Dysregulation of Kisspeptin and Leptin, as Anorexigenic Agents, Plays Role in the Development of Obesity in Postmenopausal Women

The kisspeptin system in and beyond reproduction: exploring intricate pathways and potential links between endometriosis and polycystic ovary syndrome

Endometriosis and polycystic ovary syndrome (PCOS) are two common female reproductive disorders with a significant impact on the health and quality of life of women affected. A novel hypothesis by evolutionary biologists suggested that these two diseases are inversely related to one another, representing a pair of diametrical diseases in terms of opposite alterations in reproductive physiological processes but also contrasting phenotypic traits. However, to fully explain the phenotypic features observed in women with these conditions, we need to establish a potential nexus system between the reproductive system and general biological functions. The recent discovery of kisspeptin as pivotal mediator of internal and external inputs on the hypothalamic-pituitary-gonadal axis has led to a new understanding of the neuroendocrine upstream regulation of the human reproductive system. In this review, we summarize the current knowledge on the physiological roles of kisspeptin in human reproduction, as well as its involvement in complex biological functions such as metabolism, inflammation and pain sensitivity. Importantly, these functions are known to be dysregulated in both PCOS and endometriosis. Within the evolving scientific field of "kisspeptinology", we critically discuss the clinical relevance of these discoveries and their potential translational applications in endometriosis and PCOS. By exploring the possibilities of manipulating this complex signaling system, we aim to pave the way for novel targeted therapies in these reproductive diseases.

Serum Level of Inhibin B and Kisspeptin, as well as Their Correlation with Biochemical Factors in Obese Adult Patients

Obesity is one of the most important global health problems causing serious health risks and early death in human. It is also associated with disturbance of homeostasis of hormones and immunological biochemical factors inside the human body. This study aimed to evaluate the serum level of inhibin B and kisspeptin among Iraqi obese adult people and other biochemical parameters correlated with obesity. Inhibin B and levels of kisspeptin were evaluated in the samples of serum from 40 Iraqi obese adult patients and 30 healthy non-obese individuals. A significant decrease (P<0.0001) was observed in the kisspeptin level in both males and females, compared to the control group. Moreover, inhibin B decreased significantly in obese females only (P<0.001), while there was no differences between males and the control group in this regard. Finally, body mass index, serum glutamic pyruvic transaminase (SGPT), and leptin showed negative correlation with kisspeptin (0.01, 0.5, and 0.01), respectively. However, a positive association was observed with the level of Ca in the serum. On the other hand, inhibin B confirmed a positive correlation with SGPT. The present study revealed a significant increase in inhibin B and kisspeptin, with SGPT and Ca in the serum of obese patients, which could lead to complications and health problems among these patients.

Metabolic actions of kisspeptin signaling: Effects on body weight, energy expenditure, and feeding

Kisspeptin (encoded by the Kiss1 gene) and its receptor, KISS1R (encoded by the Kiss1r gene), have well-established roles in stimulating reproduction via central actions on reproductive neural circuits, but recent evidence suggests that kisspeptin signaling also influences metabolism and energy balance. Indeed, both Kiss1 and Kiss1r are expressed in many metabolically-relevant peripheral tissues, including both white and brown adipose tissue, the liver, and the pancreas, suggesting possible actions on these tissues or involvement in their physiology. In addition, there may be central actions of kisspeptin signaling, or factors co-released from kisspeptin neurons, that modulate metabolic, feeding, or thermoregulatory processes. Accumulating data from animal models suggests that kisspeptin signaling regulates a wide variety of metabolic parameters, including body weight and energy expenditure, adiposity and adipose tissue function, food intake, glucose metabolism, respiratory rates, locomotor activity, and thermoregulation. Herein, the current evidence for the involvement of kisspeptin signaling in each of these physiological parameters is reviewed, gaps in knowledge identified, and future avenues of important research highlighted. Collectively, the discussed findings highlight emerging non-reproductive actions of kisspeptin signaling in metabolism and energy balance, in addition to previously documented roles in reproductive control, but also emphasize the need for more research to resolve current controversies and uncover underlying molecular and physiological mechanisms.

