A green tea catechin extract upregulates the hepatic low-density lipoprotein receptor in rats

The effect of green tea (Camellia sinensis) on lipid profiles and renal function in people with type 2 diabetes and nephropathy: a randomized controlled clinical trial

Introduction

Diabetic nephropathy is one of the most important microvascular complications of diabetes. Despite the modern treatments, herbs or medicinal plants have gained wide attention. One of these herbs is green tea (Camellia sinensis), which may have an impact on renal function, lipid profiles, and HbA1c. However, the evidence for this is unclear and limited. The present study aimed to evaluate the effect of different doses of green tea on these parameters in type 2 diabetes patients (T2DM) with nephropathy.

Methods

Sixty-six individuals with T2DM nephropathy (aged 30-70 years) were randomly assigned to receive three cups of green tea/day (n = 22), two cups of green tea/day (n = 22), and the control group (n = 22) for 12 weeks. Lipid profiles, glycated hemoglobin A1c (HbA1c), and renal markers were measured before and after intervention. Data were analyzed using SPSS software version 23. One-way analysis of variance (ANOVA), least significant difference (LSD) post hoc, and analysis of covariance were used to compare quantitative variables.

Results

In total, 64 participants completed the study. Consuming three cups of infusion green tea per day (7.5 gr) led to a significant reduction in serum levels of total cholesterol (p = 0.009) and HbA1c (p = 0.006) and increased in high-density lipoprotein cholesterol (HDL-C) (p = 0.02) compared with the control group who did not drink green tea. However, no significant differences were observed for other variables.

Conclusion

In general, it was found that drinking three cups of green tea infusion (7.5 gr) per day produced beneficial effects on some lipid profiles and HbA1c without any adverse effects on renal function in patients with T2DM nephropathy. More studies are needed to fully elucidate these findings.

Clinical trial registration

Iranian Registry of Clinical Trials (www.irct.ir) under registry number: IRCT2014020114538N2.

The effect of Green green tea consumption on body mass index, lipoprotein, liver enzymes, and liver cancer: An updated systemic review incorporating a meta-analysis

INTRODUCTION

Green tea is related to the reduction of liver enzymes, lipoprotein, and body mass index. However, some reports related green tea to the risk of developing liver cancer, but their outcomes were conflicting. Hence, the present study aimed to determine the relationship between green tea intake and lipoprotein, liver enzymes, body mass index, and liver cancer.

METHODS

A systematic literature search up to January 2022 was performed and 22 studies with a total of 169599 subjects participated in the studies with 97316 subjects of them used green tea intake. Odds ratio (OR) or standardized mean difference (MD) with 95% confidence intervals (CIs) was calculated to evaluate the relationship between green tea intake and lipoprotein, liver enzymes, body mass index, and liver cancer using the dichotomous or the contentious method with a random effect model.

RESULTS

Green tea intake significantly lowered the risk of developing liver cancer (OR, 0.85; 95% CI, 0.74 to 0.97, p = 0.02), and body mass index (MD, -0.69; 95% CI, -0.95to -0.42, p < 0.001) compared to no green tea intake. Also, there was a significant lowering effect of green tea intake on liver enzymes including alanine aminotransferase (MD, -0.65; 95% CI, -0.92 to -0.38, p < 0.001), and aspartate aminotransferase (MD, -0.77; 95% CI, -1.40 to -0.14, p = 0.02) compared to no green tea intake. There was also a significant lowering effect of green tea intake on lipoprotein including triglycerides (MD, -0.70; 95% CI, -1.35 to -0.04, p = 0.04), total cholesterol (MD, -0.39; 95% CI, -0.74 to -0.04, p = 0.03) and law-density lipoprotein (MD, -0.44; 95% CI, -0.69- -0.19, p < 0.001) compared to no green tea intake. However, no significant different was found between green tea intake and no green tea intake on high-density lipoprotein (MD, 0.16; 95% CI, -0.11 to 0.44, p = 0.24).

