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Background: Leptin is predominant in regulating body weight by stimulating energy expenditure through its neuronal action in the brain. Moreover, it is projected to adipose tissue and induces adipocyte browning by activating the β3-adrenergic receptor (β3AR). However, the expression of leptin receptor (Lep-R) and β3AR in people with obesity is downregulated., Aim: We hypothesized that Hibiscus sabdariffa Linn. extract (HSE) would increase hypothalamus arcuate nucleus (ARC) Lep-R and white adipose tissue (WAT) β3AR mRNA expression in DIO rats. This study also analyzed the potency of H. sabdariffa bioactive compounds as activators of Lep-R and β3AR by an in-silico experiment., Methods: Twenty-four male Sprague-Dawley rats were divided into four groups: Control (standard food), DIO (high-fat diet), DIO-Hib200 (HFD+HSE 200 mg/kg BW), and DIO-Hib400 (HFD+HSE400 mg/kg BW). HSE was administered orally for five weeks, once a day., Results: HSE administration significantly (p <0,05) increased the ARC Lep-R expression. The Lee index significantly decreased to the normal range (≤ 310) with p <0,001 for DIO-Hib200 and p <0,01 for DIO-Hib400. Among 39 bioactive compounds, 5-O-caffeoyl shikimic acid exhibited high free binding scores (-8,63) for Lep-R, and myricetin&#95;3&#95;arabinogalactoside had high free binding scores (-9,39) for β3AR. These binding predictions could activate Lep-R and β3AR., Conclusion: This study highlights that HSE could be a potential therapeutic target for obesity by increasing LepR mRNA and leptin sensitivity, enhancing energy expenditure, and reducing obesity., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Aim: to study the association of the levels of leptin and its soluble receptor in blood serum with nonalcoholic fatty liver disease (NAFLD) in obese or overweight patients. Material and methods: the open study included 105 patients with obesity or excess body weight. Patients were examined for NAFLD and divided into two groups: the treatment group included patients with NAFLD (n = 77) and the control group included patients without NAFLD (n = 28). Results: complaints of pain in the right upper quadrant, hypertension and diabetes type 2, as well as waist circumference, body mass index, glucose and triglyceride levels were reported significantly more frequently in the group of patients with NAFLD. Leptin was positively and the level of its receptors was negatively correlated with the degree of weight gain. Between these parameters in the group of patients with obesity and excess body weight, an overall moderate negative correlation was reported (rs = (-0.370), p

Objective: Loss of function FTO mutations significantly impact body composition in humans and mice, with Fto-deficient mice reported to resist the development of obesity in response to a high-fat diet (HFD). We aimed to further explore the interactions between FTO and HFD and determine if FTO can influence the adverse metabolic consequence of HFD. Methods: We studied mice deficient in FTO in two well validated models of leptin resistance (HFD feeding and central palmitate injection) to determine how Fto genotype may influence the action of leptin. Using transcriptomic analysis of hypothalamic tissue to identify relevant pathways affected by the loss of Fto, we combined data from co-immunoprecipitation, yeast 2-hybrid and luciferase reporter assays to identify mechanisms through which FTO can influence the development of leptin resistant states. Results: Mice deficient in Fto significantly increased their fat mass in response to HFD. Fto+/− and Fto−/− mice remained sensitive to the anorexigenic effects of leptin, both after exposure to a HFD or after acute central application of palmitate. Genes encoding components of the NFкB signalling pathway were down-regulated in the hypothalami of Fto-deficient mice following a HFD. When this pathway was reactivated in Fto-deficient mice with a single low central dose of TNFα, the mice became less sensitive to the effect of leptin. We identified a transcriptional coactivator of NFкB, TRIP4, as a binding partner of FTO and a molecule that is required for TRIP4 dependent transactivation of NFкB. Conclusions: Our study demonstrates that, independent of body weight, Fto influences the metabolic outcomes of a HFD through alteration of hypothalamic NFкB signalling. This supports the notion that pharmacological modulation of FTO activity might have the potential for therapeutic benefit in improving leptin sensitivity, in a manner that is influenced by the nutritional environment.

Leptin is a regulatory protein from adipokines family, that maintain energy homeostasis of the body and deter obesity development. Impaired transfer of leptin signals to hypothalamus leads to leptin resistance and its adverse complications. Understanding of leptin resistance mechanisms is pivotal for the development of preventive and treatment procedures aiming to decrease the risk of atherosclerosis,

Abstract A large part of the daily intake of children in the U.S. consists of snacks, with the average child consuming three snacks per day. Despite this, little research has been conducted to determine the metabolic and behavioral effects of snacking. Using a developing female rat model, our studies aimed to determine the effects of snacking during development before the protective effects of estrogen on weight gain would be relevant. Additionally, to determine if snack composition is important, we created one healthy and one unhealthy snacking group provided with chow and three snacks each in addition to a chow-only group. We found that both snacking groups experienced increased weight gain, elevated abdominal fat pad mass, prolonged leptin resistance into adulthood, and insulin insensitivity that was not observed in their non-snacking counterparts. These physiological differences were measured despite both snacking groups having a similar caloric intake as the chow-only group throughout the study. In addition to physiological changes, both snacking groups showed a preference for snacks over chow and ate more often during the inactive light phase than typical for rats, with the unhealthy snacking group presenting this behavioral change earlier than the healthy snacking group. Our results suggest that constant access to palatable snacks, which is often the case for children in western countries, alters feeding behaviors in relation to food choice and time of day when eating occurs. Snacking during development seemed to promote signs of metabolic syndrome in adulthood even when excess caloric intake was not observed. Our work further suggests that development is a vulnerable time for palatable snack presentation when prepubertal females lack the protective effects of estrogen and exhibit reduced leptin feedback on food intake. Thus snacking from weaning onward could be a contributor to the current childhood obesity crisis. Highlights • Snacking promotes excess weight gain and fat pad mass without excess caloric intake. • Snacking induces an sustained insulin response to glucose gavage. • Leptin resistance, observed in all young rats, persists only in adult snacking rats. • Snacking alters food choice and meal-time preferences. • Glucose absorption following a glucose gavage is blunted in adult snacking rats. [ABSTRACT FROM AUTHOR]

