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Biomedical subjects

S Franks

Publications and source records attributed to S Franks.

At least 55 records · Page 3Linked to original sources
PubMed1997

Evidence for a primary abnormality of thecal cell steroidogenesis in the polycystic ovary syndrome.

OBJECTIVE: Polycystic ovary syndrome (PCOS) is a common endocrinopathy of unknown aetiology. The aims of this study were to identify whether ovarian thecal cell steroidogenesis is abnormally regulated in PCOS by measuring steroid responses to a single dose of hCG before, and during, suppression of endogenous LH levels by GnRH analogue (GnRHa). DESIGN: Serum levels of LH, FSH, 17 alpha hydroxyprogesterone (17OHP), androstenedione, testosterone and dehydroepiandrosterone sulphate were measured before, and 48 hours after, a single intramuscular injection of 10,000 IU hCG. The test was repeated 4 weeks after suppression of endogenous LH levels by GnRHa. PATIENTS: The ovarian responses to hCG were compared in three groups of women. Eleven women had normal ovaries and regular cycles, eight had polycystic ovaries but not clinical features of the syndrome (PCO group) and eight had polycystic ovaries, anovulation and either severe hirsutism or alopecia (PCOS group). RESULTS: Before GnRHa treatment, LH levels were significantly higher in the PCOS group but hCG stimulated a similar rise in 17OHP in all three groups. Following analogue, LH levels were suppressed in all three groups but the 17OHP responses to hCG were significantly higher in both the PCO and PCOS groups compared with normal controls. CONCLUSIONS: These findings provide further evidence in favour of an intrinsic abnormality of thecal cell steroidogenesis in the polycystic ovary.

17-alpha-Hydroxyprogesterone↗
PubMed1997

Association of the steroid synthesis gene CYP11a with polycystic ovary syndrome and hyperandrogenism.

Biochemical data implicate an underlying disorder of androgen biosynthesis and/or metabolism in the aetiology of polycystic ovary syndrome (PCOS). We have examined the segregation of the genes coding for two key enzymes in the synthesis and metabolism of androgens, cholesterol side chain cleavage (CYP11a) and aromatase (CYP19), with PCOS in 20 multiply-affected families. All analyses excluded CYP19 cosegregation with PCOS, demonstrating that this locus is not a major determinant of risk for the syndrome. However, our results provide evidence for linkage to the CYP11a locus (NPL score = 3.03, p = 0.003). Parametric analysis using a dominant model suggests genetic heterogeneity, generating a maximum HLOD score of 2.7 (alpha = 0.63). An association study of 97 consecutively identified Europids with PCOS and matched controls demonstrates significant allelic association of a CYP11a 5' UTR pentanucleotide repeat polymorphism with hirsute PCOS subjects (p = 0.03). A strong association was also found between alleles of this polymorphism and total serum testosterone levels in both affected and unaffected individuals (p = 0.002). Our data demonstrate that variation in CYP11a may play an important role in the aetiology of hyperandrogenaemia which is a common characteristic of polycystic ovary syndrome.

Aromatase↗
PubMed1997

The genetic basis of polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is the most common endocrinopathy in women of reproductive age. Familial clustering of cases suggests that genetic factors play an important part in its aetiology. A number of studies of families with several cases of PCOS have produced results suggesting an autosomal dominant trait. Detailed analysis of a large number of affected families has, however, cast some doubt about the mode of inheritance. An autosomal dominant trait remains possible but a more complex aetiology seems more likely. The results of our recent studies support the concept of an oligogenic disorder in which genes affecting metabolic pathways in glucose homeostasis and steroid biosynthesis are both involved. We review evidence for an important role for the insulin gene minisatellite in the aetiology of anovulatory PCOS and for the gene coding for P450 cholesterol side chain cleavage (CYP11a) in the mechanism of excessive androgen secretion in women with polycystic ovaries. We propose that the heterogeneity of clinical and biochemical features in PCOS can be explained by the interaction of a small number of key genes with environmental, particularly nutritional, factors.

Cholesterol Side-Chain Cleavage Enzyme↗
PubMed1997

Oestradiol feedback stimulation of androgen biosynthesis by human theca cells.

