Pregnancy complicated by obesity induces global transcript expression alterations in visceral and subcutaneous fat.

Maternal obesity is a significant risk factor for development of both maternal and fetal metabolic complications. Increase in visceral fat and insulin resistance is a metabolic hallmark of pregnancy, yet not much is known how obesity alters adipose cellular function and how this may contribute to pregnancy morbidities. We sought to identify alterations in genome-wide transcription expression in both visceral (omental) and abdominal subcutaneous fat deposits in pregnancy complicated by obesity. Visceral and abdominal subcutaneous fat deposits were collected from normal weight and obese pregnant women (n = 4/group) at the time of scheduled uncomplicated cesarean section. A genome-wide expression array (Affymetrix Human Exon 1.0 st platform), validated by quantitative real-time PCR, was utilized to establish the gene transcript expression profile in both visceral and abdominal subcutaneous fat in normal weight and obese pregnant women. Global alteration in gene expression was identified in pregnancy complicated by obesity. These regions of variations led to identification of indolethylamine N-methyltransferase, tissue factor pathway inhibitor-2, and ephrin type-B receptor 6, not previously associated with fat metabolism during pregnancy. In addition, subcutaneous fat of obese pregnant women demonstrated increased coding protein transcripts associated with apoptosis as compared to lean counterparts. Global alteration of gene expression in adipose tissue may contribute to adverse pregnancy outcomes associated with obesity.

Comparison between surrogate indexes of insulin sensitivity/resistance and hyperinsulinemic euglycemic clamp estimates in rats.

Assessing insulin resistance in rodent models gives insight into mechanisms that cause type 2 diabetes and the metabolic syndrome. The hyperinsulinemic euglycemic glucose clamp, the reference standard for measuring insulin sensitivity in humans and animals, is labor intensive and technically demanding. A number of simple surrogate indexes of insulin sensitivity/resistance have been developed and validated primarily for use in large human studies. These same surrogates are also frequently used in rodent studies. However, in general, these indexes have not been rigorously evaluated in animals. In a recent validation study in mice, we demonstrated that surrogates have a weaker correlation with glucose clamp estimates of insulin sensitivity/resistance than in humans. This may be due to increased technical difficulties in mice and/or intrinsic differences between human and rodent physiology. To help distinguish among these possibilities, in the present study, using data from rats substantially larger than mice, we compared the clamp glucose infusion rate (GIR) with surrogate indexes, including QUICKI, HOMA, 1/HOMA, log (HOMA), and 1/fasting insulin. All surrogates were modestly correlated with GIR (r = 0.34-0.40). Calibration analyses of surrogates adjusted for body weight demonstrated similar predictive accuracy for GIR among all surrogates. We conclude that linear correlations of surrogate indexes with clamp estimates and predictive accuracy of surrogate indexes in rats are similar to those in mice (but not as substantial as in humans). This additional rat study (taken with the previous mouse study) suggests that application of surrogate insulin sensitivity indexes developed for humans may not be appropriate for determining primary outcomes in rodent studies due to intrinsic differences in metabolic physiology. However, use of surrogates may be appropriate in rodents, where feasibility of clamps is an obstacle and measurement of insulin sensitivity is a secondary outcome.

Enhanced activation of a "nutrient-sensing" pathway with age contributes to insulin resistance.

Calorie restriction improves life span whereas nutrient excess leads to obesity and unfavorable metabolic consequences, supporting the role for a cellular "nutrient sensor" in aging. Hexosamine biosynthetic pathway (HBP) is a candidate nutrient-sensing pathway. We hypothesized that altered nutrient sensing (by HBP) with age may provide a link among aging, nutrient flux, and insulin resistance. Using a hyperinsulinemic clamp in young rats, we show that experimental activation of HBP, through the systemic infusion of glucosamine, induced severe insulin resistance (36% decline in peripheral insulin action; P<0.05), increased adipose tissue gene expression of fat-derived peptides (PAI-1 by 4-fold, angiotensinogen 3-fold, leptin 2-fold, resistin 4-fold, and adiponectin 4-fold; P<0.01 compared with young saline-infused), and enhanced glycosylation of transcription factors, thus mimicking a physiological and biological phenotype of aging. We further demonstrate a greater activation of nutrient-sensing HBP with age in both old ad libitum-fed and calorie-restricted rats. Interestingly, old calorie-restricted animals rapidly develop insulin resistance when exposed to glucosamine, despite their "young" phenotype. These results suggest that altered nutrient sensing by HBP with age may be the link among nutrients, insulin resistance, and age-related diabetes.

