Methionine sulfoxide reductase A affects insulin resistance by protecting insulin receptorfunction

Oxidative stress plays a significant role in the development of insulin resistance; however, the cellular targets of oxidation that cause insulin resistance have yet to be fully elucidated. Methionine sulfoxide reductases reduce oxidized methionine residues, thereby repairing and protecting proteins from oxidation. Recently, several genome-wide analyses have found human obesity to be strongly correlated with polymorphisms near the methionine sulfoxide reductase A (MsrA) locus. In this study, we tested whether modulation of MsrA expression significantly alters the development of obesity and/or insulin resistance in mice. We show that mice lacking MsrA (MsrA^−/−) are prone to the development of high-fat-diet-induced insulin resistance and a reduced physiological insulin response compared to high-fat-fed wild-type mice. We also show that oxidative stress in C2C12 cell cultures reduces both insulin-stimulated phosphorylation and autophosphorylation of the insulin receptor. Tissues from high-fat-fed mice show similar reduction in insulin receptor function and increase in insulin receptor oxidation, which are further exacerbated by the lack of MsrA. Together, these data demonstrate for the first time that MsrA and protein oxidation play a role in the regulation of glucose homeostasis. In addition, these data support a novel hypothesis that obesity-induced insulin resistance is caused in part by reduced function of insulin signaling proteins arising from protein oxidation.     

Mitochondrial stress: a bridge between mitochondrial dysfunction and metabolic diseases?

Under pathophysiological conditions such as obesity, excessive oxidation of nutrients may induce mitochondrial stress, leading to mitochondrial unfolded protein response (UPR^mt) and initiation of a retrograde stress signaling pathway. Defects in the UPR^mt and the retrograde signaling pathways may disrupt the integrity and homeostasis of the mitochondria, resulting in endoplasmic reticulum stress and insulin resistance. Improving the capacity of mitochondria to reduce stress may be an effective approach to improve mitochondria function and to suppress obesity-induced metabolic disorders such as insulin resistance and type 2 diabetes.     

Oxidative damage associated with obesity is prevented by overexpression of CuZn- or Mn-superoxide dismutase

The development of insulin resistance is the primary step in the etiology of type 2 diabetes mellitus. There are several risk factors associated with insulin resistance, yet the basic biological mechanisms that promote its development are still unclear. There is growing literature that suggests mitochondrial dysfunction and/or oxidative stress play prominent roles in defects in glucose metabolism. Here, we tested whether increased expression of CuZn-superoxide dismutase (Sod1) or Mn-superoxide dismutase (Sod2) prevented obesity-induced changes in oxidative stress and metabolism. Both Sod1 and Sod2 overexpressing mice were protected from high fat diet-induced glucose intolerance. Lipid oxidation (F₂-isoprostanes) was significantly increased in muscle and adipose with high fat feeding. Mice with increased expression of either Sod1 or Sod2 showed a significant reduction in this oxidative damage. Surprisingly, mitochondria from the muscle of high fat diet-fed mice showed no significant alteration in function. Together, our data suggest that targeting reduced oxidative damage in general may be a more applicable therapeutic target to prevent insulin resistance than is improving mitochondrial function.     

Alterations in hepatic mitochondrial compartment in a model of obesity and insulin resistance

The objective of this paper is to evaluate adaptations in hepatic mitochondrial protein mass, function and efficiency in a rat model of high-fat diet-induced obesity and insulin resistance that displays several correlates to human obesity. Adult male rats were fed a high-fat diet for 7 weeks. Mitochondrial state 3 and state 4 respiratory capacities were measured in liver homogenate and isolated mitochondria by using nicotinamide adenine dinucleotide, flavin adenine dinucleotide and lipid substrates. Mitochondrial efficiency was evaluated by measuring proton leak kinetics. Mitochondrial mass was assessed by ultrastructural observations and citrate synthase (CS) activity measurements. Mitochondrial oxidative damage and antioxidant defence were also considered by measuring lipid peroxidation, aconitase and superoxide dismutase (SOD) specific activity. Whole body metabolic characteristics were obtained by measuring 24-h oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and nonprotein respiratory quotient (NPRQ), using indirect calorimetry with urinary nitrogen analysis. Whole body glucose homeostasis was assessed by measuring plasma insulin and glucose levels after a glucose load. Adult rats fed a high-fat diet for 7 weeks, exhibit not only obesity, insulin resistance and hepatic steatosis, but also reduced respiratory capacity and increased oxidative stress in liver mitochondria. Our present results indicate that alterations in the mitochondrial compartment induced by a high-fat diet are associated with the development of insulin resistance and ectopic fat storage in the liver. Our results thus fit in with the emerging idea that mitochondrial dysfunction can led to the development of metabolic diseases, such as obesity, type 2 diabetes mellitus and nonalcoholic steatohepatitis.     