This study analysed the effect of oestradiol on basal and LH-stimulated production of androstenedione and progesterone by human theca cells in monolayer culture. Incubations were carried out for either 2 days (seven experiments) or 4 days (four experiments), in the presence or absence of luteinizing hormone (LH), oestradiol (10(-9)-10(-6) M) or inhibin. Medium collected at 48 and 96 h was stored until radioimmunoassay for steroid content. Theca pooled from small follicles (<10 mm) was used in all but two experiments; in these, ovaries were obtained from ovulatory women in the mid-follicular phase of their cycle and theca from small and large follicles was pooled. Oestradiol inhibited progesterone production in a dose-dependent manner in all experiments, irrespective of follicle size, ovulatory status and ovarian morphology, with maximum effect at 10(-6) M. At this dose, oestradiol had no effect on androstenedione production by theca from four anovulatory women with polycystic ovaries but produced a significant augmentation of both basal and LH-stimulated androstenedione production in theca from five of the seven ovulatory women, with maximal response in theca from the two pre-ovulatory subjects. During the 48-96 h period of incubation, oestradiol augmented androstenedione production in all four experiments and had a greater stimulatory effect than the physiological dose of inhibin (10 ng/ml). This is the first report of oestradiol regulating human theca cell steroidogenesis in a dose-dependent manner.

Adult↗
PubMed1997

Modulation of the insulin-like growth factor-binding proteins by follicle size in the human ovary.

The IGFs are believed to play an important role in the regulation of steroidogenesis and follicular maturation in the human ovary. The activities of the IGFs are regulated by a family of binding proteins (IGFBPs) which are subject to a number of potential post-translational modifications. The aim of this study was to investigate both the production and modification of the IGFBPs in follicular fluid and in medium conditioned by granulosa cells and theca from individual follicles at different stages of maturation. In follicular fluid from healthy, dominant follicles there was an increase in the amount of IGFBP-2, -3 and -4 present as lower molecular weight forms (23 kDa, 29 kDa and 16.5 kDa respectively) in comparison to that seen in atretic follicles from the same ovary. Furthermore for IGFBP-4, this fragmentation was confirmed to be attributable to the presence of a specific protease which could be inhibited not only by the addition of metal ion chelators or serine protease inhibitors, but also by the addition of other recombinant unsaturated IGFBPs, particularly IGFBP-3. IGF-I did not modulate the activity of the IGFBP-4 protease in solution but was able to prevent the inhibition seen with IGFBP-3. Analysis of granulosa cell conditioned medium from the same series of healthy and atretic follicles revealed that IGFBP-2 and -4 were the predominant IGFBPs with no fragments seen on immunoblotting. In contrast, IGFBP-3 in conditioned medium from theca of atretic follicles was always found as an intact doublet, but was found partially fragmented (30 and 32 kDa) in medium conditioned by theca from healthy, dominant follicles with the proportion of IGFBP-3 in this lower molecular weight or fragmented doublet increasing with follicular maturation. A similar situation was also found for IGFBP-4 with the progressive increase in the amount of the 15 and 16.5 kDa fragments. IGFBP-2 was always found to be intact. Finally, IGFBP production from stroma explants was also examined. This revealed a wide variation in IGFBP pattern between different ovaries, although there was a remarkable degree of consistency between different stroma explant cultures from the same ovary. Immunoblotting for IGFBP-3 revealed that, where present, it existed as both an intact and a lower molecular weight doublet and that IGFBP-2 was again always found to be intact. In conclusion we have demonstrated alterations in the proteolytic modification of the IGFBPs which differ in the various follicular compartments and are closely linked to the stage of follicular development.

Adult↗
PubMed1997

The insulin-like growth factors (IGFs) in follicular fluid are predominantly bound in the ternary complex.

