Attenuated mTOR signaling and enhanced autophagy in adipocytes from obese patients with type 2 diabetes

Autophagy alterations in obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease: the evidence from human studies

Autophagy is an evolutionarily conserved process that plays a pivotal role in the maintenance of cellular homeostasis and its impairment has been implicated in the pathogenesis of various metabolic diseases including obesity, type 2 diabetes (T2D), and metabolic dysfunction-associated steatotic liver disease (MASLD). This review synthesizes the current evidence from human studies on autophagy alterations under these metabolic conditions. In obesity, most data point to autophagy upregulation during the initiation phase of autophagosome formation, potentially in response to proinflammatory conditions in the adipose tissue. Autophagosome formation appears to be enhanced under hyperglycemic or insulin-resistant conditions in patients with T2D, possibly acting as a compensatory mechanism to eliminate damaged organelles and proteins. Other studies have proposed that prolonged hyperglycemia and disrupted insulin signaling hinder autophagic flux, resulting in the accumulation of dysfunctional cellular components that can contribute to β-cell dysfunction. Evidence from patients with MASLD supports autophagy inhibition in disease progression. Nevertheless, given the available data, it is difficult to ascertain whether autophagy is enhanced or suppressed in these conditions because the levels of autophagy markers depend on the overall metabolism of specific organs, tissues, experimental conditions, or disease duration. Owing to these constraints, determining whether the observed shifts in autophagic activity precede or result from metabolic diseases remains challenging. Additionally, autophagy-modulating strategies are shortly discussed. To conclude, more studies investigating autophagy impairment are required to gain a more comprehensive understanding of its role in the pathogenesis of obesity, T2D, and MASLD and to unveil novel therapeutic strategies for these conditions.

Roles of lipid droplets and related proteins in metabolic diseases

Lipid droplets (LDs), which are active organelles, derive from the monolayer membrane of the endoplasmic reticulum and encapsulate neutral lipids internally. LD-associated proteins like RAB, those in the PLIN family, and those in the CIDE family participate in LD formation and development, and they are active players in various diseases, organelles, and metabolic processes (i.e., obesity, non-alcoholic fatty liver disease, and autophagy). Our synthesis on existing research includes insights from the formation of LDs to their mechanisms of action, to provide an overview needed for advancing research into metabolic diseases and lipid metabolism.

Dysregulation of pancreatic β-cell autophagy and the risk of type 2 diabetes

Macroautophagy/autophagy is an essential degradation process that removes abnormal cellular components, maintains homeostasis within cells, and provides nutrition during starvation. Activated autophagy enhances cell survival during stressful conditions, although overactivation of autophagy triggers induction of autophagic cell death. Therefore, early-onset autophagy promotes cell survival whereas late-onset autophagy provokes programmed cell death, which can prevent disease progression. Moreover, autophagy regulates pancreatic β-cell functions by different mechanisms, although the precise role of autophagy in type 2 diabetes (T2D) is not completely understood. Consequently, this mini-review discusses the protective and harmful roles of autophagy in the pancreatic β cell and in the pathophysiology of T2D.

A pH-Sensitive Double Chromophore Fluorescent Dye for Live-Tracking of Lipophagy

Lipid droplet (LD) degradation provides metabolic energy and important building blocks for various cellular processes. The two major LD degradation pathways include autophagy (lipophagy), which involves delivery of LDs to autolysosomes, and lipolysis, which is mediated by lipases. While abnormalities in LD degradation are associated with various pathological disorders, our understanding of lipophagy is still rudimentary. In this study, we describe the development of a lipophilic dye containing two fluorophores, one of which is pH-sensitive and the other pH-stable. We further demonstrate that this "Lipo-Fluddy" can be used to visualize and quantify lipophagy in living cells, in an easily applicable and protein label-free approach. After estimating the ability of compound candidates to penetrate LDs, we synthesized several BODIPY and (pH-switchable) rhodol dyes, whose fluorescence properties (incl. their photophysical compatibility) were analyzed. Of three Lipo-Fluddy dyes synthesized, one exhibited the desired properties and allowed observation of lipophagy by fluorescence microscopy. Also, this dye proved to be non-toxic and suitable for the examination of various cell lines. Moreover, a method was developed to quantify the lipophagy process using flow cytometry, which could be applied in the future in the identification of lipophagy-related genes or in the screening of potential drugs against lipophagy-related diseases.

The role of autophagy in insulin resistance and glucolipid metabolism and potential use of autophagy modulating natural products in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a severe, long-term condition characterised by disruptions in glucolipid and energy metabolism. Autophagy, a fundamental cellular process, serves as a guardian of cellular health by recycling and renewing cellular components. To gain a comprehensive understanding of the vital role that autophagy plays in T2DM, we conducted an extensive search for high-quality publications across databases such as Web of Science, PubMed, Google Scholar, and SciFinder and used keywords like 'autophagy', 'insulin resistance', and 'type 2 diabetes mellitus', both individually and in combinations. A large body of evidence underscores the significance of activating autophagy in alleviating T2DM symptoms. An enhanced autophagic activity, either by activating the adenosine monophosphate-activated protein kinase and sirtuin-1 signalling pathways or inhibiting the mechanistic target of rapamycin complex 1 signalling pathway, can effectively improve insulin resistance and balance glucolipid metabolism in key tissues like the hypothalamus, skeletal muscle, liver, and adipose tissue. Furthermore, autophagy can increase β-cell mass and functionality in the pancreas. This review provides a narrative summary of autophagy regulation with an emphasis on the intricate connection between autophagy and T2DM symptoms. It also discusses the therapeutic potentials of natural products with autophagy activation properties for the treatment of T2DM conditions. Our findings suggest that autophagy activation represents an innovative approach of treating T2DM.

LncRNA-associated competing endogenous RNA network analysis uncovered key lncRNAs involved in temozolomide resistance and tumor recurrence of glioblastoma

Temozolomide (TMZ) is a common alkylating chemotherapeutic agent used to treat brain tumors such as glioblastoma multiforme (GBM) and anaplastic astrocytoma. GBM patients develop resistance to this drug, which has an unclear and complicated molecular mechanism. The competing endogenous RNAs (ceRNAs) play critical roles in tumorigenesis, drug resistance, and tumor recurrence in cancers. This study aims to predict ceRNAs, their possible involvement, and underlying molecular mechanisms in TMZ resistance. Therefore, we analyzed coding and non-coding RNA expression levels in TMZ-resistant GBM samples compared to sensitive GBM samples and performed pathway analysis of mRNAs differentially expressed (DE) in TMZ-resistant samples. We next applied a mathematical model on 950 DE long non-coding RNAs (lncRNAs), 116 microRNAs (miRNAs), and 7977 mRNAs and obtained 10 lncRNA-associated ceRNAs that may be regulating potential target genes involved in cancer-related pathways by sponging 25 miRNAs in TMZ-resistant GBM. Among these, two lncRNAs named ARFRP1 and RUSC2 regulate five target genes (IRS1, FOXG1, GNG2, RUNX2, and CACNA1E) involved in AMPK, AKT, mTOR, and TGF-β signaling pathways that activate or inhibit autophagy causing TMZ resistance. The novel lncRNA-associated ceRNA network predicted in GBM offers a fresh viewpoint on TMZ resistance, which might contribute to treating this malignancy.

