Characterization of osteoarthritis in patients with diabetes mellitus type 2

Investigation of the clinical and pathogenesis aspects of osteoarthritis in combinations with diabetes mellitus type 2. Were studied 80 patients with osteoarthritis, 52 of them has a comorbidity disease such as diabetes mellitus type 2. Were investigated the clinical and radiological signs of disease severity, the levels of cytokines, NO, leptin, and CRP in serum, and levels of blood glucose, and levels of glycated hemoglobin, and SSE. Were found significant differences in body weight, data of ESR, features functional status of the joints and the quality of life in patients with osteoarthritis in combination with type 2 diabetes compared with those without the metabolic disturbance. Moreover, in patients with osteoarthritis of comorbidity for T2DM was established elevated level of IL-6, IL-18, NO and leptin in serum. Were determined differences in the features of the clinical symptoms of osteoarthritis in patients with type 2 diabetes based on blood glucose level, and data of glycated hemoglobin. Were obtained some correlations between of the levels of cytokines in the blood serum with the parameters of the functional status of the joints, and with the quality of life in patients with osteoarthritis in combination with type 2 diabetes. Osteoarthritis in combinations with diabetes mellitus type 2 characterized by a more pronounced severity of clinical symptoms, and functions impairment. Abbreviations: OA: osteoarthritis; T2DM: diabetes mellitus type 2; IL-1β: interleukin 1 beta; IL-6: interleukin 6; IL-10: interleukin 10; IL-18: interleukin 18; TNF-α: tumor necrosis factor alpha; NO: nitrite oxide; CRP: C-reactive protein; SSE: subsidence of erythrocytes; BWI: body weight index


Introduction
Diabetes mellitus (DM) is affected more than 180 million people worldwide [1]. DM type 2 (T2DM) is combined functional insufficiency of β-cells and resistance to insulin. The excess of hyperglycemia leads to development of a metabolic syndrome which initiates a chronic inflammation in patients with T2DM [2]. Osteoarthritis (OA) is the most common joint disorder in peoples with 60 years or more in worldwide, moreover, on elder people often presents the combination of OA and T2DM [3][4]. Some researcher, allocate a special phenotype of OA "diabetes-induced OA phenotype" [5]. Both of these pathologies are characterized by a chronic current, association with age and obesity [6]. It is shown that existence of T2DM in patients with OA exerts impact on clinical efficiency [3]. In pathogenesis of T2DM and OA the essential part is assigned to cytokines [7][8]. So, dysfunction of β-cells at T2DM is caused by the inflammatory reaction initiated by IL-1β and NFκB. At T2DM are raised the IL-1β, and IL-12 levels, and CCL2, and CCL13 [2]. In patients with OA found increased levels of pro-inflammatory cytokines (IL-6, TNF-α). It is known that pro-inflammatory cytokines promote OA emergence/progression, indirectly through change of levels of an expression of genes of MMP, through stimulation of production of ROS, through changes a metabolism in chondrocytes, and also through activation an osteoblast -the mediated resorption of a bone tissue [8]. The disorders in lipid metabolism and hyperglycemia can directly influence a metabolism in cartilage, bone tissue and serve as triggers of development of OA in patients with T2DM [4].
The aim of the present study was to evaluate clinical and pathogen aspects of OA in patients with T2DM.  /HOOS indicators  also transformed to a scale from 0 to 100, at the same time the shift of  values to the right on a scale indicates smaller expressiveness of pain and symptoms, and also smaller decline in quality of life of patients. Quality of life of patients (level of pain, depression, the general health, "a coping strategy" overcoming of pain) was estimated on a scale of SF-36 (Short form of index quality of life), VAS (visual analog scale), PHQ-9 and CSQ. Anthropometric research included determination of weight, volume of a waist and calculation of the body weight index (BWI). For dosage of the concentration of serum cytokines, a blood sample (5 mL) was taken from cubital vein between 8 am and 10 am. The sera samples were obtained after centrifugation at 500 g and 4 0 C and aliquoted in Eppendorf Cryotubes (Hamburg, Germany) and stored at -80 0 C until use. A human ELISA for IL-1β, IL-6, IL-10, IL-18 (Vector, Novosibirsk) and Leptin ELISA (Diagnostics Biochem, Canada) was used to quantitatively measure serum concentrations according to the manufacturer's instructions. To determine amount of nitrites and nitrates in the serum nitrite oxide (NO) inhibition assay was conducted using Griess reagent kit for nitrite determination (Molecular Probes). The amount of NO was calculated using a sodium nitrite standard curve. Level of C reactive protein (CRP) in serum defined with use of a set of the Vital Development Corporation (Russia). Levels of the speed of subsidence of erythrocytes (SSE) investigated on Vestegren. Levels of glycated hemoglobin (Hgb A1s) estimated by means of a calorimetric method on the Specol device (Carl Zeiss, Germany). Sugar of blood was investigated with use of a glucometer of AccuCheck Advantage (Roche; Germany). The Kolmogorov-Smirnov adjustment test for a normal distribution for all study variables was used. Quantitative characteristics of the patients were described in two groups with the use of median, lower and upper quartiles. Statistical comparisons were made between patients with OA and OA+DM-2 by Mann-Whitney U test where data were not normally distributed. The correlation between data was done by Spirmen (r). Data analysis was done by Statistica 10.0 (Stat Soft, USA). Statistical significance was set at P < 0.05, two tailed.

