Dietary Eicosapentaenoic Acid and Docosahexaenoic Acid Ethyl Esters Influence the Gut Microbiota and Bacterial Metabolites in Rats

A metagenomic survey of the fecal microbiome of the African savanna elephant (Loxodonta africana)

The African savanna elephant (Loxodonta africana) is the largest terrestrial animal on Earth and is found primarily in Southern and Eastern Africa. It is a hindgut, colonic fermenter and subsists on a diet of raw plant materials found in its grazing area. In this study the bacterial, archaeal and fungal populations of seven African savanna elephant fecal metagenomes were first characterized using amplicon sequencing. On the genus level it was observed that the p-1088-a5 gut group in the bacteriome, Methanocorpusulum and Methanobrevibacter in the archaeome and Alternaria, Aurobasidium, Didymella and Preussia in the mycome, predominated. Subsequently, metagenomic shotgun sequencing was employed to identify possible functional pathways and carbohydrate-active enzymes (CAZymes). Carbohydrate catabolic pathways represented the main degradation pathways, and the fecal metagenome was enriched in the glycohydroside (GH) class of CAZymes. Additionally, the top GH families identified - GH43, GH2, GH13 and GH3 - are known to be associated with cellulytic, hemicellulytic and pectolytic activities. Finally, the CAZymes families identified in the African savanna elephant were compared with those found in the Asian elephant and it was demonstrated that there is a unique repository of CAZymes that could be leveraged in the biotechnological context such as the degradation of lignocellulose for the production of second-generation biofuels and energy.

Can the gut microbiome inform the effects of omega-3 fatty acid supplementation trials on cognition?

PURPOSE OF REVIEW

Most omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation clinical trials report inconsistent or null findings on measures of cognition or Alzheimer's disease (AD) with a relatively large variability in the response to n-3 PUFA supplementation. The purpose of this review is to identify whether the gut microbiome together with the metabolome can provide critical insights to understand this heterogeneity in the response to n-3 PUFA supplementation.

RECENT FINDINGS

A Western diet with high saturated fat and omega-6 fatty acid content, obesity, and lack of exercise puts strain on the gut microbiome resulting in imbalance, dysbiosis, reduced bacterial diversity, and increased abundance of the pro-inflammatory taxa. A plant-based diet has beneficial effects on the gut microbiota even when deficient in n-3 PUFAs. Human and animal studies show that increased intake of the n-3 PUFAs correlates with increased beneficial intestinal bacteria when compared to a Western diet.

SUMMARY

The composition of the gut microbiota can help define the effects of n-3 PUFA supplementation on the brain and lead to more personalized nutritional interventions.

Microalgae oil from Schizochytrium sp. alleviates obesity and modulates gut microbiota in high-fat diet-fed mice

Omega-3 PUFAs rich in fish oil are believed to prevent obesity by improving lipid metabolism and regulating gut microbiota. Microalgae oil is considered as an alternative source of omega-3 PUFAs owing to diminishing fish resources. Schizochytrium microalgae oil (SMO), with a high DHA proportion, is a promising source for commercial DHA production. However, its weight-loss and gut microbiota-regulating properties are not well studied. Here we compared the obesity reducing effects of SMO, commercial fish oil (FO) and a weight-loss drug, Orlistat (OL), in a high-fat diet (HFD) induced obesity mouse model. We found that SMO is comparable to commercial FO and OL with regard to weight loss, and it even exhibits the weight-loss effects earlier than FO and OL. It can efficiently inhibit the expression of lipogenesis-related genes and induce the expression of lipolysis-related genes. Moreover, SMO has different gut microbiota modulating effects from those of FO and OL. It does not influence the diversity of bacterial community, but does increase the abundance of several beneficial SCFAs-producing bacteria and inhibits obesity-promoting Desulfovibrio and several pathogens. We also found that SMO recovers the HFD-disturbed metabolic capability of gut microbiota. It can increase the abundance of several metabolism-related pathways, such as those of amino acids, SCFAs and bile acid, and decrease the level of the LPS biosynthesis pathway, which probably contributes to an improvement of lipid metabolism and restoration of the colonic mucosal barrier impaired by HFD. Our data suggest that SMO can be used as a superior dietary supplement for alleviating obesity.