Mitochondrial DNA Damage and Dysfunction,and Oxidative Stress Are Associated with Endoplasmic Reticulum Stress,Protein Degradation and Apoptosis in High Fat Diet-Induced Insulin Resistance Mice

Background

Recent studies showed a link between a high fat diet (HFD)-induced obesity and lipid accumulation in non-adipose tissues, such as skeletal muscle and liver, and insulin resistance (IR). Although the mechanisms responsible for IR in those tissues are different, oxidative stress and mitochondrial dysfunction have been implicated in the disease process. We tested the hypothesis that HFD induced mitochondrial DNA (mtDNA) damage and that this damage is associated with mitochondrial dysfunction, oxidative stress, and induction of markers of endoplasmic reticulum (ER) stress, protein degradation and apoptosis in skeletal muscle and liver in a mouse model of obesity-induced IR.

Methodology/Principal Findings

C57BL/6J male mice were fed either a HFD (60% fat) or normal chow (NC) (10% fat) for 16 weeks. We found that HFD-induced IR correlated with increased mtDNA damage, mitochondrial dysfunction and markers of oxidative stress in skeletal muscle and liver. Also, a HFD causes a change in the expression level of DNA repair enzymes in both nuclei and mitochondria in skeletal muscle and liver. Furthermore, a HFD leads to activation of ER stress, protein degradation and apoptosis in skeletal muscle and liver, and significantly reduced the content of two major proteins involved in insulin signaling, Akt and IRS-1 in skeletal muscle, and Akt in liver. Basal p-Akt level was not significantly influenced by HFD feeding in skeletal muscle and liver.

Conclusions/Significance

This study provides new evidence that HFD-induced mtDNA damage correlates with mitochondrial dysfunction and increased oxidative stress in skeletal muscle and liver, which is associated with the induction of markers of ER stress, protein degradation and apoptosis.     

Mitochondrial energy metabolism and redox responses to hypertriglyceridemia

In this work we review recent findings that explain how mitochondrial bioenergetic functions and redox state respond to a hyperlipidemic in vivo environment and may contribute to the maintenance of a normal metabolic phenotype. The experimental model utilized to evidence these adaptive mechanisms is especially useful for these studies since it exhibits genetic hypertriglyceridemia and avoids complications introduced by high fat diets. Liver from hypertrigliceridemic (HTG) mice have a greater content of glycerolipids together with increased mitochondrial free fatty acid oxidation. HTG liver mitochondria have a higher resting respiration rate but normal oxidative phosphorylation efficiency. This is achieved by higher activity of the mitochondrial potassium channel sensitive to ATP (mitoK_ATP). The mild uncoupling mediated by mitoK_ATP accelerates respiration rates and reduces reactive oxygen species generation. Although this response is not sufficient to inhibit lipid induced extra-mitochondrial oxidative stress in whole liver cells it avoids amplification of this redox imbalance. Furthermore, higher mitoK_ATP activity increases liver, brain and whole body metabolic rates. These mitochondrial adaptations may explain why these HTG mice do not develop insulin resistance and obesity even under a severe hyperlipidemic state. On the contrary, when long term high fat diets are employed, insulin resistance, fatty liver and obesity develop and mitochondrial adaptations are inefficient to counteract energy and redox imbalances.     

CLPP deficiency protects against metabolic syndrome but hinders adaptive thermogenesis

Mitochondria are fundamental for cellular metabolism as they are both a source and a target of nutrient intermediates originating from converging metabolic pathways, and their role in the regulation of systemic metabolism is increasingly recognized. Thus, maintenance of mitochondrial homeostasis is indispensable for a functional energy metabolism of the whole organism. Here, we report that loss of the mitochondrial matrix protease CLPP results in a lean phenotype with improved glucose homeostasis. Whole‐body CLPP‐deficient mice are protected from diet‐induced obesity and insulin resistance, which was not present in mouse models with either liver‐ or muscle‐specific depletion of CLPP. However, CLPP ablation also leads to a decline in brown adipocytes function leaving mice unable to cope with a cold‐induced stress due to non‐functional adaptive thermogenesis. These results demonstrate a critical role for CLPP in different metabolic stress conditions such as high‐fat diet feeding and cold exposure providing tools to understand pathologies with deregulated Clpp expression and novel insights into therapeutic approaches against metabolic dysfunctions linked to mitochondrial diseases.     

