Inositol cycling and phosphoinositide metabolism in rat pancreatic islets.

The effects of extracellular inositol and LiCl on intra-islet inositol cycling were investigated in isolated rat islets. Islets were cultured for 7 days in inositol-free RPMI 1640 containing 11.1 mM glucose and labeled with 3.7 MBq myo-[2-3H] inositol for the final 3 days. The labeled islets were then perifused under various conditions. There was a persistent increase in [3H] efflux from labeled islets stimulated with 16.7 mM glucose for 60 min. Addition of 5 mM inositol resulted in marked release of [3H] from islets and a decrease in radioactive inositol-lipid. When islets were perifused with 5 mM LiCl, the glucose-induced efflux of [3H] was greatly inhibited. The inhibitory effect of LiCl on [3H] efflux was partially corrected by the addition of 5 mM inositol. A prominent effect of LiCl was an increase in inositol monophosphate, indicating increased phospholipase C activity. This was detected within 5 min after glucose stimulation. The present data suggest that there is always very active intra-islet inositol cycling and that glucose can augument inositol-lipid metabolism.

Glycogen and enzymes of glycogen metabolism in rat embryos and fetal organs.

Glycogen content and the enzymes of glycogen metabolism have been measured in the postimplantation rat embryo over a period ranging from 9.5 to 18.5 days of gestation. The earliest periods studied were at days 9.5 and 10.5 of gestation, when the yolk sac becomes vascularized and heart beat is first established. The next intervals were at days 10.5-11.5 when vascular connections via the allantoic placenta are formed. At 14.5 and 18.5 days of development, 4 entire organs were analyzed; heart, liver, kidney and brain. The metabolic apparatus of glycogen metabolism was concentrated in the embryo at 10.5 days, then the heart region, and in the heart itself at later stages.

Correlations between antepartum maternal metabolism and newborn behavior.

We suggested that antepartum maternal metabolism may affect later cognitive and behavioral function of progeny by impacting on developing brain cells in utero. This study reports on the observed relationships between serial characterizations of maternal fuels during pregnancy and Brazelton neonatal behavioral assessment scale ratings of offspring from 73 well-controlled pregestational diabetic patients, 112 gestational diabetic patients, and 24 nondiabetic patients. After controlling for the effects of premature birth on the Brazelton neonatal behavioral assessment scale, significant correlations were found between second- and third-trimester glycemic regulation (hemoglobin A1c and fasting plasma glucose levels) and three of four newborn behavioral dimensions of the Brazelton neonatal behavioral assessment scale. In each case, as maternal glucose increased, the newborns' Brazelton neonatal behavioral assessment scale responses were poor. Results were not substantially different when gestational and pregestational diabetic patients were analyzed separately, nor can they be attributed to various perinatal events (neonatal asphyxia, hypoglycemia) or differences in socioeconomic status or ethnicity. The presence of fuel-related neurobehavioral deficits in neonates of diabetic mothers suggests that such infants start their interactions with care givers from a modified base.

Amniotic fluid insulin concentration as a predictor of obesity.

Longitudinal correlations were obtained between amniotic fluid insulin concentration at 32 to 38 weeks' gestation and anthropometric characteristics at the age of 6 years in 56 children of diabetic mothers. The prospective studies indicated that at the age of 6 years, as at birth, the greatest increase in weight in relation to height (relative obesity) was seen in children who experienced the greatest exposures to insulin in the uterus (as judged by amniotic fluid insulin concentration). Significant correlations between amniotic fluid insulin and relative obesity at the age of 6 years were found after adjustment for maternal obesity and macrosomia at birth. The highest amniotic fluid insulin values are clustered in the subgroup of 14 children who were obviously obese by the age of 6 years. These findings are consistent with the hypothesis that there is an association between anthropometric development and intrauterine metabolism, and suggest that premature and excessive exposure to insulin during gestation may predispose to obesity in childhood. The amniotic fluid insulin concentration may predict this eventuality.

Glucose-induced dysmorphogenesis in the cultured rat conceptus: prevention by supplementation with myo-inositol.

Growth retardation and dysmorphogenesis in the rat conceptus are accompanied by diminished tissue myo-inositol following culture from day 9.5 to 11.5 of development in the presence of increased amounts of glucose. Reductions of myo-inositol and increased malformations are not corrected by aldose reductase inhibitors. In contrast, supplementation of culture medium with myo-inositol (1.5 mg/ml) restores tissue myo-inositol content, lowers the incidence of dysmorphogenic embryos (from 51.1 to 28.6%, P less than 0.001) and reduces the incidence of neural tube defects to control levels (from 33.3 to 6%, P less than 0.001). These results suggest that myo-inositol depletion is involved in the mechanism of diabetic embryopathy.

