Gout in Maoris

Dietary supplements for chronic gout

BACKGROUND

Dietary supplements are frequently used for the treatment of several medical conditions, both prescribed by physicians or self administered. However, evidence of benefit and safety of these supplements is usually limited or absent.

OBJECTIVES

To assess the efficacy and safety of dietary supplementation for people with chronic gout.

SEARCH METHODS

We updated the original search by searching CENTRAL, MEDLINE, Embase, CINAHL, and four trials registers (August 2020). We applied no date or language restrictions. We also handsearched the abstracts from the 2010 to 2019 American College of Rheumatology and European League against Rheumatism conferences, and checked the references of all included studies.

SELECTION CRITERIA

We considered all published randomised controlled trials (RCTs) or quasi-RCTs that compared dietary supplements with no supplements, placebo, another supplement, or pharmacological agents for adults with chronic gout for inclusion. Dietary supplements included, but were not limited to, amino acids, antioxidants, essential minerals, polyunsaturated fatty acids, prebiotic agents, probiotic agents, and vitamins. The major outcomes were acute gout flares, study withdrawal due to adverse events (AEs), serum uric acid (sUA) reduction, joint pain reduction, participant global assessment, total number of AEs, and tophus regression.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

Two previously included RCTs (160 participants) met our inclusion criteria; we did not identify any new trials for this update. As these two trials evaluated different diet supplements (enriched skim milk powder (SMP) and vitamin C) with different outcomes (gout flare prevention for enriched SMP, and sUA reduction for vitamin C), we reported the results separately. One trial (120 participants), at unclear risk of selection and detection bias, compared SMP enriched with glycomacropeptides (GMP) with un-enriched SMP, and with lactose, over three months. Participants were predominantly men, aged in their 50s, who had severe gout. The results for all major outcomes were imprecise, except for pain. None of the results were clinically significant. The frequency of acute gout attacks, measured as the number of flares per month, decreased in all three groups over the three-month study period. The effects of enriched SMP (SMP/GMP/G600) compared with the combined control groups (SMP and lactose powder) at three months in terms of mean number of gout flares per month were not clinically significant (mean (standard deviation (SD)) flares per month: 0.49 (1.52) in SMP/GMP/G60 group versus 0.70 (1.28) in the control groups; absolute risk difference: mean difference (MD) -0.21 flares per month, 95% confidence interval (CI) -0.76 to 0.34; low-quality evidence). The number of withdrawals due to adverse effects was similar between groups (7/40 in SMP/GMP/G600 group versus 11/80 in control groups; (risk ratio (RR) 1.27, 95% CI 0.53 to 3.03); there were 4% more withdrawals in the SMP/lactose groups (10% fewer to 18% more; low-quality evidence). Serum uric acid reduction was similar across groups (mean (SD) -0.025 (0.067) mmol/L in SMP/GMP/G60 group versus -0.010 (0.069) in control groups; MD -0.01, 95% CI -0.04 to 0.01; low-quality evidence). Pain from self-reported gout flares (measured on a 10-point Likert scale) improved slightly more in the GMP/G600 SMP group compared with controls (mean (SD) -1.97 (2.28) in SMP/GMP/G600 group versus -0.94 (2.25) in control groups; MD -1.03, 95% CI -1.89 to -0.17). This was an absolute reduction of 10% (95% CI 20% to 1% reduction; low-quality evidence), which may not be of clinical relevance. The risk of adverse events was similar between groups (19/40 in SMP/GMP/G600 group versus 39/80 in control groups; RR 0.97, 95% CI 0.66 to 1.45); the absolute risk difference was 1% fewer adverse events (1% fewer to 2% more), low-quality evidence). Gastrointestinal events such as nausea, flatulence and diarrhoea were the most commonly reported adverse effects. Data for participant global assessment were not available for analysis; the study did not report tophus regression. One trial (40 participants), at high risk of selection, performance, and detection bias, compared vitamin C alone with allopurinol, and with allopurinol plus vitamin C, in a three-arm study. We only included data from the vitamin C versus allopurinol comparison in this review. Participants were predominantly middle-aged men, and their severity of gout was representative of gout in general. Allopurinol reduced sUA levels more than vitamin C (MD 0.10 mmol/L, 95% CI 0.06 to 0.15), low-quality evidence. The study reported no adverse events; none of the participants withdrew due to adverse events. The study did not assess the rate of gout attacks, joint pain reduction, participant global assessment, or tophus regression.

