Regulation of hepatic glucose metabolism in health and disease

LYPLAL1 enzyme activity is linked to hepatic glucose metabolism

The serine hydrolase LYPLAL1 is a poorly characterised enzyme with emerging roles in hepatic metabolism. A multitude of association studies have shown links between variants of this gene locus and metabolic conditions such as obesity and insulin resistance. However, the enzyme's function is still largely unknown. Recent biochemical studies have revealed that it may play a role in hepatic glucose metabolism and that its activity is allosterically regulated. Herein, we use a selective activity-based probe to delineate LYPLAL1's involvement in hepatic metabolism. We show that the enzyme's activity is modulated during metabolic stress, specifically pointing to a putative role in negatively regulating gluconeogenesis and upregulating glycolysis. We also determine that knock-out of the enzyme does not affect liver lipid profiles and bring forth evidence for insulin-mediated control of LYPLAL1 in HepG2 cells. Furthermore, LYPLAL1 activity appears to be largely post-translationally regulated as gene expression levels remain largely constant under insulin and glucagon treatments. Taken together these data point to an enzymatic role in regulating glucose metabolism that may be part of a feedback mechanism of signal transduction.

Carnitine supplementation improves insulin sensitivity and skeletal muscle acetylcarnitine formation in patients with type 2 diabetes

AIM/HYPOTHESIS

Recently, we reported that increasing free carnitine availability resulted in elevated skeletal muscle acetylcarnitine concentrations and restored metabolic flexibility in individuals who have impaired glucose tolerance. Metabolic flexibility is defined as the capacity to switch from predominantly fat oxidation while fasted to carbohydrate oxidation while insulin stimulated. Here we investigated if carnitine supplementation enhances the capacity of skeletal muscle to form acetylcarnitine and thereby improves insulin sensitivity and glucose homeostasis in patients with type 2 diabetes (T2DM).

METHODS

Thirty-two patients followed a 12-week L-carnitine treatment (2970 mg/day, orally). Insulin sensitivity was assessed by a two-step hyperinsulinemic-euglycemic clamp. In vivo skeletal muscle acetylcarnitine concentrations at rest and post-exercise (30 min, 70% Wmax) and intrahepatic lipid content (IHL) were determined by proton magnetic resonance spectroscopy (1H-MRS). All measurements were performed before and after 12 weeks of carnitine supplementation.

RESULTS

Compliance with the carnitine supplementation was good (as indicated by increased plasma-free carnitine levels (p < 0.01) and pill count (97.1 ± 0.7%)). Insulin-induced suppression of endogenous glucose production (31.9 ± 2.9 vs. 39.9 ± 3.2%, p = 0.020) and peripheral insulin sensitivity (Δ rate of glucose disappearance (ΔRd): 10.53 ± 1.85 vs. 13.83 ± 2.02 μmol/kg/min, p = 0.005) improved after supplementation. Resting (1.18 ± 0.13 vs. 1.54 ± 0.17 mmol/kgww, p = 0.008) and post-exercise (3.70 ± 0.22 vs. 4.53 ± 0.30 mmol/kgww, p < 0.001) skeletal muscle acetylcarnitine concentrations were both elevated after carnitine supplementation. Plasma glucose (p = 0.083) and IHL (p = 0.098) tended to be reduced after carnitine supplementation.

CONCLUSION

Carnitine supplementation improved insulin sensitivity and tended to lower IHL and fasting plasma glucose levels in patients with type 2 diabetes. Furthermore, carnitine supplementation increased acetylcarnitine concentration in muscle, which may underlie the beneficial effect on insulin sensitivity.

Malus hupehensis leaves: a functional beverage for alleviating hepatic inflammation and modulating gut microbiota in diabetic mice

Malus hupehensis leaves (MHL), consumed as a daily beverage in Chinese folk tradition and recently recognized as a new food material, are abundant in polyphenols and bioactive compounds that demonstrate hypoglycemic, lipid-lowering, and anti-inflammatory effects. However, the antidiabetic mechanisms have not been fully elucidated. This study aimed to investigate the protective mechanisms of Malus hupehensis leaves' extract (MHLE) against type 2 diabetes mellitus (T2DM). The results showed that MHLE effectively ameliorated glucose and lipid metabolic abnormalities in db/db mice, and attenuated hepatic macrophage activation. Transcriptomic analysis of the liver revealed that MHLE primarily affects genes involved in inflammatory responses and inhibited the TLR4/MAPK pathway to reduce hepatic inflammation. Metagenomic sequencing identified changes in gut microbiota composition and showed that MHLE restored the abundance of Lachnospiraceae bacterium, Oscillospiraceae bacterium, and Clostridia bacterium while reducing the abundance of Escherichia coli, thereby ameliorating gut dysbiosis. The integrated regulation of metabolism, immune response, and the microbial environment by MHLE significantly alleviated symptoms of T2DM. This study offers strong scientific evidence for the potential use of MHL as a functional food.

Effects and Mechanisms of Steviol Glycosides on Glucose Metabolism: Evidence From Preclinical Studies

The natural sweeteners of steviol glycosides (SGs) have been widely used as a substitute for sugar due to their high sweetness, low-calorie properties, and potential health benefits. Some studies reported that SGs could regulate glucose metabolism and prevent Type 2 diabetes mellitus (T2DM); however, the detailed mechanisms remained further elucidated. Therefore, in this review, we aimed to systematically summarize the effects and mechanisms of SGs on glucose metabolism based on evidence from preclinical studies. We searched PubMed and Web of Science (up to March 31, 2024), and included a total of 40 animal and 5 cell studies for review. Results showed that SGs could improve glucose metabolism by enhancing insulin secretion, simulating insulin effects, improving insulin resistance, advancing key enzyme activities, or regulating gut microbiota. To conclude, if further validated in clinical trials and population studies, the sugar substitute of SGs may serve as a potential nutritional strategy for effective prevention and treatment of T2DM.

RAP1A suppresses hepatic steatosis by regulating amino acid-mediated mTORC1 activation

Background & Aims

Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by triglyceride (TG) build-up in hepatocytes; however, our understanding of the underlying molecular mechanisms is limited. Here, we investigated the role of hepatic GTPase RAP1A in MASLD and its more progressive form, metabolic dysfunction-associated steatohepatitis (MASH).

Methods

RAP1A was silenced or activated by AAV8-TBG-mediated gene expression or treating mice with a small molecule RAP1 activator (n = 4-12 per group). Primary hepatocytes were used to further probe the newly elucidated pathway. Liver samples from patients with MASH and control livers were analyzed for active RAP1A levels (n = 4 per group).

Results

Activation of hepatic RAP1A is suppressed in obese mice with MASLD and restoring its activity decreases liver steatosis. RAP1A activation lowers hepatic TG accumulation through decreasing sterol regulatory element-binding protein 1 (SREBP1) cleavage by inhibiting the mechanistic target of rapamycin complex 1 (mTORC1). The mechanism linking RAP1A activation to suppression of mTORC1 involves the lowering of membrane-bound amino acid transporters, which leads to reduced hepatocyte amino acid uptake, decreased intracellular amino acid levels, and inhibition of amino acid-mediated mTORC1 activation. Furthermore, we observed that active-RAP1A levels were decreased in mice fed a MASH-provoking diet (98% lower, p <0.01) and liver extracts from patients with MASH (86% lower, p <0.05). Accordingly, restoration of RAP1A activity in mice liver lowered liver fibrotic gene expression and prevented fibrosis formation, whereas RAP1A silencing promoted the progression of MASH.

Conclusions

Activation of hepatic RAP1A lowers MASLD and MASH formation by suppressing amino acid-mediated mTORC1 activation and decreasing cleaved SREBP1. These data provide mechanistic insight into amino acid-mediated mTORC1 regulation and raise the possibility that hepatic RAP1A may serve as a mechanistic node linking obesity with MASLD and MASH.

Impact and implications

Metabolic dysfunction-associated liver pathologies are inadequately treated with currently available therapy. Here we demonstrate that the small GTPase RAS-associated protein 1A (RAP1A) protects against liver steatosis and fibrosis development by decreasing hepatocyte amino acid levels, which results in lower mTORC1 activity and SREBP1 cleavage. The results may present new targets against metabolic dysfunction related liver diseases.

Notch1 Signalling Is Downregulated by Aerobic Exercise, Leading to Improvement of Hepatic Metabolism in Obese Mice

BACKGROUND AND AIMS

Notch1 protein plays a significant role in hepatic metabolism, as evidenced by its correlation with insulin resistance in the livers of obese individuals, making it an intriguing research target. Therefore, this study aims to investigate the impact of aerobic exercise on Notch1 pathways in the hepatic tissue of obese mice and its role in controlling hepatic metabolism.

METHODS

Therefore, we conducted a cross-sectional study utilising liver biopsies from lean and obese humans, as well as an intervention study involving mice subjected to a high-fat diet. The obese-trained mice group underwent a treadmill-running protocol for 4 weeks.

RESULTS

Our findings revealed that obese individuals exhibited increased NOTCH1 mRNA levels compared to lean subjects. The detrimental effects of Notch1 signalling were confirmed by Notch1-overexpressed HepG2 cell lines. Obese mice with higher hepatic Notch1 signalling demonstrated a reduction in this pathway when subjected to a 4-week treadmill running. Another benefit noticed in this trained group was the amelioration of insulin resistance, as well as a reduction in pyruvate intolerance and gluconeogenic enzymes. Additionally, we observed that these protective findings were accompanied by a decrease in mTORC1 pathway activity and lipid accumulation in the liver. Pharmacological inhibition of Notch1 in obese mice led to an increase in mitochondrial respiration in the liver.

