Dunnigan lipodystrophy syndrome: French National Diagnosis and Care Protocol (PNDS; Protocole National de Diagnostic et de Soins)

Dunnigan syndrome, or Familial Partial Lipodystrophy type 2 (FPLD2; ORPHA 2348), is a rare autosomal dominant disorder due to pathogenic variants of the LMNA gene. The objective of the French National Diagnosis and Care Protocol (PNDS; Protocole National de Diagnostic et de Soins), is to provide health professionals with a guide to optimal management and care of patients with FPLD2, based on a critical literature review and multidisciplinary expert consensus. The PNDS, written by members of the French National Reference Center for Rare Diseases of Insulin Secretion and Insulin Sensitivity (PRISIS), is available on the French Health Authority website (in French). Dunnigan syndrome is characterized by a partial atrophy of the subcutaneous adipose tissue and by an insulin resistance syndrome, associated with a risk of metabolic, cardiovascular and muscular complications. Its prevalence, assessed at 1/100.000 in Europe, is probably considerably underestimated. Thorough clinical examination is key to diagnosis. Biochemical testing frequently shows hyperinsulinemia, abnormal glucose tolerance and hypertriglyceridemia. Elevated hepatic transaminases (hepatic steatosis) and creatine phosphokinase, and hyperandrogenism in women, are common. Molecular analysis of the LMNA gene confirms diagnosis and allows for family investigations. Regular screening and multidisciplinary monitoring of the associated complications are necessary. Diabetes frequently develops from puberty onwards. Hypertriglyceridemia may lead to acute pancreatitis. Early atherosclerosis and cardiomyopathy should be monitored. In women, polycystic ovary syndrome is common. Overall, the management of patients with Dunnigan syndrome requires the collaboration of several health care providers. The attending physician, in conjunction with the national care network, will ensure that the patient receives optimal care through regular follow-up and screening. The various elements of this PNDS are described to provide such a support.

Ghrelin concentration as an indicator of eating-disorder risk in obese women

AIM

Eating disorders (EDs), disordered eating (DE) and obesity are thought to have overlapping aetiological processes. DE in obesity can jeopardize weight-loss results, and acyl ghrelin (AG) is a hormone that stimulates food intake and reward processes. The main study objective was to determine whether higher-than-expected concentrations of AG in common obesity are associated with DE symptoms.

METHODS

The study population included 84 women, aged 20-55 years, free of established EDs: 55 were severely obese (OB) and 29 were of normal weight (NW). OB participants were stratified into two groups according to their median concentration of fasting AG distribution. The OB women with a high fasting plasma ghrelin concentration (HGC) were compared with both OB women with a low fasting plasma ghrelin concentration (LGC) and NW women. Participants were assessed by the Eating Disorder Inventory (EDI-2), Three-Factor Eating Questionnaire (TFEQ) and Hospital Anxiety and Depression Scale (HADS). Fasting glucose, insulin, leptin and ghrelin plasma concentrations were also quantified.

RESULTS

Between the two AG groups of OB women, there was no statistical difference in either anthropometric or metabolic parameters, HADS, TFEQ or fasting hunger scores. However, the HGC group scored significantly higher than the LGC group on the drive-for-thinness subscale of EDI-2 (9.30±0.99 vs. 6.46±0.83, respectively; P=0.033).

CONCLUSION

Results support the hypothesis of a potential relationship between fasting plasma AG concentrations and ED risk, regardless of mood and anxiety. AG may be considered a potential biomarker of vulnerability for developing EDs.

Greater weight loss with the omega loop bypass compared to the Roux-en-Y gastric bypass: a comparative study

BACKGROUND

Despite similar initial results on weight loss and metabolic control, with a better feasibility than the Roux-en-Y gastric bypass (RYGBP), the omega loop bypass (OLB) remains controversial. The aim of this study was to compare the short-term outcomes of the laparoscopic OLB versus the RYGBP in terms of weight loss, metabolic control, and safety.

METHODS

Two groups of consecutive patients who underwent laparoscopic gastric bypass surgery were selected: 20 OLB patients and 61 RYGBP patients. Patients were matched for age, gender, and initial body mass index (BMI). Data concerning weight loss, metabolic outcomes, and complications were collected prospectively.

