This Month in Gastroenterology

Abstract

Altered Prostaglandin Pathways in Slow-Transit ConstipationSlow-transit constipation is a relatively rare form of severe refractory constipation that is most frequently encountered in young women. Previous studies indicated a role for increased muscle sensitivity to normal circulating levels of progesterone, attributable to nuclear over-expression of progesterone receptors. However, the mechanism through which increased sensitivity to progesterone inhibits colonic contractility remains to be elucidated.In this issue of Gastroenterology, Cong et al report on studies of the prostaglandin and cyclooxygenase (COX) pathways in colonic smooth muscle from women with slow-transit constipation. Surgical specimens were obtained from the descending colon in 8 women with slow-transit constipation and 8 women in the control group who underwent surgery for adenocarcinoma. The authors performed smooth muscle contractility studies and expression studies for prostaglandins, thromboxane, COX enzymes, and progesterone receptors.Muscle strips from patients with slow-transit constipation had decreased basal contractility, and this was associated with decreased levels of PGF2α and TxB2 and increased levels of PGE2 in colonic smooth muscle (Figure 1). PGF2α and TXA2 contract while PGE2 relaxes colonic circular muscle. Smooth muscle from patients with slow-transit constipation also had a decreased expression of COX-1 and an increased expression of COX-2 enzymes and progesterone receptors.Incubation of dissociated colonic smooth muscle cells from control subjects with progesterone 10–5 mol for 6 hours induced all of these changes, namely, a reduction in PGF2α and TXB2 levels, an increase in PGE2 levels and COX-2 expression, as well as reduced COX-1 expression. Inhibition of COX-1 decreased PGF2α and TxA2 levels, whereas inhibition of COX-2 decreased PGE2 levels.These observations help to further elucidate the mechanisms underlying impaired colonic propulsive contractility in women with slow-transit constipation. Colonic smooth muscle in these patients is characterized by lower levels of prostaglandins that cause contraction, such as TxA2 and PGF2α, and higher levels of prostaglandins that cause relaxation, such as PGE2. The abnormalities in prostaglandin levels are due to lower COX-1 expression and COX-2 expression, which can be induced by progesterone treatment. These observations support and extend the role of over-expression of progesterone receptors as a mechanism underlying slow-transit constipation in women.See page 445.Hepatic and Visceral Fat in the Metabolic SyndromeThe Western world currently faces a growing epidemic of obesity, which is causally associated with major morbidity, mortality, and economic impacts. Abdominal obesity, rather than a high body mass index, is the major risk factor for abnormalities in glucose and lipid metabolism, referred to as the metabolic syndrome. Both increased visceral adipose tissue (VAT) and increased hepatic fat have been linked to hepatic insulin resistance in obesity and in type 2 diabetes mellitus. Release of free fatty acids from VAT has been hypothesized to enhance hepatic gluconeogenesis and insulin resistance. However, a strong association exists between nonalcoholic fatty liver disease and hepatic insulin resistance, and this relationship does not seem to be explained by obesity or visceral fat content alone. So far, the relationships between glucose tolerance, gluconeogenesis, and visceral or liver fat content has not been addressed in a single comprehensive study.In this issue of Gastroenterology, Gastaldelli et al studied insulin resistance in 43 subjects with type 2 diabetes mellitus with a wide range of body mass indices (23–39 kg/m2) and 14 lean, normal, glucose-tolerant control subjects. The participants underwent a euglycemic hyperinsulinemic clamp study to measure hepatic and total body insulin sensitivity, measurement of lean body mass through the distribution volume of an intravenous bolus of 3H2O, magnetic resonance imaging to quantify subcutaneous and visceral fat content, and magnetic resonance spectroscopy to quantify liver fat content.Both VAT and liver fat content increased with age. In diabetic patients, the liver fat content was increased, even in those with a normal body mass index. Liver fat content was significantly correlated with VAT, but not subcutaneous fat area, both in controls and in type 2 diabetes.Basal total endogenous glucose production was increased in type 2 diabetics, and this was not correlated with body mass index, or subcutaneous, visceral, or liver fat content. Increased gluconeogenesis was associated with VAT, but not with hepatic fat content (Figure 2). During euglycemic insulin clamp, impaired suppression of endogenous glucose production was correlated with both increased VAT and liver fat content. Accelerated gluconeogenesis was associated with elevated basal plasma free fatty acid levels; impaired suppression of gluconeogenesis was associated with impaired suppression of plasma free fatty acid levels by insulin.Figure 2Relationship between basal gluconeogenic flux versus liver fat (%) and visceral adipose tissue (VAT) in nondiabetic (solid circles) and diabetic (open circles) subjects.