High-fat diets rich in medium- versus long-chain fatty acids induce distinct patterns of tissue specific insulin resistance

A Medium Chain Fatty Acid, 6-hydroxyhexanoic acid (6-HHA), Protects Against Obesity and Insulin Resistance

Obesity, a worldwide health problem, increases the risk for developing metabolic diseases such as insulin resistance and diabetes. It is well recognized that obesity-associated chronic inflammation plays a key role in the pathogenesis of systemic metabolic dysfunction. Previously, we revealed an anti-inflammatory role for spent culture supernatants isolated from the oral commensal bacterial species Streptococcus gordonii (Sg-SCS). Here, we identified that 6-hydroxyhexanoic acid (6-HHA), a medium chain fatty acid (MCFA), is the one of the key components of Sg-SCS . We found that treatment of 6-HHA in mice fed a high-fat diet (HFD) significantly reduced HFD-mediated weight gain which was largely attributed to a decrease in fat mass. Systemically, 6-HHA improves obesity-associated glucose intolerance and insulin resistance. Furthermore, administration of 6-HHA suppressed obesity-associated systemic inflammation and dyslipidemia. At the cellular level, treatment of 6-HHA ameliorated aberrant inflammatory and metabolic transcriptomic signatures in white adipose tissue of mice with diet-induced obesity (HFD). Mechanistically, we found that 6-HHA suppressed adipocyte-proinflammatory cytokine production and lipolysis, the latter through Gαi-mediated signaling. This work provides direct evidence for the anti-obesity effects of a novel MCFA, which could be a new therapeutic treatment for combating obesity.

KEY POINTS

Hydroxyhexanoic medium chain fatty acids (MCFAs) are dietary and bacterial-derived energy sources, however, the outcomes of using MCFAs in treating metabolic disorders are diverse and complex. The MCFA 6-hydroxyhexanoic acid (6-HHA) is a metabolite secreted by the oral bacterial commensal species Streptococcus gordonii; here we investigated its role in modulating high-fat diet (HFD)-induced metabolic dysfunction. In a murine model of obesity, we found 6-HHA-mediated improvement of diet-mediated adiposity, insulin resistance and inflammation were in part due to actions on white adipose tissue (WAT).6-HHA suppressed proinflammatory cytokine production and lipolysis through Gi-mediated signaling in differentiated white adipocytes.

Dietary Long-Chain Fatty Acids Accelerate Metabolic Dysfunction in Guinea Pigs with Non-Alcoholic Steatohepatitis

The composition of dietary fatty acids may be important for the development and progression of metabolic syndrome and non-alcoholic steatohepatitis (NASH). This study investigated the effect of two high-fat diets based on coconut oil, containing predominantly medium-chain fatty acids (MCFA), or cocoa butter, containing mainly long-chain fatty acids (LCFA), on glucose homeostasis and NASH in guinea pigs following 16 and 32 weeks of diet. At week 16, glucose intolerance was increased in the LCFA animals compared to the MCFA animals (p < 0.001), with both groups differing from the controls by week 32 (p < 0.0001), supported by increased hemoglobin A1c (p < 0.05). NASH was present in both high-fat groups from week 16, with advancing fibrosis appearing more progressive in the LCFA animals at week 16. In agreement, gene expression showed overall increased expression of NASH target genes in the LCFA animals compared to the MCFA animals at weeks 16 and 32 (p < 0.05 and p < 0.0001, respectively). The LCFA animals also displayed increased plasma uric acid at both time points (p < 0.05), a phenomenon linked to NASH in humans. In conclusion, this study reports that a diet high in LCFA promotes metabolic imbalance and may accelerate NASH-associated hepatic fibrosis. This highlights the importance of a critical evaluation of fatty acid composition when investigating NASH-associated endpoints.

