Isolating mononuclear cells from fetal bone and liver for metabolic, functional, and immunophenotypic analyses in nonhuman primates

Studying fetal hematopoiesis is challenging as hematopoiesis transitions from the liver to bone marrow. Obtaining human samples is not possible, and small animal models may not provide sufficient biological material. Here, we present a protocol for isolating hematopoietic cells from the nonhuman primate fetal liver and bone. We describe steps for using cells from the same fetus for fluorescence lifetime imaging microscopy to measure metabolism, assessing cellular function, and flow cytometry for immunophenotyping at the single-cell level. For complete details on the use and execution of this protocol, please refer to Nash et al. (2023).1.

Endotoxin biomarkers, hepatic fat fraction, liver volume and liver stiffness among adolescents at high-risk for non-alcoholic fatty liver disease: The HEROES study

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is on the rise among youth. Identifying biomarkers of NAFLD progression/risk can aid in prevention efforts.

AIMS

This pilot study investigated associations of two endotoxin biomarkers-lipopolysaccharide-binding protein (LBP) and anti-endotoxin core immunoglobulin G (EndoCab)-with markers of NAFLD among 99 Latino/Latina adolescents (11-19 years) with obesity.

MATERIALS & METHODS

We used linear regression to examine associations of each endotoxin biomarker (per 1-SD) with hepatic fat fraction (HFF), liver volume, and liver stiffness.

RESULTS

We found positive associations of LBP with HFF and liver volume. Each 1-SD increment in LBP corresponded with 2.35% (95% CI: 0.46%, 4.23%) higher HFF and 0.14 (0.06, 0.23) L greater liver volume after adjusting for age, sex, and maternal education. Accounting for abdominal adiposity and Tanner stage did not change results. Excluding 72 participants with NAFLD attenuated associations of LBP with HFF but associations with liver volume persisted (0.11 [0.01, 0.21] L). EndoCab was not associated with any liver outcomes. Neither endotoxin biomarker predicted liver stiffness.

DISCUSSION/CONCLUSION

While additional research is warranted, our results support LBP as a biomarker of NAFLD risk/progression in high-risk youth.

Maternal diet alters long-term innate immune cell memory in fetal and juvenile hematopoietic stem and progenitor cells in nonhuman primate offspring

Maternal overnutrition increases inflammatory and metabolic disease risk in postnatal offspring. This constitutes a major public health concern due to increasing prevalence of these diseases, yet mechanisms remain unclear. Here, using nonhuman primate models, we show that maternal Western-style diet (mWSD) exposure is associated with persistent pro-inflammatory phenotypes at the transcriptional, metabolic, and functional levels in bone marrow-derived macrophages (BMDMs) from 3-year-old juvenile offspring and in hematopoietic stem and progenitor cells (HSPCs) from fetal and juvenile bone marrow and fetal liver. mWSD exposure is also associated with increased oleic acid in fetal and juvenile bone marrow and fetal liver. Assay for transposase-accessible chromatin with sequencing (ATAC-seq) profiling of HSPCs and BMDMs from mWSD-exposed juveniles supports a model in which HSPCs transmit pro-inflammatory memory to myeloid cells beginning in utero. These findings show that maternal diet alters long-term immune cell developmental programming in HSPCs with proposed consequences for chronic diseases featuring altered immune/inflammatory activation across the lifespan.

Maternal Western diet is associated with distinct preclinical pediatric NAFLD phenotypes in juvenile nonhuman primate offspring

Pediatric NAFLD has distinct and variable pathology, yet causation remains unclear. We have shown that maternal Western-style diet (mWSD) compared with maternal chow diet (CD) consumption in nonhuman primates produces hepatic injury and steatosis in fetal offspring. Here, we define the role of mWSD and postweaning Western-style diet (pwWSD) exposures on molecular mechanisms linked to NAFLD development in a cohort of 3-year-old juvenile nonhuman primates offspring exposed to maternal CD or mWSD followed by CD or Western-style diet after weaning. We used histologic, transcriptomic, and metabolomic analyses to identify hepatic pathways regulating NAFLD. Offspring exposed to mWSD showed increased hepatic periportal collagen deposition but unchanged hepatic triglyceride levels and body weight. mWSD was associated with a downregulation of gene expression pathways underlying HNF4α activity and protein, and downregulation of antioxidant signaling, mitochondrial biogenesis, and PPAR signaling pathways. In offspring exposed to both mWSD and pwWSD, liver RNA profiles showed upregulation of pathways promoting fibrosis and endoplasmic reticulum stress and increased BiP protein expression with pwWSD. pwWSD increased acylcarnitines and decreased anti-inflammatory fatty acids, which was more pronounced when coupled with mWSD exposure. Further, mWSD shifted liver metabolites towards decreased purine catabolism in favor of synthesis, suggesting a mitochondrial DNA repair response. Our findings demonstrate that 3-year-old offspring exposed to mWSD but weaned to a CD have periportal collagen deposition, with transcriptional and metabolic pathways underlying hepatic oxidative stress, compromised mitochondrial lipid sensing, and decreased antioxidant response. Exposure to pwWSD worsens these phenotypes, triggers endoplasmic reticulum stress, and increases fibrosis. Overall, mWSD exposure is associated with altered expression of candidate genes and metabolites related to NAFLD that persist in juvenile offspring preceding clinical presentation of NAFLD.

Endotoxin Biomarkers Are Associated With Adiposity and Cardiometabolic Risk Across 6 Years of Follow-up in Youth

CONTEXT

Metabolic endotoxemia may be a shared mechanism underlying childhood obesity and early-onset metabolic diseases (eg, type 2 diabetes, nonalcoholic fatty liver disease).

OBJECTIVE

Examine prospective associations of serum endotoxin biomarkers lipopolysaccharide (LPS) and its binding protein, LPS binding protein (LBP), and anti-endotoxin core immunoglobulin G (EndoCab IgG) with adiposity and cardiometabolic risk in youth.

DESIGN/SETTING

This prospective study included 393 youth in the Exploring Perinatal Outcomes Among Children cohort in Colorado. Participants were recruited from 2006 to 2009 at age 10 years (baseline) and followed for 6 years (follow-up). We examined associations of endotoxin biomarkers at baseline with adiposity [body mass index (BMI) z-score, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), skinfolds, waist circumference] and cardiometabolic risk (insulin, glucose, adipokines, lipid profile, blood pressure) across both visits using mixed-effects regression, and with hepatic fat fraction (HFF) at follow-up using linear regression.

RESULTS

Higher LPS and LBP predicted greater adiposity across follow-up. Each 1-unit log-transformed LPS corresponded with 0.23 (95% CI 0.03, 0.43) units BMI z-score, 5.66 (95% CI 1.99, 9.33) mm3 VAT, 30.7 (95% CI 8.0, 53.3) mm3 SAT, and 8.26 (95% CI 4.13, 12.40) mm skinfold sum. EndoCab IgG was associated with VAT only [3.03 (95% CI 0.34, 5.71) mm3]. LPS was associated with higher insulin [1.93 (95% CI 0.08, 3.70) µU/mL] and leptin [2.28 (95% CI 0.66, 3.90) ng/mL] and an adverse lipid profile. No association was observed with HFF. Accounting for pubertal status and lifestyle behaviors did not change findings. However, adjustment for prepregnancy BMI and gestational diabetes attenuated most associations.

CONCLUSIONS

Serum endotoxin may be a marker of pathophysiological processes underlying development of childhood obesity and cardiometabolic conditions associated with exposure to fetal overnutrition.

