Further insights into the metabolically healthy obese phenotype: the role of magnesium

Magnesium intake is associated with the metabolically healthy obese phenotype

Although magnesium intake is inversely associated with the risk of metabolic abnormalities, whether magnesium intake plays a role on metabolically healthy obese (MHO) phenotype has not been explored. Therefore, the purpose of this study was to determine whether the magnesium intake is associated with the MHO phenotype. Apparently, healthy women and men aged 20-65 years with obesity were enrolled in a cross-sectional study. Subjects were allocated into MHO (n=124) and metabolically unhealthy obese (MUO) (n=123) groups. MHO phenotype was defined by abdominal obesity (waist circumference ≥90 cm in men and ≥80 cm in women) and none, or not more than one of the following risk factors: triglyceride levels ≥150 mg/dL; high-density lipoprotein cholesterol (HDL-C) levels <40 mg/dL in men and <50 mg/dL in women; fasting glucose ≥100 mg/dL; and systolic blood pressure ≥130 mm Hg and/or diastolic blood pressure ≥85 mm Hg. The MUO individuals were characterized by abdominal obesity and the presence of two or more of the aforementioned criteria. The proportion of individuals with high blood pressure (40.7% vs 5.6%, p<0.001), hyperglycemia (69.1% vs 16.9%, p<0.001), hypertriglyceridemia (84.6% vs 36.3%, p<0.001), and low HDL-C (51.2% vs 12.9%, p<0.001) was significantly higher in the MUO individuals as compared with individuals in the MHO group. The logistic regression analysis adjusted by sex and age showed that dietary magnesium intake is significantly associated with the MHO phenotype (OR=1.17; 95% CI 1.07 to 1.25, p=0.005). Our results show that magnesium intake is significantly associated with the MHO phenotype.

Differential Modulation of Cancellous and Cortical Distal Femur by Fructose and Natural Mineral-Rich Water Consumption in Ovariectomized Female Sprague Dawley Rats

Bone mineral density (BMD) and microstructure depend on estrogens and diet. We assessed the impact of natural mineral-rich water ingestion on distal femur of fructose-fed estrogen-deficient female Sprague Dawley rats. Ovariectomized rats drank tap or mineral-rich waters, with or without 10%-fructose, for 10 weeks. A sham-operated group drinking tap water was included (n = 6/group). Cancellous and cortical bone compartments were analyzed by microcomputed tomography. Circulating bone metabolism markers were measured by enzyme immunoassay/enzyme-linked immunosorbent assay or multiplex bead assay. Ovariectomy significantly worsened cancellous but not cortical bone, significantly increased circulating degradation products from C-terminal telopeptides of type I collagen and receptor activator of nuclear factor-kappaB ligand (RANKL), and significantly decreased circulating osteoprotegerin and osteoprotegerin/RANKL ratio. In ovariectomized rats, in cancellous bone, significant water effect was observed for all microstructural properties, except for the degree of anisotropy, and BMD (neither a significant fructose effect nor a significant interaction between water and fructose ingestion effects were observed). In cortical bone, it was observed a significant (a) water effect for medullary volume and cortical endosteal perimeter; (b) fructose effect for cortical thickness, medullary volume, cross-sectional thickness and cortical endosteal and periosteal perimeters; and (c) interaction effect for mean eccentricity. In blood, significant fructose and interaction effects were found for osteoprotegerin (no significant water effect was seen). For the first time in ovariectomized rats, the positive modulation of cortical but not of cancellous bone by fructose ingestion and of both bone locations by natural mineral-rich water ingestion is described.

Ingestion of a natural mineral-rich water in an animal model of metabolic syndrome: effects in insulin signalling and endoplasmic reticulum stress

BACKGROUND

High-fructose and/or low-mineral diets are relevant in metabolic syndrome (MS) development. Insulin resistance (IR) represents a central mechanism in MS development. Glucocorticoid signalling dysfunction and endoplasmic reticulum (ER) and oxidative stresses strongly contribute to IR and associate with MS. We have described that natural mineral-rich water ingestion delays fructose-induced MS development, modulates fructose effects on the redox state and glucocorticoid signalling and increases sirtuin 1 expression. Here, we investigated mineral-rich water ingestion effects on insulin signalling and ER homeostasis of fructose-fed rats.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats had free access to standard-chow diet and different drinking solutions (8 weeks): tap water (CONT), 10%-fructose/tap water (FRUCT) or 10%-fructose/mineral-rich water (FRUCTMIN). Hepatic and adipose (visceral, VAT) insulin signalling and hepatic ER homeostasis (Western blot or PCR) as well as hepatic lipid accumulation were evaluated.

RESULTS

Hepatic p-IRS1Ser307/IRS1 (tendency), p-IRS1Ser307, total JNK and (activated IRE1α)/(activated JNK) decreased with fructose ingestion, while p-JNK tended to increase; mineral-rich water ingestion, totally or partially, reverted all these effects. Total PERK, p-eIF2α (tendency) and total IRS1 (tendency) decreased in both fructose-fed groups. p-ERK/ERK and total IRE1α increasing tendencies in FRUCT became significant in FRUCTMIN (similar pattern for lipid area). Additionally, unspliced-XBP1 increased with mineral-rich water. In VAT, total ERK fructose-induced increase was partially prevented in FRUCTMIN.

CONCLUSIONS

Mineral-rich water modulation of fructose-induced effects on insulin signalling and ER homeostasis matches the better metabolic profile previously reported. Increased p-ERK/ERK, adding to decreased IRE1α activation, and increased unspliced-XBP1 and lipid area may protect against oxidative stress and IR development in FRUCTMIN.