Unsaturated fats and progression of diabetic retinopathy

Associations between fatty acid intake and diabetic retinopathy in a Japanese population

Residents of Chikusei City, aged 40-74 years, underwent systemic and ophthalmological screening, and participants with diabetes were included in this analysis. Dietary intake was assessed using a food frequency questionnaire and calculated as a percentage of the total energy. The presence of diabetic retinopathy (DR) was defined as Early Treatment Diabetic Retinopathy Study levels ≥ 20 in either eye. The association between dietary fatty acid intake and DR has been examined in a cross-sectional study. Among the 647 diabetic participants, 100 had DR. The mean total fat and saturated fatty acid (SFA) intakes were 22.0% and 7.3% of the total energy intake, respectively. After adjusting for potential confounders, the highest quartiles of total fat and SFA intake were positively associated with the presence of DR compared with the lowest quartiles (odds ratios (95% confidence intervals), 2.61 (1.07-6.39), p for trend = 0.025, and 2.40 (1.12-5.17), p for trend = 0.013, respectively). No significant associations were found between DR prevalence and monounsaturated or unsaturated fatty acid intake. These results suggest that a high intake of fat and SFA may affect the development of DR, even in individuals whose total fat intake is generally much lower than that of Westerners.

Dietary Intake and Diabetic Retinopathy: A Systematic Review of the Literature

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus. The evidence connecting dietary intake and DR is emerging, but uncertain. We conducted a systematic review to comprehensively summarize the current understanding of the associations between dietary consumption, DR and diabetic macular edema (DME). We systematically searched PubMed, Embase, Medline, and the Cochrane Central Register of Controlled Trials between January 1967 to May 2022 for all studies investigating the effect of diet on DR and DME. Of the 4962 articles initially identified, 54 relevant articles were retained. Our review found that higher intakes of fruits, vegetables, dietary fibers, fish, a Mediterranean diet, oleic acid, and tea were found to have a protective effect against DR. Conversely, high intakes of diet soda, caloric intake, rice, and choline were associated with a higher risk of DR. No association was seen between vitamin C, riboflavin, vitamin D, and milk and DR. Only one study in our review assessed dietary intake and DME and found a risk of high sodium intake for DME progression. Therefore, the general recommendation for nutritional counseling to manage diabetes may be beneficial to prevent DR risk, but prospective studies in diverse diabetic populations are needed to confirm our findings and expand clinical guidelines for DR management.

[Bacterial hepatobiliary infections : Pathogen spectrum, antimicrobial resistance and current treatment concepts]

Ascending cholangitis and pyogenic liver abscesses are acute febrile bacterial hepatobiliary diseases. Nowadays they frequently occur in patients with structural changes of the biliary system and are usually treated by a combination of interventional drainage procedures and antimicrobial therapy. While Gram-negative Enterobacterales were identified as major causes in the past, biliary tract interventions and antibiotic exposure have contributed to an increase in enterococcal species and extended spectrum beta-lactamase (ESBL)-producing Enterobacterales. When selecting an appropriate empirical treatment the treating internist must consider local and individual risk factors for antimicrobial resistance in addition to pharmacokinetic aspects and disease severity to reduce the likelihood of treatment failure.

Serum ω-6/ω-3 polyunsaturated fatty acids ratio and diabetic retinopathy: A propensity score matching based case-control study in China

BACKGROUND

Optimal ω-6/ω-3 polyunsaturated fatty acids ratio (PUFAR) is reported to exert protective effects against chronic diseases. However, data on PUFAR and diabetic retinopathy (DR) remains scarce. We aimed to thoroughly quantify whether and how PUFAR was related to DR as well as its role in DR detection.

METHODS

This two-centre case-control study was conducted from August 2017 to June 2018 in China, participants were matched using a propensity score matching algorithm. We adopted multivariable logistic regression models and restricted cubic spline analyses to estimate the independent association of PUFAR with DR, adjusting for confounders identified using a directed acyclic graph. The value of PUFAR as a biomarker for DR identification was further evaluated by receiver operating characteristic analyses and Hosmer-Lemeshow tests.

FINDINGS

An apparent negative relationship between PUFAR and DR was observed. Adjusted odds of DR decreased by 79% (OR: 0·21, 95% CI: 0·10-0·40) with an interquartile range increase in PUFAR. Similar results were also obtained in tertile analysis. As compared to those in the 1st tertile of PUFAR, the adjusted odds of DR decreased by 76% (OR: 0·24, 95% CI: 0·08-0·66) and 93% (OR: 0·07, 95% CI: 0·03-0·22) for subjects in the 2nd and 3rd tertiles, respectively. Good calibration and discrimination of the PUFAR associated predictive model were detected and PUFAR = 35 would be an ideal cut-off value for DR identification.

INTERPRETATION

Our results suggest that serum PUAFR is inversely associated with DR. Although PUFAR-alteration is not observed amongst different stages of DR, it can serve as an ideal biomarker in distinguishing patients with DR from those without DR.

FUNDING

This study was funded by Natural Science Foundation of Zhejiang Province, Zhejiang Basic Public Welfare Research Project, the Major Project of the Eye Hospital of Wenzhou Medical University, and the Academician's Science and Technology Innovation Program in Zhejiang province. Part of this work was also funded by the National Nature Science Foundation of China, and Research Project for College Students in Wenzhou Medical University.

Low circulating dihomo-gamma-linolenic acid is associated with diabetic retinopathy: a cross sectional study of KAMOGAWA-DM cohort study

Diabetic retinopathy (DR), one of the major complications of diabetes, can cause blindness and reduce quality of life. Dyslipidemia is reported to be associated with DR, whereas arachidonic acid may have a protective effect against DR. We aimed to investigate the association of circulating n-3 and n-6 polyunsaturated fatty acids (PUFAs) with DR. In this cross-sectional study, 190 Japanese patients with type 2 diabetes were classified as no diabetic retinopathy (NDR), simple diabetic retinopathy (SDR), or proliferative diabetic retinopathy (PDR) including pre-proliferative diabetic retinopathy. Circulating fatty acids (FAs) were measured by gas chromatograph-mass spectrometry. Logistic regression analysis was performed to investigate the association between the levels of FAs and the presence of DR. The average age, body mass index and the duration of diabetes were 62.7 ± 12.1 years, 25.0 ± 4.5 kg/m², and 9.8 ± 8.7 years, respectively. Twenty-seven patients were diagnosed with DR. Circulating levels of dihomo-gamma-linolenic acid (DGLA) in the NDR (n = 163), SDR (n = 13) and PDR (n = 14) groups were 28.3 ± 11.0 μg/mL, 24.4 ± 9.7 μg/mL, and 21.8 ± 6.2 μg/mL, respectively (p = 0.032). The logarithm of circulating DGLA levels was associated with the presence of DR after adjusting for covariates (OR of 1-unit increment: 0.79, 95% CI: 0.62-1.00, p = 0.049). Circulating DGLA was negatively associated with the presence of DR.

