Differences in insulin receptors between men and menstruating women and influence of sex hormones on insulin binding during the menstrual cycle

Performance of the MiniMed 780G system on mitigating menstrual cycle-dependent glycaemic variability

AIM

To map the glycaemic variabilities and insulin requirements across different phases of the menstrual cycle and assess the efficacy and performance of the MiniMed 780G system on mitigating glycaemic variabilities during phases of the menstrual cycle.

MATERIALS AND METHODS

A pilot study recruiting 15 adolescent and young adult females with type 1 diabetes was conducted. Only females with regular spontaneous menstruation were enrolled in the current study. Phases of each menstrual cycle were determined as either follicular phase or luteal phase. The study analysed continuous glucose monitoring metrics during two study periods: the open loop period (OLP) and the advanced hybrid closed-loop (AHCL) period; each period lasted 3 consecutive months.

RESULTS

During the OLP, the mean time in range (TIR) significantly decreased during the luteal phase compared with the follicular phase (65.13% ± 3.07% vs. 70.73% ± 2.05%) (P < .01). The mean time above range significantly increased from 21.07% ± 2.58% during the follicular phase to 24.87% ± 2.97% during the luteal phase (P < .01). After initiating the AHCL period, TIR was comparable during both phases of the menstrual cycle (P = .72), without increasing the time spent below 70 mg/dL (P > .05). Regarding insulin delivery during the AHCL period, the percentage of Auto basal and Auto correction delivered by the algorithm increased by 13.55% and 30.6%, respectively (P < .01), during the luteal phase.

CONCLUSIONS

The fully automated adaptive algorithm of the MiniMed 780G system mitigated menstrual cycle-dependent glycaemic variability, successfully attaining the recommended glycaemic outcomes with a TIR greater than 70% throughout the entire menstrual cycle.

Menstrual Cycle, Glucose Control and Insulin Sensitivity in Type 1 Diabetes: A Systematic Review

The correlation between the menstrual cycle and glucose control in type 1 diabetes has been the focus of several studies since the 1920s, but a few critical aspects made it particularly challenging to reach conclusive evidence. The aim of this systematic review is to reveal more solid information about the impact of the menstrual cycle on glycaemic outcomes and insulin sensitivity in type 1 diabetes and highlight the less researched areas. The literature was searched by two authors independently using PubMed/MEDLINE, Embase and Scopus (last search on 2 November 2022). The retrieved data did not allow us to perform a meta-analysis. We included 14 studies published between 1990 and 2022, with sample sizes from 4 to 124 patients. We found a wide heterogeneity in the definition of the menstrual cycle phases, glucose metrics, techniques for determining insulin sensitivity, hormonal assessment and other interfering factors considered, with an overall high risk of bias. There is no conclusive evidence, and published data do not allow us to achieve quantitative results. In a subset of patients, a possible worsening of insulin sensitivity and hyperglycaemia in the luteal phase could be observed. From the clinical standpoint, a cautious strategy based on patient-specific patterns can be considered until new, solid evidence is obtained.

The Association Between Physical Activity and Insulin Level Under Different Levels of Lipid Indices and Serum Uric Acid

Objectives

Insulin resistance (IR) has been shown to play important role in the pathogenesis of type 2 diabetes mellitus (T2DM). There is an intricate interplay between IR, dyslipidemia, and serum uric acid (SUA) in people with and without diabetes. Physical activity has a positive impact on insulin sensitivity in insulin-resistant populations. However, the effect of different intensities of physical activity on insulin levels under different lipid indices and SUA levels is unclear.

Methods

To explore the association between physical activity and insulin, we enrolled 12,982 participants aged above 18 years from the National Health and Nutrition Examination Survey (NHANES) conducted between 2009 and 2018. Next, we conducted multivariate logistic regression analyses, generated fitted smoothing curves, and visualized the data using generalized additive models.

Results

Increased intensities of physical activity can significantly reduce insulin levels. The association between physical activity and insulin persisted even after adjusting for confounding factors, with β value (95% CI) = −17.10 (−21.64, −12.56) in moderate group, β value (95% CI) = −28.60 (−33.08, −24.11) in high group, respectively. High-intensity physical activity significantly lowered insulin levels in the lower and higher SUA tertiles, and three tertiles of LDL-c, HDL-c, and TG. Moreover, the link between physical activity and insulin was stronger in male individuals.

Conclusion

This study shows that physical activity can significantly lower insulin levels, and high-intensity physical activity still has additional potential benefits for insulin levels, even in the condition of dyslipidemia and hyperuricemia.

Abnormal carbohydrate metabolism in a canine model for muscular dystrophy

The canine golden retriever muscular dystrophy (GRMD) model is the best animal model for studying Duchenne muscular dystrophy in humans. Considering the importance of glucose metabolism in the muscles, the existence of metabolic and endocrine alterations in a wide range of muscular dystrophies, and the pre-existing relationship between blood insulin concentration and muscular atrophy, the present study aimed to evaluate the postprandial glucose and insulin response in GRMD dogs. A total of eighteen golden retriever dogs were randomly distributed into three experimental groups: healthy/control (G1), female GRMD carriers (G2), and male dogs affected by GRMD (G3). Higher plasma resting glucose levels (P = 0·0047) were seen in G2 and G3 compared with G1, as was the case for minimum (P = <0·0001), mean (P = 0·0002) and maximum (P = 0·0359) glucose values for G3 compared with G1. Fructosamine concentrations were in accordance with reference values found in the literature for dogs. Insulin levels were lower in G3 compared with G1 (P = 0·0065); however, there was no evidence of insulin resistance according to the homeostasis model assessment index values obtained. As for the evaluation of postprandial responses, fluctuations of glucose (P = 0·0007) and insulin (P = 0·0149) were observed in G1 and G2, while in G3 the values remained constant. The results allowed us to identify metabolic changes related to carbohydrate metabolism in GRMD dogs, highlighting the importance of adequate food management for these animals.

