Fenofibrate: a new treatment for hyperuricaemia and gout?

Kidney Drug Transporters in Pharmacotherapy

The kidney functions not only as a metabolite elimination organ but also plays an important role in pharmacotherapy. The kidney tubule epithelia cells express membrane carriers and transporters, which play an important role in drug elimination, and can determine drug nephrotoxicity and drug-drug interactions, as well as constituting direct drug targets. The above aspects of kidney transport proteins are discussed in the review.

Uric acid and xanthine oxidase: future therapeutic targets in the prevention of cardiovascular disease?

Serum uric acid may be an independent risk factor for cardiovascular disease. This review examines this association, potential mechanisms, and explores whether strategies to reduce uric acid will improve outcomes. The recent studies of xanthine oxidase inhibition are given particular focus. Epidemiological evidence supports the theory that uric acid is an independent risk factor for cardiovascular disease. Recent studies of losartan, atorvastatin and fenofibrate suggest that uric acid reduction contributes to the risk reduction offered by these therapies. Several small studies of xanthine oxidase inhibition have shown improvements in measures of cardiovascular function of a similar magnitude to that of other proven preventative treatments. These trial data and the convincing epidemiological evidence mandate that large clinical trials of uric acid-lowering strategies are performed in patients with or at high risk of cardiovascular disease. If such approaches are shown to be effective in reducing cardiovascular events, they would represent a novel and cost-effective preventative approach.

Clinical trials in crystal arthropathy

A few clinical trials have evaluated therapeutic agents for crystal-associated arthropathy. Most of the studies are uncontrolled and observational. Management of patients who have acute crystal arthropathies usually is symptomatic with long-term management depending on crystal composition. In trials of gout, studies focus on acute symptomatic treatment, foregoing chronic management, which is aimed at reducing the concentration of serum urate. In those who have calcium crystals, however, there is no definitive or effective long-term treatment in chronic gout. The xanthine oxidase inhibitor and uricosurics are the agents used most commonly. Newer compounds in clinical trials show promise as effective and safe therapeutic options.

Gout in solid organ transplantation: a challenging clinical problem

Hyperuricaemia occurs in 5-84% and gout in 1.7-28% of recipients of solid organ transplants. Gout may be severe and crippling, and may hinder the improved quality of life gained through organ transplantation. Risk factors for gout in the general population include hyperuricaemia, obesity, weight gain, hypertension and diuretic use. In transplant recipients, therapy with ciclosporin (cyclosporin) is an additional risk factor. Hyperuricaemia is recognised as an independent risk factor for cardiovascular disease; however, whether anti-hyperuricaemic therapy reduces cardiovascular events remains to be determined. Dietary advice is important in the management of gout and patients should be educated to partake in a low-calorie diet with moderate carbohydrate restriction and increased proportional intake of protein and unsaturated fat. While gout is curable, its pharmacological management in transplant recipients is complicated by the risk of adverse effects and potentially severe interactions between immunosuppressive and hypouricaemic drugs. NSAIDs, colchicine and corticosteroids may be used to treat acute gouty attacks. NSAIDs have effects on renal haemodynamics, and must be used with caution and with close monitoring of renal function. Colchicine myotoxicty is of particular concern in transplant recipients with renal impairment or when used in combination with ciclosporin. Long-term urate-lowering therapy is required to promote dissolution of uric acid crystals, thereby preventing recurrent attacks of gout. Allopurinol should be used with caution because of its interaction with azathioprine, which results in bone marrow suppression. Substitution of mycophenylate mofetil for azathioprine avoids this interaction. Uricosuric agents, such as probenecid, are ineffective in patients with renal impairment. The exception is benzbromarone, which is effective in those with a creatinine clearance >25 mL/min. Benzbromarone is indicated in allopurinol-intolerant patients with renal failure, solid organ transplant or tophaceous/polyarticular gout. Monitoring for hepatotoxicty is essential for patients taking benzbromarone. Physicians should carefully consider therapeutic options for the management of hypertension and hyperlipidaemia, which are common in transplant recipients. While loop and thiazide diuretics increase serum urate, amlodipine and losartan have the same antihypertensive effect with the additional benefit of lowering serum urate. Atorvastatin, but not simvastatin, may lower uric acid, and while fenofibrate may reduce serum urate it has been associated with a decline in renal function. Gout in solid organ transplantation is an increasing and challenging clinical problem; it impacts adversely on patients' quality of life. Recognition and, if possible, alleviation of risk factors, prompt treatment of acute attacks and early introduction of hypouricaemic therapy with careful monitoring are the keys to successful management.

