The role of adenovirus 36 as a risk factor in obesity: the first clinical study made in the fatty tissues of adults in Turkey

Adenovirus 36 Infection in People Living with HIV-An Epidemiological Study of Seroprevalence and Associations with Cardiovascular Risk Factors

Background. With the life expectancy of people living with HIV (PLHIV) rapidly approaching that of the general population, cardiovascular health in this group is as relevant as ever. Adenovirus 36 (Adv36) is one of the few viruses suspected to be a causative factor in promoting obesity in humans, yet there is a lack of data on this infection in PLHIV. Methods. PLHIV on stable suppressive antiretroviral therapy were included in the study, with assessment of anthropometric measures, blood pressure, serum lipid levels, fasting serum glucose and insulin, non-classical serum cardiovascular risk markers related to inflammation (hsCRP, resistin, calprotectin), and anti-Adv36 antibodies during a routine check-up. Results. 91 participants were recruited, of which 26.4% were Adv36-seropositive (Adv36(+)). Compared to Adv36-seronegative (Adv36(−)) controls, Adv36(+) individuals had a lower waist circumference (Adv36(+) 89.6 ± 7.7 cm, Adv36(−) 95.5 ± 11.7 cm, p = 0.024) and a lower waist-to-hip ratio (Adv36(+) 0.88 ± 0.06, Adv36(−) 0.92 ± 0.09, p = 0.014), but this did not reach statistical significance in the multivariate analysis (p > 0.05). Adv36(+) participants were less likely to be on lipid-lowering treatment (Adv36(+) 12.5%, Adv36(−) 34.3%, p = 0.042), even after adjustment for relevant baseline characteristics (OR = 0.23, 95%CI = 0.04−0.91), but no differences in cholesterol or triglyceride levels were found. No other statistically significant associations were observed. Conclusions. We found no evidence to support the claim that past Adv36-infection is associated with an increased prevalence of cardiovascular risk factors or with elevated inflammatory markers in PLHIV. More research is needed to replicate these findings in other samples of PLHIV and to compare them with the HIV-negative population.

Adenovirus 36 infection and obesity risk: current understanding and future therapeutic strategies

INTRODUCTION

Obesity, a multifactorial disease caused by the interaction between genetic characteristics, metabolism, lifestyle, and environmental factors, is a major global health problem and is currently defined as a pandemic phenomenon. This disease is determined by an interaction of several factors, but the imbalance between energy consumption and expenditure seems to be the crucial point. In some cases, there is no linearity between exposure to those factors that cause the onset of obesity. A striking example of the occurrence of obesity despite no obvious risk factors is that of obesity induced by viral infections. The most important of such viruses appears to be human adenovirus 36 (Adv36).

AREAS COVERED

This review covers the relation between obesity and infection by Adv36 in humans. Also, discussed are the opportunities of prevention or treatment for the effects of Adv36 in human body.

EXPERT OPINION

The role of Ad36 in the development of obesity has already been established. Future research should focus on the development of vaccines against this agent, drug discovery for infected individuals, and effective therapeutic uses of E4orf1 gene protein for diabetes and other diseases in clinical practice.

Association of adenovirus 36 infection and obesity; An updated meta-analysis of community-based studies

As a health problem, obesity has several risk factors; it has been suggested that human adenovirus type 36 (HAdV-36) infections may possibly be associated with obesity. This updated meta-analysis was designed and conducted with an emphasis on articles published from 2015 to 2020. The PubMed, Web of Science, and Scopus databases were searched up to 1 December 2020. Overall, pooled prevalence and odds ratio of antibodies against HAdV-36 in people with obesity and controls was assessed among different ages. Case-control and cohort studies were included in the analysis. The overall prevalence of HAdV-36 infection in obese population was 31% (CI: 0.24%-0.38%) which was 32% in cases and 27% in controls, respectively; a significant association was found between the cases and the controls (OR, 1.84; 95% CI, 1.39-2.43), especially in children younger than 18 years of age (OR, 2.44; 95% CI, 1.85-3.22). A significant association between adenovirus infection and obesity was found, especially in adolescents.

