Habenular TCF7L2 links nicotine addiction to diabetes

Acute nicotine activates orectic and inhibits anorectic brain regions in rats exposed to chronic nicotine

Nicotine use produces psychoactive effects, and chronic use is associated with physiological and psychological symptoms of addiction. However, chronic nicotine use is known to decrease food intake and body weight gain, suggesting that nicotine also affects central metabolic and appetite regulation. We recently showed that acute nicotine self-administration in nicotine-dependent animals produces a short-term increase in food intake, contrary to its long-term decrease of feeding behavior. As feeding behavior is regulated by complex neural signaling mechanisms, this study aimed to test the hypothesis that nicotine intake in animals exposed to chronic nicotine may increase activation of pro-feeding regions and decrease activation of pro-satiety regions to produce the acute increase in feeding behavior. FOS immunohistochemistry revealed that acute nicotine intake in nicotine self-administering animals increased activation of the pro-feeding arcuate and lateral hypothalamic nuclei and decreased activation of the pro-satiety parabrachial nucleus. Regional correlational analysis also showed that acute nicotine changes the functional connectivity of the hunger/satiety network. Further dissection of the role of the arcuate nucleus using electrophysiology found that putative POMC neurons in animals given chronic nicotine exhibited decreased firing following acute nicotine application. These brain-wide central signaling changes may contribute to the acute increase in feeding behavior we see in rats after acute nicotine and provide new areas of focus for studying both nicotine addiction and metabolic regulation.

Neuroscience in addiction research

The prevention and treatment of addiction (moderate to severe substance use disorder-SUD) have remained challenging because of the dynamic and complex interactions between multiple biological and social determinants that shape SUD. The pharmacological landscape is ever changing and the use of multiple drugs is increasingly common, requiring an unraveling of pharmacological interactions to understand the effects. There are different stages in the trajectory from drug use to addiction that are characterized by distinct cognitive and emotional features. These are directed by different neurobiological processes that require identification and characterization including those that underlie the high co-morbidity with other disorders. Finally, there is substantial individual variability in the susceptibility to develop SUD because there are multiple determinants, including genetics, sex, developmental trajectories and times of drug exposures, and psychosocial and environmental factors including commercial determinants that influence drug availability. Elucidating how these factors interact to determine risk is essential for identifying the biobehavioral basis of addiction and developing prevention and treatment strategies. Basic research is tasked with addressing each of these challenges. The recent proliferation of technological advances that allow for genetic manipulation, visualization of molecular reactions and cellular activity in vivo, multiscale whole brain mapping across the life span, and the mining of massive data sets including multimodality human brain imaging are accelerating our ability to understand how the brain functions and how drugs influence it. Here, we highlight how the application of these tools to the study of addiction promises to illuminate its neurobiological basis and guide strategies for prevention and treatment.

The interaction between insulin resistance and Alzheimer's disease: a review article

Insulin serves multiple functions as a growth-promoting hormone in peripheral tissues. It manages glucose metabolism by promoting glucose uptake into cells and curbing the production of glucose in the liver. Beyond this, insulin fosters cell growth, drives differentiation, aids protein synthesis, and deters degradative processes like glycolysis, lipolysis, and proteolysis. Receptors for insulin and insulin-like growth factor-1 are widely expressed in the central nervous system. Their widespread presence in the brain underscores the varied and critical functions of insulin signaling there. Insulin aids in bolstering cognition, promoting neuron extension, adjusting the release and absorption of catecholamines, and controlling the expression and positioning of gamma-aminobutyric acid (GABA). Importantly, insulin can effortlessly traverse the blood-brain barrier. Furthermore, insulin resistance (IR)-induced alterations in insulin signaling might hasten brain aging, impacting its plasticity and potentially leading to neurodegeneration. Two primary pathways are responsible for insulin signal transmission: the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway, which oversees metabolic responses, and the mitogen-activated protein kinase (MAPK) pathway, which guides cell growth, survival, and gene transcription. This review aimed to explore the potential shared metabolic traits between Alzheimer's disease (AD) and IR disorders. It delves into the relationship between AD and IR disorders, their overlapping genetic markers, and shared metabolic indicators. Additionally, it addresses existing therapeutic interventions targeting these intersecting pathways.

β-catenin/TCF4-induced SCUBE3 upregulation promotes ovarian cancer development via HIF-1 signaling pathway

The precise involvement and mechanistic role of the signal peptide-CUB-EGF-like domain-containing protein 3 (SCUBE3) in ovarian cancer (OV) remain poorly understood. Here, leveraging comprehensive data from the Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, we unveil the selective overexpression of SCUBE3 in ovarian cancer tissues and cells. Intriguingly, elevated SCUBE3 expression levels correlate with an unfavorable prognosis in patients. Through meticulous manipulation of SCUBE3 expression, we elucidate its consequential impact on in vitro proliferation and invasion of ovarian cancer cells, as well as in vivo tumor growth in mice. Our multifaceted investigations, encompassing luciferase reporter assays, chromatin immunoprecipitation (ChIP) experiments, and mining of public databases, successfully identify SCUBE3 as a direct downstream target gene of TCF4-a pivotal positive regulator within the β-catenin/TCF4 complex. Furthermore, utilizing a recessive mutant mouse line (kta41) harboring a functionally impaired point mutation at position 882 in the SCUBE3 gene, we uncover SCUBE3's involvement in the intricate regulation of angiogenesis and epithelial-mesenchymal transition (EMT). Strikingly, Spearman correlation coefficient analysis unveils a close association between SCUBE3 and HIF1A in OV, with SCUBE3 exerting tight control over HIF1A mRNA expression. Moreover, functional inhibition of HIF1A significantly impedes the pro-proliferative and invasive capabilities of SCUBE3-overexpressing ovarian cancer cells. Collectively, our findings underscore the pivotal role of SCUBE3 in driving ovarian cancer progression, shedding light on its intricate molecular mechanisms and establishing it as a potential therapeutic target for this devastating disease.

G9a Inhibition Promotes Neuroprotection through GMFB Regulation in Alzheimer's Disease

Epigenetic alterations are a fundamental pathological hallmark of Alzheimer's disease (AD). Herein, we show the upregulation of G9a and H3K9me2 in the brains of AD patients. Interestingly, treatment with a G9a inhibitor (G9ai) in SAMP8 mice reversed the high levels of H3K9me2 and rescued cognitive decline. A transcriptional profile analysis after G9ai treatment revealed increased gene expression of glia maturation factor β (GMFB) in SAMP8 mice. Besides, a H3K9me2 ChIP-seq analysis after G9a inhibition treatment showed the enrichment of gene promoters associated with neural functions. We observed the induction of neuronal plasticity and a reduction of neuroinflammation after G9ai treatment, and more strikingly, these neuroprotective effects were reverted by the pharmacological inhibition of GMFB in mice and cell cultures; this was also validated by the RNAi approach generating the knockdown of GMFB/Y507A.10 in Caenorhabditis elegans. Importantly, we present evidence that GMFB activity is controlled by G9a-mediated lysine methylation as well as we identified that G9a directly bound GMFB and catalyzed the methylation at lysine (K) 20 and K25 in vitro. Furthermore, we found that the neurodegenerative role of G9a as a GMFB suppressor would mainly rely on methylation of the K25 position of GMFB, and thus G9a pharmacological inhibition removes this methylation promoting neuroprotective effects. Then, our findings confirm an undescribed mechanism by which G9a inhibition acts at two levels, increasing GMFB and regulating its function to promote neuroprotective effects in age-related cognitive decline.

Insulin Resistance/Diabetes and Schizophrenia: Potential Shared Genetic Factors and Implications for Better Management of Patients with Schizophrenia

Schizophrenia is a complex psychotic disorder with co-occurring conditions, including insulin resistance and type 2 diabetes (T2D). It is well established that T2D and its precursors (i.e., insulin resistance) are more prevalent in patients with schizophrenia who are treated with antipsychotics, as well as in antipsychotic-naïve patients experiencing their first episode of psychosis, compared with the general population. However, the mechanism(s) underlying the increased susceptibility, shared genetics, and possible cause-effect relationship between schizophrenia and T2D remain largely unknown. The objective of this narrative review was to synthesize important studies, including Mendelian randomization (MR) analyses that have integrated genome-wide association studies (GWAS), as well as results from in vitro models, in vivo models, and observational studies of patients with schizophrenia. Both GWAS and MR studies have found that schizophrenia and T2D/insulin resistance share genetic risk factors, and this may mediate a connection between peripheral or brain insulin resistance and T2D with cognition impairment and an increased risk of developing prediabetes and T2D in schizophrenia. Moreover, accumulating evidence supports a causal role for insulin resistance in schizophrenia and emphasizes the importance of a genetic basis for susceptibility to T2D in patients with schizophrenia before they receive psychotic treatment. The present findings and observations may have clinical implications for the development of better strategies to treat patients with schizophrenia, with both pharmacological (i.e., samidorphan, empagliflozin) and/or nonpharmacological (i.e., lifestyle changes) approaches. Additionally, this review may benefit the design of future studies by physicians and clinical investigators.

