Feeding pregnant rats a low-protein diet alters the hepatic expression of SREBP-1c in their offspring via a glucocorticoid-related mechanism

Low Protein Programming Causes Increased Mitochondrial Fusion and Decreased Oxygen Consumption in the Hepatocytes of Female Rats

The liver is one of the major organs involved in the regulation of glucose and lipid homeostasis. The effectiveness of metabolic activity in hepatocytes is determined by the quality and quantity of its mitochondria. Mitochondrial function is complex, and they act via various dynamic networks, which rapidly adapt to changes in the cellular milieu. Our present study aims to investigate the effects of low protein programming on the structure and function of mitochondria in the hepatocytes of adult females. Pregnant rats were fed with a control or isocaloric low-protein diet from gestational day 4 until delivery. A normal laboratory chow was given to all dams after delivery and to pups after weaning. The rats were euthanized at 4 months of age and the livers were collected from female offspring for investigating the mitochondrial structure, mtDNA copy number, mRNA, and proteins expression of genes associated with mitochondrial function. Primary hepatocytes were isolated and used for the analysis of the mitochondrial bioenergetics profiles. The mitochondrial ultrastructure showed that the in utero low-protein diet exposure led to increased mitochondrial fusion. Accordingly, there was an increase in the mRNA and protein levels of the mitochondrial fusion gene Opa1 and mitochondrial biogenesis genes Pgc1a and Essra, but Fis1, a fission gene, was downregulated. Low protein programming also impaired the mitochondrial function of the hepatocytes with a decrease in basal respiration ATP-linked respiration and proton leak. In summary, the present study suggests that the hepatic mitochondrial dysfunction induced by an in utero low protein diet might be a potential mechanism linking glucose intolerance and insulin resistance in adult offspring.

Maternal low protein diet and fetal programming of lean type 2 diabetes

Maternal nutrition is found to be the key factor that determines fetal health in utero and metabolic health during adulthood. Metabolic diseases have been primarily attributed to impaired maternal nutrition during pregnancy, and impaired nutrition has been an immense issue across the globe. In recent years, type 2 diabetes (T2D) has reached epidemic proportion and is a severe public health problem in many countries. Although plenty of research has already been conducted to tackle T2D which is associated with obesity, little is known regarding the etiology and pathophysiology of lean T2D, a variant of T2D. Recent studies have focused on the effects of epigenetic variation on the contribution of in utero origins of lean T2D, although other mechanisms might also contribute to the pathology. Observational studies in humans and experiments in animals strongly suggest an association between maternal low protein diet and lean T2D phenotype. In addition, clear sex-specific disease prevalence was observed in different studies. Consequently, more research is essential for the understanding of the etiology and pathophysiology of lean T2D, which might help to develop better disease prevention and treatment strategies. This review examines the role of protein insufficiency in the maternal diet as the central driver of the developmental programming of lean T2D.

Panel of suitable reference genes and its gender differences of fetal rat liver under physiological conditions and exposure to dexamethasone during pregnancy

The panel of suitable reference genes in the fetal liver have not been reported. In this study, five commonly used reference genes (GAPDH, β-actin, Rn18 s, Rpl13a, and Rps29) were firstly selected as candidates. Bestkeeper, GeNorm, and NormFinder software were then used to screen out the panel of suitable reference genes of male and female fetal rat liver under physiological and prenatal dexamethasone exposure (PDE) conditions. Finally, we verified the reliability of the screened panel of reference genes by standardizing sterol regulatory element binding protein 1c (SREBP1c) expression with different reference genes. The results showed that GAPDH + Rn18 s and GAPDH + Rpl13a were respectively the panel of suitable reference genes in male and female rat fetal liver under the physiological model, while Rn18 s + Rps29 and GAPDH + Rn18 s were respectively under the PDE model. The results showed that different reference genes affected the statistical results of SREBP1c expression, and the screened panel of suitable reference genes under the PDE model had smaller intragroup differences, when compared with other reference genes under physiological and PDE models. In conclusion, we screened and determined that the panel of suitable reference genes were GAPDH + Rn18 s and Rn18 s + Rps29 in the male rat fetal liver under physiological and PDE models, while they were GAPDH + Rpl13a and GAPDH + Rn18 s in the females, and confirmed that the selection of the panel of suitable reference genes in the fetal liver had gender differences and pathological model specificity.

