Hepatic Adaptation Research Articles

Gluconeogenic Signals Regulate Iron Homeostasis via Hepcidin in Mice

Background & AimsHepatic gluconeogenesis provides fuel during starvation, and is abnormally induced in obese individuals or those with diabetes. Common metabolic disorders associated with active gluconeogenesis and insulin resistance (obesity, metabolic syndrome, diabetes, and nonalcoholic fatty liver disease) have been associated with alterations in iron homeostasis that disrupt insulin sensitivity and promote disease progression. We investigated whether gluconeogenic signals directly control Hepcidin, an important regulator of iron homeostasis, in starving mice (a model of persistently activated gluconeogenesis and insulin resistance).MethodsWe investigated hepatic regulation of Hepcidin expression in C57BL/6Crl, 129S2/SvPas, BALB/c, and Creb3l3–/– null mice. Mice were fed a standard, iron-balanced chow diet or an iron-deficient diet for 9 days before death, or for 7 days before a 24- to 48-hour starvation period; liver and spleen tissues then were collected and analyzed by quantitative reverse-transcription polymerase chain reaction and immunoblot analyses. Serum levels of iron, hemoglobin, Hepcidin, and glucose also were measured. We analyzed human hepatoma (HepG2) cells and mouse primary hepatocytes to study transcriptional control of Hamp (the gene that encodes Hepcidin) in response to gluconeogenic stimuli using small interfering RNA, luciferase promoter, and chromatin immunoprecipitation analyses.ResultsStarvation led to increased transcription of the gene that encodes phosphoenolpyruvate carboxykinase 1 (a protein involved in gluconeogenesis) in livers of mice, increased levels of Hepcidin, and degradation of Ferroportin, compared with nonstarved mice. These changes resulted in hypoferremia and iron retention in liver tissue. Livers of starved mice also had increased levels of Ppargc1a mRNA and Creb3l3 mRNA, which encode a transcriptional co-activator involved in energy metabolism and a liver-specific transcription factor, respectively. Glucagon and a cyclic adenosine monophosphate analog increased promoter activity and transcription of Hamp in cultured liver cells; levels of Hamp were reduced after administration of small interfering RNAs against Ppargc1a and Creb3l3. PPARGC1A and CREB3L3 bound the Hamp promoter to activate its transcription in response to a cyclic adenosine monophosphate analog. Creb3l3–/– mice did not up-regulate Hamp or become hypoferremic during starvation.ConclusionsWe identified a link between glucose and iron homeostasis, showing that Hepcidin is a gluconeogenic sensor in mice during starvation. This response is involved in hepatic metabolic adaptation to increased energy demands; it preserves tissue iron for vital activities during food withdrawal, but can cause excessive iron retention and hypoferremia in disorders with persistently activated gluconeogenesis and insulin resistance.

Combining metformin and aerobic exercise training in the treatment of type 2 diabetes and NAFLD in OLETF rats

Here, we sought to compare the efficacy of combining exercise and metformin for the treatment of type 2 diabetes and nonalcoholic fatty liver disease (NAFLD) in hyperphagic, obese, type 2 diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats (age: 20 wk, hyperglycemic and hyperinsulinemic; n = 10/group) were randomly assigned to sedentary (O-SED), SED plus metformin (O-SED + M; 300 mg·kg(-1)·day(-1)), moderate-intensity exercise training (O-EndEx; 20 m/min, 60 min/day, 5 days/wk treadmill running), or O-EndEx + M groups for 12 wk. Long-Evans Tokushima Otsuka (L-SED) rats served as nonhyperphagic controls. O-SED + M, O-EndEx, and O-EndEx + M were effective in the management of type 2 diabetes, and all three treatments lowered hepatic steatosis and serum markers of liver injury; however, O-EndEx lowered liver triglyceride content and fasting hyperglycemia more than O-SED + M. In addition, exercise elicited greater improvements compared with metformin alone on postchallenge glycemic control, liver diacylglycerol content, hepatic mitochondrial palmitate oxidation, citrate synthase, and β-HAD activities and in the attenuation of markers of hepatic fatty acid uptake and de novo fatty acid synthesis. Surprisingly, combining metformin and aerobic exercise training offered little added benefit to these outcomes, and in fact, metformin actually blunted exercise-induced increases in complete mitochondrial palmitate oxidation and β-HAD activity. In conclusion, aerobic exercise training was more effective than metformin administration in the management of type 2 diabetes and NAFLD outcomes in obese hyperphagic OLETF rats. Combining therapies offered little additional benefit beyond exercise alone, and findings suggest that metformin potentially impairs exercise-induced hepatic mitochondrial adaptations.

