High affinity insulin binding and insulin receptor-effector coupling: modulation by Ca2+

Prevalence of type 2 diabetes (T2D) in Lebanon: association with inflammatory and infectious clinical markers

BACKGROUND

Diabetes is a growing health concern in the Middle East, particularly in countries with high rates of obesity and unhealthy lifestyles. Therefore, this study aimed to determine the prevalence of type 2 diabetes (T2D) in Lebanon and its association with clinical markers of inflammation and infection.

METHODS

This cross-sectional study examined retrospectively the medical laboratory record of 4093 patients from all Lebanese regions. Prevalence of T2D and its association with age, gender, calcium, vitamin D (VitD), neutrophils-to-lymphocytes ratio (NLR), and C-reactive protein (CRP) were determined. The prevalence of infection in a subpopulation of 712 patients tested from blood, body fluid, sputum, swab, tissue, and urine samples and its etiology was also assessed.

RESULTS

Overall, 17% (n = 690) of our participants had T2D, and the mean HbA1c was 5.9% ± 1.2. Age, gender, triglycerides, NLR, and calcemia were significantly associated with T2D. The prevalence of infections in a subgroup of 712 patients was 11.1% (n = 79). Urinary tract infections (UTIs) caused by Escherichia coli (E. coli) were the most common cause of infection, with the highest prevalence in the pre-diabetic group. Serum CRP level was significantly higher in the diabetic group than the pre-diabetic and control groups. Diabetic patients also presented a significantly higher percentage of NLR > 3 compared to the pre-diabetic and control groups.

CONCLUSION

The prevalence of T2D is increasing in the Lebanese population compared to prior reports. These results should be considered to guide effective public health preventive strategies.

Dietary calcium intake in relation to type-2 diabetes and hyperglycemia in adults: A systematic review and dose-response meta-analysis of epidemiologic studies

Several epidemiological studies investigated the relation of Ca intake with type 2 diabetes mellitus (T2DM), but there were inconsistencies in their findings. So, we conducted a systematic review and dose-response meta-analysis to quantify the relation of dietary Ca intake with the risk of T2DM/hyperglycemia in adults. A systematic search was conducted up to May 2021, in MEDLINE (Pubmed), Web of Science (WOS), Scopus electronic databases and Google Scholar, for epidemiological studies that investigated the relation of dietary Ca intake (as the exposure) and T2DM/hyperglycemia (as the outcome) in adults, without restriction in publication date and language. Finally, 8 cohort and 9 cross-sectional studies were included in the analysis. The body of evidence was assessed by the GRADE approach. Combining effect sizes from prospective cohort studies included 255,744 general adult population illustrated that highest level of dietary Ca intake, compared to lowest category, was related to an 18% reduced risk of T2DM (RR: 0.82; 95% CI 0.74-0.92). Based on linear dose-response analysis (including 255,744 healthy individuals and 13,531 patients with T2DM), each 300, 600 and 1000 mg/day increment in dietary Ca intake was respectively associated to 7, 14 and 23% reduced risk of T2DM. There was a steeper reduction in risk of T2DM when dietary Ca intake increased from low levels to 750 mg/day. Nevertheless, meta-analysis of cross-sectional studies revealed an inverse significant association between dietary Ca intake and T2DM/hyperglycemia only in the female population (OR: 0.66; 95% CI 0.50-0.88). This meta-analysis illustrated an inverse association between dietary Ca intake and risk of T2DM in general adult populations in prospective cohort studies, in a dose-response manner. It seems that increasing dietary Ca intake from low levels to around 750 mg/day was inversely related to risk of T2DM. In cross-sectional studies, an inverse relation between dietary Ca intake and T2DM/hyperglycemia was found only in females.

Effect of Vitamin D Supplementation on Obesity-Induced Insulin Resistance: A Double-Blind, Randomized, Placebo-Controlled Trial

OBJECTIVE

The aim was to investigate whether vitamin D supplementation, combined with a hypocaloric diet, could have an independent effect on insulin sensitivity in subjects with both overweight and hypovitaminosis D. Changes from baseline in anthropometric parameters, body composition, glucose tolerance, and insulin secretion were considered as secondary outcomes.

METHODS

Eighteen volunteers who were nondiabetic and vitamin D deficient and had BMI > 25 kg/m² were randomized (1:1) in a double-blind manner to a hypocaloric diet + either oral cholecalciferol at 25,000 IU/wk or placebo for 3 months. Hyperinsulinemic-euglycemic clamp to measure insulin sensitivity was performed at baseline and after intervention.

RESULTS

Body weight in both groups decreased significantly (-7.5% in the vitamin D group and -10% in the placebo group; P < 0.05 for both), with no between-group differences. Serum 25-hydroxyvitamin D levels in the vitamin D group increased considerably (from 36.7 ± 13.2 nmol/L to 74.8 ± 18.7 nmol/L; P < 0.001). Insulin sensitivity in the vitamin D group improved (from 4.6 ± 2.0 to 6.9 ± 3.3 mg·kg^-1 ·min^-1 ; P < 0.001), whereas no changes were observed in the placebo group (from 4.9 ± 1.1 to 5.1 ± 0.3 mg·kg^-1 ·min^-1 ; P = 0.84).

CONCLUSIONS

Cholecalciferol supplementation, combined with a weight loss program, significantly improves insulin sensitivity in healthy subjects with obesity and might represent a personalized approach for insulin-resistant subjects with obesity.

