A B S T R A C T Oxidation of the side chain of 5,3-cholestane-3a,7a,12a-triol was studied in a patient with cerebrotendinous xanthomatosis (CTX) and in control subjects, using various subcellular fractions of liver homogenate and a method based on isotope dilution-mass spectrometry.In the control, 5p8-cholestane-3a,7a,12a-triol was converted into 5f3-cholestane-3a,7a,12a,26-tetrol and 3a,7a,12a-trihydroxy-5,8-cholestanoic acid by the mitochondrial fraction, and into 5,8-cholestane-3a,7a,12a,-25-tetrol by the microsomal fraction.In the CTX patient, liver mitochondria were completely devoid of 26-hydroxylase activity. The same mitochondrial fraction catalyzed 25-hydroxylation of vitamin D3.The microsomal fraction of liver of the subject with CTX contained more than 50-fold the normal amount of 5f3-cholestane-3a,7a,12a-triol.The basic metabolic defect in CTX appears to be a lack of the mitochondrial 26-hydroxylase. The excretion in the bile of 5,p-cholestane-3a,7a,12a,25-tetrol and 5f3-cholestane-3a,7a,12a,24a,25-pentol observed in CTX patients may be secondary to the accumulation of the major substrate for the 26-hydroxylase, i.e., 5,8-cholestane-3a,7a,12a-triol, and exposure of this substrate to the normally less active microsomal 25-and 24-hydroxylases. It is concluded that the major pathway in the biosynthesis of cholic acid in human liver involves a mitochondrial C27-steroid 26-hydroxylation.

Changes in the testosterone concentrations after single sessions of endurance and strength training were measured in seven well trained men, experienced in both forms of training. Both training sessions were rated as hard to very hard on the Borg scale. Blood samples for testosterone measurements were taken before, immediately after, and 2, 4 and 6 h after the training sessions as well as the next morning. The mean testosterone concentration increased 27% (P less than 0.02) and 37% (P less than 0.02) during the strength and endurance training session, respectively. Two hours after the training sessions the mean testosterone concentration had returned to the pre-training level and remained at that level for the length of the observation period. There were no significant differences in the changes in testosterone concentration after strength and endurance training but there were large differences in the testosterone response at the level of the individual. A high correlation (r = 0.98; P less than 0.001) for individuals was found between increases in testosterone concentration after strength and after endurance training. It was concluded that the changes in mean testosterone values followed the same timecourse after single sessions of strength and endurance training of the same duration and perceived exertion. The interindividual differences in testosterone response may be of importance for individual adaptation to training.

To study changes in the rate of bone loss before and after the menopause, 19 normal premenopausal women of the same age were followed with annual measurements of appendicular bone mass for 8 yr. Their serum estrone, estradiol, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and vitamin D-binding protein levels also were measured annually. The serum estrogen levels declined before the menopause, and the rate of bone loss more than doubled at the time of the menopause. There were no significant changes in the serum 25-hydroxyvitamin D, 1,25-dihydroxyvitamin LD or vitamin D-binding protein levels from the pre- to the postmenopausal period. We conclude that changes in vitamin D metabolite levels are not associated with early postmenopausal bone loss.

No abstract

No abstract

No abstract

No abstract

To elucidate effects of chronic ethanol consumption on clinical chemical parameters reflecting overall calcium homeostasis 34 hospitalized male alcoholics and 35 age-matched controls were studied during the winter season. Serum concentrations of 25-hydroxyvitamin D3 and 1,25-dihydroxyvitamin D3 were reduced by 28% (p less than 0.01) and 24% (p less than 0.02) among the alcoholics as compared to the controls, respectively. Dietary intake of vitamin D3 did not differ significantly between the groups. The calcium level was below lower limit of reference in nine alcoholics (26%). Serum concentrations of parathyroid hormone and phosphorus were within normal ranges in both groups, and no differences were observed in levels of magnesium, vitamin D-binding protein, calcitonin, or alkaline phosphatase. In conclusion, it is possible that the activities of enzymes crucial in vitamin D3 metabolism may be altered in alcoholics.