Hani Rashed

Is gastric electrical stimulation superior to standard pharmacologic therapy in improving GI symptoms, healthcare resources, and long-term health care benefits?

Abstract  Context:  Severe upper gastrointestinal (GI) motor disorders, including gastroparesis (GP), can consume significant health care resources. Many patients are refractory to traditional drug therapy.

Gastric Electrical Stimulation Is Safe and Effective: A Long-Term Study in Patients with Drug-Refractory Gastroparesis in Three Regional Centers

Background: Drug-refractory gastroparesis has previously been without acceptable alternative therapies. Although gastric electrical stimulation has been used for over a decade, no long-term multicenter data exist. Methods: We studied 214 consecutive drug-refractory patients with the symptoms of gastroparesis (146 idiopathic, 45 diabetic, 23 after surgery) who consented to participate in a variety of clinical research and clinical protocols at three centers from January 1992 through January 2005, resulting in 156 patients implanted with a gastric electrical stimulation device and the other 58 patients serving as controls. The patients were stratified into three groups: (1) consented but never permanently implanted; (2) implanted with permanent device, and (3) consented while awaiting a permanent device. The patients were followed over time for gastrointestinal symptoms, solid gastric emptying, health-related quality of life, survival, device retention, and complications. Demographics, descriptive statistics, and t tests were used for comparison between baseline and latest follow-up. Results: At latest follow-up, median 4 years for 5,568 patient months, most patients implanted (135 of 156) were alive with intact devices, significantly reduced gastrointestinal symptoms, and improved health-related quality of life, with evidence of improved gastric emptying, and 90% of the patients had a response in at least 1 of 3 main symptoms. Most patients explanted, usually for pocket infections, were later reimplanted successfully. There were no deaths directly related to the device. Conclusion: Based on this sample of patients, implanted with gastric electrical stimulation devices at three centers and followed for up toward a decade, gastric electrical stimulation for drug-refractory gastroparesis is both safe and effective.

Epidermal Growth Factor Produces Inotropic and Chronotropic Effects in Rat Hearts by Increasing Cyclic AMP Accumulation

Previously we have shown that epidermal growth factor (EGF) stimulates cardiac adenylyl cyclase and increases cAMP accumulation in the rat heart (Nair et al., Biochem. J. 264, 563-571, 1989). Moreover, we have shown that the stimulation of adenylyl cyclase by EGF in heart is mediated via activation of the stimulatory GTP binding regulatory protein Gs alpha (Nair et al., J. Biol. Chem. 265, 21317-21322, 1990). Since cAMP increases the beating rate of hearts, studies were performed to investigate the effects of EGF on mechanical function of the heart and the role of cAMP in mediating the cardiac effects of EGF. In isolated perfused rat hearts EGF (15 nM) decreased perfusion pressure, increased ventricular contractility and heart rate in a manner similar to that observed with the beta-adrenergic receptor agonist isoproterenol (10 nM). In the presence of the adenosine A1 receptor agonist (-)-N6-(R-phenylisopropyl)-adenosine (PIA, 100 nM) which via activation of the inhibitory GTP binding protein Gi inhibits adenylyl cyclase, the effects of EGF on cAMP accumulation in the heart were markedly attenuated. PIA also decreased the ability of EGF and isoproterenol to alter cardiac contractility and beating rate. However, PIA did not attenuate the increase in heart rate and contractility induced by the alpha-adrenergic agonist phenylephrine which does not stimulate cAMP accumulation in the heart. These data suggest that EGF alters cardiac function by increasing cellular cAMP accumulation.

Charcot-Marie-Tooth disease (hereditary motor sensory neuropathies) and hereditary sensory and autonomic neuropathies.

Background:Since the description of Charcot-Marie-Tooth disease over a century ago, it is now been recognized that these conditions are not caused by generalized metabolic defects but rather have various discrete genetic origins. These disorders can also have variable phenotypes due to dysfunction of peripheral nerve axons or their myelin due to the genetic defects that affect the formation of specific nerve proteins. Review Summary:This article summarizes the clinical presentation of various phenotypes of the hereditary motor sensory neuropathies and the hereditary sensory and autonomic neuropathies, genetic mutations, and their relevant protein products. Proper identification of the genetic defects provides the opportunity for better genetic counseling and hopefully therapies in the future.

Predictors of response to a behavioral treatment in patients with chronic gastric motility disorders.

Chronic gastric motility disorders have proven intractable to most traditional therapies. Twenty-six patients with chronic nausea and vomiting were treated with a behavioral technique, autonomic training (AT) with directed imagery (verbal instructions), to help facilitate physiological control. After treatment, gastrointestinal symptoms decreased by >30% in 58% of the treated patients. We compared those improved patients to the 43% who did not improve significantly. No significant differences existed in baseline symptoms and autonomic measures between both groups. However, baseline measures of gastric emptying and autonomic function predicted treatment outcome. Patients who improved manifested mild to moderate delay in baseline gastric emptying measures. The percent of liquid gastric emptying at 60 mins and the sympathetic adrenergic measure of percent of change in the foot cutaneous blood flow in response to cold stress test predicted improvement in AT outcome, with clinical diagnostic values of 77% and 71%, respectively. We conclude that AT treatment can be efficacious in some patients with impaired gastric emptying and adrenergic dysfunction. More work is warranted to compare biofeedback therapy with gastric motility patients and controls in population-based studies.

Gastric electrical stimulation is associated with improvement in pancreatic exocrine function in humans.

