Oral magnesium supplementation improves insulin sensitivity and metabolic control in type 2 diabetic subjects: a randomized double-blind controlled trial

Supplementation with magnesium and vitamin E were more effective than magnesium alone to decrease plasma lipids and blood viscosity in diabetic rats

Although magnesium and vitamin E (VE) have differing effects on diabetes, both are beneficial. We hypothesized that preventive supplementation of magnesium combined with VE could improve the metabolism of lipids and blood viscosity more effectively than the use of magnesium or VE alone. Our objective was to detect the effects of preventive supplementation of magnesium combined with VE on lipid peroxidation, lipid metabolic parameters, and blood viscosity in diabetic rats. Six dietary groups, all fed with high-energy diets, were formed and studied for 8 weeks: control group (C); VE group (E); middle-dose magnesium group (MM); high-dose magnesium group (HM); VE plus middle-dose magnesium group (EMM); and VE plus high-dose magnesium group (EHM). Compared with C group, malondialdehyde was inhibited in the E, EMM, and EHM groups (all P < .05); total cholesterol decreased in all 5 treated groups, and significant differences were found in groups E (P = .004), MM (P = .017), EMM (P = .016), and EHM (P = .020). Compared with the C group, high-density lipoprotein levels were elevated in the HM (P = .027) and EHM (P = .021) groups, and low-density lipoprotein levels were lower in the E (P = .010), EMM (P = .025), and EHM (P = .015) groups. Differences between middle and high shear rates of blood viscosity were significant in all treated groups compared with the C group (all P <or= .001). Statistical analysis showed that there was no interaction between magnesium and VE. We concluded that preventive supplementation of VE combined with magnesium was more beneficial to improve the plasma lipid parameters and blood viscosity in diabetic rats than magnesium alone.

Posttransplantation hypomagnesemia and its relation with immunosuppression as predictors of new-onset diabetes after transplantation

New-onset diabetes after transplantation (NODAT) is a frequent complication and has an impact on patient and graft survival. Hypomagnesemia is common in both renal transplant recipients and in diabetics. This study examines the relationship between hypomagnesemia, NODAT and the type of immunosuppression in renal transplant recipients. We conducted a retrospective single-center analysis (2002-2008) in order to assess NODAT the first year posttransplantation as defined by American Diabetes Association criteria. Serum magnesium (Mg) levels were defined as the median of all Mg levels registered during the first month posttransplantation. Patients with NODAT (N = 75; 29.5%) versus non-NODAT had lower Mg levels (p < 0.001). Patients with an Mg level < versus > or = 1.9 mg/dL showed a faster development of NODAT (log-rank p < 0.001). Mg levels were lower in patients on calcineurin inhibitors (CNI) versus no CNI patients (p < 0.001). Mg levels, albumin, BMI, triglycerides, posttransplantation hyperglycemia, tacrolimus levels and the use of sirolimus were predictors of NODAT in the multivariate analysis. Hypomagnesemia was an independent predictor of NODAT in renal transplant recipients. We confirm that the use of CNI is associated with NODAT, but, to a large extent, this effect seems attributable to the induction of hypomagnesemia. After adjustment for Mg, sirolimus was also associated with NODAT.

Dietary calcium and magnesium intakes and the risk of type 2 diabetes: the Shanghai Women's Health Study

BACKGROUND

Diet plays a key role in the development of type 2 diabetes (T2D), but little is known about the contributions of specific nutrients in populations in which dietary patterns differ from Western populations.

OBJECTIVE

We examined associations between calcium and magnesium intakes and the risk of T2D in a Chinese population.

DESIGN

We used data from a population-based, prospective study of 64,191 women who were free of T2D or other chronic diseases at study recruitment and were living in urban Shanghai, China. Dietary intake, physical activity, and anthropometric measurements were assessed through in-person interviews. A Cox regression model was used to evaluate the association of the exposures under study with the risk of T2D.

RESULTS

An inverse association between calcium and magnesium intakes and T2D risk was observed. The relative risks for the lowest to the highest quintiles of calcium intake were 1.00, 0.82, 0.73, 0.67, and 0.74 (P for trend < 0.001), and for magnesium they were 1.00, 0.84, 0.84, 0.79, and 0.86 (P for trend < 0.001). Milk intake was also inversely associated with the risk of T2D.

CONCLUSION

Our data suggest that calcium and magnesium intakes may protect against the development of T2D in this population.

Effects of alpha-tocopherol on oxidative status and metabolic profile in overweight women

Despite extensive research, the effects of α-tocopherol supplementation remain controversial. Few studies have been focused on obese and overweight people. We examined the effects of α-tocopherol (AT) on the oxidative status and metabolic profile in overweight women. Sixteen overweight women between the ages of 40–60 years old, received AT, 800 IU/day during 12 weeks, followed by a 6-week washout period. Blood samples were taken at the beginning and then every 6 weeks until the end of the study. AT, retinol, malondialdehyde (MDA), total antioxidant status (TAS), selenium-dependent glutathione peroxidase (GPx) and CuZn-superoxide dismutase (SOD) were quantified to evaluate the oxidative stress. The metabolic profile was estimated by measuring glycated hemoglobin (HbA1c) in erythrocytes and glucose, phosphate, magnesium, lipid and lipoprotein concentrations in serum. Under AT administration HbA1c, serum-MDA levels and erythrocyte GPx activity were markedly reduced. TAS, AT and Mg²⁺ concentrations in serum and SOD activity in erythrocytes were higher after AT treatment. Body weight; glucose, lipid and retinol concentrations, or blood cells count were unchanged. Lipid peroxidation was considerably reduced in AT treated women and also improved serum antioxidant status was observed, but the imbalanced response between erythrocyte SOD and GPx activities could affect normal response to oxidative stress.

Thermodynamics of binding of divalent magnesium and manganese to uridine phosphates: implications for diabetes-related hypomagnesaemia and carbohydrate biocatalysis

BACKGROUND

Although the necessity of divalent magnesium and manganese for full activity of sugar nucleotidyltransferases and glycosyltransferases is well known, the role of these metal cations in binding the substrates (uridine 5'-triphosphate, glucose-1-phosphate, N-acetylglucosamine-1-phosphate, and uridine 5'-diphosphate glucose), products (uridine 5'-diphosphate glucose, uridine 5'-diphosphate N-acetylglucosamine, pyrophosphate, and uridine 5'-diphosphate), and/or enzyme is not clearly understood.

RESULTS

Using isothermal titration calorimetry we have studied the binding relationship between the divalent metals, magnesium and manganese, and uridine 5'-phosphates to determine the role these metals play in carbohydrate biosynthesis. It was determined from the isothermal titration calorimetry (ITC) data that Mg(+2) and Mn(+2) are most tightly bound to PP(i), K(b) = 41,000 +/- 2000 M(-1) and 28,000 +/- 50,000 M(-1) respectively, and UTP, K(b) = 14,300 +/- 700 M(-1) and 13,000 +/- 2,000 M(-1) respectively.

CONCLUSION

Our results indicate that the formal charge state of the phosphate containing substrates determine the binding strength. Divalent metal cations magnesium and manganese showed similar trends in binding to the sugar substrates. Enthalpy of binding values were all determined to be endothermic except for the PP(i) case. In addition, entropy of binding values were all found to be positive. From this data, we discuss the role of magnesium and manganese in both sugar nucleotidyltransferase and glycosyltransferase reactions, the differences in metal-bound substrates expected under normal physiological metal concentrations and those of hypomagnesaemia, and the implications for drug design.

