A High Phosphorus Diet Affects Lipid Metabolism in Rat Liver: A DNA Microarray Analysis

The association between dietary mineral intake and the risk of preeclampsia in Chinese pregnant women: a matched case-control study

Previous studies on the relationship between dietary minerals and preeclampsia (PE) have given inconsistent results. The aim of this study was to further clarify the relationship between dietary minerals intake and PE in Chinese pregnant women. In this study, 440 pairs of hospital-based preeclamptic and healthy women were matched 1:1. Dietary intake was obtained through a 78-item semi-quantitative food frequency questionnaire. Multivariate conditional logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs). Restricted cubic splines were plotted to evaluate the dose-response relationship between dietary minerals intake and PE. This study found significant inverse associations for dietary intake of calcium, magnesium, phosphorus, iron, copper, manganese and zinc and the risk of PE in both univariate and multivariate models (all P- trend < 0.05). After adjusting for possible confounders, compared with the lowest quartile, the odds ratio of the highest quartile was 0.74 (95% CI 0.56-0.98) for calcium, 0.63 (95% CI 0.42-0.93) for magnesium, 0.45 (95% CI 0.31-0.65) for phosphorus, 0.44 (95% CI 0.30-0.65) for iron, 0.72 (95% CI 0.53-0.97) for copper, 0.66 (95% CI 0.48-0.91) for manganese and 0.38 (95% CI 0.25-0.57) for zinc. In addition, a reverse J-shaped relationship between dietary minerals intake and PE risk was observed (P-overall association < 0.05). In Chinese pregnant women, a higher intake of dietary minerals, including calcium, magnesium, phosphorus, copper, iron, manganese, and zinc was associated with a lower odds of PE.

A High-Phosphorus Diet Moderately Alters the Lipidome and Transcriptome in the Skeletal Muscle of Adult Mice

A high phosphorus intake has been associated with various metabolic disorders, including chronic kidney disease, cardiovascular disease, and osteoporosis. Recent studies have demonstrated the effects of dietary phosphorus on lipid and glucose metabolism. This study investigated the impact of a high-phosphorus diet on mouse skeletal muscle lipid composition and gene transcription. Adult male mice (n = 12/group) received either a diet with an adequate (0.3%) or a high (1.2%) phosphorus concentration for 6 weeks. The lipidome analysis showed that among the 17 analyzed lipid classes, the concentrations of three classes were reduced in the high phosphorus group compared to the adequate phosphorus group. These classes were phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and lysophosphatidylcholine (LPC) (p < 0.05). Out of the three hundred and twenty-three individual lipid species analyzed, forty-nine showed reduced concentrations, while three showed increased concentrations in the high phosphorus group compared to the adequate phosphorus group. The muscle transcriptome analysis identified 142 up- and 222 down-regulated transcripts in the high phosphorus group compared to the adequate phosphorus group. Gene set enrichment analysis identified that genes that were up-regulated in the high phosphorus group were linked to the gene ontology terms "mitochondria" and "Notch signaling pathway", whereas genes that were down-regulated were linked to the "PI3K-AKT pathway". Overall, the effects of the high-phosphorus diet on the muscle lipidome and transcriptome were relatively modest, but consistently indicated an impact on lipid metabolism.

Klf4-Sirt3/Pparα-Lcad pathway contributes to high phosphate-induced lipid degradation

BACKGROUND

Phosphorus commonly reduces lipid deposition in the vertebrates. However, the underlying mechanisms involved in the process remain unclear.

METHODS

Yellow catfish were given three experimental diets with dietary phosphate levels of 3.22, 6.47 and 7.99 g Pi kg^- 1, respectively, for 8 weeks. The contents of triglyceride, non-esterified free fatty acids, adenosine triphosphate, nicotinamide adenine dinucleotide, nicotinamide adenine dinucleotide, enzymatic activities, mRNA and protein expression were determined in the intestinal tissues. Hematoxylin and eosin, Oil Red O staining, and transmission electron microscope were performed for intestinal tissues. Primary intestinal epithelial cells were isolated from yellow catfish intestine. Western blot analysis, Immunoprecipitation assays, Immunofluorescence staining, and RNA extraction and quantitative real-time PCR were decided. Luciferase reporter assays and electrophoretic mobility shift assay were used to evaluate the function of Sirt3, PPARα and Lcad promoters.