Maternal Pyrroloquinoline Quinone Supplementation Improves Offspring Liver Bioactive Lipid Profiles throughout the Lifespan and Protects against the Development of Adult NAFLD

Maternal obesity and consumption of a high-fat diet significantly elevate risk for pediatric nonalcoholic fatty liver disease (NAFLD), affecting 10% of children in the US. Almost half of these children are diagnosed with nonalcoholic steatohepatitis (NASH), a leading etiology for liver transplant. Animal models show that signs of liver injury and perturbed lipid metabolism associated with NAFLD begin in utero; however, safe dietary therapeutics to blunt developmental programming of NAFLD are unavailable. Using a mouse model of maternal Western-style diet (WD), we previously showed that pyrroloquinoline quinone (PQQ), a potent dietary antioxidant, protected offspring of WD-fed dams from development of NAFLD and NASH. Here, we used untargeted mass spectrometry-based lipidomics to delineate lipotoxic effects of WD on offspring liver and identify lipid targets of PQQ. PQQ exposure during pregnancy altered hepatic lipid profiles of WD-exposed offspring, upregulating peroxisome proliferator-activated receptor (PPAR) α signaling and mitochondrial fatty acid oxidation to markedly attenuate triglyceride accumulation beginning in utero. Surprisingly, the abundance of very long-chain ceramides, important in promoting gut barrier and hepatic function, was significantly elevated in PQQ-treated offspring. PQQ exposure reduced the hepatic phosphatidylcholine/phosphatidylethanolamine (PC/PE) ratio in WD-fed offspring and improved glucose tolerance. Notably, levels of protective n − 3 polyunsaturated fatty acids (PUFAs) were elevated in offspring exposed to PQQ, beginning in utero, and the increase in n − 3 PUFAs persisted into adulthood. Our findings suggest that PQQ supplementation during gestation and lactation augments pathways involved in the biosynthesis of long-chain fatty acids and plays a unique role in modifying specific bioactive lipid species critical for protection against NAFLD risk in later life.

Western diet-induced shifts in the maternal microbiome are associated with altered microRNA expression in baboon placenta and fetal liver

Maternal consumption of a high-fat, Western-style diet (WD) disrupts the maternal/infant microbiome and contributes to developmental programming of the immune system and nonalcoholic fatty liver disease (NAFLD) in the offspring. Epigenetic changes, including non-coding miRNAs in the fetus and/or placenta may also underlie this risk. We previously showed that obese nonhuman primates fed a WD during pregnancy results in the loss of beneficial maternal gut microbes and dysregulation of cellular metabolism and mitochondrial dysfunction in the fetal liver, leading to a perturbed postnatal immune response with accelerated NAFLD in juvenile offspring. Here, we investigated associations between WD-induced maternal metabolic and microbiome changes, in the absence of obesity, and miRNA and gene expression changes in the placenta and fetal liver. After ~8-11 months of WD feeding, dams were similar in body weight but exhibited mild, systemic inflammation (elevated CRP and neutrophil count) and dyslipidemia (increased triglycerides and cholesterol) compared with dams fed a control diet. The maternal gut microbiome was mainly comprised of Lactobacillales and Clostridiales, with significantly decreased alpha diversity (P = 0.0163) in WD-fed dams but no community-wide differences (P = 0.26). At 0.9 gestation, mRNA expression of IL6 and TNF in maternal WD (mWD) exposed placentas trended higher, while increased triglycerides, expression of pro-inflammatory CCR2, and histological evidence for fibrosis were found in mWD-exposed fetal livers. In the mWD-exposed fetus, hepatic expression levels of miR-204-5p and miR-145-3p were significantly downregulated, whereas in mWD-exposed placentas, miR-182-5p and miR-183-5p were significantly decreased. Notably, miR-1285-3p expression in the liver and miR-183-5p in the placenta were significantly associated with inflammation and lipid synthesis pathway genes, respectively. Blautia and Ruminococcus were significantly associated with miR-122-5p in liver, while Coriobacteriaceae and Prevotellaceae were strongly associated with miR-1285-3p in the placenta; both miRNAs are implicated in pathways mediating postnatal growth and obesity. Our findings demonstrate that mWD shifts the maternal microbiome, lipid metabolism, and inflammation prior to obesity and are associated with epigenetic changes in the placenta and fetal liver. These changes may underlie inflammation, oxidative stress, and fibrosis patterns that drive NAFLD and metabolic disease risk in the next generation.

Maternal Western diet exposure increases periportal fibrosis beginning in utero in nonhuman primate offspring

Maternal obesity affects nearly one-third of pregnancies and is a major risk factor for nonalcoholic fatty liver disease (NAFLD) in adolescent offspring, yet the mechanisms behind NAFLD remain poorly understood. Here, we demonstrate that nonhuman primate fetuses exposed to maternal Western-style diet (WSD) displayed increased fibrillar collagen deposition in the liver periportal region, with increased ACTA2 and TIMP1 staining, indicating localized hepatic stellate cell (HSC) and myofibroblast activation. This collagen deposition pattern persisted in 1-year-old offspring, despite weaning to a control diet (CD). Maternal WSD exposure increased the frequency of DCs and reduced memory CD4+ T cells in fetal liver without affecting systemic or hepatic inflammatory cytokines. Switching obese dams from WSD to CD before conception or supplementation of the WSD with resveratrol decreased fetal hepatic collagen deposition and reduced markers of portal triad fibrosis, oxidative stress, and fetal hypoxemia. These results demonstrate that HSCs and myofibroblasts are sensitive to maternal WSD-associated oxidative stress in the fetal liver, which is accompanied by increased periportal collagen deposition, indicative of early fibrogenesis beginning in utero. Alleviating maternal WSD-driven oxidative stress in the fetal liver holds promise for halting steatosis and fibrosis and preventing developmental programming of NAFLD.

Gestational Diabetes Is Uniquely Associated With Altered Early Seeding of the Infant Gut Microbiota

Gestational diabetes mellitus (GDM) is a worldwide public health problem affecting up to 27% of pregnancies with high predictive values for childhood obesity and inflammatory diseases. Compromised seeding of the infant gut microbiota is a risk factor for immunologic and metabolic diseases in the offspring; however, how GDM along with maternal obesity interact to alter colonization remains unknown. We hypothesized that GDM individually and in combination with maternal overweight/obesity would alter gut microbial composition, diversity, and short-chain fatty acid (SCFA) levels in neonates. We investigated 46 full-term neonates born to normal-weight or overweight/obese mothers with and without GDM, accounting for confounders including cesarean delivery, lack of breastfeeding, and exposure to antibiotics. Gut microbiota in 2-week-old neonates born to mothers with GDM exhibited differences in abundance of 26 microbial taxa; 14 of which showed persistent differential abundance after adjusting for pre-pregnancy BMI. Key pioneering gut taxa, including potentially important taxa for establishing neonatal immunity, were reduced. Lactobacillus, Flavonifractor, Erysipelotrichaceae, and unspecified families in Gammaproteobacteria were significantly reduced in neonates from mothers with GDM. GDM was associated with an increase in microbes involved in suppressing early immune cell function (Phascolarctobacterium). No differences in infant stool SCFA levels by maternal phenotype were noted; however, significant correlations were found between microbial abundances and SCFA levels in neonates. Our results suggest that GDM alone and together with maternal overweight/obesity uniquely influences seeding of specific infant microbiota in patterns that set the stage for future risk of inflammatory and metabolic disease.

Pediatric Non-Alcoholic Fatty Liver Disease: Nutritional Origins and Potential Molecular Mechanisms

Non-alcoholic fatty liver disease (NAFLD) is the number one chronic liver disease worldwide and is estimated to affect nearly 40% of obese youth and up to 10% of the general pediatric population without any obvious signs or symptoms. Although the early stages of NAFLD are reversible with diet and lifestyle modifications, detecting such stages is hindered by a lack of non-invasive methods of risk assessment and diagnosis. This absence of non-invasive means of diagnosis is directly related to the scarcity of long-term prospective studies of pediatric NAFLD in children and adolescents. In the majority of pediatric NAFLD cases, the mechanisms driving the origin and rapid progression of NAFLD remain unknown. The progression from NAFLD to non-alcoholic steatohepatitis (NASH) in youth is associated with unique histological features and possible immune processes and metabolic pathways that may reflect different mechanisms compared with adults. Recent data suggest that circulating microRNAs (miRNAs) are important new biomarkers underlying pathways of liver injury. Several factors may contribute to pediatric NAFLD development, including high-sugar diets, in utero exposures via epigenetic alterations, changes in the neonatal microbiome, and altered immune system development and mitochondrial function. This review focuses on the unique aspects of pediatric NAFLD and how nutritional exposures impact the immune system, mitochondria, and liver/gastrointestinal metabolic health. These factors highlight the need for answers to how NAFLD develops in children and for early stage-specific interventions.

