Comparative toxicity of high doses of vastatins currently used by clinicians, in CD-1 male mice fed with a hypercholesterolemic diet.

The CD-1 male-mouse model was employed to evaluate comparatively the toxicity of four vastatins (VTS) currently used in clinical medicine: lovastatin (LVT), simvastatin (SVT), pravastatin (PVT) and fluvastatin (FVT). Each vastatin was used orally in doses of 500 mg/Kg body weight/day, in animals with a hypercholesterolemic diet (HD) 5 days, or with a control diet (CD) 30 days. The association of high doses of VTS + HD produced a significant increase in liver weight and liver weight to body weight ratio in animals with SVT and FVT. Cholesterol (Chol) and triacylglycerols (TAG) in the liver increased significantly with FVT but not with the other VTS; Chol increased and TAG decreased in serum very significantly with FVT and SVT. The serum aminotransferases increased quite significantly with FVT but not with other VTS. In the experiment with high doses of VTS + CD, the animals receiving SVT or FVT showed a moderate loss of body weight. Liver weight and liver weight to body weight ratios were similar among all groups. Liver Chol showed a significant decrease with all VTS. Serum Chol decreased moderately with LVT and FVT. TAG in serum and liver showed a moderate decrease with all VTS. The serum aminotransferases were not modified by any vastatin. Our results indicate that high doses of VTS in male mice with a hypercholesterolemic diet result in a decreasing toxicity as follows: FVT>SVT>LVT>PVT.     

Activation and inhibition of isolation induced inter-male fighting behavior in castrate male CD-1 mice treated with steroidal hormones

Intermale fighting behavior between castrate male CD-1 mice living in isolation and castrate male CD-1 mice living in groups of 10 was activated by treating the isolated males with either testosterone or testosterone propionate. Fighting behavior was not activated by treating isolated males with androstenedione or dihydrotesterone even though these androgens were active in maintaining seminal vesicle weight at levels equal to, or greater than, those observed in gonadally intact males. Neither fighting behavior nor seminal vesicle weight was stimulated by treatment with progesterone, estradiol benzoate, or estradiol benzoate plus progesterone. Concurrent administration of progesterone inhibited fighting behavior activated by low, but not moderate to high doses of testosterone propionate. These results suggest that the hormone requirements for activation of fighting behavior in the male CD-1 mouse are more restrictive than those for maintenance of peripheral target tissues and that progesterone acts in the brain to competitively inhibit androgen-activated fighting.     

Reduction of hyperlipidemia in the LA/N-corpulent rat by dietary fish oil containing n-3 fatty acids

The LA/N rat, when homozygous for the corpulent gene (cp/cp), is obese, hyperphageous, hyperinsulinemic, hypertriglyceridemic and prone to the development of vascular and myocardial lesions. The hypertriglyceridemia, which in 3-month-old cp/cp males is 282 +/- 42 mg/dl and in females, 512 +/- 83 mg/dl, results from the presence of a large triacylglycerol-rich VLDL. The moderate hypercholesterolemia in these animals is largely due to markedly elevated HDL levels, which reach 172 +/- 21 mg total lipid/dl in males and 154 +/- 22 mg total lipid/dl in females. The LA/N-cp rat is thus an interesting animal model of endogenous hypertriglyceridemia in which to examine the hypolipidemic effects of pharmacological agents and also dietary oil supplements containing the n-3 fatty acids. In this study, 1-month-old male and female cp/cp rats were fed a normal low fat laboratory chow supplemented with either 10% olive oil or 10% redfish (Sebastes marinus) oil ad libitum for a period of 2 months. The redfish oil contained 4.9 +/- 0.1% of its total fatty acids as eicosapentaenoic (20:5(n-3)) and 2.3 +/- 0.5% as docosahexaenoic acid (22:6(n-3)), the predominant fatty acids being gondoic (20:1(n-3)), 21.9 +/- 0.9% and cetoleic acid (22:1(n-11)), 21.7 +/- 1.7%, which are of dietary origin. Daily caloric intake was similar to the oil-fed versus control rats. However, the oil-fed animals weighed significantly more than the controls after 2 months of oil supplementation. Redfish oil reduced serum triacylglycerols by 54% in males and 45% in females after 2 months. VLDL levels, after the same time period, were reduced by 44% in males and 39% in females. HDL lipid mass was significantly reduced in both sexes (by 27% in males and 49% in females). However, the levels remained above those of male LA/N +/+ rats of the same age and Long-Evens rats. Olive oil feeding significantly reduced serum cholesterol, triacyglycerols and phospholipids in male but only cholesterol and phospholipids in female animals. This oil had no significant effect upon VLDL total lipid levels in either sex, but significantly increased the particle diameter with a concomitant reduction in the cholesterol and phospholipid content. HDL total lipid levels were unaffected: However, HDL total cholesterol increased significantly in males only. Both oils markedly reduced serum LDL levels in both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Effects of feeding endophyte infected tall fescue seed on reproductive performance of female CD-1 mice via competitive breeding

