Sparse and wavy hair: a new model for hypoplasia of hair follicle and mammary glands on rat chromosome 17

Mutant animals in the skin and hair have been used to identify important genes in biomedical research. We describe a new mutant rat, sparse and wavy hair (swh), that spontaneously arose in a colony of inbred WTC rats. The mutant phenotype was characterized by sparse and wavy hair, which was most prominent at age 3-4 weeks, and was inherited in an autosomal recessive manner. The swh/swh rats showed impaired gain of body weight, and their hair follicles were reduced both in number and size, associated with hypoplasia of the sebaceous glands and the subcutaneous fat tissue. Female swh/swh rats were unable to suckle their offspring. Their mammary glands were hypoplastic, and differentiation of mammary epithelial and myoepithelial cells was impaired. Linkage analysis of 579 backcross rats localized the swh locus to a .35-cM region between D17Rat131 and D17Rat50 in the distal end of rat Chr 17. The swh locus spanned the 3.7-Mb genomic region where 24 genes have been mapped and corresponded to the centromere region of the mouse Chr 2 or the region of the human Chr 10p11.1-p14. None of the genes or loci described in mouse or human hair and skin diseases mapped to these regions. These findings suggest that the rat swh is a novel mutation associated with impaired development of the skin appendages, such as hair follicles, sebaceous glands, and mammary glands, and will provide an experimental model to clarify a gene and mechanisms for development of skin appendages.     

Reduction of enhanced mammary carcinogenesis in LA/N-cp (corpulent) rats by energy restriction

Restriction of energy intake significantly reduces mammary tumorigenesis in normal rats exposed to carcinogens. Genetically obese LA/N-cp (corpulent) female rats were given 7,12-dimethylbenz[a]anthracene and fed purified diets ad libitum or restricted to 60% of the ad libitum caloric intake. Phenotypically lean littermates were also fed ad libitum. Obese animals developed large mammary tumors more rapidly than genetically normal rats so that 100% of the animals had tumors in less than 16 weeks. Only 21% of the lean animals developed tumors; the energy restricted obese animals had a tumor incidence of 27%. Although obese rats fed the restricted diet weighed significantly less than those fed ad libitum, percent body fat was not reduced, indicating that lean tissue was affected more. Obese animals were markedly hyperinsulinemic (1003 +/- 193 microunits/ml) and energy restriction reduced this to 328 +/- 41; the lean animals had insulin levels of 12 +/- 2. Tumor-bearing rats had higher insulin levels than rats without tumors. These data suggest that body fatness is not directly associated with risk of carcinogenesis. Lean body mass, adipose tissue mass, and their interaction with insulin in its capacity as a growth factor rather than body fatness per se may be determinants of tumor promotion.     

Lack of promotion of mammary, lung and skin tumorigenesis by 20 kHz triangular magnetic fields

In order to evaluate possible tumorigenic effects of a 20 kHz intermediate frequency triangular magnetic field (IF), a frequency emitted from TV and PC monitors at 6.25 microT rms, which is the regulated exposure limit of magnetic field for the public in Korea, mammary tumors were produced in female Sprague-Dawley rats by oral intubation of dimethylbenz(a)anthracene (DMBA), lung tumors in ICR mice by scapular region injection of benzo(a)pyrene (BP), and skin tumors in female ICR mice by topical application of DMBA and tetradecanoylphorbol ester (TPA). IF was applied 8 h/day for 14 weeks beginning the day after DMBA treatment for mammary tumor experiment, for 6 weeks after weaning for lung tumor, and for 20 weeks beginning 1 week after DMBA application for skin tumor experiment. For skin tumors, TPA was applied once a week for 19 weeks. Results showed no significant differences in tumor incidence, mean tumor number and volume, and histological patterns between IF magnetic-field exposed and sham control rats in the above three tumor models. Therefore, we conclude that within the limitation or number of animals and the experimental conditions, 20 kHz IF triangular magnetic field exposure of 6.25 microT does not appear to be a strong co-tumorigenic agent in the chosen murine mammary, lung and skin models.     

Age-related changes of Renin-Angiotensin system genes in white adipose tissue of rats.

