Prospective study of gut hormone and metabolic changes after adjustable gastric banding and Roux-en-Y gastric bypass.

OBJECTIVE: The objective of this study was to quantify hormones that regulate energy and glucose homeostasis to establish possible mechanisms for the greater efficacy of Roux-en-Y gastric bypass (RYGB) compared with laparoscopic adjustable gastric banding (LAGB) in achieving weight loss and improved insulin sensitivity. DESIGN: Longitudinal study of patients undergoing LAGB (n=15) and RYGB (n=28) who were studied before surgery and at 2, 12, 26 and 52 weeks afterwards. MEASUREMENTS: Fasting blood samples were drawn at each visit. Postprandial blood samples were also obtained before surgery and at 26 and 52 weeks. Samples were assayed for peptide YY (PYY), ghrelin, glucagon-like peptide-1 (GLP-1), glucose, insulin, leptin, thyrotropic hormone, free T(4) and free T(3). RESULTS: At 1 year there was greater weight loss in RYGB compared with LAGB patients (30 vs 15%), but final body mass index was similar (34 vs 33 kg m(-2)). At week 52, area under the curve (AUC) for PYY in RYGB subjects was greater than LAGB (P<0.01). GLP-1 levels at 30 min after meal were threefold greater after RYGB compared with LAGB (P<0.001). Conversely, ghrelin AUC increased after LAGB at week 52 (P<0.05) but tended to decrease after RYGB. Fasting glucose, insulin, and leptin and homeostasis model of assessment (HOMA-IR) decreased in both groups over time but were significantly lower at week 52 after RYGB compared with LAGB. The change in leptin correlated significantly with weight loss in LAGB (r=0.86) and RYGB (r=0.77), however, HOMA-IR correlated significantly with weight loss only in LAGB (r=0.78), and not RYGB (r=0.15). There was a significant decrease in free T(3) (P<0.01) after RYGB. CONCLUSIONS: Differences in levels of gut hormones may play a role in promoting greater weight loss and insulin sensitivity after RYGB compared with LAGB, however, weight loss may be limited by decreases in free T(3) and leptin.

Effects of agouti-related protein on metabolism and hypothalamic neuropeptide gene expression.

The hypothalamic melanocortin system regulates feeding in part through interaction of the appetite stimulating peptide, agouti-related protein (AGRP), and the anorectic peptide, alpha-melanocyte stimulating hormone, a peptide derived from the pro-opiomelanocortin (POMC) polyprotein. Central administration of AGRP induces hyperphagia and increased gain in body weight in rodents, but may also exert metabolic effects even when hyperphagia is prevented. In the present studies, the effects of AGRP on hypothalamic neuropeptide gene expression and metabolism were examined in the rat. Central administration of AGRP for 3- and 7-day periods resulted in hyperphagia, increased body weight and increased plasma leptin and insulin concentrations compared to saline-injected controls. Hypothalamic concentrations of Pomc mRNA were also increased by 27% and 44% (in 3- and 7-day experiments, respectively). The hypothalamic concentration of Agrp mRNA was unchanged after 3 days, but was significantly decreased by 33% after 7 days of AGRP infusion. To determine if these changes were dependent upon AGRP-induced hyperphagia, pair-fed rats with restricted food intake receiving central administration of AGRP were also studied. In the absence of hyperphagia, intracerebralventricular administration of AGRP caused significant increases in plasma leptin and insulin concentrations (two-fold and 1.5-fold, respectively) and fat pad mass. A significant increase in hypothalamic Pomc mRNA concentrations was not detected in pair-fed rats. In contrast, Agrp mRNA concentrations remained suppressed by 45% in the pair-fed group after 7 days of AGRP infusion despite equal body weight compared to saline controls. The ratio of hypothalamic Pomc to Agrp mRNA was elevated two-fold in ad libitum and pair-fed AGRP-injected rats, which is consistent with increased stimulation of central melanocortin signalling pathways. Thus, central administration of AGRP exerts changes in hypothalamic neuropeptide gene expression and metabolic effects that are independent of the effects on food intake and body weight.

