United States

Background and Objective: Makorin Ring Finger Protein 3 (MKRN3), an inhibitor of the KISS1 and TAC3 promoters in the hypothalamic arcuate nucleus (ARC), is an important player in age of menarche and etiology of central precocious puberty. However, its potential role in delayed puberty and/or hypogonadism is not defined. Mkrn3 expression in the ARC declines prior to the onset of puberty and remains low in adulthood, supporting its role as an inhibitor of pubertal onset. Neonatal hypothalamic overexpression of Mkrn3 leads to delayed puberty in female mice; this study aimed to explore the effects of MKRN3 overexpression in the postpubertal mouse. We hypothesized that MKRN3 overexpression in the ARC of postpubertal female mice would result in suppression of the HPG axis, manifested as hypogonadotropic hypogonadism. Methods and Results: Adult female C57BL/6 mice were stereotaxically injected into the ARC with a recombinant adeno-associated virus (rAAV-Mkrn3-IRES-EGFP;n=12) to overexpress Mkrn3, or with a control virus (rAAV-EGFP;n=9). Daily vaginal smears collected six weeks post-injection showed that rAAV-Mkrn3 injected mice spent significantly more time (62.7%) in diestrus compared to controls (41.3%;P&lt;0.01). Mean body weight did not statistically differ between groups. Eight weeks after viral injection, gonad-intact females underwent stimulation tests while in diestrus. Tail vein blood samples were collected at baseline and 20, 40 and 60 minutes after stimulation. In response to the NK3R agonist, senktide, evaluated at two doses (5 nmol and 10 nmol ip, respectively), Mkrn3-overexpressing mice had a reduced peak (i.e., T20) LH response compared to controls (P&lt;0.001 for both dosing paradigms). In contrast, in response to kisspeptin-10 (1 nmol ip), mice responded with similar peak serum LH levels. Subsequently, tests were repeated seven days after ovariectomy and estradiol capsule replacement (OVX+E2). Peak LH levels (T20) were again significantly lower in response to senktide (5 nmol ip) in the rAAV-Mkrn3 injected females (P&lt;0.001). Peak serum LH levels (T20) were not different in response to kisspeptin-10 (1 nmol) or GnRH (1.25 ng/g body weight). Additionally, there were no significant differences in serum LH levels between groups 7 days after OVX or OVX + E2. Conclusions: In this novel mouse model, developed to investigate the mechanism of action of MKRN3, an important neuroendocrine controller of puberty initiation, these findings suggest that MKRN3 can exert inhibitory effects on the reproductive axis in female mice beyond the juvenile period. In these mice, response to kisspeptin and GnRH was preserved but the response to senktide was blunted. These findings suggest that Mkrn3 may act in ARC kisspeptin neurons to inhibit kisspeptin synthesis or secretion and/or potentially the action of neurokinin B via its receptor. Modulation of MKRN3 expression may be a future therapeutic target for reproductive disorders.

ENDO 2022

The Impact of Makorin Ring Finger Protein 3 (MKRN3) Overexpression in the Arcuate Nucleus of Postpubertal Female Mice on the HPG Axis

**Program**
ENDO’s comprehensive program provides attendees the opportunity to learn about the latest developments in hormone science and medicine from renowned investigators, expert clinicians, and educators from all over the world. 

This year’s education program features:
more than 100 in-person and virtual sessions with another 70+ in-person only sessions;
six plenary sessions including plenaries on Envisioning Future Therapies for Type 1 Diabetes and Addressing Challenges in Fertility and Reproduction;
over 20 Meet the Professor sessions presented both in-person and live-streamed virtually and another 20+ presented live in Atlanta;
four Basic Science Pathways, including Diabetes and Metabolism; Neuroendocrinology; Nuclear Receptors and Signaling; and Reproductive Endocrinology; and
more than 30 oral sessions and a robust virtual poster hall for accepted scientific abstracts.

**What Programming Is Included in My Virtual Meeting Registration?**
As you build your schedule during the conference, you can select the sessions that are tagged with 'Livestreamed', so you can view virtually. These sessions are being livestreamed, so they are available in real time to our virtual audience. In addition, our in-person and livestreamed sessions will be recorded, so you can access them on demand after 72 hours. We will have over 200 hours available on demand for Standard and Premium pass registrants.

Product theaters and the Communications and Career Center will also include hybrid content delivery.

**Plenaries**
Spanning the spectrum of science, clinical care, and social implications, an outstanding slate of world-renowned speakers will showcase the most cutting-edge advances on research and medicine.

