Adipose-targeted triiodothyronine therapy counteracts obesity-related metabolic complications and atherosclerosis with negligible side effects

Visceral adipocyte metabolic dysfunction in obesity related to altered chromatin accessibility to thyroid hormone receptor

OBJECTIVE

To explore the alterations in visceral adipose tissue (VAT) during obesity and identify the underlying mechanism causing the onset of VAT dysfunction.

METHODS

Histological staining on human VAT was utilized. VAT samples were collected from individuals with normal weight (n = 3, BMI 21.77 ± 0.709) and obesity (n = 3, BMI 32.95 ± 1.815). RNA-seq and ATAC-seq were employed. In vitro cell experiment, Chromatin immunoprecipitation (CHIP) assay and RNA interference were conducted.

RESULTS

Our research identified differentially expressed genes (DEGs) of VAT from individuals with normal wight or obesity enriched in pathways related to adipocyte metabolic function, thyroid hormone receptor binding sites were discovered in the accessible chromatin regions of these DEGs, including STAT5B. Motif enrichment, CHIP assay and in vitro cell experiments confirmed the decreased activation of STAT5B by triiodothyronine (T3) through binding with thyroid hormone receptor alpha (THRa) in obesity. In addition, RNA interference revealed STAT5B as a key transcription factor in maintaining the metabolic function of VAT.

CONCLUSION

In obesity, VAT metabolic function impairment is related to altered chromatin accessibility to thyroid hormone receptor. STAT5B is a key transcription factor at the core of the disrupted thyroid-adipose signaling and might be a promising target to improve obesity.

Overnutrition directly impairs thyroid hormone biosynthesis and utilization, causing hypothyroidism, despite remarkable thyroidal adaptations

Thyroid hormones (THs: T 3 and T 4 ) are key regulators of metabolic rate and nutrient metabolism. They are controlled centrally and peripherally in a coordinated manner to elegantly match T 3 -mediated energy expenditure (EE) to energy availability. Hypothyroidism reduces EE and has long been blamed for obesity; however, emerging evidence suggests that, instead, obesity may drive thyroid dysfunction. Thus, we used a mouse model of diet-induced obesity to determine its direct effects on thyroid histopathology and function, deiodinase activity, and T 3 action. Strikingly, overnutrition induced hypothyroidism within 3 weeks. Levels of thyroidal THs and their precursor protein thyroglobulin decreased, and ER stress was induced, indicating that thyroid function was directly impaired. We also observed pronounced histological and vascular expansion in the thyroid. Overnutrition additionally suppressed T 4 activation, rendering the mice resistant to T 4 and reducing EE. Our findings collectively show that overnutrition deals a double strike to TH biosynthesis and action, despite large efforts to adapt-but, fortunately, thyroid dysfunction in mice can be reversed by weight loss. In humans, BMI correlated with thyroidal vascularization, importantly demonstrating initial translatability. These studies lay the groundwork for novel obesity therapies that tackle hypothyroidism-which are much-needed, as no current obesity treatment works for everyone.

Adipose tissue-targeting nanomedicines for obesity pharmacotherapy

The increasing global prevalence of obesity presents a substantial challenge to public health. Current nutrient-stimulated hormone (NuSH)-based therapeutics are hindered by receptor desensitization, muscle loss, and weight regain. The adipose tissue, the primary organ responsible for energy storage and metabolic management, is a promising target for obesity treatment. Nanomedicine holds promise to precisely deliver medication to the adipose tissue to maximize therapeutic efficacy and minimize off-target effects; indeed, various adipose tissue-targeting nanomedicines have shown impressive anti-obesity effects by optimizing drug pharmacokinetic profiles and reducing nonspecific distribution in preclinical studies. Here we examine the current state of the art of adipose tissue-targeting nanomedicines, offering insights into recent advances, future possibilities, and the remaining challenges associated with their application in obesity treatment.

