Tea polyphenol epigallocatechin-3-gallate (EGCG) has been widely recognized for antiobesity effects. However, the molecular mechanism of lipidomic pathway related to lipid-lowering effect of EGCG is still not well understood. The aim of this study was to investigate the effects and mechanism of EGCG activated hepatic lipidomic pathways on ameliorating obesity-related complications by using newly developed leptin receptor knockout (Lepr KO) rats. Results showed that EGCG supplementation (100 mg/kg body weight) significantly decreased total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels both in the serum and liver, and significantly improved glucose intolerance. In addition, EGCG alleviated fatty liver development and restored the normal liver function in Lepr KO rats. Liver lipidomic analysis revealed that EGCG dramatically changes overall composition of lipid classes. Notably, EGCG significantly decreased an array of triglycerides (TGs) and diglycerides (DGs) levels. While EGCG increased 31 glycerophospholipid species and one sphingolipid species levels, such as phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), phosphatidylserines (PSs) and phosphatidylinositols (PIs) levels in the liver of Lepr KO rats. Moreover, 14 diversely regulated lipid species were identified as potential lipid biomarkers. Mechanistic analysis revealed that EGCG significantly activated the SIRT6/AMPK/SREBP1/FAS pathway to decrease DGs and TGs levels and upregulated glycerophospholipids synthesis pathways to increase glycerophospholipid level in the liver of Lepr KO rats. These findings suggested that the regulation of glycerolipids and glycerophospholipid homeostasis might be the key pathways for EGCG in ameliorating obesity-related complications in Lepr KO rats.

Metabolic syndrome is a chronic metabolic disorder that has turned into a severe health problem worldwide. A previous study reported that large yellow tea exhibited better anti-diabetic and lipid-lowering effects than green tea. Nevertheless, the potential mechanisms are not yet understood. In this study, we examined the prevention effects and mechanisms of large yellow tea water extract (LWE) on metabolic syndrome using leptin receptor knockout (Lepr^−/−) rats. Seven-week-old male Lepr^−/− and wild type (WT) littermate rats were divided into Lepr^−/− control group (KO) (n = 5), Lepr^−/− with LWE-treated group (KL) (n = 5), WT control group (WT) (n = 6), and WT with LWE intervention group (WL) (n = 6). Then, the rats were administered water or LWE (700 mg/kg BW) daily by oral gavage for 24 weeks, respectively. The results showed that the administration of LWE significantly reduced the serum concentrations of random blood glucose, total cholesterol, triglyceride, and free fatty acids, and increased glucose tolerance in Lepr^−/− rats. Moreover, LWE remarkably reduced hepatic lipid accumulation and alleviated fatty liver formation in Lepr^−/− rats. A mechanistic study showed that LWE obviously activated SIRT6 and decreased the expression of key lipogenesis-related molecules SREBP1, FAS, and DGAT1 in the livers of Lepr^−/− rats. Furthermore, LWE significantly improved microbiota dysbiosis via an increase in gut microbiota diversity and an abundance of the microbiota that produce short chain fatty acids (SCFAs), such as Ruminococcaceae, Faecalibaculum, Intestinimonas, and Alistipes. Finally, LWE supplementation increased the concentrations of SCFAs in the feces of Lepr^−/− rats. These results revealed that LWE attenuated metabolic syndrome of Lepr^−/− rats via the reduction of hepatic lipid synthesis through the SIRT6/SREBP1 pathway and the modulation of gut microbiota.

Huangshan Maofeng green tea (HMGT) is one of the most well-known green teas consumed for a thousand years in China. Research has demonstrated that consumption of green tea effectively improves metabolic disorders. However, the underlying mechanisms of obesity prevention are still not well understood. This study investigated the preventive effect and mechanism of long-term intervention of Huangshan Maofeng green tea water extract (HTE) on obesity-associated metabolic disorders in leptin receptor knockout (Lepr^−/−) rats by using gut microbiota and hepatic lipidomics data. The Lepr^−/− rats were administered with 700 mg/kg HTE for 24 weeks. Our results showed that HTE supplementation remarkably reduced excessive fat accumulation, as well as ameliorated hyperlipidemia and hepatic steatosis in Lepr^−/− rats. In addition, HTE increased gut microbiota diversity and restored the relative abundance of the microbiota responsible for producing short chain fatty acids, including Ruminococcaceae, Faecalibaculum, Veillonellaceae, etc. Hepatic lipidomics analysis found that HTE significantly recovered glycerolipid and glycerophospholipid classes in the liver of Lepr^−/− rats. Furthermore, nineteen lipid species, mainly from phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and triglycerides (TGs), were significantly restored increases, while nine lipid species from TGs and diglycerides (DGs) were remarkably recovered decreases by HTE in the liver of Lepr^−/− rats. Our results indicated that prevention of obesity complication by HTE may be possible through maintaining homeostasis of gut microbiota and certain hepatic lipid classes.

