Leptin--much more than a satiety signal

Leptin and Insulin in COPD: Unveiling the Metabolic-Inflammatory Axis-A Narrative Review

Chronic obstructive pulmonary disease (COPD) is a progressive and debilitating condition characterized by airflow limitations and systemic inflammation. The interaction between the metabolic and inflammatory pathways plays a key role in disease progression, with leptin and insulin emerging as pivotal metabolic regulators. Leptin, an adipokine that regulates energy homeostasis, and insulin, the primary regulator of glucose metabolism, are both altered in COPD patients. This narrative review provides an in-depth examination of the roles of leptin and insulin in COPD pathogenesis, focusing on the molecular mechanisms through which these metabolic regulators interact with inflammatory pathways and how their dysregulation contributes to a spectrum of extrapulmonary manifestations. These disturbances not only exacerbate COPD symptoms but also increase the risk of comorbidities such as metabolic syndrome, diabetes, cardiovascular disease, or muscle wasting. By exploring the underlying mechanisms of leptin and insulin dysregulation in COPD, this review underscores the significance of the metabolic-inflammatory axis, suggesting that restoring metabolic balance through leptin and insulin modulation could offer novel therapeutic strategies for improving clinical outcomes.

A Cross-Sectional Study: Systematic Quantification of Chemerin in Human Cerebrospinal Fluid

BACKGROUND

Dysregulation of adipokines is considered a key mechanism of chronic inflammation in metabolic syndrome. Some adipokines affect food intake by crossing the blood/brain barrier. The adipokine chemerin is associated with metabolic syndrome, cardiovascular diseases and immune response. Little is known about chemerin's presence in cerebrospinal fluid (CSF) and its ability to cross the blood/CSF barrier.

METHODS

We quantified chemerin levels in paired serum and CSF samples of 390 patients with different neurological diagnoses via enzyme-linked immunosorbent assay (ELISA). Correlation analyses of serum and CSF chemerin levels with anthropometric, serum and CSF routine parameters were performed.

RESULTS

Overweight patients exhibited higher chemerin levels in serum and CSF. Chemerin CSF levels were higher in men. Chemerin levels in serum were associated with BMI (body mass index) and CRP (C-reactive protein). Chemerin levels in CSF were associated with age. Neurological diseases affected chemerin levels in CSF. The chemerin CSF/serum ratio was calculated as 96.3 ± 36.8 × 10-3 for the first time.

CONCLUSIONS

Our data present a basis for the development of standard values for chemerin quantities in CSF. CSF chemerin levels are differentially regulated in neurological diseases and affected by BMI and sex. Chemerin is able to cross the blood/CSF barrier under physiological and pathophysiological conditions.

No Effect of High Eating Frequency Compared with Low Eating Frequency on Appetite and Inflammation Biomarkers: Results from a Randomized Crossover Clinical Trial

BACKGROUND

Eating frequency (EF) focuses on the total number of eating occasions per day and may influence metabolic health.

OBJECTIVES

We sought to examine the effect of high compared with low EF on appetite regulation and inflammatory biomarkers among healthy adults.

METHODS

Data are from a randomized, crossover trial (the Frequency of Eating and Satiety Hormones study). Participants (n = 50) completed 2 isocaloric 21-d study periods of low EF (3 eating occasions/d) and high EF (6 eating occasions/d) in random order with a 14-d washout period in between. Participants were free-living and consumed their own food, using study-directed, structured meal plans with identical foods and total energy in both study periods. On days 1 and 21 of each EF period, fasting blood was collected during in-person clinic visits to assess plasma concentrations of ghrelin, leptin, adiponectin, and high-sensitivity C-reactive protein (hs-CRP). Linear mixed models with EF, diet sequence, and period as fixed effects and participant as random effect were used to estimate the intervention effect. Interaction effects between EF and body fat percentage were examined.

RESULTS

Among the 50 participants who completed the trial, 39 (78%) were women, 30 (60%) were Non-Hispanic White, and 40 (80%) had a body mass index of <25 kg/m2, and the mean age was 32.1 y. The differences between high and low EF in fasting ghrelin (geometric mean difference: 17.76 ng/mL; P = 0.60), leptin (geometric mean difference: 2.09 ng/mL; P = 0.14), adiponectin (geometric mean difference: 381.7 ng/mL; P = 0.32), and hs-CRP (geometric mean difference: -0.018 mg/dL; P = 0.08) were not statistically significant. No significant interaction was observed between EF and body fat percentage on appetite regulation and inflammatory biomarkers.

CONCLUSIONS

No differences was observed in fasting ghrelin, leptin, adiponectin, and hs-CRP comparing high and low EF. Future studies are needed to understand the physiology of EF and appetite as they relate to metabolic health. This trial was registered at clinicaltrials.gov as NCT02392897.

Role of Leptin in Obesity, Cardiovascular Disease, and Type 2 Diabetes

Diabetes mellitus (DM) is a highly prevalent disease worldwide, estimated to affect 1 in every 11 adults; among them, 90-95% of cases are type 2 diabetes mellitus. This is partly attributed to the surge in the prevalence of obesity, which has reached epidemic proportions since 2008. In these patients, cardiovascular (CV) risk stands as the primary cause of morbidity and mortality, placing a substantial burden on healthcare systems due to the potential for macrovascular and microvascular complications. In this context, leptin, an adipocyte-derived hormone, plays a fundamental role. This hormone is essential for regulating the cellular metabolism and energy balance, controlling inflammatory responses, and maintaining CV system homeostasis. Thus, leptin resistance not only contributes to weight gain but may also lead to increased cardiac inflammation, greater fibrosis, hypertension, and impairment of the cardiac metabolism. Understanding the relationship between leptin resistance and CV risk in obese individuals with type 2 DM (T2DM) could improve the management and prevention of this complication. Therefore, in this narrative review, we will discuss the evidence linking leptin with the presence, severity, and/or prognosis of obesity and T2DM regarding CV disease, aiming to shed light on the potential implications for better management and preventive strategies.

Placenta DNA methylation levels of the promoter region of the leptin receptor gene are associated with infant cortisol

The intrauterine environment and early life stress regulation are widely recognized as an early foundation for lifelong physical and mental health. Methylation of CpG sites in the placenta represents an epigenetic modification that can potentially affect placental function, influence fetal development, and ultimately impact the health of offspring by programming the hypothalamic-pituitary-adrenal (HPA) axis stress response during prenatal development. Leptin, an adipokine produced by the placenta, is essential for energy homeostasis. It is also epigenetically regulated by promoter DNA methylation. Mounting evidence suggests that leptin also affects the stress response system. Though heterogeneity in the early stress response system may influence life-long mental and physical health, few studies explicitly examine the heterogeneity in the newborn stress response system. Less is known about leptin's association with the human hypothalamic-pituitary-adrenocortical (HPA) axis early in life. This study sought to serve as a proof of concept study investigating the relationship between newborn cortisol output trajectories and placental leptin DNA methylation in 117 healthy newborns from socioeconomically and racially- and ethnically-diverse families. We characterized heterogeneity in newborn cortisol output during the NICU Network Neurobehavioral Scales exam in the first week of life with latent growth mixture models. We then evaluated whether leptin promoter (LEP) methylation in placental samples was associated with newborn cortisol trajectories. Our findings suggest that increased placental LEP methylation, which corresponds to decreased leptin production, is associated with infant cortisol trajectories marked by increased cortisol output in the NNNS exam. These results provide important insights into the role of placental leptin DNA methylation in human newborn HPA axis development and subsequent developmental origins of health and disease processes.

Correlation of Metabolic Syndrome with Redox Homeostasis Biomarkers: Evidence from High-Fat Diet Model in Wistar Rats

Metabolic Syndrome (MetS) is an extremely complex disease. A non-balanced diet such as high-fat diet (HFD) induces metabolic dysfunction that could modify redox homeostasis. We here aimed at exploring redox homeostasis in male Wistar rats, following 8 weeks of HFD, correlating the eventual modification of selected biomarkers that could be associated with the clinical manifestations of MetS. Therefore, we selected parameters relative to both the glucose tolerance and lipid altered metabolism, but also oxidative pattern. We assessed some biomarkers of oxidative stress i.e., thiols balance, lipid peroxidation and antioxidant barriers, via the use of specific biochemical assays, individuating eventual cross correlation with parameters relative to MetS through a Principal Component Analysis (PCA). The present study shows that 8 weeks of HFD induce MetS in rats, altering glucose and lipid homeostasis and increasing visceral adipose tissue, but also impairing the physiological antioxidant responses that could not counteract the oxidative stress condition. Crucially, cross-correlation analysis suggested that the assessment of specific oxidative stress parameters reported here can provide information comparable to the more widely acquired biomarkers of Mets such as glucose tolerance. Lastly, hepatic steatosis in association with the oxidative stress condition was also highlighted by histological analysis. This research will elucidate the fundamental impact of these oxidative stress parameters on MetS induced in the HFD rat model, tracing paths for developing prevention approaches.

