TLQP-21, a VGF-derived peptide, increases energy expenditure and prevents the early phase of diet-induced obesity

Abstract

The vgf gene has been identified as an energy homeostasis regulator. Vgf encodes a 617-aa precursor protein that is processed to yield an incompletely characterized panel of neuropeptides. Until now, it was an unproved assumption that VGF-derived peptides could regulate metabolism. Here, a VGF peptide designated TLQP-21 was identified in rat brain extracts by means of immunoprecipitation, microcapillary liquid chromatography-tandem MS, and database searching algorithms. Chronic intracerebroventricular (i.c.v.) injection of TLQP-21 (15 mug/day for 14 days) increased resting energy expenditure (EE) and rectal temperature in mice. These effects were paralleled by increased epinephrine and up-regulation of brown adipose tissue beta2-AR (beta2 adrenergic receptor) and white adipose tissue (WAT) PPAR-delta (peroxisome proliferator-activated receptor delta), beta3-AR, and UCP1 (uncoupling protein 1) mRNAs and were independent of locomotor activity and thyroid hormones. Hypothalamic gene expression of orexigenic and anorexigenic neuropeptides was unchanged. Furthermore, in mice that were fed a high-fat diet for 14 days, TLQP-21 prevented the increase in body and WAT weight as well as hormonal changes that are associated with a high-fat regimen. Biochemical and molecular analyses suggest that TLQP-21 exerts its effects by stimulating autonomic activation of adrenal medulla and adipose tissues. In conclusion, we present here the identification in the CNS of a previously uncharacterized VGF-derived peptide and prove that its chronic i.c.v. infusion effected an increase in EE and limited the early phase of diet-induced obesity.

Fig. 1.

TLQP-21 indentification. (a) MALDI-TOF MS spectrum-immunoselected VGF peptides. (b) MicroLC MS/MS full mass spectrum recorded at a retention time of 21 min and 41 sec, showing the doubly charged ion corresponding to TLQP-21 at an m/z of 1,217.3. (c) Fragment ion spectrum.

Fig. 2.

Physiological effects in mice receiving TLQP-21. (a) EE (n = 6 per group). (b) Rectal temperature (n = 8 per group). (c) E levels. (d) NE levels. (e) TG levels. (f) FFA/TG ratio. Unless otherwise stated, n = 16–18 per group. ∗, P < 0.05.

Fig. 3.

Glucose tolerance test. Basal levels and levels 30, 60, and 120 min after oral glucose (3 mg/kg) treatment are shown for the following: insulin (a), glucose (b), FFAs (c), TGs (d), and FFA/TG ratio (e). n = 6 per group; ∗, P < 0.05 control vs. TLQP-21; °, TLQP-21 at 30 min vs. TLQP-21 at baseline, 60 min, and 120 min.

Fig. 4.

β2-AR mRNA in the BAT (a) and PPAR-δ (b), UCP1 (c), and β3-AR (d) mRNA in the WAT. Data are presented as net intensity/GAPDH expression. n = 4–6 per group; ∗, P < 0.05; §, P = 0.06.

Fig. 5.

Physiological and behavioral parameters in mice receiving a high-fat (HF) diet. Shown are body weight changes from baseline (a), food intake (b), caloric efficiency (c), and WAT/bw (d). Standard, standard chow; Con, mice treated with aCSF. n = 11–12 per group; ∗, P < 0.05.

Fig. 6.

Hormones and serological parameters in mice receiving a high-fat (HF) diet. (a) Serum levels of leptin and ghrelin. (b) Levels of TGs, FFAs, and glucose and FFA/TG ratio. Standard, standard chow; Con, mice treated with aCSF. n = 11–12 per group; ∗∗, P < 0.01.