This study was conducted to determine the effects of feeding endophyte-infected (Acremonium coenophialum ) tall fescue (Festuca arundinacea ) seed on the growth and reproductive performance of female CD-1 mice via competitive breeding. One hundred sixty female mice were randomly allocated to groups of ten and fed one of two diets. Diet 1 consisted of 50% mouse chow and 50% noninfected Ky-31 tall fescue seed (w/w). Diet 2 contained 50% chow and 50% tall fescue seed that was 80% infected with A. coenophialum . After 50 d of preconditioning on their respective diets, a single male was introduced into each group of 10 females and allowed to cohabitate for 96 h. The males were removed after the cohabitation period and the females continued through gestation on their respective diets. Body weight of dams and litter weights were recorded at parturition. There were no differences (P>0.05) in pregnancy rates between dietary Treatments 1 and 2 (50% vs 48.8%, respectively). However, the average number of pups born per litter (11.10 pups) and average total litter weight (17.21 g) was greater for those females consuming Diet 1 than for females consuming Diet 2 (9.33 pups per litter and 13.97 g total litter weight). The incidence of dead and cannibalized pups was more frequent with Diet 2 than Diet 1 (0.13 vs 0.0 dead; 0.21 vs 0.03 cannibalized, respectively). The obtained data suggest that although the pregnancy rate was similar between the two dietary treatments, the reproductive capacity (litter size and litter weight) of female CD-1 mice was affected by the consumption of endophyte infected fescue seed.     

Effects of dietary protein restriction on nephron number in the mouse

In rats, maternal protein restriction reduces nephron endowment and often leads to adult hypertension. Sex differences in these responses have been identified. The molecular and genetic bases of these phenomena can best be identified in a mouse model, but effects of maternal protein restriction on kidney development have not been examined in mice. Therefore, we determined how combined prenatal and postnatal protein restriction in mice affects organ weight, glomerular number and dimensions, and renal expression of angiotensin receptor mRNA, in both male and female offspring. C57/BL6/129sv mice received either a normal (20% wt/wt; NP) or low (9% wt/wt; LP) protein diet during gestation and postnatal life. Offspring were examined at postnatal day 30. Protein restriction retarded growth of the kidney, liver, spleen, heart, and brain. All organs except the brain weighed less in female than male offspring. Protein restriction increased normalized (to body weight) brain weight, with females having relatively heavier brains than males. The effects of protein restriction were not sex dependent, except that normalized liver weight was reduced in males but increased in females. Glomerular volume, but not number, was greater in female than in male mice. Maternal protein restriction reduced nephron endowment similarly in male and female mice. Renal expression of AT(1A) receptor mRNA was approximately sixfold greater in female than male NP mice, but similar in male LP and female LP mice. We conclude that maternal protein restriction reduces nephron endowment in mice. This effect provides a basis for future studies of developmental programming in the mouse.     

