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Omega-3, omega-6, and total dietary polyunsaturated fat for prevention and treatment of type 2 diabetes mellitus: systematic review and meta-analysis of randomised controlled trials.
Brown, TJ, Brainard, J, Song, F, Wang, X, Abdelhamid, A, Hooper, L, ,
BMJ (Clinical research ed.). 2019;:l4697
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Abstract
OBJECTIVE To assess effects of increasing omega-3, omega-6, and total polyunsaturated fatty acids (PUFA) on diabetes diagnosis and glucose metabolism. DESIGN Systematic review and meta-analyses. DATA SOURCES Medline, Embase, Cochrane CENTRAL, WHO International Clinical Trials Registry Platform, Clinicaltrials.gov, and trials in relevant systematic reviews. ELIGIBILITY CRITERIA Randomised controlled trials of at least 24 weeks' duration assessing effects of increasing α-linolenic acid, long chain omega-3, omega-6, or total PUFA, which collected data on diabetes diagnoses, fasting glucose or insulin, glycated haemoglobin (HbA1c), and/or homoeostatic model assessment for insulin resistance (HOMA-IR). DATA SYNTHESIS Statistical analysis included random effects meta-analyses using relative risk and mean difference, and sensitivity analyses. Funnel plots were examined and subgrouping assessed effects of intervention type, replacement, baseline risk of diabetes and use of antidiabetes drugs, trial duration, and dose. Risk of bias was assessed with the Cochrane tool and quality of evidence with GRADE. RESULTS 83 randomised controlled trials (mainly assessing effects of supplementary long chain omega-3) were included; 10 were at low summary risk of bias. Long chain omega-3 had little or no effect on likelihood of diagnosis of diabetes (relative risk 1.00, 95% confidence interval 0.85 to 1.17; 58 643 participants, 3.7% developed diabetes) or measures of glucose metabolism (HbA1c mean difference -0.02%, 95% confidence interval -0.07% to 0.04%; plasma glucose 0.04, 0.02 to 0.07, mmol/L; fasting insulin 1.02, -4.34 to 6.37, pmol/L; HOMA-IR 0.06, -0.21 to 0.33). A suggestion of negative outcomes was observed when dose of supplemental long chain omega-3 was above 4.4 g/d. Effects of α-linolenic acid, omega-6, and total PUFA on diagnosis of diabetes were unclear (as the evidence was of very low quality), but little or no effect on measures of glucose metabolism was seen, except that increasing α-linolenic acid may increase fasting insulin (by about 7%). No evidence was found that the omega-3/omega-6 ratio is important for diabetes or glucose metabolism. CONCLUSIONS This is the most extensive systematic review of trials to date to assess effects of polyunsaturated fats on newly diagnosed diabetes and glucose metabolism, including previously unpublished data following contact with authors. Evidence suggests that increasing omega-3, omega-6, or total PUFA has little or no effect on prevention and treatment of type 2 diabetes mellitus. SYSTEMATIC REVIEW REGISTRATION PROSPERO CRD42017064110.
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Effects of Polyunsaturated Fatty Acids on Nonspecific Typical Dry Eye Disease: A Systematic Review and Meta-Analysis of Randomized Clinical Trials.
Chi, SC, Tuan, HI, Kang, YN
Nutrients. 2019;(5)
Abstract
To investigate the effects of polyunsaturated fatty acids (PUFAs) in patients with dry eye disease (DED), a multifactorial inflammatory disorder, we searched Cochrane Library, EMBASE, PubMed, and Web of Science for randomized clinical trials (RCTs) investigating the effect of PUFAs in patients with DED before March 2019. Two reviewers independently abstracted data of tear breakup time (TBUT), Schirmer's test, osmolarity, and ocular surface disease index (OSDI). We conducted pairwise meta-analysis using means and standard deviations (SDs) in a random-effects model for continuous outcomes. Thirteen eligible RCTs with 1782 patients with nonspecific typical DED were included. Patients who received PUFA treatment without other eye medications exhibited greater improvements in TBUT (MD = 1.80; p = 0.001), Schirmer test scores (MD = 0.50; p < 0.001), osmolarity (MD = -15.95; p < 0.001), and OSDI scores (MD = -10.19; p < 0.001) than those who received placebo treatment. However, the effects of PUFAs on TBUT (p < 0.001) and OSDI scores (p = 0.03) weakened with treatment duration. PUFAs are effective in treating nonspecific typical DED, particularly as a short-term treatment, with relatively few adverse events. Therefore, in real-world clinical practice, PUFA supplements are worth being suggested to patients with nonspecific typical DED who are not concurrently using other topical or systematic eye medications.
