Glucose metabolic adaptations in the intrauterine growth-restricted adult female rat offspring

Effect of Postnatal Nutritional Environment Due to Maternal Diabetes on Beta Cell Mass Programming and Glucose Intolerance Risk in Male and Female Offspring

Besides the fetal period, the suckling period is a critical time window in determining long-term metabolic health. We undertook the present study to elucidate the impact of a diabetic suckling environment alone or associated with an in utero diabetic environment on beta cell mass development and the risk of diabetes in the offspring in the long term. To that end, we have compared two experimental settings. In setting 1, we used Wistar (W) rat newborns resulting from W ovocytes (oW) transferred into diabetic GK rat mothers (pGK). These oW/pGK neonates were then suckled by diabetic GK foster mothers (oW/pGK/sGK model) and compared to oW/pW neonates suckled by normal W foster mothers (oW/pW/sW model). In setting 2, normal W rat newborns were suckled by diabetic GK rat foster mothers (nW/sGK model) or normal W foster mothers (nW/sW model). Our data revealed that the extent of metabolic disorders in term of glucose intolerance and beta cell mass are similar between rats which have been exposed to maternal diabetes both pre- and postnatally (oW/pGK/sGK model) and those which have been exposed only during postnatal life (nW/sW model). In other words, being nurtured by diabetic GK mothers from birth to weaning was sufficient to significantly alter the beta cell mass, glucose-induced insulin secretion and glucose homeostasis of offspring. No synergistic deleterious effects of pre-and postnatal exposure was observed in our setting.

Placental insufficiency contributes to fatty acid metabolism alterations in aged female mouse offspring

Intrauterine growth restriction (IUGR) is an accepted risk factor for metabolic disorders in later life, including obesity and type 2 diabetes. The level of metabolic dysregulation can vary between subjects and is dependent on the severity and the type of IUGR insult. Classical IUGR animal models involve nutritional deprivation of the mother or uterine artery ligation. The latter aims to mimic a placental insufficiency, which is the most frequent cause of IUGR. In this study, we investigated whether IUGR attributable to placental insufficiency impacts the glucose and lipid homeostasis at advanced age. Placental insufficiency was achieved by deletion of the transcription factor AP-2y ( Tfap2c), which serves as one of the major trophoblast differentiation regulators. TdelT-IUGR mice were obtained by crossing mice with a floxed Tfap2c allele and mice with Cre recombinase under the control of the Tpbpa promoter. In advanced adulthood (9-12 mo), female and male IUGR mice are respectively 20% and 12% leaner compared with controls. At this age, IUGR mice have unaffected glucose clearance and lipid parameters (cholesterol, triglycerides, and phospholipids) in the liver. However, female IUGR mice have increased plasma free fatty acids (+87%) compared with controls. This is accompanied by increased mRNA levels of fatty acid synthase and endoplasmic reticulum stress markers in white adipose tissue. Taken together, our results suggest that IUGR by placental insufficiency may lead to higher lipogenesis in female mice in advanced adulthood, at least indicated by greater Fasn expression. This effect was sex specific for the aged IUGR females.

Intrauterine Growth Restriction: Hungry for an Answer

Intrauterine growth restriction (IUGR) has been defined in several ways, but in general describes a condition in which the fetus exhibits poor growth in utero. This complication of pregnancy poses a significant public health burden as well as increased morbidity and mortality for the offspring. In human IUGR, alteration in fetal glucose and insulin homeostasis occurs in an effort to conserve energy and survive at the expense of fetal growth in an environment of inadequate nutrient provision. Several animal models of IUGR have been utilized to study the effects of IUGR on fetal glucose handling, as well as the postnatal reprogramming of energy metabolite handling, which may be unmasked in adulthood as a maladaptive propensity for cardiometabolic disease. This developmental programming may be mediated in part by epigenetic modification of essential regulators of glucose homeostasis. Several pharmacological therapies and nonpharmacological lifestyle modifications have shown early promise in mitigating the risk for or severity of adult metabolic phenotypes but still require further study of unanticipated and/or untoward side effects.

