Activation of inflammasomes in podocyte injury of mice on the high fat diet: Effects of ASC gene deletion and silencing

Inflammasome, an intracellular inflammatory machinery, has been reported to be involved in a variety of chronic degenerative diseases such as atherosclerosis, autoinflammatory diseases and Alzheimer's disease. The present study hypothesized that the formation and activation of inflammasomes associated with apoptosis associated speck-like protein (ASC) are an important initiating mechanism resulting in obesity-associated podocyte injury and consequent glomerular sclerosis. To test this hypothesis, Asc gene knockout (Asc^−/−), wild type (Asc^+/+) and intrarenal Asc shRNA-transfected wild type (Asc shRNA) mice were fed a high fat diet (HFD) or normal diet (ND) for 12 weeks to produce obesity and associated glomerular injury. Western blot and RT-PCR analyses demonstrated that renal tissue Asc expression was lacking in Asc^−/− mice or substantially reduced in Asc shRNA transfected mice compared to Asc^+/+ mice. Confocal microscopic and co-immunoprecipitation analysis showed that the HFD enhanced the formation of inflammasome associated with Asc in podocytes as shown by colocalization of Asc with Nod-like receptor protein 3 (Nalp3). This inflammasome complex aggregation was not observed in Asc^−/− and local Asc shRNA-transfected mice. The caspase-1 activity, IL-1β production and glomerular damage index (GDI) were also significantly attenuated in Asc^−/− and Asc shRNA-transfected mice fed the HFD. This decreased GDI in Asc^−/− and Asc shRNA transfected mice on the HFD was accompanied by attenuated proteinuria, albuminuria, foot process effacement of podocytes and loss of podocyte slit diaphragm molecules. In conclusion, activation and formation of inflammasomes in podocytes are importantly implicated in the development of obesity-associated glomerular injury.     

Resistance to Diet-Induced Obesity and Associated Metabolic Perturbations in Haploinsufficient Monocarboxylate Transporter 1 Mice

The monocarboxylate transporter 1 (MCT1 or SLC16A1) is a carrier of short-chain fatty acids, ketone bodies, and lactate in several tissues. Genetically modified C57BL/6J mice were produced by targeted disruption of the mct1 gene in order to understand the role of this transporter in energy homeostasis. Null mutation was embryonically lethal, but MCT1 ^+/− mice developed normally. However, when fed high fat diet (HFD), MCT1 ^+/− mice displayed resistance to development of diet-induced obesity (24.8% lower body weight after 16 weeks of HFD), as well as less insulin resistance and no hepatic steatosis as compared to littermate MCT1 ^+/+ mice used as controls. Body composition analysis revealed that reduced weight gain in MCT1 ^+/− mice was due to decreased fat accumulation (50.0% less after 9 months of HFD) notably in liver and white adipose tissue. This phenotype was associated with reduced food intake under HFD (12.3% less over 10 weeks) and decreased intestinal energy absorption (9.6% higher stool energy content). Indirect calorimetry measurements showed ∼ 15% increase in O₂ consumption and CO₂ production during the resting phase, without any changes in physical activity. Determination of plasma concentrations for various metabolites and hormones did not reveal significant changes in lactate and ketone bodies levels between the two genotypes, but both insulin and leptin levels, which were elevated in MCT1 ^+/+ mice when fed HFD, were reduced in MCT1 ^+/− mice under HFD. Interestingly, the enhancement in expression of several genes involved in lipid metabolism in the liver of MCT1 ^+/+ mice under high fat diet was prevented in the liver of MCT1 ^+/− mice under the same diet, thus likely contributing to the observed phenotype. These findings uncover the critical role of MCT1 in the regulation of energy balance when animals are exposed to an obesogenic diet.     