The presence of IGFs and their associated binding proteins (IGFBPs) in human follicular fluid is well documented. Furthermore, most of the constituents of the IGF system in follicular fluid have been found to vary, either in total amount or by proteolytic cleavage, depending on the health status of the follicle. In this study we have examined the acid-labile subunit (ALS) and found that levels in follicular fluid (mean 146 nmol/l) were almost 50% of those in the circulation. This amount of ALS was considerably greater than that found in other extracirculatory fluids (20.9 for synovial fluid and 31.4 nmol/l for skin blister fluid). As in the circulation, ALS levels were in molar excess and did not vary between atretic and dominant follicles. Although the source of ALS is probably from blood (conditioned medium from ovarian cell cultures had no measurable ALS) it would appear that this glycoprotein is not merely diffusing from the circulation as the capillary endothelium becomes more permeable in dominant follicles and this is not reflected in the level of ALS. Analysis of the distribution of IGF-I, IGF-II and IGFBP-3 in fluid from healthy and atretic follicles revealed that the majority of these growth factors (> 80% of total IGF-II) were in the 150KDa complex, indicating that the ALS present was functional, in that it formed the ternary complex with a molecule of IGFBP-3 and IGF. No free IGF-II was found in any of the follicular fluids analysed nor was there any increase in the amount of unsaturated IGFBP-3 in atretic follicles. In summary, we have shown that the majority of IGF measured in follicular fluid, whether from healthy or atretic follicles, is bound in the ternary complex.

Culture Techniques↗
PubMed1996

Does suppressing luteinising hormone secretion reduce the miscarriage rate? Results of a randomised controlled trial.

OBJECTIVE: To determine whether prepregnancy pituitary suppression of luteinising hormone secretion with a luteinising hormone releasing hormone analogue improves the outcome of pregnancy in ovulatory women with a history of recurrent miscarriage, polycystic ovaries, and hypersecretion of luteinising hormone. DESIGN: Randomised controlled trial. SETTING: Specialist recurrent miscarriage clinic. SUBJECTS: 106 women with a history of three or more consecutive first trimester miscarriages, polycystic ovaries, and hypersecretion of luteinising hormone. INTERVENTIONS: Women were randomised before conception to receive pituitary suppression with a luteinising hormone releasing hormone analogue followed by low dose ovulation induction and luteal phase progesterone (group 1) or were allowed to ovulate spontaneously and then given luteal phase progesterone alone or luteal phase placebo alone (group 2). No drugs were prescribed in pregnancy. MAIN OUTCOME MEASURES: Conception and live birth rates over six cycles. RESULTS: Conception rates in the pituitary suppression and luteal phase support groups were 80% (40/50 women) and 82% (46/56) respectively (NS). Live birth rates were 65% (26/40) and 76% (35/46) respectively (NS). In the luteal phase support group there was no difference in the outcome of pregnancy between women given progesterone and those given placebo pessaries. Live birth rates from an intention to treat analysis were 52% (26/50 pregnancies) in the group given pituitary suppression and 63% (35/56) in the controls (NS). CONCLUSIONS: Prepregnancy suppression of high luteinising hormone concentrations in ovulatory women with recurrent miscarriage and hypersecretion of luteinising hormone does not improve the outcome of pregnancy. The outcome of pregnancy without pituitary suppression is excellent.

Abortion, Habitual↗
PubMed1996

Hypersecretion of androgens by polycystic ovaries: the role of genetic factors in the regulation of cytochrome P450c17 alpha.

A single base change has been found in the promoter region of CYP17, the gene encoding P450c17 alpha, which appears to be a significant factor in the expression of hyperandrogenism in PCO but which can be excluded as the primary genetic defect. These findings are consistent with the biochemical data from the studies of patients with PCOS reported above, in which the production of ovarian 17 hydroxyprogesterone and androstenedione were observed to be greatly increased but the generation of progesterone was also exaggerated in PCO theca. Thus, genetic factors may well be involved in the observed dysregulation of 17 hydroxylase/17,20 lyase, but this does not appear to be the whole story. It remains a tenable hypothesis that a single-gene effect is the major cause of PCOS and that a gene involved in the expression of androgen production will be implicated. On the other hand, increased androgen production may be a reflection of an 'upstream' abnormality in the ovary, perhaps involving the fundamental processes of proliferation, differentiation and atresia in ovarian follicles. It is also possible that PCOS is truly polygenic and that CYP17 is one of several genes-including those related to insulin secretion and action-that contribute to the PCOS phenotype. Further candidate genes will need to be investigated using well-characterized, large families, but if several predisposing genes are involved, other approaches may be applicable, for example analysis of shared alleles by affected sibling pairs, which has proved valuable in understanding the genetics of type 1 diabetes (Davies et al, 1994). In conclusion, PCOS--one of the most common endocrinopathies--remains an enigmatic condition but one which may prove to be an important model for understanding the interaction of genetic and environmental factors in the aetiology of endocrine disorders.