RESULTS

High dietary phosphate intake activated intestinal phosphate absorption and excretion, and reduced lipid deposition through increasing lipolysis in the intestine. Moreover, phosphate incubation increased the mRNA and protein expression of krüppel like factor 4 (klf4), silent mating-type information regulation 2 homolog 3 (sirt3), peroxisome proliferator activated receptor alpha (pparα) and long chain acyl-CoA dehydrogenase (lcad) in the intestinal epithelial cells (IECs), and klf4 knockdown attenuated the phosphate-induced increase of protein levels of Sirt3, Pparα and Lcad. Further investigation found that Klf4 overexpression increased the activity of sirt3 and pparα promoters, which in turn reduced the acetylation and protein level of Lcad.

CONCLUSION

Dietary Pi excess induced lipid degradation by the activation of the Klf4-Sirt3/Pparα-Lcad pathway in the intestine and primary IECs. Video Abstract.

A Review of Current Evidence on the Relationship between Phosphate Metabolism and Metabolic Syndrome

Phosphorus, present as phosphate in biological systems, is an essential mineral for various biological activities and biochemical processes. Numerous studies have indicated that disturbed phosphate balance may contribute to the development of metabolic syndrome (MetS). However, no consistent result was found on the association between phosphorus intake and serum phosphate concentration with MetS. It is believed that both positive and negative impacts of phosphorus/phosphate co-exist in parallel during MetS condition. Reduced phosphate level contributed to the development of obesity and hyperglycaemia. Low phosphate is believed to compromise energy production, reduce exercise capacity, increase food ingestion, and impair glucose metabolism. On the other hand, the effects of phosphorus/phosphate on hypertension are rather complex depending on the source of phosphorus and subjects' health conditions. Phosphorus excess activates sympathetic nervous system, renin-angiotensin-aldosterone system, and induces hormonal changes under pathological conditions, contributing to the blood pressure-rising effects. For lipid metabolism, adequate phosphate content ensures a balanced lipid profile through regulation of fatty acid biosynthesis, oxidation, and bile acid excretion. In conclusion, phosphate metabolism serves as a potential key feature for the development and progression of MetS. Dietary phosphorus and serum phosphate level should be under close monitoring for the management of MetS.

Dietary Phosphorus Reduced Hepatic Lipid Deposition by Activating Ampk Pathway and Beclin1 Phosphorylation Levels to Activate Lipophagy in Tilapia Oreochromis niloticus

High-phosphorus diet (HPD) reduces lipid deposition and significantly influences lipid metabolism. However, the relevant mechanism is unknown. Herein, using widely-cultured teleost tilapia Oreochromis niloticus as the experimental animals, we found that HPD and Pi incubation reduced triglyceride (TG) content (P ≤ 0.05), suppressed lipogenesis, activated AMP-activated protein kinase (AMPK) pathway and autophagy (P ≤ 0.05), and increased fatty acid β-oxidation and lipolysis in tilapia liver and hepatocytes (P ≤ 0.05). Our further investigation indicated that Pi treatments activated the lipophagy and facilitated mitochondrial fatty acid β-oxidation, and according reduced TG deposition (P ≤ 0.05). Mechanistically, phosphorus increased the AMPKα1 phosphorylation level at S496 and Beclin1 phosphorylation at S90, and Beclin1 phosphorylation by AMPKα1 was required for phosphorus-induced lipophagy and lipolysis. Our study revealed a mechanism for Beclin1 regulation and autophagy induction in response to high-phosphorus diet, and provided novel evidences for the link between dietary phosphorus addition and lipolytic metabolism via the AMPK/Beclin1 pathway. Our results also suggested that AMPK should be the potential target for the prevention and control of lipid metabolic disorders. Overall, these results suggested that HPD reduced hepatic lipid deposition by activating AMPK pathway and Beclin1 phosphorylation levels to activate lipophagy, which provided potential targets for the prevention and control of fatty liver in fish.

