Diabetes Is the Main Factor Accounting for Hypomagnesemia in Obese Subjects

OBJECTIVE: Type 2 diabetes (T2DM) and obesity are associated with magnesium deficiency. We aimed to determine whether the presence of type 2 diabetes and the degree of metabolic control are related to low serum magnesium levels in obese individuals. METHODS: A) Case-control study: 200 obese subjects [50 with T2DM (cases) and 150 without diabetes (controls)] prospectively recruited. B) Interventional study: the effect of bariatric surgery on serum magnesium levels was examined in a subset of 120 obese subjects (40 with type 2 diabetes and 80 without diabetes). RESULTS: Type 2 diabetic patients showed lower serum magnesium levels [0.75±0.07 vs. 0.81±0.06 mmol/L; mean difference -0.06 (95% CI -0.09 to -0.04); p<0.001] than non-diabetic patients. Forty-eight percent of diabetic subjects, but only 15% of non-diabetic subjects showed a serum magnesium concentration lower than 0.75 mmol/L. Significant negative correlations between magnesium and fasting plasma glucose, HbA1c, HOMA-IR, and BMI were detected. Multiple linear regression analysis showed that fasting plasma glucose and HbA1c independently predicted serum magnesium. After bariatric surgery serum magnesium increased only in those patients in whom diabetes was resolved, but remain unchanged in those who not, without difference in loss weight between groups. Changes in serum magnesium negatively correlated with changes in fasting plasma glucose and HbA1c. Absolute changes in HbA1c independently predicted magnesium changes in the multiple linear regression analysis. CONCLUSIONS: Our results provide evidence that the presence of diabetes and the degree of metabolic control are essential in accounting for the lower levels of magnesium that exist in obese subjects

Interference of H-bonding and substituent effects in nitro- and hydroxy-substituted salicylaldehydes

Two intramolecular interactions, i.e., (1) hydrogen bond and (2) substituent effect, were analyzed and compared. For this purpose, the geometry of 4- and 5-X-substituted salicylaldehyde derivatives (X = NO2, H or OH) was optimized by means of B3LYP/6-311 + G(d,p) and MP2/aug-cc-pVDZ methods. The results obtained allowed us to show that substituents (NO2 or OH) in the para or meta position with respect to either OH or CHO in H-bonded systems interact more strongly than in the case of di-substituted species: 4- and 3-nitrophenol or 4- and 3-hydroxybenzaldehyde by ∼31%. The substituent effect due to the intramolecular charge transfer from the para-counter substituent (NO2) to the proton-donating group (OH) is ∼35% greater than for the interaction of para-OH with the proton-accepting group (CHO). The total energy of H-bonding for salicylaldehyde, and its derivatives, is composed of two contributions: ∼80% from the energy of H-bond formation and ∼20% from the energy associated with reorganization of the electron structure of the systems in question

Intrinsic defects and non-stoichiometry in undoped cadmium silicate hosts

Cadmium silicates, mainly the CdSiO3 phase, are interesting materials due to their persistent and intrinsic luminescence, making them possible candidates for a number of applications. Although many of the luminescence properties of these materials are known from the experimental point of view, the current problem that still remains is to understand the origin of the intrinsic luminescence. Different types of point defects were considered in the literature and, most of them are contradictory and/or controversial and lack direct evidence for the assumptions. The aim of the present work is to investigate in depth the possible origin of the luminescence properties of cadmium silicates, focusing on the CdSiO3 phase, considering not only the possibilities reported in the literature but all other mechanisms involving intrinsic defects in these materials. Our results predicted that CdSiO3 tends to show stoichiometric deviation due to CdO pseudo-Schottky defects and the simulated structure for the deficient matrix is much closer to the experimental X-ray diffraction pattern than the stoichiometric one. This feature indicates that most of the available CdSiO3 phases are truly CdO deficient. Additionally, it was found that this defect induces the formation Si–Si bonds that are responsible for the intrinsic luminescence in this matrix. The CdO deficiency also accounts for the presence of additional cadmium silicate phases, like Cd2SiO4 or Cd3SiO5, during the synthesis of CdSiO3, a common feature found in many works in the literature. These results strongly indicate that CdO pseudo-Schottky defects, that trigger the CdO deficiency naturally present in cadmium silicate structures, should be considered not only in all luminescent models proposed, including intrinsic and extrinsic matrix, but also for the structural properties of these materials