Elevated plasma levels of vasoactive intestinal peptide in AIDS patients with refractory idiopathic diarrhoea. Effects of treatment with octreotide

Cholera and Pancreatic Cholera: Is VIP the Common Pathophysiologic Factor?

Background: Cholera remains a major global health problem, causing high output diarrhea leading to severe dehydration and shock in developing countries. We aimed to determine whether vasoactive intestinal polypeptide (VIP), the mediator of pancreatic cholera syndrome, has a role in the pathophysiology of human cholera. Methods: We conducted a prospective observational study of cholera cases hospitalized with severe dehydration. Plasma and stool water levels of VIP were measured just after admission, after complete rehydration (3–4 h), at 24 h post-rehydration and at discharge after diarrhea ceased. Results: In total, 23 cholera patients were examined between January and August 2018. The geometric mean of stool VIP (sVIP) and plasma VIP (pVIP) on admission were 207.67 and 8.34 pmol/L, respectively. pVIP values were all within the normal range (</= 30 pcmol/L); however, sVIP levels were very high at all timepoints, though less so just after rehydration. In multivariable GEE models, after adjustment for covariates, sVIP levels were significantly associated with duration of hospitalization (p = 0.026), total stool volume (p = 0.023) as well as stool output in the first 24 h (p = 0.013). Conclusions: The data suggest that VIP, which is released by intestinal nerves, may play an important role in human choleragenesis, and inhibitors of intestinal VIP merit testing for potential therapeutic benefits.

HIV infection and the pancreas: risk factors and potential management guidelines

One thousand and eighty-one evaluable HIV-infected patients were assessed for pancreatic abnormalities in a prospective case-control study including the whole follow-up period of each patient (minimum 12 months). The 435 patients (40.2%), who experienced at least one episode of confirmed pancreatic laboratory abnormality had a longer duration of seropositivity, exposure to protease inhibitors, a more frequent immunodeficiency, AIDS, chronic liver and/or biliary disease and hypertriglyceridaemia, while no relation was found with antiretroviral administration, and the duration of type of nucleoside analogues, when compared with the 646 controls. High and prolonged laboratory alterations eventually associated with signs of organ involvement occurred in 166 cases (38.2%), and were related to the administration of didanosine, stavudine, lamivudine, pentamidine, cotrimoxazole or antitubercular/antimycobacterial therapy, cytotoxic chemotherapy, illicit substance or alcohol abuse, opportunistic infections, chronic liver and/or biliary disease, a protease inhibitor-based highly active antiretroviral therapy (HAART) and hypertriglyceridaemia (usually associated with HAART administration). No difference was noticed between the 46 patients with clinical and/or imaging evidence of pancreatic involvement and the 120 asymptomatic subjects. Although recurrences of enzyme alterations involved 69.6% of patients, only in 30.1% of cases did a change of the underlying antiretroviral or antimicrobial therapy become necessary. An acute, uncomplicated pancreatitis occurred in nine of the 46 symptomatic subjects (19.6%). A two to four week gabexate and/or octreotide administration (performed in 79 cases of 166, 47.6%), achieved a significant laboratory, clinical and imaging cure or improvement in 82.3% of cases, with a better success rate of combined (gabexate mesilate plus octreotide) vs. single (gabexate mesilate or ocreotide) therapy. Reduced disease recurrences and a better tolerability of antiretroviral regimens, were also noticed.

Established and potential therapeutic applications of octreotide in palliative care

Octreotide acetate was developed as a pharmacologically stable, long-acting analogue of the hormone somatostatin. Mimicking the actions of somatostatin, octreotide has been used for its antisecretory effects. Randomized control trials have established the efficacy of octreotide for malignant bowel obstruction and for chemotherapy-induced diarrhea. Octreotide has proven to be an effective agent for symptoms of carcinoid syndrome. Newer uses include for bone marrow transplantation, infectious diarrheal syndromes, and management of hepatic metastases. More evidence is needed for the establishment of its efficacy for hypercalcemia, pain, pleural effusions, diarrhea after celiac plexus block, and malignant ascites.