Lipid metabolism dysregulation in diabetic retinopathy

Lipid metabolic abnormalities have emerged as potential risk factors for the development and progression of diabetic complications, including diabetic retinopathy (DR). This review article provides an overview of the results of clinical trials evaluating the potential benefits of lipid-lowering drugs, such as fibrates, omega-3 fatty acids, and statins, for the prevention and treatment of DR. Although several clinical trials demonstrated that treatment with fibrates leads to improvement of DR, there is a dissociation between the protective effects of fibrates in the retina, and the intended blood lipid classes, including plasma triglycerides, total cholesterol, or HDL:LDL cholesterol ratio. Guided by these findings, plasma lipid and lipoprotein-independent mechanisms are addressed based on clinical, cell culture, and animal model studies. Potential retinal-specific effects of fatty acid oxidation products, cholesterol, and ceramide, as well as lipid-independent effects of PPAR alpha activation, are summarized based on the current literature. Overall, this review highlights promising potential of lipid-based treatment strategies further enhanced by the new knowledge of intraretinal lipids and lipoproteins in DR.

Reduction in saturated fat intake for cardiovascular disease

BACKGROUND

Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from saturated fats eliminated from the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein.

OBJECTIVES

To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA), monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.

SEARCH METHODS

We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and Embase (Ovid) on 15 October 2019, and searched Clinicaltrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) on 17 October 2019.

SELECTION CRITERIA

Included trials fulfilled the following criteria: 1) randomised; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) compared with higher saturated fat intake or usual diet; 4) not multifactorial; 5) in adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 6) intervention duration at least 24 months; 7) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed inclusion, extracted study data and assessed risk of bias. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses, funnel plots and GRADE assessment.

MAIN RESULTS

We included 15 randomised controlled trials (RCTs) (16 comparisons, 56,675 participants), that used a variety of interventions from providing all food to advice on reducing saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of combined cardiovascular events by 17% (risk ratio (RR) 0.83; 95% confidence interval (CI) 0.70 to 0.98, 12 trials, 53,758 participants of whom 8% had a cardiovascular event, I² = 67%, GRADE moderate-quality evidence). Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials. The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for ~four years for one person to avoid experiencing a CVD event. In secondary prevention trials, the NNTB was 53. Subgrouping did not suggest significant differences between replacement of saturated fat calories with polyunsaturated fat or carbohydrate, and data on replacement with monounsaturated fat and protein was very limited. We found little or no effect of reducing saturated fat on all-cause mortality (RR 0.96; 95% CI 0.90 to 1.03; 11 trials, 55,858 participants) or cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 10 trials, 53,421 participants), both with GRADE moderate-quality evidence. There was little or no effect of reducing saturated fats on non-fatal myocardial infarction (RR 0.97, 95% CI 0.87 to 1.07) or CHD mortality (RR 0.97, 95% CI 0.82 to 1.16, both low-quality evidence), but effects on total (fatal or non-fatal) myocardial infarction, stroke and CHD events (fatal or non-fatal) were all unclear as the evidence was of very low quality. There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI. There was no evidence of harmful effects of reducing saturated fat intakes.

AUTHORS' CONCLUSIONS

The findings of this updated review suggest that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. Replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appear to be useful strategies, while effects of replacement with monounsaturated fat are unclear. The reduction in combined cardiovascular events resulting from reducing saturated fat did not alter by study duration, sex or baseline level of cardiovascular risk, but greater reduction in saturated fat caused greater reductions in cardiovascular events.

Reduction in saturated fat intake for cardiovascular disease

BACKGROUND

Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally, it is unclear whether the energy from saturated fats eliminated from the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein.

OBJECTIVES

To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA), monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.

SEARCH METHODS

We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and Embase (Ovid) on 15 October 2019, and searched Clinicaltrials.gov and WHO International Clinical Trials Registry Platform (ICTRP) on 17 October 2019.

SELECTION CRITERIA

Included trials fulfilled the following criteria: 1) randomised; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) compared with higher saturated fat intake or usual diet; 4) not multifactorial; 5) in adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 6) intervention duration at least 24 months; 7) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed inclusion, extracted study data and assessed risk of bias. We performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses, funnel plots and GRADE assessment.

MAIN RESULTS

We included 15 randomised controlled trials (RCTs) (16 comparisons, ~59,000 participants), that used a variety of interventions from providing all food to advice on reducing saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of combined cardiovascular events by 21% (risk ratio (RR) 0.79; 95% confidence interval (CI) 0.66 to 0.93, 11 trials, 53,300 participants of whom 8% had a cardiovascular event, I² = 65%, GRADE moderate-quality evidence). Meta-regression suggested that greater reductions in saturated fat (reflected in greater reductions in serum cholesterol) resulted in greater reductions in risk of CVD events, explaining most heterogeneity between trials. The number needed to treat for an additional beneficial outcome (NNTB) was 56 in primary prevention trials, so 56 people need to reduce their saturated fat intake for ~four years for one person to avoid experiencing a CVD event. In secondary prevention trials, the NNTB was 32. Subgrouping did not suggest significant differences between replacement of saturated fat calories with polyunsaturated fat or carbohydrate, and data on replacement with monounsaturated fat and protein was very limited. We found little or no effect of reducing saturated fat on all-cause mortality (RR 0.96; 95% CI 0.90 to 1.03; 11 trials, 55,858 participants) or cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 10 trials, 53,421 participants), both with GRADE moderate-quality evidence. There was little or no effect of reducing saturated fats on non-fatal myocardial infarction (RR 0.97, 95% CI 0.87 to 1.07) or CHD mortality (RR 0.97, 95% CI 0.82 to 1.16, both low-quality evidence), but effects on total (fatal or non-fatal) myocardial infarction, stroke and CHD events (fatal or non-fatal) were all unclear as the evidence was of very low quality. There was little or no effect on cancer mortality, cancer diagnoses, diabetes diagnosis, HDL cholesterol, serum triglycerides or blood pressure, and small reductions in weight, serum total cholesterol, LDL cholesterol and BMI. There was no evidence of harmful effects of reducing saturated fat intakes.

AUTHORS' CONCLUSIONS

The findings of this updated review suggest that reducing saturated fat intake for at least two years causes a potentially important reduction in combined cardiovascular events. Replacing the energy from saturated fat with polyunsaturated fat or carbohydrate appear to be useful strategies, while effects of replacement with monounsaturated fat are unclear. The reduction in combined cardiovascular events resulting from reducing saturated fat did not alter by study duration, sex or baseline level of cardiovascular risk, but greater reduction in saturated fat caused greater reductions in cardiovascular events.

Dyslipidemia in retinal metabolic disorders

The light‐sensitive photoreceptors in the retina are extremely metabolically demanding and have the highest density of mitochondria of any cell in the body. Both physiological and pathological retinal vascular growth and regression are controlled by photoreceptor energy demands. It is critical to understand the energy demands of photoreceptors and fuel sources supplying them to understand neurovascular diseases. Retinas are very rich in lipids, which are continuously recycled as lipid‐rich photoreceptor outer segments are shed and reformed and dietary intake of lipids modulates retinal lipid composition. Lipids (as well as glucose) are fuel substrates for photoreceptor mitochondria. Dyslipidemia contributes to the development and progression of retinal dysfunction in many eye diseases. Here, we review photoreceptor energy demands with a focus on lipid metabolism in retinal neurovascular disorders.

Omega-6 fats for the primary and secondary prevention of cardiovascular disease

BACKGROUND

Omega-6 fats are polyunsaturated fats vital for many physiological functions, but their effect on cardiovascular disease (CVD) risk is debated.

