27.07.2011 -

In each individual, the perception of the four basic tastes (sour, salty, sweet, bitter) is also linked to genetic factors. The perception of taste and, therefore, our food preferences are in fact regulated by specific genes.

 

Geneticists on the MarcoPolo project are only now starting to reveal the functions, interactions and mechanisms of these genes, which can influence both the diet of entire communities and personal tastes in food.

 

Geneticists working on the MarcoPolo project are heading to Armenia tomorrow (and to Crimea in October) where they will continue the sampling work commenced in July 2010 along the Silk Road. Once again, the expedition will be documented daily on the website www.marcopolo2011.it .

 

The MarcoPolo2011 project was conceived and realised by IRCCS Burlo Garofolo, Sissa Medialab and the Terra Madre Foundation, in collaboration with AREA Science Park and the Department of Reproductive Sciences and Development at the University of Trieste; it is sponsored by the Autonomous Region of Friuli Venezia Giulia, the Province of Trieste, the Municipality of Trieste and the Italian Embassy in Yerevan.

 

Sampling and test results

 

Taste

The link between 26 candidate genes for taste and our food preferences has been studied, and various positive associations identified. The most interesting relates to the ITPR3 gene, which appears to be associated with many food preferences with different markers. The function of this gene is to transduce intracellular signals and it would appear to be involved in food preferences in general.

 

Initially, significant associations were only found with certain foods that do not appear to be connected to each other, such as peas, pecorino cheese and watermelon. However, on checking non-significant associations, it was found that this gene appears to be involved, with similar effects, in preferences for 35 different foods.

 

Significant associations have also been found between the capsaicin receptor, the substance that makes chilli peppers taste hot, and the radish, which also has a peppery flavour. Another positive association is that between an olfactory gene and a preference for tea, which is especially plausible since the taste of tea is primarily determined by the sense of smell.

 

Lastly, it was confirmed that the sweet receptor is associated with both white wine and vodka: it is in fact well known that ethanol is able to activate the sweet receptor. For example, in the laboratory, it has been observed that mice that differ in their preference for sweet foods also show variations in their alcohol preferences. Further studies will be conducted, including functional studies, to better test this hypothesis even in isolated Italian communities.

 

 

Population genetics

This branch studies the relationships between individuals, their degree of kinship and ultimately their history, through DNA. In places such as those found along the Silk Road, which have seen different communities - characterised by the continuous movement of men and goods - coexist for centuries, this type of research can complement historic, ethnographic and linguistic studies, thus helping us to understand which relationships have interwoven the various groups of people over the centuries. Around 18 communities were analysed and their genomes characterised by around 700,000 genetic markers. Analysis of this huge amount of data is almost complete.

 

Among the preliminary results, a similarity between the Kazakh communities examined is immediately apparent (the different communities are largely overlapping, a sign of a significant genetic mix), as is the extreme homogeneity of the Zerafshan communities in Tajikistan.

 

It has also emerged that ethnically and linguistically isolated communities, such as those in the Pamir area, are now losing their typical characteristics: of the subjects examined, some stand out as having a genome that is comparable to that of the rest of the Tajik community, while others have completely unique and distinctive genomes. The last piece of data that is worthy of note is the absolute uniqueness of the Uzbeks in Qarshi, who significantly differ from all the other communities examined.

 

 

Hearing

Deafness (or hypoacusis) affects millions of people throughout the world: approximately one child in a thousand is born with hearing problems that impair the development of normal speech.

 

The causes may be genetic (due to a chromosome abnormality) or acquired (due to the following causes: infections, vascular, degenerative, autoimmune, tumours, iatrogenic, etc.). In 70% of cases, it is of genetic origin, and can be inherited in a variety of ways: autosomal recessive (75-80% of cases), autosomal dominant, X-linked and mitochondrial.

 

The aetiology can however be multifactorial, reflecting the interaction of a large number of genetic and environmental components, as is the case in presbycusis. Until now, epidemiological data has been collected in Western countries, while for many developing countries there is a lack of information.

 

Five hundred people, aged between 8 and 84, were recruited in the course of the MarcoPolo mission and asked to answer a questionnaire on their medical history and undergo an audiometric test to measure hearing. The results of this study have identified a prevalence of deafness ranging between 9% and 18%.

 

This percentage is higher than that reported by the World Health Organisation for European countries, but is comparable to that reported for countries in South East Asia. The difference could suggest that socio-economic and environmental factors play an important role in the prevention, identification and treatment of the problem.

 

The results of all the analyses carried out now need to be interpreted in the light of what we know from a historic perspective, thus helping us to understand if, for example, the cultural differences, intrinsic to each community's traditions, go hand in hand with genetic differences, or if, instead, a cultural identity does not always have a corresponding genetic and biological identity.

 

The documentary, "MarcoPolo2010: Genes and Tastes along the Silk Road" (Carlo Auriemma - Elisabetta Eördegh, Italy, 2010) was based on the scientific project. In May this year, it was awarded first place in the category "Documentaries by Research Institutes, Universities, Museums" at the XV Edition of the Vedere la Scienza Festival, the International Scientific TV, Film and AV Media Festival.



Super Quark will dedicate a special episode to the MarcoPolo2010 expedition, to be broadcast tomorrow, Thursday, 28 July at 21:10 on Rai 1.