TFOS DEWS II Sex, Gender, and Hormones Report

One of the most compelling features of dry eye disease (DED) is that it occurs more frequently in women than men. In fact, the female sex is a significant risk factor for the development of DED. This sex-related difference in DED prevalence is attributed in large part to the effects of sex steroids (e.g. androgens, estrogens), hypothalamic-pituitary hormones, glucocorticoids, insulin, insulin-like growth factor 1 and thyroid hormones, as well as to the sex chromosome complement, sex-specific autosomal factors and epigenetics (e.g. microRNAs). In addition to sex, gender also appears to be a risk factor for DED. "Gender" and "sex" are words that are often used interchangeably, but they have distinct meanings. "Gender" refers to a person's self-representation as a man or woman, whereas "sex" distinguishes males and females based on their biological characteristics. Both gender and sex affect DED risk, presentation of the disease, immune responses, pain, care-seeking behaviors, service utilization, and myriad other facets of eye health. Overall, sex, gender and hormones play a major role in the regulation of ocular surface and adnexal tissues, and in the difference in DED prevalence between women and men. The purpose of this Subcommittee report is to review and critique the nature of this role, as well as to recommend areas for future research to advance our understanding of the interrelationships between sex, gender, hormones and DED.

Developmental Issues in the Treatment of Diabetic Women

The physiological and psychological effects of diabetes on women show changes with age. Behavioral interventions on behalf of diabetic women must be based on an understanding of these life span changes. A review of selected articles from the medical and psychological literature that focus on special issues for a diabetic woman during preadolescence, adolescence, and adulthood is presented. Recommendations are made for behavioral interventions with diabetic women in regard to “sick” role adjustment, peer conformity pressures, eating disorders, sexuality, and pregnancy.

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.

[Migraine and hormones: what can we be certain of?]

Women suffer from migraine far more frequently than men. This sex difference during the reproductive years is considered to result from additional trigger factors, such as the fluctuating hormones of the menstrual cycle and with the reproductive milestones of women. The role of the female hormones on migraine is illustrated by the phenomenon of menstrual migraine, and the changes in the clinical course of migraine with menarche, pregnancy, menopause and the external application of hormones. In summary, epidemiological, clinical and experimental studies document a substantial influence of female sex hormones on the pathophysiology of migraine headache.

Are the available experimental models of type 2 diabetes appropriate for a gender perspective?

Several experimental models have so far been developed to improve our knowledge of the pathogenetic mechanisms of type 2 diabetes mellitus (T2D), to determine the possible pharmacological targets of this disease and to better evaluate diabetes-associated complications, e.g. the cardiovascular disease. In particular, the study of T2D gained the attention of several groups working with different animal species: rodents, cats or pigs, as well as other non-human primate species. Each of these species provided useful and different clues. However, T2D has to be considered as a gender-associated disease: sex differences play in fact a key role in the onset as well as in the progression of the disease and a higher mortality for cardiovascular diseases is detected in diabetic women with respect to men. The results obtained from all the available animal models appear to only partially address this issue so that the search for more precise information in this respect appears to be mandatory. In this review we summarize these concepts and literature in the field and propose a reappraisal of the various animal models for a study of T2D that would take into consideration a gender perspective.

Interactions of metabolic hormones, adipose tissue and exercise

Physiological and psychological systems work together to determine energy intake and output, and thus maintain adipose tissue. In addition, adipose tissue secretes leptin and cytokines, which induces satiety and has been linked to catecholamines, cortisol, insulin, human growth hormone, thyroid hormones, gonadotropin and lipolysis. Thus, adipose tissue is acted upon by a number of physiological stimuli, including hormones, and simultaneously, is an active component in the regulation of its own lipid content. All of the hormones mentioned above are associated with each other and respond to exercise and exercise training. Thus, exercise is one of the major links between the hormonal modulators of energy intake and output. It appears that the sympathetic nervous system and the catecholamines are key components facilitating the lipolytic activity during exercise. These two neuroendocrine factors directly affect adipose metabolism and metabolic hormones that influence adipose metabolism. Acute low- and moderate-intensity exercise causes hormonal changes that facilitate lipolytic activity. Exercise training reduces these hormonal responses, but the sensitivity to these hormones increases so that lipolysis may be facilitated. Large amounts of adipose tissue blunt the metabolic hormonal responses to exercise, but the sensitivity of these hormones is increased; thus maintaining normal lipolytic activity. Although the physiological role of the endocrine system during exercise and training is significant, other training effects may have as great, or greater influence on lipolytic activity in adipose tissue.