Maternal Fat-1 Transgene Protects Offspring from Excess Weight Gain, Oxidative Stress, and Reduced Fatty Acid Oxidation in Response to High-Fat Diet

Overweight and obesity accompanies up to 70% of pregnancies and is a strong risk factor for offspring metabolic disease. Maternal obesity-associated inflammation and lipid profile are hypothesized as important contributors to excess offspring liver and skeletal muscle lipid deposition and oxidative stress. Here, we tested whether dams expressing the fat-1 transgene, which endogenously converts omega-6 (n-6) to omega-3 (n-3) polyunsaturated fatty acid, could protect wild-type (WT) offspring against high-fat diet induced weight gain, oxidative stress, and disrupted mitochondrial fatty acid oxidation. Despite similar body mass at weaning, offspring from fat-1 high-fat-fed dams gained less weight compared with offspring from WT high-fat-fed dams. In particular, WT males from fat-1 high-fat-fed dams were protected from post-weaning high-fat diet induced weight gain, reduced fatty acid oxidation, or excess oxidative stress compared with offspring of WT high-fat-fed dams. Adult offspring of WT high-fat-fed dams exhibited greater skeletal muscle triglycerides and reduced skeletal muscle antioxidant defense and redox balance compared with offspring of WT dams on control diet. Fat-1 offspring were protected from the reduced fatty acid oxidation and excess oxidative stress observed in offspring of WT high-fat-fed dams. These results indicate that a maternal fat-1 transgene has protective effects against offspring liver and skeletal muscle lipotoxicity resulting from a maternal high-fat diet, particularly in males. Altering maternal fatty acid composition, without changing maternal dietary composition or weight gain with high-fat feeding, may highlight important strategies for n-3-based prevention of developmental programming of obesity and its complications.

Microplate Assays for Spectrophotometric Measurement of Mitochondrial Enzyme Activity

Spectrophotometric analysis of metabolic enzyme activity from homogenized tissues is a valuable method for investigating mitochondrial content and capacity. Enzyme activity is normally measured in single cuvette spectrophotometers, requiring a large sample volume and low throughput. Here, we describe microplate assays for high-throughput analysis of mitochondrial enzymes citrate synthase, β-hydroxyacyl CoA dehydrogenase, aconitase, and mitochondrial electron transport system (ETS) complexes I, II, III, and IV.

The gut microbiota in infants of obese mothers increases inflammation and susceptibility to NAFLD

Maternal obesity is associated with increased risk for offspring obesity and non-alcoholic fatty liver disease (NAFLD), but the causal drivers of this association are unclear. Early colonization of the infant gut by microbes plays a critical role in establishing immunity and metabolic function. Here, we compare germ-free mice colonized with stool microbes (MB) from 2-week-old infants born to obese (Inf-ObMB) or normal-weight (Inf-NWMB) mothers. Inf-ObMB-colonized mice demonstrate increased hepatic gene expression for endoplasmic reticulum stress and innate immunity together with histological signs of periportal inflammation, a histological pattern more commonly reported in pediatric cases of NAFLD. Inf-ObMB mice show increased intestinal permeability, reduced macrophage phagocytosis, and dampened cytokine production suggestive of impaired macrophage function. Furthermore, exposure to a Western-style diet in Inf-ObMB mice promotes excess weight gain and accelerates NAFLD. Overall, these results provide functional evidence supporting a causative role of maternal obesity-associated infant dysbiosis in childhood obesity and NAFLD.

Switching obese mothers to a healthy diet improves fetal hypoxemia, hepatic metabolites, and lipotoxicity in non-human primates

Objective

Non-alcoholic fatty liver disease (NAFLD) risk begins in utero in offspring of obese mothers. A critical unmet need in this field is to understand the pathways and biomarkers underlying fetal hepatic lipotoxicity and whether maternal dietary intervention during pregnancy is an effective countermeasure.

Methods

We utilized a well-established non-human primate model of chronic, maternal, Western-style diet induced obesity (OB-WSD) compared with mothers on a healthy control diet (CON) or a subset of OB-WSD mothers switched to the CON diet (diet reversal; OB-DR) prior to and for the duration of the next pregnancy. Fetuses were studied in the early 3rd trimester.

Results

Fetuses from OB-WSD mothers had higher circulating triglycerides (TGs) and lower arterial oxygenation suggesting hypoxemia, compared with fetuses from CON and OB-DR mothers. Hepatic TG content, oxidative stress (TBARs), and de novo lipogenic genes were increased in fetuses from OB-WSD compared with CON mothers. Fetuses from OB-DR mothers had lower lipogenic gene expression and TBARs yet persistently higher TGs. Metabolomic profiling of fetal liver and serum (umbilical artery) revealed distinct separation of CON and OB-WSD groups, and an intermediate phenotype in fetuses from OB-DR mothers. Pathway analysis identified decreased tricarboxylic acid cycle intermediates, increased amino acid (AA) metabolism and byproducts, and increased gluconeogenesis, suggesting an increased reliance on AA metabolism to meet energy needs in the liver of fetuses from OB-WSD mothers. Components in collagen synthesis, including serum protein 5-hydroxylysine and hepatic lysine and proline, were positively correlated with hepatic TGs and TBARs, suggesting early signs of fibrosis in livers from the OB-WSD group. Importantly, hepatic gluconeogenic and arginine related intermediates and serum levels of lactate, pyruvate, several AAs, and nucleotide intermediates were normalized in the OB-DR group. However, hepatic levels of CDP-choline and total ceramide levels remained high in fetuses from OB-DR mothers.

Conclusions

Our data provide new metabolic evidence that, in addition to fetal hepatic steatosis, maternal WSD creates fetal hypoxemia and increases utilization of AAs for energy production and early activation of gluconeogenic pathways in the fetal liver. When combined with hyperlipidemia and limited antioxidant activity, the fetus suffers from hepatic oxidative stress and altered intracellular metabolism which can be improved with maternal diet intervention. Our data reinforce the concept that multiple “first hits” occur in the fetus prior to development of obesity and demonstrate new biomarkers with potential clinical implications for monitoring NAFLD risk in offspring.

•

Maternal WSD increases fetal hypoxemia and utilization of AAs for gluconeogenesis.

•

Maternal WSD increases fetal oxidative stress and precursors to liver fibrosis.

•

Carnosine and l-proline uniquely correlated with fetal TG and oxidative stress.

•

Fetal TGs were correlated with fetal arterial oxygen saturation.

•

Diet reversal in obese WSD mothers prevents fetal hypoxemia and oxidative stress.

Placental lipoprotein lipase activity is positively associated with newborn adiposity

INTRODUCTION

Recent data suggest that in addition to glucose, fetal growth is related to maternal triglycerides (TG). To reach the fetus, TG must be hydrolyzed to free fatty acids (FFA) and transported across the placenta, but regulation is uncertain. Placental lipoprotein lipase (pLPL) hydrolyzes TG, both dietary chylomicron TG (CM-TG) and very-low density lipoprotein TG (VLDL-TG), to FFA. This may promote fetal fat accretion by increasing the available FFA pool for placental uptake. We tested the novel hypothesis that pLPL activity, but not maternal adipose tissue LPL activity, is associated with newborn adiposity and higher maternal TG.