Mitochondrial fission contributes to mitochondrial dysfunction and insulin resistance in skeletal muscle

Mitochondrial dysfunction in skeletal muscle has been implicated in the development of insulin resistance and type 2 diabetes. Considering the importance of mitochondrial dynamics in mitochondrial and cellular functions, we hypothesized that obesity and excess energy intake shift the balance of mitochondrial dynamics, further contributing to mitochondrial dysfunction and metabolic deterioration in skeletal muscle. First, we revealed that excess palmitate (PA), but not hyperglycemia, hyperinsulinemia, or elevated tumor necrosis factor alpha, induced mitochondrial fragmentation and increased mitochondrion-associated Drp1 and Fis1 in differentiated C2C12 muscle cells. This fragmentation was associated with increased oxidative stress, mitochondrial depolarization, loss of ATP production, and reduced insulin-stimulated glucose uptake. Both genetic and pharmacological inhibition of Drp1 attenuated PA-induced mitochondrial fragmentation, mitochondrial depolarization, and insulin resistance in C2C12 cells. Furthermore, we found smaller and shorter mitochondria and increased mitochondrial fission machinery in the skeletal muscle of mice with genetic obesity and those with diet-induced obesity. Inhibition of mitochondrial fission improved the muscle insulin signaling and systemic insulin sensitivity of obese mice. Our findings indicated that aberrant mitochondrial fission is causally associated with mitochondrial dysfunction and insulin resistance in skeletal muscle. Thus, disruption of mitochondrial dynamics may underlie the pathogenesis of muscle insulin resistance in obesity and type 2 diabetes.     

Oxidative stress and diabetes: What can we learn about insulin resistance from antioxidant mutant mouse models?

The development of metabolic dysfunctions like diabetes and insulin resistance in mammals is regulated by a myriad of factors. Oxidative stress seems to play a central role in this process as recent evidence shows a general increase in oxidative damage and a decrease in oxidative defense associated with several metabolic diseases. These changes in oxidative stress can be directly correlated with increased fat accumulation, obesity, and consumption of high-calorie/high-fat diets. Modulation of oxidant protection through either genetic mutation or treatment with antioxidants can significantly alter oxidative stress resistance and accumulation of oxidative damage in laboratory rodents. Antioxidant mutant mice have previously been utilized to examine the role of oxidative stress in other disease models, but have been relatively unexplored as models to study the regulation of glucose metabolism. In this review, we will discuss the evidence for oxidative stress as a primary mechanism linking obesity and metabolic disorders and whether alteration of antioxidant status in laboratory rodents can significantly alter the development of insulin resistance or diabetes.     

Contrasting metabolic effects of medium- versus long-chain fatty acids in skeletal muscle

Dietary intake of long-chain fatty acids (LCFAs) plays a causative role in insulin resistance and risk of diabetes. Whereas LCFAs promote lipid accumulation and insulin resistance, diets rich in medium-chain fatty acids (MCFAs) have been associated with increased oxidative metabolism and reduced adiposity, with few deleterious effects on insulin action. The molecular mechanisms underlying these differences between dietary fat subtypes are poorly understood. To investigate this further, we treated C2C12 myotubes with various LCFAs (16:0, 18:1n9, and 18:2n6) and MCFAs (10:0 and 12:0), as well as fed mice diets rich in LCFAs or MCFAs, and investigated fatty acid-induced changes in mitochondrial metabolism and oxidative stress. MCFA-treated cells displayed less lipid accumulation, increased mitochondrial oxidative capacity, and less oxidative stress than LCFA-treated cells. These changes were associated with improved insulin action in MCFA-treated myotubes. MCFA-fed mice exhibited increased energy expenditure, reduced adiposity, and better glucose tolerance compared with LCFA-fed mice. Dietary MCFAs increased respiration in isolated mitochondria, with a simultaneous reduction in reactive oxygen species generation, and subsequently low oxidative damage. Collectively our findings indicate that in contrast to LCFAs, MCFAs increase the intrinsic respiratory capacity of mitochondria without increasing oxidative stress. These effects potentially contribute to the beneficial metabolic actions of dietary MCFAs.     

