Expression of nitric oxide synthases in subcutaneous adipose tissue of nonobese and obese humans

Mikael Rydén,Peter Eneroth,Kurt Andersson,Hans Gyllenhammar,Montserrat Elizalde,Stig Ramel,Vanessa van Harmelen,Cecilia Holm,Peter Arner,Anders Ölund

doi:10.1016/s0022-2275(20)33432-5

Mikael Rydén, Peter Eneroth + Show 8 more

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https://doi.org/10.1016/s0022-2275(20)33432-5

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Abstract

Studies have shown evidence of production of nitric oxide (NO) in adipose tissue, as well as inhibition of lipolysis by NO. We have analyzed nitric oxide synthase (NOS) expression in subcutaneous adipose tissue from 13 nonobese and 18 obese male subjects. Using a competitive reverse transcription polymerase chain reaction method, endothelial (eNOS) and inducible (iNOS), but not neuronal (nNOS), nitric oxide synthase mRNA expression was detected in isolated fat cells and pieces of adipose tissue. Tissue mRNA levels for eNOS were 3,814 +/- 825 and 5,956 +/- 476 amol/mg RNA (P = 0.043), and for iNOS 306 +/- 38 and 332 +/- 48 amol/mg RNA, for nonobese and obese individuals, respectively. Western blotting revealed similar eNOS protein levels in isolated fat cells and adipose tissue pieces. Protein levels for eNOS in nonobese and obese individuals, respectively, were (in optical density [OD] units per mm(2) per 100 microgram of total protein) 0.11 +/- 0.08 and 2.80 +/- 1.30 (P = 0.043). iNOS protein was detectable, but not measurable, at low levels in a subset of obese patients (3 of 10). iNOS protein levels could not be detected in nonobese individuals. Hormone-sensitive lipase (HSL), the key regulating enzyme in lipolysis, is reduced in obesity. The expression of HSL protein in subcutaneous adipose tissue was studied in the same subset of patients; in agreement with previous results, HSL levels were reduced in obese subjects: 4.64 +/- 1.10 and 1.27 +/- 0.35 (P = 0.012) in nonobese and obese subjects, respectively. In conclusion, this study shows that eNOS and iNOS, but not nNOS, are present in human subcutaneous adipose tissue. Gene expression and protein levels of eNOS are increased, whereas HSL protein levels are decreased in obesity. It is speculated that increased NO production, preferably by eNOS, and decreased HSL levels may cause decreased subcutaneous adipose tissue lipolysis in obesity. synthases in subcutaneous adipose tissue of nonobese and obese humans.

Highlights

Studies have shown evidence of production of nitric oxide (NO) in adipose tissue, as well as inhibition of lipolysis by NO
Fat tissue specimens from abdominal subcutaneous tissue of obese and nonobese subjects were snap-frozen in liquid nitrogen and stored at Ϫ70ЊC
One hundred or 200 ␮g of total protein was loaded on poly

Summary

Introduction

Studies have shown evidence of production of nitric oxide (NO) in adipose tissue, as well as inhibition of lipolysis by NO. Using a competitive reverse transcription polymerase chain reaction method, endothelial (eNOS) and inducible (iNOS), but not neuronal (nNOS), nitric oxide synthase mRNA expression was detected in isolated fat cells and pieces of adipose tissue. The expression of HSL protein in subcutaneous adipose tissue was studied in the same subset of patients; in agreement with previous results, HSL levels were reduced in obese subjects: 4.64 ؎ 1.10 and 1.27 ؎ 0.35 (P ‫ ؍‬0.012) in nonobese and obese subjects, respectively. It is speculated that increased NO production, preferably by eNOS, and decreased HSL levels may cause decreased subcutaneous adipose tissue lipolysis in obesity.—Elizalde, M., M. Addition of NO caused an inhibition of lipolysis in intact adipose tissue in vivo, as well as in isolated fat cells in vitro in humans Together, these results suggest an important role for NO in the regulation of lipolysis in humans (4).

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