Role of insulin in the neuroendocrine control of reproduction

Diabetes Mellitus and Gynecological and Inflammation Disorders Increased the Risk of Pregnancy Loss in a Population Study

(1) Background: Diabetes mellitus (DM) induces oxidative stress and inflammation with negative effect on pregnancy outcomes. This study aimed to determine whether DM increases the risk of pregnancy loss and to identify other potential risk factors; (2) Methods: We identified female patients diagnosed with DM from 2000-2015 in the Taiwanese National Health Insurance Research Database according to the International Classification of Diseases, Ninth Edition, Clinical Modification (ICD-9 CM) code 250. The event was pregnancy loss, defined as ICD-9 CM codes 630-639, which was tracked until 31 December 2015. The control group included 4-fold more non-DM female patients who were matched for age and disease severity. Multivariate Cox regression was employed to determine the risk factors associated with pregnancy loss; (3) Results: The hazard ratio (HR) for the risk of pregnancy loss due to DM was 1.407 (95% confidence interval: 1.099-1.801, p = 0.007), and the risk factors for older age, gynecological disorders and inflammation disorders were included. (4) Conclusions: The study concluded that women with DM have a greater risk of experiencing pregnancy loss. Healthcare providers should proactively manage and educate diabetic patients to reduce their risk of pregnancy loss. Understanding other probable risk factors can help in developing targeted interventions and support systems for women to improve pregnancy outcomes.

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.

Obesity-Related Hypogonadism in Women

Obesity-related hypogonadotropic hypogonadism is a well-characterized condition in men (termed male obesity-related secondary hypogonadism; MOSH); however, an equivalent condition has not been as clearly described in women. The prevalence of polycystic ovary syndrome (PCOS) is known to increase with obesity, but PCOS is more typically characterized by increased gonadotropin-releasing hormone (GnRH) (and by proxy luteinizing hormone; LH) pulsatility, rather than by the reduced gonadotropin levels observed in MOSH. Notably, LH levels and LH pulse amplitude are reduced with obesity, both in women with and without PCOS, suggesting that an obesity-related secondary hypogonadism may also exist in women akin to MOSH in men. Herein, we examine the evidence for the existence of a putative non-PCOS "female obesity-related secondary hypogonadism" (FOSH). We précis possible underlying mechanisms for the occurrence of hypogonadism in this context and consider how such mechanisms differ from MOSH in men, and from PCOS in women without obesity. In this review, we consider relevant etiological factors that are altered in obesity and that could impact on GnRH pulsatility to ascertain whether they could contribute to obesity-related secondary hypogonadism including: anti-Müllerian hormone, androgen, insulin, fatty acid, adiponectin, and leptin. More precise phenotyping of hypogonadism in women with obesity could provide further validation for non-PCOS FOSH and preface the ability to define/investigate such a condition.

Metabolic control of puberty: 60 years in the footsteps of Kennedy and Mitra's seminal work

An individual's nutritional status has a powerful effect on sexual maturation. Puberty onset is delayed in response to chronic energy insufficiency and is advanced under energy abundance. The consequences of altered pubertal timing for human health are profound. Late puberty increases the chances of cardiometabolic, musculoskeletal and neurocognitive disorders, whereas early puberty is associated with increased risks of adult obesity, type 2 diabetes mellitus, cardiovascular diseases and various cancers, such as breast, endometrial and prostate cancer. Kennedy and Mitra's trailblazing studies, published in 1963 and using experimental models, were the first to demonstrate that nutrition is a key factor in puberty onset. Building on this work, the field has advanced substantially in the past decade, which is largely due to the impressive development of molecular tools for experimentation and population genetics. In this Review, we discuss the latest advances in basic and translational sciences underlying the nutritional and metabolic control of pubertal development, with a focus on perspectives and future directions.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

Targeted Glutamate Supply Boosts Insulin Concentrations, Ovarian Activity, and Ovulation Rate in Yearling Goats during the Anestrous Season

The neuroendocrine regulation of the seasonal reproductive axis requires the integration of internal and external signals to ensure synchronized physiological and behavioral responses. Seasonal reproductive changes contribute to intermittent production, which poses challenges for optimizing goat product yields. Consequently, a significant objective in seasonal reproduction research is to attain continuous reproduction and enhance profitability in goat farming. Glutamate plays a crucial role as a modulator in several reproductive and metabolic processes. Hence, the aim of this study was to evaluate the potential impact of exogenous glutamate administration on serum insulin concentration and ovarian function during the out-of-season period in yearling goats. During the anestrous season, animals were randomly located in individual pens to form two experimental groups: (1) glutamate (n = 10, live weight (LW) = 29.1 ± 1.02 kg, body condition score (BCS) = 3.4 ± 0.2 units) and (2) control (n = 10; LW = 29.2 ± 1.07 kg, BCS = 3.5 ± 0.2), with no differences (p < 0.05) regarding LW and BCS. Then, goats were estrus-synchronized, and blood sampling was carried out for insulin quantification. Ovaries were ultrasonographically scanned to assess ovulation rate (OR), number of antral follicles (AFs), and total ovarian activity (TOA = OR + AF). The research outcomes support our working hypothesis. Certainly, our study confirms that those yearling goats treated with exogenous glutamate displayed the largest (p < 0.05) insulin concentrations across time as well as an augmented (p < 0.05) out-of-season ovarian activity.

Opioid Receptor-Mediated Regulation of Neurotransmission in the Brain

Opioids mediate their effects via opioid receptors: mu, delta, and kappa. At the neuronal level, opioid receptors are generally inhibitory, presynaptically reducing neurotransmitter release and postsynaptically hyperpolarizing neurons. However, opioid receptor-mediated regulation of neuronal function and synaptic transmission is not uniform in expression pattern and mechanism across the brain. The localization of receptors within specific cell types and neurocircuits determine the effects that endogenous and exogenous opioids have on brain function. In this review we will explore the similarities and differences in opioid receptor-mediated regulation of neurotransmission across different brain regions. We discuss how future studies can consider potential cell-type, regional, and neural pathway-specific effects of opioid receptors in order to better understand how opioid receptors modulate brain function.

Erectile Dysfunction in Diabetic Patients: From Etiology to Management

Diabetes mellitus (DM) is a widespread chronic disease with a prevalence that is expected to further increase in the near future. The classical management of DM includes the normalization of the glycometabolic profile and the evaluation of cardiac and cerebral vascular health by the intervention of an array of different specialists. However, so far, sexual dysfunctions are still a neglected complication in patients with DM, although there is an elevated prevalence of this long-term complication in male and female patients. Furthermore, some of them may represent a sign of vascular alteration and/or hypogonadism and require timely management to prevent the onset of major adverse cardiac events. This narrative review briefly summarizes the current evidence on epidemiology, pathogenesis, diagnosis, and therapy of erectile dysfunction in male patients with DM to support diabetologists in clinical practice.

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.