Delayed Hepatic Adaptation to Weaning in ACBP−/− Mice Is Caused by Disruption of the Epidermal Barrier

We previously reported that mice deficient in acyl-CoA-binding protein (ACBP) display a delayed metabolic adaptation to weaning. This includes a delayed activation of the hepatic lipogenic gene program, which may result from hepatic accumulation of triacylglycerol and/or cholesteryl esters in the late suckling period. To further investigate the basis for this phenotype, we generated mice deficient in ACBP in hepatocytes (Alb-ACBP(-/-)) and keratinocytes (K14-ACBP(-/-)). Surprisingly, the delayed adaptation to weaning, including hepatic lipid accumulation, is caused by ACBP deficiency in the skin rather than in the liver. Similarly to ACBP(-/-) mice, K14-ACBP(-/-) mice exhibit an increased transepidermal water loss, and we show that the hepatic phenotype is caused specifically by the epidermal barrier defect, which leads to increased lipolysis in white adipose tissue. Our data demonstrate that an imperfect epidermal barrier leads to profound suppression of the hepatic SREBP gene program and lipid accumulation in the liver.

Long‐lasting morphofunctional remodelling of liver parenchyma and stroma after a single exposure to low and moderate doses of cadmium in rats

Frequent exposure to cadmium (Cd) in low doses is common; however, the long-lasting effects of this exposure are still poorly understood. Therefore in this study we have evaluated long-lasting hepatic morphofunctional adaptations in rats exposed to low and moderate doses of Cd. Five experimental groups were tested: control (0.9% saline) and other four receiving single intraperitoneal doses of 0.67, 0.74, 0.86 and 1.1mg of Cd/kg. The animals were killed after eightweeks and the following parameters were analysed: biometrics, oedema, Cd bio-accumulation, collagen, glycogen, lipid droplets, superoxide dismutase (SOD) and catalase (CAT), serum transaminases, liver histopathology and stereology. In all groups exposed to Cd there was significant increase in SOD and CAT activities, ALP levels, proportion of binucleated hepatocytes, nuclei/cytoplasm ratio, macrophages (Kupffer cells) and collagen fibres. In these groups, glycogen accumulation by hepatocytes and the proportion of sinusoidal capillaries were significantly reduced compared with controls. The liver somatic index was increased, and liver oedema was evident in animals exposed to higher dose of Cd. Areas of necrosis were found in animals exposed to the three highest doses. These results indicate that Cd is an extremely toxic bioactive heavy metal, which even at low doses is able to disrupt liver homeostasis. At low and moderate doses, Cd exposure induces morphofunctional pathological remodelling of the hepatic stroma and parenchyma, which remain active after eightweeks. In response to injury, the liver tissue triggers a reactive process by enhancing activation of antioxidant enzymes and collagenogenesis.

Comparison of hepatic adaptation in extreme metabolic phenotypes observed in early lactation dairy cows on-farm

