Possible Neuroprotective Effects of l-Carnitine on White-Matter Microstructural Damage and Cognitive Decline in Hemodialysis Patients

Comprehensive review of the expanding roles of the carnitine pool in metabolic physiology: beyond fatty acid oxidation

Traditionally, the carnitine pool is closely related to fatty acid metabolism. However, with increasing research, the pleiotropic effects of the carnitine pool have gradually emerged. The purpose of this review is to comprehensively investigate of the emerging understanding of the pleiotropic role of the carnitine pool, carnitine/acylcarnitines are not only auxiliaries or metabolites of fatty acid oxidation, but also play more complex and diverse roles, including energy metabolism, mitochondrial homeostasis, epigenetic regulation, regulation of inflammation and the immune system, tumor biology, signal transduction, and neuroprotection. This review provides an overview of the complex network of carnitine synthesis, transport, shuttle, and regulation, carnitine/acylcarnitines have the potential to be used as communication molecules, biomarkers and therapeutic targets for multiple diseases, with profound effects on intercellular communication, metabolic interactions between organs and overall metabolic health. The purpose of this review is to comprehensively summarize the multidimensional biological effects of the carnitine pool beyond its traditional role in fatty acid oxidation and to summarize the systemic effects mediated by carnitine/acylcarnitine to provide new perspectives for pharmacological research and treatment innovation and new strategies for the prevention and treatment of a variety of diseases.

Plasma trimethylamine N-oxide (TMAO): associations with cognition, neuroimaging, and dementia

BACKGROUND

The gut-derived metabolite Trimethylamine N-oxide (TMAO) and its precursors - betaine, carnitine, choline, and deoxycarnitine - have been associated with an increased risk of cardiovascular disease, but their relation to cognition, neuroimaging markers, and dementia remains uncertain.

METHODS

In the population-based Rotterdam Study, we used multivariable regression models to study the associations between plasma TMAO, its precursors, and cognition in 3,143 participants. Subsequently, we examined their link to structural brain MRI markers in 2,047 participants, with a partial validation in the Leiden Longevity Study (n = 318). Among 2,517 participants, we assessed the risk of incident dementia using multivariable Cox proportional hazard models. Following this, we stratified the longitudinal associations by medication use and sex, after which we conducted a sensitivity analysis for individuals with impaired renal function.

RESULTS

Overall, plasma TMAO was not associated with cognition, neuroimaging markers or incident dementia. Instead, higher plasma choline was significantly associated with poor cognition (adjusted mean difference: -0.170 [95% confidence interval (CI) -0.297;-0.043]), brain atrophy and more markers of cerebral small vessel disease, such as white matter hyperintensity volume (0.237 [95% CI: 0.076;0.397]). By contrast, higher carnitine concurred with lower white matter hyperintensity volume (-0.177 [95% CI: -0.343;-0.010]). Only among individuals with impaired renal function, TMAO appeared to increase risk of dementia (hazard ratio (HR): 1.73 [95% CI: 1.16;2.60]). No notable differences were observed in stratified analyses.

CONCLUSIONS

Plasma choline, as opposed to TMAO, was found to be associated with cognitive decline, brain atrophy, and markers of cerebral small vessel disease. These findings illustrate the complexity of relationships between TMAO and its precursors, and emphasize the need for concurrent study to elucidate gut-brain mechanisms.

The relationship between cognitive impairment and fatty acids and carnitine in hemodialysis patients

BACKGROUND/AIM

The prevalence of cognitive impairment (CI) is high in hemodialysis patients. In this study, the relationship between CI and serum carnitine, plasma omega-3, omega-6 and omega-3/omega-6 fatty acid ratio was evaluated in hemodialysis patients.

MATERIALS AND METHODS

Sixty two patients [male: 40 (64.5%), mean age 51±13 years] were included in this cross-sectional study. Serum total and free-carnitine levels were determined by ELISA. Plasma omega-3 [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] and omega-6 [arachidonic acid (AA), dihomo gamma linoleic acid (DGLA)] levels were measured using LC-ESI-MS/MS. According to the Montreal Cognitive Assessment (MoCA) scores, ≤24 points were considered as CI. MoCA score ≤24 and >24 were determined as Group 1 and Group 2, respectively.

RESULTS

Group 1 had significantly higher AA+DGLA/EPA+DHA ratios and lower free-carnitine, DHA and EPA+DHA levels compared to Group 2 (P=0.008, P=0.040, P=0.032, P=0.032, respectively). Group 1 had a statistically lower education level (P<0.05). Negative correlation was found between MoCA scores and AA+DGLA/EPA+DHA ratios (rs=-0.284, P=0.026). Free-carnitine levels were positively correlated with EPA and EPA+DHA levels (rs=0.278, P=0.030 and rs=0.271, P=0.034, respectively), and negative correlated with AA+DGLA/EPA+DHA ratios (rs=-0.414, P=0.001). In multivariate logistic regression analysis, MoCA scores was associated with AA+DGLA/EPA+DHA ratio (P=0.009) and education level (P<0.001).

