Effect of conjugated linoleic acid and vitamin E on glycemic control, body composition, and inflammatory markers in overweight type2 diabetics

The effects of conjugated linoleic acid supplementation on cardiovascular risk factors in patients at risk of cardiovascular disease: A GRADE-assessed systematic review and dose-response meta-analysis

The present systematic review and meta-analysis sought to evaluate the effects of conjugated linoleic acid (CLA) supplementation on cardiovascular risk factors in patients at risk of CVD. Relevant studies were obtained by searching the PubMed, SCOPUS and Web of Science databases (from inception to January 2023). Weighted mean differences (WMD) and 95% CI were pooled using a random-effects model. Heterogeneity, sensitivity analysis and publication bias were reported using standard methods. A pooled analysis of 14 randomised controlled trials (RCT) with 17 effect sizes revealed that CLA supplementation led to significant reductions in body weight (WMD: -0·72 kg, 95% CI: -1·11, -0·33, P < 0·001), BMI (WMD: -0·22 kg/m2, 95% CI: -0·44, -0·00, P = 0·037) and body fat percentage (BFP) (WMD: -1·32 %, 95% CI: -2·24, -0·40, P = 0·005). However, there was no effect on lipid profile and blood pressure in comparison with the control group. In conclusion, CLA supplementation may yield a small but significant beneficial effect on anthropometric indices in patients at risk of CVD. Moreover, CLA seems not to have adverse effects on lipid profiles and blood pressure in patients at risk of CVD. It should be noted that the favourable effects of CLA supplementation on anthropometric variables were small and may not reach clinical importance.

Single and mixed associations of composite antioxidant diet on triglyceride-glucose index

BACKGROUND

Although the relationship between oxidative stress and insulin resistance (IR) has been established, the associations of the composite dietary antioxidant index (CDAI) and its components with the surrogate index of insulin resistance (IR), triglyceride-glucose index (TyG), is still not clear.

METHODS

This study analyzed the cross-sectional data of the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2018. Multivariate linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were used to analyze the associations of the CDAI and its components with the TyG. In addition, subgroup analysis and several sensitivity analyses were conducted.

RESULTS

A total of 14,673 participants with complete data were included, with a median age of 50 years and 7,257 women (49%). Multivariate linear regression showed that after full adjustment, the CDAI was significantly negatively associated with the TyG [β: -0.005, 95% CI: (-0.008, -0.002), p = 0.002]. The model in which six nutrients were mutually corrected showed that vitamin E (per-SD increase) was most strongly associated with the TyG [β: -0.062, 95% CI: (-0.074, -0.050), p < 0.0001]. In the WQS model, the WQS index of the antioxidant diet was negatively associated with the TyG (β: -0.060; P < 0.0001). Similar effects were observed in the BKMR analysis. Notably, in the WQS and BKMR models, vitamin E became the most influential component. In addition, in the subgroup analysis, the association between the CDAI and the TyG in overweight or obese and diabetic populations was significantly weaker.

CONCLUSION

Antioxidant diets, especially vitamin E, are significantly negatively correlated with TyG. This study emphasizes the important value of supplementing vitamin E to improve IR. However, patients with poor weight management and diabetes seem to benefit less from antioxidant diets.

The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: a systematic review and dose-response meta-analysis

Prior meta-analytic investigations over a decade ago rather inconclusively indicated that conjugated linoleic acid (CLA) supplementation could improve anthropometric and body composition indices in the general adult population. More recent investigations have emerged, and an up-to-date systematic review and meta-analysis on this topic must be improved. Therefore, this investigation provides a comprehensive systematic review and meta-analysis of randomised controlled trials (RCT) on the impact of CLA supplementation on anthropometric and body composition (body mass (BM), BMI, waist circumference (WC), fat mass (FM), body fat percentage (BFP) and fat-free mass (FFM)) markers in adults. Online databases search, including PubMed, Scopus, the Cochrane Library and Web of Science up to March 2022, were utilised to retrieve RCT examining the effect of CLA supplementation on anthropometric and body composition markers in adults. Meta-analysis was carried out using a random-effects model. The I2 index was used as an index of statistical heterogeneity of RCT. Among the initial 8351 studies identified from electronic databases search, seventy RCT with ninety-six effect sizes involving 4159 participants were included for data analyses. The results of random-effects modelling demonstrated that CLA supplementation significantly reduced BM (weighted mean difference (WMD): -0·35, 95 % CI (-0·54, -0·15), P < 0·001), BMI (WMD: -0·15, 95 % CI (-0·24, -0·06), P = 0·001), WC (WMD: -0·62, 95% CI (-1·04, -0·20), P = 0·004), FM (WMD: -0·44, 95 % CI (-0·66, -0·23), P < 0·001), BFP (WMD: -0·77 %, 95 % CI (-1·09, -0·45), P < 0·001) and increased FFM (WMD: 0·27, 95 % CI (0·09, 0·45), P = 0·003). The high-quality subgroup showed that CLA supplementation fails to change FM and BFP. However, according to high-quality studies, CLA intake resulted in small but significant increases in FFM and decreases in BM and BMI. This meta-analysis study suggests that CLA supplementation may result in a small but significant improvement in anthropometric and body composition markers in an adult population. However, data from high-quality studies failed to show CLA's body fat-lowering properties. Moreover, it should be noted that the weight-loss properties of CLA were small and may not reach clinical importance.