Autophagy and Senescence: The Molecular Mechanisms and Implications in Liver Diseases

The liver is the primary organ accountable for complex physiological functions, including lipid metabolism, toxic chemical degradation, bile acid synthesis, and glucose metabolism. Liver function homeostasis is essential for the stability of bodily functions and is involved in the complex regulation of the balance between cell proliferation and cell death. Cell proliferation-halting mechanisms, including autophagy and senescence, are implicated in the development of several liver diseases, such as cholestasis, viral hepatitis, nonalcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Among various cell death mechanisms, autophagy is a highly conserved and self-degradative cellular process that recycles damaged organelles, cellular debris, and proteins. This process also provides the substrate for further metabolism. A defect in the autophagy machinery can lead to premature diseases, accelerated aging, inflammatory state, tumorigenesis, and cellular senescence. Senescence, another cell death type, is an active player in eliminating premalignant cells. At the same time, senescent cells can affect the function of neighboring cells by secreting the senescence-associated secretory phenotype and induce paracrine senescence. Autophagy can promote and delay cellular senescence under different contexts. This review decodes the roles of autophagy and senescence in multiple liver diseases to achieve a better understanding of the regulatory mechanisms and implications of autophagy and senescence in various liver diseases.

Crosstalk between autophagy and insulin resistance: evidence from different tissues

Insulin is a critical hormone that promotes energy storage in various tissues, as well as anabolic functions. Insulin resistance significantly reduces these responses, resulting in pathological conditions, such as obesity and type 2 diabetes mellitus (T2DM). The management of insulin resistance requires better knowledge of its pathophysiological mechanisms to prevent secondary complications, such as cardiovascular diseases (CVDs). Recent evidence regarding the etiological mechanisms behind insulin resistance emphasizes the role of energy imbalance and neurohormonal dysregulation, both of which are closely regulated by autophagy. Autophagy is a conserved process that maintains homeostasis in cells. Accordingly, autophagy abnormalities have been linked to a variety of metabolic disorders, including insulin resistance, T2DM, obesity, and CVDs. Thus, there may be a link between autophagy and insulin resistance. Therefore, the interaction between autophagy and insulin function will be examined in this review, particularly in insulin-responsive tissues, such as adipose tissue, liver, and skeletal muscle.

Limited Bariatric Surgery-induced Weight Loss in Subjects With Type 2 Diabetes: Predictor Variables in Adipose Tissue

CONTEXT

The impact of type 2 diabetes mellitus (T2D) at baseline on limited weight loss (WL) after bariatric surgery (BS) remains controversial, and the potential underlying mechanisms incompletely understood.

OBJECTIVE

We aimed at gaining further insight on this relationship and identifying novel associations between adipose tissue (AT) parameters and short-term WL outcomes in subjects with or without T2D undergoing BS.

METHODS

Mid-term WL trajectories after BS have been evaluated in a cohort of 1659 subjects (cohort 1) with (n = 543) and without T2D (n = 1116). Paired subcutaneous and visceral AT samples were obtained from a cohort of 48 pairs of subjects with and without T2D matched for age, sex, BMI, and type of BS (cohort 2). Differences in AT parameters between groups were evaluated and potential associations with WL response explored.

RESULTS

T2D was independently associated with a 5% lesser mid-term WL in cohort 1, while HbA1c, insulin treatment, and number of T2D medications prior to BS were only related to short-term WL outcomes. In cohort 2, a number of differentially expressed genes in AT were identified between groups, while fat cell size and fibrosis were comparable. Subcutaneous ATG7 expression was found as an independent predictor of limited WL 1 year after surgery (β: -12.21 ± 4.41, P = .008) and its addition to a clinical model significantly improved the amount of WL variability explained (R2 = 0.131 vs R2 = 0.248, F change P = .009).

CONCLUSION

Our results highlight the importance of T2D as determinant of limited WL following BS and suggest that dysregulated macroautophagy in subcutaneous AT may contribute to this association.

Amino acids contribute to adaptive thermogenesis. New insights into the mechanisms of action of recent drugs for metabolic disorders are emerging

Adaptive thermogenesis is the heat production by muscle contractions (shivering thermogenesis) or brown adipose tissue (BAT) and beige fat (non-shivering thermogenesis) in response to external stimuli, including cold exposure. BAT and beige fat communicate with peripheral organs and the brain through a variegate secretory and absorption processes - controlling adipokines, microRNAs, extracellular vesicles, and metabolites - and have received much attention as potential therapeutic targets for managing obesity-related disorders. The sympathetic nervous system and norepinephrine-releasing adipose tissue macrophages (ATM) activate uncoupling protein 1 (UCP1), expressed explicitly in brown and beige adipocytes, dissolving the electrochemical gradient and uncoupling tricarboxylic acid cycle and the electron transport chain from ATP production. Mounting evidence has attracted attention to the multiple effects of dietary and endogenously synthesised amino acids in BAT thermogenesis and metabolic phenotype in animals and humans. However, the mechanisms implicated in these processes have yet to be conclusively characterized. In the present review article, we aim to define the principal investigation areas in this context, including intestinal microbiota constitution, adipose autophagy modulation, and secretome and metabolic fluxes control, which lead to increased brown/beige thermogenesis. Finally, also based on our recent epicardial adipose tissue results, we summarise the evidence supporting the notion that the new dual and triple agonists of glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and glucagon (GCG) receptor - with never before seen weight loss and insulin-sensitizing efficacy - promote thermogenic-like amino acid profiles in BAT with robust heat production and likely trigger sympathetic activation and adaptive thermogenesis by controlling amino acid metabolism and ATM expansion in BAT and beige fat.

Computational modeling of AMPK and mTOR crosstalk in glutamatergic synapse calcium signaling

Neuronal energy consumption is vital for information processing and memory formation in synapses. The brain consists of just 2% of the human body's mass, but consumes almost 20% of the body's energy budget. Most of this energy is attributed to active transport in ion signaling, with calcium being the canonical second messenger of synaptic transmission. Here, we develop a computational model of synaptic signaling resulting in the activation of two protein kinases critical in metabolic regulation and cell fate, AMP-Activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) and investigate the effect of glutamate stimulus frequency on their dynamics. Our model predicts that frequencies of glutamate stimulus over 10 Hz perturb AMPK and mTOR oscillations at higher magnitudes by up to 36% and change the area under curve (AUC) by 5%. This dynamic difference in AMPK and mTOR activation trajectories potentially differentiates high frequency stimulus bursts from basal neuronal signaling leading to a downstream change in synaptic plasticity. Further, we also investigate the crosstalk between insulin receptor and calcium signaling on AMPK and mTOR activation and predict that the pathways demonstrate multistability dependent on strength of insulin signaling and metabolic consumption rate. Our predictions have implications for improving our understanding of neuronal metabolism, synaptic pruning, and synaptic plasticity.

From Diabetes to Diabetic Complications: Role of Autophagy

Diabetes and its complications reduce quality of life and are life-limiting. At present, diabetes treatment consists of hypoglycemic agents to control blood glucose and the use of insulin-sensitizing drugs to overcome insulin resistance. In diabetes, autophagy is impaired and thus there is poor intracellular environment homeostasis. Pancreatic β-cells and insulin target tissues are protected by enhancing autophagy. Autophagy decreases β-cell apoptosis, promotes β-cell proliferation, and alleviates insulin resistance. Autophagy in diabetes is regulated by the mammalian target of rapamycin (mTOR)/adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) pathway and others. Autophagy enhancers can likely be used as a treatment for diabetes and its complications. This review examines the evidence linking autophagy to diabetes.

