Quantitative Mass Spectrometry Reveals Food Intake-Induced Neuropeptide Level Changes in Rat Brain: Functional Assessment of Selected Neuropeptides as Feeding Regulators

Abstract

Endogenous neuropeptides are important signaling molecules that function as regulators of food intake and body weight. Previous work has shown that neuropeptide gene expression levels in a forebrain reward site, the nucleus accumbens (NAc), were changed by feeding. To directly monitor feeding-induced changes in neuropeptide expression levels within the NAc, we employed a combination of cryostat dissection, heat stabilization, neuropeptide extraction and label-free quantitative neuropeptidomics via a liquid chromatography-high resolution mass spectrometry platform. Using this methodology, we described the first neuropeptidome in NAc and discovered that feeding caused the expression level changes of multiple neuropeptides derived from different precursors, especially proSAAS-derived peptides such as Big LEN, PEN and little SAAS. We further investigated the regulatory functions of these neuropeptides derived from the ProSAAS family by performing an intra-NAc microinjection experiment using the identified ProSAAS neuropeptides, 'Big-LEN' and 'PEN'. Big LEN significantly increased rats' food and water intake, whereas both big LEN and PEN affected other behaviors including locomotion, drinking and grooming. In addition, we quantified the feeding-induced changes of peptides from hippocampus, hypothalamus and striatum to reveal the neuropeptide interplay among different anatomical regions. In summary, our study demonstrated neuropeptidomic changes in response to food intake in the rat NAc and other key brain regions. Importantly, the microinfusion of ProSAAS peptides into NAc revealed that they are behaviorally active in this brain site, suggesting the potential use of these peptides as therapeutics for eating disorders.

A Comparative Peptidomic Characterization of Cultured Skeletal Muscle Tissues Derived From db/db Mice

“…More importantly, the peptidomics is widely used to identify biological markers (31), discover new drug (32) and therapeutic targets (33). Recently, quantative peptidomics has also been conducted in endocrine studies (22, 34, 35), however, the secreted peptidomics from skeletal muscle under the insulin-resistant condition was not fully characterized.…”

Orphan neuropeptides and receptors: Novel therapeutic targets

“…Consistent with a role similar to that of NPY, transgenic animals overexpressing proSAAS are slightly overweight, and mice lacking proSAAS are leaner than wild-type littermates (Morgan et al ., 2010; Wei et al ., 2004). In addition, antibody-mediated depletion of b-LEN or PEN greatly reduced acute feeding (Wardman et al ., 2011) while injection of b-LEN into the nucleus accumbens led to elevated acute feeding (Ye et al ., 2017). Application of b-LEN to brain slices produced a rapid and reversible inhibition of synaptic glutamate release from parvocellular neurons in the hypothalamic paraventricular nucleus, a target of arcuate NPY projections (Wardman et al ., 2011).…”

From Synapse to Function: A Perspective on the Role of Neuroproteomics in Elucidating Mechanisms of Drug Addiction

“…Genetic sequence analyses predict that over 1000 potential neuropeptides may exist, with many having already been identified in CNS tissue using peptidomic approaches. In the striatum, Ye et al identified 419 m / z that correspond to potential neuropeptides and discovered that many of these peptides were regulated by behavioral manipulation [87]. Specifically, they found that proSAAS derived peptides (big LEN, PEN, and little SAAS) were decreased in mice that were unfed (hungry).…”

“…As illustrated in the studies above, traditional behavioral and molecular biology approaches can establish a functional role for neuropeptides identified using mass spectrometry. As reported by Ye et al, peptides can be site-specifically infused into brain structures to evaluate behavioral outcomes and establish a functional link with the underlying biology [87]. Likewise, peptides can be site-specifically administered by reverse-dialysis to investigate changes in levels of traditional neurotransmitters such as glutamate and GABA [93,94].…”