Dietary restriction reduces hepatocyte proliferation and enhances p53 expression but does not increase apoptosis in normal rats during development

Abstract

Dietary restriction (DR) retards physical growth, resulting in small body size, reduced liver weight and reduced number of hepatocytes in rats. We examined the effects of DR on proliferation and apoptosis of hepatocytes during development and explained these changes subcellularly using immunohistochemistry for bromodeoxyuridine (BrdU) incorporation, proliferating cell nuclear antigen (PCNA) and p53, terminal dUTP nick end labeling (TUNEL) and quantitative reverse transcription-polymerase chain reaction (RT-PCR) for TGFalpha, TGFbeta1, p53, Fas and TNF receptor (TNFr). Tissue samples included the livers of 3-month-old male Fischer 344 rats fed ad libitum (AL) or on 70% DR. DR significantly reduced the proportions of BrdU-positive and PCNA-strongly-positive hepatocytes compared with AL rats but not the proportions of PCNA-positive hepatocytes and TUNEL-positive hepatocytes. On the other hand, DR enhanced the expression of p53 and Fas mRNAs but failed to influence the expression of TGFalpha, TGFbeta1 and TNFr mRNAs. Moreover, DR significantly increased the proportion of p53-positive hepatocytes. Our findings suggest that DR suppresses the proliferation of hepatocytes, resulting in a reduced number of hepatocytes during development. This process may be mediated by overexpression of p53 suppressor gene. While DR accelerates the expression of Fas antigen, this result does not influence the rate of apoptosis of hepatocytes under physiological conditions.

Conservation of Hearing and Protection of Auditory Hair Cells against Trauma-Induced Losses by Local Dexamethasone Therapy: Molecular and Genetic Mechanisms

“…For detection of amplification products in ß-actin, TNFR1, Bax, Bcl-2, and Bcl-xl PCR, we used a BioRad iCycler Thermal Cycler (BioRad) and iQ SYBR Green Supermix (BioRad Laboratories, Inc. Hercules, CA, USA) with 25-µL reaction mixes. The sequence of specific primers used are: ß-actin forward (fwd), 5'-CGTTGACATCCGTAAAGACC-3'; ß-actin reverse (rev), 5'-AGCCACCAATCCACACAGAG-3' [173-base pair (bp) fragment] (Higami et al, 2000;Nudel et al, 1983); TNFR1 fwd, 5'-GAACACCGT-GTGTAACTGCC-3'; TNFR1 rev, 5'-ATTCCTTCACCCTCCACCTC-3' (301 bp fragment) (Raina & Jeejeebhoy, 2004); Bax fwd, 5'-CTGCAGAGGATGATTGCT-GA-3'; Bax rev, 5'-GATCAGCTCGGGCACTTTAG-3' (174 bp fragment); Bcl-2 fwd, 5'-GCTACGAGTGGGATACTGG-3'; Bcl-2 rev, 5'-GTGTGCAGATGCCGGTTCA-3' (472 bp fragment); Bcl-xl fwd, 5'-AGGATACAGCTGGAGTCAG-3'; and Bcl-xl figure 2 Fluorscein isothiocyanate (FITC)-phalloidin stained organ of Corti explants after 4 days in vitro. A) Shows an explant exposed to an ototoxic level of TNF-α (i.e.…”

Can Short-Term Dietary Restriction and Fasting Have a Long-Term Anticarcinogenic Effect?

“…The rate of cellular proliferation is an important determinant of the growth of preneoplastic and neoplastic lesions during the promotion and progression stages of carcinogenesis. Fasting and various short-and long-term DR protocols almost uniformly result in reduced rates of cellular proliferation in the majority of tissues and organs, including the liver [31][32][33][34][35], bladder [36,37], skin [32,36], kidney, heart [32], mammary gland, esophagus, jejunum [36] and colorectum [36,38] (table 1). This reduction in proliferation may in part explain the anticarcinogenic effect of DR.…”

“…Most studies focused on the effect of fasting and DR on the rate of an active cell death, apoptosis, in the liver. Apoptosis seems to be enhanced by DR or fasting under most circumstances [31,33,35,39,40], although a mild DR regimen applied to young, rapidly growing animals may not be sufficient to induce apoptosis [34] (table 1). Induction of apoptosis by DR has also been reported for the bladder [37], colon [38] and mammary gland [41] (table 1).…”

Expression patterns of cytokine, growth factor and cell cycle-related genes after partial hepatectomy in rats with thioacetamide-induced cirrhosis

“…Prof. Chang Chan Fong (Department of Biochemistry, National University of Singapore). The other primers were as previously reported [38,52,53] .…”