Alterations in the dynamics of circulating ghrelin, adiponectin, and leptin in human obesity

Aqueous and methanol extracts of Vernonia amygdalina leaves exert their anti-obesity effects through the modulation of appetite-regulatory hormones

CONTEXT

Aqueous and methanol extracts of Vernonia amygdalina Del. (Asteraceae) (AEVA and MEVA, respectively) leaves are reported to possess anti-obesity properties, exerted through unknown mechanisms.

OBJECTIVE

This study investigated the effects of AEVA and MEVA on relevant hormones and enzymes in high-fat diet (HFD)-induced obese rats.

MATERIALS AND METHODS

Forty-two Wistar rats were placed into seven groups. The test groups received 100 mg/kg.bw AEVA (AEVA100), 500 mg/kg.bw AEVA (AEVA500), 50 mg/kg.bw MEVA (MEVA50) and 200 mg/kg.bw MEVA (MEVA200), respectively. The positive control (PC) group received 20 mg/kg.bw Orlistat, while the negative control (NeC) and normal control (NoC) groups received distilled water. The extracts were given orally daily for 12 weeks. Thereafter, the concentrations/activities of relevant hormones/enzymes in their sera were determined.

RESULTS

Insulin concentrations (ng/ml) in the test groups ranged from 1.08 ± 0.01 (AEVA100) to 1.09 ± 0.01 (AEVA500). They were all similar (p > .05) to the NoC and PC controls. Leptin concentrations (pg/ml) in the test rats ranged from 0.02 ± 0.01 (AEVA500) to 0.03 ± 0.00 (MEVA50), and were all similar to the NoC group. The ghrelin concentrations of only the AEVA500 and MEVA200 groups were similar to those of the PC group (0.10 ± 0.01 pg/ml). AEVA100 and MEVA200 resulted in adiponectin concentrations (ng/ml) of the rats (0.27 ± 0.04 and 0.28 ± 0.04 respectively) that were similar to the PC group. The activities of lipoprotein lipase and the concentrations of intestinal amylase in the test rats were similar to values obtained for the control groups.

CONCLUSION

Appetite regulation may be the mechanism through which the weight-loss properties of AEVA and MEVA are expressed.

Taurine Treatment Modulates Circadian Rhythms in Mice Fed A High Fat Diet

Close ties have been made among certain nutrients, obesity, type 2 diabetes and circadian clocks. Among nutrients, taurine has been documented as being effective against obesity and type 2 diabetes. However, the impact of taurine on circadian clocks has not been elucidated. We investigated whether taurine can modulate or correct disturbances in daily rhythms caused by a high-fat diet in mice. Male C57BL/6 mice were divided in four groups: control (C), control + taurine (C+T), high-fat diet (HFD) and HFD + taurine (HFD+T). They were administered 2% taurine in their drinking water for 10 weeks. Mice were euthanized at 6:00, 12:00, 18:00, and 24:00. HFD mice increased body weight, visceral fat and food intake, as well as higher levels of glucose, insulin and leptin, throughout the 24 h. Taurine prevented increments in food intake, body weight and visceral fat, improved glucose tolerance and insulin sensitivity and reduced disturbances in the 24 h patterns of plasma insulin and leptin. HFD downregulated the expression of clock genes Rev-erbα, Bmal1, and Per1 in pancreatic islets. Taurine normalized the gene and protein expression of PER1 in beta-cells, which suggests that it could be beneficial for the correction of daily rhythms and the amelioration of obesity and diabetes.

Low adiponectin levels at baseline and decreasing adiponectin levels over 10 years of follow-up predict risk of the metabolic syndrome

AIM

Adiponectin is the most abundant adipokine and may play a key role in the interplay between obesity, inflammation, insulin resistance and the metabolic syndrome (MetS). Thus, this large population-based cohort investigated whether adiponectin at baseline and/or a decrease in adiponectin during follow-up is associated prospectively with the risk of incident MetS.

METHODS

Using a prospective study design, the development of MetS was examined in 1134 healthy participants from the community. Plasma adiponectin was measured at study entry and again after a median follow-up of 9.4 years (IQR: 9.2-9.7). During follow-up, 187 participants developed MetS, and 439 presented with at least two components of MetS.

RESULTS

During follow-up, adiponectin decreased in participants who developed MetS, whereas adiponectin was increased in those who did not develop MetS (P<0.001). Those with low adiponectin levels (quartile 1) at baseline had an increased risk of developing MetS (OR: 2.92, 2.08-6.97; P<0.001) compared with those with high levels (quartile 4). After adjusting for confounding variables, low adiponectin levels at baseline remained independently associated with MetS (OR: 2.24, 1.11-4.52; P=0.017). Similarly, participants with a decrease in adiponectin during follow-up also had an increased risk of MetS (OR: 2.96, 2.09-4.18; P<0.001). This association persisted after multivariable adjustments, including for baseline adiponectin (OR: 4.37, 2.77-6.97; P<0.001). Finally, adiponectin levels at follow-up were inversely associated with an increase in the number of components of MetS (P<0.001); geometric mean adiponectin levels were 9.5mg/L (95% CI: 9.0-10.0) for participants with no components vs 7.0mg/L (95% CI: 6.3-7.9) for those with four to five components.

CONCLUSIONS/INTERPRETATION

Low plasma adiponectin levels at baseline and decreasing adiponectin levels during follow-up are both associated with an increased risk of MetS.

The ghrelin and leptin responses to short-term starvation vs a carbohydrate-free diet in men with type 2 diabetes; a controlled, cross-over design study

Background

We recently have reported the 24-hour glucose, insulin and glucagon responses to a 72-hour fast compared to a 72-hour macronutrient-sufficient, carbohydrate-free diet in men with type 2 diabetes. The 72-hour time period was used because it is the time required for the major metabolic adjustments to a lack of food to be instituted. As part of that study, ghrelin and leptin responses were monitored.

Methods

Twenty-four-hour total ghrelin and overnight fasting leptin concentrations were determined in males with type 2 diabetes when ingesting a standard, mixed meal diet (control), followed by a carbohydrate-free diet for 72 h or were starved for 72 h, using a crossover design.

Results

A rise in ghrelin concentration before and a decrease after meals was present when the standard diet was ingested. However, in contrast to literature reports in normal subjects, a circadian variation was not apparent. Meal related changes were absent with starvation. A carbohydrate-free diet resulted in a daylong decrease in ghrelin. It also resulted in a 19 % decrease in the overnight fasting leptin concentration. Leptin was decreased 54 % with total starvation.

Conclusion

Ingestion of a typical mixed-meal diet results in meal-related changes in ghrelin similar to those reported in normal subjects, although the circadian rhythm was not apparent. Except for the lack of meal-related changes, starvation did not change the concentration. A carbohydrate-free, high fat diet resulted in a daylong suppression of ghrelin. The leptin concentration was decreased by both the carbohydrate-free diet and starvation.

Trial registration

ClinicalTrials.gov Identifier: NCT01469104.