Endospanin 1 (Endo1), a protein encoded in humans by the same gene than the leptin receptor (ObR), and increased by diet-induced obesity, is an important regulator of ObR trafficking and cell surface exposure, determining leptin signaling strength. Defective intracellular trafficking of the leptin receptor to the neuronal plasma membrane has been proposed as a mechanism underlying the development of leptin resistance observed in human obesity. More recently, Endo1 has emerged as a mediator of "selective leptin resistance." The underlying mechanisms of the latter are not completely understood, but the possibility of differential activation of leptin signaling pathways was suggested among others. In this respect, the expression level of Endo1 is crucial for the appropriate balance between different leptin signaling pathways and leptin functions in the hypothalamus and is likely participating in selective leptin resistance for the control of energy and glucose homeostasis. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study was to investigate the molecular mechanism of pancreatic islet-derived mesenchymal stem cell (PID-MSC) differentiation into beta-cells in the presence of insulin and leptin resistance stimulators. We determined that beta-cell differentiation was stimulated by glucose, insulin, and leptin. Co-administration of insulin and leptin resulted in greater, at a further stage of differentiation but non-functional beta-cell formation. The levels of p-AKT(Ser473) did not change; SOCS3, PTP1B, p-IRS1(Ser307), PTEN levels increased and p-IRS1(Try) levels decreased due to insulin and leptin co-administration. These findings suggest that co-administration of insulin and leptin to PID-MSCs results in the development of both insulin and leptin resistance together. We showed that this differentiation signaling is mainly mediated by AKT/GSK-3β/β-catenin and Tub. Moreover, β-catenin and Tub were linked to each other in the nucleus under this condition. Furthermore, we found that Tub and β-catenin contributes to insulin production by increasing the expression of transcription factors by binding to the promoter regions of ins1 , ins2 , and pdx1 genes. In addition, Tub is also bound to the promoter region of the MafA gene. These findings demonstrate that when insulin and leptin resistance develop together in rat PID-MSCs beta-cell differentiation increases markedly via β-catenin and Tub. New therapeutic agents that inhibit AKT/GSK-3β/β-catenin and in particular Tub may help prevent the development or retard the progression of type 2 diabetes. Highlights • Insulin and leptin cause higher, more mature but non-functional β-cell formation. • This differentiation signaling is mainly mediated by AKT/GSK-3β/β-catenin and Tub. • Tub and β-catenin are linked to each other in the nucleus. • Tub binded to promoter regions of ins1, ins2, pdx1 and MafA genes [ABSTRACT FROM AUTHOR]

Obesity is a global health problem and treatment options are still insufficient. When chronically treated with the angiotensin II receptor blocker telmisartan (TEL), rodents do not develop diet-induced obesity (DIO). However, the underlying mechanism for this is still unclear. Here we investigated whether TEL prevents leptin resistance by enhancing leptin uptake across the blood-brain barrier (BBB). To address this question, we fed C57BL/6 mice a high-fat diet (HFD) and treated them daily with TEL by oral gavage. In addition to broadly characterizing the metabolism of leptin, we determined leptin uptake into the brain by measuring BBB transport of radioactively labeled leptin after long-term and short-term TEL treatment. Additionally, we assessed BBB integrity in response to angiotensin II in vitro and in vivo. We found that HFD markedly increased body weight, energy intake, and leptin concentration but that this effect was abolished under TEL treatment. Furthermore, glucose control and, most importantly, leptin uptake across the BBB were impaired in mice on HFD, but, again, both were preserved under TEL treatment. BBB integrity was not impaired due to angiotensin II or blocking of angiotensin II receptors. However, TEL did not exhibit an acute effect on leptin uptake across the BBB. Our results confirm that TEL prevents DIO and show that TEL preserves leptin transport and thereby prevents leptin resistance. We conclude that the preservation of leptin sensitivity is, however, more a consequence than the cause of TEL preventing body weight gain. [ABSTRACT FROM AUTHOR]

Aim: To study if the leptin to adiponectin (L:A) ratio, can be a potential biomarker for postprandial triglyceride clearance, insulin resistance (IR) or leptin resistance (LR) in apparently healthy obese, and obese individuals with established metabolic disease.Methods and Results: Fifty adult subjects with obesity (BMI ≥30); of which 36 metabolic healthy obese (MHO), and 14 metabolic dysregulated obese (MDO), with clinical and/or biochemical signs of metabolic disease were included. Seventeen healthy, normal weight subjects represented the control group. Postprandial triglyceride (TG) levels were measured in an 8 h oral fat tolerance test (OFTT). IR by HOMA-IR, L:A ratio and indirect LR were measured. In the MHO group, 71.4%, 69.4% and 86.1%, had delayed TG clearance, IR and LR, respectively; whereas in the MDO group this was detected in 85.7%, 71.4% and 91.7%, respectively. A combination of all three metabolic risk factors was found in 39.8% of the MHO and in 42.9% of the MDO patients. Receiver operating characteristics (ROC) analysis revealed that a cut-off value for the L:A ratio of >1.65 for the control group (PPV 1.0, NPV 0.91) and >3.65 for the obese subjects (PPV 0.86, NPV 0.48) predicted the delayed TG clearance with a good specificity and sensitivity. Detecting a combined risk with at least 2/3 metabolic risk factors, the ROC yielded the most suitable L:A ratio cut-off at >1.88.Conclusion: L:A ratio was able to detect early metabolic disturbances in obese individuals, and may be a potential useful clinical surrogate biomarker of metabolic disorders. [ABSTRACT FROM AUTHOR]

Abstract Leptin-mediated DNA-binding activity of STAT3 in hypothalamus plays crucial roles in the maintenance of energy homeostasis in lean mice; however its effects still remains unclear in case of leptin resistance in mice with diet induced obesity (DIO). In this study significant elevation of both basal and exogenously leptin-treated DNA-binding activity of STAT3 was detected using EMSA in the hypothalamus of male C57BL/6J mice fed high-fat diet for 10 wks, in concomitant with hyperleptinemia, high body weight, high fat mass, and hyperphagia as well as decreased POMC expression. The studies in vitro showed that both DNA binding activity and the proximal SBE of POMC promoter was essential to leptin-mediated POMC expression. However, the diminution of STAT3 phosphorylation, achieved by S3I-201 or a FoxO1 mutant, facilitated leptin-mediated POMC expression. The findings here demonstrated excess STAT3 activity negatively regulated POMC expression in hypothalamus of DIO mice, and suggested the limitation of STAT3 activity may promote leptin signaling. Highlights • The DNA-binding activity of STAT3 significantly increased, POMC expression decreased in the hypothalamus of DIO mice. • The reduction of STAT3 phosphorylation facilitated leptin-mediated POMC expression in cultured cells. • The DNA-binding activity of STAT3 and the proximal SBE of POMC promoter was essential to leptin-mediated POMC transcription. [ABSTRACT FROM AUTHOR]