The adipose tissue renin-angiotensin system has been implicated in the regulation of adipocyte growth and differentiation. We studied the influence of age, body weight, total body fat content, anatomical localization, and diet on the expression of angiotensinogen (AGT) and angiotensin II type 1 (AT 1 )-receptor genes in white adipose tissue of normal and postnatal overfed rats. Relative gene expression was measured in epididymal adipose tissue and liver of control and postnatal overfed (PNO) rats at the age of 4, 8, and 12 weeks using real time RT-PCR. Body fat content was determined by carcass analysis. Body weight and body fat content were only significantly greater in PNO rats when compared to control rats at the age of 4 weeks. At the age of 12 weeks, AGT expression was significantly decreased in both tissues. Furthermore, expression of the AT 1 -receptor gene was significantly decreased in liver but not in adipose tissue at 12 weeks of age. Postnatal overfeeding did not influence the expression levels of either gene at any time-point in either liver or adipose tissue. At the age of 24 weeks, AGT expression was significantly greater in epididymal than in subcutaneous adipose tissue, whereas no site-specific differences could be found for the AT 1 -receptor. We conclude that age and depot-specific mechanisms are of more importance for the expression of AGT and AT 1 -receptor genes during the first 12 weeks of age than a short period of overfeeding.     

Development of the Mouse Dermal Adipose Layer Occurs Independently of Subcutaneous Adipose Tissue and Is Marked by Restricted Early Expression of FABP4

The laboratory mouse is a key animal model for studies of adipose biology, metabolism and disease, yet the developmental changes that occur in tissues and cells that become the adipose layer in mouse skin have received little attention. Moreover, the terminology around this adipose body is often confusing, as frequently no distinction is made between adipose tissue within the skin, and so called subcutaneous fat. Here adipocyte development in mouse dorsal skin was investigated from before birth to the end of the first hair follicle growth cycle. Using Oil Red O staining, immunohistochemistry, quantitative RT-PCR and TUNEL staining we confirmed previous observations of a close spatio-temporal link between hair follicle development and the process of adipogenesis. However, unlike previous studies, we observed that the skin adipose layer was created from cells within the lower dermis. By day 16 of embryonic development (e16) the lower dermis was demarcated from the upper dermal layer, and commitment to adipogenesis in the lower dermis was signalled by expression of FABP4, a marker of adipocyte differentiation. In mature mice the skin adipose layer is separated from underlying subcutaneous adipose tissue by the panniculus carnosus. We observed that the skin adipose tissue did not combine or intermix with subcutaneous adipose tissue at any developmental time point. By transplanting skin isolated from e14.5 mice (prior to the start of adipogenesis), under the kidney capsule of adult mice, we showed that skin adipose tissue develops independently and without influence from subcutaneous depots. This study has reinforced the developmental link between hair follicles and skin adipocyte biology. We argue that because skin adipocytes develop from cells within the dermis and independently from subcutaneous adipose tissue, that it is accurately termed dermal adipose tissue and that, in laboratory mice at least, it represents a separate adipose depot.     

Tumour necrosis factor alpha (cachectin) mimics some of the effects of tumour growth on the disposal of a [14C]lipid load in virgin, lactating and litter-removed rats.

Tumour necrosis factor alpha (cachectin) was administered to virgin, lactating and litter-removed rats, and subsequent disposal of an oral [1-14C]triolein (glycerol tri[1-14C]oleate) load examined. Absorption of the lipid and 14CO2 production were significantly depressed in all three groups. [14C]Lipid accumulation was decreased in carcass, liver and adipose tissue (brown and white) of virgin and litter-removed rats and the mammary gland of lactating rats. The plasma triacylglycerol concentration was increased in all three groups, and lipoprotein lipase activity was decreased in the white adipose tissue of virgin and litter-removed animals and in the mammary gland of lactating animals. Some, but not all, of these effects mimic tumour burden in the same physiological states [Evans & Williamson (1988) Biochem. J. 252, 65-72].     

