Osteoprotegerin and biomarkers of vascular inflammation in type 2 diabetes

Osteoprotegerin/Receptor Activator of Nuclear Factor-Kappa B Ligand/Receptor Activator of Nuclear Factor-Kappa B Axis in Obesity, Type 2 Diabetes Mellitus, and Nonalcoholic Fatty Liver Disease

PURPOSE OF REVIEW

To summarize evidence on the potential involvement of the osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B (NF-κΒ) ligand (RANKL)/receptor activator of NF-κΒ (RANK) axis in the pathogenesis of metabolic diseases.

RECENT FINDINGS

The OPG-RANKL-RANK axis, which has been originally involved in bone remodeling and osteoporosis, is now recognized as a potential contributor in the pathogenesis of obesity and its associated comorbidities, i.e., type 2 diabetes mellitus and nonalcoholic fatty liver disease. Besides bone, OPG and RANKL are also produced in adipose tissue and may be involved in the inflammatory process associated with obesity. Metabolically healthy obesity has been associated with lower circulating OPG concentrations, possibly representing a counteracting mechanism, while elevated serum OPG levels may reflect an increased risk of metabolic dysfunction or cardiovascular disease. OPG and RANKL have been also proposed as potential regulators of glucose metabolism and are potentially involved in the pathogenesis of type 2 diabetes mellitus. In clinical terms, type 2 diabetes mellitus has been consistently associated with increased serum OPG concentrations. With regard to nonalcoholic fatty liver disease, experimental data suggest a potential contribution of OPG and RANKL in hepatic steatosis, inflammation, and fibrosis; however, most clinical studies showed reduction in serum concentrations of OPG and RANKL. The emerging contribution of the OPG-RANKL-RANK axis to the pathogenesis of obesity and its associated comorbidities warrants further investigation by mechanistic studies and may have potential diagnostic and therapeutic implications.

The mediating role of vascular inflammation in traffic-related air pollution associated changes in insulin resistance in healthy adults

AIM

The precise pathophysiologic pathway linking traffic-related air pollution (TRAP) to diabetes mellitus is not well elucidated. We aimed to investigate whether activation of vascular inflammation can be a mechanistic linkage between ambient TRAP and insulin resistance.

METHODS

Study outcomes were determined by assessing a series of circulating biomarkers indicative of insulin resistance and vascular inflammation among 73 healthy adults who underwent repeated clinical visits in Beijing, China, 2014-2016. Concomitantly, concentrations of ambient TRAP indices, including particulate matter in diameter <2.5 μm (PM_2.5), particles in size fractions of 5-560 nm, black carbon, carbon monoxide, nitrogen dioxide, and oxides of nitrogen, were continuously monitored.

RESULTS

Participants experienced extremely high levels of TRAP exposures, with mean (standard deviation) PM_2.5 concentrations of 91.8 (48.3) μg/m³, throughout the study. We found that interquartile range increases in exposure to moving average concentrations of various TRAP indices at prior up to 7 days were associated with significant elevations of 8.9-49.6% in insulin levels. Higher pollutant levels were also related to worsening metrics of insulin resistance (soluble insulin receptor ectodomain, adipokines, and homeostasis model assessment of insulin resistance) and heightened vascular inflammatory responses, particularly disruptions of the receptor activator of nuclear factor κB ligand/osteoprotegerin system balance and elevations of monocyte/macrophage and T cell activation markers. Mediation analyses showed that activation of vascular inflammation could explain up to 66% of the alterations in metrics of insulin resistance attributable to air pollution.

CONCLUSION

Our results suggest that ambient traffic pollution exposure was capable of promoting insulin resistance possibly via generating vascular inflammation.

Effect of Resistance Exercise on Serum Osteoprotegerin Levels and Insulin Resistance in Middle-Aged Women with Metabolic Syndrome

Background

Osteoprotegerin (OPG) is a soluble glycoprotein that belongs to the tumor necrosis factor (TNF) receptor superfamily. OPG is mainly secreted by bone. The relationship between acute resistance training, serum OPG levels and metabolic syndrome, including insulin resistance, remains unclear. The purpose of this study was to determine the effect of resistance exercise on serum OPG levels and insulin resistance in middle-aged women with metabolic syndrome.

