Tiina Jauhiainen

Milk Peptides and Blood Pressure

Epidemiological studies suggest that milk consumption and dietary intake of dairy proteins are inversely related to the risk for hypertension. Also, some intervention studies have shown a blood pressure-lowering effect of milk products and dairy proteins. Milk peptides are formed from milk proteins by enzymatic breakdown by digestive enzymes or by the proteinases formed by lactobacilli during the fermentation of milk. Several milk peptides have been shown to have antihypertensive effects in animal and in clinical studies. The most studied mechanism underlying the antihypertensive effects of milk peptides is inhibition of angiotensin-converting enzyme. Milk peptides may also have other additional mechanisms to lower blood pressure such as opioid-like activities and mineral-binding and antithrombotic properties. The future challenge is to identify the antihypertensive components in milk and their mechanisms of action and thus to find more possibilities for using these constituents and products as a dietary treatment of hypertension.

Long-term intervention with Lactobacillus helveticus fermented milk reduces augmentation index in hypertensive subjects.

Background:The milk casein-derived biologically active tripeptides, isoleucyl-prolyl-proline (Ile-Pro-Pro) and valyl-prolyl-proline (Val-Pro-Pro), have documented antihypertensive effect probably related to reduced angiotensin formation. It has been suggested that these tripeptides may reduce arterial stiffness and improve endothelial function. Our aim was to evaluate whether the milk-based drink containing Ile-Pro-Pro and Val-Pro-Pro influence arterial stiffness, measured as augmentation index (AIx), and endothelial function in man.Methods:In a double-blind parallel group intervention study, 89 hypertensive subjects received daily peptide milk containing a low dose of tripeptides (5 mg/day) for 12 weeks and a high dose (50 mg/day) for the following 12 weeks, or a placebo milk drink to titrate the dose–response effect. Arterial stiffness was assessed by pulse wave analysis at the beginning and end of each intervention period. Endothelial function was tested by examining pulse wave reflection response to sublingual nitroglycerin and salbutamol inhalation. Blood pressure was measured by using office and 24-h ambulatory blood pressure measurement.Results:At the end of the second intervention period, AIx decreased significantly in the peptide group compared with the placebo group (peptide group −1.53% (95% confidence interval (CI) −2.95 to −0.12), placebo group 1.20% (95% CI 0.09–2.32), P=0·013). No change in endothelial function index was observed (peptide group 0.02 (95% CI −0.06 to 0.08), placebo group 0.04 (95% CI −0.04 to 0.12), P=0.85). There were no statistically significant differences between the effects of the peptide and placebo treatment on office and 24-h ambulatory blood pressure.Conclusions:Long-term treatment with Lactobacillus helveticus-fermented milk containing bioactive peptides reduces arterial stiffness expressed as AIx in hypertensive subjects.

Effects of low-fat hard cheese enriched with plant stanol esters on serum lipids and apolipoprotein B in mildly hypercholesterolaemic subjects

Objective:To investigate the cholesterol-lowering effects of a low-fat cheese enriched with plant stanol esters in mildly hypercholesterolaemic subjects, as part of their normal diet.Design:A randomized double-blind parallel-group study.Setting:Valio Ltd, Helsinki.Subjects:Sixty-seven mildly hypercholesterolaemic volunteers (24 men, 43 women) participated in the study, which all of them completed.Interventions:The subjects were randomly assigned to the plant stanol ester group or the control group. During the 5-week intervention, the subjects in the stanol group consumed a cheese enriched with 2 g of plant stanols per day, and the subjects in the control group, a control cheese with no plant stanols.Results:In the stanol ester group, as compared to the control group, both serum total and low-density lipoprotein (LDL) cholesterol decreased significantly, that is, by 5.8% (−0.32 mmol/l, 95% CI −0.50 to −0.15 mmol/l, P<0.001) and 10.3% (−0.36 mmol/l, 95% CI −0.53 to −0.18 mmol/l, P<0.001), respectively. There were no significant changes in high-density lipoprotein cholesterol (HDL), triglycerides or apolipoprotein B concentrations between the groups.Conclusion:Cheese enriched with 2 g of plant stanol in the form of fatty acid esters decreases serum total and LDL cholesterol significantly.