Chronic High Phosphate Intake in Mice Affects Macronutrient Utilization and Body Composition

SCOPE

In the last decades, dietary phosphate intake has increased due to a higher consumption of processed food. This higher intake has an impact on body composition and health state. Recently, we found that a high chronic phosphate diet leads to no major renal alterations, but negatively affects parameters of bone health probably due to the chronic acid load. Here we assessed the effect of high phosphate consumption on parameters of energy metabolism.

METHODS AND RESULTS

Healthy mature adult mice were fed for 1 year or four months with either a standard (0.6 % w/w) or a high phosphate (1.2 % w/w) diet. Males and females of two different genetic backgrounds were investigated. Mice fed the high phosphate diet showed an attenuated body-weight gain, lower respiratory exchange ratio, decreased body fat mass and increased lean-to-fat mass ratio. Moreover, the high phosphate diet led to fasting hypoglycemia with no differences in the glucose response to an oral glucose tolerance test. Triglycerides and cholesterol in blood were similar independently of dietary phosphate content. However, 1-methylhistidine was lower in animals fed a chronic high phosphate intake.

CONCLUSIONS

High phosphate diet attenuates body weight gain, but induces hypoglycaemia and may alter muscle homeostasis. This article is protected by copyright. All rights reserved.

Anti-miR33 therapy improved hepatopancreatic lipid and immune metabolism disorders in grass carp, Ctenopharyngodon idella

Lipid metabolism disorders are found ubiquitously in farmed fish and occur as a result of excessive fat accumulation. Previous studies have found that miR-33 is involved in lipid metabolism; however, its role in fish lipid metabolism is unclear. We sought to clarify this relationship in grass carp in vivo and in vitro. Our findings revealed the length of miR-33 to be 65 bp. Phylogenetic tree analysis showed that grass carp miR-33 was most closely related to fish miR-33 (Siganus canaliculatus). Hepatocytes transfected with miR-33 mimic displayed markedly raised TG content (P < 0.05) as well as increased levels of lipid synthesis-related transcription factors (P < 0.05). Compared with blank and saline groups, total serum cholesterol, AST, and LDL levels were suppressed in groups treated with the miR-33 antagomir (P < 0.05). Moreover, the expression levels of PPARγ and SREBP-1c mRNA were significantly decreased in contrast to those found in the control group (P < 0.05). Similar findings were noted in the expression of immune-related proinflammatory molecules (TNFα, IL-1β, IL-6, and NF-κB), which also demonstrated decreased levels (P < 0.05). Conversely, high expressions of anti-inflammatory factors (TGF-β1 and IL-10) were noted (P < 0.05). This investigation strongly supports the role of miR-33 in hepatopancreas-based lipid metabolism and immunity. miR-33 may have been highly conserved in early vertebrates in order to facilitate liver-specific metabolic and immunomodulatory functions. Our findings provide a basis for further investigations exploring the mechanisms surrounding fish lipid metabolism and may aid in preventing and treating immunocompromised fish as well as fish with fatty hepatopancreas, and other metabolic diseases.

High-phosphorus diets reduce aortic lesions and cardiomyocyte size and modify lipid metabolism in Ldl receptor knockout mice

The consumption of phosphorus in Western populations largely exceeds the recommended intake, while vitamin D supply is often insufficient. Both situations are linked to an increased cardiovascular risk. A 17-week two-factorial study with Ldl receptor^-/- mice was conducted to investigate the cardiovascular impact of dietary phosphorus [adequate (0.3%; P_0.3) vs. high (1.5%; P_1.5)] in combination with a low (50 IU/kg; D₅₀) or adequate vitamin D diet (1000 IU/kg; D₁₀₀₀). The data demonstrate that mice fed the P_1.5 vs. P_0.3 diets developed smaller vascular lesions (p = 0.013) and cardiac hypotrophy (p = 0.011), which were accompanied by diminished IGF1 and insulin signalling activity in their hearts. Vitamin D showed no independent effect on atherogenesis and heart morphology. Feeding P_1.5 vs. P_0.3 diets resulted in markedly reduced serum triacylglycerols (p < 0.0001) and cholesterol (p < 0.0001), higher faecal lipid excretion (p < 0.0001) and a reduced mRNA abundance of hepatic sterol exporters and lipoprotein receptors. Minor hypocholesterolaemic and hypotriglyceridaemic effects were also found in mice fed the D₁₀₀₀ vs. D₅₀ diets (p = 0.048, p = 0.026). To conclude, a high phosphorus intake strongly affected the formation of vascular lesions, cardiac morphology, and lipid metabolism, although these changes are not indicative of an increased cardiovascular risk.