Deficiency of lipopolysaccharide binding protein facilitates adipose browning, glucose uptake and oxygen consumption in mouse embryonic fibroblasts via activating PI3K/Akt/mTOR pathway and inhibiting autophagy

This study aimed to explore the role of lipopolysaccharide-binding protein (LBP) in adipose browning. Mouse embryonic fibroblasts (MEFs) were treated with differentiation induction reagents and Perifosine (Akt inhibitor), with the transfection of Atg5, short hairpin RNA targeting LBP (shLBP), and Atg5 (shAtg5). The expression levels of LBP, inflammatory markers , brown fat markers, lipid metabolism marker, autophagy markers, insulin signaling-related molecules , p-mTOR, mTOR, p-Akt, Akt, p-PI3K, and PI3K were quantified or determined by Western blot, qRT-PCR, and immunofluorescence assay. The formation of lipid was examined through Oil red O staining assay. The consumption of oxygen was assessed using a Seahorse XF96 analyzer, and the uptake of glucose was evaluated by [³H]-2-deoxy-D-glucose uptake assay. Deficiency of LBP promoted adipose browning, oxygen consumption, glucose uptake, and insulin sensitivity in differentiated MEFs, where it inhibited inflammation and autophagy. All of the effects above were reversed by Atg5 overexpression. Meanwhile, the knockdown of Atg5 strengthened the activation of PI3K/Akt/mTOR pathway induced by the depletion of LBP, while Perifosine partly reversed the activation of differentiated MEFs. The knockdown of LBP facilitated adipose browning, glucose uptake, and oxygen consumption in MEFs via the activation of PI3K/Akt/mTOR pathway and the inhibition of autophagy.

Carica Papaya Reduces High Fat Diet and Streptozotocin-Induced Development of Inflammation in Adipocyte via IL-1β/IL-6/TNF-α Mediated Signaling Mechanisms in Type-2 Diabetic Rats

The prevalence of obesity in contemporary society has brought attention to how serious it is all around the world. Obesity, a proinflammatory condition defined by hypertrophied adipocytes and immune cells that reside in adipose tissue, is characterized by elevated circulating levels of proinflammatory cytokines. The pro-inflammatory mediators trigger a number of inflammatory pathways and affect the phosphorylation of a number of insulin-signaling pathways in peripheral tissues. In this work, we pointed the outcome of the leaves of Carica papaya (C. papaya) on the inflammatory molecules by in vivo and in silico analysis in order to prove its mechanisms of action. Adipocytokines, antioxidant enzymes, gene and protein expression of pro-inflammatory signaling molecules (mTOR, TNF-α, IL-1β, IL-6 and IKKβ) by q-RT-PCR and immunohistochemistry, as well as histopathological analysis, in adipose tissues were carried out. C. papaya reinstated the levels of adipocytokines, antioxidant enzymes and mRNA levels of mTOR, TNF-α, IL-1β, IL-6 and IKKβ in the adipose tissues of type 2 diabetic rats. Molecular docking and dynamics simulation studies revealed that caffeic acid, transferulic acid and quercetin had the top hit rates against IKKβ, TNF-α, IL-6, IL-1β, and mTOR. This study concludes that C. papaya put back the altered effects in fatty tissue of type 2 diabetic rats by restoring the adipocytokines and the gene expression.

The Neuronal and Non-Neuronal Pathways of Sodium-Glucose Cotransporter-2 Inhibitor on Body Weight-Loss and Insulin Resistance

With the emergence of sodium-glucose cotransporter 2 inhibitors (SGLT2i), the treatment of type 2 diabetes mellitus (T2DM) has achieved a new milestone, of which the insulin-independent mechanism could produce weight loss, improve insulin resistance (IR) and exert other protective effects. Besides the well-acknowledged biochemical processes, the dysregulated balance between sympathetic and parasympathetic activity may play a significant role in IR and obesity. Weight loss caused by SGLT-2i could be achieved via activating the liver-brain-adipose neural axis in adipocytes. We previously demonstrated that SGLT-2 are widely expressed in central nervous system (CNS) tissues, and SGLT-2i could inhibit central areas associated with autonomic control through unidentified pathways, indicating that the role of the central sympathetic inhibition of SGLT-2i on blood pressure and weight loss. However, the exact pathway of SGLT2i related to these effects and to what extent it depends on the neural system are not fully understood. The evidence of how SGLT-2i interacts with the nervous system is worth exploring. Therefore, in this review, we will illustrate the potential neurological processes by which SGLT2i improves IR in skeletal muscle, liver, adipose tissue, and other insulin-target organs via the CNS and sympathetic nervous system/parasympathetic nervous system (SNS/PNS).

The PTP1B inhibitor MSI-1436 ameliorates liver insulin sensitivity by modulating autophagy, ER stress and systemic inflammation in Equine metabolic syndrome affected horses

BACKGROUND

Equine metabolic syndrome (EMS) is a multifactorial pathology gathering insulin resistance, low-grade inflammation and past or chronic laminitis. Among the several molecular mechanisms underlying EMS pathogenesis, increased negative insulin signalling regulation mediated by protein tyrosine phosphatase 1 B (PTP1B) has emerged as a critical axis in the development of liver insulin resistance and general metabolic distress associated to increased ER stress, inflammation and disrupted autophagy. Thus, the use of PTP1B selective inhibitors such as MSI-1436 might be considered as a golden therapeutic tool for the proper management of EMS and associated conditions. Therefore, the present investigation aimed at verifying the clinical efficacy of MSI-1436 systemic administration on liver metabolic balance, insulin sensitivity and inflammatory status in EMS affected horses. Moreover, the impact of MSI-1436 treatment on liver autophagy machinery and associated ER stress in liver tissue has been analysed.

METHODS

Liver explants isolated from healthy and EMS horses have been treated with MSI-1436 prior to gene and protein expression analysis of main markers mediating ER stress, mitophagy and autophagy. Furthermore, EMS horses have been intravenously treated with a single dose of MSI-1436, and evaluated for their metabolic and inflammatory status.

RESULTS

Clinical application of MSI-1436 to EMS horses restored proper adiponectin levels and attenuated the typical hyperinsulinemia and hyperglycemia. Moreover, administration of MSI-1436 further reduced the circulating levels of key pro-inflammatory mediators including IL-1β, TNF-α and TGF-β and triggered the Tregs cells activation. At the molecular level, PTP1B inhibition resulted in a noticeable mitigation of liver ER stress, improvement of mitochondrial dynamics and consequently, a regulation of autophagic response. Similarly, short-term ex vivo treatment of EMS liver explants with trodusquemine (MSI-1436) substantially enhanced autophagy by upregulating the levels of HSC70 and Beclin-1 at both mRNA and protein level. Moreover, the PTP1B inhibitor potentiated mitophagy and associated expression of MFN2 and PINK1. Interestingly, inhibition of PTP1B resulted in potent attenuation of ER stress key mediators' expression namely, CHOP, ATF6, HSPA5 and XBP1.

CONCLUSION

Presented findings shed for the first time promising new insights in the development of an MSI-1436-based therapy for proper equine metabolic syndrome intervention and may additionally find potential translational application to human metabolic syndrome treatment.

Yunpi Heluo decoction reduces ectopic deposition of lipids by regulating the SIRT1-FoxO1 autophagy pathway in diabetic rats

CONTEXT

Yunpi Heluo (YPHL) decoction is a Chinese herbal formula with particular advantages for treating type 2 diabetes. Yet, its exact mechanism of action is not fully understood.

OBJECTIVE

To examine the therapeutic effect of YPHL on ectopic lipid deposition (EDL) in Zucker diabetic fatty (ZDF) rats and the underlying mechanism.

MATERIALS AND METHODS

The ZDF Rats were randomized into five groups, including model, YPHL (200 mg/kg/d for 10 weeks), SIRT1-overexpression (injected with HBAAV2/9-r-SIRT1-3'-flag-GFP), NC (injected with HBAAV2/9-CMV-GFP as blank control) and control group. Pancreatic β-cells obtained from high-lipid-high-glucose fed rats were treated with YPHL (10 mg/mL) for 48 h. Lipid deposition and autophagosomes were analyzed by transmission electron microscopy. Intracellular H₂O₂ and ROS concentrations were measured by flow cytometry. SIRT1, FOXO1, LC3 and P62 mRNA and protein levels were analyzed using qRT-PCR and Western blots.