The effects of conjugated linoleic acid supplementation on glycemic control, adipokines, cytokines, malondialdehyde and liver function enzymes in patients at risk of cardiovascular disease: a GRADE-assessed systematic review and dose-response meta-analysis

BACKGROUND

The present systematic review and meta-analysis sought to evaluate the effects of conjugated linoleic acid (CLA) supplementation on glycemic control, adipokines, cytokines, malondialdehyde (MDA) and liver function enzymes in patients at risk of cardiovascular disease.

METHODS

Relevant studies were obtained by searching the PubMed, SCOPUS and Web of Science databases (from inception to January 2023). Weighted mean differences (WMD) and 95% confidence intervals (CIs) were pooled using a random-effects model. Heterogeneity, sensitivity analysis, and publication bias were reported using standard methods.

RESULTS

A pooled analysis of 13 randomized controlled trials (RCTs) revealed that CLA supplementation led to a significant increment in fasting blood glucose (FBG) (WMD: 4.49 mg/dL; 95%CI: 2.39 to 6.59; P < 0.001), and aspartate aminotransferase (AST) (WMD: 2.54 IU/L; 95%CI: 0.06 to 5.01; P = 0.044). Moreover, CLA supplementation decreased leptin (WMD: -1.69 ng/ml; 95% CI: -1.80 to -1.58; P < 0.001), and interleukin 6 (IL-6) (WMD: -0.44 pg/ml; 95%CI: -0.86 to -0.02; P = 0.037). However, there was no effect on hemoglobin A1c (HbA1c), homeostatic model assessment for insulin resistance (HOMA-IR), C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), and alanine aminotransferase (ALT) adiponectin compared to the control group.

CONCLUSION

Our findings showed the overall favorable effect of CLA supplementation on the adipokines and cytokines including serum IL-6, and leptin, while increasing FBG and AST. It should be noted that the mentioned metabolic effects of CLA consumption were small and may not reach clinical importance.

PROSPERO REGISTERATION COD

CRD42023426374.

Conjugated linoleic acid (CLA) as a functional food: Is it beneficial or not?

Conjugated linoleic acid (CLA) has attracted great attention in recent years as a popular class of functional food that is broadly used. It refers to a group of geometric and positional isomers of linoleic acid (LA) with a conjugated double bond. The main natural sources of CLA are dairy products, beef and lamb, whereas only trace amounts occur naturally in plant lipids. CLA has been shown to improve various health issues, having effects on obesity, inflammatory, anti-carcinogenicity, atherogenicity, immunomodulation, and osteosynthesis. Also, compared to studies on humans, many animal researches reveal more positive benefits on health. CLA represents a nutritional avenue to improve lifestyle diseases and metabolic syndrome. Most of these effects are attributed to the two major CLA isomers [conjugated linoleic acid cis-9,trans-11 isomer (c9,t11), and conjugated linoleic acid trans-10,cis-12 isomer (t10,c12)], and their mixture (CLA mix). In contrast, adverse effects of CLA have been also reported, such as glucose homeostasis, insulin resistance, hepatic steatosis and induction of colon carcinogenesis in humans, as well as milk fat inhibition in ruminants, lowering chicken productivity, influencing egg quality and altering growth performance in fish. This review article aims to discuss the health benefits of CLA as a nutraceutical supplement and highlight the possible mechanisms of action that may contribute to its outcome. It also outlines the feasible adverse effects of CLA besides summarizing the recent peer-reviewed publications on CLA to ensure its efficacy and safety for proper application in humans.

Effect of vitamin E intake on glycemic control and insulin resistance in diabetic patients: an updated systematic review and meta-analysis of randomized controlled trials

Since a 2014 meta-analysis, several randomized controlled trials (RCTs) evaluating the effect of vitamin E intake on glycemic indices and insulin resistance in adults with diabetes have reached inconsistent conclusions. Therefore, we updated the previous meta-analysis to summarize the current evidence in this regard. Online databases including PubMed, Scopus, ISI Web of Science, and Google Scholar were searched to identify relevant studies published up to September 30, 2021, using relevant keywords. Random-effects models were used to obtain overall mean difference (MD) comparing vitamin E intake with a control group. In total, 38 RCTs with a total sample size of 2171 diabetic patients (1110 in vitamin E groups and 1061 in control groups) were included. Combining the results from 28 RCTs on fasting blood glucose, 32 RCTs on HbA1c, 13 RCTs on fasting insulin, and 9 studies on homeostatic model assessment for insulin resistance (HOMA-IR) showed a summary MD of -3.35 mg/dL (95% CI: -8.10 to 1.40, P = 0.16), -0.21% (95% CI: -0.33 to -0.09, P = 0.001), -1.05 µIU/mL (95% CI: -1.53 to -0.58, P < 0.001), and -0.44 (95% CI: -0.82 to -0.05, P = 0.02), respectively. This indicates a significant lowering effect of vitamin E on HbA1c, fasting insulin and HOMA-IR, while no significant effect on fasting blood glucose in diabetic patients. However, in subgroup analyses, we found that vitamin E intake significantly reduced fasting blood glucose in studies with an intervention duration of < 10 weeks. In conclusion, vitamin E intake has a beneficial role in improving HbA1c and insulin resistance in a population with diabetes. Moreover, short-term interventions with vitamin E have resulted in lower fasting blood glucose in these patients. This meta-analysis was registered in PROSPERO with code CRD42022343118.

