Pharmacogenomics of metabolic effects of rosiglitazone

Nutrigenetic Interaction of Spontaneously Hypertensive Rat Chromosome 20 Segment and High-Sucrose Diet Sensitizes to Metabolic Syndrome

Several corresponding regions of human and mammalian genomes have been shown to affect sensitivity to the manifestation of metabolic syndrome via nutrigenetic interactions. In this study, we assessed the effect of sucrose administration in a newly established congenic strain BN.SHR20, in which a limited segment of rat chromosome 20 from a metabolic syndrome model, spontaneously hypertensive rat (SHR), was introgressed into Brown Norway (BN) genomic background. We mapped the extent of the differential segment and compared the genomic sequences of BN vs. SHR within the segment in silico. The differential segment of SHR origin in BN.SHR20 spans about 9 Mb of the telomeric portion of the short arm of chromosome 20. We identified non-synonymous mutations e.g., in ApoM, Notch4, Slc39a7, Smim29 genes and other variations in or near genes associated with metabolic syndrome in human genome-wide association studies. Male rats of BN and BN.SHR20 strains were fed a standard diet for 18 weeks (control groups) or 16 weeks of standard diet followed by 14 days of high-sucrose diet (HSD). We assessed the morphometric and metabolic profiles of all groups. Adiposity significantly increased only in BN.SHR20 after HSD. Fasting glycemia and the glucose levels during the oral glucose tolerance test were higher in BN.SHR20 than in BN groups, while insulin levels were comparable. The fasting levels of triacylglycerols were the highest in sucrose-fed BN.SHR20, both compared to the sucrose-fed BN and the control BN.SHR20. The non-esterified fatty acids and total cholesterol concentrations were higher in BN.SHR20 compared to their respective BN groups, and the HSD elicited an increase in non-esterified fatty acids only in BN.SHR20. In a new genetically defined model, we have isolated a limited genomic region involved in nutrigenetic sensitization to sucrose-induced metabolic disturbances.

ZBTB16 and metabolic syndrome: a network perspective

Metabolic syndrome is a prevalent, complex condition. The search for genetic determinants of the syndrome is currently undergoing a paradigm enhancement by adding systems genetics approaches to association studies. We summarize the current evidence on relations between an emergent new candidate, zinc finger and BTB domain containing 16 (ZBTB16) transcription factor and the major components constituting the metabolic syndrome. Information stemming from studies on experimental models with altered Zbtb16 expression clearly shows its effect on adipogenesis, cardiac hypertrophy and fibrosis, lipid levels and insulin sensitivity. Based on current evidence, we provide a network view of relations between ZBTB16 and hallmarks of metabolic syndrome in order to elucidate the potential functional links involving the ZBTB16 node. Many of the identified genes interconnecting ZBTB16 with all or most metabolic syndrome components are linked to immune function, inflammation or oxidative stress. In summary, ZBTB16 represents a promising pleiotropic candidate node for metabolic syndrome.

Single-Gene Congenic Strain Reveals the Effect of Zbtb16 on Dexamethasone-Induced Insulin Resistance

BACKGROUND

Glucocorticoids (GCs) are potent therapeutic agents frequently used for treatment of number of conditions, including hematologic, inflammatory, and allergic diseases. Both their therapeutic and adverse effects display significant interindividual variation, partially attributable to genetic factors. We have previously isolated a seven-gene region of rat chromosome 8 sensitizing to dexamethasone (DEX)-induced dyslipidemia and insulin resistance (IR) of skeletal muscle. Using two newly derived congenic strains, we aimed to investigate the effect of one of the prime candidates for this pharmacogenetic interaction, the Zbtb16 gene.

METHODS

Adult male rats of SHR-Lx.PD5^PD-Zbtb16 (n = 9) and SHR-Lx.PD5^SHR-Zbtb16 (n = 8) were fed standard diet (STD) and subsequently treated with DEX in drinking water (2.6 µg/ml) for 3 days. The morphometric and metabolic profiles of both strains including oral glucose tolerance test, triacylglycerols (TGs), free fatty acids, insulin, and C-reactive protein levels were assessed before and after the DEX treatment. Insulin sensitivity of skeletal muscle and visceral adipose tissue was determined by incorporation of radioactively labeled glucose.

