SIRT3 is required for liver regeneration but not for the beneficial effect of nicotinamide riboside
Sarmistha Mukherjee, … , Karthikeyani Chellappa, Joseph A. Baur
Sarmistha Mukherjee, … , Karthikeyani Chellappa, Joseph A. Baur
Published March 9, 2021
Citation Information: JCI Insight. 2021;6(7):e147193. https://doi.org/10.1172/jci.insight.147193.
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Research Article Hepatology Metabolism

SIRT3 is required for liver regeneration but not for the beneficial effect of nicotinamide riboside

Abstract

Liver regeneration is critical to survival after traumatic injuries, exposure to hepatotoxins, or surgical interventions, yet the underlying signaling and metabolic pathways remain unclear. In this study, we show that hepatocyte-specific loss of the mitochondrial deacetylase SIRT3 drastically impairs regeneration and worsens mitochondrial function after partial hepatectomy. Sirtuins, including SIRT3, require NAD as a cosubstrate. We previously showed that the NAD precursor nicotinamide riboside (NR) promotes liver regeneration, but whether this involves sirtuins has not been tested. Here, we show that despite their NAD dependence and critical roles in regeneration, neither SIRT3 nor its nuclear counterpart SIRT1 is required for NR to enhance liver regeneration. NR improves mitochondrial respiration in regenerating WT or mutant livers and rapidly increases oxygen consumption and glucose output in cultured hepatocytes. Our data support a direct enhancement of mitochondrial redox metabolism as the mechanism mediating improved liver regeneration after NAD supplementation and exclude signaling via SIRT1 and SIRT3. Therefore, we provide the first evidence to our knowledge for an essential role for a mitochondrial sirtuin during liver regeneration and insight into the beneficial effects of NR.

Authors

Sarmistha Mukherjee, James Mo, Lauren M. Paolella, Caroline E. Perry, Jade Toth, Mindy M. Hugo, Qingwei Chu, Qiang Tong, Karthikeyani Chellappa, Joseph A. Baur

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Figure 2

NR enhances mitochondrial respiration in regenerating liver and in primary hepatocytes.

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NR enhances mitochondrial respiration in regenerating liver and in prima...
Male C57BL6/J mice 10–16 weeks of age were supplemented for 2 weeks with NR at a dose of 500 mg/kg body weight and then were subjected to two-thirds partial hepatectomy (PHx). (A) Mitochondria from livers of H2O- and NR-treated mice were isolated 24 hours after PHx (n = 6 per group) and were analyzed for fatty acid oxidation capacity using palmitoyl carnitine as a substrate. (B and C) Mitochondrial NAD and NADH content in organelles from control or NR-treated mice at 48 hours after PHx (n = 4–5 per group). Primary hepatocytes were isolated from overnight fasted C57BL6/J WT mice, cultured in glucose-free media with gluconeogenic substrates with or without NR for 5 hours. Mitochondria were then isolated from treated or untreated hepatocytes (n = 4–9 per group). (D) Oxygen consumption of primary hepatocytes. (E and F) Hepatocyte NAD and NADH content after treatment. (G and H) Final glucose and β-hydroxybutyrate concentration in the media. (I) Plasma β-hydroxybutyrate content at the indicated time points after PHx in H2O- and NR-treated mice (n = 3 per group at 12 hours and n = 8–14 per group in all other time points). (J and K) Blood glucose and plasma lactate levels in prior to and 24 hours after PHx in H2O- and NR-treated mice (n = 11–14 per group). (L) Mitochondrial NAD and NADH content in treated and untreated hepatocytes (n = 3 per group). (M) State 3-coupled mitochondrial oxygen consumption using pyruvate plus malate as substrates. In vivo data are represented by open circles and squares, and hepatocyte data are denoted by filled circles and squares. Data are shown as the mean ± SEM. *P < 0.05; **P < 0.01; ***P < 0.001; 2-tailed Student’s t test.