Diet-Induced Obesity and the Mechanism of Leptin Resistance

Spexin is a biomarker of the process that regulates leptin sensitivity

The rising prevalence of obesity poses a critical threat to global health, prompting an urgent need for a comprehensive understanding of its underlying mechanisms. This study aimed to delve into the relationship between obesity, leptin sensitivity, and gut hormones, focusing on spexin, glucagon-like peptide-1 (GLP-1), and gastric inhibitory polypeptide (GIP). We examined patients undergoing body contouring surgeries to assess how these hormones and leptin interact. Blood samples were collected at three different time points, and hormone levels were analyzed. Our findings indicated that increases in GLP-1 and decreases in GIP correlated with improved leptin sensitivity, indicated by decreased plasma leptin levels and associated with increase in steepness of the plasma leptin-spexin slope. These results suggest that spexin may serve as a biomarker for leptin sensitivity, the latter influenced by gut hormones in obese individuals. The study provides further evidence that the modulation of leptin sensitivity by gut hormones could be key in addressing obesity and its metabolic consequences.

Dysregulation of Metabolic Peptides Precedes Hyperinsulinemia and Inflammation Following Exposure to Rotenone in Rats

Rotenone, a naturally occurring compound derived from the roots of tropical plants, is used as a broad-spectrum insecticide, piscicide, and pesticide. It is a classical, high-affinity mitochondrial complex I inhibitor that causes not only oxidative stress, α-synuclein phosphorylation, DJ-1 (Parkinson's disease protein 7) modifications, and inhibition of the ubiquitin-proteasome system but it is also widely considered an environmental contributor to Parkinson's disease (PD). While prodromal symptoms, such as loss of smell, constipation, sleep disorder, anxiety/depression, and the loss of dopaminergic neurons in the substantia nigra of rotenone-treated animals, have been reported, alterations of metabolic hormones and hyperinsulinemia remain largely unknown and need to be investigated. Whether rotenone and its effect on metabolic peptides could be utilized as a biomarker for its toxic metabolic effects, which can cause long-term detrimental effects and ultimately lead to obesity, hyperinsulinemia, inflammation, and possibly gut-brain axis dysfunction, remains unclear. Here, we show that rotenone disrupts metabolic homeostasis, altering hormonal peptides and promoting infiltration of inflammatory T cells. Specifically, our results indicate a significant decrease in glucagon-like peptide-1 (GLP-1), C-peptide, and amylin. Interestingly, levels of several hormonal peptides related to hyperinsulinemia, such as insulin, leptin, pancreatic peptide (PP), peptide YY (PYY), and gastric inhibitory polypeptide (GIP), were significantly upregulated. Administration of rotenone to rats also increased body weight and activated macrophages and inflammatory T cells. These data strongly suggest that rotenone disrupts metabolic homeostasis, leading to obesity and hyperinsulinemia. The potential implications of these findings are vast, given that monitoring these markers in the blood could not only provide a crucial tool for assessing the extent of exposure and its relevance to obesity and inflammation but could also open new avenues for future research and potential therapeutic strategies.

Chronic sleep deprivation disturbs energy balance modulated by suprachiasmatic nucleus efferents in mice

BACKGROUND

Epidemiologic researches show that short sleep duration may affect feeding behaviors resulting in higher energy intake and increased risk of obesity, but the further mechanisms that can interpret the causality remain unclear. The circadian rhythm is fine-tuned by the suprachiasmatic nucleus (SCN) as the master clock, which is essential for driving rhythms in food intake and energy metabolism through neuronal projections to the arcuate nucleus (ARC) and paraventricular nucleus (PVN).

RESULTS

We showed that chronic SD-induced aberrant expressions of AgRP/NPY and POMC attributed to compromised JAK/STAT3 signals and reduced energy expenditure in the mice, which can be rescued with AAV-genetic overexpression of BMAL1 into SCN. The potential mechanism may be related to the disruptions of SCN efferent mediated by BMAL1.

CONCLUSIONS

Chronic SD impairs energy balance through directly dampening BMAL1 expression, probably in the transcription level, in the SCN, which in turn affects the neuron projections to ARC and PVN. Remarkably, we provide evidence that may explain the causal mechanisms associated with sleep curtailment and obesity in adolescents.

CREB coactivator CRTC1 in melanocortin-4 receptor-expressing cells regulate dietary fat intake

Cyclic adenosine monophosphate-response element-binding protein-1-regulated transcription coactivator-1 (CRTC1), a cytoplasmic coactivator that translocates to the nucleus in response to cAMP, is associated with obesity. We previously reported that CRTC1 deficiency in melanocortin-4 receptor (MC4R)-expressing neurons, which regulate appetite and energy metabolism in the brain, causes hyperphagia and obesity under a high-fat diet (HFD). HFD is preferred for mice, and the dietary fat in HFD is the main factor contributing to its palatability. These findings, along with our previous results, suggest that CRTC1 regulates the appetite for dietary fat. Therefore, in this study, we aimed to investigate the dietary fat intake behavior and energy metabolism of MC4R neuron-specific CRTC1 knockout mice fed soybean oil or lard. CRTC1 deficiency increased the intake of soybean oil and significantly increased body weight gain. Furthermore, obesity induced by soybean oil intake was partially due to leptin resistance. No significant changes in soybean oil intake were observed between young CRTC1-deficient and wild-type mice; however, soybean oil intake increased with age. Moreover, lard intake did not significantly affect the body weight. Overall, our findings highlighted the crucial role of CRTC1 in the regulation of spontaneous dietary fat intake. Furthermore, the role of CRTC1 becomes increasingly significant with age.

Impact of Physical Activity on Cellular Metabolism Across Both Neurodegenerative and General Neurological Conditions: A Narrative Review

BACKGROUND

Regular physical activity plays a crucial role in modulating cellular metabolism and mitigating the progression of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Multiple Sclerosis.

OBJECTIVE

The objective of this review is to evaluate the molecular mechanisms by which exercise influences cellular metabolism, with a focus on its potential as a therapeutic intervention for neurological disorders.

METHODS

A comprehensive literature review was conducted using peer-reviewed scientific articles, with a focus on the period between 2015 and 2024, to analyze the effects of exercise on mitochondrial function, oxidative stress, and metabolic health.

RESULTS

The findings indicate that exercise promotes mitochondrial biogenesis, enhances oxidative phosphorylation, and reduces reactive oxygen species, contributing to improved energy production and cellular resilience. These metabolic adaptations are associated with delayed disease progression and reduced symptoms in patients with neurodegenerative conditions. Additionally, integrating exercise with nutritional strategies may further enhance therapeutic outcomes by addressing metabolic disturbances comprehensively.

CONCLUSIONS

This review concludes that personalized exercise protocols should be developed to optimize metabolic benefits for patients with neurological diseases, while future research should focus on biomarker development for individualized treatment approaches. These findings highlight the importance of non-pharmacological interventions in managing neurodegenerative diseases.

The association between maternal factors and milk hormone concentrations: a systematic review

Background

Breast milk is the gold standard for infant feeding. It is a dynamic biological fluid rich in numerous bioactive components. Emerging research suggests that these components, including hormones, may serve as signals between mother and offspring. From an evolutionary perspective, maternal hormonal signals could allow co-adaptation of maternal and offspring phenotype, with implications for their Darwinian fitness. However, a series of steps need to be considered to establish the role of a component as a signal and this systematic review focuses on one step: 'Do maternal factors influence the concentration of milk hormones?'

Objective

To systematically review human studies which analyze the association between maternal factors and the concentration of hormones in breast milk.

Methods

Three databases were searched for studies reporting the association of maternal factors including body mass index (BMI), weight, fat mass, age, ethnicity, smoking with hormones such as adiponectin, leptin, insulin, ghrelin, and cortisol in breast milk.

Results

Thirty-three studies were eligible for inclusion. Maternal BMI was positively associated with milk leptin (20/21 studies) and with milk insulin (4/6 studies). Maternal weight also displayed a positive correlation with milk leptin levels, and maternal diabetes status was positively associated with milk insulin concentrations. Conversely, evidence for associations between maternal fat mass, smoking, ethnicity and other maternal factors and hormone levels in breast milk was inconclusive or lacking.

Conclusion

Current evidence is consistent with a signaling role for leptin and insulin in breast milk, however other steps need to be investigated to understand the role of these components as definitive signals. This review represents a first step in establishing the role of signaling components in human milk and highlights other issues that need to be considered going forward.

Obesity, Dietary Patterns, and Hormonal Balance Modulation: Gender-Specific Impacts

Understanding the intricate relationship between nutrition, hormonal balance, and gender-specific factors is crucial for developing targeted interventions to mitigate obesity-related endocrine disruptions and improve metabolic health. This narrative review examines the impact of various dietary patterns on hormonal regulation in both men and women, focusing on their effects on hormonal balance and metabolic health in the context of obesity. Calorie restriction, the Western diet, high-fat diets, low-CHO diets, plant-based diets, and the Mediterranean diet are analyzed in relation to their influence on obesity-related endocrine disruptions and metabolic health. Future research directions include investigating the specific mechanisms underlying dietary influences on hormonal regulation, addressing the gender-specific metabolic differences and body fat distribution, and exploring the dietary needs of individuals undergoing gender transition. Personalized dietary interventions tailored to individual metabolic and hormonal profiles are essential for optimizing health outcomes across the gender spectrum. By integrating gender-specific considerations into dietary recommendations, healthcare professionals can better support individuals in achieving optimal metabolic health and hormonal balance.

