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Emma Ahlqvist, Rashmi B Prasad, and Leif Groop

Type 2 diabetes (T2D) is one of the fastest increasing diseases worldwide. Although it is defined by a single metabolite, glucose, it is increasingly recognized as a highly heterogeneous disease with varying clinical manifestations. Identification of different subtypes at an early stage of disease when complications might still be prevented could hopefully allow for more personalized medicine. An important step toward precision medicine would be to target the right resources to the right patients, thereby improving patient health and reducing health costs for the society. More well-defined disease populations also offer increased power in experimental, genetic and clinical studies. In a recent study, we used six clinical variables (glutamate decarboxylase autoantibodies, age at onset of diabetes, glycated hemoglobin, BMI and simple measures of insulin resistance and insulin secretion (so called HOMA estimates) to cluster adult-onset diabetes patients into five subgroups. These subgroups have been robustly reproduced in several populations worldwide and are associated with different risks of diabetic complications and responses to treatment. Importantly, the group with severe insulin-deficient diabetes had increased risk of retinopathy and neuropathy, whereas the severe insulin-resistant diabetes group has the highest risk for diabetic kidney disease (DKD) and fatty liver. This emphasizes the key role of insulin resistance in the pathogenesis of DKD and fatty liver in T2D. In conclusion, this novel subclassification, breaking down T2D in clinically meaningful subgroups, provides the prerequisite framework for expanded personalized medicine in diabetes beyond what is already available for monogenic and to some extent type 1 diabetes.

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Taylor Landry, Daniel Shookster, Alec Chaves, Katrina Free, Tony Nguyen, and Hu Huang

Recent evidence identifies a potent role for aerobic exercise to modulate the activity of hypothalamic neurons related to appetite; however, these studies have been primarily performed in male rodents. Since females have markedly different neuronal mechanisms regulating food intake, the current study aimed to determine the effects of acute treadmill exercise on hypothalamic neuron populations involved in regulating appetite in female mice. Mature, untrained female mice were exposed to acute sedentary, low- (10 m/min), moderate- (14 m/min), and high (18 m/min)-intensity treadmill exercise in a randomized crossover design. Mice were fasted 10 h before exercise, and food intake was monitored for 48 h after bouts. Immunohistochemical detection of cFOS was performed 3 h post-exercise to determine the changes in hypothalamic neuropeptide Y (NPY)/agouti-related peptide (AgRP), pro-opiomelanocortin (POMC), tyrosine hydroxylase (TH), and SIM1-expressing neuron activity concurrent with the changes in food intake. Additionally, stains for pSTAT3tyr705 and pERKthr202/tyr204 were performed to detect exercise-mediated changes in intracellular signaling. Briefly, moderate- and high-intensity exercises increased 24-h food intake by 5.9 and 19%, respectively, while low-intensity exercise had no effects. Furthermore, increases in NPY/AgRPARC, SIM1PVN, and TH neuron activity were observed 3 h after high-intensity exercise, with no effects on POMCARC neurons. While no effects of exercise on pERKthr202/tyr204 were observed, pSTAT3tyr705 was elevated specifically in NPY/AgRP neurons 3 h post-exercise. Overall, aerobic exercise increased the activity of several appetite-stimulating neuron populations in the hypothalamus of female mice, which may provide insight into previously reported sexual dimorphisms in post-exercise feeding.

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Ming-sheng Ye, Liping Luo, Qi Guo, Tian Su, Peng Cheng, and Yan Huang

Brown adipose tissue (BAT) is emerging as a target to beat obesity through the dissipation of chemical energy to heat. However, the molecular mechanisms of brown adipocyte thermogenesis remain to be further elucidated. Here, we show that KCTD10, a member of the polymerase delta-interacting protein 1 family, was reduced in BAT by cold stress and a β3 adrenoceptor agonist. Moreover, KCTD10 level increased in the BAT of obese mice, and KCTD10 overexpression attenuates uncoupling protein 1 expression in primary brown adipocytes. BAT-specific KCTD10 knockdown mice had increased thermogenesis and cold tolerance protecting from high-fat diet (HFD)-induced obesity. Conversely, overexpression of KCTD10 in BAT caused reduced thermogenesis, cold intolerance, and obesity. Mechanistically, inhibiting Notch signaling restored the KCTD10 overexpression-suppressed thermogenesis. Our study presents that KCTD10 serves as an upstream regulator of Notch signaling pathway to regulate BAT thermogenesis and whole-body metabolic function.