RESULTS

Mean duration of the surgical procedure was shorter in the OLB group (105 vs. 152 min in the RYGBP group; p < 0.001). Mean excess BMI loss percent (EBL%) at 6 months and at 1 year was greater in the OLB group (76.3 vs. 60.0%, p = 0.001, and 89.0 vs. 71.0%, p = 0.002, respectively). After adjustment for age, sex, initial BMI, and history of previous bariatric surgery, the OLB procedure was still associated with a significantly greater 1-year EBL%. Diabetes improvement at 6 months was similar between both groups. The early and late complication rates were not statistically different. There were three anastomotic ulcers in the OLB group, in smokers, over 60 years old, who were not taking proton pump inhibitor medication.

CONCLUSIONS

In this short-term study, we observed a greater weight loss with OLB and similar efficiency on metabolic control compared to RYGBP. Long-term evaluation is necessary to confirm these outcomes.

Increased TSH in obesity: Evidence for a BMI-independent association with leptin

AIM

This study aimed to determine whether the association between thyroid-stimulating hormone (TSH) and body mass index (BMI) is related to leptin concentration in obese individuals.

METHODS

Plasma TSH and leptin assays were performed in 800 consecutive patients, hospitalized for a nutritional checkup, with a BMI ≥ 30 kg/m(2). Various anthropometric, hormonal and metabolic parameters, including age, weight, BMI, insulin, leptin and TSH, were measured or calculated. Univariate and multivariate regression analyses were performed to identify any significant relationships between these parameters. Also, characteristics of the patients in the lowest and highest quartiles of TSH distribution were compared.

RESULTS

TSH was positively correlated with both BMI and leptin. When multiple regression analysis was performed, TSH and leptin maintained a significant association independent of BMI. Patients in the fourth quartile of TSH distribution displayed higher BMI and higher leptin levels in comparison to the first quartile.

CONCLUSION

Our study has confirmed an increase in TSH in conjunction with BMI in obese subjects. This increase was correlated with leptin independently of BMI. It is hypothesized that the increase in TSH observed in obese subjects was the consequence of both fat mass accumulation and a positive energy-balance.

Regulation of energy metabolism and mitochondrial function in skeletal muscle during lipid overfeeding in healthy men

CONTEXT/OBJECTIVE

The aim of this study was to evaluate the regulation of the fuel partitioning and energy metabolism in skeletal muscle during lipid overfeeding in healthy men. Design/Participants/Intervention: Thirty-nine healthy volunteers were overfed for 56 days with a high-fat diet (3180 kJ/d). Energy metabolism (indirect calorimetry) was characterized in the fasting state and during a test meal before and at the end of the diet. Skeletal muscle biopsies were taken at day 0 and day 56.

MAIN OUTCOME MEASURES

Change in gene expression, mitochondrial respiration, nicotinamide adenine dinucleotide (NAD(+)) content, and acetylation of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) in skeletal muscle was measured.

RESULTS

Overfeeding increased body weight (+2.6 kg) and fat mass concomitantly with a shift in the use of substrates as energy fuel toward preferential oxidation of carbohydrates instead of lipids. Changes in lipid metabolic gene expression supported this observation, with a reduction in pyruvate dehydrogenase kinase 4 expression that could be the consequences of decreased NAD(+) concentration and reduced deacetylase activity of the sirtuins, as supported by hyperacetylation of PGC-1α after overfeeding. Interestingly, this reduction of the sirtuin PGC-1α pathway was associated with increased mitochondrial gene expression and higher respiration rate under these conditions.

CONCLUSION

Adaptation to lipid overfeeding and regulation of fuel partitioning in human muscle appear to rely on a dissociation between the regulatory functions of the sirtuin-PGC-1α pathway on fatty acid oxidation and on mitochondrial regulation. This may facilitate lipid storage during a period of positive energy balance while maintaining mitochondrial functions and oxidative capacities.

Predictive factors of type 2 diabetes remission 1 year after bariatric surgery: impact of surgical techniques

Type 2 diabetes (T2D) remission after bariatric procedures has been highlighted in many retrospective and some recent prospective studies. However, in the most recent prospective study, more than 50 % of patients did not reach T2D remission at 1 year. Our aim was to identify baseline positive predictors for T2D remission at 1 year after bariatric surgery and to build a preoperative predictive score. We analysed the data concerning 161 obese operated on between June 2007 and December 2010. Among them, 46 were diabetic and were included in the study-11 laparoscopic adjustable gastric banding (LAGB), 26 Roux-en-Y gastric bypass (RYGB) and 9 sleeve gastrectomy (SG). We compared anthropometric and metabolic features during 1 year of follow-up. A receiver operating characteristic analysis was performed to predict T2D remission. RYGB and SG were similarly efficient for body weight loss and more efficient than LAGB; 62.8 % of patients presented with T2DM remission at 1 year, with no significant difference according to the surgical procedure. A 1-year body mass index (BMI) <35 kg m(-2) was predictive of T2DM remission whatever the procedure. The preoperative predictive factors of diabetes remission were baseline BMI ≤50 kg m(-2), duration of type 2 diabetes ≤4 years, glycated haemoglobin ≤7.1 %, fasting glucose <1.14 g/l and absence of insulin therapy. A short duration of diabetes and good preoperative glycaemic control increase the rate of T2DM remission 1 year after surgery. Preoperative metabolic data could be of greater importance than the choice of bariatric procedure.