OBJECTIVES

To assess effects of increasing omega-6 fats (linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA)) on CVD and all-cause mortality.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to May 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing higher versus lower omega-6 fat intake in adults with or without CVD, assessing effects over at least 12 months. We included full texts, abstracts, trials registry entries and unpublished studies. Outcomes were all-cause mortality, CVD mortality, CVD events, risk factors (blood lipids, adiposity, blood pressure), and potential adverse events. We excluded trials where we could not separate omega-6 fat effects from those of other dietary, lifestyle or medication interventions.

DATA COLLECTION AND ANALYSIS

Two authors independently screened titles/abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias of included trials. We wrote to authors of included studies. Meta-analyses used random-effects analysis, while sensitivity analyses used fixed-effects and limited analyses to trials at low summary risk of bias. We assessed GRADE quality of evidence for 'Summary of findings' tables.

MAIN RESULTS

We included 19 RCTs in 6461 participants who were followed for one to eight years. Seven trials assessed the effects of supplemental GLA and 12 of LA, none DGLA or AA; the omega-6 fats usually displaced dietary saturated or monounsaturated fats. We assessed three RCTs as being at low summary risk of bias.Primary outcomes: we found low-quality evidence that increased intake of omega-6 fats may make little or no difference to all-cause mortality (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.88 to 1.12, 740 deaths, 4506 randomised, 10 trials) or CVD events (RR 0.97, 95% CI 0.81 to 1.15, 1404 people experienced events of 4962 randomised, 7 trials). We are uncertain whether increasing omega-6 fats affects CVD mortality (RR 1.09, 95% CI 0.76 to 1.55, 472 deaths, 4019 randomised, 7 trials), coronary heart disease events (RR 0.88, 95% CI 0.66 to 1.17, 1059 people with events of 3997 randomised, 7 trials), major adverse cardiac and cerebrovascular events (RR 0.84, 95% CI 0.59 to 1.20, 817 events, 2879 participants, 2 trials) or stroke (RR 1.36, 95% CI 0.45 to 4.11, 54 events, 3730 participants, 4 trials), as we assessed the evidence as being of very low quality. We found no evidence of dose-response or duration effects for any primary outcome, but there was a suggestion of greater protection in participants with lower baseline omega-6 intake across outcomes.Additional key outcomes: we found increased intake of omega-6 fats may reduce myocardial infarction (MI) risk (RR 0.88, 95% CI 0.76 to 1.02, 609 events, 4606 participants, 7 trials, low-quality evidence). High-quality evidence suggests increasing omega-6 fats reduces total serum cholesterol a little in the long term (mean difference (MD) -0.33 mmol/L, 95% CI -0.50 to -0.16, I² = 81%; heterogeneity partially explained by dose, 4280 participants, 10 trials). Increasing omega-6 fats probably has little or no effect on adiposity (body mass index (BMI) MD -0.20 kg/m², 95% CI -0.56 to 0.16, 371 participants, 1 trial, moderate-quality evidence). It may make little or no difference to serum triglycerides (MD -0.01 mmol/L, 95% CI -0.23 to 0.21, 834 participants, 5 trials), HDL (MD -0.01 mmol/L, 95% CI -0.03 to 0.02, 1995 participants, 4 trials) or low-density lipoprotein (MD -0.04 mmol/L, 95% CI -0.21 to 0.14, 244 participants, 2 trials, low-quality evidence).

AUTHORS' CONCLUSIONS

This is the most extensive systematic assessment of effects of omega-6 fats on cardiovascular health, mortality, lipids and adiposity to date, using previously unpublished data. We found no evidence that increasing omega-6 fats reduces cardiovascular outcomes other than MI, where 53 people may need to increase omega-6 fat intake to prevent 1 person from experiencing MI. Although benefits of omega-6 fats remain to be proven, increasing omega-6 fats may be of benefit in people at high risk of MI. Increased omega-6 fats reduce serum total cholesterol but not other blood fat fractions or adiposity.

Polyunsaturated fatty acids for the primary and secondary prevention of cardiovascular disease

BACKGROUND

Evidence on the health effects of total polyunsaturated fatty acids (PUFA) is equivocal. Fish oils are rich in omega-3 PUFA and plant oils in omega-6 PUFA. Evidence suggests that increasing PUFA-rich foods, supplements or supplemented foods can reduce serum cholesterol, but may increase body weight, so overall cardiovascular effects are unclear.

OBJECTIVES

To assess effects of increasing total PUFA intake on cardiovascular disease and all-cause mortality, lipids and adiposity in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to April 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing higher with lower PUFA intakes in adults with or without cardiovascular disease that assessed effects over 12 months or longer. We included full texts, abstracts, trials registry entries and unpublished data. Outcomes were all-cause mortality, cardiovascular disease mortality and events, risk factors (blood lipids, adiposity, blood pressure), and adverse events. We excluded trials where we could not separate effects of PUFA intake from other dietary, lifestyle or medication interventions.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias. We wrote to authors of included trials for further data. Meta-analyses used random-effects analysis, sensitivity analyses included fixed-effects and limiting to low summary risk of bias. We assessed GRADE quality of evidence.

MAIN RESULTS

We included 49 RCTs randomising 24,272 participants, with duration of one to eight years. Eleven included trials were at low summary risk of bias, 33 recruited participants without cardiovascular disease. Baseline PUFA intake was unclear in most trials, but 3.9% to 8% of total energy intake where reported. Most trials gave supplemental capsules, but eight gave dietary advice, eight gave supplemental foods such as nuts or margarine, and three used a combination of methods to increase PUFA.Increasing PUFA intake probably has little or no effect on all-cause mortality (risk 7.8% vs 7.6%, risk ratio (RR) 0.98, 95% confidence interval (CI) 0.89 to 1.07, 19,290 participants in 24 trials), but probably slightly reduces risk of coronary heart disease events from 14.2% to 12.3% (RR 0.87, 95% CI 0.72 to 1.06, 15 trials, 10,076 participants) and cardiovascular disease events from 14.6% to 13.0% (RR 0.89, 95% CI 0.79 to 1.01, 17,799 participants in 21 trials), all moderate-quality evidence. Increasing PUFA may slightly reduce risk of coronary heart disease death (6.6% to 6.1%, RR 0.91, 95% CI 0.78 to 1.06, 9 trials, 8810 participants) andstroke (1.2% to 1.1%, RR 0.91, 95% CI 0.58 to 1.44, 11 trials, 14,742 participants, though confidence intervals include important harms), but has little or no effect on cardiovascular mortality (RR 1.02, 95% CI 0.82 to 1.26, 16 trials, 15,107 participants) all low-quality evidence. Effects of increasing PUFA on major adverse cardiac and cerebrovascular events and atrial fibrillation are unclear as evidence is of very low quality.Increasing PUFA intake probably slightly decreases triglycerides (by 15%, MD -0.12 mmol/L, 95% CI -0.20 to -0.04, 20 trials, 3905 participants), but has little or no effect on total cholesterol (mean difference (MD) -0.12 mmol/L, 95% CI -0.23 to -0.02, 26 trials, 8072 participants), high-density lipoprotein (HDL) (MD -0.01 mmol/L, 95% CI -0.02 to 0.01, 18 trials, 4674 participants) or low-density lipoprotein (LDL) (MD -0.01 mmol/L, 95% CI -0.09 to 0.06, 15 trials, 3362 participants). Increasing PUFA probably has little or no effect on adiposity (body weight MD 0.76 kg, 95% CI 0.34 to 1.19, 12 trials, 7100 participants).Effects of increasing PUFA on serious adverse events such as pulmonary embolism and bleeding are unclear as the evidence is of very low quality.