Maternal serum alpha-fetoprotein levels in pregnancies complicated by diabetes: implications for screening programs.

Maternal serum alpha-fetoprotein may be reduced in diabetic pregnancies, but the association with elevated glycosylated hemoglobin has been controversial. We tested the hypothesis that reductions in maternal serum alpha-fetoprotein may reflect the same phenomena that can also impair normal rates of embryo growth in the presence of poorly compensated maternal diabetes. If so, associations would be expected among maternal serum alpha-fetoprotein, embryo rates of growth, and levels of glycosylated hemoglobin reflective of regulation of maternal diabetes during the period of organogenesis. We found maternal serum alpha-fetoprotein levels in 93 pregnant patients with diabetes to be negatively associated with the earliest (4 to 12 weeks) glycosylated hemoglobin determinations. At glycosylated hemoglobin values greater than 9.6% (which approximates the upper quartile), all maternal serum alpha-fetoprotein values fell below the median for patients without diabetes (below 0.8 multiple of the median after weight adjustment). Moreover, there was a trend for pregnancies with lower maternal serum alpha-fetoprotein levels and higher glycosylated hemoglobin values to also demonstrate early fetal growth delay as measured by ultrasonography.

Infants of diabetic mothers with accelerated fetal growth by ultrasonography: are they all alike?

We studied longitudinal ultrasonographic growth patterns (abdominal circumference, biparietal diameter) initiated early in gestation in 52 pregnancies complicated by pregestational diabetes mellitus and 19 controls. Three predominant patterns of growth were ascertained including a heretofore unrecognized pattern characterized by accelerated abdominal circumference growth (greater than 90th percentile) before 24 weeks' gestational age. Maternal and neonatal anthropometric and metabolic parameters were contrasted for the three patterns. The findings suggest that in some cases of diabetic macrosomia that can be recognized before 24 weeks' gestation, augmented growth may be influenced by factors other than fetal hyperinsulinism.

Amniotic fluid prolactin in the third trimester of pregnancies complicated by gestational or pregestational diabetes mellitus.

Amniotic fluid concentrations of immunoreactive prolactin were measured during the third trimester in 184 diabetic gravidas and correlated with concurrent levels of prolactin in maternal plasma. Prolactin measurements concorded with previously published estimates in normal gravid women and averaged 825 +/- 32 ng/mL (mean +/- SEM) in amniotic fluid and 168 +/- 6.5 ng/mL in simultaneously sampled plasma. Cross-sectional and longitudinal analyses indicated that the prolactin levels in amniotic fluid of pregnant diabetics declined significantly between weeks 32 and 40 of gestation, whereas plasma levels did not change consistently during the same interval. Mean values for amniotic fluid prolactin did not correlate with simultaneous prolactin concentrations in plasma, nor with maternal age, clinical estimates of polyhydramnios, amniotic fluid creatinine content, or lecithin/sphingomyelin (L/S) ratios or subsequent birth weight of the offspring. Clear-cut correlations with overall maternal glucose regulation could not be demonstrated. However, subtle effects may be operative since amniotic fluid prolactin displayed weak but significant correlations with concurrent levels of maternal plasma glucose, and mean values for hemoglobin A1c (HbA1c) but not with mean values for fasting plasma glucose (FPG). Amniotic fluid prolactin concentrations were significantly greater in patients with pregestational diabetes (White classes C, D, and F) than in women with gestational diabetes mellitus (GDM) (our classes A1, A2, and B1). The differences could not be accounted for by differences in metabolic regulation, maternal age, or weights of these two populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake of myo-inositol by early-somite rat conceptus. Transport kinetics and effects of hyperglycemia.

