Cholesterol metabolism in distance runners

Critical Analysis on Characterization, Systemic Effect, and Therapeutic Potential of Beta-Sitosterol: A Plant-Derived Orphan Phytosterol

Beta-sitosterol (BS) is a phytosterol, widely distributed throughout the plant kingdom and known to be involved in the stabilization of cell membranes. To compile the sources, physical and chemical properties, spectral and chromatographic analytical methods, synthesis, systemic effects, pharmacokinetics, therapeutic potentials, toxicity, drug delivery and finally, to suggest future research with BS, classical as well as on-line literature were studied. Classical literature includes classical books on ethnomedicine and phytochemistry, and the electronic search included Pubmed, SciFinder, Scopus, the Web of Science, Google Scholar, and others. BS could be obtained from different plants, but the total biosynthetic pathway, as well as its exact physiological and structural function in plants, have not been fully understood. Different pharmacological effects have been studied, but most of the mechanisms of action have not been studied in detail. Clinical trials with BS have shown beneficial effects in different diseases, but long-term study results are not available. These have contributed to its current status as an "orphan phytosterol". Therefore, extensive research regarding its effect at cellular and molecular level in humans as well as addressing the claims made by commercial manufacturers such as the cholesterol lowering ability, immunological activity etc. are highly recommended.

Voluntary wheel running increases bile acid as well as cholesterol excretion and decreases atherosclerosis in hypercholesterolemic mice

OBJECTIVE

Regular physical activity decreases the risk for atherosclerosis but underlying mechanisms are not fully understood. We questioned whether voluntary wheel running provokes specific modulations in cholesterol turnover that translate into a decreased atherosclerotic burden in hypercholesterolemic mice.

METHODS

Male LDLR-deficient mice (8 weeks old) had either access to a voluntary running wheel for 12 weeks (RUN) or remained sedentary (CONTROL). Both groups were fed a western-type/high cholesterol diet. Running activity and food intake were recorded. At 12 weeks of intervention, feces, bile and plasma were collected to determine fecal, biliary and plasma parameters of cholesterol metabolism and plasma cytokines. Atherosclerotic lesion size was determined in the aortic root.

RESULTS

RUN weighed less (∼13%) while food consumption was increased by 17% (p=0.004). Plasma cholesterol levels were decreased by 12% (p=0.035) and plasma levels of pro-atherogenic lipoproteins decreased in RUN compared to control. Running modulated cholesterol catabolism by enhancing cholesterol turnover: RUN displayed an increased biliary bile acid secretion (68%, p=0.007) and increased fecal bile acid (93%, p=0.009) and neutral sterol (33%, p=0.002) outputs compared to control indicating that reverse cholesterol transport was increased in RUN. Importantly, aortic lesion size was decreased by ∼33% in RUN (p=0.033).

CONCLUSION

Voluntary wheel running reduces atherosclerotic burden in hypercholesterolemic mice. An increased cholesterol turnover, specifically its conversion into bile acids, may underlie the beneficial effect of voluntary exercise in mice.

Exercise enhances whole-body cholesterol turnover in mice

PURPOSE

Regular exercise reduces cardiovascular risk in humans by reducing cholesterol levels, but the underlying mechanisms have not been fully explored. Exercise might provoke changes in cholesterol and bile acid metabolism and thereby reduce cardiovascular risk. We examined whether voluntary wheel running in mice modulates cholesterol and bile acid metabolism.

METHODS

Male mice (10 wk old) were randomly assigned to have access to a voluntary running wheel for 2 wk (RUN group) or remained sedentary (SED group). Running wheel activity was recorded daily. In a first experiment, fecal sterol outputs, fecal bile acid profiles, plasma parameters, and expression levels of genes involved in cholesterol and bile acid metabolism were determined. In a second experiment, bile flow, biliary bile acid profile, and biliary secretion rates of cholesterol, phospholipids, and bile acids were determined.

RESULTS

The RUN group ran an average of 10 km.d and displayed lower plasma cholesterol compared with SED (P = 0.030). Fecal bile acid loss was induced by approximately 30% in running mice compared with SED (P = 0.0012). A approximately 30% increase in fecal cholesterol output in RUN (P = 0.014) was consistent with changes in parameters of cholesterol absorption, such as reduced plasma plant sterol-cholesterol ratio (P = 0.044) and decreased jejunal expression of Npc1l1 (P = 0.013). Supportive of an increased cholesterol synthesis to compensate for fecal sterol loss were increased hepatic mRNA levels of HMGCoA reductase (P = 0.006) and an increased plasma lathosterol-cholesterol ratio (P = 0.0011) in RUN.

CONCLUSIONS

Voluntary wheel running increased cholesterol turnover in healthy mice owing to an increased fecal bile acid excretion and a decreased intestinal cholesterol absorption. Enhanced cholesterol turnover may contribute to the established reduction of cardiovascular risk induced by regular exercise.