Limits...
The Neuropeptide Allatostatin A Regulates Metabolism and Feeding Decisions in Drosophila.

Hentze JL, Carlsson MA, Kondo S, Nässel DR, Rewitz KF - Sci Rep (2015)

Bottom Line: Silencing of Dar-2 in these cells results in changes in gene expression and physiology associated with reduced DILP and AKH signaling and animals lacking AstA accumulate high lipid levels.Furthermore, AstA and Dar-2 are regulated differentially by dietary carbohydrates and protein and AstA-neuronal activity modulates feeding choices between these types of nutrients.Our results suggest that AstA is involved in assigning value to these nutrients to coordinate metabolic and feeding decisions, responses that are important to balance food intake according to metabolic needs.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, Roskilde 4000, Denmark [2] Department of Biology, University of Copenhagen, Universitetsparken 15, Copenhagen 2100, Denmark.

ABSTRACT
Coordinating metabolism and feeding is important to avoid obesity and metabolic diseases, yet the underlying mechanisms, balancing nutrient intake and metabolic expenditure, are poorly understood. Several mechanisms controlling these processes are conserved in Drosophila, where homeostasis and energy mobilization are regulated by the glucagon-related adipokinetic hormone (AKH) and the Drosophila insulin-like peptides (DILPs). Here, we provide evidence that the Drosophila neuropeptide Allatostatin A (AstA) regulates AKH and DILP signaling. The AstA receptor gene, Dar-2, is expressed in both the insulin and AKH producing cells. Silencing of Dar-2 in these cells results in changes in gene expression and physiology associated with reduced DILP and AKH signaling and animals lacking AstA accumulate high lipid levels. This suggests that AstA is regulating the balance between DILP and AKH, believed to be important for the maintenance of nutrient homeostasis in response to changing ratios of dietary sugar and protein. Furthermore, AstA and Dar-2 are regulated differentially by dietary carbohydrates and protein and AstA-neuronal activity modulates feeding choices between these types of nutrients. Our results suggest that AstA is involved in assigning value to these nutrients to coordinate metabolic and feeding decisions, responses that are important to balance food intake according to metabolic needs.

No MeSH data available.


Related in: MedlinePlus

AstA regulates expression of genes related to AKH and DILP signaling and starvation resistance.(A,B) Expression of key metabolic genes related to AKH (A) and DILP (B) signaling in flies with increased (AstA > NaChBac) or decreased (AstA > TeTxLC.tnt) AstA neuron activity. Changes in expression of several DILP and AKH related genes in AstA > NaChBac and AstA > TeTxLC.tnt animals, indicate that AstA affects DILP and AKH signaling. Ctrl: AstA-Gal4/+. (C) Starvation resistance in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) compared to AstASK1/+ heterozygous flies and controls (y2cho2v1, y1w1118 and y2cho2v1 x y1w1118: offspring from crossing these lines). AstASK1 and AstASK1/Df(3R)BSC519 flies were significantly starvation resistant compared to AstASK1/+ heterozygous flies and controls (logrank test: P < 0.0001). (D) Expression of the AKH and DILP target gene tobi in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) or Akh (AkhSK1). Controls are the same as in C. Error bars indicate standard errors (n = 3–5) (E) Starvation resistance in response to Akh overexpression (Akh > Akh), Dar-2 knock down (Akh > Dar-2-RNAi), Dar-2 knock down and combined with overexpression of Akh (Akh > Akh, Dar-2-RNAi), Akh knock down (Akh > Akh-RNAi) or Akh and Dar-2 knocked down simultaneously (Akh > Akh-RNAi, Dar-2-RNAi). Increased starvation resistance of Akh > Dar-2-RNAi animals compared to the control indicates that knock down of Dar-2 in the APCs reduces AKH signaling. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the control in all starvation experiments (logrank test: P < 0.0001). Likewise Akh > Akh flies were significantly starvation-sensitive (logrank test: P < 0.0001). (F) Starvation resistance in flies with reduced Dar-2 expression in the IPCs (dilp2 > Dar-2-RNAi) or the DAR-2 producing cells (Dar-2 > Dar-2-RNAi). Increased starvation resistance of dilp2 > Dar-2-RNAi indicates reduced insulin signaling in these animals. Together, this suggests that AstA is a positive regulator of both AKH and DILP. Consistently, starvation resistance was also increased in Dar-2 > Dar-2-RNAi animals with reduced Dar-2 expression in cells expressing the receptor, including the APCs and IPCs. UAS-Dicer2 was included since efficient neuronal knock down often requires overexpression of Dicer2. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the wild type control in all starvation experiments (logrank test: P < 0.0001). *: P < 0.05; **: P < 0.01; ***: P < 0.001 (Student’s t-test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4485031&req=5