CONCLUSIONS

Based on this meta-analysis, green tea intake had a significant lowering effect on the risk of developing liver cancer and had a significantly improving effect on body mass index, liver enzymes, and lipoprotein compared to no green tea intake. These results suggest that green tea may be added to the daily dietary program to improve cardiovascular status with no possible risk of liver cancer. It even may have a protecting effect against liver cancer in the usual daily number of cups.

Hepatopreventive properties of hydroxytyrosol and mannitol-rich extracts obtained from exhausted olive pomace using green extraction methods

Hydroxytyrosol and mannitol rich extracts from exhausted olive pomace were obtained by green extraction methodologies. Supplementation of these extracts alleviated CCl4-induced hepatic damage and protected DNA.

Dietary Supplementation with Natural Extracts Mixture: Effects on Reproductive Performances, Blood Biochemical and Antioxidant Parameters in Rabbit Does

The present study evaluates the effects of natural extracts on reproductive performance, haematochemical parameters, and antioxidant status of rabbit does. A total of sixty New Zealand White second parity does were divided into three groups: the first group was fed a control diet (CON), the second (T1) and the third groups (T2) were fed the same diet supplemented with prebiotic polysaccharides from brown seaweeds (Laminaria spp.) plus phenolic acid, hydroxycinnamic acids, tannins, and flavonoids from plant extracts (0.3% and 0.6%, respectively). The trial was conducted for two consecutive reproductive cycles (75 days). Reproductive performance was recorded. Blood samples were collected before the first insemination, 10 d after the first kindling, and 10 d after the second one. At the first reproductive cycle, productive parameters were negatively affected (P<0.05) by a high dosage of the dietary supplement (T2 group). At the second reproductive cycle, no differences (P>0.05) between dietary treatments on reproductive and productive performances were observed. Bilirubin was affected by dietary treatment (P<0.001) and decreased in relation to sampling time (P<0.001). The HDL cholesterol decreased by dietary treatment (P<0.01). All the plasma antioxidant markers were positively affected (P<0.001) by dietary supplementation and sampling time. No previous study has reported the effects of brown seaweeds and polyphenols on rabbit does and the present data shows that this natural extract supplement improved the antioxidant status of rabbit does.

The Effects of Green Tea Amino Acid L-Theanine Consumption on the Ability to Manage Stress and Anxiety Levels: a Systematic Review

The green tea amino acid, L-theanine (L-THE) is associated with several health benefits, including improvements in mood, cognition and a reduction of stress and anxiety-like symptoms. This systematic review evaluated the effect of pure L-THE intake, in the form of orally administered nutritional supplements, on stress responses and anxiety levels in human randomised controlled trials. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, 9 peer-reviewed journal articles were identified where L-THE as a supplement was compared to a control. Our findings suggest that supplementation of 200-400 mg/day of L-THE may assist in the reduction of stress and anxiety in people exposed to stressful conditions. Despite this finding, longer-term and larger cohort clinical studies, including those where L-THE is incorporated into the diet regularly, are needed to clinically justify the use of L-THE as a therapeutic agent to reduce stress and anxiety in people exposed to stressful conditions.

Curcumin Inhibits Age-Related Vascular Changes in Aged Mice Fed a High-Fat Diet

Inhibiting the onset of arteriosclerotic disease, which has been increasing due to the westernized diet and aging, is a significant social challenge. Curcumin, a type of polyphenol, has anti-oxidative effects and anti-inflammatory action and is expected to treat and to have prophylactic effects on different diseases. In this study, we examined the effects of long-term administration of curcumin on vascular aging and chronic inflammation—the causes of arteriosclerotic disease. Eight-week-old C57BL/6J mice were fed with high fat diet (HFD) or 0.1% curcumin-mixed HFD (HFD + Cu) until 80 weeks old (n = 20 for each group). After the breeding, we examined the expression of antioxidant enzymes, heme oxygenase-1 (HO-1), oxidative stress, vascular aging, and inflammatory changes in the aorta. In the HFD group, oxidative stress increased with decreased sirt1 expression in the aorta followed by increased senescent cells and enhanced inflammation. Whereas in the HFD + Cu group, HO-1 was induced in the aorta with the suppression of oxidative stress. Additionally, it was shown that sirt1 expression in the aorta in the HFD + Cu group remained at a level comparable to that of the 8-week-old mice with suppression of increased senescent cells and enhanced inflammation. Consequently, disorders associated with HFD were resolved. These results suggest that curcumin might be a food with a prophylactic function against arteriosclerotic disease.

