{"id":2447,"date":"2014-12-08T14:24:41","date_gmt":"2014-12-08T19:24:41","guid":{"rendered":"https:\/\/www.bu.edu\/federal\/?p=2447"},"modified":"2014-12-16T14:46:00","modified_gmt":"2014-12-16T19:46:00","slug":"pass-the-salt","status":"publish","type":"post","link":"https:\/\/www.bu.edu\/federal\/2014\/12\/08\/pass-the-salt\/","title":{"rendered":"Pass the Salt?"},"content":{"rendered":"

Researcher probes the link between salt and hypertension<\/h2>\n
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\"Richard<\/p>\n

Richard Wainford studies the connection between salt and high blood pressure. Photo by Michael D. Spencer<\/em><\/p>\n<\/div>\n

Let\u2019s face it: salt is delicious. Sprinkle it on tomatoes and they pop with flavor; shake it over popcorn and it\u2019s movie time. Even Nelson Mandela noted its worth in his inaugural address: \u201cLet there be work, bread, water, and salt for all,\u201d he said.<\/p>\n<\/header>\n

But when it comes to diet and high blood pressure, salt has long been one of the bad guys, right up there with (and related to) bacon and bologna. Too much sodium can make your body retain water, increasing pressure within blood vessels and leading to hypertension. And runaway blood pressure can lead to a host of maladies, from kidney damage and vision loss to stroke and heart disease. Hypertension is directly responsible for almost 13 percent of all global deaths, according to the World Health Organization<\/a>,\u00a0and the American Heart Association<\/a>\u00a0urges us to take an online pledge to trim salt from our diets. Their slogan: \u201cI love you salt, but you\u2019re breaking my heart.\u201d<\/p>\n

Most Americans do eat too much salt\u20143.5 grams of salt each day, more than 7 times what we need, according to the Centers for Disease Control<\/a>. But the extra salt doesn\u2019t affect everyone equally. According to Richard Wainford<\/a>, assistant professor of pharmacology and medicine in the Boston University School of Medicine (MED) department of pharmacology and experimental therapeutics, only an estimated half of adults are salt-sensitive: if they eat too much salt, their blood pressure goes up. For the other half, salt has little or no effect on blood pressure. But nobody knows exactly why, and there\u2019s no easy way to tell who\u2019s who.<\/p>\n

\u201cSomething has got to be working in your body to get rid of that salt,\u201d says Wainford, who heads a laboratory at the Whitaker Cardiovascular Institute<\/a>. \u201cWe don\u2019t know what that is. So if we don\u2019t know what\u2019s working in a healthy patient, how can we expect to fix something when it\u2019s broken? That\u2019s where I come in.\u201d<\/p>\n

Wainford specializes in the complex science of homeostasis\u2014how the body maintains a stable balance of substances like sodium, glucose, and iron throughout its tissues and how this impacts blood pressure regulation. His research, funded by two grants from the National Institutes of Health\u2019s National Heart, Lung, and Blood Institute<\/a>, has already led to several insights about how our bodies regulate salt. His ultimate goal is to develop biomarkers for salt-sensitivity, which could lead to better diagnostics and treatment for high blood pressure.<\/p>\n

\u201cSomething has got to be working in your body to get rid of that salt. We don\u2019t know what that is.\u201d \u2013 Richard Wainford<\/p><\/blockquote>\n

\u201cWe do see salt as a contributor to high blood pressure, but it also does a lot of other things,\u201d says Haralambos Gavras<\/a>, a MED professor of medicine and an expert on hypertension. \u201cIt\u2019s important to find out the mechanisms\u2014that way, we can be more decisive in the treatments.\u201d<\/p>\n

One of the key organs for human homeostasis is the kidney, which helps regulate water, salt, and iron in the blood by choosing to excrete certain substances in the urine. Another key organ is the brain, which helps control the kidneys. Wainford studies the kidney-brain conversation by examining a particular signaling pathway, one that sends messages through certain molecules, known as g\u03b1i2-<\/sub>proteins<\/a>, in the brain. When a person eats or drinks salt, signals along this pathway tell the brain to slow down communication from the brain to the kidney, and also for the kidney to increase the amount of salt in urine. The kidneys, left to their own devices and receiving constant communication from the brain, excrete less sodium in the urine. It\u2019s a complicated chain of events, and Wainford wants to know exactly how this convoluted system comes together. So he studies how it works in rats.\u00a0\u201cIn a simple sense, we study how rats pee,\u201d says Wainford. \u201cIt\u2019s a simple way to gain insight into the conversation between the brain and kidney.\u201d<\/p>\n

