Meta-regression analysis of the effect of trans fatty acids on low-density lipoprotein cholesterol

New research development on trans fatty acids in food: Biological effects, analytical methods, formation mechanism, and mitigating measures

The trans fatty acids (TFAs) in food are mainly generated from the ruminant animals (meat and milk) and processed oil or oil products. Excessive intake of TFAs (>1% of total energy intake) caused more than 500,000 deaths from coronary heart disease and increased heart disease risk by 21% and mortality by 28% around the world annually, which will be eliminated in industrially-produced trans fat from the global food supply by 2023. Herein, we aim to provide a comprehensive overview of the biological effects, analytical methods, formation and mitigation measures of TFAs in food. Especially, the research progress on the rapid, easy-to-use, and newly validated analytical methods, new formation mechanism, kinetics, possible mitigation mechanism, and new or improved mitigation measures are highlighted. We also offer perspectives on the challenges, opportunities, and new directions for future development, which will contribute to the advances in TFAs research.

High-fat diets containing different types of fatty acids modulate gut-brain axis in obese mice

Background

Excessive consumption of high-fat diets is associated with disordered metabolic responses, which may lead to chronic diseases. High-fat diets containing different types of fatty acids lead to distinct alterations in metabolic responses of gut-brain axis.

Methods

In our study, normal male C57BL/6J mice were fed to multiple high fatty acid diets (long-chain and medium-chain saturated fatty acid, LCSFA and MCSFA group; n-3 and n-6 polyunsaturated fatty acid, n-3 and n-6 PUFA group; monounsaturated fatty acid, MUFA group; trans fatty acid, TFA group) and a basic diet (control, CON group) for 19 weeks. To investigate the effects of high-fat diets on metabolic responses of gut-brain axis in obese mice, blood lipids were detected by fast gas chromatography, and related proteins in brain and intestine were detected using Western blotting, ELISA, and immunochemistry analysis.

Results

All high-fat diets regardless of their fatty acid composition induced obesity, lipid disorders, intestinal barrier dysfunction, and changes in gut-brain axis related factors except basal diet in mice. For example, the protein expression of zonula occludens-1 (ZO-1) in ileum in the n-3 PUFA group was higher than that in the MCSFA group (P < 0.05). The expressions of insulin in hippocampus and leptin in ileum in the MCSFA group significantly increased, compared with other groups (all Ps < 0.05).

Conclusion

The high MCSFA diet had the most effect on metabolic disorders in gut-brain axis, but the high n-3 PUFA diet had the least effect on changes in metabolism.

Elaidate, a trans fatty acid, suppresses insulin signaling for glucose uptake in a manner distinct from that of stearate

The dietary intake of elaidate (elaidic acid), a trans-fatty acid, is associated with the development of various diseases. Since elaidate is a C18 unsaturated fatty acid with a steric structure similar to that of a C18 saturated fatty acid (stearate), we previously revealed that insulin-dependent glucose uptake was impaired in adipocytes exposed to elaidate prior to and during differentiation similar to stearate. However, it is still unknown whether the mechanism of impairment of insulin-dependent glucose uptake due to elaidate is similar to that of stearate. Here, we indicate that persistent exposure to elaidate has particular effects on insulin signaling and GLUT4 dynamics. Insulin-induced accumulation of Akt at the plasma membrane (PM) and elevations of phosphorylated Akt and AS160 levels in whole cells were suppressed in adipocytes persistently exposed to 50 μM elaidate. Interestingly, persistent exposure to the same concentration of stearate has no effect on the phosphorylated Akt and AS160 levels. When cells were exposed to these fatty acids, elaidate suppressed insulin-induced fusion, but not translocation, of GLUT4 storage vesicles in the PM, whereas stearate did not suppress the fusion and translocation of GLUT4 storage, indicating that elaidate has suppressive effects on the accumulation of Akt and fusion of GLUT4 storage vesicles and that both elaidate and stearate vary in the mechanisms by which they impair insulin-dependent glucose uptake.

Dietary treatment to lower cholesterol and triglyceride and reduce cardiovascular risk

PURPOSE OF REVIEW

To provide an update on dietary measures to lower levels of LDL-C and triglyceride and reduce cardiovascular (CVD) outcomes.

