Glucagon regulates hepatic kisspeptin to impair insulin secretion

Hepatic PKA Mediates Liver and Pancreatic α-Cell Cross Talk

Glucagon stimulates hepatic glucose production, in part by promoting the uptake and catabolism of amino acids. Inhibition of the liver glucagon receptor (GCGR) results in elevated plasma amino acids, which triggers the proliferation of pancreatic α-cells, forming a liver-α-cell loop. This study aims to delineate hepatic signaling molecules downstream of GCGR that mediate the liver-α-cell loop. We knocked down liver GCGR, its G-coupled protein GNAS, and two GNAS downstream effectors, PKA and EPAC2 (RAPGEF4). Mice with GCGR, GNAS, and PKA knockdown had similar suppression of hepatic amino acid catabolism genes, hyperaminoacidemia, and α-cell hyperplasia, but those with EPAC2 knockdown did not. We then demonstrated that activating liver PKA was sufficient to reverse hyperaminoacidemia and α-cell hyperplasia caused by GCGR blockade. These results suggest that liver GCGR signals through PKA to control amino acid metabolism and that hepatic PKA plays a critical role in the liver-α-cell loop.

ARTICLE HIGHLIGHTS

A liver-α-cell loop exists, where inhibition of the liver glucagon receptor (GCGR) causes hyperaminoacidemia and pancreatic α-cell hyperplasia, but the GCGR downstream factors responsible for these effects are not clear. We silenced GCGR, its G-coupled protein GNAS, and two GNAS downstream effectors, PKA and EPAC2, to assess their effects on the liver-α-cell loop. Inhibition of the GCGR-GNAS-PKA pathway suppresses amino acid catabolism and causes α-cell hyperplasia, whereas PKA activation promotes amino acid catabolism and reduces alpha cell mass even when GCGR is blocked. Our study establishes hepatic PKA as the critical regulator of the liver-α-cell loop.

Kisspeptin Receptor Agonists and Antagonists: Strategies for Discovery and Implications for Human Health and Disease

The kisspeptin/kisspeptin receptor (KISS1/KISS1R) system has emerged as a vital regulator of various physiological processes, including cancer progression, metabolic function, and reproduction. KISS1R, a member of the G protein-coupled receptor family, is crucial for regulating the hypothalamic/pituitary/gonadal axis. A growing number of KISS1R agonists are currently being investigated in clinical trials, whereas the number of antagonists remains limited. Most existing ligands are synthetic peptides, with only a few small-molecule compounds, such as musk ambrette, having been identified. In this article, we provide an overview of the KISS1/KISS1R system and its involvement in diseases such as reproductive disorders, cancer, diabetes, and cardiovascular disease. We also highlight the various technologies used to identify KISS1R ligands, including radioligand binding assays, calcium flux assays, IP1 formation assays, ERK phosphorylation assays, qRT-PCR, and AI-based virtual screening. Furthermore, we discuss the latest advances in identifying KISS1R agonists and antagonists, highlighting ongoing challenges and future directions in research. These insights lay the groundwork for future research aimed at leveraging this system for developing innovative therapeutic strategies across a range of medical conditions.

Association between PFAS exposure and metabolic-related biomarkers in Spanish adolescents

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) exert endocrine disruptive effects on the endocrine-metabolic axis. Emerging knowledge suggests that kisspeptin may play a key role in these effects.

OBJECTIVE

To assess the cross-sectional association of blood PFAS concentrations with kisspeptin levels, KISS1 gene DNA methylation, and metabolic-related biomarkers in adolescent males from the Spanish INMA-Granada cohort.

METHODS

Seven PFAS and twelve biomarkers (glucose-GLU, total cholesterol-TC, triglycerides, LDL, HDL, ALP, AST, ALT, GGT, total bilirubin-BILT, direct bilirubin-BILD, and urea) were measured in plasma and serum, respectively, from 129 adolescent males (15-17 yrs). Systolic and diastolic blood pressure (SBP, DBP), pulse, z-scored body mass index, kisspeptin protein levels (n = 104) and whole blood KISS1 DNA methylation (n = 117) were determined. Linear regression models, weighted quantile sum (WQS), and Bayesian kernel machine (BKMR) were fit.

RESULTS

PFHpA was associated with lower GLU levels [% change per log-unit increase in plasma concentrations (95%CI) = -4.73 (-8.98;-0.28)], and PFUnDA with higher GLU, TC, and HDL levels. In models adjusted by kisspeptin level, PFOS was associated with higher SBP [3.42 (-0.12; 7.09)]. Additionally, PFNA and total PFAS concentrations were associated with higher kisspeptin levels [3.91 (0.55; 7.37) and 6.14 (0.47; 12.13), respectively]. Mixture models showed that combined PFAS exposure was associated with higher HDL, lower hepatic biomarkers (ALT, BILD) and higher kisspeptin levels.

CONCLUSION

Certain PFAS (e.g. PFUnDA) and their mixture were associated with metabolic-related biomarkers, mainly GLU, HDL, and SBP. These associations may be influenced by kisspeptin levels. More studies are needed to verify these observations.

Diabetes mellitus secondary to endocrine diseases: a position statement of the working group of the club of the Italian society of endocrinology (SIE)-Nutrition hormones and metabolism

PURPOSE

This position statement addressed the limited scientific literature on the management of diabetes mellitus secondary to endocrinopathies, despite its frequent occurrence in hormonal diseases such as acromegaly, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and neuroendocrine tumors. The aim was to review the pathophysiological mechanisms, clinical features, and management strategies, focusing on nutritional and pharmacological approaches.

METHODS

A comprehensive review of existing literature was conducted regarding studies on diabetes secondary to endocrinopathies and the effects of treatments for these conditions, such as somatostatin analogues and pancreatic surgery. Particular emphasis was placed on understanding glucose metabolism derangements and the interplay between endocrine excess and therapeutic interventions.

RESULTS

Secondary diabetes arises not only from hormone excess but also as a consequence of treatments for endocrine disorders. For instance, somatostatin analogues, while effective in resolving hormone hypersecretion, impair glucose metabolism by inhibiting pancreatic insulin secretion. Similarly, pancreatic surgery for neuroendocrine tumors often exacerbates glycemic disturbances. The management of secondary diabetes requires a multidisciplinary approach that includes treating the underlying endocrine disorder, tailoring antidiabetic therapy, and optimizing nutritional strategies to mitigate metabolic disruptions.

CONCLUSION

Diabetes secondary to endocrinopathies presents unique challenges due to its complex etiology and the metabolic effects of treatments. This position statement underscores the importance of an integrated management approach, offering guidance for clinicians in addressing this multifaceted condition. Further research is needed to develop evidence-based guidelines for optimal care.

The Investigation of Kisspeptin, Spexin and Galanin in Euthyroid Women with Hashimoto's Thyroiditis

OBJECTIVE

The hallmarks of Hashimoto's thyroiditis (HT) include the destruction of thyroid cells by leading to insulin resistance (IR), hypothyroidism, and metabolic abnormalities. Kisspeptin, spexin, and galanin control appetite and body weight (BW) to regulate metabolisms. Here, we sought to determine if galanin, kisspeptin, and spexin are linked to the pathophysiology of HT in euthyroid female individuals.

METHODS

Forty-five women with HT and 45 healthy control women of the same age participated in the current study. The enzyme-linked immunosorbent assay (ELISA) method was used to measure the serum levels of galanin, spexin, and kisspeptin.

RESULTS

In comparison to the controls, HT patients had significantly higher levels of kisspeptin (p < 0.01), galanin (p < 0.01), anti-thyroid peroxidase (anti-TPO) (p < 0.001), anti-thyroglobulin (anti-Tg) (p < 0.001), and body mass index (BMI) (p < 0.05). The two groups were comparable in terms of spexin, free triiodothyronine-3 (fT3), fT4, thyroid-stimulating hormone (TSH) levels, and homeostatic model assessment for insulin resistance (HOMA-IR). Galanin and kisspeptin were seen to have a positive correlation (p < 0.01; r = 0.786).

CONCLUSIONS

Euthyroid women with HT were found to have higher levels of kisspeptin and galanin. These results imply that kisspeptin and galanin may be linked to the pathogenesis of hypothyroidism, and as a result, we believe that these markers may be beneficial in the early detection and treatment of HT patients.

Intermittent Fasting and Probiotics: Synergistic Modulation of Gut Health for Therapeutic Advantages

Intermittent fasting (IF) is an increasingly popular dietary approach involving alternating fasting and eating periods. This review aims to summarize the growing body of literature demonstrating that IF is a potential nutritional practice that involves alternating periods of fasting and eating and the numerous benefits of IF, especially in the modulation of healthy gut microbiota. The positive impact of intermittent fasting on gut microbiota not only promotes gastrointestinal health but also has far-reaching effects on critical systems throughout the body. Additionally, the evidence presented in this review highlights the significant preventive and therapeutic effects of intermittent fasting on a wide range of disorders. This includes reducing the risk of diabetes, and neurological disorders, alleviating obesity, and enhancing the functioning of the liver, ultimately contributing to the maintenance of metabolic equilibrium. Perhaps most notably, these effects play a substantial role in preventing diabetes, a global health concern of increasing significance. This comprehensive investigation delves into the scientific foundations of intermittent fasting's impact on gut microbiota and its implications for averting chronic diseases, providing valuable insights for future research and therapeutic applications.