CONCLUSIONS

We conclude that Notch1 signalling may be a potentially useful therapeutic target in obesity, while aerobic exercise training suppresses the Notch1 pathway in the liver, contributing to the regulation of hepatic glucose and lipid metabolism in obese mice.

Glucose metabolism in the perfused liver did not improve with resistance training in male Swiss mice under caloric restriction

CONTEXT

Energy homeostasis is a primary factor for the survival of mammals. Many tissues and organs, among which is the liver, keep this homeostasis in varied circumstances, including caloric restriction (CR) and physical activity.

OBJECTIVE

This study investigated glucose metabolism using the following groups of eight-week-old male Swiss mice: CS, sedentary and fed freely; RS, sedentary and RT, trained, both under 30% CR (n = 20-23 per group).

RESULTS

Organs and fat depots of groups RS and RT were similar to CS, although body weight was lower. CR did not impair training performance nor affected systemic or hepatic glucose metabolism. Training combined with CR (group RT) improved in vivo glucose tolerance and did not affect liver gluconeogenesis.

CONCLUSIONS

The mice tolerated the prolonged moderate CR without impairment of their well-being, glucose homeostasis, and resistance training performance. But the higher liver gluconeogenic efficiency previously demonstrated using this training protocol in mice was not evidenced under CR.

Vitronectin stimulates hepatic gluconeogenesis by activating the cAMP/PKA/CREB axis in the liver

Vitronectin, a protein derived the human placenta, has been identified as an inducer of insulin resistance in trophoblast cells in gestational diabetes mellitus (GDM). As a secreted protein, vitronectin may have systemic effects on dysregulated glucose metabolism in GDM. To address this speculation, we generated a GDM mouse model using high-fat diet-induced obese mice. Consistent with findings in placentas of GDM patients, GDM mouse placentas showed higher vitronectin expression, accompanied by increased serum vitronectin levels. Reduced insulin signaling transduction was observed in both the placentas and livers of GDM mice, along with enhanced hepatic gluconeogenesis. To further explore the role of vitronectin in hepatic gluconeogenesis, we constructed an adeno-associated virus expressing Vtn (AAV-VTN), which was administered to mice via tail vein injection. In AAV-VTN-treated mice, glucose production from exogenous pyruvate increased, and the expression of gluconeogenic genes in the liver was upregulated, indicating that hepatic gluconeogenesis was stimulated by vitronectin. Mechanistically, vitronectin binds to its receptor CD51/61, activating the cAMP/PKA/CREB axis in hepatocytes, thereby promoting hepatic gluconeogenesis. In summary, our findings suggest that placenta-derived vitronectin plays a critical role in inducing insulin resistance in the liver in GDM. Moreover, vitronectin stimulates hepatic gluconeogenesis through activation of the cAMP/PKA/CREB axis. These results point to vitronectin as a potential therapeutic target for managing hyperglycemia in GDM.

Clerodane diterpenoids from the vine stems of Fibraurea recisa Pierre and their hepatic gluconeogenesis inhibitory activity

Fibraurea recisa Pierre is a vine plant and its vine stems are used as a traditional Chinese medicine to treat heat toxin, constipation, diarrhea, sore throat, eye inflammation, carbuncles, and skin ulcers. The alkaloid chemical composition of this plant has been extensively studied; however, investigations into non-alkaloid components remain limited. In this study, phytochemical studies of the vine stems of F. recisa were conducted, leading to the isolation and identification of twenty highly oxidized clerodane diterpenoids, including ten previously undescribed compounds, designated fibrecins A-J (1-10). The structures and absolute configurations of 1-10 were determined through comprehensive spectroscopic methods (IR, HRESIMS, 1D and 2D NMR), electronic circular dichroism data, and single-crystal X-ray diffraction. Notably, compounds 1 and 2 are rare 18-nor-clerodane diterpenoids. Excessive hepatic gluconeogenesis is an important cause of hyperglycemia and type 2 diabetes mellitus. Herein, compounds 1, 9, 14, and 15 were found to exhibit moderate hepatic gluconeogenesis inhibitory activity in primary mouse hepatocytes, suggesting that these compounds might have potential effect on ameliorating the hyperglycaemia.

Controversy and multiple roles of the solitary nucleus receptor Nur77 in disease and physiology

Neuron-derived clone 77 (Nur77), a member of the orphan nuclear receptor family, is expressed and activated rapidly in response to diverse physiological and pathological stimuli. It exerts complex biological functions, including roles in the nervous system, genome integrity, cell differentiation, homeostasis, oxidative stress, autophagy, aging, and infection. Recent studies suggest that Nur77 agonists alleviate symptoms of neurodegenerative diseases, highlighting its potential as a therapeutic target in such conditions. In cancer, Nur77 demonstrates dual roles, acting as both a tumor suppressor and promoter, depending on the cancer type and stage, making it a controversial yet promising anticancer target. This review provides a structured analysis of the functions of Nur77, focusing on its physiological and pathological roles, therapeutic potential, and existing controversies. Emphasis is placed on its emerging applications in neurodegenerative diseases and cancer, offering key insights for future research and clinical translation.

Design of self-assembled micelles based on natural dual-targeting strategies and evaluation of their anti-liver cancer effects as drug delivery systems

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in the world and in China, Most patients are already in an advanced stage at the time of diagnosis, and the chance of complete surgical resection is lost, therefore, drug treatment is particularly important. Angelica sinensis polysaccharide (ASP) has natural liver-targeting properties, berberine (BBR) is a lipophilic cation with anticancer activities and mitochondrial-targeting properties, and honokiol (HNK) has mitochondria-dependent anticancer effects against cancer. Therefore, the aim of the present work was to synthesize Angelica sinensis polysaccharide-berberineamphiphilic polymer (ASP-SS-BBR) loaded with HNK to prepare the micelles ASP-BBR-PM@HNK to improve the hepatic targeting ability of the nanoparticles and the mitochondrial targeting ability in HCC cells and to enhance the anti-HCC effect of HNK. The findings of this study demonstrate the successful synthesis of ASP-BBR-PM@HNK, characterized by a particle size of 48.6 ± 1.13 nm. The formulation exhibits commendable stability, a sustained-release profile, and the capability for glutathione (GSH)-responsive release. ASP-BBR-PM@HNK is efficiently internalized by HepG2 cells, exhibiting the highest rate of cell inhibition. Additionally, the use of Gal and Man as receptor blockers confirmed the formulation's superior targeting capabilities, including exceptional mitochondrial targeting. Subsequent in vivo experiments employing BALB/c nude mice as a model further corroborated these experimental outcomes. This research has successfully developed an effective natural dual-targeting system, offering a novel approach for the precise treatment of liver cancer.

Plant Derived Exosome-Like Nanoparticles and Their Therapeutic Applications in Glucolipid Metabolism Diseases

Plant derived exosome-like nanoparticles (PELNs) are membrane structures isolated from different plants, which encapsulate many active substances such as proteins, lipids, and nucleic acids, which exert a substantial influence on many physiological processes such as plant growth and development, self-defense, and tissue repair. Compared with synthetic nanoparticles and mammalian cell derived exosomes (MDEs), PELNs have lower toxicity and immunogenicity and possess excellent biocompatibility. The intrinsic properties of PELNs establish a robust basis for their applications in the therapeutic management of a diverse array of pathologies. It is worth mentioning that PELNs have good biological targeting, which promotes them to load and deliver drugs to specific tissues, offering a superior development pathway for the construction of a new drug delivery system (DDS). Glucose and lipid metabolism is a vital life process for the body's energy and material supply. The maintenance of homeostatic balance provides a fundamental basis for the body's ability to adjust to modifications in both its internal and external environment. Conversely, homeostatic imbalance can lead to a range of severe metabolic disorders. This work provides a comprehensive overview of the extraction and representation methods of PELNs, their transportation and storage characteristics, and their applications as therapeutic agents for direct treatment and as delivery vehicles to enhance nutrition and health. Additionally, it examines the therapeutic efficacy and practical applications of PELNs in addressing abnormalities in glucose and lipid metabolism. Finally, combined with the above contents, the paper summarizes and provides a conceptual framework for the better application of PELNs in clinical disease treatment.

The hypoglycemic effect of mulberry (Morus atropurpurea) fruit lacking fructose and glucose by regulation of the gut microbiota

Mulberries are known to be rich in hypoglycemic active substances such as anthocyanins and dietary fiber, which primarily aid in regulating gut microbiota. However, their high sugar content, such as fructose, hinders their application in hypoglycemic functional foods. This research utilized microbial fermentation technology to remove the fructose and glucose in mulberries (FM), subsequently evaluating their hypoglycemic properties and balancing gut microbiota. Results indicated that administering varying doses of FM to type 2 diabetic mice for five weeks notably decreased blood sugar and insulin levels, improved dyslipidemia and insulin resistance, enhanced antioxidant capacity, repaired organ damage, and regulated hypoglycemic activity by influencing mRNA expression of key signaling factors in the PI3K/Akt and AMPK pathways. Analysis of the intestinal microbiota composition revealed that FM can modulate specific bacterial populations, increasing beneficial bacteria like Lactobacillus, Bifidobacterium and Akkermansia while inhibiting harmful bacteria like Escherichia-Shigella and Helicobacter. This restoration of the intestinal microecological balance helped regulate host sugar metabolism homeostasis and affect the secretion of short chain fatty acid (SCFA) synthase in the gut microbiota to increase the production of SCFAs. These findings offer significant support for the potential use of FM in the treatment of diabetes.

