The Effect of Cinnamaldehyde on iNOS Activity and NO-Induced Islet Insulin Secretion in High-Fat-Diet Rats

Zomorrod Ataie,Mohammad Dastjerdi,Zahra Ghiravani,Khadijeh Farrokhfall,Reza B Jalili

doi:10.1155/2021/9970678

Abstract

Introduction Obesity and insulin resistance are associated with alterations in nitric oxide level and insulin secretion. Previous studies demonstrated that cinnamaldehyde (CNMA) improved islet insulin secretion and restored nitric oxide (NO) level, but its underlying mechanisms have not been investigated. This study aimed to investigate the effect of CNMA on inducible nitric oxide synthase (iNOS) activity and NO-induced islet insulin secretion in high-fat-diet (HFD) treated rats. Materials and Methods Forty male Wistar rats (12 weeks old) were randomly divided into four equal groups, namely, control, CNMA, HFD, and HFD + CNMA. Control and CNMA groups were treated with standard laboratory animals' diet, while HFD and HDF + CNMA groups were fed with an HFD diet enriched with 25% W/W tail fat for 16 weeks. CNMA was administrated orally (20 mg/kg body weight, daily) during the study period. Islet insulin secretion and the inducible NOS activity in the presence or absence of L-NAME (NO synthase inhibitor, 5 mmol/L) were evaluated. Results L-NAME-suppressed insulin secretion in control, HFD, and HFD + CNMA groups; however, in the CNMA group, it could not exhibit such effect (P < 0.01). Islets of HFD-treated animals showed significantly higher iNOS activity than controls. CNMA treatment significantly suppressed iNOS activities in CNMA and HFD + CNMA groups compared with control and HFD, respectively. Conclusion These results suggest that the beneficial effect of CNMA on insulin secretion might be due to its inhibitory effect on iNOS activity.

Highlights

Obesity and insulin resistance are associated with alterations in nitric oxide level and insulin secretion
To investigate the effects of the two chemically different NO synthase (NOS) inhibitors L-NAME and AG on islet insulin secretion, we assessed the insulin release from isolated islets incubated at 16.7 mM glucose in the presence/absence of these inhibitors
At this high concentration of glucose (16.7 mmol/L), the insulin secretion was lower in islets of control (−50%) and HFD (−42%) groups. is effect was much more pronounced in the presence of L-NAME. e diet and CNMA consumption significantly reduced NOinduced islet insulin secretion. e addition of AG (10 mmol/L, 60 min incubation) [2] markedly decreased insulin secretion from islets of both control and HFD groups (Figure 2). e results of two-way ANOVA revealed that

Summary

Introduction

Obesity and insulin resistance are associated with alterations in nitric oxide level and insulin secretion. Previous studies demonstrated that cinnamaldehyde (CNMA) improved islet insulin secretion and restored nitric oxide (NO) level, but its underlying mechanisms have not been investigated. Is study aimed to investigate the effect of CNMA on inducible nitric oxide synthase (iNOS) activity and NO-induced islet insulin secretion in high-fat-diet (HFD) treated rats. Ese results suggest that the beneficial effect of CNMA on insulin secretion might be due to its inhibitory effect on iNOS activity. To study the pathophysiology of MS, numerous animal models of dietary approaches to imitate the disease condition in humans have been established. In this approach, single-type diets (high fructose, high sucrose, or high fat) or combinations of diets (high fructose/fat or high sucrose/fat) are frequently used [5]. Several high-fat diets (HFD) with different fat sources (plant- or animal-derived) as well as fat contents (vary between 20 and 60% of total energy) have been extensively used [5,6,7]

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