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Dietary unsaturated fat increases HDL metabolic pathways involving apoE favorable to reverse cholesterol transport.
Morton, AM, Furtado, JD, Mendivil, CO, Sacks, FM
JCI insight. 2019;(7)
Abstract
BACKGROUND HDL that contains apolipoprotein E (apoE) is a subspecies especially active in steps in reverse cholesterol transport, a process that brings cholesterol from peripheral cells to the liver. Here, we studied the effect of dietary unsaturated fat compared with carbohydrate on the metabolism of HDL containing apoE. METHODS We enrolled 9 adults who were overweight or obese and had below-average HDL-cholesterol in a crossover study of a high-fat diet, primarily unsaturated, and a low-fat, high-carbohydrate diet. A metabolic tracer study was performed after each diet period. RESULTS Dietary fat increased the secretion, metabolism, and clearance of HDL subspecies containing apoE. Dietary fat increased the rate of clearance of large cholesterol-rich HDL containing apoE and increased their conversion to small HDL containing apoE, indicating selective cholesterol ester delivery to the liver. The high-unsaturated-fat diet did not affect the metabolism of HDL lacking apoE. CONCLUSION HDL containing apoE is a diet-responsive metabolic pathway that renders HDL more biologically active in reverse cholesterol transport. This may be a mechanism by which unsaturated fat protects against coronary heart disease. Protein-based HDL subspecies such as HDL containing apoE may be used to identify additional atheroprotective treatment targets not evident in the total HDL-cholesterol measurement. TRIAL REGISTRATION ClinicalTrials.gov NCT01399632. FUNDING NIH and the National Center for Advancing Translational Science.
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Effects of Replacing Dietary Monounsaturated Fat With Carbohydrate on HDL (High-Density Lipoprotein) Protein Metabolism and Proteome Composition in Humans.
Andraski, AB, Singh, SA, Lee, LH, Higashi, H, Smith, N, Zhang, B, Aikawa, M, Sacks, FM
Arteriosclerosis, thrombosis, and vascular biology. 2019;(11):2411-2430
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Abstract
OBJECTIVE Clinical evidence has linked low HDL (high-density lipoprotein) cholesterol levels with high cardiovascular disease risk; however, its significance as a therapeutic target remains unestablished. We hypothesize that HDLs functional heterogeneity is comprised of metabolically distinct proteins, each on distinct HDL sizes and that are affected by diet. Approach and Results: Twelve participants were placed on 2 healthful diets high in monounsaturated fat or carbohydrate. After 4 weeks on each diet, participants completed a metabolic tracer study. HDL was isolated by Apo (apolipoprotein) A1 immunopurification and separated into 5 sizes. Tracer enrichment and metabolic rates for 8 HDL proteins-ApoA1, ApoA2, ApoC3, ApoE, ApoJ, ApoL1, ApoM, and LCAT (lecithin-cholesterol acyltransferase)-were determined by parallel reaction monitoring and compartmental modeling, respectively. Each protein had a unique, size-specific distribution that was not altered by diet. However, carbohydrate, when replacing fat, increased the fractional catabolic rate of ApoA1 and ApoA2 on alpha3 HDL; ApoE on alpha3 and alpha1 HDL; and ApoM on alpha2 HDL. Additionally, carbohydrate increased the production of ApoC3 on alpha3 HDL and ApoJ and ApoL1 on the largest alpha0 HDL. LCAT was the only protein studied that diet did not affect. Finally, global proteomics showed that diet did not alter the distribution of the HDL proteome across HDL sizes. CONCLUSIONS This study demonstrates that HDL in humans is composed of a complex system of proteins, each with its own unique size distribution, metabolism, and diet regulation. The carbohydrate-induced hypercatabolic state of HDL proteins may represent mechanisms by which carbohydrate alters the cardioprotective properties of HDL.
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Investigation of the effect of dietary docosahexaenoic acid (DHA) supplementation on macular function in subjects with autosomal recessive Stargardt macular dystrophy.