Host genetics and gut microbiota jointly regulate blood biochemical indicators in chickens

Blood biochemical indicators play a crucial role in assessing an individual's overall health status and metabolic function. In this study, we measured five blood biochemical indicators, including total cholesterol (CHOL), low-density lipoprotein cholesterol (LDL-CH), triglycerides (TG), high-density lipoprotein cholesterol (HDL-CH), and blood glucose (BG), as well as 19 growth traits of 206 male chickens. By integrating host whole-genome information and 16S rRNA sequencing of the duodenum, jejunum, ileum, cecum, and feces microbiota, we assessed the contributions of host genetics and gut microbiota to blood biochemical indicators and their interrelationships. Our results demonstrated significant negative phenotypic and genetic correlations (r =  - 0.20 ~  - 0.67) between CHOL and LDL-CH with growth traits such as body weight, abdominal fat content, muscle content, and shin circumference. The results of heritability and microbiability indicated that blood biochemical indicators were jointly regulated by host genetics and gut microbiota. Notably, the heritability of HDL-CH was estimated to be 0.24, while the jejunal microbiability for BG and TG reached 0.45 and 0.23. Furthermore, by conducting genome-wide association study (GWAS) with the single-nucleotide polymorphism (SNPs), insertion/deletion (indels), and structural variation (SV), we identified RAP2C, member of the RAS oncogene family (RAP2C), dedicator of cytokinesis 11 (DOCK11), neurotensin (NTS) and BOP1 ribosomal biogenesis factor (BOP1) as regulators of HDL-CH, and glycerophosphodiester phosphodiesterase domain containing 5 (GDPD5), dihydrodiol dehydrogenase (DHDH), and potassium voltage-gated channel interacting protein 1 (KCNIP1) as candidate genes of BG. Moreover, our findings suggest that cecal RF39 and Clostridia_UCG_014 may be linked to the regulation of CHOL, and jejunal Streptococcaceae may be involved in the regulation of TG. Additionally, microbial GWAS results indicated that the presence of gut microbiota was under host genetic regulation. Our findings provide valuable insights into the complex interaction between host genetics and microbiota in shaping the blood biochemical profile of chickens. KEY POINTS: • Multiple candidate genes were identified for the regulation of CHOL, HDL-CH, and BG. • RF39, Clostridia_UCG_014, and Streptococcaceae were implicated in CHOL and TG modulation. • The composition of gut microbiota is influenced by host genetics.

Investigating Habenula Functional Connectivity and Reward-Related Activity in Obesity Using Human Connectome Project Data

Introduction: The habenula, a brain region involved in aversion, might negatively modulate caloric intake. Functional magnetic resonance imaging (fMRI) studies reported associations between weight loss and habenula functional connectivity. However, whether habenula resting-state functional connectivity (rsFC) and reward-related activity are altered in obesity is yet unknown. Methods: Using data from the Human Connectome Project, we included 300 subjects with various body mass indexes (BMIs) and a healthy long-term blood glucose (hemoglobin A1c [HbA1c]). In addition, we investigated a potential BMI × HbA1c interaction in a separate cohort including subjects with prediabetes (n = 72). Habenula rsFC was assessed using a region of interest (ROI)-to-ROI analysis. Furthermore, a separate analysis using gambling task fMRI data focused on reward-related habenula activity. Results: We did not find an association between BMI and habenula rsFC for any of the ROIs. For the exploratory analysis of the BMI × HbA1c effect, a significant interaction effect was found for the habenula-ventral tegmental area (VTA) connection, but this did not survive multiple comparisons correction. Monetary punishment compared with reward activated the bilateral habenula in the BMI sample, but this activity was not associated with BMI. Discussion: In conclusion, we did not find evidence for an association between BMI and habenula rsFC or reward-related activity. However, there might be an interaction between BMI and HbA1c for the habenula-VTA rsFC, suggestive of a role of the habenula in glucose regulation. Future studies should focus on metabolic parameters in their experimental design to confirm our findings and explore the precise role of the habenula in metabolism.

Advanced neurobiological tools to interrogate metabolism

Engineered neurobiological tools for the manipulation of cellular activity, such as chemogenetics and optogenetics, have become a cornerstone of modern neuroscience research. These tools are invaluable for the interrogation of the central control of metabolism as they provide a direct means to establish a causal relationship between brain activity and biological processes at the cellular, tissue and organismal levels. The utility of these methods has grown substantially due to advances in cellular-targeting strategies, alongside improvements in the resolution and potency of such tools. Furthermore, the potential to recapitulate endogenous cellular signalling has been enriched by insights into the molecular signatures and activity dynamics of discrete brain cell types. However, each modulatory tool has a specific set of advantages and limitations; therefore, tool selection and suitability are of paramount importance to optimally interrogate the cellular and circuit-based underpinnings of metabolic outcomes within the organism. Here, we describe the key principles and uses of engineered neurobiological tools. We also highlight inspiring applications and outline critical considerations to be made when using these tools within the field of metabolism research. We contend that the appropriate application of these biotechnological advances will enable the delineation of the central circuitry regulating systemic metabolism with unprecedented potential.

Central and peripheral actions of nicotine that influence blood glucose homeostasis and the development of diabetes

Cigarette smoking has long been recognized as a risk factor for type 2 diabetes (T2D), although the precise causal mechanisms underlying this relationship remain poorly understood. Recent evidence suggests that nicotine, the primary reinforcing component in tobacco, may play a pivotal role in connecting cigarette smoking and T2D. Extensive research conducted in both humans and animals has demonstrated that nicotine can elevate blood glucose levels, disrupt glucose homeostasis, and induce insulin resistance. The review aims to elucidate the genetic variants of nicotinic acetylcholine receptors associated with diabetes risk and provide a comprehensive overview of the available data on the mechanisms through which nicotine influences blood glucose homeostasis and the development of diabetes. Here we emphasize the central and peripheral actions of nicotine on the release of glucoregulatory hormones, as well as its effects on glucose tolerance and insulin sensitivity. Notably, the central actions of nicotine within the brain, which encompass both insulin-dependent and independent mechanisms, are highlighted as potential targets for intervention strategies in diabetes management.

The controversial effect of smoking and nicotine in SARS-CoV-2 infection

The effects of nicotine and cigarette smoke in many diseases, notably COVID-19 infection, are being debated more frequently. The current basic data for COVID-19 is increasing and indicating the higher risk of COVID-19 infections in smokers due to the overexpression of corresponding host receptors to viral entry. However, current multi-national epidemiological reports indicate a lower incidence of COVID-19 disease in smokers. Current data indicates that smokers are more susceptible to some diseases and more protective of some other. Interestingly, nicotine is also reported to play a dual role, being both inflammatory and anti-inflammatory. In the present study, we tried to investigate the effect of pure nicotine on various cells involved in COVID-19 infection. We followed an organ-based systematic approach to decipher the effect of nicotine in damaged organs corresponding to COVID-19 pathogenesis (12 related diseases). Considering that the effects of nicotine and cigarette smoke are different from each other, it is necessary to be careful in generalizing the effects of nicotine and cigarette to each other in the conducted researches. The generalization and the undifferentiation of nicotine from smoke is a significant bias. Moreover, different doses of nicotine stimulate different effects (dose-dependent response). In addition to further assessing the role of nicotine in COVID-19 infection and any other cases, a clever assessment of underlying diseases should also be considered to achieve a guideline for health providers and a personalized approach to treatment.

GLP-1 and nicotine combination therapy engages hypothalamic and mesolimbic pathways to reverse obesity

Glucagon-like peptide-1 receptor (GLP-1R) agonists promote nicotine avoidance. Here, we show that the crosstalk between GLP-1 and nicotine extends beyond effects on nicotine self-administration and can be exploited pharmacologically to amplify the anti-obesity effects of both signals. Accordingly, combined treatment with nicotine and the GLP-1R agonist, liraglutide, inhibits food intake and increases energy expenditure to lower body weight in obese mice. Co-treatment with nicotine and liraglutide gives rise to neuronal activity in multiple brain regions, and we demonstrate that GLP-1R agonism increases excitability of hypothalamic proopiomelanocortin (POMC) neurons and dopaminergic neurons in the ventral tegmental area (VTA). Further, using a genetically encoded dopamine sensor, we reveal that liraglutide suppresses nicotine-induced dopamine release in the nucleus accumbens in freely behaving mice. These data support the pursuit of GLP-1R-based therapies for nicotine dependence and encourage further evaluation of combined treatment with GLP-1R agonists and nicotinic receptor agonists for weight loss.