RESULTS

Compared with the model group, blood glucose levels in YPHL and si-SIRT1 groups were reduced by 19.3% and 27.9%, respectively. In high-lipid-high-glucose cells treated with YPHL, lipid droplets were reduced and decrease in apoptosis rate (38.6%), H₂O₂ (31.2%) and ROS (44.5%) levels were observed. After YPHL intervention or SIRT1 overexpression, LC3 and p62 expression increased. Protein expression of SIRT1 and LC3 in model, si-SIRT1, si-NC and si-SIRT1 + YPHL groups was lower than those in control group, while FoxO1 expression was increased. All of these protein level alterations were reversed in the si-NC + YPHL group.

DISCUSSION AND CONCLUSIONS

YPHL reduced EDL by regulating the SIRT1-FoxO1 autophagy pathway in diabetic rats, which could lead to future perspectives for the treatment of diabetes.

Effects of captopril on glucose metabolism and autophagy in liver and muscle from mice with type 1 diabetes and diet-induced obesity

Impaired metabolic functions underlie the pathophysiology of diabetes and obesity. The renin-angiotensin system (RAS) is one pathway related to the pathophysiology of both diseases. RAS activation in metabolically active tissues exerts pro-inflammatory effects via angiotensin II (Ang II), linked to dysfunction in cellular processes such as autophagy, which is associated with obesity and diabetes. Here, we determined whether RAS is involved in metabolic dysregulations in a Type 1 Diabetes (T1D) mouse model, treated with captopril, and in an obesity mouse model (Agt-Tg) that overexpresses angiotensinogen (Agt) in adipose tissue. T1D mice had lower plasma leptin, resistin and higher non-esterified fatty acids (NEFA) compared to wild type (Wt) mice, even under captopril treatment. Further, mRNA levels for Agt, At1, Insr, and Beclin1 were upregulated in muscle and liver of T1D mice with captopril compared to Wt. Moreover, autophagy markers LC3 and p62 proteins were decreased, regardless of captopril treatment in the liver from T1D mice. In obese Wt mice, captopril increased muscle Irs1 gene levels. Further, captopril reduced mRNA levels of At1, Insr, Ampk, Beclin1, Atg12, and Lc3 in the liver from both Wt and Agt-Tg mice, while Agt, At1, Insr, and Atg12 expression was reduced in Agt-Tg mice without captopril treatment. Irs1 expression was decreased in the liver from obese Wt mice treated with captopril. Our results suggest that captopril treatment upregulates components of RAS, insulin signaling, and autophagy in both muscle and liver, indicating potential utility of captopril in targeting both insulin sensitivity and autophagy in diabetes and obesity.

Autophagy in adipogenesis: Molecular mechanisms and regulation by bioactive compounds

White adipose tissue expands rapidly due to increased adipocyte number (hyperplasia) and size (hypertrophy), which results in obesity. Adipogenesis is a process of the formation of mature adipocytes from precursor cells. Additionally, obesity-related metabolic complications, such as fatty liver and insulin resistance, are linked to adipogenesis. On the contrary, autophagy is a catabolic process; essential to maintain cellular homeostasis via the degradation or recycling of unnecessary or damaged components. Importantly, autophagy dictates obesity and adipogenesis. Hence, a clear understanding of how autophagy regulates adipogenesis is crucial for drug development and the prevention and treatment of obesity and its associated disorders, such as type 2 diabetes, cardiovascular disease, and cancer. In this review, we highlighted recent findings regarding the crosstalk between adipogenesis and autophagy, as well as the molecules involved. Furthermore, the review discussed how bioactive compounds regulate adipogenesis by manipulating autophagy and underlying molecular mechanisms. Based on in vitro and animal studies, we summarized the effects of bioactive compounds on adipogenesis and autophagy. Hence, human studies are necessary to validate the effectiveness and optimal dosage of these bioactive compounds.

Evolution of drug-eluting coronary stents: a back-and-forth journey from the bench-to-bedside

Coronary stents have revolutionized the treatment of coronary artery disease. Compared with balloon angioplasty, bare-metal stents effectively prevented abrupt vessel closure but were limited by in-stent restenosis due to smooth muscle cell proliferation and neointimal hyperplasia. The first-generation drug-eluting stent (DES), with its antiproliferative drug coating, offered substantial advantages over bare-metal stents as it mitigated the risk of in-stent restenosis. Nonetheless, they had several design limitations that increased the risk of late stent thrombosis. Significant advances in stent design, including thinner struts, enhanced polymers' formulation, and more potent antiproliferative agents, have led to the introduction of new-generation DES with a superior safety profile. Cardiologists have over 20 different DES types to choose from, each with its unique features and characteristics. This review highlights the evolution of stent design and summarizes the clinical data on the different stent types. We conclude by discussing the clinical implications of stent design in high-risk subsets of patients.

Integrating the effects of sucrose intake on the brain and white adipose tissue: Could autophagy be a possible link?

Excess dietary sucrose is associated with obesity and metabolic diseases. This relationship is driven by the malfunction of several cell types and tissues critical for the regulation of energy balance, including hypothalamic neurons and white adipose tissue (WAT). However, the mechanisms behind these effects of dietary sucrose are still unclear and might be independent of increased adiposity. Accumulating evidence has indicated that dysregulation of autophagy, a fundamental process for maintenance of cellular homeostasis, alters energy metabolism in hypothalamic neurons and WAT, but whether autophagy could mediate the detrimental effects of dietary sucrose on hypothalamic neurons and WAT that contribute to weight gain is a matter of debate. In this review, we examine the hypothesis that dysregulated autophagy in hypothalamic neurons and WAT is an adiposity-independent effect of sucrose that contributes to increased body weight gain. We propose that excess dietary sucrose leads to autophagy unbalance in hypothalamic neurons and WAT, which increases caloric intake and body weight, favoring the emergence of obesity and metabolic diseases.

Early metabolic impairment as a contributor to neurodegenerative disease: Mechanisms and potential pharmacological intervention

The metabolic syndrome comprises a family of clinical and laboratory findings, including insulin resistance, hyperglycemia, hypertriglyceridemia, low high-density lipoprotein cholesterol levels, and hypertension, in addition to central obesity. The syndrome confers a high risk of cardiovascular mortality. Indeed, metabolic dysfunction has been shown to cause a direct insult to smooth muscle and endothelial components of the vasculature, which leads to vascular dysfunction and hyperreactivity. This, in turn, causes cerebral vasoconstriction and hypoperfusion, eventually contributing to cognitive deficits. Moreover, the metabolic syndrome disrupts key homeostatic processes in the brain, including apoptosis, autophagy, and neurogenesis. Impairment of such processes in the context of metabolic dysfunction has been implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer, Parkinson, and Huntington diseases. The aim of this review is to elucidate the role that the metabolic syndrome plays in the pathogenesis of the latter disorders, with a focus on the role of perivascular adipose inflammation in the peripheral-to-central transduction of the inflammatory insult. This review delineates common signaling pathways that contribute to these pathologies. Moreover, the role of therapeutic agents aimed at treating the metabolic syndrome, as well as their risk factors that interfere with the aforementioned pathways, are discussed as potential interventions for neurodegenerative diseases.

