Transitions to food democracy through multilevel governance

Food systems in Europe are largely unjust and not sustainable. Despite substantial negative consequences for individual health, the environment and public sector health and care services, large multi-national corporations continue to benefit from the way food systems are designed—perpetuating “Lose–Lose–Lose–Win” food systems that see these large corporations benefit at the expense of health, the environment and public sector finances. Transitioning to “Win–Win–Win–Win” food systems is challenging because of the heterogeneity, complexity and unpredictable nature of food systems—one-size fits-all solutions to correct imbalances and injustices cannot exist. To address these challenges, we propose the use of heuristics—solutions that can flexibly account for different contexts, preferences and needs. Within food systems, food democracy could be a heuristic solution that provides the processes and can form the basis for driving just transitions. However, ensuring that these transition processes are fair, equitable, sustainable and constructive, requires an approach that can be used across vertical and horizontal governance spheres to ensure the voices of key stakeholders across space, time and spheres of power are accounted for. In this manuscript we outline a new Horizon project, FEAST, that aims to use multilevel governance approaches across vertical and horizontal spheres of governance to realize constructive food democracy. We envisage this as a means to inform just processes that can be used to design and implement policies, in line with food democracy, to facilitate transitions to “Win–Win–Win–Win” food systems across Europe that makes it easy for every European to eat a healthy and sustainable diet.

Fingerfoods: a feasibility study to enhance fruit and vegetable consumption in Dutch patients with dementia in a nursing home

BACKGROUND

Eating problems are highly prevalent in older patients with dementia and as a consequence, these patients are at greater risk of becoming malnourished. Fingerfoods, snacks that can be picked with thumb and forefinger, could be used to counteract malnutrition in patients with dementia. The aim of this feasibility study was to evaluate whether providing fruit and vegetable rich fingerfoods in the form of recognizable and familiar snacks on top of the normal intake was feasible for both patients with dementia and caregivers as a means to increase patients' nutritional status.

METHODS

Institutionalised patients with dementia (N = 15, 93% female, mean age = 85 years) were included in this feasibility study in the Netherlands. The residents received their regular diet supplemented with fingerfoods, comprising quiches and cakes rich in fruit or vegetables, for 6 weeks. Daily fingerfood consumption together with compensation behaviour at dinner of residents was administered with a checklist and food diaries at the start and end of the intervention as dose delivered. Furthermore, caregivers were asked to fill out a feedback form at the end of the intervention to measure fidelity and appreciation of the intervention.

RESULTS

Patients consumed on average 1.4 pieces (70 g) of fingerfoods daily, containing 41 g of fruit and/or vegetables. Fruit and vegetable consumption increased during the provision of the fingerfoods and the residents seemed not to compensate this intake during the rest of the day. The intervention was generally positively received by the majority of caregivers, depending on the type of fingerfood and state of the resident.

CONCLUSION

This feasibility study showed that providing recognizable fruit and vegetable rich fingerfoods to patients with dementia seems feasible for both patients and caregivers and could provide a pragmatic approach to enhance fruit and vegetable consumption and total food intake in institutionalized elderly. In an up-scaled study, effects of fingerfoods on nutritional status and quality of life should be investigated.

Truncation of Pik3r1 causes severe insulin resistance uncoupled from obesity and dyslipidaemia by increased energy expenditure

OBJECTIVE

Insulin signalling via phosphoinositide 3-kinase (PI3K) requires PIK3R1-encoded regulatory subunits. C-terminal PIK3R1 mutations cause SHORT syndrome, as well as lipodystrophy and insulin resistance (IR), surprisingly without fatty liver or metabolic dyslipidaemia. We sought to investigate this discordance.

METHODS

The human pathogenic Pik3r1 Y657∗ mutation was knocked into mice by homologous recombination. Growth, body composition, bioenergetic and metabolic profiles were investigated on chow and high-fat diet (HFD). We examined adipose and liver histology, and assessed liver responses to fasting and refeeding transcriptomically.

