Search Results (28)

The advanced glycation end product (AGE)–RAGE axis has been implicated in the pathophysiology of diabetic bladder dysfunction (DBD). However, no previous studies have explored the effects of RAGE blockade on this condition. Here, we explored the effects of the selective RAGE inhibitor TTP488 (azeliragon) at the functional and molecular levels of bladder dysfunction in ob/ob leptin-deficient mice. Female B6.V-Lep ob/JUnib (ob/ob) and wild-type (WT) C57BL/6 mice were used as lean controls. Treatment with TTP488 in ob/ob mice resulted in no changes in body weight, fasting glucose, or insulin resistance; however, it reduced total AGE and MG-H1 levels without altering RAGE levels in bladder tissues. TTP488 normalized glyoxalase-1, glutathione reductase, glutathione peroxidase, and superoxide dismutase activities in bladder tissues. Marked increases in collagen intensity were also observed in ob/ob mice, an effect fully reversed by TTP488 treatment. TTP488 reduced total void volume, volume per void, and ex vivo bladder contractility in response to electrical-field stimulation and carbachol. Our finding that TTP488 mitigates DBD in ob/ob mice supports the proposal that RAGE blockade could serve as a promising therapeutic strategy for managing DBD. Full article

Leptin-deficient (ob/ob) and leptin receptor (Lepr)-deficient db/db mice develop a mild form of osteoclast-rich osteopetrosis, most evident in long bone epiphyses, implying leptin is important for normal replacement of cartilage during skeletal maturation. However, it is unclear whether leptin acts as a permissive or regulatory factor and whether its actions are mediated via peripheral pathways. Here we show the osteopetrotic phenotype is not evident in ob/+ or db/+ mice, suggesting that leptin acts as a critical but permissive factor for skeletal maturation. The importance of leptin is further supported by our results showing that interventions known to increase bone resorption (mild cold stress, simulated microgravity, or particle-induced inflammation) did not advance skeletal maturation in ob/ob mice whereas long-duration hypothalamic leptin gene therapy was effective. Additionally, administration of leptin by subcutaneously implanted osmotic pumps (400 ng/h) for 2 weeks accelerated skeletal maturation in ob/ob mice. Because leptin has the potential to act on the skeleton through peripheral pathways, we interrogated osteoclast-lineage cells for the presence of Lepr and evaluated skeletal response to the introduction of bone marrow Lepr⁺ cells into db/db mice. We identified Lepr on marrow MCSFR⁺CD11b⁺ osteoclast precursors and on osteoclasts generated in vitro. We then adoptively transferred Lepr⁺ marrow cells from GFP mice or wildtype (WT) mice into Lepr^- db/db mice. Following engraftment, most MCSFR⁺ CD11b⁺ cells in marrow expressed GFP. Whereas db/db→db/db had minimal influence on epiphyseal cartilage, WT→db/db decreased cartilage. These findings suggest peripheral leptin signaling is required for normal osteoclast-dependent replacement of cartilage by bone during skeletal maturation. Full article

Fibroblast growth factor 21 (FGF21), a hormone-like protein, plays a crucial role in enhancing glucose and lipid metabolism, offering promising therapeutic avenues for conditions such as nonalcoholic steatohepatitis and severe hypertriglyceridemia. Despite its potential, this protein’s limited stability and brief half-life pose significant challenges for its use in clinical settings. In this study, we created an FGF21 analog (named FGF21-164) that is a mutant of FGF21 and fused it with the tandem repeat sequence of human CD164. FGF21-164, characterized by extensive glycosylation and sialylation, exhibits enhanced pharmacokinetic properties, particularly in terms of its significantly longer half-life compared to its native form. The in vitro efficacy of FGF21-164 was evaluated using 3T3-L1-induced adipocytes. The protein demonstrated a dose-dependent increase in glucose uptake and effectively decreased lipid droplet accumulation surrounding the adipocytes. The in vivo activity of FGF21-164 was evaluated in leptin-deficient (ob/ob) and diet-induced obesity (DIO) mice. A single subcutaneous dose of FGF21-164 led to a rapid decrease in blood glucose levels and sustained normal fasting glucose levels for up to 28 days. Additionally, repeated dosing of FGF21-164 significantly curbed weight gain and reduced hepatic fat accumulation in DIO mice. Full article