The aim was to study the variation in metabolic responses in early-lactating dairy cows (n=232) on-farm that were pre-selected for a high milk fat content (>45g/l) and a high fat/protein ratio in milk (>1.5) in their previous lactation. Blood was assayed for concentrations of metabolites and hormones. Liver was measured for mRNA abundance of 25 candidate genes encoding enzymes and receptors involved in gluconeogenesis (6), fatty acid β-oxidation (6), fatty acid and triglyceride synthesis (5), cholesterol synthesis (4), ketogenesis (2) and the urea cycle (2). Two groups of cows were formed based on the plasma concentrations of glucose, non-esterified fatty acids (NEFA) and β-hydroxybutyric acid (BHBA) (GRP+, high metabolic load; glucose <3.0mm, NEFA >300μm and BHBA >1.0mm, n=30; GRP-, low metabolic load; glucose >3.0mm, NEFA <300μm and BHBA <1.0mm, n=30). No differences were found between GRP+ and GRP- for the milk yield at 3weeks post-partum, but milk fat content was higher (p<0.01) for GRP+ than for GRP-. In week 8 post-partum, milk yield was higher in GRP+ in relation to GRP- (37.5 vs. 32.5kg/d; p<0.01). GRP+ in relation to GRP- had higher (p<0.001) NEFA and BHBA and lower glucose, insulin, IGF-I, T3 , T4 concentrations (p<0.01). The mRNA abundance of genes related to gluconeogenesis, fatty acid β-oxidation, fatty acid and triglyceride synthesis, cholesterol synthesis and the urea cycle was different in GRP+ compared to GRP- (p<0.05), although gene transcripts related to ketogenesis were similar between GRP+ and GRP-. In conclusion, high metabolic load post-partum in dairy cows on-farm corresponds to differences in the liver in relation to dairy cows with low metabolic load, even though all cows were pre-selected for a high milk fat content and fat/protein ratio in milk in their previous lactation.

Nrf2 Participates in Regulating Maternal Hepatic Adaptations to Pregnancy

Pregnancy induces widespread adaptive responses in maternal organ systems including the liver. The maternal liver exhibits significant growth by increasing the number and size of hepatocytes, by largely unknown mechanisms. Nrf2 mediates cellular defense against oxidative stress and inflammation and also regulates liver regeneration. To determine whether Nrf2 is involved in the regulation of maternal hepatic adaptations to pregnancy, we assessed the proliferation and size of maternal hepatocytes and the associated molecular events in wild-type and Nrf2-null mice at various stages of gestation. We found that wild-type maternal hepatocytes underwent proliferation and size reduction during the first half, and size increase without overt replication during the second half, of pregnancy. Although pregnancy decreased Nrf2 activity in the maternal liver, Nrf2 deficiency caused a delay in maternal hepatocyte proliferation, concomitant with dysregulation of the activation of Cyclin D1, E1, and, more significantly, A2. Remarkably, as a result of Nrf2 absence, the maternal hepatocytes were largely prevented from reducing their sizes during the first half of pregnancy, which was associated with an increase in mTOR activation. During the second half of pregnancy, maternal hepatocytes of both genotypes showed continuous volume increase accompanied by persistent activation of mTOR. However, the lack of Nrf2 resulted in dysregulation of the activation of the mTOR upstream regulator AKT1 and the mTOR target p70SK6 and thus disruption of the AKT1/mTOR/p70S6K pathway, which is known to control cell size. This suggests an mTOR-dependent and AKT1- and p70S6K-independent compensatory mechanism when Nrf2 is deficient. In summary, our study demonstrates that Nrf2 is required for normal maternal hepatic adjustments to pregnancy by ensuring proper regulation of the number and size of maternal hepatocytes.

Glucose Intolerance and Lipid Metabolic Adaptations in Response to Intrauterine and Postnatal Calorie Restriction in Male Adult Rats