The effects of conjugated linoleic acid supplementation on inflammatory cytokines and adipokines in adults: A GRADE-assessed systematic review and dose-response meta-analysis

Background and aims

Many studies have investigated the effect of conjugated linoleic acid (CLA) supplementation on inflammatory cytokines and adipokines. However, the results of these studies are not consistent. Therefore, this systematic review and meta-analysis were designed to comprehensively evaluate the effect of CLA supplementation on inflammatory cytokines and adipokines.

Methods

Randomized controlled trials (RCTs) examining the effects of CLA supplementation on C-reactive protein (CRP), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), adiponectin, and leptin, published up to March 2022, were identified through PubMed, SCOPUS, and ISI Web of Science databases. A random-effects model was used to calculate weighted mean differences (WMDs) with 95% confidence intervals (CI) for 42 studies that included 1,109 participants.

Results

Findings from 42 studies with 58 arms indicated that CLA supplementation significantly decreased IL-6 and TNF-α levels and also slightly increased CRP levels. However, adiponectin and leptin levels did not change after CLA supplementation. A subgroup analysis found that CLA supplementation reduced adiponectin and leptin in women.

Conclusion

Our results demonstrated that CLA supplementation increased CRP levels and decreased TNF-α and IL-6 levels. Therefore, it seems that CLA can have both proinflammatory and anti-inflammatory roles.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier (CRD42022331110).

The effects of conjugated linoleic acid supplementation on lipid profile in adults: A systematic review and dose-response meta-analysis

Background

The findings of trials investigating the effect of conjugated linoleic acid (CLA) administration on lipid profile are controversial. This meta-analysis of randomized controlled trials (RCTs) was performed to explore the effects of CLA supplementation on lipid profile.

Methods

Two authors independently searched electronic databases including PubMed, Web of Science, and Scopus until March 2022, in order to find relevant RCTs. The random effects model was used to evaluate the mean and standard deviation.

Results

In total, 56 RCTs with 73 effect sizes met the inclusion criteria and were eligible for the meta-analysis. CLA supplementation significantly alter triglycerides (TG) (WMD: 1.76; 95% CI: -1.65, 5.19), total cholesterols (TC) (WMD: 0.86; 95% CI: -0.42, 2.26), low-density lipoprotein cholesterols (LDL-C) (WMD: 0.49; 95% CI: -0.75, 2.74), apolipoprotein A (WMD: -3.15; 95% CI: -16.12, 9.81), and apolipoprotein B (WMD: -0.73; 95% CI: -9.87, 8.41) concentrations. However, CLA supplementation significantly increased the density lipoprotein cholesterol (HDL-C) (WMD: -0.40; 95% CI: -0.72, -0.07) concentrations.

Conclusion

CLA supplementation significantly improved HDL-C concentrations, however, increased concentrations of TG, TC, LDL-C, apolipoprotein A, and apolipoprotein B.

Systematic review registration

https://www.crd.york.ac.uk/prospero/#recordDetails, identifier: CRD42022331100.

Effects of Antioxidant Supplementation on Metabolic Disorders in Obese Patients from Randomized Clinical Controls: A Meta-Analysis and Systematic Review

Purpose

This systematic review and meta-analysis aim at elucidating the heterogeneity in beneficial effects of antioxidant supplementation in obese adults by exploring the differential effects of antioxidant supplementation on basic indicators of obesity, lipid metabolism, systemic antioxidant capacity, inflammatory biomarkers, and liver function.

Methods

The inclusion criteria specified randomized controlled trials with antioxidant intervention for adults (mean body mass index (BMI) > 30), from inception to Aug. 8, 2021, in the PubMed, Embase, The Cochrane Library, Web of Science, and Scopus databases. Meta-analysis and publication bias were performed using RevMan 5.4 software. Stata16 software was used to detect publication bias with Egger's and Begg's methods being mainly used. The data of basic indicators of obesity, lipid metabolism index, oxidative stress index, inflammatory biomarkers, and liver function index were collected to analyze the beneficial effects of antioxidant supplementation in obese patients.