Role of Placental VDR Expression and Function in Common Late Pregnancy Disorders

Vitamin D, besides its classical role in bone metabolism, plays a distinct role in multiple pathways of the feto-maternal unit. Calcitriol is the major active ligand of the nuclear vitamin D receptor (VDR). The vitamin D receptor (VDR) is expressed in different uteroplacental parts and exerts a variety of functions in physiologic pregnancy. It regulates decidualisation and implantation, influences hormone secretion and placental immune modulations. This review highlights the role of the vitamin D receptor in physiologic and disturbed pregnancy, as preeclampsia, fetal growth restriction, gestational diabetes and preterm birth. We discuss the existing literature regarding common VDR polymorphisms in these pregnancy disorders.

Serum calcium changes and risk of type 2 diabetes mellitus in Asian population

AIMS

We examined the association between changes in serum calcium levels with the incidence of type 2 diabetes mellitus (T2DM) in apparently healthy South Korean subjects.

METHODS

A retrospective longitudinal analysis was conducted with subjects who had participated in comprehensive health check-ups at least four times over a 7-year period (between 2006 and 2012). In total, 23,121 subjects were categorized into tertiles based on changes in their albumin-adjusted serum calcium levels. Multivariate Cox regression models were fitted to assess the association between changes in serum calcium levels during follow-up and the relative risk of diabetes incidence.

RESULTS

After a median follow-up of 57.4months, 1,929 (8.3%) new cases of T2DM occurred. Simple linear regression analysis showed serum calcium level changes correlated positively with changes in HbA1c and fasting plasma glucose (FPG) levels (B=5.72, p<0.001 for FPG; B=0.13, p<0.001 for HbA1c). An increase in albumin-adjusted serum calcium levels during follow-up was related to an increased risk of T2DM. After adjustment for potential confounders, the risk of T2DM was 1.6 times greater for subjects whose albumin-adjusted serum calcium levels were in the highest change tertile during follow-up than for subjects whose levels were in the lowest tertile (HR 1.65, 95% CI 1.44-1.88, P<0.001).

CONCLUSIONS

The elevation of albumin-adjusted serum calcium levels was associated with an increased risk of T2DM, independent of baseline glycemic status.

The Role of Vitamin D in the Prevention of Type 2 Diabetes: To D or Not to D?

Evidence on biological plausibility from mechanistic studies and highly consistent data from observational studies raise the possibility that optimizing vitamin D status may reduce the risk of type 2 diabetes. However, the observational nature of cohort studies precludes a definitive assessment of cause and effect because residual confounding or reverse causation cannot be excluded. Confounding is especially problematic with studies of vitamin D because blood 25-hydoxyvitamin D concentration is not only an excellent biomarker of vitamin D status, reflecting intake or biosynthesis, but also an excellent marker of good overall health. Results from underpowered trials and post hoc analyses of trials designed for nondiabetic outcomes do not support a role of vitamin D supplementation for prevention of type 2 diabetes among people with normal glucose tolerance. Whether vitamin D supplementation may have a role in the prevention of diabetes in high-risk populations remains to be seen. Adequately powered, randomized trials in well-defined populations (e.g., prediabetes) are ongoing and expected to establish whether vitamin D supplementation lowers risk of diabetes.

Effect of vitamin D on stress-induced hyperglycaemia and insulin resistance in critically ill patients

AIM

Effects of vitamin D supplementation on the glycaemic indices and insulin resistance in diabetic and non-diabetic patients were studied. In this study, effects of vitamin D supplementation on stress-induced hyperglycaemia and insulin resistance were evaluated in non-diabetic surgical critically ill patients.

METHODS

Adult surgical patients with stress-induced hyperglycaemia within the first 24 h of admission to the ICU were recruited. The patients randomly assigned to receive either vitamin D or placebo. Patients in the vitamin D group received a single dose of 600,000 IU vitamin D3 as intramuscular injection at time of recruitment. Besides demographic and clinical characteristics of the patients, plasma glucose, insulin, 25(OH) D and adiponectin levels were measured at the time of ICU admission and day 7. Homoeostasis model assessment for insulin resistance (HOMA-IR) and homestasis model assessment adiponectin (HOMA-AD) ratio were considered at the times of assessment.

RESULTS

Comparing with the baseline, plasma 25(OH) D level significantly increased in the subjects who received vitamin D (p = 0.04). Improvement in fasting plasma glucose levels was detected in day 7 of the study compared with the baseline status in both groups. HOMA-IR showed a decrement pattern in vitamin D group (p = 0.09). Fasting plasma adiponectin levels increased significantly in the vitamin D group (p = 0.007), but not in the placebo group (p = 0.38). Finally, changes in HOMA-AD ratio were not significant in the both groups.

CONCLUSION

Vitamin D supplementation showed positive effect on plasma adiponectin level, as a biomarker of insulin sensitivity in surgical critically ill patients with stress-induced hyperglycaemia. However, effects of vitamin D supplementation on HOMA-IR and HOMA-AD as indicators of insulin resistance were not significant.