Mechanism and kinetics of metalloenzyme phosphomannose isomerase: measurement of dissociation constants and effect of zinc binding using ESI-FTICR mass spectrometry

Electrospray ionization Fourier transform ion cyclotron resonance (ESI-FTICR) mass spectrometry was used to study the noncovalent complexation of a metalloenzyme, phosphomannose isomerase (PMI), which catalyzes the interconversion of mannose 6-phosphate and fructose 6-phosphate. The zinc cofactor binding effect and the noncovalent interactions of the holoenzyme with its two natural substrates and two inhibitors, erythrose 4-phosphate and mannitol 1-phosphate, were investigated. Under nondenaturing conditions, the intact zinc-containing monomeric protein ions were reproducibly observed with no dissociation. Molecular ions corresponding to apo-PMI monomer were obtained by dialyzing the holoenzyme against EDTA. The binding/release of the metal ion did not alter the charge-state distributions of the protein to any significant extent, but changed the binding affinity of the substrates by at least 5-fold. Using ESI-FTICR mass spectrometry, the binding stoichiometry and specificity of the enzyme-substrate and enzyme-inhibitor complexes were directly determined. The first time report of the apparent dissociation constant for the isomeric substrates of PMI was measured to be 88.8 microM. The relative dissociation constant of the two inhibitors derived from gas-phase noncovalent complexation was very similar to the relative inhibition constant derived from solution phase kinetics.

A double blind, randomized, placebo-controlled phase II study to assess the safety and efficacy of orally administered SP-303 for the symptomatic treatment of diarrhea in patients with AIDS

OBJECTIVE

The aim of this study was to investigate the safety and effectiveness of orally administered SP-303 in patients with AIDS and diarrhea.

METHODS

This is a multicenter, phase II, randomized, double blind, placebo-controlled study. HIV-positive subjects with a history of a CD4 count <200 or an AIDS-defining illness were admitted to an inpatient study unit and screened for diarrhea defined as at least three abnormal (i.e., soft or watery) stools and >200 g of abnormal stool weight over a 24-h period. Subjects discontinued all antidiarrheal agents >24 h before enrollment. Stool samples were studied for routine pathogens. Subjects received 500 mg p.o. of SP-303 or placebo every 6 h for 96 h (4 days). Stool frequency and weights were recorded. Subjects were monitored for symptoms and side effects and were seen 1 wk later in follow-up.

RESULTS

A total of 26 subjects received SP-303, and 25 received placebo. There were no significant demographic differences between treatment arms. A total of 41 subjects (80%) were receiving antiretroviral therapy and 39 subjects (77%) were receiving at least one protease inhibitor. Stool studies revealed no pathogens in 48 of 51 patients (94%). There were no serious adverse events or laboratory abnormalities. The SP-303 treatment group demonstrated a mean reduction from baseline stool weight of 451 g/24 h versus 150 g/24 h with placebo on day 4 of treatment (p = 0.14), and a mean reduction in abnormal stool frequency of three abnormal stools in 24 h versus two in 24 h in the placebo group (p = 0.30). Daily measures analysis over 4 days of treatment demonstrated that SP-303 subjects had a significant reduction in stool weight (p = 0.008) and abnormal stool frequency (p = 0.04) when compared to placebo-treated subjects.

CONCLUSIONS

SP-303 is safe and well tolerated. These results suggest that SP-303 may be effective in reducing stool weight and frequency in patients with AIDS and diarrhea.

Pathophysiology of HIV-associated diarrhea

Considerable advances have been made in the evaluation and treatment of diarrhea in HIV-infected individuals, although gaps in knowledge still exist. The availability of newer and more powerful antiretroviral agents should allow a better definition of the effect of local HIV infection on intestinal function. Further attention to the pathophysiology of diarrhea should lead to improvements in diagnosis and treatment.

