Central GIP signaling stimulates peripheral GIP release and promotes insulin and pancreatic polypeptide secretion in nonhuman primates

Glucose-dependent insulinotropic polypeptide (GIP) has important actions on whole body metabolic function. GIP and its receptor are also present in the central nervous system and have been linked to neurotrophic actions. Metabolic effects of central nervous system GIP signaling have not been reported. We investigated whether centrally administered GIP could increase peripheral plasma GIP concentrations and influence the metabolic response to a mixed macronutrient meal in nonhuman primates. An infusion and sampling system was developed to enable continuous intracerebroventricular (ICV) infusions with serial venous sampling in conscious nonhuman primates. Male baboons (Papio sp.) that were healthy and had normal body weights (28.9 ± 2.1 kg) were studied (n = 3). Animals were randomized to receive continuous ICV infusions of GIP (20 pmol·kg−1·h−1) or vehicle before and over the course of a 300-min mixed meal test (15 kcal/kg, 1.5g glucose/kg) on two occasions. A significant increase in plasma GIP concentration was observed under ICV GIP infusion (66.5 ± 8.0 vs. 680.6 ± 412.8 pg/ml, P = 0.04) before administration of the mixed meal. Increases in postprandial, but not fasted, insulin (P = 0.01) and pancreatic polypeptide (P = 0.04) were also observed under ICV GIP. Effects of ICV GIP on fasted or postprandial glucagon, glucose, triglyceride, and free fatty acids were not observed. Our data demonstrate that central GIP signaling can promote increased plasma GIP concentrations independent of nutrient stimulation and increase insulin and pancreatic polypeptide responses to a mixed meal

Central GIP signaling stimulates peripheral GIP release and promotes insulin and pancreatic polypeptide secretion in nonhuman primates

Glucose-dependent insulinotropic polypeptide (GIP) has important actions on whole body metabolic function. GIP and its receptor are also present in the central nervous system and have been linked to neurotrophic actions. Metabolic effects of central nervous system GIP signaling have not been reported. We investigated whether centrally administered GIP could increase peripheral plasma GIP concentrations and influence the metabolic response to a mixed macronutrient meal in nonhuman primates. An infusion and sampling system was developed to enable continuous intracerebroventricular (ICV) infusions with serial venous sampling in conscious nonhuman primates. Male baboons (Papio sp.) that were healthy and had normal body weights (28.9 +/- 2.1 kg) were studied (n = 3). Animals were randomized to receive continuous ICV infusions of GIP (20 pmol.kg(-1).h(-1)) or vehicle before and over the course of a 300-min mixed meal test (15 kcal/kg, 1.5g glucose/kg) on two occasions. A significant increase in plasma GIP concentration was observed under ICV GIP infusion (66.5 +/- 8.0 vs. 680.6 +/- 412.8 pg/ml, P = 0.04) before administration of the mixed meal. Increases in postprandial, but not fasted, insulin (P = 0.01) and pancreatic polypeptide (P = 0.04) were also observed under ICV GIP. Effects of ICV GIP on fasted or postprandial glucagon, glucose, triglyceride, and free fatty acids were not observed. Our data demonstrate that central GIP signaling can promote increased plasma GIP concentrations independent of nutrient stimulation and increase insulin and pancreatic polypeptide responses to a mixed meal3114E661E670Kronkosky Foundation (San Antonio, TX) Health and Human Services Program; Southwest National Primate Research Center Grant from the Office of Research Infrastructure Programs (ORIP) of the National Institutes of Health (NIH); United States Department of Health & Human Services; National Institutes of Health (NIH) - US

Analysis of Prostate-Specific Antigen Transcripts in Chimpanzees, Cynomolgus Monkeys, Baboons, and African Green Monkeys