Purpose: Obesity may lead to male hypogonadism, the underlying mechanism of which remains unclear. In the present study, we established a murine model of male hypogonadism caused by high-fat diet-induced obesity to verify the following hypotheses: 1) an increased leptin level may be related to decreased secretion of GnRH in obese males, and 2) repression of kisspeptin/GPR54 in the hypothalamus, which is associated with increased leptin levels, may account for the decreased secretion of GnRH and be involved in secondary hypogonadism (SH) in obese males.Methods: Male mice were fed high-fat diet for 19 weeks and divided by body weight gain into diet-induced obesity (DIO) and diet-induced obesity resistant (DIO-R) group. The effect of obesity on the reproductive organs in male mice was observed by measuring sperm count and spermatozoid motility, relative to testis and epididymis weight, testosterone levels, and pathologic changes. Leptin, testosterone, estrogen, and LH in serum were detected by ELISA method. Leptin receptor (Ob-R), Kiss1, GPR54, and GnRH mRNA were measured by real-time PCR in the hypothalamus. Expression of kisspeptin and Ob-R protein was determined by Western blotting. Expression of GnRH and GPR54 protein was determined by immunohistochemical analysis.Results: We found that diet-induced obesity decreased spermatozoid motility, testis and epididymis relative coefficients, and plasma testosterone and luteinizing hormone levels. An increased number and volume of lipid droplets in Leydig cells were observed in the DIO group compared to the control group. Significantly, higher serum leptin levels were found in the DIO and DIO-R groups. The DIO and DIO-R groups showed significant downregulation of the GnRH, Kiss1, GPR54, and Ob-R genes. We also found decreased levels of GnRH, kisspeptin, GPR54, and Ob-R protein in the DIO and DIO-R groups.Conclusions: These lines of evidence suggest that downregulation of Ob-R and kisspeptin/GPR54 in the murine hypothalamus may contribute to male hypogonadism caused by high-fat diet-induced obesity. [ABSTRACT FROM AUTHOR]

The effects of hyperleptinemia and leptin resistance during gestation are unclear. Leptin, an important neuroendocrine regulator, has anorexic effects, but its interactions with other metabolic hormones during pregnancy are unclear. We examined potential roles of leptin in regulating prolactin (PRL), GH, and melatonin plasma concentrations during pregnancy in Polish Longwool ewes. Twelve estrus-synchronized ewes carrying twins after mating were randomly assigned to receive i.v. injections of saline or recombinant ovine leptin (2.5 or 5.0 µg/kg BW). Blood samples were collected (15-min intervals over 4 h) immediately before the first injection at dusk and kept under red light. Treatments were repeated at 2-wk intervals, starting before mating and continuing from days 30 to 135 of gestation. Concentrations of plasma PRL, GH, and melatonin were determined using a validated RIA. The effects of leptin on hormone plasma concentrations varied depending on pregnancy stage and leptin dose. PRL plasma concentrations were affected at most stages of pregnancy and before gestation. In non-, very early- (day 30), and late- (day 120 and 135) pregnant ewes, exogenous leptin stimulated PRL (P < 0.001) plasma concentrations, while during the second month of gestation, it decreased PRL concentrations (P < 0.01). Leptin affected GH plasma concentrations (P < 0.05) only during the first 2 mo of pregnancy, with no effects during the second part of gestation or before pregnancy. In early- pregnant ewes (day 30 and 45), leptin decreased melatonin plasma concentrations (P < 0.05), but at day 60, leptin stimulated melatonin plasma concentrations at low (P < 0.01) and high doses (P < 0.05), with no effects in ewes after 105 d of gestation. These data indicate specific pregnancy- induced endocrine adaptations to changes in energy homeostasis, supporting the hypothesis that leptin affects PRL, GH, and melatonin release during gestation. [ABSTRACT FROM AUTHOR]

Objective The inability of leptin to suppress food intake in diet-induced obesity, sometimes referred to as leptin resistance, is associated with several distinct pathological hallmarks. One prevailing theory is that impaired transport of leptin across the blood–brain barrier (BBB) represents a molecular mechanism that triggers this phenomenon. Recent evidence, however, has challenged this notion, suggesting that leptin BBB transport is acquired during leptin resistance. Methods To resolve this debate, we utilized a novel cerebral Open Flow Microperfusion (cOFM) method to examine leptin BBB transport in male C57BL/6J mice, fed a chow diet or high fat diet (HFD) for 20 days. Results Basal plasma leptin levels were 3.8-fold higher in HFD-fed mice (p < 0.05). Leptin administration (2.5 mg/kg) elicited similar pharmacokinetic profiles of circulating leptin. However, while leptin reduced food intake by 20% over 22 h in chow-fed mice, it did not affect food intake in HFD-fed mice. In spite of this striking functional difference, hypothalamic leptin levels, as measured by cOFM, did not differ between chow-fed mice and HFD-fed mice following leptin administration. Conclusions These data suggest that leptin transport across the BBB is not impaired in non-obese leptin resistant mice and thus unlikely to play a direct role in the progression of pharmacological leptin resistance. [ABSTRACT FROM AUTHOR]

Summary: Obesity is an epidemic disease that is increasing worldwide and is a major risk factor for many metabolic diseases. However, effective agents for the prevention or treatment of obesity remain limited. Therefore, it is urgent to clarify the pathophysiological mechanisms underlying the development and progression of obesity and exploit potential agents to cure and prevent this disease. According to a recent study series, obesity is associated with the development of endoplasmic reticulum stress and the activation of its stress responses (unfolded protein response) in metabolically active tissues, which contribute to the development of obesity‐related insulin and leptin resistance, inflammation and energy imbalance. Hypothalamic endoplasmic reticulum stress is the central mechanism underlying the development of obesity‐associated leptin resistance and disruption of energy homeostasis; thus, targeting endoplasmic reticulum stress offers a promising therapeutic strategy for improving leptin sensitivity, increasing energy expenditure and ultimately combating obesity. In this review, we highlight the relationship between and mechanism underlying hypothalamic endoplasmic reticulum stress and obesity‐associated leptin resistance and energy imbalance and provide new insight regarding strategies for the treatment of obesity. [ABSTRACT FROM AUTHOR]