f2: AstA regulates expression of genes related to AKH and DILP signaling and starvation resistance.(A,B) Expression of key metabolic genes related to AKH (A) and DILP (B) signaling in flies with increased (AstA > NaChBac) or decreased (AstA > TeTxLC.tnt) AstA neuron activity. Changes in expression of several DILP and AKH related genes in AstA > NaChBac and AstA > TeTxLC.tnt animals, indicate that AstA affects DILP and AKH signaling. Ctrl: AstA-Gal4/+. (C) Starvation resistance in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) compared to AstASK1/+ heterozygous flies and controls (y2cho2v1, y1w1118 and y2cho2v1 x y1w1118: offspring from crossing these lines). AstASK1 and AstASK1/Df(3R)BSC519 flies were significantly starvation resistant compared to AstASK1/+ heterozygous flies and controls (logrank test: P < 0.0001). (D) Expression of the AKH and DILP target gene tobi in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) or Akh (AkhSK1). Controls are the same as in C. Error bars indicate standard errors (n = 3–5) (E) Starvation resistance in response to Akh overexpression (Akh > Akh), Dar-2 knock down (Akh > Dar-2-RNAi), Dar-2 knock down and combined with overexpression of Akh (Akh > Akh, Dar-2-RNAi), Akh knock down (Akh > Akh-RNAi) or Akh and Dar-2 knocked down simultaneously (Akh > Akh-RNAi, Dar-2-RNAi). Increased starvation resistance of Akh > Dar-2-RNAi animals compared to the control indicates that knock down of Dar-2 in the APCs reduces AKH signaling. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the control in all starvation experiments (logrank test: P < 0.0001). Likewise Akh > Akh flies were significantly starvation-sensitive (logrank test: P < 0.0001). (F) Starvation resistance in flies with reduced Dar-2 expression in the IPCs (dilp2 > Dar-2-RNAi) or the DAR-2 producing cells (Dar-2 > Dar-2-RNAi). Increased starvation resistance of dilp2 > Dar-2-RNAi indicates reduced insulin signaling in these animals. Together, this suggests that AstA is a positive regulator of both AKH and DILP. Consistently, starvation resistance was also increased in Dar-2 > Dar-2-RNAi animals with reduced Dar-2 expression in cells expressing the receptor, including the APCs and IPCs. UAS-Dicer2 was included since efficient neuronal knock down often requires overexpression of Dicer2. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the wild type control in all starvation experiments (logrank test: P < 0.0001). *: P < 0.05; **: P < 0.01; ***: P < 0.001 (Student’s t-test).

Mentions: To investigate whether AstA regulates DILP and AKH signaling, expression of TeTxLC.tnt, the tetanus toxin light chain, which inhibits neurotransmitter exocytosis28, and NaChBac, a bacterial sodium channel that increases neuronal excitability29, was targeted to the AstA-producing neurons using AstA-Gal4 (AstA>). Previously, it has been shown that expression of NaChBac using AstA>, which expresses Gal4 specifically in AstA-positive neurons, is sufficient to change the activity of the AstA neurons18. To examine the effects of AstA neuronal activity on APC and IPC activities, we measured changes in expression of Akh, dilp2 and dilp3, and metabolic genes that are influenced by AKH and DILP signaling. Although the expression of Akh was not influenced in AstA > TeTxLC.tnt and AstA > NaChBac animals, the expression of the AKH receptor gene (akhr) was increased in AstA > TeTxLC.tnt animals where the activity of AstA-neurons is inhibited (Fig. 2A). Increased akhr expression may indicate an upregulation of the receptor in response to reduced levels of AKH in circulation. Moreover, activation of the AstA-neurons (AstA > NaChBac) induced target of brain insulin (tobi), an α-glucosidase homolog which is stimulated by both AKH and the DILPs released from the IPCs30. Activation of the AstA neurons also promoted the expression of both dilp2 and dilp3 consistent with the increased expression of tobi (Fig. 2B). Although dilp2 was also upregulated by inhibition of the AstA neurons (AstA > TeTxLC.tnt), a dramatic drop in dilp3 expression was observed under these conditions. This suggests that AstA neuronal activity influences dilp expression in the IPCs, and especially dilp3 seems to be tightly associated with the activity the AstA producing neurons. In comparison, the moderate upregulation of dilp2 expression by both activation and inactivation of AstA neurons may indicate a more indirect and perhaps a compensatory regulation of dilp2 expression by AstA neuronal activity. The transcription of eIF4E-binding protein (4EBP), encoding an inhibitor of translation which is suppressed by DILP signaling3132, was not significantly changed.


The Neuropeptide Allatostatin A Regulates Metabolism and Feeding Decisions in Drosophila.

