Aging significantly affects social and financial resources; by 2050, 20 percent of the global population will be 60 years of age or older. (Cannata, Marcon et al. 2017) Living longer is a double edge-sword, as it brings healthy aging to some and debilitating chronic degenerative diseases affecting many organs to others.
How Can Lifestyle Choices Improve Health?
Exercise and lifestyle throughout life are vital to maintain health during all stages of life and may reduce the risk of chronic disease.(Russell and Lamon 2015) However, older individuals have a reduced capacity to induce muscle hypertrophy with resistance exercise which can lead to sarcopenia.(McGregor, Poppitt et al. 2014) Interestingly, a study of older versus younger men demonstrated a reduced adaptability of aging muscle to exercise as demonstrated by the absence of microRNA (miRNA) regulation and blunted transcription of mRNAs. There is a mechanistic role of miRNA in the adaptation of muscle to anabolic stimulation, and it is clear that there is an impairment in exercise-induced miRNA/mRNA regulation with aging.(Rivas, Lessard et al. 2014)
Nutrients in the diet are powerful tools to modulate aging; however, nutrient sensing pathways deregulate and lose effectiveness with age.(Mico, Berninches et al. 2017) mRNAs have emerged as important regulators of cellular function and can be modified by the diet. Some mRNAs target genes encoding proteins and enzymes belonging to nutrient sensing pathways and may play a major role in the modulation of the aging process. Some nutrient sensing pathways impaired by aging play key roles in the regulation of protein synthesis, cell cycle, DNA replication, autophagy, stress responses, and glucose homeostasis.
What Biological Hallmarks Contribute to Aging?
There are many biological hallmarks that contribute to aging: (Lopez-Otin, Blasco et al. 2013)
- Genetic and epigenetic factors
- Telomere shortening
- Impaired signaling pathways
- Reduced stem cell pluripotency
- Cellular senescence
- Mitochondrial and immune dysfunction
- Alterations in nutrient sensing pathways
In addition, a prominent alteration in intercellular communication with aging is “inflammaging.” This is a term describing the smoldering proinflammatory phenotype that accompanies the process of getting older. Inflammaging likely has many causes, but at the core of the problem is a failure of the inter-connected immune system (innate and acquired) to effectively resolve the inflammation and return to homeostasis.
How Can Clinicians Support Healthy Aging?
Given all of the challenges of inflammation associated with aging and infection, what should the clinician do to support healthy aging and reduce chronic inflammatory conditions? Typically, clinicians will prescribe non-steroidal anti-inflammatory drugs to immuno-suppress (block or inhibit) the inflammation pathway. However, use of anti-inflammatory agents may actually prolong the inflammatory tone and cause unwanted side effects such as chronic inflammation. (Serhan 2017).
In addition to healthy diet and lifestyle, there is now an emerging strategy to support the natural pro-resolution pathway via a super-family of chemical mediators that stimulate the resolution of the response, known as specialized pro-resolving mediators (SPMs). SPMs are intracellular enzymatic oxidation derivatives of long chain n-3 fatty acids (eicosapentaenoic acid, EPA 20:5n3 and docosahexaenoic acid, DHA 22:6n3), as well as long chain n-6 derived intermediates of arachidonic acid, (AA 20:4n6). Collectively, SPMs, derived from the diet and also called resolvins, are physiologic mediators and pharmacologic agonists that stimulate resolution of inflammation and infection. (Wang, Colas et al. 2016; Whelan, Gowdy et al. 2016; Zhu, Wang et al. 2016; Chiang, de la Rosa et al. 2017; Perretti, Cooper et al. 2017)
Additionally, one type of SPM, resolvin D1 (RVD1) has been shown to engage an RvD1 receptor-dependent regulation of specific miRNA involved in the inflammatory response. RvD1 targets resolvin-regulated miRNAs involved in the inflammatory cascade such as miR-146b (NFκB signaling) and miR-219 (targeted 5 lipoxygenase), resulting in reduced leukotriene production. Thus, clinicians may recommend n-3 fatty acids to enrich tissues with EPA and DHA to increase membrane fluidity and to support the resolution of inflammation with resolvins.(Recchiuti, Krishnamoorthy et al. 2011; Recchiuti and Serhan 2012)
A healthy diet and a lifestyle that involves regular exercise both continue to be excellent clinical management tools for clinicians that are managing patients with inflammation. The importance of diet is nicely illustrated in animal trials in which vitamin E supplementation reduced atherosclerosis and mortality, but not if the animals were consuming a Western style diet.(Meydani, Kwan et al. 2014) Not only can excellent nutritional quality reduce the incidence of age-related disease, it can also improve the prognosis for age-related disease. Factors that positively and negatively influence nutritional health are nicely illustrated in the Figure adapted from Shlisky et al.(Shlisky, Bloom et al. 2017) Adults older than sixty years have increased incidence of infectious and inflammatory diseases with prolonged recovery time, higher morbidity, and higher mortality from these diseases. Researchers largely attribute disease onset to immune dysregulation in which the cell-mediated immune response is compromised in part through reduced nutritional status and bioactive dietary components: polyphenols, omega-3 long chain fatty acids, and others.
An important consideration when evaluating the elderly is the degree of nutritional quality and consumption of nutrient-rich foods. The elderly may have a reduced capacity to absorb and utilize essential nutrients than in their younger years, even without dietary changes. Thus, supplementation of essential nutrients and bioactive components, including bioactive fatty acids, may enhance the function of the immune system and may be an effective strategy to reduce the morbidity and mortality associated with age-related diseases.(Echeverri Tirado and Yassin 2017; Nadjar, Leyrolle et al. 2017; Shlisky, Bloom et al. 2017)
Read part 10 of the Immune System Series: Implications for Clinicians in Support of a Healthy Immune System.