Striatal dopamine D2/3 receptor availability increases after long-term bariatric surgery-induced weight loss

In several studies reduced striatal dopamine D2/3 receptor (D2/3R) availability was reported in obese subjects compared to lean controls. Whether this is a reversible phenomenon remained uncertain. We previously determined the short-term effect of Roux-en-Y gastric bypass surgery (RYGB) on striatal D2/3R availability (using [(123)I]IBZM SPECT) in 20 morbidly obese women. Striatal D2/3R availability was lower compared to controls at baseline, and remained unaltered after 6 weeks, despite significant weight loss. To determine whether long-term bariatric surgery-induced weight loss normalizes striatal D2/3R binding, we repeated striatal D2/3R binding measurements at least 2 years after RYGB in 14 subjects of the original cohort. In addition, we assessed long-term changes in body composition, eating behavior and fasting plasma levels of leptin, ghrelin, insulin and glucose. Mean body mass index declined from 46±7kg/m(2) to 32±6kg/m(2), which was accompanied by a significant increase in striatal D2/3R availability (p=0.031). Striatal D2/3R availability remained significantly reduced compared to the age-matched controls (BMI 22±2kg/m(2); p=0.01). Changes in striatal D2/3R availability did not correlate with changes in body weight/fat, insulin sensitivity, ghrelin or leptin levels. Scores on eating behavior questionnaires improved and changes in the General Food Craving Questionnaire-State showed a borderline significant correlation with changes in striatal D2/3R availability. These findings show that striatal D2/3R availability increases after long-term bariatric-surgery induced weight loss, suggesting that reduced D2/3R availability in obesity is a reversible phenomenon.

Gastric ghrelin, GOAT, leptin, and leptinR expression as well as peripheral serotonin are dysregulated in humans with obesity

BACKGROUND

Gastrointestinal hormone release and the regulation of appetite and body weight are thought to be dysbalanced in obesity. However, human data investigating the expression of gastrointestinal hormones in the obese are rare. We studied the expression of ghrelin, leptin, and the serotonergic system in stomach tissue and serum of obese and non-obese individuals.

METHODS

Gastric tissue and serum were collected from 29 adult obese (BMI 48.7 ± 10.6 kg/m(2) ; mean ± SD) who underwent laparoscopic sleeve gastrectomy. Gastric biopsies, surgery specimen or serum was obtained from 35 adult non-obese humans (BMI 22.7 ± 1.9 kg/m(2) ). Ghrelin, ghrelin O-acyl transferase (GOAT), leptin, leptin receptor, and tryptophan hydroxylase 1 (TPH1) mRNA expression were measured by qRT-PCR. Serotonin (5HT) and leptin protein concentration were quantified in tissue extracts and serum; GOAT and ghrelin-positive cells were immunohistologically quantified in tissue. Additionally, 21 blood immune markers were analyzed.

KEY RESULTS

In gastric tissue, GOAT-positive cells were reduced (p < 0.01), but ghrelin-positive cells and mRNA were increased (both p < 0.05) in obese compared with non-obese individuals. Gastric leptin (p < 0.001) and leptin receptor (p < 0.001) mRNA expression, as well as leptin concentrations in serum (p < 0.001), were increased in obese compared with non-obese individuals. Serum 5HT was reduced (p < 0.05), while tissue 5HT and TPH1 mRNA were reduced only by trend. Interleukin 1 receptor a (IL1Ra), IL-8, IL-12, and monocyte chemoattractant protein 1 (IL1Ra) were increased and IL1Ra correlated negatively with serum leptin.

CONCLUSIONS & INFERENCES

Our data indicate that obesity causes a dysregulation of gastrointestinal hormones at the tissue level and serum, including a negative correlation with an increased marker of subclinical inflammation.

Ghrelin: A link between memory and ingestive behavior

Feeding is a highly complex behavior that is influenced by learned associations between external and internal cues. The type of excessive feeding behavior contributing to obesity onset and metabolic deficit may be based, in part, on conditioned appetitive and ingestive behaviors that occur in response to environmental and/or interoceptive cues associated with palatable food. Therefore, there is a critical need to understand the neurobiology underlying learned aspects of feeding behavior. The stomach-derived "hunger" hormone, ghrelin, stimulates appetite and food intake and may function as an important biological substrate linking mnemonic processes with feeding control. The current review highlights data supporting a role for ghrelin in mediating the cognitive and neurobiological mechanisms that underlie conditioned feeding behavior. We discuss the role of learning and memory on food intake control (with a particular focus on hippocampal-dependent memory processes) and provide an overview of conditioned cephalic endocrine responses. A neurobiological framework is provided through which conditioned cephalic ghrelin secretion signals in neurons in the hippocampus, which then engage orexigenic neural circuitry in the lateral hypothalamus to express learned feeding behavior.

Leptin secretory dynamics and associated disordered eating psychopathology across the weight spectrum

OBJECTIVE

Leptin secretory dynamics across the weight spectrum and their relationship with disordered eating psychopathology have not been studied. Our objective was to compare leptin secretory dynamics in 13 anorexia nervosa (AN), 12 overweight/obese (OB) and 12 normal-weight women using deconvolution analysis.

METHODS

In this cross-sectional study conducted at a tertiary referral center, serum leptin levels were obtained every 20  min from 2000 to 0800  h. Dual energy X-ray absorptiometry was used to measure percent body fat. Disordered eating psychopathology was assessed by the Eating Disorders Examination-Questionnaire (EDE-Q) and the Eating Disorders Inventory-2 (EDI-2).

RESULTS

The groups differed for basal leptin secretion (BASAL) (P=0.02). Mean leptin pulse amplitude, pulse mass, total pulsatile secretion (TPS) and area under the curve (AUC) were significantly different between groups before and after adjustment for BASAL (P<0.0001 for all). Leptin AUC correlated strongly with TPS (r=0.97, P<0.0001) and less with BASAL (r=0.35, P=0.03). On multivariate analysis, only TPS was a significant predictor of leptin AUC (P<0.0001). TPS was inversely associated with most EDE-Q and EDI-2 parameters and the associations remained significant for EDE-Q eating concern (P=0.01), and EDI-2 asceticism, ineffectiveness and social insecurity (P<0.05) after adjusting for BASAL. These relationships were not significant when controlled for percent body fat.

CONCLUSION

Secretory dynamics of leptin differ across weight spectrum, with mean pulse amplitude, mean pulse mass and TPS being low in AN and high in OB. Pulsatile, rather than basal secretion, is the major contributor to leptin AUC. Decreased pulsatile leptin is associated with disordered eating psychopathology, possibly reflecting low percent body fat in AN.

A Follow-Up Study of 50 Chronic Hepatitis C Patients: Adiponectin as a Resilience Biomarker for Major Depression

OBJECTIVE

Major depression (MD) is a condition associated with both hepatitis C virus (HCV) infection and pegylated interferon (IFN)-α treatment. IFN induces a depressive syndrome that is associated with an inflammatory profile. We aimed to investigate whether there is any specific alteration in plasma biomarkers associated with MD.

METHODS

HCV-monoinfected patients, with and without IFN treatment, were followed up for 18 months and went through structured psychiatric evaluation. We assessed plasma levels of brain-derived neurotrophic factor, tumor necrosis factor (TNF) and its soluble type 1 and type 2 receptors (sTNFR1 and sTNFR2, respectively), and adipokines (adiponectin, leptin and resistin) using ELISA.

