Effects of n-3 PUFA on insulin resistance after an oral fat load

Assessing the Highest Level of Evidence from Randomized Controlled Trials in Omega-3 Research

Over the years, there has been heightened interest in the health benefits of n-3 polyunsaturated fatty acids (PUFA) in reducing chronic diseases such as, cardiovascular disease (CVD), cancer, type 2 diabetes, and acute macular degeneration (AMD). Due to inconsistent findings in the evidence, a review to critically examine the plethora of evidence from randomized controlled trials (RCTs) in n-3 PUFA research was undertaken. The aim of this review is to study the highest level of evidence and to identify gaps in n-3 PUFA research. RCTs were originally designed for pharmaceutical research and later adopted for nutrition and food-related research. RCTs with active diseases assume that n-3 PUFA will have "drug" like effects, and this high expectation may have led to the inconsistent evidence in the literature. The inconsistency in the literature may be related to varying doses of n-3 PUFA, sources of n-3 PUFA (food vs. supplement; plant vs. marine), type of n-3 PUFA (mixture vs. purified), trial duration, population characteristics, sample size, and genetic variation. For future research, there is a need to distinguish between primary and secondary prevention, and to focus RCTs on primary prevention of chronic diseases by n-3 PUFA which is lacking in the literature.

Fish oil supplementation during pregnancy and postpartum in mothers with overweight and obesity to improve body composition and metabolic health during infancy: A double-blind randomized controlled trial

BACKGROUND

Maternal obesity during pregnancy is associated with an increased risk of obesity and metabolic disease in the offspring. Supplementation with fish oil (FO), which is insulin sensitizing, during pregnancy in mothers with overweight or obesity may prevent the development of greater adiposity and metabolic dysfunction in their children.

OBJECTIVES

To determine the effects of FO supplementation throughout the second half of pregnancy and lactation in mothers with overweight or obesity on infant body composition and metabolism.

METHODS

A double-blind randomized controlled trial of 6 g FO (3.55 g/d of n-3 PUFAs) compared with olive oil (control) from mid-pregnancy until 3 mo postpartum. Eligible women had singleton pregnancies at 12-20 wk of gestation, and BMI ≥ 25 kg/m². The primary outcome was the infant body fat percentage (DXA scans) at 2 wk of age. Secondary outcomes included maternal metabolic markers during pregnancy, infant anthropometry at 2 wk and 3 mo of age, and metabolic markers at 3 mo.

RESULTS

A total of 129 mothers were randomized, and 98 infants had a DXA scan at 2 wk.

PRIMARY OUTCOME

Imputed and nonimputed analyses showed no effects of FO supplementation on infant body fat percentage at age 2 wk.

SECONDARY OUTCOMES

There were no treatment effects on infant outcomes at 2 wk, but FO infants had a higher BMI z-score (P = 0.025) and ponderal index (P = 0.017) at age 3 mo. FO supplementation lowered maternal triglycerides by 17% at 30 wk of pregnancy (P = 0.0002) and infant triglycerides by 21% at 3 mo of age (P = 0.016) but did not affect maternal or infant insulin resistance. The rate of emergency cesarean section was lower with FO supplementation [aRR = 0.38 (95%CI 0.16, 0.90); P = 0.027].

CONCLUSIONS

FO supplementation of mothers with overweight or obesity during pregnancy did not impact infant body composition. There is a need to follow up the offspring to determine whether the observed metabolic effects persist.

CLINICAL TRIAL REGISTRY NUMBER

This study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617001078347p). In addition, the Universal Trial Number, WHO, was obtained (U1111-1199-5860).