MacDonald, IM, Sieving, PA
Ophthalmic genetics. 2018;(4):477-486
Abstract
PURPOSE To test the effect of docosahexanoic acid (DHA) dietary supplementation on macular function in patients with Stargardt disease. MATERIALS AND METHODS A single center, double-masked, randomized placebo-controlled trial of 11 subjects (2 males, 9 females) with Stargardt disease in a crossover design (NCT00060749). Six participants were randomized to two sequences of three month periods of DHA supplementation (2000 mg/day) followed by three months of placebo. Five participants were randomized to the opposite sequence. All participants were evaluated with a food frequency and NEI-VF25 questionnaires, complete ophthalmic examination, multifocal electroretinography (ERG, primary outcome), 30-Hz flicker ERG, Humphrey 10-2 visual field, D15 color tests and serum lipid analysis. RESULTS During periods of DHA supplementation, serum rose and then fell with transition to periods of placebo. None of the participants experienced greater than 20% change from baseline values of the mfERG during periods of DHA supplementation or placebo, while the average change in peak amplitude and phase angle of the flicker ERG remained similar at all visits. No significant change was observed for any of the secondary outcome measures. Eight adverse events occurred but these were not considered to be due to the treatment. CONCLUSIONS No perceived effect of DHA supplementation on macular function was observed in a small sample of Stargardt patients who were compliant with the protocol as estimated by changes in serum DHA. This study will help design future studies of the effect of DHA supplementation on retinal function in cohorts with retinal dystrophies.
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Dietary n-6 polyunsaturated fatty acids and cardiovascular disease: Epidemiologic evidence.
Wang, DD
Prostaglandins, leukotrienes, and essential fatty acids. 2018;:5-9
Abstract
Epidemiologists have been studying the effect of n-6 polyunsaturated fatty acids (PUFAs) intake on the risk of cardiovascular disease (CVD) for many decades. Abundant evidence from prospective studies on the clinical endpoints of CVD, including cohort studies measuring n-6 PUFA intake by food frequency questionnaires and nested case-control studies using biomarkers of intake level, strongly support that higher intakes of n-6 PUFAs are associated with a lower risk of CVD. Furthermore, a significant reduction in CVD risk can be achieved when saturated fatty acids (SFAs) is replaced by n-6 PUFAs. Evidence from appropriately designed and vigorously executed randomized controlled trials support that high-PUFA (predominantly linoleic acid) and low-SFA diets, compared to high-SFA diets, reduced the risk of coronary heart disease. Overall, epidemiologic studies provide a solid evidence base of the current dietary guidelines that recommend replacing SFA by PUFA, both n-6 and n-3 PUFA, for CVD prevention.
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Glycemic Effects of a Low-Carbohydrate Enteral Formula Compared With an Enteral Formula of Standard Composition in Critically Ill Patients: An Open-Label Randomized Controlled Clinical Trial.
van Steen, SC, Rijkenberg, S, Sechterberger, MK, DeVries, JH, van der Voort, PHJ
JPEN. Journal of parenteral and enteral nutrition. 2018;(6):1035-1045
Abstract
BACKGROUND Enteral low-carbohydrate formulas (LCFs) could serve as a noninsulin alternative for the treatment of stress hyperglycemia in critically ill patients. We compared the glycemic effects of an LCF with a standard formula. METHODS We conducted an open-label randomized trial in patients admitted to our intensive care unit between September 2015 and June 2016. Adult patients with an indication for enteral nutrition were randomized to an LCF (Glucerna 1.5 kcal) or a standard enteral formula (Fresubin Energy Fibre, with additional protein supplement). Primary outcome was glucose variability defined as mean absolute glucose (MAG) change (mmol/L/h). Secondary outcomes were mean glucose, time in target, hypoglycemic and hyperglycemic events, and insulin requirements. We assessed glycemic outcomes per blinded continuous glucose monitoring (CGM) system and compared outcomes with glucose measurements per blood gas analysis and point-of-care device. RESULTS We randomized 107 patients (LCF: n = 53; standard: n = 54). Six patients had no CGM data, leaving 101 patients (n = 52; n = 49) for the intention-to-treat analysis. MAG change and time in target range were not different between groups. LCF gave a lower mean glucose measured per point-of-care device (7.8 ± 1.0 vs 8.4 ± 1.1 mmol/L, P = .007). LCF patients required significantly less insulin on the second study day (46.8 vs 68.0 IU, P = .036). CONCLUSION LCF showed a trend toward a modestly reduced mean glucose and significantly lower insulin requirements as compared with standard feeding but had no effect on glucose variability or time in target range.
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Dietary Fatty Acid Composition Modulates Obesity and Interacts with Obesity-Related Genes.
