Atherosclerosis and tuberculosis: are they both chronic infectious diseases?

Mycobacterium tuberculosis: An Adaptable Pathogen Associated With Multiple Human Diseases

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), is an extremely successful pathogen that adapts to survive within the host. During the latency phase of infection, M. tuberculosis employs a range of effector proteins to be cloud the host immune system and shapes its lifestyle to reside in granulomas, sophisticated, and organized structures of immune cells that are established by the host in response to persistent infection. While normally being restrained in immunocompetent hosts, M. tuberculosis within granulomas can cause the recrudescence of TB when host immunity is compromised. Aside from causing TB, accumulating evidence suggests that M. tuberculosis is also associated with multiple other human diseases, such as pulmonary complications, autoimmune diseases, and metabolic syndromes. Furthermore, it has been recently appreciated that M. tuberculosis infection can also reciprocally interact with the human microbiome, which has a strong link to immune balance and health. In this review, we highlight the adaptive survival of M. tuberculosis within the host and provide an overview for regulatory mechanisms underlying interactions between M. tuberculosis infection and multiple important human diseases. A better understanding of how M. tuberculosis regulates the host immune system to cause TB and reciprocally regulates other human diseases is critical for developing rational treatments to better control TB and help alleviate its associated comorbidities.

Tuberculosis comorbidity with communicable and non-communicable diseases: integrating health services and control efforts

Recent data for the global burden of disease reflect major demographic and lifestyle changes, leading to a rise in non-communicable diseases. Most countries with high levels of tuberculosis face a large comorbidity burden from both non-communicable and communicable diseases. Traditional disease-specific approaches typically fail to recognise common features and potential synergies in integration of care, management, and control of non-communicable and communicable diseases. In resource-limited countries, the need to tackle a broader range of overlapping comorbid diseases is growing. Tuberculosis and HIV/AIDS persist as global emergencies. The lethal interaction between tuberculosis and HIV coinfection in adults, children, and pregnant women in sub-Saharan Africa exemplifies the need for well integrated approaches to disease management and control. Furthermore, links between diabetes mellitus, smoking, alcoholism, chronic lung diseases, cancer, immunosuppressive treatment, malnutrition, and tuberculosis are well recognised. Here, we focus on interactions, synergies, and challenges of integration of tuberculosis care with management strategies for non-communicable and communicable diseases without eroding the functionality of existing national programmes for tuberculosis. The need for sustained and increased funding for these initiatives is greater than ever and requires increased political and funder commitment.

Carotid atherosclerosis is not related to past tuberculosis in hypercholesterolemic patients

BACKGROUND

Tuberculosis is a chronic recurrent infection and inflammation is part of the disease which may remain undiagnosed for months. Furthermore immunization with recombinant heat shock protein-65-rich mycobacterium tuberculosis increased atherogenesis in hypercholesterolemic animal models.

OBJECTIVE

To investigate the potential interrelationships between past tuberculosis with carotid and femoral atherosclerosis in hypercholesterolemic patients.

DESIGN AND SETTING

Case control study in a university hospital.

PATIENTS

Two groups of hypercholesterolemic patient group (n=147) studied in a cardiovascular prevention unit during the same quarter, age (+/-1 year) and sex-matched. The first group presented a history of tuberculosis in the past and the second group never.

METHODS

Atherosclerosis was assessed by carotid and femoral external echography. Measurements of maximum plaque diameter were done in longitudinal planes, and the extent of atherosclerosis was graded according to the most severe visible changes on the scanned arteries.

RESULTS

The frequency and the distribution of atherosclerosis was similar in the two groups, whatever the arterial site explored, carotid or femoral. None of the clinical and biological studied variables were different between the two groups of patients.

CONCLUSION

Past tuberculosis is not associated with increased frequency of atherosclerotic lesions in hypercholesterolemic patients.

Heart disease: the greatest 'risk' factor of them all

By the turn of the last century, flying in the face of over a hundred years of research and clinical observation to the contrary, medicine abandoned the link between infection and atherogenesis; not because it was ever proven wrong, but because it did not fit in with the trends of a medical establishment convinced that chronic disease such as heart disease must be multifactorial, degenerative and non-infectious. Yet it was the very inability of 'established' risk factors such as hypercholesterolemia, hypertension and smoking to completely explain the incidence and trends in cardiovascular disease that resulted in historically repeated calls to search out an infectious cause, a search that began more than a century ago. Today, half of US heart attack victims have acceptable cholesterol levels and 25% or more have none of the "risk factors" associated with heart disease, including smoking, high blood pressure or obesity, most of which are not inconsistent with being caused by infection. Even the case of the traditionalist's latest 2003 JAMA assault to 'debunk' what they call the "50% risk factor myth" falls woefully short under scrutiny. In one group 30% died of heart disease with a cholesterol of at least 240 mg/dl, a condition which also existed in 21% who did not die during the same period. And the overlap was obvious throughout the so-called risk categories. Under such scrutiny, lead author Greenland conceded that if obesity, inactivity and elevated cholesteriol in the elderly are included, just about everyone has a risk factor and he likened the dilemma of people who do or do not wind up with heart disease akin to the susceptibility of people who are exposed to tuberculosis but do not get the disease. In Infections and Atherosclerosis: New Clues from an old Hypothesis? Nieto stressed the need to extend the possible role of infectious agents beyond the three infections which have in recent years been the focus of research: Cytomegalovirus (CMV) Chlamydia pneumoniae and Helicobactor pylori. Mycobacterial disease shares interesting connections to heart disease. Not only is tuberculosis the only microorganism to depend on cholesterol for its pathogenesis but CDC maps for cardiovascular disease bear a striking similarity to those of State and regional TB case rates. Ellis, Hektoen, Osler, McCallum, Swartz, Livingston and Alexander-Jackson all saw clinical and laboratory evidence of a causative relationship between the mycobacteria and heart disease. And Xu showed that proteins of mycobacterial origin actually led to experimental atherosclerosis in laboratory animals Furthermore present day markers suggested as indicators for heart disease susceptibility such as C-Reactive Protein (CRP), interleukin-6 and homocysteine are all similarly elevated in tuberculosis. It therefore behooves us to explore the link between heart disease and typical and atypical tuberculosis.