**Symposia**
Our ENDO 2022 lineup of sessions offers a unique opportunity to dive into topics from nearly every major therapeutic area of endocrinology and hormone science. Listen, learn, and be inspired by world-class faculty who are at the forefront of scientific discovery and high-quality health care.

**Basic Science Pathways**

These special “meeting-within-a-meeting” tracks integrate focused discussions, poster sessions, and networking opportunities to provide you with the latest research in:
Diabetes and Metabolism
Neuroendocrinology
Nuclear Receptors and Signaling
Reproductive Endocrinology

**Meet the Professor & Meet the Scientist**
Discover insights from experts on treating a variety of endocrine conditions and emerging science in the field of endocrinology, and learn the latest in patient care and scientific research.

ENDO’s comprehensive program provides attendees the opportunity to learn about the latest developments in hormone science and medicine from renowned investigators, expert clinicians, and educators from all over the world. 

Background and Objective: Makorin Ring Finger Protein 3 (MKRN3), an inhibitor of the KISS1 and TAC3 promoters in the hypothalamic arcuate nucleus (ARC), is an important player in age of menarche and etiology of central precocious puberty. However, its potential role in delayed puberty and/or hypogonadism is not defined. Mkrn3 expression in the ARC declines prior to the onset of puberty and remains low in adulthood, supporting its role as an inhibitor of pubertal onset. Neonatal hypothalamic overexpression of Mkrn3 leads to delayed puberty in female mice; this study aimed to explore the effects of MKRN3 overexpression in the postpubertal mouse. We hypothesized that MKRN3 overexpression in the ARC of postpubertal female mice would result in suppression of the HPG axis, manifested as hypogonadotropic hypogonadism. Methods and Results: Adult female C57BL/6 mice were stereotaxically injected into the ARC with a recombinant adeno-associated virus (rAAV-Mkrn3-IRES-EGFP;n=12) to overexpress Mkrn3, or with a control virus (rAAV-EGFP;n=9). Daily vaginal smears collected six weeks post-injection showed that rAAV-Mkrn3 injected mice spent significantly more time (62.7%) in diestrus compared to controls (41.3%;P<0.01). Mean body weight did not statistically differ between groups. Eight weeks after viral injection, gonad-intact females underwent stimulation tests while in diestrus. Tail vein blood samples were collected at baseline and 20, 40 and 60 minutes after stimulation. In response to the NK3R agonist, senktide, evaluated at two doses (5 nmol and 10 nmol ip, respectively), Mkrn3-overexpressing mice had a reduced peak (i.e., T20) LH response compared to controls (P<0.001 for both dosing paradigms). In contrast, in response to kisspeptin-10 (1 nmol ip), mice responded with similar peak serum LH levels. Subsequently, tests were repeated seven days after ovariectomy and estradiol capsule replacement (OVX+E2). Peak LH levels (T20) were again significantly lower in response to senktide (5 nmol ip) in the rAAV-Mkrn3 injected females (P<0.001). Peak serum LH levels (T20) were not different in response to kisspeptin-10 (1 nmol) or GnRH (1.25 ng/g body weight). Additionally, there were no significant differences in serum LH levels between groups 7 days after OVX or OVX + E2. Conclusions: In this novel mouse model, developed to investigate the mechanism of action of MKRN3, an important neuroendocrine controller of puberty initiation, these findings suggest that MKRN3 can exert inhibitory effects on the reproductive axis in female mice beyond the juvenile period. In these mice, response to kisspeptin and GnRH was preserved but the response to senktide was blunted. These findings suggest that Mkrn3 may act in ARC kisspeptin neurons to inhibit kisspeptin synthesis or secretion and/or potentially the action of neurokinin B via its receptor. Modulation of MKRN3 expression may be a future therapeutic target for reproductive disorders.