Early life famine exposure, adulthood obesity patterns and the risk of nonalcoholic fatty liver disease

BACKGROUND

Early life exposure to famine and adulthood obesity increased the risk of nonalcoholic fatty liver disease (NAFLD) in adulthood. However, the joint effects on adulthood NAFLD risk are not clear.

AIM

This study aimed to explore the joint effects of famine exposure and adulthood obesity on NAFLD risk in later life.

METHODS

We included 7632 subjects aged ≥40 years from a community-dwelling population. Participants were divided into 4 famine exposure groups according to the birth year, including nonexposed (1963-1974), fetal-exposed (1959-1962), childhood-exposed (1949-1958) and adolescent-exposed (1941-1948). General obesity was assessed by body mass index (BMI: overweight ≥24.0 kg/m² , obesity ≥28.0 kg/m² ) and abdominal obesity assessed by waist-to-hip ratio (WHR, men/women: moderate ≥0.90/0.85, high ≥0.95/0.90).

RESULTS

Compared with nonexposed, fetal- and childhood-exposed participants show an increased risk of NAFLD with multivariable-adjusted odds ratio (OR) and 95% confidence interval (CI) of 1.28 (1.02-1.61) and 1.40 (1.04-1.88) respectively. After further adjusting BMI and WHR, the increased risk was observed only in childhood-exposed participants (OR = 1.46, 95% CI = 1.04-2.05). Significant interaction between famine exposure and general obesity on the risk of NAFLD was observed in women (P for interaction = .02). No significant interactions were detected between famine exposure and abdominal obesity (all P for interaction >.05). Compared with normal-BMI and -WHR participants, those with both general and abdominal obesity in adulthood had 20.74 (95% CI: 12.00-35.96), 14.45 (8.76-23.86), 23.02 (16.28-32.57) and 13.04 (8.30-20.48)-fold higher risk in nonexposed, fetal-, childhood- and adolescent-exposed groups respectively.

CONCLUSION

Coexistence of early life famine exposure and adulthood obesity was associated with a higher risk of NAFLD.

Perinatal programming of metabolic diseases: The role of glucocorticoids

The worldwide increase in metabolic diseases has urged the scientific community to improve our understanding about the mechanisms underlying its cause and effects. A well supported area of studies had related maternal stress with early programming to the later metabolic diseases. Mechanisms upon origins of metabolic disturbances are not yet fully understood, even though stressful factors rising glucocorticoids have been put out as pivotal trigger by programming metabolic diseases as long-term consequence. Considering energy balance and glucose homeostasis, by producing and/or sensing regulator signals, hypothalamus-pituitary-adrenal axis and endocrine pancreas are directly affected by glucocorticoids excess. We focus on the evidences reporting the role of increased glucocorticoids due to perinatal insults on the physiological systems involved in the metabolic homeostasis and in the target organs such as endocrine pancreas, white adipose tissue and blood vessels. Besides, we review some mechanisms underlining the malprogramming of type 2 diabetes, obesity and hypertension. Studies on this field are currently ongoing and even there is a good understanding regarding the effects of glucocorticoids addressing metabolic diseases, few is known about the relationship between maternal insults rising glucocorticoids to pups' metabolic disturbances, a thorough understanding about that may provide pivotal clinical clues regarding those disorders.