RESULTS

Like humans with SHORT syndrome, Pik3r1WT/Y657∗ mice were small with severe IR, and adipose expansion on HFD was markedly reduced. Also as in humans, plasma lipid concentrations were low, and insulin-stimulated hepatic lipogenesis was not increased despite hyperinsulinemia. At odds with lipodystrophy, however, no adipocyte hypertrophy nor adipose inflammation was found. Liver lipogenic gene expression was not significantly altered, and unbiased transcriptomics showed only minor changes, including evidence of reduced endoplasmic reticulum stress in the fed state and diminished Rictor-dependent transcription on fasting. Increased energy expenditure, which was not explained by hyperglycaemia nor intestinal malabsorption, provided an alternative explanation for the uncoupling of IR from dyslipidaemia.

CONCLUSIONS

Pik3r1 dysfunction in mice phenocopies the IR and reduced adiposity without lipotoxicity of human SHORT syndrome. Decreased adiposity may not reflect bona fide lipodystrophy, but rather, increased energy expenditure, and we suggest that further study of brown adipose tissue in both humans and mice is warranted.

Lifestyle medicine for type 2 diabetes: practice-based evidence for long-term efficacy of a multicomponent lifestyle intervention (Reverse Diabetes2 Now)

Introduction

A wealth of evidence supports short-term efficacy of lifestyle interventions in type 2 diabetes (T2D). However, little is known about long-term effects of lifestyle interventions in real-life settings.

Methods

This observational, single-arm study evaluated long-term impact of ‘Voeding Leeft: Reverse-Diabetes2-Now’, a 6-month multicomponent lifestyle programme, on glycaemic control and glucose-lowering medication (GLmed) use, other T2D parameters and quality of life in 438 T2D participants at 6, 12, 18 and 24 months using paired sample t-tests, χ² and generalised linear models.

Results

At 24 months, 234 participants provided information on GLmed and HbA1c (‘responders’). 67% of the responders used less GLmed, and 28% ceased all GLmed. Notably, 71% of insulin users at baseline (n=47 of 66 insulin users) were off insulin at 24 months. Mean HbA1c levels were similar at 24 months compared with baseline (55.6±12.8 vs. 56.3±10.5 mmol/mol, p=0.43), but more responders had HbA1c levels ≤53 mmol/mol at 24 months (53% vs 45% at baseline). Furthermore, triglyceride levels (−0.34±1.02 mmol/L, p=0.004), body weight (−7.0±6.8 kg, p<0.001), waist circumference (−7.9±8.2 cm, p<0.001), body mass index (−2.4±2.3 kg/m², p<0.001) and total cholesterol/high-density lipoprotein (HDL) ratio (−0.22±1.24, p=0.044) were lower, while HDL (+0.17 ± 0.53 mmol/L, p<0.001) and low-density lipoprotein-cholesterol levels (+0.18 ± 1.06 mmol/L, p=0.040) were slightly higher. No differences were observed in fasting glucose or total cholesterol levels. Quality of life and self-reported health significantly improved.

Conclusion

This study indicates robust, durable real-life benefits of this lifestyle group programme after up to 24 months of follow-up, particularly in terms of medication use, body weight and quality of life in T2D patients.

Programming of central and peripheral insulin resistance by low birthweight and postnatal catch-up growth in male mice

AIMS

Intra-uterine growth restriction (IUGR) followed by accelerated postnatal growth is associated with an increased risk of obesity and type 2 diabetes. We aimed to determine central and peripheral insulin sensitivity in mice that underwent IUGR followed by postnatal catch-up growth and investigate potential molecular mechanisms underpinning their physiology.