RESULTS

Among the 50 patients included in the study, 14 were treated with IFN during the follow-up. Being older, not married, presenting higher body mass index, higher liver inflammatory activity, lower baseline adiponectin levels and use of IFN were associated with MD development. Higher levels of sTNFR1 during IFN treatment were associated with sustained virological response. The lack of a control group without HCV infection did not allow any assumption of a biomarker change exclusively due to the infection itself.

CONCLUSION

Adiponectin may be a resilience biomarker for MD in HCV-infected patients.

Milk Leptin Surge and Biological Rhythms of Leptin and Other Regulatory Proteins in Breastmilk

A significant number of chronic diseases are linked to perinatal nutrition, and prevention may be associated to naturally occurring components of breast milk. One key hormone in breast milk is leptin, related with the protection from obesity in the adulthood, thus knowing its changes through the day or lactation is crucial. We aimed to investigate the daily rhythms in the milk levels of leptin, together with other two related hormones, ghrelin and adiponectin, during lactation (days 5, 10 and 15) in rat dams, and the relation with morphometric parameters (dams and pups). Summarizing the main results, the existence of biological rhythms, but not daily and maybe circasemidian, was confirmed for the three hormones at the earliest period of lactation. The correlations performed generally showed a possible dependence of milk hormone levels on plasma levels at the early phase of lactation, while with the progression of lactation this dependence may fade and the hormone levels are suggested to be more dependent on mammary gland production/maturation. There was also a correlation between milk leptin and adiponectin levels, especially in the first half of lactation, suggesting a possible parallel regulation. Interestingly, we describe a milk leptin surge around the mid of lactation (at day 10) which may be related with pup´s growth (males and females) and with the well-known (in the literature) plasma leptin surge in pups. All this knowledge may be crucial for future applications in the development of formula milk and in relation with the role of leptin surge during lactation.

Dietary Carbohydrate and Nocturnal Sleep Duration in Relation to Children's BMI: Findings from the IDEFICS Study in Eight European Countries

Previous research has found an association between being overweight and short sleep duration. We hypothesized that this association could be modified by a high carbohydrate (HC) diet and that the timing and type (starch or sugar) of intake may be an important factor in this context. Participants in the prospective, eight-country European study IDEFICS were recruited from September 2007 to June 2008, when they were aged two to nine years. Data on lifestyle, dietary intake and anthropometry were collected on two occasions. This study included 5944 children at baseline and 4301 at two-year follow-up. For each meal occasion (morning, midday, and evening), starch in grams and sugar in grams were divided by total energy intake (EI), and quartiles calculated. HC-starch and HC-sugar intake categories were defined as the highest quartile for each meal occasion. In a mutually adjusted linear regression model, short sleep duration as well as HC-starch in the morning were positively associated with body mass index (BMI) z-scores at baseline. HC-starch at midday was positively associated with body mass index (BMI) z-scores in children with short sleep duration, and negatively associated with BMI z-scores in those with normal sleep. After adjustment for baseline BMI z-scores, associations between total HC from starch or sugar and high BMI z-scores at two-year follow-up did not persist. Our observations offer a perspective on optimal timing for macronutrient consumption, which is known to be influenced by circadian rhythms. Reduced carbohydrate intake, especially during morning and midday meals, and following nocturnal sleep duration recommendations are two modifiable factors that may protect children from being overweight in the future.

Pedunculopontine Gamma Band Activity and Development

This review highlights the most important discovery in the reticular activating system in the last 10 years, the manifestation of gamma band activity in cells of the reticular activating system (RAS), especially in the pedunculopontine nucleus, which is in charge of waking and rapid eye movement (REM) sleep. The identification of different cell groups manifesting P/Q-type Ca(2+) channels that control waking vs. those that manifest N-type channels that control REM sleep provides novel avenues for the differential control of waking vs. REM sleep. Recent discoveries on the development of this system can help explain the developmental decrease in REM sleep and the basic rest-activity cycle.

Role of the clock gene Bmal1 and the gastric ghrelin-secreting cell in the circadian regulation of the ghrelin-GOAT system

As adequate food intake is crucial to survival, organisms have evolved endogenous circadian clocks to generate optimal temporal patterns of food-related behavior and physiology. The gastric ghrelin-secreting cell is thought to be part of this network of peripheral food-entrainable oscillators (FEOs), regulating the circadian release of this orexigenic peptide. This study aimed to determine the role of the core clock gene Bmal1 and the gastric ghrelin-secreting cell as an FEO in the circadian rhythmicity of ghrelin expression and secretion in vivo and in vitro. Bmal1-deficient mice not only lacked circadian rhythmicity in plasma ghrelin levels and food intake, but also showed decreased gastric mRNA expression of ghrelin and ghrelin O-acyltransferase (GOAT), the ghrelin activating enzyme. Furthermore, in the absence of the hypothalamic master clock, food-related stimuli entrained the molecular clock of gastric ghrelinoma cells to regulate the rhythmic release of ghrelin. Divergent responses in octanoyl and total ghrelin release towards different food cues were observed, suggesting that the FEO also regulates the circadian rhythmicity of GOAT. Collectively, these findings indicate that circadian rhythmicity of ghrelin signaling requires Bmal1 and is driven by a food-responsive clock in the gastric ghrelin-secreting cell that not only regulates ghrelin, but also GOAT activity.

Early Effect of Bariatric Surgery on the Circadian Rhythms of Adipokines in Morbidly Obese Women

BACKGROUND

The circadian pattern of adipokines is blunted in obese subjects, and we tested the hypothesis that bariatric surgery could normalize the 24-hr pattern of adipokines. Therefore, this study was designed to examine the early impact of the newly designed sleeve gastrectomy with transit bipartition (SGTB) surgery on the circadian pattern of leptin, adiponectin, and resistin in morbidly obese subjects.

METHODS

The study group included six morbidly obese women [body mass index (BMI) 41.3 ± 1.53 kg/m(2)] who underwent SGTB and four lean women (BMI 18.61 ± 0.92 kg/m(2)). Blood from all subjects was collected before and 3 months after bariatric surgery every 6 hr throughout the 24-hr period. The circadian pattern of leptin, adiponectin, and resistin was measured by enzyme-linked immunosorbent assay or Luminex techniques.

RESULTS

Lean women exhibited rise of plasma leptin levels at nighttime, whereas obese women had an increase in the overall plasma leptin levels throughout the 24-hr period, lacking the physiological rise of nocturnal leptin levels compared to controls. Obese women had a decrease in 24-hr adiponectin levels and similar plasma resistin levels compared to controls. Three months after SGTB, obese women lost 16.0% (P < 0.005) of their initial body weight and had a decrease in overall 24-hr leptin levels. However, there was no recovery of the nocturnal rise in leptin levels 3 months after SGTB. The 24-hr adiponectin levels were still decreased after SGTB surgery compared to controls, while resistin levels were decreased only during night time after SGTB.

CONCLUSIONS

These results suggested that SGTB is an efficient innovative procedure to rapidly decrease 24-hr leptin levels. However, after 3 months, SGTB was not enough to recover the physiological nocturnal rise of leptin levels present in lean subjects.