In one of his first experiments, Wainford worked with several breeds of salt-resistant rats, animals that can eat as much salt as they want with no effect on blood pressure. (Some rats are born that way, some bred.) \u201cThey maintain sodium balance\u2014what goes in comes out. So they\u2019re doing fine. But how is that happening?\u201d asks Wainford. \u201cWe wanted to know if this protein pathway\u2014the g\u03b1i2 <\/sub>pathway\u2014is involved. So we did the most simple experiment ever. I took these little rats that don\u2019t get high blood pressure. We fed them salty diets for three weeks, and then we took their brains and looked at the expression of these proteins.\u201d<\/p>\n

\u201cIn a simple sense, we study how rats pee,\u201d says Wainford. \u201cIt\u2019s a simple way to gain insight into the conversation between the brain and kidney.\u201d<\/p><\/blockquote>\n

He found a dramatic increase of this protein pathway in a brain region known as a \u201chot spot\u201d for cardiovascular regulation. \u201cIt sends communications directly to the kidney and it sends communications directly to other brain centers,\u201d says Wainford. \u201cAnd we were like, \u2018Wow. That\u2019s kind of interesting.\u2019 So then we took it away.\u201d In the same rats, Wainford blocked the signal pathway by infusing the rats with a specific sequence of DNA that prevented them from making the g\u03b1i2-<\/sub>protein. Then he gave the animals salty food again, but this time, they couldn\u2019t get rid of the extra salt. As a result, they got high blood pressure.<\/p>\n

\u201cWhen healthy people eat salt, the activity of their central nervous system is turned down to get rid of it,\u201d says Wainford. \u201cWhen you remove this protein pathway in the brain of salt-resistant rats, that doesn\u2019t happen. They\u2019re not able to turn down the activity of the brain to that same extent.\u201d Wainford, who published this research in Hypertension<\/a><\/i>\u00a0in 2013, believes this signaling pathway is one of several that affect the control of blood pressure. Other studies in humans have shown that a tiny defect in the gene for this protein\u2014one single base pair off\u2014is linked to hypertension. But Wainford\u2019s group is the first to find how it works: a clear molecular mechanism that regulates the communication between the brain and the kidney.<\/p>\n

\u201cIt\u2019s an interesting piece of work,\u201d says Gavras, who cautions that this is still basic research and much more remains to be done. \u201cIt\u2019s promising, but let\u2019s see where it goes in the long run.\u201d<\/p>\n

Wainford followed this study with similar tests on salt-sensitive rats, and with a more drastic measure of removing the animal\u2019s renal nerves entirely, severing all communication between the brain and kidneys. Surprisingly, this kept the rats\u2019 blood pressure low and seemed to have no other ill effects. (The SYMPLICITY<\/a> trials on humans have tried the same tactic of removing renal nerves from treatment-resistant hypertensive patients, with mixed results.)<\/p>\n

\u201cClearly the impact of the renal nerves on blood pressure regulation in human subjects is complicated. I think the removal of the renal nerves is a very powerful technique; it just needs to be done right, and studied right, and in the right population,\u201d says Wainford. \u201cUltimately, our goal is to more fully understand the mechanisms of how the brain and the kidney interact to regulate blood pressure. The more we understand that, the better we can treat patients.\u201d<\/p>\n

A version of this story was published on <\/em>BU Research<\/a>.<\/p>\n

Author, Barbara Moran can be reached at bmoran@bu.edu<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Researcher probes the link between salt and hypertension Richard Wainford studies the connection between salt and high blood pressure. Photo by Michael D. Spencer Let\u2019s face it: salt is delicious. Sprinkle it on tomatoes and they pop with flavor; shake it over popcorn and it\u2019s movie time. Even Nelson Mandela noted its worth in his […]<\/p>\n","protected":false},"author":7048,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[8],"tags":[56,48,60,61,13,55,5],"_links":{"self":[{"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/posts\/2447"}],"collection":[{"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/users\/7048"}],"replies":[{"embeddable":true,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/comments?post=2447"}],"version-history":[{"count":5,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/posts\/2447\/revisions"}],"predecessor-version":[{"id":2452,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/posts\/2447\/revisions\/2452"}],"wp:attachment":[{"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/media?parent=2447"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/categories?post=2447"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.bu.edu\/federal\/wp-json\/wp\/v2\/tags?post=2447"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}