High-Fat Diets Associated with Substantial Alterations in Brain Structure
A new study has revealed that high-fat diets during adolescence can cause significant changes in the brain, behaviour, and impulsivity in rats. The findings suggest that similar diet-induced vulnerabilities may exist in human adolescents, highlighting the importance of healthy nutrition during this critical developmental window.
The research, conducted on adolescent rats, found that high-fat and high-sugar diets led to a reduction in the number of parvalbumin-positive (PV+) interneurons and perineuronal nets (PNNs) in the medial prefrontal cortex (mPFC). This disruption impairs neuroplasticity, particularly in brain regions critical for cognition and impulse control such as the prefrontal cortex and hippocampus.
High-fat diets were also found to induce structural and mechanical remodeling of cerebral parenchymal arterioles (PAs), with sex-dependent differences observed. Male rats showed increased arterial stiffness, impaired spatial memory, reduced myelin basic protein in the brain, and microglial hypertrophy, indicating neuroinflammation. Females showed remodeling but maintained cognitive function.
In terms of neurochemical alterations, high-fat diets reduced levels of brain-derived neurotrophic factor (BDNF) in the hippocampus, impairing learning and memory. Additionally, they decreased GABA concentrations and reduced iGABAergic PV+ interneurons in both the prefrontal cortex and hippocampus, which undermines inhibitory control and cognitive processes.
Rats exposed to high-fat diets during adolescence exhibited enhanced impulsivity and diminished behavioural control. Male rodents tended to show more immediate and persistent impulsivity, while females developed these behaviours more gradually. Short exposure to high-fat and high-sugar diets in adolescent rodents was also found to rapidly induce anxiety-like and depression-like behaviours, vulnerabilities not seen in adult rats under the same conditions.
High-fat diets activated the mesocorticolimbic dopamine pathway, leading to enhanced reward-seeking, which may contribute to overeating and obesity. Supplementing diets with omega-3 fatty acids has shown promise in reducing impulsive behaviours in earlier research.
The long-term effects of high-fat diets during adolescence could influence long-term brain health, potentially increasing the risk of cognitive decline and neurodegenerative diseases like dementia. The association of high-fat diets with reduced BDNF and white matter injury in rats parallels risk factors for these conditions in humans, suggesting that early dietary habits could have a significant impact on brain health.
The findings also suggest that high-fat diets increase motor impulsivity without significantly affecting cognitive impulsivity or compulsivity. The study utilized various behavioural tasks to examine the effects of high-fat diets on different aspects of impulsivity.
Changes in gut metabolism were observed with high-fat diets, including altered levels of fatty acids, glucose, and other metabolites. The brain-derived neurotrophic factor (BDNF) levels increased with high-fat diets in male rats but decreased in female rats.
In summary, high-fat diets during adolescence cause lasting impairments in brain structure and function, increase impulsivity and anxiety-like behaviours, and alter reward pathways in rats, with sex-dependent effects. These findings underscore the sensitivity of the adolescent brain to environmental factors, particularly high-fat diets. The impact of high-fat diets extends beyond the brain, affecting behaviour without necessarily leading to consistent weight gain.
Understanding how specific nutrients influence the brain's development and functioning could lead to targeted interventions, potentially mitigating the risks associated with high-fat diets during adolescence. Future studies are needed to explore the underlying mechanisms in greater detail.
- The study's findings on rats suggest that high-fat diets during adolescence may affect not only physical health but also mental health, impairing neuroplasticity, learning, and memory, and potentially contributing to increased impulsivity.
- In light of the research, the importance of health-and-wellness, including nutrition, fitness-and-exercise, and mental-health, becomes paramount during adolescence due to the potential long-term impact on brain structure and function, and subsequent health risks such as cognitive decline and neurodegenerative diseases like dementia.
