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Regulation of dipeptidyl peptidase 4 production in adipocytes by glucose.

Das SS, Hayashi H, Sato T, Yamada R, Hiratsuka M, Hirasawa N - Diabetes Metab Syndr Obes (2014)

Bottom Line: However, this difference gradually disappeared over 6 weeks.The stimulation of adipocytes with TNF-α increased the release of DPP4 irrespective of glucose concentration.Our results suggest that the observed increase in serum DPP4 levels may be attributed to increased production of DPP4 in adipocytes and an enhancement in TNF-α-induced release.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, Japan.

ABSTRACT

Objective: Type 1 and 2 diabetes are characterized by elevated blood glucose levels and increased dipeptidyl peptidase 4 (DPP4) activity levels in the serum. However, previous studies reported a negative correlation between glucose concentrations and DPP4 levels. The purpose of this study was to elucidate the connection between glucose and DPP4 in adipocytes under physiological and diabetic conditions, because DPP4 is an adipokine.

Methods: Blood glucose and serum DPP4 levels were measured, and adipocytes were collected from mice under normal, high-fat diet fed, and diabetic conditions. The adipocytes obtained were incubated for 24 hours in medium containing 5.5 or 25 mM glucose, and 3T3-L1 preadipocytes were differentiated under 5.5 or 25 mM glucose. Adipocytes from mice and 3T3-L1 were stimulated by tumor necrosis factor-α (TNF-α) for 24 hours. The levels of released and intracellular DPP4 were determined by enzyme-linked immunosorbent assay.

Results: Mice fed high-fat diet had lower serum DPP4 levels in the first and second week than controls. However, this difference gradually disappeared over 6 weeks. The differentiation of 3T3-L1 adipocytes under 25 mM glucose produced lower DPP4 levels than those differentiated under 5.5 mM; this was also observed in isolated adipocytes from mice. However, these effects of glucose were lost in adipocytes from diabetic mice, and an increase in total DPP4 levels was observed. The stimulation of adipocytes with TNF-α increased the release of DPP4 irrespective of glucose concentration.

Conclusion: The production of DPP4 in adipocytes was negatively regulated by 25 mM glucose under physiological conditions, but not in diabetic mice. Our results suggest that the observed increase in serum DPP4 levels may be attributed to increased production of DPP4 in adipocytes and an enhancement in TNF-α-induced release.

No MeSH data available.


Related in: MedlinePlus

Increased release of DPP4 in streptozotocin-induced diabetic mice.Notes: C57BL/6 mice were injected with streptozotocin to induce type 1 diabetes. (A) Body weights were measured on Day 0 and 7 days after the administration of streptozotocin. *P<0.05 versus (vs) Day 0. n=6. (B) Fasting blood glucose levels and (C) serum DPP4 levels were determined 2 and 7 days after the streptozotocin injection. **P<0.01 vs Day 0. n=6. Adipocytes prepared from (D) control and (E) type 1 diabetic mice were incubated for 24 hours in serum-free DMEM containing 5.5 (closed columns) or 25 mM glucose (open columns). Intracellular and released DPP4 was determined by enzyme-linked immunosorbent assay. n=3. *P<0.05 and †P<0.05 vs release and intracellular groups. (F) Adipocytes obtained from high-fat diet-fed mice fed for 4 weeks were incubated in 5.5 (closed columns) or 25 mM glucose (open columns), and intracellular and released DPP4 levels were determined, as described above. †P<0.05 vs between 5.5 and 25 mM glucose. n=3. DPP4 mRNA levels in different tissues obtained normal mice (closed columns) and diabetic mice (open columns) (G) 48 hours and (H) 4 weeks after the administration of STZ. *P<0.05 and ††P<0.01 vs control tissues. n=4. Housekeeping gene; PPIA. The control values were set to 1.0.Abbreviations: AU, arbitrary units; DPP4, dipeptidyl peptidase 4; mRNA, messenger ribonucleic acid; PPIA, peptidylprolyl isomerase A; STZ, streptozotocin.
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f4-dmso-7-185: Increased release of DPP4 in streptozotocin-induced diabetic mice.Notes: C57BL/6 mice were injected with streptozotocin to induce type 1 diabetes. (A) Body weights were measured on Day 0 and 7 days after the administration of streptozotocin. *P<0.05 versus (vs) Day 0. n=6. (B) Fasting blood glucose levels and (C) serum DPP4 levels were determined 2 and 7 days after the streptozotocin injection. **P<0.01 vs Day 0. n=6. Adipocytes prepared from (D) control and (E) type 1 diabetic mice were incubated for 24 hours in serum-free DMEM containing 5.5 (closed columns) or 25 mM glucose (open columns). Intracellular and released DPP4 was determined by enzyme-linked immunosorbent assay. n=3. *P<0.05 and †P<0.05 vs release and intracellular groups. (F) Adipocytes obtained from high-fat diet-fed mice fed for 4 weeks were incubated in 5.5 (closed columns) or 25 mM glucose (open columns), and intracellular and released DPP4 levels were determined, as described above. †P<0.05 vs between 5.5 and 25 mM glucose. n=3. DPP4 mRNA levels in different tissues obtained normal mice (closed columns) and diabetic mice (open columns) (G) 48 hours and (H) 4 weeks after the administration of STZ. *P<0.05 and ††P<0.01 vs control tissues. n=4. Housekeeping gene; PPIA. The control values were set to 1.0.Abbreviations: AU, arbitrary units; DPP4, dipeptidyl peptidase 4; mRNA, messenger ribonucleic acid; PPIA, peptidylprolyl isomerase A; STZ, streptozotocin.

