Adipose Tissue CLK2 Promotes Energy Expenditure during High-Fat Diet Intermittent Fasting

Circular RNAs mediate the regulation of maternal placental nutrient transport and fetal development by sugar-sweetened beverages

Epidemiological and experimental studies have demonstrated a strong association between maternal diet and fetal birth weight, obesity, and metabolic syndrome. We investigated the pathways and modes of action of circular RNAs (circRNAs) that mediate the regulation of maternal reproductive performance and fetal development by sugar-sweetened beverages (20 % sucrose water, SSBs) using C57BL/6J mice as a model. Results showed that SSBs significantly increased the reproductive performance (P<0.05), body weight (P<0.01), fetal birth weight (P<0.05), placental weight (P<0.01), and the expression of nutrient transporter genes in the placenta and fetal liver (P<0.05), mainly by accelerating the maternal energy metabolism during pregnancy. However, maternal serum biochemical indices, antioxidant indices, and pathological damage to the liver and placenta predicted that the mother would be at greater health risks during this period. Moreover, transcriptomics results indicated that the differentially expressed (DE) circRNAs in the placenta regulate the maternal multiple metabolic pathways and the placental nutrient transport efficiency by sponging miRNAs and forming growth factors and proteins, ultimately improving the maternal reproductive performance. In addition, we verified the reliability of the sequencing results using reverse transcription polymerase chain reaction and identified the possibility of DE circRNAs binding to nutrient transporter genes using targeting relationship prediction. Finally, we constructed a correlation network that regulates maternal placental nutrient transport based on DE circRNAs, targeted miRNAs and nutrient transport-related genes. This study will provide scientific dietary guidance for pregnant women and new research ideas for preventing and treating pregnancy complications.

Adipose thermogenic mechanisms by cold, exercise and intermittent fasting: Similarities, disparities and the application in treatment

Given its nonnegligible role in metabolic homeostasis, adipose tissue has been the target for treating metabolic disorders such as obesity, diabetes and cardiovascular diseases. Besides its lipolytic function, adipose thermogenesis has gained increased interest due to the irreplaceable contribution to dissipating energy to restore equilibrium, and its therapeutic effects have been testified in various animal models. In this review, we will brief about the canonical cold-stimulated adipose thermogenic mechanisms, elucidate on the exercise- and intermittent fasting-induced adipose thermogenic mechanisms, with a focus on the similarities and disparities among these signaling pathways, in an effort to uncover the overlapped and specific targets that may yield potent therapeutic efficacy synergistically in improving metabolic health.

From fasting to fat reshaping: exploring the molecular pathways of intermittent fasting-induced adipose tissue remodeling

Obesity, characterised by excessive fat accumulation, is a complex chronic condition that results from dysfunctional adipose tissue expansion due to prolonged calorie surplus. This leads to rapid adipocyte enlargement that exceeds the support capacity of the surrounding neurovascular network, resulting in increased hypoxia, inflammation, and insulin resistance. Intermittent fasting (IF), a dietary regimen that cycles between periods of fasting and eating, has emerged as an effective strategy to combat obesity and improve metabolic homeostasis by promoting healthy adipose tissue remodeling. However, the precise molecular and cellular mechanisms behind the metabolic improvements and remodeling of white adipose tissue (WAT) driven by IF remain elusive. This review aims to summarise and discuss the relationship between IF and adipose tissue remodeling and explore the potential mechanisms through which IF induces alterations in WAT. This includes several key structural changes, including angiogenesis and sympathetic innervation of WAT. We will also discuss the involvement of key signalling pathways, such as PI3K, SIRT, mTOR, and AMPK, which potentially play a crucial role in IF-mediated metabolic adaptations.

Intermittent fasting and health outcomes: an umbrella review of systematic reviews and meta-analyses of randomised controlled trials

Background

Benefits of Intermittent fasting (IF) on health-related outcomes have been found in a range of randomised controlled trials (RCTs). Our umbrella review aimed to systematically analyze and synthesize the available causal evidence on IF and its impact on specific health-related outcomes while evaluating its evidence quality.

Methods

We comprehensively searched the PubMed, Embase, Web of Science, and Cochrane databases (from inception up to 8 January 2024) to identify related systematic reviews and meta-analyses of RCTs investigating the association between IF and human health outcomes. We recalculated the effect sizes for each meta-analysis as mean difference (MD) or standardized mean difference (SMD) with corresponding 95% confidence intervals (CIs). Subgroup analyses were performed for populations based on three specific status: diabetes, overweight or obesity, and metabolic syndrome. The quality of systematic reviews was evaluated using A Measurement Tool to Assess Systematic Reviews (AMSTAR), and the certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) system. This study is registered with PROSPERO (CRD42023382004).

Findings

A total of 351 associations from 23 meta-analyses with 34 health outcomes were included in the study. A wide range of outcomes were investigated, including anthropometric measures (n = 155), lipid profiles (n = 83), glycemic profiles (n = 57), circulatory system index (n = 41), appetite (n = 9), and others (n = 6). Twenty-one (91%) meta-analyses with 346 associations were rated as high confidence according to the AMSTAR criteria. The summary effects estimates were significant at p < 0.05 in 103 associations, of which 10 (10%) were supported by high certainty of evidence according to GRADE. Specifically, compared with non-intervention diet in adults with overweight or obesity, IF reduced waist circumference (WC) (MD = -1.02 cm; 95% CI: -1.99 to -0.06; p = 0.038), fat mass (MD = -0.72 kg; 95% CI: -1.32 to -0.12; p = 0.019), fasting insulin (SMD = -0.21; 95% CI: -0.40 to -0.02; p = 0.030), low-density lipoprotein cholesterol (LDL-C) (SMD = -0.20; 95% CI: -0.38 to -0.02; p = 0.027), total cholesterol (TC) (SMD = -0.29; 95% CI: -0.48 to -0.10; p = 0.003), and triacylglycerols (TG) (SMD = -0.23; 95% CI: -0.39 to -0.06; p = 0.007), but increased fat free mass (FFM) (MD = 0.98 kg; 95% CI: 0.18-1.78; p = 0.016). Of note, compared with the non-intervention diet, modified alternate-day fasting (MADF) reduced fat mass (MD = -0.70 kg; 95% CI: -1.38 to -0.02; p = 0.044). In people with overweight or obesity, and type 2 diabetes, IF increases high-density lipoprotein cholesterol (HDL-C) levels compared to continuous energy restriction (CER) (MD = 0.03 mmol/L; 95% CI: 0.01-0.05; p = 0.010). However, IF was less effective at reducing systolic blood pressure (SBP) than a CER diet in adults with overweight or obesity (SMD = 0.21; 95% CI: 0.05-0.36; p = 0.008).