Material/Methods

Twenty-four middle-aged women were divided into those with metabolic syndrome (n=12) and a normal control group without metabolic syndrome or insulin resistance (n=12). Metabolic syndrome was diagnosed according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) criteria. The quantitative insulin-sensitivity check index (QUICKI) and the homeostatic model assessment (HOMA) index for assessing beta-cell function and insulin resistance were used. The intensity of the resistance exercise was 60–70% of the repetition maximum, for 40 minutes with 10–12 repetitions, performed three times per week. Venous blood samples were tested using standard laboratory procedures.

Results

Before exercise, the metabolic syndrome group showed a significant increase in waist circumference (P=0.030) and serum triglyceride (TG) (P=0.014), and lower high-density lipoprotein-cholesterol (HDL-C) (P=0.010) compared with the control group. After the eight-week resistance exercise program, waist circumference, and the QUICKI decreased and OPG levels were significantly increased in the metabolic syndrome group compared with the normal control group.

Conclusions

A resistance exercise program was effective in reducing factors associated with metabolic syndrome including insulin resistance and increases serum levels of OPG in middle-aged women.

The role of OPG/RANKL in the pathogenesis of diabetic cardiovascular disease

Cardiovascular (CV) disease is the leading cause of mortality in patients with type 2 diabetes mellitus. A major factor in the pathogenesis of CV disease is vascular calcification (VC), which is accelerated in type 2 diabetes mellitus. Calcification of the vessel wall contributes to vascular stiffness and left ventricular hypertrophy whereas intimal calcification may predispose to plaque rupture and CV death. The pathogenesis of VC is complex but appears to be regulated by the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) signaling pathway, which is involved in bone remodeling. Within the bone, OPG prevents RANKL from binding to receptor activator of nuclear factor-κB and inhibiting bone resorption. Outside of the bone, the clinical significance of OPG blocking RANKL is not well understood, but OPG knockout mice that lack OPG develop early and severe VC. This minireview outlines some of the research on OPG/RANKL in the pathogenesis of VC and discusses potential therapies, which may reduce VC and CV burden in humans.

Intricate Assessment and Evaluation of Long-term Implant Success as affected by Clinicomicrobial and Salivary Diagnostics in Type II Diabetic Patients: A Longitudinal Study

INTRODUCTION

Replacement of missing teeth by dental implants is one of the most common methods employed these days. Because of significant advancement in the design of implants and modifications in the procedure of dental implant surgery, the survival rate of the dental implants has reached up to approximately 95%. Osseointegration is one of the important factors affecting the survival of dental implants. Apart from these, the body's physiologic alterations can also predispose the dental implants for failure. Diabetes is one such metabolic disease characterized by abnormal or delayed wound healing. Hence, we assessed the clinicomicrobial and salivary profile of diabetic patients undergoing rehabilitation by dental implants.

MATERIALS AND METHODS

This study included diabetic patients who underwent dental implant surgeries for prosthetic rehabilitation. Follow-up records of the patients' up to 1 year were maintained. Various clinicoradiographic and periodontal parameters were measured at various time intervals during follow-up time; 25 mL of salivary and blood sample was taken from all the subjects and was sent to the laboratories for assessment of various salivary biomarkers. All the results were analyzed by Statistical Package for the Social Sciences software.

RESULTS

The mean level of interleukin-p at baseline time was found to be 2.38 and 2.21 in diabetic group and control group respectively. While comparing the levels of osteoprotegerin in both study groups, a significant correlation was obtained. In diabetic and control group, 62 and 61 years was the mean age of the patients respectively. No significant correlation was obtained while comparing the microbial flora of diabetic and control group.

CONCLUSION

In both diabetic and nondiabetic patients, similar microbial, salivary marker, and clinicoradiological patterns were seen.

CLINICAL SIGNIFICANCE

Diabetic patients who maintain their body's metabolic rate show similar success rate of dental implants as seen in nondiabetic patients.