Alleles↗
PubMed1996

Dyslipidaemia is associated with insulin resistance in women with polycystic ovaries.

OBJECTIVE: Polycystic ovary syndrome (PCOS) is characterized by hyperinsulinaemia and insulin resistance. Previous reports of lipid abnormalities in the syndrome have produced conflicting results which may, in part, be related to the lack of appropriate controls for the obese women with PCOS. Only one study has related lipid levels to insulin sensitivity. The objective of this study was to assess lipids and lipoproteins in women with PCOS, to compare the results with weight matched controls, and to relate the findings to indices of insulin secretion and action, and to menstrual history. DESIGN: A cross-sectional study of insulin sensitivity and lipids in a cohort of PCO subjects compared to weight and ethnic group matched controls. PATIENTS AND METHODS: We have therefore investigated glucose tolerance, plasma lipids and lipoproteins in 19 lean (LP) and 55 obese (OP) patients with PCO and compared the results with those in 22 lean (LC) and 15 obese (OC) control women. Insulin sensitivity was measured in the same subjects with a short insulin (0.05 U/kg i.v. insulin) tolerance test (LP, n = 18; OP, n = 20; LC, n = 19; OC, n = 11). RESULTS: Results are expressed as mean +/- SEM or median (interquartile range). Fasting plasma glucose levels were similar in the four groups but the plasma glucose area was higher after oral glucose (75 g) in both the lean and obese PCOS groups than in their controls (LC 32.4 +/- 0.7 vs LP 35.2 +/- 1.2, P < 0.01; OC 34.7 +/- 1.8 vs OP 37.8 +/- 1.5 mmol/l/3 h, P < 0.01). Insulin sensitivity was significantly reduced in obese PCOS women (LC 196 +/- 9 vs LP 179 +/- 9, NS; OC 168 +/- 12 vs OP 133 +/- 9 mmol/l/min, P < 0.01). Total serum cholesterol levels were similar in the four groups but HDL2-cholesterol was reduced in both obese and lean PCOS (LC 0.42 (0.38-0.62), LP 0.31 (0.26-0.44), P < 0.05; OC 0.34 (0.21-0.47), OP 0.21 (0.12-0.32) mmol/l, P < 0.01). Total HDL-cholesterol was decreased significantly only in the obese PCOS group. Body mass index correlated significantly and negatively with total HDL-cholesterol and with HDL2-cholesterol levels both within the PCOS group and the control women. Using multiple regression insulin insensitivity contributes significantly beyond BMI to the low HDL-cholesterol in women with polycystic ovaries. CONCLUSION: Polycystic ovary syndrome is associated with biochemical risk factors for premature vascular disease, which cannot be explained by obesity alone.

Adult↗
PubMed1996

Successful induction ovulation and completed pregnancy using recombinant human luteinizing hormone and follicle stimulating hormone in a woman with Kallmann's syndrome.

The induction of ovulation in women with hypogonadotrophic hypogonadism requires follicle stimulating hormone (FSH) for follicular growth and both FSH and luteinizing hormone (LH) to induce optimal follicular steroidogenesis. The development of human recombinant FSH and LH means that individually tailored doses of both hormones can be used with the aim of inducing unifollicular ovulation. This report describes the use of recombinant human FSH and LH for the induction of ovulation and conception in the second cycle of treatment, and subsequently a successfully completed pregnancy in a woman with Kallmann's syndrome.

Adult↗
PubMed1996

Insulin-like growth factor (IGF) I and II, IGF-binding proteins, and IGF-binding protein proteases are produced by theca and stroma of normal and polycystic human ovaries.

