Impact of various high fat diets on gene expression and the microbiome across the mouse intestines

High fat diets (HFDs) have been linked to several diseases including obesity, diabetes, fatty liver, inflammatory bowel disease (IBD) and colon cancer. In this study, we examined the impact on intestinal gene expression of three isocaloric HFDs that differed only in their fatty acid composition-coconut oil (saturated fats), conventional soybean oil (polyunsaturated fats) and a genetically modified soybean oil (monounsaturated fats). Four functionally distinct segments of the mouse intestinal tract were analyzed using RNA-seq-duodenum, jejunum, terminal ileum and proximal colon. We found considerable dysregulation of genes in multiple tissues with the different diets, including those encoding nuclear receptors and genes involved in xenobiotic and drug metabolism, epithelial barrier function, IBD and colon cancer as well as genes associated with the microbiome and COVID-19. Network analysis shows that genes involved in metabolism tend to be upregulated by the HFDs while genes related to the immune system are downregulated; neurotransmitter signaling was also dysregulated by the HFDs. Genomic sequencing also revealed a microbiome altered by the HFDs. This study highlights the potential impact of different HFDs on gut health with implications for the organism as a whole and will serve as a reference for gene expression along the length of the intestines.

HNF4α isoforms regulate the circadian balance between carbohydrate and lipid metabolism in the liver

Hepatocyte Nuclear Factor 4α (HNF4α), a master regulator of hepatocyte differentiation, is regulated by two promoters (P1 and P2) which drive the expression of different isoforms. P1-HNF4α is the major isoform in the adult liver while P2-HNF4α is thought to be expressed only in fetal liver and liver cancer. Here, we show that P2-HNF4α is indeed expressed in the normal adult liver at Zeitgeber time (ZT)9 and ZT21. Using exon swap mice that express only P2-HNF4α we show that this isoform orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions, including with different clock proteins at different times of the day leading to subtle differences in circadian gene regulation. Furthermore, deletion of the Clock gene alters the circadian oscillation of P2- (but not P1-)HNF4α RNA, revealing a complex feedback loop between the HNF4α isoforms and the hepatic clock. Finally, we demonstrate that while P1-HNF4α drives gluconeogenesis, P2-HNF4α drives ketogenesis and is required for elevated levels of ketone bodies in female mice. Taken together, we propose that the highly conserved two-promoter structure of the Hnf4a gene is an evolutionarily conserved mechanism to maintain the balance between gluconeogenesis and ketogenesis in the liver in a circadian fashion.

Impact of Various High Fat Diets on Gene Expression and the Microbiome Across the Mouse Intestines

High fat diets (HFDs) have been linked to several diseases including obesity, diabetes, fatty liver, inflammatory bowel disease (IBD) and colon cancer. In this study, we examined the impact on intestinal gene expression of three isocaloric HFDs that differed only in their fatty acid composition - coconut oil (saturated fats), conventional soybean oil (polyunsaturated fats) and a genetically modified soybean oil (monounsaturated fats). Four functionally distinct segments of the mouse intestinal tract were analyzed using RNA-seq - duodenum, jejunum, terminal ileum and proximal colon. We found considerable dysregulation of genes in multiple tissues with the different diets, including those encoding nuclear receptors and genes involved in xenobiotic and drug metabolism, epithelial barrier function, IBD and colon cancer as well as genes associated with the microbiome and COVID-19. Network analysis shows that genes involved in metabolism tend to be upregulated by the HFDs while genes related to the immune system are downregulated; neurotransmitter signaling was also dysregulated by the HFDs. Genomic sequencing also revealed a microbiome altered by the HFDs. This study highlights the potential impact of different HFDs on gut health with implications for the organism as a whole and will serve as a reference for gene expression along the length of the intestines.