RESULTS

The differential segment of SHR-Lx.PD5^SHR-Zbtb16 rat strain spans 563 kb and contains six genes: Htr3a, Htr3b, Usp28, Zw10, Tmprss5, and part of Drd2. The SHR-Lx.PD5^PD-Zbtb16 minimal congenic strain contains only Zbtb16 gene on SHR genomic background and its differential segment spans 254 kb. Total body weight was significantly increased in SHR-Lx.PD5^PD-Zbtb16 strain compared with SHR-Lx.PD5^SHR-Zbtb16 , however, no differences in the weights of adipose tissue depots were observed. While STD-fed rats of both strains did not show major differences in their metabolic profiles, after DEX treatment the SHR-Lx.PD5^PD-Zbtb16 congenic strain showed increased levels of TGs, glucose, and blunted inhibition of lipolysis by insulin. Both basal and insulin-stimulated incorporation of radioactively labeled glucose into skeletal muscle glycogen were significantly reduced in SHR-Lx.PD5^PD-Zbtb16 strain, but the insulin sensitivity of adipose tissue was comparable between the two strains.

CONCLUSION

The metabolic disturbances including impaired glucose tolerance, dyslipidemia, and IR of skeletal muscle observed after DEX treatment in the congenic SHR-Lx.PD5^PD-Zbtb16 reveal the Zbtb16 locus as a possible sensitizing factor for side effects of GC therapy.

Heterozygous connexin 50 mutation affects metabolic syndrome attributes in spontaneously hypertensive rat

BACKGROUND

Several members of connexin family of transmembrane proteins were previously implicated in distinct metabolic conditions. In this study we aimed to determine the effects of complete and heterozygous form of connexin50 gene (Gja8) mutation L7Q on metabolic profile and oxidative stress parameters in spontaneously hypertensive inbred rat strain (SHR).

METHODS

Adult, standard chow-fed male rats of SHR, heterozygous SHR-Dca+/- and SHR-Dca-/- coisogenic strains were used. At the age of 4 months, dexamethasone (2.6 μg/ml) was administered in the drinking water for three days. The lipidemic profile (cholesterol and triacylglycerol concentration in 20 lipoprotein fractions, chylomicron, VLDL, LDL and HDL particle sizes) together with 33 cytokines and hormones in serum and several oxidative stress parameters in plasma, liver, kidney and heart were assessed.

RESULTS

SHR and SHR-Dca-/- rats had similar concentrations of triacylglycerols and cholesterol in all major lipoprotein fractions. The heterozygotes reached significantly highest levels of total (SHR-Dca+/-: 51.3 ± 7.2 vs. SHR: 34.5 ± 2.4 and SHR-Dca-/-: 34.4 ± 2.5 mg/dl, p = 0.026), chylomicron and VLDL triacylglycerols. The heterozygotes showed significantly lowest values of HDL cholesterol (40.9 ± 2.3 mg/dl) compared both to SHR (51.8 ± 2.2 mg/dl) and SHR-Dca-/- (48.6 ± 2.7 mg/dl). Total and LDL cholesterol in SHR-Dca+/- was lower compared to SHR. Glucose tolerance was improved and insulin concentrations were lowest in SHR-Dca-/- (1.11 ± 0.20 pg/ml) in comparison with both SHR (2.32 ± 0.49 pg/ml) and SHR-Dca+/- (3.04 ± 0.21 pg/ml). The heterozygous rats showed profile suggestive of increased oxidative stress as well as highest serum concentrations of several pro-inflammatory cytokines including interleukins 6, 12, 17, 18 and tumor necrosis factor alpha.

CONCLUSIONS

Our results demonstrate that connexin50 mutation in heterozygous state affects significantly the lipid profile and the oxidative stress parameters in the spontaneously hypertensive rat strain.