Results
The study includes 28 patients with OA (23 females and 5 males, aged 44-76) and 52 patients with OA+ T2DM (42 females and 10 males, aged 52-76). Table 1 shows that patients with combination OA and DM-2 were on average statistically heavy (body weight, volume of a waist, and BWI) than patients with OA (P < 0.05). Also, patients with combination OA and T2DM had a statistically significant increased SSE compared to patients with OA (P < 0.05). Other baseline characteristics of OA activity, such as the pain, overall health, morning stiffness, and assessment of disease the doctor on VAS scale was statistically significantly differ between groups (P < 0.05). Moreover, we found statistically significant differ on functional status of joints (KOOS, WOMAC), and quality of life of patients (SF-36, and PHQ-9) between groups (P < 0.05). On age, height, and duration of illness of OA did not differ statistically between groups (P > 0.05).
Thus, patients with combination OA and T2DM are characterized by tendency to obesity and more expressed clinical manifestation of OA (morning stiffness, changes in general health), and also more expressed decline in quality of life.
In table 2 summarized the levels in blood serum biological active agents involved in pathogenesis of OA and T2DM. So, in patients with combination OA and T2DM observed statistically significant higher levels of IL-6, and IL-18, and NO, and leptin compared to patients with OA (P < 0.05).
Only in 7 patients with combination OA and T2DM glucose level in blood didn't exceed 6 mM/L (13,46%). Proceeding of this fact, we analyzed clinical, functional and biochemical parameters in OA+ T2DM group taking into account glucose level in blood lower or higher 6 mM/L (Table 3).
In patients with lower glucose level in blood statistically significant differ on duration of illness T2DM and duration of illness OA, and on the level of Hgb A1c in serum compare to patients with higher level of glucose in blood (P < 0.05). Other baseline characteristics of OA didn't differ between patients with lower or patients with higher glucose levels in blood (P > 0.05).
Other indicator of the severity of the T2DM in patients is the Hgb A1c level in blood [9]. We have carried out the analysis of clinical and biochemical parameters in group of patients with combination OA and T2DM depending on the Hgb A1c level less than 8% and more than 8% in blood (Table 4). Patients with Hgb A1c level less than 8% had statistically significant lower duration of illness of DM-2 and duration of illness of OA, and glucose level in blood compare with patients whom had a higher level of Hgb A1c in blood (P < 0.05). Also, for patients with lower level in blood of Hgb A1c is typically lower levels of IL-10 in serum (P < 0.05). Moreover, we estimated statistically significant differ on functional status of joints (KOOS, WOMAC), and quality of life of patients (SF-36, and PHQ-9) compared to patients with a higher blood level of Hgb A1c (P < 0.05).
The correlation analysis of the patients with combination OA and T2DM has revealed direct high and statistically significant interrelation of duration of illness T2DM and OA (r=0,79; p=0,0000001), what indirectly confirms the available risk of development of OA in patients with T2DM. Moreover, glucose blood levels are associated with OA disease duration (r=0,45; p=0,0007).

