Effects of Conjugated Linoleic Acid Intake in the Form of Dietary Supplement or Enriched Food on C-Reactive Protein and Lipoprotein (a) Levels in Humans: A Literature Review and Meta-Analysis.

BACKGROUND: C-reactive protein (CRP) and lipoprotein (a) (Lp[a]) play essential roles in cardiovascular disease incidence. This study aimed to review the association between the intake of conjugated linoleic acid (CLA) in the form of dietary supplement or enriched food with different treatment durations and the levels of Lp(a) and CRP in human studies. METHODS: All the articles published in Cochrane Library, ProQuest, Scopus, and Google Scholar from November 2014 to October 2015 were searched and the clinical trials on the effects of CLA on Lp(a) and CRP levels were assessed. Of the 2249 articles initially retrieved, 21 eligible randomized clinical trials were enrolled in this systematic review. The publication dates of the eligible articles ranged from 2005 to 2013. The mean difference and the standard deviation of changes in CRP and Lp(a) levels in intervention and control groups were used as effect-size measures for meta-analysis. The obtained data from the eligible randomized controlled trials were meta-analyzed using Stata, version 13. RESULTS: The intake of CLA as a dietary supplement led to a significant increase in CRP levels (standardized mean difference [SMD]=0.41, 95% CI: 0.28 to 0.54; P=0.001). Subgroup analysis based on the duration of CLA consumption showed that CLA consumption more than 24 weeks resulted in a significant increase in the levels of CRP (SMD=0.52, 95% CI: 0.36 to 0.68; P=0.001) and Lp(a) (SMD=0.24, 95% CI: 0.01 to 0.47; P=0.04). CONCLUSION: The current systematic review and meta-analysis showed that the long-term consumption of CLA increases the levels of CRP and Lp(a).

Relationship between Body Mass Index, Waist-to-Hip Ratio, and Serum Lipid Concentrations and Thyroid-Stimulating Hormone in the Euthyroid Adult Population.

The aim of this cross-sectional study was to investigate the relationship between body mass index (BMI), waist-to-hip ratio, and lipid parameters and serum thyroid-stimulating hormone (TSH) levels in healthy euthyroid individuals. This cross-sectional study was conducted between June 1st and July 20th, 2013, at Bushehr University of Medical Sciences. One hundred forty euthyroid individuals were divided into 2 groups: a high-TSH group (TSH between 2.0 and 5.5 mIU/L, n=67) and a low-TSH group (TSH between 0.3 and 2.0 mIU/L, n=73). After overnight fast, total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), TSH, thyroxine (T4), and triiodothyronine (T3) were measured. Height and weight were measured with a stadiometer, and BMI was calculated as weight in kilograms divided by the square of height in meters. Waist-to-hip ratio was determined as waist circumference divided by hip circumference. The simple independent t-test and a general linear model were used for statistical analysis. All statistical analyses were done using the SPSS, version 15, statistical software package. BMI and LDL-C were significantly higher in the high-TSH group than in the low-TSH group after adjustment for age, sex, calorie intake, total fat and carbohydrate intakes, and physical activity. No significant differences were found between the groups in TG, cholesterol, and HDL-C. The association between TSH levels andT4 was significant. Individuals with TSH levels at the upper limit of normality might be at risk of hypercholesterolemia and obesity.

Effect of Conjugated Linoleic Acid as a Supplement or Enrichment in Foods on Blood Glucose and Waist Circumference in Humans: A Metaanalysis.

BACKGROUND: Controversy persists regarding the effect of mixtures of conjugated linoleic acids (c9, t11- and t10, c12-CLA) in fasting blood glucose (FBG) and waist circumference (WC) in humans. OBJECTIVE: The aim of this meta-analysis is to explore the effect of CLA on FBG and WC. METHOD: PubMed, Google Scholar, Cochrane Library, Science Direct, Pro-Quest and Ovid were searched up to January 2015. Studies that examined the effect of CLA supplementation or foods enriched with CLA on FBG and WC in healthy adults were included. Studies in animals or unhealthy individuals and studies other than clinical trials were excluded. Of the 3,095 articles initially retrieved, 32 eligible randomized clinical trials were included in this systematic review. The mean difference and standard deviation of changes in FBG and WC in the intervention and control groups were used as effect size measures for the meta-analysis. RESULTS: Subgroup analysis showed that CLA supplement consumption did not significantly influence FBG (standardized mean differences [SMD] = 0.075 mg/dL; 95% confidence interval (CI) = -0.099 to 0.249; p = 0.399) or WC (SMD = -0.149 cm; 95% CI = -0.522 to 0.225; p = 0.435). Foods enriched in CLA also showed no significant effect on FBG (SMD = 0.126 mg/dL; 95% CI = -0.100 to 0.352; p = 0.274) or WC (SMD = -0.233 cm; 95% CI = -0.625 to 0.159; p = 0.244). CONCLUSION: We conclude that c9, t11- and t10, c12-CLA administered as a supplement or used to enrich foods does not affect FBG or WC in humans.