Rosiglitazone ameliorates diffuse axonal injury by reducing loss of tau and up-regulating caveolin-1 expression

Rosiglitazone up-regulates caveolin-1 levels and has neuroprotective effects in both chronic and acute brain injury. Therefore, we postulated that rosiglitazone may ameliorate diffuse axonal injury via its ability to up-regulate caveolin-1, inhibit expression of amyloid-beta precursor protein, and reduce the loss and abnormal phosphorylation of tau. In the present study, intraperitoneal injection of rosiglitazone significantly reduced the levels of amyloid-beta precursor protein and hyperphosphorylated tau (phosphorylated at Ser⁴⁰⁴(p-tau (S⁴⁰⁴)), and it increased the expression of total tau and caveolin-1 in the rat cortex. Our results show that rosiglitazone inhibits the expression of amyloid-beta precursor protein and lowers p-tau (S⁴⁰⁴) levels, and it reduces the loss of total tau, possibly by up-regulating caveolin-1. These actions of rosiglitazone may underlie its neuroprotective effects in the treatment of diffuse axonal injury.

Pharmacogenomics and pharmacogenetics of thiazolidinediones: role in diabetes and cardiovascular risk factors

The most important goal in the treatment of patients with diabetes is to prevent the risk of cardiovascular disease (CVD), the first cause of mortality in these subjects. Thiazolidinediones (TZDs), a class of antidiabetic drugs, act as insulin sensitizers increasing insulin-dependent glucose disposal and reducing hepatic glucose output. TZDs including pioglitazone, rosiglitazone and troglitazone, by activating PPAR-γ have shown pleiotropic effects in reducing vascular risk factors and atherosclerosis. However, troglitazone was removed from the market due to its hepatoxicity, and rosiglitazone and pioglitazone both have particular warnings due to being associated with heart diseases. Specific genetic variations in genes involved in the pathways regulated by TDZs have demonstrated to modify the variability in treatment with these drugs, especially in their side effects. Therefore, pharmacogenomics and pharmacogenetics are an important tool in further understand intersubject variability per se but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization.

The beta-3 adrenergic agonist (CL-316,243) restores the expression of down-regulated fatty acid oxidation genes in type 2 diabetic mice

Background

The hallmark of Type 2 diabetes (T2D) is hyperglycemia, although there are multiple other metabolic abnormalities that occur with T2D, including insulin resistance and dyslipidemia. To advance T2D prevention and develop targeted therapies for its treatment, a greater understanding of the alterations in metabolic tissues associated with T2D is necessary. The aim of this study was to use microarray analysis of gene expression in metabolic tissues from a mouse model of pre-diabetes and T2D to further understand the metabolic abnormalities that may contribute to T2D. We also aimed to uncover the novel genes and pathways regulated by the insulin sensitizing agent (CL-316,243) to identify key pathways and target genes in metabolic tissues that can reverse the diabetic phenotype.

Methods

Male MKR mice on an FVB/n background and age matched wild-type (WT) FVB/n mice were used in all experiments. Skeletal muscle, liver and fat were isolated from prediabetic (3 week old) and diabetic (8 week old) MKR mice. Male MKR mice were treated with CL-316,243. Skeletal muscle, liver and fat were isolated after the treatment period. RNA was isolated from the metabolic tissues and subjected to microarray and KEGG database analysis.

Results

Significant decreases in the expression of mitochondrial and peroxisomal fatty acid oxidation genes were found in the skeletal muscle and adipose tissue of adult MKR mice, and the liver of pre-diabetic MKR mice, compared to WT controls. After treatment with CL-316,243, the circulating glucose and insulin concentrations in the MKR mice improved, an increase in the expression of peroxisomal fatty acid oxidation genes was observed in addition to a decrease in the expression of retinaldehyde dehydrogenases. These genes were not previously known to be regulated by CL-316,243 treatment.

Conclusions

This study uncovers novel genes that may contribute to pharmacological reversal of insulin resistance and T2D and may be targets for treatment. In addition, it explains the lower free fatty acid levels in MKR mice after treatment with CL-316,243 and furthermore, it provides biomarker genes such as ACAA1 and HSD17b4 which could be further probed in a future study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0003-8) contains supplementary material, which is available to authorized users.