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Multivariate analysis confirmed that gluconeogenesis was related only to VAT content, whereas basal hepatic and adipose insulin resistance indices and residual hepatic endogenous glucose production during insulin clamp were related to both VAT and liver fat content. Increased liver fat was also correlated to adipose tissue insulin resistance and impaired suppression of plasma free fatty acids concentration during the insulin clamp.The study by Gastaldelli et al provides important insights in the role of visceral and hepatic adipose tissue in the manifestations of the metabolic syndrome. They are supportive of the portal hypothesis, where free fatty acids and other factors released from VAT contribute to increased hepatic gluconeogenesis. In turn, increased free fatty acids may contribute to the promotion of hepatic fat accumulation. Increased liver fat content was closely correlated to both peripheral and hepatic insulin resistance, and the underlying mechanisms here need to be addressed in further studies.See page 496.A Villus-Phased, Tcf3-Dependent Wnt Signal in Mouse Intestinal DevelopmentWnt signaling is an important pathway that prepares intestinal epithelial progenitor cells to replicate and differentiate into mature lineages, and disruption of this pathway is a key mediator for colon cancer pathogenesis in adulthood. The establishment of Wnt signaling patterns in the intestine during embryogenesis to achieve mature cells, however, is not clear.In the study by Kim et al, patterning of Wnt signaling in villi and intervillus cell development were studied using TOP-GAL transgenic mice, which carry a β-galactosidase gene under the control of a Wnt/Tcf-responsive promoter and faithfully report canonical Wnt activity. Although adult mice express Wnt signals restricted to the crypt base and are particularly seen in Paneth cells, developing embryo intestines do not display Wnt signaling until after E14 that increases steadily until E18.5 then persists until 2 days after birth. The Wnt signal is active in the newly formed villi (including downstream effector expression of nuclear β-catenin and c-Myc) and absent in intervillus cells that give rise to the crypts, and the villus expression predominates until birth when shifting to the crypts occurs completely by 2 days after birth (Figure 3). The embryonic villus Wnt signal is not associated with epithelial proliferation as determined by BrdU pulsing (which is readily apparent in the non-Wnt intervillus areas), and which appears to have Tcf3 instead of Tcf4 as its effector as determined by immunostained protein location. Premature activation of β-catenin in the embryologic intestine by forced expression caused individual villi to separate improperly owing to the lack of formation of secondary lumina needed to separate villi.Figure 3Relation of canonical Wnt signaling in perinatal intestinal villi to cell proliferation and to other markers of Wnt activity. (A) β-Galactosidase in situ hybridization on E16.5 TOP-GAL mouse intestine, confirming mRNA expression in villus but not intervillus cells in prospective duodenum. (B) Transition from intestinal villus to intervillus concentration of Wnt activity in neonatal mice. The LacZ signal diminishes in TOP-GAL villus tips, and although villus activity remains, β-galactosidase activity is detected for the first time in approximately 20% of intervillus regions (black compared with green arrowheads) in duodenum. (C) In older mice (P20), nuclear β-catenin is restricted to crypts, especially in Paneth cells at the base (arrowheads). (D) Immunohistochemistry for activated nuclear β-catenin. (F) c-Myc in E18.5 duodenum provides independent evidence for canonical Wnt signaling in villus but not intervillus cells in late fetal stages.View Large Image Figure ViewerDownload Hi-res image Download (PPT)The study indicates that the developing