Flavonoids and Their Metabolites: Prevention in Cardiovascular Diseases and Diabetes

The occurrence of atherosclerosis and diabetes is expanding rapidly worldwide. These two metabolic disorders often co-occur, and are part of what is often referred to as the metabolic syndrome. In order to determine future therapies, we propose that molecular mechanisms should be investigated. Once the aetiology of the metabolic syndrome is clear, a nutritional intervention should be assessed. Here we focus on the protective effects of some dietary flavonoids, and their metabolites. Further studies may also pave the way for development of novel drug candidates.

A Review of the Efficacy, Safety, and Clinical Implications of Naturally Derived Dietary Supplements for Dyslipidemia

Dyslipidemia is recognized as a major cause of cardiovascular disease. A number of evidence-based guidelines recommend conventional synthetic drugs as standard therapy for dyslipidemia in clinical practice. However, antihyperlipidemic drugs have some serious side effects. Naturally derived dietary supplements are becoming attractive as an alternative strategy because of their high efficacy and safety, as supported by numerous data. Moreover, they could be considered an initial treatment for dyslipidemia. The aims of this literature review were to demonstrate the efficacy, safety, and clinical implications of dietary supplements for treating dyslipidemia. We reviewed the literature, including data from in vitro, in vivo, and human studies, and clinical guideline recommendations. We classified dietary supplements by their proposed mechanisms of action on lipid metabolism and also collected daily dosage recommendations, interactions with concurrent drugs and/or foods, dosage forms, and examples of commercially available products. Various types of naturally derived dietary supplements exhibit lipid-improving properties. Efficacy and safety are acceptable; however, their use in clinical practice will require further well-designed investigations and the support of scientific data.

Effect of dietary Lippia citriodora extract on reproductive and productive performance and plasma biochemical parameters in rabbit does

Two doses of natural extract from Lippia citriodora (titrated in verbascoside) were assessed in New Zealand White rabbit does evaluating selected reproductive, productive and plasma biochemical parameters. After 1 week of adaptation period, the trial on 45 rabbit does for three consecutive reproductive cycles was conducted; does were divided into three groups of 15 animals each, homogenous by age (1 year ± 2 weeks), bodyweight (4.77 ± 0.21 kg) and parity (2 ± 1). A control group (CON) did not receive the dietary supplement in the feed and the other two groups received 1 g of natural extract supplement in the feed (5 mg verbascoside/kg feed; LNE) and 2 g of natural extract (10 mg verbascoside/kg feed; HNE). The use of a dietary NE supplement improved kit bodyweight at weaning (934 vs 1104 g; P < 0.001), and average daily weight gain from birth to weaning (24.7 vs 29.7 g/day; P < 0.001), with no NE dose effect. In the LNE and HNE groups serum triglycerides, total cholesterol, low density lipoprotein cholesterol, bilirubin, and activities of alkaline phosphatase, alanine aminotransferase (P < 0.05) and aspartate aminotransferase (P < 0.01) decreased and high density lipoprotein cholesterol (P < 0.01) increased, according to the cycle effect. The dietary supplement also improved blood oxidative status markers in the experimental groups due to an increase in the concentrations of plasma vitamin A and E (P < 0.01) and a decrease in plasma reactive oxygen metabolites and thiobarbituric acid reactive substances values (P < 0.01). In conclusion, the dietary Lippia NE supplement improved selected productive and reproductive parameters and the animal welfare of does, expressed by a general improvement of blood profile, with no effect of the dose.