Hammad, SS, Jones, PJ
Lipids. 2017;(10):803-822
Abstract
The prevalence of obesity is skyrocketing worldwide. The scientific evidence has associated obesity risk with many independent factors including the quality of dietary fat and genetics. Dietary fat exists as the main focus of dietary guidelines targeting obesity reduction. To prevent/minimize the adipogenic effect of dietary fatty acids (FA), intakes of long-chain saturated- and trans-FA should be reduced and substituted with unsaturated FA. The optimal proportions of dietary unsaturated FA are yet to be defined, along with a particular emphasis on the need to achieve a balanced ratio of n-3:n-6 polyunsaturated FA and to increase monounsaturated FA consumption at the expense of saturated FA. However, inter-individual variability in weight loss in response to a dietary intervention is evident, which highlights the importance of exploring gene-nutrient interactions that can further modulate the risk for obesity development. The quality of dietary fat was found to modulate obesity development by interacting with genes involved in fatty acid metabolism, adipogenesis, and the endocannabinoid system. This review summarizes the current knowledge on the effect of the quality of dietary fat on obesity phenotype and obesity-related genes. The evidence is not only supporting the modulatory effect of fat quality on obesity development but also presenting a number of interactions between obesity-related genes and the quality of dietary fat. The identified gene-FA interaction may have a clinical importance and holds a promise for the possibility of using genetically targeted dietary interventions to reduce obesity risk in the future.
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Membrane lipid alterations in the metabolic syndrome and the role of dietary oils.
Perona, JS
Biochimica et biophysica acta. Biomembranes. 2017;(9 Pt B):1690-1703
Abstract
The metabolic syndrome is a cluster of pathological conditions, including hypertension, hyperglycemia, hypertriglyceridemia, obesity and low HDL levels that is of great concern worldwide, as individuals with metabolic syndrome have an increased risk of type-2 diabetes and cardiovascular disease. Insulin resistance, the key feature of the metabolic syndrome, might be at the same time cause and consequence of impaired lipid composition in plasma membranes of insulin-sensitive tissues like liver, muscle and adipose tissue. Diet intervention has been proposed as a powerful tool to prevent the development of the metabolic syndrome, since healthy diets have been shown to have a protective role against the components of the metabolic syndrome. Particularly, dietary fatty acids are capable of modulating the deleterious effects of these conditions, among other mechanisms, by modifications of the lipid composition of the membranes in insulin-sensitive tissues. However, there is still scarce data based of high-level evidence on the effects of dietary oils on the effects of the metabolic syndrome and its components. This review summarizes the current knowledge on the effects of dietary oils on improving alterations of the components of the metabolic syndrome. It also examines their influence in the modulation of plasma membrane lipid composition and in the functionality of membrane proteins involved in insulin activity, like the insulin receptor, GLUT-4, CD36/FAT and ABCA-1, and their effect in the metabolism of glucose, fatty acids and cholesterol, and, in turn, the key features of the metabolic syndrome. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
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Unsaturated Fatty Acids Improve Atherosclerosis Markers in Obese and Overweight Non-diabetic Elderly Patients.
de Oliveira, PA, Kovacs, C, Moreira, P, Magnoni, D, Saleh, MH, Faintuch, J
Obesity surgery. 2017;(10):2663-2671
Abstract
BACKGROUND Several studies have demonstrated the benefits of replacing trans and saturated fats with unsaturated fatty acids on cardiovascular diseases. We aimed to demonstrate the effect of polyunsaturated and monounsaturated fat supplementation on the biochemical and endothelial markers of atherosclerotic disease in obese or overweight non-diabetic elderly patients. METHOD Seventy-nine patients were randomly divided into three groups: flaxseed oil, olive oil, and sunflower oil; patients in each group received 30 mL of oil for 90 days. Patients were subjected to anthropometric and bioimpedance assessments; biochemical and endothelial evaluations were performed through ultrasonography of the brachial artery and carotid artery for endothelium-dependent dilation and intima-media thickness assessment, respectively, before and after the intervention. The participants' usual diet remained unchanged. RESULTS The flaxseed oil group had improved ultra-sensitive C-reactive protein levels (p = 0.074) and reduced carotid intima-media thickness (CIMT) (p = 0.028); the olive oil group exhibited an improved apolipoprotein (Apo)B/ApoA ratio (p = 0.021), reduced CIMT (p = 0.028), and improved flow-mediated vasodilation (FMV) (p = 0.054); and similarly, the sunflower oil group showed an improved ApoB/ApoA ratio (p = 0.024), reduced CIMT (p = 0.048), and improved FMV (p = 0.001). CONCLUSION Unsaturated fatty acid supplementation using the three vegetable oils attenuated pro-inflammatory properties and improved prothrombotic conditions. Therefore, introducing or replacing saturated and trans fat with unsaturated fatty acids is beneficial for cardiovascular risk reduction in obese or overweight non-diabetic elderly people. Further studies are needed to determine which unsaturated fat best prevents cardiovascular disease in elderly patients.