Exercise as an intervention to improve metabolic outcomes after intrauterine growth restriction

Individuals born after intrauterine growth restriction (IUGR) are at an increased risk of developing diabetes in their adult life. IUGR impairs β-cell function and reduces β-cell mass, thereby diminishing insulin secretion. IUGR also induces insulin resistance, with impaired insulin signaling in muscle in adult humans who were small for gestational age (SGA) and in rodent models of IUGR. There is epidemiological evidence in humans that exercise in adults can reduce the risk of metabolic disease following IUGR. However, it is not clear whether adult IUGR individuals benefit to the same extent from exercise as do normal-birth-weight individuals, as our rat studies suggest less of a benefit in those born IUGR. Importantly, however, there is some evidence from studies in rats that exercise in early life might be able to reverse or reprogram the long-term metabolic effects of IUGR. Studies are needed to address gaps in current knowledge, including determining the mechanisms involved in the reprogramming effects of early exercise in rats, whether exercise early in life or in adulthood has similar beneficial metabolic effects in larger animal models in which insulin resistance develops after IUGR. Human studies are also needed to determine whether exercise training improves insulin secretion and insulin sensitivity to the same extent in IUGR adults as in control populations. Such investigations will have implications for customizing the recommended level and timing of exercise to improve metabolic health after IUGR.

Induction of the hepatic stearoyl-CoA desaturase 1 gene in offspring after isocaloric administration of high fat sucrose diet during gestation

Adverse early nutrition leads to metabolic aberrations in adulthood. Molecular and cellular mechanisms responsible are emerging; specific nutritional causes remain unclarified. We investigated gestational dietary intake and its influences on metabolism in offspring. Three groups of pregnant Sprague-Dawley rats were fed either AIN93G standard diet as control, isocaloric high fat sucrose diet or calorie restriction diet (50% of control) until delivery. All dams were fed control diet ad libitum during lactation. Offsprings’ metabolic parameters were assessed at three weeks. Visceral fat and plasma triglycerides of high fat sucrose diet offspring were significantly higher than those of control diet and calorie restriction diet offspring. Plasma leptin level was higher in high fat sucrose diet than control offspring. Conversely, plasma adiponectin was lower in high fat sucrose diet and calorie restriction diet offspring compared to controls. Significant inductions of hepatic mRNA expression of stearoyl-CoA desaturase1 and Δ-5 desaturase genes, were observed in high fat sucrose diet and calorie restriction diet offspring. Gestational high sugar and fat intake even without over energy intake would be more detrimental to metabolisms of offspring compared to calorie restriction.

Prenatal food restriction induces a hypothalamic-pituitary-adrenocortical axis-associated neuroendocrine metabolic programmed alteration in adult offspring rats

BACKGROUND AND AIMS

Intrauterine growth restriction produces susceptibility to adult metabolic syndrome, which may be caused by the permanent alteration of the hypothalamic-pituitary-adrenocortical (HPA) axis. We aimed to verify that HPA axis-associated neuroendocrine metabolic programming is altered in food-restricted (FR) offspring.

METHODS

Maternal rats were fed a restricted diet from gestational day 11 until full-term delivery, all pups were fed a high-fat diet after weaning and exposed to unpredictable chronic stress (UCS) during postnatal weeks 17-20.

RESULTS

Serum levels of adrenocorticotrophic hormone and corticosterone in adult offspring of the prenatal FR group were lower than the control (CN) rats before UCS but increased significantly after UCS. Serum glucose levels in the FR group were normal before UCS but increased after UCS. Serum insulin levels were significantly decreased in FR males but showed a slight increase in FR females before UCS; however, insulin levels decreased significantly in the FR male and female rats after UCS. Before UCS, serum lipid levels were higher in the FR males but were normal in the FR females; after UCS, FR males had a slight decrease and FR females had an increasing trend in serum lipids levels. Lipid droplets in the hypothalamus, pituitary gland, and livers of the FR group indicated steatosis.

