Fatty acids and glycerol or lactate are required to induce gluconeogenesis from alanine in isolated rabbit renal cortical tubules

Lietz, Tadeusz; Rybka, Jacek; Bryła, Jadwiga

doi:10.1007/bf01318884

Cited by 15 publications

(6 citation statements)

References 40 publications

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“…Although alanine can be converted to pyruvate by transamination (61,64) and is a potential substrate for gluconeogenesis (33,61), studies in both isolated renal proximal tubules (31,47) and human volunteers (12,57) have shown that alanine is a poor substrate for renal gluconeogenesis compared with lactate. These studies support the interpretation that substrate flux through the glycolytic pathway is required for V-ATPase activation.…”

Section: Discussionmentioning

confidence: 99%

Glucose activates H⁺-ATPase in kidney epithelial cells

Nakamura

2004

American Journal of Physiology-Cell Physiology

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The vacuolar H(+)-ATPase (V-ATPase) acidifies compartments of the vacuolar system of eukaryotic cells. In renal epithelial cells, it resides on the plasma membrane and is essential for bicarbonate transport and acid-base homeostasis. The factors that regulate the H(+)-ATPase remain largely unknown. The present study examines the effect of glucose on H(+)-ATPase activity in the pig kidney epithelial cell line LLC-PK(1). Cellular pH was measured by performing ratiometric fluorescence microscopy using the pH-sensitive indicator BCECF-AM. Intracellular acidification was induced with NH(3)/NH(4)(+) prepulse, and rates of intracellular pH (pH(i)) recovery (after in situ calibration) were determined by the slopes of linear regression lines during the first 3 min of recovery. The solutions contained 1 microM ethylisopropylamiloride and were K(+) free to eliminate Na(+)/H(+) exchange and H(+)-K(+)-ATPase activity. After NH(3)/NH(4)(+)-induced acidification, LLC-PK(1) cells had a significant pH(i) recovery rate that was inhibited entirely by 100 nM of the V-ATPase inhibitor concanamycin A. Acute removal of glucose from medium markedly reduced V-ATPase-dependent pH(i) recovery activity. Readdition of glucose induced concentration-dependent reactivation of V-ATPase pH(i) recovery activity within 2 min. Glucose replacement produced no significant change in cell ATP or ADP content. H(+)-ATPase activity was completely inhibited by the glycolytic inhibitor 2-deoxy-d-glucose (20 mM) but only partially inhibited by the mitochondrial electron transport inhibitor antimycin A (20 microM). The phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin (500 nM) abolished glucose activation of V-ATPase, and activity was restored after wortmannin removal. Glucose activates V-ATPase activity in kidney epithelial cells through the glycolytic pathway by a signaling pathway that requires PI3K activity. These findings represent an entirely new physiological effect of glucose, linking it to cellular proton secretion and vacuolar acidification.

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Section: Discussionmentioning

confidence: 99%

Glucose activates H⁺-ATPase in kidney epithelial cells

Nakamura

2004

American Journal of Physiology-Cell Physiology

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“…In contrast to rabbit hepatocytes [23], freshly isolated kidney‐cortex tubules produce glucose from amino acids efficiently only in the presence of glycerol or lactate and either fatty acids or ketone bodies [21]. Therefore, in all experiments basal medium for primary culture of renal tubules was supplemented with 2 m m alanine, 0.5 m m octanoate and 5 m m glycerol or lactate.…”

Section: Resultsmentioning

confidence: 99%

“…Intracellular cAMP content was measured with the cyclic AMP ( 3 H) assay system of Amersham. Isotopic studies used for investigation of the contribution of alanine and glycerol to glucose formation were performed according to [20, 21]. Protein was measured according to [22].…”

Section: Biochemical Analysismentioning

confidence: 99%

Melatonin‐induced modulation of glucose metabolism in primary cultures of rabbit kidney‐cortex tubules

