Association of Timing of Moderate-to-Vigorous Physical Activity With Changes in Glycemic Control Over 4 Years in Adults With Type 2 Diabetes From the Look AHEAD Trial

OBJECTIVE

We aimed to determine the association of the time-of-day of bout-related moderate-to-vigorous physical activity (bMVPA) with changes in glycemic control across 4 years in adults with overweight/obesity and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Among 2,416 participants (57% women; mean age, 59 years) with 7-day waist-worn accelerometry recording at year 1 or 4, we assigned bMVPA timing groups based on the participants' temporal distribution of bMVPA at year 1 and recategorized them at year 4. The time-varying exposure of bMVPA (≥10-min bout) timing was defined as ≥50% of bMVPA occurring during the same time period (morning, midday, afternoon, or evening), <50% of bMVPA in any time period (mixed), and ≤1 day with bMVPA per week (inactive).

RESULTS

HbA1c reduction at year 1 varied among bMVPA timing groups (P = 0.02), independent of weekly bMVPA volume and intensity. The afternoon group had the greatest HbA1c reduction versus inactive (-0.22% [95%CI -0.39%, -0.06%]), the magnitude of which was 30-50% larger than the other groups. The odds of discontinuation versus maintaining or initiating glucose-lowering medications at year 1 differed by bMVPA timing (P = 0.04). The afternoon group had the highest odds (odds ratio 2.13 [95% CI 1.29, 3.52]). For all the year-4 bMVPA timing groups, there were no significant changes in HbA1c between year 1 and 4.

CONCLUSION

bMVPA performed in the afternoon is associated with improvements in glycemic control in adults with diabetes, especially within the initial 12 months of an intervention. Experimental studies are needed to examine causality.

Exercise training remodels inguinal white adipose tissue through adaptations in innervation, vascularization, and the extracellular matrix

Inguinal white adipose tissue (iWAT) is essential for the beneficial effects of exercise training on metabolic health. The underlying mechanisms for these effects are not fully understood, and here, we test the hypothesis that exercise training results in a more favorable iWAT structural phenotype. Using biochemical, imaging, and multi-omics analyses, we find that 11 days of wheel running in male mice causes profound iWAT remodeling including decreased extracellular matrix (ECM) deposition and increased vascularization and innervation. We identify adipose stem cells as one of the main contributors to training-induced ECM remodeling, show that the PRDM16 transcriptional complex is necessary for iWAT remodeling and beiging, and discover neuronal growth regulator 1 (NEGR1) as a link between PRDM16 and neuritogenesis. Moreover, we find that training causes a shift from hypertrophic to insulin-sensitive adipocyte subpopulations. Exercise training leads to remarkable adaptations to iWAT structure and cell-type composition that can confer beneficial changes in tissue metabolism.

Single-cell dissection of the obesity-exercise axis in adipose-muscle tissues implies a critical role for mesenchymal stem cells

Exercise training is critical for the prevention and treatment of obesity, but its underlying mechanisms remain incompletely understood given the challenge of profiling heterogeneous effects across multiple tissues and cell types. Here, we address this challenge and opposing effects of exercise and high-fat diet (HFD)-induced obesity at single-cell resolution in subcutaneous and visceral white adipose tissue and skeletal muscle in mice with diet and exercise training interventions. We identify a prominent role of mesenchymal stem cells (MSCs) in obesity and exercise-induced tissue adaptation. Among the pathways regulated by exercise and HFD in MSCs across the three tissues, extracellular matrix remodeling and circadian rhythm are the most prominent. Inferred cell-cell interactions implicate within- and multi-tissue crosstalk centered around MSCs. Overall, our work reveals the intricacies and diversity of multi-tissue molecular responses to exercise and obesity and uncovers a previously underappreciated role of MSCs in tissue-specific and multi-tissue beneficial effects of exercise.

