Stimulation of lipolysis in humans by physiological hypercortisolemia

The Subcutaneous Adipose Microenvironment as a Determinant of Body Fat Development in Polycystic Ovary Syndrome

Context

Adipose steroid metabolism modifies body fat development in polycystic ovary syndrome (PCOS).

Objective

To determine whether subcutaneous (SC) abdominal adipose aldo-keto reductase 1C3 (AKR1C3; a marker of testosterone generation) is increased in normal-weight women with PCOS vs age- and body mass index (BMI)-matched normoandrogenic ovulatory women (controls) and is related to SC abdominal adipose activator protein-1 (AP-1; a marker of adipocyte differentiation) and/or androgen receptor (AR) protein expression in predicting fat accretion.

Design

Prospective cohort study.

Setting

Academic center.

Patients

Eighteen normal-weight PCOS women; 17 age- and BMI-matched controls.

Interventions

Circulating hormone/metabolic determinations, intravenous glucose tolerance testing, total body dual-energy x-ray absorptiometry, SC abdominal fat biopsy, immunohistochemistry.

Main Outcome Measures

Clinical characteristics, hormonal concentrations, body fat distribution, SC adipose AKR1C3, AR, and AP-1 protein expression.

Results

Women with PCOS had significantly higher serum androgen levels and greater android/gynoid fat mass ratios than controls. SC adipose AKR1C3, AR, and AP-1 protein expressions were comparable between the study groups, but groups differed in correlations. In PCOS women vs controls, SC adipose AKR1C3 protein expression correlated positively with android and gynoid fat masses and negatively with SC adipose AP-1 protein expression. SC adipose AR protein expression correlated negatively with fasting serum free fatty acid and high-density lipoprotein levels. In both study groups, SC adipose AKR1C3 protein expression negatively correlated with serum cortisol levels.

Conclusion

In normal-weight PCOS women, SC abdominal adipose AKR1C3 protein expression, in combination with intra-adipose AP-1 and AR-dependent events, predicts fat accretion in the presence of physiological cortisol levels.

High-fat diet-induced increase in glucocorticoids contributes to adipogenesis in obese mice

BACKGROUND

This study was designed to examine how glucocorticoids (GCs) induced by a long-term ingestion of high-fat diet (HFD) mediate the HFD-induced adipose expansion and obesity.

MATERIAL AND METHODS

To address this goal, we used a unique L/L mouse model that fails to induce its corticosterone (CORT) level, a major type of GCs in rodents, after prolonged exposure to an HFD.

RESULTS

We found that, after receiving a 12-week HFD feeding, the L/L mice show less weight gain, milder adipose expansion, and higher plasma levels of triglycerides than the wild-type mice. These changes were reversed by replenishing CORT to L/L mice. When examining the expression levels of various molecules linked to lipid uptake and de novo lipogenesis in CORT-induced adipose expansion, we observed a reduction in the expression of adipose preadipocyte factor 1 (Pref-1), a key regulator in adipogenesis. In 3T3-L1 preadipocyte-like cells, dexamethasone, an agonist of the glucocorticoid receptor, also reduced expressions of Pref-1 and facilitated intracellular accumulation of lipids.

CONCLUSIONS

Our results suggest that fat ingestion-induced release of CORT contributes to adipose expansion and development of obesity and highlight the pathogenic role of CORT-mediated downregulation of adipose Pref-1 in diet-induced obesity.

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

Hypoglycaemia in adrenal insufficiency

Adrenal insufficiency encompasses a group of congenital and acquired disorders that lead to inadequate steroid production by the adrenal glands, mainly glucocorticoids, mineralocorticoids and androgens. These may be associated with other hormone deficiencies. Adrenal insufficiency may be primary, affecting the adrenal gland's ability to produce cortisol directly; secondary, affecting the pituitary gland's ability to produce adrenocorticotrophic hormone (ACTH); or tertiary, affecting corticotrophin-releasing hormone (CRH) production at the level of the hypothalamus. Congenital causes of adrenal insufficiency include the subtypes of Congenital Adrenal Hyperplasia, Adrenal Hypoplasia, genetic causes of Isolated ACTH deficiency or Combined Pituitary Hormone Deficiencies, usually caused by mutations in essential transcription factors. The most commonly inherited primary cause of adrenal insufficiency is Congenital Adrenal Hyperplasia due to 21-hydroxylase deficiency; with the classical form affecting 1 in 10,000 to 15,000 cases per year. Acquired causes of adrenal insufficiency can be subtyped into autoimmune (Addison's Disease), traumatic (including haemorrhage or infarction), infective (e.g. Tuberculosis), infiltrative (e.g. neuroblastoma) and iatrogenic. Iatrogenic acquired causes include the use of prolonged exogenous steroids and post-surgical causes, such as the excision of a hypothalamic-pituitary tumour or adrenalectomy. Clinical features of adrenal insufficiency vary with age and with aetiology. They are often non-specific and may sometimes become apparent only in times of illness. Features range from those related to hypoglycaemia such as drowsiness, collapse, jitteriness, hypothermia and seizures. Features may also include signs of hypotension such as significant electrolyte imbalances and shock. Recognition of hypoglycaemia as a symptom of adrenal insufficiency is important to prevent treatable causes of sudden deaths. Cortisol has a key role in glucose homeostasis, particularly in the counter-regulatory mechanisms to prevent hypoglycaemia in times of biological stress. Affected neonates particularly appear susceptible to the compromise of these counter-regulatory mechanisms but it is recognised that affected older children and adults remain at risk of hypoglycaemia. In this review, we summarise the pathogenesis of hypoglycaemia in the context of adrenal insufficiency. We further explore the clinical features of hypoglycaemia based on different age groups and the burden of the disease, focusing on hypoglycaemic-related events in the various aetiologies of adrenal insufficiency. Finally, we sum up strategies from published literature for improved recognition and early prevention of hypoglycaemia in adrenal insufficiency, such as the use of continuous glucose monitoring or modifying glucocorticoid replacement.

Ketogenic diet promotes tumor ferroptosis but induces relative corticosterone deficiency that accelerates cachexia

Glucose dependency of cancer cells can be targeted with a high-fat, low-carbohydrate ketogenic diet (KD). However, in IL-6-producing cancers, suppression of the hepatic ketogenic potential hinders the utilization of KD as energy for the organism. In IL-6-associated murine models of cancer cachexia, we describe delayed tumor growth but accelerated cachexia onset and shortened survival in mice fed KD. Mechanistically, this uncoupling is a consequence of the biochemical interaction of two NADPH-dependent pathways. Within the tumor, increased lipid peroxidation and, consequently, saturation of the glutathione (GSH) system lead to the ferroptotic death of cancer cells. Systemically, redox imbalance and NADPH depletion impair corticosterone biosynthesis. Administration of dexamethasone, a potent glucocorticoid, increases food intake, normalizes glucose levels and utilization of nutritional substrates, delays cachexia onset, and extends the survival of tumor-bearing mice fed KD while preserving reduced tumor growth. Our study emphasizes the need to investigate the effects of systemic interventions on both the tumor and the host to accurately assess therapeutic potential. These findings may be relevant to clinical research efforts that investigate nutritional interventions such as KD in patients with cancer.

Interplay of Cortisol, Testosterone, and Abdominal Fat Mass in Normal-weight Women With Polycystic Ovary Syndrome

Context

Ovarian and adrenal steroidogenesis underlie endocrine-metabolic dysfunction in polycystic ovary syndrome (PCOS). Adipocytes express aldo-keto reductase 1C3 and type 1 11β-hydroxysteroid dehydrogenase, which modulate peripheral androgen and cortisol production.

Objectives

To compare serum adrenal steroids, including 11-oxygenated androgens (11-oxyandrogens), cortisol, and cortisone between normal-weight women with PCOS and body mass index- and age-matched ovulatory women with normal-androgenic profiles (controls), and assess whether adrenal steroids associate with abdominal adipose deposition.

Design

Prospective, cross-sectional, cohort study.

Setting

Academic medical center.

Patients

Twenty normal-weight women with PCOS and 20 body mass index-/age-matched controls.

Interventions

Blood sampling, IV glucose tolerance testing, and total-body dual-energy x-ray absorptiometry.

Main Outcome Measures

Clinical characteristics, hormonal concentrations, and body fat distribution.

Results

Women with PCOS had higher serum total/free testosterone (T) and androstenedione (A4) levels and a greater android/gynoid fat mass than controls (androgens P < .001; android/gynoid fat mass ratio, P = .026). Serum total/free T and A4 levels correlated positively with android/gynoid fat mass ratio in all women combined (P < .025, all values). Serum 11ß-hydroxyA4, 11-ketoA4, 11ß-hydroxyT, 11-ketoT, cortisol, and cortisone levels were comparable between female types and unrelated to body fat distribution. Serum 11-oxyandrogens correlated negatively with % total body fat, but lost significance adjusting for cortisol. Serum cortisol levels, however, correlated inversely with android fat mass (P = .021), with a trend toward reduced serum cortisol to cortisone ratio in women with PCOS vs controls (P = .075), suggesting diminished 11β-hydroxysteroid dehydrogenase activity.

