The impact of obesity on the immune response to infection

Abstract

There is strong evidence indicating that excess adiposity negatively impacts immune function and host defence in obese individuals. This is a review of research findings concerning the impact of obesity on the immune response to infection, including a discussion of possible mechanisms. Obesity is characterised by a state of low-grade, chronic inflammation in addition to disturbed levels of circulating nutrients and metabolic hormones. The impact of these metabolic abnormalities on obesity-related comorbidities has undergone intense scrutiny over the past decade. However, relatively little is known of how the immune system and host defence are influenced by the pro-inflammatory and excess energy milieu of the obese. Epidemiological data suggest obese human subjects are at greater risk for nosocomial infections, especially following surgery. Additionally, the significance of altered immunity in obese human subjects is emphasised by recent studies reporting obesity to be an independent risk factor for increased morbidity and mortality following infection with the 2009 pandemic influenza A (H1N1) virus. Rodent models offer important insight into how metabolic abnormalities associated with excess body weight can impair immunity. However, more research is necessary to understand the specific aspects of immunity that are impaired and what factors are contributing to reduced immunocompetence in the obese. Additionally, special consideration of how infection in this at-risk population is managed is required, given that this population may not respond optimally to antimicrobial drugs and vaccination. Obesity impacts millions globally, and greater understanding of its associated physiological disturbances is a key public health concern.

Proposal for new selection criteria considering pre‐transplant muscularity and visceral adiposity in living donor liver transplantation

“…This imbalance between adipokines and myokines in older adults or sarcopenic populations has been shown to lead to immunosenescence, particularly of the natural killer lymphocytes involved in innate immunity 32. On the other hand, visceral adiposity paradoxically impairs immune function by altering leukocyte counts, as well as cell‐mediated immune responses, although excessive adipose tissue activates various kinds of immune cells through increases in leptin and decreases in adiponectin 33. On the basis of these findings, we speculate that low muscularity and visceral adiposity induce an inflammatory microenvironment through imbalances between adipokines and other cytokines, which could impair immune function and increase mortality risk.…”

Risk factors of acute cellulitis in adult patients: A case-control study

“…Several epidemiological investigations and emerging data indicate obesity may increases infection susceptibility in clinical settings (18). It is mediated by the effect of obesity on the immune response through a variety of immune mediators, which leads to susceptibility to infections (19). Significant association between BMI and risk of cellulitis was not reported in some studies.…”

Infectious complications in obese patients after trauma

“…Primary adipose derived pro-inflammatory cytokines TNFα, IL-6, and IL-1β are produced in excess in obese individuals and are thought to desensitize immune cells to inflammatory responses during actual infections [15]. In addition, adiponectin, an immunomudlatory adipokine, has decreased levels in obese patients which alter natural killer cell cytotoxicity and cytokine production by myeloid cells [15].…”

“…Primary adipose derived pro-inflammatory cytokines TNFα, IL-6, and IL-1β are produced in excess in obese individuals and are thought to desensitize immune cells to inflammatory responses during actual infections [15]. In addition, adiponectin, an immunomudlatory adipokine, has decreased levels in obese patients which alter natural killer cell cytotoxicity and cytokine production by myeloid cells [15]. These conditions, which reduce the ability to fight infection, coupled with the trauma/ICU setting that is already associated with increased risk of infection due to patients' decreased mobility after injury, use of ventilation assisted breathing, and invasive line placement, likely account for the significant increase in infectious complications observed in obese patients following traumatic injury.…”