Magnesium supplementation enhances insulin sensitivity and decreases insulin resistance in diabetic rats.

OBJECTIVES: Diabetes mellitus has been suggested to be the most common metabolic disorder associated with magnesium deficiency. This study aimed to investigate the effects and mechanisms of magnesium supplementation on insulin receptor activity in elderly type 2 diabetes using a rat model and to provide experimental evidence for insulin resistance improvement by magnesium supplementation. MATERIALS AND METHODS: Rat model of type 2 diabetes was developed using a high-fat diet along with low dose streptozotocin (STZ) treatment. Magnesium supplement was given orally by mixing with the high-fat diet. Serum insulin level, insulin sensitivity, and insulin receptor affinity were assessed using radioimmunoassay (RIA). Insulin receptor, insulin receptor substrate (IRS-2), and ß-Arrestin-2 gene and protein expression levels were measured using immunohistochemistry and RT-PCR. Xanthine oxidase assay, thiobarbituric acid reactive substance assay (TCA method), colorimetric assay, and ELISA were used to determine the serum SOD, MDA, T-AOC, and ox-LDL levels, respectively. RESULTS: Magnesium supplementation enhanced insulin sensitivity and decreased insulin resistance in diabetic rats mainly through increasing insulin receptor expression, affinity, and augmenting insulin receptor signaling. Magnesium supplementation also inhibited lipid peroxidation in diabetic rats and protected against pancreatic cell injury in diabetic rats. In addition, we found that ß-arrestin-2 gene expression was suppressed in diabetes, which was possibly attributed to gene methylation modification, as ß-arrestin 2 promotor was rich in methylation-regulating sites. Magnesium supplementation could affect ß-arrestin-2 gene expression and methylation. CONCLUSION: Magnesium supplementation has a positive effect on insulin receptor activity and insulin sensitivity in type 2 diabetes.

The Effect of Dried Beancurd on Bone Mineral Density in Postmenopausal Chinese Women: A 2-Year Randomized Controlled Trial.

Soy foods contain several components such as isoflavones, calcium and protein that potentially modulate bone turnover and increase bone mineral density (BMD) in postmenopausal women. The study is to evaluate the effect of dried beancurd supplementation on skeletal health in postmenopausal Chinese women. Three hundred postmenopausal women aged 50-65 years were assigned into two groups, receiving 100 g dried beancurd or rice cake a day for 2 years. BMD at the lumbar spine and right proximal femur were measured with a dual-energy X-ray absorptiometry. The bone turnover biomarkers of serum alkaline phosphatase (ALP), bone Gla protein (BGP) and urinary N-telopeptide cross-links of collagen normalized for creatinine (NTX/CRT) were also determined. Serum isoflavone concentration was analyzed by high performance liquid chromatography. The 2-year dried beancurd supplementation generated a significant increase in lumbar spine BMD. An obvious decrease was found in urinary NTX/CRT, and a significant increase was detected in serum isoflavone concentration. The dried beancurd supplementation had no effect on changes of right proximal femur BMD and concentrations of serum ALP and BGP. Daily supplementation of dried beancurd could increase BMD of lumbar spine, but does not slow bone loss at right proximal femur in postmenopausal Chinese women.

Evaluation of the Effect of Sprout Soybeans on the Iron Status of Anemic Adolescent Girls in Rural China.

