Dianne Deplewski

Growth hormone and insulin-like growth factors have different effects on sebaceous cell growth and differentiation.

Several observations suggest that GH stimulates sebaceous gland growth and development. Therefore, we studied the effects of GH and insulin-like growth factors (IGFs), alone and with androgen, on sebaceous epithelial cell (sebocyte) growth and differentiation in vitro. The rat preputial cell culture model system was used to judge differentiation (induction of lipid-forming colonies, LFCs) and DNA synthesis. GH increased sebocyte differentiation. At a dose of 10(-8) M in the presence of micromolar insulin, GH was 3.8 times more potent than IGF-I (38.1+/-4.2%, SEM, vs. 10+/-1.5% LFCs) and 6 times more potent than IGF-II (6+/-0.5% LFCs). IGF-I 10(-8) M alone stimulated a similar amount of differentiation as insulin 10(-6) M, although it was less effective than insulin in augmenting the effect of GH on differentiation. GH had no effect on sebocyte uptake of 3H-thymidine at doses up to 10(-6) M. On the other hand, IGF-I was the most potent stimulus of DNA synthesis (168% of control; P < 0.001 vs. all others). IGF-II 10(-8) M stimulated 3H-thymidine incorporation similarly to insulin 10(-6) M. In the presence of insulin, dihydrotestosterone (DHT) 10(-6) M induced 31.4+/-1.7% LFCs, and there was a tendency of DHT and GH to interact in promoting differentiation. When insulin was omitted from the system, differentiation was decreased overall, but GH +/- DHT slightly improved differentiation. The IGFs had no effect on the response to DHT. DHT decreased DNA synthesis by 40%, an effect unaltered by GH or IGFs. These results suggest that GH and IGFs have different functions in sebaceous cell growth and differentiation: GH stimulated differentiation beyond that found with IGFs or insulin, yet had no effect on DNA synthesis, a parameter stimulated most potently by IGF-I. While GH augmented the effect of DHT on differentiation, the IGFs had no effect on the response of DHT. These data indicate that GH may in part act directly on sebocytes rather than indirectly through IGF production. These data are consistent with the concept that increases in GH and IGF production contribute in complementary ways to the increase in sebum production during puberty and in acromegaly.

Mechanisms of Androgen Induction of Sebocyte Differentiation

It has been difficult to induce the expected sebocyte differentiation in vitro with dihydrotestosterone (DHT). We reasoned that our culture system lacks differentiating factors, and peroxisome proliferator-activated receptors (PPARs) were the prime candidates. We tested PPAR activators informative about diverse PPAR subtypes, with and without DHT (10–6 M): BRL-49653 (10–6 M, PPAR-γ), WY-14643 (10–6 M, PPAR-α), and linoleic acid (LIN, 10–4 M, PPAR-d). Treatments were added in serum-free medium to cultures of rat preputial sebocytes. Control, DHT, BRL and BRL + DHT treatments caused 11, 25, 66 and 80%, respectively, of preputial cell colonies to differentiate into lipid-forming colonies (LFCs) (p <0.001). WY induced 20% and LIN over 95% LFC formation. PPAR-γ mRNA was identified in preputial sebocytes by the RNase protection assay. These data suggest that differentiation of sebocytes is transduced by PPARs and have implications for the development of new treatments for acne.

Peroxisome Proliferator-Activated Receptors and Skin Development

PPARs are nuclear hormone receptors. PPAR subtypes (α, γ, δ, the latter a xPPARβ homologue) were initially investigated in skin because of their known role in regulating lipid metabolism. Studies adding specific PPAR ligand activators to cultured skin or skin cells are compatible with the concepts that PPARα activation mediates early lipogenic steps common to the function of both skin epidermal cells (keratinocytes) and sebaceous cells (sebocytes), PPARγ activation plays a unique role in stimulating sebocyte lipogenesis, and PPARδ activation may contribute to lipid biosynthesis in both sebocytes and keratinocytes under certain circumstances. Epidermal keratinocytes appear to express small amounts of PPARα and PPARδ mRNA and a trace of PPARγ mRNA which is up-regulated with differentiation. Sebocytes express all subtypes; PPARγ gene expression excedes that in epidermis. The emerging data on PPAR protein expression suggests that epidermis normally expresses predominantly PPARα, while sebocytes express more PPARγ than PPARα. These expression patterns may change during hyperplasia, differentiation and inflammation. Gene disruption studies in mice are compatible with a contribution of PPARα to skin barrier function, suggest that PPARγ is necessary for sebocyte differentiation, and indicate that PPARδ can ameliorate inflammatory responses in skin. PPARs appear to play a role in keratinocyte synthesis of the lipids that they export to the intercellular space to form the skin permeability barrier. They also appear to be important for sebocyte formation of the intracellular fused lipid droplets that constitute the holocrine secretion of the sebaceous gland. In addition, they may play roles in keratinocyte growth and differentiation and the inhibition of skin inflammation by diverse mechanisms not necessarily related to fat metabolism.

Role of androgens in the developmental biology of the pilosebaceous unit

The growth and development of pilosebaceous units in their characteristic pattern depends on the interaction of androgens and diverse biologic factors. Stromal-epithelial interactions are essential features. Considerable evidence suggests that androgens stimulate the growth of sensitive pilosebaceous units primarily by acting on specific stromal cells and that androgens and retinoic acid interact to regulate specific stages of sebocyte differentiation.

