Regulation of fatty acid homeostasis in cells: novel role of leptin

Research advances in understanding crosstalk between organs and pancreatic β-cell dysfunction

Obesity has increased dramatically worldwide. Being overweight or obese can lead to various conditions, including dyslipidaemia, hypertension, glucose intolerance and metabolic syndrome (MetS), which may further lead to type 2 diabetes mellitus (T2DM). Previous studies have identified a link between β-cell dysfunction and the severity of MetS, with multiple organs and tissues affected. Identifying the associations between pancreatic β-cell dysfunction and organs is critical. Research has focused on the interaction between the liver, gut and pancreatic β-cells. However, the mechanisms and related core targets are still not perfectly elucidated. The aims of this review were to summarize the mechanisms of β-cell dysfunction and to explore the potential pathogenic pathways and targets that connect the liver, gut, adipose tissue, muscle, and brain to pancreatic β-cell dysfunction.

LEP inhibits intramuscular adipogenesis through the AMPK signaling pathway in vitro

Leptin can indirectly regulate fatty-acid metabolism and synthesis in muscle in vivo and directly in incubated muscle ex vivo. In addition, non-synonymous mutations in the bovine leptin gene (LEP) are associated with carcass intramuscular fat (IMF) content. However, the effects of LEP on lipid synthesis of adipocytes have not been clearly studied at the cellular level. Therefore, this study focused on bovine primary intramuscular preadipocytes to investigate the effects of LEP on the proliferation and differentiation of intramuscular preadipocytes, as well as its regulatory mechanism in lipid synthesis. The results showed that both the LEP and leptin receptor gene (LEPR) were highly expressed in IMF tissues, and their mRNA expression levels were positively correlated at different developmental stages of intramuscular preadipocytes. The overexpression of LEP inhibited the proliferation and differentiation of intramuscular preadipocytes, while interference with LEP had the opposite effect. Additionally, LEP significantly promoted the phosphorylation level of AMPKα by promoting the protein expression of CAMKK2. Meanwhile, rescue experiments showed that the increasing effect of AMPK inhibitors on the number of intramuscular preadipocytes was significantly weakened by the overexpression of LEP. Furthermore, the overexpression of LEP could weaken the promoting effect of AMPK inhibitor on triglyceride content and droplet accumulation, and prevent the upregulation of adipogenic protein expression (SREBF1, FABP4, FASN, and ACCα) caused by AMPK inhibitor. Taken together, LEP acted on the AMPK signaling pathway by regulating the protein expression of CAMKK2, thereby downregulating the expression of proliferation-related and adipogenic-related genes and proteins, ultimately reducing intramuscular adipogenesis.

Sex-specific resilience of neocortex to food restriction

Mammals have evolved sex-specific adaptations to reduce energy usage in times of food scarcity. These adaptations are well described for peripheral tissue, though much less is known about how the energy-expensive brain adapts to food restriction, and how such adaptations differ across the sexes. Here, we examined how food restriction impacts energy usage and function in the primary visual cortex (V1) of adult male and female mice. Molecular analysis and RNA sequencing in V1 revealed that in males, but not in females, food restriction significantly modulated canonical, energy-regulating pathways, including pathways associated waith AMP-activated protein kinase, peroxisome proliferator-activated receptor alpha, mammalian target of rapamycin, and oxidative phosphorylation. Moreover, we found that in contrast to males, food restriction in females did not significantly affect V1 ATP usage or visual coding precision (assessed by orientation selectivity). Decreased serum leptin is known to be necessary for triggering energy-saving changes in V1 during food restriction. Consistent with this, we found significantly decreased serum leptin in food-restricted males but no significant change in food-restricted females. Collectively, our findings demonstrate that cortical function and energy usage in female mice are more resilient to food restriction than in males. The neocortex, therefore, contributes to sex-specific, energy-saving adaptations in response to food restriction.

Leptin's Inverse Association With Brain Morphology and Depressive Symptoms: A Discovery and Confirmatory Study Across 2 Independent Samples

BACKGROUND

Major depressive disorder has a complex, bidirectional relationship with metabolic dysfunction, but the neural correlates of this association are not well understood.

METHODS

In this cross-sectional investigation, we used a 2-step discovery and confirmatory strategy utilizing 2 independent samples (sample 1: 288 participants, sample 2: 196 participants) to examine the association between circulating indicators of metabolic health (leptin and adiponectin) and brain structures in individuals with major depressive disorder.

RESULTS

We found a replicable inverse correlation between leptin levels and cortical surface area within essential brain areas responsible for emotion regulation, such as the left posterior cingulate cortex, right pars orbitalis, right superior temporal gyrus, and right insula (standardized beta coefficient range: -0.27 to -0.49, puncorrected < .05). Notably, this relationship was independent of C-reactive protein levels. We also identified a significant interaction effect of leptin levels and diagnosis on the cortical surface area of the right superior temporal gyrus (standardized beta coefficient = 0.26 in sample 1, standardized beta coefficient = 0.30 in sample 2, puncorrected < .05). We also observed a positive correlation between leptin levels and atypical depressive symptoms in both major depressive disorder groups (r = 0.14 in sample 1, r = 0.29 in sample 2, puncorrected < .05).

CONCLUSIONS

The inverse association between leptin and cortical surface area in brain regions that are important for emotion processing and leptin's association with atypical depressive symptoms support the hypothesis that metabolic processes may be related to emotion regulation. However, the molecular mechanisms through which leptin may exert these effects should be explored further.

Correlation of Leptin in Patients With Type 2 Diabetes Mellitus

The exponential increase in diabetes mellitus (DM) poses serious public health concerns. In this review, we focus on the role of leptin in type 2 DM. The peripheral actions of leptin consist of upregulating proinflammatory cytokines which play an important role in the pathogenesis of type 2 DM and insulin resistance. Moreover, leptin is known to inhibit insulin secretion and plays a significant role in insulin resistance in obesity and type 2 DM. A literature search was conducted on Medline, Cochrane, Embase, and Google Scholar for relevant articles published until December 2023. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "Leptin," "NPY," and "Biomarker." This article aims to discuss the physiology of leptin in type 2 DM, its glucoregulatory actions, its relationship with appetite, the impact that various lifestyle modifications can have on leptin levels, and, finally, explore leptin as a potential target for various treatment strategies.

High-throughput Second-generation Sequencing Technology Assisted Diagnosis of Familial Partial Lipodystrophy (Type 2 Kobberling-Dunnigan Syndrome): A Case Report

BACKGROUND

Whole exome sequencing (WES) provides support for clinical diagnosis and treatment of genetically related diseases based on specific probe capture and high-throughput second-generation sequencing technology. Familial partial lipodystrophy 2 (FPLD2; OMIM # 151660) or type 2 Köbberling-Dunnigan syndrome with insulin resistance syndrome is uncommon in mainland China and elsewhere.

AIMS

We report the case in order to have a further understanding of FPLD2 or type 2 Kobberling- Dunnigan syndrome) with the assistance of WES and improve the clinical and genetic understanding and diagnosis of this disease.

CASE REPORT

A 30-year-old woman was admitted to the cadre department of our hospital at 14:00 on July 11, 2021, because of hyperglycemia, a rapid heart rate, and excessive sweating during pregnancy. An oral glucose tolerance test (OGTT) showed that insulin and C-peptide increased slowly after glucose stimulation, and the peak value was extended backward (Table 1). It was suggested that the patient had developed insulin antibodies, resulting in insulin resistance. Her clinical features and familial inheritance were consistent with FPLD2 (type 2 Kobberling-Dunnigan syndrome). The results of WES indicated that a heterozygous mutation occurred in exon 8 of the LMNA gene, because the base C at position 1444 was mutated into T during transcription. This mutation changed the amino acid position 482 of the encoded protein from Arg to Trp. Type 2 Kobberling- Dunnigan syndrome is associated with an LMNA gene mutation. According to the patient's clinical manifestations, hypoglycemic and lipid-lowering therapy is recommended.

CONCLUSION

WES can assist in the simultaneous clinical investigation or confirmation of FPLD2 and help identify diseases with similar clinical phenotypes. This case demonstrates that familial partial lipodystrophy is associated with an LMNA gene mutation on chromosome 1q21-22. This is one of the few cases of familial partial lipodystrophy diagnosed by WES.

