Accumulation Of Fat Cells Research Articles

Mouse model of skeletal muscle adiposity: A glycerol treatment approach

Fat cell accumulation in skeletal muscle is a major characteristic of various disorders, such as obesity, sarcopenia and dystrophies. Moreover, these fat cells could be involved in muscle homeostasis regulation as previously described for adipocytes in bone marrow. Despite recent advances on the topic, no clearly characterized mouse model is currently available to study fat accumulation within skeletal muscle. Here, we report a detailed characterization of a mouse model of skeletal muscle fat cell accumulation after degeneration induced by intra-muscular injection of glycerol. Information is provided on the kinetics of degeneration/fat deposition, including the quantity of fat deposited based on various parameters such as glycerol concentration, age, sex and strain of mice. Finally, these fat cells are characterized as true white adipocytes morphologically and molecularly. Our study shows that the mouse adipocyte accumulation within skeletal muscle after glycerol degeneration is a reproducible, transposable and easy model to use. This mouse model should allow a more comprehensive understanding of the impact of adipocyte accumulation in skeletal muscle pathophysiology.

Mal-Development of the Penis and Loss of Fertility in Male Rats Treated Neonatally with Female Contraceptive 17α-Ethinyl Estradiol: A Dose-Response Study and a Comparative Study with a Known Estrogenic Teratogen Diethylstilbestrol

The objectives of this study were to find a minimal dose of 17alpha-ethinyl estradiol (EE) that is detrimental to the developing penis and fertility and to compare estrogenic effects between EE and diethylstilbestrol (DES). Neonatal rats received EE at 10 ng (1 microg/kg), 100 ng, 1 microg, or 10 microg per pup on alternate days from postnatal days 1 to 11 (dose-response study) or received EE or DES at 100 ng per pup daily from postnatal days 1 to 6 (comparative study). Effects of EE were dose dependent, with > or = 100-ng dose inducing significant (p < 0.05) reductions in penile length, weight, and diameter. Additionally, the penis was malformed, characterized by underdeveloped os penis and accumulation of fat cells. Fertility was 0% in the > or = 1-microg groups, in contrast to 60% in the 100-ng group and 100% in the 10-ng and control groups. Animals treated with > or = 10 ng had significant reductions in the weight of bulbospongious muscle, testis, seminal vesicle, epididymal fat pad, and in epididymal sperm numbers. A comparison of EE and DES effects showed similar reductions in penile weight and length and the weight of bulbospongiosus muscle, testis, seminal vesicle, epididymis, and epididymal fat pad in both adolescent and adult rats. While 5/6 control males sired, only 1/6 in the EE group and 0/6 in the DES group sired. Hence, neonatal exposure to EE at 10 ng (environmentally relevant dose) adversely affects male reproductive organs. A dose ten times higher than this leads to permanently mal-developed penis and infertility. Furthermore, EE and DES exposures show similar level of toxicity to male reproductive organs.

SMOKING AFFECTS WOMENS' SEX HORMONE–REGULATED BODY FORM

Saarni et al.1 recently published an interesting study using Finnish twins to examine the association between adolescent smoking and adult abdominal obesity and overweight. They found that smoking was a risk for abdominal obesity in females.1 Unfortunately, they were unable to provide any explanation for the phenomenon, and did not realize that this probably affects the attractiveness of the female body.2 Here we propose why smoking may increase abdominal obesity in women and reduce attractiveness. The study by Saarni et al.1 is consistent with previous studies that have found that smoking females have a significantly higher waist-to-hip ratio.3 It is well known that the waist-to-hip ratio is regulated by sex hormones. Previous studies have also shown that females with a lower waist-to-hip ratio and larger breasts have higher 17-β-oestradiol levels than females with a higher waist-to-hip ratio and smaller breasts.4 Likewise, women with higher testosterone levels have a higher waist-to-hip ratio,5 because testosterone causes the accumulation of fat cells around the waist and the inhibition of fat cells in the hip region.6 The effect of estrogen is the opposite. Women who smoke have more circulating testosterone5 and lower free estradiol levels than do women who do not smoke.7 Higher testosterone levels in women have been suggested to lead to an increased risk of smoking.8 Thus, the higher testosterone levels of women who smoke probably cause the accumulation of fat cells around the waist and the inhibition of fat cells in the hip region,6 and may explain the observed pattern of increased abdominal obesity in women who smoke.3 On the other hand, it seems possible that smoking per se increases testosterone levels and reduces estrogen levels, although experimental studies on humans are lacking in this area. Saarni et al.'s study gives elegant support to this interpretation, because they found that the smoking twin was more likely to be abdominally obese.1 The change in sex hormone levels as a result of smoking probably affects females' body fat distribution, causing it to become more tubular. In western cultures, a low waist-to-hip ratio is considered sexually more attractive in women.2 It can thus be concluded that smoking reduces the sexual attractiveness of the female body. This should be highlighted in publicizing the negative effects of smoking, especially among young women who smoke, or those who are considering starting.

