Dietary fat, genes and insulin sensitivity

Effect of Linoleic Acid on Cholesterol Levels in a High-Fat Diet-Induced Hypercholesterolemia Rat Model

Cardiovascular disease is the leading cause of morbidity and mortality worldwide, accounting for almost one-third of all deaths. The risk factors for developing this disease include high levels of serum total cholesterol (TC), triglycerides (TG), and low-density lipoprotein (LDL), alongside low levels of high-density lipoprotein (HDL). Dietary linoleic acid has been suggested to reduce these risk factors. This study aims to determine the effects of linoleic acid on cholesterol levels, liver function tests, and structural changes in liver tissue in comparison with fenofibrate in a hypercholesterolemic rat model. Thirty-six male Sprague Dawley rats (150-180 g) were divided into non-hypercholesterolemic and hypercholesterolemic groups. Hypercholesterolemia was induced in the rats by feeding them with a high-fat diet for two weeks. After two weeks, the non-hypercholesterolemic and hypercholesterolemic rats were equally divided into six groups (n = 6): control non-hypercholesterolemic rats, non-hypercholesterolemic rats treated with fenofibrate (60 mg/kg), non-hypercholesterolemic rats treated with linoleic acid (5 mg/kg), control hypercholesterolemic rats, hypercholesterolemic rats treated with fenofibrate (60 mg/kg), and hypercholesterolemic rats treated with linoleic acid (5 mg/kg). The changes in the rats' body weight, serum lipid profiles, atherogenic indices, and liver function test results were obtained. The rats' liver tissues were stained for histopathological analysis. The linoleic acid-treated hypercholesterolemic rats exhibited significantly reduced serum TC, TG, LDL, aspartate aminotransferase, and alanine aminotransferase levels, as well as increased HDL levels compared with the control hypercholesterolemic rats. These linoleic acid effects were comparable to those in the fenofibrate-treated hypercholesterolemic rats. In conclusion, linoleic acid possesses early anti-hypercholesterolemic properties, which may be due to the reductions in serum cholesterol levels and mild early structural changes in the liver tissues of hypercholesterolemic rats. Therefore, continued studies on linoleic acid in atherosclerotic and/or obese animal models are suggested.

A systematic review and meta-analysis of association between brain-derived neurotrophic factor and type 2 diabetes and glycemic profile

Several epidemiologic studies have evaluated the relation between serum/plasma brain-derived neurotrophic factor (BDNF) levels and glycemic parameters, but the findings were conflicting. We performed a systematic review and meta-analysis to compare circulating BDNF levels in individuals with type 2 diabetes (T2D) or other glycemic disorders with healthy controls and to evaluate correlation between BDNF concentrations with glycemic profile. A systematic search up to July 2020 was conducted in reliable electronic databases (MEDLINE (Pubmed), EMBASE, Scopus) and Google scholar. Sixteen observational studies compared serum/plasma BDNF levels in diabetic patients (or individuals with glycemic disorders) vs. healthy controls or reported correlations between serum BDNF levels and glycemic parameters in adults were included in the review. Overall weighted mean difference (WMD) of circulating BDNF levels in 1306 patients with T2D (or other glycemic disorders) was 1.12 ng/mL lower than 1250 healthy subjects (WMD: − 1.12; 95%CI − 1.37, − 0.88, I² = 98.7%, P < 0.001). Subgroup analysis revealed that both diabetic patients and subjects with other glycemic disorders had lower serum/plasma BDNF levels than healthy controls (WMD: − 1.74; 95%CI − 2.15, − 1.33 and WMD: − 0.49; 95%CI − 0.82, − 0.16, respectively). No significant correlation was found between BDNF levels and glycemic parameters [fasting blood glucose (FBG) (Fisher’s Z = 0.05; 95%CI − 0.21, 0.11; n = 1400), homeostatic model assessment for insulin resistance (HOMA-IR) (Fisher’s Z = 0.12; 95%CI − 0.20, 0.44; n = 732) and glycosylated hemoglobin (HbA1c) (Fisher’s Z = 0.04; 95%CI − 0.05, 0.12; n = 2222)]. We found that diabetic patients and subjects with glycemic disorders had lower circulating BDNF levels than healthy controls. However, there was no significant correlation between BDNF concentrations and glycemic parameters including FBG, HOMA-IR and HbA1c. Further prospective investigations are required to confirm these findings.