CONCLUSIONS

These results suggest that prenatal food restriction alters HPA axis-associated neuroendocrine metabolism in adult offspring fed a high-fat diet, which may originate from the intrauterine programming and increase the susceptibility to adult metabolic diseases.

Embryo-transfer of the F2 postnatal calorie restricted female rat offspring into a control intra-uterine environment normalizes the metabolic phenotype

OBJECTIVE

Postnatal calorie and growth restriction (PNGR) in the first generation (F1) rat female offspring causes a lean and glucose tolerant phenotype associated with hypoinsulinemia and reduced glucose-stimulated insulin secretion (GSIS). Despite the absence of gestational hyperglycemia in the F1 PNGR female, naturally born second generation (F2) PNGR female adult offspring reportedly exhibit obesity, hyperglycemia with insulin resistance. The objective of this study was to determine the role of the intrauterine environment on the heritability of the trans-generational phenotypic expression in the F2 PNGR female adult offspring.

MATERIALS/METHODS

We performed embryo transfer (ET) of the F2 embryos from the procreating F1 pregnant PNGR or control (CON) females to gestate in control recipient rat mothers. Employing stable isotopes glucose metabolic kinetics was determined.

RESULTS

Birth weight, postnatal growth pattern and white adipose tissue in female F2 ET-PNGR were similar to ET-CON. Similarly, no differences in basal glucose and insulin concentrations, GSIS, glucose futile cycling and glucose clearance were seen. When compared to F2 ET-CON, F2 ET-PNGR showed no overall difference in glucose or hepatic glucose production (HGP) AUCs with minimal hyperglycemia (p<0.04) as a result of unsuppressed endogenous HGP (p<0.02) observed only during the first phase of IVGTT.

CONCLUSIONS

We conclude that the lean, glucose tolerant and hypoinsulinemic phenotype with reduced GSIS in the F1 generation is nearly normalized when the embryo-transferred F2 offspring gestates in a normal metabolic environment. This observation supports a role for the intra-uterine environment in modifying the heritability of the trans-generational PNGR phenotype.

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.

Early life nutrient restriction impairs blood-brain metabolic profile and neurobehavior predisposing to Alzheimer's disease with aging

Prenatal nutrient restriction (NR) culminating in intra-uterine growth restriction (IUGR) with postnatal catch up growth leads to diabesity. In contrast, postnatal NR with growth restriction (PNGR) superimposed on IUGR (IPGR) protects young and aging adults from this phenotype. We hypothesized that PNGR/IPGR will compromise the blood-brain metabolic profile impairing neurobehavior and predisposing to Alzheimer's disease (AD). NR (50%) in late gestation followed by cross-fostering of rat pups to either ad lib fed (CON) or NR (50%) lactating mothers generated CON, IUGR, PNGR and IPGR male (M) and female (F) offspring that were examined through the life span. In PNGR/IPGR plasma/CSF glucose and lactate decreased while ketones increased in (M) and (F) (PN21, PN50). In addition increased brain glucose transporters, Glut1 & Glut3, greater brain derived neurotrophic factor (BDNF), reduced Glut4, with unchanged serotonin transporter concentrations were noted in (F) (PN50-60). While (F) displayed more hyperactivity, both (F) and (M) exhibited anxiety although socially and cognitively unimpaired (PN25-28&50). Aging (15-17 m) (F) not (M), expressed low plasma insulin, reduced brain IRS-2, pAkt, and pGSK-3β(Ser9), unchanged pPDK1, pTau or lipoprotein receptor related protein 1 (LRP1), higher glial fibrillary acidic protein (GFAP) and spinophilin but a 10-fold increased amyloid-β42. We conclude that therapeutically superimposing PNGR on IUGR (IPGR) should be carefully weighed in light of unintended consequences related to perturbed neurobehavior and potential predilection for AD.