gut follows a specific nonproliferating but differentiating pattern of Wnt signaling in the villus that is likely mediated by Tcf3, and changes to this pattern result in malformed gut villi. This pattern is markedly different than the crypt Wnt signaling program in adults.See page 529.Endogenous and Bone Marrow–Derived, Bidifferentiating Oval Cells Are Increased by G-CSF Administration in Rats: A Potential Aid for Hepatic RegenerationHepatic oval cells are considered stem cells because the can bidifferentiate into hepatocytes and cholangiocytes, 2 major parenchymal cell populations in the liver. A portion of hepatic oval cells are derived from the bone marrow, and pharmacologically increasing the number of oval cells in the liver endogenously or from bone marrow may improve regeneration of the liver in diseased states. Granulocyte-colony stimulating factor (G-CSF) may be effective in mobilizing cells for liver regeneration, but it is unclear if G-CSF acts only by recruiting cells from the bone marrow, or can act locally in the liver for eventual regeneration.In the study by Piscaglia et al, oval cell recruitment by G-CSF was examined using rats treated with 2-acetylaminofluorene (2AAF) to inhibit hepatocyte proliferation prior to partial hepatectomy (PH), a well-established model of oval cell recruitment that peaks about 11 days after the PH, with hepatocyte differentiation by 14 days. Additionally, dipeptidyl-peptidase-IV (DPPIV+) bone marrow cells were used for transplantation into DPPIV-deficient rats (DPPIV−) to detect the degree of donor-derived bone marrow cells in the recipients after 2AAF/PH. Expression of the G-CSF receptor (G-CSFR), which is absent in normal liver, was induced in the 2AAF/PH model and localized to ductular and periductular cells after oval cell activation, and G-CSF also co-localized with G-CSFR to activated oval cells. Using 2 different formulations of exogenous recombinant G-CSF, G-CSF increased the number of OV6+ oval cells 2–5 times control on day 11, and persisted at a 5- to 9-fold increase on day 28 after 2AAF/PH (Figure 4A). Although the number of bone marrow-derived oval cells in the liver is small normally (<1%), G-CSF significantly increased this 4-fold on day 11 and persisted at 6-fold on day 28 after 2AAF/PH (Figure 4B). In vitro isolation of oval cells from rat livers indicate that G-CSF directly causes proliferation and cell migration at a dose of 100 ng/mL, whereas lower or higher doses are not as effective.Figure 4(A) Average OV6+ cells/field in livers of animals treated with both pegylated and nonpegylated G-CSF at 11 and 28 days after 2-acetylaminofluorene/partial hepatectomy (2AAF/PH), as compared with 2AAF/PH alone (control, cnt). (B) Average dipeptidyl-peptidase-IV (DPPIV+) cells/field in livers of animals treated with both pegylated and nonpegylated G-CSF at 11 and 28 days after 2AAF/PH, as compared with 2AAF/PH alone (cnt). Data represent the mean value ± SD of cell counts, normalized with respect to control (*P < .05).View Large Image Figure ViewerDownload Hi-res image Download (PPT)This study indicates that G-CSF may act in an autocrine and paracrine fashion to enhance both the engraftment of bone marrow-derived oval cells into the liver and the endogenous hepatic oval cell activation. This supports the possibility that G-CSF could be an adjunct to aid liver regeneration.See page 619. Altered Prostaglandin Pathways in Slow-Transit ConstipationSlow-transit constipation is a relatively rare form of severe refractory constipation that is most frequently encountered in young women. Previous studies indicated a role for increased muscle sensitivity to normal circulating levels of progesterone, attributable to nuclear over-expression of progesterone receptors. However, the mechanism through which increased sensitivity to progesterone inhibits colonic contractility remains to be elucidated.In this issue of Gastroenterology, Cong et al report on studies of the prostaglandin and cyclooxygenase (COX) pathways in colonic smooth muscle from women with slow-transit constipation. Surgical specimens were obtained from the descending colon in 8 women with slow-transit constipation and 8 women in the control group who underwent surgery for adenocarcinoma. The authors performed smooth muscle contractility studies and expression studies for prostaglandins, thromboxane, COX enzymes, and progesterone receptors.Muscle strips from patients with slow-transit constipation had decreased basal contractility, and this was associated with decreased levels of PGF2α and TxB2 and increased levels of PGE2 in