Alterations in plasma non-esterified fatty acid (NEFA) kinetics and relationship with insulin resistance in polycystic ovary syndrome

Alterations in nonesterified free fatty acid trafficking rather than hyperandrogenism contribute to metabolic health in obese women with polycystic ovary syndrome

OBJECTIVE

To determine whether alterations in nonesterified fatty acid (NEFA) dynamics or degree of hyperandrogenism (HA) contribute to the difference in insulin sensitivity between women with metabolically healthy obese polycystic ovary syndrome (PCOS) (MHO-PCOS) and women with metabolically unhealthy obese PCOS (MUO-PCOS).

DESIGN

Prospective cross-sectional study.

SETTING

Tertiary-care academic center.

PATIENTS

One hundred twenty-five obese women with PCOS.

INTERVENTION

Consecutive obese (body mass index [BMI] ≥ 30 kg/m2) oligo-ovulatory women (n = 125) with PCOS underwent an oral glucose tolerance test and a subgroup of 16 participants underwent a modified frequently sampled intravenous glucose tolerance test to determine insulin-glucose and -NEFA dynamics.

MAIN OUTCOME MEASURES

Degree of insulin resistance (IR) in adipose tissue (AT) basally (Adipo-IR) and dynamically (the nadir in NEFA levels observed [NEFAnadir], the time it took for NEFA levels to reach nadir [TIMEnadir], and the percent suppression in plasma NEFA levels from baseline to nadir [%NEFAsupp]); peak lipolysis rate (SNEFA) and peak rate of NEFA disposal from plasma pool (KNEFA); whole-body insulin-glucose interaction (acute response of insulin to glucose [AIRg], insulin sensitivity index [Si], glucose effectiveness [Sg], and disposition index [Di]); and HA (hirsutism score, total and free testosterone levels, and dehydroepiandrosterone sulfate levels).

RESULTS

A total of 85 (68%) women were MUO-PCOS and 40 (32%) were MHO-PCOS using the homeostasis model of assessment of IR. Subjects with MUO-PCOS and MHO-PCOS did not differ in mean age, BMI, waist-to-hip ratio, HA, and lipoprotein levels. By a modified frequently sampled intravenous glucose tolerance test, eight women with MUO-PCOS had lesser Si, KNEFA, and the percent suppression in plasma NEFA levels from baseline to nadir (%NEFAsupp) and greater TIMEnadir, NEFAnadir, and baseline adipose tissue IR index (Adipo-IR) than eight subjects with MHO-PCOS, but similar fasting NEFA levels and SNEFA. Women with MUO-PCOS had a higher homeostasis model of assessment-β% and fasting insulin levels than women with MHO-PCOS. In bivalent analysis, Si correlated strongly and negatively with Adipo-IR and NEFAnadir, weakly and negatively with TIMEnadir, and positively with KNEFA and %NEFAsupp, in women with MUO-PCOS only.

CONCLUSION

Independent of age and BMI, women with MUO-PCOS have reduced NEFA uptake and altered insulin-mediated NEFA suppression, but no difference in HA, compared with women with MHO-PCOS. Altered insulin-mediated NEFA suppression, rather than HA or lipolysis rate, contributes to variations in insulin sensitivity among obese women with PCOS.

Adipose Tissue Dysfunction in Polycystic Ovary Syndrome

PURPOSE

Polycystic ovary syndrome (PCOS) is a complex genetic trait and the most common endocrine disorder of women, clinically evident in 5% to 15% of reproductive-aged women globally, with associated cardiometabolic dysfunction. Adipose tissue (AT) dysfunction appears to play an important role in the pathophysiology of PCOS even in patients who do not have excess adiposity.

METHODS

We undertook a systematic review concerning AT dysfunction in PCOS, and prioritized studies that assessed AT function directly. We also explored therapies that targeted AT dysfunction for the treatment of PCOS.