Effects of leptin receptor mutation on Agrp gene expression in fed and fasted lean and obese (LA/N-faf) rats.

Agouti-related protein provides an orexigenic signal, probably through interaction with central melanocortin receptors. Expression of Agrp is markedly increased in the hypothalamus of mice deficient in leptin (Lep(ob)/Lep(ob)) or its receptor (Lepr(db)/Lepr(db)), suggesting that leptin mediates signals suppressing Agouti-related protein production. The regulation of Agrp expression in the rat hypothalamus has not been reported. We, therefore, analyzed the expression of Agrp in the medial basal hypothalamus of lean (+/+, +/fa(f)) and obese leptin receptor-deficient (fa(f)/fa(f)) LA/N rats. Using a sensitive solution hybridization/S1 nuclease protection assay, we found no significant difference in Agrp messenger RNA (mRNA) levels (pg/microg total RNA +/- SEM) in obese rats (n = 5), compared with lean controls (n = 5): 0.46 +/- 0.06 vs. 0.47 +/- 0.06 (P = 0.9). Similarly, no difference in Agrp expression was found using in situ hybridization or semiquantitative RT-PCR. In contrast to Agrp, Pomc mRNA levels were significantly suppressed in the obese, compared with the lean, rats (P = 0.001). Thus, the ratio of Pomc to Agrp mRNA is decreased in the obese rats and may be an important modulator of food intake. To assess the physiological regulation of Agrp in rats, we examined the effect of food deprivation in lean Sprague Dawley (SD) rats. There was a 273% increase in medial basal hypothalamus Agrp mRNA in SD rats fasted for 48 h (n = 8), compared with rats fed ad libitum (n = 8): 0.82 +/- 0.23 vs. 0.30 +/- 0.08 (P = 0.0001). Lean LA/N rats (n = 7) fasted for 48 h also showed a 231% increase in Agrp expression, compared with fed lean controls (n = 8): 0.74 +/- 0.11 vs. 0.32 +/- 0.03 (P = 0.002), whereas Pomc expression was decreased by 32% in fasted animals from the same experiment (0.34 +/- 0.05 vs. 0.50 +/- 0.07; P = 0.03). There were no significant differences in Agrp or Pomc mRNA levels between fasted and fed obese LA/N-fa(f) rats. These results suggest that, in the rat, the Agrp response to fasting may involve leptin-mediated phenomena, but factors in addition to leptin must also be involved in the regulation of Agrp gene expression.

Glucocorticoid regulation of hypothalamic proopiomelanocortin.

Although glucocorticoids clearly inhibit proopiomelanocortin (POMC) gene transcription and peptide synthesis in the anterior pituitary, the effects of glucocorticoids on POMC in the hypothalamus are still unclear, even though most POMC neurons in the arcuate nucleus are known to have glucocorticoid receptors. In this study, we have therefore examined the effect of adrenalectomy (ADX) and glucocorticoid replacement on POMC mRNA and peptide (beta-EP and alpha-MSH) levels in the medial basal hypothalamus (MBH) of the rat. POMC mRNA was measured by a sensitive solution hybridization S1 nuclease protection assay, and beta-EP and alpha-MSH were measured by radioimmunoassay. In a first experiment, animals were studied 7 days after ADX or sham surgery. The mean POMC mRNA concentration was 1.01+/-0.14 pg/microg RNA (means+/-SE) in the intact animals and decreased to 0.55+/-0.07 pg/microg RNA in the MBH of the ADX animals (p < 0.005). Beta-EP levels decreased in parallel from 4.30+/-0.18 to 3.36+/-0.11 ng/mg protein (p < 0.001); alpha-MSH levels decreased from 3.25+/-0.21 to 2.41+/-0.16 ng/mg protein (p < 0.005). In a second experiment, animals were studied 2 weeks after ADX. POMC mRNA levels again fell significantly from 1.15+/-0.19 pg/microg RNA in the intact animals to 0.51+/-0.06 pg/microg in the ADX animals (p < 0.01). Beta-EP levels fell also, but this was not significant. In a third experiment, all animals underwent ADX, and half of them received daily subcutaneous injections of dexamethasone (20 microg). Nine days after ADX, the mean POMC mRNA level was 0.66+/-0.04 pg/microg RNA in the saline-treated animals and increased to 0.98+/-0.08 pg/microg RNA in the dexamethasone-treated animals (p < 0.005). A parallel increase in beta-EP levels from 5.03+/-0.41 to 6.01+/-0.53 ng/mg protein was also noted, but this was not statistically significant. We conclude that POMC gene expression is significantly inhibited in the MBH at 1 and 2 weeks after ADX. This effect was reversed by glucocorticoid replacement with doses close to the physiological range. The parallel changes in POMC mRNA and peptide levels strongly suggest that, in contrast to the anterior pituitary, low doses of glucocorticoids stimulate the biosynthesis of POMC in the MBH of ADX rats.