Understanding the habenula: A major node in circuits regulating emotion and motivation

Over the last decade, the understanding of the habenula has rapidly advanced from being an understudied brain area with the Latin name 'habena" meaning "little rein", to being considered a "major rein" in the control of key monoaminergic brain centers. This ancient brain structure is a strategic node in the information flow from fronto-limbic brain areas to brainstem nuclei. As such, it plays a crucial role in regulating emotional, motivational, and cognitive behaviors and has been implicated in several neuropsychiatric disorders, including depression and addiction. This review will summarize recent findings on the medial (MHb) and lateral (LHb) habenula, their topographical projections, cell types, and functions. Additionally, we will discuss contemporary efforts that have uncovered novel molecular pathways and synaptic mechanisms with a focus on MHb-Interpeduncular nucleus (IPN) synapses. Finally, we will explore the potential interplay between the habenula's cholinergic and non-cholinergic components in coordinating related emotional and motivational behaviors, raising the possibility that these two pathways work together to provide balanced roles in reward prediction and aversion, rather than functioning independently.

Nicotine rebalances NAD+ homeostasis and improves aging-related symptoms in male mice by enhancing NAMPT activity

Imbalances in NAD⁺ homeostasis have been linked to aging and various diseases. Nicotine, a metabolite of the NAD⁺ metabolic pathway, has been found to possess anti-inflammatory and neuroprotective properties, yet the underlying molecular mechanisms remained unknown. Here we find that, independent of nicotinic acetylcholine receptors, low-dose nicotine can restore the age-related decline of NAMPT activity through SIRT1 binding and subsequent deacetylation of NAMPT, thus increasing NAD⁺ synthesis. ¹⁸F-FDG PET imaging revealed that nicotine is also capable of efficiently inhibiting glucose hypermetabolism in aging male mice. Additionally, nicotine ameliorated cellular energy metabolism disorders and deferred age-related deterioration and cognitive decline by stimulating neurogenesis, inhibiting neuroinflammation, and protecting organs from oxidative stress and telomere shortening. Collectively, these findings provide evidence for a mechanism by which low-dose nicotine can activate NAD⁺ salvage pathways and improve age-related symptoms.

TCF7L2 acts as a molecular switch in midbrain to control mammal vocalization through its DNA binding domain but not transcription activation domain

Vocalization is an essential medium for social signaling in birds and mammals. Periaqueductal gray (PAG) a conserved midbrain structure is believed to be responsible for innate vocalizations, but its molecular regulation remains largely unknown. Here, through a mouse forward genetic screening we identified one of the key Wnt/β-catenin effectors TCF7L2/TCF4 controls ultrasonic vocalization (USV) production and syllable complexity during maternal deprivation and sexual encounter. Early developmental expression of TCF7L2 in PAG excitatory neurons is necessary for the complex trait, while TCF7L2 loss reduces neuronal gene expressions and synaptic transmission in PAG. TCF7L2-mediated vocal control is independent of its β-catenin-binding domain but dependent of its DNA binding ability. Patient mutations associated with developmental disorders, including autism spectrum disorders, disrupt the transcriptional repression effect of TCF7L2, while mice carrying those mutations display severe USV impairments. Therefore, we conclude that TCF7L2 orchestrates gene expression in midbrain to control vocal production through its DNA binding but not transcription activation domain.

Electrochemical Nanosensors for Sensitization of Sweat Metabolites: From Concept Mapping to Personalized Health Monitoring

Sweat contains a broad range of important biomarkers, which may be beneficial for acquiring non-invasive biochemical information on human health status. Therefore, highly selective and sensitive electrochemical nanosensors for the non-invasive detection of sweat metabolites have turned into a flourishing contender in the frontier of disease diagnosis. A large surface area, excellent electrocatalytic behavior and conductive properties make nanomaterials promising sensor materials for target-specific detection. Carbon-based nanomaterials (e.g., CNT, carbon quantum dots, and graphene), noble metals (e.g., Au and Pt), and metal oxide nanomaterials (e.g., ZnO, MnO2, and NiO) are widely used for modifying the working electrodes of electrochemical sensors, which may then be further functionalized with requisite enzymes for targeted detection. In the present review, recent developments (2018-2022) of electrochemical nanosensors by both enzymatic as well as non-enzymatic sensors for the effectual detection of sweat metabolites (e.g., glucose, ascorbic acid, lactate, urea/uric acid, ethanol and drug metabolites) have been comprehensively reviewed. Along with this, electrochemical sensing principles, including potentiometry, amperometry, CV, DPV, SWV and EIS have been briefly presented in the present review for a conceptual understanding of the sensing mechanisms. The detection thresholds (in the range of mM-nM), sensitivities, linear dynamic ranges and sensing modalities have also been properly addressed for a systematic understanding of the judicious design of more effective sensors. One step ahead, in the present review, current trends of flexible wearable electrochemical sensors in the form of eyeglasses, tattoos, gloves, patches, headbands, wrist bands, etc., have also been briefly summarized, which are beneficial for on-body in situ measurement of the targeted sweat metabolites. On-body monitoring of sweat metabolites via wireless data transmission has also been addressed. Finally, the gaps in the ongoing research endeavors, unmet challenges, outlooks and future prospects have also been discussed for the development of advanced non-invasive self-health-care-monitoring devices in the near future.

[Smoking, heated tobacco products, alcohol and diabetes mellitus (update 2023)]

Smoking and second-hand smoke strongly increase incidence of diabetes and probability for its complications. Smoking cessation can lead to weight gain and increased diabetes risk; however, it decreases cardiovascular and total mortality. A basal diagnostics (Fagerström Test, exhaled CO) is the basis for successful smoking cessation. Supporting medication include Varenicline, Nicotine Replacement Therapy and Bupropion. Socio-economic as well as psychological factors play an important role for smoking and smoking cessation. Heated tobacco products (like the E‑cigarette) are no healthy alternative to cigarettes and are associated with increased morbidity and mortality.Moderate consumption of alcohol possibly decreases risk for diabetes and cardiovascular diseases. Selection bias and underreporting in studies maybe contribute to a too optimistic view. On the other hand, alcohol increases in a dose dependant fashion excess morbidity and disability adjusted life years, especially by cancer, liver diseases and infections.

Impaired Awareness of Hypoglycemia in Type 1 Diabetes: A Report of An NIDDK Workshop in October 2021

Hypoglycemia remains a limiting factor in the optimal treatment of type 1 diabetes. Repeated episodes of hypoglycemia result in impaired awareness of subsequent hypoglycemic events, inducing a vicious feed-forward cycle and increasing the risk of morbidity and mortality. Why this occurs and how to manage the problem in clinical practice remain uncertain. To address the obstacles and barriers that have hindered progress in this clinically important area, the National Institute of Diabetes and Digestive and Kidney Diseases convened a workshop on 14-15 October 2021. This perspective offers a summary of this outstanding meeting, which brought clinical and basic scientists from the fields of diabetes, neuroscience, psychology, psychiatry, and imaging together, on how to best advance the field of impaired awareness of hypoglycemia and hypoglycemia in general in patients with diabetes.

Hedgehog-interacting protein acts in the habenula to regulate nicotine intake

Hedgehog-interacting protein (HHIP) sequesters Hedgehog ligands to repress Smoothened (SMO)-mediated recruitment of the GLI family of transcription factors. Allelic variation in HHIP confers risk of chronic obstructive pulmonary disease and other smoking-related lung diseases, but underlying mechanisms are unclear. Using single-cell and cell-type-specific translational profiling, we show that HHIP expression is highly enriched in medial habenula (MHb) neurons, particularly MHb cholinergic neurons that regulate aversive behavioral responses to nicotine. HHIP deficiency dysregulated the expression of genes involved in cholinergic signaling in the MHb and disrupted the function of nicotinic acetylcholine receptors (nAChRs) through a PTCH-1/cholesterol-dependent mechanism. Further, CRISPR/Cas9-mediated genomic cleavage of the Hhip gene in MHb neurons enhanced the motivational properties of nicotine in mice. These findings suggest that HHIP influences vulnerability to smoking-related lung diseases in part by regulating the actions of nicotine on habenular aversion circuits.