Reduced phosphorus intake throughout gestation and lactation of sows is mitigated by transcriptional adaptations in kidney and intestine

Background

The environmental impact of pig farming need to be reduced, with phosphorus (P) being of particular interest. Specified dietary regimens and management systems contribute to meet environmental concerns and reduce economic constrains. However, pregnant and lactating sows represent vulnerable individuals, whose reproductive potential and metabolic health status relies on adequate supply of macro- and micronutrients. The aim of this study was to investigate, whether sows fed with a dietary P content that is below or above current recommendations are capable to maintain mineral homeostasis during the reproduction cycle and which endogenous mechanisms are retrieved therefore in kidney and jejunum. Nulliparous gilts were fed iso-energetic diets with recommended (M), reduced (L), or high (H) amounts of mineral P supplements throughout gestation and lactation periods. Blood metabolites and hormones referring to the P homeostasis were retrieved prior to term (110 days of gestation) and at weaning (28 days of lactation). Transcriptional responses in kidney cortex and jejunal mucosa were analyzed using RNA sequencing.

Results

The variable dietary P content neither led to an aberration on fertility traits such as total weaned piglets nor to an effect on the weight pattern throughout gestation and lactation. Serum parameters revealed a maintained P homeostasis as reflected by unaltered inorganic P and calcium levels in L and H fed groups. The serum calcitriol levels were increased in lactating L sows. The endocrine responses to the dietary challenge were reflected at the transcriptional level. L diets led to an increase in CYP27B1 expression in the kidney compared to the H group and to an altered gene expression associated with lipid metabolism in the kidney and immune response in the jejunum.

Conclusions

Our results suggest that current P requirements for gestating and lactating sows are sufficient and over supplementation of mineral P is not required. Shifts in renal and jejunal expression patterns between L and H groups indicate an affected intermediate metabolism, which long-term relevance needs to be further clarified.

Effects of phosphorus and calcium to phosphorus consumption ratio on mineral metabolism and cardiometabolic health

Phosphorus is a common additive used in food processing that is typically consumed in excess of the recommended daily allowance; however, our knowledge of its effects on health, in the context of normal renal function, is limited. Unlike phosphorus, calcium intake is generally less than recommended, and it has been hypothesized that the calcium to phosphorus ratio may be partly responsible for the proposed negative health consequences. Therefore, this study sought to determine the effects of increased phosphorus additive intake, in the context of high calcium consumption, on endocrine markers of mineral metabolism and cardiometabolic health. An outpatient feeding study was performed in which healthy adults were fed a run-in control diet for 2 weeks followed by a phosphorus additive enhanced diet with supplemental calcium to an approximate ratio of 1 (experimental diet) for 2 weeks. Blood and urine samples were collected, and participants had brachial flow-mediated dilatation measured, with analyses comparing follow-up measures to baseline. Two weeks of experimental diet increased serum fibroblast growth factor 23 concentrations but lowered body weight and serum leptin; however, other phosphorus responsive factors such as osteopontin and osteocalcin did not increase. A complementary study in male mice also demonstrated that the regulation of known dietary phosphorus responsive factors was mostly abrogated when dietary calcium was raised in parallel with phosphorus. In conclusion, the study identifies weight, leptin and insulin as responsive to dietary phosphorus and that certain aspects of the systemic phosphorus response are attenuated by a corresponding high calcium intake.

Obesity and adiposity: the culprit of dietary protein efficacy

Obesity and increased body adiposity have been alarmingly increasing over the past decades and have been linked to a rise in food intake. Many dietary restrictive approaches aiming at reducing weight have resulted in contradictory results. Additionally, some policies to reduce sugar or fat intake were not able to decrease the surge of obesity. This suggests that food intake is controlled by a physiological mechanism and that any behavioural change only leads to a short-term success. Several hypotheses have been postulated, and many of them have been rejected due to some limitations and exceptions. The present review aims at presenting a new theory behind the regulation of energy intake, therefore providing an eye-opening field for energy balance and a potential strategy for obesity management.

