Olufeyi Adegoke

Mechanism of delayed puberty in rats whose mothers consumed Hibiscus sabdariffa during lactation.

Context: Extract of the calyx of Hibiscus sabdariffa Linn. (HS) (Malvaceae) has been reported to decrease fluid and food intake in lactating rats through a mechanism not yet fully understood. It has also been reported that rat pups undernourished during lactation have delayed puberty onset, suggesting a link between nutrition and onset of puberty. There is paucity of data addressing the effect of maternal consumption of HS during lactation on the onset of puberty in the female offspring. Objective: The present study was designed to investigate whether consumption of HS during lactation will affect the onset of puberty and to examine the possible mechanism underlying this. Materials and methods: Lactating Sprague-Dawley rats were randomly grouped into three on postnatal day one. One group had tap water (control); another had 0.6 g aqueous HS extract/100 mL, while the third had 1.8 g aqueous HS extract/100 mL as their drinking solution throughout lactation. Maternal fluid consumption, food consumption, weight gain, plasma Na+ and corticosterone concentrations were determined. Offspring weights were recorded at 0, 21, 28, 35, and 42 days. Ages at onset of puberty and body weights were also recorded. Results: A decreased maternal fluid and food intake and an increased maternal plasma Na+ and corticosterone concentration were observed in HS dams. The HS treated female offspring showed delayed onset of puberty. Discussion and Conclusion: The accelerated growth and delayed puberty in the HS offspring may be through increased corticosterone and decreased leptin delivery through breast milk.

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.

Kisspeptin neurones in the posterodorsal medial amygdala modulate sexual partner preference and anxiety in male mice

The posterodorsal medial amygdala (MePD) is a neural site in the limbic brain involved in regulating emotional and sexual behaviours. There is, however, limited information available on the specific neuronal cell type in the MePD functionally mediating these behaviours in rodents. The recent discovery of a significant kisspeptin neurone population in the MePD has raised interest in the possible role of kisspeptin and its cognate receptor in sexual behaviour. The present study therefore tested the hypothesis that the MePD kisspeptin neurone population is involved in regulating attraction towards opposite sex conspecifics, sexual behaviour, social interaction and the anxiety response by selectively stimulating these neurones using the novel pharmacosynthetic DREADDs (designer receptors exclusively activated by designer drugs) technique. Adult male Kiss‐Cre mice received bilateral stereotaxic injections of a stimulatory DREADD viral construct (AAV‐hSyn‐DIO‐hM3D(Gq)‐mCherry) targeted to the MePD, with subsequent activation by i.p. injection of clozapine‐N‐oxide (CNO). Socio‐sexual behaviours were assessed in a counter‐balanced fashion after i.p. injection of either saline or CNO (5 mg kg‐1). Selective activation of MePD kisspeptin neurones by CNO significantly increased the time spent by male mice in investigating an oestrous female, as well as the duration of social interaction. Additionally, after CNO injection, the mice appeared less anxious, as indicated by a longer exploratory time in the open arms of the elevated plus maze. However, levels of copulatory behaviour were comparable between CNO and saline‐treated controls. These data indicate that DREADD‐induced activation of MePD kisspeptin neurones enhances both sexual partner preference in males and social interaction and also decreases anxiety, suggesting a key role played by MePD kisspeptin in sexual motivation and social behaviour.

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.

Mechanism of the decreased food consumption and weight gain in rats following consumption of aqueous extract of the calyx of Hibiscus sabdariffa during pregnancy

Abstract Objective To investigate the possible mechanisms of the decreasing fluid and food consumption following Hibiscus sabdariffa (HS) consumption. Methods On the 1st day of pregnancy, rats were randomly divided into three groups with six animals per each group. One group was given tap water, one was given with extract at 0.6 g/100 mL while the third group was given with extract at 1.8 g/100 mL as their drinking solution. All groups received normal rat chow and drinking solution ad libitum . Fluid& food intake and weight were measured daily throughout pregnancy and Na + concentration in plasma was determined on the 18th day of pregnancy. Results Results showed decreased fluid and food consumption, decreased weight gain and increased sodium ion concentration in plasma of rats with HS extract compared with the control group. Conclusions Consumption of aqueous extract of the calyx of HS during pregnancy decreases food consumption and weight gain through mechanisms that may depend on Na + in HS content and elevating Na + concentration.

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.

Kisspeptin in the posterodorsal medial amygdala modulates sexual partner preference and anxiety in male mice

This work was supported by the Medical Research Council, UK. DAA is a Commonwealth Scholar funded by the UK Government.

Metabolic Action Of Sex Steroids: The Effects Of Testosterone and Progestins On Hepatic Glycogen Deposition

It has been widely reported that sex steroids affect carbohydrate metabolism and may have influences on hepatic enzymes. There have also been reports that glucocorticoids and sex steroids sometimes bind to similar receptors. All these suggest possible functional similarities or antagonism between glucocorticoids and sex steroids. The aim of the present work was to determine the effect of four sex steroids testosterone, progesterone, nestorone and levonorgestred on hepatic glycogen deposition which is normally enhanced by glucocorticoids. The steroids were administered on rats, and hepatic glycogen content was measured. Results show that the four sex steroids had no direct effect on hepatic glycogen deposition. However the natural steroids testosterone and progesterone enhanced the stimulatory action of dexamethasone. This implies that although testosterone and progesterone may not affect carbohydrate metabolism by directly causing hepatic glycogenesis they probably have the potential to do so. Nigerian Quarterly Journal of Hospital Medicine Vol. 9, No. 1 (1999) pp. 71-73