The effect of pre-eclampsia on human placental corticotrophin-releasing hormone content and processing.

Prior studies have shown that levels of corticotrophin-releasing hormone (CRH) in the umbilical cord blood of infants born after pregnancies complicated by pre-eclampsia are significantly higher than fetal plasma CRH concentrations in uncomplicated pregnancies. In the present study we have measured CRH by radioimmunoassay in the placenta and fetal membranes from 13 pregnancies complicated by pre-eclampsia and compared them to 24 uncomplicated pregnancies. In addition we have investigated the effect of chronic intrauterine fetal stress on the processing of CRH in the placenta and fetal membranes. Placental CRH peptide content was significantly higher in the pregnancies complicated by pre-eclampsia, 12,900 +/- 4230 pg/g tissue, than in the uncomplicated pregnancies, 3130 +/- 430 pg/g of tissue (P < 0.01). Gel filtration of the homogenates of normal placenta revealed a major peak of CRH immunoactivity eluting in the same position as synthetic human CRH. A second smaller molecular weight peak of CRH-immunoactivity was also present and in both the amnion and the chorion, the CRH eluted in the position of the smaller molecular weight peak. In contrast, the bulk of the CRH immunoactivity in the placenta and fetal membranes obtained after pregnancies complicated by pre-eclampsia eluted in the position of intact synthetic human CRH. Thus, in pregnancy complicated by pre-eclampsia, both placental CRH release into fetal plasma and CRH peptide content is higher than in uncomplicated pregnancy.

Concentrations of corticotrophin-releasing hormone in the umbilical-cord blood of pregnancies complicated by pre-eclampsia.

The effect of pre-eclampsia on concentrations of corticotrophin releasing hormone (CRH) in umbilical-cord blood of fetuses at delivery was studied in order to determine if fetal CRH is elevated in this disorder when compared with uncomplicated pregnancy. Placental CRH may be a regulator of fetal pituitary-adrenal function and we therefore also measured ACTH, cortisol and dehydroepiandrosterone sulfate (DHEAS) in the umbilical-cord blood. The mean umbilical-cord plasma CRH in the fetuses from pregnancies complicated by pre-eclampsia, 667 +/- 153 pg mL-1, was significantly higher than the plasma CRH in the fetuses from normotensive pregnancies, 185 +/- 22 pg mL-1 (P < 0.001). The mean fetal cortisol concentration was significantly higher in pre-eclampsia, than in the normotensive, pregnancies (pre-eclampsia, 13.5 +/- 1.8; normotensive, 7.6 +/- 1.3 micrograms dL-1; P < 0.001). Plasma DHEAS was 217 +/- 23 micrograms dL-1 in the umbilical-cord blood of the fetuses from pregnancies complicated by pre-eclampsia and 281 +/- 35 micrograms dL-1 in the normotensive pregnancies (P < 0.01). Placental CRH synthesis and release, in contrast to hypothalamic CRH, appears to be stimulated by glucocorticoids. In pregnancies complicated by uteroplacental insufficiency, as may occur in pre-eclampsia, placental CRH production may be enhanced by increased fetal glucocorticoids. In turn, placental CRH may modulate fetal pituitary-adrenal steroidogenesis to favour increased cortisol secretion. Thus, placental CRH may play an important role in the fetal response to a compromised intrauterine environment.

