The addition of sitagliptin to ongoing metformin therapy significantly improves glycemic control in Chinese patients with type 2 diabetes

BACKGROUND

  The present study was conducted to evaluate the efficacy, safety and tolerability of sitagliptin added to ongoing metformin therapy in Chinese patients with type 2 diabetes (T2DM) who failed to achieve adequate glycemic control with metformin monotherapy.

METHODS

  After a metformin titration/stabilization period and a 2-week, single-blind, placebo run-in period, 395 Chinese patients with T2DM aged 25-77 years (baseline HbA1c 8.5%) were randomized (1:1) to double-blind placebo or sitagliptin 100 mg q.d. added to ongoing open-label metformin (1000 or 1700 mg/day) for 24 weeks.

RESULTS

  Significant (P < 0.001) changes from baseline in HbA1c (-0.9%), fasting plasma glucose (-1.2 mmol/L), and 2-h post-meal plasma glucose (-1.9 mmol/L) were seen with sitagliptin compared with placebo. There were no significant differences between sitagliptin and placebo in the incidence of hypoglycemia or gastrointestinal adverse events. A small decrease from baseline body weight was observed in the placebo group compared with no change in the sitagliptin group (between-group difference 0.5kg; P=0.018).

CONCLUSIONS

  The addition of sitagliptin 100 mg to ongoing metformin therapy significantly improved glycemic control and was generally well tolerated in Chinese patients with T2DM who had inadequate glycemic control on metformin alone.

Mechanisms for the antihyperglycemic effect of sitagliptin in patients with type 2 diabetes

CONTEXT

Dipeptidyl peptidase IV (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes. The underlying mechanisms (incretin effect, β-cell function, endogenous glucose production) are not well known.

OBJECTIVE

The aim of the study was to examine mechanisms of the antihyperglycemic effect of DPP-4 inhibitors.

DESIGN, SETTING, AND PATIENTS

We administered a mixed meal with glucose tracers ([6,6-(2)H(2)]-glucose infused, [1-(2)H]-glucose ingested), and on a separate day, a glucose infusion matched the glucose responses to the meal (isoglycemic test) in 50 type 2 diabetes patients (hemoglobin A(1c) = 7.4 ± 0.8%) and seven controls; 47 diabetic completers were restudied after 6 wk. Glucose fluxes were calculated, and β-cell function was assessed by mathematical modeling. The incretin effect was calculated as the ratio of oral to iv insulin secretion.

INTERVENTION

We conducted a 6-wk, double-blind, randomized treatment with sitagliptin (100 mg/d; n = 25) or placebo (n = 22).

RESULTS

Relative to placebo, meal-induced changes in fasting glucose and glucose area under the curve (AUC) were greater with sitagliptin, in parallel with a lower appearance of oral glucose [difference (post-pre) AUC = -353 ± 915 vs. +146 ± 601 μmol · kg(-1) · 5 h] and greater suppression of endogenous glucose production. Insulin sensitivity improved 10%, whereas total insulin secretion was unchanged. During the meal, β-cell glucose sensitivity improved (+19[29] vs. 5[21] pmol · min(-1) · m(-2) · mm(-1); median [interquartile range]) and glucagon AUC decreased (19.6 ± 7.5 to 17.3 ± 7.1 ng · ml(-1) · 5 h), whereas intact glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 AUC increased with sitagliptin vs. placebo. The incretin effect was unchanged because sitagliptin increased β-cell glucose sensitivity also during the isoglycemic test.

CONCLUSIONS

Chronic sitagliptin treatment improves glycemic control by lowering the appearance of oral glucose, postprandial endogenous glucose release, and glucagon response, and by improving insulin sensitivity and β-cell glucose sensing in response to both oral and iv glucose.

Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids

We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.).

Effects of MK-0941, a novel glucokinase activator, on glycemic control in insulin-treated patients with type 2 diabetes

OBJECTIVE

To assess the efficacy and safety of MK-0941, a glucokinase activator (GKA), when added to stable-dose insulin glargine in patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In this double-blind study, 587 patients taking stable-dose insulin glargine (±metformin ≥1,500 mg/day) were randomized (1:1:1:1:1) to MK-0941 10, 20, 30, or 40 mg or matching placebo t.i.d. before meals (a.c.). This study included an initial 14-week, dose-ranging phase followed by a 40-week treatment phase during which patients were to be uptitrated as tolerated to 40 mg (or placebo) t.i.d. a.c. The primary efficacy end point was change from baseline in A1C at Week 14.