The Hypothalamus and Pituitary Gland Regulate Reproduction and Are Involved in the Development of Polycystic Ovary Syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a complex condition with unclear mechanisms, posing a challenge for prevention and treatment of PCOS. The role of the hypothalamus and pituitary gland in regulating female reproduction is critical. Abnormalities in the hypothalamus and pituitary can impair reproductive function. It is important to study hypothalamic and pituitary changes in patients with PCOS.

SUMMARY

This article reviews articles on the hypothalamus and PCOS with the goal of summarizing what abnormalities of the hypothalamic-pituitary-ovarian axis are present in patients with PCOS and to clarify the pathogenesis of PCOS. We find that the mechanisms by which the hypothalamus and pituitary regulate reproduction in girls are complex and are associated with altered sex hormone levels, obesity, and insulin resistance. Different animal models of PCOS are characterized by different alterations in the hypothalamus and pituitary and respond differently to different treatments, which correspond to the complex pathogenesis of patients with PCOS.

KEY MESSAGES

Arcuate nucleus (ARC) is associated with luteinizing hormone (LH) surges. Suprachiasmatic nucleus, ARC, and RP3V are associated with LH surges. Animal models of PCOS have different characteristics.

Examining the liver-pancreas crosstalk reveals a role for the molybdenum cofactor in β-cell regeneration

Regeneration of insulin-producing β-cells is an alternative avenue to manage diabetes, and it is crucial to unravel this process in vivo during physiological responses to the lack of β-cells. Here, we aimed to characterize how hepatocytes can contribute to β-cell regeneration, either directly or indirectly via secreted proteins or metabolites, in a zebrafish model of β-cell loss. Using lineage tracing, we show that hepatocytes do not directly convert into β-cells even under extreme β-cell ablation conditions. A transcriptomic analysis of isolated hepatocytes after β-cell ablation displayed altered lipid- and glucose-related processes. Based on the transcriptomics, we performed a genetic screen that uncovers a potential role of the molybdenum cofactor (Moco) biosynthetic pathway in β-cell regeneration and glucose metabolism in zebrafish. Consistently, molybdenum cofactor synthesis 2 (Mocs2) haploinsufficiency in mice indicated dysregulated glucose metabolism and liver function. Together, our study sheds light on the liver-pancreas crosstalk and suggests that the molybdenum cofactor biosynthesis pathway should be further studied in relation to glucose metabolism and diabetes.

Kisspeptin Alleviates Human Hepatic Fibrogenesis by Inhibiting TGFβ Signaling in Hepatic Stellate Cells

The peptide hormone kisspeptin attenuates liver steatosis, metabolic dysfunction-associated steatohepatitis (MASH), and fibrosis in mouse models by signaling via the kisspeptin 1 receptor (KISS1R). However, whether kisspeptin impacts fibrogenesis in the human liver is not known. We investigated the impact of a potent kisspeptin analog (KPA) on fibrogenesis using human precision-cut liver slices (hPCLS) from fibrotic livers from male patients, in human hepatic stellate cells (HSCs), LX-2, and in primary mouse HSCs. In hPCLS, 48 h and 72 h of KPA (3 nM, 100 nM) treatment decreased collagen secretion and lowered the expression of fibrogenic and inflammatory markers. Immunohistochemical studies revealed that KISS1R is expressed and localized to HSCs in MASH/fibrotic livers. In HSCs, KPA treatment reduced transforming growth factor b (TGFβ)-the induced expression of fibrogenic and inflammatory markers, in addition to decreasing TGFβ-induced collagen secretion, cell migration, proliferation, and colony formation. Mechanistically, KISS1R signaling downregulated TGFβ signaling by decreasing SMAD2/3 phosphorylation via the activation of protein phosphatases, PP2A, which dephosphorylates SMAD 2/3. This study revealed for the first time that kisspeptin reverses human hepatic fibrogenesis, thus identifying it as a new therapeutic target to treat hepatic fibrosis.

Jiawei Buzhong Yiqi Decoction attenuates polycystic ovary syndrome through regulating kisspeptin-GPR54-AKT-SHBG system

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most common reproductive endocrine disorders. Accumulated evidence has suggested the indispensable role of kisspeptin-G protein-coupled receptor (GPR54) system and SHBG in development of PCOS. However, potential mechanisms and their relationship are unclear. Jiawei Buzhong Yiqi Decoction (JWBZYQ) has been reported to ameliorate obese PCOS. Whereas, potential mechanisms remain elusive.

PURPOSE

To determine whether JWBZYQ attenuates PCOS by regulating the kisspeptin-GPR54 system and SHBG production. And to explore potential mechanisms.

METHODS

An overweight PCOS rat model was developed with testosterone propionate (TP) and high-fat diet (HFD). The efficacy of JWBZYQ was assessed by tracking changes in weight, estrous cycle, ovarian morphology, and serum sex hormone levels. Additionally, kisspeptin-GPR54 system expression in multiple organs and PI3K-AKT pathway activity in liver of different rats were detected. Modifications in SHBG production were also measured. Kisspeptin54 was administered to establish a cellular model. The levels of AKT phosphorylation and SHBG protein within HepG2 cells were analyzed. Finally, confirmatory studies were performed using AKT phosphorylation activator and inhibitor.

RESULTS

JWBZYQ effectively attenuated the overweight, disrupted estrous cycle, altered sex hormone levels, and aberrant ovarian morphology in PCOS rats. Meanwhile, PCOS rats exhibited elevated levels of kisspeptin and GPR54, along with reduced SHBG levels, which could be reversed by JWBZYQ. These alterations might be connected with the activation of AKT phosphorylation. In vitro experiment identified that JWBZYQ could rectify the hyperactivated AKT phosphorylation and deficient production of SHBG caused by kisspeptin54.

CONCLUSIONS

Overexpressed kisspeptin-GPR54 system inhibited SHBG synthesis in PCOS. JWBZYQ curtailed the exorbitant expression of kisspeptin and GPR54, which moderated the rise in AKT phosphorylation and subsequently promoted the production of SHBG.

Sex difference in human diseases: mechanistic insights and clinical implications

Sex characteristics exhibit significant disparities in various human diseases, including prevalent cardiovascular diseases, cancers, metabolic disorders, autoimmune diseases, and neurodegenerative diseases. Risk profiles and pathological manifestations of these diseases exhibit notable variations between sexes. The underlying reasons for these sex disparities encompass multifactorial elements, such as physiology, genetics, and environment. Recent studies have shown that human body systems demonstrate sex-specific gene expression during critical developmental stages and gene editing processes. These genes, differentially expressed based on different sex, may be regulated by androgen or estrogen-responsive elements, thereby influencing the incidence and presentation of cardiovascular, oncological, metabolic, immune, and neurological diseases across sexes. However, despite the existence of sex differences in patients with human diseases, treatment guidelines predominantly rely on male data due to the underrepresentation of women in clinical trials. At present, there exists a substantial knowledge gap concerning sex-specific mechanisms and clinical treatments for diverse diseases. Therefore, this review aims to elucidate the advances of sex differences on human diseases by examining epidemiological factors, pathogenesis, and innovative progress of clinical treatments in accordance with the distinctive risk characteristics of each disease and provide a new theoretical and practical basis for further optimizing individualized treatment and improving patient prognosis.

Structural basis for the ligand recognition and G protein subtype selectivity of kisspeptin receptor

Kisspeptin receptor (KISS1R), belonging to the class A peptide-GPCR family, plays a key role in the regulation of reproductive physiology after stimulation by kisspeptin and is regarded as an attractive drug target for reproductive diseases. Here, we demonstrated that KISS1R can couple to the Gi/o pathway besides the well-known Gq/11 pathway. We further resolved the cryo-electron microscopy (cryo-EM) structure of KISS1R-Gq and KISS1R-Gi complexes bound to the synthetic agonist TAK448 and structure of KISS1R-Gq complex bound to the endogenous agonist KP54. The high-resolution structures provided clear insights into mechanism of KISS1R recognition by its ligand and can facilitate the design of targeted drugs with high affinity to improve treatment effects. Moreover, the structural and functional analyses indicated that conformational differences in the extracellular loops (ECLs), intracellular loops (ICLs) of the receptor, and the "wavy hook" of the Gα subunit may account for the specificity of G protein coupling for KISS1R signaling.