Enhanced de novo lipogenesis (DNL), an adult hepatic adaption, is seen with high carbohydrate or low-fat diets. We hypothesized that ad libitum intake after prenatal calorie restriction will result in adult-onset glucose intolerance and enhanced DNL with modified lipid metabolic gene expression profile. Stable isotopes were used in 15-month-old adult male rat offspring exposed to prenatal (IUGR), pre- and postnatal (IPGR), or postnatal (PNGR) caloric restriction vs. controls (CON). IUGR vs. CON were heavier with hepatomegaly but unchanged visceral white adipose tissue (WAT), glucose intolerant with reduced glucose-stimulated insulin secretion (GSIS), pancreatic β-cell mass, and total glucose clearance rate but unsuppressed hepatic glucose production. Liver glucose transporter (Glut) 1 and DNL increased with decreased hepatic acetyl-CoA carboxylase (ACC) and fatty acid synthase but increased WAT fatty acid transport protein-1 and peroxisomal proliferator-activated receptor-γ, resistin, and visfatin gene expression. In contrast, PNGR and IPGR were lighter, had reduced visceral WAT, and were glucose tolerant with unchanged hepatic glucose production but with increased GSIS, β-cell mass, glucose clearance rate, and WAT insulin receptor. Hepatic Glut1 and DNL were also increased in lean IPGR and PNGR with increased hepatic ACC, phosphorylated ACC, and pAMPK and reduced WAT fatty acid transport protein-1, peroxisomal proliferator-activated receptor-γ, and ACCα. We conclude the following: 1) the heavy, glucose-intolerant and insulin-resistant IUGR adult phenotype is ameliorated by postnatal caloric restriction; 2) increased DNL paralleling hepatic Glut1 is a biomarker of exposure to early caloric restriction rather than the adult metabolic status; 3) hepatic lipid enzyme expression reflects GSIS rather than DNL; and 4) WAT gene expression reflects an obesogenic vs. lean phenotype.

Comparative NMR-Based Metabonomic Investigation of the Metabolic Phenotype Associated with Tienilic Acid and Tienilic Acid Isomer

An NMR-based metabonomic approach was applied to study the systems level metabolic effects of two closely related thiophene compounds, tienilic acid (TA) and tienilic acid isomer (TAI). The metabonomic data were anchored with traditional clinical chemistry and histopathologic analyses. TA was removed from the market as a result of suspected immune-mediated hepatotoxicity, whereas TAI is an intrinsic hepatotoxin. Equimolar doses of TA and TAI were administered to Sprague-Dawley rats, and sampling was conducted at 2, 6, and 24 h post-treatment. Histopathologic analyses revealed development of a significant hepatic lesion 24 h post-TAI treatment with a parallel increase in plasma alanine aminotransferase (ALT) activity. In contrast, TA was not associated with the development of a hepatic lesion or an increase in plasma ALT activity. High-resolution NMR spectral metabolic profiles were generated for liver extracts, plasma, and urine at multiple time points. Multivariate statistical tools were applied to model the metabolic profiles and identify discriminatory metabolites that reflected both the adaptation to TA administration and the onset and progression of TAI-induced hepatotoxicity. TAI was shown to induce marked metabolic effects on the metabolome at all time points, with dramatic metabolic perturbations at 24 h post-treatment correlating with the histopathologic and clinical chemistry evidence of a hepatic lesion. The TAI-induced metabolic perturbations provided evidence for the generation of electrophilic reactive metabolites and a significant impairment of bioenergetic metabolic pathways. TA induced early metabolic perturbations that were largely resolved by 24 h post-treatment, suggesting the reestablishment of metabolic homeostasis and the ability to adapt to the intervention, with hepatic hypotaurine potentially representing a means of assessment of hepatic adaptation. This comparative metabonomic approach enabled the discrimination of metabolic perturbations that were common to both treatments and were interpreted as nontoxic thiophene-induced perturbations. Importantly, this approach enabled the identification of temporal metabolic perturbations that were unique to TAI or TA treatment and hence were of relevance to the development of toxicity or the ability to adapt. This approach is applicable to the future study of pharmacologically and structurally similar compounds and represents a refined means of identification of biomarkers of toxicity.