Minerals as ergogenic aids

Chromium, magnesium, zinc, and selenium are essential minerals for humans. They all are involved in a number of metabolic reactions in the body; many of these reactions are involved in energy metabolism, and hence it is thought that they may exert an ergogenic effect. However, the data on their effects as ergogenic aids have been equivocal. Longitudinal research is required (including supplementation studies) to follow athletes over time and properly evaluate effects of these minerals upon performance. The purpose of this review is to evaluate the ergogenic effects of chromium, magnesium, zinc, and selenium.

Magnesium, the metabolic syndrome, insulin resistance, and type 2 diabetes mellitus

Magnesium is an essential mineral and has been established as a cofactor for over 300 metabolic reactions in the body. Some research has indicated that lower intakes of magnesium and lower serum magnesium concentrations may lead to and are associated with the metabolic syndrome, insulin resistance, and/or type 2 diabetes mellitus. The goal of this review is to examine the research conducted on: 1) magnesium status, metabolic syndrome, insulin resistance, and type 2 diabetes mellitus, and 2) the effects of magnesium intake and/or supplementation on metabolic syndrome, insulin resistance, and type 2 diabetes mellitus. To make this review as current as possible, the majority of research articles reviewed were from 2000 to the present.

Coffee and Tea Consumption and Risk of Stroke Subtypes in Male Smokers

Background and Purpose— Coffee and tea consumption could potentially reduce the risk of stroke because these beverages have antioxidant properties, and coffee may improve insulin sensitivity. We examined the associations of coffee and tea consumption with risk of stroke subtypes.

Methods— We used prospective data from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a cohort study of 26 556 male Finnish smokers aged 50 to 69 years without a history of stroke at baseline. Coffee and tea consumption was assessed at baseline using a validated food-frequency questionnaire. During a mean follow-up of 13.6 years, from 1985 through December 2004, 2702 cerebral infarctions, 383 intracerebral hemorrhages, and 196 subarachnoid hemorrhages were ascertained from national registries.

Results— After adjustment for age and cardiovascular risk factors, both consumption of coffee and tea was statistically significantly inversely associated with the risk of cerebral infarction but not intracerebral or subarachnoid hemorrhage. The multivariate relative risk of cerebral infarction for men in the highest category of coffee consumption (≥8 cups/d) was 0.77 (95% CI, 0.66 to 0.90; P for trend <0.001) compared with those in the lowest category (<2 cups/d). The corresponding relative risk comparing men in the highest category of tea consumption (≥2 cups/d) with those in the lowest category (nondrinkers) was 0.79 (95% CI, 0.68 to 0.92; P for trend=0.002).

Conclusions— These results suggest that high consumption of coffee and tea may reduce the risk of cerebral infarction among men, independent of known cardiovascular risk factors.

Hypomagnesaemia and risk for metabolic glucose disorders: a 10-year follow-up study

BACKGROUND

Although several lines of evidence suggest that hypomagnesaemia is a risk factor for developing type 2 diabetes, there are no studies regarding the association between hypomagnesaemia and the risk for developing impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). Our objective was to examine the association between serum magnesium levels and the risk for developing IFG, IGT and type 2 diabetes.

MATERIALS AND METHODS

A total of 1122 individuals (20-65 years of age) were enrolled between 1996 and 1997, and 817 individuals re-examined about 10 years later. New-onset IFG (5.6-7.0 mmol L(-1) fasting glucose), IGT (7.8-11.1 mmol L(-1) glucose 2-h postload), and type 2 diabetes were determined from the number of subjects who had these conditions at the second examination without evidence that they were present at the first one. The relative risk of new-onset metabolic glucose disorders and diabetes (dependent variables) was computed using Poisson regression model adjusted for age, sex, family history of diabetes, waist circumference and homeostasis model assessment for insulin resistance index. Serum magnesium levels of < 0.74 mmol L(-1) (independent variable) defined the exposed group.

RESULTS

At baseline, 420 (51.4%) individuals had hypomagnesaemia. New-onset IFG and IGT was identified in 276 (33.8%) individuals. The relative risk for IFG, IGT and IFG + IGT was 1.11 (95% confidence interval, 0.5-5.1), 1.38 (95% confidence interval, 1.1-6.3) and 1.49 (95% confidence interval, 1.1-4.9), respectively. New-onset diabetes was identified in 78 (9.5%) individuals (relative risk 2.54; 95% confidence interval, 1.1-4.1).

CONCLUSIONS

Hypomagnesaemia is independently associated with the development of IGT, IFG + IGT and type 2 diabetes, but not with the development of IFG.

Obesity, inflammation, and the potential application of pharmaconutrition

Obesity is an emerging problem worldwide. Hospitalized obese patients often have a worse outcome than patients of normal weight, particularly in the setting of trauma and critical care. Obesity creates a low-grade systemic inflammatory response syndrome (SIRS) that is similar (but on a much smaller scale) to gram-negative sepsis. This process involves up-regulation of systemic immunity, is characterized clinically by insulin resistance and the metabolic syndrome, and puts the patient at increased risk for organ failure, infectious morbidity, and mortality. Through lipotoxicity and cytokine dysregulation, obesity may act to prime the immune system, predisposing to an exaggerated subsequent immune response when a second clinical insult occurs (such as trauma, burns, or myocardial infarction). Specialized nutrition therapy for such patients currently consists of a hypocaloric, high-protein diet. However, this approach does not address the putative pathophysiologic mechanisms of inflammation and altered metabolism associated with obesity. A number of dietary agents such as arginine, fish oil, and carnitine may correct these problems at the molecular level. Pharmaconutrition formulas may provide exciting innovations for the nutrition therapy of the obese patient.

Clinical consequences and management of hypomagnesemia

Magnesium deficiency and hypomagnesemia remain quite prevalent, particularly in patients in intensive care units, and may have important clinical consequences. Magnesium should be measured directly in clinical circumstances in which a risk for magnesium deficiency exists and appropriately corrected when found. This commentary reviews the current knowledge of magnesium homeostasis and the risk factors and clinical consequences of magnesium deficiency and outlines approaches to therapy.

The effects of a whole grain-enriched hypocaloric diet on cardiovascular disease risk factors in men and women with metabolic syndrome

BACKGROUND

Whole-grain foods are associated in observational studies with a lower body mass index and lower cardiovascular disease (CVD) risk. However, few clinical trials have tested whether incorporating whole grains into a hypocaloric diet increases weight loss and improves CVD risk factors.

OBJECTIVE

The aim of this study was to determine whether including whole-grain foods in a hypocaloric (reduced by 500 kcal/d) diet enhances weight loss and improves CVD risk factors.

DESIGN

Obese adults (25 M, 25 F) with metabolic syndrome were randomly assigned to receive dietary advice either to avoid whole-grain foods or to obtain all of their grain servings from whole grains for 12 wk. All participants were given the same dietary advice in other respects for weight loss.

RESULTS

Body weight, waist circumference, and percentage body fat decreased significantly (P<0.001) in both groups over the study period, but there was a significantly (P=0.03) greater decrease in percentage body fat in the abdominal region in the whole-grain group than in the refined-grain group. C-reactive protein (CRP) decreased 38% in the whole-grain group independent of weight loss but was unchanged in the refined-grain group (P=0.01 for group x time interaction). Total, LDL, and HDL cholesterol decreased in both diet groups (P<0.05). Dietary fiber and magnesium intakes increased in the whole-grain but not the refined-grain group (P=0.007 and P<0.001, respectively, for group x time interaction).

