Regulation of adipocyte autophagy--the potential anti-obesity mechanism of high density lipoprotein and ApolipoproteinA-I

The role of statins in amyotrophic lateral sclerosis: protective or not?

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease of motor neurons characterized by muscle weakness, muscle twitching, and muscle wasting. ALS is regarded as the third-most frequent neurodegenerative disease, subsequent to Alzheimer's disease (AD) and Parkinson's disease (PD). The World Health Organization (WHO) in 2007 declared that prolonged use of statins may induce development of ALS-like syndrome and may increase ALS risk. Subsequently, different studies have implicated statins in the pathogenesis of ALS. In contrast, results from preclinical and clinical studies highlighted the protective role of statins against ALS neuropathology. Recently, meta-analyses and systematic reviews illustrated no association between long-term use of statins and ALS risk. These findings highlighted controversial points regarding the effects of statins on ALS pathogenesis and risk. The neuroprotective effects of statins against the development and progression of ALS may be mediated by regulating dyslipidemia and inflammatory changes. However, the mechanism for induction of ALS neuropathology by statins may be related to the dysregulation of liver X receptor signaling (LXR) signaling in the motor neurons and reduction of cholesterol, which has a neuroprotective effect against ALS neuropathology. Nevertheless, the exact role of statins on the pathogenesis of ALS was not fully elucidated. Therefore, this narrative review aims to discuss the role of statins in ALS neuropathology.

High-density lipoprotein regulates angiogenesis by affecting autophagy via miRNA-181a-5p

We previously demonstrated that normal high-density lipoprotein (nHDL) can promote angiogenesis, whereas HDL from patients with coronary artery disease (dHDL) is dysfunctional and impairs angiogenesis. Autophagy plays a critical role in angiogenesis, and HDL regulates autophagy. However, it is unclear whether nHDL and dHDL regulate angiogenesis by affecting autophagy. Endothelial cells (ECs) were treated with nHDL and dHDL with or without an autophagy inhibitor. Autophagy, endothelial nitric oxide synthase (eNOS) expression, miRNA expression, nitric oxide (NO) production, superoxide anion (O2•-) generation, EC migration, and tube formation were evaluated. nHDL suppressed the expression of miR-181a-5p, which promotes autophagy and the expression of eNOS, resulting in NO production and the inhibition of O2•- generation, and ultimately increasing in EC migration and tube formation. dHDL showed opposite effects compared to nHDL and ultimately inhibited EC migration and tube formation. We found that autophagy-related protein 5 (ATG5) was a direct target of miR-181a-5p. ATG5 silencing or miR-181a-5p mimic inhibited nHDL-induced autophagy, eNOS expression, NO production, EC migration, tube formation, and enhanced O2•- generation, whereas overexpression of ATG5 or miR-181a-5p inhibitor reversed the above effects of dHDL. ATG5 expression and angiogenesis were decreased in the ischemic lower limbs of hypercholesterolemic low-density lipoprotein receptor null (LDLr-/-) mice when compared to C57BL/6 mice. ATG5 overexpression improved angiogenesis in ischemic hypercholesterolemic LDLr-/- mice. Taken together, nHDL was able to stimulate autophagy by suppressing miR-181a-5p, subsequently increasing eNOS expression, which generated NO and promoted angiogenesis. In contrast, dHDL inhibited angiogenesis, at least partially, by increasing miR-181a-5p expression, which decreased autophagy and eNOS expression, resulting in a decrease in NO production and an increase in O2•- generation. Our findings reveal a novel mechanism by which HDL affects angiogenesis by regulating autophagy and provide a therapeutic target for dHDL-impaired angiogenesis.