Resistance to leptin action is the major determinant of hepatic triglyceride accumulation in vivo.

Impairment of both insulin and leptin action has been implicated in the pathogenesis of nonalcoholic fatty liver disease. By assessing hepatic triglyceride (TG) stores in response to modulation of leptin action (by leptin infusion), we attempted to determine whether leptin has the major role in hepatic TG accumulation. TG were markedly decreased (by 63%, P<0.05) in young animals treated with leptin. However, this was also associated with improvement in hepatic insulin action (2-fold decrease in HGP during clamp, P<0.05). These effects on hepatic TG stores and insulin action were abolished in old rats who demonstrate leptin resistance. Since these experiments could not discern the role of leptin from the role of hepatic insulin action on hepatic TG stores, we further examined the effect of improvement of hepatic insulin action by visceral fat removal (VF-). Enhancement of hepatic insulin action in old VF-rats was associated with reduced hepatic TG stores (by 64% P<0.01). Because this manipulation may have induced an improvement in leptin action as well, we studied VF removal in a genetically leptin-resistant model (Zucker Diabetic Fatty rats, ZDF). Only in this mode was exclusive improvement of hepatic insulin action by VF removal not associated with reduced hepatic TG stores, suggesting that improved hepatic insulin action is not necessary for modulation of hepatic TG stores. By dissociating action of leptin from that of insulin, we suggest that the failure of leptin action is the major physiological mechanism for hepatic steatosis.

Central and opposing effects of IGF-I and IGF-binding protein-3 on systemic insulin action.

IGF-I is recognized as an insulin sensitizer at the liver and muscle, while recent evidence suggests that IGF-binding protein (IGFBP)-3 acts as an insulin antagonist. As there is a paucity of IGF-I receptors in the liver and as the IGF-IGFBP system in the central nervous system is emerging as physiologically relevant, we examined whether the effects of IGF-I and IGFBP-3 on insulin action are mediated through central mechanisms. Intracerebroventricular (ICV) infusion of IGF-I during the insulin clamp (3 mU x kg(-1) x min(-1)) resulted in significant improvement in hepatic insulin action (50%, P < 0.05). In contrast, ICV infusion of IGFBP-3 significantly impaired insulin action at the liver (45% increase in hepatic glucose production, P < 0.01). While IGF-I marginally increased peripheral glucose uptake, IGFBP-3 significantly decreased peripheral glucose uptake (approximately 30%, P < 0.01). As the nuclear localization signal mutant IGFBP-3, which has a normal affinity to IGFs but binds other IGFBP-3 partners poorly and fails to normally internalize, has reduced central activity on metabolism, we conclude that the effects of IGFBP-3 on the hypothalamus involve activity mediated by interfacing with other molecules in addition to IGFs. Marked, opposing, and independent physiological effects of IGF-I and IGFBP-3 through central mechanisms may have implications on potential strategies in specific modulation of peripheral insulin action.

Differential responses of visceral and subcutaneous fat depots to nutrients.