CONCLUSIONS

Both hypocaloric diets were effective means of improving CVD risk factors with moderate weight loss. There were significantly (P<0.05) greater decreases in CRP and percentage body fat in the abdominal region in participants consuming whole grains than in those consuming refined grains.

Magnesium intake, glucose and insulin serum levels in pre-school very-low-birth weight pre-term children

AIMS

To evaluate cross-sectional associations between dietary magnesium intake and the metabolic pattern of very-low-birth-weight (VLBW, <1500 g) pre-term children, in pre-school years (>2 and <6 years).

METHODS AND RESULTS

Fifty-eight Italian children without major congenital malformations/conditions were enrolled; dietary intakes, clinical and (in 34 cases) laboratory characteristics were evaluated. Subjects with lower magnesium intake showed significantly higher fasting glucose, insulin and Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) levels. At simple regression analysis, fasting glucose was significantly associated with magnesium intake (inversely) and catch-up growth (CUG). Fasting insulin and HOMA-IR values were inversely associated with intakes of magnesium and fibres, and directly with Body Mass Index (BMI) and CUG. In a multiple regression model, after adjusting for multiple confounders and fibre intake, magnesium intake was inversely associated with glucose (beta=-0.018; 95%CI -0.026 to -0.010), but not with insulin or HOMA-IR levels. In the same model, dietary fibres remained inversely associated with insulin (beta=-0.075; -0.14 to -0.008) and HOMA-IR levels (beta=-0.06; -0.11 to -0.01).

CONCLUSION

These results suggest a significant association between reduced magnesium intake and fasting glucose, and between reduced fibre intake and insulin resistance and this is present even in earlier childhood, and independently of BMI and growth characteristics.

Magnesium metabolism in hypertension and type 2 diabetes mellitus

The increasing evidence for the clinical relevance of altered magnesium metabolism to states of altered insulin resistance confirms the role of magnesium deficit as a possible underlying common mechanism of the "insulin resistance" of hypertension and altered glucose tolerance. The pioneer work of Lawrence M. Resnick and his group using the cellular ion-based approach that we are only partially presenting here has consistently contributed to the progress of the field, demonstrating (a) the critical importance of magnesium metabolism in regulating insulin sensitivity as well as vascular tone, and blood-pressure homeostasis; (b) that magnesium deficiency, defined on the basis of intracellular free magnesium levels, and or serum ionized magnesium is a common feature of both diabetic and hypertensive states as well as various other cardiovascular and metabolic processes and aging; (c) the ability of environmental factors such as dietary nutrient-sugar and mineral content to alter the set point of steady-state cell ion activity; and (d) that magnesium supplementation is indicated in conditions associated with magnesium deficit although well-designed therapeutic trials of magnesium in essential hypertension and type 2 diabetes mellitus are needed in the near future.

Depressive Symptoms and Hypomagnesemia in Older Diabetic Subjects

BACKGROUND

We undertook this study to assess the hypothesis that hypomagnesemia is associated with depressive symptoms in older people with diabetes.

METHODS

A total of 55 type 2 diabetic patients, aged 65 years or older, with depressive symptoms were compared with a control group of diabetic subjects without depressive symptoms in an age- and gender-matched case/control study. A score >or=11 points in the Yesavage's scale was used for defining depressive symptoms, and hypomagnesemia was defined by serum magnesium levels <0.74 mmol/L. Well-known causes for depression as well as diseases and drugs that may cause depressive symptoms or hypomagnesemia were exclusion criteria.

RESULTS

Serum magnesium levels were significantly lower among depressive than control diabetic subjects (0.74 +/- 0.25 vs. 0.86 +/- 0.29 mmol/L, p = 0.02). Twenty four (43.6%) and 7 (12.7%) individuals in the case and control group exhibited low serum magnesium levels (p = 0.0006). The adjusted logistic regression analysis showed an independent association between hypomagnesemia and depressive symptoms (OR 1.79; CI(95%) 1.1-6.9, p = 0.03).

CONCLUSIONS

Our results suggest that hypomagnesemia is independently associated with depressive symptoms in older people with diabetes.

Prediction of all-cause mortality in a patient population with hypertension and type 2 DM by using traditional risk factors and serum-phosphate,-calcium and-magnesium

The aim of this study is to investigate whether the prediction of all-cause mortality from traditional risk factors is improved by adding electrolytes (serum-phosphate (S-P), serum-calcium (S-Ca) and serum-magnesium (S-Mg)) in a Cox regression. The study uses an 18-year follow-up of patients (n=2504) referred by physicians in primary health care and hospitals to the Vindeln Patient Education (VPE) Center, mainly with a diagnosis of hypertension (HT), type 2 diabetes mellitus (DM) and/or obesity. Cox regression, with the latest registered value and baseline values for risk factors, was used to study all-cause mortality in men and women. 221 out of 1096 men and 157 out of 1408 women died during the 18-year follow-up (20% and 11% respectively). The Cox regression analysis reveals that high blood glucose (B-Glu) and low S-Mg were significantly associated with increased all-cause mortality in the whole patient population as well as in men and women separately. Among women, type 2 DM and systolic blood pressure (SBP) and among men, high S-Ca, S-P, S-urate and body mass index (BMI) were the main predictors of all-cause mortality. There is significantly improved prediction of all-cause mortality with electrolytes added to the traditional risk factors. High B-Glu and low S-Mg in both men and women, and high S-Ca and S-P in men, are significantly associated with all-cause mortality. The metabolic disturbance in this high-risk group of patients can be more fully understood if ionic imbalance is included in the prediction of mortatlity.

Magnesium intake and risk of type 2 diabetes: a meta-analysis

OBJECTIVE

To assess the association between magnesium intake and risk of type 2 diabetes.

DESIGN

Meta-analysis of prospective cohort studies.

DATA SOURCES

We retrieved studies published in any language by systematically searching MEDLINE from 1966 to February 2007 and by manually examining the references of the original articles.

STUDY SELECTION

We included prospective cohort studies reporting relative risks with 95% confidence intervals for the association between magnesium intake and incidence of type 2 diabetes.

RESULTS

The seven identified cohort studies of magnesium intake [from foods only (n = 4) or from foods and supplements combined (n = 3)] and incidence of type 2 diabetes included 286,668 participants and 10,912 cases. All but one study found an inverse relation between magnesium intake and risk of type 2 diabetes, and in four studies the association was statistically significant. The overall relative risk for a 100 mg day(-1) increase in magnesium intake was 0.85 (95% CI, 0.79-0.92). Results were similar for intake of dietary magnesium (RR, 0.86; 95% CI, 0.77-0.95) and total magnesium (RR, 0.83; 95% CI, 0.77-0.89). There was no evidence of publication bias (P = 0.99).

CONCLUSIONS

Magnesium intake was inversely associated with incidence of type 2 diabetes. This finding suggests that increased consumption of magnesium-rich foods such as whole grains, beans, nuts, and green leafy vegetables may reduce the risk of type 2 diabetes.

Intake of dietary magnesium and the prevalence of the metabolic syndrome among U.S. adults

OBJECTIVE

Limited data suggest that people with the metabolic syndrome have lower intakes or circulating concentrations of magnesium than those who do not have the syndrome. The aim of this study was to examine the associations between dietary intake of magnesium and the prevalence of the metabolic syndrome in a nationally representative sample of U.S. adults.

