An increase in dietary protein improves the blood glucose response in persons with type 2 diabetes

Association between total, animal, and plant protein intake and type 2 diabetes risk in adults: A systematic review and dose-response meta-analysis of prospective cohort studies

BACKGROUND AND AIMS

While clinical studies indicate that dietary protein may benefit glucose homeostasis in type 2 diabetes (T2D), the impact of dietary protein, including whether the protein is of animal or plant origin, on the risk of T2D is uncertain. We conducted a systematic review and meta-analysis to evaluate the associations of total, animal, and plant protein intakes with the risk of T2D.

METHODS

A systematic search was performed using multiple data sources, including PubMed/Medline, ISI Web of Science, Scopus, and Google Scholar, with the data cut-off in May 2023. Our selection criteria focused on prospective cohort studies that reported risk estimates for the association between protein intake and T2D risk. For data synthesis, we calculated summary relative risks and 95% confidence intervals for the highest versus lowest categories of protein intake using random-effects models. Furthermore, we conducted both linear and non-linear dose-response analyses to assess the dose-response associations between protein intake and T2D risk.

RESULTS

Sixteen prospective cohort studies, involving 615,125 participants and 52,342 T2D cases, were identified, of which eleven studies reported data on intake of both animal and plant protein. Intakes of total (pooled effect size: 1.14, 95% CI: 1.04-1.24) and animal (pooled effect size: 1.18, 95% CI: 1.09-1.27) protein were associated with an increased risk of T2D. These effects were dose-related - each 20-g increase in total or animal protein intake increased the risk of T2D by ∼3% and ∼7%, respectively. In contrast, there was no association between intake of plant protein and T2D risk (pooled effect size: 0.98, 95% CI: 0.89-1.08), while replacing animal with plant protein intake (per each 20 g) was associated with a reduced risk of T2D (pooled effect size: 0.80, 95% CI: 0.76-0.84).

CONCLUSIONS

Our findings indicate that long-term consumption of animal, but not plant, protein is associated with a significant and dose-dependent increase in the risk of T2D, with the implication that replacement of animal with plant protein intake may lower the risk of T2D.

Meeting the global protein supply requirements of a growing and ageing population

Human dietary patterns are a major cause of environmental transformation, with agriculture occupying ~ 50% of global land space, while food production itself is responsible for ~ 30% of all greenhouse gas emissions and 70% of freshwater use. Furthermore, the global population is also growing, such that by 2050, it is estimated to exceed ~ 9 billion. While most of this expansion in population is expected to occur in developing countries, in high-income countries there are also predicted changes in demographics, with major increases in the number of older people. There is a growing consensus that older people have a greater requirement for protein. With a larger and older population, global needs for protein are set to increase. This paper summarises the conclusions from a Rank Prize funded colloquium evaluating novel strategies to meet this increasing global protein need.

Intestinal gluconeogenesis: A translator of nutritional information needed for glycemic and emotional balance

At the interface between the outside world and the self, the intestine is the first organ receiving nutritional information. One intestinal function, gluconeogenesis, is activated by various nutrients, particularly diets enriched in fiber or protein, and thus results in glucose production in the portal vein in the post-absorptive period. The detection of portal glucose induces a nervous signal controlling the activity of the central nuclei involved in the regulation of metabolism and emotional behavior. Induction of intestinal gluconeogenesis is necessary for the beneficial effects of fiber or protein-enriched diets on metabolism and emotional behavior. Through its ability to translate nutritional information from the diet to the brain's regulatory centers, intestinal gluconeogenesis plays an essential role in maintaining physiological balance.

Impacts of dietary animal and plant protein on weight and glycemic control in health, obesity and type 2 diabetes: friend or foe?

It is well established that high-protein diets (i.e. ~25-30% of energy intake from protein) provide benefits for achieving weight loss, and subsequent weight maintenance, in individuals with obesity, and improve glycemic control in type 2 diabetes (T2D). These effects may be attributable to the superior satiating property of protein, at least in part, through stimulation of both gastrointestinal (GI) mechanisms by protein, involving GI hormone release and slowing of gastric emptying, as well as post-absorptive mechanisms facilitated by circulating amino acids. In contrast, there is evidence that the beneficial effects of greater protein intake on body weight and glycemia may only be sustained for 6-12 months. While both suboptimal dietary compliance and metabolic adaptation, as well as substantial limitations in the design of longer-term studies are all likely to contribute to this contradiction, the source of dietary protein (i.e. animal vs. plant) has received inappropriately little attention. This issue has been highlighted by outcomes of recent epidemiological studies indicating that long-term consumption of animal-based protein may have adverse effects in relation to the development of obesity and T2D, while plant-based protein showed either protective or neutral effects. This review examines information relating to the effects of dietary protein on appetite, energy intake and postprandial glycemia, and the relevant GI functions, as reported in acute, intermediate- and long-term studies in humans. We also evaluate knowledge relating to the relevance of the dietary protein source, specifically animal or plant, to the prevention, and management, of obesity and T2D.

Phytochemical analysis and biological evaluation of essential oils and extracts from Heracleum pastinacifolium subsp. incanum (Boiss. & A.Huet) P.H.Davis, an endemic plant from Turkey

Essential oil content of and phenolic compounds flower-fruit, root, and aerial parts of Heracleum pastinacifolium subsp. incanum were analysed by GC/MS and LC/MS methods, respectively. Antidiabetic, anticholinesterase, and antioxidant activities of flower-fruit, root, aerial parts methanol extracts were evaluated. Apiole (35.0%), myristicine (72.2%), and myristicine (15.1%) were found as major compounds of fruit-flower mixture, root, aerial part essential oils, respectively. Hesperidin was found the highest amount in aerial part and flower-fruit extracts with 8904.2621 ng/mL and 11558.3634 ng/mL values, respectively. Fruit-flower extract showed the highest activity against α-glucosidase (24%). Root extract demonstrating the highest activity (18%) against AChE enzyme. Flowers-fruits mixture methanol extract had a higher % inhibition value on ABTS·+ and DPPH•. Flowers-fruits mixture methanol extract was rich in total phenol, total tannin, and protein content. All the extracts were determined as genetoxically safe according to the results of Ames/Salmonella, Escherichia coli WP2 and Allium cepa assays.

Dietary isoleucine content defines the metabolic and molecular response to a Western diet

The amino acid composition of the diet has recently emerged as a critical regulator of metabolic health. Consumption of the branched-chain amino acid isoleucine is positively correlated with body mass index in humans, and reducing dietary levels of isoleucine rapidly improves the metabolic health of diet-induced obese male C57BL/6J mice. However, it is unknown how sex, strain, and dietary isoleucine intake may interact to impact the response to a Western Diet (WD). Here, we find that although the magnitude of the effect varies by sex and strain, reducing dietary levels of isoleucine protects C57BL/6J and DBA/2J mice of both sexes from the deleterious metabolic effects of a WD, while increasing dietary levels of isoleucine impairs aspects of metabolic health. Despite broadly positive responses across all sexes and strains to reduced isoleucine, the molecular response of each sex and strain is highly distinctive. Using a multi-omics approach, we identify a core sex- and strain- independent molecular response to dietary isoleucine, and identify mega-clusters of differentially expressed hepatic genes, metabolites, and lipids associated with each phenotype. Intriguingly, the metabolic effects of reduced isoleucine in mice are not associated with FGF21 - and we find that in humans plasma FGF21 levels are likewise not associated with dietary levels of isoleucine. Finally, we find that foods contain a range of isoleucine levels, and that consumption of dietary isoleucine is lower in humans with healthy eating habits. Our results demonstrate that the dietary level of isoleucine is critical in the metabolic and molecular response to a WD, and suggest that lowering dietary levels of isoleucine may be an innovative and translatable strategy to protect from the negative metabolic consequences of a WD.

