Osteoprotegerin in relation to insulin resistance and blood lipids in sub-Saharan African women with and without abdominal obesity

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.

OPG is associated with thyroid nodule development in type 2 diabetes

Background

Thyroid nodule prevalence is increasing lately, especially in diabetes, but the mechanism of which is not clear. In this study, we investigated if osteoprotegerin (OPG) is involved in the pathogenesis of thyroid nodules in diabetes.

Methods

A total of 7568 individuals with detailed information and ultrasound examination results were studied for the prevalence of thyroid nodules. Among them, 1883 were with type 2 diabetes and 5685 were non‐diabetic. Then, 1120 individuals were randomly selected for the measurement of OPG. Diabetic rats were made by feeding a high‐fat‐high‐fructose diet for 28 weeks. Rats fed with a normal diet were as controls. Fresh thyroid tissues were obtained and fixed, dehydrated, and embedded in paraffin for hematoxylin‐eosin staining and observing pathological changes. qPCR and western blot were used to detect OPG expression in rat thyroid tissues.

Results

We found that HbA1c is an independent risk factor for thyroid nodules (Exp [β] = 1.158, p < 0.001). The prevalence of thyroid nodules in type 2 diabetes was higher than that in non‐diabetes (53.9% vs. 46.7%, p < 0.001). Serum OPG levels were significantly elevated in the diabetes group than in the non‐diabetes group (3160.17 pg/ml vs. 2819.39 pg/ml, p < 0.01). The expression of OPG increased significantly in the thyroid tissues of diabetic rats.

Conclusion

Osteoprotegerin may be associated with thyroid nodule development in diabetes.

Comparison of novel markers of metabolic complications and cardiovascular risk factors between obese non-diabetic and obese type 1 diabetic children and young adults

INTRODUCTION

For the past years, the prevalence of obesity is growing in the general population of children, as well as among diabetic patients, resulting in increased risk of cardiovascular complications. Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases in children and young adults, leading to decreased life quality and lifespan, with obesity being recognized recently as a major contributing factor to these health problems. The objective of this study was to analyze and compare the selected novel markers for metabolic complications of obesity and vascular risk factors between obese non-diabetic and obese T1DM children and young adults.

METHODS

One hundred four subjects, aged between 10 and 24 years (31 with T1DM and excessive body weight, 41 with obesity without diabetes, and 32 with T1DM and normal weight), and 32 matched lean controls were included in the study. Clinical characteristics, blood pressure measurements, daily requirement for insulin, HbA1c%, plasma lipids, fetuin-A, E-selectin, and osteoprotegerin levels were compared with respect to body mass index (BMI), body mass index standard deviation score (BMI-SDS), and carotid intima-media thickness (cIMT) of common carotid arteries.

RESULTS

Patients with T1DM and excessive body weight compared to non-diabetic obese subjects had similar values of systolic blood pressure (125.6 ± 8.2 vs. 127.3 ± 12.9 mmHg, p = 0.515), diastolic blood pressure (78.19 ± 7.03 vs. 78.02 ± 8.01 mmHg, p = 0.918), cholesterol (175.26 ± 34.1 vs. 163.51 ± 26.08 mg/dl, p = 0.102), LDL (108.03 ± 32.55 vs. 112.22 ± 26.36 mg/dl, p = 0.548), and triglyceride levels (118.19 ± 71.20 vs. 117 ± 55.80 mg/dl, p = 0.937); all values were found to be higher compared to non-obese T1DM and healthy controls. HbA1c level and insulin resistance indices were significantly worse in T1DM obese vs. T1DM non-obese patients. Fetuin-A levels were higher among obese non-diabetic patients (p = 0.01), and E-selectin and osteoprotegerin levels were similar in both groups with obesity, but higher than in the reference group. There were no statistical differences in cIMT with T1DM with normal weight, excessive weight, and non-diabetic obese children; however, the cIMT value was higher compared to the reference group.

DISCUSSION

Novel markers of metabolic complications of obesity are similar between obese T1DM and non-diabetic subjects. Obesity in patients with T1DM results in worse metabolic control, insulin resistance, and increased risk for vascular complications.

Increased osteoprotegerin level is associated with impaired cardiovagal modulation in type-2 diabetic patients treated with oral antidiabetic drugs

Background

An increased osteoprotegerin (OPG) level has been reported in both type-2 diabetes mellitus (T2DM) and cardiovascular diease (CVD) that are linked to sympathovagal imbalance (SVI). We explored the link of osteoprotegerin with cardiovagal modulation in T2DM.

Methods

We assessed fasting serum OPG, high-sensitive C-reactive protein (hsCRP), glucose, insulin and lipid profile in patients having T2DM receiving oral antidiabetic drugs (OAD) (n = 42) compared with age, gender and body composition-matched healthy participants without diabetes (n = 42). Rate pressure product (RPP), spectral indices of heart rate variability (HRV) and body composition were recorded in both the groups. Association of HOMA-IR and OPG with various parameters were assessed.

