Advances in preclinical therapeutics development using small animal imaging and molecular analyses: the gastrointestinal stromal tumors model

The large use of target therapies in the treatment of gastrointestinal stromal tumors (GISTs) highlighted the urgency to integrate new molecular imaging technologies, to develop new criteria for tumor response evaluation and to reach a more comprehensive definition of the molecular target. These aspects, which come from clinical experiences, are not considered enough in preclinical research studies which aim to evaluate the efficacy of new drugs or new combination of drugs with molecular target. We developed a xenograft animal model GIST882 using nude mice. We evaluated both the molecular and functional characterization of the tumor mass. The mutational analysis of KIT receptor of the GIST882 cell lines and tumor mass showed a mutation on exon 13 that was still present after in vivo cell growth. The glucose metabolism and cell proliferation was evaluated with a small animal PET using both FDG and FLT. The experimental development of new therapies for GIST treatment requires sophisticated animal models in order to represent the tumor molecular heterogeneity already demonstrated in the clinical setting and in order to evaluate the efficacy of the treatment also considering the inhibition of tumor metabolism, and not only considering the change in size of tumors. This approach of cancer research on GISTs is crucial and essential for innovative perspectives that could cross over to other types of cancer.

Experimental results and related clinical implications of PET detection of epidermal growth factor receptor (EGFr) in cancer

The epidermal growth factor receptor (EGFr) is one of the most studied molecules as a target for cancer therapy. Over these last few years, several studies attempting to identify predictive biomarkers of treatment response, such as the receptor status or other molecules related to the downstream signalling pathway, have been conducted. However, from a clinical point of view, the information obtained from ex vivo analyses still has various limitations that may be overcome by the combination with molecular imaging technologies which may provide a noninvasive, global, in vivo evaluation of the molecular tumour background. The aim of this review is to report the preclinical results of all positron emission tomography (PET) tracers synthesized until now for in vivo detection of EGFr in cancer. Two classes of PET compounds have been developed: labelled small molecules such as tyrosine kinase inhibitors and labelled monoclonal antibodies. The in vitro and in vivo results of these PET tracers are very different depending on the chemical properties, positron emission radionuclide, or animal models. As a consequence, various critical questions are still open, and the implications of a translation in the clinical setting for EGFr imaging in cancer patients is discussed.

Molecular imaging and targeted therapies in oncology: new concepts in treatment response assessment. a collection of cases

The widespread use of several new non-cytotoxic drugs and the significant improvements in functional imaging highlights a number of difficulties in monitoring, interpreting and predicting treatment response in clinical practice. Certain guidelines for disease assessment after therapy are already available: the traditional Response Evaluation Criteria in Solid Tumours guidelines based on tumour size variations using conventional imaging technologies, the recent combined method developed by Choi and colleagues in gastrointestinal stromal tumour treated with tyrosine kinase inhibitors based on tumour density variations using computed tomography (CT), and the European Organization for Research and Treatment of Cancer criteria based on tumour glucose metabolism variations using fluorodeoxyglucose (FDG) positron emission tomography (PET). At the moment combined PET/CT response criteria are still not available. A number of new PET compounds other than FDG are also currently being developed to visualize specific cellular and molecular tumour pathways but their role in assessment and prediction of cancer treatment response has not yet been thoroughly investigated in a large series. However, in clinical practice many oncologists treat cancer patients with targeted therapies or chemotherapy and evaluate the response using conventional or functional imaging without appropriate and standardized guidelines. The aim of this study was to present a selection of clinical cases that illustrate the usefulness of new PET tracers and efficacy evaluation of new drugs. In the era of molecular imaging and molecular therapies, these cases highlight the urgency to develop new criteria for treatment assessment and the exigency of correctly interpreting the biological information obtained from new technologies, and introduce new concepts that require further investigation in clinical trials.

Radiolabelling, quality control and radiochemical purity assessment of the Octreotide analogue 68Ga DOTA NOC

Somatostatin receptors 1-5 are over expressed in neuroendocrine tumours (NETs). 68Ga-labelled [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-1-Nal3-Octreotide (DOTA NOC), a recent synthesized somatostatin analogue, shows high affinity for those receptors. Herein, modifications of a commercial module for the labelling of DOTA NOC with 68Ga, as well as the assessment of time course of the radiochemical purity variation are described. The evaluation of radiochemical stability was done by two different chromatographic methods: reversed-phase radio HPLC and fast TLC analysis. Labelled compound has been found radiochemically stable within 3h from the end of labelling (EOL) and radiochemical purity was always higher than 99%. After 73 labelling sessions the system showed great reproducibility and high radiochemical yield.