Gender-dependent effect of ageing on peripheral insulin action

The aim of the present study was to investigate the effect of both gender and age on insulin secretion, peripheral insulin effectiveness and insulin-receptor binding. Eighty healthy volunteers, 40 females of mean age 38.47 +/- 11.37 years and mean BMI 21.99 +/- 2.06 kg/m(2) and 40 males of mean age 34.87 +/- 11.22 years and mean BMI 22.65 +/- 2.31 kg/m(2), with normal glucose tolerance participated in the study. Peripheral insulin effectiveness was measured by the artificial endocrine pancreas, using the euglycaemic hyperinsulinaemic clamp technique and insulin-receptor binding on circulating mononuclear blood cells. Peripheral insulin sensitivity was significantly higher in females as compared to males (p < 0.001), while males demonstrated higher total number of insulin receptors (p < 0.0001) and number of high-affinity receptors (p < 0.01). Peripheral insulin sensitivity decreased with ageing in both males and females, the reduction in females being more pronounced (p < 0.05). In the group under 40 years, the females demonstrated significantly higher insulin sensitivity as compared to males (p < 0.001) and lower insulin-receptor binding. Over 40 years, females presented higher peripheral insulin sensitivity and higher insulin-receptor binding. The percentage of specifically bound insulin increased significantly with ageing in females and decreased in males. We consider that probably the higher androgen level in males affects the post-receptor processes in insulin action and despite the higher insulin-receptor binding, males have lower insulin sensitivity. The androgen levels in females increase with ageing, which could probably affect peripheral insulin sensitivity at the post-receptor level. In conclusion, our results demonstrate that when analysing peripheral insulin effectiveness and insulin-receptor binding, one should always consider both gender and age.

17β-Estradiol transcriptionally represses human insulin receptor gene expression causing cellular insulin resistance

In this study, we demonstrate that 17beta-estradiol (E(2)) inhibits human insulin receptor (IR) gene expression in a dose- and time-dependent manner in U-937 human promonocytic cells. Using cells transfected with the -1819 to -271 bp fragment of the human IR promoter (wild type promoter) and treated with E(2), we show that this repression is regulated at the transcriptional level. The steroid was also found to diminish the insulin responsiveness of the cells in terms of cell survival, DNA synthesis, glucose transport, and glucose oxidation, this last effect possibly involving reduced phosphatidylinositol 3-kinase (PI3-kinase) activity. These data provide new information on the molecular mechanisms of estrogen-inducing insulin resistance in human cells.

Cyclic changes in glycemia assessed by continuous glucose monitoring system during multiple complete menstrual cycles in women with type 1 diabetes

Many women with diabetes notice changes in glucose control perimenstrually. To describe the pattern of changes in glucose control throughout the complete menstrual cycle, and the reproducibility of these changes, we performed a pilot study evaluating glycemic profiles continuously for three cycles in four women with type 1 diabetes. All participants had hemoglobin A1c <7.5% and regular menstrual periods off oral contraceptives. They used Medtronic MiniMed (Northridge, CA) Continuous Glucose Monitoring System (CGMS) devices continuously for three complete menstrual cycles, checked capillary glucose measurements six times daily, changed their own sensors every 3 days, and were seen seven times per menstrual cycle to download data and draw blood. Prolonged monitoring was safely carried out over three consecutive menstrual cycles. We observed two different patterns of glycemic control in relation to the menstrual cycle in these women. The first pattern, seen in two women, was characterized by increased frequency of hyperglycemia in the luteal phase. One of these women also had a hyperglycemic peak in the follicular phase. In the other two women, no characteristic cycle-related pattern was noted. The glucose profiles appeared reproducible between cycles in all women, but varied between women. Thus the menstrual cycle has a reproducible effect on glucose control in a subset of women with type 1 diabetes. Prolonged use of continuous glucose monitoring was safe in the subjects studied, and is the first method clinically available to monitor glucose control over prolonged periods in individuals with diabetes.

Efficacy and safety of oral and transdermal hormonal replacement treatment containing levonorgestrel

OBJECTIVES

The oral combined formulation of levonorgestrel with estradiol valerate (LNG+EV) has demonstrated to be effective on some postmenopausal symptoms. The availability of a transdermal HRT in sequential formulation with 17-beta-estradiol plus levonorgestrel (TSE2+TSLNG) induced us to do this control-study with the aim to evaluate the efficacy and safety of both oral and transdermal treatments.

METHODS

At baseline, the psychological symptoms with the psychometric scale SCL-90, the bone resorption with the measurement of the urinary levels of pyridinoline and dexoxypirydinoline, and the insulin and lipid metabolism were assessed in 30 postmenopausal women (PMW) and in 18 premenopausal women. Then, the PMW women were randomly divided in three groups: group A (N=10) assumed EV+LNG, group B (N=10) did not assume any treatment, group C (N=10) was treated with TSE2+TSLNG. The length of the study was 12 months. The aforementioned assessments were repeated at different time-intervals up to the end of the study.

RESULTS

The total score of SCL-90, the bone resorption, the levels of LDL-cholesterol, total-cholesterol and the parameters of insulin metabolism were higher in PMW than in premenopausal women. During the study, the SCL-90, the bone resorption, total-cholesterol, and LDL-cholesterol levels significantly decreased only in the groups A and C. By contrast, in the group B bone resorption significantly increased at the 12th month. During the treatments, insulin metabolism did not change in the groups A and B. In the group C the secretion of C-peptide and the C-peptide:insulin ratio after OGTT were significantly higher at the 12th month than before treatment. In all groups the endometrium thickness did not change during the study.

CONCLUSION

A 12-month of either oral or transdermal HRT containing levonorgestrel seems to exert beneficial effects on the main postmenopausal symptoms without negative interferences on the endometrium.