Effect of Astaxanthin, Vitamin E, and Vitamin C in Combination with Calorie Restriction on Sperm Quality and Quantity in Male Rats.

The aim of this study was to investigate the effect of calorie restriction and dietary antioxidant supplementation, separately or in combination, on the quality and quantity of sperm in male rats. Forty male rats were randomly allocated to four groups of 10 animals each, and fed for at least 86 days with an ad libitum diet (group 1), a restricted diet (group 2), an ad libitum diet and astaxanthin, vitamin E, and vitamin C supplements (group 3), or a restricted diet with astaxanthin, vitamin E, and vitamin C supplements (group 4). At the end of the study period, sperm count and motility were determined with a hemocytometer, and differences between the groups were analyzed by analysis of variance. In addition, total antioxidant capacity and 8-epi prostaglandin F2 alpha were measured at the beginning and end of the study period with an enzyme-linked immunosorbent assay method. After 86 days, a significantly higher sperm count was seen in group 4 compared to other groups. The percentage of immotile sperm was significantly decreased in groups 2, 3, and 4 compared to group 1. A significant increase in total antioxidant capacity was observed in group 3 (p = 0.02) and group 4 (p = 0.02) compared to groups 1 and 2. Antioxidant supplementation with or without calorie restriction had no significant effect on the serum isoprostane level in any group. Astaxanthinin, combined with vitamin E, vitamin C, and calorie restriction, was able to ameliorate, in part, infertility in male rats.

Comparative effects of red and white grapes on oxidative markers and lipidemic parameters in adult hypercholesterolemic humans.

The present study compared the effects of consuming red versus white whole grapes on oxidative and lipidemic indices in people with hypercholesterolemia. Sixty nine patients were randomized into three groups. The two treatment groups consumed 500 g of either Condori red grapes or Shahroodi white grapes daily for 8 weeks, and the third group served as a control. Plasma glucose, triacylglycerol (TG), cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), thiobarbituric acid reactive substances (TBARS) and total antioxidant capacity (TAC) were determined by colorimetric methods at baseline and at the end of the study. In addition, the polyphenol and fiber content of the two grape varieties was measured. TBARS was reduced in both study groups compared to the control group, and the reduction was greater in the group that consumed red grapes compared to the white grapes. TAC was increased significantly in both red and white grape consuming groups compared to the control group. Total cholesterol and LDL-C were decreased in the red grape group compared to the control group. No significant changes in fasting blood glucose, TG or HDL-C were observed among the groups. The results of this study suggest that consumption of the whole fruit of red grapes has more potent anti-oxidative and hypolipidemic effects compared to the white grapes in hyperlipidemic adult humans. Hence, the whole fruit of red grapes may be an excellent fruit choice not only to prevent oxidative stress related metabolic disorders but also cholesterol related cardiovascular diseases, particularly in hyperlipidemic adult humans.

The effect of Stevia rebaudiana on serum omentin and visfatin level in STZ-induced diabetic rats.