Structural basis for hormone recognition and distinctive Gq protein coupling by the kisspeptin receptor

Kisspeptin signaling through its G protein-coupled receptor, KISS1R, plays an indispensable role in regulating reproduction via the hypothalamic-pituitary-gonadal axis. Dysregulation of this pathway underlies severe disorders like infertility and precocious puberty. Here, we present cryo-EM structures of KISS1R bound to the endogenous agonist kisspeptin-10 and a synthetic analog TAK-448. These structures reveal pivotal interactions between peptide ligands and KISS1R extracellular loops for receptor activation. Both peptides exhibit a conserved binding mode, unveiling their common activation mechanism. Intriguingly, KISS1R displays a distinct 40° angular deviation in its intracellular TM6 region compared to other Gq-coupled receptors, enabling distinct interactions with Gq. This study reveals the molecular intricacies governing ligand binding and activation of KISS1R, while highlighting its exceptional ability to couple with Gq. Our findings pave the way for structure-guided design of therapeutics targeting this physiologically indispensable receptor.

Adipose Kiss1 controls aerobic exercise-related adaptive responses in adipose tissue energy homeostasis

Kisspeptin signaling regulates energy homeostasis. Adiposity is the principal source and receiver of peripheral Kisspeptin, and adipose Kiss1 metastasis suppressor (Kiss1) gene expression is stimulated by exercise. However, whether the adipose Kiss1 gene regulates energy homeostasis and plays a role in adaptive alterations during prolonged exercise remains unknown. Here, we investigated the role of Kiss1 role in mice and adipose tissues and the adaptive changes it induces after exercise, using adipose-specific Kiss1 knockout (Kiss1adipoq-/-) and adeno-associated virus-induced adipose tissue Kiss1-overexpressing (Kiss1adipoq over) mice. We found that adipose-derived kisspeptin signal regulates lipid and glucose homeostasis to maintain systemic energy homeostasis, but in a sex-dependent manner, with more pronounced metabolic changes in female mice. Kiss1 regulated adaptive alterations of genes and proteins in tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OxPhos) pathways in female gWAT following prolonged aerobic exercise. We could further show that adipose Kiss1 deficiency leads to reduced peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α) protein content of soleus muscle and maximum oxygen uptake (VO2 max) of female mice after prolonged exercise. Therefore, adipose Kisspeptin may be a novel adipokine that increases organ sensitivity to glucose, lipids, and oxygen following exercise.

IGF-1 Acts through Kiss1-expressing Cells to Influence Metabolism and Reproduction

Objective

Kisspeptin, encoded by the Kiss1 gene, ties puberty and fertility to energy status; however, the metabolic factors that control Kiss1-expressing cells need to be clarified.

Methods

To evaluate the impact of IGF-1 on the metabolic and reproductive functions of kisspeptin producing cells, we created mice with IGF-1 receptor deletion driven by the Kiss1 promoter (IGF1RKiss1 mice). Previous studies have shown IGF-1 and insulin can bind to each other's receptor, permitting IGF-1 signaling in the absence of IGF1R. Therefore, we also generated mice with simultaneous deletion of the IGF1R and insulin receptor (IR) in Kiss1-expressing cells (IGF1R/IRKiss1 mice).

Results

Loss of IGF1R in Kiss1 cells caused stunted body length. In addition, female IGF1RKiss1 mice displayed lower body weight and food intake plus higher energy expenditure and physical activity. This phenotype was linked to higher proopiomelanocortin (POMC) expression and heightened brown adipose tissue (BAT) thermogenesis. Male IGF1RKiss1 mice had mild changes in metabolic functions. Moreover, IGF1RKiss1 mice of both sexes experienced delayed puberty. Notably, male IGF1RKiss1 mice had impaired adulthood fertility accompanied by lower gonadotropin and testosterone levels. Thus, IGF1R in Kiss1-expressing cells impacts metabolism and reproduction in a sex-specific manner. IGF1R/IRKiss1 mice had higher fat mass and glucose intolerance, suggesting IGF1R and IR in Kiss1-expressing cells together regulate body composition and glucose homeostasis.

Conclusions

Overall, our study shows that IGF1R and IR in Kiss1 have cooperative roles in body length, metabolism, and reproduction.

Beta-Cell Tipe1 Orchestrates Insulin Secretion and Cell Proliferation by Promoting Gαs/cAMP Signaling via USP5

Inadequate β-cell mass and insulin secretion are essential for the development of type 2 diabetes (T2D). TNF-α-induced protein 8-like 1 (Tipe1) plays a crucial role in multiple diseases, however, a specific role in T2D pathogenesis remains largely unexplored. Herein, Tipe1 as a key regulator in T2D, contributing to the maintenance of β cell homeostasis is identified. The results show that the β-cell-specific knockout of Tipe1 (termed Ins2-Tipe1BKO) aggravated diabetic phenotypes in db/db mice or in mice with high-fat diet-induced diabetes. Notably, Tipe1 improves β cell mass and function, a process that depends on Gαs, the α subunit of the G-stimulating protein. Mechanistically, Tipe1 inhibited the K48-linked ubiquitination degradation of Gαs by recruiting the deubiquitinase USP5. Consequently, Gαs or cAMP agonists almost completely restored the dysfunction of β cells observed in Ins2-Tipe1BKO mice. The findings characterize Tipe1 as a regulator of β cell function through the Gαs/cAMP pathway, suggesting that Tipe1 may emerge as a novel target for T2D intervention.

Kisspeptin a potential therapeutic target in treatment of both metabolic and reproductive dysfunction

Kisspeptins (KPs) are proteins that were first recognized to have antimetastatic action. Later, the critical role of this peptide in the regulation of reproduction was proved. In recent years, evidence has been accumulated supporting a role for KPs in regulating metabolic processes in a sexual dimorphic manner. It has been proposed that KPs regulate metabolism both indirectly via gonadal hormones and/or directly via the kisspeptin receptor in the brain, brown adipose tissue, and pancreas. The aim of the review is to provide both experimental and clinical evidence indicating that KPs are peptides linking metabolism and reproduction. We propose that KPs could be used as a potential target to treat both metabolic and reproductive abnormalities. Thus, we focus on the consequences of disruptions in KPs and their receptors in metabolic conditions such as diabetes, undernutrition, obesity, and reproductive disorders (hypogonadotropic hypogonadism and polycystic ovary syndrome). Data from both animal models and human subjects indicate that alterations in KPs in the case of metabolic imbalance lead also to disruptions in reproductive functions. Changes both in the hypothalamic and peripheral KP systems in animal models of the aforementioned disorders are discussed. Finally, an overview of current clinical studies involving KP in fertility and metabolism show fewer studies on metabolism (15%) and only one to date on both. Presented data indicate a dynamic and emerging field of KP studies as possible therapeutic targets in treatments of both reproductive and metabolic dysfunctions.

Kisspeptin upregulates β-cell serotonin production during pregnancy

During pregnancy the maternal pancreatic islets of Langerhans undergo adaptive changes to compensate for gestational insulin resistance. The lactogenic hormones are well established to play a key role in regulating the islet adaptation to pregnancy, and one of the mechanisms through which they act is through upregulating β-cell serotonin production. During pregnancy islet serotonin levels are significantly elevated, where it is released from the β-cells to drive the adaptive response through paracrine and autocrine effects. We have previously shown that placental kisspeptin (KP) also plays a role in promoting the elevated insulin secretion and β-cell proliferation observed during pregnancy, although the precise mechanisms involved are unclear. In the present study we investigated the effects of KP on expression of pro-proliferative genes and serotonin biosynthesis within rodent islets. Whilst KP had limited effect on pro-proliferative gene expression at the time points tested, KP did significantly stimulate expression of the serotonin biosynthesis enzyme Tph-1. Furthermore, the islets of pregnant β-cell-specific GPR54 knockdown mice were found to contain significantly fewer serotonin-positive β-cells when compared to pregnant controls. Our previous studies suggested that reduced placental kisspeptin production, with consequent impaired kisspeptin-dependent β-cell compensation, may be a factor in the development of GDM in humans. These current data suggest that, similar to the lactogenic hormones, KP may also contribute to serotonin biosynthesis and subsequent islet signalling during pregnancy. Furthermore, upregulation of serotonin biosynthesis may represent a common mechanism through which multiple signals might influence the islet adaptation to pregnancy.

The Emerging Therapeutic Potential of Kisspeptin and Neurokinin B

Kisspeptin (KP) and neurokinin B (NKB) are neuropeptides that govern the reproductive endocrine axis through regulating hypothalamic gonadotropin-releasing hormone (GnRH) neuronal activity and pulsatile GnRH secretion. Their critical role in reproductive health was first identified after inactivating variants in genes encoding for KP or NKB signaling were shown to result in congenital hypogonadotropic hypogonadism and a failure of pubertal development. Over the past 2 decades since their discovery, a wealth of evidence from both basic and translational research has laid the foundation for potential therapeutic applications. Beyond KP's function in the hypothalamus, it is also expressed in the placenta, liver, pancreas, adipose tissue, bone, and limbic regions, giving rise to several avenues of research for use in the diagnosis and treatment of pregnancy, metabolic, liver, bone, and behavioral disorders. The role played by NKB in stimulating the hypothalamic thermoregulatory center to mediate menopausal hot flashes has led to the development of medications that antagonize its action as a novel nonsteroidal therapeutic agent for this indication. Furthermore, the ability of NKB antagonism to partially suppress (but not abolish) the reproductive endocrine axis has supported its potential use for the treatment of various reproductive disorders including polycystic ovary syndrome, uterine fibroids, and endometriosis. This review will provide a comprehensive up-to-date overview of the preclinical and clinical data that have paved the way for the development of diagnostic and therapeutic applications of KP and NKB.