There is increasing evidence for an important regulatory role for the insulin-like growth factor (IGF) system in the human ovary. IGF-I and -II and IGF-binding proteins (IGFBPs)-1 to -4 have been identified by analysis of follicular fluid and granulosa cell-conditioned medium and by in situ hybridization and Northern and dot blot analyses of ovarian tissues. It has been suggested that abnormalities of intraovarian IGF-I or IGFBPs may play a part in the pathogenesis of polycystic ovary syndrome. The aim of this study was to identify production of IGF-I and -II and IGFBP-1 to -4 by unstimulated normal and polycystic ovaries. IGF-I and -II were measured by RIA after acid-gel exclusion chromatography in medium conditioned by incubation for 48 h with granulosa cells or explants of theca or stroma. Both IGF-I and -II were present in the low nanograms per mL range in theca- and stroma-conditioned medium (T+SCM). IGFBPs in T+SCM were initially analyzed by Western ligand blotting, which revealed that low mol wt IGFBPs were predominant, especially IGFBP-2 (35 kDa). There was a band corresponding to 26 kDa with smaller amounts of a 31-kDa band, but only a trace of IGFBP-3 (44 and 40 kDa, confirmed by immunoblot). We found no consistent differences between normal and polycystic ovary syndrome ovaries, and although there was a trend toward increased IGFBP accumulation in response to LH, this was not consistent. We were unable to detect IGFs or IGFBPs by Western ligand blotting in granulosa cell-conditioned medium. In further studies we attempted to measure IGFBP-3 by RIA using two different antisera (alpha-BP-3gl and 1287-2-14) that detect different epitopes of IGFBP-3 and allow the presence of proteolytic activity to be demonstrated. Results obtained using alpha-BP-3gl were lower than those using 1287-2-14, suggesting proteolysis of IGFBP-3 in the medium. There was no evidence of proteolysis of serum IGFBP-3 after incubation with conditioned medium, but in contrast, radiolabeled [125I]IGFBP-3 was cleaved after incubation with T+SCM. Immunoblotting revealed intact IGFBP-2 (35 kDa) and bands of various sizes between 16-33 kDa. Immunoreactive fragments of IGFBP-3 between 13-40 kDa were seen. In conclusion, T+SCM contained IGF-I and -II. IGFBP-2 and -4 were the predominant species of IGFBP in T+SCM. T+SCM also contained significant protease activity directed toward IGFBP-2 and -3. Proteolytic activity may be an important mechanism by which bioactive IGFs are made available to these tissues.

Blotting, Western↗
PubMed1996

Modulation by insulin of follicle-stimulating hormone and luteinizing hormone actions in human granulosa cells of normal and polycystic ovaries.

Anovulation in polycystic ovary syndrome (PCOS) is associated with hyperinsulinemia and insulin resistance, but it has been unclear whether the ovary is insulin resistant in women with PCOS. The aims of this study were, firstly, to determine whether human granulosa cells respond to physiological concentrations of insulin and, secondly, to investigate insulin and gonadotropin interactions in vitro in granulosa cells obtained from normal (N) and polycystic ovaries (PCO). Granulosa cells were incubated with insulin with or without gonadotropins for 48 h. Insulin augmented not only basal production of estradiol and progesterone, but also LH-stimulated steroid accumulation in granulosa cell cultures from N and PCO. Insulin enhanced FSH-stimulated progesterone production by granulosa cells from N and PCO, but the effect on FSH-stimulated estradiol production was variable, ranging from no effect for granulosa cells from N to synergistic for granulosa cells from PCO of anovulatory subjects. Preincubation with insulin for 48 h increased subsequent basal and LH-induced, but not FSH-stimulated, steroid production. These data demonstrate that granulosa cells from PCO respond to insulin despite the association, in vivo, of PCOS with peripheral insulin resistance. Insulin preincubation enhances the subsequent response of human granulosa cells to LH. We propose that in anovulatory women with PCOS, elevated levels of insulin interacting with LH may contribute to the mechanism of anovulation.

Adult↗
PubMed1996

Expression of insulin-like growth factor (IGF), IGF-binding protein, and IGF receptor messenger ribonucleic acids in normal and polycystic ovaries.