Conventional and novel PET tracers for imaging in oncology in the era of molecular therapy

In the last ten years, the development of several novel targeted drugs and the refinement of state of the art technologies such as the genomics and proteomics and their introduction to clinical practice have revolutionized the management of patients affected by cancer. However, everyday practice points out several clinical questions: the difficulty of response assessment to new drugs especially using standard RECIST criteria that do not provide information on biological, vascular or metabolic variations; the inadequate selection of patients who are likely to benefit from a targeted therapy excluding those with breast cancer and gastrointestinal stromal tumours; the need to know the global biological background of diseases especially in metastatic setting using repeatable non-invasive procedures. Molecular imaging could provide information on in vivo distribution of biological markers in response to targeted therapy and could improve the selection of patients before therapies. The aim of this review is to analyze the current role of conventional and innovative positron emission tomography (PET) radiotracers in clinical practice and to explore the promising perspectives of molecular imaging in cancer research.

Mutational analysis of the inhibin alpha gene in preeclamptic women

BACKGROUND

Preeclampsia (PE) is a disorder that occurs in at least 5% of pregnancies and affects both the mother and the unborn baby. A dramatic increase of maternal serum inhibin A concentration in the second and third trimester of pregnancy is a common feature of PE and inhibin A measurement may add significant prognostic information for predicting PE in pregnant women.

DESIGN

We evaluated the presence and prevalence of gene polymorphisms for inhibin alpha subunit (INHalpha) in patients affected by PE (no.=50; study group), and in the general population (control group composed of 103 women and 42 men).

METHODS

DNA extraction, single strand conformation polymorphism analysis, DNA sequencing, restriction fragment length polymorphism analysis, and Fisher's exact test were used.

RESULTS

A 769G-->A transition was found in INHalpha1, but not in INHalpha2 or INHalpha3 fragment. This variant was found in 10/145 normal controls (7,6%), and in 1/50 preeclamptic patients (2%), without significant difference between the two groups (p=0.29).

CONCLUSIONS

The prevalence of INHalpha gene variants is not increased in PE. Due to its frequency, the 769G-->A transition may be considered a polymorphism present in the general Italian population.

A meal stimulation test in the diagnosis of pancreatic endocrine tumors in multiple endocrine neoplasia type 1

The diagnostic value of the determination of the serum pancreatic polypeptide (PP) and gastrin concentrations after a standard meal for early diagnosis of patients with multiple endocrine neoplasia type 1 (MEN 1) is controversial. The aim of this study was to clarify this issue. Thirteen patients with MEN 1, seven healthy family members, and eight healthy controls were studied. Plasma PP and serum gastrin were measured before and after the ingestion of a standardized meal. The meal caused a statistically significant (p < 0.05) increase of both PP and gastrin in all three groups studied. Concerning PP, no statistically significant difference was observed between patients and controls. In family members, the values were significantly (p < 0.05) lower than in the other two groups. On the whole, no significant differences in gastrin levels were noted between patients and controls; in family members, the values were significantly (p < 0.05) lower than in patients. All patients who had abnormally high postprandial values of PP and gastrin also had abnormally high basal values of these two peptides. The determination of serum PP and gastrin levels after a meal stimulation test in patients with MEN 1 adds no information about the presence of pancreatic endocrine tumors over that provided by basal values of the two peptides.