In Situ Localization and Rhythmic Expression of Ghrelin and ghs-r1 Ghrelin Receptor in the Brain and Gastrointestinal Tract of Goldfish (Carassius auratus)

Ghrelin is a gut-brain peptide hormone, which binds to the growth hormone secretagogue receptor (GHS-R) to regulate a wide variety of biological processes in fish. Despite these prominent physiological roles, no studies have reported the anatomical distribution of preproghrelin transcripts using in situ hybridization in a non-mammalian vertebrate, and its mapping within the different encephalic areas remains unknown. Similarly, no information is available on the possible 24-h variations in the expression of preproghrelin and its receptor in any vertebrate species. The first aim of this study was to investigate the anatomical distribution of ghrelin and GHS-R1a ghrelin receptor subtype in brain and gastrointestinal tract of goldfish (Carassius auratus) using immunohistochemistry and in situ hybridization. Our second aim was to characterize possible daily variations of preproghrelin and ghs-r1 mRNA expression in central and peripheral tissues using real-time reverse transcription-quantitative PCR. Results show ghrelin expression and immunoreactivity in the gastrointestinal tract, with the most abundant signal observed in the mucosal epithelium. These are in agreement with previous findings on mucosal cells as the primary synthesizing site of ghrelin in goldfish. Ghrelin receptor was observed mainly in the hypothalamus with low expression in telencephalon, pineal and cerebellum, and in the same gastrointestinal areas as ghrelin. Daily rhythms in mRNA expression were found for preproghrelin and ghs-r1 in hypothalamus and pituitary with the acrophase occurring at nighttime. Preproghrelin, but not ghs-r1a, displayed a similar daily expression rhythm in the gastrointestinal tract with an amplitude 3-fold higher than the rest of tissues. Together, these results described for the first time in fish the mapping of preproghrelin and ghrelin receptor ghs-r1a in brain and gastrointestinal tract of goldfish, and provide the first evidence for a daily regulation of both genes expression in such locations, suggesting a possible connection between the ghrelinergic and circadian systems in teleosts.

Dysregulated metabolism contributes to oncogenesis

Cancer is a disease characterized by unrestrained cellular proliferation. In order to sustain growth, cancer cells undergo a complex metabolic rearrangement characterized by changes in metabolic pathways involved in energy production and biosynthetic processes. The relevance of the metabolic transformation of cancer cells has been recently included in the updated version of the review "Hallmarks of Cancer", where dysregulation of cellular metabolism was included as an emerging hallmark. While several lines of evidence suggest that metabolic rewiring is orchestrated by the concerted action of oncogenes and tumor suppressor genes, in some circumstances altered metabolism can play a primary role in oncogenesis. Recently, mutations of cytosolic and mitochondrial enzymes involved in key metabolic pathways have been associated with hereditary and sporadic forms of cancer. Together, these results demonstrate that aberrant metabolism, once seen just as an epiphenomenon of oncogenic reprogramming, plays a key role in oncogenesis with the power to control both genetic and epigenetic events in cells. In this review, we discuss the relationship between metabolism and cancer, as part of a larger effort to identify a broad-spectrum of therapeutic approaches. We focus on major alterations in nutrient metabolism and the emerging link between metabolism and epigenetics. Finally, we discuss potential strategies to manipulate metabolism in cancer and tradeoffs that should be considered. More research on the suite of metabolic alterations in cancer holds the potential to discover novel approaches to treat it.

Inter-relationships of the chronobiotic, melatonin, with leptin and adiponectin: implications for obesity

Obesity and its medical complications represent a significant problem throughout the world. In recent decades, mechanisms underlying the progression of obesity have been intensively examined. The involvement of both the behavioral aspects, such as calorie-rich diet, low physical activity and sleep deprivation, and the intrinsic factors, including adipose tissue deregulation, chronic inflammation, oxidative stress, and chronodisruption, has been identified. The circadian disturbances of the adipose tissue endocrine function have been correlated with obesity. Leptin and adiponectin are adipokines strongly associated with glucose and lipid metabolism and with energy balance. Their synthesis and secretion display circadian rhythms that are disturbed in the obese state. Hyperleptinemia resulting in leptin resistance, and hypo-adiponectinemia have been linked to the pathophysiology of the obesity-related disorders. A deficiency of melatonin, one of the consequences of sleep deprivation, has also been demonstrated to correlate with obesity. Melatonin is a pineal secretory product involved in numerous actions, such as regulation of internal biological clocks and energy metabolism, and it functions as an antioxidant and as an anti-inflammatory agent. There exists a substantial amount of evidence supporting the beneficial effects of melatonin supplementation on obesity and its complications. In the current review, the results of studies related to the interactions between melatonin, and both leptin and adiponectin are discussed. Despite the existence of some inconsistencies, melatonin has been found to normalize the expression and secretion patterns of both adipokines. These results support the concept of melatonin as a potential therapeutic agent for obesity and related disorders.

Serum Concentrations of Ghrelin and Leptin according to Thyroid Hormone Condition, and Their Correlations with Insulin Resistance

BACKGROUND

Thyroid hormones can influence energy metabolism and insulin sensitivity via their interaction with adipocytokines and gut hormones. The aims of this study were to evaluate differences in serum ghrelin and leptin concentrations according to thyroid hormone levels, and to investigate the correlation of insulin resistance.

METHODS

A total of 154 patients (57 hyperthyroid patients, 61 euthyroid patients, and 36 hypothyroid patients; mean age, 47.9 years) were enrolled. Serum leptin, ghrelin, and insulin levels were measured and insulin resistance was calculated using the formula of the homeostasis model assessment of insulin resistance (HOMA-IR).

RESULTS

There were no differences in mean concentrations of ghrelin or leptin among the three groups. There were no significant differences in insulin levels between the groups (P=0.06), although hyperthyroid patients had borderline statistically significantly higher levels of insulin than did euthyroid subjects by post hoc test (26.4 μIU/mL vs. 16.1 μIU/mL, P=0.057). Regarding HOMA-IR index, the mean levels were highest in the hyperthyroid group among those of the three groups (hyperthyroid vs. euthyroid vs. hypothyroid, 6.7 vs. 3.8 vs. 4.4, P=0.068). Plasma levels of ghrelin were significantly negatively correlated with age, insulin, glucose, body mass index (BMI), and HOMA-IR. Plasma levels of leptin showed significant positive correlation with BMI and triglyceride. There were no significant correlations among thyroid hormone, thyrotropin, ghrelin, leptin, or insulin.

CONCLUSION

The present study found that serum ghrelin, leptin, and insulin levels didn't differ according to thyroid function conditions. Further studies with larger numbers of patients are required to establish a direct relationship between plasma ghrelin, leptin, and thyroid hormone.

Contribution of daily and seasonal biorhythms to obesity in humans

While the significance of obesity as a serious health problem is well recognized, little is known about whether and how biometerological factors and biorhythms causally contribute to obesity. Obesity is often associated with altered seasonal and daily rhythmicity in food intake, metabolism and adipose tissue function. Environmental stimuli affect both seasonal and daily rhythms, and the latter are under additional control of internal molecular oscillators, or body clocks. Modifications of clock genes in animals and changes to normal daily rhythms in humans (as in shift work and sleep deprivation) result in metabolic dysregulation that favours weight gain. Here, we briefly review the potential links between biorhythms and obesity in humans.