The utilization of ketone bodies by the interscapular brown adipose tissue of the rat

The activities of 3-oxo acid-CoA transferase (EC 2.8.3.5, 13-15 micromol/min per g) and acetoacetyl-CoA thiolase (EC 2.3.1.9, 18-21 micromol/min per g) in interscapular brown adipose tissue of the rat are comparable to the activities reported for heart and kidney. The incorporation of D-3-hydroxy[3-14C]butyrate into lipid in vivo was about 30-fold higher in interscapular brown adipose tissue than in white adipose tissue of virgin rats. In lactating rats, the mammary gland was the major site of ketone body incorporation into lipid and incorporation of D-3-hydroxy-[3-14C]butyrate into lipid in brown adipose tissue was lower than in virgin rats. After an oral load of medium chain triacylglycerol, which inhibits lipogenesis in lactating mammary gland, the incorporation of ketone bodies into lipid was decreased in mammary gland but increased in brown adipose tissue. The rate of oxidation of D-3-hydroxy[3-14C]butyrate by brown adipose tissue slices in vitro was higher than the rate of incorporation into lipid.     

Adipose tissue deficiency and chronic inflammation in diabetic Goto-Kakizaki rats

Type 2 diabetes (T2DM) is a heterogeneous group of diseases that is progressive and involves multiple tissues. Goto-Kakizaki (GK) rats are a polygenic model with elevated blood glucose, peripheral insulin resistance, a non-obese phenotype, and exhibit many degenerative changes observed in human T2DM. As part of a systems analysis of disease progression in this animal model, this study characterized the contribution of adipose tissue to pathophysiology of the disease. We sacrificed subgroups of GK rats and appropriate controls at 4, 8, 12, 16 and 20 weeks of age and carried out a gene array analysis of white adipose tissue. We expanded our physiological analysis of the animals that accompanied our initial gene array study on the livers from these animals. The expanded analysis included adipose tissue weights, HbA1c, additional hormonal profiles, lipid profiles, differential blood cell counts, and food consumption. HbA1c progressively increased in the GK animals. Altered corticosterone, leptin, and adiponectin profiles were also documented in GK animals. Gene array analysis identified 412 genes that were differentially expressed in adipose tissue of GKs relative to controls. The GK animals exhibited an age-specific failure to accumulate body fat despite their relatively higher calorie consumption which was well supported by the altered expression of genes involved in adipogenesis and lipogenesis in the white adipose tissue of these animals, including Fasn, Acly, Kklf9, and Stat3. Systemic inflammation was reflected by chronically elevated white blood cell counts. Furthermore, chronic inflammation in adipose tissue was evident from the differential expression of genes involved in inflammatory responses and activation of natural immunity, including two interferon regulated genes, Ifit and Iipg, as well as MHC class II genes. This study demonstrates an age specific failure to accumulate adipose tissue in the GK rat and the presence of chronic inflammation in adipose tissue from these animals.     

Fatty acid synthesis in vitro in the liver and adipose tissue of rats of various ages.

In white male Wistar rats aged 2, 4, 6, 9, 12, 18 and 32 months, receiving a standard laboratory diet (25 cal% proteins, 22 cal% fat and 53 cal% glycides) we assessed the total amount of fatty acids in the carcass and in vitro lipogenesis in liver and adipose tissue by the means of glucose-14C(U). The amount of body fat increased with age; the highest rate of increase in the percentage of body fat occurs 2 to 4 months after birth. Incorporation of 14C of glucose into total liver lipids attains maximum values in the group of rats age 2 to 4 months. By the age of 6 months lipogenesis decreased to a level observed in all the remaining age groups. In adipose tissue, the incorporation of 14C into total lipids decreased between the age of 2 to 4 months, a further decrease was observed around the age of 6 months. No appreciable changes were noted in any of the older age groups.     

The influence of energy restriction and developmental state on DNA 5-methyldeoxycytidine in rat mammary and liver tissues

Female rats were fed either ad libitum or 30% energy-restricted diets from 5 weeks through 25 weeks of age. Genomic DNA was extracted from mammary tissue and liver at 7, 9, 14 (mid-pregnancy), 16.5 (mid-lactation), and 25 weeks of age. The 5-methyldeoxycytidine content of DNA was determined by high pressure liquid chromatography. As animals aged from 7–25 weeks, 5-methyldeoxycytidine increased in mammary tissue, whereas in liver it decreased. This suggests that 5-methyldeoxycytidine exhibits tissue specific patterns. No changes in 5-methyldeoxycytidine content due to 30% energy restriction were observed in either mammary tissue or liver.     