Conclusion

Reduced cortisol may protect against preferential abdominal fat mass in normal-weight PCOS women with normal serum 11-oxyandrogens.

Biomarkers of post-match recovery in semi-professional and professional football (soccer)

High-level football (soccer) players face intense physical demands that result in acute and residual fatigue, impairing their physical performance in subsequent matches. Further, top-class players are frequently exposed to match-congested periods where sufficient recovery times are not achievable. To evaluate training and recovery strategies, the monitoring of players' recovery profiles is crucial. Along with performance and neuro-mechanical impairments, match-induced fatigue causes metabolic disturbances denoted by changes in chemical analytes that can be quantified in different body fluids such as blood, saliva, and urine, thus acting as biomarkers. The monitoring of these molecules might supplement performance, neuromuscular and cognitive measurements to guide coaches and trainers during the recovery period. The present narrative review aims to comprehensively review the scientific literature on biomarkers of post-match recovery in semi-professional and professional football players as well as provide an outlook on the role that metabolomic studies might play in this field of research. Overall, no single gold-standard biomarker of match-induced fatigue exists, and a range of metabolites are available to assess different aspects of post-match recovery. The use of biomarker panels might be suitable to simultaneously monitoring these broad physiological processes, yet further research on fluctuations of different analytes throughout post-match recovery is warranted. Although important efforts have been made to address the high interindividual heterogeneity of available markers, limitations inherent to these markers might compromise the information they provide to guide recovery protocols. Further research on metabolomics might benefit from evaluating the long-term recovery period from a high-level football match to shed light upon new biomarkers of post-match recovery.

Effects of ACTH-Induced Long-Term Hypercortisolism on the Transcriptome of Canine Visceral Adipose Tissue

Cushing’s syndrome, or hypercortisolism (HC), a common endocrinopathy in adult dogs, is caused by chronic hypercortisolemia. Among different metabolic disorders, this syndrome is associated with enhanced subcutaneous lipolysis and visceral adiposity. However, effects of HC in adipose tissue, especially regarding visceral adipose tissue (VAT), are still poorly understood. Herein, the transcriptomic effects of chronic HC on VAT of dogs were evaluated. For this, subcutaneously implanted ACTH-releasing pumps were used, followed by deep RNA sequencing of the canine VAT. Prolonged HC seems to affect a plethora of regulatory mechanisms in VAT of treated dogs, with 1190 differentially expressed genes (DEGs, p and FDR < 0.01) being found. The 691 downregulated DEGs were mostly associated with functional terms like cell adhesion and migration, intracellular signaling, immune response, extracellular matrix and angiogenesis. Treatment also appeared to modulate local glucocorticoid and insulin signaling and hormonal sensitivity, and several factors, e.g., TIMP4, FGF1, CCR2, CXCR4 and HSD11B1/2, were identified as possible important players in the glucocorticoid-related expansion of VAT. Modulation of their function during chronic HC might present interesting targets for further clinical studies. Similarities in the effects of chronic HC on VAT of dogs and humans are highlighted.

Blocking endogenous IL-6 impairs mobilization of free fatty acids during rest and exercise in lean and obese men

Lack of interleukin-6 (IL-6) leads to expansion of adipose tissue mass in rodents and humans. The exact underlying mechanisms have not been identified. In this placebo-controlled, non-randomized, participant-blinded crossover study, we use the IL-6 receptor antibody tocilizumab to investigate the role of endogenous IL-6 in regulating systemic energy metabolism at rest and during exercise and recovery in lean and obese men using tracer dilution methodology. Tocilizumab reduces fatty acid appearance in the circulation under all conditions in lean and obese individuals, whereas lipolysis (the rate of glycerol appearance into the circulation) is mostly unaffected. The fact that fatty acid oxidation is unaffected by IL-6 receptor blockade suggests increased re-esterification of fatty acids. Glucose kinetics are unaffected. We find that blocking endogenous IL-6 signaling with tocilizumab impairs fat mobilization, which may contribute to expansion of adipose tissue mass and, thus, affect the health of individuals undergoing anti-IL-6 therapy (Clinicaltrials.gov: NCT03967691).

Genomic and Non-Genomic Actions of Glucocorticoids on Adipose Tissue Lipid Metabolism

Glucocorticoids (GCs) are hormones that aid the body under stress by regulating glucose and free fatty acids. GCs maintain energy homeostasis in multiple tissues, including those in the liver and skeletal muscle, white adipose tissue (WAT), and brown adipose tissue (BAT). WAT stores energy as triglycerides, while BAT uses fatty acids for heat generation. The multiple genomic and non-genomic pathways in GC signaling vary with exposure duration, location (adipose tissue depot), and species. Genomic effects occur directly through the cytosolic GC receptor (GR), regulating the expression of proteins related to lipid metabolism, such as ATGL and HSL. Non-genomic effects act through mechanisms often independent of the cytosolic GR and happen shortly after GC exposure. Studying the effects of GCs on adipose tissue breakdown and generation (lipolysis and adipogenesis) leads to insights for treatment of adipose-related diseases, such as obesity, coronary disease, and cancer, but has led to controversy among researchers, largely due to the complexity of the process. This paper reviews the recent literature on the genomic and non-genomic effects of GCs on WAT and BAT lipolysis and proposes research to address the many gaps in knowledge related to GC activity and its effects on disease.

Arginine vasopressin: Direct and indirect action on metabolism

From its identification and isolation in 1954, arginine vasopressin (AVP) has attracted attention, not only for its peripheral functions such as vasoconstriction and reabsorption of water from kidney, but also for its central effects. As there is now considerable evidence that AVP plays a crucial role in feeding behavior and energy balance, it has become a promising therapeutic target for treating obesity or other obesity-related metabolic disorders. However, the underlying mechanisms for AVP regulation of these central processes still remain largely unknown. In this review, we will provide a brief overview of the current knowledge concerning how AVP controls energy balance and feeding behavior, focusing on physiological aspects including the relationship between AVP, circadian rhythmicity, and glucocorticoids.

Downregulating carnitine palmitoyl transferase 1 affects disease progression in the SOD1 G93A mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease characterized by death of motor neurons. The etiology and pathogenesis remains elusive despite decades of intensive research. Herein, we report that dysregulated metabolism plays a central role in the SOD1 G93A mouse model mimicking ALS. Specifically, we report that the activity of carnitine palmitoyl transferase 1 (CPT1) lipid metabolism is associated with disease progression. Downregulation of CPT1 activity by pharmacological and genetic methods results in amelioration of disease symptoms, inflammation, oxidative stress and mitochondrial function, whereas upregulation by high-fat diet or corticosterone results in a more aggressive disease progression. Finally, we show that downregulating CPT1 shifts the gut microbiota communities towards a protective phenotype in SOD1 G93A mice. These findings reveal that metabolism, and specifically CPT1 lipid metabolism plays a central role in the SOD1 G93A mouse model and shows that CPT1 might be a therapeutic target in ALS.

Analysis of Glucocorticoid-Related Genes Reveal CCHCR1 as a New Candidate Gene for Type 2 Diabetes

Glucocorticoids have multiple therapeutic benefits and are used both for immunosuppression and treatment purposes. Notwithstanding their benefits, glucocorticoid use often leads to hyperglycemia. Owing to the pathophysiologic overlap in glucocorticoid-induced hyperglycemia (GIH) and type 2 diabetes (T2D), we hypothesized that genetic variation in glucocorticoid pathways contributes to T2D risk. To determine the genetic contribution of glucocorticoid action on T2D risk, we conducted multiple genetic studies. First, we performed gene-set enrichment analyses on 3 collated glucocorticoid-related gene sets using publicly available genome-wide association and whole-exome data and demonstrated that genetic variants in glucocorticoid-related genes are associated with T2D and related glycemic traits. To identify which genes are driving this association, we performed gene burden tests using whole-exome sequence data. We identified 20 genes within the glucocorticoid-related gene sets that are nominally enriched for T2D-associated protein-coding variants. The most significant association was found in coding variants in coiled-coil α-helical rod protein 1 (CCHCR1) in the HLA region (P = .001). Further analyses revealed that noncoding variants near CCHCR1 are also associated with T2D at genome-wide significance (P = 7.70 × 10-14), independent of type 1 diabetes HLA risk. Finally, gene expression and colocalization analyses demonstrate that variants associated with increased T2D risk are also associated with decreased expression of CCHCR1 in multiple tissues, implicating this gene as a potential effector transcript at this locus. Our discovery of a genetic link between glucocorticoids and T2D findings support the hypothesis that T2D and GIH may have shared underlying mechanisms.

