Insulin infusion acutely augments ovarian androgen production in normal women**Supported in part by the Sealy Foundation, Galveston, Texas; by grants DK 33749 and CA 45181 from the National Institutes of Health, and by grant M01-RR00073 from the National Institutes of Health General Clinical Research Center, Bethesda, Maryland

Polycystic Ovary Syndrome: A Literature Review With a Focus on Diagnosis, Pathophysiology, and Management

In females with polycystic ovarian syndrome (PCOS), the most prevalent endocrine condition is chronic anovulation and hyperandrogenism. This illness influences females from conception to death, posing several risks to the health of a female, thus reducing the quality of life. It also increases the rates of mortality and morbidity. The first years of puberty are when PCOS symptoms first show. Menstrual irregularities, anovulation, and acne are features of both PCOS and typical puberty in females. There are many various phenotypes that fall under the same illness, so it is necessary to examine each one independently because they may need different treatments and result in different outcomes. Depending on the diagnostic criteria, approximately 6%-20% of females in the reproductive age group are believed to be affected by PCOS. As long as PCOS is still a syndrome, no single diagnostic indicator, such as hyperandrogenism or polycystic ovary (PCO), can be used to make a clinical diagnosis. The management of females with PCOS depends on the symptoms. These could include menstruation problems, androgen-related symptoms, or infertility caused by ovulatory disruption. In females with PCOS, anovulation is linked to low follicle-stimulating hormone (FSH) levels and a halt in antral follicle growth during the last stages of maturation. The condition may be treated surgically with laparoscopic ovarian drilling or medically with medications such as aromatase inhibitors, metformin, glucocorticoids, clomiphene citrate (CC), tamoxifen, or gonadotropins. Patients will experience different androgenic symptoms, such as hirsutism, acne, and/or baldness. Patients who appear with these troubling symptoms need to receive appropriate care. The review emphasizes the role it plays in the management of various conditions.

Follicle isolation methods reveal plasticity of granulosa cell steroidogenic capacity during mouse in vitro follicle growth

Follicles are the functional unit of the ovary and several methods have been developed to grow follicles ex vivo, which recapitulate key events of oogenesis and folliculogenesis. Enzymatic digestion protocols are often used to increase the yield of follicles from the ovary. However, the impact of these protocols on the outermost theca and granulosa cells, and thereby follicle function, is not well defined. To investigate the impact of enzymatic digestion on follicle function, we collected preantral follicles from CD1 mice either by enzymatic digestion (Enzy-FL) or mechanical isolation (Mech-FL) and compared follicle growth, steroidogenesis and cell differentiation within an encapsulated in vitro follicle growth system which maintains the 3D architecture of the oocyte and its surrounding somatic cells. Follicles were encapsulated in 0.5% alginate and cultured for 8 days. Compared with Enzy-FL, Mech-FL grew more rapidly and produced significantly higher levels of androstenedione, estradiol and progesterone. The expression of theca-interstitial cell marker genes, Cyp17a1, which encodes 17-hydroxylase/17, 20-lyase and catalyzes the hydroxylation of pregnenolone and progesterone to 17-hydroxypregnenolone and 17-hydroxyprogesterone, and the conversion of these products into dehydroepiandrosterone and androstenedione, and Star, which encodes a transport protein essential for cholesterol entry into mitochondria, were also higher in Mech-FL than in Enzy-FL. Mech-FL maintained an intact theca-interstitial layer on the outer edge of the follicle that phenocopied in vivo patterns as confirmed by alkaline phosphatase staining, whereas theca-interstitial cells were absent from Enzy-FL from the onset of culture. Therefore, preservation of the theca cell layer at the onset of culture better supports follicle growth and function. Interestingly, granulosa cells in the outermost layers of Enzy-FL expressed CYP17A1 by Day 4 of culture while maintaining inhibin α-subunit expression and a cuboidal nucleus. Thus, in the absence of theca-interstitial cells, granulosa cells have the potential to differentiate into androgen-producing cells. This work may have implications for human follicle culture, where enzymatic isolation is required owing to the density of the ovarian cortex.

