The effect of L-carnitine supplementation on insulin resistance, sex hormone-binding globulin and lipid profile in overweight/obese women with polycystic ovary syndrome: a randomized clinical trial

Different supplements improve insulin resistance, hormonal functions, and oxidative stress on overweight and obese women with polycystic ovary syndrome: a systematic review and meta-analysis

Objectives

To investigate various supplements that improve insulin resistance, hormonal status, and oxidative stress in overweight or obese women with polycystic ovarian syndrome (PCOS).

Methods

A literature search was conducted on four different databases, which led to the discovery of twenty - five randomized controlled trials (RCTs). These RCTs evaluated the efficacy of various supplements in improving insulin resistance (IR), hormonal status, and oxidative stress among overweight or obese women diagnosed with PCOS. Subsequently, data extraction and analysis were carried out to determine the quality of the study's methodological design and the potential for bias. Moreover, a meta-analysis was performed using the data from the RCTs.

Results

A total of 25 RCTs were carried out, and 1636 women were enrolled. All participants were overweight or obese. The standardized mean differences (SMD) were as follows: For fasting plasma glucose (FPG), it was -0.34 (95% confidence interval [CI], -0.49 to -0.19, p = 0.123, I2 = 30.8%); for insulin, it was -0.67 (95% CI, -0.83 to -0.52, p = 0.208, I2 = 24%); for fasting insulin (FI), it was -0.26 (95% CI, -0.52 to -0.00, p = 0.269, I2 = 21.9%); for homeostatic model assessment-insulin resistance index (HOMA-IR), it was -0.59 (95% CI, -0.73 to -0.45, p = 0.015, I2 = 48.7%); for homoeostatic model assessment beta - cell function (HOMA-B), it was -0.51 (95% CI, -0.75 to -0.27, p = 0.547, I2 = 0%); for quantitative insulin sensitivity check index (QUICKI), it was 0.94 (95% CI, 0.76 to -1.12, p = 0.191, I2 = 27.5%); for total testosterone, it was -0.61 (95% CI, -1.14 to -0.09, p = 0.00, I2 = 78.5%); for testosterone, it was -0.38 (95% CI, -0.86 to 0.10, p = 0.03, I2 = 71.5%); for follicle - stimulating hormone (FSH), it was 0.16 (95% CI, -0.08 to 0.40, p = 0.470, I2 = 0%); for luteinizing hormone (LH), it was -0.56 (95% CI, -1.32 to 0.20, p = 0.000, I2 = 91.1%); for sex hormone - binding globulin (SHBG), it was 0.35 (95% CI, 0.02 to 0.69, p = 0.000, I2 = 78%); for dehydroepiandrosterone (DHEAS), it was -0.27 (95% CI, -0.76 to 0.21, p = 0.001, I2 = 78.7%); for plasma total antioxidant capacity (TAC), it was 0.87 (95% CI, 0.45 to 1.30, p = 0.004, I2 = 71.3%); for plasma malondialdehyde (MDA), it was -0.57 (95% CI, -0.79 to -0.36, p = 0.992, I2 = 0.0%).

Conclusion

This study's findings indicate that, in comparison with a placebo, supplements have a favorable effect on IR, hormonal functions, and oxidative stress in PCOS. Nevertheless, it is crucial to note that the above-drawn conclusions need to be verified by more high-quality studies, given the limitations regarding the number and quality of the included studies.

New insights on mitochondrial heteroplasmy observed in ovarian diseases

BACKGROUND

The reportedly high mutation rate of mitochondrial DNA (mtDNA) may be attributed to the absence of histone protection and complete repair mechanisms. Mitochondrial heteroplasmy refers to the coexistence of wild-type and mutant mtDNA. Most healthy individuals carry a low point mutation load (<1 %) in their mtDNA, typically without any discernible phenotypic effects. However, as it exceeds a certain threshold, it may cause the onset of various diseases. Since the ovary is a highly energy-intensive organ, it relies heavily on mitochondrial function. Mitochondrial heteroplasmy can potentially contribute to a variety of significant ovarian disorders.