Effects of feeding endophyte-infected tall fescue seed on the reproductive performance in male and female CD-1 mice by combination crosses

The present study was undertaken to assess the effects of endophyte-infected Acremonium coenophialum tall fescue (KY 31) seed (80% infected) on the reproductive performance of male and female CD-1 mice by combination crosses. Forty-eight male and 48 female 30-d-old mice were randomly allocated to two diet treatments. Twenty-four males and 24 females were fed Diet 1, consisting of 50% non-infected fescue and 50% mouse chow; the remaining animals were fed Diet 2, containing 50% infected fescue. At the end of 50 d, the animals were paired in groups (n = 12) as follows: 1) Diet 1 males and females; 2) Diet 2 males and Diet 1 females; 3) Diet 1 males and Diet 2 females; and 4) Diet 2 males and females. The pairs were maintained on the diets of their female partners and were allowed to cohabitate for 96 h. After this period the males were removed and the females were carried to term. Pregnancy rates among the four treatment groups were 100, 83.3, 75.0 and 54.5%, respectively. Similarly, the average number of pups born per litter among the four groups were 11.5, 8.0, 9.7, and 7.5, respectively. Also, the weights (grams) of pups born per litter were 17.5, 12.6, 12.4, and 9.8, respectively. The results point out that the reproductive capacity of both male and female mice are affected (P < 0.05) by the ingestion of endophyte-infected fescue seeds. Such negative effects were more severe in the female than the male (P < 0.05).     

Effects of p-nonylphenol and resveratrol on body and organ weight and in vivo fertility of outbred CD-1 mice

The aim of this study was to analyse the multigenerational effects of para-nonylphenol (NP) and resveratrol (RES) on the body weight, organ weight and reproductive fitness of outbred CD-1 mice. The data indicate that in male mice, NP had an effect on the weight of selected reproductive organs and the kidneys in the parental (P) generation males. Effects on selected reproductive organs, the liver and kidneys in the F1-generation males were also seen. In females, effects of NP on body weight and kidney weight were seen in the P generation, but no effects on any measured parameter were seen in the F1 generation. RES had no effect on body weight but did have some effect on selected male and female reproductive organs in the P generation. RES altered the spleen and liver weights of P-generation males and the kidney weight of F1-generation males. Acrosomal integrity (using a monoclonal antibody against intra-acrosomal sperm proteins) was assessed for both generations of NP- and RES-treated mice. A significant reduction in acrosomal integrity was seen in both generations of NP-treated, but not in RES-treated, mice. Fewer offspring were observed in the second litter of the F2 generation of mice treated with NP; no similar effect was seen in RES-treated mice. The litter sex ratio was not different from controls. Unlike RES, NP had a negative effect on spermatogenesis and sperm quality with a resultant impact on in vivo fertility.     

Mice with deletion of the mitochondrial glycerol-3-phosphate dehydrogenase gene exhibit a thrifty phenotype: effect of gender

To define the role of mitochondrial glycerol-3-phosphate dehydrogenase (mGPD; EC 1.1.99.5) in energy balance and intermediary metabolism, we studied transgenic mice not expressing mGPD (mGPD-/-). These mice had approximately 14% lower blood glucose; approximately 50% higher serum glycerol; approximately 80% higher serum triglycerides; and at thermoneutrality, their energy expenditure (Qo(2)) was 15% lower than in wild-type (WT) mice. Glycerol-3-phosphate levels and lactate-to-pyruvate ratios were threefold elevated in muscle, but not in liver, of mGPD-/- mice. WT and mGPD-/- mice were then challenged with a high-fat diet, fasting, or food restriction. The high-fat diet caused more weight gain and adiposity in mGPD-/- than in WT female mice, without the genotype differentially affecting Qo(2) or energy intake. After a 30-h fast, WT female lost 60% more weight than mGPD-/- mice but these latter became more hypothermic. When energy intake was restricted to 50-70% of the ad libitum intake for 10 days, mGPD-/- female mice lost less weight than WT controls, but they had lower Qo(2) and body temperature. WT and mGPD-/- male mice did not differ significantly in their responses to these challenges. These results show that the lack of mGPD causes significant alterations of intermediary metabolism, which are more pronounced in muscle than liver and lead to a thrifty phenotype that is more marked in females than males. Lower T(4)-to-T(3) conversion in mGPD-/- females and a greater reliance of normal females on mGPD to respond to high-fat diets make the lack of the enzyme more consequential in the female gender.     