Metabolism configures immune response across multi-systems: Lessons from COVID-19

Several studies over the last decade demonstrate the recruitment of immune cells, increased inflammatory cytokines, and chemokine in patients with metabolic diseases, including heart failure, parenchymal inflammation, obesity, tuberculosis, and diabetes mellitus. Metabolic rewiring of immune cells is associated with the severity and prevalence of these diseases. The risk of developing COVID-19/SARS-CoV-2 infection increases in patients with metabolic dysfunction (heart failure, diabetes mellitus, and obesity). Several etiologies, including fatigue, dyspnea, and dizziness, persist even months after COVID-19 infection, commonly known as Post-Acute Sequelae of CoV-2 (PASC) or long COVID. A chronic inflammatory state and metabolic dysfunction are the factors that contribute to long COVID. Here, this study explores the potential link between pathogenic metabolic and immune alterations across different organ systems that could underlie COVID-19 and PASC. These interactions could be utilized for targeted future therapeutic approaches.

Contribution of animal models to diabetes research: Its history, significance, and translation to humans

Diabetes mellitus is still expanding globally and is epidemic in developing countries. The combat of this plague has caused enormous economic and social burdens related to a lowered quality of life in people with diabetes. Despite recent significant improvements of life expectancy in patients with diabetes, there is still a need for efforts to elucidate the complexities and mechanisms of the disease processes to overcome this difficult disorder. To this end, the use of appropriate animal models in diabetes studies is invaluable for translation to humans and for the development of effective treatment. In this review, a variety of animal models of diabetes with spontaneous onset in particular will be introduced and discussed for their implication in diabetes research.

Dietary choline, but not L-carnitine, increases circulating lipid and lipoprotein concentrations, without affecting body composition, energy expenditure or respiratory quotient in lean and obese male cats during weight maintenance

Introduction

Due to the involvement in one-carbon metabolism and lipid mobilization, choline and L-carnitine supplementation have been recommended to minimize hepatic lipid accumulation and support fat oxidation, respectively. This study investigated the lipotropic benefits of choline or L-carnitine supplementation in lean and obese cats maintaining body weight (BW).

Methods

Lean [n = 9; body condition score (BCS): 4-5/9] and obese (n = 9; BCS: 8-9/9) adult male neutered colony cats were used in a replicated 3 x 3 complete Latin square design. Treatments included choline (378 mg/kg BW0.67), L-carnitine (200 mg/kg BW) and control (no supplement). Treatments were supplemented to the food for 6 weeks each, with a 2-week washout between treatments. Cats were fed once daily to maintenance energy requirements, and BW and BCS were assessed weekly. Fasted blood collection, indirect calorimetry, and dual-energy X-ray absorptiometry occurred at the end of each treatment period. Serum was analyzed for cholesterol (CHOL), high-density lipoprotein CHOL (HDL-C), triglycerides (TAG), non-esterified fatty acids (NEFA), glucose, creatinine (CREAT), urea, alkaline phosphatase (ALP) and alanine aminotransferase (ALT). Very low-density lipoprotein CHOL (VLDL) and low-density lipoprotein CHOL (LDL-C) were calculated. Data were analyzed using proc GLIMMIX, with group and period as random effects, and treatment, body condition, and their interaction as fixed effects, followed by a Tukey's post-hoc test when significance occurred.

Results

Cats supplemented choline had lower food intake (P = 0.025). Treatment did not change BW, BCS and body composition (P > 0.05). Obese cats had greater ALP, TAG, and VLDL, and lower HDL-C compared to lean cats (P < 0.05). Choline resulted in greater CHOL, HDL-C, LDL-C and ALT (P < 0.05). L-carnitine resulted in lower CREAT (P = 0.010). Following the post-hoc test, differences between treatment means were not present for ALP (P = 0.042). No differences were found for glucose, urea or NEFA (P > 0.05). Obese cats had a lower fed respiratory quotient (RQ), regardless of treatment (P = 0.045). Treatment did not affect fed or fasted RQ and energy expenditure (P > 0.05).

Discussion

Choline appeared to increase circulating lipid and lipoprotein concentrations regardless of body condition, likely through enhanced lipid mobilization and hepatic elimination. Neither dietary choline or L-carnitine altered body composition or energy metabolism in the lean or obese cats, as compared to control.

Is increased myocardial triglyceride content associated with early changes in left ventricular function? A 1H-MRS and MRI strain study

Background

Type 2 diabetes (T2D) and obesity induce left ventricular (LV) dysfunction. The underlying pathophysiological mechanisms remain unclear, but myocardial triglyceride content (MTGC) could be involved.

Objectives

This study aimed to determine which clinical and biological factors are associated with increased MTGC and to establish whether MTGC is associated with early changes in LV function.

Methods

A retrospective study was conducted using five previous prospective cohorts, leading to 338 subjects studied, including 208 well-phenotyped healthy volunteers and 130 subjects living with T2D and/or obesity. All the subjects underwent proton magnetic resonance spectroscopy and feature tracking cardiac magnetic resonance imaging to measure myocardial strain.

Results

MTGC content increased with age, body mass index (BMI), waist circumference, T2D, obesity, hypertension, and dyslipidemia, but the only independent correlate found in multivariate analysis was BMI (p=0.01; R²=0.20). MTGC was correlated to LV diastolic dysfunction, notably with the global peak early diastolic circumferential strain rate (r=-0.17, p=0.003), the global peak late diastolic circumferential strain rate (r=0.40, p<0.0001) and global peak late diastolic longitudinal strain rate (r=0.24, p<0.0001). MTGC was also correlated to systolic dysfunction via end-systolic volume index (r=-0.34, p<0.0001) and stroke volume index (r=-0.31, p<0.0001), but not with longitudinal strain (r=0.009, p=0.88). Interestingly, the associations between MTGC and strain measures did not persist in multivariate analysis. Furthermore, MTGC was independently associated with LV end-systolic volume index (p=0.01, R²=0.29), LV end-diastolic volume index (p=0.04, R²=0.46), and LV mass (p=0.002, R²=0.58).

Conclusions

Predicting MTGC remains a challenge in routine clinical practice, as only BMI independently correlates with increased MTGC. MTGC may play a role in LV dysfunction but does not appear to be involved in the development of subclinical strain abnormalities.

Lipid droplet biogenesis and functions in health and disease

Ubiquitous yet unique, lipid droplets are intracellular organelles that are increasingly being recognized for their versatility beyond energy storage. Advances uncovering the intricacies of their biogenesis and the diversity of their physiological and pathological roles have yielded new insights into lipid droplet biology. Despite these insights, the mechanisms governing the biogenesis and functions of lipid droplets remain incompletely understood. Moreover, the causal relationship between the biogenesis and function of lipid droplets and human diseases is poorly resolved. Here, we provide an update on the current understanding of the biogenesis and functions of lipid droplets in health and disease, highlighting a key role for lipid droplet biogenesis in alleviating cellular stresses. We also discuss therapeutic strategies of targeting lipid droplet biogenesis, growth or degradation that could be applied in the future to common diseases, such as cancer, hepatic steatosis and viral infection.

Maternal elevated inflammation impairs placental fatty acids β-oxidation in women with gestational diabetes mellitus

Introduction

An adverse proinflammatory milieu contributes to abnormal cellular energy metabolism response. Gestational diabetes mellitus (GDM) is closely related to an altered maternal inflammatory status. However, its role on lipid metabolism regulation in human placenta has not yet been assessed. The aim of this study was to examine the impact of maternal circulating inflammatory mediators ([TNF]-α, [IL]-6, and Leptin) on placental fatty acid metabolism in GDM pregnancies.

Methods

Fasting maternal blood and placental tissues were collected at term deliveries from 37 pregnant women (17 control and 20 GDM). Molecular approach techniques as radiolabeled lipid tracers, ELISAs, immunohistochemistry and multianalyte immunoassay quantitative analysis, were used to quantify serum inflammatory factors' levels, to measure lipid metabolic parameters in placental villous samples (mitochondrial fatty acid oxidation [FAO] rate and lipid content [Triglycerides]), and to analyze their possible relationships. The effect of potential candidate cytokines on fatty acid metabolism in ex vivo placental explants culture following C-section a term was also examined.

Results

Maternal serum IL-6, TNF-α and leptin levels were significantly increased in GDM patients compared with control pregnant women (9,9±4,5 vs. 3,00±1,7; 4,5±2,8 vs. 2,1±1,3; and 10026,7±5628,8 vs. 5360,2±2499,9 pg/ml, respectively). Placental FAO capacity was significantly diminished (~30%; p<0.01), whereas triglyceride levels were three-fold higher (p<0.01) in full-term GDM placentas. Uniquely the maternal IL-6 levels showed an inverse and positive correlation with the ability to oxidize fatty acids and triglyceride amount in placenta, respectively (r= -0,602, p=0.005; r= 0,707, p=0.001). Additionally, an inverse correlation between placental FAO and triglycerides was also found (r=-0.683; p=0.001). Interestingly, we ex vivo demonstrated by using placental explant cultures that a prolonged exposure with IL-6 (10 ng/mL) resulted in a decline in the fatty acid oxidation rate (~25%; p=0.001), along to acute increase (2-fold times) in triglycerides accumulation (p=0.001), and in lipid neutral and lipid droplets deposits.