RESEARCH METHODS AND PROCEDURES

We used data for 7669 participants > or =20 years of age of the Third National Health and Nutrition Examination Survey (1988 to 1994). The metabolic syndrome was defined using the criteria of the National Cholesterol Education Program. Magnesium intake was determined from a single dietary 24-hour recall.

RESULTS

The unadjusted prevalences of the metabolic syndrome were 29.0% (quintile of lowest magnesium intake), 27.5%, 25.8%, 23.9%, and 21.8% for increasing quintiles of magnesium intake (p for trend = 0.002). After multiple adjustment, the odds ratios for the second through the fifth quintiles (highest intake) of magnesium intake among all participants included in the analysis were 0.84 [95% confidence interval (CI): 0.58, 1.23], 0.76 (95% CI: 0.54, 1.07), 0.62 (95% CI: 0.40, 0.98), and 0.56 (95% CI: 0.34, 0.92), respectively (p for trend = 0.029). The associations were similar for men and women.

DISCUSSION

Our results showing an inverse association between dietary magnesium intake and the prevalence of the metabolic syndrome add to the evidence that adequate magnesium intake or a diet rich in magnesium may be important for maintaining good cardiometabolic health.

Magnesium intake and colorectal cancer risk in the Netherlands Cohort Study

Energy-adjusted magnesium intake was nonsignificantly inversely related to risk of colorectal cancer (n=2328) in the Netherlands Cohort Study on Diet and Cancer that started in 1986 (n=58 279 men and 62 573 women). Statistically significant inverse trends in risk were observed in overweight subjects for colon and proximal colon cancer across increasing quintiles of magnesium uptake (P-trend, 0.05 and 0.02, respectively). Although an overall protective effect was not afforded, our results suggest an effect of magnesium in overweight subjects, possibly through decreasing insulin resistance.

Magnesium metabolism in type 2 diabetes mellitus, metabolic syndrome and insulin resistance

Type 2 diabetes is characterized by cellular and extracellular Mg depletion. Epidemiologic studies showed a high prevalence of hypomagnesaemia and lower intracellular Mg concentrations in diabetic subjects. Insulin and glucose are important regulators of Mg metabolism. Intracellular Mg plays a key role in regulating insulin action, insulin-mediated-glucose uptake and vascular tone. Reduced intracellular Mg concentrations result in a defective tyrosine-kinase activity, post-receptorial impairment in insulin action, and worsening of insulin resistance in diabetic patients. Mg deficit has been proposed as a possible underlying common mechanism of the "insulin resistance" of different metabolic conditions. Low dietary Mg intake is also related to the development of type 2 diabetes. Benefits of Mg supplementation on metabolic profile in diabetic subjects have been found in most, but not all clinical studies, and larger prospective studies are needed to support the potential role of dietary Mg supplementation as a possible public health strategy in diabetes risk.

Hypomagnesemia in patients with type 2 diabetes

Hypomagnesemia has been reported to occur at an increased frequency among patients with type 2 diabetes compared with their counterparts without diabetes. Despite numerous reports linking hypomagnesemia to chronic diabetic complications, attention to this issue is poor among clinicians. This article reviews the literature on the metabolism of magnesium, incidence of hypomagnesemia in patients with type 2 diabetes, implicated contributing factors, and associated complications. Hypomagnesemia occurs at an incidence of 13.5 to 47.7% among patients with type 2 diabetes. Poor dietary intake, autonomic dysfunction, altered insulin metabolism, glomerular hyperfiltration, osmotic diuresis, recurrent metabolic acidosis, hypophosphatemia, and hypokalemia may be contributory. Hypomagnesemia has been linked to poor glycemic control, coronary artery diseases, hypertension, diabetic retinopathy, nephropathy, neuropathy, and foot ulcerations. The increased incidence of hypomagnesemia among patients with type 2 diabetes presumably is multifactorial. Because current data suggest adverse outcomes in association with hypomagnesemia, it is prudent to monitor magnesium routinely in this patient population and treat the condition whenever possible.

Algorithm for Complementary and Alternative Medicine Practice and Research in Type 2 Diabetes

OBJECTIVE

To develop a model to direct the prescription of nutritional and botanical medicines in the treatment of type 2 diabetes for both clinical and research purposes.

METHODS

Available literature on nutritional and botanical medicines was reviewed and categorized as follows: antioxidant/anti-inflammatory; insulin sensitizer; and beta-cell protectant/insulin secretagogue. Literature describing laboratory assessment for glycemic control, insulin resistance, and beta-cell reserve was also reviewed and a clinical decision tree was developed.

RESULTS

Clinical algorithms were created to guide the use of nutritional and botanic medicines using validated laboratory measures of glycemic control, insulin sensitivity, and beta-cell reserve. Nutrient and botanic medicines with clinical trial research support include coenzyme Q10, carnitine, alpha-lipoic acid, N-acetylcysteine, vitamin D, vitamin C, vitamin E, chromium, vanadium, omega-3 fatty acids, cinnamon (Cinnamomum cassia), fenugreek (Trigonella foenum-graecum), and gymnema (Gymnema sylvestre).

CONCLUSIONS

Clinical algorithms can direct supplementation in clinical practice and provide research models for clinical investigation. Algorithms also provide a framework for integration of future evidence as it becomes available. Research funding to investigate potentially beneficial practices in complementary medicine is critically important for optimal patient care and safety.

Magnesium Intake Is Related to Improved Insulin Homeostasis in the Framingham Offspring Cohort

OBJECTIVE

Higher dietary intake of magnesium may protect against development of type 2 diabetes. The aim of this study was to examine the association between dietary magnesium intake and metabolic risk factors for diabetes.

METHODS

We examined cross-sectional associations between magnesium intake and fasting glucose and insulin, 2-hour post-challenge plasma glucose and insulin, and insulin resistance assessed by the homeostasis model (HOMA-IR) in 1223 men and 1485 women without diabetes from the Framingham Offspring cohort. Magnesium intake was assessed by a food frequency questionnaire and magnesium intake was categorized into quintile categories. Geometric mean insulin, glucose, 2-hour post challenge plasma glucose and insulin concentrations and HOMA-IR were estimated across quintile categories of magnesium intake using Generalized Linear Models.

RESULTS

After adjustment for potential confounding factors, magnesium intake was inversely associated with fasting insulin (mean: 29.9 vs 26.7 microU/mL in the lowest vs highest quintiles of magnesium intake; P trend <0.001), post-glucose challenge plasma insulin (86.4 vs 72 microU/mL; P trend <0.001), and HOMA-IR (7.0 vs 6.2; P trend <0.001). No significant association was found between magnesium intake and fasting glucose or 2-hour post challenge glucose.

CONCLUSIONS

Improved insulin sensitivity may be one mechanism by which higher dietary magnesium intake may reduce the risk of developing type 2 DM.

Dietary magnesium and fiber intakes and inflammatory and metabolic indicators in middle-aged subjects from a population-based cohort

BACKGROUND

Type 2 diabetes (DM), metabolic syndrome (MetS), and inflammation are linked to reduced magnesium and fiber intakes; these associations are attenuated by adjustment for each of these nutrients.

OBJECTIVE

We investigated the association among magnesium and fiber intakes, metabolic variables, and high-sensitivity C-reactive protein (hs-CRP) values.

DESIGN

Cross-sectional analyses were performed in a representative cohort of 1653 adults and in a subgroup with normal body mass index without dysmetabolisms (n = 205). A validated semiquantitative food-frequency questionnaire was used; magnesium intake was computed by multiplying its content in each food by the frequency of food consumption.