METHODS

We used a C57BL/6J mouse model of maternal diet-induced IUGR (maternal diet, 8% protein) followed by cross-fostering to a normal nutrition dam (maternal diet, 20% protein) and litter size manipulation to cause accelerated postnatal catch-up growth. We performed intracerebroventricular insulin injection and hyperinsulinaemic-euglycaemic clamp studies to examine the effect of this early nutritional manipulation on central and peripheral insulin resistance. Furthermore, we performed quantitative real-time PCR and western blotting to examine the expression of key insulin-signalling components in discrete regions of the hypothalamus.

RESULTS

IUGR followed by accelerated postnatal growth caused impaired glucose tolerance and peripheral insulin resistance. In addition, these 'recuperated' animals were resistant to the anorectic effects of central insulin administration. This central insulin resistance was associated with reduced protein levels of the p110β subunit of phosphoinositide 3-kinase (PI3K) and increased serine phosphorylation of IRS-1 in the arcuate nucleus (ARC) of the hypothalamus. Expression of the gene encoding protein tyrosine phosphatase 1B (PTP1B; Ptpn1) was also increased specifically in this region of the hypothalamus.

CONCLUSIONS/INTERPRETATION

Mice that undergo IUGR followed by catch-up growth display peripheral and central insulin resistance in adulthood. Recuperated offspring show changes in expression/phosphorylation of components of the insulin signalling pathway in the ARC. These defects may contribute to the resistance to the anorectic effects of central insulin, as well as the impaired glucose homeostasis seen in these animals.

Aberrant ribonucleotide incorporation and multiple deletions in mitochondrial DNA of the murine MPV17 disease model

All DNA polymerases misincorporate ribonucleotides despite their preference for deoxyribonucleotides, and analysis of cultured cells indicates that mammalian mitochondrial DNA (mtDNA) tolerates such replication errors. However, it is not clear to what extent misincorporation occurs in tissues, or whether this plays a role in human disease. Here, we show that mtDNA of solid tissues contains many more embedded ribonucleotides than that of cultured cells, consistent with the high ratio of ribonucleotide to deoxynucleotide triphosphates in tissues, and that riboadenosines account for three-quarters of them. The pattern of embedded ribonucleotides changes in a mouse model of Mpv17 deficiency, which displays a marked increase in rGMPs in mtDNA. However, while the mitochondrial dGTP is low in the Mpv17^−/− liver, the brain shows no change in the overall dGTP pool, leading us to suggest that Mpv17 determines the local concentration or quality of dGTP. Embedded rGMPs are expected to distort the mtDNA and impede its replication, and elevated rGMP incorporation is associated with early-onset mtDNA depletion in liver and late-onset multiple deletions in brain of Mpv17^−/− mice. These findings suggest aberrant ribonucleotide incorporation is a primary mtDNA abnormality that can result in pathology.

A Western-style obesogenic diet alters maternal metabolic physiology with consequences for fetal nutrient acquisition in mice

KEY POINTS

In the Western world, obesogenic diets containing high fat and high sugar (HFHS) are commonly consumed during pregnancy, although their effects on the metabolism of the mother, in relation to feto-placental glucose utilization and growth, are unknown. In the present study, the consumption of an obesogenic HFHS diet compromised maternal glucose tolerance and insulin sensitivity in late pregnancy in association with dysregulated lipid and glucose handling by the dam. These maternal metabolic changes induced by HFHS feeding were related to altered feto-placental glucose metabolism and growth. A HFHS diet during pregnancy therefore causes maternal metabolic dysfunction with consequences for maternal nutrient allocation for fetal growth. These findings have implications for the health of women and their infants, who consume obesogenic diets during pregnancy.