Anorexigenic pro-opiomelanocortin (Pomc)/alpha-melanocyte stimulating hormone (αMSH) neurons of the hypothalamic melanocortin system function as key regulators of energy homeostasis, also controlling somatic growth across different species. However, the mechanisms of melanocortin-dependent growth control still remain ill-defined. Here, we reveal a thus-far-unrecognized structural and functional connection between Pomc neurons and the somatotropic hypothalamo-pituitary axis. Excessive feeding of larval zebrafish causes leptin resistance and reduced levels of the hypothalamic satiety mediator pomca. In turn, this leads to reduced activation of hypophysiotropic somatostatin (Sst)-neurons that express the melanocortin receptor Mc4r, elevated growth hormone (GH) expression in the pituitary, and enhanced somatic growth. Mc4r expression and αMSH responsiveness are conserved in Sst-expressing hypothalamic neurons of mice. Thus, acquired leptin resistance and attenuation of pomca transcription in response to excessive caloric intake may represent an ancient mechanism to promote somatic growth when food resources are plentiful. • Sst neurons are second-order neurons of the central melanocortin system • Pomc neurons stimulate Sst neurons, resulting in reduced growth hormone levels • Excessive feeding leads to leptin resistance and decreased pomc expression • Reduced pomca transcription favors somatic growth when food resources are plentiful The melanocortin system controls energy homeostasis and somatic growth, but the underlying mechanisms are elusive. Löhr et al. identify a functional neural circuit in which Pomc neurons stimulate hypothalamic somatostatin neurons, thereby inhibiting hypophyseal growth hormone production. Excessive feeding and acquired leptin resistance attenuate this pathway, allowing faster somatic growth when food resources are rich. [ABSTRACT FROM AUTHOR]

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Melatonin (Mel), a molecule that conveys photoperiodic information to the organisms, is also involved in the regulation of energy homeostasis. Mechanisms of action of Mel in the energy balance remain unclear; herein we investigated how Mel regulates energy intake and expenditure to promote a proper energy balance. Male Wistar rats were assigned to control, control + Mel, pinealectomized (PINX) and PINX + Mel groups. To restore a 24-h rhythm, Mel (1 mg/kg) was added to the drinking water exclusively during the dark phase for 13 weeks. After this treatment period, rats were subjected to a 24-h fasting test, an acute leptin responsiveness test and cold challenge. Mel treatment reduced food intake, body weight, and adiposity. When challenged to 24-h fasting, Mel-treated rats also showed reduced hyperphagia when the food was replaced. Remarkably, PINX rats exhibited leptin resistance; this was likely related to the capacity of leptin to affect body weight, food intake, and hypothalamic signal-transducer and activator of transcription 3 phosphorylation, all of which were reduced. Mel treatment restored leptin sensitivity in PINX rats. An increased hypothalamic expression of agouti-related peptide (Agrp), neuropeptide Y, and Orexin was observed in the PINX group while Mel treatment reduced the expression of Agrp and Orexin. In addition, PINX rats presented lower UCP1 protein levels in the brown adipose tissue and required higher tail vasoconstriction to get a proper thermogenic response to cold challenge. Our findings reveal a previously unrecognized interaction of Mel and leptin in the hypothalamus to regulate the energy balance. These findings may help to explain the high incidence of metabolic diseases in individuals exposed to light at night.

Objective: During pregnancy, women normally increase their food intake and body fat mass, and exhibit insulin resistance. However, an increasing number of women are developing metabolic imbalances during pregnancy, including excessive gestational weight gain and gestational diabetes mellitus. Despite the negative health impacts of pregnancy-induced metabolic imbalances, their molecular causes remain unclear. Therefore, the present study investigated the molecular mechanisms responsible for orchestrating the metabolic changes observed during pregnancy. Methods: Initially, we investigated the hypothalamic expression of key genes that could influence the energy balance and glucose homeostasis during pregnancy. Based on these results, we generated a conditional knockout mouse that lacks the suppressor of cytokine signaling-3 (SOCS3) only in leptin receptor-expressing cells and studied these animals during pregnancy. Results: Among several genes involved in leptin resistance, only SOCS3 was increased in the hypothalamus of pregnant mice. Remarkably, SOCS3 deletion from leptin receptor-expressing cells prevented pregnancy-induced hyperphagia, body fat accumulation as well as leptin and insulin resistance without affecting the ability of the females to carry their gestation to term. Additionally, we found that SOCS3 conditional deletion protected females against long-term postpartum fat retention and streptozotocin-induced gestational diabetes. Conclusions: Our study identified the increased hypothalamic expression of SOCS3 as a key mechanism responsible for triggering pregnancy-induced leptin resistance and metabolic adaptations. These findings not only help to explain a common phenomenon of the mammalian physiology, but it may also aid in the development of approaches to prevent and treat gestational metabolic imbalances.

As the population of the world ages, the prevalence of neurodegenerative disease continues to rise, accompanied by increases in disease burden related to obesity and metabolic disorders. Thus, it will be essential to develop tools for preventing and slowing the progression of these major disease entities. Epidemiologic studies have shown strong associations between obesity, metabolic dysfunction, and neurodegeneration, while animal models have provided insights into the complex relationships between these conditions. Experimentally, the fat-derived hormone leptin has been shown to act as a neuroprotective agent in various animal models of dementia, toxic insults, ischemia/reperfusion, and other neurodegenerative processes. Specifically, leptin minimizes neuronal damage induced by neurotoxins and pro-apoptotic conditions. Leptin has also demonstrated considerable promise in animal models of obesity and metabolic disorders via modulation of glucose homeostasis and energy intake. However, since obesity is known to induce leptin resistance, we hypothesize that resistance to the neuroprotective effects of leptin contributes to the pathogenesis of obesity-associated neurodegenerative diseases. This review aims to explore the literature pertinent to the role of leptin in the protection of neurons from the toxic effects of aging, obesity and metabolic disorders, to investigate the physiological state of leptin resistance and its causes, and to consider how leptin might be employed therapeutically in the prevention and treatment of neurodegenerative disease.

Leptin resistance in the hypothalamus has an essential role in obesity. Saturated fatty acids such as palmitate bind to Toll-like receptor 4 (TLR4) and lead to endoplasmic reticulum (ER) stress and leptin resistance. In this study, we evaluated whether extracts of Ecklonia cava would attenuate the ER stress induced by palmitate and reduce leptin resistance in hypothalamic neurons and microglia. We added palmitate to these cells to mimic the environment induced by high-fat diet in the hypothalamus and evaluated which of the E. cava phlorotannins—dieckol (DK), 2,7-phloroglucinol-6,6-bieckol (PHB), pyrogallol-phloroglucinol-6,6-bieckol (PPB), or phlorofucofuroeckol-A (PFFA)—had the most potent effect on attenuating leptin resistance. TLR4 and NF-κB expression induced by palmitate was attenuated most effectively by PPB in both hypothalamic neurons and microglia. ER stress markers were increased by palmitate and were attenuated by PPB in both hypothalamic neurons and microglia. Leptin resistance, which was evaluated as an increase in SOCS3 and a decrease in STAT3 with leptin receptor expression, was increased by palmitate and was decreased by PPB in hypothalamic neurons. The culture medium from palmitate-treated microglia increased leptin resistance in hypothalamic neurons and this resistance was attenuated by PPB. In conclusion, PPB attenuated leptin resistance by decreasing ER stress in both hypothalamic neurons and microglia.