Personalizing Nutrition Strategies: Bridging Research and Public Health

In recent years, although life expectancy has increased significantly, non-communicable diseases (NCDs) continue to pose a significant threat to the health of the global population. Therefore, eating habits have been recognized as key modifiable factors that influence people's health and well-being. For this reason, it is interesting to study dietary patterns, since the human diet is a complex mixture of macronutrients, micronutrients, and bioactive compounds, and can modulate multiple physiological processes, including immune function, the metabolism, and inflammation. To ensure that the data we acquired were current and relevant, we searched primary and secondary sources, including scientific journals, bibliographic indexes, and databases in the last 15 years with the most relevant articles. After this search, we observed that all the recent research on NCDs suggests that diet is a critical factor in shaping an individual's health outcomes. Thus, cardiovascular, metabolic, mental, dental, and visual health depends largely on the intake, habits and patterns, and nutritional behaviors. A diet high in processed and refined foods, added sugars, and saturated fats can increase the risk of developing chronic diseases. On the other hand, a diet rich in whole, nutrient-dense foods, such as vegetables, fruits, nuts, legumes, and a high adherence to Mediterranean diet can improve health's people.

Single-cell transcriptome analysis reveals immunosuppressive landscape in overweight and obese colorectal cancer

BACKGROUND

Overweight and obesity are established risk factors for various types of cancers including colorectal cancer (CRC). However the underlying molecular mechanisms remain unclear. An in-depth understanding of the oncologic characteristics of overweight and obese CRC at the single-cell level can provide valuable insights for the development of more effective treatment strategies for CRC.

METHODS

We conducted single-cell RNA sequencing (scRNA-seq) analysis on tumor and adjacent normal colorectal samples from 15 overweight/obese and 15 normal-weight CRC patients. Immunological and metabolic differences between overweight/obese CRC and non-obese CRC were characterized.

RESULTS

We obtained single-cell transcriptomics data from a total of 192,785 cells across all samples. By evaluating marker gene expression patterns, we annotated nine main cell types in the CRC ecosystem. Specifically, we found that the cytotoxic function of effector T cells and NK cells was impaired in overweight/obese CRC compared with non-obese CRC, relating to its metabolic dysregulation. CD4+T cells in overweight/obese CRC exhibited higher expression of immune checkpoint molecules. The antigen-presenting ability of DCs and B cells is down-regulated in overweight/obese CRC, which may further aggravate the immunosuppression of overweight/obese CRC. Additionally, dysfunctional stromal cells were identified, potentially promoting invasion and metastasis in overweight/obese CRC. Furthermore, we discovered the up-regulated metabolism of glycolysis and lipids of tumor cells in overweight/obese CRC, which may impact the metabolism and function of immune cells. We also identified inhibitory interactions between tumor cells and T cells in overweight/obese CRC.

CONCLUSIONS

The study demonstrated that overweight/obese CRC has a more immunosuppressive microenvironment and distinct metabolic reprogramming characterized by increased of glycolysis and lipid metabolism. These findings may have implications for the development of novel therapeutic strategies for overweight/obese CRC patients.

The burden of colorectal cancer attributable to dietary risk in Middle East and North African from 1990 to 2019

The incidence of colorectal cancer (CRC) is increasing in low- and middle-income countries. This study aimed to estimate the burden of CRC attributable to nutritional risk in the Middle East and North Africa (MENA) region. The GBD 2019 methods were used to estimate age-standardized mortality rates (ASMRs) and disability-adjusted life-years (DALYs) in 2019 and over the past three decades. We evaluated the 30-year trend in DALYs and mortality rates from nutrition-related risks of CRC, from 1990 to 2019 by sex and age groups in 21 countries in the MENA region. The rate of DALYs/100,000 due to diet-related risks for CRC in 2019 was 79.71 (95% UI: 56.79, 98.44) and 65.16 (95% UI: 45.86, 80.95) in men and women, respectively. The percent changes of DALYs/100,000 in men and women were 8.15% and 2.50%, respectively, between 1990 and 2019. The percent changes in ASMRs in men and women were 8.32% and 3.44%, respectively. The highest DALYs and ASMRs were observed in both sexes in the age group 75-79 years and above. The highest percent changes in DALYs/100,000 and ASMRs were observed between 1990 and 2019 in Afghanistan, Egypt, Iran, Iraq, Lebanon, Libya, Morocco, Palestine, Qatar, Saudi Arabia, Sudan and Yemen. DALYs and ASMRs attributed to dietary risk for CRC increased in 21 countries in the MENA region from 1990 to 2019. A modified diet with more fiber, dairy products and less red meat intake is a highly recommended strategy for prevention CRC.

Multi-Faceted Role of Cancer-Associated Adipocytes in Colorectal Cancer

Colorectal cancer (CRC) is one of the most commonly diagnosed types of cancer, especially in obese patients, and the second cause of cancer-related death worldwide. Based on these data, extensive research has been performed over the last decades to decipher the pivotal role of the tumor microenvironment (TME) and its cellular and molecular components in CRC development and progression. In this regard, substantial progress has been made in the identification of cancer-associated adipocytes' (CAAs) characteristics, considering their active role in the CCR tumor niche, by releasing a panel of metabolites, growth factors, and inflammatory adipokines, which assist the cancer cells' development. Disposed in the tumor invasion front, CAAs exhibit a fibroblastic-like phenotype and establish a bidirectional molecular dialogue with colorectal tumor cells, which leads to functional changes in both cell types and contributes to tumor progression. CAAs also modulate the antitumor immune cells' response and promote metabolic reprogramming and chemotherapeutic resistance in colon cancer cells. This review aims to report recent cumulative data regarding the molecular mechanisms of CAAs' differentiation and their activity spectrum in the TME of CRC. A better understanding of CAAs and the molecular interplay between CAAs and tumor cells will provide insights into tumor biology and may open the perspective of new therapeutic opportunities in CRC patients.

[Obesity and Colorectal Cancer]

The prevalence of obesity has increased significantly worldwide, and this trend is likely to continue in the coming years. There is substantial evidence that obesity plays a crucial role in the development of colorectal cancer. Epidemiological data have consistently demonstrated a correlation between obesity and colorectal cancer. Insulin resistance, hyperinsulinemia, chronic inflammation, altered levels of growth factors, adipocytokines, and various hormones are plausible biological mechanisms. In addition, obesity has been shown to have an impact on recurrence, treatment success, and overall survival. There are some reports, although the evidence is not conclusive, that weight loss and lifestyle changes such as dietary modification and physical activity can reduce the risk of colorectal cancer. The understanding that obesity is a potentially modifiable risk factor that can affect the incidence and prognosis of colorectal cancer is crucial knowledge that can have an impact on the prevention and treatment of the condition.

Obesity-induced thymic involution and cancer risk

Declining thymic functions associated either with old age (i.e., age-related thymic involution), or with acute involution as a result of stress, infectious disease, or cytoreductive therapies (e.g., chemotherapy/radiotherapy), have been associated with cancer development. A key mechanism underlying such increased cancer risk is the thymus-dependent debilitation of adaptive immunity, which is responsible for orchestrating immunoediting mechanisms and tumor immune surveillance. In the past few years, a blooming set of evidence has intriguingly linked obesity with cancer development and progression. The majority of such studies has focused on obesity-driven chronic inflammation, steroid/sex hormone and adipokine production, and hyperinsulinemia, as principal factors affecting the tumor microenvironment and driving the development of primary malignancy. However, experimental observations about the negative impact of obesity on T cell development and maturation have existed for more than half a century. Here, we critically discuss the molecular and cellular mechanisms of obesity-driven thymic involution as a previously underrepresented intermediary pathology leading to cancer development and progression. This knowledge could be especially relevant in the context of childhood obesity, because impaired thymic function in young individuals leads to immune system abnormalities, and predisposes to various pediatric cancers. A thorough understanding behind the molecular and cellular circuitries governing obesity-induced thymic involution could therefore help towards the rationalized development of targeted thymic regeneration strategies for obese individuals at high risk of cancer development.

Cannabinoid receptor type 1 (CB1R) inhibits hypothalamic leptin signaling via β-arrestin1 in complex with TC-PTP and STAT3

Molecular interactions between anorexigenic leptin and orexigenic endocannabinoids, although of great metabolic significance, are not well understood. We report here that hypothalamic STAT3 signaling in mice, initiated by physiological elevations of leptin, is diminished by agonists of the cannabinoid receptor 1 (CB1R). Measurement of STAT3 activation by semi-automated confocal microscopy in cultured neurons revealed that this CB1R-mediated inhibition requires both T cell protein tyrosine phosphatase (TC-PTP) and β-arrestin1 but is independent of changes in cAMP. Moreover, β-arrestin1 translocates to the nucleus upon CB1R activation and binds both STAT3 and TC-PTP. Consistently, CB1R activation failed to suppress leptin signaling in β-arrestin1 knockout mice in vivo, and in neural cells deficient in CB1R, β-arrestin1 or TC-PTP. Altogether, CB1R activation engages β-arrestin1 to coordinate the TC-PTP-mediated inhibition of the leptin-evoked neuronal STAT3 response. This mechanism may restrict the anorexigenic effects of leptin when hypothalamic endocannabinoid levels rise, as during fasting or in diet-induced obesity.