CD36-deficient congenic strains show improved glucose tolerance and distinct shifts in metabolic and transcriptomic profiles

Deficiency of fatty acid translocase Cd36 has been shown to have a major role in the pathogenesis of metabolic syndrome in the spontaneously hypertensive rat (SHR). We have tested the hypothesis that the effects of Cd36 mutation on the features of metabolic syndrome are contextually dependent on genomic background. We have derived two new congenic strains by introgression of limited chromosome 4 regions of SHR origin, both including the defective Cd36 gene, into the genetic background of a highly inbred model of insulin resistance and dyslipidemia, polydactylous (PD) rat strain. We subjected standard diet-fed adult males of PD and the congenic PD.SHR4 strains to metabolic, morphometric and transcriptomic profiling. We observed significantly improved glucose tolerance and lower fasting insulin levels in PD.SHR4 congenics than in PD. One of the PD.SHR4 strains showed lower triglyceride concentrations across major lipoprotein fractions combined with higher levels of low-density lipoprotein cholesterol compared with the PD progenitor. The hepatic transcriptome assessment revealed a network of genes differentially expressed between PD and PD.SHR4 with significant enrichment by members of the circadian rhythmicity pathway (Arntl (Bmal1), Clock, Nfil3, Per2 and Per3). In summary, the introduction of the chromosome 4 region of SHR origin including defective Cd36 into the PD genetic background resulted in disconnected shifts of metabolic profile along with distinct changes in hepatic transcriptome. The synthesis of the current results with those obtained in other Cd36-deficient strains indicates that the eventual metabolic effect of a deleterious mutation such as that of SHR-derived Cd36 is not absolute, but rather a function of complex interactions between environmental and genomic background, upon which it operates.

Berberine-improved visceral white adipose tissue insulin resistance associated with altered sterol regulatory element-binding proteins, liver x receptors, and peroxisome proliferator-activated receptors transcriptional programs in diabetic hamsters

The diabetic "lipotoxicity" hypothesis presents that fat-induced visceral white adipose tissue insulin resistance plays a central role in the pathogenesis of type 2 diabetes. Berberine, a hypolipidemic agent, has been reported to have antidiabetic activities. The molecular mechanisms for this property are, however, not well clarified. Therefore in this study type 2 diabetic hamsters were induced by high-fat diet with low-dose streptozotocin. Then, we investigated the gene expression alterations and explored the molecular mechanisms underlying the therapeutic effect of berberine on fat-induced visceral white adipose tissue insulin resistance in diabetic hamsters by microarray analysis followed by real-time reverse transcription-polymerase chain reaction (RT-PCR) confirmation. Type 2 diabetic hamsters exhibited hyperglycemia and relative hyperinsulinemia, glucose intolerance, insulin resistance, intra-adipocyte lipid accumulation, significant increase in body weight and visceral white adipose tissue weight, abnormal serum adipokines levels, and deleterious dyslipidemia. Furthermore, they had increased sterol regulatory element-binding proteins (SREBPs) expression and decreased liver X receptors (LXRs) and peroxisome proliferator-activated receptors (PPARs) expression in visceral white adipose tissue. After 9-week berberine treatment, fat-induced insulin resistance and diabetic phenotype in type 2 diabetic hamsters were significantly improved. Compared with diabetic hamsters, expression of LXRs and PPARs significantly increased and SREBPs significantly decreased in visceral white adipose tissue from berberine-treated diabetic hamsters. These results suggest that altered visceral white adipose tissue LXRs, PPARs, and SREBPs transcriptional programs are involved in the therapeutic mechanisms of berberine on fat-induced visceral white adipose tissue insulin resistance in type 2 diabetic hamsters.