The role of selected nutraceuticals in management of prediabetes and diabetes: An updated review of the literature

Dysglycemia is a disease state preceding the onset of diabetes and includes impaired fasting glycemia and impaired glucose tolerance. This review aimed to collect and analyze the literature reporting the results of clinical trials evaluating the effects of selected nutraceuticals on glycemia in humans. The results of the analyzed trials, generally, showed the positive effects of the nutraceuticals studied alone or in association with other supplements on fasting plasma glucose and post-prandial plasma glucose as primary outcomes, and their efficacy in improving insulin resistance as a secondary outcome. Some evidences, obtained from clinical trials, suggest a role for some nutraceuticals, and in particular Berberis, Banaba, Curcumin, and Guar gum, in the management of prediabetes and diabetes. However, contradictory results were found on the hypoglycemic effects of Morus, Ilex paraguariensis, Omega-3, Allium cepa, and Trigonella faenum graecum, whereby rigorous long-term clinical trials are needed to confirm these data. More studies are also needed for Eugenia jambolana, as well as for Ascophyllum nodosum and Fucus vesiculosus which glucose-lowering effects were observed when administered in combination, but not alone. Further trials are also needed for quercetin.

Long-term effects of increasing omega-3, omega-6 and total polyunsaturated fats on inflammatory bowel disease and markers of inflammation: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIM

Effects of long-chain omega-3 (LCn3) and omega-6 fatty acids on prevention and treatment of inflammatory bowel diseases (IBD, including Crohn's Disease, CD and ulcerative colitis, UC), and inflammation are unclear. We systematically reviewed long-term effects of omega-3, omega-6 and total polyunsaturated fats (PUFA) on IBD diagnosis, relapse, severity, pharmacotherapy, quality of life and key inflammatory markers.

METHODS

We searched Medline, Embase, Cochrane CENTRAL, and trials registries, including RCTs in adults with or without IBD comparing higher with lower omega-3, omega-6 and/or total PUFA intake for ≥ 24 weeks that assessed IBD-specific outcomes or inflammatory biomarkers.

RESULTS

We included 83 RCTs (41,751 participants), of which 13 recruited participants with IBD. Increasing LCn3 may reduce risk of IBD relapse (RR 0.85, 95% CI 0.72-1.01) and IBD worsening (RR 0.85, 95% CI 0.71-1.03), and reduce erythrocyte sedimentation rate (ESR, SMD - 0.23, 95% CI - 0.44 to - 0.01), but may increase IBD diagnosis risk (RR 1.10, 95% CI 0.63-1.92), and faecal calprotectin, a specific inflammatory marker for IBD (MD 16.1 μg/g, 95% CI - 37.6 to 69.8, all low-quality evidence). Outcomes for alpha-linolenic acid, omega-6 and total PUFA were sparse, but suggested little or no effect where data were available.

CONCLUSION

This is the most comprehensive meta-analysis of RCTs investigating long-term effects of omega-3, omega-6 and total PUFA on IBD and inflammatory markers. Our findings suggest that supplementation with PUFAs has little or no effect on prevention or treatment of IBD and provides little support for modification of long-term inflammatory status.

Omega-3 fats in pregnancy: could a targeted approach lead to better metabolic health for children?

The prevalence of childhood obesity is increasing worldwide, and the children of women who are obese during pregnancy are at greatest risk. This risk may be mediated by exaggeration of the normal insulin resistance of pregnancy. Omega-3 (n-3) fats are insulin sensitizing. Supplementation during pregnancy may reduce metabolic risk and adiposity in the children. Though results from animal studies are encouraging, completed clinical trials have not demonstrated this benefit. However, to our knowledge, previous studies have not targeted women who are overweight or obese while pregnant-the group at greatest risk for insulin resistance and most likely to benefit from n-3. In this narrative review, the importance of performing clinical trials restricted to women who are overweight or obese is discussed, as is the potential importance of n-3 dose, oil source and quality, and the timing of the intervention.

Effect of omega-3 fatty acids supplementation on adipokines: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Although a large body of literature reported the beneficial effects of omega-3 fatty acids (omega-3 FAs) consumption on adipokines levels, but recent findings from clinical trials are not univocal. The aim of this systematic review and meta-analysis was to evaluate the effect of omega-3 FAs supplements on adipokines.

