Changes in insulin receptors during oral contraception

The effectiveness of metformin, oral contraceptives, and lifestyle modification in improving the metabolism of overweight women with polycystic ovary syndrome: a network meta-analysis

PURPOSE

We designed a network meta-analysis that investigated relatively different interventions that included the effects of metformin, oral contraceptives, and lifestyle modification on the metabolic parameters of patients with polycystic ovary syndrome. In addition, we searched for eligible interventions that improved the metabolism of glucose and lipids.

METHODS

We searched the PubMed, EMBASE, and Cochrane Central databases from inception to May 2018. Publication types that were categorized as randomized controlled trials met our inclusion criteria. The main outcome included the homeostasis model assessment of insulin resistance, total cholesterol, low-density lipoprotein cholesterol, and total triglycerides. We performed both a pairwise meta-analysis and a network meta-analysis to evaluate the mean difference value and 95% credibility intervals, and we calculated the surface cumulative rank curve.

RESULTS

There were a total of 12 kinds of interventions: metformin, 2 mg cyproterone acetate plus 0.05 mg ethinylestradiol (EE/CA), 0.15 mg desogestrel plus 0.03 mg ethinylestradiol (EE/DSG), and 3 mg drospirenone plus 0.03 mg ethinylestradiol (EE/DRSP), lifestyle, exercise, diet, metformin + lifestyle, metformin + diet, EE/CA + lifestyle, metformin + EE/CA, and EE/DRSP + lifestyle from the 20 eligible RCTs that were included in this study. Our meta-analysis results showed that metformin + lifestyle (MD = -2.04, 95% CrI = -3.64 to -0.41), EE/CA + lifestyle (MD = -2.23, 95% CrI = -4.11 to -0.35), and EE/DRSP + lifestyle (MD = -2.59, 95% CrI = -4.66 to -0.50) resulted in lower in the levels of total cholesterol. Women treated with metformin + lifestyle (MD = -1.82, 95% CrI = -2.88 to -0.79), EE/CA + lifestyle (MD = -2.25, 95% CrI = -3.58 to -1.08), or EE/DRSP + lifestyle (MD = -2.29, 95% CrI = -3.69 to -1.07) exhibited significantly lower low-density lipoprotein cholesterol when compared with the placebo group. There was no significant difference between any of the interventions compared with a placebo in the levels of homeostasis model assessment of insulin resistance and total triglycerides. The surface cumulative rank curve revealed that metformin + lifestyle might be the best intervention with respect to the improvement of the homeostasis model of assessment insulin resistance and EE/DRSP + lifestyle appeared to be the best intervention for the reduction of total cholesterol and low-density lipoprotein cholesterol. Moreover, the metformin + diet intervention was more effective in reducing the level of total triglycerides.

CONCLUSIONS

For overweight polycystic ovary syndrome patients, our evidence revealed that EE/CA and EE/SRSP combined with metformin or lifestyle changes can reduce the adverse effects on glucose and lipid metabolism of the use of oral contraceptive agents alone. Conventional PCOS treatments, such as metformin, EE/CA, and EE/DRSP, combined with lifestyle control can be particularly effective in improving the homeostasis model assessment of insulin resistance and lipid metabolism.

Pathophysiology, risk factors, and screening methods for prediabetes in women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a syndrome associated with insulin resistance (IR), obesity, infertility, and increased cardiometabolic risk. This is a descriptive review of several mechanisms that can explain the IR among women with PCOS, other risk factors for the development of diabetes, and the screening methods used for the detection of glucose intolerance in women with PCOS. Few mechanisms can explain IR in women with PCOS such as obesity, insulin receptor signaling defects, and inhibition of insulin-mediated glucose uptake in adipocytes. Women with PCOS have additional risk factors for the development of glucose intolerance such as family history of diabetes, use of oral contraceptives, anovulation, and age. The Androgen Society in 2007 and the Endocrine Society in 2013 recommended using oral glucose tolerance test as a screening tool for abnormal glucose tolerance in all women with PCOS. The approach to detection of glucose intolerance among women with PCOS varies among health care providers. Large prospective studies are still needed for the development of guidelines with strong evidence. When assessing risk of future diabetes in women with PCOS, it is important to take into account the method used for screening as well as other risk factors that these women might have.

Insulin and insulin like growth factor II endocytosis and signaling via insulin receptor B

Background

Insulin and insulin-like growth factors (IGFs) act on tetrameric tyrosine kinase receptors controlling essential functions including growth, metabolism, reproduction and longevity. The insulin receptor (IR) binds insulin and IGFs with different affinities triggering different cell responses.

Results

We showed that IGF-II induces cell proliferation and gene transcription when IR-B is over-expressed. We combined biotinylated ligands with streptavidin conjugated quantum dots and visible fluorescent proteins to visualize the binding of IGF-II and insulin to IR-B and their ensuing internalization. By confocal microscopy and flow cytometry in living cells, we studied the internalization kinetic through the IR-B of both IGF-II, known to elicit proliferative responses, and insulin, a regulator of metabolism.

Conclusions

IGF-II promotes a faster internalization of IR-B than insulin. We propose that IGF-II differentially activates mitogenic responses through endosomes, while insulin-activated IR-B remains at the plasma membrane. This fact could facilitate the interaction with key effector molecules involved in metabolism regulation.

Comparison of effects of 3 mg drospirenone plus 20 μg ethinyl estradiol alone or combined with metformin or cyproterone acetate on classic metabolic cardiovascular risk factors in nonobese women with polycystic ovary syndrome

OBJECTIVE

To evaluate the effects of a pill with drospirenone (3 mg) plus ethinyl E(2) (20 μg) (DRP/20EE) alone or associated with metformin or cyproterone acetate (CPA) on some metabolic cardiovascular risk factors in women with polycystic ovary syndrome (PCOS).

DESIGN

Randomized, open-label clinical trial.

SETTING

Academic medical clinic.

PATIENT(S)

Forty-eight hirsute women with PCOS.

INTERVENTION(S)

Patients were randomized to treatment with DRP/20EE or with DRP/20EE plus metformin (1,500 mg/d) or with DRP/20EE plus CPA (12.5 mg/d, 10 days per cycle) for 6 months.

