Effects of probiotic supplementation on calcium absorption and bone health status in ovariectomized rats

Osteoporosis is a bone metabolism disorder which is explained by low bone mass and deterioration of bone tissue which is mostly due to the aging or menopause. The possibility of wrist, hip or spine fracture due to osteoporosis is estimated as parallel to the risk of heart disease. Therefore, the aim of the current study is to examine the effect of probiotics (Bifidobacterium. longum, and Lactobacillis. helveticus) as a single species or double strain on calcium absorption and bone health status in ovariectomized rats. For this purpose, 56 female Sprague–Dawley rats of 10 weeks old were used in this study. Bilateral ovariectomy (Ovx) and sham-ovx (S-ovx) were performed on the rats. After 2 weeks of surgery the rats were randomly divided into 6 groups of Ovx and one group of Sovx.The surgical process and diet were as follow: G1: S-ovx, G2: Ovx, G3: Ovx + Ca, G4:Ovx + B. longum, G5: Ovx + L. helveticus, G6: Ovx + mixture of L. helveticus and B.longum, and G7: Ovx + mixture of L. helveticus and B. longum + Ca. The urine, fecal, and serum of the rats were collected and apparent Ca absorption and Ca retention were measured. Serum biomarkers were evaluated. Bone mineral contents (BMC) were analysed from the femur using atomic absorption spectrophotometer (AAS). BMD, trabecular structures, percentage of bone volume/total volume (BV/TV %), and percentage of total porosity were assessed using micro CT-scan. Breaking force of the femur was analysed by three point bending test using universal testing machine. Bone cellular structures were measured as static histomorphometric measurements. The fold changes of the expression of the genes were quantified with Real-time quantitative polymerase chain reaction (RTqPCR). The results of the research showed combination of mixed bacteria and Ca in G7 and L.helveticus in G5 as a single species have increased significantly BMD of the femur compared to Ovx-non treated group (0.96±0.02, and 0.90±0.05 vs 0.74±0.05 gr.cm-3 respectively). B. longum treated group showed a higher Th.Th and a lower total porosity percentage (p<0.05) as compared to Ovx- non treated group. In addition, a higher strength of the femur have found in G7 (mixed bacteria + Ca) (p<0.05) (0.88±0.16 vs 0.54±0.11 N.m2). Single species bacteria have increased the expression of runt related transcription factor (RUNX-2), bone morphometric protein2 (BMP-2), secreted protein acidic and rich in cysteine (SPARC), Collagen type 1 & 2 (Col 1&2), osterix (OSX), as well as calcium sensing receptor (CaSR) genes (p<0.05), and have decreased parathyroid receptor (PTHr) (p<0.05) as compared to Ovx non-treated group. However, mixed bacteria only altered the expression of CaSR, SPARC and PTHr. In addition, liver toxicity was not reported with the selected dosage of bacteria consumption, since treated and non-treated Ovx were not significantly different in histology changes of the liver and liver serum biomarkers. This study found that L. helveticus, and B. longum as a probiotics supplementation, have resistance to acid and bile in gastrointestinal tract. This meant that, selected bacteria after their passage through the gastrointestinal tract were alive. In this regards, single species showed a higher potential effect on changes of BMD of the femur as compared to mixed strains. Thus, B. longum and L. helveticus, specially as a single species have shown a great potential on bone health. Therefore, choosing appropriate probiotics as a single species or mixed strains is important to act on the target organ for intervention or treatment of the specific disease, such as bone in order to prevent osteoporosis.

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