Maternal cafeteria diet influences kisspeptin (Kiss1), kisspeptin receptor(Gpr54), and sirtuin (Sirt1) genes, hormonal and metabolic profiles, and reproductive functions in rat offspring in a sex-specific manner†

Kisspeptin (KP, encoded by Kiss1, binding to the Gpr54 receptor) is a neuropeptide conveying information on the metabolic status to the hypothalamic-pituitary-gonadal axis. KP acts together with dynorphin A (encoded by Pdyn) and neurokinin B (encoded by Tac2) to regulate reproduction. KP is crucial for the onset of puberty and is under the control of sirtuin (encoded by Sirt1). We hypothesize that the maternal cafeteria (CAF) diet has adverse effects on the offspring's hormonal, metabolic, and reproductive functions due to sex-specific alterations in the expression of Kiss1, Gpr54, Pdyn, Tac2, and Sirt1 in the hypothalamus, and Kiss1, Gpr54, and Sirt1 in the liver. Rats were fed a CAF diet before pregnancy, during pregnancy, and during lactation. The vaginal opening was monitored. Offspring were sacrificed in three age points: PND 30, PND 35, and PND 60 (females) and PND 40, PND 45, and PND 60 (males). Their metabolic and hormonal status was assessed. mRNA for Kiss1, Gpr54, Pdyn, Tac2, and Sirt1 were measured by real-time PCR in the hypothalamus and/or livers. We found that CAF offspring had lower weight and altered body composition; increased cholesterol and triglyceride levels, sex-specific changes in glucose and insulin levels; sex-dependent changes in Sirt1/Kiss1 mRNA ratio in the hypothalamus; sex-specific alterations in Kiss1 and Sirt1 mRNA in the liver with more diversity in males; and a delayed puberty onset in females. We concluded that the mother's CAF diet leads to sex-specific alterations in metabolic and reproductive outcomes via Kiss1/Gpr54 and Sirt1 systems in offspring.

Steatotic hepatocyte-derived extracellular vesicles promote β-cell apoptosis and diabetes via microRNA-126a-3p

Extracellular vesicles (EVs) have emerged as a unique mediator of interorgan communications, playing important roles in the pathophysiologic process of various diseases, including diabetes and other metabolic diseases. Here, we reported that the EVs released by steatotic hepatocytes exerted a detrimental effect on pancreatic β cells, leading to β-cell apoptosis and dysfunction. The effect was profoundly attributable to an up-regulation of miR-126a-3p in the steatotic hepatocyte-derived EVs. Accordingly, overexpression of miR-126a-3p promoted, whereas inhibition of miR-126a-3p prevented β-cell apoptosis, through a mechanism related to its target gene, insulin receptor substrate-2. Moreover, inhibition of miR-126a-3p by its specific antagomir was able to partially reverse the loss of β-cell mass and ameliorate hyperglycaemia in diabetic mice. Thus, the findings reveal a novel pathogenic role of steatotic hepatocyte-derived EVs, which mechanistically links nonalcoholic fatty liver disease to the development of diabetes.

Precocious Puberty: Types, Pathogenesis and Updated Management

Precocious puberty (PP) means the appearance of secondary sexual characters before the age of eight years in girls and nine years in boys. Puberty is indicated in girls by the enlargement of the breasts (thelarche) in girls and in boys by the enlargement of the testes in either volume or length (testicular volume = 4 mL, testicular length = 25 mm, or both). Two types of PP are recognized - namely central PP (CPP) and peripheral PP (PPP). This paper aims to describe the clinical findings and laboratory workup of PP and to illustrate the new trends in the management of precocious sexual maturation. Gonadotropin-releasing hormone (GnRH)-independent type (PPP) refers to the development of early pubertal maturation not related to the central activation of the hypothalamic-pituitary-gonadal (HPG) axis. It is classified into genetic or acquired disorders. The most common forms of congenital or genetic causes involve McCune-Albright syndrome (MAS), familial male-limited PP, and congenital adrenal hyperplasia. The acquired causes include exogenous exposure to androgens, functioning tumors or cysts, and the pseudo-PP of profound primary hypothyroidism. On the other hand, CPP is the most common and it is a gonadotropin-dependent form. It is due to premature maturation of the HPG axis. CPP may occur as genetic alterations, such as MKRN3, DLK1, or KISS1;as a part of mutations in the epigenetic factors that regulate the HPG axis, such as Lin28b and let-7; or as a part of syndromes, central lesions such as hypothalamic hamartoma, and others. A full, detailed history and physical examination should be taken. Furthermore, several investigations should be conducted for both types of PP, including the estimation of serum gonadotropins such as luteinizing and follicle-stimulating hormones and sex steroids, in addition to a radiographic workup and thyroid function tests. Treatment depends on the type of PP: Long-acting GnRHa, either intramuscularly or implanted, is the norm of care for CPP management, while in PPP, especially in congenital adrenal hyperplasia, the goal of management is to suppress adrenal androgen secretion by glucocorticoids. In addition, anastrozole and letrozole - third-generation aromatase inhibitors - are more potent for MAS.

Practical therapeutic approach in the management of diabetes mellitus secondary to Cushing's syndrome, acromegaly and neuroendocrine tumours

Cushing's syndrome, acromegaly and neuroendocrine disorders are characterized by an excess of counterregulatory hormones, able to induce insulin resistance and glucose metabolism disorders at variable degrees and requiring immediate treatment, until patients are ready to undergo surgery. This review focuses on the management of diabetes mellitus in endocrine disorders related to an excess of counterregulatory hormones. Currently, the landscape of approved agents for treatment of diabetes is dynamic and is mainly patient-centred and not glycaemia-centred. In addition, personalized medicine is more and more required to provide a precise approach to the patient's disease. For this reason, we aimed to define a practical therapeutic algorithm for management of diabetes mellitus in patients with glucagonoma, pheochromocytoma, Cushing's syndrome and acromegaly, based on our practical experience and on the physiopathology of the specific endocrine disease taken into account. This document is addressed to all specialists who approach patients with diabetes mellitus secondary to endocrine disorders characterized by an excess of counterregulatory hormones, in order to take better care of these patients. Care and control of diabetes mellitus should be one of the primary goals in patients with an excess of counterregulatory hormones requiring immediate and aggressive treatment.

Deletion of GABAB receptors from Kiss1 cells affects glucose homeostasis without altering reproduction in male mice

Kisspeptin and γ-amino butyric acid (GABA), synthesized in the central nervous system, are critical for reproduction. Both are also expressed in peripheral organs/tissues critical to metabolic control (liver/pancreas/adipose). Many kisspeptin neurons coexpress GABAB receptors (GABABR) and GABA controls kisspeptin expression and secretion. We developed a unique mouse lacking GABABR exclusively from kisspeptin cells/neurons (Kiss1-GABAB1KO) to evaluate the impact on metabolism/reproduction. We confirmed selective deletion of GABABR from Kiss1 cells in the anteroventral periventricular nucleus/periventricular nucleus continuum (AVPV/PeN; immunofluorescence and PCR) and arcuate nucleus (ARC), medial amygdala (MeA), pituitary, liver, and testes (PCR). Young Kiss1-GABAB1KO males were fertile, with normal LH and testosterone. Kiss1 expression was similar between genotypes in AVPV/PeN, ARC, MeA, bed nucleus of the stria terminalis (BNST), and peripheral organs (testis, liver, pituitary). Kiss1-GABAB1KO males presented higher fasted glycemia and insulin levels, an impaired response to a glucose overload, reduced insulin sensitivity, and marked insulin resistance. Interestingly, when Kiss1-GABAB1KO males got older (9 mo old) their body weight (BW) increased, in part due to an increase in white adipose tissue (WAT). Old Kiss1-GABAB1KO males showed higher fasted insulin, increased pancreatic insulin content, insulin resistance, and significantly decreased pancreatic kisspeptin levels. In sum, lack of GABABR specifically in Kiss1 cells severely impacts glucose homeostasis in male mice, reinforcing kisspeptin involvement in metabolic regulation. These alterations in glucose homeostasis worsened with aging. We highlight the impact of GABA through GABABR in the regulation of the pancreas kisspeptin system in contrast to liver kisspeptin that was not affected.NEW & NOTEWORTHY We developed a unique mouse lacking GABAB receptors specifically in Kiss1 cells to evaluate the impact on reproduction and metabolism. Knockout males showed a severe impact on glucose homeostasis, which worsened with aging. These results reinforce the proposed kisspeptin involvement in metabolic regulation and highlight the impact of GABA through GABABR in the regulation of the peripheral pancreas kisspeptin system.