Insulin resistance and cancer: molecular links and clinical perspectives

The association between insulin resistance (IR), type 2 diabetes mellitus (T2DM), and cancer is increasingly recognized and poses an escalating global health challenge, as the incidence of these conditions continues to rise. Studies indicate that individuals with T2DM have a 10-20% increased risk of developing various solid tumors, including colorectal, breast, pancreatic, and liver cancers. The relative risk (RR) varies depending on cancer type, with pancreatic and liver cancers showing a particularly strong association (RR 2.0-2.5), while colorectal and breast cancers demonstrate a moderate increase (RR 1.2-1.5). Understanding these epidemiological trends is crucial for developing integrated management strategies. Given the global rise in T2DM and cancer cases, exploring the complex relationship between these conditions is critical. IR contributes to hyperglycemia, chronic inflammation, and altered lipid metabolism. Together, these factors create a pro-tumorigenic environment conducive to cancer development and progression. In individuals with IR, hyperinsulinemia triggers the insulin-insulin-like growth factor (IGF1R) signaling pathway, activating cancer-associated pathways such as mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PIK3CA), which promote cell proliferation and survival, thereby supporting tumor growth. Both IR and T2DM are linked to increased morbidity and mortality in patients with cancer. By providing an in-depth analysis of the molecular links between insulin resistance and cancer, this review offers valuable insights into the role of metabolic dysfunction in tumor progression. Addressing insulin resistance as a co-morbidity may open new avenues for risk assessment, early intervention, and the development of integrated treatment strategies to improve patient outcomes.

Liver-derived Neuregulin1α stimulates compensatory pancreatic β cell hyperplasia in insulin resistance

Compensatory pancreatic islet hyperplasia is an adaptive response to increased systemic insulin demand, although factors meditating this response remain poorly understood. Here, we show that a liver-derived secreted protein, Neuregulin1α, promotes compensatory proliferation of pancreatic β cells in type 2 diabetes. Liver Neuregulin1α expression and serum Neuregulin1α levels increase in male mice fed an obesity-inducing diet. Male mice lacking either Neuregulin1 in liver or its receptor, ErbB3, in β cells deteriorate systemic glucose disposal due to impaired β cell expansion with reduced insulin secretion when fed the obesity-inducing diet. Mechanistically, Neuregulin1α activates ERBB2/3-ERK signaling to stimulate β cell proliferation without altering glucose-stimulated insulin secretion potential. In patients with metabolic dysfunction-associated steatotic liver disease (MASLD) and obesity but without type 2 diabetes serum Neuregulin1α levels increase, while in patient with MASLD and type 2 diabetes show markedly reduced levels of Neuregulin1α. These results suggest that Neuregulin1α serves as a hepatokine that can expand functional β cell mass in type 2 diabetes.

Chronic Exposure to Environmental Concentrations of Tetrabromobisphenol A Disrupts Insulin and Lipid Homeostasis in Diet-Induced Obese Mice

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardant in consumer products, has raised significant health concerns. However, the long-term metabolic effects of chronic exposure to environmentally relevant TBBPA concentrations, particularly in the context of modern high-calorie diets, remain poorly understood. Here, we show that C57BL/6J mice fed a high-fat diet and exposed to 20 or 50 nmol/kg/day TBBPA for 120 days exhibited increased body weight, aggravated fat accumulation, impaired glucose tolerance, insulin resistance, and dyslipidemia. Mechanistic investigations revealed that TBBPA exposure led to decreased norepinephrine levels, consequently reducing energy expenditure. It disrupts hepatic insulin signaling and upregulates G6Pase, thereby increasing the level of liver glucose production. Furthermore, TBBPA enhances hepatic cholesterol synthesis by elevating protein levels of HMGCR, which is the rate-limiting enzyme in cholesterol biosynthesis. This effect is mediated through increased expression of USP20, a specific deubiquitinating enzyme for HMGCR. Additionally, TBBPA modestly enhances fatty acid biosynthesis without significantly affecting lipolysis or fatty acid oxidation. Our research reveals novel molecular pathways through which environmental TBBPA exposure disrupts metabolic balance, potentially exacerbating obesity-related health issues. These findings highlight the synergistic effects between environmental pollutants and modern calorie-dense diets on metabolic health, emphasizing the importance of considering multiple factors in obesity-related disorders.

Current understanding of insulin dysregulation and its relationship with carbohydrate and protein metabolism in horses

Insulin dysregulation (ID) is a common metabolic disorder in horses, characterized by hyperinsulinemia and/or peripheral insulin resistance. The critical role of hyperinsulinemia in endocrinopathic laminitis has driven research into the insulinotropic effects of dietary nutrients and the reciprocal impact of ID on nutrient metabolism. The relationship between ID and carbohydrate metabolism has been extensively studied; however, the effects of ID on protein metabolism in horses remain largely unexplored. This review begins with an overview of the importance of insulin in the regulation of muscle protein synthesis and degradation and then examines the current understanding of the interplay between ID and protein and carbohydrate metabolism in horses. Horses with ID exhibit altered resting plasma amino acid concentrations and shifts in postprandial amino acid dynamics. Recent work illustrated that ID horses had higher levels of plasma amino acids following a protein meal and delayed postprandial clearance from the blood compared to non-ID horses. The postprandial muscle synthetic response does not seem to be diminished in ID horses, but alterations in key cellular signaling molecules have been reported. ID horses display a pronounced hyperinsulinemic response following the consumption of feeds providing a range of protein, non-structural carbohydrate, starch and water-soluble carbohydrate intakes. Recent studies have shown that ID horses have an increased postprandial incretin response, contributing to the observed hyperinsulinemia. To minimize the postprandial insulin response, thresholds for carbohydrate consumption have recently been proposed. Similar thresholds should be established for protein to aid in the refinement of nutritional strategies to manage ID horses.

Roles of Gut Microbiota Metabolites and Circadian Genes in the Improvement of Glucose and Lipid Metabolism in KKAy Mice by Theabrownin

Theabrownin (TB), a prominent pigment in fermented dark tea, exhibits beneficial effects on adiposity reduction. Our study revealed that TB derived from Fu brick tea significantly lowered fasting blood glucose levels and insulin resistance in obese/diabetic KKAy mice. Furthermore, TB demonstrated potent anti-inflammatory effects in the liver, adipose tissue, and intestines, as well as enhancing intestinal integrity. Additionally, TB was found to inhibit hepatic gluconeogenesis and promote fatty acid oxidation. Notably, TB altered gut metabolites, particularly l-palmitoylcarnitine, which showed an elevation in serum, liver, and adipose tissue following TB intervention. l-Palmitoylcarnitine reduced gluconeogenesis in primary hepatocytes and decreased lipid deposition in both primary hepatocytes and 3T3-L1 adipocytes in vitro. However, these effects were abolished when the circadian gene Period 3 (Per3) was knocked down. Our findings suggest that l-palmitoylcarnitine may play a crucial role in improving TB-mediated glucose homeostasis and lipid metabolism by regulating Per3.

Dual targeting PPARα and NPC1L1 metabolic vulnerabilities blocks tumorigenesis

Dysregulated lipid metabolism is linked to tumor progression. In this study, we identified Niemann-Pick C1-like 1 (NPC1L1) as a downstream effector of PKM2. In breast cancer cells, PKM2 knockout (KO) enhanced NPC1L1 expression while downregulating peroxisome proliferator-activated receptor α (PPARα) signaling pathway. PPARα and nuclear factor-E2 p45-related factor 1/2(Nrf1/2) are transcription factors regulating NPC1L1. In vitro PKM2 KO enhanced recruitment of Nrf1/2 to the NPC1L1 promoter region. Fenofibrate, a PPARα activator, promoted NPC1L1 expression; ezetimibe, an NPC1L1 inhibitor and effective Nrf2 activator, also elevated NPC1L1 expression. Combined administration of fenofibrate and ezetimibe significantly induced cytoplasmic vacuolation, and cell apoptosis. Mechanistically, this combined administration activated inositol required enzyme 1α(IRE1α) and produced the spliced form of X-box binding protein (XBP1s), which in turn enhanced lysine demethylase 6B (KDM6B) transcription. XBP1s interacts with KDM6B to activate genes involved in the unfolded protein response by demethylating di- and tri-methylated lysine 27 of histone H3 (H3K27), consequently increasing H3K27 acetylation levels in breast cancer cell lines. Fenofibrate and ezetimibe synergistically inhibited tumor growth in vivo. Our findings reveal that dual targeting of PPARα and NPC1L1 may represent a novel therapeutic regimen for breast cancer therapy.

Glucokinase: from allosteric glucose sensing to disease variants

Human glucokinase (GCK) functions as a glucose sensor in the pancreas and liver, where GCK activity regulates insulin secretion and glycogen synthesis, respectively. GCK's low affinity for glucose and the sigmoidal substrate dependency of enzymatic turnover enables it to act as a sensor that makes cells responsive to changes in circulating glucose levels. Its unusual kinetic properties are intrinsically linked to the enzyme's conformational dynamics. Accordingly, genetic variants that alter the dynamics or other aspects of GCK function are linked to three glucose homeostasis diseases. In this review, we describe the enzyme GCK, focusing on its role as a glucose sensor, its unusual kinetic properties, and recent large-scale efforts to assess GCK variant effects.

Is the triglyceride-glucose index ready for cardiovascular risk assessment?

AIMS

Insulin resistance is a major risk factor for cardiovascular disease. Thus, early identification of insulin resistance is important for classifying individuals at high cardiovascular risk. All the tools commonly used in epidemiological studies and clinical practice to assess insulin resistance require measuring insulin levels, which is a limitation. Hence, simpler methods have been proposed to overcome these limitations. One of the most promising is the triglyceride-glucose index. Therefore, this narrative review focuses on the most significant epidemiological findings concerning the relationship between the triglyceride-glucose index and cardiovascular risk. Furthermore, it also highlights this new tool's strengths, limitations, and perspectives for assessing cardiovascular risk.