Opioid peptides attenuate blood pressure increase in acute respiratory failure

Plasma opioid peptides, norepinephrine, atrial natriuretic factor (ANF) and blood pressure (BP) were assessed in 24 chronic obstructive pulmonary disease patients with acute respiratory failure. Hypoxemic-hypercapnic patients had high BP, beta-endorphin, Met-enkephalin and dynorphin B, whereas hypoxemic-normocapnic and hypoxemic-hypocapnic patients showed normal BP, high beta-endorphin, and normal Met-enkephalin and dynorphin B. Norepinephrine and ANF were high in all patients, particularly in hypoxemic-hypercapnic patients. Infusion with the opioid antagonist naloxone hydrochloride significantly increased systolic blood pressure (SBP) in hypoxemic-hypercapnic (182.0 +/- 3.2 versus 205.1 +/- 3.0 mmHg; P < 0.01), hypoxemic-normocapnic (149.3 +/- 1.8 versus 169.1 +/- 2.2 mmHg; P < 0.01) and hypoxemic-hypocapnic (147.3 +/- 1.3 versus 166.8 +/- 2.2 mmHg; P < 0.01) patients, norepinephrine in hypoxemic-hypercapnic patients (3583.2 +/- 371.8 versus 5371.3 +/- 260.0 fmol/ml; P < 0.01), and reduced ANF in hypoxemic-normocapnic (18.3 +/- 0.8 versus 11.9 +/- 1.0 fmol/ml; P < 0.05) and hypoxemic-hypocapnic (18.1 +/- 1.2 versus 12.1 +/- 2.1 fmol/ml; P < 0.05) patients. These results indicate that the endogenous opioid system attenuates SBP responses in acute respiratory failure by affecting norepinephrine or ANF release.

Luteinzing hormone activity in menotropins optimizes folliculogenesis and treatment in controlled ovarian stimulation

Although the role that LH plays in folliculogenesis is still controversial, recent evidence points toward facilitatory actions of LH activity in ovulation induction. Thus, we compared the response to either highly purified FSH (75 IU FSH/ampoule; group A, 25 subjects) or human menopausal gonadotropin (75 IU FSH and 75 IU LH/ampoule; group B, 25 subjects) in normoovulatory GnRH agonist-suppressed women, candidates for intrauterine insemination. A fixed regimen of 2 daily ampoules of highly purified FSH or human menopausal gonadotropin was administered in the initial 14 days of treatment; menotropin dose adjustments were allowed thereafter. Treatment was monitored with daily blood samples for the measurement of LH, FSH, 17beta-estradiol (E(2)), progesterone, testosterone, hCG, inhibin A, and inhibin B, and transvaginal pelvic ultrasound was performed at 2-day intervals. Although preovulatory E(2) levels were similar, both the duration of treatment (16.1 +/- 0.8 vs. 12.6 +/- 0.5 days; P< 0.005) and the per cycle menotropin dose (33.6 +/- 2.4 vs. 23.6 +/- 1.1 ampoules; P < 0.005) were lower in group B. In the initial 14 treatment days the area under the curve of FSH, progesterone, testosterone, inhibin A, and inhibin B did not differ between the 2 groups, whereas LH, hCG, and E(2) areas under the curve were higher in group B. The occurrence of small follicles (<10 mm) and the inhibin B/A ratio in the late follicular phase were significantly reduced in group B. A nonsignificant trend toward a higher multiple gestation rate was present in group A (60% vs. 17%). We conclude that ovulation induction with LH activity-containing menotropins is associated with 1) shorter treatment duration, 2) lower menotropin consumption, and 3) reduced development of small ovarian follicles. These features can be exploited to develop regimens that optimize treatment outcome, lower costs, and reduce occurrence of complications such as multiple gestation and ovarian hyperstimulation.

Mechanisms of hypertension in patients with chronic obstructive pulmonary disease and acute respiratory failure

PURPOSE

To investigate the effects of hypoxemia, hypercapnia, and cardiovascular hormones (norepinephrine, endothelin-1, and atrial natriuretic factor) on blood pressure during acute respiratory failure.

PATIENTS AND METHODS

Patients with chronic obstructive pulmonary disease and acute respiratory failure were divided into four groups of 10 patients each: hypoxemia-normocapnia, hypoxemia-hypercapnia, hypoxemia-hypocapnia, and normoxemia-hypercapnia. Plasma norepinephrine levels were determined by high-performance liquid chromatography with electrochemical detection. Plasma endothelin-1 and atrial natriuretic factor levels were radioimmunoassayed after chromatographic preextraction.

RESULTS

Systolic blood pressure and cardiovascular hormone levels were greater in patients with hypercapnia (whether or not they also had hypoxemia) than in those with normocapnia and hypoxemia. For example, in patients with hypercapnia and normoxemia, the mean (+/- SD) systolic blood pressure was 183+/-31 mm Hg and the mean norepinephrine level was 494+/-107 pg/mL, as compared with 150+/- 6 mm Hg and 243+/-58 pg/mL in those with normocapnia and hypoxemia (both P<0.05). Similar results were seen for endothelin-1 and atrial natriuretic factor levels, and for the comparisons of hypoxemic patients who were hypercapnic with those who were normocapnic.

