A Century of Prolactin: Emerging Perspectives as a Metabolic Regulator.

Prolactin, a hormone that has been studied for almost a century, has evolved from a reproductive regulator to a key player in metabolic health. Initially identified for its lactogenic role, the impact of prolactin on glucose and lipid metabolism became evident in the 1970s, leading to a paradigm shift in our understanding. Deviations in prolactin levels, including hyperprolactinaemia and hypoprolactinaemia, have been associated with adverse effects on glucose and lipid metabolism. Mechanistically, prolactin regulates metabolic homoeostasis by maintaining islet abundance, regulating the hypothalamic energy regulatory centre, balancing adipose tissue expansion, and regulating hepatic metabolism. Given the widespread use of pharmaceutical agents that affect prolactin levels, it is important to examine prolactin-related metabolic effects. Recently, a profound exploration of the intricate metabolic role of prolactin has been conducted, encompassing its rhythm-dependent regulatory influence on metabolism and its correlation with cognitive impairment associated with metabolic diseases. In this review, we highlight the role of prolactin as a metabolic regulator, summarise its metabolic effects, and discuss topics related to the association between prolactin and metabolic comorbidities.

Excessive free fatty acid sensing in pituitary lactotrophs elicits steatotic liver disease by decreasing prolactin levels.

The pituitary is the central endocrine gland with effects on metabolic dysfunction-associated steatotic liver disease (MASLD). However, it is not clear whether the pituitary responds to free fatty acid (FFA) toxicity, thus dysregulating hepatic lipid metabolism. Here, we demonstrate that decreased prolactin (PRL) levels are involved in the association between FFA and MASLD based on a liver biospecimen-based cohort. Moreover, overloaded FFAs decrease serum PRL levels, thus promoting liver steatosis in mice with both dynamic diet intervention and stereotactic pituitary FFA injection. Mechanistic studies show that excessive FFA sensing in pituitary lactotrophs inhibits the synthesis and secretion of PRL in a cell-autonomous manner. Notably, inhibiting excessive lipid uptake using pituitary stereotaxic virus injection or a specific drug delivery system effectively ameliorates hepatic lipid accumulation by improving PRL levels. Targeted inhibition of pituitary FFA sensing may be a potential therapeutic target for liver steatosis.

Lower serum PRL is associated with the development of non-alcoholic fatty liver disease: a retrospective cohort study.

BACKGROUND: Non-alcoholic fatty liver disease (NAFLD) has become an epidemic worldwide and has been linked to a series of metabolic co-morbidities. Prolactin (PRL) has recently been found to have a negative effect on NAFLD, but a causal relationship is not well-understood. Here we investigated the causative relationship between PRL and NAFLD occurrence. METHODS: In this retrospective cohort study, we enrolled patients without NAFLD who were diagnosed by abdominal ultrasonography undergone serum PRL testing at 8.00 a.m. at baseline, and followed up for a median of 32 (19, 46) months. RESULTS: This study enrolled 355 persons [215 men and 140 women; media age 56 (49, 64) years], in which 72 (20.28%) patients who eventually developed NAFLD. Compared with those in the non-NAFLD group, basal serum PRL levels of patients were lower in the NAFLD group [male: 7.35 (5.48, 10.60) vs. 9.13 (6.92, 12.50) ug/L, P = 0.002; female: 5.66 (4.67, 9.03) vs. 9.01 (6.31, 11.60) ug/L, P = 0.009]. The prevalence of NAFLD was significantly decreased along with the increased quartile of basal serum PRL levels in both genders (P < 0.05). Serum PRL concentration was independently associated with NAFLD development [male: OR, 0.881 (0.777, 0.998), P = 0.047; female: OR, 0.725 (0.554, 0.949), P = 0.019]. CONCLUSION: Our study is the first to find that basal serum PRL level can predict the occurrence of NAFLD and it may be a potential biomarker to prevent and treat NAFLD.