Oat protein modulates cholesterol metabolism and improves cardiac systolic function in high fat, high sucrose fed rats

Oats are recognized to provide many health benefits that are mainly associated with its dietary fibre, β-glucan. However, the protein derived from oats is largely understudied with respect to its ability to maintain health and attenuate risk factors of chronic diseases. The goal of the current study was to investigate the metabolic effects of oat protein consumption in lieu of casein as the protein source in high fat, high sucrose (HF/HS) fed Wistar rats. Four-week-old rats were divided into three groups and were fed three different experimental diets: a control diet with casein as the protein source, an HF/HS diet with casein, or an HF/HS diet with oat protein for 16 weeks. Heart structure and function were determined by echocardiography. Blood pressure measurements, an oral glucose tolerance test, and markers of cholesterol metabolism, oxidative stress, inflammation, and liver and kidney damage were also performed. Our study results show that incorporation of oat protein in the diet was effective in preserving systolic heart function in HF/HS fed rats. Oat protein significantly reduced serum total and low-density lipoprotein cholesterol levels. Furthermore, oat protein normalized liver HMG-CoAR activity, which, to our knowledge, is the first time this has been reported in the literature. Therefore, our research suggests that oat protein can provide hypocholesterolemic and cardioprotective benefits in a diet-induced model of metabolic syndrome.

High Plant Protein Diet Ameliorated Hepatic Lipid Accumulation Through the Modulation of Gut Microbiota

SCOPE

Substituting plant protein for animal protein has emerged as a promising strategy for managing atherogenic lipids. However, the impact of long-term intake of a high plant protein diet (HPD) on hepatic lipid disorder remains unclear.

METHODS AND RESULTS

Eight-week-old apolipoprotein E deficient (apoE-/- ) mice are fed with either a normal protein diet (NCD) or HPD for 12 weeks. HPD intervention results in decreased body weight accompanied by increased energy expenditure, with no significant effect on glycemic control. Long-term intake of HPD improves the serum and hepatic lipid and cholesterol accumulation by suppressing hepatic squalene epoxidase (SQLE) expression, a key enzyme in cholesterol biosynthesis. Integrated analysis of 16S rDNA sequencing and metabolomics profiling reveals that HPD intervention increases the abundance of the Lachnospiraece family and serum levels of 12,13-DiHOME. Furthermore, in vivo studies demonstrate that 12,13-DiHOME significantly inhibits lipid accumulation, as well as SQLE expression induced by oleic acid in HepG2 cells.

CONCLUSION

Diet rich in plant protein diet alleviates hyperlipidemia via increased microbial production of 12,13-DiHOME.

Resistance exercise protects mice from protein-induced fat accretion

Low-protein (LP) diets extend the lifespan of diverse species and are associated with improved metabolic health in both rodents and humans. Paradoxically, many athletes and bodybuilders consume high-protein (HP) diets and protein supplements, yet are both fit and metabolically healthy. Here, we examine this paradox using weight pulling, a validated progressive resistance exercise training regimen, in mice fed either an LP diet or an isocaloric HP diet. We find that despite having lower food consumption than the LP group, HP-fed mice gain significantly more fat mass than LP-fed mice when not exercising, while weight pulling protected HP-fed mice from this excess fat accretion. The HP diet augmented exercise-induced hypertrophy of the forearm flexor complex, and weight pulling ability increased more rapidly in the exercised HP-fed mice. Surprisingly, exercise did not protect from HP-induced changes in glycemic control. Our results confirm that HP diets can augment muscle hypertrophy and accelerate strength gain induced by resistance exercise without negative effects on fat mass, and also demonstrate that LP diets may be advantageous in the sedentary. Our results highlight the need to consider both dietary composition and activity, not simply calories, when taking a precision nutrition approach to health.

A Narrative Review on Strategies for the Reversion of Prediabetes to Normoglycemia: Food Pyramid, Physical Activity, and Self-Monitoring Innovative Glucose Devices

In 2019, "Nutrition Therapy for Adults with Diabetes or Prediabetes: A Consensus Report" was published. This consensus report, however, did not provide an easy way to illustrate to subjects with prediabetes (SwPs) how to follow a correct dietary approach. The purpose of this review is to evaluate current evidence on optimum dietary treatment of SwPs and to provide a food pyramid for this population. The pyramid built shows that everyday consumption should consist of: whole-grain bread or potatoes eaten with their skins (for fiber and magnesium) and low glycemic index carbohydrates (GI < 55%) (three portions); fruit and vegetables (5 portions), in particular, green leafy vegetables (for fiber, magnesium, and polyphenols); EVO oil (almost 8 g); nuts (30 g, in particular, pistachios and almonds); three portions of dairy products (milk/yogurt: 300-400 g/day); mineral water (almost 1, 5 L/day for calcium intake); one glass of wine (125 mL); and three cups of coffee. Weekly portions should include fish (four portions), white meat (two portions), protein plant-based food (four portions), eggs (egg portions), and red/processed meats (once/week). At the top of the pyramid, there are two pennants: a green one means that SwPs need some personalized supplementation (if daily requirements cannot be satisfied through diet, vitamin D, omega-3, and vitamin B supplements), and a red one means there are some foods and factors that are banned (simple sugar, refined carbohydrates, and a sedentary lifestyle). Three to four times a week of aerobic and resistance exercises must be performed for 30-40 min. Finally, self-monitoring innovative salivary glucose devices could contribute to the reversion of prediabetes to normoglycemia.

Research progress in the role and mechanism of Leucine in regulating animal growth and development

Leucine, a branched-chain amino acid, is essential in regulating animal growth and development. Recent research has uncovered the mechanisms underlying Leucine's anabolic effects on muscle and other tissues, including its ability to stimulate protein synthesis by activating the mTORC1 signaling pathway. The co-ingestion of carbohydrates and essential amino acids enhances Leucine's anabolic effects. Moreover, Leucine has been shown to benefit lipid metabolism, and insulin sensitivity, making it a promising strategy for preventing and treating metabolic diseases, including type 2 diabetes and obesity. While emerging evidence indicates that epigenetic mechanisms may mediate Leucine's effects on growth and development, more research is needed to elucidate its mechanisms of action fully. Specific studies have demonstrated that Leucine promotes muscle growth and metabolic health in animals and humans, making it a promising therapeutic agent. However, it is essential to note that Leucine supplementation may cause digestive issues or interact with certain medications, and More study is required to determine definitively optimal dosages. Therefore, it is important to understand how Leucine interacts with other nutrients, dietary factors, and lifestyle habits to maximize its benefits. Overall, Leucine's importance in human nutrition is far-reaching, and its potential to prevent muscle loss and enhance athletic performance warrants further investigation.

Regulation of Macronutrients in Insulin Resistance and Glucose Homeostasis during Type 2 Diabetes Mellitus

Insulin resistance is an important feature of metabolic syndrome and a precursor of type 2 diabetes mellitus (T2DM). Overnutrition-induced obesity is a major risk factor for the development of insulin resistance and T2DM. The intake of macronutrients plays a key role in maintaining energy balance. The components of macronutrients distinctly regulate insulin sensitivity and glucose homeostasis. Precisely adjusting the beneficial food compound intake is important for the prevention of insulin resistance and T2DM. Here, we reviewed the effects of different components of macronutrients on insulin sensitivity and their underlying mechanisms, including fructose, dietary fiber, saturated and unsaturated fatty acids, and amino acids. Understanding the diet-gene interaction will help us to better uncover the molecular mechanisms of T2DM and promote the application of precision nutrition in practice by integrating multi-omics analysis.

Type 2 Diabetes Mellitus and Sarcopenia as Comorbid Chronic Diseases in Older Adults: Established and Emerging Treatments and Therapies

Type 2 diabetes mellitus (T2DM) and sarcopenia (low skeletal muscle mass and function) share a bidirectional relationship. The prevalence of these diseases increases with age and they share common risk factors. Skeletal muscle fat infiltration, commonly referred to as myosteatosis, may be a major contributor to both T2DM and sarcopenia in older adults via independent effects on insulin resistance and muscle health. Many strategies to manage T2DM result in energy restriction and subsequent weight loss, and this can lead to significant declines in muscle mass in the absence of resistance exercise, which is also a first-line treatment for sarcopenia. In this review, we highlight recent evidence on established treatments and emerging therapies targeting weight loss and muscle mass and function improvements in older adults with, or at risk of, T2DM and/or sarcopenia. This includes dietary, physical activity and exercise interventions, new generation incretin-based agonists and myostatin-based antagonists, and endoscopic bariatric therapies. We also highlight how digital health technologies and health literacy interventions can increase uptake of, and adherence to, established and emerging treatments and therapies in older adults with T2DM and/or sarcopenia.

