Cpt1a silencing in AgRP neurons improves cognitive and physical capacity and promotes healthy aging in male mice

International Union of Basic and Clinical Pharmacology. CXIX. Fundamental insights and clinical relevance regarding the carnitine palmitoyltransferase family of enzymes

The carnitine palmitoyltransferases (CPTs) play a key role in controlling the oxidation of long-chain fatty acids and are potential therapeutic targets for diseases with a strong metabolic component, such as obesity, diabetes, and cancer. Four distinct proteins are CPT1A, CPT1B, CPT1C, and CPT2, differing in tissue expression and catalytic activity. CPT1s are finely regulated by malonyl-CoA, a metabolite whose intracellular levels reflect the cell's nutritional state. Although CPT1C does not exhibit significant catalytic activity, it is capable of modulating the functioning of other neuronal proteins. Structurally, all CPTs share a Y-shaped catalytic tunnel that allows the entry of 2 substrates and accommodation of the acyl group in a hydrophobic pocket. Several molecules targeting these enzymes have been described, some showing potential in normalizing blood glucose levels in diabetic patients, and others that, through a central mechanism, are anorexigenic and enhance energy expenditure. However, given the critical roles that CPTs play in certain tissues, such as the heart, liver, and brain, it is essential to fully understand the differences between the various isoforms. We analyze in detail the structure of these proteins, their cellular and physiological functions, and their potential as therapeutic targets in diseases such as obesity, diabetes, and cancer. We also describe drugs identified to date as having inhibitory or activating capabilities for these proteins. This knowledge will support the design of new drugs specific to each isoform, and the development of nanomedicines that can selectively target particular tissues or cells. SIGNIFICANCE STATEMENT: Carnitine palmitoyltransferase (CPT) proteins, as gatekeepers of fatty acid oxidation, have great potential as pharmacological targets to treat metabolic diseases like obesity, diabetes, and cancer. In recent years, significant progress has been made in understanding the 3-dimensional structure of CPTs and their pathophysiological functions. A deeper understanding of the differences between the various CPT family members will enable the design of selective drugs and therapeutic approaches with fewer side effects.

Impact of aerobic exercise on brain metabolism: Insights from spatial metabolomic analysis

BACKGROUND

Exercise is acknowledged for its beneficial effects on brain health; however, the intricate underlying molecular mechanisms remain poorly understood.

AIMS

This study aimed to explore aerobic exercise-induced metabolic alterations in the brain.

METHODS

We conducted an eight-week treadmill running exercise program in two-month-old male C57/BL6J mice. Body weight, serum lipid, glucose levels, and spatial cognition were measured. Spatial metabolomic analysis was performed to compare the metabolomic profiles across different brain regions. Immunohistochemical methods were used to compare the expression of carnitine palmitoyltransferase 1c (CPT1c).

RESULTS

Exercise induced significant changes in the analysed metabolomic profiles. There were 904 differentially expressed metabolites (DEMs) detected in the whole brain section. Notable alterations in lipid profiles were observed, and among the 292 lipids detected, there were 74 (25.34 %), 85 (29.11 %), and 78 (26.71 %) lipids differentially expressed in the hippocampus, thalamus, and hypothalamus of the Exe group, respectively. Lipid metabolism related pathways and enzymes were also altered, with L-carnitine and CPT1c upregulated in the three regions (p<0.05), and epinephrine levels decreased in the hippocampus (p<0.05). Furthermore, the vitamin B6 metabolism pathway was altered in the hypothalamus.

CONCLUSIONS

This study highlighted the significant changes in lipid metabolism induced by involuntary exercise in the brains of young male mice. Exercise also altered epinephrine levels and the vitamin B12 metabolic pathway in specific brain regions, which indicated the multifaceted effects of exercise on the brain.

Cpt1a silencing in AgRP neurons improves cognitive and physical capacity and promotes healthy aging in male mice

Orexigenic neurons expressing agouti-related protein (AgRP) and neuropeptide Y in the arcuate nucleus (ARC) of the hypothalamus are activated in response to dynamic variations in the metabolic state, including exercise. We previously observed that carnitine palmitoyltransferase 1a (CPT1A), a rate-limiting enzyme of mitochondrial fatty acid oxidation, is a key factor in AgRP neurons, modulating whole-body energy balance and fluid homeostasis. However, the effect of CPT1A in AgRP neurons in aged mice and during exercise has not been explored yet. We have evaluated the physical and cognitive capacity of adult and aged mutant male mice lacking Cpt1a in AgRP neurons (Cpt1a KO). Adult Cpt1a KO male mice exhibited enhanced endurance performance, motor coordination, locomotion, and exploration compared with control mice. No changes were observed in anxiety-related behavior, cognition, and muscle strength. Adult Cpt1a KO mice showed a reduction in gastrocnemius and tibialis anterior muscle mass. The cross-sectional area (CSA) of these muscles were smaller than those of control mice displaying a myofiber remodeling from type II to type I fibers. In aged mice, changes in myofiber remodeling were maintained in Cpt1a KO mice, avoiding loss of physical capacity during aging progression. Additionally, aged Cpt1a KO mice revealed better cognitive skills, reduced inflammation, and oxidative stress in the hypothalamus and hippocampus. In conclusion, CPT1A in AgRP neurons appears to modulate health and protects against aging. Future studies are required to clarify whether CPT1A is a potential antiaging candidate for treating diseases affecting memory and physical activity.