Objective: Osteoprotegerin (OPG) is a newly identified inhibitor of bone resorption. Recent studies indicate that OPG also acts as an important regulatory molecule in the vasculature. Plasma levels of OPG seem to be elevated in subjects with diabetes as well as in non-diabetic subjects with cardiovascular disease. The aim of the present study was to examine the association between plasma OPG levels and microvascular complications and glycemic control in patients with type 2 diabetes. Design and methods: Four groups of 20 subjects in each, individually matched for age and gender, were included in the study: (i) subjects with normal glucose tolerance (NGT); (ii) subjects with impaired glucose tolerance (IGT); (iii) type 2 diabetic patients without retinopathy; and (iv) type 2 diabetic patients with diabetic maculopathy (DMa). Plasma concentration of OPG was measured in duplicate by a sandwich ELISA method. Furthermore, fundus photography, flourescein angiography, and measurements of urinary albumin excretion rate (RIA) were performed. Results: Plasma OPG was significantly higher in diabetic (iii þ iv) than in NGT (i) subjects (3.04^0.15 vs 2.54^0.16 ng/l, P , 0.05). Plasma OPG was significantly higher in the DMa (iv) group than in the NGT (i) group (3.25^0.23 vs 2.54^0.16 ng/l, P ¼ 0.01). Moreover, plasma OPG was significantly higher (3.61^0.36 ng/l) in the group of diabetic subjects with both microalbuminuria and DMa (n ¼ 7) than in the NGT (i) (2.54^0.16 ng/l, P , 0.01), IGT (ii) (2.82^0.21 ng/l, P , 0.05), and no retinopathy (iii) groups (2.83^0.20 ng/l, P , 0.05). Conclusions: We found increased levels of OPG in plasma from diabetic patients with microvascular complications. This finding indicates that OPG may be involved in the development of vascular dysfunction in diabetes.

Enforced swimming of animals has been some experiments, colonic temperatures were utilized by many investigators as a method obtained continuously while the animals of inducing and evaluating physiological and swam, thus weighting the animal by an addipsychological stress. However, the time re-tional 2 g. The mice utilized to obtain these quired to produce a state of exhaustion has cooling curves were not utilized in any other shown considerable variation not only among experiments. Cooling curves were obtained individual animals, but in the mean times from 2 mice of each type while swimming reported by various investigators(4,5,8,10). at water temperatures of 15, 20 and 28°C. Some of the variability reported could have Since some investigators swam animals in been due to variations in water temperature groups, a few experiments were conducted ( l ) , in nutritional state of the animals( lo), comparing the 2 strains of mice under similar in the criteria for exhaustion or in species conditions. differences. Griffiths (6) found that domestic Swimming times were measured to the rats swam for a longer period of time than nearest second by means of a stop watch. 2 strains of wild rats, except when treated Initially, the end point was considered to with a drug (stilazine) or had their vibrissae be the onset of disorientation, the typical removed. Richter (9) has also observed dif-criteria utilized by most investigators. Howferences between wild and domestic rats and ever, this proved to be unsatisfactory and has noted that trimming of whiskers resulted a more precise end point, i.e., the time at in a quick death for all wild rats thus treated which the animal was unable to return to prior to enforced swimming. Since many the surface of the water, was finally employed. swimming experiments are conducted on mice it appeared that a comparison of the responses of wild and domestic mice would be of value, especially if more objective methods of evaluating final exhaustion were employed.Methods. A plastic cylinder, 26.5 cm d i m . with a water depth of 24 cm was utilized for the swimming tests. A wetting agent was added to the water and air was bubbled through the water column. Water temperatures of 15, 20, 28, 37, or 42OC were maintained within * 0.2"C and continuously monitored. This temperature as well as the colonic temperatures of the mice were measured utilizing thermistors and a Yellow Springs bridge. The thermistor probe was placed to a depth of 3.5-4 cm in the colon. The majority of measurements of colonic temperature were obtained at the point of exhaustion or termination of the swim. In