Ayodele Morakinyo

Antifertility effect of calcium channel blockers on male rats: association with oxidative stress

PURPOSE Calcium ions are vital in many biologic processes including a variety of enzymatic reactions, activation of excitable cells, coupling of electrical activation to cellular secretion, haemostasis, bone metabolism and sperm functions. Calcium channel blockers (CCB) appear to have a reversible anti-fertility effect on male rats which does not occur through inhibition of the pituitary-gonadal axis. While the effects of CCB on male reproductive function have been investigated, less information is available regarding other reproductive indices and the underlying mechanism in the pathogenesis of male reproductive dysfunction. Therefore, the involvement of oxidative mechanisms in the adverse manifestation induced by CCB on male reproductive functions is investigated in this study. METHODS For this purpose, lipid peroxidation; enzymatic antioxidants such as superoxide dismutase, catalase and glutathione reduced; epididymal sperm count, motility; histopathology of the testes, epididymis, seminal vesicle, prostate glands; and reproductive performance were determined. RESULTS CCB administration in rats causes significant oxidative stress in the male reproductive milieu in term of increase in malondialdehyde (MDA) level and a concomitant decrease in catalase, superoxide dismutase and reduced glutathione enzyme activities in the testes. In addition, CCB treatment significantly decreased the sperm count, sperm motility, fertility index, implantation count, and litter size in this study. CONCLUSION There is substantial evidence that CCB induces significant oxidative stress in the testes, which appears to be responsible for the adverse effects of decreased sperm count and motility ultimately leading to reduced fertility in rats.

Calcium antagonists modulate oxidative stress and acrosomal reaction in rat spermatozoa.

Introduction Calcium ions are vital in many biological processes and qualify as an almost ubiquitous intracellular second messenger. This indicates the multiplicity of the effects associated with drug actions aimed at interfering with calcium ions. To examine the cellular process involved in the induction of infertility in males by calcium antagonist (CA) even in the presence of normal semen parameters, we studied the effects of different CA namely; nifedipine, verapamil and diltiazem on oxidative balance and acrosome reaction in the sperm. Material and methods For this purpose, lipid peroxidation, antioxidants such as superoxide dismutase, catalase and reduced glutathione, and acrosomal reaction were determined in sperm samples of rats. Results Calcium antagonist causes significant oxidative stress in the epididymal sperm with increased malondialdehyde level and a concomitant decrease in antioxidant activities of catalase and superoxide dismutase. The percentage value of acrosomal-reacted sperm in the nifedipine, verapamil and diltiazem-treated rats were 41 ±2.45, 39 ±2.92 and 42 ±1.22 respectively, compared with the control group value of 86 ±2.92. Conclusions It appears CA oxidatively modify the sperm resulting in functional inhibition of acrosomal reaction. Suppression of the sperm acrosomal reaction is known to have serious adverse implications for fertilization.

Reproductive parameters and oxidative stress status of male rats fed with low and high salt diet

BACKGROUND: Deficiency of minerals and micronutrients has been reported to impair the process of spermatogenesis. Historically, salt has been used by women on their husbands to increase their libido, however, the role of salt diet on sperm parameters are yet to be ascertained. AIM: The present study was designed to determine the effect of low and high salt diet on sperm parameters, oxidative status and reproductive hormone levels of male rats. MATERIALS AND METHODS: A total of 18 rats were divided into three groups: Group I: (control) received 0.3% salt diet, Group II: low salt (received 0.14% salt diet) and Group III: high salt (received 8% salt diet). All animals were treated for 6 weeks; after which epididymal sperm parameters; oxidative stress markers (malondialdehyde, glutathione, catalase and superoxide dismutase) in the testes and epididymal tissues, as well as follicle stimulating hormone (FSH), luteinizing hormone (LH) and testosterone levels were determined. RESULTS: The results showed decreased sperm count in the low salt diet rats while increased sperm count was observed in the high salt diet treated rats. Both low salt and high salt diet fed rats exhibited increased abnormal sperm cells and increased epididymal oxidative stress when compared with their respective control. FSH and testosterone levels were increased in the high salt fed rats while LH level was decreased when compared with the control values. CONCLUSION: This study suggests that both low and high salt diet play a negative role in the fertility of male rats.