TSH-stimulated hepatocyte exosomes modulate liver-adipose triglyceride accumulation via the TGF-β1/ATGL axis in mice

Subclinical hypothyroidism (SCH) contributes to obesity, with the liver acting as a crucial metabolic regulator. Thyroid-stimulating hormone (TSH) affects systemic lipid balance, potentially linking SCH to obesity. While the direct impact of TSH on hepatic lipid metabolism has been extensively documented, its role in modulating lipid dynamics in peripheral organs through liver-mediated pathways remains insufficiently understood. This study identifies TSH-stimulated hepatocyte-derived exosomes (exosomesTSH) as key mediators in liver-adipose communication, promoting triglyceride accumulation in adipocytes via the transforming growth factor-beta 1 (TGF-β1)/adipose triglyceride lipase (ATGL) axis. ExosomesTSH enhance lipid storage in adipocytes, significantly increasing triglyceride content and lipid droplet formation while reducing lipolysis, effects that are dependent on TSH receptor (TSHR) activation in hepatocytes. In vivo, exosomesTSH induce weight gain and adipose tissue expansion, impairing glucose metabolism in both chow- and high-fat diet-fed mice. Mechanistically, exosomesTSH upregulate TGF-β1 and downregulate ATGL in adipocytes, establishing the TGF-β1/ATGL pathway as essential for exosome-mediated lipid accumulation. Further, miR-139-5p is identified as a modulator of TGF-β1 expression within this pathway, with overexpression of miR-139-5p alleviating exosomesTSH-induced lipid accumulation in adipocytes. This study elucidates a novel miR-139-5p-dependent mechanism through which TSH modulates lipid metabolism via liver-derived exosomes, highlighting the pivotal role of miR-139-5p in linking SCH to adipose lipid accumulation through the TGF-β1/ATGL signaling axis.

A quick paster type of soluble nanoparticle microneedle patch for the treatment of obesity

Obesity is a major public burden on the working population and induces chronic diseases. Its treatment often requires long-term medication, which makes patient compliance difficult. In this study, we reported the value of HORN-MN, which comprised a fast-soluble hyaluronic acid microneedle matrix and a weak acid-degradable oleanolic acid dimer of rosiglitazone nanoparticles. The results showed that the microneedles easily punctured the stratum corneum and dissolved in the dermis of the abdominal wall within 5 min, followed by the release of rosiglitazone nanoparticles. Thereafter, the nanoparticles were endocytosed by macrophages and white adipocytes, then degraded to oleanolic acid in the lysosomes, thereby, releasing rosiglitazone. Oleanolic acid significantly improved the inflammatory status of obese adipose tissue and promoted white adipocyte browning, and rosiglitazone significantly potentiated WAC browning. Accordingly, the patch demonstrated a remarkable obesity-reducing efficacy in mice. In conclusion, this study developed a quick paster type of soluble rosiglitazone nanoparticle microneedle for the treatment of obesity. This patch can be suitable for working people, with an evident obesity-reducing efficacy but no effect on skin integrity despite multiple administrations.

Emerging Roles of ncRNAs in Type 2 Diabetes Mellitus: From Mechanisms to Drug Discovery

Type 2 diabetes mellitus (T2DM), a high-incidence chronic metabolic disorder, has emerged as a global health issue, where most patients need lifelong medication. Gaining insights into molecular mechanisms involved in T2DM development is expected to provide novel strategies for clinical prevention and treatment. Growing evidence validates that non-coding RNAs (ncRNAs) including microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs (circRNAs) function as crucial regulators in multiple biological processes of T2DM, inspiring various potential targets and drug candidates. In this review, we summarize the current understanding of ncRNA roles in T2DM and discuss the potential use of ncRNAs as targets and active molecules for drug discovery.

Increased thyroid hormone sensitivity is correlated with visceral obesity in patients with type 2 diabetes

OBJECTIVE

The study aimed to assess whether thyroid hormone (TH) sensitivity is related to visceral fat area (VFA) and visceral obesity in euthyroid subjects with type 2 diabetes (T2D).

METHODS

750 euthyroid patients with T2D were enrolled. A VFA of 80 cm2 or more was considered visceral obesity. Central TH sensitivity was conducted using thyrotrophic thyroxine resistance index (TT4RI), thyrotropin index (TSHI), and thyroid feedback quantile-based index (TFQI). Free triiodothyronine to free thyroxine (FT3/FT4) was utilized for assessing peripheral TH sensitivity.

