Intergenerational Inheritance of Hepatic Steatosis in a Mouse Model of Childhood Obesity: Potential Involvement of Germ-Line microRNAs.

Childhood obesity increases the risk of developing metabolic syndrome later in life. Moreover, metabolic dysfunction may be inherited into the following generation through non-genomic mechanisms, with epigenetics as a plausible candidate. The pathways involved in the development of metabolic dysfunction across generations in the context of childhood obesity remain largely unexplored. We have developed a mouse model of early adiposity by reducing litter size at birth (small litter group, SL: 4 pups/dam; control group, C: 8 pups/dam). Mice raised in small litters (SL) developed obesity, insulin resistance and hepatic steatosis with aging. Strikingly, the offspring of SL males (SL-F1) also developed hepatic steatosis. Paternal transmission of an environmentally induced phenotype strongly suggests epigenetic inheritance. We analyzed the hepatic transcriptome in C-F1 and SL-F1 mice to identify pathways involved in the development of hepatic steatosis. We found that the circadian rhythm and lipid metabolic process were the ontologies with highest significance in the liver of SL-F1 mice. We explored whether DNA methylation and small non-coding RNAs might be involved in mediating intergenerational effects. Sperm DNA methylation was largely altered in SL mice. However, these changes did not correlate with the hepatic transcriptome. Next, we analyzed small non-coding RNA content in the testes of mice from the parental generation. Two miRNAs (miR-457 and miR-201) appeared differentially expressed in the testes of SL-F0 mice. They are known to be expressed in mature spermatozoa, but not in oocytes nor early embryos, and they may regulate the transcription of lipogenic genes, but not clock genes, in hepatocytes. Hence, they are strong candidates to mediate the inheritance of adult hepatic steatosis in our murine model. In conclusion, litter size reduction leads to intergenerational effects through non-genomic mechanisms. In our model, DNA methylation does not seem to play a role on the circadian rhythm nor lipid genes. However, at least two paternal miRNAs might influence the expression of a few lipid-related genes in the first-generation offspring, F1.

GSDMD drives canonical inflammasome-induced neutrophil pyroptosis and is dispensable for NETosis.

Neutrophils are the most prevalent immune cells in circulation, but the repertoire of canonical inflammasomes in neutrophils and their respective involvement in neutrophil IL-1ß secretion and neutrophil cell death remain unclear. Here, we show that neutrophil-targeted expression of the disease-associated gain-of-function Nlrp3A350V mutant suffices for systemic autoinflammatory disease and tissue pathology in vivo. We confirm the activity of the canonical NLRP3 and NLRC4 inflammasomes in neutrophils, and further show that the NLRP1b, Pyrin and AIM2 inflammasomes also promote maturation and secretion of interleukin (IL)-1ß in cultured bone marrow neutrophils. Notably, all tested canonical inflammasomes promote GSDMD cleavage in neutrophils, and canonical inflammasome-induced pyroptosis and secretion of mature IL-1ß are blunted in GSDMD-knockout neutrophils. In contrast, GSDMD is dispensable for PMA-induced NETosis. We also show that Salmonella Typhimurium-induced pyroptosis is markedly increased in Nox2/Gp91Phox -deficient neutrophils that lack NADPH oxidase activity and are defective in PMA-induced NETosis. In conclusion, we establish the canonical inflammasome repertoire in neutrophils and identify differential roles for GSDMD and the NADPH complex in canonical inflammasome-induced neutrophil pyroptosis and mitogen-induced NETosis, respectively.

Nlrp3 inflammasome activation in macrophages suffices for inducing autoinflammation in mice.

Cryopyrin-associated periodic syndromes (CAPS) are a spectrum of autoinflammatory disorders caused by gain-of-function NLRP3 mutant proteins that form hyperactive inflammasomes leading to overproduction of the pro-inflammatory cytokines IL-1ß and IL-18. Expressing the murine gain-of-function Nlrp3A350V mutant selectively in neutrophils recapitulates several autoinflammatory features of human CAPS, but the potential contribution of macrophage inflammasome hyperactivation to CAPS development is poorly defined. Here, we show that expressing Nlrp3A350V in macrophages is sufficient for driving severe multi-organ autoinflammation leading to perinatal lethality in mice. In addition, we show that macrophages contribute to autoinflammation also in adult mice, as depleting macrophages in mice ubiquitously expressing Nlrp3A350V significantly diminishes splenic and hepatic IL-1ß production. Interestingly, inflammation induced by macrophage-selective Nlrp3A350V expression does not provoke an influx of mature neutrophils, while neutrophil influx is still occurring in macrophage-depleted mice with body-wide Nlrp3A350V expression. These observations identify macrophages as important cellular drivers of CAPS in mice and support a cooperative cellular model of CAPS development in which macrophages and neutrophils act independently of each other in propagating severe autoinflammation.