Therapeutic Effect of Curcumin on 5/6Nx Hypertriglyceridemia: Association with the Improvement of Renal Mitochondrial β-Oxidation and Lipid Metabolism in Kidney and Liver

Chronic kidney disease (CKD) prevalence is constantly increasing, and dyslipidemia in this disease is characteristic, favoring cardiovascular events. However, the mechanisms of CKD dyslipidemia are not fully understood. The use of curcumin (CUR) in CKD models such as 5/6 nephrectomy (5/6Nx) has shown multiple beneficial effects, so it has been proposed to correct dyslipidemia without side effects. This work aimed to characterize CUR's potential therapeutic effect on dyslipidemia and alterations in lipid metabolism and mitochondrial ß-oxidation in the liver and kidney in 5/6Nx. Male Wistar rats were subjected to 5/6Nx and progressed by 4 weeks; meanwhile, CUR (120 mg/kg) was administered for weeks 5 to 8. Our results showed that CUR reversed the increase in liver and kidney damage and hypertriglyceridemia induced by 5/6Nx. CUR also reversed mitochondrial membrane depolarization and β-oxidation disorders in the kidney and the increased lipid uptake and the high levels of proteins involved in fatty acid synthesis in the liver and kidney. CUR also decreased lipogenesis and increased mitochondrial biogenesis markers in the liver. Therefore, we concluded that the therapeutic effect of curcumin on 5/6Nx hypertriglyceridemia is associated with the restoration of renal mitochondrial ß-oxidation and the reduction in lipid synthesis and uptake in the kidneys and liver.

Obesity, inflammation, and cancer in dogs: Review and perspectives

Obesity is the most common nutritional disease in dogs, and its prevalence has increased in recent decades. Several countries have demonstrated a prevalence of obesity in dogs similar to that observed in humans. Chronic low-grade inflammation is a prominent basis used to explain how obesity results in numerous negative health consequences. This is well known and understood, and recent studies have pointed to the association between obesity and predisposition to specific types of cancers and their complications. Such elucidations are important because, like obesity, the prevalence of cancer in dogs has increased in recent decades, establishing cancer as a significant cause of death for these animals. In the same way, intensive advances in technology in the field of human and veterinary medicine (which even proposes the use of animal models) have optimized existing therapeutic methods, led to the development of innovative treatments, and shortened the time to diagnosis of cancer. Despite the great challenges, this review aims to highlight the evidence obtained to date on the association between obesity, inflammation, and cancer in dogs, and the possible pathophysiological mechanisms that link obesity and carcinogenesis. The potential to control cancer in animals using existing knowledge is also presented.

Metabolic milieu and localization of ovarian leptin and receptor in queens under different reproduction phases

Metabolic profile and leptin presence and expression of receptor in the ovary of 8 queens were analyzed. All queens were assessed for nutritional state and underwent ovariectomy in accordance with Italian law for the control of stray cats and dogs. Three queens were at early gestation, three prepubescent and two non-pregnant. All animals appeared healthy but underweight. Haemogram and biochemical profile did not show to be of prognostic value. On microscopy, granulosa cells of secondary follicles tested positive to leptin in pregnant queens, while testing negative in non-pregnant ones. Muscular layer of vessels of the ovary in non-pregnant queens tested positive to receptor, but negative in those found pregnant. Results suggest that leptin is produced and receptor expressed in the different tissues of the ovary in underweight queens. Additionally, the expression of receptor did not necessarily imply local leptin production and clearly displayed to vary according to the reproduction phase. Taken altogether, these findings allow to conclude that the expression of receptor can be interpreted as the pillar bridging ovary tissues as target sites of circulating leptin produced elsewhere. Arguably, ovary removal may affect hormonal cross-talk at the systemic level, likely affecting different systemic functions, including the nutritional status.

Eat, Train, Sleep-Retreat? Hormonal Interactions of Intermittent Fasting, Exercise and Circadian Rhythm

The circadian rhythmicity of endogenous metabolic and hormonal processes is controlled by a complex system of central and peripheral pacemakers, influenced by exogenous factors like light/dark-cycles, nutrition and exercise timing. There is evidence that alterations in this system may be involved in the pathogenesis of metabolic diseases. It has been shown that disruptions to normal diurnal rhythms lead to drastic changes in circadian processes, as often seen in modern society due to excessive exposure to unnatural light sources. Out of that, research has focused on time-restricted feeding and exercise, as both seem to be able to reset disruptions in circadian pacemakers. Based on these results and personal physical goals, optimal time periods for food intake and exercise have been identified. This review shows that appropriate nutrition and exercise timing are powerful tools to support, rather than not disturb, the circadian rhythm and potentially contribute to the prevention of metabolic diseases. Nevertheless, both lifestyle interventions are unable to address the real issue: the misalignment of our biological with our social time.

Recent advances and future avenues in understanding the role of adipose tissue cross talk in mediating skeletal muscle mass and function with ageing

Sarcopenia, broadly defined as the age-related decline in skeletal muscle mass, quality, and function, is associated with chronic low-grade inflammation and an increased likelihood of adverse health outcomes. The regulation of skeletal muscle mass with ageing is complex and necessitates a delicate balance between muscle protein synthesis and degradation. The secretion and transfer of cytokines, long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), both discretely and within extracellular vesicles, have emerged as important communication channels between tissues. Some of these factors have been implicated in regulating skeletal muscle mass, function, and pathologies and may be perturbed by excessive adiposity. Indeed, adipose tissue participates in a broad spectrum of inter-organ communication and obesity promotes the accumulation of macrophages, cellular senescence, and the production and secretion of pro-inflammatory factors. Pertinently, age-related sarcopenia has been reported to be more prevalent in obesity; however, such effects are confounded by comorbidities and physical activity level. In this review, we provide evidence that adiposity may exacerbate age-related sarcopenia and outline some emerging concepts of adipose-skeletal muscle communication including the secretion and processing of novel myokines and adipokines and the role of extracellular vesicles in mediating inter-tissue cross talk via lncRNAs and miRNAs in the context of sarcopenia, ageing, and obesity. Further research using advances in proteomics, transcriptomics, and techniques to investigate extracellular vesicles, with an emphasis on translational, longitudinal human studies, is required to better understand the physiological significance of these factors, the impact of obesity upon them, and their potential as therapeutic targets in combating muscle wasting.

Current Knowledge on the Multifactorial Regulation of Corpora Lutea Lifespan: The Rabbit Model

Simple Summary

Corpora lutea (CL) are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. A variety of regulatory factors come into play in modulating the functional lifespan of CL, with luteotropic and luteolytic effects. Many aspects of luteal phase physiology have been clarified, yet many others have not yet been determined, including the molecular and/or cellular mechanisms that maintain the CL from the beginning of luteolysis during early CL development. This paper summarizes our current knowledge of the endocrine and cellular mechanisms involved in multifactorial CL lifespan regulation, using the pseudopregnant rabbit model.

Abstract

Our research group studied the biological regulatory mechanisms of the corpora lutea (CL), paying particular attention to the pseudopregnant rabbit model, which has the advantage that the relative luteal age following ovulation is induced by the gonadotrophin-releasing hormone (GnRH). CL are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. It is now clear that, besides the classical regulatory mechanism exerted by prostaglandin E2 (luteotropic) and prostaglandin F2α (luteolytic), a considerable number of other effectors assist in the regulation of CL. The aim of this paper is to summarize our current knowledge of the multifactorial mechanisms regulating CL lifespan in rabbits. Given the essential role of CL in reproductive success, a deeper understanding of the regulatory mechanisms will provide us with valuable insights on various reproductive issues that hinder fertility in this and other mammalian species, allowing to overcome the challenges for new and more efficient breeding strategies.

Leptin Distribution in Rat Foetal and Extraembryonic Tissues in Late Gestation: A Physiological View of Amniotic Fluid Leptin

Prenatal leptin is key to regulating foetal growth and early metabolic programming. The presence of intact leptin in rat foetal (at late gestation) and neonatal (immediately after birth) stomach content and mucosa has been previously described, suggesting that it may act as a regulatory nutrient for the neonate rats, be internalised by the stomach, and play a physiological role early in life, which requires to be further investigated, including its origin. We aimed to study the ontogeny of the presence of leptin in the foetal stomach and key extraembryonic tissues in rats at late gestation (days 18-21). Leptin concentration was determined by enzyme-linked immunosorbent assay, and placental leptin immunolocalisation was analysed by immunohistochemistry. Leptin showed a sudden appearance in the amniotic fluid (AF) at day 20 of gestation, gastric content (swallowed AF), stomach, and umbilical cord, significantly increasing at day 21. Leptin levels in these fluids and tissues were positively correlated. In the placenta, leptin was detectable at all the studied days, but its localisation changed from widespread throughout the placenta at day 18 to well-defined in the labyrinth zone from day 19 onwards. The results support a possible internalisation of AF leptin by the immature stomach of near-term foetuses and suggest that changes in placental leptin localisation might help to explain the sudden appearance of leptin in AF at gestational day 20, with potential physiological significance regarding short-term feeding control and metabolic programming in the developing offspring.