AUTHORS' CONCLUSIONS

While dietary supplements may be widely used for gout, this review found no high-quality that supported or refuted the use of glycomacropeptide-enriched skim milk powder or vitamin C for adults with chronic gout.

Gout: a review of nonmodifiable and modifiable risk factors

Gout is a common inflammatory arthritis triggered by the crystallization of uric acid within the joints. Gout affects millions worldwide and has an increasing prevalence. Recent research has been carried out to better qualify and quantify the risk factors predisposing individuals to gout. These can largely be broken into nonmodifiable risk factors, such as gender, age, race, and genetics, and modifiable risk factors, such as diet and lifestyle. Increasing knowledge of factors predisposing certain individuals to gout could potentially lead to improved preventive practices. This review summarizes the nonmodifiable and modifiable risk factors associated with development of gout.

Dietary supplements for chronic gout

BACKGROUND

Dietary supplements are frequently used for the treatment of several medical conditions, both prescribed by physicians or self administered. However, evidence of benefit and safety of these supplements is usually limited or absent.

OBJECTIVES

To assess the efficacy and safety of dietary supplementation for people with chronic gout.

SEARCH METHODS

We performed a search in the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and CINAHL on 6 June 2013. We applied no date or language restrictions. In addition, we performed a handsearch of the abstracts from the 2010 to 2013 American College of Rheumatology (ACR) and European League against Rheumatism (EULAR) conferences, checked the references of all included studies and trial registries.

SELECTION CRITERIA

We considered all published randomised controlled trials (RCTs) or quasi-RCTs that compared dietary supplements with no supplements, placebo, another supplement or pharmacological agents for adults with chronic gout for inclusion. Dietary supplements included, but were not limited to, amino acids, antioxidants, essential minerals, polyunsaturated fatty acids, prebiotic agents, probiotic agents and vitamins. The main outcomes were reduction in frequency of gouty attacks and trial participant withdrawal due to adverse events. We also considered pain reduction, health-related quality of life, serum uric acid (sUA) normalisation, function (i.e. activity limitation), tophus regression and the rate of serious adverse events.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We identified two RCTs (160 participants) that fulfilled our inclusion criteria. As these two trials evaluated different diet supplements (enriched skim milk powder (SMP) and vitamin C) with different outcomes (gout flare prevention for enriched SMP and sUA reduction for vitamin C), we reported the results separately.One trial including 120 participants, at moderate risk of bias, compared SMP enriched with glycomacropeptides (GMP) with unenriched SMP and with lactose over three months. Participants were predominantly men aged in their 50's who had severe gout. The frequency of acute gout attacks, measured as the number of flares per month, decreased in all three groups over the study period.The effects of enriched SMP (SMP/GMP/G600) compared with the combined control groups (SMP and lactose powder) at three months in terms of mean number of gout flares per month were uncertain (mean ± standard deviation (SD) flares per month: 0.49 ± 1.52 in SMP/GMP/G60 group versus 0.70 ± 1.28 in control groups; mean difference (MD) -0.21, 95% confidence interval (CI) -0.76 to 0.34; low-quality evidence). The number of withdrawals due to adverse effects was similar in both groups although again the results were imprecise (7/40 in SMP/GMP/G600 group versus 11/80 in control groups; risk ratio (RR) 1.27, 95% CI 0.53 to 3.03; low-quality evidence). The findings for adverse events were also uncertain (2/40 in SMP/GMP/G600 group versus 3/80 in control groups; RR 1.33, 95% CI 0.23 to 7.66; low-quality evidence). Gastrointestinal events were the most commonly reported adverse effects. Pain from self reported gout flares (measured on a 10-point Likert scale) improved slightly more in the SMP/GMP/G600 group compared with controls (mean ± SD reduction -1.97 ± 2.28 points in SMP/GMP/G600 group versus -0.94 ± 2.25 in control groups; MD -1.03, 95% CI -1.96 to -0.10; low-quality evidence). This was an absolute reduction of 10% (95% CI 20% to 1% reduction), which may not be of clinical relevance. Results were imprecise for the outcome improvement in physical function (mean ± SD Health Assessment Questionnaire (HAQ)-II (scale 0 to 3, 0 = no disability): 0.08 ± 0.23 in SMP/GMP/G60 group versus 0.11 ± 0.31 in control groups; MD -0.03, 95% CI -0.14 to 0.08; low-quality evidence). Similarly, results for sUA reduction were imprecise (mean ± SD reduction: -0.025 ± 0.067 mmol/L in SMP/GMP/G60 group versus -0.010 ± 0.069 in control groups; MD -0.01, 95% CI -0.04 to 0.01; low-quality evidence). The study did not report tophus regression and health-related quality of life impact.One trial including 40 participants, at moderate to high risk of bias, compared vitamin C alone with allopurinol and with allopurinol plus vitamin C in a three-arm trial. We only compared vitamin C with allopurinol in this review. Participants were predominantly middle-aged men, and their severity of gout was representative of gout in general. The effect of vitamin C on the rate of gout attacks was not assessed. Vitamin C did not lower sUA as much as allopurinol (-0.014 mmol/L in vitamin C group versus -0.118 mmol/L in allopurinol group; MD 0.10, 95% CI 0.06 to 0.15; low-quality evidence). The study did not assess tophus regression, pain reduction or disability or health-related quality of life impact. The study reported no adverse events and no participant withdrawal due to adverse events.