Plin5, a New Target in Diabetic Cardiomyopathy

Abnormal lipid accumulation is commonly observed in diabetic cardiomyopathy (DC), which can create a lipotoxic microenvironment and damage cardiomyocytes. Lipid toxicity is an important pathogenic factor due to abnormal lipid accumulation in DC. As a lipid droplet (LD) decomposition barrier, Plin5 can protect LDs from lipase decomposition and regulate lipid metabolism, which is involved in the occurrence and development of cardiovascular diseases. In recent years, studies have shown that Plin5 expression is involved in the pathogenesis of DC lipid toxicity, such as oxidative stress, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, and insulin resistance (IR) and has become a key target of DC research. Therefore, understanding the relationship between Plin5 and DC progression as well as the mechanism of this process is crucial for developing new therapeutic approaches and exploring new therapeutic targets. This review is aimed at exploring the latest findings and roles of Plin5 in lipid metabolism and DC-related pathogenesis, to explore possible clinical intervention approaches.

Roux-en-Y Gastric Bypass Modulates AMPK, Autophagy and Inflammatory Response in Leukocytes of Obese Patients

Obesity is characterized by low-grade chronic inflammation, metabolic overload, and impaired endothelial and cardiovascular function. Roux-en-Y gastric bypass (RYGB) results in amelioration of the pro-oxidant status of leukocytes and the metabolic profile. Nevertheless, little is known about the precise mechanism that drives systemic and metabolic improvements following bariatric surgery. In this cohort study, we investigated the effect of RYGB on molecular pathways involving energy homeostasis in leukocytes in 43 obese subjects one year after surgery. In addition to clinical and biochemical parameters, we determined protein expression of systemic proinflammatory cytokines by Luminex®, different markers of inflammation, endoplasmic reticulum (ER) stress, autophagy/mitophagy by western blot, and mitochondrial membrane potential by fluorescence imaging. Bariatric surgery induced an improvement in metabolic outcomes that was accompanied by a systemic drop in hsCRP, IL6, and IL1β levels, and a slowing down of intracellular inflammatory pathways in leukocytes (NF-κB and MCP-1), an increase in AMPK content, a reduction of ER stress (ATF6 and CHOP), augmented autophagy/mitophagy markers (Beclin 1, ATG5, LC3-I, LC3-II, NBR1, and PINK1), and a decrease of mitochondrial membrane potential. These findings shed light on the specific molecular mechanisms by which RYGB facilitates metabolic improvements, highlighting the relevance of pathways involving energy homeostasis as key mediators of these outcomes. In addition, since leukocytes are particularly exposed to physiological changes, they could be used in routine clinical practice as a good sensor of the whole body’s responses.

The mixed blessing of AMPK signaling in Cancer treatments

Background

Nutrient acquisition and metabolism pathways are altered in cancer cells to meet bioenergetic and biosynthetic demands. A major regulator of cellular metabolism and energy homeostasis, in normal and cancer cells, is AMP-activated protein kinase (AMPK). AMPK influences cell growth via its modulation of the mechanistic target of Rapamycin (mTOR) pathway, specifically, by inhibiting mTOR complex mTORC1, which facilitates cell proliferation, and by activating mTORC2 and cell survival. Given its conflicting roles, the effects of AMPK activation in cancer can be counter intuitive. Prior to the establishment of cancer, AMPK acts as a tumor suppressor. However, following the onset of cancer, AMPK has been shown to either suppress or promote cancer, depending on cell type or state.

Methods

To unravel the controversial roles of AMPK in cancer, we developed a computational model to simulate the effects of pharmacological maneuvers that target key metabolic signalling nodes, with a specific focus on AMPK, mTORC, and their modulators. Specifically, we constructed an ordinary differential equation-based mechanistic model of AMPK-mTORC signaling, and parametrized the model based on existing experimental data.

Results

Model simulations were conducted to yield the following predictions: (i) increasing AMPK activity has opposite effects on mTORC depending on the nutrient availability; (ii) indirect inhibition of AMPK activity through inhibition of sirtuin 1 (SIRT1) only has an effect on mTORC activity under conditions of low nutrient availability; (iii) the balance between cell proliferation and survival exhibits an intricate dependence on DEP domain-containing mTOR-interacting protein (DEPTOR) abundance and AMPK activity; (iv) simultaneous direct inhibition of mTORC2 and activation of AMPK is a potential strategy for suppressing both cell survival and proliferation.

Conclusions

Taken together, model simulations clarify the competing effects and the roles of key metabolic signalling pathways in tumorigenesis, which may yield insights on innovative therapeutic strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09211-1.

Autophagy: a molecular switch to regulate adipogenesis and lipolysis

Obesity is a complex epidemic disease caused by an imbalance of adipose tissue function that results in hyperglycemia, hyperlipidemia and insulin resistance which further develop into type 2 diabetes, cardiovascular disease and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. Adipose tissue is responsible for fat storage; white adipose tissue stores excess energy as fat for availability during starvation, whereas brown adipose tissue regulates thermogenesis through fat oxidation using uncoupling protein 1. However, hypertrophic fat storage results in inflammation and increase the chances for obesity which triggers autophagy genes and lipolytic enzymes to regulate lipid metabolism. Autophagy degrades cargo molecule with the help of lysosome and redistributes the energy back to the cell. Autophagy regulates adipocyte differentiation by modulating master regulators of adipogenesis. Adipogenesis is the process which stores excessive energy in the form of lipid droplets. Lipid droplets (LD) are dynamic cellular organelles that store toxic free-fatty acids into neutral triglycerides in adipose tissue. LD activates both lipolysis and lipophagy to degrade excess triglycerides. In obese tissue, autophagy is activated via pro-inflammatory cytokines produced by surplus fat stored in the adipose tissue. This review focused on the process of autophagy and adipogenesis and the transcription factors that regulate lipogenesis and lipolysis in the adipose tissue. We have also discussed about the importance of autophagic regulation within adipose tissue which controls the onset of obesity and its associated diseases.

The Association Between Leucine and Diabetic Retinopathy in Different Genders: A Cross-Sectional Study in Chinese Patients With Type 2 Diabetes

OBJECTIVE

To explore the association between serum leucine (leu) and diabetic retinopathy (DR) in patients with type 2 diabetes (T2D) and then to analyze the influence of gender on the association.

METHOD

The electronic medical records of 1,149 T2D patients who met inclusion and exclusion criteria were retrieved from the Second Affiliated Hospital of Dalian Medical University and the First Affiliated Hospital of Jinzhou Medical University. Serum leu levels of all subjects were measured by liquid chromatography-mass spectrometry. Logistic regression was used to obtain the odds ratio (OR) and CI of leu-DR risk in multiple models. When using these models, restricted cubic spline (RCS) was used to test the potential non-linear relationship between multiple continuous independent variables, such as leu and DR (classification), and dependent variables. We also used the additive interaction method to evaluate the interaction effect between leu and gender on DR.

RESULTS

Leu was a protective factor of DR [0.78 (0.66, 0.92)]. When gender was divided into male and female, the above relationship was statistically significant only in men [0.73 (0.58, 0.94)]. Three indicators of additive interaction-RERI, AP, and S-suggested that there is no interaction between gender and leu on the risk of DR.

CONCLUSIONS

Male T2D patients with high leu levels may have a lower risk of DR.

Impact of Bariatric Surgery on Adipose Tissue Biology

Bariatric surgery (BS) procedures are actually the most effective intervention to help subjects with severe obesity achieve significant and sustained weight loss. White adipose tissue (WAT) is increasingly recognized as the largest endocrine organ. Unhealthy WAT expansion through adipocyte hypertrophy has pleiotropic effects on adipocyte function and promotes obesity-associated metabolic complications. WAT dysfunction in obesity encompasses an altered adipokine secretome, unresolved inflammation, dysregulated autophagy, inappropriate extracellular matrix remodeling and insufficient angiogenic potential. In the last 10 years, accumulating evidence suggests that BS can improve the WAT function beyond reducing the fat depot sizes. The causal relationships between improved WAT function and the health benefits of BS merits further investigation. This review summarizes the current knowledge on the short-, medium- and long-term outcomes of BS on the WAT composition and function.