Effects of Early Intensive Insulin Therapy on Endothelial Progenitor Cells in Patients with Newly Diagnosed Type 2 Diabetes.

AIM: This study aimed to investigate the alteration of circulating CD34+KDR+CD133+ endothelial progenitor cells (EPCs) in patients with newly diagnosed type 2 diabetes and the mechanism of the effect of early intensive insulin therapy. METHODS: In this study, 36 patients with newly diagnosed type 2 diabetes and 22 control subjects matched by age and gender were enrolled. All of the patients with diabetes received intensive insulin therapy. The number of EPCs was assessed by flow cytometry based on the expression of CD34, CD133, and kinase insert domain-containing receptor (KDR). RESULTS: Levels of circulating CD34+KDR+CD133+ EPCs were higher in patients with diabetes compared to control subjects and significantly decreased after intensive insulin therapy. Levels of vascular endothelial growth factor (VEGF), a major contributor to EPC mobilization, were significantly higher in patients with diabetes compared to control subjects, and dramatically decreased after insulin therapy. Importantly, VEGF levels correlated with number of EPCs. Moreover, compared with control subjects, pro-inflammatory cytokines and oxidative stress were significantly higher in patients with diabetes and markedly decreased after intensive insulin therapy. CONCLUSIONS: These results showed that type 2 diabetes is associated with an increase of circulating CD34+KDR+CD133+ EPCs at the onset of diabetes, indicating increased compensatory mobilization. Additionally, early intensive insulin therapy exerts a preserving effect on EPC level partly through improving inflammation status and oxidative stress, thereby implying a putative long-term beneficial effect on vascular integrity via suspending excessive EPC exhaustion. CLINICAL TRIAL NUMBER: NCT03710811.

Association of Omental Adipocyte Hypertrophy and Fibrosis with Human Obesity and Type 2 Diabetes.

OBJECTIVE: Morphological alterations including adipocyte hypertrophy and fibrosis deposition are important surrogate markers of visceral adipose tissue function, but the relationships between these morphological changes and type 2 diabetes mellitus (T2DM) and impaired insulin sensitivity are poorly defined. METHODS: Omental adipose tissue was obtained from 66 individuals with obesity but without T2DM (OB group), 93 individuals with both obesity and T2DM (T2DM group), and 15 individuals with normal BMI and normal glucose tolerance (NGT group). Adipocyte diameter and volume were measured through pathological section analysis. Pericellular and perilobular fibrosis was determined through picrosirius red staining and immunochemistry, while fibrosis-related genes were tested through gene expression and hydroxyproline content. RESULTS: Compared with the NGT and OB groups, individuals from the T2DM group displayed increased adipocyte diameter and volume levels. Increased adipocyte size (diameter and volume) was positively associated with hyperglycemia and insulin resistance and inversely correlated with insulin sensitivity (using the Matsuda whole-body insulin sensitivity index assessment of insulin sensitivity) and ß-cell function (disposition index 30 and disposition index 120). The fibrosis levels of the OB group were the highest out of the three groups, whereas the fibrosis levels of T2DM individuals were lower than the OB group but higher than the NGT group. Although fibrosis was negatively correlated with T2DM, fibrosis deposition was not remarkably associated with impaired systemic insulin sensitivity and glucose metabolism. CONCLUSIONS: Compared with fibrosis deposition, adipocyte hypertrophy is more closely associated with T2DM and impaired systemic insulin sensitivity.

Correction to: A newly noninvasive model for prediction of non-alcoholic fatty liver disease: utility of serum prolactin levels.

Following publication of the original article [1], we have been notified that the given name of one of the authors was spelled incorrectly.

Modulation of gut microbiota contributes to effects of intensive insulin therapy on intestinal morphological alteration in high-fat-diet-treated mice.

