Abstract Background Parvovirus B19 (B19V) is the most common type of virus found in endomyocardial biopsies (EMB) from patients with inflammatory heart disease. However, the detection of genomic B19V-DNA appears to have little clinical significance and is often considered an incidental finding. Recent analyses of a large cohort of B19V-positive patients revealed that the detection of RNA transcripts rather than DNA is of clinical importance, as B19V-RNA-positive patients have a significantly worse cardiovascular outcome. Here, we applied machine learning (ML) methods to assess the impact of B19V transcriptional activity on cardiac inflammation and patient clinical outcome. Methods and results A total of 305 patients with a known clinical course and a positive endomyocardial B19V-DNA test were included in this study. Follow-up measurements of the B19V-specific transcripts VP1/2 and NS1 revealed significantly worse clinical courses than in patients without B19V-RNA detection (P=0.019, hazard ratio (95% CI)=1.62 (1.10-2.57)). LVEF at follow-up was significantly lower in patients with detected B19V-RNA (P=0.007), and adverse events such as worsening LV function (P=0.003) or stable systolic dysfunction (P=0.013) were more frequent in this group. Importantly, analysis of inflammatory markers in EMB showed no difference in patients with and without RNA detection (P=0.432), suggesting that the deterioration in clinical outcome was related to B19V transcriptional activity rather than an increase in inflammation. The analysis of area under the receiver operating characteristic curve (AUROC) of B19V-RNA-negative patients revealed that the macrophage marker MAC-1 (AUROC=0.66, P=0.002) was the single most prognostically relevant parameter, while the T cell marker CD3 (AUROC=0.73, P<0.001) was identified as the most prognostically relevant marker in B19V-RNA-positive patients. The linear combination of several inflammatory markers increased the AUROC value to 0.67 in B19V-RNA-negative patients and to 0.74 in B19V-RNA-positive patients. To further increase prognostic accuracy, we trained ML models on features derived from EMB inflammatory markers. For the prediction of major adverse cardiac events within 60 months, the best ML-models achieved an AUROC of 0.87 in B19V-RNA-positive and of 0.86 in B19V-RNA-negative patients, while models that neglect the differentiation of patients with regard to the presence of B19V RNA transcripts only achieved an AUROC of up to 0.76. Conclusions These results show that B19V transcriptional activity is an independent risk marker for adverse cardiac events in patients with viral cardiomyopathy and thus confirm the clinical-therapeutic importance of myocardial biopsy. Furthermore, we present an ML-based algorithm that accurately indicates disease progression in B19V-positive cardiomyopathy patients and is thus helpful for appropriate therapy recommendation.

Abstract Background Viral infection of the heart muscle is a common cause of myocarditis and viral persistence can lead to chronic inflammatory cardiomyopathies (DCMi). A number of viruses including parvovirus B19 (B19V), adenovirus (AdV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), herpes virus 6 (HHV-6) and enteroviruses (EV) are known to infect the myocardium, but their prevalence and role in persisting DCMi are not well understood. Virological etiologies can only be determined via endomyocardial biopsy (EMB), but the low tissue amount limits the number of conventional viral nucleic acid tests (virus-specific PCR) that can be performed in parallel. This study aimed to detect known and novel cardiotropic viruses in EMB of DCMi patients using a targeted next generation sequencing (NGS) approach. Methods A cohort of 33 patients with inflammatory cardiomyopathy (DCMi) (LVEF=29±12%) were retrospectively analyzed and compared to previous results of virus-specific PCR. DNA and RNA extracted from EMB were used for sequencing library preparation, and viral nucleic acids were enriched via a custom myBaits hybridization capture approach. Enriched libraries were sequenced on an Illumina MiSeq-platform in paired-end mode (500.000 reads/sample), and reads were taxonomically classified via Kraken2 and mapped against viral reference genomes using BWA-MEM2 or HiSat2, and subsequently deduplicated. Viral reads detected via both Kraken2 and mapping were classified as valid. Results Targeted NGS confirmed 19 out of 22 (86%) of the previous PCR-based viral detections. However, NGS was able to detect B19V DNA and RNA in an additional 11 and 15 patient samples respectively; CMV DNA/RNA in additional 5 and 4 samples respectively; EBV DNA/RNA in additional 5 and 1 samples respectively; and HHV-6 DNA/RNA in additional 3 and 1 samples respectively. Furthermore, viral reads of adenovirus type 2, adenovirus-associated virus type 2 (AAV-2), herpes viruses 7 and 8, and human parvovirus 4 were also found among the cohort. Thus, targeted NGS was able to identify 82 viral infections in a cohort of 33 DCMi patients, while only 22 were found using routine PCR tests. For routinely tested B19V, the use of the new NGS diagnostic approach improved sensitivity by 42% and specificity by 72%. Conclusions The presented NGS method represents a powerful new tool for the diagnosis of viral and inflammatory heart disease. The sensitivity is significantly higher than with conventional PCR approaches and the taxonomic classification is more specific. This enables the detection of previously false-negative routine viruses as well as potentially new cardiotropic pathogens from limited bioptic patient material – thus significantly increasing the diagnostic yield of EMB. In addition, our study demonstrates a high prevalence of non-enteroviral cardiotropic viruses in DCMi patients, shedding new light on the etiology of this heterogenous diseases and paving the way for more specific future treatments.

