Gastrectomy osteopenia in the rat: the role of vitamin B12 deficiency and the type of reconstruction of the digestive tract

Vitamin K2 improves femoral bone strength without altering bone mineral density in gastrectomized rats

Gastrectomy (GX) induces osteopenia in rats. The present study examined the skeletal effects of vitamin K2 in GX rats. Thirty male Sprague-Dawley rats (12 wk old) were randomized by the stratified weight method into the following three groups of 10 animals each: sham operation (control) group; GX group; and GX+oral vitamin K2 (menatetrenone, 30 mg/kg, 5 d/wk) group. Treatment was initiated at 1 wk after surgery. After 6 wk of treatment, the bone mineral content (BMC), bone mineral density (BMD), and mechanical strength of the femoral diaphysis and distal metaphysis were determined by peripheral quantitative computed tomography and mechanical strength tests, respectively. GX induced decreases in the BMC, BMD, and ultimate force of the femoral diaphysis and distal metaphysis. Vitamin K2 did not significantly influence the BMC or BMD of the femoral diaphysis or distal metaphysis in GX rats, but attenuated the decrease in the ultimate force and increased the stiffness of the femoral diaphysis. The present study showed that administration of vitamin K2 to GX rats improved the bone strength of the femoral diaphysis without altering the BMC or BMD, suggesting effects of vitamin K2 on the cortical bone quality.

Is gastrectomy-induced high turnover of bone with hyperosteoidosis and increase of mineralization a typical osteomalacia?

Gastrectomy (GX) is thought to result in osteomalacia due to deficiencies in Vitamin D and Ca. Using a GX rat model, we showed that GX induced high turnover of bone with hyperosteoidosis, prominent increase of mineralization and increased mRNA expression of both osteoclast-derived tartrate-resistant acid phosphatase 5b and osteocalcin. The increased 1, 25(OH)2D3 level and unchanged PTH and calcitonin levels suggested that conventional bone and Ca metabolic pathways were not involved or changed in compensation. Thus, GX-induced bone pathology was different from a typical osteomalacia. Gene expression profiles through microarray analysis and data mining using Ingenuity Pathway Analysis indicated that 612 genes were up-regulated and 1,097 genes were down-regulated in the GX bone. These genes were related functionally to connective tissue development, skeletal and muscular system development and function, Ca signaling and the role of osteoblasts, osteoclasts and chondrocytes. Network analysis indicated 9 genes (Aldehyde dehydrogenase 1 family, member A1; Aquaporin 9; Interleukin 1 receptor accessory protein; Very low density lipoprotein receptor; Periostin, osteoblast specific factor; Aggrecan; Gremlin 1; Angiopoietin-like 4; Wingless-type MMTV integration site family, member 10B) were hubs connected with tissue development and immunological diseases. These results suggest that chronic systemic inflammation might underlie the GX-induced pathological changes in bone.

Influence of gastrectomy on cortical and cancellous bones in rats

The aim of the present study was to examine the influence of gastrectomy (GX) on cortical and cancellous bones in rats. Twenty male Sprague-Dawley rats were randomized into the two groups of 10 animals each: a sham operation (control) group and a GX group. Seven weeks after surgery, the bone mineral content and density (BMC and BMD, resp.) and the mechanical strength of the femur were determined, and bone histomorphometric analyses were performed on the tibia. GX induced decreases in the BMC, BMD, ultimate force, work to failure, and stiffness of the femoral distal metaphysis and the BMC, BMD, and ultimate force of the femoral diaphysis. GX induced a decrease in cancellous bone mass, characterized by an increased osteoid thickness, osteoid surface, osteoid volume, and bone formation. GX also induced a decrease in cortical bone mass, characterized by increased endocortical bone resorption. The GX induced reductions in the bone mass and strength parameters were greater in cancellous bone than in cortical bone. The present study showed that the response of bone formation, resorption, and osteoid parameters to GX and the degree of GX-induced osteopenia and the deterioration of bone strength appeared to differ between cortical and cancellous bones in rats.

Hyperphosphaturia after kidney transplantation in syngeneic rats: effects on nephrocalcinosis and bone metabolism?

BACKGROUND

Studies on kidney transplantation have thus far mainly dealt with surgical techniques, immunology, and transplant tolerance. Disturbed mineral metabolism after renal denervation has not received much attention. Basic physiological research in short-term experiments has shown that experimental renal denervation in rats leads to parathormone (PTH)-independent hyperphosphaturia (HPU). HPU and other metabolic complications also have been described after clinical kidney transplantation. Furthermore, there is an unexpected increase in the risk of bone fracture. However, these studies have examined an organism pre-damaged with regard to the parathyroid and immunosuppression. Experimental investigations in syngeneic rats were performed to see whether HPU also occurs after transplantation and thus after denervation and which target organs are involved.

METHODS

Thirty-six male Lewis rats subjected to laparotomy (n = 12), unilateral nephrectomy (n = 12), or unilateral transplantation and bilateral nephrectomy (n = 12) were observed for 18 weeks.

RESULTS

Animals that underwent transplantation had a significant loss of phosphate in the urine not associated with decreased calcium, phosphate, or magnesium in bone. Stability test showed no deterioration, despite a slight increase in the bone parameters of alkaline phosphatase, cyclic AMP, and hydroxyproline with unchanged calciotropic hormones. Nephrocalcinosis was not observed. Parallel to HPU, there was a compensatory reduction in fecal phosphate excretion.

CONCLUSIONS

The loss of phosphate after clinical kidney transplantation in the predamaged parathyroid hormone control system as well as immunosuppression and a surprising increase in the incidence of bone fractures may be explained by the denervation-related loss of phosphate. The lack of intestinal counter-regulation could be an important pathomechanism.