The micronutrient content of the diet is correlated with serum glucose biomarkers and lipid profile and is associated with the odds of being overweight/obese-a case-control study

Background

A low micronutrient intake has been reported to contribute to the double-burden of obesity, increasing the risk for chronic diseases such as cardiovascular disease, diabetes, cancer, and mental disorders. This case-control study compared micronutrient intake profiles in overweight/obese vs. normal-weight individuals. We hypothesized that a low intake of certain micronutrients would increase the odds of being overweight/obese.

Methods

The case group (n = 812 adults) consisted of individuals with a BMI of ≥25  kg/m², and the control group (n = 793) had BMIs of 17.9-24.9  kg/m². A validated 124-item food frequency questionnaire was used to determine micronutrient-related dietary-quality, using the index of nutritional quality (INQ), calculated as the fraction of a micronutrient consumed vs. its dietary requirement. In addition, body surface area (BSA) was calculated according to the Mosteller formula.

Results

The control group had significantly higher INQ-scores of vitamin A, vitamin C, calcium, magnesium, and selenium compared to the case group. Furthermore, individuals with normal BSA (≤1.91 m² for men; ≤1.71  m² for women) had significantly higher INQ scores of vitamin C, calcium, magnesium, and zinc compared to participants with high BSA. In multivariable adjustment regression models, INQs of vitamin C (OR_BMI = 0.79, 95%CI: 0.64-0.97; OR_BSA = 0.81, 95%CI, 0.68-0.97) and magnesium (OR_BMI = 0.69, 95%CI: 0.47-0.99; OR_BSA = 0.71, 95%CI: 0.52-0.97) were significantly associated with the odds of obesity/overweight (in both BMI and BSA categories).

Conclusion

The significant association between micronutrient levels of the diet, especially of vitamin C and magnesium, with both obesity criteria, emphasized the importance of certain micronutrients in the obesity/overweight causal network.

Early Mid-pregnancy Blood-Based Proteins as Possible Biomarkers of Increased Infant Birth Size in Sex-Stratified Analyses

The objective of this study was to evaluate the associations of 92 maternal blood-based proteins with increased infant birth size. The study was performed at the Uppsala University Hospital, Sweden, and included 857 mother and child dyads. The mean age of the women was 30.3 years, and 53.2% were nulliparous. Blood samples were collected at mean 18 + 2 weeks' gestation, and the Olink cardiovascular II panel was used to measure 92 proteins, either known to be or suspected to be markers of cardiovascular and inflammatory disease in humans. Multiple linear regression models adjusted for maternal age, parity, pre-conception BMI, height, and smoking were performed to evaluate the association of each individual protein with infant birth size. We also performed sex-stratified analyses. Eight proteins (Matrix metalloproteinase-12 (MMP-12), Prostasin (PRSS8), Adrenomedullin (ADM), Pappalysin-1 (PAPP-A), Angiotensin-converting enzyme 2 (ACE2), Sortilin (SORT1), Lectin-like oxidized LDL receptor 1 (LOX-1), and Thrombomodulin (TM)) were associated with infant birth size after false discovery rate adjustment. In the analyses including only female infants, ten proteins (MMP-12, Growth/differentiation factor 2 (GDF-2), PRSS8, SORT1, ADM, Interleukin-1 receptor antagonist protein (IL-1ra), Leptin (LEP), ACE2, TM, and Tumor necrosis factor receptor superfamily member 11A (TNFRSF11A)) were associated with infant birth size. Two proteins (PAPP-A and PRSS8) were associated with infant birth size among male infants. Our study suggests several proteins as potential biomarkers for increased birth weight, and our findings could act as a base for future research to identify new potential markers that could be added to improve screening for large infants.

A novel anti-obesity mechanism for liraglutide by improving adipose tissue leptin resistance in high-fat diet-fed obese mice

Liraglutide has been approved for the treatment of obesity in the past few years. Both oxidative stress and leptin resistance are the critical drivers of obesity. The present study investigated the mechanism of liraglutide protection against obesity by ameliorating leptin resistance and oxidative stress. Male C57BL/6J mice were fed a high-fat diet (HFD) and subcutaneously injected with 200 μg/kg/d liraglutide for 20 weeks. Body weight, fat mass, serum levels of leptin, insulin, and superoxide dismutase (SOD) activities were measured. In addition, glucose and insulin tolerance tests were performed. The expressions of leptin, its signaling genes, and antioxidant enzymes were detected using RT-qPCR and western blot methods in liver and white adipose tissue (WAT) of mice. The results depicted that liraglutide treatment significantly slowed weight gain of body, reduced the fat mass, ameliorated glucose and lipid metabolism, and hepatic steatosis in HFD-fed obese mice. Further study demonstrated that liraglutide treatment resulted in decreased serum levels and the transcript levels of leptin as well as leptin signaling inhibitory regulators. However, it increased leptin receptor expression and the phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) in WAT (p < 0.05). In addition, the antioxidant enzyme expression was elevated in both liver and WAT of liraglutide-treated mice (p < 0.05). In conclusion, liraglutide conspicuously prevented obesity and ameliorated glucose and lipid metabolism in obese mice through a novel mechanism that improves peripheral leptin resistance in WAT and enhance the antioxidant enzyme expression in both liver and WAT.

Colon Cancer and Obesity: A Narrative Review

Obesity has played a crucial role in the pathogenesis of various cancers, including colorectal cancer (CRC). Obesity has shown to increase the blood levels of insulin, insulin-like growth factor-1 (IGF-1), leptin, resistin, inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), monocyte chemoattractant protein-1 (MCP-1) which in turn acts via various signaling pathways to induce colonic cell proliferation and in turn CRC development. It has been shown that estrogen can prevent and cause CRC based on which receptor it acts. Obese patients have relatively low levels of ghrelin and adiponectin that inhibit cell proliferation which further adds to their risk of developing CRC. Obesity can alter the microbial flora of the gut in such a way as to favor carcinogenesis. Weight loss and good physical activity have been related to a reduced incidence of CRC; obese individuals should be screened for CRC and counseled about the importance of weight reduction, diet, and exercise. The best way of screening is using BMI and waist circumference (WC) to calculate the CRC risk in obese people. This study has reviewed the association between obesity and its pathophysiological association with CRC development.

Regulation of Metabolic Health by an "Olfactory-Hypothalamic Axis" and Its Possible Implications for the Development of Therapeutic Approaches for Obesity and T2D

The olfactory system is responsible for the reception, integration and interpretation of odors. However, in the last years, it has been discovered that the olfactory perception of food can rapidly modulate the activity of hypothalamic neurons involved in the regulation of energy balance. Conversely, the hormonal signals derived from changes in the metabolic status of the body can also change the sensitivity of the olfactory system, suggesting that the bidirectional relationship established between the olfactory and the hypothalamic systems is key for the maintenance of metabolic homeostasis. In the first part of this review, we describe the possible mechanisms and anatomical pathways involved in the modulation of energy balance regulated by the olfactory system. Hence, we propose a model to explain its implication in the maintenance of the metabolic homeostasis of the organism. In the second part, we discuss how the olfactory system could be involved in the development of metabolic diseases such as obesity and type two diabetes and, finally, we propose the use of intranasal therapies aimed to regulate and improve the activity of the olfactory system that in turn will be able to control the neuronal activity of hypothalamic centers to prevent or ameliorate metabolic diseases.

Importance of ideal cardiovascular health metrics in the risk of colorectal cancer among people aged 50 years or older: a UK Biobank cohort study

OBJECTIVE

To explore the correlation between the ideal cardiovascular health metrics (ICVHMs) and the incidence of colorectal cancer (CRC) among people aged 50 years or older.

DESIGN

Prospective cohort study.

SETTING

The UK Biobank, a prospective cohort of middle-aged participants recruited between 2006 and 2010.

PARTICIPANTS

The study included 342 226 participants from the UK Biobank aged 50 years or older without prevalent cancer.

EXPOSURE

The ICVHMs consist of four behavioural factors (abstinence from smoking, ideal body mass index (BMI), physical activity at goal and consumption of healthy diet) and three cardiometabolic factors (untreated total cholesterol <200 mg/dL, untreated blood pressure <120/80 mm Hg and untreated fasting plasma glucose <100 mg/dL).

MAIN OUTCOMES

The outcome was ascertained by linkage to cancer and death registries using the International Classification of Diseases, Tenth codes C18-C20.

RESULTS

During a median follow-up time of 8.72 years, 3060 CRC cases were identified. Compared with the reference (participants with ICVHMs ≤2), the multivariable-adjusted HRs for subgroups with 3, 4, 5 and ≥6 ICVHM factors were 0.98 (95% CI 0.85 to 1.12), 0.90 (95% CI 0.77 to 1.02), 0.85 (95% CI 0.71 to 0.98) and 0.69 (95% CI 0.48 to 0.90), respectively. Among the seven ICVHM factors, lower BMI, healthier diet and ideal fasting plasma glucose were significantly associated with lower risk of CRC (HR: 0.86, 95% CI 0.78 to 0.95; HR: 0.92, 95% CI 0.84 to 0.99; HR: 0.90, 95% CI 0.80 to 0.99).

CONCLUSIONS

Adherence to the ICVHMs was associated with a lower risk of CRC among people aged 50 years or older. Among the seven ICVHM factors, BMI, diet and fasting plasma glucose played a more critical role in the prevention of CRC. These findings imply that adherence to ICVHMs should be encouraged to reduce the burden of cardiovascular disease as well as CRC.

