| Dietary xylitol in the prevention of experimental osteoporosis. Beneficial effects on bone resorption, structure and biomechanics | ||
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The animals were fed a basal powder diet, Lactamin R3 (Labfor, Stockholm, Sweden) in the studies I and IV, and RM1 (Special Diet Services, Witham, Essex, UK) in the studies II, III and V, according to the diet in use at the Laboratory Animal Center of the University of Oulu.
The Lactamin R3 diet consists of 28% barley meal, 20% wheat meal, 20% wheat germs, 10% wheat middlings, 7% soya meal, 7% fish meal, 3% fodder yeast, 3% minerals, 1% vitamins and trace elements, and 1% fat. The diet contains 1,1% calcium, 0,8% phosphorus, and 1500 IU/kg Vitamin D3.
The RM1 diet consists of 88,5% cereal products (wheat, barley and wheatfeed), 6% vegetable proteins, 2,5% animal proteins (whey powder), 0,5% soybean oil, and 2,5% vitamins, minerals and amino acids. The diet contains 0,71% calcium, 0,5% phosphorus, and 600 IU/kg vitamin D3.
The rats in all studies had free access to tap water ad libitum.
To study the effects of orally administered xylitol, the diet of rats in studies I, III, IV and V was supplemented with xylitol (Xyrofin Co., Kotka, Finland). Xylitol concentrations in different groups were 5, 10 and 20% by weight (w/w). This corresponds to 50 g, 100 g and 200 g xylitol per 1 kg of the diet.
To compare the effects of different polyols, rats in study II were given a diet supplemented with either xylitol, D-glucitol (generally called sorbitol) (Serestar, Kreseld, Germany), D-mannitol (Sigma Chemical Co., St.Louis, MO) or meso-erythritol (generally called erythritol) (Fluka Chemie AG, Buchs, Switzerland). The polyol concentration in the diet was 1 mol/kg, corresponding to 152 g xylitol, 182 g sorbitol or D-mannitol and 122 g erythritol per 1 kg of the diet.
To study the effects of dietary xylitol during experimental osteoporosis (studies III and V), three-month old female rats were bilaterally ovariectomized by the dorsal approach (Waynforth 1980). A single longitudinal skin incision was made on the dorsal midline at the level of the kidneys. The ovaries were exposed, and after ligating removed together with their surrounding fat, oviduct and a small portion of the uterus. Animals of the control group underwent sham operations, during which the ovary was exposed but left intact. The surgery was done under anesthesia, using a 1:1:2 mixture of Hypnorm (Janssen Pharmaceutica, Beerse, Belgium), Dormicum (F. Hoffmann-La Roche AG, Basel, Switzerland), and water, 0.2-0.4 ml/100 g body weight, intraperitoneally. At the end of the experimental period, the success of ovariectomy was confirmed by verifying the absence of any ovarian tissue, and noting the marked atrophy of uterine horns.