Is energy expenditure reduced in obese mice with mutations in the leptin/leptin receptor genes?

Rodents with mutations in the leptin, or leptin receptor, genes have been extensively used to investigate the regulation of energy balance and the factors that underlie the development of obesity. The excess energy gain of these mutants has long been considered as being due in part to increased metabolic efficiency, consequent to reduced energy expenditure, but this view has recently been challenged. We argue, particularly though not exclusively, from data on ob/ob mice, that three lines of evidence support the proposition that reduced expenditure is important in the aetiology of obesity in leptin pathway mutants (irrespective of the genetic background): (i) milk intake is similar in suckling ob/ob and +/? mice; (ii) ob/ob mice deposit excess energy when pair-fed to the ad libitum food intake of lean siblings; (iii) in several studies mutant mice have been shown to exhibit a lower RMR ‘per animal’ at temperatures below thermoneutrality. When metabolic rate is expressed ‘per unit body weight’ (inappropriately, because of body composition differences), then it is invariably lower in the obese than the lean. It is important to differentiate the causes from the consequences of obesity. Hyperphagic, mature obese animals weighing 2–3 times their lean siblings may well have higher expenditure ‘per animal’, reflecting the costs of being larger and of enhanced obligatory diet-induced thermogenesis resulting from the increased food intake. This cannot, however, be used to inform the aetiology of their obesity.

Birth anthropometry and cord blood leptin in Korean appropriate-for-gestational-age infants born at ≥ 28 weeks' gestation: a cross sectional study

Background

We investigated whether leptin during the third trimester was associated with fetal growth compared to IGF-1.

Methods

One hundred five appropriate-for-gestational-age (AGA) infants born at ≥28 weeks’ gestation were enrolled. Cord blood leptin and insulin like growth factor 1 (IGF-1) were collected simultaneously during delivery. Enrolled infants were stratified into three groups according to GA as follows: 28 to < 34 weeks’ gestation, very preterm (VP); 34 to < 37 weeks’ gestation, late preterm (LP); and 37 to < 41 weeks’ gestation, term. Birth weight (BW), birth length (BL), head circumference (HC), and body mass index (BMI) were measured. Leptin and IGF-1 were logarithmically transformed to normalize their distributions in multivariable regression analysis.

Results

Sixty-eight infants out of 105 infants were preterm (32.5 ± 2.5 weeks), and 37 infants were term (37.8 ± 1.2 weeks). BW, BL, HC, and BMI were higher with increasing gestational age among the three gestational age-specific groups. With regard to hormones, leptin and IGF-1 were higher with increasing gestational age. Log cord serum leptin was independently associated with BW and BL in multivariable linear regression analysis, after adjustment for confounding factors including gestational age, delivery mode, multiple pregnancy, pregnancy induced hypertension, gestational diabetes mellitus, infant’s BMI, and log cord blood IGF-1 levels.

Conclusions

During the third trimester, cord serum leptin was independently associated with fetal growth.

Review: Diabetes, Obesity, and Cancer-Pathophysiology and Clinical Implications

Obesity and diabetes have both been associated with an increased risk of cancer. In the face of increasing obesity and diabetes rates worldwide, this is a worrying trend for cancer rates. Factors such as hyperinsulinemia, chronic inflammation, antihyperglycemic medications, and shared risk factors have all been identified as potential mechanisms underlying the relationship. The most common obesity- and diabetes-related cancers are endometrial, colorectal, and postmenopausal breast cancers. In this review, we summarize the existing evidence that describes the complex relationship between obesity, diabetes, and cancer, focusing on epidemiological and pathophysiological evidence, and also reviewing the role of antihyperglycemic agents, novel research approaches such as Mendelian Randomization, and the methodological limitations of existing research. In addition, we also describe the bidirectional relationship between diabetes and cancer with a review of the evidence summarizing the risk of diabetes following cancer treatment. We conclude this review by providing clinical implications that are relevant for caring for patients with obesity, diabetes, and cancer and provide recommendations for improving both clinical care and research for patients with these conditions.

The Clinical Utility of Salivary Biomarkers in the Identification of Type 2 Diabetes Risk and Metabolic Syndrome

Type 2 diabetes is traditionally diagnosed by the use of an oral glucose tolerance test and/or HbA1c, both of which require serum collection. Various biomarkers, which are measurable biological substances that provide clinical insight on disease state, have also been effective in the early identification and risk prediction of inflammatory diseases. Measuring biomarker concentrations has traditionally been obtained through serum collection as well. However, numerous biomarkers are detectable in saliva. Salivary analysis has more recently been introduced into research as a potential non-invasive, cost-effective diagnostic for the early identification of type 2 diabetes risk in adults and youth. Therefore, the purpose of this review was to compare 6 established inflammatory biomarkers of type 2 diabetes, in serum and saliva, and determine if similar diagnostic effectiveness is seen in saliva. A lack of standardized salivary analysis, processing, and collection accounts for errors and inconsistencies in conclusive data amongst studies. Proposing a national standardization in salivary analysis, coupled with increased data and research on the utility of saliva as a diagnostic, poses the potential for salivary analysis to be used in diagnostic settings.

Impact of leptin deficiency compared with neuronal-specific leptin receptor deletion on cardiometabolic regulation

The main goal of this study was to compare the impact of total body leptin deficiency with neuronal-specific leptin receptor (LR) deletion on metabolic and cardiovascular regulation. Liver fat, diacylglycerol acyltransferase-2 (DGTA2), and CD36 protein content were measured in wild-type (WT), nervous system LR-deficient (LR/Nestin-Cre), and leptin deficient (ob/ob) mice. Blood pressure (BP) and heart rate (HR) were recorded by telemetry, and motor activity (MA) and oxygen consumption (V̇o₂) were monitored at 24 wk of age. Female and male LR/Nestin-Cre and ob/ob mice were heavier than WT mice (62 ± 5 and 61 ± 3 vs. 31 ± 1 g) and hyperphagic (6.2 ± 0.5 and 6.1 ± 0.7 vs. 3.5 ± 1.0 g/day), with reduced V̇o₂ (27 ± 1 and 33 ± 1 vs 49 ± 3 ml·kg^-1·min^-1) and decreased MA (3 ± 1 and 7 ± 2 vs 676 ± 105 cm/h). They were also hyperinsulinemic and hyperglycemic compared with WT mice. LR/Nestin-Cre mice had high levels of plasma leptin, while ob/ob mice had undetectable leptin levels. Despite comparable obesity, LR/Nestin-Cre mice had lower liver fat content, DGTA2, and CD36 protein levels than ob/ob mice. Male WT, LR/Nestin-Cre, and ob/ob mice exhibited similar BP (111 ± 3, 110 ± 1 and 109 ± 2 mmHg). Female LR/Nestin-Cre and ob/ob mice, however, had higher BP than WT females despite similar metabolic phenotypes compared with male LR/Nestin-Cre and ob/ob mice. These results indicate that although nervous system LRs play a crucial role in regulating body weight and glucose homeostasis, peripheral LRs regulate liver fat deposition. In addition, our results suggest potential sex differences in the impact of obesity on BP regulation.

Leptin trajectories from birth to mid-childhood and cardio-metabolic health in early adolescence

OBJECTIVES

Leptin is a hormone produced by adipose tissue that promotes satiety, and some evidence suggests that greater early life leptin exposure prevents excessive adiposity gain in later life. However, few studies have analyzed dynamic changes in leptin throughout childhood in relation to later cardio-metabolic health. Our study aims to identify distinct leptin trajectories in childhood, and to examine their associations with cardio-metabolic outcomes in adolescence.

METHODS

Among children in the Project Viva cohort born 1999-2002 in Massachusetts, we used latent class growth models to identify leptin trajectories independent of maternal BMI, child sex, race/ethnicity, size at birth and current age and size among 1360 children with leptin measured at least once at birth, early childhood (mean 3.3 ± SD 0.3 years), or mid-childhood (7.9 ± 0.8 years). At research visits in early adolescence (13.2 ± 0.9 years), we assessed cardio-metabolic outcomes including adiposity measures, fasting biomarkers, and blood pressure among 855 children. We then applied multiple regression models to examine associations of the leptin trajectories with these cardio-metabolic outcomes in early adolescence, adjusting for child age at outcome, maternal age, education, prenatal smoking and glucose, total gestational weight gain and paternal BMI.