Xenobiotics Delivered by Electronic Nicotine Delivery Systems: Potential Cellular and Molecular Mechanisms on the Pathogenesis of Chronic Kidney Disease

Chronic kidney disease (CKD) is characterized as sustained damage to the renal parenchyma, leading to impaired renal functions and gradually progressing to end-stage renal disease (ESRD). Diabetes mellitus (DM) and arterial hypertension (AH) are underlying diseases of CKD. Genetic background, lifestyle, and xenobiotic exposures can favor CKD onset and trigger its underlying diseases. Cigarette smoking (CS) is a known modified risk factor for CKD. Compounds from tobacco combustion act through multi-mediated mechanisms that impair renal function. Electronic nicotine delivery systems (ENDS) consumption, such as e-cigarettes and heated tobacco devices, is growing worldwide. ENDS release mainly nicotine, humectants, and flavorings, which generate several byproducts when heated, including volatile organic compounds and ultrafine particles. The toxicity assessment of these products is emerging in human and experimental studies, but data are yet incipient to achieve truthful conclusions about their safety. To build up the knowledge about the effect of currently employed ENDS on the pathogenesis of CKD, cellular and molecular mechanisms of ENDS xenobiotic on DM, AH, and kidney functions were reviewed. Unraveling the toxic mechanisms of action and endpoints of ENDS exposures will contribute to the risk assessment and implementation of proper health and regulatory interventions.

Smoking causes the disorder of glucose metabolism under different levels of blood pressure in male occupational population

Smoking is an important modifiable factor in the risk of type 2 diabetes. Type 2 diabetes and hypertension overlap in the population. The present study investigated effects of smoking on glucose metabolism under different blood pressure (BP) levels in occupational population. A smoking survey among occupational groups was conducted in 2018. The general linear model was used to analyze the differences of glucose metabolism indexes and BP indexes influenced by different smoking intensity (never 0, mild <10, moderate <20, heavy ≥20 pack‐years). Odds ratios of developing diabetes and β‐cell deficiency were analyzed by using logistic regression model. BP was further taken into account in the relationship between smoking and glucose metabolism. As a result, 1730 male workers aged 21 to 60 years were included in the analysis finally. Compared to never smokers, heavy smokers had significantly increased fasting plasma glucose. Moderate and above smokers had significantly increased glycosylated hemoglobin, decreased fasting plasma insulin and β‐cell function, after adjustment for covariates. Further, smoking intensity was found to have a dose‐dependent relationship with impaired β‐cell function and diabetes. In conclusion, smoking has a positive dose‐dependent relationship with β‐cell deficiency and diabetes. Male smoking workers, especially the moderate or higher smoking, with high‐normal and high BP levels are at high risk of abnormal glucose metabolism.

The Plasma Oxylipidome Links Smoking Status to Peripheral Artery Disease

Peripheral artery disease (PAD) is prevalent among individuals with a history of tobacco smoking. Although oxidation of lipids may contribute to atherogenesis in vascular disease, enzymatically and nonenzymatically produced oxidized lipids can have varying and contrasting physiological effects. The underlying mechanisms of atherogenic vulnerability can be better elucidated with the recent advances in oxylipidome quantification using HPLC-MS/MS technology. In a randomized, controlled clinical trial, the plasma oxylipidome was analyzed in participants living with PAD by smoking status (n = 98) and in nonsmoking comparators without chronic disease (n = 20). Individuals with PAD had approximately a four-fold higher level of total plasma oxylipins versus the comparator. Cessation of smoking in individuals with PAD was associated with significantly lower levels of linoleic acid-derived TriHOMEs, greater levels of omega-3 fatty acid-derived oxylipins, and greater levels of nonfragmented oxidized phosphatidylcholines (OxPCs). Individuals living with PAD but without a history of smoking, exhibited higher levels of the putative atherogenic fragmented OxPCs versus individuals who currently or previously smoked. These data implicate the plasma oxylipidome in PAD and that smoking cessation is associated with a less inflammatory profile. Furthermore, fragmented OxPCs may play a more significant role in the pathophysiology of PAD in individuals without a history of smoking.

MiR-203 is an anti-obese miRNA by targeting ASBT

Obesity is characterized by excessive fat deposition within the body. Bile acids (BA) are important regulators for controlling the absorption of lipid. Here we show that miR-203 exerts weight-loss and lipid-lowering effects by increasing total BA excretion in obese rodents. miR-203 overexpression transgenic mice are resistant to high-fat diet (HFD)-induced obesity and dyslipidemia. Moreover, the knockdown of miR-203 deteriorates metabolic disorders. ASBT plays important role in regulating BA homeostasis and is a direct target of miR-203. In human intestinal epithelial cells, overexpression of miR-203 decreases the cellular uptake of BA by inhibiting ASBT. Furthermore, TCF7L2 is downregulated in obese mice and acts as a transcription factor of miR-203. The ASBT mRNA level was positively correlated with the body mass index (BMI) of population, while the miR-203 level was negatively associated with BMI. Taken together, these data suggest miR-203 could be a new therapeutic BA regulator for obesity and dyslipidemia.

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miR-203 is downregulated in obese rodents and overweight/obese population

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ASBT is a direct target of miR-203 in obesity

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TCF7L2 acts as an upstream activator of miR-203 in obesity

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miR-203 ameliorates obesity and dyslipidemia by increasing TBAs and lipids excretion

Effect of race on cardiometabolic responses to once-weekly exenatide: insights from the Exenatide Study of Cardiovascular Event Lowering (EXSCEL)

Background

To determine whether there were racial differences in short-term cardiometabolic responses to once-weekly exenatide (EQW) in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL).

Methods

EXSCEL enrolled 14,752 patients with type 2 diabetes (hemoglobin A_1c (HbA_1c) 6.5–10.0% [48–86 mmol/mol]) with or without cardiovascular disease who were randomized double-blind to EQW or placebo. Background glucose-lowering/other cardiovascular therapies were unaltered for 6 months post-randomization unless clinically essential, facilitating comparison of EQW-associated effects in 14,665 evaluable participants self-identifying as White (n = 11,113), Asian (n = 1444), Black (n = 870), or Other Race (n = 1,238. Placebo-adjusted 6 month absolute changes in cardiometabolic variables were assessed using generalized linear models.

Results

Mean 6-month placebo-adjusted HbA_1c reductions were similar in the four groups (range 0.54–0.67% [5.9 to 7.3 mmol/mol], P = 0.11 for race×treatment interaction), with no significant difference in Asians (reference) versus other groups after covariate adjustment (all P ≥ 0.10). Six-month placebo-adjusted mean changes in systolic (−1.8 to 0.0 mmHg) and diastolic (0.2 to 1.2 mmHg) blood pressure, serum LDL (− 0.06 to 0.02 mmol/L) and HDL (0.00 to 0.01 mmol/L) cholesterol, and serum triglycerides (−0.1 to 0.0 mmol/L) were similar in the racial groups (P ≥ 0.19 for race×treatment interaction and all P ≥ 0.13 for comparisons of Asians with other races). Resting pulse rate increased more in Asians (4 beats/min) than in other groups (≤ 3 beats/min, P = 0.016 for race×treatment interaction and all P ≤ 0.050 for comparisons of Asians with other races).

Conclusions

Short-term cardiometabolic responses to EQW were similar in the main racial groups in EXSCEL, apart from a greater pulse rate increase in Asians.

Trial registration: https://clinicaltrials.gov NCT01144338.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01555-z.

TCF7L2 promotes ER stress signaling in diabetic retinopathy

Diabetic retinopathy (DR) is one of the most common blindness in working-age adults. Transcription factor 7 like 2 (TCF7L2) is a susceptibility gene of DR, however, its roles in the pathogenesis of DR are still largely unknown. In this study, we found that TCF7L2 was mainly located in the cell nucleus of retinal ganglion cell layer (GCL) and inner nuclear layer (INL), while it was not expressed in the cell nucleus of retinal outer nuclear layer (ONL). Expression of TCF7L2 was significantly elevated in the retinas of db/db diabetic mice and oxygen-induced retinopathy (OIR) mice. Also, in Ad-hTCF7L2 treated hiPSCs-derived retinal progenitor cells (RPCs), activating transcription factor 6 (ATF6)-related endoplasmic reticulum (ER) stress signaling was remarkably activated. Moreover, knockdown of TCF7L2 significantly inhibited ATF6-related ER stress signaling. Furthermore, the data of endothelial permeability assay showed that RPCs pretreated with Ad-hTCF7L2 lead to enhanced monolayer permeability of human umbilical vein endothelial cells (HUVECs), and knockdown of TCF7L2 or ATF6 in RPCs could alleviate the monolayer permeability of HUVECs. Thus, our results showed that TCF7L2 could trigger ATF6-related ER stress signaling and promote vein endothelial cell permeability, which will provide important insight into the role of TCF7L2 in the pathogenesis of DR and contribute to designing potential therapies.