We have shown that myo-inositol in the cultured rat embryo is diminished whenever malformations are induced by hyperglycemia and that the malformations and reductions of tissue myo-inositol content are not corrected by aldose reductase inhibitors. This study was designed to evaluate the kinetics of myo-[3H]inositol uptake in vitro during 1-, 3-, and 24-h intervals in the 10.5-day rat conceptus (10-12 somites). We found that the equilibration between tissue and medium is relatively slow and that the concentration of free myo-inositol in tissue is only approximately threefold greater than in the medium even after 24 h. The integrated uptake of free myo-inositol by the intact 10.5-day conceptus is a saturable process with a Km (246 +/- 16 microM) consistent with a low-affinity system. The net rate of accumulation into the tissue pool of free myo-inositol exceeds the rate of incorporation of the accumulated myo-inositol into lipid components. Ambient glucose inhibits net myo-inositol uptake in a concentration-dependent fashion, and the inhibition is competitive in nature. The glucose-mediated inhibitions of myo-inositol transport also compromise the concurrent incorporation of myo-[3H]inositol into lipid components, although to a lesser extent. These inhibitory effects are relatively specific for D-glucose and not replicated by equimolar additions of D-mannose or D-galactose. myo-Inositol accumulation by the 10.5-day rat conceptus is also impaired by relatively specific inhibitors of D-glucose transport such as phloridzin or ouabain.(ABSTRACT TRUNCATED AT 250 WORDS)

Accelerated starvation in late pregnancy: a comparison between obese women with and without gestational diabetes mellitus.

We compared the glucose, insulin, free fatty acid, and 3-hydroxybutyrate responses to a briefly extended overnight fast during the third trimester of pregnancy between two groups: obese women with normal glucose tolerance (n = 10) and age- and weight-matched women with gestational diabetes mellitus (n = 10). After a 12-hour overnight fast, plasma glucose (95 +/- 4 vs. 78 +/- 2 mg/dl; p less than 0.01), insulin (32 +/- 5 vs. 17 +/- 2 microU/ml; p less than 0.02), and free fatty acid (860 +/- 63 vs. 639 +/- 79 mmol/L; p less than 0.05) levels were higher in the patients with gestational diabetes mellitus. 3-Hydroxybutyrate levels were similar in the two groups at that time (0.23 +/- 0.04 vs. 0.18 +/- 0.03 mmol/L; p greater than 0.3). When the fast was extended to 18 hours by having the patients skip breakfast, glucose levels fell more rapidly in the group with gestational diabetes mellitus but remained elevated compared with the nondiabetic women. Insulin levels declined at a similar rate in the two groups. Free fatty acid levels did not increase significantly in the group with gestational diabetes mellitus during the extended fast. In contrast, free fatty acid levels increased by 44% in the normal pregnant women, reaching the level observed in the group with gestational diabetes mellitus after 18 hours. 3-Hydroxybutyrate levels remained virtually identical in the two groups throughout the brief fast. Thus, compared with that of normal pregnant women, the response of obese women with gestational diabetes mellitus to brief caloric deprivation during late pregnancy was characterized by a greater fall in plasma glucose values without a greater propensity to ketosis. Our findings may have important implications for the dietary management of obese patients with gestational diabetes mellitus.

Insulin sensitivity and B-cell responsiveness to glucose during late pregnancy in lean and moderately obese women with normal glucose tolerance or mild gestational diabetes.

We used the minimal model technique to obtain concurrent measurements of whole-body insulin sensitivity and pancreatic B-cell responsiveness to glucose during the third trimester of pregnancy. Insulin sensitivity in normal pregnant women (n = 8) was reduced to only one third that of a group of nonpregnant women (n = 7) of similar age and relative weight. This marked insulin resistance was compensated by reciprocal enhancement of the first and second-phase insulin responses to intravenous glucose, which were increased threefold as compared with the nonpregnant women. Women with gestational diabetes mellitus (n = 16) had mean insulin sensitivity that was similar to that of the normal pregnant group, which indicates that insulin action was appropriate for the late phase of pregnancy in the gestational diabetic group. By contrast, the mean first-phase insulin response was significantly reduced in women with gestational diabetes mellitus, as compared with that of normal pregnant women (p less than 0.001). However, approximately one fifth of the group with gestational diabetes mellitus had first-phase responses that did not fall below the 95% confidence interval for the mean in normal pregnant women. The mean second-phase response was also lower in the group with gestational diabetes, although the difference was of borderline statistical significance (p less than 0.09). Our findings reveal the quantitative nature of the reciprocal changes in insulin sensitivity and B-cell function that normally accompany late pregnancy. They further indicate that during the third trimester, mild gestational diabetes is characterized by an impairment of pancreatic B-cell function rather than an exaggeration of the normal insulin resistance of late pregnancy.

Access of maternal insulin to the rat conceptus prior to allantoic placentation.