AUTHORS' CONCLUSIONS

While dietary supplements may be widely used for gout, this review has shown a paucity of high-quality evidence assessing dietary supplementation.

Hyperuricaemia in the Pacific: why the elevated serum urate levels?

Pacific Island populations, particularly those of Polynesian descent, have a high prevalence of hyperuricaemia and gout. This is due to an inherently higher urate level among these populations with a demonstrated genetic predisposition. While an excess of urate can cause pathology, urate is also important for human health. It has been implicated as an antioxidant, has a neuroprotective role and is involved in innate immune responses. This paper provides a brief review of urate levels worldwide, with a particular focus on island Southeast Asia and the Pacific. We then present possible evolutionary explanations for the elevated serum urate levels among Pacific populations in the context of the physiological importance of urate and of the settlement history of the region. Finally, we propose that ancestry may play a significant role in hyperuricaemia in these populations and that exposure to malaria prior to population expansion into the wider Pacific may have driven genetic selection for variants contributing to high serum urate.

Racial and gender disparities among patients with gout

Gout affects 8.3 million Americans according to NHANES 2007-2008, approximately 3.9 % of the US population. Gout has substantial effect on physical function, productivity, health-related quality of life (HRQOL), and health care costs. Uncontrolled gout is also associated with significant use of emergency care services. Women are less likely to have gout than men, but in the postmenopausal years the gender difference in disease incidence decreases. Compared with whites, racial and/or ethnic minorities, especially blacks, have higher prevalence of gout. Blacks are also less likely to receive quality gout care, leading to disproportionate morbidity. Women are less likely than men to receive allopurinol, and less likely to undergo joint aspirations for crystal analysis to establish diagnosis, but those on urate-lowering therapy are as likely as, or more likely than, men to undergo serum urate check within six months of initiation. Although a few studies provide the knowledge related to gender and race and/or ethnicity disparities for gout, several knowledge gaps exist in gout epidemiology and outcomes differences by gender and race and/or ethnicity. These should be investigated in future studies.

Hypothesis: could excessive fructose intake and uric acid cause type 2 diabetes?

We propose that excessive fructose intake (>50 g/d) may be one of the underlying etiologies of metabolic syndrome and type 2 diabetes. The primary sources of fructose are sugar (sucrose) and high fructose corn syrup. First, fructose intake correlates closely with the rate of diabetes worldwide. Second, unlike other sugars, the ingestion of excessive fructose induces features of metabolic syndrome in both laboratory animals and humans. Third, fructose appears to mediate the metabolic syndrome in part by raising uric acid, and there are now extensive experimental and clinical data supporting uric acid in the pathogenesis of metabolic syndrome. Fourth, environmental and genetic considerations provide a potential explanation of why certain groups might be more susceptible to developing diabetes. Finally, we discuss the counterarguments associated with the hypothesis and a potential explanation for these findings. If diabetes might result from excessive intake of fructose, then simple public health measures could have a major impact on improving the overall health of our populace.