Adipocyte Membrane Lysis Observed After Cellulite Treatment Is Performed with Radiofrequency

Cellulite is considered a disease of the subcutaneous fat layer that appears mostly in women and consists of changes in fat cell accumulation together with disturbed lymphatic drainage, affecting the external appearance of the skin [1]. Changes observed in the fibrotic septae between fat cells, reduction of the metabolic rate, and thus congesting tissue affect the external aspect of skin, with alteration of the skin surface that appears bumpy and uneven. Cellulite starts at puberty in almost all women, and when the deposition becomes excessive, it is a condition that is difficult to control and treat. Various treatment modalities with varying degrees of success have been proposed [2]. Reports suggest that radiofrequency (RF) electrical energy is effective when used on and absorbed by the affected tissue [3, 4]. RF current produces a heating effect that depends on current mode and intensity as well as on the natural resistance or impedance of the skin to the passage of electricity. Electrical impedance of the skin rises with increasing depth and coarser collagen elastin fibers. Impedance will decrease with an increase in blood content in the treated area due to continuous application of treatment. On the other hand, progressive heating of tissue leads to reduced impedance. The RF thermal effect is ‘‘blind’’ to the natural skin pigmentation and is transmitted deeper than light, thus exerting action on the subcutaneous layer. RF can be monopolar or bipolar. In most monopolar RF devices, a single electrode is applied to the skin while the other electrode is fixed to a remote part of the patient’s body. In bipolar RF, electricity passes along a well-defined arc through the target tissue from one electrode to the other. For bipolar RF, the depth reached by the electricity, according to physics, is one half the distance between the electrodes. The idea of combining RF with infrared (IR) light treatment for a more superficial heating, together with mechanical massage and suction, has gained support in the past few years [5]. Synergistic action on treating cellulite has been achieved with promising clinical results [6]. The product Vela Smooth (Syneron", Yokneam, Israel) incorporates mechanical massage and suction, IR light, and RF electrical current. The latter delivers up to 20 W at 1 MHz, and IR light is emitted over a waveband of 700–2000 nm. Both energies, electrical and optical, are applied simultaneously to the cellulite area. At the same time, mechanical massage is given together with suction action up to around 400 mbar of negative pressure. All these combined treatments are delivered through the handpiece which is manually applied to the skin by the person giving the treatment. The specific geometry of the electrodes and the vacuum impact upon inserting the skin between electrodes provide deep RF penetration when the handpiece is moved over the skin. The handpiece permits treatment at different intensities. Treatment in the trials of this report was given at the highest intensity. The purpose of our study was to check the histologic condition of cellulite in the buttock before and 2 h after a single treatment. The study was approved by the Ethics Committees of the Antoni de Gimbernat Foundation. All ten patients selected for the study had a similar cellulite condition in both buttocks, i.e., degree 3 according to the classification by Rossi [7]. Patients were informed of the purpose of the study and signed a consent form for biopsies. Sets of parameters for treatment were constant during the M. A. Trelles (&) ! S. R. Mordon Instituto Medico Vilafortuny, Antoni De Gimbernat Foundation, Av. Vilafortuny, 31, 43850 Cambrils, Spain e-mail: imv@laser-spain.com

Human Bone Marrow Adipocytes Block Granulopoiesis Through Neuropilin-1-Induced Granulocyte Colony-Stimulating Factor Inhibition