Snacks contribute considerably to total dietary intakes among adults stratified by glycemia in the United States

Little is known about the snacking patterns among adults with type 2 diabetes. The contribution of snacks to energy and nutrient intakes is important to further understand dietary patterns and glycemic control. The purpose of this study is to evaluate snack consumption among adults according to diabetes status in the United States. One NHANES 24-hour dietary recall for each participant collected between 2005-2016 was utilized for analysis (n = 23,708). Analysis of covariance was used to compare differences in nutrient and food groups intakes from snacks across levels of glycemic control, while controlling for age, race/ethnicity, income, marital status, and gender. Results of this analysis inform that adults with type 2 diabetes consume less energy, carbohydrates, and total sugars from snacks than adults without diabetes. Those with controlled type 2 diabetes consumed more vegetables and less fruit juice than other groups, yet adults with type 2 diabetes in general consumed more cured and luncheon meats than adults without diabetes or with prediabetes. Protein from all snacks for those without diabetes is higher than all other groups. This study elucidates common snacking patterns among US adults with diabetes and highlights the need for clinicians and policymakers to take snacking into consideration when evaluating and providing dietary recommendations.

Animal and plant-based proteins have different postprandial effects on energy expenditure, glycemia, insulinemia, and lipemia: A review of controlled clinical trials

Dietary proteins have been shown to stimulate thermogenesis, increase satiety, and improve insulin sensitivity in the short and long term. Animal-based proteins (AP) and plant-based proteins (PP) have different amino acid profiles, bioavailability, and digestibility, so it seems to have various short- and long-term effects on metabolic responses. This review aimed to compare the findings of controlled clinical trials on postprandial effects of dietary Aps versus PPs on energy expenditure (EE), lipemia, glycemia, and insulinemia. Data are inconclusive regarding the postprandial effects of APs and PPs. However, there is some evidence indicating that APs increase postprandial EE, DIT, and SO more than PPs. With lipemia and glycemia, most studies showed that APs reduce or delay postprandial glycemia and lipemia and increase insulinemia more than PPs. The difference in amino acid composition, digestion and absorption rate, and gastric emptying rate between APs and PPs explains this difference.

Optimising blood glucose control with portioned meal box in type 2 diabetes mellitus patients: a randomised control trial

Background

The impact of dietary factors on glycaemic control in type 2 diabetes mellitus (T2DM) is well established. However, the effectiveness of transforming portion control into a practical innovation for glycaemic control in T2DM has not yet been established for counselling in nutrition. The aim of this study was to compare the effect of general counselling in nutrition (GCN) and a portioned meal box (PMB) on fasting blood glucose, glycated haemoglobin (HbA1c) and body composition.

Methods

A randomised, parallel intervention trial was conducted over 12 weeks, with GCN: carbohydrate portion control concept by using food exchange lists (n = 25) and PMB: portioned meal box was set by energy requirements (n = 25).

Results

Both GCN and PMB demonstrated reductions in HbA1c levels at the 6th and 12th weeks compared to baseline. However, no significant difference in HbA1c was observed between GCN and PMB at either the 6th or 12th week. Using PMB at least four times a week significantly decreased HbA1c during the intervention period (p = 0.021 and p < 0.001 for weeks 6 and 12 when compared with baseline, respectively). Changes in body composition were observed: body weight decrease in PMB only, body fat decrease and constant muscle mass in both groups. Both methods tended to relieve hunger and increased satiety in both groups. The satisfaction evaluation showed that participants preferred to use PMB over GCN (p = 0.001). Additionally, participants consumed less energy, carbohydrate and fat in PMB (p = 0.001, p = 0.019, and p = 0.001, respectively) and less energy and fat in GCN (p = 0.006 and p = 0.001, respectively).

Conclusion

A better diet, either through GCN or PMB, can play an important role in improving dietary intake compliance and controlling blood glucose.

Regulation of metabolic health by dietary histidine in mice

Low-protein (LP) diets are associated with a decreased risk of diabetes in humans, and promote leanness and glycaemic control in both rodents and humans. While the effects of an LP diet on glycaemic control are mediated by reduced levels of the branched-chain amino acids, we have observed that reducing dietary levels of the other six essential amino acids leads to changes in body composition. Here, we find that dietary histidine plays a key role in the response to an LP diet in male C57BL/6J mice. Specifically reducing dietary levels of histidine by 67% reduces the weight gain of young, lean male mice, reducing both adipose and lean mass without altering glucose metabolism, and rapidly reverses diet-induced obesity and hepatic steatosis in diet-induced obese male mice, increasing insulin sensitivity. This normalization of metabolic health was associated not with caloric restriction or increased activity, but with increased energy expenditure. Surprisingly, the effects of histidine restriction do not require the energy balance hormone Fgf21. Histidine restriction that was started in midlife promoted leanness and glucose tolerance in aged males but not females, but did not affect frailty or lifespan in either sex. Finally, we demonstrate that variation in dietary histidine levels helps to explain body mass index differences in humans. Overall, our findings demonstrate that dietary histidine is a key regulator of weight and body composition in male mice and in humans, and suggest that reducing dietary histidine may be a translatable option for the treatment of obesity. KEY POINTS: Protein restriction (PR) promotes metabolic health in rodents and humans and extends rodent lifespan. Restriction of specific individual essential amino acids can recapitulate the benefits of PR. Reduced histidine promotes leanness and increased energy expenditure in male mice. Reduced histidine does not extend the lifespan of mice when begun in midlife. Dietary levels of histidine are positively associated with body mass index in humans.

Effects of a High-Protein Diet on Kidney Injury under Conditions of Non-CKD or CKD in Mice

Considering the prevalence of obesity and global aging, the consumption of a high-protein diet (HPD) may be advantageous. However, an HPD aggravates kidney dysfunction in patients with chronic kidney disease (CKD). Moreover, the effects of an HPD on kidney function in healthy individuals are controversial. In this study, we employed a remnant kidney mouse model as a CKD model and aimed to evaluate the effects of an HPD on kidney injury under conditions of non-CKD and CKD. Mice were divided into four groups: a sham surgery (sham) + normal diet (ND) group, a sham + HPD group, a 5/6 nephrectomy (Nx) + ND group and a 5/6 Nx + HPD group. Blood pressure, kidney function and kidney tissue injury were compared after 12 weeks of diet loading among the four groups. The 5/6 Nx groups displayed blood pressure elevation, kidney function decline, glomerular injury and tubular injury compared with the sham groups. Furthermore, an HPD exacerbated glomerular injury only in the 5/6 Nx group; however, an HPD did not cause kidney injury in the sham group. Clinical application of these results suggests that patients with CKD should follow a protein-restricted diet to prevent the exacerbation of kidney injury, while healthy individuals can maintain an HPD without worrying about the adverse effects.

Development of a nutrition screening tool to identify need for dietetic intervention in female infertility

BACKGROUND

One in seven couples are impacted by infertility in the UK, and female infertility is often associated with several health conditions impacted by nutrition. Despite many studies aimed at identifying the critical role of nutrition in infertility, there is currently no screening tool that identifies nutritional risk factors for infertility.

AIM

To propose a self-administered screening tool to identify women who would benefit from nutritional intervention to promote fertility.

METHODS

A narrative review was carried out to identify and summarise modifiable nutritional risk factors that can influence female fertility, including comorbidities that can influence nutrition intake, absorption, and metabolism.

KEY FINDINGS

A nutrition screening tool outlining modifiable nutrition risk factors potentially improving female fertility has been proposed, comprising of BMI, medical history and quality of diet and lifestyle which would aid in designing evidence based dietetic services for female infertility.

A randomised crossover trial: Exploring the dose-response effect of carbohydrate restriction on glycaemia in people with well-controlled type 2 diabetes

BACKGROUND

Trials investigating the role of carbohydrate restriction in the management of glycaemia in type 2 diabetes (T2D) have been confounded by multiple factors, including degree of calorie restriction and dietary protein content, as well as by no clear definition of a low-carbohydrate diet. The present study aimed to provide insight into the relationship between carbohydrate restriction and glycaemia by testing the effect of varying doses of carbohydrate on continuous glucose concentrations within a range of intakes defined as low-carbohydrate at the same time as controlling for confounding factors.