Translational relevance of forward genetic screens in animal models for the study of psychiatric disease

Psychiatric disorders represent a significant burden in our societies. Despite the convincing evidence pointing at gene and gene-environment interaction contributions, the role of genetics in the etiology of psychiatric disease is still poorly understood. Forward genetic screens in animal models have helped elucidate causal links. Here we discuss the application of mutagenesis-based forward genetic approaches in common animal model species: two invertebrates, nematodes (Caenorhabditis elegans) and fruit flies (Drosophila sp.); and two vertebrates, zebrafish (Danio rerio) and mice (Mus musculus), in relation to psychiatric disease. We also discuss the use of large scale genomic studies in human populations. Despite the advances using data from human populations, animal models coupled with next-generation sequencing strategies are still needed. Although with its own limitations, zebrafish possess characteristics that make them especially well-suited to forward genetic studies exploring the etiology of psychiatric disorders.

A distinct hypothalamus-to-β cell circuit modulates insulin secretion

The central nervous system has long been thought to regulate insulin secretion, an essential process in the maintenance of blood glucose levels. However, the anatomical and functional connections between the brain and insulin-producing pancreatic β cells remain undefined. Here, we describe a functional transneuronal circuit connecting the hypothalamus to β cells in mice. This circuit originates from a subpopulation of oxytocin neurons in the paraventricular hypothalamic nucleus (PVN^OXT), and it reaches the islets of the endocrine pancreas via the sympathetic autonomic branch to innervate β cells. Stimulation of PVN^OXT neurons rapidly suppresses insulin secretion and causes hyperglycemia. Conversely, silencing of these neurons elevates insulin levels by dysregulating neuronal signaling and secretory pathways in β cells and induces hypoglycemia. PVN^OXT neuronal activity is triggered by glucoprivation. Our findings reveal that a subset of PVN^OXT neurons form functional multisynaptic circuits with β cells in mice to regulate insulin secretion, and their function is necessary for the β cell response to hypoglycemia.

The regulation of PKA signaling in obesity and in the maintenance of metabolic health

The cAMP-dependent protein kinase (PKA) system represents a primary cell-signaling pathway throughout systems and across species. PKA facilitates the actions of hormones, neurotransmitters and other signaling molecules that bind G-protein coupled receptors (GPCR) to modulate cAMP levels. Through its control of synaptic events, exocytosis, transcriptional regulation, and more, PKA signaling regulates cellular metabolism and emotional and stress responses making it integral in the maintenance and dysregulation of energy homeostasis. Neural PKA signaling is regulated by afferent and peripheral efferent signals that link specific neural cell populations to the regulation of metabolic processes in adipose tissue, liver, pancreas, adrenal, skeletal muscle, and gut. Mouse models have provided invaluable information on the roles for PKA subunits in brain and key metabolic organs. While limited, human studies infer differential regulation of the PKA system in obese compared to lean individuals. Variants identified in PKA subunit genes cause Cushing syndrome that is characterized by metabolic dysregulation associated with endogenous glucocorticoid excess. Under healthy physiologic conditions, the PKA system is exquisitely regulated by stimuli that activate GPCRs to alter intracellular cAMP concentrations, and by PKA cellular localization and holoenzyme stability. Adenylate cyclase activity generates cAMP while phosphodiesterase-mediated cAMP degradation to AMP decreases cAMP levels downstream of GPCRs. Chronic perturbations in PKA signaling appear to be capable of resetting PKA regulation at several levels; in addition, sex differences in PKA signaling regulation, while not well understood, impact the physiologic consequences of metabolic dysregulation and obesity. This review explores the roles for PKA signaling in the pathogenesis of metabolic diseases including obesity, type 2 diabetes mellitus and associated co-morbidities through neural-peripheral crosstalk and cAMP/PKA signaling pathway targets that hold therapeutic potential.

Smoking Status and Type 2 Diabetes, and Cardiovascular Disease: A Comprehensive Analysis of Shared Genetic Etiology and Causal Relationship

OBJECTIVE

This study aimed to explore shared genetic etiology and the causality between smoking status and type 2 diabetes (T2D), cardiovascular diseases (CVDs), and related metabolic traits.

METHODS

Using summary statistics from publicly available genome-wide association studies (GWASs), we estimated genetic correlations between smoking status and T2D, 6 major CVDs, and 8 related metabolic traits with linkage disequilibrium score regression (LDSC) analysis; identified shared genetic loci with large-scale genome-wide cross-trait meta-analysis; explored potential shared biological mechanisms with a series of post-GWAS analyses; and determined causality with Mendelian randomization (MR).

RESULTS

We found significant positive genetic associations with smoking status for T2D (Rg = 0.170, p = 9.39 × 10^-22), coronary artery disease (CAD) (Rg = 0.234, p = 1.96 × 10^-27), myocardial infarction (MI) (Rg = 0.226, p = 1.08 × 10^-17), and heart failure (HF) (Rg = 0.276, p = 8.43 × 10^-20). Cross-trait meta-analysis and transcriptome-wide association analysis of smoking status identified 210 loci (32 novel loci) and 354 gene-tissue pairs jointly associated with T2D, 63 loci (12 novel loci) and 37 gene-tissue pairs with CAD, 38 loci (6 novel loci) and 17 gene-tissue pairs with MI, and 28 loci (3 novel loci) and one gene-tissue pair with HF. The shared loci were enriched in the exo-/endocrine, cardiovascular, nervous, digestive, and genital systems. Furthermore, we observed that smoking status was causally related to a higher risk of T2D (β = 0.385, p = 3.31 × 10^-3), CAD (β = 0.670, p = 7.86 × 10^-11), MI (β = 0.725, p = 2.32 × 10^-9), and HF (β = 0.520, p = 1.53 × 10^-6).

CONCLUSIONS

Our findings provide strong evidence on shared genetic etiology and causal associations between smoking status and T2D, CAD, MI, and HF, underscoring the potential shared biological mechanisms underlying the link between smoking and T2D and CVDs. This work opens up a new way of more effective and timely prevention of smoking-related T2D and CVDs.

Neurobiological Mechanisms of Nicotine Reward and Aversion

Neuronal nicotinic acetylcholine receptors (nAChRs) regulate the rewarding actions of nicotine contained in tobacco that establish and maintain the smoking habit. nAChRs also regulate the aversive properties of nicotine, sensitivity to which decreases tobacco use and protects against tobacco use disorder. These opposing behavioral actions of nicotine reflect nAChR expression in brain reward and aversion circuits. nAChRs containing α4 and β2 subunits are responsible for the high-affinity nicotine binding sites in the brain and are densely expressed by reward-relevant neurons, most notably dopaminergic, GABAergic, and glutamatergic neurons in the ventral tegmental area. High-affinity nAChRs can incorporate additional subunits, including β3, α6, or α5 subunits, with the resulting nAChR subtypes playing discrete and dissociable roles in the stimulatory actions of nicotine on brain dopamine transmission. nAChRs in brain dopamine circuits also participate in aversive reactions to nicotine and the negative affective state experienced during nicotine withdrawal. nAChRs containing α3 and β4 subunits are responsible for the low-affinity nicotine binding sites in the brain and are enriched in brain sites involved in aversion, including the medial habenula, interpeduncular nucleus, and nucleus of the solitary tract, brain sites in which α5 nAChR subunits are also expressed. These aversion-related brain sites regulate nicotine avoidance behaviors, and genetic variation that modifies the function of nAChRs in these sites increases vulnerability to tobacco dependence and smoking-related diseases. Here, we review the molecular, cellular, and circuit-level mechanisms through which nicotine elicits reward and aversion and the adaptations in these processes that drive the development of nicotine dependence. SIGNIFICANCE STATEMENT: Tobacco use disorder in the form of habitual cigarette smoking or regular use of other tobacco-related products is a major cause of death and disease worldwide. This article reviews the actions of nicotine in the brain that contribute to tobacco use disorder.

