Journal of Tea Science Research, 2024, Vol.14, No.1, 19-43 http://hortherbpublisher.com/index.php/jtsr 34 4.2.1 Metabolic diseases Metabolic diseases are disorders that negatively affect a wide range of normal metabolic processes, the prevalence of which has increased significantly in recent decades and poses a serious threat to human health (Anaeigoudari et al., 2021). White tea has been shown to be effective in the treatment of some of the most common metabolic diseases, including diabetes, obesity, cardiovascular disease, and non-alcoholic fatty liver disease. Two major mechanisms are involved in these therapeutic functions: the regulation of glucose and lipid metabolisms. Recent animal and cell studies suggest that white tea may be particularly effective in ameliorating abnormal lipid metabolism. A tea cocktail containing white tea partially prevented hyperlipidemia, reduced serum high-density lipoprotein levels, insulin resistance, and increased C-reactive protein levels, while completely preventing left ventricular hypertrophy in mice fed with a high-fat diet (Ferreira et al., 2020). Another study found that WTE ameliorated obesity, lipid accumulation, hepatic steatosis, and liver injury in a mouse model of nonalcoholic fatty liver disease (Li et al., 2022). Compared with the other tea types, WTE showed the best anti-obesity effects in reducing the body weight and white fat accumulation in obese mice (Liu et al., 2019). Recent in vivo and vitro gene ontology and pathway analysis revealed that white tea can regulate pathways related to lipid metabolism and energy expenditure. A cell-based study found that WTE reduced very-low-density lipoprotein production by downregulating gene expression of apolipoprotein B, microsomal triglyceride transfer protein, and triglycerides synthesis, while stimulating low-density lipoprotein cholesterol uptake by targeting the low-density lipoprotein receptor (Luo et al., 2020). In vivo evidence showed that WTE can improve the lipid metabolism by regulating pathways associated not only with lipid synthesis but also with energy expenditure, such as respiratory electron transport, oxidative phosphorylation, ATP metabolism, and other energy metabolism pathways (Li et al., 2022). The superior anti-obesity effect of white tea may be due to both increased energy expenditure and inhibition of fatty acid synthesis, whereas the other teas were only able to regulate the latter (Liu et al., 2019). White tea has been shown to be effective in regulating glucose metabolism and a typical example is the treatment of T2DM. T2DM is a severe endocrine metabolic disorder that causes serious complications in various organs, either as a result of excessive glucose or in response to the altered hormone levels (Zhao et al., 2019). WTE treatment for 30 days significantly decreased serum glucose levels in diabetic rats suffering from hyperglycemia (Amanzadeh et al., 2020). White tea-treated T2DM mice showed significantly lower glycemic responses to glucose administration than the control group and significantly attenuated the accumulation of renal advanced glycation end products in T2DM mice, thereby inhibiting the structural changes of the kidneys (Xia et al., 2021). The ability of white tea to regulate hyperglycemia may be due to its inhibitory effects on α-amylase and α-glucosidase, which are key dietary enzymes related to T2DMin vitro and break down carbohydrate before absorption (Xu et al., 2019). 4.2.2 Oral health The active components in WTE are well known to help maintain oral health and prevent dental problems such as plaque and caries. Dental plaque contains highly organized microbial communities that adhere to the surface of hard dental tissues and is a major cause of various oral and pharyngeal diseases (Digel et al., 2020). In a clinical study, mouth rinsing with steeped 2.5% white tea steeped twice daily for four days significantly improved the plaque index, indicating a reduction in plaque accumulation on teeth (Damhuji et al., 2022). A similar study reported that white tea mouthwash was a potent antiplaque agent when used for 10 d, although less effective than chlorhexidine, a gold standard for plaque (Nagar et al., 2018). Furthermore, white tea has the potential to fight caries, as human enamel and rat jawbone samples with or without the demineralization-remineralization treatment were hardened after immersion in a white tea-xylitol solution (Auerkari et al., 2018). The effective elimination of harmful oral bacteria by white tea is responsible for its functions in maintaining oral hygiene. White tea mouthwash can significantly inhibit the growth of several bacteria that contribute to dental caries and/or periodontal disease, including Streptococcus mutans, Streptococcus sobrinus, Lactobacillus acidophilus, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans (Auerkari et al., 2018,
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