King Khalid University Journal of Health Sciences

ORIGINAL ARTICLE
Year
: 2020  |  Volume : 5  |  Issue : 2  |  Page : 71--75

Serum osteocalcin levels in saudi females with type 2 diabetes mellitus in Al Madinah Al Munawarah


Walaa Mohammedsaeed, Lobnah Saber 
 Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Madina, Saudi Arabia

Correspondence Address:
Dr. Walaa Mohammedsaeed
Department of Medical Laboratories Technology, Faculty of Applied Medical Sciences, Taibah University, Madina
Saudi Arabia

Abstract

Background: Osteocalcin (OC), a bone-derived protein hormone, regulates glucose and fat metabolism. In Saudi population, the relationship between serum OC levels and Type 2 diabetes mellitus (DM) is limited. The association of OC with cardiovascular disease (CVD) is also not clear. Objectives: We performed a case–control study to explore the relationship between OC and Type 2 DM and CVD among Saudi females in Almadinah. Materials and Methods: A case–control study was conducted between January 2017 and January 2019 for 50 female patients with Type 2 DM attending Prince Abdelaziz Ben Maged Ben Abdelaziz Diabetic Center in Almadinah enrolled as research subjects. Fifty Type 2 DM female patients, aged about 30–55 years, and 50 age-matched healthy female control subjects were enrolled in our study. After overnight fasting, total OC, glucose, glycated hemoglobin (HbA1c), and lipid profile were analyzed to determine association of OC with glucose intolerance and lipid profile. Data processing was performed using GraphPad Prism 7 (GraphPad Software, CA, USA). Results: There was a significant elevation in the frequency of low OC levels in Type 2 DM patients compared with controls (P < 0.001). Fasting serum glucose varied inversely with the OC tertials (P = 0.049). However, no statistically significant difference was noted in HbA1c or lipid levels with the OC tertials. The Atherogenic Index of Plasma (AIP = Log10 [TG/HDL]) was 36% among Type 2 DM patients, indicating higher cardiovascular risk, while 26% had intermediate risk, with increased frequency of low OC levels in patients with high and intermediate cardiovascular risk compared to low-risk patients group (P = 0.047). Conclusions: Low serum OC level was associated with impaired glucose metabolism and increased cardiovascular risk in Type 2 diabetes.



How to cite this article:
Mohammedsaeed W, Saber L. Serum osteocalcin levels in saudi females with type 2 diabetes mellitus in Al Madinah Al Munawarah.King Khalid Univ J Health Sci 2020;5:71-75


How to cite this URL:
Mohammedsaeed W, Saber L. Serum osteocalcin levels in saudi females with type 2 diabetes mellitus in Al Madinah Al Munawarah. King Khalid Univ J Health Sci [serial online] 2020 [cited 2021 May 14 ];5:71-75
Available from: https://www.kkujhs.org/text.asp?2020/5/2/71/309613


Full Text

 Introduction



The International Diabetes Federation reported that in 2019, the overall prevalence of diabetes mellitus (DM) in adults was estimated to be 79%.[1] DM is a vital public health issue in the Saudi Arabia, and it requires special care and consideration as it is widely distributed among the population throughout the kingdom.[2] Saudi Arabia is recognized as one of the top countries worldwide which has elevated rates of prevalence of diabetes and obesity that involve more than one-third of adult population and the diabetic's complications were expand and enhance the risk of getting cardiovascular disease (CVD), liver, and kidney diseases.[3]