Hepatic mitochondrial bioenergetic and dynamic behaviour adaptations in response to high-fat feeding

Hepatic mitochondrial bioenergetic and dynamic behaviour adaptations in response to high-fat feeding

Aneuploidy as a mechanism for stress-induced liver adaptation

Over half of the mature hepatocytes in mice and humans are aneuploid and yet retain full ability to undergo mitosis. This observation has raised the question of whether this unusual somatic genetic variation evolved as an adaptive mechanism in response to hepatic injury. According to this model, hepatotoxic insults select for hepatocytes with specific numerical chromosome abnormalities, rendering them differentially resistant to injury. To test this hypothesis, we utilized a strain of mice heterozygous for a mutation in the homogentisic acid dioxygenase (Hgd) gene located on chromosome 16. Loss of the remaining Hgd allele protects from fumarylacetoacetate hydrolase (Fah) deficiency, a genetic liver disease model. When adult mice heterozygous for Hgd and lacking Fah were exposed to chronic liver damage, injury-resistant nodules consisting of Hgd-null hepatocytes rapidly emerged. To determine whether aneuploidy played a role in this phenomenon, array comparative genomic hybridization (aCGH) and metaphase karyotyping were performed. Strikingly, loss of chromosome 16 was dramatically enriched in all mice that became completely resistant to tyrosinemia-induced hepatic injury. The frequency of chromosome 16-specific aneuploidy was approximately 50%. This result indicates that selection of a specific aneuploid karyotype can result in the adaptation of hepatocytes to chronic liver injury. The extent to which aneuploidy promotes hepatic adaptation in humans remains under investigation.

Biochemical tolerance during low dose propylene glycol exposure in neonates: A formulation-controlled evaluation

Background and purpose of the studyPropylene glycol (PG) is a frequently co-administered solvent in formulations administered to neonates, but reports on its (in)tolerance are limited. We aimed to report on renal, metabolic and hepatic tolerance before, during and following intravenous (iv) PG-paracetamol exposure and compared these data with similar datasets reported in literature on neonates exposed to PG without paracetamol or paracetamol without PG.MethodsRenal (diuresis, creatinemia, sodium), metabolic (Base Excess, Anion Gap, lactate, bicarbonate) and hepatic (liver enzymes, bilirubinemia) indicators before, during and following iv paracetamol-PG exposure in neonates as included in the PARANEO (paracetamol in neonates) study (intra-individual trends, ANOVA) were collected and analysed. Comparison with observations collected in cases exposed to either iv phenobarbital-PG or iv paracetamol-mannitol (inter-individual comparison, Mann Whitney-U test) were made.ResultsPG exposure (median 34.1 mg/kg/24 h) did not affect postnatal renal, metabolic and hepatic adaptations in 60 cases exposed to paracetamol-PG. These indicators were similar when compared to 29 cases exposed to phenobarbital-PG or 172 cases exposed to paracetamol-mannitol.Major conclusionBased on observations in 89 neonates, low dose PG exposure was tolerated well. Studies on PG pharmacokinetics and its covariates are needed to estimate the upper level of PG tolerance in neonates.

Metabolic development in the liver and the implications of the n-3 fatty acid supply

The n-3 fatty acids contribute to regulation of hepatic fatty acid oxidation and synthesis in adults and accumulate in fetal and infant liver in variable amounts depending on the maternal diet fat composition. Using 2D gel proteomics and matrix-assisted laser desorption/ionization time of flight mass spectrometry, we recently identified altered abundance of proteins associated with glucose and amino acid metabolism in neonatal rat liver with increased n-3 fatty acids. Here, we extend studies on n-3 fatty acids in hepatic metabolic development to targeted gene and metabolite analyses and map the results into metabolic pathways to consider the role of n-3 fatty acids in glucose, fatty acid, and amino metabolism. Feeding rats 1.5% compared with <0.1% energy 18:3n-3 during gestation led to higher 20:5n-3 and 22:6n-3 in 3-day-old offspring liver, higher serine hydroxymethyltransferase, carnitine palmitoyl transferase, and acyl CoA oxidase and lower pyruvate kinase and stearoyl CoA desaturase gene expression, with higher cholesterol, NADPH and glutathione, and lower glycine (P < 0.05). Integration of the results suggests that the n-3 fatty acids may be important in facilitating hepatic metabolic adaptation from in utero nutrition to the postnatal high-fat milk diet, by increasing fatty acid oxidation and directing glucose and amino acids to anabolic pathways.

