A diet high in saturated fat and cholesterol accelerates disease progression and death in monkeys infected with the simian immunodeficiency virus, say US researchers in the October 15th edition of the Journal of Infectious Diseases.
They believe the finding could have important implications for HIV-infected individuals because they suggest dietary changes and tackling high cholesterol levels could slow progression of HIV disease.
There is a growing body of evidence that dietary fat and cholesterol could play a role in HIV infection. Fatty tissue in the human body - or adipose tissue - is known to contain cells and chemicals involved in the immune response and increased dietary fat could lead to alterations in the way HIV interacts with the body’s immune system. Fat and cholesterol are also thought to directly alter viral replication.
Now researchers at the Harvard’s University New England Primate Research Center have studied the effect of a diet high in fat in eight macaques infected with SIV and compared survival rates, viral loads and immune responses with 52 SIV-infected macaques fed a normal diet.
They found that macaques on the high-fat diet had a marked increase in the speed of disease progression. In fact they were over five times more likely to die of the disease (hazard ratio, 5.4; 95% CI, 1.7 – 70, p
Peak viral load was also higher in the high fat diet group - 7.75 versus 7.19 log10 SIV RNA ( p= 0.032) – and the rebound in CD4 count, usually seen after acute viraemia in macaques, was absent in those on the high fat diet.
The researchers also saw a striking difference in interleukin-18 (IL-18) levels between the two groups of monkeys. IL-18 is a recently discovered member of the interleukin family and has been found to be an important regulator of innate and acquired immune responses.
Levels of IL-18 are also known to be higher in obese individuals and are associated with increased risk of cardiovascular disease.
In the macaques fed a high fat diet not only were IL-18 levels higher, but they were independently associated with higher viral load and survival.
The researchers say fatty tissue and dietary fat may prove to be significant and overlooked factors integral to the progression of HIV infection, especially given the high prevalence of obesity in Western countries.
They conclude: ‘If findings in the macaque model are substantiated in human subjects it would seem that dietary changes and manipulation of cholesterol … in HIV-infected patients could offer potential benefits by slowing disease progression and delaying required treatment with antiretrovirals.’
Mansfield KG. A diet high in saturated fat and cholesterol accelerates simian immunodeficiency virus disease progression. Journal of Infectious Diseases 196: 1202-1210, 2007.