EXPLORATION OF EMIRATI DIET AND GENETICS REVEALS HIGH SALT TRIGGER

Eating habits may not only be attributed to our culture, upbringing, and personal preferences. A recent research project, led by a University of Sharjah professor, has found a potential genetic cause for the preference for a high salt diet recorded in the Emirati population, and the results may be leveraged to improve personalized health.

As human beings, we share about 99.9% of our genes, but it is the differences in the remaining 0.1% that produce the huge variation seen in humanity. Genes determine not only our physical characteristics like skin and eye color, but also some health traits and habits. Whether a characteristic is due to nature or nurture, genetics, or personal choice, is still being clarified by scientists.

A specific liver hormone called fibroblast growth factor 21 (FGF-21), which is encoded in the FGF-21 gene, has been linked in recent research to some dietary habits. FGF-21 is known to affect a number of biological functions, including the central mechanisms of appetite control and insulinsensitizing properties. Variations of the FGF-21 gene have previously been found to be linked to high sugar consumption in some Caucasian populations, which in turn was correlated to hypertension and high waist-hip ratio. Given the high rate of obesity, type-2 diabetes, and hypertension among Emirati populations, Dr. Maha SaberAyed, Associate Professor of Pharmacology at the University of Sharjah (UOS), sought to explore its role in Emirati eating habits.

“Gene variants in FGF-21 have been linked to sweet preference in other populations,” Dr. Saber-Ayed explained, citing the Denmark study, which was published in the leading journal Cell Metabolism in 2017. The research studied 13,016 Danish people, and found that variations in the FGF-21 gene related to increased consumption of sugar and nominal increased consumption of alcohol and cigarettes. A later study of British people with European ancestry also found a common FGF-21 allele to be associated with high sugar intake, waist-hip ratio, and blood pressure.

“The Emirati population is unique, and very few studies have sought to identify key markers, in the form of gene variants, to see if there is an affinity among the population for certain food types. In support of increasing scientific understanding for the greater public health of the UAE, we undertook the first study of its kind in the region to show the link between genetics and diet,” she said.

Improving public health is a key part of the UAE’s national strategy. The UAE Vision 2021 specifically outlines the goal to reduce the number of deaths from cardiovascular disease (CVD) and cancer, as well as the prevalence of diabetes and childhood obesity.

Dr. Saber-Ayad’s project collaborators from the UOS included Assistant Professor of Clinical Nutrition Dr. Hadia Radwan, PhD students Sarah Hammoudeh and Shaista Manzoor, Dr. Hussein Jabbar, Dr. Rahaf Wardeh, Dr. Ahmed Ashraf, and Professor of Molecular Pathology and Genetics Dr. Rifat Hammoudi. Peter Habib, from the Egyptian International Center for Agricultural Research in Dry Areas, and Alsamman M. Alsamman, from the Egyptian Agricultural Genetic Engineering Research Institute, also contributed to the project. A paper on their research was published in the Journal of Advanced Research.

To ascertain the role of FGF-21 in Emirati eating habits, the researchers selected 196 healthy Emirati participants, ranging in age from 18 to 73 years, with a balance of both genders (56% women and 44% men). The weight and body mass index information for each study participant was recorded. The participants were given visual aids to show the standard portion of each food item and then asked to complete a food frequency questionnaire that collected information on the types of food and beverages they consume, the amount they consume, and the frequency with which they consume them. This was used to calculate their daily portion intake using diet analysis software. Saliva samples were collected from all participants 30 minutes after eating, which were used for DNA extraction and genetic analysis.

The genetic analysis focused on chromosome 19, to check for specific FGF-21 variations in each individual. The most common type of genetic variation

ANALYSIS OF THE GENETIC SAMPLES DID FIND A SLIGHT CORRELATION BETWEEN FGF-21 ALLELES AND CARBOHYDRATE AND SUGAR CONSUMPTION IN EMIRATIS, BUT WHAT WAS SURPRISING WAS THE STRONG LINK WITH SALT INTAKE

among people is single-nucleotide polymorphisms (SNPs). Each SNP represents a difference in a single DNA building block. If an SNP occurs within a gene, then the gene is described as having more than one allele. Alleles influence the way our bodies’ cells work, determining traits and characteristics. Humans inherit one allele from each parent for each gene. In the context of this research project, two SNPs on the FGF-21 gene were examined – rs838133 and rs838145 (allele A and allele G respectively) – for their role in influencing dietary habits.

Analysis of the genetic samples did find a slight correlation between FGF-21 alleles and carbohydrate and sugar consumption in Emiratis, but what was surprising was the strong link with salt intake. Participants who reported high salt intake had a higher proportion of FGF-21 SNPs.

Males with the minor G allele had a significantly higher intake of total sodium, while females with the same genotype had a higher intake of vitamin D. BMI did not appear to be affected by the genotype of either SNP. Salt intake was found to positively correlate with fruit and vegetable intake in those with both SNPs.

This was not the case for those who received the same allele from both parents. The positive correlation between vegetable and salt intake may be due to the consumption of salad seasoning, as sodium and salad seasoning intake were found to be linked in participants aged 18 to 35. Other foods found to be prevalent in the diets of those with high salt intake include cheese, falafel, pizza, salted nuts, and white bread. Carbohydrate intake was found to significantly correlate with sweet intake across all age groups.

Participants aged 18 to 24, who received the same allele from both parents – either two copies of allele A, or two copies of allele G – had a higher total carbohydrate and overall caloric intake, however, the role of the FGF-21 gene alleles in sugar/ carbohydrate consumption was not considered statistically significant.

Although discovering a link between salt consumption and the FGF-21 gene was not the goal of the project, Dr. Saber-Ayad said the results were notable and useful.

The UAE’s average total sodium intake has been estimated at nine grams per day, which is nearly double the five grams recommended by the World Health Organization (WHO). Salt is mostly made up of sodium, which is known to have impacts on human health. High salt intake is linked to high blood pressure, heart and kidney diseases, and may also be associated with obesity, asthma, osteoporosis, and stomach cancer. Sodium can damage blood vessels, making them hard and rigid, making high salt consumption harmful to those with cardiovascular and hypertensive health conditions.

“High salt intake can lead to increased risk of CVD, which is a major health problem in the UAE. High salt intake can lead to high blood pressure, which has been found to be present in 35% of patients, while 14.4% of

patients have a history of coronary artery disease,” Dr. Saber-Ayad explained. The WHO reported in 2018 that CVDs accounted for 40% of deaths in the UAE, making it the single leading cause of death in the country.

Dr. Saber-Ayad believes this research can help guide doctors to better prevent or reduce high salt intake as a contributor to CVD. It could also contribute to personalized medicine, she suggested, in which information about a patient’s genes informs their disease prevention, diagnosis, and treatment.

“Our research findings reflect a geneenvironment interaction and taste preference that may lead to certain chronic diseases related to high salt intake, such as hypertension. Emirati individuals with the two markers (gene variants) will have high salt intake, so it is worth checking whether people with high salt intake have the two markers, and if so, they may need to see a specialist nutritionist to ensure they go on a low salt diet. This might prevent them from developing diseases such as CVD and others in the future,” Dr. Saber-Ayad said.

The research team plans to continue their exploration of correlations between Emirati gene variants and health and habits. As a next step, they will investigate a potential link between the FGF-21 variants and high blood pressure and the efficacy of blood pressure treatments.