RESULTS

The latent class growth model identified 3 distinct leptin trajectories: "low stable" (n = 1031, 75.8%), "high-decreasing" (n = 219, 16.1%) and "intermediate-increasing" (n = 110, 8.1%). In adjusted models, the intermediate-increasing leptin trajectory was associated with higher early adolescence adiposity measures (e.g. BMI z-score: 0.62 units; 95% confidence interval: 0.28, 0.96 and odds of obesity: 2.84: 1.17, 6.94), but lower systolic blood pressure (-0.46 z-score units; -0.74, -0.18), compared to the low-stable group.

CONCLUSIONS

Our findings on leptin trajectories in childhood suggest important differences and associations with later metabolic outcomes.

Translational Pharmacology and Physiology of Brown Adipose Tissue in Human Disease and Treatment

Human brown adipose tissue (BAT) is experimentally modeled to better understand the biology of this important metabolic tissue, and also to enable the potential discovery and development of novel therapeutics for obesity and sequelae resulting from the persistent positive energy balance. This chapter focuses on translation into humans of findings and hypotheses generated in nonhuman models of BAT pharmacology. Given the demonstrated challenges of sustainably reducing caloric intake in modern humans, potential solutions to obesity likely lie in increasing energy expenditure. The energy-transforming activities of a single cell in any given tissue can be conceptualized as a flow of chemical energy from energy-rich substrate molecules into energy-expending, endergonic biological work processes through oxidative degradation of organic molecules ingested as nutrients. Despite the relatively tight coupling between metabolic reactions and products, some expended energy is incidentally lost as heat, and in this manner a significant fraction of the energy originally captured from the environment nonproductively transforms into heat rather than into biological work. In human and other mammalian cells, some processes are even completely uncoupled, and therefore purely energy consuming. These molecular and cellular actions sum up at the physiological level to adaptive thermogenesis, the endogenous physiology in which energy is nonproductively released as heat through uncoupling of mitochondria in brown fat and potentially skeletal muscle. Adaptive thermogenesis in mammals occurs in three forms, mostly in skeletal muscle and brown fat: shivering thermogenesis in skeletal muscle, non-shivering thermogenesis in brown fat, and diet-induced thermogenesis in brown fat. At the cellular level, the greatest energy transformations in humans and other eukaryotes occur in the mitochondria, where creating energetic inefficiency by uncoupling the conversion of energy-rich substrate molecules into ATP usable by all three major forms of biological work occurs by two primary means. Basal uncoupling occurs as a passive, general, nonspecific leak down the proton concentration gradient across the membrane in all mitochondria in the human body, a gradient driving a key step in ATP synthesis. Inducible uncoupling, which is the active conduction of protons across gradients through processes catalyzed by proteins, occurs only in select cell types including BAT. Experiments in rodents revealed UCP1 as the primary mammalian molecule accounting for the regulated, inducible uncoupling of BAT, and responsive to both cold and pharmacological stimulation. Cold stimulation of BAT has convincingly translated into humans, and older clinical observations with nonselective 2,4-DNP validate that human BAT's participation in pharmacologically mediated, though nonselective, mitochondrial membrane decoupling can provide increased energy expenditure and corresponding body weight loss. In recent times, however, neither beta-adrenergic antagonism nor unselective sympathomimetic agonism by ephedrine and sibutramine provide convincing evidence that more BAT-selective mechanisms can impact energy balance and subsequently body weight. Although BAT activity correlates with leanness, hypothesis-driven selective β3-adrenergic agonism to activate BAT in humans has only provided robust proof of pharmacologic activation of β-adrenergic receptor signaling, limited proof of the mechanism of increased adaptive thermogenesis, and no convincing evidence that body weight loss through negative energy balance upon BAT activation can be accomplished outside of rodents. None of the five demonstrably β3 selective molecules with sufficient clinical experience to merit review provided significant weight loss in clinical trials (BRL 26830A, TAK 677, L-796568, CL 316,243, and BRL 35135). Broader conclusions regarding the human BAT therapeutic hypothesis are limited by the absence of data from most studies demonstrating specific activation of BAT thermogenesis in most studies. Additionally, more limited data sets with older or less selective β3 agonists also did not provide strong evidence of body weight effects. Encouragingly, β3-adrenergic agonists, catechins, capsinoids, and nutritional extracts, even without robust negative energy balance outcomes, all demonstrated increased total energy expenditure that in some cases could be associated with concomitant activation of BAT, though the absence of body weight loss indicates that in no cases did the magnitude of negative energy balance reach sufficient levels. Glucocorticoid receptor agonists, PPARg agonists, and thyroid hormone receptor agonists all possess defined molecular and cellular pharmacology that preclinical models predicted to be efficacious for negative energy balance and body weight loss, yet their effects on human BAT thermogenesis upon translation were inconsistent with predictions and disappointing. A few new mechanisms are nearing the stage of clinical trials and may yet provide a more quantitatively robust translation from preclinical to human experience with BAT. In conclusion, translation into humans has been demonstrated with BAT molecular pharmacology and cell biology, as well as with physiological response to cold. However, despite pharmacologically mediated, statistically significant elevation in total energy expenditure, translation into biologically meaningful negative energy balance was not achieved, as indicated by the absence of measurable loss of body weight over the duration of a clinical study.

Human Placental Growth Hormone Variant in Pathological Pregnancies

Growth hormone (GH), an endocrine hormone, primarily secreted from the anterior pituitary, stimulates growth, cell reproduction, and regeneration and is a major regulator of postnatal growth. Humans have two GH genes that encode two versions of GH proteins: a pituitary version (GH-N/GH1) and a placental GH-variant (GH-V/GH2), which are expressed in the syncytiotrophoblast and extravillous trophoblast cells of the placenta. During pregnancy, GH-V replaces GH-N in the maternal circulation at mid-late gestation as the major circulating form of GH. This remarkable change in spatial and temporal GH secretion patterns is proposed to play a role in mediating maternal adaptations to pregnancy. GH-V is associated with fetal growth, and its circulating concentrations have been investigated across a range of pregnancy complications. However, progress in this area has been hindered by a lack of readily accessible and reliable assays for measurement of GH-V. This review will discuss the potential roles of GH-V in normal and pathological pregnancies and will touch on the assays used to quantify this hormone.

Leptin reverses hyperglycemia and hyperphagia in insulin deficient diabetic rats by pituitary-independent central nervous system actions

The hypothalamic-pituitary-adrenal (HPA) axis has been postulated to play a major role in mediating the antidiabetic effects of leptin. We tested if the pituitary is essential for the chronic central nervous system mediated actions of leptin on metabolic and cardiovascular function in insulin-dependent diabetic and non-diabetic rats. Male 12-week-old hypophysectomized Sprague-Dawley rats (Hypo, n = 5) were instrumented with telemetry probes for determination of mean arterial pressure (MAP) and heart rate (HR) 24-hrs/day and an intracerebroventricular (ICV) cannula was placed into the brain lateral ventricle for continuous leptin infusion. In additional groups of Hypo and control rats (n = 5/group), diabetes was induced by single injection of streptozotocin (50 mg/kg, IP). Hypo rats were lighter, had lower MAP and HR (83±4 and 317±2 vs 105±4 mmHg and 339±4 bpm), with similar caloric intake per kilogram of body weight and fasting plasma glucose levels (84±4 vs 80±4 mg/dl) compared to controls. Chronic ICV leptin infusion (7 days, 0.62 μg/hr) in non-diabetic rats reduced caloric intake and body weight (-10%) in Hypo and control rats and markedly increased HR in control rats (~25 bpm) while causing only modest HR increases in Hypo rats (8 bpm). In diabetic Hypo and control rats, leptin infusion reduced caloric intake, body weight and glucose levels (323±74 to 99±20 and 374±27 to 108±10 mg/dl), respectively; however, the effects of leptin on HR were abolished in Hypo rats. These results indicate that hypophysectomy attenuates leptin’s effect on HR regulation without altering leptin’s ability to suppress appetite or normalize glucose levels in diabetes.

Obesity-Induced Hypertension: Brain Signaling Pathways

Obesity greatly increases the risk for cardiovascular, metabolic, and renal diseases and is one of the most significant and preventable causes of increased blood pressure (BP) in patients with essential hypertension. This review highlights recent advances in our understanding of central nervous system (CNS) signaling pathways that contribute to the etiology and pathogenesis of obesity-induced hypertension. We discuss the role of excess adiposity and activation of the brain leptin-melanocortin system in causing increased sympathetic activity in obesity. In addition, we highlight other potential brain mechanisms by which increased weight gain modulates metabolic and cardiovascular functions. Unraveling the CNS mechanisms responsible for increased sympathetic activation and hypertension and how circulating hormones activate brain signaling pathways to control BP offer potentially important therapeutic targets for obesity and hypertension.