RESULTS

The subjects had a mean age of 51.5 ± 11.1 years, and 540 (72.0%) of them were men. In multivariable regression analyses, there was a positive correlation of FT3/FT4 tertile with visceral obesity, after full adjustment for confounding variables (P < 0.05). The middle and highest FT3/FT4 tertiles were correlated with a 134% [95% CI (1.24, 4.44)] and 98% [95% CI (1.04, 3.78)] higher prevalence of visceral obesity than the lowest tertile, respectively. Conversely, elevated TFQI levels were linked to a decreased prevalence of visceral obesity. Stratified analysis revealed that these associations were particularly pronounced in participants who are neither overweight nor obese and those aged less than 60 years (all P < 0.05).

CONCLUSIONS

Higher TH sensitivity is correlated with visceral obesity and elevated VFA in euthyroid patients with T2D, particularly among those younger than 60 years and individuals who are neither overweight nor obese.

The growing complexity of the control of the hypothalamic pituitary thyroid axis and brown adipose tissue by leptin

The balance between food intake and energy expenditure is precisely regulated to maintain adipose stores. Leptin, which is produced in and released from adipose in direct proportion to its size, is a major contributor to this control and initiates its homeostatic responses largely via binding to leptin receptors (LepR) in the hypothalamus. Decreases in hypothalamic LepR binding signals starvation, leading to hunger and reduced energy expenditure, whereas increases in hypothalamic LepR binding can suppress food intake and increase energy expenditure. However, large gaps persist in the specific hypothalamic sites and detailed mechanisms by which leptin increases energy expenditure, via the parallel activation of the hypothalamic pituitary thyroid (HPT) axis and brown adipose tissue (BAT). The purpose of this review is to develop a framework for the complex mechanisms and neurocircuitry. The core circuitry begins with leptin binding to receptors in the arcuate nucleus, which then sends projections to the paraventricular nucleus (to regulate the HPT axis) and the dorsomedial hypothalamus (to regulate BAT). We build on this core by layering complexities, including the intricate and unsettled regulation of arcuate proopiomelanocortin neurons by leptin and the changes that occur as the regulation of the HPT axis and BAT is engaged or modified by challenges such as starvation, hypothermia, obesity, and pregnancy.

Hormone-based pharmacotherapy for metabolic dysfunction-associated fatty liver disease

Metabolic dysfunction-associated fatty liver disease (MAFLD) has reached epidemic proportions globally in parallel to the rising prevalence of obesity. Despite its significant burden, there is no approved pharmacotherapy specifically tailored for this disease. Many potential drug candidates for MAFLD have encountered setbacks in clinical trials, due to safety concerns or/and insufficient therapeutic efficacy. Nonetheless, several investigational drugs that mimic the actions of endogenous metabolic hormones, including thyroid hormone receptor β (THRβ) agonists, fibroblast growth factor 21 (FGF21) analogues, and glucagon-like peptide-1 receptor agonists (GLP-1RAs), showed promising therapeutic efficacy and excellent safety profiles. Among them, resmetirom, a liver-targeted THRβ-selective agonist, has met the primary outcomes in alleviation of metabolic dysfunction-associated steatohepatitis (MASH), the advanced form of MAFLD, and liver fibrosis in phase-3 clinical trials. These hormone-based pharmacotherapies not only exhibit varied degrees of therapeutic efficacy in mitigating hepatic steatosis, inflammation and fibrosis, but also improve metabolic profiles. Furthermore, these three hormonal agonists/analogues act in a complementary manner to exert their pharmacological effects, suggesting their combined therapies may yield synergistic therapeutic benefits. Further in-depth studies on the intricate interplay among these metabolic hormones are imperative for the development of more efficacious combination therapies, enabling precision management of MAFLD and its associated comorbidities.