RECENT FINDINGS

Fifty-year follow-up in the Seven Countries Study confirmed that cholesterol levels correlate with saturated fat intake and all-cause mortality and age at death. In the PURE study, refined carbohydrate increased CVD risk whereas saturated fat did not despite increasing LDL-C levels; limitations are discussed. Reports on CVD risk with eggs provide conflicting results. Plant-based diets with healthful complex carbohydrates reduced CVD. The REDUCE-IT trial lowered triglyceride 21.6% and reduced CVD events 26.1% with an omega-3 fatty acid, An omega-3 fatty acid index at least 4% with EPA and docosahexaenoic acid prevented coronary plaque progression. A clinician guide to counsel patients on nutrition and heart healthy diets was recently published.

SUMMARY

Based on the evidence, individuals should continue to minimize saturated fats and refined carbohydrates, eliminate trans-fat and increase fruits, vegetables, whole grains, low-fat dairy, and fish or other omega-3 fatty acids. Adhering to a Mediterranean diet is strongly recommended because of lowering CVD and total mortality. High-dose omega-3 fatty acids lower triglyceride, reduce CVD and prevent coronary plaque progression.

Probabilistic Quantitative Assessment of Coronary Heart Disease Risk From Dietary Exposure to Industrially Produced Trans-Fatty Acids in Partially Hydrogenated Oils

We conducted a probabilistic evaluation of changes in coronary heart disease (CHD) risk and public health burdens from industrially produced trans-fatty acids (IP-TFAs) exposure from the uses of partially hydrogenated oils in food. Our analyses used four quantitative methods based on human studies considering the uncertainty associated with risk parameters for CHD and IP-TFA daily dietary exposure of 0.05% of energy. Method 1 used experimental controlled feeding trial data for changes in low-density lipoprotein cholesterol; Method 2 used changes in both low-density lipoprotein cholesterol and high-density lipoprotein cholesterol; Method 3 used changes in a combination of three emerging CHD risk factor biomarkers; and method 4 used prospective observational studies of CHD cases associated with long-term dietary exposure of trans-fatty acids. We estimated mean percent changes in CHD risk and annual CHD cases in U.S. adults, with lower and upper 95% uncertainty intervals. Our results show that consuming 0.05% of energy from IP-TFA, instead of cis-monounsaturated fatty acids, can cause annual mean increases in CHD cases of 814 (510–1151, method 1), 1502 (990–2043, method 2), or 6877 (3611–10 694, method 4) in U.S. adults. Results for method 3 were intermediate between those for methods 2 and 4. Sensitivity analyses using alternate risk parameters or an alternate exposure scenario resulted in minor changes in public health burden estimates. The results demonstrate that IP-TFA exposure as low as 0.05% of energy from partially hydrogenated oil uses in food can cause substantial public health burdens in the United States from increased CHD risk.

Comparison of plasma levels of different species of trans fatty acids in Japanese male patients with acute coronary syndrome versus healthy men

BACKGROUND AND AIMS

It remains unclear how trans fatty acid (TFA) at low-level intake affect lipid levels and the development of acute coronary syndrome (ACS). The study aimed to investigate how plasma TFA composition differs between male patients with ACS and healthy men.

METHODS

Plasma fatty acid (FA) composition (as determined by gas chromatography) was analyzed in ACS patients on hospital admission and compared to that of age-adjusted healthy men.

RESULTS

Total FA and TFA levels were similar between ACS and control subjects. Palmitelaidic acid, ruminant-derived TFA (R-TFA), levels were lower in ACS patients (0.17 ± 0.06 vs. 0.20 ± 0.06 of total FA, in ACS and control, respectively, p<0.01), and were significantly directly associated with HDL cholesterol (HDL-C) (rho = 0.269) and n-3 polyunsaturated FA (n-3 PUFA) (rho = 0.442). Linoleic trans isomers (total C18:2 TFA), primary industrially-produced TFA (IP-TFAs), were significantly higher in ACS patients (0.68 ± 0.17 vs. 0.60 ± 0.20 of total FA, in ACS and control, respectively). Total trans-C18:1 isomers were comparable between ACS and control. Differences between ACS and controls in C18:1 trans varied by specific C18:1 trans species. Absolute concentrations of trans-C18:2 isomers were significantly directly associated with LDL-C and non-HDL-C in ACS men. The ACS patients showed significantly lower levels of both n-6 and n-3 PUFA (i.e., eicosapentaenoic, docosahexaenoic and arachidonic acids).