Conclusions

Enhanced maternal proinflammatory cytokines levels (essentially IL-6) is closely associated with an altered placental fatty acid metabolism in pregnancies with GDM, which may interfere with adequate delivery of maternal fat across the placenta to the fetus.

The regulatory effects of second-generation antipsychotics on lipid metabolism: Potential mechanisms mediated by the gut microbiota and therapeutic implications

Second-generation antipsychotics (SGAs) are the mainstay of treatment for schizophrenia and other neuropsychiatric diseases but cause a high risk of disruption to lipid metabolism, which is an intractable therapeutic challenge worldwide. Although the exact mechanisms underlying this lipid disturbance are complex, an increasing body of evidence has suggested the involvement of the gut microbiota in SGA-induced lipid dysregulation since SGA treatment may alter the abundance and composition of the intestinal microflora. The subsequent effects involve the generation of different categories of signaling molecules by gut microbes such as endogenous cannabinoids, cholesterol, short-chain fatty acids (SCFAs), bile acids (BAs), and gut hormones that regulate lipid metabolism. On the one hand, these signaling molecules can directly activate the vagus nerve or be transported into the brain to influence appetite via the gut-brain axis. On the other hand, these molecules can also regulate related lipid metabolism via peripheral signaling pathways. Interestingly, therapeutic strategies directly targeting the gut microbiota and related metabolites seem to have promising efficacy in the treatment of SGA-induced lipid disturbances. Thus, this review provides a comprehensive understanding of how SGAs can induce disturbances in lipid metabolism by altering the gut microbiota.

Effects of Nutritionally Induced Obesity on Metabolic Pathways of Zebrafish

Human obesity has become a global epidemic that can lead to many metabolic diseases, including insulin resistance, type 2 diabetes, dyslipidemia, hypertension and nonalcoholic fatty liver. The development of obesity is closely associated with excess food intake and energy imbalance, family history, lifestyle, psychology and other factors, but molecular mechanisms underlying the induction and development of obesity remain to be intensively studied under a variety of internal and external pathogenesis conditions. In this study, we generated two obesity models of zebrafish that were treated with a high-fat diet (HFD) or an overfeeding diet (DIO). Both HFD and DIO zebrafish exhibited higher levels of lipid accumulation, fat distribution, microvascular steatosis and ectopic accumulation of lipid droplets in liver and muscle than normal diet (NOD) fish. The comparison of transcriptome sequencing data for the livers of HFD, DIO and NOD groups identified common and specific genes and signaling pathways that are potentially associated with zebrafish obesity induced by HFD and/or DIO. These findings provide clues for further understanding the mechanisms of obesity development and preventing nutritionally induced obesity through targeting the common signaling pathways and biological processes.

Specific triacylglycerol, diacylglycerol, and lyso-phosphatidylcholine species for the prediction of type 2 diabetes: a ~ 16-year prospective study in Chinese

Background

Bioactive lipids play an important role in insulin secretion and sensitivity, contributing to the pathophysiology of type 2 diabetes (T2D). This study aimed to identify novel lipid species associated with incident T2D in a nested case–control study within a long-term prospective Chinese community-based cohort with a median follow-up of ~ 16 years.

Methods

Plasma samples from 196 incident T2D cases and 196 age- and sex-matched non-T2D controls recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS) were first analyzed using untargeted lipidomics. Potential predictive lipid species selected by the Boruta analysis were then verified by targeted lipidomics. The associations between these lipid species and incident T2D were assessed. Effects of novel lipid species on insulin secretion in mouse islets were investigated.

Results

Boruta analysis identified 16 potential lipid species. After adjustment for body mass index (BMI), triacylglycerol/high-density lipoprotein (TG/HDL) ratio and the presence of prediabetes, triacylglycerol (TG) 12:0_18:2_22:6, TG 16:0_11:1_18:2, TG 49:0, TG 51:1 and diacylglycerol (DG) 18:2_22:6 were independently associated with increased T2D risk, whereas lyso-phosphatidylcholine (LPC) O-16:0, LPC P-16:0, LPC O-18:0 and LPC 18:1 were independently associated with decreased T2D risk. Addition of the identified lipid species to the clinical prediction model, comprised of BMI, TG/HDL ratio and the presence of prediabetes, achieved a 3.8% improvement in the area under the receiver operating characteristics curve (AUROC) (p = 0.0026). Further functional study revealed that, LPC O-16:0 and LPC O-18:0 significantly potentiated glucose induced insulin secretion (GSIS) in a dose-dependent manner, whereas neither DG 18:2_22:6 nor TG 12:0_18:2_22:6 had any effect on GSIS.

Conclusions

Addition of the lipid species substantially improved the prediction of T2D beyond the model based on clinical risk factors. Decreased levels of LPC O-16:0 and LPC O-18:0 may contribute to the development of T2D via reduced insulin secretion.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01677-4.

Effect of Lauric vs. Oleic Acid-Enriched Diets on Leptin Autoparacrine Signalling in Male Mice

High-fat diets enriched with lauric acid (SOLF) do not enhance leptin production despite expanding white adipose tissue (WAT). Our study aimed at identifying the influence of SOLF vs. oleic acid-enriched diets (UOLF) on the autoparacrine effect of leptin and was carried out on eight-week-old mice consuming control chow, UOLF or SOLF. Phosphorylation of kinases integral to leptin receptor (LepR) signalling pathways (705Tyr-STAT3, 473Ser-Akt, 172Thr-AMPK), adipocyte-size distribution, fatty acid content, and gene expression were analyzed in WAT. SOLF enhanced basal levels of phosphorylated proteins but reduced the ability of leptin to enhance kinase phosphorylation. In contrast, UOLF failed to increase basal levels of phosphorylated proteins and did not modify the effect of leptin. Both SOLF and UOLF similarly affected adipocyte-size distribution, and the expression of genes related with adipogenesis and inflammation. WAT composition was different between groups, with SOLF samples mostly containing palmitic, myristic and lauric acids (>48% w/w) and UOLF WAT containing more than 80% (w/w) of oleic acid. In conclusion, SOLF appears to be more detrimental than UOLF to the autoparacrine leptin actions, which may have an impact on WAT inflammation. The effect of SOLF and UOLF on WAT composition may affect WAT biophysical properties, which are able to condition LepR signaling.

Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes

The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.

Leptin Signaling in Obesity and Colorectal Cancer

Obesity and colorectal cancer (CRC) are among the leading diseases causing deaths in the world, showing a complex multifactorial pathology. Obesity is considered a risk factor in CRC development through inflammation, metabolic, and signaling processes. Leptin is one of the most important adipokines related to obesity and an important proinflammatory marker, mainly expressed in adipose tissue, with many genetic variation profiles, many related influencing factors, and various functions that have been ascribed but not yet fully understood and elucidated, the most important ones being related to energy metabolism, as well as endocrine and immune systems. Aberrant signaling and genetic variations of leptin are correlated with obesity and CRC, with the genetic causality showing both inherited and acquired events, in addition to lifestyle and environmental risk factors; these might also be related to specific pathogenic pathways at different time points. Moreover, mutation gain is a crucial factor enabling the genetic process of CRC. Currently, the inconsistent and insufficient data related to leptin's relationship with obesity and CRC indicate the necessity of further related studies. This review summarizes the current knowledge on leptin genetics and its potential relationship with the main pathogenic pathways of obesity and CRC, in an attempt to understand the molecular mechanisms of these associations, in the context of inconsistent and contradictory data. The understanding of these mechanisms linking obesity and CRC could help to develop novel therapeutic targets and prevention strategies, resulting in a better prognosis and management of these diseases.

Leptin Receptor Deficiency Results in Hyperphagia and Increased Fatty Acid Mobilization during Fasting in Rainbow Trout (Oncorhynchus mykiss)

Leptin is a pleiotropic hormone known for regulating appetite and metabolism. To characterize the role of leptin signaling in rainbow trout, we used CRISPR/Cas9 genome editing to disrupt the leptin receptor (LepR) genes, lepra1 and lepra2. We compared wildtype (WT) and mutant fish that were either fed to satiation or feed deprived for six weeks. The LepR mutants exhibited a hyperphagic phenotype, which led to heavier body weight, faster specific growth rate, increased viscero- and hepatosomatic indices, and greater condition factor. Muscle glycogen, plasma leptin, and leptin transcripts (lepa1) were also elevated in fed LepR mutant fish. Expression levels of several hypothalamic genes involved in feed regulation were analyzed (agrp, npy, orexin, cart-1, cart-2, pomc-a1, pomc-b). No differences were detected between fed WT and mutants except for pomc-b (proopiomelanocortin-b), where levels were 7.5-fold higher in LepR fed mutants, suggesting that pomc-b expression is regulated by leptin signaling. Fatty acid (FA) content did not statistically differ in muscle of fed mutant fish compared to WT. However, fasted mutants exhibited significantly lower muscle FA concentrations, suggesting that LepR mutants exhibit increased FA mobilization during fasting. These data demonstrate a key role for leptin signaling in lipid and energy mobilization in a teleost fish.