Liver-Derived S100A6 Propels β-Cell Dysfunction in NAFLD

Nonalcoholic fatty liver disease (NAFLD) is an independent predictor of systemic insulin resistance and type 2 diabetes mellitus (T2DM). However, converse correlates between excess liver fat content and β-cell function remain equivocal. Specifically, how the accumulation of liver fat consequent to the enhanced de novo lipogenesis (DNL) leads to pancreatic β-cell failure and eventually to T2DM is elusive. Here, we have identified that low-molecular-weight calcium-binding protein S100A6, or calcyclin, inhibits glucose-stimulated insulin secretion (GSIS) from β cells through activation of the receptor for the advanced glycation end products and diminution of mitochondrial respiration. Serum S100A6 level is elevated both in human patients with NAFLD and in a high-fat diet-induced mouse model of NAFLD. Although serum S100A6 levels are negatively associated with β-cell insulin secretory capacity in human patients, depletion of hepatic S100A6 improves GSIS and glycemia in mice, suggesting that S100A6 contributes to the pathophysiology of diabetes in NAFLD. Moreover, transcriptional induction of hepatic S100A6 is driven by the potent regulator of DNL, carbohydrate response element-binding protein (ChREBP), and ectopic expression of ChREBP in the liver suppresses GSIS in a S100A6-sensitive manner. Together, these data suggest elevated serum levels of S100A6 may serve as a biomarker in identifying patients with NAFLD with a heightened risk of developing β-cell dysfunction. Overall, our data implicate S100A6 as, to our knowledge, a hitherto unknown hepatokine to be activated by ChREBP and that participates in the hepato-pancreatic communication to impair insulin secretion and drive the development of T2DM in NAFLD.

DNA hypermethylation of Kiss1r promoter and reduction of hepatic Kiss1r in female rats with type 2 diabetes

Kisspeptin, produced from the brain and peripheral tissues, may constitute an important link in metabolic regulation in response to external cues, such as diet. The kisspeptin system is well described in the brain. However, its function and regulation in the peripheral tissues, especially in relation to metabolic disease and sex differences, remain to be elucidated. As Kiss1 and Kiss1r, encoding for kisspeptin and kisspeptin receptors, respectively, are altered by overnutrition/fasting and regulated by DNA methylation during puberty and cancer, epigenetic mechanisms in metabolic disorders are highly probable. In the present study, we experimentally induced type 2 diabetes mellitus (DM2) in female Wistar rats using high-fat diet/streptozocin. We analysed expression and DNA methylation of Kiss1 and Kiss1r in the peripheral tissues, using quantitative-reverse-transcription PCR (qRT-PCR) and pyrosequencing. We discovered differential expression of Kiss1 and Kiss1r in peripheral organs in DM2 females, as compared with healthy controls, and the profile differed from patterns reported earlier in males. DM2 in females was linked to the increased Kiss1 mRNA in the liver and increased Kiss1r mRNA in the liver and adipose tissue. However, Kiss1r promoter was hypermethylated in the liver, suggesting gene silencing. Indeed, the increase in DNA methylation of Kiss1r promoter was accompanied by a reduction in Kiss1r protein, implying epigenetic or translational gene repression. Our results deliver novel evidence for tissue-specific differences in Kiss1 and Kiss1r expression in peripheral organs in DM2 females and suggest DNA methylation as a player in regulation of the hepatic kisspeptin system in DM2.

The role of Kisspeptin signaling in Oocyte maturation

Kisspeptins (KPs) secreted from the hypothalamic KP neurons act on KP receptors (KPRs) in gonadotropin (GPN) releasing hormone (GnRH) neurons to produce GnRH. GnRH acts on pituitary gonadotrophs to induce secretion of GPNs, namely follicle stimulating hormone (FSH) and luteinizing hormone (LH), which are essential for ovarian follicle development, oocyte maturation and ovulation. Thus, hypothalamic KPs regulate oocyte maturation indirectly through GPNs. KPs and KPRs are also expressed in the ovarian follicles across species. Recent studies demonstrated that intraovarian KPs also act directly on the KPRs expressed in oocytes to promote oocyte maturation and ovulation. In this review article, we have summarized published reports on the role of hypothalamic and ovarian KP-signaling in oocyte maturation. Gonadal steroid hormones regulate KP secretion from hypothalamic KP neurons, which in turn induces GPN secretion from the hypothalamic-pituitary (HP) axis. On the other hand, GPNs secreted from the HP axis act on the granulosa cells (GCs) and upregulate the expression of ovarian KPs. While KPs are expressed predominantly in the GCs, the KPRs are in the oocytes. Expression of KPs in the ovaries increases with the progression of the estrous cycle and peaks during the preovulatory GPN surge. Intrafollicular KP levels in the ovaries rise with the advancement of developmental stages. Moreover, loss of KPRs in oocytes in mice leads to failure of oocyte maturation and ovulation similar to that of premature ovarian insufficiency (POI). These findings suggest that GC-derived KPs may act on the KPRs in oocytes during their preovulatory maturation. In addition to the intraovarian role of KP-signaling in oocyte maturation, in vivo, a direct role of KP has been identified during in vitro maturation of sheep, porcine, and rat oocytes. KP-stimulation of rat oocytes, in vitro, resulted in Ca2+ release and activation of the mitogen-activated protein kinase, extracellular signal-regulated kinase 1 and 2. In vitro treatment of rat or porcine oocytes with KPs upregulated messenger RNA levels of the factors that favor oocyte maturation. In clinical trials, human KP-54 has also been administered successfully to patients undergoing assisted reproductive technologies (ARTs) for increasing oocyte maturation. Exogenous KPs can induce GPN secretion from hypothalamus; however, the possibility of direct KP action on the oocytes cannot be excluded. Understanding the direct in vivo and in vitro roles of KP-signaling in oocyte maturation will help in developing novel KP-based ARTs.

Socs3 ablation in kisspeptin cells partially prevents lipopolysaccharide-induced body weight loss

Many cytokines have been proposed to regulate reproduction due to their actions on hypothalamic kisspeptin cells, the main modulators of gonadotropin-releasing hormone (GnRH) neurons. Hormones such as leptin, prolactin and growth hormone are good examples of cytokines that lead to Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway activation, consequently exerting effects in kisspeptin neurons. Different studies have investigated how specific components of the JAK/STAT signaling pathway affect the functions of kisspeptin cells, but the role of the suppressor of cytokine signaling 3 (SOCS3) in mediating cytokine actions in kisspeptin cells remains unknown. Cre-Loxp technology was used in the present study to ablate Socs3 expression in kisspeptin cells (Kiss1/Socs3-KO). Then, male and female control and Kiss1/Socs3-KO mice were evaluated for sexual maturation, energy homeostasis features, and fertility. It was found that hypothalamic Kiss1 mRNA expression is significantly downregulated in Kiss1/Socs3-KO mice. Despite reduced hypothalamic Kiss1 mRNA content, these mice did not present any sexual maturation or fertility impairments. Additionally, body weight gain, leptin sensitivity and glucose homeostasis were similar to control mice. Interestingly, Kiss1/Socs3-KO mice were partially protected against lipopolysaccharide (LPS)-induced body weight loss. Our results suggest that Socs3 ablation in kisspeptin cells partially prevents the sickness behavior induced by LPS, suggesting that kisspeptin cells can modulate energy metabolism in mice in certain situations.

Targeting hepatic kisspeptin receptor ameliorates nonalcoholic fatty liver disease in a mouse model

Nonalcoholic fatty liver disease (NAFLD), the most common liver disease, has become a silent worldwide pandemic. The incidence of NAFLD correlates with the rise in obesity, type 2 diabetes, and metabolic syndrome. A hallmark featureof NAFLD is excessive hepatic fat accumulation or steatosis, due to dysregulated hepatic fat metabolism, which can progress to nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Currently, there are no approved pharmacotherapies to treat this disease. Here, we have found that activation of the kisspeptin 1 receptor (KISS1R) signaling pathway has therapeutic effects in NAFLD. Using high-fat diet-fed mice, we demonstrated that a deletion of hepatic Kiss1r exacerbated hepatic steatosis. In contrast, enhanced stimulation of KISS1R protected against steatosis in wild-type C57BL/6J mice and decreased fibrosis using a diet-induced mouse model of NASH. Mechanistically, we found that hepatic KISS1R signaling activates the master energy regulator, AMPK, to thereby decrease lipogenesis and progression to NASH. In patients with NAFLD and in high-fat diet-fed mice, hepatic KISS1/KISS1R expression and plasma kisspeptin levels were elevated, suggesting a compensatory mechanism to reduce triglyceride synthesis. These findings establish KISS1R as a therapeutic target to treat NASH.