DATA SYNTHESIS

Even though the assessment of this index is relatively recent, there are numerous papers on this topic, and their number is constantly increasing. Observational studies have shown a substantial positive association between the triglyceride-glucose index and cardiovascular risk, although some conflicting results have been observed.

CONCLUSIONS

The index is strongly associated with cardiovascular mortality and cardiovascular risk factors. However, some gaps need to be addressed.

Improved Afternoon Hepatic Glucose Disposal and Storage Requires Morning Engagement of Hepatic Insulin Receptors

Glucose tolerance improves significantly upon consuming a second, identical meal later in the day (second-meal phenomenon). We previously established that morning hyperinsulinemia primes the liver for increased afternoon hepatic glucose uptake (HGU). Although the route of insulin delivery is an important determinant of the mechanisms by which insulin regulates liver glucose metabolism (direct hepatic vs. indirect insulin action), it is not known whether insulin's delivery route affects the second-meal response. To determine whether morning peripheral insulin delivery (as occurs clinically, i.e., subcutaneously) can enhance afternoon HGU, conscious dogs were treated in the morning with insulin delivered either via the portal vein or peripherally (leg vein), while glucose was infused to maintain euglycemia. Consequently, arterial insulin levels increased similarly in both groups, but relative hepatic insulin deficiency occurred with peripheral insulin delivery. In the afternoon, all animals were challenged with the same hyperinsulinemic-hyperglycemic clamp to simulate identical postprandial-like conditions. The substantial enhancement of HGU in the afternoon caused by morning portal vein insulin delivery was lost when insulin was delivered peripherally. This indicates that morning insulin does not cause the second-meal phenomenon via its indirect actions on the liver but, rather, through direct activation of hepatic insulin signaling.

ARTICLE HIGHLIGHTS

Morning insulin delivery primes the liver for increased hepatic glucose uptake (HGU) later in the day, but until now, the mechanism (direct hepatic and/or indirect insulin action) remained unclear. This study compared insulin infusion via endogenous (hepatic portal vein) and clinical (peripheral) routes to assess their impact on afternoon hepatic glucose disposal. Arterial hyperinsulinemia in the morning, without a concomitant increase in insulin at the liver, failed to induce a significant enhancing effect on afternoon HGU and glycogen storage, unlike morning hepatic portal vein insulin delivery, which did. These findings highlight the importance of achieving appropriate hepatic insulin exposure in the morning to effectively prime the liver for enhanced glucose disposal later in the day.

LGR4 is a key regulator of hepatic gluconeogenesis

AIMS/HYPOTHESIS

Emerging evidence underscored the significance of leucine-rich repeat-containing G protein-coupled receptor (LGR) 4 in endocrine and metabolic disorders. Despite this, its role in LGR4 in hepatic glucose metabolism remains poorly understood. In this study we set out to test whether LGR4 regulates glucose production in liver through a specific signaling pathway.

METHODS

Hepatic glucose production and gluconeogenic gene expressions were detected after silence of LGR4 in three obese mice models. Then, whole-body LGR4-deficient (LGR4 KO) mice, liver-specific LGR4 knockout (LGR4LKO) mice, and liver-specific LGR4 overexpression (LGR4LOV) mice were generated, in which we analyzed the effects of LGR4 on hepatic glucose metabolism upon HFD feeding, among which live imaging and quantitative analysis of hepatic phosphoenolpyruvate carboxykinase (PEPCK)-luciferase activity were conducted.

RESULTS

LGR4 expression was significantly upregulated in the liver of three obese mouse models, and presented dynamic expression patterns in response to nutritional fluxes. We utilized global and liver-specific LGR4 knockouts (LGR4LKO), along with adenoviral-mediated LGR4 knockdown in mice, to show improved glucose tolerance and decreased hepatic gluconeogenesis. Specifically, the expression of rate-limiting gluconeogenic enzymes, PEPCK was significantly downregulated. Conversely, mouse model with adenovirus-mediated LGR4 overexpression (LGR4LOV) exhibited elevated gluconeogenesis and PEPCK expression and reversed the suppression observed in LGR4 knockout models. Notably, neither RANKL nor PKA signaling pathways, which were reported to take part in LGR4's function, were involved in the process of LGR4 regulating PEPCK. Instead, TopFlash reporter system and inhibitors application suggested that LGR4's influence on hepatic gluconeogenesis operates through the canonical Wnt/β-catenin/TCF7L2 signaling pathway.

CONCLUSIONS/INTERPRETATION

Overall, these findings underscore a novel mechanism by which LGR4 regulates hepatic gluconeogenesis, presenting a potential therapeutic target for diabetes management.

Hepatic Metabolic Memory Triggered by AM Exposure to Glucagon Alters Afternoon Glucose Metabolism

The second meal effect describes an improved glycemic response observed after consuming a second identical meal. We previously showed that morning (AM) exposure to hyperinsulinemia primes the liver for enhanced hepatic glucose uptake and glycogen storage in the afternoon (PM), with no significant effect on PM non-hepatic glucose uptake. Given that meals often trigger both insulin and glucagon secretion, we aimed to determine if AM hyperglucagonemia alters the priming effect of AM hyperinsulinemia on PM hepatic glucose metabolism. To test this, dogs were exposed to a 4h AM hyperinsulinemic-euglycemic clamp, with insulin delivered in a pattern mimicking the insulin profile observed earlier during a 4h AM duodenal glucose infusion. This period of hyperinsulinemia was paired with either basal (Prime, n=8) or elevated (Prime + ↑GGN, n=8) glucagon, maintaining a consistent insulin-to-glucagon molar ratio throughout the AM clamp. After a 1.5h rest period, the dogs underwent a 2.5h PM hyperinsulinemic-hyperglycemic clamp, during which glucose, insulin, and glucagon levels, along with the artery-to-portal vein glucose gradient, were carefully controlled to replicate postprandial conditions. During the PM clamp, the mean net hepatic glucose uptake (NHGU) in the Prime + ↑GGN group was only 59% of that in the Prime group (3.6±0.4 vs. 6.1±0.6 mg/kg/min, P<0.0027, respectively). Additionally, PM direct glycogen synthesis was two-fold greater in the Prime group compared to the Prime + ↑GGN group (3.2±0.7 vs. 1.5±0.2 mg/kg/min, P<0.0014, respectively). The observed difference in PM NHGU between the groups was not due to enhanced PM hepatic glucose uptake (HGU), which was similar in both groups (5.7±0.5 mg/kg/min in the Prime group vs. 5.2±0.3 mg/kg/min in the Prime + ↑GGN group), but rather a prolonged effect of AM hyperglucagonemia on PM hepatic glucose production (HGP) (-0.3±0.3 mg/kg/min in the Prime group vs. 1.7±0.4 mg/kg/min in the Prime + ↑GGN group, P<0.0072). This increase in PM HGP in the Prime + ↑GGN group was not driven by differences in PM gluconeogenic flux but by futile glucose cycling between glucose and glucose-6-phosphate, as well as hepatic glycogen storage and breakdown. In summary, these findings suggest that morning exposure to elevated glucagon shifts the insulin-driven priming effect on afternoon hepatic glucose metabolism by promoting sustained glucose cycling at the expense of glycogen synthesis and glycolysis, leading to persistent HGP despite identical PM insulin, glucose, and glucagon levels.

Liver ALKBH5 regulates glucose and lipid homeostasis independently through GCGR and mTORC1 signaling

Maintaining glucose and lipid homeostasis is crucial for health, with dysregulation leading to metabolic diseases such as type 2 diabetes mellitus (T2DM) and metabolic dysfunction-associated fatty liver disease (MAFLD). This study identifies alkylation repair homolog protein 5 (ALKBH5), an RNA N6-methyladenosine (m6A) demethylase, as a major regulator in metabolic disease. ALKBH5 is up-regulated in the liver during obesity and also phosphorylated by protein kinase A, causing its translocation to the cytosol. Hepatocyte-specific deletion of Alkbh5 reduces glucose and lipids by inhibiting the glucagon receptor (GCGR) and mammalian target of rapamycin complex 1 (mTORC1) signaling pathways. Targeted knockdown of hepatic Alkbh5 reverses T2DM and MAFLD in diabetic mice, highlighting its therapeutic potential. This study unveils a regulatory mechanism wherein ALKBH5 orchestrates glucose and lipid homeostasis by integrating the GCGR and mTORC1 pathways, providing insight into the regulation of metabolic diseases.

Arctiin attenuated NASH by inhibiting glycolysis and inflammation via FGFR2/CSF1R signaling

The present work was conducted to evaluate the pharmacological effect of Arctiin(ARC) on high fat diet(HFD)-induced Non-alcoholic steatohepatitis(NASH) and investigate its potential mechanism. The network pharmacology and bioinformatic analyses predicted that FGFR2 might be the potential target of ARC. Palmitic acid(PA)-induced AML12 cell was employed as the in vitro model. ARC reduced the levels of ALT, AST, TC, TG, and attenuated histopathological alteration. ARC inhibited inflammatory cytokines, inflammatory molecules, downregulated the expressions of FGFR2/CSF1R, inhibited glycolysis and promoted oxidative phosphorylation both in vivo and in vitro. ARC enhanced mitochondrial membrane potential and reduced oxidative stress. The application of FGFR2-OE plasmid, CSF1R-OE plasmid, CSF1R inhibitor PLX indicated that ARC attenuated glycolysis and inflammation in PA-induced AML12 cells via FGFR2/CSF1R signaling. HIF1A was proved to be involved in this process using HIF1A agonist DEF and HIF1A inhibitor PX478. Molecular docking and molecular dynamic suggested that ARC might combine with FGFR2. In conclusion, the present study demonstrated that ARC ameliorated NASH by inhibiting glycolysis and inflammation via FGFR2/CSF1R signaling.