Metabolic Messengers: Thyroid Hormones

Thyroid hormones (THs) are key hormones that regulate development and metabolism in mammals. In man, the major target tissues for TH action are the brain, liver, muscle, heart, and adipose tissue. Defects in TH synthesis, transport, metabolism, and nuclear action have been associated with genetic and endocrine diseases in man. Over the past few years, there has been renewed interest in TH action and the therapeutic potential of THs and thyromimetics to treat several metabolic disorders such as hypercholesterolemia, dyslipidaemia, non-alcoholic fatty liver disease (NAFLD), and TH transporter defects. Recent advances in the development of tissue and TH receptor isoform-targeted thyromimetics have kindled new hope for translating our fundamental understanding of TH action into an effective therapy. This review provides a concise overview of the historical development of our understanding of TH action, its physiological and pathophysiological effects on metabolism, and future therapeutic applications to treat metabolic dysfunction.

Obesity - Standards, trends and advances

Obesity continues to be a significant global health concern, giving rise to various complications. This review article explores the current standards and emerging innovations in diagnosing and treating obesity, including recent disease name change, staging system or therapeutic goals. This narrative review has been based on recent scientific articles from PubMed database, limiting the scope of topics to current standards and upcoming developments and breakthroughs in the diagnosis and treatment of obesity. The educational and informative nature of the review has been maintained in order to make the information presented accessible to both researchers and clinical practitioners. The recognition of diverse obesity phenotypes has prompted a paradigm shift towards a complex and patient-centered approach to diagnosis and therapy. Pharmacotherapy for obesity is evolving rapidly, with ongoing research focusing on novel molecular targets and metabolic pathways. Promising developments include dual or triple incretin analogs, oral incretin drugs, neurotransmitter-based therapies, muscle mass-increasing treatments, and therapies targeting visceral adipose tissue browning. Despite current evidence-based international standards, the field of obesity diagnosis and treatment continues to expand, with new diagnostic tools and pharmacotherapies potentially replacing current practices. Therapeutic management should be tailored to individual patients, considering obesity phenotype, health status, lifestyle, and preferences. Looking ahead, the future holds promising opportunities for obesity management, but further research is required to assess the efficacy and safety of emerging therapies. A multifactorial and personalized approach will be pivotal in addressing the diverse challenges posed by obesity.

Subclinical Hypothyroidism in Patients with Obesity and Metabolic Syndrome: A Narrative Review

The literature on the connection between obesity, metabolic syndrome, and subclinical hypothyroidism is critically analyzed in this narrative review. These conditions are frequently observed among adult populations and various studies and meta-analyses have assessed their association. The prevalence of subclinical hypothyroidism in obese individuals is higher than in non-obese subjects and this trend is more pronounced in unhealthy obesity phenotypes. However, the diagnosis and treatment of subclinical hypothyroidism can be difficult in obese patients. Exaggerated body fat is linked to thyroid hypoechogenicity as evident through ultrasonography and euthyroid obese people have greater TSH, FT3, and FT3/FT4 ratios than non-obese individuals in a euthyroid condition. Moreover, a reduced expression of the TSH receptor and altered function of deiodinases has been found in the adipose tissue of obese patients. Current data do not support the necessity of a pharmacological correction of the isolated hyperthyrotropinemia in euthyroid obese patients because treatment with thyroid hormone does not significantly improve weight loss and the increase in serum TSH can be reversible after hypocaloric diet or bariatric surgery. On the other hand, obesity is linked to elevated leptin levels. Inflammation can raise the risk of Hashimoto thyroiditis, which increases the likelihood that obese patients will experience overt or subclinical hypothyroidism. Both metabolic syndrome and subclinical hypothyroidism are associated with atherosclerosis, liver and kidney disease. Hence, the association of these two illnesses may potentiate the adverse effects noted in each of them. Subclinical hypothyroidism should be identified in patients with obesity and treated with appropriate doses of L-thyroxine according to the lean body mass and body weight. Randomized controlled trials are necessary to verify whether treatment of thyroid deficiency could counteract the expected risks.