Elevated levels of umbilical cord plasma corticotropin-releasing hormone in growth-retarded fetuses.

CRH is synthesized in the hypothalamus and released in response to stress into the portal hypophyseal blood; an additional site of synthesis, the placenta, is present only during pregnancy. Placental CRH is released into the maternal and fetal circulation during human pregnancy, and we hypothesized that the chronic fetal stress associated with fetal growth retardation may stimulate placental CRH release. We measured plasma CRH concentrations in the umbilical cord blood of 28 growth-retarded fetuses and 28 normally grown fetuses matched for gestational age and mode of delivery. Plasma ACTH, dehydroepiandrosterone sulfate (DHEAS), and cortisol were also measured in the umbilical cord samples to determine if CRH levels were correlated with levels of pituitary and adrenal hormones. The mean umbilical cord plasma CRH level in the growth-retarded fetuses was 206 +/- 25.8 pmol/L, which was significantly higher than that in the normally grown fetuses matched for gestational age, presence or absence of labor, and mode of delivery (49.4 +/- 16.7 pmol/L; P < 0.01). The mean plasma ACTH level in the growth-retarded fetuses (5.7 +/- 1.2 pmol/L) was significantly higher than that in the normally grown fetuses (3.3 +/- 0.7 pmol/L; P < 0.05). The mean cortisol concentration in the growth-retarded fetuses was 260 +/- 32.5 nmol/L, and that in the normally grown fetuses was 220 +/- 40 nmol/L. The mean DHEAS level was significantly lower in the growth-retarded fetuses (4.8 +/- 0.6 mumol/L) than that in the normally grown fetuses (7.7 +/- 0.6 mumol/L; P < 0.001). There was a significant correlation between umbilical cord plasma CRH and both ACTH and cortisol concentrations as well as a significant negative correlation between CRH and DHEAS levels in the growth-retarded fetuses. The umbilical cord plasma CRH level is extremely elevated in growth-retarded fetuses compared to that in normal fetuses. Placental CRH, like hypothalamic CRH, may be stimulated in conditions of chronic stress and may modulate fetal pituitary-adrenal function in high risk pregnancies.

Placental corticotropin-releasing hormone and pituitary-adrenal function during pregnancy.

The placenta secretes large amounts of the hypothalamic releasing hormone, corticotropin-releasing hormone (CRH), into both the maternal and fetal circulation during pregnancy. We characterized the relationship between maternal plasma CRH and products of the pituitary and adrenal in order to investigate the physiologic role of placental CRH in modulating maternal pituitary-adrenal function. Plasma was obtained from 8 women at biweekly intervals between 21 and 40 weeks of full-term pregnancy for CRH, adrenocorticotropin (ACTH), alpha-melanocyte-stimulating hormone (alpha MSH), cortisol, and dehydroepiandrosterone sulfate (DHEAS) measurements by radioimmunoassay. Eighteen women were also studied once at 22-34 weeks of pregnancy with plasma CRH and 24-hour urinary free cortisol measurement. Eight nonpregnant women served as control subjects. Plasma CRH was undetectable in the nonpregnant subjects and rose over the time period studied in the pregnant women. Concentrations of afternoon ACTH and cortisol also rose during pregnancy while DHEAS levels declined in the pregnant women. The alpha-MSH levels were beneath the level of detection (< 20 pg/ml) in both the pregnant and nonpregnant subjects. The overall mean afternoon ACTH concentration was higher in the pregnant than in the nonpregnant women (11.4 +/- 1.8 vs. 5.9 +/- 1.8 pg/ml; p < 0.05), although the ACTH levels in both groups remained within the normal range. The mean plasma cortisol concentrations were higher in the pregnant women, while the mean DHEAS levels were lower in the pregnant women when compared to the nonpregnant subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Corticotropin releasing hormone concentrations in umbilical cord blood of preterm fetuses.