Results

A total of 30 studies were included in this study with a sample of 845 obese patients from the antioxidant supplementation group and 766 obese patients from the placebo control group. The meta-analysis showed that obese patients with antioxidant supplementation had lower BMI (mean difference (MD): − 0.44 [95%confidence interval (CI): − 0.84, −0.04], p = 0.03), waist circumference (MD : −0.78 [95%CI:−1.45, −0.11], p = 0.02), fasting blood glucose (FBG) level (standardized mean difference (SMD): − 4.92 [95%CI:−6.87, −2.98], p < 0.001) and homeostasis model assessment of insulin resistance (MD : −0.45 [95%CI:−0.61, −0.3], p < 0.001) when compared to the placebo group. Obese patients on antioxidant supplementation had lower levels of total cholesterol (SMD : −0.43 [95%CI:−0.84, −0.02], p = 0.04), triglycerides (SMD : −0.17 [95%CI:−0.31, −0.04], p = 0.01), low-density lipoprotein (SMD : −0.15 [95%CI:−0.29, −0.01], p = 0.03), malondialdehyde (SMD : −1.67 [95%CI:−2.69, −0.65], p = 0.001), and tumor necrosis factor-alpha (SMD : −0.29 [95%CI:−0.56, −0.02], p = 0.03), respectively, when compared to the placebo group. In addition, obese patients with antioxidant supplementation had higher levels of high-density lipoprotein (SMD : 0.25 [95%CI : 0.03, 0.46], p = 0.03) and superoxide dismutase (SMD : 1.09 [95%CI : 0.52, 1.65], p < 0.001) when compared to the placebo group. Antioxidant supplementation had no effects on other analyzed parameters including waist–hip ratio, leptin, fat mass, interleukin-6, C-reactive protein, alanine transaminase, and aspartate transaminase in obese patients.

Conclusion

The meta-analysis results indicated that antioxidant supplementation exerted potential beneficial effects in obese patients by regulating FBG, oxidative stress, and inflammation, whilst more high-quality studies are required to confirm these effects. The present study may provide important insights for the treatment of clinical obesity and obesity-associated complications.

The effect of Conjugated Linoleic Acid intake on oxidative stress parameters and antioxidant enzymes: a systematic review and meta-analysis of randomized clinical trials

Conjugated Linoleic Acid (CLA) are thought to pose beneficial effects on inflammatory responses and oxidative stress (OS). Thus, the present systematic review and meta-analysis of randomized controlled trials (RCTs) aimed to assess the net effects of CLA supplementation on various OS parameters and antioxidant enzymes. PubMed/MEDLINE, Scopus, Web of Science, and Cochrane Central Register of Controlled Trials databases were searched for publications on CLA supplementation effects on OS parameters up to March 2021. The data extracted from eligible studies were expressed as standardized mean difference with 95% confidence intervals and then combined into meta-analysis using the random-effects model. Overall, 11 RCTs (enrolling 586 participants) met the inclusion criteria and were included in meta-analysis; however, since those trials evaluated different OS parameters, meta-analysis was carried out considering different sets for each parameter separately. According to our results, CLA supplementation significantly increases 8-iso-PGF_2α urinary concentration (SMD: 2; 95% CI: 0.74, 3.27; I²=87.7%). On contrary, the intervention does not seem to change 15-keto-dihydro-PGF_2α urinary concentration, nor the serum levels of CAT, SOD, GPx and MDA. Taken all together, CLA supplementation does not appear to have substantial effects on OS markers in general; albeit due to relatively small sample size and high level of heterogeneity between studies, the obtained findings should be interpreted with caution. Further large well-designed RCTs, investigating the impact of CLA and including various groups of patients, are still needed.

Systematic review and meta-analyses of vitamin E (alpha-tocopherol) supplementation and blood lipid parameters in patients with diabetes mellitus

BACKGROUND AND AIMS

The studies have shown that α-tocopherol supplementation could improve lipid profile in diabetes mellitus (DM) patients. Nonetheless, the result remains inconsistent. Therefore, this meta-analysis was performed to evaluate the efficacy of α-tocopherol supplement on lipid parameters in DM patients.

METHODS

We conducted an extensive search via Cochrane Library, PubMed, Scopus, and Web of Science databases to acquire the reported RCTs up to October 2020.

RESULTS

The results showed no effects of α-tocopherol supplementation on lipid profile in DM patients except when used ≥12 weeks.

CONCLUSIONS

α-tocopherol supplementation in DM patients had no significant effect on lipid profiles.

Evaluation of nutritional composition of Citrullus lanatus Linn. (watermelon) seed and biochemical assessment of the seed oil in rats

The present study investigated the nutritional composition of watermelon seeds and the effect of extracted oil on the biochemical parameters in rats after 28 days of oral administration. The watermelon seeds showed considerable proximate values but with less moisture, crude fiber, ash, and phytochemical components. The maximal dose of 50 ml/kg of watermelon seed oil (WMSO) showed no sign of toxicity in rats. WMSO significantly decreased serum cholesterol, triglyceride, LDL, ALT, and MDA but enhanced the level of HDL, VLDL, SOD, and CAT without compromising the liver integrity. For glucose tolerance, a positive oral glucose-lowering was observed. The fatty acid analysis showed the presence of three major fatty acids; 9,12-octadecadienoic acid (52.32%), n-hexadecenoic acid (21.23%), and oleic acid (10.11%) with good oxidative stability and fatty acid ratio. The outcome of this study suggests that the seeds and oil from watermelon could have a beneficial effect on man. PRACTICAL APPLICATIONS: Plant-based oils have gained significant interest globally as a source of food, cosmetics, and compounds with therapeutic potential against certain human diseases. The watermelon seed oil is a rich source of oleic acid, linoleic, and palmitic acid. These prominent biologically active fatty acid components have contributed to the robust biochemical effects observed in this study. Based on the data obtained in this work on the nutritional analysis of the watermelon seed and potent antioxidative capacity, improved liver biomarkers, good oxidative stability, and the fatty acid ratio of WMSO, we proposed that consumption of the seed and its oil could offer a cheap and affordable nutraceutical for human benefits. However, we recommend further studies on the biological activity and safety aspect of watermelon seed oil for its long-term usage.

