Defined stereoisomers of 2″-amino NAD+ and their activity against human sirtuins and a bacterial (ADP-ribosyl) transferase

Nicotinamide adenine dinucleotide (NAD⁺) is an important biomolecule with essential roles at the intersection of energy metabolism, epigenetic regulation and cell signalling. Synthetic analogues of NAD⁺ are therefore of great interest as chemical tools for medicinal chemistry, chemical biology and drug discovery. Herein, we report the chemical synthesis and full analytical characterisation of three stereoisomers of 2″-amino NAD⁺, and their biochemical evaluation against two classes of NAD⁺-consuming enzymes: the human sirtuins 1-3, and the bacterial toxin TccC3. To rationalise the observed activities, molecular docking experiments were carried out with SIRT1 and SIRT2, which identified the correct orientation of the pyrophosphate linkage as a major determinant for activity in this series. These results, together with results from stability tests and a conformational analysis, allow, for the first time, a side-by-side comparison of the chemical and biochemical features, and analytical properties, of different 2″-amino NAD⁺ stereoisomers. Our findings provide insight into the recognition of co-substrate analogues by sirtuins, and will greatly facilitate the application of these important NAD⁺ analogues as chemical tool compounds for mechanistic studies with these as well as other NAD⁺-dependent enyzmes.

The influence of hyperthyroidism on the hypothalamic-pituitary-gonadal axis

We have investigated the function of the hypothalamic-pituitary-gonadal (H-P-G)-axis in patients with severe, untreated Graves' disease. We studied 7 male and 6 female healthy volunteers, and 7 male and 7 female patients with Graves' disease. Hormone profiles were developed by blood sampling every 10 min for an 8 hour period. In women this was done in the early follicular phase of menstrual cycle. LH-, FSH-, and PRL levels were measured using immunoradiometric assays and testosterone (T), estradiol (E2), sex-hormone binding globulin (SHBG), and progesterone (P) were measured with standard assays. The pulsatility of LH, FSH and PRL was calculated using the programmes Pulsar, Cluster and Desade. The temporal relationship of plasma LH, FSH, and PRL pulses was also investigated using specific concordance analysis. Data were evaluated by means of non-parametric statistics. LH-secretion was increased in all hyperthyroid patients, while FSH-secretion was increased in hyperthyroid men only. Pulsatile characteristics of LH- and FSH-secretion (frequency, peak shape) in patients were not different from controls. No change in PRL-secretion was shown. Significant copulsatility occurred between LH and FSH, and LH and PRL. This was more pronounced in hyperthyroid than in healthy study subjects. Plasma levels of steroid hormones and sex-hormone-binding globulin were significantly (p<0.005) increased in hyperthyroid men. Free Androgen Index was significantly (p<0.005) decreased in hyperthyroid males. No other auto immune diseases were noticed. Our results indicate that the function of the H-P-G axis is not impaired in hyperthyroid patients, but gonadotropin levels are increased. Hyperthyroid men show relative primary gonadal insufficiency that may be due to exaggerated SHBG levels. The copulsatility of LH and FSH, and of LH and PRL was confirmed both in patients and controls.