Uric acid, evolution and primitive cultures

Hypertension is epidemic and currently affects 25% of the world's population and is a major cause of stroke, congestive heart failure, and end-stage renal disease. Interestingly, there is evidence that the increased frequency of hypertension is a recent event in human history and correlates with dietary changes associated with Westernization. In this article, we review the evidence that links uric acid to the cause and epidemiology of hypertension. Specifically, we review the evidence that the mutation of uricase that occurred in the Miocene that resulted in a higher serum uric acid in humans compared with most other mammals may have occurred as a means to increase blood pressure in early hominoids in response to a low-sodium and low-purine diet. We then review the evidence that the epidemic of hypertension that evolved with Westernization was associated with an increase in the intake of red meat with a marked increase in serum uric acid levels. Indeed, gout and hyperuricemia should be considered a part of the obesity, type 2 diabetes, and hypertension epidemic that is occurring worldwide. Although other mechanisms certainly contribute to the pathogenesis of hypertension, the possibility that serum uric acid level may have a major role is suggested by these studies.

Potential functional foods in the traditional Maori diet

The Maori people were early New Zealand settlers of Polynesian descent. The incidence of non-infectious diseases appears to have been low in these people, perhaps in part due to the presence of protective chemical constituents within their food plant supply. Three of the tropical crops they introduced are still eaten here today: the sweet potato or kumara (Ipomoea batatas), the taro (Colocasia esculenta) and the cabbage tree or ti (Cordyline terminalis). Sporamins A and B, the major storage proteins of kumara tubers, act as proteinase inhibitors, and may have other anti-cancer properties. The tubers also contain the anti-coagulant coumarins, scopoletin, aesculetin, and umbelliferone. The corms of taro contain the anthocyanins, cyanidin 3-glucoside, pelargonidin 3-glucoside and cyanidin 3-rhamnoside, reported to have antioxidant and anti-inflammatory properties. Anthocyanins are also major components of a so-called "Maori potato", a variety officially known as Ureniki, which has a purple skin and flesh and was widely eaten in the early 1900s. Anthocyanins are also present in ripe berries of the ramarama (Lophomyrtus bullata) and rohutu (Neomyrtus pedunculata). Both the leaves and seeds of the introduced cabbage tree (Cordyline terminalis) and the native Cordyline spp., C. australis, C. indivisa, and C. pumilo, were eaten. The seeds of C. australis, of some Astelia spp., and of hinau (Elaeocarpus dentatus) are good sources of various essential fatty acids, generally regarded as protective against cardiovascular disease. Shoots and leaves from a wide range of native species were traditionally eaten as greens, especially "sow thistle" or puha (Sonchus spp.), reportedly high in Vitamin C and various phenolics. "New Zealand spinach" (Tetragonia tetragonioides or T. expansa) has anti-ulcerogenic activity that has been traced to two cerebrosides and anti-inflammatory activity that has been traced to novel water-soluble polysaccharides, as well as antioxidant phenylpropanoids including caffeic acid. Leaves of the "hen and chickens" fern (Asplenium bulbiferum) contain antioxidant flavonoids such as kaempferol glucosides. Native seaweeds also have useful nutritive properties.

