BackgroundDeep frying in oil is a popular cooking method around the world. However, the safety of deep-fried edible oil, which is ingested with fried food, is a concern, because the oil is exposed continuously to be re-used at a high temperature, leading to a number of well-known chemical reactions. Thus, this study investigates the changes in energy metabolism, colon histology and gut microbiota in rats following deep-fried oil consumption and explores the mechanisms involved in above alterations.MethodsDeep-fried oil was prepared following a published method. Adult male Wistar rats were randomly divided into three groups (n = 8/group). Group 1: basal diet without extra oil consumption (control group); Group 2: basal diet supplemented with non-heated canola oil (NEO group); Group 3: basal diet supplemented with deep-fried canola oil (DFEO group). One point five milliliters (1.5 mL) of non-heated or heated oil were fed by oral gavage using a feeding needle once daily for 6 consecutive weeks. Effect of DFEO on rats body weight, KEGG pathway regarding lipids metabolism, gut histology and gut microbiota were analyzed using techniques of RNA sequencing, HiSeq Illumina sequencing platform, etc.ResultsAmong the three groups, DFEO diet resulted in a lowest rat body weight. Metabolic pathway analysis showed 13 significantly enriched KEGG pathways in Control versus NEO group, and the majority of these were linked to carbohydrate, lipid and amino acid metabolisms. Comparison of NEO group versus DFEO group, highlighted significantly enriched functional pathways were mainly associated with chronic diseases. Among them, only one metabolism pathway (i.e. glycerolipid metabolism pathway) was found to be significantly enriched, indicating that inhibition of this metabolism pathway (glycerolipid metabolism) may be a response to the reduction in energy metabolism in the rats of DFEO group. Related gene analysis indicated that the down-regulation of Lpin1 seems to be highly associated with the inhibition of glycerolipid metabolism pathway. Histological analysis of gastrointestinal tract demonstrated several changes induced by DFEO on intestinal mucosa with associated destruction of endocrine tissue and the evidence of inflammation. Microbiota data showed that rats in DFEO group had the lowest proportion of Prevotella and the highest proportion of Bacteroides among the three groups. In particular, rats in DFEO group were characterized with higher presence of Allobaculum (Firmicutes), but not in control and NEO groups.ConclusionThis study investigated the negative effect of DFEO on health, in which DFEO could impair glycerolipid metabolism, destroy gut histological structure and unbalance microbiota profile. More importantly, this is the first attempt to reveal the mechanism involved in these changes, which may provide the guideline for designing health diet.Electronic supplementary materialThe online version of this article (doi:10.1186/s12944-016-0252-1) contains supplementary material, which is available to authorized users.

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Purpose The objective of the present study was to assess the differences in soil total C and N, microbial biomass C and N, soil soluble organic C and N among eight monoand mixed species forest ecosystems (18-year-old restoration) in subtropical China. Materials and methods Soil samples were taken at the 0-10 and 10-20-cm depths from each of the eight forest ecosystems: Masson pine (CP1); Pitch pine (CP2); mixed Slash pine and Sweetgum (CBMP1); mixed Slash pine and Camphortree (CBMP2); mixed Masson pine, Sweetgum, and Chinese Gugertree (CBMP3); mixed Sweetgum and Chinese Gugertree (BMP); Chinese Gugertree (BP1); and Sweetgum (BP2). Soil soluble organic C and N pools were measured using hot water and KCl extraction methods. Microbial biomass C (MBC) and N (MBN) were measured by fumigation-extraction method. Soil total C and N were determined using an isotope ratio mass spectrometer. Results and discussion Concentrations of soil soluble organic N (SON) extracted by KCl solution (35.1-116.9 and 11.2-78.2 mg kg -1 ) were greater than those by hot water (20.7-72.8 and 8.4-30.6 mg kg -1 ) in the 0-10 and 10-20-cm soils, while concentrations of soluble organic C (SOC) extracted by KCl solution were lower than those extracted by hot water in the 0-10 cm. Soil soluble C and N pools extracted by both hot water and KCl solution and the MBC and MBN were greatest under the broadleaf forest ecosystems, followed by the mixed conifer-broadleaf forest ecosystems, and then the conifer forest ecosystems. Conclusions Different restored forest ecosystems had significant impacts on soil SOC and SON, and MBC and MBN. The broadleaf forest ecosystems could be a better choice for the restoration of red soil chemical and biological prosperities than the conifer-broadleaf forest ecosystem and coniferous forest ecosystems. A further study is necessary to sample over seasons in order to understand whether the significant impacts on soil properties are related to the sample time. In addition, soil microbial community composition and microbial activity should be measured in such studies to understand mechanisms involved in the dynamics of soil SOC and SON pools.