High Salt Intake Linked to Gene for Hypertension

• Gene HSD11B2 is associated with increased salt intake
• Study performed on mice without the gene
• The study mice found to consume three times more salt water when compared to ordinary mice
• Drug development could target the gene for controlling salt intake

New research has found an association between the gene HSD11B2 and salt intake which holds promise for controlling the consumption of salt. Salt is one of the essential ingredients in our food and while its intake is necessary for good health, too much salt could prove to be detrimental.

Facts About Salt in Our Body

• Warm blooded animals require salt for their existence.
• The cerebrospinal fluid is essentially a sac of salt water which circulates throughout the spinal cord as well as the brain.
• Amniotic fluid too contains salt.
• Salt is lost from our body when we sweat as well as when we shed tears.
• Our bones contain 27% of the salt in our body.

Functions of Sodium

• Aids in muscle contraction and relaxation
• Nerve impulse transmission
• Maintenance of fluid balance in the body

Kidneys play a key role in maintaining the level of sodium in the body. If there is a low amount of sodium in the blood, then the kidneys do not excrete them, instead they hold onto the sodium. When sodium is present in excess, then the kidneys eliminate sodium, however, the kidneys cannot eliminate a lot of sodium. This leads to a build up of sodium which is harmful to health.

Sodium has the capacity of holding onto water which leads to an increase in blood volume. This leads to added pressure on the heart to pump more volume of blood, which can lead to hypertension.

Conditions Caused Due to High Salt Intake

• Congestive heart failure
• Cirrhosis (scarring of the liver)
• Chronic kidney failure
• Stroke
• Diarrhea
• Hypertension

Optimum Salt Intake Levels

• Normal individual - 2300mg of salt per day
• Individuals older than 51 years of age - 1500mg per day

People at Risk of Health Problems Due to High Salt Intake

• People over 50 years of age
• People with diabetes or with elevated blood pressure
• Certain ethnic groups like African Americans

Indians consume alarmingly high levels of salt, drastically increasing the risk for hypertension, according to a study by Demla S and Verma K titled “ Salt Intake In India – An Alarming Situation” Published in the Journal International Journal of Food, Agriculture and Veterinary Sciences (2015).

Consumption of Salt in Various Parts of India

• Rural Andhra Pradesh - 42.3g/day
• Tamilnadu - 12g/day
• Delhi - 9g/day
• Chennai - 8.5g/day

The latest study by Dr M Bailey and colleagues which identifies a gene associated with the high salt intake is a promising find, especially for cultures that include a lot of salt in their diet.

The gene for salt intake was first identified by M Bailey and colleagues in a study titled “ Hsd11b2 haplo insufficiency in mice causes salt sensitivity of blood pressure” and published in the Journal Hypertension. (2011 March). In this study, mice which were heterozygous for the gene Hsd11b2 (+/-) i.e. one gene was active while the other was a null mutation. The lowered efficiency of the gene was found to have the following effect on the mice.

• Promoted retention of salt
• Wasting of potassium
• Hypertension

This study opened doorways for further research into this gene published in the Journal Circulation In March 2016 titled “ Conditional Deletion of Hsd11b2 in the Brain Causes Salt Appetite and Hypertension.”

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11βHSD2 Brain specific knockout mice were used in the study and it was found that they consumed three times more salt water than normal mice, but their sodium renal excretion was not affected. The study highlights the following:

• Change from salt resistance to salt sensitivity
• Increased intake of salt
• No direct relation of the gene with hypertension
• An antagonist that blocks the effect of the gene in the brain of an individual could potentially prevent the need for high salt intake, aiding in control of hypertension.

This study is highly significant in a country like India which thrives on a high salt diet. People especially from the rural areas, are unable to control the salt in the diet, which could have a genetic basis. Further studies that focus on developing an antagonist that blocks the effect of the gene on salt intake could save people from hypertension and medical costs incurred due to that.

References:

1. http://www.watercure2.org/salt.htm
2. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/sodium/art-20045479
3. https://www.ncbi.nlm.nih.gov/pubmed/26951843
4. http://hyper.ahajournals.org/content/57/3/515.long
5. http://www.hsph.harvard.edu/nutritionsource/salt-and-sodium/sodium-health-risks-and-disease/

Source-Medindia