Diet high in linoleic acid dysregulates the intestinal endocannabinoid system and increases susceptibility to colitis in Mice

Inflammatory bowel disease (IBD) is a multifactorial disease with increasing incidence in the U.S. suggesting that environmental factors, including diet, are involved. It has been suggested that excessive consumption of linoleic acid (LA, C18:2 omega-6), which must be obtained from the diet, may promote the development of IBD in humans. To demonstrate a causal link between LA and IBD, we show that a high fat diet (HFD) based on soybean oil (SO), which is comprised of ~55% LA, increases susceptibility to colitis in several models, including IBD-susceptible IL10 knockout mice. This effect was not observed with low-LA HFDs derived from genetically modified soybean oil or olive oil. The conventional SO HFD causes classical IBD symptoms including immune dysfunction, increased intestinal epithelial barrier permeability, and disruption of the balance of isoforms from the IBD susceptibility gene Hepatocyte Nuclear Factor 4α (HNF4α). The SO HFD causes gut dysbiosis, including increased abundance of an endogenous adherent invasive Escherichia coli (AIEC), which can use LA as a carbon source. Metabolomic analysis shows that in the mouse gut, even in the absence of bacteria, the presence of soybean oil increases levels of LA, oxylipins and prostaglandins. Many compounds in the endocannabinoid system, which are protective against IBD, are decreased by SO both in vivo and in vitro. These results indicate that a high LA diet increases susceptibility to colitis via microbial and host-initiated pathways involving alterations in the balance of bioactive metabolites of omega-6 and omega-3 polyunsaturated fatty acids, as well as HNF4α isoforms.

Developmental exposure to indoor flame retardants and hypothalamic molecular signatures: Sex-dependent reprogramming of lipid homeostasis

Polybrominated diphenyl ethers (PBDEs) are a class of flame-retardant organohalogen pollutants that act as endocrine/neuroendocrine disrupting chemicals (EDCs). In humans, exposure to brominated flame retardants (BFR) or other environmentally persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and novel organophosphate flame retardants has been associated with increasing trends of diabetes and metabolic disease. However, the effects of PBDEs on metabolic processes and their associated sex-dependent features are poorly understood. The metabolic-disrupting effects of perinatal exposure to industrial penta-PBDE mixture, DE-71, on male and female progeny of C57BL/6N mouse dams were examined in adulthood. Dams were exposed to environmentally relevant doses of PBDEs daily for 10 weeks (p.o.): 0.1 (L-DE-71) and 0.4 mg/kg/d (H-DE-71) and offspring parameters were compared to corn oil vehicle controls (VEH/CON). The following lipid metabolism indices were measured: plasma cholesterol, triglycerides, adiponectin, leptin, and liver lipids. L-DE-71 female offspring were particularly affected, showing hypercholesterolemia, elevated liver lipids and fasting plasma leptin as compared to same-sex VEH/CON, while L- and H-DE-71 male F1 only showed reduced plasma adiponectin. Using the quantitative Folch method, we found that mean liver lipid content was significantly elevated in L-DE-71 female offspring compared to controls. Oil Red O staining revealed fatty liver in female offspring and dams. General measures of adiposity, body weight, white and brown adipose tissue (BAT), and lean and fat mass were weighed or measured using EchoMRI. DE-71 did not produce abnormal adiposity, but decreased BAT depots in L-DE-71 females and males relative to same-sex VEH/CON. To begin to address potential central mechanisms of deregulated lipid metabolism, we used RT-qPCR to quantitate expression of hypothalamic genes in energy-regulating circuits that control lipid homeostasis. Both doses of DE-71 sex-dependently downregulated hypothalamic expression of Lepr, Stat3, Mc4r, Agrp, Gshr in female offspring while H-DE-71 downregulated Npy in exposed females relative to VEH/CON. In contrast, exposed male offspring displayed upregulated Stat3 and Mc4r. Intestinal barrier integrity was measured using FITC-dextran since it can lead to systemic inflammation that leads to liver damage and metabolic disease, but was not affected by DE-71 exposure. These findings indicate that maternal transfer of PBDEs disproportionately endangers female offspring to lipid metabolic reprogramming that may exaggerate risk for adult metabolic disease.