Prediabetes remission to reduce the global burden of type 2 diabetes

Prediabetes is a highly prevalent and increasingly common condition affecting a significant proportion of the global population. The heterogeneous nature of prediabetes presents a challenge in identifying individuals who particularly benefit from lifestyle or other therapeutic interventions aiming at preventing type 2 diabetes (T2D) and associated comorbidities. The phenotypic characteristics of individuals at risk for diabetes are associated with both specific risk profiles for progression and a differential potential to facilitate prediabetes remission and reduce the risk of future T2D. This review examines the current definition and global prevalence of prediabetes and evaluates the potential of prediabetes remission to reduce the alarming increase in the global burden of T2D.

Mitogen-Activated Protein Kinase Phosphatase-2 Deletion Promotes Hyperglycemia and Susceptibility to Streptozotocin-Induced Diabetes in Female Mice In Vivo

The development of type 2 diabetes (T2D) is largely dependent on the maintenance of pancreatic islet function and mass. Sexual dimorphism in T2D is evident in many areas, such as pathophysiology, treatment, and prevention. Mitogen-activated protein kinase phosphatase-2 (MKP-2) has a distinct role in the regulation of cell proliferation and the development of metabolic disorders. However, whether there is a causal relationship between MKP-2 and diabetes onset is unclear. The aim of this study was to determine the role of MKP-2 in the regulation of whole-body glucose homeostasis and the impact on pancreatic islet function using streptozotocin-induced pancreatic injury. Here, we show that female mice with whole-body deletion of MKP-2 exhibit hyperglycemia in mouse models treated with multiple low doses of streptozotocin (STZ). In comparison, both male MKP-2 wild-type and knockout mice were hyperglycemic. Consistent with the hyperglycemia, female MKP-2-deficient mice exhibited reduced islet size. Under T2D conditions, MKP-2-deficient mice display enhanced pancreatic JNK and ERK phosphorylation that is associated with the downregulation of genes important for pancreatic islet development and function, Pdx-1 and MafA. Furthermore, we found impaired metabolic flux in adipose tissue that is consistent with hyperglycemia and dysfunctional pancreas. MKP-2 deletion results in reduced Akt activation that is associated with increased adiposity and insulin resistance in female MKP-2 KO mice. These studies demonstrate the critical role of MKP-2 in the development of T2D diabetes in vivo. This suggests that MKP-2 may have a gender-specific role in diabetes development. This discovery raises the possibility that postmenopausal prevention of T2D may benefit from the activation of MKP-2 activity in islet cells.

Transcriptome analysis to explore the molecular mechanisms involved in the dormancy-arousal process in Pomacea canaliculata (Lamarck, 1819)

The apple snail, Pomacea canaliculata (Lamarck, 1819), a freshwater snail listed as a pernicious invasive alien species by the World Conservation Union (IUCN), has caused serious agricultural and ecological harm worldwide. This species has inflicted significant agricultural and ecological damage on a global scale. Under conditions of extreme environmental stress, the apple snail enters a state of dormancy and remains in this dormant phase until environmental conditions become favorable again, which serves as a crucial survival strategy. In our study, we subjected apple snails to 30 days of air-exposure stress followed by rehydration to reactivate them. Our objective was to elucidate the underlying mechanisms associated with drought tolerance, dormancy, and subsequent arousal based on transcriptomic analyses. The results indicated that the groups subjected to 5-, 15- and 30-day air-exposure stress treatments (DRY05, DRY15 and DRY30) exhibited a general down-regulation of metabolism-related pathways. These pathways included starch and sucrose metabolism, linoleic acid metabolism, glutathione metabolism and glycosaminoglycan degradation, compared with the control (CK). In addition, the weighted correlation network analysis (WGCNA) identified two critical pathways: toll-like receptor signaling pathway and adherens junction. The down-regulation of these pathways indicated a decrease in immune levels during dormancy in apple snails. This may further lead to the inhibition of apoptosis and a reduction in energy expenditure, thereby sustaining vital activities. The up-regulation of intercellular adhesion and immune-related pathways upon reawakening (RCY01) further substantiates the presence of this tolerance mechanism during dormancy in the apple snail. This study provides a reference for understanding the tolerance of apple snails to extreme environments, and provides a basic theory for apple snail biocontrol research.

Integrated control of leukocyte compartments as a feature of adaptive physiology

As a highly diverse and mobile organ, the immune system is uniquely equipped to participate in tissue responses in a tunable manner, depending on the number, type, and nature of cells deployed to the respective organ. Most acute organismal stressors that threaten survival-predation, infection, poisoning, and others-induce pronounced redistribution of immune cells across tissue compartments. Here, we review the current understanding of leukocyte compartmentalization under homeostatic and noxious conditions. We argue that leukocyte shuttling between compartments is a function of local tissue demands, which are linked to the organ's contribution to adaptive physiology at steady state and upon challenge. We highlight the neuroendocrine signals that relay and organize this trafficking behavior and outline mechanisms underlying the functional diversification of leukocyte responses. In this context, we discuss important areas of future inquiry and the implications of this scientific space for clinical medicine in the era of targeted immunomodulation.

Molecular mechanisms in liver repair and regeneration: from physiology to therapeutics

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

The Effect of HBV Therapy on Glycemic Control in HBV-Infected Patients With Diabetes: A 90-day Multicenter Study

Patients with diabetes are at increased risk of HBV infection; however, the effects of HBV infection and anti-HBV therapy on the management of type 1 diabetes (T1D), type 2 diabetes (T2D), and latent autoimmune diabetes in adults (LADA) remain unclear. From 2016 to 2023, we recruited a multicenter cohort of 355 HBV-infected inpatients, including 136 with T1D, 140 with T2D, and 79 with LADA. The control group included 525 HBV-uninfected inpatients, comparing 171 with T1D, 204 with T2D and 150 with LADA. We employed propensity-score matching between cases and controls to minimize confounding effects. Hemoglobin A1c (HbA1c) was monitored at baseline and at months 1, 2, and 3. At baseline, median HbA1c was significantly higher in HBV-infected patients compared to their HBV-uninfected controls: T1D (10.4% vs. 7.5%, p < 0.01), T2D (9.6% vs. 8.6%, p = 0.01), and LADA (9.4% vs. 8.4%, p = 0.03). Baseline HbA1c levels were significantly lower in HBV-treated patients compared to those HBV-untreated patients, regardless of whether they were on antidiabetic therapy (p < 0.05). A 90-day follow-up consistently indicated lower HbA1c levels at baseline, as well as at months 1, 2, and 3 among HBV-treated patients with T1D, T2D, or LADA. Both univariate and multivariate analyses identified HBV therapy (OR = 0.44, p < 0.001) and antidiabetic treatment(OR = 0.51, p = 0.031) as protective factors for glycemic control in HBV-infected patients with diabetes. Poor glycemic control is found in HBV-infected patients with diabetes, but the intervention of anti-HBV therapy and antidiabetic treatment contributes to improved glycemic control in HBV-infected patients with T1D, T2D, or LADA.

The gut-liver axis links the associations between serum carotenoids and non-alcoholic fatty liver in a 7.8-year prospective study

Background

Many studies have shown that carotenoids are beneficial to non-alcoholic fatty liver disease (NAFLD). Therefore, we explored potential biomarkers of gut microbiota and fecal and serum metabolites linking the association between serum carotenoids and NAFLD in adults.

Methods

This 7.8-year prospective study included 2921 participants with serum carotenoids at baseline and determined NAFLD by ultrasonography (ULS-NAFLD) every 3 years. A total of 828 subjects additionally underwent magnetic resonance imaging to identify NAFLD (MRI-NAFLD). Gut microbiota was analyzed by 16S rRNA sequencing in 1,661 participants, and targeted metabolomics profiling in 893 feces and 896 serum samples was performed by ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in the middle term.

Results

A total of 2,522 participants finished follow-up visits. Of these participants, 770, 301, 474, and 977 were categorized into NAFLD-free, improved, new-onset, and persistent NAFLD groups based on their ULS-NAFLD status changes, respectively, and 342/828 were MRI-verified NALFD. Longitudinal analyses showed an inverse association between carotenoids and NALFD risk/presence (P-trend <0.05). Multivariable-adjusted odds ratios (ORs)/hazard ratio (HR) [95% confidence intervals (CIs)] of NAFLD for quartile 4 (vs. quartile 1) of total carotenoids were 0.63 (0.50, 0.80) for incident ULS-NAFLD, 0.20 (0.15, 0.27) for persistent ULS-NAFLD, 1.53 (1.10, 2.12) for improved-NAFLD, and 0.58 (0.39, 0.87) for MRI-NAFLD. The biomarkers in the gut-liver axis significantly associated with both serum carotenoids and NAFLD included sixteen microbial genera mainly in Ruminococcaceae and Veillonellaceae family, nineteen fecal metabolites containing medium-chain fatty acids (MCFAs), bile acids, and carnitines, and sixteen serum metabolites belonging to organic acids and amino acids. The total carotenoids-related scores of significant microbial genera, fecal and serum metabolites mediated the carotenoids-NAFLD association by 8.72%, 12.30%, and 16.83% (all P<0.05) for persistent NAFLD and 9.46%, 8.74%, and 15.7% for incident-NAFLD, respectively.

Conclusions

Our study reveals a beneficial association of serum carotenoids and incident and persistent NAFLD. The identified gut-liver axis biomarkers provided mechanistic linkage for the epidemiological association.