Intractable early childhood obesity as the initial sign of insulin resistant hyperinsulinism and precursor of polycystic ovary syndrome.

OBJECTIVE We report that intractable early childhood obesity may be associated with severe insulin resistance syndromes (pseudo-Cushings syndrome and pseudo-acromegaly) and precede polycystic ovary syndrome (PCOS). STUDY DESIGN/RESULTS Patient 1 had prepubertal obesity followed by early puberty and was diagnosed with pseudo-Cushings syndrome and insulin resistance at 10.3 years. Oligomenorrhea, androgen excess, and type 2 diabetes mellitus (DM2) emerged at 13.5 years. Patient 2 developed intractable prepubertal obesity followed by atypical true sexual precocity and pseudo-Cushings syndrome in early childhood. By 11.3 years, oligomenorrhea, androgen excess, and DM2 had appeared. Patient 3 had prepubertal overgrowth in weight and height and was diagnosed with pseudo-acromegaly, menstrual irregularity, androgen excess, and impaired glucose tolerance at 14.3 years of age. Patient 4 had prepubertal overgrowth that evolved into pseudo-acromegaly, insulin resistance, secondary amenorrhea, and androgen excess at 15.6 years. CONCLUSIONS Intractable prepubertal obesity was recognized to culminate in early childhood pseudo-Cushings syndrome or pseudo-acromegaly, which are manifestations of insulin-resistant hyperinsulinism, and to herald adolescent PCOS.

Preputial Sebocyte 5α-Reductase Isoform Specificity1

We determined whether the 5α-reductase (5α-R) isozyme specificity in rat preputial sebocytes is in accordance with that of sebaceous glands (type 1 isoform) or with that of other genital tract androgen-dependent organs (type 2). Immunostaining indicated expression of type 1 5α-R in preputial epithelial cells in the gland as well as in culture. Northern blots and ribonuclease protection assays both showed the presence of the type 1 isozyme in preputial sebocytes, with little if any expression of the type 2 messenger RNA. Ribonuclease protection assay demonstrated that both homogenized preputial gland and freshly dispersed preputial cells express 2-fold more 5α-R type 1 messenger RNA than does skin and 7-fold more than cultured preputial cells. Since cultured preputial cells do not fully differentiate in monolayer culture, these findings suggest that 5α-R is increasingly expressed as sebaceous cells differentiate. The predominance of the type 1 isoform in preputial sebocytes is important because it indicate...

Unique Mode of Lipogenic Activation in Rat Preputial Sebocytes

Lipoprotein delivery of fatty acids and cholesterol is linked with peroxisome proliferator-activated receptor (PPAR) activation in adipocytes and macrophages. We postulated that similar interactions exist in sebaceous epithelial cells (sebocytes) in which PPAR activation induces differentiation. High-density lipoprotein (HDL) and very low-density lipoprotein (VLDL) markedly enhanced sebocyte differentiation above that found with PPAR agonists and were more potent than explicable by their lipid content. The PPARγ antagonist GW5393 reduced sebocyte differentiation to all PPAR isoform agonists, HDL and VLDL, suggesting that the lipoprotein effect on differentiation occurs partially through activation of PPARγ. Furthermore, we found that sebocytes expressed a unique pattern of lipogenic genes. Our results demonstrate that HDL and VLDL are the most potent inducers of sebocyte differentiation tested to date, and these actions are partially inhibited by PPAR antagonists. This suggests that substrates provided by lipoproteins are targeted to sebocytes and affect their own disposition via PPAR activation.

Evidence of a mechanism for isodicentric chromosome Y formation in a 45,X/46,X,idic(Y)(p11.31)/46,X,del(Y)(p11.31) mosaic karyotype

Abnormalities involving sex chromosomes account for approximately 0.5% of live births. The phenotypes of individuals with mosaic cell lines having structural aberrations of the X and Y chromosomes are variable and hard to accurately predict. Phenotypes associated with sex chromosome mosaicism range from Turner syndrome to males with infertility, and often present with ambiguous genitalia. Previous studies of individuals with an 45,X/46,X,idic(Y)(p11) karyotype suggest that the presence of both cell lines should result from an intermediate, 46,XY cell line. Here we report a 2.5 year old female with phenotypic features of Turner syndrome with an isodicentric Y chromosome and a cell line with a deleted Y with a final karyotype of 45,X/46,X,idic(Y)(p11.31)/46,X,del(Y)(p11.31). Fluorescence in situ hybridization (FISH) mapping of the Y chromosome breakpoint revealed very low percentages of the deleted Y cells, but suggested a potential mechanism for the formation of the isodicentric Y chromosome. To our knowledge, the 46,X,del(Y) intermediate cell line in our patient has not been previously reported in individuals with mosaic sex chromosome structural abnormalities.

Puberty and Pediatric-Onset Inflammatory Bowel Disease

The term “delayed growth and sexual maturation” is cited extensively in literature describing inflammatory bowel disease (IBD) with onset during childhood and adolescence. Indeed, evidence suggests that many of the nutritional, inflammatory/immunological, and endocrine factors which result from IBD affect both growth and the onset and progression of puberty. This chapter will address how puberty can be affected in children with IBD, and how disorders in puberty can influence other aspects of health in the pediatric age population with IBD.