Glucocorticoid-Induced Fatty Liver Disease

Glucocorticoids (GCs) are commonly used at high doses and for prolonged periods (weeks to months) in the treatment of a variety of diseases. Among the many side effects are increased insulin resistance with disturbances in glucose/insulin homeostasis and increased deposition of lipids (mostly triglycerides) in the liver. Here, we review the metabolic pathways of lipid deposition and removal from the liver that become altered by excess glucocorticoids. Pathways of lipid deposition stimulated by excess glucocorticoids include 1) increase in appetite and high caloric intake; 2) increased blood glucose levels due to GC-induced stimulation of gluconeogenesis; 3) stimulation of de novo lipogenesis that is augmented by the high glucose and insulin levels and by GC itself; and 4) increased release of free fatty acids from adipose stores and stimulation of their uptake by the liver. Pathways that decrease hepatic lipids affected by glucocorticoids include a modest stimulation of very-low-density lipoprotein synthesis and secretion into the circulation and inhibition of β-oxidation of fatty acids. Role of 11β-hydroxysteroid dehydrogenases-1 and -2 and the reversible conversion of cortisol to cortisone on intracellular levels of cortisol is examined. In addition, GC control of osteocalcin expression and the effect of this bone-derived hormone in increasing insulin sensitivity are discussed. Finally, research focused on gaining a better understanding of the dose and duration of treatment with glucocorticoids, which leads to increased triglyceride deposition in the liver, and the reversibility of the condition is highlighted.

Regulation of metabolism during hibernation in brown bears (Ursus arctos): Involvement of cortisol, PGC-1α and AMPK in adipose tissue and skeletal muscle

The purpose of this study was to investigate changes in expression of known cellular regulators of metabolism during hyperphagia (Sept) and hibernation (Jan) in skeletal muscle and adipose tissue of brown bears and determine whether signaling molecules and transcription factors known to respond to changes in cellular energy state are involved in the regulation of these metabolic adaptations. During hibernation, serum levels of cortisol, glycerol, and triglycerides were elevated, and protein expression and activation of AMPK in skeletal muscle and adipose tissue were reduced. mRNA expression of the co-activator PGC-1α was reduced in all tissues in hibernation whereas mRNA expression of the transcription factor PPAR-α was reduced in the vastus lateralis muscle and adipose tissue only. During hibernation, gene expression of ATGL and CD36 was not altered; however, HSL gene expression was reduced in adipose tissue. During hibernation gene expression of the lipogenic enzyme DGAT in all tissues and the expression of the FA oxidative enzyme LCAD in the vastus lateralis muscle were reduced. Gene and protein expression of the glucose transporter GLUT4 was decreased in adipose tissue in hibernation. Our data suggest that high cortisol levels are a key adaptation during hibernation and link cortisol to a reduced activation of the AMPK/PGC-1α/PPAR-α axis in the regulation of metabolism in skeletal muscle and adipose tissue. Moreover, our results indicate that during this phase of hibernation at a time when metabolic rate is significantly reduced metabolic adaptations in peripheral tissues seek to limit the detrimental effects of unduly large energy dissipation.

Associations among tourist camp management, high and low tourist seasons, and welfare factors in female Asian elephants in Thailand

This study investigated how camp management and tourist activities affect body condition, adrenocortical function, lipid profiles and metabolic status in female tourist elephants. We compared twice monthly serum insulin, glucose, fructosamine, total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), and fecal glucocorticoid metabolite (FGM) concentrations to body condition scores (BCS) at five camps with different management styles (e.g., tourist activities, work type, diet) between the High (November–February) and Low (March–October) tourist seasons. There were significant camp effects on health parameters, with BCS, TC, HDL, insulin and glucose being among the highest, and G:I being the lowest (less heathy) in elephants at an observation camp compared to those at camps where elephants received exercise by providing rides to tourists. Differences between High and Low tourist season months also were found for all measures, except TG and FGM concentrations. Both work time and walking distance were negatively correlated to glucose, fructosamine and insulin, while walking distance was negatively related to FGM concentrations. By contrast, positive associations were found between tourist number and BCS, TG, and insulin, perhaps related to tourists feeding elephants. Quantity of supplementary diet items (e.g., bananas, sugar cane, pumpkin) were positively correlated with FGM concentrations, glucose, fructosamine, and insulin. This study provides evidence that body condition, adrenal activity, metabolic markers, and lipid profiles in captive elephants may be affected by visitor numbers, work activities, and the amount of supplementary foods offered by tourists. Some activities appear to have negative (e.g., feeding), while others (e.g., exercise) may have positive effects on health and welfare. We conclude that camps adopting a more hands-off approach to tourism need to ensure elephants remain healthy by providing environments that encourage activity and rely on more natural diets or foraging.

Role of cadmium and arsenic as endocrine disruptors in the metabolism of carbohydrates: Inserting the association into perspectives

Endocrine disrupting chemicals (EDCs) have widespread environmental distribution originated from both natural and anthropogenic sources. From the last few decades, their contamination has been raised dramatically owing to continuous discharge in sewage and untreated industrial effluents. They have rapidly gained a considerable attention due to their critical role in the development of multiple endocrine-related disorders notably diabetes mellitus (DM). Cadmium and arsenic, among the most hazardous EDCs, are not only widely spread in our environment, but they are also found to be associated with wide range of health hazards. After entering into the human body, they are preferably accumulated in the liver, kidney and pancreas where they exhibit deleterious effects on carbohydrate metabolism pathways notably glycolysis, glucogenesis and gluconeogenesis through the modification and impairment of relevant key enzymes activity. Impairment of hepatic glucose homeostasis plays a crucial role in the pathogenesis of DM. Along with compromised function of pancreas and muscles, diminished liver and kidney functions also contribute considerably to increase the blood glucose level. These metals have potential to bring conformational changes in these enzymes and make them inactive. Additionally, these metals also disturb the hormonal balance, such as insulin, glucocorticoids and catecholamines; by damaging pancreas and adrenal gland, respectively. Moreover, these metals also enhance the production of reactive oxygen species and depress the anti-oxidative defense mechanism with subsequent disruption of multiple organs. In this article, we have briefly highlighted the impact of arsenic and cadmium on the metabolism of carbohydrates and the enzymes that are involved in carbohydrate metabolism and glucose homeostasis.

Body condition and adrenal glucocorticoid activity affects metabolic marker and lipid profiles in captive female elephants in Thailand

Studies in western zoo elephants have found relationships between body condition and physiological function, and identified mitigating management strategies to optimize health and welfare. A similar methodological approach was used in this study, which evaluated a body condition score (BCS; 1 = thinnest, 5 = fattest) every other month and fecal glucocorticoid metabolite (FGM) concentrations twice monthly in 33 tourist camp elephants in Thailand for a 1-year period to assess seasonal variations, and determine how lipid profiles [total cholesterol (TC), low density lipoproteins (LDL), high density lipoproteins (HDL), triglycerides (TG)] and metabolic parameters [insulin, glucose, fructosamine, glucose to insulin ratio (G:I)] related to measures of body condition and adrenal function. The most prevalent BCS was 3-3.5 (60.6%), with 27.3% at BCS = 4 (overweight) and 12.1% at BCS = 4.5-5 (very overweight); no elephants had a BCS <2. BCSs were higher in rainy and winter seasons compared to summer, with FGM, TG, HDL, LDL, and insulin also higher in the rainy and/or winter seasons (p<0.05). By contrast, TC and glucose were lowest in the rainy season. FGM measures were negatively associated with two environmental factors: temperature and rainfall, but not humidity. Positive correlations were found between BCS and TC, LDL, and HDL, and between FGM and TC, HDL, glucose, and insulin (p<0.05), whereas BCS and FGM were both negatively associated with the G:I (p<0.05). However, there was no relationship between BCS and FGM among the camp elephants. Using BCS and FGM measures as outcome variables in separate regression models, this study found high BCS and elevated FGM concentrations were associated with altered lipid profiles and metabolic status in elephants. Furthermore, more work hours/day was associated with better body condition and health measures. Thus, being overweight and exposed to factors that increase adrenal activity could adversely affect health status, requiring alterations in management for some individuals, whereas exercise appears to have a protective effect.

The effect of gestational period on the association between maternal prenatal salivary cortisol and birth weight: A systematic review and meta-analysis

BACKGROUND

Studies exploring the relations between maternal stress and fetal development show an association between increased maternal stress and adverse birth outcomes. A frequently proposed mechanism linking maternal prenatal stress and adverse birth outcomes is heightened concentrations of maternal cortisol. To date, studies exploring this association have reported conflicting results because of the diverse approaches taken to measuring cortisol and the wide variety of possible birth outcomes explored. To add clarity to the growing body of literature, this systematic review and meta-analysis reports empirical findings on the association between maternal prenatal salivary cortisol and newborn birth weight.

METHODS

Searches for relevant papers published up until November 2017 were run in MEDLINE, EMBASE, PsycINFO, and CINAHL. Non-English language papers were included and experts were contacted when necessary. We included data from human observational studies that were designed or had an underlying intention to measure maternal prenatal salivary cortisol and newborn birth weight. We only included data from measurements of salivary cortisol to prevent rendering of the review unsuitable for meta-analysis. Two independent reviewers assessed study eligibility and quality. For every maternal-fetal dyad, an area under the curve with respect to ground (AUCg) of maternal cortisol was calculated to determine a Pearson's correlation coefficient with a continuous measure of newborn birth weight. Correlation coefficients were then pooled across all stages of gestation. To examine if there are critical gestational periods in which the fetus may be more susceptible to elevated concentration of maternal salivary cortisol, a meta-analysis was performed on separate correlations calculated from gestational trimesters.