Dietary Approaches to Stop Hypertension (DASH): potential mechanisms of action against risk factors of the metabolic syndrome

The metabolic syndrome is a cluster of disorders dominated by abdominal obesity, hypertriacylglycerolaemia, low HDL-cholesterol, high blood pressure and high fasting glucose. Diet modification is a safe and effective way to treat the metabolic syndrome. Dietary Approaches to Stop Hypertension (DASH) is a dietary pattern rich in fruits, vegetables and low-fat dairy products, and low in meats and sweets. DASH provides good amounts of fibre, K, Ca and Mg, and limited quantities of total fat, saturated fat, cholesterol and Na. Although DASH was initially designed for the prevention or control of hypertension, using a DASH diet has other metabolic benefits. In the present review, the effect of each dietary component of DASH on the risk factors of the metabolic syndrome is discussed. Due to limited fat and high fibre and Ca content, individuals on the DASH diet are less prone to overweight and obesity and possess lower concentrations of total and LDL-cholesterol although changes in TAG and HDL-cholesterol have been less significant and available evidence in this regard is still inconclusive. Moreover, high amounts of fruit and vegetables in DASH provide great quantities of K, Mg and fibre, all of which have been shown to reduce blood pressure. K, Mg, fibre and antioxidants have also been effective in correcting glucose and insulin abnormalities. Evidence is provided from cross-sectional investigations, cohort studies and randomised controlled trials, and, where available, from published meta-analyses. Mechanisms are described according to human studies and, in the case of a lack of evidence, from animal and cell culture investigations.

VCE-004.8, A Multitarget Cannabinoquinone, Attenuates Adipogenesis and Prevents Diet-Induced Obesity

Over the past few years, the endocannabinoid system (ECs) has emerged as a crucial player for the regulation of food intake and energy metabolism, and its pharmacological manipulation represents a novel strategy for the management of metabolic diseases. The discovery that VCE-004.8, a dual PPARγ and CB₂ receptor agonist, also inhibits prolyl-hydroxylases (PHDs) and activates the HIF pathway provided a rationale to investigate its effect in in vitro models of adipogenesis and in a murine model of metabolic syndrome, all processes critically regulated by these targets of VCE-004.8. In accordance with its different binding mode to PPARγ compared to rosiglitazone (RGZ), VCE-004.8 neither induced adipogenic differentiation, nor affected osteoblastogenesis. Daily administration of VCE-004.8 (20 mg/kg) to HFD mice for 3-wks induced a significant reduction in body weight gain, total fat mass, adipocyte volume and plasma triglycerides levels. VCE-004.8 could also significantly ameliorate glucose tolerance, reduce leptin levels (a marker of adiposity) and increase adiponectin and incretins (GLP-1 and GIP) levels. Remarkably, VCE-004.8 increased the FGF21 mRNA expression in white and brown adipose, as well as in a BAT cell line, qualifying cannabinoaminoquinones as a class of novel therapeutic candidates for the management of obesity and its common metabolic co-morbidities.

Biologically anchored knowledge expansion approach uncovers KLF4 as a novel insulin signaling regulator

One of the biggest challenges in analyzing high throughput omics data in biological studies is extracting information that is relevant to specific biological mechanisms of interest while simultaneously restricting the number of false positive findings. Due to random chances with numerous candidate targets and mechanisms, computational approaches often yield a large number of false positives that cannot easily be discerned from relevant biological findings without costly, and often infeasible, biological experiments. We here introduce and apply an integrative bioinformatics approach, Biologically Anchored Knowledge Expansion (BAKE), which uses sequential statistical analysis and literature mining to identify highly relevant network genes and effectively removes false positive findings. Applying BAKE to genomic expression data collected from mouse (Mus musculus) adipocytes during insulin resistance progression, we uncovered the transcription factor Krueppel-like Factor 4 (KLF4) as a regulator of early insulin signaling. We experimentally confirmed that KLF4 controls the expression of two key insulin signaling molecules, the Insulin Receptor Substrate 2 (IRS2) and Tuberous Sclerosis Complex 2 (TSC2).

