Heat-treated high-fat diet modifies gut microbiota and metabolic markers in apoe−/− mice

Nittaya Marungruang, Frida Fåk, Eden Tareke

High-fat diet has been known to have adverse effects on metabolic markers, as well as the gut microbiota. However, the effect of heat processing of high-fat diet, which leads to formations of advanced glycation end products (AGEs) has not been clearly distinguished from the effect of unheated fat. This study compared the effect of high-fat diet with heat-treated high-fat diet on adiposity, atherosclerosis and gut microbiota composition in the caecum of apoe (-/-) mice. Male apoe (-/-) mice were fed either low-fat (LF) control diet, high-fat (40 E% saturated fat, HF) control diet, or heat-treated high-fat (200 °C for 10 min, HT) diet, for 8 weeks. The plasma samples were used in the analysis of Nε-carboxy-methyl-lysine (CML) and Nε-carboxy-ethyl-lysine (CEL). The heart samples were analysed for atherosclerotic plaques, and the DNA from caecum was extracted and analysed for microbiota composition using 16S rRNA gene sequencing on a Miseq instrument. Additionally, the functions of microbial communities were also predicted based on the bacterial 16S rRNA gene sequence using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Here we found that HT modifies gut microbiota composition and host adiposity. Prediction of bacterial gene functions based on 16S rRNA gene sequence revealed that HF increased bacterial genera enriched in lipid metabolism genes, while HT did not. Plasma CML and CEL increased 1.7 and 2.5 times, respectively, in mice fed HT as compared to mice fed HF. Despite lower adiposity, mice fed HT maintained atherosclerosis and displayed enlarged spleens. The results suggested that heat processing of high-fat diet modifies the substrates reaching the lower gut of apoe (-/-) mice, resulting in different effects on gut microbiota composition. AGEs seem to maintain the effect on atherosclerosis, despite lower adiposity, and causing enlarged spleens, which possibly reflect elevated levels of inflammation in the body.