The Effect of Leptin and Adiponectin on KiSS-1 and KissR mRNA Expression in Rat Islets of Langerhans and CRI-D2 Cell Line

Influences of Serotonin Hydrochloride on Adiponectin, Ghrelin and KiSS1 Genes Expression

Background:

Serotonin and kisspeptin stimulates gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) release while ghrelin and adiponectin inhibit them. In the present experimental study, the effects of central injection of serotonin were investigated on LH concentration, KiSS1, adiponectin, and ghrelin genes expression.

Materials and Methods:

Fifteen Wistar male rats in three groups received saline or serotonin hydrochloride via the third cerebral ventricle. Blood samples were collected via the tail vein. Serum LH concentration and relative gene expression were evaluated by radioimmunoassay and real-time polymerase chain reaction method, respectively.

Results:

Serotonin significantly increased the mean serum LH concentration and KiSS1 gene expression levels compared to the saline group. Serotonin significantly decreased the mean ghrelin and adiponectin genes expression levels compared to the saline group.

Conclusion:

The serotonergic pathway may have stimulatory effects on hypothalamic kisspeptin synthesis, partly via inhibiting hypothalamic ghrelin and adiponectin neural activity.

Combined effects of obesity and di-(2-ethylhexyl) phthalate on testosterone levels and kisspeptin/GPR54 expression in hypothalamus and testes of male mice

BACKGROUND

This study evaluated whether obese male mice exposed to di-(2-ethylhexyl) phthalate (DEHP) showed synergistic effects on testosterone levels and the potential underlying mechanism.

METHODS

Forty-eight male mice were assigned to six groups for 12-week treatments as follows: normal, DEHP100, diet-induced obesity (DIO), DIO + DEHP30, DIO + DEHP100, and DIO + DEHP300. Serum hormone levels, including testosterone (T), luteinizing hormone (LH), and leptin, were detected by ELISA. The levels of Ob-R, kisspeptin, and GPR54 protein expression in hypothalamus and testicular tissues were measured by western blot.

RESULTS

There were significantly lower levels of serum T and LH, higher levels of serum leptin and Ob-R, and kisspeptin and GPR54 protein expression were reduced in hypothalamus and testicular tissues in the DIO and DEHP groups compared with controls. Moreover, serum T and leptin levels were more severe in the combined DIO and DEHP exposure group than in the single exposure groups. Serum LH levels and GPR54 expression in the testis were significantly decreased in DIO + DEHP300 mice compared with DIO mice (p < 0.05).

CONCLUSION

Obesity- and DEHP-only exposure had adverse effects on testosterone levels in mice, which may be due to high leptin levels and decreased Ob-R, kisspeptin, and GPR54 expression. Obesity combined with DEHP exposure had an additive adverse effect on testosterone levels in mice. One of the potential mechanisms is higher leptin levels and decreased GPR54 expression in the testes.

The KiSS-1/GPR54 system: Essential roles in physiological homeostasis and cancer biology

KiSS-1, first identified as an anti-metastasis gene in melanoma, encodes C-terminally amidated peptide products, including kisspeptin-145, kisspeptin-54, kisspeptin-14, kisspeptin-13 and kisspeptin-10. These products are endogenous ligands coupled to G protein-coupled receptor 54 (GPR54)/hOT7T175/AXOR12. To date, the regulatory activities of the KiSS-1/GPR54 system, such as puberty initiation, antitumor metastasis, fertility in adulthood, hypothalamic-pituitary-gonadal axis (HPG axis) feedback, and trophoblast invasion, have been investigated intensively. Accumulating evidence has demonstrated that KiSS-1 played a key role in reproduction and served as a promising biomarker relative to the diagnosis, identification of therapeutic targets and prognosis in various carcinomas, while few studies have systematically summarized its subjective factors and concluded the functions of KiSS-1/GPR54 signaling in physiology homeostasis and cancer biology. In this review, we retrospectively summarized the regulators of the KiSS-1/GPR54 system in different animal models and reviewed its functions according to physiological homeostasis regulations and above all, cancer biology, which provided us with a profound understanding of applying the KiSS-1/GPR54 system into medical applications.

