Cholestanol resembles cholesterol, but its significance has remained unclear because of its low concentration in the body. However, in cerebrotendinous xanthomatosis, a genetic disorder of cholesterol metabolism, deposition of cholestanol produces several pathological conditions such as tendon xanthomas, cerebellar ataxia, pyramidal signs, cataracts and dementia. We have been investigating this disease for 23 years from the viewpoint of biochemical diagnosis. We established a procedure for quantification of cholestanol by HPLC, and also an assay method for sterol 27-hydroxylase. We also found several mutations of the CYP 27 gene in 10 CTX families. Furthermore, we established experimental animals with CTX by feeding then a cholestanol diet, and produced corneal dystrophy and gallstones in mice, and apoptosis of cerebellar neuronal cells from rats. CTX can be treated with chenodeoxycholic acid, which reduces the cholestanol concentration in serum. These findings suggest that cholestanol has a toxic effect. It will be necessary to determine the cholestanol content of food for the treatment of CTX patients and to prevent the clinical manifestations produced by cholestanol administration.
Numerous clinical and epidemiological studies have indicated that a high sodium intake, even within the range of the amounts contained in habitual diets, is associated with high urinary calcium excretion in both young and adult healthy subjects of both sexes. Results of some clinical and epidemiological studies on elderly women also show that high sodium intake accelerates urinary excretion of deoxypyridinoline, a specific marker of bone resorption. Furthermore, in two epidemiological studies of postmenopausal women, negative associations between sodium intake and bone mineral content were observed. These findings suggest that habitual excess dietary salt (NaCI) could be a factor resulting in bone loss through the promotion of bone resorption, at least in elderly women.