MAIN OUTCOME MEASURE(S)

Blood pressure, lipid profile, and indexes of glucose tolerance and insulin sensitivity were assessed before and after 6 months of treatment.

RESULT(S)

Body mass index and blood pressure were not modified by any treatment. Treatment with DRP/EE20 did not change the lipid profile; DRP/EE20 plus metformin significantly increased high-density lipoprotein cholesterol concentrations; DRP/EE20 plus CPA significantly increased triglycerides and total cholesterol. The area under the curve for insulin was significantly decreased by DRP/EE20 and DRP/EE20 plus metformin, but it was significantly increased by DRP/EE20 plus CPA. Treatment with DRP/EE20 plus CPA significantly increased the homeostasis model assessment of insulin resistance index and significantly reduced the glucose to insulin ratio index. Treatment with DRP/EE20 significantly increased the glucose to insulin ratio index.

CONCLUSION(S)

Treatment with DRP/EE20 improved insulin sensitivity in hirsute women with PCOS, with no deterioration of lipid profile. This effect was not ameliorated by the addition of metformin. The positive metabolic effects of DRP are abolished by the concomitant use of CPA.

Insulin receptor isoforms and insulin receptor/insulin-like growth factor receptor hybrids in physiology and disease

In mammals, the insulin receptor (IR) gene has acquired an additional exon, exon 11. This exon may be skipped in a developmental and tissue-specific manner. The IR, therefore, occurs in two isoforms (exon 11 minus IR-A and exon 11 plus IR-B). The most relevant functional difference between these two isoforms is the high affinity of IR-A for IGF-II. IR-A is predominantly expressed during prenatal life. It enhances the effects of IGF-II during embryogenesis and fetal development. It is also significantly expressed in adult tissues, especially in the brain. Conversely, IR-B is predominantly expressed in adult, well-differentiated tissues, including the liver, where it enhances the metabolic effects of insulin. Dysregulation of IR splicing in insulin target tissues may occur in patients with insulin resistance; however, its role in type 2 diabetes is unclear. IR-A is often aberrantly expressed in cancer cells, thus increasing their responsiveness to IGF-II and to insulin and explaining the cancer-promoting effect of hyperinsulinemia observed in obese and type 2 diabetic patients. Aberrant IR-A expression may favor cancer resistance to both conventional and targeted therapies by a variety of mechanisms. Finally, IR isoforms form heterodimers, IR-A/IR-B, and hybrid IR/IGF-IR receptors (HR-A and HR-B). The functional characteristics of such hybrid receptors and their role in physiology, in diabetes, and in malignant cells are not yet fully understood. These receptors seem to enhance cell responsiveness to IGFs.

A comparative study on the effects of a contraceptive vaginal ring NuvaRing®and an oral contraceptive on carbohydrate metabolism and adrenal and thyroid function

OBJECTIVES

To compare carbohydrate metabolism, adrenal and thyroid function during use of a combined contraceptive vaginal ring (NuvaRing, NV Organon, Oss, The Netherlands) with those of a combined oral contraceptive.

METHODS

Healthy women aged 18-40 years used either the vaginal ring, delivering 15 microg ethinylestradiol and 120 microg of etonogestrel per day, or a combined oral contraceptive containing 30 microg ethinylestradiol and 150 microg levonorgestrel, for six cycles. Each cycle comprised 3 weeks of use of the ring or the pill followed by 1 ring- or pill-free week. The following parameters were measured at baseline and at the end of cycles 3 and 6: carbohydrate metabolism (glucose, insulin, glycosylated hemoglobin); adrenal function (total cortisol, cortisol binding globulin, dehydroepiandrosterone sulfate); thyroid function (thyroid stimulating hormone, free thyroxine).

RESULTS

Small and similar increases in insulin were seen in both groups. Concentrations of cortisol binding globulin and total cortisol rose significantly less during ring use than during combined oral contraceptive use (cycle 3, p= 0.0002; cycle 6, p < 0.0001). Levels of dehydroepiandrosterone sulfate did not change in either group. Thyroid stimulating hormone levels increased significantly more in the ring group at cycle 3 (p = 0.0016) but free thyroxine levels were unchanged in both groups.

CONCLUSIONS

Both the vaginal ring and the oral contraceptive have no clinically relevant effects on carbohydrate metabolism, adrenal or thyroid function.

Insulin sensitivity and lipid metabolism with oral contraceptives containing chlormadinone acetate or desogestrel: a randomized trial

BACKGROUND

Second-generation and third-generation oral contraceptives containing 30 mcg or more of ethinylestradiol (EE) decrease insulin sensitivity (SI). In this study, we investigated whether SI is decreased by contraceptives containing lower doses EE or by progestins with antiandrogenic properties.

STUDY DESIGN

Twenty-eight young healthy women were randomly allocated to receive 20 mcg of EE and 150 mcg of desogestrel (DSG) (n=14) or 30 mcg of EE and 2 mg of chlormadinone acetate (CMA) (n=14) for 6 months. SI and glucose utilization independent of insulin (Sg) were investigated by the minimal model method. Lipid modifications were also analyzed.

RESULTS

SI decreased with EE/DSG (7.09+/-1.4 vs. 4.30+/-0.91; p=.04; n=12), but not with EE/CMA (5.79+/-0.93 vs. 6.79+/-1.1; p=.48; n=12). SI modifications observed in the two groups were significantly different (-2.79+/-1.15 vs. 1.0+/-1.38; p=.05). Sg did not vary with either treatment. The response of C-peptide to glucose increased, but significantly so only with EE/CMA (p=.01). The C-peptide/insulin response increased with both EE/DSG (p=.05) and EE/CMA (p=.04). High-density lipoprotein (HDL) cholesterol (p=.02) and triglycerides (p=.02 and p=.01) increased in both groups, but HDL/low-density lipoprotein cholesterol (p=.02), apoprotein A1 (Apo-A1) (p=.04) and Apo-A1/apoprotein B (p=.048) increased significantly only with EE/CMA.