AIM OF REVIEW

In this review, we have elucidated the close relationship between mtDNA heteroplasmy and ovarian diseases, and summarized novel avenues and strategies for the potential treatment of these ovarian diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Mitochondrial heteroplasmy can potentially contribute to a variety of significant ovarian disorders, including polycystic ovary syndrome, premature ovarian insufficiency, and endometriosis. Current strategies related to mitochondrial heteroplasmy are untargeted and have low bioavailability. Nanoparticle delivery systems loaded with mitochondrial modulators, mitochondrial replacement/transplantation therapy, and mitochondria-targeted gene editing therapy may offer promising paths towards potentially more effective treatments for these diseases, despite ongoing challenges.

Adiposity in mares induces insulin dysregulation and mitochondrial dysfunction which can be mitigated by nutritional intervention

Obesity is a complex disease associated with augmented risk of metabolic disorder development and cellular dysfunction in various species. The goal of the present study was to investigate the impacts of obesity on the metabolic health of old mares as well as test the ability of diet supplementation with either a complex blend of nutrients designed to improve equine metabolism and gastrointestinal health or L-carnitine alone to mitigate negative effects of obesity. Mares (n = 19, 17.9 ± 3.7 years) were placed into one of three group: normal-weight (NW, n = 6), obese (OB, n = 7) or obese fed a complex diet supplement for 12 weeks (OBD, n = 6). After 12 weeks and completion of sample collections, OB mares received L-carnitine alone for an additional 6 weeks. Obesity in mares was significantly associated with insulin dysregulation, reduced muscle mitochondrial function, and decreased skeletal muscle oxidative capacity with greater ROS production when compared to NW. Obese mares fed the complex diet supplement had better insulin sensivity, greater cell lipid metabolism, and higher muscle oxidative capacity with reduced ROS production than OB. L-carnitine supplementation alone did not significantly alter insulin signaling, but improved lipid metabolism and muscle oxidative capacity with reduced ROS. In conclusion, obesity is associated with insulin dysregulation and altered skeletal muscle metabolism in older mares. However, dietary interventions are an effective strategy to improve metabolic status and skeletal muscle mitochondrial function in older mares.

L-carnitine: food sources, adequate and clinically effective doses

L-carnitine plays a key role in cell bioenergetics, it belongs to vitamin-like substances, but unlike vitamins, it not only comes from food, but is also synthesized in the body. Endogenous synthesis decreases with age, under certain physiological conditions, taking medications. In this regard, specialized food products (SFP) and food supplements are being developed, containing L-carnitine as one of the functional ingredients. Comparison of doses of L-carnitine approved for use in biologically active food supplements and specialized food products with doses that provide a clinical effect.A review of existing literature on this issue in recent years was carried out using the RSCI, Pubmed databases and in the Google Scholar, ResearchGate systems. The amount of L-carnitine contained in a daily portion of SPP is established by domestic regulatory documents based on an adequate level of daily intake for adults, which is 300 mg and the upper permissible level of daily intake in the composition of SFP and food supplements is 900 mg/day. Reception of L-carnitine 1–2 g per day. within 5–12 weeks led to an increase in its concentration in the blood plasma, and also improved the indicators of the antioxidant status. Long-term intake of L-carnitine in doses of 2–3 g in patients with dyslipidemia, type 2 diabetes (DM2) and cardiovascular diseased (CVD) led to an improvement in the lipid profile of blood plasma, glycemic control, and had an anti-inflammatory effect. The condition for achieving a clinical effect in patients is long-term use and high doses. The intake of physiological doses of L-carnitine is appropriate for individuals from risk groups. Clinically effective doses of L-carnitine, when used for at least 12 weeks, correspond to or are 2 times higher than the upper permissible intake level in the composition of SPP and dietary supplements.

Serum betaine and dimethylglycine in mid-pregnancy and the risk of gestational diabetes mellitus: a case-control study

PURPOSE

To investigate the associations of choline, betaine, dimethylglycine (DMG), L-carnitine, and Trimethylamine-N-oxide (TMAO) with the risk of Gestational diabetes mellitus (GDM) as well as the markers of glucose homeostasis.

METHODS

We performed a case-control study including 200 diagnosed GDM cases and 200 controls matched by maternal age (±2 years) and gestational age (±2 weeks). Concentrations of serum metabolites were measured by the high-performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS).

