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Glycerol Production from Glucose and Fructose by 3T3-L1 Cells: A Mechanism of Adipocyte Defense from Excess Substrate.

Romero Mdel M, Sabater D, Fernández-López JA, Remesar X, Alemany M - PLoS ONE (2015)

Bottom Line: Fructose conversion to lactate and glycerol was lower than that of glucose.When both hexoses were present, the effects of fructose on gene expression prevailed over those of glucose.A phosphatase pathway such as that described may have a potential regulatory function, and explain the production of glycerol by adipocytes in the absence of lipolytic stimulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition and Food Science, Faculty of Biology, University of Barcelona, Av.Diagonal 643, 08028, Barcelona, Spain; Institute of Biomedicine, University of Barcelona, Barcelona, Spain; CIBER Obesity and Nutrition, Barcelona, Spain.

ABSTRACT
Cultured adipocytes (3T3-L1) produce large amounts of 3C fragments; largely lactate, depending on medium glucose levels. Increased glycolysis has been observed also in vivo in different sites of rat white adipose tissue. We investigated whether fructose can substitute glucose as source of lactate, and, especially whether the glycerol released to the medium was of lipolytic or glycolytic origin. Fructose conversion to lactate and glycerol was lower than that of glucose. The fast exhaustion of medium glucose was unrelated to significant changes in lipid storage. Fructose inhibited to a higher degree than glucose the expression of lipogenic enzymes. When both hexoses were present, the effects of fructose on gene expression prevailed over those of glucose. Adipocytes expressed fructokinase, but not aldolase b. Substantive release of glycerol accompanied lactate when fructose was the substrate. The mass of cell triacylglycerol (and its lack of change) could not justify the comparatively higher amount of glycerol released. Consequently, most of this glycerol should be derived from the glycolytic pathway, since its lipolytic origin could not be (quantitatively) sustained. Proportionally (with respect to lactate plus glycerol), more glycerol was produced from fructose than from glucose, which suggests that part of fructose was catabolized by the alternate (hepatic) fructose pathway. Earlier described adipose glycerophophatase activity may help explain the glycolytic origin of most of the glycerol. However, no gene is known for this enzyme in mammals, which suggests that this function may be carried out by one of the known phosphatases in the tissue. Break up of glycerol-3P to yield glycerol, may be a limiting factor for the synthesis of triacylglycerols through control of glycerol-3P availability. A phosphatase pathway such as that described may have a potential regulatory function, and explain the production of glycerol by adipocytes in the absence of lipolytic stimulation.

No MeSH data available.


Related in: MedlinePlus

Lactate and glycerol efflux from 3T3-L1 adipocytes exposed to a medium with varying concentration of glucose, fructose or a combination of both.Each dot represent the mean ± sem of three different wells. Lactate or glycerol release are expressed in pmol per cell and day. There were statistically significant (two-way anova) differences (P<0.05) for lactate release at 11 mM and 22 mM glucose on day 1 vs. days 2 and 3. There were significant differences for concentrations from 5.5 mM onwards in the production of lactate from medium fructose compared with glucose for all three days. Glycerol release showed significant differences for 22 mM glucose on days 1 vs 2 and 3 and for 11 mM glucose for day 1 vs day 3. There were significant differences between glycerol release from fructose vs. glucose at 11 mM and 22 mM for days 2 and 3. In the graphs where glucose + fructose were present in the medium, the X-axis legend shows the concentration of each of both hexoses.
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pone.0139502.g003: Lactate and glycerol efflux from 3T3-L1 adipocytes exposed to a medium with varying concentration of glucose, fructose or a combination of both.Each dot represent the mean ± sem of three different wells. Lactate or glycerol release are expressed in pmol per cell and day. There were statistically significant (two-way anova) differences (P<0.05) for lactate release at 11 mM and 22 mM glucose on day 1 vs. days 2 and 3. There were significant differences for concentrations from 5.5 mM onwards in the production of lactate from medium fructose compared with glucose for all three days. Glycerol release showed significant differences for 22 mM glucose on days 1 vs 2 and 3 and for 11 mM glucose for day 1 vs day 3. There were significant differences between glycerol release from fructose vs. glucose at 11 mM and 22 mM for days 2 and 3. In the graphs where glucose + fructose were present in the medium, the X-axis legend shows the concentration of each of both hexoses.

Mentions: The fate of the glucose taken from the medium can be easily deduced from Fig 3, where the appearance (production rates) of lactate in the medium was parallel to the rates of glucose consumption, showing, again, lower rates for day 1. The production of lactate from fructose was lower, and stabilized to a level, which was also lower than that obtained with glucose.


