Research unravels the secrets of salt and taste

New research into the molecular basis of salty taste has been released by the Nestlé Research Center in Switzerland.

The research team discovered that so-called Claudins, a family of molecules usually found to seal the contact between epithelial cells, are distributed in a unique and specific way throughout the taste bud.

Specific members of the Claudin family are used to seal the taste pore, whereas others facilitate specific pathways within the tastebud for certain molecules.

Much is known on the mechanisms by which tastebuds on the tongue are stimulated by sweet, bitter, sour and the savoury umami taste, yet only little understanding on the molecular level is available for salty taste. Coding of taste signalling, or the way individual tastes are projected into the brain, is believed to begin in the tastebud.

The scientists at Nestlé Research Center used a novel approach. Instead of analysing the content of the cells constituting a tastebud, they analysed the matrix between the cells. They found that Claudins, which reinforce the contact between cells, are distributed in a specific pattern throughout the bud. Claudins specific for sodium diffusion were observed to surround a subset of tastebud cells.

The scientists conclude that salt is channelled through the Claudin network to activate only a specific subset of taste cells. According to Dr Johannes le Coutre, the head of the team, "This adds a totally new dimension to the longstanding question of taste coding.

"So far, we thought that individual taste cells are uniquely equipped with specific receptors sensitive to sweet, bitter, sour or umami molecules only. Our findings suggest that specific tastants may stimulate different cell groups, depending on the surrounding network of Claudin molecules. We cannot any more only study the cell activity in taste signal coding, but we also have to understand the regulation of the cell environment."

This discovery has the potential for an enormous impact on public health. Excess dietary sodium is linked to high blood pressure and cardiovascular diseases in some countries. Salt reduction calls for molecules that taste salty without containing sodium. These have remained elusive because of the lack of understanding on the molecular physiology of salt taste.

The Nestlé team is intensively following up the Claudin hypothesis. After sweet, bitter, sour and umami, the salty taste may finally lift the veil of its intimate molecular secrets.

The research has been published in the April edition of the Journal of Comparative Neurology.