Interpretation

Our findings suggest that IF may have beneficial effects on a range of health outcomes for adults with overweight or obesity, compared to CER or non-intervention diet. Specifically, IF may decreased WC, fat mass, LDL-C, TG, TC, fasting insulin, and SBP, while increasing HDL-C and FFM. Notably, it is worth noting that the SBP lowering effect of IF appears to be weaker than that of CER.

Funding

This work was supported by the National Key Research and Development Program of China (Q-JW), the Natural Science Foundation of China (Q-JW and T-TG), Outstanding Scientific Fund of Shengjing Hospital of China Medical University (Q-JW), and 345 Talent Project of Shengjing Hospital of China Medical University (T-TG).

The role of TRPV ion channels in adipocyte differentiation: What is the evidence?

Obesity is a complex disorder, and the incidence of obesity continues to rise at an alarming rate worldwide. In particular, the growing incidence of overweight and obesity in children is a major health concern. However, the underlying mechanisms of obesity remain unclear and the efficacy of several approaches for weight loss is limited. As an important calcium-permeable temperature-sensitive cation channel, transient receptor potential vanilloid (TRPV) ion channels directly participate in thermo-, mechano-, and chemosensory responses. Modulation of TRPV ion channel activity can alter the physiological function of the ion channel, leading to neurodegenerative diseases, chronic pain, cancer, and skin disorders. In recent years, increasing studies have demonstrated that TRPV ion channels are abundantly expressed in metabolic organs, including the liver, adipose tissue, skeletal muscle, pancreas, and central nervous system, which has been implicated in various metabolic diseases, including obesity and diabetes mellitus. In addition, as an important process for the pathophysiology of adipocyte metabolism, adipocyte differentiation plays a critical role in obesity. In this review, we focus on the role of TRPV ion channels in adipocyte differentiation to broaden the ideas for prevention and control strategies for obesity.

Effects and possible mechanisms of intermittent fasting on health and disease: a narrative review

The imbalance between energy intake and expenditure in an environment of continuous food availability can lead to metabolic disturbances in the body and increase the risk of obesity and a range of chronic noncommunicable diseases. Intermittent fasting (IF) is one of the most popular nonpharmacological interventions to combat obesity and chronic noncommunicable diseases. The 3 most widely studied IF regimens are alternate-day fasting, time-restricted feeding, and the 5:2 diet. In rodents, IF helps optimize energy metabolism, prevent obesity, promote brain health, improve immune and reproductive function, and delay aging. In humans, IF's benefits are relevant for the aging global population and for increasing human life expectancy. However, the optimal model of IF remains unclear. In this review, the possible mechanisms of IF are summarized and its possible drawbacks are discussed on the basis of the results of existing research, which provide a new idea for nonpharmaceutical dietary intervention of chronic noncommunicable diseases.

Intermittent fasting reduces mouse body fat while maintaining muscle mass by regulating protein synthesis and autophagy

OBJECTIVES

The aim of this study is to investigate the effect of intermittent fasting (IF) on the regulation of skeletal muscle protein metabolism in response to nutrient supplementation during fasting.

METHODS

Twelve-week-old male C57BL/6J mice were assigned to two groups: ad libitum and IF, with the latter having access to food for only 3 h/d. After 6 wk of experimental periods, an oral glucose tolerance test was performed. One week later, phosphate-buffered saline or a glucose and branched-chain amino acid mixture was administered orally, and blood and tissues were collected 30 min later.

RESULTS

The oral glucose tolerance test results revealed that the IF group had better insulin sensitivity. They also had lower body and fat weights while maintaining the same level of skeletal muscle mass as the ad libitum group. The phosphorylation of ribosomal protein S6 in the skeletal muscle, a marker for the activation of protein translation, was greater in the IF group after glucose and branched-chain amino acid mixture administration. Microtubule-associated protein light chain 3-II-to-light chain 3-I ratio, a marker for autophagosome formation, in skeletal muscle during fasting was significantly lower in the IF group than that in the ad libitum group.

CONCLUSIONS

Our findings suggest that adaptation to IF regulates protein synthesis and breakdown, leading to the maintenance of skeletal muscle mass while reducing body fat.

Functions of SRPK, CLK and DYRK kinases in stem cells, development, and human developmental disorders

Human developmental disorders encompass a wide range of debilitating physical conditions and intellectual disabilities. Perturbation of protein kinase signalling underlies the development of some of these disorders. For example, disrupted SRPK signalling is associated with intellectual disabilities, and the gene dosage of DYRKs can dictate the pathology of disorders including Down's syndrome. Here, we review the emerging roles of the CMGC kinase families SRPK, CLK, DYRK, and sub-family HIPK during embryonic development and in developmental disorders. In particular, SRPK, CLK, and DYRK kinase families have key roles in developmental signalling and stem cell regulation, and can co-ordinate neuronal development and function. Genetic studies in model organisms reveal critical phenotypes including embryonic lethality, sterility, musculoskeletal errors, and most notably, altered neurological behaviours arising from defects of the neuroectoderm and altered neuronal signalling. Further unpicking the mechanisms of specific kinases using human stem cell models of neuronal differentiation and function will improve our understanding of human developmental disorders and may provide avenues for therapeutic strategies.