The patients with Type 2 DM have a higher bone mass than the healthy individuals, compared to patients with Type 1 DM.[4] A novel model has recently been proposed, wherein an endocrine loop, mediated by osteocalcin (OC), links the osteoblasts with the islets and the adipocytes. OC, also known as bone gamma-carboxyglutamic acid-containing protein (BGLAP), is secreted by osteoblasts, one of the main organic ingredients of the bone matrix,[5],[6] and an essential protein component for bone mineral balance that binds with calcium to regulate blood glucose levels. It is released into the circulation in carboxylated form that stimulates insulin secretion and regulates glucose homeostasis.[6] On the other hand, insulin stimulates OC expression in osteoblasts.[7] Skeletal muscle and adipose tissue respond to OC via increased sensitivity to insulin. OC may also play a role in the control of bone remodeling. OC produced by osteocytes inhibits the excessive bone formation in the vicinity of osteocytes. OC may bind to a specific receptor on osteoblasts to fulfill its function and can be used as a marker of osteoblastic activity and bone turnover, rather than bone formation marker.[7] However, OC levels increase in patients with metabolic bone diseases associated with enhanced osteoid (the basic structural unit of compact bone) formation, such as hyperparathyroidism, osteomalacia in adults, rickets in children, osteoporosis, renal osteodystrophy, acromegaly, thyrotoxicosis, bone metastasis, and in case of fractures.[8] A recent study in mice has shown that un-carboxylated OC increases expression and secretion of insulin in pancreatic islet β-cells and of adiponectin in adipocytes, thereby resulting in improved glucose tolerance and insulin sensitivity.[8] Observational studies in humans have reported the association of low OC levels with insulin resistance, severe hyperglycemia, Type 2 DM, or lower degree of glycemic control.[9] However, in humans, the results are controversial and inconsistent as patients with Type 2 DM have been found to have significantly decreased serum levels of OC than healthy controls in some studies.[9],[10] Hence, the molecular mechanisms underlying the modulation of OC expression and its potential role in diabetes pathogenesis and treatment need to be thoroughly investigated.

The present study proposes to investigate the serum OC levels in Saudi females with Type 2 DM and the possible role of OC in the macro- and microvascular diabetic complications. The interplay between bone marker and different extra-osseous tissues may open up new window for the detection a novel therapeutic target for highly prevalent diseases such as DM, CVD, and osteoporosis.

 Subjects and Methods



Study subjects

Fifty female patients with Type 2 DM attending Prince Abdelaziz Ben Maged Ben Abdelaziz Diabetic Center in Almadinah, Saudi Arabia, were enrolled as research subjects, referring to the 1999 WHO diagnostic criteria of DM.[2] The study included 50 healthy females as a control group. The age, medication history, menstruation, course of DM, and complications of every patient were noted from the patient's records and files.

Selection of cases

The research subjects were selected in accordance with the inclusion/exclusion criteria. The inclusion criteria comprised female Type 2 DM patients ≥30 years of age and who gave consent for participation in the study. The exclusion criteria of the study were: patients suffering from Type 1 diabetes, acute pancreatitis, anemia, hepatic dysfunction, renal injury, psoriasis, hypothyroidism, systemic lupus erythematosus, anorexia nervosa, organ transplantation, skeletal muscle damage or trauma, acute lymphoblastic leukemia, cancer of breast, ovary, or pancreas, patients already on folic acid, pyridoxine, and vitamin B12 therapy, and those who refrained from signing a consent form for participation in the study.

Specimen collection

Three milliliter of the venous blood was collected from all the cases and controls after an overnight fasting of at least 12 h, and the levels of fasting serum glucose (FSG), glycated hemoglobin (HbA1c), and lipid profile were estimated by Siemens Dimension XP auto analyzer. Meanwhile, 2 ml of residual blood sample was centrifuged (1000 × g, 5 min), and the serum was kept at –20°C to carry out the investigation for OC. Atherogenic Index of Plasma (AIP = Log10 (TG/HDL-C), triglycerides (TGs), and high-density lipoprotein (HDL) were calculated for the diabetic group to predict cardiovascular risk as follows: AIP < 0.11 indicates low risk; AIP (0.11–0.21), intermediate risk; and AIP > 0.21, the highest risk.[2] OC level in the serum was detected by electrochemiluminescence immunoassay using the Cobas b 311, automated immunoassay analyzer according to the manufacturer's instructions (Roche Diagnostics, GmbH, Germany). The reference range of OC was taken as 11–18 ng/ml as per the kit's manual.

This study was approved by the Medical Ethical Committee of Faculty of Applied Medical Sciences at Taibah University (MLT 201621). All the participants signed the written informed consent.

