Long-lasting anti-diabetic efficacy of PEGylated FGF-21 and liraglutide in treatment of type 2 diabetic mice

Intestinal BMP-9 locally upregulates FGF19 and is down-regulated in obese patients with diabetes

Bone morphogenetic protein (BMP)-9, a member of the TGFβ-family of cytokines, is believed to be mainly produced in the liver. The serum levels of BMP-9 were reported to be reduced in newly diagnosed diabetic patients and BMP-9 overexpression ameliorated steatosis in the high fat diet-induced obesity mouse model. Furthermore, injection of BMP-9 in mice enhanced expression of fibroblast growth factor (FGF)21. However, whether BMP-9 also regulates the expression of the related FGF19 is not clear. Because both FGF21 and 19 were described to protect the liver from steatosis, we have further investigated the role of BMP-9 in this context. We first analyzed BMP-9 levels in the serum of streptozotocin (STZ)-induced diabetic rats (a model of type I diabetes) and confirmed that BMP-9 serum levels decrease during diabetes. Microarray analyses of RNA samples from hepatic and intestinal tissue from BMP-9 KO- and wild-type mice (C57/Bl6 background) pointed to basal expression of BMP-9 in both organs and revealed a down-regulation of hepatic Fgf21 and intestinal Fgf19 in the KO mice. Next, we analyzed BMP-9 levels in a cohort of obese patients with or without diabetes. Serum BMP-9 levels did not correlate with diabetes, but hepatic BMP-9 mRNA expression negatively correlated with steatosis in those patients that did not yet develop diabetes. Likewise, hepatic BMP-9 expression also negatively correlated with serum LPS levels. In situ hybridization analyses confirmed intestinal BMP-9 expression. Intestinal (but not hepatic) BMP-9 mRNA levels were decreased with diabetes and positively correlated with intestinal E-Cadherin expression. In vitro studies using organoids demonstrated that BMP-9 directly induces FGF19 in gut but not hepatocyte organoids, whereas no evidence of a direct induction of hepatic FGF21 by BMP-9 was found. Consistent with the in vitro data, a correlation between intestinal BMP-9 and FGF19 mRNA expression was seen in the patients' samples. In summary, our data confirm that BMP-9 is involved in diabetes development in humans and in the control of the FGF-axis. More importantly, our data imply that not only hepatic but also intestinal BMP-9 associates with diabetes and steatosis development and controls FGF19 expression. The data support the conclusion that increased levels of BMP-9 would most likely be beneficial under pre-steatotic conditions, making supplementation of BMP-9 an interesting new approach for future therapies aiming at prevention of the development of a metabolic syndrome and liver steatosis.

Fibroblast Growth Factor 21 (FGF21) Administration Sex-Specifically Affects Blood Insulin Levels and Liver Steatosis in Obese Ay Mice

FGF21 is a promising candidate for treating obesity, diabetes, and NAFLD; however, some of its pharmacological effects are sex-specific in mice with the A^y mutation that evokes melanocortin receptor 4 blockade, obesity, and hepatosteatosis. This suggests that the ability of FGF21 to correct melanocortin obesity may depend on sex. This study compares FGF21 action on food intake, locomotor activity, gene expression, metabolic characteristics, and liver state in obese A^y males and females. A^y mice were administered FGF21 for seven days, and metabolic parameters and gene expression in different tissues were assessed. Placebo-treated females were more obese than males and had lower levels of blood insulin and liver triglycerides, and higher expression of genes for insulin signaling in the liver, white adipose tissue (WAT) and muscles, and pro-inflammatory cytokines in the liver. FGF21 administration did not affect body weight, and increased food intake, locomotor activity, expression of Fgf21 and Ucp1 in brown fat and genes related to lipolysis and insulin action in WAT regardless of sex; however, it decreased hyperinsulinemia and hepatic lipid accumulation and increased muscle expression of Cpt1 and Irs1 only in males. Thus, FGF21’s beneficial effects on metabolic disorders associated with melanocortin obesity are more pronounced in males.

