Cholesterol and Tuberculosis

One-third of the world's population is infected by Mycobacterium tuberculosis (TB), yet only approximately 10% will develop the overt clinical disease due to the presence in our bodies of a mysterious risk factor, recently identified to be low cholesterol. The higher your cholesterol the lower your risk of the tuberculosis illness.

As a medical student in the 1955 era, 5% of our entering class had the classic Ghon's complex of an old scar in the apex of the lung, accompanied by a single calcified lymph node draining the diseased area - absolute documentation of a previous encounter with tuberculosis but their immune systems had overcome it by imprisoning the disease in scar tissue and calcium.

This silent process, this relatively brief skirmish in a never ending battle with disease organisms, had been overcome because of relatively high cholesterol levels according to data only recently identified by Perez-Guzman and Vargas, in their paper, "Hypocholesterolemia: A major risk factor for developing pulmonary tuberculosis?" Published in Medical Hypotheses (2006) 66, 1227-1230 ( hypocholesterolemia = abnormally low levels of cholesterol in the blood.)

Tuberculous patients characteristically have low serum cholesterol, the authors state. Their previous study of patients having different forms of tuberculosis found total cholesterol levels significantly lower (150 mg/dl ) than those observed in three large national surveys (190 mg/dl ) and also noted that in the more serious forms of tuberculosis, miliary for example, total cholesterol values of less that 90mg/dl frequently were observed.

They reported that 25 pulmonary tuberculosis patients categorized as new, open cases had a much lower lipid profile than 44 household contacts, undoubtedly heavily exposed to patient secretions. They also found that many conditions traditionally considered major risk factors for tuberculosis are characteristically accompanied by low total cholesterol values.

The authors note that conditions traditionally considered as risk factors for developing tuberculosis include a wide array of diverse conditions including HIV infection, malnutrition, aging, gastrectomy, intravenous drug use, leukemias, other cancers, chronic renal failure, and measles. Not surprisingly the common feature of all these conditions is that they are accompanied by low serum cholesterol values.

It was only five years ago that I could call attention to cholesterol's vital role in essential hormone synthesis and in memory formation in the brain. Now our research has found that the role of cholesterol is far more involved. Basically it is involved in everything. It is like CoQ10 and dolichols only much more complex in scope. And to think a multi-billion dollar industry is trying desperately to stay in business by lowering our natural cholesterol values.

The authors postulate that elevated cholesterol has a beneficial effect on tuberculosis resistance through the immune syustem. They cite the well known fact that cholesterol constitutes about one-third of the cell membrane lipids content and participates in the fluidity of this structure, in the activity of membrane-bound enzymes and in membrane functions, such as phagocytosis and cell growth. They propose that cholesterol is important for the adequate functioning of the immune system in several steps and call attention to the recent cell membrane work on lipid rafts to support this.

In the last few years, specialized regions of the cell membrane known as lipid rafts have attracted growing interest due to their critical role in receptor-mediated signaling and cell to cell interactions. In contrast to the rest of the cell membrane, which is composed by phospholipids in a disordered phase, lipid rafts are composed by gangliosides tightly packed by cholesterol into well-ordered phases.

Cholesterol is essential in the correct assembly of these regions, since its removal leads to dissociation of most proteins from rafts and renders them non-functional. In recent years researchers have demonstrated again and again that cholesterol reduction leads to dissociation of these lipid rafts with bizarre effects on the resulting physiologic outcomes. Cholesterol is thereby critical to the proper functioning of the immune system.

In a recent clinical trial, the authors demonstrated that a cholesterol-rich diet ( 750 mg daily ) significantly accelerated the bacteriological sterilization of sputum during the intensive phase of the four-drug antitubercular treatment in patients with pulmonary tuberculosis (new cases) who were hospitalized during 8 weeks. The result of this study strongly suggested that hypocholesterolemia, instead of being a consequence of the disease, was a deleterious factor for the host in its fight against mycobacteria.

Memory formation, essential hormone production and now fighting tuberculosis - all dependent upon our natural cholesterol levels. I wonder, does the statin industry have the slightest idea what they have done?

Duane Graveline MD MPH
Former USAF Flight Surgeon
Former NASA Astronaut
Retired Family Doctor

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