High-fat diet linked to altered microflora and inflammation in heart failure, mice study finds

04 Mar 2019 --- High-fat diets rich in omega 6 fatty acids and aging are significant contributors to health risks ranging from diabetes to heart failure, according to a new study. How these two factors regulate the immune response is not currently well-understood, but researchers’ experiments with mice have shown the involvement of gut bacteria in heart pathology.

Ganesh Halade, Ph.D., Associate Professor in the Division of Cardiovascular Disease at UAB Department of Medicine, and his colleagues at the University of Alabama in Birmingham have investigated how aging and an obesity-generating omega 6-enriched diet impact microflora in the gut and subsequent immune responses to heart failure.

In the study, published in the FASEB Journal, the researchers report that a calorie-dense, obesity-generating diet in aging mice disrupted the composition of the gut microbiome, and that correlated with the development of a system-wide non-resolving inflammation in acute heart failure, with disruptions of the immune cell profile – notably the neutrophil-leukocyte ratio.

It is also known that diet interacts with gut microbes to calibrate the body’s immune defense capacity. The UAB-led researchers examined this further with regard to aging and high-fat diets.

They found that the obesity-generating diet caused a sharp increase in bacteria belonging to the genus Allobaculum, phylum Firmicutes. The obesity-generating diet also increased the proportion of neutrophils in the blood of young mice. In aged mice, a similar increase in the percentage of neutrophils was found for both old mice fed a standard diet and old mice fed the obesity-generating diet.

The spleen, a secondary immune organ, is a known reservoir for leukocytes that are released after heart injury. Those splenic leukocytes move to the heart to begin tissue repair and help resolve inflammation.

Halade and his colleagues found that the obesity-generating diet and aging led to neutrophil swarming and an altered leukocyte profile after a heart attack. They also observed splenic structural deformities in these mice and a decrease in splenic CD169-positive macrophages.

Importantly, young mice fed the obesity-generating diet were able to resolve inflammation after a heart attack, even though the diet had already altered their gut microflora. In contrast, in aged mice fed the obesity-generating diet, the heart attack triggered non-resolving inflammation and such inflammation is associated with heart failure.

“Thus, the data strongly indicates that the obesity-generating diet develops an inflammatory microenvironment, even in young mice, that amplifies with aging,” Halade comments. 

“This study highlights that diet and age are critical factors that have a differential impact with age and it highlights the spleen and heart as an inter-organ communication system with the immune defense system,” he concludes.

In March 2018, NutritionInsight reported that a University of Eastern Finland study suggested that omega 6 fatty acids help prevent premature death and keep cardiovascular diseases at bay. The study lent its support to findings from earlier population-based studies which have linked a higher dietary intake of linoleic acid and a higher blood linoleic acid level to a smaller risk of cardiovascular diseases and type 2 diabetes, without increasing the risk of cancer. The observed association of arachidonic acid (a type of polyunsaturated omega 6 fatty acid) with a reduced risk of death, was a new finding.