Intergenerational Transmission of Paternal Epigenetic Marks: Mechanisms Influencing Susceptibility to Post-Concussion Symptomology in a Rodent Model

Epigenetic transmission of phenotypic variance has been linked to paternal experiences prior to conception and during perinatal development. Previous reports indicate that paternal experiences increase phenotypic heterogeneity and may contribute to offspring susceptibility to post-concussive symptomology. This study sought to determine if epigenetic tags, specifically DNA methylation of promoter regions, are transmitted from rodent fathers to their sons. Using MethyLight, promoter methylation of specific genes involved in recovery from concussion and brain plasticity were analyzed in sperm and brain tissue. Promoter methylation in sperm differed based on paternal experience. Differences in methylation were often identified in both the sperm and brain tissue obtained from their sons, demonstrating transmission of epigenetic tags. For certain genes, methylation in the sperm was altered following a concussion suggesting that a history of brain injury may influence paternal transmission of traits. As telomere length is paternally inherited and linked to neurological health, this study examined paternally derived differences in telomere length, in both sperm and brain. Telomere length was consistent between fathers and their sons, and between brain and sperm, with the exception of the older fathers. Older fathers exhibited increased sperm telomere length, which was not evident in sperm or brain of their sons.

Role of autonomic nervous system in chronic CNS-mediated antidiabetic action of leptin

This study tested whether ganglionic blockade or hepatic vagotomy attenuates the chronic central nervous system (CNS)-mediated antidiabetic and cardiovascular effects of leptin. Male Sprague-Dawley rats were instrumented with telemetry probes and arterial and venous catheters for determination of blood pressure (BP), heart rate (HR), blood sampling, and intravenous (iv) infusions. An intracerebroventricular (ICV) cannula was placed into the brain lateral ventricle for infusion of leptin or vehicle. After control measurements, streptozotocin (STZ) was injected iv (50 mg/kg) to induce diabetes, and 5 days later leptin (n = 6) or saline vehicle (n = 5) was infused ICV for 12 days via osmotic pumps. Beginning on day 6 of leptin treatment, the ganglionic blocker hexamethonium (15 mg·kg^-1·day^-1 iv) was infused, while leptin infusion was continued, to assess the role of the autonomic nervous system. Induction of diabetes was associated with increases in blood glucose (98 ± 7 to 350 ± 19 mg/dl), food intake (23 ± 3 to 43 ± 3 g/day), decreases in HR (-70 ± 11 beats/min), polyuria, and increased water consumption, which were all completely normalized by ICV leptin infusion. Although hexamethonium attenuated leptin's effect on HR, it failed to impair leptin's ability to restore euglycemia or to prevent the polyuria or increased water intake in STZ-diabetic rats. We also found that after pretreatment with hexamethonium (n = 8), ICV leptin infusion, during continued ganglionic blockade, completely normalized blood glucose in diabetic rats. In addition, selective hepatic vagotomy did not attenuate leptin's ability to restore euglycemia in diabetic rats. These results suggest that leptin's powerful chronic CNS antidiabetic actions are mediated primarily via nonautonomic mechanisms.

Randomized Trial Testing the Effects of Eating Frequency on Two Hormonal Biomarkers of Metabolism and Energy Balance

BACKGROUND

Eating frequency (EF) may influence obesity-related disease risk by attenuating postprandial fluctuations in hormones involved in metabolism, appetite regulation, and inflammation.

MATERIALS/METHODS

This randomized crossover intervention trial tested the effects of EF on fasting plasma insulin-like growth factor-I (IGF-1) and leptin. Fifteen subjects (4 males, 11 females) completed two eucaloric intervention phases lasting 21 days each: low EF ("low-EF"; 3 eating occasions/day) and high EF ("high-EF"; 8 eating occasions/day). Subjects were free-living and consumed their own meals using individualized structured meal plans with instruction from study staff. Subjects completed fasting blood draws and anthropometry on the first and last day of each study phase. The generalized estimated equations modification of linear regression tested the intervention effect on fasting serum IGF-1 and leptin.

RESULTS

Mean (± SD) age was 28.5 ± 8.70 years, and mean (± SD) Body Mass Index was 23.3 (3.4) kg/m². We found lower mean serum IGF-1 following the high-EF condition compared to the low-EF condition (P < 0.001). There was no association between EF and plasma leptin (P = 0.83).

CONCLUSION

These results suggest that increased EF may lower serum IGF-1, which is a hormonal biomarker linked to increased risk of breast, prostate, and colorectal cancer.

Cord blood leptin levels in relation to child growth trajectories

OBJECTIVE

Leptin represents a potential modulator of developmental programming of childhood obesity. We investigated the association of cord blood leptin with growth trajectories from birth to early childhood.

MATERIALS/METHODS

We used data from the prospective mother-child cohort "Rhea", Crete, Greece. Cord blood samples from 642 neonates were collected. 578 (90%) children had complete follow up data from birth to 4years. We measured child weight, height, waist circumference, skinfold thicknesses, blood pressure, and serum lipids, leptin, adiponectin and C-reactive protein in early childhood (median 4.2years). We estimated growth trajectories from 3months up to 4years using random-effects linear-spline models. Multivariable logistic and linear regression models were used adjusting for confounders.

RESULTS

Mean cord blood leptin levels were 7.3ng/mL (standard deviation: 6.3). Children with high cord blood leptin (>90th percentile) exhibited lower weight, height and body mass index from 6months to early childhood. Each SD increase in cord blood leptin was associated with lower weight at the age of 4 by 242g (95% CI: -416, -69). In a stratified analysis, the reverse association was observed in children born small for gestational age (p for interaction=0.001), and in those exhibiting rapid infant growth during the first 3months of life (p for interaction=0.002). Cord blood leptin levels were not associated with cardiometabolic risk factors at 4years.

CONCLUSIONS

Long term programming effects of in utero exposure to leptin extends beyond infancy into early childhood. Further studies are needed to explore potential effect modification by intrauterine and early infancy growth patterns.

Different physical forms of one diet fed to growing pigs induce morphological changes in mandubular glands and local leptin (Ob) production and receptor (ObR) expression

The physical form of the diet plays an important role for morphological adaptations of organs in the gastrointestinal tract. It was hypothesized that different physical forms of one diet could exert extra-enteric effects, under local and systemic neuroendocrine regulation. Gross morphology, fresh mass and cytoarchitecture of mandibular glands (MG) were studied in growing pigs fed with one diet processed under four different physical forms. Four dietary treatments were offered for 4 weeks to 32 growing pigs (initial BW: 8.30 ± 0.83 kg) allotted into 4 experimental groups: FP, finely ground pellet (dMean, 0.46 mm); CM, coarsely ground meal (dMean, 0.88 mm); CP, coarsely ground pellet (dMean, 0.84); CE, coarsely ground extruded (dMean, 0.66). Conventional and immuonohistochemical techniques were used to immunolocalize, in particular, leptin (Ob) and its receptor (ObR). A significant effect was observed on the relative mass of the MG, depending on the diet (p < 0.03) and on the BW (p < 0.04), with no interactions (diet*BW). The immunohistochemical reactions for Ob and ObR showed a marked positivity in the MG from the group fed with the CM diet, displaying Ob-positive acinar cells and ObR-positive cells in the striated ducts, together with endocrine-like cells. The intensity of chromogenic reactions positively testing to ObR was used to evaluate the cytoarchitecture of the MG and its possible correlations. Pearson's correlation coefficient resulted to positively link (p < 0.0001) the ObR expression with the absolute mass of MG in the 61.1% of pigs. The physical form of the diet is related to extra-enteral effects, inducing changes in gross and microscopic morphology of the MG in the growing pig. The local production of Ob and the expression of the respective ObR in the striated duct cells shed a new light on the mitogenic activity of Ob in extra-enteral organs, like the MG, in relation to the physical form of the diet.