RESULTS

Various mechanisms of AT dysfunction in PCOS were identified including dysregulation in storage capacity, hypoxia, and hyperplasia; impaired adipogenesis; impaired insulin signaling and glucose transport; dysregulated lipolysis and nonesterified free fatty acids (NEFAs) kinetics; adipokine and cytokine dysregulation and subacute inflammation; epigenetic dysregulation; and mitochondrial dysfunction and endoplasmic reticulum and oxidative stress. Decreased glucose transporter-4 expression and content in adipocytes, leading to decreased insulin-mediated glucose transport in AT, was a consistent abnormality despite no alterations in insulin binding or in IRS/PI3K/Akt signaling. Adiponectin secretion in response to cytokines/chemokines is affected in PCOS compared to controls. Interestingly, epigenetic modulation via DNA methylation and microRNA regulation appears to be important mechanisms underlying AT dysfunction in PCOS.

CONCLUSION

AT dysfunction, more than AT distribution and excess adiposity, contributes to the metabolic and inflammation abnormalities of PCOS. Nonetheless, many studies provided contradictory, unclear, or limited data, highlighting the urgent need for additional research in this important field.

Adiposity and lipid metabolism indicators mediate the adverse effect of glucose metabolism indicators on oogenesis and embryogenesis in PCOS women undergoing IVF/ICSI cycles

BACKGROUND

Polycystic ovary syndrome (PCOS) women have high incidences of dyslipidemia, obesity, impaired glucose tolerance (IGT), diabetes, and insulin resistance (IR) and are fragile to female infertility. Obesity and dyslipidemia may be the intermediate biological mechanism for the associations between glucose metabolism dysfunction and abnormal oogenesis and embryogenesis.

METHODS

This retrospective cohort study was performed at a university-affiliated reproductive center. A total of 917 PCOS women aged between 20 and 45 undergoing their first IVF/ICSI embryo transfer cycles from January 2018 to December 2020 were involved. Associations between glucose metabolism indicators, adiposity and lipid metabolism indicators, and IVF/ICSI outcomes were explored using multivariable generalized linear models. Mediation analyses were further performed to examine the potential mediation role of adiposity and lipid metabolism indicators.

RESULTS

Significant dose-dependent relationships were found between glucose metabolism indicators and IVF/ICSI early reproductive outcomes and between glucose metabolism indicators and adiposity and lipid metabolism indicators (all P < 0.05). Also, we found significant dose-dependent relationships between adiposity and lipid metabolism indicators and IVF/ICSI early reproductive outcomes (all P < 0.05). The mediation analysis indicated that elevated FPG, 2hPG, FPI, 2hPI, HbA1c, and HOMA2-IR were significantly associated with decreased retrieved oocyte count, MII oocyte count, normally fertilized zygote count, normally cleaved embryo count, high-quality embryo count, or blastocyst formation count after controlling for adiposity and lipid metabolism indicators. Serum TG mediated 6.0-31.0% of the associations; serum TC mediated 6.1-10.8% of the associations; serum HDL-C mediated 9.4-43.6% of the associations; serum LDL-C mediated 4.2-18.2% of the associations; and BMI mediated 26.7-97.7% of the associations.

CONCLUSIONS

Adiposity and lipid metabolism indicators (i.e., serum TG, serum TC, serum HDL-C, serum LDL-C, and BMI) are significant mediators of the effect of glucose metabolism indicators on IVF/ICSI early reproductive outcomes in PCOS women, indicating the importance of preconception glucose and lipid management and the dynamic equilibrium of glucose and lipid metabolism in PCOS women.

Polycystic ovary syndrome and adipose tissue

Polycystic ovary syndrome (PCOS) is the most common endocrine metabolic disorder in women of reproductive age. Typically, it is associated with ovulatory dysfunction: dysovulation or anovulation, and symptoms of hyperandrogenism. It incurs risk of metabolic disorders such as diabetes, dyslipidemia and fatty liver. As a key endocrine organ in metabolic homeostasis, adipose tissue is often implicated in these complications. Studies of white adipose tissue (WAT) in PCOS have focused on the mechanism of insulin resistance in this tissue. Clinically, abnormalities in WAT distribution are seen, with decreased waist-to-hip ratio and increased ratio of adipose to lean mass. Such abnormalities are greater when total circulating androgens are elevated. At tissue level, white adipocyte hyperplasia occurs, along with infiltration of macrophages. Secretion of adipokines, cytokines and chemo-attractant proteins is increased in a pro-inflammatory manner, leading to reduced insulin sensitivity via alteration of glucose transporters, and hence decreased glucose uptake. The kinetics of non-esterified fatty acids (or free fatty acids) is also altered, leading to lipotoxicity. In recent years, brown adipose tissue (BAT) has been studied in women with PCOS. Although abundance is low in the body, BAT appears to play a significant role in energy expenditure and metabolic parameters. Both supra-clavicular skin temperature, which reflects BAT activity, and BAT mass are reduced in women with PCOS. Moreover, BAT mass and body mass index (BMI) are inversely correlated in patients. In the adipocyte, increased total circulating androgen levels reduce expression of uncoupling protein 1 (UCP1), a key protein in the brown adipocyte, leading to reduced biogenesis and mitochondrial respiration and hence a reduction in post-prandial thermogenesis. BAT is currently being investigated as a possible new therapeutic application.

