We investigated the ability of genistein and daidzein, two soybean isoflavones, compared with that of 17 alpha-ethinylestradiol, to prevent bone loss in ovariectomized rats, a model for postmenopausal osteoporosis. Female Wistar rats (n = 65; 12 mo old) were either sham-operated (SH; n = 13) or ovariectomized (OVX; n = 52). On d 0, OVX rats were randomly assigned to groups as follows: 13 received genistein [G; 10 mcg/(g body weight. d)], 13 were treated with daidzein [D; 10 mcg/(g body weight. d)], 13 received 17 alpha-ethinylestradiol [E(2); 30 mcg/kg body weight. d)] and 13 were untreated (OVX). Compounds were mixed with a soy protein-free powdered semipurified diet and given orally for 3 mo. On d 90, the bone mineral density (BMD) in lumbar vertebrae, femur and its metaphyseal and diaphyseal zones (rich in cancellous and cortical bone, respectively) was lower in OVX than in SH (P < 0.01). In D or E(2), the four BMD were not different from SH, whereas in G, only the diaphyseal BMD was not different from SH. Image analysis performed in the distal femur metaphysis revealed that the cancellous bone area was lower in OVX than in SH (P < 0.01). Only the area in D was not different from that in SH. Finally, the bone turnover, which was higher in OVX than in SH (P < 0.005 and P < 0.05 for plasma osteocalcin concentration and urinary deoxypyridinoline excretion, respectively), was not different in G, D or E(2) compared with SH. Therefore, consumption of 17 alpha-ethinylestradiol or daidzein was more efficient than genistein in preventing ovariectomy-induced bone loss in rats.

Several studies suggest that polyphenols might exert a protective effect against osteopenia. The present experiment was conducted to observe the effects of rutin (quercetin-3-O-glucose rhamnose) on bone metabolism in ovariectomized (OVX) rats. Thirty 3-month-old Wistar rats were used. Twenty were OVX while the 10 controls were sham-operated (SH). Among the 20 OVX, for 90 days after surgery 10 were fed the same synthetic diet as the SH or OVX ones, but 0. 25% rutin (OVX ؉ R) was added. At necropsy, the decrease in uterine weight was not different in OVX and OVX ؉ R rats. Ovariectomy also induced a significant decrease in both total and distal metaphyseal femoral mineral density, which was prevented by rutin consumption. Moreover, femoral failure load, which was not different in OVX and SH rats, was even higher in OVX ؉ R rats than in OVX or SH rats. In the same way, on day 90, both urinary deoxypyridinoline (DPD) excretion (a marker for bone resorption) and calciuria were higher in OVX rats than in OVX ؉ R or SH rats. Simultaneously, plasma osteocalcin (OC) concentration (a marker for osteoblastic activity) was higher in OVX ؉ R rats than in SH rats. High-performance liquid chromatography (HPLC) profiles of plasma samples from OVX ؉ R rats revealed that mean plasma concentration of active metabolites (quercetin and isorhamnetin) from rutin was 9.46 ؉ 1 M, whereas it was undetectable in SH and OVX rats. These results indicate that rutin (and/or its metabolites), which appeared devoid of any uterotrophic activity, inhibits ovariectomyinduced trabecular bone loss in rats, both by slowing down resorption and increasing osteoblastic activity.

We assessed the dose-dependent effects of daily soybean isoflavone (IF) consumption in reversing bone loss in adult ovariectomized rats. On d 0, female Wistar rats (7 mo old; n = 55) were either sham-operated (SH; n = 14) or ovariectomized (n = 41). On d 80, intermediate rats (SH: n = 5; ovariectomized: n = 5) were killed to confirm the ovariectomy-induced bone loss. The remaining ovariectomized rats were randomly assigned to one of four groups of nine rats each and fed soybean IF (mixed with a soy protein-free semipurified diet) at 0 (OVX), 20 (IF20), 40 (IF40) or 80 (IF80) mg/(kg body. d) for 84 d. Simultaneously, SH rats were fed the semipurified diet without any additional compound and killed on d 164, as were the other rats. As expected, both bone mineral density in the total femur and in its diaphyseal and metaphyseal subregions and cancellous bone area/measured surface in the distal femur metaphysis were lower in OVX than in SH rats (P: < 0.05). OVX rats had higher plasma osteocalcin concentration and urinary deoxypyridinoline excretion than SH rats (P: < 0.05). On d 164, osteocalcin and deoxypyridinoline concentrations were lower in IF40 or IF80 rats than in OVX rats (P: < 0.05). Nevertheless, neither bone mineral density nor cancellous bone area was greater in IF-fed rats than in OVX rats. Therefore, in adult ovariectomized rats, daily soybean IF consumption decreased bone turnover but did not reverse established osteopenia.