METHODS

This was a randomised crossover trial in participants with T2D (HbA1c: 6.6 ± 0.6%, 49 ± 0.9 mmol mol^-1 ) testing five different 6-day eucaloric dietary treatments with varying carbohydrate content (10%, 15%, 20%, 25%, and 30% kcal). Diets exchanged %kcal from carbohydrate with fat, keeping protein constant at 15% kcal. Daily self-weighing was employed to ensure weight stability throughout each treatment arm. Between dietary treatments, participants underwent a washout period of at least 7 days and were advised to maintain their habitual diet. Glycaemic control was assessed using a continuous glucose monitoring device.

RESULTS

Twelve participants completed the study. There were no differences in 24-h and post-prandial sensor glucose concentrations between the 30 and 10%kcal doses (7.4 ± 1.1 mmol L^-1 vs. 7.6 ± 1.3 mmol L^-1 [p = 0.28] and 8.1 ± 1.5 mmol L^-1 vs. 8.5 ± 1.4 mmol L^-1 [p = 0.28], respectively). In our exploratory analyses, we did not find any dose-response relationship between carbohydrate intake and glycaemia. A small amount of weight loss occurred in each treatment arm (range: 0.4-1.1 kg over the 6 days) but adjusting for these differences did not influence the primary or secondary outcomes.

CONCLUSIONS

Modest changes in dietary carbohydrate content in the absence of weight loss at the same time as keeping dietary protein intake constant do not appear to influence glucose concentrations in people with well-controlled T2D.

SUMMARY

This study randomised people with T2D to receive five different doses of carbohydrate from 10% to 30% of calories in random order to see what effect it had on their blood glucose.

Effect of unsaturated fat and protein intake on liver fat in people at risk of unhealthy aging: 1-year results of a randomized controlled trial

BACKGROUND

Short-term trials indicate improvement of intrahepatic lipids (IHLs) and metabolism by dietary protein or unsaturated fatty acids (UFAs) beyond weight loss.

OBJECTIVES

We aimed to assess the effect of a dietary intervention high in protein and UFAs on IHLs and metabolic outcome after 12 mo, as long-term effects of such a combined intervention are unknown.

METHODS

Within a 36-mo randomized controlled trial, eligible subjects (aged 50 to 80 y, ≥1 risk factor for unhealthy aging) were randomly assigned to either intervention group (IG) with high intake of mono-/poly-UFAs [15-20 percent of total energy (%E)/10%-15%E, respectively], plant protein (15%-25%E), and fiber (≥30 g/d), or control group [CG, usual care, dietary recommendations of the German Nutrition Society (fat 30%E/carbohydrates 55%E/protein 15%E)]. Stratification criteria were sex, known cardiovascular disease, heart failure, arterial hypertension, type 2 diabetes, and cognitive or physical impairment. Nutritional counseling and supplementation of foods mirroring the intended dietary pattern were performed in the IG. Diet-induced effects on IHLs, analyzed by magnetic resonance spectroscopy, as well as on lipid and glucose metabolism were predefined secondary endpoints.

RESULTS

IHL content was analyzed in 346 subjects without significant alcohol consumption at baseline and in 258 subjects after 12 mo. Adjusted for weight loss, sex, and age, we observed a comparable decline of IHLs in IG and CG (-33.3%; 95% CI: -49.3, -12.3%; n = 128 compared with -21.8%; 95% CI: -39.7, 1.5%; n = 130; P = 0.179), an effect that became significant by comparing adherent IG subjects to adherent CG subjects (-42.1%; 95% CI: -58.1, -20.1%; n = 88 compared with -22.2%; 95% CI: -40.7, 2.0%; n = 121; P = 0.013). Compared with the CG, decline of LDL cholesterol (LDL-C) and total cholesterol (TC) was stronger in the IG (for LDL-C P = 0.019, for TC P = 0.010). Both groups decreased in triglycerides and insulin resistance (P for difference between groups P = 0.799 and P = 0.124, respectively).

CONCLUSIONS

Diets enriched with protein and UFAs have beneficial long-term effects on liver fat and lipid metabolism in adherent older subjects. This study was registered at the German Clinical Trials Register, https://www.drks.de/drks_web/setLocale_EN.do, DRKS00010049. Am J Clin Nutr 20XX;xx:xx-xx.

Comparative efficacy of different eating patterns in the management of type 2 diabetes and prediabetes: An arm-based Bayesian network meta-analysis

AIMS/INTRODUCTION

Diet therapy is a vital approach to manage type 2 diabetes and prediabetes. However, the comparative efficacy of different eating patterns is not clear enough. We aimed to compare the efficacy of various eating patterns for glycemic control, anthropometrics, and serum lipid profiles in the management of type 2 diabetes and prediabetes.

MATERIALS AND METHODS

We conducted a network meta-analysis using arm-based Bayesian methods and random effect models, and drew the conclusions using the partially contextualized framework. We searched twelve databases and yielded 9,534 related references, where 107 studies were eligible, comprising 8,909 participants.

RESULTS

Eleven diets were evaluated for 14 outcomes. Caloric restriction was ranked as the best pattern for weight loss (SUCRA 86.8%) and waist circumference (82.2%), low-carbohydrate diets for body mass index (81.6%), and high-density lipoprotein (84.0%), and low-glycemic-index diets for total cholesterol (87.5%) and low-density lipoprotein (86.6%). Other interventions showed some superiorities, but were imprecise due to insufficient participants and needed further investigation. The attrition rates of interventions were similar. Meta-regression suggested that macronutrients, energy intake, and weight may modify outcomes differently. The evidence was of moderate-to-low quality, and 38.2% of the evidence items met the minimal clinically important differences.

CONCLUSIONS

The selection and development of dietary strategies for diabetic/prediabetic patients should depend on their holistic conditions, i.e., serum lipid profiles, glucometabolic patterns, weight, and blood pressure. It is recommended to identify the most critical and urgent metabolic indicator to control for one specific patient, and then choose the most appropriate eating pattern accordingly.

Culinary strategies to manage glycemic response in people with type 2 diabetes: A narrative review

Diet plays a critical role in the management of many chronic diseases. It is well known that individuals with type 2 diabetes (T2D) need to pay close attention to foods rich in carbohydrates to better manage their blood sugar. Usually, individuals are told to increase their dietary fiber intake which is associated with better glycemic control and limit their overall carbohydrate consumption. However, there are many other cooking strategies available to reduce the glycemic response to meals rich in carbohydrates and with a high glycemic index, such as adding fats, proteins, or vinegar, modifying the cooking or preparation processes, and even the selection and storage of foods consumed. The aim of the present narrative review is to summarize some of these existing strategies applied to the cooking process and their ability to modulate glycemic response to meals in individuals with T2D.

Effects of a low-carbohydrate/high-protein diet on metabolic health in individuals with chronic spinal cord injury: An exploratory analysis of results from a randomized controlled trial

We explored the impact of a low-carbohydrate/high-protein diet (LC/HP, ~30% energy from protein, 40% energy from carbohydrate) on indices of metabolic function and body composition in individuals with chronic spinal cord injury (SCI). Adults with SCI (≥3 years post-injury, C4-L2, AIS A-D) and insulin resistance or pre-diabetes were randomly assigned to an 8-week iso-caloric LC/HP diet group (n = 11) or control group (n = 14). All LC/HP meals were delivered weekly to participants' homes, and participants in the control group consumed their habitual diet. Each participant underwent an oral glucose tolerance test (OGTT) to assess glucose tolerance, insulin, area under the curve (AUC) for glucose and insulin, Matsuda Index, glucose-stimulated insulin secretion (GSIS), disposition index, and hepatic insulin extraction (HIE). Fasting blood lipid and inflammation were assessed, and body composition was estimated using dual-energy x-ray absorptiometry. A linear mixed model was used to evaluate the main effect of diet, time, and their interaction. Compared to the control group, participants in the LC/HP group had reduced total body fat mass (LC/HP: -5.9%, Control: 0.7%), visceral fat mass (LC/HP: -16.2%, Control: 5.2%), total- (LC/HP: -20.1, Control: 3.7 mg/dl), and LDL-cholesterol (LC/HP: -13.9, Control: 3.1 mg/dl) (pdiet*time  < 0.05 for all). Regardless of group, AUCinsulin and peak insulin during the OGTT decreased, and HIE increased over time (ptime  < 0.05). A trend for diet*time interaction was observed for glucoseOGTT120min (LC/HP: -20.7, Control: 3.0 mg/dl, pdiet*time  = 0.09) and peak C-peptide (LC/HP: -2.1, Control: 0.0 ng/ml, pdiet*time  = 0.07). HDL-cholesterol, lean body mass, Matsuda Index, fasting glucose, insulin, insulinOGTT120min , AUCglucose , pancreatic beta cell function (GSIS, disposition index), and inflammation (C-reactive protein, IL-6, IL-8, IL-10, TNF-α) did not change over time. In conclusion, our results suggest that individuals with SCI and insulin resistance may adopt an LC/HP diet to improve body composition and lipid profiles. Its impact on glucose metabolism and inflammation remains inconclusive and warrants future investigations.

