The enzyme carnitine palmitoyltransferase-1 (CPT1) regulates long-chain fatty acid (LCFA) entry into mitochondria, where the LCFAs undergo beta-oxidation. To investigate the mechanism(s) by which central metabolism of lipids can modulate energy balance, we selectively reduced lipid oxidation in the hypothalamus. We decreased the activity of CPT1 by administering to rats a ribozyme-containing plasmid designed specifically to decrease the expression of this enzyme or by infusing pharmacological inhibitors of its activity into the third cerebral ventricle. Either genetic or biochemical inhibition of hypothalamic CPT1 activity was sufficient to substantially diminish food intake and endogenous glucose production. These results indicated that changes in the rate of lipid oxidation in selective hypothalamic neurons signaled nutrient availability to the hypothalamus, which in turn modulated the exogenous and endogenous inputs of nutrients into the circulation.

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 g͞day 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 ␤2-AR (␤2 adrenergic receptor) and white adipose tissue (WAT) PPAR-␦ (peroxisome proliferator-activated receptor ␦), ␤3-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.autonomic nervous system ͉ ␤ adrenergic receptor ͉ MALDI-TOF ͉ neuropeptide ͉ peroxisome proliferator-activated receptor ␦ E nergy homeostasis is a complex physiological function that is coordinated at multiple levels. Stimulated by the discovery of leptin and the pandemic diffusion of obesity and type-2 diabetes, the regulation of energy homeostasis has received increasing attention (1-4). New players are being continuously identified and screened as molecular candidates to counteract obesity (5-10). Vgf, initially identified as a nerve growth factor-responsive gene, is also robustly induced by BDNF and neurotrophin 3 and marginally induced by epidermal and fibroblast growth factors, IL-6, and insulin (11-13). Vgf received great attention after the observation that VGF-deficient mice are lean, hypermetabolic, and resistant to various types of obesity (14, 15). In the rat brain, VGF is abundant in the cortex, hypothalamus, hippocampus, and olfactory system and in a number of thalamic, septal, amygdaloid, and brainstem nuclei, with the local availability of neurotrophins for receptor occupation being the critical parameter in determining its selective expression (12, 13). Changes in vgf expression also increase in the arcuate nucleus of fasted rats (14) and hamsters that are exposed to a short or long day's length (16). However, up until now, it was still unproved that VGF-derived peptides are metabolic neuromodulators (...

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OBJECTIVEWe have developed a new antihyperglycemic agent (teglicar) through the selective and reversible inhibition of the liver isoform of carnitine palmitoyl-transferase 1 (L-CPT1).RESEARCH DESIGN AND METHODSGlucose production was investigated in isolated hepatocytes and during pancreatic clamps in healthy rats. Chronic treatments on C57BL/6J, db/db, high-fat fed mice, and rats were performed to understand glucose metabolism and insulin sensitivity.RESULTSIn isolated hepatocytes, teglicar concentration dependently reduced ketone bodies and glucose production up to 72 and 50%, respectively. In rats, teglicar reduced the endogenous glucose production (−62%) without affecting peripheral glucose utilization. Heart 2-[3H]deoxyglucose uptake in mice was also not affected, confirming in vivo the drug selectivity toward L-CPT1. Chronic treatment in db/db mice (50 mg/kg/bid; 45 days) reduced postabsorptive glycemia (−38%), water consumption (−31%), and fructosamine (−30%). Such antidiabetic activity was associated with an improved insulin sensitivity assessed by the insulin tolerance test. A significant 50% increase in hepatic triglyceride content (HTGC) was found, although plasma alanineaminotransferase was not altered. In addition, long-term teglicar administration to high-fat fed C57BL/6J mice normalized glycemia (−19%) and insulinemia (−53%). Long-term teglicar administration (30 days, 80 mg/kg) in healthy overnight-fasted rats slightly reduced basal glycemia (−20%, ns), reduced basal insulin levels by 60%, doubled triglycerides, and increased free-fatty acids (+53%). HTGC was markedly increased, but liver and peripheral insulin sensitivity assessed by hyperinsulinemiceuglycemic clamp were not affected.CONCLUSIONSTeglicar, in vitro and in animal models, reduces gluconeogenesis and improves glucose homeostasis, refreshing the interest in selective and reversible L-CPT1 inhibition as a potential antihyperglycemic approach.

The synthesis and pharmacological activity of reversible CPT I inhibitors as potential antiketotic and antidiabetic drugs are reported. Such inhibitors constitute a series of enantiomerically pure aminocarnitine derivatives having the general formula (CH3)3N+CH2CH(ZR)CH2COO- (with Z = ureido, carbamate, sulfonamide, and sulfamide moieties; R = C7-C14 linear alkyl chains). A primary pharmacological screening based on the evaluation of CPT I activity in intact rat liver (L-CPT I) mitochondria revealed the best activity for the (R) forms of ureidic derivative 17 (ZR = NHCONHR, R = C14), sulfonamidic derivative 7 (ZR = NHSO2R, R = C12), and sulfamidic derivative 9 (ZR = NHSO2NHR, R = C11). The IC50 values are 1.1, 0.7, and 0.8 microM, respectively. For the carbamic derivative 11 (ZR = NHCOOR, R = C8), an IC50 of 9.5 microM was observed. In addition, an extraordinarily high selectivity toward the liver isoform with respect to the heart isoform (muscle-CPT I identical with M-CPT I) was found for the ureidic compound 17 (IC50(M-CPT I) vs IC50(L-CPTI) = 39.4), as well as for other ureidic or carbamic compounds. Diabetic db/db mice treated orally with 17 and 7 for 45 days at a dose of 50 mg/kg twice a day showed a good reduction of serum glucose levels with respect to the untreated db/db mice (p < 0.01). In addition, 17 showed antiketotic activity in normal fasted rats. 17 has been selected for development as a potential antiketotic and antidiabetic drug.