On average, the weight of chickens fed the control diet increased by 240 g during the four-week trial. In the current study, we found chickens fed a diet supplemented with δ-tocotrienol gained significantly less weight. This finding differs from results of earlier trials demonstrating that diet supplementation with δ-tocotrienol produced either no change, or an increase in weight gain [43, 51]. Quercetin, amiloride, and dexamethasone yielded significantly lower weight gain, whereas riboflavin and (-) Corey lactone had no significant effect on weight gain. Interestingly, combined supplementation consisting of δ-tocotrienol plus either (-) Corey lactone or amiloride significantly increased weight gain; the combination of δ-tocotrienol and quercetin produced a weight gain equal to that of the control. Thus for (-) Corey lactone, amiloride, and quercetin, additional supplementation with δ-tocotrienol appeared to increase weight gains, as compared to dietary supplementation with each of these compounds alone. The addition of δ-tocotrienol to riboflavin did not improve weight gains compared to dietary supplementation with riboflavin alone. As reported elsewhere, dietary supplementation with dexamethasone markedly reduced weight gain compared to control [59, 60], and this detrimental effect was enhanced by combining dexamethasone with δ-tocotrienol.
Histological examination demonstrated decreased inflammation in livers from chickens receiving individual treatments. Treatments combining δ-tocotrienol with either riboflavin, (-) Corey lactone, or amiloride yielded further decreases in hepatic inflammation and fatty infiltration. On the other hand δ-tocotrienol potentiated the toxic impact of dexamethasone. Dexamethasone toxicity, previously demonstrated in rats, was manifested by impaired growth, enlarged livers, and elevated serum total cholesterol and triglyceride levels [59–61].
All predictors of cardiovascular risk evaluated in this study were substantially decreased by all compounds with the exception of dexamethasone. Summarizing the overall effects of the individual compound on the five serum factors under consideration (TNF-α, NO, total cholesterol, LDL-cholesterol, and triglyceride) leads to the conclusion that the cumulative risk of atherosclerosis is reduced effectively by δ-tocotrienol, quercetin, riboflavin, and (-) Corey lactone.
Serum TNF-α levels of chickens receiving each of the compounds were uniformly lower than those recorded for chickens fed the control diet. Serum levels of TNF-α of chickens treated with δ-tocotrienol, quercetin, riboflavin, and (-) Corey lactone were reduced by approximately 80%. Serum TNF-α levels of chickens treated with dexamethasone and amiloride were reduced by approximately 41% and 70%, respectively. These findings are consistent with prior reports of the effects riboflavin [62–64], quercetin [5, 9, 10, 65], δ-tocotrienol [15–17], amiloride  and dexamethasone in vitro[9, 10, 15–17, 21] and in vivo[62–64] on TNF-α level.
δ-Tocotrienol produced a 45% reduction in the serum NO level. Quercetin, riboflavin, (-) Corey lactone, amiloride, and dexamethasone reduced serum NO levels by 14%, 14%, 31%, 25%, and 67%, respectively. Quercetin has been reported to down-regulate inducible-NO synthase (iNOS) activity in vitro[5–10, 68], and riboflavin, delivered by injection or infusion, inhibits NO synthesis and the concomitant increases in serum NO level in LPS-challenged mice [62–64]. Perhaps the most important result of the present study is the finding that combining δ-tocotrienol with other dietary supplements enhances suppression of serum NO and TNF-α levels, as compared to single compound supplementation; these results are particularly striking for NO level. Although, reduction of serum NO level with δ-tocotrienol alone closely resembles the reductions of δ-tocotrienol combined with other compounds, which may be due to maximal attenuations achieved with a dose of δ-tocotrienol (50 ppm) used in the present study. In our earlier dose-response study of δ-tocotrienol effects on the serum levels of total cholesterol and LDL-cholesterol in chickens, the maximum effective dose was found to be 200 ppm (51). Therefore, a minimum effective dose of 50 ppm was selected for the present study. This is the first report that describes the effects of δ-tocotrienol for avian pro-inflammatory markers (TNF-α and NO), which is consistent with findings that δ-tocotrienol is very potent anti-inflammatory compound as reported recently (47), and it is possible a lower dosage (10 or 20 ppm) of δ-tocotrienol may potentiate the anti-inflammatory actions of quercetin, riboflavin and (-) Corey lactone.