Weight loss improves β-cell function independently of dietary carbohydrate restriction in people with type 2 diabetes: A 6-week randomized controlled trial

Background

Carbohydrate restriction may benefit β-cell function and glucose metabolism in type 2 diabetes (T2D) but also leads to weight loss which in itself is beneficial.

Methods

In order to determine the additional effect of carbohydrate restriction in addition to a fixed body weight loss, we randomly assigned 72 adults with T2D and obesity (mean ± SD HbA_1c 7.4 ± 0.7%, BMI 33 ± 5 kg/m²) to a carbohydrate-reduced high-protein diet (CRHP; energy percent from carbohydrate/protein/fat: 30/30/40) or an isocaloric conventional diabetes diet (CD; 50/17/33) for 6 weeks. All foods were provided free of charge and total energy intake was tailored individually, so both groups lost 6% of baseline body weight.

Results

Despite significantly greater reductions in HbA_1c (mean [95% CI] −1.9 [−3.5, −0.3] mmol/mol) after 6 weeks, the CRHP diet neither improved glucose tolerance, β-cell response to glucose, insulin sensitivity, during a 4-h oral glucose tolerance test, nor basal proinsulin secretion when compared to the CD diet, but increased C-peptide concentration and insulin secretion rate (area under the curve [AUC] and peak) significantly more (~10%, P ≤ 0.03 for all). Furthermore, compared with the CD diet, the CRHP diet borderline increased basal glucagon concentration (16 [−0.1, 34]%, P = 0.05), but decreased glucagon net AUC (−2.0 [−3.4, −0.6] mmol/L ×240 min, P < 0.01), decreased basal triglyceride and total AUC (~20%, P < 0.01 for both), and increased gastric inhibitory polypeptide total AUC (14%, P = 0.01).

Conclusion

A moderately carbohydrate-restricted diet for 6 weeks decreased HbA_1c but did not improve β-cell function or glucose tolerance beyond the effects of weight loss when compared with a conventional diabetes diet in people with T2D.

Clinical trials registration

www.Clinicaltrials.gov, Identifier: NCT02472951.

Association between RAC1 gene variation, redox homeostasis and type 2 diabetes mellitus

BACKGROUND

Increased production of reactive oxygen species (ROS) and oxidative stress are known to play a key role in the pathogenesis of type 2 diabetes (T2D); however, the relationship between genes encoding a multi-subunit ROS-generated enzyme NADPH oxidase and disease susceptibility remains unexplored.

AIMS

The present pilot study investigated whether single-nucleotide polymorphisms (SNP) at the RAC1 gene (Rac family small GTPase 1), a molecular switcher of NADPH oxidase, are associated with the risk of T2D, glucose metabolism and redox homeostasis.

MATERIALS & METHODS

DNA samples from 3206 unrelated Russian subjects (1579 T2D patients and 1627 controls) were genotyped for six common SNPs rs4724800, rs7784465, rs10951982, rs10238136, rs836478 and rs9374 of RAC1 using the MassArray-4 system.

RESULTS

SNP rs7784465 was associated with an increased risk of T2D (p = .0003), and significant differences in the RAC1 haplotypes occurred between the cases and controls (p = .005). Seventeen combinations of RAC1 genotypes showed significant associations with T2D risk (FDR <0.05). Associations of RAC1 polymorphisms with T2D were modified by environmental factors such as sedentary lifestyle, psychological stresses, a dietary deficit of fresh fruits/vegetables and increased carbohydrate intake. RAC1 polymorphisms were associated with biochemical parameters in diabetics: rs7784465 (p = .015) and rs836478 (p = .028) with increased glycated haemoglobin, rs836478 (p = .005) with increased fasting blood glucose, oxidized glutathione (p = .012) and uric acid (p = .034). Haplotype rs4724800A-rs7784465C-rs10951982G-rs10238136A-rs836478C-rs9374G was strongly associated with increased levels of hydrogen peroxide (p < .0001).

CONCLUSION

Thus, polymorphisms in the RAC1 gene represent novel genetic markers of type 2 diabetes, and their link with glucose metabolism and disease pathogenesis is associated with the changes in redox homeostasis.

Dose-dependent effect of carbohydrate restriction for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND

Carbohydrate restriction is effective for type 2 diabetes management.

OBJECTIVES

We aimed to evaluate the dose-dependent effect of carbohydrate restriction in patients with type 2 diabetes.

METHODS

We systematically searched PubMed, Scopus, and Web of Science to May 2021 for randomized controlled trials evaluating the effect of a carbohydrate-restricted diet (≤45% total calories) in patients with type 2 diabetes. The primary outcome was glycated hemoglobin (HbA1c). Secondary outcomes included fasting plasma glucose (FPG); body weight; serum total, LDL, and HDL cholesterol; triglyceride (TG); and systolic blood pressure (SBP). We performed random-effects dose-response meta-analyses to estimate mean differences (MDs) for a 10% decrease in carbohydrate intake.

RESULTS

Fifty trials with 4291 patients were identified. At 6 months, compared with a carbohydrate intake between 55%-65% and through a maximum reduction down to 10%, each 10% reduction in carbohydrate intake reduced HbA1c (MD, -0.20%; 95% CI, -0.27% to -0.13%), FPG (MD, -0.34 mmol/L; 95% CI, -0.56 to -0.12 mmol/L), and body weight (MD, -1.44 kg; 95% CI, -1.82 to -1.06 kg). There were also reductions in total cholesterol, LDL cholesterol, TG, and SBP. Levels of HbA1c, FPG, body weight, TG, and SBP decreased linearly with the decrease in carbohydrate intake from 65% to 10%. A U-shaped effect was seen for total cholesterol and LDL cholesterol, with the greatest reduction at 40%. At 12 months, a linear reduction was seen for HbA1c and TG. A U-shaped effect was seen for body weight, with the greatest reduction at 35%.

CONCLUSIONS

Carbohydrate restriction can exert a significant and important reduction on levels of cardiometabolic risk factors in patients with type 2 diabetes. Levels of most cardiometabolic outcomes decreased linearly with the decrease in carbohydrate intake. U-shaped effects were seen for total cholesterol and LDL cholesterol at 6 months and for body weight at 12 months.

Dietary pH Enhancement Improves Metabolic Outcomes in Diet-Induced Obese Male and Female Mice: Effects of Beef vs. Casein Proteins

(1) Consumption of diets that are caloric dense but not nutrient dense have been implicated in metabolic diseases, in part through low-grade metabolic acidosis. Mitigation strategies through dietary intervention to alleviate acidosis have not been previously reported. Our objective is to determine the effects of pH enhancement (with ammonia) in high fat diet-induced obese mice that were fed beef or casein as protein sources compared to low fat diet-fed mice. (2) Methods: B6 male and female mice were randomized (n = 10) into eight diets that differ in protein source, pH enhancement of the protein, and fat content, and fed for 13 weeks: low fat (11% fat) casein (LFC), LF casein pH-enhanced (LFCN), LF lean beef (LFB), LFBN, high fat (46%) casein (HFC), HFCN, HF beef (HFB), and HFBN. Body weights and composition, and glucose tolerance tests were conducted along with terminal serum analyses. Three-way ANOVA was performed. (3) Results: A significant effect of dietary fat (LF vs. HF) was observed across all variables in both sexes (final body weight, fat mass, glucose clearance, and serum leptin). Importantly, pH enhancement significantly reduced adiposity (males only) and final body weights (females only) and significantly improved glucose clearance in both sexes. Lastly, clear sex differences were observed across all variables. (4) Conclusions: Our findings demonstrate metabolic benefits of increasing dietary pH using ammonia, while high fat intake per se (not protein source) is the major contributor to metabolic dysfunctions. Additional research is warranted to determine mechanisms underlying the beneficial effects of pH enhancement, and interactions with dietary fat content and proteins.

