Pasteur's Quadrant and malnutrition

Leptin Functions in Infectious Diseases

Leptin, a pleiotropic protein has long been recognized to play an important role in the regulation of energy homeostasis, metabolism, neuroendocrine function, and other physiological functions through its effects on the central nervous system (CNS) and peripheral tissues. Leptin is secreted by adipose tissue and encoded by the obese (ob) gene. Leptin acts as a central mediator which regulates immunity as well as nutrition. Importantly, leptin can modulate both innate and adaptive immune responses. Leptin deficiency/resistance is associated with dysregulation of cytokine production, increased susceptibility toward infectious diseases, autoimmune disorders, malnutrition and inflammatory responses. Malnutrition induces a state of immunodeficiency and an inclination to death from communicable diseases. Infectious diseases are the disease of poor who invariably suffer from malnutrition that could result from reduced serum leptin levels. Thus, leptin has been placed at the center of many interrelated functions in various pathogenic conditions, such as bacterial, viruses and parasitic infections. We review herein, the recent advances on the role of leptin in malnutrition in pathogenesis of infectious diseases with a particular emphasis on parasitic diseases such as Leishmaniasis, Trypanosomiasis, Amoebiasis, and Malaria.

Link between insulin resistance and hypertension: What is the evidence from evolutionary biology?

Insulin resistance and hypertension are considered as prototypical "diseases of civilization" that are manifested in the modern environment as plentiful food and sedentary life. The human propensity for insulin resistance and hypertension is a product, at least in part, of our evolutionary history. Adaptation to ancient lifestyle characterized by a low sodium, low-calorie food supply and physical stress to injury response has driven our evolution to shape and preserve a thrifty genotype, which is favorite with energy-saving and sodium conservation. As our civilization evolved, a sedentary lifestyle and sodium- and energy-rich diet, the thrifty genotype is no longer advantageous, and may be maladaptive to disease phenotype, such as hypertension, obesity and insulin resistance syndrome. This article reviews human evolution and the impact of the modern environment on hypertension and insulin resistance.

Effects of antioxidants on glutathione levels and clinical recovery from the malnutrition syndrome kwashiorkor – a pilot study

Kwashiorkor is a severe edematous form of malnutrition with high prevalence and lethality in many African countries, and repeatedly has been reported to be associated with oxidative stress. The therapy of kwashiorkor is still ineffective. In this pilot study, we tested the hypothesis that oral application of thiol-containing antioxidants increases glutathione status and is beneficial for the clinical recovery of kwashiorkor patients. The longitudinal clinical intervention study was carried out at St Joseph's Hospital, Jirapa, Ghana. Children with severe kwashiorkor were randomly assigned to either a standard treatment (ST) receiving a therapeutic protocol based on the recommendations of the WHO or to one of three study groups receiving in addition 2 x 600 mg reduced glutathione or 2 x 50 mg alpha-lipoic acid or 2 x 100 mg N-acetylcysteine per day. Patients were followed up clinically and biochemically for 20 days and compared with 37 healthy controls. Both glutathione and alpha-lipoic acid supplementation had positive effects on survival. Also, the blood glutathione concentrations correlated positively with survival rates. Furthermore, the initial skin lesions, glutathione and total protein concentrations were found to be strong predictors of survival. The data strongly suggest that a therapy restoring the antioxidative capacity by applying cysteine equivalents in the form of glutathione and/or alpha-lipoic acid is beneficial for biochemical and clinical recovery of kwashiorkor patients.

Cyclophilin-A: a potential screening marker for vascular disease in type-2 diabetes

The pathophysiology of vascular disease in diabetes involves abnormalities in endothelial cells, vascular smooth muscle cells, and monocytes. The metabolic abnormalities that characterize diabetes, such as hyperglycemia, increased free fatty acids, and insulin resistance, each provoke molecular mechanisms that contribute to vascular dysfunction. Several molecules have been identified as risk markers, and have been studied to prevent progression of disease and long-term complications. Markers such as C-reactive protein and monocyte chemoattractant protein-1 are used to assess risk for adverse cardiac events, but elevated levels are possible due to the presence of other risk factors as part of the natural physiological defense mechanism. In this review we discuss potential of cyclophilin-A, a secreted oxidative-stress-induced immunophilin with diverse functions. We present evidence for a significant role of cyclophilin-A in the pathogenesis of atherosclerosis in diabetes, and its potential as a marker for vascular disease in type-2 diabetes.