The C57BL/6J Niemann–Pick C1 mouse model with decreased gene dosage has impaired glucose tolerance independent of body weight

The human Niemann–Pick C1 (NPC1) gene has been found to be associated with extreme (early-onset and morbid-adult) obesity and type 2 diabetes independent of body weight. We previously performed growth studies using BALB/cJ Npc1 normal (Npc1^+/+) and Npc1 heterozygous (Npc1^+/−) mice and determined that decreased Npc1 gene dosage interacts with a high-fat diet to promote weight gain and adiposity. The present study was performed using both BALB/cJ and C57BL/6J Npc1^+/+ and Npc1^+/− mice to determine if decreased Npc1 gene dosage predisposes to metabolic features associated with type 2 diabetes. The results indicated that C57BL/6J Npc1^+/− mice, but not BALB/cJ Npc1^+/− mice, have impaired glucose tolerance when fed a low-fat diet and independent of body weight. The results also suggest that an accumulation of liver free fatty acids and hepatic lipotoxicity marked by an elevation in the amount of plasma alanine aminotransferase (ALT) may be responsible for hepatic insulin resistance and impaired glucose tolerance. Finally, the peroxisome-proliferator activated receptor α (PPARα) and sterol regulatory element-binding protein-1 (SREBP-1) pathways known to have a central role in regulating free fatty acid metabolism were downregulated in the livers, but not in the adipose or muscle, of C57BL/6J Npc1^+/− mice compared to C57BL/6J Npc1^+/+ mice. Therefore, decreased Npc1 gene dosage among two different mouse strains interacts with undefined modifying genes to manifest disparate yet often related metabolic diseases.     

Sar1b transgenic male mice are more susceptible to high-fat diet-induced obesity,insulin insensitivity and intestinal chylomicron overproduction

In the intracellular secretory network, nascent proteins are shuttled from the endoplasmic reticulum to the Golgi by transport vesicles requiring Sar1b, a small GTPase. Mutations in this key enzyme impair intestinal lipid transport and cause chylomicron retention disease. The main aim of this study was to assess whether Sar1b overexpression under a hypercaloric diet accelerated lipid production and chylomicron (CM) secretion, thereby inducing cardiometabolic abnormalities. To this end, we generated transgenic mice overexpressing human Sar1b (Sar1b^+/+) using pBROAD3-mcs that features the ubiquitous mouse ROSA26 promoter. In response to a high-fat diet (HFD), Sar1b^+/+ mice displayed significantly increased body weight and adiposity compared with Sar1b^+/+ mice under the same regimen or with wild-type (WT) mice exposed to chow diet or HFD. Furthermore, Sar1b^+/+ mice were prone to liver steatosis as revealed by significantly elevated hepatic triglycerides (TG) and cholesterol in comparison with WT animals. They also exhibited augmented levels of plasma TG along with alterations in fatty acid composition. Concomitantly, they showed susceptibility to develop insulin insensitivity and they responded abnormally to oral glucose tolerance test. Finally, Sar1b^+/+ mice that have been treated with Triton WR-1330 (to inhibit TG catabolism) and orotic acid (to block secretion of very low-density lipoprotein by the liver) responded more efficiently to fat meal tests as reflected by the rise in plasma TG and CM concentrations, indicating exaggerated intestinal fat absorption. These results suggest that Sar1b^+/+ under HFD can elicit cardiometabolic traits as revealed by incremental weight gain, fat deposition, dyslipidemia, hepatic steatosis, insulin insensitivity and intestinal fat absorption.     

Ablation of TRPM5 in Mice Results in Reduced Body Weight Gain and Improved Glucose Tolerance and Protects from Excessive Consumption of Sweet Palatable Food when Fed High Caloric Diets

