VGF-Derived Peptide TLQP-21: Biology and Pathophysiology

The Vgf gene is a member of the extended granin family of peptides [1]. VGF encodes a 615 amino acid protein (617 in rodents) that is stored in dense core granules and processed to yield several bioactive peptides, released through the regulated pathway. 

At least 7 peptides have been shown to possess non redundant biological functions in rodents while VGF fragments are increasingly recognized as useful biomarkers for human disease [1]. We have recently identified and functionally characterized the C-terminal internal fragment designated TLQP-21 [2]. TLQP-21 is a multifunctional peptide active in the regulation of energy balance, glucose homeostasis, gastric function, nociception, reproduction and stress [1]. Intracerebroventricular infusion of TLQP-21 increases energy expenditure and prevents obesity without activating central hypothalamic neuropeptides or feeding [2]. In periphery, TLQP-21 [3] is co-stored with norepinephrine-synthesizing enzyme tyrosine hydroxylase in sympathetic nerves innervating the adipose organ; 

increases lipolysis downstream of β-adrenergic receptor signaling pathway; increases sympathetic innervation to adipose fat pads and decreases adipocytes diameters without exerting negative cardiovascular effects or activating energy expenditure [3]. TLQP-21 is active at the C3aR1 receptor [4,5]. We demonstrated that TLQP-21 activates C3aR1 with a folding upon binding mechanism and that the C-terminal amonoacids are required for TLQP-21 biological activity [5]. Furthermore, we demonstrated that TLQP-21 albeit having a short half life in plasma [6] exerts an anti-obesity effect in mice with a mechanism requiring C3aR1 and β-adrenergic receptors activation [7]. 

In a recent structure-function relationship study we identified a cluster of mutations within the C3aR1 receptor and the TLQP-21 peptide in the Murinae sub-family of rodents resulting in enhanced binding affinity and potency, leading to potentiation of adrenergic-induced lipolysis [8]. Consistently, the mouse-TLQP-21 but not the human-TLQP-21 potentiates adrenergic induced lipolysis in human adipocytes [8]

We are currently investigating the central and peripheral mechanism of TLQP-21 induced pro-lipolytic and anti-obesity effect, the biochemical mechanism of TLQP-21 activation of C3aR1 and its biological role in human model systems.

The long term goal is to use molecular and physiological knowledge to develop innovative drugs for the treatment of obesity and type 2 diabetes.

References: 1. Bartolomucci et al., Endocr Rev. 2011;32:755-97; 2. Bartolomucci et al., Proc Natl Acad Sci USA. 2006;103:14584-9; 3. Possenti et al., Biochem J. 2012;441:511-22. 4. Hannedouche S et al., J Biol Chem. 2013;288:27434-43. 5. Cero et al. Structure 2014. 6. Guo et al., Neuropeptides. 2018 Oct;71:97-103. 7. Cero et al., Mol Metabol 2017;6:148-158 8. Sahu et al. Cell Reports, 2019;28:2567–2580.

Recent review papers:

Granins and catecholamines: functional interaction in chromaffin cells and adipose tissue.

The extended granin family: structure, function, and biomedical implications.

Granins as disease-biomarkers: translational potential for psychiatric and neurological disorders.

Supported by NIH/NIDDK R01DK102496, R01DK117504 and Minnesota Partnership for Biotechnology and Medical Genomics, Decade of Discovery in Diabetes Grant.

Mechanisms of chronic stress-induced aging-associated diseases.

The extraordinary extension of human lifespan over the past five generations has exponentially increased the prevalence of a myriad of aging-associated chronic diseases, including heart failure, atherosclerosis, osteoarthritis, Alzheimer`s disease (AD) and AD-related dementias (AD/ADRD), chronic kidney disease,glaucoma, osteoporosis, and pulmonary fibrosis. Epidemiological and clinical studies suggest that prolonged life stress, low socio-economic status (SES) and health disparity exacerbate aging-associated diseases and increase mortality rate in humans and animal models. However how remains poorly established.

We developed a unique mouse model of chronic psychosocial stress [1,2]. Briefly stable resident/intruder pairs of adult male mice are established after a baseline period. In the stress phase resident/intruder pairs live in the same cage separated by a perforated partition, which allows sensory but not physical contact and are allowed a brief daily physical interaction which lasted a maximum of 10 min. Subordinate and dominant mice are identified by direct observation. 

We demonstrated that subordinate mice (mice having low social rank) manifest acomplex syndrome characterized by a depression-like behavior, increasedanxiety, neuroimmune and neuroendocrine abnormalities as well as vulnerabilityto diet induced obesity [3-7].

Recent work from our lab also established that chronic stress is a novel physiological stimulus promoting the recruitment and activation of the brown adipose tissue in mouse housed at thermoneutrality, thereby exerting an anti obesity effect [7].

Another recent project established for the first time that lifelong chronic psychosocial stress shortens lifespan in subordinate mice, and is associated with earlier onset of aging-associated diseases including atherosclerosis as well as with an increase in molecular markers of cellular senescence [8].

Ongoing projects:

The mechanism of stress-induced accumulation of senescent cells.

The long term consequences of chronic social stress on mortality and disease of ageing.

Stress-induced exacerbation of genetic and environmentally-induced cardiometabolic and neuromuscular diseases.

References:1. Bartolomucci A,et al. Physiol Behav. 2001. 2. Bartolomucci et al., NeurosciBiobehav Rev. 2005. 3. Sanghez et al.,Psychoneuroendocrinology 2013. 4. Sanghez et al., Stress, 2016. 5. Razzoli et al.,Mol Metabol 2016. 6. Razzoli et al., Front Nutr 2015. 7. Razzoli et al., Mol Metabol 2016. 7. Razzoli et al., Aging Cell 2018.

Recent review papers:

Stress, overeating, and obesity: Insights from human studies and pre-clinical models.

The Dichotomous Effect of Chronic Stress on Obesity.

Stress revisited: a critical evaluation of the stress concept.

Supported by NIH/NIA R01AG043972, Minnesota Partnership for Biotechnology and Medical Genomics, Summer`s Wish Fund, Greg Marzolf Jr.Foundation Research Grant, Center on Aging, Wallin Neuroscience Discovery Fund.

In vivo

Indirect calorimetry to determine energy expenditure (Columbus Instruments)

Echo MRI 3-in-1 to determine body-tissue composition (Echo Medical System)

BioDAQ for Food and liquid intake measurements and meal  pattern analysis (Research Diets, Inc)

Chronic psychosocial stress model (Custom made)

Phenotyper for home cage phenotyping (Noldus)

Actimeter for home cage locomotor activity (TecnoSmart)

Behavioral tests for anxiety/social interaction/feeding behavior (Manifactured by TecnoSmart)

GTT; ITT; restratin stress

In vitro

Cell culture (3T3L1)

Glycerol assay in mature adipocytes

Multi Channel Real-time PCR (BioRad)

Bio Plex 200 with Luminex Technology (Biorad)

Nexcellom Vision – Cellometer (Nexcellom)

Tissue homogenizer (Pracellis)

Western blot; ELISA, etc.