Lipid Droplets' Role in the Regulation of β-Cell Function and β-Cell Demise in Type 2 Diabetes

During development of type 2 diabetes (T2D), excessive nutritional load is thought to expose pancreatic islets to toxic effects of lipids and reduce β-cell function and mass. However, lipids also play a positive role in cellular metabolism and function. Thus, proper trafficking of lipids is critical for β cells to maximize the beneficial effects of these molecules while preventing their toxic effects. Lipid droplets (LDs) are organelles that play an important role in the storage and trafficking of lipids. In this review, we summarize the discovery of LDs in pancreatic β cells, LD lifecycle, and the effect of LD catabolism on β-cell insulin secretion. We discuss factors affecting LD formation such as age, cell type, species, and nutrient availability. We then outline published studies targeting critical LD regulators, primarily in rat and human β-cell models, to understand the molecular effect of LD formation and degradation on β-cell function and health. Furthermore, based on the abnormal LD accumulation observed in human T2D islets, we discuss the possible role of LDs during the development of β-cell failure in T2D. Current knowledge indicates that proper formation and clearance of LDs are critical to normal insulin secretion, endoplasmic reticulum homeostasis, and mitochondrial integrity in β cells. However, it remains unclear whether LDs positively or negatively affect human β-cell demise in T2D. Thus, we discuss possible research directions to address the knowledge gap regarding the role of LDs in β-cell failure.

Pregnancy Is Enough to Provoke Deleterious Effects in Descendants of Fructose-Fed Mothers and Their Fetuses

The role of fructose in the global obesity and metabolic syndrome epidemic is widely recognized. However, its consumption is allowed during pregnancy. We have previously demonstrated that maternal fructose intake in rats induces detrimental effects in fetuses. However, these effects only appeared in adult descendants after a re-exposure to fructose. Pregnancy is a physiological state that leads to profound changes in metabolism and hormone response. Therefore, we wanted to establish if pregnancy in the progeny of fructose-fed mothers was also able to provoke an unhealthy situation. Pregnant rats from fructose-fed mothers (10% w/v) subjected (FF) or not (FC) to a fructose supplementation were studied and compared to pregnant control rats (CC). An OGTT was performed on the 20th day of gestation, and they were sacrificed on the 21st day. Plasma and tissues from mothers and fetuses were analyzed. Although FF mothers showed higher AUC insulin values after OGTT in comparison to FC and CC rats, ISI was lower and leptinemia was higher in FC and FF rats than in the CC group. Accordingly, lipid accretion was observed both in liver and placenta in the FC and FF groups. Interestingly, fetuses from FC and FF mothers also showed the same profile observed in their mothers on lipid accumulation, leptinemia, and ISI. Moreover, hepatic lipid peroxidation was even more augmented in fetuses from FC dams than those of FF mothers. Maternal fructose intake produces in female progeny changes that alter their own pregnancy, leading to deleterious effects in their fetuses.

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.

Pathophysiology of NAFLD and NASH in Experimental Models: The Role of Food Intake Regulating Peptides

Obesity, diabetes, insulin resistance, sedentary lifestyle, and Western diet are the key factors underlying non-alcoholic fatty liver disease (NAFLD), one of the most common liver diseases in developed countries. In many cases, NAFLD further progresses to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and to hepatocellular carcinoma. The hepatic lipotoxicity and non-liver factors, such as adipose tissue inflammation and gastrointestinal imbalances were linked to evolution of NAFLD. Nowadays, the degree of adipose tissue inflammation was shown to directly correlate with the severity of NAFLD. Consumption of higher caloric intake is increasingly emerging as a fuel of metabolic inflammation not only in obesity-related disorders but also NAFLD. However, multiple causes of NAFLD are the reason why the mechanisms of NAFLD progression to NASH are still not well understood. In this review, we explore the role of food intake regulating peptides in NAFLD and NASH mouse models. Leptin, an anorexigenic peptide, is involved in hepatic metabolism, and has an effect on NAFLD experimental models. Glucagon-like peptide-1 (GLP-1), another anorexigenic peptide, and GLP-1 receptor agonists (GLP-1R), represent potential therapeutic agents to prevent NAFLD progression to NASH. On the other hand, the deletion of ghrelin, an orexigenic peptide, prevents age-associated hepatic steatosis in mice. Because of the increasing incidence of NAFLD and NASH worldwide, the selection of appropriate animal models is important to clarify aspects of pathogenesis and progression in this field.

Hospitalizations and emergency department visits in heart failure patients after bariatric surgery

BACKGROUND

Heart failure is a disease with significant healthcare utilization and a prioritized target for readmission prevention. Although obesity is related to heart failure morbidity, the effects of bariatric surgery in obese patients with heart failure are not well studied.

OBJECTIVES

To evaluate the impact of bariatric surgery on hospital-based healthcare utilization for patients with heart failure.

SETTING

Administrative statewide database.

METHODS

The New York Statewide Planning and Research Cooperative System database was used to identify patients with obesity and heart failure who underwent bariatric surgery from 2005 to 2015. Emergency department (ED) visits and hospitalization records from 1 year presurgery and up to 2 years postsurgery were compared.

RESULTS

Our study identified 899 patients with heart failure who underwent bariatric surgery. In the year presurgery, 11.48% of patients had any ED visit or hospitalization with a primary diagnosis of heart failure. The rate decreased drastically in the first year after surgery, with only 3.70% of patients having any heart failure-related hospital visits. The rate of heart failure-related visits was also lower in the second year postsurgery (3.44%) compared with the year before surgery. The risk of heart failure-related hospital visits was lower in both the first year (odds ratio [OR], .29; 95% confidence interval [CI], .19-.43) and second year postsurgery (OR, .26; 95% CI, .17-.41; P < .0001) than in the year before surgery.

CONCLUSIONS

These findings suggest that bariatric interventions might be associated with decreased risks of ED visits or hospitalizations due to heart failure exacerbations in obese patients with preexisting heart failure.

A Variant of Leptin Gene Decreases the Risk of Gastric Cancer in Chinese Individuals: Evidence from a Case-Control Study

Background

A host of studies have explored the potential connection between leptin (LEP) G19A polymorphism and the risk of cancers, but the relationship between gastric cancer (GC) susceptibility and LEP G19A polymorphism was not revealed before. The aim of this study was to investigate this relationship in Chinese Han population.

Methods

Thus, this case–control study with 380 GC cases and 465 controls was designed to unearth the link between LEP G19A polymorphism and GC susceptibility. Genotyping was accomplished by a custom-made 48-Plex SNP scanTM kit. Relative LEP gene expression was detected by real-time reverse transcription-polymerase chain reaction.

Results

LEP G19A polymorphism was shown to relate with a decreased risk of GC. Subgroup analyses uncovered significant connections in the males, nondrinkers, and those at age <60 years. G19A polymorphism was also linked with tumor size and location and pathological type of GC. Last, LEP gene expression in gastric tissues was considerably less than in control tissues.

Conclusion

This study shows that G19A polymorphism of LEP gene is linked with a lower risk of GC in the tested Chinese Han individuals.

Oxidative Stress, Nutrition and Cancer: Friends or Foes?

The relationship between cancer and nutrition, as well as nutrition and oxidative stress, shares puzzling aspects that current research is investigating as the possible components of an intriguing regulating mechanism involving the complex interplay between adipose tissue and other compartments. Along the very recent biological evolution, humans underwent a rapid change in their lifestyles and henceforth the role of the adipocytes earned a much more complex task in the fine tuning of the tissue microenvironment. A lipidic signaling language probably evolved in association with the signaling role of reactive oxygen species, which gained a fundamental part in the regulation of cell stem and plasticity. The possible relationship with cancer onset might have some causative mechanism in the impairment of this complex task, usually deregulated by drastic changes in one's own lifestyle and dietary habit. This review tries to address this issue.

Cytokines and Abnormal Glucose and Lipid Metabolism

Clear evidence indicates that cytokines, for instance, adipokines, hepatokines, inflammatory cytokines, myokines, and osteokines, contribute substantially to the development of abnormal glucose and lipid metabolism. Some cytokines play a positive role in metabolism action, while others have a negative metabolic role linking to the induction of metabolic dysfunction. The mechanisms involved are not fully understood, but are associated with lipid accumulation in organs and tissues, especially in the adipose and liver tissue, changes in energy metabolism, and inflammatory signals derived from various cell types, including immune cells. In this review, we describe the roles of certain cytokines in the regulation of metabolism and inter-organ signaling in regard to the pathophysiological aspects. Given the disease-related changes in circulating levels of relevant cytokines, these factors may serve as biomarkers for the early detection of metabolic disorders. Moreover, based on preclinical studies, certain cytokines that can induce improvements in glucose and lipid metabolism and immune response may emerge as novel targets of broader and more efficacious treatments and prevention of metabolic disease.