Effects of dietary genistein on mouse reproduction, postnatal development and weight-regulation

Genistein is a soy isoflavone with estrogenic activity present in plant-based food items and health foods and used as an alternative therapy for cancer, cardiovascular diseases, menopausal symptoms and osteoporosis. The aim of this study was to investigate the effects of dietary genistein (8 mg/kg body weight/day) on the reproduction, postnatal development and weight regulation of mice across two generations. Genistein treatment decreased the relative food consumption in females at 1 and 5 weeks and in males at 5 weeks. In female pups, the relative kidney weights were lower due to genistein exposure. Furthermore, the genistein-exposed male pups had greater relative prostate and seminal vesicles weights than the control pups. In adult males, genistein treatment decreased the plasma estradiol concentrations and increased levels of the plasma HDL cholesterol and triglycerides in adult females. Also the plasma ghrelin concentrations decreased in the adult genistein treated female mice. Genistein increased the plasma triglyceride levels of male pups and triiodothyronine levels of female pups. Reproduction of the mice was not endangered due to genistein exposure.     

Onset of puberty in CD-1 mouse pups exposed prenatally through weaning to endophyte-infected tall fescue seed

This study was undertaken to investigate the effects of feeding endophyte - infected (Acremonium coenophialum ) tall fescue seed to CD-1 mouse dams (P(1)) during gestation and lactation, and on the subsequent growth and sexual maturity (onset of puberty) of their male and female offspring (F(1)). Forty-eight 21 d old pups (24 male and 24 female F(1) mice) were weaned from dams fed one of two diets containing 50% rodent chow (w/w) and 50% KY-31 tall fescue (Festuca arundinacea ) seed. The seed in Diet 1 was noninfected, while the seed in Diet 2 was 80% endophyte-infected. At weaning (21 d), the F(1) pups were fed rodent chow, ad libitum throughout the remaining experimental period. At 24 d, they were paired with sexually mature non-treated virgin CD-1 mice (fed 100% rodent chow) for one parturition cycle. Male F(1) mice were sacrificed at 84 d to determine testicular development. The age at the birth of the first litter for Diet 2 F(1) male (76.8 +/- 2.2 d) and female (58.4 +/- 2.1 d) was significantly greater (P<0.05) than the age at parturition for Diet 1 male and female F(1) test mice (64.1 +/- 1.8 and 51.9 +/- 1.2 d, respectively). At parturition, the female F(1) mice showed no significant differences (P>0.05) in either mean parturition weight or number of F(2) pups born per litter. However, total F(2) litter wight (11.38 +/- 1.14 g) and mean weight per F(2) pup (1.40 +/- 0.04 g) for Diet 2 female F(1) mice litters were lower (P<0.05) when compared with Diet 1 females (14.53 +/- 0.57 g and 1.66 +/- 0.02 g, respectively). No significant differences were observed between the two male F(1) treatment groups, for total F(2) litter weight or the number of pups born per F(2) litter. Although Diet 2 F(1) males weighed significantly less (P<0.05) at weaning and at pairing, final body weights at sacrifice (84 d) were not different (P>0.05) from the Diet 1 males.     

Vitamin E and fatty acids in the grey seal (Halichoerus grypus)

Summary Vitamin E levels in serum, liver and blubber (subcutaneous adipose tissue) were determined for 66 male and female grey seals of varying age in the pupping colony on Sable Island in the Northwest Atlantic by high-performance liquid chromatography (HPLC). Fatty acid concentrations were determined for all blubber specimens. Adult males and pups had significantly higher levels of vitamin E and cholesterol in serum than females and juveniles. A close relationship between vitamin E and cholesterol in serum could be observed. Suckling pups had significantly higher levels of vitamin E in liver (191 mg·kg^–1) than juveniles and adults (21–41 mg·kg^–1). Levels of vitamin E in blubber showed an age-dependent increase, with the highest levels being found in adult males; overall, these levels were much lower than in man. Vitamin E levels in blubber and liver of lactating females were only half that of adult males. This might be due to an intensive transfer of vitamin E from mother to pup during lactation, a process which may also explain the much higher levels of vitamin E in serum and liver of nursing pups. The low levels of vitamin E in blubber of seals might be a result of its high percentage of unsaturated fatty acids (79%). Highest percentage was represented by 18:1, 16:1, 22:6 and 16:0. Pups had lower values of monounsaturated, and a higher percentage of saturated fatty acids compared to mothers.     