Testosterone promotes glucose intolerance, lipid disorder and oxidative stress in type 1 diabetic rats

Abstract Background: A bidirectional relationship has been established between testosterone deficiency (TD) and type 2 diabetes mellitus (T2DM). Low testosterone level has been reported to be a predisposing factor to T2DM, whereas recent clinical studies have shown a high prevalence of low testosterone in diabetic individuals. However, it is not known if any relationship exists between type 1 diabetes mellitus (T1DM) and testosterone level. This study was designed to investigate the effects of TD on T1DM. Twenty-four Sprague-Dawley rats were randomly divided into four groups designated as control, diabetic, orchiectomized and orchiectomized-diabetic. Methods: Diabetes was induced with an intravenous injection of alloxan, and orchiectomy was done under sterile conditions. Fasting blood glucose (FBG), insulin level, lipid and oxidative parameters were determined in all experimental rats. Results: The area under the curve during oral glucose tolerance test showed that the orchiectomized-diabetic group expressed an enhanced ability to metabolize glucose than the diabetic group. The malondialdehyde level in the diabetic group was significantly higher compared with that in the control and orchiectomized groups. Moreover, there was a significant decrease in glutathione (GSH) activity and an increase in superoxide dismutase activity in the diabetic group compared with control. Meanwhile, the activities of GSH and catalase were significantly reduced in the orchiectomized as well as the orchiectomized-diabetic group when compared with both control and diabetic groups. Conclusions: These data indicate that TD attenuates glucose intolerance under diabetic conditions and is equally associated with a considerable reduction in oxidative stress, which implies that testosterone may be a pro-oxidant.

Niacin improves adiponectin secretion, glucose tolerance and insulin sensitivity in diet-induced obese rats

Abstract The present study examined the effect of dietary niacin supplementation on fat mass, glucose control, insulin sensitivity, lipid profile, and adiponectin level in diet-induced obese rats. Male Sprague-Dawley rats (n = 21) were initially divided into 2 groups of seven and fourteen rats; the group of 14 rats was fed with a high-fat diet (HFD) and the other group of 7 rats consumed the control diet. Eight weeks after the diet regimen started, half of the rats from the HFD group were shifted to the niacin-supplemented diet (HFND; 1 mg niacin/kg diet) while the remaining rats continued on the HFD for another 6 weeks. Results obtained showed that HFD-fed obese rats exhibited significant increase in body weight gain, reduced glucose tolerance, insulin sensitivity and increased adiposity, as well as altered lipid profile after 8 weeks of feeding compared with the controls. However, niacin-supplemented rats showed reduced weight gain and body weight compared with HFD-induced obese rats even in the absence of a significant difference in the food intake among the groups in the experiment. In addition, the rats showed an improved time-course glucose control and insulin sensitivity as demonstrated by a significantly lower area under curve (AUC) values for the glucose curves. The plasma levels of cholesterol, triglycerides and low density lipoprotein (LDL) returned towards control values in rats supplemented with niacin compared with obese rats. The findings suggest that niacin exerts beneficial effect on adiposity, glucose tolerance and insulin sensitivity, and plasma lipids, and that it specifically modulates the level of serum adiponectin under obese condition.

Glucometabolic effects of single and repeated exposure to forced-swimming stressor in Sprague-Dawley rats

