Intake of polyunsaturated fat in relation to mortality among statin users and non-users in the Southern Community Cohort Study

A Description of Risk Factors for Non-alcoholic Fatty Liver Disease in the Southern Community Cohort Study: A Nested Case-Control Study

Background: Non-alcoholic fatty liver disease (NAFLD) is associated with obesity and hypercholesterolemia. In addition, total fat and folate intake have been associated with NAFLD.

Aims: We investigated risk factors for NAFLD among individuals of largely low socioeconomic status, and whether these associations differed by race.

Methods: A nested case-control study was conducted within the Southern Community Cohort Study. Through linkage of the cohort with Centers for Medicare and Medicaid Services, International Classification of Diseases, Ninth Revision, Clinical Modification codes were used to identify incident NAFLD cases. Controls were matched 4:1 to cases on enrollment age, sex, and race. A logistic regression was used to estimate odds ratios for the associations of NAFLD with covariates of interest.

Results: Neither total fat nor folate intake was significantly associated with NAFLD. Hypercholesterolemia (odds ratio 1.21) and body mass index (75th vs. 25th percentile) for blacks (odds ratio 1.96) and whites (odds ratio 2.33) were associated with an increased risk of non-alcoholic fatty liver disease. No significant interaction with race for any of the studied variables was noted.

Conclusions: Both hypercholesterolemia and increasing body mass index, but not total fat and folate intake, were risk factors for NAFLD in the Southern Community Cohort Study.

The Role of n-3 Long Chain Polyunsaturated Fatty Acids in Cardiovascular Disease Prevention, and Interactions with Statins

Decreases in global cardiovascular disease (CVD) mortality and morbidity in recent decades can be partly attributed to cholesterol reduction through statin use. n-3 long chain polyunsaturated fatty acids are recommended by some authorities for primary and secondary CVD prevention, and for triglyceride reduction. The residual risk of CVD that remains after statin therapy may potentially be reduced by n-3 long chain polyunsaturated fatty acids. However, the effects of concomitant use of statins and n-3 long chain polyunsaturated fatty acids are not well understood. Pleiotropic effects of statins and n-3 long chain polyunsaturated fatty acids overlap. For example, cytochrome P450 enzymes that metabolize statins may affect n-3 long chain polyunsaturated fatty acid metabolism and vice versa. Clinical and mechanistic study results show both synergistic and antagonistic effects of statins and n-3 long chain polyunsaturated fatty acids when used in combination.

Race- and Sex-related Differences in Nephrolithiasis Risk Among Blacks and Whites in the Southern Community Cohort Study

OBJECTIVE

To investigate race-sex associations with risk among whites and blacks in the southeastern United States. The relationship between race, sex, and kidney stone risk is poorly understood.

METHODS

Participants were 42,136 black and white adults enrolled in the Southern Community Cohort Study between 2002 and 2009, with no history of kidney stones and receiving Medicare or Medicaid services. Incident kidney stone diagnoses through December 2014 were determined via linkage with Centers for Medicare and Medicaid Services research files. Hazard ratios (HRs) for associations with race and sex were computed from multivariable Cox proportional hazards models adjusting for baseline characteristics, comorbid diseases, and dietary intakes.

RESULTS

During 116,931 and 270,917 person-years of follow-up for whites and blacks, respectively, age-adjusted incidence rates (95% confidence interval [CI]) were 5.98 (4.73-7.23) and 4.50 (3.86-5.14) per 1000 person-years for white men and women, respectively, while corresponding rates among blacks were 2.19 (1.71-2.67) and 2.47 (2.19-2.75) per 1000 person-years. Risk was higher among whites compared to blacks (HR = 2.23, 95% CI 1.97-2.53). Male sex was significantly associated with risk among whites (HR = 1.45, 95% CI 1.20-1.75), but not among blacks (HR = 0.90, 95% CI 0.75-1.07). Formal tests of interaction by race and sex were statistically significant for all models (P = .01 for fully adjusted model).

CONCLUSION

The association of incident kidney stones with sex differs between whites and blacks. White men have the highest risk, while no difference in risk is observed between black men and women.

Docosahexaenoic acid regulates vascular endothelial cell function and prevents cardiovascular disease