Subcutaneous and total fat at L4-L5 and subcutaneous, visceral and total fat at L3-L4 are important contributors of fasting and postprandial adiponectin levels

OBJECTIVES

Insulin resistance and central obesity have been implicated in the pathogenesis of hypoadiponectinemia in obesity. The aim of this study is to evaluate circulating post-prandial adiponectin in relation to glucose and insulin metabolism, indexes of insulin resistance and sensitivity and, indexes of body fat accumulation and distribution in obese men.

METHODS

Twenty-eight non-diabetic men underwent an OGTT followed by an oral fat load and were studied at baseline and for 5 h post-prandially for serum adiponectin, glucose and insulin. Insulin resistance was estimated by Homeostasis model assessment (HOMA) and insulin sensitivity by Matsuda index. Body fat accumulation and distribution were evaluated by anthropometric indexes and multiple slices MRI of the abdomen and hip.

RESULTS

Adiponectin was negatively correlated to insulin levels. Fasting and area under the curve (AUC) adiponectin levels were negatively correlated to HOMA (both p < 0.01) and positively to Matsuda index (both p < 0.05). Negative correlations between fasting adiponectin and total fat (r = -0.408, p < 0.05), AUC adiponectin and subcutaneous, visceral and total fat (r = -0.375, -0.413 and -0.475 respectively, all p < 0.05) at L3-L4 were found, and negative correlations between fasting adiponectin and subcutaneous (r = -0.402, p < 0.05) and total fat (r = -0.491, p < 0.05) and between AUC adiponectin and subcutaneous and total fat (r = -0.506 and -0.547, respectively, both p < 0.01) were present at L4-L5.

CONCLUSIONS

Circulating adiponectin is inversely correlated to both visceral and subcutaneous fat in non-diabetic men, implying that both compartments are important for adiponectin levels. The best correlation is found at measurement site L4-L5.

The regulation of circulating ghrelin - with recent updates from cell-based assays

Ghrelin is a stomach-derived orexigenic hormone with a wide range of physiological functions. Elucidation of the regulation of the circulating ghrelin level would lead to a better understanding of appetite control in body energy homeostasis. Earlier studies revealed that circulating ghrelin levels are under the control of both acute and chronic energy status: at the acute scale, ghrelin levels are increased by fasting and decreased by feeding, whereas at the chronic scale, they are high in obese subjects and low in lean subjects. Subsequent studies revealed that nutrients, hormones, or neural activities can influence circulating ghrelin levels in vivo. Recently developed in vitro assay systems for ghrelin secretion can assess whether and how individual factors affect ghrelin secretion from cells. In this review, on the basis of numerous human, animal, and cell-based studies, we summarize current knowledge on the regulation of circulating ghrelin levels and enumerate the factors that influence ghrelin 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.

Adipokines as emerging depression biomarkers: a systematic review and meta-analysis

Adiponectin, leptin and resistin may play a role in the pathophysiology of major depressive disorder (MDD). However, differences in peripheral levels of these hormones are inconsistent across diagnostic and intervention studies. Therefore, we performed meta-analyses of diagnostic studies (i.e., MDD subjects versus healthy controls) and intervention investigations (i.e., pre-vs. post-antidepressant treatment) in MDD. Adiponectin (N = 1278; Hedge's g = -0.35; P = 0.16) and leptin (N = 893; Hedge's g = -0.018; P = 0.93) did not differ across diagnostic studies. Meta-regression analyses revealed that gender and depression severity explained the heterogeneity observed in adiponectin diagnostic studies, while BMI and the difference in BMI between MDD individuals and controls explained the heterogeneity of leptin diagnostic studies. Subgroup analyses revealed that adiponectin peripheral levels were significantly lower in MDD participants compared to controls when assayed with RIA, but not ELISA. Leptin levels were significantly higher in individuals with mild/moderate depression versus controls. Resistin serum levels were lower in MDD individuals compared to healthy controls (N = 298; Hedge's g = -0.25; P = 0.03). Leptin serum levels did not change after antidepressant treatment. However, heterogeneity was significant and sample size was low (N = 108); consequently meta-regression analysis could not be performed. Intervention meta-analyses could not be performed for adiponectin and resistin (i.e., few studies met inclusion criteria). In conclusion, this systematic review and meta-analysis underscored that relevant moderators/confounders (e.g., BMI, depression severity and type of assay) should be controlled for when considering the role of leptin and adiponectin as putative MDD diagnostic biomarkers.

Leptin promotes metastasis by inducing an epithelial-mesenchymal transition in A549 lung cancer cells

Leptin, an adipocyte-derived cytokine associated with obesity, has been reported to participate in carcinogenesis. Epithelial-mesenchymal transition (EMT) is also considered as a key event in tumor metastasis. The aim of this study is to investigate the mechanism of leptin in the promotion of EMT leading to metastasis in A549 lung cancer cells. We investigated the effect of leptin on migration of A549 cells using wound healing and transwell assays. The incidence of EMT in A549 cells was examined by real-time PCR and immunofluorescence staining. The expression of TGF-β in A549 cells was detected by real-time PCR, and blocking of TGF-β in A549 cells was achieved by siRNA techniques. Additional work was performed using 100 patient samples, which included samples from 50 patients diagnosed with lung cancer and an additional 50 patients diagnosed with lung cancer with metastatic bone lesions. Leptin expression was measured using immunohistochemistry techniques. We demonstrated that leptin can effectively enhance the metastasis of human lung cancer A549 cell line using both wound healing and transwell assays. We also found the incidence of EMT in A549 cells after leptin exposure. Furthermore, we detected the expression of TGF-β in A549 cells, which had been reported to play an important role in inducing EMT. We showed that leptin can significantly upregulate TGF-β at both the mRNA and protein levels in A549 cells. Using siRNA to block the expression of TGF-β in A549 cells, we confirmed the role of TGF-β in the promotion of metastasis and induction of EMT. Furthermore, we found that in patient samples leptin was present at higher levels in samples associated with diagnosis of lung cancer bone metastases tissue than lung cancer tissue. Our results indicated that leptin promoted the metastasis of A549 human lung cancer cell lines by inducing EMT in a TGF-β-dependent manner.