Recently the role of adipocytokines in relationship to incidence of diabetes has been demonstrated. One of the medicinal plants that are used in the treatment of diabetes is stevia. This study investigates the effect of stevia on serum omentin and visfatin levels as novel adipocytokines in diabetic induced rats to find potential mechanisms for the anti hyperglycemic effect of stevia. Forty male wistar rats weighing 180-250 g were induced with diabetes by intraperitoneal injection of streptozotocin (STZ). The animals were divided into 5 groups of 8. Rats in group 1 (non-diabetic control) and group 2 (diabetic control) were treated with distilled water, and the rats in the treated groups, group 3 (T250), group 4 (T500), and group 5 (T750) were treated with stevia, gavaged every day at 9 a.m. in doses of 250, 500, and 750 mg/kg, respectively. At the end of the study significant reductions in fasting blood sugar (FBS), the homeostasis model assessment insulin resistance (HOMA-IR), triglyceride (TG), alkaline phosphatase (ALP), and Omentin level were found in groups 3 and 4 in comparison with group 2. Pancreatic histopathology slides demonstrated that stevia extract did not induce any increase in the number of ß-cells. The conclusion is that prescription of stevia in the doses of 250 and 500 mg/kg/d decreases the omentin level indirectly via activating insulin sensitivity and lowering blood glucose in STZ-induced diabetic rats.

Effect of EPA and vitamin C on superoxide dismutase, glutathione peroxidase, total antioxidant capacity and malondialdehyde in type 2 diabetic patients.

OBJECTIVES: The aim of this study is to investigate the effect of eicosapentaenoic acid combined with vitamin C in comparison with the pure form of eicosapentaenoic acid on the serum concentration of malondialdehyde, erythrocyte activity of superoxide dismutase, glutathione peroxidase, and the serum level of total antioxidant capacity in patients with type 2 diabetes. METHODS: Eighty one male diabetic patients, aged 33-63 years, were randomly assigned to one of 4 groups. The subjects consumed 500 mg/d pure eicosapentaenoic acid, 200 mg/d vitamin C, 500 mg eicosapentaenoic acid and 200 mg/d vitamin C or placebo depending on their groups. In fasting blood samples, superoxide dismutase and glutathione peroxidase activities were determined via the enzymatic method (Randox kit) and the serum total antioxidant capacity, malondialdehyde and vitamin C concentrations were estimated by colorimetric methods. RESULTS: Administration of pure eicosapentaenoic acid in diabetic patients increased superoxide dismutase by 4%, glutathione peroxidase 53%, total antioxidant capacity 36% and decreased malondialdehyde significantly by 25%. Prescription of eicosapentaenoic acid combined with vitamin C demonstrated a significant increment for superoxide dismutase activity by 3% and for glutathione peroxidase activity by 52% during the study, but no significant change was seen for total antioxidant capacity and malondialdehyde, respectively. There was a significant decrease in FBS and HbA1c following prescription of eicosapentaenoic acid with/without vitamin C along the study, although these changes were not significant between the study groups. CONCLUSION: It is concluded that prescription of eicosapentaenoic acid in the pure form reduces oxidative stress in type 2 diabetic patients; albeit, it does not alleviate hyperglycemia. Combination of vitamin C and eicosapentaenoic acid does not improve antioxidant property of eicosapentaenoic acid.

Relationship among plasma adipokines, insulin and androgens level as well as biochemical glycemic and lipidemic markers with incidence of PCOS in women with normal BMI.

Polycystic ovary syndrome (PCOS) is an endocrine disorder in women. Omentin-1 and vaspin are secretary adipokines that are produced by the visceral adipose tissue. These levels change in obese women with PCOS. The aim of this study is to investigate whether omentin and vaspin levels change in nonobese PCOS subjects. This study is a cross-sectional case control study in which 39 women with PCOS were picked out for this study. The inclusion criteria were based on the Rotterdam 2003 diagnostic criteria. The control group consisted of 39 women with normal pelvic sonographic reports having regular menstruation and showing no signs of infertility. The fasting plasma glucose (FPG), triglyceride (TG), Chol, and high-density lipoprotein cholesterol (HDL-C), insulin, testosterone, omentin and vaspin were measured by the enzymatic methods. The differences within these groups were calculated by the un-paired t-test and the Mann-Whitney test. The results from this study show a significant increase in the amount of insulin, testosterone, homeostasis model assessments for insulin resistance, TG and lower HDL in the patient group. No significant differences were seen in omentin, vaspin, FPG, Cho, low-density lipoprotein, very low-density lipoprotein cholesterol, blood urea nitrogen, Cr and homeostasis model assessments for B cell function levels between groups. Results show that PCOS is not a determinant of decreased omentin and vaspin plasma levels and those high androgen level and insulin resistances are warning signs of PCOS.