Increased fibroblast growth factor-21 in chronic kidney disease is a trade-off between survival benefit and blood pressure dysregulation

Circulating levels of fibroblast growth factor-21 (FGF21) start increasing in patients with chronic kidney disease (CKD) since early stages during the cause of disease progression. FGF21 is a liver-derived hormone that induces responses to stress through acting on hypothalamus to activate the sympathetic nervous system and the hypothalamus-pituitary-adrenal endocrine axis. However, roles that FGF21 plays in pathophysiology of CKD remains elusive. Here we show in mice that FGF21 is required to survive CKD but responsible for blood pressure dysregulation. When introduced with CKD, Fgf21^−/− mice died earlier than wild-type mice. Paradoxically, these Fgf21^−/− CKD mice escaped several complications observed in wild-type mice, including augmentation of blood pressure elevating response and activation of the sympathetic nervous system during physical activity and increase in serum noradrenalin and corticosterone levels. Supplementation of FGF21 by administration of an FGF21-expressing adeno-associated virus vector recapitulated these complications in wild-type mice and restored the survival period in Fgf21^−/− CKD mice. In CKD patients, high serum FGF21 levels are independently associated with decreased baroreceptor sensitivity. Thus, increased FGF21 in CKD can be viewed as a survival response at the sacrifice of blood pressure homeostasis.

Systems biology identifies cytosolic PLA2 as a target in vascular calcification treatment

Although cardiovascular disease (CVD) is the leading cause of morbimortality worldwide, promising new drug candidates are lacking. We compared the arterial high-resolution proteome of patients with advanced versus early-stage CVD to predict, from a library of small bioactive molecules, drug candidates able to reverse this disease signature. Of the approximately 4000 identified proteins, 100 proteins were upregulated and 52 were downregulated in advanced-stage CVD. Arachidonyl trifluoromethyl ketone (AACOCF3), a cytosolic phospholipase A2 (cPLA2) inhibitor was predicted as the top drug able to reverse the advanced-stage CVD signature. Vascular cPLA2 expression was increased in patients with advanced-stage CVD. Treatment with AACOCF3 significantly reduced vascular calcification in a cholecalciferol-overload mouse model and inhibited osteoinductive signaling in vivo and in vitro in human aortic smooth muscle cells. In conclusion, using a systems biology approach, we have identified a potentially new compound that prevented typical vascular calcification in CVD in vivo. Apart from the clear effect of this approach in CVD, such strategy should also be able to generate novel drug candidates in other complex diseases.

High phosphate diet suppresses lipogenesis in white adipose tissue

Excessive phosphate intake has been positively associated with renal and vascular dysfunction, conversely negatively associated with body fat accumulation. We investigated the effect of a high-phosphate diet on the expression of lipid metabolic genes in white adipose tissue and liver. Male 8-week-old Sprague-Dawley rats were fed a control diet containing 0.6% phosphate or a high-phosphate diet containing 1.5% phosphate for 4 weeks. In comparison to the control group, the HP group showed a significantly lower body fat mass and fasting plasma insulin level alongside decreased lipogenic and increased lipolytic gene expression in visceral fat. Additionally, the expression of genes involved in hepatic lipogenesis, hepatic glycogenesis, and triglyceride accumulation decreased in the high-phosphate group. Exogenous phosphate, parathyroid hormone, and fibroblast growth factor 23 did not directly affect the expression of lipolytic or lipogenic genes in 3T3-L1 adipocytes and HepG2 hepatocytes. Thus, the high-phosphate diet suppressed the activity of white adipose tissue by increasing lipolytic gene expression and decreasing lipogenic gene expression. These effects could have been caused by the lowered fasting plasma insulin level that occurred in response to the high-phosphate diet, but were not directly caused by the increases in plasma phosphate or phosphaturic hormones.