RESULTS

At Week 14, A1C and 2-h postmeal glucose (PMG) improved significantly versus placebo with all MK-0941 doses. Maximal placebo-adjusted least squares mean changes from baseline in A1C (baseline A1C 9.0%) and 2-h PMG were -0.8% and -37 mg/dL (-2 mmol/L), respectively. No significant effects on fasting plasma glucose were observed at any dose versus placebo. By 30 weeks, the initial glycemic responses noted at 14 weeks were not sustained. MK-0941 at one or more doses was associated with significant increases in the incidence of hypoglycemia, triglycerides, systolic blood pressure, and proportion of patients meeting criteria for predefined limits of change for increased diastolic blood pressure.

CONCLUSIONS

In patients receiving stable-dose insulin glargine, the GKA MK-0941 led to improvements in glycemic control that were not sustained. MK-0941 was associated with an increased incidence of hypoglycemia and elevations in triglycerides and blood pressure.

Hazardous gas releases in urban areas: assessment of consequences through CFD modelling

Release of hazardous materials in urban areas is a major concern in industrial risk assessment. The presence of high population density in such areas multiplies the magnitude of the consequences. In urban areas, many buildings with complex geometries are involved leading to 3D flow fields that strongly influence gas dispersion. Representing such complex geometries simply but realistically in detailed simulation models can be cumbersome and often limit their utility. In this work, a methodology for the construction of 3D urban models and their importation into CFD models was developed through the access to spatial geodatabases, leading to a relatively fast and simple domain design technique. Moreover, since the magnitude of consequences depends on the absorbed dose which in turn depends on both concentration and exposure time, a simple methodology for dose evaluation was developed and implemented in a CFD code that enables the estimation of regions with a given death probability. The approach was developed and applied to a case study with different atmospheric stratification conditions. The results were then compared with those obtained using integral models. It was found that integral models can both overestimate and underestimate the magnitude of consequences related to hazardous material releases in urban areas.

Sitagliptin 100 mg daily effect on DPP-4 inhibition and compound-specific glycemic improvement

OBJECTIVE

In clinical trials, the degree of glucose lowering with sitagliptin has been correlated with the magnitude of dipeptidyl peptidase-4 (DPP-4) inhibition over 24 h. Previous studies evaluating sitagliptin doses ranging from 25 to 200 mg/day demonstrated that the daily dose of 100 mg provided maximal glucose-lowering efficacy for this compound in patients with type 2 diabetes. However, sitagliptin 200 mg once daily provided numerically greater percent plasma DPP-4 inhibition compared with 100 mg once daily. The purpose of this study was to evaluate whether sitagliptin 200 mg once daily provides greater improvement in glycemic efficacy as assessed by weighted mean glucose (WMG) over 24 h relative to sitagliptin 100 mg once daily and to relate the percent DPP-4 inhibition achieved with these doses to any between-treatment differences in glycemic efficacy.

METHODS

In a double-blind crossover study, patients with type 2 diabetes (fasting plasma glucose [FPG] 130-250 mg/dL) were randomized to one of six treatment sequences over three treatment periods (placebo, sitagliptin 100 mg once daily, or sitagliptin 200 mg once daily). Each of the treatment periods was 7 days in duration, with 28-day washout periods between treatments. After each treatment period, patients underwent blood sampling at various time points over 24 h to determine 24-h WMG. Plasma DPP-4 activity was assessed at trough, 24 h following dosing on day 7; percent DPP-4 inhibition was corrected for sample assay dilution.

RESULTS

The 103 randomized patients had a baseline mean FPG of 172 mg/dL. Following a planned interim analysis, the study was stopped because the 24-h WMG values were not different between the sitagliptin doses. Furthermore, a significant carryover effect across periods was observed for FPG; thus, efficacy results from period 1 are presented herein. The 24-h WMG values were significantly (p < 0.01) lower with sitagliptin relative to placebo, but the difference between sitagliptin doses was not significant (p = 0.365). Corrected percent plasma DPP-4 inhibition at trough was not significantly (p = 0.791) different with sitagliptin 200 mg (LS mean [95% CI] 96.9% [90.0, 100.0]) compared with sitagliptin 100 mg (95.6% [88.4, 100.0]). The early termination and the carryover effect described above are limitations to this study.

