Dietary 2-oxoglutarate mitigates gastrectomy-evoked structural changes in cartilage of female rats

Abstract

Gastrectomy (Gx) leads to osteopenia/osteoporosis in humans and animals. However, little is known about the influence of Gx on the cartilage in this regard. Recent studies have demonstrated a protective effect of 2-oxoglutaric acid (2-Ox) on bone and cartilage. Hence, the purpose of this study was to investigate whether 2-Ox can mitigate eventual Gx-induced cartilage impairment. Twenty female Sprague-Dawley rats were subjected to Gx and randomly divided into two groups: Gx + 2-Ox and Gx. Another 20 rats were sham-operated (ShO) and randomly divided into two groups: ShO + 2-Ox and ShO. The daily dose of 2-Ox administered to the rats in the drinking water was 0.43 g per 100 g rat. After eight weeks, rats were euthanized and femora and tibiae were collected. Histology and histomorphometry analyses of the articular cartilage and the growth plate were done. Gx resulted in a 32% (±44.5 femur, ±35.8 tibia) decrease in overall thickness of articular cartilage in both bones (femur: ShO 279.1 ± 48.5 vs. Gx 190.2 ± 38.4 µm, tibia: ShO 222.9 ± 50.3 µm vs. Gx 151.3 ± 52.6 µm) (in some zones up to 58 ± 28.0%), and in the growth plate up to 20% (±22.4) (femur: ShO 243.0 ± 34.0 vs. Gx 207.0 ± 33.7 µm, tibia: ShO 220.0 ± 24.6 µm vs. Gx 171.1 ± 16.1 µm). Gx altered the spatial distribution of thick and thin collagen fibers, and chondrocyte shape and size. 2-Ox administration prevented the reduction in both cartilages thickness (Gx + 2-Ox: articular cartilage 265.2 ± 53.8 µm, 235.6 ± 42.7 µm, growth plate 236.7 ± 39.2 µm, 191.3 ± 16.5 µm in femur and tibia, respectively), and abolished the spatial changes in collagen distribution and structure induced by Gx. Gx affects cartilage structure and thickness, however, 2-Ox administration mitigates these effects and showed protective and stimulatory properties. Our observations suggest that dietary 2-Ox can be used to offset some of the changes in hyaline cartilage, in particular articular cartilage, following bariatric surgeries.

Keywords: 2-oxoglutaric acid; Histology; development; gastrectomy; histomorphometry; skeleton.

Figure 1

The location selection and the size of areas of interest analyzed in individual bones. a: femoral distal epiphysis, b: tibial proximal epiphysis, c: femoral sagittal section, and d: tibial sagittal section. The site of sections are marked by black parallel lines and the distance between lines is approximately 360 µm. Square boxes indicate regions of interest in cartilage analysis. Scale bars: 1 mm

Figure 2

The effect of gastrectomy (Gx) and dietary 2-oxoglutaric acid (2-Ox) administration on the thickness of femoral (a) and tibial (b) articular cartilage of female rats. Appropriate zones of articular cartilage are indicated by different shades of gray scale and marked by segmented lines on cartilage section on the sample photograph (c). Different letters above the columns of the same color indicate differences between the groups with P < 0.05. ShO: sham operated rats. The 2-oxoglutaric acid sodium salt (0.43 g/100 g rat per day) was administered in the drinking water. Bars represent the mean, whiskers represent standard deviation

Figure 3

The effect of gastrectomy (Gx) and dietary 2-oxoglutaric acid (2-Ox) administration on the thickness of femoral (a) and tibial (b) growth plate cartilage of female rats. Appropriate zones of the growth plate are indicated by different shades of gray scale and marked by segmented lines on cartilage section on the sample photograph (c). Different letters above the columns of the same color indicate differences between the groups with P < 0.05. ShO: sham operated rats. The 2-oxoglutaric acid sodium salt (0.43 g/100 g rat per day) was administered in the drinking water. Bars represent the mean, whiskers represent standard deviation

Figure 4

The effect of gastrectomy (Gx) and dietary 2-oxoglutaric acid (2-Ox) administration on the distribution of thick and thin collagen fibers of femoral and tibial articular cartilage of female rats. Representative samples of the microscopic images collected in polarized light. Magnification for each image in the row indicated by white scale bar. The larger collagen fibers are orange to red, and the thinner ones, including reticular fibers, are green. The surface of the cartilage is directed toward the top of every sample picture. White arrowheads indicate green, thin collagen fibers. ShO: sham operated rats. The 2-oxoglutaric acid sodium salt (0.43 g/100 g rat per day) was administered in the drinking water. (A color version of this figure is available in the online journal.)