Caroline Doyle, PhD
University of Pittsburgh (Postdoctoral Scholar)
As health psychologists, lipids are of interest as objective markers of metabolic health and predictors of atherosclerotic cardiovascular disease (ASCVD). Triglycerides and LDL-C are lipids we might be interested in measuring before and after that shiny new behavioral intervention for weight loss we are trying to test.
But what does “good” and “bad” cholesterol really mean?
Let’s try to wrap our heads around what cholesterol is and how we currently measure it. Lipids, like cholesterol, are packed and carried around in the blood by lipoproteins (e.g., “LDL” = low density lipoprotein) because they are not water soluble. So, is it the cholesterol or the lipoprotein that contributes to ASCVD?
A building literature demonstrates that the number of lipid particles may actually be a better predictor of atherosclerosis compared to cholesterol concentration. For example, a 2011 analysis of 6,814 people free of cardiovascular disease (CVD) at baseline in the Multi-Ethnic Study of Atherosclerosis (MESA) found that LDL particle number was more predictive of incident CVD compared to LDL-C concentration. Typical blood assays often estimate LDL-C as a percentage of total cholesterol by subtracting HDL-C. However, this measure doesn’t have anything to do with the number of lipid particles. Thus, the question remains, how do we measure number of lipid particles?
It just so happens that atherogenic lipid particles are tagged with a small protein called “apolipoprotein-B” or “apoB” for short. By counting the number of apoBs, we can count the number of lipid particles. Though the 2018 lipid guidelines only mention targets for apoB measurement in certain populations “if measured” (Grundy et al., 2018), there is a growing number of lipidologists who advocate for apoB measurement as a more accurate predictor of ASCVD than LDL-C, based on accumulating data.
What does this have to do with our behavioral interventions that we test or deliver to patients? Is number of lipid particles modifiable through lifestyle?
The good news is yes. Diet is one lever we can pull in terms of decreasing apoB. One review suggests the Mediterranean diet over others for this purpose. What about exercise? The good news is evidence suggests that exercise does have an effect on number of lipid particles as measured by apoB. For example, in one 1-year open randomized trial of 219 healthy middle-aged men allocated to exercise or no exercise, exercise decreased apoB levels significantly compared to non-exercisers, while having no significant change on LDL-C (Holme et al., 2007). Medication is also effective at decreasing lipid particles, but not all medications work equally in this way. If this is a concern for your patient, encourage them to talk to their doctor about lipids.
In terms of behavioral research, we should consider adding apoB assessment to blood assays that we take in our clinical studies. Learning more about which behaviors impact apoB and about how lipid particles might impact other aspects of health that, such as mood or cognition, may in turn help us better understand the interrelationships between lipids and key aspects of physical and mental health.
References
Grundy, S. M., Stone, N. J., Bailey, A. L., Beam, C., Birtcher, K. K., Blumenthal, R. S., Braun, L. T., de Ferranti, S., Faiella-Tommasino, J., Forman, D. E., Goldberg, R., Heidenreich, P. A., Hlatky, M. A., Jones, D. W., Lloyd-Jones, D., Lopez-Pajares, N., Ndumele, C. E., Orringer, C. E., Peralta, C. A., Saseen, J. J., … Yeboah, J. (2019). 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation, 139(25), e1082–e1143. https://doi.org/10.1161/CIR.0000000000000625
Holme, I., Høstmark, A. T., & Anderssen, S. A. (2007). ApoB but not LDL-cholesterol is reduced by exercise training in overweight healthy men. Results from the 1-year randomized Oslo Diet and Exercise Study. Journal of internal medicine, 262(2), 235–243. https://doi.org/10.1111/j.1365-2796.2007.01806.
Otvos, J. D., Mora, S., Shalaurova, I., Greenland, P., Mackey, R. H., & Goff, D. C., Jr (2011). Clinical implications of discordance between low-density lipoprotein cholesterol and particle number. Journal of clinical lipidology, 5(2), 105–113. https://doi.org/10.1016/j.jacl.2011.02.001
Lamantia, V., Sniderman, A., & Faraj, M. (2016). Nutritional management of hyperapoB. Nutrition research reviews, 29(2), 202–233. https://doi.org/10.1017/S0954422416000147