Natural infection of Delta mutant of SARS-CoV-2 in Asiatic lions of India

The current pandemic caused by a novel coronavirus (SARS‐CoV‐2) has underlined the importance of emerging diseases of zoonotic importance. Along with human beings, several species of wild and pet animals have been demonstrated to be infected by SARS‐CoV‐2, both naturally and experimentally. In addition, with constant emergence of new variants, the species susceptibility might further change which warrants intensified screening efforts. India is a vast and second most populated country, with a habitat of a very diverse range of animal species. In this study we place on record of SARS‐CoV‐2 infections in three captive Asiatic lions. Detailed genomic characterization revealed involvement of Delta mutant (Pango lineage B.1.617.2) of SARS‐CoV‐2 at two different locations. Interestingly, no other feline species enclosed in the zoo/park were found infected. The epidemiological and molecular analysis will contribute to the understanding of the emerging mutants of SARS‐CoV‐2 in wild and domestic animals.

Palmitic acid negatively regulates tumor suppressor PTEN through T366 phosphorylation and protein degradation

Chronic elevated free fatty (FFA) levels are linked to metabolic disorders and tumorigenesis. However, the molecular mechanism by which FFAs induce cancer remains poorly understood. Here, we show that the tumor suppressor PTEN protein levels were decreased in high fat diet (HFD) fed mice. As palmitic acid (PA, C16:0) showed a significant increase in the HFD fed mice, we further investigated its role in PTEN down regulation. Our studies revealed that exposure of cells to high doses of PA induced mTOR/S6K-mediated phosphorylation of PTEN at T366. The phosphorylation subsequently enhanced the interaction of PTEN with the E3 ubiquitin ligase WW domain-containing protein 2 (WWP2), which promoted polyubiquitination of PTEN and protein degradation. Consistent with PTEN degradation, exposure of cells to increased concentrations of PA also promoted PTEN-mediated AKT activation and cell proliferation. Significantly, a higher level of S6K activation, PTEN T366 phosphorylation, and AKT activation were also observed in the livers of the HFD fed mice. These results provide a molecular mechanism by which a HFD and elevated PA regulate cell proliferation through inactivation of tumor suppressor PTEN.

SUN-LB119 Role of HNF4a Isoforms in the Carbohydrate/Lipid Switch in the Liver and Responsiveness to AMPK

Hepatocyte Nuclear Factor 4α (HNF4α), the master regulator of liver-specific gene expression, is regulated by two promoters (P1 and P2) which drive expression of two groups of HNF4α isoforms referred to here as HNF4α1 and HNF4α7. HNF4α is a known regulator of gluconeogenesis and is mutated in maturity onset diabetes of the young one (MODY1). Conventionally, it was thought that HNF4α1, but not HNF4α7, is expressed in the normal adult liver, with HNF4α1 downregulated and HNF4α7 upregulated in liver cancer. Now, we identify a previously undescribed role for HNF4α7 in the normal adult mouse liver - one involved in the diurnal variations of lipid and carbohydrate metabolism. More specifically, HNF4α1 appears to be a major driver of gluconeogenesis while HNF4α7 is a driver of ketogenesis: we hypothesize that alterations in the levels of the HNF4α isoforms during the day function as a molecular switch between the two. Moreover, our preliminary data show that HNF4α7 is required for increased levels of circulating ketone bodies in female mice, suggesting interactions with the estrogen pathway. AMP-Activated Protein Kinase (AMPK), an energy-sensing kinase that also plays a major role in carbohydrate and lipid metabolism, has been shown to phosphorylate HNF4α1 in vitro, but effects in vivo and on HNF4α7 are not known. In order to investigate the impact of AMPK on HNF4α isoforms, we employed HNF4α isoform-specific mice α7HMZ (express only HNF4α7) and α1HMZ mice (express only HNF4α1), as well as heterozygous mice which express both. Intraperitoneal injection of the mice with AMPK activator AICAR leads to a rapid decrease in glucose. Interestingly, half the α7HMZ males and all the females began seizing 30 min post injection, while very few α1HMZ males/females and none of the heterozygous mice seized. Moreover, there were differences in the survival of the different genotypes: a third of α1HMZ mice die within 24hrs, while two thirds of α7HMZ mice die within a week, with all heterozygous mice surviving. We suspect the seizures could be due to an electrolyte imbalance exacerbated by AICAR or extremely low glucose caused by AICAR. The α7HMZ females have significantly lower potassium levels compared to α1HMZ and wildtype mice. Additionally, AMPK is known to regulate Na+/glucose transporters, and HNF4α1 is expressed in the proximal tubules in the kidney (responsible for Na+ uptake). To elucidate the cause of the seizures, AICAR injections were repeated with α1HMZ males followed by a glucose or saline gavage. Interestingly, half of the glucose-gavaged mice died within 24hrs, while all of the saline-gavaged mice survived. Our work underscores the critical role that the HNF4α isoforms play in the metabolic switch, and suggests that the kidney as well as the liver could be involved.