The role of calcium in the prevention of cardiovascular disease--a review of observational studies and randomized clinical trials

Calcium is a mineral that is important for bone health and has also been suggested to play a role in the prevention of cardiovascular disease (CVD). Lately, the potential effects of both inadequate and excessive calcium intake have received growing attention. In this review, we summarize the evidence from experimental, epidemiologic, and clinical studies investigating the role of calcium intake, either from the diet or from supplements, as well as blood concentrations, in relation to the risk of CVD in adults. In vitro and in vivo laboratory studies suggest that calcium may be involved in CVD development through multiple pathways, including blood cholesterol, insulin secretion and sensitivity, vasodilation, inflammatory profile, thrombosis, obesity, and vascular calcification. Several prospective epidemiologic studies have examined how dietary or supplemental calcium intake is associated with CVD incidence or mortality in middle-aged and older adults, and the results are inconsistent. Prospective studies investigating blood concentrations of calcium have also reported mixed results. However, changes in blood calcium concentrations may reflect a disturbed calcium phosphate balance, which is associated with increased risk of CVD. To date there is no randomized clinical trial that has been designed specifically to test the effect of calcium supplementation on the risk of CVD as the primary end point. Existing trials have performed secondary analyses, and most of them have been conducted among postmenopausal women. These trials suggest that calcium supplementation has no effect on CVD development; however, they do not allow a definitive conclusion to be drawn. The average daily intake of calcium is low in many populations; however, the evidence for a potential role of dietary or supplemental calcium in the prevention of CVD remains insufficient and inconclusive. Only large-scale randomized trials designed to investigate the effects of calcium supplementation on CVD events as the primary end point, as well as short-term trials investigating the effect on coronary biomarkers, can provide a definitive answer.

Vitamin D and diabetes

There has been increasing evidence that vitamin D may have a role in modifying risk of diabetes. Vitamin D has both direct and indirect effects on various mechanisms related to the pathophysiology of type 2 diabetes, including pancreatic beta cell dysfunction, impaired insulin action and systemic inflammation. This article describes the biologic plausibility behind the potential association between vitamin D and type 2 diabetes and summarizes the current evidence from human studies that suggests but does not prove a relation between vitamin D and type 2 diabetes, and briefly reports on the potential association between vitamin D and type 1 diabetes.

Vitamin D deficiency: a new risk factor for type 2 diabetes?

Recent compelling evidence suggests a role of vitamin D deficiency in the pathogenesis of insulin resistance and insulin secretion derangements, with a consequent possible interference with type 2 diabetes mellitus. The mechanism of this link is incompletely understood. In fact, vitamin D deficiency is usually detected in obesity in which insulin resistance is also a common finding. The coexistence of insulin resistance and vitamin D deficiency has generated several hypotheses. Some cross-sectional and prospective studies have suggested that vitamin D deficiency may play a role in worsening insulin resistance; others have identified obesity as a risk factor predisposing individuals to exhibit both vitamin D deficiency and insulin resistance. The available data from intervention studies are largely confounded, and inadequate considerations of seasonal effects on 25(OH)D concentrations are also a common design flaw in many studies. On the contrary, there is strong evidence that obesity might cause both vitamin D deficiency and insulin resistance, leaving open the possibility that vitamin D and diabetes are not related at all. Although it might seem premature to draw firm conclusions on the role of vitamin D supplementation in reducing insulin resistance and preventing type 2 diabetes, this manuscript will review the circumstances leading to vitamin D deficiency and how such a deficiency can eventually independently affect insulin sensitivity.

Correlation of hair mineral concentrations with insulin resistance in Korean males

Calcium and magnesium that are associated with insulin resistance play an antagonistic role with each other in cells. This study was conducted to investigate the relationship between hair mineral concentrations and insulin resistance in Korean adult males. A total of 123 male subjects (63 patients with metabolic syndrome and 60 normal control patients) were recruited and fasting plasma glucose, total cholesterol, triglyceride, as well as HDL cholesterol levels, HOMA-IR, and hair mineral concentrations were measured. The ratio of calcium/magnesium in hair showed a significantly positive correlation with the HOMA-IR (r = 0.191, P = 0.038) and insulin (r = 0.198, P = 0.031). The result of multiple regression analysis after adjusting the age also showed a significant correlation of the Ca/Mg ratio with HOMA-IR (R² = 0.115, P = 0.047). The hair chromium concentration was lower in the metabolic syndrome group than in the control group, and it showed a significantly negative correlation with the fasting blood glucoseand the triglyceride. The result of this study showed that insulin resistance increased as the ratio of Ca/Mg increased, or as the chromium concentration in hair decreased.

Role of vitamin D in insulin resistance

Vitamin D is characterized as a regulator of homeostasis of bone and mineral metabolism, but it can also provide nonskeletal actions because vitamin D receptors have been found in various tissues including the brain, prostate, breast, colon, pancreas, and immune cells. Bone metabolism, modulation of the immune response, and regulation of cell proliferation and differentiation are all biological functions of vitamin D. Vitamin D may play an important role in modifying the risk of cardiometabolic outcomes, including diabetes mellitus (DM), hypertension, and cardiovascular disease. The incidence of type 2 DM is increasing worldwide and results from a lack of insulin or inadequate insulin secretion following increases in insulin resistance. Therefore, it has been proposed that vitamin D deficiency plays an important role in insulin resistance resulting in diabetes. The potential role of vitamin D deficiency in insulin resistance has been proposed to be associated with inherited gene polymorphisms including vitamin D-binding protein, vitamin D receptor, and vitamin D 1alpha-hydroxylase gene. Other roles have been proposed to involve immunoregulatory function by activating innate and adaptive immunity and cytokine release, activating inflammation by upregulation of nuclear factor κB and inducing tumor necrosis factor α, and other molecular actions to maintain glucose homeostasis and mediate insulin sensitivity by a low calcium status, obesity, or by elevating serum levels of parathyroid hormone. These effects of vitamin D deficiency, either acting in concert or alone, all serve to increase insulin resistance. Although there is evidence to support a relationship between vitamin D status and insulin resistance, the underlying mechanism requires further exploration. The purpose of this paper was to review the current information available concerning the role of vitamin D in insulin resistance.