RESULTS

The prevalence of DM, MetS, and hs-CRP >/= 3 mg/L significantly decreased from the lowest to the highest tertile of magnesium and fiber intakes. Subjects within the lowest tertiles of magnesium and fiber intakes were 3-4 times as likely to have DM, MetS, and hs-CRP >/= 3 mg/L, after multiple adjustments. After the analysis was additionally controlled for fiber intake, associations with hs-CRP >/= 3 mg/L proved to be significant (odds ratio: 2.05; 95% CI: 1.30, 3.25), whereas reduced magnesium intake and DM and MetS were no longer significant. The lowest tertile of fiber intake remained associated with DM, hs-CRP >/= 3 mg/L, and MetS after adjustments for multiple confounders and magnesium intake. In the lean, healthy subject subgroup, hs-CRP values were inversely associated with magnesium and fiber intakes in a multivariate model (P < 0.001).

CONCLUSIONS

Reduced fiber intake was significantly associated with metabolic abnormalities; the magnesium effect might be confounded by fiber being in foods that also provided magnesium. Lower magnesium and fiber intakes were linked to hs-CRP >/= 3 mg/L in both the entire cohort and healthy persons.

Toward a core nutraceutical program for cancer management

As previously suggested, it may be feasible to impede tumorevoked angiogenesis with a nutraceutical program composed of glycine, fish oil, epigallocatechin-3-gallate, selenium, and silymarin, complemented by a low-fat vegan diet, exercise training, and, if feasible, a salicylate and the drug tetrathiomolybdate. It is now proposed that the scope of this program be expanded to address additional common needs of cancer patients: blocking the process of metastasis; boosting the cytotoxic capacity of innate immune defenses (natural killer [NK] cells); preventing cachexia, thromboembolism, and tumor-induced osteolysis; and maintaining optimal micronutrient status. Modified citrus pectin, a galectin-3 antagonist, has impressive antimetastatic potential. Mushroombeta-glucans and probiotic lactobacilli can amplify NK activity via stimulatory effects on macrophages. Selenium, beta-carotene, and glutamine can also increase the number and/or cytotoxic activity of NK cells. Cachectic loss of muscle mass can be opposed by fish oil, glutamine, and beta-hydroxy-beta-methylbutyrate. Fish oil, policosanol, and vitamin D may have potential for control of osteolysis. High-dose aspirin or salicylates, by preventing NF-B activation, can be expected to aid prevention of metastasis and cachexia while down-regulating osteolysis, but their impacts on innate immune defenses will not be entirely favorable. A nutritional insurance formula crafted for the special needs of cancer patients can be included in this regimen. To minimize patient inconvenience, this complex core nutraceutical program could be configured as an oil product, a powder, and a capsule product, with the nutritional insurance formula provided in tablets. It would be of interest to test this program in nude mouse xenograft models.

Effects of oral magnesium supplementation on glycaemic control in Type 2 diabetes: a meta-analysis of randomized double-blind controlled trials

AIMS

The aim of this study was to assess the evidence on the effect of oral magnesium supplementation on glycaemic control in patients with Type 2 diabetes.

METHODS

We searched the electronic databases of medline, embase and the Cochrane Controlled Trials Register up to January 2005. We identified nine randomized double-blind controlled trials with a total of 370 patients with Type 2 diabetes and of duration 4-16 weeks. The median dose of oral magnesium supplementation was 15 mmol/day (360 mg/day) in the treatment groups. The primary outcome was glycaemic control, as measured by glycated haemoglobin (HbA(1c)) or fasting blood glucose levels; the secondary outcomes included body mass index, blood pressure (BP) and lipids. Using a random-effects model, we calculated the weighted mean differences (WMD) and 95% confidence interval (CI).

RESULTS

After a median duration of 12 weeks, the weighted mean post-intervention fasting glucose was significantly lower in the treatment groups compared with the placebo groups [-0.56 mmol/l (95% CI, -1.10 to -0.01); P for heterogeneity = 0.02]. The difference in post-intervention HbA(1c) between magnesium supplementation groups and control groups was not significant [-0.31% (95% CI, -0.81 to 0.19); P for heterogeneity = 0.10]. Neither systolic nor diastolic BP was significantly changed. Magnesium supplementation increased on high-density lipoprotein (HDL) cholesterol levels [0.08 mmol/l (95% CI, 0.03 to 0.14); P for heterogeneity = 0.36] but had no effect on total cholesterol, low-density lipoprotein (LDL) cholesterol and triglyceride.

CONCLUSIONS

Oral magnesium supplementation for 4-16 weeks may be effective in reducing plasma fasting glucose levels and raising HDL cholesterol in patients with Type 2 diabetes, although the long-term benefits and safety of magnesium treatment on glycaemic control remain to be determined.

Coffee, diabetes, and weight control

Several prospective epidemiologic studies over the past 4 y concluded that ingestion of caffeinated and decaffeinated coffee can reduce the risk of diabetes. This finding is at odds with the results of trials in humans showing that glucose tolerance is reduced shortly after ingestion of caffeine or caffeinated coffee and suggesting that coffee consumption could increase the risk of diabetes. This review discusses epidemiologic and laboratory studies of the effects of coffee and its constituents, with a focus on diabetes risk. Weight loss may be an explanatory factor, because one prospective epidemiologic study found that consumption of coffee was followed by lower diabetes risk but only in participants who had lost weight. A second such study found that both caffeine and coffee intakes were modestly and inversely associated with weight gain. It is possible that caffeine and other constituents of coffee, such as chlorogenic acid and quinides, are involved in causing weight loss. Caffeine and caffeinated coffee have been shown to acutely increase blood pressure and thereby to pose a health threat to persons with cardiovascular disease risk. One short-term study found that ground decaffeinated coffee did not increase blood pressure. Decaffeinated coffee, therefore, may be the type of coffee that can safely help persons decrease diabetes risk. However, the ability of decaffeinated coffee to achieve these effects is based on a limited number of studies, and the underlying biological mechanisms have yet to be elucidated.

Metabolic characteristics of soleus muscle in relation to insulin action in the offspring of hypertensive parents