Intermittent Fasting Primes the Tumor Microenvironment and Improves Nanomedicine Delivery in Hepatocellular Carcinoma

Fasting has many health benefits, including reduced chemotherapy toxicity and improved efficacy. It is unclear how fasting affects the tumor microenvironment (TME) and tumor-targeted drug delivery. Here the effects of intermittent (IF) and short-term (STF) fasting are investigated on tumor growth, TME composition, and liposome delivery in allogeneic hepatocellular carcinoma (HCC) mouse models. To this end, mice are inoculated either subcutaneously or intrahepatically with Hep-55.1C cells and subjected to IF for 24 d or to STF for 1 d. IF but not STF significantly slows down tumor growth. IF increases tumor vascularization and decreases collagen density, resulting in improved liposome delivery. In vitro, fasting furthermore promotes the tumor cell uptake of liposomes. These results demonstrate that IF shapes the TME in HCC towards enhanced drug delivery. Finally, when combining IF with liposomal doxorubicin treatment, the antitumor efficacy of nanochemotherapy is found to be increased, while systemic side effects are reduced. Altogether, these findings exemplify that the beneficial effects of fasting on anticancer therapy outcomes go beyond modulating metabolism at the molecular level.

CLK2 in GABAergic neurons is critical in regulating energy balance and anxiety-like behavior in a gender-specific fashion

Introduction

Cdc2-like kinase (CLK2) is a member of CLK kinases expressed in hypothalamic neurons and is activated in response to refeeding, leptin, or insulin. Diet-induced obesity and leptin receptor-deficient db/db mice lack CLK2 signal in the hypothalamic neurons. The neurotransmiter gamma-aminobutyric acid (GABA) is among the most prevalent in the central nervous system (CNS), particularly in the hypothalamus. Given the abundance of GABA-expressing neurons and their potential influence on regulating energy and behavioral homeostasis, we aimed to explore whether the deletion of CLK2 in GABAergic neurons alters energy homeostasis and behavioral and cognitive functions in both genders of mice lacking CLK2 in Vgat-expressing neurons (Vgat-Cre; Clk2loxP/loxP) on chow diet.

Methods

We generated mice lacking Clk2 in Vgat-expressing neurons (Vgat-Cre; Clk2loxP/loxP) by mating Clk2loxP/loxP mice with Vgat-IRES-Cre transgenic mice and employed behavior, and physiological tests, and molecular approaches to investigate energy metabolism and behavior phenotype of both genders.

Results and discussion

We showed that deletion of CLK2 in GABAergic neurons increased adiposity and food intake in females. The mechanisms behind these effects were likely due, at least in part, to hypothalamic insulin resistance and upregulation of hypothalamic Npy and Agrp expression. Besides normal insulin and pyruvate sensitivity, Vgat-Cre; Clk2loxP/loxP females were glucose intolerant. Male Vgat-Cre; Clk2loxP/loxP mice showed an increased energy expenditure (EE). Risen EE may account for avoiding weight and fat mass gain in male Vgat-Cre; Clk2loxP/loxP mice. Vgat-Cre; Clk2loxP/loxP mice had no alteration in cognition or memory functions in both genders. Interestingly, deleting CLK2 in GABAergic neurons changed anxiety-like behavior only in females, not males. These findings suggest that CLK2 in GABAergic neurons is critical in regulating energy balance and anxiety-like behavior in a gender-specific fashion and could be a molecular therapeutic target for combating obesity associated with psychological disorders in females.

Gut microbiota and transcriptome dynamics in every-other-day fasting are associated with neuroprotection in rats with spinal cord injury

Introduction

Every-other-day fasting (EODF) is a classical intermittent fasting (IF) mode with neuroprotective effects that promotes motor function recovery after spinal cord injury (SCI) in rats. However, its dynamic effects on the gut microbiota and spinal cord transcriptome remain unknown.

Methods

In this study, 16S rRNA sequencing and RNA-seq analysis were used to investigate the effects of ad libitum (AL) and EODF dietary modes on the structural characteristics of rat gut microbiota in rats and the spinal cord transcriptome at various time points after SCI induction.

Results

Our results showed that both dietary modes affected the bacterial community composition in SCI rats, with EODF treatment inducing and suppressing dynamic changes in the abundances of potentially anti-inflammatory and pro-inflammatory bacteria. Furthermore, the differentially expressed genes (DEGs) enriched after EODF intervention in SCI rats were associated with various biological events, including immune inflammatory response, cell differentiation, protein modification, neural growth, and apoptosis. In particular, significant spatiotemporal differences were apparent in the DEGs associated with neuroprotection between the EODF and AL interventions. These DGEs were mainly focused on days 1, 3, and 7 after SCI. The relative abundance of certain genera was significantly correlated with DEGs associated with neuroprotective effects in the EODF-SCI group.

Discussion

Our results showed that EODF treatment may exert neuroprotective effects by modulating the transcriptome expression profile following SCI in rats. Furthermore, gut microbiota may be partially involved in mediating these effects.

