Increasing age among middle aged
Increasing age among middle-aged subjects (30–59years old) was associated with higher levels of cholesterol synthesis markers (although without statistical significance) and also of cholesterol nf-κb pathway markers (with statistical significance for campesterol and sitosterol); this finding is consistent with some, but not all of the prior data available , which could be explained by the fact that serum plant sterol levels vary substantially within and across different populations. The greatest of this variability is attributed to the method used to measure these levels; however, the data are also affected by genetics, sex, diet, and disease .
Among those aged 60–65years, compared to middle-aged subjects, there is some indication of an apparent attenuation of cholesterologenesis in both serum NCS and lipid profiles, which is a logical age-related diminishing anabolic process, also closely associated with multimorbidity, as observed by Tilvis et al. .
Although the mechanisms are incompletely characterized, some evidence demonstrates that the causes of age-related disruption of lipid homeostasis include the gradual decline in clearance of LDL-C with increasing age (a 50% reduction in the rate of hepatic clearance may translate into an increase of LDL-C level up to 116mg/dL ), and the progressively reduced ability to remove cholesterol through conversion to bile acids, the decreased activity of the rate-limiting enzyme in bile acid biosynthesis, cholesterol-7-α-hydroxylase (C7αOH) .
Furthermore, there is accumulating evidence that higher cholesterol intestinal absorption markers (and lower hepatic synthesis) are associated with increased cardiovascular risk , , , , .
In our study, although a significant positive correlation was found between sitosterol and the consumption of oily fish (a type of fish which is well known for the effects of its n-3 polyunsaturated fatty acids on improving lipid abnormalities, especially that of lowering the concentrations of TG in a dose–response manner ), we cannot explain the differences in absorption markers by differences in eating habits. Moreover, the associations observed could have been influenced by factors we could not control, such as genetic variability/genotype, the cholesterol and phytosterol content of diets, and the level of physical activity.
Conflict of interest
Introduction Cholesterol homeostasis is maintained by intestinal cholesterol absorption, cholesterol synthesis, and excretion. Since an excessively high level of plasma cholesterol is one of the major risk factors for atherosclerosis and cardiovascular diseases, the reduction of cholesterol levels is desired for hypercholesterolemia. Besides lifestyle modification, medications could be another recommended alternative for management of hypercholesterolemia. Drugs such as statins and ezetimibe are the common options. A statin, which is a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, may exert its effect by suppressing cholesterol biosynthesis pathway. Ezetimibe, a cholesterol absorption inhibitor, plays a role in inhibiting cholesterol uptake into the enterocyte by blocking the Niemann-Pick C1 like 1 (NPC1L1) cholesterol transporter.3, 4 However, several adverse events associated with ezetimibe or statins used, e.g., hepatotoxicity, severe cholestatic hepatitis, rhabdomyolysis, and myopathy, were reported. Therefore, functional foods and nutraceuticals are becoming popular as alternative therapies for lowering plasma cholesterol levels, especially in individuals whose blood cholesterol levels are marginally high, but who are not recommended to undergo drug treatments. Spirogyra neglecta (SN) is an edible freshwater macroalga and a common ingredient used in Northern Thai cuisine. SN contains many nutritional constituents including fat, proteins, carbohydrate, fibers, multivitamins, minerals, and antioxidants. In addition, it has been reported to exhibit antigastric ulcer, antiinflammatory, antihyperglycemic, and antihyperlipidemic properties. Recently, SN was able to reduce plasma triglyceride in in type 2 diabetic rats. However, evidence to support the hypocholesterolemic effect of SN and its mechanism still remains unclear. Normally, the possible target is intestinal cholesterol absorption, which has a major role in influencing plasma cholesterol level. Cholesterol absorption involves multistep processes including digestion of dietary lipids and micellar solubilization of cholesterol, and protein transporters. Therefore, we determined the impact of SN extract on cholesterol uptake by using Caco-2 cells, in vitro bile acid binding, micelles size, and cholesterol solubility. Meanwhile, the cholesterol synthesis study was evaluated by using in vitro HMG-CoA reductase activity.