Regulation by Androgen of Levels of the β Subunit of Nerve Growth Factor and Its mRNA in Selected Regions of the Mouse Brain

Abstract: Our previous studies showed that the concentration of the β subunit of nerve growth factor (β-NGF) in nervous tissues is higher in male than in female mice. To identify the brain regions that are affected by androgens, the amounts of β-NGF protein and its mRNAs were measured in male, female, and castrated male CD-1 mice and testicular feminization mice at 3–4 months of age. Among tissues examined, the hypophysis of males contained the highest average concentration of β-NGF protein. In most regions of the brain, individual levels were more variable in males than in females. However, after the castration, such variations in β-NGF levels disappeared. Average levels of β-NGF protein in males were higher in the cerebellum (eightfold higher), olfactory bulb (12-fold higher), hypothalamus (sixfold higher), and hypophysis (72-fold higher) than thope in corresponding regions of females. No significant differences were observed in levels of β-NGF protein in the hippocampus, cerebral cortex, striatum, septum, and brainstem. The castration of male mice caused a reduction in levels of β-NGF protein in the hypothalamus and hypophysis, but not in the cerebellum and olfactory bulb, to the femgle levels. The concentrations of β-NGF protein in testicular feminization mice were similar to those in female CD-1 mice in all regions. The concentrations of mRNA for β-NGF in the olfactory bulb and hypophysis from males were higher than those from females. By contrast, northern blots showed no remarkable differences in the amounts of brain-derived neurotrophic factor and neurotrophin-3 between the two sexes. Thus, in some regions of the brain, the production of β-NGF appears to be regulated by testosterone, but the regulatory mechanisms do not appear to be simple. Our present results indicate that the binding of testosterone to its receptor is an important step in the regulation of the level of β-NGF in these region.     

Prolonged melatonin administration in 6-month-old Sprague-Dawley rats: metabolic alterations

The aim of this work was to evaluate the effect of prolonged melatonin administration on chosen metabolic and hormonal variables in male and female Sprague-Dawley rats. Melatonin was administered in tap water (4 microg/ml) daily from the 6th month of age. Rats were fed a standard type of diet ad libitum and were kept in a light regimen L:D--12:12h. The experiment was terminated after 12 weeks of melatonin administration. Melatonin decreased body mass during the whole experiment in females and from the 42nd day of the experiment in males. Relative heart muscle weight in females and absolute/relative thymus weight in males were increased after melatonin administration. Melatonin decreased glycaemia, heart muscle glycogen concentration in females and liver glycogen concentration in both sexes. Serum insulin concentration in males was decreased; serum corticosterone concentration was increased in both males and females. Serum triacylglycerol and heart muscle cholesterol concentration in females were decreased, however in males serum and heart muscle cholesterol concentration was increased. Liver phospholipid concentration in females was decreased and heart muscle phospholipid concentration in males was increased. Melatonin increased malondialdehyde concentration in heart muscle in males and in liver in both sexes. Melatonin induced prominent sex-dependent changes in both carbohydrate and lipid metabolism.     

Gender-dependent differences in serum profiles of insulin and leptin in caloric restricted rats

In the present study, we have investigated whether differences between male and female rats described in response to 40% caloric restriction (CR) were influenced by circulating level variations of sex hormones and/or insulin and leptin. Body weights (BW), organ weights, and adipose depot weights (ADW) were also measured. The most affected tissues by CR were the fat depots. Metabolically active organs were the least affected, especially more in females than in males (male weight lost: 24.3% vs. female: 17.3%). Testosterone and estradiol circulating levels did not show changes by CR. Insulin levels were decreased by CR in both genders, but was more evident in female rats than males. Leptin serum levels were higher in male rats than in females, and CR caused a circulating leptin level reduction only in males. In conclusion, our results indicate that leptin and insulin could be one of the keys of the different hormonal control of energy homeostasis in response to CR between female and male rats. In this sense, leptin serum levels correlated statistically with BW and with individual ADW only in male rats, whereas insulin serum levels correlated statistically with BW and with any of the ADW studied only in females.     