Mentions: To clarify why the negative regulation of DPP4 expression by the higher glucose concentration was lost in high-fat diet-fed mice at 4 and 6 weeks, mice were administered streptozotocin, which caused an increase in serum glucose levels within 1 week without an increase in body weight (Figure 4A). In this model, serum DPP4 levels and blood glucose levels significantly increased 2 and 7 days after the streptozotocin injection (Figure 4B and C). Adipocytes prepared from normal and streptozotocin-treated mice (2 days after the streptozotocin injection) were incubated under the serum-free 5.5 or 25 mM glucose condition for 24 hours. Consistent with in vitro results, adipocytes from normal mice incubated under the 25 mM glucose condition also had decreased intracellular and released DPP4 levels (Figure 4D). The levels of both intracellular and released DPP4 in adipocytes from streptozotocin-treated mice (2 days after the streptozotocin injection) were higher than those from normal mice. Furthermore, the negative regulation of DPP4 by 25 mM glucose was absent (Figure 4E). The increased levels of intracellular and released DPP4 and lack of glucose regulation were also observed in adipocytes prepared from high-fat diet-fed mice (Figure 4F). An increase in the expression of DPP4 mRNA was observed in the adipose tissues of mice treated with streptozotocin for 48 hours (Figure 4G). The determination of DPP4 mRNA levels in various tissues indicated that an increase in the expression of DPP4 mRNA was only observed in the adipose tissue of streptozotocin-treated mice. The expression of DPP4 mRNA expression remained high in adipose tissue, even after the administration of streptozotocin for 4 weeks (Figure 4H).


Regulation of dipeptidyl peptidase 4 production in adipocytes by glucose.

Das SS, Hayashi H, Sato T, Yamada R, Hiratsuka M, Hirasawa N - Diabetes Metab Syndr Obes (2014)