Tripartite cell networks for glucose homeostasis

Controlling the excess and shortage of energy is a fundamental task for living organisms. Diabetes is a representative metabolic disease caused by the malfunction of energy homeostasis. The islets of Langerhans in the pancreas release long-range messengers, hormones, into the blood to regulate the homeostasis of the primary energy fuel, glucose. The hormone and glucose levels in the blood show rhythmic oscillations with a characteristic period of 5-10 min, and the functional roles of the oscillations are not clear. Each islet has [Formula: see text] and [Formula: see text] cells that secrete glucagon and insulin, respectively. These two counter-regulatory hormones appear sufficient to increase and decrease glucose levels. However, pancreatic islets have a third cell type, [Formula: see text] cells, which secrete somatostatin. The three cell populations have a unique spatial organization in islets, and they interact to perturb their hormone secretions. The mini-organs of islets are scattered throughout the exocrine pancreas. Considering that the human pancreas contains approximately a million islets, the coordination of hormone secretion from the multiple sources of islets and cells within the islets should have a significant effect on human physiology. In this review, we introduce the hierarchical organization of tripartite cell networks, and recent biophysical modeling to systematically understand the oscillations and interactions of [Formula: see text], [Formula: see text], and [Formula: see text] cells. Furthermore, we discuss the functional roles and clinical implications of hormonal oscillations and their phase coordination for the diagnosis of type II diabetes.

The leptin receptor mutation of the obese Zucker rat causes sciatic nerve demyelination with a centripetal pattern defect

Young male Zucker rats with a leptin receptor mutation are obese, have a non-insulin-dependent diabetes mellitus (NIDDM), and other endocrinopathies. Tibial branches of the sciatic nerve reveal a progressive demyelination that progresses out of the Schwann cells (SCs) where electron-contrast deposits are accumulated while the minor lines or intermembranous SC contacts display exaggerated spacings. Cajal bands contain diversely contrasted vesicles adjacent to the abaxonal myelin layer with blemishes; they appear dispatched centripetally out of many narrow electron densities, regularly spaced around the myelin annulus. These anomalies widen and yield into sectors across the stacked myelin layers. Throughout the worse degradations, the adaxonal membrane remains along the axonal neuroplasm. This peripheral neuropathy with irresponsive leptin cannot modulate hypothalamic-pituitary-adrenal axis and SC neurosteroids, thus exacerbates NIDDM condition. Additionally, the ultrastructure of the progressive myelin alterations may have unraveled a peculiar, centripetal mode of trafficking maintenance of the peripheral nervous system myelin, while some adhesive glycoproteins remain between myelin layers, somewhat hindering the axon mutilation. Heading title: Peripheral neuropathy and myelin.

Genetic Variation in Acid Ceramidase Predicts Non-completion of an Exercise Intervention

Genetic variation is associated with a number of lifestyle behaviours; it may be associated with adherence and individual responses to exercise training. We tested single nucleotide polymorphisms (SNPs) in the acid ceramidase gene (ASAH1) for association with subject adherence and physiologic benefit with exercise training in two well-characterised randomised, controlled 8-month exercise interventions: STRRIDE I (n = 239) and STRRIDE II (n = 246). Three ASAH1 non-coding SNPs in a linkage disequilibrium block were associated with non-completion: rs2898458(G/T), rs7508(A/G), and rs3810(A/G) were associated with non-completion in both additive (OR = 1.8, 1.8, 2.0; P < 0.05 all) and dominant (OR = 2.5, 2.6, 3.5; P < 0.05 all) models; with less skeletal muscle ASAH expression (p < 0.01) in a subset (N = 60); and poorer training response in cardiorespiratory fitness (peak VO₂ change rs3810 r² = 0.29, P = 0.04; rs2898458 r² = 0.29, P = 0.08; rs7508 r² = 0.28, p = 0.09); and similar in direction and magnitude in both independent exploratory and replication studies. Adherence to exercise may be partly biologically and genetically moderated through metabolic regulatory pathways participating in skeletal muscle adaptation to exercise training.

Brain Glucose-Sensing Mechanism and Energy Homeostasis

The metabolic and energy state of the organism depends largely on the availability of substrates, such as glucose for ATP production, necessary for maintaining physiological functions. Deregulation in glucose levels leads to the appearance of pathological signs that result in failures in the cardiovascular system and various diseases, such as diabetes, obesity, nephropathy, and neuropathy. Particularly, the brain relies on glucose as fuel for the normal development of neuronal activity. Regions adjacent to the cerebral ventricles, such as the hypothalamus and brainstem, exercise central control in energy homeostasis. These centers house nuclei of neurons whose excitatory activity is sensitive to changes in glucose levels. Determining the different detection mechanisms, the phenotype of neurosecretion, and neural connections involving glucose-sensitive neurons is essential to understanding the response to hypoglycemia through modulation of food intake, thermogenesis, and activation of sympathetic and parasympathetic branches, inducing glucagon and epinephrine secretion and other hypothalamic-pituitary axis-dependent counterregulatory hormones, such as glucocorticoids and growth hormone. The aim of this review focuses on integrating the current understanding of various glucose-sensing mechanisms described in the brain, thereby establishing a relationship between neuroanatomy and control of physiological processes involved in both metabolic and energy balance. This will advance the understanding of increasingly prevalent diseases in the modern world, especially diabetes, and emphasize patterns that regulate and stimulate intake, thermogenesis, and the overall synergistic effect of the neuroendocrine system.

Pioglitazone Attenuates Palmitate-Induced Inflammation and Endoplasmic Reticulum Stress in Pancreatic β-Cells

BACKGROUND

The nuclear receptor peroxisome proliferator-activator gamma (PPARγ) is a useful therapeutic target for obesity and diabetes, but its role in protecting β-cell function and viability is unclear.

METHODS

To identify the potential functions of PPARγ in β-cells, we treated mouse insulinoma 6 (MIN6) cells with the PPARγ agonist pioglitazone in conditions of lipotoxicity, endoplasmic reticulum (ER) stress, and inflammation.

RESULTS

Palmitate-treated cells incubated with pioglitazone exhibited significant improvements in glucose-stimulated insulin secretion and the repression of apoptosis, as shown by decreased caspase-3 cleavage and poly (adenosine diphosphate [ADP]-ribose) polymerase activity. Pioglitazone also reversed the palmitate-induced expression of inflammatory cytokines (tumor necrosis factor α, interleukin 6 [IL-6], and IL-1β) and ER stress markers (phosphor-eukaryotic translation initiation factor 2α, glucose-regulated protein 78 [GRP78], cleaved-activating transcription factor 6 [ATF6], and C/EBP homologous protein [CHOP]), and pioglitazone significantly attenuated inflammation and ER stress in lipopolysaccharide- or tunicamycin-treated MIN6 cells. The protective effect of pioglitazone was also tested in pancreatic islets from high-fat-fed KK-Ay mice administered 0.02% (wt/wt) pioglitazone or vehicle for 6 weeks. Pioglitazone remarkably reduced the expression of ATF6α, GRP78, and monocyte chemoattractant protein-1, prevented α-cell infiltration into the pancreatic islets, and upregulated glucose transporter 2 (Glut2) expression in β-cells. Moreover, the preservation of β-cells by pioglitazone was accompanied by a significant reduction of blood glucose levels.

CONCLUSION

Altogether, these results support the proposal that PPARγ agonists not only suppress insulin resistance, but also prevent β-cell impairment via protection against ER stress and inflammation. The activation of PPARγ might be a new therapeutic approach for improving β-cell survival and insulin secretion in patients with diabetes mellitus.

