Low levels of serum 25(OH)D are associated with depressive symptoms, but no effect was found with vitamin D supplementation.

Three isozymes of human tyrosine hydroxylase (hTH1, hTH2 and hTH4) were expressed in Escherichia Cali and purified to homogeneity. Natural catecholamines and related synthetic compounds were found to be potent inhibitors, competitive to the tetrahydrobiopterin cofactor, of all the isozymes. Combining visible spectroscopy and equilibrium-binding studies, it was found that catecholamines bind to hTHZ and hTH2 with a stoichiometry of about 1 .O mol/mol enzyme subunit, interacting with the catalytic iron at the active site. All the isozymes tested were excellent substrates for CAMP-dependent protein kinase ( K , = 5 ~L M , V,,, = 9.5 pmol . min-' . mg kinase-'). The incorporation of about 1 .O mol phosphate/subunit at Ser40 decreased the affinity of dopamine binding by a factor of 10. Conversely, the addition of stoichiometric amounts of Fe(I1) and dopamine to the apoenzymes reduced both the affinity and stoichiometry of phosphorylation by CAMP-dependent protein kinase by 2-3-fold. These data provide evidence for a mutual interaction between the presumed regulatory and catalytic domains of hTH, and show that activation of the enzyme by phosphorylation and inactivation by binding of catecholamines are related events, which probably represent important mechanisms for the regulation of the enzyme activity in vivo.Tyrosine hydroxylase (TH) catalyses the rate-limiting step in the biosynthesis of catecholamines [I], and is regulated in vivo by long-term and short-term mechanisms. The long-term mechanism involves a modulation of TH gene expression[2], while short-term regulation involves activation of the enzyme by phosphorylation [2 -41 and feedback inhibition by catecholamines [5, 61.Human TH (hTH) exists as four different isozyme forms (hTH1-4), generated by alternative splicing of pre-mRNA [7-91. All four isozymes have been detected in the human adrenal medulla [lo], although hTHl and hTH2 seem to be the most abundant species [7-lo]. Three of the isozymes (hTH1, hTH2 and hTH4) have recently been expressed in Escherichia roli as metal-free apoenzymes, and found to be activated by Fe(I1) on binding of 1 Fe/subunit [ll]. Little is known about their regulatory properties in vitro, except that both hTHl and hTH2 are inhibited by catecholamines [12]. This inhibition seems to be partially reversed by phosphorylation [I 21. Furthermore, the isozymes have different phosphorylation sites and may be regulated by different secondmessenger systems [12].

MK-7 taken as Natto over 1 year reduced serum levels of ucOC but did not influence bone loss rates in early menopausal women.

In the circulation 25-hydroxyvitamin D (25(OH)D) is bound to vitamin D-binding protein (DBP) and albumin. Only a small fraction is in the unbound, free form. According to the ' free-hormone-hypothesis ' only the free form is biologically active. Genetic differences in DBP may affect the binding to 25(OH)D and thereby the amount of free 25(OH)D. In the present study sera were obtained from 265 postmenopausal women with low bone mass density (BMD). Serum 25(OH) D, DBP and albumin were measured and the free and bio-available (free ϩ albumin-bound) 25(OH)D calculated. Based on genotyping of the polymorphisms rs7041 and rs4588, the six common DBP phenotypes were identifi ed and the free and bio-available 25(OH)D calculated according to the corresponding binding coeffi cients. Relations between measures of 25(OH)D and PTH and BMD were evaluated with linear regression adjusted for age and BMI. The calculated amount of free and bio-available 25(OH)D was 0.03% and 13.1%, respectively, of the measured total serum 25(OH)D. Adjusting for DBP phenotype affected the calculated free and bio-available 25(OH)D levels up to 37.5%. All measures of 25(OH)D correlated signifi cantly with PTH, whereas a signifi cant association with BMD was only seen for the free and bio-available 25(OH)D measures. Adjusting for the DBP phenotypes improved the associations. These relations were almost exclusively seen in subjects not using vitamin D and/or calcium supplements. In conclusion, the free and bio-available forms of 25(OH) D may be a more informative measure of vitamin D status than total 25(OH)D. Adjustment for DBP phenotype may improve this further.

Vitamin D deficiency is prevalent during the school year among adolescents in northern Norway, particularly among boys.

Tyrosine hydroxylase (TH), the rate-limiting enzyme in the synthesis of catecholamines, is activated by phosphorylationdependent binding to 14-3-3 proteins. The N-terminal domain of TH is also involved in interaction with lipid membranes. We investigated the binding of the N-terminal domain to its different partners, both in the unphosphorylated (TH-(1-43)) and Ser 19 -phosphorylated (THp-(1-43)) states by surface plasmon resonance. THp-(1-43) showed high affinity for 14-3-3 proteins (K d ϳ 0.5 M for 14-3-3␥ and -and 7 M for 14-3-3 ). The domains also bind to negatively charged membranes with intermediate affinity (concentration at half-maximal binding S 0.5 ‫؍‬ 25-58 M (TH-(1-43)) and S 0.5 ‫؍‬ 135-475 M (THp-(1-43)), depending on phospholipid composition) and concomitant formation of helical structure. 14-3-3␥ showed a preferential binding to membranes, compared with 14-3-3 , both in chromaffin granules and with liposomes at neutral pH. The affinity of 14-3-3␥ for negatively charged membranes (S 0.5 ‫؍‬ 1-9 M) is much higher than the affinity of TH for the same membranes, compatible with the formation of a ternary complex between Ser 19 -phosphorylated TH, 14-3-3␥, and membranes. Our results shed light on interaction mechanisms that might be relevant for the modulation of the distribution of TH in the cytoplasm and membrane fractions and regulation of L-DOPA and dopamine synthesis.

One year treatment with 6,500 IU vitamin D(3)/day was not better than 800 IU/day regarding BMD in vitamin D-replete postmenopausal women with reduced bone mass and was less efficient in reducing bone turnover.

OBJECTIVEVitamin D deficiency is associated with an unfavorable metabolic profile in observational studies. The intention was to compare insulin sensitivity (the primary end point) and secretion and lipids in subjects with low and high serum 25(OH)D (25-hydroxyvitamin D) levels and to assess the effect of vitamin D supplementation on the same outcomes among the participants with low serum 25(OH)D levels.RESEARCH DESIGN AND METHODSParticipants were recruited from a population-based study (the Tromsø Study) based on their serum 25(OH)D measurements. A 3-h hyperglycemic clamp was performed, and the participants with low serum 25(OH)D levels were thereafter randomized to receive capsules of 20,000 IU vitamin D3 or identical-looking placebo twice weekly for 6 months. A final hyperglycemic clamp was then performed.RESULTSThe 52 participants with high serum 25(OH)D levels (85.6 ± 13.5 nmol/L [mean ± SD]) had significantly higher insulin sensitivity index (ISI) and lower HbA1c and triglycerides (TGs) than the 108 participants with low serum 25(OH)D (40.3 ± 12.8 nmol/L), but the differences in ISI and TGs were not significant after adjustments. After supplementation, serum 25(OH)D was 142.7 ± 25.7 and 42.9 ± 17.3 nmol/L in 49 of 51 completing participants randomized to vitamin D and 45 of 53 randomized to placebo, respectively. At the end of the study, there were no statistically significant differences in the outcome variables between the two groups.CONCLUSIONSVitamin D supplementation to apparently healthy subjects with insufficient serum 25(OH)D levels does not improve insulin sensitivity or secretion or serum lipid profile.