Relationship of ghrelin, acid uric and proinflammatory adipocytokines in different degrees of obesity or diabetes

We compared and examined factors associated with ghrelin and uric acid in obese subjects (OB), obese plus type 2 diabetes mellitus (OBDM) and healthy controls (C). Methods. We analyzed blood count, renal function, liver enzymes, lipids, resistin, leptin, IL-6, uric acid and ghrelin in OB, OBDM and C. We included 76 subjects with different body mass index (BMI): 36 C (24 ± 3), 11 OB<40 (30-39.9), 20 OB>40 (40-60), and 9 OBDM (45.9 ± 9). Results. Metabolic profile was as follows: HOMA-IR 4.7 ± 3 and 5 ± 3 vs 2 ± 1 (p < 0.01), resistin 8.7 ± 2 and 9.4 ± 2 vs 5.4 ± 2 ng/mL (p < 0.001), leptin 6.2 ± 3.9 and 5.3 ± 2 vs 3.6 ± 1.8 ng/mL (p = 0.001) and IL-6 197.5 ± 78.9 and 223.6 ± 115 vs 7.4 ± 8.3 pg/mL (p = 0.001) in OB and OBDM vs C, respectively. Ghrelin was higher in OB<40 compared to C (1780 ± 197 vs 1465 ± 12 pg/mL, p < 0.05), and lower in OBDM (987.4 ± 114 pg/mL, p < 0.05). BMI showed a positive correlation with resistin (p < 0.001); leptin (p = 0.004), IL-6 (p = 0.001), uric acid (p = 0.0005) and negative with ghrelin (r = -0.431, p = 0.028). Resistin was directly correlated with leptin (p < 0.001) and inversely correlated with renal function (p = 0.03). Conclusion. Severe obesity and obesity-associated diabetes affected ghrelin and uric acid levels. This may well be associated with proinflammatory adipocytokines, insulin resistance, liver enzymes or renal function.

Systematic review of ghrelin response to food intake in pediatric age, from neonates to adolescents

OBJECTIVE

Food intake and energy balance are regulated during the lifespan with critical changes in each specific period (infancy, adulthood, aging). Some of ghrelin's changes may contribute to the regulation of food intake and weight in children. We aimed to analyze the ghrelin response to feeding in lean or obese subjects from birth to adolescence.

METHODS

We searched PubMed, Scopus, Google Scholar, Cochrane, and EMBASE (December 1999 to February 2013) and identified 62 relevant articles, of which 29 were suitable to be included.

RESULTS AND CONCLUSIONS

Total ghrelin response to meals is particular, with refractoriness in neonates and lean children and an inhibition that starts from puberty. Total ghrelin levels are decreased after meals, irrespective of pubertal stages in obese children and adolescents. Conversely, total ghrelin is decreased after an oral glucose tolerance test in all ages, with the exception of neonates. Data on unacylated ghrelin response are scant but resemble those of total ghrelin. The acylated ghrelin response to meals or oral glucose tolerance test is discordant, although a precocious inhibition followed by a rise back is present in both lean and obese children. The post-feeding profile in children with Prader-Willi syndrome is also peculiar, with a conserved and deeper inhibition of all ghrelin forms.

Central adiponectin acutely improves glucose tolerance in male mice

Adiponectin, an adipocyte-derived hormone, regulates glucose and lipid metabolism. It is also antiinflammatory. During obesity, adiponectin levels and sensitivity are reduced. Whereas the action of adiponectin in the periphery is well established the neuroendocrine role of adiponectin is largely unknown. To address this we analyzed the expression of adiponectin and the 2 adiponectin receptors (AdipoR1 and AdipoR2) in response to fasting and to diet-induced and genetic obesity. We also investigated the acute impact of adiponectin on central regulation of glucose homeostasis. Adiponectin (1 μg) was injected intracerebroventricularly (ICV), and glucose tolerance tests were performed in dietary and genetic obese mice. Finally, the influence of ICV adiponectin administration on central signaling cascades regulating glucose homeostasis and on markers of hypothalamic inflammation was assessed. Gene expression of adiponectin was down-regulated whereas AdipoR1 was up-regulated in the arcuate nucleus of fasted mice. High-fat (HF) feeding increased AdipoR1 and AdipoR2 gene expression in this region. In mice on a HF diet and in leptin-deficient mice acute ICV adiponectin improved glucose tolerance 60 minutes after injection, whereas normoglycemia in control mice was unaffected. ICV adiponectin increased pAKT, decreased phospho-AMP-activated protein kinase, and did not change phospho-signal transducer and activator of transcription 3 immunoreactivity. In HF-fed mice, ICV adiponectin reversed parameters of hypothalamic inflammation and insulin resistance as determined by the number of phospho-glycogen synthase kinase 3 β(Ser9) and phospho-c-Jun N-terminal kinase (Thr183/Tyr185) immunoreactive cells in the arcuate nucleus and ventromedial hypothalamus. This study demonstrates that the insulin-sensitizing properties of adiponectin are at least partially based on a neuroendocrine mechanism that involves centrally synthesized adiponectin.

Changes in levels of peripheral hormones controlling appetite are inconsistent with hyperphagia in leptin-deficient subjects

Congenital leptin deficiency, a rare genetic disorder due to a homozygous mutation in the leptin gene (LEP), is accompanied by extreme obesity and hyperphagia. A number of gastrointestinal hormones have been shown to critically regulate food intake but their physiological role in hyperphagic response in congenital leptin deficiency has not been elucidated. This study is the first to evaluate the fasting and postprandial profiles of gut-derived hormones in homozygous and heterozygous carriers of LEP mutation. The study subjects from two consanguineous families consisted of five homozygous and eight heterozygous carriers of LEP mutation, c.398delG. Ten wild-type normal-weight subjects served as controls. Fasting and 1-h postprandial plasma ghrelin, glucagon-like peptide (GLP) 1, peptide YY (PYY), leptin and insulin levels were measured by immunoassays. Fasting plasma ghrelin levels in homozygotes remained remarkably unchanged following food consumption (P = 0.33) in contrast to a significant decline in heterozygous (P < 0.03) and normal (P < 0.02) subjects. A significant postprandial increase in PYY was observed in heterozygous (P < 0.02) and control subjects (P < 0.01), but not in the homozygous group (P = 0.22). A postprandial rise in GLP-1 levels was significant (P < 0.02) in all groups. Interestingly, fasting leptin levels in heterozygotes were not significantly different from controls and did not change significantly following meal. Our results demonstrate that gut hormones play little or no physiological role in driving the hyperphagic response of leptin-deficient subjects. In contrast, fasting and postprandial levels of gut hormones in heterozygous mutation carriers were comparable to those of normal-weight controls.

Physiological responses to food intake throughout the day

Circadian rhythms act to optimise many aspects of our biology and thereby ensure that physiological processes are occurring at the most appropriate time. The importance of this temporal control is demonstrated by the strong associations between circadian disruption, morbidity and disease pathology. There is now a wealth of evidence linking the circadian timing system to metabolic physiology and nutrition. Relationships between these processes are often reciprocal, such that the circadian system drives temporal changes in metabolic pathways and changes in metabolic/nutritional status alter core molecular components of circadian rhythms. Examples of metabolic rhythms include daily changes in glucose homeostasis, insulin sensitivity and postprandial response. Time of day alters lipid and glucose profiles following individual meals whereas, over a longer time scale, meal timing regulates adiposity and body weight; these changes may occur via the ability of timed feeding to synchronise local circadian rhythms in metabolically active tissues. Much of the work in this research field has utilised animal and cellular model systems. Although these studies are highly informative and persuasive, there is a largely unmet need to translate basic biological data to humans. The results of such translational studies may open up possibilities for using timed dietary manipulations to help restore circadian synchrony and downstream physiology. Given the large number of individuals with disrupted rhythms due to, for example, shift work, jet-lag, sleep disorders and blindness, such dietary manipulations could provide widespread improvements in health and also economic performance.