METHODS

Twenty mothers (n = 13 normal-weight; n = 7 obese) were prospectively recruited. Maternal glucose, insulin, TG (total, CM-TG, VLDL-TG), and FFA were measured at 14-16, 26-28, and 36-37 weeks, and adipose tissue LPL was measured at 26-28 weeks. At term delivery, placental villous biopsies were immediately analyzed for pLPL enzymatic activity. Newborn percent body fat (newborn %fat) was assessed by skinfolds.

RESULTS

Placental LPL activity was positively correlated with birthweight (r = 0.48;P = 0.03) and newborn %fat (r = 0.59;P = 0.006), further strengthened by correcting for gestational age at delivery (r = 0.75;P = 0.0001), but adipose tissue LPL was not. Maternal TG and BMI were not correlated with pLPL activity. Additionally, pLPL gene expression, while modestly correlated with enzymatic activity (r = 0.53;P < 0.05), was not correlated with newborn adiposity.

DISCUSSION

This is the first study to show a positive correlation between pLPL activity and newborn %fat. Placental lipase regulation and the role of pLPL in pregnancies characterized by nutrient excess and fetal overgrowth warrant further investigation.

Pyrroloquinoline quinone prevents developmental programming of microbial dysbiosis and macrophage polarization to attenuate liver fibrosis in offspring of obese mice

Increasingly, evidence suggests that exposure to maternal obesity creates an inflammatory environment in utero, exerting long‐lasting postnatal signatures on the juvenile innate immune system and microbiome that may predispose offspring to development of fatty liver disease. We found that exposure to a maternal Western‐style diet (WD) accelerated fibrogenesis in the liver of offspring and was associated with early recruitment of proinflammatory macrophages at 8‐12 weeks and microbial dysbiosis as early as 3 weeks of age. We further demonstrated that bone marrow‐derived macrophages (BMDMs) were polarized toward an inflammatory state at 8 weeks of age and that a potent antioxidant, pyrroloquinoline quinone (PQQ), reversed BMDM metabolic reprogramming from glycolytic toward oxidative metabolism by restoring trichloroacetic acid cycle function at isocitrate dehydrogenase. This resulted in reduced inflammation and inhibited collagen fibril formation in the liver at 20 weeks of age, even when PQQ was withdrawn at 3 weeks of age. Beginning at 3 weeks of age, WD‐fed mice developed a decreased abundance of Parabacteroides and Lactobacillus, together with increased Ruminococcus and decreased tight junction gene expression by 20 weeks, whereas microbiota of mice exposed to PQQ retained compositional stability with age, which was associated with improved liver health. Conclusion: Exposure to a maternal WD induces early gut dysbiosis and disrupts intestinal tight junctions, resulting in BMDM polarization and induction of proinflammatory and profibrotic programs in the offspring that persist into adulthood. Disrupted macrophage and microbiota function can be attenuated by short‐term maternal treatment with PQQ prior to weaning, suggesting that reshaping the early gut microbiota in combination with reprogramming macrophages during early weaning may alleviate the sustained proinflammatory environment, preventing the rapid progression of nonalcoholic fatty liver disease to nonalcoholic steatohepatitis in offspring of obese mothers. (Hepatology Communications 2018;2:313‐328)

Maternal obesity alters fatty acid oxidation, AMPK activity, and associated DNA methylation in mesenchymal stem cells from human infants

Objective

Infants born to mothers with obesity have greater adiposity, ectopic fat storage, and are at increased risk for childhood obesity and metabolic disease compared with infants of normal weight mothers, though the cellular mechanisms mediating these effects are unclear.

Methods

We tested the hypothesis that human, umbilical cord-derived mesenchymal stem cells (MSCs) from infants born to obese (Ob-MSC) versus normal weight (NW-MSC) mothers demonstrate altered fatty acid metabolism consistent with adult obesity. In infant MSCs undergoing myogenesis in vitro, we measured cellular lipid metabolism and AMPK activity, AMPK activation in response to cellular nutrient stress, and MSC DNA methylation and mRNA content of genes related to oxidative metabolism.

Results

We found that Ob-MSCs exhibit greater lipid accumulation, lower fatty acid oxidation (FAO), and dysregulation of AMPK activity when undergoing myogenesis in vitro. Further experiments revealed a clear phenotype distinction within the Ob-MSC group where more severe MSC metabolic perturbation corresponded to greater neonatal adiposity and umbilical cord blood insulin levels. Targeted analysis of DNA methylation array revealed Ob-MSC hypermethylation in genes regulating FAO (PRKAG2, ACC2, CPT1A, SDHC) and corresponding lower mRNA content of these genes. Moreover, MSC methylation was positively correlated with infant adiposity.

Conclusions

These data suggest that greater infant adiposity is associated with suppressed AMPK activity and reduced lipid oxidation in MSCs from infants born to mothers with obesity and may be an important, early marker of underlying obesity risk.

•

Mesenchymal stem cells from infants of obese mothers have greater lipid content in vitro.

•

This is attributable to lower fatty acid oxidation, not greater fatty acid uptake.

•

AMPK is dysregulated in these cells and corresponds to higher infant adiposity.

•

Epigenetic differences in genes regulating these pathways are observed in the cells.

Metabolic Inflexibility with Obesity and the Effects of Fenofibrate on Skeletal Muscle Fatty Acid Oxidation

This study was designed to investigate mechanisms of lipid metabolic inflexibility in human obesity and the ability of fenofibrate (FENO) to increase skeletal muscle fatty acid oxidation (FAO) in primary human skeletal muscle cell cultures (HSkMC) exhibiting metabolic inflexibility. HSkMC from 10 lean and 10 obese, insulin resistant subjects were treated with excess fatty acid for 24 h (24hFA) to gauge lipid-related metabolic flexibility. Metabolically inflexible HSkMC from obese individuals were then treated with 24hFA in combination with FENO to determine effectiveness for increasing FAO. Mitochondrial enzyme activity and FAO were measured in skeletal muscle from subjects with prediabetes (n=11) before and after 10 weeks of fenofibrate in vivo. 24hFA increased FAO to a greater extent in HSkMC from lean versus obese subjects (+49% vs. +9%, for lean vs. obese, respectively; p<0.05) indicating metabolic inflexibility with obesity. Metabolic inflexibility was not observed for measures of cellular respiration in permeabilized cells using carbohydrate substrate. Fenofibrate co-incubation with 24hFA, increased FAO in a subset of HSkMC from metabolically inflexible, obese subjects (p<0.05), which was eliminated by PPARα antagonist. In vivo, fenofibrate treatment increased skeletal muscle FAO in a subset of subjects with prediabetes but did not affect gene transcription or mitochondrial enzyme activity. Lipid metabolic inflexibility observed in HSkMC from obese subjects is not due to differences in electron transport flux, but rather upstream decrements in lipid metabolism. Fenofibrate increases the capacity for FAO in human skeletal muscle cells, though its role in skeletal muscle metabolism in vivo remains unclear.

Early PQQ supplementation has persistent long-term protective effects on developmental programming of hepatic lipotoxicity and inflammation in obese mice

Nonalcoholic fatty liver disease (NAFLD) is widespread in adults and children. Early exposure to maternal obesity or Western-style diet (WD) increases steatosis and oxidative stress in fetal liver and is associated with lifetime disease risk in the offspring. Pyrroloquinoline quinone (PQQ) is a natural antioxidant found in soil, enriched in human breast milk, and essential for development in mammals. We investigated whether a supplemental dose of PQQ, provided prenatally in a mouse model of diet-induced obesity during pregnancy, could protect obese offspring from progression of NAFLD. PQQ treatment given pre- and postnatally in WD-fed offspring had no effect on weight gain but increased metabolic flexibility while reducing body fat and liver lipids, compared with untreated obese offspring. Indices of NAFLD, including hepatic ceramide levels, oxidative stress, and expression of proinflammatory genes (Nos2, Nlrp3, Il6, and Ptgs2), were decreased in WD PQQ-fed mice, concomitant with increased expression of fatty acid oxidation genes and decreased Pparg expression. Notably, these changes persisted even after PQQ withdrawal at weaning. Our results suggest that supplementation with PQQ, particularly during pregnancy and lactation, protects offspring from WD-induced developmental programming of hepatic lipotoxicity and may help slow the advancing epidemic of NAFLD in the next generation.-Jonscher, K. R., Stewart, M. S., Alfonso-Garcia, A., DeFelice, B. C., Wang, X. X., Luo, Y., Levi, M., Heerwagen, M. J. R., Janssen, R. C., de la Houssaye, B. A., Wiitala, E., Florey, G., Jonscher, R. L., Potma, E. O., Fiehn, O. Friedman, J. E. Early PQQ supplementation has persistent long-term protective effects on developmental programming of hepatic lipotoxicity and inflammation in obese mice.