Melatonin (Mel), a molecule that conveys photoperiodic information to the organisms, is also involved in the regulation of energy homeostasis. Mechanisms of action of Mel in the energy balance remain unclear; herein we investigated how Mel regulates energy intake and expenditure to promote a proper energy balance. Male Wistar rats were assigned to control, control + Mel, pinealectomized (PINX) and PINX + Mel groups. To restore a 24-h rhythm, Mel (1 mg/kg) was added to the drinking water exclusively during the dark phase for 13 weeks. After this treatment period, rats were subjected to a 24-h fasting test, an acute leptin responsiveness test and cold challenge. Mel treatment reduced food intake, body weight, and adiposity. When challenged to 24-h fasting, Mel-treated rats also showed reduced hyperphagia when the food was replaced. Remarkably, PINX rats exhibited leptin resistance; this was likely related to the capacity of leptin to affect body weight, food intake, and hypothalamic signal-transducer and activator of transcription 3 phosphorylation, all of which were reduced. Mel treatment restored leptin sensitivity in PINX rats. An increased hypothalamic expression of agouti-related peptide (Agrp), neuropeptide Y, and Orexin was observed in the PINX group while Mel treatment reduced the expression of Agrp and Orexin. In addition, PINX rats presented lower UCP1 protein levels in the brown adipose tissue and required higher tail vasoconstriction to get a proper thermogenic response to cold challenge. Our findings reveal a previously unrecognized interaction of Mel and leptin in the hypothalamus to regulate the energy balance. These findings may help to explain the high incidence of metabolic diseases in individuals exposed to light at night. [ABSTRACT FROM AUTHOR]

We have previously shown that following oral delivery in dodecyl maltoside (DDM), [D-Leu-4]-OB3 and its myristic acid conjugate, MA-[D-Leu-4]-OB3, improved energy balance and glucose homeostasis in genetically obese/diabetic mouse models. More recently, we have provided immunohistochemical evidence indicating that these synthetic peptide leptin mimetics cross the blood-brain barrier and concentrate in the area of the arcuate nucleus of the hypothalamus in normal C57BL/6J and Swiss Webster mice, in genetically obese ob/ob mice, and in diet-induced obese (DIO) mice. In the present study, we describe the effects of oral delivery of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 on glycemic control in diet-induced (DIO) mice, a non-genetic rodent model of obesity and its associated insulin resistance, which more closely recapitulates common obesity and diabetes in humans. Male C57BL/6J and DIO mice, 17, 20, and 28 weeks of age, were maintained on a low-fat or high-fat diet and given vehicle (DDM) alone or [D-Leu-4]-OB3 or MA-[D-Leu-4]-OB3 in DDM by oral gavage for 12 or 14 days. Body weight gain, food and water intake, fasting blood glucose, oral glucose tolerance, and serum insulin levels were measured. Our data indicate that (1) [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 restore glucose tolerance in male DIO mice maintained on a high-fat diet to levels comparable to those of non-obese C57BL/6J wild-type mice of the same age and sex maintained on a low-fat diet; and (2) the influence of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 on glycemic control appears to be independent of their effects on energy balance. These results suggest that [D-Leu-4]-OB3 and/or MA-[D-Leu-4]-OB3 may have application to the management of the majority of cases of common obesity in humans, a state characterized at least in part, by leptin resistance resulting from a defect in leptin transport across the blood-brain barrier. They further suggest that these small molecule synthetic peptide leptin mimetics, through their influence on glycemic control, may prevent the pre-diabetic state associated with most cases of common obesity from escalating into overt type 2 diabetes mellitus. [ABSTRACT FROM AUTHOR]

Objectives Body fatness is widely assumed to be regulated by a lipostatic set-point system, which has evolved in response to trade-offs in the risks of mortality. Increasing fatness makes the risk of starvation lower but increases the risk of predation. Yet other models are available. The aim of this work is to evaluate using mathematical modeling whether set-point systems are more likely to evolve than the alternatives. Methods I modeled the trade-off in mortality risks using a simple mathematical model, which generates an optimum level of fatness that is presumed to be the driver for the evolution of a set-point. I then mimicked the likely errors in this optimum level, that derive from the variation in the component parameters of the mortality curves using Markov Chain Monte Carlo (MCMC) simulation by Bayesian inference Using Gibbs Sampling (BUGS). Results The error propagation generated by the simulations showed that even very small errors in the model parameters were magnified enormously in the location of the optimum fatness level. If the model parameters had coefficients of variation of just 1% then the coefficient of variation in the optimum level of fatness was between 20 and 90%. In that situation, a set-point centered at the mathematical optimum from the component curves would be at the correct level of fatness that minimizes mortality, and hence maximizes fitness, on less than 8% of occasions. Conclusions Set-point regulation of body fatness is hence highly unlikely to evolve where there is any realistic level of variation in the parameters that define mortality risks. Using further MCMC modeling, I show that a dual-intervention point system is more likely to evolve. This mathematical simulation work has important implications for how we interpret molecular work concerning regulation of adiposity. [ABSTRACT FROM AUTHOR]

Brains of females are more sensitive to the acute catabolic actions of leptin. However, sex differences in the long-term physiological responses to central leptin receptor modulation are unknown. Accordingly, we centrally delivered a viral vector to overexpress leptin (Leptin), a neutral leptin receptor antagonist (Leptin-Antagonist) or a green fluorescence protein (GFP) (Control). We examined chronic changes in body weight and composition in male and female rats. Females displayed greater and sustained responses to Leptin, whereas males rapidly lost physiological effects and developed leptin resistance as confirmed by lower acute leptin-mediated phosphorylation of signal transducer and activator of transcription 3 (P-STAT3). Surprisingly, despite persistent physiological responses, Leptin-females also exhibited reduced acute leptin-mediated P-STAT3, suggesting an onset of leptin resistance near time of death. In line with this interpretation, Leptin-females and Control-females consumed the same amount of food on the last day of the experiment. Both Leptin-Antagonist groups gained similar percentages of their initial body weight and fat mass, whereas only Leptin-Antagonist- females gained lean body mass. Consequently, the lean/fat mass ratio with Leptin-Antagonist was preserved in females and decreased in males, suggesting a deterioration of body composition in males. In summary, the present study establishes that females are more responsive to long-term central leptin overexpression than males and that leptin antagonism has a greater physiological impact in males. The hormone environment may have played a role in these processes; however, future studies are needed to establish whether such physiological responses are mediated by female or male sex hormones. [ABSTRACT FROM AUTHOR]