Elevated TCA cycle function in the pathology of diet-induced hepatic insulin resistance and fatty liver

The manner in which insulin resistance impinges on hepatic mitochondrial function is complex. Although liver insulin resistance is associated with respiratory dysfunction, the effect on fat oxidation remains controversial, and biosynthetic pathways that traverse mitochondria are actually increased. The tricarboxylic acid (TCA) cycle is the site of terminal fat oxidation, chief source of electrons for respiration, and a metabolic progenitor of gluconeogenesis. Therefore, we tested whether insulin resistance promotes hepatic TCA cycle flux in mice progressing to insulin resistance and fatty liver on a high-fat diet (HFD) for 32 weeks using standard biomolecular and in vivo (2)H/(13)C tracer methods. Relative mitochondrial content increased, but respiratory efficiency declined by 32 weeks of HFD. Fasting ketogenesis became unresponsive to feeding or insulin clamp, indicating blunted but constitutively active mitochondrial β-oxidation. Impaired insulin signaling was marked by elevated in vivo gluconeogenesis and anaplerotic and oxidative TCA cycle flux. The induction of TCA cycle function corresponded to the development of mitochondrial respiratory dysfunction, hepatic oxidative stress, and inflammation. Thus, the hepatic TCA cycle appears to enable mitochondrial dysfunction during insulin resistance by increasing electron deposition into an inefficient respiratory chain prone to reactive oxygen species production and by providing mitochondria-derived substrate for elevated gluconeogenesis.     

Lack of skeletal muscle liver kinase B1 alters gene expression,mitochondrial content,inflammation and oxidative stress without affecting high-fat diet-induced obesity or insulin resistance

Ad libitum high-fat diet (HFD) induces obesity and skeletal muscle metabolic dysfunction. Liver kinase B1 (LKB1) regulates skeletal muscle metabolism by controlling the AMP-activated protein kinase family, but its importance in regulating muscle gene expression and glucose tolerance in obese mice has not been established. The purpose of this study was to determine how the lack of LKB1 in skeletal muscle (KO) affects gene expression and glucose tolerance in HFD-fed, obese mice.KO and littermate control wild-type (WT) mice were fed a standard diet or HFD for 14 weeks. RNA sequencing, and subsequent analysis were performed to assess mitochondrial content and respiration, inflammatory status, glucose and insulin tolerance, and muscle anabolic signaling.KO did not affect body weight gain on HFD, but heavily impacted mitochondria-, oxidative stress-, and inflammation-related gene expression. Accordingly, mitochondrial protein content and respiration were suppressed while inflammatory signaling and markers of oxidative stress were elevated in obese KO muscles. KO did not affect glucose or insulin tolerance. However, fasting serum insulin and skeletal muscle insulin signaling were higher in the KO mice. Furthermore, decreased muscle fiber size in skmLKB1-KO mice was associated with increased general protein ubiquitination and increased expression of several ubiquitin ligases, but not muscle ring finger 1 or atrogin-1. Taken together, these data suggest that the lack of LKB1 in skeletal muscle does not exacerbate obesity or insulin resistance in mice on a HFD, despite impaired mitochondrial content and function and elevated inflammatory signaling and oxidative stress.     

Mitochondrial oxidative stress and inflammation: an slalom to obesity and insulin resistance

Mitochondria, in addition to energy transformation, play a role in important metabolic tasks such as apoptosis, cellular proliferation, heme/steroid synthesis as well as in the cellular redox state regulation. The mitochondrial phosphorylation process is very efficient, but a small percentage of electrons may prematurely reduce oxygen forming toxic free radicals potentially impairing the mitochondria function. Furthermore, under certain conditions, protons can reenter the mitochondrial matrix through different uncoupling proteins (UCPs), affecting the control of free radicals production by mitochondria. Disorders of the mitochondrial electron transport chain, overgeneration of reactive oxygen species (ROS) and lipoperoxides or impairments in antioxidant defenses have been reported in situations of obesity and type-2 diabetes. On the other hand, obesity has been associated to a low degree pro-inflammatory state, in which impairments in the oxidative stress and antioxidant mechanism could be involved. Indeed, reactive oxygen species have been attributed a causal role in multiple forms of insulin resistance. The scientific evidence highlights the importance of investigating the relationships between oxidative stress and inflammation with obesity/diabetes onset and underlines the need to study in mitochondria from different tissues, the interactions of such factors either as a cause or consequence of obesity and insulin resistance.     

Mitochondrial dysfunction in non-alcoholic fatty liver disease and insulin resistance: Cause or consequence?