Hyperinsulinemia: An Early Indicator of Metabolic Dysfunction

Hyperinsulinemia is strongly associated with type 2 diabetes. Racial and ethnic minority populations are disproportionately affected by diabetes and obesity-related complications. This mini-review provides an overview of the genetic and environmental factors associated with hyperinsulinemia with a focus on racial and ethnic differences and its metabolic consequences. The data used in this narrative review were collected through research in PubMed and reference review of relevant retrieved articles. Insulin secretion and clearance are regulated processes that influence the development and progression of hyperinsulinemia. Environmental, genetic, and dietary factors are associated with hyperinsulinemia. Certain pharmacotherapies for obesity and bariatric surgery are effective at mitigating hyperinsulinemia and are associated with improved metabolic health. Hyperinsulinemia is associated with many environmental and genetic factors that interact with a wide network of hormones. Recent studies have advanced our understanding of the factors affecting insulin secretion and clearance. Further basic and translational work on hyperinsulinemia may allow for earlier and more personalized treatments for obesity and metabolic diseases.

Conserved insulin signaling in the regulation of oocyte growth, development, and maturation

Insulin signaling regulates various aspects of physiology, such as glucose homeostasis and aging, and is a key determinant of female reproduction in metazoans. That insulin signaling is crucial for female reproductive health is clear from clinical data linking hyperinsulinemic and hypoinsulinemic condition with certain types of ovarian dysfunction, such as altered steroidogenesis, polycystic ovary syndrome, and infertility. Thus, understanding the signaling mechanisms that underlie the control of insulin-mediated ovarian development is important for the accurate diagnosis of and intervention for female infertility. Studies of invertebrate and vertebrate model systems have revealed the molecular determinants that transduce insulin signaling as well as which biological processes are regulated by the insulin-signaling pathway. The molecular determinants of the insulin-signaling pathway, from the insulin receptor to its downstream signaling components, are structurally and functionally conserved across evolution, from worms to mammals-yet, physiological differences in signaling still exist. Insulin signaling acts cooperatively with gonadotropins in mammals and lower vertebrates to mediate various aspects of ovarian development, mainly owing to evolution of the endocrine system in vertebrates. In contrast, insulin signaling in Drosophila and Caenorhabditis elegans directly regulates oocyte growth and maturation. In this review, we compare and contrast insulin-mediated regulation of ovarian functions in mammals, lower vertebrates, C. elegans, and Drosophila, and highlight conserved signaling pathways and regulatory mechanisms in general while illustrating insulin's unique role in specific reproductive processes.

Diabetes and the female reproductive system

The insulin/insulin-like growth factor (IGF) pathways and glucose metabolism act as mediators of human ovarian function and female fertility. In normal insulin action, insulin binds to its own receptors in the ovary to mediate steroidogenesis and act as a co-gonadotropin. Insulin with other factors may influence ovarian growth and cyst formation. The IGF pathway also seems to influence normal ovarian function. Insulin signaling affects reproductive function. Dysregulation of this pathway leads to altered puberty, ovulation, and fertility. Better understanding of the normal physiology and pathophysiology of insulin, IGF, and glucose effects on the human reproductive system will allow for better outcomes.

Insulin-stimulated translocation of glucose transporter (GLUT) 12 parallels that of GLUT4 in normal muscle

CONTEXT

GLUT4 is the predominant glucose transporter isoform expressed in fat and muscle. In GLUT4 null mice, insulin-stimulated glucose uptake into muscle was diminished but not eliminated, suggesting that another insulin-sensitive system was present.

OBJECTIVE

This study was intended to determine whether insulin caused GLUT12 translocation in muscle.

DESIGN

Six normal volunteers had muscle biopsies before and after euglycemic insulin infusions.

SETTING

Infusions and biopsies were performed in an outpatient clinic.

PARTICIPANTS

Subjects were nonobese, young adults with no family history of diabetes.