Effects of green tea catechin extract on serum lipids in postmenopausal women: a randomized, placebo-controlled clinical trial

BACKGROUND

Green tea has been suggested to improve cardiovascular disease risk factors, including circulating lipid variables. However, current evidence is predominantly based on small, short-term randomized controlled trials conducted in diverse populations.

OBJECTIVE

The aim of this study was to examine the efficacy and impact of green tea extract (GTE) supplementation high in epigallocatechin gallate (EGCG) on blood lipids in healthy postmenopausal women.

DESIGN

This was an ancillary study of a double-blind, randomized, placebo-controlled, parallel-arm trial investigating the effects of a GTE supplement containing 1315 mg catechins (843 mg EGCG) on biomarkers of breast cancer risk. Participants were randomly assigned to receive GTE (n = 538) or placebo (n = 537) and were stratified by catechol-O-methyltransferase (COMT) genotype activity (high COMT compared with low or intermediate COMT genotype activity). They consumed either 4 GTE or identical placebo capsules daily for 12 mo. A total of 936 women completed this substudy. Circulating lipid panels including total cholesterol (TC), HDL cholesterol, and triglycerides were measured at baseline and at months 6 and 12.

RESULTS

Compared with placebo, 1-y supplementation with GTE capsules resulted in a significant reduction in circulating TC (-2.1% compared with 0.7%; P = 0.0004), LDL cholesterol (-4.1% compared with 0.9%; P < 0.0001) and non-HDL cholesterol (-3.1% compared with 0.4%; P = 0.0032). There was no change in HDL-cholesterol concentration, but triglyceride concentrations increased by 3.6% in the GTE group, whereas they decreased by 2.5% in the placebo group (P = 0.046). A significant reduction in TC was observed only among women with high (i.e., ≥200 mg/dL) baseline TC concentrations (P-interaction = 0.01) who consumed GTE capsules. The effect of GTE on the increase in triglycerides was mainly observed among obese women and statin users (P-interaction = 0.06).

CONCLUSION

Supplementation with GTE significantly reduced circulating TC and LDL-cholesterol concentrations, especially in those with elevated baseline TC concentrations. This trial was registered at clinicaltrials.gov as NCT00917735.

Lipid-modifying effects of nutraceuticals: An evidence-based approach

The present review provides an up-to-date summary of the findings on the lipid-lowering effects of the most important nutraceuticals and functional foods. Based on current knowledge, nutraceuticals might exert significant lipid-lowering, and their use has several advantages: A number of important questions remain to be addressed, including whether longer durations of therapy would result in a better response and the exact safety profile of nutraceuticals, especially at doses higher than those consumed in an average diet. Additionally, data regarding the effects of nutraceutical supplementation on the incidence of cardiovascular outcomes are lacking, and it is not clear whether additional lipid lowering by nutraceuticals can modify the residual cardiovascular risk that remains after statin therapy.

Food Inhibits the Oral Bioavailability of the Major Green Tea Antioxidant Epigallocatechin Gallate in Humans

The bioavailability of the most abundant and most active green tea antioxidant, epigallocatechin gallate (EGCG) remains uncertain. Therefore, the systemic absorption of EGCG was tested in healthy fasted humans. It was administered as capsules with water or with a light breakfast, or when incorporated within a strawberry sorbet. The results for plasma EGCG clearly revealed that taking EGCG capsules without food was better; the AUC was 2.7 and 3.9 times higher than when EGCG capsules were taken with a light breakfast (p = 0.044) or with EGCG imbedded in the strawberry sorbet (p = 0.019), respectively. This pattern was also observed for Cmax and Cav. Therefore, ingesting food at the same time as EGCG, whether it was imbedded or not in food, substantially inhibited the absorption of the catechin. As with some types of medications that are affected by food, it appears that EGCG should be taken without food in order to maximise its systemic absorption. Therefore, based on these findings, ingesting EGCG with water on an empty stomach is the most appropriate method for the oral delivery of EGCG in clinical trials where EGCG is to be investigated as a potential bioactive nutraceutical in humans.