Amylin (AMY) is a 37 amino acid peptide cosecreted with insulin (INS) by pancreatic ␤-cells and absent in type 1 diabetes, a condition frequently associated with osteopenia. AMY binds to calcitonin receptors, lowers plasma calcium concentration, inhibits osteoclast activity, and stimulates osteoblasts. In the present study, we examined the effects of AMY replacement on bone loss in a streptozotocin (STZ)-induced rodent model type 1 diabetes. Of 50 male Wistar rats studied, 40 were made diabetic with intraperitoneal STZ (50 mg/kg; plasma glucose concentrations >11 mM within 5 days). Ten nondiabetic control (CONT) rats received citrate buffer without STZ. Diabetic rats were divided into four groups (n ‫؍‬ 10/group) and injected subcutaneously with rat AMY (45 mg/kg), INS (12 U/kg), both (same doses), or saline (STZ; diabetic controls) once per day. After 40 days of treatment and five 24-h periods of urine collection for deoxypyridinoline (DPD), the animals were killed, blood was sampled, and femurs were removed. The left femur was tested for mechanical resistance (three-point bending). The right femur was tested for total, diaphyseal (cortical bone), and metaphyseal (trabecular bone) bone densities using dual-energy X-ray absorptiometry (DXA). Bone was ashed to determine total bone mineral (calcium) content. None of the treatments had any significant effect on femoral length and diameter. Untreated diabetic rats (STZ; 145 ؎ 7N) had lower bone strength than did nondiabetic CONT (164 ؎ 38; p < 0.05). Total bone mineral density (BMD; g/cm 2 ) was significantly lower in STZ (0. 2523 ؎ 0. 0076) than in CONT (0.2826 ؎ 0.0055), as were metaphyseal and diaphyseal densities. Diabetic rats treated with AMY, INS, or both had bone strengths and bone densities that were indistinguishable from those in nondiabetic CONT. Changes in bone mineral content paralleled those for total BMD (T-BMD). Plasma osteocalcin (OC) concentration, a marker for osteoblastic activity, was markedly lower in untreated diabetic rats (7. 6 ؎ 0. 9 ng/ml); p < 0. 05) than in nondiabetic CONT (29. 8 ؎ 1. 7; p < 0. 05) or than in AMY (20. 1 ؎ 0. 7; p < 0. 05). Urinary DPD excretion, a marker for bone resorption, was similar in untreated and AMY-treated diabetic rats (

Some controversy exists in the literature concerning bone mineral densitry (BMD) in obese, diabetic, leptin-resistant Zucker rats. To investigate this question further, we measured body composition and femoral bone mineral density (BMD) (by dual energy X-ray absorptiometry) in 10 male and 10 female 6 month-old Zucker rats and their homozygous lean controls. Fat mass (percent from body weight) was about 3 times higher in fatty rats than in lean controls. Total, diaphyseal, and distal metaphyseal BMD, total femoral Ca content, and femoral failure load were lower in Zucker rats than in controls. Moderate treadmill running (35% - 40% VO2 max, 20-50 minutes day, 6 days/ week, for 89 days) increased BMD in these animals, possibly by inhibiting bone resorption, as evidenced by no change in plasma osteocalcin concentration but decreased urinary deoxypyridinoline excretion in fatty runners.

Voluntary food intake, milk yield and composition, and blood metabolites were measured during the first 2 mo of lactation in draft broodmares fed diets containing either 95% hay and 5% concentrates (Diet F) or 50% hay and 50% concentrates (Diet C). Voluntary food intake was higher for mares fed Diet C than for those fed Diet F (22.9 vs. 21.4 kg dry matter in wk 4). Both diets, especially Diet C, were eaten in amounts exceeding the energy requirements. Daily milk yield in wk 4 was 26.4 kg and 23.4 kg for mares fed Diets C and F, respectively. Milk fat and protein concentrations were higher (P less than 0.01) for mares fed Diet F than for those fed Diet C and decreased (P less than 0.01) from colostrum (48 +/- 12 h after foaling to wk 8); lactose concentration was higher (P less than 0.05) for mares fed Diet C than for those fed Diet F and increased (P less than 0.01) from colostrum to wk 8. Minerals varied mainly with lactation stage. Milk fat was higher in linolenic acid and lower in linoleic acid for mares fed Diet F than for those fed Diet C. Glucose concentration was higher in plasma of mares fed Diet C; 3-hydroxybutyrate and acetate concentrations were higher in plasma of mares fed Diet F.

The dose-dependent bone-sparing effects of dietary isoflavones (IF) were investigated in adult (7-month-old) Wistar rats. Forty animals were ovariectomised, allocated into four groups of ten rats each, and immediately treated orally with IF at 0 (OVX), 20 (IF20), 40 (IF40) or 80 (IF80) mg/g body weight per d for 91 d; ten sham-operated (SH) controls received the same diet without added IF. Animals were killed on day 91. Both femoral failure load and total femoral, diaphyseal or metaphyseal bone mineral densities (BMD) were lower in OVX animals than in SH animals. Urinary deoxypyridinoline (DPD) excretion, a marker of bone resorption, and plasma osteocalcin (OC) levels, a marker of osteoblast activity, were higher in OVX animals than in SH animals. Total femoral and diaphyseal BMD and femoral failure load were similar in IF-treated rats and SH rats. Although metaphyseal BMD in IF40 or IF80 rats was similar to that in SH rats, its value was lower in IF20 rats than in controls. The day 91 urinary DPD excretion in IF40 and IF80 rats, but not in IF20 rats, was similar to that in SH rats. Day 91 plasma OC concentrations in IF-treated rats were similar to day 45 values, but were decreased in OVX and SH rats. Thus, daily IF consumption prevented ovariectomy-induced bone loss, both by depressing bone resorption and stimulating osteoblast activity. Moreover, as only the highest IF level induced a weak uterotrophic activity, the optimal IF dose which preserves both cancellous and cortical bone, but exhibits no oestrogen-like effects on the uterus, was 40 mg/g body weight per d.

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