Inhibition of lipolysis in Type 2 diabetes normalizes glucose disposal without change in muscle glycogen synthesis rates

Revised Protein Sparing Diet in Obesity and Type 2 Diabetes Mellitus

Effective nutrition therapy is a pressing issue in obesity and type 2 diabetes mellitus (T2DM) management. As such, this research aimed to determine the performance of a revised dietary strategy built on the protein-sparing diet in obesity and type 2 diabetes mellitus with regard to obtaining a rapid and stable improvement in glucometabolic control, body weight, body composition, and energy metabolism when applying the strategy in just twenty-one days. The revised protein-sparing diet differs from the traditional protein-sparing modified fast (PSMF) because it does not include foods. The daily calorie intake of this diet is exclusively derived from Isolate whey protein in addition to a formulation of Isolate whey protein enriched with essential amino acids in free form, with the addition of lipids such as extra virgin olive oil and coconut oil as a source of medium chain fatty acids, where the latter is taken for only the first four days of the diet, together with the use, for the same duration, of extended-release metformin, as the only antihyperglycemic allowed. Anthropometric measurements, bioimpedance analysis, indirect calorimetry, and blood chemistry assessments were conducted at the beginning of the study, time 0 (T0), and at the end, time 1 (T1), i.e., on the 21st day. The main outcomes of the revised protein-sparing diet after only twenty-one days were a reduction in body weight with the predominant loss of visceral atherogenic abdominal fat and, therefore, a possible contextual reduction in ectopic fat deposits together with a simultaneous reduction in insulin resistance and normalization of insulin levels, maintenance of free fat mass and basal metabolism, restoration of metabolic flexibility, and improvement of the glucometabolic and lipidic parameters. These results demonstrate the promising potential of the revised protein-sparing diet as an "etiologic tool" in the integrated nutritional treatment of metabolic diseases such as obesity and type 2 diabetes mellitus.

Diosgenin: An ingress towards solving puzzle for diabetes treatment

The consumption and composition of food in daily life predict our health in long run. The relation of diabetes to sweets is quite popular. Diabetes hampers the glucose and insulin regulation in the human body by damaging pancreatic β cells. Diabetes has a strong potential towards altering cellular mechanisms of organs causing unlawful performance. Diabetes alters pathways like TLR4, AChE, NF-ĸB, LPL, and PPAR at different sites that affect the normal cellular machinery and cause damage to the local tissue and organ. The long-lasting effect of diabetes was observed in vascular, cardia, nervous, skeletal, reproductive, hepatic, ocular, and renal systems. The increasing awareness of diabetes and its concern has awakened the common people more enthusiastically. Due to rising harm from diabetes, scientific researchers tend to have more eyes toward it. While searching for diabetes solutions, fenugreek diosgenin could pop up with some positive effects in curing the same. Diosgenin helps to lower the scathe of diabetes by modifying cellular pathways in favor of healthy bodily functions. Diosgenin altered the pathways for renewal of pancreatic β cells for better insulin secretion, initiate GLUT4, enhanced DHEA, modify ER-α-mediated PI3K/Akt pathways. Diosgenin can be an appropriate insult for diabetes in a much evolving way for a healthy lifestyle. PRACTICAL APPLICATIONS: Diabetes is one of the most death causing diseases in the medical world. Regrettably the cure of diabetes is yet to be found. Various scientific team working on the same to look after the most appropriate way for diabetes treatment. There is enormous growth of nutraceutical in the market claiming for cure of different metabolic disorders. Among various bioactive compound fenugreek's diosgenin could took a leap over other in curing and preventing the damage caused by diabetes to different organs. The role of diosgenin in curing various metabolic disorders is quite popular from some time. This article also emphasizes over beneficiary effect of diosgenin in curing the damages caused by diabetes by altering cellular metabolism processes. Hence diosgenin could be a better way for researchers to develop a method for diabetes treatment.