Increasing breast milk betaine modulates Akkermansia abundance in mammalian neonates and improves long-term metabolic health.

Accelerated postnatal growth is a potentially modifiable risk factor for future obesity. To study how specific breast milk components contribute to early growth and obesity risk, we quantified one-carbon metabolism-related metabolites in human breast milk and found an inverse association between milk betaine content and infant growth. This association was replicated in an independent and geographically distinct cohort. To determine the potential role of milk betaine in modulating offspring obesity risk, we performed maternal betaine supplementation experiments in mice. Higher betaine intake during lactation increased milk betaine content in dams and led to lower adiposity and improved glucose homeostasis throughout adulthood in mouse offspring. These effects were accompanied by a transient increase in Akkermansia spp. abundance in the gut during early life and a long-lasting increase in intestinal goblet cell number. The link between breast milk betaine and Akkermansia abundance in the gut was also observed in humans, as infants exposed to higher milk betaine content during breastfeeding showed higher fecal Akkermansia muciniphila abundance. Furthermore, administration of A. muciniphila to mouse pups during the lactation period partially replicated the effects of maternal breast milk betaine, including increased intestinal goblet cell number, lower adiposity, and improved glucose homeostasis during adulthood. These data demonstrate a link between breast milk betaine content and long-term metabolic health of offspring.

Neonatal overfeeding during lactation rapidly and permanently misaligns the hepatic circadian rhythm and programmes adult NAFLD.

Childhood obesity is a strong risk factor for adult obesity, type 2 diabetes, and cardiovascular disease. The mechanisms that link early adiposity with late-onset chronic diseases are poorly characterised. We developed a mouse model of early adiposity through litter size reduction. Mice reared in small litters (SLs) developed obesity, insulin resistance, and hepatic steatosis during adulthood. The liver played a major role in the development of the disease. OBJECTIVE: To gain insight into the molecular mechanisms that link early development and childhood obesity with adult hepatic steatosis and insulin resistance. METHODS: We analysed the hepatic transcriptome (Affymetrix) of control and SL mice to uncover potential pathways involved in the long-term programming of disease in our model. RESULTS: The circadian rhythm was the most significantly deregulated Gene Ontology term in the liver of adult SL mice. Several core clock genes, such as period 1-3 and cryptochrome 1-2, were altered in two-week-old SL mice and remained altered throughout their life course until they reached 4-6 months of age. Defective circadian rhythm was restricted to the periphery since the expression of clock genes in the hypothalamus, the central pacemaker, was normal. The period-cryptochrome genes were primarily entrained by dietary signals. Hence, restricting food availability during the light cycle only uncoupled the central rhythm from the peripheral and completely normalised hepatic triglyceride content in adult SL mice. This effect was accompanied by better re-alignment of the hepatic period genes, suggesting that they might have played a causal role in mediating hepatic steatosis in the adult SL mice. Functional downregulation of Per2 in hepatocytes in vitro confirmed that the period genes regulated lipid-related genes in part through peroxisome proliferator-activated receptor alpha (Ppara). CONCLUSIONS: The hepatic circadian rhythm matures during early development, from birth to postnatal day 30. Hence, nutritional challenges during early life may misalign the hepatic circadian rhythm and secondarily lead to metabolic derangements. Specific time-restricted feeding interventions improve metabolic health in the context of childhood obesity by partially re-aligning the peripheral circadian rhythm.

Epigenetic programming at the Mogat1 locus may link neonatal overnutrition with long-term hepatic steatosis and insulin resistance.

Postnatal overfeeding increases the risk of chronic diseases later in life, including obesity, insulin resistance, hepatic steatosis, and type 2 diabetes. Epigenetic mechanisms might underlie the long-lasting effects associated with early nutrition. Here we aimed to explore the molecular pathways involved in early development of insulin resistance and hepatic steatosis, and we examined the potential contribution of DNA methylation and histone modifications to long-term programming of metabolic disease. We used a well-characterized mouse model of neonatal overfeeding and early adiposity by litter size reduction. Neonatal overfeeding led to hepatic insulin resistance very early in life that persisted throughout adulthood despite normalizing food intake. Up-regulation of monoacylglycerol O-acyltransferase ( Mogat) 1 conceivably mediates hepatic steatosis and insulin resistance through increasing intracellular diacylglycerol content. Early and sustained deregulation of Mogat1 was associated with a combination of histone modifications that might favor Mogat1 expression. In sum, postnatal overfeeding causes extremely rapid derangements of hepatic insulin sensitivity that remain relatively stable until adulthood. Epigenetic mechanisms, particularly histone modifications, could contribute to such long-lasting effects. Our data suggest that targeting hepatic monoacylglycerol acyltransferase activity during early life might provide a novel strategy to improve hepatic insulin sensitivity and prevent late-onset insulin resistance and fatty liver disease.-Ramon-Krauel, M., Pentinat, T., Bloks, V. W., Cebrià, J., Ribo, S., Pérez-Wienese, R., Vilà, M., Palacios-Marin, I., Fernández-Pérez, A., Vallejo, M., Téllez, N., Rodríguez, M. À., Yanes, O., Lerin, C., Díaz, R., Plosch, T., Tietge, U. J. F., Jimenez-Chillaron, J. C. Epigenetic programming at the Mogat1 locus may link neonatal overnutrition with long-term hepatic steatosis and insulin resistance.