The calcium activated cation channel transient receptor potential channel type M5 (TRPM5) is part of the downstream machinery of the taste receptors and have been shown to play a central role in taste signalling. In addition it is also found in other types of chemosensory cells in various parts of the body as well as in pancreatic β-cells. The aim of this study was to investigate the effects of TRPM5 gene ablation on body weight, insulin sensitivity and other metabolic parameters in long-term high caloric diet induced obesity. Trpm5 ^-/- mice gained significantly less body weight and fat mass on both palatable carbohydrate and fat rich cafeteria diet and 60% high fat diet (HFD) and developed less insulin resistance compared to wild type mice. A main finding was the clearly improved glucose tolerance in Trpm5 ^-/- mice compared to wild type mice on cafeteria diet, which was independent of body weight. In addition, it was shown that Trpm5 ^-/- mice consumed the same amount of calories when fed a HFD only or a HFD in combination with a palatable chocolate ball, which is in contrast to wild type mice that increased their caloric intake when fed the combination, mainly due to excessive consumption of the chocolate ball. Thus the palatable sugar containing diet induced overeating was prevented in Trpm5 ^-/- mice. This indicates that sweet taste induced overeating may be a cause for the increased energy intake and glucose intolerance development seen for wild type mice on a sugar and high fat rich cafeteria diet compared to when on a high fat diet. This study point to an important role for the taste signalling system and TRPM5 in diet induced glucose intolerance.     

Pathology of Tnf-deficient mice infected with Plasmodium chabaudi adami 408XZ

Tumor necrosis factor alpha (Tnf) plays a pleiotropic role in murine malaria. Some investigations have correlated Tnf with hypothermia, hyperlactatemia, hypoglycemia, and a suppression of the erythropoietic response, although others have not. In this study, we have evaluated parasitemia, survival rate and several pathological features in C57BL/6JTnf^−/− and C57BL/6JTnf^+/+ mice after infection with Plasmodium chabaudi adami 408XZ. Compared to the C57BL/6JTnf^+/+ mice, C57BL/6JTnf^−/− mice showed increased parasitemia and decreased survival rate, whereas blood glucose, blood lactate and body weight were not significantly different. However, C57BL/6JTnf^−/− mice suffered significantly more from severe anemia and hypothermia than C57BL/6JTnf^+/+ mice. These results suggest that Tnf is an important mediator of parasite control, but not of anemia development. We hypothesize that the high mortality observed in the Tnf knock-out mice is due to increased anemia and pathology as a direct result of increased levels of parasitemia.     

The role of mitochondrial glycerol-3-phosphate acyltransferase-1 in regulating lipid and glucose homeostasis in high-fat diet fed mice

Glycerol-3-phosphate acyltransferase (GPAT) is involved in triacylglycerol (TAG) and phospholipid synthesis, catalyzing the first committed step. In order to further investigate the in vivo importance of the dominating mitochondrial variant, GPAT1, a novel GPAT1^−/− mouse model was generated and studied. Female GPAT1^−/− mice had reduced body weight-gain and adiposity when fed chow diet compared with littermate wild-type controls. Furthermore, GPAT1^−/− females on chow diet showed decreased liver TAG content, plasma cholesterol and TAG levels and increased ex vivo liver fatty acid oxidation and plasma ketone bodies. However, these beneficial effects were abolished and the glucose tolerance tended to be impaired when GPAT1^−/− females were fed a long-term high-fat diet (HFD). GPAT1-deficiency was not associated with altered whole body energy expenditure or respiratory exchange ratio. In addition, there were no changes in male GPAT1^−/− mice fed either diet except for increased plasma ketone bodies on chow diet, indicating a gender-specific phenotype. Thus, GPAT1-deficiency does not protect against HFD-induced obesity, hepatic steatosis or whole body glucose intolerance.     