The evolutionary aspects of aquaporin family

Aquaporins (AQPs) were originally identified as channels facilitating water transport across the plasma membrane. They have a pair of highly conserved signature sequences, asparagine-proline-alanine (NPA) boxes, to form a pore. However, some have little conserved amino acid sequences around the NPA boxes unclassifiable to two previous AQP subfamilies, classical AQPs and aquaglyceroporins. These will be called unorthodox AQPs in this review. Interestingly, these unorthodox AQPs have a highly conserved cysteine residue downstream of the second NPA box. AQPs also have a diversity of functions: some related to water transport such as fluid secretion, fluid absorption, and cell volume regulation, and the others not directly related to water transport such as cell adhesion, cell migration, cell proliferation, and cell differentiation. Some AQPs even permeate nonionic small molecules, ions, metals, and possibly gasses. AQP gene disruption studies have revealed their physiological roles: water transport in the kidney and exocrine glands, glycerol transport in fat metabolism and in skin moisture, and nutrient uptakes in plants. Furthermore, AQPs are also present at intracellular organelles, including tonoplasts, mitochondria, and the endoplasmic reticulum. This review focuses on the evolutionary aspects of AQPs from bacteria to humans in view of the structural and functional diversities of AQPs.

Microarray evidences the role of pathologic adipose tissue in insulin resistance and their clinical implications

Clustering of insulin resistance and dysmetabolism with obesity is attributed to pathologic adipose tissue. The morphologic hallmarks of this pathology are adipocye hypertrophy and heightened inflammation. However, it's underlying molecular mechanisms remains unknown. Study of gene function in metabolically active tissues like adipose tissue, skeletal muscle and liver is a promising strategy. Microarray is a powerful technique of assessment of gene function by measuring transcription of large number of genes in an array. This technique has several potential applications in understanding pathologic adipose tissue. They are: (1) transcriptomic differences between various depots of adipose tissue, adipose tissue from obese versus lean individuals, high insulin resistant versus low insulin resistance, brown versus white adipose tissue, (2) transcriptomic profiles of various stages of adipogenesis, (3) effect of diet, cytokines, adipokines, hormones, environmental toxins and drugs on transcriptomic profiles, (4) influence of adipokines on transcriptomic profiles in skeletal muscle, hepatocyte, adipose tissue etc., and (5) genetics of gene expression. The microarray evidences of molecular basis of obesity and insulin resistance are presented here. Despite the limitations, microarray has potential clinical applications in finding new molecular targets for treatment of insulin resistance and classification of adipose tissue based on future risk of insulin resistance syndrome.

Berberine regulates peroxisome proliferator-activated receptors and positive transcription elongation factor b expression in diabetic adipocytes

Berberine has hypoglycemic and hypolipidemic effects on diabetic rats. This study investigated the relationship between hypoglycemic and hypolipidemic effects of berberine and peroxisome proliferator-activated receptors (PPARs) and positive transcription elongation factor b (P-TEFb) (including cyclin-dependent kinase 9 (CDK9) and cyclin T1) in white adipose tissue of diabetic rats and RNA interference-treated 3T3-L1 cells. Berberine promoted differentiation and inhibited lipid accumulation of 3T3-L1 cells, further decreased PPARα/δ/γ, CDK9 and cyclin T1 mRNA and protein expression and decreased tumor necrosis factor α content in supernatants of both control and RNA interference-treated 3T3-L1 cells. After a 16-week induction with 35 mg/kg streptozotocin (i.p.) and high-carbohydrate/high-fat diet, diabetic rats were treated with 75, 150 and 300 mg/kg berberine and 100 mg/kg fenofibrate or 4 mg/kg rosiglitazone for another 16 weeks. Berberine decreased white adipose tissue to body weight ratio and adipocyte size and increased adipocyte number. Berberine upregulated PPARα/δ/γ, CDK9 and cyclin T1 mRNA and protein expression in adipose tissue, decreased tumor necrosis factor α and free fatty acid content and increased lipoprotein lipase activity in serum and adipose tissue. Berberine modulated metabolic related PPARs expression and differentiation related P-TEFb expression in adipocytes, which are associated with its hypoglycemic and hypolipidemic effects.