technical paper

Context: Familial central precocious puberty (CPP) is a prevalent form (about 27.5%) of precocious puberty. Loss-of-function mutations in two maternally imprinted genes, MKRN3 and DLK1, were identified in families with CPP showing dominant autosomal inheritance with paternal transmission. Maternally transmitted CPP was previously demonstrated in up to 60% of families using pedigree analysis, however, no definitive genetic abnormality has been identified so far.
Objectives: To estimate the prevalence of familial cases in a multiethnic cohort with CPP. To characterize the genetic basis and the mode of inheritance of the affected families. To compare clinical and hormonal features of patients with familial CPP due to different modes of transmission.
Patients and Methods: Clinical and hormonal data were obtained from medical registries of 495 patients with CPP and no brain MRI alterations. Familial CPP was defined as the presence of one or more close relatives with CPP or precocious menarche (≤9 yr). Sanger sequencing of MKRN3 and DLK1 was performed in 427 index cases. Targeted gene panel sequencing was performed in 79 cases, while whole exome sequencing was performed in 101 cases from 36 families
Results: Among 495 index cases, 159 had familial CPP (31%). The mode of transmission of CPP was identified as paternal in 58 (35%), maternal in 59 (38%), indeterminate in 34 (22%), and both maternal and paternal transmission in 8 (5%). Most families with paternal or maternal transmission had 2 generations known to be affected (51 and 77%, respectively). Notably, 67% of index cases with maternally transmitted CPP had their mother affected. In girls with CPP, the median age of thelarche was 6.5 yr in the paternally transmitted group, 6.9 yr in the maternally transmitted group, and 7.3 yr in the indeterminate group (p= 0.547). Median bone age advancement was 2.1, 2.3 and 1.2 yr, respectively (p= 0.013). Basal LH levels were higher in girls with paternally transmitted CPP (p= 0.047). Among those with paternally transmitted CPP, MKRN3 and DLK1 mutations were identified in, respectively, 63.8% and 10.3% of the families.
Conclusions: A significant prevalence (31%) of familial CPP was demonstrated in a multiethnic cohort. Maternally transmitted CPP represented the most frequent form of familial CPP (38%). MKRN3 loss-of-function mutations were responsible for most paternally transmitted CPP cases (63.8%), followed by DLK1 loss-of-function mutations (10.3%).

Clinical, Hormonal and Genetic Characterization of Familial Central Precocious Puberty

Objectives: The 17β-hydroxysteroid dehydrogenase type 3 (17βHSD3) enzyme, expressed in the testes, converts androstenedione to testosterone. Deficiency of 17βHSD3 causes a 46,XY difference of sex development (DSD). Until recently, just 12 cases of 17βHSD3 deficiency had been reported in the literature in the United States. We report a series of 16 patients diagnosed at five children's hospitals in the United States.
Methods: We performed a multi-center chart review of patients with 17βHSD3 deficiency diagnosed based on hormone values and/or sequencing and deletion/duplication analysis of the HSD17B3 gene.
Results: Sixteen patients were identified, ranging in age at diagnosis from birth to 22.3 years (average age 9.5 years). One patient, assigned female at birth, was diagnosed due to a positive family history of the condition. Three patients underwent testing due to discordance between the sex predicted by prenatal cell-free DNA testing and the external genital appearance on prenatal ultrasound or at birth (two were assigned female, one was assigned male). An additional four patients had non-binary (atypical) appearing external genitalia at birth (two assigned female, two assigned male). Two children assigned female at birth were diagnosed after undescended testes were identified during hernia repair in early childhood. Six patients who were assigned female at birth came to medical attention peri-pubertally due to signs of excess/undesired androgen effects and/or primary amenorrhea. Data on gender identity is limited by the current age of many of the patients, but as of most recent follow-up, one patient assigned male and one assigned female are reported to be exploring their gender identities.
Four patients had a prior diagnosis of complete or partial androgen insensitivity syndrome and 8 had a prior diagnosis of 46,XY DSD of unknown etiology. Eleven patients had genetic testing confirming pathogenic or likely pathogenic variants in the HSD17B3 gene (two identified on whole exome, one on a DSD-specific multi-gene panel, and the remaining 8 on single gene testing). Of the patients without genetically confirmed 17βHSD3 deficiency, one had a clinical diagnosis due to a genetically-confirmed diagnosis in a sibling. The remaining four declined or have not completed genetic testing, but had hormonal testing consistent with the diagnosis.
Conclusions: 17βHSD3 deficiency is likely much more common in the US than previously appreciated, and can present at any age with a range of physical findings. Accurate diagnosis is important, as the broad category of 46,XY DSD encompasses a wide spectrum of gonadal malignancy risk, potential for pubertal hormone function and fertility, and gender identity outcomes. We suggest evaluating for this potential diagnosis with genetic and/or hormonal testing in cases of 46,XY DSD with absent uterus.