ADAMTS5 deficiency in mice does not affect cardiac function

The aggrecanase ADAMTS5 (A Disintegrin and Metalloproteinase with ThromboSpondin type 1 motifs, member 5) and the cleavage of its substrate versican have been implicated in the development of heart valves. Furthermore, ADAMTS5 deficiency was shown to protect against diet‐induced obesity, a known risk factor for cardiovascular disease. Therefore, in this study, we investigated the potential role of ADAMTS5 in cardiac function using ADAMTS5‐deficient (Adamts5^?/?) mice and their wild‐type (Adamts5^+/+) counterparts exposed to a standard‐fat or a high‐fat diet (HFD). Eight‐weeks‐old Adamts5^?/? and Adamts5^+/+ mice were exposed to each diet for 15 weeks. Cardiac function and electrophysiology were analyzed by transthoracic echocardiogram and electrocardiogram at the end of the study. Cleavage of versican, as detected by the appearance of the DPEEAE neo‐epitope on western blotting with protein extracts, was defective in the heart of HFD‐treated Adamts5^?/? as compared with Adamts5^+/+ mice. ADAMTS5 deficiency led to statistically significant increases in diastolic posterior wall thickness (0.94 ± 0.023 vs. 0.82 ± 0.036 mm; P = 0.0056) and left ventricle volume (47 ± 4.5 vs. 31 ± 2.5 μL; P = 0.0043) in comparison to Adamts5^+/+ mice, but only in animals on a HFD. Cardiac function parameters such as ejection fraction, fractional shortening, and stroke volume were unaffected by ADAMTS5 deficiency or diet. Electrocardiogram analysis revealed no ADAMTS5‐specific changes in either diet group. Thus, in the absence of ADAMTS5, cleavage of versican in the cardiac extracellular matrix is impaired, but cardiac function, even upon exposure to a HFD, is not markedly affected.     

Impaired de Novo Choline Synthesis Explains Why Phosphatidylethanolamine N-Methyltransferase-deficient Mice Are Protected from Diet-induced Obesity

Phosphatidylcholine (PC) is synthesized from choline via the CDP-choline pathway. Liver cells can also synthesize PC via the sequential methylation of phosphatidylethanolamine, catalyzed by phosphatidylethanolamine N-methyltransferase (PEMT). The current study investigates whether or not hepatic PC biosynthesis is linked to diet-induced obesity. Pemt^+/+ mice fed a high fat diet for 10 weeks increased in body mass by 60% and displayed insulin resistance, whereas Pemt^−/− mice did not. Compared with Pemt^+/+ mice, Pemt^−/− mice had increased energy expenditure and maintained normal peripheral insulin sensitivity; however, they developed hepatomegaly and steatosis. In contrast, mice with impaired biosynthesis of PC via the CDP-choline pathway in liver became obese when fed a high fat diet. We, therefore, hypothesized that insufficient choline, rather than decreased hepatic phosphatidylcholine, was responsible for the lack of weight gain in Pemt^−/− mice despite the presence of 1.3 g of choline/kg high fat diet. Supplementation with an additional 2.7 g of choline (but not betaine)/kg of diet normalized energy metabolism, weight gain, and insulin resistance in high fat diet-fed Pemt^−/− mice. Furthermore, Pemt^+/+ mice that were fed a choline-deficient diet had increased oxygen consumption, had improved glucose tolerance, and gained less weight. Thus, de novo synthesis of choline via PEMT has a previously unappreciated role in regulating whole body energy metabolism.     

Increased dietary cholesterol promotes enhanced mutagenesis in DNA polymerase kappa-deficient mice

DNA polymerase kappa (Polκ) bypasses planar polycyclic N²-guanine adducts in an error-free manner. Cholesterol derivatives may interact with DNA to form similarly bulky lesions. In accordance, these studies examined whether increased mutagenesis of DNA accompanies hypercholesterolemia in Polk^−/− mice. These mice also carried apoE gene knockouts to ensure increased levels of plasma cholesterol following exposure to a high cholesterol diet. The mice carried a reporter transgene (the λ-phage cII gene) for subsequent quantitative analysis of mutagenesis in various tissues. We observed significantly increased mutation frequencies in several organs of apoE^−/−Polk^−/− mice following a high cholesterol diet, compared to those remaining on a standard diet. Regardless of dietary regime, the mutation frequency in many organs was significantly higher in apoE^−/−Polk^−/− than in apoE^−/−Polk^+/+ mice. As expected for polycyclic guanine adducts, the mutations mainly consisted of G:C transversions. The life expectancy of apoE^−/−Polk^−/− mice maintained on a high cholesterol diet was reduced compared to apoE^−/−Polk^+/+ mice. Overall, this study demonstrates a role for Polκ in bypass of cholesterol-induced guanine lesions.     