Muscle Function, Body Composition, Insulin Sensitivity and Physical Activity in Adolescents Born Preterm: Impact of Gestation and Vitamin D Status

Whilst several studies have explored adolescent metabolic and cognitive function after preterm birth, few have explored muscle function and physical activity. We set out to examine the relationship between gestational age and muscle metabolism in a cohort of adolescents who were born preterm. Participants were recruited from the Newcastle preterm birth growth study cohort. They did not have severe neurological disease and were not on daily medication. Participants underwent an assessment of oxidative muscle function using phosphorus magnetic resonance spectroscopy that included the half-time for recovery of equilibrium of phosphocreatine, τ½PCr. In addition, we measured key variables that might affect muscle function including physical activity levels determined by 3-day accelerometry, body composition using air displacement plethysmography, insulin sensitivity using the homeostatic model assessment/Matsuda index and serum vitamin D concentrations. 60 adolescents (35F) median age 15.6 years (range 12.1−18.8) with a median gestation of 31 weeks (range 24 to 34 weeks) underwent a single assessment. Males were more active and spent less time in sedentary mode. Time spent in light activity was associated with insulin sensitivity (IS) (Matsuda Index; p < 0.05) but there were no strong correlations between activity levels and gestational age. Greater fat mass, waist circumference and body mass index were all associated with lower IS. Gestational age was negatively associated with adjusted measures of oxidative muscle function (τ½PCr). In a stepwise multivariate linear regression model, gestational age at birth was the most significant predictor of oxidative muscle function (p = 0.005). Higher serum vitamin D levels were also associated with faster phosphocreatine recovery time (p = 0.045). Oxidative function in the skeletal muscle of adolescents born preterm is associated with gestational age and vitamin D concentrations. Our study suggests that being born preterm may have a long-term impact on muscle metabolism.

Effects of a Personalized VLCKD on Body Composition and Resting Energy Expenditure in the Reversal of Diabetes to Prevent Complications

The reversion of diabetes and the treatment of long-term obesity are difficult challenges. The failure mechanisms of rapid weight loss are mainly related to the wasting of lean mass. This single-arm study aims to evaluate the effects of a very low-calorie ketogenic diet (VLCKD) on body composition and resting energy expenditure in the short term reversal of diabetes mellitus Type 2. For eight weeks, subjects were administered a personalized VLCKD with protein intake based on lean mass and synthetic amino acidic protein supplementation. Each subject was assessed by anthropometry, Dual-energy X-ray Absorptiometry(DXA), bioimpedentiometric analysis (BIA), indirect calorimetry, and biochemical analysis. The main findings were the saving of lean mass, the reduction of abdominal fat mass, restored metabolic flexibility, the maintenance of resting energy expenditure, and the reversion of diabetes. These results highlight how the application of preventive, predictive, personalized, and participative medicine to nutrition may be promising for the prevention of diabetes and enhancement of obesity treatment.

Interorgan Metabolic Crosstalk in Human Insulin Resistance

Excessive energy intake and reduced energy expenditure drive the development of insulin resistance and metabolic diseases such as obesity and type 2 diabetes mellitus. Metabolic signals derived from dietary intake or secreted from adipose tissue, gut, and liver contribute to energy homeostasis. Recent metabolomic studies identified novel metabolites and enlarged our knowledge on classic metabolites. This review summarizes the evidence of their roles as mediators of interorgan crosstalk and regulators of insulin sensitivity and energy metabolism. Circulating lipids such as free fatty acids, acetate, and palmitoleate from adipose tissue and short-chain fatty acids from the gut effectively act on liver and skeletal muscle. Intracellular lipids such as diacylglycerols and sphingolipids can serve as lipotoxins by directly inhibiting insulin action in muscle and liver. In contrast, fatty acid esters of hydroxy fatty acids have been recently shown to exert a series of beneficial effects. Also, ketoacids are gaining interest as potent modulators of insulin action and mitochondrial function. Finally, branched-chain amino acids not only predict metabolic diseases, but also inhibit insulin signaling. Here, we focus on the metabolic crosstalk in humans, which regulates insulin sensitivity and energy homeostasis in the main insulin-sensitive tissues, skeletal muscle, liver, and adipose tissue.

Pro-inflammatory cytokine-induced lipolysis after an episode of acute pancreatitis

CONTEXT

Pro-inflammatory cytokine-stimulated lipolysis is one of the mechanisms underlying the pathogenesis of type 2 diabetes. However, whether it plays a role in the pathogenesis of post-pancreatitis diabetes mellitus (PPDM) remains unknown.

OBJECTIVE

To investigate the associations between markers of lipid metabolism and pro-inflammatory cytokines in individuals after acute pancreatitis (AP) in general, and in individuals with abnormal glucose metabolism (AGM) following AP in particular.