An interdisciplinary therapy for lifestyle change is effective in improving psychological and inflammatory parameters in women with grade I obesity

Obesity and depression, disorders associated with inflammation, have high incidences in women. Understanding the derangements present in the initial phase of obesity may point to factors that could help avoiding disease aggravation. The present study aimed at investigating the effects of a 6-months interdisciplinary therapy for weight loss in women with grade I obesity. Before and after the therapy, 37 middle-aged women donated blood and responded to questionnaires for depression and anxiety symptoms. Inflammatory parameters were evaluated in serum and a preliminary screening of the plasma proteome was performed. The therapy decreased anthropometric, psychological scores, and serum levels of inflammatory parameters. Depression and anxiety scores correlated positively with some inflammatory parameters. The proteomic analysis showed changes in proteins related to cholesterol metabolism and inflammatory response. Interdisciplinary therapy improves anthropometric and inflammatory statuses and ameliorating psychological symptoms. The decrease of MCP-1 levels after interdisciplinary therapy has not been reported so far, at the best of our knowledge. The present demonstration of positive associations of inflammatory markers and psychological scores indicate that these mediators may be useful to monitor psychological status in obesity. The present proteome data, although preliminary, pointed to plasma alterations indicative of improvement of inflammation after interdisciplinary therapy.

Association of Apolipoprotein A1, High Density Lipoprotein Cholesterol, and Their Ratio with Inflammatory Marker in Chinese Adults with Coronary Artery Disease

Sparse data assessed the association of apolipoprotein A1 (ApoA1) and high density lipoprotein cholesterol (HDL-C) with inflammation. We investigated this association in a hospital-based cross-sectional pilot study that included 7296 patients with coronary artery disease (CAD). In multivariate analysis, negative associations of ApoA1 and HDL-C with C-reactive protein (CRP), high sensitivity CRP (hsCRP), and tumor necrosis factor-α (TNF-α) were shown. The corresponding CRP, hsCRP, and TNF-α values were 5.28 (vs 11.70 mg/L), 4.50 (vs 11.50 mg/L), and 7.68 (vs 10.90 pg/mL) for ApoA1, and 7.13 (vs 10.60 mg/L), 6.27 (vs 9.19 mg/L), and 8.11 (vs 11.86 pg/mL) for HDL-C in the fourth quartiles compared with the first quartiles. ApoA1/HDL-C ratio was inversely associated with hsCRP and interleukin-6 (IL-6). No significant associations of ApoA1 and HDL-C with IL-6 and IL-8, and of ApoA1/HDL-C ratio with CRP, IL-8, and TNF-α were observed. In path analyses, there was no evidence of mediating effects of body mass index on the "ApoA1 and HDL-C-inflammation" relationship. Generally, our study of CAD patients identified graded and inverse associations of ApoA1, HDL-C, and ApoA1/HDL-C ratio with inflammatory marker (CRP, hsCRP, IL-6, IL-8, or TNF-α) levels.

Serum apolipoprotein A1 rather than apolipoprotein B is associated with hypertension prevalence in Chinese people with coronary artery disease

OBJECTIVE

Studies on the association of apolipoprotein A1 (ApoA1) and apolipoprotein B (ApoB) with hypertension (HTN) prevalence in patients with coronary artery disease (CAD) are limited. This cross-sectional study aimed to investigate this association in Chinese people in Wuhan, China.

METHODS

Serum ApoA1 and ApoB levels were measured by immunoturbidimetry assay. Logistic regression analysis was used to estimate the associations of ApoA1 and ApoB level and ApoB/A1 ratio with HTN prevalence.

RESULTS

We included 5192 individuals (3060 men, mean age 61 years; 4412 HTN cases) in this study. After adjusting for covariates, serum ApoA1 but not ApoB level or ApoB/A1 ratio was inversely associated with HTN prevalence. HTN prevalence was reduced with the fifth versus first quintile of ApoA1 level [odds ratio = 0.78 (95% confidence interval 0.62-0.98)]. In stratified analyses based on sex, the probability of HTN with the fifth versus first ApoA1 level was 0.71 (0.53-0.96) for men. The probability of HTN with the fifth versus first quintile of ApoB/A1 ratio was 1.54 (1.11-2.13) after adjustment. With quintiles 2-5 versus of ApoB level, the probability of HTN did not differ in both men and women. On path analyses, the association of ApoA1 level and ApoB/A1 ratio with HTN was mediated by BMI (β coefficients: -0.179 to 0.133).

CONCLUSION

In general, high serum ApoA1 level may be associated with a reduced probability of HTN prevalence in patients with CAD in China, and this association may be mediated by BMI.