Fibroblast growth factor 21 attenuates salt-sensitive hypertension-induced nephropathy through anti-inflammation and anti-oxidation mechanism

BACKGROUND

Patients with salt-sensitive hypertension are often accompanied with severe renal damage and accelerate to end-stage renal disease, which currently lacks effective treatment. Fibroblast growth factor 21 (FGF21) has been shown to suppress nephropathy in both type 1 and type 2 diabetes mice. Here, we aimed to investigate the therapeutic effect of FGF21 in salt-sensitive hypertension-induced nephropathy.

METHODS

Changes of FGF21 expression in deoxycorticosterone acetate (DOCA)-salt-induced hypertensive mice were detected. The influence of FGF21 knockout in mice on DOCA-salt-induced nephropathy were determined. Recombinant human FGF21 (rhFGF21) was intraperitoneally injected into DOCA-salt-induced nephropathy mice, and then the inflammatory factors, oxidative stress levels and kidney injury-related indicators were observed. In vitro, human renal tubular epithelial cells (HK-2) were challenged by palmitate acid (PA) with or without FGF21, and then changes in inflammation and oxidative stress indicators were tested.

RESULTS

We observed significant elevation in circulating levels and renal expression of FGF21 in DOCA-salt-induced hypertensive mice. We found that deletion of FGF21 in mice aggravated DOCA-salt-induced nephropathy. Supplementation with rhFGF21 reversed DOCA-salt-induced kidney injury. Mechanically, rhFGF21 induced AMPK activation in DOCA-salt-treated mice and PA-stimulated HK-2 cells, which inhibited NF-κB-regulated inflammation and Nrf2-mediated oxidative stress and thus, is important for rhFGF21 protection against DOCA-salt-induced nephropathy.

CONCLUSION

These findings indicated that rhFGF21 could be a promising pharmacological strategy for the treatment of salt-sensitive hypertension-induced nephropathy.

Effects of GLP-1RA and SGLT2i, Alone or in Combination, on Mouse Models of Type 2 Diabetes Representing Different Disease Stages

Glucagon-like peptide-1 receptor agonist (GLP-1RA) and sodium-dependent glucose transporter 2 inhibitor (SGLT2i), in addition to lowering glucose, have pleiotropic effects on the heart, kidneys, and liver. These drugs have thus come into widespread use for treating type 2 diabetes (T2DM). However, mechanistic comparisons and effects of combining these drugs have not been adequately studied. Employing diet-induced obese (DIO) mice and db/db mice as models of the early and advanced stages of T2DM, we evaluated effects of single or combined use of liraglutide (a GLP-1RA) and ipragliflozin (a SGLT2i). Treatments with liraglutide and/or ipragliflozin for 28 days improved glycemic control and reduced hepatic lipid accumulation similarly in DIO mice. In contrast, in db/db mice, despite similar favorable effects on fatty liver, liraglutide exerted no beneficial effects on glycemic control. Improved glycemic control in db/db mice treated with ipragliflozin was accompanied by increased pancreatic β-cell area and insulin content, both of which tended to rise further when ipragliflozin was combined with liraglutide. Our data suggest that liraglutide is more efficient at an earlier stage and ipragliflozin can be effective in both stages. In addition, their combined use is a potential option for treating advanced stage diabetes with fatty liver disease.