Statistical analysis

Data processing was performed using GraphPad Prism 7 (GraphPad Software, CA, San Diego, USA). Quantitative data which are normally distributed were expressed as mean ± standard deviation Student's t-test and Chi-square analyses were used to compare the baseline continuous characteristics of the two groups (healthy control and Type 2 DM). Differences between the control group and diabetics were analyzed using one-way analysis of variance (ANOVA). The association between the different parameters was assessed using simple correlations. P < 0.05 indicated statistical significance.

 Results



A comparison of baseline clinical parameters was done between diabetic and nondiabetic groups

The baseline clinical characteristics of the participants are represented in [Table 1]. The data revealed significantly higher levels of glucose, HbA1c, and ALP among diabetics compared with the control group (P < 0.05), whereas the level of OC was significantly lower in the diabetics compared to the control (P < 0.05). The two groups also displayed significant differences in the lipid profile (P < 0.05). The TG concentration increased in the diabetics, whereas the serum HDL-cholesterol (HDL-C) levels decreased significantly in Type 2 DM patients as compared to the nondiabetic healthy control group (P < 0.05).{Table 1}

In addition, Chi-square test detected a statistically significant difference between patients and controls with respect to low OC levels (P < 0.001). The frequency of patients having low OC level (below normal reference levels) was much higher in Type 2 DM patients over controls, with an odds ratio of (17.515) and 95% confidence interval is 2.204–39.205 [Table 2].{Table 2}

Characteristics of the diabetic patients according to osteocalcin levels

The diabetic patients were categorized into three groups based on OC levels: patients with OC lower tertial (OC <11 ng/ml, n = 17), OC middle tertial (OC = 11–18 ng/ml, n = 17), and OC upper tertial (OC >18 ng/ml, n = 16). Analysis of variance using ANOVA revealed statistically significant differences in clinical characteristics of the three studied groups. There was a statistically significant difference in FSG (P < 0.05) and nonsignificant difference in all the other studied parameters (P > 0.05) [Table 3].{Table 3}

Simple correlations between osteocalcin levels and glucose status in the diabetic group

The clinical characteristics of diabetic group and the associations of OC with glucose status are presented in [Table 4]. Serum OC was negatively associated with FSG. A significant negative association was also observed between OC, HbA1c, and ALP.{Table 4}

OC levels in the cardiovascular risk group among patients with Type 2 DM

The data indicated that TG/HDL (atherogenic dyslipidemia) was significantly high in the diabetic patients (P < 0.001, [Table 5]). Our results showed that 36% of diabetics had increased CVD risk, while 26% had intermediate risk, as revealed from AIP values. The results showed that the low serum OC levels were found at significantly higher frequency in the moderate and high risk of CVD groups than the lower risk group. The estimation of cardiovascular risk is related to log10 (TG/HDL-C), so decreased serum OC level was found to be more related to high log10 (TG/HDL-C) (P < 0.05).{Table 5}

 Discussion



In the present study, we aimed to investigate the relationship of OC with respect to glucose status and lipid profile in diabetic Saudi women. Our results revealed that serum OC levels were significantly decreased in diabetic patients compared with controls. In agreement with our results and consistent with animal studies, decreased OC levels have been reported in Type 2 DM patients that is inversely related to the levels of insulin resistance and adiposity in humans.[11],[12],[13] Postmenopausal women with Type 2 DM had lower OC levels compared to nondiabetic controls.[14],[15] In another study, postmenopausal women with Type 2 DM were reported to have reduced levels of serum OC compared with normal blood glucose and impaired fasting glucose groups.[16] In our study, there was a statistically significant difference between diabetic patients with low OC level and patients with normal OC level with respect to fasting plasma glucose levels; patients with low OC had significantly higher fasting plasma glucose levels and higher percentage of HbA1c. Our results are in concordance with studies that showed an inverse relationship between levels of OC and HbA1c in diabetic people.[17],[18],[19] Furthermore, in a cross-sectional study on Type 2 DM patients carried out by Kanazawa et al., it was found that OC correlated inversely with glucose levels in men, while a negative correlation was observed between OC and glucose as well as HbA1c in diabetic postmenopausal women.[20] The negative association of OC with abnormal glucose metabolism could be attributed to reduced bone turnover at higher glucose levels as in diabetes. This partly contributes to the higher risk of hip fractures in adults with Type 2 DM and lower OC.[20],[21] Studies have demonstrated impaired glucose metabolism resulting from ablation of osteoblasts in adult mice.[22],[23] Partial ablation of osteoblast population caused hypoinsulinemia, hyperglycemia, glucose intolerance, and decreased insulin sensitivity, as with OC deficiency; the levels of blood glucose and insulin returned to normalcy with improved glucose intolerance upon administration of OC in the mice.[22],[23],[24]