Results

Osteoprotegerin, HOMA-IR, hsCRP, coronary lipid risk factor were significantly increased, markers of cardiovagal modulation (TP, SDNN, RMSSD) were considerably decreased, ratio of low-frequency to high-frequency (LH-HF ratio), the indicator of SVI, and RPP, the marker of myocardial work stress were significantly higher in patients with diabetes, suggesting an overall elevated CVD risks in them. HOMA-IR was correlated with RMSSD, lipid risk factors and OPG. Rise in OPG was correlated with decreased cardiovagal modulation in patients with diabetes. There was significant contribution of OPG in decreasing TP, suggesting impaired cardiovagal modulation.

Conclusion

T2DM patients receiving OAD had higher cardiometabolic risks compared to age, gender and body composition-matched healthy individuals. Increased level of OPG is linked to decreased cardiovagal modulation in T2DM patients.

Osteoprotegerin increases parallel to insulin resistance in obese adolescents

Purpose/Aim of the Study: Osteoprotegerin (OPG) is an α tumor necrosis factor receptor superfamily glucoprotein that acts as a decoy receptor for the receptor activator of nuclear factor kappa B ligand (RANKL), exerting an antiresoptive bone effect. It was recently shown that OPG/RANKL axis is activated during vascular calcification, contributing to atherosclerotic lesions formation. Additionally, OPG levels are charachterized as an independent risk factor for overall vascular mortality in obese adults. We aimed to investigate OPG levels in children/adolescents with obesity and explore possible relations with obesity-related insulin resistance (IR).

MATERIAL AND METHODS

A total of 160 participants (85 obese) were enrolled. Participants with obesity underwent an oral glucose tolerance test. IR was evaluated according to the homeostasis model assessment-insulin resistance index. Serum OPG levels were determined.

RESULTS

OPG levels did not differ significantly between obese subjects and controls in the total sample (p = 0.133). However, in the adolescents' subgroup, serum OPG levels were significantly increased in obesity (p = 0.019). After stratifying participants according to their IR status, only subjects with both obesity and IR exhibited increased OPG levels compared to controls (p < 0.001). Factor analysis further associated OPG levels variation to insulin levels variation and to IR.

CONCLUSIONS

Obese individuals demonstrate increased serum OPG levels during puberty. Obesity per se is not the potent factor for this increase; indeed, IR accompanying obesity seems to exert a fundamental role in OPG upregulation.

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.

Circulating osteoprotegerin in postmenopausal osteoporotic women: marker of impaired glucose regulation or impaired bone metabolism

OBJECTIVE

Osteoprotegerin (OPG) is closely related to insulin resistance and bone remodeling. However, no studies have examined the role of OPG in postmenopausal women with coexistent impaired glucose and bone regulation. The present study investigated the relationship of OPG to glucose homeostasis and insulin resistance in postmenopausal osteoporotic women with different types of glucose tolerance.

METHODS

In all, 114 postmenopausal osteoporotic women were divided into three groups according to glucose tolerance status: 51 with normal glucose tolerance (NGT, group 1), 31 with impaired glucose tolerance (IGT, group 2), and 32 with type 2 diabetes mellitus (DM, group 3). Study participants were evaluated for metabolic parameters, OPG, Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), and bone mineral density parameters.

RESULTS

The OPG levels differed significantly across groups and increased from group 1 to group 3 in a continuous fashion (analysis of variance, P < 0.0001). In post-hoc analysis, OPG was significantly lower in osteoporotic women with NGT, than participants with IGT and DM (P < 0.05 and P < 0.0001, respectively). OPG was positively associated with HOMA-IR (P < 0.0001). No association between serum OPG levels and measures of BMD was observed. In a multiple regression analysis, OPG emerged as an independent predictor of HOMA-IR even after controlling for age, body mass index, and creatinine.

CONCLUSIONS

OPG is significantly higher in postmenopausal osteoporotic women with impaired glucose regulation (IGT and DM) than women with NGT. OPG was independently associated with insulin resistance assessed by HOMA-IR. Thus, measurement of OPG may potentially be considered as a prediabetic state screening in postmenopausal osteoporotic women.

Role of osteoprotegerin/receptor activator of nuclear factor kappa B/receptor activator of nuclear factor kappa B ligand axis in nonalcoholic fatty liver disease

Concomitantly with the increase in the prevalences of overweight/obesity, nonalcoholic fatty liver disease (NAFLD) has worldwide become the main cause of chronic liver disease in both adults and children. Patients with fatty liver display features of metabolic syndrome (MetS), like insulin resistance (IR), glucose intolerance, hypertension and dyslipidemia. Recently, epidemiological studies have linked obesity, MetS, and NAFLD to decreased bone mineral density and osteoporosis, highlighting an intricate interplay among bone, adipose tissue, and liver. Osteoprotegerin (OPG), an important symbol of the receptor activator of nuclear factor-B ligand/receptor activator of nuclear factor kappa B/OPG system activation, typically considered for its role in bone metabolism, may also play critical roles in the initiation and perpetuation of obesity-related comorbidities. Clinical data have indicated that OPG concentrations are associated with hypertension, left ventricular hypertrophy, vascular calcification, endothelial dysfunction, and severity of liver damage in chronic hepatitis C. Nonetheless, the relationship between circulating OPG and IR as a key feature of MetS as well as between OPG and NAFLD remains uncertain. Thus, the aims of the present review are to provide the existent knowledge on these associations and to discuss briefly the underlying mechanisms linking OPG and NAFLD.