MAIN OUTCOME MEASURES

GLUT12, GLUT4, and GLUT1 proteins were quantified in muscle biopsy fractions. Cultured myoblasts were used to determine whether GLUT12 translocation was phosphatidyl inositol-3 kinase (PI3-K)-dependent.

INTERVENTION

Insulin was infused at 40 mU/m(2) x min for 3 h.

RESULTS

In human muscle, insulin caused a shift of a portion of GLUT12 from intracellular low-density microsomes to the plasma membrane (PM) fraction (17% in PM at baseline, 38% in PM after insulin). Insulin increased GLUT4 in PM from 13 to 42%. GLUT1 was predominantly in the PM fractions at baseline and did not change significantly after insulin. L6 myoblasts in culture also expressed and translocated GLUT12 in response to insulin, but inhibiting PI3-K prevented the translocation of GLUT12 and GLUT4.

CONCLUSIONS

Insulin causes GLUT12 to translocate from an intracellular location to the plasma membrane in normal human skeletal muscle. Translocation of GLUT12 in cultured myoblasts was dependent on activation of PI3-K. GLUT12 may have evolutionarily preceded GLUT4 and now provides redundancy to the dominant GLUT4 system in muscle.

Gender risk of nonfatal stroke in type 2 diabetic patients differs depending on the type of treatment

BACKGROUND

The gender differences in stroke risk among diabetic patients with different treatments have not been studied previously. We aim to determine if there is a gender difference in nonfatal stroke risk in diabetic patients receiving different types of glucose-lowering treatments.

METHODS

In December 2005, data of type 2 diabetic patients were extracted from a nationwide population-based diabetes registry covering 11 Ukrainian regions. Male/female odds ratios (OR) for nonfatal stroke were calculated in three treatment groups: diet only 7,273/15,901, oral glucose-lowering drugs 15,109/33,913, and insulin 5,529/12,462 male/female. Male/female ORs of stroke were estimated using a logistic regression model.

RESULTS

The age-adjusted ORs of stroke were higher among diabetic men compared with diabetic women with oral glucose-lowering drug treatment (OR 1.37, 95% CI 1.22-1.54) and diet treatment only (OR 1.53, 95% CI 1.35-1.73). No differences were found among patients who used insulin (OR 0.97, 95% CI 0.84-1.11). Further adjustment for duration of type 2 diabetes, body mass index (BMI), systolic blood pressure, total cholesterol, and smoking affected the results only slightly.

CONCLUSIONS

The gender risks of nonfatal stroke in patients with type 2 diabetes appear to differ considerably depending on treatment types.

Effects of raloxifene on insulin sensitivity, beta-cell function, and hepatic insulin extraction in normal postmenopausal women

OBJECTIVE

To investigate the effect of raloxifene on insulin sensitivity, beta-cell function, hepatic insulin clearance, and glucose tolerance in postmenopausal women.

DESIGN

Prospective study.

SETTING

University of Texas Medical Branch at Galveston, Texas.

PATIENT(S)

Twenty normal postmenopausal women.

INTERVENTION(S)

An oral glucose tolerance test (OGTT) was performed on all study participants before and after treatment with 60 mg of raloxifene daily for 3 months. Blood samples were obtained at baseline and 1, 2, and 3 hours after 75-g oral glucose administration for measurement of glucose, insulin, proinsulin, and c-peptide levels. Insulin tolerance test (ITT) and euglycemic clamp studies were also performed before and after treatment.

MAIN OUTCOME MEASURE(S)

Glucose and insulin area under curve (AUC) were calculated. The c-peptide to insulin ratio was determined to assess hepatic clearance of insulin. The homeostasis model assessment (HOMA) was used to calculate the index of insulin resistance (HOMA-IR) and beta-cell function (HOMA-%beta). Insulin sensitivity was assessed by insulin tolerance test and glucose infusion rate (GIR) during euglycemic clamp studies.

