Jia-Ying Xu

Effect of milk tripeptides on blood pressure: a meta-analysis of randomized controlled trials.

OBJECTIVE To better understand and summarize the relation between milk peptide intake and blood pressure (BP), we conducted a meta-analysis of randomized controlled trials to assess the effects of the milk-derived tripeptides isoleucine-proline-proline and valine-proline-proline on BP in prehypertensive and hypertensive subjects. METHODS Nine studies including 12 trials published between 1996 and 2005 with a total of 623 participants were included. Two researchers independently extracted data from the original publications. A fixed-effects model was used for meta-analysis because of the homogeneity among trials. RESULTS Significant decreases of 4.8 mmHg (95% confidence interval 3.7-6.0) in systolic BP and 2.2 mmHg (95% confidence interval 1.3-3.1) in diastolic BP were found after the pooling of these trials. When trials were separated by BP status, hypotensive effects appeared to be larger in hypertensive subjects than in prehypertensive subjects. As a trend, the hypotensive effects became more obvious as the intervention lengthened. CONCLUSION Our analysis provided evidence that milk-derived tripeptides have hypotensive effects in prehypertensive and hypertensive subjects.

Dairy Consumption and Risk of Cardiovascular Disease: An Updated Meta‐analysis of Prospective Cohort Studies

BACKGROUND Epidemiological studies to-date provided inconsistent findings on the effects of dairy consumption on the risk of cardiovascular disease (CVD). We aimed to examine the association of dairy consumption and its specific subtypes with CVD risk, including the risk of stroke and coronary heart disease (CHD) by a metaanalysis. METHODS PubMed, EMBASE, and Cochrane Library databases were searched for articles published up to February 2014 to identify prospective cohort studies. Random-effects model or fix-effects model was used to compute the summary risk estimates. RESULTS A total of 22 studies were eligible for analysis. An inverse association was found between dairy consumption and overall risk of CVD [9 studies; relative risk (RR)=0.88, 95% confidence interval (CI): 0.81, 0.96] and stroke (12 studies; RR=0.87, 95% CI: 0.77, 0.99). However, no association was established between dairy consumption and CHD risk (12 studies; RR=0.94, 95% CI: 0.82, 1.07). Stroke risk was significantly reduced by consumption of low-fat dairy (6 studies; RR=0.93, 95% CI: 0.88, 0.99) and cheese (4 studies; RR=0.91, 95% CI: 0.84, 0.98), and CHD risk was significantly lowered by cheese consumption (7 studies; RR=0.84, 95% CI: 0.71, 1.00). Restricting studies according to various inclusion criteria yielded similar results for CVD and CHD analyses, but showed attenuated results for stroke analysis. Heterogeneity across studies was found for stroke and CHD analyses, and publication bias was found for stroke analysis. CONCLUSION This meta-analysis provided further evidence supporting the beneficial effect of dairy consumption on CVD. Low-fat dairy products and cheese may protect against stroke or CHD incidence.

Effect of dietary fiber on circulating C-reactive protein in overweight and obese adults: a meta-analysis of randomized controlled trials

Abstract Previous studies suggested that dietary fiber intake may have a lowing effect on circulating C-reactive protein (CRP) level, a sensitive marker of inflammation, in overweight/obese adults with inconsistent results. A literature search was performed in April 2014 for related randomized controlled trials (RCTs) and meta-analysis was conducted. Meta-analysis including 14 RCTs showed that intervention with dietary fiber or fiber-rich food, compared with control, produced a slight, but significant reduction of 0.37 mg/L (95% CI −0.74, 0) in circulating CRP level among this population. Subgroup analyses showed that such a significant reduction was only observed after combining studies where the total fiber intake was 8 g/d higher in the intervention group than in the control group. No obvious heterogeneity and publication bias were found in the meta-analysis. In conclusion, this meta-analysis provides evidence that dietary fiber or food naturally rich in fiber has beneficial effects on circulating CRP level in overweight/obese adults.

Whole-grain intake and total, cardiovascular, and cancer mortality: a systematic review and meta-analysis of prospective studies