Intermittent Fasting Sustainably Improves Glucose Tolerance in Normal Weight Male Mice Through Histone Hyperacetylation

To explore the mechanism by which intermittent fasting (IF) exerts prolonged effects after discontinuation, we examined mice that had been subjected to 4 cycles of fasting for 72 hours and ad libitum feeding for 96 hours per week (72hIF), followed by 4 weeks of ad libitum feeding, focusing on expression of genes for lipid metabolism in the skeletal muscle and histone acetylation in the promoter region. The 72hIF regimen resulted in metabolic remodeling, characterized by enhanced lipid utilization and mitochondrial activation in the muscle. This long-term IF (72hIF) caused stronger metabolic effects than alternate day fasting (24hIF) wherein fasting and refeeding are repeated every 24 hours. Upregulation of lipid oxidation genes and an increase in oxygen utilization were sustained even at 4 weeks after discontinuation of 72hIF, associated with histone hyperacetylation of the promoter region of uncoupling protein 3 (Ucp3) and carnitine palmitoyl transferase 1b (Cpt1b) genes. An increase in leucine owing to fasting-induced muscle degradation was suggested to lead to the histone acetylation. These findings support the previously unappreciated notion that sustainable promotion of histone acetylation in lipid oxidation genes of the muscle and adipose tissues during and after IF may contribute to sustained metabolic effects of IF.

Adipocyte YTH N(6)-methyladenosine RNA-binding protein 1 protects against obesity by promoting white adipose tissue beiging in male mice

Obesity, one of the most serious public health issues, is caused by the imbalance of energy intake and energy expenditure. N(6)-methyladenosine (m⁶A) RNA modification has been recently identified as a key regulator of obesity, while the detailed mechanism is elusive. Here, we find that YTH RNA binding protein 1 (YTHDF1), an m⁶A reader, acts as an essential regulator of white adipose tissue metabolism. The expression of YTHDF1 decreases in adipose tissue of male mice fed a high-fat diet. Adipocyte-specific Ythdf1 deficiency exacerbates obesity-induced metabolic defects and inhibits beiging of inguinal white adipose tissue (iWAT) in male mice. By contrast, male mice with WAT-specific YTHDF1 overexpression are resistant to obesity and shows promotion of beiging. Mechanistically, YTHDF1 regulates the translation of diverse m⁶A-modified mRNAs. In particular, YTHDF1 facilitates the translation of bone morphogenetic protein 8b (Bmp8b) in an m⁶A-dependent manner to induce the beiging process. Here, we show that YTHDF1 may be an potential therapeutic target for the management of obesity-associated diseases.

Structural mechanism for inhibition of PP2A-B56α and oncogenicity by CIP2A

The protein phosphatase 2A (PP2A) heterotrimer PP2A-B56α is a human tumour suppressor. However, the molecular mechanisms inhibiting PP2A-B56α in cancer are poorly understood. Here, we report molecular level details and structural mechanisms of PP2A-B56α inhibition by an oncoprotein CIP2A. Upon direct binding to PP2A-B56α trimer, CIP2A displaces the PP2A-A subunit and thereby hijacks both the B56α, and the catalytic PP2Ac subunit to form a CIP2A-B56α-PP2Ac pseudotrimer. Further, CIP2A competes with B56α substrate binding by blocking the LxxIxE-motif substrate binding pocket on B56α. Relevant to oncogenic activity of CIP2A across human cancers, the N-terminal head domain-mediated interaction with B56α stabilizes CIP2A protein. Functionally, CRISPR/Cas9-mediated single amino acid mutagenesis of the head domain blunted MYC expression and MEK phosphorylation, and abrogated triple-negative breast cancer in vivo tumour growth. Collectively, we discover a unique multi-step hijack and mute protein complex regulation mechanism resulting in tumour suppressor PP2A-B56α inhibition. Further, the results unfold a structural determinant for the oncogenic activity of CIP2A, potentially facilitating therapeutic modulation of CIP2A in cancer and other diseases.

Overexpression of Pregnancy Zone Protein in Fat Antagonizes Diet-Induced Obesity Under an Intermittent Fasting Regime

The intermittent fasting regimen (IFR) has been certified as an effective strategy for improving metabolism. But the underlying mechanism is still obscure. Beige induction in white adipose tissue (WAT) by IFR may account for this. It has been demonstrated that the erupting of pregnancy zone protein (PZP) from the liver coincides with membrane translocation of grp78 in brown adipocytes during IFR to activate brown adipose tissue (BAT), which may partly explain the metabolic benefits of IFR. Liver-derived PZP appears to be responsible for all metabolic regulatory functions; the effect of boosting energy expenditure disappeared in liver-deficient mice. To verify whether any liver-specific modification was essential for functional PZP, we used the PZP adipose tissue-specific overexpression mice model (PZP TG). We found that the metabolic disorders induced by high-fat diet were improved in PZP TG mice under IFR. Additionally, in addition to the activation of BAT, UCP1 protein and angiogenesis were increased in WAT, as well as the expression of genes associated with glucose utilization. These results demonstrate that PZP fat-specific TG increased the energy conversion of WAT, indicating that WAT may be another direct target for PZP during IFR.

An update on brown adipose tissue and obesity intervention: Function, regulation and therapeutic implications

Overweight and obesity have become a world-wide problem. However, effective intervention approaches are limited. Brown adipose tissue, which helps maintain body temperature and contributes to thermogenesis, is dependent on uncoupling protein1. Over the last decade, an in-creasing number of studies have found that activating brown adipose tissue and browning of white adipose tissue can protect against obesity and obesity-related metabolic disease. Brown adipose tissue has gradually become an appealing therapeutic target for the prevention and re-versal of obesity. However, some important issues remain unresolved. It is not certain whether increasing brown adipose tissue activity is the cause or effect of body weight loss or what the risks might be for sympathetic nervous system-dependent non-shivering thermogenesis. In this review, we comprehensively summarize approaches to activating brown adipose tissue and/or browning white adipose tissue, such as cold exposure, exercise, and small-molecule treatment. We highlight the functional mechanisms of small-molecule treatment and brown adipose tissue transplantation using batokine, sympathetic nervous system and/or gut microbiome. Finally, we discuss the causality between body weight loss induced by bariatric surgery, exercise, and brown adipose tissue activity.