Increased release of DPP4 in streptozotocin-induced diabetic mice.Notes: C57BL/6 mice were injected with streptozotocin to induce type 1 diabetes. (A) Body weights were measured on Day 0 and 7 days after the administration of streptozotocin. *P<0.05 versus (vs) Day 0. n=6. (B) Fasting blood glucose levels and (C) serum DPP4 levels were determined 2 and 7 days after the streptozotocin injection. **P<0.01 vs Day 0. n=6. Adipocytes prepared from (D) control and (E) type 1 diabetic mice were incubated for 24 hours in serum-free DMEM containing 5.5 (closed columns) or 25 mM glucose (open columns). Intracellular and released DPP4 was determined by enzyme-linked immunosorbent assay. n=3. *P<0.05 and †P<0.05 vs release and intracellular groups. (F) Adipocytes obtained from high-fat diet-fed mice fed for 4 weeks were incubated in 5.5 (closed columns) or 25 mM glucose (open columns), and intracellular and released DPP4 levels were determined, as described above. †P<0.05 vs between 5.5 and 25 mM glucose. n=3. DPP4 mRNA levels in different tissues obtained normal mice (closed columns) and diabetic mice (open columns) (G) 48 hours and (H) 4 weeks after the administration of STZ. *P<0.05 and ††P<0.01 vs control tissues. n=4. Housekeeping gene; PPIA. The control values were set to 1.0.Abbreviations: AU, arbitrary units; DPP4, dipeptidyl peptidase 4; mRNA, messenger ribonucleic acid; PPIA, peptidylprolyl isomerase A; STZ, streptozotocin.
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f4-dmso-7-185: Increased release of DPP4 in streptozotocin-induced diabetic mice.Notes: C57BL/6 mice were injected with streptozotocin to induce type 1 diabetes. (A) Body weights were measured on Day 0 and 7 days after the administration of streptozotocin. *P<0.05 versus (vs) Day 0. n=6. (B) Fasting blood glucose levels and (C) serum DPP4 levels were determined 2 and 7 days after the streptozotocin injection. **P<0.01 vs Day 0. n=6. Adipocytes prepared from (D) control and (E) type 1 diabetic mice were incubated for 24 hours in serum-free DMEM containing 5.5 (closed columns) or 25 mM glucose (open columns). Intracellular and released DPP4 was determined by enzyme-linked immunosorbent assay. n=3. *P<0.05 and †P<0.05 vs release and intracellular groups. (F) Adipocytes obtained from high-fat diet-fed mice fed for 4 weeks were incubated in 5.5 (closed columns) or 25 mM glucose (open columns), and intracellular and released DPP4 levels were determined, as described above. †P<0.05 vs between 5.5 and 25 mM glucose. n=3. DPP4 mRNA levels in different tissues obtained normal mice (closed columns) and diabetic mice (open columns) (G) 48 hours and (H) 4 weeks after the administration of STZ. *P<0.05 and ††P<0.01 vs control tissues. n=4. Housekeeping gene; PPIA. The control values were set to 1.0.Abbreviations: AU, arbitrary units; DPP4, dipeptidyl peptidase 4; mRNA, messenger ribonucleic acid; PPIA, peptidylprolyl isomerase A; STZ, streptozotocin.
Mentions: To clarify why the negative regulation of DPP4 expression by the higher glucose concentration was lost in high-fat diet-fed mice at 4 and 6 weeks, mice were administered streptozotocin, which caused an increase in serum glucose levels within 1 week without an increase in body weight (Figure 4A). In this model, serum DPP4 levels and blood glucose levels significantly increased 2 and 7 days after the streptozotocin injection (Figure 4B and C). Adipocytes prepared from normal and streptozotocin-treated mice (2 days after the streptozotocin injection) were incubated under the serum-free 5.5 or 25 mM glucose condition for 24 hours. Consistent with in vitro results, adipocytes from normal mice incubated under the 25 mM glucose condition also had decreased intracellular and released DPP4 levels (Figure 4D). The levels of both intracellular and released DPP4 in adipocytes from streptozotocin-treated mice (2 days after the streptozotocin injection) were higher than those from normal mice. Furthermore, the negative regulation of DPP4 by 25 mM glucose was absent (Figure 4E). The increased levels of intracellular and released DPP4 and lack of glucose regulation were also observed in adipocytes prepared from high-fat diet-fed mice (Figure 4F). An increase in the expression of DPP4 mRNA was observed in the adipose tissues of mice treated with streptozotocin for 48 hours (Figure 4G). The determination of DPP4 mRNA levels in various tissues indicated that an increase in the expression of DPP4 mRNA was only observed in the adipose tissue of streptozotocin-treated mice. The expression of DPP4 mRNA expression remained high in adipose tissue, even after the administration of streptozotocin for 4 weeks (Figure 4H).

Bottom Line: However, this difference gradually disappeared over 6 weeks.The stimulation of adipocytes with TNF-α increased the release of DPP4 irrespective of glucose concentration.Our results suggest that the observed increase in serum DPP4 levels may be attributed to increased production of DPP4 in adipocytes and an enhancement in TNF-α-induced release.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Pharmacotherapy of Life-Style Related Diseases, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, Japan.

ABSTRACT

Objective: Type 1 and 2 diabetes are characterized by elevated blood glucose levels and increased dipeptidyl peptidase 4 (DPP4) activity levels in the serum. However, previous studies reported a negative correlation between glucose concentrations and DPP4 levels. The purpose of this study was to elucidate the connection between glucose and DPP4 in adipocytes under physiological and diabetic conditions, because DPP4 is an adipokine.

Methods: Blood glucose and serum DPP4 levels were measured, and adipocytes were collected from mice under normal, high-fat diet fed, and diabetic conditions. The adipocytes obtained were incubated for 24 hours in medium containing 5.5 or 25 mM glucose, and 3T3-L1 preadipocytes were differentiated under 5.5 or 25 mM glucose. Adipocytes from mice and 3T3-L1 were stimulated by tumor necrosis factor-α (TNF-α) for 24 hours. The levels of released and intracellular DPP4 were determined by enzyme-linked immunosorbent assay.

Results: Mice fed high-fat diet had lower serum DPP4 levels in the first and second week than controls. However, this difference gradually disappeared over 6 weeks. The differentiation of 3T3-L1 adipocytes under 25 mM glucose produced lower DPP4 levels than those differentiated under 5.5 mM; this was also observed in isolated adipocytes from mice. However, these effects of glucose were lost in adipocytes from diabetic mice, and an increase in total DPP4 levels was observed. The stimulation of adipocytes with TNF-α increased the release of DPP4 irrespective of glucose concentration.

Conclusion: The production of DPP4 in adipocytes was negatively regulated by 25 mM glucose under physiological conditions, but not in diabetic mice. Our results suggest that the observed increase in serum DPP4 levels may be attributed to increased production of DPP4 in adipocytes and an enhancement in TNF-α-induced release.

No MeSH data available.


Related in: MedlinePlus