A Decade of Mighty Lipophagy: What We Know and What Facts We Need to Know?

Lipids are integral cellular components that act as substrates for energy provision, signaling molecules, and essential constituents of biological membranes along with a variety of other biological functions. Despite their significance, lipid accumulation may result in lipotoxicity, impair autophagy, and lysosomal function that may lead to certain diseases and metabolic syndromes like obesity and even cell death. Therefore, these lipids are continuously recycled and redistributed by the process of selective autophagy specifically termed as lipophagy. This selective form of autophagy employs lysosomes for the maintenance of cellular lipid homeostasis. In this review, we have reviewed the current literature about how lipid droplets (LDs) are recruited towards lysosomes, cross-talk between a variety of autophagy receptors present on LD surface and lysosomes, and lipid hydrolysis by lysosomal enzymes. In addition to it, we have tried to answer most of the possible questions related to lipophagy regulation at different levels. Moreover, in the last part of this review, we have discussed some of the pathological states due to the accumulation of these LDs and their possible treatments under the light of currently available findings.

Downregulation of MAPK/MAK/MRK overlapping kinase 1 in peripheral blood mononuclear cells of pediatric patients with type 1 diabetes mellitus

Background: Type 1 diabetes mellitus (T1DM) is one of the most common endocrine diseases in children. T-cell autoreactivity toward β-cells is controlled by significant changes in metabolism of T cells. Mammalian target of rapamycin (mTOR) is an important intracellular regulator of metabolism and cell growth. MAPK/MAK/MRK overlapping kinase 1 (MOK1) is one of the less known regulators of mTOR. We sought to investigate if MOK1 and mTOR mRNA levels in peripheral blood mononuclear cells (PBMCs) of T1DM pediatric patients are different compared to healthy subjects. Methods: This study included 172 adolescents with T1DM and 36 healthy adolescent volunteers designated for control group (CG). MOK1 and mTOR mRNA levels were determined in PBMCs by qPCR. Results: T1DM patients have significant downregulation of MOK1 mRNA levels in PBMCs compared CG (P=0.018), while there was no significant difference in mTOR mRNA levels (P=0.891). Furthermore, in T1DM patients, MOK1 significantly correlated with age, BMI, triglycerides and mTOR, while mTOR correlated significantly with BMI and systolic blood pressure. Overweight T1DM subjects had significantly lower MOK1 (P=0.034) and mTOR (P=0.017) mRNA levels, together with significantly higher levels of systolic blood pressure (P<0.001), total cholesterol (P=0.001), LDL-cholesterol (P=0.001) and CRP (P<0.001). Multivariate analysis showed that MOK1 was independently negatively associated with T1DM when adjusted for sex, age, HDL-C and CRP (OR=0.417 (95%CI: 0.175-0.997), p=0.049). Conclusion: Our study demonstrated for the first time that T1DM is associated with MOK1 downregulation. In addition, downregulation of both mTOR and MOK1 gene expressions was associated with cardiovascular risk factors in overweight T1DM patients.

Mitophagy in Diabetic Cardiomyopathy: Roles and Mechanisms

Cardiovascular disease is the leading complication of diabetes mellitus (DM), and diabetic cardiomyopathy (DCM) is a major cause of mortality in diabetic patients. Multiple pathophysiologic mechanisms, including myocardial insulin resistance, oxidative stress and inflammation, are involved in the development of DCM. Recent studies have shown that mitochondrial dysfunction makes a substantial contribution to the development of DCM. Mitophagy is a type of autophagy that takes place in dysfunctional mitochondria, and it plays a key role in mitochondrial quality control. Although the precise molecular mechanisms of mitophagy in DCM have yet to be fully clarified, recent findings imply that mitophagy improves cardiac function in the diabetic heart. However, excessive mitophagy may exacerbate myocardial damage in patients with DCM. In this review, we aim to provide a comprehensive overview of mitochondrial quality control and the dual roles of mitophagy in DCM. We also propose that a balance between mitochondrial biogenesis and mitophagy is essential for the maintenance of cellular metabolism in the diabetic heart.

The effects of dietary vitamin D supplementation and in vitro 1,25 dihydroxyvitamin D3 treatment on autophagy in bone marrow-derived dendritic cells from high-fat diet-induced obese mice

Obesity is associated with the dysregulation of vitamin D metabolism and altered immune responses in bone marrow-derived dendritic cells (BMDCs). Vitamin D can affect the differentiation, maturation, and activation of dendritic cells (DCs) and regulate autophagy via vitamin D receptor signaling. Autophagy was shown to be involved in the functions of DCs. We investigated the effects of dietary vitamin D supplementation and in vitro 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) treatment on autophagy in BMDCs from control diet (CON)-fed lean and high-fat diet (HFD)-induced obese mice. C57BL/6 male mice were fed CON or HFD with 10% or 45% kcal fat, respectively, supplemented with 1,000 or 10,000 IU vitamin D/kg diet (vDC or vDS) for 12 weeks. BMDCs were generated by culturing bone marrow cells from the mice with 20 ng/mL rmGM-CSF and treated with 1 nM 1,25(OH)₂D₃. Maturation of BMDCs was induced by lipopolysaccharide (50 ng/mL) stimulation. Treatment with 1,25(OH)₂D₃ inhibited the expression of phenotypes related to DC function (MHC class Ⅱ, CD86, CD80) and production of IL-12p70 by BMDCs from control and obese mice, regardless of dietary vitamin D supplementation. LC3Ⅱ/Ⅰ and VPS34 protein levels increased, and p62 expression decreased, after 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC only. Vdr mRNA levels decreased following 1,25(OH)₂D₃ treatment of BMDCs in the HFD-vDC. In conclusion, autophagy flux was increased by 1,25(OH)₂D₃ treatment of the BMDCs in CON-vDC but not in the HFD-vDC group. This suggests that the decreased expression of Vdr following 1,25(OH)₂D₃ treatment might have affected autophagy flux in BMDCs from obese mice.

A nexus of miR-1271, PAX4 and ALK/RYK influences the cytoskeletal architectures in Alzheimer's Disease and Type 2 Diabetes

Alzheimer's Disease (AD) and Type 2 Diabetes (T2D) share a common hallmark of insulin resistance. Reportedly, two non-canonical Receptor Tyrosine Kinases (RTKs), ALK and RYK, both targets of the same micro RNA miR-1271, exhibit significant and consistent functional down-regulation in post-mortem AD and T2D tissues. Incidentally, both have Grb2 as a common downstream adapter and NOX4 as a common ROS producing factor. Here we show that Grb2 and NOX4 play critical roles in reducing the severity of both the diseases. The study demonstrates that the abundance of Grb2 in degenerative conditions, in conjunction with NOX4, reverse cytoskeletal degradation by counterbalancing the network of small GTPases. PAX4, a transcription factor for both Grb2 and NOX4, emerges as the key link between the common pathways of AD and T2D. Down-regulation of both ALK and RYK through miR-1271, elevates the PAX4 level by reducing its suppressor ARX via Wnt/β-Catenin signaling. For the first time, this study brings together RTKs beyond Insulin Receptor (IR) family, transcription factor PAX4 and both AD and T2D pathologies on a common regulatory platform.