Gut microbiota-a positive contributor in the process of intermittent fasting-mediated obesity control

Historically, intermittent fasting (IF) has been considered as an effective strategy for controlling the weight of athletes before competition. Along with excellent insight into its application in various spaces by numerous studies, increasing IF-mediated positive effects have been reported, including anti-aging, neuroprotection, especially obesity control. Recently, the gut microbiota has been considered as an essential manipulator for host energy metabolism and its structure has been reported to be sensitive to dietary structure and habits, indicating that there is a potential and strong association between IF and gut microbiota. In this paper, we focus on the crosstalk between these symbionts and energy metabolism during IF which hold the promise to optimize host energy metabolism at various physical positions, including adipose tissue, liver and intestines, and further improve milieu internal homeostasis. Moreover, this paper also discusses the positive function of a potential recommendatory strain (Akkermansia muciniphila) based on the observational data for IF-mediated alternated pattern of gut microbiota and a hopefully regulatory pathway (circadian rhythm) for gut microbiota in IF-involved improvement on host energy metabolism. Finally, this review addresses the limitation and perspective originating from these studies, such as the association with tissue-specific bio-clock and single strain research, which may continuously reveal novel viewpoints and mechanisms to understand the energy metabolism and develop new strategies for treating obesity, diabetes, and metabolic disorders.

Hepatokine Pregnancy Zone Protein Governs the Diet-Induced Thermogenesis Through Activating Brown Adipose Tissue

Intermittent fasting (IF), as a dietary intervention for weight loss, takes effects primarily through increasing energy expenditure. However, whether inter-organ systems play a key role in IF remains unclear. Here, a novel hepatokine, pregnancy zone protein (PZP) is identified, which has significant induction during the refeeding stage of IF. Further, loss of function studies and protein therapeutic experiment in mice revealed that PZP promotes diet-induced thermogenesis through activating brown adipose tissue (BAT). Mechanistically, circulating PZP can bind to cell surface glucose-regulated protein of 78 kDa (GRP78) to promote uncoupling protein 1 (UCP1) expression via a p38 MAPK-ATF2 signaling pathway in BAT. These studies illuminate a systemic regulation in which the IF promotes BAT thermogenesis through the endocrinal system and provide a novel potential target for treating obesity and related disorders.

Development of Cdc2-like Kinase 2 Inhibitors: Achievements and Future Directions

Cdc2-like kinases (CLKs; CLK1-4) are associated with various neurodegenerative disorders, metabolic regulation, and viral infection and have been recognized as potential drug targets. Human CLK2 has received increasing attention as a regulator that phosphorylates serine- and arginine-rich (SR) proteins and subsequently modulates the alternative splicing of precursor mRNA (pre-mRNA), which is an attractive target for degenerative disease and cancer. Numerous CLK2 inhibitors have been identified, with several molecules currently in clinical development. The first CLK2 inhibitor Lorecivivint (compound 1) has recently entered phase 3 clinical trials. However, highly selective CLK2 inhibitors are rarely reported. This Perspective summarizes the biological roles and therapeutic potential of CLK2 along with progress on the development of CLK2 inhibitors and discusses the achievements and future prospects of CLK2 inhibitors for therapeutic applications.

Inhibition of a Novel CLK1-THRAP3-PPARγ Axis Improves Insulin Sensitivity

Increasing energy expenditure by promoting "browning" in adipose tissues is a promising strategy to prevent obesity and associated diabetes. To uncover potential targets of cold exposure, which induces energy expenditure, we performed phosphoproteomics profiling in brown adipose tissue of mice housed in mild cold environment at 16°C. We identified CDC2-like kinase 1 (CLK1) as one of the kinases that were significantly downregulated by mild cold exposure. In addition, genetic knockout of CLK1 or chemical inhibition in mice ameliorated diet-induced obesity and insulin resistance at 22°C. Through proteomics, we uncovered thyroid hormone receptor-associated protein 3 (THRAP3) as an interacting partner of CLK1, further confirmed by co-immunoprecipitation assays. We further demonstrated that CLK1 phosphorylates THRAP3 at Ser243, which is required for its regulatory interaction with phosphorylated peroxisome proliferator-activated receptor gamma (PPARγ), resulting in impaired adipose tissue browning and insulin sensitivity. These data suggest that CLK1 plays a critical role in controlling energy expenditure through the CLK1-THRAP3-PPARγ axis.

Childhood Obesity-Related Mechanisms: MicroRNome and Transcriptome Changes in a Nested Case-Control Study

Childhood obesity could contribute to adulthood obesity, leading to adverse health outcomes in adults. However, the mechanisms for how obesity is developed are still unclear. To determine the epigenome-wide and genome-wide expression changes related with childhood obesity, we compared microRNome and transcriptome levels as well as leptin protein levels in whole bloods of 12 obese and 24 normal children aged 6 years. miR-328-3p, miR-1301-3p, miR-4685-3p, and miR-6803-3p were negatively associated with all obesity indicators. The four miRNAs were also associated with 3948 mRNAs, and separate 475 mRNAs (185 among 3948 mRNAs) were associated with all obesity indicators. The 2533 mRNAs (64.2%) among the 3948 mRNAs and 286 mRNAs (60.2%) among the 475 mRNAs were confirmed as targets of the four miRNAs in public databases through miRWalk 2.0. Leptin protein was associated with miR-6803-3p negatively and all obesity indicators positively. Using DAVID bioinformatics resources 6.8, top three pathways for obesity-related gene set were metabolic pathways, pathways in cancer, and PI3K-Akt signaling pathway. The top three obesity-related disease classes were metabolic, cardiovascular, and chemdependency. Our results support that childhood obesity could be developed through miRNAs-related epigenetic mechanism and, further, these obesity-related epigenetic changes could control the pathways related with the development of various diseases.

