Dynamic of TLQP-peptides upon fasting

NERP-1 modifications in amyotrophic lateral sclerosis

VGF peptides, such as NERPs (neuroendocrine regulatory peptides 1 and 2), are derived from amino acids 282-306 and 313-350, respectively, of the human proVGF, which is produced in spinal cord motor neurons. Although certain VGF-derived peptides are changed in ALS, less is known about NERPs. Possible modulations of NERPs and additional VGF peptides (NAPP and TPGH) were investigated using specific antibodies through competitive ELISA in the plasma of ALS patients (at both the initial and advanced phases; n = 46 each vs. 46 controls). As additional controls, naïve PD patients were also enrolled (n = 19 vs. 18 controls) while the potential VGF peptide role in oxidative stress was investigated using a motoneuron-like cell line (NSC34) stressed with sodium arsenate (SA). Western blot (WB) and sephadex chromatography (SC) were used to identify the molecular weight (MW) forms recognized by the VGF antibodies. Exclusively NERP-1 immunoreactivity was changed (elevated) in all plasma samples of ALS patients (compared to controls). Therefore, the NERP-1 antibody was the sole antibody used in ELISA with PD samples and NSC-34 cells. No alterations were seen in PD samples (vs. controls) while NERP-1 immunoreactivity decreased within SA-treated cells but increased in their culture medium. The viability test performed by adding NERP-1 to the stressed cells showed no protective effect. Using WB and SC, we revealed NERP-1 antibody reactivity against various MW forms, including those compatible with the NERP-1 peptide and/or proVGF. NERP-1 is suggested as a possible ALS blood biomarker.

VGF and Its Derived Peptides in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by a progressive degeneration in the neurons of the frontal cortex, spinal cord, and brainstem, altering the correct release of neurotransmitters. The disease affects every muscle in the body and could cause death three to five years after symptoms first occur. There is currently no efficient treatment to stop the disease's progression. The lack of identification of potential therapeutic strategies is a consequence of the delayed diagnosis due to the absence of accurate ALS early biomarkers. Indeed, neurotransmitters altered in ALS are not measurable in body fluids at quantities that allow for testing, making their use as diagnostic tools a challenge. Contrarily, neuroproteins and neuropeptides are chemical messengers produced and released by neurons, and most of them have the potential to enter bodily fluids. To find out new possible ALS biomarkers, the research of neuropeptides and proteins is intensified using mass spectrometry and biochemical-based assays. Neuropeptides derived from the proVGF precursor protein act as signaling molecules within neurons. ProVGF and its derived peptides are expressed in the nervous and endocrine systems but are also widely distributed in body fluids such as blood, urine, and cerebrospinal fluid, making them viable options as disease biomarkers. To highlight the proVGF and its derived peptides' major roles as ALS diagnostic biomarkers, this review provides an overview of the VGF peptide alterations in spinal cord and body fluids and outlines the limitations of the reported investigations.

Lower Plasma Levels of Selective VGF (Non-Acronymic) Peptides in Bipolar Disorder: Comparative Analysis Reveals Distinct Patterns across Mood Disorders and Healthy Controls

INTRODUCTION

Discriminating bipolar disorder (BD) from major depressive disorder (MDD) remains a challenging clinical task. Identifying specific peripheral biosignatures that can differentiate between BD and MDD would significantly increase diagnostic accuracy. Dysregulated neuroplasticity is implicated in BD and MDD, and psychotropic medications restore specific disrupted processes by increasing neurotrophic signalling. The nerve growth factor inducible vgf gene (non-acronymic) encodes a precursor protein named proVGF, which undergoes proteolytic processing to produce several VGF peptides, some of which were suggested to be implicated in mood disorders and have antidepressant effects. Since the presence of VGF peptides in humans has been exclusively investigated in brain and cerebrospinal fluid, we aimed to identify which VGF peptides are present in the plasma and to investigate whether their levels could differentiate BD from MDD as well as responders from non-responders to pharmacological interventions.

