Stimulating intestinal GIP release reduces food intake and body weight in mice

OBJECTIVE

Glucose dependent insulinotropic polypeptide (GIP) is well established as an incretin hormone, boosting glucose-dependent insulin secretion. However, whilst anorectic actions of its sister-incretin glucagon-like peptide-1 (GLP-1) are well established, a physiological role for GIP in appetite regulation is controversial, despite the superior weight loss seen in preclinical models and humans with GLP-1/GIP dual receptor agonists compared with GLP-1R agonism alone.

METHODS

We generated a mouse model in which GIP expressing K-cells can be activated through hM3Dq Designer Receptor Activated by Designer Drugs (DREADD, GIP-Dq) to explore physiological actions of intestinally-released GIP.

RESULTS

In lean mice, Dq-stimulation of GIP expressing cells increased plasma GIP to levels similar to those found postprandially. The increase in GIP was associated with improved glucose tolerance, as expected, but also triggered an unexpected robust inhibition of food intake. Validating that this represented a response to intestinally-released GIP, the suppression of food intake was prevented by injecting mice peripherally or centrally with antagonistic GIPR-antibodies, and was reproduced in an intersectional model utilising Gip-Cre/Villin-Flp to limit Dq transgene expression to K-cells in the intestinal epithelium. The effects of GIP cell activation were maintained in diet induced obese mice, in which chronic K-cell activation reduced food intake and attenuated body weight gain.

CONCLUSIONS

These studies establish a physiological gut-brain GIP-axis regulating food intake in mice, adding to the multi-faceted metabolic effects of GIP which need to be taken into account when developing GIPR-targeted therapies for obesity and diabetes.

The local GLP-1 system in the olfactory bulb is required for odor-evoked cephalic phase of insulin release in mice

OBJECTIVE

The olfactory bulb (OB) codes for sensory information and contributes to the control of energy metabolism by regulating foraging and cephalic phase responses. Mitral cells are the main output neurons of the OB. The Glucagon Like Peptide-1 (GLP-1)/GLP-1 receptor (GLP-1R) system in the OB (GLP-1^OB) has been shown to be a major regulator of mitral cell activity but its function in vivo is unclear. Therefore, we investigated the role of GLP-1^OB in foraging behavior and odor-evoked Cephalic Phase Insulin Release (CPIR).

METHODS AND RESULTS

By fluorescent labeling, we confirmed the presence of GLP-1 producing neurons and the expression of GLP-1R in the mouse OB. In response to food odor presentation, we collected blood, quantified plasma insulin by ELISA and showed the existence of an odor-evoked CPIR in lean mice but its absence in obese animals. Injection of shRNA against preproglucagon mRNA in the OB resulted in blunted CPIR in lean mice. Injecting Exendin (9-39), a GLP-1R antagonist, into the OB of lean mice also resulted in decreased CPIR. Since parasympathetic cholinergic input to the pancreas is known to be partly responsible for CPIR, we systemically administered the muscarinic M3 receptor antagonist 4-DAMP which resulted in a reduced odor-evoked CPIR. Finally, local injection of Exendin (9-39) in the OB extinguished olfactory foraging in lean mice whereas the injection of the GLP-1R agonist Exendin-4 rescued the loss of foraging behavior in obese mice.

CONCLUSIONS

Our results demonstrate that GLP-1^OB controls olfactory foraging and is required for odor-evoked CPIR. We describe a new crucial brain function for GLP-1 and GLP-1R expressed within the brain.

Obesity in Midlife Hampers Resting and Sensory-Evoked Cerebral Blood Flow in Mice

OBJECTIVE

This study aimed to investigate the effects of a high-fat diet (HFD) and aging on resting and activity-dependent cerebral blood flow (CBF).

METHODS

To run a comparison between obese and age-matched control animals, 6-week-old mice were fed either with regular chow or an HFD for 3 months or 8 months. Glucose tolerance and insulin sensitivity were assessed for metabolic phenotyping. Resting and odor-evoked CBF at the microvascular scale in the olfactory bulb (OB) was investigated by multiexposure speckle imaging. Immunolabeling-enabled imaging of solvent-cleared organs was used to analyze vascular density. The ejection fraction was studied by using cardioechography. Olfactory sensitivity was tested by using a buried-food test.