CONCLUSIONS

The present study confirms that DSG, even when associated with low EE dose, decreases SI. By contrast, EE/CMA does not deteriorate SI and induces a favorable lipid profile.

Effect of low-dose oral contraceptives on metabolic risk factors in African-American women

CONTEXT

The effect of oral contraceptive pill (OCP) use on cardiovascular risk in African-American women is unknown.

OBJECTIVE

Our objective was to examine in African-American women the effect of OCP use on insulin resistance, glucose intolerance, and triglycerides (TGs).

DESIGN

This was a cross-sectional study.

SETTING

The study was conducted at the National Institutes of Health Clinical Research Center.

PARTICIPANTS

A total of 104 healthy nondiabetic African-American women [21 OCP users, 83 controls, age mean +/- sd, 34.7 +/- 7.6 yr, body mass index (BMI) 31 +/- 8.4 kg/m(2)] was included in the study.

INTERVENTIONS

Subjects had oral glucose tolerance tests, insulin-modified frequently sampled iv glucose tolerance tests, and fasting lipid profiles. Insulin resistance was determined by the insulin sensitivity index (S(I)).

MAIN OUTCOME MEASURES

Insulin resistance, glucose tolerance status, and TG levels were determined.

RESULTS

Fasting glucose did not differ between OCP users and controls (P = 0.27). In contrast, compared with controls, 2-h glucose (135 +/- 23 vs.120 +/- 25 mg/dl; P = 0.01) and fasting TGs (73 +/- 31 vs.57 +/- 27 mg/dl; P = 0.02) were higher in OCP users. OCP users tended to be more insulin resistant than controls (S(I): 2.51 +/- 2.01 vs. 3.46 +/- 2.09; P = 0.09). Multiple regression analysis revealed that BMI, age, and OCP use were significant determinants of 2-h glucose (adjusted R(2) = 0.37; P < 0.001) and TG levels (adjusted R(2) = 0.21; P < 0.001). As BMI was a determinant of both 2-h glucose and TGs, participants were divided into nonobese and obese groups, and the analyses repeated. Among the nonobese women, the OCP users were more insulin resistant (S(I): 2.91 +/- 1.58 vs. 4.35 +/- 1.88; P = 0.03) and had a higher prevalence of glucose intolerance than controls (odds ratio 5.7; 95% confidence interval 1.4-24; P = 0.01).

CONCLUSION

In African-American women, OCP use is associated with an increase in markers of cardiovascular risk manifested by increased insulin resistance, glucose intolerance, and elevated TGs.

Polycystic ovaries and associated clinical and biochemical features in young women

OBJECTIVE

To determine the prevalence of polycystic ovaries as identified by ultrasound in a group of young, postmenarcheal women in the normal population, and to investigate how polycystic ovaries are related to the spectrum of clinical and biochemical symptoms associated with the polycystic ovary syndrome (PCOS).

DESIGN

Cross-sectional observational study.

SUBJECTS AND METHODS

Volunteers were recruited from two universities and two general practice surgeries in Oxford. 230 women aged 18-25 years participated. Information collected and measurements performed included: a menstrual history, anthropometric measurements, clinical observation of acne and hirsutism, transabdominal pelvic ultrasound, and biochemical analysis of a fasting blood sample.

MAIN OUTCOME MEASURES

Prevalence of polycystic ovaries and their association with symptoms of the polycystic ovary syndrome.

RESULTS

Polycystic ovarian morphology was identified in 74 (33%, 95% CI = 27-39%) of the 224 women who attended for an ultrasound scan. In the non-users of hormonal contraception, irregular menstrual cycles were 20% more common in women with polycystic ovaries than in women with normal ovaries (P = 0.07). There were no significant differences in acne, hirsutism, body mass index or body fat percentage between women with polycystic and normal ovaries. Analysis of biochemical data showed that women with polycystic ovaries had higher total serum testosterone concentrations (P = 0.03). The prevalence of PCOS in this age group was as low as 8% or as high as 26% depending on which criteria were applied to define the syndrome. Sub-group analyses of women according to ovarian morphology and features of PCOS revealed greater mean BMI in women with PCOS, and also indicated lower fasting insulin concentrations and greater insulin sensitivity in polycystic ovary and PCOS groups when compared to women with normal ovaries.

CONCLUSIONS

Polycystic ovaries are very common in this age group but are not necessarily associated with other symptomatology. The prevalence of polycystic ovary syndrome varies widely according to the definition applied. Sub-group analysis of women with polycystic ovaries according to the presence or absence of features of polycystic ovary syndrome does not reveal an increasing trend for progression of endocrine abnormalities usually associated with polycystic ovary syndrome.

Progesterone administration induced impairment of insulin suppression of hepatic glucose production

OBJECTIVE

To assess whether P administration impairs insulin-mediated glucose uptake.

DESIGN

Two-step euglycemic hyperinsulinemic clamp studies.

SETTING

Rats studied with (n = 11) or without (n = 10) P treatment.

PARTICIPANTS

Conscious, unstressed, oophorectomized female rats.

MAIN OUTCOME MEASURES

Plasma glucose and insulin levels and the rates of glucose turnover results.

RESULTS

Fasting glucose (115 +/- 5 versus 109 +/- 4 mg/dL; conversion factor to SI units 0.05551) and insulin (1.67 +/- 0.24 versus 1.51 +/- 0.22 ng/mL; conversion factor to SI units 174.5) levels were not significantly different in the control and P treated groups, respectively. However, the basal rate of glucose turnover was significantly higher in P-treated rats (8.38 +/- 0.50 versus 6.59 +/- 0.35 mg/kg per minute in controls. During low-dose insulin infusion (2 mU/kg per minute), there was no difference in glucose or insulin levels, or the rate of glucose utilization; however, residual hepatic glucose production was significantly greater in the P group (5.34 +/- 0.68 versus 2.57 +/- 1.00 mg/kg per minute) in controls. At high-dose insulin infusion (10 mU/kg per minute), hepatic glucose production was completely suppressed in both groups; there was no difference in insulin sensitivity as assessed by the glucose utilization rate or the ratio of glucose uptake to insulin level.