Early postnatal caloric restriction protects adult male intrauterine growth-restricted offspring from obesity

Postnatal ad libitum caloric intake superimposed on intrauterine growth restriction (IUGR) is associated with adult-onset obesity, insulin resistance, and type 2 diabetes mellitus (T2DM). We hypothesized that this paradigm of prenatal nutrient deprivation-induced programming can be reversed with the introduction of early postnatal calorie restriction. Ten-month-old male rats exposed to either prenatal nutrient restriction with ad libitum postnatal intake (IUGR), pre- and postnatal nutrient restriction (IPGR), or postnatal nutrient restriction limited to the suckling phase (50% from postnatal [PN]1 to PN21) (PNGR) were compared with age-matched controls (CON). Visceral adiposity, metabolic profile, and insulin sensitivity by hyperinsulinemic-euglycemic clamps were examined. The 10-month-old male IUGR group had a 1.5- to 2.0-fold increase in subcutaneous and visceral fat (P < 0.0002) while remaining euglycemic, insulin sensitive, inactive, and exhibiting metabolic inflexibility (Vo(2)) versus CON. The IPGR group remained lean, euglycemic, insulin sensitive, and active while maintaining metabolic flexibility. The PNGR group was insulin sensitive, similar to IPGR, but less active while maintaining metabolic flexibility. We conclude that IUGR resulted in obesity without insulin resistance and energy metabolic perturbations prior to development of glucose intolerance and T2DM. Postnatal nutrient restriction superimposed on IUGR was protective, restoring metabolic normalcy to a lean and active phenotype.

Pre- and postnatal calorie restriction perturbs early hypothalamic neuropeptide and energy balance

Energy balance is regulated by circulating leptin concentrations and hypothalamic leptin receptor (ObRb) signaling via STAT3 but is inhibited by SOCS3 and PTP1B. Leptin signaling enhances anorexigenic neuropeptides and receptor (POMC, MC3-R, MC4-R) activation while suppressing orexigenic neuropeptides (NPY, AgRP). We investigated in a sex-specific manner the early (PN2) and late (PN21) postnatal hypothalamic mechanisms in response to intrauterine (IUGR), postnatal (PNGR), and combined (IPGR) calorie and growth restriction. At PN2, both male and female IUGR were hypoleptinemic, but hypothalamic leptin signaling in females was activated as seen by enhanced STAT3. In addition, increased SOCS3 and PTP1B supported early initiation of leptin resistance in females that led to elevated AgRP but diminished MC3-R and MC4-R. In contrast, males demonstrated leptin sensitivity seen as a reduction in PTP1B and MC3-R and MC4-R with no effect on neuropeptide expression. At PN21, with adequate postnatal caloric intake, a sex-specific dichotomy in leptin concentrations was seen in IUGR, with euleptinemia in males indicative of persisting leptin sensitivity and hyperleptinemia in females consistent with leptin resistance, both with normal hypothalamic ObRb signaling, neuropeptides, and energy balance. In contrast, superimposition of PNGR upon IUGR (IPGR) led to diminished leptin concentrations with enhanced PTP1B and an imbalance in arcuate nuclear NPY/AgRP and POMC expression that favored exponential hyperphagia and diminished energy expenditure postweaning. We conclude that IUGR results in sex-specific leptin resistance observed mainly in females, whereas PNGR and IPGR abolish this sex-specificity, setting the stage for acquiring obesity after weaning.