C/EBPβ in bone marrow is essential for diet induced inflammation, cholesterol balance, and atherosclerosis

BACKGROUND AND OBJECTIVE

Atherosclerosis is both a chronic inflammatory disease and a lipid metabolism disorder. C/EBPβ is well documented for its role in the development of hematopoietic cells and integration of lipid metabolism. However, C/EBPβ's role in atherosclerotic progression has not been examined. We assessed the impact of hematopoietic CEBPβ deletion in ApoE(-/-) mice on hyperlipidemia, inflammatory responses and lesion formation in the aorta.

METHODS AND RESULTS

ApoE(-/-) mice were reconstituted with bone marrow cells derived from either WT or C/EBPβ(-/-) mice and placed on low fat or high fat/high cholesterol diet for 11 weeks. Hematopoietic C/EBPβ deletion in ApoE(-/-) mice reduced blood and hepatic lipids and gene expression of hepatic stearoyl CoA desaturase 1 and fatty acid synthase while expression of ATP binding cassette transporter G1, cholesterol 7-alpha-hydroxylase, and liver X receptor alpha genes were significantly increased. ApoE(-/-) mice reconstituted with C/EBPβ(-/-) bone marrow cells also significantly reduced blood cytokine levels and reduced lesion area in aortic sinuses compared with ApoE(-/-) mice reconstituted with WT bone marrow cells. Silencing of C/EBPβ in RAW264.7 macrophage cells prevented oxLDL-mediated foam cell formation and inflammatory cytokine secretion in conditioned medium.

CONCLUSION

C/EBPβ in hematopoietic cells is crucial to regulate diet-induced inflammation, hyperlipidemia and atherosclerosis development.

Women With Gestational Diabetes Mellitus Randomized to a Higher-Complex Carbohydrate/Low-Fat Diet Manifest Lower Adipose Tissue Insulin Resistance, Inflammation, Glucose, and Free Fatty Acids: A Pilot Study

OBJECTIVE

Diet therapy in gestational diabetes mellitus (GDM) has focused on carbohydrate restriction but is poorly substantiated. In this pilot randomized clinical trial, we challenged the conventional low-carbohydrate/higher-fat (LC/CONV) diet, hypothesizing that a higher-complex carbohydrate/lower-fat (CHOICE) diet would improve maternal insulin resistance (IR), adipose tissue (AT) lipolysis, and infant adiposity.

RESEARCH DESIGN AND METHODS

At 31 weeks, 12 diet-controlled overweight/obese women with GDM were randomized to an isocaloric LC/CONV (40% carbohydrate/45% fat/15% protein; n = 6) or CHOICE (60%/25%/15%; n = 6) diet. All meals were provided. AT was biopsied at 37 weeks.

RESULTS

After ∼7 weeks, fasting glucose (P = 0.03) and free fatty acids (P = 0.06) decreased on CHOICE, whereas fasting glucose increased on LC/CONV (P = 0.03). Insulin suppression of AT lipolysis was improved on CHOICE versus LC/CONV (56 vs. 31%, P = 0.005), consistent with improved IR. AT expression of multiple proinflammatory genes was lower on CHOICE (P < 0.01). Infant adiposity trended lower with CHOICE (10.1 ± 1.4 vs. 12.6 ± 2%, respectively).

CONCLUSIONS

A CHOICE diet may improve maternal IR and infant adiposity, challenging recommendations for a LC/CONV diet.

Skeletal muscle MnSOD, mitochondrial complex II, and SIRT3 enzyme activities are decreased in maternal obesity during human pregnancy and gestational diabetes mellitus

CONTEXT

Insulin resistance and systemic oxidative stress are prominent features of pregnancies complicated by maternal obesity or gestational diabetes mellitus (GDM). The role of skeletal muscle oxidative stress or mitochondrial capacity in obese pregnant women or obese women with GDM is unknown.

OBJECTIVE

We investigated whether obese pregnant women, compared with normal weight (NW) pregnant women, demonstrate decreased skeletal muscle mitochondrial enzyme activity and elevated markers of oxidative stress, and if these differences are more severe in obese women diagnosed with GDM.

DESIGN

We measured mitochondrial enzyme activity and markers of oxidative stress in skeletal muscle tissue from NW pregnant women (n = 10), obese pregnant women with normal glucose tolerance (NGT; n = 10), and obese pregnant women with GDM (n = 8), undergoing cesarean delivery (∼37 wk gestation).

RESULTS

Electron transport complex-II and manganese superoxide dismutase (MnSOD) enzyme activities were decreased in obese-NGT and obese-GDM, compared with NW women. The glutathione redox ratio (GSH:GSSG) was decreased in obese-NGT and obese-GDM, indicative of increased oxidative stress. Mitochondrial sirtuin (SIRT)3 mRNA content and enzyme activity were lower in skeletal muscle of obese-NGT and obese-GDM women. Importantly, acetylation of MnSOD, a SIRT3 target, was increased in obese-NGT and obese-GDM vs NW women and was inversely correlated with SIRT3 activity (r = -0.603), suggesting a mechanism for reduced MnSOD activity.

CONCLUSIONS

These data show that obese pregnant women demonstrate decreased skeletal muscle mitochondrial respiratory chain enzyme activity and decreased mitochondrial antioxidant defense. Furthermore, reduced skeletal muscle SIRT3 activity may play a role in the increased oxidative stress associated with pregnancies complicated by obesity.

Transgenic increase in N-3/n-6 Fatty Acid ratio reduces maternal obesity-associated inflammation and limits adverse developmental programming in mice

Maternal and pediatric obesity has risen dramatically over recent years, and is a known predictor of adverse long-term metabolic outcomes in offspring. However, which particular aspects of obese pregnancy promote such outcomes is less clear. While maternal obesity increases both maternal and placental inflammation, it is still unknown whether this is a dominant mechanism in fetal metabolic programming. In this study, we utilized the Fat-1 transgenic mouse to test whether increasing the maternal n-3/n-6 tissue fatty acid ratio could reduce the consequences of maternal obesity-associated inflammation and thereby mitigate downstream developmental programming. Eight-week-old WT or hemizygous Fat-1 C57BL/6J female mice were placed on a high-fat diet (HFD) or control diet (CD) for 8 weeks prior to mating with WT chow-fed males. Only WT offspring from Fat-1 mothers were analyzed. WT-HFD mothers demonstrated increased markers of infiltrating adipose tissue macrophages (P<0.02), and a striking increase in 12 serum pro-inflammatory cytokines (P<0.05), while Fat1-HFD mothers remained similar to WT-CD mothers, despite equal weight gain. E18.5 Fetuses from WT-HFD mothers had larger placentas (P<0.02), as well as increased placenta and fetal liver TG deposition (P<0.01 and P<0.02, respectively) and increased placental LPL TG-hydrolase activity (P<0.02), which correlated with degree of maternal insulin resistance (r = 0.59, P<0.02). The placentas and fetal livers from Fat1-HFD mothers were protected from this excess placental growth and fetal-placental lipid deposition. Importantly, maternal protection from excess inflammation corresponded with improved metabolic outcomes in adult WT offspring. While the offspring from WT-HFD mothers weaned onto CD demonstrated increased weight gain (P<0.05), body and liver fat (P<0.05 and P<0.001, respectively), and whole body insulin resistance (P<0.05), these were prevented in WT offspring from Fat1-HFD mothers. Our results suggest that reducing excess maternal inflammation may be a promising target for preventing adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.