Abstract Background Endomyocardial biopsy (EMB) is an important diagnostic tool for evaluating various cardiac diseases such as myocarditis and storage disorders as well as for the monitoring heart transplant patients. Despite advances in non-invasive imaging techniques to characterize myocardial tissue, EMB remains the gold standard for definitive diagnosis and initiation of specific therapy. Here we report EMB laboratory results from over 8,000 patients and demonstrate the diagnostic utility of EMB. Methods and results We retrospectively reviewed EMB analyses performed at our institution. EMBs for monitoring graft rejection were not included in this study. Clinical data, suspected clinical diagnoses and EMB-based laboratory results were collected. Histopathological, immunohistochemical and molecular biology biopsy findings were recorded and reviewed for degree of concordance with clinical diagnosis. In total, EMBs from N=8,085 consecutive patients with unexplained heart failure were analyzed. The comprehensive EMB analysis revealed that N=616 (7.6%) patients had cardiac storage disease, most of whom had cardiac amyloidosis (N=606). N=357 (4.4%) patients were diagnosed with acute forms of myocarditis, including N=95 cases with active myocarditis, N=148 cases with giant cell myocarditis, N=95 cases with sarcoidosis and N=19 cases with eosinophilic myocarditis. A total of N=3,392 (42%) patients were found to have inflammatory heart disease such as inflammatory cardiomyopathy and borderline myocarditis, whereby a differentiation of the inflammatory infiltrates revealed considerable differences in the quality of inflammation. Viral genomes were found in the myocardium of N=6,072 (75%) patients, with treatment-relevant viral infections detected in N=2,015 (25%) cases. The remaining N=1,705 (21%) patients were diagnosed with other cardiomyopathies, including dilated cardiomyopathy (N=1,252), heart failure with preserved ejection fraction (N=325), hypertrophic cardiomyopathy (N=117) and arrhythmogenic right ventricular cardiomyopathy (N=11). Conclusions This retrospective study of over 8,000 patients with heart failure clearly shows that a definitive diagnosis is only possible with a comprehensive EMB diagnosis and leads to specific therapy in 79% of the cases. In the remaining 21% of patients, infectious and inflammatory causes could be excluded in order to initiate standard heart failure therapy. It is important to emphasize here that the quality of the inflammation and therapy-relevant viral infections cannot be detected with imaging techniques, which underlines the clinical-therapeutic importance of endomyocardial biopsy.