Case Series of 16 Patients With 17β-Hydroxysteroid Dehydrogenase Type 3 Deficiency at Five Children's Hospitals in the United States

Introduction: Classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21OHD) is a rare autosomal recessive disease characterized by deficiency of cortisol and oftentimes aldosterone, with elevated adrenocorticotropic hormone (ACTH) and steroid precursors that are then shunted toward excess androgen production. A phase 2 study of adults with classic 21OHD demonstrated that crinecerfont—an oral, non-steroidal, selective corticotropin-releasing factor type 1 (CRF₁) receptor antagonist—substantially reduced elevated hormone markers after 14 days of treatment [1]. The current study evaluated the effect of crinecerfont in adolescents with classic 21OHD, who may be especially challenging to manage for multiple reasons including the hormonal changes associated with puberty [2].
Methods: Eligible adolescents (14─17 years of age) with classic 21OHD received open-label crinecerfont (50 mg BID) for 14 days. ACTH, 17-hydroxyprogesterone (17OHP), androstenedione, and testosterone were assessed over 24 hours prior to (baseline) and after 14 days of crinecerfont treatment. Morning window values were defined as the average of samples collected at 0700h and 1000h, before the morning glucocorticoid dose. The participants' glucocorticoid and fludrocortisone regimens were maintained stable during crinecerfont treatment.
Results: In 8 participants (3 males, 5 females, ages 14-16 years), baseline median hormone concentrations (based on morning window) were as follows: plasma ACTH, 226.2 pg/mL; serum 17OHP, 7703.7 ng/dL; serum androstenedione, 367.9 ng/dL; and in females, serum testosterone, 63.5 ng/dL. After 14 days of crinecerfont treatment, median percent reductions from baseline were: ACTH, -57.1%; 17OHP, -69.5%; androstenedione, -58.3%; and in females, testosterone, ‑76.2%. A ≥50% reduction from baseline to Day 14 in ACTH, 17OHP, and androstenedione was observed in 62.5%, 75.0%, and 50.0% of participants, respectively. Furthermore, 60% (3/5) of females had ≥50% reduction from baseline in testosterone. Thirteen treatment-emergent adverse events (TEAEs) were reported; all but 1 (bruising) were assessed as mild. The majority of TEAEs were assessed as unrelated by the investigator, with the most common being headache (n=2). There were no serious AEs, discontinuations due to AEs, or safety concerns related to routine laboratory tests, vital signs, or electrocardiograms.
Conclusions: In adolescents with classic 21OHD, substantial median reductions (57-76%) in adrenal androgens and androgen precursors were observed after 14 days of crinecerfont treatment, consistent with reported results from a similar study of adults with classic 21OHD. Further studies are warranted to evaluate whether longer-term treatment with crinecerfont can allow for lower, more physiologic glucocorticoid dosing by directly reducing adrenal androgens, and thereby improving clinical outcomes (weight, metabolic risk, growth/development, fertility, etc.), via antagonism of the CRF₁ receptor.

Crinecerfont (NBI-74788), a Novel CRF1 Receptor Antagonist, Lowers Adrenal Androgens and Precursors in Adolescents with Classic Congenital Adrenal Hyperplasia

Objectives:
Vosoritide is a C-type natriuretic peptide analog which binds its receptor on chondrocytes, leading to increased chondrocyte proliferation and differentiation via its inhibition of the ERK1/2-MAPK pathway. It was recently approved for increasing linear growth in children with achondroplasia. Our study aims to assess the safety and efficacy of vosoritide in children with genetic mutations in 6 categories: hypochondroplasia, Rasopathies (including Noonan syndrome), aggrecan deficiency, carriers of heterozygous NPR2 mutations, CNP deficiency, and SHOX deficiency.
Methods:
This is a prospective, Phase II study with a goal N of 35 subjects. All subjects must have a documented genetic mutation in one of the 6 categories, be prepubertal between the ages of 3 and 11 for boys and 3 and 10 for girls, and have a height < -2.25 SD. Subjects are followed for a 6-month observation period to establish a baseline annualized growth velocity (AGV) and then receive daily subcutaneous vosoritide (15 mcg/kg/day) for 12 months. The primary outcomes are rate of AEs and change in AGV from baseline. Pharmacokinetic studies and pharmacodynamic studies, using cGMP production as a pharmacodynamic marker, are completed at Day 1 and Months 6 and 12.
Results:
To date, 27 subjects have enrolled in the trial (20 hypochondroplasia, 3 Noonan, 2 NPR2, 2 Aggrecan). Median baseline height is -3.1 SD (IQR -3.6, -2.6). 14 subjects have initiated on vosoritide, and 10 completed 6 months of therapy. Median increase in AGV was 3.9 cm/yr (IQR 2.2, 4.6). The two subjects with NPR2 mutations had increased AGVs of 4.4 and 9.2 cm/yr. The two subjects with Noonan syndrome had an increase in AGV of 7.5 and 3.3 cm/yr. One subject with Noonan syndrome, a 4-year-old male, had previously been treated with growth hormone (GH) for 2 years. His AGV was 6.7 cm/yr while on GH, 4.1 cm/yr during the 6-month observation period, and 11.6 cm/year during the first 6 months of vosoritide treatment. There were no serious adverse events related to vosoritide treatment. One subject had a brief episode of syncope with her first injection which self-resolved, and she continued on therapy with no further incidents. PK parameters were similar to previously published parameters for vosoritide in children with achondroplasia. In preliminary data, vosoritide Cmax and AUC correlated strongly with peak increase in cGMP (r=0.70, p=0.01;r=0.84, p<0.01, respectively) but not with increase in AGV (r=0.35, p=0.32).
Conclusions:
This is the first clinical trial of vosoritide for children with genetic short stature who do not have achondroplasia. Vosoritide treatment may work as a precision therapy to improve growth in multiple genetic conditions which interact with the ERK1/2-MAPK pathway.