<div><p>The function of prostate-specific antigen (PSA) is to liquefy the semen coagulum so that the released sperm can fuse with the ovum. Fifteen spliced variants of the <i>PSA</i> gene have been reported in humans, but little is known about alternative splicing in nonhuman primates. Positive selection has been reported in sex- and reproductive-related genes from sea urchins to <i>Drosophila</i> to humans; however, there are few studies of adaptive evolution of the <i>PSA</i> gene. Here, using polymerase chain reaction (PCR) product cloning and sequencing, we study <i>PSA</i> transcript variant heterogeneity in the prostates of chimpanzees (<i>Pan troglodytes</i>), cynomolgus monkeys (<i>Macaca fascicularis</i>), baboons <i>(Papio hamadryas anubis),</i> and African green monkeys <i>(Chlorocebus aethiops)</i>. Six <i>PSA</i> variants were identified in the chimpanzee prostate, but only two variants were found in cynomolgus monkeys, baboons, and African green monkeys. In the chimpanzee the full-length transcript is expressed at the same magnitude as the transcripts that retain intron 3. We have found previously unidentified splice variants of the <i>PSA</i> gene, some of which might be linked to disease conditions. Selection on the <i>PSA</i> gene was studied in 11 primate species by computational methods using the sequences reported here for African green monkey, cynomolgus monkey, baboon, and chimpanzee and other sequences available in public databases. A codon-based analysis (dN/dS) of the <i>PSA</i> gene identified potential adaptive evolution at five residue sites (Arg45, Lys70, Gln144, Pro189, and Thr203).</p></div

Alignment of the predicted amino acid sequences of the PSA-1 transcripts (panel A) and PSA-2 transcripts (panel B).

<p>The signal peptide is indicated in red italics. The residues that make up the catalytic triad are in blue and are indicated by arrows. The activation sequence is in bold and underlined. The unique 16-residue sequence that emanates from use of intron 3 is shown in green bold italic. The alignments were carried out using the CLUTALW program available at <a href="http://www.ebi.ac.uk/toolsmsa/clustalw2/" target="_blank">http://www.ebi.ac.uk/toolsmsa/clustalw2/</a> (Thompson et al., 1994 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094522#pone.0094522-Thompson1" target="_blank">[41]</a>).</p

Primer sequences used for real-time quantification of chimpanzee full-length and short-version <i>PSA</i> transcripts.

<p>Primer sequences used for real-time quantification of chimpanzee full-length and short-version <i>PSA</i> transcripts.</p

Structure of the PSA variants identified in cynomolgus monkey, baboon, African green monkey, and chimpanzee prostates.

<p>The retained intronic sequences are shown in blue, and the missing parts of exons are shown by blank boxes. The molecular weight (MW) and open reading frame (ORF) length of each predicted translation product were determined using the computational tool located at the EXPASY website (<a href="http://expasy.org/" target="_blank">http://expasy.org/</a>) and are shown to the right of the corresponding transcript. The residues that make up the catalytic triad are shown by asterisks.</p

Relative real-time PCR quantitation of chimpanzee transcripts that use intron 3 sequences compared to those that do not (mean ± standard deviation, <i>n</i> = 3).

<p>Individual tissue samples were reverse-transcribed and <i>PSA</i> transcript mRNA was quantitated using the primer/probe sets described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0094522#pone-0094522-t002" target="_blank">Table 2</a>. Relative levels of the <i>PSA</i> variants were normalized to the 18s RNA levels in the same samples.</p

Summary of <i>PSA</i> gene splice events in chimpanzee (<i>Pan troglodytes</i>), cynomolgus monkeys (<i>Macaca fascicularis</i>), baboons (<i>Papio hamadryas anubis</i>), and African green monkeys (<i>Chlorocebus aethiops</i>).

<p>Summary of <i>PSA</i> gene splice events in chimpanzee (<i>Pan troglodytes</i>), cynomolgus monkeys (<i>Macaca fascicularis</i>), baboons (<i>Papio hamadryas anubis</i>), and African green monkeys (<i>Chlorocebus aethiops</i>).</p

Multiple sequence comparison by log expectation (MUSCLE) program guided alignments of <i>PSA-1</i> transcripts from 11 species.

<p>The codons that are under positive selection are indicated by arrows. Fully conserved residues are indicated by asterisks, partly conserved residues by colons, and weakly conserved residues by periods. The species' complete scientific names are as follows: <i>Pan troglodytes</i>, <i>Pan paniscus</i>, <i>Homo sapiens</i>, <i>Pongo pygmaeus</i>, <i>Gorilla gorilla</i>, <i>Nomascus leucogenys</i>, <i>Macaca fascicularis</i>, <i>Macaca fuscata</i>, <i>Macaca mulatta</i>, <i>Papio hamadryas anubis</i>, and <i>Chlorocebus aethiops</i>.</p