CONCLUSIONS

Chronic P therapy does not alter insulin-mediated glucose utilization in peripheral tissues but does reduce the ability of insulin to suppress endogenous hepatic glucose production.

The effects of hormonal replacement therapy on insulin sensitivity in surgically postmenopausal cynomolgus monkeys (Macaca fascicularis)

OBJECTIVE

Our purpose was to evaluate the effect of hormone replacement therapy on insulin resistance in postmenopausal cynomolgus monkeys (Macaca fascicularis).

STUDY DESIGN

We studied 37 surgically postmenopausal cynomolgus monkeys that were fed a moderately atherogenic diet for 12 weeks with either no treatment (control), conjugated equine estrogens, medroxyprogesterone acetate, combination conjugated equine estrogens and medroxyprogesterone acetate, or tamoxifen. Insulin sensitivity and glucose effectiveness were determined by the frequent-sampling intravenous tolerance test by means of the minimal model analysis.

RESULTS

There were no differences in body weight, total plasma cholesterol, or body fat distribution between control and conjugated equine estrogens, medroxyprogesterone acetate, or combination treatment groups. However, compared with control animals (insulin sensitivity = 5.9 +2- 1.2 x 10(-4) min-1 microU-1 ml) or conjugated equine estrogens treatment (6.3 +/- 1.1 x 10(-4) min-1 microU-1 ml) insulin sensitivity was significantly decreased in animals treated with medroxyprogesterone acetate (2.9 +/- 0.4 x 10(-4) min-1 microU-1 ml, p < 0.001) or conjugated equine estrogens and medroxyprogesterone acetate (2.8 +/- 0.6 x 10(-4) min-1 microU-1 ml, p < 0.001). Although insulin sensitivity was shown to be decreased in the tamoxifen-treated animals (insulin sensitivity = 4.6 +/- 0.6 x 10(-4) min-1 microU -1 ml), the difference was not statistically significant compared with the control or conjugated equine estrogens-treated animals. No significant differences were seen for glucose effectiveness comparing control animals (glucose effectiveness = 0.043 +/- 0.006 min-1) to animals treated with medroxyprogesterone acetate (glucose effectiveness = 0.046 +/- 0.009 min-1), conjugated equine estrogens and medroxyprogesterone acetate (0.048 +/- 0.008 min-1) or tamoxifen (0.039 +/- 0.006 min-1).

CONCLUSION

These results suggest that progestins alone or in combination with estrogens can induce insulin resistance in postmenopausal monkeys while having no effect on plasma lipid concentrations or glucose effectiveness.

Insulin responses following glucose administration in menstruating women

OBJECTIVE

The aim of the study was to investigate changes in insulin sensitivity during the menstrual cycle, in a group of regularly menstruating black African women.

METHOD

Insulin responses to intravenous glucose (300 mg/kg) were assessed, for up to 3 h, in 3 groups of age- and body mass-matched non-obese sedentary Nigerian women: Group A, 7 women in the menstrual follicular phase; Group B, 7 women in the menstrual luteal phase; C, 7 men.

RESULT

Women in the menstrual luteal phase had the greatest integrated first-phase insulin response and insulin/glucose ratios, much higher than the similar values for these variables obtained in other groups. This suggests that the menstrual luteal phase is associated with relative insulin resistance.

CONCLUSION

Black African women in the menstrual luteal phase demonstrate an exaggerated insulin response to an acute glucose load and are thus relatively insulin-insensitive. This confirms previous observations in Caucasians.

An open prospective study on the effects on carbohydrate metabolism of an oral monophasic contraceptive containing gestodene (WL-70)

The effects of a monophasic oral contraceptive (gestodene 75mcg + ethinylestradiol 30 mcg) on plasma glucose (PG) and insulin (IRI) responses to an oral glucose load (OGTT) and on glycosylated haemoglobin Alc (HbAlc), fructosamine (Fr), total cortisol (FT) and transcortin (CBG) were studied in 30 healthy women. Blood samples were taken before treatment and after 6 and 12 cycles. After 6 and 12 months, OGTT-PG and IRI levels showed substantially unchanged values; for HbAlc and Fr the same behaviour was seen with the exception of the latter between 6 and 12 months; FT and CBG showed significant rises. All recorded values were in the normal range. The basal and dynamic PG and IRI behaviour failed to show any significant variations between pre-treatment values and those after 6 and 12 months of OC administration. Other data showed a substantial neutrality for this oral contraceptive containing gestodene.

Mechanism of action of oral contraceptives on carbohydrate metabolism at the cellular level

Although the available scientific data on the undesired metabolic effects of sex steroids have accumulated rapidly, most are of a descriptive nature, and only a few studies elucidate the impact at the cellular level and the possible interrelationship between different metabolic systems. This review summarizes the influence of different contraceptive steroid combinations on glucose metabolism and points to the possible mechanisms behind a disturbance of the euglycemic homeostasis with a concomitant change in lipid metabolism. Today the general concept is that the influence of combined sex steroid products on glucose metabolism is mainly caused by the progestogen components, although artificial estrogens may act synergistically. The diabetogenic effects of the progestogens make it important to consider the development during the last decade of the new more selective progestogens of the gonane type. From recent studies it seems, however, that intake of contraceptive combinations of ethinyl estradiol in combination with these types of gonanes, such as desogestrel and gestodene, may also be accompanied by increased insulin resistance, specifically, a hyperinsulinemic response to a glucose challenge despite unchanged glucose values compared with a baseline test. This is similar to observations made with combinations of ethinyl estradiol and other more traditional types of progestogens of the gonane and estrane type. It is conceivable that the diabetogenic effects of the progestogens are caused by a change in insulin receptor binding or a postreceptor defect in the cellular insulin action. The clinical implications of the diabetogenic effects of the sex steroids are hard to interpret, but more long-term exposure of arterial tissue to elevated concentrations of glucose and insulin results in inhibition of lipolysis and synthesis of cholesterol and triglycerides, which result in the development of lipid-filled lesions--fatty streaks--similar to those of early atherosclerosis.

