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Neprilysin, obesity and the metabolic syndrome.

Standeven KF, Hess K, Carter AM, Rice GI, Cordell PA, Balmforth AJ, Lu B, Scott DJ, Turner AJ, Hooper NM, Grant PJ - Int J Obes (Lond) (2010)

Bottom Line: In a murine model of diet-induced insulin resistance, plasma NEP levels were significantly higher in high-fat diet (HFD)-fed compared with normal chow diet (NCD)-fed animals (1642 ± 529 and 820 ± 487 pg μl(-1), respectively; P<0.01).Tissue NEP was increased in mesenteric fat in HFD compared with NCD-fed mice (P<0.05).NEP knockout mice did not display any changes in insulin resistance, glucose tolerance, or body and epididymal fat pad weight compared with wild-type mice.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiovascular and Diabetes Research, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, UK.

ABSTRACT

Objective: Neprilysin (NEP), a zinc metalloendopeptidase, has a role in blood pressure control and lipid metabolism. The present study tested the hypothesis that NEP is associated with insulin resistance and features of the metabolic syndrome (MetS) in a study of 318 healthy human subjects and in murine obesity, and investigated NEP production by adipocytes in-vitro.

Methods and results: In 318 white European males, plasma NEP was elevated in the MetS and increased progressively with increasing MetS components. Plasma NEP activity correlated with insulin, homoeostasis model assessment and body mass index (BMI) in all subjects (P<0.01). Quantitative reverse transcriptase PCR (RT-PCR) and western blotting showed that in human pre-adipocytes NEP expression is upregulated 25- to 30-fold during differentiation into adipocytes. Microarray analysis of mRNA from differentiated human adipocytes confirmed high-NEP expression comparable with adiponectin and plasminogen activator inhibitor-1. In a murine model of diet-induced insulin resistance, plasma NEP levels were significantly higher in high-fat diet (HFD)-fed compared with normal chow diet (NCD)-fed animals (1642 ± 529 and 820 ± 487 pg μl(-1), respectively; P<0.01). Tissue NEP was increased in mesenteric fat in HFD compared with NCD-fed mice (P<0.05). NEP knockout mice did not display any changes in insulin resistance, glucose tolerance, or body and epididymal fat pad weight compared with wild-type mice.

Conclusion: In humans, NEP activity correlated with BMI and measures of insulin resistance with increasing levels in subjects with multiple cardiovascular risk factors. NEP protein production in human adipocytes increased during cell differentiation and plasma and adipose tissue levels of NEP were increased in obese insulin-resistant mice. Our results indicate that NEP associates with cardiometabolic risk in the presence of insulin resistance and increases with obesity.

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NEP plasma and tissue levels in a mouse model of high-fat diet (HFD) induced insulin resistanceA: After 7 and 15 weeks of diet, mice were bled from the lateral saphenous vein and NEP protein levels were measured. Grey bar: NCD-fed mice, white bar: HFD-fed mice. Results are presented as mean±SEM from n=8 mice. * p<0.05 vs. NCD, ** p<0.01 vs. NCD, # p<0.05 vs. HFD week 7. B: Tissues were harvested after 15 weeks of diet and NEP protein levels were measured in mesenteric adipose tissue (AT), epididymal AT, perirenal AT, liver, and kidney. Grey bar: NCD-fed, white bar: HFD-fed. NEP levels are expressed as a ratio of ng NEP to mg total protein. Data are presented as median and 25th and 75th percentile from n=8 mice. *p < 0.05 vs. NCD.
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Figure 4: NEP plasma and tissue levels in a mouse model of high-fat diet (HFD) induced insulin resistanceA: After 7 and 15 weeks of diet, mice were bled from the lateral saphenous vein and NEP protein levels were measured. Grey bar: NCD-fed mice, white bar: HFD-fed mice. Results are presented as mean±SEM from n=8 mice. * p<0.05 vs. NCD, ** p<0.01 vs. NCD, # p<0.05 vs. HFD week 7. B: Tissues were harvested after 15 weeks of diet and NEP protein levels were measured in mesenteric adipose tissue (AT), epididymal AT, perirenal AT, liver, and kidney. Grey bar: NCD-fed, white bar: HFD-fed. NEP levels are expressed as a ratio of ng NEP to mg total protein. Data are presented as median and 25th and 75th percentile from n=8 mice. *p < 0.05 vs. NCD.