Diet-induced obesity is associated with hypothalamic inflammation and this phenomenon has been proposed to explain leptin resistance. In the present study, we used a short-term high-fat diet ( HFD) paradigm for 10 days and analysed the cellular and physiological responses to leptin administration in C57 BL6 mice. In parallel, we performed glial fibrillary acidic protein immunostaining to measure the presence of astrocytes in the arcuate nucleus of the hypothalamus ( ARH) after 10 days and 20 weeks of HFD. Interestingly, the results obtained demonstrate that the presence of star-like astrocytes is significantly increased after 10 days of HFD, although this is not associated with the absence of cellular and physiological response to leptin administration in mice. Taken together, the results of the present study suggest that star-like astrocytes rapidly increase in numbers in the ARH in response to HFD, although this phenomenon cannot explain the development of leptin resistance by itself. [ABSTRACT FROM AUTHOR]

Objective In visceral obesity, an overactive endocannabinoid/CB 1 receptor (CB 1 R) system promotes increased caloric intake and decreases energy expenditure, which are mitigated by global or peripheral CB 1 R blockade. In mice with diet-induced obesity (DIO), inhibition of food intake by the peripherally restricted CB 1 R antagonist JD5037 could be attributed to endogenous leptin due to the rapid reversal of hyperleptinemia that maintains leptin resistance, but the signaling pathway engaged by leptin has remained to be determined. Methods We analyzed the hypothalamic circuitry targeted by leptin following chronic treatment of DIO mice with JD5037. Results Leptin treatment or an increase in endogenous leptin following fasting/refeeding induced STAT3 phosphorylation in neurons in the arcuate nucleus (ARC) in lean and JD5037-treated DIO mice, but not in vehicle-treated DIO animals. Co-localization of pSTAT3 in leptin-treated mice was significantly less common with NPY + than with POMC + ARC neurons. The hypophagic effect of JD5037 was absent in melanocortin-4 receptor (MC4R) deficient obese mice or DIO mice treated with a MC4R antagonist, but was maintained in NPY −/− mice kept on a high-fat diet. Conclusions Peripheral CB 1 R blockade in DIO restores sensitivity to endogenous leptin, which elicits hypophagia via the re-activation of melanocortin signaling in the ARC. [ABSTRACT FROM AUTHOR]

Background: Recent data indicates that adults with Down syndrome (DS) are at increased risk for cardiovascular disease (CVD) that significantly contributes to their morbidity and mortality. Although identification of cardiometabolic risk factors during childhood is desirable to design preventive interventions, the data on such risk factors in children with DS is scarce. The aim of this study was to study the cardiometabolic risk factors such as insulin resistance (IR), leptin and adiponectin concentrations, lipid abnormalities and leptin resistance in non-obese children with DS. Methods: This cross-sectional case control study included karyotype confirmed trisomy-21 DS children aged 2-12 years and their matched healthy controls. After detailed anthropometry, weight, height and body mass index (BMI) standard deviation scores (SDSs) were calculated with reference data. Laboratory evaluation included determination of fasting lipid parameters, insulin, glucose, leptin and adiponectin concentrations. The homeostasis model assessment method (HOMA-IR) was used to assess IR and the ratio of leptin to BMI was used as an index of leptin resistance. Results: Seventy-seven children (39 with DS and 38 controls) comprised the study cohort. The anthropometric parameters were similar in the two groups. Children with DS showed significantly higher mean leptin concentrations (2.098 ± 1.68 ng/mL vs. 1.44 ± 0.52 ng/mL, p-value: 0.00) and higher indices of leptin resistance (0.127 ± 0.085 vs. 0.09 ± 0.03, p-value: 0.001) as compared to controls. Fasting adiponectin concentrations were lower (20.64 ± 19.87 ng/mL vs. 32.58 ± 34.25 ng/mL, p-value: 0.21) and fasting glucose higher (89.25 ± 8.12 mg/dL vs. 85.71 ± 5.52 mg/dL, p-value: 0.06) in the DS group as compared to the controls but the differences did not reach statistical significance. The concentrations of insulin, various lipid parameters and calculated HOMA-IR values were similar in the two groups. In the DS group, five children were identified to have high (>75th centile) leptin levels and four as impaired fasting glucose as compared to none in the controls. Conclusions: Alterations of several cardiometabolic risk factors, in particular, leptin concentrations and leptin resistance are present in children with DS. The presence of hyperleptinemia without hyperinsulinemia suggests a probable inherent genetic basis for increased leptin resistance in patients with DS. There is a need for larger studies to further understand increased leptin resistance in DS that may contribute to increased CVD related morbidity and mortality in these patients. [ABSTRACT FROM AUTHOR]

This study describes the localization of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3, synthetic peptide leptin mimetics, in the hypothalamus of Swiss Webster and C57BL/6J wild-type mice, leptin-deficient ob/ob mice, and leptin-resistant diet-induced obese (DIO) mice. The mice were given [D-Leu-4]-OB3 or MA-[D-Leu-4]-OB3 in 0.3% dodecyl maltoside by oral gavage. Once peak serum concentrations were reached, the mice received a lethal dose of pentobarbital and were subjected to intracardiac perfusion fixation. The brains were excised, post-fixed in paraformaldehyde, and cryo-protected in sucrose. Free-floating frozen coronal sections were cut at 25-µm and processed for imaging by immunofluorescence microscopy. In all four strains of mice, dense staining was concentrated in the area of the median eminence, at the base and/or along the inner wall of the third ventricle, and in the brain parenchyma at the level of the arcuate nucleus. These results indicate that [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 cross the blood-brain barrier and concentrate in an area of the hypothalamus known to regulate energy balance and glucose homeostasis. Most noteworthy is the localization of [D-Leu-4]-OB3 immunoreactivity within the hypothalamus of DIO mice via a conduit that is closed to leptin in this rodent model, and in most cases of human obesity. Together with our previous studies describing the effects of [D-Leu-4]-OB3 and MA-[D-Leu-4]-OB3 on energy balance, glucose regulation, and signal transduction pathway activation, these findings are consistent with a central mechanism of action for these synthetic peptide leptin mimetics, and suggest their potential usefulness in the management of leptin-resistant obesity and type 2 diabetes in humans. [ABSTRACT FROM AUTHOR]