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Ines Ross, Denzel B Omengan, Guo N Huang, and Alexander Y Payumo

While adult zebrafish and newborn mice possess a robust capacity to regenerate their hearts, this ability is generally lost in adult mammals. The logic behind the diversity of cardiac regenerative capacity across the animal kingdom is not well understood. We have recently reported that animal metabolism is inversely correlated to the abundance of mononucleated diploid cardiomyocytes in the heart, which retain proliferative and regenerative potential. Thyroid hormones are classical regulators of animal metabolism, mitochondrial function, and thermogenesis, and a growing body of scientific evidence demonstrates that these hormonal regulators also have direct effects on cardiomyocyte proliferation and maturation. We propose that thyroid hormones dually control animal metabolism and cardiac regenerative potential through distinct mechanisms, which may represent an evolutionary tradeoff for the acquisition of endothermy and loss of heart regenerative capacity. In this review, we describe the effects of thyroid hormones on animal metabolism and cardiomyocyte regeneration and highlight recent reports linking the loss of mammalian cardiac regenerative capacity to metabolic shifts occurring after birth.

Free access

Sarah J Richardson and Alberto Pugliese

We review the current knowledge of pancreas pathology in type 1 diabetes. During the last two decades, dedicated efforts toward the recovery of pancreas from deceased patients with type 1 diabetes have promoted significant advances in the characterization of the pathological changes associated with this condition. The implementation of autoantibody screening among organ donors has also allowed examining pancreas pathology in the absence of clinical disease, but in the presence of serological markers of autoimmunity. The assessment of key features of pancreas pathology across various disease stages allows driving parallels with clinical disease stages. The main pathological abnormalities observed in the pancreas with type 1 diabetes are beta-cell loss and insulitis; more recently, hyperexpression of HLA class I and class II molecules have been reproduced and validated. Additionally, there are changes affecting extracellular matrix components, evidence of viral infections, inflammation, and ER stress, which could contribute to beta-cell dysfunction and the stimulation of apoptosis and autoimmunity. The increasing appreciation that beta-cell loss can be less severe at diagnosis than previously estimated, the coexistence of beta-cell dysfunction, and the persistence of key features of pancreas pathology for years after diagnosis impact the perception of the dynamics of this chronic process. The emerging information is helping the identification of novel therapeutic targets and has implications for the design of clinical trials.

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Patricia Cristine Borck, Sarah Rickli, Jean Franciesco Vettorazzi, Thiago Martins Batista, Antonio Carlos Boschero, Elaine Vieira, and Everardo Magalhães Carneiro

Disruption of biological rhythms due to exposure to artificial light at night (ALAN) has emerged as a new risk factor for metabolic diseases. However, the effects of ALAN exposure on energy metabolism with concomitant misalignment in the circadian system caused by nutritional imbalance remain largely unexplored. Here, we evaluate whether a low-protein (LP) diet could enhance the effects induced by exposure to ALAN on the energy metabolism and consequently predispose to metabolic disorders. Male C57BL6/J mice were weaned on a normal protein (NP) or a LP diet and housed on 12 h light:12 h darkness (LD) cycle. After 6 weeks, mice maintained on their respective diets were subdivided into normal light/darkness cycle (NP/LD; LP/LD) or exposed to ALAN (NP/LL; LP/LL) for 8 weeks. We observed that exposure to ALAN concomitant to LP diet disrupts the behavioral rhythms, without shifting the timing of food intake. Furthermore, exposure to ALAN leads to increased body and fat pad weights, higher levels of fast and fed glycemia and glucose intolerance independent of the diet consumed. Importantly, the effects of ALAN on circadian regulation of insulin sensitivity were diet-dependent with LP/LL mice showing insulin resistance in an opposite time of day than NP/LL. At the molecular level, exposure to ALAN concurrent with LP diet increased the expression of phosphoenolpyruvate carboxykinase 1 in both periods analyzed and inverted the pattern of fibroblast growth factor 21 (Fgf21) expression in the liver. Our data suggest that dietary protein restriction modulates the effects induced by nighttime light exposure on glucose metabolism, which could be partially related with the dysregulation of hepatic Fgf21 expression.