Treatment of type 2 diabetes: challenges, hopes, and anticipated successes

Despite the successful development of new therapies for the treatment of type 2 diabetes, such as glucagon-like peptide-1 (GLP-1) receptor agonists and sodium-glucose cotransporter-2 inhibitors, the search for novel treatment options that can provide better glycaemic control and at reduce complications is a continuous effort. The present Review aims to present an overview of novel targets and mechanisms and focuses on glucose-lowering effects guiding this search and developments. We discuss not only novel developments of insulin therapy (eg, so-called smart insulin preparation with a glucose-dependent mode of action), but also a group of drug classes for which extensive research efforts have not been rewarded with obvious clinical impact. We discuss the potential clinical use of the salutary adipokine adiponectin and the hepatokine fibroblast growth factor (FGF) 21, among others. A GLP-1 peptide receptor agonist (semaglutide) is now available for oral absorption, and small molecules activating GLP-1 receptors appear on the horizon. Bariatric surgery and its accompanying changes in the gut hormonal milieu offer a background for unimolecular peptides interacting with two or more receptors (for GLP-1, glucose-dependent insulinotropic polypeptide, glucagon, and peptide YY) and provide more substantial glycaemic control and bodyweight reduction compared with selective GLP-1 receptor agonists. These and additional approaches will help expand the toolbox of effective medications needed for optimising the treatment of well delineated subgroups of type 2 diabetes or help develop personalised approaches for glucose-lowering drugs based on individual characteristics of our patients.

Converging Relationships of Obesity and Hyperuricemia with Special Reference to Metabolic Disorders and Plausible Therapeutic Implications

BACKGROUND

Obesity and hyperuricemia mutually influence metabolic syndrome. This study discusses the metabolic relationships between obesity and hyperuricemia in terms of pathophysiology, complications, and treatments.

METHODS

We searched for preclinical or clinical studies on the pathophysiology, complications, and therapy of obesity and hyperuricemia on the PubMed database.

RESULTS

In this systemic review, we summarized our searching results on topics of pathophysiology, complications and therapeutic strategy. In pathophysiology, we firstly introduce genetic variations for obesity, hyperuricemia and their relationships by genetic studies. Secondly, we talk about the epigenetic influences on obesity and hyperuricemia. Thirdly, we describe the central metabolic regulation and the role of hyperuricemia. Then, we refer to the character of adipose tissue inflammation and oxidative stress in the obesity and hyperuricemia. In the last part of this topic, we reviewed the critical links of gut microbiota in the obesity and hyperuricemia. In the following part, we review the pathophysiology of major complications in obesity and hyperuricemia including insulin resistance and type 2 diabetes mellitus, chronic kidney disease, cardiovascular diseases, and cancers. Finally, we recapitulate the therapeutic strategies especially the novel pharmaceutic interventions for obesity and hyperuricemia, which concurrently show the mutual metabolic influences between two diseases.

CONCLUSION

The data reviewed here delineate the metabolic relationships between obesity and hyperuricemia, and provide a comprehensive overview of the therapeutic targets for the management of metabolic syndromes.

Translational Pharmacology and Physiology of Brown Adipose Tissue in Human Disease and Treatment