Insulin resistance affecting skeletal muscle metabolism is present in the prehypertensive state. The aim of our study was to test the hypothesis that blood pressure value is related to skeletal muscle composition, measured by (31)P magnetic resonance (MR) spectroscopy, and to insulin sensitivity in the offspring of hypertensive parents (OH) and healthy controls. Study groups consisted of 10 healthy young lean OH with normal glucose tolerance, confirmed with oral glucose tolerance test, and 13 controls matched for age, sex, and body mass index. Insulin action was estimated as glucose disposal (M), glucose metabolic clearance rate (MCR), and insulin sensitivity index (M/I) during a 10-hour hyperinsulinemic euglycemic clamp. The sum of immunoreactive insulin values from the oral glucose tolerance test was calculated. (31)P MR spectroscopy was performed on a whole-body MR scanner (Siemens Vision, Erlangen, Germany) operating at 1.5 T and equipped with actively shielded gradient coils. There were no differences in common metabolic and anthropometric parameters between OH and controls except for the blood pressure, which was in the range of normal to high-normal level in OH. Mean blood pressure was significantly higher in OH (95.73 +/- 4.39 vs 83.76 +/- 3.95 mm Hg; P < .001). Trend toward insulin resistance was registered in OH with significantly lower M/I (0.74 +/- 0.47 vs 1.42 +/- 0.65 mg x kg(-1) x min(-1) x mIU(-1) x L(-1); P < .05). There were no significant differences in total serum magnesium (sMg) levels between OH and controls, although a positive correlation exists between sMg and insulin sensitivity expressed as M (r = 0.63, P < .01), MCR (r = 0.54, P < .01), and M/I (r = 0.51, P < .05). No differences in signal intensities of phosphocreatine (PCr), phosphomonoesters, phosphodiesters, inorganic phosphates (Pi), adenosine triphosphates (Patp and betaATP), and calculated concentrations of intracellular ionized magnesium (Mgi) and H(+) ions between the groups were detected. Systolic blood pressure correlates positively with PCr/Patp (r = 0.43, P < .05), Pi/Patp (r = 0.413, P < .05), and Pi/betaATP (r = 0.48, P < .05). Diastolic blood pressure correlates positively only with the ratio Pi/betaATP (r = 0.42, P < .05). The sum of immunoreactive insulin values correlates with PCr/betaATP (r = 0.53, P < .01) and with Pi/betaATP (r = 0.6, P < .01). In conclusion, increase in blood pressure and insulin resistance were confirmed in offspring of OH. Insulin sensitivity is related to sMg and the elevation of blood pressure is associated with the activation of energy metabolism in skeletal muscle. The relationship between muscle energetic characteristics and markers of insulin resistance suggests that the alteration of energy metabolism may be present in early stages of metabolic syndrome.

Dairy, magnesium, and calcium intake in relation to insulin sensitivity: approaches to modeling a dose-dependent association

Dairy intake has been inversely associated with insulin resistance, which may be partly due to the specific effects of calcium and magnesium. Data from the Insulin Resistance Atherosclerosis Study (1992-1999) for 1,036 US adults without diabetes at baseline were examined to evaluate the cross-sectional association of habitual dairy, magnesium, and calcium intake with insulin sensitivity at baseline and after 5 years of follow-up. Insulin sensitivity was directly measured with a validated, 12-sample, insulin-enhanced, intravenous glucose tolerance test with minimal model analysis. Dietary intake was assessed by a validated food frequency interview, and dietary supplement dose was confirmed by reviewing the supplement label. Several statistical approaches were used to ensure appropriate modeling of the dose-dependent association. No association was found between dairy intake and insulin sensitivity (p=0.41); however, associations were positive for magnesium and calcium intake (p=0.016) after adjusting for demographic, nondietary lifestyle and dietary factors, and food groups. Furthermore, magnesium intake was associated with insulin sensitivity in a threshold fashion, with a Bayesian method-estimated threshold (325 mg) (beta=0.0607/100 mg, p=0.0008 for <325 mg of magnesium/day; and beta=-0.001/100 mg, p=0.82 for >or=325 mg of magnesium/day). This study suggests that magnesium and calcium intake specifically, but not dairy intake, is associated with insulin sensitivity.

Coffee and health: a review of recent human research

Coffee is a complex mixture of chemicals that provides significant amounts of chlorogenic acid and caffeine. Unfiltered coffee is a significant source of cafestol and kahweol, which are diterpenes that have been implicated in the cholesterol-raising effects of coffee. The results of epidemiological research suggest that coffee consumption may help prevent several chronic diseases, including type 2 diabetes mellitus, Parkinson's disease and liver disease (cirrhosis and hepatocellular carcinoma). Most prospective cohort studies have not found coffee consumption to be associated with significantly increased cardiovascular disease risk. However, coffee consumption is associated with increases in several cardiovascular disease risk factors, including blood pressure and plasma homocysteine. At present, there is little evidence that coffee consumption increases the risk of cancer. For adults consuming moderate amounts of coffee (3-4 cups/d providing 300-400 mg/d of caffeine), there is little evidence of health risks and some evidence of health benefits. However, some groups, including people with hypertension, children, adolescents, and the elderly, may be more vulnerable to the adverse effects of caffeine. In addition, currently available evidence suggests that it may be prudent for pregnant women to limit coffee consumption to 3 cups/d providing no more than 300 mg/d of caffeine to exclude any increased probability of spontaneous abortion or impaired fetal growth.

Magnesium and diabetes mellitus: Their relation

The aim of this review was to elaborate a synthesis about the discussions on magnesium and diabetes mellitus, in the last 14 years. The magnesium deficiency has been associated with chronic diseases, amongst them, diabetes mellitus. Epidemiological studies had shown low levels of magnesium ingestion in the general population, as well as a relation between the ingestion of food rich in magnesium and the reduction of diabetes installation and its complications. Hypomagnesemia is frequently present in diabetic patients, however there is not an exact elucidation of the mechanism of magnesium deficiency in diabetes mellitus. On the other hand, in the presence of this illness, it is observed that inadequate metabolic control can affect the corporal concentrations of magnesium, developing hypomagnesemia, which may be still directly related with some micro and macrovascular complications observed in diabetes, as cardiovascular disease, retinopathy and neuropathy. This way, the chronic complications of diabetes can appear precociously. Based on this, the supplementation with magnesium has been suggested in patients with diabetes mellitus who have proven hypomagnesemia and the presence of its complications.

Cereal fiber improves whole-body insulin sensitivity in overweight and obese women

OBJECTIVE

Cereal fiber intake is linked to reduced risk of type 2 diabetes in epidemiological observations. The pathogenic background of this phenomenon is unknown. Based on recent findings, we hypothesized that intake of purified insoluble oat fiber may improve whole-body insulin sensitivity.

RESEARCH DESIGN AND METHODS

A randomized, controlled, single-blind, cross-over study was performed, and 17 overweight or obese subjects with normal glucose metabolism were analyzed. After consumption of nine macronutrient-matched portions of fiber-enriched bread (white bread enriched with 31.2 g insoluble fiber/day) or control (white bread) over a time period of 72 h, whole-body insulin sensitivity was assessed by euglycemic-hyperinsulinemic clamp. Energy intake was individually adjusted by providing standardized liquid meals. Hydrogen breath tests were performed to control for dietary adherence.

RESULTS

When analyzing the entire cohort, whole-body glucose disposal was improved after fiber consumption (M value 6.56 +/- 0.32 vs. 6.07 +/- 0.27 mg . min(-1) . kg(-1); P = 0.043). Thirteen subjects had increased hydrogen breath test concentrations after fiber consumption, indicating probable dietary adherence. Restricting analysis to these subjects, improvements in M value (6.85 +/- 0.34 vs. 6.06 +/- 0.32 mg . min(-1) . kg(-1); P = 0.003) and insulin sensitivity, expressed as M/I ratio (M value divided by mean serum insulin at steady state: 3.73 +/- 0.23 vs. 3.21 +/- 0.27; P = 0.02), after fiber consumption were more pronounced. Plasma lipids, serum magnesium, ghrelin, and adiponectin concentrations, as well as substrate utilization and body weight, were not significantly changed by fiber intake (P > 0.15).

CONCLUSIONS

Increased insoluble dietary fiber intake for 3 days significantly improved whole-body insulin sensitivity. These data suggest a potential mechanism linking cereal fiber intake and reduced risk of type 2 diabetes.