Abstract

Non-alcoholic fatty liver disease (NAFLD) is considered the hepatic manifestation of the metabolic syndrome and refers to a spectrum of disorders ranging from steatosis to steatohepatitis, a disease stage characterized by inflammation, fibrosis, cell death and insulin resistance (IR). Due to its association with obesity and IR the impact of NAFLD is growing worldwide. Consistent with the role of mitochondria in fatty acid (FA) metabolism, impaired mitochondrial function is thought to contribute to NAFLD and IR. Indeed, mitochondrial dysfunction and impaired mitochondrial respiratory chain have been described in patients with non-alcoholic steatohepatitis and skeletal muscle of obese patients. However, recent data have provided evidence that pharmacological and genetic models of mitochondrial impairment with reduced electron transport stimulate insulin sensitivity and protect against diet-induced obesity, hepatosteatosis and IR. These beneficial metabolic effects of impaired mitochondrial oxidative phosphorylation may be related not only to the reduction of reactive oxygen species production that regulate insulin signaling but also to decreased mitochondrial FA overload that generate specific metabolites derived from incomplete FA oxidation (FAO) in the TCA cycle. In line with the Randle cycle, reduced mitochondrial FAO rates may alleviate the repression on glucose metabolism in obesity. In addition, the redox paradox in insulin signaling and the delicate mitochondrial antioxidant balance in steatohepatitis add another level of complexity to the role of mitochondria in NAFLD and IR. Thus, better understanding the role of mitochondria in FA metabolism and glucose homeostasis may provide novel strategies for the treatment of NAFLD and IR.     

Mice Lacking C1q Are Protected from High Fat Diet-induced Hepatic Insulin Resistance and Impaired Glucose Homeostasis

Complement activation is implicated in the development of obesity and insulin resistance, and loss of signaling by the anaphylatoxin C3a prevents obesity-induced insulin resistance in mice. Here we have identified C1q in the classical pathway as required for activation of complement in response to high fat diets. After 8 weeks of high fat diet, wild-type mice became obese and developed glucose intolerance. This was associated with increased apoptotic cell death and accumulation of complement activation products (C3b/iC3b/C3c) in liver and adipose tissue. Previous studies have shown that high fat diet-induced apoptosis is dependent on Bid; here we report that Bid-mediated apoptosis was required for complement activation in adipose and liver. Although C1qa deficiency had no effect on high fat diet-induced apoptosis, accumulation of complement activation products and the metabolic complications of high fat diet-induced obesity were dependent on C1q. When wild-type mice were fed a high fat diet for only 3 days, hepatic insulin resistance was associated with the accumulation of C3b/iC3b/C3c in the liver. Mice deficient in C3a receptor were protected against this early high fat diet-induced hepatic insulin resistance, whereas mice deficient in the negative complement regulator CD55/DAF were more sensitive to the high fat diet. C1qa^−/− mice were also protected from high fat diet-induced hepatic insulin resistance and complement activation. Evidence of complement activation was also detected in adipose tissue of obese women compared with lean women. Together, these studies reveal an important role for C1q in the classical pathway of complement activation in the development of high fat diet-induced insulin resistance.     

Dissociation of obesity and insulin resistance in transgenic mice with skeletal muscle expression of uncoupling protein 1.

We evaluated the effect of skeletal muscle mitochondrial uncoupling on energy and glucose metabolism under different diets. For 3 mo, transgenic HSA-mUCP1 mice with ectopic expression of uncoupling protein 1 in skeletal muscle and wild-type littermates were fed semisynthetic diets with varying macronutrient ratios (energy % carbohydrate-protein-fat): HCLF (41:42:17), HCHF (41:16:43); LCHF (11:45:44). Body composition, energy metabolism, and insulin resistance were assessed by NMR, indirect calorimetry, and insulin tolerance test, respectively. Gene expression in different organs was determined by real-time PCR. In wild type, both high-fat diets led to an increase in body weight and fat. HSA-mUCP1 mice considerably increased body fat on HCHF but stayed lean on the other diets. Irrespective of differences in body fat content, HSA-mUCP1 mice showed higher insulin sensitivity and decreased plasma insulin and liver triglycerides. Respiratory quotient and gene expression indicated overall increased carbohydrate oxidation of HSA-mUCP1 but a preferential channeling of fatty acids into muscle rather than liver with high-fat diets. Evidence for increased lipogenesis in white fat of HSA-mUCP1 mice suggests increased energy dissipating substrate cycling. Retinol binding protein 4 expression in white fat was increased in HSA-mUCP1 mice despite increased insulin sensitivity, excluding a causal role in the development of insulin resistance. We conclude that skeletal muscle mitochondrial uncoupling does not protect from the development of obesity in all circumstances. Rather it can lead to a "healthy" obese phenotype by preserving insulin sensitivity and a high metabolic flexibility, thus protecting from the development of obesity associated disturbances of glucose homeostasis.     

