Melatonin increases brown adipose tissue mass and function in Zücker diabetic fatty rats: implications for obesity control

Melatonin limits obesity in rodents without affecting food intake and activity, suggesting a thermogenic effect. Previously we demonstrated that melatonin browns subcutaneous fat in Zücker diabetic fatty (ZDF) rats. Other works pointed to melatonin as a signal that increases brown adipose tissue (BAT) mass and function in rodents. However, direct proof of thermogenic properties (uncoupled mitochondria) of the newly recruited BAT in response to melatonin is still lacking. Therefore, in this work, we investigated if melatonin recruits thermogenic BAT in ZDF rats. Zücker lean (ZL) and ZDF animals were subdivided into two groups, control (C) and treated with oral melatonin (M) for 6 weeks. Mitochondrial mass, activity of citrate synthase (CS), and respiratory chain complexes I and IV were lower in C‐ZDF than in C‐ZL animals (P < .001). Melatonin treatment increased BAT weight in ZDF rats (P < .001). Also, it rose mitochondrial mass (P < .01) and activities of CS and complexes I and IV (P < .001) in both, ZDF and ZL rats. Uncoupling protein 1 (UCP1) mRNA and protein were 50% lower in BAT from obese rats. Also, guanosine diphosphate (GDP) binding was lower in ZDF than in lean rats (P < .01). Melatonin treatment of obese rats restored the expression of UCP1 and GDP binding to levels of lean rats and sensitized the thermogenic response to cold exposure. These data demonstrated that melatonin recruits thermogenic BAT in ZDF rats. This may contribute to melatonin's control of body weight and its metabolic benefits.     

Melatonin down‐regulates MDM2 gene expression and enhances p53 acetylation in MCF‐7 cells

Compelling evidence demonstrated that melatonin increases p53 activity in cancer cells. p53 undergoes acetylation to be stabilized and activated for driving cells destined for apoptosis/growth inhibition. Over‐expression of p300 induces p53 acetylation, leading to cell growth arrest by increasing p21 expression. In turn, p53 activation is mainly regulated in the nucleus by MDM2. MDM2 also acts as E3 ubiquitin ligase, promoting the proteasome‐dependent p53 degradation. MDM2 entry into the nucleus is finely tuned by two different modulations: the ribosomal protein L11, acts by sequestering MDM2 in the cytosol, whereas the PI3K‐AkT‐dependent MDM2 phosphorylation is mandatory for MDM2 translocation across the nuclear membrane. In addition, MDM2‐dependent targeting of p53 is regulated in a nonlinear fashion by MDM2/MDMX interplay. Melatonin induces both cell growth inhibition and apoptosis in MCF7 breast cancer cells. We previously reported that this effect is associated with reduced MDM2 levels and increased p53 activity. Herein, we demonstrated that melatonin drastically down‐regulates MDM2 gene expression and inhibits MDM2 shuttling into the nucleus, given that melatonin increases L11 and inhibits Akt‐PI3K‐dependent MDM2 phosphorylation. Melatonin induces a 3‐fold increase in both MDMX and p300 levels, decreasing simultaneously Sirt1, a specific inhibitor of p300 activity. Consequently, melatonin‐treated cells display significantly higher values of both p53 and acetylated p53. Thus, a 15‐fold increase in p21 levels was observed in melatonin‐treated cancer cells. Our results provide evidence that melatonin enhances p53 acetylation by modulating the MDM2/MDMX/p300 pathway, disclosing new insights for understanding its anticancer effect.     

T2 mapping with magnetization‐prepared 3D TSE based on a modified BIR‐4 T2 preparation

The purpose of this work was to investigate the performance of the modified BIR‐4 T₂ preparation for T₂ mapping and propose a method to remove T₂ quantification errors in the presence of large B₁ and B₀ offsets. The theoretical investigation of the magnetization evolution during the T₂ preparation in the presence of B₁ and B₀ offsets showed deviations from a mono‐exponential T₂ decay (two parameter fit). A three parameter fit was used to improve T₂ accuracy. Furthermore, a two parameter fit with an additional saturation preparation scan was proposed to improve T₂ accuracy and precision. These three fitting methods were compared based on simulations, phantom measurements and an in vivo healthy volunteer study of the neck musculature using a 3D TSE readout. The results based upon the pure two parameter fit overestimated T₂ in regions with high B₀ offsets (up to 40% in phantoms). The three parameter fit T₂ values were robust to B₀ offsets but with higher standard deviation (up to 40% in simulations). The two parameter fit with the saturation preparation yielded high robustness towards B₀ offsets with a noise performance comparable to that of the two parameter fit. In the volunteer study the T₂ values obtained by the pure two parameter fit showed a dependence on the field inhomogeneities, whereas the T₂ values from the proposed fitting approach were shown to be insensitive to B₀ offsets. The proposed method enabled accurate and precise T₂ mapping in the presence of large B₁ and B₀ offsets.     

Cystic fibrosis transmembrane conductance regulator mutations in azoospermic and oligospermic men and their partners

The objective of this study was to investigate the contribution of cystic fibrosis transmembrane conductance regulator (CFTR) to human infertility and to define screening and counselling procedures for couples asking for assisted reproduction treatment. Extended CFTR mutation screening was performed in 310 infertile men (25 with congenital absence of the vas deferens (CAVD), 116 with non-CAVD azoospermia, 169 with severe oligospermia), 70 female partners and 96 healthy controls. CFTR mutations were detected in the majority (68%) of CAVD patients and in significant proportions in azoospermic (31%) and oligospermic (22%) men. Carrier frequency among partners of infertile men was 16/70, exceeding that of controls (6/96) significantly (P = 0.0005). Thus, in 23% of infertile couples both partners were carriers, increasing the risk for their offspring to inherit two mutations to 25% or 50%. This study emphasizes the necessity to offer extended CFTR mutation screening and counselling not only to patients with CAVD but also to azoospermic and oligozoospermic men and their partners before undergoing assisted reproduction techniques. The identification of rare and/or mild mutations will not be a reason to abstain from parenthood, but will allow adequate treatment in children at risk for atypical or mild cystic fibrosis as soon as they develop any symptoms.