CONCLUSION

Across sitagliptin doses in this study, the similarity of the 24-h WMG concentrations and the similarity of the corrected DPP-4 inhibition values support prior findings that the maximal glucose-lowering efficacy of sitagliptin is achieved with once-daily dosing of 100 mg. Clinicaltrials.gov: NCT00541229.

Levothyroxine therapy in preventing nodular recurrence after hemithyroidectomy: a retrospective study

AIM

To determine the effect of levothyroxine (L-T4) therapy on the recurrence rate of nodular disease in patients previously treated with lobectomy for benign nodular goiter.

METHODS

Two hundred and thirty-tree patients (38 males, 195 females; age 49.9+/-13.1 yr) with no post-surgical evidence of nodular disease in the remnant, were followed- up yearly with serum TSH and ultrasound (US). Nodular recurrence was defined as a lesion of at least 5 mm at US. Patients were divided in 2 groups based on whether or not they had been treated with L-T4 after surgery: Group 1 (45 patients) who did not receive any L-T4, and Group 2 (188 patients) treated with L-T4. Group 2 was further subdivided in Group 2a (123 patients) receiving L-T4 substitutive therapy (TSH>or=0.5 and <or=3 mUI/l) and Group 2b (65 patients) receiving L-T4 at TSH-suppressive dose (TSH<0.5 mUI/l).

RESULTS

Mean observation period was 5.8+/-4.7 yr. Overall, 71 out of 233 (30.5%) patients experienced recurrence of thyroid nodular disease: 29 patients (64.4%) in Group 1, 24 (19.5%) patients in Group 2a, and 18 (27.7%) patients in Group 2b. The recurrence rate was significantly lower (p<0.001) in Group 2 compared with Group 1, but no significant difference was observed between Groups 2a and 2b.

CONCLUSION

In patients who have undergone hemithyroidectomy for benign monolobar nodular disease, L-T4 therapy may prevent recurrence of nodular disease. TSH suppression may not be required for prevention of recurrence in the remnant thyroid tissue.

Efficacy and safety of sitagliptin added to ongoing metformin therapy in patients with type 2 diabetes

OBJECTIVE

The purpose of this study was to evaluate the efficacy and safety of sitagliptin as an add-on to metformin therapy in patients with moderately severe (hemoglobin A(1c) >or= 8.0% and <or= 11.0%) type 2 diabetes mellitus (T2DM).

RESEARCH DESIGN AND METHODS

This was a multinational, randomized, placebo-controlled, parallel-group, double-blind study conducted in 190 patients with T2DM. After >or= 6 weeks of stable metformin monotherapy (>or= 1500 mg/day), patients were randomized to either the addition of sitagliptin 100 mg once daily or placebo to ongoing metformin for 30 weeks.

MAIN OUTCOME MEASURES

The primary efficacy endpoint was reduction in hemoglobin A(1c) (HbA(1c)) measured after 18 weeks of sitagliptin treatment. Key secondary endpoints included reduction in fasting plasma glucose (FPG) and 2-hour (2-h) postprandial plasma glucose (PPG) at 18 weeks, and HbA(1c) at 30 weeks. The proportion of patients meeting the goal of HbA(1c) < 7.0% was also analyzed.

RESULTS

Sitagliptin significantly reduced HbA(1c), FPG, and 2-h PPG, compared with placebo (all p < 0.001). The net improvement in HbA(1c) was - 1.0% at both 18 and 30 weeks, and a significantly greater proportion of patients treated with sitagliptin achieved HbA(1c) < 7.0% by the end of the study (22.1% vs. 3.3%, p < 0.001). Sitagliptin was well-tolerated. Compared with placebo, sitagliptin had a neutral effect on body weight and did not significantly increase the risk of hypoglycemia or gastrointestinal adverse events.

CONCLUSIONS

Addition of sitagliptin 100 mg once daily to ongoing metformin therapy was well-tolerated and resulted in significant glycemic improvement in patients with moderately severe T2DM who were treated for 30 weeks.