Adipocytes are part of hematopoietic microenvironment, even though up to now in humans, their role in hematopoiesis is still questioned. We have previously shown that accumulation of fat cells in femoral bone marrow (BM) coincides with increased expression of neuropilin-1 (NP-1), while it is weakly expressed in hematopoietic iliac crest BM. Starting from this observation, we postulated that adipocytes might exert a negative effect on hematopoiesis mediated through NP-1. To test this hypothesis, we set up BM adipocytes differentiated into fibroblast-like fat cells (FLFC), which share the major characteristics of primitive unilocular fat cells, as an experimental model. As expected, FLFCs constitutively produced macrophage colony stimulating factor and induced CD34(+) differentiation into macrophages independently of cell-to-cell contact. By contrast, granulopoiesis was hampered by cell-to-cell contact but could be restored in transwell culture conditions, together with granulocyte colony stimulating factor production. Both functions were also recovered when FLFCs cultured in contact with CD34(+) cells were treated with an antibody neutralizing NP-1, which proved its critical implication in contact inhibition. An inflammatory cytokine such as interleukin-1 beta or dexamethasone modulates FLFC properties to restore granulopoiesis. Our data provide the first evidence that primary adipocytes exert regulatory functions during hematopoiesis that might be implicated in some pathological processes. Disclosure of potential conflicts of interest is found at the end of this article.

Estrogen receptor-α mediates estrogen-inducible abnormalities in the developing penis

Previously, we reported an association between estrogen receptor-alpha (ERalpha) upregulation and detrimental effects of neonatal diethylstilbestrol (DES) exposure in the rat penis. The objective of this study was to employ the ERalpha knockout (ERalphaKO) mouse model to test the hypothesis that ERalpha mediates DES effects in the developing penis. ERalphaKO and wild-type C57BL/6 mice received oil or DES at a dose of 0.2 microg/pup per day (0.1 mg/kg) on alternate days from postnatal days 2 to 12. Fertility was tested at 80-240 days of age and tissues were examined at 96-255 days of age. DES caused malformation of the os penis, significant reductions in penile length, diameter, and weight, accumulation of fat cells in the corpora cavernosa penis, and significant reductions in weight of the bulbospongiosus and levator ani muscles in wild-type mice. Conversely, ERalphaKO mice treated with DES developed none of the above abnormalities. While nine out of ten male mice sired pups in the wild-type/control group, none did in the wild-type/DES group. ERalphaKO mice, despite normal penile development, are inherently infertile. Both plasma and intratesticular testosterone levels were unaltered in the DES-treated wild-type or DES-treated ERalphaKO mice when compared with controls, although testosterone concentration was much higher in the ERalphaKO mice. Hence, the resistance of ERalphaKO mice to developing penile abnormalities provides unequivocal evidence of an obligatory role for ERalpha in mediating the harmful effects of neonatal DES exposure in the developing penis.

Injections of leptin into rat ventromedial hypothalamus increase adipocyte apoptosis in peripheral fat and in bone marrow

The accumulation of fat cells (adipocytes) in bone marrow is now thought to be a factor contributing to age-related bone loss. Women with osteoporosis have higher numbers of marrow adipocytes than women with healthy bone, and bone formation rate is inversely correlated with adipocyte number in bone tissue biopsies from both men and women. Adipogenic differentiation of bone marrow stromal cells increases with age, but the factors regulating populations of mature adipocytes are not well understood. Leptin is thought to regulate adipose tissue mass via its receptors in the ventromedial hypothalamus (VMH). We have therefore tested the hypothesis that stimulation of leptin receptors in the VMH regulates adipocyte number in bone marrow. Results indicate that unilateral twice-daily injections of leptin into the rat VMH for only 4 or 5 days cause a significant reduction in the number of adipocytes in peripheral fat pads and bone marrow and indeed eliminate adipocytes almost entirely from bone marrow of the proximal tibia. Osteoblast surface is not affected with leptin treatment. Apoptosis assays performed on bone marrow samples from control and treated rats have revealed a significant increase in protein concentration of the apoptosis marker caspase-3 with leptin treatment. We conclude that stimulation of leptin receptors in the VMH significantly decreases the adipocyte population in bone marrow, primarily through apoptosis of marrow adipocytes. Elimination of marrow adipocytes via this central pathway may represent a useful strategy for the treatment and prevention of osteoporosis.