Evaluation of Hepatic Glucose and Palmitic Acid Metabolism in Rodents on High-Fat Diet Using Deuterium Metabolic Imaging

BACKGROUND

One of the main features of several metabolic disorders is dysregulation of hepatic glucose and lipid metabolism. Deuterium metabolic imaging (DMI) allows for assessing the uptake and breakdown of 2H-labeled substrates, giving specific insight into nutrient processing in healthy and diseased organs. Thus, DMI could be a useful approach for analyzing the differences in liver metabolism of healthy and diseased subjects to gain a deeper understanding of the alterations related to metabolic disorders.

PURPOSE

Evaluating the feasibility of DMI as a tool for the assessment of metabolic differences in rodents with healthy and fatty livers (FLs).

STUDY TYPE

Animal Model.

POPULATION

18 male Sprague Dawley rats on standard (SD, n = 9, healthy) and high-fat diet (HFD, n = 9, FL disease).

FIELD STRENGTH/SEQUENCE

Phase-encoded 1D pulse-acquire sequence and anatomy co-registered phase-encoded 3D pulse-acquire chemical shift imaging for 2H at 9.4T.

ASSESSMENT

Localized and nonlocalized liver spectroscopy was applied at eight time points over 104 minutes post injection. The obtained spectra were preprocessed and quantified using jMRUI (v7.0) and the resulting amplitudes translated to absolute concentration (mM) according to the 2H natural abundance water peak.

STATISTICAL TESTS

Two-way repeated measures ANOVA were employed to assess between-group differences, with statistical significance at P < 0.05.

RESULTS

DMI measurements demonstrated no significant difference (P = 0.98) in the uptake of [6,6'-2H2]glucose between healthy and impaired animals (AUCSD = 1966.0 ± 151.5 mM - minutes vs. AUCHFD = 2027.0 ± 167.6 mM·minutes). In the diseased group, the intrahepatic uptake of palmitic acid d-31 was higher (AUCHFD = 57.4 ± 17.0 mM·minutes, AUCSD = 33.3 ± 10.5 mM·minutes), but without statistical significance owing to substantial in-group variation (P = 0.73).

DATA CONCLUSION

DMI revealed higher concentrations of palmitic acid in rats with FL disease and no difference in hepatic glucose concentration between healthy and impaired animals. Thus, DMI appears to be a useful tool for evaluating metabolism in rodents with FL disease.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 3.

Role of hepatocyte RIPK1 in maintaining liver homeostasis during metabolic challenges

As a central hub for metabolism, the liver exhibits strong adaptability to maintain homeostasis in response to food fluctuations throughout evolution. However, the mechanisms governing this resilience remain incompletely understood. In this study, we identified Receptor interacting protein kinase 1 (RIPK1) in hepatocytes as a critical regulator in preserving hepatic homeostasis during metabolic challenges, such as short-term fasting or high-fat dieting. Our results demonstrated that hepatocyte-specific deficiency of RIPK1 sensitized the liver to short-term fasting-induced liver injury and hepatocyte apoptosis in both male and female mice. Despite being a common physiological stressor that typically does not induce liver inflammation, short-term fasting triggered hepatic inflammation and compensatory proliferation in hepatocyte-specific RIPK1-deficient (Ripk1-hepKO) mice. Transcriptomic analysis revealed that short-term fasting oriented the hepatic microenvironment into an inflammatory state in Ripk1-hepKO mice, with up-regulated expression of inflammation and immune cell recruitment-associated genes. Single-cell RNA sequencing further confirmed the altered cellular composition in the liver of Ripk1-hepKO mice during fasting, highlighting the increased recruitment of macrophages to the liver. Mechanically, our results indicated that ER stress was involved in fasting-induced liver injury in Ripk1-hepKO mice. Overall, our findings revealed the role of RIPK1 in maintaining liver homeostasis during metabolic fluctuations and shed light on the intricate interplay between cell death, inflammation, and metabolism.

Gegen Qinlian Decoction inhibits liver ferroptosis in type 2 diabetes mellitus models by targeting Nrf2

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes mellitus (T2DM) is a metabolic disease that can lead to complications affecting multiple organs, including the liver. Gegen Qinlian Decoction (GQD) has demonstrated considerable efficacy in the management of T2DM and its complications in accordance with the tenets of modern Chinese medicine. However, the molecular mechanism by which GQD alleviates diabetic liver injury is unclear.

AIM OF THE STUDY

To explore the effect and mechanism of GQD to ameliorate liver injury in T2DM.

MATERIALS AND METHODS

The active constituents of GQD were analyzed using UPLC. An in vivo T2DM mouse model was established by 6 weeks of high-fat diet and multiple streptozotocin (50 mg/kg/day) induction, followed by GQD administration. The evaluation of liver function, histopathology, oxidative stress, lipid peroxidation, and iron levels was conducted. In vitro experiments involved a high-glucose-induced AML12 cell model to assess oxidative stress, lipid peroxidation, and iron levels.

RESULTS

UPLC identified four main components in GQD: puerarin, baicalin, berberine and liquiritin. GQD administration resulted in enhanced liver function and a reduction in injury, accompanied by elevated antioxidant enzyme activity, increased GPX4 expression and diminished reactive oxygen species in T2DM mice. GQD treatment reduced lipid peroxidation and regulated iron transport proteins, thereby alleviating iron overload. In AML12 cells, GQD administration resulted in regulated mitochondrial morphology.

CONCLUSION

Our findings demonstrated that GQD ameliorated liver injury in T2DM by inhibiting ferroptosis through the modulation of Nrf2.

Targeted Theranostic Nanoprobes Assisted In Vivo NIR-II Fluorescence Imaging-Guided Surgery Therapy for Alveolar Echinococcosis

Alveolar echinococcosis (AE) is a serious parasitic infectious disease that is highly invasive and destructive to the liver and has a high mortality rate. However, currently, there is no effective targeted imaging and treatment method for the precise detection and therapy of AE. We proposed a new two-step targeting strategy (TSTS) for AE based on poly(lactic-co-glycolic acid) (PLGA). We designed and constructed a novel type of ICG@PLGA@Lips nanoprobe with integrated imaging and treatment properties. First, we used the characteristics of PLGA gluconeogenic raw material to target the liver during blood circulation. Then, we utilized the characteristics of PLGA specifically penetrating the AE shell to achieve specific identification of AE in the liver. Under 808 nm laser excitation, ICG@PLGA@Lips effectively achieved accurate imaging of AE based on near-infrared II (NIR-II, 900-1700 nm) fluorescence imaging methods and achieved AE treatment through PDT effects. PLGA improved the optical properties of ICG, while liposomes further improved the biocompatibility of the nanoprobe. As ICG@PLGA@Lips showed strong NIR-II fluorescence emission and good biocompatibility, ICG@PLGA@Lips showed advantages in the specific fluorescence navigation of AE surgical resection lesions. Thus, with the assistance of ICG@PLGA@Lips, we achieved precise targeted and real-time NIR-II fluorescence imaging of AE for the first time. We successfully obtained in vivo NIR-II fluorescence imaging-guided photodynamic/surgical therapy of AE. This TSTS-based AE imaging and treatment exploration provided a new strategy for accurate imaging and treatment of early AE, which is expected to significantly improve the prognosis of patients.

Insulin Sensitivity and Insulin Secretion in Adults With Friedreich's Ataxia: The Role of Skeletal Muscle

INTRODUCTION

Friedreich's ataxia (FRDA) is a multisystem disorder caused by frataxin deficiency. FRDA-related diabetes mellitus (DM) is common. Frataxin supports skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, a mediator of insulin sensitivity. Our objective was to test the association between skeletal muscle health and insulin sensitivity and secretion in adults with FRDA without DM.

METHODS

Case-control study (NCT02920671). Glucose and insulin metabolism (stable-isotope oral glucose tolerance tests), body composition (dual-energy x-ray absorptiometry), physical activity (self-report), and skeletal muscle OXPHOS capacity (creatine chemical exchange saturation transfer magnetic resonance imaging) were assessed.

RESULTS

Participants included 11 individuals with FRDA (4 female), median age 27 years (interquartile range 23, 39), body mass index 26.9 kg/m2 (24.1, 29.4), and 24 controls (11 female), 29 years (26, 39), 24.4 kg/m2 (21.8, 27.0). Fasting glucose was higher in FRDA [91 vs 83 mg/dL (5.0 vs 4.6 mmol/L), P < .05]. Individuals with FRDA had lower insulin sensitivity (whole-body insulin sensitivity index 2.8 vs 5.3, P < .01), higher postprandial insulin secretion (insulin secretory rate incremental area under the curve 30-180 minutes, 24 652 vs 17,858, P < .05), and more suppressed postprandial endogenous glucose production (-.9% vs 26.9% of fasting endogenous glucose production, P < .05). In regression analyses, lower OXPHOS and inactivity explained some of the difference in insulin sensitivity. More visceral fat contributed to lower insulin sensitivity independent of FRDA. Insulin secretion accounting for sensitivity (disposition index) was not different.

CONCLUSION

Lower mitochondrial OXPHOS capacity, inactivity, and visceral adiposity contribute to lower insulin sensitivity in FRDA. Higher insulin secretion appears compensatory and, when inadequate, could herald DM. Further studies are needed to determine if muscle- or adipose-focused interventions could delay FRDA-related DM.

