Diet modification and metformin have a beneficial effect in a fly model of obesity

and mucormycosis

Fazal Shirazi, PhD

Advantages of Drosophila as a Model Host for Studies of Fungal Pathogenesis

• Inexpensive, logistically less laborious• Simple, evolutionarily conserved immunity (Toll pathway), no

immunosuppression is needed• Less complex metabolism• > 60% genes have human homologues (including 75% of

disease-related genes) • Less ethical considerations

Chamilos G and Kontoyiannis DP. Lancet Infect Dis 2008, Gonzalez C. Nat Rev Cancer 2013

•Obesity predisposes to insulin resistance and is a major risk factor for development of type 2 diabetes mellitus. •1 in 6 adults are obese, 1 in 10 have diabetes (WHO, The World Health

Statistics 2012).

•Independent of diabetes, obesity is an emerging risk factor for more frequent and severe infections (Kwong et al, CID 2011).

•Mucormycosis is a severe, frequently fatal, infection in diabetics and immunocompromised cancer patients (Kontoyiannis and Lewis,

Blood 2012).

•Better understanding of mucormycosis pathogenesis may lead to novel treatment approaches.

Background

Aims

• To establish a fly model of obesity and hyperglycemia and study the natural history of mucormycosis in that model

Hypotheses

A) Mortality from mucormycosis is higher in obese and hyperglycemic flies, compared to normal flies

B) Diet and/or metformin-induced weight loss have a beneficial effect on mucormycosis-associated mortality

Experimental design and groups studied

Flies fed on 30% coconut oil become obese after 48 hrs

The mean body weight, triglyceride and glucose levels of flies fed on HFD were higher than RF

Flies fed on 30% coconut oil become obese leading to increased body weight followed by increased TAG and glucose levels

Body weight, Triglyceride and glucose levels in uninfected flies progressively increase with obesity and are normalized by

metformin and diet

High-fat diet led to weight gain and increase in TAG and glucose levels, which was restored back to normal with regular diet or metformin administration.

Glucose levels increase in infected flies, more in obese than normal flies, and are restored by diet and metformin

Metformin treatment of adult Drosophila activates AMPK

Slack et al. PloS One. 2012; Luong et al. Cell Met. 2006

Drosophila TOR regulates lipid metabolism

A) Nile Red staining of control third instar larvae fat body.B) Nile Red staining of the dTOR7/P mutant larvae fat body. DNA stained with DAPI.C) Reduction of dTOR function results in increased lipase mRNA levels.F) Reduction of dTOR function results in elevated ketone bodies.

Drosophila TOR regulates DILP and glucose homeostasis

Luong et al. Cell Met. 2006

A) DILP2 shows expression in the cytoplasm of the NSC cell body and into the axonal processes in the WT.B) The dTOR7/P mutant has increased DILP2 staining in both the cell body and axons. C) DILP2 mRNA levels in the dTOR7/P mutant. D) The dTOR7/P mutant glucose levels are significantly decreased (p = .0086) compared to control.

The dTOR7/P mutant flies exhibited a significantly extended lifespan

Luong et al. Cell Met. 2006

High fat diet reduces the survival of obese non-hyperglycemic Drosophila flies infected with Rhizopus

Metformin administration improves survival of obese non-hyperglycemic Drosophila flies infected with Rhizopus

Administration of metformin might be beneficial over diet alone.

Metformin administration improves survival of obese hyperglycemic Drosophila flies infected with Rhizopus

Obese flies infected with R. oryzae which are on diet or metformin have less fungal burden, compared to obese infected flies

1. Obesity and hyperglycemia increase the lethality of Rhizopus infection in Drosophila flies.

2. Both diet and metformin lead to weight loss and decrease mortality in obese and hyperglycemic flies with Rhizopus infection.

3. Administration of metformin might be more beneficial than diet alone.

4. Our fly model of obesity bears intriguing similarities to the pathophysiology of obesity and diabetes in humans, and could provide new insights into the pathogenesis and treatment of infections in obese and diabetic patients.

Conclusions

Acknowledgements

Prof. Dimitrios P KontoyiannisProf. Kim-Anh Do

Dimitrios Farmakiotis

Nathaniel D. Albert

Thank You

Future studies-we want to address the following objectives

1. To assess the functional consequences of metabolic syndrome in

the pathogenesis of mucormycosis in flies.

a. Drosophila genome wide screen for mucormycosis, lean, obesity and

diabetes genes.

b. To study the effects of caloric restriction on different cellular

parameters, experimentally described to be involved in the

increased life span by changes in transcriptional profiling under

different conditions.

c. To study expression of microRNAs: to establish potential molecular

link between obesity, diabetes and mucormycosis.

2. To assess the effect of gut microbiome on mucormycosis

pathogenesis to determine the link between microbiome, obesity and

mucormycosis.

a.Compare how the microbiome of normal, obese flies and obese flies

treated with metformin affects flies survival after infection.

b.To determine how microbiome transplantation effects obesity and

resistance to mucormycosis and how change in microbiome affects the

immune system

Mucor circinelloides

Obese-non-hyperglycemic

Hyperglycemic