Metformin improves in vivo and in vitro B cell function in individuals with obesity and Type-2 Diabetes
Introduction
An important goal of translational aging research is the identification of therapeutic strategies to prevent, delay or treat deleterious age-related effects which may contribute to increased morbidity and mortality in elderly individuals. New opportunities could arise from currently approved drugs for the discovery of optimal novel therapeutic effects. One candidate, Metformin (MET), the best treatment for overweight and obese Type-2 Diabetes (T2D) patients with normal renal function, is the only hypoglycemic drug also influencing cellular processes associated with the development of chronic conditions of old age, including inflammation, oxidative damage, increased glycation of proteins, diminished autophagy, cell senescence and apoptosis. Although not fully understood, the pleiotropic effects of MET are thought to be mediated primarily through regulation of the activity of 5′-adenosine monophosphate (AMP)-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR). MET has been shown to activate AMPK which is an attractive target because its activity is decreased in the liver, muscle and adipose tissue of obese or Insulin Resistant (IR) animals and humans [1].
Published results have suggested that MET not only reduces chronic inflammation through the reduction of hyperglycemia, IR and atherogenic dyslipidemia, but is also has direct anti-inflammatory effects. For example, it has been shown that MET reduces lipopolysaccharide-induced proinflammatory responses in monocyes and macrophages [2], down-regulates Th17 cells in Rheumatoid Arthritis patients [3], decreases TNF-α receptor signaling and NF-kB activation in endothelial cells [4], [5] and smooth muscle cells [6], and inhibits intestinal inflammation and colitis-associated colon cancer in intestinal epithelial cells [7]. MET has also been suggested to have cardioprotective effects through its reduction of inflammation, improvement of lipid profiles [8] and endothelial cell function [9], and retardation of the process of coronary artery calcification [10].
T2D patients are at risk for infections due to influenza or for complications related to it [11], [12], [13] and therefore annual influenza vaccination is highly recommended [11]. Viral and bacterial infections and consequent diseases are associated with increased morbidity and mortality in T2D patients, causing loss of metabolic control leading to an increase of glycosylated serum proteins, ketoacidosis which may result in an increased hospitalization rate and mortality rate, and prolonged complications [14], [15]. Previously published results have measured T cell function in vaccinated young [12] and elderly [16] T2D patients and have shown reduced [12] or similar [16] responses in patients versus healthy controls. When B cell responses were measured in vaccinated young [17] and elderly [17], [18] T2D patients, no differences were found in both age groups. Our interpretation of these results showing no different responses between T2D patients and age-matched healthy controls was that all T2D patients recruited were taking MET or other hypoglycemic drugs, such as sulfonylurea or repaglinide, and it is known that a better T2D control, such as glucose and metabolic-related parameters, positively influence the response to the influenza vaccine [18]. No studies have been conducted so far to evaluate the effects of MET on influenza vaccine responses and on B cell function in T2D patients and this is the topic of our present study.
We have investigated the effects of obesity and T2D on in vivo and in vitro B cell responses in 2 groups of patients: those recently diagnosed but not taking anti-diabetic drugs, and patients taking MET. Our in vivo model for immune response uses the influenza vaccine. Our results show that B cell function and vaccine responses, hampered by obesity and T2D, are improved by MET. We have used activation-induced cytidine deaminase (AID) as a marker for optimal B cell function in these studies because we have shown that it positively and significantly correlates with the ability of B cells to undergo class switch [19] and somatic hypermutation, necessary for affinity maturation of antibodies [20]. Moreover, MET used in vitro to stimulate B cells from recently diagnosed T2D patients is also able to reduce B cell-intrinsic inflammation and increase antibody responses, similar to what we have seen in B cells from patients taking MET, who invariably show increased responses to the influenza vaccine in vivo. These results may have significant implications for public health.
Section snippets
Study subjects
Experiments were conducted using blood isolated from individuals with obesity and T2D (age 57–63 years), after appropriate signed informed consent and were approved with IRB protocol #20070481. T2D patients, screened and diagnosed according to the American Diabetes Association guidelines, were divided into 2 groups: (a) recently diagnosed not taking MET (8 individuals), (b) patients taking MET (15 individuals). Patients were taking 1000 mgs of MET (oral tablet), twice/day. Patients were on MET
MET improves the in vivo and in vitro antibody response to the influenza vaccine
We evaluated the effect of taking MET on the in vivo antibody response to influenza vaccination measured by the HAI assay. Fig. 1A shows that vaccine-specific titers after vaccination are significantly higher in patients taking MET as compared with patients MET naïve, indicating better overall immune cell function.
Then, we wanted to test the effect of taking MET on the in vitro antibody response to the vaccine. To do this, we stimulated PBMC from the same individuals as above, before or after
Disclosures
Conflicts of interest: none.
Author contributions
AD, BBB, DF conceived the experiments. AD, MR, TV, DF carried out the experiments and analyzed data. AD, DF, SL performed statistical analyses. All authors were involved in writing the paper and had final approval of the submitted and published versions.
Acknowledgements
The authors thank the volunteers who participated in this study. The authors also thank the personnel of the Department of Family Medicine and Common Health at the University of Miami Miller School of Medicine; and the Sylvester Comprehensive Cancer Center Flow Cytometry Core Resource. This study was supported by NIH R01 AG32576 (BBB), R21 AI096446 and R21 AG042826 (BBB/DF), R56 AG32576 (DF/BBB).
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