Insulin and insulin signaling play a critical role in fat induction of insulin resistance in mouse

The primary player that induces insulin resistance has not been established. Here, we studied whether or not fat can cause insulin resistance in the presence of insulin deficiency. Our results showed that high-fat diet (HFD) induced insulin resistance in C57BL/6 (B6) mice. The HFD-induced insulin resistance was prevented largely by the streptozotocin (STZ)-induced moderate insulin deficiency. The STZ-induced insulin deficiency prevented the HFD-induced ectopic fat accumulation and oxidative stress in liver and gastrocnemius. The STZ-induced insulin deficiency prevented the HFD- or insulin-induced increase in hepatic expression of long-chain acyl-CoA synthetases (ACSL), which are necessary for fatty acid activation. HFD increased mitochondrial contents of long-chain acyl-CoAs, whereas it decreased mitochondrial ADP/ATP ratio, and these HFD-induced changes were prevented by the STZ-induced insulin deficiency. In cultured hepatocytes, we observed that expressions of ACSL1 and -5 were stimulated by insulin signaling. Results in cultured cells also showed that blunting insulin signaling by the PI3K inhibitor LY-294002 prevented fat accumulation, oxidative stress, and insulin resistance induced by the prolonged exposure to either insulin or oleate plus sera that normally contain insulin. Finally, knockdown of the insulin receptor prevented the oxidative stress and insulin resistance induced by the prolonged exposure to insulin or oleate plus sera. Together, our results show that insulin and insulin signaling are required for fat induction of insulin resistance in mice and cultured mouse hepatocytes.     

Obesity reduces methionine sulphoxide reductase activity in visceral adipose tissue

Visceral obesity is linked to insulin resistance and cardiovascular disease. A recent genetic study indicated that the gene locus for the anti-oxidant defense enzyme methionine sulphoxide reductase A (MsrA) is positively associated with the development of visceral adiposity. This work tested the hypothesis that Msr activity is diminished in visceral fat as a result of obesity. It used two animal models of obesity, wild-type rats fed a high-fat (45% of calories from fat) diet and Zucker rats fed a 10% fat calorie diet. The data indicate that MsrA activity was selectively reduced by ～ 25% in the visceral adipose, but not subcutaneous adipose or liver, of both rat models as compared to control, wild type rats receiving a 10% fat calorie diet. MsrB activity was similarly reduced only in visceral fat. The data indicate that Msr activity is reduced by obesity and may alter oxidative stress signalling of obesity.     

Intermittent fasting preserves beta-cell mass in obesity-induced diabetes via the autophagy-lysosome pathway

Obesity-induced diabetes is characterized by hyperglycemia, insulin resistance, and progressive beta cell failure. In islets of mice with obesity-induced diabetes, we observe increased beta cell death and impaired autophagic flux. We hypothesized that intermittent fasting, a clinically sustainable therapeutic strategy, stimulates autophagic flux to ameliorate obesity-induced diabetes. Our data show that despite continued high-fat intake, intermittent fasting restores autophagic flux in islets and improves glucose tolerance by enhancing glucose-stimulated insulin secretion, beta cell survival, and nuclear expression of NEUROG3, a marker of pancreatic regeneration. In contrast, intermittent fasting does not rescue beta-cell death or induce NEUROG3 expression in obese mice with lysosomal dysfunction secondary to deficiency of the lysosomal membrane protein, LAMP2 or haplo-insufficiency of BECN1/Beclin 1, a protein critical for autophagosome formation. Moreover, intermittent fasting is sufficient to provoke beta cell death in nonobese lamp2 null mice, attesting to a critical role for lysosome function in beta cell homeostasis under fasting conditions. Beta cells in intermittently-fasted LAMP2- or BECN1-deficient mice exhibit markers of autophagic failure with accumulation of damaged mitochondria and upregulation of oxidative stress. Thus, intermittent fasting preserves organelle quality via the autophagy-lysosome pathway to enhance beta cell survival and stimulates markers of regeneration in obesity-induced diabetes.