Management of acute and chronic gouty arthritis: present state-of-the-art

There are three stages in the management of gout: (i) treating the acute attack; (ii) lowering excess stores of uric acid to prevent flares of gouty arthritis and to prevent tissue deposition of urate; and (iii) providing prophylaxis to prevent acute flares. It is important to distinguish between therapy to reduce acute inflammation in acute gout and therapy to manage hyperuricaemia in patients with chronic gouty arthritis. During the acute gouty attack nonpharmacological treatments such as topical ice and rest of the inflamed joint are useful. NSAIDs are the preferred treatment in acute gout. The most important determinant of therapeutic success is not which NSAID is chosen, but rather how soon NSAID therapy is initiated. Other treatments include oral and intravenous colchicine, intra-articular and systemic corticosteroids, and intramuscular corticotropin. Optimal treatment of chronic gout requires long-standing reduction in serum uric acid. The urate-lowering drugs used to treat chronic gout are the uricosuric drugs, the uricostatic drugs, which are xanthine oxidase inhibitors, and the uricolytic drugs. Xanthine oxidase inhibitors such as allopurinol, oxipurinol and febuxastat should be used as first-line treatment in patients with renal calculi, renal insufficiency, concomitant diuretic therapy and ciclosporin (cyclosporine) therapy, and urate overproduction. Uricosuric drugs include probenecid, benzbromarone, micronised fenofibrate and losartan. They are the urate-lowering drugs of choice in allopurinol-allergic patients and underexcretors with normal renal function and no history of urolithiasis. The use of recombinant urate oxidase in patients with chronic gout is limited by the need for parenteral administration, the potential antigenicity and production of anti-urate oxidase antibodies, and declining efficacy. The effectiveness of colchicine prophylaxis as an isolated therapy is still to be confirmed by placebo-controlled trials. Another issue is prophylaxis with NSAIDs. There are no comparative studies with colchicine.

Serum uric acid-lowering therapies: Where are we heading in management of hyperuricemia and the potential role of uricase

Although allopurinol has been available for approximately 50 years, hyperuricemia and its sequelae are not only prevalent, but the incidence and costs associated with this disorder continue to increase. However, several new therapies have been developed. Recombinant urate oxidase has been useful in the treatment of tumor lysis hyperuricemia, and pegylated urate oxidase shows promise in patients with hyperuricemia and gout. Febuxostat and Y-700 are new oral xanthine oxidase inhibitors that are in human clinical trials. Tailoring of antilipid therapy in selected hyperuricemic and hyperlipidemic patients with fenofibrate may be of benefit in lowering blood cholesterol and uric acid levels. Similarly, treatment of selected hyperuricemic patients who also are hypertensive with losartan or amlodipine may be beneficial in lowering blood pressure and hyperuricemia. Despite these advances, new treatments for hyperuricemia are needed.

Primary prevention in rheumatology: the importance of hyperuricemia

Hyperuricemia (HU) is present in 5-30% of the general population, although the prevalence is higher among some ethnic groups and seems to be increasing worldwide. Classically, chronic HU has been considered a risk factor for gout or lithiasis and is associated with alcoholism, obesity, hypertension, dyslipidemia, hyperglycemia/diabetes mellitus, renal failure and intake of certain drugs. HU is also associated with cardiovascular diseases such as hypertension, vascular disease, pre-eclampsia, pulmonary arterial hypertension, stroke, heart failure, ischemic heart disease and also metabolic syndrome, renal disease and increased mortality. It is uncertain if these associations are dependent or not, especially cardiovascular and renal diseases. Patients with chronic HU and also those with gout require both medical investigation for associated diseases or drugs as well as nutritional counseling and life-style changes. HU should alert physicians to possible complications.