Lower FSH With Normal Fertility in Male Mice Lacking Gonadotroph Kisspeptin Receptor

The kisspeptin receptor, crucial for hypothalamic control of puberty and reproduction, is also present in the pituitary gland. Its role in the pituitary gland is not defined. Kisspeptin signaling via the Kiss1r could potentially regulate reproductive function at the level of pituitary gonadotrope. Using Cre/Lox technology, we deleted the Kiss1r gene in pituitary gonadotropes (PKiRKO). PKiRKO males have normal genital development (anogenital distance WT: 19.1 ± 0.4 vs. PKiRKO: 18.5 ± 0.4 mm), puberty onset, testes cell structure on gross histology, normal testes size, and fertility. PKiRKO males showed significantly decreased serum FSH levels compared to WT males (5.6 ± 1.9 vs. 10.2 ± 1.8 ng/ml) with comparable LH (1.1 ± 0.2 vs. 1.8 ± 0.4 ng/ml) and testosterone levels (351.8 ± 213.0 vs. 342.2 ± 183.0 ng/dl). PKiRKO females have normal puberty onset, cyclicity, LH and FSH levels and fertility. Overall, these findings indicate that absence of pituitary Kiss1r reduces FSH levels in male mice without affecting testis function. PKiRKO mice have normal reproductive function in both males and females.

Sexual Dimorphism in Kisspeptin Signaling

Kisspeptin (KP) and kisspeptin receptor (KPR) are essential for the onset of puberty, development of gonads, and maintenance of gonadal function in both males and females. Hypothalamic KPs and KPR display a high degree of sexual dimorphism in expression and function. KPs act on KPR in gonadotropin releasing hormone (GnRH) neurons and induce distinct patterns of GnRH secretion in males and females. GnRH acts on the anterior pituitary to secrete gonadotropins, which are required for steroidogenesis and gametogenesis in testes and ovaries. Gonadal steroid hormones in turn regulate the KP neurons. Gonadal hormones inhibit the KP neurons within the arcuate nucleus and generate pulsatile GnRH mediated gonadotropin (GPN) secretion in both sexes. However, the numbers of KP neurons in the anteroventral periventricular nucleus and preoptic area are greater in females, which release a large amount of KPs in response to a high estrogen level and induce the preovulatory GPN surge. In addition to the hypothalamus, KPs and KPR are also expressed in various extrahypothalamic tissues including the liver, pancreas, fat, and gonads. There is a remarkable difference in circulating KP levels between males and females. An increased level of KPs in females can be linked to increased numbers of KP neurons in female hypothalamus and more KP production in the ovaries and adipose tissues. Although the sexually dimorphic features are well characterized for hypothalamic KPs, very little is known about the extrahypothalamic KPs. This review article summarizes current knowledge regarding the sexual dimorphism in hypothalamic as well as extrahypothalamic KP and KPR system in primates and rodents.

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.

Kisspeptin impacts on circadian and ultradian rhythms of core body temperature: Evidence in kisspeptin receptor knockout and kisspeptin knockdown mice

Kisspeptin is vital for the regulation of both fertility and metabolism. Kisspeptin receptor (Kiss1r) knockout (KO) mice exhibit increased adiposity and reduced energy expenditure in adulthood. Kiss1r mRNA is expressed in brown adipose tissue (BAT) and Kiss1r KO mice exhibit reduced Ucp1 mRNA in BAT and impaired thermogenesis. We hypothesised that mice with diminished kisspeptin signalling would exhibit reduced core body temperature (Tc) and altered dynamics of circadian and ultradian rhythms of Tc. Tc was recorded every 15-min over 14-days in gonadectomised wild-type (WT), Kiss1r KO, and also Kiss1-Cre (95% reduction in Kiss1 transcription) mice. Female Kiss1r KOs had higher adiposity and lower Ucp1 mRNA in BAT than WTs. No change was detected in Kiss1-Cre mice. Mean Tc during the dark phase was lower in female Kiss1r KOs versus WTs, but not Kiss1-Cre mice. Female Kiss1r KOs had a lower mesor and amplitude of the circadian rhythm of Tc than did WTs. In WT mice, there were more episodic ultradian events (EUEs) of Tc during the dark phase than the light phase, but this measure was similar between dark and light phases in Kiss1r KO and Kiss1-Cre mice. The amplitude of EUEs was higher in the dark phase in female Kiss1r KO and male Kiss1-Cre mice. Given the lack of clear metabolic phenotype in Kiss1-Cre mice, 5% of Kiss1 transcription may be sufficient for proper metabolic control, as was shown for fertility. Moreover, the observed alterations in Tc suggest that kisspeptin has a role in circadian and ultradian rhythm-driven pathways.

Conserved functions of hypothalamic kisspeptin in vertebrates

Hypothalamic kisspeptin encoded by KISS1/Kiss1 gene emerged as a regulator of the reproductive axis in mammals following the discovery of the kisspeptin receptor (Kissr) and its role in reproduction. Kisspeptin-Kissr systems have been investigated in various vertebrates, and a conserved sequence of kisspeptin-Kissr has been identified in most vertebrate species except in the avian linage. In addition, multiple paralogs of kisspeptin sequences have been identified in the non-mammalian vertebrates. The allegedly conserved role of kisspeptin-Kissr in reproduction became debatable when kiss/kissr genes-deficient zebrafish and medaka showed no apparent effect on the onset of puberty, sexual development, maturation and reproductive capacity. Therefore, it is questionable whether the role of kisspeptin in reproduction is conserved among vertebrate species. Here we discuss from a comparative and evolutional aspect the diverse functions of kisspeptin and its receptor in vertebrates. Primarily this review focuses on the role of hypothalamic kisspeptin in reproductive and non-reproductive functions that are conserved in vertebrate species.

The mitochondrial β-oxidation enzyme HADHA restrains hepatic glucagon response by promoting β-hydroxybutyrate production

Disordered hepatic glucagon response contributes to hyperglycemia in diabetes. The regulators involved in glucagon response are less understood. This work aims to investigate the roles of mitochondrial β-oxidation enzyme HADHA and its downstream ketone bodies in hepatic glucagon response. Here we show that glucagon challenge impairs expression of HADHA. Liver-specific HADHA overexpression reversed hepatic gluconeogenesis in mice, while HADHA knockdown augmented glucagon response. Stable isotope tracing shows that HADHA promotes ketone body production via β-oxidation. The ketone body β-hydroxybutyrate (BHB) but not acetoacetate suppresses gluconeogenesis by selectively inhibiting HDAC7 activity via interaction with Glu543 site to facilitate FOXO1 nuclear exclusion. In HFD-fed mice, HADHA overexpression improved metabolic disorders, and these effects are abrogated by knockdown of BHB-producing enzyme. In conclusion, BHB is responsible for the inhibitory effect of HADHA on hepatic glucagon response, suggesting that HADHA activation or BHB elevation by pharmacological intervention hold promise in treating diabetes.

Interorgan crosstalk in pancreatic islet function and pathology

Pancreatic β cells secrete insulin in response to glucose, a process that is regulated at multiple levels, including a network of input signals from other organ systems. Impaired islet function contributes to the pathogenesis of type 2 diabetes mellitus (T2DM), and targeting inter-organ communications, such as GLP-1 signalling, to enhance β-cell function has been proven to be a successful therapeutic strategy in the last decade. In this review, we will discuss recent advances in inter-organ communication from the metabolic, immune and neural system to pancreatic islets, their biological implication in normal pancreas endocrine function and their role in the (mal)adaptive responses of islet to nutrition-induced stress.

Multi-Organ Crosstalk with Endocrine Pancreas: A Focus on How Gut Microbiota Shapes Pancreatic Beta-Cells

Type 2 diabetes (T2D) results from impaired beta-cell function and insufficient beta-cell mass compensation in the setting of insulin resistance. Current therapeutic strategies focus their efforts on promoting the maintenance of functional beta-cell mass to ensure appropriate glycemic control. Thus, understanding how beta-cells communicate with metabolic and non-metabolic tissues provides a novel area for investigation and implicates the importance of inter-organ communication in the pathology of metabolic diseases such as T2D. In this review, we provide an overview of secreted factors from diverse organs and tissues that have been shown to impact beta-cell biology. Specifically, we discuss experimental and clinical evidence in support for a role of gut to beta-cell crosstalk, paying particular attention to bacteria-derived factors including short-chain fatty acids, lipopolysaccharide, and factors contained within extracellular vesicles that influence the function and/or the survival of beta cells under normal or diabetogenic conditions.