Can vitamin E supplementation affect obesity indices? A systematic review and meta-analysis of twenty-four randomized controlled trials

BACKGROUND

Several mechanisms have been proposed for the effect of vitamin E on weight loss. Yet various interventional studies with wide ranges of doses and durations have reported contradictory results.

METHODS

Cochrane Library, PubMed, Scopus, and Embase databases were searched up to December 2020. Meta-analysis was performed using random-effect method. Effect size was presented as weighted mean difference (WMD) and 95% confidence interval (CI). Heterogeneity was evaluated using the I² index. In order to identification of potential sources of heterogeneity, predefined subgroup and meta regression analyses was conducted.

RESULTS

A total of 24 studies with 33 data sets were included. There was no significant effect of vitamin E on weight (WMD: 0.15, 95% CI: -1.35 to 1.65, P = 0.847), body mass index (BMI) (WMD = 0.04, 95% CI: -0.29 to 0.37, P = 0.815), and waist circumference (WC) (WMD = -0.19 kg, 95% CI: -2.06 to 1.68, P = 0.842), respectively. However, subgroup analysis revealed that vitamin E supplementation in studies conducted on participants with normal BMI (18.5-24.9) had increasing impact on BMI (P = 0.047).

CONCLUSION

There was no significant effect of vitamin E supplementation on weight, BMI and WC. However, vitamin E supplementation might be associated with increasing BMI in people with normal BMI (18.5-24.9).

The effect of vitamin E supplementation on selected inflammatory biomarkers in adults: a systematic review and meta-analysis of randomized clinical trials

The previous meta-analysis of clinical trials revealed a beneficial effect of vitamin E supplementation on serum C-reactive protein (CRP) concentrations; however, it is unknown whether this vitamin has the same influence on other inflammatory biomarkers. Also, several clinical trials have been published since the release of earlier meta-analysis. Therefore, we aimed to conduct a comprehensive meta-analysis to summarize current evidence on the effects of vitamin E supplementation on inflammatory biomarkers in adults. We searched the online databases using relevant keywords up to November 2019. Randomized clinical trials (RCTs) investigating the effect of vitamin E, compared with the placebo, on serum concentrations of inflammatory cytokines were included. Overall, we included 33 trials with a total sample size of 2102 individuals, aged from 20 to 70 years. Based on 36 effect sizes from 26 RCTs on serum concentrations of CRP, we found a significant reduction following supplementation with vitamin E (− 0.52, 95% CI − 0.80, − 0.23 mg/L, P < 0.001). Although the overall effect of vitamin E supplementation on serum concentrations of interleukin-6 (IL-6) was not significant, a significant reduction in this cytokine was seen in studies that used α-tocopherol and those trials that included patients with disorders related to insulin resistance. Moreover, we found a significant reducing effect of vitamin E supplementation on tumor necrosis factor-α (TNF-α) concentrations at high dosages of vitamin E; such that based on dose–response analysis, serum TNF-α concentrations were reduced significantly at the dosages of ≥ 700 mg/day vitamin E (P_{non-linearity} = 0.001). Considering different chemical forms of vitamin E, α-tocopherol, unlike other forms, had a reducing effect on serum levels of CRP and IL-6. In conclusion, our findings revealed a beneficial effect of vitamin E supplementation, particularly in the form of α-tocopherol, on subclinical inflammation in adults. Future high-quality RCTs should be conducted to translate this anti-inflammatory effect of vitamin E to the clinical setting.

Fermentation of Milk into Yoghurt and Cheese Leads to Contrasting Lipid and Glyceride Profiles

There is mounting evidence that the consumption of fermented dairy products such as cheese and yoghurt is associated with a reduced risk of type II diabetes. This effect is greater than in fresh milk and differs between cheese and yoghurt. However, the molecular components responsible for the effect are not known. We tested the hypothesis that the lipid and/or glyceride profiles of yoghurts and cheeses are distinct from one another and fresh milk. We developed a novel sample preparation technique for high-fat samples that can be used with Direct Infusion–Mass Spectrometry. We found that the lipid and glyceride profiles of cheddars from the UK, Ireland and France, and hard cheeses from Sweden and Italy were similar to one another but distinct from unfermented dairy products. The lipid and glyceride profile of yoghurts was varied and included types that may be similar to fresh milk. Several odd-chain-containing triglycerides were more abundant, while a variety of others were less abundant, in fermented milk samples. Phosphatidylcholines and phosphatidylethanolamines were more abundant in cheeses, with evidence that the phosphatidylethanomine profile is re-modelled in a way that reflects the bacterial cell envelope. We concluded that a combination of microorganismal metabolism, concentration of the lipid/glyceride fraction and oxidation during fermentation contribute to the observed lipid profile if fermented dairy foods. These differences in the lipid and glyceride profile provide a new avenue for understanding why different fermented dairy foods show a different association with reduced disease risk compared to unfermented dairy.