Musculoskeletal features of disorders of lipid metabolism and multicentric reticulohistiocytosis

PURPOSE OF REVIEW

Musculoskeletal features of hyperlipidemia are well known, although rarely encountered by rheumatologists. New data have been collected on the beneficial and adverse effects of lipid-lowering drugs, which are of interest to rheumatologists. Multicentric reticulohistiocytosis is a rare systemic disorder of which joint involvement is an important and frequent feature. Recent advances in its pathophysiology and management have been made.

RECENT FINDINGS

Little has been added to the knowledge about the musculoskeletal features of hyperlipidemia in the recent literature. In contrast, the interest in fenofibrate for treating hyperuricemia in patients with lipid disorders or in those intolerant of allopurinol has been further supported. Muscle toxicity of statins continue to retain attention, and the ability of these drugs to induce low-grade myopathy, without increasing serum creatine kinase, has been defended. Multicentric reticulohistiocytosis has been the subject of a number of articles, including reports on the efficacy of cyclosporine and of etanercept in one patient each.

SUMMARY

Several issues of therapeutic importance are discussed in this brief review.

Effect of Fenofibrate on Uric Acid Metabolism in Japanese Hyperlipidemic Patients

Forty Type IIb or IV hyperlipidemic patients (serum triglyceride concentrations were higher than 150 mg/dl) were treated with fenofibrate (300 mg/day) for 12 weeks. Lipid profile and uric acid metabolism were evaluated before and after the treatment; the serum concentrations of total cholesterol and triglyceride respectively decreased from 224 +/- 41.9 mg/dl to 199 +/- 35.2 mg/dl and from 205 +/- 71.7 mg/dl to 134 +/- 67.5 mg/dl (p < 0.001). The uric acid concentrations in the serum also significantly decreased from 7.0 +/- 1.58 mg/dl to 5.2 +/- 1.57 mg/dl (p < 0.001). Fenofibrate treatment did not cause any change in the serum xanthine and hypoxanthine concentrations. Instead the urinary concentrations of uric acid decreased from 7.0 +/- 1.58 mg/dl to 5.2 +/- 1.57 mg/dl (p < 0.01), while the clearance ratio of uric acid and creatinin increased from 6.1 +/- 2.56 to 9.9 +/- 3.87 (p = 0.02) by the fenofibrate treatment. Fenofibrate decreases uric acid concentrations in the serum not as a result of inhibition of uric acid production but by increasing the urinary excretion of uric acid.

Update on fenofibrate

Fenofibrate is a fibric acid derivative that has been marketed since the mid-1970's (1998 in the United States). Its active metabolite, fenofibric acid, is responsible for the primary pharmacodynamic effects of the drug: reductions in total plasma cholesterol, low density lipoprotein cholesterol, triglycerides, and very low-density lipoprotein concentrations and increases in high-density lipoprotein cholesterol and apolipoproteins AI and AII concentrations. These effects are mediated by activation of peroxisome proliferator-activated receptor-alpha (PPAR(alpha)). The drug has broad spectrum utility, with documented efficacy in Fredrickson types IIa, IIb, III, IV, and V hyperlipidemias. Fenofibrate is well tolerated, with digestive and musculoskeletal side effects similar to those of other fibrates. Results of the initial cardiovascular morbidity/mortality outcomes study with fenofibrate (known as DAIS [Diabetes Atherosclerosis Intervention Study]) were encouraging vis-à-vis slowing of atherosclerotic progression in the coronary vasculature of type II diabetics. The results of other ongoing outcome trials are eagerly awaited. These results will help to establish the overall place of fenofibrate in the hypolipidemic armamentarium.

Hyperuricemia and gout

Gout is not a new disease for clinicians; nevertheless, there are still many secrets awaiting discovery for improving knowledge with respect to uric acid metabolism and monosodium urate crystal-induced inflammation. This review of the literature will focus on new insights on the pathogenesis of idiopathic hyperuricemia, and on secondary hyperuricemia and gout. There are also important advances on the pathophysiology of acute gout, especially as a self-limited process (switch from monocyte to macrophage, peroxisome proliferator activated receptor-gamma, and nitric oxide), but also of chronic gouty arthropathy. Armaments for treating hyperuricemia and gout may be already improved by losartan or fenofibrate and, in the future, by urate oxydase-polyethylene glycol 20 and renal handling regulatory molecules. Finally, control of hyperuricemia may also be considered in the prevention and treatment of cardiovascular disease.