Abstract Objectives. We aimed to evaluate the effects of a single (acute) and repeated (chronic) exposure to forced-swimming stressor on glucose tolerance, insulin sensitivity, lipid profile and glycogen content in male rats. Methods. Thirty adult male Sprague-Dawley rats (12 weeks old) were divided randomly into five groups: control group, single exposure (SE) to forced-swim stressor, repeated exposure to forced-swim stressor for 7 days (RE7), 14 days (RE14) and 28 days (RE28). Glucose tolerance test and Homeostatic Model Assessment-Insulin Resistance (HOMA-IR) were undertaken on fasting rats to obtain glucose and insulin profiles. ELISA was performed to assess plasma insulin and corticosterone levels. Total cholesterol, triglyceride, high- and low-density lipoproteins, hepatic and skeletal glycogen content were also determined. Results. Repeated exposure to stressor induced glucose intolerance and insulin resistance in the experimental rats. Results showed that all RE groups exhibited a significantly higher area under the curve compared with others (p=0.0001); similarly, HOMA-IR increased (p=0.0001) in all RE groups compared with control. Prolonged exposure to stressor significantly increased the plasma insulin and corticosterone levels but decreased the glycogen content in the liver and skeletal muscle when compared with the control group. Additionally, chronic stressor significantly increased the total cholesterol and triglyceride levels, however, acute stressor produced significantly elevated high-density lipoproteins level. Conclusions. In conclusion, repeated exposure to forced-swimming stressor induced glucose intolerance and insulin resistance in rats by disrupting the insulin sensitivity as well as heightening the glycogenolysis in the liver and skeletal muscle. Acute stressor was unable to cause glucose intolerance and insulin resistance but it appears that may have a positive effect on the lipid metabolism.

Role of amygdala kisspeptin in pubertal timing in female rats

To investigate the mechanism by which maternal obesity disrupts reproductive function in offspring, we examined Kiss1 expression in the hypothalamic arcuate (ARC) and anteroventral periventricular (AVPV) nuclei, and posterodorsal medial amygdala (MePD) of pre-pubertal and young adult offspring. Sprague-Dawley rats were fed either a standard or energy-dense diet for six weeks prior to mating and throughout pregnancy and lactation. Male and female offspring were weaned onto normal diet on postnatal day (pnd) 21. Brains were collected on pnd 30 or 100 for qRT-PCR to determine Kiss1 mRNA levels. Maternal obesity increased Kiss1 mRNA expression in the MePD of pre-pubertal male and female offspring, whereas Kiss1 expression was not affected in the ARC or AVPV at this age. Maternal obesity reduced Kiss1 expression in all three brain regions of 3 month old female offspring, but only in MePD of males. The role of MePD kisspeptin on puberty, estrous cyclicity and preovulatory LH surges was assessed directly in a separate group of post-weanling and young adult female rats exposed to a normal diet throughout their life course. Bilateral intra-MePD cannulae connected to osmotic mini-pumps for delivery of kisspeptin receptor antagonist (Peptide 234 for 14 days) were chronically implanted on pnd 21 or 100. Antagonism of MePD kisspeptin delayed puberty onset, disrupted estrous cyclicity and reduced the incidence of LH surges. These data show that the MePD plays a key role in pubertal timing and ovulation and that maternal obesity may act via amygdala kisspeptin signaling to influence reproductive function in the offspring.

Dynamics of inflammatory reaction and oxidative stress across maternal serum, placenta and amniotic fluid in laboratory rats and the role played by genistein aglycone

Abstract Background Genistein was reported to adversely influence fetal development although this is yet to be fully understood as a mechanism. Methods In this study, pregnant rats were divided into control (Cont.) and genistein force-fed (2-mg/kg and 4-mg/kg) groups. Each group was divided further into five subgroups: GD-0, GD-6, GD-13, GD-18, and GD-20 based on the terminal gestational day (GD). On the respective terminal GD, the rats were sacrificed and blood samples and amniotic fluid were carefully collected and separated and placenta homogenates were prepared. These samples were evaluated for oxidative stress and inflammatory reaction. The weights of embryonic implant and placenta tissue were also recorded. Heat shock protein (Hsp) (60 and 90), corticosterone, and oxidative stress biomarkers were determined in all the samples. Results Fetal and placental weights in all genistein-exposed groups were significantly decreased. A fluctuation in the level of the Hsp was recorded with a significant decrease recorded in Hsp90 level in the placenta and amniotic fluid towards GD-20 along with a concomitant increase in the corticosterone level in the amniotic fluid in all genistein groups compared to control. Maternal serum at GD-18 and GD -20 recorded a significant increase in antioxidant level (SOD, GSH, CAT) in all genistein-exposed groups. However, these antioxidants were significantly reduced in the placenta and the amniotic fluid compared to control. Conclusions Genistein enhances the placenta function in attenuating the risk of oxidative stress in the amniotic fluid and deferentially suppressed inflammatory activities in the placenta during early gestation and towards late gestation period.

