The tolerability and biochemical effects of high-dose bolus vitamin D2 and D3 supplementation in patients with vitamin D insufficiency.

OBJECTIVES: To investigate the practicality and tolerability of high-dose intramuscular (i.m.) vitamin D2 or oral vitamin D3 replacement in vitamin D-insufficient patients, and to evaluate the biochemical efficacy of each formulation. METHODS: Sixty-nine patients with vitamin D insufficiency [25-hydroxyvitamin D (25(OH)D) <40 nmol/L] were recruited from the Rheumatology Outpatient Department of St George's Hospital, London. In study 1, 50 patients received 300 000 IU i.m. vitamin D2 (ergocalciferol). In study 2, 19 patients received 300 000 IU oral vitamin D3 (cholecalciferol) under observation. Biochemical response was measured at baseline, and at 12 and 24 weeks. RESULTS: Bolus i.m. vitamin D2 or oral vitamin D3 was well tolerated. The change from baseline in serum 25(OH)D was significantly greater at 6 and 12 weeks in study 2 (p<0.0001 and <0.0001, respectively). In study 1, a modest increase in mean serum 25(OH)D at 6, 12, and 24 weeks was observed but no patients achieved a serum 25(OH)D concentration > or = 50 nmol/L. PTH remained elevated in 42% of patients with secondary hyperparathyroidism at 12 weeks. In study 2, 100% and 89% of patients had serum 25(OH)D>50 nmol/L at 6 and 12 weeks, respectively. All patients with elevated baseline PTH were fully suppressed at 12 weeks. No cases of hypercalcaemia were observed in either group. CONCLUSION: The 300 000-IU bolus of vitamin D2 or D3 was practical, well tolerated, and safe. Vitamin D3 had greater potency than equimolar vitamin D2, with a higher, sustained serum 25(OH)D response and efficacious PTH suppression. To adequately treat vitamin D insufficiency we would recommend administering 300,000 IU oral vitamin D3 approximately three times per year.

Clinical aspects of vitamin D in the management of rheumatoid arthritis.

There is an increasing interest in the role of vitamin D as a potential treatment for a number of disparate diseases. In addition to its role in calcium homeostasis, vitamin D has a plethora of effects including immunomodulation, pleiotropic effects, modulating propensity to infection and blood pressure regulation. Detection and treatment of vitamin D deficiency in selected patients with RA is relevant as deficiency is common. Vitamin D therapy may modify the increased risk of falls and fracture in this group, and possibly exert additional immunomodulatory effects on disease onset and activity although data are largely epidemiological. Currently, there is no consensus view on vitamin D replacement regimens, nor an agreed optimal level of serum 25-hydroxyvitamin D [25(OH)D] for health. Indeed levels may vary for different organ systems and the concept of 'tissue specific vitamin D deficiency' needs to be considered. Therefore, there is clinical uncertainty regarding both when and how to correct vitamin D deficiency. Older patients, particularly post-menopausal women, and others at high risk of vitamin D deficiency should be preferentially targeted since they are likely to benefit most from supplementation. Clinicians should be aware of the technical difficulties associated with measuring and interpreting 25(OH)D levels. The administration of high-dose vitamin D as an oral weekly bolus is safe and can rapidly correct vitamin D deficiency followed by regular lower doses to maintain adequate levels.

Drosophila Amphiphysin is a post-synaptic protein required for normal locomotion but not endocytosis.

Clathrin-mediated endocytosis is required to recycle synaptic vesicles for fast and efficient neurotransmission. Amphiphysins are thought to be multiprotein adaptors that may contribute to this process by bringing together many of the proteins required for endocytosis. Their in vivo function, however, has yet to be determined. Here, we show that the Drosophila genome encodes a single amphiphysin gene that is broadly expressed during development. We also show that, unlike its vertebrate counterparts, Drosophila Amphiphysin is enriched postsynaptically at the larval neuromuscular junction. To determine the role of Drosophila Amphiphysin, we also generated null mutants which are viable but give rise to larvae and adults with pronounced locomotory defects. Surprisingly, the locomotory defects cannot be accounted for by alterations in the morphology or physiology of the neuromuscular junction. Moreover, using stimulus protocols designed to test endocytosis under moderate and extreme vesicle cycling, we could not detect any defect in the neuromuscular junction of the amphiphysin mutant. Taken together, our findings suggest that Amphiphysin is not required for viability, nor is it absolutely required for clathrin-mediated endocytosis. However, Drosophila Amphiphysin function is required in both larvae and adults for normal locomotion.