PKC-mediated modulation of L-type calcium channels may contribute to fat-induced insulin resistance

Increased intracellular free calcium [Ca2+]i has been noted in adipocytes, platelets, and leukocytes of subjects with insulin resistance syndrome or allied disorders. In rodent studies, measures which increase [Ca2+]i in adipocytes and skeletal muscle are associated with impaired insulin signaling, attributable at least in part to diminished ability of insulin to activate phosphoserine phosphatase-1 (PP-1). In fat-fed insulin resistant rats, pre-treatment with a drug that selectively chelates intracellular calcium eliminates about half of the decrement in insulin-stimulated glucose uptake induced by fat feeding; since this chelator does not influence the insulin sensitivity of chow-fed rats, it is reasonable to suspect that fat feeding boosts [Ca2+]i in skeletal muscle, and that this effect is partially responsible for the associated reduction in insulin sensitivity. Clinical insulin resistance is associated with increased levels of triglycerides and other fatty acid metabolites in muscle fibers; this can give rise to diacylglycerol-mediated activation of PKC, which in turn compromises insulin signaling by triggering kinase cascades that phosphorylate IRS-1 on key serine residues. Yet there is also evidence that, in skeletal muscle, PKC activity up-regulates the function of L-type calcium channels, increasing their maximal conductance while left-shifting their voltage dependence. Thus, the PKC activation associated with fat overexposure might be expected to boost basal [Ca2+]i in skeletal muscle, potentially impeding insulin-mediated activation of PP-1. This hypothesis is consistent with several clinical studies demonstrating that long-acting inhibitors of L-type calcium channels can improve insulin sensitivity in overweight hypertensives; it should be readily testable in rodent models of fat-induced insulin resistance. Since parathyroid hormone can act on adipocytes and muscle to boost [Ca2+]i, mild secondary hyperparathyroidism associated with low calcium intakes and poor vitamin D status may contribute to insulin resistance, consistent with certain clinical and epidemiological findings. Magnesium, often thought of as a mild calcium antagonist, appears to have favorable effects on insulin sensitivity and risk for diabetes, and recent evidence indicates that increases of intracellular magnesium within the physiological range can diminish calcium influx through phosphorylated L-type calcium channels. It will be of interest to determine whether calcium antagonism does indeed underlie the favorable influence of good magnesium status on insulin function. A report that chromium picolinate can induce the plasmalemmal Ca2+-ATPase in smooth muscle cells, raises the possibility that modulation of calcium transport might play a role in the insulin-sensitizing efficacy of bioactive chromium.

Deficiência de magnésio e resistência à insulina em pacientes com diabetes mellitus tipo 2

O magnésio é um íon predominantemente intra-celular, que participa como co-fator de mais de 300 reações enzimáticas, dentre elas na atividade da tirosino-cinase. Sua deficiência pode aumentar a resistência periférica à insulina, especialmente em pacientes com síndrome metabólica e diabetes mellitus tipo 2 (DM2). Este trabalho avaliou, em 27 pacientes com DM2 descompensado, o conteúdo intra-celular de magnésio, correlacionando-o com índices laboratoriais de resistência insulínica e controle glicêmico. Hipomagnesemia foi encontrada em 75% dos pacientes e déficit intra-celular em 30,8%. Houve correlação negativa do Mg intra-celular (Mg IC) com HbA1 e com IMC. 59,2% dos pacientes apresentaram HOMA IR > 3,5, e tendência para correlação negativa com o Mg IC, porém sem significância estatística. Apesar do número pequeno de pacientes, ressalta-se que uma vez que deficiência de magnésio é comum em pacientes com diabetes, sua relação com resistência insulínica deve ser mais estudada.

Impact of cereal fibre on glucose-regulating factors

AIMS/HYPOTHESIS

Insoluble dietary fibre intake is associated, by unknown mechanisms, with a reduced risk of type 2 diabetes. We investigated whether a short-term dietary intervention with purified insoluble fibres influences acute and delayed responses of glucose, insulin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1.

METHODS

Fourteen healthy women with NGT were studied for 300 min on six to eight occasions. Subjects consumed three matched portions of control (C) or fibre-enriched bread (10.4-10.6 g/portion; wheat fibre [WF], oat fibre [OF], and, in a substudy [n=9], resistant starch [RS]) followed by control (C-C, C-WF, C-OF, C-RS) on subsequent days.

RESULTS

Fibre enrichment accelerated the early insulin response (fibrextime interaction p=0.026 for WF, p<0.001 for OF, p=0.126 for RS; time of maximal concentration [T(max)], C 57.9+/-5.9, WF 49.3+/-2.5 [p=0.086], OF 46.1+/-2.9 [p=0.026], RS 46.7+/-5.8 min [p=0.029]). It was also associated with an earlier postprandial GIP response after OF (T(max), C 83.6+/-7.2, WF 70.7+/-6.0 [p=0.054], OF 64.3+/-6.9 [p=0.022], RS 60.0+/-5.0 [p>0.15]). Increased fibre intake for 24 h was further associated with a reduced postprandial glucose response on the following day subsequent to ingestion of a control meal (AUC(C-C) 4,140+/-401, AUC(C-WF) 2,850+/-331 [p=0.007], AUC(C-OF) 2,830+/-277 [p=0.011]), with no difference in maximal concentration and T(max) of glucose responses. No differences in insulin responses were observed 24 h after the fibre-enriched diets compared with control (p>0.15). Colonic fermentation was increased only on study days C-OF (p=0.017) and C-RS (p=0.016).

CONCLUSIONS/INTERPRETATION

The consumption of highly purified insoluble dietary fibres accelerated the acute GIP and insulin response and was further associated with enhanced postprandial carbohydrate handling the following day upon ingestion of a control meal.

Disturbances of phosphate metabolism: another feature of metabolic syndrome

BACKGROUND

Despite important recent advances in the understanding of the consequences of metabolic syndrome, its pathophysiological characteristics remain unclear. It has been proposed that disturbances in phosphate metabolism may contribute to the development of this constellation of cardiovascular risk factors. However, there have been insufficient clinical data supporting this hypothesis to date. The aim of our study is to confirm the presence of hypophosphatemia in patients with metabolic syndrome, as well as investigate mechanisms that may underlie the disturbances in phosphate metabolism in this patient group.

METHODS

Two hundred fifty-five individuals were enrolled. The diagnosis of metabolic syndrome was based on Adult Treatment Panel III guidelines. Subjects with fewer than 3 criteria served as controls.

RESULTS

Patients with metabolic syndrome showed significantly lower phosphate and magnesium levels compared with controls. Because fractional excretion of phosphate was similar in both groups, we assume that hypophosphatemia in patients with metabolic syndrome can be attributed to decreased dietary intake, as well as internal redistribution of this element. Lower magnesium values in the patient group may result from the same mechanisms as lower phosphate levels. In addition, hyperinsulinemia-induced renal magnesium wasting also may be a contributory factor.

CONCLUSION

Patients with metabolic syndrome show significantly lower phosphate and magnesium levels compared with healthy individuals. The clinical significance of these disturbances, as well as their importance as targets for preventive or therapeutic interventions, remains to be established.

The impact of nuts on diabetes and diabetes risk

Nuts have many nutritional benefits: they are high in monounsaturated and polyunsaturated fats, fiber, vitamin, minerals, and phytonutrients. Population studies indicate that individuals who regularly consume nuts have reduced risk for cardiovascular disease and diabetes. In clinical trials, nuts appear to have a neutral effect on glucose and insulin, and a beneficial effect on lipid profile. Thus, nuts can be a healthy dietary component for individuals with diabetes or those at risk for diabetes, providing overall caloric intake is regulated to maintain a healthy body weight.