Glycerol Production from Glucose and Fructose by 3T3-L1 Cells: A Mechanism of Adipocyte Defense from Excess Substrate.

Romero Mdel M, Sabater D, Fernández-López JA, Remesar X, Alemany M - PLoS ONE (2015)

Lactate and glycerol efflux from 3T3-L1 adipocytes exposed to a medium with varying concentration of glucose, fructose or a combination of both.Each dot represent the mean ± sem of three different wells. Lactate or glycerol release are expressed in pmol per cell and day. There were statistically significant (two-way anova) differences (P<0.05) for lactate release at 11 mM and 22 mM glucose on day 1 vs. days 2 and 3. There were significant differences for concentrations from 5.5 mM onwards in the production of lactate from medium fructose compared with glucose for all three days. Glycerol release showed significant differences for 22 mM glucose on days 1 vs 2 and 3 and for 11 mM glucose for day 1 vs day 3. There were significant differences between glycerol release from fructose vs. glucose at 11 mM and 22 mM for days 2 and 3. In the graphs where glucose + fructose were present in the medium, the X-axis legend shows the concentration of each of both hexoses.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591265&req=5

pone.0139502.g003: Lactate and glycerol efflux from 3T3-L1 adipocytes exposed to a medium with varying concentration of glucose, fructose or a combination of both.Each dot represent the mean ± sem of three different wells. Lactate or glycerol release are expressed in pmol per cell and day. There were statistically significant (two-way anova) differences (P<0.05) for lactate release at 11 mM and 22 mM glucose on day 1 vs. days 2 and 3. There were significant differences for concentrations from 5.5 mM onwards in the production of lactate from medium fructose compared with glucose for all three days. Glycerol release showed significant differences for 22 mM glucose on days 1 vs 2 and 3 and for 11 mM glucose for day 1 vs day 3. There were significant differences between glycerol release from fructose vs. glucose at 11 mM and 22 mM for days 2 and 3. In the graphs where glucose + fructose were present in the medium, the X-axis legend shows the concentration of each of both hexoses.
Mentions: The fate of the glucose taken from the medium can be easily deduced from Fig 3, where the appearance (production rates) of lactate in the medium was parallel to the rates of glucose consumption, showing, again, lower rates for day 1. The production of lactate from fructose was lower, and stabilized to a level, which was also lower than that obtained with glucose.

Bottom Line: Fructose conversion to lactate and glycerol was lower than that of glucose.When both hexoses were present, the effects of fructose on gene expression prevailed over those of glucose.A phosphatase pathway such as that described may have a potential regulatory function, and explain the production of glycerol by adipocytes in the absence of lipolytic stimulation.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition and Food Science, Faculty of Biology, University of Barcelona, Av.Diagonal 643, 08028, Barcelona, Spain; Institute of Biomedicine, University of Barcelona, Barcelona, Spain; CIBER Obesity and Nutrition, Barcelona, Spain.

ABSTRACT
Cultured adipocytes (3T3-L1) produce large amounts of 3C fragments; largely lactate, depending on medium glucose levels. Increased glycolysis has been observed also in vivo in different sites of rat white adipose tissue. We investigated whether fructose can substitute glucose as source of lactate, and, especially whether the glycerol released to the medium was of lipolytic or glycolytic origin. Fructose conversion to lactate and glycerol was lower than that of glucose. The fast exhaustion of medium glucose was unrelated to significant changes in lipid storage. Fructose inhibited to a higher degree than glucose the expression of lipogenic enzymes. When both hexoses were present, the effects of fructose on gene expression prevailed over those of glucose. Adipocytes expressed fructokinase, but not aldolase b. Substantive release of glycerol accompanied lactate when fructose was the substrate. The mass of cell triacylglycerol (and its lack of change) could not justify the comparatively higher amount of glycerol released. Consequently, most of this glycerol should be derived from the glycolytic pathway, since its lipolytic origin could not be (quantitatively) sustained. Proportionally (with respect to lactate plus glycerol), more glycerol was produced from fructose than from glucose, which suggests that part of fructose was catabolized by the alternate (hepatic) fructose pathway. Earlier described adipose glycerophophatase activity may help explain the glycolytic origin of most of the glycerol. However, no gene is known for this enzyme in mammals, which suggests that this function may be carried out by one of the known phosphatases in the tissue. Break up of glycerol-3P to yield glycerol, may be a limiting factor for the synthesis of triacylglycerols through control of glycerol-3P availability. A phosphatase pathway such as that described may have a potential regulatory function, and explain the production of glycerol by adipocytes in the absence of lipolytic stimulation.

No MeSH data available.


Related in: MedlinePlus