RESULTS

Nine studies with a total of 1606 maternal-fetal dyads demonstrated a negative correlation between pooled maternal salivary cortisol and birth weight (-0.24, 95% CI -0.28 to -0.20), but there was a high degree of heterogeneity between studies (I² = 88.9%). To investigate heterogeneity, subgroup analysis by trimester of the pooled correlation between salivary cortisol and birth weight was performed with the following correlations found: first trimester, -0.18 (95% CI -0.32 to -0.03, I² = 97.3%); second trimester, -0.20 (95% CI -0.28 to -0.12, I² = 98.3%); and third trimester, -0.30 (95% CI -0.33 to -0.26, I² = 85.4%).

DISCUSSION

A consistently negative association was observed between maternal cortisol and infant birth weight. The review highlights specific gaps in the literature on the relationship between maternal prenatal salivary cortisol and newborn birth weight. Although a significant negative correlation was found, substantial heterogeneity of effects and the likelihood of publication bias exist. The third trimester was revealed as a possible critical gestational period for heightened maternal cortisol concentration to affect birth weight. Challenges faced in this body of research and recommendations for future research are discussed.

Theophylline suppresses interleukin-6 expression by inhibiting glucocorticoid receptor signaling in pre-adipocytes

Adipose tissues in obese individuals are characterized by a state of chronic low-grade inflammation. Pre-adipocytes and adipocytes in this state secrete pro-inflammatory adipokines, such as interleukin 6 (IL-6), which induce insulin resistance and hyperglycemia. Theophylline (1,3-dimethylxanthine) exerts anti-inflammatory effects, but its effects on pro-inflammatory adipokine secretion by pre-adipocytes and adipocytes have not been examined. In this study, we found that theophylline decreased IL-6 secretion by 3T3-L1 pre-adipocytes and mouse-derived primary pre-adipocytes. The synthetic glucocorticoid dexamethasone (DEX) induced IL-6 expression in 3T3-L1 pre-adipocytes, and this effect was suppressed by theophylline at the mRNA level. Knockdown of CCAAT/enhancer binding protein (C/EBP) δ inhibited DEX-induced IL-6 expression, and theophylline suppressed C/EBPδ expression. Furthermore, theophylline suppressed transcriptional activity of the glucocorticoid receptor (GR) through suppression of nuclear localization of GR. In vivo, glucocorticoid corticosterone treatment (100 μg/mL) increased fasting blood glucose and plasma IL-6 levels in C57BL/6 N mice. Theophylline administration (0.1% diet) reduced corticosterone-increased fasting blood glucose, plasma IL-6 levels, and Il6 gene expression in adipose tissues. These results show that theophylline administration attenuated glucocorticoid-induced hyperglycemia and IL-6 production by inhibiting GR activity. The present findings indicate the potential of theophylline as a candidate therapeutic agent to treat insulin resistance and hyperglycemia.

Glucocorticoids suppress brown adipose tissue function in humans: A double-blind placebo-controlled study

AIM

To investigate the effect of glucocorticoids on brown adipose tissue (BAT) function in humans.

MATERIALS AND METHODS

In a randomized double-blind cross-over design, 13 healthy adults underwent 1 week of oral prednisolone treatment (15 mg/d) and placebo with an intervening 2-week wash-out period. BAT function was assessed in response to cooling (19°C) and to a standardized meal, by measuring fluoro-deoxyglucose (FDG) uptake using positron emission tomography-computed tomography and skin temperatures overlying the supraclavicular (SCL) BAT depots using infrared thermography. Postprandial energy and substrate metabolism was assessed by indirect calorimetry.

RESULTS

During cooling, prednisolone significantly reduced BAT FDG uptake (standardized uptake value, SUV_max, 6.1 ± 2.2 vs 3.7 ± 1.2; P < .05) and SCL temperature (-0.45 ± 0.1 vs -1.0 ± 0.1°C; P < .01) compared to placebo. Postprandially, prednisolone significantly blunted the rise in SCL temperature (+0.2 ± 0.1 vs -0.3 ± 0.1°C; P < .05), enhanced energy production (+221 ± 17 vs +283 ± 27 kcal/d; P < .01) and lipid synthesis (+16.3 ± 3.2 vs +23.6 ± 4.9 mg/min; P < .05). The prednisolone-induced reduction in SCL temperature significantly correlated with the reduction in FDG uptake (r = 0.65, P < .05), while the increase in energy production significantly correlated with the increase in lipogenesis (r = 0.6, P < .05).

CONCLUSION

Prolonged exposure to glucocorticoid suppresses the function of human BAT. The enhancement of energy production and lipogenesis in the face of reduced dissipation of energy as heat suggests that glucocorticoids channel energy towards fat storage after nutrient intake. This is a novel mechanism of glucocorticoid-induced obesity.

Metabolomics Based Profiling of Dexamethasone Side Effects in Rats

Dexamethasone (Dex) is a synthetic glucocorticoid that has anti-inflammatory and immunosuppressant effects and is used in several conditions such as asthma and severe allergy. Patients receiving Dex, either at a high dose or for a long time, might develop several side effects such as hyperglycemia, weight change, or osteoporosis due to its in vivo non-selectivity. Herein, we used liquid chromatography-tandem mass spectrometry-based comprehensive targeted metabolomic profiling as well as radiographic imaging techniques to study the side effects of Dex treatment in rats. The Dex-treated rats suffered from a ∼20% reduction in weight gain, hyperglycemia (145 mg/dL), changes in serum lipids, and reduction in total serum alkaline phosphatase (ALP) (∼600 IU/L). Also, compared to controls, Dex-treated rats showed a distinctive metabolomics profile. In particular, serum amino acids metabolism showed six-fold reduction in phenylalanine, lysine, and arginine levels and upregulation of tyrosine and hydroxyproline reflecting perturbations in gluconeogenesis and protein catabolism which together lead to weight loss and abnormal bone metabolism. Sorbitol level was markedly elevated secondary to hyperglycemia and reflecting activation of the polyol metabolism pathway causing a decrease in the availability of reducing molecules (glutathione, NADPH, NAD+). Overexpression of succinylacetone (4,6-dioxoheptanoic acid) suggests a novel inhibitory effect of Dex on hepatic fumarylacetoacetate hydrolase. The acylcarnitines, mainly the very long chain species (C12, C14:1, C18:1) were significantly increased after Dex treatment which reflects degradation of the adipose tissue. In conclusion, long-term Dex therapy in rats is associated with a distinctive metabolic profile which correlates with its side effects. Therefore, metabolomics based profiling may predict Dex treatment-related side effects and may offer possible novel therapeutic interventions.

Fat-brain connections: Adipocyte glucocorticoid control of stress and metabolism

Glucocorticoids act via multiple mechanisms to mobilize energy for maintenance and restoration of homeostasis. In adipose tissue, glucocorticoids can promote lipolysis and facilitate adipocyte differentiation/growth, serving both energy-mobilizing and restorative processes during negative energy balance. Recent data suggest that adipose-dependent feedback may also be involved in regulation of stress responses. Adipocyte glucocorticoid receptor (GR) deletion causes increased HPA axis stress reactivity, due to a loss of negative feedback signals into the CNS. The fat-to-brain signal may be mediated by neuronal mechanisms, release of adipokines or increased lipolysis. The ability of adipose GRs to inhibit psychogenic as well as metabolic stress responses suggests that (1) feedback regulation of the HPA axis occurs across multiple bodily compartments, and (2) fat tissue integrates psychogenic stress signals. These studies support a link between stress biology and energy metabolism, a connection that has clear relevance for numerous disease states and their comorbidities.

Selective Pharmacogenetic Activation of Catecholamine Subgroups in the Ventrolateral Medulla Elicits Key Glucoregulatory Responses

Catecholamine (CA) neurons in the ventrolateral medulla (VLM) contribute importantly to glucoregulation during glucose deficit. However, it is not known which CA neurons elicit different glucoregulatory responses or whether selective activation of CA neurons is sufficient to elicit these responses. Therefore, to selectively activate CA subpopulations, we injected male or female Th-Cre+ transgenic rats with the Cre-dependent DREADD construct, AAV2-DIO-hSyn-hM3D(Gq)-mCherry, at one of four rostrocaudal levels of the VLM: rostral C1 (C1r), middle C1 (C1m), the area of A1 and C1 overlap (A1/C1), and A1. Transfection was highly selective for CA neurons at each site. Systemic injection of the Designer Receptor Exclusively Activated by Designer Drugs (DREADD) receptor agonist, clozapine-N-oxide (CNO), stimulated feeding in rats transfected at C1r, C1m, or A1/C1 but not A1. CNO increased corticosterone secretion in rats transfected at C1m or A1/C1 but not A1. In contrast, CNO did not increase blood glucose or induce c-Fos expression in the spinal cord or adrenal medulla after transfection of any single VLM site but required dual transfection of both C1m and C1r, possibly indicating that CA neurons mediating blood glucose responses are more sparsely distributed in C1r and C1m than those mediating feeding and corticosterone secretion. These results show that selective activation of C1 CA neurons is sufficient to increase feeding, blood glucose levels, and corticosterone secretion and suggest that each of these responses is mediated by CA neurons concentrated at different levels of the C1 cell group.