Investigation of the prognostic predictive value of serum lipid profiles in amyotrophic lateral sclerosis: roles of sex and hypermetabolism

The prognostic predictive value of lipid profiling in amyotrophic lateral sclerosis (ALS) remains unclear. Here, we aimed to clarify the value of the levels of serum lipids, including high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), and triglycerides (TG), for predicting the prognosis in ALS. This was a single-center retrospective study of 78 patients with ALS. The serum lipid profiles at the first hospital visit after symptom onset were analyzed to determine the correlations of lipids with survival and physical parameters, including nutritional, respiratory, and metabolic conditions. The cutoff level for high HDL was defined as the third quartile, while that of low LDL and TG, as the first quartile. Hypermetabolism was defined as the ratio of resting energy expenditure to lean soft tissue mass ≥ 38 kcal/kg. High HDL was an independent factor for poor prognosis in all patients (hazards ratio [HR]: 9.87, p < 0.001) in the Cox proportional hazard model, including %vital capacity and the monthly decline rate in body mass index and the Revised Amyotrophic Lateral Functional Rating Scale score from symptom onset to diagnosis. Low LDL was a factor for poor prognosis (HR: 6.59, p = 0.017) only in women. Moreover, subgroup analyses with log-rank tests revealed that the prognostic predictive value of high HDL was evident only in the presence of hypermetabolism (p = 0.005). High HDL predicts poor prognosis in all patients, whereas low LDL, only in women. Hypermetabolism and high HDL synergistically augment the negative effect on prognosis.

PEX-168 improves insulin resistance, inflammatory response and adipokines in simple obese mice: a mechanistic exploration

BACKGROUND

Polyethylene glycol loxenatide (PEX-168) is a new antidiabetic drug; as such, there are not yet any reports on its weight loss effect. Therefore, this trial was designed to investigate the effect of PEX-168 on simple obese mice.

METHODS

Thirty healthy male C57BL/6 mice were randomly selected and divided into a control group (NC) and an obesity model group. The high-fat diet-induced simple obesity mice were divided into a model control group (HF) and three intervention groups. The intervention groups were injected with different doses of PEX-168 intraperitoneally once a week for 12 weeks (low (LD), medium (MD) and high (HD)). Fasting blood glucose (FBG), body weight and food intake were measured from 1 to 12 weeks after PEX-168 injection. The serum insulin (INS), C-reactive protein (CRP), chemerin and omentin levels were measured after 12 weeks.

RESULTS

Compared with the HF group, the low dose of PEX-168 reduced the body weight of the mice in a short period of time (8 weeks), and the mice in the MD and HD groups showed a significant decrease in body weight (P < 0.05). The low dose of PEX-168 could effectively improve the blood glucose and homeostasis model assessment of insulin resistance (Homa-IR) of the mice (FBG P < 0.05 INS, Homa-IR P < 0.001), but there was no significant difference between different doses (P > 0.05). CRP levels in the MD and HD groups were significantly improved (P < 0.05). The levels of serum chemerin and omentin in the intervention groups were also significantly improved (P < 0.01), but there was no significant difference between the different doses (P > 0.05).

CONCLUSIONS

PEX-168 significantly reduced the body weight of simple obese mice and improved the insulin resistance. PEX-168 may regulate the expression of chemerin and omentin through its hypoglycaemic effect, and the weight-reducing effect of PEX-168 is unlikely to be the reason for the changes in both.

Lipoproteins and the Tumor Microenvironment

The tumor microenvironment (TME) plays a key role in enhancing the growth of malignant tumors and thus contributing to "aggressive phenotypes," supporting sustained tumor growth and metastasis. The precise interplay between the numerous components of the TME that contribute to the emergence of these aggressive phenotypes is yet to be elucidated and currently under intense investigation. The purpose of this article is to identify specific role(s) for lipoproteins as part of these processes that facilitate (or oppose) malignant growth as they interact with specific components of the TME during tumor development and treatment. Because of the scarcity of literature reports regarding the interaction of lipoproteins with the components of the tumor microenvironment, we were compelled to explore topics that were only tangentially related to this topic, to ensure that we have not missed any important concepts.

