Acute in vivo chylomicron metabolism and postalimentary lipoprotein alterations in normolipidemic male smokers

Best practices for the design, laboratory analysis, and reporting of trials involving fatty acids

Fatty acids are among the most studied nutrients in human metabolism and health. Endogenous fatty acid status influences health and disease via multiple mechanisms at all stages of the life cycle. Despite widespread interest, attempts to summarize the results of multiple studies addressing similar fatty acid-related outcomes via meta-analyses and systematic reviews have been disappointing, largely because of heterogeneity in study design, sampling, and laboratory and data analyses. Our purpose is to recommend best practices for fatty acid clinical nutrition and medical studies. Key issues in study design include judicious choice of sampled endogenous pools for fatty acid analysis, considering relevant physiologic state, duration of intervention and/or observation, consideration of specific fatty acid dynamics to link intake and endogenous concentrations, and interpretation of results with respect to known fatty acid ranges. Key laboratory considerations include proper sample storage, use of sample preparation methods known to be fit-for-purpose via published validation studies, detailed reporting or methods to establish proper fatty acid identification, and quantitative analysis, including calibration of differential response, quality control procedures, and reporting of data on a minimal set of fatty acids to enable comprehensive interpretation. We present a checklist of recommendations for fatty acid best practices to facilitate design, review, and evaluation of studies with the intention of improving study reproducibility.

Metabolic syndrome and gender differences in postprandial lipaemia

BACKGROUND

Postprandial hyperlipidaemia may be a predictor of vascular risk.

DESIGN

We evaluated postprandial lipaemia after an oral fat tolerance test (OFTT) in men (n=41) and women (n=21) with metabolic syndrome (MetS).

METHODS

Triglyceride (TG) levels were measured before and 2, 4, 6 and 8 h after the fat load.

RESULTS

Men showed a greater plasma TG response 8 h after the fat load (284+/-117 versus 224+/-126 mg/dl, P=0.029). Only fasting TG levels significantly predicted the TG area under the curve (AUC) and incremental AUC.

CONCLUSIONS

Men had a more pronounced postprandial hypertriglyceridaemia and seem to have delayed TG clearance.

Effect of cigarette smoking on serum α-tocopherol and the lipid profile in a Portuguese population

BACKGROUND

The present study was conducted to determine the effects of cigarette smoking on the levels of serum alpha-tocopherol and on the lipid profile in humans from the Lisbon population.

METHODS

Serum alpha-tocopherol was evaluated by a reverse-phase HPLC method with UV detection. Enzymatic tests were used for the evaluation of the lipid profile.

RESULTS

Smokers in general and female smokers in particular had decreased alpha-tocopherol levels when compared with nonsmokers. Smokers had also lower HDL cholesterol (HDL-C) contents, but this difference was statistically significant only for females. Regardless of sex, in smokers, there was a positive correlation between alpha-tocopherol and triglyceride (TG) levels. Cluster analysis showed a sex-independent separation between smokers and nonsmokers.

CONCLUSION

These results suggest a different interaction of these blood parameters in smokers versus nonsmokers that should be further investigated.

Vitamin E kinetics in smokers and nonsmokers

Does cigarette smoking increase vitamin E utilization in vivo? A trial was carried out in 6 smokers and 5 nonsmokers of comparable ages and serum lipids. Subjects consumed 75 mg each d(3)-RRR and d(6)-all rac-alpha-tocopheryl acetates (natural and synthetic vitamin E, respectively) daily for 7 d with a standardized breakfast. Fasting blood samples were drawn on days -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 9, 14, 21 (negative days indicate supplementation). In both groups, plasma d(3)-alpha-tocopherol concentrations were approximately double of d(6)-alpha-tocopherol. At day 0, the %d(3) alpha-tocopherols (d(3)-alpha-tocopherol/total-alpha-tocopherol x 100) were similar in both smokers and nonsmokers. Subsequently, there was a trend toward a faster exponential disappearance of the plasma %d(3) alpha-tocopherol in smokers compared with nonsmokers (0.30 +/- 0.04 compared with 0.24 +/- 0.05, p =.0565). The calculated %d(3) half-lives were 55.6 +/- 7.4 h in smokers and 72.1 +/- 17.3 h in nonsmokers (p =.0630). By day 21, the %d(3) in smokers had decreased to 1.4% +/- 0.3% while it was 2.2% +/- 0.7% (p =.0418) in the nonsmokers. These data suggest that smoking increases plasma vitamin E disappearance, but further studies are needed to confirm this finding and to assess its cause.