CONCLUSIONS

These results suggest that blood carbon dioxide levels, rather than oxygen levels, are responsible for hypertension during acute respiratory failure, perhaps as a result of enhanced sympatho-adrenergic activity.

Protective effects of delapril combined with indapamide or hydrochlorothiazide in spontaneously hypertensive stroke-prone rats: a comparative dose-response analysis

In previous articles, we have shown that the combination of the angiotensin-converting enzyme (ACE) inhibitor delapril (12 mg/kg/day) and the diuretic indapamide (1 mg/kg/ day) was able to prolong the life span significantly in salt-loaded stroke-prone spontaneously hypertensive rats (SHRsp). Because this finding was partly dependent on the antagonism of salt-loading effects by pharmacologic induction of diuresis, which prevented any increase in blood pressure values, we decided to evaluate whether lower doses of the combination could be equally protective without changing the progression of hypertension. Thus, we studied several treatments with progressively lower doses of delapril (6, 3, or 1.5 mg/kg/day) combined with indapamide (0.5, 0.25, or 0.125 mg/kg/day) or hydrochlorothiazide (2.5, 1.25, or 0.625 mg/kg/day) in salt-loaded SHRsp. Salt-loaded untreated animals were considered to be the control group. In agreement with previous experiments, control rats reached 50% mortality approximately 7 weeks after the beginning of salt loading. The combination of delapril and hydrochlorothiazide at the two lowest doses was not able to delay animal death significantly, whereas treatment with delapril and indapamide at the lowest dose was effective (50% survival rate, 15 weeks). The groups treated with the highest dose of delapril and hydrochlorothiazide or with the intermediate or highest dose of delapril and indapamide did not reach 50% mortality by the end of the experiment, at 44 weeks of treatment (i.e., when animals reached age 1 year). Only the highest delapril and indapamide doses were able to increase diuresis, but for a relatively short period. None of the treatments was able to lower or control blood pressure levels adequately. Therefore, blood pressure levels by themselves were not predictive of rat mortality. In contrast, the maximal value of proteinuria in the weeks preceding death was inversely correlated with the survival time. In conclusion, this study shows that low doses of an ACE inhibitor in combination with a diuretic can be effectively protective in a model of severe hypertension, independent of any change in blood pressure levels.

Opioid peptide modulation of circulatory response to hyperventilation in humans

After hyperventilation, systolic blood pressure (SBP) significantly decreased in 10 subjects (group 1), did not change in eight (group 2) and increased in 15 (group 3). Diastolic blood pressure and heart rate increased in all groups. The decrease in SBP was associated with a decrease in plasma catecholamines and increase in beta-endorphin, whereas the increase in SBP was accompanied by an increase in catecholamine and Met-enkephalin levels. Naloxone abolished the hyperventilation-induced SBP and catecholamine decrease only in group 1. These findings show an activation of the endogenous opioid system after hyperventilation and the role of beta-endorphin in reducing SBP in response to the test.

Relationship of systemic hemodynamics, left ventricular structure and function, and plasma natriuretic peptide concentrations during pregnancy complicated by preeclampsia

OBJECTIVE

This study was done to evaluate left ventricular structure and function among pregnant patients with preeclampsia and compare them with those of normotensive pregnant and nonpregnant subjects. It also tested the hypothesis that abnormalities in left ventricular structure and function are associated with elevated plasma levels of natriuretic peptides.

STUDY DESIGN

The study compared 75 pregnant women (n = 40 with preeclampsia; n = 35 normotensive pregnant women) and 10 nonpregnant normotensive control subjects undergoing an echocardiographic and biohumoral (renin activity and aldosterone, atrial natriuretic peptide, and brain natriuretic peptide concentrations) evaluation. The statistical analysis was carried out by analysis of variance, and significance was set at P <.05.

RESULTS

Comparison of pregnant patients with preeclampsia versus both normotensive pregnant women and nonpregnant women showed significant increases in left ventricular mass and left ventricular endsystolic and end-diastolic volumes and significant reductions in left ventricular ejection fraction and percentage of fractional shortening. These changes coincided with increases in plasma levels of atrial natriuretic peptide and brain natriuretic peptide that were linearly related to the left ventricular structural and functional changes observed in patients with preeclampsia.