Effect of Giardia duodenalis in protein malnourished and renourished mice

The present study was designed to delineate the effect of Giardia duodenalis in malnourished and renourished BALB/c mice. Control and renourished mice were fed with a standard pellet diet while malnourished mice were fed with a low protein (4.3 %) diet both before and after being challenged orally with actively growing G. duodenalis trophozoites. It was observed that malnourished mice had a greater severity and longer duration of Giardia infection compared with renourished mice. These malnourished mice also had less body mass but higher cyst and trophozoite counts. Malnourished mice infected with Giardia had significantly decreased level of total serum proteins, albumin, globulins, hemoglobin, leukocyte, and differential leukocyte counts compared with renourished mice. From the data it is concluded that protein malnutrition profoundly affects the anthropometric and physiological parameters of the body indicating greater susceptibility and severity of the disease.

Leptin as an immunomodulator

Leptin is an adipocyte-derived hormone/cytokine that links nutritional status with neuroendocrine and immune functions. In humans, leptin influences energy homeostasis and regulates neuroendocrine function primarily in states of energy deficiency. Initially described as an antiobesity hormone, leptin has subsequently been shown also to influence basal metabolism, hematopoiesis, thermogenesis, reproduction, and angiogenesis. As a cytokine, leptin can affect thymic homeostasis and the secretion of acute-phase reactants such as interleukin-1 (IL-1) and tumor-necrosis factor-alpha (TNF-α). Leptin links nutritional status and proinflammatory T helper 1 (Th1) immune responses and the decrease in leptin plasma concentration during food deprivation leads to impaired immune function. Similar to other pro-inflammatory cytokines, leptin promotes Th1-cell differentiation and can modulate the onset and progression of autoimmune responses in several animal models of disease. Here, we review the advances and controversy for a role of leptin in the pathophysiology of immune responses and discuss novel possible therapeutic implications for leptin modulators.

Pasteur's Quadrant: preparing training programs for "use-inspired" surgical research

Ensuring that scientific research is an integral element of surgical residency training is critical to the future viability of the field. The ability to nurture surgeon-scientists, invoke them to ask pertinent questions, design experiments, and translate these findings into clinical applications will set this specialty apart from competing fields. Involving residents and younger faculty in this process of translational research is crucial to develop academic leaders and improve patient care. It is as critical as it is complex. Here, we propose that this objective can be attained only if academic departments of surgery recognize its value, create a solid framework of support, encourage partnerships, and above all provide the patient and essential mentorship that residents and young faculty need to pursue meaningful surgical research. To provide usable frameworks, a unique 2-dimensional quadrant termed "Pasteur's Quadrant" is generated based on the original work of Stokes. Briefly, it creates 4 quadrants that separate pure basic science or discovery (X-axis) from applied research or innovation (Y-axis). In doing so, it also defines a median-research that satisfies both goals: scientific advancement AND clinical improvement. This novel use-inspired method of categorizing research provides guidelines to select research programs prudently. Using the Pasteur's Quadrant approach to the conduct of resident-performed surgical research offers several advantages: It is clinically applicable; it advances goals of fundamental scientific research; it is provocative, productive, and retains high visibility; and it makes it attractive to funding agencies and industry alike. Lastly, it charts a vibrant course for their main beneficiaries, residents and academic surgical programs.

Malnutrition and infection: complex mechanisms and global impacts

The authors discuss current concepts and controversies surrounding the complex influences of malnutrition on infection and immunity, and point to practical consequences of countermeasures in acute malnutrition.

Inflammation, stress, and diabetes

Over the last decade, an abundance of evidence has emerged demonstrating a close link between metabolism and immunity. It is now clear that obesity is associated with a state of chronic low-level inflammation. In this article, we discuss the molecular and cellular underpinnings of obesity-induced inflammation and the signaling pathways at the intersection of metabolism and inflammation that contribute to diabetes. We also consider mechanisms through which the inflammatory response may be initiated and discuss the reasons for the inflammatory response in obesity. We put forth for consideration some hypotheses regarding important unanswered questions in the field and suggest a model for the integration of inflammatory and metabolic pathways in metabolic disease.

