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In this analysis, we showed that the phytosterols campesterol and sitosterol, the nonphytosterol cholestanol, and total biomarker absorption sterols were progressively lower in the OIR than in the LIR participants and in the LIR than in the LIS participants. These results suggest diminished cholesterol absorption with increasing insulin resistance and obesity. We previously showed that the LIR and OIR participants had one-third to one-half the rise in LDL cholesterol, respectively after consuming 4 eggs daily for 1 mo than did the LIS participants (). A similar effect, a diminished effect of feeding or restricting dietary cholesterol in obesity, was seen previously in ≥10 studies (see reference for a review), beginning with Bronsgeest-Shoute et al () and Beynen and Katan (). The novelty of our current findings was the finding that cholesterol absorption markers were lower, whereas cholesterol synthesis markers were higher in this cohort of insulin-resistant participants who had one-third to one-half the rise in LDL cholesterol with egg feeding.
Additionally, LDL is required for the transport of cholesterol, which is used to synthesize steroidal hormones such as pregnenolone, cortisol, DHEA, estrogen and testosterone.
Cholesterol Biosynthesis Regulation
Apart from processing technique, variability may reflect the differences in the growing season of the oilseed plant source. Some plant characteristics are affected by season of harvest. All the oil sample brands used for the study showed that the concentration of cholesterol depends on the sensitivity of the method. While the Libermann-Burchard method gave the highest cholesterol values, followed by Ojiako and Akubugwo, the HPLC method however, shows that only Lesieur and coconut oil brands have no cholesterol. The HPLC, due to its sensitivity confirms that there is really no cholesterol free oil in our markets as advertised. It is pertinent that oil producers and marketers should label their products correctly with the quantity of cholesterol in the oil brand no matter how minute the quantity therein. It is then left to the consumers to make up their minds which oil brand satisfies their culinary needs.
The inborn errors of cholesterol synthesis are an interesting ..
We previously reported that feeding 4 eggs daily for 1 mo was associated with a 2–3-fold greater rise in LDL cholesterol in LIS participants than in LIR and OIR participants, respectively (). These observations suggest that LIR and OIR participants had less cholesterol absorption than did LIS participants. However, LIR and OIR participants had higher baseline concentrations of LDL cholesterol and non-HDL cholesterol than did LIS participants, which suggested higher cholesterol synthesis. Similarly, the rise in HDL cholesterol with egg feeding was also less in LIR and OIR than in LIS participants, which points to a common effect of cholesterol absorption on lipoproteins (, ).
and decreased cholesterol synthesis.
We used these measures of cholesterol-related sterols in a subset of LIS, LIR, and OIR men and women from the parent egg-feeding study () to understand the role of cholesterol absorption and synthesis in obesity and insulin resistance. Specifically, we wished to understand whether differences exist to explain the discrepancy seen in the LDL-cholesterol response to egg feeding between insulin-sensitive and insulin-resistant individuals.
this phenomenon was associated with decreased cholesterol synthesis.
Obesity and insulin resistance portend a significant risk of atherosclerotic disease (–). Elevated triglycerides, moderate elevations in small dense LDL cholesterol, and decreased HDL cholesterol define the atherogenic dyslipidemia (combined hyperlipidemia) of insulin resistance (–). The dietary contribution to this dyslipidemia is poorly understood but likely relates to amounts of cholesterol absorbed and synthesized endogenously.