Adenovirus 36 prevalence and association with human obesity: a systematic review

INTRODUCTION

Obesity has numerous etiologies and includes biological factors. Studies have demonstrated that the human adenovirus subtype 36 (Adv36) is an adipogenic agent and causes metabolic alterations. Study results on the prevalence of Adv36 and clinical effects in humans vary substantially. This was a systematic review to summarize the studies on the prevalence of Adv36 infection and its association with human obesity.

METHODS

A systematic literature review was conducted using the preferred reporting items for systematic reviews and meta-analysis (PRISMA). Observational or experimental studies found in the Medline, Embase, LILACS, Science Direct and SciELO databases that presented results on the prevalence of Adv36 in humans were included.

RESULTS

Thirty-seven studies were screened. A total of 10,300 adults aged 18-70 years and 4585 children and adolescents aged 3-18 years were assessed. The average prevalence of Adv36 among adults was 22.9%, ranging from 5.5% to 49.8%. Among children and adolescents, the average prevalence of Adv36 was 28.9%, ranging from 7.5% to 73.9%. There was a positive statistical relationship between Adv36 and weight gain, obesity, or metabolic changes in 31 studies. However, in four studies there was no association with obesity, and in one, no association was described. One of the studies showed an inverse correlation, i.e., Adv36 was a protective factor against obesity.

CONCLUSION

Strong evidence suggested a positive association between viral infection and obesity. However, due to the multi-causality of obesity and heterogeneity of studies, diagnostic tests should be standardized and easily accessible by the population to estimate the overall prevalence of Adv36 infection and its association with obesity.

Presence of Adenovirus-36 DNA in Adipose Tissue of Women: Relationship with Adipocyte Morphology and the Expression of C/EBPβ and HIF-1α

BACKGROUND

Human adenovirus 36 (HAd36) infection has been associated with obesity. Experiments using 3T3-L1 adipocyte cultured cells and human adipose stem cells (hASCc) have shown that HAd36 stimulates the expression of genes implicated in cell differentiation and increased lipid accumulation. The presence of HAd36 in adipose tissue of overweight and obese women has also been confirmed. This study aims to analyze the presence of HAd36 DNA in the adipose tissue of women undergoing surgery for weight reduction and its relationship with obesity through changes in adipocyte morphology as well as the expression of C/EBPβ and HIF-1α.

METHODS

Fifty-two subcutaneous adipose tissue biopsies were collected. The anthropometric parameters measured were weight, height, skin folds, body circumferences, and body fat percentage. Biochemical measures were performed for glucose, cholesterol, triglycerides, cholesterol HDL-c, and LDL-c. The presence of HAd36 DNA was performed by conventional PCR. Adipocyte morphology was analyzed in H&E-stained sections using ImageJ/Fiji software. The expression of genes C/EBPβ, HIF-1α and β-actin was determined using TaqMan probes.

RESULTS

HAd36 DNA was detected in 31% of adipose tissue samples. The presence of viral DNA was not significantly associated with anthropometric, clinical, or metabolic measurements, or with changes in adipose tissue morphology. The levels of mRNA expression for C/EBPβ and HIF-1α did not show significant differences between positive and negative samples for HAd36 (p>0.05).

CONCLUSION

The presence of HAd36 DNA in adipose tissue was identified, but it was not related to morphological changes of adipocytes, or the expression of C/EBPβ and HIF-1α. Further studies are needed to confirm these findings.