Blood Glucose Response of a Low-Carbohydrate Oral Nutritional Supplement with Isomaltulose and Soluble Dietary Fiber in Individuals with Prediabetes: A Randomized, Single-Blind Crossover Trial

A high-energy-type oral dietary supplement (ONS), with a low proportion of available carbohydrate (LC-ONS), which contains a slowly digestible carbohydrate, isomaltulose, and is fortified with soluble dietary fiber, was newly developed for individuals with diabetes or prediabetes. This study aimed to evaluate the impact of LC-ONS on blood glucose levels after ingestion in individuals with prediabetes. A single-blind, randomized crossover clinical trial was performed on 20 individuals with prediabetes. After overnight fasting, all subjects ingested one serving (200 kcal/125 mL) of either LC-ONS (40% energy proportion of available carbohydrates) or standard ONS (ST-ONS, 54% energy proportion of available carbohydrates) on two separate days. The incremental area under the curve of blood glucose levels for 120 min was significantly lower after LC-ONS ingestion compared to ST-ONS (2207 ± 391 mg/dL·min (least mean square value ± standard error) and 3735 ± 391 mg/dL·min, respectively; p < 0.001). The LC-ONS showed significantly lower blood glucose levels than the ST-ONS at all time points, except at baseline. Similarly, the incremental area under the curve of plasma insulin was significantly lower after LC-ONS ingestion. These results suggest that LC-ONS is useful as an ONS for energy supply in individuals with postprandial hyperglycemia.

Macronutrient Determinants of Obesity, Insulin Resistance and Metabolic Health

Obesity caused by the overconsumption of calories has increased to epidemic proportions. Insulin resistance is often associated with an increased adiposity and is a precipitating factor in the development of cardiovascular disease, type 2 diabetes, and altered metabolic health. Of the various factors contributing to metabolic impairments, nutrition is the major modifiable factor that can be targeted to counter the rising prevalence of obesity and metabolic diseases. However, the macronutrient composition of a nutritionally balanced "healthy diet" are unclear, and so far, no tested dietary intervention has been successful in achieving long-term compliance and reductions in body weight and associated beneficial health outcomes. In the current review, we briefly describe the role of the three major macronutrients, carbohydrates, fats, and proteins, and their role in metabolic health, and provide mechanistic insights. We also discuss how an integrated multi-dimensional approach to nutritional science could help in reconciling apparently conflicting findings.

Mitochondrial dynamics in skeletal muscle insulin resistance and type 2 diabetes

The traditional view of mitochondria as isolated, spherical, energy producing organelles, is undergoing a revolutionary change. Emerging data show that mitochondria form a dynamic reticulum that is regulated by cycles of fission and fusion. The discovery of proteins that modulate these activities has led to important advances in understanding human disease. Here, we review the latest evidence that connects the emerging field of mitochondrial dynamics to skeletal muscle insulin resistance and propose some potential mechanisms that may explain the long debated link between mitochondria and the development of type 2 diabetes.

Hexanoic, Octanoic and Decanoic Acids Promote Basal and Insulin-Induced Phosphorylation of the Akt-mTOR Axis and a Balanced Lipid Metabolism in the HepG2 Hepatoma Cell Line

Metabolic illnesses such as non-alcoholic fatty liver disease (NAFLD) are in constant increase worldwide. Highly consumed long chain fatty acids (LCFA) are among the most obesogenic and steatogenic nutrients. Hepatic steatosis is associated with several complications such as insulin resistance. Growing evidence points to medium chain fatty acids (MCFA), more efficiently oxidized than LCFA, as a promising dietary alternative against NAFLD. However, reports on the hepatic effects of MCFA are sometimes conflicting. In this study we exposed HepG2 cells, a human hepatocellular model, to 0.25 mM of hexanoic (C6), or octanoic (C8), and decanoic (C10) acids separately or in a C8 + C10 equimolar mix reflecting commercially available MCFA-rich oils. We found that C6, a poorly studied MCFA, as well as C8 and C10 did not provoke the deleterious lipid anabolism runaway typically induced by LCFA palmitate. MCFA tended, instead, to promote a balanced metabolic profile and were generally non-cytotoxic. Accordingly, mitochondrial integrity was mostly preserved following MCFA treatment. However, treatments with C8 induced a mitochondrial membrane potential decrease, suggesting prolonged exposure to this lipid could be problematic. Finally, MCFA treatments maintained optimal insulin sensitivity and even fostered basal and insulin-dependent phosphorylation of the Akt-mTOR pathway. Overall, MCFA could constitute an effective nutritional tool to manage liver steatosis and hepatic insulin resistance.

Modeling insulin resistance in rodents by alterations in diet: what have high-fat and high-calorie diets revealed?