Osteoprotegerin rich tumor microenvironment: implications in breast cancer

Osteoprotegerin (OPG) is a soluble decoy receptor for tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL). It belongs to the tumor necrosis factor receptor superfamily (TNFRSF). OPG was initially discovered to contribute to homeostasis of bone turnover due to its capability of binding to receptor activator of nuclear factor-kappaB (NF-kB). However, apart from bone turnover, OPG plays important and diverse role(s) in many biological functions. Besides having anti-osteoclastic activity, OPG is thought to exert a protective anti-apoptotic action in OPG-expressing tumors by overcoming the physiologic mechanism of tumor surveillance exerted by TRAIL. Along with inhibiting TRAIL induced apoptosis, it can induce proliferation by binding to various cell surface receptors and thus turning on the canonical cell survival and proliferative pathways. OPG also induces angiogenesis, one of the hallmarks of cancer, thus facilitating tumor growth. Recently, the understanding of OPG and its different roles has been augmented substantially. This review is aimed at providing a very informative overview as to how OPG affects cancer progression especially breast cancer.

The impact of high total cholesterol and high low-density lipoprotein on avascular necrosis of the femoral head in low-energy femoral neck fractures

Background

Avascular necrosis of the femoral head (AVNFH) typically constitutes 5 to 15% of all complications of low-energy femoral neck fractures, and due to an increasingly ageing population and a rising prevalence of femoral neck fractures, the number of patients who develop AVNFH is increasing. However, there is no consensus regarding the relationship between blood lipid abnormalities and postoperative AVNFH. The purpose of this retrospective study was to investigate the relationship between blood lipid abnormalities and AVNFH following the femoral neck fracture operation among an elderly population.

Methods

A retrospective, comparative study was performed at our institution. Between June 2005 and November 2009, 653 elderly patients (653 hips) with low-energy femoral neck fractures underwent closed reduction and internal fixation with cancellous screws (Smith and Nephew, Memphis, Tennessee). Follow-up occurred at 1, 6, 12, 18, 24, 30, and 36 months after surgery. Logistic multi-factor regression analysis was used to assess the risk factors of AVNFH and to determine the effect of blood lipid levels on AVNFH development. Inclusion and exclusion criteria were predetermined to focus on isolated freshly closed femoral neck fractures in the elderly population. The primary outcome was the blood lipid levels. The secondary outcome was the logistic multi-factor regression analysis.

Results

A total of 325 elderly patients with low-energy femoral neck fractures (AVNFH, n = 160; control, n = 165) were assessed. In the AVNFH group, the average TC, TG, LDL, and Apo-B values were 7.11 ± 3.16 mmol/L, 2.15 ± 0.89 mmol/L, 4.49 ± 1.38 mmol/L, and 79.69 ± 17.29 mg/dL, respectively; all of which were significantly higher than the values in the control group. Logistic multi-factor regression analysis showed that both TC and LDL were the independent factors influencing the postoperative AVNFH within femoral neck fractures.

Conclusions

This evidence indicates that AVNFH was significantly associated with blood lipid abnormalities in elderly patients with low-energy femoral neck fractures. The findings of this pilot trial justify a larger study to determine whether the result is more generally applicable to a broader population.

Serum Osteoprotegerin Is a Potential Biomarker of Insulin Resistance in Chinese Postmenopausal Women with Prediabetes and Type 2 Diabetes

The aim of this study is to investigate the circulating OPG levels in postmenopausal women with diabetes and prediabetes and explore the relationships between serum OPG and insulin resistance. A total of 271 unrelated Chinese postmenopausal women were recruited in this study. The subjects were divided into type 2 diabetes mellitus (T2DM) group (n = 93), impaired glucose regulation (IGR) (n = 90), and normal glucose regulation group (NGR) (n = 88), according to different glucose regulation categories. Serum OPG levels were measured by enzyme-linked immunosorbent assay. The serum OPG concentration in NGR group, 151.00 ± 45.72 pg/mL, was significantly lower than that in IGR group (169.28 ± 64.91 pg/mL) (p = 0.031) and T2DM group (183.20 ± 56.53 pg/mL) (p < 0.01), respectively. In multiple linear regression analysis, HOMA-IR, age, 2hPG, AST, ALP, and eGFR were found to be independent predictors of OPG. Increased serum OPG levels (OR = 1.009, p = 0.006) may be a risk factor for insulin resistance. The present study suggests that OPG might be implicated in the pathogenesis of diabetes and is a potential biomarker of insulin resistance in subjects with diabetes and prediabetes.