Researchers here provide evidence for alterations in the gut microbiome to be an important contributing case of raised blood pressure, or hypertension. Fasting reduces blood pressure, and here it is demonstrated that this is due in part to improvements in the state of the microbial populations of the gut. It is well known that the gut microbiome changes with age, losing beneficial populations and gaining harmful populations. This study suggests that some of those changes contribute to age-related hypertension, providing yet another reason to put resources into the near term development of therapies that can reverse the aging of the gut microbiome, such as flagellin vaccination or fecal microbiota transplantation.
"Previous studies from our lab have shown that the composition of the gut microbiota in animal models of hypertension, such as the SHRSP (spontaneously hypertensive stroke-prone) rat model, is different from that in animals with normal blood pressure. Further, transplanting dysbiotic gut microbiota from a hypertensive animal into a normotensive one results in the recipient developing high blood pressure. This result told us that gut dysbiosis is not just a consequence of hypertension, but is actually involved in causing it. This ground work led to the current study in which we proposed to answer two questions. First, can we manipulate the dysbiotic microbiota to either prevent or relieve hypertension? Second, how are the gut microbes influencing the animal's blood pressure?"
Researchers drew on previous research showing that fasting was both one of the major drivers of the composition of the gut microbiota and a promoter of beneficial cardiovascular effects. Working with the SHRSP model of spontaneous hypertension and normal rats, the researchers set up two groups. One group had SHRSP and normal rats that were fed every other day, while the control group had SHRSP and normal rats with unrestricted food availability. Nine weeks after the experiment began, the researchers observed that, as expected, the rats in the SHRSP control had higher blood pressure than the normal control rats. Interestingly, in the group that fasted every other day, the SHRSP rats had significantly reduced blood pressure when compared with the SHRSP rats that had not fasted.
The researchers transplanted the microbiota of the rats that had either fasted or fed without restrictions into germ-free rats, which have no microbiota of their own. The germ-free rats that received the microbiota of normally fed SHRSP rats had higher blood pressure than the germ-free rats receiving microbiota from normal control rats, just like their corresponding microbiota donors. Additionally, germ-free rats that received microbiota from the fasting SHRSP rats had significantly lower blood pressure than the rats that had received microbiota from SHRSP control rats.