It suggested that administration of KO caused significant change in body weight and the KO had good weight lose effect similar to the lipid-reducing medicine. It has also been reported that different types of fatty acids have different effects on body weight gain and insulin resistance. Saturated fatty acids (SFAs) produce more weight gain and insulin resistance than polyunsaturated fatty acids (PUFAs) in some studies [15
]. Of all the PUFAs, EPA and DHA exert more favorable influence on body weight [17
]. It was reported body weight of the diet group supplement with fish oil increased by 25% [18
]. Fatty acids derived from fish oil had been shown to alter proinflammatory cytokine production and acute-phase protein (APP) synthesis in vitro. The presence of APP has been suggested to contribute to weight loss. The administration of PUFAs to hepatocytes had suggested that EPA may have direct effects on the modulation of APP production [19
]. The mechanism of the KO used in the present study and the relative contributions of its components requires further study.
The present study proved that KO could significantly decrease the TC, TG and LDL-C levels of serum, while slightly increase the HDL-C levels as well. It was reported the long-term intake of egg-white hydrolysed (hEW) for 20 weeks had a lowering effect on TG and TC, while no changes were observed in HDL-C [20
]. It was also found that some natural active substances could significantly decrease the TC, TG and LDL-C levels, but there were no significance in HDL-C [21
]. A great deal of findings indicated that EPA and DHA could reduce body blood TG, TC and LDL-C. It had been reported that fish oil had cholesterol-lowering effect because it increased DHA content in the membrane and could improve membrane fluidity. Thus, it increased removal rate of VLDL-C and LDL-C particles from plasma by improving hepatic microsomal membrane fluidity, and thus, it decreased the TG, TC, LDL-C significantly. But it didn't increase the HDL-C level. Unlike fish oil and KO, corn oil significantly increased plasma HDL-C levels and reduced the risk factor for CVD since HDL-C had the important role of reversing cholesterol transport [23
]. The reason may be the difference of various food composition, operation mechanism, or different animal study itself (great individual differences), the complex of metabolism of HDL-C and so on.
As far as we know, this is the first report showing the anti-cancer effect of KO on human colon cancer cells. However, more detailed studies are required to determine the exact mechanism(s). KO contains four constituents which may reduce the risk of developing the colon cancer: EPA, DHA, ALA, sphingolipid. Many reports indicated that EPA and DHA could inhibit the growth of some cancer cells, such as breast, prostate cancer [24
]and so on. Fish oil was known to reduce growth of certain tumors, such as colon, breast and prostate cancers [26
]. These effects were attributed to the content of PUFAs of the n-3 family in fish oil, in particular EPA and DHA, which regulate cellular signaling paths. Several PUFAs are known regulators of the ligand-activated transcription factors known as peroxisome proliferators-activated receptors (PPARs) [27
]. Originally implicated in the regulation of lipid metabolism and adipocyte differentiation, the PPARs have also been implicated in cell differentiation, cell proliferation, and in inflammatory responses [5
]. However, the mechanism(s) underlying of the anti-cancer effects were not fully understood. ALA alters the fatty acid composition of cell membranes in crucial ways and inhibits the release of pro-inflammatory eicosanoids, which control the growth and invasiveness of tumor cells and modulate the cycle of cell apoptosis among the many factors [28
As was known, sphingomyelin which existed in cell plasma membrane of most mammalian was the main component of myelin sheath. It was rich in cell membrane of brain and nerve. Several studies had demonstrated altered total sphingolipid composition, both increases and decreases, in cancer cells. It is unclear what effect changes in sphingolipid composition and metabolism(s) have on the sensitivity of cancer cells to therapy. It was reported that dietary sphingomyelin protected against apoptosis and hyperproliferation caused by the hydrophobic bile salt deoxycholate potential implications for colon cancer. They thought the use of sphingomyelin to boost the chemotherapy response of cancer cells could have a significant impact on treatment outcome [29
]. Numerous epidemiologic studies have provided a gist for the development cancer chemoprevention protocols using bio-active dietary agents capable of eliminating pre-malignant or malignant cells. The results of this study suggested KO had the potential to affect the steady state cell population.