Resistance to Aging-Associated Obesity in Capsaicin-Desensitized Rats One Year after Treatment

Previous studies demonstrated reduced weight of abdominal white adipose tissue depots and of carcass fat in capsaicin-desensitized (Cap-Des) rats up to 8 months after treatment. The objective of the present study was to find out whether aging-associated obesity and hyperplasia of retroperitoneal white adipose tissue was prevented in older (13.5 month old) Cap-Des rats, one year after treatment with Cap (done when they were 1.5 months old). The prevalence of obesity is known to increase in rats by this age. Abdominal white adipose tissue depots weighed less in old Cap-Des rats, both epididymal (9% less) and retroperitoneal (30% less). The number of mature white adipocytes was 28% less in the retroperitoneal depot but was not significantly different in the epididymal depot. Adipocyte size was not different. Carcass fat was less, both total and as percent of body weight. Food intake was normal for their reduced body size. The exponential increase in retroperitoneal white adipose tissue weight characteristic of aging rats that are becoming obese was virtually absent in Cap-Des rats. We conclude that lack of function of capsaicin-sensitive afferent autonomic nerves, known to be destroyed in Cap-Des rats, results in an alteration in energy balance conducive to leanness. We suggest that the attenuated age-associated increase in circulating CGRP (derived mainly from capsaicin-sensitive nerves) in the Cap-Des rat results in a lower degree of aging-associated insulin-resistance, hence in a lesser degree of obesity.     

Lipoprotein lipase activity in white adipose tissue of rats subjected to exercise--rest cycles

This study was conducted to determine serum lipid levels and the activity of lipoprotein lipase in epididymal white adipose tissue of rats undergoing exercise training. During the 8-week period of treatment, one group of rats was kept sedentary and the remaining animals were exercise trained either continually (1 h of daily treadmill running) or intermittently (alternate weeks of daily running and inactivity). Exercise training, either continual or intermittent, decreased postprandial serum total and high-density lipoprotein cholesterol concentrations, which returned to sedentary levels in the intermittently trained animals following a week of rest. Lipoprotein lipase activity in whole epididymal adipose pad was lower in rats trained continually than in the sedentary group at the end of the treatment. The intermittent training program elicited large fluctuations in both the specific (per milligram of protein) and total (per tissue) activity of lipoprotein lipase in white adipose tissue. During rest periods, enzyme activity rose to levels that were higher than those of sedentary rats, whereas lipase activity was below that of sedentary animals following a week of running. In the last exercise--rest cycle, body weight gain of the intermittently trained rats was nearly abolished during the week of running, but it increased above that of sedentary animals during weeks of rest. The present results suggest that the modulation of lipoprotein lipase activity in white adipose tissue is one of the adaptations that take place to accommodate the fluctuations in the rate of energy deposition that occur in the rat during an intermittent training program.     

The effect of adlay oil on plasma lipids, insulin and leptin in rat.

This study was designed to investigate the effect of dietary adlay oil on plasma lipids, insulin and lipid peroxidation levels in rats. Twenty-four male Wistar rats fed diet containing adlay oil and cholesterol were studied for 4 weeks. The animals were divided into three groups: (1) 10% lard (control) group; (2) 5% lard + 5% adlay oil (5% adlay oil) group; and (3) 10% adlay oil group. Although there was no significant difference in body weight at the end of the feeding study, rats fed a diet containing adlay oil showed a significant decrease in adipose tissue weight and relative adipose weight. In addition, the rats fed the adlay oil showed significantly decreased low-density lipoprotein cholesterol (LDL-C), insulin, leptin and thiobarbituric acid reactive substance (TBARS) concentrations after 4 weeks of the feeding study. Although a significant decrease in total plasma cholesterol was observed in rats fed the 5% adlay oil diet, no significant difference was observed between the 10% adlay oil and control groups, and neither was a significant difference in liver TBARS concentration found between the dietary groups. Results from this study suggest that dietary adlay oil can reduce leptin, adipose tissue and LDL-C levels in rats.     