Obesity is a major public health concern globally. Plant-based ingredients have been proposed as alternative treatments for obesity. L-Theanine (THE), a unique nutraceutical component of tea, is known for its neuroprotective and cognitive benefits. However, there are few reports on THE’s effects and mechanisms in improving obesity and its complications. In this study, the alleviating effects and potential mechanisms of THE on obesity-related complications (ORCs) induced by a high-fat diet(HFD) in mice were explored by performing biochemical, hepatic transcriptomics, and plasma metabolomics analyses. The results indicated THE (900 mg/kg of body weight) was effective in mitigating ORCs by decreasing body weight gain and fat deposition, improving glycolipid metabolism disorders, inflammation dysregulation, and alleviating fatty liver formation due to long-term HFD. The hepatic transcriptomics data suggested that THE intervention suppresses the lipid metabolism and inflammation pathways in HFD-fed mice, thereby inhibiting hepatic steatosis and inflammation. Moreover, plasma metabolomics analysis revealed that THE exhibited positive effects on the homeostasis of plasma metabolite balance, such as phosphatidylcholine (PC(14:0/18:1)), phosphatidylethanolamine (Lyso-PE(14:0)), phosphatidic acid (PA(16:0e/18:0)), stigmasterol, and deoxycholic acid glycine conjugate. These metabolites were strongly correlated with ORC-related indicators. Our results indicated that THE, as a functional food additive, possesses potential for ORC alleviation. However, the exact molecular mechanism of how THE alleviates ORCs needs to be investigated in the future.

Toona sinensis (“Heiyouchun”) is a traditional Chinese woody vegetable, the leaves of which can also be processed into tea, known for its distinctive flavor and diverse bioactivities. However, the effects of leaf maturity and processing methods on its phytochemical composition and functional properties remain unclear. In this study, metabolomic analysis revealed 35 significantly different metabolites between tender and mature leaves, with higher concentrations of flavonoids, flavonoid glycosides, limonoids, and amino acids in tender leaves. Additionally, comparative analysis revealed that black tea fermentation preserves bioactive compounds more effectively than hot-air drying, particularly in tender leaves. In vitro activity assays showed that toon leaf tea extracts exhibited significant antioxidant and hypoglycemic effects, with black tea fermented tender leaves displaying the most potent bioactivity. Correlation analysis further confirmed a strong positive relationship between flavonoid/polyphenol content and bioactivity. These findings provide a theoretical foundation for optimizing processing techniques to enhance the functional properties of toon leaf tea.

The tender buds of “Heiyouchun” (Toona sinensis), a traditional Chinese specialty variety, are highly favored as a unique woody vegetable. However, the mature leaves exhibit distinct bitterness and lack aromatic compounds, resulting in low resource utilization. This study innovatively developed toon leaf tea (TLT) using black tea processing techniques. Through integrated metabolomic analysis and health benefit evaluation, we systematically compared the differences in chemical composition and hypoglycemic effect between TLT and traditionally dried mature toon leaves (TOL). Metabolomic analysis revealed that the two processing methods induced significant changes in 41 metabolites. Compared with TOL, TLT demonstrated significant enrichment in functional components including flavonoids (e.g., quercetin derivatives), limonoids, and amino acids, along with a marked reduction in phenolic acids and organic acids. The synergistic effects of these components effectively improved product flavor and enhanced bioactivity. In vitro and in vivo experiments confirmed that the α – glucosidase/α – amylase inhibitory activity of TLT and the hypoglycemic effect on diabetes model mice are significantly better than that of TOL. This study not only elucidates the transformation patterns of chemical constituents in mature toon leaves under different processing methods but also provides a scientific basis for the resource utilization of mature toon leaves.