colonic smooth muscle (Figure 1). PGF2α and TXA2 contract while PGE2 relaxes colonic circular muscle. Smooth muscle from patients with slow-transit constipation also had a decreased expression of COX-1 and an increased expression of COX-2 enzymes and progesterone receptors.Incubation of dissociated colonic smooth muscle cells from control subjects with progesterone 10–5 mol for 6 hours induced all of these changes, namely, a reduction in PGF2α and TXB2 levels, an increase in PGE2 levels and COX-2 expression, as well as reduced COX-1 expression. Inhibition of COX-1 decreased PGF2α and TxA2 levels, whereas inhibition of COX-2 decreased PGE2 levels.These observations help to further elucidate the mechanisms underlying impaired colonic propulsive contractility in women with slow-transit constipation. Colonic smooth muscle in these patients is characterized by lower levels of prostaglandins that cause contraction, such as TxA2 and PGF2α, and higher levels of prostaglandins that cause relaxation, such as PGE2. The abnormalities in prostaglandin levels are due to lower COX-1 expression and COX-2 expression, which can be induced by progesterone treatment. These observations support and extend the role of over-expression of progesterone receptors as a mechanism underlying slow-transit constipation in women.See page 445. Slow-transit constipation is a relatively rare form of severe refractory constipation that is most frequently encountered in young women. Previous studies indicated a role for increased muscle sensitivity to normal circulating levels of progesterone, attributable to nuclear over-expression of progesterone receptors. However, the mechanism through which increased sensitivity to progesterone inhibits colonic contractility remains to be elucidated. In this issue of Gastroenterology, Cong et al report on studies of the prostaglandin and cyclooxygenase (COX) pathways in colonic smooth muscle from women with slow-transit constipation. Surgical specimens were obtained from the descending colon in 8 women with slow-transit constipation and 8 women in the control group who underwent surgery for adenocarcinoma. The authors performed smooth muscle contractility studies and expression studies for prostaglandins, thromboxane, COX enzymes, and progesterone receptors. Muscle strips from patients with slow-transit constipation had decreased basal contractility, and this was associated with decreased levels of PGF2α and TxB2 and increased levels of PGE2 in colonic smooth muscle (Figure 1). PGF2α and TXA2 contract while PGE2 relaxes colonic circular muscle. Smooth muscle from patients with slow-transit constipation also had a decreased expression of COX-1 and an increased expression of COX-2 enzymes and progesterone receptors. Incubation of dissociated colonic smooth muscle cells from control subjects with progesterone 10–5 mol for 6 hours induced all of these changes, namely, a reduction in PGF2α and TXB2 levels, an increase in PGE2 levels and COX-2 expression, as well as reduced COX-1 expression. Inhibition of COX-1 decreased PGF2α and TxA2 levels, whereas inhibition of COX-2 decreased PGE2 levels. These observations help to further elucidate the mechanisms underlying impaired colonic propulsive contractility in women with slow-transit constipation. Colonic smooth muscle in these patients is characterized by lower levels of prostaglandins that cause contraction, such as TxA2 and PGF2α, and higher levels of prostaglandins that cause relaxation, such as PGE2. The abnormalities in prostaglandin levels are due to lower COX-1 expression and COX-2 expression, which can be induced by progesterone treatment. These observations support and extend the role of over-expression of progesterone receptors as a mechanism underlying slow-transit constipation in women. See page 445. Hepatic and Visceral Fat in the Metabolic SyndromeThe Western world currently faces a growing epidemic of obesity, which is causally associated with major morbidity, mortality, and economic impacts. Abdominal obesity, rather than a high body mass index, is the major risk factor for abnormalities in glucose and lipid metabolism, referred to as the metabolic syndrome. Both increased visceral adipose tissue (VAT) and increased hepatic fat have been linked to hepatic insulin resistance in obesity and in type 2 diabetes mellitus. Release of free fatty acids from VAT has been hypothesized to enhance hepatic gluconeogenesis and insulin resistance. However, a strong association exists between nonalcoholic fatty liver disease and hepatic insulin resistance, and this relationship does not seem