Scientists at the University of Minnesota, USA, have initiated a study entitled “the Hmong Microbiome and Gout, Obesity, Vitamin C (HMANGO-C) study” to determine the effect of vitamin C supplementation on serum urate levels in Hmong adults with or without gout. Hmong (pronounced mung) is a racial group originally from the Southwest of China.
They have published the protocol of this phase II clinical study in the journal PLOS ONE.
Study: Hmong microbiome ANd Gout, Obesity, Vitamin C (HMANGO-C): A phase II clinical study protocol. Image Credit: Doucefleur / Shutterstock
Gout is a common form of inflammatory arthritis characterized by persistently high serum urate levels. With a global prevalence of 0.1% - 10%, the disease increases the risk of cardiometabolic complications and is associated with significant morbidity and mortality.
In the United States, the prevalence of gout is almost 4%, with certain ethnicities exhibiting even higher prevalence. The Hmong community residing in Minnesota has a 2-fold higher prevalence of gout and a 5-fold higher prevalence of uric acid renal stones compared to the non-Hmong population.
Studies investigating various dietary supplements have shown that Vitamin C helps reduce serum urate levels and the risk of gout in healthy individuals. Mechanistically, vitamin C has been found to cause increased excretion of uric acid in the urine by inhibiting renal urate reabsorption in the renal tubule in gout patients.
The HMANGO study is a prospective open-labeled clinical trial designed to explore the impact of vitamin C supplementation on serum urate levels in high-risk Hmong adults living in Minnesota.
The study also aims to explore the interplay between vitamin C supplementation, taxonomic and functional patterns of gut microbiota, and serum urate-lowering effect of vitamin C. Moreover, the study will explore the relationship between obesity, gut microbiota, and gout. The study will screen for differential microbial biomarkers and selected genetic variations impacting the urate-lowering ability of vitamin C in Hmong adults with or without gout.
The study utilized a community-based participatory research (CBPR) approach to evaluate the study question. This particular approach engages both community members and researchers in egalitarian partnerships to work collaboratively.
Maintaining the coronavirus disease 2019 (COVID-19)-related restrictions, the study has started recruiting participants since March 2021 through face-to-face and remote community outreach initiatives. A total of 180 Hmong adults, including 120 with gout and 60 without gout, were enrolled in the study.
The participants were asked to orally consume 500 mg of vitamin C (capsule) twice daily for 8 weeks. To increase treatment adherence, participants were asked to maintain a record of their vitamin C intake. Follow-up reminders were also sent to them at weeks 1, 4, and 7.
The participants self-collected stool, urine, and saliva samples using the kits provided by researchers to them. Urine and stool samples collected before and after the treatment will be used to analyze urate levels and gut microbiota. Saliva samples will be analyzed to identify genetic markers related to uric acid disposition.
The participants underwent health and food surveys during the study period. In the health survey, they were asked to provide information on personal and family medical history, lifestyle activities, and medication history. In the food survey, they were asked to provide 1-month food recall history, including gout episode-triggering foods.
The presence of gout was assessed by asking participants to complete a gout symptom online assessment tool using an established swollen joint count tool. In addition, they were asked to complete a modified gout assessment questionnaire version 2.0, which assesses overall gout concerns, gout medication side effects, unmet treatment goals, well-being during gout attacks, and concerns during gout attacks.
The study findings, including vital signs, anthropometry, renal functions, serum urate levels, COVID-19 antibodies, genetics, and microbiome results, will be mailed to all participants after the completion of the study. The findings will also be shared with local physicians and pharmacists involved in the study. In addition, the general audience will get to know about the study outcome through conferences and published articles.
The study is expected to provide an in-depth understanding of the utility of gut microbiota and genetic information in identifying high-risk gout patients who could be benefited from vitamin C supplementation.