Pharmacogenetic interaction between dexamethasone and Cd36-deficient segment of spontaneously hypertensive rat chromosome 4 affects triacylglycerol and cholesterol distribution into lipoprotein fractions

Dexamethasone (DEX) is known to induce diabetes and dyslipidemia. We have compared fasting triacylglycerol and cholesterol concentrations across 20 lipoprotein fractions and glucose tolerance in control (standard diet) and DEX-treated 7-month-old males of two rat strains, Brown Norway (BN) and congenic BN.SHR-(Il6-Cd36)/Cub (BN.SHR4). These two inbred strains differ in a defined segment of chromosome 4, originally transferred from the spontaneously hypertensive rat (SHR) including the mutant Cd36 gene, a known target of DEX. Compared to BN, the standard-diet-fed BN.SHR4 showed higher cholesterol and triacylglycerol concentrations across many lipoprotein fractions, particularly in small VLDL and LDL particles. Total cholesterol was decreased by DEX by more than 21% in BN.SHR4 contrasting with the tendency to increase in BN (strain*DEX interaction p = 0.0017). Similar pattern was observed for triacylglycerol concentrations in LDL. The LDL particle size was significantly reduced by DEX in both strains. Also, while control BN and BN.SHR4 displayed comparable glycaemic profiles during oral glucose tolerance test, we observed a markedly blunted DEX induction of glucose intolerance in BN.SHR4 compared to BN. In summary, we report a pharmacogenetic interaction between limited genomic segment with mutated Cd36 gene and dexamethasone-induced glucose intolerance and triacylglycerol and cholesterol redistribution into lipoprotein fractions.

Pharmacogenetic model of retinoic acid-induced dyslipidemia and insulin resistance

Aims: Therapeutic administration of retinoids is often accompanied with undesirable side effects, including an increase in lipid levels in up to 45% of treated patients. We tested the hypothesis of whether spontaneously hypertensive rat (SHR) and congenic SHR.PD-(D8Rat42-D8Arb23)/Cub (SHR-Lx) strains, differing only in a 14-gene region of chromosome 8 and previously shown to display differential sensitivity to the teratogenic effects of retinoic acid, could serve as a pharmacogenetic model set of the metabolic side effects of retinoid therapy. Materials & methods: Male, 15-week old rats (n = 12/strain) of SHR and SHR-Lx strains were fed a high-sucrose diet for 2 weeks and subsequently treated either with all-trans retinoic acid (15 mg/kg) or only with a vehicle for 16 days (n = 6/strain/treatment), while still on the high-sucrose diet. We assessed the morphometric and metabolic profiles of all groups, including glucose tolerance tests, levels of insulin, adiponectin, free fatty acids, concentrations of triglycerides and cholesterol in 20 lipoprotein fractions under conditions of both high-sucrose diet and high-sucrose diet plus all-trans retinoic acid administration. Results & conclusion: SHR-Lx displayed substantially greater sensitivity to a number of all-trans retinoic acid-induced metabolic dysregulations compared with SHR, resulting in impairment of glucose tolerance, increased visceral adiposity, and substantially greater increase of circulating triglyceride concentrations, accompanied by a shift towards their less favorable distribution into the lipoprotein fractions. These observations closely mimic the common side effects of retinoid therapy in humans, rendering SHR-Lx an experimental pharmacogenetic model of atRA-induced dyslipidemia.

Aquaporin water channels in mammals

Water channels, aquaporins (AQPs), are a family of small integral plasma membrane proteins that primarily transport water across the plasma membrane. There are 13 members (AQP0-12) in humans. This number is final as the human genome project has been completed. They are divided into three subgroups based on the primary sequences: water selective AQPs (AQP0, 1, 2, 4, 5, 6, 8), aquaglyceroporins (AQP3, 7, 9, 10), and superaquaporins (AQP11, 12). Since no specific inhibitors are yet available, functional roles of AQPs are suggested by AQP null mice and humans. Abnormal water metabolism was shown with AQP1, 2, 3, 4, 5 null mice, especially with AQP2 null mice: fatal at neonate due to diabetes insipidus. Abnormal glycerol transport was shown with AQP3, 7, 9 null mice, although they appeared normal. AQP0 null mice suffer from cataracts, although the pathogenesis is not clear. Unexpectedly, AQP11 null mice die from uremia as a result of polycystic kidneys. Interestingly, AQP6, 8, 10, 12 null mice are almost normal. AQP null humans have been reported with AQP0, 1, 2, 3, 7: only AQP2 null humans show an outstanding phenotype, diabetes insipidus. This review summarizes the current knowledge on all mammalian AQPs and hopefully will stimulate future research in both clinical and basic fields.