Figure 3

Chronic Stim dysfunction causes fat body cell hypertrophy and obesity in Drosophila. Images of day 1 (A) and days 21 (B) Stim-TRiPI flies display the expanded abdomen developed at day 21 of Stim-TRiPI On (encircled by red rectangle) as compared to Stim-TRiPI Off (encircled by light red rectangle) adult male flies. (C) Increased wet body weight of day 21 Stim-TRiPI On adult male flies as compared to Stim-TRiPI Off flies. (D) Major neutral lipid classes at day 0 and day 21 of Stim-TRiPI On and the Stim-TRiPI Off adult male flies, separated by thin layer chromatography illustrates specific accumulation of storage fat (triacylglycerol; TAG); MAG: Monoacylglycerol; DAG: Diacylglycerol; FA: Fatty acids; Standard refers to a defined mixture of FA, MAG, DAG, and TAG. (E) Integrated intensity quantification of the TAG bands in (D). Dissected flies show similar morphology of fat body tissue (white tissues encircled by green stippled lines) at day 1 but more fat tissue (the area is highlighted by blue arrow) at day 21 of Stim-TRiPI On (F,G; under the red line) as compared to age-matched Stim-TRiPI Off (F’,G’; under the light red line) adult male flies. Scale bar in F, F’, G, G’ represents 0.5 mm. Visualization of lipid droplets (stained by LD540; red), cell membranes (stained by Cell Mask Deep red; white) and nuclei (stained by DAPI; blue) in abdominal fat body tissue of adult male flies at day 1 (H) and day 21 of Stim-TRiPI On (I) and the corresponding control male (Stim-TRiPI Off) flies at day 1 (H’) and day 21 (I’) shows an increased size of fat body cells (J) and increased lipid droplets (LD) area in fat cells (K) at day 21. Scale bars in H, H’, I and I’ represent 50 μm. Data are presented as means ± standard deviations from 3–6 replicates. All data were analyzed by the two-tailed unpaired Student’s t-test. No. *p ≥ 0.05, *p < 0.05, **p < 0.01, ***p < 0.001.