ABSTRACT
Several epidemiological studies have shown a lower prevalence of osteoporotic hip fractures in osteoarthritis patients. Other studies have demonstrated elevated bone mineral density in osteoarthritis patients [OA]. The prevailing view is that there may be an inverse relationship between osteoarthritis and osteoporosis. High leptin levels are associated with obesity, which is a risk factor for osteoarthritis. Interestingly, in osteoarthritis patients leptin is present in synovial fluid and is expressed by articular chondrocytes and normal human chondrocytes express the functional Ob-Rb leptin receptor isoform. To determine the relationship of leptin to osteoarthritis as well as osteoporosis and to assess the hypothesis that osteoarthritis is protective from the occurrence of osteoporosis. This study included sixty subjects: thirty osteoarthritis patients and thirty age and sex matched apparently healthy controls. All patients were selected from the Outpatient Clinics of the Rheumatology and Rehabilitation and Intenal Medicine Departments of Ain Shams University Hospitals. The patients were classified according to the body mass index [BMI] into two groups: Group I [BMI < 25] and Group II [BMI >25]. Group I were 13 patients with mean age +/- standard deviation [SD] 49.2 +/- 7.4 and Group II were 17 patients with mean age +/- standard deviation [SD] 49.7 +/- 8.1. Another classification was done according to the menopausal state of the patients. The patients were also classified into two groups: Premenopausal OA patients [Group A] and postmenopausal OA patients [Group B]. Group A were 16 patients with mean age +/- standard deviation [SD] 42.87 +/- 1.14, Group B were 14 patients with mean age +/- standard deviation [SD] 57.07 +/- 4.06. Patients were subjected to: 1. Detailed medical history taking. 2. Thorough clinical examination: with particular attention to Body mass index [BMI] and Local examination of the knees.3. Radiological assessment: with Plain X-rays for both knees of patients and controls. Analysis was done according to the Kellgren and Lawrence, [1957] scoring system as a radiographic grading of OA and assessment of bone mineral density [BMD, g/cm[2]] of the left femoral neck and lumbar spine [L1-L4] were measured using dual energy X-ray absorptiometry [DEXA] 4. Laboratory investigations: Assay of serum leptin, bone alkaline phosphatase [B-ALP] and serum osteocalcin [OC] was done. 6. Statistical Analysis was done for all the results. Comparative study between all OA patients and controls showed a highly significant difference as regards serum leptin, x-ray score and DEXA of the spine and hip [p<0.001]. It also showed a significant difference as regards B-ALP [p<0.05], it showed anon-significant difference as regards age, osteocalcin and BMI [p>0.05]. Comparative study between OA patients with BMI < 25 [Group I] and controls showed highly a significant difference as regard serum leptin, x- ray score and DEXA of the spine and hip [p<0.001]. It also showed a significant difference as regards B-ALP and BMI [p<0.05]. It showed a non-significant difference as regards age and osteocalcin [p>0.05]. Comparative study between OA patients with BMI > 25 [Group II] and controls showed a highly significant difference as regards x-ray score, serum leptin, BMI and BMD of the hip [p<0.001]. It also showed a significant difference as regards the BMD of the spine and it showed avnon-significant difference as regards other parameters. Comparative study between OA patients with BMI < 25 [Group I] and OA patients with BMI > 25 [Group II] showed a highly significant difference as regards x-ray score, BMI, serum leptin and BMD of the spine and hip [p<0.001]. It also showed a significant difference as regards pain score [p<0.05] and a non- significant difference as regards other parameters. All premenopausal osteoarthritis patients showed BMD within normal. As regards postmenopausal patients, 6 patients [42.8%] showed osteopenia, two patients [14.4%] showed osteoporosis and 6 patients [42.8%] showed non-significant decrease in BMD. Comparative study between pre- and post-menopausal groups showed highly significant difference as regards age, disease duration, joint pain score, B-ALP, OC and BMD of the spine and hip [p<0.001]. It also showed a significant difference as regards x-ray score [p<0.05] and a non-significant difference as regards serum leptin and BMI. In all the patients, serum leptin showed a highly significant correlation with BMI [p<0.001]. It also showed a significant correlation with joint pain score [p<0.05] and a non-significant correlation with disease duration, x-ray score and, B-ALP, OC and BMD of the spine and hip. Serum leptin level is higher in osteoarthritis patients than controls even when the BMI was insignificant indicating a possible role of leptin in the pathogenesis of this disease irrelevant to obesity. Meanwhile, it is neither correlated to the BMD nor to the biomarkers of bone formation indicating that it has no role in oteoporosis. In our study, osteoarthritis is not protective against osteoporosis since; osteopenia and osteoporosis were present in osteoarthritis patients