Role of adiponectin in ovarian follicular development and ovarian reserve

Adiponectin levels are associated with anti-Müllerian hormone (AMH) and kisspeptin levels in non-ovarian tissues. The objective of the present study was to investigate the association between adiponectin and the genes important for ovarian follicular development and ovarian reserve, specifically AMH and kisspeptin, and their corresponding receptors. In the first experiment, the mRNA levels of anti-Müllerian hormone (amh) and its receptor (Amhr2), as well as those of kisspeptin (Kiss1) and its receptor (Kiss1r), were quantified by reverse transcription-polymerase chain reaction analysis in the ovaries of two groups of mice [adiponectin-knockout (KO) vs. control] that underwent oophorectomy. The second experiment measured follicular phase serum AMH and follicular fluid adiponectin levels in 25 women who underwent controlled ovarian hyperstimulation for in vitro fertilization. Compared with the control mice, adiponectin-KO mice had 6.5 times lower Kiss1 mRNA levels (P=0.009) and a tendency for lower ovarian Kiss1r mRNA expression levels (P=0.06). However, adiponectin-KO mice had significantly higher Amhr2 mRNA levels (P=0.01). In all women participants, there was a positive correlation between serum AMH and follicular fluid adiponectin concentrations (r=0.54, P=0.006). The findings of the present study indicate that adiponectin may play a role in ovarian physiology through its impact on genes crucial for ovarian follicular development and ovarian reserve, such as kisspeptin and AMH. Understanding the role of adiponectin in ovarian function may improve our knowledge of the pathophysiology underlying ovulatory dysfunction in obese women, who usually have low adiponectin levels, and overcome reproductive barriers.

Downregulation of leptin receptor and kisspeptin/GPR54 in the murine hypothalamus contributes to male hypogonadism caused by high-fat diet-induced obesity

PURPOSE

Obesity may lead to male hypogonadism, the underlying mechanism of which remains unclear. In the present study, we established a murine model of male hypogonadism caused by high-fat diet-induced obesity to verify the following hypotheses: 1) an increased leptin level may be related to decreased secretion of GnRH in obese males, and 2) repression of kisspeptin/GPR54 in the hypothalamus, which is associated with increased leptin levels, may account for the decreased secretion of GnRH and be involved in secondary hypogonadism (SH) in obese males.

METHODS

Male mice were fed high-fat diet for 19 weeks and divided by body weight gain into diet-induced obesity (DIO) and diet-induced obesity resistant (DIO-R) group. The effect of obesity on the reproductive organs in male mice was observed by measuring sperm count and spermatozoid motility, relative to testis and epididymis weight, testosterone levels, and pathologic changes. Leptin, testosterone, estrogen, and LH in serum were detected by ELISA method. Leptin receptor (Ob-R), Kiss1, GPR54, and GnRH mRNA were measured by real-time PCR in the hypothalamus. Expression of kisspeptin and Ob-R protein was determined by Western blotting. Expression of GnRH and GPR54 protein was determined by immunohistochemical analysis.

RESULTS

We found that diet-induced obesity decreased spermatozoid motility, testis and epididymis relative coefficients, and plasma testosterone and luteinizing hormone levels. An increased number and volume of lipid droplets in Leydig cells were observed in the DIO group compared to the control group. Significantly, higher serum leptin levels were found in the DIO and DIO-R groups. The DIO and DIO-R groups showed significant downregulation of the GnRH, Kiss1, GPR54, and Ob-R genes. We also found decreased levels of GnRH, kisspeptin, GPR54, and Ob-R protein in the DIO and DIO-R groups.

CONCLUSIONS

These lines of evidence suggest that downregulation of Ob-R and kisspeptin/GPR54 in the murine hypothalamus may contribute to male hypogonadism caused by high-fat diet-induced obesity.

Kisspeptin-10 inhibits proliferation and regulates lipolysis and lipogenesis processes in 3T3-L1 cells and isolated rat adipocytes

INTRODUCTION

Kisspeptin, which is encoded by the KISS1 gene and acts via GPR54, plays a role in the regulation of reproductive functions. Expression of KISS1 and GRPR54 has been found in peripheral tissues, including adipose tissue, and was shown to be influenced by metabolic status.

PURPOSE

We hypothesized that kisspeptin could be involved in regulation of lipid metabolism in the mouse 3T3-L1 cell line and in isolated rat adipocytes.