Intragastric safflower yellow and its main component HSYA improve leptin sensitivity before body weight change in diet-induced obese mice

Our previous studies found that safflower yellow (SY) and its main component hydroxysafflor yellow A (HSYA) could alleviate obesity and improve leptin resistance in high-fat diet (HFD) induced obese mice. Therefore, our present study aimed to investigate whether the above effect of SY/HSYA was a direct effect or follow-up effect of weight loss and whether leptin was essential for the anti-obesity effect of SY/HSYA or not. HFD-induced obese mice were treated with SY or HSYA for 4 weeks, while ob/ob mice were treated with SY for 10 weeks. Body weight, food intake, fat mass, and serum leptin levels were measured. The leptin sensitivity experiment was conducted in HFD-induced obese mice. The expressions of leptin and its signaling-related genes were detected by RT-qPCR and Western blot methods. SY/HSYA treatment had no effect on food intake, energy expenditure, body weight, fat mass, and serum leptin levels in HFD-induced obese mice. However, the leptin sensitivity experiment showed that the food intake decreased by 18.4% in the HFD-SY group and the body weight gain decreased by 104.6% in the HFD-HSYA group, respectively (both P < 0.05). Furthermore, the expressions of leptin and leptin signaling inhibitory regulators were significantly decreased, while the phosphorylation of signal transducer and activator of transcription 3 (p-STAT3) were notably increased in WAT of HFD-induced obese mice, fully differentiated 3T3-L1 adipocytes after SY/HSYA intervention (all P < 0.05). Interestingly, SY treatment was ineffective on body weight, fat mass, and glucose metabolism in leptin-deficient ob/ob mice. SY/HSYA administration could firstly improve peripheral leptin resistance in adipose tissue of HFD-induced obese mice before their body weight was significantly changed, and leptin was essential for the anti-obesity effect of SY.

Mechanisms of reduced leptin-mediated satiety signaling during obesity

BACKGROUND/OBJECTIVES

Disrupted leptin signaling in vagal afferent neurons contributes to hyperphagia and obesity. Thus, we tested the hypothesis that intrinsic negative regulators of leptin signaling, suppressor of cytokine signaling 3 (SOCS3) and protein tyrosine phosphatase 1B (PTP1B) underlie dysfunctional leptin-mediated vagal afferent satiety signaling during obesity.

METHODS

Experiments were performed on standard chow-fed control mice, high-fat fed (HFF), or low-fat fed (LFF) mice. SOCS3 and PTP1B expression were quantified using western blot and quantitative PCR. Nodose ganglion neuronal excitability and jejunal afferent sensitivity were measured by patch clamp and extracellular afferent recordings, respectively.

RESULTS

Increased expression of SOCS3 and PTP1B were observed in the jejunum of HFF mice. Prolonged incubation with leptin attenuated nodose ganglion neuronal excitability, and this effect was reversed by inhibition of SOCS3. Leptin potentiated jejunal afferent nerve responses to CCK in LFF mice but decreased them in HFF mice. Inhibition of SOCS3 restored impaired vagal afferent neuronal excitability and afferent nerve responses to satiety mediators during obesity. Two-pore domain K⁺ channel (K_2P) conductance and nitric oxide (NO) production that we previously demonstrated were elevated during obesity were decreased by inhibitions of SOCS3 or PTP1B.

CONCLUSIONS

This study suggests that obesity impairs vagal afferent sensitivity via SOCS3 and PTP1B, likely as a consequence of obesity-induced hyperleptinemia. The mechanisms underlying leptin resistance appear also to cause a more global impairment of satiety-related vagal afferent responsiveness.

TNF-α Antagonizes the Effect of Leptin on Insulin Secretion through FOXO1-Dependent Transcriptional Suppression of LepRb in INS-1 Cells

Proinflammatory cytokines play a causal role in the development of hyperinsulinemia and T2MD. FOXO1, a transcription factor which is known to enhance proinflammation, was recently shown to be involved in obesity-induced β cell dysfunction. However, molecular mechanisms for the association remained elusive. In this study, we first found that both leptin (10 nM) and TNF-α (20 ng/ml) significantly inhibited glucose-stimulated insulin secretion (GSIS) of INS-1E cells. When in combination, the GSIS function of INS-1E cells was significantly increased compared with that of the leptin alone treatment, indicating that TNF-α attenuated the inhibiting effect of leptin on GSIS of INS-1E cells. Similarly, we found that TNF-α has the same inhibitory effect on leptin in regulating insulin synthesis and secretion, and the survival and apoptosis of insulin cells. Further studies showed that TNF-α blocks leptin pathway by reducing the expression of leptin receptor (LepRb, also called OBRb) and inhibiting the activation of STAT3, a key molecule involved in the leptin signaling pathway in INS-1E cells. Besides, the downregulated expression of phosphorylated FOXO1 was found to be involved in the possible mechanism of TNF-α. Overexpression of constitutively active FOXO1 markedly aggravated the LepRb reduction by TNF-α treatment of INS-1E cells, and the endogenous FOXO1 knockdown abolished the effect of TNF-α on INS-1E cells. Furthermore, we have proved that FOXO1 could directly bind to the promoter of LepRb as a negative transcription regulator. Taken together, the results of this study reveal that TNF-α-induced LepRb downregulated in pancreatic β cells and demonstrate that transcriptional reduction of FOXO1 might be the primary mechanism underlying TNF-α promoting INS-1E leptin resistance and β cell dysfunction. Conclusions. Our current studies based on INS-1E cells in vitro indicate that the inflammatory factor TNF-α plays an important role in the development of INS-1E leptin resistance and glucose metabolism disorders, probably through FOXO1-induced transcription reduction of LepRb promoter in pancreatic β cells, and FOXO1 may be a novel target for treating β cell dysfunction in obesity-induced hyperinsulinemia and T2DM.

Leptin: A Potential Link Between Obstructive Sleep Apnea and Obesity

Chronic intermittent hypoxia (CIH), a pathophysiological manifestation of obstructive sleep apnea (OSA), is strongly correlated with obesity, as patients with the disease experience weight gain while exhibiting elevated plasma levels of leptin. This study was done to determine whether a relationship may exist between CIH and obesity, and body energy balance and leptin signaling during CIH. Sprague-Dawley rats were exposed to 96 days of CIH or normoxic control conditions, and were assessed for measures of body weight, food and water intake, and food conversion efficiency. At the completion of the study leptin sensitivity, locomotor activity, fat pad mass and plasma leptin levels were determined within each group. Additionally, the hypothalamic arcuate nucleus (ARC) was isolated and assessed for changes in the expression of proteins associated with leptin receptor signaling. CIH animals were found to have reduced locomotor activity and food conversion efficiency. Additionally, the CIH group had increased food and water intake over the study period and had a higher body weight compared to normoxic controls at the end of the study. Basal plasma concentrations of leptin were significantly elevated in CIH exposed animals. To test whether a resistance to leptin may have occurred in the CIH animals due to the elevated plasma levels of leptin, an acute exogenous (ip) leptin (0.04 mg/kg carrier-free recombinant rat leptin) injection was administered to the normoxic and CIH exposed animals. Leptin injections into the normoxic controls reduced their food intake, whereas CIH animals did not alter their food intake compared to vehicle injected CIH animals. Within ARC, CIH animals had reduced protein expression of the short form of the obese (leptin) receptor (isoform OBR₁₀₀) and showed a trend toward an elevated protein expression of the long form of obese (leptin) receptor (OBRb). In addition, pro-opiomelanocortin (POMC) protein expression was reduced, but increased expression of the phosphorylated extracellular-signal-regulated kinase 1/2 (pERK1/2) and of the suppressor of cytokine signaling 3 (SOCS3) proteins was observed in the CIH group, with little change in phosphorylated signal transducer and activator of transcription 3 (pSTAT3). Taken together, these data suggest that long-term exposure to CIH, as seen in obstructive sleep apnea, may contribute to a state of leptin resistance promoting an increase in body weight.

Therapeutic Target Analysis and Molecular Mechanism of Melatonin - Treated Leptin Resistance Induced Obesity: A Systematic Study of Network Pharmacology

BACKGROUND

Obesity is a medical problem with an increased risk for other metabolic disorders like diabetes, heart problem, arthritis, etc. Leptin is an adipose tissue-derived hormone responsible for food intake, energy expenditure, etc., and leptin resistance is one of the significant causes of obesity. Excess leptin secretion by poor diet habits and impaired hypothalamic leptin signaling leads to LR. Melatonin a sleep hormone; also possess antioxidant and anti-inflammatory properties. The melatonin can attenuate the complications of obesity by regulating its targets towards LR induced obesity.

AIM

The aim of this study includes molecular pathway and network analysis by using a systems pharmacology approach to identify a potential therapeutic mechanism of melatonin on leptin resistance-induced obesity.

METHODS

The bioinformatic methods are used to find therapeutic targets of melatonin in the treatment of leptin resistance-induced obesity. It includes target gene identification using public databases, Gene ontology, and KEGG pathway enrichment by 'ClusterProfiler' using the R language, network analysis by Cytoscape, and molecular Docking by Autodock.