The Physiological Role of Irisin in the Regulation of Muscle Glucose Homeostasis

Irisin is a myokine that primarily targets adipose tissue, where it increases energy expenditure and contributes to the beneficial effects of exercise through the browning of white adipose tissue. As our knowledge has deepened in recent years, muscle has been found to be a major target organ for irisin as well. Several studies have attempted to characterize the role of irisin in muscle to improve glucose metabolism through mechanisms such as reducing insulin resistance. Although they are very intriguing reports, some contradictory results make it difficult to grasp the whole picture of the action of irisin on muscle. In this review, we attempted to organize the current knowledge of the role of irisin in muscle glucose metabolism. We discussed the direct effects of irisin on glucose metabolism in three types of muscle, that is, skeletal muscle, smooth muscle, and the myocardium. We also describe irisin’s effects on mitochondria and its interactions with other hormones. Furthermore, to consider the relationship between the irisin-induced improvement of glucose metabolism in muscle and systemic disorders of glucose metabolism, we reviewed the results from animal interventional studies and human clinical studies.

Nutrient regulation of inflammatory signalling in obesity and vascular disease

Despite obesity and diabetes markedly increasing the risk of developing cardiovascular diseases, the molecular and cellular mechanisms that underlie this association remain poorly characterised. In the last 20 years it has become apparent that chronic, low-grade inflammation in obese adipose tissue may contribute to the risk of developing insulin resistance and type 2 diabetes. Furthermore, increased vascular pro-inflammatory signalling is a key event in the development of cardiovascular diseases. Overnutrition exacerbates pro-inflammatory signalling in vascular and adipose tissues, with several mechanisms proposed to mediate this. In this article, we review the molecular and cellular mechanisms by which nutrients are proposed to regulate pro-inflammatory signalling in adipose and vascular tissues. In addition, we examine the potential therapeutic opportunities that these mechanisms provide for suppression of inappropriate inflammation in obesity and vascular disease.

Communication Between Autophagy and Insulin Action: At the Crux of Insulin Action-Insulin Resistance?

Insulin is a paramount anabolic hormone that promotes energy-storage in adipose tissue, skeletal muscle and liver, and these responses are significantly attenuated in insulin resistance leading to type 2 diabetes. Contrasting with insulin's function, macroautophagy/autophagy is a physiological mechanism geared to the degradation of intracellular components for the purpose of energy production, building-block recycling or tissue remodeling. Given that both insulin action and autophagy are dynamic phenomena susceptible to the influence of nutrient availability, it is perhaps not surprising that there is significant interaction between these two major regulatory mechanisms. This review examines the crosstalk between autophagy and insulin action, with specific focus on dysregulated autophagy as a cause or consequence of insulin resistance.

Impact of diabetes mellitus on vascular healing process after everolimus-eluting stent implantation: An optical coherence tomography study

BACKGROUND/PURPOSE

To study the impact of diabetes mellitus (DM) on vascular healing process after implantation of everolimus-eluting stent (EES).

METHODS/MATERIALS

Data from 3 prospective studies (HEAL-EES, REVER, and RESERVOIR), including patients with EES implantation and OCT follow-up, were merged. Differences in vascular healing process assessed by OCT were compared between DM and non-DM using generalized estimating equations. Neointimal proliferation, neointimal signal pattern (high, low, and layered), and uncovered/malapposed struts were evaluated.

RESULTS

A total of 96 lesions (61 DM lesions and 35 non-DM lesions) were included. Mean OCT follow-up time was 8.9 ± 1.5 months and comparable between groups. DM were older, high frequently female and acute coronary syndrome, and received smaller stent than non-DM. No differences were observed in quantitative vascular healing process between groups. However, DM exhibited higher low and layered signal pattern neointima compared to non-DM at lesion level (p = 0.030) and cross-section level (p < 0.001). Uncovered/malapposed struts were comparable between groups.

CONCLUSIONS

Quantitative vascular healing process was comparable between groups. However, DM was significantly associated with low signal pattern, which is characteristic of focal inflammation, after EES implantation. Further study might be required to study relationship between neointimal signal pattern and clinical events.

Understanding the molecular mechanisms and role of autophagy in obesity

Vital for growth, proliferation, subsistence, and thermogenesis, autophagy is the biological cascade, which confers defence against aging and various pathologies. Current research has demonstrated de novo activity of autophagy in stimulation of biological events. There exists a significant association between autophagy activation and obesity, encompassing expansion of adipocytes which facilitates β cell activity. The main objective of the manuscript is to enumerate intrinsic role of autophagy in obesity and associated complications. The peer review articles published till date were searched using medical databases like PubMed and MEDLINE for research, primarily in English language. Obesity is characterized by adipocytic hypertrophy and hyperplasia, which leads to imbalance of lipid absorption, free fatty acid release, and mitochondrial activity. Detailed evaluation of obesity progression is necessary for its treatment and related comorbidities. Data collected in regard to etiological sustaining of obesity, has revealed hypothesized energy misbalance and neuro-humoral dysfunction, which is stimulated by autophagy. Autophagy regulates chief salvaging events for protein clustering, excessive triglycerides, and impaired mitochondria which is accompanied by oxidative and genotoxic stress in mammals. Autophagy is a homeostatic event, which regulates biological process by eliminating lethal cells and reprocessing physiological constituents, comprising of proteins and fat. Unquestionably, autophagy impairment is involved in metabolic syndromes, like obesity. According to an individual's metabolic outline, autophagy activation is essential for metabolism and activity of the adipose tissue and to retard metabolic syndrome i.e. obesity. The manuscript summarizes the perception of current knowledge on autophagy stimulation and its effect on the obesity.

New insight into the role of isorhamnetin as a regulator of insulin signaling pathway in type 2 diabetes mellitus rat model: Molecular and computational approach

We intended to examine the molecular mechanism of action of isorhamnetin (IHN) to regulate the pathway of insulin signaling. Molecular analysis, immunofluorescence, and histopathological examination were used to assess the anti-hyperglycemic and insulin resistance lowering effects of IHN in streptozotocin /high fat diet-induced type 2 diabetes using Wistar rats. At the microscopic level, treatment with IHN resulted in the restoration of myofibrils uniform arrangement and adipose tissue normal architecture. At the molecular level, treatment with IHN at three different doses showed a significant decrease in m-TOR, IGF1-R & LncRNA-RP11-773H22.4. expression and it up-regulated the expression of AKT2 mRNA, miR-1, and miR-3163 in both skeletal muscle and adipose tissue. At the protein level, IHN treated group showed a discrete spread with a moderate faint expression of m-TOR in skeletal muscles as well as adipose tissues. We concluded that IHN could be used in the in ameliorating insulin resistance associated with type 2 diabetes mellitus.

Delivery of RGD-modified liposome as a targeted colorectal carcinoma therapy and its autophagy mechanism

Liposomes are among the most extensively applied drug carriers due to their excellent biocompatibility, controllable size and ease of modification. In the present study, we prepared untargeted liposomes (LP) and targeting liposomes modified with Arg-Gly-Asp (RGD-LP), and Doxorubicin Hydrochloride (DOX) or fluorescent probe was loaded. RGD-LP/DOX was identified to be uniformly spherical in size 131.2 ± 2.7 nm. Based on flow cytometry analysis and the confocal laser scanning microscopy, RGD-LP had a higher uptake into HRT-18 colorectal cancer cells than LP. Further, in vivo imaging study further suggested that RGD-LP could significantly increase the liposome accumulation in the tumour tissues of the mice bearing subcutaneous tumours. By investigating the targeting mechanism of RGD-LP, we found that they entered the cell via macropinocytosis. When loaded with DOX, RGD-LP exerted stronger tumour growth inhibitory activity against tumours of colorectal carcinoma compared to LP. Moreover, RGD-LP induced autophagy. Therefore, RGD-LP have the potential to be applied as a targeted colorectal carcinoma therapy.