Dysregulation of Hypothalamic Gene Expression and the Oxytocinergic System by Soybean Oil Diets in Male Mice

Soybean oil consumption has increased greatly in the past half-century and is linked to obesity and diabetes. To test the hypothesis that soybean oil diet alters hypothalamic gene expression in conjunction with metabolic phenotype, we performed RNA sequencing analysis using male mice fed isocaloric, high-fat diets based on conventional soybean oil (high in linoleic acid, LA), a genetically modified, low-LA soybean oil (Plenish), and coconut oil (high in saturated fat, containing no LA). The 2 soybean oil diets had similar but nonidentical effects on the hypothalamic transcriptome, whereas the coconut oil diet had a negligible effect compared to a low-fat control diet. Dysregulated genes were associated with inflammation, neuroendocrine, neurochemical, and insulin signaling. Oxt was the only gene with metabolic, inflammation, and neurological relevance upregulated by both soybean oil diets compared to both control diets. Oxytocin immunoreactivity in the supraoptic and paraventricular nuclei of the hypothalamus was reduced, whereas plasma oxytocin and hypothalamic Oxt were increased. These central and peripheral effects of soybean oil diets were correlated with glucose intolerance but not body weight. Alterations in hypothalamic Oxt and plasma oxytocin were not observed in the coconut oil diet enriched in stigmasterol, a phytosterol found in soybean oil. We postulate that neither stigmasterol nor LA is responsible for effects of soybean oil diets on oxytocin and that Oxt messenger RNA levels could be associated with the diabetic state. Given the ubiquitous presence of soybean oil in the American diet, its observed effects on hypothalamic gene expression could have important public health ramifications.

Dimethyl Sulfoxide Decreases Levels of Oxylipin Diols in Mouse Liver

Dimethylsulfoxide (DMSO) is widely used as a solvent and cryopreservative in laboratories and considered to have many beneficial health effects in humans. Oxylipins are a class of biologically active metabolites of polyunsaturated fatty acids (PUFAs) that have been linked to a number of diseases. In this study, we investigated the effect of DMSO on oxylipin levels in mouse liver. Liver tissue from male mice (C57Bl6/N) that were either untreated or injected with 1% DMSO at 18 weeks of age was analyzed for oxylipin levels using ultrahigh performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). A decrease in oxylipin diols from linoleic acid (LA, C18:2n6), alpha-linolenic acid (ALA, C18:3n3) and docosahexeanoic acid (DHA, C22:6n3) was observed 2 h after injection with DMSO. In contrast, DMSO had no effect on the epoxide precursors or other oxylipins including those derived from arachidonic acid (C20:4n6) or eicosapentaenoic acid (EPA, C20:5n3). It also did not significantly affect the diol:epoxide ratio, suggesting a pathway distinct from, and potentially complementary to, soluble epoxide hydrolase inhibitors (sEHI). Since oxylipins have been associated with a wide array of pathological conditions, from arthritis pain to obesity, our results suggest one potential mechanism underlying the apparent beneficial health effects of DMSO. They also indicate that caution should be used in the interpretation of results using DMSO as a vehicle in animal experiments.