Potential Therapeutic Targeting Neurotransmitter Receptors in Diabetes

Neurotransmitters are signaling molecules secreted by neurons to coordinate communication and proper function among different sections in the central neural system (CNS) by binding with different receptors. Some neurotransmitters as well as their receptors are found in pancreatic islets and are involved in the regulation of glucose homeostasis. Neurotransmitters can act with their receptors in pancreatic islets to stimulate or inhibit the secretion of insulin (β cell), glucagon (α cell) or somatostatin (δ cell). Neurotransmitter receptors are either G-protein coupled receptors or ligand-gated channels, their effects on blood glucose are mainly decided by the number and location of them in islets. Dysfunction of neurotransmitters receptors in islets is involved in the development of β cell dysfunction and type 2 diabetes (T2D).Therapies targeting different transmitter systems have great potential in the prevention and treatment of T2D and other metabolic diseases.

Diabetes, cigarette smoking and transcription factor 7-like 2 (Tcf7L2) in the UK Biobank cohort

Background —

Smokers are 30 to 40 percent more likely to develop type 2 diabetes than non-smokers. A type 2 diabetes gene, Tcf7L2, which had lost activity, caused rats to consume more nicotine. In the present study, we used data from the UK Biobank to examine the relationship of smoking, type 2 diabetes, and Tcf7L2 in human subjects.

Methods —

The Tcf7L2 gene has two SNPs, rs7903146 and rs4506565, reported to be associated with type 2 diabetes. They have approximately equal power to estimate risk for type 2 diabetes, and the results from one correlate 92% with the other. We examined the genotypes of these SNPs and cigarette consumption.

Results —

Genotype TT, linked to type 2 diabetes, smoked the least. But because of the large sample size (approximately 111,000 subjects) the tiny difference in cigarettes smoked daily by each genotype group (effect size), while statistically significant, is probably clinically meaningless. The average subject smoked 19 cigarettes daily, with a difference of 0.12 cigarette between each genotype group.

Conclusion —

The fact that Tcf7L2 is involved in nicotine addiction in rats but not in humans, as UKBB data suggest, is hardly surprising. Humans and rodents descended from a common ancestor about 80 million years ago, with rats and mice diverging between 12 and 24 million years ago. Thus, over millions of years Tcf7L2 may have developed vastly different functions in rodents and humans. Genome Wide Association Studies have revealed at least 65 different loci linked to type 2 diabetes. Genes associated with type 2 diabetes include Tcf7L2, PPARG, FTO, KCNJ11, NOTCH2, WFS1, IGF2BP2, SLC30A8, JAZF1, HHEX, DGKB, CDKN2A, CDKN2B, KCNQ1, HNF1A, HNF1B MC4R, GIPR, HNF4A, MTNR1B, PARG6, ZBED3, SLC30A8, CDKAL1, GLIS3, GCK, GCKR, among others. Perhaps one or more of these genes might be the intermediary between type 2 diabetes and cigarette smoking. Further studies are warranted.

Substance Use Affects Type 1 Diabetes Pancreas Pathology: Implications for Future Studies

Access to human pancreas samples from organ donors has greatly advanced our understanding of type 1 diabetes pathogenesis; however, previous studies have shown that donors have a high rate of substance use, and its impact on pancreatic histopathology in this disease is not well described. One-hundred-thirty-one type 1 diabetes and 111 control organ donor pancreata from persons 12-89 years of age (mean 29.8 ± 15.5 years) within the Network for Pancreatic Organ donors with Diabetes (nPOD) were examined for insulin positivity, insulitis, amyloid staining, acute and chronic pancreatitis, and chronic exocrine changes (acinar atrophy, fibrosis, fatty infiltration, or periductal fibrosis); findings were compared by history of substance use. A secondary analysis compared exocrine pancreatic histopathologic findings in type 1 diabetes versus control organ donors regardless of substance use history. We observed a high but congruent rate of substance use in type 1 diabetes and control organ donors (66.4% and 64% respectively). Among donors with type 1 diabetes (but not controls), islet amyloid (OR 9.96 [1.22, 81.29]) and acute pancreatitis (OR 3.2 [1.06, 9.63]) were more common in alcohol users while chronic exocrine changes (OR 8.86 [1.13, 69.31]) were more common in cocaine users. Substance use impacted the pancreata of donors with type 1 diabetes more than controls. Overall, despite similar rates of substance use, acute pancreatitis (15.3% versus 4.5%, p=0.0061), chronic pancreatitis (29.8% versus 9.9%, p=0.0001), and chronic exocrine changes (73.3% versus 36.9%, p<0.0001) were more common in type 1 diabetes donors than controls. Alcohol and/or cocaine use in type 1 diabetes organ donors increases exocrine pancreas pathology and islet amyloid deposition but does not affect insulitis or insulin positivity. Exocrine pathology in type 1 diabetes donors is common, and further study of the pathophysiology of these changes is needed.

Central Australian Aboriginal women's placental and neonatal outcomes following maternal smokeless tobacco, cigarette or no tobacco use

OBJECTIVE

To describe the placental characteristics and neonatal outcomes of Central Australian Aboriginal women based on maternal self-report of tobacco use.

METHODS

Placental and neonatal variables were collected from a prospective maternal cohort of 19 smokeless tobacco chewers, 23 smokers and 31 no-tobacco users.

RESULTS

Chewers had the lowest placental weight (460 g) while the no-tobacco group had the heaviest placental weight (565 g). Chewers and the no-tobacco group had placental areas of similar size (285 cm² and 288 cm² , respectively) while the placentas of smokers were at least 13 cm² smaller (272 cm² ). There were two stillbirths in the study and more than one-third (36%) of neonates (newborns) were admitted to the Special Care Nursery, with the chewers' neonates having a higher admission rate compared with smokers' neonates (44% vs. 23%). The cohort mean birthweight (3348 g) was not significantly different between the groups. When stratified for elevated maternal glucose, the chewers' neonates had the lowest mean birthweight (2906 g) compared to the neonates of the no-tobacco group (3242 g) and smokers (3398 g).

CONCLUSIONS

This research is the first to demonstrate that the maternal use of Australian Nicotiana spp. (pituri) as smokeless tobacco may negatively impact placental and neonatal outcomes. Implications for public health: Maternal smokeless tobacco use is a potential source of placental and foetal nicotine exposure. Maternal antenatal screening should be expanded to capture a broader range of tobacco and nicotine products, and appropriate cessation support is required.

TCF4 enhances hepatic metastasis of colorectal cancer by regulating tumor-associated macrophage via CCL2/CCR2 signaling

Colorectal cancer (CRC) liver metastasis is a significant clinical problem for which better therapies are urgently needed. Tumor-associated macrophage, a major cell population in the tumor microenvironment, is a known contributor to primary cancer progression and cancer metastasis. Here, we found TAM recruitment and M2 polarization were increased in the hepatic metastatic lesion compared with the primary site of human CRC tissues. Moreover, Pearson correlation analysis showed that TAM recruitment and polarization were closely correlated with the elevated TCF4 expression in the metastatic site. To investigate the role of TCF4 in CRC liver metastasis, we generated a syngeneic mouse model using MC38 cells splenic injection. Results from in vivo experiments and mouse models revealed that TCF4 deficiency in MC38 cells does not affect their proliferation and invasion; however, it reduces TAM infiltration and M2 polarization in the metastasis site. Further studies indicated that these effects are mediated by the TCF4 regulated CCL2 and CCR2 expression. TCF4 or CCL2 silencing in the tumor cells prevent CRC liver metastasis in the mouse model. Altogether, these findings suggest that the TCF4-CCL2-CCR2 axis plays an essential role in CRC liver metastasis by enhancing TAMs recruitment and M2 polarization.

Associations of clinical, psychological, and socioeconomic characteristics with nicotine dependence in smokers

Cigarette smoking is a risk factor of mortality and morbidity from various cancerous, respiratory, and myocardial diseases. Nicotine dependence is assessed based on the degree of physical dependence. We aimed to determine the clinical, socioeconomic and psychological factors associated with the smoking status and degree of nicotine dependence of smokers. From April 2009 to September 2010, we retrospectively collected data from 17,577 subjects aged ≥ 18 years who had undergone a general health examination at a health promotion center. The instruments used included the Fagerström Tolerance Questionnaire (FTQ), Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), Stress Response Inventory (SRI), and Alcohol Use Disorder Identification Test (AUDIT). Of the current smokers (N = 3946), 2345 (59%), 1154 (29%), and 447 (12%) had low, moderate, and high nicotine dependence, respectively. In multiple logistic analysis, predictors of high nicotine dependence were male sex (odds ratio [OR] 3.705, 95% confidence interval [CI] 1.997–6.945), older age (≥ 65 years) (OR 1.016, 95% CI 1.004–1.029), higher body mass index (BMI) (OR 1.048, 95% CI 1.018–1.078), diabetes (OR 1.870, 95% CI 1.251–2.794), single marital status (OR 1.575, 95% CI 1.186–2.092), lower education level (OR 1.887, 95% CI 1.463–2.433), and a higher stress level (OR 1.018, 95% CI 1.997–6.945). Thus, clinical, psychological, socioeconomic status including male, older age, higher BMI, diabetes, single marital status, lower education, and higher stress should be taken into consideration by promoting smoking cessation.