Vitamin A deficiency does not influence longitudinal growth in mice

OBJECTIVE

Growth hormone (GH) stimulates longitudinal growth, directly and indirectly, through the mediation of circulating and locally produced insulin-like growth factor 1 (IGF-1). The exact role of individual vitamins in modulating GH secretion or action, and somatic growth in general, is still not completely understood. It has been suggested that vitamin A (VA) and its physiologic active metabolite retinoic acid influence longitudinal growth by promoting the differentiation of pituitary cells toward GH-secreting cells and by stimulating secretion of GH. Accordingly, epidemiologic studies have shown that short children have lower VA intake than do children with normal stature.

METHODS

To determine whether VA deficiency causes impairment of GH secretion, we have investigated the effect of a severely VA-deficient diet on growth in mice. Ten male mice born from mothers fed with VA-deficient diet since conception were maintained on a VA-deficient diet until the end of week 8 of life. Ten male mice born from mothers fed with a VA-sufficient diet and receiving a normal diet after weaning served as the control group. At the end of the study, we measured animals' weight and length, body composition, tibia and femur lengths, liver retinol and retinyl esters storages, serum IGF-1, serum thyroxine, serum GH, and pituitary GH mRNA levels.

RESULTS

Despite evidence of significant VA deficiency, we observed no effect on longitudinal growth or changes in pituitary GH mRNA, serum thyroxine, serum GH, or serum IGF-1 levels.

CONCLUSION

VA deficiency does not negatively affect longitudinal growth and pituitary GH content and action in mice.

Once-daily administration of CJC-1295, a long-acting growth hormone-releasing hormone (GHRH) analog, normalizes growth in the GHRH knockout mouse

Although the majority of children with isolated growth hormone (GH) deficiency have a good growth response to GH-releasing hormone (GHRH), the use of this therapeutic agent is limited by its very short half-life. Indeed, we have shown that, in mice with GHRH gene ablation (GHRH knockout; GHRHKO), even twice-daily injections of a GHRH analog are unable to normalize growth. CJC-1295 is a synthetic GHRH analog that selectively and covalently binds to endogenous albumin after injection, thereby extending its half-life and duration of action. We report the effects of CJC-1295 administration in GHRHKO animals. Three groups of 1-wk-old GHRHKO mice were treated for 5 wk with 2 microg of CJC-1295 at intervals of 24, 48, and 72 h. Placebo-treated GHRHKO mice and mice heterozygous for the GHRHKO allele served as controls. GHRHKO animals receiving daily doses of CJC-1295 exhibited normal body weight and length. Mice treated every 48 and 72 h reached higher body weight and length than placebo-treated animals, without full growth normalization. Femur and tibia length remained normal in animals treated every 24 and 48 h. Relative lean mass and subcutaneous fat mass were normal in all treated groups. CJC-1295 caused an increase in total pituitary RNA and GH mRNA, suggesting that proliferation of somatotroph cells had occurred, as confirmed by immunohistochemistry images. These findings demonstrate that treatment with once-daily administration of CJC-1295 is able to maintain normal body composition and growth in GHRHKO mice. The same dose is less effective when administered every 48 or 72 h.

A new mutation in the growth hormone-releasing hormone receptor gene in two Israeli Arab families

BACKGROUND

Mutations in the GHRH receptor gene (GHRH-R) are emerging as a common cause of familial isolated GH deficiency (IGHD).

DESIGN

We searched for GHRH-R mutations in 10 patients with IGHD of Israeli-Arab origin, belonging to two highly consanguineous families.

METHODS

Analysis of the 13 coding exons, the intron-exon boundaries, and the proximal promoter of the GHRH-R was performed by denaturing gradient gel electrophoresis. Abnormally migrating bands were sequenced. The newly found mutation was inserted into GHRH-R cDNA. Wild type and mutant receptor were expressed in Chinese hamster ovary (CHO) cells, and the cAMP response to GHRH was measured.

RESULTS

All patients were homozygous for a novel GHRH-R missense mutation in exon 11 that replaces arginine with cysteine (R357C). Functional assay demonstrated complete inactivity of the mutant receptor in vitro. The prevalence of the mutant allele in the Israeli-Arab population was found to be 2%. All the patients had low but detectable GH reserve, proportionate short stature, and growth retardation since early childhood, with good growth response to GH treatment. Magnetic resonance imaging, performed in 3 patients, revealed a normal sized anterior pituitary in one patient evaluated at early childhood, and a borderline hypoplastic gland in the 2 patients evaluated at puberty.