The effect of green tea on blood pressure and lipid profile: a systematic review and meta-analysis of randomized clinical trials

INTRODUCTION

Many different dietary supplements are currently marketed for the management of hypertension, but the evidence for effectiveness is mixed. The aim of this systematic review was to evaluate the evidence for or against the effectiveness of green tea (Camellia sinensis) on blood pressure and lipid parameters.

METHODS AND RESULTS

Electronic searches were conducted in Medline, Embase, Amed, Cinahl and the Cochrane Library to identify relevant human randomized clinical trials (RCTs). Hand searches of bibliographies were also conducted. The reporting quality of included studies was assessed using a checklist adapted from the CONSORT Statement. Two reviewers independently determined eligibility, assessed the reporting quality of the included studies, and extracted the data. As many as 474 citations were identified and 20 RCTs comprising 1536 participants were included. There were variations in the designs of the RCTs. A meta-analysis revealed a significant reduction in systolic blood pressure favouring green tea (MD: -1.94 mmHg; 95% CI: -2.95 to -0.93; I(2) = 8%; p = 0.0002). Similar results were also observed for total cholesterol (MD: -0.13 mmol/l; 95% CI: -0.2 to -0.07; I(2) = 8%; p < 0.0001) and LDL cholesterol (MD: -0.19 mmol/l; 95% CI: -0.3 to -0.09; I(2) = 70%; p = 0.0004). Adverse events included rash, elevated blood pressure, and abdominal discomfort.

CONCLUSION

Green tea intake results in significant reductions in systolic blood pressure, total cholesterol, and LDL cholesterol. The effect size on systolic blood pressure is small, but the effects on total and LDL cholesterol appear moderate. Longer-term independent clinical trials evaluating the effects of green tea are warranted.

Antiartherosclerotic effects of plant flavonoids

Atherosclerosis is the process of hardening and narrowing the arteries. Atherosclerosis is generally associated with cardiovascular diseases such as strokes, heart attacks, and peripheral vascular diseases. Since the usage of the synthetic drug, statins, leads to various side effects, the plants flavonoids with antiartherosclerotic activity gained much attention and were proven to reduce the risk of atherosclerosis in vitro and in vivo based on different animal models. The flavonoids compounds also exhibit lipid lowering effects and anti-inflammatory and antiatherogenic properties. The future development of flavonoids-based drugs is believed to provide significant effects on atherosclerosis and its related diseases. This paper discusses the antiatherosclerotic effects of selected plant flavonoids such as quercetin, kaempferol, myricetin, rutin, naringenin, catechin, fisetin, and gossypetin.

Reduced risk of dyslipidaemia with oolong tea consumption: a population-based study in southern China

Experimental studies have suggested that tea consumption could lower the risk of dyslipidaemia. However, epidemiological evidence is limited, especially in southern China, where oolong tea is the most widely consumed beverage. We conducted a population-based case-control study to evaluate the association between consumption of tea, especially oolong tea, and risk of dyslipidaemia in Shantou, southern China, from 2010 to 2011. Information on tea consumption, lifestyle characteristics and food consumption frequency of 1651 patients with newly diagnosed dyslipidaemia and 1390 controls was obtained using a semi-quantitative questionnaire. Anthropometric variables and serum biochemical indices were determined. Drinking more than 600 ml (2 paos) of green, oolong or black tea daily was found to be associated with the lowest odds of dyslipidaemia risk (P< 0.001) when compared with non-consumption, but only oolong tea consumption was found to be associated with low HDL-cholesterol levels. A dose-response relationship between duration of tea consumption and risk of dyslipidaemia (OR 0.10, 95% CI 0.06, 0.16), as well as that between amount of dried tea leaves brewed and risk of dyslipidaemia (OR 0.34, 95% CI 0.24, 0.48), was found. Moreover, consumption of oolong tea for the longest duration was found to be associated with 3.22, 11.99 and 6.69% lower blood total cholesterol, TAG and LDL-cholesterol levels, respectively. In conclusion, the present study indicates that long-term oolong tea consumption may be associated with a lower risk of dyslipidaemia in the population of Shantou in southern China.