Corticotrophin releasing hormone (CRH), dehydroepiandrosterone sulfate (DHEAS) and cortisol were measured in umbilical cord plasma obtained from 90 preterm and 98 term fetuses. Maternal plasma was obtained from 23 women who delivered preterm and from 23 women matched for gestational age who ultimately delivered term infants. Mean umbilical cord plasma CRH concentration was significantly higher in the preterm fetuses (n = 69, 538 +/- 63 pg/ml) compared to the term fetuses (n = 98, 280 +/- 22 pg/ml, P < 0.01). Mean DHEAS level in the preterm fetuses was 208 +/- 22 mg/dl (n = 56), cortisol level was 7 +/- 1 mg/dl (n = 58). Umbilical plasma CRH concentrations (808 +/- 170 pg/ml) were significantly higher at 24-27 weeks than at 28-31 or 31-34 weeks gestation. Cortisol levels (12 +/- 3 micrograms/dl) were highest at 24-27 weeks. Mode of delivery and the presence of labor did not affect fetal CRH levels. The highest fetal CRH levels were measured in the pregnancies complicated by hypertension as well as prematurity; however, fetal CRH levels remained higher in the preterm group compared to the term group when hypertensive pregnancies were excluded. Maternal plasma CRH levels were significantly higher in the group that delivered preterm compared to women who delivered at term matched for gestational age (1058 +/- 184 pg/ml compared to 456 +/- 71 pg/ml, P < 0.00).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated maternal plasma corticotropin releasing hormone levels in twin gestation.

The placenta secretes large amounts of the hypothelamic hormone, corticotropin releasing hormone (CRH) into the maternal and fetal circulation during pregnancy. We and other investigators have shown that during normal pregnancy, maternal plasma CRH levels begin to rise in the second trimester with a dramatic increase in CRH levels during the 5-6 weeks preceding the onset of labor. This rise in maternal plasma CRH is parallel to the rise of placental CRH mRNA which has been reported to occur with gestational maturation. Mechanisms underlying the control of CRH secretion by the placenta have not yet been determined. In twin gestation, increased fetal-placental mass has been shown to be associated with elevated maternal levels of several placental hormones as compared to singleton gestation. We measured maternal plasma CRH in both twin and singleton gestation to investigate whether the larger size of the fetal-placental unit in twin gestation is associated with elevated maternal CRH levels. Seventy-six serial venous blood samples were collected from 20 women with twin gestation and 40 samples were obtained from 27 women with uncomplicated singleton gestation. Gestational age was determined by history of a known last menstrual period and first trimester clinical examination and confirmed by ultrasound examination. CRH was extracted from 1-2 ml plasma with SEP-Pak C18 cartridges and eluted with triethylamine-formic-acid propranolol. CRH was measured by radioimmunoassay (RIA) with human CRH standard and antiserum to human CRH raised in our laboratory. Mean CRH levels were calculated for four week intervals. In both singleton and twin gestation, the maternal plasma CRH levels increased with advancing gestational age. After 29 weeks of gestation, maternal plasma CRH levels in twin gestation were significantly higher than those in singleton gestation (p less than 0.01). At 37 to 40 weeks of gestation, mean maternal CRH was 1167 +/- 237 pg/ml in singleton gestation as compared to 6927 +/- 1725 pg/ml in twin gestation (p less than 0.05). In addition, the rapid rise in plasma CRH levels which occurs near term in singleton gestation, occurred earlier in twin gestation. This early rise in maternal CRH levels persisted when the data from twin pregnancies complicated by preterm labor were removed from the analysis.(ABSTRACT TRUNCATED AT 250 WORDS)