Calcium intake and risk of cardiovascular disease: a review of prospective studies and randomized clinical trials

The potential effects of inadequate or excessive calcium supply on cardiovascular disease (CVD) are receiving growing attention. We review experimental, epidemiologic, and clinical evidence regarding the role of calcium intake in the development of CVD in adults. In vitro and in vivo laboratory studies have shown that calcium may affect the risk of developing CVD through multiple mechanisms including blood cholesterol, insulin secretion and sensitivity, vasodilation, inflammatory profile, thrombosis, obesity, and vascular calcification. A number of prospective epidemiologic studies have examined the relationship between dietary calcium intake and CVD incidence or mortality in middle-aged and older adults. The results were inconsistent, and the pooled data do not strongly support a significant effect of greater dietary calcium intake on the risk of coronary artery disease (CAD) or stroke. Only a few prospective studies have examined calcium supplement use in association with risk of CVD. The pooled data show no significant benefits of calcium supplement use in reducing the risk of CAD or stroke. No randomized clinical trial has specifically tested the effect of calcium supplementation on CVD as its primary endpoint. Secondary analyses in existing trials to date suggest a neutral effect of calcium (with or without vitamin D) supplements on CVD events, but do not allow for a definitive conclusion. A large percentage of Americans, particularly older adults, fail to meet the US recommendations for optimal calcium intake and are encouraged to increase daily calcium consumption. More prospective cohort studies and large-scale randomized trials are needed to further evaluate the risks or benefits of calcium supplementation on CVD endpoints as the primary pre-specified outcome.

Effect of calcium treatment on blood parameters, gonadal development and the structure of bone in immature female rats

Calcium is an essential nutrient required for critical biological functions. Calcium supplementation is to be evaluated using immature female rats. The present study focused on some blood parameters, gonadal development and bone structure. Forty immature female Sprague-Dawley rats were randomly divided into four equal-sized groups (80 g average body weight) to receive calcium chloride dihydrate (group I: control; groups II, III and IV: received 20 mg, 40 mg and 60 mg per kg body weight, respectively) for 5 weeks. Rats were decapitated, and their trunk blood was sampled for biochemical assays. Cholesterol, triglycerides, glucose and calcium were measured. Gonadal and bone structure were histologically evaluated. Results revealed that treatment of developing female rats with three calcium doses used have no marked effect on the serum calcium and cholesterol levels. However, serum triglyceride level and body weight gain are significantly decreased in rats treated with all of the three calcium doses. Serum glucose level showed a marked increase in animals treated with the higher calcium doses. Moreover, observable histological alterations are recognized in the ovaries. Bones of the experimental animals also showed morphological alterations. These results suggest that increasing calcium supplementation decreases triglycerides and percentage body weight gain and positively affects the bone and gonadal development.

Is vitamin D status a predictor glycaemic regulation and cardiac complication in type 2 diabetes mellitus patients?

OBJECTIVE

To evaluate vitamin D as a predictor of glycaemic regulation in type 2 diabetes mellitus patients.

RESEARCH DESIGN AND METHODS

In observational study 171 type 2 diabetic patients who are followed for median (range) of 10.15 (3-18) years. Mean ± SD age was 56 ± 10. Plasma 25-hydroxyvitamin D3 levels were determined by high-performance liquid chromatography/tandem mass spectrometry on baseline samples. Vitamin D deficiency was defined as a 25-OHD level of less than 20 ng/ml. Vitamin D levels between 20 and 30 ng/ml are termed 'insufficient'. Vitamin D levels greater than 30 ng/ml are termed 'optimal'.

RESULTS

125 patients have vitamin D deficiency, 14 patients have insufficient and the others have optimal. Vitamin D levels were not associated with sex, age, BMI, HDL, LDL, kreatinin, hypertension and smoking. But vitamin D deficiency patients had more longer duration (p=0.011), more higher uric acid (p=0.021), fasting glucose (p=0.037), postprandial glucose (p=0.001) and HbA1c (p=0.026).

CONCLUSIONS

In our study type 2 diabetic patients have 73% of vitamin D deficiency. Vitamin D deficiency predicts higher fasting and postprandial blood glucose and diabetes disregulation. Type 2 DM patients and low 25-OH vitamin D levels could increased cardiovascular disease directly or indirectly (low HDL and high uric acid in 25-OH vitamin D <20 ng/ml). Whether vitamin D substitution improves prognosis remains to be investigated.

Serum calcium is positively correlated with fasting plasma glucose and insulin resistance, independent of parathyroid hormone, in male patients with type 2 diabetes mellitus

Patients with primary hyperparathyroidism have impaired glucose tolerance more often than do controls, and parathyroid resection sometimes improves this derangement. However, it is unclear whether serum calcium (Ca) or parathyroid hormone (PTH) is more strongly related to impaired glucose metabolism in subjects without primary hyperparathyroidism. In this cross-sectional study, we examined patients with type 2 diabetes mellitus (DM) (271 men and 209 women) and analyzed the relationships between serum concentrations of Ca or intact PTH and DM-related variables. Simple regression analyses showed that the level of serum Ca was significantly and positively correlated with the levels of fasting plasma glucose, immunoreactive insulin, and homeostasis model assessment insulin resistance in men (P < .05), but not in women. In contrast, intact PTH was not significantly correlated with DM-related parameters in either sex. Multiple regression analyses showed that the significant and positive correlations between serum Ca vs fasting plasma glucose and homeostasis model assessment insulin resistance in men still remained after adjustment for intact PTH as well as age, body weight, height, creatinine, albumin, phosphate, bone metabolic markers, and estradiol (P < .05). Serum Ca level is positively associated with impaired glucose metabolism, independent of PTH or bone metabolism, in men with type 2 DM.