For over half a century, researchers have been feeding different diets to rodents to examine the effects of macronutrients on whole body and tissue insulin action. During this period, the number of different diets and the source of macronutrients employed have grown dramatically. Because of the large heterogeneity in both the source and percentage of different macronutrients used for studies, it is not surprising that different high-calorie diets do not produce the same changes in insulin action. Despite this, diverse high-calorie diets continue to be employed in an attempt to generate a "generic" insulin resistance. The high-fat diet in particular varies greatly between studies with regard to the source, complexity, and ratio of dietary fat, carbohydrate, and protein. This review examines the range of rodent dietary models and methods for assessing insulin action. In almost all studies reviewed, rodents fed diets that had more than 45% of dietary energy as fat or simple carbohydrates had reduced whole body insulin action compared with chow. However, different high-calorie diets produced significantly different effects in liver, muscle, and whole body insulin action when insulin action was measured by the hyperinsulinemic-euglycemic clamp method. Rodent dietary models remain an important tool for exploring potential mechanisms of insulin resistance, but more attention needs to be given to the total macronutrient content and composition when interpreting dietary effects on insulin action.

High fat diet attenuates hyperglycemia, body composition changes, and bone loss in male streptozotocin-induced type 1 diabetic mice

There is a growing and alarming prevalence of obesity and the metabolic syndrome in type I diabetic patients (T1DM), particularly in adolescence. In general, low bone mass, higher fracture risk, and increased marrow adipose tissue (MAT) are features of diabetic osteopathy in insulin-deficient subjects. On the other hand, type 2 diabetes (T2DM) is associated with normal or high bone mass, a greater risk of peripheral fractures, and no change in MAT. Therefore, we sought to determine the effect of weight gain on bone turnover in insulin-deficient mice. We evaluated the impact of a 6-week high-fat (HFD) rich in medium chain fatty acids or low-fat diet (LFD) on bone mass and MAT in a streptozotocin (STZ)-induced model using male C57BL/6J mice at 8 weeks of age. Dietary intervention was initiated after diabetes confirmation. At the endpoint, lower non-fasting glucose levels were observed in diabetic mice fed with high fat diet compared to diabetic mice fed the low fat diet (STZ-LFD). Compared to euglycemic controls, the STZ-LFD had marked polydipsia and polyphagia, as well as reduced lean mass, fat mass, and bone parameters. Interestingly, STZ-HFD mice had higher bone mass, namely less cortical bone loss and more trabecular bone than STZ-LFD. Thus, we found that a HFD, rich in medium chain fatty acids, protects against bone loss in a T1DM mouse model. Whether this may also translate to T1DM patients who are overweight or obese in respect to maintenance of bone mass remains to be determined through longitudinal studies.

Effect of GPR84 deletion on obesity and diabetes development in mice fed long chain or medium chain fatty acid rich diets

PURPOSE

Although there is good evidence showing that diets rich in medium chain fatty acids (MCFAs) have less marked obesogenic and diabetogenic effects than diets rich in long chain fatty acids (LCFAs), the role of the pro-inflammatory, medium chain fatty acid receptor (GPR84) in the aetiology of obesity and glucose intolerance is not well characterised. We set out to determine whether GPR84 expression influences obesity and glucose intolerance susceptibility in MCFA and LCFA rich diet fed mice.

METHODS

Wild type (WT) and GPR84 knockout (KO) mice were fed a control, MCFA or LCFA diet, and body mass, heart, liver and epididymal fat mass was assessed, as well as glucose tolerance and adipocyte size.

RESULTS

LCFA diets increased body mass and decreased glucose tolerance in both WT and GPR84 KO animals while MCFA diets had no effect on these parameters. There were no differences in body weight when comparing WT and GPR84 KO mice on the respective diets. Glucose tolerance was also similar in WT and GPR84 KO mice irrespective of diet. Liver mass was increased following LCFA feeding in WT but not GPR84 KO mice. Hepatic triglyceride content was increased in GPR84 KO animals fed MCFA, and myocardial triglyceride content was increased in GPR84 KO animals fed LCFA.

CONCLUSIONS

GPR84 deletion had no effects on body weight or glucose tolerance in mice fed either a high MCFA or LCFA diet. GPR84 may influence lipid metabolism, as GPR84 KO mice had smaller livers and increased myocardial triglyceride accumulation when fed LCFA diets, and increased liver triglyceride accumulation in responses to increased dietary MCFAs.