Investigation of TCF7L2, LEP and LEPR polymorphisms with esophageal squamous cell carcinomas

Single nucleotide polymorphisms (SNPs) in energy metabolism related gene may be key agents in the development of human malignancies. In this study, we aimed to examine the association of transcription factor 7-like 2, Leptin (LEP) and LEP receptor (LEPR) polymorphisms with esophageal squamous cell carcinoma (ESCC). A total of 507 ESCC cases and 1,496 controls were enrolled. We found that LEPR rs6588147 AA genotype was associated with ESCC risk (AA vs. GG/GA: adjusted OR=1.90, 95%CI=1.00-3.61, P=0.049). In the stratified analyses, LEPR rs6588147 G>A polymorphism increased the risk of ESCC (<63 years subgroup: AA vs. GG: adjusted OR=2.58, 95%CI=1.00-6.62, P=0.049 and AA vs. GA/GG: adjusted OR=2.71, 95%CI=1.06-6.91, P=0.038; male subgroup: AA vs. GG: adjusted OR=2.19, 95%CI=1.02-4.67, P=0.044 and AA vs. GA/GG: adjusted OR=2.26, 95%CI=1.06-4.80, P=0.035). However, LEP rs7799039 A>G decreased the risk of ESCC (≥63 years subgroup: GG vs. AA: adjusted OR=0.47, 95%CI=0.23-0.95, P=0.035 and GG vs. AA/AG: adjusted OR=0.48, 95%CI=0.24-0.96, P=0.038; BMI≥24 kg/m² subgroup: AG vs. AA: adjusted OR=0.66, 95%CI=0.45-0.99, P=0.044). In addition, LEPR rs1137101 G>A polymorphism decreased ESCC risk in some subgroups (ever smoking subgroup: GA vs. GG: adjusted OR=0.66, 95%CI=0.44-1.00, P=0.049; ever drinking subgroup: GA vs. GG: adjusted OR=0.54, 95%CI=0.31-0.95, P=0.031 and GA/AA vs. GG: adjusted OR=0.54, 95%CI=0.31-0.93, P=0.027). Our findings suggest that LEPR rs6588147 G>A polymorphism is associated with the increased risk of ESCC; however, LEP rs7799039 A>G and LEPR rs1137101 G>A polymorphisms may be protective factors for ESCC.

Sclerostin does not play a major role in the pathogenesis of skeletal complications in type 2 diabetes mellitus

In contrast to previously reported elevations in serum sclerostin levels in diabetic patients, the present study shows that the impaired bone microarchitecture and cellular turnover associated with type 2 diabetes mellitus (T2DM)-like conditions in ZDF rats are not correlated with changes in serum and bone sclerostin expression.

INTRODUCTION

T2DM is associated with impaired skeletal structure and a higher prevalence of bone fractures. Sclerostin, a negative regulator of bone formation, is elevated in serum of diabetic patients. We aimed to relate changes in bone architecture and cellular activities to sclerostin production in the Zucker diabetic fatty (ZDF) rat.

METHODS

Bone density and architecture were measured by micro-CT and bone remodelling by histomorphometry in tibiae and femurs of 14-week-old male ZDF rats and lean Zucker controls (n = 6/group).

RESULTS

ZDF rats showed lower trabecular bone mineral density and bone mass compared to controls, due to decreases in bone volume and thickness, along with impaired bone connectivity and cortical bone geometry. Bone remodelling was impaired in diabetic rats, demonstrated by decreased bone formation rate and increased percentage of tartrate-resistant acid phosphatase-positive osteoclastic surfaces. Serum sclerostin levels (ELISA) were higher in ZDF compared to lean rats at 9 weeks (+40 %, p < 0.01), but this difference disappeared as their glucose control deteriorated and by week 14, ZDF rats had lower sclerostin levels than control rats (-44 %, p < 0.0001). Bone sclerostin mRNA (qPCR) and protein (immunohistochemistry) were similar in ZDF, and lean rats at 14 weeks and genotype did not affect the number of empty osteocytic lacunae in cortical and trabecular bone.

CONCLUSION

T2DM results in impaired skeletal architecture through altered remodelling pathways, but despite altered serum levels, it does not appear that sclerostin contributes to the deleterious effect of T2DM in rat bone.

Triglycerides Revisited to the Serial

This review discusses the role of triglycerides (TGs) in the normal cardiovascular system as well as in the development and clinical manifestation of cardiovascular diseases. Regulation of TGs at the enzymatic and genetic level, in addition to their possible relevance as preclinical and clinical biomarkers, is discussed, culminating with a description of available and emerging treatments. Due to the high complexity of the subject and the vast amount of material in the literature, the objective of this review was not to exhaust the subject, but rather to compile the information to facilitate and improve the understanding of those interested in this topic. The main publications on the topic were sought out, especially those from the last 5 years. The data in the literature still give reason to believe that there is room for doubt regarding the use of TG as disease biomarkers; however, there is increasing evidence for the role of hypertriglyceridemia on the atherosclerotic inflammatory process, cardiovascular outcomes, and mortality.

Diabetes (db/db) Mutation-Induced Ovarian Involution: Progressive Hypercytolipidemia

Ovarian atrophy and reproductive tract incompetence are recognized consequences of the progressive expression of the overt, diabetes-obesity syndrome (DOS) in C57BL/KsJ (db/db) mutant mice. The present studies evaluated the progressive changes in ovarian cytoarchitecture, endocrine expression, and reproductive tract cytolipidemic parameters that promote reproductive failure and ovarian involution during the pre-onset, initial, progressive, and chronic expression stages of the DOS. Paired littermate control (normal: +/?) and diabetic (mutant: db/db) C57BL/KsJ females were selected for analysis of ovarian parameters at 2 weeks (pre-onset expression of DOS), 4 weeks (initial DOS expression), 8 weeks (progressive DOS: hyperglycemic/lipidemic), and 16 weeks (overt/chronic DOS expression) of age. All 4- to 16-week-old (db/db) groups were obese, hyperglycemic, and hyperinsulinemic as compared with age-matched (+/?) controls. Prior to phenotypic expression of the DOS (2 week groups), ovarian interstitial cytolipidemia characterized the perifollicular and cortical regions of db/db tissue samples relative to +/? indices, while comparable body weight, blood glucose, as well as serum insulin and ovarian steroid hormone concentrations characterized both the +/? and db/db groups. Overt DOS expression in the 4-week-old db/db groups was characterized by body obesity, systemic hyperglycemia-hyperinsulinemia, and extensive hypercytolipidemia of ovarian folliculothecal compartments, as well as enhanced tissue lipase activities. By 8 weeks of age, progressive hypercytolipidemia characterized interstitial, thecal, and follicular granulosa cell layers of db/db tissue samples concurrent with suppressed ovarian steroid hormone production, enhanced lipid sequestration, and exacerbation of systemic hyperglycemia/insulinemia. By 16 weeks of age, the chronic-DOS was characterized by extensive ovarian follicular involution, cortical perivascular hyperlipidemic infiltration, thecal cell atrophy, and follicular granulosa lipid imbibition. These data indicate that db/db mutation-induced ovarian structural and functional involution is a direct reflection of the cellular metabolic shift towards lipogenesis, indicated by the progressive cytoarchitectural transformation into adipocyte-like entities. The cytological indications of cellular metabolic compromise, which precede the phenotypic expression of the DOS indices, suggests that correction of these abnormal shifts in ovarian endocrine and cellular metabolism may restore, delay, or prevent the further compromise of ovarian function by db/db mutation expression.

A new leptin-mediated mechanism for stimulating fatty acid oxidation: a pivotal role for sarcolemmal FAT/CD36

Leptin stimulates fatty acid oxidation in muscle and heart; but, the mechanism by which these tissues provide additional intracellular fatty acids for their oxidation remains unknown. We examined, in isolated muscle and cardiac myocytes, whether leptin, via AMP-activated protein kinase (AMPK) activation, stimulated fatty acid translocase (FAT/CD36)-mediated fatty acid uptake to enhance fatty acid oxidation. In both mouse skeletal muscle and rat cardiomyocytes, leptin increased fatty acid oxidation, an effect that was blocked when AMPK phosphorylation was inhibited by adenine 9-β-d-arabinofuranoside or Compound C. In wild-type mice, leptin induced the translocation of FAT/CD36 to the plasma membrane and increased fatty acid uptake into giant sarcolemmal vesicles and into cardiomyocytes. In muscles of FAT/CD36-KO mice, and in cardiomyocytes in which cell surface FAT/CD36 action was blocked by sulfo-N-succinimidyl oleate, the leptin-stimulated influx of fatty acids was inhibited; concomitantly, the normal leptin-stimulated increase in fatty acid oxidation was also prevented, despite the normal leptin-induced increase in AMPK phosphorylation. Conversely, in muscle of AMPK kinase-dead mice, leptin failed to induce the translocation of FAT/CD36, along with a failure to stimulate fatty acid uptake and oxidation. Similarly, when siRNA was used to reduce AMPK in HL-1 cardiomyocytes, leptin failed to induce the translocation of FAT/CD36. Our studies have revealed a novel mechanism of leptin-induced fatty acid oxidation in muscle tissue; namely, this process is dependent on the activation of AMPK to induce the translocation of FAT/CD36 to the plasma membrane, thereby stimulating fatty acid uptake. Without increasing this leptin-stimulated, FAT/CD36-dependent fatty acid uptake process, leptin-stimulated AMPK phosphorylation does not enhance fatty acid oxidation.