Sex and genetic background define the metabolic, physiologic, and molecular response to protein restriction

Low-protein diets promote metabolic health in humans and rodents. Despite evidence that sex and genetic background are key factors in the response to diet, most protein intake studies examine only a single strain and sex of mice. Using multiple strains and both sexes of mice, we find that improvements in metabolic health in response to reduced dietary protein strongly depend on sex and strain. While some phenotypes were conserved across strains and sexes, including increased glucose tolerance and energy expenditure, we observed high variability in adiposity, insulin sensitivity, and circulating hormones. Using a multi-omics approach, we identified mega-clusters of differentially expressed hepatic genes, metabolites, and lipids associated with each phenotype, providing molecular insight into the differential response to protein restriction. Our results highlight the importance of sex and genetic background in the response to dietary protein level, and the potential importance of a personalized medicine approach to dietary interventions.

An Exploratory Study of the Role of Dietary Proteins in the Regulation of Intestinal Glucose Absorption

Several studies have demonstrated that high protein diets improve glucose homeostasis. Nevertheless, the mechanisms underlying this effect remain elusive. This exploratory study aims to screen and compare the acute effects of dietary proteins from different sources on intestinal glucose absorption. Six dietary proteins from various sources were thus selected and digested thanks to the INFOGEST static gastrointestinal digestion protocol. The digested proteins were able to decrease intestinal glucose absorption in vitro and ex vivo. Moreover, acute ingestion of casein and fish gelatin led to improved glucose tolerance in Wistar rats without significant effect on insulin secretion. In parallel, GLUT2 mRNA expression in enterocytes was decreased following short-term incubation with some of the digested proteins. These results strengthen the evidence that digested protein-derived peptides and amino acids are key regulators of glucose homeostasis and highlight their role in intestinal glucose absorption.

Variety and quantity of dietary protein intake from different sources and risk of new-onset diabetes: a Nationwide Cohort Study in China

BACKGROUND

The relation of the variety and quantity of different sources of dietary proteins intake and diabetes remains uncertain. We aimed to investigate the associations between the variety and quantity of proteins intake from eight major food sources and new-onset diabetes, using data from the China Health and Nutrition Survey (CHNS).

METHODS

16,260 participants without diabetes at baseline from CHNS were included. Dietary intake was measured by three consecutive 24-h dietary recalls combined with a household food inventory. The variety score of protein sources was defined as the number of protein sources consumed at the appropriate level, accounting for both types and quantity of proteins. New-onset diabetes was defined as self-reported physician-diagnosed diabetes or fasting glucose ≥7.0mmol/L or glycated hemoglobin ≥6.5% during the follow-up.

RESULTS

During a median follow-up of 9.0 years, 1100 (6.8%) subjects developed diabetes. Overall, there were U-shaped associations of percentages energy from total protein, whole grain-derived and poultry-derived proteins with new-onset diabetes; J-shaped associations of unprocessed or processed red meat-derived proteins with new-onset diabetes; a reverse J-shaped association of the fish-derived protein with new-onset diabetes; L-shaped associations of egg-derived and legume-derived proteins with new-onset diabetes; and a reverse L-shaped association of the refined grain-derived protein with new-onset diabetes (all P values for nonlinearity<0.001). Moreover, a significantly lower risk of new-onset diabetes was found in those with a higher variety score of protein sources (per score increment; HR, 0.69; 95%CI, 0.65-0.72).

CONCLUSIONS

There was an inverse association between the variety of proteins with appropriate quantity from different food sources and new-onset diabetes.

Mendelian randomization study reveals a population-specific putative causal effect of type 2 diabetes in risk of cataract

BACKGROUND

The epidemiological association between type 2 diabetes and cataract has been well established. However, it remains unclear whether the two diseases share a genetic basis, and if so, whether this reflects a putative causal relationship.

METHODS

We used East Asian population-based genome-wide association studies (GWAS) summary statistics of type 2 diabetes (Ncase = 36 614, Ncontrol = 155 150) and cataract (Ncase = 24 622, Ncontrol = 187 831) to comprehensively investigate the shared genetics between the two diseases. We performed: (i) linkage disequilibrium score regression (LDSC) and heritability estimation from summary statistics (ρ-HESS) to estimate the genetic correlation and local genetic correlation pattern between type 2 diabetes and cataract; (ii) multiple Mendelian randomization (MR) analyses to infer the putative causality between type 2 diabetes and cataract; and (iii) summary-data-based Mendelian randomization (SMR) to identify candidate risk genes underling the putative causality. Moreover, to investigate the extent of the population-specific genetic effect size underlying the shared genetics between type 2 diabetes and cataract, we applied the same analytical pipeline to perform a comparative analysis on European population-based GWAS of type 2 diabetes (Ncase = 62 892, Ncontrol = 596 424) and cataract (Ncase = 5045, Ncontrol = 356 096).

RESULTS

Using East Asian population-based GWAS summary data, we observed a strong genetic correlation [rg = 0.58, 95% confidence interval (CI) = 0.33, 0.83), P-value = 5.60 × 10-6] between type 2 diabetes and cataract. Both ρ-HESS and multiple MR methods consistently showed a putative causal effect of type 2 diabetes on cataract, with estimated liability-scale MR odds ratios (ORs) at around 1.10 (95% CI = 1.06, 1.17). In contrast, no evidence supports a causal effect of cataract on type 2 diabetes. SMR analysis identified two novel genes MIR4453HG (βSMR = -0.34, 95% CI = -0.46, -0.22, P-value = 6.41 × 10-8) and KCNK17 (βSMR = -0.07, 95% CI = -0.09, -0.05, P-value = 2.49 × 10-10), whose expression levels were likely involved in the putative causality of type 2 diabetes on cataract. On the contrary, our comparative analysis on European population provided universally weak evidence on the genetic correlation and causal relationship between the two diseases.

CONCLUSIONS

Our results provided robust evidence supporting a putative causal effect of type 2 diabetes on the risk of cataract in East Asians, and revealed potential genetic heterogeneity in the shared genetics underlying type 2 diabetes and cataract between East Asians and Europeans. These findings posed new paths on guiding the prevention and early-stage diagnosis of cataract in type 2 diabetes patients.

Metabolomics analysis of urine from rats given long-term high-protein diet using ultra-high-performance liquid chromatography-mass spectrometry

Previous studies have indicated high-protein diet (HPD) promotes weight loss and improves metabolic parameters, but most of these studies have focused on the impact of short-term, long-term effects remain unclear. In this study, male Wistar rats were fed two diets for 88 weeks: normal control diet (NCD, 20.5% of energy as protein) or HPD (30.5% of energy as protein). At 88 weeks intervention, compared to NCD rats, HPD rats had lower fat tissue and higher skeletal muscle to body weight ratio, but there were no significantly differences in body weight and food intake. To explore the mechanism underlying metabolism and diet, we further collected rat urine samples at 16, 40, 64 and 88 weeks diet treatment and analyzed metabolomics profiles using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). Partial least squares-discriminant analysis (PLS-DA) scores plots from ESI- or ESI+ model revealed a perfect separation between two diets at four time points. We identified 11 dramatically different metabolites (with VIP cut-off value > 1) in HPD, including 3 up-regulated and 8 down-regulated. And these 11 metabolites were identified as effective biomarkers, which were significantly related to HPD-induced metabolism related outcomes (fat tissue and skeletal muscle to body weight ratio). Our results provided vital information regarding metabolism in long-term HPD and more importantly, a few potentially promising metabolites were firstly identified which may related to metabolic responses.

Macroalgal protein hydrolysates from Palmaria palmata influence the 'incretin effect' in vitro via DPP-4 inhibition and upregulation of insulin, GLP-1 and GIP secretion

PURPOSE

This study investigated metabolic benefits of protein hydrolysates from the macroalgae Palmaria palmata, previously shown to inhibit dipeptidylpeptidase-4 (DPP-4) activity in vitro.

METHODS

Previously, Alcalase/Flavourzyme-produced P. palmata protein hydrolysate (PPPH) improved glycaemia and insulin production in streptozotocin-induced diabetic mice. Here the PPPH, was compared to alternative Alcalase, bromelain and Promod-derived hydrolysates and an unhydrolysed control. All PPPH's underwent simulated gastrointestinal digestion (SGID) to establish oral bioavailability. PPPH's and their SGID counterparts were tested in pancreatic, clonal BRIN-BD11 cells to assess their insulinotropic effect and associated intracellular mechanisms. PPPH actions on the incretin effect were assessed via measurement of DPP-4 activity, coupled with GLP-1 and GIP release from GLUTag and STC-1 cells, respectively. Acute in vivo effects of Alcalase/Flavourzyme PPPH administration on glucose tolerance and satiety were assessed in overnight-fasted mice.