CCAAT/enhancer binding protein β deletion increases mitochondrial function and protects mice from LXR-induced hepatic steatosis

Drugs designed specifically to activate liver X receptors (LXRs) have beneficial effects on lowering cholesterol metabolism and inflammation but unfortunately lead to severe hepatic steatosis. The transcription factor CCAAT/enhancer binding protein beta (C/EBPβ) is an important regulator of liver gene expression but little is known about its involvement in LXR-based steatosis and cholesterol metabolism. The present study investigated the role of C/EBPβ expression in LXR agonist (T0901317)-mediated alteration of hepatic triglyceride (TG) and lipogenesis in mice. C/EBPβ deletion in mice prevented LXR agonist-mediated induction of lipogenic gene expression in liver in conjunction with significant reduction of liver TG accumulation. Surprisingly, C/EBPβ(-/-) mice showed a major increase in liver mitochondrial electron chain function compared to WT mice. Furthermore, LXR activation in C/EBPβ(-/-) mice increased the expression of liver ATP-binding cassette transporter ABCG1, a gene implicated in cholesterol efflux and reducing blood levels of total and LDL-cholesterol. Together, these findings establish a central role for C/EBPβ in the LXR-mediated steatosis and mitochondrial function, without impairing the influence of LXR activation on lowering LDL and increasing HDL-cholesterol. Inactivation of C/EBPβ might therefore be an important therapeutic strategy to prevent LXR activation-mediated adverse effects on liver TG metabolism without disrupting its beneficial effects on cholesterol metabolism.

Increased phosphoenolpyruvate carboxykinase gene expression and steatosis during hepatitis C virus subgenome replication: role of nonstructural component 5A and CCAAT/enhancer-binding protein β

Chronic hepatitis C virus (HCV) infection greatly increases the risk for type 2 diabetes and nonalcoholic steatohepatitis; however, the pathogenic mechanisms remain incompletely understood. Here we report gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) transcription and associated transcription factors are dramatically up-regulated in Huh.8 cells, which stably express an HCV subgenome replicon. HCV increased activation of cAMP response element-binding protein (CREB), CCAAT/enhancer-binding protein (C/EBPβ), forkhead box protein O1 (FOXO1), and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) and involved activation of the cAMP response element in the PEPCK promoter. Infection with dominant-negative CREB or C/EBPβ-shRNA significantly reduced or normalized PEPCK expression, with no change in PGC-1α or FOXO1 levels. Notably, expression of HCV nonstructural component NS5A in Huh7 or primary hepatocytes stimulated PEPCK gene expression and glucose output in HepG2 cells, whereas a deletion in NS5A reduced PEPCK expression and lowered cellular lipids but was without effect on insulin resistance, as demonstrated by the inability of insulin to stimulate mobilization of a pool of insulin-responsive vesicles to the plasma membrane. HCV-replicating cells demonstrated increases in cellular lipids with insulin resistance at the level of the insulin receptor, increased insulin receptor substrate 1 (Ser-312), and decreased Akt (Ser-473) activation in response to insulin. C/EBPβ-RNAi normalized lipogenic genes sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor γ, and liver X receptor α but was unable to reduce accumulation of triglycerides in Huh.8 cells or reverse the increase in ApoB expression, suggesting a role for increased lipid retention in steatotic hepatocytes. Collectively, these data reveal an important role of NS5A, C/EBPβ, and pCREB in promoting HCV-induced gluconeogenic gene expression and suggest that increased C/EBPβ and NS5A may be essential components leading to increased gluconeogenesis associated with HCV infection.

CCAAT/enhancer-binding protein β (C/EBPβ) expression regulates dietary-induced inflammation in macrophages and adipose tissue in mice

Strong evidence exists for a link between chronic low level inflammation and dietary-induced insulin resistance; however, little is known about the transcriptional networks involved. Here we show that high fat diet (HFD) or saturated fatty acid exposure directly activates CCAAT/enhancer-binding protein β (C/EBPβ) protein expression in liver, adipocytes, and macrophages. Global C/EBPβ deletion prevented HFD-induced inflammation and surprisingly increased mitochondrial gene expression in white adipose tissue along with brown adipose tissue markers PRDM16, CIDEa, and UCP1, consistent with a resistance to HFD-induced obesity. In isolated peritoneal macrophages from C/EBPβ(-/-) mice, the anti-inflammatory gene LXRα and its targets SCD1 and DGAT2 were strikingly up-regulated along with IL-10, while NLRP3, a gene important for activating the inflammasome, was suppressed in response to palmitate. Using RAW 264.7 macrophage cells or 3T3-L1 adipocytes, C/EBPβ knockdown prevented palmitate-induced inflammation and p65-NFκB DNA binding activity, while C/EBPβ overexpression induced NFκB binding, JNK activation, and pro-inflammatory cytokine gene expression directly. Finally, chimeric bone marrow mice transplanted with bone marrow lacking C/EBPβ(-/-) demonstrated reduced systemic and adipose tissue inflammatory markers, macrophage content, and maintained insulin sensitivity on HFD. Taken together, these results demonstrate that HFD or palmitate exposure triggers C/EBPβ expression that controls expression of distinct aspects of alternative macrophage activation. Reducing C/EBPβ in macrophages confers protection from HFD-induced systemic inflammation and insulin resistance, suggesting it may be an attractive therapeutic target for ameliorating obesity-induced inflammatory responses.

Regulation of pyruvate dehydrogenase kinase 4 (PDK4) by CCAAT/enhancer-binding protein beta (C/EBPbeta)

The conversion of pyruvate to acetyl-CoA in mitochondria is catalyzed by the pyruvate dehydrogenase complex (PDC). Activity of PDC is inhibited by phosphorylation via the pyruvate dehydrogenase kinases (PDKs). Here, we examined the regulation of Pdk4 gene expression by the CCAAT/enhancer-binding protein β (C/EBPβ). C/EBPβ modulates the expression of multiple hepatic genes including those involved in metabolism, development, and inflammation. We found that C/EBPβ induced Pdk4 gene expression and decreased PDC activity. This transcriptional induction was mediated through two C/EBPβ binding sites in the Pdk4 promoter. C/EBPβ participates in the hormonal regulation of gluconeogenic genes. Previously, we reported that Pdk4 was induced by thyroid hormone (T(3)). Therefore, we investigated the role of C/EBPβ in the T(3) regulation of Pdk4. T(3) increased C/EBPβ abundance in primary rat hepatocytes. Knockdown of C/EBPβ with siRNA diminished the T(3) induction of the Pdk4 and carnitine palmitoyltransferase (Cpt1a) genes. CPT1a is an initiating step in the mitochondrial oxidation of long chain fatty acids. Our results indicate that C/EBPβ stimulates Pdk4 expression and participates in the T(3) induction of the Cpt1a and Pdk4 genes.

C/EBPβ is AMP kinase sensitive and up-regulates PEPCK in response to ER stress in hepatoma cells

Diabetes and obesity are associated with activation of endoplasmic reticulum (ER) stress; however a direct link between ER stress and increased hepatic gluconeogenesis remains unclear. Here we show that ER stress triggers a significant increase in expression of CCAAT/enhancer-binding protein (C/EBPβ) and phosphorylated CREB together with reduced phospho-AMP-activated protein kinase (pAMPK) in hepatoma cells. ER stress contributed to transcriptional activation of the gluconeogenic phosphoenolpyruvate carboxykinase (PEPCK) promoter in Huh7 and HepG2 cells via cAMP binding motif (CRE site). Chromatin immunoprecipitation assays demonstrate that C/EBPβ is recruited to the PEPCK promoter during ER stress and is reversed by pre-treatment with a JNK inhibitor that relieves ER stress. C/EBPβ but not pCREB was suppressed by the AMPK-activator AICAR or constitutively active AMPK, while dominant negative AMPK increased C/EBPβ expression. These data suggest that ER stress triggers suppression of AMPK while increasing C/EBPβ and pCREB expression which activates PEPCK gene transcription. Understanding how ER stress suppresses AMPK activation and increases C/EBPβ expression could lead to a potentially novel pathway for treatment of diabetes.