Diabetes Mellitus, Nonalcoholic Fatty Liver Disease, and Conjugated Linoleic Acid (Omega 6): What Is the Link?

BACKGROUND AND OBJECTIVE

Type 2 DM and obesity are the coming epidemics and their association with NAFLD is well established; essential fatty acids are vital for body health yet the body cannot make them; 2 essential fatty acids are especially important: linoleic (omega-6) and alpha-linoleic (omega-3) acids; they can be considered as "bioactive lipids" and serve as functional foods.

METHODS

50 type 2 Egyptian diabetic patients controlled on oral hypoglycemic drugs together with 20 age- and sex-matched healthy participants were enrolled in the study; all were subjected to complete history taking, BMI, fasting plasma glucose, HOMA-IR, ALT, AST, GGT, urea and creatinine, total lipid profile, hepatitis markers including hepatitis B surface antigen and hepatitis C virus antibodies, conjugated linoleic fatty acid "CLA," and abdominal ultrasound for grading of NAFLD.

RESULTS

Our study in Egyptian diabetics with NAFLD revealed a low level of serum CLA compared to healthy control; such deficiency was more marked with advanced grades of NAFLD; lowest levels were observed in those with severe steatosis (NASH) with definite association between CLA and obesity.

CONCLUSION

Insulin resistance is the main link between NAFLD, diabetes, and obesity. Conjugated linoleic acid (CLA) has a role in fat deposition in the liver and in development and improvement of insulin resistance. Fatty food had a documented role in the pathogenesis of obesity and diabetes but it can also be the cure.

The effect of conjugated linoleic acid on oxidative stress and matrix metalloproteinases 2 and 9 in patients with COPD

Background

Natural antioxidants in foods may be used in prevention and treatment of oxidative stress and inflammation in COPD. Therefore, this study aimed to evaluate the effect of conjugated linoleic acid (CLA) supplement as natural antioxidants on oxidative stress levels, and MMP2 and MMP9 serum levels in COPD patients.

Materials and methods

This clinical trial study was conducted on 90 (supplement group=45 and control group=45) COPD patients in Ardabil city, Iran, in 2015. After obtaining written consent, general information was collected from each patient using a validated and reliable questionnaire. Supplement group received 3.2 g of CLA and those in the control group were given 3.2 g of placebo for 6 weeks on a daily basis. Fasting blood samples were taken from all of the patients for testing of malondialdehyde (MDA), MMP2, and MMP9 levels at the beginning and end of the study. Data were analyzed using Kolmogorov–Smirnov test, independent samples t-test, paired sample t-test, chi-square test, and ANOVA.

Results

There were no significant differences between the two groups with regard to mean age, smoking status, and serum level of MDA at the beginning of the study. In the supplement group, the serum level of MDA decreased significantly at the end of the 6th week compared to that in the beginning of the study (p=0.0004), while in the placebo group, the difference was found to be insignificant. The serum level of MMP9 decreased significantly in the supplement group, while in the placebo group its level increased significantly as compared to that at the beginning of the study (p<0.05). The serum levels of MMP2 indicated no significant differences between the two groups neither at the beginning nor at the end of the study.

Conclusion

These findings indicated that CLA supplementation may be helpful for COPD patients through inhibiting the production of oxidative stress and controlling MMP9 serum levels.

The human microbiome and metabolomics: Current concepts and applications

The mammalian gastrointestinal tract has co-developed with a large number of microbes in a symbiotic relationship over millions of years. Recent studies indicate that indigenous bacteria are intimate with the intestine and play essential roles in health and disease. In the quest to maintain a stable niche, these prokaryotes influence multiple host metabolic pathways, resulting from an interactive host-microbiota metabolic signaling and impacting strongly on the metabolic phenotypes of the host. Since dysbiosis of the gut bacteria result in alteration in the levels of certain microbial and host co-metabolites, identifying these markers could enhance early detection of diseases. Also, identification of these metabolic fingerprints could give us clues as to how to manipulate the microbiome to promote health or treat diseases. This review provides an overview of our current knowledge of the microbiome and metablomics, applications and the future perspectives.

Conjugated linoleic acid improves glycemic response, lipid profile, and oxidative stress in obese patients with non-alcoholic fatty liver disease: a randomized controlled clinical trial

Aim

To investigate if conjugated linoleic acid supplementation (CLA) affects metabolic factors and oxidative stress in non-alcoholic fatty liver disease (NAFLD).

Methods

The study was a randomized, controlled clinical trial conducted in specialized and subspecialized clinics of Tabriz University of Medical Sciences from January 2014 to March 2015. 38 obese NAFLD patients were randomly allocated into either the intervention group, receiving three 1000 mg softgel of CLA with a weight loss diet and 400 IU vitamin E, or into the control group, receiving only weight loss diet and 400 IU vitamin E for eight weeks. Dietary data and physical activity, as well as anthropometric, body composition, metabolic factors, and oxidative stress were assessed at baseline and at the end of the study.