Lipid metabolism in patients with chronic hyperglycemia after an episode of acute pancreatitis

BACKGROUND

The importance of dyslipidemia is well recognized in the context of both risk factor for acute pancreatitis and prognostic factor for its in-hospital outcomes. With a growing appreciation of post-pancreatitis diabetes mellitus, there is a need to catalogue changes in lipid metabolism after hospitalization due to an acute pancreatitis attack and their associations with glucose metabolism.

OBJECTIVE

To investigate lipid metabolism in patients with impaired glucose homeostasis following acute pancreatitis.

METHODS

There were two study groups: newly diagnosed chronic hyperglycemia or normoglycemia after acute pancreatitis. During the fasting state, venous blood samples were collected to analyse markers of lipid metabolism (triglycerides, glycerol, low density lipoprotein, high density lipoprotein, total cholesterol, free fatty acids, and apolipoprotein-B) and glucose metabolism (HbA1c, insulin, index of adipose tissue insulin resistance (Adipo-IR), and HOMA-IR). Binary logistic and linear regression analyses were conducted, and potential confounders were adjusted for in multivariate analyses.

RESULTS

The study included 64 patients with normoglycemia and 19 - with chronic hyperglycemia. Glycerol was significantly associated with the development of chronic hyperglycemia in both unadjusted (p=0.02) and adjusted (p=0.006) models. Triglycerides were significantly associated with the development of chronic hyperglycemia in adjusted (p=0.019) model. Other markers of lipid metabolism did not differ significantly between the two groups. None of the markers of lipid metabolism was significantly associated with Adipo-IR or HOMA-IR.

CONCLUSION

Overall, patients with chronic hyperglycemia after acute pancreatitis appear to have a lipid profile indicative of an up-regulation of lipolysis, which is not significantly affected by either general or adipose tissue-specific insulin resistance.

Systemic Effects of Repeated Intraocular Dexamethasone Intravitreal Implant in Diabetic Patients: A Retrospective Study

INTRODUCTION

The objective of this study is to evaluate the influence of repeated intraocular dexamethasone implant (Ozurdex) injections on metabolic control in type 2 diabetic patients.

METHODS

Retrospective study of 165 type 2 diabetic patients starting Ozurdex treatment who received no less than three consecutive injections. Glycated hemoglobin (HbA1c), serum creatinine, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides (TGs) were evaluated during 15 months of follow-up after Ozurdex treatment onset.

RESULTS

Fifty-seven patients met inclusion criteria. Mean baseline values for HbA1c, creatinine, total cholesterol, HDL cholesterol, and TGs before treatment (7.1%, 1.3, 176.7, 51.1, and 125.6 mg/dl, respectively) were similar to mean values after Ozurdex onset (Wilcoxon test p values were 0.68, 0.41, 0.06, 0.87, and 0.33, respectively) and remained stable during the follow-up period. Mean LDL cholesterol levels increased slightly after Ozurdex treatment onset (90.1 vs 88.2 mg/dl, p = 0.04) but after 15 months of follow-up they had returned to baseline values. Transient increase in LDL cholesterol was remarkable in the group of 24 bilaterally treated patients (96.8 vs 88.4 mg/dl, p = 0.03). A third of these patients increased their baseline LDL values by more than 20%. Even with continuous injections of Ozurdex, LDL cholesterol levels also declined back to baseline by month 15.

CONCLUSION

Ozurdex injections had no influence on HbA1c or renal function. Lipid profile changes were mild and transient. However, a significant temporary increase has been found in LDL cholesterol levels in patients receiving simultaneous bilateral injections. Lipid levels should be monitored in patients starting with bilateral Ozurdex injections especially in those with recent history of acute myocardial infarction.

Sleep apnea: An overlooked cause of lipotoxicity?

Obstructive sleep apnea (OSA) is a common sleep disorder associated with diabetes and cardiovascular disease. However, the mechanisms by which OSA causes cardiometabolic dysfunction are not fully elucidated. OSA increases plasma free fatty acids (FFA) during sleep, reflecting excessive adipose tissue lipolysis. In animal studies, intermittent hypoxia simulating OSA also increases FFA, and the increase is attenuated by beta-adrenergic blockade. In other contexts, excessive plasma FFA can lead to ectopic fat accumulation, insulin resistance, vascular dysfunction, and dyslipidemia. Herein, we propose that OSA is a cause of excessive adipose tissue lipolysis contributing towards systemic "lipotoxicity". Since visceral and upper-body obesity contributes to OSA pathogenesis, OSA-induced lipolysis may further aggravate the consequences of this metabolically harmful state. If this hypothesis is correct, then OSA may represent a reversible risk factor for cardio-metabolic dysfunction, and this risk might be mitigated by preventing OSA-induced lipolysis during sleep.

Acute physiological effects of glucocorticoids on fuel metabolism in humans are permissive but not direct

BACKGROUND AND AIMS

The effects of glucocorticoids on fuel metabolism are complex. Acute glucocorticoid excess promotes lipolysis but chronic glucocorticoid excess causes visceral fat accumulation. We hypothesized that interactions between cortisol and insulin and adrenaline account for these conflicting results. We tested the effect of cortisol on lipolysis and glucose production with and without insulin and adrenaline in humans both in vivo and in vitro.

MATERIALS AND METHODS

A total of 20 healthy men were randomized to low and high insulin groups (both n = 10). Subjects attended on 3 occasions and received low (c. 150 nM), medium (c. 400 nM) or high (c. 1400 nM) cortisol infusion in a randomized crossover design. Deuterated glucose and glycerol were infused intravenously along with a pancreatic clamp (somatostatin with replacement of glucagon, insulin and growth hormone) and adrenaline. Subcutaneous adipose tissue was obtained for analysis. In parallel, the effect of cortisol on lipolysis was tested in paired primary cultures of human subcutaneous and visceral adipocytes.

RESULTS

In vivo, high cortisol increased lipolysis only in the presence of high insulin and/or adrenaline but did not alter glucose kinetics. High cortisol increased adipose mRNA levels of ATGL, HSL and CGI-58 and suppressed G0S2. In vitro, high cortisol increased lipolysis in the presence of insulin in subcutaneous, but not visceral, adipocytes.

CONCLUSIONS

The acute lipolytic effects of cortisol require supraphysiological concentrations, are dependent on insulin and adrenaline and are observed only in subcutaneous adipose tissue. The resistance of visceral adipose tissue to cortisol's lipolytic effects may contribute to the central fat accumulation observed with chronic glucocorticoid excess.

Metabolic Flexibility in Health and Disease

Metabolic flexibility is the ability to respond or adapt to conditional changes in metabolic demand. This broad concept has been propagated to explain insulin resistance and mechanisms governing fuel selection between glucose and fatty acids, highlighting the metabolic inflexibility of obesity and type 2 diabetes. In parallel, contemporary exercise physiology research has helped to identify potential mechanisms underlying altered fuel metabolism in obesity and diabetes. Advances in "omics" technologies have further stimulated additional basic and clinical-translational research to further interrogate mechanisms for improved metabolic flexibility in skeletal muscle and adipose tissue with the goal of preventing and treating metabolic disease.

Evaluating morphometric and metabolic markers of body condition in a small cetacean, the harbor porpoise (Phocoena phocoena)

Mammalian body condition is an important individual fitness metric as it affects both survival and reproductive success. The ability to accurately measure condition has key implications for predicting individual and population health, and therefore monitoring the population‐level effects of changing environments. No consensus currently exists on the best measure to quantitatively estimate body condition in many species, including cetaceans. Here, two measures of body condition were investigated in the harbor porpoise (Phocoena phocoena). First, the most informative morphometric body condition index was identified. The mass/length² ratio was the most appropriate morphometric index of 10 indices tested, explaining 50% of the variation in condition in stranded, male porpoises with different causes of death and across age classes (n = 291). Mass/length² was then used to evaluate a second measure, blubber cortisol concentration, as a metabolic condition marker. Cortisol is the main glucocorticoid hormone involved in the regulation of lipolysis and overall energy balance in mammals, and concentrations could provide information on physiological state. Blubber cortisol concentrations did not significantly vary around the girth (n = 20), but there was significant vertical stratification through the blubber depth with highest concentrations in the innermost layer. Concentrations in the dorsal, outermost layer were representative of concentrations through the full blubber depth, showed variation by sex and age class, and were negatively correlated with mass/length². Using this species as a model for live cetaceans from which standard morphometric measurements cannot be taken, but from which blubber biopsy samples are routinely collected, cortisol concentrations in the dorsal, outermost blubber layer could potentially be used as a biomarker of condition in free‐ranging animals.