METHODS

We searched Medline, Web of Science, Scopus, Embase, and Cochrane Library from inception to August 2020 without any particular language limitations. Outcomes were summarized as standardized mean difference (SMD) with 95% confidence intervals (CIs) estimated from Hedge's g and random effects modeling.

RESULTS

Fifty-two trials involving 4,568 participants were included. Omega-3 FAs intake was associated with a significant increase in plasma adiponectin levels (n = 43; 3,434 participants; SMD: 0.21, 95% CI: 0.04, 0.37; p = 0.01; I²= 80.14%). This meta-analysis indicates that supplementing participants with omega-3 fatty acids more than 2000 mg daily and more than 10 weeks resulted in a significant and more favorable improvement in plasma adiponectin levels. However, omega-3 FAs intake had no significant effect on leptin levels (SMD: -0.02, 95% CI: -0.20, 0.17, I²= 54.13%).

CONCLUSION

The evidence supports a beneficial effect of omega-3 FAs intake on serum adiponectin levels but does not appear to impact on leptin concentrations. Larger well-designed RCTs are still required to evaluate the effect of omega-3 FAs on leptin in specific diseases.

Omega-3 supplementation and diabetes: A systematic review and meta-analysis

This study aimed to review the literature on studies that evaluated the effects of omega-3 supplementation on parameters of diabetes in humans. An online search was conducted in the following databases: Pubmed, LILACS, Scielo, Scopus, and Web of Science. It included experimental studies that investigated the effects of omega-3 supplementation for diabetes treatment or prevention and its relationship with fasting blood glucose, insulin resistance, and glycated hemoglobin. Observational, non-human studies and non-randomized clinical trials were excluded. The Cochrane scale assessed the quality of the studies. A meta-analysis was carried out to evaluate the effect of omega-3 on fasting blood glucose, insulin resistance, and glycated hemoglobin. Thirty studies were included in the review. Almost 70% (n = 20) demonstrated at least one significant effect of the omega-3 supplementation related to diabetes. In the meta-analysis, there was a significant effect on the reduction of fasting blood glucose [SMD: -0.48; CI95%: -0.76, -0.19; p = 0.01; I2 = 88%] and insulin resistance [SMD: -0.61; CI95%: -0.98, -0.24; p = 0.01; I2 = 90%]. For glycated hemoglobin, there was no significant effect in the meta-analysis. This systematic review with meta-analysis demonstrated that supplementation with omega-3 has protective effects on diabetes parameters.

Effects on oral fat load of a nutraceutical combination of fermented red rice, sterol esters and stanols, curcumin, and olive polyphenols: A randomized, placebo controlled trial

BACKGROUND

In literature, there are several studies about the effects of nutraceutical combinations at fasting, but data in post-prandial phase are lacking.

PURPOSE

We planned a study to evaluate the efficacy and safety of a nutraceutical agent containing fermented red rice, phytosterols and olive polyphenols compared to placebo in a sample of Caucasian patients with low cardiovascular risk, both at fasting and after an oral fat load.

STUDY DESIGN

Eighty patients were randomized to receive, as addition to diet and physical activity, a nutraceutical combination containing fermented red rice, sterol esters and stanols, curcumin, and olive polyphenols or placebo (control group), once a day.

METHODS

We evaluated at baseline, and after 3 months: body mass index, fasting plasma glucose, lipid profile, soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and soluble endothelial-leukocyte adhesion molecule-1. We evaluated these parameters both at fasting, and after an oral fat load.

RESULTS

Nutraceutical combination gave a reduction of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, both compared to baseline (p < 0.05 for all), and to placebo (p < 0.05 for all). We recorded a reduction of soluble intercellular adhesion molecule-1, soluble vascular cell adhesion molecule-1, and sE-selectin in the group treated with nutraceutical combination, both compared to baseline (p < 0.05 for all), and to placebo (p < 0.05 for all). Parameters recorded during oral fat load improved compared to the oral fat load performed at baseline with the nutraceutical combination.