AUTHORS' CONCLUSIONS

This is the most extensive systematic review of RCTs conducted to date to assess effects of increasing PUFA on cardiovascular disease, mortality, lipids or adiposity. Increasing PUFA intake probably slightly reduces risk of coronary heart disease and cardiovascular disease events, may slightly reduce risk of coronary heart disease mortality and stroke (though not ruling out harms), but has little or no effect on all-cause or cardiovascular disease mortality. The mechanism may be via TG reduction.

US dietary guidelines: is saturated fat a nutrient of concern?

US public health dietary advice was announced by the Select Committee on Nutrition and Human needs in 1977 and was followed by UK public health dietary advice issued by the National Advisory Committee on Nutritional Education in 1983. Dietary recommendations in both cases focused on reducing dietary fat intake; specifically to (i) reduce overall fat consumption to 30% of total energy intake and (ii) reduce saturated fat consumption to 10% of total energy intake. The recommendations were an attempt to address the incidence of coronary heart disease. These guidelines have been reiterated in the Dietary Guidelines for Americans since the first edition in 1980. The most recent edition has positioned the total fat guideline with the use of 'Acceptable Macronutrient Distribution Ranges'. The range given for total fat is 20%-35% and the AMDR for saturated fat is given as <10%-both as a percentage of daily calorie intake. In February 2018, the Center for Nutrition Policy and Promotion announced 'The US Departments of Agriculture and Health and Human Services currently are asking for public comments on topics and supporting scientific questions to inform our development of the 2020-2025 Dietary Guidelines for Americans'. Public comments were invited on a number of nutritional topics. The question asked about saturated fats was: 'What is the relationship between saturated fat consumption (types and amounts) during adulthood and risk of cardiovascular disease?' This article is a response to that question.

Polyunsaturated fatty acids for the primary and secondary prevention of cardiovascular disease

BACKGROUND

Evidence on the health effects of total polyunsaturated fatty acids (PUFA) is equivocal. Fish oils are rich in omega-3 PUFA and plant oils in omega-6 PUFA. Evidence suggests that increasing PUFA-rich foods, supplements or supplemented foods can reduce serum cholesterol, but may increase body weight, so overall cardiovascular effects are unclear.

OBJECTIVES

To assess effects of increasing total PUFA intake on cardiovascular disease and all-cause mortality, lipids and adiposity in adults.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to April 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing higher with lower PUFA intakes in adults with or without cardiovascular disease that assessed effects over 12 months or longer. We included full texts, abstracts, trials registry entries and unpublished data. Outcomes were all-cause mortality, cardiovascular disease mortality and events, risk factors (blood lipids, adiposity, blood pressure), and adverse events. We excluded trials where we could not separate effects of PUFA intake from other dietary, lifestyle or medication interventions.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias. We wrote to authors of included trials for further data. Meta-analyses used random-effects analysis, sensitivity analyses included fixed-effects and limiting to low summary risk of bias. We assessed GRADE quality of evidence.

MAIN RESULTS

We included 49 RCTs randomising 24,272 participants, with duration of one to eight years. Eleven included trials were at low summary risk of bias, 33 recruited participants without cardiovascular disease. Baseline PUFA intake was unclear in most trials, but 3.9% to 8% of total energy intake where reported. Most trials gave supplemental capsules, but eight gave dietary advice, eight gave supplemental foods such as nuts or margarine, and three used a combination of methods to increase PUFA.Increasing PUFA intake probably has little or no effect on all-cause mortality (risk 7.8% vs 7.6%, risk ratio (RR) 0.98, 95% confidence interval (CI) 0.89 to 1.07, 19,290 participants in 24 trials), but probably slightly reduces risk of coronary heart disease events from 14.2% to 12.3% (RR 0.87, 95% CI 0.72 to 1.06, 15 trials, 10,076 participants) and cardiovascular disease events from 14.6% to 13.0% (RR 0.89, 95% CI 0.79 to 1.01, 17,799 participants in 21 trials), all moderate-quality evidence. Increasing PUFA may slightly reduce risk of coronary heart disease death (6.6% to 6.1%, RR 0.91, 95% CI 0.78 to 1.06, 9 trials, 8810 participants) andstroke (1.2% to 1.1%, RR 0.91, 95% CI 0.58 to 1.44, 11 trials, 14,742 participants, though confidence intervals include important harms), but has little or no effect on cardiovascular mortality (RR 1.02, 95% CI 0.82 to 1.26, 16 trials, 15,107 participants) all low-quality evidence. Effects of increasing PUFA on major adverse cardiac and cerebrovascular events and atrial fibrillation are unclear as evidence is of very low quality.Increasing PUFA intake slightly reduces total cholesterol (mean difference (MD) -0.12 mmol/L, 95% CI -0.23 to -0.02, 26 trials, 8072 participants) and probably slightly decreases triglycerides (MD -0.12 mmol/L, 95% CI -0.20 to -0.04, 20 trials, 3905 participants), but has little or no effect on high-density lipoprotein (HDL) (MD -0.01 mmol/L, 95% CI -0.02 to 0.01, 18 trials, 4674 participants) or low-density lipoprotein (LDL) (MD -0.01 mmol/L, 95% CI -0.09 to 0.06, 15 trials, 3362 participants). Increasing PUFA probably causes slight weight gain (MD 0.76 kg, 95% CI 0.34 to 1.19, 12 trials, 7100 participants).Effects of increasing PUFA on serious adverse events such as pulmonary embolism and bleeding are unclear as the evidence is of very low quality.

AUTHORS' CONCLUSIONS

This is the most extensive systematic review of RCTs conducted to date to assess effects of increasing PUFA on cardiovascular disease, mortality, lipids or adiposity. Increasing PUFA intake probably slightly reduces risk of coronary heart disease and cardiovascular disease events, may slightly reduce risk of coronary heart disease mortality and stroke (though not ruling out harms), but has little or no effect on all-cause or cardiovascular disease mortality. The mechanism may be via lipid reduction, but increasing PUFA probably slightly increases weight.

Omega-6 fats for the primary and secondary prevention of cardiovascular disease

BACKGROUND

Omega-6 fats are polyunsaturated fats vital for many physiological functions, but their effect on cardiovascular disease (CVD) risk is debated.

OBJECTIVES

To assess effects of increasing omega-6 fats (linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA)) on CVD and all-cause mortality.

SEARCH METHODS

We searched CENTRAL, MEDLINE and Embase to May 2017 and clinicaltrials.gov and the World Health Organization International Clinical Trials Registry Platform to September 2016, without language restrictions. We checked trials included in relevant systematic reviews.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing higher versus lower omega-6 fat intake in adults with or without CVD, assessing effects over at least 12 months. We included full texts, abstracts, trials registry entries and unpublished studies. Outcomes were all-cause mortality, CVD mortality, CVD events, risk factors (blood lipids, adiposity, blood pressure), and potential adverse events. We excluded trials where we could not separate omega-6 fat effects from those of other dietary, lifestyle or medication interventions.