Can we slow the rising incidence of childhood-onset autoimmune diabetes? The overload hypothesis

Overload of the beta cell, mediated by a variety of mechanisms, may sensitise it to immune damage and apoptosis, and thus accelerate ongoing autoimmune processes leading to its destruction. Environmental risk determinants that may exert such overload effects include insulin resistance due to excess fat cell accumulation, and increased insulin requirement due to a high growth rate, physical stress (infection, inflammation) or psychological stress. The increasing incidence of childhood diabetes, and the shift to younger age at onset, is unlikely to be driven by environmental risk factors that have been associated with initiation of autoimmunity, e.g. virus infections or early infant feeding. Risk factors that may accelerate beta cell destruction have shown a steady increase in the population, and are more plausible causes of such a pattern of change. Child growth, weight and birthweight are well-established estimates of community wealth and increase in most countries of Europe. Overfeeding of children early in life leads to both accelerated growth and weight, and even a moderate excess of child growth, not necessarily associated with obesity, is associated with risk of type 1 diabetes. New, safe and effective immune-modulating drugs for possible arrest of the autoimmune process may become available in time, but in the interim these accelerating factors may be targeted. Public health programmes for pregnant mothers and young families, aiming at changing overfeeding and the sedentary lifestyle of the children would be preferable to other alternatives. Interventions such as these would be safe and could potentially influence future risks of type 1 and type 2 diabetes and other major threats to adult health.

Estrogen-Induced Abnormal Accumulation of Fat Cells in the Rat Penis and Associated Loss of Fertility Depends upon Estrogen Exposure during Critical Period of Penile Development

We previously reported that diethylstilbestrol (DES) or estradiol valerate (EV) exposure at a dose of 0.10-0.12 mg/kg, or higher, per day, on alternate days, from postnatal days 2-12, resulted in abnormal penis development and infertility (H. O. Goyal et al., 2005, J. Androl. 26, 32-43). The objective of this study was to identify a critical developmental period(s) during which EV exposure results in the observed penile abnormalities. Male pups received EV at a dose of 0.10-0.12 mg/kg on postnatal day(s) 1, 1-3, 4-6, 1-6, 7-12, 13-18, 19-24, or 25-30. Fertility was tested at 102-115 days of age and tissues were examined at 117-137 days. Both penile morphology and fertility were unaltered in rats treated with EV after 12 days of age. Conversely, except in rats treated on postnatal day 1 only, none of the males treated prior to 12 days of age sired pups, and all had abnormal penises, including varying degrees of abnormal accumulation of fat cells and loss of cavernous spaces and smooth muscle cells in the corpora cavernosa penis, which were maximal in the 1-6-day group. Also, the preputial sheath was partially released or its release was delayed, and the weight of the bulbospongiosus muscle was significantly reduced. Plasma testosterone (T) in the 1-6- and 4-6-day groups and intratesticular T in the 4-6-day group were significantly lower. The testosterone surge, characteristic of controls in the first week of life, was suppressed in the 1-3-day group. Estrogen receptor alpha mRNA expression was enhanced in the body of the penis in the 1-3-day group, but not in the 13-18-day group. Hence, EV exposure prior to 12 days of age (as short as 1-3 days postnatal), but not after 12 days of age, results in long-term abnormal penile morphology, characterized by abnormal accumulation of fat cells in the corpora cavernosa penis and, consequently, loss of fertility.

Exposure of neonatal male rats to estrogen induces abnormal morphology of the penis and loss of fertility

The research objectives are to determine whether estrogen-induced infertility is associated with abnormal morphology of the penis and if morphological alterations can be reversed by testosterone (T). Male pups received diethylstilbestrol (DES) on alternate days from postnatal days 2 to 12. They received T or empty implants at 180 days, were tested for fertility at 188 days, and terminated at 200 days. While 5/7 control males sired pups, only 1/6 did in the DES group, and 0/8 in the DES plus T group. In addition to reductions in penile length and weight, the novel structural change induced by DES, and not reversed by T, was a replacement of cavernous spaces by fat cells in the penis body. Hence, T substitution for 8 days at adulthood did not reverse infertility in rats treated neonatally with DES and provided evidence that infertility probably resulted from absence of cavernous spaces and/or accumulation of fat cells in the penis body.

A glucocorticoid‐induced leucine‐zipper protein, GILZ, inhibits adipogenesis of mesenchymal cells

Mesenchymal stem cells have the potential to differentiate into various cell lineages, including adipocytes and osteoblasts. The induction of adipocyte differentiation by glucocorticoids (GCs) not only causes the accumulation of fat cells in bone marrow, but also depletes the supply of osteoblasts for new bone formation, thus leading to osteoporosis. We have shown that a GC-induced leucine-zipper protein (GILZ) antagonizes adipocyte differentiation. GILZ binds to a tandem repeat of CCAAT/enhancer-binding protein (C/EBP) binding sites in the promoter of the gene encoding peroxisome-proliferator-activated receptor-gamma2 (PPAR-gamma2), and inhibits its transcription as a sequence-specific transcriptional repressor. We have also shown that ectopic expression of GILZ blocks GC-induced adipocyte differentiation. Furthermore, adipogenic marker genes (for example, those encoding PPAR-gamma2, C/EBP-alpha, lipoprotein lipase and adipsin) are also inhibited by GILZ. Our results reveal a novel GC antagonistic mechanism that has potential therapeutic applications for the inhibition of GC-induced adipocyte differentiation.