ABSTRACT

In the Western world, obesogenic diets containing high fat and high sugar (HFHS) are commonly consumed during pregnancy. However, the impacts of a HFHS diet during pregnancy on maternal insulin sensitivity and signalling in relation to feto-placental growth and glucose utilization are unknown. The present study examined the effects of a HFHS diet during mouse pregnancy on maternal glucose tolerance and insulin resistance, as well as, on feto-placental glucose metabolism. Female mice were fed a control or HFHS diet from day (D) 1 of pregnancy (term = D20.5). At D16 or D19, dams were assessed for body composition, metabolite and hormone concentrations, tissue abundance of growth and metabolic signalling pathways, glucose tolerance and utilization and insulin sensitivity. HFHS feeding perturbed maternal insulin sensitivity in late pregnancy; hepatic insulin sensitivity was higher, whereas sensitivity of the skeletal muscle and white adipose tissue was lower in HFHS than control dams. These changes were accompanied by increased adiposity and reduced glucose production and glucose tolerance of HFHS dams. The HFHS diet also disturbed the hormone and metabolite milieu and altered expression of growth and metabolic signalling pathways in maternal tissues. Furthermore, HFHS feeding was associated with impaired feto-placental glucose metabolism and growth. A HFHS diet during pregnancy therefore causes maternal metabolic dysfunction with consequences for maternal nutrient allocation for fetal growth. These findings have implications for the health of women and their infants, who consume HFHS diets during pregnancy.

Proximity to Delivery Alters Insulin Sensitivity and Glucose Metabolism in Pregnant Mice

In late pregnancy, maternal insulin resistance occurs to support fetal growth, but little is known about insulin-glucose dynamics close to delivery. This study measured insulin sensitivity in mice in late pregnancy at day 16 (D16) and near term at D19. Nonpregnant (NP) and pregnant mice were assessed for metabolite and hormone concentrations, body composition by DEXA, tissue insulin signaling protein abundance by Western blotting, glucose tolerance and utilization, and insulin sensitivity using acute insulin administration and hyperinsulinemic-euglycemic clamps with [(3)H]glucose infusion. Whole-body insulin resistance occurred in D16 pregnant dams in association with basal hyperinsulinemia, insulin-resistant endogenous glucose production, and downregulation of several proteins in hepatic and skeletal muscle insulin signaling pathways relative to NP and D19 values. Insulin resistance was less pronounced at D19, with restoration of NP insulin concentrations, improved hepatic insulin sensitivity, and increased abundance of hepatic insulin signaling proteins. At D16, insulin resistance at whole-body, tissue, and molecular levels will favor fetal glucose acquisition, while improved D19 hepatic insulin sensitivity will conserve glucose for maternal use in anticipation of lactation. Tissue sensitivity to insulin, therefore, alters differentially with proximity to delivery in pregnant mice, with implications for human and other species.

MPV17 Loss Causes Deoxynucleotide Insufficiency and Slow DNA Replication in Mitochondria

MPV17 is a mitochondrial inner membrane protein whose dysfunction causes mitochondrial DNA abnormalities and disease by an unknown mechanism. Perturbations of deoxynucleoside triphosphate (dNTP) pools are a recognized cause of mitochondrial genomic instability; therefore, we determined DNA copy number and dNTP levels in mitochondria of two models of MPV17 deficiency. In Mpv17 ablated mice, liver mitochondria showed substantial decreases in the levels of dGTP and dTTP and severe mitochondrial DNA depletion, whereas the dNTP pool was not significantly altered in kidney and brain mitochondria that had near normal levels of DNA. The shortage of mitochondrial dNTPs in Mpv17^-/- liver slows the DNA replication in the organelle, as evidenced by the elevated level of replication intermediates. Quiescent fibroblasts of MPV17-mutant patients recapitulate key features of the primary affected tissue of the Mpv17^-/- mice, displaying virtual absence of the protein, decreased dNTP levels and mitochondrial DNA depletion. Notably, the mitochondrial DNA loss in the patients’ quiescent fibroblasts was prevented and rescued by deoxynucleoside supplementation. Thus, our study establishes dNTP insufficiency in the mitochondria as the cause of mitochondrial DNA depletion in MPV17 deficiency, and identifies deoxynucleoside supplementation as a potential therapeutic strategy for MPV17-related disease. Moreover, changes in the expression of factors involved in mitochondrial deoxynucleotide homeostasis indicate a remodeling of nucleotide metabolism in MPV17 disease models, which suggests mitochondria lacking functional MPV17 have a restricted purine mitochondrial salvage pathway.