CONCLUSIONS

We describe a novel missense mutation in the GHRH-R. The high incidence of the mutant allele in Israeli Arabs suggests that the mutation may be a common cause of familial IGHD in this population.

Influence of estrogen administration on the growth response to growth hormone (GH) in GH-deficient mice

In women who are growth hormone (GH) deficient, exogenous estrogens increase the dosage of GH that is needed to normalize circulating levels of insulin-like growth factor (IGF-1). Serum IGF-1 derives mostly from the liver, and it is unknown whether the peripheral effects of GH are also impaired by estrogens. Because the ultimate effect of GH is longitudinal growth, we have investigated the influence of estrogen administration on the growth response to recombinant mouse GH therapy in prepubertal GH-deficient (GHD) GHRH knockout (GHRHKO) female mice. Twenty-four GHRHKO female mice (4 animals/group) were treated for 4 weeks (from the second to sixth week of age) with the following schedules: Group I, GH only (25 microg/day); Group II, subcutaneous (sc) ethynil estradiol (EE) (0.035 ES01247g/day); Group III, GH + scEE; Group IV, oral (po) EE (0.035 microg/day); Group V, GH + poEE; Group VI, placebo. At the end of the treatment period, we measured uterine weight, total body weight (TBW), body length (nose-anus, N-A), and femur length. In addition, serum IGF-1 levels were measured. Uteri of mice treated with oral or scEE showed similar increases in weight. There was no difference in the increase in longitudinal growth parameters between mice treated with GH alone or with GH in association with oral or scEE. Serum IGF-1 decreased in animals treated with GH + scEE, compared with GH group, but no group was significantly different from placebo. These results show that subcutaneous or oral EE does not reduce the growth response to GH in female GHD mice.

Effects of long-term treatment with growth hormone-releasing peptide-2 in the GHRH knockout mouse

Growth hormone (GH) secretagogues (GHS) stimulate GH secretion in vivo in humans and in animals. They act on the ghrelin receptor, expressed in both the hypothalamus and the pituitary. It is unknown whether GHSs act predominantly by increasing the release of hypothalamic GH-releasing hormone (GHRH) or by acting directly on the somatotroph cells. We studied whether a potent GHS could stimulate growth in the absence of endogenous GHRH. To this end, we used GHRH knockout (GHRH-KO) mice. These animals have proportionate dwarfism due to severe GH deficiency (GHD) and pituitary hypoplasia due to reduced somatotroph cell mass. We treated male GHRH-KO mice for 6 wk (from week 1 to week 7 of age) with GH-releasing peptide-2 (GHRP-2, 10 microg s.c. twice a day). Chronic treatment with GHRP-2 failed to stimulate somatotroph cell proliferation and GH secretion and to promote longitudinal growth. GHRP-2-treated mice showed an increase in total body weight compared with placebo-treated animals, due to worsening of the body composition alterations typical of GHD animals. These data demonstrate that GHRP-2 failed to reverse the severe GHD caused by lack of GHRH.

Naturally-occurring missense mutations in the human growth hormone-releasing hormone receptor alter ligand binding

Growth hormone (GH) releasing hormone (GHRH) is a hypothalamic factor that stimulates GH secretion. It acts by activating a seven transmembrane domain G protein-coupled receptor of 423 amino acids expressed by the somatotroph cells of the pituitary gland (GHRH receptor, GHRH-R). Familial isolated growth hormone deficiency (IGHD) can be caused by mutations in the GHRH-R gene both in humans and mice. We have described six disease-causing missense mutations in this gene in IGHD patients (H137L, L144H, A176V, A222E, F242C, K329E). These mutations are inherited as autosomal recessive traits, and cause impairment of the receptor to transmit GHRH signalling. The aim of this study is to investigate the mechanisms through which these mutations cause receptor malfunction. To this end, we transiently expressed each mutated receptor into Chinese hamster ovary cells. Cells expressing each of the mutated receptors did not show an increase in intracellular cyclic AMP in response to GHRH. Immunoprecipitation and immunofluorescence studies indicated that the amino acid changes do not cause protein degradation, and do not alter the proper insertion of the receptor into the cell membrane. Binding studies with human 125I-GHRH showed that the lack of response to GHRH is due to inability of all the mutated receptors to bind the ligand. These studies demonstrate that abnormal ligand binding is a common mechanism by which naturally occurring missense mutation alter GHRH-R function.

