ADV36 adipogenic adenovirus in human liver disease

Microbiome-centered therapies for the management of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant global health issue, affecting over 30% of the population worldwide due to the rising prevalence of metabolic risk factors such as obesity and type 2 diabetes mellitus. This spectrum of liver disease ranges from isolated steatosis to more severe forms such as steatohepatitis, fibrosis, and cirrhosis. Recent studies highlight the role of gut microbiota in MASLD pathogenesis, showing that dysbiosis significantly impacts metabolic health and the progression of liver disease. This review critically evaluates current microbiome-centered therapies in MASLD management, including prebiotics, probiotics, synbiotics, fecal microbiota transplantation, and emerging therapies such as engineered bacteria and bacteriophage therapy. We explore the scientific rationale, clinical evidence, and potential mechanisms by which these interventions influence MASLD. The gut-liver axis is crucial in MASLD, with notable changes in microbiome composition linked to disease progression. For instance, specific microbial profiles and reduced alpha diversity are associated with MASLD severity. Therapeutic strategies targeting the microbiome could modulate disease progression by improving gut permeability, reducing endotoxin-producing bacteria, and altering bile acid metabolism. Although promising, these therapies require further research to fully understand their mechanisms and optimize their efficacy. This review integrates findings from clinical trials and experimental studies, providing a comprehensive overview of microbiome-centered therapies' potential in managing MASLD. Future research should focus on personalized strategies, utilizing microbiome features, blood metabolites, and customized dietary interventions to enhance the effectiveness of these therapies.

Reducing endogenous insulin is linked with protection against hepatic steatosis in mice

Background

Obesity and type 2 diabetes (T2D) are closely associated with hepatic steatosis (HS), which if untreated can advance to serious liver conditions. Since insulin promotes hepatic lipogenesis, reducing hyperinsulinemia may help in treating HS. E4orf1 is an adenovirus-derived protein that improves glucose clearance independent of insulin, lowers insulin amount required for glucose disposal, and reduces HS. As a next step, we evaluated the mechanism for E4orf1-induced reduction in HS and tested that E4orf1 does not induce hypoglycemia, an important attribute for its application as a potential anti-diabetic agent.

Methods

C57Bl/6J mice that transgenically express E4orf1 in adipose tissue (E4orf-Tg) and wild-type (WT) mice received a chow diet for 6 weeks, followed by a high-fat (HF) diet for additional 10 weeks. Body composition, blood glucose, and serum insulin levels upon glucose load were measured at 0, 6, 7, and 16 weeks. Serum free fatty acid (FFA), triglyceride (TG), and hepatic TG were measured at study termination. We compared histology and the mRNA/protein markers of hepatic and adipose tissue lipid metabolism between the two groups of mice.

Results

On chow diet, both groups remained normoglycemic, but E4orf1 expression reduced insulin response. On HF diet, glycemic control in WT deteriorated, whereas E4orf1 significantly enhanced glycemic control, lowered insulin response, reduced hepatic triglycerides, and serum FFA. Overall, a comparison of hepatic mRNA and/or protein expression suggested that E4orf1 expression significantly decreased de novo lipogenesis (DNL) and intracellular lipid transport and increased fat oxidation and TG export. Adipose tissue mRNA and protein markers suggested that E4orf1 expression lowered DNL and increased lipolysis.

Conclusion

Considering that E4orf1 is not secreted in circulation, we postulate that reduced endogenous insulin in E4orf1 mice indirectly contributes to reduce HS by altering hepatic lipid metabolism, including lipogenesis. This study underscores the possibility of indirectly impacting HS by manipulating adipose tissue metabolism.

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.