CONCLUSIONS

The nutraceutical combination of fermented red rice, sterol esters and stanols, curcumin, and olive polyphenols seems to be effective in improving lipid profile and markers of endothelial damage in dyslipidemic patients in primary prevention at low risk for developing cardiovascular disease. The true novelty of this study, however, is the improvement of endothelial damage after an oral fat load compared to placebo.

The role of polyunsaturated fatty acids (n-3 PUFAs) on the pancreatic β-cells and insulin action

Polyunsaturated Fatty acids have multiple effects in peripheral tissues and pancreatic beta cell function. The n-3 Polyunsaturated Fatty acids prevent and reverse high-fat-diet induced adipose tissue inflammation and insulin resistance. Insulin secretion is stimulated by glucose, amino acids, and glucagon- like peptide-1 in tissue containing high levels of n-3 Polyunsaturated Fatty acids than lower level of n-3 Polyunsaturated Fatty acids. Also, n-3 Polyunsaturated Fatty acids led to decreased production of prostaglandin, which in turn contributed to the elevation of insulin secretion. N-3 polyunsaturated fatty acids prevent cytokine-induced cell death in pancreatic islets. Supplementation of n-3 Polyunsaturated Fatty acids for human subjects prevent beta cell destruction and insulin resistance. It also enhances insulin secretion, reduction in lipid profiles and glucose concentration particularly in type II diabetes patients. Therefore there should be a focus on the treatment mechanism of insulin related obesity and diabetes by n-3 polyunsaturated fatty acids.

Nutraceuticals for the treatment of metabolic diseases: evidence from clinical practice

The aim of this review is to describe some types of supplements that have been shown to be good co-adjuvants along with diet and drug treatment in improving insulin resistance and dyslipidemia. We can conclude that some nutraceuticals, such as l-carnitine, berberine, omega-3 polyunsaturated fatty acids, krill oil and red yeast rice, can be helpful in reducing hypercholesterolemia or insulin resistance, as reported in clinical trials. Nutraceuticals can be associated with conventional pharmacological treatments to achieve an improved lipid profile without increasing statin dosage. Similarly, although nutraceuticals cannot replace conventional antidiabetic treatments, they may be useful as an adjuvant to standard therapy, improving insulin resistance. However, not all nutraceuticals are the same and their natural origin does not mean that everyone can take them or that they cannot be dangerous; nutraceuticals should be used only under medical prescription and should be combined with a well-balanced diet.

Berberis aristata/Silybum marianum fixed combination (Berberol(®)) effects on lipid profile in dyslipidemic patients intolerant to statins at high dosages: a randomized, placebo-controlled, clinical trial

AIM

to evaluate the efficacy of Berberis aristata/Silybum marianum (Berberol(®)) in a sample of dyslipidemic patients intolerant to statins at high dosages in a randomized, double blind, placebo-controlled clinical trial.

METHODS

we enrolled 175 euglycemic, dyslipidemic subjects, intolerant to statins at high dosages. During the run-in period, statins were stopped for 1 month, then they were re-introduced at the half of the previously taken dose. After that, patients were randomized to placebo or Berberol(®), 1 tablet during the lunch and 1 tablet during the dinner, for 6 months. Anthropometric, metabolic and inflammatory parameters were assessed at randomization, at 3 and 6 months.

RESULTS

fasting plasma glucose, insulin, and HOMA-index levels were reduced by Berberol(®), but not by placebo; moreover they were lower than the ones recorded with placebo. Total cholesterol, LDL-C, triglycerides, and myeloperoxidase did not change after 6 months since the reduction of statin dosage and the introduction of Berberol(®), while they increased in the placebo group, and were higher compared to the ones obtained with active treatment. No patients had serious adverse events in both groups.

CONCLUSIONS

our study displays the rationale of the combination of Berberol(®) and a reduced dosage of statin for the treatment of hyperlipidemia in patients intolerant to statins at high dosage.