Menstrual cycle effects on common medical conditions

Menstrual cycle-related exacerbation of common medical conditions such as migraine, epilepsy, asthma, irritable bowel syndrome, and diabetes, is a well-recognized phenomenon. Accurate documentation of symptoms on a menstrual calendar allows identification of women with cyclic alterations in disease activity.

Changes in insulin sensitivity, secretion and glucose effectiveness during menstrual cycle

BACKGROUND

Several clinical conditions suggest an effect of sex steroids on glucose homeostasis in women. Studies examining this phenomenon have yielded controversial results.

METHODS

To investigate the effect of the menstrual cycle on insulin sensitivity, glucose effectiveness and acute insulin response to glucose using the tolbutamide-modified intravenous glucose tolerance test (IVGTT) during the follicular (day 8 +/- 1) and luteal (day 23 +/- 1) phases of the menstrual cycle, the authors recruited 12 healthy regularly menstruating women. All had fasting glucose concentration of < 100 mg/dl [corrected] (89.7 +/- 6.2) with no family history of diabetes mellitus; their body mass indices were < 25 kg/m2 (22.41 +/- 1.44 kg/m2).

RESULTS

The mean insulin sensitivity (Si) values decreased during the cycle. Insulin sensitivity (Si x 10(-4)/min.mU/ml) was higher in the follicular phase (5.03 +/- 0.72) and decreased in the luteal phase (2.22 +/- 0.45) (p < 0.001). Glucose effectiveness (Sg min-1) did not change as a function of the phase of the menstrual cycle. Sg estimates were 0.0229 +/- 0.00323 in the follicular phase, and 0.0225 +/- 0.00319 (p = NS) in the luteal phase, respectively. Acute insulin response (AIRg mU/ml) was 276.4 +/- 27.8 in the follicular phase. An adaptive increase (304.4 +/- 51.1) in response to the insulin resistance during the luteal phase was observed, but this increase was not statistically significant (p = NS).

CONCLUSIONS

Knowledge of the variations in insulin sensitivity that occur during the normal menstrual cycle provides a basis of comparison for studies of other clinical conditions. Also, this phenomenon should be considered if the determination of insulin resistance is the purpose of certain epidemiological studies.

Training-induced alterations of carbohydrate metabolism in women: women respond differently from men

We examined the hypothesis that glucose flux was directly related to relative exercise intensity both before and after a 12-wk cycle ergometer training program [5 days/wk, 1-h duration, 75% peak O2 consumption (VO2 peak)] in healthy female subjects (n = 17; age 23.8 +/- 2.0 yr). Two pretraining trials (45 and 65% of VO2 peak) and two posttraining trials [same absolute workload (65% of old VO2 peak) and same relative workload (65% of new VO2 peak)] were performed on nine subjects by using a primed-continuous infusion of [1-13C]- and [6,6-2H]glucose. Eight additional subjects were studied by using [6, 6-2H]glucose. Subjects were studied postabsorption for 90 min of rest and 1 h of cycling exercise. After training, subjects increased VO2 peak by 25.2 +/- 2.4%. Pretraining, the intensity effect on glucose kinetics was evident between 45 and 65% of VO2 peak with rates of appearance (Ra: 4.52 +/- 0.25 vs. 5.53 +/- 0.33 mg . kg-1 . min-1), disappearance (Rd: 4.46 +/- 0.25 vs. 5.54 +/- 0.33 mg . kg-1 . min-1), and oxidation (Rox: 2.45 +/- 0.16 vs. 4.35 +/- 0.26 mg . kg-1 . min-1) of glucose being significantly greater (P </= 0.05) in the 65% than in the 45% trial. Training reduced Ra (4.7 +/- 0.30 mg . kg-1 . min-1), Rd (4.69 +/- 0.20 mg . kg-1 . min-1), and Rox (3.54 +/- 0.50 mg . kg-1 . min-1) at the same absolute workload (P </= 0. 05). When subjects were tested at the same relative workload, Ra, Rd, and Rox were not significantly different after training. However, at both workloads after training, there was a significant decrease in total carbohydrate oxidation as determined by the respiratory exchange ratio. These results show the following in young women: 1) glucose use is directly related to exercise intensity; 2) training decreases glucose flux for a given power output; 3) when expressed as relative exercise intensity, training does not affect the magnitude of blood glucose flux during exercise; but 4) training does reduce total carbohydrate oxidation.

Effects of estradiol on substrate turnover during exercise in amenorrheic females