Acute Hypercortisolemia Exerts Depot-Specific Effects on Abdominal and Femoral Adipose Tissue Function

CONTEXT

Glucocorticoids have pleiotropic metabolic functions, and acute glucocorticoid excess affects fatty acid metabolism, increasing systemic lipolysis. Whether glucocorticoids exert adipose tissue depot-specific effects remains unclear.

OBJECTIVE

To provide an in vivo assessment of femoral and abdominal adipose tissue responses to acute glucocorticoid administration.

DESIGN AND OUTCOME MEASURES

Nine healthy male volunteers were studied on two occasions, after a hydrocortisone infusion (0.2 mg/kg/min for 14 hours) and a saline infusion, respectively, given in randomized double-blind order. The subjects were studied in the fasting state and after a 75-g glucose drink with an in vivo assessment of femoral adipose tissue blood flow (ATBF) using radioactive xenon washout and of lipolysis and glucose uptake using the arteriovenous difference technique. In a separate study (same infusion design), eight additional healthy male subjects underwent assessment of fasting abdominal ATBF and lipolysis only. Lipolysis was assessed as the net release of nonesterified fatty acids (NEFAs) from femoral and abdominal subcutaneous adipose tissue.

RESULTS

Acute hypercortisolemia significantly increased basal and postprandial ATBF in femoral adipose tissue, but the femoral net NEFA release did not change. In abdominal adipose tissue, hypercortisolemia induced substantial increases in basal ATBF and NEFA release.

CONCLUSIONS

Acute hypercortisolemia induces differential lipolysis and ATBF responses in abdominal and femoral adipose tissue, suggesting depot-specific glucocorticoid effects. Abdominal, but not femoral, adipose tissue contributes to the hypercortisolemia-induced systemic NEFA increase, with likely contributions from other adipose tissue sources and intravascular triglyceride hydrolysis.

Maternal Cortisol During Pregnancy and Infant Adiposity: A Prospective Investigation

CONTEXT

Glucocorticoids play a key role during intrauterine development in cellular growth and differentiation. Evidence suggests that exposure to inappropriate concentrations of glucocorticoids during sensitive developmental periods may produce alterations in physiological systems that impact obesity risk.

OBJECTIVE

To elucidate the magnitude and stage-of-gestation-specific association of maternal cortisol concentrations during pregnancy with infant adiposity.

DESIGN, PARTICIPANTS, AND SETTING

Sixty-seven mother-child dyads recruited in early pregnancy at university-based obstetric clinics in Southern California were followed with serial assessments from early gestation through birth until 6 months postnatal age. Maternal cumulative cortisol production was assessed over each of 4 consecutive days in early (≅13 weeks), mid (≅24 weeks), and late pregnancy (≅30 weeks) (5 saliva samples/d × 4 days × 3 trimesters = 60 saliva samples/subject). Infant body composition was serially assessed in newborns (at ∼25 days postnatal age) and at ∼6 months age with dual-energy X-ray absorptiometry imaging.

RESULTS

After adjusting for key prenatal, birth, and postnatal covariates, higher maternal cortisol during the early third trimester (conditioned on prior early and midgestation cortisol concentrations) was significantly associated with a greater change in infant percent body fat from 1 to 6 months of age [partial r (adjusted for covariates) = 0.379, P = 0.007], accounting for ∼14% of the variance in this measure of childhood obesity risk.

CONCLUSION

The present findings suggest a stage-of-gestation-specific effect of maternal cortisol on infant adiposity gain in early postnatal life and provide evidence in humans to support the role of glucocorticoids in fetal programming of childhood obesity risk.

Circadian Rhythms in Adipose Tissue Physiology

The different types of adipose tissues fulfill a wide range of biological functions-from energy storage to hormone secretion and thermogenesis-many of which show pronounced variations over the course of the day. Such 24-h rhythms in physiology and behavior are coordinated by endogenous circadian clocks found in all tissues and cells, including adipocytes. At the molecular level, these clocks are based on interlocked transcriptional-translational feedback loops comprised of a set of clock genes/proteins. Tissue-specific clock-controlled transcriptional programs translate time-of-day information into physiologically relevant signals. In adipose tissues, clock gene control has been documented for adipocyte proliferation and differentiation, lipid metabolism as well as endocrine function and other adipose oscillations are under control of systemic signals tied to endocrine, neuronal, or behavioral rhythms. Circadian rhythm disruption, for example, by night shift work or through genetic alterations, is associated with changes in adipocyte metabolism and hormone secretion. At the same time, adipose metabolic state feeds back to central and peripheral clocks, adjusting behavioral and physiological rhythms. In this overview article, we summarize our current knowledge about the crosstalk between circadian clocks and energy metabolism with a focus on adipose physiology. © 2017 American Physiological Society. Compr Physiol 7:383-427, 2017.

Role of cannabinoid receptor 1 in human adipose tissue for lipolysis regulation and insulin resistance

We recently showed that the peripheral cannabinoid receptor type 1 (CNR1) gene is upregulated by the synthetic glucocorticoid dexamethasone. CNR1 is highly expressed in the central nervous system and has been a drug target for the treatment of obesity. Here we explore the role of peripheral CNR1 in states of insulin resistance in human adipose tissue. Subcutaneous adipose tissue was obtained from well-controlled type 2 diabetes subjects and controls. Subcutaneous adipose tissue gene expression levels of CNR1 and endocannabinoid synthesizing and degrading enzymes were assessed. Furthermore, paired human subcutaneous adipose tissue and omental adipose tissue from non-diabetic volunteers undergoing kidney donation or bariatric surgery, was incubated with or without dexamethasone. Subcutaneous adipose tissue obtained from volunteers through needle biopsy was incubated with or without dexamethasone and in the presence or absence of the CNR1-specific antagonist AM281. CNR1 gene and protein expression, lipolysis and glucose uptake were evaluated. Subcutaneous adipose tissue CNR1 gene expression levels were 2-fold elevated in type 2 diabetes subjects compared with control subjects. Additionally, gene expression levels of CNR1 and endocannabinoid-regulating enzymes from both groups correlated with markers of insulin resistance. Dexamethasone increased CNR1 expression dose-dependently in subcutaneous adipose tissue and omental adipose tissue by up to 25-fold. Dexamethasone pre-treatment of subcutaneous adipose tissue increased lipolysis rate and reduced glucose uptake. Co-incubation with the CNR1 antagonist AM281 prevented the stimulatory effect on lipolysis, but had no effect on glucose uptake. CNR1 is upregulated in states of type 2 diabetes and insulin resistance. Furthermore, CNR1 is involved in glucocorticoid-regulated lipolysis. Peripheral CNR1 could be an interesting drug target in type 2 diabetes and dyslipidemia.

Endocrinologic Adaptations to Wintertime Fasting in the Male American Mink (Mustela vison)

The aim of this study was to investigate the endocrine response to wintertime starvation in the male American mink (Mustela vison) fasted for 16 hrs, 2 days, 3 days, 5 days, or 7 days (n–10 per group). After 2 days of fasting, the plasma leptin concentrations decreased, along with the triiodothyronine, testosterone, and progesterone levels, and the blood monocyte counts. Leptin also seems to trigger the response to fasting in mustelids by inducing immunosuppression and downregulation of the reproductive and thyroid axes. The dramatic increase in the peptide YY concentrations after 3 days of fasting may be required to suppress gastrointestinal processes during food scarcity. The plasma insulin levels decreased, and those of glucagon increased after 5 days of fasting in association with efficient glucose sparing and lipid mobilization. Body energy stores cannot be wasted for growth during nutritional scarcity and, thus, the growth hormone levels of the minks decreased after 5 days of fasting. The plasma noradrenaline and cortisol concentrations also decreased after 3 and 7 days without food, respectively. The plasma ghrelin, adiponectin, resistin, thyroxine, adrenaline, or estradiol levels did not respond to fasting. The endocrine response to food deprivation is remarkably similar in divergent mammalian orders, indicating that the hormonal signals enhancing survival during nutritional scarcity must be evolutionarily old and well conserved.

Effects of prednisolone on energy and fat metabolism in patients with rheumatoid arthritis: tissue-specific insulin resistance with commonly used prednisolone doses

OBJECTIVE

Glucocorticoids can cause postprandial hyperglycaemia, but the effects on postprandial energy and fat metabolism are uncertain. We investigated the effects of acute and chronic low-dose prednisolone on fasting and postprandial energy expenditure and substrate metabolism.

DESIGN

An open interventional and cross-sectional study was undertaken.