to be explained by obesity or visceral fat content alone. So far, the relationships between glucose tolerance, gluconeogenesis, and visceral or liver fat content has not been addressed in a single comprehensive study.In this issue of Gastroenterology, Gastaldelli et al studied insulin resistance in 43 subjects with type 2 diabetes mellitus with a wide range of body mass indices (23–39 kg/m2) and 14 lean, normal, glucose-tolerant control subjects. The participants underwent a euglycemic hyperinsulinemic clamp study to measure hepatic and total body insulin sensitivity, measurement of lean body mass through the distribution volume of an intravenous bolus of 3H2O, magnetic resonance imaging to quantify subcutaneous and visceral fat content, and magnetic resonance spectroscopy to quantify liver fat content.Both VAT and liver fat content increased with age. In diabetic patients, the liver fat content was increased, even in those with a normal body mass index. Liver fat content was significantly correlated with VAT, but not subcutaneous fat area, both in controls and in type 2 diabetes.Basal total endogenous glucose production was increased in type 2 diabetics, and this was not correlated with body mass index, or subcutaneous, visceral, or liver fat content. Increased gluconeogenesis was associated with VAT, but not with hepatic fat content (Figure 2). During euglycemic insulin clamp, impaired suppression of endogenous glucose production was correlated with both increased VAT and liver fat content. Accelerated gluconeogenesis was associated with elevated basal plasma free fatty acid levels; impaired suppression of gluconeogenesis was associated with impaired suppression of plasma free fatty acid levels by insulin.Multivariate analysis confirmed that gluconeogenesis was related only to VAT content, whereas basal hepatic and adipose insulin resistance indices and residual hepatic endogenous glucose production during insulin clamp were related to both VAT and liver fat content. Increased liver fat was also correlated to adipose tissue insulin resistance and impaired suppression of plasma free fatty acids concentration during the insulin clamp.The study by Gastaldelli et al provides important insights in the role of visceral and hepatic adipose tissue in the manifestations of the metabolic syndrome. They are supportive of the portal hypothesis, where free fatty acids and other factors released from VAT contribute to increased hepatic gluconeogenesis. In turn, increased free fatty acids may contribute to the promotion of hepatic fat accumulation. Increased liver fat content was closely correlated to both peripheral and hepatic insulin resistance, and the underlying mechanisms here need to be addressed in further studies.See page 496. The Western world currently faces a growing epidemic of obesity, which is causally associated with major morbidity, mortality, and economic impacts. Abdominal obesity, rather than a high body mass index, is the major risk factor for abnormalities in glucose and lipid metabolism, referred to as the metabolic syndrome. Both increased visceral adipose tissue (VAT) and increased hepatic fat have been linked to hepatic insulin resistance in obesity and in type 2 diabetes mellitus. Release of free fatty acids from VAT has been hypothesized to enhance hepatic gluconeogenesis and insulin resistance. However, a strong association exists between nonalcoholic fatty liver disease and hepatic insulin resistance, and this relationship does not seem to be explained by obesity or visceral fat content alone. So far, the relationships between glucose tolerance, gluconeogenesis, and visceral or liver fat content has not been addressed in a single comprehensive study. In this issue of Gastroenterology, Gastaldelli et al studied insulin resistance in 43 subjects with type 2 diabetes mellitus with a wide range of body mass indices (23–39 kg/m2) and 14 lean, normal, glucose-tolerant control subjects. The participants underwent a euglycemic hyperinsulinemic clamp study to measure hepatic and total body insulin sensitivity, measurement of lean body mass through the distribution volume of an intravenous bolus of 3H2O, magnetic resonance imaging to quantify subcutaneous and visceral fat content, and magnetic resonance spectroscopy to quantify liver fat content. Both VAT and liver fat content increased with age. In diabetic patients, the liver fat content was increased, even in those with a normal body mass index. Liver fat content was significantly correlated with VAT, but not subcutaneous fat area, both in controls and in type 2 diabetes. Basal