The purpose of this investigation was to determine the effects of transdermal estradiol (E2) replacement on substrate utilization during exercise. Amenorrheic females (N = 6) performed three exercise trials following 72 h of placebo (C 72) and 72 and 144 h of medicated transdermal estradiol (E2) treatment (E2 72 and E2 144). Exercise involved 90 min of treadmill running at 65% VO2max followed by timed exercise to exhaustion at 85% VO2max. Resting blood samples were obtained for glucose, insulin, free fatty acids (FFA), and E2. Exercise blood samples were obtained for E2, lactate, epinephrine, and norepinephrine. Rates of appearance and disposal were calculated for glucose and glycerol using a primed, continuous infusion of [6,6-2H] glucose and [2H5] glycerol. Medicated transdermal placement increased E2 significantly at rest, before exercise (35.03 +/- 12.3, 69.5 +/- 20.1, and 73.1 +/- 31.6 pg.mL-1 for the C 72, E2 72, and E2 144 trials, respectively, P < 0.05). Resting FFA increased significantly following E2 treatment (0.28 +/- 0.16, 0.41 +/- 0.27, and 0.40 +/- 0.21 mmol.L-1 for the C 72, E2 72, and E2 144 trials, respectively, P < 0.05). Glucose Ra was significantly decreased during exercise as a result of E2 replacement (21.9 +/- 7.7, 18.9 +/- 6.2, and 18.9 +/- 5.6 mumol.kg-1.min-1 for the C 72, E2 72, and E2 144 trials, respectively, P < 0.05). Average glucose Rd also decreased during exercise as a result of E2 replacement (21.3 +/- 7.8, 18.5 +/- 6.4, and 18.6 +/- 5.8 mumol.kg-1.min-1 for the C 72, E2 72, and E2 144 trials, respectively, P < 0.05). However, the estimated relative contribution of plasma glucose and muscle glycogen to total carbohydrate oxidation was similar among the trials. Epinephrine values were significantly lower late in exercise during the E2 72 and E2 144 trials, compared with the C 72 trial (P < 0.05). These results indicate that elevated E2 levels can alter glucose metabolism at rest and during moderate intensity exercise as a result of decreased gluconeogenesis, epinephrine secretion, and/or glucose transport.

Effects of obesity and gender on insulin receptor expression in liver of SHHF/Mcc-FAcp rats

In SHHF/Mcc-FAcp rats (formerly SHR/Mcc-cp), obesity and male gender synergistically modulate hyperinsulinemia, insulin resistance and predisposition to diabetes. Our previous studies showed gender and obesity modulate hepatic cell surface insulin binding and insulin clearance additively. Hepatic insulin receptors (IR) bind insulin as a first step in insulin clearance through internalization and degradation. We hypothesize that the synergistic effects of obesity and gender on hepatic insulin binding and clearance result from interaction of these two factors on hepatic IR expression. To address IR expression in SHHF/Mcc-FAcp rats, we quantitated IR protein levels in detergent-solubilized liver homogenates by Western blotting and IR mRNA levels by a solution hybridization/RNase protection assay. Obesity reduced total hepatic IR content in males and females, 50% and 68% respectively. Male gender reduced IR protein content 24% in lean, but had no effect on IR protein content in obese rats. Neither gender nor obesity affected hepatic IR mRNA content. Thus, obesity appears to affect hepatic IR protein content and cell surface binding through post-transcriptional mechanisms; similarly, male gender in lean rats reduces IR protein levels and cell surface binding through mechanisms not involving changes in mRNA levels. In obese rats, the synergistic effects of male gender appears to involve changes in IR trafficking and consequently cell surface insulin binding and processing.

Symptoms at the menopausal and premenopausal years: their relationship with insulin, glucose, cortisol, FSH, prolactin, obesity and attitudes towards sexuality

The symptoms of 81 premenopausal and 70 menopausal women were studied to determine the association with obesity, attitudes towards sexuality (ATS), and diverse hormone values: fasting and postprandial glucose (FG, PG) and insulin (FI, PI), cortisol, prolactin, follicle-stimulating hormone (FSH). The mean age of the women studied was 49.1 years. The frequency of symptoms was 35.4% for depression, 34.3% for nonspecific symptoms of depression (NSSD), 38.6% for empty nest syndrome (ENS), and 42.3% for anxiety. NSSD, ENS, FSH and cortisol levels all possessed higher values at late-menopausal stage. A multiple regression analysis revealed the following results; NSSD was associated to ATS (negative); sleep alterations were correlated to prolactin, FSH, PI/PG, FI/FG and waist/hip ratio; FSH was associated with both a decreased sexual interest and depression. In the study of hormone levels it was found that cortisol, insulin and FI/FG were associated with ATS; PI, cortisol, FI/FG and PI/PG were associated with body mass index (BMI) and FSH; prolactin and FI/FG were associated with age. We concluded that: (1) data indicative of insulin resistance correlated to both depression and sleep alterations; (2) overweight is related to NSSD, sleep alterations, and hormonal changes.

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.

Metabolic control, food intake and mood during the menstrual cycle in patients with insulin-dependent diabetes

The impact of menstruation on metabolic control was studied among 20 insulin-dependent diabetics (IDDM) and 20 healthy controls during two menstrual cycles. No systematic fluctuation in glycated protein, blood glucose levels, food intake, intake of mono- and disaccharides, body weight, or mood could be seen during different weeks in the menstrual cycle. A tendency towards menstruation-related variations in the number of insulin reactions and amount of extra injected insulin was observed in the patient group. Levels of glycated protein were significantly (P < 0.05) higher during the premenstruational than during the postmenstruational week, although the difference was small in absolute terms. A poorer mood during the premenstruation weeks (indicating premenstruation syndrome) was associated with a high number of hypoglycemic events (P < 0.01) and frequent changes in insulin doses (P < 0.01). Thus, taken as a group diabetic women do not experience great changes in food intake or metabolic control during the menstrual cycle. This does not exclude the possibility that a small proportion of women have major menstruation related difficulties in controlling their diabetes.

