischemic muscles. This article provides a comprehensive review of the pathophysiology involved, diagnosis of IC and existing and emerging pharmacotherapies with rationale for their use in its treatment.