Human brown adipose tissue (BAT) is experimentally modeled to better understand the biology of this important metabolic tissue, and also to enable the potential discovery and development of novel therapeutics for obesity and sequelae resulting from the persistent positive energy balance. This chapter focuses on translation into humans of findings and hypotheses generated in nonhuman models of BAT pharmacology. Given the demonstrated challenges of sustainably reducing caloric intake in modern humans, potential solutions to obesity likely lie in increasing energy expenditure. The energy-transforming activities of a single cell in any given tissue can be conceptualized as a flow of chemical energy from energy-rich substrate molecules into energy-expending, endergonic biological work processes through oxidative degradation of organic molecules ingested as nutrients. Despite the relatively tight coupling between metabolic reactions and products, some expended energy is incidentally lost as heat, and in this manner a significant fraction of the energy originally captured from the environment nonproductively transforms into heat rather than into biological work. In human and other mammalian cells, some processes are even completely uncoupled, and therefore purely energy consuming. These molecular and cellular actions sum up at the physiological level to adaptive thermogenesis, the endogenous physiology in which energy is nonproductively released as heat through uncoupling of mitochondria in brown fat and potentially skeletal muscle. Adaptive thermogenesis in mammals occurs in three forms, mostly in skeletal muscle and brown fat: shivering thermogenesis in skeletal muscle, non-shivering thermogenesis in brown fat, and diet-induced thermogenesis in brown fat. At the cellular level, the greatest energy transformations in humans and other eukaryotes occur in the mitochondria, where creating energetic inefficiency by uncoupling the conversion of energy-rich substrate molecules into ATP usable by all three major forms of biological work occurs by two primary means. Basal uncoupling occurs as a passive, general, nonspecific leak down the proton concentration gradient across the membrane in all mitochondria in the human body, a gradient driving a key step in ATP synthesis. Inducible uncoupling, which is the active conduction of protons across gradients through processes catalyzed by proteins, occurs only in select cell types including BAT. Experiments in rodents revealed UCP1 as the primary mammalian molecule accounting for the regulated, inducible uncoupling of BAT, and responsive to both cold and pharmacological stimulation. Cold stimulation of BAT has convincingly translated into humans, and older clinical observations with nonselective 2,4-DNP validate that human BAT's participation in pharmacologically mediated, though nonselective, mitochondrial membrane decoupling can provide increased energy expenditure and corresponding body weight loss. In recent times, however, neither beta-adrenergic antagonism nor unselective sympathomimetic agonism by ephedrine and sibutramine provide convincing evidence that more BAT-selective mechanisms can impact energy balance and subsequently body weight. Although BAT activity correlates with leanness, hypothesis-driven selective β3-adrenergic agonism to activate BAT in humans has only provided robust proof of pharmacologic activation of β-adrenergic receptor signaling, limited proof of the mechanism of increased adaptive thermogenesis, and no convincing evidence that body weight loss through negative energy balance upon BAT activation can be accomplished outside of rodents. None of the five demonstrably β3 selective molecules with sufficient clinical experience to merit review provided significant weight loss in clinical trials (BRL 26830A, TAK 677, L-796568, CL 316,243, and BRL 35135). Broader conclusions regarding the human BAT therapeutic hypothesis are limited by the absence of data from most studies demonstrating specific activation of BAT thermogenesis in most studies. Additionally, more limited data sets with older or less selective β3 agonists also did not provide strong evidence of body weight effects. Encouragingly, β3-adrenergic agonists, catechins, capsinoids, and nutritional extracts, even without robust negative energy balance outcomes, all demonstrated increased total energy expenditure that in some cases could be associated with concomitant activation of BAT, though the absence of body weight loss indicates that in no cases did the magnitude of negative energy balance reach sufficient levels. Glucocorticoid receptor agonists, PPARg agonists, and thyroid hormone receptor agonists all possess defined molecular and cellular pharmacology that preclinical models predicted to be efficacious for negative energy balance and body weight loss, yet their effects on human BAT thermogenesis upon translation were inconsistent with predictions and disappointing. A few new mechanisms are nearing the stage of clinical trials and may yet provide a more quantitatively robust translation from preclinical to human experience with BAT. In conclusion, translation into humans has been demonstrated with BAT molecular pharmacology and cell biology, as well as with physiological response to cold. However, despite pharmacologically mediated, statistically significant elevation in total energy expenditure, translation into biologically meaningful negative energy balance was not achieved, as indicated by the absence of measurable loss of body weight over the duration of a clinical study.