NDRG1 Activity in Fat Depots Is Associated With Type 2 Diabetes and Impaired Incretin Profile in Patients With Morbid Obesity

OBJECTIVE

We aimed to investigate insulin-, mTOR- and SGK1-dependent signaling basal states in morbidly obese patients' fat. We analyzed the correlation between the signaling activity, carbohydrate metabolism, and incretin profiles of patients.

METHODS

The omental and subcutaneous fat was obtained in patients with obesity. The omental study included 16 patients with normal glucose tolerance (NGT) and 17 patients with type 2 diabetes mellitus (T2DM); the subcutaneous study included 9 NGT patients and 12 T2DM patients. Insulin resistance was evaluated using the hyperinsulinemic euglycemic clamp test and HOMA-IR index. The oral glucose tolerance test (OGTT) for NGT patients and mixed meal tolerance test (MMTT) for T2DM patients were performed. The levels of incretins (GLP-1, GIP, oxyntomodulin) and glucagon were measured during the tests. Signaling was analyzed by Western blotting in adipose tissue biopsies.

RESULTS

We have shown equal levels of basal phosphorylation of insulin- and mTOR-dependent signaling in omental fat depot in NGT and T2DM obese patients. Nevertheless, pNDRG1-T346 was decreased in omental fat of T2DM patients. Correlation analysis has shown an inverse correlation of pNDRG1-T346 in omental fat and diabetic phenotype (HbA1c, impaired incretin profile (AUC GLP-1, glucagon)). Moreover, pNDRG1-T346 in subcutaneous fat correlated with impaired incretin levels among obese patients (inverse correlation with AUC glucagon and AUC GIP).

CONCLUSIONS

According to results of the present study, we hypothesize that phosphorylation of pNDRG1-T346 can be related to impairment in incretin hormone processing. pNDRG1-T346 in adipose tissue may serve as a marker of diabetes-associated impairments of the systemic incretin profile and insulin sensitivity.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Adipose Morphology: a Critical Factor in Regulation of Human Metabolic Diseases and Adipose Tissue Dysfunction

Emerging evidence highlights that dysfunction of adipose tissue contributes to impaired insulin sensitivity and systemic metabolic deterioration in obese state. Of note, adipocyte hypertrophy serves as a critical event which associates closely with adipose dysfunction. An increase in cell size exacerbates hypoxia and inflammation as well as excessive collagen deposition, finally leading to metabolic dysregulation. Specific mechanisms of adipocyte hypertrophy include dysregulated differentiation and maturation of preadipocytes, enlargement of lipid droplets, and abnormal adipocyte osmolarity sensors. Also, weight loss therapies exert profound influence on adipocyte size. Here, we summarize the critical role of adipocyte hypertrophy in the development of metabolic disturbances. Future studies are required to establish a standard criterion of size measurement to better clarify the impact of adipocyte hypertrophy on changes in metabolic homeostasis.

Surface-associated lipid droplets: an intermediate site for lipid transport in human adipocytes?

Adipose tissue plays a major role in regulating whole-body energy metabolism. While the biochemical processes regulating storage and release of excess energy are well known, the temporal organization of these events is much less defined. In this study, we have characterized the presence of small surface-associated lipid droplets, distinct from the central droplet, in primary human adipocytes. Based on microscopy analyses, we illustrate the distribution of mitochondria, endoplasmic reticulum and lysosomes in the vicinity of these specialized lipid droplets. Ultrastructure analysis confirmed the presence of small droplets in intact adipose tissue. Further, CIDEC, known to bind and regulate lipid droplet expansion, clearly localized at these lipid droplets. Neither acute or prolonged stimulation with insulin or isoprenaline, or pharmacologic intervention to suppress lipid flux, affected the presence of these lipid droplets. Still, phosphorylated perilipin and hormone-sensitive lipase accumulated at these droplets following adrenergic stimuli, which supports metabolic activity at these locations. Altogether, we propose these lipid droplet clusters represent an intermediate site involved in lipid transport in primary adipocytes.

Role of Flavonoids in The Interactions among Obesity, Inflammation, and Autophagy

Nowadays, obesity is considered as one of the main concerns for public health worldwide, since it encompasses up to 39% of overweight and 13% obese (WHO) adults. It develops because of the imbalance in the energy intake/expenditure ratio, which leads to excess nutrients and results in dysfunction of adipose tissue. The hypertrophy of adipocytes and the nutrients excess trigger the induction of inflammatory signaling through various pathways, among others, an increase in the expression of pro-inflammatory adipocytokines, and stress of the endoplasmic reticulum (ER). A better understanding of obesity and preventing its complications are beneficial for obese patients on two facets: treating obesity, and treating and preventing the pathologies associated with it. Hitherto, therapeutic itineraries in most cases are based on lifestyle modifications, bariatric surgery, and pharmacotherapy despite none of them have achieved optimal results. Therefore, diet can play an important role in the prevention of adiposity, as well as the associated disorders. Recent results have shown that flavonoids intake have an essential role in protecting against oxidative damage phenomena, and presents biochemical and pharmacological functions beneficial to human health. This review summarizes the current knowledge of the anti-inflammatory actions and autophagic flux of natural flavonoids, and their molecular mechanisms for preventing and/or treating obesity.

Calcium-Sensing Receptor in Adipose Tissue: Possible Association with Obesity-Related Elevated Autophagy

Autophagy is upregulated in adipose tissue (AT) from people with obesity. We showed that activation of the calcium-sensing receptor (CaSR) elevates proinflammatory cytokines through autophagy in preadipocytes. Our aim is to understand the role of CaSR on autophagy in AT from humans with obesity. We determined mRNA and protein levels of CaSR and markers of autophagy by qPCR and western blot in human visceral AT explants or isolated primary preadipocytes (60 donors: 72% female, 23-56% body fat). We also investigated their association with donors' anthropometric variables. Donors' % body fat and CaSR mRNA expression in AT were correlated (r = 0.44, p < 0.01). CaSR expression was associated with mRNA levels of the autophagy markers atg5 (r = 0.37, p < 0.01), atg7 (r = 0.29, p < 0.05) and lc3b (r = 0.40, p < 0.01). CaSR activation increased becn and atg7 mRNA expression in AT. CaSR activation also upregulated LC3II by ~50%, an effect abolished by the CaSR inhibitor. Spermine (CaSR agonist) regulates LC3II through the ERK1/2 pathway. Structural equation model analysis suggests a link between donors' AT CaSR expression, AT autophagy and expression of Tumor Necrosis Factor alpha TNF-α. CaSR expression in visceral AT is directly associated with % body fat, and CaSR activation may contribute to obesity-related disruption in AT autophagy.

Hypoglycemic effects of polysaccharides from Gomphidiaceae rutilus fruiting bodies and their mechanisms

Insulin resistance is the main cause of type 2 diabetes, fatty liver and obesity. Our previous study found that mushroom polysaccharides improved insulin resistance in vitro, but the underlying mechanisms were still unknown. Thus, we investigate the hypoglycemic effects of polysaccharides from Gomphidiaceae rutilus fruiting bodies and their mechanisms. The total polysaccharides (AGRP) from Gomphidiaceae rutilus fruiting bodies and the neutral polysaccharide (AGRP-N) fraction both enhance insulin-stimulated glucose uptake in an autophagy-dependent manner in high glucose and fatty acid-treated hepatic cells, but not the acidic polysaccharide (AGRP-A) fraction. Further, we elucidate the oral hypoglycemic effects of polysaccharides on ob/ob mice. AGRP and AGRP-N lower blood glucose and improve insulin sensitivity. They inhibit liver lipid deposition, not only by activating AMPK to increase autophagy but also by increasing the expressions of PPARα and CPT-1a to enhance lipolysis. Our results provide a basis for the development of polysaccharides from Gomphidiaceae rutilus as a hypoglycemic healthy food.