Increased visceral adiposity is a pivotal component of the metabolic syndrome. Differential gene expression patterns of fat-derived peptides (FDPs) in visceral fat and subcutaneous fat have been characterized in the fasting state. Here we examined whether delivery of nutrients differentially affects the expression of FDPs in visceral fat versus subcutaneous fat (in the fed state). We increased the rate of glucose flux into adipose tissue of normal rats (n = 16) by hyperglycemia or hyperinsulinemia using the clamp technique. Glucose uptake was associated with increased expression of FDPs, including resistin ( approximately 5-fold), adiponectin ( approximately 2-fold), leptin ( approximately 15-fold), plasminogen activating inhibitor-1 ( approximately 10-fold), and angiotensinogen ( approximately 4-fold) in visceral fat, but markedly less in subcutaneous fat. Cytokine expression derived mainly from vascular/stromal/macrophage components of adipose tissue was less dramatically increased. Infusion of glucosamine amplified the results obtained by increasing glucose uptake into adipose tissue, suggesting that flux through the hexosamine biosynthetic pathway may serve as a mechanism for "nutrient sensing." Nutrient-dependent expression of FDPs in visceral fat was also associated with increased plasma levels of several FDPs. Because a biologic sensing pathway can dynamically couple daily food intake to abnormal plasma levels of important FDPs, we challenge the practice of obtaining plasma levels after fasting to assess risk factors for metabolic syndrome.

Multigenerational effects of maternal undernutrition.

Intrauterine exposure to reduced nutrient availability can have major effects in determining susceptibility to chronic disease later in life. Martínez et al. (2014) demonstrate multigenerational effects of poor maternal nutrition and evidence of germline transmission through alterations in DNA methylation.

Sexual dimorphism in epigenomic responses of stem cells to extreme fetal growth.

Extreme fetal growth is associated with increased susceptibility to a range of adult diseases through an unknown mechanism of cellular memory. We tested whether heritable epigenetic processes in long-lived CD34(+) haematopoietic stem/progenitor cells showed evidence for re-programming associated with the extremes of fetal growth. Here we show that both fetal growth restriction and over-growth are associated with global shifts towards DNA hypermethylation, targeting cis-regulatory elements in proximity to genes involved in glucose homeostasis and stem cell function. We find a sexually dimorphic response; intrauterine growth restriction is associated with substantially greater epigenetic dysregulation in males, whereas large for gestational age growth predominantly affects females. The findings are consistent with extreme fetal growth interacting with variable fetal susceptibility to influence cellular ageing and metabolic characteristics through epigenetic mechanisms, potentially generating biomarkers that could identify infants at higher risk for chronic disease later in life.

The meta-epigenomic structure of purified human stem cell populations is defined at cis-regulatory sequences.

The mechanism and significance of epigenetic variability in the same cell type between healthy individuals are not clear. Here we purify human CD34+ haematopoietic stem and progenitor cells (HSPCs) from different individuals and find that there is increased variability of DNA methylation at loci with properties of promoters and enhancers. The variability is especially enriched at candidate enhancers near genes transitioning between silent and expressed states, and encoding proteins with leukocyte differentiation properties. Our findings of increased variability at loci with intermediate DNA methylation values, at candidate 'poised' enhancers and at genes involved in HSPC lineage commitment suggest that CD34+ cell subtype heterogeneity between individuals is a major mechanism for the variability observed. Epigenomic studies performed on cell populations, even when purified, are testing collections of epigenomes, or meta-epigenomes. Our findings show that meta-epigenomic approaches to data analysis can provide insights into cell subpopulation structure.

Minireview: Epigenetics of obesity and diabetes in humans.

Understanding the determinants of human health and disease is overwhelmingly complex, particularly for common, late-onset, chronic disorders, such as obesity and diabetes. Elucidating the genetic and environmental factors that influence susceptibility to disruptions in energy homeostasis and metabolic regulation remain a challenge, and progress will entail the integration of multiple assessments of temporally dynamic environmental exposures in the context of each individual's genotype. To meet this challenge, researchers are increasingly exploring the epigenome, which is the malleable interface of gene-environment interactions. Epigenetic variation, whether innate or induced, contributes to variation in gene expression, the range of potential individual responses to internal and external cues, and risk for metabolic disease. Ultimately, advancement in our understanding of chronic disease susceptibility in humans will depend on refinement of exposure assessment tools and systems biology approaches to interpretation. In this review, we present recent progress in epigenetics of human obesity and diabetes, existing challenges, and the potential for new approaches to unravel the complex biology of metabolic dysregulation.