Gender differences in substrate utilisation during exercise

The selection and utilisation of metabolic substrates during endurance exercise are regulated by a complex array of effectors. These factors include, but are not limited to, endurance training and cardiorespiratory fitness, exercise intensity and duration, muscle morphology and histology, hormonal factors and diet. Although the effects of these factors on substrate utilisation patterns are well understood, the variation in substrate utilisation during endurance exercise between males and females is not. Because of the extreme heterogeneity in exercise protocols and individuals studied, the differences in substrate utilisation between males and females remain somewhat inconclusive. Regardless of heterogeneity, if the results from studies are interpreted collectively, an apparent gender difference in the selection and metabolism of substrates can be seen in sedentary individuals. However, this difference between genders diminishes as the level of cardiorespiratory fitness is increased to that of highly trained individuals. During rest and lower intensity exercise, the preferential metabolism of lipid occurs with a concomitant sparing of muscle glycogen. However, as the intensity of exercise is increased, the relative contribution of carbohydrate also increases. The exercise intensity at which the shift from lipid to carbohydrate is determined and regulated by the previously mentioned factors. Because the intensity and duration of exercise play a predominant role, the variation in exercise protocols poses a methodological concern when interpreting previous research. When attempting to compare the metabolism of substrates during endurance exercise, appropriate selection and interpretation of measurement techniques are necessary. Measurement techniques include the nonprotein respiratory exchange ratio, muscle and fat biopsies and the measurement of various blood metabolites, such as free fatty acids and glycerol. Similarly, in vitro analysis of lipolytic activity has also been demonstrated in males and females in response to varying levels of female gonadotrophic hormones. When comparing the substrate utilisation patterns between males and females, the area of hormonal regulation has received less attention. Often the catecholamine response to endurance exercise is measured; however, the gonadotrophic hormones, particularly those of the female, have received less attention when comparing genders. Indeed, the regulatory nature of the female gonadotrophic hormones has been demonstrated. Collectively, the effects of elevated estrogen, as in the luteal phase of menstruation, appear to promote lipolytic activity. Estrogen-mediated lipolytic activation occurs by apparently altering the sensitivity to lipoprotein lipase and by increasing the levels of human growth hormone (somatotropin), an activator of lipolysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Prospective evaluation of insulin resistance and lipid metabolism in women receiving oral contraceptives

OBJECTIVES

It has been suggested that normal women receiving oral contraceptives (OC) may develop a series of metabolic side-effects which relate to the risk of cardiovascular disease. These metabolic disturbances include changes in glucose and insulin metabolism, raised serum lipid and lipoprotein concentrations and elevated blood pressure. All these changes indicate that OC might cause insulin resistance. We have prospectively examined the effect of OC on insulin resistance and lipid metabolism including Lp(a) values.

PATIENTS

The study group comprised 13 normally menstruating Chinese women.

DESIGN

The study subjects were given a combined triphasic oral contraceptive which was administered on a 21-day on, 7-day off medication cyclic regimen, the first pill being administered on day 5 from the beginning of menses. The metabolic investigations were carried out during luteal phase before OC and again the third week of the third month of OC administration.

MEASUREMENTS

Metabolic evaluation including insulin secretion and insulin-mediated glucose uptake were evaluated by oral glucose tolerance test and the modification of insulin suppression test. Fasting triglyceride, cholesterol, HDL-cholesterol and Lp(a) concentrations were also measured.

RESULTS

The plasma glucose and insulin responses during a 75-g oral glucose challenge increased significantly (P < 0.05 and P < 0.03, respectively). The steady-state plasma glucose (SSPG) concentrations achieved during constant infusion of glucose, insulin and somatostatin increased significantly after 3 cycles of OC administration (glucose 7.5 +/- 0.8 vs 12.4 +/- 0.7 mmol/l, P < 0.001) while the steady-state plasma insulin (SSPI) concentrations were relatively similar (410 +/- 14 vs 391 +/- 7 pmol/l, NS). Plasma triglyceride levels increased significantly (0.81 +/- 0.12 vs 1.09 +/- 0.19 mmol/l, P < 0.03) following OC administration. Fasting plasma cholesterol, HDL cholesterol and calculated LDL cholesterol concentrations did not change as compared with baseline values, nor did the ratio of total cholesterol to HDL cholesterol. The Lp(a) concentrations did not change during the administration of OC (81 +/- 25 vs 71 +/- 21 mg/l, NS).

CONCLUSIONS

These data indicated that intake of OC for 3 cycles induced glucose intolerance, hyperinsulinaemia and insulin resistance in normal menstruating Chinese women. These changes occurred in association with elevated plasma triglyceride concentrations and no alteration in Lp(a) or other lipid values.

Altered regulation of cholesterol metabolism in type I diabetic women during the menstrual cycle

This study examines the relationship of cellular cholesterol metabolism to oestrogen and progesterone during the menstrual cycle in diabetic and non-diabetic subjects. Nine premenopausal diabetic women were compared to nine non-diabetic women of the same age. Oestrogen, progesterone, lipoproteins, including lipoprotein (a) (Lp(a)) and cholesteryl ester transfer protein (CETP) were determined in serum. Cellular cholesterol content and cellular cholesterol synthesis were measured in mononuclear leucocytes. There was no significant change in serum lipoproteins including Lp(a) during the cycle in either group. CETP activity was significantly higher over the 4 weeks in the diabetic patients compared with non-diabetic subjects (mean 463 +/- 30 mumol l-1 h-1 vs 405 +/- 28 mumol l-1 h-1, p < 0.01). Serum high density lipoprotein (HDL) cholesterol was significantly lower during the 4 weeks in the diabetic patients (1.7 +/- 0.1 mmol l-1 vs 1.8 +/- 0.1 mmol-1, p < 0.05). Cellular cholesterol synthesis decreased steadily up to the third week in cells from the control subjects whereas there was no significant change in cells from diabetic patients whose cellular cholesterol synthesis was higher at week 3 compared with non-diabetic subjects (663 +/- 54 nmol mg-1 cell protein vs 432 +/- 43 nmol mg-1 cell protein, two-way interaction p < 0.05). There was a significant negative correlation between cellular cholesterol synthesis and serum oestrogen in the non-diabetic subjects (p < 0.05) but not in the diabetic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin binding to erythrocytes of nonpregnant women: a reevaluation, underlining the importance of body weights even in nonobese subjects