Challenges of liver cancer: Future emerging tools in imaging and urinary biomarkers

Chronic liver disease has become a global health problem as a result of the increasing incidence of viral hepatitis, obesity and alcohol misuse. Over the past three decades, in the United Kingdom alone, deaths from chronic liver disease have increased both in men and in women. Currently, 2.5% of deaths worldwide are attributed to liver disease and projected figures suggest a doubling in hospitalisation and associated mortality by 2020. Chronic liver diseases vary for clinical manifestations and natural history, with some individuals having relatively indolent disease and others with a rapidly progressive course. About 30% of patients affected by hepatitis C has a progressive disease and develop cirrhosis over a 20 years period from the infection, usually 5-10 years after initial medical presentation. The aim of the current therapeutic strategies is preventing the progression from hepatitis to fibrosis and subsequently, cirrhosis. Hepatic steatosis is a risk factor for chronic liver disease and is affecting about the half of patients who abuse alcohol. Moreover non-alcoholic fatty liver disease is part of the metabolic syndrome, associated with obesity, hypertension, type II diabetes mellitus and dyslipidaemia, and a subgroup of patients develops non-alcoholic steatohepatitis and fibrosis with subsequent cirrhosis. The strengths and pitfalls of liver biopsy are discussed and a variety of new techniques to assess liver damage from transient elastography to experimental techniques, such as in vitro urinary nuclear magnetic resonance spectroscopy. Some of the techniques and tests described are already suitable for more widespread clinical application, as is the case with ultrasound-based liver diagnostics, but others, such as urinary metabonomics, requires a period of critical evaluation or development to take them from the research arena to clinical practice.

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.

Role of adenoviruses in obesity

Five human adenovirus subtypes, Ad5, Ad9, Ad31, Ad36, and Ad37, and a non-human adenovirus, SMAM1, are linked to increased adiposity in vitro or in vivo. Experimental infection with Ad5, Ad36, and Ad37 produced excess adiposity or weight gain in animals. Ad9 and Ad31 increase fat storage in tissue culture but are not associated with animal or human obesity. Ad36 is the most extensively studied adipogenic adenovirus and is correlated with some measure of overweight/obesity in humans from multiple countries. The correlation is strongest and most consistent in children, but some studies have been negative in both children and adults. About 30% of overweight/obese children and adults and about 15-20% of lean individuals have Ad36 antibodies in epidemiologic studies. The mechanisms of action of Ad36 are due to the early gene 4, open reading frame 1 (E4-ORF1). Blocking E4-ORF1 with siRNA prevents the effects of Ad36, and transfection of lentivirus with E4-ORF1 reproduces the Ad36 effects. Increased adiposity is caused by stimulation of at least three pathways by Ad36. Cell membrane glucose receptors are increased via the Ras pathway, leading to increased intracellular glucose. Fatty acid synthase is increased, which converts the glucose to fatty acids. Finally, peroxisome proliferator-activated receptor-γ is increased, resulting in differentiation of adult stem cells into adipocytes.

CONCLUSIONS

several adenoviruses increase adiposity in animals and are associated with obesity in humans. There are critical gaps in the literature needing further investigation including evaluation of other adenovirus subtypes and better research designs to improve the strength of causal inferences.

Targeting species D adenoviruses replication to counteract the epidemic keratoconjunctivitis

Human adenoviruses are non-enveloped DNA viruses causing various infections; their pathogenicity varies dependent on virus species and type. Although acute infections can sometimes take severe courses, they are rarely fatal in immune-competent individuals. Adenoviral conjunctivitis and epidemic keratoconjunctivitis are hyperacute and highly contagious infections of the eye caused by human adenovirus types within species D. Currently there is no causal treatment available to counteract these diseases effectively. The E2B region of the adenovirus genome encodes for the viral DNA polymerase, which is required for adenoviral DNA replication. Here we propose novel model systems to test this viral key factor, DNA polymerase, as a putative target for the development of efficient antiviral therapy based on RNA interference. Using our model cell lines we found that different small interfering RNAs mediate significant suppression (up to 90%) of expression levels of viral DNA polymerase upon transfection. Moreover, permanent expression of short hairpin RNA based on the most effective small interfering RNA led to a highly significant, more than tenfold reduction in replication for different human group D adenoviruses involved in ocular infections.