DATA COLLECTION AND ANALYSIS

Two authors independently screened titles/abstracts, assessed trials for inclusion, extracted data, and assessed risk of bias of included trials. We wrote to authors of included studies. Meta-analyses used random-effects analysis, while sensitivity analyses used fixed-effects and limited analyses to trials at low summary risk of bias. We assessed GRADE quality of evidence for 'Summary of findings' tables.

MAIN RESULTS

We included 19 RCTs in 6461 participants who were followed for one to eight years. Seven trials assessed the effects of supplemental GLA and 12 of LA, none DGLA or AA; the omega-6 fats usually displaced dietary saturated or monounsaturated fats. We assessed three RCTs as being at low summary risk of bias.Primary outcomes: we found low-quality evidence that increased intake of omega-6 fats may make little or no difference to all-cause mortality (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.88 to 1.12, 740 deaths, 4506 randomised, 10 trials) or CVD events (RR 0.97, 95% CI 0.81 to 1.15, 1404 people experienced events of 4962 randomised, 7 trials). We are uncertain whether increasing omega-6 fats affects CVD mortality (RR 1.09, 95% CI 0.76 to 1.55, 472 deaths, 4019 randomised, 7 trials), coronary heart disease events (RR 0.88, 95% CI 0.66 to 1.17, 1059 people with events of 3997 randomised, 7 trials), major adverse cardiac and cerebrovascular events (RR 0.84, 95% CI 0.59 to 1.20, 817 events, 2879 participants, 2 trials) or stroke (RR 1.36, 95% CI 0.45 to 4.11, 54 events, 3730 participants, 4 trials), as we assessed the evidence as being of very low quality. We found no evidence of dose-response or duration effects for any primary outcome, but there was a suggestion of greater protection in participants with lower baseline omega-6 intake across outcomes.Additional key outcomes: we found increased intake of omega-6 fats may reduce myocardial infarction (MI) risk (RR 0.88, 95% CI 0.76 to 1.02, 609 events, 4606 participants, 7 trials, low-quality evidence). High-quality evidence suggests increasing omega-6 fats reduces total serum cholesterol a little in the long term (mean difference (MD) -0.33 mmol/L, 95% CI -0.50 to -0.16, I2 = 81%; heterogeneity partially explained by dose, 4280 participants, 10 trials). Increasing omega-6 fats probably has little or no effect on adiposity (body mass index (BMI) MD -0.20 kg/m2, 95% CI -0.56 to 0.16, 371 participants, 1 trial, moderate-quality evidence). It may make little or no difference to serum triglycerides (MD -0.01 mmol/L, 95% CI -0.23 to 0.21, 834 participants, 5 trials), HDL (MD -0.01 mmol/L, 95% CI -0.03 to 0.02, 1995 participants, 4 trials) or low-density lipoprotein (MD -0.04 mmol/L, 95% CI -0.21 to 0.14, 244 participants, 2 trials, low-quality evidence).

AUTHORS' CONCLUSIONS

This is the most extensive systematic assessment of effects of omega-6 fats on cardiovascular health, mortality, lipids and adiposity to date, using previously unpublished data. We found no evidence that increasing omega-6 fats reduces cardiovascular outcomes other than MI, where 53 people may need to increase omega-6 fat intake to prevent 1 person from experiencing MI. Although benefits of omega-6 fats remain to be proven, increasing omega-6 fats may be of benefit in people at high risk of MI. Increased omega-6 fats reduce serum total cholesterol but not other blood fat fractions or adiposity.

Dietary intake and diabetic retinopathy: A systematic review

INTRODUCTION

The evidence linking dietary intake with diabetic retinopathy (DR) is growing but unclear. We conducted a systematic review of the association between dietary intake and DR.

METHODS

We systematically searched PubMed, Embase, Medline, and the Cochrane Central register of controlled trials, for publications between January 1967 and January 2017 using standardized criteria for diet and DR. Interventional and observational studies investigating micro- and macro-nutrient intakes; food and beverage consumptions; and dietary patterns were included. Study quality was evaluated using a modified Newcastle-Ottawa scale for observational studies, and the Cochrane collaboration tool for interventional studies.

RESULTS

Of 4265 titles initially identified, 31 studies (3 interventional, 28 Observational) were retained. Higher intakes of dietary fibre, oily fish, and greater adherence to a Mediterranean diet were protective of DR. Conversely, high total caloric intake was associated with higher risk of DR. No significant associations of carbohydrate, vitamin D, and sodium intake with DR were found. Associations of antioxidants, fatty acids, proteins and alcohol with DR remain equivocal.

CONCLUSIONS

Dietary fibre, oily fish, a Mediterranean diet and a reduced caloric intake are associated with lower risk of DR. Longitudinal data and interventional models are warranted to confirm our findings and better inform clinical guidelines.

The role of dyslipidemia in diabetic retinopathy

Diabetic retinopathy (DR) affects over 93million people worldwide and is the number one cause of blindness among working age adults. These indicators coupled with the projected rise of patients diagnosed with diabetes, makes DR a serious and prevalent vision threating disease. Data from recent clinical trials demonstrate that in addition to the well accepted role of hyperglycemia, dyslipidemia is an important, but often overlooked factor in the development of DR. The central aim of this review article is to showcase the critical role of dyslipidemia in DR progression as well as highlight novel therapeutic solutions that take advantage of the vital roles lipid metabolism plays in DR progression.

Statins and Fibrates for Diabetic Retinopathy: Protocol for a Systematic Review

Background

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus, and more than 75% of patients who have had diabetes for more than 20 years will have some degree of DR. This disease is highly destructive to self-esteem and puts a high burden on public health and pension systems due to the effects that it has on people of working age. The current mainstay of treatment is laser photocoagulation, which causes impairment of vision and discomfort to patients. Thus, finding a systemic drug that could act on all microcirculation and prevent direct manipulation of the eyes would be highly desirable.

Objective

To assess the efficacy and safety of the drugs in the statin and/or fibrate groups for the prevention and treatment of DR.

Methods

In this systematic review, we will select randomized controlled trials of fibrates or statins used for the treatment or prevention of DR. Our search strategy will include free text terms and controlled vocabulary (eg, MeSH, Emtree) for, “diabetic retinopathy”, “statins”, “fibrates”, “hypolipidemic agents”, and for drugs from both groups. Databases that will be used include Medical Literature Analysis and Retrieval System/PubMed, Embase, Cochrane Central Register of Controlled Trials, Latin American and Caribbean Center on Health Sciences Information, Clinicaltrials.gov, World Health Organization International Clinical Trials Registry Platform, and OpenGrey, and we will not have language or date limits. Two review authors will independently select eligible studies and assess the risk of bias using the Cochrane Collaboration’s tool. We will report structured summaries of the included studies and, if possible, conduct meta-analyses.

Results

This is a protocol for a systematic review, therefore results are not available. We registered a short version of this protocol before progressing in the review and we are currently in the process of selecting the studies for inclusion.