Does the OPG/RANKL system contribute to the bone-vascular axis in chronic kidney disease? A systematic review

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and is strongly associated with cardiovascular mortality and morbidity. Accumulating evidence over the past decade has challenged the hypothesis of close interaction between bone and VC what raises the possibility of a common underlying pathophysiological mechanism. Lately, bone regulatory proteins such as: osteoprotegerin (OPG) and Receptor Activator for Nuclear Factor κB Ligand (RANKL) has attracted attention of researchers as a possible key mediators of bone-vascular calcification imbalance. The literature search was carried out using the MEDLINE/PubMed database and a combination of keywords and MeSH terms, and only papers published since January 2005 to July 2016 were selected. The search resulted in 562 potential articles. After selection according to the eligibility criteria, 107 studies fulfilled were included (102 full texts and 5 was case reports). OPG and RANKL plays essential role in the regulation of bone metabolism and may be regarded as a possible link between VC, bone and mineral metabolism in CKD patients. Further studies are required to determine the diagnostic significance of these proteins in evaluation of progression and severity of VC process in CKD patients. Finally, the efficacy and safety, especially in regard to VC, of anti-RANKL therapy in CKD patients requires well-designed prospective, randomized trials.

Soluble TRAIL Concentration in Serum Is Elevated in People with Hypercholesterolemia

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a multi-functional cytokine, which is involved in the pathophysiological processes of cardiovascular and metabolic diseases. Previously, we demonstrated that TRAIL stimulated lipid uptake and foam cell formation in macrophages in vitro. Several clinical studies have suggested that the serum concentration of TRAIL may be increased in humans with elevated blood cholesterol; however, the current data appear to be inconclusive in this regard. In the present study, we examined the relationships between the serum TRAIL concentration and cholesterol levels in 352 generally healthy subjects undergoing the routine annual health check. We showed that there were significant correlations between TRAIL concentration and levels of total and low-density lipoprotein cholesterols. The level of TRAIL was significantly elevated in subjects with hypercholesterolemia, although this relationship might be also associated with changes of other metabolic factors. Moreover, we showed that the level of blood cholesterol was significantly higher in subjects in the upper quartile of serum TRAIL. In conclusion, our data demonstrate that the serum TRAIL concentration is elevated in people with hypercholesterolemia.

Osteoprotegerin in Cardiometabolic Disorders

Osteoprotegerin (OPG), a glycoprotein traditionally implicated in bone remodelling, has been recently related to cardiovascular disease (CVD). Human studies show a positive relationship between circulating OPG, vascular damage, and CVD, and as such OPG has emerged as a potential biomarker for CVD. This review focuses on the relationship between circulating OPG and different endocrine cardiometabolic alterations such as type 1 and 2 diabetes. The association of OPG with diabetic complications (neuropathy, nephropathy, or retinopathy) as well as with atherosclerosis, coronary artery calcification, morbidity, and mortality is pointed out. Moreover, OPG modulation by different treatments is also established. Besides, other associated diseases such as obesity, hypertension, and metabolic syndrome, which are known cardiovascular risk factors, are also considered.

Circulating osteoprotegerin is increased in the metabolic syndrome and associates with subclinical atherosclerosis and coronary arterial calcification

CONTEXT

The relationship between osteoprotegerin (OPG) a glycoprotein related to bone metabolism and the metabolic syndrome (MS) has not been established.

OBJECTIVE

The aim of this study is to evaluate OPG concentration in patients with MS and its association with subclinical atherosclerosis and coronary arterial calcification (CAC).

MATERIALS/METHODS

The study included 238 asymptomatic patients. MS was diagnosed according to the NCEP/ATPIII guidelines. OPG was measured by ELISA. All subjects underwent ultrasonography of the common carotid arteries to measure intima-media thickness (IMT) and evaluate the presence of atheroma plaques. In a subgroup (n=39) CAC was quantified by ECG-triggered cardiac computed tomography. Adipose tissue was excised from 25 patients and OPG expression by RT-PCR and immunohistochemistry was studied.

RESULTS

Patients with the MS (n=60) had higher OPG than patients without (n=178) (p<0.05). OPG correlated with IMT (r=0.2, p=0.005) and patients with atheroma plaques had higher OPG (p=0.008) and also those with coronary artery calcification (p<0.05). OPG expression was confirmed in adipose tissue (n=12) and the expression was significantly higher in patients with MS than in those without (p=0.003).

CONCLUSIONS

This study shows that OPG may potentially be a biomarker for cardiovascular risk/damage in the MS and identifies adipose tissue as a potential source of OPG.

Osteoprotegerin is associated with subclinical left ventricular systolic dysfunction in diabetic hypertensive patients: a speckle tracking study

BACKGROUND

Recently, the role of osteoprotegerin (OPG) in the pathogenesis of heart failure through different mechanisms has received much attention. Subclinical changes in left ventricular (LV) function can be identified using quantification of myocardial strain, and global longitudinal strain (GLS) is a superior predictor of outcomes than ejection fraction. We hypothesized that increased OPG levels could predict subclinical LV systolic dysfunction in treated diabetic hypertensive patients with preserved LV ejection fraction.

