"Our next question was, 'Why do the low-carb mice have such an increase in atherosclerosis?'" says Foo. Searching for an explanation, she and her coauthors proceeded to measure the usual markers thought to contribute to vascular disease, including the animals' cholesterol and triglyceride levels, oxidative stress, insulin and glucose, as well as levels of some inflammatory cytokines.

"In each case, there was either no difference in measurements compared with the mice on the Western Diet [which contains the same amount of fat and cholesterol] or the numbers slightly favored the low-carb cohort," she adds. "None of these results explained why the animals' blood had more atherosclerotic blockages and looked so bad."

Since there was no difference in the noxious or inflammatory stimuli that the animals' blood vessels were exposed to, Foo wondered whether the restorative capacity of the animals might be contributing to the difference. The investigators, therefore, looked at the animals' endothelial or vascular progenitor cell (EPC) counts. Derived from bone marrow, the EPC cells may play a role in vessel regrowth and repair following injury.

"Examinations of the animals' bone marrow and peripheral blood showed that the measures of EPC cells dropped fully 40 percent among the mice on the low-carb diet - after only two weeks," says Rosenzweig. "Although the precise nature and role of these cells is still being worked out - and caution is always warranted in extrapolating from effects in mice to a clinical situation - these results succeeded in getting me off the low-carb diet."

Even more important, he notes, the findings point out that there can be a disconnect between weight loss or serum markers and vascular health, and that vascular health can be affected by macronutrients other than fat and cholesterol - in this case, protein and carbohydrates.

"Understanding the mechanisms responsible for these effects, as well as the potential restorative capacity that may counteract vascular disease, could ultimately help guide doctors in advising their patients," adds Rosenzweig. "This issue is particularly important given the growing epidemic of obesity and its adverse consequences. For now, it appears that a moderate and balanced diet, coupled with regular exercise, is probably best for most people."

Source: Beth Israel Deaconess Medical Center