Comparison of vildagliptin and glimepiride: effects on glycaemic control, fat tolerance and inflammatory markers in people with type 2 diabetes

AIMS

To compare the effects of vildagliptin with those of glimepiride on glycaemic control, fat tolerance and inflammatory markers in people with Type 2 diabetes mellitus receiving metformin treatment.

METHODS

A total of 167 participants were randomized to vildagliptin 50 mg twice a day or glimepiride 2 mg three times a day, for 6 months. We evaluated the following variables: BMI; glycaemic control; fasting plasma insulin; homeostatic model assessment of insulin resistance index; fasting plasma proinsulin; glucagon; lipid profile; adiponectin; high-sensitivity C-reactive protein; interleukin-6; and tumour necrosis factor-α. A euglycaemic-hyperinsulinaemic clamp procedure and an oral fat load test were also performed.

RESULTS

Despite a similar decrease in HbA1c levels (P = 0.009, and P = 0.008, respectively), body weight increased with glimepiride (P = 0.048 vs baseline) and decreased with vildagliptin (P = 0.041 vs baseline and vs glimepiride). Fasting plasma insulin and homeostatic model assessment of insulin resistance index were significantly lower with vildagliptin compared with glimepiride (P = 0.035 and 0.047). M value, an index of insulin sensitivity, increased with vildagliptin, both compared with baseline and with glimepiride (P = 0.028 and 0.039, respectively). Vildagliptin improved all post-oral fat load peaks of lipid profile compared with glimepiride. Adiponectin levels were higher (P = 0.035) and high-sensitivity C-reactive protein levels were lower (P = 0.038) with vildagliptin vs glimepiride. During the oral fat load test, interleukin-6, high-sensitivity C-reactive protein and tumour necrosis factor-α peaks were lower and adiponectin peak was higher in the vildagliptin group than in the glimepiride group. There was a higher dropout rate as a result of hypoglycaemia in the glimepiride group than in the vildagliptin group.

CONCLUSIONS

Vildagliptin was more effective than glimepiride in reducing post-oral fat load peaks of lipid-trafficking adipocytokines and inflammatory markers.

Vildagliptin compared to glimepiride on post-prandial lipemia and on insulin resistance in type 2 diabetic patients

OBJECTIVES

To evaluate the effects of vildagliptin compared to glimepiride on glycemic control, insulin resistance and post-prandial lipemia.

MATERIAL AND METHODS

167 type 2 diabetic patients, not adequately controlled by metformin, were randomized to vildagliptin 50 mg twice a day or glimepiride 2 mg three times a day for 6 months, in a double blind, randomized clinical trial. We evaluated: body mass index (BMI), glycemic control, fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), fasting plasma proinsulin (FPPr), glucagon, lipid profile, resistin, retinol binding protein-4 (RBP-4), visfatin and vaspin. Furthermore, at the randomization and at the end of the study all patients underwent an euglycemic hyperinsulinemic clamp to evaluate M value and an oral fat load.

RESULTS

Despite a similar decrease of glycated hemoglobin, there were an increase of body weight with glimepiride + metformin and a decrease with vildagliptin + metformin. Fasting plasma insulin increased with glimepiride + metformin, while it did not change with vildagliptin + metformin. Vildagliptin + metformin improved lipid profile. Regarding insulin sensitivity, vildagliptin + metformin increased M value. Resistin, RBP-4, vaspin and visfatin were decreased by vildagliptin + metformin, but in group to group comparison, only vaspin reduction resulted statistically significant. Vildagliptin + metformin reduced post-prandial lipemia and insulinemia compared to glimepiride + metformin.

CONCLUSION

Vildagliptin, in addition to metformin, was more effective than glimepiride + metformin in reducing insulin resistance and post-prandial lipemia.

Berberis aristata/Silybum marianum fixed combination on lipid profile and insulin secretion in dyslipidemic patients

BACKGROUND

Relatively large number of dietary supplements and nutraceuticals have been studied for their supposed or demonstrated ability to reduce cholesterolemia in humans.