Theflavins and theasinensin A derived from fermented tea have antihyperglycemic and hypotriacylglycerolemic effects in KK-A(y) mice and Sprague-Dawley rats

Although tea polyphenols are reported to improve serum glucose and lipid levels by inhibiting amylase activity and reducing lipid absorption, in vivo data are lacking. We evaluated in vivo the antihyperglycemic and hypotriacylglycerolemic effects of theaflavins (TFs) and theasinensin A (TSA) refined from fermented tea to purities of 12 and 59%, respectively. Feeding male KK-A(y) mice diets with 0.1% TFs or TSA for 6 weeks reduced serum glucose levels by >30% compared to a control diet. Rats fed diets containing 0.2% TFs or TSA for 4 weeks had higher fecal fat excretion and 33% lower hepatic triacylglycerol; hepatic fatty acid synthase activity was not affected. Oral administration of TFs or TSA reduced the increase in serum triacylglycerol after an oral bolus of a fat emulsion. These results indicate TFs and TSA induce antihyperglycemic responses in diabetic mice and are hypotriacylglycerolemic in rats by suppressing intestinal fat absorption.

Hypotriglyceridemic potential of fermented mixed tea made with third-crop green tea leaves and camellia (Camellia japonica) leaves in Sprague-Dawley rats

Fermented mixed tea made with third-crop green tea leaves and camellia leaves by a tea-rolling process has been developed. The objective of this study was to investigate hypotriglyceridemic potential of the mixed tea in rats. The mixed tea contained theasinensins and theaflavins. Rats fed the mixed tea extract at the level of 1% exerted significantly lower body weight and adipose tissue weight compared to animals fed third-crop green tea or camellia tea extract alone for 4 weeks. Serum and hepatic triglyceride was significantly and dose-dependently decreased by the mixed tea. This decrease was associated with lowered lipogenic enzyme activities in the liver. Furthermore, an oral administration of 4 or 8% of the mixed tea extract followed by fat emulsion suppressed the increment of serum triglyceride level. These results suggest that the mixed tea has hypotriglyceridemic action, partially via delaying triglyceride absorption in the small intestine and repressing hepatic lipogenic enzymes.

Assessment of a natural dietary extract, titrated in phenylpropanoid glycosides, on blood parameters and plasma oxidative status in intensively reared Italian hares (Lepus corsicanus)

Two different doses of a natural extract titrated in phenylpropanoid glycosides (PPGs) were evaluated for their effect on blood parameters and plasma oxidative status in pairs of intensively reared Italian hares. The study lasted 210 days, during which 45 couples of hares were divided into three homogeneous groups. A control group (CON) was fed a control diet while the two experimental groups were fed a diet supplemented with 1 or 2 kg/t of a supplement titrated in PPGs. Blood samples were obtained at 0, 70, 140 and 210 days and assayed for plasma lipid profiles, bilirubin, haematological parameters and indicators of oxidative status (reactive oxygen metabolites (ROMs), thiobarbituric acid reactive substances (TBARS), vitamins A and E). Although dietary treatment did affect the levels of triglycerides, total cholesterol and total bilirubin, all of which decreased markedly (P < 0.05), while significantly increasing the (P < 0.01) HDL cholesterol values, it also significantly improved the oxidative status of the blood, which displayed an increase in both vitamin E (P < 0.01) and vitamin A (P < 0.05) and a decrease in ROMs (P < 0.01) and TBARS (P < 0.05). The improvements in the blood parameters, lipid profile and plasma oxidative status continued to increase significantly as the trial progressed, indicating a positive effect with increased length of treatment. The results of this study demonstrate an important role for feed supplementation with respect to antioxidant activity on some blood parameters, including the lipid profile and the oxidative status of blood.