Abstract Introduction Dilated cardiomyopathy (DCM) characterized by left ventricular dilation and impaired left ventricular function represents a common and severe cause of heart failure (HF). Predominantly affecting younger patients, it is considered a leading cause for sudden cardiac death and heart transplantation. Several studies identified myocarditis as a substantive precursor and potential cause of DCM. Inflammatory cardiomyopathy (DCMi) can lead to cardiomyocytal damage and exposure of cardiac myosin and other heart proteins. This cascade can in susceptible individuals trigger an altered immune response consecutively leading to autoimmunity and chronic inflammation. A variety of inflammatory and immunologic agents are discussed to be involved in the pathophysiology of myocardial inflammation. Several studies suggested a role of Interleukin -17 (IL-17) and Interferon-γ (IFN-γ) in chronic HF, myocardial infarction and other cardiovascular diseases. Underlying pathomechanisms, however, are poorly understood. Methods In this study we measured IL-17 and IFN-γ levels in serum by ELISA in patients in which an endomyocardial biopsy (EMB) was performed due to chronic unexplained heart failure symptoms after exclusion of ischemic or valvular heart disease at our center. All patients underwent transthoracic echocardiography prior to EMB sampling. Patients were classified according to the histological presence of inflammation into DCMi, DCM and patients with preserved left ventricular ejection fraction (LVEF) without inflammation. EMB specimens were analyzed including histology, immunohistochemistry and molecular virology. Results A total of 289 patients were included into the final analysis. Mean age was 47 years and 71% were male. Mean LVEF was 50% and mean left ventricular end-diastolic diameter (LVEDD) was 57 mm. Based on EMB results, 71 (25%) samples were categorized as DCMi and 113 (39%) as DCM. 105 (36%) samples were assigned to the group without myocardial inflammation and normal LVEF. The groups differed significantly in their inflammatory profiles. Levels of IL-17 (p < 0.001) and IFN-γ (p < 0.01) were significantly higher in patients with DCMi compared to the DCM as well as the normal LVEF group (Figure 1, Figure 2). Therefore, this effect is not specific for heart failure, but seems to be an important mediator in inflammatory cardiomyopathy. Conclusion Our data showed a significant elevation of IL-17 and IFN-γ in patients with inflammatory dilated cardiomyopathy. These findings suggest that these agents play an important role in the disease entity development and progression that remains poorly understood. So far treatment strategies in DCMi are unspecific. Therefore, blocking IL-17 expression could be an interesting potential therapeutic target in future (personalized) treatment for a wide group of patients with heart failure generated by inflammatory causes.Serum IL-17 levels.t-SNE analysis of the different groups.

Objective Dysregulation of skeletal muscle (SM) metabolism and insulin resistance are key defects of type 2 diabetes. Since dietary restriction and exercise are promising strategies to improve muscle insulin sensitivity, we aimed to uncover the underlying transcriptional signatures.

Abstract Background/Introduction Preclinical data indicate that plasminogen activator inhibitor-1 (PAI-1) is cardioprotective by repressing cardiac fibrosis through TGF-β and plasminogen mediated pathways. In addition it is linked to the recruitment and polarization of non-classical M2 macrophages in cancer. Purpose The role of cardiac PAI-1 in fibrogenesis and macrophage polarization is investigated in patients with dilated cardiomyopathy (DCM) and inflammatory dilated cardiomyopathy (DCMi). Methods We retrospectively analyzed endomyocardial biopsies (EMBs) of patients with DCM (n=27) and DCMi (n=149) for PAI-1 expression, number of activated myofibroblasts and M1/M2 macrophage polarization. Results Patients with high-grade DCMi (DCMi-high, CD3+ lymphocytes >30 cells/mm2) had significantly increased PAI-1 levels compared to DCM and low grade DCMi patients (DCMi-low, CD3+ lymphocytes = 14 - 30 cells/mm2) (15.5±0.4% vs. 1.0±0.1% and 4.0±0.1%, p≤0.001). Elevated PAI-1 expression in DCMi-high subjects was accompanied by a reduced number of alpha smooth muscle actin (α-SMA) positive myofibroblasts and an increased number of CD16+ CD68+ M2 macrophages, indicating anti-fibrogenic and M2 macrophage-favoring properties of PAI-1 in DCMi. Conclusion Our findings give evidence that elevated expression of PAI-1 suppresses cardiac fibrosis and promotes M2 macrophage polarization. Thus, PAI-1 could serve as a potential prognostic biomarker of cardiac fibrosis and inflammation, as well as possible therapeutic target in inflammatory cardiomyopathies. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): ERA-Net on Cardiovascular Diseases (ERA-CVD) of the German Research Foundation (DFG)Transregional Collaborative Research Center “Inflammatory Cardiomyopathy-Molecular Pathogenesis and Therapy”