The Genetic Basis of the Polycystic Ovary Syndrome: A Literature Review Including Discussion of PPAR-gamma

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder of the women of reproductive age. Familial clustering of PCOS has been consistently reported suggesting that genetic factors play a role in the development of the syndrome although PCOS cases do not exhibit a clear pattern of Mendelian inheritance. It is now well established that PCOS represents a complex trait similar to type-2 diabetes and obesity, and that both inherited and environmental factors contribute to the PCOS pathogenesis. A large number of functional candidate genes have been tested for association or linkage with PCOS phenotypes with more negative than positive findings. Lack of universally accepted diagnostic criteria, difficulties in the assignment of male phenotype, obscurity in the mode of inheritance, and particularly small sample size of the study populations appear to be major limitations for the genetic studies of PCOS. In the near future, utilizing the genome-wide scan approach and the HapMap project will provide a stronger potential for the genetic analysis of the syndrome.

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.

Peroxisome proliferator-activated receptor-gamma agonist improves skeletal muscle insulin signaling in the pregestational intrauterine growth-restricted rat offspring

The effect of early intervention with a peroxisome proliferator-activated receptor-gamma (PPARgamma) agonist on skeletal muscle GLUT4 translocation and insulin signaling was examined in intrauterine (IUGR) and postnatal (PNGR) growth-restricted pregestational female rat offspring. Rosiglitazone [11 mumol/day provided from postnatal day (PN)21 to PN60] improved skeletal muscle insulin sensitivity and GLUT4 translocation in prenatal nutrient restriction [50% calories from embryonic day (e)11 to e21; IUGR] with (IUGR+PNGR) and without (IUGR) postnatal nutrient restriction (50% calories from PN1 to PN21; PNGR) similar to that of control (ad libitum feeds throughout; Con) (n = 6 each). This was accomplished by diminished basal and improved insulin-responsive GLUT4 association with the plasma membrane in IUGR, IUGR+PNGR, and PNGR mimicking that in Con (P < 0.005). While no change in p85-phosphatidylinositol 3-kinase (PI3-K) and phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was observed, a decrease in protein tyrosine phosphatase 1B (PTP1B; P < 0.0002) and SH2-containing protein tyrosine phosphatase 2 (SHP2; P < 0.05) contributing to the rosiglitazone-induced insulin sensitivity was seen only in IUGR+PNGR. In contrast, an increase in phosphorylated 5'-adenosine monophosphate kinase (pAMPK; P < 0.04) and insulin responsiveness of phosphorylated phosphoinositide-dependent protein kinase-1 (pPDK1; P < 0.05), pAkt (P < 0.01), and particularly pPKCzeta (P < 0.0001) and its corresponding enzyme activity (P < 0.005) were observed in all four experimental groups. We conclude that early introduction of PPARgamma agonist improved skeletal muscle activation of AMPK and insulin signaling, resulting in insulin-independent AMPK and insulin-responsive GLUT4 association with plasma membranes in IUGR, IUGR+PNGR, and PNGR adult offspring, similar to that of Con. These findings support a role for insulin sensitizers in preventing the subsequent development of gestational or type 2 diabetes mellitus in intrauterine and postnatal growth-restricted offspring.

Early exercise regimen improves insulin sensitivity in the intrauterine growth-restricted adult female rat offspring

We examined the effect of early exercise training (Ex) on glucose kinetics, basal, and insulin-stimulated skeletal muscle (SKM) plasma membrane (PM) GLUT4 in pre- and/or postnatal nutrient-restricted adult rat offspring compared with sedentary (Sed) state. Pregestational control female (Ex CON vs. Sed CON) and offspring exposed to prenatal (Ex IUGR vs. Sed IUGR), postnatal (Ex PNGR vs. Sed PNGR), or pre- and postnatal (Ex IUGR + PNGR vs. Sed IUGR + PNGR) nutrient restriction were studied. The combined effect of exercise and pre/postnatal nutrition in the Ex IUGR demonstrated positive effects on basal and glucose-stimulated plasma insulin response (GSIR) with suppression of endogenous hepatic glucose production (HGP) compared with sedentary state. Ex PNGR was hyperglycemic after glucose challenge with no change in glucose-stimulated insulin production or HGP compared with sedentary state. Ex IUGR + PNGR remained glucose tolerant with unchanged glucose-stimulated insulin production but increased endogenous HGP compared with sedentary state. Basal SKM PM-associated GLUT4 was unchanged by exercise in all four groups. Whereas Ex PNGR and Ex IUGR + PNGR insulin responsiveness was similar to that of Ex CON, Ex IUGR remained nonresponsive to insulin. Early introduction of regular Ex in the pregestational female offspring had a positive effect on hepatic adaptation to GSIR and HGP in IUGR and IUGR + PNGR, with no effect in PNGR. Change in insulin responsiveness of SKM GLUT4 translocation was observed in exercised IUGR + PNGR and PNGR but not in exercised IUGR.