Smoking status links habenular volume to glycated hemoglobin: Findings from the Human Connectome Project-Young Adult

BACKGROUND

The habenula-pancreas axis regulates the stimulatory effects of nicotine on blood glucose levels and may participate in the emergence of type 2 diabetes in human tobacco smokers. This secondary analysis of young adults from the Human Connectome Project (HCP-YA) evaluated whether smoking status links the relationship between habenular volume and glycated hemoglobin (HbA1c), a marker of long-term glycemic control.

METHODS

Habenula segmentation was performed using a fully-automated myelin content-based approach in HCP-YA participants and the results were inspected visually (n = 693; aged 22-37 years). A linear regression analysis was used with habenular volume as the dependent variable, the smoking-by-HbA1c interaction as the independent variable of interest, and age, gender, race, ethnicity, education, income, employment status, body mass index, and total gray matter volume as covariates.

RESULTS

Habenula volume and HbA1c were similar in smokers and nonsmokers. There was a significant interaction effect (F_{(1, 673)}= 5.03, p = 0.025) indicating that habenular volume was related to HbA1c in a manner that depended on smoking status. Among participants who were smokers (n = 120), higher HbA1c was associated with apparently larger habenular volume (β = 6.74, standard error=2.36, p = 0.005). No such association between habenular volume and HbA1c was noted among participants who were nonsmokers (n = 573).

DISCUSSION

Blood glucose levels over an extended time period, reflected by HbA1c, were correlated with habenular volume in smokers, consistent with a relationship between the habenula and blood glucose homeostasis in smokers. Future studies are needed to evaluate how habenular function relates to glycemic control in smokers and nonsmokers.

Genetic determinants of increased body mass index mediate the effect of smoking on increased risk for type 2 diabetes but not coronary artery disease

Clinical observations have linked tobacco smoking with increased type 2 diabetes risk. Mendelian randomization analysis has recently suggested smoking may be a causal risk factor for type 2 diabetes. However, this association could be mediated by additional risk factors correlated with smoking behavior, which have not been investigated. We hypothesized that body mass index (BMI) could help to explain the association between smoking and diabetes risk. First, we confirmed that genetic determinants of smoking initiation increased risk for type 2 diabetes (OR 1.21, 95% CI: 1.15–1.27, P = 1 × 10⁻¹²) and coronary artery disease (CAD; OR 1.21, 95% CI: 1.16–1.26, P = 2 × 10⁻²⁰). Additionally, 2-fold increased smoking risk was positively associated with increased BMI (~0.8 kg/m², 95% CI: 0.54–0.98 kg/m², P = 1.8 × 10⁻¹¹). Multivariable Mendelian randomization analyses showed that BMI accounted for nearly all the risk smoking exerted on type 2 diabetes (OR 1.06, 95% CI: 1.01–1.11, P = 0.03). In contrast, the independent effect of smoking on increased CAD risk persisted (OR 1.12, 95% CI: 1.08–1.17, P = 3 × 10⁻⁸). Causal mediation analyses agreed with these estimates. Furthermore, analysis using individual-level data from the Million Veteran Program independently replicated the association of smoking behavior with CAD (OR 1.24, 95% CI: 1.12–1.37, P = 2 × 10⁻⁵), but not type 2 diabetes (OR 0.98, 95% CI: 0.89–1.08, P = 0.69), after controlling for BMI. Our findings support a model whereby genetic determinants of smoking increase type 2 diabetes risk indirectly through their relationship with obesity. Smokers should be advised to stop smoking to limit type 2 diabetes and CAD risk. Therapeutic efforts should consider pathophysiology relating smoking and obesity.

The Emerging Science of Interoception: Sensing, Integrating, Interpreting, and Regulating Signals within the Self

Interoception refers to the representation of the internal states of an organism, and includes the processes by which it senses, interprets, integrates, and regulates signals from within itself. This review presents a unified research framework and attempts to offer definitions for key terms to describe the processes involved in interoception. We elaborate on these definitions through illustrative research findings, and provide brief overviews of central aspects of interoception, including the anatomy and function of neural and non-neural pathways, diseases and disorders, manipulations and interventions, and predictive modeling. We conclude with discussions about major research gaps and challenges.

Glucose metabolic crosstalk and regulation in brain function and diseases

Brain glucose metabolism, including glycolysis, the pentose phosphate pathway, and glycogen turnover, produces ATP for energetic support and provides the precursors for the synthesis of biological macromolecules. Although glucose metabolism in neurons and astrocytes has been extensively studied, the glucose metabolism of microglia and oligodendrocytes, and their interactions with neurons and astrocytes, remain critical to understand brain function. Brain regions with heterogeneous cell composition and cell-type-specific profiles of glucose metabolism suggest that metabolic networks within the brain are complex. Signal transduction proteins including those in the Wnt, GSK-3β, PI3K-AKT, and AMPK pathways are involved in regulating these networks. Additionally, glycolytic enzymes and metabolites, such as hexokinase 2, acetyl-CoA, and enolase 2, are implicated in the modulation of cellular function, microglial activation, glycation, and acetylation of biomolecules. Given these extensive networks, glucose metabolism dysfunction in the whole brain or specific cell types is strongly associated with neurologic pathology including ischemic brain injury and neurodegenerative disorders. This review characterizes the glucose metabolism networks of the brain based on molecular signaling and cellular and regional interactions, and elucidates glucose metabolism-based mechanisms of neurological diseases and therapeutic approaches that may ameliorate metabolic abnormalities in those diseases.

Addiction-related neuroadaptations following chronic nicotine exposure

The addiction-relevant molecular, cellular, and behavioral actions of nicotine are derived from its stimulatory effects on neuronal nicotinic acetylcholine receptors (nAChRs) in the central nervous system. nAChRs expressed by dopamine-containing neurons in the ventral midbrain, most notably in the ventral tegmental area (VTA), contribute to the reward-enhancing properties of nicotine that motivate the use of tobacco products. nAChRs are also expressed by neurons in brain circuits that regulate aversion. In particular, nAChRs expressed by neurons in the medial habenula (mHb) and the interpeduncular nucleus (IPn) to which the mHb almost exclusively projects regulate the "set-point" for nicotine aversion and control nicotine intake. Different nAChR subtypes are expressed in brain reward and aversion circuits and nicotine intake is titrated to maximally engage reward-enhancing nAChRs while minimizing the recruitment of aversion-promoting nAChRs. With repeated exposure to nicotine, reward- and aversion-related nAChRs and the brain circuits in which they are expressed undergo adaptations that influence whether tobacco use will transition from occasional to habitual. Genetic variation that influences the sensitivity of addiction-relevant brain circuits to the actions of nicotine also influence the propensity to develop habitual tobacco use. Here, we review some of the key advances in our understanding of the mechanisms by which nicotine acts on brain reward and aversion circuits and the adaptations that occur in these circuits that may drive addiction to nicotine-containing tobacco products.