Modification of the fatty acid composition of an obesogenic diet improves the maternal and placental metabolic environment in obese pregnant mice

Peri-conceptional exposure to maternal obesogenic nutrition is associated with in utero programming of later-life overweight and metabolic disease in the offspring. We aimed to investigate whether dietary intervention with a modified fatty acid quality in an obesogenic high-calorie (HC) diet during the preconception and gestational phases can improve unfavourable effects of an adipogenic maternal environment. In NMRI mice, peri-conceptional and gestational obesity was induced by feeding a HC diet (controls), and they were compared with dams on a fat-modified (Fat-mod) HC diet of the same energy content but enriched with medium-chain fatty acids (MCFAs) and adjusted to a decreased ratio of n-6 to n-3 long-chain polyunsaturated fatty acids (LC-PUFAs). Effects on maternal and placental outcomes at delivery (day 17.5 post coitum) were investigated. Despite comparable energy assimilation between the two groups of dams, the altered fatty acid composition of the Fat-mod HC diet induced lower maternal body weight, weights of fat depots, adipocyte size, and hepatic fat accumulation compared to the unmodified HC diet group. Further, there was a trend towards lower fasting glucose, insulin and leptin concentrations in dams fed the Fat-mod HC diet. Phenotypic changes were accompanied by inhibition of transcript and protein expression of genes involved in hepatic de novo lipogenesis comprising PPARG2 and its target genes Fasn, Acaca, and Fabp4, whereas regulation of other lipogenic factors (Srebf1, Nr1h3, Abca1) appeared to be more complex. The modified diet led to a sex-specific placental response by upregulating PPARG-dependent fatty acid transport gene expression in female versus male placentae. Qualitative modification of the fatty acid spectrum of a high-energy maternal diet, using a combination of both MCFAs and n-3 LC-PUFAs, seems to be a promising interventional approach to ameliorate the adipogenic milieu of mice before and during gestation.

A rich medium-chain triacylglycerol diet benefits adiposity but has adverse effects on the markers of hepatic lipogenesis and beta-oxidation

We investigated the increasing amounts of medium-chain triacylglycerol (MCT) in the diet on hepatic lipid metabolism.

Lauric acid-rich medium-chain triglycerides can substitute for other oils in cooking applications and may have limited pathogenicity

Recently, medium-chain triglycerides (MCTs) containing a large fraction of lauric acid (LA) (C12)-about 30%-have been introduced commercially for use in salad oils and in cooking applications. As compared to the long-chain fatty acids found in other cooking oils, the medium-chain fats in MCTs are far less likely to be stored in adipose tissue, do not give rise to 'ectopic fat' metabolites that promote insulin resistance and inflammation, and may be less likely to activate macrophages. When ingested, medium-chain fatty acids are rapidly oxidised in hepatic mitochondria; the resulting glut of acetyl-coenzyme A drives ketone body production and also provokes a thermogenic response. Hence, studies in animals and humans indicate that MCT ingestion is less obesogenic than comparable intakes of longer chain oils. Although LA tends to raise serum cholesterol, it has a more substantial impact on high density lipoprotein (HDL) than low density lipoprotein (LDL) in this regard, such that the ratio of total cholesterol to HDL cholesterol decreases. LA constitutes about 50% of the fatty acid content of coconut oil; south Asian and Oceanic societies which use coconut oil as their primary source of dietary fat tend to be at low cardiovascular risk. Since ketone bodies can exert neuroprotective effects, the moderate ketosis induced by regular MCT ingestion may have neuroprotective potential. As compared to traditional MCTs featuring C6-C10, laurate-rich MCTs are more feasible for use in moderate-temperature frying and tend to produce a lower but more sustained pattern of blood ketone elevation owing to the more gradual hepatic oxidation of ingested laurate.

Effects of low-stearate palm oil and high-stearate lard high-fat diets on rat liver lipid metabolism and glucose tolerance

Background

Excess consumption of energy-dense, high-fat Western diets contributes to the development of obesity and obesity-related disorders, such as fatty liver disease. However, not only the quantity but also the composition of dietary fat may play a role in the development of liver steatosis. The aim of this study was to determine the effects of low-stearate palm oil and high-stearate lard high-fat diets on in vivo liver lipid metabolism.