PATIENTS AND MEASUREMENTS

Eighteen patients who had not taken oral glucocorticoids for ≥6 months were studied before and after 7 days prednisolone (6 mg/day) to assess the acute effects of prednisolone. Baseline data from patients, not on glucocorticoids, were compared with 18 patients on long-term prednisolone (6·5 ± 1·8 mg/day for >6 months) to assess the chronic effects. Energy expenditure and substrate oxidation were measured using indirect calorimetry before and after a mixed meal. Adipocyte insulin resistance index and insulin-mediated suppression of NEFA were calculated from fasting and postprandial insulin and NEFA concentrations.

RESULTS

There were no significant differences in resting energy expenditure or diet-induced thermogenesis with prednisolone. Acute (-2·1 ± 6·2 vs -16·3 ± 4·8 mg/min, P = 0·01) and chronic (-1·4 ± 2·8 vs -16·3 ± 4·8 mg/min, P = 0·01) prednisolone attenuated postprandial suppression of fat oxidation. Chronic (31·6 ± 3·8 vs 17·0 ± 3·3, P = 0·007), but not acute, prednisolone increased adipocyte insulin resistance index. However, insulin-mediated suppression of NEFA was not significantly different after acute or chronic prednisolone.

CONCLUSIONS

Prednisolone does not alter energy expenditure. However, even at low doses, prednisolone exerts adverse effects on fat metabolism, which could exacerbate insulin resistance and increase cardiovascular risk. Attenuated postprandial suppression of fat oxidation, but not lipolysis, suggests that prednisolone causes greater insulin resistance in skeletal muscle than in adipocytes.

Impact of Glucocorticoid Excess on Glucose Tolerance: Clinical and Preclinical Evidence

Glucocorticoids (GCs) are steroid hormones that exert important physiological actions on metabolism. Given that GCs also exert potent immunosuppressive and anti-inflammatory actions, synthetic GCs such as prednisolone and dexamethasone were developed for the treatment of autoimmune- and inflammatory-related diseases. The synthetic GCs are undoubtedly efficient in terms of their therapeutic effects, but are accompanied by significant adverse effects on metabolism, specifically glucose metabolism. Glucose intolerance and reductions in insulin sensitivity are among the major concerns related to GC metabolic side effects, which may ultimately progress to type 2 diabetes mellitus. A number of pre-clinical and clinical studies have aimed to understand the repercussions of GCs on glucose metabolism and the possible mechanisms of GC action. This review intends to summarize the main alterations that occur in liver, skeletal muscle, adipose tissue, and pancreatic islets in the context of GC-induced glucose intolerance. For this, both experimental (animals) and clinical studies were selected and, whenever possible, the main cellular mechanisms involved in such GC-side effects were discussed.

Human β-defensin 3 suppresses Porphyromonas gingivalis lipopolysaccharide-induced inflammation in RAW 264.7 cells and aortas of ApoE-deficient mice

Human beta-defensin 3 (hBD3) is an antimicrobial peptide showing immunomodulatory effect on both innate and acquired immune response. Atherosclerosis is an inflammatory disease characterized by accumulation of lipids in the vascular wall. In this study, we evaluated whether hBD3 could attenuate the atherosclerosis development accelerated by Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) with apolipoprotein E-deficient (ApoE(-/-)) mice. We observed that, in vivo, hBD3 inhibited serum MCP-1, sICAM-1 levels of ApoE-deficient mice exposed to Pg-LPS in a chronic inflammation model. Serum levels of total cholesterol (TC) and low-density lipoprotein (LDL) were also markedly reduced with hBD3 intervention. In addition, thinned vascular walls, less macrophage infiltration and the formation of atherosclerotic lesions were observed in the hBD3-treated group. Furthermore, in vitro, hBD3 profoundly suppressed the production of TNF-α and IL-6 in RAW 264.7 cells induced by Pg-LPS in a dose-dependent manner. Moreover, hBD3 attenuated the phosphorylation of p38 and ERK1/2 in the mitogen-activated protein kinase (MAPK) pathway. Taken together, our work has revealed that hBD3 exhibits potent anti-inflammatory properties both in vitro and in vivo, and this effect might be correlated with inhibition of MAPK pathway.

AMERICAN ASSOCIATION OF CLINICAL ENDOCRINOLOGISTS AND AMERICAN COLLEGE OF ENDOCRINOLOGY POSITION STATEMENT ON THE ASSOCIATION OF SGLT-2 INHIBITORS AND DIABETIC KETOACIDOSIS

ABBREVIATIONS

AACE = American Association of Clinical Endocrinologists ACE = American College of Endocrinology DKA = diabetic ketoacidosis EMA = European Medicines Agency FDA = U.S. Food and Drug Administration SGLT-2 = sodium glucosecotransporter 2 T1D = type 1 diabetes T2D = type 2 diabetes.

Altered DNA methylation of glucose transporter 1 and glucose transporter 4 in patients with major depressive disorder

Alterations in brain glucose metabolism and in peripheral glucose metabolism have frequently been observed in major depressive disorder (MDD). The insulin independent glucose transporter 1 (GLUT1) plays a key role in brain metabolism while the insulin-dependent GLUT4 is the major glucose transporter for skeletal and cardiac muscle. We therefore examined methylation of GLUT1 and GLUT4 in fifty-two depressed inpatients and compared data to eighteen healthy comparison subjects. DNA methylation of the core promoter regions of GLUT1 and GLUT4 was assessed by bisulfite sequencing. Further factors determined were fasting glucose, cortisol, insulin, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). We found significantly increased methylation of the GLUT1 in depressed inpatients compared to healthy comparison subjects (CG). Further findings comprise increased concentrations of fasting cortisol, glucose, insulin, and increased IL-6 and TNF-α. After six weeks of inpatient treatment, significantly lower GLUT1 methylation was observed in remitted patients compared to non-remitters. GLUT4 methylation was not different between depressed patients and CG, and did not differ between remitted and non-remitted patients. Although preliminary we conclude from our results that the acute phase of major depressive disorder is associated with increased GLUT1 methylation and mild insulin resistance. The successful treatment of depression is associated with normalization of GLUT1 methylation in remitters, indicating that this condition may be reversible. Failure of normalization of GLUT1 methylation in non-remitters may point to a possible role of impeded brain glucose metabolism in the maintenance of MDD.

Relationships between Rodent White Adipose Fat Pads and Human White Adipose Fat Depots

The objective of this review was to compare and contrast the physiological and metabolic profiles of rodent white adipose fat pads with white adipose fat depots in humans. Human fat distribution and its metabolic consequences have received extensive attention, but much of what has been tested in translational research has relied heavily on rodents. Unfortunately, the validity of using rodent fat pads as a model of human adiposity has received less attention. There is a surprisingly lack of studies demonstrating an analogous relationship between rodent and human adiposity on obesity-related comorbidities. Therefore, we aimed to compare known similarities and disparities in terms of white adipose tissue (WAT) development and distribution, sexual dimorphism, weight loss, adipokine secretion, and aging. While the literature supports the notion that many similarities exist between rodents and humans, notable differences emerge related to fat deposition and function of WAT. Thus, further research is warranted to more carefully define the strengths and limitations of rodent WAT as a model for humans, with a particular emphasis on comparable fat depots, such as mesenteric fat.

The glucocorticoid receptor: cause of or cure for obesity?

Glucocorticoid hormones (GCs) are important regulators of lipid metabolism, promoting lipolysis with acute treatment but lipogenesis with chronic exposure. Conventional wisdom posits that these disparate outcomes are mediated by the classical glucocorticoid receptor GRα. There is insufficient knowledge of the GC receptors (GRα and GRβ) in metabolic conditions such as obesity and diabetes. We present acute models of GC exposure that induce lipolysis, such as exercise, as well as chronic-excess models that cause obesity and lipid accumulation in the liver, such as hepatic steatosis. Alternative mechanisms are then proposed for the lipogenic actions of GCs, including induction of GC resistance by the GRβ isoform, and promotion of lipogenesis by GC activation of the mineralocorticoid receptor (MR). Finally, the potential involvement of chaperone proteins in the regulation of adipogenesis is considered. This reevaluation may prove useful to future studies on the steroidal basis of adipogenesis and obesity.

Interaction of low dose of fish oil and glucocorticoids on insulin sensitivity and lipolysis in healthy humans: A randomized controlled study

SCOPE

This study examined the interaction of fish oil (FO) with dexamethasone on glucose and lipid metabolisms in healthy subjects.

METHODS AND RESULTS

The study included two consecutive parts. Part A (randomized) in 16 subjects studied the effects of dexamethasone (2 days, 2 mg/day) versus placebo (lactose), part B (two parallel subgroups of eight) studied the interaction of FO (3 wk, 840 mg/day of EPA + DHA) with dexamethasone. Insulin sensitivity of lipolysis (d5-glycerol infusion + microdialysis), endogenous glucose production, and muscle glucose uptake were assessed by a three-step hot insulin clamp and substrate oxidation by indirect calorimetry. Dexamethasone induced liver and peripheral insulin resistance, an increase in fat oxidation, and a decrease in suppression of plasma nonesterified fatty acids (NEFAs). FO amplified the effects of dexamethasone by increasing liver and muscle insulin resistance, by reducing suppression of plasma NEFAs and fat oxidation and by increasing adipose tissue (AT) lipolysis.