Body fat mobilization during lactation in high-producing sows fed varied omega-6 to omega-3 fatty acid ratios

The effects of reducing dietary omega (n)-6 to n-3 fatty acid (FA) ratios on body fat mobilization in lactating sows (n = 100) were investigated. Treatments consisted of a control (tallow, low polyunsaturated FA, 8:1 n-6:n-3 ratio), 3 diets with plant oil based ratios (9:1P, 5:1P, and 1:1P), and a 5:1 fish oil diet (5:1F). An epinephrine [1.6 μg kg−1 body weight (BW)] challenge was used to measure adipose tissue lipolytic activity (glycerol, NEFA, and leptin) on d 5 of lactation from a subset of sows (9:1P and 1:1P groups) fitted with jugular catheters. Lactation feed intake was greatest for control and 5:1P-fed sows (8.3 kg d−1), lowest for 1:1P-fed sows (7.4 kg d−1), and intermediate for 9:1P- and 5:1F-fed sows (7.7 kg d−1; P = 0.047). Piglet average daily gain (ADG) and estimated milk output were unaffected by diet (P > 0.10). The 1:1P-fed sows had (P < 0.10) greater backfat thickness, increased circulating leptin, and reduced feed intake, which are correlated (P < 0.10) with increased circulating glycerol and NEFA. Sows fed a plant oil based 1:1 n-6:n-3 FA ratio appeared to be in a state of negative energy balance; however, as no effects were observed on piglet ADG, these sows were able to provide the same level of nutrients to their offspring as the 9:1P fed sows.

Can low-level laser therapy (LLLT) associated with an aerobic plus resistance training change the cardiometabolic risk in obese women? A placebo-controlled clinical trial

INTRODUCTION

Obesity is one of the most important link factors to coronary artery disease development mainly due to the pro-inflammatory and pro-thrombotic states favoring atherosclerosis progression. The LLLT acts in the cellular metabolism and it is highly effective to improve inflammation. The same occur in response to different kinds of exercise. However, we have not known the associate effects using LLLT therapies with aerobic plus resistance training as strategy specifically with target at human obesity control and its comorbidities.

OBJECTIVE

Investigate the effects of the LLLT associated with aerobic plus resistance training on cardiometabolic risk factors in obese women.

METHODOLOGY

Women aged 20-40 years (BMI ≥ 30 kg/m(2)), were divided into 2 groups: Phototherapy (PHOTO) and Placebo. They were trained aerobic plus resistance exercises (in a concurrent mode), 1h, 3 times/week during 16 weeks. Phototherapy was applied after each exercise session for 16 min, with infrared laser, wavelength 808 nm, continuous output, power 100 mW, and energy delivery 50 J. The body composition was measured with bioimpedance. Inflammatory mark concentrations were measured using a commercially available multiplex.

RESULTS

LLLT associated with aerobic plus resistance training was effective in decrease neck (P=0.0003) and waist circumferences (P=0.02); percentual of fat (P=0.04); visceral fat area (P=0.02); HOMA-IR (P=0.0009); Leptin (P=0.03) and ICAM (P=0.03). Also, the reduction in leptin (P=0.008) and ICAM-1 (0, 05) was much more expressive in the phototherapy group in comparison to placebo group when analyzed by delta values.

CONCLUSION

LLLT associated with concurrent exercise (aerobic plus resistance training) potentiates the exercise effects of decreasing the cardiometabolic risk factors in obese woman. These results suggest the LLLT associated with exercises as a new therapeutic tool in the control of obesity and its comorbidities for obese people, targeting to optimize the strategies to control the cardiometabolic risk factors in these populations.

Regulation of Blood Pressure, Appetite, and Glucose by Leptin After Inactivation of Insulin Receptor Substrate 2 Signaling in the Entire Brain or in Proopiomelanocortin Neurons

Insulin receptor substrate 2 (IRS2) is one of the 3 major leptin receptor signaling pathways, but its role in mediating the chronic effects of leptin on blood pressure, food intake, and glucose regulation is unclear. We tested whether genetic inactivation of IRS2 in the entire brain (IRS2/Nestin-cre mice) or specifically in proopiomelanocortin (POMC) neurons (IRS2/POMC-cre mice) attenuates the chronic cardiovascular, metabolic, and antidiabetic effects of leptin. Mice were instrumented with telemetry probes for measurement of blood pressure and heart rate and with venous catheters for intravenous infusions. After a 5-day control period, mice received leptin infusion (2 μg/kg per minute) for 7 days. Compared with control IRS2(flox/flox) mice, IRS2/POMC-cre mice had similar body weight and food intake (33±1 versus 35±1 g and 3.6±0.5 versus 3.8±0.2 g per day) but higher mean arterial pressure (MAP) and heart rate (110±2 versus 102±2 mm Hg and 641±9 versus 616±5 bpm). IRS2/Nestin-cre mice were heavier (38±2 g), slightly hyperphagic (4.5±1.0 g per day), and had higher MAP and heart rate (108±2 mm Hg and 659±9 bpm) compared with control mice. Leptin infusion gradually increased MAP despite decreasing food intake by 31% in IRS2(flox/flox) and in Nestin-cre control mice. In contrast, leptin infusion did not change MAP in IRS2/Nestin-cre or IRS2/POMC-cre mice. The anorexic and antidiabetic effects of leptin, however, were similar in all 3 groups. These results indicate that IRS2 signaling in the central nervous system, and particularly in POMC neurons, is essential for the chronic actions of leptin to raise MAP but not for its anorexic or antidiabetic effects.

Interactions between adipose tissue and the immune system in health and malnutrition

Adipose tissue provides the body with a storage depot of nutrients that is drained during times of starvation and replenished when food sources are abundant. As such, it is the primary sensor for nutrient availability in the milieu of an organism, which it communicates to the body through the excretion of hormones. Adipose tissue regulates a multitude of body functions associated with metabolism, such as gluconeogenesis, feeding and nutrient uptake. The immune system forms a vital layer of protection against micro-organisms that try to gain access to the nutrients contained in the body. Because infections need to be resolved as quickly as possible, speed is favored over energy-efficiency in an immune response. Especially when immune cells are activated, they switch to fast, but energy-inefficient anaerobic respiration to fulfill their energetic needs. Despite the necessity for an effective immune system, it is not given free rein in its energy expenditure. Signals derived from adipose tissue limit immune cell numbers and activity under conditions of nutrient shortage, whereas they allow proper immune cell activity when food sources are sufficiently available. When excessive fat accumulation occurs, such as in diet-induced obesity, adipose tissue becomes the site of pathological immune cell activation, causing chronic low-grade systemic inflammation. Obesity is therefore associated with a number of disorders in which the immune system plays a central role, such as atherosclerosis and non-alcoholic steatohepatitis. In this review, we will discuss the way in which adipose tissue regulates activity of the immune system under healthy and pathological conditions.

Adulthood dietary exposure to a common pesticide leads to an obese-like phenotype and a diabetic profile in apoE3 mice

Increasing evidence links the widespread exposure to organophosphate (OP) pesticides to the global epidemics of type 2 diabetes and obesity. Our recent data highlighted gene×environment interactions: mice expressing the human apolipoprotein E3 (apoE3) isoform were more prone to develop obesity than those expressing apoE2 or apoE4 upon dietary challenge with chlorpyrifos (CPF), the most used OP worldwide. Thus, we aimed to further explore the contribution of the APOE3 genotype on the emergence of obesity and related metabolic dysfunctions upon subchronic exposure to CPF. Seven-month-old targeted replacement apoE3 and C57BL/6N male mice were orally exposed to CPF at 0 or 2mg/kg body weight/day for 8 consecutive weeks. We examined body weight status, food and water intake, lipid and glucose homeostasis, metabolic biomarkers concentrations, insulin levels and insulin resistance, and leptin and ghrelin profiles. CPF exposure generally increased food ingestion, glucose and total cholesterol concentrations, and tended to elevate acyl ghrelin levels. Nonetheless, excess weight gain and increased leptin levels were inherent to apoE3 mice. Moreover, the propensity towards a diabetic profile was markedly higher in these animals than in C57BL/6N, as they showed a higher homeostatic model assessment for insulin resistance index and higher insulin levels. Although both genotypes were metabolically affected by CPF, the results of the present investigation revealed that apoE3 mice were the most vulnerable to developing obesity and related disturbances following CPF administration through the diet. Since the APOE3 genotype is the most prevalent worldwide, current findings have particular implications for human health.

Overweight, Obesity, and Postmenopausal Invasive Breast Cancer Risk: A Secondary Analysis of the Women's Health Initiative Randomized Clinical Trials

IMPORTANCE

More than two-thirds of US women are overweight or obese, placing them at increased risk for postmenopausal breast cancer.

OBJECTIVE

To investigate in this secondary analysis the associations of overweight and obesity with risk of postmenopausal invasive breast cancer after extended follow-up in the Women's Health Initiative (WHI) clinical trials.

DESIGN, SETTING, AND PARTICIPANTS

The WHI clinical trial protocol incorporated measured height and weight, baseline and annual or biennial mammography, and adjudicated breast cancer end points in 67 142 postmenopausal women ages 50 to 79 years at 40 US clinical centers. The women were enrolled from 1993 to 1998 with a median of 13 years of follow-up through 2010; 3388 invasive breast cancers were observed.

