Male offspring of mice fed a diet deficient in omega-3 polyunsaturated fatty acids (PUFAs) during pregnancy, were found to have increased numbers of gut bacteria linked to metabolic disease, found researchers writing in the British Journal of Nutrition.
“We found that the mice who ate the diet with no omega-3 (deficient diet) had an altered gut microbiota composition. This included a greater relative abundance of certain species that have been associated with metabolic disorders,” commented first author Dr. Ruari Robertson, formerly of the APC Microbiome Institute, University College, Cork (UCC) and currently the Sir Henry Wellcome Postdoctoral Research Fellow at the Centre for Genomics and Child Health, Queen Mary University of London.
The three types of bacteria were Tenericutes, Anaeroplasma and Coriobacteriaceae.
“These changes were found in the gut microbiota from the caecum, an area of the large intestine that contains the most microbes. Interestingly, the gut microbiota composition differed in faecal samples suggesting that there may be microbial differences in different regions of the intestines,” continued Robertson.
“The mice on the omega-3 deficient diet also produced less short chain fatty acids (SCFA) which are beneficial chemicals that are produced by the gut microbiota.
“These results suggest that dietary omega-3 PUFA play a crucial role in structuring gut microbiota composition and metabolic activity. Dietary omega-3 deficiency appears to induce gut microbial imbalance, which may contribute to impaired SCFA production.”
Significance
SCFA production has previously been shown to be important in the regulation of cholesterol, glucose and lipid metabolism.
“SCFA help to maintain intestinal homeostasis by maintaining the integrity of the intestinal wall. They also have other functions including controlling appetite by signalling to the brain. There were also some differences in other metabolites in the gut,” said Robertson
The impaired SCFA production found in this study suggests that omega-3 deficiency disrupts the balance of the intestinal environment, which may have implications for metabolic disease, the researchers suggested.
“The western diet is insufficient in omega-3 fats (especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) which come from oily fish). These fats are essential, meaning the body cannot produce them. Instead, the western diet is rich in omega-6 fats which are found in vegetable oils. The optimal dietary ratio of omega-6/omega-3 fats is <4:1 however the western diet is as high as 10-40:1.
This imbalance in dietary fats, especially across generations may contribute to a number of chronic metabolic diseases,” explained Robertson.
“Here we have shown that this dietary imbalance alters both the gut microbiota composition and the metabolites that it produces. This gut microbial disturbance may be one of the pathways by which omega-6/omega-3 imbalance contributes to chronic diseases.”
Study details
“This study aimed to examine the effect of different levels of dietary omega-3 fats on the gut microbiota in mice,” said Robertson.
Describing the study procedures, he continued:
“We fed mice three different diets:
(1) A normal diet which contains normal amounts of omega-3 fats (primarily alpha-linolenic acid (ALA), an omega-3 fat found in certain plant-based foods)
(2) A diet with extra omega-3 fats (primarily EPA and DHA, omega-3 fats primarily found in oily fish)
(3) A diet with no omega-3 fats at all.
“These diets were fed to pregnant mothers and subsequently to their offspring until they reached adulthood. We then checked how these different diets affected their gut bacteria (gut microbiota). The gut microbiota play a huge role in various aspects of health and disease including weight gain, cardiovascular disease and even brain development.”
The researchers used 16S sequencing to determine composition of the caecal microbiome of mothers and offspring. The scientists also conducted caecal metabolomics and SCFA analysis.
Further work
The researchers are looking at a new study investigating the impact of omega-6/ omega-3 balance during pregnancy and its effect on the gut microbiome of the offspring, weight management and metabolic markers.
“Further research is required to elucidate the long-term impact of such altered microbiota and metabolomic profiles on chronic disease progression. However, this novel information may inform future research into microbiota-targeted nutritional therapies for metabolic disorders,” concluded the researchers.
Source: British Journal of Nutrition
Published online 27th November 2017. DOI: 10.1017/S0007114517002999
“Deficiency of essential dietary n-3 PUFA disrupts the caecal microbiome and metabolome in mice”
Authors: Ruairi C. Robertson, et al.