Moderate alcohol consumption is associated with improved insulin sensitivity, reduced basal insulin secretion rate and lower fasting glucagon concentration in healthy women

AIMS/HYPOTHESIS

Moderate alcohol consumption is associated with a reduced risk of type 2 diabetes with a stronger effect in women. As the underlying mechanisms remain poorly characterised, we investigated its relationship with insulin resistance, insulin secretion, clearance of insulin and glucagon concentration.

METHODS

One-thousand two-hundred and seventy-six non-diabetic individuals from the RISC (relationship between insulin sensitivity and cardiovascular disease) study without high alcohol consumption were studied; all had a euglycaemic-hyperinsulinaemic clamp and an OGTT with assessment of insulin sensitivity, secretion and clearance.

RESULTS

Alcohol consumption was positively associated with insulin sensitivity in women (β = 0.15, p ( trend ) = 0.005) and in men (β = 0.07, p ( trend ) = 0.07) after controlling for age, centre, waist, smoking and physical activity. In women, this association persisted after adjustment for adiponectin but was attenuated after controlling for HDL-cholesterol, suggesting that part of the protection is related to a higher HDL-cholesterol concentration. Higher alcohol consumption was associated with lower basal insulin secretion in women only (β = -0.10, p ( trend ) = 0.004) and this association persisted after adjustment for insulin sensitivity. In men, increasing alcohol consumption was associated with enhanced insulin clearance and increased fasting NEFA concentrations, independently of insulin sensitivity. Fasting glucagon decreased with increasing alcohol in women only (abstainers 9.2 ± 4.4; <28 g/week 8.6 ± 4.0; 28-64 g/week 8.1 ± 3.7; >64 g/week 7.5 ± 3.1 pmol/l; p ( trend ) = 0.01).

CONCLUSIONS/INTERPRETATION

Light-to-moderate alcohol consumption was associated in healthy women with enhanced insulin sensitivity, reduced basal insulin secretion rate and lower fasting plasma glucagon concentration, providing consistent mechanisms for the reduced risk of diabetes.

How can we measure insulin sensitivity/resistance?

Insulin resistance represents a major public health problem, as it plays a major role in the pathophysiology of type 2 diabetes mellitus; it is also associated with increased cardiovascular risk and atherogenic dyslipidaemia, and is a central component of the cluster of metabolic abnormalities that comprise the metabolic syndrome. Thus, the development of tools to quantify insulin sensitivity/resistance has been the main objective of a number of studies. Insulin resistance can be estimated with the use of several biological measurements that evaluate different aspects of this complex situation. To that end, it requires various resources, ranging from just a single fasting blood sample for simple indices, such as the HOMA or QUICKI, to a research setting in which to perform the gold-standard hyperinsulinaemic-euglycaemic clamp test. The choice of method for evaluating insulin resistance depends on the nature of the information required (classification of individual subjects, group comparisons, precise measurement of either global, muscle or liver insulin sensitivity/resistance) and on the available resources. The aim of this review is to analyze the most frequently used assay methods in an attempt to evaluate when and why these methods may be useful.

Systemic ghrelin and reward: effect of cholinergic blockade

AIMS

Ghrelin is one of the most potent orexigens known to date. Recent data suggested that ghrelin is involved in reward-mediated processes such as the rewarding value of food. Whereas the neuronal pathways by which ghrelin regulates energy balance are well described, those involved in ghrelin-induced reward are still confusing. Therefore, we attempted to delineate the involvement of physiological and pharmacological rises in plasma ghrelin in the modulation of food reward seeking behaviours, using the classical conditioned place preference (CPP) procedure in C57BL6J mice, as well as in mice lacking the ghrelin receptor (GHSR1a -/-). We also determined whether these effects on reward-related behaviours could be partly mediated by cholinergic pathways by pre-treating mice with mecamylamine.