Effects of feeding endophyte-infected tall fescue seed on reproductive performance in male CD-1 mice by competitive breeding

The objective of this study was to assess the effects of endophyte-infected tall fescue (KY-31) seed (80% infected, containing Acremonium coenophialum ) on the reproductive performance of male CD-1 mice measured by competitive breeding. Sixteen mature CD-1 male mice were randomly allocated to one of two dietary treatments containing 50% mouse chow and either 1) 50% noninfected tall fescue seed, restricted to the daily feed intake of dietary treatment 2, or 2) 50% infected tall fescue seed (w/w) fed ad libitum. Mice were preconditioned on their respective diets for 50 d prior to 96 h of cohabitation with 10 mature CD-1 females. Following removal of males, the females were carried to full term. Males were sacrificed, and testicular, epididymal weights, sperm motility and progressive sperm motility were assessed. The results showed no differences (P>0.05) in average daily weight gain (ADG) and body weight changes during the course of the experiment between the two dietary treatments. There were significant reductions (P<0.05) in total testes weight (0.238 vs 0.214 g), epididymal weight (0.087 vs 0.073 g), sperm motility (82.5 vs 58.7%), and progressive motility (3.7 vs 2.6; scale 0 to 4) between dietary treatments 1 and 2, respectively. Similarly, significant differences in pregnancy rates were 53.8 and 45.0%, and the average numbers of pups born per litter were 10.67 and 9.84, respectively. These data suggest that 50% endophyte-infected fescue seed in the diet of male CD-1 mice can affect their reproductive capacity by influencing the testicular-epididymal weights, and subsequently, the quality of spermatozoa and overall fecundity.     

Circulating isoflavonoid levels in CD-1 mice: effect of oral versus subcutaneous delivery and frequency of administration

The CD-1 mouse is a commonly used animal model to understand the biological effects of early-life exposure to soy isoflavones in infants. Most studies using CD-1 mice have administered isoflavones by daily subcutaneous injection, while infants receive oral feeds every few hours. The study objectives were to compare the total serum levels of genistein (GEN), daidzein (DAI) and the DAI metabolites equol and O-desmethyl-angolensin (O-DMA), after subcutaneous injection and oral dosing and to determine if frequency of oral administration results in different circulating levels of isoflavones using the CD-1 mouse model. From postnatal days 1 to 5, pups randomly received corn oil or soy isoflavones (total daily dose, 0.010 mg DAI+0.025 mg GEN) by subcutaneous injection once a day, orally once a day or orally every 4 hours. On postnatal day 5, 1 h posttreatment, mice were killed and serum was collected. Mice treated with soy isoflavones had higher (P<.05) serum GEN (female: 1895–3391 ng/ml and male: 483–578 ng/ml) and DAI (female: 850–1580 ng/ml and male: 248–322 ng/ml) concentrations versus control (5–20 ng/ml) mice, regardless of route or frequency of administration, and were similar among dosing strategies. Total serum concentrations of GEN and DAI were higher (P<.05) among females (GEN: 2714 ± 393 ng/ml and DAI: 1205 ± 164 ng/ml) than males (GEN: 521 ± 439 ng/ml and DAI: 288 ± 184 ng/ml) across treatment groups. Serum equol and O-DMA concentrations were negligible (<3 ng/ml) across groups. In conclusion, different routes of delivery and frequency of administration resulted in similar total serum levels of GEN, DAI¸ equol or O-DMA.     

Gender-divergent profile of bile acid homeostasis during aging of mice

Aging is a physiological process with a progressive decline of adaptation and functional capacity of the body. Bile acids (BAs) have been recognized as signaling molecules regulating the homeostasis of glucose, lipid, and energy. The current study characterizes the age-related changes of individual BA concentrations by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) in serum and liver of male and female C57BL/6 mice from 3 to 27 months of age. Total BA concentrations in serum increased 340% from 3 to 27 months in female mice, whereas they remained relatively constant with age in male mice. During aging, male and female mice shared the following changes: (1) BA concentrations in liver remained relatively constant; (2) the proportions of beta-muricholic acid (βMCA) increased and deoxycholic acid (DCA) decreased between 3 and 27 months in serum and liver; and (3) total BAs in serum and liver became more hydrophilic between 3 and 27 months. In female mice, (1) the mRNAs of hepatic BA uptake transporters, the Na(+)/taurocholate cotransporting polypeptide (Ntcp) and the organic anion transporting polypeptide 1b2 (Oatp1b2), decreased after 12 months, and similar trends were observed for their proteins; (2) the mRNA of the rate-limiting enzyme for BA synthesis, cholesterol 7α-hydroxylase (Cyp7a1), increased from 3 to 9 months and remained high thereafter. However, in male mice, Ntcp, Oatp1b2, and Cyp7a1 mRNAs remained relatively constant with age. In summary, the current study shows gender-divergent profiles of BA concentrations and composition in serum and liver of mice during aging, which is likely due to the gender-divergent expression of BA transporters Ntcp and Oatp1b2 as well as the synthetic enzyme Cyp7a1.     

