The nutritional environment to which animals are exposed in early life can lead to epigenetic changes in the genome that influence the risk of obesity in later life. Here, we demonstrate that the fibroblast growth factor-21 gene (Fgf21) is subject to peroxisome proliferator-activated receptor (PPAR) α–dependent DNA demethylation in the liver during the postnatal period. Reductions in Fgf21 methylation can be enhanced via pharmacologic activation of PPARα during the suckling period. We also reveal that the DNA methylation status of Fgf21, once established in early life, is relatively stable and persists into adulthood. Reduced DNA methylation is associated with enhanced induction of hepatic FGF21 expression after PPARα activation, which may partly explain the attenuation of diet-induced obesity in adulthood. We propose that Fgf21 methylation represents a form of epigenetic memory that persists into adulthood, and it may have a role in the developmental programming of obesity.

The metabolic function of the liver changes sequentially during early life in mammals to adapt to the marked changes in nutritional environment. Accordingly, hepatic fatty acid b-oxidation is activated after birth to produce energy from breast milk lipids. However, how it is induced during the neonatal period is poorly understood. Here we show DNA demethylation and increased mRNA expression of the fatty acid b-oxidation genes in the postnatal mouse liver. The DNA demethylation does not occur in the fetal mouse liver under the physiologic condition, suggesting that it is specific to the neonatal period. Analysis of mice deficient in the nuclear receptor peroxisome proliferator-activated receptor a (PPARa) and maternal administration of a PPARa ligand during the gestation and lactation periods reveal that the DNA demethylation is PPARa dependent. We also find that DNA methylation of the fatty acid b-oxidation genes are reduced in the adult human liver relative to the fetal liver. This study represents the first demonstration that the ligand-activated PPARa-dependent DNA demethylation regulates the hepatic fatty acid b-oxidation genes during the neonatal period, thereby highlighting the role of a lipid-sensing nuclear receptor in the gene-and lifestage-specific DNA demethylation of a particular metabolic pathway.

BackgroundSarcopenic obesity, defined as reduced skeletal muscle mass and power with increased adiposity, was reported to be associated with cardiovascular disease risks in previous cross-sectional studies. Whole body dual-energy X-ray absorptiometry (DXA) can simultaneously evaluate both fat and muscle mass, therefore, whole body DXA may be suitable for the diagnosis of sarcopenic obesity. However, little is known regarding whether sarcopenic obesity determined using whole body DXA could predict incident cardiovascular disease (CVD). The aim of this study was to investigate the impact of sarcopenic obesity on incident CVD in patients with type 2 diabetes.MethodsA total of 716 Japanese patients (mean age 65 ± 13 years; 47.0% female) were enrolled. Android fat mass (kg), gynoid fat mass (kg), and skeletal muscle index (SMI) calculated as appendicular non-fat mass (kg) divided by height squared (m2), were measured using whole body DXA. Sarcopenic obesity was defined as the coexistence of low SMI and obesity determined by four patterns of obesity as follows: android to gynoid ratio (A/G ratio), android fat mass or percentage of body fat (%BF) was higher than the sex-specific median, or body mass index (BMI) was equal to or greater than 25 kg/m2. The study endpoint was the first occurrence or recurrence of CVD.ResultsOver a median follow up of 2.6 years (IQR 2.1–3.2 years), 53 patients reached the endpoint. Sarcopenic obesity was significantly associated with incident CVD even after adjustment for the confounding variables, when using A/G ratio [hazard ratio (HR) 2.63, 95% CI 1.10–6.28, p = 0.030] and android fat mass (HR 2.57, 95% CI 1.01–6.54, p = 0.048) to define obesity, but not %BF (HR 1.67, 95% CI 0.69–4.02, p = 0.252), and BMI (HR 1.55, 95% CI 0.44–5.49, p = 0.496).ConclusionsThe present data suggest that the whole body DXA is valuable in the diagnosis of sarcopenic obesity (high A/G ratio or android fat mass with low SMI) to determine the risk of CVD events in patients with type 2 diabetes. Meanwhile, sarcopenic obesity classified with low SMI, and high %BF or BMI was not associated with incident CVD.Electronic supplementary materialThe online version of this article (10.1186/s12933-018-0700-5) contains supplementary material, which is available to authorized users.