Carbohydrate metabolic studies during twelve months of treatment with a low-dose combination oral contraceptive

Carbohydrate metabolism was evaluated in twenty healthy women volunteers using a low-dose combination oral contraceptive (OC) containing 30 micrograms of ethinyl estradiol and 500 micrograms of dl-norgestrel by measurement of serum glucose and insulin levels during 3-hour oral glucose tolerance test (OGTT) before and after 3, 6 and 12 months of medication. There were no significant differences in body weight or blood pressure between pretreatment and posttreatment. Fasting serum glucose levels were slightly reduced, though not significantly, during all periods of treatment. But serum glucose levels were increased at 1, 2 and 3 hours in association with high insulin responses during OGTT in all periods of OC therapy, indicating mild to moderate insulin resistance. These data suggest that the low-dose combination OC used in the study exerts alterations on carbohydrate metabolism in women during one year of OC use.

Use of combined oral contraceptive preparations alters the insulin sensitivity of fatty acid and ketone metabolism

Eight women taking low-dose-oestrogen combined oral contraceptive preparations were compared to eight women in the luteal phase of the menstrual cycle during hourly incremental insulin infusions of 0 (basal), 0.005, 0.01 and 0.05 U/kg/h short-acting insulin. Dose-response relationships between insulin and intermediary metabolites were sought by analysis of variance applied to regression. For insulin (log) and glucose the slope of the relationship was significantly shallower in the oral contraceptive group. For insulin (log) and non-esterified fatty acids the slopes of the regression lines were not different between groups but lines were significantly displaced. For insulin (log) and total ketone bodies (log) slopes of the regression lines were not different but significant displacement was observed. At identical insulin concentrations women taking an oral contraceptive had higher non-esterified fatty acids (NEFA) (difference between groups +0.15 mmol/l, P less than 0.001) and total ketone bodies (log: -0.26 mmol/l, P less than 0.001). The potency of insulin action in oral contraceptive users versus the luteal group was 0.47 (P less than 0.01) for NEFA and 0.38 (P less than 0.001) for total ketone bodies. The results demonstrate, for the first time, in-vivo insulin resistance of NEFA and ketone bodies' metabolism induced by oral contraceptive use.

Diabetes and pregnancy

Prior to the introduction of insulin, a vast majority of pregnancies complicated by diabetes ended in perinatal death, with an associated risk of maternal death. Currently, virtually all diabetic women can undergo pregnancy with the expectation of good maternal and fetal outcome. However, many challenges still remain in preventing congenital anomalies and macrosomia.

Progesterone and synthetic steroids produce insulin resistance at the post-receptor level in adipocytes of female rats

The effects of progesterone, its agonists (progestin RU-5020, glucocorticoid RU-26988) and antagonist (antiprogesterone, anti-glucocorticoid RU-486) were tested on isolated fat cells in vitro. When added to the incubation medium, all four steroids decreased basal glucose oxidation. The inhibitory effect of the steroids appeared early (20 min incubation) and was sustained during a 2-h incubation. The early inhibitory effect was less marked for progesterone agonist RU-5020 than for the other three steroids. When incubation was prolonged for 2 h, the lowest inhibitory effect was observed with progesterone antagonist RU-486. Insulin-stimulated glucose oxidation was inhibited by progesterone, its antagonist RU-486, one of its agonists RU-26988, but not by the other agonist RU-5020. Analysis of the dose response curves showed that progesterone, RU-26988, and RU-486 decreased fat cells' responsiveness and, only for RU-486, sensitivity to insulin. Adipocytes isolated from ovariectomized, progesterone-treated rats showed a decreased maximal response to insulin and decreased insulin sensitivity in opposition to cells incubated directly with the steroid. No inhibition of 125I-labeled insulin binding was seen as an acute or chronic effect of progesterone. It is concluded that progesterone and the studied related steroids decrease glucose oxidation by mechanism(s) distal to insulin binding to its specific receptors.

Alterations in carbohydrate metabolism as they apply to reproductive endocrinology

This review has characterized the current state of knowledge of four clinical situations in which an interrelationship of gynecology, endocrinology and carbohydrate metabolism is recognized. The literature contains conflicting descriptions of changes in glucose homeostasis during the menstrual cycle and while using birth control pills. Physiologic changes in receptor number have been demonstrated in each of these situations, so failure to observe differences using glucose tolerance testing may reflect an in vivo homeostatic response to changes in these hormone levels. Thus, in vivo identification of alterations in carbohydrate metabolism induced by endogenous or exogenous steroids may require utilization of models that prevent these homeostatic mechanisms. The association between hyperandrogenism and hyperinsulinism has been better characterized, but the relationship is complicated by the frequent coexistence of obesity. The association may be due to insulin-stimulated ovarian androgen production, and insulin insensitivity may reflect a postreceptor defect. Insulin and its metabolic effects have also been implicated in ovulatory dysfunction in women with diabetes mellitus and identified as a factor affecting all levels of the hypothalamic-pituitary-ovarian axis. A clearer understanding of these relationships and their application to clinical management await further study.

Lack of metabolic effects of a triphasic formulation containing norethindrone in normal women studied prospectively

The glucose and insulin responses to oral glucose tolerance tests and lipid values in normal women taking a triphasic pill containing norethindrone (Ortho 7/7/7) were performed. After three months, no significant changes in these metabolic indices were found. These results confirm and expand the knowledge regarding the metabolic safety of norethindrone-containing triphasic formulations.

The effects of piretanide in patients with congestive heart failure and diabetes mellitus: a double-blind comparison with furosemide

A double-blind parallel group study was carried out to compare the effects of piretanide on daily glucose profiles, symptoms of congestive heart failure and serum electrolytes with those of furosemide in 24 diabetic in-patients suffering from congestive heart failure. After a 3-day run-in period on placebo, patients were allocated at random to receive 10-days' treatment with either 6 mg piretanide or 40 mg furosemide once daily. The results showed that there were no differences between the glucose profiles between the first and the last day of treatment, nor were there any differences between the two treatments. Piretanide and furosemide both produced a significant reduction in the number of symptoms of congestive heart failure. There were no significant changes in biochemical variables within the groups, nor were there any differences between the groups, except for an increase in uric acid and decrease in total protein values after furosemide. Mean triglyceride values decreased significantly after piretanide treatment, and SGOT values decreased after both treatments, the latter change being of no clinical relevance. Side-effects were generally mild in both groups and did not require any counter-measures.