Maternal Obesity during Gestation Impairs Fatty Acid Oxidation and Mitochondrial SIRT3 Expression in Rat Offspring at Weaning

In utero exposure to maternal obesity increases the offspring's risk of obesity in later life. We have also previously reported that offspring of obese rat dams develop hepatic steatosis, mild hyperinsulinemia, and a lipogenic gene signature in the liver at postnatal day (PND)21. In the current study, we examined systemic and hepatic adaptations in male Sprague-Dawley offspring from lean and obese dams at PND21. Indirect calorimetry revealed decreases in energy expenditure (p<0.001) and increases in RER values (p<0.001), which were further exacerbated by high fat diet (45% kcals from fat) consumption indicating an impaired ability to utilize fatty acids in offspring of obese dams as analyzed by PRCF. Mitochondrial function is known to be associated with fatty acid oxidation (FAO) in the liver. Several markers of hepatic mitochondrial function were reduced in offspring of obese dams. These included SIRT3 mRNA (p = 0.012) and mitochondrial protein content (p = 0.002), electron transport chain complexes (II, III, and ATPase), and fasting PGC-1α mRNA expression (p<0.001). Moreover, hepatic LCAD, a SIRT3 target, was not only reduced 2-fold (p<0.001) but was also hyperacetylated in offspring of obese dams (p<0.005) suggesting decreased hepatic FAO. In conclusion, exposure to maternal obesity contributes to early perturbations in whole body and liver energy metabolism. Mitochondrial dysfunction may be an underlying event that reduces hepatic fatty acid oxidation and precedes the development of detrimental obesity associated co-morbidities such as insulin resistance and NAFLD.

Gestational Exposure to Maternal Obesity Decreases Mitochondrial SIRT3 and Components of Oxidative Phosphorylation in Offspring Liver

Exposure to maternal overweight (OW) during development influences the risk of obesity in adult‐life. We reported that by postnatal day (PND) 120 male offspring from OW rat dams have greater body weight and fat mass (p&lt;0.005), and develop insulin resistance when fed high‐fat diets (HFD, 45% fat). OW dam offspring develop hepatic steatosis and lipogenic gene expression signature at PND21, prior to obesity. Here we examined systemic and hepatic metabolic adaptations in offspring from lean and OW dams at PND21. Offspring from OW dams had decreased energy expenditure (p&lt;0.05) and higher respiratory exchange ratio (RER) values (p&lt;0.05) on AIN‐93G diet. HFD consumption further exacerbated the decrease in EE and RER as compared to offspring of lean dams, indicating an impaired capacity to utilize fatty acids (FA). Mitochondrial function in the liver is an important regulator of FA utilization. Liver protein content of electron transport chain complexes (II, III, and ATPase) was decreased (p&lt;0.03) in offspring from OW dams. Hepatic mRNA and protein expression of SIRT3, an important epigenetic regulator of mitochondrial oxidative capacity was decreased (p&lt;0.002) in offspring from OW dams. In conclusion, mitochondrial dysfunction may precede the development of energy utilization perturbations, hepatic steatosis, adiposity, and insulin resistance in offspring from OW rat dams at weaning. Support NIHR01‐DK084225

Disruption of the Acyl-CoA-binding Protein Gene Delays Hepatic Adaptation to Metabolic Changes at Weaning

The acyl-CoA-binding protein (ACBP)/diazepam binding inhibitor is an intracellular protein that binds C(14)-C(22) acyl-CoA esters and is thought to act as an acyl-CoA transporter. In vitro analyses have indicated that ACBP can transport acyl-CoA esters between different enzymatic systems; however, little is known about the in vivo function in mammalian cells. We have generated mice with targeted disruption of ACBP (ACBP(-/-)). These mice are viable and fertile and develop normally. However, around weaning, the ACBP(-/-) mice go through a crisis with overall weakness and a slightly decreased growth rate. Using microarray analysis, we show that the liver of ACBP(-/-) mice displays a significantly delayed adaptation to weaning with late induction of target genes of the sterol regulatory element-binding protein (SREBP) family. As a result, hepatic de novo cholesterogenesis is decreased at weaning. The delayed induction of SREBP target genes around weaning is caused by a compromised processing and decreased expression of SREBP precursors, leading to reduced binding of SREBP to target sites in chromatin. In conclusion, lack of ACBP interferes with the normal metabolic adaptation to weaning and leads to delayed induction of the lipogenic gene program in the liver.