CONCLUSIONS

There were several case-control differences in specific TFA that could potential affect risk for ACS. Japanese ACS patients, especially middle-aged patients, may consume less R-TFA.

Meta-regression analysis of the effects of dietary cholesterol intake on LDL and HDL cholesterol

Background

Elevated low-density lipoprotein (LDL) cholesterol is a major risk factor for cardiovascular disease. Dietary guidance recommends reducing saturated fatty acid, trans fatty acid, and cholesterol intakes to reduce circulating LDL cholesterol. Cholesterol intake may also affect high-density lipoprotein (HDL)-cholesterol concentrations, but its impact has not been fully quantified.

Objectives

The aims of this study were to investigate the dose-response relation between changes in dietary cholesterol intake and changes in lipoprotein-cholesterol markers for cardiovascular disease risk and to provide a reference for clinicians on how changes in dietary cholesterol intake affect circulating cholesterol concentrations, after accounting for intakes of fatty acids.

Methods

We used a Bayesian approach to meta-regression analysis, which uses Markov chain Monte Carlo techniques, to assess the relation between the change in dietary cholesterol (adjusted for dietary fatty acids) and changes in LDL and HDL cholesterol based on the use of data from randomized dietary intervention trials.

Results

Fifty-five studies (2652 subjects) were included in the analysis. The nonlinear Michaelis-Menten (MM) and Hill models best described the data across the full spectrum of dietary cholesterol changes studied (0-1500 mg/d). Mean predicted changes in LDL cholesterol for an increase of 100 mg dietary cholesterol/d were 1.90, 4.46, and 4.58 mg/dL for the linear, nonlinear MM, and Hill models, respectively.

Conclusions

The change in dietary cholesterol was positively associated with the change in LDL-cholesterol concentration. The linear and MM models indicate that the change in dietary cholesterol is modestly inversely related to the change in circulating HDL-cholesterol concentrations in men but is positively related in women. The clinical implications of HDL-cholesterol changes associated with dietary cholesterol remain uncertain.

Existing Regulatory Approaches to Reducing Exposures to Chemical- and Product-Based Risk and Their Applicability to Diet-Related Chronic Disease

We aimed to identify and categorize the types of policies that have been adopted to protect Americans from harmful exposures that could also be relevant for addressing diet-related chronic diseases. This article examines and categorizes the rationales behind government regulation. Our interest in the historical analysis is to inform judgments about how best to address newly emergent risks involving diet-related chronic disease within existing regulatory and information-based frameworks. We assessed exemplars of regulation with respect to harmful exposures from air, water, and food, as well as regulations that are intended to modify voluntary behaviors. Following the comparative analysis, we explored how exposures that lead to diet-related chronic diseases among the general population fit within models of regulation adopted for other comparable risks. We identified five rationales and five approaches that protect people from harmful exposures. Reasons for regulation include: protection from involuntary exposure to risk, high risk of death or chronic illness, ubiquity of risk, counteraction to limit compulsive behaviors, and promotion of population health. Regulatory approaches include: mandatory limits on use, mandatory limits on exposure, mandatory controls on quality, mandatory labeling, and voluntary guidance. In contrast to the use of mandates, the prevention of diet-related chronic diseases thus far has largely relied on information-only approaches and voluntary adoption of guidelines. There is ample precedent for mandatory regulatory approaches that could address harms related to exposure to unhealthy diets, but several barriers to action would need to be overcome.

Biological effects of trans fatty acids and their possible roles in the lipid rafts in apoptosis regulation

A large number of recent studies are focused on evaluating the mechanism of action of trans fatty acids (TFAs) on the progression of apoptosis. A strong positive association has been reported between TFA and coronary heart disease (CHD), obesity and nonalcoholic steatohepatitis and so on. The present study reviewed the biological effects of trans fatty acids (TFA) and their possible roles in lipid rafts in regulating apoptosis. The following aspects of TFA were included: the research about TFA and diseases affecting serum lipid levels, inducing system inflammation and immune response, and the correlation between TFA and apoptosis. The primary purpose of the review article was to comprehensively evaluate the potential correlation between lipid rafts and apoptosis induced by different structures of TFA and provide some new research progress and future directions about it.