Obesity and Diabetes in an Arab population: Role of Adenovirus 36 Infection

Prior infection with adenovirus 36 (Adv36) has been associated with increased adiposity, improved insulin sensitivity, and a lower prevalence of diabetes. This study investigated the prevalence of Adv36 seropositivity and its association with obesity and diabetes among adults attending a diabetes centre in the UAE.Participants (N = 973) with different weight and glucose tolerance categories were recruited. Adv36 seropositivity (Adv36 + ) was assessed using ELISA. Differences among groups were analyzed using statistical tests as appropriate to the data. Prevalence of Adv36+ in the study population was 47%, with no significant difference in obese and non-obese subgroups (42.5% vs 49.6% respectively; p=non-significant). Females were more likely to be Adv36+ compared to males (odds ratio 1.78; 95% CI 1.36–2.32, p < 0.001). We found no significant association between Adv36 seropositivity and different BMI categories, or glucose tolerance status. In our population, the effect of Adv36 infection on lipid profile varied between healthy individuals and individuals with obesity. Adv36 infection is more prevalent in the UAE than in other countries but has no association with obesity. Our study found that females were more likely to be Adv36 positive regardless of weight or diabetes status.

Twenty-five years of research about adipogenic adenoviruses: A systematic review

Infectious etiology is implicated in chronic diseases such as gastric ulcer or atherosclerosis. However, "infection" is a recent term in the field of obesity. Since the first report in 1982 of obesity due to infection, several microbes have been linked to obesity. Among the adipogenic microbes, avian adenovirus SMAM-1 and human adenovirus Ad36 have been studied most extensively for the past 25 years. Here, we present a systematic review of literature about SMAM-1 and Ad36. Reports from North America, Europe, and Asia reveal strong evidence that Ad36 causes obesity in animals and paradoxically improves glycemic control, and in vitro data provides mechanistic explanation. Considering that experimental Ad36 infection of humans is unlikely, its causative role in human obesity or glycemic control has not been demonstrated unequivocally. Nonetheless, most, but not all, observational studies in children and adults link Ad36 infection to obesity and improvement in glycemic control. The E4orf1 gene of Ad36 was identified as responsible for better glycemic control. Overall, 25 years have considerably advanced knowledge about the role of infection in obesity. Potential translational benefits include the development of vaccines to prevent Ad36-induced obesity and drug development based on the E4orf1 protein to improve glycemic control.

Adenovirus 36 seropositivity is related to obesity risk, glycemic control, and leptin levels in Chilean subjects

BACKGROUND

Adenovirus 36 (Ad-36) has been associated to adiposity in animal and in vitro studies. Ad-36 seropositivity has also been reported to contribute to obesity risk in children and adult populations. We investigated the relationship of Ad-36 serology with obesity and metabolic parameters in a Chilean population.

SUBJECTS AND METHODS

Clinical and anthropometric data were obtained and blood samples were drawn from 99 lean (BMI: 18.5-24.9 kg/m²) and 151 obese (BMI > 30 kg/m²) subjects. Laboratory tests included lipid profile as well as glucose, insulin, leptin, and adiponectin levels. Ad-36 seropositivity was evaluated in serum samples by enzyme-linked immunosorbent assay.

RESULTS

Seroprevalence of Ad-36 was higher in the obese group (58%) than in lean controls (34%) demonstrating that individuals previously infected with Ad-36 have higher risk of obesity in the study population (OR: 2.67, 95%CI: 1.58-4.51, p < 0.001). Interestingly, Ad-36 was related to lower concentrations of triglycerides and VLDL cholesterol in lean subjects (p = 0.049) and lower leptin in obese individuals (p = 0.014). Previous Ad-36 infection was also related to lower glycemia, insulinemia, and HOMA-IR (p < 0.05) in obese subjects who were not under antidiabetic drugs.

CONCLUSIONS

Our results provide evidence of the contribution of previous Ad-36 infection to an increased risk of obesity in adult Chilean population. Ad-36 seropositivity was also associated to lipid profile, glycemic control, and leptin levels in adult Chilean population.