total endogenous glucose production was increased in type 2 diabetics, and this was not correlated with body mass index, or subcutaneous, visceral, or liver fat content. Increased gluconeogenesis was associated with VAT, but not with hepatic fat content (Figure 2). During euglycemic insulin clamp, impaired suppression of endogenous glucose production was correlated with both increased VAT and liver fat content. Accelerated gluconeogenesis was associated with elevated basal plasma free fatty acid levels; impaired suppression of gluconeogenesis was associated with impaired suppression of plasma free fatty acid levels by insulin. Multivariate analysis confirmed that gluconeogenesis was related only to VAT content, whereas basal hepatic and adipose insulin resistance indices and residual hepatic endogenous glucose production during insulin clamp were related to both VAT and liver fat content. Increased liver fat was also correlated to adipose tissue insulin resistance and impaired suppression of plasma free fatty acids concentration during the insulin clamp. The study by Gastaldelli et al provides important insights in the role of visceral and hepatic adipose tissue in the manifestations of the metabolic syndrome. They are supportive of the portal hypothesis, where free fatty acids and other factors released from VAT contribute to increased hepatic gluconeogenesis. In turn, increased free fatty acids may contribute to the promotion of hepatic fat accumulation. Increased liver fat content was closely correlated to both peripheral and hepatic insulin resistance, and the underlying mechanisms here need to be addressed in further studies. See page 496. A Villus-Phased, Tcf3-Dependent Wnt Signal in Mouse Intestinal DevelopmentWnt signaling is an important pathway that prepares intestinal epithelial progenitor cells to replicate and differentiate into mature lineages, and disruption of this pathway is a key mediator for colon cancer pathogenesis in adulthood. The establishment of Wnt signaling patterns in the intestine during embryogenesis to achieve mature cells, however, is not clear.In the study by Kim et al, patterning of Wnt signaling in villi and intervillus cell development were studied using TOP-GAL transgenic mice, which carry a β-galactosidase gene under the control of a Wnt/Tcf-responsive promoter and faithfully report canonical Wnt activity. Although adult mice express Wnt signals restricted to the crypt base and are particularly seen in Paneth cells, developing embryo intestines do not display Wnt signaling until after E14 that increases steadily until E18.5 then persists until 2 days after birth. The Wnt signal is active in the newly formed villi (including downstream effector expression of nuclear β-catenin and c-Myc) and absent in intervillus cells that give rise to the crypts, and the villus expression predominates until birth when shifting to the crypts occurs completely by 2 days after birth (Figure 3). The embryonic villus Wnt signal is not associated with epithelial proliferation as determined by BrdU pulsing (which is readily apparent in the non-Wnt intervillus areas), and which appears to have Tcf3 instead of Tcf4 as its effector as determined by immunostained protein location. Premature activation of β-catenin in the embryologic intestine by forced expression caused individual villi to separate improperly owing to the lack of formation of secondary lumina needed to separate villi.The study indicates that the developing gut follows a specific nonproliferating but differentiating pattern of Wnt signaling in the villus that is likely mediated by Tcf3, and changes to this pattern result in malformed gut villi. This pattern is markedly different than the crypt Wnt signaling program in adults.See page 529. Wnt signaling is an important pathway that prepares intestinal epithelial progenitor cells to replicate and differentiate into mature lineages, and disruption of this pathway is a key mediator for colon cancer pathogenesis in adulthood. The establishment of Wnt signaling patterns in the intestine during embryogenesis to achieve mature cells, however, is not clear. In the study by Kim et al, patterning of Wnt signaling in villi and intervillus cell development were studied using TOP-GAL transgenic mice, which carry a β-galactosidase gene under the control of a Wnt/Tcf-responsive promoter and faithfully report canonical Wnt activity. Although adult mice express Wnt signals restricted to the crypt base and are particularly seen in Paneth cells, developing embryo intestines do not display Wnt signaling until after E14 