CONCLUSION

Pregnant patients with preeclampsia showed adaptation to the increase in systemic blood pressure, with significant modification of left ventricular structure and function related to the plasma levels of both atrial natriuretic peptide and brain natriuretic peptide. A simple evaluation of plasma natriuretic peptide concentrations could help to discriminate patients with preeclampsia who have a condition of mild left ventricular overload.

[Comparison of two different protocols on change of medication in central venous catheterization in patients with bone marrow transplantation: results of a randomized multicenter study]

Care of central venous catheter (CVC) in patients undergoing bone marrow transplantation (BMT) raises significant problems related to the high risk of local infections, to the immunodeficient status, which in itself is a predisposing factor for systematic blood stream infections. Although frequent changes of CVC dressing might theoretically reduce the incidence of infections, they are also accompanied by significant skin toxicity and patient discomfort. No study has yet addressed these points. The objective of this study was to compare two different time interval protocols for CVC dressing, in order to assess the effects on local infections and toxicity. In a multicentre study, 339 bone marrow transplant (BMT) patients with a tunnelled CVC (group A, 230 pts) or a non tunnelled one (Group B, 169 patients) were randomly allocated to receive CVC dressing changes every 5 or 10 days if belonging to group A or 2 or 5 days if in group B. Transparent impermeable polyurethane dressings were used for all patients. The rate of local infection at the site of CVC insertion was assessed by microbiological assay every 10 days, while severity of skin toxicity was measured according to the ECOG scale. Sixty-five per cent of enrolled patients were finally evaluable. Patients (in both groups) receiving CVC dressing changes at longer intervals did not show a significant increase in the rate of local infections, while those who received dressing every two days had a significant increase in local skin toxicity. Longer intervals were accompanied by a reduction in costs. The results of this study demonstrate that the increase in time interval between CVC dressing changes in BMT patients did not increment the risk of local infections, while significantly reducing patients discomfort and costs.

Coping with psychotic symptoms in the early phases of schizophrenia

How people diagnosed with schizophrenia cope with positive symptoms after their first hospitalization is explored, along with the relationship of their coping strategies to their psychosocial functioning. The strategies most frequently endorsed were cognitive in type, while those considered most helpful were behavioral. Respondents identifying an active strategy as most helpful displayed better psychosocial functioning at 24-month follow-up.

Comparison of two different time interval protocols for central venous catheter dressing in bone marrow transplant patients: results of a randomized, multicenter study. The Italian Nurse Bone Marrow Transplant Group (GITMO)

BACKGROUND AND OBJECTIVE

Care of central venous catheter (CVC) in patients undergoing bone marrow transplantation (BMT) raises significant problems related to the high risk of local infections due to the immunodeficient status, which in itself is a predisposing factor for systemic blood-stream infections. Although frequent changes of CVC dressing might theoretically reduce the incidence of infections, they are also accompanied by significant skin toxicity and patient discomfort. No study has yet addressed these points. The objective of this study was to compare two different time interval protocols for CVC dressing in order to assess the effects on local infections and toxicity.

DESIGN AND METHODS

In a multicenter study, 399 bone marrow transplant (BMT) patients with a tunneled CVC (Group A, 230 pts) or a non-tunneled one (Group B, 169 pts) were randomly allocated to receive CVC dressing changes every 5 or 10 days, if belonging to Group A, or 2 or 5 days, if in Group B. Transparent, impermeable polyurethane dressings were used for all patients. The rate of local infections at the site of CVC insertion was assessed by microbiological assays every 10 days, while the severity of skin toxicity was measured according to the ECOG scale.

RESULTS

Sixty-five per cent of enrolled patients were finally evaluable. Patients (in both Groups) receiving CVC dressing changes at longer intervals did not show a significant increase in the rate of local infections, while those who received dressing every 2 days had a significant increase in local skin toxicity. Longer intervals were accompanied by a reduction in costs.

INTERPRETATION AND CONCLUSIONS

The results of this study demonstrate that the increase in time interval between CVC dressing changes in BMT patients did not raise the risk of local infections, while significantly reducing patient discomfort and costs.