Glucose transporter isoform-3-null heterozygous mutation causes sexually dimorphic adiposity with insulin resistance

We examined male and female glucose transporter isoform-3 (GLUT3; placenta)-null heterozygous(+/-) mutation-carrying mice and compared them with age- and sex-matched wild-type(+/+) littermates. No difference in postnatal (1-2 days, 6-7 days, 12-13 days, 20-21 days), postsuckling (1-2 mo), and adult (3-6 mo) growth pattern was seen except for an increase in body weight of 9- to 11-mo-old male but not female GLUT3(+/-) mice. This change in male mutant mice was associated with increased total body fat mass, perirenal and epididymal white adipose tissue weight, and hepatic lipid infiltration. These minimally glucose-intolerant male mutant mice demonstrated no change in caloric intake but a decline in basal metabolic rate and insulin resistance. No perturbation in basal circulating glucose concentrations but an increase in insulin concentrations, triglycerides, and total cholesterol was observed in GLUT3(+/-) male mice. Tissue analysis in males and females demonstrated diminished GLUT3 protein in GLUT3(+/-) brain and skeletal muscle with no change in brain and adipose tissue GLUT1 protein concentrations. Furthermore, the male GLUT3(+/-) mice expressed decreased insulin-responsive GLUT4 in white adipose tissue and skeletal muscle sarcolemma. We conclude that the GLUT3(+/-) male mice develop adult-onset adiposity with insulin resistance.

Histone code modifications repress glucose transporter 4 expression in the intrauterine growth-restricted offspring

We examined transcriptional and epigenetic mechanism(s) behind diminished skeletal muscle GLUT4 mRNA in intrauterine growth-restricted (IUGR) female rat offspring. An increase in MEF2D (inhibitor) with a decline in MEF2A (activator) and MyoD (co-activator) binding to the glut4 promoter in IUGR versus control was observed. The functional role of MEF2/MyoD-binding sites and neighboring three CpG clusters in glut4 gene transcription was confirmed in C2C12 muscle cells. No differential methylation of these three and other CpG clusters in the glut4 promoter occurred. DNA methyltransferase 1 (DNMT1) in postnatal, DNMT3a, and DNMT3b in adult was differentially recruited with increased MeCP2 (methyl CpG-binding protein) concentrations to bind the IUGR glut4 gene. Covalent modifications of the histone (H) code consisted of H3.K14 de-acetylation by recruitment of histone deacetylase (HDAC) 1 and enhanced association of HDAC4 enzymes. This set the stage for Suv39H1 methylase-mediated di-methylation of H3.K9 and increased recruitment of heterochromatin protein 1alpha, which partially inactivates postnatal and adult IUGR glut4 gene transcription. Further increased interactions in the adult IUGR between DNMT3a/DNMT3b and HDAC1 and MEF2D and HDAC1/HDAC4 and decreased association between MyoD and MEF2A existed. We conclude that epigenetic mechanisms consisting of histone code modifications repress skeletal muscle glut4 transcription in the postnatal period and persist in the adult female IUGR offspring.

The timing of nutrient restriction during rat pregnancy/lactation alters metabolic syndrome phenotype

OBJECTIVE

Modulation of growth of intrauterine growth restricted (IUGR) newborns causes either adult obesity or normalization of body weight and fat. We investigated the impact of rapid versus delayed catch-up growth of IUGR offspring on glucose and lipid profiles.

