Infections and immunity: associations with obesity and related metabolic disorders

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.

Obesity-related complications: few biochemical phenomena with reference to tumorigenesis

Overweight or obesity is currently a common health problem in westernized societies globally. Obesity is linked with a sizeable number of disease aetiologies, notably type-2 diabetes, cardiovascular disorders and certain cancers, perhaps through some common mechanisms that favor persistent low-grade infl ammation. Both epidemiological and laboratory studies have demonstrated that the pathogenesis of certain cancers and the related prognosis are infl uenced by obesity. Clinically, a complex situation is present in obesity, which usually shows higher blood levels of various biomolecules, e.g., lipids like triglycerides, hormones like insulin, and fat cell-secreted adipokines like leptin. On the contrary, obesity is associated with lower concentrations of substances like sex hormone-binding globulin and adiponectin. Many of these biochemical compounds are used routinely for clinical diagnosis and assessment during the follow-up period. Nonetheless, approximately one-fi fth of the total cancer burden is associated with obesity. Excess adipose tissue and different hormonal substances possibly play a signifi cant role in this complex obesity-related carcinogenesis. A precise understanding of the pertinent pathological processes is defi nitely useful in early diagnosis, clinical management, and designing of novel pharmaceutical agents.