Polyunsaturated fatty acids and inflammatory bowel disease

The rationale for supplementation with n-3 fatty acids to promote the health of the gastrointestinal tract lies in the antiinflammatory effects of these lipid compounds. The first evidence of the importance of dietary intake of n-3 polyunsaturated fatty acids was derived from epidemiologic observations of the low incidence of inflammatory bowel disease in Eskimos. The aim of this paper was to briefly review the literature on the use of n-3 fatty acids in inflammatory bowel disease (ulcerative colitis and Crohn disease), the results of which are controversial. The discrepancies between studies may reside in the different study designs used as well as in the various formulations and dosages used, some of which may lead to a high incidence of side effects. Choosing a formulation that lowers the incidence of side effects, selecting patients carefully, and paying strict attention to experimental design are critical when investigating further the therapeutic potential of these lipids in inflammatory bowel disease.

[Critical ischemia in elderly patients. Evaluation of the effect of two different methods of Iloprost therapy on the efficacy, tolerance, modification of quality of life and self-sufficiency]

BACKGROUND

The use of Iloprost in the treatment of critical leg ischemia in very old patients can lead to tolerability problems, related to the drug used and to the kind of patient treated. The aim of this study was to evaluate the impact of this therapy on the activities of daily living and on the quality of life of the patient together with its efficacy and tolerability.

METHODS

We studied 20 subjects (mean age 74 +/- 6.8) divided in 2 groups homogeneous for age, seriousness of the disease and presence of diabetes mellitus. In the first group Iloprost was administered for 6 hours, for 28 consecutive days, in the second group for 6 hours, two times a day for 14 consecutive days. In each group we observed the following parameters before and after treatment: clinical evaluation of pain and use of analgesics, ADL and SK39 questionnaire, ankle/arm index c.w. Doppler, strain gauge plethismography of lower limbs, TcPO2 at the back-feet level.

RESULTS

Treatment was well tolerated in both groups where we observed a similar reduction of pain, a reduction in the instrumental indexes which express the microcirculatory activity, an improvement in the quality of life and in the capacity to carry out everyday activities. The double daily administration of Iloprost did not cause any significant side effect in the subjects studied, and a better responsiveness to the pain symptomatology was observed.

CONCLUSIONS

Iloprost can be used in the treatment of critical leg ischemia even for very old patients with good tolerability and effectiveness. In the double daily administration no relevant side effect was observed. This approach is to be preferred also in terms of cost-effectiveness.

Low growth hormone-binding protein in infants with congenital hypothyroidism

We evaluated the circulating levels of GH, insulin-like growth factor I (IGF-I), GH-binding protein (GHBP), and IGF-binding protein-3 (IGFBP-3) before L-T4 therapy in 19 infants with congenital hypothyroidism (CH), aged 12-29 days, diagnosed by neonatal screening and in a group of age- and sex-matched control infants. The same parameters were reevaluated after several months of treatment. Serum GHBP was measured by the high performance liquid chromatography-gel filtration method; serum GH, IGF-I, and IGFBP-3 levels were determined by commercial kits. The hypothyroid patients, before beginning therapy, presented significantly lower GHBP values than controls (P < 0.0001); during treatment, these values increased significantly; however, after 6 months they were still significantly lower than control values (P < 0.01). The pretreatment levels of GH were not significantly different from control values; after 1 month of treatment, GH did not show the decrease observed in controls and, therefore, was significantly higher (P < 0.01). The pretreatment levels of IGF-I were not significantly different from control values, but were lower in patients with severe than in those with mild hypothyroidism. They decreased at about 4 months of life and became significantly lower than control values at about 7 months of age (P < 0.05). In conclusion, it may be hypothesized that the condition of CH induces a change in GHBP expression, perhaps beginning in fetal life. The intrauterine production of IGF-I seems to be independent of the levels of GHBP and partially affected by fetal thyroid function.

Hypothalamic neuropeptide Y and galanin in overweight rats fed a cafeteria diet

We evaluated neuropeptide Y (NPY) and galanin (GAL) immunoreactivity (IR) and mRNA in the paraventricular and arcuate nucleus, respectively, in rats that became overweight (Ov) or not (NOv) when fed a cafeteria diet. After 2 months of diet, NOv rats showed a significant increase in NPY IR, whereas Ov rats showed a significant increase in GAL mRNA levels. None of these changes was present in rats overfed for 6.5 months. These differential changes in hypothalamic GAL and NPY transmissions may contribute to the different susceptibility of the two rat subpopulations to the weight-promoting effects of the hypercaloric diet.