RESULTS

Glucose intolerance and compromised odor-evoked CBF were observed in obese mice in the younger group. Prolonged HFD feeding triggered insulin resistance and stronger impairment in activity-dependent CBF. Aging had a specific negative impact on resting CBF. There was no decrease in vascular density in the OB of obese mice, although cardiac function was impaired at both ages. In addition, decreased olfactory sensitivity was observed only in the older, middle-aged obese mice.

CONCLUSIONS

OB microvasculature in obese mice showed a specific functional feature characterized by impaired sensory-evoked CBF and a specific deleterious effect of aging on resting CBF.

New roles for prokineticin 2 in feeding behavior, insulin resistance and type 2 diabetes: Studies in mice and humans

Objective

Prokineticin 2 (PROK2) is a hypothalamic neuropeptide that plays a critical role in the rhythmicity of physiological functions and inhibits food intake. PROK2 is also expressed in the main olfactory bulb (MOB) as an essential factor for neuro-and morphogenesis. Since the MOB was shown to be strongly involved in eating behavior, we hypothesized that PROK2 could be a new target in the regulation of food intake and energy homeostasis, through its effects in the MOB. We also asked whether PROK2 could be associated with the pathophysiology of obesity, the metabolic syndrome (MetS), and type 2 diabetes (T2D) in humans.

Methods

We assessed in wild type mice whether the expression of Prok2 in the MOB is dependent on the nutritional status. We measured the effect of human recombinant PROK2 (rPROK2) acute injection in the MOB on food intake and olfactory behavior. Then, using a lentivirus expressing Prok2-shRNA, we studied the effects of Prok2 underexpression in the MOB on feeding behavior and glucose metabolism. Metabolic parameters and meal pattern were determined using calorimetric cages. In vivo 2-deoxyglucose uptake measurements were performed in mice after intraperitoneally insulin injection. Plasmatic PROK2 dosages and genetic associations studies were carried out respectively on 148 and more than 4000 participants from the D.E.S.I.R. (Data from an Epidemiologic Study on the Insulin Resistance Syndrome) cohort.

Results

Our findings showed that fasting in mice reduced Prok2 expression in the MOB. Acute injection of rPROK2 in the MOB significantly decreased food intake whereas Prok2-shRNA injection resulted in a higher dietary consumption characterized by increased feeding frequency and decreased meal size. Additionally, Prok2 underexpression in the MOB induced insulin resistance compared to scrambled shRNA-injected mice. In the human D.E.S.I.R. cohort, we found a significantly lower mean concentration of plasma PROK2 in people with T2D than in those with normoglycemia. Interestingly, this decrease was no longer significant when adjusted for Body Mass Index (BMI) or calorie intake, suggesting that the association between plasma PROK2 and diabetes is mediated, at least partly, by BMI and feeding behavior in humans. Moreover, common Single Nucleotide Polymorphisms (SNPs) in PROK2 gene were genotyped and associated with incident T2D or impaired fasting glycemia (IFG), MetS, and obesity.

Conclusions

Our data highlight PROK2 as a new target in the MOB that links olfaction with eating behavior and energy homeostasis. In humans, plasma PROK2 is negatively correlated with T2D, BMI, and energy intake, and PROK2 genetic variants are associated with incident hyperglycemia (T2D/IFG), the MetS and obesity.

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Fasting alters prokineticin 2 (Prok2) expression in the main olfactory bulb (MOB).

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Acute injection of PROK2 into the MOB diminishes food intake.

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Partial deletion of MOB-Prok2 affects meal pattern and induces insulin resistance.

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Type 2 diabetes (T2D) in humans is correlated with lower plasma PROK2 level.

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Polymorphisms of PROK2 gene associate with incident T2D and the metabolic syndrome.