METHODS

The study was composed of 86 diabetic hypertensive and 30 nondiabetic hypertensive patients. All patients underwent echocardiography and venous blood samples were taken for determination of OPG. The relation between OPG levels and LV GLS was investigated using 2-dimensional speckle tracking echocardiography.

RESULTS

Diabetic hypertensive patients had higher diastolic peak early/early diastolic tissue velocity and lower systolic tissue velocity, GLS, GLS rate systolic, and GLS rate early diastolic than nondiabetic hypertensive patients (P = 0.009, P = 0.049, P < 0.001, P = 0.004, and P < 0.001, respectively). Diabetic hypertensive patients were divided into 2 groups according to median GLS value (> 18.5 and ≤ 18.5). The patients with GLS ≤ 18.5 had higher diastolic blood pressure (mm Hg; P = 0.048), OPG (pmol/L; P < 0.001), and hemoglobin A1c (%; P = 0.042) values than those with GLS > 18.5. In multivariate logistic regression analysis, OPG was found to be an independent predictor of impaired GLS (P = 0.001). Receiver operating characteristic curve analysis revealed that OPG values of > 6.45 (pmol/L) identified the patients with GLS ≤ 18.5.

CONCLUSIONS

Plasma OPG values could predict subclinical LV systolic dysfunction in diabetic hypertensive patients.

On the TRAIL of obesity and diabetes

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) has been extensively studied for its preferential ability to induce apoptosis of cancer cells. Beyond the cytotoxic capacity of TRAIL, new physiological and pathological roles for TRAIL have been identified, and there is now growing evidence supporting its involvement in the development of obesity and diabetes. This review summarizes the most recent findings associating TRAIL with obesity and diabetes in both humans and experimental settings. We also present and discuss some of the reported controversies behind TRAIL signaling and function. Understanding TRAIL mechanism(s) in vivo and its involvement in disease may lead to novel strategies to combat the growing pandemic of obesity and diabetes worldwide.

The role of osteoprotegerin in cardiovascular disease

Osteoprotegerin (OPG) is a 401 amino acid N-glycosylated protein, which is highly expressed in a large number of tissues. OPG mainly binds to two ligands, i.e. RANKL (receptor activator of nuclear factor κB ligand) and TRAIL (tumor necrosis factor- related apoptosis-inducing ligand). Upon binding to the former ligand, OPG inhibits the activation of osteoclasts and promotes apoptosis of osteoclasts, whereas the binding of OPG with TRAIL prevents apoptosis of tumor cells. There is now emerging evidence that OPG participates in the pathogenesis of atherosclerosis and cardiovascular diseases by amplifying the adverse effects of inflammation and several traditional risk factors such as hyperlipidemia, endothelial dysfunction, diabetes mellitus, and hypertension. Some epidemiological studies also showed a positive association between OPG levels and cardiovascular morbidity and mortality. The aim of this article is to provide an overview of the main biochemical, physiological, and pathological aspects of OPG biology in cardiovascular disease.

Clinical, microbiological, and salivary biomarker profiles of dental implant patients with type 2 diabetes

OBJECTIVE

Regulators of peri-implant bone loss in patients with diabetes appear to involve multiple risk factors that have not been clearly elucidated. This study was conducted to explore putative local etiologic factors on implant bone loss in relation to type 2 diabetes mellitus, including clinical, microbial, salivary biomarker, and psychosocial factors.

MATERIALS AND METHODS

Thirty-two subjects (divided into type 2 diabetes mellitus and non-diabetic controls), having at least one functional implant and six teeth, were enrolled in a 1-year longitudinal investigation. Analyses of clinical measurements and standardized intra-oral radiographs, saliva and serum biomarkers (via protein arrays for 20 selected markers), and plaque biofilm (via qPCR for eight periodontal pathogens) were performed at baseline and 1 year. In addition, the subjects were asked to respond to questionnaires to assess behavioral and psychosocial variables.