Derlacz

Popławski

Napierała

et al. 2004

Journal of Pineal Research

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The effect of melatonin on glucose metabolism in the presence and absence of insulin has been investigated in the primary cultures of renal tubules grown in a defined medium. In the absence of glucose in the medium containing 5 microg/mL of insulin and 2 mm alanine + 5 mm glycerol + 0.5 mm octanoate, 100 nm melatonin stimulated both glucose and lactate synthesis, while in the medium devoid of insulin melatonin action was negligible. Melatonin-induced increase in glucose and lactate synthesis was accompanied by an enhancement of alanine and glycerol consumption. In view of measurements of [U-14C]L-alanine and [U-14C]L-glycerol incorporation into glucose, it is likely that melatonin increased alanine utilization for glucose production, while accelerated lactate synthesis was because of an enhanced glycerol consumption. As (i) 10 nm luzindole attenuated the stimulatory action of melatonin on glucose formation and (ii) the indole induced a decrease in intracellular cAMP level, it seems likely that in renal tubules melatonin binds to ML1 membrane receptor subtype. In view of a decline of intracellular fructose-1,6-bisphosphate content accompanied by a significant rise in hexose-6-phosphate and glucose levels, melatonin might result in an acceleration of flux through fructose-1,6-bisphosphatase probably because of an increase in the active, dephosphorylated form of this enzyme. Thus, the administration of melatonin in combination with insulin might be beneficial for diabetic therapy because of protection against hypoglycemia.

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“…First, taking into account the intracellular water (approximately 1.8 L per mg of dry weight Lietz et al 1999) and the protein content (about 0.9 mg per mg of dry weight, K. Winiarska, personal communication 2013) of the primary cultured renal tubules, the intracellular renal F6P concentrations (10.2 ± 1.3 mol/L and 14.8 ± 2.0 mol/L without and with insulin + peptide C, respectively; Fig. 4) are of the same order of magnitude as the GPI K m value for F6P, as displayed in Table 2 (40.5 ± 5.5 mol/L).…”

Section: Discussionmentioning

confidence: 99%

Proinsulin C-peptide potentiates the inhibitory action of insulin on glucose synthesis in primary cultured rabbit kidney-cortex tubules: Metabolic studies

Usarek

Jagielski

Krempa

et al. 2014

Biochem. Cell Biol.

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Effects of equimolar concentrations of proinsulin C-peptide and insulin on glucose synthesis were studied in primary cultures of rabbit kidney-cortex tubules grown in the presence of alanine, glycerol, and octanoate. The rhodamine-labeled C-peptide entered renal tubular cells and localized in nuclei, both in the presence and absence of insulin; preincubations with the unlabeled compound inhibited internalization. C-peptide did not affect glucose formation when added alone but potentiated the inhibitory action of insulin by about 20% due to a decrease in flux through glucose-6-phosphate isomerase (GPI) and (or) glucose-6-phosphatase (G6Pase). GPI inhibition was caused by: (i) increased intracellular contents of fructose-1,6-bisphosphate and fructose-1-phosphate, inhibitors of the enzyme and (ii) reduced level of the phosphorylated GPI, which exhibits higher enzymatic activity in the presence of casein kinase 2. A decrease in flux through G6Pase, due to diminished import of G6P by G6P-transporter from the cytoplasm into endoplasmic reticulum lumen, is also suggested. The data show for the first time that in the presence of insulin and C-peptide, both GPI and G6P-ase may act as regulatory enzymes of renal gluconeogenic pathway.

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Fatty acids and glycerol or lactate are required to induce gluconeogenesis from alanine in isolated rabbit renal cortical tubules

Cited by 15 publications

References 40 publications

Glucose activates H⁺-ATPase in kidney epithelial cells

Glucose activates H⁺-ATPase in kidney epithelial cells

Melatonin‐induced modulation of glucose metabolism in primary cultures of rabbit kidney‐cortex tubules

Proinsulin C-peptide potentiates the inhibitory action of insulin on glucose synthesis in primary cultured rabbit kidney-cortex tubules: Metabolic studies

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Fatty acids and glycerol or lactate are required to induce gluconeogenesis from alanine in isolated rabbit renal cortical tubules

Cited by 15 publications

References 40 publications

Glucose activates H+-ATPase in kidney epithelial cells

Glucose activates H+-ATPase in kidney epithelial cells

Melatonin‐induced modulation of glucose metabolism in primary cultures of rabbit kidney‐cortex tubules

Proinsulin C-peptide potentiates the inhibitory action of insulin on glucose synthesis in primary cultured rabbit kidney-cortex tubules: Metabolic studies

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Glucose activates H⁺-ATPase in kidney epithelial cells

Glucose activates H⁺-ATPase in kidney epithelial cells