Diabetic females in the current study had low OC levels as well as increased levels of ALP compared to the controls. ALP is considered as a biochemical marker for bone disease.[25] These results are in agreement with Miyake H et al. who established that the low OC and high bone-specific ALP inversely correlated with increased risk of vertebral fractures in men with Type 2 DM.[26] Conversely, the present results were not compatible with a study that indicated reduced levels of serum OC and bone-specific ALP in diabetic patients as compared to the healthy controls, in men but not in women.[27]

A host of animal studies have analyzed the relationship between OC and lipid profile. In a study, where mice were put on a high-fat diet for 6 weeks, it was found that the body weight of the Esp-/+ mice increased at a lower rate than the wild-type mice.[11],[12],[13],[14],[15],[16],[17] In these mice, there was deletion of Esp gene encoding a receptor-like protein tyrosine phosphatase (OST-PTP) in osteoblasts and sertoli cells. In another model of Ocn-/+ mice, wherein the OC gene was knocked out, it was observed that the mice were obese and had significantly enhanced fat mass and number of adipocytes.[11],[12],[13],[14],[15],[16],[17] These studies are in agreement with our study, indicating that levels of OC inversely correlated with TG and positively with HDL-C that are markers for obesity and fat mass. In our investigation, there was a significant elevation in TG levels and reduced HDL levels in the diabetics as compared to the controls, as well as significant correlations in some lipid values. Another study on a large sample of the healthy population provided useful information on the relationship between OC and lipid metabolism. The results of this study suggested that circulating OC played a vital role in regulating obesity and blood glucose but not insulin resistance.[28],[29] However, further studies are warranted in this respect as inconsistent results have also been reported. The reasons for the varying reports could be due to the use of OC in different forms (carboxylated OC and undercarboxylated OC) and the problem of standardization. The relationship between OC and lipid metabolism remains undefined based on the limited number of existing studies in humans. In the present study, we assessed the dependent impact of OC on the three phenotypes of lipid metabolism, namely TG, LDL-cholesterol, and HDL-C.

Moreover, it is well known that escalation in serum TC is an independent risk factor that predisposes to CVD.[30],[31] OC may be considered as a promising candidate for CVD risk assessment and a potential intervention target. In men with Type 2 DM, serum level of OC has been shown to be negatively associated with the thickness of intima-media of the common carotid artery.[20],[21],[22],[23],[24],[25],[26],[27],[28],[29],[30],[31],[32] Our current findings indicated that moderate and high cardiovascular risks in diabetic female patients corresponded with low levels of OC.

 Conclusion



Female Saudi patients with Type 2 DM have low OC levels with a strong association between this marker and the measures of glycemia (glycated HbA1c and FSG) and lipid profiles. Low OC tertials' group of patients differs significantly from the middle and upper tertials' OC groups regarding glucose levels, as a significant inverse relation between glucose and OC levels was observed. This finding would indicate that prolonged hyperglycemia and uncontrolled diabetes negatively affect the OC level. The AIP suggests that a low OC is directly related to an atherogenic and dyslipidemic profile that would otherwise increase the cardiovascular risk in Type 2 DM female patients. The current study indicates a strong association between diabetes, bone, and cardiovascular markers such as serum OC that was inversely associated, suggesting a link to glucose/fat metabolism. Therefore, it is recommended to monitor diabetes-associated complications such as bone diseases and CVD, especially in Type 2 diabetic female patients via this marker.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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