In enterocytes, protein RS1 (RSC1A1) mediates an increase of glucose absorption after ingestion of glucose-rich food via upregulation of Na+-d-glucose cotransporter SGLT1 in the brush-border membrane (BBM). Whereas RS1 decelerates the exocytotic pathway of vesicles containing SGLT1 at low glucose levels between meals, RS1-mediated deceleration is relieved after ingestion of glucose-rich food. Regulation of SGLT1 is mediated by RS1 domain RS1-Reg, in which Gln-Ser-Pro (QSP) is effective. In contrast to QSP and RS1-Reg, Gln-Glu-Pro (QEP) and RS1-Reg with a serine to glutamate exchange in the QSP motif downregulate the abundance of SGLT1 in the BBM at high intracellular glucose concentrations by about 50%. We investigated whether oral application of QEP improves diabetes in db/db mice and affects the induction of diabetes in New Zealand obese (NZO) mice under glucolipotoxic conditions. After 6-day administration of drinking water containing 5 mM QEP to db/db mice, fasting glucose was decreased, increase of blood glucose in the oral glucose tolerance test was blunted, and insulin sensitivity was increased. When QEP was added for several days to a high fat/high carbohydrate diet that induced diabetes in NZO mice, the increase of random plasma glucose was prevented, accompanied by lower plasma insulin levels. QEP is considered a lead compound for development of new antidiabetic drugs with more rapid cellular uptake. In contrast to SGLT1 inhibitors, QEP-based drugs may be applied in combination with insulin for the treatment of type 1 and type 2 diabetes, decreasing the required insulin amount, and thereby may reduce the risk of hypoglycemia.

Objective: Ectopic fat accumulation in the pancreas in response to obesity and its implication on the onset of type 2 diabetes remain poorly understood. Intermittent fasting (IF) is known to improve glucose homeostasis and insulin resistance. However, the effects of IF on fat in the pancreas and beta-cell function remain largely unknown. Our aim was to evaluate the impact of IF on pancreatic fat accumulation and its effects on islet function. Methods: New Zealand Obese (NZO) mice were fed a high-fat diet ad libitum (NZO-AL) or fasted every other day (intermittent fasting, NZO-IF) and pancreatic fat accumulation, glucose homoeostasis, insulin sensitivity, and islet function were determined and compared to ad libitum-fed B6.V-Lep(ob/ob) (ob/ob) mice. To investigate the crosstalk of pancreatic adipocytes and islets, co-culture experiments were performed. Results: NZO-IF mice displayed better glucose homeostasis and lower fat accumulation in both the pancreas (-32%) and the liver (-35%) than NZO-AL mice. Ob/ob animals were insulin-resistant and had low fat in the pancreas but high fat in the liver. NZO-AL mice showed increased fat accumulation in both organs and exhibited an impaired islet function. Co-culture experiments demonstrated that pancreatic adipocytes induced a hypersecretion of insulin and released higher levels of free fatty adds than adipocytes of inguinal white adipose tissue. Conclusions: These results suggest that pancreatic fat participates in diabetes development, but can be prevented by IF. (C) 2019 Published by Elsevier Inc.

Obesity is associated with a dysfunctional adipose tissue and ectopic fat deposition in liver, muscle and pancreas. Under a high-fat diet (HFD), New Zealand Obese (NZO) mice develop obesity as well as type 2 diabetes (T2D), whereas obese B6.V-ob/ob (ob/ob) mice are diabetes-resistant. Intermittent fasting (IF) has been shown to lower T2D risk in mice and humans. The aim of the study was to investigate whether IF prevents pancreatic fat cell infiltration and whether pancreatic adipocytes directly affect islet function.

The transcription factor C/EBPβ regulates hematopoiesis, bone, liver, fat, and skin homeostasis, and female reproduction. C/EBPβ protein expression from its single transcript occurs by alternative in-frame translation initiation at consecutive start sites to generate three isoforms, two long (LAP*, LAP) and one truncated (LIP), with the same C-terminal bZip dimerization domain. The long C/EBPβ isoforms are considered gene activators, whereas the LIP isoform reportedly acts as a dominant-negative repressor. Here, we tested the putative repressor functions of the C/EBPβ LIP isoform in mice by comparing monoallelic WT or LIP knockin mice with Cebpb knockout mice, in combination with monoallelic Cebpa mice. The C/EBPβ LIP isoform was sufficient to function in coordination with C/EBPα in murine development, adipose tissue and sebocyte differentiation, and female fertility. Thus, the C/EBPβ LIP isoform likely has more physiological functions than its currently known role as a dominant-negative inhibitor, which are more complex than anticipated.

Obesity results from a constant and complex interplay between environmental stimuli and predisposing genes. Recently, we identified the IFN-activated gene Ifi202b as the most likely gene responsible for the obesity quantitative trait locus Nob3 (New Zealand Obese [NZO] obesity 3). The aim of this study was to evaluate the effects of Ifi202b on body weight and adipose tissue biology, and to clarify the functional role of its human orthologue IFI16.