The relationship between human adenovirus 36 and obesity in Chinese Han population

The study aimed to explore the prevalence of human adenovirus-36 (HAdV-36) infection and the association of HAdV-36 with obesity in Chinese Han population. A qualitative determination using ELISA was performed to determine by duplication of the antibodies to HAdV-36 in the serum samples. Logistic regression analysis was used to analyze the association between HAdV-36 seropositivity and obesity. The overall HAdV-36 seroprevalence was 49.8% amongst 824 participants. The prevalence of HAdV-36 seropositive was 42.9 and 51.4% in the obese and non-obese participants, respectively, which was not statistically significant (P=0.05). There were significant differences in the anthropometric and biochemical parameters observed between the two groups except for height (P=0.067) and total cholesterol (TC) (P<0.29). After the adjustment for age and gender, HAdV-36 seropositivity was a protective factor for obesity (odds ratio (OR) = 0.69, 95% confidence intervals (95% CI) = 0.48-0.97, P=0.03). In the male population, the adjusted OR for AD-36 antibody-positive status was statistically decreased for obese adults (OR = 0.59; 95% CI = 0.39-0.91; P=0.02). However, the similar result was not obtained in the female population (OR = 0.90; 95% CI = 0.48-1.67; P=0.73). We found a high prevalence of HAdV-36 infection in China and significant association between HAdV-36 infection and obesity or weight gain after the adjustment for age and gender. The HAdV-36 infection may be related to the weight loss in Chinese Han population, especially in the male group, which needs to be further confirmed.

Infectobesity: the evaluation of adenovirus-36 infection and obesity

Obesity, which causes some cancer types and other diseases, is not only a global public health problem, but also a factor that affects country's economy. Endocrinal, environmental, neuronal and genetic factors have important roles on the etiology of obesity. When the possibility that SMAM‐1 animal virus could have a relationship with obesity was observed, obesity studies focused on human adenoviruses. Adenovirus‐36 was first isolated in 1978 and was the first human adenovirus to be tested in terms of infectobesity. Both in vivo and in vitro studies proved the strong relationship between adenovirus‐36 presence and obesity. Therefore, a large-scale study incorporating various ethnicities and age groups is required to investigate the worldwide epidemic of obesity and its links with viruses.

Human Adenovirus 36 Infection Increased the Risk of Obesity: A Meta-Analysis Update

Human adenovirus 36 (HAdV-36), as the key pathogen, was supposed and discussed to be associated with obesity. We searched the references on the association between HAdV-36 infection and obesity with the different epidemiological methods, to explore the relationship with a larger sample size by meta-analysis and compare the differences of epidemiological methods and population subsets by the subgroup analyses.We conducted literature search on the association between HAdV-36 infections and obesity in English or Chinese published up to July 1, 2015. The primary outcome was the HAdV-36 infection rate in the obese and lean groups; the secondary outcomes were the BMI level and BMI z-score in the HAdV-36 positive and negative groups. The pooled odds ratio (OR) was calculated for the primary outcome; the standardized mean differences (SMDs) were calculated for the secondary and third outcomes. Prediction interval (PI) was graphically presented in the forest plot of the random effect meta-analyses. Metaregression analysis and subgroup analysis were performed.Finally 24 references with 10,191 study subjects were included in the meta-analysis. The obesity subjects were more likely to be infected with HAdV-36 compared to the lean controls (OR = 2.00; 95%CI: 1.46, 2.74; PI: 0.59, 6.76; P < 0.001) with a high heterogeneity (I = 80.1%; P < 0.001) estimated by the random effect model. Subgroup analysis demonstrated that the pooled OR of HAdV-36 infection for obesity were 1.77 (95%CI: 1.19, 2.63; PI: 0.44, 7.03; P = 0.005) and 2.26 (95%CI: 1.67, 3.07; PI: 1.45, 3.54; P < 0.001) in the adults and children, respectively. Compared to the HAdV-36 negative subjects, the SMD of BMI was 0.28 (95% CI: 0.08, 0.47; PI: -0.53, 1.08; P = 0.006) in the HAdV-36 positive subjects with a high heterogeneity (I = 86.5%; P < 0.001). The BMI z-score in the children with HAdV-36 infection was higher than those without HAdV-36 infection (SMD = 0.19; 95%CI: -0.31, 0.70; PI: -2.10, 2.49), which had no significantly statistical difference (P = 0.453).HAdV-36 infection increased the risk of obesity. HAdV-36 also increased the risk of weight gain in adults, which was not observed in children.