Comparison of the effect of the Dietary Approaches to Stop Hypertension diet with usual dietary advice on expression of peroxisome proliferators-activated receptor gamma gene in women: A randomized controlled clinical trial

BACKGROUND

Peroxisome proliferator-activated receptor gamma (PPAR-γ) which controls body weight, glucose homeostasis, and adipocyte differentiation is a valuable candidate gene for insulin resistance (IR). The present study aimed to compare the effects of the Dietary Approaches to Stop Hypertension (DASH) diet and usual dietary advice (UDA) on PPAR-γ gene expression in women at risk for cardiovascular disease (CVD).

METHODS

This randomized controlled trial was performed on 44 women aged 20-50 years at risk for CVD (BMI > 25 kg/m2 and low physical activity). Participants were randomly assigned to the UDA (n = 22) or DASH (n = 22) diets for 12 weeks. The DASH diet was rich in fruits, vegetables, whole grains and low-fat dairy products and low in saturated fat, total fat, cholesterol, refined grains and sweets, with a total of 2400 mg/day sodium. The UDA diet was a regular diet with healthy dietary advice. Anthropometric indices and PPAR-γ gene expression were measured and compared between the two groups at the end of the study.

RESULTS

After the intervention, body mass index (BMI) and waist circumference (WC) significantly decreased in the DASH group (P < 0.050) but the results showed no significant differences between the two groups. At the end of the trial, PPAR-γ gene expression was significantly different between the UDA and the DASH diet groups (P = 0.040) and this difference remained significant after adjustment for BMI, and physical activity (P = 0.030).

CONCLUSION

The result of the study showed that the DASH diet significantly decreased the expression of PPAR-γ. This finding was unexpected and future studies on the current topic are therefore recommended.

Nutritional Strategies for the Individualized Treatment of Non-Alcoholic Fatty Liver Disease (NAFLD) Based on the Nutrient-Induced Insulin Output Ratio (NIOR)

Nutrients play a fundamental role as regulators of the activity of enzymes involved in liver metabolism. In the general population, the action of nutrients may be affected by gene polymorphisms. Therefore, individualization of a diet for individuals with fatty liver seems to be a fundamental step in nutritional strategies. In this study, we tested the nutrient-induced insulin output ratio (NIOR), which is used to identify the correlation between the variants of genes and insulin resistance. We enrolled 171 patients, Caucasian men (n = 104) and women (n = 67), diagnosed with non-alcoholic fatty liver disease (NAFLD). From the pool of genes sensitive to nutrient content, we selected genes characterized by a strong response to the NIOR. The polymorphisms included Adrenergic receptor (b3AR), Tumor necrosis factor (TNFα), Apolipoprotein C (Apo C III). Uncoupling Protein type I (UCP-1), Peroxisome proliferator activated receptor γ2 (PPAR-2) and Apolipoprotein E (APOEs). We performed three dietary interventions: a diet consistent with the results of genotyping (NIOR (+)); typical dietary recommendations for NAFLD (Cust (+)), and a diet opposite to the genotyping results (NIOR (−) and Cust (−)). We administered the diet for six months. The most beneficial changes were observed among fat-sensitive patients who were treated with the NIOR (+) diet. These changes included improvements in body mass and insulin sensitivity and normalization of blood lipids. In people sensitive to fat, the NIOR seems to be a useful tool for determining specific strategies for the treatment of NAFLD.

Proteome from patients with metabolic syndrome is regulated by quantity and quality of dietary lipids

Background

Metabolic syndrome is a multi-component disorder associated to a high risk of cardiovascular disease. Its etiology is the result of a complex interaction between genetic and environmental factors, including dietary habits. We aimed to identify the target proteins modulated by the long-term consumption of four diets differing in the quality and quantity of lipids in the whole proteome of peripheral blood mononuclear cells (PBMC).

Results

A randomized, controlled trial conducted within the LIPGENE study assigned 24 MetS patients for 12 weeks each to 1 of 4 diets: a) high-saturated fatty acid (HSFA), b) high-monounsaturated fatty acid (HMUFA), c) low-fat, high-complex carbohydrate diets supplemented with placebo (LFHCC) and d) low-fat, high-complex carbohydrate diets supplemented with long chain (LC) n-3 polyunsaturated fatty acids (PUFA) (LFHCC n-3). We analyzed the changes induced in the proteome of both nuclear and cytoplasmic fractions of PBMC using 2-D proteomic analysis. Sixty-seven proteins were differentially expressed after the long-term consumption of the four diets. The HSFA diet induced the expression of proteins responding to oxidative stress, degradation of ubiquitinated proteins and DNA repair. However, HMUFA, LFHCC and LFHCC n-3 diets down-regulated pro-inflammatory and oxidative stress-related proteins and DNA repairing proteins.