A field study on characteristics and diversity of gene expression in the liver of dairy cows during the transition period

Metabolic and endocrine adaptations to support milk production during the transition period vary between individual cows. This variation between cows to adapt to lactation may have a genetic basis. The present field study was carried out to determine hepatic adaptations occurring from late pregnancy through early lactation by measuring mRNA abundance of candidate genes in dairy cows on-farm. Additionally, the objective was to observe the diversity in inter-individual variation for the candidate genes that may give indications where individual adaptations at a molecular level can be found. This study was carried out on-farm including 232 dairy cows (parity >3) from 64 farms in Switzerland. Blood and liver samples were collected on d 20±7 before parturition, on d 24±2, and on d 89±4 after parturition. Blood plasma was assayed for concentrations of glucose, nonesterified fatty acids, β-hydroxybutyrate, cholesterol, triglycerides, urea, albumin, protein, insulin, insulin-like growth factor-1, leptin, 3,5,3′-triiodothyronine, and thyroxine. Liver samples were obtained at the same time points and were measured for mRNA abundance of 26 candidate genes encoding enzymes and nuclear receptors involved in gluconeogenesis, fatty acid β-oxidation, fatty acid and triglyceride synthesis, ketogenesis, citric acid cycle, cholesterol synthesis, and the urea cycle. The cows in the present study experienced a marked metabolic load in early lactation, as presented by changes in plasma metabolites and hormones, and responded accordingly with upregulation and downregulation of almost all candidate genes involved in metabolic processes in the liver. The observed inter-individual variation for the candidate genes, which was highest for acetyl-CoA-carboxylase and glycerol-3-phosphate dehydrogenase 2, should be further investigated to unravel the regulation at molecular level for optimal adaptive performance in dairy cows.

The Best Approach to Reintroducing Tuberculosis Treatment after Hepatotoxicity Is Still Open to Debate

To the Editor—The best approach of reintroducing tuberculosis drugs after hepatotoxicity is still open to debate. Sharma et al [1] suggested that simultaneous reintroduction of isoniazid, rifampin, and pyrazinamide after drug-induced hepatotoxicity did not yield statistically significantly different results from sequential reintroduction with regard to the risk of recurrent hepatotoxicity. An editorial attempted to attribute the negative finding to mere hepatic adaptation or incidental liver function derangement for many of the initial events and to noncompliance during reintroduction [2]. We would like to share slightly different views in the interpretation of the findings.

A Maternal “Junk Food” Diet in Pregnancy and Lactation Promotes Nonalcoholic Fatty Liver Disease in Rat Offspring

With rising obesity rates, nonalcoholic fatty liver disease is predicted to become the main cause of chronic liver disease in the next decades. Rising obesity prevalence is attributed to changes in dietary habits with increased consumption of palatable junk foods, but maternal malnutrition also contributes to obesity in progeny. This study examines whether a maternal junk food diet predisposes offspring to nonalcoholic fatty liver disease. The 144 rat offspring were fed either a balanced chow diet alone or with palatable junk foods rich in energy, fat, sugar, and/or salt during gestation, lactation, and/or after weaning up to the end of adolescence. Offspring fed junk food throughout the study exhibited exacerbated hepatic steatosis, hepatocyte ballooning, and oxidative stress response compared with offspring given free access to junk food after weaning only. These offspring also displayed sex differences in their hepatic molecular metabolic adaptation to diet-induced obesity with increased expression of genes associated with insulin sensitivity, de novo lipogenesis, lipid oxidation, and antiinflammatory properties in males, whereas the gene expression profile in females was indicative of hepatic insulin resistance. Hepatic inflammation and fibrosis were not detected indicating that offspring had not developed severe steatohepatitis by the end of adolescence. Hepatic steatosis and increased oxidative stress response also occurred in offspring born to junk food-fed mothers switched to a balanced chow diet from weaning, highlighting a degree of irreversibility. This study shows that a maternal junk food diet in pregnancy and lactation contributes to the development of nonalcoholic fatty liver disease in offspring.