Transcription profiling in the liver of undernourished male rat offspring reveals altered lipid metabolism pathways and predisposition to hepatic steatosis

Clinical and animal studies have reported an association between low birth weight and the development of nonalcoholic fatty liver disease (NAFLD) in offspring. Using a model of prenatal maternal 70% food restriction diet (FR30) in the rat, we previously showed that maternal undernutrition predisposes offspring to altered lipid metabolism in adipose tissue, especially on a high-fat (HF) diet. Here, using microarray-based expression profiling combined with metabolic, endocrine, biochemical, histological, and lipidomic approaches, we assessed whether FR30 procedure sensitizes adult male offspring to impaired lipid metabolism in the liver. No obvious differences were noted in the concentrations of triglycerides, cholesterol, and bile acids in the liver of 4-mo-old FR30 rats whichever postweaning diet was used. However, several clues suggest that offspring's lipid metabolism and steatosis are modified by maternal undernutrition. First, lipid composition was changed (i.e., higher total saturated fatty acids and lower elaidic acid) in the liver, whereas larger triglyceride droplets were observed in hepatocytes of undernourished rats. Second, FR30 offspring exhibited long-term impact on hepatic gene expression and lipid metabolism pathways on a chow diet. Although the transcriptome profile was globally modified by maternal undernutrition, cholesterol and bile acid biosynthesis pathways appear to be key targets, indicating that FR30 animals were predisposed to impaired hepatic cholesterol metabolism. Third, the FR30 protocol markedly modifies hepatic gene transcription profiles in undernourished offspring in response to postweaning HF. Overall, FR30 offspring may exhibit impaired metabolic flexibility, which does not enable them to properly cope with postweaning nutritional challenges influencing the development of nonalcoholic fatty liver.

Effects of glucocorticoids on lipid metabolism and AMPK in broiler chickens' liver

Adenosine monophosphate-activated protein kinase (AMPK) plays a pivotal role in the regulation of carbohydrate, lipid, and protein metabolism in animals. In this study, we examined whether any cross talk exists between glucocorticoids and AMPK in the regulation of the liver bile acid biosynthesis pathway. Dexamethasone treatment decreased the growth performance of broiler chickens. The liver mRNA levels of fatty acid transport protein (FATP-1), farnesoid X receptor (FXR), AMPK alpha 1 subunit (AMPKα1), and glucocorticoid receptor were significantly upregulated in DEX-treated broilers; the gene expression of liver cholesterol 7 alpha-hydroxylase (CYP7A1) was significantly downregulated. The protein level of liver CYP7A1 was significantly decreased by DEX treatment at both 24 and 72 h, while the protein level of p-AMPK/ t-AMPK stayed unchanged. In the in vitro cultured hepatocytes, compound C pretreatment blocked the increase in CYP7A1 protein level by DEX and significantly suppressed FATP-1, SREBP-1c, FXR, and CYP7A1 gene expression stimulated by DEX. Compound C treatment significantly reduces the protein level of p-AMPK, and the combination of compound C and DEX significantly reduces the protein level of t-AMPK. Thus, glucocorticoids affected liver AMPK and the bile acid synthesis signal pathway, and AMPK might be involved in the glucocorticoid effect of liver bile acid synthesis.

Oxytocin, a main breastfeeding hormone, prevents hypertension acquired in utero: A therapeutics preview

Hypertension is a major risk factor for ischemic heart disease and stroke, leading causes of morbidity and death worldwide. Intrauterine growth restriction (IUGR), caused by an excess of glucocorticoid exposure to the fetus, produces an imbalance in oxidative stress altering many biochemical and epigenetic gene transcription processes exposing the fetus and neonate to the 'thrifty' phenotype and pervasive polymorphisms appearance damaging health, cognitive, and behavioral processes in later life. OT is a major regulator of oxidative stress radicals that plays a major role in neonatal maturation of the central nervous system and many peripheral tissues expressing oxytocin/oxytocin-receptor (OT/OTR) system in the early postnatal period. OT and OTR are damaged by IUGR and early stress. This review highlights the fact that hypertension is likely to be a legacy of preterm birth due to IUGR and failure to meet nutritional needs in early infancy when fed formula instead of breastfeeding or human milk.