Serum 25-hydroxyvitamin D, calcium intake, and risk of type 2 diabetes after 5 years: results from a national, population-based prospective study (the Australian Diabetes, Obesity and Lifestyle study)

OBJECTIVE

To examine whether serum 25-hydroxyvitamin D (25OHD) and dietary calcium predict incident type 2 diabetes and insulin sensitivity.

RESEARCH DESIGN AND METHODS

A total of 6,537 of the 11,247 adults evaluated in 1999-2000 in the Australian Diabetes, Obesity and Lifestyle (AusDiab) study, returned for oral glucose tolerance test (OGTT) in 2004-2005. We studied those without diabetes who had complete data at baseline (n = 5,200; mean age 51 years; 55% were women; 92% were Europids). Serum 25OHD and energy-adjusted calcium intake (food frequency questionnaire) were assessed at baseline. Logistic regression was used to evaluate associations between serum 25OHD and dietary calcium on 5-year incidence of diabetes (diagnosed by OGTT) and insulin sensitivity (homeostasis model assessment of insulin sensitivity [HOMA-S]), adjusted for multiple potential confounders, including fasting plasma glucose (FPG).

RESULTS

During the 5-year follow-up, 199 incident cases of diabetes were diagnosed. Those who developed diabetes had lower serum 25OHD (mean 58 vs. 65 nmol/L; P < 0.001) and calcium intake (mean 881 vs. 923 mg/day; P = 0.03) compared with those who remained free of diabetes. Each 25 nmol/L increment in serum 25OHD was associated with a 24% reduced risk of diabetes (odds ratio 0.76 [95% CI 0.63-0.92]) after adjusting for age, waist circumference, ethnicity, season, latitude, smoking, physical activity, family history of diabetes, dietary magnesium, hypertension, serum triglycerides, and FPG. Dietary calcium intake was not associated with reduced diabetes risk. Only serum 25OHD was positively and independently associated with HOMA-S at 5 years.

CONCLUSIONS

Higher serum 25OHD levels, but not higher dietary calcium, were associated with a significantly reduced risk of diabetes in Australian adult men and women.

Effect of vitamin D supplementation in type 2 diabetes patients with pulmonary tuberculosis

AIM

Diabetes and vitamin D deficiency are widely prevalent in India. Studies have proven correlation between low vitamin D levels and pulmonary tuberculosis (PTB) and low vitamin D levels and insulin resistance. We evaluated the effects of vitamin D supplementation on type 2 diabetes mellitus patients with pulmonary tuberculosis (PTB).

METHODS

Forty-five subjects (M:F=34:11) were screened. Inclusion criteria were age >15 years, newly diagnosed PTB cases with uncontrolled diabetes, serum vitamin D<20 ng/ml. The patients with vitamin D level<20 ng/ml were randomly assigned to 2 groups. Group 1 subjects received oral cholecalceferol (60,000 units/week) and calcium carbonate (1g/day) along with anti tubercular treatment (ATT), while group 2 subjects did not. Sputum was checked at interval of 2 weeks for 12 weeks. Primary end point was time to achieve sputum smear conversion.

RESULTS

Fifteen patients having vitamin D>20 ng/ml were excluded. Age of the patients was 42.9±13.2 years and serum vitamin D levels were 18.4±15.3 ng/ml. Sputum smear conversion was 6 weeks in group 1 versus 8 weeks in group 2 (p=0.067). Glycated hemoglobin levels reduced from 11.1±1.3 to 7.7±0.9 in group 1 versus 10.3±1.2 to 7.8±1.1 (p>0.1).

CONCLUSION

Vitamin D can serve as adjuvant treatment of tuberculosis in diabetics with vitamin D deficiency. Further studies are required to validate this observation and define a cut off for vitamin D level to prevent immunological alterations.

25-Hydroxyvitamin D concentration correlates with insulin-sensitivity and BMI in obesity

The prevalence of hypovitaminosis D is high among obese subjects. Further, low 25-hydroxyvitamin D (25(OH)D) concentration has been postulated to be a risk factor for type 2 diabetes, although its relation with insulin-sensitivity is not well investigated. Thus, we aimed to investigate the relationship between 25(OH)D concentration and insulin-sensitivity, using the glucose clamp technique. In total, 39 subjects with no known history of diabetes mellitus were recruited. The association of 25(OH)D concentration with insulin-sensitivity was evaluated by hyperinsulinemic euglycemic clamp. Subjects with low 25(OH)D (<50 nmol/l) had higher BMI (P = 0.048), parathyroid hormone (PTH) (P = 0.040), total cholesterol (P = 0.012), low-density lipoprotein (LDL) cholesterol (P = 0.044), triglycerides (P = 0.048), and lower insulin-sensitivity as evaluated by clamp study (P = 0.047). There was significant correlation between 25(OH)D and BMI (r = -0.58; P = 0.01), PTH (r = -0.44; P < 0.01), insulin-sensitivity (r = 0.43; P < 0.01), total (r = -0.34; P = 0.030) and LDL (r = -0.40; P = 0.023) (but not high-density lipoprotein (HDL)) cholesterol, and triglycerides (r = 0.45; P = 0.01). Multivariate analysis using 25(OH)D concentration, BMI, insulin-sensitivity, HDL cholesterol, LDL cholesterol, total cholesterol, and triglycerides, as the cofactors was performed. BMI was found to be the most powerful predictor of 25(OH)D concentration (r = -0.52; P < 0.01), whereas insulin-sensitivity was not significant. Our study suggested that there is no cause-effect relationship between vitamin D and insulin-sensitivity. In obesity, both low 25(OH)D concentration and insulin-resistance appear to be dependent on the increased body size.