A Prospective Clinical Trial of Vosoritide in Selected Genetic Causes of Short Stature

Background: Turner syndrome (TS) is a chromosomal anomaly occurring in females which presents with numerous medical and developmental manifestations including skeletal deformities. A specific developmental skeletal dyplasia seen in TS patients is Madelung deformity (MD), characterized by a growth deficiency of the distal radial physis that causes excessive radial inclination and volar tilt, with resultant ulnocarpal impaction. Surgical intervention, particularly in early stages, can halt progression of or reverse MD. Despite a considerable body of literature highlighting the presence of MD in TS, it is often underdiagnosed, in part due to a lack of data documenting the epidemiology and natural history. Objective: Analyze the frequency of diagnosis of MD in patients meeting key radiographic threshold criteria and document the time course of the deformity in these patients using these parameters. Methods: From a database of 264 patients with a confirmed diagnosis of TS, bone age radiographs for 187 (71%) were retrospectively measured against generally accepted cutoffs for MD using two parameters: ulnar tilt = UT and lunate subsidence = LS. For patients meeting general inclusion criteria of UT > 33° or LS < 0 mm, historical measurements of UT and LS were obtained using past bone ages and patients' charts were reviewed to determine if a clinical diagnosis of MD was made. Results: 7 patients (7/187 = 3.7%) met overall inclusion criteria and had radiographs consistent with Madelung Deformity. Of these 7, only one clinical diagnosis (14%) of MD was made; this patient underwent subsequent surgical intervention. The 6 undiagnosed patients had an average UT and LS of 40.5 degrees and -4.4 mm at the time of most recent bone age (~16.3 years old). The time-courses for 4 (UT) and 3 (LS) of the 6 non-surgical patients were plotted over time from 7.2 – 18.9 years of age. Patients crossed threshold at an average age of 15.3 and 13.6 years for UT and LS, respectively. Average maximum read-to-read growth rates of 5.3 degrees and 3.5 mm occurred at an average age of 15.3 (UT) and 14.2 years (LS). Conclusion: Our results suggest MD is significantly underdiagnosed in patients with TS, highlighting the need for better screening tools to make this diagnosis. This would include physical examination looking for the characteristic wrist deformity and careful analysis of bone age radiographs at an earlier age, when corrective surgery is more likely to succeed. We recommend careful scrutiny of yearly bone age radiographs from 10-15 years of age to ensure that the diagnosis of MD is not missed, and obtaining bilateral wrist radiographs (PA and Lateral views) for verification. Future research should focus on documenting disease progression using radiographic trends, as well as assessing how onset and progression are affected by therapeutic interventions such as growth hormone.