TP53INP2 Promotes Bovine Adipocytes Differentiation Through Autophagy Activation

Simple Summary

In this article explore the role of the bovine TP53INP2 gene in adipocyte differentiation and its function in autophagy during the early stage of adipocyte differentiation. In our work we found that a novel, important autophagy related protein TP53INP2 can activate autophagy during the early stage of differentiation in bovine adipocytes and positively regulate adipocyte differentiation by affecting autophagy. Furthermore, we demonstrated that peroxisome proliferator-activated receptor gamma (PPARγ) also contributed to the function of TP53INP2 in modulating adipocyte differentiation. The study of the function of bovine TP53INP2 gene on adipocyte differentiation has not been reported, therefore, we have decided to focus on Qinchuan cattle, one of the five important cattle breeds in China. We propose that the TP53INP2 gene may affect the meat quality of Qinchuan cattle by regulating lipid deposition, and may shed new light on the developmental mechanisms of adipose development.

Abstract

Tumor protein p53 inducible nuclear protein 2 (TP53INP2) is a key positive regulator of autophagy, and it has been shown to modulate adipocyte differentiation. However, the molecular mechanism involved in autophagy regulation during adipocyte differentiation has not been clarified. Our experiments were intended to investigate whether TP53INP2 is involved in the regulation of autophagy during bovine adipocyte differentiation and how TP53INP2 affects the differentiation of bovine adipocytes. In our research, using RT-qPCR and Western blot methods, we found that the overexpression of TP53INP2 resulted in the upregulation of adipogenesis and autophagy-related genes, and autophagy flux and the degree of differentiation were detected by LipidTOX™ Deep Red Neutral Lipid staining and dansylcadaverine staining, respectively. The knockdown of TP53INP2 produced results that were the inverse of those produced by the overexpression of TP53INP2. Overall, our results suggested that TP53INP2 can activate autophagy during the early stage of differentiation in bovine adipocytes and positively regulate adipocyte differentiation by affecting autophagy. Additionally, peroxisome proliferator-activated receptor gamma (PPARγ) also contributed to the function of TP53INP2 in modulating adipocyte differentiation.

Peptides and Peptidomimetics as Potential Antiobesity Agents: Overview of Current Status

There is a high occurrence of obesity worldwide without many new medications being approved for its treatment. Therefore, there is an urgent need to introduce new approaches for treating obesity. Bioactive peptides have been used to treat metabolic disorders- such as type-2 diabetes and obesity; while also possessing anti-oxidant, anti-inflammatory, anti-microbial, and anti-viral properties. However, the development of these peptides has taken backstage due to their size, reduced stability, poor delivery and bioavailability, fast rate of degradation etc. But with the emergence of newer techniques for multifunctional peptides, mimetics, peptide analogs, and aptamers, there is a sudden revival in this therapeutic field. An increased attention is required for development of the natural peptides from food and marine sources which can mimic the function of mediators involved in weight management to avoid obesity. Herein, the search for the structures of anti-obesity peptides was carried out in order to establish their potential for drug development in future. An extensive search for the current status of endogenous, food and marine peptides, with reference to novel and interesting experimental approaches based on peptidomimetics for controlling obesity, was performed. Apolipoprotein A-I (apoA-I), melanocortin-4 receptor (MC4R)-specific agonist, GLP-1 dual and triple agonists, neuropeptides and prolactin-releasing peptide mimetics were specifically examined for their anti-obesity role. Novel peptides, mimetics, and synthesis interventions are transpiring and might offer safer alternatives for otherwise scarcely available safe antiobesity drug. A deeper understanding of peptides and their chemistry through the use of peptide engineering can be useful to overcome the disadvantages and select best mimetics and analogs for treatment in future.