Insulin binding to erythrocytes was measured in 18 healthy, non-obese women in the follicular phase and in 6 women in the mid-luteal phase of the same menstrual cycle. The presence of 55 nM and 220 nM monoclonal anti-IGF I receptor antibody (alpha-IR3) reduced only the number of low affinity binding sites for insulin by 20% and 33%, respectively. Women with relative body weights 110-119% had a lower number of high affinity receptors and an increased high affinity compared to women with relative body weights 91-109%. In women with relative body weights greater than or equal to 100%, maximum specific binding and high affinity constants increased and the receptor numbers decreased from the follicular to the luteal phase, whereas in women with relative body weights less than 100% the parameter changes were reverted. The data indicate: (1) erythrocytes contain two different classes of binding sites for insulin, (2) IGF I receptors might contribute to low-affinity binding of insulin to erythrocytes and (3) the relative body weight must be considered even for 'non-obese' control groups used in insulin binding studies of various clinical conditions.

Red blood cell insulin receptors in health and disease

CONTENTS

Structure and characteristics of erythrocyte insulin receptor. Red blood cell age and insulin receptors. Insulin receptors in human disease states. Obesity. Chronic renal failure. Acanthosis nigricans. Miscellaneous disease states. Insulin receptors in children. Insulin receptors in women during pregnancy. Insulin binding and other hormones. Comparison of biosynthetic insulin, pancreatic human insulin and porcine insulin binding to erythrocytes. Effect of exercise on insulin binding to red blood cells of normal human volunteers. Miscellaneous insulin binding studies. Insulin internalization and degradation. Insulin and erythrocyte metabolism. Summary and conclusion.

Effect of phase of menstrual cycle on insulin sensitivity, peripheral blood flow and cardiovascular responses to hyperinsulinaemia in young women with type 1 diabetes

Disturbances of blood glucose control around the time of menstruation are often reported by women with Type 1 diabetes. To investigate the possibility that such changes may be due to alterations in insulin sensitivity or peripheral blood flow we have studied 9 women with Type 1 diabetes during the follicular and luteal phases of the menstrual cycle. Insulin sensitivity was assessed by the glucose clamp technique with insulin doses of 40 (low dose) and 100 (high dose) mU m-2 min-1. Glucose disposal rates were 2.5 +/- 0.3 (mean +/- SE) mg kg-1 min-1 during the follicular phase and 3.2 +/- 0.3 mg kg-1 min-1 in the luteal phase with low dose insulin, and 5.9 +/- 0.4 and 6.4 +/- 0.6 mg kg-1 min-1, respectively, with high dose insulin. These differences were not statistically significant. Forearm blood flow, heart rate, and blood pressure were similar during both phases.

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.

Characterization of differences in insulin receptors from young and old red blood cells

It has been demonstrated that young RBCs (reticulocytes and early mature erythrocytes) possess more insulin receptors than old RBCs (late mature erythrocytes) but it is not yet known whether insulin receptors on young and old RBCs are regulated similarly. In the present investigation insulin receptors on young and old RBCs have, therefore, been studied in five normal male subjects before and after 2 days dexamethasone ingestion (0.5 mg tablet every 6 h) and, in the same subjects, before and 5 h after ingestion of 75 g glucose. The results obtained clearly demonstrate that dexamethasone increases insulin receptor concentration while glucose ingestion increases both insulin receptor affinity and concentration on young RBCs. By contrast, neither stimuli modify insulin receptors on old RBCs. Studies on RBCs are usually performed on the whole RBC population not taking into account this differential responsiveness of receptors on young versus old RBCs; consequently, this phenomenon might be responsible of the fact that some data reported on RBCs are not in agreement with those reported on monocytes or adipocytes and it should be taken into consideration when using RBCs to evaluate insulin receptor regulation.

The treatment of poorly controlled non-insulin-dependent diabetic subjects with granulated guar gum

The treatment of poorly controlled, non-compliant non-insulin-dependent diabetic subjects for one month with guar granules (Guarem) was associated with significant improvements in fasting serum glucose and insulin and urinary glucose excretion. No significant change was observed in either oral glucose tolerance, erythrocyte insulin receptor binding, serum calcium, cholesterol, triglyceride or HbA1. Subjects reported significant side effects including excessive flatus, increased bowel frequency and fullness. The limited advantages of Guarem treatment must be measured against the possibility of these side effects which to a large extent may be avoided by special attention to the means of administration. Prudent supplementation of the diet with Guarem has undoubted potential for diabetic control.

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.