Nanomedicine for Diagnosis and Treatment of Atherosclerosis

With the changing disease spectrum, atherosclerosis has become increasingly prevalent worldwide and the associated diseases have emerged as the leading cause of death. Due to their fascinating physical, chemical, and biological characteristics, nanomaterials are regarded as a promising tool to tackle enormous challenges in medicine. The emerging discipline of nanomedicine has filled a huge application gap in the atherosclerotic field, ushering a new generation of diagnosis and treatment strategies. Herein, based on the essential pathogenic contributors of atherogenesis, as well as the distinct composition/structural characteristics, synthesis strategies, and surface design of nanoplatforms, the three major application branches (nanodiagnosis, nanotherapy, and nanotheranostic) of nanomedicine in atherosclerosis are elaborated. Then, state-of-art studies containing a sequence of representative and significant achievements are summarized in detail with an emphasis on the intrinsic interaction/relationship between nanomedicines and atherosclerosis. Particularly, attention is paid to the biosafety of nanomedicines, which aims to pave the way for future clinical translation of this burgeoning field. Finally, this comprehensive review is concluded by proposing unresolved key scientific issues and sharing the vision and expectation for the future, fully elucidating the closed loop from atherogenesis to the application paradigm of nanomedicines for advancing the early achievement of clinical applications.

A review of the role of liposome-encapsulated phytochemicals targeting PPAR Ɣ and associated pathways to combat obesity

A limited number of studies have directly examined the effects of liposomal encapsulated phytochemicals and their anti-obesity effects in adults. This study aimed to summarize the evidence on the effect of liposomal encapsulated phytochemicals and their role in regulating major pathways involved in the anti-obesity mechanism. A systematic search was performed using several search engines like Science Direct, Google Scholar, and other online journals, focusing on laboratory research, systematic reviews, clinical trials, and meta-analysis that focused on liposomal encapsulated phytochemicals with anti-obesity properties, and followed the preferred reporting terms for this systematic review. An initial search provided a result of 1810 articles, and 93 papers were selected after the inclusion and exclusion criteria. Very few studies have been conducted on the liposomal encapsulation of phytochemicals or its synergistic study to combat obesity; hence this review paves the way for future obesity research and is mainly helpful for the pediatric obesity population. Liposomal encapsulation of phytochemicals has improved the efficiency of freely administered phytochemicals. Targeted delivery improved drug utilization and regulated the anti-obesity pathways. PPARƔ is a major therapeutic target for obesity as it inhibits adipocyte differentiation and maintains energy homeostasis.

pNaKtide Inhibits Na/K-ATPase Signaling and Attenuates Obesity

Obesity is a growing public health crisis across the world and has been recognized as an underlying risk factor for metabolic syndrome. Growing evidence demonstrates the critical role of oxidative stress in the pathophysiological mechanisms of obesity and related metabolic dysfunction. As we have established previously that Na/K-ATPase can amplify oxidative stress signaling, we aimed to explore the effect of inhibition of this pathway on obesity phenotype using the peptide antagonist, pNaKtide. The experiments performed in murine preadipocytes showed the dose-dependent effect of pNaKtide in attenuating oxidant stress and lipid accumulation. Furthermore, these in vitro findings were confirmed in C57Bl6 mice fed a high-fat diet. Interestingly, pNaKtide could significantly reduce body weight, ameliorate systemic oxidative and inflammatory milieu and improve insulin sensitivity in obese mice. Hence the study demonstrates the therapeutic utility of pNaKtide as an inhibitor of Na/K-ATPase oxidant amplification signaling to alleviate obesity and associated comorbidities.

Stimulation of the beta-2-adrenergic receptor with salbutamol activates human brown adipose tissue

While brown adipose tissue (BAT) is activated by the beta-3-adrenergic receptor (ADRB3) in rodents, in human brown adipocytes, the ADRB2 is dominantly present and responsible for noradrenergic activation. Therefore, we performed a randomized double-blinded crossover trial in young lean men to compare the effects of single intravenous bolus of the ADRB2 agonist salbutamol without and with the ADRB1/2 antagonist propranolol on glucose uptake by BAT, assessed by dynamic 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography scan (i.e., primary outcome). Salbutamol, compared with salbutamol with propranolol, increases glucose uptake by BAT, without affecting the glucose uptake by skeletal muscle and white adipose tissue. The salbutamol-induced glucose uptake by BAT positively associates with the increase in energy expenditure. Notably, participants with high salbutamol-induced glucose uptake by BAT have lower body fat mass, waist-hip ratio, and serum LDL-cholesterol concentration. In conclusion, specific ADRB2 agonism activates human BAT, which warrants investigation of ADRB2 activation in long-term studies (EudraCT: 2020-004059-34).