RESULTS

Compared to the control group, GDM group had significantly lower serum betaine concentration and betaine/choline ratio, and higher DMG concentration. Furthermore, decreased betaine concentration and betaine/choline ratio, increased DMG concentration showed significant association with the risk of GDM. In addition, serum betaine concentrations were negatively associated with blood glucose levels at 1-h post-glucose load (OGTT-1h), and both betaine and L-carnitine concentrations were positively associated with 1,5-anhydroglucitol levels. Betaine/choline ratio was negatively associated with OGTT-1h and blood glucose levels at 2-h post-glucose load (OGTT-2h) and serum choline concentrations were negatively associated with fasting blood glucose and positively associated with OGTT-2h.

CONCLUSION

Decreased serum betaine concentrations and betaine/choline ratio, and elevated DMG concentrations could be significant risk factors for GDM. Furthermore, betaine may be associated with blood glucose regulation and short-term glycemic fluctuations.

Assessing the In Vitro and In Vivo Performance of L-Carnitine-Loaded Nanoparticles in Combating Obesity

Addressing obesity is a critical health concern of the century, necessitating urgent attention. L-carnitine (LC), an essential water-soluble compound, plays a pivotal role in lipid breakdown via β-oxidation and facilitates the transport of long-chain fatty acids across mitochondrial membranes. However, LC’s high hydrophilicity poses challenges to its diffusion through bilayers, resulting in limited bioavailability, a short half-life, and a lack of storage within the body, mandating frequent dosing. In our research, we developed LC-loaded nanoparticle lipid carriers (LC-NLCs) using economically viable and tissue-localized nanostructured lipid carriers (NLCs) to address these limitations. Employing the central composite design model, we optimized the formulation, employing the high-pressure homogenization (HPH) method and incorporating Poloxamer® 407 (surfactant), Compritol® 888 ATO (solid lipid), and oleic acid (liquid oil). A comprehensive assessment of nanoparticle physical attributes was performed, and an open-field test (OFT) was conducted on rats. We employed immunofluorescence assays targeting CRP and PPAR-γ, along with an in vivo rat study utilizing an isolated fat cell line to assess adipogenesis. The optimal formulation, with an average size of 76.4 ± 3.4 nm, was selected due to its significant efficacy in activating the PPAR-γ pathway. Our findings from the OFT revealed noteworthy impacts of LC-NLC formulations (0.1 mg/mL and 0.2 mg/mL) on adipocyte cells, surpassing regular L-carnitine formulations’ effects (0.1 mg/mL and 0.2 mg/mL) by 169.26% and 156.63%, respectively (p < 0.05).

Assessing the In Vitro and In Vivo Performance of L-Carnitine-Loaded Nanoparticles in Combating Obesity

Addressing obesity is a critical health concern of the century, necessitating urgent attention. L-carnitine (LC), an essential water-soluble compound, plays a pivotal role in lipid breakdown via β-oxidation and facilitates the transport of long-chain fatty acids across mitochondrial membranes. However, LC's high hydrophilicity poses challenges to its diffusion through bilayers, resulting in limited bioavailability, a short half-life, and a lack of storage within the body, mandating frequent dosing. In our research, we developed LC-loaded nanoparticle lipid carriers (LC-NLCs) using economically viable and tissue-localized nanostructured lipid carriers (NLCs) to address these limitations. Employing the central composite design model, we optimized the formulation, employing the high-pressure homogenization (HPH) method and incorporating Poloxamer® 407 (surfactant), Compritol® 888 ATO (solid lipid), and oleic acid (liquid oil). A comprehensive assessment of nanoparticle physical attributes was performed, and an open-field test (OFT) was conducted on rats. We employed immunofluorescence assays targeting CRP and PPAR-γ, along with an in vivo rat study utilizing an isolated fat cell line to assess adipogenesis. The optimal formulation, with an average size of 76.4 ± 3.4 nm, was selected due to its significant efficacy in activating the PPAR-γ pathway. Our findings from the OFT revealed noteworthy impacts of LC-NLC formulations (0.1 mg/mL and 0.2 mg/mL) on adipocyte cells, surpassing regular L-carnitine formulations' effects (0.1 mg/mL and 0.2 mg/mL) by 169.26% and 156.63%, respectively (p < 0.05).