SUN-023 HNF4a Isoforms Regulate the Circadian Balance between Carbohydrate and Fatty Acid Metabolism in the Liver

Nuclear receptor genes often contain alternative promoters but the physiological relevance of the different promoters or the proteins they generate is largely unknown. Hepatocyte Nuclear Factor 4α (HNF4α), master regulator of hepatocyte differentiation and the most abundant nuclear receptor in the liver, is regulated by two promoters (P1 and P2). P1-HNF4α, a tumor suppressor, is the major isoform in the adult liver while P2-HNF4α is expressed in fetal liver and liver cancer: a role for P2-HNF4α in normal adult liver has not been identified. Here we show for the first time that P2-HNF4α is expressed at ZT9 and ZT21 in the normal adult liver and use P2-HNF4α-expressing exon swap mice and ‘omics approaches to demonstrate that P2-HNF4α orchestrates a distinct transcriptome and metabolome via unique chromatin and protein-protein interactions. Cytochrome P450 and sex-specific gene expression is impacted as well as carbohydrate and fatty acid metabolism. The exon swap mice exhibit subtle differences in circadian gene regulation and disruption of the clock increases expression of P2-HNF4α. They also exhibit notable differences in carbohydrate versus fatty acid metabolism with P1-HNF4α driving gluconeogenesis and P2-HNF4α driving ketogenesis. Our results also show that P2-HNF4α is required for the elevated levels of ketone bodies in female mice. Taken together, we propose that the highly conserved two-promoter structure in the Hnfa gene is designed, at least in part, to respond to the availability of food resources and maintain the balance between gluconeogenesis and ketogenesis in a circadian and sex-specific fashion. (Funding: NIH NIDDK, West Cost Metabolomics Center, NIEHS T32, USDA NIFA, CCFA, Superfund Research Program)

SUN-101 Dysregulation of Hypothalamic Gene Expression by Soybean Oil Diets in Mice

Soybean oil is a major component of the American diet and its increased consumption correlates positively with the prevalence of obesity and diabetes in the U.S. Our previous findings showed that a high fat diet (HFD) enriched in soybean oil, similar to the American diet, induces more obesity, diabetes, insulin resistance and fatty liver in male mice than an isocaloric diet consisting of coconut oil (CO), as well as a substantial dysregulation of liver gene expression (PMID:28970503, 26200659). Here, RNA-seq analysis reveals that HFDs based on conventional soybean oil (SO), which is high in linoleic acid (LA), and a genetically modified, low-LA soybean oil called Plenish, have similar, albeit non identical, effects on hypothalamic gene expression; in contrast, a CO HFD has a negligible effect compared to the low fat vivarium chow (Viv) diet. Genes related to inflammation and oxidative stress, metabolism, obesity and diabetes, as well as those linked to neurological disorders, are dysregulated by SO and Plenish. Oxt, which encodes the neuropeptide oxytocin (OXT), is the only gene with metabolic and neurological significance upregulated by both soybean oil diets, but not CO, suggesting that Oxt gene expression is altered by neither LA nor the saturated fatty acids present in CO. In contrast, immunohistochemistry (IHC) shows that the two soybean oil diets reduce oxytocin protein (OXT) levels in the supraoptic and paraventricular nuclei of the hypothalamus, while OXT peptide levels are increased in the circulating blood, suggesting that a decrease in hypothalamic OXT may be responsible for SO-induced obesity and diabetes. The phytosterol stigmasterol found in both the SO and Plenish diets did not induce either obesity or diabetes nor affect the oxytocin pathway, suggesting that a component in soybean oil other than LA or stigmasterol is responsible for its metabolic effects. Given the impact that Oxt can have on metabolic processes as well as developmental disorders of social behavior including autism, depression and schizophrenia, the American diet based largely on soybean oil may have a broader impact on human health than previously appreciated.(Funding: NIH NIDDK, NIEHS T32, CCFA, Seed Grant-UCR).