METHODS

VGF peptides were investigated in plasma from patients diagnosed with MDD (n = 37) or BD (n = 40 under lithium plus n = 29 never exposed to lithium), as well as healthy controls (HC; n = 36).

RESULTS

Three VGF peptides (TLQP-11, AQEE-14, and NAPP-19) were identified using spectrometry analysis of plasma from HC. These peptides were then measured in the entire sample using ELISA, which showed significantly lower levels of AQEE and NAPP in BD than in HC and MDD (p = 5.0 × 10-5, p = 0.001, respectively).

CONCLUSION

Our findings suggest that lower plasma levels of NAPP and AQEE are specifically associated with BD, thus possibly representing a diagnostic biomarker in mood disorders.

VGF modifications related to nigrostriatal dopaminergic neurodegeneration induced by the pesticide fipronil in adult male rats

BACKGROUND

Dopamine is reduced in the brain of rats treated with fipronil, a broad-spectrum insecticide. VGF (no acronym) is a neurotrophin-inducible protein expressed as the 75 kDa form (precursor or pro-VGF) or its truncated peptides. VGF immunostaining has been revealed using an antibody against the C-terminal nonapeptide of the rat pro-VGF in the nerve terminals of the rat substantia nigra, where it was reduced after 6-hydroxydopamine treatment. It is unknown whether pro-VGF and/or its shortened peptides are present in these neurons. Therefore, the aim of this study was first to determine which types of VGF are expressed in the normal substantia nigra (and striatum) and then to determine VGF modulations and whether they occur in parallel with locomotor changes after fipronil injection.

METHODS

Rats were divided into two groups that received a unilateral intranigral infusion of either fipronil (25 µg) diluted in dimethyl sulfoxide (DMSO) or DMSO alone, and then were tested for locomotor activity. An untreated group of rats (n=4) was used for identification of the VGF fragments using high performance liquid chromatography-mass spectrometry and western blot, while changes in treated groups (fipronil vs DMSO, each n=6) were investigated by immunohistochemistry using an antibody against the rat pro-VGF C-terminal nonapeptide in parallel with the anti-tyrosine hydroxylase antibody.

RESULTS

In untreated rats, the VGF C-terminal antibody identified mostly a 75 kDa band in the substantia nigra and striatum, supporting the finding of high-resolution mass spectrometry, which revealed fragments covering the majority of the pro-VGF sequence. Furthermore, several shortened VGF C-terminal forms (varying from 10 to 55 kDa) were also found by western blot, while high-resolution mass spectrometry revealed a C-terminal peptide overlapping the immunogen used to create the VGF antibody in both substantia nigra and striatum. In the substantia nigra of fipronil-treated rats, immunostaining for tyrosine hydroxylase and VGF was reduced compared to DMSO-treated rat group, and this was related with significant changes in locomotor activity.

CONCLUSION

Fipronil has the ability to modulate the production of pro-VGF and/or its C-terminal truncated peptides in the nigrostriatal system indicating its intimate interaction with the dopaminergic neurotransmission and implying a potential function in modulating locomotor activity.

Brain-Biomarker Changes in Body Fluids of Patients with Parkinson's Disease

Parkinson's disease (PD) is an incurable neurodegenerative disease that is rarely diagnosed at an early stage. Although the understanding of PD-related mechanisms has greatly improved over the last decade, the diagnosis of PD is still based on neurological examination through the identification of motor symptoms, including bradykinesia, rigidity, postural instability, and resting tremor. The early phase of PD is characterized by subtle symptoms with a misdiagnosis rate of approximately 16-20%. The difficulty in recognizing early PD has implications for the potential use of novel therapeutic approaches. For this reason, it is important to discover PD brain biomarkers that can indicate early dopaminergic dysfunction through their changes in body fluids, such as saliva, urine, blood, or cerebrospinal fluid (CSF). For the CFS-based test, the invasiveness of sampling is a major limitation, whereas the other body fluids are easier to obtain and could also allow population screening. Following the identification of the crucial role of alpha-synuclein (α-syn) in the pathology of PD, a very large number of studies have summarized its changes in body fluids. However, methodological problems have led to the poor diagnostic/prognostic value of this protein and alternative biomarkers are currently being investigated. The aim of this paper is therefore to summarize studies on protein biomarkers that are alternatives to α-syn, particularly those that change in nigrostriatal areas and in biofluids, with a focus on blood, and, eventually, saliva and urine.