CONCLUSION

It was determined that high AA+DGLA/EPA+DHA ratio and low education level could be independent risk factors of the CI. It has been shown that free-carnitine level can have positive effects on plasma EPA+DHA and AA+DGLA distributions. Low omega-3 fatty acid levels may be associated with CI in hemodialysis patients, and low carnitine level may contribute partially to this process. In addition, cognitive education programs may have an effect on preventing CI in hemodialysis patients with low education levels.

The relationship between cognitive impairment and fatty acids and carnitine in hemodialysis patients

BACKGROUND/AIM

The prevalence of cognitive impairment (CI) is high in hemodialysis patients. In this study, the relationship between CI and serum carnitine, plasma omega-3, omega-6 and omega-3/omega-6 fatty acid ratio was evaluated in hemodialysis patients.

MATERIALS AND METHODS

Sixty two patients [male: 40 (64.5%), mean age 51±13 years] were included in this cross-sectional study. Serum total and free-carnitine levels were determined by ELISA. Plasma omega-3 [eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA)] and omega-6 [arachidonic acid (AA), dihomo gamma linoleic acid (DGLA)] levels were measured using LC-ESI-MS/MS. According to the Montreal Cognitive Assessment (MoCA) scores, ≤24 points were considered as CI. MoCA score ≤24 and >24 were determined as Group 1 and Group 2, respectively.

RESULTS

Group 1 had significantly higher AA+DGLA/EPA+DHA ratios and lower free-carnitine, DHA and EPA+DHA levels compared to Group 2 (P=0.008, P=0.040, P=0.032, P=0.032, respectively). Group 1 had a statistically lower education level (P<0.05). Negative correlation was found between MoCA scores and AA+DGLA/EPA+DHA ratios (rs=-0.284, P=0.026). Free-carnitine levels were positively correlated with EPA and EPA+DHA levels (rs=0.278, P=0.030 and rs=0.271, P=0.034, respectively), and negative correlated with AA+DGLA/EPA+DHA ratios (rs=-0.414, P=0.001). In multivariate logistic regression analysis, MoCA scores was associated with AA+DGLA/EPA+DHA ratio (P=0.009) and education level (P<0.001).

CONCLUSION

It was determined that high AA+DGLA/EPA+DHA ratio and low education level could be independent risk factors of the CI. It has been shown that free-carnitine level can have positive effects on plasma EPA+DHA and AA+DGLA distributions. Low omega-3 fatty acid levels may be associated with CI in hemodialysis patients, and low carnitine level may contribute partially to this process. In addition, cognitive education programs may have an effect on preventing CI in hemodialysis patients with low education levels.

Lean-to-fat tissue ratio as a risk factor for cognitive impairment in patients undergoing maintenance hemodialysis

OBJECTIVE

The relationship between body mass index (BMI) and cognitive impairment (CI) remains controversial, and no research has been done to explore the effect of lean-to-fat (L/F) tissue ratio on the risk of CI in patients undergoing maintenance hemodialysis (MHD) so far. This study aimed to explore the effect of L/F tissue ratio on the risk of incident CI in patients undergoing MHD.

METHODS

In this observational cohort study, 3356 patients were recruited and followed up for a median of 2 years. Global cognitive function was measured using Mini-Mental State Examination score. Lean tissue mass (LTM) and fat tissue mass (FTM) were analyzed using body composition monitor based on bioimpedance spectroscopy (BCM-BIS), and L/F tissue ratio was calculated by LTM divided by FTM. Hazard ratios (HRs) for incident CI were determined by Cox regression.

RESULTS

The median age of the cohort was 55 years, and 68.7% patients were less educated. During the follow-up period, 1249 patients (37.2%) experienced incident CI. Patients with lower L/F tissue ratios had significantly higher risks of CI (HR 1.51, 95% confidence interval 1.24-1.84; p < 0.001) than those with higher L/F tissue ratios. The association between L/F tissue ratio and incident CI persisted in all subgroups stratified by sex, age, education status, especially in older and less educated participants. Both in all our patients and subgroups, BMI and CI occurrence were not independently relevant.

CONCLUSION

The L/F tissue ratio rather than BMI was an independent risk factor of incident cognitive impairment in patients undergoing MHD.

Recent Advances in Clinical Nutrition in Stroke Rehabilitation

Stroke is a common cause of death and disability worldwide [...].