Conclusion

The long-term consumption of HSFA, compared to HMUFA, LFHCC and LFHCC n-3, seems to increase the cardiovascular disease (CVD) risk factors associated with metabolic syndrome, such as inflammation and oxidative stress, and seem lead to DNA damage as a consequence of high oxidative stress.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1725-8) contains supplementary material, which is available to authorized users.

[Rosuvastatin improves insulin sensitivity in overweight rats induced by high fat diet. Role of SIRT1 in adipose tissue]

OBJECTIVE

To study the effects of rosuvastatin on insulin resistance in overweight rats induced by high fat diet, as well as potential mediators.

METHODS

We used male Wistar rats fed with a standard diet (CT) or high fat diet (33.5% fat) (HFD); half of the animals HFD were treated with rosuvastatin (15mg/kg/day) (HFD+Rosu) for 7 weeks.

RESULTS

HFD rats showed increased body, epididymal and lumbar adipose tissue weights. Treatment with Rosu did not modify body weight or the weight of the adipose packages in HFD rat. Plasma glucose and insulin levels and HOMA index were higher in HFD rats, and rosuvastatin treatment reduced them. Leptin/adiponectin ratio in plasma and lumbar adipose tissue were higher in HDF rats, and were reduced by rosuvastatin. SIRT-1, PPAR-γ and GLUT-4 protein expression in lumbar adipose tissue were lower in HFD rats and Rosu normalized expression of the three mediators.

CONCLUSIONS

Rosuvastatin ameliorates insulin sensitivity induced by HFD in rats. This effect is mediated by several mechanisms including reduction of leptin and enhancement of SIRT-1, PPAR-γ and GLUT-4 expression in white adipose tissue. SIRT1 could be considered a major mediator of the beneficial effects of rosuvastatin on insulin sensitivity in overweight rats induced by diet.

Dietary fat modifies lipid metabolism in the adipose tissue of metabolic syndrome patients

Adipose tissue (AT) is a key organ in the regulation of total body lipid homeostasis, which is responsible for the storage and release of fatty acids according to metabolic needs. We aimed to investigate the effect of the quantity and quality of dietary fat on the lipogenesis and lipolysis processes in the AT of metabolic syndrome (MetS) patients. A randomized, controlled trial conducted within the LIPGENE study assigned MetS patients to one of four diets: (a) high-saturated fatty acid (HSFA) (b) high-monounsaturated fatty acid, and (c, d) two low-fat, high-complex carbohydrate diets supplemented with long chain (LC) n-3 (LFHCC n-3) polyunsaturated fatty acids (PUFA) or placebo (LFHCC), for 12 weeks each. A fat challenge reflecting the same fatty acid composition as the original diets was conducted post-intervention. Long-term consumption of the LFHCC diet induced an increase in the fasting expression levels of the sterol regulatory element binding protein-1 and stearoyl-CoA desaturase D9-desaturase genes, whereas the supplementation of this diet with n-3 PUFA reversed this effect (p = 0.007). In contrast, long-term consumption of the HSFA diet increased the expression of the adipose triglyceride lipase (ATGL) gene, at both fasting and postprandial states (both, p < 0.001). Our results showed the anti-lipogenic effect exerted by LC n-3 PUFA when administered together with a LFHCC diet. Conversely, a diet high in saturated fat increased the expression of the lipolytic gene ATGL relative to the other diets.

A gene variation (rs12691) in the CCAT/enhancer binding protein α modulates glucose metabolism in metabolic syndrome

BACKGROUND AND AIMS

CCAAT/enhancer-binding protein alpha (CEBPA) is a transcription factor involved in adipogenesis and energy homeostasis. Caloric restriction reduces CEBPA protein expression in patients with metabolic syndrome (MetS). A previous report linked rs12691 SNP in CEBPA to altered concentration of fasting triglycerides. Our objective was to assess the effects of rs12691 in glucose metabolism in Metabolic Syndrome (MetS) patients.