Inflammation, stress, and diabetes

Over the last decade, an abundance of evidence has emerged demonstrating a close link between metabolism and immunity. It is now clear that obesity is associated with a state of chronic low-level inflammation. In this article, we discuss the molecular and cellular underpinnings of obesity-induced inflammation and the signaling pathways at the intersection of metabolism and inflammation that contribute to diabetes. We also consider mechanisms through which the inflammatory response may be initiated and discuss the reasons for the inflammatory response in obesity. We put forth for consideration some hypotheses regarding important unanswered questions in the field and suggest a model for the integration of inflammatory and metabolic pathways in metabolic disease.

Inflammation, stress, and diabetes

Over the last decade, an abundance of evidence has emerged demonstrating a close link between metabolism and immunity. It is now clear that obesity is associated with a state of chronic low-level inflammation. In this article, we discuss the molecular and cellular underpinnings of obesity-induced inflammation and the signaling pathways at the intersection of metabolism and inflammation that contribute to diabetes. We also consider mechanisms through which the inflammatory response may be initiated and discuss the reasons for the inflammatory response in obesity. We put forth for consideration some hypotheses regarding important unanswered questions in the field and suggest a model for the integration of inflammatory and metabolic pathways in metabolic disease.

Leptin indirectly activates human neutrophils via induction of TNF-alpha

Leptin, the satiety hormone, appears to act as a link between nutritional status and immune function. It has been shown to elicit a number of immunoregulatory effects, including the promotion of T cell proliferative responses, and the induction of proinflammatory cytokines. Leptin deficiency is associated with an increased susceptibility to infection. As polymorphonuclear neutrophils (PMN) play a major role in innate immunity and host defense against infection, this study evaluated the influence of leptin on PMN activation. The presence of leptin receptor in human PMN was determined both at mRNA and protein levels, and the effect of leptin on PMN activation, as assessed by CD11b expression, was evaluated using flow cytometry. In contrast to monocytes, which express both the short and long forms of the leptin receptor (Ob-Ra and Ob-Rb, respectively), PMN expressed only Ob-Ra. Leptin up-regulated the expression of CD11b, an early marker of PMN activation, on PMN in whole blood, yet it had no effect on purified PMN, even those treated by submaximal doses of TNF-alpha or PMA. The kinetics of leptin-induced activation in whole blood were consistent with an indirect effect mediated by monocytes, and 71% of the leptin-stimulatory effect on PMN was blocked by a TNF-alpha inhibitor. Leptin-mediated induction of CD11b expression was observed when purified PMN were coincubated with purified monocytes. In conclusion, although leptin activates PMN, it does so indirectly via TNF-alpha release from monocytes. These findings provide an additional link among the obesity-derived hormone leptin, innate immune function, and infectious disease.

Lung alveoli: endogenous programmed destruction and regeneration

Mammalian alveoli, complex architectural and cellular units with dimensions that are linked to the organism's O2 consumption (VO2), are thought to be destroyed only by disease and not to spontaneously regenerate. Calorie restriction of adult mammals lowers VO2, and ad libitum refeeding returns VO2 to pre-calorie-restriction values. We took advantage of these relationships and tested the hypothesis in adult mice that calorie restriction (two-thirds reduction for 2 wk) followed by ad libitum refeeding (3 wk) would cause alveolar destruction and regeneration, respectively. Calorie restriction diminished alveolar number 55% and alveolar surface area 25%. Refeeding fully reversed these changes. Neither manipulation altered lung volume. Within 72 h, calorie restriction increased alveolar wall cell apoptosis and diminished lung DNA (approximately 20%). By 72 h of refeeding, alveolar wall cell replication increased and lung DNA rose to amounts in mice that were never calorie restricted. We conclude that adult mice have endogenous programs to destroy and regenerate alveoli, thereby raising the danger of inappropriate activation but the possibility of therapeutic induction, if similar programs exist in humans.