High-Dose Perinatal Folic-Acid Supplementation Alters Insulin Sensitivity in Sprague-Dawley Rats and Diminishes the Expression of Adiponectin

ABSTRACT The possible intake of folate in excess of the recommended upper levels is a matter of critical importance. This study was conducted to investigate the effects of prenatal and postnatal high folic acid supplementation (FAS) on glucose tolerance, insulin sensitivity, lipid metabolism, and expression of adiponectin in rats. The study included 20 female rats divided into two groups: control group and FAS group (receiving high folic acid supplemented diet). Both groups of female rats were mated and pregnancy confirmed. At parturition, the diet of 5 dams that were fed with control diet during gestation and their litters was changed to FAS diet and continued throughout lactation. Similarly, half of the dams that were previously fed with FAS diet during gestation and their litters were also changed to control diet. The remaining 5 dams in each group continued on their respective diets throughout lactation with their litters. Other dams remained on their respective diets throughout lactation. Food and water intake, body weight, lipid concentrations, insulin, and the expression of adiponectin were determined. Glucose tolerance and insulin sensitivity were also measured to evaluate glucose homeostasis. FAS significantly increased the postweaning food, water intake, triglyceride, and insulin levels but diminished insulin sensitivity in adult offspring. The expression of adiponectin in insulin-sensitive tissues was also significantly decreased and these were consistent with insulin resistance of FAS offspring. High-dose FAS may promote insulin resistance and dyslipidemia and disrupt glucose metabolism possibly by depressing adiponectin expression. Although this is an animal model and the effects of the diets cannot be directly transposed to humans, this study provides indications of the possible adverse effects of FAS maternal diet on glucose metabolism in the offspring.

Magnesium upregulates insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide-induced type-2 diabetic rats

Abstract Objective. We investigated the effects of magnesium supplementation on glucose tolerance, insulin sensitivity, oxidative stress as well as the concentration of insulin receptor and glucose transporter-4 in streptozotocin-nicotinamide induced type-2 diabetic (T2D) rats. Methods. Rats were divided into four groups designated as: 1) control (CTR); 2) diabetic untreated (DU); 3) diabetic treated with 1 mg of Mg/kg diet (Mg1-D); and 4) diabetic treated with 2 mg of Mg/kg diet (Mg2-D). T2D was induced with a single intraperitoneal (i.p.) injection of freshly prepared streptozotocin (55 mg/kg) aft er an initial i.p. injection of nicotinamide (120 mg/kg). Glucose tolerance, insulin sensitivity, lipid profile, malondialdehyde (MAD) and glutathione content, insulin receptors (INSR) and glucose transporter-4 (GLUT4), fasting insulin and glucose levels were measured, and insulin resistance index was calculated using the homeostatic model assessment of insulin resistance (HOMA-IR). Results. Magnesium supplementation improved glucose tolerance and lowered blood glucose levels almost to the normal range. We also recorded a noticeable increase in insulin sensitivity in Mg-D groups when compared with DU rats. Lipid perturbations associated T2D were significantly attenuated by magnesium supplementation. Fasting glucose level was comparable to control values in the Mg-D groups while the HOMA-IR index was significantly lower compared with the DU rats. Magnesium reduced MDA but increased glutathione concentrations compared with DU group. Moreover, INSR and GLUT4 levels were elevated following magnesium supplementation in T2D rats. Conclusion. These findings demonstrate that magnesium may mediate effective metabolic control by stimulating the antioxidant defense, and increased levels of INSR and GLUT4 in diabetic rats.