Neuroendocrine Profile in the Night Eating Syndrome

Night eating syndrome (NES) has recently been getting more attention as a recognized eating disorder. NES is characterized by a delay in the circadian pattern of food intake, associated with morning anorexia, evening hyperphagia, awakenings from sleep with ingestion of food, depressed mood, and obesity. Although the behavioral characteristics of NES were first described in 1955, the neuroendocrine characteristics have only been described recently. Researchers have examined several hormones that appear to differ in night eaters compared to controls, including melatonin, leptin, and cortisol. Researchers have more recently examined the hypothalamic-pituitary-adrenal axis in more detail, with emphasis on corticotrophin releasing hormone. Further studies have examined ghrelin, growth hormone, prolactin, and IGF-1, with differences observed in the circadian pattern of these hormones in those with NES compared to controls. Despite increasing interest in the neuroendocrine profile of night eating behavior, the biological basis of NES is still not well understood.

The therapeutic potential of nuclear receptor modulators for treatment of metabolic disorders: PPARγ, RORs, and Rev-erbs

Nuclear receptors (NRs) play central roles in metabolic syndrome, making them attractive drug targets despite the challenge of achieving functional selectivity. For instance, members of the thiazolidinedione class of insulin sensitizers offer robust efficacy but have been limited due to adverse effects linked to activation of genes not involved in insulin sensitization. Studies reviewed here provide strategies for targeting subsets of PPARγ target genes, enabling development of next-generation modulators with improved therapeutic index. Additionally, emerging evidence suggests that targeting the NRs ROR and Rev-erb holds promise for treating metabolic syndrome based on their involvement in circadian rhythm and metabolism.

Ghrelin-Derived Peptides: A Link between Appetite/Reward, GH Axis, and Psychiatric Disorders?

Psychiatric disorders are often associated with metabolic and hormonal alterations, including obesity, diabetes, metabolic syndrome as well as modifications in several biological rhythms including appetite, stress, sleep-wake cycles, and secretion of their corresponding endocrine regulators. Among the gastrointestinal hormones that regulate appetite and adapt the metabolism in response to nutritional, hedonic, and emotional dysfunctions, at the interface between endocrine, metabolic, and psychiatric disorders, ghrelin plays a unique role as the only one increasing appetite. The secretion of ghrelin is altered in several psychiatric disorders (anorexia, schizophrenia) as well as in metabolic disorders (obesity) and in animal models in response to emotional triggers (psychological stress …) but the relationship between these modifications and the physiopathology of psychiatric disorders remains unclear. Recently, a large literature showed that this key metabolic/endocrine regulator is involved in stress and reward-oriented behaviors and regulates anxiety and mood. In addition, preproghrelin is a complex prohormone but the roles of the other ghrelin-derived peptides, thought to act as functional ghrelin antagonists, are largely unknown. Altered ghrelin secretion and/or signaling in psychiatric diseases are thought to participate in altered appetite, hedonic response and reward. Whether this can contribute to the mechanism responsible for the development of the disease or can help to minimize some symptoms associated with these psychiatric disorders is discussed in the present review. We will thus describe (1) the biological actions of ghrelin and ghrelin-derived peptides on food and drugs reward, anxiety and depression, and the physiological consequences of ghrelin invalidation on these parameters, (2) how ghrelin and ghrelin-derived peptides are regulated in animal models of psychiatric diseases and in human psychiatric disorders in relation with the GH axis.

Anticipation of a psychosocial stressor differentially influences ghrelin, cortisol and food intake among emotional and non-emotional eaters

Negative emotions trigger eating in some individuals (emotional eaters) possibly by influencing stress hormones that contribute to eating regulation (e.g., cortisol), or eating-related peptides (e.g., ghrelin) signaling food initiation. The present study assessed whether stressor-elicited cortisol and ghrelin changes would differ between emotional and non-emotional eaters, and whether eating would influence these neuroendocrine responses. Undergraduate women (N=103) who completed measures of emotional eating, were assigned to anticipate either a stressful (public speaking) or non-stressful event. During this period, participants were or were not offered food. Blood samples were taken continuously over a 40-min period to assess changes of cortisol and ghrelin levels, and mood was assessed after the anticipation period. Baseline ghrelin levels were lower in emotional than non-emotional eaters, and this relation was mediated by percent body fat. Ghrelin levels were elevated among women anticipating a stressor, compared to those in the control condition. Additionally, the normal decline of ghrelin following food consumption was not apparent among emotional eaters. Although food intake was not tied to hormone responses, reported hunger was associated with greater food intake for women in the stressor condition. It was suggested that emotional eating coupled with subjective feelings of hunger, might contribute to eating in response to an acute stressor. Additionally, feedback mechanisms controlling the normalization of ghrelin levels might be disturbed in emotional eaters. The similarity of the ghrelin profile of emotional eaters to that of binge eaters and obese individuals, raises the possibility that disturbed ghrelin response might be a risk factor for such conditions.

Changes in daily leptin, ghrelin and adiponectin profiles following a diet with carbohydrates eaten at dinner in obese subjects

BACKGROUND AND AIMS

Our recently published randomised clinical trial evaluated the effect of a low-calorie diet with carbohydrates eaten at dinner. This dietary pattern led to lower hunger scores, and better anthropometric, biochemical and inflammatory outcomes compared to a standard low-calorie diet. In the same study, changes in diurnal secretion patterns of leptin, ghrelin and adiponectin were investigated.

METHODS AND RESULTS

Seventy-eight police officers (body mass index (BMI) > 30) were randomly allocated to experimental (carbohydrates at dinner) or control weight loss diets for 6 months. Sixty-three subjects finished the programme. On days 0, 7, 90 and 180 blood samples and hunger scores were collected every 4 h from 8:00 to 20:00. Hormonal profiles were available for 39. The dietary manipulation led to changes in daylight hormonal profiles in the experimental group. Leptin's secretion curve became convex, with a nadir later in the day (significant difference compared to baseline at morning and evening, p = 0.023, p = 0.021, respectively). Ghrelin's secretion curve became concave, peaking only in the evening hours. Adiponectin's curve was elevated only after the experimental diet (significant difference compared to baseline at afternoon, p = 0.044).

CONCLUSIONS

We propose that a low-calorie diet with carbohydrates eaten at dinner can modulate daytime hormonal profiles. Taken together with our earlier results, we believe this diet regime may prevent mid-day hunger, better support weight loss and improve metabolic outcomes compared to conventional weight loss diets. The trial is registered at controlled-trials.com, ISRCTN37829376, December 2009.

Biological aging alters circadian mechanisms in murine adipose tissue depots

Biological aging alters the metabolism and volume of adipose tissue depots. Recent evidence suggests that circadian mechanisms play a role in promoting adipogenesis, obesity, and lipodystrophy. The current study compared cohorts of younger (5-9 months) and older (24-28 months) C57BL/6 mice as a function of biological age and circadian time. Advanced age significantly reduced the weight of the brown, epididymal, inguinal, and retroperitoneal adipose depots but not total body weight. The older mice reduced their physical activity by >50% and delayed their activity initiation after light offset. The expressed transcriptome in brown and white adipose depots and liver of both cohorts displayed evidence of circadian rhythmicity; however, the oscillating mRNAs differed significantly between age groups and across tissues. The amplitude of Cry1, a component of the negative arm of the circadian apparatus, and downstream regulators such as Rev-erbα were elevated in the older relative to the younger cohorts as a function of circadian time. Overall, transcript levels differed significantly for 557 (inguinal adipose), 1,016 (liver), and 1,021 (brown adipose) expressed sequences between the cohorts as a function of age. These included transcripts encoding proteins within the canonical and non-canonical Wnt pathways. Since the Wnt pathway regulates adipose stem cell differentiation and shares a critical enzyme, glycogen synthase kinase 3β, with the circadian mechanism, the intersection between these two fundamental regulatory mechanisms merits further investigation with respect to biological aging of adipose tissues.