Metabolic effects of combined oral contraceptive preparations

Fasting intermediary metabolite concentrations were measured in comparable groups of women either in the follicular or luteal phase of the menstrual cycle or taking low-dose estrogen combined oral contraceptive preparations. Blood total ketone bodies concentrations were significantly elevated in oral contraceptive users (p less than 0.05 v follicular and luteal groups) whilst blood alanine levels were lower (p less than 0.01 v follicular).

Metabolic effects of oral contraceptives

Combination oral contraceptives (OCs) are probably not an independent risk factor for cardiovascular disease but through their metabolic actions, may partly amplify the effects of known risk factors for cardiovascular disease. This review of the literature and our own data indicate that use of high-dose, progestogen-dominant OCs induces a potentially atherogenic lipoprotein profile (high low-density lipoprotein-cholesterol:high-density lipoprotein-cholesterol ratio), mostly attributable to the antiestrogenic action of the progestogen content of these OCs. In contrast, lower-dose combination OCs with reduced amounts of progestogens and slight estrogen dominance, either monophasic or multiphasic, produce strikingly fewer adverse effects on lipoproteins. Moreover, use of low-dose, as opposed to high-dose, OCs results in almost unchanged glucose tolerance, marginally increased or unchanged insulin and glucagon responses to glucose, and probably unchanged levels and activity of peripheral insulin receptors. Further in-depth studies of low-dose OC formulations are mandatory to ascertain reduced metabolic risk of these OCs.

Effect of seven low-dose combined oral contraceptive preparations on carbohydrate metabolism

The effect of seven low-dose oral contraceptive preparations on carbohydrate metabolism was investigated in groups of 10 healthy volunteers. All preparations contained a similar amount of ethinyl estradiol but differed in the content and type of progestogen. The following progestogens were used: levonorgestrel (monophasic and triphasic), norethisterone (monophasic), cyproterone acetate (monophasic), desogestrel (monophasic and biphasic) and gestodene (triphasic). An oral glucose tolerance test was performed before and after 6 months of treatment; glucose disappearance and insulin response curve were determined. Long-term glucose homeostasis was assessed by the estimation of the extent of glycosylation of plasma proteins and hemoglobin A1. The area under the curve for insulin and glucose did not change during treatment with any of the preparations. In addition the representative variables for long-term glucose control did not increase for any of the preparations during treatment. We conclude from these results that the low-dose pills investigated in this study do not have any adverse effects on glucose metabolism after treatment for 6 months.

Oral contraceptives and insulin receptor binding in normal women and those with previous gestational diabetes

The effect of a low-dose triphasic oral contraceptive (ethinyl estradiol and levonorgestrel) on glucose tolerance, plasma insulin response to a glucose challenge, and insulin receptor binding to monocytes and erythrocytes was investigated in seven women with previous gestational diabetes and seven nondiabetic control subjects. Investigations were performed in the luteal phase before the hormonal intake and after hormonal treatment for 2 and 6 months. Before treatment, women with previous gestational diabetes had significantly impaired glucose tolerance (p less than 0.05) when compared with the healthy controls, but no differences in insulin receptor binding were observed. Glucose tolerance and the insulin response to oral glucose remained unchanged in both groups during the treatment period. In the control subjects a significant decrease (p less than 0.05) in insulin receptor binding to monocytes was observed after hormonal intake for 6 months whereas the insulin receptor binding remained unchanged in the women with previous gestational diabetes. No correlation was found between the receptor binding data obtained from monocytes and erythrocytes in either group of women. The study demonstrates that in lean nondiabetic women and women with previous gestational diabetes of normal weight without first-degree history of diabetes there is no apparent direct association between glucose tolerance, plasma insulin levels, and insulin binding to erythrocytes and monocytes during intake of low-dose oral contraceptives.

Carbohydrate metabolism in women who used oral contraceptives containing levonorgestrel or desogestrel: a 6-month prospective study

Blood glucose and pyruvate, plasma insulin, and glucagon levels as well as erythrocyte insulin receptors were measured during an oral glucose tolerance test in 38 normal women before and after 6 months' use of one of three new oral contraceptives containing low doses of 19 nortestosterone-derived progestogens, levonorgestrel, and desogestrel. A slight deterioration of glucose tolerance was observed, with the area under the glucose curve increasing by only 7%, 9%, and 12% after Ovidol (Aaciphar SA, Brussels, Belgium), Marvelon (Organon, SA, Brussels, Belgium), and Trigynon (Schering SA, Brussels, Belgium) administration, respectively. We did not find any argument in favor of the development of a state of insulin resistance in women using these compounds, because erythrocyte receptor binding was not modified and plasma insulin responses to glucose were decreased. The glucose-induced suppression of plasma glucagon levels seemed less effective for treatment with the desogestrel-containing preparations than with the levonorgestrel-containing oral contraceptives.

A comparative study of the metabolic effects of injectable and oral contraceptives

The metabolic effects of an injectable contraceptive, Depo-provera (medroxyprogesterone acetate), an oral contraceptive pill containing 50 micrograms ethinyl estradiol and 500 micrograms norgestrel and a control group (not on contraceptives) were compared in 3 groups, each comprising 32 women. The subjects were matched for race, age and parity. Mean duration of treatment was 41.7 +/- 18.3 months for Depo-provera and 59.6 +/- 29.0 months for the pill group. Glucose tolerance was impaired in both treatment groups. The combination pill showed more changes in both glucose tolerance and insulin response. Lipid levels remained unchanged in both treatment groups.