Do GLP-1 Analogs Have a Place in the Treatment of PCOS? New Insights and Promising Therapies

Polycystic ovary syndrome (PCOS) is the most prevalent endocrinopathy in women of reproductive age. This condition is characterized by hyperandrogenism and either oligo- or anovulation. PCOS patients often present comorbidities such as obesity, insulin resistance, impaired glucose metabolism, dyslipidemia, hypertension, metabolic syndrome, and an increased risk of diabetes. Given the profound implications of metabolic impairment in PCOS, the accurate diagnosis and management of these facets are imperative. The first-line approach to treatment involves lifestyle modifications, including dietary adjustments and exercise aimed at achieving weight loss, a strategy consistently emphasized across the literature. Supplementation with probiotics, vitamin D, and L-carnitine have also provided additional benefits to patients. In select cases, pharmacological interventions are needed for optimal therapeutic results. The most common medications used in PCOS include metformin, thiazolidinediones, inositols, and two classes of antidiabetic agents: dipeptidyl peptidase-IV (DPP-IV) inhibitors, and sodium-glucose cotransporter-2 (SGLT-2) inhibitors. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) are a new addition to the therapeutic arsenal for the metabolic management of PCOS. GLP-1 receptor agonists cause insulin release in a glucose-dependent manner, yielding clinical benefits such as heightened satiety, reduced appetite, and appetite regulation. GLP-1RAs have demonstrated efficacy in reducing glycated hemoglobin levels and promoting weight loss while ameliorating hyperlipidemia. Prior to initiating GLP-1RA therapy, patients should undergo screening for contraindications, including history of pancreatitis, diabetic retinopathy, or thyroid cancer. The effects of treatment should be monitored using laboratory testing and body weight measurements. Effective communication between clinician and patient should be maintained with regular check-in for a period of 6 to 12 months.

Effects of carnitine on glucose and lipid metabolic profiles and fertility outcomes in women with polycystic ovary syndrome: A systematic review and meta-analysis

OBJECTIVES

To quantify the effect of carnitine on glucose and lipid metabolic profiles and fertility outcomes in women with Polycystic ovary syndrome (PCOS).

DESIGN

A systematic review and meta-analysis were conducted.

PATIENTS

Women with PCOS diagnosed by Rotterdam or Androgen Excess Society (AES) criteria and taking carnitine supplement were assessment.

MEASUREMENTS

Fertility outcomes (ovulation, clinical pregnancy, live birth, and miscarriage), lipid parameters (BMI, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein), fasting glucose and insulin, and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR).

RESULTS

In total, 839 participants were included in this analysis. The dosage of carnitine and treatment duration reported by studies varied from 250 mg to 3000 mg daily and 84 to 90 days, respectively. The publication bias was absent. Compared with placebo, carnitine significantly improved ovulation rates (RR 3.42, 95% CI 2.39 to 4.89, I2 = 0%) and pregnancy rates (RR 11.05, 95% CI 1.21 to 100.58, I2 = 79%). None of included studies reported live birth. After treatment, carnitine resulted in significant reductions relative to baseline in body mass index (BMI, MD -0.93 kg/m2, 95% CI -1.15 to -0.70, I2 = 55.0%), insulin levels (MD -2.47 mIU/L, 95% CI -4.49 to -0.45, I2 = 0%) and the Homeostasis Model Assessment index (MD -0.67, 95% CI -1.20 to -0.14, I2 = 0%) than placebo, but not for lipid profiles including triglyceride, total cholesterol, and low-density lipoprotein.

CONCLUSION

With the available literature, carnitine seems to improve ovulation and clinical pregnancy and insulin resistance, BMI in women with PCOS. These effects are warranted to be further validated, due to insufficient statistical power.