In vivo knockdown of p85alpha with an antisense oligonucleotide improves insulin sensitivity in Lep(ob/ob) and diet-induced obese mice

Phosphoinositide 3-kinase is a key signaling intermediate necessary for the metabolic actions of insulin. In this study, we assessed the effects of in vivo knockdown of the p85alpha subunit of phosphoinositide 3-kinase on insulin sensitivity, using an antisense oligonucleotide, in lean mice, diet-induced obese mice, and obese leptin-deficient Lep (ob/ob) mice. Mice were injected with either p85alpha-targeted antisense oligonucleotide or saline twice weekly for 4 weeks. Fasting levels of glycemia and insulinemia and insulin and glucose tolerance tests were used to determine insulin sensitivity. Western blot analysis and real-time polyacrylamide chain reaction were used to assess p85alpha protein and mRNA expression. IN VIVO administration of antisense oligonucleotide resulted in 50 and 60% knockdown of liver p85alpha protein and mRNA, respectively, in the lean, diet-induced obese and Lep (ob/ob) mice. This was associated with increased phosphoinositide 3-kinase activity and improved insulin sensitivity in diet-induced obese and Lep (ob/ob) mice. Thus, p85alpha could be an important therapeutic target to ameliorate insulin resistance.

Fenofibrate and PBA prevent fatty acid-induced loss of adiponectin receptor and pAMPK in human hepatoma cells and in hepatitis C virus-induced steatosis

Adiponectin receptors play a key role in steatosis and inflammation; however, very little is known about regulation of adiponectin receptors in liver. Here, we examined the effects of palmitate loading, endoplasmic reticulum (ER) stress, and the hypolipidemic agent fenofibrate on adiponectin receptor R2 (AdipoR2) levels and AMP-activated protein kinase (AMPK) in human hepatoma Huh7 cells and in Huh.8 cells, a model of hepatitis C-induced steatosis. Palmitate treatment reduced AdipoR2 protein and basal AMPK phosphorylation in Huh7 cells. Fenofibrate treatment preserved AdipoR2 and phosphorylated AMPK (pAMPK) levels in palmitate-treated cells accompanied by reduced triglyceride (TG) accumulation and less activation of ER stress markers CCAAT/enhancer binding (C/EBPbeta) and eukaryotic translation initiation factor 2 alpha. ER stress agents thapsigargin and tunicamycin suppressed AdipoR2 and pAMPK levels in Huh7 cells, while fenofibrate and the chemical chaperone 4-phenylbutyrate (PBA) prevented these changes. AdipoR2 levels were lower in Huh.8 cells and fenofibrate treatment increased AdipoR2 while reducing activation of c-Jun N-terminal kinase and C/EBPbeta expression without changing TG levels. Taken together, these results suggest that fatty acids and ER stress reduce AdipoR2 protein and pAMPK levels, while fenofibrate and PBA might be important therapeutic agents to correct lipid- and ER stress-mediated loss of AdipoR2 and pAMPK associated with nonalcoholic steatohepatitis.

Skeletal muscle-specific deletion of lipoprotein lipase enhances insulin signaling in skeletal muscle but causes insulin resistance in liver and other tissues

OBJECTIVE

Skeletal muscle-specific LPL knockout mouse (SMLPL(-/-)) were created to study the systemic impact of reduced lipoprotein lipid delivery in skeletal muscle on insulin sensitivity, body weight, and composition.

RESEARCH DESIGN AND METHODS

Tissue-specific insulin sensitivity was assessed using a hyperinsulinemic-euglycemic clamp and 2-deoxyglucose uptake. Gene expression and insulin-signaling molecules were compared in skeletal muscle and liver of SMLPL(-/-) and control mice.

RESULTS

Nine-week-old SMLPL(-/-) mice showed no differences in body weight, fat mass, or whole-body insulin sensitivity, but older SMLPL(-/-) mice had greater weight gain and whole-body insulin resistance. High-fat diet feeding accelerated the development of obesity. In young SMLPL(-/-) mice, insulin-stimulated glucose uptake was increased 58% in the skeletal muscle, but was reduced in white adipose tissue (WAT) and heart. Insulin action was also diminished in liver: 40% suppression of hepatic glucose production in SMLPL(-/-) vs. 90% in control mice. Skeletal muscle triglyceride was 38% lower, and insulin-stimulated phosphorylated Akt (Ser473) was twofold greater in SMLPL(-/-) mice without changes in IRS-1 tyrosine phosphorylation and phosphatidylinositol 3-kinase activity. Hepatic triglyceride and liver X receptor, carbohydrate response element-binding protein, and PEPCK mRNAs were unaffected in SMLPL(-/-) mice, but peroxisome proliferator-activated receptor (PPAR)-gamma coactivator-1alpha and interleukin-1beta mRNAs were higher, and stearoyl-coenzyme A desaturase-1 and PPARgamma mRNAs were reduced.

CONCLUSIONS

LPL deletion in skeletal muscle reduces lipid storage and increases insulin signaling in skeletal muscle without changes in body composition. Moreover, lack of LPL in skeletal muscle results in insulin resistance in other key metabolic tissues and ultimately leads to obesity and systemic insulin resistance.

CCAAT/enhancing binding protein beta deletion in mice attenuates inflammation, endoplasmic reticulum stress, and lipid accumulation in diet-induced nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, inflammation, and oxidative stress. To investigate whether the transcription factor CCAAT/Enhancer binding protein (C/EBPbeta) is involved in the development of NASH, C57BL/6J wild-type (WT) or C/EBPbeta knockout (C/EBPbeta-/-) mice were fed either a methionine and choline deficient (MCD) diet or standard chow. These WT mice fed a MCD diet for 4 weeks showed a 2- to 3-fold increase in liver C/EBPbeta messenger RNA and protein, along with increased expression of lipogenic genes peroxisome proliferators-activated receptor gamma and Fas. WT mice also showed increased levels of the endoplasmic reticulum stress pathway proteins phosphorylated eukaryotic translation initiation factor alpha, phosphorylated pancreatic endoplasmic reticulum kinase, and C/EBP homologous protein, along with inflammatory markers phosphorylated nuclear factor kappaB and phosphorylated C-jun N-terminal kinase compared to chow-fed controls. Cytochrome P450 2E1 protein and acetyl coA oxidase messenger RNA involved in hepatic lipid peroxidation were also markedly increased in WT MCD diet-fed group. In contrast, C/EBPbeta-/- mice fed a MCD diet showed a 60% reduction in hepatic triglyceride accumulation and decreased liver injury as evidenced by reduced serum alanine aminotransferase and aspartate aminotransferase levels, and by H&E staining. Immunoblots and real-time qPCR data revealed a significant reduction in expression of stress related proteins and lipogenic genes in MCD diet-fed C/EBPbeta-/- mice. Furthermore, circulating TNFalpha and expression of acute phase response proteins CRP and SAP were significantly lower in C/EBPbeta-/- mice compared to WT mice. Conversely, C/EBPbeta over-expression in livers of WT mice increased steatosis, nuclear factor-kappaB, and endoplasmic reticulum stress, similar to MCD diet-fed mice.

CONCLUSION

Taken together, these data suggest a previously unappreciated molecular link between C/EBPbeta, hepatic steatosis and inflammation and suggest that increased C/EBPbeta expression may be an important factor underlying events leading to NASH.

