Abstract
This study investigated the effect of insulin and telmisartan on the expression of
adiponectin and its receptors, oxidative stress, and inflammatory cytokines in the
testis of streptozotocin-induced diabetic rats. Male Wistar rats were randomly divided
into control (C, n=8), diabetic (D, n=8), diabetic treated with insulin (DI, n=8),
and diabetic treated with telmisartan (DT, n=8). Diabetic was induced by the peritoneal
injection of a single dose of streptozotocin. Eight weeks later, bilateral testes
were immediately removed after the rat was sacrificed. Epididymis was harvested to
prepare sperm suspension. Plasma adiponectin, testicular interleukin-6 (IL-6), and
tumor necrosis factor α (TNF-α) were detected by enzyme linked immunosorbent assay
(ELISA). The mRNA or protein expression of testicular adiponectin receptor 1 (adipoR1)
and 2 (adipoR2), p22phox, transcription factor NF-E2 associated factor 2 (Nrf2), NAD(P)H
quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), AMPK-α, Akt, and eNOS was
assayed by real-time fluorescence quantitative PCR or Western blot. There were significant
pathological changes in the testes of diabetic rats. The levels of testicular weight,
sperm number and motility, serum and testicular testosterone, plasma insulin and adiponectin,
testicular adiponectin and its receptor 1, Nrf2, NQO1, HO-1, and phosphorylated-AMPK
were significantly decreased in diabetic rats. The levels of blood glucose and lipids,
and the levels of testicular p22phox, IL-6, TNF-α, phosphorylated-AKT, e-NOS, and
nitric oxide (NO) were significantly increased in diabetic rats. These changes could
be significantly reversed by insulin treatment. Similar results were observed with
telmisartan treatment except for NQO1 mRNA and phosphorylated-AMPK. There was no significant
difference in the expression of testicular adiponectin receptor 2 among 4 groups.
The decreased adiponectin and its receptors, and the increased oxidative stress and
inflammatory cytokines may play an important role in the testopathy of type 1 diabetic
rats. Insulin and telmisartan may produce the protective effect on the testes of diabetic
rats by upregulating the expression of adiponectin and its receptors and downregulating
the level of oxidative stress and inflammatory cytokines.
Key words
adiponectin - adiponectin receptors - testes - insulin - telmisartan - oxidative stress
- inflammatory cytokines