Taurine supplementation prevents morpho-physiological alterations in high-fat diet mice pancreatic β-cells

Taurine (Tau) is involved in beta (β)-cell function and insulin action regulation. Here, we verified the possible preventive effect of Tau in high-fat diet (HFD)-induced obesity and glucose intolerance and in the disruption of pancreatic β-cell morpho-physiology. Weaning Swiss mice were distributed into four groups: mice fed on HFD diet (36 % of saturated fat, HFD group); HTAU, mice fed on HFD diet and supplemented with 5 % Tau; control (CTL); and CTAU. After 19 weeks of diet and Tau treatments, glucose tolerance, insulin sensitivity and islet morpho-physiology were evaluated. HFD mice presented higher body weight and fat depots, and were hyperglycemic, hyperinsulinemic, glucose intolerant and insulin resistant. Their pancreatic islets secreted high levels of insulin in the presence of increasing glucose concentrations and 30 mM K⁺. Tau supplementation improved glucose tolerance and insulin sensitivity with a higher ratio of Akt phosphorylated (pAkt) related to Akt total protein content (pAkt/Akt) following insulin administration in the liver without altering body weight and fat deposition in HTAU mice. Isolated islets from HTAU mice released insulin similarly to CTL islets. HFD intake induced islet hypertrophy, increased β-cell/islet area and islet and β-cell mass content in the pancreas. Tau prevented islet and β-cell/islet area, and islet and β-cell mass alterations induced by HFD. The total insulin content in HFD islets was higher than that of CTL islets, and was not altered in HTAU islets. In conclusion, for the first time, we showed that Tau enhances liver Akt activation and prevents β-cell compensatory morpho-functional adaptations induced by HFD.     

Impact of the loss of caveolin-1 on lung mass and cholesterol metabolism in mice with and without the lysosomal cholesterol transporter,Niemann–Pick type C1

Caveolin-1 (Cav-1) is a major structural protein in caveolae in the plasma membranes of many cell types, particularly endothelial cells and adipocytes. Loss of Cav-1 function has been implicated in multiple diseases affecting the cardiopulmonary and central nervous systems, as well as in specific aspects of sterol and lipid metabolism in the liver and intestine. Lungs contain an exceptionally high level of Cav-1. Parameters of cholesterol metabolism in the lung were measured, initially in Cav-1-deficient mice (Cav-1^−/−), and subsequently in Cav-1^−/− mice that also lacked the lysosomal cholesterol transporter Niemann–Pick C1 (Npc1) (Cav-1^−/−:Npc1^−/−). In 50-day-old Cav-1^−/− mice fed a low- or high-cholesterol chow diet, the total cholesterol concentration (mg/g) in the lungs was marginally lower than in the Cav-1^+/+ controls, but due to an expansion in their lung mass exceeding 30%, whole-lung cholesterol content (mg/organ) was moderately elevated. Lung mass (g) in the Cav-1^−/−:Npc1^−/− mice (0.356 ± 0.022) markedly exceeded that in their Cav-1^+/+:Npc1^+/+ controls (0.137 ± 0.009), as well as in their Cav-1^−/−:Npc1^+/+ (0.191 ± 0.013) and Cav-1^+/+:Npc1^−/− (0.213 ± 0.022) littermates. The corresponding lung total cholesterol contents (mg/organ) in mice of these genotypes were 6.74 ± 0.17, 0.71 ± 0.05, 0.96 ± 0.05 and 3.12 ± 0.43, respectively, with the extra cholesterol in the Cav-1^−/−:Npc1^−/− and Cav-1^+/+:Npc1^−/− mice being nearly all unesterified (UC). The exacerbation of the Npc1 lung phenotype and increase in the UC level in the Cav-1^−/−:Npc1^−/− mice imply a regulatory role of Cav-1 in pulmonary cholesterol metabolism when lysosomal sterol transport is disrupted.     