Fasting plasma ghrelin levels are reduced, but not suppressed during OGTT in obese African American adolescents

OBJECTIVE

Our study aimed to evaluate total plasma ghrelin (TGh) concentration and its correlation with leptin and insulin in obese African American (AA) adolescents with a family history of type 2 diabetes.

PARTICIPANTS AND METHODS

Insulin, leptin, and TGh were measured for 15 non-obese controls in fasted state and 19 obese AA adolescents on samples collected during oral glucose tolerance test (OGTT) using radioimmunoassay kits. The hormonal concentrations were compared at fasting levels between obese and non-obese AA adolescents. Insulin, leptin, and TGh concentrations were also compared during OGTT in the obese group.

RESULTS

Fasting TGh was significantly lower in obese AA adolescents compared to non-obese controls, while fasting leptin and insulin were significantly higher in obese AA adolescents compared to non-obese controls. During OGTT, for the obese group, TGh increased significantly and plasma leptin decreased significantly. A significant negative correlation was found between TGh and leptin at 30 and 120 min, but at no other time points (0, 60, and 90 min). A significant positive correlation was found between TGh and insulin at 30 min during OGTT, but no other time points.

CONCLUSIONS

TGh was lower in obese AA adolescents with a family history of type 2 diabetes and a significant correlation occurred between TGh and leptin and TGh and insulin during OGGT at specific time points in our obese group. These findings indicate that insulin resistant obese AA adolescents have impaired ghrelin suppression.

Circadian clocks and metabolism

Circadian clocks maintain periodicity in internal cycles of behavior, physiology, and metabolism, enabling organisms to anticipate the 24-h rotation of the Earth. In mammals, circadian integration of metabolic systems optimizes energy harvesting and utilization across the light/dark cycle. Disruption of clock genes has recently been linked to sleep disorders and to the development of cardiometabolic disease. Conversely, aberrant nutrient signaling affects circadian rhythms of behavior. This chapter reviews the emerging relationship between the molecular clock and metabolic systems and examines evidence that circadian disruption exerts deleterious consequences on human health.

Circadian rhythms and obesity in mammals

Obesity has become a serious public health problem and a major risk factor for the development of illnesses, such as insulin resistance and hypertension. Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating the circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding (RF), calorie restriction (CR), and intermittent fasting (IF), provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat (HF) diet leads to disrupted circadian expression of metabolic factors and obesity. This paper focuses on circadian rhythms and their link to obesity.

Implications of sleep restriction and recovery on metabolic outcomes

CONTEXT

Alongside the growing epidemics of obesity and diabetes mellitus, chronic partial sleep restriction is also increasingly common in modern society, and the metabolic implications of this have not been fully illustrated as yet. Whether recovery sleep is sufficient to offset these detriments is an area of ongoing research.

OBJECTIVE

This review seeks to summarize the relevant epidemiological and experimental data in the areas of altered metabolic consequences of both shortened sleep and subsequent recovery sleep.

DATA ACQUISITION

The medical literature from 1970 to March 2012 was reviewed for key articles.

DATA SYNTHESIS

Epidemiological studies suggest associations between shortened sleep and future obesity and diabetes. Experimental data thus far show a probable link between shortened sleep and altered glucose metabolism as well as appetite dysregulation.

CONCLUSION

Sleep often seems undervalued in modern society, but this may have widespread metabolic consequences as described in this review. Acute sleep loss is often unavoidable, but chronic sleep restriction ideally should not be. Understanding the implications of both sleep restriction and recovery on metabolic outcomes will guide public health policy and allow clinical recommendations to be prescribed.

Ghrelin in obesity

Ghrelin was discovered for its ability to bind the growth hormone secretagogue receptor (GHSR1a) and stimulate growth hormone release. However, much research conducted with this novel stomach hormone is focused on proposed roles for it to participate in regulating energy balance. Exogenous administration of ghrelin stimulates food consumption in experimental animals and humans, presenting the hormone as the first to stimulate appetite after peripheral administration and implicates it for an etiology of obesity. The hormone also presents other exceptional characteristics that solicit need for future study. The peptide is modified by acylation with a mediumchain fatty acid on its third residue, and it is that ghrelin peptide that binds GHS-R1a. Enzymes or transfer proteins responsible for such acylation and de-acylation remain unknown. Specific assays for both acyl- and des-acyl ghrelin are not available nor are methods to prevent de-acylation in blood samples. Such knowledge is important because des-acyl ghrelin is reported to bestow biology distinct from that of ghrelin and that signal may actually oppose those prescribed for its acylated parent. This review of ghrelin data relating to obesity recognizes the complexity of ghrelin endocrinology and attempts to be cautious when discussing studies that measured ghrelin during different physiological states. Although much more exploration is needed, we placed more emphasis on reviewing studies during different physiological states when conclusions are less dependent on measurement of ghrelin. Despite these shortcomings, we conclude that there is ample evidence indicating ghrelin participates in regulating energy balance.

Glucose Tolerance and Skeletal Muscle Gene Expression in Response to Alternate Day Fasting

OBJECTIVE

Alternate day fasting may extend lifespan in rodents and is feasible for short periods in nonobese humans. The aim of this study was to examine the effects of 3 weeks of alternate day fasting on glucose tolerance and skeletal muscle expression of genes involved in fatty acid transport/oxidation, mitochondrial biogenesis, and stress response.

RESEARCH METHODS AND PROCEDURES

Glucose and insulin responses to a standard meal were tested in nonobese subjects (eight men and eight women; BMI, 20 to 30 kg/m(2)) at baseline and after 22 days of alternate day fasting (36 hour fast). Muscle biopsies were obtained from a subset of subjects (n = 11) at baseline and on day 21 (12-hour fast).

RESULTS

Glucose response to a meal was slightly impaired in women after 3 weeks of treatment (p < 0.01), but insulin response was unchanged. However, men had no change in glucose response and a significant reduction in insulin response (p < 0.03). There were no significant changes in the expression of genes involved in mitochondrial biogenesis or fatty acid transport/oxidation, although a trend toward increased CPT1 expression was observed (p < 0.08). SIRT1 mRNA expression was increased after alternate day fasting (p = 0.01).

DISCUSSION

Alternate day fasting may adversely affect glucose tolerance in nonobese women but not in nonobese men. The gene expression results indicate that fatty acid oxidation and mitochondrial biogenesis are unaffected by alternate day fasting. However, the increased expression in SIRT1 suggests that alternate day fasting may improve stress resistance, a commonly observed feature of calorie-restricted rodents.