METHODS AND RESULTS

Glucose metabolism was assessed by static (glucose, insulin, adiponectin, leptin and resistin plasma concentrations) and dynamic (disposition index, insulin sensitivity index, HOMA-IR and acute insulin response to glucose) indices, performed at baseline and after 12 weeks of 4 dietary interventions (high saturated fatty acid (SFA), high monounsaturated fatty acid (MUFA), low-fat and low-fat-high-n3 polyunsaturated fatty acid (PUFA)) in 486 subjects with MetS. Carriers of the minor A allele of rs12691 had altered disposition index (p = 0.0003), lower acute insulin response (p = 0.005) and a lower insulin sensitivity index (p = 0.025) indicating a lower insulin sensitivity and a lower insulin secretion, at baseline and at the end of the diets. Furthermore, A allele carriers displayed lower HDL concentration.

CONCLUSION

The presence of the A allele of rs12691 influences glucose metabolism of MetS patients.

Gene-nutrient interactions on the phosphoenolpyruvate carboxykinase influence insulin sensitivity in metabolic syndrome subjects

BACKGROUND & AIMS

Genetic background may interact with habitual dietary fat composition, and affect development of the metabolic syndrome (MetS). The phosphoenolpyruvate carboxykinase gene (PCK1) plays a significant role regulating glucose metabolism, and fatty acids are key metabolic regulators, which interact with transcription factors and influence glucose metabolism. We explored genetic variability at the PCK1 gene locus in relation to degree of insulin resistance and plasma fatty acid levels in MetS subjects. Moreover, we analyzed the PCK1 gene expression in the adipose tissue of a subgroup of MetS subjects according to the PCK1 genetic variants.

METHODS

Insulin sensitivity, insulin secretion, glucose effectiveness, plasma concentrations of C-peptide, fatty acid composition and three PCK1 tag-single nucleotide polymorphisms (SNPs) were determined in 443 MetS participants in the LIPGENE cohort.

RESULTS

The rs2179706 SNP interacted with plasma concentration of n - 3 polyunsaturated fatty acids (n - 3 PUFA), which were significantly associated with plasma concentrations of fasting insulin, peptide C, and HOMA-IR. Among subjects with n - 3 PUFA levels above the population median, carriers of the C/C genotype exhibited lower plasma concentrations of fasting insulin (P = 0.036) and HOMA-IR (P = 0.019) as compared with C/C carriers with n - 3 PUFA below the median. Moreover, homozygous C/C subjects with n - 3 PUFA levels above the median showed lower plasma concentrations of peptide C as compared to individuals with the T-allele (P = 0.006). Subjects carrying the T-allele showed a lower gene PCK1 expression as compared with carriers of the C/C genotype (P = 0.015).

CONCLUSIONS

The PCK1 rs2179706 polymorphism interacts with plasma concentration of n - 3 PUFA levels modulating insulin resistance in MetS subjects.

Insulin receptor substrate-2 gene variants in subjects with metabolic syndrome: association with plasma monounsaturated and n-3 polyunsaturated fatty acid levels and insulin resistance

SCOPE

Several insulin receptor substrate-2 (IRS-2) polymorphisms have been studied in relation to insulin resistance and type 2 diabetes. To examine whether the genetic variability at the IRS-2 gene locus was associated with the degree of insulin resistance and plasma fatty acid levels in metabolic syndrome (MetS) subjects.

METHODS AND RESULTS

Insulin sensitivity, insulin secretion, glucose effectiveness, plasma fatty acid composition and three IRS-2 tag-single nucleotide polymorphisms (SNPs) were determined in 452 MetS subjects. Among subjects with the lowest level of monounsaturated (MUFA) (below the median), the rs2289046 A/A genotype was associated with lower glucose effectiveness (p<0.038), higher fasting insulin concentrations (p<0.028) and higher HOMA IR (p<0.038) as compared to subjects carrying the minor G-allele (A/G and G/G). In contrast, among subjects with the highest level of MUFA (above the median), the A/A genotype was associated with lower fasting insulin concentrations and HOMA-IR, whereas individuals carrying the G allele and with the highest level of ω-3 polyunsaturated fatty acids (above the median) showed lower fasting insulin (p<0.01) and HOMA-IR (p<0.02) as compared with A/A subjects.