Remodeling of the gut microbiome during Ramadan-associated intermittent fasting

BACKGROUND

Intermittent fasting is a popular dietary intervention with perceived relatively easy compliance and is linked to various health benefits, including weight loss and improvement in blood glucose concentrations. The mechanistic explanations underlying the beneficial effects of intermittent fasting remain largely obscure but may involve alterations in the gut microbiota.

OBJECTIVES

We sought to establish the effects of 1 mo of intermittent fasting on the gut microbiome.

METHODS

We took advantage of intermittent fasting being voluntarily observed during the Islamic faith-associated Ramadan and sampled feces and blood, as well as collected longitudinal physiologic data in 2 cohorts, sampled in 2 different years. The fecal microbiome was determined by 16S sequencing. Results were contrasted to age- and body weight-matched controls and correlated to physiologic parameters (e.g., body mass and calorie intake).

RESULTS

We observed that Ramadan-associated intermittent fasting increased microbiome diversity and was specifically associated with upregulation of the Clostridiales order-derived Lachnospiraceae [no fasting 24.6 ± 13.67 compared with fasting 39.7 ± 15.9 in relative abundance (%); linear discriminant analysis = 4.9, P < 0.001 by linear discriminant analysis coupled with effect size measurements] and Ruminococcaceae [no fasting 13.4 ± 6.9 compared with fasting 23.2 ± 12.9 in relative abundance (%); linear discriminant analysis = 4.7, P < 0.001 by linear discriminant analysis coupled with effect size measurements] bacterial families. Microbiome composition returned to baseline upon cessation of intermittent feeding. Furthermore, changes in Lachnospiraceae concentrations mirrored intermittent fasting-provoked changes in physiologic parameters.

CONCLUSIONS

Intermittent fasting provokes substantial remodeling of the gut microbiome. The intermittent fasting-provoked upregulation of butyric acid-producing Lachnospiraceae provides an obvious possible mechanistic explanation for health effects associated with intermittent fasting.

CDC2-like (CLK) protein kinase inhibition as a novel targeted therapeutic strategy in prostate cancer

Dysregulation of alternative splicing is a feature of cancer, both in aetiology and progression. It occurs because of mutations in splice sites or sites that regulate splicing, or because of the altered expression and activity of splice factors and of splice factor kinases that regulate splice factor activity. Recently the CDC2-like kinases (CLKs) have attracted attention due to their increasing involvement in cancer. We measured the effect of the CLK inhibitor, the benzothiazole TG003, on two prostate cancer cell lines. TG003 reduced cell proliferation and increased apoptosis in PC3 and DU145 cells. Conversely, the overexpression of CLK1 in PC3 cells prevented TG003 from reducing cell proliferation. TG003 slowed scratch closure and reduced cell migration and invasion in a transwell assay. TG003 decisively inhibited the growth of a PC3 cell line xenograft in nude mice. We performed a transcriptomic analysis of cells treated with TG003. We report widespread and consistent changes in alternative splicing of cancer-associated genes including CENPE, ESCO2, CKAP2, MELK, ASPH and CD164 in both HeLa and PC3 cells. Together these findings suggest that targeting CLKs will provide novel therapeutic opportunities in prostate cancer.

Health Effects of Alternate Day Fasting Versus Pair-Fed Caloric Restriction in Diet-Induced Obese C57Bl/6J Male Mice

Alternate day fasting (ADF) induces weight loss and improves various markers of health in rodents and humans. However, it is unclear whether the benefits of ADF are derived from the lower caloric intake of ADF or from the 24-h fasting period. Therefore, this study directly compared selected markers for health – such as glucose control, body weight, liver triglycerides, T cell frequencies, and others – in high-fat (60% calories from fat) diet-induced obese mice subjected to either ADF or caloric restriction (CR). Obese mice were randomly assigned to one of four groups: (1) ADF: remained on the high-fat diet, but fed on alternate days (n = 5), (2) PF: remained on the high-fat diet, but pair-fed to the ADF group (n = 5), (3) LF: moved to a chow ad libitum diet (n = 5; 17% calories from fat), and (4) HF: remained on the high-fat ad libitum diet (n = 5). An additional group of non-obese mice maintained on a chow diet since weaning were used as controls (CON: n = 5). After 10 weeks, ADF, PF, and LF mice ate fewer kcals, had a lower body mass, had smaller epididymal fat pads, improved glucose tolerance, and had a lower hepatic triglyceride content relative to HF mice (p < 0.05), but none reached that of CON mice in these measures. T cell frequencies of the spleen, blood, and mesenteric lymph nodes were reduced in ADF, PF, and HF compared to the CON group. Importantly, there were no significant differences between the ADF and PF groups in any of the measurements made in the current study. These data suggest that ADF, PF, and LF diets each lead to improved markers of health relative to high-fat diet-induced obese mice, and that the caloric restriction associated with ADF is the major factor for the noted improvements.

Understanding Dietary Intervention-Mediated Epigenetic Modifications in Metabolic Diseases

The global prevalence of metabolic disorders, such as obesity, diabetes and fatty liver disease, is dramatically increasing. Both genetic and environmental factors are well-known contributors to the development of these diseases and therefore, the study of epigenetics can provide additional mechanistic insight. Dietary interventions, including caloric restriction, intermittent fasting or time-restricted feeding, have shown promising improvements in patients' overall metabolic profiles (i.e., reduced body weight, improved glucose homeostasis), and an increasing number of studies have associated these beneficial effects with epigenetic alterations. In this article, we review epigenetic changes involved in both metabolic diseases and dietary interventions in primary metabolic tissues (i.e., adipose, liver, and pancreas) in hopes of elucidating potential biomarkers and therapeutic targets for disease prevention and treatment.

