Vitamin C prevents hypogonadal bone loss

Abstract

Epidemiologic studies correlate low vitamin C intake with bone loss. The genetic deletion of enzymes involved in de novo vitamin C synthesis in mice, likewise, causes severe osteoporosis. However, very few studies have evaluated a protective role of this dietary supplement on the skeleton. Here, we show that the ingestion of vitamin C prevents the low-turnover bone loss following ovariectomy in mice. We show that this prevention in areal bone mineral density and micro-CT parameters results from the stimulation of bone formation, demonstrable in vivo by histomorphometry, bone marker measurements, and quantitative PCR. Notably, the reductions in the bone formation rate, plasma osteocalcin levels, and ex vivo osteoblast gene expression 8 weeks post-ovariectomy are all returned to levels of sham-operated controls. The study establishes vitamin C as a skeletal anabolic agent.

Figure 1. Oral Vitamin C Prevents Ovariectomy-Induced Bone Loss in Mice.

Bone mineral density (BMD) measurements by Piximus (GE Lunar) at the total body, and the lumbar spine (L4–L6), left femur and tibia, measured 0, 4 and 8 weeks following ovariectomy (OVX) or sham operation (C) in 6 month-old mice. The mice were allowed to ingest vitamin C (VC) (5 mg/day) in drinking water ad libitum. Statistics: comparisons were made for differences between ovariectomized and sham-operated mice (*p<0.05, **p<0.01), and within the sham-operated and ovariectomized groups, between vitamin C treated and controls (∧p<0.05, ∧∧p<0.01); n = 5 mice per group.

Figure 2. Oral Vitamin C Prevents Structural Deterioration in Ovariectomized Mice.

Measurements by micro-CT (Scanco μCT40) of static parameters, including bone mineral density (volumetric) (A), bone volume fraction (BV/TV) (B), trabecular number (TbN) (C), trabecular thickness (TbTh) (D), trabecular spacing (TbS) (E), and bone volume (BV) (F), measured 8 weeks following ovariectomy (OVX) or sham operation (C) in 6 month-old mice. The mice were allowed to ingest vitamin C (VC) (5 mg/day) in drinking water ad libitum. Panel G shows representative μ-CT images from the respective groups. Statistics: comparisons were made for differences between ovariectomized and sham-operated mice (*p<0.05, **p<0.01), and within the sham-operated and ovariectomized groups, between vitamin C treated and controls (∧p<0.05, ∧∧p<0.01); n = 5 mice per group.

Figure 3. Oral Vitamin C Stimulates Bone Formation in Ovariectomized Mice.

Representative reverse phase contrast (showing trabecular structure) (A) and fluorescence micrographs (showing calcein labels) (B) 8 weeks following ovariectomy (OVX) or sham operation (C) in 6 month-old mice. The mice were allowed to ingest vitamin C (VC) (5 mg/day) in drinking water ad libitum. Measurements of dynamic parameters, including mineralizing surface (MS) (C), mineral apposition rate (MAR) (D), bone formation rate (BFR) (E) and tartrate-resistant acid phosphatase- (TRAP-) labeled surfaces (Resorbed S./BPm) (F). Markers of bone turnover measured in plasma, namely osteocalcin (formation) (G) and C-telopeptide (resorption) (H). Statistics: comparisons were made for differences between ovariectomized and sham-operated mice (*p<0.05, **p<0.01), and within the sham-operated and ovariectomized groups, between vitamin C treated and controls (∧p<0.05, ∧∧p<0.01); n = 5 mice per group.