Perinephric and epididymal fat affect hepatic metabolism in rats.

The present study examined whether the perinephric and epididymal visceral fat (PEVF) depot under short-term excess nutrient protected the liver by trapping nutrient-derived nonesterified free fatty acids (NEFAs) or had deleterious effects on hepatic triglycerides (TGs) accumulation and insulin resistance due to adipokine secretion. Young rats pre-emptively underwent surgical PEVF removal or sham operations and were fed with either high-fat diet (HFD) (PEVF-HFD) or regular chow (RC) (PEVF-RC) for 3 days. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp. Liver TG, serum NEFA, and fat-derived adipokines were assessed. Insulin and lipogenesis signaling were assessed by western blots. Pre-emptive PEVF removal significantly decreases insulin-induced suppression of hepatic glucose production (HGP) both in RC and in HFD-fed rats. In accordance with the clamp results, hepatic TG accumulation is also significantly reduced by PEVF excision both in RC and HFD-fed rats. These results are further validated by insulin signaling results, which show that pre-emptive PEVF removal increases phosphorylation of hepatic Akt, irrespective of diet. Notably, high levels of serum leptin induced by HFD are significantly reduced by pre-emptive PEVF excision. Additionally, expression of lipogenic enzyme p-acetyl-CoA-carboxylase, denoting reduced lipogenesis, is increased in the PEVF-HFD rats. In conclusion, PEVF has a deleterious effect on the liver as a source of insulin resistance-inducing adipokines irrespective of diet, and does not serve as a buffer for excess nutrients.

Bilateral internal carotid artery dissection in the postpartum period.

BACKGROUND: Bilateral internal carotid artery dissection is a rare event associated with pregnancy, especially in a patient without any predisposing risk factors. CASE: A 34-year-old woman presented with postpartum unilateral weakness, headaches, and blurry vision 14 days after vaginal delivery. Radiologic imaging revealed bilateral cervical internal carotid artery dissections and cerebral infarctions. She was treated with anticoagulation and showed radiographic and clinical improvement. CONCLUSION: The pathophysiology of cervical artery dissection appears multifactorial, with evidence suggesting environmental and genetic contributions. Intimal injury related to the Valsalva maneuver during labor as well as hemodynamic and hormonal changes related to pregnancy are presumed causes of peripartum spontaneous carotid artery dissection. Antithrombotic therapy for at least 3 to 6 months after dissection and follow-up neuroimaging are suggested.

Diabetes in pregnancy: glycemia control guidelines and rationale.

PURPOSE OF REVIEW: Little consensus exists on the definition of gestational diabetes (GDM), how the condition should be diagnosed, and if interventions for mild maternal hyperglycemia are of any benefit to the mother or fetus. Today, after several large multicenter clinical trials, we are closer than ever to a national and international consensus. RECENT FINDINGS: Glucose tolerance in pregnancy is a continuum, which has a fundamental link to fetal growth. The relationship between maternal glycemia and adverse outcomes is continuous, with no distinct inflection point for increased risk. As a result, any cut-off for the diagnosis of GDM is somewhat arbitrary. Treatment for GDM, even mild cases, significantly reduces the rate of certain adverse perinatal and maternal outcomes, warranting intervention. SUMMARY: Clinical guidelines for the diagnosis of GDM are expected to change in the near future provided that recommendations from the International Association of Diabetes and Pregnancy Study Group are accepted by professional organizations. The criteria for the diagnosis will likely be based on a single 75 g, 2-h oral glucose tolerance test with at least one abnormal value. The proposed threshold values are based on an international consensus regarding risk of adverse pregnancy outcomes. The public health implications for these changes are anticipated to be significant.

Epigenetic basis for fetal origins of age-related disease.

