High salt diets disrupt the gut microbiome and impair memory in mice
A recent study found that both high-salt and severely low-salt diets impair memory in mice. While high salt triggers inflammation, extreme salt restriction starves the gut microbiome of metabolic byproducts needed for optimal brain function.
A new research study conducted by scientists at Zhejiang University in China has revealed that both extreme high and low salt diets can lead to cognitive impairment in mice, but through different biological mechanisms. The researchers utilized a technique called microbiome humanization to make their findings more applicable to human biology, introducing human gut bacteria into mice through fecal matter.
After feeding these humanized mice varying salt diets for 14 weeks, the researchers observed significant memory and anxiety impairments in both high and low salt groups compared to a control group with normal salt intake.
The high-salt diet group exhibited the most severe cognitive deficits, along with heightened anxiety and increased water consumption. In contrast, the low-salt diet group experienced memory impairments without the additional anxiety or thirst symptoms. The hippocampus, a brain region crucial for learning and memory, was particularly affected by these diets.
Both extreme diets reduced the abundance of key synaptic proteins and essential growth factors, with the high-salt diet causing widespread reductions in synapse structural proteins and the low-salt diet primarily impacting proteins involved in structural stability and synaptic adaptability.
The researchers also analyzed the microbiome of the mice, observing that the high-salt diet led to an increase in inflammation-linked bacteria, while the low-salt diet caused a slight rise in specialized bacteria but reduced the overall beneficial microbial population. Furthermore, both extreme diets decreased the levels of short-chain fatty acids produced by gut bacteria, which are vital for immune regulation and brain nourishment.
The high-salt group also showed signs of severe oxidative stress and increased pro-inflammatory fats, while the low-salt group experienced a decline in lipids supporting neuronal membranes without showing oxidative stress.
The study concludes that severe salt restriction, like extreme salt consumption, is biologically disruptive and not neutral. The cognitive impairments observed in mice fed extreme salt diets suggest that maintaining a balanced salt intake is essential for optimal brain function.
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