Consumption of high-fat diet (HFD) induces energy imbalance and consequently obesity. In the pathogenesis of obesity, HFD triggers inflammation in the hypothalamus including arcuate nucleus (ARC). Interleukin-10 (IL-10) is a representative anti-inflammatory cytokine, known to ameliorate the adipose tissue inflammation and insulin resistance in obesity. However, the effect of IL-10 on the hypothalamic inflammation remains less defined. We here report the effect of over-expression of murine IL-10 using adeno-associated virus (AAV) vector on the inflammation in ARC and feeding behavior in HFD-induced obese (DIO) mice. DIO mice exhibited reduced POMC expression and elevated IKKs (IκB kinases) and SOCS3 expression in ARC. Overexpression of mIL-10 using AAV vector ameliorated obesity in parallel with restoration of ARC POMC expression in DIO mice. Moreover, IL-10 treatment suppressed IKKs activation and SOCS3 expression in ARC of DIO mice. These results suggest that IL-10 gene transfer provides an effective approach for counteracting HFD-induced inflammation and leptin resistance in ARC to prevent progression of obesity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mice supplemented with low-dose coconut oil presents hypothalamic endoplasmic reticulum stress in healthy mice. • Mice supplemented with low-dose coconut oil develops hypothalamic leptin resistance. • Insulin signaling in hypothalamus, liver, and white adipose tissue was impaired in mice supplemented with higher dose of coconut oil. The consumption of saturated fatty acids (SFA), the main compound in coconut oil (CO), can promote insulin and leptin resistance and are associated with inflammation and obesity. We investigated the effects of CO supplementation on leptin signaling in healthy mice. Swiss male mice received oral supplementation for eight weeks with 300 μL of water for the control group (CV) or CO (100 or 300 μL). Sensitivity to leptin/insulin was evaluated after eight weeks of supplementation. The CO induced endoplasmic reticulum stress and leptin resistance in the hypothalamus, as demonstrated by reduced effect on the energy expenditure, hypothalamic pJAK2 and pSTAT3, and POMC expression. In the adipose tissue, lipogenesis was favored and STAT3 and JAK2 signaling was impaired after CO supplementation. Furthermore, the supplementation with CO reduced pAKT in the hypothalamus, liver and white adipose tissue. These results show that CO induces hypothalamic and peripheral resistance to leptin and insulin in healthy mice. [ABSTRACT FROM AUTHOR]

Age-related obesity significantly increases the risk of chronic diseases such as type 2 diabetes, cardiovascular diseases, hypertension, and certain cancers. The insulin-leptin axis is crucial in understanding metabolic disturbances associated with age-related obesity. Rho GTPase Cdc42 is a member of the Rho family of GTPases that participates in many cellular processes including, but not limited to, regulation of actin cytoskeleton, vesicle trafficking, cell polarity, morphology, proliferation, motility, and migration. Cdc42 functions as an integral part of regulating insulin secretion and aging. Some novel roles for Cdc42 have also been recently identified in maintaining glucose metabolism, where Cdc42 is involved in controlling blood glucose levels in metabolically active tissues, including skeletal muscle, adipose tissue, pancreas, etc., which puts this protein in line with other critical regulators of glucose metabolism. Importantly, Cdc42 plays a vital role in cellular processes associated with the insulin and leptin signaling pathways, which are integral elements involved in obesity development if misregulated. Additionally, a change in Cdc42 activity may affect senescence, thus contributing to disorders associated with aging. This review explores the complex relationships among age-associated obesity, the insulin-leptin axis, and the Cdc42 signaling pathway. This article sheds light on the vast molecular web that supports metabolic dysregulation in aging people. In addition, it also discusses the potential therapeutic implications of the Cdc42 pathway to mitigate obesity since some new data suggest that inhibition of Cdc42 using antidiabetic drugs or antioxidants may promote weight loss in overweight or obese patients.

Disruption of leptin (LEP) signaling in the hypothalamus caused by type 2 diabetes (T2D) can impair appetite regulation. The aim of this study was to investigate whether the improvement in appetite regulation induced by high-intensity interval training (HIIT) in rats with T2D can be mediated by LEP signaling. In this study, 20 male Wister rats were randomly assigned to one of four groups: CO (non-type 2 diabetes control), T2D (type 2 diabetes), EX (non-type 2 diabetes exercise), and T2D + EX (type 2 diabetes + exercise).To induce T2D, a combination of a high-fat diet for 2 months and a single dose of streptozotocin (35 mg/kg) was administered. Rats in the EX and T2D + EX groups performed 4-10 intervals of treadmill running at 80-100% of their maximum velocity (Vmax). Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), serum levels of insulin (INS) and LEP (LEPS) as well as hypothalamic expression of LEP receptors (LEP-R), Janus kinase 2 (JAK-2), signal transducer and activator of transcription 3 (STAT-3), neuropeptide Y (NPY), agouti-related protein (AGRP), pro-opiomelanocortin cocaine (POMC), amphetamine-related transcript (CART), suppressor of cytokine signaling (SOCS3), forkhead box protein O1 (FOXO1) were assessed. ANOVA and Tukey post hoc tests were used to compare the results between the groups. The levels of LEPS and INS, as well as the levels of LEP-R, JAK-2, STAT-3, POMC, and CART in the hypothalamus were found to be higher in the T2D + EX group compared to the T2D group. On the other hand, the levels of HOMA-IR, NPY, AGRP, SOCS3, and FOXO1 were lower in the T2D + EX group compared to the T2D group (P < 0.0001). The findings of this study suggest that HIIT may improve appetite regulation in rats with T2D, and LEP signaling may play a crucial role in this improvement. Graphical abstract (leptin signaling in the hypothalamus), Leptin (LEP), Leptin receptor (LEP-R), Janus kinase 2 (JAK2), Signal transducer and activator of transcription 3 (STAT3), expressing Neuropeptide Y (NPY), Agouti-related protein (AGRP), anorexigenic neurons (expressing pro-opiomelanocortin cocaine (POMC), Amphetamine-related transcript (CART), suppressor of cytokine signaling (SOCS3), forkhead box protein O1 (FOXO1)., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Leptin (LEP) can cross the blood-brain barrier and facilitate cross-talk between the adipose tissue and central nerve system (CNS). This study aimed to investigate the effect of 8-week high-intensity interval training (HIIT) on the LEP signaling in the hippocampus of rats with type 2 diabetes. 20 rats were randomly divided into four groups: (i) control (Con), (ii) type 2 diabetes (T2D), (iii) exercise (EX), and (iv) type 2 diabetes + exercise (T2D + EX). The rats in the T2D and T2D + EX were fed a high-fat diet for two months, then a single dose of STZ (35 mg/kg) was injected to induce diabetes. The EX and T2D + EX groups performed 4-10 intervals of treadmill running at 80-100% of V max . Serum and hippocampal levels of LEP as well as hippocampal levels of LEP receptors (LEP-R), Janus kinase 2 (JAK-2), signal transducer and activator of transcription 3 (STAT-3), activated protein kinase (AMP-K), proxy zoster receptor α (PGC-1α), beta-secretase 1 (BACE1), Beta-Amyloid (Aβ), Phosphoinositide 3-kinases (PI3K), protein kinase B (AKT), mammalian target of rapamycin (mTOR), Glycogen Synthase Kinase 3 Beta (GSK3β), and hyperphosphorylated tau proteins (TAU) were measured. One-way ONOVA and Tukey post-hoc tests were used to analyze the data. Serum and hippocampal levels of LEP as well as hippocampal levels of LEP-R, JAK-2, STAT-3, AMP-K, PGC1α, PI3K, AKT, and mTOR were increased while hippocampal levels of BACE1, GSK3B, TAU, and Aβ were decreased in T2D + EX compared with T2D group. Serum LEP and hippocampal levels of LEP, LEP-R, JAK-2, STAT-3, AMP-K, PGC1α, PI3K, AKT, and mTOR were decreased. Conversely hippocampal levels of BACE1, GSK3B, TAU, and Aβ were increased in T2D group compared with CON group. HIIT could improve LEP signaling in the hippocampus of rats with type 2 diabetes and decrease the accumulation of Tau and Aβ, which may reduce the risk of memory impairments., (© 2023. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

