Cardiovascular disease and type 2 diabetes in evolutionary perspective: A critical role for helminths?

Abstract

Heart disease and type 2 diabetes are commonly believed to be rare among contemporary subsistence-level human populations, and by extension prehistoric populations. Although some caveats remain, evidence shows these diseases to be unusual among well-studied hunter-gatherers and other subsistence populations with minimal access to healthcare. Here we expand on a relatively new proposal for why these and other populations may not show major signs of these diseases. Chronic infections, especially helminths, may offer protection against heart disease and diabetes through direct and indirect pathways. As part of a strategy to insure their own survival and reproduction, helminths exert multiple cardio-protective effects on their host through their effects on immune function and blood lipid metabolism. Helminths consume blood lipids and glucose, alter lipid metabolism, and modulate immune function towards Th-2 polarization—which combined can lower blood cholesterol, reduce obesity, increase insulin sensitivity, decrease atheroma progression, and reduce likelihood of atherosclerotic plaque rupture. Traditional cardiometabolic risk factors, coupled with the mismatch between our evolved immune systems and modern, hygienic environments may interact in complex ways. In this review, we survey existing studies in the non-human animal and human literature, highlight unresolved questions and suggest future directions to explore the role of helminths in the etiology of cardio-metabolic disease.

Allostasis and Adaptation: Biocultural Processes Integrating Lifestyle, Life History, and Blood Pressure Variation

“…Average casual arterial blood pressure measurements among adults over seventyfive years old are not functionally different from those among forty-to forty-four-year-old adults, and the adult levels of CVD are the lowest reported of any population recorded to date (Kaplan et al 2017). Interestingly, there is also a high infectious-disease burden in this population, and it has been recently speculated that chronic infections (especially with helminths) may offer cardiovascular protection, as these types of parasites alter lipid levels and metabolism and modulate immune function, changes that could slow or decrease atherosclerotic processes (Gurven et al 2016).…”

“…Interestingly, there is also a high infectious‐disease burden in this population, and it has been recently speculated that chronic infections (especially with helminths) may offer cardiovascular protection, as these types of parasites alter lipid levels and metabolism and modulate immune function, changes that could slow or decrease atherosclerotic processes (Gurven et al. ).…”

Old friends and friendly fire: Pregnancy, hookworm infection, and anemia among tropical horticulturalists

“…Mixed cross‐sectional and longitudinal data were collected between 2005 and 2014 by the on‐going Tsimane Health and Life History Project (THLHP) (Gurven et al, ). Data collection followed the standard THLHP protocol (explained in detail in Blackwell et al, ; Blackwell, Tamayo, Beheim, Trumble, Stieglitz, et al, ; Martin, Blackwell, Gurven, & Kaplan, ; Blackwell, Trumble, Suarez, Beheim, et al, ; Gurven, Trumble, et al, ). The THLHP team made annual or biannual trips to provide medical assistance and collect data.…”

Helminth infection during pregnancy: insights from evolutionary ecology

“…However, helminth infections affect blood glucose, insulin resistance, and diabetes, leading to improved glucose tolerance and lower blood levels 99–104. Thus, helminths might also help modulate blood glucose during pregnancy 22.…”