Hentze JL, Carlsson MA, Kondo S, Nässel DR, Rewitz KF - Sci Rep (2015)

AstA regulates expression of genes related to AKH and DILP signaling and starvation resistance.(A,B) Expression of key metabolic genes related to AKH (A) and DILP (B) signaling in flies with increased (AstA > NaChBac) or decreased (AstA > TeTxLC.tnt) AstA neuron activity. Changes in expression of several DILP and AKH related genes in AstA > NaChBac and AstA > TeTxLC.tnt animals, indicate that AstA affects DILP and AKH signaling. Ctrl: AstA-Gal4/+. (C) Starvation resistance in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) compared to AstASK1/+ heterozygous flies and controls (y2cho2v1, y1w1118 and y2cho2v1 x y1w1118: offspring from crossing these lines). AstASK1 and AstASK1/Df(3R)BSC519 flies were significantly starvation resistant compared to AstASK1/+ heterozygous flies and controls (logrank test: P < 0.0001). (D) Expression of the AKH and DILP target gene tobi in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) or Akh (AkhSK1). Controls are the same as in C. Error bars indicate standard errors (n = 3–5) (E) Starvation resistance in response to Akh overexpression (Akh > Akh), Dar-2 knock down (Akh > Dar-2-RNAi), Dar-2 knock down and combined with overexpression of Akh (Akh > Akh, Dar-2-RNAi), Akh knock down (Akh > Akh-RNAi) or Akh and Dar-2 knocked down simultaneously (Akh > Akh-RNAi, Dar-2-RNAi). Increased starvation resistance of Akh > Dar-2-RNAi animals compared to the control indicates that knock down of Dar-2 in the APCs reduces AKH signaling. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the control in all starvation experiments (logrank test: P < 0.0001). Likewise Akh > Akh flies were significantly starvation-sensitive (logrank test: P < 0.0001). (F) Starvation resistance in flies with reduced Dar-2 expression in the IPCs (dilp2 > Dar-2-RNAi) or the DAR-2 producing cells (Dar-2 > Dar-2-RNAi). Increased starvation resistance of dilp2 > Dar-2-RNAi indicates reduced insulin signaling in these animals. Together, this suggests that AstA is a positive regulator of both AKH and DILP. Consistently, starvation resistance was also increased in Dar-2 > Dar-2-RNAi animals with reduced Dar-2 expression in cells expressing the receptor, including the APCs and IPCs. UAS-Dicer2 was included since efficient neuronal knock down often requires overexpression of Dicer2. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the wild type control in all starvation experiments (logrank test: P < 0.0001). *: P < 0.05; **: P < 0.01; ***: P < 0.001 (Student’s t-test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4485031&req=5

