Ketogenic diets linked to cellular aging in vital organs, new study finds

In a recent study published in the journal Science Advances, a large team of researchers in the United States examined the detrimental effects of ketogenic diets. The study used murine models and reported that ketogenic diets can cause cellular senescence in various organs, such as the kidneys and heart. This cellular senescence is dependent on adenosine monophosphate-activated protein kinase (AMPK) and tumor protein 53 (p53).

Study: Ketogenic diet induces p53-dependent cellular senescence in multiple organs. Image Credit: SewCreamStudio / Shutterstock

Background

Ketogenic diets have become extremely popular as an effective weight loss method in recent decades. The diet is based on the principle that avoiding carbohydrates will induce the breakdown of fat for the production of ketones in the liver, which serve as an alternate source of energy. Ketogenic diets have also been used to treat refractory epilepsy and have shown benefits against neurodegenerative disorders and cancer.

Studies using murine models have also reported that ketogenic diets could have anti-inflammatory effects and be beneficial against obesity, metabolic, and neurological phenotypes. However, other studies have reported that the low-carbohydrate content of ketogenic diets results in pro-inflammatory effects and increases the risk of kidney damage and cardiac fibrosis.

The use of ketogenic diets to treat intractable epilepsy in children has also been associated with a higher risk of bone fractures, growth disturbances, and kidney stones. However, there is a paucity of information on the mechanisms contributing to these contrasting outcomes.

About the study

In the present study, the researchers used two different ketogenic diets on mice to examine the detrimental effects of ketogenic diets and subsequently used knock-out studies to understand the mechanisms through which ketogenic diets have a negative impact on health. The two types of ketogenic diets tested in this study were the Crisco-based diet and the cocoa butter-based diet, given the significant difference in saturated versus unsaturated fats in the two diets.

Approximately six-week-old mice were randomly assigned to a control diet group or the ketogenic diet group. The control group’s calorific content was 17% fats and 58% carbohydrates. In comparison, the calorific percentages of the two ketogenic diets were 90.5% fats and only 0.3% carbohydrates. The ketogenic diet here was Crisco-based and had approximately 84% unsaturated fats.

In the alternate experiment, the ketogenic diet was cocoa butter-based and derived 90% of the calories from fats and the rest from proteins, with no carbohydrates. The control diet for this experiment consisted of 80% calories from carbohydrates and 10% each from fats and proteins.

Ketone bodies were monitored using whole blood samples to measure the levels of β-hydroxybutyrate, and the mice were also subjected to insulin and glucose tolerance tests. The mice were euthanized one to three weeks after the diet initiation, and all the tissues were harvested for analysis. Some of the mice were switched to the control diet after the conclusion of the ketogenic diet to observe the persistence of the ketogenic diet-induced cellular senescence.

The tissues harvested from the mice were subject to a wide range of analyses such as immunohistochemistry, western blotting, extraction of ribonucleic acid (RNA) and messenger RNA (mRNA) expression analysis, chromatin immunoprecipitation, total RNA sequencing, caspase-2 enzyme activity assay, and enzyme-linked immunosorbent assays.

Results

The results showed that the ketogenic diet caused changes such as senescent cell accumulation in various vital organs, including the kidneys and the heart. This build-up of senescent cells led to inflammation, which the researchers believe also had other clinical implications. They mentioned other studies that found dysregulation of mitochondrial function and cardiac fibrosis associated with long-term ketogenic diets and suggest that cellular senescence could be implicated.

The ingenuity pathway analysis used to analyze the RNA sequencing data and identify upstream regulators and enriched pathways found that the peroxisome proliferator-activated receptor α and proteins p53 and p21 were upstream regulators that were activated in ketogenic diets. Furthermore, 89 genes involved in cellular senescence and regulated by p53 were found to be enriched in the liver, kidneys, and heart.

By knocking out caspase-2 and p53 and using inhibitors of caspase-2, p21, and AMPK, the study also found that phosphorylated AMPKα and the inactivation of mouse double minute 2 through the cleavage of caspase-2 led to the accumulation of p53, and the activation of p21 in mice on ketogenic diets.

Additionally, the analysis of mouse serum and human plasma samples from individuals enrolled in ketogenic diet clinical trials reported that the senescence-associated secretory phenotype (SASP) biomarker was elevated in association with ketogenic diets. The researchers stated that broad-spectrum senolytics such as navitoclax or following intermittent ketogenic diets could help eliminate the cellular senescence resulting from ketogenic diets.

Conclusions

Overall, the findings suggested that long-term ketogenic diets caused the enrichment of cellular senescence pathways involving p53 and p21, resulting in the accumulation of senescent cells in major organs such as the kidneys and the heart, which could potentially lead to cardiac fibrosis and other clinical consequences. However, following a ketogenic diet intermittently and using a senolytic could help eliminate cellular senescence.