Does etiology of gastroparesis determine clinical outcomes in gastric electrical stimulation treatment of gastroparesis?

BACKGROUND: Gastroparesis is a condition characterized by impaired gastric motility that may result in weight loss and malnutrition. There have been promising studies demonstrating improvement in symptoms after gastric electrical stimulation (GES) implantation for medically refractory gastroparetics [1-10]. With the heterogeneous population of gastroparetics, the aim of this study was to assess if etiology correlated with response to GES. METHODS: A retrospective review and analysis was performed on patients who underwent GES over a 10-year period at a single institution. Each patient was stratified into an etiological subset (diabetes, idiopathic, post-surgical). Patients were compared by demographics, medical and surgical history, subsequent GES explantation vs continued therapy, need for supplemental nutrition postoperatively, weight gain, weight loss or weight maintenance, and readmission rates. RESULTS: 183 patients underwent GES from 2005 to 2015. 50% were diabetic (n = 91), 42% idiopathic (n = 76), and 9% post-surgical (n = 16). Diabetic patients (DM) demonstrated the highest likelihood of continued therapy compared to post-surgical (PS) and idiopathic patients (ID) (54.7% vs 9.5% vs 35.8%, respectively, p < 0.05). DM patients saw a greater incidence of weight gain > 4 kg, compared to PS and IS patients (67.6% vs 8.1% vs. 24.3%, respectively, p < 0.05). ID patients were most likely to have it removed compared to DM and PS patients (65.7% vs 28.6% vs 5.7%, respectively, p = < 0.05). PS patients were least likely to have their GES removed. They were also least likely to utilize supplemental nutrition compared to DM and ID (9.4% vs 49.1% vs 41.51%, respectively, p < 0.05). CONCLUSIONS: Patients with gastroparesis had different clinical outcomes after GES therapy based on underlying etiology. By gaining a better understanding of the effects of GES, it can be offered to the appropriate patient.

Deacetylation of Miro1 by HDAC6 blocks mitochondrial transport and mediates axon growth inhibition.

Inhibition of histone deacetylase 6 (HDAC6) was shown to support axon growth on the nonpermissive substrates myelin-associated glycoprotein (MAG) and chondroitin sulfate proteoglycans (CSPGs). Though HDAC6 deacetylates α-tubulin, we find that another HDAC6 substrate contributes to this axon growth failure. HDAC6 is known to impact transport of mitochondria, and we show that mitochondria accumulate in distal axons after HDAC6 inhibition. Miro and Milton proteins link mitochondria to motor proteins for axon transport. Exposing neurons to MAG and CSPGs decreases acetylation of Miro1 on Lysine 105 (K105) and decreases axonal mitochondrial transport. HDAC6 inhibition increases acetylated Miro1 in axons, and acetyl-mimetic Miro1 K105Q prevents CSPG-dependent decreases in mitochondrial transport and axon growth. MAG- and CSPG-dependent deacetylation of Miro1 requires RhoA/ROCK activation and downstream intracellular Ca2+ increase, and Miro1 K105Q prevents the decrease in axonal mitochondria seen with activated RhoA and elevated Ca2+ These data point to HDAC6-dependent deacetylation of Miro1 as a mediator of axon growth inhibition through decreased mitochondrial transport.