Post-graduate medical education in the time of COVID-19: Not a remotely simple task

The COVID-19 pandemic has stimulated a rapid shift towards telemedicine, which has had tremendous repercussions on all domains of the healthcare ecosystem. The effects of the transition to telemedicine on post-graduate medical education and on patient care provided by trainees have not been fully elucidated. Focusing on the multifaceted scope of endocrinology teaching clinics, the experience garnered by endocrinology fellows, preceptors, and patients through the adoption of virtual visits has shed new light on relevant challenges that require specific attention. First, we identified a divergent trend in glycated hemoglobin in people with type 1 diabetes according to their use of continuous glucose monitoring (CGM). Second, the patient's perspective highlighted positive aspects, including expanded options for clinical care, but also limitations in communication with clinicians for people without access to videoconferencing tools or EHR-based portals. Finally, regarding medical training evaluation and skills-based learning, academic centers, professional organizations, and clinical educators should develop new teaching curricula suitable for a telemedicine-based environment. While simultaneously facing numerous pressures, fellows can potentially spearhead new models of care delivery and innovative approaches to clinical education leveraging telemedicine.

Exercise Training Promotes Sex-Specific Adaptations in Mouse Inguinal White Adipose Tissue

Recent studies demonstrate that adaptations to white adipose tissue (WAT) are important components of the beneficial effects of exercise training on metabolic health. Exercise training favorably alters the phenotype of subcutaneous inguinal WAT (iWAT) in male mice, including decreasing fat mass, improving mitochondrial function, inducing beiging, and stimulating the secretion of adipokines. In this study, we find that despite performing more voluntary wheel running compared with males, these adaptations do not occur in the iWAT of female mice. Consistent with sex-specific adaptations, we report that mRNA expression of androgen receptor coactivators is upregulated in iWAT from trained male mice and that testosterone treatment of primary adipocytes derived from the iWAT of male, but not female mice, phenocopies exercise-induced metabolic adaptations. Sex specificity also occurs in the secretome profile, as we identify cysteine-rich secretory protein 1 (Crisp1) as a novel adipokine that is only secreted from male iWAT in response to exercise. Crisp1 expression is upregulated by testosterone and functions to increase glucose and fatty acid uptake. Our finding that adaptations to iWAT with exercise training are dramatically greater in male mice has potential clinical implications for understanding the different metabolic response to exercise training in males and females and demonstrates the importance of investigating both sexes in studies of adipose tissue biology.

Placental superoxide dismutase 3 mediates benefits of maternal exercise on offspring health

Poor maternal diet increases the risk of obesity and type 2 diabetes in offspring, adding to the ever-increasing prevalence of these diseases. In contrast, we find that maternal exercise improves the metabolic health of offspring, and here, we demonstrate that this occurs through a vitamin D receptor-mediated increase in placental superoxide dismutase 3 (SOD3) expression and secretion. SOD3 activates an AMPK/TET signaling axis in fetal offspring liver, resulting in DNA demethylation at the promoters of glucose metabolic genes, enhancing liver function, and improving glucose tolerance. In humans, SOD3 is upregulated in serum and placenta from physically active pregnant women. The discovery of maternal exercise-induced cross talk between placenta-derived SOD3 and offspring liver provides a central mechanism for improved offspring metabolic health. These findings may lead to novel therapeutic approaches to limit the transmission of metabolic disease to the next generation.

Association of Objectively Measured Timing of Physical Activity Bouts With Cardiovascular Health in Type 2 Diabetes

OBJECTIVE

Moderate- to vigorous-intensity physical activity (MVPA) improves cardiovascular health. Few studies have examined MVPA timing. We examined the associations of timing of bout-related MVPA with cardiorespiratory fitness and cardiovascular risk in adults with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Baseline 7-day hip-worn accelerometry data from Look AHEAD participants (n = 2,153, 57% women) were analyzed to identify bout-related MVPA (≥3 METs/min for ≥10 min). Cardiorespiratory fitness was assessed by maximal graded exercise test. Participants were categorized into six groups on the basis of the time of day with the majority of bout-related MVPA (METs × min): ≥50% of bout-related MVPA during the same time window (morning, midday, afternoon, or evening), <50% of bout-related MVPA in any time category (mixed; the reference group), and ≤1 day with bout-related MVPA per week (inactive).