CONCLUSION

FO, given at a moderate dose in healthy subjects prior to a very short-term (2 days) low dose of a synthetic glucocorticoid, worsened its deleterious effects on insulin sensitivity. The enhancing effect of FO on fat oxidation and AT lipolysis might be a protective effect toward an increase in fat mass.

Gene expression changes in subcutaneous adipose tissue due to Cushing's disease

Glucocorticoids have major effects on adipose tissue metabolism. To study tissue mRNA expression changes induced by chronic elevated endogenous glucocorticoids, we performed RNA sequencing on the subcutaneous adipose tissue from patients with Cushing's disease (n=5) compared to patients with nonfunctioning pituitary adenomas (n=11). We found a higher expression of transcripts involved in several metabolic pathways, including lipogenesis, proteolysis and glucose oxidation as well as a decreased expression of transcripts involved in inflammation and protein synthesis. To further study this in a model system, we subjected mice to dexamethasone treatment for 12 weeks and analyzed their inguinal (subcutaneous) fat pads, which led to similar findings. Additionally, mice treated with dexamethasone showed drastic decreases in lean body mass as well as increased fat mass, further supporting the human transcriptomic data. These data provide insight to transcriptional changes that may be responsible for the comorbidities associated with chronic elevations of glucocorticoids.

Subchronic sleep restriction causes tissue-specific insulin resistance

CONTEXT

Short sleep duration is associated with an increased risk of type 2 diabetes. Subchronic sleep restriction (SR) causes insulin resistance, but the mechanisms and roles of specific tissues are unclear.

OBJECTIVE

The purpose of this article was to determine whether subchronic SR altered (1) hepatic insulin sensitivity, (2) peripheral insulin sensitivity, and (3) substrate utilization.

DESIGN

This was a randomized crossover study in which 14 subjects underwent 2 admissions separated by a washout period. Each admission had 2 acclimatization nights followed by 5 nights of either SR (4 hours time in bed) or normal sleep (8 hours time in bed). MAIN OUTCOME MEASURE/METHODS: Insulin sensitivity (measured by hyperinsulinemic-euglycemic clamp) and hepatic insulin sensitivity (measured by stable isotope techniques) were measured. In addition, we assayed stress hormone (24-hour urine free cortisol, metanephrine, and normetanephrine), nonesterified fatty acid (NEFA), and β-hydroxybutyrate (β-OH butyrate) levels. Resting energy expenditure (REE) and respiratory quotient (RQ) were measured by indirect calorimetry.

RESULTS

Compared to normal sleep, whole-body insulin sensitivity decreased by 25% (P = .008) with SR and peripheral insulin sensitivity decreased by 29% (P = .003). Whereas hepatic insulin sensitivity (endogenous glucose production) did not change significantly, percent gluconeogenesis increased (P = .03). Stress hormones increased modestly (cortisol by 21%, P = .04; metanephrine by 8%, P = .014; normetanephrine by 18%, P = .002). Fasting NEFA and β-OH butyrate levels increased substantially (62% and 55%, respectively). REE did not change (P = 0.98), but RQ decreased (0.81 ± .02 vs 0.75 ± 0.02, P = .045).

CONCLUSION

Subchronic SR causes unique metabolic disturbances characterized by peripheral, but not hepatic, insulin resistance; this was associated with a robust increase in fasting NEFA levels (indicative of increased lipolysis), decreased RQ, and increased β-OH butyrate levels (indicative of whole-body and hepatic fat oxidation, respectively). We postulate that elevated NEFA levels are partially responsible for the decrease in peripheral sensitivity and modulation of hepatic metabolism (ie, increase in gluconeogenesis without increase in endogenous glucose production). Elevated cortisol and metanephrine levels may contribute to insulin resistance by increasing lipolysis and NEFA levels.

Circadian Clocks and the Interaction between Stress Axis and Adipose Function

Many physiological processes and most endocrine functions show fluctuations over the course of the day. These so-called circadian rhythms are governed by an endogenous network of cellular clocks and serve as an adaptation to daily and, thus, predictable changes in the organism's environment. Circadian clocks have been described in several tissues of the stress axis and in adipose cells where they regulate the rhythmic and stimulated release of stress hormones, such as glucocorticoids, and various adipokine factors. Recent work suggests that both adipose and stress axis clock systems reciprocally influence each other and adrenal-adipose rhythms may be key players in the development and therapy of metabolic disorders. In this review, we summarize our current understanding of adrenal and adipose tissue rhythms and clocks and how they might interact to regulate energy homoeostasis and stress responses under physiological conditions. Potential chronotherapeutic strategies for the treatment of metabolic and stress disorders are discussed.

Glucocorticoid treatment and endocrine pancreas function: implications for glucose homeostasis, insulin resistance and diabetes

Glucocorticoids (GCs) are broadly prescribed for numerous pathological conditions because of their anti-inflammatory, antiallergic and immunosuppressive effects, among other actions. Nevertheless, GCs can produce undesired diabetogenic side effects through interactions with the regulation of glucose homeostasis. Under conditions of excess and/or long-term treatment, GCs can induce peripheral insulin resistance (IR) by impairing insulin signalling, which results in reduced glucose disposal and augmented endogenous glucose production. In addition, GCs can promote abdominal obesity, elevate plasma fatty acids and triglycerides, and suppress osteocalcin synthesis in bone tissue. In response to GC-induced peripheral IR and in an attempt to maintain normoglycaemia, pancreatic β-cells undergo several morphofunctional adaptations that result in hyperinsulinaemia. Failure of β-cells to compensate for this situation favours glucose homeostasis disruption, which can result in hyperglycaemia, particularly in susceptible individuals. GC treatment does not only alter pancreatic β-cell function but also affect them by their actions that can lead to hyperglucagonaemia, further contributing to glucose homeostasis imbalance and hyperglycaemia. In addition, the release of other islet hormones, such as somatostatin, amylin and ghrelin, is also affected by GC administration. These undesired GC actions merit further consideration for the design of improved GC therapies without diabetogenic effects. In summary, in this review, we consider the implication of GC treatment on peripheral IR, islet function and glucose homeostasis.

Chronic glucocorticoid exposure-induced epididymal adiposity is associated with mitochondrial dysfunction in white adipose tissue of male C57BL/6J mice

Prolonged and excessive glucocorticoids (GC) exposure resulted from Cushing's syndrome or GC therapy develops central obesity. Moreover, mitochondria are crucial in adipose energy homeostasis. Thus, we tested the hypothesis that mitochondrial dysfunction may contribute to chronic GC exposure-induced epididymal adiposity in the present study. A total of thirty-six 5-week-old male C57BL/6J mice (∼20 g) were administrated with 100 µg/ml corticosterone (CORT) or vehicle through drinking water for 4 weeks. Chronic CORT exposure mildly decreased body weight without altering food and water intake in mice. The epididymal fat accumulation was increased, but adipocyte size was decreased by CORT. CORT also increased plasma CORT, insulin, leptin, and fibroblast growth factor 21 concentrations as measured by RIA or ELISA. Interestingly, CORT increased plasma levels of triacylglycerols and nonesterified fatty acids, and up-regulated the expression of both lipolytic and lipogenic genes as determined by real-time RT-PCR. Furthermore, CORT impaired mitochondrial biogenesis and oxidative function in epididymal WAT. The reactive oxygen species production was increased and the activities of anti-oxidative enzymes were reduced by CORT treatment as well. Taken together, these findings reveal that chronic CORT administration-induced epididymal adiposity is, at least in part, associated with mitochondrial dysfunction in mouse epididymal white adipose tissue.

Effects of acute glucocorticoid blockade on metabolic dysfunction in patients with Type 2 diabetes with and without fatty liver

To investigate the potential of therapies which reduce glucocorticoid action in patients with Type 2 diabetes we performed a randomized, double-blinded, placebo-controlled crossover study of acute glucocorticoid blockade, using the glucocorticoid receptor antagonist RU38486 (mifepristone) and cortisol biosynthesis inhibitor (metyrapone), in 14 men with Type 2 diabetes. Stable isotope dilution methodologies were used to measure the rates of appearance of glucose, glycerol, and free fatty acids (FFAs), including during a low-dose (10 mU·m⁻² ·min⁻¹) hyperinsulinemic clamp, and subgroup analysis was conducted in patients with high or low liver fat content measured by magnetic resonance spectroscopy (n = 7/group). Glucocorticoid blockade lowered fasting glucose and insulin levels and improved insulin sensitivity of FFA and glycerol turnover and hepatic glucose production. Among this population with Type 2 diabetes high liver fat was associated with hyperinsulinemia, higher fasting glucose levels, peripheral and hepatic insulin resistance, and impaired suppression of FFA oxidation and FFA and glycerol turnover during hyperinsulinemia. Glucocorticoid blockade had similar effects in those with and without high liver fat. Longer term treatments targeting glucocorticoid action may be useful in Type 2 diabetes with and without fatty liver.