Effects of recombinant mouse growth hormone treatment on growth and body composition in GHRH knock out mice

OBJECTIVE

GH deficiency (GHD) causes growth failure and alterations in body composition both in humans and mice. Mouse models of GHD are used to study the effect of GH replacement therapy on these parameters. As the administration of human GH to mice causes development of antibodies and progressive reduction of its effectiveness, the use of species-specific GH is recommended. To determine the optimal GH replacement schedule in GHD mice, and to study its effect on body composition, we treated mice with targeted ablation of the GHRH gene (GHRH knock out-GHRHKO) with recombinant mouse GH (rmGH).

DESIGN

One week-old GHRHKO male animals received either placebo or one of two different regimens of escalating doses of rmGH: R1: 30 microg/daily (1st week), 50 microg/daily (2nd week), 70 microg/daily (3rd-4th week); R2: 15 microg/twice a day (1st week), 25 microg/twice a day (2nd week), 35 microg/twice a day (3rd-4th week). Sex- and age-matched wild-type (WT) animals served as controls. At the end of the study we measured body length and weight, tibia and femur length, and body composition.

RESULTS

While R1 normalized all growth parameters (TBW, N-A, femur, tibia length), R2 mice achieved significantly higher TBW, N-A and femur length when compared to WT. Body composition abnormalities (increased subcutaneous fat and reduced lean mass) were completely reverted by both treatment schedules. None of the GH-induced parameter modification described above was reflected in parallel changes in circulating serum IGF-1 and liver IGF-1 mRNA.

CONCLUSIONS

Our findings indicate that in GHD mice body composition changes are reverted by rmGH and that twice/daily is more effective than daily administration.

Partial reversibility of growth hormone (GH) deficiency in the GH-releasing hormone (GHRH) knockout mouse by postnatal treatment with a GHRH analog

The proliferation of pituitary somatotroph cells and the synthesis and secretion of GH require the hypothalamic peptide GH-releasing hormone (GHRH). Accordingly, we have shown that mice with targeted disruption [knockout (KO)] of the GHRH gene (GHRHKO) have isolated GH deficiency (GHD) and anterior pituitary hypoplasia. The weight of GRHRKO mice is about 60% that of normal mice by 12 wk of age. The phenotype is strikingly similar to that observed in the mouse with mutated GHRH receptor (little). It is not known whether exposure to endogenous GHRH during intrauterine growth is necessary for postnatal GH secretion, and whether GHD due to congenital lack of GHRH activity would be reversible by treatment with GHRH during the postnatal period. To answer this question, we treated GHRHKO mice with a long-acting superactive GHRH analog (JI-38) at two ages: from wk 2-6 (2 microg, twice a day) and from wk 12-16 (4 microg, twice a day). Normal littermates served as controls. At both ages JI-38 caused growth acceleration, increase in size of the pituitary gland, increase in pituitary GH mRNA and GH protein levels and serum GH, and significant increase in liver IGF-I mRNA, although none of these parameters was fully normalized. Our findings demonstrate that GHD and pituitary hypoplasia in GHRHKO mice may be partially reversed by long-term treatment with a GHRH analog, and that somatotroph cells maintain responsiveness to GHRH even if this factor is absent during intrauterine development.

Effects of combined long-term treatment with a growth hormone-releasing hormone analogue and a growth hormone secretagogue in the growth hormone-releasing hormone knock out mouse

GH secretagogues (GHS) are synthetic ghrelin receptor agonists that stimulate GH secretion. It is not clear whether they act predominantly by stimulating the secretion of hypothalamic growth hormone-releasing hormone (GHRH), or directly on the somatotrope cells. In addition, it is not known whether combined treatment with GHRH and GHS has synergistic effects on growth. To address these questions, we used the GH-deficient GHRH knock out (GHRHKO) mouse model, which has severe somatotrope cell hypoplasia. We treated GHRHKO mice for 5 weeks (from week 1 to week 6 of age) with the GHRH analogue JI-38 alone, or in combination with a GHS (GHRP-2), and at the end of the treatment we examined their response to an acute stimulus with GHRP-2 or GHRP-2 plus JI-38. We used placebo-treated GHRHKO mice and animals heterozygous for the GHRHKO allele as controls. Animals treated with JI-38+GHRP-2 reached higher body length and weight than animals treated with JI-38 alone. All the animals receiving JI-38 (with or without GHRP-2) showed similar correction of somatotrope cell hypoplasia. None of the GHRHKO animals showed a serum GH response to the acute stimulation with GHRP-2 alone, while both treated groups responded to the combined test with JI-38 + GHRP-2. These data demonstrate that in GHRHKO mice, GHRP-2 has a growth-stimulating effect that augments the response induced by JI-38. In addition, the presence of GHRH seems necessary for the stimulation of GH secretion by GHRP-2.