Soybeans are a major source of nonheme iron in Chinese diet. Germination is considered to be effective in improving iron bioavailability in soybeans. The study is to evaluate the effect of sprout soybean supplementation on the iron status of anemic adolescent girls in rural area of China and to compare it with the effect of soybeans. Two hundred and eighty eight adolescent girls were assigned to receive one of three dietary supplements (100 mL) a day for 6 m: 1) rice milk as the control (C); 2) sprout soybean milk (SS); 3) soybean milk (S). In addition to anthropometric measurements, iron status was measured at baseline and at the end of the study. After six months, the concentration of hemoglobin and plasma ferritin of participants in sprout soybean group were 138.6 ± 6.3 g/L and 43.3 ± 12.6 µg/L, significantly higher than those of the control. Significant decreases in the rate of anemia, iron deficiency and free erythrocyte protoporphyrin (FEP) concentration were found both in sprout soybean and soybean group. An obvious decrease in plasma transferritin receptor was found in the sprout soybean group comparing with the control, but not in the soybean group. Small but not significant differences were found in all iron indicators between the sprout soybean and soybean group. Sprout soybeans and soybeans could improve the iron status of anemic adolescent girls. Although sprout soybeans exhibited some priority to soybeans, no absolutely significant difference was found between them.

Sesquiterpenoids from the twigs and leaves of Fokienia hodginsii.

A rare carotane-type sesquiterpenoid, forkienin A (1), a new eudesmane-type sesquiterpenoid, forkienin B (2), and a new natural eudesmane-type sesquiterpenoid, forkienin C (3), were isolated from the twigs and leaves of Fokienia hodginsii, along with eight known sesquiterpenoids. The structures of the new compounds were elucidated on the basis of their spectroscopic analysis, including 1D and 2D NMR methods. All compounds were evaluated for cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7, and SW480 cell lines.

[Influence of magnesium supplementation on insulin receptor affinity in erythrocytes of type 2 diabetes rats].

OBJECTIVE: To observe the influence of oral magnesium supplementation on insulin receptor affinity in erythrocytes of type 2 diabetes rats. METHOD: diabetes rats were induced by high-fat-diet and intraperitoneal injection of streptozocin, and divided into 4 groups. Magnesium was supplemented in high-fat-diet at the dose of 2000, 1000, 200 and 0 mg/kg,respectively. Normal control rats were fed with ordinary diet. Rats were killed after four weeks. Erythrocytes insulin receptor number, combination constants, combined capacity, fasting insulin level and fasting glucose levels were measured, and insulin resistance index and insulin sensitivity index were calculated. RESULTS: High affinity insulin receptor combination constant, combined capacity and receptor number in high dosage group were (1.24 +/- 0.47) x 10(9) L/mol, (1.26 +/- 0.53) x 10(14)/L and 80.23 +/- 0.47 respectively, significantly higher than diabetes control group. Insulin resistance index decreased and insulin sensitivity index increased in high dosage group than diabetes control. CONCLUSION: Magnesium supplementation could improve erythrocyte insulin receptor affinity and improve insulin resistance in type 2 diabetic rats.

Mechanisms of genistein protection on pancreas cell damage in high glucose condition.

AIM: An adequate ß cell number is important to prevent the onset and development of type 2 diabetes. The aim of this study was to determine if phytoestrogen gesintein has protective effects against high glucose-induced cell apoptosis in human pancreas cells, and to try to determine the possible mechanism for this protection. METHODS: Human pancreatic ß cells were subjected to normal (5 mM) or high glucose (25 mM) with and without the presence of 100 nM genistein, and also in the presence and absence of the pure anti-estrogen ICI-182780 (100 nM). Bcl-2 siRNA transfection was performed to investigate if the effect of genistein was also Bcl-2 dependent. Cell proliferation and apoptosis were determined by Tritiated Thymidine Incorporation Assay and Cell Apoptosis Detection ELISA. Estrogen receptor and Bcl-2 mRNA expression was measured by Real-time Quantitative PCR. RESULTS: High glucose concentration caused cell proliferation inhibition and apoptosis in cultured human pancreatic ß cells, and these effects were significantly reversed by genistein (P<0.01). Estrogen receptor beta was expressed in the cultured cells, and genistein protection was blocked by ICI-182780 administration as well as Bcl-2 siRNA transfection. CONCLUSION: Phytoestrogen gave protection against high glucose-induced pancreatic cell damage through estrogen receptor beta and Bcl-2 dependent pathways.