FGF21 ameliorates nonalcoholic fatty liver disease by inducing autophagy

The aim of this study is to evaluate the role of fibroblast growth factor 21 (FGF21) in nonalcoholic fatty liver disease (NAFLD) and seek to determine if its therapeutic effect is through induction of autophagy. In this research, Monosodium L-glutamate (MSG)-induced obese mice or normal lean mice were treated with vehicle, Fenofibrate, and recombinant murine FGF21, respectively. After 5 weeks of treatment, metabolic parameters including body weight, blood glucose and lipid levels, hepatic and fat gene expression levels were monitored and analyzed. Also, fat-loaded HepG2 cells were treated with vehicle or recombinant murine FGF21. The expression levels of proteins associated with autophagy were detected by western blot, real-time PCR, and transmission electron microscopy (TEM). Autophagic flux was monitored by laser confocal microscopy and western blot. Results showed that FGF21 significantly reduced body weight (P < 0.01) and serum triglyceride, improved insulin sensitivity, and reversed hepatic steatosis in the MSG model mice. In addition, FGF21 significantly increased the expression of several proteins related to autophagy both in MSG mice and fat-loaded HepG2 cells, such as microtubule associated protein 1 light chain 3, Bcl-2-interacting myosin-like coiled-coil protein-1 (Beclin-1), and autophagy-related gene 5. Furthermore, the evidence of TEM revealed an increased number of autophagosomes and lysosomes in the model cells treated with FGF21. In vitro experimental results also showed that FGF21 remarkably increased autophagic flux. Taken together, FGF21 corrects multiple metabolic parameters on NAFLD in vitro and in vivo by inducing autophagy.

Modulation of energy balance by fibroblast growth factor 21

Fibroblast growth factors (FGFs) are a superfamily of 22 proteins related to cell proliferation and tissue repair after injury. A subgroup of three proteins, FGF19, FGF21, and FGF23, are major endocrine mediators. These three FGFs have low affinity to heparin sulfate during receptor binding; in contrast they have a strong interaction with the cofactor Klotho/β-Klotho. FGF21 has received particular attention because of its key role in carbohydrate, lipids, and energy balance regulation. FGF21 improves glucose and lipids metabolism as well as increasing energy expenditure in animal models and humans. Conditions that induce human physical stress such as exercise, lactation, obesity, insulin resistance, and type 2 diabetes influence FGF21 circulating levels. FGF21 also has an anti-oxidant function in human metabolic diseases which contribute to understanding the FGF21 compensatory increment in obesity, the metabolic syndrome, and type 2 diabetes. Interestingly, energy expenditure and weight loss is induced by FGF21. The mechanism involved is through "browning" of white adipose tissue, increasing brown adipose tissue activity and heat production. Therefore, clinical evaluation of therapeutic action of exogenous FGF21 administration is warranted, particularly to treat diabetes and obesity.

Pilot-scale production and characterization of PEGylated human FGF-21 analog

FGF-21 has become a potential drug candidate for the treatment of type 2 diabetes. Previous studies have demonstrated that PEGylation of FGF-21 could significantly increase its in vivo half-life and provide its long-lasting blood glucose-lowering effect. To accelerate the development of PEGylated FGF-21 for clinical application as a long-acting antidiabetes drug, we prepared ahmFGF-21 (FGF-21 mutant) and PEGylated ahmFGF-21 in Escherichia coli Rosetta (DE3) by high cell density fermentation at a 50-L scale and pilot-scale purification. The physical and chemical properties of the purified proteins were analyzed in this study, including purity, molecular weight, isoelectric point, bacterial endotoxin, PEGylated site and second structure. As well as the in vitro glucose uptake activity and in vivo anti-diabetic effect were evaluated. Under the optimal fermentation and purification conditions, the average bacterial yield and expression level of target protein of three batches attained 52.2±4.6g/L and 223.92±5.41mg/L, respectively. The purity of pilot product was above 98% by SDS-PAGE (non-reducing or reducing) and HPLC (SEC or RPC) analysis and the final yield of PEGylated ahmFGF-21 was 87.91±1.49mg/L, which indicated that the pilot-scale production process was relatively stable. N-terminal sequencing and circular dichroism (CD) spectroscopy results showed that modification site of PEGylated ahmFGF-21 was alanine at N-terminal and the second structure of ahmFGF-21 had no obvious changes after PEGylation. Compared with ahmFGF-21, the long-acting hypoglycemic effect of PEGylated ahmFGF-21 prepared in the pilot-scale production was significantly improved in type 2 diabetic db/db mice. Our results demonstrated that the pilot-scale production process of PEGylated ahmFGF-21 was successfully established, which was very important for the clinical application.