that increases steadily until E18.5 then persists until 2 days after birth. The Wnt signal is active in the newly formed villi (including downstream effector expression of nuclear β-catenin and c-Myc) and absent in intervillus cells that give rise to the crypts, and the villus expression predominates until birth when shifting to the crypts occurs completely by 2 days after birth (Figure 3). The embryonic villus Wnt signal is not associated with epithelial proliferation as determined by BrdU pulsing (which is readily apparent in the non-Wnt intervillus areas), and which appears to have Tcf3 instead of Tcf4 as its effector as determined by immunostained protein location. Premature activation of β-catenin in the embryologic intestine by forced expression caused individual villi to separate improperly owing to the lack of formation of secondary lumina needed to separate villi. The study indicates that the developing gut follows a specific nonproliferating but differentiating pattern of Wnt signaling in the villus that is likely mediated by Tcf3, and changes to this pattern result in malformed gut villi. This pattern is markedly different than the crypt Wnt signaling program in adults. See page 529. Endogenous and Bone Marrow–Derived, Bidifferentiating Oval Cells Are Increased by G-CSF Administration in Rats: A Potential Aid for Hepatic RegenerationHepatic oval cells are considered stem cells because the can bidifferentiate into hepatocytes and cholangiocytes, 2 major parenchymal cell populations in the liver. A portion of hepatic oval cells are derived from the bone marrow, and pharmacologically increasing the number of oval cells in the liver endogenously or from bone marrow may improve regeneration of the liver in diseased states. Granulocyte-colony stimulating factor (G-CSF) may be effective in mobilizing cells for liver regeneration, but it is unclear if G-CSF acts only by recruiting cells from the bone marrow, or can act locally in the liver for eventual regeneration.In the study by Piscaglia et al, oval cell recruitment by G-CSF was examined using rats treated with 2-acetylaminofluorene (2AAF) to inhibit hepatocyte proliferation prior to partial hepatectomy (PH), a well-established model of oval cell recruitment that peaks about 11 days after the PH, with hepatocyte differentiation by 14 days. Additionally, dipeptidyl-peptidase-IV (DPPIV+) bone marrow cells were used for transplantation into DPPIV-deficient rats (DPPIV−) to detect the degree of donor-derived bone marrow cells in the recipients after 2AAF/PH. Expression of the G-CSF receptor (G-CSFR), which is absent in normal liver, was induced in the 2AAF/PH model and localized to ductular and periductular cells after oval cell activation, and G-CSF also co-localized with G-CSFR to activated oval cells. Using 2 different formulations of exogenous recombinant G-CSF, G-CSF increased the number of OV6+ oval cells 2–5 times control on day 11, and persisted at a 5- to 9-fold increase on day 28 after 2AAF/PH (Figure 4A). Although the number of bone marrow-derived oval cells in the liver is small normally (<1%), G-CSF significantly increased this 4-fold on day 11 and persisted at 6-fold on day 28 after 2AAF/PH (Figure 4B). In vitro isolation of oval cells from rat livers indicate that G-CSF directly causes proliferation and cell migration at a dose of 100 ng/mL, whereas lower or higher doses are not as effective.This study indicates that G-CSF may act in an autocrine and paracrine fashion to enhance both the engraftment of bone marrow-derived oval cells into the liver and the endogenous hepatic oval cell activation. This supports the possibility that G-CSF could be an adjunct to aid liver regeneration.See page 619. Hepatic oval cells are considered stem cells because the can bidifferentiate into hepatocytes and cholangiocytes, 2 major parenchymal cell populations in the liver. A portion of hepatic oval cells are derived from the bone marrow, and pharmacologically increasing the number of oval cells in the liver endogenously or from bone marrow may improve regeneration of the liver in diseased states. Granulocyte-colony stimulating factor (G-CSF) may be effective in mobilizing cells for liver regeneration, but it is unclear if G-CSF acts only by recruiting cells from the bone marrow, or can act locally in the liver for eventual regeneration. In the study by Piscaglia et al, oval cell recruitment by G-CSF was examined using rats treated with 2-acetylaminofluorene (2AAF) to inhibit hepatocyte proliferation prior to partial hepatectomy (PH), a well-established model of oval cell recruitment