Differential effects of alcohol upon gluconeogenesis from lactate in young and old hepatocytes Ken D. Sumida * , Suzanne C. Crandall, Puja L. Chadha, Tauseef Qureshi Department of Biological Sciences, Chapman University, One University Drive, Orange, CA 92866, USA Received 1 November 2004; received in revised form 13 January 2005; accepted 18 January 2005 Available online 5 February 2005 Abstract The purpose of this study was to determine the effect of age upon hepatic gluconeogenesis (HGN) from lactate in the presence of various concentrations of alcohol from young (3 months) and old (24 months) male rats. After a 24-hour fast, livers were perfused with collagenase and the hepatocytes were isolated. Aliquots of the cell suspension were placed in Krebs–Henseleit buffer and incubated with lactate, [U– 14 C]lactate, and nine different concentrations of ethanol (EtOH) for 30 min. Dose–effect curves were generated for the determination of maximal and half-maximal alcohol-induced inhibition on gluconeogenesis. There were no significant differences in basal HGN (lactate only and no EtOH) between young and old hepatocytes, 86.9G6.3 nmol/mg protein/30 min. The addition of ethanol significantly reduced HGN from lactate in both groups. At the highest ethanol concentration (15 mM), the glucose production was inhibited more from old, 46.1G 1.2 nmol/mg protein/30 min, compared to young hepatocytes, 56.0G1.6 nmol/mg protein/30 min. The greater age-related reduction in HGN was confirmed by the minimal glycogenolysis, and the concomitant decline in [U– 14 C]glucose production, lactate uptake, and [U– 14 C]lactate uptake. The results suggest that alcohol elicits a greater inhibition upon HGN from lactate in old compared to young liver cells. q 2005 Elsevier Inc. All rights reserved. Keywords: Ethanol; Rats; [U– 14 C]lactate; [U– 14 C]glucose production The maintenance of blood glucose is essential for optimal performance of the central nervous system. Significant decrements in the blood glucose concentration can lead to dizziness, irritability, headache, loss of consciousness, and even death (Williams, 1984). When glucose homeostasis is threatened, we have the capability to mount a counter-regulatory response to help resist the detrimental effects of hypoglycemia. A potential concern for the elderly is the decline in the function of various organs associated with senescence. Previous examinations on the liver from old animals have reported a decreased ability to mobilize glycogen (Stith and McCallum, 1985; Odio and Brodish, 1988) and, while not a consistent observation, age-related declines in gluconeogenic capacity (Podolin et al., 1994, 1996). Thus, senescence may decrease the efficacy for hepatic glucose output which could compromise the counter-regulatory response to hypoglyce- mia for the elderly. Ethanol (hereafter also referred to as ‘alcohol’) has been observed to inhibit hepatic glucose production capacity (Krebs, 1968; Arky and Freinkel, 1969; Krebs et al., 1969). In a comprehensive study, Krebs et al. (1969) examined the impact of various doses of alcohol on gluconeogenesis from lactate in perfused livers of adult rats. He reported marked declines in hepatic gluconeogenic capacity at alcohol doses up to 10 mM (Krebs, 1968; Krebs et al., 1969) which corresponded to the increase in alcohol dehydrogenase activity. Krebs et al. (1969) proposed that the activity of alcohol dehydrogenase elevates in response to the increased doses of ethanol. The alteration in the redox state limits the conversion of lactate to pyruvate resulting in the con- comitant decline in glucose production. While this classic study of Krebs (Krebs, 1968; Krebs et al., 1969) employed the use of perfused livers of adult animals, to our knowledge, no one has determined the effects of advanced age on the inhibitory effects of alcohol on hepatic Experimental Gerontology 40 (2005) 324–329 www.elsevier.com/locate/expgero 0531-5565/$ - see front matter q 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.exger.2005.01.005 * Corresponding author. Tel.: C1 714 997 6995; fax: C1 714 532 6048. E-mail address: sumida@chapman.edu (K.D. Sumida).