J Pathol Transl Med.  2023 Jan;57(1):28-42. 10.4132/jptm.2022.11.14.

Infections and immunity: associations with obesity and related metabolic disorders

• Ray A
• Bonorden MJL
• Pandit R
• Nkhata KJ
• Bishayee A

• KMID: 2539034
• DOI: http://doi.org/10.4132/jptm.2022.11.14

Abstract

About one-fourth of the global population is either overweight or obese, both of which increase the risk of insulin resistance, cardiovascular diseases, and infections. In obesity, both immune cells and adipocytes produce an excess of pro-inflammatory cytokines that may play a significant role in disease progression. In the recent coronavirus disease 2019 (COVID-19) pandemic, important pathological characteristics such as involvement of the renin-angiotensin-aldosterone system, endothelial injury, and pro-inflammatory cytokine release have been shown to be connected with obesity and associated sequelae such as insulin resistance/type 2 diabetes and hypertension. This pathological connection may explain the severity of COVID-19 in patients with metabolic disorders. Many studies have also reported an association between type 2 diabetes and persistent viral infections. Similarly, diabetes favors the growth of various microorganisms including protozoal pathogens as well as opportunistic bacteria and fungi. Furthermore, diabetes is a risk factor for a number of prion-like diseases. There is also an interesting relationship between helminths and type 2 diabetes; helminthiasis may reduce the pro-inflammatory state, but is also associated with type 2 diabetes or even neoplastic processes. Several studies have also documented altered circulating levels of neutrophils, lymphocytes, and monocytes in obesity, which likely modifies vaccine effectiveness. Timely monitoring of inflammatory markers (e.g., C-reactive protein) and energy homeostasis markers (e.g., leptin) could be helpful in preventing many obesity-related diseases.

Keyword

Metabolic disorders; Infections; COVID-19; Parasites; Immune cells

Figure

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  Fig. 1. Relationship among pro-inflammatory adipokines, interleukin-6 (IL-6), and C-reactive protein (CRP) in obesity. Infiltration of macrophages in excess adipose tissue is a common phenomenon. The pleiotropic pro-inflammatory cytokine IL-6, secreted by monocytes/macrophages, induces the biosynthesis of CRP from the liver.

• 

  Fig. 2. Principal intracellular signaling pathways of leptin in connection with the chronic low-grade inflammatory state found in obesity. AKT, protein kinase B/serine-threonine kinase; ERK, extracellular signal-regulated kinase; JAK, Janus kinase; MAPK, mitogen-activated protein kinase; MEK, mitogen-activated protein kinase kinase; mTOR, mechanistic/mammalian target of rapamycin; Ob-R, leptin receptor; PI3K, phosphatidylinositol-3-kinase; STAT, signal transducer and activator of transcription.

Reference

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