Gene profiling of maternal hepatic adaptations to pregnancy

Maternal metabolic demands change dramatically during the course of gestation and must be co-ordinated with the needs of the developing placenta and fetus. The liver is critically involved in metabolism and other important functions. However, maternal hepatic adjustments to pregnancy are poorly understood. The aim of the study was to evaluate the influences of pregnancy on the maternal liver growth and gene expression profile. Holtzman Sprague-Dawley rats were mated and sacrificed at various stages of gestation and post-partum. The maternal livers were analysed in gravimetric response, DNA content by PicoGreen dsDNA quantitation reagent, hepatocyte ploidy by flow cytometry and hepatocyte proliferation by ki-67 immunostaining. Gene expression profiling of non-pregnant and gestation d18.5 maternal hepatic tissue was analysed using a DNA microarray approach and partially verified by northern blot or quantitative real-time PCR analysis. During pregnancy, the liver exhibited approximately an 80% increase in size, proportional to the increase in body weight of the pregnant animals. The pregnancy-induced hepatomegaly was a physiological event of liver growth manifested by increases in maternal hepatic DNA content and hepatocyte proliferation. Pregnancy did not affect hepatocyte polyploidization. Pregnancy-dependent changes in hepatic expression were noted for a number of genes, including those associated with cell proliferation, cytokine signalling, liver regeneration and metabolism. The metabolic demands of pregnancy cause marked adjustments in maternal liver physiology. Central to these adjustments are an expansion in hepatic capacity and changes in hepatic gene expression. Our findings provide insights into pregnancy-dependent hepatic adaptations.

Early exposure of the pregestational intrauterine and postnatal growth-restricted female offspring to a peroxisome proliferator-activated receptor-{gamma} agonist.

Prenatal nutrient restriction with intrauterine growth restriction (IUGR) alters basal and glucose-stimulated insulin response and hepatic metabolic adaptation. The effect of early intervention with insulin-sensitizing peroxisome proliferator-activated receptor gamma agonists was examined in the metabolically maladapted F(1) pregestational IUGR offspring with a propensity toward pregnancy-induced gestational diabetes. The effect of rosiglitazone maleate [RG; 11 micromol/day from postnatal day (PN) 21 to PN60] vs. placebo (PL) on metabolic adaptations in 2-mo-old F(1) female rats subjected to prenatal (IUGR), postnatal (PNGR), or pre- and postnatal (IUGR + PNGR) nutrient restriction was investigated compared with control (CON). RG vs. PL had no effect on body weight or plasma glucose concentrations but increased subcutaneous white and brown adipose tissue and plasma cholesterol concentrations in all three experimental groups. Glucose tolerance tests with a 1:1 mixture of [2-(2)H(2)]- and [6,6-(2)H(2)]glucose in RG IUGR vs. PL IUGR revealed glucose tolerance with a lower glucose-stimulated insulin release (GSIR) and suppressed endogenous hepatic glucose production (HGP) with no difference in glucose clearance (GC) and recycling (GR). RG PNGR, although similar to PL CON, was hyperglycemic vs. PL PNGR with reduced GR but no difference in the existent low GSIR, HGP, and GC. RG IUGR + PNGR overall was no different from the PL counterpart. Insulin tolerance tests revealed perturbed recovery to baseline from the exaggerated hypoglycemia in RG vs. the PL groups with the only exception being RG PNGR where further worsening of hypoglycemia over PL PNGR was minimal with full recovery to baseline. These observations support that early intervention with RG suppressed HGP in IUGR vs. PL IUGR, without increasing GSIR similar to that seen in CON. Although RG reversed PNGR to the PL CON metabolic state, no such insulin-sensitizing effect was realized in IUGR + PNGR.