RESULTS

We obtained the common top 33 potential therapeutic targets of melatonin and LR-induced obesity from the total melatonin targets 254 and common LR obesity targets 212 using the data screening method. They are involved in biological processes related to sleep and obesity, including the cellular response to external stimulus, chemical stress, and autophagy. From a total of 180 enriched pathways, we took the top ten pathways for further analysis, including lipid and atherosclerosis, endocrine, and AGE-RAGE signaling pathway in diabetic complications. The top 10 pathways interacted with the common 33 genes and created two functional modules. Using Cytoscape network analysis, the top ten hub genes (TP53, AKT1, MAPK3, PTGS2, TNF, IL6, MAPK1, ERBB2, IL1B, MTOR) were identified by the MCC algorithm of the CytoHubba plugin. From a wide range of pathway classes, melatonin can reduce LR-induced obesity risks by regulating the major six classes. It includes signal transduction, endocrine system, endocrine and metabolic disease, environmental adaptation, drug resistance antineoplastic, and cardiovascular disease.

CONCLUSION

The pharmacological mechanism of action in this study shows the ten therapeutic targets of melatonin in LR-induced obesity.

Sparse System Identification of Leptin Dynamics in Women With Obesity

The prevalence of obesity is increasing around the world at an alarming rate. The interplay of the hormone leptin with the hypothalamus-pituitary-adrenal axis plays an important role in regulating energy balance, thereby contributing to obesity. This study presents a mathematical model, which describes hormonal behavior leading to an energy abnormal equilibrium that contributes to obesity. To this end, we analyze the behavior of two neuroendocrine hormones, leptin and cortisol, in a cohort of women with obesity, with simplified minimal state-space modeling. Using a system theoretic approach, coordinate descent method, and sparse recovery, we deconvolved the serum leptin-cortisol levels. Accordingly, we estimate the secretion patterns, timings, amplitudes, number of underlying pulses, infusion, and clearance rates of hormones in eighteen premenopausal women with obesity. Our results show that minimal state-space model was able to successfully capture the leptin and cortisol sparse dynamics with the multiple correlation coefficients greater than 0.83 and 0.87, respectively. Furthermore, the Granger causality test demonstrated a negative prospective predictive relationship between leptin and cortisol, 14 of 18 women. These results indicate that increases in cortisol are prospectively associated with reductions in leptin and vice versa, suggesting a bidirectional negative inhibitory relationship. As dysregulation of leptin may result in an abnormality in satiety and thereby associated to obesity, the investigation of leptin-cortisol sparse dynamics may offer a better diagnostic methodology to improve better treatments plans for individuals with obesity.

Effect of sleeve gastrectomy, Roux-en-Y gastric bypass, and ileal transposition on myocardial ischaemia-reperfusion injury in non-obese non-diabetic rats

Bariatric surgery (BS) improves outcomes in patients with myocardial infarction (MI). Here we tested the hypothesis that BS-mediated reduction in fatal MI could be attributed to its infarct-limiting effect. Wistar rats were randomized into five groups: control (CON), sham (SHAM), Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), and ileotransposition (IT). Ten weeks later, animals were subjected to 30-min myocardial ischemia plus 120-min reperfusion. Infarct size (IS) and no-reflow area were determined histochemically. Fasting plasma levels of glucagon-like peptide-1 (GLP-1), leptin, ghrelin, and insulin were measured using ELISA. Compared with SHAM, RYGB and SG reduced IS by 22% (p = 0.011) and 10% (p = 0.027), and no-reflow by 38% (p = 0.01) and 32% (p = 0.004), respectively. IT failed to reduce IS and no-reflow. GLP-1 level was increased in the SG and RYGB groups compared with CON. In both the SG and RYGB, leptin level was decreased compared with CON and SHAM. In the SG group, ghrelin level was lower than that in the CON and SHAM. Insulin levels were not different between groups. In conclusion, RYGB and SG increased myocardial tolerance to ischemia-reperfusion injury of non-obese, non-diabetic rats, and their infarct-limiting effect is associated with decreased leptin and ghrelin levels and increased GLP-1 level.

Obesity Impairs Enthesis Healing After Rotator Cuff Repair in a Rat Model

BACKGROUND

Being overweight or obese is associated with poor outcomes and an increased risk of failure after rotator cuff (RC) surgery. However, the effect of obesity on enthesis healing has not been well characterized.

HYPOTHESES

Diet-induced obesity (DIO) would result in inferior enthesis healing in a rat model of RC repair, and a dietary intervention in the perioperative period would improve enthesis healing.

STUDY DESIGN

Controlled laboratory study.

METHODS

Male Sprague-Dawley rats were divided into 3 weight-matched groups (n = 26 per group): control diet (CD), high-fat diet (HFD), or HFD until surgery and then CD thereafter (HF-CD). After 12 weeks, the left supraspinatus tendon was detached, followed by immediate repair. Animals were sacrificed, and RCs were harvested at 2 and 12 weeks after surgery for biomechanical and histological evaluations. Metabolic end points were assessed using dual-energy X-ray absorptiometry and plasma analyses.

RESULTS

DIO was established in the HFD and HF-CD groups before surgery and subsequently reversed in the HF-CD group after surgery. At 12 weeks after surgery, the body fat percentage (P = .0021) and plasma leptin concentration (P = .0025) were higher in the HFD group compared with the CD group. Histologically, the appearance of the repaired entheses was poorer in both the HFD and HF-CD groups compared with the CD group at 12 weeks after surgery, with semiquantitative scores of 6.20 (P = .0078), 4.98 (P = .0003), and 8.68 of 15, respectively. The repaired entheses in the HF-CD group had a significantly lower load to failure (P = .0278) at 12 weeks after surgery compared with the CD group, while the load to failure in the HFD group was low but not significantly different (P = .0960). There were no differences in the biomechanical and histological results between the groups at 2 weeks after surgery. Body mass at the time of surgery, plasma leptin concentration, and body fat percentage were negatively correlated with histology scores and plasma leptin concentration was correlated with load to failure at 12 weeks after surgery.

CONCLUSION

DIO impaired enthesis healing in this rat RC repair model, with inferior biomechanical and histological outcomes. Restoring a normal weight with dietary changes after surgery did not improve healing outcomes.

CLINICAL RELEVANCE

Obesity is a potentially modifiable factor that impairs RC healing and increases the risk of failure after surgery. Exploring interventions that improve the metabolic state of obese patients and counseling patients appropriately about their modest expectations after repair should be considered.

Obesity Attenuates Ventilator-Induced Lung Injury by Modulating the STAT3-SOCS3 Pathway

Background

Ventilator-induced lung injury (VILI) is characterized by vascular barrier dysfunction and suppression of alveolar fluid clearance (AFC). Obesity itself leads to chronic inflammation, which may initiate an injurious cascade to the lungs and simultaneously induce a protective feedback. In this study, we investigated the protective mechanism of obesity on VILI in a mouse model.

Methods

The VILI model was set up via 6-h mechanical ventilation with a high tidal volume. Parameters including lung injury score, STAT3/NFκB pathway, and AFC were assessed. Mice with diet-induced obesity were obtained by allowing free access to a high-fat diet since the age of 3 weeks. After a 9-week diet intervention, these mice were sacrificed at the age of 12 weeks. The manipulation of SOCS3 protein was achieved by siRNA knockdown and pharmaceutical stimulation using hesperetin. WNK4 knockin and knockout obese mice were used to clarify the pathway of AFC modulation.

Results

Obesity itself attenuated VILI. Knockdown of SOCS3 in obese mice offset the protection against VILI afforded by obesity. Hesperetin stimulated SOCS3 upregulation in nonobese mice and provided protection against VILI. In obese mice, the WNK4 axis was upregulated at the baseline, but was significantly attenuated after VILI compared with nonobese mice. At the baseline, the manipulation of SOCS3 by siRNA and hesperetin also led to the corresponding alteration of WNK4, albeit to a lesser extent. After VILI, WNK4 expression correlated with STAT3/NFκB activation, regardless of SOCS3 status. Obese mice carrying WNK4 knockout had VILI with a severity similar to that of wild-type obese mice. The severity of VILI in WNK4-knockin obese mice was counteracted by obesity, similar to that of wild-type nonobese mice only.

Conclusions

Obesity protects lungs from VILI by upregulating SOCS3, thus suppressing the STAT3/NFκB inflammatory pathway and enhancing WNK4-related AFC. However, WNK4 activation is mainly from direct NFκB downstreaming, and less from SOCS3 upregulation. Moreover, JAK2-STAT3/NFκB signaling predominates the pathogenesis of VILI. Nevertheless, the interaction between SOCS3 and WNK4 in modulating VILI in obesity warrants further investigation.

Diet-induced obesity leads to alterations in behavior and gut microbiota composition in mice

The high prevalence of obesity and associated metabolic disorders are one of the major public health problems worldwide. Among the main causal factors of obesity, excessive consumption of food rich in sugar and fat stands out due to its high energy density. The regulation of food intake relies on hypothalamic control by the action of several neuropeptides. Excessive consumption of hypercaloric diets has impact in the behavior and in the gut microbiota. In the present study, we used a high-sugar and fat (HSB) diet for 12 weeks to induce obesity in C57BL/6 mice and to investigate its effects on the gut microbiota, hypothalamic peptides, and behavior. We hypothesize that chronic consumption of HSB diet can change the behavior. Additionally, we also hypothesize that changes in gut microbiota can be associated with changes in the transcriptional regulation of hypothalamic peptides and behavior. To evaluate the gut microbiota, we performed the sequencing of 16S rRNA gene, which demonstrate that HSB diet modulates the gut microbiota with an increase in the Firmicutes and Actinobacteria phylum and a decrease of Bacteroidetes phylum. The real time qPCR revealed that HSB-fed mice presented changes in the transcriptional regulation of hypothalamic neuropeptides genes such as Npy, Gal and Galr1. The Marble-burying and Light/dark box tests also showed an alteration in anxiety and impulsive behaviors for the HSB-fed mice. Our data provides evidence that obesity induced by HSB diet consumption is associated with alterations in gut microbiota and behavior, highlighting the multifactorial characteristics of this disease.