A mouse with targeted ablation of the growth hormone-releasing hormone gene: a new model of isolated growth hormone deficiency

The proliferation of pituitary somatotroph cells and the synthesis and secretion of GH are under the stimulatory control of the hypothalamic peptide GHRH. GHRH is initially synthesized as pre-prohormone and then enzymatically cleaved to its mature form (44 amino acids in humans and 42 in mice). Although mutations in the GHRH receptor cause isolated GH deficiency (IGHD) both in humans and mice, mutations in the GHRH gene have never been described. To determine the consequences of generalized lack of GHRH, we have created a mouse with targeted disruption (knockout) of the GHRH gene (GHRHKO). We have substituted a portion of the gene that encodes for the initial 14 amino acids of the 1-42 GHRH with a neomycin resistance cassette. Heterozygous founder (+/-) mice were mated to obtain -/- animals. The expected Mendelian ratio was conserved (25.8% of offspring were +/+, 52.8% were +/-, and 21.4% were -/-), showing no lethality in the GHRHKO embryos. GHRHKO mice appeared normal at birth. Starting at 3 wk of age, -/- mice showed significant growth retardation. By 12 wk of age, their weight was about 60% of +/+ and +/- littermates. Growth retardation was due to IGHD, as shown by reduced pituitary GH mRNA and protein content, reduced serum IGF-I, and reduced liver IGF-I mRNA. The phenotype of the GHRHKO mice is similar to the one observed in the mouse with mutated GHRH receptor, including pituitary hypoplasia. Heterozygous mice had normal growth, although adult +/- males (but not females) had mild reduction in serum IGF-I. In conclusion, we demonstrate that ablation of the GHRH gene causes IGHD in mice. The GHRHKO mouse will be the new useful model of IGHD.

Variability in anterior pituitary size within members of a family with GH deficiency due to a new splice mutation in the GHRH receptor gene

OBJECTIVE

Mutations in the GHRH receptor (GHRHR) gene (GHRHR) cause autosomal recessive isolated GH deficiency (IGHD), and are usually associated with anterior pituitary hypoplasia (APH) (defined as pituitary height more than 2 SDS below normal). We searched for GHRHR mutations and studied pituitary morphology in three prepubertal sibs with severe IGHD, who were born from consanguineous parents.

DESIGN

We sequenced the 13 exons and the intron-exon boundaries of the GHRHR of the index patient. After identifying a novel mutation, we sequenced the same area in the other family members. In addition, we performed magnetic resonance imaging (MRI) study of the pituitary (at age 8, 4 and 3 years) in the three affected subjects.

RESULTS

The three children were homozygous for a new GHRHR mutation that alters the second base of the invariant 5' splice site (GT) of intron 12 [IVS12 + 2T-->A]. The parents and an unaffected sibling were heterozygous for the same change. MRI did not show frank APH (by height criteria) in any of the subjects: pituitary height was normal (5.6 mm, +1.8 SDS) in the oldest sibling, and it was low but not below 2 SDS by age-adjusted criteria in the second (3 mm, -1.4 SDS), and third sibling (2.8 mm, -1.7 SDS). Calculated pituitary volume was below -2 SDS in the youngest patient.

CONCLUSIONS

These data demonstrate that pituitary height may fall within 2 SDS from the norm in patients with severe IGHD due to a homozygous GHRHR mutation, and that pituitary size may vary within patients with identical mutations who belong to the same family.