Cold Exposure Partially Corrects Disturbances in Lipid Metabolism in a Male Mouse Model of Glucocorticoid Excess

High glucocorticoid concentrations are accompanied by metabolic side effects such as high plasma triglyceride (TG) concentrations. Liver, brown adipose tissue (BAT) and white adipose tissue are important regulators of plasma TG. Exposure to 4°C reduces plasma TG concentrations, and we therefore aimed to study the interaction between glucocorticoid excess and 24 hours of exposure to 4°C on lipid metabolism. For this, mice were implanted with 50-mg corticosterone or control pellets and housed for 24 hours at 23°C or 4°C 1 week later, after which various aspects of TG metabolism in liver, BAT, and white adipose tissue were studied. Corticosterone treatment resulted in a 3.8-fold increase of plasma TG concentrations. Increased TG was normalized by cold exposure, an effect still present 24 hours after cold exposure. Corticosterone treatment increased hepatic TG content by 3.5-fold and provoked secretion of large, TG-rich very low density lipoprotein particles. Cold exposure reduced very low density lipoprotein-TG secretion by approximately 50%. Corticosterone strongly decreased BAT activity: BAT weight increased by 3.5-fold, whereas uncoupling protein 1 (Ucp1) mRNA expression and Ucp1 protein content of BAT were reduced by 75% and 60%, respectively. Cold exposure partially normalized these parameters of BAT activity. The uptake of TG by BAT was not affected by corticosterone treatment but was increased 4.5-fold upon cold exposure. In conclusion, cold exposure normalizes corticosterone-induced hypertriglyceridemia, at least partly via activating BAT.

Programming of Essential Hypertension: What Pediatric Cardiologists Need to Know

Hypertension is recognized as one of the major contributing factors to cardiovascular disease, but its etiology remains incompletely understood. Known genetic and environmental influences can only explain a small part of the variability in cardiovascular disease risk. The missing heritability is currently one of the most important challenges in blood pressure and hypertension genetics. Recently, some promising approaches have emerged that move beyond the DNA sequence and focus on identification of blood pressure genes regulated by epigenetic mechanisms such as DNA methylation, histone modification and microRNAs. This review summarizes information on gene-environmental interactions that lead toward the developmental programming of hypertension with specific reference to epigenetics and provides pediatricians and pediatric cardiologists with a more complete understanding of its pathogenesis.

Developmental Programming of Nonalcoholic Fatty Liver Disease: The Effect of Early Life Nutrition on Susceptibility and Disease Severity in Later Life

Nonalcoholic fatty liver disease (NAFLD) is fast becoming the most common liver disease globally and parallels rising obesity rates. The developmental origins of health and disease hypothesis have linked alterations in the early life environment to an increased risk of metabolic disorders in later life. Altered early life nutrition, in addition to increasing risk for the development of obesity, type 2 diabetes, and cardiovascular disease in offspring, is now associated with an increased risk for the development of NAFLD. This review summarizes emerging research on the developmental programming of NAFLD by both maternal obesity and undernutrition with a particular focus on the possible mechanisms underlying the development of hepatic dysfunction and potential strategies for intervention.

Maternal high-protein diet during pregnancy, but not during suckling, induced altered expression of an increasing number of hepatic genes in adult mouse offspring

PURPOSE

Indirect effects of a high-protein maternal diet are not well understood. In this study, we analyzed short-term and sustainable effects of a prenatal versus early postnatal maternal high-protein diet on growth and hepatic gene expression in mouse offspring.

METHODS

Dams were exposed to an isoenergetic high-protein (HP, 40 % w/w) diet during pregnancy or lactation. Growth and hepatic expression profiles of male offspring were evaluated directly after weaning and 150 days after birth. Offspring from two dietary groups, high-protein diet during pregnancy and control diet during lactation (HPC), and control diet during pregnancy and high-protein diet during lactation (CHP), were compared with offspring (CC) from control-fed dams.