CCAAT/enhancer-binding protein beta deletion reduces adiposity, hepatic steatosis, and diabetes in Lepr(db/db) mice

CCAAT/enhancer-binding protein beta (C/EBPbeta) plays a key role in initiation of adipogenesis in adipose tissue and gluconeogenesis in liver; however, the role of C/EBPbeta in hepatic lipogenesis remains undefined. Here we show that C/EBPbeta inactivation in Lepr(db/db) mice attenuates obesity, fatty liver, and diabetes. In addition to impaired adipogenesis, livers from C/EBPbeta(-/-) x Lepr(db/db) mice had dramatically decreased triglyceride content and reduced lipogenic enzyme activity. C/EBPbeta deletion in Lepr(db/db) mice down-regulated peroxisome proliferator-activated receptor gamma2 (PPARgamma2) and stearoyl-CoA desaturase-1 and up-regulated PPARalpha independent of SREBP1c. Conversely, C/EBPbeta overexpression in wild-type mice increased PPARgamma2 and stearoyl-CoA desaturase-1 mRNA and hepatic triglyceride content. In FAO cells, overexpression of the liver inhibiting form of C/EBPbeta or C/EBPbeta RNA interference attenuated palmitate-induced triglyceride accumulation and reduced PPARgamma2 and triglyceride levels in the liver in vivo. Leptin and the anti-diabetic drug metformin acutely down-regulated C/EBPbeta expression in hepatocytes, whereas fatty acids up-regulate C/EBPbeta expression. These data provide novel evidence linking C/EBPbeta expression to lipogenesis and energy balance with important implications for the treatment of obesity and fatty liver disease.

Selection of RNA amide synthases

BACKGROUND

It is generally accepted that, during evolution, replicating RNA molecules emerged from pools of random polynucleotides. This prebiotic RNA world was followed by an era of RNA-mediated catalysis of amide-bond formation. RNA would thus have provided the machinery responsible for the assembly of peptides and the beginning of the protein world of today. Naturally occurring ribozymes, which catalyze the cleavage or ligation of oligonucleotide phosphodiester bonds, support the idea that RNA could self-replicate. But was RNA constrained to this path and were RNA-acylated carriers required before RNA could catalyze the formation of amide bonds?

RESULTS

We have isolated RNA catalysts that are capable of mediating amide-bond synthesis without the need for specifically designed templates to align the substrates, and we have kinetically characterized these catalysts. The rate enhancement observed for these RNA amide synthases exceeds the noncatalyzed amidation rate by a factor of approximately 10(4). In addition, Cu2+ ions caused a change in the affinity of RNA for the substrate rather than being directly involved in amide-bond formation.

CONCLUSIONS

The discovery of these new amide synthases shows how functionally modified nucleic acids can facilitate covalent-bond formation without templating. Previously unforeseen RNA-evolution pathways can, therefore, be considered; for example, to guide amide-bond formation, en route to the protein world, it appears that substrate-binding pockets were formed that are analogous to those of protein enzymes.

Linkage between stature and a region on chromosome 20 and analysis of a candidate gene, bone morphogenetic protein 2

Sib-pair linkage analysis of the quantitative trait, structure, in over 500 Pima Indians indicates that a genetic determinant of governing stature is located on chromosome 20. Analysis of 10 short tandem repeat polymorphisms localized this linkage to a 3.2cM region that includes D20S98 and D20S66. Using all possible sib-pair combinations, linkage was detected to both stature (P = 0.0001) and to leg length (P = 0.001), but not to sitting height. Single-strand conformational polymorphism analysis of exon 3 of the bone morphogenetic protein 2 (BMP2) gene, a candidate gene in this region, in genomic DNA of 20 of the tallest and 20 of the shortest individuals did not show any consistent differences associated with leg length or height. Sequence analysis of the region encoding the mature protein revealed a single nucleotide substitution, a T to G transversion, not detected by single-strand conformational polymorphism (SSCP) analysis. This transversion results in a conservative amino acid substitution of glycine for valine at codon 80 of BMP2. The frequency of this allele was 0.23 in the sample. No significant differences in height were noted in persons carrying either allele. This indicates that this structural alteration is the mature BMP2 protein does not contribute to the differences in stature observed in the Pima Indians, nor is this structural change in the mature protein likely to be responsible for the linkage observed with stature on chromosome 20.

Evidence for linkage between a region on chromosome 1p and the acute insulin response in Pima Indians

A low acute insulin response (AIR) is a predictor of non-insulin-dependent diabetes mellitus (NIDDM) in insulin-resistant Pima Indians. We have initiated a search for regions of the genome linked with the AIR using sib-pair linkage analysis as a first step in identifying genes that are determinants of this phenotype. Eighteen short tandem-repeat polymorphisms from chromosome 1 were genotyped in over 900 Pima Indians and tested for linkage with NIDDM and in a subset of Pima Indians for linkage with AIR. The anonymous DNA marker D1S198 on chromosome 1p was linked with AIR (P = 0.000056) in 175 sib pairs from 60 families, all with normal glucose tolerance, but no linkage was observed between D1S198 and NIDDM (P = 0.44, 996 sib pairs). Additional markers genotyped on chromosome 1 did not show linkage with AIR or NIDDM. This study indicates that a locus on chromosome 1p may be a determinant of the phenotypic variation seen in the AIR.

Variability of the pancreatic islet beta cell/liver (GLUT 2) glucose transporter gene in NIDDM patients

The purpose of these experiments was to test the hypothesis that impaired glucose-stimulated insulin secretion in NIDDM is due to mutations in the islet beta cell/liver glucose transporter (GLUT 2) gene. Using oligonucleotide primers flanking each of the 11 exons, the structural portion of the gene was studied by PCR-SSCP analysis. DNA from African-American females (n = 48), who had gestational diabetes but developed overt NIDDM after delivery, was studied. Each SSCP variant was sequenced directly from genomic DNA. Two amino acid substitutions from the previously reported sequence were found, one in exon 3 and the other in exon 4B. Four additional silent mutations in the coding region, and six intron mutations outside the splice junction consensus sequences, were also identified. The mutation GTC x ATC in exon 4B substituted Val197 to Ile197. This amino acid substitution was found in only one NIDDM patient in a single allele, and was not found in 52 control subjects. This residue exists in the fifth membrane spanning domain, and Val at this position is conserved in mouse and rat GLUT 2, and human GLUT 1 to GLUT 4. The other codon change in exon 3, ACT x ATT, substituted Thr110 to Ile110 in the second membrane spanning domain. To determine the frequency of this non-conservative amino acid substitution, a PCR-LCR assay was developed. This assay was simple and highly specific for detection of this single nucleotide substitution. The allelic frequency of the ATT (Ile110) in NIDDM patients (39.6%, n = 48) and that in controls (47.1%, n = 52) did not differ (p = 0.32, Fisher's exact test).(ABSTRACT TRUNCATED AT 250 WORDS)

Linkage analysis of acute insulin secretion with GLUT2 and glucokinase in Pima Indians and the identification of a missense mutation in GLUT2

The acute insulin response (AIR), a measure of pancreatic beta-cell function, aggregates in families and is a predictor for the development of non-insulin-dependent diabetes mellitus (NIDDM) in insulin-resistant Pima Indians. To assess the genetic components of AIR and NIDDM, polymorphic dinucleotide repeat regions in two candidate genes, the liver/islet glucose transporter gene (GLUT2) and the glucokinase gene, were evaluated. Sib-pair linkage analyses were performed to determine if linkage exists between these marker loci and measurements of AIR and NIDDM. No linkage was found between glucokinase and either AIR or NIDDM. Robust sib-pair linkage analyses suggest linkage between GLUT2 and acute insulin response (P = 0.04), but no linkage was observed with NIDDM. The coding region of the GLUT2 gene was screened for mutations using polymerase chain reaction-single-strand conformation polymorphism analysis. A single base change was identified in exon 3 in approximately 5% of the study population, and it constitutes the first reported mutation in the human GLUT2 gene. This base change resulted in an amino acid substitution (Thr110-->Ile110) in the second membrane-spanning region of the GLUT2 protein. No significant association was noted between AIR and the presence or absence of the mutation. Thus, this mutation in GLUT2 is unlikely the cause of a low AIR in Pima Indians.