AIMS: Disturbance of intestinal homeostasis promotes the development of type 2 diabetes. Although intensive insulin therapy has been shown to promote extended glycemic remission in newly diagnosed type 2 diabetic patients through multiple mechanisms, its effect on intestinal homeostasis remains unknown. METHODS: This study evaluated the effects of intensive insulin therapy on intestinal morphometric parameters in a hyperglycemic mice model induced by high-fat diet (HFD). 16S rRNA V4 region sequencing and multivariate analysis were utilized to evaluate the structural changes of gut microbiota. RESULTS: HFD-induced increases in the lengths of villus, microvillus and crypt depth were significantly reversed after intensive insulin therapy. Moreover, intestinal proliferation was notably decreased after intensive insulin therapy, whereas intestinal apoptosis was further increased. Importantly, intensive insulin therapy significantly shifted the overall structure of the HFD-disrupted gut microbiota toward that of mice fed a normal diet and changed the gut microbial composition. The abundances of 54 operational taxonomic units (OTUs) were changed by intensive insulin therapy. Thirty altered OTUs correlated with two or more intestinal morphometric parameters and were designated 'functionally relevant phylotypes.' CONCLUSIONS: For the first time, our data indicate that intensive insulin therapy recovers diabetes-associated gut structural abnormalities and restores the microbiome landscape. Moreover, specific altered 'functionally relevant phylotypes' correlates with improvement in diabetes-associated gut structural alterations.

A newly noninvasive model for prediction of non-alcoholic fatty liver disease: utility of serum prolactin levels.

BACKGROUNDS: To investigate the value of prolactin (PRL) in diagnosing non-alcoholic fatty liver disease (NAFLD). METHODS: Metabolic parameters and serum PRL levels were measured in 452 males and 421 females, who were randomized to the estimation or the validation group as a 1:1 ratio. Hepatic steatosis was diagnosed via abdominal ultrasound. Variables that significantly associated with NAFLD in univariate analysis were included in multiple logistic regression. We used the receiver operator characteristic (ROC) curves to test the model performance. Besides, 147 patients underwent metabolic and liver biopsy were analyzed to validate the diagnostic value of this model. RESULTS: Body mass index, alanine aminotransferase, prolactin, high density lipoprotein cholesterol and HbA1c were included into models. In males, the area under ROC curve (AUC) was 0.86 (95%CI: 0.82-0.91) for the validation group. With two cut-off points (- 0.79 and 1.71), the sensitivity and specificity for predicting NALFD was 95.2 and 91.1% in the validation group, respectively. In females, the AUC was 0.82 (95%CI: 0.76-0.88) for the validation group. With two cut-off points (- 0.68 and 2.16), the sensitivity and specificity for predicting NALFD was 97.1 and 91.4% in the validation group, respectively. In subjects with liver pathology, the AUC was higher than that of fatty liver index. A positive correlation between the scores of the model and the severities of NAFLD was observed. Importantly, we demonstrated a potential value of this model in predicting nonalcoholic steatohepatitis. CONCLUSION: We established a mathematic model that can conveniently and effectively diagnose the existence and severities of NAFLD.

Adipose group 1 innate lymphoid cells promote adipose tissue fibrosis and diabetes in obesity.

Pathogenic factors driving obesity to type 2 diabetes (T2D) are not fully understood. Group 1 innate lymphoid cells (ILC1s) are effectors of innate immunity and enriched in inflamed tissues. Here we show that the number of adipose ILC1s increases in obese T2D patients and correlates with glycemic parameters and with the number of ILC1s in the blood; circulating ILC1 numbers decrease as a result of metabolic improvements after bariatric surgery. In vitro co-culture experiments show that human adipose ILC1s promote adipose fibrogenesis and CD11c+ macrophage activation. Reconstruction of the adipose ILC1 population in Prkdc-/-IL2rg-/- mice by adoptive transfer drives adipose fibrogenesis through activation of TGFß1 signaling; however, transfer of Ifng-/- ILC1s has no effect on adipose fibrogenesis. Furthermore, inhibiting adipose accumulation of ILC1s using IL-12 neutralizing antibodies attenuates adipose tissue fibrosis and improves glycemic tolerance. Our data present insights into the mechanisms of local immune disturbances in obesity-related T2D.