f2: AstA regulates expression of genes related to AKH and DILP signaling and starvation resistance.(A,B) Expression of key metabolic genes related to AKH (A) and DILP (B) signaling in flies with increased (AstA > NaChBac) or decreased (AstA > TeTxLC.tnt) AstA neuron activity. Changes in expression of several DILP and AKH related genes in AstA > NaChBac and AstA > TeTxLC.tnt animals, indicate that AstA affects DILP and AKH signaling. Ctrl: AstA-Gal4/+. (C) Starvation resistance in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) compared to AstASK1/+ heterozygous flies and controls (y2cho2v1, y1w1118 and y2cho2v1 x y1w1118: offspring from crossing these lines). AstASK1 and AstASK1/Df(3R)BSC519 flies were significantly starvation resistant compared to AstASK1/+ heterozygous flies and controls (logrank test: P < 0.0001). (D) Expression of the AKH and DILP target gene tobi in flies lacking AstA (AstASK1 and AstASK1/Df(3R)BSC519) or Akh (AkhSK1). Controls are the same as in C. Error bars indicate standard errors (n = 3–5) (E) Starvation resistance in response to Akh overexpression (Akh > Akh), Dar-2 knock down (Akh > Dar-2-RNAi), Dar-2 knock down and combined with overexpression of Akh (Akh > Akh, Dar-2-RNAi), Akh knock down (Akh > Akh-RNAi) or Akh and Dar-2 knocked down simultaneously (Akh > Akh-RNAi, Dar-2-RNAi). Increased starvation resistance of Akh > Dar-2-RNAi animals compared to the control indicates that knock down of Dar-2 in the APCs reduces AKH signaling. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the control in all starvation experiments (logrank test: P < 0.0001). Likewise Akh > Akh flies were significantly starvation-sensitive (logrank test: P < 0.0001). (F) Starvation resistance in flies with reduced Dar-2 expression in the IPCs (dilp2 > Dar-2-RNAi) or the DAR-2 producing cells (Dar-2 > Dar-2-RNAi). Increased starvation resistance of dilp2 > Dar-2-RNAi indicates reduced insulin signaling in these animals. Together, this suggests that AstA is a positive regulator of both AKH and DILP. Consistently, starvation resistance was also increased in Dar-2 > Dar-2-RNAi animals with reduced Dar-2 expression in cells expressing the receptor, including the APCs and IPCs. UAS-Dicer2 was included since efficient neuronal knock down often requires overexpression of Dicer2. Ctrl: UAS-Dicer2, UAS-Dar-2-RNAi/+. All RNAi flies were significantly starvation resistant compared to the wild type control in all starvation experiments (logrank test: P < 0.0001). *: P < 0.05; **: P < 0.01; ***: P < 0.001 (Student’s t-test).
Mentions: To investigate whether AstA regulates DILP and AKH signaling, expression of TeTxLC.tnt, the tetanus toxin light chain, which inhibits neurotransmitter exocytosis28, and NaChBac, a bacterial sodium channel that increases neuronal excitability29, was targeted to the AstA-producing neurons using AstA-Gal4 (AstA>). Previously, it has been shown that expression of NaChBac using AstA>, which expresses Gal4 specifically in AstA-positive neurons, is sufficient to change the activity of the AstA neurons18. To examine the effects of AstA neuronal activity on APC and IPC activities, we measured changes in expression of Akh, dilp2 and dilp3, and metabolic genes that are influenced by AKH and DILP signaling. Although the expression of Akh was not influenced in AstA > TeTxLC.tnt and AstA > NaChBac animals, the expression of the AKH receptor gene (akhr) was increased in AstA > TeTxLC.tnt animals where the activity of AstA-neurons is inhibited (Fig. 2A). Increased akhr expression may indicate an upregulation of the receptor in response to reduced levels of AKH in circulation. Moreover, activation of the AstA-neurons (AstA > NaChBac) induced target of brain insulin (tobi), an α-glucosidase homolog which is stimulated by both AKH and the DILPs released from the IPCs30. Activation of the AstA neurons also promoted the expression of both dilp2 and dilp3 consistent with the increased expression of tobi (Fig. 2B). Although dilp2 was also upregulated by inhibition of the AstA neurons (AstA > TeTxLC.tnt), a dramatic drop in dilp3 expression was observed under these conditions. This suggests that AstA neuronal activity influences dilp expression in the IPCs, and especially dilp3 seems to be tightly associated with the activity the AstA producing neurons. In comparison, the moderate upregulation of dilp2 expression by both activation and inactivation of AstA neurons may indicate a more indirect and perhaps a compensatory regulation of dilp2 expression by AstA neuronal activity. The transcription of eIF4E-binding protein (4EBP), encoding an inhibitor of translation which is suppressed by DILP signaling3132, was not significantly changed.

Bottom Line: Silencing of Dar-2 in these cells results in changes in gene expression and physiology associated with reduced DILP and AKH signaling and animals lacking AstA accumulate high lipid levels.Furthermore, AstA and Dar-2 are regulated differentially by dietary carbohydrates and protein and AstA-neuronal activity modulates feeding choices between these types of nutrients.Our results suggest that AstA is involved in assigning value to these nutrients to coordinate metabolic and feeding decisions, responses that are important to balance food intake according to metabolic needs.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Science, Systems and Models, Roskilde University, Universitetsvej 1, Roskilde 4000, Denmark [2] Department of Biology, University of Copenhagen, Universitetsparken 15, Copenhagen 2100, Denmark.

ABSTRACT
Coordinating metabolism and feeding is important to avoid obesity and metabolic diseases, yet the underlying mechanisms, balancing nutrient intake and metabolic expenditure, are poorly understood. Several mechanisms controlling these processes are conserved in Drosophila, where homeostasis and energy mobilization are regulated by the glucagon-related adipokinetic hormone (AKH) and the Drosophila insulin-like peptides (DILPs). Here, we provide evidence that the Drosophila neuropeptide Allatostatin A (AstA) regulates AKH and DILP signaling. The AstA receptor gene, Dar-2, is expressed in both the insulin and AKH producing cells. Silencing of Dar-2 in these cells results in changes in gene expression and physiology associated with reduced DILP and AKH signaling and animals lacking AstA accumulate high lipid levels. This suggests that AstA is regulating the balance between DILP and AKH, believed to be important for the maintenance of nutrient homeostasis in response to changing ratios of dietary sugar and protein. Furthermore, AstA and Dar-2 are regulated differentially by dietary carbohydrates and protein and AstA-neuronal activity modulates feeding choices between these types of nutrients. Our results suggest that AstA is involved in assigning value to these nutrients to coordinate metabolic and feeding decisions, responses that are important to balance food intake according to metabolic needs.

No MeSH data available.


Related in: MedlinePlus