Literature Review

Hippocampal cerebral blood flow upped with antihypertensive use in Alzheimer’s


 

FROM HYPERTENSION

Patients with mild or moderate Alzheimer’s disease who took nilvadipine experienced increases in cerebral blood flow in the hippocampus, according to a new study.

Jurgen A.H.R. Claassen, MD, PhD, of Radboud University Medical Center in Nijmegen, the Netherlands copyright Radboud University Medical Center

Dr. Jurgen A.H.R. Claassen

Cerebral blood flow in other regions of the brain did not significantly change in patients who took the antihypertensive drug nilvadipine, according to a report on the trial published in Hypertension. Reduced cerebral blood flow is an early marker of Alzheimer’s disease, and the SPRINT MIND study suggests that intensive blood pressure control may reduce the risk of cognitive impairment.

“These findings [of the new study] not only indicate preserved cerebral autoregulation in Alzheimer’s disease but also point toward beneficial cerebrovascular effects of antihypertensive treatment,” said Jurgen A.H.R. Claassen, MD, PhD of Radboud University Medical Center in Nijmegen, the Netherlands, and coauthors. “An important question is whether this observed increase in [cerebral blood flow] translates to clinical benefits. Unfortunately, sample sizes were too small and follow-up time too short to reliably study the effects ... on structural brain measures and cognitive measures.”

Nilvadipine is a dihydropyridine calcium antagonist used to treat hypertension. In the NILVAD trial, investigators assessed the effects of nilvadipine versus placebo in approximately 500 patients with Alzheimer’s disease. The 18-month trial found no beneficial effects of nilvadipine on cognitive function, but subgroup analyses suggested a potential benefit among patients in the early stages of the disease (PLoS Med. 2018 Sep 24;15[9]:e1002660.).

The cerebral blood flow analysis was a preplanned substudy of NILVAD designed to assess how 6 months of treatment with the drug affects cerebral blood flow as measured using MRI arterial spin labeling. The researchers looked at cerebral blood flow in whole-brain gray matter and in specific regions such as the hippocampus.

The substudy analysis included 22 patients who received nilvadipine and 22 who received placebo during the randomized, double-blind study. Participants had a mean age of 72.8 years and a mean Mini-Mental State Examination score of 20.4.

At 6 months, nilvadipine lowered systolic BP by 11.5 mm Hg, and whole-brain gray matter cerebral blood flow remained stable. Blood flow to the hippocampus increased by approximately 20% among patients treated with nilvadipine – by 24.4 mL/100 g per minute to the left hippocampus and by 20.1 mL/100 g per minute to the right hippocampus.

The increased hippocampal cerebral blood flow could be related to nilvadipine’s antihypertensive effects or its effects on amyloid-beta, the authors noted.

“These findings indicate that the known decrease in [cerebral blood flow] in patients with [Alzheimer’s disease] can in some regions be reversed,” they wrote.

“Even though no medical treatment is without risk, getting treatment for high blood pressure could be important to maintain brain health in patients with Alzheimer’s disease,” Dr. Claassen said in a statement. “In the future, we need to find out whether the improvement in blood flow, especially in the hippocampus, can be used as a supportive treatment to slow down progression of Alzheimer’s disease, especially in earlier states of disease.”

The researchers wrote they lacked biomarkers to confirm Alzheimer’s disease pathology. Most of the study participants were white Europeans, which “limits extrapolation [of the findings] to other populations,” they added.

The Alzheimer’s Drug Discovery Foundation and the Dutch Alzheimer Society funded the NILVAD cerebral blood flow substudy. NILVAD was funded by the European Commission Framework 7 Program Health Theme. Dr. Claassen had no disclosures; one coauthor disclosed a pending patent for nilvadipine.

SOURCE: Claassen JAHR et al. Hypertension. 2019 Jun 17. doi: 10.1161/HYPERTENSIONAHA.119.12892.

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