We have investigated the availability of circulating maternal insulin to the postimplantation rat conceptus during early organogenesis, before the insulin-impermeable allantoic placeta is established. Virtual distribution equilibrium for "tracer" quantities of 125I-porcine insulin was achieved by continuous infusions into pregnant rats on day 11 of gestation (day 10.3 of embryo development). During continuing infusion, following 210 min of iodoinsulin delivery, intact conceptuses (embryo, amnion, and yolk sac), and portions of adjacent decidua, liver, and spleen were excised, rinsed, and frozen in liquid N2 within 2 min. Subsequent analysis by trichloroacetic acid (TCA) precipitation or immunoprecipitation revealed the presence of intact iodoinsulin in all tissues. Both analytical approaches disclosed the same pattern of iodoinsulin distribution, i.e., liver and spleen greater than decidua and conceptus. Assayable iodoinsulin could not be demonstrated in embryos excised from the intact conceptuses; however the embryo observations were limited by the amount of accessible tissue and the requisite preparative delay. Our studies indicate that during early organogenesis, before the establishment of the allantoic placenta, maternal insulin has access to at least the outer portion of the postimplantation rat conceptus, including yolk sac, where insulin-specific receptors are known to occur.

Diabetic embryopathy and fuel-mediated organ teratogenesis: lessons from animal models.

The growing recognition that faulty maternal metabolism during early organogenesis may be implicated in the increased incidence of birth defects in pregnancies complicated by diabetes has prompted worldwide efforts to institute improved preconceptional metabolic regulation. However, the failure to identify the periods of greatest risk for diabetic embryopathy, the mediating teratogen(s), and the underlying mechanisms have complicated attempts to establish precise therapeutic guidelines and targets. Some of the reported in vivo and in vitro experiences with rodent models have been reviewed to derive relevant insights. Substantial literature indicates that diabetes (experimental as well as spontaneous) in pregnant rats and mice is attended by retardation of growth and developmental delay during embryogenesis, and a variable incidence of birth defects. Poor metabolic regulation of the diabetic mother during early organogenesis may also be followed by subsequent resorption of the conceptus at the site of implantation. Vulnerability to diabetes-related resorptions and all other forms of embryopathy appears to begin during the early postimplantation period and is greatest near the onset of neurolation. Overall susceptibility is markedly influenced by genetic factors and may be modified by the antecedent metabolic exposures of the conceptus ("carry-over effects"). Mediation for the anomalous embryo development in pregnancies of diabetic rodents appears to be multifactorial; all the aberrant fuels and fuel-related components of "the diabetic state" (e.g. high glucose; ketones; somatomedin inhibitor(s); osmolality, etc.) which have been tested to date display dysmorphogenic potential ("fuel-mediated organ terato-genesis") in vitro. All tissues in the conceptus appear to be at risk. Dose-response relationships for the individual metabolic teratogens may be influenced by additive and synergistic interactions so that the integrated possibilities cannot be assessed fully by measurements confined to a single fuel or fuel-related component. In the context of the day-to-day variability in diabetes "control" of the poorly regulated mother, and the relatively longer duration of organogenesis, these multifactorial possibilities may account for the multiple birth defects that can occur in individual offspring, and the seemingly non-specific pattern of diabetic embryopathy. Insulin therapy diminishes the dysmorphogenic effects of "the diabetic state" in rodents with experimental or spontaneous diabetes.(ABSTRACT TRUNCATED AT 400 WORDS)

Fuel-mediated teratogenesis: symmetric growth retardation in the rat fetus at term after a circumscribed exposure to D-mannose during organogenesis.

We previously infused the D-glucose epimer D-mannose into pregnant rats to deliver a brief metabolic insult to the early postimplantation conceptus. This insult caused developmental anomalies and growth retardation that were apparent in the embryos 2 days later. We now report the long-range effects on intrauterine development of such a circumscribed metabolic insult during organogenesis. Ten pregnant animals were infused with D-mannose for 12 hours during early neurulation (day 9.5 to 10 of development). Ten control animals were infused with equimolar D-glucose during this same time interval. Mannose infusions produced maternal plasma mananose concentrations in the embryotoxic range; glucose infusions caused only slight and transient hyperglycemia. Fetuses were removed at term and examined for evidence of developmental anomalies and growth retardation. None of 137 fetuses from the mannose group or 138 fetuses from the glucose group exhibited gross anomalies. However, an excess of resorbed conceptions in the mannose group (21 versus six in the glucose group; p less than 0.01) suggested some lethal toxicity from mannose exposure during embryogenesis. Among viable fetuses, the mean body weight of those from the mannose group was significantly reduced compared with those from the glucose group (5.62 +/- 0.04 versus 5.89 +/- 0.03 gm, respectively; p less than 0.001). Reductions of a similar magnitude were noted in the mean wet weight and protein content of fetal brains, hearts, livers, and kidneys from the mannose group (range, 3.4% to 7.1% below the glucose group), indicating a symmetric pattern of fetal growth retardation. In addition, analysis of fetal ossification sites after Alizarin Red S staining revealed a significant delay of skeletal development in the mannose group. These results indicate that a relatively brief metabolic insult to embryos during early organogenesis may cause lethal developmental anomalies as well as growth retardation and delayed skeletal development that are manifested in the fetus at term.