RFamide peptides, the novel regulators of mammalian HPG axis: A review

The RFamide-related peptides (RFRPs) are the group of neuropeptides synthesized predominantly from the hypothalamus that negatively affects the hypothalamo-hypophyseal-gonadal (hypothalamic–pituitary–gonadal [HPG]) axis. These peptides are first identified in quail brains and emerged as the mammalian orthologs of avian gonadotropin inhibitory hormones. The RFRP-3 neurons in the hypothalamus are present in several mammalian species. The action of RFRP-3 is mediated through a G-protein-coupled receptor called OT7T022. The predominant role of RFRP-3 is the inhibition of HPG axis with several other effects such as the regulation of metabolic activity, stress regulation, controlling of non-sexual motivated behavior, and sexual photoperiodicity in concert with other neuropeptides such as kisspeptin, neuropeptide-Y (NPY), pro-opiomelanocortin, orexin, and melanin. RFamide peptides synthesized in the granulosa cells, interstitial cells, and seminiferous tubule regulate steroidogenesis and gametogenesis in the gonads. The present review is intended to provide the recent findings that explore the role of RFRP-3 in regulating HPG axis and its potential applications in the synchronization of reproduction and its therapeutic interventions to prevent stress-induced amenorrhea.

Growth Hormone (GH) Treatment Decreases Plasma Kisspeptin Levels in GH-Deficient Adults with Prader-Willi Syndrome

Obesity and growth hormone (GH)-deficiency are consistent features of Prader-Willi syndrome (PWS). Centrally, kisspeptin is involved in regulating reproductive function and can stimulate hypothalamic hormones such as GH. Peripherally, kisspeptin signaling influences energy and metabolic status. We evaluated the effect of 12-month GH treatment on plasma kisspeptin levels in 27 GH-deficient adult PWS patients and analyzed its relationship with metabolic and anthropometric changes. Twenty-seven matched obese subjects and 22 healthy subjects were also studied. Before treatment, plasma kisspeptin concentrations in PWS and obese subjects were similar (140.20 (23.5-156.8) pg/mL vs. 141.96 (113.9-165.6) pg/mL, respectively, p = 0.979)) and higher (p = 0.019) than in healthy subjects (124.58 (107.3-139.0) pg/mL); plasma leptin concentrations were similar in PWS and obese subjects (48.15 (28.80-67.10) ng/mL vs. 33.10 (20.50-67.30) ng/mL, respectively, p = 0.152) and higher (p < 0.001) than in healthy subjects (14.80 (11.37-67.30) ng/mL). After GH therapy, lean body mass increased 2.1% (p = 0.03), total fat mass decreased 1.6% (p = 0.005), and plasma kisspeptin decreased to levels observed in normal-weight subjects (125.1(106.2-153.4) pg/mL, p = 0.027). BMI and leptin levels remained unchanged. In conclusion, 12-month GH therapy improved body composition and decreased plasma kisspeptin in GH deficient adults with PWS. All data are expressed in median (interquartile range).

Leptin promotes adipocytes survival in non-vascularized fat grafting via perfusion increase

BACKGROUND

Though autologous fat transplantation is regularly and successfully performed in plastic surgery, little is known about the factors that contribute to the rise of preadipocytes and how the viability of adipocytes is regulated. As sufficient blood supply is a key parameter for the transplant's survival, we opted to analyse the development of preadipocytes within the fat transplant via stimulation of tissue perfusion with the angiogenesis enhancing hormone leptin.

METHODS

In a murine (C57BL/6N) model inguinal fat was autologously transplanted into a dorsal skinfold chamber. In the intervention group the fat transplant was treated with local administration of leptin (3 μg/ml) at days 3, 7 and 10 after transplantation. Saline solution was administered respectively in the control group. On the postoperative days 3, 7, 10, and 15 intra vital microscopy was done to assess the functional vessel density, vessel diameter, adipocyte survival and preadipocyte development. The study was completed by histological tissue analysis on days 15 after transplantation.