Nonhuman primate models of atherosclerosis: potential for the study of diabetes mellitus and hyperinsulinemia

Nonhuman primates have been used for many years to investigate the pathogenesis and progression of atherosclerosis. The use of these animal models has resulted in a better understanding of the risk factors associated with atherosclerosis. Nonhuman primates that have consumed an atherogenic diet for several years develop lesions that are comparable to those found in human beings. Diabetes, both spontaneous and chemically induced, has been described in a number of nonhuman primate species. These diabetic models may be used to understand the accelerated progression and vascular complications of atherosclerosis in diabetic human beings.

Differences in insulin sensitivity between normal men and women

An incremental intravenous low-dose insulin infusion has been used to examine differences in insulin sensitivity between normal young men and women. Fasting blood glucose concentration did not differ significantly at the start of the infusion but women had significantly higher plasma insulin and C-peptide concentrations. Similar changes in blood glucose occurred during insulin infusion but insulin concentrations were higher in women. Blood total ketone bodies and alanine were lower in women over the four hours of infusion. Significant differences were found between normal men and women for the effect of insulin upon blood glucose concentration.

Metabolic responses to physical training in young insulin-dependent diabetics

Insulin-dependent (type 1) diabetics, aged 14-17 years, were studied according to two protocols. During a 6-month training period of moderate intensity (six participants) the aerobic work capacity and the erythrocyte insulin binding increased by 19% and 28%, respectively. Glycosylated haemoglobin (HbA1) was not significantly reduced. A 2-week intensive physical training program (10 participants) was associated with a 50% decrease of blood glucose values, which did not last beyond the training period. Plasma ketone bodies were markedly reduced. We conclude that young type 1 diabetics may participate in strenuous, short-term physical training. The improved aerobic work capacity and increased cellular insulin binding observed during training of moderate intensity is of potential benefit in the long-term management of the patients.

Quality control of insulin radioreceptor assay for human erythrocytes. Effect of ageing of mono-125I-Tyr-A14-insulin preparation

The quality control of insulin radioreceptor assay for human erythrocytes is based on the storage of erythrocyte preparations in Hepes buffer of pH 8.0, containing 10 g/l of albumin and 20 mmol/l of glucose. The change of erythrocytes into spherocytes and crenated cells reduces the apparent number of insulin receptors in a relatively constant way by less than 8% a week after 10 days of storage. At the same time the dissociation constants of the insulin-receptor complex increase rapidly. Thus the use of a preparation must be limited to controlling the determination of the insulin binding sites of erythrocytes, and not to the measurement of the affinities of the receptors. When mono-125I-Tyr-A14-insulin gets old, a slow decrease in the insulin binding sites can be measured, but the dissociation constants of the insulin receptor complex are not affected.

Binding of tyrosine-A-14(125I)-monoiodoinsulin to human erythrocytes

We have studied the method for the determination of human erythrocyte insulin receptor concentrations using tyrosine-A-14-monoiodoinsulin as the labelled ligand with increasing amounts of unlabelled insulin in a saturation assay. An overnight incubation at 0-+4 degrees C was found to give the highest receptor concentrations and highest affinities for the ligand. Insulin receptor concentrations were found to be very low and lower in erythrocytes from normal females than from normal male subjects (7.0 +/- 1.9 and 10.5 +/- 1.6 receptors per erythrocyte, respectively). Our results suggest that an initially homogenous class of insulin binding sites upon exposure to insulin can appear in different forms with different binding affinities for the ligand. This was deduced from the changes in the forms of Scatchard plots when the saturation assay was performed at different times at low temperature. Variability in the forms of Scatchard plots (linear to biphasic or vice versa) in samples obtained on different occasions from the same subjects also support this view. The apparent dissociation constants (mean values) were 150 and 550 pmol/l for the linear components of the biphasic plots and 300 pmol/l for the linear plot. These values lie well within the normal plasma concentrations of insulin. Addition of spermine to the incubation mixture was shown to further accentuate the high affinity part of the Scatchard plot. The high and low affinity forms of the receptor could provide an ideal means to rapidly regulate the response to insulin.

Human erythrocyte insulin receptors in normal male and female subjects

Human red blood cells (RBC) have been shown to have highly specific insulin receptors. We have studied the binding characteristics of insulin to these receptors in erythrocytes from normal male and female subjects on their usual diet and physical activity. There were no significant differences in insulin binding in erythrocytes from females between the two phases of the menstrual cycle. However, the receptor concentration was higher in the 2nd half of the cycle accompanied by a reduction in affinity. Binding curves of 125-I-insulin to RBC from males were higher than females in either phases of the menstrual cycle, primarily due to an increase in receptor concentration when compared to females in the follicular phase and mediated by an increased affinity at low receptor occupancy when compared to females in the luteal phase. We speculated that the differences in the binding characteristics of 125I-insulin to RBC insulin receptors are mediated by differences in the levels of sex hormones.

Decreased insulin binding to red blood cells in liver cirrhosis

eleven male cirrhotic subjects, all with impaired glucose tolerance (IGT), were studied. Insulin binding to circulating erythrocytes was evaluated. The specific bound fraction was decreased compared to normals (5.95 +/-0.76 vs 7.08 +/- 0.84%; p less than 0.005). An negative correlation was found between fasting insulin and bound fraction (r = -0.68; p less than 0.05). We suggest that serum insulin may be chronically augmented as a consequence of liver damage. This induces a down-regulation of insulin receptors that is responsible for insulin resistance and at least in part for the impairment of glucose tolerance.

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.