RESULTS

There was a significant increase from baseline to 1 year in the probing depth of implants in the diabetes group (1.95 mm to 2.35 mm, P = 0.015). The average radiographic bone loss during the study period marginally increased at dental implants compared to natural teeth over the study period (0.08 mm vs. 0.05 mm; P = 0.043). The control group harbored higher levels of Treponema denticola at their teeth at baseline (P = 0.046), and the levels of the pathogen increased significantly over time around the implants of the same group (P = 0.003). Salivary osteoprotegerin (OPG) levels were higher in the diabetes group than the control group at baseline only; in addition, the salivary levels of IL-4, IL-10, and OPG associated with host defense were significantly reduced in the diabetes group (P = 0.010, P = 0.019, and P = 0.024), while controls showed an increase in the salivary OPG levels (P = 0.005). For psychosocial factors, there were not many significant changes over the observation period, except for some findings related to coping behaviors at baseline.

CONCLUSIONS

The study suggests that the clinical, microbiological, salivary biomarker, and psychosocial profiles of dental implant patients with type 2 diabetes who are under good metabolic control and regular maintenance care are very similar to those of non-diabetic individuals. Future studies are warranted to validate the findings in longer-term and larger clinical trials (ClinicalTrials.gov # NCT00933491).

A comparison of osteoprotegerin with adiponectin and high-sensitivity C-reactive protein (hsCRP) as a marker for insulin resistance

OBJECTIVE

Insulin resistance (IR) is associated with low adiponectin and elevated high sensitivity C-reactive protein (hsCRP). Osteoprotegerin (OPG) has been shown to be elevated in type 2 diabetes, but whether it reflects underlying IR is unclear. We aimed to compare the ability of serum OPG with adiponectin and hsCRP to act as a marker for IR in individuals with normal and abnormal glucose tolerance.

MATERIALS/METHODS

115 men underwent a 75 g oral glucose tolerance test. OPG, hsCRP and adiponectin were measured using ELISA. IR was assessed using the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

Men with abnormal glucose tolerance (n=38) were older (58.3±11.2 vs 47.3±11.4 years, P<.001), had higher body mass index (BMI) (31.1±2.9 vs 27.9±3.2 kg/m(2), P<.001) and were more insulin resistant (median (I.Q.) HOMA-IR 5.88 (3.38) vs 1.13 (1.14), P<.001) than those with normal glucose tolerance (n=77). After adjustment for age and BMI, OPG (6.28 (2.32) vs 5.16 (1.86) pmol/L, P<.001) and hsCRP (2.07 (5.47) vs 0.78 (1.05) mg/L, P<.001) were higher and adiponectin (3.02±1.17 vs 4.78±2.38 μg/mL, P<.001) was lower in those with AGT. After adjustment for age and BMI, adiponectin (r=-0.317, P<.001) and hsCRP (r=0.318, P<.001), but not OPG (r=0.126, P=.196) correlated with HOMA-IR. On multiple linear regression analysis, adiponectin and hsCRP but not OPG were independent predictors of HOMA-IR.

CONCLUSIONS

OPG is higher in individuals with abnormal glucose tolerance, but unlike adiponectin and hsCRP, does not correlate with HOMA-IR, suggesting its elevation within this cohort of individuals is due to factors other than insulin resistance.

No influence of OPG and its ligands, RANKL and TRAIL, on proliferation and regulation of the calcification process in primary human vascular smooth muscle cells

The aim of this study was to examine the effects of the OPG-RANKL-TRAIL system on proliferation, regulation of calcification-associated genes and calcification of human vascular smooth muscle cells (HVSMCs). Small interfering (si)RNA-mediated knockdown of OPG was followed by treatment of HVSMCs with recombinant RANKL or TRAIL. Regulation of a calcification-associated gene set was assayed by pathway analysis of microarray results. The lack of OPG in HVSMCs or treatment with RANKL or TRAIL did not affect proliferation of HVSMCs. In addition, OPG, RANKL or TRAIL did not modify the regulation of a calcification-associated gene set. Finally, in the long term calcification assay, we found that cells isolated from seven different human donors showed a great variability in the response to RANKL and insulin. However, overall RANKL and/or insulin did not affect the development of calcification of HVSMCs. These studies indicate that OPG knockdown does not alter the calcification process in HVSMCs.