Objective: To define the possible effects of gastric electrical stimulation (GES) for gastroparesis on pancreatic function, we performed 2 related human studies. Methods: Fecal elastase values were compared in 2 patient groups: (1) GES devices ON and (2) GES devices OFF and (2) in 3 control groups: (1) no response (NR) to prokinetic medications, (2) positive response (RES) to medications, and (3) normal controls. Polypeptide levels in 7 of 9 GES patients with device ON and OFF, elastase results, GI symptoms (TSS), and heart rate variability (HRV) were compared by paired t tests and/or ANOVA and reported as mean ± SE. Results: Elastase was different for GES-ON and OFF (508.0 ± 92.2 vs. GES-OFF 378.6 ± 87.4, P < 0.05). Elastase was lower in medication NR and RES than in normal controls. Postprandial pancreatic polypeptide was greater with GES ON than OFF (P = 0.07). HRV revealed a lower percentage of change with device ON versus OFF (44.2 ± 5.5 vs. 48.5 ± 5.2, P = 0.08) and lower TSS with ON versus OFF (15.9 ± 4.5 vs. 25.7 ± 5.3, P < 0.05). Conclusions: GES improves exocrine pancreatic release, effects autonomic control, and improves GI symptoms, suggesting a possible role for GES in the treatment of pancreatic insufficiency associated with gastroparesis.

Regulation of hepatic glycolysis and gluconeogenesis by atrial natriuretic peptide

Recently we reported the presence of both the guanylyl cyclase-linked (116 kDa) and the ANF-C (66 kDa) atrial natriuretic peptide receptors in the rat liver. Since ANF 103-125 (atriopeptin II) stimulates cGMP production in livers and because cGMP has previously been shown to mimic the actions of cAMP in regulating hepatic carbohydrate metabolism, studies were performed to investigate the effects of atriopeptin II on hepatic glycolysis and gluconeogenesis. Additionally, employing analogs of atrial natriuretic hormone [des-(Q116, S117, G118, L119, G120) ANF 102-121 (C-ANF) and des-(C105,121) ANF 104-126 (analog I)] which bind only the ANF-C receptors, the role of the ANF-C receptors in the hepatic actions of atriopeptin II was evaluated. In perfused livers of fed rats atriopeptin II, but not C-ANF and analog I, inhibited hepatic glycolysis and stimulated glucose production. Moreover, analog I did not alter the ability of atriopeptin II to inhibit hepatic glycolysis. Atriopeptin II, but not C-ANF and analog I, also stimulated cGMP production in perfused rat livers. Furthermore, while atriopeptin II inhibited the activity ratio of pyruvate kinase by 30%, C-ANF did not alter hepatic pyruvate kinase activity. Finally, in rat hepatocytes, atriopeptin II stimulated the synthesis of [14C]glucose from [2-14C]pyruvate by 50% and this effect of atriopeptin II was mimicked by the exogenously supplied cGMP analog, 8-bromo cGMP. Thus atriopeptin II increases hepatic gluconeogenesis and inhibits glycolysis, in part by inhibiting pyruvate kinase activity, and the effects of atriopeptin II are mediated via activation of guanylyl cyclase-linked ANF receptors which elevate cGMP production.

Assessment of gastric electrical activity and autonomic function among diabetic and nondiabetic patients with symptoms of gastroesophageal reflux.

Gastroesophageal reflux disease (GERD) may present differently in patients with diabetes mellitus (DM) than in nondiabetics (NDM). We compared three tests in two patient groups with GERD symptoms: a DM group (n = 10) and a NDM group (n = 13). The tests were 24-hr esophageal pH, autonomic function testing (AFT), and electrogastrography (EGG). Analysis of the 23 patients revealed the DM group had normal 24-hr pH values (9 of 10 patients, mean pH 3.1 ± 1.7), while NDM displayed abnormal pH values (9 of 13 patients, mean pH 21.2 ± 5.9). AFT results were abnormal in DM (demonstrating cholinergic/adrenergic dysfunction), but normal in NDM. EGG values were abnormal in both groups (mean 3.31 ± 0.1 in each). We conclude that in GERD-symptomatic patients, those with DM frequently have normal 24-hr pH, but abnormal autonomic functioning, in contrast to NDM, who have abnormal 24-hr pH but normal autonomic function. Both groups had identically abnormal mean EGG values.

Role of calcium in synaptosomal substrate oxidation

The effect of veratridine-mediated depolarization on rat brain synaptosomal respiration in the presence and absence of calcium was investigated. Studies on respiration were performed employing three different pretreatments of the synaptosomes which attempted to deplete endogenous substrates. First, synaptosomes were preincubated for 10 min in the absence of any substrates in medium either containing or devoid of calcium. Second, synaptosomes were preincubated for either 15 or 60-min periods in the presence and absence of calcium, and the incubation medium was changed by centrifugation and resuspension of synaptosomes in their respective media. Irrespective of the prior treatment, maximal stimulation of respiration (400-600%) during veratridine (100 microM) elicited depolarization was observed only when calcium was present in the incubation media. In incubations performed in the absence of calcium, veratridine addition either modestly stimulated (10- and 15-min preincubated synaptosomes) or did not affect (60-min preincubated synaptosomes) the rate of respiration. However, when calcium was added back to these incubations the rate of respiration in the presence of veratridine was stimulated by five- to six-fold. Similarly, the rates of 14CO2 production from [1-14C]- and [2-14C]pyruvate were increased by veratridine only when synaptosomes were incubated in calcium-replete medium. These data indicate that calcium plays an obligatory role in depolarization-elicited stimulation of synaptosomal oxidative processes.

Long term treatment at gastric electrical stimulation is associated with changes in neuro enteric function

Long term treatment at gastric electrical stimulation is associated with changes in neuro enteric function