Effects of empagliflozin on the expression of kisspeptin gene and reproductive system function in streptozotocin-induced diabetic male rats

One of the main health concerns of diabetes is testicular dysfunction and impairment of reproductive function and sperm quality which can cause male infertility. kisspeptin is a hypothalamic neuropeptide hormone that is involved in the regulation of energy metabolism, gonadotrophin-releasing hormone (GnRH), and reproductive function. In the present study, the therapeutic effects of empagliflozin (sodium-glucose co-transporter 2 inhibitors) on kisspeptin expression along with reproductive function were investigated in diabetic male Wistar rats. Diabetes was induced by a single dose injection of 60 mg/kg streptozotocin. Empagliflozin in doses of 10 and 25 mg/kg body weight was used for 8 weeks. Serum samples, testis, epididymis, and pancreas tissues were collected at the end of the experiments. Lipid profiles, oxidative stress markers, blood hormones, expression of kisspeptin along with pathological alterations of the testis were assayed using real-time PCR, biochemical, and histological technics. Data have shown that empagliflozin improved hyperglycemia, reproductive impairment, oxidative stress condition, and histopathological alterations of pancreatic and testis tissues in diabetic animals. It improved the serum levels of sex hormones, insulin, leptin, and the expression of kisspeptin in the testes tissues. Spermatogenesis is also improved in treated animals. Data indicated that the administration of empagliflozin can ameliorate symptoms of diabetes. It probably has promising antidiabetic potential and may improve the male infertility of diabetic subjects. To our knowledge, this is the first experimental evidence for the potential impact of empagliflozin on kisspeptin expression in diabetic male rats.

Metabolic effects of prolactin and the role of dopamine agonists: A review

Prolactin is a polypeptide hormone that is well known for its role in reproductive physiology. Recent studies highlight its role in neurohormonal appetite regulation and metabolism. Elevated prolactin levels are widely associated with worsening metabolic disease, but it appears that low prolactin levels could also be metabolically unfavorable. This review discusses the pathophysiology of prolactin related metabolic changes, and the less commonly recognized effects of prolactin on adipose tissue, pancreas, liver, and small bowel. Furthermore, the effect of dopamine agonists on the metabolic profiles of patients with hyperprolactinemia are discussed as well.

Long-term effectiveness and safety of quadruple combination therapy with empagliflozin versus dapagliflozin in patients with type 2 diabetes: 3-year prospective observational study

AIMS

To investigate the long-term effectiveness and safety of two distinct sodium-glucose co-transporter 2 (SGLT2) inhibitors, empagliflozin and dapagliflozin, in inadequately controlled type 2 diabetes (T2D) despite a combined administration of metformin, glimepiride and dipeptidyl peptidase-4 inhibitor.

METHODS

A total of 362 patients with T2D were enrolled for this 3-year open-label, prospective observational study. Empagliflozin (25 mg/day, n = 185) or dapagliflozin (10 mg/day, n = 177) was added to the existing triple drug regimen. HbA1c, fasting plasma glucose (FPG), body weight, and other cardiometabolic variables and adverse events were evaluated.

RESULTS

At 3 years, changes in HbA1c and FPG were -1.7% (standard error [SE] 0.10) and -60.0 mg/dL(2.2), and -1.1%(0.12) and -48.1 mg/dL(3.6), for empagliflozin and dapagliflozin group, respectively (P = 0.001 and P = 0.055). Empagliflozin group showed significantly greater body weight reduction (-4.5 kg [SE 0.35] vs. -1.0 kg [SE 0.40], P = 0.024) and had beneficial effects on HDL cholesterol and LDL cholesterol (both P < 0.05). The overall incidence of adverse events, cardiovascular events and mortality did not differ between the two groups.

CONCLUSIONS

Quadruple combination therapy with either empagliflozin or dapagliflozin showed a positive long-term effect in the glycemic control and body weight reduction with generally well tolerance. In general, the use of empagliflozin performed better than dapagliflozin. Clinical Trial Number NCT03748810 (ClinicalTrials.gov).

Deletion of Stim1 in Hypothalamic Arcuate Nucleus Kiss1 Neurons Potentiates Synchronous GCaMP Activity and Protects against Diet-Induced Obesity

Kisspeptin (Kiss1) neurons are essential for reproduction, but their role in the control of energy balance and other homeostatic functions remains unclear. High-frequency firing of hypothalamic arcuate Kiss1 (Kiss1^ARH) neurons releases kisspeptin into the median eminence, and neurokinin B (NKB) and dynorphin onto neighboring Kiss1^ARH neurons to generate a slow EPSP mediated by TRPC5 channels that entrains intermittent, synchronous firing of Kiss1^ARH neurons. High-frequency optogenetic stimulation of Kiss1^ARH neurons also releases glutamate to excite the anorexigenic proopiomelanocortin (POMC) neurons and inhibit the orexigenic neuropeptide Y/agouti-related peptide (AgRP) neurons via metabotropic glutamate receptors. At the molecular level, the endoplasmic reticulum (ER) calcium-sensing protein stromal interaction molecule 1 (STIM1) is critically involved in the regulation of neuronal Ca²⁺ signaling and neuronal excitability through its interaction with plasma membrane (PM) calcium (e.g., TRPC) channels. Therefore, we hypothesized that deletion of Stim1 in Kiss1^ARH neurons would increase neuronal excitability and their synchronous firing, which ultimately would affect energy homeostasis. Using optogenetics in combination with whole-cell recording and GCaMP6 imaging in slices, we discovered that deletion of Stim1 in Kiss1 neurons significantly increased the amplitude and duration of the slow EPSP and augmented synchronous [Ca²⁺]i oscillations in Kiss1^ARH neurons. Deletion of Stim1 in Kiss1^ARH neurons amplified the actions of NKB and protected ovariectomized female mice from developing obesity and glucose intolerance with high-fat dieting (HFD). Therefore, STIM1 appears to play a critical role in regulating synchronous firing of Kiss1^ARH neurons, which ultimately affects the coordination between energy homeostasis and reproduction.SIGNIFICANCE STATEMENT Hypothalamic arcuate kisspeptin (Kiss1^ARH) neurons are essential for stimulating the pulsatile release of gonadotropin-releasing hormone (GnRH) and maintaining fertility. However, Kiss1^ARH neurons appear to be a key player in coordinating energy balance with reproduction. The regulation of calcium channels and hence calcium signaling is critically dependent on the endoplasmic reticulum (ER) calcium-sensing protein stromal interaction molecule 1 (STIM1), which interacts with the plasma membrane (PM) calcium channels. We have conditionally deleted Stim1 in Kiss1^ARH neurons and found that it significantly increased the excitability of Kiss1^ARH neurons and protected ovariectomized female mice from developing obesity and glucose intolerance with high-fat dieting (HFD).

Gut microbiota-a positive contributor in the process of intermittent fasting-mediated obesity control

Historically, intermittent fasting (IF) has been considered as an effective strategy for controlling the weight of athletes before competition. Along with excellent insight into its application in various spaces by numerous studies, increasing IF-mediated positive effects have been reported, including anti-aging, neuroprotection, especially obesity control. Recently, the gut microbiota has been considered as an essential manipulator for host energy metabolism and its structure has been reported to be sensitive to dietary structure and habits, indicating that there is a potential and strong association between IF and gut microbiota. In this paper, we focus on the crosstalk between these symbionts and energy metabolism during IF which hold the promise to optimize host energy metabolism at various physical positions, including adipose tissue, liver and intestines, and further improve milieu internal homeostasis. Moreover, this paper also discusses the positive function of a potential recommendatory strain (Akkermansia muciniphila) based on the observational data for IF-mediated alternated pattern of gut microbiota and a hopefully regulatory pathway (circadian rhythm) for gut microbiota in IF-involved improvement on host energy metabolism. Finally, this review addresses the limitation and perspective originating from these studies, such as the association with tissue-specific bio-clock and single strain research, which may continuously reveal novel viewpoints and mechanisms to understand the energy metabolism and develop new strategies for treating obesity, diabetes, and metabolic disorders.

Clinical and biochemical characteristics and analysis of risk factors for euglycaemic diabetic ketoacidosis in type 2 diabetic individuals treated with SGLT2 inhibitors: A review of 72 cases over a 4.5-year period

BACKGROUND AND AIMS

To study euglycemic diabetic ketoacidosis (euDKA) outcomes associated with sodium-glucose co-transporter 2 inhibitors (SGLT2is) METHODS: Review of 72 euDKA cases in T2DM between September 2015 and January 2020 (PUBMED).

RESULTS

euDKA could occur at any time during SGLT2is treatment, with nausea, abdominal pain and vomiting as main symptoms. Hyperglycemia did not correlate with pH and β-hydroxybutyrates. Low pH and high β-hydroxybutyrates were significantly associated with euDKA. In biguanides users, acidosis was unrelated to lactic acidosis. euDKA occurred during fasting, surgery, acute infection, insulin deprivation (endogenous or exogenous).

CONCLUSIONS

These data support avoidance of euDKA risk states in SGLT2i users.

