Effects of pharmacological doses of niacin on subacute glucocorticoid-induced testicular damage in rats

Abstract

Glucocorticoid excess adversely affects male reproduction. This study evaluates effects of pharmacological doses of niacin on testicular structure and function in dexamethasone-treated rats. Adult rats (48) were randomly assigned to 6 equal groups: (1) Negative control (NC): normal rats; (2) Positive control (PC): dexamethasone at 7 mg/kg/day by intraperitoneal injections for 7 days; groups 3-6 (N50, N100, N200, and N400): dexamethasone and concomitant treatment with niacin at 50, 100, 200, and 400 mg/kg/day by oral gavages. Testicular weight and volume of PC rats were significantly lower than the NC group (p < .05). Testicular volume of rats in the N50 and N200 groups was statistically similar to the NC group. Significant decreases in serum testosterone with a slight LH increase were detected in the PC group. Nacin at 50 mg/kg reversed serum testosterone to NC levels and increased serum LH concentration. Niacin only slightly increased epididymal spermatozoa number while all groups of niacin-treated rats had significantly higher percentages of motile spermatozoa compared with the PC group. Hypospermatogenesis, germ cell degeneration and depletion, epithelial vacuolization, and degenerated Leydig cells were observed in PC rats. Lesions were relatively milder in niacin-treated rats. Johnsen scores were also significantly higher in niacin-treated rats. Niacin reduced apoptosis as shown by TUNEL assay. In conclusion, niacin administration at pharmacological doses dose-dependently ameliorates the destructive effects of dexamethasone on sperm motility, Johnsen score, and testicular cell apoptosis in rats with the latter can be considered a decisive mechanism for its positive effects on testis.

Keywords: glucocorticoid; niacin; rats; testes.

FIGURE 1

Testicular weight and volume (mean and SD) of rats in different groups (n = 8). N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200, and 400 mg/kg, respectively; NC, normal rats; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days. Columns with no common superscript letter are significantly different (p < .05).

FIGURE 2

Serum testosterone and LH levels (mean and SD) of rats in different groups (n = 8). N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200 and 400 mg/kg, respectively; NC, normal rats; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days. Columns with no common superscript letter are significantly different (p < .05).

FIGURE 3

Number of spermatozoa and percentage of motile sperms (mean and SD) of rats in different groups (n = 8). NC, normal rats; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days; N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200, and 400 mg/kg, respectively. Columns with no common superscript letter are significantly different (p < .05).

FIGURE 4

Photomicrograph of testicular tissue in rats of the PC group that received dexamethasone at 7 mg/kg/day for 7 days. Left: vacuolization of epithelial cell, Right: hypospermatogenesis (long arrow) and germ cell degeneration (short arrow) (H & E staining, Magnification: 400×).

FIGURE 5

Johnsen scores (mean and SD) of rats in different groups (n = 8). N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200, and 400 mg/kg, respectively; NC, normal rats; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days. Columns with no common superscript letter are significantly different (p < .05).

FIGURE 6

DAPI staining of DNA and FITC staining for DNA fragmentation of representative tissue sections from different groups (Magnification: 200X and bar = 50 μm). N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200, and 400 mg/kg, respectively; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days.

FIGURE 7

TUNEL fluorescence intensity (mean and SD) of micrographs prepared from testicular tissue of rats in different groups (n = 8). N50, N100, N200, and N400, dexamethasone‐treated rats that concomitantly received niacin at 50, 100, 200, and 400 mg/kg, respectively; NC, normal rats; PC, rats that received dexamethasone at 7 mg/kg/day for 7 days. Columns with no common superscript letter are significantly different (p < .05).