Fatty acid binding protein 4 (FABP4) and metabolic-related parameters in systemic lupus erythematosus active and non-active episode

OBJECTIVE

To assess serum FABP4 and other metabolic-related parameters in Systemic Lupus Erythematosus (SLE) active and non-active episode.

METHODS

Fifty-four SLE patients in Hasan Sadikin General Hospital, Bandung, Indonesia in 2018-2019 were recruited and serum samples were collected in their active and non-active episode status. Serum was analyzed for FABP4, leptin, glucose, and triglycerides. The clinical characteristics were analyzed from medical records. Disease activity was assessed with the SLEDAI-2K (≥4 defined as an active; <4 as non-active episode).

RESULTS

Significantly correlation of Systolic Blood Pressure (SBP) (p = 0.001, r = 0.59) and C3 (p = 0.04, r = 0.47) between active and non-active episode. In non-active episode, there was significant correlation of FABP4 with Diastolic Blood Pressure (DBP) (p = 0.04, r = 0.26) and blood glucose (p = 0.01, r = -0.39). In active episode, there was significant correlation FABP4 with SBP (p = 0.04, r = -0.28) and triglyceride (p = 0.002, r = 0.55).

CONCLUSION

FABP4 correlates with high DBP in the non-active and high triglyceride serum in the active episode.

Role of Leptin in the Digestive System

Leptin is a pluripotent peptide hormone produced mainly by adipocytes, as well as by other tissues such as the stomach. Leptin primarily acts on the central nervous system, particularly the hypothalamus, where this hormone regulates energy homeostasis and neuroendocrine function. Owing to this, disruption of leptin signaling has been linked with numerous pathological conditions. Recent studies have also highlighted the diverse roles of leptin in the digestive system including immune regulation, cell proliferation, tissue healing, and glucose metabolism. Of note, leptin acts differently under physiological and pathological conditions. Here, we review the current knowledge on the functions of leptin and its downstream signaling in the gastrointestinal tract and accessory digestive organs, with an emphasis on its physiological and pathological implications. We also discuss the current therapeutic uses of recombinant leptin, as well as its limitations.

Adipotropic effects of heavy metals and their potential role in obesity

Epidemiological studies demonstrated an association between heavy metal exposure and the incidence of obesity and metabolic syndrome. However, the particular effects of metal toxicity on adipose tissue functioning are unclear. Therefore, recent findings of direct influence of heavy metals (mercury, cadmium, and lead) and metalloid (arsenic) on adipose tissue physiology are discussed while considering existing gaps and contradictions. Here, we provide a literature review addressing adipose tissue as a potential target of heavy metal toxicity. Experimental in vivo studies demonstrated a significant influence of mercury, cadmium, lead, and arsenic exposure on body adiposity. In turn, in vitro experiments revealed both up- and downregulation of adipogenesis associated with aberrant expression of key adipogenic pathways, namely CCAAT/enhancer-binding protein (C/EBP) and peroxisome proliferator-activated receptor gamma (PPARγ). Comparison of the existing studies on the basis of dose and route of exposure demonstrated that the effects of heavy metal exposure on adipose tissue may be dose-dependent, varying from increased adipogenesis at low-dose exposure to inhibition of adipose tissue differentiation at higher doses. However, direct dose-response data are available in a single study only for arsenic. Nonetheless, both types of these effects, irrespective of their directionality, contribute significantly to metabolic disturbances due to dysregulated adipogenesis. Particularly, inhibition of adipocyte differentiation is known to reduce lipid-storage capacity of adipose tissue, leading to ectopic lipid accumulation. In contrast, metal-associated stimulation of adipogenesis may result in increased adipose tissue accumulation and obesity. However, further studies are required to reveal the particular dose- and species-dependent effects of heavy metal exposure on adipogenesis and adipose tissue functioning.

The Role of Hypothalamic Inflammation in Diet-Induced Obesity and Its Association with Cognitive and Mood Disorders

Obesity is often associated with cognitive and mood disorders. Recent evidence suggests that obesity may cause hypothalamic inflammation. Our aim was to investigate the hypothesis that there is a causal link between obesity-induced hypothalamic inflammation and cognitive and mood disorders. Inflammation may influence hypothalamic inter-connections with regions important for cognition and mood, while it may cause dysregulation of the Hypothalamic-Pituitary-Adrenal (HPA) axis and influence monoaminergic systems. Exercise, healthy diet, and glucagon-like peptide receptor agonists, which can reduce hypothalamic inflammation in obese models, could improve the deleterious effects on cognition and mood.

Eating behaviour in contrasting adiposity phenotypes: Monogenic obesity and congenital generalized lipodystrophy

Most known types of nonsyndromic monogenic obesity are caused by rare mutations in genes of the leptin-melanocortin pathway controlling appetite and adiposity. In contrast, congenital generalized lipodystrophy represents the most extreme form of leanness in humans caused by recessive mutations in four genes involved in phospholipid/triglyceride synthesis and lipid droplet/caveolae structure. In this disease, the inability to store triglyceride in adipocytes results in hypoleptinemia and ectopic hepatic and muscle fat accumulation leading to fatty liver, hypertriglyceridemia and severe insulin resistance. As a result of hypoleptinemia, patients with lipodystrophy show alterations in eating behaviour characterized by constant increased energy intake. As it occurs in obesity caused by genetic leptin deficiency, exogenous leptin rapidly reduces hunger scores in patients with congenital generalized lipodystrophy, with additional beneficial effects on glucose homeostasis and metabolic profile normalization. The melanocortin-4 receptor agonist setmelanotide has been used in the treatment of monogenic obesities. There is only one report on the effect of setmelanotide in a patient with partial lipodystrophy resulting in mild reductions in hunger scores, with no improvements in metabolic status. The assessment of contrasting phenotypes of obesity/leanness represents an adequate strategy to understand the pathophysiology and altered eating behaviour associated with adipose tissue excessive accumulation/paucity.

Effect of Leptin on Chronic Inflammatory Disorders: Insights to Therapeutic Target to Prevent Further Cardiovascular Complication

In response to obesity-associated chronic inflammatory disorders, adipose tissue releases a biologically active peptide known as leptin. Leptin activates the secretion of chemical mediators, which contribute to the pathogenesis of chronic inflammatory disorders, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and psoriasis. Conversely, adiposity and obesity are the major aggravating risk factors in the pathogenesis of metabolic syndrome (MetS), including type II diabetes mellitus and obesity-associated hypertension. Elevated level of leptin in obesity-associated hypertension causes an increase in the production of aldosterone, which also results in elevation of arterial blood pressure. Hyperleptinemia is associated with the progress of the atherosclerosis through secretion of pro-inflammatory cytokines, like interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), IL-17, and other cytokines to promote inflammation. The release of those cytokines leads to chronic inflammatory disorders and obesity-associated MetS. Thus, the aberrant leptin level in both MetS and chronic inflammatory disorders also leads to the complication of cardiovascular diseases (CVD). Therapeutic target of leptin regarding its pro-inflammatory effect and dysregulated sympathetic nervous system activity may prevent further cardiovascular complication. This review mainly assesses the mechanism of leptin on the pathogenesis and further cardiovascular risk complication of chronic inflammatory disorders.

CB1R regulates soluble leptin receptor levels via CHOP, contributing to hepatic leptin resistance

The soluble isoform of leptin receptor (sOb-R), secreted by the liver, regulates leptin bioavailability and bioactivity. Its reduced levels in diet-induced obesity (DIO) contribute to hyperleptinemia and leptin resistance, effects that are regulated by the endocannabinoid (eCB)/CB₁R system. Here we show that pharmacological activation/blockade and genetic overexpression/deletion of hepatic CB₁R modulates sOb-R levels and hepatic leptin resistance. Interestingly, peripheral CB₁R blockade failed to reverse DIO-induced reduction of sOb-R levels, increased fat mass and dyslipidemia, and hepatic steatosis in mice lacking C/EBP homologous protein (CHOP), whereas direct activation of CB₁R in wild-type hepatocytes reduced sOb-R levels in a CHOP-dependent manner. Moreover, CHOP stimulation increased sOb-R expression and release via a direct regulation of its promoter, while CHOP deletion reduced leptin sensitivity. Our findings highlight a novel molecular aspect by which the hepatic eCB/CB₁R system is involved in the development of hepatic leptin resistance and in the regulation of sOb-R levels via CHOP.

When the human body has stored enough energy from food, it releases a hormone called leptin that travels to the brain and stops feelings of hunger. This hormone moves through the bloodstream and can affect other organs, such as the liver, which also help control our body’s energy levels. Most people with obesity have very high levels of leptin in their blood, but are resistant to its effects and will therefore continue to feel hungry despite having stored enough energy.

One of the proteins that controls the levels of leptin is a receptor called sOb-R, which is released by the liver and binds to leptin as it travels in the blood. Individuals with high levels of this receptor often have less free leptin in their bloodstream and a lower body weight. Another protein that helps the body to regulate its energy levels is the cannabinoid-1 receptor, or CB1R for short. In people with obesity, this receptor is overactive and has been shown to contribute to leptin resistance, which is when the brain becomes less receptive to leptin. Previous work in mice showed that blocking CB1R reduced the levels of leptin and allowed mice to react to this hormone normally again, but it remained unclear whether CB1R affects how other organs, such as the liver, respond to leptin.