Dipeptidyl peptidase 4 (DPP4) is known to be elevated in metabolic disturbances such as obesity, type 2 diabetes and fatty liver disease. Lowering DPP4 concentration by pharmacological inhibition improves glucose homeostasis and exhibits beneficial effects to reduce hepatic fat content. As factors regulating the endogenous expression of Dpp4 are unknown, the aim of this study was to examine whether the Dpp4 expression is epigenetically regulated in response to dietary components. Primary hepatocytes were treated with different macronutrients, and Dpp4 mRNA levels and DPP4 activity were evaluated. Moreover, dietary low-protein intervention was conducted in New Zealand obese (NZO) mice, and subsequently, effects on Dpp4 expression, methylation as well as plasma concentration and activity were determined. Our results indicate that Dpp4 mRNA expression is mediated by DNA methylation in several tissues. We therefore consider the Dpp4 southern shore as tissue differentially methylated region. Amino acids increased Dpp4 expression in primary hepatocytes, whereas glucose and fatty acids were without effect. Dietary protein restriction in NZO mice increased Dpp4 DNA methylation in liver leading to diminished Dpp4 expression and consequently to lowered plasma DPP4 activity. We conclude that protein restriction in the adolescent and adult states is a sufficient strategy to reduce DPP4 which in turn contributes to improve glucose homeostasis.

Aims/hypothesis Low-protein diets are well known to improve glucose tolerance and increase energy expenditure. Increases in circulating fibroblast growth factor 21 (FGF21) have been implicated as a potential underlying mechanism. Methods We aimed to test whether low-protein diets in the context of a high-carbohydrate or high-fat regimen would also protect against type 2 diabetes in New Zealand Obese (NZO) mice used as a model of polygenetic obesity and type 2 diabetes. Mice were placed on high-fat diets that provided protein at control (16 kJ%; CON) or low (4 kJ%; low-protein/high-carbohydrate [LP/HC] or low-protein/high-fat [LP/HF]) levels. Results Protein restriction prevented the onset of hyperglycaemia and beta cell loss despite increased food intake and fat mass. The effect was seen only under conditions of a lower carbohydrate/fat ratio (LP/HF). When the carbohydrate/fat ratio was high (LP/HC), mice developed type 2 diabetes despite the robustly elevated hepatic FGF21 secretion and increased energy expenditure. Conclusion/interpretation Prevention of type 2 diabetes through protein restriction, without lowering food intake and body fat mass, is compromised by high dietary carbohydrates. Increased FGF21 levels and elevated energy expenditure do not protect against hyperglycaemia and type 2 diabetes per se.

In obesity, a dysfunction of adipose tissue results in ectopic fat deposition in non-adipose tissue organs such as liver, muscle but also pancreas. Following a caloric-enriched diet, New Zealand Obese (NZO) mice develop obesity and type 2 diabetes due to a β-cell loss while B6.V-ob/ob (ob/ob) obese mice are diabetes-resistant because of a massive β-cell proliferation. Intermittent fasting (IF) has been shown to have positive effects on diabetes susceptibility in human and animal, due to an improved liver metabolism in NZO mice. However, the effects of IF on fat infiltration in the pancreas, β-cell function and glucose homeostasis remain unknown.

Objective: Intracellular vesicle trafficking maintains cellular structures and functions. The assembly of cargo-laden vesicles at the trans-Golgi network is initiated by the ARF family of small GTPases. Here, we demonstrate the role of the trans-Golgi localized monomeric GTPase ARFRP1 in endosomal-mediated vesicle trafficking of mature adipocytes. Methods: Control (Arfrp1(flox/flox)) and inducible fat-specific Arfrp1 knockout (Arfrp1(iAT-/-)) mice were metabolically characterized. In vitro experiments on mature 3T3-L1 cells and primary mouse adipocytes were conducted to validate the impact of ARFRP1 on localization of adiponectin and the insulin receptor. Finally, secretion and transferrin-based uptake and recycling assays were performed with HeLa and HeLa M-C1 cells. Results: We identified the ARFRP1-based sorting machinery to be involved in vesicle trafficking relying on the endosomal compartment for cell surface delivery. Secretion of adiponectin from fat depots was selectively reduced in Arfrp1(iAT-/-) mice, and Arfrp1-depleted 3T3-L1 adipocytes revealed an accumulation of adiponectin in Rab11-positive endosomes. Plasma adiponectin deficiency of Arfrp1(iAT-/-) mice resulted in deteriorated hepatic insulin sensitivity, increased gluconeogenesis and elevated fasting blood glucose levels. Additionally, the insulin receptor, undergoing endocytic recycling after ligand binding, was less abundant at the plasma membrane of adipocytes lacking Arfrp1. This had detrimental effects on adipose insulin signaling, followed by insufficient suppression of basal lipolytic activity and impaired adipose tissue expansion. Conclusions: Our findings suggest that adiponectin secretion and insulin receptor surface targeting utilize the same post-Golgi trafficking pathways that are essential for an appropriate systemic insulin sensitivity and glucose homeostasis. (C) 2017 The Authors. Published by Elsevier GmbH.