OBJECTIVES

The aim of this study was to evaluate the efficacy as antihypercholesterolemic and insulin-sensitizing agent of a combination of Berberis aristata/Silybum marianum extract (Berberol®) in a sample of dyslipidemic patients. A total of 102 dyslipidemic subjects were enrolled. After a 6 months run-in period of diet and physical activity, the patients were randomized to placebo or Berberis aristata/Silybum marianum extract 588 mg/105 mg, twice a day for 3 months. Berberis aristata/Silybum marianum and placebo were then interrupted for 2 months (washout period), and then restarted for further 3 months. Anthropometric and metabolic parameters were assessed; moreover, all patients underwent a glucagon stimulation test.

RESULTS

Berberis aristata/Silybum marianum reduced total cholesterol, triglycerides and low-density lipoprotein cholesterol and increased high-density lipoprotein cholesterol after 3 months from randomization and compared to placebo group. When Berberis aristata/Silybum marianum was interrupted, lipid profile worsened, and it improved again when nutraceutical combination was reintroduced. During the glucagon stimulation test, a higher increase of C-peptide levels and a lower increase in glycemia after the test with Berberis aristata/Silybum marianum compared to placebo, to baseline and to randomization were recorded. No patients had serious adverse events in both groups.

CONCLUSION

Berberis aristata/Silybum marianum is effective and safe in improving lipid profile and insulin secretion in euglycemic dyslipidemic patients.

Effects of berberine on lipid profile in subjects with low cardiovascular risk

OBJECTIVE

To evaluate the efficacy as antihypercholesterolemic agent of berberine in patients with low cardiovascular risk.

RESEARCH DESIGN AND METHODS

144 Caucasian subjects were enrolled. After a 6-month run-in period following diet and practicing physical activity, patients were randomized to take placebo or berberine 500 mg twice a day, for 3 months, in a double-blind, placebo-controlled design. Berberine and placebo were then interrupted for 2 months (washout period), and all patients continued with only diet and physical activity. At the end of the washout period, patients restarted berberine or placebo twice a day for further 3 months. Anthropometric and metabolic parameters were assessed during the run-in period, at randomization, before and after the washout period.

RESULTS

A decrease of body weight and BMI was observed after the run-in period. Berberine reduced total cholesterol, triglycerides and LDL cholesterol and increased HDL cholesterol after 3 months from randomization and compared with placebo. After the washout period, lipid profile worsened; afterward, when berberine was reintroduced, lipid profile improved again both compared with the washout period, and with placebo.

CONCLUSIONS

Berberine is effective and safe to mildly improve lipid profile in subjects with low risk for cardiovascular disease.

ω-3 polyunsaturated fatty acid supplementation does not influence body composition, insulin resistance, and lipemia in women with type 2 diabetes and obesity

To evaluate the influence of ω-3 polyunsaturated fatty acid (ω-3 PUFA) supplementation on body composition, insulin resistance, and lipemia of women with type 2 diabetes, the authors evaluated 41 women (60.64 ± 7.82 years) with high blood pressure and diabetes mellitus in a randomized and single-blind longitudinal intervention study. The women were divided into 3 groups: GA (2.5 g/d fish oil), GB (1.5 g/d fish oil), and GC (control). The capsules with the supplement contained 21.9% of eicosapentaenoic acid and 14.1% of docosapentaenoic acid. Biochemical (glucose, glycated hemoglobin, total and fractional cholesterol, triglycerides, and insulin) and anthropometric (body mass, stature, waist circumference [WC], and body composition) evaluations were performed before and after the 30 days of intervention. Homeostasis model assessment-insulin resistance and the Quantitative Insulin Sensitivity Check Index were used to evaluate the insulin resistance and insulin sensitivity (IS), respectively. GB presented a greater loss of body mass and WC (P < .05), greater frequency of glycemic and total cholesterol reduction, and an increase of high-density lipoprotein cholesterol compared with GA. Thus, a high dose of ω-3 PUFA can reduce IS. A lower dose of ω-3 PUFA positively influenced body composition and lipid metabolism.