Association of severity of menstrual dysfunction with hyperinsulinemia and dysglycemia in polycystic ovary syndrome

STUDY QUESTION

Is the severity of menstrual cyclicity related to hyperinsulinemia and dysglycemia in women with hyperandrogenic polycystic ovary syndrome (PCOS)?

SUMMARY ANSWER

Hyperandrogenic PCOS women with amenorrhea, compared to those with oligomenorrhea or eumenorrhea, had a greater risk of post-challenge hyperinsulinemia, which may explain their higher prevalence of dysglycemia.

WHAT IS KNOWN ALREADY

PCOS is associated with metabolic dysregulation including insulin resistance (IR) and hyperinsulinemia, risk factors for type 2 diabetes mellitus (T2DM) and other vascular-metabolic morbidities. Although the severity of menstrual cyclicity is associated with IR in PCOS, it is unclear whether, and to what extent, it is related to hyperinsulinemia and glycemic abnormalities.

STUDY DESIGN, SIZE, DURATION

We prospectively compared the degree of menstrual cyclicity with the presence of dysglycemia (elevated 1-h plasma glucose ≥155 mg/dl; abnormal glucose tolerance [AGT], including prediabetes and T2DM; and AUC for glucose [G-AUC]) or dynamic state hyperinsulinemia (peak insulin levels either at 1 or 2 h of the oral glucose tolerance test (oGTT) and AUC for insulin [I-AUC]) in 333 hyperandrogenic PCOS women.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In a tertiary care setting, hyperandrogenic PCOS participants with ovulatory eumenorrhea (Ov-Eumeno, n = 25), anovulatory eumenorrhea (Anov-Eumeno, n = 33), oligomenorrhea (Oligo, n = 150) and amenorrhea (Ameno, n = 125) underwent comprehensive phenotyping and a 2-h 75 g oGTT.

MAIN RESULTS AND THE ROLE OF CHANCE

Mean BMI was greater among Ameno women than among Oligo, Anov-Eumeno or Ov-Eumeno women. Adjusting for BMI, the Ameno group demonstrated higher mean 1- and 2-h insulin and glucose, peak insulin and I-AUC and G-AUC, and either had a higher, or tended toward having a higher, prevalence of elevated 1-h glucose level and prevalence of AGT than the Oligo, Anov-Eumeno or Ov-Eumeno groups. In logistic regression, adjusting for BMI, Ameno women were more likely to have: AGT than Oligo women (odds ratio [OR]: 2.3; 95% CI: 1.3 to 4.2); elevated 1-h glucose (OR: 10.2; CI: 1.3-79.7) than those with Ov-Eumeno; and both AGT (OR: 1.7; CI: 1.1-2.6) and elevated 1-h glucose (OR: 1.8; CI: 1.1-2.8) than those with Anov-Eumeno or Ov-Eumeno when combined. Race/ethnicity, age, waist-to-hip ratio, fasting insulin and glucose, and biochemical or clinical measures of hyperandrogenism were similar across the four menstrual categories.

LIMITATIONS, REASONS FOR CAUTION

Our study was limited by its cross-sectional nature and by studying women affected by PCOS as defined by the Androgen Excess & PCOS Society criteria (i.e. Rotterdam Phenotypes A, B and C) who were identified in the clinical setting. Consequently, extrapolation of the present data to other PCOS phenotypes (e.g. PCOS Phenotype D) should be made with caution.