Tracking the Diagnosis and Progression of Madelung Deformity in Pediatric Turner Syndrome Patients

In many types of cells and tissues, the nuclear receptor corepressor 1 (Ncor1) is known as a main corepressor that interacts with thyroid hormone receptors (i.e., TRα, TRβ1, and TRβ2). In the absence of thyroid hormone (T3), NCOR1 is recruited by TRs to inhibit gene transcription. In the liver, the deletion of Ncor1 increases hepatic triglyceride levels. However, the detailed mechanism of how NCOR1 is involved in thyroid hormone signaling in different types of tissues is not fully understood. Our previous study showed that TRβ1 is expressed in the adrenal gland inner cortex and T3 treatment leads to the hypertrophy of this area. To determine the role of NCOR1 in the regulation of thyroid hormone signaling in adrenocortical cells, we generated the mice with a conditional deletion of Ncor1 in the adrenal cortex by crossing the Ncor1 floxed mice with the steroidogenic factor 1 (SF1) Cre mice. The RNA-seq data showed that only 76 genes were differentially expressed in adrenal glands due to the deletion of Ncor1 in adrenocortical cells. Gene ontology (GO) analysis revealed that 'cholesterol synthesis' was the top GO term associated with these 76 genes. Interestingly, 24-dehydrocholesterol reductase (Dhcr24), the key enzyme for cholesterol synthesis, was upregulated in knockout mice adrenal glands in both sexes. This phenotype fits the results in our previous studies that (1) Dhcr24 is significantly increased under T3 treatment in wild-type mice adrenal glands and (2) the DHCR24-expressing zone in the inner cortex is the primary responsive adrenal cortical layer under T3 treatment which leads to increased lipid accumulation in this area. To further study how DHCR24 is involved in this T3-induced lipid accumulation in the adrenal gland inner cortex, we generated Dhcr24 conditional knockout mice. We found that the T3-induced lipid accumulation in the adrenal gland inner cortex was sharply decreased in the Dhcr24;Sf1-Cre mice. In summary, with the Ncor1 conditional knockout mice, we found that the regulation of the cholesterol synthesis through DHCR24 is the primary function of NCOR1 in the adrenal gland inner cortex; by using the Dhcr24 conditional knockout mice, we further confirmed that the T3-induced lipid accumulation in the adrenal inner cortex can be blocked by the deletion of DHCR24. This study used genetic mouse models to decipher the connection between nuclear receptor corepressor Ncor1, the cholesterol synthesis enzyme Dhcr24, and how they control de novo cholesterol synthesis in the adrenal gland inner cortex.

Ncor1 Regulates the Expression of Dhcr24, which Controls de novo Cholesterol Synthesis in the Adrenal Gland Inner Cortex

Programmed death-ligand 1 (PD‐L1) is a strong immunosuppressor that inhibits T-cell activation by binding to its receptor (PD-1) on T-cells. Blocking the PD-L1/PD-1 interaction by monoclonal antibodies (mAbs) is an effective therapy for several cancers via activation of T-cells. Destructive thyroiditis and hypothyroidism often develop during anti-PD-L1 (αPD-L1) therapy but the pathogenic mechanisms are not known. We evaluated in vivo, the role of PD-L1 and its interactions with inflammatory triggers in the development of autoimmune thyroiditis (AIT). NOD.H-2h4 mice were treated with either αPD-L1 or isotype control (CTR) for two weeks and AIT evaluated after six weeks. αPD-L1 treated mice showed significantly higher Abs (p = 6x10e-4) and T-cell responses (p = 0.02) to thyroglobulin (Tg) compared with CTR mice. Serum fT4 levels were lower (p = 0.01) and TSH higher (p = 0.05) in αPD-L1 treated vs. CTR mice. Seven of the eight αPD-L1 treated mice (and none of the CTR mice) developed thyroid lymphocytic infiltration characterized by the presence of the CD4+, CD8+, FoxP3+ T- cells and B220+ B- cells. To gain insight into the pathways regulated by PD-L1 in the thyroid we assessed gene expression in the thyroid of αPD-L1 treated mice using RNA-seq. PD-L1 blockade was associated with upregulation of pathways of lymphocyte activation (p = 1.3x10e-5), lymphocyte proliferation (p = 2x10e-5), chemotaxis (p = 3.8x10e-12), and inflammatory response (p = 7.9x10e-7). Specifically, blocking PD-L1 was associated with upregulation of cytokine/chemokine genes that have a critical role in Th1 differentiation: IFNγ, IL-12, IL-15, CCL1 to CCL5, CD300, CXCL10, CXCL11. Ingenuity Pathway Analysis identified IFNγ and TNF as the top regulators of these activated gene networks. These results indicate that blockade of PD-L1 in thyroid promoted the Th1 mediator, IFNγ, inducing activation and proliferation of thyroidal CD4+ and CD8+ T cells, triggering thyroid tissue damage and AIT. Since PD-L1 mediates immune responses to inflammatory stressors (e.g. viral infections), we evaluated PD-L1 interaction with a known inflammatory trigger of AIT, interferon alpha (IFNα). Treatment with αPD-L1 + IFNα accelerated AIT in NOD.H-2h4 mice that developed high Tg Ab and T-cell responses and thyroidal lymphocytic infiltration only two weeks after treatment. Moreover, thyroiditis was more severe in mice receiving αPD-L1 + IFNα than αPD-L1 alone, manifesting by higher T-cell responses (p = 5x10e-3), and significantly more profound hypothyroidism. These results suggest that PDL-1 has a protective role in the thyroid against inflammatory stressors, and that its blockade exposes the thyroid to inflammatory damage. Therefore, in patients undergoing αPD-L1 therapy, inflammatory conditions (e.g. infections) can be a "second hit" that accelerates the onset of thyroiditis and augments thyroidal inflammation.