Methods

Wistar rats were fed with either normal chow (CON), a high-fat diet based on palm oil (HFP), or a high-fat diet based on lard (HFL). After 10 weeks of diet, magnetic resonance spectroscopy was applied for the in vivo determination of intrahepatocellular lipid content and the uptake and turnover of dietary fat after oral administration of ¹³C-labeled lipids. Derangements in liver lipid metabolism were further assessed by measuring hepatic very-low density lipoprotein (VLDL) secretion and ex vivo respiratory capacity of liver mitochondria using fat-derived substrates. In addition, whole-body and hepatic glucose tolerance were determined with an intraperitoneal glucose tolerance test.

Results

Both high-fat diets induced liver lipid accumulation (p < 0.001), which was accompanied by a delayed uptake and/or slower turnover of dietary fat in the liver (p < 0.01), but without any change in VLDL secretion rates. Surprisingly, liver lipid content was higher in HFP than in HFL (p < 0.05), despite the increased fatty acid oxidative capacity in isolated liver mitochondria of HFP animals (p < 0.05). In contrast, while both high-fat diets induced whole-body glucose intolerance, only HFL impaired hepatic glucose tolerance.

Conclusion

High-fat diets based on palm oil and lard similarly impair the handling of dietary lipids in the liver, but only the high-fat lard diet induces hepatic glucose intolerance.

Mitochondrial dysfunction as a central event for mechanisms underlying insulin resistance: the roles of long chain fatty acids

Insulin resistance is characterized by hyperglycaemia, dyslipidaemia and oxidative stress prior to the development of type 2 diabetes mellitus. To date, a number of mechanisms have been proposed to link these syndromes together, but it remains unclear what the unifying condition that triggered these events in the progression of this metabolic disease. There have been a steady accumulation of data in numerous experimental studies showing the strong correlations between mitochondrial dysfunction, oxidative stress and insulin resistance. In addition, a growing number of studies suggest that the raised plasma free fatty acid level induced insulin resistance with the significant alteration of oxidative metabolism in various target tissues such as skeletal muscle, liver and adipose tissue. In this review, we herein propose the idea of long chain fatty acid-induced mitochondrial dysfunctions as one of the key events in the pathophysiological development of insulin resistance and type 2 diabetes. The accumulation of reactive oxygen species, lipotoxicity, inflammation-induced endoplasmic reticulum stress and alterations of mitochondrial gene subset expressions are the most detrimental that lead to the developments of aberrant intracellular insulin signalling activity in a number of peripheral tissues, thereby leading to insulin resistance and type 2 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.

Changes in food intake, metabolic parameters and insulin resistance are induced by an isoenergetic, medium-chain fatty acid diet and are associated with modifications in insulin signalling in isolated rat pancreatic islets

Long-chain fatty acids are capable of inducing alterations in the homoeostasis of glucose-stimulated insulin secretion (GSIS), but the effect of medium-chain fatty acids (MCFA) is poorly elucidated. In the present study, we fed a normoenergetic MCFA diet to male rats from the age of 1 month to the age of 4 months in order to analyse the effect of MCFA on body growth, insulin sensitivity and GSIS. The 45% MCFA substitution of whole fatty acids in the normoenergetic diet impaired whole body growth and resulted in increased body adiposity and hyperinsulinaemia, and reduced insulin-mediated glucose uptake in skeletal muscle. In addition, the isolated pancreatic islets from the MCFA-fed rats showed impaired GSIS and reduced protein kinase Ba (AKT1) protein expression and extracellular signal-related kinase isoforms 1 and 2 (ERK(1/2)) phosphorylation, which were accompanied by increased cellular death. Furthermore, there was a mildly increased cholinergic sensitivity to GSIS. We discuss these findings in further detail, and advocate that they might have a role in the mechanistic pathway leading to the compensatory hyperinsulinaemic status found in this animal model.

