Melatonin prevents maternal fructose intake‐induced programmed hypertension in the offspring: roles of nitric oxide and arachidonic acid metabolites

Abstract

Fructose intake has increased globally and is linked to hypertension. Melatonin was reported to prevent hypertension development. In this study, we examined whether maternal high fructose (HF) intake causes programmed hypertension and whether melatonin therapy confers protection against the process, with a focus on the link to epigenetic changes in the kidney using next-generation RNA sequencing (NGS) technology. Pregnant Sprague-Dawley rats received regular chow or chow supplemented with HF (60% diet by weight) alone or with additional 0.01% melatonin in drinking water during the whole period of pregnancy and lactation. Male offspring were assigned to four groups: control, HF, control + melatonin (M), and HF + M. Maternal HF caused increases in blood pressure (BP) in the 12-wk-old offspring. Melatonin therapy blunted the HF-induced programmed hypertension and increased nitric oxide (NO) level in the kidney. The identified differential expressed gene (DEGs) that are related to regulation of BP included Ephx2, Col1a2, Gucy1a3, Npr3, Aqp2, Hba-a2, and Ptgs1. Of which, melatonin therapy inhibited expression and activity of soluble epoxide hydrolase (SEH, Ephx2 gene encoding protein). In addition, we found genes in arachidonic acid metabolism were potentially involved in the HF-induced programmed hypertension and were affected by melatonin therapy. Together, our data suggest that the beneficial effects of melatonin are attributed to its ability to increase NO level in the kidney, epigenetic regulation of genes related to BP control, and inhibition of SEH expression. The roles of DEGs by the NGS in long-term epigenetic changes in the adult offspring kidney require further clarification.

Maternal fructose-intake-induced renal programming in adult male offspring

“…Pregnant SD rats (n=8) were randomly assigned to receive regular chow (n=4) or chow supplemented with fructose (60% diet by weight, n=4) during the whole period of pregnancy and lactation [11]. Since cardiovascular events occur at a higher rate and at an earlier age in males than females [12,13], only male offspring was selected from each litter and used in subsequent experiments.…”

“…RNA was extracted according to the previously described procedures [11]. Two-step qPCR was conducted using Quantitect SYBR Green PCR Reagents (Qiagen, Valencia, CA, USA) on an iCycler iQ Multi-color Real-Time PCR Detection System (Bio-Rad, Hercules, CA, USA).…”

“…Kidneys were harvested after perfusion with phosphate-buffered saline, divided into cortex and medulla regions, and snap frozen. Blood pressure (BP) was measured in conscious rats on postnatal weeks 3, 4, 8 and 12 by an indirect tail-cuff method (BP-2000; Visitech Systems, Inc., Apex, NC, USA) described previously [11]. Renal level of 14,15-dihydroxyeicosatrienoic acids (DHET), lipid mediators synthesized from arachidonic acid [14], was measured using a commercially available enzyme-linked immunosorbent assay kit (Detroit R&D Inc., Detroit, MI, USA) following manufacturer's protocol.…”

“…We recently observed that renal programming and hypertension developed in the adult male offspring of mother rats exposed to caloric restriction [6,7], diabetes [8], dexamethasone treatment [9,10] and high-fructose (HF) diet [11]. A number of mechanisms, including glucocorticoid effects, oxidative stress, epigenetic regulation, alterations of renin-angiotensin system (RAS), impaired tubular sodium handling and reduction in nephron numbers, have been put forward to interpret renal programming [2][3][4].…”

“…Nephrogenesis occurs predominantly from late gestation to weaning period by postnatal weeks 1-2 in rodents. Our previous report demonstrated that programmed hypertension developed in the 3-month-old adult male offspring exposed to maternal HF diet [11]. Therefore, we employed the whole-genome RNA next-generation sequencing (NGS) to quantify the abundance of RNA transcripts in the offspring kidneys to capture commonality in transcriptional regulatory gene networks from 1-day-(i.e., nephrogenesis stage), 3-week-(completion of nephrogenesis stage) and 3-month-old (hypertensive stage) offspring in response to maternal HF exposure.…”