Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2012 Mar;4(3):206-23.
doi: 10.18632/aging.100435.

dSir2 Deficiency in the Fatbody, but Not Muscles, Affects Systemic Insulin Signaling, Fat Mobilization and Starvation Survival in Flies

Affiliations
Free PMC article

dSir2 Deficiency in the Fatbody, but Not Muscles, Affects Systemic Insulin Signaling, Fat Mobilization and Starvation Survival in Flies

Kushal Kr Banerjee et al. Aging (Albany NY). .
Free PMC article

Abstract

Sir2 is an evolutionarily conserved NAD+ dependent protein. Although, SIRT1 has been implicated to be a key regulator of fat and glucose metabolism in mammals, the role of Sir2 in regulating organismal physiology, in invertebrates, is unclear. Drosophila has been used to study evolutionarily conserved nutrient sensing mechanisms, however, the molecular and metabolic pathways downstream to Sir2 (dSir2) are poorly understood. Here, we have knocked down endogenous dSir2 in a tissue specific manner using gene-switch gal4 drivers. Knockdown of dSir2 in the adult fatbody leads to deregulated fat metabolism involving altered expression of key metabolic genes. Our results highlight the role of dSir2 in mobilizing fat reserves and demonstrate that its functions in the adult fatbody are crucial for starvation survival. Further, dSir2 knockdown in the fatbody affects dilp5 (insulin-like-peptide) expression, and mediates systemic effects of insulin signaling. This report delineates the functions of dSir2 in the fatbody and muscles with systemic consequences on fat metabolism and insulin signaling. In conclusion, these findings highlight the central role that fatbody dSir2 plays in linking metabolism to organismal physiology and its importance for survival.

Conflict of interest statement

The authors of this manuscript have no conflict of interest to declare.