Familial Growth Hormone Deficiency and Mutations in the GHRH Receptor Gene

Growth hormone (GH)-releasing hormone (GHRH) is necessary for the proliferation of the somatotropic cells of the anterior pituitary and the synthesis and secretion of GH. GHRH is released by the hypothalamus into the portal hypophysial circulation to bind to a membrane surface receptor [GHRH receptor (GHRHR)] expressed by the somatotropic cells. Because of the need of GHRH for GH secretion, it is to be expected that alterations in synthesis or action of GHRH would result in isolated GH deficiency (IGHD). Indeed, although GHRH gene mutations have never been reported, mutations in the GHRHR gene (GHRHR) are emerging as a relatively common cause of inherited autosomal recessive IGHD. The first human GHRHR mutations were discovered in families with a history of parental consanguinity. More recently, kindreds in which IGHD subjects are compound heterozygotes for two distinct mutations indicate that faulty GHRHR alleles may be prevalent and that these mutations may need to be suspected even in sporadic IGHD cases. Patients with two faulty GHRHR alleles have normal weight at birth. Growth failure becomes apparent during the first year of life. Biochemical studies show low serum insulin-like growth factor-1 level, and absent or markedly reduced GH response to a variety of stimuli. Magnetic resonance imaging shows hypoplasia of the anterior pituitary. In this chapter, we describe the GHRHR mutations reported to date and the phenotype of affected individuals.

X-ray synchrotron study of liquid-vapor interfaces at short length scales: effect of long-range forces and bending energies

We have investigated the small-scale structure of the liquid-vapor interface using synchrotron x-ray scattering for liquids with different molecular structures and interactions. The effective momentum-dependent surface energy first decreases from its macroscopic value due to the effect of long-range forces, and then increases with increasing wave vector. The results are analyzed using a recent density functional theory. The large wave-vector increase is attributed to a bending energy for which local and nonlocal contributions are equally important.

[The phrenic nerve stimulator, a valid ventilatory support in the management of quadriplegic patients receiving home health care services. A case report]

The authors describe the case of a quadriplegic child with post-traumatic respiratory insufficiency and total dependency on mechanical ventilation. The child was a long-term inpatient at the Pediatric Intensive Care Unit of Palermo. Considering the patient's long life expectancy, psychological distress and determination of the patient and family members to have the patient at home again, the plan for dehospitalization included the use of a phrenic stimulator as a supplement to conventional mechanical ventilation that would simplify home health care and improve the patient's quality of life. Electromyography, fluoroscopy and gas analysis were conducted to evaluate whether the patient was physically fit to receive a stimulator. The device was then implanted at the Spinal Cord Injury Treatment Unit in Sondalo. The stimulator is compact in design, operates silently, and affords more natural ventilation without interfering with breathing rhythm, and maintains muscle trophism. In combination with mechanical ventilation, the pacing device is an ideal system for home respiratory assistance. Additional benefits include increased patient mobility outside the home and improved quality of life. The system provides good respiration, as shown by EtCO2 and SpO2 measurements and long-term monitoring performed at our unit.

[Hematuria revealing primary hyperparathyroidism in a child]

BACKGROUND

Hematuria rarely reveals primary hyperparathyroidism in the child.

CASE REPORT

A 10-year-old boy presented with gross hematuria and urolithiasis. Biological findings showed hypercalcemia and hypercalciuria. Initially, parathormone plasma levels remained within normal range, but raised after a few months and at that time, ultrasound scan examination showed a parathyroid adenoma. Nevertheless, two surgical explorations were necessary to cure hypercalcemia and hyperparathyroidism. Histological aspects of parathyroid adenoma were not found on pathological examination.

CONCLUSION

Symptomatic hypercalciuria may be the first symptom revealing primary hyperparathyroidism in children. Surgical treatment remains difficult in such a case.

Gastric, intestinal and colonic absorption of metoprolol in the rat

The absorption of metoprolol from the stomach, small intestine and colon of anaesthetized rats has been evaluated using an in situ technique. Absorption rates were measured in terms of the rate of disappearance of metoprolol fumarate from the lumen between 5 and 30 min after dosing. Adsorption was estimated from the initial rapid fall in luminal content within the first 5 min after drug administration. The rate of drug absorption from the stomach was low or negligible. In the small intestine, the absorption rate constants, ka, at pH 6.2 and 7.5 were 0.66 and 0.81 h-1, respectively. In the colon, the rate of drug absorption at pH 7.5 was faster (ka = 1.21 h-1) than in other segments of the gut. Drug adsorption in the stomach amounted to 11% of the administered dose. In the small intestine adsorption was greater (16-22%), presumably because of the larger surface area in this segment of the gut, but in the colon adsorption was negligible.