Expression of the messenger ribonucleic acids (mRNAs) for insulin-like growth factors (IGFs), their binding proteins (IGFBP1 through IGFBP-6), and receptors was examined in normal and polycystic human ovaries (PCO). Northern and dot blots and RT-PCR were used to evaluate mRNA levels. The IGF system was studied in fresh granulosa, stromal, and thecal samples and in thecal tissue after incubation with LH and GH. IGF-II expression was high in granulosa and thecal compartments, whereas IGF-I was only weakly detectable, suggesting the importance of IGF-II in the human ovarian IGF system. Northern blot analysis revealed IGFBP-2 and -4 mRNA in all ovarian compartments and IGFBP-5 mRNA in stroma and theca. IGFBP-2 mRNA was the most abundant IGFBP mRNA in the human ovary. No IGFBP-1 or -3 mRNA was detected in fresh ovarian tissues. IGFBP-6 and type 1 and 2 IGF receptor mRNA expression was detectable in all ovarian compartments only by RT-PCR. In cultured theca, the expression of IG-FBP-1, -3, and 4 was induced. Only IGFBP-5 expression showed some dependence on trophic hormone (LH) stimulation during theca incubation. Otherwise, GH and LH had no effect on IGF or IGFBP expression in thecal tissue. This study indicates that thecal tissue is an essential part of the IGF system in the human ovary. However, no differences were found between normal ovaries and PCO in IGF, IGFBP, or IGF receptor expression. Thus, our results (from a limited number of patients) together with recent in situ hybridization and immunohistochemistry data of others provide no evidence for a role for IGFs in the functional disturbances related to PCO. Interestingly, our data show that in cultured thecal samples, the IGF and IGFBP expression pattern is different from that in fresh tissue.

Adult↗
PubMed1996

Regulation of epidermal growth factor receptor synthesis by ovarian steroids in human endometrial cells in culture.

The aim of this study was to investigate the effect of oestradiol and progesterone on epidermal growth factor (EGF) binding in human endometrial glands and stromal cells in culture. Monolayers of isolated glands or stromal cells were cultured for 6 days in the presence or absence of steroids which were replenished daily. Binding of 125I-labelled EGF was measured in the presence and absence of unlabelled EGF. Over a 6 day period, oestradiol caused a dose-dependent increase in the number of EGF receptors in stromal cells, with a maximum effect of 150% control at a concentration of 10 nmol l-1. The effect of progesterone was also dose dependent and reached a maximum of 170% control at 100 nmol progesterone l-1. Oestradiol and progesterone in combination caused a greater increase in EGF receptor concentration than did either steroid alone (control, 100 +/- 11%; oestradiol, 144 +/- 11% control; progesterone, 200 +/- 20% control; oestradiol and progesterone, 288 +/- 6% control). Steroid treatment did not alter the affinity of the receptor for EGF. The stage of the cycle of the tissue did not affect the response to steroids. The effect of oestradiol was inhibited by the anti-oestrogen ICI182780, and that of progesterone by the anti-progestin RU486. In endometrial glands, neither oestradiol nor progesterone affected the number of EGF receptors, but the two steroids in combination induced an increase of 140 +/- 23% control where control was 100 +/- 15%. These data demonstrate that oestradiol and progesterone increase the number of EGF receptors in vitro, and suggest that EGF is involved in mediating the actions of these steroids on the processes of proliferation and differentiation in the human endometrium.

Cell Culture Techniques↗
PubMed1996

Nutrition, insulin and polycystic ovary syndrome.

The adverse effects of obesity on reproductive function in women are well recognized, but women with polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility, seem particularly vulnerable to the effects of excessive intake of calories. Polycystic ovary syndrome is associated with hyperinsulinaemia and insulin resistance, the causes of which remain unclear. These metabolic abnormalities are, in turn, related to a disorder of energy expenditure, characterized by reduced post-prandial thermogenesis. It is proposed that these closely interlinked phenomena that, particularly in overweight subjects, are associated with anovulation, may confer a biological advantage for women with PCOS at times of food deprivation, when such women may reproduce more successfully than those without PCOS. A possible causal link between hyperinsulinaemia and ovulation is explored by reference to the interaction of insulin and LH in granulosa cells.

Energy Intake↗