Complementary therapies for diabetes: the case for chromium, magnesium, and antioxidants

A growing body of interest on the possible beneficial role of chromium, magnesium, and antioxidant supplements in the treatment of diabetes has contributed to debate about their value for reaching metabolic control and to prevent chronic complications in diabetic subjects. In this article we use a systematic approach focused on clinically based evidence from clinical trials regarding the benefits of chromium, magnesium, and antioxidant supplements as complementary therapies in type 2 diabetes. Chromium, magnesium, and antioxidants are essential elements involved in the action of insulin and energetic metabolism, without serious adverse effects. However, at present there is insufficient clinically based evidence and its routine use in the treatment of type 2 diabetes is still controversial. Because the most frequent origin of deficiencies in micronutrients is an inadequate diet, health care providers should invest more effort on nutrition counseling rather than focusing on micronutrient supplementation in order to reach metabolic control of their patients. Results from long-term trials are needed in order to assess the safety and beneficial role of chromium, magnesium, and antioxidant supplements as complementary therapies in the management of type 2 diabetes.

Regulation of heart insulin receptor tyrosine kinase activity by magnesium and spermine

Insulin action and aspects of the insulin-signaling pathway have been studied in the heart although the direct regulation of the heart's insulin receptor has not been explored. This study describes the first purification and characterization of the mammalian (rabbit, rat and bovine) heart insulin receptor. The rabbit heart IR showed maximum insulin binding of 18 microg/mg (approximately 1 mole insulin/mole (alpha2beta2) receptor) and a curvilinear Scatchard plot with a high affinity KD for insulin binding of approximately 4 nM at optimal pH (7.8) and NaCl concentration (150 mM). The insulin receptor tyrosine kinase activity was stimulated by insulin, Mg2+ (half-maximum response at approximately 5.6-10.6 nM and approximately 8.5 mM, respectively) and by the physiological polyamines, spermine and spermidine. The stimulation by Mg2+ and the polyamines occurred with and without insulin. These characteristics of the heart insulin receptor provide a mechanism for regulating the activity of the receptor's tyrosine kinase activity by the intracellular free Mg2+ concentration and the polyamines in the absence and presence of insulin.

Dietary glycemic index, glycemic load, cereal fiber, and plasma adiponectin concentration in diabetic men

OBJECTIVE

Adiponectin may improve insulin sensitivity, reduce inflammation, and ameliorate glycemic control. However, few studies have evaluated dietary predictors of plasma adiponectin levels, especially among subjects with type 2 diabetes.

RESEARCH DESIGN AND METHODS

To examine the associations of dietary glycemic load, glycemic index, and fibers with plasma adiponectin levels, we conducted a cross-sectional analysis in 780 diabetic men from the Health Professionals' Follow-up Study. Dietary information was obtained in 1986, 1990, and 1994 using semiquantitative food-frequency questionnaires.

RESULTS

After adjustment for age, BMI, smoking, alcohol consumption, physical activity, aspirin use, HbA(1c), history of hypertension or hypercholesterolemia, and fiber intake, dietary glycemic index and glycemic load were inversely associated with plasma adiponectin in a dose-dependent fashion (P for trend = 0.005 for glycemic index and 0.004 for glycemic load). Adiponectin levels were 13% lower in the highest quintile of dietary glycemic index than in the lowest quintile. For dietary glycemic load, adiponectin levels were 18% lower in the highest quintile than in the lowest. In contrast, high intake of cereal fiber was associated with increased plasma adiponectin levels, adjusting for lifestyle factors and dietary glycemic load (P for trend = 0.003). Adiponectin levels were 19% higher in the highest quintile than in the lowest quintile. Higher magnesium intake was also associated with increased plasma adiponectin.

CONCLUSIONS

Diets low in glycemic load and high in fiber may increase plasma adiponectin concentrations in diabetic patients.

Caffeine ingestion is associated with reductions in glucose uptake independent of obesity and type 2 diabetes before and after exercise training

OBJECTIVE

We investigated the effect of caffeine ingestion on insulin sensitivity in sedentary lean men (n = 8) and obese men with (n = 7) and without (n = 8) type 2 diabetes. We also examined whether chronic exercise influences the relationship between caffeine and insulin sensitivity in these individuals.

RESEARCH DESIGN AND METHODS

Subjects underwent two hyperinsulinemic-euglycemic clamp procedures, caffeine (5 mg/kg body wt) and placebo, in a double-blind, randomized manner before and after a 3-month aerobic exercise program. Body composition was measured by magnetic resonance imaging.

RESULTS

At baseline, caffeine ingestion was associated with a significant reduction (P < 0.05) in insulin sensitivity by a similar magnitude in the lean (33%), obese (33%), and type 2 diabetic (37%) groups in comparison with placebo. After exercise training, caffeine ingestion was still associated with a reduction (P < 0.05) in insulin sensitivity by a similar magnitude in the lean (23%), obese (26%), and type 2 diabetic (36%) groups in comparison with placebo. Exercise was not associated with a significant increase in insulin sensitivity in either the caffeine or placebo trials, independent of group (P > 0.10).

CONCLUSIONS

Caffeine consumption is associated with a substantial reduction in insulin-mediated glucose uptake independent of obesity, type 2 diabetes, and chronic exercise.

Oral magnesium administration prevents vascular complications in STZ-diabetic rats

Vascular disease is one of the complicating features of diabetes mellitus. Magnesium deficiency has recently been proposed as a novel factor implicated in the pathogenesis of diabetes complications. Several studies have indicated that hypertension in diabetic patients is an independent altered reaction of blood vessels to neurotransmitters and circulating hormones. Since magnesium has been proposed to decrease vascular sensitivity to vasoconstrictor agents, the present study was designed to determine whether chronic magnesium sulfate administration could prevent vascular complications of STZ-induced diabetes in rats. The animals were divided into six groups: two groups served as controls and received tap water for 8 weeks, while in the other four groups, made diabetic with a single IV injection of 40 mg/kg STZ, two groups treated with magnesium sulfate (10 g/L) added to the drinking water, and the other two groups received tap water only. After 8 weeks, in 3 groups (control, diabetic and Mg-treated), left common carotid artery was cannulated for continuous recording of blood pressure. All animals in these groups were decapitated and blood samples were drawn for glucose, Ca and Mg measurements. In the 3 remaining groups (again divided into control, diabetic and Mg-treated), the mesenteric vascular bed was perfused according to the McGregor method, and descending thoracic aortas were used for measurement of elasticity. In diabetic rats, plasma glucose was significantly increased and plasma magnesium was significantly decreased compared to controls and Mg-treated animals. Although plasma magnesium of Mg-treated animals increased significantly, it failed to reach to the magnesium level of the control group. Ca/Mg ratio was also increased compared to the control and Mg-treated animals. Mean arterial blood pressure in diabetics was significantly higher than control and Mg-treated rats. Similarly, there was a significant difference in mean arterial blood pressure of Mg-treated rats compared to control animals. Baseline perfusion pressure of diabetic group was significantly higher than control and Mg-treated groups with intact and denuded endothelium. Magnesium sulfate treatment decreased mean perfusion pressure of mesenteric vascular bed in intact and denuded endothelium in comparison with non-treated diabetic rats. There was a significant increase in passive tension in the aorta of diabetic rats compared to control and Mg-treated rats. However, there was no significant difference between Mg-treated and control rats. From the results of this study it may be concluded that magnesium could control STZ-induced diabetes and prevent its vascular complications.