that peaks about 11 days after the PH, with hepatocyte differentiation by 14 days. Additionally, dipeptidyl-peptidase-IV (DPPIV+) bone marrow cells were used for transplantation into DPPIV-deficient rats (DPPIV−) to detect the degree of donor-derived bone marrow cells in the recipients after 2AAF/PH. Expression of the G-CSF receptor (G-CSFR), which is absent in normal liver, was induced in the 2AAF/PH model and localized to ductular and periductular cells after oval cell activation, and G-CSF also co-localized with G-CSFR to activated oval cells. Using 2 different formulations of exogenous recombinant G-CSF, G-CSF increased the number of OV6+ oval cells 2–5 times control on day 11, and persisted at a 5- to 9-fold increase on day 28 after 2AAF/PH (Figure 4A). Although the number of bone marrow-derived oval cells in the liver is small normally (<1%), G-CSF significantly increased this 4-fold on day 11 and persisted at 6-fold on day 28 after 2AAF/PH (Figure 4B). In vitro isolation of oval cells from rat livers indicate that G-CSF directly causes proliferation and cell migration at a dose of 100 ng/mL, whereas lower or higher doses are not as effective. This study indicates that G-CSF may act in an autocrine and paracrine fashion to enhance both the engraftment of bone marrow-derived oval cells into the liver and the endogenous hepatic oval cell activation. This supports the possibility that G-CSF could be an adjunct to aid liver regeneration. See page 619. Abnormalities of Prostaglandins and Cyclooxygenase Enzymes in Female Patients With Slow-Transit ConstipationGastroenterologyVol. 133Issue 2PreviewBackground & Aims: Chronic constipation due to slow transit (STC) is more common in female than in male patients. We have previously shown that these gender differences may be due to over expression of progesterone (PG) receptors that alter G protein patterns. We sought to elucidate the mechanisms responsible for the impaired basal colonic motility in female patients with STC. Methods: Muscle tissues from females with STC and controls with adeno-carcinoma of the colon were studied. Prostaglandins were determined by immunoassay, COX enzymes by Western blot and COX enzymes and progesterone receptors mRNA by RT-PCR. Full-Text PDF Relationship Between Hepatic/Visceral Fat and Hepatic Insulin Resistance in Nondiabetic and Type 2 Diabetic SubjectsGastroenterologyVol. 133Issue 2PreviewBackground & Aims: Abdominal fat accumulation (visceral/hepatic) has been associated with hepatic insulin resistance (IR) in obesity and type 2 diabetes (T2DM). We examined the relationship between visceral/hepatic fat accumulation and hepatic IR/accelerated gluconeogenesis (GNG). Methods: In 14 normal glucose tolerant (NGT) (body mass index [BMI] = 25 ± 1 kg/m2) and 43 T2DM (24 nonobese, BMI = 26 ± 1; 19 obese, BMI = 32 ± 1 kg/m2) subjects, we measured endogenous (hepatic) glucose production (3-3H-glucose) and GNG (2H2O) in the basal state and during 240 pmol/m2/min euglycemic-hyperinsulinemic clamp, and liver (LF) subcutaneous (SAT)/visceral (VAT) fat content by magnetic resonance spectroscopy/magnetic resonance imaging. Full-Text PDF Phases of Canonical Wnt Signaling During the Development of Mouse Intestinal EpitheliumGastroenterologyVol. 133Issue 2PreviewBackground & Aims: Intestinal crypts constitute a niche in which epithelial progenitors respond to Wnt signals, replicate, and prepare to differentiate. Because mutations in Wnt pathway genes lead to intestinal cancer, the role of Wnt signaling in gut epithelial homeostasis is a subject of intense investigation. We studied how Wnt signaling is established during intestine development. Methods: We studied spatiotemporal features of Wnt signaling at formative stages in mouse embryos, when villous projections appear and crypt precursors occupy intervillus regions. Full-Text PDF Granulocyte–Colony Stimulating Factor Promotes Liver Repair and Induces Oval Cell Migration and Proliferation in RatsGastroenterologyVol. 133Issue 2PreviewBackground & Aims: Hepatic regeneration is a heterogeneous phenomenon involving several cell populations. Oval cells are considered liver stem cells, a portion of which derive from bone marrow (BM). Recent studies have shown that granulocyte–colony stimulating factor (G-CSF) may be effective in facilitating liver repair. However, it remains unclear if G-CSF acts by mobilizing BM cells, or if it acts locally within the liver microenvironment to facilitate the endogenous restoration program. In the present study, we assessed the involvement of G-CSF during oval cell activation. Full-Text PDF