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Pannexin 1 is required for full activation of insulin-stimulated glucose uptake in adipocytes.

Adamson SE, Meher AK, Chiu YH, Sandilos JK, Oberholtzer NP, Walker NN, Hargett SR, Seaman SA, Peirce-Cottler SM, Isakson BE, McNamara CA, Keller SR, Harris TE, Bayliss DA, Leitinger N - Mol Metab (2015)

Bottom Line: Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients.Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP.We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA ; Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.

ABSTRACT

Objective: Defective glucose uptake in adipocytes leads to impaired metabolic homeostasis and insulin resistance, hallmarks of type 2 diabetes. Extracellular ATP-derived nucleotides and nucleosides are important regulators of adipocyte function, but the pathway for controlled ATP release from adipocytes is unknown. Here, we investigated whether Pannexin 1 (Panx1) channels control ATP release from adipocytes and contribute to metabolic homeostasis.

Methods: We assessed Panx1 functionality in cultured 3T3-L1 adipocytes and in adipocytes isolated from murine white adipose tissue by measuring ATP release in response to known activators of Panx1 channels. Glucose uptake in cultured 3T3-L1 adipocytes was measured in the presence of Panx1 pharmacologic inhibitors and in adipocytes isolated from white adipose tissue from wildtype (WT) or adipocyte-specific Panx1 knockout (AdipPanx1 KO) mice generated in our laboratory. We performed in vivo glucose uptake studies in chow fed WT and AdipPanx1 KO mice and assessed insulin resistance in WT and AdipPanx1 KO mice fed a high fat diet for 12 weeks. Panx1 channel function was assessed in response to insulin by performing electrophysiologic recordings in a heterologous expression system. Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients.

Results: Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP. Pharmacologic inhibition or selective genetic deletion of Panx1 from adipocytes decreased insulin-induced glucose uptake in vitro and in vivo and exacerbated diet-induced insulin resistance in mice. Further, we identify insulin as a novel activator of Panx1 channels. In obese humans Panx1 expression in adipose tissue is increased and correlates with the degree of insulin resistance.

Conclusions: We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis.

No MeSH data available.


Related in: MedlinePlus

Pannexin 1 expression in human adipose tissue is associated with obesity and insulin resistance. (A) Data from NCBI gene array (GDS1498[ACCN]) [49] were analyzed for Panx1 expression in subcutaneous adipose tissue from lean male (n = 10), lean female (n = 10), and obese male (n = 9) and obese female (n = 10) human subjects. Data are normalized to lean samples, each point represents one human subject, error bars indicate s.d. *p < 0.0001 by 2 way ANOVA with Sidak's multiple comparison test. (B) Omental fat samples were obtained from human subjects prior to bariatric surgery and analyzed for Panx1 mRNA levels normalized to 18S mRNA. The average of all samples was set to 1 and log 10 values of Panx1 mRNA were plotted against the blood glucose levels of patients at time of surgery, revealing a positive and significant correlation (r2 = 0.181 and p = 0.04 by linear regression). The correlation of Panx1 levels with blood glucose levels was particularly pronounced in Caucasian females (r2 = 0.56, n = 11, black line). Each point represents one human subject, female subjects are shown as gray (non-Caucasian) and black (Caucasian) squares, male subjects as white squares. (C) Samples from B were grouped into tertiles based on low (<0.5 fold, n = 8), medium (0.5–1.5 fold, n = 10), and high Panx1 expression (>1.5 fold, n = 5) and plotted against HOMA-IR, a clinical measure of insulin resistance. *p < 0.02 by Student's t-test. Each point represents one human subject; error bars represent s.e.m.
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fig5: Pannexin 1 expression in human adipose tissue is associated with obesity and insulin resistance. (A) Data from NCBI gene array (GDS1498[ACCN]) [49] were analyzed for Panx1 expression in subcutaneous adipose tissue from lean male (n = 10), lean female (n = 10), and obese male (n = 9) and obese female (n = 10) human subjects. Data are normalized to lean samples, each point represents one human subject, error bars indicate s.d. *p < 0.0001 by 2 way ANOVA with Sidak's multiple comparison test. (B) Omental fat samples were obtained from human subjects prior to bariatric surgery and analyzed for Panx1 mRNA levels normalized to 18S mRNA. The average of all samples was set to 1 and log 10 values of Panx1 mRNA were plotted against the blood glucose levels of patients at time of surgery, revealing a positive and significant correlation (r2 = 0.181 and p = 0.04 by linear regression). The correlation of Panx1 levels with blood glucose levels was particularly pronounced in Caucasian females (r2 = 0.56, n = 11, black line). Each point represents one human subject, female subjects are shown as gray (non-Caucasian) and black (Caucasian) squares, male subjects as white squares. (C) Samples from B were grouped into tertiles based on low (<0.5 fold, n = 8), medium (0.5–1.5 fold, n = 10), and high Panx1 expression (>1.5 fold, n = 5) and plotted against HOMA-IR, a clinical measure of insulin resistance. *p < 0.02 by Student's t-test. Each point represents one human subject; error bars represent s.e.m.