Dissecting Thyroidal Pathways Activated by PD-L1 Blockade Identifies New Mechanisms for Thyroiditis Triggered by Immune Checkpoint Inhibitors

Introduction: Low levels of triiodothyronine (T3) are common in patients with heart failure (HF). It has been proposed that the decreased levels of T3 contribute to metabolic and cardiac dysfunction in HF. We aimed to evaluate the effects of treatment with low dose and high dose of T3 in an animal model of HF with preserved ejection fraction (HFpEF). Materials and Methods: We evaluated four groups: ZSF1 Lean (Lean-Ctrl, n=8), ZSF1 obese (rat model of metabolic syndrome with HFpEF, HFpEF-Ctrl, n=13), ZSF1 obese supplemented with a replacement dose of T3 (initially 0.04mg/ml, increased to 0.06mg/ml after 4 weeks; HFpEF-T3high, n=8), and ZSF1 Obese supplemented with a low-dose of T3 (0.03mg/mL; HFpEF-T3low, n=8). T3 was supplemented in drinking water from week 13 to 24. The animals were submitted to anthropometric and metabolic evaluation, echocardiography, VO2max evaluation, hemodynamic evaluation, single cardiomyocyte evaluation, and myocardial tissue collection at 24 weeks. Results: HFpEF-Ctrl animals had lower serum and myocardial thyroid hormone levels than Lean-Ctrl. Treatment with low dose and high dose of T3 did not correct serum T3 levels, but increased myocardial T3 levels, with normalization of myocardial T3 levels in the HFpEF-T3high group. In comparison to HFpEF-Ctrl, body weight was significantly decreased in HFpEF-T3low and HFpEF-T3high groups (616±39g, 572±24g and 535±18g respectively, p<0.001). An improvement in glucose metabolism was observed only in HFpEF-T3high, with a decreased AUC of glucose during OGTT and insulin tolerance test. Both treated groups presented an improvement in diastolic function (with decreased isovolumetric relaxation time) and systolic function (with increased peak systolic velocity and decreased ejection time) comparing to HFpEF-Ctrl. These results were supported by enhanced Ca2+ transients during diastole and sarcomere relaxation. Comparing with HFpEF-Ctrl, animals treated with T3 had higher myocardial expression of the calcium transporter RYR2, of the transcriptional coactivator PGC-1α, and of the α-myosin heavy chain (MHC), with a lower expression of β-MHC. VO2max was improved with low-dose and high-dose T3 compared with HFpEF-Ctrl. Comparing with HFpEF-Ctrl, heart rate was increased with high-dose (277.9±30.2 vs 313.5±35.8, p=0.049) but not significantly with low-dose (277.9±30.2 vs 299.8±30.9 bpm, p=0.13). Mortality was increased in the HFpEF-T3high comparing with the other groups (no animals died during the protocol in the Lean-Ctrl, HFpEF-Ctrl and HFpEF-T3low groups; three animals had sudden death in the HFpEF-T3high group). Conclusion: Treatment with T3 improves metabolic function, myocardial calcium handling, diastolic and systolic function, and exercise capacity in this animal model of HFpEF. While the low dose was well tolerated and safe, the high dose was associated with increased heart rate and a higher risk of sudden death. Modulation of thyroid hormones may be a potential therapeutic target in HFpEF; however such approaches must take into account a narrow therapeutic window of T3 in HFpEF.