Efficacy and Safety of Basal Analog Regimens in Type 2 Diabetes Mellitus: Systematic Review and Meta-Analysis of Randomized Controlled Trials.

INTRODUCTION: This study compared basal analog (BA: glargine U100/mL and detemir) and premix (PM: human, lispro and aspart biphasic) insulin regimens in terms of their efficacy and safety in type 2 diabetes mellitus patients. METHODS: Searches of MEDLINE, Embase, and CENTRAL identified primary randomized controlled trials (RCTs) ≥ 12 weeks in duration that compared BA or PM insulin regimens in adults with T2DM, with ≥ 30 patients per arm. A systematic literature review and a pairwise meta-analysis were performed using a random effects model adjusted for between-study variability. Analyses were conducted based on frequency of bolus insulin and PM injections, PM ratio and type, BA type, race, follow-up period, and baseline glycosylated hemoglobin (HbA1c). RESULTS: Twenty-two primary RCTs with 9691 patients were included. The BA and PM regimens yielded similar changes in HbA1c and postprandial glucose levels, with a statistically significant reduction in fasting glucose [mean difference (MD) - 0.61 mmol/L (95% confidence interval (CI) - 0.90, - 0.32), I2 = 89.6%]. The BA regimens showed significantly reduced rates of total hypoglycemia [odds ratio (OR) 0.77 (95% CI 0.64, 0.92), I2 = 65.3%] and changes in body weight [MD - 0.48 kg (95% CI - 0.86, - 0.11), I2 = 75.7%] compared to PM regimens. Stratification by PM type and dosing ratio demonstrated statistically significant reductions in HbA1c favoring BA compared to human [MD - 0.39% (95% CI - 0.60, - 0.18), I2 = 61.8%] or 50/50-ratio [MD - 0.22% (95% CI - 0.40, - 0.04), I2 = 0.0%] PM regimens. Other subgroup analyses found no difference in HbA1c change between the BA and PM regimens. CONCLUSION: When compared to PM regimens, BA regimens yielded similar efficacies and better safety profiles in patients with type 2 diabetes mellitus. FUNDING: Sanofi (Shanghai, China).

Hepatic expression of Yin Yang 1 (YY1) is associated with the non-alcoholic fatty liver disease (NAFLD) progression in patients undergoing bariatric surgery.

BACKGROUND: This study is to investigate the association between the hepatic expression of Yin Yang 1 (YY1) and the progression of non-alcoholic fatty liver disease (NAFLD) in patients undergoing bariatric surgery. METHODS: Obese patients undergoing bariatric surgery were included. Liver tissues were subjected to the quantitative real-time PCR, Western blot analysis, and immunohistochemical assay, to determine the expression levels of YY1. RESULTS: Totally 88 patients were included. According to the NAFLD activity score (NAS), these patients were divided into the control (n = 12), steatosis (n = 20), non-defining NASH (n = 38), and NASH (n = 18) groups. Significant differences in the serum glucose, insulin, ALT, AST, and HOMA-IR levels were observed among these different NAFLD groups. Hepatic YY1 expression had correlation with serum glucose, insulin, HOMA-IR, ALT, AST, triglycerides, HDL, and GGT. Immunohistochemical analysis showed that, compared with the control group, the expression levels of YY1 were significantly higher in the non-defining NASH and NASH groups. In addition, multivariate regression model showed that the serum ALT and YY1 levels were strongly associated with the NAFLD activity. CONCLUSIONS: Several factors are associated with NAFLD progression, including the expression of YY1. Our findings contribute to understanding of the pathogenesis of NAFLD. TRIAL REGISTRATION: NCT03296605 , registered on September 28, 2017.

Insulin Glargine Combined with Oral Antidiabetic Drugs for Asians with Type 2 Diabetes Mellitus: A Pooled Analysis to Identify Predictors of Dose and Treatment Response.