Mentions: Neither expression levels nor potential functional roles of Panx1 in adipose tissue have been reported in the context of human pathology. A previous study compared global gene expression in subcutaneous adipose tissue between lean and obese Pima Indians using gene arrays [49]. Data extracted from the data sets deposited at NCBI (GDS1498[ACCN]) demonstrate that Panx1 expression in both males and females was significantly increased in obese compared to lean subjects (Figure 5A). Thus, we examined Panx1 expression in visceral adipose tissue obtained from 23 morbidly obese patients during bariatric surgery. We found that relative Panx1 mRNA expression levels significantly correlated with fasting blood glucose levels, and this correlation was especially strong in Caucasian females (Figure 5B). Subjects in the tertile with the highest relative Panx1 mRNA levels also had significantly higher HOMA-IR scores (a measure of insulin resistance) (Figure 5C). These data suggest that Panx1 may also play a role in adipocyte metabolism in humans, in a way that increased Panx1 expression may help counterbalance decreasing insulin sensitivity.


Pannexin 1 is required for full activation of insulin-stimulated glucose uptake in adipocytes.

Adamson SE, Meher AK, Chiu YH, Sandilos JK, Oberholtzer NP, Walker NN, Hargett SR, Seaman SA, Peirce-Cottler SM, Isakson BE, McNamara CA, Keller SR, Harris TE, Bayliss DA, Leitinger N - Mol Metab (2015)

Pannexin 1 expression in human adipose tissue is associated with obesity and insulin resistance. (A) Data from NCBI gene array (GDS1498[ACCN]) [49] were analyzed for Panx1 expression in subcutaneous adipose tissue from lean male (n = 10), lean female (n = 10), and obese male (n = 9) and obese female (n = 10) human subjects. Data are normalized to lean samples, each point represents one human subject, error bars indicate s.d. *p < 0.0001 by 2 way ANOVA with Sidak's multiple comparison test. (B) Omental fat samples were obtained from human subjects prior to bariatric surgery and analyzed for Panx1 mRNA levels normalized to 18S mRNA. The average of all samples was set to 1 and log 10 values of Panx1 mRNA were plotted against the blood glucose levels of patients at time of surgery, revealing a positive and significant correlation (r2 = 0.181 and p = 0.04 by linear regression). The correlation of Panx1 levels with blood glucose levels was particularly pronounced in Caucasian females (r2 = 0.56, n = 11, black line). Each point represents one human subject, female subjects are shown as gray (non-Caucasian) and black (Caucasian) squares, male subjects as white squares. (C) Samples from B were grouped into tertiles based on low (<0.5 fold, n = 8), medium (0.5–1.5 fold, n = 10), and high Panx1 expression (>1.5 fold, n = 5) and plotted against HOMA-IR, a clinical measure of insulin resistance. *p < 0.02 by Student's t-test. Each point represents one human subject; error bars represent s.e.m.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4563021&req=5

