Relation between changes in neural responsivity and reductions in desire to eat high-calorie foods following gastric bypass surgery

Reductions in reward-related (e.g. striatal) neural activation have been noted following obesity surgery. It has been speculated that these postoperative neural changes may be related to documented postoperative changes in food preferences; however, this relation has not been previously established. In this study, functional magnetic resonance imaging and rating scales were used to assess neural responsivity, desire to eat (i.e. wanting), and liking for high- and low-calorie food cues in 14 females one month pre- and one month post-Roux-en-Y gastric bypass (RYGB) surgery. Pre- to post-RYGB changes in all variables were assessed, and postoperative changes in neural responsivity were regressed on postoperative changes in desire to eat and liking of foods. Results revealed significant postoperative reductions in mesolimbic (e.g. striatal) neural responsivity, desire to eat (wanting), and liking for high- relative to low-calorie food cues. Postoperative reductions in mesolimbic responsivity were associated with postoperative reductions in wanting, but not liking, for high- versus low-calorie foods. Interestingly, reductions in food wanting were also related to reductions in inhibitory (e.g. dorsolateral prefrontal cortex) activation following RYGB. Results are consistent with the hypothesized delineation between wanting and liking, supporting the notion that wanting, but not liking, is processed through the dopaminergic reward pathway. Concurrent reductions in both reward-related and inhibitory activation-predicted reductions in desire to eat might suggest that less dietary inhibition was elicited to resist potential overconsumption as the anticipated reward value of high-calorie foods decreased following RYGB.

Multiple Sclerosis Severity Scale and whole-brain N-acetylaspartate concentration for patients' assessment

BACKGROUND

The ability to predict the course of multiple sclerosis (MS) is highly desirable but lacking.

OBJECTIVE

To test whether the MS Severity Scale (MSSS) and global neuronal viability, assessed through the quantification of the whole-brain N-acetylaspartate concentration (WBNAA), concur or complement the assessment of individual patients' disease course.

METHODS

The MSSS and average WBNAA loss rate (ΔWBNAA, extrapolated based on one current measurement and the assumption that at disease onset neural sparing was similar to healthy controls, obtained with proton magnetic resonance (MR) spectroscopy and magnetic resonance imaging (MRI)) from 61 patients with MS (18 male and 43 female) with long disease duration (15 years or more) were retrospectively examined. Some 27 patients exhibited a 'benign' disease course, characterized by an Expanded Disability Status Scale score (EDSS) of 3.0 or less, and 34 were 'non-benign': EDSS score higher than 3.0.

RESULTS

The two cohorts were indistinguishable in age and disease duration. Benign patients' EDSS and MSSS (2.1 ± 0.7, 1.15 ± 0.60) were significantly lower than non-benign (4.6 ± 1.0, 3.6 ± 1.2; both p < 10(-4)). Their respective average ΔWBNAA, 0.10 ± 0.16 and 0.11 ± 0.12 mM/year, however, were not significantly different (p > 0.7). While MSSS is both sensitive to (92.6%) and specific for (97.0%) benign MS, ΔWBNAA is only sensitive (92.6%) but not specific (2.9%).

CONCLUSION

Since the WBNAA loss rate is similar in both phenotypes, the only difference between them is their clinical classification, characterized by MSSS and EDSS. This may indicate that 'benign' MS probably reflects fortuitous sparing of clinically eloquent brain regions and better utilization of brain plasticity.

A network approach to assessing cognition in disorders of consciousness

OBJECTIVE

Conventional assessments of consciousness rely on motor responses to indicate awareness. However, overt behaviors may be absent or ambiguous in patients with disorders of consciousness (DOC) resulting in underrating capacity for cognition. fMRI during a silent picture-naming task was evaluated as an indicator of command following when conventional methods are not sufficient.

METHODS

A total of 10 patients with and without conventional evidence of awareness, who met diagnostic criteria for the minimally conscious state (MCS) (n = 5), vegetative state (VS) (n = 3), emerged from MCS (EMCS) (n = 1), and locked-in syndrome (LIS) (n = 1), participated in this observational fMRI study.

RESULTS

The LIS and EMCS patients engaged a complete network of essential language-related regions during the object-naming task. The MCS and 2 of the VS patients demonstrated both complete and partial preservation of the object-naming system. Patients who engaged a complete network scored highest on the Coma Recovery Scale-Revised.

CONCLUSIONS

This study supports the view that fMRI during object naming can elicit brain activations in patients with DOC similar to those observed in healthy subjects during command following, and patients can be stratified by completeness of the engaged neural system. These results suggest that activity of the language network may serve as an indicator of high-level cognition and possibly volitional processes that cannot be discerned through conventional behavioral assessment alone.

Infusion of mature megakaryocytes into mice yields functional platelets

Thrombopoiesis, the process by which circulating platelets arise from megakaryocytes, remains incompletely understood. Prior studies suggest that megakaryocytes shed platelets in the pulmonary vasculature. To better understand thrombopoiesis and to develop a potential platelet transfusion strategy that is not dependent upon donors, of which there remains a shortage, we examined whether megakaryocytes infused into mice shed platelets. Infused megakaryocytes led to clinically relevant increases in platelet numbers. The released platelets were normal in size, displayed appropriate surface markers, and had a near-normal circulating half-life. The functionality of the donor-derived platelets was also demonstrated in vivo. The infused megakaryocytes mostly localized to the pulmonary vasculature, where they appeared to shed platelets. These data suggest that it may be unnecessary to generate platelets from ex vivo grown megakaryocytes to achieve clinically relevant increases in platelet numbers.

The role of adipose cell size and adipose tissue insulin sensitivity in the carbohydrate intolerance of human obesity

Glucose metabolism and insulin sensitivity of isolated human adipose tissue was studied as a function of adipose cell size and number. Glucose metabolism by these tissues was closely related to the number of cells in the fragment, irrespective of cell size. Adipose cells of obese individuals metabolized glucose to carbon dioxide and triglyceride at rates similar to adipose cells of nonobese subjects. In contrast, insulin responsiveness of adipose tissue was dependent upon adipose cell size. The larger its adipose cells the less insulin sensitive was the tissue. Thus, adipose tissue of obese subjects, with enlarged cells, showed a diminished response to insulin. After weight loss and reduction in adipose cell size, insulin sensitivity of the adipose tissue of obese patients was restored to normal. When adipose tissue of obese individuals showed impaired responsiveness to insulin, their plasma insulin levels, after oral glucose, were elevated. Weight loss and reduction in adipose cell size restored plasma insulin concentration to normal, concomitant with the return of normal tissue insulin sensitivity.