De novo variants in TCF7L2 are associated with a syndromic neurodevelopmental disorder

TCF7L2 encodes transcription factor 7-like 2 (OMIM 602228), a key mediator of the evolutionary conserved canonical Wnt signaling pathway. Although several large-scale sequencing studies have implicated TCF7L2 in intellectual disability and autism, both the genetic mechanism and clinical phenotype have remained incompletely characterized. We present here a comprehensive genetic and phenotypic description of 11 individuals who have been identified to carry de novo variants in TCF7L2, both truncating and missense. Missense variation is clustered in or near a high mobility group box domain, involving this region in these variants' pathogenicity. All affected individuals present with developmental delays in childhood, but most ultimately achieved normal intelligence or had only mild intellectual disability. Myopia was present in approximately half of the individuals, and some individuals also possessed dysmorphic craniofacial features, orthopedic abnormalities, or neuropsychiatric comorbidities including autism and attention-deficit/hyperactivity disorder (ADHD). We thus present an initial clinical and genotypic spectrum associated with variation in TCF7L2, which will be important in informing both medical management and future research.

miR-20a/TCF4 axis-mediated inhibition of hepatocytes proliferation impairs liver regeneration in mice PHx model by regulating CDC2 and CDC6

MicroRNAs have emerged as essential regulators in the biological process of liver regeneration by modulating the post‐transcriptional expression of the target genes. In the present study, we found miR‐20a expression is decreased remarkably in three rodent liver regeneration models using miRNA PCR array and Venn diagram analysis. Inhibition of miR‐20a expression enhanced hepatocytes proliferation in vivo and in vitro. In contrast, overexpression of miR‐20a reduces hepatocytes proliferation and subsequently impaired liver regeneration in the mouse PHx model. Moreover, we have identified TCF4 as a target gene of miR‐20a using the PCR Array and luciferase assay. Next, mice with TCF4 deficiency were used to establish the PHx model and subjected to the examination of liver regeneration capacity. We found TCF4‐deficient mice exhibited impaired liver regeneration compared with control. Given that TCF4 acts as a transcription factor, we sort to elucidate the downstream genes involved in liver regeneration. Promoter analysis and Chip assay confirmed that TCF4 enhances CDC2 and CDC6 expression through binding to the promoter region and leads to the proliferation and cell cycle progression in hepatocytes. In conclusion, this study provides evidence that the miR20a‐TCF4‐CDC2/6 axis plays an essential role during liver regeneration.

Mechanisms of Nicotine Addiction

Tobacco smoking results in more than five million deaths each year and accounts for ∼90% of all deaths from lung cancer.³ Nicotine, the major reinforcing component of tobacco smoke, acts in the brain through the neuronal nicotinic acetylcholine receptors (nAChRs). The nAChRs are allosterically regulated, ligand-gated ion channels consisting of five membrane-spanning subunits. Twelve mammalian α subunits (α2-α10) and three β subunits (β2-β4) have been cloned. The predominant nAChR subtypes in mammalian brain are those containing α4 and β2 subunits (denoted as α4β2* nAChRs). The α4β2* nAChRs mediate many behaviors related to nicotine addiction and are the primary targets for currently approved smoking cessation agents. Considering the large number of nAChR subunits in the brain, it is likely that nAChRs containing subunits in addition to α4 and β2 also play a role in tobacco smoking. Indeed, genetic variation in the CHRNA5-CHRNA3-CHRNB4 gene cluster, encoding the α5, α3, and β4 nAChR subunits, respectively, has been shown to increase vulnerability to tobacco dependence and smoking-associated diseases including lung cancer. Moreover, mice, in which expression of α5 or β4 subunits has been genetically modified, have profoundly altered patterns of nicotine consumption. In addition to the reinforcing properties of nicotine, the effects of nicotine on appetite, attention, and mood are also thought to contribute to establishment and maintenance of the tobacco smoking habit. Here, we review recent insights into the behavioral actions of nicotine, and the nAChR subtypes involved, which likely contribute to the development of tobacco dependence in smokers.

The role of transcription factor 7-like 2 in metabolic disorders

Transcription factor 7-like 2 (TCF7L2), a member of the T cell factor/lymphoid enhancer factor family, generally forms a complex with β-catenin to regulate the downstream target genes as an effector of the canonical Wnt signalling pathway. TCF7L2 plays a vital role in various biological processes and functions in many organs and tissues, including the liver, islet and adipose tissues. Further, TCF7L2 down-regulates hepatic gluconeogenesis and promotes lipid accumulation. In islets, TCF7L2 not only affects the insulin secretion of the β-cells but also has an impact on other cells. In addition, TCF7L2 influences adipogenesis in adipose tissues. Thus, an out-of-control TCF7L2 expression can result in metabolic disorders. The TCF7L2 gene is composed of 17 exons, generating 13 different transcripts, and has many single-nucleotide polymorphisms (SNPs). The discovery that these SNPs have an impact on the risk of type 2 diabetes (T2D) has attracted thorough investigations in the study of TCF7L2. Apart from T2D, TCF7L2 SNPs are also associated with type 1, posttransplant and other types of diabetes. Furthermore, TCF7L2 variants affect the progression of other disorders, such as obesity, cancers, metabolic syndrome and heart diseases. Finally, the interaction between TCF7L2 variants and diet also needs to be investigated.

Converging vulnerability factors for compulsive food and drug use

Highly palatable foods and substance of abuse have intersecting neurobiological, metabolic and behavioral effects relevant for understanding vulnerability to conditions related to food (e.g., obesity, binge eating disorder) and drug (e.g., substance use disorder) misuse. Here, we review data from animal models, clinical populations and epidemiological evidence in behavioral, genetic, pathophysiologic and therapeutic domains. Results suggest that consumption of highly palatable food and drugs of abuse both impact and conversely are regulated by metabolic hormones and metabolic status. Palatable foods high in fat and/or sugar can elicit adaptation in brain reward and withdrawal circuitry akin to substances of abuse. Intake of or withdrawal from palatable food can impact behavioral sensitivity to drugs of abuse and vice versa. A robust literature suggests common substrates and roles for negative reinforcement, negative affect, negative urgency, and impulse control deficits, with both highly palatable foods and substances of abuse. Candidate genetic risk loci shared by obesity and alcohol use disorders have been identified in molecules classically associated with both metabolic and motivational functions. Finally, certain drugs may have overlapping therapeutic potential to treat obesity, diabetes, binge-related eating disorders and substance use disorders. Taken together, data are consistent with the hypotheses that compulsive food and substance use share overlapping, interacting substrates at neurobiological and metabolic levels and that motivated behavior associated with feeding or substance use might constitute vulnerability factors for one another. This article is part of the special issue on 'Vulnerabilities to Substance Abuse'.

Spatial analysis of metformin use compared with nicotine and caffeine consumption through wastewater-based epidemiology in China

Monitoring the consumption of pharmaceuticals and licit drugs is important for assessing the needs of public health owing to the impact on individuals as well as society. The present work applied wastewater-based epidemiology to profile the spatial patterns of metformin, nicotine, and caffeine use and their correlations. Influent wastewater samples were collected from 27 wastewater treatment plants in 22 typical Chinese cities that covered all geographic regions of the country. The consumption of metformin ranged from 0.02 g/d/1000 inh to 8.92 g/d/1000 inh, whereas caffeine and nicotine consumption ranged from 4.33 g/d/1000 inh to 394 g/d/1000 inh and 0.17 g/d/1000 inh to 1.88 g/d/1000 inh, respectively. There were significant regional differences in the consumption of caffeine, with the highest consumption in East China and the lowest consumption in Northeast China. The consumption and concentration of caffeine were related to the gross domestic product and per capita disposable income of urban residents, respectively. There was a correlation between the concentrations of caffeine and cotinine (a nicotine metabolite), thereby indicating that individuals that use one of these substances are likely to use the other substance. A significant relationship was found between the concentration of metformin and cotinine, thereby implying that the use of tobacco may be correlated with type 2 diabetes. Co-analysis of these substances in wastewater may provide a more accurate picture of substance use situations within different communities and provide more information on human health, human behavior, and the economy. This report describes the newest study related to the consumption of metformin among the general population in China.

Insulin restores the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats

This study examined whether insulin modulates the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats. The rats received vehicle or streptozotocin (STZ) to induce hypoinsulinemia. A subset of STZ-treated rats was implanted with insulin pellets that rapidly normalized glucose levels. Two-weeks later, dialysis probes were implanted into the nucleus accumbens (NAc) and ipsilateral ventral tegmental area (VTA). The next day, dialysate samples were collected during baseline and then following systemic administration of nicotine. Samples were also collected following intra-VTA administration of the gamma-aminobutyric acid (GABA)A receptor antagonist, bicuculline. Dopamine, GABA, glutamate, and acetylcholine (ACh) levels were assessed using liquid chromatography/mass spectrometry (LC/MS). The results revealed that vehicle-treated rats displayed a nicotine-induced increase in NAc dopamine levels. In contrast, STZ-treated rats did not display any changes in NAc dopamine following nicotine administration, an effect that was likely related to a concomitant increase in GABA and decrease in glutamate levels in both the NAc and VTA. Intra-VTA administration of bicuculline increased NAc dopamine in vehicle-treated rats, and this effect was absent in STZ-treated rats. Vehicle-treated rats displayed a nicotine-induced increase in ACh levels in the NAc (but not VTA), an effect that was lower in the NAc of STZ-treated rats. Insulin supplementation normalized the neurochemical effects of nicotine in the NAc and VTA of STZ-treated rats, suggesting that insulin modulates the neurochemical effects of nicotine in the mesolimbic pathway of diabetic rats.