MAIN OUTCOMES AND MEASURES

Height and weight were measured at baseline, and weight was measured annually thereafter. Data were collected on demographic characteristics, personal and family medical history, and personal habits (smoking, physical activity). Women underwent annual or biennial mammograms. Breast cancers were verified by medical records reviewed by physician adjudicators.

RESULTS

Women who were overweight and obese had an increased invasive breast cancer risk vs women of normal weight. Risk was greatest for obesity grade 2 plus 3 (body mass index [BMI], calculated as weight in kilograms divided by height in meters squared, >35.0) (hazard ratio [HR] for invasive breast cancer, 1.58; 95% CI, 1.40-1.79). A BMI of 35.0 or higher was strongly associated with risk for estrogen receptor-positive and progesterone receptor-positive breast cancers (HR, 1.86; 95% CI, 1.60-2.17) but was not associated with estrogen receptor-negative cancers. Obesity grade 2 plus 3 was also associated with advanced disease, including larger tumor size (HR, 2.12; 95% CI, 1.67-2.69; P = .02), positive lymph nodes (HR, 1.89; 95% CI, 1.46-2.45; P = .06), regional and/or distant stage (HR, 1.94; 95% CI, 1.52-2.47; P = .05), and deaths after breast cancer (HR, 2.11; 95% CI, 1.57-2.84; P < .001). Women with a baseline BMI of less than 25.0 who gained more than 5% of body weight over the follow-up period had an increased breast cancer risk (HR, 1.36; 95% CI, 1.1-1.65), but among women already overweight or obese we found no association of weight change (gain or loss) with breast cancer during follow-up. There was no effect modification of the BMI-breast cancer relationship by postmenopausal hormone therapy, and the direction of association across BMI categories was similar for never, past, and current hormone therapy use.

CONCLUSIONS AND RELEVANCE

Obesity is associated with increased invasive breast cancer risk in postmenopausal women. These clinically meaningful findings should motivate programs for obesity prevention.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00000611.

Dietary intake alters behavioral recovery and gene expression profiles in the brain of juvenile rats that have experienced a concussion

Concussion and mild traumatic brain injury (mTBI) research has made minimal progress diagnosing who will suffer from lingering symptomology or generating effective treatment strategies. Research demonstrates that dietary intake affects many biological systems including brain and neurological health. This study determined if exposure to a high fat diet (HFD) or caloric restriction (CR) altered post-concussion susceptibility or resiliency using a rodent model of pediatric concussion. Rats were maintained on HFD, CR, or standard diet (STD) throughout life (including the prenatal period and weaning). At postnatal day 30, male and female rats experienced a concussion or a sham injury which was followed by 17 days of testing. Prefrontal cortex and hippocampus tissue was collected for molecular profiling. Gene expression changes in BDNF, CREB, DNMT1, FGF-2, IGF1, LEP, PGC-1α, SIRT1, Tau, and TERT were analyzed with respect to injury and diet. Analysis of telomere length (TL) using peripheral skin cells and brain tissue found that TL in skin significantly correlated with TL in brain tissue and TL was affected by dietary intake and injury status. With respect to mTBI outcomes, diet was correlated with recovery as animals on the HFD often displayed poorer performance than animals on the CR diet. Molecular analysis demonstrated that diet induced epigenetic changes that can be associated with differences in individual predisposition and resiliency to post-concussion syndrome.

Chronic subordination stress induces hyperphagia and disrupts eating behavior in mice modeling binge-eating-like disorder

Background: Eating disorders are associated with physical morbidity and appear to have causal factors like stressful life events and negative affect. Binge-eating disorder (BED) is characterized by eating in a discrete period of time a larger than normal amount of food, a sense of lack of control over eating, and marked distress. There are still unmet needs for the identification of mechanisms regulating excessive eating, which is in part due to the lack of appropriate animal models. We developed a naturalistic murine model of subordination stress-induced hyperphagia associated with the development of obesity. Here, we tested the hypotheses that the eating responses of subordinate mice recapitulate the BED and that limiting hyperphagia could prevent stress-associated metabolic changes.

Methods: Adult male mice were exposed to a model of chronic subordination stress (CSS) associated with the automated acquisition of food intake and we performed a detailed meal pattern analysis. Additionally, using a pair-feeding protocol we tested the hypothesis that the manifestation of obesity and the metabolic syndrome could be prevented by limiting hyperphagia.

Results: The architecture of feeding of subordinate mice was disrupted during the stress protocol due to disproportionate amount of food ingested at higher rate and with shorter satiety ratio than control mice. Subordinate mice hyperphagia was further exacerbated in response to either hunger or to the acute application of a social defeat. Notably, the obese phenotype but not the fasting hyperglycemia of subordinate mice was abrogated by preventing hyperphagia in a pair-feeding paradigm.

Conclusion: Overall, these results support the validity of our CSS to model BED allowing for the determination of the underlying molecular mechanisms and the generation of testable predictions for innovative therapies, based on the understanding of the regulation and the control of food intake.

Synergy of leptin/STAT3 with HER2 receptor induces tamoxifen resistance in breast cancer cells through regulation of apoptosis-related genes

PURPOSE

Tamoxifen is a major treatment modality for estrogen receptor positive breast cancer, but the occurrence of resistance remains a problem. Recently, obesity-related leptin has been found to interfere with tamoxifen in breast cancer MCF-7 cells. In the present study we investigated the effect of leptin on three tamoxifen-treated breast cancer cell types (i.e., MDA-MB-231, MCF-7 and MCF-7/HER2).

METHODS

The effect of tamoxifen/leptin treatment was evaluated using a MTT cell viability assay. mRNA expression was assessed by real time PCR and protein expression by Western blotting. WWOX, Survivin and BCL2 gene promoter activities were evaluated by chromatin immunoprecipitation.

RESULTS

Cell viability assays revealed that estrogen receptor negative MDA-MB-231 cells were resistant, that estrogen receptor positive MCF-7 cells were sensitive and that MCF-7/HER2 cells were relatively resistant to tamoxifen, while leptin co-administration 'rescued' MCF-7 and, especially, MCF-7/HER2 cells from the anti-proliferative effect of tamoxifen. The cell lines also exhibited a different phosphorylation status of STAT3, a transcription factor that is activated by the obesity related leptin receptor b (Ob-Rb). Most importantly, chromatin immunoprecipitation assays revealed differential STAT3 binding to the anti-apoptotic BCL2 and pro-apoptotic WWOX gene promoters in MCF-7 and MCF-7/HER2 cells, leading to concomitant modifications of its mRNA/protein expression levels, thus providing a selective advantage to HER2 over-expressing MCF-7/HER2 cells after treatment with tamoxifen and tamoxifen plus leptin.

CONCLUSIONS

Our study provides novel evidence indicating that synergy between the leptin/Ob-Rb/STAT3 signalling pathway and the HER2 receptor protects tamoxifen-treated HER2 over-expressing cells from the inhibitory effect of tamoxifen through differential regulation of apoptosis-related genes.

Systemic and placental leptin and its receptors in pregnancies associated with obesity

This study aimed to gain new insights into both systemic and placental leptin and its receptors, with reference to the maternal prepregnancy body mass index (BMI). Thus, 84 women (29 lean, 24 overweight, and 31 obese) were recruited and maternal, cord blood, and placental tissues collected prior to term labor. Plasma levels were measured by enzyme-linked immunosorbent assay and for placenta, immunohistochemistry and messenger RNAs (mRNAs) were quantitated. We confirmed that maternal leptin increased linearly as the soluble receptor decreased with BMI (P = .001). Fetal leptin increased with maternal BMI (P = .02) and birth weight (P = .006) and was higher in female infants (P < .001). Placental mRNA levels of leptin and its receptors showed no change in BMI. However, we show a significant (P = .043) linear increase in leptin in the placental vascular endothelial cells with maternal obesity, while leptin in syncytiotrophoblast showed no statistical change. Leptin receptors localized to syncytiotrophoblast and intravillous macrophages and were unchanged with BMI.

Hypoxia and adipocyte physiology: implications for adipose tissue dysfunction in obesity

Hypoxia develops in white adipose tissue in obese mice, resulting in changes in adipocyte function that may underpin the dysregulation that leads to obesity-associated disorders. Whether hypoxia occurs in adipose tissue in human obesity is unclear, with recent studies contradicting earlier reports that this was the case. Adipocytes, both murine and human, exhibit extensive functional changes in culture in response to hypoxia, which alters the expression of up to 1,300 genes. These include genes encoding key adipokines such as leptin, interleukin (IL)-6, vascular endothelial growth factor (VEGF), and matrix metalloproteinase-2 (MMP-2), which are upregulated, and adiponectin, which is downregulated. Hypoxia also inhibits the expression of genes linked to oxidative metabolism while stimulating the expression of genes associated with glycolysis. Glucose uptake and lactate release by adipocytes are both stimulated by hypoxia, and insulin sensitivity falls. Preadipocytes and macrophages in adipose tissue also respond to hypoxia. The hypoxia-signaling pathway may provide a new target for the treatment of obesity-associated disorders.

