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Differential metabolic response in AIDS-related chronic protozoal diarrhoea
D Sharpstone1, M Phelan, B Gazzard
1Department of HIV/GUM, Chelsea and Westminster Hospital, London, UK.
Objective:
As the pro-inflammatory cytokine tumour necrosis factor-alpha is greater in microsporidiosis than cryptosporidiosis, there may be a distinct metabolic response between the two organisms.
Design:
Male HIV seropositive subjects with an untreated AIDS-defining diagnosis of microsporidiosis or cryptosporidiosis had measurement of oxygen consumption and carbon dioxide production by indirect calorimetry and body composition analysis to express resting energy expenditure (REE) and substrate oxidation per kilogram of metabolically active tissue.
Methods:
Resting energy expenditure (REE), non-protein respiratory quotient (NPRQ), fat and carbohydrate oxidation were calculated from respiratory gas analysis. Fat, fat-free and appendicular muscle masses were measured by dual-energy X-ray absorptiometry. Subjects with protozoal diarrhoea were compared to other newly diagnosed, active opportunistic infections. Controls were asymptomatic HIV-seropositive men matched by peripheral CD4 count.
Results:
Seven subjects with microsporidiosis and six with cryptosporidiosis were compared with 24 subjects with other AIDS-defining diagnosis (Pneumocystis carinii pneumonia, cytomegalovirus enteritis and Mycobacterium avium-intracellulare) and 10 controls free from secondary infection. Subjects with cryptosporidiosis had a decreased REE, a significantly increased NPRQ (P< 0.05), decreased fat oxidation (P < 0.05) and increased carbohydrate oxidation compared to microsporidiosis. Subjects with other AIDS diagnoses had an increased REE (P < 0.01) and fat oxidation and decreased carbohydrate oxidation compared to cryptosporidiosis, and a similar metabolic response to microsporidiosis.
Conclusions:
The metabolic response to cryptosporidiosis differs from microsporidiosis and associated weight loss may be mediated by different mechanisms. Metabolism in other AIDS diagnoses, including microsporidiosis, is compatible with a cachectic response.
Insights
The metabolic response to cryptosporidiosis differs from microsporidiosis in HIV-positive individuals. Weight loss mechanisms may vary, with microsporidiosis aligning with a cachectic response in AIDS.
Area of Science:
- Infectious Diseases
- Metabolic Medicine
- HIV/AIDS Research
Background:
- Microsporidiosis and cryptosporidiosis are opportunistic infections in HIV-positive individuals.
- Tumor necrosis factor-alpha levels are higher in microsporidiosis than cryptosporidiosis, suggesting distinct host responses.
Purpose of the Study:
- To investigate the distinct metabolic responses to microsporidiosis and cryptosporidiosis in male HIV-seropositive subjects.
- To compare the metabolic profiles of these infections with other AIDS-defining diagnoses and healthy controls.
Main Methods:
- Indirect calorimetry measured oxygen consumption and carbon dioxide production to determine resting energy expenditure (REE) and substrate oxidation.
- Dual-energy X-ray absorptiometry assessed body composition, including fat mass and appendicular muscle mass.
- Metabolic parameters (REE, non-protein respiratory quotient, fat/carbohydrate oxidation) were calculated and normalized to metabolically active tissue.
Main Results:
- Cryptosporidiosis was associated with decreased REE, increased non-protein respiratory quotient, decreased fat oxidation, and increased carbohydrate oxidation compared to microsporidiosis.
- Other AIDS diagnoses, including microsporidiosis, showed an increased REE and fat oxidation, and decreased carbohydrate oxidation, consistent with a cachectic response.
- Subjects with cryptosporidiosis exhibited a significantly different metabolic profile compared to those with microsporidiosis.
Conclusions:
- The metabolic response to cryptosporidiosis is distinct from that of microsporidiosis.
- Weight loss in these infections may be driven by different underlying mechanisms.
- The metabolic state in microsporidiosis and other AIDS-defining illnesses aligns with a cachectic response.