High expression of CPT1b in skeletal muscle in metabolically healthy older subjects.

AIM: Ageing is often associated with metabolic abnormalities such as insulin resistance, although some people remain metabolically healthy throughout their lives. The aim of this study was to gain more insight into metabolic health with increasing age. METHODS: Two groups of robust and of frail subjects, respectively, were identified based on a composite ageing indicator and recruited from the French SU.VI.MAX 2 cohort of older disease-free subjects. In all, 14 men and 12 women, aged 67±4 years, with similar anthropometric and metabolic characteristics at baseline (BMI: 24.5±2.9kg.m-2) were included in the Compaliclamp study. Skeletal muscle biopsy was performed to assess expression of a set of metabolic and sirtuin (SIRT) genes. Also, whole-body substrate oxidation and insulin sensitivity were determined using the euglycaemic-hyperinsulinaemic clamp and indirect calorimetry techniques. RESULTS: Robust subjects were more insulin-sensitive, oxidized more lipid in a fasting state and stored more glucose during the euglycaemic - hyperinsulinaemic clamp than did frail subjects. At the gene-expression level in skeletal muscle, carnitine palmitoyltransferase 1b (CPT1b) messenger RNA (mRNA) levels were around four times higher in the robust compared with frail counterparts. Moreover, both SIRT2 and SIRT6 expression was lower in robust subjects and correlated with CPT1b expression. CONCLUSION: CPT1b overexpression could be helping to maintain metabolic health with increasing age. Thus, it is suggested that targeting CPT1b expression might be an interesting strategy to counteract frailty at an early stage. In addition, future studies should examine the role of sirtuin in CPT1b expression regulation.

Astroglial Control of the Antidepressant-Like Effects of Prefrontal Cortex Deep Brain Stimulation.

Although deep brain stimulation (DBS) shows promising efficacy as a therapy for intractable depression, the neurobiological bases underlying its therapeutic action remain largely unknown. The present study was aimed at characterizing the effects of infralimbic prefrontal cortex (IL-PFC) DBS on several pre-clinical markers of the antidepressant-like response and at investigating putative non-neuronal mechanism underlying DBS action. We found that DBS induced an antidepressant-like response that was prevented by IL-PFC neuronal lesion and by adenosine A1 receptor antagonists including caffeine. Moreover, high frequency DBS induced a rapid increase of hippocampal mitosis and reversed the effects of stress on hippocampal synaptic metaplasticity. In addition, DBS increased spontaneous IL-PFC low-frequency oscillations and both raphe 5-HT firing activity and synaptogenesis. Unambiguously, a local glial lesion counteracted all these neurobiological effects of DBS. Further in vivo electrophysiological results revealed that this astrocytic modulation of DBS involved adenosine A1 receptors and K(+) buffering system. Finally, a glial lesion within the site of stimulation failed to counteract the beneficial effects of low frequency (30 Hz) DBS. It is proposed that an unaltered neuronal-glial system constitutes a major prerequisite to optimize antidepressant DBS efficacy. It is also suggested that decreasing frequency could heighten antidepressant response of partial responders.

A 5-HT3 receptor antagonist potentiates the behavioral, neurochemical and electrophysiological actions of an SSRI antidepressant.

More effective treatments for major depression are needed. We studied if the selective 5-HT3 receptor antagonist ondansetron can potentiate the antidepressant potential of the selective serotonin (5-HT) reuptake inhibitor (SSRI) paroxetine using behavioral, neurochemical and electrophysiological methods. Flinders Sensitive Line (FSL) rats, treated with ondansetron, and/or a sub-effective dose of paroxetine, were assessed in the forced swim test. The effects of an acute intravenous administration of each compound alone and in combination were evaluated with respect to 5-HT neuronal firing rate in the dorsal raphe nucleus (DRN). Effects of s.c. administration of the compounds alone and in combination on extracellular levels of 5-HT were assessed in the ventral hippocampus of freely moving rats by microdialysis. The results showed that ondansetron enhanced the antidepressant activity of paroxetine in the forced swim test. It partially prevented the suppressant effect of paroxetine on DRN 5-HT neuronal firing and enhanced the paroxetine-induced increase of hippocampal extracellular 5-HT release. These findings indicate that 5-HT3 receptor blockade potentiates the antidepressant effects of SSRIs. Since both paroxetine and ondansetron are used clinically, it might be possible to validate this augmentation strategy in depressed patients.

Increased TSH in obesity: Evidence for a BMI-independent association with leptin.

AIM: This study aimed to determine whether the association between thyroid-stimulating hormone (TSH) and body mass index (BMI) is related to leptin concentration in obese individuals. METHODS: Plasma TSH and leptin assays were performed in 800 consecutive patients, hospitalized for a nutritional checkup, with a BMI ≥ 30 kg/m(2). Various anthropometric, hormonal and metabolic parameters, including age, weight, BMI, insulin, leptin and TSH, were measured or calculated. Univariate and multivariate regression analyses were performed to identify any significant relationships between these parameters. Also, characteristics of the patients in the lowest and highest quartiles of TSH distribution were compared. RESULTS: TSH was positively correlated with both BMI and leptin. When multiple regression analysis was performed, TSH and leptin maintained a significant association independent of BMI. Patients in the fourth quartile of TSH distribution displayed higher BMI and higher leptin levels in comparison to the first quartile. CONCLUSION: Our study has confirmed an increase in TSH in conjunction with BMI in obese subjects. This increase was correlated with leptin independently of BMI. It is hypothesized that the increase in TSH observed in obese subjects was the consequence of both fat mass accumulation and a positive energy-balance.