RESULTS

Cardiorespiratory fitness was highly associated with timing of bout-related MVPA (P = 0.0005), independent of weekly bout-related MVPA volume and intensity. Importantly, this association varied by sex (P = 0.02). In men, the midday group had the lowest fitness (β = -0.46 [95% CI -0.87, -0.06]), while the mixed group in women was the least fit. Framingham risk score (FRS) was associated with timing of bout-related MVPA (P = 0.02), which also differed by sex (P = 0.0007). The male morning group had the highest 4-year FRS (2.18% [0.70, 3.65]), but no association was observed in women.

CONCLUSIONS

Timing of bout-related MVPA is associated with cardiorespiratory fitness and cardiovascular risk in men with type 2 diabetes, independent of bout-related MVPA volume and intensity. Prospective studies are needed to determine the impacts of MVPA timing on cardiovascular health.

Abnormal Exercise Test or CVD History on Weight Loss or Fitness: the Look AHEAD Trial

PURPOSE

Obesity and type 2 diabetes are associated with an increased risk of cardiovascular disease (CVD) and the combination of weight loss and increased physical exercise are commonly recommended to reduce CVD. This study examined whether people with obesity and type 2 diabetes with an abnormal graded exercise tolerance test (GXT) or a history of CVD would have less success in achieving weight loss and improved fitness, compared to adults without these conditions.

METHODS

The Look AHEAD Study examined whether an intensive lifestyle intervention (ILI) compared with diabetes support and education (DSE) reduced cardiovascular events in adults with overweight/obesity and type 2 diabetes. Participants underwent a baseline maximal GXT and provided medical history data. Weight loss and fitness change were examined in 5011 participants over four years in those with or without an abnormal baseline GXT and/or history of CVD.

RESULTS

After four years, weight loss in both ILI and DSE were significantly greater in those without a prior history of CVD than in those with a CVD history (6.69% vs 5.98%, p=0.02, in ILI and 0.73 vs -.07% (weight gain), p=0.01, in DSE). Likewise, those without a prior history of CVD experienced greater improvements in fitness in both ILI and DSE relative to those with a history of CVD. Having an abnormal GXT at baseline did not affect weight loss or fitness.

CONCLUSIONS

A history of CVD at baseline modestly lessened weight loss and fitness changes at 4 years, whereas having any abnormality on the baseline GXT did not affect these outcomes. Thus, weight loss and improved fitness are achievable in adults with a history of CVD or ECG abnormalities.

TGF-β2 is an exercise-induced adipokine that regulates glucose and fatty acid metabolism

Exercise improves health and well-being across diverse organ systems, and elucidating mechanisms underlying the beneficial effects of exercise can lead to new therapies. Here, we show that transforming growth factor-β2 (TGF-β2) is secreted from adipose tissue in response to exercise and improves glucose tolerance in mice. We identify TGF-β2 as an exercise-induced adipokine in a gene expression analysis of human subcutaneous adipose tissue biopsies after exercise training. In mice, exercise training increases TGF-β2 in scWAT, serum, and its secretion from fat explants. Transplanting scWAT from exercise-trained wild type mice, but not from adipose tissue-specific Tgfb2−/− mice, into sedentary mice improves glucose tolerance. TGF-β2 treatment reverses the detrimental metabolic effects of high fat feeding in mice. Lactate, a metabolite released from muscle during exercise, stimulates TGF-β2 expression in human adipocytes. Administration of the lactate-lowering agent dichloroacetate during exercise training in mice decreases circulating TGF-β2 levels and reduces exercise-stimulated improvements in glucose tolerance. Thus, exercise training improves systemic metabolism through inter-organ communication with fat via a lactate-TGF-β2-signaling cycle.

12,13-diHOME: An Exercise-Induced Lipokine that Increases Skeletal Muscle Fatty Acid Uptake

Circulating factors released from tissues during exercise have been hypothesized to mediate some of the health benefits of regular physical activity. Lipokines are circulating lipid species that have recently been reported to affect metabolism in response to cold. Here, lipidomics analysis revealed that a bout of moderate-intensity exercise causes a pronounced increase in the circulating lipid 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME) in male, female, young, old, sedentary, and active human subjects. In mice, both a single bout of exercise and exercise training increased circulating 12,13-diHOME and surgical removal of brown adipose tissue (BAT) negated the increase in 12,13-diHOME, suggesting that BAT is the tissue source for exercise-stimulated 12,13-diHOME. Acute 12,13-diHOME treatment of mice in vivo increased skeletal muscle fatty acid uptake and oxidation, but not glucose uptake. These data reveal that lipokines are novel exercise-stimulated circulating factors that may contribute to the metabolic changes that occur with physical exercise.