All treatments, except those involving dexamethasone, resulted in significantly lower serum total cholesterol, LDL-cholesterol and triglyceride levels. The effects of δ-tocotrienol and (-) Corey lactone on serum levels of total and LDL-cholesterol were significantly greater than those of the other compounds (Figures 5, 6, 8). Our current study appears to be the first observation of the cholesterol-lowering impact of (-) Corey lactone. δ-Tocotrienol is widely reported to effectively suppress HMG-CoA reductase activity and concomitantly lower serum total cholesterol and LDL-cholesterol levels [30–34, 40–43, 69, 70]. Quercetin suppresses HMG-CoA reductase activity in vitro and in vivo, and dietary intake of quercetin has been inversely correlated with total cholesterol and LDL-cholesterol levels in Japanese women . Cholesterol levels in an elderly population were inversely correlated with serum riboflavin levels . Thus, our findings that quercetin, and more potently, riboflavin lowered serum cholesterol levels are supported by the literature [72–74]. We also found that diet supplementation with amiloride, an FDA approved diuretic, was least effective in reducing total cholesterol level (9%). This finding is somewhat similar to results of a human study which showed that serum total cholesterol levels were not altered in subjects receiving amiloride concomitantly with hydrochlorothiazide . Amiloride also failed to impact serum levels of cardioprotective HDL-cholesterol in the current study. HDL-cholesterol levels in chickens receiving quercetin, riboflavin or (-) Corey lactone were modestly reduced. Combining δ-tocotrienol with these compounds failed to raise HDL-cholesterol. On the other hand, the anti-inflammatory compound, dexamethasone, dramatically increased serum HDL-cholesterol level.
All compounds other than dexamethasone resulted in a significant lowering of serum triglyceride levels (Figure 8). The additive effect of combining δ-tocotrienol with another compound, with the exception of amiloride, on serum triglyceride was insignificant (Figure 8).
A recent report points to the superiority of the HDL-cholesterol/total cholesterol (HDL-chol/TC) ratio for monitoring cardiovascular risk compared to serum total cholesterol and LDL-cholesterol levels . With the exceptions of those incorporating dexamethasone, all treatments resulted in higher HDL-chol/TC ratios than that calculated for the control group (0.51). Within the individual treatment group δ-tocotrienol (0.65; 127%), riboflavin (0.61, 120%), (-) Corey lactone (0.68, 133%) appear to be most effective in improving the ratios. The ratio calculated for δ-tocotrienol + quercetin (0.65, 127%) was modestly improved relative to that calculated for the quercetin group (0.56, 110%). These modest improvements were also observed by δ-tocotrienol combination with riboflavin (129%), and (-) Corey lactone (145%), without improving amiloride or dexamethasone ratios. In addition to the potential ability of quercetin, to reduce the cumulative serum risk factors for cardiovascular disease (total cholesterol, LDL-cholesterol, triglyceride, NO and TNF-α levels) we found exceptional risk-reducing value in two vitamins, δ-tocotrienol (a member of the vitamin E group; Figure 1), and riboflavin when fed at levels 4- and 10-times higher, respectively, than those normally found in commercial chicken feed. Based on the data presented in this study, it is reasonable to propose that supplementing a 2500 kcal diet with 40 mg of either vitamin (i.e. δ-tocotrienol or riboflavin) could be potentially beneficial in reducing cardiovascular disease risk in humans.
Microarray analyses of liver samples identified 62 genes whose expression was up-regulated (39 genes) or down-regulated (23 genes) by all compounds suggesting common impact on serum levels of TNF-α, NO, and lipid parameters. The most important up-regulated gene expression modulated by these compounds were associated with cytokine signaling, NFκB and ubiquitin protein lipase (inflammation), heat shock protein, RIKEN cDNA, T cell receptor gamma (ageing), FAS, myosin, squalene epoxidase, NADH dehydrogenase, Prostaglandin D (cardiovascular disease), and RAN, member RAS oncogene family (cancer). The down-regulated genes were associated with proteasome, tumor necrosis factor (inflammation), carnitine palmitoyltransferase1A (ageing), glycogen synthase kinase, glutathione S-transferase (cardiovascular disease), and Jun oncogene (cancer) as reported earlier [76–80]. The microarray array analyses further identified several other genes whose expression was differentially impacted by the compounds shown to lower serum lipid levels and dexamethasone, associated with markedly elevated serum lipids.