Study Finds Celiac Disease in Native South American Toba People

Celiac.com 10/21/2015 - Celiac disease has been traditionally recognized among Caucasians, with an estimated prevalence of about 1%. Latin America features a the population with European ancestry, along with native communities sharing a diverse degree of mix with European colonizers.

The population of native Toba people comprises more than 60,000 individuals living with a clusters of villages in a forest called 'The Impenetrable' in Northeastern Argentina.

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In recent years, as a consequence of governmental food aid programs aimed at improving nutritional conditions in the community, the Toba people have undergone a drastic change in dietary habits, with wheat replacing their ancestral food sources.

In general celiac disease can only occur in individuals with certain class II human leukocyte antigen (HLA) molecules – namely, HLA DQ2 and/or DQ8, but little information exists about the prevalence of HLA DQ2 and DQ8, and of celiac disease in native South Americans.

The research team included Horacio Vázquez MD, María de la Paz Temprano RD, Emilia Sugai MS, Stella M Scacchi MS, Cecilia Souza MD,Daniel Cisterna MS, Edgardo Smecuol MD, María Laura Moreno MD, Gabriela Longarini MD, Roberto Mazure MD, María A Bartellini MS, Elena F Verdú MD2, Andrea González RD, Eduardo Mauriño MD, and Julio C Bai MD. They are variously affiliated with the Small Bowel Section, Department of Medicine, Hospital de Gastroenterología C Bonorino Udaondo. Buenos Aires, Argentina and the Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario.

For their study, the research team set out to prospectively assess environmental, genetic and serological conditions associated with celiac disease among members of the Toba native population attending a multidisciplinary sanitary mission. Using an established questionnaire, an expert nutritionist determined daily gluten intake. The team then conducted gene typing for the human leuko-cyte antigen (HLA) class II alleles using DNA extracted from peripheral blood (HLA DQ2/DQ8 haplotype).

The team then measured serum antibodies were immunoglobulin (Ig) A tissue transglutaminase (tTG) and the composite deamidated gliadin peptides/tTG Screen test. They tested positive cases for IgA endomysial antibodies.

The team screened a total of 144 subjects, 55% of those female. Estimated average gluten consumption was 43 grams per day, ranging from 3 grams per day up to 185 grams per day. Genetic typing showed that 73 of 144 subjects had alleles associated with celiac disease; 69 of these subjects had alleles for HLA DQ8, while four had DQ2.

Four and six subjects had antibody concentrations above the cut-off established by the authors' laboratory (>3 times the upper limit of normal) for IgA tTG and deamidated gliadin peptides/tTG screen, respectively. Four of these had concomitant positivity for both assays and endomysial anti-bodies were positive in three subjects who also presented a predispos-ing haplotype.

The present study was the first to detect celiac disease in Native Americans. The native Toba ethnic population has very high daily gluten consumption, and a predisposing genetic background.

This study found subjects with persistent celiac disease autoimmunity and, at least, three of them met serological criteria for celiac disease diagnosis. 

This study invites some questions about gluten and celiac disease in the tribe. For example, does the amount of gluten in the diet of people with genetic predisposition have an impact on the likelihood of celiac disease? Given that many of these people likely had DQ2/DQ8 positivity for many generations, did the introduction of wheat into their diets trigger their celiac disease?

Much remains to be understood about celiac disease, and studies like this can be important and insightful.

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