FGF21 is considered a promising therapeutic candidate for the treatment of diabetes, but is elevated in obese and diabetic conditions, suggesting impaired FGF21 action. Therefore, we tested if obese and diabetes-susceptible NZO mice are FGF21 resistant.

Dipeptidyl peptidase 4 (DPP4) has recently been described as novel adipokine upregulated in obesity. Furthermore, patients suffering from non-alcoholic fatty liver disease exhibit elevated hepatic DPP4 expression. We analyzed the capacity of livers to release DPP4 compared with that of adipose tissue and investigated the epigenetic regulation of hepatic DPP4 expression.

Objective: Increased hepatic expression of dipeptidyl peptidase 4 (DPP4) is associated with non-alcoholic fatty liver disease (NAFLD). Whether this is causative for the development of NAFLD is not yet clarified. Here we investigate the effect of hepatic DPP4 overexpression on the development of liver steatosis in a mouse model of diet-induced obesity.Methods: Plasma DPP4 activity of subjects with or without NAFLD was analyzed. Wild-type (WT) and liver-specific Dpp4 transgenic mice (Dpp4-Liv-Tg) were fed a high-fat diet and characterized for body weight, body composition, hepatic fat content and insulin sensitivity. In vitro experiments on HepG2 cells and primary mouse hepatocytes were conducted to validate cell autonomous effects of DPP4 on lipid storage and insulin sensitivity.Results: Subjects suffering from insulin resistance and NAFLD show an increased plasma DPP4 activity when compared to healthy controls. Analysis of Dpp4-Liv-Tg mice revealed elevated systemic DPP4 activity and diminished active GLP-1 levels. They furthermore show increased body weight, fat mass, adipose tissue inflammation, hepatic steatosis, liver damage and hypercholesterolemia. These effects were accompanied by increased expression of PPAR gamma and CD36 as well as severe insulin resistance in the liver. In agreement, treatment of HepG2 cells and primary hepatocytes with physiological concentrations of DPP4 resulted in impaired insulin sensitivity independent of lipid content.Conclusions: Our results give evidence that elevated expression of DPP4 in the liver promotes NAFLD and insulin resistance. This is linked to reduced levels of active GLP-1, but also to auto- and paracrine effects of DPP4 on hepatic insulin signaling. (C) 2017 The Authors. Published by Elsevier GmbH.

By positional cloning we identified the transcriptional modulator Ifi202b as putative novel obesity gene. Ifi202b is mainly expressed in white adipose tissue of obese NZO but absent in lean B6 mice due to a loss-of-function mutation. The aim of this study was to identify downstream targets of Ifi202b and to clarify the mechanisms how it induces obesity.

Aims/hypothesis Fibroblast growth factor 21 (FGF21) is considered to be a promising therapeutic candidate for the treatment of type 2 diabetes. However, as FGF21 levels are elevated in obese and diabetic conditions we aimed to test if exogenous FGF21 is sufficient to prevent diabetes and beta cell loss in New Zealand obese (NZO) mice, a model for polygenetic obesity and type 2 diabetes. Methods Male NZO mice were treated with a specific dietary regimen that leads to the onset of diabetes within 1 week. Mice were treated subcutaneously with PBS or FGF21 to assess changes in glucose homeostasis, energy expenditure, food intake and other metabolic endpoints. Results FGF21 treatment prevented islet destruction and the onset of hyperglycaemia, and improved glucose clearance. FGF21 increased energy expenditure by inducing browning in subcutaneous white adipose tissue. However, as a result of a compensatory increased food intake, body fat did not decrease in response to FGF21 treatment, but exhibited elevated Glut4 expression. Conclusions/interpretation FGF21 prevents the onset of diet-induced diabetes, without changing body fat mass. Beneficial effects are mediated via white adipose tissue browning and elevated thermogenesis. Furthermore, these data indicate that obesity does not induce FGF21 resistance in NZO mice.