Efficacy of octreotide in diarrhoea due to Vibrio cholerae: a randomized, controlled trial

Although octreotide, a long-acting analogue of somatostatin, is currently used in the treatment of chronic secretory diarrhoea due to various causes, its role in the management of acute secretory diarrhoea is not well established. In the present study, therefore, the therapeutic value of octreotide in the management of cholera, a classical example of acute secretory diarrhoea, was investigated. During an outbreak of cholera, patients admitted with acute secretory diarrhoea of < or = 24 h duration and a purging rate > 100 ml/h were enrolled on the study and randomly assigned to octreotide (N = 17) and control (N = 16) groups. All 33 patients received intravenous fluid replacement and antibiotic treatment (200 mg ofloxacin twice daily for 3 days, by mouth). Each patient in the octreotide group was also given a subcutaneous injection containing 100 micrograms octreotide every 8 h for a maximum of six doses. The stool output of each patient was recorded every hour until there had been none for an hour, which was taken as the endpoint. Mean (S.D.) total stool output was lower [6.56 (3.7) v. 9.7 (6.5) litres] and the mean (S.D.) duration of diarrhoea after admission was shorter [32.9 (15.6) v. 47.8 (22.3); P < 0.05] in the octreotide group than in the control group. However, as both groups generally had similar purging rates, the higher volume of stools from the control group was simply the result of the longer period of diarrhoea in this group. Octreotide therefore only decreased the duration of diarrhoea in the cholera patients.

Gastrointestinal manifestations of HIV infection

The harrowing picture of emaciated terminally ill AIDS patients is a reminder of our lack of understanding of immunological mechanisms that normally control opportunistic infections. Many gastrointestinal pathogens in patients with AIDS are resistant to treatment and lead inexorably to weight loss and death. Although knowledge of the pathogenesis and clinical significance of weight loss has improved considerably, this has not yet led to a sustained effort to improve nutritional status during early stages of disease.

Palliative care for patients with acquired immunodeficiency syndrome

This article provides a clinically-oriented overview of palliative care for patients with AIDS. Indicators of decreased survival time are divided into categories of infections/illnesses, clinical signs and symptoms, immunological and serological markers, and psychosocial factors. Primary symptoms in AIDS are discussed according to etiology and treatment. However, treatments of opportunistic infections per se are not directly addressed in this article. Problems discussed include pain, confusion, depression and anxiety, fatigue, fever, dyspnea, nausea and vomiting, diarrhea, wasting, and dehydration. The article also briefly addresses clinical and ethical questions and challenges presented by AIDS to hospice or palliative care providers, and the various stages of HIV infection.

Differential effect of the immunomodulatory hormone somatostatin on replication of human immunodeficiency virus type 1 in CD4+ and CD8+ T lymphocytes

The long-acting somatostatin analog octreotide (SMS 201-995) possesses immunosuppressive properties and has been successfully used for the management of human immunodeficiency virus (HIV)-associated diarrhea, a condition commonly observed in the absence of known enteric pathogens. Since HIV type 1 (HIV-1) replication can occur in both CD4+ and CD8+ lymphocytes, we hypothesized that this benefit might be due to local effects on HIV-1 replication in these two T-cell subsets. As a model, we studied the effects of two synthetic molecules, SRIH 1-14 and SRIH 1-28, closely related to naturally occurring forms of somatostatin, as well as SMS 201-995 on HIV-1 replication in CD4+ and CD8+ cells derived from peripheral blood mononuclear cells (PBMC). We found that HIV-1 replication was inhibited in CD8+ cells but enhanced in infected CD4+ lymphocytes, as measured by p24 antigen levels in culture fluids. These differential effects were drug concentration dependent. We also observed that somatostatin inhibited the mitogen-induced proliferative responsiveness of both cell types. These effects on both HIV-1 replication and cell proliferation were independent of somatostatin gene expression, since somatostatin mRNAs were not detected in mitogen-stimulated PBMC, as determined by reverse transcription-PCR.

Vasoactive intestinal polypeptide (VIP) secretion and refractory diarrhea in patients with AIDS or AIDS-related complex (ARC)

Elevated plasma levels of vasoactive intestinal polypeptide (VIP) (as assessed by a radio-immunoassay), were found in 7/11 patients with AIDS or AIDS-related Complex (ARC), evaluated because of prolonged intractable diarrhea with either an infectious (6 cases) or a non-infectious (5 cases) etiology. Six subjects have been treated with the somatostatin analogue octreotide, which gave both a favourable clinical response and a significant reduction in plasma VIP concentrations. Evaluation of plasma VIP levels may provide a pathophysiological basis for explaining the efficacy of octreotide therapy in HIV-infected patients suffering from both infectious and non-infectious refractory diarrhea.