Differential development of glucose intolerance and pancreatic islet adaptation in multiple diet induced obesity models

Background: The C57BL/6 mouse fed a high fat diet is a common and valuable model in experimental studies of obesity and type 2 diabetes (T2D). Different high fat diets are used and in order to determine which diet produces a model most accurately resembling human T2D, they need to be compared head-to-head. Methods: Four different diets, the 60% high fat diet (HFD) and the 58% high fat-high sucrose Surwit diet (HFHS) and their respective controls, were compared in C57BL/6J mice using glucose tolerance tests (IVGTT) and the euglycemic clamp. Results: Mice fed a HFD gained more weight than HFHS fed mice despite having similar energy intake. Both high fat diet models were glucose intolerant after eight weeks. Mice fed the HFD had elevated basal insulin, which was not seen in the HFHS group. The acute insulin response (AIR) was unchanged in the HFD group, but slightly increased in the HFHS diet group. The HFHS diet group had a threefold greater total insulin secretion during the IVGTT compared to its control, while no differences were seen in the HFD group. Insulin sensitivity was decreased fourfold in the HFD group, but not in the HFHS diet group. Conclusion: The HFD and HFHS diet models show differential effects on the development of insulin resistance and beta cell adaptation. These discrepancies are important to acknowledge in order to select the appropriate diet for specific studies.

Long- and medium-chain fatty acids induce insulin resistance to a similar extent in humans despite marked differences in muscle fat accumulation

CONTEXT

Animal studies revealed that medium-chain fatty acids (MCFA), due to their metabolic characteristics, are not stored in skeletal muscle and may therefore not give rise to potentially hazardous lipid species impeding insulin signaling.

OBJECTIVE

We here hypothesized that infusion of medium-chain triacylglycerols (MCT) in healthy lean subjects does not lead to ectopic fat accumulation and hence does not result in lipid-induced insulin resistance.

DESIGN AND METHODS

Nine healthy lean male subjects underwent a 6-h hyperinsulinemic-euglycemic clamp with simultaneous infusion of 1) a 100% long-chain triacylglycerols (LCT) emulsion, 2) a 50/50% MCT/LCT emulsion, or 3) glycerol in a randomized crossover design. Muscle biopsies were taken before and after each clamp.

RESULTS

MCT/LCT infusion raised plasma free fatty acid levels to a similar level compared with LCT infusion alone. Despite elevated free fatty acid levels, intramyocellular triacylglycerol (IMTG) levels were not affected by the MCT/LCT emulsion, whereas LCT infusion resulted in an approximately 1.6-fold increase in IMTG. These differences in muscle fat accumulation did not result in significant differences in lipid-induced insulin resistance between LCT (-28%, P = 0.003) and MCT/LCT (-20%, P < 0.001). Total skeletal muscle ceramide content as well as lactosyl- and glucosylceramide levels were not affected by any of the interventions. In addition, the distribution pattern of all ceramide species remained unaltered.

CONCLUSIONS

Although we confirm that MCFA do not lead to ceramide and IMTG accumulation in skeletal muscle tissue in humans, they do induce insulin resistance. These results indicate that, in humans, MCFA may not be beneficial in preventing peripheral insulin resistance.

Treatment of genetically obese mice with the iminosugar N-(5-adamantane-1-yl-methoxy-pentyl)-deoxynojirimycin reduces body weight by decreasing food intake and increasing fat oxidation

Obesity and its associated conditions such as type 2 diabetes mellitus are major causes of morbidity and mortality. The iminosugar N-(5-adamantane-1-yl-methoxy-pentyl)-deoxynojirimycin (AMP-DNM) improves insulin sensitivity in rodent models of insulin resistance and type 2 diabetes mellitus. In the current study, we characterized the impact of AMP-DNM on substrate oxidation patterns, food intake, and body weight gain in obese mice. Eight ob/ob mice treated with 100 mg/(kg d) AMP-DNM mixed in the food and 8 control ob/ob mice were placed in metabolic cages during the first, third, and fifth week of the experiment for measurement of substrate oxidation rates, energy expenditure, activity, and food intake. Mice were killed after 6 weeks of treatment. Initiation of treatment with AMP-DNM resulted in a rapid increase in fat oxidation by 129% (P = .05), a decrease in carbohydrate oxidation by 35% (P = .01), and a reduction in food intake by approximately 26% (P < .01) compared with control mice. Treatment with AMP-DNM decreased hepatic triglyceride content by 66% (P < .01) and, in line with the elevated fat oxidation rates, increased hepatic carnitine palmitoyl transferase 1a expression. Treatment with AMP-DNM increased plasma levels of the appetite-regulating peptide YY compared with control mice. Treatment with AMP-DNM rapidly reduces food intake and increases fat oxidation, resulting in improvement of the obese phenotype. These features of AMP-DNM, together with its insulin-sensitizing capacity, make it an attractive candidate drug for the treatment of obesity and its associated metabolic derangements.