fig5: Pannexin 1 expression in human adipose tissue is associated with obesity and insulin resistance. (A) Data from NCBI gene array (GDS1498[ACCN]) [49] were analyzed for Panx1 expression in subcutaneous adipose tissue from lean male (n = 10), lean female (n = 10), and obese male (n = 9) and obese female (n = 10) human subjects. Data are normalized to lean samples, each point represents one human subject, error bars indicate s.d. *p < 0.0001 by 2 way ANOVA with Sidak's multiple comparison test. (B) Omental fat samples were obtained from human subjects prior to bariatric surgery and analyzed for Panx1 mRNA levels normalized to 18S mRNA. The average of all samples was set to 1 and log 10 values of Panx1 mRNA were plotted against the blood glucose levels of patients at time of surgery, revealing a positive and significant correlation (r2 = 0.181 and p = 0.04 by linear regression). The correlation of Panx1 levels with blood glucose levels was particularly pronounced in Caucasian females (r2 = 0.56, n = 11, black line). Each point represents one human subject, female subjects are shown as gray (non-Caucasian) and black (Caucasian) squares, male subjects as white squares. (C) Samples from B were grouped into tertiles based on low (<0.5 fold, n = 8), medium (0.5–1.5 fold, n = 10), and high Panx1 expression (>1.5 fold, n = 5) and plotted against HOMA-IR, a clinical measure of insulin resistance. *p < 0.02 by Student's t-test. Each point represents one human subject; error bars represent s.e.m.
Mentions: Neither expression levels nor potential functional roles of Panx1 in adipose tissue have been reported in the context of human pathology. A previous study compared global gene expression in subcutaneous adipose tissue between lean and obese Pima Indians using gene arrays [49]. Data extracted from the data sets deposited at NCBI (GDS1498[ACCN]) demonstrate that Panx1 expression in both males and females was significantly increased in obese compared to lean subjects (Figure 5A). Thus, we examined Panx1 expression in visceral adipose tissue obtained from 23 morbidly obese patients during bariatric surgery. We found that relative Panx1 mRNA expression levels significantly correlated with fasting blood glucose levels, and this correlation was especially strong in Caucasian females (Figure 5B). Subjects in the tertile with the highest relative Panx1 mRNA levels also had significantly higher HOMA-IR scores (a measure of insulin resistance) (Figure 5C). These data suggest that Panx1 may also play a role in adipocyte metabolism in humans, in a way that increased Panx1 expression may help counterbalance decreasing insulin sensitivity.

Bottom Line: Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients.Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP.We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Virginia, Charlottesville, VA 22908, USA ; Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.

ABSTRACT

Objective: Defective glucose uptake in adipocytes leads to impaired metabolic homeostasis and insulin resistance, hallmarks of type 2 diabetes. Extracellular ATP-derived nucleotides and nucleosides are important regulators of adipocyte function, but the pathway for controlled ATP release from adipocytes is unknown. Here, we investigated whether Pannexin 1 (Panx1) channels control ATP release from adipocytes and contribute to metabolic homeostasis.

Methods: We assessed Panx1 functionality in cultured 3T3-L1 adipocytes and in adipocytes isolated from murine white adipose tissue by measuring ATP release in response to known activators of Panx1 channels. Glucose uptake in cultured 3T3-L1 adipocytes was measured in the presence of Panx1 pharmacologic inhibitors and in adipocytes isolated from white adipose tissue from wildtype (WT) or adipocyte-specific Panx1 knockout (AdipPanx1 KO) mice generated in our laboratory. We performed in vivo glucose uptake studies in chow fed WT and AdipPanx1 KO mice and assessed insulin resistance in WT and AdipPanx1 KO mice fed a high fat diet for 12 weeks. Panx1 channel function was assessed in response to insulin by performing electrophysiologic recordings in a heterologous expression system. Finally, we measured Panx1 mRNA in human visceral adipose tissue samples by qRT-PCR and compared expression levels with glucose levels and HOMA-IR measurements in patients.

Results: Our data show that adipocytes express functional Pannexin 1 (Panx1) channels that can be activated to release ATP. Pharmacologic inhibition or selective genetic deletion of Panx1 from adipocytes decreased insulin-induced glucose uptake in vitro and in vivo and exacerbated diet-induced insulin resistance in mice. Further, we identify insulin as a novel activator of Panx1 channels. In obese humans Panx1 expression in adipose tissue is increased and correlates with the degree of insulin resistance.

Conclusions: We show that Panx1 channel activity regulates insulin-stimulated glucose uptake in adipocytes and thus contributes to control of metabolic homeostasis.

No MeSH data available.


Related in: MedlinePlus