To answer this question, Drori et al. blocked the CB1R receptor in the liver of mice eating a high-fat diet, either by using a drug or by deleting the gene that codes for this protein. This caused mice to have higher levels of sOb-R circulating in their bloodstream. Further experiments showed that this change in sOb-R was caused by the levels of a protein called CHOP increasing in the liver when CB1R was blocked. Drori et al. found that inhibiting CB1R caused these obese mice to lose weight and have healthier, less fatty livers as a result of their livers no longer being resistant to the effects of leptin.

Scientists, doctors and pharmaceutical companies are trying to develop new strategies to combat obesity. The results from these experiments suggest that blocking CB1R in the liver could allow this organ to react to leptin appropriately again. Drugs blocking CB1R, including the one used in this study, will be tested in clinical trials and could provide a new approach for treating obesity.

Magnetic resonance assessment of the cerebral alterations associated with obesity development

Obesity is a current threat to health care systems, affecting approximately 13% of the world's adult population, and over 18% children and adolescents. The rise of obesity is fuelled by inadequate life style habits, as consumption of diets rich in fats and sugars which promote, additionally, the development of associated comorbidities. Obesity results from a neuroendocrine imbalance in the cerebral mechanisms controlling food intake and energy expenditure, including the hypothalamus and the reward and motivational centres. Specifically, high-fat diets are known to trigger an early inflammatory response in the hypothalamus that precedes weight gain, is time-dependent, and eventually extends to the remaining appetite regulating regions in the brain. Multiple magnetic resonance imaging (MRI) and spectroscopy (MRS) methods are currently available to characterize different features of cerebral obesity, including diffusion weighted, T2 and volumetric imaging and 1H and 13C spectroscopic evaluations. In particular, consistent evidences have revealed increased water diffusivity and T2 values, decreased grey matter volumes, and altered metabolic profiles and fluxes, in the brain of animal models and in obese humans. This review provides an integrative interpretation of the physio-pathological processes associated with obesity development in the brain, and the MRI and MRS methods implemented to characterize them.

Chronic Timed Sleep Restriction Attenuates LepRb-Mediated Signaling Pathways and Circadian Clock Gene Expression in the Rat Hypothalamus

The sleep duration of adolescents has continued to decline over the past 20 years. Sleep insufficiency is one of the most important risk factors for obesity, but the mechanisms underlying the association are unclear. Therefore, the hypothalamic-regulated mechanisms of appetite and the circadian clock gene expression were examined in sleep-restricted rats. Rats aged 7 weeks were randomly divided into two groups: the control group and sleep restriction group (7 rats/group) rats were sleep-restricted for 4 weeks. Body weight gain and amount of food/water consumption were quantified. The expression of genes or proteins which regulated appetite and energy metabolism via leptin receptor signaling and the circadian clock in the hypothalamus were assessed. Chronic sleep restriction induced increased food intake and weight gain in adolescent and young adult rats from the second week of initiation of sleep restriction. Phosphorylation of Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) was decreased, although levels of circulating leptin or leptin receptor expression were unaltered. Furthermore, insulin receptor substrate (IRS)/phosphoinositide 3-kinase (PI3K)/AKT/mTOR and forkhead box O1 (FoxO1) signaling pathways were also compromised. Moreover, core circadian clock genes were also decreased in the sleep restriction group compared with the control. Chronic timed sleep restriction induced hyperphagic behaviors, attenuated leptin receptor-mediated signaling pathways, and depleted the expression of circadian clock gene in the hypothalamus of adolescent and young adult rats.

Linking Obesity with Colorectal Cancer: Epidemiology and Mechanistic Insights

The incidence of obesity and colorectal cancer (CRC) has risen rapidly in recent decades. More than 650 million obese and 2 billion overweight individuals are currently living in the world. CRC is the third most common cancer. Obesity is regarded as one of the key environmental risk factors for the pathogenesis of CRC. In the present review, we mainly focus on the epidemiology of obesity and CRC in the world, the United States, and China. We also summarize the molecular mechanisms linking obesity to CRC in different aspects, including nutriology, adipokines and hormones, inflammation, gut microbiota, and bile acids. The unmet medical needs for obesity-related CRC are still remarkable. Understanding the molecular basis of these associations will help develop novel therapeutic targets and approaches for the treatment of obesity-related CRC.

Selected Indonesian Medicinal Plants for the Management of Metabolic Syndrome: Molecular Basis and Recent Studies

Increased prevalence of metabolic syndrome (MetS) in the world influences quality of health in all respective countries, including Indonesia. Data from Indonesian Family Life Survey reported in 2019 showed that the prevalence of MetS in Indonesia currently is 21.66%, estimated with the provincial incidence ranging up to 50%; additionally, the most common components of MetS discovered in Indonesia were poor high-density lipoprotein (HDL) cholesterol and hypertension. Management treatment of MetS involves a combination of lifestyle changes and pharmacological interventions to decrease cerebrovascular disease. Various natural substances have been shown to govern any cardiovascular or metabolic disorders through different mechanisms, such as triggering anti-inflammation, lipid profile correction, sensitization of insulin reception, or blood glucose control. In Indonesia, the utilization of natural compounds is part of the nation's culture. The community widely uses them; even though in general, their effectiveness and safety have not been thoroughly assessed by rigorous clinical trials. Scientific evidence suggested that cinnamon, mangosteen, and curcumin, as well as their derived components possess a broad spectrum of pharmacological activity. In this review, an enormous potential of cinnamon, mangosteen, and curcumin, which originated and are commonly used in Indonesia, could be treated against MetS, such as diabetes, hyperlipidemia, hypertension, and obesity. The findings suggested that cinnamon, mangosteen, curcumin and their derivatives may reflect areas of promise in the management of MetS.

Acid sphingomyelinase downregulation alleviates vascular endothelial leptin resistance in rats

Leptin resistance in endothelial cells leads to vascular endothelial dysfunction, which is the beginning and crucial link of atherosclerosis. However, the mechanism of leptin resistance remains obscure. Acid sphingomyelinase (ASM) catalyzes the hydrolysis of sphingomyelin to produce ceramide, which plays an important role in the progression of metabolic and cardiovascular diseases. In this study, we investigated whether ASM could regulate leptin resistance in vascular endothelial cells. We induced endothelial leptin resistance in rat aortic endothelial cells through treatment with palmitic acid (0.3 mM) or knockdown of leptin receptor (Ob-Rb), which resulted in the increase of suppressor of cytokine signaling 3 expression, the decrease of Ob-Rb expression, and signal transducer and activator of transcription 3 (STAT3) phosphorylation at Tyr705. We found that these indicators of leptin resistance were reversed by knockdown of ASM or by the selective ASM inhibitors amitriptyline (AMI) and imipramine (IMI). Supplementation of ceramide inhibited Ob-Rb expression and STAT3 phosphorylation by inhibiting extracellular signal-regulated kinase 1/2 activation. Furthermore, we found that knockdown of ASM enhanced endothelial nitric oxide (NO) synthase activity and NO production, as well as the Akt phosphorylation at ser473, which was regulated by STAT3. High-fat diet (HFD) feeding-induced leptin resistance in rats in vivo; administration of AMI and IMI (10 mg· kg⁻¹ per day, intraperitoneally, for 2 weeks) increased the release of endothelial NO to relieve the vasodilatory response and improved the endothelial leptin resistance in the aorta of HFD-fed rats. These results suggest that ASM downregulation reverses endothelial leptin resistance, and consequently improves vascular endothelial dysfunction. This study highlighted ASM as a potential therapeutic target for endothelial leptin resistance.

Associations of maternal diet and placenta leptin methylation

BACKGROUND

Maternal diet is an important factor in prenatal development that also has implications for disease risk later in life. The adipokine leptin is a key regulator of energy homeostasis and may be involved in the association between maternal nutrition, maternal obesity, and infant outcomes. DNA methylation of placenta genes may occur in response to exposures and may program subsequent infant development. This study examined maternal diet, placenta leptin gene DNA methylation, and neonatal growth in a sample of healthy neonates and their mothers.

METHODS

Mothers and their healthy neonates (N = 135) were recruited within 1-2 days following delivery at Women and Infants Hospital in Providence, RI. A structured interview was conducted to assess maternal dietary intake. Maternal pre-pregnancy weight, weight gain during pregnancy, maternal health, medications, and vitamin use were obtained from medical records. Bisulfite pyrosequencing was used to measure methylation of CpG sites in the promoter region of the placenta leptin gene and determine genotype of the leptin single nucleotide polymorphism (SNP) rs2167270, which is known to influence leptin methylation. Bivariate analyses and linear regression models were used to evaluate associations of demographics, diet, and mean leptin methylation.

RESULTS

Genotype was a significant predictor of placenta leptin DNA methylation (p < .01), and after controlling for this and other relevant maternal and infant covariates, lower levels of leptin methylation were significantly associated with greater intake of carbohydrates (p < .05), in particular added sugars (p < .05) and white/refined carbohydrates (p < .05). Total caloric intake was also associated with placenta leptin methylation (p < .05), however after controlling for relevant covariates, significance diminished to trend-level. There were no significant associations of placenta leptin methylation and intake of protein (p > .05) or fat (p > .05).