Quantitative gas-liquid chromatographic analysis of rodent milk triglycerides

A comparison has been made of the milk and adipose tissue triglycerides of rabbits and guinea pigs provided with one diet and of rats and mice provided with another. Both intact triglycerides and component fatty acids were analyzed by gas-liquid chromatography. Good correlation of the data obtained by the two techniques was obtained by calculating the average chain length of the fatty acid moieties. Little difference was found in the triglyceride composition of the adipose tissue of the different species. However, wide variation in the triglyceride composition of the milk was found between the species: the average fatty acid chain length in milk was 11.7 for rabbits, 14.2 for rats, 15.3 for mice, and 17.2 for guinea pigs. The corresponding values for adipose tissue were in the range 16.9-17.4 in all animals. The significance of enzymes that synthesize short-chain fatty acids in mammary gland is discussed.     

Lipoprotein lipase and lipogenic enzyme activities in adipose tissue from rats fed different lipid sources

This work was designed to study the effect of different lipid sources on the activities of lipoprotein lipase and lipogenic enzymes in adipose tissue from rats fedad libitum or energy-controlled diets. Male Wistar rats were fed diets containing 40% of energy as fat (olive oil, sunflower oil, palm oil or beef tallow), for 4 wk. Underad libitum feeding no differences were found among dietary fat groups in final body weight, adipose tissue weights and total body fat. Under energy-controlled feeding, despite isoenergetic intake, rats fed the beef tallow diet gained significantly less weight than rats fed the other three diets. Beef tallow fed rats showed the lowest values for adipose tissue weights and total body fat. When rats had free access to food no effect of dietary lipid source on lipogenic enzyme activities was found. In contrast, under energy-controlled feeding rats fed the beef tallow diet showed significantly higher activities of glucose-6-phosphate dehydrogenase and fatty acid synthase than rats fed the other three diets. Heparin-releasable lipoprotein lipase activity in perirenal and subcutaneous adipose tissues was not different among rats fed olive oil, safflower oil, palm oil or beef tallow. When comparing both adipose tissue anatomical locations, significantly higher activities were found in subcutaneous than in perirenal fat pad independently of dietary fat. In conclusion, under our experimental protocol, lipogenesis in rat adipose tissue does not seem to be affected by dietary fat type.     

Impaired hormonal regulation of lipolysis and the interference with adenosine in adipose tissue from hyperglycemic sand rats in vitro

Sand rats (Psammomys obesus) developed in response to different food intake various states of hyperglycemia and hyperinsulinism. 12 normo- and 10 hyperglycemic animals were selected by means of a weekly control of plasma glucose and plasma insulin over a period of 12 weeks after separation from the mother. During this time also the development of body weight gain was checked. In both groups of rats the hormonal regulation of glycerol release by incubated adipose tissue was investigated. In any case, the fat tissue from hyperglycemic sand rats showed a lower lipolytic responsiveness to noradrenaline stimulation than that of their normoglycemic controls. This correlates well with previous results in hyperglycemic sand rats in which the catecholamine-stimulated cAMP production was disturbed (Knospe and K?hler 1981). Degradation of released adenosine by addition of adenosine deaminase significantly enhanced the noradrenaline action on glycerol release in both groups of sand rats. Even though the noradrenaline-stimulated lipolytic activity of adipose tissue from normo- and hyperglycemic animals was enhanced in the presence of adenosine deaminase, the hormone resistance of adipose tissue from hyperglycemic sand rats was nevertheless not abolished. The theophylline-mediated adenosine receptor blockade gave further evidence that particularly endogenous adenosine released during incubation of adipose tissue from sand rats inhibited the noradrenaline action on lipolysis. The antilipolytic action of insulin on glycerol release is negligibly low in normoglycemic as well as hyperglycemic sand rats. The degradation of adenosine by adenosine deaminase failed to improve the insulin action. Adenosine addition completely blocked the stimulating effects of noradrenaline on glycerol release.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enlargement of interscapular brown adipose tissue in growth hormone antagonist transgenic and in growth hormone receptor gene-disrupted dwarf mice