Cdc-Like Kinases (CLKs): Biology, Chemical Probes, and Therapeutic Potential

Protein kinases represent a very pharmacologically attractive class of targets; however, some members of the family still remain rather unexplored. The biology and therapeutic potential of cdc-like kinases (CLKs) have been explored mainly over the last decade and the first CLK inhibitor, compound SM08502, entered clinical trials only recently. This review summarizes the biological roles and therapeutic potential of CLKs and their heretofore published small-molecule inhibitors, with a focus on the compounds' potential to be utilized as quality chemical biology probes.

Intermittent Fasting: Physiological Implications on Outcomes in Mice and Men

Intermittent fasting (IF) is a widely practiced dietary method that encompasses periodic restriction of food consumption. Due to its protective benefits against metabolic diseases, aging, and cardiovascular and neurodegenerative diseases, IF continues to gain attention as a preventative and therapeutic intervention to counteract these chronic diseases. Although numerous animal studies have reported positive health benefits of IF, its feasibility and efficacy in clinical settings remain controversial. Importantly, since dietary interventions such as IF have systemic effects, thoroughly investigating the tissue-specific changes in animal models is crucial to identify IF's mechanism and evaluate its potential adverse effects in humans. As such, we will review and compare the outcomes and underlying mechanisms of IF in both animal and human studies. Moreover, the limitations of IF and inconsistencies between preclinical and clinical studies will be discussed to provide insight into the gaps between translating research from bench to bedside.

Reduced meal frequency alleviates high-fat diet-induced lipid accumulation and inflammation in adipose tissue of pigs under the circumstance of fixed feed allowance

PURPOSE

The present study was conducted to determine whether reduced meal frequency (MF) could restore high-fat diet (HFD)-modified phenotypes and microbiota under the condition of fixed feed allowance.

METHODS

A total of 32 barrows with initial weight of 61.6 ± 0.8 kg were assigned to two diets [control diet (CON) versus HFD] and two meal frequencies [12 equal meals/day (M12) versus 2 equal meals/day (M2)], the trial lasted 8 weeks. The lipid metabolism and inflammatory response in adipose tissue as well as the profiles of intestinal microbiota and bacterial-derived metabolites were determined.

RESULTS

M2 versus M12 feeding regimen decreased perirenal fat weight and serum triglyceride and liposaccharide (LPS) concentrations in HFD-fed pigs (P < 0.05). Reduced MF down-regulated mRNA expression of lipoprotein lipase, CD36 molecule, interleukin 1 beta, tumor necrosis factor alpha, toll-like receptor 4, myeloid differentiation factor 88 (MYD88), and nuclear factor kappa beta 1 as well as protein expression of MYD88 in perirenal fat of HFD-fed pigs (P < 0.05). M2 feeding regimen increased abundance of Prevotella and decreased abundance of Bacteroides in colonic content of HFD-fed pigs (P < 0.05). No difference in short-chain fatty acids (SCFAs) profile in colonic content was observed among four groups (P > 0.05).

CONCLUSION

Our results suggested that M2 versus M12 feeding regimen ameliorated HFD-induced fat deposition and inflammatory response by decreasing fatty acid uptake and deactivating LPS/TLR4 signaling pathway in adipose tissue and restoring microbiota composition in distal intestine, without affecting SCFAs profile in distal luminal content.

Autoregulation of the human splice factor kinase CLK1 through exon skipping and intron retention

Alternative splicing is a key process required for the regulation of gene expression in normal development and physiology. It is regulated by splice factors whose activities are in turn regulated by splice factor kinases and phosphatases. The CDC-like protein kinases are a widespread family of splice factor kinases involved in normal physiology and in several diseases including cancer. In humans they include the CLK1, CLK2, CLK3 and CLK4 genes. The expression of CLK1 is regulated through alternative splicing producing both full-length catalytically active and truncated catalytically inactive isoforms, CLK^T1 (arising from exon 4 skipping) and CLK^T2 (arising from intron 4 retention). We examined CLK1 alternative splicing in a range of cancer cell lines, and report widespread and highly variable rates of exon 4 skipping and intron 4 retention. We also examined the effect of severe environmental stress including heat shock, osmotic shock, and exposure to the alkaloid drug harmine on CLK1 alternative splicing in DU145 prostate cancer cells. All treatments rapidly reduced exon 4 skipping and intron 4 retention, shifting the balance towards full-length CLK1 expression. We also found that the inhibition of CLK1 with the benzothiazole TG003 reduced exon 4 skipping and intron 4 retention suggesting an autoregulatory mechanism. CLK1 inhibition with TG003 also resulted in modified alternative splicing of five cancer-associated genes.

cAMP-inducible coactivator CRTC3 attenuates brown adipose tissue thermogenesis

In response to cold exposure, placental mammals maintain body temperature by increasing sympathetic nerve activity in brown adipose tissue (BAT). Triggering of β-adrenergic receptors on brown adipocytes stimulates thermogenesis via induction of the cAMP/PKA pathway. Although cAMP response element-binding protein (CREB) and its coactivators-the cAMP-regulated transcriptional coactivators (CRTCs)-mediate transcriptional effects of cAMP in most tissues, other transcription factors such as ATF2 appear critical for induction of thermogenic genes by cAMP in BAT. Brown adipocytes arise from Myf5-positive mesenchymal cells under the control of PRDM16, a coactivator that concurrently represses differentiation along the skeletal muscle lineage. Here, we show that the CREB coactivator CRTC3 is part of an inhibitory feedback pathway that antagonizes PRDM16-dependent differentiation. Mice with a knockout of CRTC3 in BAT (BKO) have increased cold tolerance and reduced adiposity, whereas mice overexpressing constitutively active CRTC3 in adipose tissue are more cold sensitive and have greater fat mass. CRTC3 reduced sympathetic nerve activity in BAT by up-regulating the expression of miR-206, a microRNA that promotes differentiation along the myogenic lineage and that we show here decreases the expression of VEGFA and neurotrophins critical for BAT innervation and vascularization. Sympathetic nerve activity to BAT was enhanced in BKO mice, leading to increases in catecholamine signaling that stimulated energy expenditure. As reexpression of miR-206 in BAT from BKO mice reversed the salutary effects of CRTC3 depletion on cold tolerance, our studies suggest that small-molecule inhibitors against this coactivator may provide therapeutic benefit to overweight individuals.