Identifying coronary artery disease in men with type 2 diabetes: osteoprotegerin, pulse wave velocity, and other biomarkers of cardiovascular risk

OBJECTIVES

In patients with type 2 diabetes, high serum levels of osteoprotegerin (OPG) have been associated with a greater risk of cardiovascular events. However, it remains unclear how well OPG performs when compared with traditional biomarkers of cardiovascular risk such as high-sensitivity C-reactive protein (hsCRP). Furthermore, OPG levels are also high in the presence of diabetes-related microvascular disease, and it is unclear whether OPG can distinguish microvascular disease from large-vessel atherosclerosis. The first aim of this study was to compare OPG levels against other biomarkers of cardiovascular risk in the identification of patients with documented multivessel coronary artery disease (CAD). The second aim was to compare OPG levels in patients with microvascular complications (microalbuminuria) against those with established CAD.

METHODS

Three groups of male patients with type 2 diabetes were recruited: patients without microvascular complications or large-vessel atherosclerosis (n = 24), patients with microalbuminuria only (n = 23), and patients with microalbuminuria and documented multivessel CAD (n = 25). OPG, hsCRP, interleukin 6, urate, and pulse wave velocity were measured.

RESULTS

Serum OPG levels were significantly higher in patients with a combination of microalbuminuria and CAD than in those with microalbuminuria alone. There were no significant differences in any of the other biomarkers between the groups.

CONCLUSION

OPG was found to be superior to the other biomarkers studied in identifying patients with documented CAD. The presence of CAD was a greater determinant of serum OPG levels than microalbuminuria in our population. These findings support the use of OPG as a biomarker of cardiovascular risk.

Association between vascular calcification and osteoporosis in men with type 2 diabetes

Atherosclerotic vascular disease is common in diabetes, and some data support a link with bone loss. This study evaluates the association between osteoporosis and clinical and metabolic factors and chronic complications of diabetes. We studied 59 diabetic men aged 50-80 yr who were assessed with bone densitometry (dual-energy X-ray absorptiometry). Of them, 10.2% of the patients were found to have osteoporosis in the lumbar spine and 45.8% osteopenia, whereas in the femoral neck, 11.8% had osteoporosis and 49% had osteopenia. There was a significant association of osteoporosis in the lumbar spine L1-L4 (p=0.004) and in the femoral neck (p=0.036) with iliac artery calcification. In addition, there was no association with any other metabolic factors, clinical factors, or chronic complications of diabetes evaluated, except for an association between a previous personal history of fractures (p=0.016) and low bone mineral density in the femoral neck. In conclusion, we found a positive association between the iliac artery calcification and osteoporosis in type 2 diabetic male patients.

The role of osteoprotegerin (OPG) receptor activator for nuclear factor kappaB ligand (RANKL) in cardiovascular pathology - a review

Initially described as key regulators in metabolic bone disease osteoprotegerin (OPG), receptor activator of nuclear factor kappa B (RANK) and RANK ligand (RANKL) have also been discriminated as regulators in immunologic function. Cardiovascular diseases (CVD) develop over many years in life and are often triggered by inflammatory processes within the vessel wall that lead to vascular remodeling. Recently some study groups have described OPG as a prognostic parameter for mortality and morbidity in cardiovascular patients.

Serum osteoprotegerin and tumor necrosis factor related apoptosis inducing-ligand (TRAIL) are elevated in type 2 diabetic patients with albuminuria and serum osteoprotegerin is independently associated with the severity of diabetic nephropathy

Osteoprotegerin (OPG) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) have recently been reported to be associated with diabetic nephropathy in an in vitro study. However, the literature regarding serum OPG and TRAIL in type 2 diabetes mellitus patients is scarce. To investigate the role of OPG/TRAIL in diabetic nephropathy, we measured the serum concentrations of OPG and TRAIL in type 2 diabetes mellitus patients with different stages of nephropathy by enzyme-linked immunosorbent assay. One hundred seventy-nine subjects with type 2 diabetes mellitus were studied and stratified according to urinary microalbumin and serum creatinine measurements. The serum concentrations of OPG and TRAIL were significantly elevated in patients with microalbuminuria (OPG, 2154.2 ± 922.1 pg/mL; TRAIL, 80.2 ± 24.1 pg/mL) and macroalbuminuria (OPG, 2251.5 ± 925.7 pg/mL; TRAIL, 88.1 ± 23.8 pg/mL) as compared with patients with normoalbuminuria (OPG, 1690.1 ± 627.2 pg/mL; TRAIL, 70.7 ± 23.3 pg/mL). Serum OPG and TRAIL levels were increased in parallel and were significantly associated with each other. Using multivariate stepwise regression analysis, serum OPG was found to be an independent factor associated with the severity of diabetic nephropathy. Our results suggested that serum OPG may be a marker for the severity of diabetic nephropathy. Further studies are necessary to investigate the role of elevated serum OPG in the pathogenesis of diabetic nephropathy.