CONCLUSION

The rs2289046 polymorphism at the IRS2 gene locus may influence insulin sensitivity by interacting with certain plasma fatty acids in MetS subjects.

Insulin receptor substrate 1 gene variation modifies insulin resistance response to weight-loss diets in a 2-year randomized trial: the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial

BACKGROUND

Common genetic variants in the insulin receptor substrate 1 (IRS1) gene have been recently associated with insulin resistance and hyperinsulinemia. We examined whether the best-associated variant modifies the long-term changes in insulin resistance and body weight in response to weight-loss diets in Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial.

METHODS AND RESULTS

We genotyped IRS1 rs2943641 in 738 overweight adults (61% were women) who were randomly assigned to 1 of 4 diets varying in macronutrient contents for 2 years. We assessed the progress in fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and weight loss by genotypes. At 6 months, participants with the risk-conferring CC genotype had greater decreases in insulin (P=0.009), HOMA-IR (P=0.015), and weight loss (P=0.018) than those without this genotype in the highest-carbohydrate diet group whereas an opposite genotype effect on changes in insulin and HOMA-IR (P≤0.05) was observed in participants assigned to the lowest-carbohydrate diet group. No significant differences were observed across genotypes in the other 2 diet groups. The tests for genotype by intervention interactions were all significant (P<0.05). At 2 years, the genotype effect on changes in insulin and HOMA-IR remained significant in the highest-carbohydrate diet group (P<0.05). The highest carbohydrate diet led to a greater improvement of insulin and HOMA-IR (P for genotype-time interaction ≤0.009) in participants with the CC genotype than those without this genotype across 2-year intervention.

CONCLUSIONS

Individuals with the IRS1 rs2943641 CC genotype might obtain more benefits in weight loss and improvement of insulin resistance than those without this genotype by choosing a high-carbohydrate and low-fat diet.

CLINICAL TRIAL REGISTRATION

http:www.clinicaltrials.gov. Unique identifier: NCT00072995.

Glucokinase regulatory protein genetic variant interacts with omega-3 PUFA to influence insulin resistance and inflammation in metabolic syndrome

Glucokinase Regulatory Protein (GCKR) plays a central role regulating both hepatic triglyceride and glucose metabolism. Fatty acids are key metabolic regulators, which interact with genetic factors and influence glucose metabolism and other metabolic traits. Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been of considerable interest, due to their potential to reduce metabolic syndrome (MetS) risk.

Objective

To examine whether genetic variability at the GCKR gene locus was associated with the degree of insulin resistance, plasma concentrations of C-reactive protein (CRP) and n-3 PUFA in MetS subjects.

Design

Homeostasis model assessment of insulin resistance (HOMA-IR), HOMA-B, plasma concentrations of C-peptide, CRP, fatty acid composition and the GCKR rs1260326-P446L polymorphism, were determined in a cross-sectional analysis of 379 subjects with MetS participating in the LIPGENE dietary cohort.

Results

Among subjects with n-3 PUFA levels below the population median, carriers of the common C/C genotype had higher plasma concentrations of fasting insulin (P = 0.019), C-peptide (P = 0.004), HOMA-IR (P = 0.008) and CRP (P = 0.032) as compared with subjects carrying the minor T-allele (Leu446). In contrast, homozygous C/C carriers with n-3 PUFA levels above the median showed lower plasma concentrations of fasting insulin, peptide C, HOMA-IR and CRP, as compared with individuals with the T-allele.

Conclusions

We have demonstrated a significant interaction between the GCKR rs1260326-P446L polymorphism and plasma n-3 PUFA levels modulating insulin resistance and inflammatory markers in MetS subjects. Further studies are needed to confirm this gene-diet interaction in the general population and whether targeted dietary recommendations can prevent MetS in genetically susceptible individuals.

Trial Registration

ClinicalTrials.gov NCT00429195

Calpain-10 interacts with plasma saturated fatty acid concentrations to influence insulin resistance in individuals with the metabolic syndrome

BACKGROUND

Calpain-10 protein (intracellular Ca(2+)-dependent cysteine protease) may play a role in glucose metabolism, pancreatic β cell function, and regulation of thermogenesis. Several CAPN10 polymorphic sites have been studied for their potential use as risk markers for type 2 diabetes and the metabolic syndrome (MetS). Fatty acids are key metabolic regulators that may interact with genetic factors and influence glucose metabolism.