In children with hypertension we identified various metabolic disorders and the role of insulin resistance in their development, as well as compensatory mechanisms of maintaining normoglycemia.

Obesity has emerged as one of the most burdensome conditions in modern society. In this context, understanding the mechanisms controlling food intake is critical. At present, the adipocyte-derived hormone leptin and the pancreatic β-cell derived hormone insulin are considered the principal anorexigenic hormones. Although leptin and insulin signal transduction pathways are distinct, their regulation of body weight maintenance is concerted. Resistance to the central actions of leptin or insulin is linked to the emergence of obesity and diabetes mellitus. A growing body of evidence suggests a convergence of leptin and insulin intracellular signaling at the insulin–receptor–substrate–phosphatidylinositol-3-kinase (IRS-PI3K) level. Moreover, numerous factors mediating the pathophysiology of leptin resistance, a hallmark of obesity, such as endoplasmic reticulum (ER) stress, protein tyrosine phosphatase 1B (PTP1B) and suppressor of cytokine signaling 3 (SOCS3) also contribute to insulin resistance. Recent studies have also indicated that insulin potentiates leptin-induced signaling. Thus, a greater understanding of the overlapping functions of leptin and insulin in the central nervous system (CNS) is vital to understand the associated physiological and pathophysiological states. This mini-review focuses on the crosstalk and integrative signaling of leptin and insulin in the regulation of energy homeostasis in the brain.

Increasing leptin resistance and methylglyoxal (MG) levels have been observed in patients with obesity, which is characterized by an imbalance in energy metabolism and abnormal fat accumulation. MG is highly reactive and easily glycates proteins, impairing their physiological functions in cells. Whether MG glycates leptin and results in leptin resistance are untested. Therefore, we hypothesized that MG might directly affect leptin structure and activity or indirectly affect leptin gene and receptor expression, thereby triggering leptin resistance. The fruit of Indian gooseberry (Phyllanthus emblica L.) is rich in phenolic compounds (β-glucogallin, gallic acid, and ellagic acid) and can trap MG. This study aimed to evaluate the effect of a water extract from Indian gooseberry fruit (WEIG) on MG-induced leptin resistance in HepG2 cells. Protein cross-linking and carbonyl content measurement results showed that leptin resistance was induced by MG glycation but improved by WEIG treatment. Moreover, WEIG and its phenolic compounds (gallic acid and ellagic acid) significantly increased the mRNA expression of leptin receptors (Ob-Rb and HuB219.1), and this was accompanied by the suppression of SOCS3 and lipogenesis-associated signaling cascade (SREBP-1/ACC/FAS) gene expression and the activation of the JAK2/STAT3/AMPK/PPAR-α/CPT-1 pathway in human HepG2 liver cells exposed to free fatty acid. In conclusion, WEIG (150 μg/mL) dramatically alleviated leptin resistance and lipid accumulation by MG trapping and inhibiting MG-leptin glycation, indicating that MG is a risk factor for leptin resistance that WEIG can suppress. This finding will increase the application potential of P. emblica L. in anti-obesity functional food industrial development. WEIG significantly restored leptin activity via MG trapping, enhanced fatty acid β-oxidation, and decreased lipogenesis in MGLep- and FFA-treated HepG2 cells. [Display omitted] • The function of leptin was directly affected by MG-triggered leptin resistance. • MG-glycated leptin (MGLep) was dramatically suppressed by WEIG incubation. • Lipid metabolism was inhibited in HepG2 cells subjected to MGLep treatment. • WEIG, GA, and EA enhanced lipid metabolism in FFA-treated HepG2 cells. • Lipid accumulation, ROS, and inflammatory cytokines were reduced by WEIG. [ABSTRACT FROM AUTHOR]

Low-grade chronic inflammation in obesity is associated with leptin resistance. In order to alleviate this pathological condition, bioactive compounds capable of attenuating oxidative stress and inflammation have been researched, and bergamot (Citrus bergamia) presents these properties. The aim was to evaluate the effect of bergamot leaves extract on leptin resistance in obese rats. Animals were divided into 2 groups: control diet (C, n = 10) and high sugar-fat diet (HSF, n = 20) for 20 weeks. After detecting hyperleptinemia, animals were divided to begin the treatment with bergamot leaves extract (BLE) for 10 weeks: C + placebo (n = 7), HSF + placebo (n = 7), and HSF + BLE (n = 7) by gavage (50 mg/kg). Evaluations included nutritional, hormonal and metabolic parameters; adipose tissue dysfunction; inflammatory, oxidative markers and hypothalamic leptin pathway. HSF group presented obesity, metabolic syndrome, adipose tissue dysfunction, hyperleptinemia and leptin resistance compared to control group. However, the treated group showed a decrease in caloric consumption and attenuation of insulin resistance. Moreover, dyslipidemia, adipose tissue function, and leptin levels showed an improvement. At the level of the hypothalamus, the treated group showed a reduction of oxidative stress, inflammation and modulation of leptin signaling. In conclusion, BLE properties were able to improve leptin resistance through recovery of the hypothalamic pathway. [Display omitted] • Chronic inflammation present in obesity is associated with leptin resistance. • Bergamot attenuated inflammation and oxidative stress in the hypothalamus. • Bergamot leaves extract attenuated metabolic syndrome. • Bergamot leaves extract treatment recovered leptin pathway in the hypothalamus. [ABSTRACT FROM AUTHOR]