Calcioic acid: In vivo detection and quantification of the terminal C24-oxidation product of 25-hydroxyvitamin D3 and related intermediates in serum of mice treated with 24,25-dihydroxyvitamin D3.

Calcitroic acid, the excretory form of vitamin D, is the terminal product of a 5-step pathway catalyzed by CYP24A1, commencing with C24-hydroxylation of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). Catabolism of 25-hydroxyvitamin D3 (25-OH-D3) proceeds via analogous steps culminating in calcioic acid; however this C23-truncated acid has not been reported in the circulation. It has recently been shown that 24,25-dihydroxyvitamin D3 (24,25-(OH)2D3) is an important factor in optimal bone fracture healing acting via an effector molecule FAM57B2 to produce lactosylceramide. Administration of 24,25-(OH)2D3 was found to restore normal fracture repair in Cyp24a1-/- mice devoid of 24,25-(OH)2D3. We set out to study the multi-step catabolism of D3 metabolites in vivo using LC-MS/MS methods in vehicle or 24,25-(OH)2D3-treated mice. Vehicle-treated Cyp24a1+/- mice possessed normal levels of serum 24,25-(OH)2D3 (7 ng/mL) and 25-OH-D3-26,23-lactone (4 ng/mL). We also detected 24-oxo-25-OH-D3 (3 ng/mL) and 24-oxo-23,25-(OH)2D3 (0.4 ng/mL); which were not detectable in vehicle-treated Cyp24a1-/- mice. In 24,25-(OH)2D3-treated Cyp24a1+/- mice, serum 24,25-(OH)2D3 rose to 200 ng/mL while 25-OH-D3-26,23-lactone remained unchanged in comparison to vehicle-treated Cyp24a1+/- mice Concentration of serum 24-oxo-25-OH-D3 and 24-oxo-23,25-(OH)2D3 rose by 10-fold, when Cyp24a1+/- mice were treated with 24,25-(OH)2D3 Calcioic acid was increased to 0.030 ng/mL for 24,25-(OH)2D3-treated Cyp24a1+/- mice. In 24,25-(OH)2D3-treated Cyp24a1-/- mice, serum 24,25-(OH)2D3 rose further to a striking 830 ng/mL due to lack of catabolism of the 24,25-(OH)2D3 dose. Serum 1,25-(OH)2D3 levels were suppressed in 24,25-(OH)2D3-treated Cyp24a1+/- and Cyp24a1-/- mice. Circulating 1,24,25-(OH)3D3 rose from 73 pg/mL to 106 pg/mL when Cyp24a1+/- mice were treated with 24,25-(OH)2D3. While undetectable in vehicle-treated Cyp24a1-/- mice, 1,24,25-(OH)3D3 rose unexpectedly to 153 pg/mL in 24,25-(OH)2D3-treated nulls suggesting conversion of 24,25-(OH)2D3 to 1,24,25-(OH)3D3 via 1-hydroxylation. Taken together, amplification of 24,25-(OH)2D3 catabolism by exogenous doses of this metabolite have enabled detection of downstream C24-oxidation pathway products in vivo, including calcioic acid; and provides a platform for studying alternative routes of vitamin D metabolism that may occur in pathological states including hypervitaminosis D and idiopathic infantile hypercalcemia caused by mutations of CYP24A1.

An audit of Colposcopy referrals from a GU/STD clinic.

BACKGROUND: Cervical cancer is increasing at 1.5% per year in Ireland with 50% mortality giving 2.2% of all cancer deaths. In the Mid-West region a pilot screening programme has begun to screen all women 25-60 years. 66% of Genitourinary/Sexually transmitted disease (GU/STD) clinics' abnormal smears are <25 years. Requests to abandon "opportunistic" screening prompted this GU/STD clinic audit. METHODS: 221(8.4%) patients referred to colposcopy over 4 years were audited. Retrospective analysis was carried out on GU/STD clinic files, hospital files and computer records for biopsy reports. Ethical approval was prospectively granted. RESULTS: 2637 smears were carried out from November 1999 - September 2003.221 patients referred to colposcopy were audited.1%, 3%, 5% had severe, moderate and, mild dyskaryosis, respectively, on cervical screening while 0.8%, 1.2%, 1.5% had CIN3, CIN2, CIN1 abnormalities, respectively, on biopsy with 3.5% having no abnormality (Cervical Intraepithelial Neoplasia = CIN).53% referred to colposcopy were <25 years. CONCLUSION: 2% had high grade lesions. 37% of high grade lesions are <25 years.Of the high grade lesions 13% had Chlamydia trachomatis (27% of CIN3) and 44% had HPV despite Relative Risks (RR) being 0.75 and 1.09 respectively. Older women had higher grade changes. No statistical difference was found for progression, regression and persistence in those over and under 25.