Results

Weight, body composition, and serum oxidative stress, insulin, and lipid profile significantly improved in both groups, while hemoglobin A1c (HbA1c) levels (P = 0.004), total cholesterol to high density lipoprotein ratio (P = 0.008), low density lipoprotein to high density lipoprotein ratio (LDL/HDL) (P = 0.002), and alanine aminotransferase to aspartate aminotransferase (ALT/AST) ratio (P = 0.025) significantly decreased in the intervention group. At the end of the study, fat mass (P = 0.001), muscle mass (P = 0.023), total body water (P = 0.004), HbA1c (P < 0.001), triglycerides (P = 0.006), LDL/HDL ratio (P = 0.027), and ALT/AST ratio (P = 0.046) were significantly better in the CLA group than in the control group.

Conclusion

CLA improved insulin resistance, lipid disturbances, oxidative stress, and liver function in NAFLD. Therefore, it could be considered as an effective complementary treatment in NAFLD.

Registration number: IRCT2014020516491N1.

Impact of Conjugated Linoleic Acid (CLA) on Skeletal Muscle Metabolism

Conjugated linoleic acid (CLA) has garnered special attention as a food bioactive compound that prevents and attenuates obesity. Although most studies on the effects of CLA on obesity have focused on the reduction of body fat, a number of studies have demonstrated that CLA also increases lean body mass and enhances physical performances. It has been suggested that these effects may be due in part to physiological changes in the skeletal muscle, such as changes in the muscle fiber type transformation, alteration of the intracellular signaling pathways in muscle metabolism, or energy metabolism. However, the mode of action for CLA in muscle metabolism is not completely understood. The purpose of this review is to summarize the current knowledge of the effects of CLA on skeletal muscle metabolism. Given that CLA not only reduces body fat, but also improves lean mass, there is great potential for the use of CLA to improve muscle metabolism, which would have a significant health impact.

A review on effects of conjugated linoleic fatty acid (CLA) upon body composition and energetic metabolism

Conjugated linoleic acid (CLA) is highly found in fats from ruminants and it appears to favorably modify the body composition and cardiometabolic risk factors. The capacity of CLA to reduce the body fat levels as well as its benefic actions on glycemic profile, atherosclerosis and cancer has already been proved in experimental models. Furthermore, CLA supplementation may modulate the immune function, help re-synthetize of glycogen and potentiate the bone mineralization. CLA supplementation also could increase the lipolysis and reduce the accumulation of fatty acids on the adipose tissue; the putative mechanisms involved may be its action in reducing the lipase lipoprotein activity and to increase the carnitine-palmitoil-transferase-1 (CAT-1) activity, its interaction with PPARγ, and to raise the expression of UCP-1. Although studies made in human have shown some benefits of CLA supplementation as the weight loss, the results are still discordant. Moreover, some have shown adverse effects, such as negative effects on glucose metabolism and lipid profile. The purpose of this article is to review the available data regarding the benefits of CLA on the energetic metabolism and body composition, emphasizing action mechanisms.

Conjugated Linoleic Acid Supplementation has no Impact on Aerobic Capacity of Healthy Young Men

This study investigated the effect of conjugated linoleic acid (CLA) on the aerobic capacity and anthropometric measurements of humans. Although this effect has been shown in animal studies, human studies have reported controversial results. In this double-blind, placebo-controlled, randomized clinical trial, 80 non-trained healthy young men received a 50:50 mixture of cis-9,trans-11 and trans-10 cis-12 CLA (CLA 4 × 0.8 g day(-1)) ora placebo (PLA; soybean oil) in an 8-week intervention. Maximal oxygen consumption (VO2 max), time to exhaustion, weight, body mass index (BMI) and waist circumference (WC) were measured. CLA had no effect on VO2 max (p = 0.5) also no change was seen in time to exhaustion (p = 0.51), weight (p = 0.7), BMI (p = 0.7) and WC (p = 0.8) vs PLA. Our results suggest that CLA has no significant effect on VO2 max, time to exhaustion and anthropometric measurements in untrained healthy young male students.

Effect of conjugated linoleic acid on blood pressure: a meta-analysis of randomized, double-blind placebo-controlled trials

Background

Numerous studies on animals evidenced that conjugated linoleic acid (CLA) could decrease blood pressure (BP) in several rat models. However, such beneficial effect is not completely supported by studies on humans.

Methods

We searched the Pubmed, Cochrane Library, and the ClinicalTrials.gov databases for relevant randomized, double-blind placebo-controlled trials up to August 2014 to perform a meta-analysis. A random-effects model was used to calculate the combined treatment effects.

Results

Eight studies with nine trials, which involved 638 participants with CLA supplementation ranging from 2.0 g/day to 6.8 g/day, were included in this meta-analysis. Compared with placebo, the pooled estimate of change was −0.03 mm Hg (95% CI: −2.29, 2.24, P = 0.98) and 0.69 mm Hg (95% CI: −1.41, 2.80, P = 0.52) in systolic and diastolic BPs, respectively. No significant heterogeneity across studies for systolic BP; however, substantial heterogeneity for diastolic BP was identified. Publication bias was not found for both systolic and diastolic BPs.