The current concept of fetal origins of adult diseases describes in utero programming, or adaptation to a spectrum of adverse environmental conditions that ultimately leads to increased susceptibility to age-related diseases (e.g., type 2 diabetes and cardiovascular disease) later in life. Although the precise mechanism of this biological memory remains unclear, mounting evidence suggests an epigenetic basis. The increased susceptibility to chronic disease and involvement of multiple organ systems that is observed is analogous to the decline in resistance to disease that is typical of normal aging. Although the cumulative environment over the course of a lifetime can induce increasing epigenetic dysregulation, we propose that adverse events that occur during early development can induce significant additional dysregulation of the epigenome. Here, we describe the current evidence for fetal origins of adult disease and the associated role of epigenetic dysregulation. In addition, we present a new perspective on the induction of epigenetic alterations in utero, which subsequently lead to an aging phenotype marked by increased susceptibility to age-related diseases.

Aging per se increases the susceptibility to free fatty acid-induced insulin resistance.

Elevations in systemic free fatty acids (FFA) contribute to insulin resistance. To determine the effects of an acute elevation in FFA on insulin action with aging, we infused saline or intralipid (IL) during a hyperinsulinemic-euglycemic clamp in three groups of rats: young ad libitum-fed (YAL), old ad libitum-fed (OAL), and old on lifelong calorie restriction (OCR). The OCR group was included to distinguish between aging per se and age-related changes in body fat distribution. IL induced marked insulin resistance in both YAL and OCR, but the onset of insulin resistance was approximately two to three times more rapid in OCR as compared with YAL. In response to IL infusion, plasminogen-activating inhibitor-1 (PAI-1) expression was increased in subcutaneous fat from OAL animals. In visceral fat, a marked increase in PAI-1 and interleukin-6 expression was observed in OAL and OCR rats, but not YAL, in response to IL treatment. Thus, aging per se increases the inflammatory response to excess nutrients and vulnerability to FFA-induced insulin resistance with aging.

Humanin: a novel central regulator of peripheral insulin action.

BACKGROUND: Decline in insulin action is a metabolic feature of aging and is involved in the development of age-related diseases including Type 2 Diabetes Mellitus (T2DM) and Alzheimer's disease (AD). A novel mitochondria-associated peptide, Humanin (HN), has a neuroprotective role against AD-related neurotoxicity. Considering the association between insulin resistance and AD, we investigated if HN influences insulin sensitivity. METHODS AND FINDINGS: Using state of the art clamp technology, we examined the role of central and peripheral HN on insulin action. Continuous infusion of HN intra-cerebro-ventricularly significantly improved overall insulin sensitivity. The central effects of HN on insulin action were associated with activation of hypothalamic STAT-3 signaling; effects that were negated by co-inhibition of hypothalamic STAT-3. Peripheral intravenous infusions of novel and potent HN derivatives reproduced the insulin-sensitizing effects of central HN. Inhibition of hypothalamic STAT-3 completely negated the effects of IV HN analog on liver, suggesting that the hepatic actions of HN are centrally mediated. This is consistent with the lack of a direct effect of HN on primary hepatocytes. Furthermore, single treatment with a highly-potent HN analog significantly lowered blood glucose in Zucker diabetic fatty rats. Based upon the link of HN with two age-related diseases, we examined if there were age associated changes in HN levels. Indeed, the amount of detectable HN in hypothalamus, skeletal muscle, and cortex was decreased with age in rodents, and circulating levels of HN were decreased with age in humans and mice. CONCLUSIONS: We conclude that the decline in HN with age could play a role in the pathogenesis of age-related diseases including AD and T2DM. HN represents a novel link between T2DM and neurodegeneration and along with its analogues offers a potential therapeutic tool to improve insulin action and treat T2DM.

Accretion of visceral fat and hepatic insulin resistance in pregnant rats.