Triphasic oral contraception: metabolic effects in normal women and those with previous gestational diabetes

The effect of a low-dose triphasic oral contraceptive (ethinyl estradiol and levonorgestrel) on glucose tolerance, plasma insulin and glucagon responses to glucose, fasting plasma cortisol, triglycerides, free fatty acids, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and very--low-density lipoprotein cholesterol was investigated in 16 women with previous gestational diabetes and in 19 normal women. Investigations were performed prior to the hormonal intake and after treatment for 2 and 6 months. Before treatment, the women with previous gestational diabetes had significantly elevated fasting glucose (p less than 0.05) and impaired glucose tolerance (p less than 0.05) when compared to those of the healthy control subjects. The glucose, insulin, and glucagon responses to oral glucose remained unchanged during the treatment period. Plasma cortisol increased in both groups (p less than 0.05) whereas plasma triglycerides increased in the control subjects only (p less than 0.05). Plasma free fatty acids, lipoproteins, and high-density lipoprotein cholesterol/total cholesterol ratio remained unchanged in both groups. The results suggest that a low-dose triphasic oral contraceptive (ethinyl estradiol and levonorgestrel) is suitable as contraception even in women with a previous deterioration of glucose tolerance during pregnancy.

Developmental changes in insulin receptors of pig red blood cells

Scatchard analysis of the insulin binding to pig reticulocytes, fetal red cells, and adult erythrocytes showed the maximum number of high-affinity binding sites per cell to be 274, 147, and 29, respectively. All three cell types displayed a practically identical dissociation constant of approximately 1.22 X 10(-8) M at the high-affinity region. A long-term in vitro incubation of the fetal red cells and reticulocytes under tissue culture conditions was accompanied by a significant loss of insulin-binding capacity without any appreciable alteration of the dissociation constant. The isolation and characterization of insulin-receptor complexes from these cell types were carried out to establish whether the difference in insulin-binding capacity was due to the difference in the amount of the same species or due to different species of insulin receptors. Membrane proteins were extracted with Triton X-102 and fractionated by DEAE-Sephacel ion-exchange column chromatography. Each peak sample was complexed with 125I-insulin, and the complexes were covalently crosslinked and then applied to a Sepharose CL-6B column. A 95,000-Da complex was obtained from adult pig erythrocyte membranes; 220,000- and and 95,000-Da complex was obtained from adult pig erythrocyte membranes; 220,000- and 95,000-Da complexes from pig reticulocyte membranes; and greater than 600,000-, 220,000-, and 95,000-Da complexes from pig fetal cell membranes. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis under a nonreducing condition, the 95,000-Da complex was dissociated into a 53,000-Da component; the greater than 600,000-Da complex into greater than 320,000-, 130,000-, and 53,000-Da components; and the 220,000-Da complex was dissociated into 220,000-, 130,000-, and 53,000-Da components. These findings strongly suggest that the decrease in insulin binding during the developmental changes of red blood cells is due to a disappearance of high-molecular-weight insulin receptors rather than a decrease in the amount of the smaller receptor molecules.

The insulin receptor

Cells are endowed with specific cognitive molecules that function as receptors for hormones, neurotransmitters, and other intercellular messengers. The receptor molecules may be present in the plasma membrane, cytoplasm, or nucleus. When occupied by the messenger, the receptor is coupled to the cellular machinery that responds to the message-bearing molecules. For some hormones the events following attachment of the messenger to the receptor are well known. An example is the generation of cAMP after combination of glucagon with its receptor and the series of steps culminating in activation of phosphorylase. In the case of many other messengers, including insulin, the nature of these coupling steps is not known. Receptors are subject to the regulatory processes of synthesis, degradation, and conformational change; alterations in receptor properties may have significant effects on the qualitative and quantitative responses of the cell to the extracellular messenger. The insulin receptor is located in the plasma membrane, is composed of two pairs of subunits, and has a molecular weight of about 350,000. It is located in cells such as adipocytes, hepatocytes, and skeletal muscle cells as well as in cells not considered to be typical target organ cells. Insulin receptors in nonfetal cells are downregulated by exposure of the cells to high concentrations of insulin. Other factors that regulate insulin binding include muscular exercise, diet, thyroid hormones, glucocorticoids, androgens, estrogens, and cyclic nucleotides. The fetus has high concentrations of insulin receptors in several tissues. These begin to appear early in fetal life and may outnumber those found in adult tissues. Fetal insulin receptors are unusual in that they may not undergo downregulation but may experience the opposite when exposed to insulin in high concentrations. Thus the offspring of a mother with poorly controlled diabetes may be placed in double jeopardy by fetal hyperinsulinemia and augmented insulin binding by the receptors. Many disorders in children and adults are associated with changes in the properties of the insulin receptor. In general, the alterations have been measured in receptor-bearing cells that are readily accessible, such as circulating monocytes and erythrocytes. The receptors on these cells generally reflect the status of receptors on the major target organs of insulin, although exceptions are known, and conclusions drawn from studies of receptors on circulating cells must be made with caution.(ABSTRACT TRUNCATED AT 400 WORDS)

The effect of sex steroids on insulin binding by target tissues in the rat

The effect of estradiol, progesterone and norgestrel on serum insulin and glucose levels and on insulin binding to adipocytes, hepatocytes and diaphragm muscle cell membranes has been evaluated in castrated male rats. Estradiol administration (5 micrograms/day X 6) significantly increased basal plasma insulin levels and the amount of insulin bound to fat and liver cells as well as muscle cell membranes. Progesterone treatment (5 mg/day X 6) caused a slight increase of basal insulin levels and a decrease of insulin binding to fat cells. Norgestrel treatment (5 mg/day X 6) decreased both insulin levels and the amount of insulin bound to adipocytes; a much lower dose of norgestrel, 6 micrograms/day X 7, also caused a decline in adipocyte insulin binding due to an apparent increase in the dissociation constant of the high affinity binding sites. These studies demonstrate that ovarian sex steroids have a significant effect on insulin binding to target cells. This animal model would assist in determining the mechanisms involved in changes of carbohydrate metabolism which occur during the menstrual cycle, pregnancy, the menopausal state and with the use of oral contraceptives.