Effect of 2-month controlled green tea intervention on lipoprotein cholesterol, glucose, and hormone levels in healthy postmenopausal women

There have been no controlled intervention studies to investigate the effects of green tea on circulating hormone levels, an established breast cancer risk factor. We conducted a double-blind, randomized, placebo-controlled intervention study to investigate the effect of the main green tea catechin, epigallocatechin gallate (EGCG), taken in a green tea extract, polyphenon E (PPE). Postmenopausal women (n = 103) were randomized into three arms: placebo, 400-mg EGCG as PPE, or 800-mg EGCG as PPE as capsules per day for 2 months. Urinary tea catechin and serum estrogen, androgen, lipid, glucose-related markers, adiponectin, and growth factor levels were measured at baseline and at the end of months 1 and 2 of intervention. On the basis of urinary tea catechin concentrations, compliance was excellent. Supplementation with PPE did not produce consistent patterns of changes in estradiol (E2), estrone (E1), or testosterone (T) levels. Low-density lipoprotein (LDL)-cholesterol decreased significantly in both PPE groups but was unchanged in the placebo group; the change in LDL-cholesterol differed between the placebo and PPE groups (P = 0.02). Glucose and insulin levels decreased nonsignificantly in the PPE groups but increased in the placebo group; statistically significant differences in changes in glucose (P = 0.008) and insulin (P = 0.01) were found. In summary, green tea (400- and 800-mg EGCG as PPE; ∼5-10 cups) supplementation for 2 months had suggestive beneficial effects on LDL-cholesterol concentrations and glucose-related markers.

Green tea intake lowers fasting serum total and LDL cholesterol in adults: a meta-analysis of 14 randomized controlled trials

BACKGROUND

The effect of green tea beverage and green tea extract on lipid changes is controversial.

OBJECTIVE

We aimed to identify and quantify the effect of green tea and its extract on total cholesterol (TC), LDL cholesterol, and HDL cholesterol.

DESIGN

We performed a comprehensive literature search to identify relevant trials of green tea beverages and extracts on lipid profiles in adults. Weighted mean differences were calculated for net changes in lipid concentrations by using fixed-effects or random-effects models. Study quality was assessed by using the Jadad score, and a meta-analysis was conducted.

RESULTS

Fourteen eligible randomized controlled trials with 1136 subjects were enrolled in our current meta-analysis. Green tea consumption significantly lowered the TC concentration by 7.20 mg/dL (95% CI: -8.19, -6.21 mg/dL; P < 0.001) and significantly lowered the LDL-cholesterol concentration by 2.19 mg/dL (95% CI: -3.16, -1.21 mg/dL; P < 0.001). The mean change in blood HDL-cholesterol concentration was not significant. Subgroup and sensitivity analyses showed that these changes were not influenced by the type of intervention, treatment dose of green tea catechins, study duration, individual health status, or quality of the study. Overall, no significant heterogeneity was detected for TC, LDL cholesterol, and HDL cholesterol; and results were reported on the basis of fixed-effects models.

CONCLUSION

The analysis of eligible studies showed that the administration of green tea beverages or extracts resulted in significant reductions in serum TC and LDL-cholesterol concentrations, but no effect on HDL cholesterol was observed.

Application of GC/MS-based metabonomic profiling in studying the lipid-regulating effects of Ginkgo biloba extract on diet-induced hyperlipidemia in rats

AIM

To evaluate the lipid-regulating effects of extract from Ginkgo biloba leaves (EGB) using pharmacological methods and metabonomic profiling in a rat model of diet-induced hyperlipidemia.

METHODS

EGB was orally administered at a dose level of 40 mg/kg in both the EGB-prevention and -treatment groups. All rat samples obtained were examined for known and potential biomarkers and enzyme activity using commercial assay kits and GC/MS-based metabonomic profiling coupled with principal component analysis (PCA).