RESULTS

Maternal CHP treatment was associated with sustained offspring growth retardation, but decreased numbers of affected hepatic genes in adults compared to weanlings. In contrast, offspring of the HPC group did not show persistent effects on growth parameters, but the number of affected hepatic genes was even increased at adult age. In both dietary groups, however, only a small subset of genes was affected in weanlings as well as in adults.

CONCLUSIONS

We conclude that (1) prenatal and early postnatal maternal HP diet caused persistent, but (2) different effects and partially complementary trends on growth characteristics and on the hepatic transcriptome and associated pathways and that (3) only a small number of genes and associated upstream regulators might be involved in passing early diet-induced imprints to adulthood.

Obesity-related hypertension: possible pathophysiological mechanisms

Hypertension is one of the major risk factors of cardiovascular diseases, but despite a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. The same is true for obesity, which is recognized as a major global epidemic health problem nowadays. Obesity is associated with an increasing prevalence of the metabolic syndrome, a cluster of risk factors including hypertension, abdominal obesity, dyslipidemia, and hyperglycemia. Epidemiological studies have shown that excess weight gain predicts future development of hypertension, and the relationship between BMI and blood pressure (BP) appears to be almost linear in different populations. There is no doubt that obesity-related hypertension is a multifactorial and polygenic trait, and multiple potential pathogenetic mechanisms probably contribute to the development of higher BP in obese humans. These include hyperinsulinemia, activation of the renin-angiotensin-aldosterone system, sympathetic nervous system stimulation, abnormal levels of certain adipokines such as leptin, or cytokines acting at the vascular endothelial level. Moreover, some genetic and epigenetic mechanisms are also in play. Although the full manifestation of both hypertension and obesity occurs predominantly in adulthood, their roots can be traced back to early ontogeny. The detailed knowledge of alterations occurring in the organism of experimental animals during particular critical periods (developmental windows) could help to solve this phenomenon in humans and might facilitate the age-specific prevention of human obesity-related hypertension. In addition, better understanding of particular pathophysiological mechanisms might be useful in so-called personalized medicine.

Genome-wide methylation and gene expression changes in newborn rats following maternal protein restriction and reversal by folic acid

A large body of evidence from human and animal studies demonstrates that the maternal diet during pregnancy can programme physiological and metabolic functions in the developing fetus, effectively determining susceptibility to later disease. The mechanistic basis of such programming is unclear but may involve resetting of epigenetic marks and fetal gene expression. The aim of this study was to evaluate genome-wide DNA methylation and gene expression in the livers of newborn rats exposed to maternal protein restriction. On day one postnatally, there were 618 differentially expressed genes and 1183 differentially methylated regions (FDR 5%). The functional analysis of differentially expressed genes indicated a significant effect on DNA repair/cycle/maintenance functions and of lipid, amino acid metabolism and circadian functions. Enrichment for known biological functions was found to be associated with differentially methylated regions. Moreover, these epigenetically altered regions overlapped genetic loci associated with metabolic and cardiovascular diseases. Both expression changes and DNA methylation changes were largely reversed by supplementing the protein restricted diet with folic acid. Although the epigenetic and gene expression signatures appeared to underpin largely different biological processes, the gene expression profile of DNA methyl transferases was altered, providing a potential link between the two molecular signatures. The data showed that maternal protein restriction is associated with widespread differential gene expression and DNA methylation across the genome, and that folic acid is able to reset both molecular signatures.

Adaptive responses by mouse fetus to a maternal HLE diet by downregulating SREBP1: a microarray- and bio-analytic-based study

Maternal diet has long been recognized as a significant factor affecting offspring development and health, but the target genes affected by a maternal high-lipid diet are currently unknown. In this study, the gene expression profile of neonatal mouse liver was analyzed using gene chips to identify genes with significant up- or downregulated expression levels due to maternal high-fat diet during gestation. Real-time PCR and Western blotting were used to measure key genes selected using microarray. Serum lipid, glucose, and insulin levels in adult offspring from dams fed with chow or a high-lipid diet were measured using commercial kits. Results indicate that the expression of genes involved in cholesterol and fatty acid synthesis were significantly inhibited, while the expression of genes involved in glycolysis were significantly decreased by maternal high-lipid diet during gestation. SREBP1 might be the key gene regulating genes involved in fatty acid, glucose, and cholesterol metabolism in response to a maternal high-fat diet.