Mitochondrial DNA depletion syndrome (MDS) is a genetically heterogeneous condition characterized by a decrease of mitochondrial DNA (mtDNA) copy number and decreased activities of respiratory chain enzymes. Depletion of mtDNA has been associated with mutations in several genes, which encode either proteins directly involved in mtDNA replication or factors regulating the homeostasis of the mitochondrial deoxynucleotide pool. However, for some genes the mechanism linking mutations and mtDNA depletion is not known. One such gene is MPV17, whose loss-of-function causes mtDNA abnormalities in human, mouse and yeast. Here we show that MPV17 dysfunction leads to a shortage of the precursors for DNA synthesis in the mitochondria, slowing DNA replication in the organelle. Not only does mtDNA copy number correlate with dNTP pool size in both mouse tissues and human cells, deoxynucleoside supplementation of the growth medium prevents depletion and restores mtDNA copy number in quiescent MPV17-deficient cells. Hence, our study links MPV17 deficiency, insufficiency of mitochondrial dNTPs, and slow replication in mitochondria to depletion of mtDNA manifesting in the human disease, and places MPV17-related disease firmly in the category of mtDNA disorders caused by deoxynucleotide perturbation. The prevention and reversal of mtDNA loss in MPV17 patient-derived cells identifies potential therapeutic strategy for a currently untreatable disease.

Diabetes risk gene and Wnt effector Tcf7l2/TCF4 controls hepatic response to perinatal and adult metabolic demand

Most studies on TCF7L2 SNP variants in the pathogenesis of type 2 diabetes (T2D) focus on a role of the encoded transcription factor TCF4 in β cells. Here, a mouse genetics approach shows that removal of TCF4 from β cells does not affect their function, whereas manipulating TCF4 levels in the liver has major effects on metabolism. In Tcf7l2(-/-) mice, the immediate postnatal surge in liver metabolism does not occur. Consequently, pups die due to hypoglycemia. By combining chromatin immunoprecipitation with gene expression profiling, we identify a TCF4-controlled metabolic gene program that is acutely activated in the postnatal liver. In concordance, adult liver-specific Tcf7l2 knockout mice show reduced hepatic glucose production during fasting and display improved glucose homeostasis when maintained on high-fat diet. Furthermore, liver-specific TCF4 overexpression increases hepatic glucose production. These observations imply that TCF4 directly activates metabolic genes and that inhibition of Wnt signaling may be beneficial in metabolic disease.

A new role for lipocalin prostaglandin d synthase in the regulation of brown adipose tissue substrate utilization

In this study, we define a new role for lipocalin prostaglandin D synthase (L-PGDS) in the control of metabolic fuel utilization by brown adipose tissue (BAT). We demonstrate that L-PGDS expression in BAT is positively correlated with BAT activity, upregulated by peroxisome proliferator-activated receptor γ coactivator 1α or 1β and repressed by receptor-interacting protein 140. Under cold-acclimated conditions, mice lacking L-PGDS had elevated reliance on carbohydrate to provide fuel for thermogenesis and had increased expression of genes regulating glycolysis and de novo lipogenesis in BAT. These transcriptional differences were associated with increased lipid content in BAT and a BAT lipid composition enriched with de novo synthesized lipids. Consistent with the concept that lack of L-PGDS increases glucose utilization, mice lacking L-PGDS had improved glucose tolerance after high-fat feeding. The improved glucose tolerance appeared to be independent of changes in insulin sensitivity, as insulin levels during the glucose tolerance test and insulin, leptin, and adiponectin levels were unchanged. Moreover, L-PGDS knockout mice exhibited increased expression of genes involved in thermogenesis and increased norepinephrine-stimulated glucose uptake to BAT, suggesting that sympathetically mediated changes in glucose uptake may have improved glucose tolerance. Taken together, these results suggest that L-PGDS plays an important role in the regulation of glucose utilization in vivo.