VGF: A prospective biomarker and therapeutic target for neuroendocrine and nervous system disorders

Neuroendocrine regulatory polypeptide VGF (nerve growth factor inducible) was firstly found in the rapid induction of nerve growth factor on PC12 cells. It was selectively distributed in neurons and many neuroendocrine tissues. This paper reviewed the latest literatures on the gene structure, transcriptional regulation, protein processing, distribution and potential receptors of VGF. The neuroendocrine roles of VGF and its derived polypeptides in regulating energy, water electrolyte balance, circadian rhythm and reproductive activities were also summarized. Furthermore, based on the experimental evidence in vivo and in vitro, dysregulation of VGF in different neuroendocrine diseases and the possible mechanism mediated by VGF polypeptides were discussed. We next discussed the potential as the clinical diagnosis and therapy for VGF related diseases in the future.

The molecular mechanism of vgf in appetite, lipids, and insulin regulation

Obesity is an indication of an imbalance between energy expenditure and food intake. It is a complicated disease of epidemic proportions as it involves many factors and organs. Sedentary lifestyles and overeating have caused a substantial rise in people with obesity and type 2 diabetes. Thus, the discovery of successful and sustainable therapies for these chronic illnesses is critical. However, the mechanisms of obesity and diabetes and the crosstalk between these diseases are still ambiguous. Numerous studies are being done to study these mechanisms, with updates made frequently. VGF peptide and its derivatives are anticipated to have a role in the development of obesity and diabetes. However, contradictory studies have produced conflicting findings on the function of VGF. Therefore, in this review, we attempt to clarify and explain the role of VGF peptides in the brain, pancreas, and adipose tissue in the development of obesity.

TLQP-21 changes in response to a glucose load

BACKGROUND

The TLQP-21 peptide potentiates glucose-stimulated insulin secretion, hence we investigated its endogenous response to glucose.

METHODS

Fasted mice received intraperitoneal glucose (3 g/kg), or saline (controls), and were sacrificed 30 and 120 min later (4 groups, n = 6/group). We investigated TLQP-21 in pancreas and plasma using immunohistochemistry, enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography (HPLC), as well as TLQP-21 receptors (gC1q-R and C3a-R1) expression in pancreas by immunohistochemistry.

RESULTS

In pancreas, TLQP-immunoreactivity (TLQP-ir.) was shown in insulin-, glucagon- and somatostatin-containing cells. Upon glucose, TLQP-ir. decreased at 30 min (∼40 % vs. controls), while returning to basal values at 120 min. In all groups, C3a-R1 was localized in ∼50 % of TLQP labelled islet cells (mostly central), while gC1q-R was detected in ∼25 % of TLQP cells (mainly peripheral). HPLC fractions of control pancreas extracts, assessed by ELISA, confirmed the presence of a TLQP-21 compatible-form (∼2.5 kDa MW). In plasma, TLQP-ir. increased at 30 min (∼30 %), with highest concentrations at 120 min (both: p<0.05 vs. controls), while HPLC fractions showed an increase in the TLQP-21 compatible form.

CONCLUSIONS

Upon hyperglycaemia, TLQP-21 would be released from islets, to enhance insulin secretion but we cannot exclude an autocrine activity which may regulate insulin storage/secretion.