RESULTS

PPPH's (0.02-2.5 mg/ml) elicited varying insulinotropic effects (p < 0.05-0.001). SGID of the unhydrolysed protein control, bromelain and Promod PPPH's retained, or improved, bioactivity regarding insulin secretion, DPP-4 inhibition and GIP release. Insulinotropic effects were retained for all SGID-hydrolysates at higher PPPH concentrations. DPP-4 inhibitory effects were confirmed for all PPPH's and SGID counterparts (p < 0.05-0.001). PPPH's were shown to directly influence the incretin effect via upregulated GLP-1 and GIP (p < 0.01-0.001) secretion in vitro, largely retained after SGID. Alcalase/Flavourzyme PPPH produced the greatest elevation in cAMP (p < 0.001, 1.7-fold), which was fully retained post-SGID. This hydrolysate elicited elevations in intracellular calcium (p < 0.01) and membrane potential (p < 0.001). In acute in vivo settings, Alcalase/Flavourzyme PPPH improved glucose tolerance (p < 0.01-0.001) and satiety (p < 0.05-0.001).

CONCLUSION

Bioavailable PPPH peptides may be useful for the management of T2DM and obesity.

Association between the food security status and dietary patterns with polycystic ovary syndrome (PCOS) in overweight and obese Iranian women: a case-control study

Background

Polycystic ovary syndrome (PCOS), as one of the significant endocrine disorders, is common among women worldwide. Food insecurity (FI) and unhealthy dietary patterns can negatively affect reproductive health. The effects of the lifestyle modifications, especially dietary components, on PCOS are contradictory. The aim was the assessment of association between PCOS with food security status and dietary patterns among overweight or obese women.

Methods

This case-control study was performed on 240 overweight and obese women with and without PCOS (ratio 1:1) referred to the infertility clinic of Arash Hospital, Tehran, Iran. The general and socioeconomic characteristics, anthropometrics (weight, height, body mass index (BMI), waist circumference, hip circumference), physical activity, food security status, and dietary intakes (or patterns) were assessed using valid questionnaires, scales, stadiometer, and tape meter. The significant p-value was < 0.05.

Results

The prevalence of FI was 60% in women with PCOS and 30% in healthy women. PCOS risk was positively related to FI, quasi-western dietary patterns, low economic levels, waist circumference, and menstrual age and negatively with physical activity and healthy dietary patterns, even after controlling the potential confounders (P <  0.05). PCOS women had a higher intake of saturated fats, monounsaturated fats, oleic acid, fluorine, sucrose, and caffeine and a lower intake of vitamins A, B₅, B₆, B₁₂, C, and D, potassium, proteins, carbohydrates, cholesterols, docosahexaenoic acid, potassium, carotenes, lutein, beta-cryptoxanthin, lycopene, calcium, iron, thiamine, riboflavin, niacin, tetra- and dihydrofolate, biotin, phosphorus, magnesium, zinc, copper, fiber (total, insoluble, and crude), glucose, galactose, fructose, and lactose compared to the healthy women (P <  0.05).

Conclusions

FI, quasi-western dietary patterns, low economic levels, and waist circumference were significantly associated with the higher risk of PCOS. The lifestyle changes, especially dietary patterns, may be an essential strategy for reducing PCOS. Further studies are warranted to confirm these findings and to identify the underlying mechanisms.

Low Carbohydrate Dietary Approaches for People With Type 2 Diabetes-A Narrative Review

Although carbohydrate restriction is not a new approach for the management of Type 2 diabetes, interest in its safety and efficacy has increased significantly in recent years. The purpose of the current narrative review is to summarise the key relevant research and practical considerations in this area, as well as to explore some of the common concerns expressed in relation to the use of such approaches. There is a strong physiological rationale supporting the role of carbohydrate restriction for the management of Type 2 diabetes, and available evidence suggests that low carbohydrate dietary approaches (LCDs) are as effective as, or superior to, other dietary approaches for its management. Importantly, LCDs appear to be more effective than other dietary approaches for facilitating a reduction in the requirement for certain medications, which leads to their effects on other health markers being underestimated. LCDs have also been demonstrated to be an effective method for achieving remission of Type 2 diabetes for some people. The available evidence does not support concerns that LCDs increase the risk of cardiovascular disease, that such approaches increase the risk of nutrient deficiencies, or that they are more difficult to adhere to than other dietary approaches. A growing number of organisations support the use of LCDs as a suitable choice for individuals with Type 2 diabetes.

Efficacy of Dietary and Supplementation Interventions for Individuals with Type 2 Diabetes

The prevalence of Type 2 diabetes (T2D) is increasing, which creates a large economic burden. Diet is a critical factor in the treatment and management of T2D; however, there are a large number of dietary approaches and a general lack of consensus regarding the efficacy of each. Therefore, the purpose of this narrative review is twofold: (1) to critically evaluate the effects of various dietary strategies on diabetes management and treatment, such as Mediterranean diet, plant-based diet, low-calorie and very low-calorie diets, intermittent fasting, low-carbohydrate and very low-carbohydrate diets, and low glycemic diets and (2) to examine several purported supplements, such as protein, branched-chain amino acids, creatine, and vitamin D to improve glucose control and body composition. This review can serve as a resource for those wanting to evaluate the evidence supporting the various dietary strategies and supplements that may help manage T2D.

Paternal High-Protein Diet Programs Offspring Insulin Sensitivity in a Sex-Specific Manner

The impact of maternal nutrition on offspring is well documented. However, the implication of pre-conceptional paternal nutrition on the metabolic health of the progeny remains underexplored. Here, we investigated the impact of paternal high-protein diet (HPD, 43.2% protein) consumption on the endocrine pancreas and the metabolic phenotype of offspring. Male Wistar rats were given HPD or standard diet (SD, 18.9% protein) for two months. The progenies (F1) were studied at fetal stage and in adulthood. Body weight, glycemia, glucose tolerance (GT), glucose-induced insulin secretion in vivo (GIIS) and whole-body insulin sensitivity were assessed in male and female F1 offspring. Insulin sensitivity, GT and GIIS were similar between F1 females from HPD (HPD/F1) and SD fathers (SD/F1). Conversely, male HPD/F1 exhibited increased insulin sensitivity (p < 0.05) and decreased GIIS (p < 0.05) compared to male SD/F1. The improvement of insulin sensitivity in HPD/F1 was sustained even after 2 months of high-fat feeding. In male HPD/F1, the β cell mass was preserved and the β cell plasticity, following metabolic challenge, was enhanced compared to SD/F1. In conclusion, we provide the first evidence of a sex-specific impact of paternal HPD on the insulin sensitivity and GIIS of their descendants, demonstrating that changes in paternal nutrition alter the metabolic status of their progeny in adulthood.

The metabolic impact of small intestinal nutrient sensing

The gastrointestinal tract maintains energy and glucose homeostasis, in part through nutrient-sensing and subsequent signaling to the brain and other tissues. In this review, we highlight the role of small intestinal nutrient-sensing in metabolic homeostasis, and link high-fat feeding, obesity, and diabetes with perturbations in these gut-brain signaling pathways. We identify how lipids, carbohydrates, and proteins, initiate gut peptide release from the enteroendocrine cells through small intestinal sensing pathways, and how these peptides regulate food intake, glucose tolerance, and hepatic glucose production. Lastly, we highlight how the gut microbiota impact small intestinal nutrient-sensing in normal physiology, and in disease, pharmacological and surgical settings. Emerging evidence indicates that the molecular mechanisms of small intestinal nutrient sensing in metabolic homeostasis have physiological and pathological impact as well as therapeutic potential in obesity and diabetes.

The gastrointestinal tract participates in maintaining metabolic homeostasis in part through nutrient-sensing and subsequent gut-brain signalling. Here the authors review the role of small intestinal nutrient-sensing in regulation of energy intake and systemic glucose metabolism, and link high-fat diet, obesity and diabetes with perturbations in these pathways.