RESULT(S)

There was no change in fasting or AUC glucose levels. Fasting insulin levels were not statistically significantly different, but the insulin levels at 2 hours and insulin AUC were higher after treatment compared with before treatment. Proinsulin, c-peptide levels, and HOMA-%beta did not change. The c-peptide to insulin molar ratio was statistically significantly decreased after treatment. There was no change in insulin sensitivity.

CONCLUSION(S)

These results indicate that raloxifene has no adverse effect on insulin sensitivity or glucose tolerance, and it does not affect beta-cell function. After glucose load, raloxifene decreases hepatic insulin extraction and thus conserves insulin, which may be beneficial to patients with decreased beta-cell reserve or those predisposed to type 2 diabetes.

Effect of gonadotropin-releasing hormone hypogonadism on insulin action as assessed by hyperglycemic clamp studies in men

OBJECTIVE

To investigate the effects of decreasing androgen levels on insulin action, in view of the relationship between hyperandrogenism and impaired insulin action in women with polycystic ovary syndrome.

DESIGN

Prospective, clinical study.

SETTING

University hospital.

PATIENT(S)

Ten normal healthy men.

INTERVENTION(S)

Gonadotropin-releasing hormone (GnRH) agonist, 3.75 mg, administered monthly for 3 months.

MAIN OUTCOME MEASURE(S)

Insulin action (M/I ratio).

RESULT(S)

The M/I ratio decreased from 0.24 +/- 0.04 to 0.17 +/- 0.04 after GnRH agonist therapy.

CONCLUSION(S)

In normal men, administration of a GnRH analogue was associated with a decrease in both testosterone levels and insulin action.

Influence of insulin and testosterone on adrenocortical steroidogenesis in vitro: preliminary studies

OBJECTIVE

The mechanisms underlying the adrenal androgen (AA) excess of polycystic ovary syndrome (PCOS) remain unclear, although it is possible that the adrenocortical dysfunction may be a response to other, extraadrenal factors. Consistent with the pathophysiology of PCOS and with in vivo data in normal and PCOS women, we have hypothesized that insulin inhibits and that T stimulates AA secretion in vitro.

DESIGN

In vitro experimental study.

SETTING

University medical center.

PATIENT(S)

Normal human adrenals (n = 4 women, ages 25-57 years) were obtained with consent at the time of organ donation.

INTERVENTION(S)

Fresh adrenal tissue minces were incubated in serum-free medium with 10-microM pregnenolone substrate and 1-microM ACTH-(1-24). Challenge doses of 0.2, 1, 5, 20, and 100 nM of insulin and 1, 10, 100, 1,000, and 10,000 nM of T were added, and the media were sampled after 8 hours of incubation at 37 degrees C, 4% CO2. Dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEAS), and cortisol (F) were measured by radioimmunoassay (significant effects compared with the case of zero-dose control).

MAIN OUTCOME MEASURE(S)

The production of DHEA, DHEAS, and F in the media of the adrenal minces was compared between different subjects and at different concentrations of T and insulin.

RESULT(S)

Analysis of the combined data from all donors indicated that insulin stimulated DHEAS and suppressed DHEA production but had no consistent effect on F. Similar analyses of the combined data indicated that T had no significant predictable effect on the production of DHEAS, DHEA, or F. When examining donor data individually, insulin and T did elicit significant increases and/or decreases in steroid production within subjects, although no consistent trends were observed.

CONCLUSION(S)

On the basis of these data, it is clear that extra-adrenal factors such as insulin and T have some adrenal regulatory capacity. In general, insulin stimulated DHEAS and decreased DHEA production, suggesting that it increases adrenocortical sulfotransferase activity. However, although in the individual subjects studied, both insulin and T frequently altered the production of DHEAS, DHEA or F, these effects did not appear to be uniform or consistent from subject to subject. Expanded studies are required to confirm these results.