BACKGROUND The potential role of whole grain in preventing various mortality outcomes has been inconsistently reported in a wealth of prospective observational studies. OBJECTIVE We evaluated the relations between whole-grain intake and risks of dying from any cause, cardiovascular disease (CVD), and cancer through a meta-analytic approach. DESIGN Relevant studies were identified by searching PubMed and EMBASE databases and bibliographies of retrieved full publications. Summary RRs with 95% CIs were calculated with a random-effects model. RESULTS Thirteen studies on total mortality (104,061 deaths), 12 on CVD mortality (26,352 deaths), and 8 on cancer mortality (34,797 deaths) were included. Three studies reported whole-grain intake, and the remaining studies reported whole-grain product intake. In the dose-response analysis in which the intake of whole-grain products was converted to the amount of whole grain, the summary RRs for an increment in whole-grain intake of 50 g/d were 0.78 (95% CI: 0.67, 0.91) for total mortality, 0.70 (95% CI: 0.61, 0.79) for CVD mortality, and 0.82 (95% CI: 0.69, 0.96) for cancer mortality. A similar reduction was observed for the mortality from ischemic heart disease (RR: 0.68; 95% CI: 0.55, 0.84) but not from stroke (RR: 0.93; 95% CI: 0.54, 1.62). There was evidence of nonlinear associations of whole-grain intake with total (P-nonlinearity < 0.001) and CVD mortality (P-nonlinearity <0.001), but not with cancer mortality (P-nonlinearity = 0.12), with the curves for the associations appearing slightly steeper at lower ranges (<35 g/d) of the intake than at higher ranges. CONCLUSIONS Our findings suggest significant inverse relations between whole-grain intake and mortality due to any cause, CVD, or cancer. The findings support the recommendation of increasing whole-grain intake to improve public health.

Dietary fiber prevents obesity-related liver lipotoxicity by modulating sterol-regulatory element binding protein pathway in C57BL/6J mice fed a high-fat/cholesterol diet

Adequate intake of dietary fibers has proven metabolic and cardiovascular benefits, molecular mechanisms remain still limited. This study was aimed to investigate the effects of cereal dietary fiber on obesity-related liver lipotoxicity in C57BL/6J mice fed a high-fat/cholesterol (HFC) diet and underlying mechanism. Forty-eight adult male C57BL/6J mice were randomly given a reference chow diet, or a high fat/choleserol (HFC) diet supplemented with or without oat fiber or wheat bran fiber for 24 weeks. Our results showed mice fed oat or wheat bran fiber exhibtied lower weight gain, lipid profiles and insulin resistance, compared with HFC diet. The two cereal dietary fibers potently decreased protein expressions of sterol regulatory element binding protein-1 and key factors involved in lipogenesis, including fatty acid synthase and acetyl-CoA carboxylase in target tissues. At molecular level, the two cereal dietary fibers augmented protein expressions of peroxisome proliferator-activated receptor alpha and gamma, liver X receptor alpha, and ATP-binding cassette transporter A1 in target tissues. Our findings indicated that cereal dietary fiber supplementation abrogated obesity-related liver lipotoxicity and dyslipidemia in C57BL/6J mice fed a HFC diet. In addition, the efficacy of oat fiber is greater than wheat bran fiber in normalizing these metabolic disorders and pathological profiles.

Effect of Whey Supplementation on Circulating C-Reactive Protein: A Meta-Analysis of Randomized Controlled Trials

Whey supplementation is beneficial for human health, possibly by reducing the circulating C-reactive protein (CRP) level, a sensitive marker of inflammation. Thus, a meta-analysis of randomized controlled trials was conducted to evaluate their relationship. A systematic literature search was conducted in July, 2014, to identify eligible studies. Either a fixed-effects model or a random-effects model was used to calculate pooled effects. The meta-analysis results of nine trials showed a slight, but no significant, reduction of 0.42 mg/L (95% CI −0.96, 0.13) in CRP level with the supplementation of whey protein and its derivates. Relatively high heterogeneity across studies was observed. Subgroup analyses showed that whey significantly lowered CRP by 0.72 mg/L (95% CI −0.97, −0.47) among trials with a daily whey dose ≥20 g/day and by 0.67 mg/L (95% CI −1.21, −0.14) among trials with baseline CRP ≥3 mg/L. Meta-regression analysis revealed that the baseline CRP level was a potential effect modifier of whey supplementation in reducing CRP. In conclusion, our meta-analysis did not find sufficient evidence that whey and its derivates elicited a beneficial effect in reducing circulating CRP. However, they may significantly reduce CRP among participants with highly supplemental doses or increased baseline CRP levels.

Cheese Consumption and Risk of All-Cause Mortality: A Meta-Analysis of Prospective Studies

The association between cheese consumption and risk for major health endpoints has been investigated in many epidemiologic studies, but findings are inconsistent. As all-cause mortality can be viewed as the final net health effect of dietary intakes, we conducted a meta-analysis to examine the long-term association of cheese consumption with all-cause mortality. Relevant studies were identified by a search of the PubMed database through May 2016. Reference lists from retrieved articles were also reviewed. Summary relative risks (RR) and 95% confidence intervals (CI) were calculated using a random-effects model. Pre-specified stratified and dose-response analyses were also performed. The final analysis included nine prospective cohort studies involving 21,365 deaths. The summary RR of all-cause mortality for the highest compared with the lowest cheese consumption was 1.02 (95% CI: 0.97, 1.06), and little evidence of heterogeneity was observed. The association between cheese consumption and risk of all-cause mortality did not significantly differ by study location, sex, age, number of events, study quality score or baseline diseases excluded. There was no dose-response relationship between cheese consumption and risk of all-cause mortality (RR per 43 g/day = 1.03, 95% CI: 0.99–1.07). No significant publication bias was observed. Our findings suggest that long-term cheese consumption was not associated with an increased risk of all-cause mortality.