Background/Objectives: UFMylation, a newly identified ubiquitin-like modification, modulates a variety of physiological processes, including endoplasmic reticulum homeostasis maintenance, DNA damage response, embryonic development, and tumor progression. Recent reports showed that UFMylation plays a protective role in preventing liver steatosis and fibrosis, serving as a defender of liver homeostasis in the development of metabolic dysfunction-associated steatotic liver disease (MASLD). However, the regulation of UFMylation in MASLD remains unclear. This study aimed to determine the expressed patterns of UFMylation components in multiple tissues of leptin-deficient ob/ob mice and high-fat diet (HFD)-fed mice, which are mimicking the conditions of MASLD. Methods: The ob/ob mice and HFD-fed mice were sacrificed to collect tissues indicated in this study. Total RNA and proteins were extracted from tissues to examine the expressed patterns of UFMylation components, including UBA5, UFC1, UFL1, DDRGK1, UFSP1, UFSP2 and UFM1, by real-time PCR and western blot analysis. Results: The protein levels of UBA5, UFC1 and UFL1 were down-regulated in liver, brown adipose tissue (BAT) and inguinal white adipose tissue (iWAT), whereas the messenger RNA (mRNA) levels of Ufl1 and Ufsp1 were both decreased in skeletal muscle, BAT, iWAT and epididymal white adipose tissue (eWAT) of ob/ob mice. In contrast, the mRNA levels of Ufsp1 in skeletal muscle, BAT, iWAT and heart, and the protein levels of UFL1 were decreased in BAT, iWAT, heart and cerebellum of HFD-fed mice. Conclusions: Our findings established the expressed profiles of UFMylaiton in multiple tissues of mice mimicking MASLD, indicating an important regulation for UFMylation in these tissues’ homeostasis maintenance. Full article

Chalcones constitute an important group of natural compounds abundant in fruits and comestible plants. They are a subject of increasing interest because of their biological activities, including anti-diabetic and anti-obesity effects. The simple chalcone structural scaffold can be modified at multiple sites with different chemical moieties. Here, we generated an artificial chalcone, i.e., 3,5-dimethyl-2,4,6-trimethoxychalcone (TriMetChalc), derived from 2′,4′-Dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC). DMC is a major compound of Cleistocalyx operculatus, a plant widely used in Asia for its anti-hyperglycemic activity. Using ob/ob mice as an obesity model, we report that, after 3 weeks of per os administration, TriMetChalc modified food intake through the specific activation of brain structures dedicated to the regulation of energy balance. TriMetChalc also decreased weight gain, glucose intolerance, and hepatic steatosis. Moreover, through extensive liver lipidomic analysis, we identified TriMetChalc-induced modifications that could contribute to improving the liver status of the animals. Hence, TriMetChalc is a chalcone derivative capable of reducing food intake and the addition of glucose intolerance and hepatic steatosis in a mouse model of obesity. In light of these results, we believe that TriMetChalc action deserves to be more deeply evaluated over longer treatment periods and/or in combination with other chalcones with protective effects on the liver. Full article