Hair tissue mineral analysis and metabolic syndrome

Deficiency of minerals causes functional abnormality of enzymes, frequently resulting in metabolic disturbance. We investigated possible relationship between minerals and metabolic syndrome by analysis of hair tissue minerals. We selected 848 subjects older than 20 years of age at Ajou University Hospital from May 2004 to February 2007. We excluded the subjects who had cancers, steroid and thyroid medication, and incomplete record from the study. Finally, 343 subjects were eligible. We performed cross-sectional analysis for the relationship between minerals and metabolic syndrome. The contents of calcium, magnesium, and copper in the metabolic syndrome group were significantly lower than those of the normal group, whereas the amounts of sodium, potassium, and mercury in the metabolic syndrome group were significantly higher than those of the normal group. By dividing the subjects into quartile with the level of calcium, magnesium, and mercury concentrations, we carried out logistic regression analysis to study the subjects and found that the subjects in the third quartile of calcium and magnesium concentrations had significantly lower odds ratio (OR) of the metabolic syndrome compared with that of the lowest quartile group [OR = 0.30, confidence interval (CI) = 0.10-0.89; OR = 0.189, CI = 0.063-0.566] and that the subjects in the highest mercury quartile had significantly higher OR of the metabolic syndrome compared with that of the lowest mercury quartile group (OR = 7.35, CI = 1.73-31.1). As part of the metabolic syndrome, the optimal calcium and magnesium concentrations in hair tissue may reflect decreased risk of metabolic syndrome, whereas high mercury concentration in hair tissue may indicate increased risk of metabolic syndrome.

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.

Plasma C-peptide is inversely associated with calcium intake in women and with plasma 25-hydroxy vitamin D in men

The consumption of calcium, vitamin D, and dairy products may be associated with a reduced risk of type 2 diabetes mellitus. However, whether this reduction is due to calcium, vitamin D, or other components of dairy products is not clear. We examined intakes of total calcium and vitamin D, and plasma concentrations of 25 hydroxyvitamin D [25(OH)D] in relation to fasting plasma concentrations of C-peptide in 2 cross-sectional studies among healthy men from the Health Professionals Follow-up Study and among healthy women from the Nurses' Health Study I. Intake of total calcium was modestly inversely associated with C-peptide concentration in women (P-trend = 0.05); however, the inverse association was not significant in men (P = 0.7). Concentrations of C-peptide were 20% lower among men who had plasma concentrations of 25(OH)D in the highest quartile compared with those in the lowest quartile (P-trend = 0.08); there was no association in women (P = 0.3). The inverse association between calcium intake and the plasma C-peptide concentration was stronger in hypertensive individuals of both sexes. The difference in the C-peptide concentrations between extreme quartiles of calcium intake was 17% in men and 20% in women. Plasma concentrations of C-peptide for the combination of the highest tertiles of calcium intake and plasma 25(OH)D compared with the opposite extreme were 35% lower (P = 0.03) in men and 12% lower (P = 0.01) in women. The results suggest that calcium intake or systemic vitamin D status, after adjustment for intake of dairy products, is associated with decreased insulin secretion.

The role of vitamin D and calcium in type 2 diabetes. A systematic review and meta-analysis

CONTEXT

Altered vitamin D and calcium homeostasis may play a role in the development of type 2 diabetes mellitus (type 2 DM). EVIDENCE ACQUISITION AND ANALYSES: MEDLINE review was conducted through January 2007 for observational studies and clinical trials in adults with outcomes related to glucose homeostasis. When data were available to combine, meta-analyses were performed, and summary odds ratios (OR) are presented.

EVIDENCE SYNTHESIS

Observational studies show a relatively consistent association between low vitamin D status, calcium or dairy intake, and prevalent type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM prevalence, 0.36 (0.16-0.80) among nonblacks for highest vs. lowest 25-hydroxyvitamin D; metabolic syndrome prevalence, 0.71 (0.57-0.89) for highest vs. lowest dairy intake]. There are also inverse associations with incident type 2 DM or metabolic syndrome [OR (95% confidence interval): type 2 DM incidence, 0.82 (0.72-0.93) for highest vs. lowest combined vitamin D and calcium intake; 0.86 (0.79-0.93) for highest vs. lowest dairy intake]. Evidence from trials with vitamin D and/or calcium supplementation suggests that combined vitamin D and calcium supplementation may have a role in the prevention of type 2 DM only in populations at high risk (i.e. glucose intolerance). The available evidence is limited because most observational studies are cross-sectional and did not adjust for important confounders, whereas intervention studies were short in duration, included few subjects, used a variety of formulations of vitamin D and calcium, or did post hoc analyses.

CONCLUSIONS

Vitamin D and calcium insufficiency may negatively influence glycemia, whereas combined supplementation with both nutrients may be beneficial in optimizing glucose metabolism.