RESULTS

Upon moderate caloric restriction, systemic ghrelin levels increased from 108 ± 21 to 148 ± 39 pg/ml in C57BL6J mice and from 111 ± 24 to 179 ± 41 pg/ml in GHSR1a-null mice. Short exposure to rewarding food elicited a strong CPP and stimulation of locomotor activity in GHSR1a wild-type and C57BL6J mice. Conversely, the GHSR1a -/- mice did not exhibit such a food CPP, despite a negative energy balance. Pharmacological rise in systemic ghrelin further increased the time spent in the food-paired side with a higher CPP score (+71%) and this effect was blunted after cholinergic blockade by mecamylamine.

CONCLUSIONS

The ghrelin receptor is obligatory to acquire a food-CPP. The level of plasma ghrelin during conditioning determines the strength of food-induced reward seeking behaviours. The cholinergic pathway partly mediates the further enhancement of food reward induced by pharmacological rises in plasma ghrelin, but not that induced by physiological increases in ghrelin.

Bariatric surgery for diabetes treatment: why should we go rapidly to surgery

Surgical treatment of morbid obesity has been shown to be efficient for long-term weight loss and to improve obesity-related complications. The improvement of type 2 diabetes (T2DM) is dependent of the type of surgery, and is more frequent with gastric bypass than with gastric band. Normalization of glucose metabolism is rapid, often occurring before weight loss, and shown to be related to both a decrease in insulin resistance and an increase in insulin secretion. Some factors limiting the efficiency of gastric bypass on T2DM is the duration of diabetes and the residual beta-cell mass. However, a decrease in diabetes-related death has been found in a large series of surgical cases. These data constitute a good argument for proposing surgery in T2DM obese patients as soon as possible. Nevertheless, whether or not this suggests changing the usual indications for bariatric surgery in T2DM patients, such as a body mass index (BMI) score of<35 kg/m(2), remains controversial.

Microarray analysis of genes with impaired insulin regulation in the skeletal muscle of type 2 diabetic patients indicates the involvement of basic helix-loop-helix domain-containing, class B, 2 protein (BHLHB2)

AIMS/HYPOTHESIS

One of the major processes by which insulin exerts its multiple biological actions is through gene expression regulation. Thus, the identification of transcription factors affected by insulin in target tissues represents an important challenge. The aim of the present study was to gain a greater insight into this issue through the identification of transcription factor genes with insulin-regulated expression in human skeletal muscle.

METHODS

Using microarray analysis, we defined the sets of genes modulated during a 3 h hyperinsulinaemic-euglycaemic clamp (2 mU min(-1) kg(-1)) in the skeletal muscle of insulin-sensitive control volunteers and in moderately obese insulin-resistant type 2 diabetic patients.

RESULTS

Of the 1,529 and 1,499 genes regulated during the clamp in control and diabetic volunteers, respectively, we identified 30 transcription factors with impaired insulin-regulation in type 2 diabetic patients. Analysis of the promoters of the genes encoding these factors revealed a possible contribution of the transcriptional repressor basic helix-loop-helix domain-containing, class B, 2 protein (BHLHB2), insulin regulation of which is strongly altered in the muscle of diabetic patients. Gene ontology analysis of BHLHB2 target genes, identified after BHLHB2 overexpression in human primary myotubes, demonstrated that about 10% of the genes regulated in vivo during hyperinsulinaemia are potentially under the control of this repressor. The data also suggested that BHLHB2 is situated at the crossroads of a complex transcriptional network that is able to modulate major metabolic and biological pathways in skeletal muscle, including the regulation of a cluster of genes involved in muscle development and contraction.

CONCLUSIONS/INTERPRETATION

We have identified BHLHB2 as a potential novel mediator of insulin transcriptional action in human skeletal muscle.

A lipid-parameter-based index for estimating insulin sensitivity and identifying insulin resistance in a healthy population

AIM

Insulin resistance needs to be identified as early as possible in its development to allow targeted prevention programmes. Therefore, we compared various fasting surrogate indices for insulin sensitivity using the euglycaemic insulin clamp in an attempt to develop the most appropriate method for assessing insulin resistance in a healthy population.

METHODS

Glucose, insulin, proinsulin, glucagon, glucose tolerance, fasting lipids, liver enzymes, blood pressure, anthropometric parameters and insulin sensitivity (Mffm/I) using the euglycaemic insulin clamp were obtained for 70 normoglycaemic non-obese individuals. Spearman's rank correlations were used to examine the association between Mffm/I and various fasting surrogate indices of insulin sensitivity. A regression model was used to determine the weighting for each variable and to derive a formula for estimating insulin resistance. The clinical value of the surrogate indices and the new formula for identifying insulin-resistant individuals was evaluated by the use of receiver operating characteristic (ROC) curves.