Critical developmental periods in the pathogenesis of hypertension

Hypertension is one of the major risk factor of cardiovascular diseases, but after a century of clinical and basic research, the discrete etiology of this disease is still not fully understood. One reason is that blood pressure is a quantitative trait with multifactorial determination. Numerous genes, environmental factors as well as epigenetic factors should be considered. There is no doubt that although the full manifestation of hypertension and other cardiovascular diseases usually occurs predominantly in adulthood and/or senescence, the roots can be traced back to early ontogeny. The detailed knowledge of the ontogenetic changes occurring in the cardiovascular system of experimental animals during particular critical periods (developmental windows) could help to solve this problem in humans and might facilitate the age-specific prevention of human hypertension. We thus believe that this approach might contribute to the reduction of cardiovascular morbidity among susceptible individuals in the future.

11β-hydroxysteroid dehydrogenase type 1 is expressed in human sebaceous glands and regulates glucocorticoid-induced lipid synthesis and toll-like receptor 2 expression in SZ95 sebocytes

BACKGROUND

Glucocorticoids (GCs) affect the pathophysiology of sebaceous glands, causing development or exacerbation of acne. The availability of GCs is regulated by isoenzymes of 11β-hydroxysteroid dehydrogenase (11βHSD) at tissue-specific levels. 11βHSD type 1 (HSD11β1) is a reductase, catalysing the conversion of cortisone to active cortisol, and is highly expressed in liver and adipose tissue. Recently, HSD11β1 was observed in human skin in keratinocytes and fibroblasts.

OBJECTIVES

To investigate the expression of HSD11β1 in sebaceous glands of normal and acne-involved skin, and to examine the role of HSD11β1 in GC-induced lipid synthesis and toll-like receptor 2 (TLR2) expression in sebocytes.

METHODS

  Expression of HSD11β1 was examined by immunohistochemistry in acne lesional skin and normal skin of healthy volunteers. The cultured SZ95 sebocytes were treated with dexamethasone, and the lipid synthesis and mRNA levels of sterol regulatory element binding protein 1 (SREBP-1) and TLR2 were determined. Use of an HSD11β1 inhibitor and the small interference RNA (siRNA) approach were used to investigate the role of HSD11β1 on the GC regulation of sebocyte functions.

RESULTS

  HSD11β1 was expressed in human sebaceous glands and upregulated in acne lesional skin. HSD11β1 mRNA was enhanced by dexamethasone and cytokines in SZ95 sebocytes. Dexamethasone enhanced lipid synthesis, partially through the transcriptional induction of SREBP-1, and also by increasing TLR2 mRNA levels. Inhibition of HSD11β1 by PF-915275 or siRNA significantly inhibited the GC-induced lipid synthesis and the mRNA expression of SREBP-1 and TLR2.

CONCLUSIONS

  Our results indicate that HSD11β1 plays a key role in the modulation of GC action on sebocytes, including sebum production and TLR2-mediated inflammation, thereby influencing the pathogenesis of acne.

Corticosterone regulation of ovarian follicular development is dependent on the energy status of laying hens