Long-lasting hypoglycemic effect of modified FGF-21 analog with polyethylene glycol in type 1 diabetic mice and its systematic toxicity

Fibroblast growth factor-21 (FGF-21) is a novel metabolic regulator and has the potential to become a powerful therapy to treat diabetes mellitus. However, we found that the clinical application of wild type FGF-21 was influenced by its low intrinsic bio-stability and poor hypoglycemic potency. In this study, The N-terminus of FGF-21 analog (mFGF-21) was PEGylated in a site-specific manner by 20kD methoxy poly-ethylene glycol-propionaldehyde (mPEG-ALD). PEGylated mFGF-21 was isolated by Capto Q anion exchange chromatography. The properties of PEGylated mFGF-21 including the in vitro bio-stability and biological activity were evaluated. As well as the anti-diabetic effect of PEGylated mFGF-21 were studied in streptozotocin (STZ)-induced type 1 diabetic mice. Results demonstrated that PEGylated mFGF-21 had a similar capacity of stimulating glucose uptake in HepG2 cells with mFGF-21 and PEGylation of mFGF-21 significantly enhanced the anti-protease ability and the long acting anti-diabetic effect in type 1 diabetic mice. Furthermore, the preliminary safety of PEGylated mFGF-21 following subcutaneously injection was assessed using healthy mice by measuring the body weight, histopathology and clinical biochemical parameters, and the results showed no subacute toxicity to major organs or tissues and no significant changes in physiological and biochemical parameters in healthy mice. Taken together, under the premise of remaining the in vitro biological activity of mFGF-21, PEGylation significantly improves the long lasting hypoglycemic effect of mFGF-21 in type 1 diabetic mice. Our valuation shows that PEGylated mFGF-21 is a potential drug for the effective treatment of type 1 diabetes.

Non-alcoholic steatohepatitis: emerging molecular targets and therapeutic strategies

Non-alcoholic fatty liver disease - the most common chronic liver disease - encompasses a histological spectrum ranging from simple steatosis to non-alcoholic steatohepatitis (NASH). Over the next decade, NASH is projected to be the most common indication for liver transplantation. The absence of an effective pharmacological therapy for NASH is a major incentive for research into novel therapeutic approaches for this condition. The current focus areas for research include the modulation of nuclear transcription factors; agents that target lipotoxicity and oxidative stress; and the modulation of cellular energy homeostasis, metabolism and the inflammatory response. Strategies to enhance resolution of inflammation and fibrosis also show promise to reverse the advanced stages of liver disease.

Fibroblast growth factor-21, energy balance and obesity

Fibroblast growth factor (FGF)-21 is an endocrine member of the FGF family with healthy effects on glucose and lipid metabolism. FGF21 reduces glycemia and lipidemia in rodent models of obesity and type 2 diabetes. In addition to its effects improving insulin sensitivity, FGF21 causes weight loss by increasing energy expenditure. Activation of the thermogenic activity of brown adipose tissue and promotion of the appearance of the so-called beige/brite type of brown adipocytes in white fat are considered the main mechanisms underlying the leaning effects of FGF21. Paradoxically, however, obesity in rodents and humans is characterized by high levels of FGF21 in the blood. Some degree of resistance to the actions of FGF21 has been proposed as part of the endocrine alterations in obesity. The resistance in adipose tissue from obese rodents and patients is likely attributable to abnormally low levels of the FGF co-receptor β-Klotho, required for FGF21 cellular action. However, native FGF21 and FGF21 derivatives retain their healthy metabolic and weight-loss effects when used as pharmacological agents to treat obese rodents and humans. FGF21 derivatives or molecules mimicking FGF21 action appear to be interesting candidates for the development of novel anti-obesity drugs designed to increase energy expenditure.