Osteoblasts from a mandibuloacral dysplasia patient induce human blood precursors to differentiate into active osteoclasts

Mandibuloacral dysplasia type A (MADA) is a rare disease caused by mutations in the LMNA gene encoding A type lamins. Patients affected by mandibuloacral dysplasia type A suffer from partial lipodystrophy, skin abnormalities and accelerated aging. Typical of mandibuloacral dysplasia type A is also bone resorption at defined districts including terminal phalanges, mandible and clavicles. Little is known about the biological mechanism underlying osteolysis in mandibuloacral dysplasia type A. In the reported study, we analyzed an osteoblast primary culture derived from the cervical vertebrae of a mandibuloacral dysplasia type A patient bearing the homozygous R527H LMNA mutation. Mandibuloacral dysplasia type A osteoblasts showed nuclear abnormalities typical of laminopathic cells, but they proliferated in culture and underwent differentiation upon stimulation with dexamethasone and beta-glycerophosphate. Differentiated osteoblasts showed proper production of bone mineral matrix until passage 8 in culture, suggesting a good differentiation activity. In order to evaluate whether mandibuloacral dysplasia type A osteoblast-derived factors affected osteoclast differentiation or activity, we used a conditioned medium from mandibuloacral dysplasia type A or control cultures to treat normal human peripheral blood monocytes and investigated whether they were induced to differentiate into osteoclasts. A higher osteoclast differentiation and matrix digestion rate was obtained in the presence of mandibuloacral dysplasia type A osteoblast medium with respect to normal osteoblast medium. Further, TGFbeta 2 and osteoprotegerin expression were enhanced in mandibuloacral dysplasia type A osteoblasts while the RANKL/osteoprotegerin ratio was diminished. Importantly, inhibition of TGFbeta 2 by a neutralizing antibody abolished the effect of mandibuloacral dysplasia type A conditioned medium on osteoclast differentiation. These data argue in favor of an altered bone turnover in mandibuloacral dysplasia type A, caused by upregulation of bone-derived stimulatory cytokines, which activate non-canonical differentiation stimuli. In this context, TGFbeta 2 appears as a major player in the osteolytic process that affects mandibuloacral dysplasia type A patients.

Cytokines and bone-related factors in systemically healthy patients with chronic periodontitis and patients with type 2 diabetes and chronic periodontitis

BACKGROUND

This study compares the levels of cytokines and bone-related factors in the gingival crevicular fluid (GCF) of systemically healthy patients with chronic periodontitis (CP); and better-controlled, and poorly controlled patients with type 2 diabetes and CP.

METHODS

Thirty-seven patients with type 2 diabetes and CP and 20 systemically healthy patients with CP were enrolled in this study. The patients with diabetes mellitus were categorized as better-controlled (n = 17; HbA(1c) levels ≤8%) or poorly controlled (n = 20; glycated hemoglobin values >8%). Levels of tumor necrosis factor-α, interleukin (IL)-4, interferon (IFN)-γ, IL-23, IL-17, soluble receptor activator of nuclear factor-kappa B ligand (sRANKL), and osteoprotegerin (OPG) in GCF of diseased sites were analyzed by enzyme-linked immunosorbent assay.

RESULTS

Type 2 diabetes mellitus, as a whole, upregulates the levels of OPG, sRANKL, IFN-γ, IL-17, and IL-23 and downregulates the production of IL-4 in sites with CP (P <0.05). Better-controlled individuals exhibited the highest levels of IFN-γ, whereas poorly controlled patients presented the highest levels of IL-17 (P <0.05). There were no differences in the levels of tumor necrosis factor-α, OPG, and IL-23 among systemically healthy, better-controlled, and poorly controlled patients with diabetes (P >0.05).

CONCLUSIONS

Increased levels of proinflammatory cytokines and RANKL were observed in the GCF of patients with type 2 diabetes with CP, compared to patients without diabetes. In addition, poor or good glycemic status seems to modulate osteo-immunoinflammatory mediators in a different manner.