METHODS

Fasting blood samples were collected to measure markers of lipid metabolism (apolipoprotein-B, cholesterol, free fatty acids (FFA), glycerol, high and low-density lipoproteins, triglycerides) and cytokines (interleukin (IL)-6, monocyte chemoattractant protein (MCP)-1, and tumour necrosis factor (TNF) α). Linear regression analysis was conducted. Four statistical models were used to adjust for patient- and pancreatitis-related characteristics.

RESULTS

A total of 83 patients were recruited. IL-6 was significantly associated with glycerol in all models (p < .05), with glycerol levels increasing by 106% in individuals with AGM after AP (p <.05) compared to a 30.3% increase in individuals with normal glucose metabolism (NGM) (p >.05). TNFα was significantly associated with FFA (p = .015) in individuals with AGM after AP in the most adjusted model, with FFA levels increasing by 314% in these individuals compared to a 162% decrease in individuals with NGM after AP (p >.05).

CONCLUSIONS

Lipolysis appears to be an important pathogenetic mechanism in glucose derangements after diseases of the exocrine pancreas. IL-6 and TNFα are the driving forces behind lipolysis in individuals with AGM after AP. Modulation of lipolysis may be a promising therapeutic modality.

Phosphorylation of Beta-3 adrenergic receptor at serine 247 by ERK MAP kinase drives lipolysis in obese adipocytes

OBJECTIVE

The inappropriate release of free fatty acids from obese adipose tissue stores has detrimental effects on metabolism, but key molecular mechanisms controlling FFA release from adipocytes remain undefined. Although obesity promotes systemic inflammation, we find activation of the inflammation-associated Mitogen Activated Protein kinase ERK occurs specifically in adipose tissues of obese mice, and provide evidence that adipocyte ERK activation may explain exaggerated adipose tissue lipolysis observed in obesity.

METHODS AND RESULTS

We provide genetic and pharmacological evidence that inhibition of the MEK/ERK pathway in human adipose tissue, mice, and flies all effectively limit adipocyte lipolysis. In complementary findings, we show that genetic and obesity-mediated activation of ERK enhances lipolysis, whereas adipose tissue specific knock-out of ERK2, the exclusive ERK1/2 protein in adipocytes, dramatically impairs lipolysis in explanted mouse adipose tissue. In addition, acute inhibition of MEK/ERK signaling also decreases lipolysis in adipose tissue and improves insulin sensitivity in obese mice. Mice with decreased rates of adipose tissue lipolysis in vivo caused by either MEK or ATGL pharmacological inhibition were unable to liberate sufficient White Adipose Tissue (WAT) energy stores to fuel thermogenesis from brown fat during a cold temperature challenge. To identify a molecular mechanism controlling these actions, we performed unbiased phosphoproteomic analysis of obese adipose tissue at different time points following acute pharmacological MEK/ERK inhibition. MEK/ERK inhibition decreased levels of adrenergic signaling and caused de-phosphorylation of the β3-adrenergic receptor (β3AR) on serine 247. To define the functional implications of this phosphorylation, we showed that CRISPR/Cas9 engineered cells expressing wild type β3AR exhibited β3AR phosphorylation by ERK2 and enhanced lipolysis, but this was not seen when serine 247 of β3AR was mutated to alanine.

CONCLUSION

Taken together, these data suggest that ERK activation in adipocytes and subsequent phosphorylation of the β3AR on S247 are critical regulatory steps in the enhanced adipocyte lipolysis of obesity.

Type 2 Diabetes: The Pathologic Basis of Reversible β-Cell Dysfunction

The reversible nature of early type 2 diabetes has been demonstrated in in vivo human studies. Recent in vivo and in vitro studies of β-cell biology have established that the β-cell loses differentiated characteristics, including glucose-mediated insulin secretion, under metabolic stress. Critically, the β-cell dedifferentiation produced by long-term excess nutrient supply is reversible. Weight loss in humans permits restoration of first-phase insulin secretion associated with the return to normal of the elevated intrapancreatic triglyceride content. However, in type 2 diabetes of duration greater than 10 years, the cellular changes appear to pass a point of no return. This review summarizes the evidence that early type 2 diabetes can be regarded as a reversible β-cell response to chronic positive calorie balance.