Insulin receptors in normal and disease states

The binding of insulin to its receptor has been studied under various physiological and pathological conditions. Quantitative studies have involved human circulating cells such as monocytes and erythrocytes, adipocytes, placental cells, and cultured cells such as fibroblasts and transformed lymphocytes. In animals, other target tissues such as liver and muscle have been studied and correlated with the human studies. Various physiological conditions such as diurnal rhythm, diet, age, exercise and the menstrual cycle affect insulin binding; in addition, many drugs perturb the receptor interaction. Disease affecting the insulin receptor can be divided into five general categories: (1) Receptor regulation--this involves diseases characterized by hyper- or hypoinsulinaemia. Hyperinsulinaemia in the basal state usually leads to receptor 'down' regulation as seen in obesity, type II diabetes, acromegaly and islet cell tumours. Hypoinsulinaemia such as seen in anorexia nervosa or type I diabetes may lead to elevated binding. (2) Antireceptor antibodies--these immunoglobulins bind to the receptor and competitively inhibit insulin binding. They may act as agonists, antagonists or partial agonists. (3) Genetic diseases which produce fixed alterations in both freshly isolated and cultured cells. (4) Diseases of receptor specificity where insulin may bind with different affinity to its own receptor or related receptors such as receptors for insulin-like growth factors. (5) Disease of affinity modulation where physical factors such as pH, temperature, ions, etc. may modify binding. In this review, we have considered primarily abnormality in insulin receptor binding. There are numerous other functions of the receptor such as coupling and transmission of the biological signal. These mechanisms are frequently referred to as postreceptor events, but more properly should be referred to as postbinding events since the receptor subserves other functions in addition to recognition and binding of insulin.

Effect of estrogens on blood sugar, serum insulin and serum free fatty acids, and pancreas cytology in female dogs

We analyzed the changes in blood sugar (BS), serum immunoreactive insulin (IRI), circulating free fatty acids (FFA) and pancreatic cytology caused by estrogenization at low pharmacological dosage in female dogs. Vehicle-injected and untreated controls (anestrus) were studied as well. Neither mean basal BS nor basal serum IRI was modified by the treatments, while the mean basal serum FFA value was raised. Glucose tolerance was not modified by the estrogens while glucose y-mean was significantly raised. Hyperglycemia was higher for a longer time in estrogenized animals compared to both controls, while the profiles of hyperinsulinemia coincided. In the estrogen-treated bitches, the pancreatic B-cells contained scarse brown-stained granules near their vascular pole, as shown by an immunochemical method. In the peripheral part of the pancreas, near the acini, some solitary, poorly beta-granulated B-cells were present. During the IVGTT, serum FFA reached lower values for a longer time in the estrogenized bitches as compared to those found in both control groups. Insulin-induced hypoglycemia in the estrogenized animals coincided with the one evoked in the vehicle controls; in the semilog relationship of serum IRI and time, y-mean was lower than that observed in oil-injected controls, and insulin space was larger. The serum FFA levels of these estrogenized bitches, very high in the basal conditions, did not respond to insulin administration, and were above those found in untreated controls and also in vehicle-injected controls just at the beginning of the test. These results are discussed. We came to the conclusion that estrogenization causes some glucose intolerance in bitches while insulin sensitivity remains normal in the IVITT as studied measuring BS. The glucose intolerance is thought to be related to a reduction in glucose space and occurs despite the normality of the serum IRI response. The pancreas must have an intense secretory response in vivo as as to maintain normal IRI activity despite degranulation of the islets of Langerhans and poor islet hypertrophy and neoformation. The serum FFA changes are thought to contribute towards the tendency to adiposity in these animals.

Insulin binding to erythrocytes from pregnant, postpartum, follicular and luteal states

Specific binding of [125I] insulin to isolate erythrocytes from four groups of women was investigated: (A) pregnant subjects between weeks 38 and 40 of pregnancy (n = 18), (B) postpartum subjects within 6 days after delivery (n = 20), (C) normal women during the follicular phase of the menstrual cycle (n = 12) and (D) normal women during the luteal phase of the menstrual cycle (N = 11). Specific [125I] insulin binding (fraction), fasting plasma glucose concentrations (mmol/l) and the corresponding insulin concentrations (mU/l) were 0.074 +/- 0.012 / 4.00 +/- 0.58 / 29.4 +/- 21.4 for group A, 0.065 +/- 0.016 / 4.40 +/- 0.75 / 41.5 +/- 26.2 for group B, 0.052 +/- 0.008 / 4.58 +/- 0.62 / 6.7 +/- 4.0 for group C and 0.054 +/- 0.011 / 4.49 +/- 0.63 / 8.3 +/- 5.9 for group D. By using a modified Scatchard analysis, statistically significant differences were observed between the receptor affinities of the groups A and D, B and D, A and C. The receptor affinities and concentrations were not significantly different between the follicular and the luteal phases. From the data, no inverse correlation between the plasma insulin concentration and receptor binding was seen, i.e. the phenomenon of downregulation of insulin receptor concentration with hyperinsulinaemia seemed not to apply to erythrocytes.

Carbohydrate metabolism during treatment with estrogen, progestogen, and low-dose oral contraceptives

The combination oral contraceptives have generally been shown to have an adverse effect on carbohydrate metabolism with resultant elevations of both blood glucose and insulin in users. Studies of the individual steroid components suggest that the estrogen is not at fault. The 19-norprogestins can produce these carbohydrate changes and seen to act at the insulin receptor level. Norgestrel, ethynodiol diacetate, and norethindrone alter carbohydrate metabolism, but norgestrel produces the most marked changes. Use of oral contraceptives containing less than 50 microgram of estrogen resulted in fewer metabolic changes than were seen with the drugs containing higher doses of estrogen.

Carbohydrate metabolism studies in women using Brevicon, a low-estrogen type of oral contraceptive, for one year

A prospective study of carbohydrate metabolism was done in 12 normal women over 1 year's time while they were using the low-estrogen type of oral contraceptive Brevicon, which contains 0.035 mg of ethinyl estradiol and 0.5 mg of norethindrone. The women had a 3-hour oral glucose tolerance test before starting the drug and then in 12 months, both blood glucose and plasma insulin levels were measured. After 1 year, there was no significant change in weight, blood pressure, or plasma insulin levels. There was a slight decrease in the fasting blood glucose value after 1 year's use (67.5 +/- 1.5 versus 63.2 +/- 1.3 mg/dl). The other glucose values were unchanged. The importance of these data in terms of mechanisms of action of the steroids on metabolism and the safety of oral contraceptive usage is discussed.