RESULTS

The variables that best predicted insulin sensitivity were the HDL-to-total cholesterol ratio, the fasting NEFA and fasting insulin. The use of the lipid-parameter-based formula Mffm/I=12x[2.5x(HDL-c/total cholesterol)-NEFA] - fasting insulin appeared to have high clinical value in predicting insulin resistance. The correlation coefficient between Mffm/I and the new fasting index was higher than those with the most commonly used fasting surrogate indices for insulin sensitivity.

CONCLUSION

A lipid-parameter-based index using fasting samples provides a simple means of screening for insulin resistance in the healthy population.

Isoform-specific defects of insulin stimulation of Akt/protein kinase B (PKB) in skeletal muscle cells from type 2 diabetic patients

AIMS/HYPOTHESIS

The serine/threonine kinase Akt/protein kinase B (PKB) is required for the metabolic actions of insulin. Controversial data have been reported regarding Akt defective activation in the muscle of type 2 diabetic patients. Because three Akt isoforms exist, each having a distinct physiological role, we investigated the contribution of isoform-specific defects to insulin signalling in human muscle.

METHODS

The phosphorylation pattern and kinase activity of each Akt isoform were compared in primary myotubes from healthy control participants and type 2 diabetic patients. Phosphorylation of Ser(473) and of Thr(308) in each isoform was determined after immunoprecipitation in myotubes treated or not with insulin.

RESULTS

Muscle cells from diabetic patients displayed defective insulin action and a drastic reduction of insulin-stimulated activity of all Akt isoforms. This was associated with specific defects of their phosphorylation pattern in response to insulin, with impaired Akt2- (and to a lower extent Akt3-) Ser(473) phosphorylation, and with altered Akt1-Thr(308) phosphorylation. These defects were not due to faulty phosphoinositide-dependent protein kinase 1 (PDK1) production or activation. Rather, we found higher levels of the Akt2-Ser(473)-specific protein phosphatase PH domain leucine-rich repeat protein phosphatase 1 (PHLPP1) in muscle from diabetic patients, which may contribute to the alteration of Akt2-Ser(473) phosphorylation.

CONCLUSIONS/INTERPRETATION

These results suggest that several mechanisms affecting Akt isoforms, including deregulated production of PHLPP1, could underlie the alterations of skeletal muscle insulin signalling in type 2 diabetes. Taking into account the recently described isoform-specific metabolic functions of Akt, our results provide mechanistic insight that may contribute to the defective regulation of glucose and lipid metabolisms in the muscle of diabetic patients.

Activation of liver X receptors promotes lipid accumulation but does not alter insulin action in human skeletal muscle cells

AIMS/HYPOTHESIS

The aim of this study was to investigate the effects of liver X receptor (LXR) activation on lipid metabolism and insulin action in human skeletal muscle cells prepared from control subjects and from patients with type 2 diabetes.

SUBJECTS AND METHODS

Cultured myotubes were obtained from muscle biopsies of 11 lean, healthy control subjects and ten patients with type 2 diabetes. The mRNA levels of LXR isoforms and lipogenic genes were estimated by RT-quantitative PCR, and the effects of LXR agonists on insulin action were evaluated by assays of protein kinase B serine 473 phosphorylation and glycogen synthesis.

RESULTS

Both LXRalpha and LXRbeta were expressed in human skeletal muscle and adipose tissue and there was no difference in their mRNA abundance in tissues from patients with type 2 diabetes compared with control subjects. In cultured muscle cells, LXR activation by T0901317 strongly increased expression of the genes encoding lipogenic enzymes, including sterol regulatory element binding protein 1c, fatty acid synthase and stearoyl-CoA desaturase 1, and also promoted triglyceride accumulation in the presence of a high glucose concentration. Importantly, these effects on lipid metabolism did not affect protein kinase B activation by insulin. Furthermore, LXR agonists did not modify insulin action in muscle cells from patients with type 2 diabetes.

CONCLUSIONS/INTERPRETATION

These data suggest that LXR agonists may lead to increased utilisation of lipids and glucose in muscle cells without affecting the mechanism of action of insulin. However, the long-term consequences of triglyceride accumulation in muscle should be evaluated before the development of effective LXR-based therapeutic agents.