Effects of LEP G2548A and LEPR Q223R Polymorphisms on Serum Lipids and Response to Simvastatin Treatment in Chinese Patients With Primary Hyperlipidemia

Objectives:

To investigate whether LEP G2548A and LEPR Q223R polymorphisms influence serum lipid levels and whether the 2 polymorphisms affect the efficacy of simvastatin treatment in Chinese patients with primary hyperlipidemia.

Methods:

We used an extreme sampling approach by selecting 212 individuals from the top and bottom 15% of adjusted lipid-lowering response residuals to simvastatin (n = 106 in each group of good or bad response) from a total of 734 samples with primary hyperlipidemia. They were treated with simvastatin orally 20 mg/d. Fasting serum lipids were measured at baseline and after 4 and 8 weeks of treatment. Genotyping was carried out using polymerase chain reaction-restriction fragment length polymorphism.

Results:

More patients in the good response group (27%) had LEPR Q223R than in the bad response group (16%, P = .046). Secondary stratified analyses showed that patients carrying the RR genotype of the LEPR Q223R gene had significantly higher high-density lipoprotein cholesterol levels than those with the QR genotype at baseline ( P = .034) among good responders. After 29 consecutive days of treatment with simvastatin, patients carrying the RR genotype had a significantly larger decrease in triglycerides (change: −0.74 ± 0.92, P = .036) and total cholesterol levels (change: −1.77 ± 0.68, P = .023) compared with those carrying QR genotype among bad responders. After Bonferroni correction, the results were not statistically significant.

Conclusion:

LEPR Q223R polymorphism, but not LEP G2548A, could modulate the efficacy of simvastatin in Chinese patients with primary hyperlipidemia.

Serum saturated fatty acid decreases plasma adiponectin and increases leptin throughout pregnancy independently of BMI

OBJECTIVE

The aim of this study was to investigate whether serum concentrations of total saturated fatty acids (SFAs), polyunsaturated fatty acids (PUFAs), and their fractions are associated with plasma adiponectin and leptin concentrations throughout pregnancy.

METHODS

A prospective cohort of 201 pregnant women was followed from gestational weeks 5 to 13, 20 to 26, and 30 to 36. Blood samples were collected at the three visits after 12 h of fasting. Fatty acid concentrations were determined using fast gas-liquid chromatography. Plasma adiponectin (μg/mL) and leptin (ng/dL) concentrations were evaluated using enzyme-linked immunosorbent assay kits. Statistical analyses included median adipokine concentrations according to the tertiles of fatty acid distribution and multiple linear mixed-effect models adjusted for body mass index, gestational age, total energy intake, alcohol consumption, and smoking.

RESULTS

Women classified in the third SFA concentration tertile had lower median values of adiponectin compared with those in the first tertile ([first trimester: first tertile = 5.36; third tertile = 5.00]; [second trimester: first tertile = 6.39; third tertile = 4.47]; [third trimester: first tertile = 6.46; third tertile = 4.60]). Similar trends were observed for the 14:0, 16:0 and 18:0 fractions. In the multiple longitudinal models, total SFA (β = -41.039; P = 0.008) and 16:0 were negatively associated with plasma adiponectin (16:0, β = -0.511; P = 0.001). Total PUFA ω-6 (β = 28.961; P = 0.002) and 18:2 ω-6 (β = 0.259, P = 0.006) were positively associated with the adiponectin. Total SFA (β = 0.110, P = 0.007), 14:0 (β = 0.072, P = 0.011), and 20:3 ω-6 (β = 0.039; P = 0.035) were positively associated with plasma leptin.

CONCLUSIONS

Total serum SFA and the 16:0 fraction were negatively associated with plasma adiponectin and positively associated with leptin concentrations. Total ω-6 PUFA was positively associated only with plasma adiponectin concentrations throughout pregnancy.

The impacts of obesity on the cardiovascular and renal systems: cascade of events and therapeutic approaches

There is a neglected epidemic of both obesity and metabolic syndrome in industrialized and unindustrialized countries all over the globe. Both conditions are associated with a high incidence of other serious pathologies, such as cardiovascular and renal diseases. In this article, we review the potential underlying mechanisms by which obesity and metabolic syndrome promote hypertension, including changes in cardiovascular-renal physiology induced by leptin, the sympathetic nervous system, the renin-angiotensin-aldosterone system, insulin resistance, free fatty acids, natriuretic peptides, and proinflammatory cytokines. We also discuss the potential underlying mechanisms by which obesity promotes other cardiovascular and renal conditions, as well as available nonpharmacologic and pharmacologic approaches for treating obesity-induced hypertension. The findings presented herein suggest that adipocytes may be a key regulator of cardiovascular and renal function.

Fenugreek lactone attenuates palmitate-induced apoptosis and dysfunction in pancreatic β-cells

AIM

To investigate the effect of fenugreek lactone (FL) on palmitate (PA)-induced apoptosis and dysfunction in insulin secretion in pancreatic NIT-1 β-cells.

METHODS

Cells were cultured in the presence or absence of FL and PA (0.25 mmol/L) for 48 h. Then, lipid droplets in NIT-1 cells were observed by oil red O staining, and the intracellular triglyceride content was measured by colorimetric assay. The insulin content in the supernatant was determined using an insulin radio-immunoassay. Oxidative stress-associated parameters, including total superoxide dismutase, glutathione peroxidase and catalase activity and malondialdehyde levels in the suspensions were also examined. The expression of upstream regulators of oxidative stress, such as protein kinase C-α (PKC-α), phospho-PKC-α and P47phox, were determined by Western blot analysis and real-time PCR. In addition, apoptosis was evaluated in NIT-1 cells by flow cytometry assays and caspase-3 viability assays.

RESULTS

Our results indicated that compared to the control group, PA induced an increase in lipid accumulation and apoptosis and a decrease in insulin secretion in NIT-1 cells. Oxidative stress in NIT-1 cells was activated after 48 h of exposure to PA. However, FL reversed the above changes. These effects were accompanied by the inhibition of PKC-α, phospho-PKC-α and P47phox expression and the activation of caspase-3.

CONCLUSION

FL attenuates PA-induced apoptosis and insulin secretion dysfunction in NIT-1 pancreatic β-cells. The mechanism for this action may be associated with improvements in levels of oxidative stress.

Chronic cocaine use and its association with myocardial steatosis evaluated by 1H magnetic resonance spectroscopy in African Americans

OBJECTIVES

Cardiac steatosis is a manifestation of ectopic fat deposition and is associated with obesity. The impact of chronic cocaine use on obesity measures and on the relationship between obesity measures and cardiac steatosis is not well-characterized. The objectives of this study were to compare obesity measures in chronic cocaine users and nonusers, and to explore which factors, in addition to obesity measures, are associated with myocardial triglyceride in African Americans, using noninvasive magnetic resonance spectroscopy.

METHODS

Between June 2004 and January 2014, 180 healthy African American adults without HIV infection, hypertension, and diabetes were enrolled in an observational proton magnetic resonance spectroscopy and imaging study investigating factors associated with cardiac steatosis.

RESULTS

Among these 180 participants, 80 were chronic cocaine users and 100 were nonusers. The median age was 42 (interquartile range, 34-47) years. Obesity measures trended higher in cocaine users than in nonusers. The median myocardial triglyceride was 0.6% (interquartile range, 0.4%-1.1%). Among the factors investigated, years of cocaine use, leptin, and visceral fat were independently associated with myocardial triglyceride. Body mass index and visceral fat, which were significantly associated with myocardial triglyceride in noncocaine users, were not associated with myocardial triglyceride content in cocaine users.

CONCLUSIONS

This study shows (1) cocaine users may have more fat than nonusers and (2) myocardial triglyceride is independently associated with duration of cocaine use, leptin, and visceral fat in all subjects, whereas leptin and high-density lipoprotein cholesterol, but not visceral fat or body mass index, in cocaine users, suggesting that chronic cocaine use may modify the relationships between obesity measures and myocardial triglyceride.

The Association of Serum Leptin with Mortality in Older Adults

Objective

Elevated levels of serum leptin are associated with increased adiposity and production of pro-inflammatory cytokines. Both cytokines and body adiposity have been shown to predict cardiovascular events and mortality. The primary objective of the present study is to explore the associations between serum leptin and all-cause mortality and mortality from cardiovascular disease (CVD) over a span of 10 years, controlling for body adiposity and proinflammatory cytokines.

Methods

The Health, Aging and Body Composition (Health ABC) study is a prospective cohort of 3,075 older adults aged 70 to 79 years. This analysis includes 2,919 men and women with complete serum leptin and vital status data. Data on all-cause mortality and incident cardiovascular events (including Coronary Heart Disease and Congestive Heart Failure) were collected over 10 years of follow-up (mean 8.4 years).