Dietary supplemental vitamin D3enhances phosphorus absorption and utilisation by regulating gene expression of related phosphate transporters in the small intestine of broilers

The present study was carried out to evaluate the effect of dietary supplemental vitamin D3(VD3) on P absorption and utilisation as well as its related mechanisms in the small intestine of broilers. A total of 384 1-d-old Arbor Acres male broilers were assigned randomly into four treatments following a completely randomised design with a 2 (dietary non-phytate P (NPP) contents: 0·43 and 0·22 %)×2 (dietary VD3supplemental levels: 0 and 87·5 μg/kg) factorial arrangement. The experiment lasted for 22 d. The results showed that P contents in serum from the hepatic portal vein and tibia ash of broilers were higher (P<0·05) for 0·43 % NPP than for 0·22 % NPP. The type IIb Na-dependent phosphate cotransporter (NaP-IIb) protein expressions in the duodenum and ileum were higher (P<0·05) also for 0·43 % NPP than 0·22 % NPP. Supplementation of VD3enhanced (P<0·05) tibia P retention rate and type III Na-dependent phosphate cotransporter (PiT)-1 protein expression in the duodenum of all broilers. Moreover, VD3supplementation decreased (P<0·002) mortality and increased (P<0·02) serum P content from the hepatic portal vein after 4 h of feeding, tibia ash content, tibia ash P content and protein expressions of NaP-IIb and PiT-1 in the jejunum of broilers fed diet with 0·22 % NPP. Thus, dietary supplemental VD3promoted intestinal P absorption and bone P utilisation, and this effect might be associated with enhanced PiT-1 levels in the duodenum and PiT-1 and NaP-IIb levels in the jejunum respectively when dietary NPP is limiting.

Hypocaloric Diet Prevents the Decrease in FGF21 Elicited by High Phosphorus Intake

The effect of dietary phosphorus (P) on fibroblast growth factor 21 (FGF21)/β-klotho axis was investigated in rats that were fed diets with: Normal (NP) or high P (HP) and either normal (NC), high (HC) or low calories (LC). Sampling was performed at 1, 4 and 7 months. Plasma FGF21 concentrations were higher (p < 0.05) in NC and HC than in LC groups. Increasing P intake had differing effects on plasma FGF21 in rats fed NC and HC vs. rats fed LC at the three sampling times. When compared with the NP groups, FGF21 concentrations decreased at the three sampling points in rats fed NC-HP (80 vs. 194, 185 vs. 382, 145 vs. 403 pg/mL) and HC-HP (90 vs. 190, 173 vs. 353, 94 vs. 434 pg/mL). However, FGF21 did not decrease in rats fed LC-HP (34 vs. 20, 332 vs. 164 and 155 vs. 81 pg/mL). In addition, LC groups had a much lower liver FGF21 messenger ribonucleic acid/glyceraldehyde 3-phosphate dehydrogenase (mRNA/GAPDH) ratio (0.51 ± 0.08 and 0.56 ± 0.07) than the NC-NP (0.97 ± 0.14) and HC-NP (0.97 ± 0.22) groups. Increasing P intake reduced liver FGF21 mRNA/GAPDH in rats fed NC and HC to 0.42 ± 0.05 and 0.37 ± 0.04. Liver β-klotho mRNA/GAPDH ratio was lower (p < 0.05) in LC groups (0.66 ± 0.06 and 0.59 ± 0.10) than in NC (1.09 ± 0.17 and 1.03 ± 0.14) and HC (1.19 ± 0.12 and 1.34 ± 0.19) groups. A reduction (p < 0.05) in β-klotho protein/α-tubulin ratio was also observed in LC groups (0.65 ± 0.05 and 0.49 ± 0.08) when compared with NC (1.12 ± 0.11 and 0.91 ± 0.11) and HC (0.93 ± 0.17 and 0.87 ± 0.09) groups. In conclusion β-klotho is potently regulated by caloric restriction but not by increasing P intake while FGF21 is regulated by both caloric restriction and increased P intake. Moreover, increased P intake has a differential effect on FGF21 in calorie repleted and calorie depleted rats.