Bioinert UHPLC system improves sensitivity and peak shapes for ionic metabolites

The analysis of ionic compounds by liquid chromatography is challenging due to the interaction of analytes with the metal surface of the instrument and the column, leading to poor peak shape and decreased sensitivity. The use of bioinert materials in the chromatographic system minimizes these unrequired interactions. In this work, the ultrahigh-performance liquid chromatography (UHPLC) with bioinert components was connected to a high-resolution mass spectrometer to develop a method for untargeted metabolomic analysis. 81 standards of metabolites were used for the development and optimization of the method. In comparison to the conventional chromatographic system, the application of bioinert technology resulted in significantly improved peak shapes and increased sensitivity, especially for metabolites containing phosphate groups. The calibration curves were constructed for the evaluation of the method performance, showing a wide dynamic range, low limit of detection, and linear regression coefficients higher than 0.99 for all standards. The optimized method was applied to the analysis of NIST SRM 1950 human plasma, which allowed the detection of 156 metabolites and polar lipids based on the combination of mass accuracy in the full-scan mass spectra in both polarity modes, characteristic fragment ions in MS/MS, and logical chromatographic behavior leading to the high confidence level of annotation/identification. We have demonstrated an improvement in the peak shapes and sensitivity of ionic metabolites using bioinert technology, which indicates the potential for the analysis of other ionic compounds, e.g., molecules containing phosphate groups.

ZBED3 exacerbates hyperglycemia by promoting hepatic gluconeogenesis through CREB signaling

BACKGROUND

Elevated hepatic glucose production (HGP) is a prominent manifestation of impaired hepatic glucose metabolism in individuals with diabetes. Increased hepatic gluconeogenesis plays a pivotal role in the dysregulation of hepatic glucose metabolism and contributes significantly to fasting hyperglycemia in diabetes. Previous studies have identified zinc-finger BED domain-containing 3 (ZBED3) as a risk gene for type 2 diabetes (T2DM), and its single nucleotide polymorphism (SNPs) is closely associated with the fasting blood glucose level, suggesting a potential correlation between ZBED3 and the onset of diabetes. This study primarily explores the effect of ZBED3 on hepatic gluconeogenesis and analyzes the relevant signaling pathways that regulate hepatic gluconeogenesis.

METHODS

The expression level of ZBED3 was assessed in the liver of insulin-resistant (IR)-related disease. RNA-seq and bioinformatics analyses were employed to examine the ZBED3-related pathway that modulated HGP. To investigate the role of ZBED3 in hepatic gluconeogenesis, the expression of ZBED3 was manipulated by upregulation or silencing using adeno-associated virus (AAV) in mouse primary hepatocytes (MPHs) and HHL-5 cells. In vivo, hepatocyte-specific ZBED3 knockout mice were generated. Moreover, AAV8 was employed to achieve hepatocyte-specific overexpression and knockdown of ZBED3 in C57BL/6 and db/db mice. Immunoprecipitation and mass spectrometry (IP-MS) analyses were employed to identify proteins that interacted with ZBED3. Co-immunoprecipitation (co-IP), glutathione S-transferase (GST) - pulldown, and dual-luciferase reporter assays were conducted to further elucidate the underlying mechanism of ZBED3 in regulating hepatic gluconeogenesis.

RESULTS

The expression of ZBED3 in the liver of IR-related disease models was found to be increased. Under the stimulation of glucagon, ZBED3 promoted the expression of hepatic gluconeogenesis-related genes PGC1A, PCK1, G6PC, thereby increasing HGP. Consistently, the rate of hepatic gluconeogenesis was found to be elevated in mice with hepatocyte-specific overexpression of ZBED3 and decreased in those with ZBED3 knockout. Additionally, the knockdown of ZBED3 in the liver of db/db mice resulted in a reduction in hepatic gluconeogenesis. Moreover, the study revealed that ZBED3 facilitated the nuclear translocation of protein arginine methyltransferases 5 (PRMT5) to influence the regulation of PRMT5-mediated symmetrical dimethylation of arginine (s-DMA) of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB), which in turn affects the phosphorylation of CREB and ultimately promotes HGP.

CONCLUSIONS

This study indicates that ZBED3 promotes hepatic gluconeogenesis and serves as a critical regulator of the progression of diabetes.

Leupaxin promotes hepatic gluconeogenesis and glucose metabolism by coactivation with hepatic nuclear factor 4α

BACKGROUND

As the primary source of glucose during fasting, hepatic gluconeogenesis is rigorously regulated to maintain euglycemia. Abnormal gluconeogenesis in the liver can lead to hyperglycemia, a key diagnostic marker and the primary pathological contributor to type 2 diabetes (T2D) and metabolic disorders. Hepatic nuclear factor-4 (HNF4α) is an important regulator of gluconeogenesis. In this study, we identify leupaxin (LPXN) as a novel coactivator for HNF4α. Although previous studies have shown that LPXN is highly correlated with cancer types such as B-cell differentiation and hepatocellular carcinoma progression, the role of LPXN in gluconeogenesis remains unknown.

METHODS

We initially used protein pull-down assays, mass spectrometry and luciferase assays to identify the coactivator that interacts with HNF4α in gluconeogenesis. We further leveraged cell cultures and mouse models to validate the functional importance of molecular pathway during gluconeogenesis by using adenovirus-mediated overexpression and adeno-associated virus shRNA-mediated knockdown both in vivo and ex vivo, such as in ob/db/DIO mice, HepG2 and primary hepatocytes. Following, we used CUT&Tag and chip qPCR to identify the LPXN-mediated mechanisms underlying the observed abnormal gluconeogenesis. Additionally, we assessed the translational relevance of our findings using human liver tissues from both healthy donors and patients with obesity/type 2 diabetes.

RESULTS

We found that LPXN interacts with HNF4α to participate in gluconeogenesis. Knockdown of LPXN expression in the liver effectively enhanced glucose metabolism, while its overexpression in the liver effectively inhibited it. Mechanistically, LPXN could translocate into the nucleus and was essential for regulating gluconeogenesis by binding to the PEPCK promoter, which controlled the expression of an enzyme involved in gluconeogenesis, mainly through the Gcg-cAMP-PKA pathway. Additionally, LPXN expression was found to be increased in the livers of patients with steatosis and diabetes, supporting a pathological role of LPXN.

CONCLUSIONS

Taken together, our study provides evidence that LPXN plays a critical role in modulating hepatic gluconeogenesis, thereby reinforcing the fact that targeting LPXN may be a potential approach for the treatment of diabetes and metabolic disorders.

Enhancing metabolic and inflammatory status in insulin-resistant rats: Acute intervention with cocoa flavanols and submaximal aerobic exercise activates intracellular signaling pathways for glucose metabolism

INTRODUCTION

Type 2 diabetes, characterized by hyperglycemia, is closely linked to obesity and low-grade inflammation. Acute cocoa flavanols (CF) intake has demonstrated benefits in vasoreactivity, cognitive functions, and antioxidant enzyme activity. However, the physiological mechanisms of CF concerning glucose uptake, inflammatory mediators, and their interplay with aerobic exercise remain unclear in populations with metabolic diseases.

OBJECTIVE

This study aims to investigate the acute effects of CF, alone or combined with acute aerobic exercise on mechanisms involved in glucose uptake and inflammatory mediators in the liver, skeletal muscle, pancreas, and adipose tissue in insulin-resistant (IR) rats.

METHODS

Sixty-four Wistar rats (250 ± 10g; 15 weeks age) were subjected to a regular chow (CON) or an obesity-associated insulin-resistant (IR) state induced by a high-fat diet and fructose-rich beverage for 30 days. Seventy-two hours after an incremental maximal treadmill running test, rats received a placebo solution or CF supplementation (45 mg·kg-1 of body weight). One hour later, they either rested or ran on a treadmill at 60 % of peak oxygen uptake (VO2peak) for 30 min. Euthanasia occurred 30 min post-experimental sessions. Inflammatory and anti-inflammatory cytokines were assayed using ELISA in the liver, pancreas, gastrocnemius muscle, and epididymal adipose tissues. TRB3 and CPT1 mRNA were assessed by q-RTPCR in the liver and gastrocnemius muscle while Akt and AMPK phosphorylation were examined by immunohistochemistry.

RESULTS

CF attenuated hyperglycemia observed after submaximal aerobic exercise in IR rats (p < 0.001). In the liver, CF exhibited additive effects to aerobic exercise, enhancing Akt protein phosphorylation, potentially contributing to improved glucose uptake in IR rats. Submaximal aerobic exercise and CF increased AMPK protein phosphorylation in the liver (p < 0.001) and skeletal muscle (p < 0.001), reduced TRB3 gene expression (p < 0.01), elevated CPT-1a gene expression (p < 0.001), and ameliorated the inflammatory milieu in the pancreas, adipose tissue, liver, and gastrocnemius muscle.

CONCLUSION

Acute intake, of CF combined with submaximal aerobic exercise activates key proteins and genes involved in glucose uptake and lipid metabolism, improving the inflammatory milieu. This synergistic effect may contribute to mitigating metabolic complications associated with insulin resistance.

A feeding-induced myokine modulates glucose homeostasis

Maintaining blood glucose homeostasis during fasting and feeding is crucial for the prevention of dysregulation that can lead to either hypo- or hyperglycaemia. Here we identified feimin, encoded by a gene with a previously unknown function (B230219D22Rik in mice, C5orf24 in humans), as a key modulator of glucose homeostasis. Feimin is secreted from skeletal muscle during feeding and binds to its receptor, receptor protein tyrosine kinase Mer (MERTK), promoting glucose uptake and inhibiting glucose production by activation of AKT. Administration of feimin and insulin synergistically improves blood glucose homeostasis in both normal and diabetic mice. Notably, a specific single nucleotide polymorphism (rs7604639, G>A) within the MERTK gene, causing an amino acid substitution (R466K) within the feimin-MERTK binding region, leads to reduced association with feimin and elevated postprandial blood glucose and insulin levels in humans. Our findings underscore a role of the feimin-MERTK signalling axis in glucose homeostasis, providing valuable insights into potential therapeutic avenues for diabetes.