Alternate pathways of bile acid synthesis in the cholesterol 7alpha-hydroxylase knockout mouse are not upregulated by either cholesterol or cholestyramine feeding

Bile acids are synthesized via the classic pathway initiated by cholesterol 7alpha-hydroxylase (CYP7A1), and via alternate pathways, one of which is initiated by sterol 27-hydroxylase (CYP27). These studies used mice lacking cholesterol 7alpha-hydroxylase (Cyp7a1(-/-)) to establish whether the loss of the classic pathway affected cholesterol homeostasis differently in males and females, and to determine if the rate of bile acid synthesis via alternate pathways was responsive to changes in the enterohepatic flux of cholesterol and bile acids. In both the Cyp7a1(-/-) males and females, the basal rate of bile acid synthesis was only half of that in matching Cyp7a1(+/+) animals. Although bile acid pool size contracted markedly in all the Cyp7a1(-/-) mice, the female Cyp7a1(-/-) mice maintained a larger, more cholic acid-rich pool than their male counterparts. Intestinal cholesterol absorption in the Cyp7a1(-/-) males fell from 46% to 3%, and in the matching females from 58% to 17%. Bile acid synthesis in Cyp7a1(+/+) males and females was increased 2-fold by cholesterol feeding, and 4-fold by cholestyramine treatment, but was not changed in matching Cyp7a1(-/-) mice by either of these manipulations. In the Cyp7a1(-/-) mice fed cholesterol, hepatic cholesterol concentrations increased only marginally in the males, but rose almost 3-fold in the females. CYP7A1 activity and mRNA levels were greater in females than in males, and were increased by cholesterol feeding in both sexes. CYP27 activity and mRNA levels did not vary as a function of CYP7A1 genotype, gender, or dietary cholesterol intake. We conclude that in the mouse the rate of bile acid synthesis via alternative pathways is unresponsive to changes in the enterohepatic flux of cholesterol and bile acid, and that factors governing gender-related differences in bile acid synthesis, pool size, and pool composition play an important role in determining the impact of CYP7A1 deficiency on cholesterol homeostasis in this species.     

Thiazide-induced hypercholesterolemia: sex differences

Thiazide diuretics are used commonly to treat hypertension. Unfortunately, they also are known to elevate serum cholesterol levels. Because serum lipid fraction levels differ between the sexes, possible sex-related differences in thiazide-induced changes in serum total cholesterol (TC), triglycerides (TG) and high density lipoprotein cholesterol (HDL-C) levels were examined. Four groups of male and female hamsters were treated for a minimum of 3 months with hydrochlorothiazide (HCTZ) at zero, 1, 2 or 4 mg/kg/day. At zero dose, there was no difference in TG levels between the sexes; however, females had significantly higher TG concentrations than did males at 1, 2 and 4 mg HCTZ (all p less than 0.05). Females demonstrate a significant dose response with HCL-C levels increasing with increasing doses of HCTZ, (r = 0.983; p less than 0.02); in contrast males had a similar increase in HDL-C at all dose levels (all p less than 0.05) thus there was no demonstrable dose response (r = 0.539). Total cholesterol concentrations were significantly higher in the females than in males (p less than 0.05) at all 3 dose levels as well as at zero dose. Further, the females demonstrated a direct dose response in TC levels (r = 0.986; p less than 0.02) while the males showed no such dose response (r = 0.824; p less than 0.01). Based on these findings we conclude that: 1) HCTZ increases TG, TC and HDL-C levels in both male and female hamsters; 2) TC levels are higher in females than in males regardless of HCTZ dose; 3) only females show a dose-dependent increase in HCL-C and TC in response to HCTZ. These sex-related changes in lipid fractions occurring with HCTZ treatment, if they occur in humans, may contribute to sex-related differences in rates and severity of atherosclerosis in HCTZ-treated populations.