Conclusion

The findings of this meta-analysis did not support the overall favorable effect of CLA supplementation on BP regulation.

Pros and cons of CLA consumption: an insight from clinical evidences

This comprehensive review critically evaluates whether supposed health benefits propounded upon human consumption of conjugated linoleic acids (CLAs) are clinically proven or not. With a general introduction on the chemistry of CLA, major clinical evidences pertaining to intervention strategies, body composition, cardio-vascular health, immunity, asthma, cancer and diabetes are evaluated. Supposed adverse effects such as oxidative stress, insulin resistance, irritation of intestinal tract and milk fat depression are also examined. It seems that no consistent result was observed even in similar studies conducted at different laboratories, this may be due to variations in age, gender, racial and geographical disparities, coupled with type and dose of CLA supplemented. Thus, supposed promising results reported in mechanistic and pre-clinical studies cannot be extrapolated with humans, mainly due to the lack of inconsistency in analyses, prolonged intervention studies, follow-up studies and international co-ordination of concerted studies. Briefly, clinical evidences accumulated thus far show that CLA is not eliciting significantly promising and consistent health effects so as to uphold it as neither a functional nor a medical food.

Does omega-3 fatty acids supplementation affect circulating leptin levels? A systematic review and meta-analysis on randomized controlled clinical trials

BACKGROUND

Omega-3 fatty acids have attracted researchers for their effect on circulatory hormone-like peptides affecting weight control.

OBJECTIVE

Our objective was to conduct a systematic review and meta-analysis on randomized controlled trials (RCTs) assessed the effects of omega-3 supplementation on serum leptin concentration and to find the possible sources of heterogeneity in their results.

METHODS

We searched PubMed/Medline, Google Scholar, Ovid, SCOPUS and ISI web of science up to April 2014. RCTs conducted among human adults, examined the effect of omega-3 fatty acid supplements on serum leptin concentrations as an outcome variable were included. The mean difference and standard deviation (SD) of changes in serum leptin levels were used as effect size for the meta-analysis. Summary mean estimates with their corresponding SDs were derived using random effects model.

RESULTS

Totally 14 RCTs were eligible to be included in the systematic review, and the meta-analysis was performed on 13 articles. Our analysis showed that omega-3 supplementation significantly reduces leptin levels (mean difference (MD) = -1·71 ng/ml 95% confidence interval (CI): -3·17 to -0·24, P = 0·022). Subgroup analysis based on BMI status showed that the omega-3 supplementation reduces leptin when used for nonobese subjects (MD = -3·60 ng/ml; 95% CI -6·23 to -0·90; P = 0·011); however, this was not true for obese participants (MD = -0·86 ng/ml; 95% CI: -2·63 to -0·90; P = 0·296). Subgroup analysis based on omega-3 source also showed that omega-3 from marine sources may significantly reduce leptin levels (MD = -1·73 ng/ml; 95% CI -3·25 to -0·2; P = 0·026), but plant sources do not significantly affect serum leptin levels (MD = -1·48 ng/ml; 95% CI -6·78 to 3·23; P = 0·585). Our results were highly sensitive to one study.

CONCLUSIONS

Omega-3 supplementation might moderately decrease circulatory leptin levels only among nonobese adults. RCTs with longer follow-up period, using higher doses for obese adults and exploring the effect in different genders, are needed to replicate our results.

Effect of ascorbic acid and alpha-tocopherol supplementations on serum leptin, tumor necrosis factor alpha, and serum amyloid A levels in individuals with type 2 diabetes mellitus

OBJECTIVE

Diabetes mellitus Type 2 is one of the most widespread chronic metabolic diseases. In most cases, this type of diabetes is associated with alterations in levels of some inflammatory cytokines and hormones. Considering anti-inflammatory properties of plant extracts rich in ascorbic acid (vitamin C) and alpha-tocopherol (vitamin E), anti-diabetic properties of these two well-known antioxidant vitamins were investigated through measurement of serum levels of high-sensitivity C-reactive protein (hs-CRP), insulin, leptin, tumor necrosis factor alpha (TNF-α), and serum amyloid A (SAA) in patients with diabetes mellitus type 2.

MATERIALS AND METHODS

Male patients (n=80) were randomly divided into two groups each consisted of 40 subjects. Test groups were supplemented with ascorbic acid (1000 mg/day) or alpha-tocopherol (300 mg/day) orally during four weeks. Before and after treatment, serum biochemical factors of subjects were measured and compared.

RESULTS

Our results showed that both ascorbic acid and alpha-tocopherol could induce significant anti-inflammatory effects by decreasing the level of inflammatory factors such as TNF-α, SAA, and hs-CRP in diabetes mellitus type 2 patients. Effects of alpha-tocopherol and ascorbic acid in decreasing serum leptin level were similar. Ascorbic acid in contrast to alpha-tocopherol diminished fasting insulin and HOMA index but had no effect on LDL serum level.

CONCLUSION

Concerning the obtained results, it is concluded that consumption of supplementary vitamins C and E could decrease induced inflammatory response in patients with diabetes mellitus type 2. It is also possible that vitamin C and vitamin E supplementation can attenuate incidence of some proposed pathological effects of diabetes mellitus.