Calorie restriction and reversal of type 2 diabetes

Type 2 diabetes causes major global health problems and has been believed to be a lifelong condition with inevitable worsening. Steadily increasing numbers of drugs appeared to be required to achieve even modest control. Early type 2 diabetes has now been shown to be reversed by substantial weight loss and this has allowed temporal tracking of the underlying pathophysiological changes. Areas covered: In early type 2 diabetes, negative calorie balance decreases liver fat within days, and allows return of normal control of hepatic glucose production. Over 8 weeks, the negative calorie balance allows the raised levels of intra-pancreatic fat and simultaneously first phase insulin secretion to normalise. These findings are consistent with the 2008 Twin Cycle Hypothesis of the etiology and pathogenesis of type 2 diabetes. Individuals develop type 2 diabetes when they exceed their personal fat threshold for safe storage of fat and there is no difference in pathophysiology between those with BMI above or below 30 kg/m². Expert commentary: Type 2 diabetes can now be understood as a state of excess fat in liver and pancreas, and remains reversible for at least 10 years in most individuals.

Ingestion of glucose or sucrose prevents liver but not muscle glycogen depletion during prolonged endurance-type exercise in trained cyclists

The purpose of this study was to define the effect of glucose ingestion compared with sucrose ingestion on liver and muscle glycogen depletion during prolonged endurance-type exercise. Fourteen cyclists completed two 3-h bouts of cycling at 50% of peak power output while ingesting either glucose or sucrose at a rate of 1.7 g/min (102 g/h). Four cyclists performed an additional third test for reference in which only water was consumed. We employed (13)C magnetic resonance spectroscopy to determine liver and muscle glycogen concentrations before and after exercise. Expired breath was sampled during exercise to estimate whole body substrate use. After glucose and sucrose ingestion, liver glycogen levels did not show a significant decline after exercise (from 325 ± 168 to 345 ± 205 and 321 ± 177 to 348 ± 170 mmol/l, respectively; P > 0.05), with no differences between treatments. Muscle glycogen concentrations declined (from 101 ± 49 to 60 ± 34 and 114 ± 48 to 67 ± 34 mmol/l, respectively; P < 0.05), with no differences between treatments. Whole body carbohydrate utilization was greater with sucrose (2.03 ± 0.43 g/min) vs. glucose (1.66 ± 0.36 g/min; P < 0.05) ingestion. Both liver (from 454 ± 33 to 283 ± 82 mmol/l; P < 0.05) and muscle (from 111 ± 46 to 67 ± 31 mmol/l; P < 0.01) glycogen concentrations declined during exercise when only water was ingested. Both glucose and sucrose ingestion prevent liver glycogen depletion during prolonged endurance-type exercise. Sucrose ingestion does not preserve liver glycogen concentrations more than glucose ingestion. However, sucrose ingestion does increase whole body carbohydrate utilization compared with glucose ingestion. This trial was registered at https://www.clinicaltrials.gov as NCT02110836.

Reduction of non-esterified fatty acids improves insulin sensitivity and lowers oxidative stress, but fails to restore oxidative capacity in type 2 diabetes: a randomised clinical trial

AIMS/HYPOTHESIS

Muscle mitochondrial function can vary during fasting, but is lower during hyperinsulinaemia in insulin-resistant humans. Ageing and hyperlipidaemia may be the culprits, but the mechanisms remain unclear. We hypothesised that (1) insulin would fail to increase mitochondrial oxidative capacity in non-diabetic insulin-resistant young obese humans and in elderly patients with type 2 diabetes and (2) reducing NEFA levels would improve insulin sensitivity by raising oxidative capacity and lowering oxidative stress.

METHODS

Before and after insulin (4, 40, 100 nmol/l) stimulation, mitochondrial oxidative capacity was measured in permeabilised fibres and isolated mitochondria using high-resolution respirometry, and H2O2 production was assessed fluorimetrically. Tissue-specific insulin sensitivity was measured with hyperinsulinaemic-euglycaemic clamps combined with stable isotopes. To test the second hypothesis, in a 1-day randomised, crossover study, 15 patients with type 2 diabetes recruited via local advertisement were assessed for eligibility. Nine patients fulfilled the inclusion criteria (BMI <35 kg/m(2); age <65 years) and were allocated to and completed the intervention, including oral administration of 750 mg placebo or acipimox. Blinded randomisation was performed by the pharmacy; all participants, researchers performing the measurements and those assessing study outcomes were blinded. The main outcome measures were insulin sensitivity, oxidative capacity and oxidative stress.

