2.2 Obesity – Associated Immune Dysfunction
When coming to compare the immunity status in lean and obese people as well as the mechanism implicated, our knowledge is finite, and the scientific information involved is limited and often controversial. In this context, in order to elucidate and clarify more deeply the implications arisen by the alterations of immunity caused by obesity, more extensive research is necessary and of high essentiality. Nevertheless, only the most certain, albeit limited aspects of the interaction between obesity and immunity are discussed here, in order to acquire a more concrete view about the process that could be hidden behind.
First and foremost, obesity is ...view middle of the document...
33 Moreover, obesity is associated with ICU infections such as severe sepsis,34 septic shock and ventilator-associated, hospital-acquired pneumonia.33
Obesity lowers the expression of antiviral cytokines such as INF-α, and –β, followed by a substantial reduction in NK cell cytotoxicity,36 and number especially in the elderly,34 leading to increased susceptibility to viral infections with a significantly high risk of mortality.36 Some of the most important viruses involved include: Influenza virus type A, Hepatitis B virus and Coxsackievirus.33 Lastly, obesity is associated with increased inflammatory states secondary to an increased production and release of proinflammatory cytokines. As a consequence, it is possible that chronic exposure to these cytokines, may desensitize immune cells, minimizing their inflammatory responses during an actual infection, further compromising immunocompetence. (see fig. 5)
The most typical obesity-induced infections usually affect the respiratory (RT), urinary (UT) and gastrointestinal (GIT) systems. In GIT, some of the most common infections include: periodontal disease, H. pylori chronic gastritis, extensive hepatic steatosis and fibrosis, occurring secondary to chronic Hepatitis C viral infection and cholecystitis/cholecystolithiasis accompanied by pancreatitis. In UT, the most typical infection is the hematogenous pyelonephritis, especially encountered in the female population; or ascending UT infections occurring secondary to catheterization-associated nosocomial infections. In RT, the most common infectious disease is Influenza A virus (IVA) infection-related typical, community-acquired, bacterial superinfection pneumonia. In the 2009 H1N1 IVA pandemic, there was a great increase in morbidity and mortality, associated with prolonged ICU hospitalization and resource consumption.33 In addition, Respiratory Syncytial Virus (RSV)-related infection is another RT infection, especially affecting children.33,37 On the other hand, some studies showed that obese people are not at greater risk for acquiring RT infection. This controversy indicates that our understanding of the effect of obesity on risk for pulmonary infection remains unclear. One possibility explaining this is that there may be some non-immune mechanisms contributing to the impaired immunity associated with increased susceptibility to infections. Besides the two above-mentioned two pathogens, very little is known about the correlations between obesity and other respiratory tract infections.37 Other obesity-associated conditions include skin infections, especially cellulitis. Moreover, a recent study showed that there was an apparent increase in cases of Herpes Simplex Virus-1 (HSV-1) infection too.33
When coming to antimicrobial (ATM) therapy, obesity affects the volume of distribution (Vd) of drugs, increasing it in case of lipophilic ATMs (e.g. fluorquinolones), and decreasing it in case of hydrophilic ATMs (e.g. amikacin). Furthermore, obesity...