OBJECTIVE

The objective was to examine whether the genetic variability at the CAPN10 gene locus is associated with the degree of insulin resistance and plasma fatty acid concentrations in subjects with MetS.

DESIGN

The insulin sensitivity index, glucose effectiveness, insulin resistance [homeostasis model assessment of insulin resistance (HOMA-IR)], insulin secretion (disposition index, acute insulin response, and HOMA of β cell function), plasma fatty acid composition, and 5 CAPN10 single nucleotide polymorphisms (SNPs) were determined in a cross-sectional analysis of 452 subjects with MetS participating in the LIPGENE dietary intervention cohort.

RESULTS

The rs2953171 SNP interacted with plasma total saturated fatty acid (SFA) concentrations, which were significantly associated with insulin sensitivity (P < 0.031 for fasting insulin, P < 0.028 for HOMA-IR, and P < 0.012 for glucose effectiveness). The G/G genotype was associated with lower fasting insulin concentrations, lower HOMA-IR, and higher glucose effectiveness in subjects with low SFA concentrations (below the median) than in subjects with the minor A allele (G/A and A/A). In contrast, subjects with the G/G allele with the highest SFA concentrations (above the median) had higher fasting insulin and HOMA-IR values and lower glucose effectiveness than did subjects with the A allele.

CONCLUSION

The rs2953171 polymorphism at the CAPN10 gene locus may influence insulin sensitivity by interacting with the plasma fatty acid composition in subjects with MetS. This trial was registered at clinicaltrials.gov as NCT00429195.

Macronutrients and insulin resistance in cholesterol gallstone disease

Cholelithiasis is a major source of digestive morbidity worldwide. Cholesterol stones account for the majority of gallstones in the United States and other Western countries. The pathogenesis of cholesterol gallstone disease is multifactorial with key factors including cholesterol supersaturation of bile, altered biliary motility, and nucleation and growth of cholesterol crystals. Increasing evidence suggests that many, but not all, causative factors of cholesterol gallstones are related to insulin resistance which, in association with obesity, has reached an epidemic level worldwide. Experimental studies show that hyperinsulinemia, a key feature of insulin resistance, may cause increased hepatic cholesterol secretion and cholesterol supersaturation of bile and gallbladder dysmotility, and thereby may enhance gallstone formation. Insulin resistance syndrome can be modified by environmental factors, including dietary factors. The impact of diet on insulin sensitivity is mediated by both dietary composition and its energy content. The contribution of specific dietary elements to the prevalence and incidence of cholesterol gallstone disease has been explored in animal and human studies. There is considerable evidence to suggest that different types of fatty acids, independent of the total amount of fat consumption, affect insulin sensitivity and cholesterol gallstone disease differently. The effects of salt intake, consumption of protein and carbohydrates, and alcohol drinking on insulin resistance are controversial. Additional intervention trials and controlled experimental feeding studies are needed to further clarify these relationships and to provide useful prophylactic and therapeutic strategies.

Adrenocortical dysregulation as a major player in insulin resistance and onset of obesity

The aim of this review is to explore the dysregulation of adrenocortical secretions as a major contributor in the development of obesity and insulin resistance. Disturbance of adipose tissue physiology is one of the primary events in the development of pathologies associated with the metabolic syndrome, such as obesity and type 2 diabetes. Several studies indicate that alterations in metabolism of glucocorticoids (GC) and androgens, as well as aldosterone in excess, are involved in the emergence of metabolic syndrome. Cross talk among adipose tissue, the hypothalamo-pituitary complex, and adrenal gland activity plays a major role in the control of food intake, glucose metabolism, lipid storage, and energy balance. Perturbation of this cross talk induces alterations in the regulatory mechanisms of adrenocortical steroid synthesis, secretion, degradation, and/or recycling, at the level of the zonae glomerulosa (aldosterone), fasciculata (GC and GC metabolites), and reticularis (androgens and androgen precursors DHEA and DHEAS). As a whole, these adrenocortical perturbations contribute to the development of metabolic syndrome at both the paracrine and systemic level by favoring the physiological dysregulation of organs responsive to aldosterone, GC, and/or androgens, including adipose tissue.