Hyperlipidemia is a frequent metabolic disorder that is closely associated with diet.  It is believed that brown rice, containing the outer bran layer and germ, is beneficial for the remission of hyperlipidemia.  This study established a rat model of hyperlipidemia by feeding a high-fat diet.  The hypolipidemic potential of germinated brown rice (Gbrown) and germinated black rice (a germinated black-pigmented brown rice, Gblack) were explored in the model rats, mainly in the aspects of blood lipids, lipases, apolipoproteins, and inflammation.  The gut microbiota in hyperlipidemic rats receiving diverse dietary interventions was determined by 16S rDNA sequencing.  The results showed that the intervention of Gbrown/Gblack alleviated the hyperlipidemia in rats, evidenced by decreased TC, TG, LDL-C, and apolipoprotein B, and increased HDL-C, HL, LPL, LCAT, and apolipoprotein A1.  Gbrown/Gblack also weakened the inflammation in hyperlipidemia rats, evidenced by decreased TNF-α, IL-6, and ET-1.  In addition, 16S rDNA sequencing revealed that the diet of Gbrown/Gblack elevated the abundance and diversity of gut microbiota in hyperlipidemia rats.  At the phylum level, Gbrown/Gblack decreased Firmicutes, increased Bacteroidetes, and decreased the F/B ratio in hyperlipidemia rats.  At the genus level, Gbrown/Gblack decreased Streptococcus and increased Ruminococcus and Allobaculum in hyperlipidemia rats.  Some differential microbial genera relating to lipid metabolism were also determined, such as the Lachnospira and Ruminococcus in the Gblack group, and the Phascolarctobacterium, Dorea, Turicibacter, and Escherichia-Shigella in the Gbrown group.  Notably, the beneficial effect of Gblack was stronger than Gbrown.  To sum up, the dietary interventions of Gbrown/Gblack contributed to the remission of hyperlipidemia by alleviating the dysbiosis of gut microbiota.

Germination and processing are always accompanied by significant changes in the metabolic compositions of rice.  In this study, polished rice (rice), brown rice, wet germinated brown rice (WGBR), high temperature and pressure-treated WGBR (WGBR-HTP), and low temperature-treated WGBR (WGBR-T18) were enrolled.  An untargeted metabolomics assay isolated 6 122 positive ions and 4 224 negative ions (multiple difference ≥1.2 or ≤0.8333, P<0.05, and VIP≥1) by liquid chromatography-mass spectrum.  These identified ions were mainly classified into three categories, including the compounds with biological roles, lipids, and phytochemical compounds.  In addition to WGBR-T18 vs. WGBR, massive differential positive and negative ions were revealed between rice of different forms.  Flavonoids, fatty acids, carboxylic acids, and organoxygen compounds were the dominant differential metabolites.  Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, there 7 metabolic pathways (phenylalanine/tyrosine/tryptophan biosynthesis, histidine metabolism, betalain biosynthesis, C5-branched dibasic acid metabolism, purine metabolism, zeatin biosynthesis, and carbon metabolism) were determined between brown rice and rice.  Germination changed the metabolic pathways of porphyrin and chlorophyll, pyrimidine, and purine metabolisms in brown rice.  In addition, phosphonate and phosphinate metabolism, and arachidonic acid metabolism were differential metabolic pathways between WGBR-HTP and WGBR-T18.  To sum up, there were obvious variations in metabolic compositions of rice, brown rice, WGBR, and WGBR-HTP.  The changes of specific metabolites, such as flavonoids contributed to the anti-oxidant, anti-inflammatory, anti-cancer, and immunomodulatory effects of GBR.  HTP may further improve the nutrition and storage of GBR through influencing specific metabolites, such as flavonoids and fatty acids.