Treatment of Heart Failure with Preserved Ejection Fraction (HFpEF) with Low and High Dose of Triiodothyronine: an Animal Model of Metabolic Syndrome with HFpEF

Thyroid cancer affects ethnic groups at different rates and severity. Despite this, thyroid cancer health disparities are still an understudied area. Our laboratory has shown a differential expression of vitamin D binding protein (DBP) in Filipino Americans (FA) versus European Americans (EA) [1]. Higher DBP levels correlate to a better prognosis. A study has revealed a DBP-dependent vitamin D receptor (VDR) promoter activation. In this study, we investigated whether VDR and DBP are expressed differentially in different ethnic groups, such as African Americans (AA), Hispanic Americans (HA), EA, and FA. We were also able to determine the differential DBP polymorphisms, VDR variant expressions, and DBP-VDR interactions within different ethnicities. By PCR-Restriction Fragment Length Polymorphism (PCR-RFLP), we determined a higher frequency of DBP gene polymorphism in FA versus EA. Analyzing the Cancer Genome Atlas (TCGA) thyroid cancer datasets with the UALCAN assay, we found the differential expressions of DBP and VDR genes based on cancer stages, sample types, race, and histological subtypes. By immunohistochemistry, we detected strong nuclear VDR (nVDR) and very low membranous VDR (mVDR) expression that correlated with low DBP in FA thyroid cancer tissues. In contrast, there was a higher expression of both mVDR and DBP in HA versus the other ethnicities. Co-immunoprecipitation analysis revealed a stronger DBP interaction with mVDR in FA compared to other ethnicities. Our data suggest that low DBP correlates with low mVDR in FA, whereas high DBP correlates with high mVDR in the other ethnicities. In conclusion, the strong interaction of DBP with mVDR in FA may implicate the potential role of DBP-mVDR crosstalk in aggressive thyroid cancer. Future research goals will be aimed at determining pathways involved in BDP-mVDR crosstalk in thyroid cancer health disparities.

B. Mull, R. Davis, I. Munir, M.C. Perez, A.A. Simental, S. Khan, Differential expression of Vitamin D binding protein in thyroid cancer health disparities, Oncotarget 12(7) (2021) 596-607.

Differential Interactions of Vitamin D Binding Protein and Vitamin D Receptor in Different Ethnic Groups with Aggressive Thyroid Cancer

Thyroid hormones (THs) thyroxine (T4) and triiodothyronine (T3) are under homeostatic and circadian control by the hypothalamic-pituitary-thyroid axis while their free plasma concentrations are strongly buffered by three TH binding proteins (THBPs): thyroxine-binding globulin (TBG), transthyretin (TTR), and albumin (ALB). The THBPs are crucial to the even delivery of THs from the blood to tissues, but their relative contributions and spatial kinetics within tissues are unclear. Many endocrine-disrupting chemicals (EDCs) can interfere with the regulation and actions of THs, some of which are structurally similar to THs with comparable or even higher binding affinities for THBPs. It has been suspected that by disrupting the binding of THs with THBPs, EDCs may alter the plasma TH concentrations and the delivery to tissues. Given that the majority of the binding sites on THBPs are unoccupied—thus available for EDC binding—it is uncertain whether TH homeostasis can be tangibly perturbed by EDC exposure. To answer these questions, we constructed a spatial multi-compartment human physiologically based kinetic (PBK) model of TH production, distribution, and metabolism. The model contains the thyroid, liver, and rest-of-body compartments with explicit descriptions of the reversible binding kinetics between THs and THBPs in the blood. The model was parameterized and validated extensively based on literature data. Here we reported several novel findings: (1) The contribution to TH tissue delivery by each THBP is not spatially constant across a tissue: ALB always contributes more THs to the arterial side of the tissue while TBG contributes more to the venous side.  (2) THBPs are essential for a uniform TH tissue delivery but are cross-compensatory in this role. (3) Contrary to the long-held assumption that ALB is the dominant contributor, TBG contributes more of the THs delivered to a tissue overall than ALB and TTR. (4) Bode plot analysis using control theory suggests that a circadian signal driving T4-to-T3 conversion in the extra-thyroidal tissue is crucial to establish the distinct phase and amplitude profiles of circulating T3 and T4 in humans. (5) Displacement of THs from THBPs by high-affinity EDCs has a negligible effect on free plasma THs even under high exposures. (6) Daily exposure to THBP-binding EDCs does not affect the circadian variations in tissue delivery of THs. The PBK model can be further elaborated in the future to make tissue-specific predictions of TH kinetics.

The Impact of Makorin Ring Finger Protein 3 (MKRN3) Overexpression in the Arcuate Nucleus of Postpubertal Female Mice on the HPG Axis

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