CONCLUSION

These findings underline the importance of intake of carbohydrate consumption for methylation of the placenta leptin gene. Because methylation reduces gene transcription, lower methylation may indicate a placenta response to high caloric intake and carbohydrate food that would result in higher levels of this hormone during fetal development. Further investigation of the developmental ramifications of epigenetic changes to placenta leptin methylation should be pursued.

Effects of gut microbiota on leptin expression and body weight are lessened by high-fat diet in mice

Aberration in leptin expression is one of the most frequent features in the onset and progression of obesity, but the underlying mechanisms are still unclear and need to be clarified. This study investigated the effects of the absence of gut microbiota on body weight and the expression and promoter methylation of the leptin. Male C57 BL/6 J germ-free (GF) and conventional (CV) mice (aged 4-5 weeks) were fed either a normal-fat diet (NFD) or a high-fat diet (HFD) for 16 weeks. Six to eight mice from each group, at 15 weeks, were administered exogenous leptin for 7 d. Leptin expression and body weight gain in GF mice were increased by NFD with more CpG sites hypermethylated at the leptin promoter, whereas there was no change with HFD, compared with CV mice. Adipose or hepatic expression of genes associated with fat synthesis (Acc1, Fas and Srebp-1c), hydrolysis and oxidation (Atgl, Cpt1a, Cpt1c, Ppar-α and Pgc-1α) was lower, and hypothalamus expression of Pomc and Socs3 was higher in GF mice than levels in CV mice, particularly with NFD feeding. Exogenous leptin reduced body weight in both types of mice, with a greater effect on CV mice with NFD. Adipose Lep-R expression was up-regulated, and hepatic Fas and hypothalamic Socs3 were down-regulated in both types of mice. Expression of fat hydrolysis and oxidative genes (Atgl, Hsl, Cpt1a, Cpt1c, Ppar-α and Pgc-1α) was up-regulated in CV mice. Therefore, the effects of gut microbiota on the leptin expression and body weight were affected by dietary fat intake.

UCP1-independent glucose-lowering effect of leptin in type 1 diabetes: only in conditions of hypoleptinemia

The possibility to use leptin therapeutically for lowering glucose levels in patients with type 1 diabetes has attracted interest. However, earlier animal models of type 1 diabetes are severely catabolic with very low endogenous leptin levels, unlike most patients with diabetes. Here, we aim to test glucose-lowering effects of leptin in novel, more human-like murine models. We examined the glucose-lowering potential of leptin in diabetic models of two types: streptozotocin-treated mice and mice treated with the insulin receptor antagonist S961. To prevent hypoleptinemia, we used combinations of thermoneutral temperature and high-fat feeding. Leptin fully normalized hyperglycemia in standard chow-fed streptozotocin-treated diabetic mice. However, more humanized physiological conditions (high-fat diets or thermoneutral temperatures) that increased adiposity - and thus also leptin levels - in the diabetic mice abrogated the effects of leptin, i.e., the mice developed leptin resistance also in this respect. The glucose-lowering effect of leptin was not dependent on the presence of the uncoupling protein-1 and was not associated with alterations in plasma insulin, insulin-like growth factor 1, food intake or corticosterone but fully correlated with decreased plasma glucagon levels and gluconeogenesis. An important implication of these observations is that the therapeutic potential of leptin as an additional treatment in patients with type 1 diabetes is probably limited. This is because such patients are treated with insulin and do not display low leptin levels. Thus, the potential for a glucose-lowering effect of leptin would already have been attained with standard insulin therapy, and further effects on blood glucose level through additional leptin cannot be anticipated.

Adipose Tissue Composition in Obesity and After Bariatric Surgery

The adipose tissue is a complex organ that regulates food intake and energy expenditure as well as induces low-grade inflammation. This review deals with changes in the composition and activity of the adipose organ after bariatric surgery, focusing on epicardial and ectopic fat and on relationships between white and brown adipose tissues. Postoperative improvements of ectopic fat and epicardial fat size and composition account for the metabolic recovery and the decreased cardiovascular risk. Following Roux-en-Y gastric bypass or biliopancreatic diversion, a proportional increase in the size and activity of the metabolically active brown adipose tissue was observed, most likely related to the postoperative rearrangement of the entero-hormonal pattern with an increase of GLP-1 production: this aspect would promote the postoperative weight loss and maintenance of post-surgery benefits.

Transgenic mice expressing human IL-32 develop adipokine profiles resembling those of obesity-induced metabolic changes

Low-grade inflammation is associated with the development of insulin resistance in obese individuals. The present study aims to provide additional evidence strengthening the role of interleukin (IL)-32 in this key process. Using an IL-32 transgenic (IL-32tg) mouse model, we observed that IL-32tg fed a normal diet had greater body weight, due to greater accumulation of white adipose tissue (WAT) along with larger sized adipocytes. This led to metabolic consequences, with significant higher leptin levels and a trend towards hyperinsulinemia, indicating a phenotype resembling the metabolic syndrome. Adipocytes of IL-32tg mice were more prone to induce a pro-inflammatory response locally, which would be expected when predisposed to insulin resistance and type2 diabetes mellitus (T2D). In conclusion, our study provides novel evidence of a direct contribution of IL-32 to pathophysiological perturbations within the adipose tissue, possibly contributing to the metabolic syndrome that precedes frank insulin resistance and T2D. Future research should focus on the role of IL-32 in the obesity epidemic.

Diagnosis of obesity and use of obesity biomarkers in science and clinical medicine

The global epidemic of obesity is a major public health problem today. Obesity increases the risk of many chronic diseases, such as type 2 diabetes, coronary heart disease, and certain types of cancer, and is associated with lower life expectancy. The body mass index (BMI), which is currently used to classify obesity, is only an imperfect measure of abnormal or excessive body fat accumulation. Studies have shown that waist circumference as a measure of fat distribution may improve disease prediction. More elaborate techniques such as magnetic resonance imaging are increasingly available to assess body fat distribution, but these measures are not readily available in routine clinical practice, and health-relevant cut-offs not yet been established. The measurement of biomarkers that reflect the underlying biological mechanisms for the increased disease risk may be an alternative approach to characterize the relevant obesity phenotype. The insulin/insulin-like growth factor (IGF) axis and chronic low-grade inflammation have been identified as major pathways. In addition, specific adipokines such as leptin, adiponectin and resistin have been related to obesity-associated health outcomes. This biomarker research, which is currently further developed with the application of high throughput methods, gives important insights in obesity-related disease etiology and pathophysiological pathways and may be used to better characterize obese persons at high risk of disease development and target disease-causing biomarkers in personalized prevention strategies.

The Role of Leptin and Adiponectin in Obesity-Associated Cognitive Decline and Alzheimer's Disease

Cross-talk between adipose tissue and central nervous system (CNS) underlies the increased risk of obese people to develop brain diseases such as cognitive and mood disorders. Detailed mechanisms for how peripheral changes caused by adipose tissue accumulation in obesity impact the CNS to cause brain dysfunction are poorly understood. Adipokines are a large group of substances secreted by the white adipose tissue to regulate a wide range of homeostatic processes including, but not limited to, energy metabolism and immunity. Obesity is characterized by a generalized change in the levels of circulating adipokines due to abnormal accumulation and dysfunction of adipose tissue. Altered adipokine levels underlie complications of obesity as well as the increased risk for the development of obesity-related comorbidities such as type 2 diabetes, cardiovascular and neurodegenerative diseases. Here, we review the literature for the role of adipokines as key mediators of the communication between periphery and CNS in health and disease. We will focus on the actions of leptin and adiponectin, two of the most abundant and well studied adipokines, in the brain, with particular emphasis on how altered signaling of these adipokines in obesity may lead to cognitive dysfunction and augmented risk for Alzheimer's disease. A better understanding of adipokine biology in brain disorders may prove of major relevance to diagnostic, prevention and therapy.

Postnatal overnutrition alters the orexigenic effects of melanin-concentrating hormone (MCH) and reduces MCHR1 hypothalamic expression on spontaneous feeding and fasting

One of the approaches to induce obesity in rodents consists in reducing litter size to 3 pups during the lactation period. Animals submitted to this manipulation are heavier, hyperphagic and develop several metabolic diseases for the rest of their lives. In the present study, under the premise that melanin-concentrating hormone (MCH), an orexigenic peptide synthesized by neurons of the lateral hypothalamus, is involved in food intake regulation, we aimed to measure the hypothalamic expression of its receptor, MCHR1, in adult early overfed obese animals and normoweight controls at both ad libitum and food deprived conditions. Additionally, we administered MCH, or an antiMCH antibody, into the third ventricle of ad libitum-fed rats, or fasted rats, respectively, and evaluated chow consumption. Typical nocturnal hyperphagia in rodents was elevated in obese animals compared to normoweight controls, accompanied by a lower expression of MCHR1 and leptin receptor (Ob-R). Following a 24 h fasting, MCHR1 remained lower in SL rats. After 4 h of re-feeding, obese animals ate more than normoweight controls. MCH failed to enhance appetite in early overfed obese animals and immunoneutralization of the peptide only reduced fasted induced-hyperphagia in normoweight controls. These results support the notion that both peptide and brain endogenous MCH exert a physiological relevant action in food intake regulation in normoweight rats, but that postnatal overnutrition disturbs this system, as reflected by MCHR1 downregulation at both ad libitum and fasted conditions and in the lack of response to MCH in both positive- and negative-energetic states in early overfed obese animals.