METHODS

First, we characterized expression profiles of KISS1 and GPR54 mRNA and proteins in adipose cells isolated from male rats. Secondly, we studied the effects of kisspeptin-10 on cell proliferation and survival in 3T3-L1 cells. Thirdly, we assessed the rapid action of kisspeptin-10 on lipid metabolism and glucose uptake using 3T3-L1 cells and rat primary adipocytes. Finally, we examined the effects of kisspeptin-10 on the secretion of leptin and adiponectin in rat adipocytes.

RESULTS

We have found that: (1) KISS1 and GPR54 were expressed in mouse 3T3-L1 cells and isolated rat adipocytes; (2) kisspeptin-10: (i) inhibited cell proliferation, viability and adipogenesis in 3T3-L1 and decreased expression of PPAR-γ and CEBPβ-genes, which are involved in the differentiation processes and adipogenesis; (ii) increased lipolysis in 3T3-L1 cells and rat adipocytes by enhancing expression of periliphin and hormone-sensitive lipase; (iii) modulated glucose uptake and lipogenesis; (iv) stimulated leptin and decreased adiponectin secretion from rat adipocytes.

CONCLUSION

Kisspeptin-10 could play a role in the regulation of lipid metabolism in mouse 3T3-L1 cells and rat adipocytes.

Chronic perfluorooctanesulfonic acid exposure disrupts lipid metabolism in zebrafish

Perfluorooctanesulfonic acid (PFOS), a ubiquitous contaminant, has been used in various industrial applications. Currently few studies have documented the effects of chronic PFOS exposure on lipid metabolism, especially in aquatic organisms. The present study defined the effects of chronic exposure to low level of PFOS on lipid metabolism in F0 adult zebrafish and F1 offspring. Our findings revealed a severe fatty degeneration in the liver of F0 males treated with 0.5 μM PFOS and significant ultrastructure changes associated with substance transport or metabolism in liver and intestines (abnormal mitochondria and endoplasmic reticulum, disordered arrangement of inner microvilli within intracellular canaliculus). To address the potential trans-generational effects of PFOS exposure, the early gene expression related to lipid metabolism was measured by real-time quantitative polymerase chain reaction in F1 derived from chronically exposed parental fish. The results indicated that lepa (leptin α), kiss1 (kisspeptins), xdh (xanthine dehydrogenases), and insr (insulin receptor) were significantly upregulated in F1 while dgat1b (diacylglycerol O-acyltransferase), hb9 (motor neuron/pancreas homeobox), and Apoa1 (apolipoprotein A-I) were downregulated. These findings provided evidence that PFOS chronic exposure adversely impacts lipid metabolism in both F0 and F1 and demonstrated the validity of using zebrafish as an alternative model for PFOS chronic toxicity screening.

The effects of vitamin d on insulin release from isolated islets of rats

BACKGROUND

Vitamin D (vit D) affects glucose metabolism. Receptors of vitamin D have been identified in β cells and studies show that vitamin D deficiency reduces glucose-stimulated insulin secretion (GSIS).

OBJECTIVES

The aim of this study was to examine the effect of vitamin D on insulin release from isolated islets of rats.

MATERIALS AND METHODS

Islets were isolated from male Wistar rats, weighing 200-250 grams, using the collagenase digestion method. Insulin release was assessed following 24 and 48 hours coincubation of islets with vitamin D (0.1, 1 and 10 nM) and glucose (5.6, 11.1 and 16.7 mM). In addition, islets were preincubated with vitamin D for 24 and 48 hours and GSIS was assessed for one hour in the presence of 5.6 and 16.7 mM glucose.

RESULTS

Coincubation of islets with vitamin D (10 nM) and 11.1 mM glucose increased islet insulin release (37.27 ± 3.75 vs. 24.64 ± 2.83 ng/islet/24 hours; P < 0.05), while vitamin D (1 and 10 nM) decreased insulin release in the presence of 16.7 mM glucose (21.14 ± 3.58 and 18.65 ± 3.84 vs. 37.71 ± 4.63 ng/ islet/24 hours; P < 0.05). Islets preincubation with vitamin D (1 and 10 nM) increased GSIS in the presence of 16.7 mM glucose (4.39 ± 0.73 and 4.39 ± 0.63 vs. 2.07 ± 0.43 ng/islet/1 hour; P < 0.05).

CONCLUSIONS

Preincubation of islets with vitamin D increased GSIS but decreased insulin release in coincubation with high levels of glucose. Insulin secretion from β cells in the presence of glucose seems to be related to the dosage of vitamin D and duration of preincubation.