Figure 5.
PCs of HSD-fed flies exhibit altered lipid metabolism and increased FAO. (A) Schematic representation demonstrating the relation between major processes involved in lipid and carbohydrate metabolism in Drosophila cells. For lipid metabolism, these processes include uptake of neutral lipids from the lypophorins by lipophorin receptors (LpR1/LpR2), lipogenesis, lipolysis, de novo fatty acid synthesis, and mobilization of fatty acids (FA) into mitochondria for FAO to feed into the TCA cycle. The enzymes involved in these processes are marked in red. Import of glucose through the glucose transporter, followed by glycolysis leads to the production of pyruvate that enters the mitochondria to support TCA cycle. (B) Changes in the levels of transcripts for the genes involved in lipogenesis, lipolysis, and de novo fatty acid synthesis in the RNA isolated from PCs and cardiac tubes of HSD-fed flies as compared with that in ND-fed flies. (C and D) Increase in the levels of lipid accumulation (BODIPY staining; green) in the PCs of HSD-fed flies (D) as compared with those reared on ND (C). (E) Quantification of the mean fluorescence intensity for BODIPY staining in the PCs flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (F) Increase in TAG levels in the PCs and cardiac tube of HSD-fed flies as compared to controls. (G–H′) Increase in the levels of free fatty acid (blue; Nile Blue A staining) in the PCs of HSD-fed flies (H and H′) as compared to those reared on ND (G and G′). G and H show Nile Blue A expression in grayscale; G′ and H′ represent the same images in blue channel. (I) Quantification of the mean fluorescence intensity for Nile Blue A staining in the PCs flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (J and K) Increase in the reporter GFP expression (green) for Hnf-Gal4 in the PCs of HSD-fed flies (K) as compared with those reared on ND (J). Phalloidin (red) marks the cardiac tube and the alary muscles. (L) Quantification of the mean fluorescence intensity for Hnf-Gal4,UAS-mCD8GFP expression in the PCs of ND or HSD-fed flies. The dots represent the number of PCs analyzed for each genotype. (M) Schematic diagram showing the different enzymes involved in the FAO pathway. (N and O) Increase in the reporter YFP expression for scully in the PCs of HSD-fed flies (O) as compared to those fed on ND (N). (P) Quantification of the mean fluorescence intensity for scully-YFP expression in the PCs of flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (Q) Increase in the transcript levels of the genes encoding different enzymes involved in FAO in the RNA isolated from PCs and cardiac tube of flies reared on HSD as compared with those reared on ND. The transcript levels are normalized to that of the constitutive ribosomal gene rp49. Genotypes are as mentioned. Data are represented as mean ± SD. P values (*P < 0.05, **P < 0.01, ***P < 1 × 10−3) were obtained by unpaired Student’s t test (two-tailed) with Welch’s correction (B, E, F, I, L, P, and Q). Scale bars, 50 μm.

PCs of HSD-fed flies exhibit altered lipid metabolism and increased FAO. (A) Schematic representation demonstrating the relation between major processes involved in lipid and carbohydrate metabolism in Drosophila cells. For lipid metabolism, these processes include uptake of neutral lipids from the lypophorins by lipophorin receptors (LpR1/LpR2), lipogenesis, lipolysis, de novo fatty acid synthesis, and mobilization of fatty acids (FA) into mitochondria for FAO to feed into the TCA cycle. The enzymes involved in these processes are marked in red. Import of glucose through the glucose transporter, followed by glycolysis leads to the production of pyruvate that enters the mitochondria to support TCA cycle. (B) Changes in the levels of transcripts for the genes involved in lipogenesis, lipolysis, and de novo fatty acid synthesis in the RNA isolated from PCs and cardiac tubes of HSD-fed flies as compared with that in ND-fed flies. (C and D) Increase in the levels of lipid accumulation (BODIPY staining; green) in the PCs of HSD-fed flies (D) as compared with those reared on ND (C). (E) Quantification of the mean fluorescence intensity for BODIPY staining in the PCs flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (F) Increase in TAG levels in the PCs and cardiac tube of HSD-fed flies as compared to controls. (G–H′) Increase in the levels of free fatty acid (blue; Nile Blue A staining) in the PCs of HSD-fed flies (H and H′) as compared to those reared on ND (G and G′). G and H show Nile Blue A expression in grayscale; G′ and H′ represent the same images in blue channel. (I) Quantification of the mean fluorescence intensity for Nile Blue A staining in the PCs flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (J and K) Increase in the reporter GFP expression (green) for Hnf-Gal4 in the PCs of HSD-fed flies (K) as compared with those reared on ND (J). Phalloidin (red) marks the cardiac tube and the alary muscles. (L) Quantification of the mean fluorescence intensity for Hnf-Gal4,UAS-mCD8GFP expression in the PCs of ND or HSD-fed flies. The dots represent the number of PCs analyzed for each genotype. (M) Schematic diagram showing the different enzymes involved in the FAO pathway. (N and O) Increase in the reporter YFP expression for scully in the PCs of HSD-fed flies (O) as compared to those fed on ND (N). (P) Quantification of the mean fluorescence intensity for scully-YFP expression in the PCs of flies reared on either ND or HSD. The dots represent the number of PCs analyzed for each genotype. (Q) Increase in the transcript levels of the genes encoding different enzymes involved in FAO in the RNA isolated from PCs and cardiac tube of flies reared on HSD as compared with those reared on ND. The transcript levels are normalized to that of the constitutive ribosomal gene rp49. Genotypes are as mentioned. Data are represented as mean ± SD. P values (*P < 0.05, **P < 0.01, ***P < 1 × 10−3) were obtained by unpaired Student’s t test (two-tailed) with Welch’s correction (B, E, F, I, L, P, and Q). Scale bars, 50 μm.

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