INTRODUCTION: In Asia, patients with type 2 diabetes mellitus (T2DM) often have suboptimal glycemic control for many years prior to initiating basal insulin. Active titration of basal insulin is also required to improve glycemic outcomes. This pooled analysis was conducted to determine the impact of patient baseline covariates on the required dose of basal insulin and treatment response, for the improved management of Asian patients with T2DM. METHODS: Data on insulin-naïve Asian patients with T2DM who initiated and fully titrated insulin glargine 100 U/mL (Gla-100) for ≥ 20 weeks were pooled from seven randomized, controlled, treat-to-target trials. Covariance and multivariate linear/logistic regression analyses were applied to determine the impact of the baseline covariates on Gla-100 dose (primary outcome) and treatment response (secondary outcomes) at week 24 for patients from Asia (N = 724) and from China alone (n = 249). Based on the multivariate analysis for the primary outcome in the Asian population, a nomogram was developed. RESULTS: The dose of Gla-100 at week 24 was negatively correlated with age and positively correlated with body mass index (BMI) and fasting plasma glucose (FPG) at baseline in both Asian and Chinese populations. In both populations, higher baseline glycated hemoglobin (HbA1c) was associated with a lower reduction in HbA1c from baseline, higher HbA1c at week 24, and a lower chance of achieving HbA1c < 7% at week 24. The constructed nomogram enables calculation of the likely dose of Gla-100 required by Asian patients with T2DM to achieve HbA1c < 7% at week 24. CONCLUSIONS: Higher doses of Gla-100 are likely to be required in younger patients or patients with higher baseline BMI or FPG. The nomogram developed in this study can aid clinicians to titrate the dose of Gla-100 appropriately. Evidence in this pooled analysis also indicates that initiating basal insulin at a lower HbA1c can lead to greater glycemic control. FUNDING: Sanofi China Investment Company.

Erythropoietin alleviates hepatic steatosis by activating SIRT1-mediated autophagy.

Erythropoietin (EPO), besides its stimulatory effect on erythropoiesis, is beneficial to insulin resistance and obesity. However, its role in hepatic steatosis remains unexplored. Activating autophagy seems a promising mechanism for improving fatty liver disease. The present study investigated the role of EPO in alleviating hepatic steatosis and sought to determine whether its function is mediated by the activation of autophagy. Here, we show that EPO decreased hepatic lipid content significantly in vivo and in vitro. Furthermore, EPO/EPO receptor (EPOR) signalling induced autophagy activation in hepatocytes as indicated by western blot assay, transmission electron microscopy, and confocal microscopy. In addition, EPO increased the co-localization of autophagosomes and cellular lipids as shown by double labelling of the autophagy marker light chain microtubule-associated protein 3 (LC3) and lipids. Importantly, suppression of autophagy by an inhibitor or small interfering RNA (siRNA) abolished the EPO-mediated alleviation hepatic steatosis in vitro. Furthermore, EPO up-regulated sirtuin 1 (SIRT1) expression, and siRNA-mediated SIRT1 silencing abrogated the EPO-induced increases in LC3 protein and deacetylation levels, thereby preventing the alleviation of hepatic steatosis. Taken together, this study revealed a new mechanism wherein EPO alleviates hepatic steatosis by activating autophagy via SIRT1-dependent deacetylation of LC3. This finding might have therapeutic value in the treatment of hepatic steatosis.

Prolactin improves hepatic steatosis via CD36 pathway.