Targeting autophagy in obesity: from pathophysiology to management

Obesity poses a severe threat to human health, including the increased prevalence of hypertension, insulin resistance, diabetes mellitus, cancer, inflammation, sleep apnoea and other chronic diseases. Current therapies focus mainly on suppressing caloric intake, but the efficacy of this approach remains poor. A better understanding of the pathophysiology of obesity will be essential for the management of obesity and its complications. Knowledge gained over the past three decades regarding the aetiological mechanisms underpinning obesity has provided a framework that emphasizes energy imbalance and neurohormonal dysregulation, which are tightly regulated by autophagy. Accordingly, there is an emerging interest in the role of autophagy, a conserved homeostatic process for cellular quality control through the disposal and recycling of cellular components, in the maintenance of cellular homeostasis and organ function by selectively ridding cells of potentially toxic proteins, lipids and organelles. Indeed, defects in autophagy homeostasis are implicated in metabolic disorders, including obesity, insulin resistance, diabetes mellitus and atherosclerosis. In this Review, the alterations in autophagy that occur in response to nutrient stress, and how these changes alter the course of obesogenesis and obesity-related complications, are discussed. The potential of pharmacological modulation of autophagy for the management of obesity is also addressed.

Targeted Deletion of Adipocyte Abca1 (ATP-Binding Cassette Transporter A1) Impairs Diet-Induced Obesity

OBJECTIVE

Adipose tissue cholesterol increases with adipocyte triglyceride content and size during development of obesity. However, how adipocyte cholesterol affects adipocyte function is poorly understood. The aim of this study was to evaluate the role of the cellular cholesterol exporter, Abca1 (ATP-binding cassette transporter A1), on adipose tissue function during diet-induced obesity.

APPROACH AND RESULTS

Adiponectin Cre recombinase transgenic mice were crossed with Abca1^flox/flox mice to generate ASKO (adipocyte-specific Abca1 knockout) mice. Control and ASKO mice were then fed a high-fat, high-cholesterol (45% calories as fat and 0.2% cholesterol) diet for 16 weeks. Compared with control mice, ASKO mice had a 2-fold increase in adipocyte plasma membrane cholesterol content and significantly lower body weight, epididymal fat pad weight, and adipocyte size. ASKO versus control adipose tissue had decreased PPARγ (peroxisome proliferator-activated receptor γ) and CCAAT/enhancer-binding protein expression, nuclear SREBP1 (sterol regulatory element-binding protein 1) protein, lipogenesis, and triglyceride accretion but similar Akt activation after acute insulin stimulation. Acute siRNA-mediated Abca1 silencing during 3T3L1 adipocyte differentiation reduced adipocyte Abca1 and PPARγ protein expression and triglyceride content. Systemic stimulated triglyceride lipolysis and glucose homeostasis were similar between control and ASKO mice.

CONCLUSIONS

Adipocyte Abca1 is a key regulator of adipocyte lipogenesis and lipid accretion, likely because of increased adipose tissue membrane cholesterol, resulting in decreased activation of lipogenic transcription factors PPARγ and SREBP1.

Association between polymorphisms in SLC15A1 and PLA2G16 genes and development of obesity in Chinese subjects

INTRODUCTION

The small peptide transporter 1 (PepT-1) and adipose phospholipase A2 (AdPLA) play a key role in the development of obesity. However, there are no data assessing the impact of PepT-1 (SLC15A1) and AdPLA (PLA2G16) variants on obesity susceptibility. Therefore, we assessed the contribution of 9 single-nucleotide polymorphisms (SNPs) between these two genes on obesity susceptibility in Chinese subjects.

MATERIALS AND METHODS

A total of 611 participants were enrolled in the study, and 9 SNPs in the SLC15A1 and PLA2G16 genes were selected. Blood samples were collected for genotyping. Overweight and obesity were established by body mass index. Regression analyses were performed to test for any association of genetic polymorphisms with weight abnormality.

RESULTS

The genotype frequencies (P=0.04 for rs9557029, P=0.027 for rs1289389) were significantly different between obese or overweight subjects and healthy controls. However, no significant difference in allele was found between these three groups (P>0.05). Further logistic regression analyses adjusted for age and sex also failed to reveal significant associations between overweight, obesity, and the selected SNPs (P>0.05).

CONCLUSION

Data indicate that the selected 9 SNPs in SLC15A1 and PLA2G16 genes were not related to obesity susceptibility in the Han Chinese population.