Effects of yoghurt enriched with free plant sterols on the levels of serum lipids and plant sterols in moderately hypercholesterolaemic subjects on a high-fat diet.

This study examined the effect of plant sterols added, together with an emulsifying agent, to a low-fat yoghurt on the serum lipid and plant sterol values in moderately hypercholesterolaemic volunteers. Study I was a randomized double-blind, cross-over trial. For 4 weeks, 15 volunteers consumed yoghurt containing 1 g plant sterols or a placebo yoghurt. Study II was a randomized, double-blind, parallel-group study. For 8 weeks, the sterol group (n=12) ingested daily two yoghurts (2 g/day plant sterols) and the placebo group (n=14) ingested two yoghurts without plant sterols. Study I: compared with the placebo, the sterol yoghurt reduced serum total cholesterol by 0.15 mmol/l (2.2%, P =0.235) and low-density lipoprotein (LDL) cholesterol by 0.19 mmol/l (4.3%, P =0.082), and increased serum campesterol by 0.26 mg/100 ml (P =0.006) and sitosterol by 0.11 mg/100 ml (P =0.015). Study II: compared with the placebo, the sterol yoghurt reduced serum total cholesterol by 0.41 mmol/l (6.3%, P =0.167) and LDL cholesterol by 0.28 mmol/l (6.4%, P =0.306), and increased serum campesterol by 0.28 mg/100 ml (P =0.016) and sitosterol by 0.40 mg/100 ml (P =0.206). Meta-analysis: the pooled treatment difference was −0.34 mmol/l (−5.2%, P =0.173) in total cholesterol and was −0.26 mmol/l (−5.8%, P =0.261) in LDL cholesterol, when the sterol yoghurt was compared with the placebo. A low-fat yoghurt enriched with 1–2 g/day plant sterols reduced serum cholesterol levels in moderately hypercholesterolaemic subjects. Campesterol and sitosterol serum levels increased, but their concentration remained in the range of normal values.

Milk Products Containing Bioactive Tripeptides Have an Antihypertensive Effect in Double Transgenic Rats (dTGR) Harbouring Human Renin and Human Angiotensinogen Genes

Tripeptides isoleucyl-prolyl-proline (IPP) and valyl-prolyl-proline (VPP) act as ACE inhibitors in vitro. Double transgenic rats (dTGR) harbouring human renin and human angiotensinogen genes develop malignant hypertension due to increased angiotensin II formation. The present study was aimed to evaluate possible antihypertensive effect of IPP and VPP in this severe model. Four-week-old dTGR were randomized in three groups to receive: (1) water (control), (2) fermented milk containing IPP and VPP, and (3) IPP and VPP dissolved in water for three weeks. Fermented milk, but not peptides in water, attenuated the development of hypertension in dTGR by 19 mmHg versus the control group (P = .023). In vitro vascular function tests showed that high concentrations of the peptides evinced ACE inhibitory properties. In other hypertension related variables, no significant differences between the treatment groups were found. In conclusion, fermented milk product containing IPP and VPP prevents development of malignant hypertension in an animal model.

Effects of long-term intake of lactotripeptides on cardiovascular risk factors in hypertensive subjects