Conclusions

Intensive glucose control and lowering blood pressure and lipids are mechanisms that protect macrocirculation in diabetic patients. Both macrovascular and microvascular events in diabetic patients appear to have a common pathway, starting with endothelial injury. Thus, prevention and treatment of microvascular events may benefit from the same interventions. In the review for which we have written this protocol, we will assess whether the use of lipid-lowering oral drugs of the statin and/or fibrate groups may prevent and/or retard progression of DR, with the added benefit of preserving visual acuity.

Trial Registration

PROSPERO CRD42016029746

Association of low oleic acid intake with diabetic retinopathy in type 2 diabetic patients: a case-control study

BACKGROUND

The objective of this study was to describe the intake of macronutrient, especially fatty acids, and explore their possible effect on diabetic retinopathy (DR) in patients with type 2 diabetes mellitus.

METHODS

In this case-control study, we included a total of 146 patients with DR and 148 without DR. The intake of macronutrient was evaluated using a validated food frequency questionnaire. We used logistic regression adjusted for sex, age, diabetes duration, energy intake, educational level, physical activity, waist circumference, systolic blood pressure, high-density lipoprotein cholesterol and diabetes treatment, to estimate odds ratio (ORs) of DR.

RESULTS

Patients with DR had significantly lower intake of fibre, monounsaturated fatty acids (MUFA), and palmitic and oleic acid. Inverse associations were observed between MUFA and oleic acid intake in DR. Subjects with intermediate and high MUFA intake were less likely to have DR than those with lower MUFA intake, with ORs of 0.46 (95 % CI: 0.22-0.93) and 0.42 (95 % CI: 0.18-0.97), respectively. Similarly, intermediate and high oleic acid intake were associated with reduced DR frequency compared with low oleic acid intake, with OR values of 0.48 (95 % CI: 0.23-0.97) and 0.37 (95 % CI: 0.16-0.85), respectively. These associations were stronger in patients with a longer diabetes duration.

CONCLUSION

In type 2 diabetes mellitus, MUFA and oleic acid intake were inversely associated with DR.

Lipids and Diabetic Retinopathy

The relationship between lipids and the development and/or severity of diabetic retinopathy (DR) is complex. Large epidemiologic studies suggest an inconsistent and overall modest association between serum triglycerides or major cholesterol species and the severity of DR; however, certain specific lipoprotein species may have stronger associations with DR severity, suggesting a pathophysiological role for lipoproteins analogous to that seen in atherosclerosis. In this lipoprotein-mediated DR pathogenesis model, damage to the blood-retinal barrier allows extravasation of lipoprotein species, which are modified in the intraretinal environment, creating substantial local damage. Additionally, hypolipidemic therapy with statins and fibrates--particularly the latter--have been shown to modulate DR in large-scale studies. Since serum lipid profile changes do not necessarily correlate with DR modulation, the efficacy of these agents may be due to their tissue-specific changes in lipoproteins and/or their anti-inflammatory, antioxidative, antiangiogenic, and antiapoptotic functions.

Mediterranean Diet, Retinopathy, Nephropathy, and Microvascular Diabetes Complications: A Post Hoc Analysis of a Randomized Trial

OBJECTIVE

To date no clinical trials have evaluated the role of dietary patterns on the incidence of microvascular diabetes complications. We hypothesized that a nutritional intervention based on the Mediterranean diet (MedDiet) would have greater protective effect on diabetic retinopathy and nephropathy than a low-fat control diet.

RESEARCH DESIGN AND METHODS

This was a post hoc analysis of a cohort of patients with type 2 diabetes participating in the PREvención con DIeta MEDiterránea (PREDIMED) study, a multicenter randomized nutritional intervention trial conducted in a population at high cardiovascular risk. Individuals with type 2 diabetes who were free of microvascular complications at enrollment (n = 3,614, aged 55-80 years) were randomly assigned to one of three dietary interventions: MedDiet supplemented with extravirgin olive oil (MedDiet+EVOO), MedDiet supplemented with mixed nuts (MedDiet+Nuts), or a low-fat control diet. Two independent outcomes were considered: new onset of diabetic retinopathy and nephropathy. Hazard ratios (HRs) were calculated using multivariable-adjusted Cox regression.

RESULTS

During a median follow-up of 6.0 years, we identified 74 new cases of retinopathy and 168 of nephropathy. Compared with the control diet, multivariable-adjusted HRs for diabetic retinopathy were 0.56 (95% CI 0.32-0.97) for the MedDiet+EVOO and 0.63 (0.35-1.11) for the MedDiet+Nuts. No between-group differences were found for nephropathy. When the yearly updated information on adherence to the MedDiet was considered, the HR for retinopathy in the highest versus the lowest quintile was 0.34 (0.13-0.89; P = 0.001 for trend). No significant associations were found for nephropathy.

CONCLUSIONS

A MedDiet enriched with EVOO may protect against diabetic retinopathy but not diabetic nephropathy.

Reduction in saturated fat intake for cardiovascular disease

BACKGROUND

Reducing saturated fat reduces serum cholesterol, but effects on other intermediate outcomes may be less clear. Additionally it is unclear whether the energy from saturated fats that are lost in the diet are more helpfully replaced by polyunsaturated fats, monounsaturated fats, carbohydrate or protein. This review is part of a series split from and updating an overarching review.

OBJECTIVES

To assess the effect of reducing saturated fat intake and replacing it with carbohydrate (CHO), polyunsaturated (PUFA) or monounsaturated fat (MUFA) and/or protein on mortality and cardiovascular morbidity, using all available randomised clinical trials.

SEARCH METHODS

We updated our searches of the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid) and EMBASE (Ovid) on 5 March 2014. We also checked references of included studies and reviews.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomised with appropriate control group; 2) intention to reduce saturated fat intake OR intention to alter dietary fats and achieving a reduction in saturated fat; 3) not multifactorial; 4) adult humans with or without cardiovascular disease (but not acutely ill, pregnant or breastfeeding); 5) intervention at least 24 months; 6) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Two review authors working independently extracted participant numbers experiencing health outcomes in each arm, and we performed random-effects meta-analyses, meta-regression, subgrouping, sensitivity analyses and funnel plots.

MAIN RESULTS

We include 15 randomised controlled trials (RCTs) (17 comparisons, ˜59,000 participants), which used a variety of interventions from providing all food to advice on how to reduce saturated fat. The included long-term trials suggested that reducing dietary saturated fat reduced the risk of cardiovascular events by 17% (risk ratio (RR) 0.83; 95% confidence interval (CI) 0.72 to 0.96, 13 comparisons, 53,300 participants of whom 8% had a cardiovascular event, I² 65%, GRADE moderate quality of evidence), but effects on all-cause mortality (RR 0.97; 95% CI 0.90 to 1.05; 12 trials, 55,858 participants) and cardiovascular mortality (RR 0.95; 95% CI 0.80 to 1.12, 12 trials, 53,421 participants) were less clear (both GRADE moderate quality of evidence). There was some evidence that reducing saturated fats reduced the risk of myocardial infarction (fatal and non-fatal, RR 0.90; 95% CI 0.80 to 1.01; 11 trials, 53,167 participants), but evidence for non-fatal myocardial infarction (RR 0.95; 95% CI 0.80 to 1.13; 9 trials, 52,834 participants) was unclear and there were no clear effects on stroke (any stroke, RR 1.00; 95% CI 0.89 to 1.12; 8 trials, 50,952 participants). These relationships did not alter with sensitivity analysis. Subgrouping suggested that the reduction in cardiovascular events was seen in studies that primarily replaced saturated fat calories with polyunsaturated fat, and no effects were seen in studies replacing saturated fat with carbohydrate or protein, but effects in studies replacing with monounsaturated fats were unclear (as we located only one small trial). Subgrouping and meta-regression suggested that the degree of reduction in cardiovascular events was related to the degree of reduction of serum total cholesterol, and there were suggestions of greater protection with greater saturated fat reduction or greater increase in polyunsaturated and monounsaturated fats. There was no evidence of harmful effects of reducing saturated fat intakes on cancer mortality, cancer diagnoses or blood pressure, while there was some evidence of improvements in weight and BMI.