Opposing roles of nuclear receptor HNF4α isoforms in colitis and colitis-associated colon cancer

HNF4α has been implicated in colitis and colon cancer in humans but the role of the different HNF4α isoforms expressed from the two different promoters (P1 and P2) active in the colon is not clear. Here, we show that P1-HNF4α is expressed primarily in the differentiated compartment of the mouse colonic crypt and P2-HNF4α in the proliferative compartment. Exon swap mice that express only P1- or only P2-HNF4α have different colonic gene expression profiles, interacting proteins, cellular migration, ion transport and epithelial barrier function. The mice also exhibit altered susceptibilities to experimental colitis (DSS) and colitis-associated colon cancer (AOM+DSS). When P2-HNF4α-only mice (which have elevated levels of the cytokine resistin-like β, RELMβ, and are extremely sensitive to DSS) are crossed with Retnlb(-/-) mice, they are rescued from mortality. Furthermore, P2-HNF4α binds and preferentially activates the RELMβ promoter. In summary, HNF4α isoforms perform non-redundant functions in the colon under conditions of stress, underscoring the importance of tracking them both in colitis and colon cancer.

Soybean Oil Is More Obesogenic and Diabetogenic than Coconut Oil and Fructose in Mouse: Potential Role for the Liver

The obesity epidemic in the U.S. has led to extensive research into potential contributing dietary factors, especially fat and fructose. Recently, increased consumption of soybean oil, which is rich in polyunsaturated fatty acids (PUFAs), has been proposed to play a causal role in the epidemic. Here, we designed a series of four isocaloric diets (HFD, SO-HFD, F-HFD, F-SO-HFD) to investigate the effects of saturated versus unsaturated fat, as well as fructose, on obesity and diabetes. C57/BL6 male mice fed a diet moderately high in fat from coconut oil and soybean oil (SO-HFD, 40% kcal total fat) showed statistically significant increases in weight gain, adiposity, diabetes, glucose intolerance and insulin resistance compared to mice on a diet consisting primarily of coconut oil (HFD). They also had fatty livers with hepatocyte ballooning and very large lipid droplets as well as shorter colonic crypt length. While the high fructose diet (F-HFD) did not cause as much obesity or diabetes as SO-HFD, it did cause rectal prolapse and a very fatty liver, but no balloon injury. The coconut oil diet (with or without fructose) increased spleen weight while fructose in the presence of soybean oil increased kidney weight. Metabolomics analysis of the liver showed an increased accumulation of PUFAs and their metabolites as well as γ-tocopherol, but a decrease in cholesterol in SO-HFD. Liver transcriptomics analysis revealed a global dysregulation of cytochrome P450 (Cyp) genes in SO-HFD versus HFD livers, most notably in the Cyp3a and Cyp2c families. Other genes involved in obesity (e.g., Cidec, Cd36), diabetes (Igfbp1), inflammation (Cd63), mitochondrial function (Pdk4) and cancer (H19) were also upregulated by the soybean oil diet. Taken together, our results indicate that in mice a diet high in soybean oil is more detrimental to metabolic health than a diet high in fructose or coconut oil.