STUDY DESIGN

From 10 days to term gestation and through lactation, control pregnant rats received ad libitum food, whereas study rats were 50% food restricted. Cross-fostering techniques were used to examine effects of food restriction during pregnancy and/or lactation periods. Glucose and lipid profiles were determined in offspring at ages 1 day, 3 weeks, and 9 months.

RESULTS

Food restriction during pregnancy produced hypoglycemic IUGR pups. Those permitted rapid catch-up growth demonstrated adult obesity with insulin resistance (hyperglycemia/hyperinsulinemia) and hypertriglyceridemia. Conversely, IUGR exhibiting delayed catch-up growth demonstrated normal adult body weight and insulin deficiency (hyperglycemia/hypoinsulinemia) and elevated cholesterol levels as compared with controls. However, these adult offspring had higher glucose though similar insulin levels as control offspring nursed by food restricted dam.

CONCLUSION

The timing and the rate of IUGR newborn catch-up growth causes markedly altered adult phenotypes. Although delayed newborn catch-up growth may be beneficial in the prevention of adult obesity, there may be significant adverse effects on pancreatic function.

Metabolic programming in the pathogenesis of insulin resistance

This review focuses on different animal models of nutrient perturbations, inclusive of restrictive and excessive states mimicking human situations during pregnancy and lactation that cause aberrations in the offspring. These aberrations consist of diminished insulin sensitivity in the presence of defective insulin production. These phenotypic changes are due to altered peripheral tissue post-insulin receptor signaling mechanisms and pancreatic beta-islet insulin synthesis and secretion defects. While these changes during in utero or postnatal life serve as essential adaptations to overcome adverse conditions, they become maladaptive subsequently and set the stage for type 2 diabetes mellitus. Pregnancy leads to gestational diabetes with trans-generational propagation of the insulin resistant phenotype. This is in response to the metabolically aberrant maternal in utero environment, and tissue specific epigenetic perturbations that permanently alter expression of critical genes transmitted to future generations. These heritable aberrations consisting of altered DNA methylation and histone modifications remodel chromatin and affect transcription of key genes. Along with an altered in utero environment, these chromatin modifications contribute to the world-wide epidemic of type 2 diabetes mellitus, with nutrient excess dominating in developed and nutrient restriction in developing countries.

Transgenerational inheritance of the insulin-resistant phenotype in embryo-transferred intrauterine growth-restricted adult female rat offspring

To determine mechanisms underlying the transgenerational presence of metabolic perturbations in the intrauterine growth-restricted second-generation adult females (F2 IUGR) despite normalizing the in utero metabolic environment, we examined in vivo glucose kinetics and in vitro skeletal muscle postinsulin receptor signaling after embryo transfer of first generation (F1 IUGR) to control maternal environment. Female F2 rats, procreated by F1 pre- and postnatally nutrient- and growth-restricted (IUGR) mothers but embryo transferred to gestate in control mothers, were compared with similarly gestating age- and sex-matched control (CON) F2 progeny. Although there were no differences in birth weight or postnatal growth patterns, the F2 IUGR had increased hepatic weight, fasting hyperglycemia, hyperinsulinemia, and unsuppressed hepatic glucose production, with no change in glucose futile cycling or clearance, compared with F2 CON. These hormonal and metabolic aberrations were associated with increased skeletal muscle total GLUT4 and pAkt concentrations but decreased plasma membrane-associated GLUT4, total pPKCzeta, and PKCzeta enzyme activity, with no change in total SHP2 and PTP1B concentrations in IUGR F2 compared with F2 CON. We conclude that transgenerational presence of aberrant glucose/insulin metabolism and skeletal muscle insulin signaling of the adult F2 IUGR female offspring is independent of the immediate intrauterine environment, supporting nutritionally induced heritable mechanisms contributing to the epidemic of type 2 diabetes mellitus.