Integrated hepatic transcriptomics and metabolomics identify Pck1 as a key factor in the broad dysregulation induced by vehicle pollutants

BACKGROUND

Exposure to air pollution is associated with worldwide morbidity and mortality. Diesel exhaust (DE) emissions are important contributors which induce vascular inflammation and metabolic disturbances by unknown mechanisms. We aimed to determine molecular pathways activated by DE in the liver that could be responsible for its cardiometabolic toxicity.

METHODS

Apolipoprotein E knockout (ApoE KO) mice were exposed to DE or filtered air (FA) for two weeks, or DE for two weeks followed by FA for 1 week. Expression microarrays and global metabolomics assessment were performed in the liver. An integrated transcriptomic and metabolomic analytical strategy was employed to dissect critical pathways and identify candidate genes that could dissect DE-induced pathogenesis. HepG2 cells were treated with an organic extract of DE particles (DEP) vs. vehicle control to test candidate genes.

RESULTS

DE exposure for 2 weeks dysregulated 658 liver genes overrepresented in whole cell metabolic pathways, especially including lipid and carbohydrate metabolism, and the respiratory electron transport pathway. DE exposure significantly dysregulated 118 metabolites, resulting in increased levels of triglycerides and fatty acids due to mitochondrial dysfunction as well as increased levels of glucose and oligosaccharides. Consistently, DEP treatment of HepG2 cells led to increased gluconeogenesis and glycogenolysis indicating the ability of the in-vitro approach to model effects induced by DE in vivo. As an example, while gene network analysis of DE livers identified phosphoenolpyruvate carboxykinase 1 (Pck1) as a key driver gene of DE response, DEP treatment of HepG2 cells resulted in increased mRNA expression of Pck1 and glucose production, the latter replicated in mouse primary hepatocytes. Importantly, Pck1 inhibitor mercaptopicolinic acid suppressed DE-induced glucose production in HepG2 cells indicating that DE-induced elevation of hepatic glucose was due in part to upregulation of Pck1 and increased gluconeogenesis.

CONCLUSIONS

Short-term exposure to DE induced widespread alterations in metabolic pathways in the liver of ApoE KO mice, especially involving carbohydrate and lipid metabolism, together with mitochondrial dysfunction. Pck1 was identified as a key driver gene regulating increased glucose production by activation of the gluconeogenesis pathway.

Phenotypic screening in zebrafish larvae identifies promising cyanobacterial strains and pheophorbide a as insulin mimetics

Diabetes is a pandemic disease that causes the loss of control of glucose regulation in the organism, in consequence of dysfunction of insulin production or functionality. In this work, the antidiabetic bioactivity of 182 fractions from 19 cyanobacteria strains derived from the LEGE Culture Collection were analysed using the 2-NBDG assay in zebrafish larvae. From this initial screening, two fractions (57 (06104_D) and 107 (03283_B)) were identified as promising insulin mimetics. These were further characterized by measuring glucose levels in whole larvae, the expression of glucose transporters (GLUT 1-3) using western blot, and the mRNA expression levels of the glut2, pepck, and insa genes using real-time qPCR. Both fractions showed a decrease in free glucose levels. Furthermore, exposure to fraction 06104_D decreased GLUT1 and increased insa mRNA levels. The chemical composition of these fractions was determined using LC-HRESIMS/MS and compared to inactive fractions of the same polarity in order to identify the unique bioactive molecules. The molecular networks constructed using the GNPS platform revealed that fraction 06104_D contained mass clusters primarily composed of chlorins, lipids, and terpenoids, while fraction 03283_B contained xanthophylls, peptides, and terpenoids. To correlate the observed activity with the chemical composition of fraction 06104_D, pheophorbide a was chosen as a representative of chlorophyll derivatives. Exposure to zebrafish larvae at 10 and 20 µM confirmed the increased glucose uptake on the 2-NBDG assay. These findings highlight the bioactivity of chlorophyll derivatives as insulin mimetic compounds, as well as cyanobacteria as a source of potential therapeutic diabetes applications.

Prediction of metabolic subphenotypes of type 2 diabetes via continuous glucose monitoring and machine learning

The classification of type 2 diabetes and prediabetes does not consider heterogeneity in the pathophysiology of glucose dysregulation. Here we show that prediabetes is characterized by metabolic heterogeneity, and that metabolic subphenotypes can be predicted by the shape of the glucose curve measured via a continuous glucose monitor (CGM) during standardized oral glucose-tolerance tests (OGTTs) performed in at-home settings. Gold-standard metabolic tests in 32 individuals with early glucose dysregulation revealed dominant or co-dominant subphenotypes (muscle or hepatic insulin-resistance phenotypes in 34% of the individuals, and β-cell-dysfunction or impaired-incretin-action phenotypes in 40% of them). Machine-learning models trained with glucose time series from OGTTs from the 32 individuals predicted the subphenotypes with areas under the curve (AUCs) of 95% for muscle insulin resistance, 89% for β-cell deficiency and 88% for impaired incretin action. With CGM-generated glucose curves obtained during at-home OGTTs, the models predicted the muscle-insulin-resistance and β-cell-deficiency subphenotypes of 29 individuals with AUCs of 88% and 84%, respectively. At-home identification of metabolic subphenotypes via a CGM may aid the risk stratification of individuals with early glucose dysregulation.

Glycogen metabolism and structure: A review

Glycogen is a glucose polymer that plays a crucial role in glucose homeostasis by functioning as a short-term energy storage reservoir in animals and bacteria. Abnormalities in its metabolism and structure can cause several problems, including diabetes, glycogen storage diseases (GSDs) and muscular disorders. Defects in the enzymes involved in glycogen synthesis or breakdown, resulting in either excessive accumulation or insufficient availability of glycogen in cells seem to account for the most common pathogenesis. This review discusses glycogen metabolism and structure, including molecular architecture, branching dynamics, and the role of associated components within the granules. The review also discusses GSD type XV and Lafora disease, illustrating the broader implications of aberrant glycogen metabolism and structure. These conditions also impart information on important regulatory mechanisms of glycogen, which hint at potential therapeutic targets. Knowledge gaps and potential future research directions are identified.

[Effects of intermittent fasting and sports performance: a narrative review]

Recently, fasted exercise has generated interest for its potential to stimulate metabolic and performance adaptations. The present study aims to analyze the effects of fasting and fasted training on performance and metabolism, acutely and chronically. The databases Medline (PubMed), Physiotherapy Evidence Database (PEDro), Cochrane, and Google Scholar were searched. In total, 767 studies were identified. Of those, 51 studies were finally included. Acutely, exercise on fasting promotes fat oxidation at low and moderate intensities, while protein catabolism is not increased. Performance is not affected in efforts lower than 1 hour. Chronically, fasting generates greater efficiency in fat metabolism and the ability to regulate blood glucose in the long term, although it has not been possible to determine whether these findings improve sports performance. More research is needed in elite athletes, with high training loads and with a periodized approach to fasting.

Biomimetic Cell Membrane Layers for the Detection of Insulin and Glucagon

The growing need for reliable and rapid insulin testing to enhance glycemic management has spurred intensive exploration of new insulin-binding bioreceptors and innovative biosensing platforms for detecting this hormone, along with glucagon, in biological samples. Here, by leveraging the native protein receptors on the HepG2 cell membrane, we construct a simple and chemical-free biomimetic molecular recognition layer for the detection of insulin and glucagon. Unlike traditional affinity sensors, which require lengthy surface modifications on the electrochemical transducers and use of two different capture antibodies to recognize each analyte, this new biomimetic sensing strategy employs a simple drop-casting of a natural cell membrane recognition layer onto the electrochemical transducer. This approach allows for the concurrent capture and detection of both insulin and glucagon. We investigate the presence of insulin and glucagon receptors on the HepG2 cell membrane and demonstrate its multiplexing bioelectronic sensing capabilities through the binding of the captured insulin and glucagon to enzyme-tagged signaling antibodies. This new molecular recognition layer offers highly sensitive simultaneous detection of insulin and glucagon under decentralized conditions, holding considerable promise for the management of diabetes and the development of diverse biomimetic diagnostic platforms.

Circ_0000284 Is Involved in Arsenite-Induced Hepatic Insulin Resistance Through Blocking the Plasma Membrane Translocation of GLUT4 in Hepatocytes via IGF2BP2/PPAR-γ

Arsenic exposure can induce liver insulin resistance (IR) and diabetes (DM), but the underlying mechanisms are not yet clear. Circular RNAs (circRNAs) are involved in the regulation of the onset of diabetes, especially in the progression of IR. This study aimed to investigate the role of circRNAs in arsenic-induced hepatic IR and its underlying mechanism. Male C57BL/6J mice were given drinking water containing sodium arsenite (0, 0.5, 5, or 50 ppm) for 12 months. The results show that sodium arsenite increased circ_0000284 expression, decreased insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) and peroxisome proliferator-activated receptor-γ (PPAR-γ), and inhibited cell membrane protein levels of insulin-responsive glucose transporter protein 4 (GLUT4) in the mouse livers, indicating that arsenic exposure causes liver damage and disruptions to glucose metabolism. Furthermore, sodium arsenite reduced glucose consumption and glycogen levels, increased the expression of circ_0000284, reduced the protein levels of IGF2BP2 and PPAR-γ, and inhibited GLUT4 protein levels in the cell membranes of insulin-treated HepG2 cells. However, a circ_0000284 inhibitor reversed arsenic exposure-induced reductions in IGF2BP2, PPAR-γ, and GLUT4 levels in the plasma membrane. These results indicate that circ_0000284 is involved in arsenite-induced hepatic insulin resistance through blocking the plasma membrane translocation of GLUT4 in hepatocytes via IGF2BP2/PPAR-γ. This study provides a scientific basis for finding early biomarkers for the control of arsenic exposure and type 2 diabetes mellitus (T2DM), and discovering new prevention and control measures.