Loss-of-function mutations in IGSF1 cause an X-linked syndrome of central hypothyroidism and testicular enlargement

Congenital central hypothyroidism occurs either in isolation or in conjunction with other pituitary hormone deficits. Using exome and candidate gene sequencing, we identified 8 distinct mutations and 2 deletions in IGSF1 in males from 11 unrelated families with central hypothyroidism, testicular enlargement and variably low prolactin concentrations. IGSF1 is a membrane glycoprotein that is highly expressed in the anterior pituitary gland, and the identified mutations impair its trafficking to the cell surface in heterologous cells. Igsf1-deficient male mice show diminished pituitary and serum thyroid-stimulating hormone (TSH) concentrations, reduced pituitary thyrotropin-releasing hormone (TRH) receptor expression, decreased triiodothyronine concentrations and increased body mass. Collectively, our observations delineate a new X-linked disorder in which loss-of-function mutations in IGSF1 cause central hypothyroidism, likely secondary to an associated impairment in pituitary TRH signaling.

UCP1 induction during recruitment of brown adipocytes in white adipose tissue is dependent on cyclooxygenase activity

BACKGROUND

The uncoupling protein 1 (UCP1) is a hallmark of brown adipocytes and pivotal for cold- and diet-induced thermogenesis.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report that cyclooxygenase (COX) activity and prostaglandin E(2) (PGE(2)) are crucially involved in induction of UCP1 expression in inguinal white adipocytes, but not in classic interscapular brown adipocytes. Cold-induced expression of UCP1 in inguinal white adipocytes was repressed in COX2 knockout (KO) mice and by administration of the COX inhibitor indomethacin in wild-type mice. Indomethacin repressed beta-adrenergic induction of UCP1 expression in primary inguinal adipocytes. The use of PGE(2) receptor antagonists implicated EP(4) as a main PGE(2) receptor, and injection of the stable PGE(2) analog (EP(3/4) agonist) 16,16 dm PGE(2) induced UCP1 expression in inguinal white adipose tissue. Inhibition of COX activity attenuated diet-induced UCP1 expression and increased energy efficiency and adipose tissue mass in obesity-resistant mice kept at thermoneutrality.

CONCLUSIONS/SIGNIFICANCE

Our findings provide evidence that induction of UCP1 expression in white adipose tissue, but not in classic interscapular brown adipose tissue is dependent on cyclooxygenase activity. Our results indicate that cyclooxygenase-dependent induction of UCP1 expression in white adipose tissues is important for diet-induced thermogenesis providing support for a surprising role of COX activity in the control of energy balance and obesity development.

Abstract 4166: Targeted expression of the Pleomorphic adenoma gene 1 in the pancreas of mice leads to islet hyperplasia

Pleomorphic adenoma gene 1 (PLAG1) encodes a transcription factor that is involved in several human neoplasias such as in pleomorphic adenomas of the salivary glands, lipoblastoma, hepatoblastoma and AML. The oncogenic capacity of PLAG1 has been further demonstrated in vivo in PLAG1 transgenic mice, in which the activation of the PLAG1 expression is Cre-mediated. Targeted expression of PLAG1 in the salivary gland or in the mammary gland leads to pleomorphic adenomas of the salivary glands and adenomyoepitheliomatous lesions of the mammary glands, respectively. Here, we investigated the impact of targeted PLAG1 expression in the pancreas. Pdx1-Cre-mediated targeted expression of PLAG1 in the whole pancreas, leads to islet hyperplasia. Although there was initially a balanced increase in the insulin, somatostatin and glucagon content of the pancreas, in older P1-Pdx1Cre mice the production of insulin and somatostatin far exceeded that of glucagon (82%, 275% and 9% respectively in 1 year old P1-Pdx1Cre mice as compared to littermate Pdx1-Cre mice). This was associated with hyperinsulinemia and an increased ability to dispose glucose in P1-Pdx1Cre mice, and progressive development of severe hypoglycaemia. Only 1/10 one year old mice developed a pancreatic tumor. We also investigated the consequence of overexpression of PLAG1 only in β-cells by using RIP-Cre mice. Similar to P1-Pdx1Cre mice, P1-RIPCre mice displayed islet hyperplasia, hyperinsulinemia and an increased ability to dispose glucose. Nevertheless, in contrast to P1-Pdx1Cre mice, P1-RIPCre mice stay normoglycemic and compensate for the hyperinsulinemia by the development of hepatic insulin resistance. In conclusion our data demonstrates that targeted expression of PLAG1 in the pancreas leads to islet hyperplasia rather than to pancreatic tumor formation.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4166.