BACKGROUND & AIMS: Prolactin (PRL) is a multifunctional polypeptide with effects on metabolism, however, little is known about its effect on hepatic steatosis and lipid metabolism. Herein, we aimed to assess the role of PRL in the development of non-alcoholic fatty liver disease (NAFLD). METHODS: The serum PRL levels of 456 patients with NAFLD, 403 controls without NAFLD diagnosed by ultrasound, and 85 individuals with liver histology obtained during metabolic surgery (44 female and 30 male patients with NAFLD and 11 age-matched non-NAFLD female individuals) were evaluated. The expression of the gene encoding the prolactin receptor (PRLR) and signalling molecules involved in hepatic lipid metabolism were evaluated in human liver and HepG2 cells. The effects of overexpression of PRLR or fatty acid translocase (FAT)/CD36 or knockdown of PRLR on hepatic lipid metabolism were tested in free fatty acid (FFA)-treated HepG2 cells. RESULTS: Circulating PRL levels were lower in individuals with ultrasound-diagnosed NAFLD (men: 7.9 [range, 5.9-10.3] µg/L; women: 8.7 [range, 6.1-12.4] µg/L) than those with non-NAFLD (men: 9.1 [range, 6.8-13.0] µg/L, p = 0.002; women: 11.6 [range, 8.2-16.1] µg/L, p <0.001). PRL levels in patients with biopsy-proven severe hepatic steatosis were lower compared with those with mild-to-moderate hepatic steatosis in both men (8.3 [range, 5.4-9.5] µg/L vs. 9.7 [range, 7.1-12.3] µg/L, p = 0.031) and women (8.5 [range, 4.2-10.6] µg/L vs. 9.8 [range, 8.2-15.7] µg/L, p = 0.027). Furthermore, hepatic PRLR gene expression was significantly reduced in patients with NAFLD and negatively correlated with CD36 gene expression. In FFA-induced HepG2 cells, PRL treatment or PRLR overexpression significantly reduced the expression of CD36 and lipid content, effects that were abrogated after silencing of PRLR. Furthermore, overexpression of CD36 significantly reduced the PRL-mediated improvement in lipid content. CONCLUSIONS: Our results reveal a novel association between the central nervous system and the liver, whereby PRL/PRLR improved hepatic lipid accumulation via the CD36 pathway. LAY SUMMARY: Our clinical study suggests a negative association between prolactin (PRL)/prolactin receptor (PRLR) and the presence of non-alcoholic fatty liver disease (NAFLD). Using cell experiments, we found that PRL ameliorates hepatic steatosis via the hepatic PRLR and fatty acid translocase (FAT)/CD36, a key transporter of free fatty acid uptake in liver. Our findings suggest a novel approach to improving NAFLD using PRL and PRLR. Clinical trial number: NCT03296605.

Modulation of gut microbiota contributes to curcumin-mediated attenuation of hepatic steatosis in rats.

BACKGROUND: Structural disruption of gut microbiota contributes to the development of non-alcoholic fatty liver disease (NAFLD) and modulating the gut microbiota represents a novel strategy for NAFLD prevention. Although previous studies have demonstrated that curcumin alleviates hepatic steatosis, its effect on the gut microbiota modulation has not been investigated. METHODS: Next generation sequencing and multivariate analysis were utilized to evaluate the structural changes of gut microbiota in a NAFLD rat model induced by high fat-diet (HFD) feeding. RESULTS: We found that curcumin attenuated hepatic ectopic fat deposition, improved intestinal barrier integrity, and alleviated metabolic endotoxemia in HFD-fed rats. More importantly, curcumin dramatically shifted the overall structure of the HFD-disrupted gut microbiota toward that of lean rats fed a normal diet and altered the gut microbial composition. The abundances of 110 operational taxonomic units (OTUs) were altered by curcumin. Seventy-six altered OTUs were significantly correlated with one or more hepatic steatosis associated parameters and designated 'functionally relevant phylotypes'. Thirty-six of the 47 functionally relevant OTUs that were positively correlated with hepatic steatosis associated parameters were reduced by curcumin. CONCLUSION: These results indicate that curcumin alleviates hepatic steatosis in part through stain-specific impacts on hepatic steatosis associated phylotypes of gut microbiota in rats. GENERAL SIGNIFICANCE: Compounds with antimicrobial activities should be further investigated as novel adjunctive therapies for NAFLD.