Figures

Figure 1
Figure 1. dSir2 activity increases in response to starvation and its absence decreases starvation resistance
(A) Starvation survival of dSir2 mutants (Sir22A.7.11) (p < 0.001) and (B) whole body dSir2RNAi (+ RU486) (p < 0.001), with respective controls (n = 60). (C) dSir2 transcript levels increase in response to 48-hours starvation in control (- RU486) but not in whole body dSir2RNAi(+ RU486) flies (n = 8/24). (D) Increase in dSir2 protein levels in control flies in response to 48-hours starvation. (E) Increase in NAD+ levels in response to 48-hours starvation in control flies (n = 36). 200 μM RU486 was used to knockdown dSir2 expression inpSw-tub-gal4>dSir2RNAi flies. Log Rank was used to plot survival curves and Mantel-Cox test was used for statistical analysis. Student's t-test and ANOVA were used to analyze statistical significance of the data (*, p < 0.05; **, p < 0.01; ***, p < 0.001 or mentioned otherwise).
Figure 2
Figure 2. dSir2 regulates fat metabolism
(A) Total body triglyceride (TAG) in dSir2 mutants (Sir22A.7.11) and whole body dSir2RNAi (+ RU486) flies, with respective controls (n = 36). (B) Oil-Red O staining of fatbodies from control and Sir22A.7.11. (C) Relative expression of fat metabolism genes lipase-3 (lip3), brummer (brmm), mitochondrial acyl carrier protein (mtACP), medium chain acyl CoA dehydrogenase (mcad), aceto acetyl CoA thiolase (ACoT), long chain acyl CoA dehydrogenase (lcad), acetyl CoA carboxylase (ACC), fatty acid synthase (fas) and diacyl glycerol synthase (dDAG) (n = 24). 200 μM RU486 was used to knockdown dSir2 expression in pSw-tub-gal4>dSir2RNAi flies. Student's t-test was used to analyze statistical significance of the data (*, p < 0.05; **, p < 0.01; ***, p < 0.001 or mentioned otherwise).
Figure 3
Figure 3. dSir2 in the fatbody, but not in the muscles regulates fat metabolism
(A) RT-PCR to show knockdown of dSir2 in the fatbody (FB) of fatbody dSir2RNAiand body wall with muscles (BWM) of muscle dSir2RNAi, with respective controls (n = 24). (B-C) Total body triglyceride levels in (B) fatbody dSir2RNAi flies and (C) muscles dSir2RNAi flies (n = 36). (D) Triglyceride levels in the isolated fatbody of fatbody dSir2RNAi flies (n = 60). (E) Relative expression of fat metabolism genes lipase-3 (lip3), brummer (brmm), medium chain acyl CoA dehydrogenase (mcad), long chain acyl CoA dehydrogenase (lcad) and fatty acid synthase (fas) in fatbody isolated from fatbody dSir2RNAi flies (n = 24). 200 μM RU486 was used to knockdown dSir2 expression pSw-S1106-gal4>dSir2RNAi and pSw-MHC-gal4> dSir2RNAi flies. Student's t-test was used to analyze statistical significance of the data (*, p < 0.05; **, p < 0.01; ***, p < 0.001 or mentioned otherwise).
Figure 4
Figure 4. Fatbody dSir2, but not muscle specific dSir2 regulates starvation survival and regulates fat mobilization
(A and B) Starvation survival in (A) fatbody dSir2 knockdown flies (p < 0.001) and (B) muscle dSir2 knockdown flies (non-significant, ns)(n = 60). 200 μM RU486 was used to knockdown dSir2 expression pSw-S1106-gal4>dSir2RNAi and pSw-MHC-gal4> dSir2RNAi flies. Log Rank was used to plot survival curves and Mantel-Cox test was used for statistical analysis. (C-D) Total body triglyceride levels in fed and starved conditions in (C) whole bodydSir2RNAiflies, with respective controls (n = 36) and (D) fatbody dSir2RNAi (n = 36). Relative expression of fat metabolism genes (E) lipase-3 (lip3), (F) brummer (brmm), (G) medium chain acyl CoA dehydrogenase (mcad), (H) fatty acid synthase (fas) in fatbody dSir2 knockdown flies under fed and starved conditions (n = 24). 200 μM RU486 was used to knockdown dSir2 expression pSw-S1106-gal4>dSir2RNAi and pSw-MHC-gal4> dSir2RNAi flies. ANOVA was used to analyze statistical significance of the data (*, p < 0.05; **, p < 0.01; ***, p < 0.001 or mentioned otherwise).
Figure 5
Figure 5. Fatbody dSir2 regulates dilp5 meditated Insulin Signaling
(A-C) Relative dilp5 levels in the heads of (A) whole body dSir2RNAi (B) fatbody dSir2RNAi and (C) muscle dSir2RNAi flies, with respective controls, under fed and starved conditions (n = 24). Relative expression of (D) dInR and (E) d4eBP in fatbody dSir2RNAi flies under fed and starved conditions (n = 24). (F) Starvation survival of fatbody dSir2 knockdown (pSw-S1106-gal4>+/+;dSir2RNAi + RU486) and control (pSw-S1106-gal4>+/+;dSir2RNAi - RU486) flies, fatbody dSir2 knockdown in chico heterozygote flies (pSw-S1106-gal4>ch+/-; dSir2RNAi + RU486) and (pSw-S1106-gal4>ch+/-; dSir2RNAi- RU486) (statistical significance indicated in supplementary figure 9) (n = 60).200 μM RU486 was used to knockdown dSir2 expression. Log Rank was used to plot survival curves and Mantel-Cox test was used for statistical analysis. Student's t-test and ANOVA were used to analyze statistical significance of the data (*, p < 0.05; **, p < 0.01; ***, p < 0.001 or mentioned otherwise).
Figure 6
Figure 6. dSir2 regulates metabolic and energy homeostasis and its functions in the fatbody affect systemic insulin signaling

Similar articles

See all similar articles

Cited by 18 articles

See all "Cited by" articles

References

    1. Haigis MC, Yankner BA. The aging stress response. Molecular Cell. 2010;40:333–344. - PMC - PubMed
    1. Mair W, Dillin A. Aging and survival: the genetics of life span extension by dietary restriction. Annual review of biochemistry. 2008;77:727–754. - PubMed
    1. Xue B, Kahn BB. AMPK integrates nutrient and hormonal signals to regulate food intake and energy balance through effects in the hypothalamus and peripheral tissues. The Journal of physiology. 2006;574:73–83. - PMC - PubMed
    1. Broughton S, Partridge L. Insulin/IGF-like signalling, the central nervous system and aging. The Biochemical journal. 2009;418:1–12. - PubMed
    1. Brown-Borg HM. Hormonal regulation of aging and life span. Trends in endocrinology and metabolism: TEM. 2003;14:151–153. - PubMed

Publication types

MeSH terms

LinkOut - more resources

Feedback