Progressive changes in pancreatic vasculature accompanying copper deficiency-induced glandular atrophy.

Pancreatic vasculature was studied in rats treated with a dietary copper-deficient regimen to assess and characterize changes in the exocrine angioarchitecture of the gland. The deficient state is known to induce progressive acinar degeneration, atrophy, and subsequent replacement with noninflammatory lipomatosis. This study was carried out since little information exists regarding changes in the vasculature that accompany acute glandular necrosis. Corrosion casts produced from Mercox injected deficient rats were studied using scanning electron microscopy and compared to injected preparations studied by light microscopy. Results show that with initial atrophy of degenerative acini (6-8 wk), pancreatic lobules decreased in size and the volume of the vascular bed reduced. From wk 8 onward, the accumulation of fat cells expanded the configuration of lobules to more normal dimensions. Although vascular interconnectivity within lobules remained reduced, its basic angioarchitecture remained intact and served to vascularize fat cells in lieu of acini. No acute angiopathic changes indicative of vascular disorganization were found. These observations support the hypothesis that the vasculature of the atrophied pancreas, although modified in regions of the gland most severely targeted by acinar necrosis, remains intact and its basic structural features preserved. Preliminary evidence also supports the observation that preservation of the basic elements of lobular angioarchitecture may form the basis for subsequent regeneration of acinar tissue in the reversed deficient state.

The appearance of lipid cells in freeze-etched preparations.

In freeze-etched preparations, epididymal adipose tissue from normal and fasted rats revealed structural differences in lipid accumulation of fat cells which were not easy to visualize. In the cleaved surface, the lipid accumulation of normal fat cells, which is encircled by a thin smooth membrane, indicated numerous globular structures in a lamellar phase. This globular appearance disappeared in fasted rats, and variable canalicular structures, arranged vertically to the surface of the lipid accumulation, were observed. A similar structural change appeared in the cleaved surface of lipid accumulation of fat cells from normal epididymal adipose tissue after incubation with epinephrine. Thus, these structural alterations in treated fat cells may be considered to correspond to biochemical and biophysical changes in lipid accumulation occurring in fat mobilization.

Triiodothyronine stimulation of cyclic adenosine 3',5'-monophosphate accumulation in fat cells.

White fat cells from normal rats treated with 200 μg of L-3,5,3’-triiodothyronine (T-3) exhibited an increased lipolytic response to norepinephrine and dibutyryl cyclic adenosine 3’, 5’-monophosphate. No increase in lipolytic response of T-3 treated cells was observed in the presence of growth hormone and dexamethasone. Cells from both hypophysectomized and normal rats treated with T-3 showed marked increases in accumulation of cyclic adenosine 3’,5’-monophosphate (cyclic AMP) and glycerol release as compared to control cells in the presence of catecholamine and theophylline. Little effect of T-3 treatment was seen on cyclic AMP accumulation in the presence of catecholamine alone or in the absence of lipolytic agents. The administration of 25 micrograms of T-3 to normal female rats 18 hours prior to sacrifice was equally as effective as 200 micrograms in stimulating cyclic AMP accumulation of fat cells incubated with catecholamines and theophylline. There was a lag period of about 5½ hours after subcutane...

Fatty acid oxidation in irradiated bone marrow cells.

A PRIMARY event of the acute radiation syndrome is depressed haematopoiesis and an associated accumulation of fat cells in the bone marrow cavity. My work has shown that the fatty change occurs only at bone marrow sites directly exposed to ionizing irradiation. On the basis of metabolic investigations, I have concluded that irradiation markedly stimulates the biosynthesis of triglycerides in the bone marrow. Although de novo synthesis of fatty acids by irradiated bone marrow cells is impaired1, both the uptake of lipid and the esterification of fatty acids into triglycerides by marrow cells are markedly stimulated in irradiated animals2. However, the matter of fatty acid oxidation by irradiated marrow cells has not previously been investigated. This communication conclusively demonstrates that fatty acid oxidation is severely inhibited by γ-radiation and that the effect is related to the total dose of radiation received.