Mechanisms of weight loss and improved metabolism following bariatric surgery

Bariatric surgery is increasingly recognized as one of the most effective interventions to help patients achieve significant and sustained weight loss, as well as improved metabolic and overall health. Unfortunately, the cellular and physiological mechanisms by which bariatric surgery achieves weight loss have not been fully elucidated, yet are critical to understanding the central role of the intestinal tract in whole-body metabolism and to developing novel strategies for the treatment of obesity. In this review, we provide an overview of potential mechanisms contributing to weight loss, including effects on regulation of energy balance and both central and peripheral nervous system regulation of appetite and metabolism. Moreover, we highlight the importance of the gastrointestinal tract, including alterations in bile acid physiology, secretion of intestinally derived hormones, and the microbiome, as a potent mediator of improved metabolism in postbariatric patients.

Concurrent Intrathyroidal Thyroid Cancer and Thyroid Cancer in Struma Ovarii: A Case Report and Literature Review

Context

The presence of differentiated thyroid cancer in mature cystic teratomas in the ovaries is rare, and usually incidentally found on surgical pathology specimens. We present a case of simultaneous intrathyroidal thyroid cancer and thyroid cancer within a struma ovarii, presenting specific diagnostic challenges.

Case Description

A 55-year-old woman had an intrathyroidal, encapsulated 1.2-cm papillary thyroid carcinoma, follicular variant, which was resected. Laboratory studies showed an elevated thyroglobulin level of 35 ng/mL while on suppressive levothyroxine therapy. During preparation for radioactive iodine ablation, thyroglobulin increased dramatically to 3490 ng/mL. A pretreatment whole-body scan showed residual tracer uptake in the thyroid bed and increased radiotracer uptake in the pelvis that raised concern for a pelvic metastasis, given the marked thyroglobulin elevation. After ablation, the posttreatment scan showed intense focal uptake in the pelvis. Single-photon emission computed tomography-computed tomography confirmed that the tracer uptake corresponded to a right adnexal mass. The patient underwent a laparoscopic bilateral salpingo-oophorecotomy with pelvic washings. The final pathology of the right ovary showed papillary thyroid carcinoma arising in a mature cystic teratoma. In addition, there was abundant normal thyroid tissue with colloid surrounding the carcinoma, indicating a source for the dramatic rise in thyroglobulin levels and suggesting that the ovarian papillary thyroid cancer arose within the teratoma and was not metastatic disease. Thyroglobulin measurements have been undetectable for 5 years since surgery and radioiodine treatment.

Conclusions

Concurrent intrathyroidal thyroid cancer and differentiated thyroid cancer in struma ovarii are very rare, but can often be distinguished on clinical grounds.

Short-term insulin requirements following gastric bypass surgery in severely obese women with type 1 diabetes

BACKGROUND

In severely obese type 2 diabetes patients, gastric bypass surgery (GB) reduces body mass index (BMI) and hemoglobin A1c (HbA1c) and allows reduced doses of insulin and other medications. Data regarding the effects of GB on severely obese patients with type 1 diabetes are limited.

METHODS

Severely obese women with type 1 diabetes (n = 9) were studied immediately before and after GB (7.7 ± 5.8 weeks, mean ± SD).

RESULTS

On average, GB reduced mean BMI by 11% and mean HbA1c by 0.9% (from 8.0 to 7.1%), with a parallel 38% decrease in basal insulin requirements (expressed per kilogram of body weight).

CONCLUSION

GB rapidly decreased BMI, HbA1c, and insulin requirements in severely obese women with type 1 diabetes. However, physiologic insulin replacement remains necessary in patients with type 1 diabetes.