RESULTS

Leptin administration leads to an increase of angiogenesis, which starts from day 7 after implantation and elevates perfusion as well as functional vessel density FVD at days 10 and 15 after transplantation. Perfusion develops first from the border zones of the transplant. Histological evaluation showed that the percentage of perilipin positive adipocytes increased markedly in the study group of mice. Moreover, fat transplants of mice of the leptin group disclosed significantly higher Pref-1 positive cells than fat transplants of the control group. The findings reported in this study indicate that the leptin can enhance the survival and the quality of grafted fat tissue, which may be due to induction of angiogenesis.

CONCLUSION

Leptin administration to fat transplants induced an increase in angiogenesis in the transplanted tissue and may play a role in reducing the resorption rate of lipoaspirates.

Association of Leptin with Total and Free Testosterone: Results from the National Health and Nutrition Examination Surveys

Introduction

Obese men can have testosterone deficiency (TD) but the etiology is uncertain. Leptin is a 16-kDa protein produced primarily by adipose tissue and, therefore, is positively associated with the amount of body fat and can affect testosterone (T) production. We hypothesized that increased leptin can be independently associated with low T.

Materials and Methods

We performed a cross-sectional analysis of men from National Health and Nutrition Examination III database to evaluate the association of leptin with serum T and calculated free testosterone (cFT). Linear regression was performed with leptin, age, waist circumference, hypertension, and diabetes as independent variables predicting cFT/T. Multiple linear regression was used to determine predictors for cFT and T using variables previously significant in the univariate analysis.

Results

A total of 1193 men were analyzed. As expected, older and obese men were associated with having lower T. Interestingly, increasing leptin levels were an independent predictor of decreasing T and cFT on multivariable analysis. Increasing 1ng/mL in leptin resulted in a decrease of 5.13 and 0.11 ng/dL of T and cFT, respectively (p < 0.05). Also, every additional year of life led to a T and cFT reduction of 2.87 and 0.13 ng/dL, respectively, and increasing 1 cm in waist circumference corresponded to decrease of 4ng/dL in T (p < 0.05).

Conclusions

We concluded that increasing leptin, age, and waist circumference were associated with decreasing of T and cFT. Elevated leptin levels could be one of the potential etiologies of TD.

Serum Kisspeptin and Its Relation to Metabolic Parameters and Glucose Metabolism in Prepubertal and Pubertal Obese Children

OBJECTIVE

Kisspeptin, a puberty control neuropeptide, has been discovered to have an additional role in metabolism and glucose homeostasis regulation. This study aimed to determine the association of serum kisspeptin with metabolic parameters and glucose metabolism in obese children. Design, Patients and Measurements. A cross-sectional study of 270 obese children was conducted. All children underwent an oral glucose tolerance test and had serum kisspeptin, glycated hemoglobin (HbA1c), and lipid profile measurements. Body fat mass was assessed by bioelectrical impedance analysis. Serum kisspeptin levels of both prepubertal and pubertal children with two HbA1c ranges, <5.7% (normal range) and 5.7-6.4% (prediabetes range), were analyzed and correlated with metabolic parameters and glucose metabolism status.

RESULTS

The median (IQR) serum kisspeptin level of only pubertal (not prepubertal) children with prediabetes HbA1c was higher than those with normal HbA1c (53.2 (33.9, 69.8) and 37.8 (29.6, 67.5) pg/mL; p = 0.015, respectively). There were no differences in serum kisspeptin levels among children with different glucose metabolism status. During pubertal progression, serum kisspeptin reached the highest level at Tanner stage II only in obese boys. Additionally, there was a positive correlation between serum kisspeptin and HbA1c after adjusting for puberty (β = 12.87; p = 0.001). No correlations between serum kisspeptin and insulin sensitivity indices, insulin secretion indices, lipid profile, blood glucose, as well as percentage of body fat were demonstrated.

CONCLUSIONS

Serum kisspeptin levels in pubertal obese children with prediabetes HbA1c were greater than those with normal HbA1c. Serum kisspeptin was positively associated with HbA1c, but not with glucose metabolism status.