Negligible Effect of Estrogen Deficiency on Development of Skeletal Changes Induced by Type 1 Diabetes in Experimental Rat Models

Unfavorable effects of memantine on the skeletal system in female rats

Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist used in the treatment of Alzheimer's disease (AD). NMDA receptors are expressed on bone cells. The aim of the present study was to investigate the effects of memantine on the rat musculoskeletal system. Taking into account that most of female AD patients are postmenopausal, the study was carried out on intact and ovariectomized (estrogen-deficient) rats. Mature Wistar rats were divided into following groups: non-ovariectomized (NOVX) control rats, NOVX rats treated with memantine, ovariectomized (OVX) control rats, and OVX rats treated with memantine. Memantine (2 mg/kg p.o.) was administered once daily for four weeks, starting one week after ovariectomy. The serum bone turnover marker and cytokine levels, bone density, mass, mineralization, mechanical properties, histomorphometric parameters of compact and cancellous bone, skeletal muscle mass and grip strength were determined. In NOVX rats, memantine slightly decreased the strength of compact bone of the femoral diaphysis (parameters in the yield point) and unfavorably affected histomorphometric parameters of cancellous bone (the femoral epiphysis and metaphysis). In OVX rats, in which estrogen deficiency induced osteoporotic changes, memantine increased the phosphorus content in the femoral bone mineral. No other effects on bone were observed in the memantine-treated OVX rats. In conclusion, the results of the present study indicated slight damaging skeletal effects of memantine in rats with normal estrogen levels.

Effects of Donepezil on the Musculoskeletal System in Female Rats

The extension of human life makes it more and more important to prevent and treat diseases of the elderly, including Alzheimer's disease (AD) and osteoporosis. Little is known about the effects of drugs used in the treatment of AD on the musculoskeletal system. The aim of the present study was to investigate the effects of donepezil, an acetylcholinesterase inhibitor, on the musculoskeletal system in rats with normal and reduced estrogen levels. The study was carried out on four groups of mature female rats: non-ovariectomized (NOVX) control rats, NOVX rats treated with donepezil, ovariectomized (OVX) control rats and OVX rats treated with donepezil. Donepezil (1 mg/kg p.o.) was administered for four weeks, starting one week after the ovariectomy. The serum concentrations of CTX-I, osteocalcin and other biochemical parameters, bone mass, density, mineralization, histomorphometric parameters and mechanical properties, and skeletal muscle mass and strength were examined. Estrogen deficiency increased bone resorption and formation and worsened cancellous bone mechanical properties and histomorphometric parameters. In NOVX rats, donepezil decreased bone volume to tissue volume ratio in the distal femoral metaphysis, increased the serum phosphorus concentration and tended to decrease skeletal muscle strength. No significant bone effects of donepezil were observed in OVX rats. The results of the present study indicate slightly unfavorable effects of donepezil on the musculoskeletal system in rats with normal estrogen levels.

Effect of Administration of Azithromycin and/or Probiotic Bacteria on Bones of Estrogen-Deficient Rats

The gut microbiota plays an important role in maintaining homeostasis, including that of the skeletal system. Antibiotics may affect the skeletal system directly or indirectly by influencing the microbiota. Probiotic bacteria have been reported to favorably affect bones in conditions of estrogen deficiency. The aim of this study was to investigate the effects of azithromycin (AZM) administered alone or with probiotic bacteria (Lactobacillus rhamnosus; LR) on bones in estrogen-deficient rats. The experiments were carried out on mature rats divided into five groups: non-ovariectomized (NOVX) control rats, ovariectomized (OVX) control rats, and OVX rats treated with: LR, AZM, or AZM with LR. The drugs were administered for 4 weeks. Serum biochemical parameters, bone mineralization, histomorphometric parameters, and mechanical properties were examined. Estrogen deficiency increased bone turnover and worsened cancellous bone microarchitecture and mechanical properties. The administration of LR or AZM slightly favorably affected some skeletal parameters of estrogen-deficient rats. The administration of AZM with LR did not lead to the addition of the effects observed for the separate treatments, indicating that the effects could be microbiota-mediated.

Silymarin from Milk Thistle Fruits Counteracts Selected Pathological Changes in the Lenses of Type 1 Diabetic Rats

Diabetes is a metabolic disease affecting many tissues and organs. The main etiological factor for diabetic complications is hyperglycemia and subsequent pathologies, such as oxidative stress. One of the organs susceptible to the development of diabetic complications is the eye with all of its elements, including the lens. The aim of this study was to evaluate the effect of silymarin, an extract obtained from milk thistle fruit husks, on the oxidative stress markers in the lenses of type 1 diabetic rats. The study was performed on male rats in which type 1 diabetes was induced with 60 mg/kg streptozotocin injection. Diabetic animals were treated via an intragastric tube with silymarin at 50 and 100 mg/kg doses for four weeks. Multiple oxidative stress and polyol pathway-related parameters were measured in the lenses, and auxiliary biochemical tests in the serum were conducted. Diabetes induced severe pathological changes both in the lenses and the serum, and silymarin counteracted several of them. Nevertheless, the qualitative analyses encompassing all tested parameters indicate that silymarin slightly improved the overall state of diabetic animals. Upon the obtained results, it can be concluded that silymarin reveals a faint positive effect on the lenses in type 1 diabetic rats.