Background & Aims-Premature neonates are predisposed to necrotizing enterocolitis (NEC), an idiopathic, inflammatory bowel necrosis. We investigated the hypothesis that NEC occurs in the preterm intestine due to incomplete 'non-inflammatory' differentiation of intestinal macrophages, which increases the risk of a severe mucosal inflammatory response to bacterial products.

Background/Aims: Obesity is a common and rapidly growing health problem today. Obesity is characterized by the increase of body fat and an excess of total body fat and, in particular, visceral fat accumulation, is considered to be a risk factor for type 2 diabetes mellitus. To determine whether the malfunction of the mesenteric adipose tissue plays an important role in the diabetic related metabolic syndrome, in this study, lipolysis and gene expression in the subcutaneous, omental and mesenteric adipose tissue of the diabetic subjects were evaluated. Methods: Lipolysis and real time PCR were utilized to determine adipocyte function. Results: Basal adipose tissue glycerol release is higher in diabetics than that of the non diabetics in all three fat depots. Isoproterenol (ISO) significantly increases glycerol release in subcutaneous, omental and mesenteric adipose tissues of non diabetic subjects but it stimulated glycerol release was significantly impaired in all three fat depots of the diabetic subjects. Gene expression studies indicate that leptin, Peroxisome proliferator-activated receptor-gamma (PPAR-gamma), Fatty acid translocase (FAT/CD36) and 11β-hydroysteroid dehydrogenase (HSD) gene expression were significantly up regulated in the mesenteric adipose tissue of the diabetic patients. Conclusion: Human mesenteric adipose tissue in obese diabetic subjects has high basal glycerol release and impaired isoproterenol stimulated glycerol release. The obesity-related gene expressions in the mesenteric adipose tissue are up regulated, suggesting that the alterations of these genes in mesentery adipose depot may play a critical role in insulin resistance of type 2 diabetes and metabolic syndrome.

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Melanocortin 4 receptor (MC4R) plays an important role in the regulation of food intake and body weight. To determine the molecular basis of human MC4R (hMC4R) responsible for ␣-melanocortin-stimulating hormone (␣-MSH) binding, in this study, we utilized both receptor domain exchange and site-directed mutagenesis studies to investigate the molecular determinants of hMC4R responsible for ␣-MSH binding and signaling. ␣-MSH is a potent agonist at hMC4R but not at hMC2R. Cassette substitutions of the second, third, fourth, fifth, and sixth transmembrane regions (TM) of the hMC4R with the homologous regions of hMC2R were performed and ␣-MSH binding and signaling were examined. Our results indicate that each chimeric receptor was expressed at the cell surface and the expression levels remain similar to that of the wild-type receptor. The cassette substitutions of the second, fourth, fifth, and sixth TMs of the hMC4R with homologous regions of the hMC2R did not significantly alter ␣-MSH binding affinity and potency except substitution of the TM3 of the hMC4R, suggesting that the conserved residues in TMs of the hMC4R are crucial for Obesity is a common and rapidly growing health problem in the United States and worldwide (1-8). The melanocortin-4 receptor (MC4R) 2 plays a key role in the regulation of food intake and body weight. Mutations of human MC4R (hMC4R) are the most common monogenic cause of human obesity described to date, accounting for up to 6% of all cases of severe early onset obesity (9 -11). MC4R is a seven-transmembrane G protein-coupled receptor expressed mainly in the hypothalamus (12-16). The endogenous agonist, ␣-melanocyte-stimulating hormone (␣-MSH), activates MC4R and inhibits food intake, whereas agouti-related protein, the endogenous antagonist, inhibits MC4R action and induces food intake (13,17,18). MC4R is a member of the family of G protein-coupled receptors and consists of a single polypeptide featuring seven ␣-helical transmembrane domains (TMs), an extracellular N terminus, three extracellular loops, three intracellular loops, and an intracellular C terminus. Pharmacologic studies have identified that the tripeptide Phe 7 -Arg 8 -Trp 9 in ␣-MSH is the minimal active fragment retaining biological activity at MC4R (85). The ligand receptor interaction between ␣-MSH and MC4R has been extensively studied based on the model generated by computer (19 -24). However, detailed information about ligand receptor interaction between ␣-MSH and MC4R remains unclear.In this study, we utilize both chimeric receptor and site-directed mutagenesis study to determine the molecular basis of hMC4R responsible for ␣-MSH binding and signaling. Both hMC4R and hMC2R are subtypes of the melanocortin receptor family and share a number of structural, functional, and pharmacological similarities. In the putative TM regions, both hMC4R and hMC2R show overall identities of 58% and similarities of 91%. They have high binding affinities for agonist ACTH and antagonist agouti signaling protein. However, hMC4R and hMC2R ex...

Our results suggest that TM3 and TM6 are important for NDP-MSH binding, while D121 in TM2 and D332 in TM7 are crucial for receptor activity and signaling. Importantly, L165 in TM3 is critical for agonist or antagonist selectivity. These results provide important information about the molecular determinants of hMC3R responsible for ligand binding and receptor signaling.