The decrease in luteinizing hormone secretion in response to weight reduction is inversely related to the severity of insulin resistance in overweight women

Controversial effects of weight reduction on gonadotropin secretion in obesity have been reported. As a result of pulsatility, single serum samples or frequent sampling studies are somewhat limited with regard to monitoring LH and FSH concentrations. We studied follicular phase nocturnal urinary (nu) LH and FSH secretion and glucose metabolism (150-min euglycemic hyperinsulinemic clamp) during 1 menstrual cycle/30-day period before and after weight reduction in 10 severely overweight infertility patients (age, 29 +/- 3.1 yr; body mass index, 37.1 +/- 3.3 kg/m2; +/-SEM). A 6-week very low calorie diet was followed by a 4-week normocaloric period. The urinary LH and FSH results reported represent samples taken 12 to 2 days before the LH surge, or 10 consecutive samples in the case of amenorrhea. We observed a decrease of 8% (P < 0.001) in percent body fat mass and a 5% (P < 0.005) reduction in waist to hip ratio. Mean nu-LH decreased by 45% [6.06 +/- 1.05 (+/-SEM) to 3.22 +/- 0.71 IU/L], whereas mean nu-FSH remained unchanged. Insulin-stimulated glucose uptake increased by 41% (P < 0.01), which was accounted for by a significant increase in nonoxidative glucose disposal (P = 0.003). Serum sex hormone-binding globulin concentrations increased by 39% (P < 0.01), and insulin-like growth factor (IGF)-binding protein-1 (IGFBP-1) levels increased by 46% (P < 0.05). Fasting serum insulin concentrations decreased by 38%, those of leptin by 37%, those of androstenedione by 32%, those of testosterone by 20% (all P < 0.01), and those of dehydroepiandrosterone sulfate by 13% (P < 0.05). The percent change in nu-LH correlated negatively with glucose uptake (r = -0.76; P < 0.01) and the increase in serum sex hormone-binding globulin (r = -0.85; P < 0.005) and positively with the percent change in waist to hip ratio (r = 0.79; P < 0.01). The absolute nu-LH levels after weight reduction correlated significantly with fasting insulin concentrations (r = 0.88; P < 0.001) and negatively with glucose uptake (r = -0.67; P < 0.05). No significant relationships were found between absolute levels or changes in nu-LH concentrations and leptin, IGF-I, IGFBP-3, or IGFBP-1 concentrations. Our findings suggest that weight reduction with a very low calorie diet results in a decrease in nu-LH concentrations, a reduction in the LH/FSH ratio, and FSH predominance favoring folliculogenesis. The decrease in LH concentrations is inversely related to the severity of insulin resistance. It is possible that the decrease in LH secretion with weight reduction is more dependent on the absolute levels of insulin sensitivity than on the degree of general adiposity.

Acanthosis nigricans as a risk factor for non-insulin dependent diabetes mellitus

The prevalences of obesity and of non-insulin dependent diabetes mellitus (NIDDM) have increased in the United States population over the past two decades, and thus diabetes prevention has become a major concern of public health agencies such as the National Institutes of Health. Identification of individuals at risk for diabetes is an essential first step in designing and implementing intervention programs. Insulin resistance is the hallmark of the pathophysiology of NIDDM. Subjects with hyperinsulinemia, impaired glucose tolerance, or gestational diabetes are well accepted as being at high risk for diabetes. We propose that the easily identifiable skin lesion, acanthosis nigricans, is common in the major minority groups in the United States and that its presence is a surrogate for laboratory-determined hyperinsulinemia.

Effects of gonadal androgens and oestrogens on adrenal androgen levels

OBJECTIVE

The physiological role of adrenal androgens in humans remains unclear. Furthermore, there are few data on the relation between sex steroids and adrenal androgen production. We have assessed the effects of sex steroid hormone administration on adrenal androgen levels, by studying a large group of transsexual patients.

DESIGN

A non-randomized intervention.

SETTING

A university teaching hospital.

PATIENTS

Thirty-one male-to-female and 22 female-to-male transsexual patients.

MEASUREMENTS

Plasma levels of adrenal androgens were measured in a group of male-to-female and female-to-male transsexual patients both before and during cross-gender hormone treatment. This treatment involves administration of testosterone esters to women and of ethinyloestradiol and cyproterone acetate to men.