Altered calcium homeostasis is correlated with abnormalities of fasting serum glucose, insulin resistance, and beta-cell function in the Newfoundland population

Alteration of extracellular calcium concentration may be involved in glucose metabolism in a number of pathways. The present study was designed to investigate the relationship between total serum calcium and 1) fasting serum glucose, 2) insulin, 3) insulin resistance, and 4) beta-cell function in 1,182 healthy subjects from the province of Newfoundland and Labrador, Canada. All variables were log10 transformed, and confounding factors including age, trunk fat percentage, serum phosphorus, magnesium, 25-OH vitamin D, and parathyroid hormone were adjusted before analyses. Significant positive correlations between glucose and insulin resistance with calcium were found in both sexes, whereas an inverse correlation between beta-cell function and calcium was found only in women. Similar results were found in medication-free women and men, as well as in pre- and postmenopausal women. Subjects with low calcium levels had the lowest concentration of glucose and the least insulin resistance, whereas subjects with high calcium levels had the highest concentration of glucose and insulin resistance in women but not in men. This relationship remained after calcium was adjusted for 25-OH vitamin D and parathyroid hormone. Our results suggest that alteration of serum calcium homeostasis is significantly correlated with the abnormality of glucose level, insulin resistance, and beta-cell function.

Interaction of oxytocin with Ca2+: I. CD and fluorescence spectral characterization and comparison with vasopressin

Extracellular Ca2+ is required for the action of oxytocin and both the hormone and its receptor have binding sites for divalent metal cations. To characterize the cation-bound form of oxytocin, we monitored the binding of Ca2+ and Mg2+ to oxytocin as well as peptides representing its ring and tail regions in trifluoroethanol, a lipid-mimetic solvent, using CD and fluorescence spectroscopy. Binding Ca2+ (Kd approximately 50 microM) caused drastic CD and fluorescence changes leading to a helical conformation. Mg2+ caused CD changes smaller than and opposite to Ca2+. However, the helical structure was enhanced when both Ca2+ and Mg2+ were present together. CD changes in the tail peptide of oxytocin showed its ability to bind Ca2+ and Mg2+ whereas the vasopressin tail peptide did not bind either cation. CD spectral changes on Ca2+ and Mg2+ binding to tocinoic acid (the ring moiety of oxytocin) were much smaller than those of oxytocin. These data suggest that the tail segment of oxytocin potentiates Ca2+ binding by the ring. While vasopressin displayed a CD spectrum similar to that of oxytocin, CD spectra of its cation-bound forms were markedly different from those of oxytocin; the Ca(2+)-induced CD changes in vasopressin were very much smaller and of opposite sign, and Mg(2+)-induced ones significantly larger than in oxytocin. Taken together, our observations bring out the structural differences between oxytocin and vasopressin in the context of their interaction with Ca2+ and Mg2+. This may be relevant to understanding the differences in the bioactive conformations and receptor interactions of the two hormones.

Abnormal cell calcium homeostasis in type 2 diabetes mellitus: a new look on old disease

Cumulative evidence reveals that diabetes is a condition in which cell Ca2+ homeostasis is impaired. Defects in cell Ca2+ regulation were found in erythrocytes, cardiac muscle, platelets, skeletal muscle, kidney, aorta, adipocytes, liver, osteoblasts, arteries, lens, peripheral nerves, brain synaptosomes, retinal tissue, and pancreatic beta cells, confirming that this defect in cell Ca2+ metabolism is a basic pathology associated with the diabetic state. Though different defects in a variety of functions that regulate cell Ca2+ homeostasis were described in diabetes, the most common finding is an increase in [Ca2+]i levels. However, it is not clear whether the defect in cell Ca2+ metabolism in diabetes precedes or succeeds the overt diabetic condition. It is also not clear which of the multiple functions involved in cell Ca2+ regulation has the primary defect. Defects in cell Ca2+ metabolism may be significant for the observed pathologies in insulin secretion and insulin action in diabetes. They may also play an important role in the vascular complications seen in this condition, such as hypertension, atherosclerosis, and microangiopathy. Therefore, better understanding of the impairment in cell Ca2+ metabolism in diabetes may markedly enhance our understanding of this condition.

Improvement in glucose tolerance and beta-cell function in a patient with vitamin D deficiency during treatment with vitamin D

Glucose metabolism was studied in a patient with vitamin D deficiency during its treatment with small doses of vitamin D. A continuous infusion of glucose test was performed to assess glucose tolerance and insulin sensitivity and beta-cell function were derived by mathematical modelling. Fasting glucose was 5.6 mmol/l and achieved glucose after the infusion was 10.4 mmol/l confirming diabetes. The test was repeated 0.5, 1, 3 and 5 months after starting treatment. Serum calcium increased glucose intolerance from 1.76 to 2.0, 2.08, 1.96 and 2.0 mmol/l, respectively; vitamin D reached supraphysiological levels initially and returned to normal levels, and parathyroid hormone levels were normalized. Her weight did not change during treatment. Glucose tolerance improved during treatment and achieved glucose was 9.4, 8.6, 9.2 and 9.0 mmol/l at 0.5, 1, 3 and 5 months, respectively; insulin sensitivity did not change. Beta-cell function improved from 101% at diagnosis to 126%, 147%, 173% and 198% at 0.5, 1, 3 and 5 months, respectively. Improvement in beta-cell function and consequently in glucose tolerance is likely to have been due to correction of hypocalcaemia, vitamin D deficiency and secondary hyperparathyroidism.