RESULTS

Insulin sensitivity and mitochondrial oxidative capacity were ~31% and ~21% lower in the obese groups than in the lean group. The obese participants also exhibited blunted substrate oxidation upon insulin stimulation. In the patients with type 2 diabetes, acipimox improved insulin sensitivity by ~27% and reduced H2O2 production by ~45%, but did not improve basal or insulin-stimulated mitochondrial oxidative capacity. No harmful treatment side effects occurred.

CONCLUSIONS/INTERPRETATION

Decreased mitochondrial oxidative capacity can also occur independently of age in insulin-resistant young obese humans. Insulin resistance is present at the muscle mitochondrial level, and is not affected by reducing circulating NEFAs in type 2 diabetes. Thus, impaired plasticity of mitochondrial function is an intrinsic phenomenon that probably occurs independently of lipotoxicity and reduced glucose uptake.

TRIAL REGISTRATION

Clinical Trials NCT00943059 FUNDING: This study was funded in part by a grant from the German Federal Ministry of Education and Research to the German Center for Diabetes Research (DZD e.V.).

Fatty acid metabolism, energy expenditure and insulin resistance in muscle

Fatty acids (FAs) are essential elements of all cells and have significant roles as energy substrates, components of cellular structure and signalling molecules. The storage of excess energy intake as fat in adipose tissue is an evolutionary advantage aimed at protecting against starvation, but in much of today's world, humans are faced with an unlimited availability of food, and the excessive accumulation of fat is now a major risk for human health, especially the development of type 2 diabetes (T2D). Since the first recognition of the association between fat accumulation, reduced insulin action and increased risk of T2D, several mechanisms have been proposed to link excess FA availability to reduced insulin action, with some of them being competing or contradictory. This review summarises the evidence for these mechanisms in the context of excess dietary FAs generating insulin resistance in muscle, the major tissue involved in insulin-stimulated disposal of blood glucose. It also outlines potential problems with models and measurements that may hinder as well as help improve our understanding of the links between FAs and insulin action.

Effects of raising muscle glycogen synthesis rate on skeletal muscle ATP turnover rate in type 2 diabetes

Mitochondrial dysfunction has been implicated in the pathogenesis of type 2 diabetes. We hypothesized that any impairment in insulin-stimulated muscle ATP production could merely reflect the lower rates of muscle glucose uptake and glycogen synthesis, rather than cause it. If this is correct, muscle ATP turnover rates in type 2 diabetes could be increased if glycogen synthesis rates were normalized by the mass-action effect of hyperglycemia. Isoglycemic- and hyperglycemic-hyperinsulinemic clamps were performed on type 2 diabetic subjects and matched controls, with muscle ATP turnover and glycogen synthesis rates measured using (31)P- and (13)C-magnetic resonance spectroscopy, respectively. In diabetic subjects, hyperglycemia increased muscle glycogen synthesis rates to the level observed in controls at isoglycemia [from 19 ± 9 to 41 ± 12 μmol·l(-1)·min(-1) (P = 0.012) vs. 40 ± 7 μmol·l(-1)·min(-1) in controls]. This was accompanied by a modest increase in muscle ATP turnover rates (7.1 ± 0.5 vs. 8.6 ± 0.7 μmol·l(-1)·min(-1), P = 0.04). In controls, hyperglycemia brought about a 2.5-fold increase in glycogen synthesis rates (100 ± 24 vs. 40 ± 7 μmol·l(-1)·min(-1), P = 0.028) and a 23% increase in ATP turnover rates (8.1 ± 0.9 vs. 10.0 ± 0.9 μmol·l(-1)·min(-1), P = 0.025) from basal state. Muscle ATP turnover rates correlated positively with glycogen synthesis rates (r(s) = 0.46, P = 0.005). Changing the rate of muscle glucose metabolism in type 2 diabetic subjects alters demand for ATP synthesis at rest. In type 2 diabetes, skeletal muscle ATP turnover rates reflect the rate of glucose uptake and glycogen synthesis, rather than any primary mitochondrial defect.