Gestational diabetes mellitus is associated with HLA-DQ beta-chain DNA endonuclease fragments.

DNA from Caucasian normal healthy control subjects, non-gravid patients with insulin-dependent diabetes mellitus (IDDM) and gravida with gestational diabetes mellitus (GDM) were analyzed with DNA probes for HLA markers associated with HLA-DR and HLA-DQ to compare the hybridization patterns of their DNA after digestion with restriction endonucleases. We report HLA-DQ beta restriction endonuclease fragments to be presented with increased frequency in Caucasian gravida with GDM as well as in subjects with IDDM. These findings provide further evidence for genetic heterogeneity in GDM and are compatible with the presence of slowly evolving IDDM in some women with "carbohydrate intolerance of variable severity with onset or first recognition during pregnancy".

Accelerated starvation in pregnancy: implications for dietary treatment of obesity and gestational diabetes mellitus.

The biological significance of ketonemia of brief duration and moderate proportions during pregnancy remains uncertain. Thus, controversy persists about whether caloric restriction for obese women during pregnancy, particularly when the obesity is complicated by gestational diabetes mellitus (GDM), constitutes appropriate therapy. We have demonstrated, in a rigorously controlled setting using a Clinical Research Center, that all of the features of 'accelerated starvation' become manifest after 14 h and before 18 h of dietary deprivation. Women with GDM exhibit the same capacity for early 'accelerated starvation' as in normal pregnancy; thus, their insulin deficiency and insulin resistance do not appear to be sufficient to render them increasedly at risk for uncontrolled catabolism. Some cautious exploration of the use of hypocaloric diets as a therapeutic approach to the metabolic disturbances of GDM may be justified.

Changes in diabetic retinopathy during pregnancy. Correlations with regulation of hyperglycemia.

Thirty-eight pregnancies in 35 women with insulin-dependent diabetes mellitus were monitored for changes in diabetic retinopathy during the institution of "tight" metabolic control by intensive medical management. Eye findings were scored on paired sets of retinal photographs obtained when enrolled in this study and shortly after delivery. These findings were then correlated with measurements of diabetic regulation. Intensive therapy for the diabetes mellitus resulted in improved glucose control by the time of delivery. However, retinal abnormalities worsened as gestation proceeded in 55% of the pregnancies. Deterioration of background retinopathy correlated significantly with the levels of plasma glucose at entry and with the magnitude of improvement in glycemia achieved during the first six to 14 weeks after entry (ie, "early changes") and by the final week before delivery (ie, "overall changes"). Our findings indicate that the changing retinopathy during pregnancy cannot be interpreted without assessment of concurrent changes in the regulation of maternal diabetes and that the abrupt institution of improved diabetic control during pregnancy may be one factor in the deterioration of background retinopathy sometimes seen during pregnancy.

The 1986 McCollum award lecture. Fuel-mediated teratogenesis during early organogenesis: the effects of increased concentrations of glucose, ketones, or somatomedin inhibitor during rat embryo culture.

Whole rat embryos were explanted at head-fold, late pre-somite stage (day 9.5 of gestation) and cultured in rat sera varyingly supplemented with glucose (3, 6, 9, or 12 mg/mL), D,L sodium beta-hydroxybutyrate (2, 4, 8, or 16 mM), or both (6 mg/mL D-glucose plus 8 mM beta-hydroxybutyrate). During 48 h culture, increasing glucose alone or beta-hydroxybutyrate alone effected growth retardation and faulty neural and extraneural organogenesis in dose-dependent fashion. Synergistic dysmorphogenic effects occurred when minimally teratogenic concentrations of glucose and beta-hydroxybutyrate were combined. Sera from diabetic animals containing somatomedin inhibitor bioactivity were also able to produce growth retardation and major developmental lesions in presence of amounts of glucose and ketones which of themselves were not teratogenic. Thus, aberrant fuels and fuel-related products can impair growth and organogenesis in early post-implantation embryo. Such fuel-mediated teratogenesis may be multifactorial and include possibilities for synergistic and additive interactions.