Dietary Betaine Supplementation Increases Fgf21 Levels to Improve Glucose Homeostasis and Reduce Hepatic Lipid Accumulation in Mice.

Identifying markers of human insulin resistance may permit development of new approaches for treatment and prevention of type 2 diabetes. To this end, we analyzed the fasting plasma metabolome in metabolically characterized human volunteers across a spectrum of insulin resistance. We demonstrate that plasma betaine levels are reduced in insulin-resistant humans and correlate closely with insulin sensitivity. Moreover, betaine administration to mice with diet-induced obesity prevents the development of impaired glucose homeostasis, reduces hepatic lipid accumulation, increases white adipose oxidative capacity, and enhances whole-body energy expenditure. In parallel with these beneficial metabolic effects, betaine supplementation robustly increased hepatic and circulating fibroblast growth factor (Fgf)21 levels. Betaine administration failed to improve glucose homeostasis and liver fat content in Fgf21(-/-) mice, demonstrating that Fgf21 is necessary for betaine's beneficial effects. Together, these data indicate that dietary betaine increases Fgf21 levels to improve metabolic health in mice and suggest that betaine supplementation merits further investigation as a supplement for treatment or prevention of type 2 diabetes in humans.

Transgenerational epigenetic inheritance of diabetes risk as a consequence of early nutritional imbalances.

In today's world, there is an unprecedented rise in the prevalence of chronic metabolic diseases, including obesity, insulin resistance and type 2 diabetes (T2D). The pathogenesis of T2D includes both genetic and environmental factors, such as excessive energy intake and physical inactivity. It has recently been suggested that environmental factors experienced during early stages of development, including the intrauterine and neonatal periods, might play a major role in predisposing individuals to T2D. Furthermore, several studies have shown that such early environmental conditions might even contribute to disease risk in further generations. In this review, we summarise recent data describing how parental nutrition during development increases the risk of diabetes in the offspring. We also discuss the potential mechanisms underlying transgenerational inheritance of metabolic disease, with particular emphasis on epigenetic mechanisms.

In utero undernutrition in male mice programs liver lipid metabolism in the second-generation offspring involving altered Lxra DNA methylation.

Obesity and type 2 diabetes have a heritable component that is not attributable to genetic factors. Instead, epigenetic mechanisms may play a role. We have developed a mouse model of intrauterine growth restriction (IUGR) by in utero malnutrition. IUGR mice developed obesity and glucose intolerance with aging. Strikingly, offspring of IUGR male mice also developed glucose intolerance. Here, we show that in utero malnutrition of F1 males influenced the expression of lipogenic genes in livers of F2 mice, partly due to altered expression of Lxra. In turn, Lxra expression is attributed to altered DNA methylation of its 5' UTR region. We found the same epigenetic signature in the sperm of their progenitors, F1 males. Our data indicate that in utero malnutrition results in epigenetic modifications in germ cells (F1) that are subsequently transmitted and maintained in somatic cells of the F2, thereby influencing health and disease risk of the offspring.

The role of nutrition on epigenetic modifications and their implications on health.

Nutrition plays a key role in many aspects of health and dietary imbalances are major determinants of chronic diseases including cardiovascular disease, obesity, diabetes and cancer. Adequate nutrition is particularly essential during critical periods in early life (both pre- and postnatal). In this regard, there is extensive epidemiologic and experimental data showing that early sub-optimal nutrition can have health consequences several decades later. The hypothesis that epigenetic mechanisms may link such nutritional imbalances with altered disease risk has been gaining acceptance over recent years. Epigenetics can be defined as the study of heritable changes in gene expression that do not involve alterations in the DNA sequence. Epigenetic marks include DNA methylation, histone modifications and a variety of non-coding RNAs. Strikingly, they are plastic and respond to environmental signals, including diet. Here we will review how dietary factors modulate the establishment and maintenance of epigenetic marks, thereby influencing gene expression and, hence, disease risk and health.