Obesity and Infection: Reciprocal Causality

Associations between different infectious agents and obesity have been reported in humans for over thirty years. In many cases, as in nosocomial infections, this relationship reflects the greater susceptibility of obese individuals to infection due to impaired immunity. In such cases, the infection is not related to obesity as a causal factor but represents a complication of obesity. In contrast, several infections have been suggested as potential causal factors in human obesity. However, evidence of a causal linkage to human obesity has only been provided for adenovirus 36 (Adv36). This virus activates lipogenic and proinflammatory pathways in adipose tissue, improves insulin sensitivity, lipid profile and hepatic steatosis. The E4orf1 gene of Adv36 exerts insulin senzitizing effects, but is devoid of its pro-inflammatory modalities. The development of a vaccine to prevent Adv36-induced obesity or the use of E4orf1 as a ligand for novel antidiabetic drugs could open new horizons in the prophylaxis and treatment of obesity and diabetes. More experimental and clinical studies are needed to elucidate the mutual relations between infection and obesity, identify additional infectious agents causing human obesity, as well as define the conditions that predispose obese individuals to specific infections.

The role of Ad-36 as a risk factor in males with gynecomastia

Gynecomastia is highly prevalent worldwide and Adenovirus-36 (Ad-36), recently implicated in increased adipose tissue deposition due to its affinity for adipose tissue, is a potential etiological agent in the development of obesity and therefore we hypothesized that Ad-36 may also play a role in the development of gynecomastia by possibly accompanying increased regional adiposity. To support our hypothesis, we conducted a study that included 33 adult males with gynecomastia (PG) and 15 adult males as the patient control group (HCG). Leptin and adiponectin levels were monitored using ELISA. A significant difference in Ad-36 antibody positivity was found between the groups (p<0.05). Average leptin levels were found to be higher, but average adiponectin levels were found to be lower in Ad-36 Ab(+) patient group. No Ad-36 DNA was detected in any tissue samples. In conclusion, we hypothesize that low-grade chronic inflammation, which was caused by Ad-36 infection, possibly caused an increase in circulating leptin. This in turn may have caused an increase in local or circulating estrogens and/or the estrogen/androgen ratio by stimulating the aromatase enzyme activity in adipose stromal cells and breast tissues. We suggest that gynecomastia may develop following an increase in aromatase enzyme activity, by which more oestrogen is produced and the estrogen-androgen balance disrupted. Also, regional adipose tissue enlargements may cause the excessive production of estrogens leading to gynecomastia. Adipose tissue has been recognized as a major endocrine organ in recent years. Another plausible explanation is excessive aromatization of androgens to estrogens by peripheral adipose tissue may promote gynecomastia in males. Moreover, our results suggest that there might be a relationship between Ad-36 and gynecomastia.

Adenovirus 36 and Obesity: An Overview

There is an epidemic of obesity starting about 1980 in both developed and undeveloped countries definitely associated with multiple etiologies. About 670 million people worldwide are obese. The incidence of obesity has increased in all age groups, including children. Obesity causes numerous diseases and the interaction between genetic, metabolic, social, cultural and environmental factors are possible cofactors for the development of obesity. Evidence emerging over the last 20 years supports the hypothesis that viral infections may be associated with obesity in animals and humans. The most widely studied infectious agent possibly linked to obesity is adenovirus 36 (Adv36). Adv36 causes obesity in animals. In humans, Adv36 associates with obesity both in adults and children and the prevalence of Adv36 increases in relation to the body mass index. In vivo and in vitro studies have shown that the viral E4orf1 protein (early region 4 open reading frame 1, Adv) mediates the Adv36 effect including its adipogenic potential. The Adv36 infection should therefore be considered as a possible risk factor for obesity and could be a potential new therapeutic target in addition to an original way to understand the worldwide rise of the epidemic of obesity. Here, the data indicating a possible link between viral infection and obesity with a particular emphasis to the Adv36 will be reviewed.