Global epidemiology of diabetic foot ulceration: a systematic review and meta-analysis †.

Diabetic foot is a severe public health issue, yet rare studies investigated its global epidemiology. Here we performed a systematic review and meta-analysis through searching PubMed, EMBASE, ISI Web of science, and Cochrane database. We found that that global diabetic foot ulcer prevalence was 6.3% (95%CI: 5.4-7.3%), which was higher in males (4.5%, 95%CI: 3.7-5.2%) than in females (3.5%, 95%CI: 2.8-4.2%), and higher in type 2 diabetic patients (6.4%, 95%CI: 4.6-8.1%) than in type 1 diabetics (5.5%, 95%CI: 3.2-7.7%). North America had the highest prevalence (13.0%, 95%CI: 10.0-15.9%), Oceania had the lowest (3.0%, 95% CI: 0.9-5.0%), and the prevalence in Asia, Europe, and Africa were 5.5% (95%CI: 4.6-6.4%), 5.1% (95%CI: 4.1-6.0%), and 7.2% (95%CI: 5.1-9.3%), respectively. Australia has the lowest (1.5%, 95%CI: 0.7-2.4%) and Belgium has the highest prevalence (16.6%, 95%CI: 10.7-22.4%), followed by Canada (14.8%, 95%CI: 9.4-20.1%) and USA (13.0%, 95%CI: 8.3-17.7%). The patients with diabetic foot ulcer were older, had a lower body mass index, longer diabetic duration, and had more hypertension, diabetic retinopathy, and smoking history than patients without diabetic foot ulceration. Our results provide suggestions for policy makers in deciding preventing strategy of diabetic foot ulceration in the future. Key messages Global prevalence of diabetic foot is 6.3% (95%CI: 5.4-7.3%), and the prevalence in North America, Asia, Europe, Africa and Oceania was 13.0% (95%CI: 10.0-15.9%), 5.5% (95%CI: 4.6-6.4%), 5.1% (95%CI: 4.1-6.0%), 7.2% (95%CI: 5.1-9.3%), and 3.0% (95% CI: 0.9-5.0%). Diabetic foot was more prevalent in males than in females, and more prevalent in type 2 diabetic foot patients than in type 1 diabetic foot patients. The patients with diabetic foot were older, had a lower body mass index, longer diabetic duration, and had more hypertension, diabetic retinopathy, and smoking history than patients without diabetic foot.

Erythropoietin alleviates hepatic insulin resistance via PPARγ-dependent AKT activation.

Erythropoietin (EPO) has beneficial effects on glucose metabolism and insulin resistance. However, the mechanism underlying these effects has not yet been elucidated. This study aimed to investigate how EPO affects hepatic glucose metabolism. Here, we report that EPO administration promoted phosphatidylinositol 3-kinase (PI3K)/AKT pathway activation in palmitic acid (PA)-treated HepG2 cells and in the liver of high-fat diet (HFD)-fed mice, whereas adenovirus-mediated silencing of the erythropoietin receptor (EPOR) blocked EPO-induced AKT signalling in HepG2 cells. Importantly, a peroxisome proliferator-activated receptor γ (PPARγ) antagonist and PPARγ small interfering RNA (siRNA) abrogated the EPO-induced increase in p-AKT in HepG2 cells. Lentiviral vector-mediated hepatic PPARγ silencing in HFD-fed C57BL/6 mice impaired EPO-mediated increases in glucose tolerance, insulin sensitivity and hepatic AKT activation. Furthermore, EPO activated the AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1) signalling pathway, and AMPKα and SIRT1 knockdown each attenuated the EPO-induced PPARγ expression and deacetylation and PPARγ-dependent AKT activation in HepG2 cells. In summary, these findings suggest that PPARγ is involved in EPO/EPOR-induced AKT activation, and targeting the PPARγ/AKT pathway via EPO may have therapeutic implications for hepatic insulin resistance and type 2 diabetes.