Mentions: Male C57BL/6J mice fed NCD or HFD, showed significant differences in weight after 6 weeks and at 14 weeks total body weight was 34.1±3.0 g and 47.6±1.8 g, respectively (p<0.05). At the end of the feeding period, there was an increase in epididymal, mesenteric and perirenal fat by 47.5%, 29.5% and 25.9% respectively, in the HFD-fed mice compared with NCD-fed mice (data not shown). Metabolic characterisation and determination of NEP levels was performed on mice after 14 weeks of diet. As described previously (27), HFD-fed mice exhibited a significant impairment in glucose tolerance compared with mice fed NCD. Consistently, insulin sensitivity was impaired at this time point (n=8; p<0.05) (data not shown). In parallel to the increase in body weight and the impairment in glucose homeostasis, plasma NEP levels were significantly higher in HFD-fed mice both at 7 and 15 weeks of diet compared to NCD-fed mice (15 weeks: HFD: 1642± 529 pg/μl, NCD: 820± 487 pg/μl; p<0.01). Furthermore the increase in NEP plasma levels comparing 7 and 15 weeks was significant in HFD-fed mice, but not in NCD-fed mice (n=8; p<0.05) (Figure 4A). NEP tissue levels at 15 weeks were significantly higher in mesenteric adipose tissue of HFD-fed mice compared with NCD-fed mice (n=8; p<0.05), but no significant changes in NEP levels in epididymal, perirenal, liver or kidney tissue were observed (Figure 4B).


Neprilysin, obesity and the metabolic syndrome.

Standeven KF, Hess K, Carter AM, Rice GI, Cordell PA, Balmforth AJ, Lu B, Scott DJ, Turner AJ, Hooper NM, Grant PJ - Int J Obes (Lond) (2010)

NEP plasma and tissue levels in a mouse model of high-fat diet (HFD) induced insulin resistanceA: After 7 and 15 weeks of diet, mice were bled from the lateral saphenous vein and NEP protein levels were measured. Grey bar: NCD-fed mice, white bar: HFD-fed mice. Results are presented as mean±SEM from n=8 mice. * p<0.05 vs. NCD, ** p<0.01 vs. NCD, # p<0.05 vs. HFD week 7. B: Tissues were harvested after 15 weeks of diet and NEP protein levels were measured in mesenteric adipose tissue (AT), epididymal AT, perirenal AT, liver, and kidney. Grey bar: NCD-fed, white bar: HFD-fed. NEP levels are expressed as a ratio of ng NEP to mg total protein. Data are presented as median and 25th and 75th percentile from n=8 mice. *p < 0.05 vs. NCD.
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Figure 4: NEP plasma and tissue levels in a mouse model of high-fat diet (HFD) induced insulin resistanceA: After 7 and 15 weeks of diet, mice were bled from the lateral saphenous vein and NEP protein levels were measured. Grey bar: NCD-fed mice, white bar: HFD-fed mice. Results are presented as mean±SEM from n=8 mice. * p<0.05 vs. NCD, ** p<0.01 vs. NCD, # p<0.05 vs. HFD week 7. B: Tissues were harvested after 15 weeks of diet and NEP protein levels were measured in mesenteric adipose tissue (AT), epididymal AT, perirenal AT, liver, and kidney. Grey bar: NCD-fed, white bar: HFD-fed. NEP levels are expressed as a ratio of ng NEP to mg total protein. Data are presented as median and 25th and 75th percentile from n=8 mice. *p < 0.05 vs. NCD.
Mentions: Male C57BL/6J mice fed NCD or HFD, showed significant differences in weight after 6 weeks and at 14 weeks total body weight was 34.1±3.0 g and 47.6±1.8 g, respectively (p<0.05). At the end of the feeding period, there was an increase in epididymal, mesenteric and perirenal fat by 47.5%, 29.5% and 25.9% respectively, in the HFD-fed mice compared with NCD-fed mice (data not shown). Metabolic characterisation and determination of NEP levels was performed on mice after 14 weeks of diet. As described previously (27), HFD-fed mice exhibited a significant impairment in glucose tolerance compared with mice fed NCD. Consistently, insulin sensitivity was impaired at this time point (n=8; p<0.05) (data not shown). In parallel to the increase in body weight and the impairment in glucose homeostasis, plasma NEP levels were significantly higher in HFD-fed mice both at 7 and 15 weeks of diet compared to NCD-fed mice (15 weeks: HFD: 1642± 529 pg/μl, NCD: 820± 487 pg/μl; p<0.01). Furthermore the increase in NEP plasma levels comparing 7 and 15 weeks was significant in HFD-fed mice, but not in NCD-fed mice (n=8; p<0.05) (Figure 4A). NEP tissue levels at 15 weeks were significantly higher in mesenteric adipose tissue of HFD-fed mice compared with NCD-fed mice (n=8; p<0.05), but no significant changes in NEP levels in epididymal, perirenal, liver or kidney tissue were observed (Figure 4B).