Insulin resistance (IR) is a hallmark of pregnancy. Because increased visceral fat (VF) is associated with IR in nonpregnant states, we reasoned that fat accretion might be important in the development of IR during pregnancy. To determine whether VF depots increase in pregnancy and whether VF contributes to IR, we studied three groups of 6-mo-old female Sprague-Dawley rats: 1) nonpregnant sham-operated rats (Nonpreg; n = 6), 2) pregnant sham-operated rats (Preg; n = 6), and 3) pregnant rats in which VF was surgically removed 1 mo before mating (PVF-; n = 6). VF doubled by day 19 of pregnancy (Nonpreg 5.1 +/- 0.3, Preg 10.0 +/- 1.0 g, P < 0.01), and PVF- had similar amounts of VF compared with Nonpreg (PVF- 4.6 +/- 0.8 g). Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp in late gestation in chronically catheterized unstressed rats. Glucose IR (mg.kg(-1).min(-1)) was highest in Nonpreg (19.4 +/- 2.0), lowest in Preg (11.1 +/- 1.4), and intermediate in PVF- (14.7 +/- 0.6; P < 0.001 between all groups). During the clamp, Nonpreg had greater hepatic insulin sensitivity than Preg [hepatic glucose production (HGP): Nonpreg 4.5 +/- 1.3, Preg 9.3 +/- 0.5 mg.kg(-1).min(-1); P < 0.001]. With decreased VF, hepatic insulin sensitivity was similar to nonpregnant levels in PVF- (HGP 4.9 +/- 0.8 mg.kg(-1).min(-1)). Both pregnant groups had lower peripheral glucose uptake compared with Nonpreg. In parallel with hepatic insulin sensitivity, hepatic triglyceride content was increased in pregnancy (Nonpreg 1.9 +/- 0.4 vs. Preg 3.2 +/- 0.3 mg/g) and decreased with removal of VF (PVF- 1.3 +/- 0.4 mg/g; P < 0.05). Accretion of visceral fat is an important component in the development of hepatic IR in pregnancy, and accumulation of hepatic triglycerides is a mechanism by which visceral fat may modulate insulin action in pregnancy.

Visceral adipose tissue modulates mammalian longevity.

Caloric restriction (CR) can delay many age-related diseases and extend lifespan, while an increase in adiposity is associated with enhanced disease risk and accelerated aging. Among the various fat depots, the accrual of visceral fat (VF) is a common feature of aging, and has been shown to be the most detrimental on metabolic syndrome of aging in humans. We have previously demonstrated that surgical removal of VF in rats improves insulin action; thus, we set out to determine if VF removal affects longevity. We prospectively studied lifespan in three groups of rats: ad libitum-fed (AL-fed), CR (Fed 60% of AL) and a group of AL-fed rats with selective removal of VF at 5 months of age (VF-removed rats). We demonstrate that compared to AL-fed rats, VF-removed rats had a significant increase in mean (p < 0.001) and maximum lifespan (p < 0.04) and significant reduction in the incidence of severe renal disease (p < 0.01). CR rats demonstrated the greatest mean and maximum lifespan (p < 0.001) and the lowest rate of death as compared to AL-fed rats (0.13). Taken together, these observations provide the most direct evidence to date that a reduction in fat mass, specifically VF, may be one of the possible underlying mechanisms of the anti-aging effect of CR.

The impact of protease inhibitors on maternal serum screening analyte levels in pregnant women who are HIV positive.

OBJECTIVE: The purpose of this study was to compare alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol levels in women who take protease inhibitors and those women who do not. STUDY DESIGN: This retrospective review from August 2000 to May 2003 was performed for maternal serum screen results, medication use, pregnancy, and perinatal outcomes. RESULTS: Thirty-nine women met study criteria. Sixteen women were treated with protease inhibitors, and 23 women were not treated with protease inhibitors. There was no difference in initial viral load or initial CD4 count between the groups. No difference was found for human chorionic gonadotropin and estriol levels; significantly lower alpha-fetoprotein multiples of the median were found for the women who were treated with protease inhibitors compared with the women who were not (0.97 +/- 0.32 [SD] MoM vs 1.2 +/- 0.4 MoM, respectively; P = .04). Six of 39 women (15%) had positive maternal serum screens. All the babies were normal at birth, and there were no cases of perinatal transmission of human immunodeficiency virus. CONCLUSION: Protease inhibitors are associated with lower alpha-fetoprotein levels in women who are infected with human immunodeficiency virus.