Discussion
Osteoarthrosis is a heterogeneous group of the diseases of various etiology having the general biological, morphological and clinical manifestations caused by defeat of all components of a joint as a result of violation the reparative processes in a subchondral bone and cartilaginous tissue [10][11][12].
Violation of a metabolism and structure of a cartilage at OA amplifies cytokines (IL-1β, TNF-α), MMP (a collagenase, srtomelysin), and reparative processes -growth factors (IGF, TGFβ) [8,11]. With an arterial hypertension or T2DM are characteristic of patients with OA statistically significant reduction of thickness of a bone in a subchondral zone of a knee joint, and also reduction of mineral density in comparison with patients with the isolated OA [14]. In patients with T2DM are revealed increases levels of the IL-1β, TNF-α in blood serum [2,15].
The combination of OA and T2DM leads to change of functional activity of chondrocytes. So, at stimulation of chondrocytes, obtained from patients with combination OA and T2DM, by IL-1β increases the level of production of IL-6 and PGE 2 in comparison with chondrocytes from patients with OA without violation of a carbohydrate exchange. At the level of expression by chondrocytes mRNA of IL-6 and COX-2, and at the level of production IL-6, and PGE 2 , and NO can influence the level of glucose in culture media. The production of IL-6 by chondrocytes rapidly decreased under addition in culture media Cytochalasin B (the glucose transport inhibitor) [16]. Authors [17], demonstrated effect of glucose levels in culture media on human chondrocytes functional activity. So, they indicated increased of mRNA MMP1 and MMP 13 levels by chondrocytes from patients with OA, and only increased MMP 1 levels in chondrocytes obtained from healthy man. This finding indicates at the strengthening of catabolic processes in cartilaginous tissue and, thereby, to confirm weighting of inflammatory and degenerate processes in patients with combination of OA and T2DM.
It is known that the hyperglycemia is connected with risk of development of OA. In patients with hyperglycemia increased formation AGE (product of interaction of glucose with free amino-acid remains in proteins), especially in the tissues enriched with collagen that leads to mechanical and biomechanical change of tissues including a cartilage [18].
The course of OA at patients with T2DM differs from that at patients with OA without T2DM. For patients with combination of OA and T2DM are typically obesity, more expressed changes of the functional status and quality of life in comparison with patients with sick OA without violations of a carbohydrate exchange. Moreover, in patients with combination of OA and T2DM observed higher serum levels of IL-6, IL-18, NO and leptin compared to patient with OA alone.
In our study we showed that in patients with combination of OA and T2DM whom has glucose blood level lower than 6 mM/L and Hgb A1c lower than 8% are typically smaller duration of illness and expressiveness of violation of functional activity of joints, qualities of life that indirectly indicates an involvement of violations of a carbohydrate exchange into pathogenesis of OA.
The revealed increase in blood serum in patients with combination of OA and T2DM levels of pro-inflammatory cytokines (IL-6, IL-18) doesn't contradict literary data on increase in their contents at OA, indicates activation of degenerate and inflammatory processes in bodies and tissues [8]. NO is considered as the indicator of inflammatory processes and collects at damage of tissues. Existence of association with the IL-1β, IL-6 and IL-10 levels testifies to an involvement of cytokines into pathogenesis of OA. Moreover, in patients with combination of OA and T2DM the higher levels of leptin didn't contradict the literary data indicating his increasing in patients with T2DM, OA, especially at persons with excess body weight [19][20][21]. We have shown the presence of association of leptin with the functional status and quality of life in patients with combination of OA and T2DM that indirectly confirms a role of leptin in pathogenesis of a disease.

Conclusion
Thus, patients with combination OA and T2DM are characterized by heavier course of inflammatory and degenerate processes in cartilaginous tissue in joints. The hyperglycemia, excess body weight initiated an inflammation, a progression of a degeneration of cartilaginous tissue.