Exercise Effects on White Adipose Tissue: Beiging and Metabolic Adaptations

Regular physical activity and exercise training have long been known to cause adaptations to white adipose tissue (WAT), including decreases in cell size and lipid content and increases in mitochondrial proteins. In this article, we discuss recent studies that have investigated the effects of exercise training on mitochondrial function, the "beiging" of WAT, regulation of adipokines, metabolic effects of trained adipose tissue on systemic metabolism, and depot-specific responses to exercise training. The major WAT depots in the body are found in the visceral cavity (vWAT) and subcutaneously (scWAT). In rodent models, exercise training increases mitochondrial biogenesis and activity in both these adipose tissue depots. Exercise training also increases expression of the brown adipocyte marker uncoupling protein 1 (UCP1) in both adipose tissue depots, although these effects are much more pronounced in scWAT. Consistent with the increase in UCP1, exercise training increases the presence of brown-like adipocytes in scWAT, also known as browning or beiging. Training results in changes in the gene expression of thousands of scWAT genes and an altered adipokine profile in both scWAT and vWAT. Transplantation of trained scWAT in sedentary recipient mice results in striking improvements in skeletal muscle glucose uptake and whole-body metabolic homeostasis. Human and rodent exercise studies have indicated that exercise training can alter circulating adipokine concentration as well as adipokine expression in adipose tissue. Thus, the profound changes to WAT in response to exercise training may be part of the mechanism by which exercise improves whole-body metabolic health.

A novel role for subcutaneous adipose tissue in exercise-induced improvements in glucose homeostasis

Exercise training improves whole-body glucose homeostasis through effects largely attributed to adaptations in skeletal muscle; however, training also affects other tissues, including adipose tissue. To determine whether exercise-induced adaptations to adipose tissue contribute to training-induced improvements in glucose homeostasis, subcutaneous white adipose tissue (scWAT) from exercise-trained or sedentary donor mice was transplanted into the visceral cavity of sedentary recipients. Remarkably, 9 days post-transplantation, mice receiving scWAT from exercise-trained mice had improved glucose tolerance and enhanced insulin sensitivity compared with mice transplanted with scWAT from sedentary or sham-treated mice. Mice transplanted with scWAT from exercise-trained mice had increased insulin-stimulated glucose uptake in tibialis anterior and soleus muscles and brown adipose tissue, suggesting that the transplanted scWAT exerted endocrine effects. Furthermore, the deleterious effects of high-fat feeding on glucose tolerance and insulin sensitivity were completely reversed if high-fat-fed recipient mice were transplanted with scWAT from exercise-trained mice. In additional experiments, voluntary exercise training by wheel running for only 11 days resulted in profound changes in scWAT, including the increased expression of ∼1,550 genes involved in numerous cellular functions including metabolism. Exercise training causes adaptations to scWAT that elicit metabolic improvements in other tissues, demonstrating a previously unrecognized role for adipose tissue in the beneficial effects of exercise on systemic glucose homeostasis.

Brown adipose tissue regulates glucose homeostasis and insulin sensitivity

Brown adipose tissue (BAT) is known to function in the dissipation of chemical energy in response to cold or excess feeding, and also has the capacity to modulate energy balance. To test the hypothesis that BAT is fundamental to the regulation of glucose homeostasis, we transplanted BAT from male donor mice into the visceral cavity of age- and sex-matched recipient mice. By 8-12 weeks following transplantation, recipient mice had improved glucose tolerance, increased insulin sensitivity, lower body weight, decreased fat mass, and a complete reversal of high-fat diet-induced insulin resistance. Increasing the quantity of BAT transplanted into recipient mice further improved the metabolic effects of transplantation. BAT transplantation increased insulin-stimulated glucose uptake in vivo into endogenous BAT, white adipose tissue (WAT), and heart muscle but, surprisingly, not skeletal muscle. The improved metabolic profile was lost when the BAT used for transplantation was obtained from Il6-knockout mice, demonstrating that BAT-derived IL-6 is required for the profound effects of BAT transplantation on glucose homeostasis and insulin sensitivity. These findings reveal a previously under-appreciated role for BAT in glucose metabolism.