Mice Abundant in Muricholic Bile Acids Show Resistance to Dietary Induced Steatosis,Weight Gain,and to Impaired Glucose Metabolism

High endogenous production of, or treatment with muricholic bile acids, strongly reduces the absorption of cholesterol. Mice abundant in muricholic bile acids may therefore display an increased resistance against dietary induced weight gain, steatosis, and glucose intolerance due to an anticipated general reduction in lipid absorption. To test this hypothesis, mice deficient in steroid 12-alpha hydroxylase (Cyp8b1^-/-) and therefore abundant in muricholic acids were monitored for 11 weeks while fed a high fat diet. Food intake and body and liver weights were determined, and lipids in liver, serum and feces were measured. Further, responses during oral glucose and intraperitoneal insulin tolerance tests were evaluated.On the high fat diet, Cyp8b1^-/- mice displayed less weight gain compared to wildtype littermates (Cyp8b1^+/+). In addition, liver enlargement with steatosis and increases in serum LDL-cholesterol were strongly attenuated in Cyp8b1^-/- mice on high fat diet. Fecal excretion of cholesterol was increased and there was a strong trend for doubled fecal excretion of free fatty acids, while excretion of triglycerides was unaltered, indicating dampened lipid absorption. On high fat diet, Cyp8b1^-/- mice also presented lower serum glucose levels in response to oral glucose gavage or to intraperitoneal insulin injection compared to Cyp8b1^+/+.In conclusion, following exposure to a high fat diet, Cyp8b1^-/- mice are more resistant against weight gain, steatosis, and to glucose intolerance than Cyp8b1^+/+ mice. Reduced lipid absorption may in part explain these findings. Overall, the results suggest that muricholic bile acids may be beneficial against the metabolic syndrome.     

Serpina3c protects against high-fat diet-induced pancreatic dysfunction through the JNK-related pathway

BackgroundSerpina3 is a member of the serine protease inhibitor family and is involved in the inflammatory response. In this study, we investigated the effect of Serpina3c on pancreatic function in hypercholesterolemic mice.MethodsTo investigate the role of Serpina3c in hyperlipidaemia, Serpina3c knockout mice were bred with Apoe-knockout mice (on a C57BL/6 background) to generate heterozygous Serpina3c-Apoe double knockout (Serpina3c^+/−/Apoe^+/−) mice and were then bred to obtain homozygotes. C57BL/6, Serpina3c^−/−, Apoe^−/−, and Apoe^−/-Serpina3c^−/− mice were fed normal chow, and Apoe^−/− and Apoe^−/-Serpina3c^−/− mice were fed a high-fat diet (HFD). After feeding for 3 months, the mice were monitored for body weight, blood glucose, glucose tolerance, and insulin tolerance test (ITT). ELISA and immunohistochemistry were used to detect insulin levels and glucagon expression. Immunohistochemical staining for macrophages in the pancreas was also performed. Western blot analysis was performed on pancreatic tissues to detect the protein levels of insulin-associated molecules, the metalloproteinase MMP2, the tissue inhibitor TIMP2 and components of the JNK-related pathway.ResultsBlood glucose levels, glucose tolerance, and ITT were not significantly different among the groups. Serpina3c knockout resulted in blood lipid abnormalities in mice under HFD conditions. Insulin secretion was decreased in Apoe^−/-Serpina3c^−/− mice compared with Apoe^−/− mice under normal chow conditions. In addition, Apoe^−/-Serpina3c^−/− mice exhibited increased insulin and glucagon secretion and expression after three months of HFD feeding, but insulin secretion was decreased in Apoe^−/-Serpina3c^−/− mice compared with Apoe^−/− mice after the fifth month of HFD feeding. Serpina3c knockout increased MMP2 protein levels, whereas TIMP2 levels in the pancreas were decreased. Furthermore, Serpina3c knockout significantly upregulated the number of macrophages in the pancreas under HFD conditions. The JNK/AKT/FOXO1/PDX-1 axis was found to be involved in Serpina3c-regulated insulin secretion.ConclusionThese novel findings show that Serpina3c could play a protective role in insulin secretion partly through the JNK-related pathway under HFD conditions.     