Docosahexaenoic acid (DHA) is present in high concentrations in salmon, herring, and trout. Epidemiologic studies have shown that high dietary consumption of these and other oily fish is associated with reduced rates of myocardial infarction, atherosclerosis, and other ischemic pathologies. Atherosclerosis is induced by inflammation and can lead to acute cardiovascular events and extensive plaque. DHA inhibits the development of inflammation in endothelial cells, alters the function and regulation of vascular biomarkers, and reduces cardiovascular risk. It also affects vascular relaxation and constriction by controlling nitric oxide and endothelin 1 production in endothelial cells. DHA also contributes to the prevention of arteriosclerosis by regulating the expression of oxidized low density lipoprotein receptor 1, plasminogen activator inhibitor 1, thromboxane A2 receptor, and adhesion molecules such as vascular cell adhesion molecule-1, monocyte chemoattractant protein-1, and intercellular adhesion molecule 1 in endothelial cells. Recent research showed that DHA reduces the increase in adhesion factor expression induced by lipopolysaccharide by suppressing toll-like receptor 4. A new mechanism of action of DHA has been described that is mediated through endothelial free fatty acid receptor 4, associated with heme oxygenase 1 induction by Nrf2. However, the efficacy and mechanisms of action of DHA in cardiovascular disease prevention are not yet completely understood. The aim of this paper was to review the effects of DHA on vascular endothelial cells and recent findings on their potential for the prevention of circulatory diseases.

The effect of replacing saturated fat with mostly n-6 polyunsaturated fat on coronary heart disease: a meta-analysis of randomised controlled trials

BACKGROUND

A cornerstone of conventional dietary advice is the recommendation to replace saturated fatty acids (SFA) with mostly n-6 polyunsaturated fatty acids (PUFA) to reduce the risk of coronary heart disease (CHD). Many clinical trials aimed to test this advice and have had their results pooled in several meta-analyses. However, earlier meta-analyses did not sufficiently account for major confounding variables that were present in some of those trials. Therefore, the aim of the study was to account for the major confounding variables in the diet heart trials, and emphasise the results from those trials that most accurately test the effect of replacing SFA with mostly n-6 PUFA.

DESIGN

Clinical trials were identified from earlier meta-analyses. Relevant trials were categorised as 'adequately controlled' or 'inadequately controlled' depending on whether there were substantial dietary or non-dietary differences between the experimental and control groups that were not related to SFA or mostly n-6 PUFA intake, then were subject to different subgroup analyses.

RESULTS

When pooling results from only the adequately controlled trials there was no effect for major CHD events (RR = 1.06, CI = 0.86-1.31), total CHD events (RR = 1.02, CI = 0.84-1.23), CHD mortality (RR = 1.13, CI = 0.91-1.40) and total mortality (RR = 1.07, CI = 0.90-1.26). Whereas, the pooled results from all trials, including the inadequately controlled trials, suggested that replacing SFA with mostly n-6 PUFA would significantly reduce the risk of total CHD events (RR = 0.80, CI = 0.65-0.98, P = 0.03), but not major CHD events (RR = 0.87, CI = 0.70-1.07), CHD mortality (RR = 0.90, CI = 0.70-1.17) and total mortality (RR = 1.00, CI = 0.90-1.10).

CONCLUSION

Available evidence from adequately controlled randomised controlled trials suggest replacing SFA with mostly n-6 PUFA is unlikely to reduce CHD events, CHD mortality or total mortality. The suggestion of benefits reported in earlier meta-analyses is due to the inclusion of inadequately controlled trials. These findings have implications for current dietary recommendations.

Dietary polyunsaturated fatty acids and incidence of end-stage renal disease in the Southern Community Cohort Study

BACKGROUND

Whether polyunsaturated fatty acids (PUFA) are associated with end-stage renal disease (ESRD) in populations with a high burden of risk factors for kidney disease is unknown. We sought to determine whether PUFA intake is associated with ESRD.

METHODS

We conducted a nested case-control study of ESRD within the Southern Community Cohort Study (SCCS), a prospective cohort of low-income blacks and whites in the southeastern US (2002-2009). Through 2012, 1,074 incident ESRD cases were identified by linkage with the United States Renal Data System and matched to 3,230 controls by age, sex and race. Dietary intake of total, n-3 or n-6 PUFA was assessed from a validated food frequency questionnaire administered at baseline. Odds ratios (ORs) and 95 % confidence intervals (CIs) were computed from logistic regression models that included matching variables, body mass index, smoking, diabetes, hypertension, education, income, total energy intake and percent energy from protein and saturated fat.

RESULTS

The mean (SD) age of participants was 55 (9) years. Most participants were women (55 %), black (87 %), with hypertension (67 %) and on average obtained 8 % of their energy from PUFA. Higher PUFA intake was marginally associated with a lower risk of ESRD in adjusted analyses. The adjusted odds ratios (95 % confidence intervals) for ESRD for the 5th vs. 1st quintile of PUFA were 0.79 (0.60-1.05; P trend = 0.06) for total PUFA, 0.81 (0.61-1.06; P trend = 0.04) for n-6 PUFA and 0.93 (0.71-1.21; P trend = 0.45) for n-3 PUFA.

CONCLUSIONS

We observed a marginally significant inverse trend between dietary PUFA intake and ESRD incidence, mainly driven by n-6 fatty acid intake. Our findings require replication but suggest that a diet rich in n-6 PUFA may prevent ESRD development in a population with a high burden of kidney disease risk factors.