WIDER IMPLICATIONS OF THE FINDINGS

In hyperandrogenic PCOS phenotypes, a history of amenorrhea, compared to oligomenorrhea or eumenorrhea, suggests a more severe cardiometabolic risk, including a higher degree of hyperinsulinemia and greater prevalence of glycemic abnormalities. These findings may assist in refining the treatment and screening guidelines for glycemic abnormalities in PCOS.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported in part by grants R01-DK073632 and R01-HD29364 from the NIH and an endowment of the Helping Hand of Los Angeles, Inc. (to R.A.). M.D.P. has no competing interests to declare. U.E. is an investor in Concentric Analgesics, Inc. R.A. serves as a consultant for Spruce Biosciences and Fortress Biotech and an advisor for Aurora Forge.

TRIAL REGISTRATION NUMBER

N/A.

Impact of dyslipidemia on the cumulative pregnancy outcomes after first ovarian stimulation

OBJECTIVES

To investigate the cumulative live birth rate (CLBR) according to lipid metabolism in patients with or without polycystic ovarian syndrome (PCOS) undergoing their first complete in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles.

PATIENTS

A total of 1,470 patients with PCOS and 3,232 patients without PCOS who underwent their first complete IVF/ICSI cycles from January 2016 to June 2018 were included. During a minimum of 2 years of follow-up, they had achieved at least one live birth or used all available embryos. The cumulative pregnancy outcomes were compared based on the patients' blood lipid parameters, including triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), in the two populations. Patients with an abnormal level of one or more of these four indicators were considered the dyslipidemia group. Patients whose four indicators were normal were considered the control group.

RESULTS

Among 1,470 patients with PCOS, the cumulative pregnancy outcomes were similar in the dyslipidemia group and control group. Logistic regression analysis showed that the TC levels were significantly negatively associated with the cumulative live birth rate (CLBR) after adjustment for confounding factors such as age and BMI (aOR 0.81, 95% CI 0.66-0.98, P<0.05). Among the 3,232 patients without PCOS, there was no significant difference in the cumulative pregnancy outcomes between the dyslipidemia group and the control group. No significant correlations were found in other logistic regression analyses.

CONCLUSIONS

TC negatively impacts the CLBR after first ovarian stimulation in PCOS patients. PCOS patients with dyslipidemia caused by elevated TC may have a poor CLBR.

Adipocyte Insulin Resistance in PCOS: Relationship With GLUT-4 Expression and Whole-Body Glucose Disposal and β-Cell Function

CONTEXT

Impaired sensitivity to the antilipolytic action of insulin in adipose tissue (AT) may play a role in determining metabolic dysfunction in polycystic ovary syndrome (PCOS).

OBJECTIVES

To test the hypothesis that insulin resistance (IR) in AT is associated with whole-body insulin sensitivity and β-cell function in PCOS.

RESEARCH DESIGN AND SETTING

Prospective cross-sectional study.

METHODS

Eighteen participants with PCOS and 18-matched control participants underwent a modified frequently sampled intravenous glucose tolerance test (mFSIVGTT); subgroups underwent single-slice computed tomography scans determining AT distribution and adipocyte glucose transporter type 4 (GLUT-4) expression.

MAIN OUTCOME MEASURES

IR in AT in basal (by the adipose insulin resistance index [Adipo-IR]) and dynamic (mFSIVGTT-derived indices of insulin-mediated nonesterified fatty acids [NEFA] suppression [NEFAnadir, TIMEnadir, and %NEFAsupp]) states; whole-body insulin-mediated glucose uptake and insulin secretion in basal (by homeostatic model assessment [HOMA]-IR and HOMA-β%) and dynamic (mFSIVGTT-derived insulin sensitivity index [Si], acute insulin response to glucose [AIRg], and disposition index [Di]) states.

RESULTS

Participants with PCOS had higher HOMA-IR and HOMA-β%, lower Si and Di, higher longer TIMEnadir, higher Adipo-IR and NEFAnadir, and a trend toward lower GLUT-4, than the control group participants. Adipo-IR was associated with dynamic state IR in AT (NEFAnadir TIMEnadir, and %NEFAsupp), but only in PCOS, and with HOMA-IR and HOMA-β% in both groups. NEFAnadir and TIMEnadir were negatively and %NEFAsupp positively associated with Si only in PCOS, but not with AIRg and Di, or GLUT-4 expression.

CONCLUSION

Women with PCOS demonstrated increased IR in AT, which is closely associated with whole-body IR but not with dynamic state β-cell function or adipocyte GLUT-4 gene expression.