RESULTS

High dose sex steroid administration had marked effects on adrenal androgens levels, which decreased by 27-48% in males treated with ethinyloestradiol and increased by 23-70% in females treated with testosterone.

CONCLUSION

We conclude that administration of high doses of testosterone and oestradiol exert opposing effects on adrenal androgen production.

Anabolic effects of insulin on bone suggest a role for chromium picolinate in preservation of bone density

Activation of osteoclasts by parathyroid hormone (PTH) is mediated by PTH stimulation of osteoblasts, and is dependent on a PTH-induced rise in protein kinase C activity. Physiological levels of insulin reduce the ability of PTH to activate protein kinase C in osteoblasts, suggesting that insulin may be a physiological antagonist of bone resorption. In addition, insulin is known to promote collagen production by osteoblasts. These findings imply that efficient insulin activity may exert an anabolic effect on bone, and rationalize the many clinical studies demonstrating reduced bone density in Type I diabetes. Recently, the insulin-sensitizing nutrient chromium picolinate has been found to reduce urinary excretion of hydroxyproline and calcium in postmenopausal women, presumably indicative of a reduced rate of bone resorption. This nutrient also raised serum levels of dehydroepiandrosterone-sulfate, which may play a physiological role in the preservation of postmenopausal bone density. The impact of chromium picolinate (alone or in conjunction with calcium and other micronutrients) on bone metabolism and bone density, merits further evaluation in controlled studies.

Hyperinsulinemia is associated with menstrual irregularity and altered serum androgens in Pima Indian women

To determine whether hyperinsulinemia is associated with menstrual irregularity or hyperandrogenemia among Pima Indians, a population with a high prevalence of hyperinsulinemia, we retrospectively studied 20 hyperinsulinemic (higher insulin [HI ) and 20 relatively nonhyperinsulinemic (lower insulin [LI]) nondiabetic Pima women 18 to 45 years of age. Reproductive histories were obtained by review of medical records. Stored serum samples were used for measurement of total testosterone, androstenedione, and dehydroepiandrosterone sulfate (DHEAS) levels. Fifty percent (nine of 18) of HI women had irregular menses, as compared with none of the LI women (0 of 19, P = .0004). HI women were significantly more obese than LI women. Serum testosterone and androstenedione levels were similar in HI and LI women (median testosterone, 1.13 v 1.13 nmol/L, P = .55; median androstenedione, 3.79 v 3.26 nmol/L, P = .90). Serum DHEAS was lower in HI than in LI women (median, 2.85 v 4.55 mumol/L, P < .01). HI women with irregular menses had significantly higher testosterone levels than HI women with regular menses (median, 1.62 v 0.76, nmol/L, P = .04). Androstenedione and DHEAS levels were not different between these women. In conclusion, the association of obesity, hyperinsulinemia, irregular menstruation, and high testosterone concentration described in the polycystic ovarian syndrome (PCO) also occurs in Pima Indian women. Moreover, low concentrations of DHEAS are associated with hyperinsulinemia in these women.

Clinical implications of hyperinsulinaemia in women

In the polycystic ovary syndrome, hyperinsulinaemia is commonly found in women with hirsutism, oligomenorrhoea and acanthosis nigricans and this subset of patients possess adverse risk factors for coronary artery disease, particularly reduced HDL2 concentrations. Conversely, raised serum insulin concentrations are not common in women with PCOS in whom raised serum LH concentrations or regular menstrual cycles are present. We postulate that both direct ovarian and indirect actions of insulin (through changes in IGFI-I, IGFBP-I and SHBG concentrations) play important roles in determining androgen concentrations in women. Many intriguing questions follow from this link between the control of nutrition and reproduction and many old observations required re-examination in this new light. Vital to our understanding in this field will be the cause of moderate hyperinsulinaemia, the action of insulin on the normal ovary, and the importance of adverse surrogate risk factors for heart disease in hyperinsulinaemic women.