[In vitro susceptibility to antibiotics and the most common Streptococcus pneumoniae serotypes: a multicenter study]

The susceptibility and serotypes of 211 strains of Streptococcus pneumoniae collected from 12 Spanish hospitals in December 2003 were studied. Susceptibility tests for eight antibiotics were carried out by E-test, and the serotype classification was carried out using pneumococcus antiserum from the Copenhagen Statens Serum Institute. Overall, the most frequent serotypes were 19 (12.2%); 6 (10.7%); 23 (10.2%); 3 (8.1%); 9 (6.6%); 14 (6.1%); and 29 (5.1%). In blood, the most frequent were 19 (16.6%) and 14 (11.9%), and 8.6% were nontypable. Under NCCLS (M7-A5) criteria, 55.6% of the strains were susceptible to penicillin (MIC < or =0.06 mg/l) and 7.9% showed high resistance (MIC > or =2 mg/l). Susceptibility to other antibiotics was 98% to moxifloxacin; 97.1% to levofloxacin; 94.6% to amoxicillin-clavulanic acid; 71.2% to cefuroxime; 84.4% to ceftriaxone; and 63.1% to clarithromycin and azithromycin. Only 13.3% of the strains showed susceptibility to the antibiotics tested. The greatest percentage of strains resistant to other antibiotics was found among the strains resistant to penicillin. Nine resistant phenotypes were detected.

[Coverage of the 23-valent pneumococcal vaccine in those older than 64 years of age in the region of Castellon and Valencia, Spain]

The different serotypes of Streptococcus pneumoniae isolated from adults aged over 64 years in the Valencia and Castellon health region of Spain from June 1999 to December 2003 were analyzed. A total of 163 strains were evaluated; 58.3% were invasive, 47.24% were from respiratory source, and 4.9% were from exudates. The greatest percentage of samples was obtained from the group of patients aged 65 to 75 years (60.7%), while the lowest percentage was obtained from the group of patients aged over 85 years (10.4%). In the latter group, 53% of the strains were invasive and 29.4% were isolated from sputum. A total of 21 serotypes were identified, with the most common (> 3%) being: serotype 3 (22.1%); serotype 19 (12.9%); serotype 6 (12.3%); serotype 9 (8.6%); serotype 14 (10.4%); serotype 23 (8%); serotype 29 (3.7%); and serotype 18 (3.1%). Serotype 3 was the most common serotype found in all samples, with the exception of exudate, while serotype 23 was not isolated in blood. In this population group, the coverage of the 23-valent vaccine was 88.4%. Serotypes not included in this vaccine but isolated from invasive samples were serotypes 16, 24, 29 and 35. No changes were observed in serotype distribution over the 4-year period of the study. However, it is necessary to continue epidemiological monitoring to determine whether serotype substitution occurs.

[Serotypes and antibiotic susceptibility of Streptococcus pneumoniae in children in the health district of Valencia and Castellón, Spain: a multicenter, prospective trial]

A study was conducted to determine the serotypes, the coverage of the heptavalent conjugate vaccine (VCN 7-v) and the antibiotic susceptibility of Streptococcus pneumoniae in children (<15 years) in the health districts of the provinces of Castellon and Valencia, Spain, from June 1999 to December 2002. A total of 271 strains were evaluated, 15.5% of which were invasive, 63.5% were of respiratory origin and 22.5% were from conjunctival and otitic exudates; 67.2% of the strains were found in children younger than 2 years of age. The distribution of the serotypes showed slight changes according to age and the origin of the sample: the most common serotypes were 19, 6, 23, 14, 3, 9 and 11; however, in children younger than 2 years of age the order changed to 19, 6, 14 and 23, 9, 11 and 3, and in the invasive strains to 19, 6, 14, 3 and 23. A total of 27.2% of the stains were susceptible to the ten antibiotics tested. For penicillin, reduced susceptibility was found in 50.4% and high resistance in 5.8%; 98.3% were susceptible to ampicillin and amoxicillin-clavulanic acid, and 80.7% to cefuroxime; 52.5% were resistant to erythromycin and 43.7% to clindamycin. No strains were resistant to rifampicin, vancomycin, levofloxacin or cefotaxime. The most susceptible serotypes were 3 and 11, and the most resistant was 14 (which consistently showed resistance to an antibiotic), 19, 6 and 23. According to these data, the theoretical coverage of VCN 7-v would be 80.1% in children younger than 2 years and 73.43% in those aged 0-14 years.