Bottom Line: In a murine model of diet-induced insulin resistance, plasma NEP levels were significantly higher in high-fat diet (HFD)-fed compared with normal chow diet (NCD)-fed animals (1642 ± 529 and 820 ± 487 pg μl(-1), respectively; P<0.01).Tissue NEP was increased in mesenteric fat in HFD compared with NCD-fed mice (P<0.05).NEP knockout mice did not display any changes in insulin resistance, glucose tolerance, or body and epididymal fat pad weight compared with wild-type mice.

View Article: PubMed Central - PubMed

Affiliation: Division of Cardiovascular and Diabetes Research, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds, UK.

ABSTRACT

Objective: Neprilysin (NEP), a zinc metalloendopeptidase, has a role in blood pressure control and lipid metabolism. The present study tested the hypothesis that NEP is associated with insulin resistance and features of the metabolic syndrome (MetS) in a study of 318 healthy human subjects and in murine obesity, and investigated NEP production by adipocytes in-vitro.

Methods and results: In 318 white European males, plasma NEP was elevated in the MetS and increased progressively with increasing MetS components. Plasma NEP activity correlated with insulin, homoeostasis model assessment and body mass index (BMI) in all subjects (P<0.01). Quantitative reverse transcriptase PCR (RT-PCR) and western blotting showed that in human pre-adipocytes NEP expression is upregulated 25- to 30-fold during differentiation into adipocytes. Microarray analysis of mRNA from differentiated human adipocytes confirmed high-NEP expression comparable with adiponectin and plasminogen activator inhibitor-1. In a murine model of diet-induced insulin resistance, plasma NEP levels were significantly higher in high-fat diet (HFD)-fed compared with normal chow diet (NCD)-fed animals (1642 ± 529 and 820 ± 487 pg μl(-1), respectively; P<0.01). Tissue NEP was increased in mesenteric fat in HFD compared with NCD-fed mice (P<0.05). NEP knockout mice did not display any changes in insulin resistance, glucose tolerance, or body and epididymal fat pad weight compared with wild-type mice.

Conclusion: In humans, NEP activity correlated with BMI and measures of insulin resistance with increasing levels in subjects with multiple cardiovascular risk factors. NEP protein production in human adipocytes increased during cell differentiation and plasma and adipose tissue levels of NEP were increased in obese insulin-resistant mice. Our results indicate that NEP associates with cardiometabolic risk in the presence of insulin resistance and increases with obesity.

Show MeSH
Related in: MedlinePlus