Effects of plant stanol or sterol-enriched diets on lipid profiles in patients treated with statins: systematic review and meta-analysis.

Efficacy and safety data from trials with suitable endpoints have shown that non-statin medication in combination with a statin is a potential strategy to further reduce cardiovascular events. We aimed to evaluate the overall effect of stanol- or sterol-enriched diets on serum lipid profiles in patients treated with statins by conducting a meta-analysis of randomized controlled trials (RCTs). We used the PubMed, Cochrane library and ClinicalTrials.gov databases to search for literature published up to December 2015. Trials were included in the analysis if they were RCTs evaluating the effect of plant stanols or sterols in patients under statin therapy that reported corresponding data on serum lipid profiles. We included 15 RCTs involving a total of 500 participants. Stanol- or sterol-enriched diets in combination with statins, compared with statins alone, produced significant reductions in total cholesterol of 0.30 mmol/L (95% CI −0.36 to −0.25) and low-density lipoprotein (LDL) cholesterol of 0.30 mmol/L (95% CI −0.35 to −0.25), but not in high-density lipoprotein cholesterol or triglycerides. These results persisted in the subgroup analysis. Our meta-analysis provides further evidence that stanol- or sterol-enriched diets additionally lower total cholesterol and LDL-cholesterol levels in patients treated with statins beyond that achieved by statins alone.

Leucine supplementation improves leptin sensitivity in high-fat diet fed rats

Background Several studies have reported the favorable effect of leucine supplementation on insulin resistance or insulin sensitivity. However, whether or not leucine supplementation improves leptin sensitivity remains unclear. Design Forty-eight male Sprague-Dawley rats were fed with either a high-fat diet (HFD) or HFD supplemented with 1.5, 3.0, and 4.5% leucine for 16 weeks. At the end of the experiment, serum leptin level was measured by ELISA, and leptin receptor (ObR) in the hypothalamus was examined by immunohistochemistry. The protein expressions of ObR and leptin-signaling pathway in adipose tissues were detected by western blot. Results No significant differences in body weight and food/energy intake existed among the four groups. Serum leptin levels were significantly lower, and ObR expression in the hypothalamus and adipose tissues was significantly higher in the three leucine groups than in the control group. These phenomena suggested that leptin sensitivity was improved in the leucine groups. Furthermore, the expressions of JAK2 and STAT3 (activated by ObR) were significantly higher, and that of SOCS3 (inhibits leptin signaling) was significantly lower in the three leucine groups than in the control group. Conclusions Leucine supplementation improves leptin sensitivity in rats on HFD likely by promoting leptin signaling.

Chia Seed Does Not Improve Cognitive Impairment in SAMP8 Mice Fed with High Fat Diet

Background: Chia seed is an ancient seed with the richest plant source of α-linolenic acid, which has been demonstrated to improve metabolic syndrome associated risk factors. Under high fat diet (HFD) condition, the senescence-accelerated mouse-prone 8 (SAMP8) mice demonstrated worsen Alzheimer’s disease (AD) related pathology compared to low fat diet fed SAMP8 mice. Objective: To explore whether chia seed supplementation might improve cognitive impairment under aging and metabolic stress via high fat diet (HFD) fed SAMP8 mice as a model. Design: SAMP8 mice and senescence-accelerated mouse-resistant 1 (SAMR1) were randomized into 4 groups, i.e., SAMR1 low fat diet group (SAMR1-LFD), SAMP8-HFD and SAMP8-HFD group supplemented with 10% chia seed (SAMP8-HFD+Chia). At the end of the intervention, cognitive function was measured via Morris water maze (MWM) test. Hippocampus and parietal cortex were dissected for further analysis to measure key markers involved AD pathology including Aβ, tau and neuro-inflammation. Results: During navigation trials of MWM test, mice in SAMP8-LFD group demonstrated impaired learning ability compared to SAMR1-LFD group, and chia seed had no effect on learning and memory ability for HFD fed SAMP8 mice. As for Alzheimer’s disease (AD) related pathology, chia seed not only increased α-secretase such as ADAM10 and insulin degrading enzyme (IDE), but also increased β-secretase including beta-secretase 1 (BACE1) and cathepsin B, with an overall effects of elevation in the hippocampal Aβ42 level; chia seed slightly reduced p-Tauser404 in the hippocampus; while an elevation in neuro-inflammation with the activation of glial fibrillary acidic protein (GFAP) and Ibα-1 were observed post chia seed supplementation. Conclusions: Chia seed supplementation did not improve cognitive impairment via MWM in HFD fed SAMP8 mice. This might be associated with that chia seed increased key enzymes involved both in non-amyloidogenic and amyloidogenic pathways, and neuro-inflammation. Future studies are necessary to confirm our present study.