Green Tomato Extract Prevents Bone Loss in Ovariectomized Rats, a Model of Osteoporosis

Abstract

Although drug therapies are available for postmenopausal osteoporosis, these drugs are not free of side effects and long-term adherence to them are low. A safe and effective nutritional approach to counter postmenopausal osteoporosis is an important research goal. We fed ovariectomized (OVX) Sprague-Dawley rats a diet supplemented with 1% or 2% green tomato extract (GTE). After 12 weeks, micro-computed tomography scans revealed that GTE supplementation effectively prevented distal femur bone loss. This prevention was due to improved bone formation and suppressed bone resorption as observed by the regulation of osteoblast and osteoclast activities. GTE supplementation also improved bone formation through Bmp2-Smad 1/5/8-Runx2 signaling, while bone resorption was regulated by the receptor activator of nuclear factor kappa-B (RANKL)/osteoprogeterin (OPG) pathway. These results suggest that GTE supplementation prevents severe postmenopausal bone loss by maintaining the regulation of bone homeostasis in OVX rats. GTE as a diet supplement might be a potential novel alternative for the prevention of postmenopausal osteoporosis.

Keywords: bone homeostasis; green tomatoes; nutritional supplement; postmenopausal osteoporosis.

Figure 1

Tomatidine profiles of green and red tomatoes. (A) Chromatogram of typical tomatidine. (B) Chromatogram of green tomatoes. (C) Chromatogram of red tomatoes. Peak identification: 1, tomatidine.

Figure 2

Body and bone phenotype changes in green tomato extract (GTE) supplemented ovariectomized (OVX) rats. (A) Weekly body weight measurement during experimental period. (B) Total weight gain of OVX rats over 12 weeks. (C) Average food intake of 12 weeks. (D) Femur weight relative to the total body weight. (E) Tibia weight relative to the total body weight. (F) Serum aminotransferase (ALT) content. (G) Serum alanine aminotransferase (AST) content. (H) Serum adiponectin/leptin ratio. Results are expressed as means ± SEM. Con, control. *** p < 0.001, ** p < 0.01, * p < 0.05, significantly different from Con.

Figure 3

Effect of GTE supplementation on bone loss in OVX rats. (A) Representative two- and three-dimensional micro-CT images of trabecular bones in the distal femurs of rats from each group. (B) Measurement of trabecular bone mass density (BMD) in the distal femurs. Measurement of the trabecular morphometric parameters of trabecular thickness (Tb.Th) (C), bone volume/total volume (BV/TV) (D), and bone surface/total volume (BS/TV) (E) in the distal femurs. Results are expressed as means ± SEM. *** p < 0.001, ** p < 0.01, * p < 0.05, significantly different from Con.

Figure 4

Effect of GTE supplementation on markers of osteoblasts and osteoclasts in serum and urine. Measurements of serum total alkaline phosphatase (tALP) (A), bone alkaline phosphatase (bALP) (B), receptor activator of nuclear factor kappa-B (RANKL) (C), and tartrate-resistant acid phosphatase 5b (TRACP5b) (D). Measurements of urine calcium (E) and deoxypyridinoline (DPD) (F). Results are expressed as means ± SEM. *** p < 0.001, ** p < 0.01, * p < 0.05, significantly different from Con.

Figure 5

Effect of GTE supplementation on bone formation-related signaling genes. The relative mRNA expression of BMP2 (A), Smad 1/5/8 (B), Runx2 (C), Osterix (D), alkaline phosphatase (ALP) (E), Collagen 1 (Col-1) (F), osteopontin (OPN) (G), and osteocalcin (OCN) (H) in tibia bones of all groups. Results are expressed as means ± SEM. *** p < 0.001, ** p < 0.01, * p < 0.05, significantly different from Con.

Figure 6

Effect of GTE supplementation on osteoclast activities. The relative mRNA expression of RANKL (A) and OPG (B) measured using quantitative RT-PCR in tibia bones of all groups. (C) Calculation of RANK/OPG ratio. (D) Relative mRNA expression of Nox-4. *** p < 0.001, ** p < 0.01, * p < 0.05, significantly different from Con.

Figure 7

Schematic diagram for the effect GTE supplementation on the prevention of postmenopausal osteoporosis.