Maternal weight status, cord blood leptin and fetal growth: a prospective mother-child cohort study (Rhea study)

BACKGROUND

Leptin is an adipocyte-secreted hormone that regulates energy homeostasis, while its role in fetal programming remains poorly understood. We aimed to evaluate the effect of maternal weight status on cord blood leptin levels and their combined effect on fetal growth.

METHODS

We included 638 mother-child pairs from the prospective mother-child cohort 'Rhea' study in Crete, Greece with singleton pregnancies, providing cord blood serum samples for leptin analysis and complete data on birth outcomes. Multivariable logistic and linear regression models were used adjusting for confounders. Generalised additive models were used to explore the form of the relationship between cord leptin and continuous birth outcomes.

RESULTS

Log cord leptin was positively associated with birthweight {β-coef: 176.5 [95% confidence interval (CI): 133.0, 220.0] }, ponderal index (β-coef: 1.0 [95% CI: 0.6, 1.4] ) and gestational age (β-coef: 0.7 [95% CI: 0.5, 0.8] ). Excessive weight gain during pregnancy was associated with a threefold increased risk for cord hyperleptinaemia {relative risk (RR): 3.0, [95% CI: 1.5, 6.3] }. Maternal pre-pregnancy overweight/obesity [body mass index (BMI) ≥25 kg/m(2) ] increased the risk of giving birth to a hyperleptinaemic neonate (RR: 2.1 [95% CI: 1.4, 3.2] and the effect of log leptin on birthweight (β-coef: 219.1 [95% CI: 152.3, 285.9] compared with women with a BMI <25 kg/m(2) (β-coef: 150.5 [95% CI: 93.1, 207.9].

CONCLUSIONS

Higher cord blood leptin levels are associated with increased size at birth and gestational age, while maternal pre-pregnancy BMI and weight gain during pregnancy represent significant indicators of cord blood leptin.

Integrated effects of leptin in the forebrain and hindbrain of male rats

Leptin receptors (ObRs) in the forebrain and hindbrain have been independently recognized as important mediators of leptin responses. It is unclear how leptin activity in these areas is integrated. We tested whether both forebrain and hindbrain ObRs have to be activated simultaneously to change energy balance and to maintain metabolic homeostasis. Previous studies used acute leptin injections in either the third ventricle (1-5 μg) or the fourth ventricle (3-10 μg); here we used 12-day infusions of low doses of leptin in one or both ventricles (0.1 μg/24 h in third, 0.6 μg/24 h in fourth). Male Sprague Dawley rats were fitted with third and fourth ventricle cannulas, and saline or leptin was infused from Alzet pumps for 6 or 12 days. Rats that received leptin into only the third or the fourth ventricle were not different from controls that received saline in both ventricles. By contrast, rats with low-dose leptin infusions into both the third and fourth ventricle showed a dramatic 60% reduction in food intake that was reversed on day 6, a 20% weight loss that stabilized on day 6, and a 50% decrease in body fat at day 12 despite the correction of food intake. They displayed normal activity and maintained energy expenditure despite weight loss, indicating inappropriately high thermogenesis that coincided with increased signal transducer and activator of transcription 3 (STAT3) phosphorylation in the brainstem. Altogether, these findings show that with low doses of leptin, chronic activation of both hypothalamic and brainstem ObRs is required to reduce body fat.

Leptin gene in rabbit: cloning and expression in mammary epithelial cells during pregnancy and lactation

Leptin is known as a cytokine mostly produced by fat cells and implicated in regulation of energy metabolism and food intake but has also been shown to be involved in many physiological mechanisms such as tissue metabolism and cell differentiation and proliferation. In particular, leptin influences the development of mammary gland. Although leptin expression in mammary gland has been studied in several species, no data are available in the rabbit. Leptin transcripts in this species have been described as being encoded by only two exons rather than three as in other species. Our focus was to clone and sequence the rabbit leptin cDNA and to prepare the recombinant biologically active protein for validation of the proper sequence and then to describe leptin expression in rabbit mammary gland during different stages of pregnancy and lactation. The leptin sequence obtained was compared with those of other species, and genome alignment demonstrated that the rabbit leptin gene is also encoded by three exons. Additionally, we analyzed the expression of leptin during pregnancy and lactation. Leptin mRNA was weakly expressed throughout pregnancy, whereas mRNA levels were higher during lactation, with a significant increase between days 3 and 16. Leptin transcripts and protein were localized in luminal epithelial cells, thus indicating that leptin synthesis occurs in this compartment. Therefore, mammary synthesized leptin may constitute a major regulator of mammary gland development by acting locally as an autocrine and/or paracrine factor. Furthermore, our results support the possible physiological role of leptin in newborns through consumption of milk.

Characterization of foamy epithelial surface cells in the canine endometrium

In mature bitches, endometrial epithelial surface cells modify function and corresponding morphology during the oestrous cycle. During late metoestrous, endometrial epithelial surface cells frequently accumulate fat and thereby adopt a foamy morphology. This cyclic appearance of foamy endometrial epithelial cells (fEECs) seems to be physiological in the dog, whereas in other species, it indicates pathological changes. Function of these fEECs has not been identified until now. Therefore, the aim of the study was to characterize the fEECs by means of transmission electron microscopy and immunohistochemistry. Different manifestations of fEECs were observed and analysed with regard to proliferative activity and presence of different epithelial adhesion molecules including PLEKHA7, β-catenin and E-cadherin. PLEKHA7 was restricted to the apical regions of the fEECs, whereas E-cadherin and β-catenin were demonstrated basolateral. The immunohistochemical detection of steroid hormone receptors demonstrated the responsiveness of the fEECs to steroid hormones. Intense progesterone receptor expression was observed in the fEECs indicating a high responsiveness to this hormone. Considering a potential function of the fEECs, we hypothesized that leptin, a hormone produced by other lipid-accumulating cells and described to be involved in reproduction, in particular during implantation, might also originate from the fEECs which was confirmed by immunohistochemical methods. Moreover, leptin receptor was found in fEECs indicating the fEECs as both, source and target for leptin. Therefore, we conclude that fEECs in the canine uterus have a potential role in early pregnancy events and that the different observed manifestations might simply reflect the variations of signs of pseudopregnancy among bitches.

[Leptin: Involvement in the pathophysiology of breast cancer]

More than one million new cases of breast cancer are diagnosed each year worldwide and more than 400,000 deaths occur due to this pathology. Obesity is a risk factor for postmenopausal breast cancer and the place held by the adipose tissue and secretions (i.e. adipokines) begins to be recognized. Indeed, firstly, plasma adipokine levels, modulated in obesity situation, could have effects "remotely" on mammary carcinogenesis and, secondly, breast cancer cells are surrounded by adipocyte microenvironment, which is probably more important in the case of obesity, and may be locally influenced by it. In this context, leptin appears to be strongly involved in mammary carcinogenesis and may contribute to the angiogenesis process and local pro-inflammatory mechanisms, especially in obese patients for whom increased metastatic potential and risk of mortality are described.

Regulation of placental nutrient transport and implications for fetal growth

Fetal macronutrient requirements for oxidative metabolism and growth are met by placental transport of glucose, amino acids, and, to a lesser extent that varies with species, fatty acids. It is becoming possible to relate the maternal–fetal transport kinetics of these molecules in vivo to the expression and distribution of specific transporters among placental cell types and subcellular membrane fractions. This is most true for glucose transport, although apparent inconsistencies among data on the roles and relative importance of the predominant placenta glucose transporters, GLUT-1 and GLUT-3, remain to be resolved. The quantity of macronutrients transferred to the fetus from the maternal bloodstream is greatly influenced by placental metabolism, which results in net consumption of large amounts of glucose and, to a lesser extent, amino acids. The pattern of fetal nutrient supply is also altered considerably by placental conversion of glucose to lactate and, in some species, fructose, and extensive transamination of amino acids. Placental capacity for transport of glucose and amino acids increases with fetal demand as gestation advances through expansion of the exchange surface area and increased expression of specific transport molecules. In late pregnancy, transport capacity is closely related to placental size and can be modified by maternal nutrition. Preliminary evidence suggests that placental expression and function of specific transport proteins are influenced by extracellular concentrations of nutrients and endocrine factors, but, in general, the humoral regulation of placental capacity for nutrient transport is poorly understood. Consequences of normal and abnormal development of placental transport functions for fetal growth, especially during late gestation, and, possibly, for fetal programming of postnatal disorders, are discussed.