Recently, we reported ppARα-dependent DNA demethylation of the Fgf21 promoter in the postnatal mouse liver, where reduced DnA methylation is associated with enhanced gene expression after ppARα activation. However, there is no direct evidence for the effect of site-specific DNA methylation on gene expression. We employed the dCas9-SunTag and single-chain variable fragment (scFv)-TET1 catalytic domain (TET1CD) system to induce targeted DnA methylation of the Fgf21 promoter both in vitro and in vivo. We succeeded in targeted DnA demethylation of the Fgf 21 promoter both in Hepa1-6 cells and PPARα-deficient mice, with increased gene expression response to ppARα synthetic ligand administration and fasting, respectively. this study provides direct evidence that the DnA methylation status of a particular gene may determine the magnitude of the gene expression response to activation cues. In mammalian cells, DNA methylation is a major epigenetic modification, which regulates gene expression without alteration of the DNA sequence and thus plays a pivotal role in a myriad of physiological and pathological processes, including cell development and differentiation, genome imprinting, and tumorigenesis 1. We reported previously that the DNA methylation status of hepatic metabolic genes dynamically changes in early life, especially during the suckling period, thereby sequentially developing metabolic function in the liver to adapt to the drastic changes in the major nutrition source 2-4. Peroxisome proliferator-activated receptor-α (PPARα) is a nuclear receptor and a key regulator of hepatic lipid metabolism, which is activated by milk lipids as ligands at the onset of lactation. PPARα governs the transcription of major hepatic metabolism-related genes, and the activation of PPARα physiologically leads to DNA demethylation of fatty acid β-oxidation genes in the postnatal mouse liver 3,4. Of note, administration of a synthetic PPARα ligand to mouse dams during the perinatal period induced enhanced reduction of DNA methylation of PPARα target genes in the offspring liver, suggesting that the DNA methylation status of PPARα target genes can be modulated with ease during the perinatal period 3,4. A genome-wide analysis of DNA methylation revealed that a few PPARα target genes undergo ligand-activated, PPARα-dependent DNA demethylation during the perinatal period, and the DNA hypomethylation status of these persists into adulthood. Among these genes, which may be referred to as "epigenetic memory genes," we focused on fibroblast growth factor 21 (FGF21), which is a metabolic hormone derived from the liver and a master regulator of glucose and lipid metabolism 5-7 .

Aim To evaluate the association between sarcopenic obesity and the decline in estimated GFR in people with type 2 diabetes. Methods We enrolled 745 people with type 2 diabetes (mean age 64.6 years, 53.6% men). Body composition was evaluated using dual‐energy X‑ray absorptiometry. Skeletal muscle index, calculated as appendicular non‐fat mass (kg) divided by height squared (m2), was used to determine sarcopenia. Sarcopenic obesity was defined as the coexistence of sarcopenia and a ratio of android to gynoid fat mass greater than the median values in each gender. The association of sarcopenic obesity both with the annual rate of decline in estimated GFR and a >30% decline in estimated GFR was evaluated using multivariate linear regression models and Cox proportional hazard models, respectively. Results Participants with sarcopenic obesity were at an increased risk of a high annual rate of decline in estimated GFR, even after adjustment for the confounding variables (standardized β = −0.228, P <0.001). Sarcopenic obesity was also significantly associated with risk of a >30% decline in estimated GFR (hazard ratio 4.52, 95% CI 2.16–9.47; P < 0.01) in multivariate model. Conclusions Sarcopenic obesity evaluated by dual energy X‑ray absorptiometry is associated with a faster decline in renal function in people with type 2 diabetes.