Loss of ABHD15 Impairs the Anti-lipolytic Action of Insulin by Altering PDE3B Stability and Contributes to Insulin Resistance

Elevated circulating fatty acids (FAs) contribute to obesity-associated metabolic complications, but the mechanisms by which insulin suppresses lipolysis are poorly understood. We show that α/β-hydrolase domain-containing 15 (ABHD15) is required for the anti-lipolytic action of insulin in white adipose tissue (WAT). Neither insulin nor glucose treatments can suppress FA mobilization in global and conditional Abhd15-knockout (KO) mice. Accordingly, insulin signaling is impaired in Abhd15-KO adipocytes, as indicated by reduced AKT phosphorylation, glucose uptake, and de novo lipogenesis. In vitro data reveal that ABHD15 associates with and stabilizes phosphodiesterase 3B (PDE3B). Accordingly, PDE3B expression is decreased in the WAT of Abhd15-KO mice, mechanistically explaining increased protein kinase A (PKA) activity, hormone-sensitive lipase (HSL) phosphorylation, and undiminished FA release upon insulin signaling. Ultimately, Abhd15-KO mice develop insulin resistance. Notably, ABHD15 expression is decreased in humans with obesity and diabetes compared to humans with obesity and normal glucose tolerance, identifying ABHD15 as a potential therapeutic target to mitigate insulin resistance.

ERRα Maintains Mitochondrial Oxidative Metabolism and Constitutes an Actionable Target in PGC1α-Elevated Melanomas

The uncontrolled growth of tumors provides metabolic dependencies that can be harnessed for therapeutic benefit. Although tumor cells exhibit these increased metabolic demands due to their rapid proliferation, these metabolic processes are general to all cells, and furthermore, targeted therapeutic intervention can provoke compensatory adaptation that alters tumors' characteristics. As an example, a subset of melanomas depends on the transcriptional coactivator PGC1α function to sustain their mitochondrial energy-dependent survival. However, selective outgrowth of resistant PGC1α-independent tumor cells becomes endowed with an augmented metastatic phenotype. To find PGC1α-dependent components that would not affect metastasis in melanomas, an unbiased proteomic analyses was performed and uncovered the orphan nuclear receptor ERRα, which supports PGC1α's control of mitochondrial energetic metabolism, but does not affect the antioxidant nor antimetastatic regulatory roles. Specifically, genetic or pharmacologic inhibition of ERRα reduces the inherent bioenergetic capacity and decreases melanoma cell growth, but without altering the invasive characteristics. Thus, within this particularly aggressive subset of melanomas, which is characterized by heighted expression of PGC1α, ERRα specifically mediates prosurvival functions and represents a tangible therapeutic target.Implications: ERRα, a druggable protein, mediates the bioenergetic effects in melanomas defined by high PGC1α expression, suggesting a rational means for therapeutic targeting of this particularly aggressive melanoma subtype. Mol Cancer Res; 15(10); 1366-75. ©2017 AACR.

Loss of ADAMTS5 enhances brown adipose tissue mass and promotes browning of white adipose tissue via CREB signaling

Objective

A potential strategy to treat obesity – and the associated metabolic consequences – is to increase energy expenditure. This could be achieved by stimulating thermogenesis through activation of brown adipose tissue (BAT) and/or the induction of browning of white adipose tissue (WAT). Over the last years, it has become clear that several metalloproteinases play an important role in adipocyte biology. Here, we investigated the potential role of ADAMTS5.

Methods

Mice deficient in ADAMTS5 (Adamts5^−/−) and wild-type (Adamts5^+/+) littermates were kept on a standard of Western-type diet for 15 weeks. Energy expenditure and heat production was followed by indirect calorimetry. To activate thermogenesis, mice were treated with the β3-adrenergic receptor (β₃-AR) agonist CL-316,243 or alternatively, exposed to cold for 2 weeks.

Results

Compared to Adamts5^+/+ mice, Adamts5^−/− mice have significantly more interscapular BAT and marked browning of their subcutaneous (SC) WAT. Thermogenic pathway analysis indicated, in the absence of ADAMTS5, enhanced β₃-AR signaling via activation of the cAMP response element-binding protein (CREB). Additional β₃-AR stimulation with CL-316,243 promoted browning of WAT in Adamts5^+/+ mice but had no additive effect in Adamts5^−/− mice. However, cold exposure induced more pronounced browning of WAT in Adamts5^−/− mice.

Conclusions

These data indicate that ADAMTS5 plays a functional role in development of BAT and browning of WAT. Hence, selective targeting of ADAMTS5 could provide a novel therapeutic strategy for treatment/prevention of obesity and metabolic diseases.

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Mice deficient in ADAMTS5 have elevated interscapular brown adipose tissue mass.

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ADAMTS5 deficient mice show increased browning of their white adipose tissue.

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The thermogenic profile is enhanced via adrenergic signaling and CREB activation.

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ADAMTS5 seems an attractive therapeutic target for metabolic diseases.