Metabolomics (liver and blood profiling) in a mouse model in response to fasting: a study of hepatic steatosis

A metabolomic approach was applied to a mouse model of starvation-induced hepatic steatosis. After 24 h of fasting it appears that starvation reduced the phospholipids (PL), free cholesterol (FC), and cholesterol esters (CE) content of low-density lipoproteins (LDL). In liver lipid profiles major changes were observed using different techniques. High performance thin layer chromatography (HPTLC)-measurements of liver-homogenates indicated a significant rise of FC with 192%, triacylglycerols (TG) with 456% and cholesterol esters (CE) with 268% after 24 h of starvation in comparison with the control group. Reversed phase liquid chromatography coupled to mass spectrometry measurements (LC-MS) of liver homogenate indicated that the intensity of Phosphatidylcholine (PC) in the 24-h starvation group dropped to 90% of the value in the control group while the intensity of CE and TG increased to 157% and 331%, respectively, of the control group. Interestingly, a 49:4-TG with an odd number of C atoms appeared during starvation. This unique triacylglycerol has all characteristics of a biomarker for detection of hepatic steatosis. These observations indicate that in mammals liver lipid profiles are a dynamic system which are readily modulated by environmental factors like starvation.

Decreased Na+-dependent taurocholate uptake and low expression of the sinusoidal Na+-taurocholate cotransporting protein (Ntcp) in livers of mdr2 P-glycoprotein-deficient mice

BACKGROUND/AIMS

Ntcp-mediated uptake of bile salts at the basolateral membrane of hepatocytes is required for maintenance of their enterohepatic circulation. Expression of Ntcp is reduced in various experimental models of cholestasis associated with increased plasma bile salt concentrations. Mdr2 P-glycoprotein-deficient mice lack biliary phospholipids and cholesterol but show unchanged biliary bile salt secretion and increased bile flow. These mice are evidently not cholestatic, but plasma bile salt concentrations are markedly increased. The aim of this study was to investigate the role of Ntcp in the elevated bile salt levels in mdr2 P-glycoprotein-deficient (-/-) mice.

METHODS

Plasma membranes were isolated from male wild-type (+/+) and mdr2 (-/-) mice for measurement of Na+-dependent taurocholate transport and assessment of Ntcp protein levels by Western blotting. Northern blot analysis and competitive reverse transcription-polymerase chain reaction were used to determine hepatic Ntcp mRNA levels.

RESULTS

Kinetic analysis showed a 2-fold decrease in the Vmax of Na+-dependent taurocholate transport, with an unaffected Km in (-/-) mice compared with (+/+) controls. Ntcp protein levels were 4-6-fold reduced in plasma membranes of (-/-) mice relative to sex-matched controls. Surprisingly, hepatic Ntcp mRNA levels were not significantly affected in the (-/-) mice.

CONCLUSIONS

Elevated plasma bile salt levels in mdr2 P-glycoprotein-deficient mice in the absence of overt cholestasis are associated with reduced Ntcp expression and transport activity. This is due to posttranscriptional down-regulation of Ntcp.