Despite efforts to elucidate the cellular adaptations induced by obesity, cellular bioenergetics is currently considered a crucial target. New strategies to delay the onset of the hazardous adaptations induced by obesity are needed. Therefore, we evaluated the effects of 4 weeks of melatonin treatment on mitochondrial function and lipid metabolism in the livers of leptin-deficient mice. Our results revealed that the absence of leptin increased lipid storage in the liver and induced significant mitochondrial alterations, which were ultimately responsible for defective ATP production and reactive oxygen species overproduction. Moreover, leptin deficiency promoted mitochondrial biogenesis, fusion, and outer membrane permeabilization. Melatonin treatment reduced the bioenergetic deficit found in ob/ob mice, alleviating some mitochondrial alterations in the electron transport chain machinery, biogenesis, dynamics, respiration, ATP production, and mitochondrial outer membrane permeabilization. Given the role of melatonin in maintaining mitochondrial homeostasis, it could be used as a therapeutic agent against adipogenic steatosis. Full article

Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling cascades upstream and downstream of Rac1 in skeletal muscle are impaired by obesity that causes insulin resistance and type 2 diabetes. In an attempt to clarify this point, we investigated Rac1 signaling in the leptin-deficient (Lep^ob/ob) mouse model. Here, we show that insulin-stimulated GLUT4 translocation and Rac1 activation are almost completely abolished in Lep^ob/ob mouse skeletal muscle. Phosphorylation of the protein kinase Akt2 and plasma membrane translocation of the guanine nucleotide exchange factor FLJ00068 following insulin stimulation were also diminished in Lep^ob/ob mice. On the other hand, the activation of another small GTPase RalA, which acts downstream of Rac1, by the constitutively activated form of Akt2, FLJ00068, or Rac1, was partially abrogated in Lep^ob/ob mice. Taken together, we conclude that insulin-stimulated glucose uptake is impaired by two mechanisms in Lep^ob/ob mouse skeletal muscle: one is the complete inhibition of Akt2-mediated activation of Rac1, and the other is the partial inhibition of RalA activation downstream of Rac1. Full article

Due to spontaneous deficiency in leptin, ob/ob mice are one of the most commonly used experimental animal models in diabetes research. In this study, we reported a quick and easy-to-conduct genotyping method using tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) to differentiate mice with a mutated allele from the wild-type genotype. The amplicon patterns of different genotypes are clearly visible and distinguishable on 1.5% agarose gel. This method can serve as a valuable tool to differentiate genotypes for breeding purposes, to maintain animal colonies, control the available space in the animal facility, and identify appropriate individuals for animal experiments. Full article

Obesity has become an extensive threat to human health due to associated chronic inflammation and metabolic diseases. Apoptosis-associated speck-like protein (ASC) is a critical link between inflammasome and apoptosis-inducing proteins. In this study, we aimed to clarify the role of ASC in lipid metabolism. With high-fat diet (HFD) and knockout leptin gene mice (ob/ob), we found that ASC expression in subcutaneous adipose tissue (SAT) correlated with obesity. It could also positively regulate the reprogramming of cellular energy metabolism. Stromal vascular fractions (SVF) cells derived from the SAT of Asc^−/− mice or SVF from wild-type (WT) mice transfected with ASC siRNA were used to further investigate the underlying molecular mechanisms. We found ASC deficiency could lead to lipogenesis and inhibit lipolysis in SAT, aggravating lipid accumulation and impairing metabolic balance. In addition, our results showed that p53 and AMPKα expression were inhibited in SAT when ASC level was low. p53 and AMP-activated protein kinase α (AMPKα) were then assessed to elucidate whether they were downstream of ASC in regulating lipid metabolism. Our results revealed that ASC deficiency could promote lipid accumulation by increasing lipogenesis and decreasing lipolysis through p53/AMPKα axis. Regulation of ASC on lipid metabolism might be a novel therapeutic target for obesity. Full article