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Amanda J Genders, Jujiao Kuang, Evelyn C Marin, Nicholas J Saner, Javier Botella, Macsue Jacques, Glenn K McConell, Victor A Andrade-Souza, Javier Chagolla, and David J Bishop

The aim of this study was to investigate the relationship between mitochondrial content and respiratory function and whole-body insulin resistance in high-fat diet (HFD) fed rats. Male Wistar rats were given either a chow diet or an HFD for 12 weeks. After 4 weeks of the dietary intervention, half of the rats in each group began 8 weeks of interval training. In vivo glucose and insulin tolerance were assessed. Mitochondrial respiratory function was assessed in permeabilised soleus and white gastrocnemius (WG) muscles. Mitochondrial content was determined by the measurement of citrate synthase (CS) activity and protein expression of components of the electron transport system (ETS). We found HFD rats had impaired glucose and insulin tolerance but increased mitochondrial respiratory function and increased protein expression of components of the ETS. This was accompanied by an increase in CS activity in WG. Exercise training improved glucose and insulin tolerance in the HFD rats. Mitochondrial respiratory function was increased with exercise training in the chow-fed animals in soleus muscle. This exercise effect was absent in the HFD animals. In conclusion, exercise training improved insulin resistance in HFD rats but without changes in mitochondrial respiratory function and content. The lack of an association between mitochondrial characteristics and whole-body insulin resistance was reinforced by the absence of strong correlations between these measures. Our results suggest that improvements in mitochondrial respiratory function and content are not responsible for improvements in whole-body insulin resistance in HFD rats.

Open access

Christina Antza, Georgios Kostopoulos, Samiul Mostafa, Krishnarajah Nirantharakumar, and Abd Tahrani

Global rates of obesity and type 2 diabetes mellitus (T2DM) are increasing globally concomitant with a rising prevalence of sleep deprivation and sleep disorders. Understanding the links between sleep, obesity and T2DM might offer an opportunity to develop better prevention and treatment strategies for these epidemics. Experimental studies have shown that sleep restriction is associated with changes in energy homeostasis, insulin resistance and β-cell function. Epidemiological cohort studies established short sleep duration as a risk factor for developing obesity and T2DM. In addition, small studies suggested that short sleep duration was associated with less weight loss following lifestyle interventions or bariatric surgery. In this article, we review the epidemiological evidence linking sleep duration to obesity and T2DM and plausible mechanisms. In addition, we review the impact of changes in sleep duration on obesity and T2DM.

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Yan Cao, Zijie Feng, Xin He, Xuyao Zhang, Bowen Xing, Yuan Wu, Taylor Hojnacki, Bryson W Katona, Jian Ma, Xiaorong Zhan, and Xianxin Hua

Gestational diabetes mellitus (GDM) is a condition of diabetes with onset or first recognition in pregnancy. Its incidence is increasing, and GDM deleteriously affects both mother and the fetus during and even after pregnancy. Previous studies in mice have shown that during pregnancy, β-cell proliferation increases in the middle and late stages of pregnancy and returns to normal levels after delivery. Hormones, such as prolactin, estradiol, and progesterone as well as protein kinases, play important roles in regulating gestation-mediated β-cell proliferation; however, the regulatory relationship between them is uncertain. We previously found that protein kinase Pbk was crucial for basal proliferation of mouse islet cells. Herein we show that Pbk is upregulated during pregnancy in mice and Pbk kinase activity is required for enhanced β- cell proliferation during pregnancy. Notably, knock-in (KI) of a kinase-inactivating Pbk mutation leads to impaired glucose tolerance and reduction of β-cell proliferation and islet mass in mice during pregnancy. Prolactin upregulates the expression of Pbk, but the upregulation is diminished by knockdown of the prolactin receptor and by the inhibitors of JAK and STAT5, which mediate prolactin receptor signaling, in β-cells. Treatment of β-cells with prolactin increases STAT5 binding to the Pbk locus, as well as the recruitment of RNA polymerase II, resulting in increased Pbk transcription. These results demonstrate that Pbk is upregulated during pregnancy, at least partly by prolactin-induced and STAT5-mediated enhancement of gene transcription, and Pbk is essential for pregnancy-induced β-cell proliferation, increase in islet mass, and maintenance of normal blood glucose during pregnancy in preclinical models. These findings provide new insights into the interplay between hormones and protein kinases that ultimately prevent the development of GDM.