Characteristics of gouty arthritis in the Guatemalan population

The purpose of this study was to determine the characteristics of gouty arthritis in an urban Guatemalan population. We reviewed the medical records of 148 (145 males and 3 females) patients with a diagnosis of acute gouty attack seen at an urban rheumatology clinic in Guatemala City between 1982 and 1993. Mean age at diagnosis was 49 years (range 21-87), mean age of onset was 42 years, mean duration of disease 7.4 years, family history of gout 42 (28%), peak prevalence 5th decade 39 (26%). Seventy-one (48%) had monarticular, 49 (33%) oligoarticular, and 22 (15%) polyarticular attacks, respectively. Podagra was seen in 34 (23%) patients; however, 108 (73%) developed it at any moment of their life. Tophaceous gout was seen in 33 (22%). Mean serum urate concentrations (enzymatic method) were higher than 7.0 mg % in 90 (60%) patients. At follow-up, 44 (30%) patients never returned to our clinic, and a large majority of them [66 (45%)] were seen only during acute attacks. Associated disorders included hypertension (43%), obesity (27%), nephrolithiasis (16%), ischaemic heart disease (7%), renal insufficiency (2%), stroke (0.6%), and diabetes mellitus (0.6%), and two died due to sepsis; high alcoholic intake was found in 58 (39%) patients. In conclusion, our findings indicate that gout is not an unusual disorder in the Guatemalan population. It presents with the same characteristics as those reported in Caucasians, with the possible exception of a lower frequency of diabetes mellitus as an associated disorder.

Gout in black South Africans: a clinical and genetic study

OBJECTIVE

To define the clinical characteristics of gout and determine if there were any genetic associations with gout in black South Africans.

METHODS

The records of 107 patients with gout seen over a five year period were retrospectively analysed. The HLA class I and class II antigens were studied in a prospective survey of 46 patients.

RESULTS

The male to female ratio was 6.6:1. The diagnosis of gout was based on identification of monosodium urate crystals from the synovial fluid, synovial tissue or tophaceous material in 62 patients (58%) and on clinical criteria in the remaining 45 patients (42%). The mode of presentation was monoarthritis in 40 patients (37.4%), pauciarthritis in 30 (28%) and polyarthritis in 37 (34.6%). The joints which were most frequently involved were the knee in 91 patients (85%), the first metatarsophalangeal in 80 (74.8%) and the ankle in 66 (61.7%). A secondary cause was identified in 52 patients (48.6%) (diuretic therapy in 48 patients and chronic renal impairment in four); 55 patients (51.4%) had primary gout. The genetic study showed an increased frequency of HLA-B14 in patients with primary gout compared with controls.

CONCLUSIONS

Gout is more common in black Africans than previously recognised and frequently presents with involvement of more than one joint. There was an increased frequency of HLA-B14 in patients with primary gout but the clinical significance of this is uncertain.

Migration and gout: the Tokelau Island migrant study

The prevalence and 14 year incidence of clinical gout and its precursors were investigated in the Polynesian population of Tokelauans living in the Pacific basin, non-migrant Tokelauans living in their isolated atoll homeland being compared with migrant Tokelauans living in urban New Zealand. The age standardised prevalence of gout in Tokelauan men in New Zealand was higher than that in non-migrant Tokelauan men, being 21.0 and 19.5/1000 subjects at the beginning of the study and 51.0 and 14.6/1000 at the end of study, respectively. Migrant men in New Zealand aged under 55 had higher mean serum uric acid concentrations than non-migrant men of the same age. The prevalence of gout was low in women in both environments. The age standardised relative risk of developing gout between 1968 and 1982 was 9.0 times higher in the migrant men than in the non-migrant men. Age, serum uric acid concentration, serum cholesterol concentration, and self reported alcohol consumption at entry to the study were the best set of predictors of gout in men. Preventive strategies to change body mass, diet, and patterns of alcohol use need to be developed in this population.

Gout in South African blacks

A retrospective study was carried out to determine the frequency, age of onset, mode of presentation, pattern of joint involvement, and incidence of primary and secondary gout in black patients with gout who were admitted to the King Edward VIII Hospital in Durban, South Africa. Nineteen patients were admitted to hospital with gout over a 5-year period from 1977 to 1981. The admission rate was found to be 4.7/100 000 hospital admissions. Five patients (26%) presented with monoarthritis and 14 patients (74%) had polyarthritis on admission. The joints most frequently involved were the knees (74%), the first metatarsophalangeal (MTP) joint (58%), and ankles (42%). The serum uric acid (SUA) was increased in 94%, and tophi were noted clinically in 47%. Eight patients (42%) with hypertension were on treatment with diuretics and 7 of these patients had a raised blood urea. These 8 patients (42%) were considered to have secondary gout, while no secondary causes were noted in the remaining 11 patients (58%) who had primary gout.