Mitochondria (Mt) are essential cellular organelles for the production of energy and thermogenesis. Mt also serve a host of functions in addition to energy production, which include cell signaling, metabolism, cell death, and aging. Due to the central role of Mt in metabolism as metabolic hubs, there has been renewed interest in how Mt impact metabolic pathways and multiple pathologies. This review shares multiple observational ultrastructural findings in multiple cells and organs to depict aberrant mitochondrial (aMt) remodeling in pre-clinical rodent models. Further, it is intended to show how remodeling of Mt are associated with obesity, insulin resistance, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM). Specifically, Mt remodeling in hypertensive and insulin-resistant lean models (Ren2 rat models), lean mice with streptozotocin-induced diabetes, obesity models including diet-induced obesity, genetic leptin-deficient ob/ob, and leptin receptor-deficient db/db diabetic mice are examined. Indeed, aMt dysfunction and damage have been implicated in multiple pathogenic diseases. Manipulation of Mt such as the induction of Mt biogenesis coupled with improvement of mitophagy machinery may be helpful to remove leaky damaged aMt in order to prevent the complications associated with the generation of superoxide-derived reactive oxygen species and the subsequent reactive species interactome. A better understanding of Mt remodeling may help to unlock many of the mysteries in obesity, insulin resistance, MetS, T2DM, and the associated complications of diabetic end-organ disease. Full article

Metabolic associated fatty liver disease (MAFLD) is a hepatic manifestation of metabolic syndrome and usually associated with obesity and diabetes. Our aim is to characterize the pathophysiological mechanism involved in MAFLD development in Black Tan and brachyuric (BTBR) insulin-resistant mice in combination with leptin deficiency (ob/ob). We studied liver morphology and biochemistry on our diabetic and obese mice model (BTBR ob/ob) as well as a diabetic non-obese control (BTBR + streptozotocin) and non-diabetic control mice (BTBR wild type) from 4–22 weeks. Lipid composition was assessed, and lipid related pathways were studied at transcriptional and protein level. Microvesicular steatosis was evident in BTBR ob/ob from week 6, progressing to macrovesicular in the following weeks. At 12th week, inflammatory clusters, activation of STAT3 and Nrf2 signaling pathways, and hepatocellular ballooning. At 22 weeks, the histopathological features previously observed were maintained and no signs of fibrosis were detected. Lipidomic analysis showed profiles associated with de novo lipogenesis (DNL). BTBR ob/ob mice develop MAFLD profile that resemble pathological features observed in humans, with overactivation of inflammatory response, oxidative stress and DNL signaling pathways. Therefore, BTBR ob/ob mouse is an excellent model for the study of the steatosis to steatohepatitis transition. Full article

The secretory glycoprotein lactoferrin (LF) is suggested to ameliorate overweight regardless of non-genetic or genetic mechanisms. Although maternal overweight represents a key predictor of offspring growth, the efficacy of LF on fertility problems in overweight and obese mothers remains unknown. To address this issue, we examined the effect of LF ingestion by analyzing overweight mice (Institute of Cancer Research (ICR) mice with high-fat diets; HF mice) and obese mice (leptin-deficient mice with type II diabetes; ob/ob mice). Plasma insulin, leptin, glucose, and cholesterol levels were measured, and thermal imaging and histological analysis were employed. The litter size of HF females was reduced due to miscarriage, which was reversed by LF ingestion. In addition, LF ingestion suppressed overweight prevalence in their offspring. The component analysis of the maternal blood demonstrated that glucose concentration in both HF females and their offspring was normalized by LF ingestion, which further standardized the concentration of insulin, but not leptin. LF ingestion was unable to reverse female infertility in ob/ob mice, although their obesity and uterine function were partially improved. Our results indicate that LF upregulates female fertility by reinforcing ovarian and uterine functions in females that are overweight due to caloric surplus. Full article