Hepatic insulin resistance in KKA(y) mice and its amelioration by pioglitazone do not involve alterations in phospholipase C activity

It has been proposed that an abnormality in the regulation of cytosolic-free Ca2+ may be the cause of some forms of insulin resistance. In support of this proposition, it was reported that phospholipase C-catalyzed hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) by liver plasma membranes from obese patients with non-insulin-dependent diabetes mellitus (NIDDM) was abnormally augmented (Thakker et al., J. Biol. Chem. 264, 7169-7175). The objective of this investigation was to determine if a novel antidiabetic agent, pioglitazone, ameliorated hepatic insulin resistance in KKA(y) mice and to identify any alterations in PIP2-phospholipase C activity of liver plasma membranes that may accompany changes in insulin sensitivity. Treatment of KKA(y) mice for 4 days with pioglitazone (20 mg/kg per day) decreased blood glucose and insulin and improved a variety of indices of hepatic insulin resistance, but did not alter the rate of PIP2 hydrolysis by liver plasma membranes. Acute treatment of isolated liver plasma membranes with pioglitazone (1-100 microM) also failed to alter PIP2-phospholipase C activity. Furthermore, the specific activity, Ca(2+)-requirement, pH-dependence and sensitivity to guanosine 5'-thiotriphosphate of the PIP2-phospholipase C in KKA(y) liver membranes were indistinguishable from those of C57BL/6J (normal) mice. Among C57BL/6J and KKA(y) mice fed either a control or pioglitazone-supplemented diet, there was no correlation between PIP2-phospholipase C activity in isolated liver membranes and either glucose or insulin concentrations in the circulation. These data indicate that an alteration in PIP2-phospholipase C activity of liver plasma membranes is neither a cause nor an obligatory consequence of insulin resistance in KKAy mice or its amelioration by pioglitazone. Alterations of liver membrane phospholipase C activity in NIDDM, therefore, may reflect diabetic pathology other than the insulin resistance associated with this disease.

Capsazepine: a competitive antagonist of the sensory neurone excitant capsaicin

1. Capsazepine is a synthetic analogue of the sensory neurone excitotoxin, capsaicin. The present study shows the capsazepine acts as a competitive antagonist of capsaicin. 2. Capsazepine (10 microM) reversibly reduced or abolished the current response to capsaicin (500 nM) of voltage-clamped dorsal root ganglion (DRG) neurones from rats. In contrast, the responses to 50 microM gamma-aminobutyric acid (GABA) and 5 microM adenosine 5'-triphosphate (ATP) were unaffected. 3. The effects of capsazepine were examined quantitatively with radioactive ion flux experiments. Capsazepine inhibited the capsaicin (500 nM)-induced 45Ca2+ uptake in cultures of rat DRG neurones with an IC50 of 420 +/- 46 nM (mean +/- s.e.mean, n = 6). The 45Ca2+ uptake evoked by resiniferatoxin (RTX), a potent capsaicin-like agonist was also inhibited. (Log concentration)-effect curves for RTX (0.3 nM-1 microM) were shifted in a competitive manner by capsazepine. The Schild plot of the data had a slope of 1.08 +/- 0.15 (s.e.) and gave an apparent Kd estimate for capsazepine of 220 nM (95% confidence limits, 57-400 nM). 4. Capsazepine also inhibited the capsaicin- and RTX-evoked efflux of 86Rb+ from cultured DRG neurones. The inhibition appeared to be competitive and Schild plots yielded apparent Kd estimates of 148 nM (95% confidence limits, 30-332 nM) with capsaicin as the agonist and 107 nM (95% confidence limits, 49-162 nM) with RTX as agonist. 5. A similar competitive inhibition by capsazepine was seen for capsaicin-induced [14C]-guanidinium efflux from segments of adult rat vagus nerves (apparent Kd = 690 nM; 95% confidence limits, 63 nM-1.45 microM). No significant difference was noted in the apparent Kd estimates for capsazepine in assays on cultured DRG neurones and vagus nerve as shown by the overlap in the 95% confidence limits.6. Capsazepine, at concentrations up to 1O microM, had no significant effects on the efflux of 86Rb+ from cultured DRG neurones evoked either by depolarization with high (50 mM) K' solutions or by acidification of the external medium to pH 5.0-5.6. Similarly capsazepine had no significant effect on he depolarization (50 mM KCl)-induced efflux of [14C]-guanidinium from vagus nerve preparations.7. Ruthenium Red was also tested for antagonism against capsaicin evoked ['4C]-guanidinium release from vague nerves and capsaicin induced 45Ca2" uptake in cultures of DRG neurones. In contrast to capsazepine the inhibition by Ruthenium Red (10-500nM in DRG and 0.5-10microM in vagus nerve experiments) was not consistent with a competitive antagonism, but rather suggested a more complex,non-competitive inhibition.

Induction of Ca2+ transport in liposomes by insulin

The requirement of extracellular Ca2+ for insulin action has been indicated by past studies. With a view to understand the interaction of insulin with Ca2+ in the vicinity of the cell membrane, we have examined the ability of insulin and its constituent polypeptide chains A and B to translocate Ca2+ and Mg2+ across the lipid bilayer in two sets of synthetic liposomes. The first were unilamellar vesicles made of dimyristoylphosphatidylcholine and contained the Ca2+ sensor dye arsenazo III. Peptide-mediated Ca2+ and Mg2+ transport in these vesicles was monitored at 37 degrees C in a neutral buffer containing CaCl2 or MgCl2 using a difference absorbance method. In the second set, multilamellar vesicles of egg lecithin containing trapped fura-2 were employed and the cation transport was followed at 20 degrees C by fluorescence changes in the dye. Control experiments indicated that the hormonal peptides caused no appreciable perturbation of the vesicles leading to leakage of contents or membrane fusion. In both liposome systems, substantial Ca2+ and Mg2+ transport was observed with insulin and the B chain; the A chain was less effective as an ionophore. Quantitative analysis of the transport kinetic data on the B chain showed a 1:1 peptide-Ca2+ complex formed inside the membrane. In light of the available structural data on Ca2+ binding by insulin and insulin receptor, our results suggest the possibility of the hormone interacting with the receptor with the bound Ca2+.