AUTHORS' CONCLUSIONS

The findings of this updated review are suggestive of a small but potentially important reduction in cardiovascular risk on reduction of saturated fat intake. Replacing the energy from saturated fat with polyunsaturated fat appears to be a useful strategy, and replacement with carbohydrate appears less useful, but effects of replacement with monounsaturated fat were unclear due to inclusion of only one small trial. This effect did not appear to alter by study duration, sex or baseline level of cardiovascular risk. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturated fats. The ideal type of unsaturated fat is unclear.

Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies

OBJECTIVE

To investigate the relation between total fat intake and body weight in adults and children.

DESIGN

Systematic review and meta-analysis of randomised controlled trials and cohort studies.

DATA SOURCES

Medline, Embase, CINAHL, and the Cochrane Central Register of Controlled Trials to June 2010.

INCLUSION CRITERIA

Randomised controlled trials and cohort studies of adults or children that compared lower versus usual total fat intake and assessed the effects on measures of body fatness (body weight, body mass index, or waist circumference) after at least six months (randomised controlled trials) or one year (in cohorts). Randomised controlled trials with any intention to reduce weight in participants or confounded by additional medical or lifestyle interventions were excluded.

DATA EXTRACTION

Data were extracted and validity was assessed independently and in duplicate. Random effects meta-analyses, subgroups, sensitivity analyses, and metaregression were done.

RESULTS

33 randomised controlled trials (73,589 participants) and 10 cohort studies were included, all from developed countries. Meta-analysis of data from the trials suggested that diets lower in total fat were associated with lower relative body weight (by 1.6 kg, 95% confidence interval -2.0 to -1.2 kg, I(2)=75%, 57,735 participants). Lower weight gain in the low fat arm compared with the control arm was consistent across trials, but the size of the effect varied. Metaregression suggested that greater reduction in total fat intake and lower baseline fat intake were associated with greater relative weight loss, explaining most of the heterogeneity. The significant effect of a low fat diet on weight was not lost in sensitivity analyses (including removing trials that expended greater time and attention on low fat groups). Lower total fat intake also led to lower body mass index (-0.51 kg/m(2), 95% confidence interval -0.76 to -0.26, nine trials, I(2)=77%) and waist circumference (by 0.3 cm, 95% confidence interval -0.58 to -0.02, 15,671 women, one trial). There was no suggestion of negative effects on other cardiovascular risk factors (lipid levels or blood pressure). GRADE assessment suggested high quality evidence for the relation between total fat intake and body weight in adults. Only one randomised controlled trial and three cohort studies were found in children and young people, but these confirmed a positive relation between total fat intake and weight gain.

CONCLUSIONS

There is high quality, consistent evidence that reduction of total fat intake has been achieved in large numbers of both healthy and at risk trial participants over many years. Lower total fat intake leads to small but statistically significant and clinically meaningful, sustained reductions in body weight in adults in studies with baseline fat intakes of 28-43% of energy intake and durations from six months to over eight years. Evidence supports a similar effect in children and young people.

Examining the role of lipid mediators in diabetic retinopathy

Diabetic retinopathy is the most disabling complication of diabetes, affecting 65% of patients after 10 years of the disease. Current treatment options for diabetic retinopathy are highly invasive and fall short of complete amelioration of the disease. Understanding the pathogenesis of diabetic retinopathy is critical to the development of more effective treatment options. Diabetic hyperglycemia and dyslipidemia are the main metabolic insults that affect retinal degeneration in diabetes. Although the role of hyperglycemia in inducing diabetic retinopathy has been studied in detail, much less attention has been paid to dyslipidemia. Recent clinical studies have demonstrated a strong association between dyslipidemia and development of diabetic retinopathy, highlighting the importance of understanding the exact changes in retinal lipid metabolism in diabetes. This review describes what is known on the role of dyslipidemia in the development of diabetic retinopathy, with a focus on retinal-specific lipid metabolism and its dysregulation in diabetes.

Reduced or modified dietary fat for preventing cardiovascular disease

BACKGROUND

Reduction and modification of dietary fats have differing effects on cardiovascular risk factors (such as serum cholesterol), but their effects on important health outcomes are less clear.

OBJECTIVES

To assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.

SEARCH METHODS

For this review update, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE, were searched through to June 2010. References of Included studies and reviews were also checked.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomised with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) adult humans with or without cardiovascular disease, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Participant numbers experiencing health outcomes in each arm were extracted independently in duplicate and random effects meta-analyses, meta-regression, sub-grouping, sensitivity analyses and funnel plots were performed.

MAIN RESULTS

This updated review suggested that reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14% (RR 0.86, 95% CI 0.77 to 0.96, 24 comparisons, 65,508 participants of whom 7% had a cardiovascular event, I(2) 50%). Subgrouping suggested that this reduction in cardiovascular events was seen in studies of fat modification (not reduction - which related directly to the degree of effect on serum total and LDL cholesterol and triglycerides), of at least two years duration and in studies of men (not of women). There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.Few studies compared reduced with modified fat diets, so direct comparison was not possible.

AUTHORS' CONCLUSIONS

The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.

Reduced or modified dietary fat for preventing cardiovascular disease

BACKGROUND

Reduction and modification of dietary fats have differing effects on cardiovascular risk factors (such as serum cholesterol), but their effects on important health outcomes are less clear.

OBJECTIVES

To assess the effect of reduction and/or modification of dietary fats on mortality, cardiovascular mortality, cardiovascular morbidity and individual outcomes including myocardial infarction, stroke and cancer diagnoses in randomised clinical trials of at least 6 months duration.

SEARCH STRATEGY

For this review update, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE, were searched through to June 2010. References of Included studies and reviews were also checked.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomised with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) adult humans with or without cardiovascular disease, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available.

DATA COLLECTION AND ANALYSIS

Participant numbers experiencing health outcomes in each arm were extracted independently in duplicate and random effects meta-analyses, meta-regression, sub-grouping, sensitivity analyses and funnel plots were performed.

MAIN RESULTS

This updated review suggested that reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14% (RR 0.86, 95% CI 0.77 to 0.96, 24 comparisons, 65,508 participants of whom 7% had a cardiovascular event, I(2) 50%). Subgrouping suggested that this reduction in cardiovascular events was seen in studies of fat modification (not reduction - which related directly to the degree of effect on serum total and LDL cholesterol and triglycerides), of at least two years duration and in studies of men (not of women). There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants). This did not alter with sub-grouping or sensitivity analysis.Few studies compared reduced with modified fat diets, so direct comparison was not possible.