RESULTS

The data obtained from the assay kits indicated that EGB reduced total cholesterol and low density lipoprotein cholesterol levels and increased high density lipoprotein cholesterol levels in rat plasma obtained from both the EGB-prevention and -treatment groups compared with those of the diet-induced hyperlipidemia group. EGB also increased the activities of lipoprotein lipase and hepatic lipase and excretion of fecal bile acid in rats from the EGB-prevention and-treatment groups. Using GC/MS-based metabonomic analysis, more than 40 endogenous metabolites were identified in rat plasma. PCA of rat plasma samples obtained using GC/MS produced a distinctive separation of the four treatment groups and sampling points within each group. Metabolic changes during hyperlipidemia formation and improvement resulting from EGB treatment were definitively monitored with PCA score plots. Furthermore, elevated levels of sorbitol, tyrosine, glutamine and glucose, and decreased levels of citric acid, galactose, palmitic acid, arachidonic acid, acetic acid, cholesterol, butyrate, creatinine, linoleate, ornithine and proline, were observed in the plasma of rats treated with EGB.

CONCLUSION

EGB exerts multi-directional lipid-lowering effects on the rat metabonome, including limitation of the absorption of cholesterol, inactivation of HMGCoA and favorable regulation of profiles of essential polyunsaturated fatty acid (EFA). Further experiments are warranted to explore the mechanisms of action underlying the lipid-regulating effects of EGB against hyperlipidemia.

Green and black tea extracts inhibit HMG-CoA reductase and activate AMP kinase to decrease cholesterol synthesis in hepatoma cells

Recent studies have demonstrated that green and black tea consumption can lower serum cholesterol in animals and in man, and suppression of hepatic cholesterol synthesis is suggested to contribute to this effect. To evaluate this hypothesis, we measured cholesterol synthesis in cultured rat hepatoma cells in the presence of green and black tea extracts and selected components. Green and black tea decreased cholesterol synthesis by up to 55% and 78%, respectively, as measured by a 3-h incorporation of radiolabeled acetate. Inhibition was much less evident when radiolabeled mevalonate was used, suggesting that the inhibition was mediated largely at or above the level of HMG-CoA reductase. Both extracts directly inhibited HMG-CoA reductase when added to microsomal preparations, although the extent of inhibition was considerably less than the decrease in cholesterol synthesis observed in whole cells. As HMG-CoA reductase activity also can be decreased by enzyme phosphorylation by AMP kinase, the phosphorylation state of HMG-CoA reductase and AMP kinase, which is activated by phosphorylation, was determined in lysates from cells treated with tea extracts. Both extracts increased AMP-kinase phosphorylation and HMG-CoA reductase phosphorylation by 2.5- to 4-fold, but with different time courses: maximal phosphorylation with green tea was evident within 30 min of treatment, whereas with black tea phosphorylation was slower to develop, with maximal phosphorylation occurring > or =3 hours after treatment. These results suggest that both green and black tea decrease cholesterol synthesis in whole cells by directly inhibiting HMG-CoA reductase and by promoting its inactivation by AMP kinase.

Cholesterol-lowering nutraceuticals and functional foods

Epidemiological studies have demonstrated that elevated levels of plasma total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) are the major risk factors for coronary heart disease (CHD), whereas high concentrations of plasma high-density lipoprotein cholesterol (HDL-C) and a low ratio of TC to HDL-C are protective against CHD. A relationship between plasma TC and the risk of CHD is well established at concentrations above 240 mg/dL. In addition to the use of three main classes of cholesterol-lowering medications, including HMG-CoA reductase inhibitors, anion-exchange resins, and fibrates, a nutritionally balanced diet that reduces saturated fat and cholesterol intake has traditionally been the first goal of dietary therapy in lowering plasma TC. In recent years, nutraceuticals and functional foods have attracted much interest as possible alternative therapies for lowering plasma TC, especially for hypercholesterolemia patients, whose blood cholesterol level is marginally high (200-240 mg/dL) but not high enough to warrant the prescription of cholesterol-lowering medications. This review summarizes the findings of recent studies on the production, application, efficacy, and mechanisms of popular cholesterol-lowering nutraceuticals and functional foods.