Beta-Hydroxybutyrate Mitigates Sensorimotor and Cognitive Impairments in a Photothrombosis-Induced Ischemic Stroke in Mice

Abstract

The consequences of stroke include cognitive deficits and sensorimotor disturbances, which are largely related to mitochondrial impairments in the brain. In this work, we have shown that the mimetic of the ketogenic diet beta-hydroxybutyrate (βHB) can improve neurological brain function in stroke. At 3 weeks after photothrombotic stroke, mice receiving βHB with drinking water before and after surgery recovered faster in terms of sensorimotor functions assessed by the string test and static rods and cognitive functions assessed by the Morris water maze. At the same time, the βHB-treated mice had lower expression of some markers of astrocyte activation and inflammation (Gfap, Il-1b, Tnf). We hypothesize that long-term administration of βHB promotes the activation of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) pathway, which leads to increased expression of antioxidant genes targeting mitochondria and genes involved in signaling pathways necessary for the maintenance of synaptic plasticity. βHB partially maintained mitochondrial DNA (mtDNA) integrity during the first days after photothrombosis. However, in the following three weeks, the number of mtDNA damages increased in all experimental groups, which coincided with a decrease in Ogg1 expression, which plays an important role in mtDNA repair. Thus, we can assume that βHB is not only an important metabolite that provides additional energy to brain tissue during recovery from stroke under conditions of mitochondrial damage but also an important signaling molecule that supports neuronal plasticity and reduces neuroinflammation.

Keywords: ischemia; mitochondria; neuroprotection; oxidative stress; stroke.

Figure 1

Effects of βHB and PT on body weight and food consumption: (A) dynamics of changes in body weight; (B) dynamics of changes in the level of feed intake.

Figure 2

The results of MWM test conducted on the 3rd and 24th days after photothrombotic stroke in mice, which were administered either water or βHB solution. (A) Dynamics of time spent searching for the platform; (B) time spent by mice searching for the platform per week on average; (C) the number of points mice scored as a function of week. * p < 0.05, ** p < 0.01, and *** p < 0.001—differences between groups are statistically significant (Kruskal–Wallis test). The histograms for (B,C) with individual data points are provided in the Supplementary Materials (Figures S1–S6).

Figure 3

The results of the string test conducted to evaluate the strength and endurance of mice (A) and the static rods test conducted to assess movement coordination (B) on the 3rd and 24th days after photothromdotic stroke in mice, which were administered either water or βHB solution. * p < 0.05—differences between groups are statistically significant (Kruskal–Wallis test).

Figure 4

The number of damages detected via PCR in six different regions of the mtDNA isolated from the penumbra zone of mouse brain on the 3rd and 24th days after photothrombotic stroke in mice, which were administered either water or βHB solution. * p < 0.05 and ** p < 0.01, and *** p < 0.001—differences between groups are statistically significant (Kruskal–Wallis test).

Figure 5

Changes in gene expression of transcription factors, regulators of mitophagy and synaptic plasticity (A), inflammatory markers (B), and antioxidant genes (C) in the penumbra zone of mouse brain on the 3rd and 24th days after photothrombotic stroke in mice, which were administered either water or βHB solution. * p < 0.05 and ** p < 0.01—differences between groups are statistically significant (Kruskal–Wallis test).

Figure 6

Correlation between time spent by mice searching for the platform and Gfap expression (A), between time and Il-1b expression (B), between the amount of mtDNA damage and Ogg1 expression (C), and between time spent by mice searching for the platform and the amount of mtDNA damage (D).

Figure 7

Correlation between Nfe2l2 and Gclc expression levels (A), Nfe2l2 and Gpx1 expression levels (B), Nfe2l2 and Txnrd2 expression levels (C), and Nfe2l2 and Prdx3 expression levels (D).

Figure 8

Time-line of the experiment.

Figure 9

Schematic of the water tank for the Morris water maze (side view) (A) and top view (B).