Abstract
We measured the contribution of glucose to hepatic cytosolic acetyl-CoA in vivo in rats and compared it with the phosphorylation state of a potentially regulatory enzyme complex [pyruvate dehydrogenase (PDH)]. Xenobiotic probes were used to sample hepatic cytosolic acetyl-CoA [acetylated sulfamethoxazole (SMX)] and UDP-glucose (glucuronidated acetaminophen) in vivo during [U-14C]glucose infusions. Percent active (dephosphorylated) form of PDH (PDH(a)) was determined on freeze-clamped liver. First, we confirmed using liver cell elutriation that acetylation of SMX occurs in parenchymal hepatocytes. Next, the fraction of cytosolic acetyl-CoA derived from [14C]glucose in vivo was shown to depend on dietary state. Specific activity of acetyl-CoA relative to plasma glucose or hepatic UDP-glucose was lower after 48 h fasting than after overnight fasting, and glucose refeeding (25 mg·kg-1·min-1 iv) maximally increased [14C]- glucose fractional contribution to acetyl-CoA within 2 h in the overnight-fasted but not in the prolonged fasted group. Hepatic PDH(a) demonstrated a similar but not identical pattern. The isotopic and enzymatic parameters showed significant correlations (r2 = 0.61 in 48-h fasted-refed group, r2 = 0.28 in over-night-fasted refed group), although [14C]glucose contribution to acetyl-CoA increased disproportionately compared with PDH(a) as refeeding progressed. The indirect pathway of UDP-glucose synthesis correlated inversely with the fractional contribution of glucose to acetyl-CoA. In summary, the fraction of hepatic acetyl-CoA derived from glucose in vivo is influenced by acute and chronic dietary factors and is only partially explained by PDH(a). Regulation of the carbon source of hepatic acetyl-CoA in vivo and interactions suggested by these results (e.g., glucose-fatty acid cycle; branch-point regulation of glucose recycling) can be addressed in a quantitative fashion using this experimental framework.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Endocrinology and Metabolism |
| Volume | 260 |
| Issue number | 6 23/6 |
| State | Published - 1991 |
| Externally published | Yes |
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Keywords
- Acetyl-coenzyme A
- Branch-point control
- Liver metabolism
- Metabolic probes
- Parenchymal hepatocytes
- Pyruvate dehydrogenase
- Xenobiotic conjugation
ASJC Scopus subject areas
- Biochemistry
- Endocrinology
- Physiology
Cite this
Fraction of hepatic cytosolic acetyl-CoA derived from glucose in vivo : Relation to PDH phosphorylation state. / Kaempfer, S.; Blackham, M.; Christiansen, M.; Wu, K.; Cesar, D.; Vary, T.; Hellerstein, M. K.
In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 260, No. 6 23/6, 1991.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Fraction of hepatic cytosolic acetyl-CoA derived from glucose in vivo
T2 - Relation to PDH phosphorylation state
AU - Kaempfer, S.
AU - Blackham, M.
AU - Christiansen, M.
AU - Wu, K.
AU - Cesar, D.
AU - Vary, T.
AU - Hellerstein, M. K.
PY - 1991
Y1 - 1991
N2 - We measured the contribution of glucose to hepatic cytosolic acetyl-CoA in vivo in rats and compared it with the phosphorylation state of a potentially regulatory enzyme complex [pyruvate dehydrogenase (PDH)]. Xenobiotic probes were used to sample hepatic cytosolic acetyl-CoA [acetylated sulfamethoxazole (SMX)] and UDP-glucose (glucuronidated acetaminophen) in vivo during [U-14C]glucose infusions. Percent active (dephosphorylated) form of PDH (PDH(a)) was determined on freeze-clamped liver. First, we confirmed using liver cell elutriation that acetylation of SMX occurs in parenchymal hepatocytes. Next, the fraction of cytosolic acetyl-CoA derived from [14C]glucose in vivo was shown to depend on dietary state. Specific activity of acetyl-CoA relative to plasma glucose or hepatic UDP-glucose was lower after 48 h fasting than after overnight fasting, and glucose refeeding (25 mg·kg-1·min-1 iv) maximally increased [14C]- glucose fractional contribution to acetyl-CoA within 2 h in the overnight-fasted but not in the prolonged fasted group. Hepatic PDH(a) demonstrated a similar but not identical pattern. The isotopic and enzymatic parameters showed significant correlations (r2 = 0.61 in 48-h fasted-refed group, r2 = 0.28 in over-night-fasted refed group), although [14C]glucose contribution to acetyl-CoA increased disproportionately compared with PDH(a) as refeeding progressed. The indirect pathway of UDP-glucose synthesis correlated inversely with the fractional contribution of glucose to acetyl-CoA. In summary, the fraction of hepatic acetyl-CoA derived from glucose in vivo is influenced by acute and chronic dietary factors and is only partially explained by PDH(a). Regulation of the carbon source of hepatic acetyl-CoA in vivo and interactions suggested by these results (e.g., glucose-fatty acid cycle; branch-point regulation of glucose recycling) can be addressed in a quantitative fashion using this experimental framework.
AB - We measured the contribution of glucose to hepatic cytosolic acetyl-CoA in vivo in rats and compared it with the phosphorylation state of a potentially regulatory enzyme complex [pyruvate dehydrogenase (PDH)]. Xenobiotic probes were used to sample hepatic cytosolic acetyl-CoA [acetylated sulfamethoxazole (SMX)] and UDP-glucose (glucuronidated acetaminophen) in vivo during [U-14C]glucose infusions. Percent active (dephosphorylated) form of PDH (PDH(a)) was determined on freeze-clamped liver. First, we confirmed using liver cell elutriation that acetylation of SMX occurs in parenchymal hepatocytes. Next, the fraction of cytosolic acetyl-CoA derived from [14C]glucose in vivo was shown to depend on dietary state. Specific activity of acetyl-CoA relative to plasma glucose or hepatic UDP-glucose was lower after 48 h fasting than after overnight fasting, and glucose refeeding (25 mg·kg-1·min-1 iv) maximally increased [14C]- glucose fractional contribution to acetyl-CoA within 2 h in the overnight-fasted but not in the prolonged fasted group. Hepatic PDH(a) demonstrated a similar but not identical pattern. The isotopic and enzymatic parameters showed significant correlations (r2 = 0.61 in 48-h fasted-refed group, r2 = 0.28 in over-night-fasted refed group), although [14C]glucose contribution to acetyl-CoA increased disproportionately compared with PDH(a) as refeeding progressed. The indirect pathway of UDP-glucose synthesis correlated inversely with the fractional contribution of glucose to acetyl-CoA. In summary, the fraction of hepatic acetyl-CoA derived from glucose in vivo is influenced by acute and chronic dietary factors and is only partially explained by PDH(a). Regulation of the carbon source of hepatic acetyl-CoA in vivo and interactions suggested by these results (e.g., glucose-fatty acid cycle; branch-point regulation of glucose recycling) can be addressed in a quantitative fashion using this experimental framework.
KW - Acetyl-coenzyme A
KW - Branch-point control
KW - Liver metabolism
KW - Metabolic probes
KW - Parenchymal hepatocytes
KW - Pyruvate dehydrogenase
KW - Xenobiotic conjugation
UR - http://www.scopus.com/inward/record.url?scp=0025917440&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0025917440&partnerID=8YFLogxK
M3 - Article
C2 - 2058663
AN - SCOPUS:0025917440
VL - 260
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 6 23/6
ER -