Background/objectives:Lactobacillus helveticus LBK-16H-fermented milk products containing tripeptides isoleucine-proline-proline and valine-proline-proline lower blood pressure in hypertensive subjects using office and home blood pressure registration. The present study was aimed to evaluate the effects of two doses of these lactotripeptides on 24-h ambulatory blood pressure and lipidomics profiles in mildly hypertensive subjects.Subjects/methods:In a randomized, double-blind, placebo-controlled parallel group study, 89 mildly hypertensive subjects ingested, after a 1-month run-in period, a fermented milk drink with 5 mg per day of lactotripeptides during 3 months, and a milk drink with 50 mg per day of lactotripeptides for the following 3 months, or a placebo milk drink without lactotripeptides. Ambulatory blood pressure (24 h) was recorded at baseline and at the end of the intervention periods. Lipidomics profiles were characterized before and after the 6-month intervention.Results:After the second intervention period (50 mg per day of lactotripeptides), systolic and diastolic 24-h blood pressures decreased significantly in the peptide, but not in the placebo group. However, the treatment effects −2.6 mm Hg (95% confidence interval (CI): −5.7 to 0.4) in systolic and −1.3 mm Hg (95% CI: −3.4 to 0.8) in diastolic blood pressure did not reach statistic significance. Ingestion of 5 mg per day of lactotripeptides for 3 months did not lower blood pressure. The peptide group was dominated by decrease in multiple phospholipids (PL).Conclusions:Ingestion of fermented milk with daily dose of 50 mg of lactotripeptides appears to lower elevated blood pressure slightly from the baseline, but not significantly compared with the placebo group and to induce significant decreases in multiple PL.

Effects of milk casein-derived tripeptides Ile-Pro-Pro, Val-Pro-Pro, and Leu-Pro-Pro on enzymes processing vasoactive precursors in vitro.

Milk-based drinks containing casein-derived tripeptides isoleucine-proline-proline (Ile-Pro-Pro) and valine-proline-proline (Val-Pro-Pro) have been shown to possess antihypertensive and vascular endothelium-protecting properties in hypertensive animal models. Furthermore in clinical intervention trials they reduce blood pressure and arterial stiffness. The exact mechanisms are not known, but inhibition of angiotensin converting enzyme 1 (ACE1) has been suggested mainly to mediate these beneficial effects. The present study investigated the in vitro effects of three tripeptides: Ile-Pro-Pro, Val-Pro-Pro and leqcine-proline-proline (Leu-Pro-Pro) on four renin-angiotensin system enzymes: ACE1, ACE2, chymase, and cathepsin G. Also their effects on arginase I, a critical enzyme in L-arginine-nitric oxide pathway, were studied. It was shown, apparently for the first time, that the inhibitory effects of Ile-Pro-Pro, Val-Pro-Pro and Leu-Pro-Pro on ACE1 at micromolar concentrations are competitive in nature. Therefore the efficacy of inhibition is largely dependent on the amount of substrate present. Inhibition of ACE2 and arginase I was reached only at concentrations three orders of magnitude greater. No inhibition of chymase and cathepsin G was observed by the tripeptides. The findings support the hypothesis that Ile-Pro-Pro, Val-Pro-Pro and Leu-Pro-Pro act favourably on blood pressure mainly by selective inhibition of ACE1.

Effects of a fibre-enriched milk drink on insulin and glucose levels in healthy subjects

BackgroundThe glycaemic response to foods is dependent on the quality and content of carbohydrates. Carbohydrates in the form of dietary fibre have favourable effects on insulin and glucose metabolism and may help to control energy intake. Dairy products have a relatively low carbohydrate content, and most of the carbohydrate is in the form of lactose which causes gastrointestinal symptoms in part of the population. In order to avoid these symptoms, dairy products can be replaced with lactose-free dairy products which are on the market in many parts of the world. However, the effects of lactose-free products on insulin and glucose metabolism have not been studied.MethodsIn the present study, we investigated the effects of 1) a lactose-free milk drink, 2) a novel fibre-enriched, fat- and lactose-free milk drink and 3) normal fat-free milk on serum glucose and insulin levels and satiety using a randomized block design. Following an overnight fast, 26 healthy volunteers ingested 200 ml of one of these drinks on three non-consecutive days. Insulin and glucose levels and subjective satiety ratings were measured before the ingestion of the milk product and 20, 40, 60, 120 and 180 minutes after ingestion. The responses were calculated as the area under the curve subtracted by the baseline value (AUC minus baseline).ResultsThe insulin response was significantly lower for the fibre-enriched milk drink than it was for the other milk products (AUC, P = 0.007). There were no differences in the response for glucose or in the AUC for the subjective satiety ratings between the studied milk products.ConclusionThe present results suggest that this novel milk drink could have positive effects on insulin response.