GLP-1(32-36)amide Pentapeptide Increases Basal Energy Expenditure and Inhibits Weight Gain in Obese Mice

The prevalence of obesity-related diabetes is increasing worldwide. Here we report the identification of a pentapeptide, GLP-1(32-36)amide (LVKGRamide), derived from the glucoincretin hormone GLP-1, that increases basal energy expenditure and curtails the development of obesity, insulin resistance, diabetes, and hepatic steatosis in diet-induced obese mice. The pentapeptide inhibited weight gain, reduced fat mass without change in energy intake, and increased basal energy expenditure independent of physical activity. Analyses of tissues from peptide-treated mice reveal increased expression of UCP-1 and UCP-3 in brown adipose tissue and increased UCP-3 and inhibition of acetyl-CoA carboxylase in skeletal muscle, findings consistent with increased fatty acid oxidation and thermogenesis. In palmitate-treated C2C12 skeletal myotubes, GLP-1(32-36)amide activated AMPK and inhibited acetyl-CoA carboxylase, suggesting activation of fat metabolism in response to energy depletion. By mass spectroscopy, the pentapeptide is rapidly formed from GLP-1(9-36)amide, the major form of GLP-1 in the circulation of mice. These findings suggest that the reported insulin-like actions of GLP-1 receptor agonists that occur independently of the GLP-1 receptor might be mediated by the pentapeptide, and the previously reported nonapeptide (FIAWLVKGRamide). We propose that by increasing basal energy expenditure, GLP-1(32-36)amide might be a useful treatment for human obesity and associated metabolic disorders.     

Relationship Between Peer Victimization and Posttraumatic Stress Among Primary School Children

Peer victimization is a common stressor experienced by children. Although peer victimization has been studied extensively, few studies have examined the potential link between peer victimization and posttraumatic stress disorder (PTSD), and no studies of which we are aware have examined this link among children in primary school. The paucity of studies examining the link between PTSD and peer victimization in primary school is surprising because peer victimization occurs more frequently and is more likely to be physical among 7‐ and 8‐year‐old children. This study assessed the relationship between peer victimization and PTSD in a sample of 358 elementary school children (ages 6–11 years). Results indicated that peer victimization accounted for 14.1% of PTSD symptom severity among boys and 10.1% among girls. Additionally, we found gender differences in the types of peer victimization that were most associated with PTSD symptom severity (d = 0.38). The long‐term developmental consequences that may be associated with peer victimization‐linked PTSD symptomatology are discussed.     

Pooled association genome scanning: validation and use to identify addiction vulnerability loci in two samples

Association genome scanning is of increasing interest for identifying the chromosomal regions that contain gene variants that contribute to vulnerability to complex disorders, including addictions. To improve the power and feasibility of this approach, we have validated "10k" microarray-based allelic frequency assessments in pooled DNA samples and have used this approach to seek allelic frequency differences between heavy poly-substance abusers and well characterized control individuals. Thirty-eight loci contain SNPs that display robust allele frequency differences between abusers and controls in both European- and African-American samples. These loci identify an alcohol/acetaldehyde dehydrogenase gene cluster and genes implicated in cellular signaling, gene regulation, development, "cell adhesion," and Mendelian disorders. The results converge with previous linkage and association results for addictions. Pooled association genome scanning provides a useful tool for elucidating molecular genetic underpinnings of complex disorders and identifies both previously understood and previously unanticipated mechanisms for addiction vulnerability.     

Identification, isolation, and characterization of daintain (allograft inflammatory factor 1), a macrophage polypeptide with effects on insulin secretion and abundantly present in the pancreas of prediabetic BB rats

A bioactive macrophage factor, the polypeptide daintain/allograft inflammatory factor 1 (AIF1), has been isolated from porcine intestine. It was discovered when searching for intestinal peptides with effects on insulin release, and its purification was monitored by the influence of the peptide fractions on pancreatic glucose-induced insulin secretion. Daintain/AIF1 is a 146-aa residue polypeptide with a mass of 16,603 Da and an acetylated N terminus. An internal 44-residue segment with the sequence pattern –KR–KK–GKR– has a motif typical of peptide hormone precursors, i.e., dibasic sites for potential activation cleavages and at the sequentially last such site, the structure GKR. The latter is a signal for C-terminal amide formation in the processing of peptide hormones. Daintain/AIF1 is immunohistochemically localized to microglial cells in the central nervous system and to dendritic cells and macrophages in several organs. A particularly dense accumulation of daintain/AIF1-immunoreactive macrophages was observed in the insulitis affecting the pancreatic islets of prediabetic BB rats. When injected intravenously in mice, daintain/AIF1 at 75 pmol/kg inhibited glucose (1 g/kg)-stimulated insulin secretion, with a concomitant impairment of the glucose elimination, whereas at higher doses (7.5 and 75 nmol/kg), daintain/AIF1 potentiated glucose-stimulated insulin secretion and enhanced the glucose elimination. Its dual influence on insulin secretion in vivo at different peptide concentrations, and the abundance of macrophages expressing daintain/AIF1 in the pancreatic islets of prediabetic rats, suggest that daintain/AIF1 may have a role in connection with the pathogenesis of insulin-dependent diabetesmellitus.     

Hepcidin,a putative mediator of anemia of inflammation,is a type II acute-phase protein

Hepcidin is a liver-made peptide proposed to be a central regulator of intestinal iron absorption and iron recycling by macrophages. In animal models, hepcidin is induced by inflammation and iron loading, but its regulation in humans has not been studied. We report that urinary excretion of hepcidin was greatly increased in patients with iron overload, infections, or inflammatory diseases. Hepcidin excretion correlated well with serum ferritin levels, which are regulated by similar pathologic stimuli. In vitro iron loading of primary human hepatocytes, however, unexpectedly down-regulated hepcidin mRNA, suggesting that in vivo regulation of hepcidin expression by iron stores involves complex indirect effects. Hepcidin mRNA was dramatically induced by interleukin-6 (IL-6) in vitro, but not by IL-1 or tumor necrosis factor alpha (TNF-alpha), demonstrating that human hepcidin is a type II acute-phase reactant. The linkage of hepcidin induction to inflammation in humans supports its proposed role as a key mediator of anemia of inflammation.     

Hepcidin--a regulator of intestinal iron absorption and iron recycling by macrophages

Hepcidin is a recently discovered peptide made in the liver, distributed in plasma and excreted in urine. This peptide hormone is the homeostatic regulator of intestinal iron absorption, iron recycling by macrophages, and iron mobilization from hepatic stores. Hepcidin acts by inhibiting the efflux of iron through ferroportin, the sole known iron exporter of enterocytes, macrophages and hepatocytes. As befits an iron-regulatory hormone, hepcidin synthesis is increased by iron loading and decreased by anemia and hypoxia. Hepcidin is markedly induced during infections and inflammation, causing iron to be sequestered in macrophages, hepatocytes and enterocytes. The resulting decrease in plasma iron levels eventually contributes to the anemia associated with infection and inflammation. These alterations in iron metabolism probably have a role in host defense by limiting the availability of iron to invading microorganisms. At the opposite extreme, early studies indicate that hepcidin deficiency--due to the dysregulation of its synthesis or mutations in the hepcidin gene itself--is the immediate cause of most forms of hemochromatosis.