Insulin resistance in polycystic ovary syndrome across various tissues: an updated review of pathogenesis, evaluation, and treatment

Polycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by chronic ovulation dysfunction and overabundance of androgens; it affects 6-20% of women of reproductive age. PCOS involves various pathophysiological factors, and affected women usually have significant insulin resistance (IR), which is a major cause of PCOS. IR and compensatory hyperinsulinaemia have differing pathogeneses in various tissues, and IR varies among different PCOS phenotypes. Genetic and epigenetic changes, hyperandrogenaemia, and obesity aggravate IR. Insulin sensitization drugs are a new treatment modality for PCOS. We searched PubMed, Google Scholar, Elsevier, and UpToDate databases in this review, and focused on the pathogenesis of IR in women with PCOS and the pathophysiology of IR in various tissues. In addition, the review provides a comprehensive overview of the current progress in the efficacy of insulin sensitization therapy in the management of PCOS, providing the latest evidence for the clinical treatment of women with PCOS and IR.

Selenium supplementation for polycystic ovary syndrome: a meta-analysis of randomized controlled trials

Introduction: The efficacy of selenium supplementation was elusive for polycystic ovary syndrome. This meta-analysis aimed to explore the efficacy of selenium supplementation for polycystic ovary syndrome. Methods: PubMed, EMbase, Web of science, EBSCO, Cochrane library database, CNKI, Chongqing VIP database and Wanfang databases have been searched through July 2022 and we included randomized controlled trials (RCTs) reporting the effect of selenium supplementation versus placebo in patients with polycystic ovary syndrome. Results: Five RCTs were included in the meta-analysis. Compared with placebo group for polycystic ovary syndrome, selenium supplementation was associated with significantly reduced total testosterone (SMD=-0.42; 95% CI=-0.78 to -0.06; p = 0.02) and cholesterol (SMD=-0.71; 95% CI=-1.41 to -0.02; p = 0.04), but revealed no remarkable influence on SHBG (SMD=-0.52; 95% CI=-1.29 to 0.25; p = 0.19), triglyceride (SMD=-1.45; 95% CI=-3.62 to 0.73; p = 0.19), LDL (SMD=-0.17; 95% CI=-0.72 to 0.37; p = 0.53), FPG (SMD=-0.95; 95% CI=-3.72 to 1.82; p = 0.50) or HOMA-IR (SMD=-0.51; 95% CI=-3.79 to 2.77; p = 0.76). Conclusions: Selenium supplementation may be able to improve the metabolic response for polycystic ovary syndrome, and this finding should be interpreted with caution.

Interactions of CDKAL1 rs7747752 polymorphism and serum levels of L-carnitine and choline are related to increased risk of gestational diabetes mellitus

BACKGROUND

Interactions between genetic, metabolic, and environmental factors lead to gestational diabetes mellitus (GDM). We aimed to examine interactive effects of cyclin-dependent kinase 5 regulatory subunit-associated protein1-like 1(CDKAL1) rs7747752 polymorphism with low serum levels of L-carnitine, choline, and betaine for GDM.

METHODS

A nested case-control study of 207 GDM women and their one-to-one, age-matched controls was organized from a prospective cohort of pregnant women in Tianjin, China. Conditional logistic regressions were used to test associations between CDKAL1 rs7747752 and serum levels of L-carnitine, choline, and betaine, and the risk of GDM. Additive interactions were performed to examine interactive effects of rs7747752 and low serum levels of L-carnitine, choline, and betaine on the risk of GDM.

RESULTS

The CDKAL1 rs7747752 G > C was associated with GDM in additive, dominant, and recessive model (P <0.05). The rs7747752 CC genotype enhanced the OR of L-carnitine ≤ vs. > 150 nmol/mL for GDM from 6.14 (2.61-14.4) to 19.6 (5.65-68.1) and the OR of choline ≤ vs. > 110 nmol/mL from 2.37 (1.07-5.28) to 12.1 (3.22-45.6), with significant additive interactions. Similarly, CG genotype also enhanced the OR of L-carnitine ≤ vs. > 150 nmol/mL for GDM from 4.70 (2.01-11.0) to 11.4 (3.98-32.9), with a significant additive interaction. However, the additive interaction between rs7747752 and betaine ≤ 200 nmol/mL on the risk of GDM was not significant.