The endocannabinoidome (expanded endocannabinoid system, eCBome)-gut microbiome (mBIome) axis plays a fundamental role in the control of energy intake and processing. The liver-expressed antimicrobial peptide 2 (LEAP2) is a recently identified molecule acting as an antagonist of the ghrelin receptor and hence a potential effector of energy metabolism, also at the level of the gastrointestinal system. Here we investigated the role of the eCBome-gut mBIome axis in the control of the expression of LEAP2 in the liver and, particularly, the intestine. We confirm that the small intestine is a strong contributor to the circulating levels of LEAP2 in mice, and show that: (1) intestinal Leap2 expression is profoundly altered in the liver and small intestine of 13 week-old germ-free (GF) male mice, which also exhibit strong alterations in eCBome signaling; fecal microbiota transfer (FMT) from conventionally raised to GF mice completely restored normal Leap2 expression after 7 days from this procedure; in 13 week-old female GF mice no significant change was observed; (2) Leap2 expression in organoids prepared from the mouse duodenum is elevated by the endocannabinoid noladin ether, whereas in human Caco-2/15 epithelial intestinal cells it is elevated by PPARγ activation by rosiglitazone; (3) Leap2 expression is elevated in the ileum of mice with either high-fat diet—or genetic leptin signaling deficiency—(i.e., ob/ob and db/db mice) induced obesity. Based on these results, we propose that LEAP2 originating from the small intestine may represent a player in eCBome- and/or gut mBIome-mediated effects on food intake and energy metabolism. Full article

About 20–30% of premenopausal women have metabolic syndrome, and the number is almost double in postmenopausal women, and these women have an increased risk of hepatosteatosis. Postmenopausal women with metabolic syndrome are often treated with hormone replacement therapy (HRT), but estrogens in currently available HRTs increase the risk of breast and endometrial cancers and Cardiovascular Disease. Therefore, there is a critical need to find safer alternatives to HRT to improve postmenopausal metabolic health. Pathway preferential estrogen 1 (PaPE-1) is a novel estrogen receptor ligand that has been shown to favorably affect metabolic tissues without adverse effects on reproductive tissues. In this study, we have examined the effects of PaPE-1 on metabolic health, in particular, examining its effects on the liver transcriptome and on plasma metabolites in two different mouse models: diet-induced obesity (DIO) and leptin-deficient (ob/ob) mice. PaPE-1 significantly decreased liver weight and lipid accumulation in both DIO and ob/ob models and lowered the expression of genes associated with fatty acid metabolism and collagen deposition. In addition, PaPE-1 significantly increased the expression of mitochondrial genes, particularly ones associated with the electron transport chain, suggesting an increase in energy expenditure. Integrated pathway analysis using transcriptomics and metabolomics data showed that PaPE-1 treatment lowered inflammation, collagen deposition, and pathways regulating fatty acid metabolism and increased metabolites associated with glutathione metabolism. Overall, our findings support a beneficial metabolic role for PaPE-1 and suggest that PaPE-1 may protect postmenopausal women from fatty liver disease without increasing reproductive cancer risk. Full article

The pancreatic islets of Langerhans consist of endocrine cells that secrete peptide hormones into the blood circulation in response to metabolic stimuli. When transplanted into the anterior chamber of the eye (ACE), pancreatic islets engraft and maintain morphological features of native islets as well as islet-specific vascularization and innervation patterns. In sufficient amounts, intraocular islets are able to maintain glucose homeostasis in diabetic mice. Islet organoids (pseudo-islets), which are formed by self-reassembly of islet cells following disaggregation and genetic manipulation, behave similarly to native islets. Here, we tested the hypothesis that genetically engineered intraocular islet organoids can serve as production sites for leptin. To test this hypothesis, we chose the leptin-deficient ob/ob mouse as a model system, which becomes severely obese, hyperinsulinemic, hyperglycemic, and insulin resistant. We generated a Tet-OFF-based beta-cell-specific adenoviral expression construct for mouse leptin, which allowed efficient transduction of native beta-cells, optical monitoring of leptin expression by co-expressed fluorescent proteins, and the possibility to switch-off leptin expression by treatment with doxycycline. Intraocular transplantation of islet organoids formed from transduced islet cells, which lack functional leptin receptors, to ob/ob mice allowed optical monitoring of leptin expression and ameliorated their metabolic phenotype by improving bodyweight, glucose tolerance, serum insulin, and C-peptide levels. Full article