Isolated central canal rupture of spinal dermoid: report of two cases

We report two cases of lumbar spinal dermoid cysts with asymptomatic rupture and migration of free fat droplets into the central canal. No fatty droplets were seen within the lumbar subarachnoid space. The presence of fat droplets within the central canal is unusual because the central canal is rudimentary in adults. We suggest that hydromyelia secondary to tumour and specific tumour morphology might facilitate the selective rupture of dermoids into the central canal. We recommend a follow up of these patients to detect any possible intracranial migration of fat droplets and resultant complications.

Spinal angiolipoma: report of three cases and review of MRI features

We report three cases of spinal angiolipoma, two intramedullary and one epidural, and review their MRI features. Diagnoses were established preoperatively in all cases. Specific MRI features including the importance of postgadolinium fat-saturated T1-weighted images and presence of vascular flow-voids are discussed with histopathological correlation. A characteristic morphological appearance of intramedullary angiolipoma has been suggested.

Spinal angiolipoma: report of three cases and review of MRI features

We report three cases of spinal angiolipoma, two intramedullary and one epidural, and review their MRI features. Diagnoses were established preoperatively in all cases. Specific MRI features including the importance of postgadolinium fat-saturated T1-weighted images and presence of vascular flow-voids are discussed with histopathological correlation. A characteristic morphological appearance of intramedullary angiolipoma has been suggested.

Epithelioid sarcoma of the sciatic nerve perineural sheath: a mimic of nerve sheath tumor

We report herein a rare case of epithelioid sarcoma, in a 39-year old lady involving the sciatic nerve. Clinically and radiologically it stimulated a nerve sheath tumor. Involvement of a nerve by an epithelioid sarcoma is extremely uncommon. To the best of our knowledge, this is the first case of an epithelioid sarcoma involving the sciatic nerve and needs documentation.

Therapeutic efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes against Mycobacterium tuberculosis infection induced in mice

One recent promising development in the modification of drug formulations to improve chemotherapy is the use of a liposome-mediated drug delivery system. The efficacies of isoniazid and rifampin encapsulated in lung-specific stealth liposomes were evaluated by injecting liposomal drugs and free drugs into tuberculous mice twice a week for 6 weeks. Liposome-encapsulated drugs at and below therapeutic concentrations were more effective than free drugs against tuberculosis, as evaluated on the basis of CFUs detected, organomegaly, and histopathology. Furthermore, liposomal drugs had marginal hepatotoxicities as determined from the levels of total bilirubin and hepatic enzymes in serum. The elimination of mycobacteria from the liver and spleen was also higher with liposomal drugs than with free drugs. The encapsulation of antitubercular drugs in lung-specific stealth liposomes seems to be a promising therapeutic approach for the chemotherapy of tuberculosis.

Lung specific stealth liposomes: stability, biodistribution and toxicity of liposomal antitubercular drugs in mice

Liposomes with enhanced affinity towards lung tissue were prepared for the development of more effective chemotherapy against tuberculosis. Modification of surface of stealth liposomes by tagging O-stearylamylopectin (O-SAP) resulted in the increased affinity of these liposomes towards lung tissue of mice. Liposomes containing egg phosphatidylcholine (ePC), cholesterol (CH), dicetylphosphate (DCP), O-SAP and monosialogangliosides (GM1)/distearylphosphatidylethanolamine-poly(ethylene glycol) 2000 (DSPE-PEG 2000) were found to be most stable in serum. Tissue distribution of these liposomes showed more accumulation in lungs than in reticuloendothelial systems (RES) of normal and tuberculous mice. Pre administration of PC and CH (2:1.5) liposomes before the injection of lung specific stealth liposomes further enhanced their uptake in lungs. In vivo stability of these liposomes demonstrated the slow and controlled release of their encapsulated contents. Isoniazid and rifampicin encapsulated in liposomes were less toxic to peritoneal macrophages as compared to free drugs. Further, encapsulated drugs also demonstrated reduced in vivo toxicity in comparison to free drug(s). These findings suggest liposomes to be better drug delivery vehicles for experimental tuberculosis.