Lifelong restriction of dietary branched-chain amino acids has sex-specific benefits for frailty and lifespan in mice

Protein restricted (PR) diets promote health and longevity in many species. While the precise components of a PR diet that mediate the beneficial effects to longevity have not been defined, we recently showed that many metabolic effects of PR can be attributed to reduced dietary levels of the branched-chain amino acids (BCAAs) leucine, isoleucine, and valine. Here, we demonstrate that restricting dietary BCAAs increases the survival of two different progeroid mouse models, delays frailty and promotes the metabolic health of wild-type C57BL/6J mice when started in midlife, and leads to a 30% increase in lifespan and a reduction in frailty in male, but not female, wild-type mice when fed lifelong. Our results demonstrate that restricting dietary BCAAs can increase healthspan and longevity in mice, and suggest that reducing dietary BCAAs may hold potential as a translatable intervention to promote healthy aging.

Gut-Based Strategies to Reduce Postprandial Glycaemia in Type 2 Diabetes

Postprandial glycemic control is an important target for optimal type 2 diabetes management, but is often difficult to achieve. The gastrointestinal tract plays a major role in modulating postprandial glycaemia in both health and diabetes. The various strategies that have been proposed to modulate gastrointestinal function, particularly by slowing gastric emptying and/or stimulating incretin hormone GLP-1, are summarized in this review.

Intestinal gluconeogenesis and protein diet: future directions

High-protein meals and foods are promoted for their beneficial effects on satiety, weight loss and glucose homeostasis. However, the mechanisms involved and the long-term benefits of such diets are still debated. We here review how the characterisation of intestinal gluconeogenesis (IGN) sheds new light on the mechanisms by which protein diets exert their beneficial effects on health. The small intestine is the third organ (in addition to the liver and kidney) contributing to endogenous glucose production via gluconeogenesis. The particularity of glucose produced by the intestine is that it is detected in the portal vein and initiates a nervous signal to the hypothalamic nuclei regulating energy homeostasis. In this context, we demonstrated that protein diets initiate their satiety effects indirectly via IGN and portal glucose sensing. This induction results in the activation of brain areas involved in the regulation of food intake. The μ-opioid-antagonistic properties of protein digests, exerted in the portal vein, are a key link between IGN induction and protein-enriched diet in the control of satiety. From our results, IGN can be proposed as a mandatory link between nutrient sensing and the regulation of whole-body homeostasis. The use of specific mouse models targeting IGN should allow us to identify several metabolic functions that could be controlled by protein diets. This will lead to the characterisation of the mechanisms by which protein diets improve whole-body homeostasis. These data could be the basis of novel nutritional strategies targeting the serious metabolic consequences of both obesity and diabetes.

Acute hyperaminoacidemia does not suppress insulin-mediated glucose turnover in healthy young men

Elevated circulating amino acids (AA) concentrations are purported to cause insulin resistance (IR) in humans. To quantify hyperaminoacidemia effects on insulin-mediated glucose turnover in healthy men, we performed 2-stage pancreatic clamps using octreotide with glucagon and growth hormone replacement. In the basal stage, insulin was infused to maintain euglycemia at postabsorptive levels. During the clamp stage, insulin was raised to postprandial levels, glycemia clamped at 5.5 mmol/L by glucose infusion, and branched-chain AA (BCAA) maintained at either postabsorptive (Hyper1; n = 8) or postprandial (Hyper2; n = 7) by AA infusion. Glucose turnover was measured by d-3-[³H]glucose dilution. Octreotide suppressed C-peptide; glucagon, growth hormone, and glycemia were maintained at postabsorptive levels throughout. Insulin did not differ at postabsorptive (72 ± 5 vs. 60 ± 5 pmol/L; Hyper1 vs. Hyper2) and increased to similar concentrations at basal (108 ± 11 vs. 106 ± 14) and clamp stages (551 ± 23 vs. 540 ± 25). Postabsorptive BCAA were maintained during Hyper1 and increased >2-fold (830 ± 26 µmol/L) during Hyper2. Endogenous glucose production was similarly suppressed (0.95 ± 0.16 vs. 1.37 ± 0.23 mg/kg lean body mass/min; Hyper1 vs. Hyper2) and basal glucose disposal (3.44 ± 0.12 vs. 3.67 ± 0.14) increased to similar levels (10.89 ± 0.56 vs. 11.11 ± 1.00) during the clamp. Thus, acute physiological elevation of AA for 3 h did not cause IR in healthy men. Novelty: A 2-step pancreatic clamp was used to quantify the effect of AA on insulin sensitivity in humans. Acute physiological elevation of circulating AA to postprandial levels does not cause IR in healthy men.

Effect of Aging Time on Meat Quality of Longissimus Dorsi from Yunling Cattle: A New Hybrid Beef Cattle

Simple Summary

Beef is in great demand in many countries. Consumers are more inclined to buy beef with good tenderness, color, flavor, and healthy fatty acid composition. Beef that has been aged is often more suitable for cooking and processing. A research gap exists regarding the analysis of meat quality during the aging process in Yunling cattle, a new hybrid beef cattle bred by Chinese researchers. This study measured a set of indicators of Yunling beef and other two breeds as controls (Simmental cattle, an excellent beef cattle breed used around the world, and Wenshan cattle, a local beef cattle breed in southern China), including the pH, water loss rate, cooking loss, Warner-Bratzler shear force, myofibrillar fragmentation index, inosine 5′-monophosphate, color, and fatty acid profiles. In addition, some growth performance and carcass characteristics were determined. The results showed that the pH, water holding capacity, growth performance, and carcass traits of Yunling and Simmental cattle were basically the same and better, respectively, than those of Wenshan cattle. Aging time had no effect on beef fatty acid composition, with Yunling beef showing a healthier fatty acid profile versus the other two breeds. With increased aging time, the tenderness and color of Yunling beef became more suitable for cooking and sensory characteristics. Therefore, this study suggests that Yunling beef should be used for cooking and processing after aging.

Abstract

The beef aging process is essential for compliance with certain major requisites, such as sensory characteristics for cooking and meat processing. Meat quality analysis of Yunling cattle, a new hybrid beef cattle bred by Chinese researchers, during the aging process, represents a major research gap. To explore Yunling beef initially, indicators associated with meat quality during the aging process of Yunling, Simmental, and Wenshan cattle were measured. In addition, some important economic traits were detected in the three breeds, including growth performance and carcass characteristics. The results showed that the growth performance, carcass traits, pH, and water holding capacity of Yunling and Simmental cattle were basically the same and better, respectively, than those of Wenshan cattle. The proportions of individual fatty acids in Yunling beef were healthier than in the other two breeds. Aging time did not affect the fatty acid profiles of the beef (p > 0.05). The contents of certain fatty acids in the three beef types displayed some differences in terms of days of aging (p < 0.05). The tenderness and meat color were better in the Yunling beef as the aging time increased, indicating that Yunling beef aged for 7 days was more suitable for cooking, exhibiting better sensory characteristics. Thus, a 7-day short-term aging process is very effective in improving the quality of Yunling beef. Our study attempted to fill a gap in the Yunling beef quality analysis during aging, providing further evidence for Yunling beef improvement.

Does high dietary protein intake contribute to the increased risk of developing prediabetes and type 2 diabetes?

Insulin resistance is a complex metabolic disorder implicated in the development of many chronic diseases. While it is generally accepted that body mass loss should be the primary approach for the management of insulin resistance-related disorders in overweight and obese individuals, there is no consensus among researchers regarding optimal protein intake during dietary restriction. Recently, it has been suggested that increased plasma branched-chain amino acids concentrations are associated with the development of insulin resistance and type 2 diabetes. The exact mechanism by which excessive amino acid availability may contribute to insulin resistance has not been fully investigated. However, it has been hypothesised that mammalian target of rapamycin (mTOR) complex 1 hyperactivation in the presence of amino acid overload contributes to reduced insulin-stimulated glucose uptake because of insulin receptor substrate (IRS) degradation and reduced Akt-AS160 activity. In addition, the long-term effects of high-protein diets on insulin sensitivity during both weight-stable and weight-loss conditions require more research. This review focusses on the effects of high-protein diets on insulin sensitivity and discusses the potential mechanisms by which dietary amino acids can affect insulin signalling. Novelty: Excess amino acids may over-activate mTOR, resulting in desensitisation of IRS-1 and reduced insulin-mediated glucose uptake.