Glucocorticoids participate in the arousal of stress responses and trigger physiological adjustments that shift energy away from reproduction toward survival. Ovarian follicular development in avians is accompanied by the supply of yolk precursors, which are mainly synthesized in the liver. Therefore, we hypothesized energy status and hepatic lipogenesis are involved in the induction of reproductive disorders by glucocorticoids in laying hens. The results show that corticosterone decreased the laying performance by suppressing follicular development in energy-deficit state, rather than in energy-sufficient state. In corticosterone-treated hens, the suppressed follicular development was associated with the reduced availability of yolk precursor, indicated by the plasma concentration of VLDL and vitellogenin and the decreased proportion of yolk-targeted VLDL (VLDLy). Corticosterone decreased the expression of apolipoprotein B and apolipoprotein VLDL-II in the liver. A drop in VLDL receptor content and an increase in the expression of tight junction proteins occludin and claudin1 were also observed in hierarchical follicles. The results suggest corticosterone-suppressed follicular development is energy dependent. The decreased apolipoprotein synthesis and VLDLy secretion by liver are responsible for the decreased availability of circulating yolk precursor, and the upregulation of occludin and claudin expression further prevents yolk deposition into oocytes.

A methyl-deficient diet fed to rats during the pre- and peri-conception periods of development modifies the hepatic proteome in the adult offspring

A methyl-deficient diet (MD) lacking folic acid and the associated methyl donors choline and methionine, fed to the laboratory rat during the periods of oocyte and embryo development, has been shown to programme glucose metabolism in the offspring. The hepatic proteome of the male offspring of female rats fed MD diets for 3 weeks prior to mating and for the first 5 days of gestation has been examined by 2-dimensional gel electrophoresis. Three groups of differentially abundant proteins associated with energy metabolism, amino acid metabolism and antioxidant defence were identified in the soluble proteins extracted from the liver from the MD offspring at both 6 and 12 months of age. Altered mitochondrial activity in other programming models leads to a similar pattern of differential protein abundance. Two of the differentially abundant proteins were identified as GAPDH and PGK-1 by mass spectrometry. Western blotting showed that there were multiple isoforms of both proteins with similar molecular weights but different isoelectric points. The differentially abundant spots reduced in the MD offspring corresponded to minor isoforms of GAPDH and PGK-1. The levels of PPAR-alpha, SREBP and glucocorticoid receptor mRNAs associated with other models of prenatal programming were unchanged in the MD offspring. The data suggest that a diet deficient in folic acid and associated methyl donors fed during the peri-conception and early preimplantation periods of mammalian development affects mitochondrial function in the offspring and that the posttranslational modification of proteins may be important.

Dexamethasone-induced hepatic lipogenesis is insulin dependent in chickens (Gallus gallus domesticus)

Hepatic lipogenesis-induced de novo by glucocorticoids (GCs) is associated with the development of obesity and diabetes mellitus. The interaction of GCs and insulin in the regulation of hepatic lipogenesis remains unclear. The effect of exogenous GC administration on hepatic lipogenesis and fat deposition was studied in broiler chickens (Gallus gallus domesticus), and the role of insulin in the effect of GCs on hepatic lipogenesis was evaluated. Dexamethasone (DEX, 2 mg/kg body mass (BM)) administration for 3-d resulted in BM loss and increased liver and cervical adipose tissue mass compared to control and pair-fed counterparts. DEX treatment significantly (P < 0.05) increased plasma level of insulin in either the fed or fasting state, whereas plasma glucose level was only increased in the fed state. In fasted chickens, DEX treatment significantly (P < 0.01) upregulated the hepatic mRNA levels of acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS). In the fed state, the mRNA levels of ACC and FAS were not significantly influenced by DEX treatment, nor was FAS activity. In cultured primary hepatocytes, combined DEX and insulin significantly upregulated the transcription of the genes for FAS (1.34-fold) and malic enzyme (1.72-fold). By contrast, the expression of sterol response element-binding protein-1 (SREBP-1) was significantly upregulated by insulin (1.67-fold) regardless of DEX. In abdominal adipose tissue, DEX treatment had no significant (P>0.05) effect on the activities and transcription of FAS. The expressions of lipoprotein lipase and peroxisome proliferator-activated receptor-γ were not significantly (P>0.05) affected by DEX treatment in either the fasting or fed state. The results indicate that DEX increased hepatic de novo lipogenesis via the increased activity and expression of lipogenic enzymes. Insulin-activated gene expression for SREBP-1 is suggested to be involved in stress-augmented hepatic lipogenesis.