Regulation of androgen production in cultured human thecal cells by insulin-like growth factor I and insulin

OBJECTIVES

To investigate if human thecal cells contain messenger ribonucleic acid (RNA) encoding insulin-like growth factor I (IGF-I) and insulin receptors and if IGF-I and insulin could stimulate androgen production in thecal cells.

DESIGN

Poly-adenine+ RNA was extracted from fresh thecal tissue, and the expression of the genes encoding insulin and IGF-I receptors were analyzed. Isolated thecal cells were cultured 4 to 6 days with and without hormones.

SETTING

Procedures were performed in a university laboratory.

PATIENTS

Eight women in the follicular phase of natural cycles were undergoing gynecological laparotomy for reasons unrelated to ovarian pathology. The leading follicle(s) was excised, and dispersed cells of the theca interna layer were isolated through combined mechanical and enzymatic techniques.

INTERVENTIONS

Luteinizing hormone (LH), IGF-I, and insulin were added to the cell cultures.

MAIN OUTCOME MEASURE

The expression of IGF-I receptor and insulin receptor transcripts were analyzed by Northern blot. Medium levels of androstenedione and testosterone were measured by radioimmunoassay.

RESULTS

In the separated thecal tissue both IGF-I receptor and insulin-receptor transcripts were detected. Insulin-like growth factor I and insulin potentiated LH-induced androgen secretion while having less pronounced effects on basal androgen production.

CONCLUSION

The present study demonstrates that both insulin and IGF-I receptor genes are expressed and that insulin and IGF-I can stimulate steroid production in human thecal cells. The study provides further support for the hypothesis that IGF-I and insulin may be involved both in physiological regulation of ovarian function as well as in its pathophysiology.

Divergent effect of dehydroepiandrosterone on energy intakes of Zucker rats

Oral dehydroepiandrosterone (DHEA) causes weight loss in the obese Zucker rat. To study this process, we fed lean and obese female Zucker rats either control chow diets alone or diets containing 0.6% DHEA for 4 weeks. DHEA treatment led to a significant increase in the caloric intake of lean-treatment rats and a significant decrease in obese-treatment rats compared to their respective controls. These phenotype-specific divergent effects began acutely and were sustained. The energy intake changes with DHEA treatment were significant after correcting for body weight. Divergent effects of DHEA were also observed in body weight changes and in the food efficiency ratios of the animals; DHEA affected obese rats but not lean ones. The results of the present study suggest that the appetite component of DHEA's antiobesity effect in the Zucker fatty rat cannot be discounted.

Influence of basal androgen levels in euandrogenic women on glucose homeostasis

OBJECTIVE

To evaluate possible relationships between insulin action and the normal variations of serum androgens in euandrogenic women.

DESIGN

Prospective evaluation of insulin action in normal nonobese women using hyperglycemic and euglycemic hyperinsulinemic clamp techniques, correlating insulin action to serum testosterone (T), free T, androstenedione (A), and dehydroepiandrosterone sulfate (DHEAS). Statistical analysis used Spearman's rank correlation.

SETTING

Yale University Clinical Research Center.

PARTICIPANTS

Nonobese females with normal oral glucose tolerance tests, on no medications known to affect glucose metabolism, having the following range of serum androgen levels: T, 0.69 to 3.12 nmol/L; free T, 0.17 to 1.25 nmol/L; A, 2.48 to 11.31 nmol/L; DHEAS, 0.68 to 10.61 mumol/L. Total number of patients studied: hyperglycemic clamps, n = 58; euglycemic hyperinsulinemic clamps, n = 43.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Pancreatic insulin secretion in response to hyperglycemia and insulin action as assessed by insulin-mediated glucose utilization using the euglycemic, hyperinsulinemic clamp technique.

RESULTS

We identified no significant correlation between serum androgens and either glucose uptake or insulin-mediated glucose utilization. Glucose-stimulated insulin release was negatively correlated with serum T and free T throughout the normal range of these hormones.

CONCLUSION

We conclude that, within the normal range, variations of serum androgens are not correlated with changes in the response to insulin. It seems unlikely, therefore, that modest increases of serum androgens within the normal range are responsible for inducing insulin resistance.