Growth hormone (GH) acts on adipose tissue by accelerating fat expenditure, preventing triglyceride accumulation, and facilitating lipid mobilization. To investigate whether GH is involved in the development and metabolism of interscapular brown adipose tissue (BAT), a site of nonshivering thermogenesis, we employed three lines of transgenic mice. Two of the lines are dwarf due to expression of a GH antagonist (GHA) or disruption of the GH receptor/binding-protein gene. A third mouse line is giant due to overexpression of a bovine GH (bGH) transgene. We have found that the body weights of those animals are proportional to their body lengths at 10 weeks of age. However, GHA dwarf mice tend to catch up with the nontransgenic (NT) littermates in body weight but not in body length at 52 weeks of age. The increase of body mass index (BMI) for GHA mice accelerates rapidly relative to controls as a function of age. We have also observed that BAT in both dwarf mouse lines but not in giant mice is enlarged in contrast to nontransgenic littermates. This enlargement occurs as a function of age. Northern analysis suggests that BAT can be a GH-responsive tissue because GHR/BP mRNAs were found there. Finally, the level of uncoupling protein-1 (UCP1) RNA was found to be higher in dwarf mice and lower in giant animals relative to controls, suggesting that GH-mediated signaling may negatively regulate UCP1 gene expression in BAT.     

Hair embolism in lungs of rat and rabbit caused by intravenous injection

Among 1422 Sprague-Dawley rats treated daily for 28 consecutive days by i.v. injection, 144 animals (10.1%) showed particles of hair in thrombi at the site of injection. 381 rats (26.8%) had pulmonary emboli with fragments of hair and skin in arterial thrombi or in giant cell granulomas. 6 weeks after cessation of treatment lesions were still found in lungs from 5 of 90 rats (5.6%) allowed to recover. After the experimental administration of 0.75 ml/100 g body wt of a hair suspension (3000 hair particles/ml) to rats, there was no influence on phagocytosis whether endogenous or foreign hairs were injected. In 8 of 64 Himalayan rabbits (12.5%) given 28 injections each into ear veins pulmonary embolism was observed.     

Total nitrogen and L-hydroxyproline content of adipose tissue from various sites in rats of different ages

The total nitrogen and L-hydroxyproline concentrations of two intra-abdominal and two subcutaneous sites of adipose tissue were measured in male and female Wistar rats. At 100 g body weight the nitrogen concentration of intra-abdominal adipose tissue was slightly lower than that of subcutaneous adipose tissue. As age advanced beyond sexual maturity, the nitrogen content of intra-abdominal adipose tissue was steadily reduced, whereas that of subcutaneous tissue did not change. The L-hydroxyproline concentration of intra-abdominal adipose tissue was also lower than in subcutaneous adipose tissue. In male rats it rose in most adipose tissue sites when sexual maturity was reached, then fell with advancing age. In female rats the pattern of change was less consistent, but the l-hydroxyproline content of intra-abdominal adipose tissue was reduced as age increased.     

Role of human adipose tissue in the production and metabolism of steroid hormones

Radioimmunological methods have been employed for the simultaneous determination of dehydroepiandrosterone, androstenedione, testosterone, oestrogens (oestradiol + oestrone), progesterone, 17 alpha-hydroxyprogesterone and cortisol in human adipose tissue and peripheral blood to compare the hormone pool of adipose tissue with that in the general circulation. Extremely high steroid concentrations in the adipose tissue and hormone pool in the fat of obese subjects were observed. For adipose tissue/serum steroid ratios, the highest values were obtained for dehydroepiandrosterone and the lowest ones for cortisol. A preliminary study showed a great accumulation of steroids in adjacent adipose tissue of breast tumors. Striking differences were observed in the adipose tissue steroid concentrations between benign and malignant mammary tumors. The present findings revealed that blood hormone determinations may be insufficient to consider the steroid hormone availability in various endocrinopathies or steroid responsive tumors, especially when the endocrine state of extremely obese subjects is observed.