AUTHORS' CONCLUSIONS

The findings are suggestive of a small but potentially important reduction in cardiovascular risk on modification of dietary fat, but not reduction of total fat, in longer trials. Lifestyle advice to all those at risk of cardiovascular disease and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates. The ideal type of unsaturated fat is unclear.

Metabolomics study of diabetic retinopathy using gas chromatography-mass spectrometry: a comparison of stages and subtypes diagnosed by Western and Chinese medicine

Diabetic retinopathy (DR) is a serious microvascular syndrome of diabetes, and is one of the most frequent causes of blindness in the world. It has three progressive stages with complex metabolic deregulations in the holistic system of Western medicine. Chinese medicine classifies DR into two different syndrome types; integrating Western and Chinese medicine to treat DR is a validated therapeutic approach in China. In this research, the systemic metabolite change of DR was investigated from the viewpoint of both Western and Chinese medicine, using metabolomics based on gas chromatography-mass spectrometry. The data revealed both perspectives can reflect the metabolic patterns, development and differentiation of DR, and the data also had good correlation and complementarity in characterizing the process of DR. Potential biomarkers of DR based on the two perspectives indicated the alterative modes of metabolites and metabolic pathways in the disease, e.g. the disturbance in fatty acids, amino acids and glucose, etc. The results showed the usefulness and validity of combining both Western and Chinese medicine to study the subtypes of DR and the mechanisms involved.

Reduced or modified dietary fat for preventing cardiovascular disease

BACKGROUND

Reduction or modification of dietary fat can improve total cholesterol levels, but may also have a variety of effects, both positive and negative, on other cardiovascular risk factors.

OBJECTIVES

The aim of this systematic review was to assess the effect of reduction or modification of dietary fats on total and cardiovascular mortality and cardiovascular morbidity over at least 6 months, using all available randomized clinical trials.

SEARCH STRATEGY

The Cochrane Library, MEDLINE, EMBASE, CAB Abstracts, CVRCT registry and related Cochrane Groups' trial registers were searched through spring 1998, SIGLE to January 1999. Trials known to experts in the field and biographies were included through May 1999.

SELECTION CRITERIA

Trials fulfilled the following criteria: 1) randomized with appropriate control group, 2) intention to reduce or modify fat or cholesterol intake (excluding exclusively omega-3 fat interventions), 3) not multi factorial, 4) healthy adult humans, 5) intervention at least six months, 6) mortality or cardiovascular morbidity data available. Inclusion decisions were duplicated, disagreement resolved by discussion or a third party.

DATA COLLECTION AND ANALYSIS

Rate data were extracted by two independent reviewers and meta-analysis performed using random effects methodology. Meta-regression and funnel plots were used.

MAIN RESULTS

Twenty seven studies were included (40 intervention arms, 30,901 person-years). There was no significant effect on total mortality (rate ratio 0.98, 95% CI 0.86 to 1.12), a trend towards protection form cardiovascular mortality (rate ratio 0.91, 95% CI 0.77 to 1.07), and significant protection from cardiovascular events (rate ratio 0.84, 95% CI 0.72 to 0.99). The latter became non-significant on sensitivity analysis. Trials where participants were involved for more than 2 years showed significant reductions in the rate of cardiovascular events and a suggestion of protection from total mortality. The degree of protection from cardiovascular events appeared similar in high and low risk groups, but was statistically significant only in the former.

REVIEWER'S CONCLUSIONS

The findings are suggestive of a small but potentially important reduction in cardiovascular risk in trials longer than two years. Lifestyle advice to all those at high risk of cardiovascular disease (especially where statins are unavailable or rationed), and to lower risk population groups, should continue to include permanent reduction of dietary saturated fat and partial replacement by unsaturates.

Phospholipid fatty acid composition and vitamin E levels in the retina of obese (fa/fa) and lean (FA/FA) Zucker rats

We have compared the fatty acid composition of the major classes of phospholipids in the retina of lean (FA/FA) and genetically obese (fa/fa) male Zucker rats. In all phospholipid fractions, there was a higher ratio of n-3 to n-6 fatty acids in obese animals whereas the total content of polyunsaturated fatty acids (PUFA) was unaffected by the genotype. Lower percentages of arachidonic acid (20:4(n-6)) were present in the phosphatidylcholine, phosphatidylinositol and phosphatidylserine fractions in the retina of obese rats. This was associated with a higher level of docosahexaenoic acid (22:6(n-3)) in these fractions. In addition, increased levels of dihomo-gamma-linolenic acid (20:3(n-6)) were present in the retinal phosphatidylcholine and phosphatidylethanolamine of obese animals. These results indicate that modifications of phospholipid fatty acid composition which have previously been reported in peripheral tissues of obese Zucker rats also affect the retina. Furthermore, the retinal levels of vitamin E were higher in obese than in lean rats suggesting differences in the tissue antioxidant status between these two genotypes.

Fatty acid composition of platelet phospholipids in non-insulin-dependent diabetics randomized for dietary advice

Two groups of patients with non-insulin-dependent diabetes mellitus (NIDDM), with dietary advice randomized between a low-carbohydrate (LC) diet and a modified-fat (MF) diet, were followed to determine the effect of diet on phospholipid fatty acid composition of platelets and on development of retinopathy in the 7 years following diagnosis. There was a tendency for retinopathy to occur more frequently in those randomized to the LC diet. This difference was not statistically significant, and fatty acid composition of platelets did not differ significantly in those with and without retinopathy. Linoleic acid values from platelet phospholipid fatty acids were significantly higher in NIDDM on an MF diet compared with an LC diet. There was no difference between the two dietary subgroups with respect to platelet arachidonic acid, but this was lower in the whole diabetic population when compared with non-diabetics. The arachidonic acid values correlated with neither glycosylated haemoglobin nor mean glycaemia. Significant correlation between the fatty acid values for platelets and plasma cholesterol esters was found only for 16:0.

Low density lipoprotein cholesterol: an association with the severity of diabetic retinopathy

Diurnal profiles of total and lipoprotein cholesterol and triglycerides were measured in 11 insulin-dependent diabetic subjects without retinopathy, 10 with background and 10 with proliferative retinopathy. The groups were closely matched for age and duration of diabetes. Total cholesterol levels were higher in patients with proliferative (5.6 +/- 0.5 mmol/l) than background (5.1 +/- 0.7 mmol/l) or no retinopathy (4.6 +/- 0.8 mmol/l, trend test; p less than 0.003), due to raised levels of low density lipoprotein (LDL) cholesterol (3.8 +/- 0.9, 3.2 +/- 0.6 and 2.8 +/- 0.8 mmol/l respectively; p less than 0.02). High density lipoprotein (HDL) levels were similar in patients with and without retinopathy and HDL/LDL ratios were lower with more severe retinopathy (p less than 0.025). Cholesterol levels were similar in diabetic subjects without retinopathy and in 12 normal subjects. Triglyceride levels were not related to retinopathy and no measure of plasma lipids correlated with HbA1 or 24-h mean plasma glucose. Total and LDL cholesterol were weakly inversely correlated with creatinine clearance but the association with retinopathy was independent of this effect.