High-density lipoprotein inhibits mechanical stress-induced cardiomyocyte autophagy and cardiac hypertrophy through angiotensin II type 1 receptor-mediated PI3K/Akt pathway

Mechanical stress triggers cardiac hypertrophy and autophagy through an angiotensin II (Ang II) type 1 (AT1) receptor-dependent mechanism. Low level of high density lipoprotein (HDL) is an independent risk factor for cardiac hypertrophy. This study was designed to evaluate the effect of HDL on mechanical stress-induced cardiac hypertrophy and autophagy. A 48-hr mechanical stretch and a 4-week transverse aortic constriction were employed to induce cardiomyocyte hypertrophy in vitro and in vivo, respectively, prior to the assessment of myocardial autophagy using LC3b-II and beclin-1. Our results indicated that HDL significantly reduced mechanical stretch-induced rise in autophagy as demonstrated by LC3b-II and beclin-1. In addition, mechanical stress up-regulated AT1 receptor expression in both cultured cardiomyocytes and in mouse hearts, whereas HDL significantly suppressed the AT1 receptor. Furthermore, the role of Akt phosphorylation in HDL-mediated action was assessed using MK-2206, a selective inhibitor for Akt phosphorylation. Our data further revealed that MK-2206 mitigated HDL-induced beneficial responses on cardiac remodelling and autophagy. Taken together, our data revealed that HDL inhibited mechanical stress-induced cardiac hypertrophy and autophagy through downregulation of AT1 receptor, and HDL ameliorated cardiac hypertrophy and autophagy via Akt-dependent mechanism.

Indicators of the metabolic syndrome in obese adolescents

INTRODUCTION

To assess the prevalence of metabolic risk indicators for the metabolic syndrome (MS) in a sample of obese Egyptian adolescents and to compare anthropometric and biochemical parameters in subjects with one or two parameters of the MS with those who meet MS criteria.

MATERIAL AND METHODS

A descriptive, cross-sectional study was conducted on 300 obese adolescents, with a mean age of 15.45 ±2.54 years. Variables examined included body mass index (BMI), waist circumference (WC), waist to hip ratio (WHR), systolic and diastolic blood pressure (BP), fasting blood glucose, cholesterol, triglycerides (TG), high-density lipoprotein (HDL), low-density lipoproteins (LDL), insulin and insulin resistance (IR) measured by Homeostasis Model Assessment-Insulin Resistance (HOMA-IR). Receiver operating characteristic (ROC) curve analysis was used to determine the predictive powers of anthropometric parameters associated with increased risk for the MS.

RESULTS

The overall prevalence of the MS was 20%. Individuals meeting 3 or more MS criteria had significantly higher levels of BP, TG, glucose, insulin and HOMA-R and low HDL levels compared with those who had 1 or 2 MS criteria. Area under the curve (AUC) for identifying the MS risk factors was the highest for WHR, followed by WC and BMI in both genders (p < 0.001).

CONCLUSIONS

The most prevalent metabolic risk factors that compose the MS were arterial hypertension, low HDL and hypertriglyceridemia; BMI tended to be the weakest index for identifying MS risk factors, while WHR was the best predictive index in both genders.

HDLs, diabetes, and metabolic syndrome

The prevalence of type 2 diabetes mellitus and of the metabolic syndrome is rising worldwide and reaching epidemic proportions. These pathologies are associated with significant morbidity and mortality, in particular with an excess of cardiovascular deaths. Type 2 diabetes mellitus and the cluster of pathologies including insulin resistance, central obesity, high blood pressure, and hypertriglyceridemia that constitute the metabolic syndrome are associated with low levels of HDL cholesterol and the presence of dysfunctional HDLs. We here review the epidemiological evidence and the potential underlying mechanisms of this association. We first discuss the well-established association of type 2 diabetes mellitus and insulin resistance with alterations of lipid metabolism and how these alterations may lead to low levels of HDL cholesterol and the occurrence of dysfunctional HDLs. We then present and discuss the evidence showing that HDL modulates insulin sensitivity, insulin-independent glucose uptake, insulin secretion, and beta cell survival. A dysfunction in these actions could play a direct role in the pathogenesis of type 2 diabetes mellitus.