High phosphate diet suppresses lipogenesis in white adipose tissue

Excessive phosphate intake has been positively associated with renal and vascular dysfunction, conversely negatively associated with body fat accumulation. We investigated the effect of a high-phosphate diet on the expression of lipid metabolic genes in white adipose tissue and liver. Male 8-week-old Sprague-Dawley rats were fed a control diet containing 0.6% phosphate or a high-phosphate diet containing 1.5% phosphate for 4 weeks. In comparison to the control group, the HP group showed a significantly lower body fat mass and fasting plasma insulin level alongside decreased lipogenic and increased lipolytic gene expression in visceral fat. Additionally, the expression of genes involved in hepatic lipogenesis, hepatic glycogenesis, and triglyceride accumulation decreased in the high-phosphate group. Exogenous phosphate, parathyroid hormone, and fibroblast growth factor 23 did not directly affect the expression of lipolytic or lipogenic genes in 3T3-L1 adipocytes and HepG2 hepatocytes. Thus, the high-phosphate diet suppressed the activity of white adipose tissue by increasing lipolytic gene expression and decreasing lipogenic gene expression. These effects could have been caused by the lowered fasting plasma insulin level that occurred in response to the high-phosphate diet, but were not directly caused by the increases in plasma phosphate or phosphaturic hormones.

Genetic architecture and regulatory impact on hepatic microRNA expression linked to immune and metabolic traits

Regulation of microRNA (miRNA) expression contributes to a wide range of target gene expression and phenotypes. The miRNA expression in the liver, the central metabolic organ, was examined in 209 pigs, and integrated with haematological and clinical biomarkers of metabolic and overall health, mRNA-target expression levels and single-nucleotide polymorphism (SNP) genotypes. The expression levels of 426 miRNA species correlated with plasma haematological or biochemical traits (r² = |0.19–0.45|, false discovery rate < 5%). Pairs of these miRNAs and their predicted target mRNAs showing expressing levels associated with the identical traits were examined to understand how immune and metabolic traits are affected by miRNA-mediated regulatory networks derived by mapping miRNA abundance as an expression quantitative trait. In total, 221 miRNA-expression-QTL correspond to 164 SNPs and 108 miRNAs, including miR-34a, miR-30e, miR-148-3p, miR-204, miR-181-5p, miR-143-5p and let-7 g that also correlate with the biomarkers. Sixty-one SNPs were simultaneously associated with 29 miRNA and 41 mRNA species. The expression levels of 13 out of 29 miRNA were correlated with one of the biochemical or haematological traits. For example, the expression levels of miR-34a were correlated with serum phosphorus and cholesterin levels; miR-204, miR-15a and miR-16b were correlated with triglyceride. For haematological traits, the expression levels of miR-652 and miR-204 were correlated with the mean corpuscular haemoglobin concentration, and the expression of miR-143 was correlated with plateletcrit. Pleiotropic association analyses revealed genetic links between mRNA and miRNA on SSC6 for miR-34a, SSC9 for miR-708 and SSC14 for miR-652. Our analysis of miRNA and mRNA transcript profiles, their correlation with clinically important plasma parameters of hepatic functions as well as information on their genetic regulation provide novel regulatory networks and potential new biomarkers for immune and metabolic traits.

Regulation of phosphate transport and AMPK signal pathway by lower dietary phosphorus of broilers

Lower available P (aP) was used as a base value in nutritional strategies for mitigating P pollution by animal excreta. We hypothesized that the mechanism regulating phosphate transport under low dietary P might be related with the AMPK signal pathway. A total of 144 one-day-old Arbor Acres Plus broilers were randomly allocated to control (HP) or trial (LP) diets, containing 0.45 and 0.23% aP, respectively. Growth performance, blood, intestinal, and renal samples were tested in 21-day-old broilers. Results shown that LP decreased body weight gain and feed intake. Higher serum Ca and fructose, but lower serum P and insulin were detected in LP-fed broilers. NaPi-IIb mRNA expression in intestine and NaPi-IIa mRNA expression in kidney were higher in the LP group. AMP: ATP, p-AMPK: total AMPK, and p-ACC: total ACC ratios in the duodenal mucosa were decreased in the LP group, whereas the p-mTOR: total mTOR ratio increased. These findings suggested that the increase in phosphate transport owing to LP diet might be regulated either directly by higher mTOR activity or indirectly by the suppressive AMPK signal, with corresponding changes in blood insulin and fructose content. A novel viewpoint on the regulatory mechanism underlying phosphate transport under low dietary P conditions was revealed, which might provide theoretical guidelines for reducing P pollution by means of nutritional regulation.