A high-fat diet and high-fat and high-cholesterol diet may affect glucose and lipid metabolism differentially through gut microbiota in mice

This study was conducted to investigate the effects of a high-fat diet (HFD) and high-fat and high-cholesterol diet (HFHCD) on glucose and lipid metabolism and on the intestinal microbiota of the host animal. A total of 30 four-week-old female C57BL/6 mice were randomly divided into three groups (n=10) and fed with a normal diet (ND), HFD, or HFHCD for 12 weeks, respectively. The HFD significantly increased body weight and visceral adipose accumulation and partly lowered oral glucose tolerance compared with the ND and HFHCD. The HFHCD increased liver weight, liver fat infiltration, liver triglycerides, and liver total cholesterol compared with the ND and HFD. Moreover, it increased serum high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and total cholesterol compared with the ND and HFD and upregulated alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase significantly. The HFHCD also significantly decreased the α-diversity of the fecal bacteria of the mice, to a greater extent than the HFD. The composition of fecal bacteria among the three groups was apparently different. Compared with the HFHCD-fed mice, the HFD-fed mice had more Oscillospira, Odoribacter, Bacteroides, and [Prevotella], but less [Ruminococcus] and Akkermansia. Cecal short-chain fatty acids were significantly decreased after the mice were fed the HFD or HFHCD for 12 weeks. Our findings indicate that an HFD and HFHCD can alter the glucose and lipid metabolism of the host animal differentially; modifications of intestinal microbiota and their metabolites may be an important underlying mechanism.     

Specific deletion of protein phosphatase 6 catalytic subunit in Sertoli cells leads to disruption of spermatogenesis

Protein phosphatase 6 (PP6) is a member of the PP2A-like subfamily, which plays significant roles in numerous fundamental biological activities. We found that PPP6C plays important roles in male germ cells recently. Spermatogenesis is supported by the Sertoli cells in the seminiferous epithelium. In this study, we crossed Ppp6c^F/F mice with AMH-Cre mice to gain mutant mice with specific depletion of the Ppp6c gene in the Sertoli cells. We discovered that the PPP6C cKO male mice were absolutely infertile and germ cells were largely lost during spermatogenesis. By combing phosphoproteome with bioinformatics analysis, we showed that the phosphorylation status of β-catenin at S552 (a marker of adherens junctions) was significantly upregulated in mutant mice. Abnormal β-catenin accumulation resulted in impaired testicular junction integrity, thus led to abnormal structure and functions of BTB. Taken together, our study reveals a novel function for PPP6C in male germ cell survival and differentiation by regulating the cell-cell communication through dephosphorylating β-catenin at S552.Subject terms: Spermatogenesis, Infertility     

Angptl 4 deficiency improves lipid metabolism, suppresses foam cell formation and protects against atherosclerosis

Angiopoietin-like protein family 4 (Angptl 4) has been shown to regulate lipoprotein metabolism through the inhibition of lipoprotein lipase (LPL). We generated ApoE^−/−Angptl 4^−/− mice to study the effect of Angptl 4 deficiency on lipid metabolism and atherosclerosis. Fasting and postolive oil-loaded triglyceride (TG) levels were largely decreased in ApoE^−/−Angptl 4^−/− mice compared with and ApoE^−/−Angptl 4^+/+ mice. There was a significant (75 ± 12%) reduction in atherosclerotic lesion size in ApoE^−/−Angptl 4^−/− mice compared with ApoE^−/− Angptl 4^+/+ mice. Peritoneal macrophages, isolated from Angptl 4^−/− mice to investigate the foam cell formation, showed a significant decrease in newly synthesized cholesteryl ester (CE) accumulation induced by acetyl low-density lipoprotein (acLDL) compared with those from Angptl 4^+/+ mice. Thus, genetic knockout of Angptl 4 protects ApoE^−/− mice against development and progression of atherosclerosis and strongly suppresses the ability of the macrophages to become foam cells in vitro.