Emerging roles of kisspeptin/galanin in age-related metabolic disease

Age is a major risk factor for developing metabolic diseases such as obesity and diabetes. There is an unprecedented rise in obesity and type 2 diabetes in recent decades. A convincing majority of brain-gut peptides are associated with a higher risk to develop metabolic disorders, and may contribute to the pathophysiology of age-related metabolic diseases. Accumulating basic studies revealed an intriguing role of kisspeptin and galanin involved in the amelioration of insulin resistance in different ways. In patients suffered from obesity and diabetes a significant, sex-related changes in the plasma kisspeptin and galanin levels occurred. Kisspeptin is anorexigenic to prevent obesity, its level is negatively correlative with obesity and insulin resistance. While galanin is appetitive to stimulate food intake and body weight, its level is positively correlative with obesity, HOMA-IR and glucose/triglyceride concentration. In turn, kisspeptin and galanin also distinctly increase glucose uptake and utilization as well as energy expenditure. This article reviews recent evidence dealing with the role of kisspeptin and galanin in the pathophysiology of age-related metabolic diseases. It should be therefore taken into account that the targeted modulation of those peptidergic signaling may be potentially helpful in the future treatment of age-related metabolic diseases.

Uterine kisspeptin receptor critically regulates epithelial estrogen receptor α transcriptional activity at the time of embryo implantation in a mouse model

Embryo implantation failure is a major cause of infertility in women of reproductive age and a better understanding of uterine factors that regulate implantation is required for developing effective treatments for female infertility. This study investigated the role of the uterine kisspeptin receptor (KISS1R) in the molecular regulation of implantation in a mouse model. To conduct this study, a conditional uterine knockout (KO) of Kiss1r was created using the Pgr-Cre (progesterone receptor-CRE recombinase) driver. Reproductive profiling revealed that while KO females exhibited normal ovarian function and mated successfully to stud males, they exhibited significantly fewer implantation sites, reduced litter size and increased neonatal mortality demonstrating that uterine KISS1R is required for embryo implantation and a healthy pregnancy. Strikingly, in the uterus of Kiss1r KO mice on day 4 (D4) of pregnancy, the day of embryo implantation, KO females exhibited aberrantly elevated epithelial ERα (estrogen receptor α) transcriptional activity. This led to the temporal misexpression of several epithelial genes [Cftr (Cystic fibrosis transmembrane conductance regulator), Aqp5 (aquaporin 5), Aqp8 (aquaporin 8) and Cldn7 (claudin 7)] that mediate luminal fluid secretion and luminal opening. As a result, on D4 of pregnancy, the lumen remained open disrupting the final acquisition of endometrial receptivity and likely accounting for the reduction in implantation events. Our data clearly show that uterine KISS1R negatively regulates ERα signaling at the time of implantation, in part by inhibiting ERα overexpression and preventing detrimentally high ERα activity. To date, there are no reports on the regulation of ERα by KISS1R; therefore, this study has uncovered an important and powerful regulator of uterine ERα during early pregnancy.

Insulin resistance and potential modulators of ovarian reserve in young reproductive-aged women with obesity and type 1 diabetes

INTRODUCTION

Both obesity and diabetes play a significant role in reproductive disorders in women and insulin resistance (IR) is a confirmed trait d'union. We evaluated the relationship between IR and an established ovarian reserve biomarker such as anti-mullerian hormone (AMH) together with other potential modulators of ovarian physiology (adiponectin and kisspeptin) in young reproductive-aged group women with obesity and type 1 diabetes (T1D).

PATIENTS AND METHODS

We recruited 32 female youths: 14 of them presented with T1D (14.6 ± 2.6 years) and 18 with obesity (15.1 ± 2.6 years). The control group included 20 age-matched normal weight females. Each patient underwent physical examination and hormonal assessment. AMH, kisspeptin and adiponectin levels were also measured. IR was calculated as the homeostasis model assessment for insulin resistance (HOMA-IR) and the glucose disposal rate (eGDR) in patients with obesity and with T1D, respectively.

RESULTS

adiponectin and kisspeptin levels were significantly different into groups (p ≤ .001), whereas AMH levels were not. Adiponectin values were higher in controls compared to patients with obesity (p < .001) and T1D (p = .02). Kisspeptin levels were lower in controls compared to patients with obesity (p = .001), without reaching statistical significance when compared to T1D (p = .06). IR was associated with lower adiponectin and higher kisspeptin levels (p < .001 and p = .02, respectively), but not with AMH.

CONCLUSIONS

IR displays a relationship with adiponectin and kisspeptin in young reproductive-aged women with obesity and T1D. Interventions to correct IR in adolescents could be part of an early approach to prevent reproductive disorders and to promote factors associated with longevity in adult women.

Polycystic οvary syndrome revisited: An interactions network approach

BACKGROUND

The polycystic ovary syndrome (PCOS) has genetic, epigenetic, metabolic and reproductive aspects, while its complex pathophysiology has not been conclusively deciphered.

AIM

The goal of this research was to screen the gene/gene products associated with PCOS and to predict any possible interactions with the highest possible fidelity.

MATERIALS AND METHODS

STRING v10.5 database and a confidence level of 0.7 were used.

RESULTS

A highly interconnected network of 48 nodes was created, where insulin (INS) appears to be the major hub. INS upstream and downstream defects were analysed and revealed that only the kisspeptin- and glucagon-coding genes were upstream of INS.

CONCLUSION

A metabolic dominance was inferred and discussed herein with its implications in puberty, obesity, infertility and cardiovascular function. This study, thus, may contribute to the resolution of a scientific conflict between the USA and EU definitions of the syndrome and/or provide a new P4 medicine approach.

Case of sodium-glucose cotransporter-2 inhibitor-associated euglycaemic diabetic ketoacidosis

Following non-elective orthopaedic surgery, a 61-year-old man with poorly controlled type 2 diabetes mellitus on empagliflozin developed high anion gap metabolic acidosis in the high-dependency unit. Metabolic acidosis persisted despite intravenous sodium bicarbonate, contributing to tachycardia and a run of non-sustained ventricular tachycardia. He was euglycaemic throughout hospital admission. Investigations revealed elevated urine and capillary ketones, and a diagnosis of sodium-glucose cotransporter-2 inhibitor-associated euglycaemic diabetic ketoacidosis was made. He was treated with an intravenous sliding scale insulin infusion and concurrent dextrose 5% with potassium chloride. Within 24 hours of treatment, his arterial pH, anion gap and serum bicarbonate levels normalised. After a further 12 hours, the intravenous insulin infusion was converted to a basal/bolus regimen of subcutaneous insulin, and he was transferred to the general ward. He was discharged well on subcutaneous insulin 6 days postoperatively.

Euglycemic Ketoacidosis as a Complication of SGLT2 Inhibitor Therapy

Sodium-glucose cotransporter-2 (SGLT2) inhibitors are drugs designed to lower plasma glucose concentration by inhibiting Na+-glucose-coupled transport in the proximal tubule. Clinical trials demonstrate these drugs have favorable effects on cardiovascular outcomes to include slowing the progression of CKD. Although most patients tolerate these drugs, a potential complication is development of ketoacidosis, often with a normal or only a minimally elevated plasma glucose concentration. Inhibition of sodium-glucose cotransporter-2 in the proximal tubule alters kidney ATP turnover so that filtered ketoacids are preferentially excreted as Na+ or K+ salts, leading to indirect loss of bicarbonate from the body and systemic acidosis under conditions of increased ketogenesis. Risk factors include reductions in insulin dose, increased insulin demand, metabolic stress, low carbohydrate intake, women, and latent autoimmune diabetes of adulthood. The lack of hyperglycemia and nonspecific symptoms of ketoacidosis can lead to delays in diagnosis. Treatment strategies and various precautions are discussed that can decrease the likelihood of this complication.

Kisspeptin and Hematologic Parameters as Predictive Biomarkers for First-Trimester Abortions

Objective

Spontaneous abortion is the most common complication of early pregnancy, affecting up to 20% of recognized pregnancies. Kisspeptin is predominantly released by placental syncytiotrophoblasts, and regulates their placental invasion into the uterine matrices. We aimed to establish an association of serum kisspeptin levels with pregnancy outcomes during the early gestational stage of the first trimester.

Method

In this prospective study, 90 pregnant women in their 7 to 8 6/7 gestational weeks were classified into three groups: (i) The control group, consisting of healthy pregnant women (n=30), (ii) the threatened abortion group (n=30), and (iii) the spontaneous abortion group (n=30). The maternal serum samples were analyzed for complete blood count parameters and kisspeptin levels.

Results

There was no statistical difference regarding body mass index (BMI) and gestational age (p=0.370). Regarding detailed obstetric notations, including gravida, parity, abortion, and living children, socioeconomic levels, and employment rates, all study groups were comparable (p>0.05, for all). No significant association was found regarding the biochemical parameters of complete blood count, including neutrophil, lymphocyte, and platelet concentrations, as well as neutrophil-to-lymphocyte ratios (NLR) and platelet-to-lymphocyte ratios (PLR) (p>0.05, for all). The median serum kisspeptin levels of the study groups did not differ between the groups (p=0.153). Correlation analysis revealed no significant relationship between serum kisspeptin levels and other study parameters in any study groups (p>0.05, for all)

Conclusion

We found no statistically significant relationship between serum kisspeptin concentrations and pregnancy outcomes in the early gestational stage of the first trimester, and serum kisspeptin concentrations did not seem to be a reliable marker to distinguish abortion status from viable pregnancy.