CONCLUSIONS

The CC or CG genotype carriers in rs7747752 of CDKAL1 who have a low serum level of L-carnitine or choline are at a particular high risk of GDM. Randomized controlled trials are warranted to test the effect of supplement of L-carnitine or choline on the risk of GDM in the high-risk group.

Effect of L-carnitine supplementation on lipid accumulation product and cardiovascular indices in women with overweight/obesity who have knee osteoarthritis: a randomized controlled trial

Background

Osteoarthritis is associated with obesity, dyslipidemia and cardiovascular diseases. It has been hypothesized that L-carnitine can improve cardiovascular risk factors. We aimed to investigate the effect of L-carnitine supplementation on lipid accumulation product (LAP) and atherogenic indices in women with overweight/obesity who have knee osteoarthritis.

Methods

In this double-blind randomized controlled trial, seventy-six women with overweight/obesity who had knee osteoarthritis were assigned into the intervention group and control group for 12 weeks. The intervention group received 1000 mg/day L-carnitine as capsule, and the control group received placebo. The primary outcomes were LAP, atherogenic index of plasma (AIP), atherogenic coefficient (AC) and Castelli risk index II (CRI-II).

Results

We found no significant difference between the groups in baseline values of LAP, AIP, AC and CRI-II. After the intervention, a significant reduction in LAP was observed in intervention group compared to the control group (− 11.05 (− 28.24 to 0.40) vs. − 5.82 (− 24.44 to 2.68); P = 0.03). However, there was no significant difference between two groups in AIP (− 0.05 ± 0.16 vs. − 0.01 ± 0.13; P = 0.19), AC (− 0.40 ± 0.81 vs. − 0.30 ± 0.67; P = 0.67) and CRI-II (− 0.20 ± 0.76 vs. − 0.21 ± 0.47; P = 0.11).

Conclusions

L-carnitine supplementation for 12 weeks can improve LAP, but it has no effect on cardiovascular outcomes. To reach a definitive conclusion, further clinical trials with larger sample sizes and higher dosages of L-carnitine are needed.

Trial registration

Registered on 27/4/2017 at Iranian Registry of Clinical Trials IRCT2017011932026N2.

A machine-learning approach for predicting the effect of carnitine supplementation on body weight in patients with polycystic ovary syndrome

The present study aimed to explore the effect of carnitine supplementation on body weight in patients with polycystic ovary syndrome (PCOS) and predict an appropriate dosage schedule using a machine-learning approach. Data were obtained from literature mining and the rates of body weight change from the initial values were selected as the therapeutic index. The maximal effect (E_max) model was built up as the machine-learning model. A total of 242 patients with PCOS were included for analysis. In the machine-learning model, the E_max of carnitine supplementation on body weight was -3.92%, the ET₅₀ was 3.6 weeks, and the treatment times to realize 25%, 50%, 75%, and 80% (plateau) E_max of carnitine supplementation on body weight were 1.2, 3.6, 10.8, and 14.4 weeks, respectively. In addition, no significant relationship of dose-response was found in the dosage range of carnitine supplementation used in the present study, indicating the lower limit of carnitine supplementation dosage, 250 mg/day, could be used as a suitable dosage. The present study first explored the effect of carnitine supplementation on body weight in patients with PCOS, and in order to realize the optimal therapeutic effect, carnitine supplementation needs 250 mg/day for at least 14.4 weeks.

Metabolic Syndrome and PCOS: Pathogenesis and the Role of Metabolites

Polycystic ovary syndrome (PCOS) is one of the most common endocrine diseases among women of reproductive age and is associated with many metabolic manifestations, such as obesity, insulin resistance (IR) and hyperandrogenism. The underlying pathogenesis of these metabolic symptoms has not yet been fully elucidated. With the application of metabolomics techniques, a variety of metabolite changes have been observed in the serum and follicular fluid (FF) of PCOS patients and animal models. Changes in metabolites result from the daily diet and occur during uncommon physiological routines. However, some of these metabolite changes may provide evidence to explain possible mechanisms and new approaches for prevention and therapy. This article reviews the pathogenesis of PCOS metabolic symptoms and the relationship between metabolites and the pathophysiology of PCOS. Furthermore, the potential clinical application of some specific metabolites will be discussed.