A Paternal Fish Oil Diet Preconception Modulates the Gut Microbiome and Attenuates Necrotizing Enterocolitis in Neonatal Mice

Epidemiology and animal studies suggest that a paternal history of toxicant exposure contributes to the developmental origins of health and disease. Using a mouse model, our laboratory previously reported that a paternal history of in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) increased his offspring’s risk of developing necrotizing enterocolitis (NEC). Additionally, our group and others have found that formula supplementation also increases the risk of NEC in both humans and mice. Our murine studies revealed that intervening with a paternal fish oil diet preconception eliminated the TCDD-associated outcomes that are risk factors for NEC (e.g., intrauterine growth restriction, delayed postnatal growth, and preterm birth). However, the efficacy of a paternal fish oil diet in eliminating the risk of disease development in his offspring was not investigated. Herein, reproductive-age male mice exposed to TCDD in utero were weaned to a standard or fish oil diet for one full cycle of spermatogenesis, then mated to age-matched unexposed females. Their offspring were randomized to a strict maternal milk diet or a supplemental formula diet from postnatal days 7–10. Offspring colon contents and intestines were collected to determine the onset of gut dysbiosis and NEC. We found that a paternal fish oil diet preconception reduced his offspring’s risk of toxicant-driven NEC, which was associated with a decrease in the relative abundance of the Firmicutes phylum, but an increase in the relative abundance of the Negativicutes class.

Excess DHA Induces Liver Injury via Lipid Peroxidation and Gut Microbiota-Derived Lipopolysaccharide in Zebrafish

Being highly unsaturated, n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) are prone to lipid peroxidation. In this study, zebrafish were fed with low-fat diet (LFD), high-fat diet (HFD), or 2% DHA-supplemented HFD (HFDHA2.0). To study the possible negative effects of the high level of dietary DHA, growth rates, blood chemistry, liver histology, hepatic oxidative stress, apoptosis, and inflammatory processes were assessed. The cell studies were used to quantify the effects of DHA and antioxidant on cellular lipid peroxidation and viability. The possible interaction between gut microbiota and zebrafish host was evaluated in vitro. HFDHA2.0 had no effect on hepatic lipid level but induced liver injury, oxidative stress, and hepatocellular apoptosis, including intrinsic and death receptor-induced apoptosis. Besides, the inclusion of 2% DHA in HFD increased the abundance of Proteobacteria in gut microbiota and serum endotoxin level. In the zebrafish liver cell model, DHA activated intrinsic apoptosis while the antioxidant 4-hydroxy-Tempo (tempo) inhibited the pro-apoptotic negative effects of DHA. The apoptosis induced by lipopolysaccharide (LPS) was unaffected by the addition of tempo. In conclusion, the excess DHA supplementation generates hepatocellular apoptosis-related injury to the liver. The processes might propagate along at least two routes, involving lipid peroxidation and gut microbiota-generated LPS.

Dietary Alaska Pollock Protein Attenuates the Experimental Colitis Induced by Dextran Sulfate Sodium via Regulation of Gut Microbiota and Its Metabolites in Mice

Protein derived from fish has not only nutritional properties but also health-promoting properties. Few studies have examined the effect of dietary Alaska pollock protein (APP) on the anticolitis effect reported to be associated with metabolic syndrome (MetS). This study investigated the effect of APP intake on colitis symptoms, gut microbiota, and its metabolites in the experimental colitis mouse model induced by dextran sulfate sodium (DSS). Male C57BL/6J mice were divided into three groups: (1) DSS-untreated mice fed an American Institute of Nutrition (AIN) 93G diet (protein source is casein), (2) DSS-treated mice fed an AIN93G diet, and (3) DSS-treated mice fed an APP diet. After the mice were fed the diets for 21 days, experimental colitis was induced by three cycles of 2% DSS administration for 5 days followed by washouts over the course of 5 days. APP-reduced body weight loss increased the disease activity index, and elevated spleen weight and alleviated colon length shortening and colonic tissue damage. Furthermore, APP altered the structure and composition of the microbiota and short-chain fatty acids in feces. Since APP intake alleviates experimental colitis induced by DSS administration through alterations in the gut microbiota and its metabolites, we deduced that APP would inhibit MetS progression via colitis suppression.