Results

Women with leptin in quartile 2 and 3 were at lower risk of all-cause mortality, and those with leptin in quartile 2 were at lower risk of mortality from CVD as compared to women with lowest leptin values when adjusted for age, race, site, years of education, alcohol use, smoking, and physical activity. When these associations were additionally adjusted for body fat, C-reactive protein and pro-inflammatory cytokines, women with leptin values in quartile 3 were at lower risk of all-cause mortality and women with leptin in quartile 2 and 3 were at lower risk of mortality from CVD than women with lowest leptin values. These associations were not significant among men after adjusting for body fat and cytokines.

Conclusions

The present study suggests that moderately elevated concentrations of serum leptin are independently associated with lower risk of all-cause mortality and CVD-related mortality among older women. Among men, serum leptin is not associated with reduced risk of all-cause and CVD mortality after controlling for body fat and cytokines.

High-density lipoproteins reduce palmitate-induced cardiomyocyte apoptosis in an AMPK-dependent manner

Palmitate has been implicated in the induction of cardiomyocyte apoptosis via reducing the activity of 5' AMP-activated protein kinase (AMPK). We sought to evaluate whether high-density lipoproteins (HDLs), known for their cardioprotective features and their potential to increase AMPK activity, can reduce palmitate-induced cardiomyocyte apoptosis and whether this effect is AMPK-dependent. Therefore, cardiomyocytes were isolated from adult Wistar rat hearts via perfusion on a Langendorff-apparatus and cultured in free fatty acid-free BSA control medium or 0.5 mM palmitate medium in the presence or absence of HDL (5 μg protein/ml) with or without 0.1 μM of the AMPK-inhibitor compound S for the analysis of Annexin V/propidium, genes involved in apoptosis and fatty acid oxidation, and cardiomyocyte contractility. We found that HDLs decreased palmitate-induced cardiomyocyte apoptosis as indicated by a reduction in Annexin V-positive cardiomyocytes and an increase in Bcl-2 versus Bax ratio. Concomitantly, HDLs increased the palmitate-impaired expression of genes involved in fatty acid oxidation. Furthermore, HDLs improved the palmitate-impaired cardiomyocyte contractility. All effects were mediated in an AMPK-dependent manner, concluding that HDLs reduce palmitate-induced cardiomyocyte apoptosis, resulting in improved cardiomyocyte contractility through a mechanism involving AMPK.

Exploring the structure and conformational landscape of human leptin. A molecular dynamics approach

Leptin is a hormone that regulates energy homeostasis, inflammation, hematopoiesis and immune response, among other functions (Houseknecht et al., 1998; Zhang et al., 1995; Paz-Filho et al., 2010). To obtain its crystallographic structure, it was necessary to substitute a tryptophan for a glutamic acid at position 100, thus creating a mutant leptin that has been reported to have biological activity comparable to the activity of the wild type but that crystallizes more readily. Here, we report a comparative study of the conformational space of WT and W100E leptin using molecular dynamics simulations performed at 300, 400, and 500 K. We detected differences between the interactions of the two proteins with local and distal effects, resulting in changes in the conformation, accessible surface area, compactness, electrostatic potential and dynamic behavior. Additionally, the series of unfolding events that occur when leptin is subjected to high temperature differs for the two constructs. We observed that both proteins are mostly unstructured after 20 ns of MD simulation at 500 K. However, WT leptin maintains a significant amount of secondary structure in helix α2, while the most stable region of W100E leptin is helix α3. Furthermore, we found that the region between residues 25 and 42 might adopt interconverting secondary structures ranging from α-helices and random coils to β-strand structures. Thus, this region can be considered an intrinsically disordered region. This atomistic description supports our understanding of leptin signaling and consequently might facilitate the use of leptin in treatments for the pathophysiologies in which it is implicated.

Maternal saturated-fat-rich diet promotes leptin resistance in fetal liver lipid catabolism and programs lipid homeostasis impairments in the liver of rat offspring

We aimed to analyze if an overload of saturated fat in maternal diet induced lipid metabolic impairments in livers from rat fetuses that persist in the offspring and to identify potential mechanisms involving fetal leptin resistance. Female rats were fed either a diet enriched in 25% of saturated fat (SFD rats) or a regular diet (controls). Fetuses of 21days of gestation and offspring of 21 and 140days of age were obtained and plasma and liver were kept for further analysis. Livers from a group of control and SFD fetuses were cultured in the presence or absence of leptin. Leptin or vehicle was administered to control fetuses during the last days of gestation and, on day 21, fetal livers and plasma were obtained. Lipid levels were assessed by thin-layer chromatography and mRNA gene expression of CPT1, ACO and PPARα by RT-PCR. Liver lipid levels were increased and CPT1 and ACO were down-regulated in fetuses and offspring from SFD rats compared to controls. After the culture with leptin, control fetal livers showed increased ACO and CPT1 expression and decreased lipid levels, while fetal livers from SFD rats showed no changes. Fetal administration of leptin induced a decrease in ACO and no changes in CPT1 expression. In summary, our results suggest that a saturated fat overload in maternal diet induces fetal leptin resistance in liver lipid catabolism, which might be contributing to liver lipid alterations that are sustained in the offspring.

The post-adipocytic phase of the adipose cell cycle

Subcutaneous white adipose tissue harvested by liposuction has been studied with the aim to understand how the adipocytes modify their morphology when subjected to the passage in a needle for liposuction and to cryopreservation. The work try to clarify the ultrastructural aspects of adipose tissue, in the conditions described before, examining samples of body fat employed in fat graft procedures, and samples after cryopreservation. Scanning and transmission electron microscopy show that the first event that occur in the adipocytes is a lesion of mild degree detectable early in the samples fixed immediately after liposuction. The sequence of events following the adipocyte stress appeared composed by different phases: plasmatic membrane interruption, loss of lipid charge, formation of cup-like adipocytes and formation of post-adipocytes (i.e. cells that survive to traumatic events and restart to internalize lipid droplets). In conclusion, the study suggests that the loss of lipid charge in adipose cell is an active process that can be due to a small hole in the cytoplasmic membrane with the preservation of a large part of the cytoplasmatic content and that at the end of the process of lipid extrusion the cell can maintain viability.

Quantum Dots in an Amphiphilic Polyethyleneimine Derivative Platform for Cellular Labeling, Targeting, Gene Delivery, and Ratiometric Oxygen Sensing

Amphiphilic polyethyleneimine derivatives (amPEIs) were synthesized and used to encapsulate dozens of quantum dots (QDs). The QD-amPEI composite was ∼100 nm in hydrodynamic diameter and had the slightly positive outer surface that suited well for cellular internalization. The QD-amPEI showed very efficient QD cellular labeling with the labeled cell fluorescence intensity more than 10 times higher than conventional techniques such as Lipofectamine-assisted QD delivery. QD-amPEI was optimal for maximal intracellular QD delivery by the large QD payload and the rapid endocytosis kinetics. QD-amPEI platform technology was demonstrated for gene delivery, cell-specific labeling, and ratiometric oxygen sensing. Our QD-amPEI platform has two partitions: positive outer surface and hydrophobic inside pocket. The outer positive surface was further exploited for gene delivery and targeting. Co-delivery of QDs and GFP silencing RNAs was successfully demonstrated by assembling siRNAs to the outer surfaces, which showed the transfection efficiency an order of magnitude higher than conventional gene transfections. Hyaluronic acids were tethered onto the QD-amPEI for cell-specific targeted labeling which showed the specific-to-nonspecific signal ratio over 100. The inside hydrophobic compartment was further applied for cohosting oxygen sensing phosphorescence Ru dyes along with QDs. The QD-Ru-amPEI oxygen probe showed accurate and reversible oxygen sensing capability by the ratiometric photoluminescence signals, which was successfully applied to cellular and spheroid models.

Modulation of glucose transporter protein by dietary flavonoids in type 2 diabetes mellitus

Diabetes mellitus (DM) is a metabolic diseases characterized by hyperglycemia due to insufficient or inefficient insulin secretory response. This chronic disease is a global problem and there is a need for greater emphasis on therapeutic strategies in the health system. Phytochemicals such as flavonoids have recently attracted attention as source materials for the development of new antidiabetic drugs or alternative therapy for the management of diabetes and its related complications. The antidiabetic potential of flavonoids are mainly through their modulatory effects on glucose transporter by enhancing GLUT-2 expression in pancreatic β cells and increasing expression and promoting translocation of GLUT-4 via PI3K/AKT, CAP/Cb1/TC10 and AMPK pathways. This review highlights the recent findings on beneficial effects of flavonoids in the management of diabetes with particular emphasis on the investigations that explore the role of these compounds in modulating glucose transporter proteins at cellular and molecular level.