Obesity is a major global health problem determined by heredity and environ ment, and its incidence is increasing yearly. In recent years, increasing evidence linking obesity to the gut microbiota has been reported. Gut microbiota manage ment has become a new method of obesity treatment. However, the complex interactions among genetics, environment, the gut microbiota, and obesity remain poorly understood. In this review, we summarize the characteristics of the gut microbiota in obesity, the mechanism of obesity induced by the gut microbiota, and the influence of genetic and environmental factors on the gut microbiota and obesity to provide support for understanding the complex relationship between obesity and microbiota. At the same time, the prospect of obesity research related to the gut microbiota is proposed.

Astaxanthin is an important antioxidant with many biological activities such as anti-tumor, anti-obesity, cardioprotective, and immuno-modulatory activities. Most of these biological activities are derived from (3S,3′S)-astaxanthin, while the activities of (3R,3′R)-astaxanthin are rarely reported. The purpose of this study was to investigate the effect of (3R,3′R)-astaxanthin on lipid metabolism and gut microbiota in mice fed with a high-fat diet. In this work, 40 male C57BL/6 mice were divided into 8 groups fed a high-fat diet supplemented or not with (3R,3′R)-astaxanthin or Xanthophyllomyces dendrorhous for 8 weeks. The weight gain, energy intake, fat index, plasma triacylglycerol and cholesterol, liver triacylglycerol and cholesterol, and gut microbiota were determined. The results showed that the addition of (3R,3′R)-astaxanthin/X. dendrorhous to the high-fat diet as a supplement prevented weight gain, reduced plasma and liver triacylglycerol, and decreased plasma and liver total cholesterol. The addition of (3R,3′R)-astaxanthin/X. dendrorhous also regulated the gut microbiota of the mice, which optimized the ratio of Bacteroides to Firmicutes and increased the content of Verrucomicrobia, especially Akkermansia. The changes in the gut microflora achieved a healthier structure, thus reducing the incidence of obesity. Thus (3R,3′R)-Astaxanthin has the function of regulating lipid metabolism and gut microbiota to prevent obesity caused by a high-fat diet. The production strain of (3R,3′R)-astaxanthin, X. dendrorhous, has the same function as astaxanthin in preventing obesity caused by a high-fat diet, which reflects its potential ability as a probiotic drug.

Chemo-resistance from cancer stem cells (CSCs) subpopulation is a current issue in cancer treatment. It is important to select alternative therapies to efficiently eradicate both bulk cancer cells and CSCs. Here, gold nanoparticles (AuNPs) have been selected regarding their biocompatibility, facile and controllable synthesis, potent anti-cancer activity and photothermal conversion performance. We reported a green synthesis of functionalized AuNPs using hyaluronic acid (HA) as a reductant, capping, stabilizing and hydrophilic substance. The resultant AuNPs were spherical-shaped with an average diameter of around 30 nm. These AuNPs displayed improved physico-chemical (yield, stability, photothermal effect) and biological properties (cellular uptake, cytotoxicity and apoptotic effect) against bulk MDA-MB-231 cells, in comparison with other organic anti-cancer drugs. The intensified bioactivity was dependent on a mitochondria-mediated cascade, reflected by the damage in mitochondria, oxidative stress, intensified Caspase 3 activity and increased/decreased expression of certain pro-apoptotic (Bax, P53, Caspase 3)/anti-apoptotic (Bcl-2) genes. Moreover, these AuNPs posed a dramatically improved inhibitory effect in cell viability and self-renewable capacity on CSC subpopulation. All the results were attributed from the nano-scaled structure of AuNPs and combined effect from NIR-induced hyperthermia. In addition, the biocompatible nature of these AuNPs supported them to be a potential candidate in the development of novel chemotherapeutic drugs.

Corynebacterium glutamicum is an important strain for the industrial production of amino acids, but the fermentation of L-methionine has not been realized. The purpose of this study is to clarify the effect of reducing power NADPH on L-methionine synthesis. Site-directed mutagenesis of zwf and gnd genes in pentose phosphate pathway relieved feedback inhibition, increased NADPH supply by 151.8%, and increased L-methionine production by 28.3%; Heterologous expression of gapC gene to introduce NADP⁺ dependent glyceraldehyde-3-phosphate dehydrogenase increased NADPH supply by 75.0% and L-methionine production by 48.7%; Heterologous expression of pntAB gene to introduce membrane-integral nicotinamide nucleotide transhydrogenase increased NADPH by 89.2% and L-methionine production by 35.9%. Finally, the engineering strain YM6 with a high NADPH supply was constructed, which increased the NADPH supply by 348.2% and the L-methionine production by 64.1%. The analysis of metabolic flux showed that YM6 significantly increased the glycolytic flux, including the metabolic flux of metabolites such as glycosyldehyde-3-phosphate, dihydroxyacetate phosphate, 3-phosphoglycate and pyruvate, and the significant increase of L-methionine flux also confirmed the increase of its synthesis. This study provides a research basis for the systematic metabolic engineering construction of L-methionine high-yield engineering strains.